Waterproof sound-permeable film and electric product

Abstract

A waterproof sound-permeable film according to an embodiment of the present invention includes polyurethane and is at least 20% bio-based. It is thereby possible to provide a waterproof sound-permeable film having reduced environmental load.

Description

Waterproof sound-permeable membranes and electrical products

[0001] The present invention relates to a waterproof sound-permeable membrane and an electrical appliance using the same.

[0002] Electrical and electronic products such as mobile phones, smartphones, cordless phones, portable media players, portable game consoles, digital cameras, and digital video cameras have sound receiving and sound generating units such as microphones and speakers in their housing structures. While the term "electrical and electronic products" is used here to refer to these products simply as "electrical products," it also encompasses electronic products. These electrical products have openings in the corresponding positions, through which sound is transmitted.

[0003] As exemplified by the widespread use of smartphones, these electrical appliances are increasingly being used outdoors, making it desirable for them to have a waterproof structure. For example, smartphones with waterproof functionality are becoming more common.

[0004] In order to transmit sound while preventing water from entering the housing, a waterproof sound-permeable membrane that is both waterproof and sound-permeable is attached to openings such as the sound generating section and sound receiving section. For example, Patent Document 1 discloses a sound-permeable membrane for a microphone made of a non-porous film such as a polytetrafluoroethylene film, and has a surface density of 30 g / m. ２ It is disclosed that sound transmission loss can be reduced by the following: Patent Document 2 discloses a sound-transmitting sheet made of an elastomer, and that excellent sound transmission can be achieved by setting the hardness of the elastomer within a predetermined range and setting the sheet thickness to 10 to 150 μm. Patent Documents 3 and 4 disclose that sound loss can be reduced by using polyurethane as a waterproof sound-transmitting membrane made of a porous synthetic resin membrane.

[0005] On the other hand, against the backdrop of global warming and the depletion of petroleum resources, there is an increasing demand for environmentally friendly materials made from biomass raw materials such as plants. From the viewpoint of reducing the environmental load, resins made from plant-derived components have been developed. For example, Patent Document 5 discloses a bio-polyurethane resin that uses a high proportion of plant-derived raw materials.

[0006] JP 2011-078089 A JP 2014-007738 A International Publication No. 2015 / 105052 International Publication No. 2022 / 186105 JP 2011-225863 A

[0007] As mentioned above, various waterproof sound-transmitting membranes have been proposed up to now, but a waterproof sound-transmitting membrane with a high bio-based content that takes environmental impact into consideration has not yet been realized.

[0008] In view of the above, an object of the present invention is to provide a waterproof sound-permeable membrane that can reduce the environmental load.

[0009] The present invention includes the following embodiments: [1] A waterproof sound-permeable membrane containing polyurethane and having a bio-based content of 20% or more. [2] A surface density of 5 to 40 g / m ２ [3] The waterproof sound-transmitting membrane according to [1], wherein the tensile strength per width at 10% elongation measured in a tensile test is 0.5 to 200 N / m. [4] The waterproof sound-transmitting membrane according to any one of [1] to [3], wherein the water swelling degree is 3% or less. [5] The waterproof sound-transmitting membrane according to any one of [1] to [4], wherein the waterproof sound-transmitting membrane is an imperforate membrane. [6] The waterproof sound-transmitting membrane according to any one of [1] to [5], wherein the acoustic loss at a frequency of 1 kHz is 10 dB or less. [7] The waterproof sound-transmitting membrane according to any one of [1] to [6], wherein the waterproof sound-transmitting membrane does not leak water when a water pressure of 60 kPa is applied to a circular area having a diameter of 3 mm for 30 minutes. [8] An electrical appliance comprising a housing having an opening for a sound receiving unit or a sound generating unit, and the waterproof sound-transmitting membrane according to any one of [1] to [7] attached to the opening.

[0010] According to this embodiment, it is possible to provide a waterproof sound-transmitting membrane that reduces the environmental load.

[0011] Cross-sectional view of a waterproof sound-transmitting member including a waterproof sound-transmitting membrane according to one embodiment. Plan view of a waterproof sound-transmitting member including a waterproof sound-transmitting membrane according to one embodiment. Schematic diagram of an acoustic loss measuring device.

[0012] The waterproof sound-permeable membrane according to this embodiment contains polyurethane and has a bio-based content of 20% or more.

[0013] A biobased content of 20% or more can reduce the environmental impact of the waterproof sound-permeable membrane. The biobased content of the waterproof sound-permeable membrane is preferably 25% or more, and more preferably 30% or more. From the perspective of environmental impact, the higher the biobased content, the better. Therefore, there is no particular upper limit, and the biobased content may be, for example, 95% or less, 80% or less, or 50% or less. In other words, the biobased content may be, for example, 20 to 95%, 25 to 80%, or 30 to 50%.

[0014] The biobased content is an index showing the proportion of biomass raw materials, and is the biobased carbon content in a waterproof sound-permeable membrane calculated in accordance with ISO 16620-2. In other words, the biobased content of a waterproof sound-permeable membrane is the proportion of the carbon mass of biomass-derived components to the total carbon mass of the waterproof sound-permeable membrane.

[0015] The waterproof sound-transmitting membrane is preferably formed mainly from a synthetic resin. For example, it is preferable that 50 mass % or more of the waterproof sound-transmitting membrane is synthetic resin, more preferably 70 mass % or more, and even more preferably 90 mass % or more.

[0016] In this embodiment, polyurethane is used as the synthetic resin that constitutes the waterproof sound-transmitting membrane. By including polyurethane in the waterproof sound-transmitting membrane in this way, a membrane that is flexible and has excellent acoustic properties can be formed. In one embodiment, the waterproof sound-transmitting membrane is preferably a resin membrane that is primarily made of polyurethane. For example, it is preferable that 60% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more of the synthetic resin that constitutes the waterproof sound-transmitting membrane is polyurethane, and 100% by mass may be polyurethane.

[0017] Examples of polyurethanes include polyester polyurethanes, polyether polyurethanes, polycarbonate polyurethanes, and polyether / carbonate polyurethanes, and any one of these may be used alone or in combination. Here, polyether / carbonate polyurethanes are polyurethanes whose molecular structure contains a polyether skeleton and a polycarbonate skeleton.

[0018] From the viewpoint of being resistant to hydrolysis and having excellent durability, it is preferable that the polyurethane contains a polycarbonate skeleton in its molecular structure. Therefore, it is preferable that the waterproof sound-permeable membrane contains polycarbonate-based polyurethane and / or polyether / carbonate-based polyurethane.

[0019] In one embodiment, from the viewpoint of reducing the degree of swelling in water of the waterproof sound-permeable membrane and improving its waterproofness, the polyurethane is preferably at least one selected from the group consisting of polyester-based polyurethanes, polycarbonate-based polyurethanes, and polyether / carbonate-based polyurethanes.

[0020] To achieve a bio-based content of 20% or more, the waterproof sound-permeable membrane preferably contains polyurethane synthesized using biomass-derived raw materials. Examples of such polyurethane include bio-polyurethanes made from at least one raw material selected from the group consisting of biomass-derived polybasic acids, biomass-derived glycols, and biomass-derived polyisocyanates.

[0021] More specifically, examples of the biopolyurethane include polyurethanes obtained by reacting at least one polyol selected from the group consisting of (A), (B), and (C) below with a petroleum-derived polyisocyanate and / or a biomass-derived polyisocyanate. (A): A biomass-derived polycarbonate polyol synthesized using a biomass-derived glycol and a petroleum-derived carbonate. (B): A biomass-derived polyester polyol synthesized using a biomass-derived glycol and a biomass-derived polybasic acid. (C) A biomass-derived polyether polyol synthesized using a biomass-derived glycol. When reacting the above polyol with the polyisocyanate, a biomass-derived glycol, a petroleum-derived glycol, and / or a petroleum-derived diamine may be included as a reaction component, as necessary. The biobased content of the biopolyurethane is not particularly limited and may be, for example, 20 to 95% or 25 to 80%.

[0022] Examples of the biomass-derived polybasic acid include sebacic acid, succinic acid, glutaric acid, and dimer acid, and any one or more of these may be used in combination. For example, sebacic acid can be obtained by alkaline thermal decomposition of ricinoleic acid obtained from castor oil.

[0023] Examples of the biomass-derived glycol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,10-decanediol, dimer diol, and isosorbide, which are obtained from plant raw materials. Any one of these can be used alone or in combination of two or more.

[0024] The biomass-derived polyisocyanate can be obtained, for example, by converting a biomass-derived dicarboxylic acid into a terminal amino group through acid amidation and reduction, and then reacting it with phosgene to convert the amino group into an isocyanate group. Specific examples include dimer acid diisocyanate (DDI), octamethylene diisocyanate, and decamethylene diisocyanate. Alternatively, a biomass-derived amino acid may be used as a raw material, and the amino group may be converted into an isocyanate group. Specific examples include lysine diisocyanate (LDI), 1,5-pentamethylene diisocyanate (1,5-PDI), and the like.

[0025] Examples of the petroleum-derived carbonate include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ethylene carbonate, diphenyl carbonate, etc. These may be used alone or in combination of two or more.

[0026] Examples of petroleum-derived polyisocyanates include aliphatic polyisocyanates, aromatic polyisocyanates, and alicyclic polyisocyanates. Examples of aliphatic polyisocyanates include methylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 1,10-decamethylene diisocyanate. Examples of aromatic polyisocyanates include xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate. Examples of alicyclic polyisocyanates include 1,4-cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate. These polyisocyanates can be used alone or in combination of two or more.

[0027] Examples of petroleum-derived glycols include ethylene glycol, diethylene glycol, propanediol, butanediol, hexanediol, polyethylene glycol, etc., and any one or two or more of these can be used in combination. Examples of petroleum-derived diamines include methylenediamine, ethylenediamine, trimethylenediamine, hexamethylenediamine, octamethylenediamine, phenylenediamine, cyclopentadiamine, cyclohexyldiamine, isophoronediamine, hydrazine, etc., and any one or two or more of these can be used in combination.

[0028] The waterproof sound-permeable membrane may be composed solely of polyurethane, or may contain synthetic resins other than polyurethane, and may further contain various additives such as surface feel improvers, water repellents, crosslinking agents, inorganic fine particles, plasticizers, antioxidants, ultraviolet absorbers, smoothing agents such as amide wax, hydrolysis inhibitors, pigments, anti-yellowing agents, and matting agents.

[0029] The surface density of the waterproof sound-permeable membrane is, for example, 3 to 40 g / m ２ Preferably, it is 5 to 40 g / m ２This low surface density and light weight, coupled with the fact that the waterproof sound-permeable membrane is made of polyurethane, a flexible material, can further improve the acoustic properties of the waterproof sound-permeable membrane. On the other hand, if the surface density is too low, the membrane strength will decrease, making it more susceptible to damage from water pressure and reducing its waterproofing. Therefore, the surface density is set to 5 g / m ２ The surface density of the waterproof sound-permeable membrane is more preferably 7 to 30 g / m ２ and more preferably 10 to 25 g / m ２ is.

[0030] The areal density is the mass per unit area of ​​the waterproof sound-transmitting membrane, and is determined by dividing the mass of the waterproof sound-transmitting membrane by the area of ​​the waterproof sound-transmitting membrane (the area of ​​the plane when the membrane is viewed as a plane).

[0031] The waterproof sound-transmitting membrane preferably has a tensile strength per width of 0.5 to 200 N / m at 10% elongation as measured in a tensile test. This flexibility of the waterproof sound-transmitting membrane reduces acoustic loss and improves acoustic characteristics. Therefore, in combination with a bio-based content of 20% or more, it is possible to achieve both acoustic characteristics and environmental performance. The tensile strength at 10% elongation is more preferably 0.5 to 100 N / m, even more preferably 1 to 50 N / m, and even more preferably 2 to 30 N / m. The tensile strength at 10% elongation can be measured by the method described in the Examples section.

[0032] In order to make the tensile force of the waterproof sound-transmitting membrane at 10% elongation as low as above, it is preferable to use, for example, a flexible material with a low tensile modulus of elasticity, for example, 100 MPa or less, more preferably 0.5 to 30 MPa, and even more preferably 1 to 20 MPa, as the membrane material that makes up the waterproof sound-transmitting membrane. Alternatively, it is preferable to reduce the areal density of the waterproof sound-transmitting membrane, for example, to within the above numerical range.

[0033] Here, the tensile modulus is the ratio of the tensile stress per cross-sectional area to the strain (elongation) generated in the stress direction. Specifically, in the measurement of the "tensile force at 10% elongation" described in the Examples section, the tensile force is calculated based on the cross-sectional area (mm ２The slope of the obtained stress-strain curve up to an initial elongation of 10% can be determined as the tensile modulus (MPa).

[0034] The thickness of the waterproof sound-permeable membrane is not particularly limited, and may be, for example, 10 to 150 μm, or 15 to 80 μm.

[0035] It is preferable that the waterproof sound-permeable membrane has a low degree of swelling in water. The degree of swelling in water may be, for example, 8% or less, but is preferably 3% or less. A water swelling degree of 3% or less makes it difficult for water to seep out when in contact with water for a long period of time, improving waterproofing. The degree of swelling in water of the waterproof sound-permeable membrane is more preferably 2% or less, and even more preferably 1% or less. The degree of swelling in water can be measured by the method described in the Examples section.

[0036] The waterproof sound-permeable membrane may be a non-porous membrane or a porous membrane.

[0037] From the viewpoint of waterproofness, the waterproof sound-transmitting membrane is preferably a non-porous membrane. Generally, non-porous membranes have superior waterproofness compared to porous membranes, but poor acoustic properties. However, by forming the membrane from a flexible material as described above, it is possible to improve both waterproofness and acoustic properties. Moreover, when the surface density is reduced as described above, a flexible and lightweight non-porous membrane can be realized using a bio-based structure. Therefore, a waterproof sound-transmitting membrane that combines excellent acoustic properties and environmental performance while improving waterproofness can be obtained. In a preferred embodiment, the waterproof sound-transmitting membrane is a non-porous membrane and has a surface density of 5 to 40 g / m ２ and the degree of swelling in water is 3% or less.

[0038] Here, the non-porous membrane refers to a solid (i.e., non-porous) membrane that does not have minute pores like a porous membrane.

[0039] The waterproof sound-transmitting membrane may be a porous membrane from the viewpoint of breathability. The porous membrane may be a resin membrane with a porous structure having minute pores inside, or may be a nonwoven fabric.

[0040] When the waterproof sound-permeable membrane is a porous membrane, the air permeability in accordance with the JIS L1096:2010 Gurley method is preferably 0.1 to 30 seconds / 100 mL. A porous membrane with high air permeability allows sound to easily propagate through the air passage, improving acoustic characteristics. On the other hand, if the air permeability is too high, waterproofing is reduced. The air permeability is more preferably 1 to 25 seconds / 100 mL, and even more preferably 5 to 22 seconds / 100 mL.

[0041] The waterproof sound-permeable membrane preferably has a water pressure resistance in accordance with JIS L1092:2009 High Water Pressure Method of 40 to 200 kPa, more preferably 45 to 150 kPa, and even more preferably 50 to 120 kPa.

[0042] The waterproof sound-permeable membrane preferably has an acoustic loss of 10 dB or less at a frequency of 1 kHz, and has excellent acoustic properties. The acoustic loss at a frequency of 1 kHz is more preferably 7 dB or less, more preferably 5 dB or less, and even more preferably 4 dB or less. The acoustic loss can be measured by the method described in the Examples section.

[0043] The waterproof sound-permeable membrane preferably does not leak water when a water pressure of 10 kPa is applied to a circular area with a diameter of 3 mm for 30 minutes, and has excellent waterproof properties. More preferably, it does not leak water when a water pressure of 60 kPa is applied to a circular area with a diameter of 3 mm for 1 minute. Even more preferably, it does not leak water when a water pressure of 60 kPa is applied to a circular area with a diameter of 3 mm for 30 minutes. This can further improve waterproof properties. Such waterproof properties can be evaluated by the method described in the Examples section.

[0044] In one embodiment, the waterproof sound-permeable membrane preferably has an acoustic loss of 10 dB or less at a frequency of 1 kHz, and does not leak water when a water pressure of 60 kPa is applied to a circular area with a diameter of 3 mm for 30 minutes.

[0045] In one embodiment, the waterproof sound-permeable membrane is preferably a non-porous membrane, has an acoustic loss of 10 dB or less at a frequency of 1 kHz, and does not leak water when a water pressure of 60 kPa is applied to a circular area with a diameter of 3 mm for 30 minutes.

[0046] In one embodiment, the waterproof sound-permeable membrane is a porous membrane, and the breathability is 0.1 to 30 seconds / 100 mL, and the acoustic loss at a frequency of 1 kHz is 10 dB or less. It is preferable that the waterproof sound-permeable membrane does not leak water when a water pressure of 10 kPa is applied to a circular area with a diameter of 3 mm for 30 minutes.

[0047] There are no particular limitations on the method for producing a waterproof sound-permeable membrane. For example, in the case of a non-porous membrane, a resin solution containing polyurethane is coated on a releasable substrate, and the solvent is dried to obtain a non-porous membrane containing the polyurethane.

[0048] For example, in the case of a porous resin film, it may be formed by a wet method, a dry method, or a laser tracking method. In the wet method, a resin solution containing polyurethane and a polar organic solvent is coated on a releasable substrate, and then coagulated in water (wet coagulation) to obtain a porous film (wet-coagulated porous film). In the dry method, a foaming agent or microcapsules is added to a resin solution containing polyurethane, and this is coated on a releasable substrate, and the solvent is dried to obtain a porous film. In the laser tracking method, a porous film is obtained by irradiating a non-porous film formed by a dry method with laser light to open a large number of holes.

[0049] The releasable substrate is not particularly limited, and examples thereof include films made of resins themselves that have releasability against synthetic resins. Examples of resins with releasability (hereinafter referred to as release agents) include olefin resins, silicone resins, etc. Further examples include release paper, release cloth, release films, etc., in which a release layer made of a release agent is laminated on a substrate such as paper, fabric, or film.

[0050] Examples of methods for applying the resin solution to the releasable substrate include methods using a floating knife coater, knife-on-roll coater, comma coater, reverse coater, lip coater, roll coater, and die coater.

[0051] In a preferred embodiment, the waterproof sound-transmitting membrane according to the embodiment can be used as a waterproof membrane attached to an opening for a sound receiving unit or a sound generating unit provided in the housing of various electrical appliances such as the above-mentioned mobile phones and smartphones. That is, an electrical appliance according to one embodiment comprises a housing having an opening for a sound receiving unit or a sound generating unit, and the above-mentioned waterproof sound-transmitting membrane attached to the opening.

[0052] In one embodiment, the waterproof sound-transmitting membrane may be configured as a waterproof sound-transmitting member by laminating a support layer on at least one side thereof. That is, the waterproof sound-transmitting member comprises the waterproof sound-transmitting membrane and a support layer laminated on at least one of the front and rear sides thereof. The support layer is laminated on part of the waterproof sound-transmitting membrane, so that the waterproof sound-transmitting member has a sound-transmitting region where the waterproof sound-transmitting membrane is exposed on both sides.

[0053] The support layer is provided, for example, to support and fix the waterproof sound-transmitting member to the housing, or to reinforce the waterproof sound-transmitting membrane and stabilize its shape. The support layer may be formed, for example, by attaching a double-sided pressure-sensitive adhesive sheet.

[0054] 1 and 2 are diagrams showing an example of a waterproof sound-transmitting member 1. A support layer 3 is provided on one side of a disk-shaped waterproof sound-transmitting membrane 2. The support layer 3 is ring-shaped and is provided around the entire periphery of one side of the waterproof sound-transmitting membrane 2. This provides a circular sound-transmitting region 4 inside the support layer 3.

[0055] The various numerical ranges described in this specification can be arbitrarily combined with their respective upper and lower limit values, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Note that the measurement and evaluation of physical properties in the following examples and comparative examples were carried out according to the following methods.

[0057] (1) Biobased content The biobased content was measured using the method of ISO16620-2. Radiocarbon (１４ C) concentration analysis revealed that the radioactive carbon ( １４ C) content was determined, and the bio-based carbon content was calculated based on this.

[0058] (2) Tensile force per width at 10% elongation A test piece measuring 50 mm wide x 80 mm long was attached to a tensile tester (product name "Autograph AG-IS type", manufactured by Shimadzu Corporation) with a grip spacing of 50 mm, and a tensile test was performed at a tensile speed of 150 mm / min. The measurement temperature was 22 ° C. and the measurement humidity was 65%. The tensile force (N) at 10% elongation was divided by the width of the test piece, 0.05 m, to determine the tensile force per unit width at 10% elongation (N / m). If the test piece broke at less than 10% elongation, the tensile force at 5% elongation was doubled, and if the test piece broke at less than 5% elongation, the tensile force at 1% elongation was multiplied by 10. Test pieces were taken from the resin film, rotated 90° vertically and horizontally, and the above measurement was performed 5 times vertically and horizontally, for a total of 10 times, to obtain the average value.

[0059] (3) Surface density The waterproof sound-permeable membrane was cut into a square of 20 cm square, the mass was measured using an electronic balance, and the surface density was calculated using the following formula. When sufficient accuracy could not be obtained with n = 10 measurements, the area of ​​the sample was increased. The measurement was performed 10 times in total, and the average value was calculated. Surface density (g / m ２ ) = Mass (g) ÷ 0.04 (m ２ )

[0060] (4) Water Swelling Degree The waterproof sound-permeable membrane was cut into a 10 cm square and a 10 cm mark was drawn diagonally. The waterproof sound-permeable membrane was immersed in water at room temperature for 30 minutes, and the length of the mark was measured, and the water swelling degree was calculated using the following formula. The measurement was repeated five times and the average value was calculated. Water swelling degree (%) = (length of mark after immersion (mm) - 100 (mm)) / 100 (mm) x 100

[0061] (5) Acoustic Loss Acoustic loss measurement will be described with reference to Figure 3. Sound was emitted from a speaker 11 in an anechoic box 16, and the output of a MEMS (ADMP401) analog microphone 12 built into a microphone jig 13 was converted to digital form by an analyzer and analyzed using analysis software (CLIO Pocket manufactured by Audiomatica) to measure the sound pressure level at a frequency of 1 kHz. The measured sound was a TSP signal containing a frequency of 1 kHz, and was a sound pressure of 94 dB in a blank measurement without the waterproof sound-permeable membrane 2 set.

[0062] The microphone jig 13 is a metal box-shaped device having an opening 14 on the outer surface through which sound enters, and an MEMS analog microphone 12 disposed in an internal space 15 .

[0063] The speaker 11, waterproof sound-transmitting membrane 2, opening 14, and MEMS analog microphone 12 are arranged in a straight line in this order without being obstructed by the structure of the microphone jig 13. The opening 14 is a circle with a diameter of 1 mm, the distance from the waterproof sound-transmitting membrane 2 to the MEMS analog microphone 12 is 6 mm, and the volume of the internal space 15 is 27 mm. ３ is.

[0064] The microphone jig 13 was placed 4.5 cm from the speaker 11 so that the plane on which the opening 14 was provided was parallel to the sound-generating part of the speaker 11 (so that sound was incident perpendicularly).

[0065] The sound pressure level measured using only the microphone jig 13 was used as the blank value. A double-sided adhesive sheet was attached to one side of a square waterproof sound-permeable membrane 2 with sides of 10 mm so that the sound-permeable region 4 was a circle with a diameter of 2 mm, to provide a support layer 3. The waterproof sound-permeable membrane 2 was attached to the microphone jig 13 via the support layer 3 so as to cover the opening 14 of the microphone jig 13, and the sound pressure level was measured. The difference in sound pressure level from the blank value was calculated as acoustic loss. The lower the acoustic loss, the higher the sound permeability. Measurements were performed on 10 samples, and the average value was calculated.

[0066] (6) Waterproofing A waterproof sound-transmitting membrane was attached to a SUS plate with a circular hole of 3 mm diameter using waterproof double-sided tape. It was set in a device conforming to JIS L1092:2009 Method B (high water pressure method) so that water pressure was applied to the waterproof sound-transmitting membrane side. The water pressure was increased at a rate of 100 kPa / min, and the pressure increase was stopped at a predetermined water pressure to maintain the water pressure, and the presence or absence of water leakage was determined. The measurement conditions were: maintaining a water pressure of 10 kPa for 30 minutes, maintaining a water pressure of 60 kPa for 1 minute, and maintaining a water pressure of 60 kPa for 30 minutes.

[0067] (7) Air Permeability The waterproof sound-permeable membrane made of a porous membrane was measured for air permeability according to JIS L1096:2010B method (Gurley method). The measurement was performed by measuring the time it took for 100 mL of air to pass through, and the time was recorded in units of "seconds / 100 mL".

[0068] (8) Water Pressure Resistance The water pressure resistance of the waterproof sound-permeable membrane was measured according to JIS L1092:2009 B Method (high water pressure method). During the measurement, in order to prevent breakage due to deformation of the porous membrane, a plain weave fabric that is less likely to affect the water pressure resistance of the porous membrane was layered and measured. The plain weave fabric was woven using 80 dtex / 24 filament 6 nylon multifilament yarn as the warp and 80 dtex / 34 filament 6 nylon multifilament yarn as the weft, with a warp density of 120 / 2.54 cm and a weft density of 90 / 2.54 cm.

[0069] Example 1 A polyurethane resin solution having the following formulation was prepared. <Formulation> Lezamin CU8543BP-30: 100 parts by mass (Dainichiseika Color & Chemicals Mfg. Co., Ltd., polyether / carbonate polyurethane, solids content 30% by mass, biobased content 26.5%), Crisbon Additive No. 10: 1 part by mass (DIC Corporation, silicone resin), methyl ethyl ketone: 40 parts by mass

[0070] Next, the polyurethane resin solution was applied to a releasable substrate using a knife-on-roll coater so that the surface density of the resulting waterproof sound-permeable membrane was 13.4 g / m ２ The coating was then dried at 100° C. for 1 minute. The releasable substrate was removed to obtain a waterproof sound-transmitting membrane that was a non-porous polyurethane membrane.

[0071] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the biobased content was 25.6%, the tensile strength at 10% elongation was 3.6 N / m, and the areal density was 13.4 g / m. ２ The waterproof sound-permeable membrane had a water swelling rate of 0% and an acoustic loss of 3.95 dB at 1 kHz. A circular sample with a diameter of 3 mm was subjected to a water pressure of 10 kPa for 30 minutes, a water pressure of 60 kPa for 1 minute, and a water pressure of 60 kPa for 30 minutes, and no water leakage occurred.

[0072] [Example 2] A waterproof sound-transmitting membrane having a surface density of 20.6 g / m2 was formed on a releasable substrate. ２ A waterproof sound-transmitting membrane, which was a non-porous polyurethane membrane, was obtained in the same manner as in Example 1, except that the coating was applied to a coating thickness of

[0073] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the biobased content was 25.6%, the tensile strength at 10% elongation was 5.6 N / m, and the areal density was 20.6 g / m. ２ The waterproof sound-permeable membrane had a water swelling rate of 0% and an acoustic loss of 4.93 dB at 1 kHz. A circular sample with a diameter of 3 mm was subjected to a water pressure of 10 kPa for 30 minutes, a water pressure of 60 kPa for 1 minute, and a water pressure of 60 kPa for 30 minutes, and no water leakage occurred.

[0074] [Example 3] A waterproof sound-transmitting membrane having an areal density of 33.9 g / m2 was formed on a releasable substrate. ２ A waterproof sound-transmitting membrane, which was a non-porous polyurethane membrane, was obtained in the same manner as in Example 1, except that the coating was applied to a coating thickness of

[0075] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the biobased content was 25.6%, the tensile strength at 10% elongation was 13.0 N / m, and the areal density was 33.9 g / m. ２The waterproof sound-permeable membrane had a water swelling rate of 0% and an acoustic loss of 6.45 dB at 1 kHz. A circular sample with a diameter of 3 mm was subjected to a water pressure of 10 kPa for 30 minutes, a water pressure of 60 kPa for 1 minute, and a water pressure of 60 kPa for 30 minutes, and no water leakage occurred.

[0076] [Example 4] A polyurethane resin solution was prepared according to the following formula, and the polyurethane resin solution was applied to a releasable substrate so that the surface density of the resulting waterproof sound-permeable membrane was 16.0 g / m ２ A waterproof sound-permeable membrane, which was a non-porous polyurethane membrane, was obtained in the same manner as in Example 1. <Formulation> Lezamin CU8543BP-50A: 100 parts by mass (Dainichiseika Color & Chemicals Mfg. Co., Ltd., polyester-based polyurethane, solids content 25% by mass, bio-based content 48%) CRISBON Additive No. 10: 1 part by mass (DIC Corporation, silicone resin) Methyl ethyl ketone: 40 parts by mass

[0077] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the biobased content was 46.1%, the tensile strength at 10% elongation was 5.5 N / m, and the areal density was 16.0 g / m. ２ The waterproof sound-permeable membrane had a water swelling rate of 0% and an acoustic loss of 3.14 dB at 1 kHz. A circular sample with a diameter of 3 mm was subjected to a water pressure of 10 kPa for 30 minutes, a water pressure of 60 kPa for 1 minute, and a water pressure of 60 kPa for 30 minutes, and no water leakage occurred.

[0078] [Example 5] A waterproof sound-transmitting membrane having a surface density of 27.8 g / m2 was formed on a releasable substrate. ２ A waterproof sound-transmitting membrane, which was a non-porous polyurethane membrane, was obtained in the same manner as in Example 4, except that the coating was applied to a coating thickness of

[0079] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the biobased content was 46.1%, the tensile strength at 10% elongation was 11.1 N / m, and the areal density was 27.8 g / m. ２The waterproof sound-permeable membrane had a water swelling rate of 0% and an acoustic loss of 8.00 dB at 1 kHz. A circular sample with a diameter of 3 mm was subjected to a water pressure of 10 kPa for 30 minutes, a water pressure of 60 kPa for 1 minute, and a water pressure of 60 kPa for 30 minutes, and no water leakage occurred.

[0080] [Example 6] A waterproof sound-transmitting membrane having a surface density of 4.0 g / m2 was formed on a releasable substrate. ２ A waterproof sound-transmitting membrane, which was a non-porous polyurethane membrane, was obtained in the same manner as in Example 4, except that the coating was applied to a coating thickness of

[0081] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the biobased content was 46.1%, the tensile strength at 10% elongation was 1.2 N / m, and the areal density was 4.0 g / m. ２ The waterproof sound-permeable membrane had a water swelling rate of 0% and an acoustic loss of 3.41 dB at 1 kHz. A 3 mm diameter circular membrane was subjected to a water pressure of 10 kPa for 30 minutes, and no water leakage occurred. However, due to the low surface density, a 3 mm diameter circular membrane leaked when a water pressure of 60 kPa was applied for 1 minute.

[0082] [Example 7] A polyurethane resin solution was prepared according to the following formula, and the polyurethane resin solution was applied to a releasable substrate so that the surface density of the resulting waterproof sound-permeable membrane was 17.3 g / m ２ A waterproof sound-permeable membrane, which was a non-porous polyurethane membrane, was obtained in the same manner as in Example 1. <Formulation> Y-239BP-40D: 100 parts by mass (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., polyether polyurethane, solids content 25% by mass, bio-based content 40%) CRISBON Additive No. 10: 1 part by mass (manufactured by DIC Corporation, silicone resin) Methyl ethyl ketone: 40 parts by mass

[0083] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the biobased content was 38.4%, the tensile strength at 10% elongation was 29.2 N / m, and the areal density was 17.3 g / m. ２The waterproof sound-transmitting membrane had a water swelling rate of 7% and an acoustic loss of 9.48 dB at 1 kHz. A circular sample with a diameter of 3 mm did not leak water when subjected to a water pressure of 10 kPa for 30 minutes and a water pressure of 60 kPa for 1 minute, but leaked water when subjected to a water pressure of 60 kPa for 30 minutes. In Example 7, the waterproof sound-transmitting membrane was made of polyether polyurethane, and therefore had a high water swelling rate, causing water to seep out after prolonged water pressure.

[0084] Example 8 A polyurethane resin solution was prepared according to the following formulation: <Formulation> Lezamin CU8543BP-30: 100 parts by mass (Dainichiseika Color & Chemicals Mfg. Co., Ltd., polyether / carbonate polyurethane, solids content 30% by mass, bio-based content 26.5%) Lezaroid LU2850M: 45 parts by mass (Dainichiseika Color & Chemicals Mfg. Co., Ltd., silica fine particle dispersion, solids content 20% by mass) N,N-dimethylformamide: 33 parts by mass

[0085] Next, the polyurethane resin solution was applied to a releasable substrate using a knife-on-roll coater so that the surface density of the resulting waterproof sound-transmitting membrane was 13.1 g / m ２ The membrane was then immersed in 20°C water for 1.5 minutes to solidify. After washing in 50°C warm water for 5 minutes, it was heat-treated at 130°C for 2 minutes and dried to obtain a waterproof sound-permeable membrane made of porous polyurethane.

[0086] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, waterproofness, breathability, and water pressure resistance. The results were: biobased content was 25.1%, tensile strength at 10% elongation was 19.2 N / m, and areal density was 13.1 g / m. ２ The waterproof sound-permeable membrane had a water swelling rate of 0%, an acoustic loss at 1 kHz of 8.66 dB, breathability of 21 seconds / 100 mL, and a water pressure resistance of 112 kPa. A 3 mm diameter circular sample was subjected to a water pressure of 10 kPa for 30 minutes, and no water leakage occurred. However, because it was a porous membrane, water leakage occurred when a 3 mm diameter circular sample was subjected to a water pressure of 60 kPa for 1 minute.

[0087] [Comparative Example 1] A polyurethane resin solution was prepared according to the following formula, and the polyurethane resin solution was applied to a releasable substrate so that the surface density of the resulting waterproof sound-permeable membrane was 16.6 g / m ２ A waterproof sound-permeable membrane, which was a non-porous polyurethane membrane, was obtained in the same manner as in Example 1. <Formulation> Lezamin CU9443M: 100 parts by mass (Dainichiseika Color & Chemicals Mfg. Co., Ltd., polycarbonate-based polyurethane, solids content 27% by mass, bio-based content 0%) CRISBON Additive No. 10: 1 part by mass (DIC Corporation, silicone resin) Methyl ethyl ketone: 40 parts by mass

[0088] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the tensile strength at 10% elongation was 3.7 N / m and the areal density was 16.6 g / m. ２ The waterproof sound-permeable membrane had a water swelling rate of 0% and an acoustic loss of 4.74 dB at 1 kHz. A circular sample with a diameter of 3 mm was subjected to a water pressure of 10 kPa for 30 minutes, a water pressure of 60 kPa for 1 minute, and a water pressure of 60 kPa for 30 minutes, and no water leakage occurred. However, in Comparative Example 1, the biobased content was 0%, and the membrane was poor in environmental load reduction performance.

[0089] [Comparative Example 2] The waterproof sound-transmitting membrane obtained was applied to a releasable substrate with a surface density of 28.1 g / m ２ A waterproof sound-transmitting membrane that was a non-porous polyurethane membrane was obtained in the same manner as in Comparative Example 1, except that the coating was applied to a coating thickness of

[0090] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results were that the tensile strength at 10% elongation was 10.2 N / m and the areal density was 28.1 g / m. ２The waterproof sound-permeable membrane had a water swelling rate of 0% and an acoustic loss of 5.20 dB at 1 kHz. A circular sample with a diameter of 3 mm was subjected to a water pressure of 10 kPa for 30 minutes, a water pressure of 60 kPa for 1 minute, and a water pressure of 60 kPa for 30 minutes, and no water leakage occurred. However, in Comparative Example 2, the biobased content was 0%, and the membrane was poor in environmental load reduction performance.

[0091] [Comparative Example 3] Instead of the polyurethane resin solution, a resin solution having the following formulation was prepared, and the resin solution was applied to a releasable substrate so that the surface density of the resulting waterproof sound-permeable membrane was 7.2 g / m ２ A waterproof sound-permeable membrane, which was a non-porous membrane of cellulose diacetate, was obtained in the same manner as in Example 1. <Formulation> L-50: 15 parts by mass (manufactured by Daicel Corporation, cellulose diacetate, solids content 100% by mass, bio-based content 60%) Methyl ethyl ketone: 85 parts by mass

[0092] The resulting waterproof sound-permeable membrane was measured for its biobased content, tensile strength at 10% elongation, areal density, water swelling, acoustic loss, and waterproofing. The results showed that the biobased content was 60%, the tensile strength at 10% elongation was 814.0 N / m, and the areal density was 7.2 g / m. ２ The waterproof sound-transmitting membrane had a water swelling rate of 1% and an acoustic loss of 16.78 dB at 1 kHz. The waterproof sound-transmitting membrane was circular and had a diameter of 3 mm. When a water pressure of 10 kPa was applied for 30 minutes, a water pressure of 60 kPa was applied for 1 minute, and a water pressure of 60 kPa was applied for 30 minutes, no water leakage occurred. In Comparative Example 3, cellulose diacetate was used instead of polyurethane, and the tensile strength at 10% elongation was high, resulting in large acoustic loss and poor acoustic properties.

[0093] The results of Examples 1 to 8 and Comparative Examples 1 to 3 are summarized in Table 1 below.

[0094] 1...Waterproof sound-transmitting member, 2...Waterproof sound-transmitting membrane, 3...Support layer, 4...Sound-transmitting area, 11...Speaker, 12...Microphone, 13...Microphone jig, 14...Opening, 15...Internal space, 16...Anechoic box

Claims

1. A waterproof sound-permeable membrane that contains polyurethane and has a bio-based content of 20% or more.

2. Surface density is 5 to 40 g / m ２ The waterproof sound-permeable membrane according to claim 1 .

3. The waterproof sound-permeable membrane according to claim 1 or 2, wherein the tensile strength per width at 10% elongation measured in a tensile test is 0.5 to 200 N / m.

4. The waterproof sound-permeable membrane according to any one of claims 1 to 3, having a degree of swelling in water of 3% or less.

5. The waterproof sound-permeable membrane according to any one of claims 1 to 4, which is a non-porous membrane.

6. The waterproof sound-permeable membrane according to any one of claims 1 to 5, having an acoustic loss of 10 dB or less at a frequency of 1 kHz.

7. The waterproof sound-permeable membrane according to any one of claims 1 to 6, which does not leak water when a water pressure of 60 kPa is applied to a circular area with a diameter of 3 mm for 30 minutes.

8. An electrical product comprising a housing having an opening for a sound receiving section or a sound producing section, and the waterproof sound-permeable membrane according to any one of claims 1 to 7 attached to the opening.

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