Polyurethane foam, sound absorbing material, and sound absorbing structure

Abstract

To provide a polyurethane foam exhibiting superior sound absorption in a high-frequency region while maintaining sufficient strength.SOLUTION: A polyurethane foam 10 having a first surface 10A with an average surface cell diameter of 200 μm or more, and a second surface 10B positioned opposite to the first surface 10A and having an average surface cell diameter of less than 200 μm, wherein the foam has a compression strength of 80 kPa or more as measured in accordance with JIS K7220:2006.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to polyurethane foams, sound absorbing materials, and sound absorbing structures. [Background technology]

[0002] Patent Document 1 discloses a flexible polyurethane foam that has excellent sound absorption properties in the high frequency range (for example, 5000 Hz). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-178207 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the flexible polyurethane foam of Patent Document 1 does not have sufficient strength and cannot be used in areas where strength is required. An object of the present disclosure is to provide a polyurethane foam that has excellent sound absorption properties in the high frequency range and also has sufficient strength. The present disclosure can be realized in the following forms. [Means for solving the problem]

[0005] a first surface having a surface average cell diameter of 200 μm or more; a second surface located opposite the first surface and having a surface average cell diameter of less than 200 μm; A polyurethane foam having a compressive strength of 80 kPa or more measured in accordance with JIS K7220:2006. [Effects of the Invention]

[0006] According to the present disclosure, a polyurethane foam having excellent sound absorption properties in the high frequency range and sufficient strength can be provided. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing a cross section of a polyurethane foam. [Figure 2] 10 is a graph showing sound absorption coefficients with the first surface as the reference surface. [Figure 3] 10 is a graph showing the sound absorption coefficient with the second surface as the reference surface. DETAILED DESCRIPTION OF THE INVENTION

[0008] Here, a preferred example of the present disclosure will be described. [1] A first surface having a surface average cell diameter of 200 μm or more; a second surface located opposite the first surface and having a surface average cell diameter of less than 200 μm; A polyurethane foam having a compressive strength of 80 kPa or more measured in accordance with JIS K7220:2006. [2] The polyurethane foam described in [1] has a sound absorption coefficient of 0.8 or more measured in accordance with JIS A1405-2:2007 at a test specimen thickness of 15 mm and a frequency of 5000 Hz, with the first surface as the reference surface. [3] A sound-absorbing material comprising the polyurethane foam described in [1] or [2]. [4] A sound-absorbing structure in which the first surface of the sound-absorbing material described in [3] is arranged facing the sound source.

[0009] The present disclosure will be described in detail below. In this specification, when a numerical range is indicated using "-", it is intended to include both the lower limit and the upper limit unless otherwise specified. For example, the expression "10-20" includes both the lower limit "10" and the upper limit "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less".

[0010] 1. Polyurethane foam 10 The polyurethane foam 10 has a first surface 10A having a surface average cell diameter of 200 μm or more and a second surface 10B located on the opposite side of the first surface 10A and having a surface average cell diameter of less than 200 μm. The polyurethane foam 10 has a compressive strength of 80 kPa or more as measured in accordance with JIS K7220:2006.

[0011] (1) Requirements for surface average cell diameter As shown in Fig. 1, polyurethane foam 10 has a first surface 10A having a surface average cell diameter of 200 µm or more and a second surface 10B located on the opposite side of first surface 10A and having a surface average cell diameter of less than 200 µm. Note that Fig. 1 is drawn schematically to facilitate understanding of the present disclosure and may not be an accurate representation.

[0012] The surface average cell diameter of the first surface 10A is 200 μm or more, preferably 210 μm or more, and may be 220 μm or more, 240 μm or more, or 250 μm or more. There is no particular upper limit to the surface average cell diameter of the first surface 10A, and it is usually 1000 μm or less. The surface average cell diameter of second surface 10B is less than 200 μm, preferably 180 μm or less, more preferably 160 μm or less, and may be 140 μm or less, or 125 μm or less. There is no particular lower limit to the surface average cell diameter of second surface 10B, and it may be 0 μm, i.e., non-porous, and is preferably 50 μm or more, more preferably 100 μm or more.

[0013] The surface average cell diameter is a value measured as follows. Specifically, the surface of polyurethane foam 10 is observed using a laser microscope (for example, Keyence Corporation's "Shape Measuring Laser Microscope VK-8700"). The observation area is a rectangular area of ​​2500 μm × 2000 μm. Within the observation area, 10 cells are selected in descending order of diameter, and the diameter of the largest inscribed circle inscribed in the cell skeleton of each cell is measured. The average value of the diameters of the measured inscribed circles is taken as the surface average cell diameter.

[0014] The polyurethane foam 10 may have, for example, a first surface 10A formed by a core 11 and a second surface 10B formed by a skin layer 12. The skin layer 12 is a layer formed on the surface of the polyurethane foam 10 during molding. The skin layer 12 can be identified as a layer having a higher density than the center of the polyurethane foam 10. The core 11 can be identified as a portion of the polyurethane foam 10 located inside the skin layer 12. The first surface 10A is, for example, the surface on which the core 11 is exposed. The second surface 10B is, for example, the surface of the skin layer 12. With this configuration, the above-mentioned requirement regarding the surface average cell diameter can be suitably achieved.

[0015] The present disclosure is not limited to an embodiment in which the first surface 10A is constituted by the core 11 and the second surface 10B is constituted by the skin layer 12. As long as the above requirement for the surface average cell diameter is satisfied, for example, both the first surface and the second surface may be constituted by the core.

[0016] From the viewpoint of improving sound absorption, the core 11 preferably has an open-cell structure. The skin layer 12 may be a skin layer having an open structure or a skin layer having a non-open structure. From the viewpoint of improving sound absorption, the skin layer 12 is preferably a skin layer having an open structure. A skin layer having an open structure can be suitably formed by using the polyether polyol (a) described below.

[0017] For example, when the skin layer 12 is cut at a position 10 mm from the surface and a test piece for measuring the air permeability of the skin layer is taken, the air permeability should be as follows: When the core 11 is cut at a position 10 mm further (20 mm from the surface) and a test piece for measuring the air permeability of the core portion is taken, the air permeability should be as follows: The air permeability of the test piece for measuring the air permeability of the skin layer measured in accordance with JIS L1096A is preferably 0.01 cm 3 / cm 2 / s or more 60cm 3 / cm 2 / s or less, and more preferably 5cm 3 / cm2 / s or more 50cm 3 / cm 2 / s or less, and more preferably 10 cm 3 / cm 2 / s or more 40cm 3 / cm 2 / s or less, and particularly preferably 15 cm 3 / cm 2 / s or more 30cm 3 / cm 2 / s or less. The air permeability of the test piece for measuring the air permeability of the core portion measured in accordance with JIS L1096A is usually greater than the air permeability of the test piece for measuring the air permeability of the skin layer, and is preferably 30 cm 3 / cm 2 / s, more preferably 40 cm 3 / cm 2 / s, and more preferably 50 cm 3 / cm 2 / s, and particularly preferably 60 cm 3 / cm 2 The upper limit of the air permeability of the test piece for measuring the air permeability of the core portion is not particularly limited, and is, for example, 300 cm 3 / cm 2 / s or less.

[0018] The closed cell ratio of the skin layer 12 as defined in accordance with ASTM D6226-21 is preferably 20% or less, 15% or less, or may be 10% or less, or 5% or less. The closed cell ratio of the skin layer 12 may be 0% or more, 0.5% or more, or 1% or more.

[0019] The thickness of the skin layer 12 is not particularly limited. The thickness of the skin layer 12 is preferably 5 μm or more, and more preferably 10 μm or more. The upper limit of the thickness of the skin layer 12 is usually 2 mm (2000 μm) or less, and may be 1 mm (1000 μm) or less. The thickness of the skin layer 12 can be measured by cutting the polyurethane foam 10 along a plane perpendicular to the surface and observing the cut surface under a microscope.

[0020] (2) Composition for producing polyurethane foam The polyurethane foam 10 of this embodiment can be suitably obtained from a composition (a polyurethane foam-producing composition) containing a polyol and a polyisocyanate. The composition may optionally contain at least one component selected from a blowing agent, a catalyst, and a foam stabilizer. Each component of the composition will now be described.

[0021] (2.1) Polyol The polyol is not particularly limited. From the viewpoint of improving sound absorption, the polyol preferably contains a polyether polyol (a) having a number average molecular weight of 2000 or more and an ethylene oxide unit content of 25 mass% or more. The polyether polyol (a) may be used alone or in combination of two or more. From the viewpoint of ensuring various physical properties, the polyol also preferably contains a polyether polyol (b) having a number average molecular weight of 2000 or more and an ethylene oxide unit content of less than 25 mass %. The polyether polyol (b) may be used alone or in combination of two or more. From the viewpoint of ensuring compressive strength, the polyol also preferably contains a polyether polyol (c) having a number average molecular weight of less than 2000, a functional group number of 3 or more, and an ethylene oxide unit content of less than 25 mass %. The polyether polyol (c) may be used alone or in combination of two or more.

[0022] In the polyol of the present disclosure, the content of ethylene oxide units is expressed as the content of ethylene oxide units when the total amount of alkylene oxide units is taken as 100% by mass. Examples of alkylene oxide units other than ethylene oxide units include propylene oxide units and butylene oxide units. "The content of ethylene oxide units is less than 25% by mass" may mean that the content of ethylene oxide units is 0% by mass. In the present disclosure, the number average molecular weight of the polyol can be measured by gel permeation chromatography (GPC).

[0023] Examples of polyether polyol (a) include polyether polyols obtained by adding one or more of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, epichlorohydrin, styrene oxide, etc. to one or more of the following initiators (compounds):

[0024] (2.1.1) Initiator (2.1.1.1) Polyhydric alcohols and alkylene oxide adducts of polyhydric alcohols Examples of polyhydric alcohols: [Difunctional alcohols] Ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, trimethylene glycol [Trifunctional alcohol] Glycerin, trimethylolpropane [Tetrafunctional alcohol] Pentaerythritol [Hexafunctional alcohol] Sorbitol [Octafunctional alcohol] Sucrose (2.1.1.2) Alkylene oxide adducts of polyhydric phenols Examples of alkylene oxide adducts of polyhydric phenols: alkylene oxide adducts of bisphenol A (2.1.1.3) Polyhydroxy compounds Examples of polyhydroxy compounds: phosphoric acid, benzene phosphoric acid, polyphosphoric acid (e.g., tripolyphosphoric acid and tetrapolyphosphoric acid), etc. (2.1.1.4) Phenol-aniline-formaldehyde ternary condensation products (2.1.1.5) Aniline-formaldehyde condensation products (2.1.1.6) Polyamines Examples of polyamines: ethylenediamine, diethylenetriamine, triethylenetetramine, methylenebisorthochloroaniline, 4,4- and 2,4'-diphenylmethanediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, etc. (2.1.1.7) Alkanolamines Examples of alkanolamines: triethanolamine, diethanolamine, etc.

[0025] The polyether polyol (a) is preferably an adduct of ethylene oxide and propylene oxide, and more preferably a random copolymer of propylene oxide and ethylene oxide.

[0026] From the viewpoint of improving sound absorption properties, the content of ethylene oxide units in the polyether polyol (a) is preferably 25% by mass or more, more preferably 28% by mass or more, and may be 100% by mass or less, 80% by mass or less, 60% by mass or less, or 50% by mass or less.

[0027] The number average molecular weight of the polyether polyol (a) is not particularly limited and is preferably 2,000 or more and 20,000 or less, more preferably 2,500 or more and 15,000 or less, and even more preferably 3,000 or more and 10,000 or less.

[0028] The number of functional groups of the polyether polyol (a) is preferably 4 or less, more preferably 3.5 or less, and even more preferably 3 or less. The number of functional groups of the polyether polyol (a) is usually 2 or more, and preferably 2.5 or more.

[0029] The content of polyether polyol (a), when the total polyol is taken as 100 parts by mass, is 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 18 parts by mass or more, and even more preferably 20 parts by mass or more, from the viewpoint of sound absorption. From the viewpoint of moldability, the content of polyether polyol (a) is 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less. From these viewpoints, the content of polyether polyol (a) is 10 parts by mass or more and 50 parts by mass or less, preferably 15 parts by mass or more and 40 parts by mass or less, more preferably 18 parts by mass or more and 35 parts by mass or less, and even more preferably 20 parts by mass or more and 30 parts by mass or less.

[0030] Examples of the polyether polyol (b) include polyether polyols obtained by adding one or more of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, epichlorohydrin, styrene oxide, etc. to one or more of the above-mentioned initiators (compounds). The polyether polyol (b) is preferably an adduct of ethylene oxide and propylene oxide, and more preferably a propylene oxide-ethylene oxide copolymer obtained by addition polymerization of propylene oxide and further addition polymerization of ethylene oxide.

[0031] The content of ethylene oxide units in polyether polyol (b) is not particularly limited. For example, the content of ethylene oxide units in polyether polyol (b) is preferably more than 0% by mass, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The upper limit of the content of ethylene oxide units in polyether polyol (b) is not particularly limited, and may be less than 25% by mass, for example, 23% by mass or less, or 20% by mass or less.

[0032] The number average molecular weight of the polyether polyol (b) is not particularly limited and is preferably 2,000 or more and 20,000 or less, more preferably 2,500 or more and 15,000 or less, and even more preferably 3,000 or more and 10,000 or less.

[0033] The number of functional groups of the polyether polyol (b) is preferably 4 or less, more preferably 3.5 or less, and even more preferably 3 or less. The number of functional groups of the polyether polyol (b) is usually 2 or more, and preferably 2.5 or more.

[0034] From the viewpoint of ensuring various physical properties, the content of polyether polyol (b) is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, based on 100 parts by mass of the total polyol. From the viewpoint of ensuring sound absorption properties by sufficiently blending the polyether polyol (a), the content of the polyether polyol (b) is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less. From these viewpoints, the content of polyether polyol (b) is preferably 15 parts by mass or more and 70 parts by mass or less, more preferably 20 parts by mass or more and 60 parts by mass or less, and even more preferably 25 parts by mass or more and 55 parts by mass or less.

[0035] Examples of the polyether polyol (c) include polyether polyols obtained by adding one or more of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, epichlorohydrin, styrene oxide, etc. to one or more of the above-mentioned initiators (compounds). From the viewpoint of ensuring the average number of functional groups in the entire polyol, the polyether polyol (c) preferably contains a polyether polyol using a pentafunctional or higher initiator, and preferably contains a polyether polyol using sucrose.

[0036] The content of ethylene oxide units in the polyether polyol (c) is not particularly limited as long as it is less than 25% by mass, and the content of ethylene oxide units in the polyether polyol (c) may be 0% by mass.

[0037] The number average molecular weight of the polyether polyol (c) is not particularly limited. The number average molecular weight of the polyether polyol (c) is preferably less than 2000, more preferably 1500 or less, even more preferably 1000 or less, and particularly preferably 800 or less. The lower limit of the number average molecular weight of the polyether polyol (c) is not particularly limited, and may be 300 or more, 400 or more, or 500 or more.

[0038] The number of functional groups of the polyether polyol (c) is preferably 3 or more, more preferably 3.5 or more, and may be 4 or more, 4.5 or more, or 5 or more. The number of functional groups of the polyether polyol (c) is usually 8 or less, and may be, for example, 7 or less, or 6 or less.

[0039] The content of polyether polyol (c), when the total polyol is taken as 100 parts by mass, is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, and may even be 30 parts by mass or more, from the viewpoint of ensuring compressive strength. The content of polyether polyol (c) is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less, from the viewpoint of ensuring sound absorption by sufficiently blending the polyether polyol (a). From these viewpoints, the content of polyether polyol (c) is preferably 20 parts by mass or more and 50 parts by mass or less, more preferably 25 parts by mass or more and 45 parts by mass or less.

[0040] The polyol may contain other polyols as long as the effects of the invention are not impaired. Examples of other polyols include polyhydric alcohols such as glycerin, ethylene glycol, propylene glycol, butanediol, butylene glycol, glycerin, and trimethylolpropane. The other polyols may be used alone or in combination of two or more.

[0041] (2.2) Foaming Agent The composition may contain a blowing agent. The blowing agent is not particularly limited. Examples of blowing agents include water, hydrohaloolefins such as hydrofluoroolefins (HFO), alkylene chlorides such as methylene chloride and ethylene chloride, and alkanes having 4 to 8 carbon atoms such as isopentane. Among these, water is preferred from the viewpoint of suitably forming interconnected cells in the skin layer and improving sound absorption properties. These may be used alone or in combination of two or more. The content of the blowing agent is not particularly limited. From the viewpoint of ensuring sound absorption properties and various physical properties, the content of the blowing agent is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 3 parts by mass or more and 8 parts by mass or less, per 100 parts by mass of the polyol.

[0042] (2.3) Catalyst The composition may contain a catalyst. The catalyst is not particularly limited. Various catalysts may be used alone or in combination of two or more. Examples of the catalyst include foaming catalysts, resinification catalysts, catalysts capable of promoting both foaming and resinification (balanced catalysts), and trimerization catalysts that promote the trimerization reaction of isocyanate groups.

[0043] Examples of foaming catalysts include tertiary amines such as bis(2-dimethylaminoethyl) ether or organic acid salts thereof, morpholine compounds, and piperazine compounds, and one or more of these can be used. Examples of the resinification catalyst include tertiary amines such as dimethylaminohexanol or organic acid salts thereof, and organic metals, and one or more of these can be used. The balance catalyst includes aliphatic amines such as methyldicyclohexylamine, and one or more of these can be used. Examples of trimerization catalysts include tertiary amines such as 1,3,5-tris(dimethylaminopropyl)hexahydro-s-triazine, quaternary ammonium salts such as triethylmethylammonium 2-ethylhexanoate, metal oxides, alkoxides, organometallic salts, and nitrogen-containing heterocyclic compounds, and one or more of these can be used. Commercially available catalysts may be used, such as Lupragen N206 (foaming catalyst), Lupragen N301 (foaming catalyst), Lupragen N107 (foaming catalyst), Kaolizer No. 25 (resinization catalyst), Polycat 12 (balance catalyst), Polycat 55 (balance catalyst), Lupragen N600 (trimerization catalyst), Ucat 18X (trimerization catalyst), TOYOCAT TR20 (trimerization catalyst), and TOYOCAT TRX (trimerization catalyst). The catalyst content is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 10 parts by mass, in total, relative to 100 parts by mass of polyol.

[0044] (2.4) Foam stabilizer The composition may contain a foam stabilizer. The foam stabilizer is not particularly limited. Examples of the foam stabilizer include silicone-based foam stabilizers and fluorine-containing compound-based foam stabilizers. Examples of the silicone-based foam stabilizer include polyether-modified silicones such as copolymers of dimethylpolysiloxane and polyether. The foam stabilizers may be used alone or in combination of two or more.

[0045] The foam stabilizer preferably comprises one or more selected from "foam stabilizers for flexible polyurethane foams" and "foam stabilizers for HR (High Resilience) molded foams." "Foam stabilizers for flexible polyurethane foams" and "foam stabilizers for HR molded foams" have superior cell opening (cell breaking) properties compared to "foam stabilizers for rigid polyurethane foams." For this reason, it is presumed that when used in combination with the above-mentioned polyol (a), openings such as interconnected cells are formed in the skin layer of the polyurethane foam 10, contributing to improved sound absorption. From the perspective of improving sound absorption in the high-frequency range (e.g., frequencies of 2000 Hz or higher), it is more preferable to use a combination of one or more "foam stabilizers for flexible polyurethane foams" and one or more "foam stabilizers for HR molded foams." Examples of "foam stabilizers for flexible polyurethane foams" include polyether-modified silicones modified with polyethers containing propylene oxide units, and polyether-modified silicones in which the terminals of modified polyethers are capped with alkoxy groups, etc. Commercially available "foam stabilizers for flexible polyurethane foams" include VORASURF SF1280A and VORASURF SZ1136 manufactured by Toray Dow Corning Co., Ltd., and Niax Silicone L895, Niax Silicone L858, Niax Silicone L838, and Niax Silicone L3636LF manufactured by Momentive Corporation. Polyether-modified silicones with relatively small molecular weights are widely used as "foam stabilizers for HR molded foams." The kinematic viscosity (based on JIS Z8803:2011) of the "foam stabilizer for HR molded foams" used in the polyurethane foam of the present disclosure is preferably 1000 mm 2 / s (25°C) or less, and more preferably 500 mm 2 / s (25°C) or less, and more preferably 300 mm 2 / s (25℃) or less. The kinematic viscosity of the above "Foam stabilizer for HR molded foam" is usually 10mm 2 / s (25°C) or more. Examples of commercially available "foam stabilizers for HR molded foam" include VORASURF SF2962A, SF2965, SF2973, SF2961, SRX253, TF1348, and TF1365 manufactured by Dow Corning Toray Co., Ltd.

[0046] The content of the foam stabilizer is preferably 0.1 parts by mass or more and 10 parts by mass or less, more preferably 0.5 parts by mass or more and 8 parts by mass or less, relative to 100 parts by mass of the polyol. When a "foam stabilizer for flexible polyurethane foams" and a "foam stabilizer for HR molded foams" are used in combination, the "foam stabilizer for flexible polyurethane foams":"foam stabilizer for HR molded foams" (mass ratio) is not particularly limited. From the viewpoints of sound absorption properties and compressive strength, the "foam stabilizer for flexible polyurethane foams":"foam stabilizer for HR molded foams" ratio is preferably 20:80-40:60 (mass ratio), and more preferably 25:75-35:65 (mass ratio).

[0047] (2.5) Isocyanates The isocyanate is not particularly limited. Examples of isocyanates that can be used include aromatic isocyanates, aliphatic isocyanates, mixtures thereof, and modified polyisocyanates obtained by modifying these. Examples of aromatic isocyanates include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, xylylene diisocyanate, and polymeric MDI. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexamethane diisocyanate. Other prepolymers can also be used.

[0048] As the isocyanate, polymeric MDI is preferred. Polymeric MDI is polyphenylene polymethylene polyisocyanate, and is, for example, a mixture of dinuclear MDI and trinuclear or higher polynuclear MDI. Polymeric MDI may be untreated crude MDI obtained by an MDI synthesis reaction, or may be MDI whose composition has been adjusted by separating a desired amount of monomeric MDI from the crude MDI by vacuum distillation or the like.

[0049] From the viewpoint of moldability, the isocyanate index (INDEX) is preferably 80 to 140, and more preferably 90 to 120. The isocyanate index is the value obtained by dividing the number of moles of isocyanate groups in the isocyanate by the total number of moles of active hydrogen groups such as hydroxyl groups in the polyol and water as a blowing agent, and multiplying the result by 100, and is calculated as [NCO equivalent of isocyanate / active hydrogen equivalent × 100].

[0050] (2.6) Other ingredients The composition may contain other components in addition to the above components, such as known additives, such as flame retardants, plasticizers, colorants, antioxidants, ultraviolet absorbers, antibacterial agents, tackifiers, and compatibilizers. Examples of the flame retardant include phosphate ester compounds such as tris(chloropropyl)phosphate, triethylphosphate, and tricresylphosphate, phosphorus compounds such as red phosphorus and ammonium polyphosphate, melamine compounds, metal hydrates, and antimony compounds. The amount of the flame retardant is preferably 1 part by mass or more and 20 parts by mass or less, and more preferably 5 parts by mass or more and 15 parts by mass or less, per 100 parts by mass of the polyol.

[0051] 2. Manufacturing method of polyurethane foam 10 For example, a prepolymer method, a one-shot method, or the like is used to manufacture the polyurethane foam 10. The prepolymer method is a method in which a polyol and an isocyanate are reacted in advance to obtain a urethane prepolymer having an isocyanate group or a hydroxyl group at its terminal, and the urethane prepolymer is used to obtain the polyurethane foam 10. The one-shot method is a method in which a polyol, an isocyanate, and the like are charged all at once and reacted.

[0052] A known molding method in which molding is performed inside a mold can be applied to produce the polyurethane foam 10. Specifically, the composition (foaming liquid) is poured into a closed mold, a urethane reaction is carried out, and after hardening, the polyurethane foam 10 is obtained by demolding.

[0053] The first surface 10A of the polyurethane foam 10 can be formed by cutting the core of the polyurethane foam 10. That is, the first surface 10A can be formed as a cut surface of the core 11. The second surface 10B can be formed by applying the surface of the skin layer 12 as is. In this way, the polyurethane foam 10 can be produced.

[0054] 3. Physical properties of polyurethane foam 10 From the viewpoint of compressive strength, the polyurethane foam 10 is preferably a rigid polyurethane foam or a semi-rigid polyurethane foam.

[0055] The polyurethane foam 10 has a compressive strength measured in accordance with JIS K7220:2006 of 80 kPa or more, preferably 85 kPa or more, and may be 90 kPa or more, 100 kPa or more, or 110 kPa or more. The upper limit of the compressive strength is not particularly limited and may be, for example, 200 kPa or less, 180 kPa or less, or 150 kPa or less. The compressive strength of the polyurethane foam 10 was measured using a test piece measuring 50 mm×50 mm×30 mm thick cut out from the core of the polyurethane foam 10 . The compressive strength of the polyurethane foam 10 can be controlled by, for example, changing the type and blending ratio of the polyol.

[0056] The apparent overall density of polyurethane foam 10 (based on JIS K7222:2005) is 30 kg / m 3 More than 40 kg / m is preferable. 3 More preferably, 45 kg / m 3 The upper limit of the apparent overall density of the polyurethane foam 10 is not particularly limited, and is, for example, 500 kg / m 3 From the viewpoint of sound absorption and weight reduction, the 3 Below 200kg / m 3 Below 100kg / m 3 Below 80kg / m 3 Below 65kg / m 3 The following may also be used.

[0057] The polyurethane foam 10 preferably has a sound absorption coefficient of 0.8 or more, measured in accordance with JIS A1405-2:2007, using a test specimen 15 mm thick at a frequency of 5000 Hz with the first surface 10A as the reference surface. The sound absorption coefficient is preferably 0.85 or more, and may be 0.9 or more. The polyurethane foam 10 may have a sound absorption coefficient of less than 0.8 measured in accordance with JIS A1405-2:2007 at a test specimen thickness of 15 mm, a frequency of 5000 Hz, and with the second surface 10B as the reference surface.

[0058] The polyurethane foam 10 of this embodiment can ensure sufficient sound absorption in the high frequency range (e.g., a frequency of 5000 Hz) when the first surface 10A is used as the reference surface. When the second surface 10B, which has a surface average cell diameter of less than 200 μm, is used as the reference surface, there is a tendency for the foam to have excellent sound absorption in the frequency range lower than 5000 Hz (e.g., frequencies of 1000 Hz to 4000 Hz). In this embodiment, since the surface average cell diameter of the first surface 10A is 200 μm or more, it is possible that the sound absorption performance of the high frequency range sound that penetrates through the first surface 10A can be sufficiently improved. Note that the technology of the present disclosure should not be limited by this speculation.

[0059] There are no particular limitations on the article in which the polyurethane foam 10 is used. The polyurethane foam 10 has excellent sound absorption properties in the high frequency range and sufficient strength, making it suitable for use as a vehicle component, such as a ceiling substrate, an interior material such as an instrument panel, a sound-absorbing material disposed around a vehicle power unit, or a sound-absorbing material disposed around a vehicle's undercarriage.

[0060] 4. Sound-absorbing materials and structures The technology of the present disclosure is suitable for a sound-absorbing material including polyurethane foam 10. The shape and thickness of the sound-absorbing material are not particularly limited. The shape and thickness of the sound-absorbing material can be appropriately set depending on the installation location. The sound-absorbing material may be, for example, in the form of a plate. The thickness of the sound-absorbing material can be, for example, 2 mm or more and 200 mm or less.

[0061] From the viewpoint of sound absorption in the high frequency range, the technology of the present disclosure is suitable for a sound absorbing structure in which a first surface 10A of a sound absorbing material is arranged facing the sound source, as shown in Fig. 1. In Fig. 1, a sound source (not shown) is located on the upper side of the page.

[0062] The sound source is not particularly limited. For example, the sound source may be one or more selected from the group consisting of a motor, an engine, a transmission, a fan, electrical equipment, and a pantograph. In addition, the sound-absorbing material is also useful for absorbing road noise, wind noise, and other sounds generated when a vehicle is traveling. The technology of the present disclosure is particularly useful in electric vehicles, hybrid vehicles, and fuel cell vehicles, which require measures to reduce noise in the high-frequency range. [Example]

[0063] Next, the above embodiment will be described in more detail with reference to examples. 1. Polyurethane foam manufacturing First, the raw material components of the compositions used for the polyurethane foams of the respective examples are shown below. Polyol (b): Propylene oxide-ethylene oxide copolymer (GL3000, manufactured by Sanyo Chemical Industries, Ltd.) having a hydroxyl value of 56 mg KOH / g, a number average molecular weight of 3,000, and a functionality of 3, and an ethylene oxide unit content of 20% by mass Polyol (a): Polyol having a hydroxyl value of 42 mg KOH / g, a number average molecular weight of 3600, and a functionality of 2.7 (manufactured by BASF, Lupranol 2048 / 2), and an ethylene oxide unit content of 30% by mass Polyol (c1): Polyether polyol (VP9346, manufactured by BASF) having a hydroxyl value of 450 mgKOH / g, a number average molecular weight of 650, and a functionality of 5.2, and having an ethylene oxide unit content of 0 mass%, which corresponds to the polyether polyol (c) described in the embodiment. Polyol (c2): Polyether polyol having a hydroxyl value of 400 mgKOH / g, a number average molecular weight of 561, and a functionality of 3.95 (manufactured by AGC, Excenol 410NE), an ethylene oxide unit content of 0 mass%, and corresponds to the polyether polyol (c) described in the embodiment. Polyol (d): Polyol having a hydroxyl value of 1810 mg KOH / g, a number average molecular weight of 124, and a functionality of 2 (ethylene glycol, manufactured by Ogami Chemical Co., Ltd.), with an ethylene oxide unit content of 100% by mass Flame retardant: tris(1-chloro-2-propyl) phosphate (TCPP, manufactured by Daihachi Chemical Co., Ltd.) Foam stabilizer 1: Foam stabilizer for flexible polyurethane foam, manufactured by Toray Dow Corning Co., Ltd., VORASURF SF1280A Foam stabilizer 2: Foam stabilizer for HR molded foam, manufactured by Toray Dow Corning Co., Ltd., VORASURF SF2962A Catalyst 1: bis(2-dimethylaminoethyl) ether, BASF Lupragen N206 (foaming catalyst) Catalyst 2: 1,3,5-tris(dimethylaminopropyl)hexahydro-s-triazine, BASF Lupragen N600 (trimerization catalyst) Catalyst 3: Dimethylaminohexanol, Kao Corporation Kaolizer No. 25 (resinification catalyst) Foaming agent: Water Isocyanate: Polymeric MDI, NCO% 31.0% (BASF, product number LUPRANATE M-20S)

[0064] The polyurethane foams of the respective examples were obtained by mixing the above components in the blending ratios shown in Table 1 below. In Table 1, blank cells indicate that the blending ratio of that component was 0 parts by mass.

[0065] The obtained polyurethane foam was sliced ​​to a thickness of 15 mm from the surface where the skin layer was formed. The cut surface of the polyurethane foam was designated as the first surface, and the surface of the skin layer was designated as the second surface.

[0066] [Table 1]

[0067] 2. Evaluation of polyurethane foam [density] In accordance with JIS K7222:2005, the apparent overall density (kg / m 3 The results are shown in Table 1. [Sound absorption performance] A cylindrical sample with a diameter of 29 mm was taken from the cut polyurethane foam and used as a test piece for measuring sound absorption coefficient. In accordance with JIS A1405-2:2007, the sound absorption coefficient of the test piece with a thickness of 15 mm was measured over the frequency range of 0 Hz to 6000 Hz. Measurements were made on the sound absorption coefficient with the first surface as the reference surface and the sound absorption coefficient with the second surface as the reference surface. Examples 1 to 3 in Fig. 2 are graphs showing the sound absorption coefficient with the first surface as the reference surface. Reference Examples 1 to 3 in Fig. 3 correspond to the polyurethane foams of Examples 1 to 3, respectively. Reference Examples 1 to 3 are graphs showing the sound absorption coefficient with the second surface as the reference surface. In Figs. 2 and 3, the horizontal axis represents frequency (Hz) and the vertical axis represents sound absorption coefficient. [Compression strength] In accordance with JIS K7220:2006, the maximum force (maximum load, N) reached within 10% of the deformation rate of the polyurethane foam was measured, and the compressive strength (kPa) was calculated. The maximum load of the polyurethane foam was measured using a 50 mm x 50 mm x 30 mm thick test piece cut from the core of each polyurethane foam. The results are shown in Table 1.

[0068] [Air permeability] For the polyurethane foam of Example 1, test pieces for measuring the air permeability of the skin layer and test pieces for measuring the air permeability of the core were taken using the method described in the embodiment, and the air permeability was measured in accordance with JIS L1096A. The results are as follows. Air permeability of test specimen for measuring skin layer air permeability: 25.0 cm 3 / cm 2 / s Core air permeability test piece: 76.6 cm 3 / cm 2 / s

[0069] [Skin layer closed cell ratio] The closed cell ratio of the skin layer of the polyurethane foam of Example 1 was calculated in accordance with ASTM D6226-21, and the results are as follows: Closed cell ratio of skin layer: 1.63%

[0070] 3.Results Examples 1 to 3 satisfy the following requirements ac. Requirement a: The first surface has an average surface cell diameter of 200 μm or more. Requirement b: The second surface is located opposite the first surface and has a surface average cell diameter of less than 200 μm. Requirement c: The compressive strength measured in accordance with JIS K7220:2006 is 80 kPa or more.

[0071] In Examples 1 to 3, the sound absorption coefficient measured at a frequency of 5000 Hz using the first surface as the reference surface was 0.8 or more. By satisfying the above requirement ac, it was found that the material had excellent sound absorption properties in the high frequency range and sufficient strength.

[0072] In Reference Examples 1 to 3, the sound absorption coefficient measured at a frequency of 5000 Hz using the second surface as the reference surface was less than 0.8. This result shows that by arranging the first surface facing the sound source, sound absorption in the high frequency range can be suitably ensured.

[0073] 4. Effects of the Example The polyurethane foams of the above examples had excellent sound absorption properties in the high frequency range and also had sufficient strength.

[0074] The present disclosure is not limited to the above-described embodiments, and various modifications and variations are possible within the scope of the claims of the present disclosure. [Explanation of symbols]

[0075] 10...Polyurethane foam 10A…First side 10B…Second side 11...Core 12...skin layer

Claims

1. a first surface having a surface average cell diameter of 200 μm or more; a second surface located opposite the first surface and having a surface average cell diameter of less than 200 μm; A polyurethane foam having a compressive strength of 80 kPa or more as measured in accordance with JIS K7220:2006.

2. 2. The polyurethane foam according to claim 1, wherein the sound absorption coefficient measured in accordance with JIS A1405-2:2007, with a test specimen having a thickness of 15 mm and a frequency of 5000 Hz, using the first surface as a reference surface, is 0.8 or more.

3. A sound-absorbing material comprising the polyurethane foam according to claim 1 or 2.

4. A sound absorbing structure in which the sound absorbing material according to claim 3 is disposed with the first surface facing a sound source.

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