Polyurethane foam, and method for producing polyurethane foam

Abstract

A polyurethane foam, at least one of the surface porosities of the main surfaces opposite to each other is 0.3% or more and 25% or less, and the air permeability measured in accordance with JIS K6400-7:2012 B method is 0.02 to 7.0 cm 3 / cm 2 / sec.

Description

Technical Field

[0001] This invention relates to polyurethane foam and a method for manufacturing polyurethane foam. Background Technology

[0002] Polyurethane foam is widely used in household goods, automotive interior materials, clothing, sports and leisure products, medical materials, and civil engineering materials. In these applications, especially in transportation machinery such as automobiles or buildings such as residences, there is a demand for high-performance noise reduction materials such as sound-absorbing and sound-insulating materials to further reduce noise.

[0003] Especially in the automotive industry, with increasingly stringent regulations on exterior noise levels, reducing low- and mid-frequency sounds (500–1200 Hz), such as engine noise and tire-radiated noise, is a pressing issue, leading to increased demand for sound-absorbing and sound-insulating materials. While increasing the thickness of the substrate can relatively easily improve noise reduction and vibration absorption, it may not guarantee sufficient space in transportation machinery or buildings. Therefore, it is necessary to reduce the thickness of the substrate while improving sound absorption and insulation performance.

[0004] Various efforts have been made in the past to improve the sound absorption and sound insulation performance. For example, Patent Document 1 discloses a sound-absorbing structure characterized by having sound absorption and / or sound insulation properties through micropores on the surface, as well as connecting paths and acoustic cavities.

[0005] Existing technical documents Patent documents Patent Document 1: International Publication No. 2012 / 008225 However, the low-frequency sound absorption characteristics of the sound-absorbing structure in Patent Document 1 cannot be considered sufficient. In the sound-absorbing structure of Embodiment 1, which shows the measurement results of the sound absorption characteristics, the sound absorption coefficient is low below 2000 Hz when the thickness of the sound-absorbing material is 10 mm, and the sound absorption coefficient does not reach 0.2 at 1000 Hz. It should be noted that the surface void area ratio of this structure, measured based on electron microscope images, is 0.1% to 10%. Summary of the Invention

[0006] The problem that the invention aims to solve Therefore, the object of the present invention is to provide a polyurethane foam and a method for manufacturing polyurethane foam, wherein the polyurethane foam exhibits high sound absorption performance over a wide frequency range, particularly below 2000 Hz, even when the substrate thickness is thin, and has a low surface porosity.

[0007] Technical solutions for solving the problem This invention provides [1] to [9].

[0008] [1] A polyurethane foam, wherein at least one of its opposing main surfaces has a surface open-cell ratio of 0.3% or more and 25% or less (which may be 0.5-22.0%, 0.5-18.0%, 0.5% or more and less than 10%, 0.5-9.0%, 0.5-8.0%, 1.0-22.0%, 1.0-18.0%, 1.0% or more and less than 10%, 1.0-9.0%, 1.0-8.0%, or greater than 1.0% and less than 22.0%). The air permeability is defined as follows: greater than 1.0% and less than 18.0%, greater than 1.0% and less than 10%, greater than 1.0% and less than 9.0%, greater than 1.0% and less than 8.0%, 2.0–22.0%, 2.0–18.0%, greater than 2.0% and less than 10%, 2.0–9.0%, 2.0–8.0%, 4.0–22.0%, 4.0–18.0%, greater than 4.0% and less than 10%, 4.0–9.0%, or 4.0–8.0%), and the air permeability measured according to JIS K6400-7:2012 Method B is 0.02–7.0 cm. 3 / cm 2 / sec (can be 0.05~7.0cm) 3 / cm 2 / sec, 0.05~5.0cm 3 / cm 2 / sec, 0.05~2.5cm 3 / cm 2 / sec, 0.05~1.8cm 3 / cm 2 / sec, 0.2~7.0cm 3 / cm 2 / sec, 0.2~5.0cm 3 / cm 2 / sec, 0.2~2.5cm 3 / cm 2 / sec, 0.2~1.8cm 3 / cm 2 / sec, 0.5~7.0cm 3 / cm 2 / sec, 0.5~5.0cm 3 / cm 2 / sec, 0.5~2.5cm 3 / cm 2 / sec or 0.5~1.8cm 3 / cm 2 / sec).

[0009] [2] A method for manufacturing polyurethane foam, wherein the polyurethane foam raw material is reacted inside a mold, and the polyurethane foam raw material is reacted while two or more release agents are sandwiched between the inner surface of the mold and the polyurethane foam raw material.

[0010] [3] According to the manufacturing method described in [2], the mold is composed of a pair of molds, and two or more of the above-mentioned release agents are attached to at least one inner surface of the mold, and the polyurethane foam raw material is introduced into the interior of the mold to react the polyurethane foam raw material.

[0011] [4] According to the manufacturing method described in [2] or [3], wherein the two or more of the above-mentioned release agents include: release agent (I) having a melting peak temperature (melting peak temperature, dissolution peak temperature) of 40°C or higher and less than 70°C; and release agent (II) having a melting peak temperature of 80°C or higher and less than 130°C.

[0012] [5] According to the manufacturing method described in [4], at least one of the above-mentioned release agent (I) and the above-mentioned release agent (II) has two or more melting peak temperatures.

[0013] [6] According to the manufacturing method described in [4] or [5], the release agent (I) has two melting peak temperatures, the melting peak temperature of the low-temperature side is above 40°C and less 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).

[0014] [7] The manufacturing 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 agent (I) and the release agent (II) is 0.60 or more and 0.97 or less.

[0015] [8] The manufacturing method according to any one of [4] to [7], wherein the above-mentioned release agent (I) is a release agent that can obtain a surface open rate of 0% or more and less than 10% when using only the above-mentioned release agent (I) as a release agent to manufacture polyurethane foam, and the above-mentioned release agent (II) is a release agent that can obtain a surface open rate of 10% or more and less than 60% when using only the above-mentioned release agent (II) as a release agent to manufacture polyurethane foam.

[0016] [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 foaming agent (E).

[0017] Invention Effects According to the present invention, a polyurethane foam and a method for manufacturing polyurethane foam are provided, wherein the polyurethane foam exhibits high sound absorption performance over a wide frequency range, particularly below 2000 Hz, even when the substrate thickness is thin, and has a low surface porosity.

[0018] It should be noted that while Patent Document 1

[0016] describes "sound absorption (sound insulation)," it does not measure sound insulation properties. Therefore, in this document, sound absorption and sound insulation are used synonymously. However, generally speaking, sound absorption is interpreted as the absorption of sound to reduce sound reflection, and sound insulation is interpreted as the reflection of sound to prevent sound leakage. From this mechanism, it is clear that it is difficult to improve sound absorption properties when the surface porosity is low. However, according to the manufacturing method of the present invention, even with a low surface porosity, it is possible to obtain polyurethane foam that exhibits high sound absorption performance over a wide frequency range, particularly below 2000 Hz. A low surface porosity contributes to sound insulation; therefore, according to the manufacturing method of the present invention, it not only contributes to improved sound absorption properties over a wide frequency range but also to excellent sound insulation. Detailed Implementation

[0019] In the polyurethane foam of this embodiment, the surface open-cell ratio of at least one of the opposing main surfaces is 0.3% or more and 25% or less, and the air permeability measured according to JIS K6400-7:2012 B method is 0.02 to 7.0 cm. 3 / cm 2 / sec. It should be noted that the surface porosity and air permeability can be measured using the methods described in the examples.

[0020] Even with a thin substrate, the aforementioned polyurethane foam does not significantly compromise its sound insulation properties and exhibits high sound absorption performance over a wide frequency range, particularly below 2000Hz. It should be noted that with a low surface porosity, it is generally difficult to improve sound absorption characteristics.

[0021] The surface porosity can be above 0.5%, above 1.0%, greater than 1.0%, above 2.0%, or above 4.0%; it can be below 22.0%, below 18.0%, less than 10%, less than 9.0%, or less than 8.0%; it can be 0.5–22.0%, 0.5–18.0%, above 0.5% and less than 10%, 0.5–9.0%, 0.5–8.0%, 1.0–22.0%, 1.0–18.0%, above 1.0% and less than 10%, 1.0–9.0%, or 1. The surface porosity is preferably 0.5% or more and 22.0% or less, more preferably 1.0% or more and 18.0% or less, more preferably greater than 1.0% and less than 10%, more than 1.0% and 9.0% or less, more than 1.0% and 8.0% or less, 2.0% to 22.0%, 2.0% to 18.0%, more than 2.0% and less than 10%, 2.0% to 9.0%, 2.0% to 8.0%, 4.0% to 22.0%, 4.0% to 18.0%, more than 4.0% and less than 10%, 4.0% to 9.0%, or 4.0% to 8.0%. More preferably, the surface porosity is 0.5% or more and 22.0% or less, further preferably 1.0% or more and 18.0% or less, even more preferably greater than 1.0% and less than 10%, and particularly preferably 2.0% or more and 9.0% or less, or 4.0% or more and 8.0% or less.

[0022] The air permeability is 0.05cm. 3 / cm 2 / sec or more, 0.2cm 3 / cm 2 / sec or more or 0.5cm 3 / cm 2 / sec or higher, can be 7.0cm. 3 / cm 2 / sec or less, 5.0cm 3 / cm 2 / sec or less, 2.5cm 3 / cm 2 / sec or less or 1.8cm 3 / cm 2 Below / sec, the range can be 0.05–7.0 cm. 3 / cm 2 / sec, 0.05~5.0cm 3 / cm 2 / sec, 0.05~2.5cm 3 / cm 2 / sec, 0.05~1.8cm 3 / cm 2 / sec, 0.2~7.0cm 3 / cm 2 / sec, 0.2~5.0cm 3 / cm 2 / sec, 0.2~2.5cm 3 / cm 2 / sec, 0.2~1.8cm 3 / cm 2 / sec, 0.5~7.0cm 3 / cm 2 / sec, 0.5~5.0cm 3 / cm 2 / sec, 0.5~2.5cm 3 / cm 2 / sec or 0.5~1.8cm 3 / cm 2 / sec. A more preferable air permeability is 0.05–7.0cm. 3 / cm 2 / sec, more preferably 0.2–5.0cm 3 / cm 2 / sec, more preferably 0.5–2.5cm 3 / cm 2 / sec, particularly preferably 0.5–1.8cm 3 / cm 2 / sec.

[0023] Air permeability is measured in the foaming direction of polyurethane foam. Here, the foaming direction refers to the direction in which the thickness of the polyurethane foam raw material increases during foaming in a mold. The resulting foam (cells) usually have a shape that extends along the thickness direction (e.g., spindle-shaped), so the foaming direction can also be determined by its shape. When polyurethane foam is molded into a sheet shape using a mold, the thickness direction is usually the foaming direction.

[0024] The polyurethane foam manufacturing method involved in the embodiments is a manufacturing method in which polyurethane foam raw material is reacted inside a mold (casting mold). The polyurethane foam raw material is reacted while two or more release agents are sandwiched between the inner surface of the mold and the polyurethane foam raw material.

[0025] The manufactured polyurethane foam can be flexible polyurethane foam, semi-rigid polyurethane foam, or rigid polyurethane foam.

[0026] Flexible polyurethane foam refers to a reversibly deformable foam with an open-cell structure that exhibits high air permeability [for example, see Gunter Oertel, "Polyurethane Handbook" (1985 edition), Hanser Publisher (Germany), pp. 161-233; Keiji Iwata, "Polyurethane Resin Handbook" (1987 first edition), Nikkan Kogyo Shimbun, pp. 150-221].

[0027] The physical properties of flexible polyurethane foam vary depending on the chemical structure of the polyols and isocyanates used in its manufacture, the amount of blowing agent, the isocyanate index, and the cell structure, making it difficult to specify precisely. However, its density (which can be determined by apparent density; the same applies below) is typically 10–100 kg / m³. 3 The range of JIS K 6401, the range of compressive strength (ILD 25%) of 2 to 80 kgf (20 to 800 N) (JIS K 6401), and the range of elongation of 80 to 500% (JIS K6301) [for example, see Gunter Oertel, “Polyurethane Handbook” (1985 edition), Hanser Publisher (Germany), pp. 184 to 191 and 212 to 218, and Keiji Iwata, “Polyurethane Resin Handbook” (1987 first edition), Nikkan Kogyo Shimbun, pp. 160 to 166 and 186 to 191].

[0028] Semi-rigid polyurethane foam refers to a foam that, while having a higher density and compressive strength than flexible polyurethane foam, possesses the same open-cell structure, exhibiting high air permeability and reversible deformation. The polyols, isocyanates, and other raw materials used in its manufacture are also the same as those used in flexible polyurethane foam. Therefore, it is often classified as flexible polyurethane foam [e.g., see Gunter Oertel, "Polyurethane Handbook" (1985 edition), Hanser Publisher (Germany), pp. 223-233; Keiji Iwata, "Polyurethane Resin Handbook" (1987 first edition), Nikkan Kogyo Shimbun, pp. 211-221]. The physical properties of semi-rigid polyurethane foam are not particularly limited, but its density typically ranges from 40 to 800 kg / m³. 3 The range is 25%, with a compressive strength of 0.1–2 kgf / cm². 2 The range is (9.8~200kPa), and the elongation range is 40~200%.

[0029] Rigid polyurethane foam is a highly cross-linked, closed-cell structure that cannot be reversibly deformed, exhibiting properties completely different from flexible and semi-rigid polyurethane foams [e.g., see Gunter Oertel, "Polyurethane Handbook" (1985 edition), Hanser Publisher (Germany), pp. 234–313; Keiji Iwata, "Polyurethane Resin Handbook" (1987 first edition), Nikkan Kogyo Shimbun, pp. 224–283]. The properties of rigid foam are not particularly limited, but its density is typically 20–100 kg / m³. 3 The range is 0.5–10 kgf / cm². 2 The range is (50~1000kPa).

[0030] The mold used in the manufacture of polyurethane foam only needs to have a cavity to accommodate the polyurethane foam raw material and be made of raw material capable of withstanding the pressure and heat generated by the reaction. Preferably, the mold is temperature-controlled and can be heated while containing the polyurethane foam raw material to allow the reaction to proceed. It should be noted that urethane esterification and foaming occur through the reaction of the polyurethane foam raw material.

[0031] The shape of the manufactured polyurethane foam is determined by the internal shape of the mold (the shape of the voids). Therefore, the internal shape of the mold can be designed in a way that forms the desired shape. For example, in the case of forming a sheet-like polyurethane foam, a mold is made of a pair of molds, and a cuboid void is generated when the pair of molds are combined.

[0032] When reacting polyurethane foam raw materials, two or more release agents are sandwiched between the inner surface (inner wall) of the mold and the polyurethane foam raw materials. Examples of sandwiching (or separating) these agents include applying two or more release agents to the inner surface of the mold (coating, spraying, etc.) before introducing the polyurethane foam raw materials into the mold. Preferably, when the mold consists of a pair of molds, two or more release agents are applied to the inner surface of at least one of the molds, and the polyurethane foam raw materials are introduced into the mold to react. It should be noted that, preferably, when the release agent contains volatile components such as organic solvents and water in addition to the release agent (wax component), the polyurethane foam raw materials are introduced into the mold after these components have evaporated.

[0033] The manufacturing method described in the embodiments is characterized by reacting the material in the presence of two or more release agents. "Two or more" includes combinations of two or more release agents with different chemical compositions, and combinations of two or more release agents that, while sharing the same chemical composition, exhibit different thermal behaviors (e.g., different melting peak temperatures). In other words, the polyurethane foam raw material can be reacted in the presence of two or more release agents with different chemical compositions and / or melting peak temperatures.

[0034] The combination of release agents can consist of 2 to 5, 2 to 4, or 2 to 3 types. In order to avoid complicating the composition of the release agents, the polyurethane foam raw materials can be reacted with two release agents in between.

[0035] The melting peak temperature of the release agent refers to the melting peak temperature according to JIS K 7121:1987. That is, by measuring the differential scanning calorimetry (DSC) curve, the temperature at the peak of the melting peak is taken as the melting peak temperature (Tpm). The DSC curve measurement can be performed after conditioning as described in the above-mentioned JIS. Specifically, for example, the test piece is placed in the container of the DSC device, heated to a temperature approximately 30°C higher than the end of the melting peak, held at this temperature for 10 minutes, and then cooled at a cooling rate of 5°C or 10°C per minute to a temperature at least approximately 50°C lower than the transition peak that appears, thereby conditioning the state. Then, immediately after conditioning, the device is stabilized, heated at a heating rate of 10°C per minute to a temperature approximately 30°C higher than the end of the melting peak, and the DSC curve is plotted. The temperature at the peak of the melting peak determined from this DSC curve is taken as the melting peak temperature. In the case of observing multiple peaks, it is assumed to have multiple melting peak temperatures. In the case of having multiple melting peak temperatures, they are sequentially referred to as the first melting peak temperature, the second melting peak temperature, etc., starting from the lower temperature side.

[0036] Two or more release agents may include: release agent (I) having a melting peak temperature of 40°C or higher and less than 70°C; and release agent (II) having a melting peak temperature of 80°C or higher and less than 130°C. At least one of release agent (I) and release agent (II) may have two or more melting peak temperatures, but in the case where the release agent has two or more melting peak temperatures, the first melting peak temperature (the melting peak temperature on the lowest temperature side) is used to determine whether it is 40°C or higher and less than 70°C or 80°C or higher and less than 130°C.

[0037] Release agent (I) has two melting peak temperatures (a first melting peak temperature and a second melting peak temperature), with the lower melting peak temperature (first melting peak temperature) being above 40°C and below 70°C. Release agent (II) may have at least one melting peak temperature between the first and second melting peak temperatures of release agent (I). For example, this corresponds to release agent (I) having a first melting peak temperature of 50°C and a second melting peak temperature of 90°C, while release agent (II) has a melting peak temperature (first melting peak temperature) of 85°C.

[0038] In the above cases, the melting peak temperature of release agent (I) can be above 40°C and below 65°C, or above 40°C and below 60°C. The melting peak temperature of release agent (II) can be above 80°C and below 120°C, or above 80°C and below 110°C.

[0039] Release agents are typically made by dissolving paraffin wax, Fischer-Tropsch wax, saxo-Sodium wax, microcrystalline wax, modified polyethylene wax, etc., in an organic solvent, or by dispersing them in water with an emulsifier. These are then applied to the mold. It should be noted that many release agents containing the aforementioned waxes are available on the market, and their melting peak temperatures vary depending on their chemical composition and structure. Therefore, the melting peak temperature can be determined using the method described above, allowing selection of a release agent equivalent to release agent (I) or release agent (II). The total coating weight of release agent (I) and release agent (II), based on solid content, can range from 0.3 to 15 g / m³. 2 Or 0.5~10g / m 2 In this invention, the solid content of the release agent coating amount refers to the mass (g) obtained by subtracting the mass of organic solvent and water from the mass of the applied release agent, divided by the coating area (m²). 2 The value obtained is ).

[0040] The mass ratio of release agent (I) to the total mass of 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, even more preferably 0.85 or more and 0.95 or less, and particularly preferably 0.88 or more and 0.92 or less.

[0041] Preferably, the release agent (I) is a release agent that can achieve a surface open-cell ratio of 0% or more and less than 10% when using only the release agent (I) as a release agent to manufacture polyurethane foam, and the release agent (II) is a release agent that can achieve a surface open-cell ratio of 10% or more and less than 60% when using only the release agent (II) as a release agent to manufacture polyurethane foam.

[0042] Regarding release agent (I), it is not necessary for all polyurethane foam raw materials to produce polyurethane foam with a surface open-cell ratio of 0% or more and less than 10%, as long as at least one polyurethane foam raw material exists that can achieve such a surface open-cell ratio. Similarly, regarding release agent (II), it is not necessary for all polyurethane foam raw materials to produce polyurethane foam with a surface open-cell ratio of 10% or more and less than 60%, as long as at least one polyurethane foam raw material exists that can achieve such a surface open-cell ratio.

[0043] As for the composition of polyurethane foam raw materials used to determine a surface open-cell ratio of 0% or more but less than 10% or a surface open-cell ratio of 10% or more but less than 60%, the isocyanate component, polyol component, catalyst, foam stabilizer, and foaming agent described in Example 1 are preferably used. Regarding the mass ratio, it can also be implemented as described in Example 1.

[0044] Examples of polyurethane foam raw materials that react inside the mold include those containing polyols (A), polyisocyanates (B), catalysts (C), foam stabilizers (D), and blowing agents (E). Polyurethane foam raw materials may also contain fillers such as calcium carbonate and barium sulfate, as well as additives and auxiliaries such as flame retardants, plasticizers, colorants, and antifungal agents.

[0045] The polyol component (A) is a component that forms polyurethane by addition polymerization with the polyisocyanate component (B), 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 1000 to 10000, more preferably 3000 to 8000, and most preferably 4000 to 8000. Additionally, it is more preferable that the nominal number of functional groups (nominal functionality) is two or more.

[0046] If the number-average molecular weight is below the lower limit, the resulting foam is prone to insufficient flexibility; if it is above the upper limit, the foam's hardness is prone to decrease. Furthermore, when the nominal functional group number is less than 2, the foam's resilience is significantly reduced, leading to problems such as the foam failing to return to its original shape when compressed. It should be noted that the nominal functional group number represents the theoretical average number of functional groups (the number of active hydrogen atoms per molecule) assuming no side reactions occur during the polymerization of the polyol.

[0047] As a polyether polyol, for example, polyoxyethylene polyol, polyoxypropylene polyol, polyoxyethylene polyoxypropylene polyol, polytetramethylene ether glycol, etc. can be used; as a polyester polyol, for example, polyester polyol formed from adipic acid and diol as a condensation-type polyester polyol, polycaprolactone polyol, etc., can be used; as a lactone-type polyester polyol, polycaprolactone polyol, etc., can be used.

[0048] From the viewpoint of improving the heat resistance of foam, at least one polyol selected from the group consisting of castor oil and castor oil-modified polyols can be used in the polyol component (A). Examples of such polyols selected from the group consisting of castor oil and castor oil-modified polyols include refined castor oil, semi-refined castor oil, unrefined castor oil, hydrogenated castor oil obtained by hydrogenation, and other derivatives of castor oil.

[0049] Furthermore, in the polyol component (A), to promote the interconnection of the polyurethane foam, a polyether polyol having polyoxyalkylene chains composed of a copolymer of ethylene oxide and propylene oxide can be included. The number average molecular weight is preferably 3000 to 8000, and the nominal number of functional groups is preferably 2 to 4. Moreover, the ethylene oxide units in this polyether polyol are preferably 60 to 90% by mass, more preferably 60 to 80% by mass.

[0050] By making the ethylene oxide units 60-90% by mass, the durability of the foam can be improved. Furthermore, from the viewpoint of low-temperature storage stability, copolymers composed of ethylene oxide and propylene oxide are preferably random copolymers.

[0051] In the polyol component (A), in order to adjust the hardness, a polymeric polyol can be obtained by polymerizing vinyl monomers in a polyol using conventional methods. Examples of such polymeric polyols include those obtained by polymerizing and stably dispersing vinyl monomers in a polyalkylene polyol in the presence of a free radical initiator.

[0052] Examples of vinyl monomers include acrylonitrile, styrene, vinylidene chloride, hydroxyalkyl methacrylate, and alkyl methacrylate, with acrylonitrile and styrene being preferred. Examples of such polymeric polyols include FA-728R, KC-900, and FS-7301 manufactured by Sanyo Chemical Industries, Ltd.

[0053] The polyisocyanate component (B) preferably uses diphenylmethane diisocyanate (hereinafter referred to as MDI), such as 4,4'-diphenylmethane diisocyanate (hereinafter referred to as 4,4'-MDI), 2,4'-diphenylmethane diisocyanate (hereinafter referred to as 2,4'-MDI), and 2,2'-diphenylmethane diisocyanate (hereinafter referred to as 2,2'-MDI), or polyphenylene polymethylene polyisocyanate (hereinafter referred to as P-MDI) as the isocyanate source. In this invention, various modifiers such as the above-mentioned MDI, mixtures of MDI and P-MDI, urethane modifiers, urea modifiers, urethane-based modifiers, urea-based modifiers, biuret modifiers, etc., can also be used.

[0054] The MDI content of the polyisocyanate component (B) is preferably in the range of 50 to 85% by mass. If the MDI content is greater than 85% by mass, the storage stability of the resulting polyisocyanate composition at low temperatures and the durability of the resulting foam may decrease. On the other hand, when it is less than 50% by mass, the elongation of the polyurethane foam decreases with the increase of crosslinking density, and it may be difficult to obtain sufficient foam strength.

[0055] Furthermore, the combined content of 2,2'-MDI and 2,4'-MDI relative to the total amount of MDI (hereinafter, isomer content) is preferably 10 to 50% by mass.

[0056] When the content of 2,2'-MDI and 2,4'-MDI relative to the total MDI is less than 10% by mass, the resulting polyisocyanate composition may suffer from impaired storage stability at low temperatures, sometimes requiring continuous heating of the isocyanate storage area, piping, and foaming machine. Furthermore, the molding stability of the polyurethane foam is compromised, potentially leading to foam collapse during foaming. On the other hand, if the content exceeds 50% by mass, problems such as reduced reactivity, prolonged molding cycle, increased single-foam ratio, and post-molding shrinkage may occur.

[0057] As catalyst (C), various carbamate esterification 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]undec-7-ene, 1,2-dimethylimidazolium, dimethylethanolamine, N,N-dimethyl-N-hexanolamine, and their organic acid salts, stannous octoate, zinc naphthenate, and other organometallic compounds. Furthermore, amine catalysts with active hydrogen, such as N,N-dimethylethanolamine and N,N-diethylethanolamine, are preferred.

[0058] The amount of catalyst added is preferably 0.01 to 10% by mass relative to the polyol component (A). If it is less than the lower limit, it is easy to become under-cured, and if it is greater than the upper limit, the formability may deteriorate.

[0059] As the foam stabilizer (D), conventional surfactants can be used, with silicone-based surfactants being preferred. Examples include SZ-1327, SZ-1325, SZ-1336, and SZ-3601 manufactured by Dow-Toray, Y-10366J and L-5309J manufactured by Momentive, 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 relative to the polyol component (A).

[0060] As a foaming agent (E), water is primarily used, and it can consist of only water. Water reacts with isocyanate groups to form high-hardness urea groups, producing carbon dioxide, thereby enabling foaming. Alternatively, any foaming agent can be used in addition to water. For example, small amounts of low-boiling-point organic compounds such as cyclopentane and isopentane can be used, or air, nitrogen, or liquefied carbon dioxide can be mixed into the stock solution using a gas loading device to achieve foaming.

[0061] The amount of foaming agent (E) added is typically 0.5–10% by mass relative to the polyol component (A), to obtain an apparent density of 25 kg / m³. 3 In the case of low-density polyurethane foam, the preferred percentage is 4.0 to 7.0% by mass, and more preferably 4.0 to 6.5% by mass. If the percentage is greater than the upper limit, the foaming may be difficult to stabilize, and if the percentage is less than the lower limit, the density of the foam may not be sufficiently reduced.

[0062] The NCO index (100 times the molar ratio of NCO to active hydrogen) when the polyisocyanate component (B) is mixed with all the isocyanate groups in the polyol component (A) and all the active hydrogen groups in the foaming agent (E) is preferably 70 to 140, and more preferably 70 to 120 as a range with good molding cycle.

[0063] When the NCO index is less than 70, the foam's uniqueness is excessively increased. When it is above 120, there may be a prolonged molding cycle due to the long-term residue of unreacted isocyanate, or foam collapse during foaming due to the delay in high molecular weight.

[0064] In the manufacture of polyurethane foam, the mold temperature when injecting the polyurethane foam raw material into the mold is typically 30–80°C, preferably 45–70°C. If the mold temperature when injecting the foaming agent into the mold is lower than 30°C, the production cycle may be prolonged due to a decrease in the reaction rate. On the other hand, if the temperature is higher than 80°C, the reaction between water and isocyanate is excessively promoted relative to the reaction between polyol and isocyanate, which may cause the foam to collapse during the foaming process.

[0065] 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 account the typical production cycle of molded foam. After the polyurethane foam raw material is foamed and cured, the molded polyurethane foam can be obtained by demolding the cured material from the mold.

[0066] When manufacturing polyurethane foam, the same process as with conventional molded foam can be used to mix polyurethane foam raw materials using high-pressure foaming machines, low-pressure foaming machines, etc.

[0067] The polyol component (A) and the polyisocyanate component (B) are preferably mixed just before foaming. Other components can be pre-mixed with the polyol component (A) or the polyisocyanate component (B) within a range that does not affect the storage stability or reactivity of the raw materials over time. These mixtures can be used immediately after mixing or used appropriately after storage. In the case of a foaming device that can simultaneously introduce more than two components into the mixing section, the polyol, foaming agent, isocyanate, catalyst, foam stabilizer, etc., can also be introduced into the mixing section separately.

[0068] Furthermore, the mixing method can be either dynamic mixing, which takes place in the mixing chamber of the foaming device's head, or static mixing, which takes place in the liquid delivery piping; alternatively, both can be used in combination. The mixing of gaseous components such as physical foaming agents with liquid components is mostly carried out through static mixing, while the mixing of components that can be stably stored as liquids is mostly carried out through dynamic mixing. The foaming device is preferably a high-pressure foaming device that does not require solvent cleaning of the mixing section.

[0069] After demolding, the polyurethane foam cell membrane can be broken down under compression or decompression using known methods. Breaking down the cell membrane improves the air permeability of the polyurethane foam.

[0070] The polyurethane foam produced by the above manufacturing method does not significantly compromise its sound insulation properties even with a thin substrate, and exhibits high sound absorption performance over a wide frequency range, particularly below 2000 Hz. It should be noted that it is generally difficult to improve sound absorption properties when the surface porosity is low.

[0071] Here, if the substrate thickness (the thickness of the polyurethane foam) is 10 mm, it can be considered sufficiently thin. If the surface porosity is 25% or less (preferably 20%, more preferably 18%) and 0% or more, it can be considered low. Polyurethane foam with low surface porosity exhibits excellent sound insulation properties. Furthermore, if the average sound absorption coefficient from 500 to 2000 Hz is 0.35 or more, it can be said to exhibit high sound absorption performance in the frequency range below 2000 Hz. The polyurethane foam obtained by the manufacturing method according to this embodiment, even with a thickness of 10 mm and a surface porosity of 25% or less, exhibits an average sound absorption coefficient of 0.35 or more from 500 to 2000 Hz. Therefore, it can be used as a sound-absorbing material or sound-insulating material in various applications. It should be noted that the sound absorption characteristics and surface porosity can be measured using the methods described in the examples.

[0072] Example The present invention will now be described in more detail with reference to embodiments and comparative examples, but the present invention is not limited to the embodiments described below. It should be noted that, unless otherwise specified, "parts" and "%" in the text refer to mass.

[0073] (Examples 1-4, Comparative Examples 1-6) [Preparation of Polyol Compositions] After purging a reactor equipped with a stirrer, cooling pipe, nitrogen inlet pipe, and thermometer with nitrogen, 60g of polyol 1, 40g of polyol 2, 1.0g of polyol 3, 0.7g of catalyst 1, 0.1g of catalyst 2, 1.0g of foam stabilizer 1, and 2.0g of water were added and stirred at 23°C for 0.5 hours to obtain a polyol composition (P-1).

[0074] [Preparation of release agent] After purging a plastic container that can be sealed with a lid with nitrogen, 7.76g of release agent A and 0.24g of release agent B were added, and the container was sealed. The mixture was stirred at 23°C for 0.5 hours using a mixing roller to obtain release agent 4. Using the same method, release agent 5 was obtained using 7.2g of release agent A and 0.8g of release agent B; release agent 6 was obtained using 6.4g of release agent A and 1.6g of release agent B; and release agent 7 was obtained using 4.8g of release agent A and 3.2g of release agent B.

[0075] [Mold forming 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 specified amount of polyisocyanate was added to the polyol composition, and after mixing for 7 seconds using a mixer (7000 rpm), the mixture was injected into a mold coated with a release agent to foam the polyurethane foam. It should be noted that in the examples and comparative examples, the types of release agents shown in Tables 1 and 2 were used.

[0076] Mold temperature: 50~65℃ Mold shape (cubic prism): 200mm × 200mm × 10mm Mold material: Aluminum Curing time: 10 minutes After the polyurethane foam has cured, it is demolded to obtain a polyurethane foam molded body. It should be noted that the polyurethane foam in Comparative Example 5 could not be demolded, and no molded body was obtained.

[0077] For the polyurethane foam molded body of Comparative Example 4, the obtained polyurethane foam molded body was compressed to break the cell membrane and adjust the air permeability.

[0078] [Raw Materials Used] • Polyol 1: Polyoxyethylene polyoxypropylene polyol with an average functional group count of 3.0 and a hydroxyl value of 33 (mgKOH / g), manufactured by AGC as EXCENOL 823 (trade name). • Polyol 2: Refined castor oil (URIC H-24 manufactured by Ito Oil Co., Ltd.) with an average functional group count of 2.7 and a hydroxyl value of 160 (mgKOH / g). • Polyol 3: Average number of functional groups = 4.0, hydroxyl value = 28 (mgKOH / g), polyether polyol with 80% by mass of ethylene oxide units, NEF-024 (trade name) manufactured by Tosoh Corporation. Catalyst 1: 33% dipropylene glycol solution of triethylenediamine (manufactured by Tosoh Corporation, trade name: TEDAL-33) Catalyst 2: 70% dipropylene glycol solution of bis(2-dimethylaminoethyl) ether (manufactured by Tosoh Corporation, trade name: TOYOCAT ET) • Foam stabilizer 1: Organosilicon foam stabilizer (manufactured by Momentive, trade name: L-5309J) • Isocyanate 1: Polyphenylene polymethylene polyisocyanate containing 70% MDI and 17.7% isomers (manufactured by Tosoh Corporation, trade name: CEF-538) • Release Agent 1: Branched-chain wax-based release agent, first melting peak 50.4℃, second melting peak 91.4℃, product name: M975, manufactured by Chukyo Oils & Fats Co., Ltd. • Release Agent 2: Linear-chain wax-based release agent, first melting peak 87.8℃, second melting peak 99.5℃, product name: T-626, manufactured by Chukyo Oils & Fats Co., Ltd. • Release Agent 3: Branched Wax-based Release Agent, First Melting Peak 80.4℃, Second Melting Peak 118.7℃, Product Name: FRX-C8, Manufactured by Neos Corporation • Release agent 4: A release agent obtained by mixing release agent 1 and release agent 2 at a weight ratio of 97:3. • Release agent 5: A release agent obtained by mixing release agent 1 and release agent 2 at a weight ratio of 90:10. • Release agent 6: A release agent obtained by mixing release agent 1 and release agent 2 at a weight ratio of 80:20. • Release agent 7: A release agent obtained by mixing release agent 1 and release agent 2 in a weight ratio of 60:40. [Apparent density] The apparent density of the polyurethane foam molding was determined using the method described in JIS K6400-1:2004.

[0079] [Thickness of polyurethane foam] The thickness of the polyurethane foam molding was measured using a vernier caliper (Azov Corporation digital vernier caliper BDC200).

[0080] [C Hardness] The thickness of polyurethane foam molded parts was determined using a rubber hardness tester (ASKER-C type) as described in JIS K7312:1996.

[0081] [F Hardness] The F-hardness of polyurethane foam molded parts was determined using an ASKER rubber hardness tester (Type F).

[0082] [Breathability] The air permeability of polyurethane foam molded parts was determined by the method described in JIS K6400-7:2012 Method B.

[0083] Average cell diameter The average cell diameter of each polyurethane foam molded body was calculated as follows: A 10mm thick polyurethane foam molded body was cut into a disc shape with a diameter of 28.8mm. For the side of the foam, an image with a field of view of 10mm in length and 16.3mm in width was taken using a microscope equipped with a lens MTL5518C-034-01 manufactured by Moritex. The cell diameter of the specified number of cells in the field of view was measured, and the average of the cell diameters was calculated.

[0084] [Surface porosity] The surface porosity of each polyurethane foam molded body was calculated as follows: A 10mm thick polyurethane foam molded body was cut into a disc shape with a diameter of 28.8mm. For the surface that contacts the upper mold during molding, an image with a diameter of 28.8mm was taken using a microscope equipped with a Moritex MM014-HR110-5M telecentric lens. The above image was binarized into the porosity and the surface area excluding it using the software "ImageJ". After calculating the total area of ​​the porosity, the porosity was calculated based on the following formula.

[0085] Surface porosity = (total area of ​​the openings / sample area) × 100… (formula).

[0086] [Sound Absorption Coefficient] Based on the method described in JIS A 1405-2:2007, the vertical incident sound absorption coefficient at 500–6300 Hz was measured using a Hottinger Brüel & Kjær Japan 4206 type acoustic tube. The sound absorption coefficient was measured under the following conditions: a polyurethane foam molded body with a diameter of 28.8 mm and a thickness of 10 mm was arranged with the lower mold forming surface of the mold facing the sound source side, and no air layer was placed behind the polyurethane foam molded body.

[0087] [Moldability] The moldability of each polyurethane foam molded body was evaluated according to the following evaluation criteria. It should be noted that in Comparative Example 5, the polyurethane foam molded body could not be demolded.

[0088] <Evaluation Criteria> A: The shape of the polyurethane foam molding body is not significantly different from the shape of the inner surface of the mold, and there is no deformation, cracking or damage during demolding.

[0089] B: The shape of the polyurethane foam molding body differs significantly from the shape of the inner surface of the mold, or any of the following occurs during demolding: deformation, cracking, or defects.

[0090] [Table 1]

[0091] [Table 2]

[0092] As shown in Examples 1, 2, 3 and 4 of Table 1, the surface porosity can be adjusted by changing the mixing ratio of the two release agents.

Claims

1. A polyurethane foam, characterized in that, The porosity of at least one of the opposing main surfaces is 0.3% to 25%, and the air permeability, as measured by JIS K6400-7:2012 Method B, is 0.02 to 7.0 cm. 3 / cm 2 / sec.

2. A method for manufacturing polyurethane foam, characterized in that, This is a method for manufacturing polyurethane foam in which the polyurethane foam raw materials react inside a mold. The polyurethane foam material is reacted while two or more release agents are sandwiched between the inner surface of the mold and the polyurethane foam material.

3. The manufacturing method according to claim 2, wherein, The mold consists of a pair of molds, with two or more of the release agents adhering to at least one inner surface of the mold, and the polyurethane foam raw material is introduced into the interior of the mold to react.

4. The manufacturing method according to claim 2 or 3, wherein, Two or more of the aforementioned release agents comprise: Release agent (I) having a melting peak temperature above 40°C and below 70°C; and Release agent (II) has a melting peak temperature of 80°C or higher and 130°C or lower.

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

6. The manufacturing method according to claim 4 or 5, wherein, The release agent (I) has two melting peak temperatures, with the lower-temperature side having a melting peak temperature above 40°C and below 70°C. The release agent (II) has at least one melting peak temperature between the two melting peak temperatures of the release agent (I).

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

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

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

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