Polyurethane foam

Abstract

To provide a polyurethane foam which has sufficient hardness while securing a high air permeation amount.SOLUTION: A polyurethane foam is obtained from a composition containing polyol and isocyanate, wherein the polyol contains polymer polyol, polyether polyol (A) having an EO rate of 60 mol% or more, and polyether polyol (B) having an EO rate of less than 60 mol% and a weight average molecular weight of 300 or more and less than 1,500, when the total amount of the polyol is 100 pts.mass, the content of the polymer polyol is more than 10 pts.mass, the content of the polyether polyol (A) is 20 pts.mass or more, and the isocyanate contains a polymeric MDI.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to polyurethane foam. [Background technology]

[0002] Patent Document 1 discloses a polyurethane foam using a mixture of a polyether polyol with a low EO ratio and a polyether polyol with a high EO ratio as the polyol component. Patent Document 1 discloses that the urethane foam can ensure sufficient air permeability. However, the polyurethane foam described in Patent Document 1 was not sufficiently rigid. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-33553 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] This disclosure is made in view of the above circumstances and aims to provide a polyurethane foam that has sufficient rigidity while ensuring high breathability. [Means for solving the problem]

[0005] [1] A polyurethane foam obtained from a composition comprising a polyol and an isocyanate, The aforementioned polyol includes, Polymer polyols and When the total amount of alkylene oxide units is taken as 100 mol%, the ethylene oxide unit content is 60 mol% or more of a polyether polyol (A), The polyether polyol (B) contains less than 60 mol% of ethylene oxide units when the total amount of alkylene oxide units is set to 100 mol%, and has a weight-average molecular weight of 300 or more and less than 1500. When the total amount of the polyol is 100 parts by mass, The content of the polymer polyol is greater than 10 parts by mass. The content of the polyether polyol (A) is 20 parts by mass or more. The aforementioned isocyanate contains polymeric MDI in this polyurethane foam. [Effects of the Invention]

[0006] According to this disclosure, it is possible to provide a polyurethane foam that has sufficient rigidity while ensuring high breathability. [Modes for carrying out the invention]

[0007] [2] A polyurethane foam having a rebound elasticity of 25% or less in accordance with JIS K6400-3 [1].

[0008] [3] Polyurethane foam having an air permeability of 50 L / min or more according to JIS K6400-7 Method A:2012 [1].

[0009] [4] A polyurethane foam having a 25% hardness of 20N or more, according to JIS K6400-2 Method D:2012.[1]

[0010] The disclosure is described in detail below. In this specification, when a numerical range is indicated using "-", it includes both the lower and upper limits unless otherwise specified. For example, the expression "10-20" includes both the lower limit "10" and the upper limit "20". In other words, "10-20" has the same meaning as "10 or more and 20 or less".

[0011] 1. Composition The composition contains a polyol and an isocyanate. The composition may optionally contain at least one component selected from blowing agents, catalysts, foam stabilizers, and crosslinking agents. Each component of the composition is described below.

[0012] (1) Polyol Polyols include polymer polyols, polyether polyols (A) in which the content of ethylene oxide units (hereinafter also referred to as "EO units") is 60 mol% or more when the total amount of alkylene oxide units is taken as 100 mol%, and polyether polyols (B) in which the content of "EO units" is less than 60 mol% (or does not contain EO units) when the total amount of alkylene oxide units is taken as 100 mol%. Polymer polyols, polyether polyols (A), and polyether polyols (B) may each contain two or more types.

[0013] (1.1) Polymer polyols The polymer polyol is not particularly limited. Examples of polymer polyols include polymer polyols obtained by polymerizing a polyether polyol (base polyol) with a vinyl monomer such as styrene and / or acrylonitrile. The polymer content of the polymer polyol (the mass ratio of the portion other than the base polyol to the total polymer polyol) is preferably 10% by mass or more and 55% by mass or less, more preferably 13% by mass or more and 50% by mass or less, and even more preferably 15% by mass or more and 45% by mass or less.

[0014] From the perspective of ensuring a hardness of 25%, when the total amount of polyol is 100 parts by mass, the content of polymer polyol is preferably more than 10 parts by mass, more preferably 13 parts by mass or more, and even more preferably 15 parts by mass or more. On the other hand, from the perspective of compression residual strain, when the total amount of polyol is 100 parts by mass, it is preferably 55 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 35 parts by mass or less. From these perspectives, the content of polymer polyol is preferably more than 10 parts by mass and 55 parts by mass or less, more preferably 13 parts by mass or more and 45 parts by mass or less, and even more preferably 15 parts by mass or more and 45 parts by mass or less.

[0015] The viscosity of the polymer polyol is not particularly limited. The viscosity of the polymer polyol at 25 °C and 60 rpm measured with a B-type rotational viscometer is preferably 1500 mPa·s or more and 10000 mPa·s or less, more preferably 3000 mPa·s or more and 8000 mPa·s or less, and even more preferably 4000 mPa·s or more and 6000 mPa·s or less.

[0016] The hydroxyl value of the polymer polyol is not particularly limited. The hydroxyl value of the polyol is preferably 20 mgKOH / g or more and 200 mgKOH / g or less, more preferably 25 mgKOH / g or more and 150 mgKOH / g or less, and even more preferably 30 mgKOH / g or more and 120 mgKOH / g or less.

[0017] (1.2) Polyether polyol (A) Polyether polyol (A) is a polyether polyol in which the content of EO units is 60 mol% or more when the total amount of alkylene oxide units is 100 mol%. From the perspective of compression residual strain, the content of EO units is preferably 70 mol% or more, more preferably 75 mol% or more, and even more preferably 80 mol% or more. The upper limit of the content of EO units is not particularly limited and may be 100 mol%. Polyether polyol (A) may be used alone or in combination of two or more. Other alkylene oxides used in the production of polyether polyol (A), besides ethylene oxide, include propylene oxide and butylene oxide, but propylene oxide is preferred. As polyether polyol (A), a polyol in which the entirety consists of propylene oxide units (hereinafter abbreviated as "PO units") except for EO units can be suitably used.

[0018] The polyether polyol (A) content is 20 parts by mass or more, based on 100 parts by mass of the total polyol. From the viewpoint of improving air permeability, the polyether polyol (A) content is more preferably 30 parts by mass or more and 40 parts by mass or more. From the viewpoint of moldability and 25% hardness, the upper limit of the polyether polyol (A) content is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less. From these viewpoints, the polyether polyol (A) content is preferably 20 parts by mass or more and 70 parts by mass or less, more preferably 30 parts by mass or more and 60 parts by mass or less, and even more preferably 40 parts by mass or more and 50 parts by mass or less, based on 100 parts by mass of the total polyol.

[0019] The weight-average molecular weight of polyether polyol (A) is not particularly limited. From the viewpoint of achieving low rebound properties, the weight-average molecular weight of polyether polyol (A) is preferably 20,000 or less, more preferably 10,000 or less, and even more preferably 6,000 or less. From the viewpoint of having high air permeability, the lower limit of the weight-average molecular weight of polyether polyol (A) is preferably 1,000 or more, more preferably 2,500 or more, and even more preferably 4,000 or more. From these viewpoints, the weight-average molecular weight of polyether polyol (A) is preferably 1,000 to 20,000, more preferably 2,500 to 10,000, and even more preferably 4,000 to 6,000. The weight-average molecular weight of polyether polyol (A) can be measured by gel permeation chromatography (GPC).

[0020] The number of functional groups in polyether polyol (A) is not particularly limited. Preferably, the number of functional groups in polyether polyol (A) is 2-5, more preferably 2-4, and even more preferably 2 or 3.

[0021] If the number of functional groups in the polyether polyol (A) is as specified above, the formation of a network structure can be suppressed when the polyol and isocyanate react. It is presumed that the polyurethane foam formed in this way will have suppressed entanglement of polyurethane molecules during compression, resulting in a polyurethane foam with low compression set. In this disclosure, the number of functional groups refers to the average number of active hydrogen groups present in each component of the polyol. If the polyol is a commercially available product, the catalog value may be used as the number of functional groups of the polyether polyol (A).

[0022] (1.3) Polyether polyol (B) The polyether polyol includes polyether polyol (B) in which the content of EO units is less than 60 mol% (or does not contain EO units) when the total amount of alkylene oxide units is set to 100 mol%. Only one type of polyether polyol (B) may be used, or two or more types may be used in combination.

[0023] Examples of polyether polyols (B) include polyether polyols containing PO units, butylene oxide units, etc., as alkylene oxide units other than EO units. Polyether polyols (B) preferably consist of polyether polyols in which the entirety of the units other than EO units is PO units.

[0024] The EO unit content of polyether polyol (B) is less than 60 mol%. For example, from the viewpoint of improving air permeability, the EO unit content of polyether polyol (B) is preferably 30 mol% or less, and more preferably 15 mol% or less. The lower limit of the EO unit content of polyether polyol (B) is not particularly limited and may be 0 mol%.

[0025] From the viewpoint of having a low compressive residual strain, the weight-average molecular weight of polyether polyol (B) is 300 or more, preferably 400 or more, and more preferably 500 or more. On the other hand, from the viewpoint of having a high 25% hardness, the weight-average molecular weight of polyether polyol (B) is less than 1500, preferably less than 1000, and more preferably less than 800. From these viewpoints, the weight-average molecular weight of polyether polyol (B) is 300 or more and less than 1500, preferably 400 or more and less than 1000, and more preferably 500 or more and less than 800. The weight-average molecular weight of polyether polyol (B) can be measured by gel permeation chromatography (GPC).

[0026] The number of functional groups in polyether polyol (B) is not particularly limited. Preferably, the number of functional groups in polyether polyol (B) is 2-5, more preferably 2-4, and even more preferably 2 or 3. If the number of functional groups in polyether polyol (B) is as described above, the formation of a network structure can be suppressed when the polyol and isocyanate react. It is presumed that the polyurethane foam formed in this way will have suppressed entanglement of polyurethane molecules during compression, resulting in a polyurethane foam with low compression residual strain. As the polyether polyol (B), polyoxyethylene / propylene glycol copolymer or polypropylene glycol with an EO unit content of less than 60 mol% is preferred, and polyoxyethylene / propylene glycol copolymer with an EO unit content of less than 60 mol% is more preferred.

[0027] (2) Isocyanates Isocyanates include polymeric MDIs. Polymeric MDIs are mixtures of diphenylmethane diisocyanates and polymethylene polyphenyl polyisocyanates. Examples of diphenylmethane diisocyanates include 2,2'-diphenylmethane diisocyanate (2,2'-MDI), 2,4'-diphenylmethane diisocyanate (2,4'-MDI), and 4,4'-diphenylmethane diisocyanate (4,4'-MDI). Polymeric MDI may be untreated crude MDI obtained by an MDI synthesis reaction, or it may be prepared by separating a desired amount of diphenylmethane diisocyanate from the crude MDI by vacuum distillation to adjust its composition. The polymeric MDI of this disclosure preferably contains 4,4'-diphenylmethane diisocyanate (4,4'-MDI).

[0028] Polymeric MDI may contain other MDI-based isocyanates. Examples of other MDI-based isocyanates include carbodiimide-modified, urethane-modified, urea-modified, allophanate-modified, biuret-modified, and isocyanurate-modified diphenylmethane diisocyanate, as well as diphenylmethane diisocyanate and MDI prepolymers obtained by reacting these modified forms with polyols. Among these, it is preferable that the other MDI-based isocyanate includes an MDI prepolymer. The other MDI-based isocyanates may include two types.

[0029] The amount of polymeric MDI added is preferably 25 to 80 parts by mass, preferably 30 to 75 parts by mass, and more preferably 35 to 70 parts by mass, per 100 parts by mass of polymer polyol.

[0030] From the viewpoint of aeration, the content of diphenylmethane diisocyanate in the total polymeric MDI is preferably 35% by mass or more, more preferably 45% by mass or more, and even more preferably 55% by mass or more. On the other hand, from the viewpoint of 25% hardness, it is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. From these viewpoints, the content of diphenylmethane diisocyanate in the total polymeric MDI is preferably 35% by mass or more and 90% by mass or less, preferably 45% by mass or more and 85% by mass or less, and even more preferably 55% by mass or more and 80% by mass or less.

[0031] From the viewpoint of compressive set, the content of polymethylene polyphenyl polyisocyanate in the total amount of polymeric MDI is preferably 10% by mass or more, more preferably 13% by mass or more, and even more preferably 15% by mass or more. On the other hand, from the viewpoint of air permeability, it is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. From these viewpoints, it is preferably 10% by mass or more and 50% by mass or less, more preferably 13% by mass or more and 40% by mass or less, and even more preferably 15% by mass or more and 30% by mass or less. By setting the mass ratio of polymethylene polyphenyl polyisocyanate contained in polymeric MDI to an appropriate value, a polyurethane foam with low compressive set and air permeability can be obtained.

[0032] From the viewpoint of 25% hardness, the isocyanate index (INDEX) is preferably 60 or higher, more preferably 70 or higher, and even more preferably 75 or higher. On the other hand, from the viewpoint of air permeability, it is preferably 120 or lower, more preferably 105 or lower, and even more preferably 95 or lower. From these viewpoints, the isocyanate index (INDEX) is preferably 60 to 120, more preferably 70 to 105, and even more preferably 75 to 95. The isocyanate index is calculated by dividing the number of moles of isocyanate groups in an isocyanate by the total number of moles of active hydrogen groups, such as hydroxyl groups in polyols and water as a foaming agent, and multiplying the result by 100. It is calculated as [NCO equivalents of isocyanate / active hydrogen equivalents × 100].

[0033] (3) Foaming agent The blowing agent can be water, a CFC substitute, or a hydrocarbon such as pentane, either alone or in combination. Water is particularly preferred as the blowing agent. In the case of water, carbon dioxide is generated during the reaction between the polyol and the isocyanate, and foaming occurs due to this carbon dioxide. The amount of water used as the blowing agent is preferably 0.5 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of polyol, more preferably 1.0 part by mass or more and 4.0 parts by mass or less, and even more preferably 2.0 parts by mass or more and 3.0 parts by mass or less.

[0034] (4) Catalyst A known catalyst for polyurethane foam can be used. Known urethane catalysts and / or foaming catalysts can be used. Examples of catalysts include amine catalysts such as N,N-dimethylcyclohexylamine, N-methyldicyclohexylamine, triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine, and tetramethylguanidine; tin catalysts such as stanus octoate and dibutyltin dilaurate; and metal catalysts (also called organometallic catalysts) such as phenylmercury propionate or lead octenoate. Amine catalysts and metal catalysts may be used in combination. Two or more types of amine catalysts and metal catalysts may be used. The amount of catalyst is preferably 0.1 parts by mass to 2.0 parts by mass, more preferably 0.2 parts by mass to 1.0 part by mass, and even more preferably 0.4 parts by mass to 0.6 parts by mass, per 100 parts by mass of the total polyol.

[0035] (5) Foam stabilizers The foam stabilizer can be any agent commonly used as a raw material for urethane foam, such as silicone compounds and nonionic surfactants. The amount of foam stabilizer is preferably 0.1 parts by mass to 4.0 parts by mass, more preferably 0.2 parts by mass to 3.0 parts by mass, and even more preferably 0.3 parts by mass to 2.0 parts by mass, per 100 parts by mass of the total amount of polyol.

[0036] (6) Crosslinking agents Crosslinking agents are added to improve the hardness and tear strength of polyurethane foam, and are particularly effective in increasing hardness. Note that crosslinking agents are optional components, and the rebound elasticity can be reduced without their addition. Examples of crosslinking agents include polyhydric alcohols such as trimethylolpropane, glycerin, 1,4-butanediol, and diethylene glycol, as well as amines such as ethanolamines and polyethylene polyamines. Two or more types of crosslinking agents may be used. The total amount of crosslinking agents is preferably 0.1 parts by mass to 10.0 parts by mass, more preferably 0.3 parts by mass to 5.0 parts by mass, and even more preferably 0.5 parts by mass to 3.0 parts by mass, per 100 parts by mass of the total amount of polyol.

[0037] (7) Other ingredients Other additives that may be added as appropriate include, for example, flame retardants and colorants.

[0038] Flame retardants are added to reduce the flammability of polyurethane foam. Examples of flame retardants include known liquid flame retardants and solid flame retardants. For example, halogenated polymers such as polyvinyl chloride, chloroprene rubber, and chlorinated polyethylene, phosphate esters and halogenated phosphate ester compounds, organic flame retardants such as melamine resin and urea resin, and inorganic flame retardants such as antimony oxide and aluminum hydroxide can be used. The flame retardant is not limited to one type, and two or more types may be used in combination. The total amount of flame retardants is preferably 0 to 10.0 parts by mass, more preferably 0.05 to 8.0 parts by mass, and even more preferably 0.1 to 6.0 parts by mass, per 100 parts by mass of the total amount of polyol. Colorants are added to the polyurethane foam to achieve the desired color, and those used are selected according to the required color. Examples of colorants include pigments and graphite.

[0039] 2. Physical properties of polyurethane foam The physical properties of the polyurethane foam can be appropriately set according to the application and other factors. Flexible polyurethane foam is preferred. The polyurethane foam preferably possesses the following physical properties.

[0040] (1) Apparent core density The apparent core density (JIS K7222) is 10 kg / m³. 3 More than 100kg / m 3 The following is preferable: 20 kg / m 3 More than 75kg / m 3 The following is more preferable: 30 kg / m 3 More than 50Kg / m 3 The following are even more preferable. (2) 25% hardness The 25% hardness (JIS K6400-2 Method D) is preferably 20N to 200N, more preferably 30N to 150N, and even more preferably 40N to 100N. (3) Rebound elasticity The rebound elasticity (JIS K6400-3) is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less. The rebound elasticity is usually 0% or more. (4) Compression residual strain The compressive residual strain (JIS K6400-4 4.5.2 Method A) is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less. Compression residual strain was calculated according to JIS K6400-4 4.5.2 Method A: the sample was compressed to 50% of its original thickness and left in a 70°C drying oven for 22 hours. After releasing the compression, the thickness was measured 30 minutes later, and the deformation (%) was calculated as the amount of deformation relative to the original thickness. (5) Air permeability The air permeability (JIS K6400-7 Method A: 2012) is preferably 50 L / min or more, more preferably 100 L / min or more, and even more preferably 150 L / min or more. The air permeability is usually 300 L / min or less.

[0041] 3. Reasons for the expected reduction in compressive residual strain The reason for the reduction in compressive residual strain in the polyurethane foam of this disclosure is not clear, but it is presumed to be as follows. However, this disclosure is not to be interpreted in any way as being limited by this presumption. By using a polyether polyol (A) with an EO unit content of 60 mol% or more, the number of side chains in the polyurethane molecule can be reduced, suppressing entanglement of polyurethane molecules when the polyurethane foam is compressed. As a result, it is presumed that when the polyurethane foam is compressed, strain caused by entanglement of polyurethane molecules will be less likely to occur, resulting in a lower compression residual strain.

[0042] 4. Method for manufacturing polyurethane foam Polyurethane foam can be produced by known foaming methods, which involve stirring and mixing a polyurethane resin composition to react a polyol with an isocyanate. Foaming methods include slab foaming and mold foaming, and any of these molding methods may be used. Slab foaming is a method in which a mixed polyurethane resin composition is discharged onto a belt conveyor and foamed under atmospheric pressure and at room temperature. On the other hand, mold foaming is a method of filling a mold with a mixed polyurethane resin composition and allowing it to foam within the mold. Molding by mold foaming is suitable for molded products with complex three-dimensional shapes. For example, it is suitable for molding cushioning materials such as seat pads, bedding such as pillows and mattresses, cushions, chair pads, and clothing pads.

[0043] 5. Uses of polyurethane foam The articles in which the polyurethane foam of this disclosure is used are not limited. The polyurethane foam is suitable for mattresses and is particularly suitable as a sheet pad for everyday items. A key performance requirement for everyday mattresses is pressure distribution. Reducing rebound elasticity is an effective way to improve pressure distribution. A key performance requirement for everyday mattresses is reduced stuffiness. Improving breathability is an effective way to reduce stuffiness during year-round use. For everyday mattresses, resistance to sagging is a key performance requirement. This resistance requires a high 25% hardness and low compression set. [Examples]

[0044] The present disclosure will be specifically described below with reference to examples. 1. Manufacturing of polyurethane foam Compositions were prepared using the proportions shown in Tables 1 and 2, and polyurethane foams for the examples and comparative examples were produced by slab foaming.

[0045] [Table 1]

[0046] [Table 2]

[0047] 2. Preparation of polyurethane foam (Examples 1-6 and Comparative Examples 1-5) Details of each raw material are as follows. Note that, assuming the total amount of alkylene oxide units in the polyether polyol is 100 mol%, the content of EO units (mol%) is shown as "EO rate" and the content of PO units (mol%) is shown as "PO rate" in the table. • Polymer polyol: Asahi Glass Urethane Co., Ltd.'s Exenol 941WF (an ether-based polymer polyol produced by graft polymerization of acrylonitrile and styrene solids onto a polyether polyol; 3 functional groups; viscosity 5100 mPa·s·25℃; hydroxyl value 32 mgKOH / g) • Polyether polyol (A): SBU Polyether Polyol S240, manufactured by Sumika Covestro Urethane Co., Ltd. (3 functional groups, weight-average molecular weight 5000, EO ratio 60 mol% or more, PO ratio 40 mol% or less: the sum of EO ratio and PO ratio is 100 mol%). • Polyether polyol (B): Manufactured by Asahi Denka Kogyo Co., Ltd., G-700 (3 functional groups, weight-average molecular weight 670, hydroxyl value 250 mgKOH / g, EO ratio 0 mol%, PO ratio 100 mol%) • Polyether polyol (C): Manufactured by Sanyo Chemical Industries, Ltd., GP3050NS (3 functional groups, weight-average molecular weight 3000, hydroxyl value 56 mgKOH / g, EO ratio 10 mol%, PO ratio 90 mol%) • Foaming agent: Water • Catalyst-1: Amine catalyst 1: DABCO NE300 manufactured by Evonik Japan Co., Ltd. • Catalyst-2: Amine catalyst 2 (triethylenediamine 33% by mass): DABCO 33LSI, manufactured by Evonik Japan Co., Ltd. • Foam stabilizer: Silicone-based foam stabilizer: SZ2904 manufactured by Toray Dow Corning Co., Ltd.

[0048] • MDI-1: Polymeric MDI (a mixture of 58% by mass of 4,4'-MDI, 20% by mass of 2,4'-MDI, and 20% by mass of polymethylene polyphenyl polyisocyanate) • MDI-2: Monomeric MDI (a mixture of 4,4'-MDI and 2,4'-MDI), manufactured by Nippon Polyurethane Co., Ltd., Millionate NM • TDI: Toluene diisocyanate, manufactured by Tosoh Corporation, Coronate T-80

[0049] (1) Status of satisfaction of each requirement in Examples 1-6 The compositions constituting the polyurethane foams of Examples 1-6 satisfy all of the following requirements (a)-(d). Requirement (a): The amount of polymer polyol added is greater than 10 parts by mass. Requirement (b): The amount of polyether polyol (A) added is 20 parts by mass or more. Requirement (c): The weight-average molecular weight of the polyether polyol (B) is 300 or more and less than 1500. Requirement (d): Contains polymeric MDI.

[0050] (2) Status of satisfaction of each requirement in Comparative Examples 1-5 In contrast, the compositions constituting the polyurethane foams of Comparative Examples 1-5 do not meet the following requirements. Comparative Example 1 does not meet requirement (c). Comparative Example 2 does not meet requirement (a). Comparative Example 3 does not meet requirement (a). Comparative Example 4 does not meet requirement (d). Comparative Example 5 does not meet requirement (d).

[0051] 3. Evaluation Method Test pieces were cut out from the polyurethane foam produced using the above raw materials, and the apparent core density, 25% hardness, resilience, compression residual strain, and air permeability were measured by the following methods. (1) Apparent Core Density (Kg / m 3 ) The apparent core density (Kg / m 3 ) was measured according to JIS K7222. The evaluation of the apparent core density was based on the following criteria. "A": 25 (Kg / m 3 ) or more and 45 (Kg / m 3 ) or less. "C": less than 25 (Kg / m 3 ), or greater than 45 (Kg / m 3 ). (2) 25% Hardness (N) The 25% hardness (N) was measured according to JIS K6400-2 D method. The evaluation of the 25% hardness (N) was based on the following criteria. "A": 40 (N) or more. "B": 20 (N) or more and 40 (N) or less. "C": less than 20 (N). (3) Resilience The resilience (%) was measured according to JIS K6400-3. The evaluation of the resilience (%) was based on the following criteria. "A": 15 (%) or less. "B": greater than 15 (%) and 25 (%) or less. "C": greater than 25 (%). (4) Compression Residual Strain The compression residual strain (%) was measured according to JIS K6400-4 4.5.2 A method. The evaluation of compressive residual strain (%) was based on the following criteria. "A": 5% or less. "B": Greater than 5% and less than or equal to 10%. "C": Greater than 10%. (5) Air permeability The airflow rate (L / min) was measured in accordance with JIS K6400-7 Method A:2012. The following criteria were used to evaluate the airflow rate (L / min). "A": 150 (L / min) or more. "B": 50 (L / min) or more. "C": Less than 50 (L / min). (6) Overall evaluation "A": All evaluation items (1)-(5) received an A rating. "B": The evaluation item (1)-(5) is rated as "A" or "B". "C": Any of the evaluation items (1)-(5) receive a "C" rating.

[0052] 4.Results The results are shown in Tables 1 and 2.

[0053] The overall evaluation result for the polyurethane foams of Examples 1-6, which satisfy all requirements (a)-(d), was A or B. The rebound elasticity of the polyurethane foams in Examples 1-6, which satisfied all requirements (a)-(d), was 25% or less in all cases. The air permeability of the polyurethane foams in Examples 1-6, which satisfy all requirements (a)-(d), was 50 L / min or more in all cases. The 25% hardness of the polyurethane foams in Examples 1-6, which satisfy all requirements (a)-(d), was 20N or higher.

[0054] 5. Discussion Example 1 showed 25% improvement in hardness, rebound elasticity, and compression residual strain compared to Comparative Example 5. The polyurethane foam of this disclosure significantly improves each of its properties by including polymethylene polyphenyl polyisocyanate. In particular, it is more preferable that the polyurethane foam of this disclosure contains polymethylene polyphenyl polyisocyanate in an amount of 15% to 30% by mass relative to the total amount of polymeric MDI. Examples 1, 2, and 3 showed improved air permeability compared to Examples 4, 5, and 6. It is more preferable that the isocyanate index of the urethane foam of this disclosure is between 75 and 95.

[0055] 6. Effects of the Examples According to the above examples, it is possible to provide a polyurethane foam that has sufficient rigidity while ensuring high breathability.

[0056] This disclosure is not limited to the embodiments detailed above, and various modifications or changes are possible within the scope of this disclosure.

Claims

1. A polyurethane foam obtained from a composition containing a polyol and an isocyanate, The aforementioned polyol includes, A polymer polyol obtained by polymerizing a vinyl monomer onto a polyether polyol, A polyether polyol (A) having a total amount of alkylene oxide units of 100 mol%, an ethylene oxide unit content of 60 mol% or more, and a weight-average molecular weight of 1000 to 20000, The polyether polyol (B) contains less than 60 mol% of ethylene oxide units when the total amount of alkylene oxide units is taken as 100 mol%, and has a weight-average molecular weight of 300 or more and less than 1500. When the total amount of the polyol is 100 parts by mass, The content of the polymer polyol is more than 10 parts by mass and 55 parts by mass or less. The content of the polyether polyol (A) is 20 parts by mass or more and 70 parts by mass or less. The aforementioned isocyanate contains polymeric MDI in this polyurethane foam.

2. The polyurethane foam according to claim 1, wherein the rebound elasticity in accordance with JIS K6400-3 is 25% or less.

3. The polyurethane foam according to claim 1, wherein the air permeability based on JIS K6400-7 Method A:2012 is 50 L / min or more.

4. The polyurethane foam according to claim 1, wherein the 25% hardness is 20 N or more, based on JIS K6400-2 Method D:2012.

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