Polyurethane foam and method for producing polyurethane foam

Abstract

Provided is a polyurethane foam having a surface aperture ratio of at least one of main surfaces facing each other of 0.3% or more and 25% or less, and air permeability measured according to JIS K6400-7: 2012 B of 0.02 to 7.0 cm3 / cm2 / sec.

Description

Polyurethane foam and method for producing polyurethane foam

[0001] The present invention relates to polyurethane foams and methods for producing polyurethane foams.

[0002] Polyurethane foams are used in a wide range of applications, including daily necessities, automotive interior materials, clothing, sports and leisure goods, medical materials, civil engineering and construction materials, etc. Among these application fields, particularly in transportation equipment such as automobiles and buildings such as houses, there is a demand for further noise reduction through the development of sound-proofing materials such as sound-absorbing and sound-insulating materials with improved performance.

[0003] In particular, in the automotive field, where external noise regulations have been applied and are expected to become even stricter in the future, reducing noise in the low- and mid-frequency range (500-1200 Hz), such as noise transmitted through the engine and noise radiated from tires, is an urgent issue, and there is a growing need for sound-absorbing and sound-proofing materials. While it is relatively easy to meet these demands by increasing the thickness of the substrate, there is a concern that a thick substrate may make it difficult to secure sufficient space in vehicles, buildings, etc. Therefore, it is necessary to improve sound-absorbing and sound-proofing performance while also reducing the thickness of the substrate.

[0004] Various efforts have been made to improve this sound absorption and insulation performance. For example, Patent Document 1 discloses a sound-absorbing structure characterized by having sound absorption and / or sound insulation properties due to the micropores, communicating passages, and acoustic holes in the surface layer.

[0005] International Publication No. 2012 / 008225

[0006] However, the sound-absorbing structure of Patent Document 1 does not have sufficient sound-absorbing properties at low frequencies. In the sound-absorbing structure of Embodiment 1, for which measurement results of sound-absorbing properties are shown, the sound absorption coefficient below 2000 Hz is low when the sound-absorbing material is 10 mm thick, and the sound absorption coefficient at 1000 Hz does not even reach 0.2. Furthermore, the surface void area ratio of this structure, based on image measurement using an electron microscope, is said to be 0.1% to 10%.

[0007] Therefore, an object of the present invention is to provide a polyurethane foam and a method for producing a polyurethane foam that exhibits high sound absorption performance over a wide frequency range, particularly in the frequency range of 2000 Hz or less, even when the substrate thickness is thin, and has a low surface open area.

[0008] The present invention provides [1] to [9].

[0009] [1] The surface porosity of at least one of the opposing main surfaces is 0.3% or more and 25% or less (0.5 to 22.0%, 0.5 to 18.0%, 0.5% or more and less than 10%, 0.5 to 9.0%, 0.5 to 8.0%, 1.0 to 22.0%, 1.0 to 18.0%, 1.0% or more and less than 10%, 1.0 to 9.0%, 1.0 to 8.0%, more than 1.0% and 22.0% or less, more than 1.0% and 1.0% or less). 8.0% or less, more than 1.0% but less than 10%, more than 1.0% but less than 9.0%, more than 1.0% but less than 8.0%, 2.0 to 22.0%, 2.0 to 18.0%, 2.0% or more but less than 10%, 2.0 to 9.0%, 2.0 to 8.0%, 4.0 to 22.0%, 4.0 to 18.0%, 4.0% or more but less than 10%, 4.0 to 9.0%, or 4.0 to 8.0%.) and the air permeability measured in accordance with JIS K6400-7:2012 Method B may be 0.02 to 7.0 cm ３ / cm ２ / sec (0.05 to 7.0 cm ３ / cm ２ / sec, 0.05 to 5.0 cm ３ / cm ２ / sec, 0.05-2.5cm ３ / cm ２ / sec, 0.05-1.8cm ３ / cm ２ / sec, 0.2 to 7.0 cm ３ / cm ２ / sec, 0.2 to 5.0 cm ３ / cm ２ / sec, 0.2-2.5cm ３ / cm ２ / sec, 0.2-1.8cm ３ / cm ２ / sec, 0.5-7.0 cm ３ / cm ２ / sec, 0.5-5.0cm ３ / cm２ / sec, 0.5-2.5cm ３ / cm ２ / sec, or 0.5 to 1.8 cm ３ / cm ２ / sec). [2] A method for producing a polyurethane foam by reacting polyurethane foam raw materials inside a mold, wherein the polyurethane foam raw materials are reacted with two or more release agents interposed between the inner surface of the mold and the polyurethane foam raw materials. [3] The method according to [2], wherein the mold is composed of a pair of dies, and two or more release agents are attached to the inner surface of at least one of the dies, and the polyurethane foam raw materials are introduced into the mold to react. [4] The method according to [2] or [3], wherein the two or more release agents include a release agent (I) having a melting peak temperature of 40°C or higher and lower than 70°C, and a release agent (II) having a melting peak temperature of 80°C or higher and 130°C or lower. [5] The method according to [4], wherein at least one of the release agent (I) and the release agent (II) has two or more melting peak temperatures. [6] The method according to [4] or [5], wherein the release agent (I) has two melting peak temperatures, the lower melting peak temperature being 40°C or higher and lower than 70°C, and the release agent (II) has at least one melting peak temperature between the two melting peak temperatures of the release agent (I). [7] The method according to any one of [4] to [6], wherein the mass ratio of the release agent (I) to the total mass of the release agents (I) and (II) is 0.60 or higher and 0.97 or lower. [8] The method according to any one of [4] to [7], wherein the release agent (I) is a release agent that can obtain a surface porosity of 0% or higher and lower than 10% when a polyurethane foam is produced using only the release agent (I) as a release agent, and the release agent (II) is a release agent that can obtain a surface porosity of 10% or higher and 60% or lower when a polyurethane foam is produced using only the release agent (II) as a release agent. [9] The manufacturing method according to any one of [2] to [8], wherein the polyurethane foam raw material contains a polyol component (A), a polyisocyanate component (B), a catalyst (C), a foam stabilizer (D), and a blowing agent (E).

[0010] According to the present invention, there are provided a polyurethane foam and a method for producing a polyurethane foam, which exhibits high sound absorption performance over a wide frequency range, particularly in the frequency range of 2000 Hz or less, even when the substrate thickness is thin, and has a low surface open area.

[0011] Incidentally, paragraph

[0016] of Patent Document 1 refers to "sound absorption (sound insulation)" and does not measure sound insulation properties. Therefore, in this document, sound absorption and sound insulation are used synonymously. However, sound absorption is generally interpreted as sound absorption to reduce sound reflection, and sound insulation as sound reflection to prevent sound leakage. As can be seen from this mechanism, it is difficult to improve sound absorption properties when the surface porosity is low. However, according to the manufacturing method of the present invention, it is possible to obtain a polyurethane foam that exhibits high sound absorption performance over a wide frequency range, particularly in the frequency range of 2000 Hz or less, despite its low surface porosity. Because a low surface porosity contributes to sound insulation, the manufacturing method of the present invention not only improves sound absorption properties over a wide frequency range, but also contributes to excellent sound insulation.

[0012] The polyurethane foam according to this embodiment has a surface porosity of 0.3% or more and 25% or less on at least one of the opposing main surfaces, and an air permeability of 0.02 to 7.0 cm as measured in accordance with JIS K6400-7:2012 B method. ３ / cm ２ The surface porosity and air permeability can be measured by the method described in the Examples.

[0013] The above-mentioned polyurethane foam exhibits high sound absorption performance over a wide frequency range, particularly in the frequency range of 2000 Hz or less, without significantly impairing sound insulation properties, even when the substrate thickness is thin. However, when the surface porosity is low, it is generally difficult to improve sound absorption properties.

[0014] The surface porosity may be 0.5% or more, 1.0% or more, more than 1.0%, 2.0% or more, 4.0% or more, 22.0% or less, 18.0% or less, less than 10%, 9.0% or less, or 8.0% or less, and may be 0.5 to 22.0%, 0.5 to 18.0%, 0.5% or more but less than 10%, 0.5 to 9.0%, 0.5 to 8.0%, 1.0 to 22.0%, 1.0 to 18.0%, 1.0% or more but less than 10%, 1.0 to 9.0 %, 1.0 to 8.0%, more than 1.0% but less than 22.0%, more than 1.0% but less than 18.0%, more than 1.0% but less than 10%, more than 1.0% but less than 9.0%, more than 1.0% but less than 8.0%, 2.0 to 22.0%, 2.0 to 18.0%, 2.0% or more but less than 10%, 2.0 to 9.0%, 2.0 to 8.0%, 4.0 to 22.0%, 4.0 to 18.0%, 4.0% or more but less than 10%, 4.0 to 9.0%, or 4.0 to 8.0%. The surface porosity is more preferably 0.5% or more but less than 22.0%, even more preferably 1.0% or more but less than 18.0%, even more preferably more than 1.0% but less than 10%, and particularly preferably 2.0% or more but less than 9.0%, or 4.0% or more but less than 8.0%.

[0015] The air permeability is 0.05 cm ３ / cm ２ / sec or more, 0.2cm ３ / cm ２ / sec or more, or 0.5 cm ３ / cm ２ / sec or more, and ３ / cm ２ / sec or less, 5.0cm ３ / cm ２ / sec or less, 2.5cm ３ / cm ２ / sec or less, or 1.8 cm ３ / cm ２ / sec or less, and 0.05 to 7.0 cm ３ / cm ２ / sec, 0.05 to 5.0 cm ３ / cm ２ / sec, 0.05-2.5cm ３ / cm ２ / sec, 0.05-1.8cm ３ / cm ２ / sec, 0.2 to 7.0 cm ３ / cm ２ / sec, 0.2 to 5.0 cm ３ / cm ２ / sec, 0.2-2.5cm ３ / cm ２ / sec, 0.2-1.8cm ３ / cm ２ / sec, 0.5-7.0 cm ３ / cm ２ / sec, 0.5-5.0cm ３ / cm ２ / sec, 0.5-2.5cm ３ / cm ２ / sec, or 0.5 to 1.8 cm ３ / cm ２ The air permeability may be 0.05 to 7.0 cm ３ / cm ２ / sec is more preferable, and 0.2 to 5.0 cm ３ / cm ２ / sec is more preferable, and 0.5 to 2.5 cm ３ / cm ２ / sec, and more preferably 0.5 to 1.8 cm ３ / cm ２ It is particularly preferable that the time is / sec.

[0016] The air permeability is measured in the foaming direction of the polyurethane foam. Here, the foaming direction refers to the direction in which the thickness of the polyurethane foam raw material increases when it foams in a mold. Since the foam (cells) formed usually have a shape that extends in the thickness direction (e.g., a spindle shape), the foaming direction can be determined from the shape. When a polyurethane foam is molded into a plate shape in a mold, the foaming direction is usually the thickness direction.

[0017] The method for producing a polyurethane foam according to the embodiment involves reacting polyurethane foam raw materials inside a mold (casting mold), with two or more release agents interposed between the inner surface of the mold and the polyurethane foam raw materials.

[0018] The polyurethane foam produced may be a flexible polyurethane foam, a semi-rigid polyurethane foam, or a rigid polyurethane foam.

[0019] The flexible polyurethane foam refers to a reversibly deformable foam that has an open cell structure and exhibits high breathability (see, for example, Gunter Oertel, "Polyurethane Handbook" (1985 edition), Hanser Publishers (Germany), pp. 161-233, and Keiji Iwata, "Polyurethane Resin Handbook" (1987 first edition), Nikkan Kogyo Shimbun, Ltd., pp. 150-221).

[0020] The physical properties of flexible polyurethane foams are difficult to specify because they vary depending on the chemical structures of polyols, isocyanates, etc. used in their production, chemical factors such as the amount of foaming agent blended, isocyanate index, and cell structure, but generally, the density (which can be measured as apparent density; the same applies below) is 10 to 100 kg / m ３ (JIS K 6401), compressive strength (ILD25%) of 2 to 80 kgf (20 to 800 N) (JIS K 6401), and elongation of 80 to 500% (JIS K 6301) [see, for example, Gunter Oertel, "Polyurethane Handbook" (1985 edition), Hanser Publishers (Germany), pp. 184-191 and 212-218; Keiji Iwata, "Polyurethane Resin Handbook" (1987 first edition), Nikkan Kogyo Shimbun, pp. 160-166 and 186-191].

[0021] Semi-rigid polyurethane foams are reversibly deformable foams that have a higher foam density and compressive strength than flexible polyurethane foams, but have an open cell structure similar to flexible polyurethane foams, exhibit high breathability, and are generally classified as flexible polyurethane foams because the raw materials used in their production, such as polyols and isocyanates, are similar to those used in flexible polyurethane foams [see, for example, Gunter Oertel, "Polyurethane Handbook" (1985 edition), Hanser Publishers (Germany), pp. 223-233, and Keiji Iwata, "Polyurethane Resin Handbook" (1987 first edition), Nikkan Kogyo Shimbun, pp. 211-221]. The physical properties of semi-rigid polyurethane foams are not particularly limited, but generally have a density of 40 to 800 kg / m ３ , 25% compressive strength is 0.1 to 2 kgf / cm ２ (9.8 to 200 kPa), and the elongation is in the range of 40 to 200%.

[0022] Rigid polyurethane foams have a highly crosslinked closed-cell structure, are non-reversibly deformable, and have properties completely different from those of flexible and semi-rigid polyurethane foams (see, for example, Gunter Oertel, "Polyurethane Handbook" (1985 edition), Hanser Publishers (Germany), pp. 234-313, and Keiji Iwata, "Polyurethane Resin Handbook" (1987 first edition), Nikkan Kogyo Shimbun, pp. 224-283). The properties of rigid foams are not particularly limited, but generally, they have a density of 20 to 100 kg / m. ３ , compression strength 0.5 to 10 kgf / cm ２ (50 to 1000 kPa).

[0023] The mold used to produce polyurethane foam may have a cavity for containing polyurethane foam raw materials and be made of a material that can withstand the pressure and heat generated by the reaction. The mold preferably has a temperature controllable, and is preferably one that can be heated while containing the polyurethane foam raw materials to promote the reaction. The reaction of the polyurethane foam raw materials promotes urethanization and foaming.

[0024] The shape of the polyurethane foam to be produced is determined by the internal shape of the mold (the shape of the void). Therefore, the internal shape of the mold can be designed to form the desired shape. For example, if you want to produce a plate-shaped polyurethane foam, you can configure the mold from a pair of molds so that when the pair of molds are combined, a rectangular void is created.

[0025] When reacting the polyurethane foam raw material, two or more release agents are interposed between the inner surface (inner wall) of the mold and the polyurethane foam raw material. Examples of interposing methods include attaching two or more release agents to the inner surface of the mold (by coating, spraying, etc.) before introducing the polyurethane foam raw material into the mold. When the mold consists of a pair of molds, it is preferable to attach two or more release agents to the inner surface of at least one of the molds, introduce the polyurethane foam raw material into the mold, and react the polyurethane foam raw material. If the release agent contains a volatile component such as an organic solvent or water as well as a release component (wax component), it is preferable to volatilize these components before introducing the polyurethane foam raw material into the mold.

[0026] The production method according to the embodiment is characterized by reacting the polyurethane foam raw materials in the presence of two or more release agents, and the term "two or more" includes a combination of two or more release agents of different chemical species, and a combination of two or more release agents of the same chemical species but exhibiting different thermal behaviors (e.g., different peak melting temperatures). In other words, the polyurethane foam raw materials can be reacted in the presence of two or more release agents of different chemical species and / or different peak melting temperatures.

[0027] The number of release agents to be combined can be 2 to 5, 2 to 4, or 2 to 3. In order to avoid complicating the release agent composition, the polyurethane foam raw material can be reacted with the release agent 2 present.

[0028] The melting peak temperature of the release agent refers to the melting peak temperature according to JIS K 7121:1987. That is, a differential scanning calorimetry (DSC) curve is measured, and the temperature at the apex of the melting peak is defined as the melting peak temperature (Tpm). The DSC curve can be measured after conditioning as described in the above JIS. Specifically, for example, a test piece is placed in the container of a DSC apparatus, heated to a temperature about 30°C higher than the end of the melting peak, melted, and maintained at that temperature for 10 minutes, and then cooled at a cooling rate of 5°C per minute or 10°C per minute to a temperature at least about 50°C lower than the transition peak that appears, thereby performing conditioning. Then, immediately after conditioning, the apparatus is stabilized and heated at a heating rate of 10°C per minute to a temperature about 30°C higher than the end of the melting peak, thereby drawing a DSC curve. The temperature at the apex of the melting peak from this DSC curve is identified as the melting peak temperature. If multiple peaks are observed, it is considered that there are multiple melting peak temperatures. When there are multiple melting peak temperatures, they are called the first melting peak temperature, the second melting peak temperature, etc. in order from the lowest temperature.

[0029] The two or more release agents may include a release agent (I) having a peak melting temperature of 40° C. or higher and lower than 70° C. and a release agent (II) having a peak melting temperature of 80° C. or higher and 130° C. At least one of the release agents (I) and (II) may have two or more peak melting temperatures. When the release agent has two or more peak melting temperatures, the first peak melting temperature (the lowest melting peak temperature) is used to determine whether the temperature is 40° C. or higher and lower than 70° C. or 80° C. or higher and 130° C. or lower.

[0030] The release agent (I) may have two melting peak temperatures (a first melting peak temperature and a second melting peak temperature), with the lower melting peak temperature (the first melting peak temperature) being 40° C. or higher and lower than 70° C. The release agent (II) may have at least one melting peak temperature between the first melting peak temperature and the second melting peak temperature of the release agent (I). For example, this corresponds to a case where the release agent (I) has a first melting peak temperature of 50° C. and a second melting peak temperature of 90° C., and the release agent (II) has a melting peak temperature (the first melting peak temperature) of 85° C.

[0031] In the above case, the melting peak temperature of the release agent (I) may be 40° C. or higher and 65° C. or lower, or 40° C. or higher and 60° C. or lower. The melting peak temperature of the release agent (II) may be 80° C. or higher and 120° C. or lower, or 80° C. or higher and 110° C. or lower.

[0032] Release agents typically use paraffin wax, Fischer-Tropsch wax, Sasol wax microcrystalline wax, modified polyethylene wax, or the like as the main component, and are used by dissolving the wax in an organic solvent or dispersing it in water using an emulsifier and applying the resulting solution to a mold. There are a great many release agents available on the market, including the waxes mentioned above, and the melting peak temperatures vary depending on the chemical species, chemical structure, and the like. Therefore, the melting peak temperature can be measured according to the above-mentioned measurement method, and a release agent corresponding to release agent (I) or release agent (II) can be selected. The total application amount of release agent (I) and release agent (II) is 0.3 to 15 g / m in terms of solid content. ２ , or 0.5 to 10 g / m ２ In the present disclosure, the solid content of the application amount of the release agent is the mass (g) of the release agent to be applied minus the mass of the organic solvent and water, multiplied by the application area (m ２ ) is the value obtained by dividing the

[0033] The mass ratio of the release agent (I) to the total mass of the release agent (I) and the release agent (II) can be 0.60 or more and 0.97 or less. This mass ratio is preferably 0.80 or more and 0.97 or less, more preferably 0.80 or more and 0.96 or less, even more preferably 0.81 or more and 0.96 or less, still more preferably 0.85 or more and 0.95 or less, and particularly preferably 0.88 or more and 0.92 or less.

[0034] It is preferred that the release agent (I) is a release agent that can provide a surface porosity of 0% or more and less than 10% when a polyurethane foam is produced using only the release agent (I), and that the release agent (II) is a release agent that can provide a surface porosity of 10% or more and 60% or less when a polyurethane foam is produced using only the release agent (II).

[0035] Here, with regard to the release agent (I), it is not necessary that all polyurethane foam raw materials be capable of producing polyurethane foams having a surface porosity of 0% or more and less than 10%, as long as there is at least one polyurethane foam raw material that can obtain such a surface porosity. Similarly, with regard to the release agent (II), it is not necessary that all polyurethane foam raw materials be capable of producing polyurethane foams having a surface porosity of 10% or more and 60% or less, as long as there is at least one polyurethane foam raw material that can obtain such a surface porosity.

[0036] The polyurethane foam raw material composition for determining the surface porosity of 0% or more and less than 10% or 10% or more and 60% or less preferably contains the isocyanate component, polyol component, catalyst, foam stabilizer, and blowing agent described in Example 1. The mass ratios can also be determined as described in Example 1.

[0037] The polyurethane foam raw material to be reacted inside the mold may contain a polyol component (A), a polyisocyanate component (B), a catalyst (C), a foam stabilizer (D), and a blowing agent (E). The polyurethane foam raw material may contain fillers such as calcium carbonate and barium sulfate, as well as additives and auxiliaries such as flame retardants, plasticizers, colorants, and antifungal agents.

[0038] The polyol component (A) is polyadded with the polyisocyanate component (B) to form a polyurethane, and is preferably at least one selected from the group consisting of polyether polyols and polyester polyols. Furthermore, the number average molecular weight is preferably 1,000 to 10,000, more preferably 3,000 to 8,000, and most preferably 4,000 to 8,000. Furthermore, those with a nominal functionality of 2 or more are more preferred.

[0039] If the number average molecular weight is below the lower limit, the flexibility of the resulting foam tends to be insufficient, while if it exceeds the upper limit, the hardness of the foam tends to decrease. Furthermore, if the nominal functionality is less than 2, the foam's rebound resilience significantly decreases, resulting in problems such as the foam not being able to return to its original shape when compressed. The nominal functionality refers to the theoretical average functionality (the number of active hydrogen atoms per molecule) assuming that no side reactions occur during the polyol polymerization reaction.

[0040] Examples of polyether polyols that can be used include polyoxyethylene polyols, polyoxypropylene polyols, polyoxyethylene polyoxypropylene polyols, and polytetramethylene ether glycols. Examples of polyester polyols that can be used include polyester polyols made from adipic acid and diols, which are polycondensation-type polyester polyols, and polycaprolactone polyols, which are lactone-based polyester polyols.

[0041] From the viewpoint of improving the heat resistance of the foam, at least one polyol selected from the group consisting of castor oil and castor oil-modified polyols can be used in combination in the polyol component (A). Examples of the at least one polyol selected from the group consisting of castor oil and castor oil-modified polyols include castor oil derivatives such as refined castor oil, semi-refined castor oil, unrefined castor oil, and hydrogenated castor oil.

[0042] Furthermore, the polyol component (A) may contain a polyether polyol having a polyoxyalkylene chain composed of a copolymer of oxyethylene and oxypropylene for the purpose of promoting interconnection of the polyurethane foam. The number average molecular weight is preferably 3,000 to 8,000, and the nominal functionality is preferably 2 to 4. Furthermore, the content of oxyethylene units in the polyether polyol is preferably 60 to 90 mass%, more preferably 60 to 80 mass%.

[0043] By adjusting the oxyethylene unit content to 60 to 90% by mass, the durability of the foam can be improved. From the viewpoint of storage stability at low temperatures, the copolymer composed of oxyethylene and oxypropylene is preferably a random copolymer.

[0044] For the purpose of adjusting hardness, the polyol component (A) may be used in combination with a polymer polyol obtained by polymerizing a vinyl monomer in a polyol by a conventional method. Examples of such polymer polyols include those obtained by polymerizing a vinyl monomer in a polyalkylene polyol in the presence of a radical initiator and stably dispersing the polymer.

[0045] Examples of vinyl monomers include acrylonitrile, styrene, vinylidene chloride, hydroxyalkyl methacrylate, and alkyl methacrylate, with acrylonitrile and styrene being preferred. Examples of such polymer polyols include FA-728R, KC-900, and FS-7301 manufactured by Sanyo Chemical Industries, Ltd.

[0046] For the polyisocyanate component (B), diphenylmethane diisocyanates (hereinafter, MDI), such as 4,4'-diphenylmethane diisocyanate (hereinafter, 4,4'-MDI), 2,4'-diphenylmethane diisocyanate (hereinafter, 2,4'-MDI), and 2,2'-diphenylmethane diisocyanate (hereinafter, 2,2'-MDI), or polyphenylene polymethylene polyisocyanate (hereinafter, P-MDI) are preferably used as the isocyanate source. In the present invention, various modifications such as the above-mentioned MDI, mixtures of MDI and P-MDI, urethane-modified products, urea-modified products, allophanate-modified products, nurate-modified products, and biuret-modified products may also be used.

[0047] The MDI content of the polyisocyanate component (B) is preferably in the range of 50 to 85% by mass. If the MDI content exceeds 85% by mass, the storage stability at low temperatures of the resulting polyisocyanate composition and the durability of the resulting foam may be reduced, while if it is less than 50% by mass, the crosslink density increases, resulting in reduced elongation of the polyurethane foam, making it difficult to obtain sufficient foam strength.

[0048] Furthermore, the sum of the content of 2,2'-MDI and the content of 2,4'-MDI relative to the total amount of MDI (hereinafter referred to as isomer content) is preferably 10 to 50% by mass.

[0049] If the content of 2,2'-MDI and 2,4'-MDI relative to the total amount of MDI is less than 10% by mass, the storage stability of the resulting polyisocyanate composition at low temperatures may be impaired, and constant heating of the isocyanate storage location, piping, and foam molding machine may be required. Furthermore, the molding stability of the polyurethane foam may be impaired, and foam collapse may occur during foaming. On the other hand, if the content exceeds 50% by mass, reactivity may decrease, leading to problems such as an extension of the molding cycle and a high closed cell ratio of the foam, which may cause shrinkage after molding.

[0050] As the catalyst (C), various urethanization catalysts can be used, such as triethylamine, tripropylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine, dimethylbenzylamine, N,N,N',N'-tetramethylhexamethylenediamine, N,N,N',N',N''-pentamethyldiethylenetriamine, bis-(2-dimethylaminoethyl)ether, triethylenediamine, 1,8-diaza-bicyclo[5.4.0]undecene-7, 1,2-dimethylimidazole, dimethylethanolamine, N,N-dimethyl-N-hexanolamine, and organic acid salts thereof, as well as organometallic compounds such as stannous octoate and zinc naphthenate. Also preferred are amine catalysts having active hydrogen, such as N,N-dimethylethanolamine and N,N-diethylethanolamine.

[0051] The amount of catalyst added is preferably 0.01 to 10% by mass relative to the polyol component (A). If the amount is less than the lower limit, insufficient curing is likely to occur, and if the amount is more than the upper limit, moldability may deteriorate.

[0052] As the foam stabilizer (D), a conventional surfactant is used, and a silicone surfactant is preferably used. Examples include SZ-1327, SZ-1325, SZ-1336, and SZ-3601 manufactured by Dow-Toray Industries, Y-10366J and L-5309J manufactured by Momentive Corporation, and B-8724LF2 and B-8715LF2 manufactured by Evonik. The amount of these foam stabilizers added is preferably 0.1 to 3.0% by mass based on the polyol component (A).

[0053] The blowing agent (E) may be primarily water or may consist solely of water. Water reacts with isocyanate groups to form high-hardness urea groups and generate carbon dioxide gas, which can cause foaming. Any blowing agent may be used in addition to water. For example, a small amount of a low-boiling organic compound such as cyclopentane or isopentane may be used in combination, or air, nitrogen gas, or liquefied carbon dioxide may be mixed and dissolved in the raw solution using a gas loading device to cause foaming.

[0054] The amount of foaming agent (E) added is usually 0.5 to 10% by mass based on the polyol component (A). ３ When a low-density polyurethane foam having the above formula is to be obtained, the content is preferably 4.0 to 7.0 mass %, and more preferably 4.0 to 6.5 mass %. If the content exceeds the upper limit, foaming may become unstable, whereas if the content is below the lower limit, the density of the foam may not be sufficiently reduced.

[0055] The NCO INDEX (the molar ratio of NCO to active hydrogen multiplied by 100) during mixing and foaming of all isocyanate groups in the polyisocyanate component (B) with all active hydrogen groups in the polyol component (A) and the blowing agent (E) is preferably 70 to 140, and more preferably 70 to 120 as a favorable range for the molding cycle.

[0056] If the NCO INDEX is less than 70, the closed cell properties of the foam will be excessively high, whereas if it is more than 120, unreacted isocyanate will remain for a long time, which may result in an extension of the molding cycle or a delay in the formation of a high molecular weight, which may result in foam collapse during foaming.

[0057] In the production of polyurethane foam, the mold temperature when the polyurethane foam raw material is poured into the mold is usually 30 to 80° C., preferably 45 to 70° C. If the mold temperature when the foaming solution is poured into the mold is less than 30° C., the reaction rate may decrease, leading to an extension of the production cycle. On the other hand, if the mold temperature is higher than 80° C., the reaction between water and isocyanate may be excessively promoted relative to the reaction between polyol and isocyanate, which may cause the foam to collapse during foaming.

[0058] The curing time for foaming and curing the polyurethane foam raw material is preferably 15 minutes or less, more preferably 10 minutes or less, taking into consideration the production cycle of a typical molded foam. After foaming and curing the polyurethane foam raw material, the cured raw material is removed from the mold to obtain a molded polyurethane foam.

[0059] When producing a polyurethane foam, the polyurethane foam raw materials can be mixed using a high-pressure foaming machine or a low-pressure foaming machine, as in the case of a normal molded foam.

[0060] The polyol component (A) and the polyisocyanate component (B) are preferably mixed immediately before foaming. Other components can be premixed with the polyol component (A) or the polyisocyanate component (B) to the extent that they do not affect the storage stability of the raw materials or the change in reactivity over time. The mixture can be used immediately after mixing, or stored and then used in the required amount. In the case of a foaming device capable of simultaneously introducing more than two components into the mixing section, the polyol, blowing agent, polyisocyanate, catalyst, foam stabilizer, etc. can also be introduced into the mixing section separately.

[0061] The mixing method may be either dynamic mixing, in which mixing is performed in the machine head mixing chamber of the foaming device, or static mixing, in which mixing is performed in a liquid delivery pipe, or a combination of both. Static mixing is often used to mix a gaseous component such as a physical foaming agent with a liquid component, while dynamic mixing is often used to mix components that can be stably stored as liquids. The foaming device is preferably a high-pressure foaming device that does not require solvent cleaning of the mixing section.

[0062] After the polyurethane foam is demolded, the cell membranes of the polyurethane foam may be destroyed under compression or reduced pressure by a known method. Destroying the cell membranes can increase the air permeability of the polyurethane foam.

[0063] The polyurethane foam obtained by the above-described production method exhibits high sound absorption performance over a wide frequency range, particularly in the frequency range of 2000 Hz or less, without significantly impairing the sound insulation properties, even when the substrate thickness is thin. However, when the surface open area ratio is low, it is generally difficult to improve the sound absorption properties.

[0064] Here, a substrate thickness (thickness of polyurethane foam) of 10 mm can be considered sufficiently thin, and a surface porosity of 25% (preferably 20%, and even more preferably 18%) or less and 0% or more can be considered low. Polyurethane foam with a low surface porosity has excellent sound insulation properties. Furthermore, if the average sound absorption coefficient between 500 and 2000 Hz is 0.35 or more, it can be said to exhibit high sound absorption performance in the frequency range of 2000 Hz or less. The polyurethane foam obtained by the manufacturing method according to this embodiment, when made 10 mm thick, exhibits an average sound absorption coefficient between 500 and 2000 Hz of 0.35 or more, even if the surface porosity is 25% or less. Therefore, it can be used in a variety of applications as a sound absorbing material or sound insulating material. The sound absorption characteristics and surface porosity can be measured by the methods described in the examples.

[0065] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, "parts" and "%" in the text are based on mass.

[0066] (Examples 1 to 4, Comparative Examples 1 to 6) [Preparation of Polyol Composition] A reactor equipped with a stirrer, a cooling tube, a nitrogen inlet tube, and a thermometer was purged with nitrogen, and then 60 g of polyol 1, 40 g of polyol 2, 1.0 g of polyol 3, 0.7 g of catalyst 1, 0.1 g of catalyst 2, 1.0 g of foam stabilizer 1, and 2.0 g of water were charged and stirred at 23°C for 0.5 hours to obtain polyol composition (P-1).

[0067] [Preparation of release agents] After replacing the air in a plastic container that can be sealed with a lid, 7.76 g of release agent A and 0.24 g of release agent B were charged and the container was sealed. The mixture was stirred for 0.5 hours at 23°C using a mixing roller to obtain release agent 4. In the same manner, release agent 5 was obtained using 7.2 g of release agent A and 0.8 g of release agent B, release agent 6 was obtained using 6.4 g of release agent A and 1.6 g of release agent B, and release agent 7 was obtained using 4.8 g of release agent A and 3.2 g of release agent B.

[0068] [Molding conditions] The liquid temperatures of the isocyanate composition and the mixture of all raw materials other than the isocyanate composition (polyol composition) were adjusted to 24°C to 26°C. A predetermined amount of the polyisocyanate component was added to the polyol composition and mixed for 7 seconds with a mixer (7,000 rpm), and then the mixture was poured into a mold coated with a release agent to foam a polyurethane foam. In the examples and comparative examples, the types of release agents used were those shown in Tables 1 and 2. Mold temperature: 50 to 65°C Mold shape (rectangular): 200 mm x 200 mm x 10 mm Mold material: aluminum Cure time: 10 minutes

[0069] After the polyurethane foam was cured, it was demolded to obtain a molded polyurethane foam. Note that the polyurethane foam of Comparative Example 5 could not be demolded, and no molded polyurethane foam could be obtained.

[0070] For the polyurethane foam molded article of Comparative Example 4, the obtained polyurethane foam molded article was compressed to destroy the cell membranes, thereby adjusting the air permeability.

[0071] [Raw materials used] Polyol 1: Polyoxyethylene polyoxypropylene polyol having an average functionality of 3.0 and a hydroxyl value of 33 (mgKOH / g), manufactured by AGC under the trade name of EXCENOL 823 Polyol 2: Refined castor oil having an average functionality of 2.7 and a hydroxyl value of 160 (mgKOH / g) (manufactured by Ito Oil Mills, Ltd. under the trade name of URIC H-24) Polyol 3: Polyoxyethylene polyoxypropylene polyol having an average functionality of 4.0 and a hydroxyl value of 28 (mgKOH / g), in which the oxyethylene units in the polyether polyol are 80% by mass, manufactured by Tosoh Corporation under the trade name of NEF-024 Catalyst 1: 33% dipropylene glycol solution of triethylenediamine (manufactured by Tosoh Corporation, trade name: TEDA L-33) Catalyst 2: 70% dipropylene glycol solution of bis(2-dimethylaminoethyl)ether (manufactured by Tosoh Corporation, trade name: TOYOCAT ET) Foam stabilizer 1: Silicone-based foam stabilizer (manufactured by Momentive, trade name: L-5309J) Isocyanate 1: Polyphenylene polymethylene polyisocyanate having an MDI content of 70% by mass and an isomer content of 17.7% by mass (manufactured by Tosoh Corporation, trade name: CEF-538) Mold release agent 1: Branched-chain wax-based mold release agent, first melting peak 50.4°C, second melting peak 91.4°C, product name: M975, manufactured by Chukyo Yushi Co., Ltd. Mold release agent 2: Linear wax-based mold release agent, first melting peak 87.8°C, second melting peak 99.5°C, product name: T-626, manufactured by Chukyo Yushi Co., Ltd. Mold release agent 3: Branched chain wax-based release agent, first melting peak 80.4°C, second melting peak 118.7°C, product name: FRX-C8, manufactured by Neos Corporation. Release agent 4: Release agent 1 and release agent 2 mixed in a weight ratio of 97:3. Release agent 5: Release agent 1 and release agent 2 mixed in a weight ratio of 90:10. Release agent 6: Release agent 1 and release agent 2 mixed in a weight ratio of 80:20. Release agent 7: Release agent 1 and release agent 2 mixed in a weight ratio of 60:40.

[0072] [Apparent Density] The apparent density of the polyurethane foam molded product was determined by the method described in JIS K 6400-1:2004.

[0073] [Thickness of Urethane Foam] The thickness of the polyurethane foam molded article was measured using a vernier caliper (Digital Caliper BDC200 manufactured by AS ONE Corporation).

[0074] [C Hardness] The thickness of the polyurethane foam molded article was measured using a rubber hardness tester (Asker C type) described in JIS K7312:1996.

[0075] [F Hardness] The F hardness of the polyurethane foam molded product was measured using an Asker rubber hardness tester, model F.

[0076] [Air Permeability] The air permeability of the polyurethane foam molded product was measured by the method described in JIS K6400-7:2012 Method B.

[0077] [Average Cell Diameter] The average cell diameter of each polyurethane foam molded product was determined by cutting out a 10 mm thick polyurethane foam molded product into a disk shape with a diameter of 28.8 mm, taking an image of the side of the foam with a field of view of 10 mm vertically and 16.3 mm horizontally using a microscope equipped with a lens MTL5518C-034-01 manufactured by Moritex Corporation, measuring the cell diameters of a predetermined number of cells present in the field of view, and then simply averaging the cell diameters.

[0078] [Surface Open Area Ratio] The surface open area ratio of each polyurethane foam molded product was determined by cutting a 10 mm thick polyurethane foam molded product into a disk shape with a diameter of 28.8 mm, taking an image of the surface that had been in contact with the upper part of the mold during molding using a microscope equipped with a Moritex Corporation telecentric lens MM014-HR110-5M, binarizing the image using software "ImageJ" to separate the open areas from the other surface layer areas, calculating the sum of the areas of the open areas, and then calculating the surface open area ratio based on the following formula: Surface open area ratio = (sum of the areas of the open areas / sample area) × 100 (formula).

[0079] [Sound absorption coefficient] The normal incident sound absorption coefficient in the range of 500 to 6,300 Hz was measured using a 4206 type acoustic tube manufactured by Hottinger Brüel & Kjær Japan, based on the method described in JIS A 1405-2: 2007. The sound absorption coefficient was measured using a polyurethane foam molded article having a diameter of 28.8 mm and a thickness of 10 mm, placed with the lower molding surface of the mold facing the sound source, with no air layer behind the polyurethane foam molded article.

[0080] [Moldability] The moldability of each urethane foam molded product was evaluated according to the following evaluation criteria. In Comparative Example 5, the polyurethane foam molded product could not be demolded. <Evaluation criteria> A: There is no significant difference between the shape of the polyurethane foam molded product and the shape of the inner surface of the mold, and no deformation, tearing, or damage occurs when demolded. B: There is a significant difference between the shape of the polyurethane foam molded product and the shape of the inner surface of the mold, or deformation, tearing, or damage occurs when demolded.

[0081]

[0082]

[0083] As shown in Examples 1, 2, 3, and 4 in Table 1, the surface porosity can be adjusted by changing the mixing ratio of the two release agents.

Claims

1. A polyurethane foam having a surface opening ratio of at least one of the main surfaces facing each other of 0.3% or more and 25% or less, and an air permeability measured according to JIS K6400-7:2012 Method B of 0.02 to 7.0 cm ３ / cm ２ / sec.

2. A method for manufacturing a polyurethane foam by reacting a polyurethane foam raw material inside a mold, the method comprising reacting the polyurethane foam raw material in a state where two or more mold release agents are interposed between the inner surface of the mold and the polyurethane foam raw material.

3. The mold is composed of a pair of molds, and two or more of the mold release agents are attached to at least one inner surface of the mold, the polyurethane foam raw material is introduced into the mold, and the polyurethane foam raw material is reacted. The manufacturing method according to claim 2.

4. The two or more mold release agents include a mold release agent (I) having a melting peak temperature of 40°C or higher and less than 70°C, and a mold release agent (II) having a melting peak temperature of 80°C or higher and 130°C or lower. The manufacturing method according to claim 2 or 3.

5. At least one of the mold release agent (I) and the mold release agent (II) has two or more melting peak temperatures. The manufacturing method according to claim 4.

6. The mold release agent (I) has two melting peak temperatures, the melting peak temperature on the low temperature side is 40°C or higher and less than 70°C, and the mold release agent (II) has at least one melting peak temperature between the two melting peak temperatures of the mold release agent (I). The manufacturing method according to claim 4 or 5.

7. The mass ratio of the mold release agent (I) to the total mass of the mold release agent (I) and the mold release agent (II) is 0.60 or higher and 0.97 or lower. The manufacturing method according to any one of claims 4 to 6.

8. The mold release agent (I) is a mold release agent that can obtain a surface open cell ratio of 0% or higher and less than 10% when manufacturing a polyurethane foam using only the mold release agent (I) as the mold release agent, and the mold release agent (II) is a mold release agent that can obtain a surface open cell ratio of 10% or higher and 60% or lower when manufacturing a polyurethane foam using only the mold release agent (II) as the mold release agent. The manufacturing method according to any one of claims 4 to 7.

9. The polyurethane foam raw material contains a polyol component (A), a polyisocyanate component (B), a catalyst (C), a foam stabilizer (D), and a blowing agent (E). The manufacturing method according to any one of claims 2 to 8.

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