Seat cushion

Abstract

The seat cushion includes a polyurethane foam, wherein the polyurethane foam exhibits a compressive residual strain [epsilon] 1 of 5.0% or less and a humid heat compressive residual strain [epsilon] 2 of 5.0% or less. "Compression residual strain [epsilon] 1" is a value measured in accordance with JIS K6400-4 (temperature 70 DEG C and compression ratio 50%). The wet and hot compression residual strain [epsilon] 2 is a value measured according to JIS K6400-4 (temperature of 50 DEG C, humidity of 95% RH and compression ratio of 50%). The polyurethane foam preferably has a 25% hardness of 150 N or more.

Description

Technical Field

[0001] The present invention relates to a seat pad, and more particularly, to a seat pad composed of a polyurethane foam having both small compressive residual strain and wet-heat compressive residual strain. Background Art

[0002] Automobile seats are classified into a type in which a seat cushion (seat surface portion) and a seat back (back surface portion) are separated from each other and a type in which both are integrated.

[0003] In addition, automotive seats usually include:

[0004] (a) a seat cushion designed to bear the load of an occupant when the occupant is seated;

[0005] (b) a frame for supporting a seat cushion; and

[0006] (c) A decorative cover covering the outer surface of the seat cushion.

[0007] Polyurethane foam is commonly used in seat cushions.

[0008] When an occupant sits on a car seat including a seat cushion, the seat cushion is compressed in the load direction in proportion to the magnitude of the load applied to the seat cushion. The magnitude of the load applied to the seat cushion varies depending on the shape of the car seat, the inclination of the seat back, the part of the human body in contact with the car seat, the posture of the occupant, and the uneven state of the road surface on which the car is traveling. Therefore, even when the shape of the seat cushion is optimized when not in use, residual strain (compression residual strain, wet heat compression residual strain) may be generated in the seat cushion due to the stuffiness, temperature, and compression stress during use, resulting in poor riding comfort of the seat.

[0009] In order to solve this problem, various proposals have been proposed in the past.

[0010] For example, Patent Document 1 discloses a seat pad which is not intended to reduce compressive residual strain and / or wet heat compressive residual strain but has different hardnesses along the thickness direction.

[0011] Patent Document 1 describes that the hardness of a seat pad varies along the thickness direction so that the weight of the seat pad can be reduced while suppressing a sense of shaking.

[0012] Patent Document 2 discloses a flexible polyurethane foam obtained by reacting raw materials including a polymer polyol (N) satisfying prescribed conditions, a polyether polyol (A1), and a polyisocyanate component (B).

[0013] Patent Document 2 records that this method provides a 25% compression hardness of 250 to 280 (N / 314 cm 2 ), flexible polyurethane foam with moderate hysteresis loss rate and reduced stress relaxation.

[0014] Patent Document 3 discloses a polyol composition comprising a polyether polyol (a1) satisfying prescribed conditions, a vinyl polymer (p), and a foam stabilizer composed of a low molecular weight siloxane (c1).

[0015] Patent Document 3 describes that use of such a polyol composition provides an elastic polyurethane foam having a low wet heat residual strain rate.

[0016] Patent Document 4 discloses a polyol component (a) comprising a polyether polyol (a1) satisfying prescribed conditions and a vinyl polymer (p).

[0017] Patent Document 4 describes that when such a polyol component (a), an organic polyisocyanate component (b) and water are subjected to a foaming reaction in the presence of a catalyst (c), an elastic polyurethane foam having a low wet heat residual strain rate is obtained.

[0018] Patent Documents 3 and 4 describe that the use of a polyol satisfying specific conditions reduces wet heat residual compressive strain when producing polyurethane foam. However, in general, when one of the wet heat residual compressive strain or the compressive residual strain decreases, the other tends to increase.

[0019] Prior art literature

[0020] Patent Literature

[0021] Patent Document 1: JP 2018-048246 A

[0022] Patent Document 2: JP 2019-031666 A

[0023] Patent Document 3: JP H09-100336 A

[0024] Patent document 4: JP H10-025328 A Summary of the invention

[0025] Problem that the invention aims to solve

[0026] An object of the present invention is to provide a seat pad which is composed of polyurethane foam and which has small both compression residual strain and wet heat compression residual strain.

[0027] Another object of the present invention is to provide a seat pad composed of polyurethane foam, having small both compression residual strain and wet heat compression residual strain and having moderate hardness.

[0028] Solutions for solving problems

[0029] In order to achieve the above object, the seat cushion according to the present invention comprises:

[0030] Polyurethane foam, and

[0031] The polyurethane foam has a compressive residual strain ε1 of 5.0% or less and a wet heat compressive residual strain ε2 of 5.0% or less.

[0032] "Compression residual strain ε1" refers to a value measured according to JIS K 6400-4 (temperature: 70°C, compression rate: 50%), and

[0033] The "wet heat compressive residual strain ε2" refers to a value measured in accordance with JIS K 6400-4 (temperature: 50°C, humidity: 95%RH, compression rate: 50%).

[0034] The polyurethane foam preferably has a 25% hardness of 150 N or more.

[0035] Preferably, the polyurethane foam is obtained by reacting a raw material mixture comprising a polyol component and a polyisocyanate component,

[0036] The polyol component comprises one or more polyether polyols A, wherein the polyether polyols A have:

[0037] (a) an EO content of 50 mol% or more,

[0038] (b) the number of functional groups is greater than 2.0 and less than 3.0, and

[0039] (c) a weight average molecular weight of 3000 or more, and

[0040] The polyisocyanate component comprises carbodiimide-modified MDI,

[0041] Provided that the case where the polyol component contains only a polyether polyol having the following (a) to (c) as the polyether polyol A is excluded,

[0042] (a) an EO content of 50 mol% or more,

[0043] (b) the number of functional groups is 2.0, and

[0044] (c) A weight average molecular weight of 3,000 or more.

[0045] Effects of the Invention

[0046] In the case of producing polyurethane foam, the use of a raw material mixture containing polyether polyol A and carbodiimide-modified MDI satisfying the specified conditions provides a polyurethane foam having both small compressive residual strain ε1 and wet heat compressive residual strain ε2. In addition, optimization of production conditions provides a polyurethane foam having a 25% hardness of 150N or more.

[0047] It is considered that the reduction in the compressive residual strain ε1 is due to the increase in the rigidity of the polyurethane foam caused by the use of the polyether polyol A having a large number of functional groups and a large weight average molecular weight.

[0048] It is considered that the reason why the wet heat compression residual strain ε2 is reduced is that the use of the polyether polyol A with a high EO content improves the water absorption and thus the restoring force by the absorbed water is improved.

[0049] Furthermore, it is considered that the hardness is moderately improved because the number of crosslinking points increases due to the use of the polyether polyol A having a large number of functional groups. DETAILED DESCRIPTION

[0050] Hereinafter, embodiments of the present invention will be described in detail.

[0051] [1. Seat cushion]

[0052] The seat cushion according to the present invention is composed of a polyurethane foam obtained by reacting a raw material mixture containing a polyol component and a polyisocyanate component. The raw material mixture generally further contains a crosslinking agent, a blowing agent and a catalyst.

[0053] [1.1. Polyurethane foam]

[0054] The polyurethane foam constituting the seat cushion is obtained by foaming and reacting a raw material mixture satisfying predetermined conditions. The details of the method for producing the polyurethane foam will be described later.

[0055] [1.2 Features]

[0056] [1.2.1. Compressive residual strain ε1]

[0057] "Compression residual strain ε1" refers to a value measured in accordance with JIS K 6400-4 (temperature: 70°C, time: 22 hours, compression rate: 50%).

[0058] The seat cushion according to the present invention is composed of a polyurethane foam obtained by reacting a raw material mixture satisfying prescribed conditions. Therefore, the polyurethane foam according to the present invention has a small compressive residual strain ε1. When the manufacturing conditions are optimized, the ε1 of the polyurethane foam is 5.0% or less. When the manufacturing conditions are further optimized, ε1 is 4.0% or less, or 3.5 or less.

[0059] [1.2.2. Hygrothermal compression residual strain ε2]

[0060] The "wet heat compressive residual strain ε2" refers to a value measured in accordance with JIS K 6400-4 (temperature: 50°C, humidity: 95% RH, time: 22 hours, compression rate: 50%).

[0061] The seat cushion according to the present invention is composed of a polyurethane foam obtained by reacting a raw material mixture that satisfies prescribed conditions. Therefore, the polyurethane foam according to the present invention has a small wet heat compressive residual strain ε2. When the manufacturing conditions are optimized, the ε2 of the polyurethane foam is 5.0% or less. When the manufacturing conditions are further optimized, ε2 is 4.0% or less, 3.5% or less, 3.0% or less, or 2.0% or less.

[0062] [1.2.3. Strain ratio ε2 / ε1]

[0063] The “strain ratio ε2 / ε1” refers to the ratio of the wet heat compressive residual strain ε2 to the compressive residual strain ε1.

[0064] In conventional polyurethane foams, when one of the compressive residual strain ε1 or the wet heat compressive residual strain ε2 decreases, the other generally increases. Therefore, conventional polyurethane foams generally have a strain ratio ε2 / ε1 of 1.0 or more.

[0065] On the other hand, the seat cushion according to the present invention is composed of a polyurethane foam obtained by reacting a raw material mixture that satisfies prescribed conditions. Therefore, both ε1 and ε2 of the polyurethane foam according to the present invention are small. In particular, the polyurethane foam according to the present invention is characterized in that the wet heat compression residual strain ε2 is smaller than the compression residual strain ε1. As a result, ε2 / ε1 is less than 1.0. When the manufacturing conditions are further optimized, ε2 / ε1 is 0.03 or more and 0.8 or less.

[0066] [1.2.4.25% hardness]

[0067] "25% hardness" refers to a value measured according to JIS K 6400-2D method (diameter of a pressing plate: 200 mm).

[0068] In the past, soft polyurethane foams with good vibration absorption generally have high density. However, when such soft polyurethane foams are used as seat cushions, the weight of the vehicle may be increased in some cases. In order to solve this problem, when the density of the soft polyurethane foam is simply reduced, the hardness of the foam is reduced. As a result, the repulsion elasticity becomes too small, and the cushioning property is deteriorated in some cases.

[0069] On the other hand, the seat cushion according to the present invention is composed of a polyurethane foam obtained by reacting a raw material mixture that satisfies prescribed conditions. Therefore, the polyurethane foam according to the present invention has a moderate hardness. When the manufacturing conditions are optimized, the 25% hardness of the polyurethane foam is 150N or more. When the manufacturing conditions are further optimized, the 25% hardness is 170N or more, or 190N or more. Due to this hardness, even if the seat cushion is thinner than a conventional seat cushion, the seat cushion has excellent vibration absorption, has good riding comfort, and can reduce weight.

[0070] On the other hand, if the 25% hardness of the polyurethane foam is too high, the riding comfort of the seat may be deteriorated. Therefore, the 25% hardness is preferably 350N or less.

[0071] [1.2.5. Hysteresis loss]

[0072] The "hysteresis loss" refers to a value measured according to JIS K 6400-2E method.

[0073] The seat cushion according to the present invention is composed of a polyurethane foam obtained by reacting a raw material mixture satisfying prescribed conditions. Therefore, the polyurethane foam according to the present invention exhibits moderate hysteresis loss. When the manufacturing conditions are optimized, the hysteresis loss of the polyurethane foam is 5 to 30%.

[0074] [1.2.6. Flexural coefficient]

[0075] The "flex coefficient" refers to a value measured according to JIS K 6400-2:2012. More specifically, the "flex coefficient" refers to the force (F) at 65% compression when the pre-compression is performed at a constant speed to 75% after 75%. 65％ ) divided by the force at 25% compression (F 25％ ) and the value obtained (=F 65％ / F 25％ ).

[0076] The seat cushion according to the present invention is composed of a polyurethane foam obtained by reacting a raw material mixture that satisfies specified conditions. Therefore, the polyurethane foam according to the present invention has a small flexural coefficient. When the manufacturing conditions are optimized, the flexural coefficient of the polyurethane foam is 2.8 or less. When the manufacturing conditions are further optimized, the flexural coefficient is 2.7 or less, 2.6 or less, or 2.5 or less.

[0077] [1.2.7. Stress relaxation]

[0078] "Stress relaxation" refers to a value measured in accordance with JIS K 6400-2 (load: 196 N, 5 min).

[0079] The seat cushion according to the present invention is composed of a polyurethane foam obtained by reacting a raw material mixture that satisfies specified conditions. Therefore, the polyurethane foam according to the present invention has low stress relaxation. When the manufacturing conditions are optimized, the stress relaxation of the polyurethane foam is 2 to 20%.

[0080] [1.2.8. Density]

[0081] "Density" refers to a value measured in accordance with JIS K7222.

[0082] In order to reduce the weight of the seat cushion, the density of the polyurethane foam is preferably 68kg / m 3 The density is more preferably 66 kg / m 3 the following.

[0083] [2. Method for producing polyurethane foam]

[0084] The polyurethane foam constituting the seat cushion is obtained by:

[0085] (a) preparing a raw material mixture comprising a polyol component and a polyisocyanate component; and

[0086] (b) reacting the raw material mixture.

[0087] Typically, the raw material mixture further comprises a crosslinking agent, a blowing agent and a catalyst.

[0088] [2.1. Main raw materials]

[0089] [2.1.1. Polyol component]

[0090] Polyol component is one of the main raw materials of polyurethane foam.

[0091] In the present invention, the polyol component comprises a polyether polyol A, wherein the polyether polyol A has:

[0092] (a) an EO content of 50 mol% or more,

[0093] (b) the number of functional groups is greater than 2.0 and less than 3.0, and

[0094] (c) A weight average molecular weight of 3,000 or more.

[0095] The polyol component may contain one polyether polyol A satisfying the above conditions, or may contain two or more polyether polyols A satisfying the above conditions.

[0096] Provided that the case where the polyol component contains only a polyether polyol having the following (a) to (c) as the polyether polyol A is excluded,

[0097] (a) an EO content of 50 mol% or more,

[0098] (b) the number of functional groups is 2.0, and

[0099] (c) A weight average molecular weight of 3,000 or more.

[0100] The polyol component may further comprise a polyether polyol B having:

[0101] (a) an EO content of 30 mol% or less, and

[0102] (b) The number of functional groups is greater than 2.0.

[0103] The polyol component may contain one polyether polyol B satisfying the above conditions, or may contain two or more polyether polyols B satisfying the above conditions.

[0104] [A. Polyether polyol A]

[0105] [A.1.EO content]

[0106] The “EO content (mol %)” of the polyether polyol A refers to the ratio of the number of moles of ethylene oxide (EO) units contained in the polyether polyol A to the total number of moles of alkylene oxide units.

[0107] The polyether polyol A may contain an alkylene oxide unit other than the EO unit. In this case, the type of the alkylene oxide unit other than the EO unit is not particularly limited, but is preferably a propylene oxide (PO) unit.

[0108] The EO content of polyether polyol A mainly affects the wet heat compression residual strain ε2. Generally, as the EO content increases, ε2 decreases. This is believed to be because:

[0109] (a) Since the EO unit is hydrophilic, the higher the EO content, the better the water absorption of the polyurethane foam, and the absorbed water helps to restore the compressed and deformed polyurethane foam to its original shape, and

[0110] (b) Unlike polyester polyol, polyether polyol is not easily hydrolyzed under high humidity environment, and ε2 is not easily degraded.

[0111] In order to obtain such an effect, the EO content of polyether polyol A is preferably 50.0 mol% or more. The EO content is more preferably 60.0 mol% or more, 70.0 mol% or more, 80.0 mol% or more, or 90.0 mol% or more. The EO content of polyether polyol A may be 100.0 mol%.

[0112] [A.2. Number of functional groups]

[0113] The number of functional groups of polyether polyol A affects the compressive residual strain ε1. Generally speaking, as the number of functional groups increases, ε1 becomes smaller. This is believed to be because as the number of functional groups increases, the number of crosslinking points increases, and the rigidity of the polyurethane foam increases. In order to obtain such an effect, the number of functional groups of polyether polyol A is preferably 2.0 or more. The number of functional groups is more preferably 2.1 or more, or 2.2 or more.

[0114] On the other hand, an excessive number of functional groups in the polyether polyol A may excessively increase the hardness of the polyurethane foam. Therefore, the number of functional groups is preferably 3.0 or less. The number of functional groups is more preferably 2.9 or less, or 2.8 or less.

[0115] [A.3. Weight average molecular weight]

[0116] If the weight average molecular weight of polyether polyol A is too small, the compressive residual strain ε1 and / or the wet heat residual strain ε2 may be deteriorated. Therefore, the weight average molecular weight is preferably 3000 or more. The weight average molecular weight is more preferably 4000 or more, or 5000 or more.

[0117] On the other hand, if the weight average molecular weight of polyether polyol A is too large, the viscosity of the raw material mixture may be excessively increased, resulting in deterioration of manufacturability. In addition, the reactivity of the raw material mixture may be reduced, and the tear strength of the polyurethane foam may be reduced. Therefore, the weight average molecular weight is preferably less than 12000. The weight average molecular weight is more preferably less than 10000, or less than 8000.

[0118] [A.4. Hydroxyl value]

[0119] If the hydroxyl value of the polyether polyol A is too large, the riding comfort of the seat cushion may be deteriorated. Therefore, the hydroxyl value is preferably 70 mgKOH / g or less. The hydroxyl value is more preferably 60 mgKOH / g or less, or 55 mgKOH / g or less.

[0120] On the other hand, if the hydroxyl value of polyether polyol A is too small, the polyurethane foam may be over-hardened, so that good riding comfort cannot be maintained when the polyurethane foam is used as a seat cushion. Therefore, the hydroxyl value is preferably 10 mgKOH / g or more. The hydroxyl value is more preferably 15 mgKOH / g or more, or 20 mgKOH / g or more.

[0121] [B. Polyether polyol B]

[0122] [B.1.EO content]

[0123] The “EO content (mol %)” of the polyether polyol B means the ratio of the number of moles of ethylene oxide (EO) units contained in the polyether polyol B to the total number of moles of alkylene oxide units.

[0124] The polyether polyol B may contain an alkylene oxide unit other than the EO unit. In this case, the kind of the alkylene oxide unit other than the EO unit is not particularly limited, but is preferably a propylene oxide (PO) unit.

[0125] Too high EO content of polyether polyol B may reduce the reactivity of the raw material mixture. In addition, the foam state and the air permeability of the foam may deteriorate. Therefore, the EO content is preferably 30 mol% or less. The EO content is more preferably 20 mol% or less, 10 mol% or less, or 5 mol% or less. The EO content may be zero.

[0126] [B.2. Number of functional groups]

[0127] The number of functional groups of the polyether polyol B may be 2.0 or more.

[0128] However, if the number of functional groups of polyether polyol B is too large, the elongation of polyurethane foam may be reduced. Therefore, the number of functional groups is preferably 4.0 or less. The number of functional groups is more preferably 3.8 or less, or 3.6 or less.

[0129] [B.3. Weight average molecular weight]

[0130] The weight average molecular weight of polyether polyol B is not particularly limited, and an optimal value can be selected according to the purpose. Generally, too small a weight average molecular weight of polyether polyol B may impair the elongation and flexibility of the polyurethane foam. Therefore, the weight average molecular weight is preferably 1000 or more. The weight average molecular weight is more preferably 2000 or more, or 3000 or more.

[0131] On the other hand, if the weight average molecular weight of the polyether polyol B is too large, the viscosity of the raw material mixture may be excessively increased, resulting in deterioration of manufacturability. Therefore, the weight average molecular weight is preferably 12000 or less. The weight average molecular weight is more preferably 10000 or less, or 8000 or less.

[0132] [2.1.2. Polyisocyanate component]

[0133] Polyisocyanate component is another main raw material of polyurethane foam.

[0134] In the present invention, the polyisocyanate component contains at least carbodiimide-modified MDI. The polyisocyanate component may contain only carbodiimide-modified MDI, or may further contain a polyisocyanate other than carbodiimide-modified MDI (hereinafter, also referred to as "polyisocyanate B").

[0135] [A. Carbodiimide-modified MDI]

[0136] Carbodiimide (—N═C═N—)-modified MDI consists of products produced by condensation of —NCO groups of diphenylmethane diisocyanate (MDI) to form CO 2 in the presence of a catalyst.

[0137] The use of carbodiimide-modified MDI as the polyisocyanate component increases the cushioning properties of the polyurethane foam, increases elasticity, reduces hysteresis losses, reduces the flexural modulus or reduces stress relaxation.

[0138] [B. Polyisocyanate B]

[0139] In the present invention, the kind of polyisocyanate B is not particularly limited, and the optimal polyisocyanate B can be selected according to the purpose.

[0140] Specific examples of the polyisocyanate B include difunctional aromatic isocyanates, difunctional alicyclic isocyanates, difunctional aliphatic isocyanates, and isocyanates having a functional group number greater than 2. The polyisocyanate component may contain any one of these polyisocyanates B, or may contain two or more thereof.

[0141] Examples of difunctional aromatic isocyanates include:

[0142] 2,4-Toluene diisocyanate, 2,6-Toluene diisocyanate,

[0143] Isocyanate, p-phenylene diisocyanate,

[0144] 4,4'-diphenylmethane diisocyanate (4,4'-MDI),

[0145] 2,4'-diphenylmethane diisocyanate (2,4'-MDI),

[0146] 2,2'-diphenylmethane diisocyanate (2,2'-MDI),

[0147] Xylylene diisocyanate,

[0148] 3,3'-dimethyl-4,4'-biphenyl diisocyanate, and

[0149] 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, and a mixture thereof may be used.

[0150] Examples of difunctional alicyclic isocyanates include:

[0151] Cyclohexane-1,4-diisocyanate, isophorone diisocyanate,

[0152] Dicyclohexylmethane-4,4'-diisocyanate, and

[0153] Methylcyclohexane diisocyanate.

[0154] Examples of difunctional aliphatic isocyanates include:

[0155] Butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, and lysine isocyanate. Examples of difunctional or higher isocyanates include polymeric MDI and trifunctional or higher isocyanates.

[0156] Examples of trifunctional or higher isocyanates include:

[0157] 1-Methylbenzene-2,4,6-triisocyanate,

[0158] 1,3,5-Trimethylbenzene-2,4,6-triisocyanate,

[0159] Biphenyl-2,4,4'-triisocyanate,

[0160] Diphenylmethane-2,4,4'-triisocyanate,

[0161] Methyl diphenylmethane-4,6,4'-triisocyanate,

[0162] 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, and

[0163] Triphenylmethane-4,4′,4″-triisocyanate.

[0164] [C. NCO group content (NCO%)]

[0165] The “NCO group content (NCO%)” refers to the ratio of the mass of the NCO group to the total mass of the polyisocyanate component.

[0166] The NCO% of the polyisocyanate component is preferably less than 35%, more preferably less than 30%, and still more preferably 29.5% or less.

[0167] [2.1.3. Cross-linking agent]

[0168] The raw material mixture may contain a cross-linking agent. The cross-linking agent is preferably a compound having at least 3 functional groups and containing a functional group having an active hydrogen atom (e.g., a hydroxyl group or an amino group). The cross-linking agent may consist only of a compound having at least 3 functional groups, or may further contain a compound having at least 2 functional groups in addition to a compound having at least 3 functional groups.

[0169] The number of functional groups of the crosslinking agent affects the compressive residual strain ε1. In order to obtain a polyurethane foam having a small compressive residual strain ε1, the number of functional groups of the crosslinking agent is preferably 3 or more.

[0170] On the other hand, if the number of functional groups of the crosslinking agent is too large, the hardness of the polyurethane foam may be excessively increased. Therefore, the number of functional groups of the crosslinking agent is preferably 6 or less.

[0171] The molecular weight of the crosslinking agent is not particularly limited, and an optimal value can be selected according to the purpose. The molecular weight of the crosslinking agent is preferably 1000 or less, 700 or less, or 500 or less.

[0172] The molecular weight of the cross-linking agent is preferably 60 or more, 90 or more, or 120 or more.

[0173] Examples of the cross-linking agent include glycerol, diethanolamine (DEA), and multifunctional polyols.

[0174] The raw material mixture may contain any one of these cross-linking agents, or may contain two or more thereof.

[0175] [2.1.4. Foaming agent]

[0176] The "foaming agent" refers to an additive for generating bubbles in the raw material mixture during the process of resinifying the liquid raw material mixture.

[0177] In the present invention, the blowing agent may be:

[0178] (a) physical blowing agents that generate gas by reducing pressure or heating, or

[0179] (b) Chemical blowing agents that generate gas by thermal decomposition or chemical reaction.

[0180] Examples of physical blowing agents include:

[0181] (a) hydrocarbons such as cyclopentane, isopentane and n-pentane, and

[0182] (b) Halogen compounds such as dichloromethane, trichlorofluoromethane, dichlorodifluoromethane, nonafluorobutyl methyl ether, pentafluoroethyl methyl ether and pentafluoroisopropyl methyl ether.

[0183] Examples of chemical blowing agents include:

[0184] (a) water which reacts with the isocyanate groups to produce CO2, and

[0185] (b) Azodicarbonamides which generate nitrogen, carbon monoxide, carbon dioxide or ammonia by thermal decomposition.

[0186] The raw material mixture may contain any one of these foaming agents, or may contain two or more thereof.

[0187] Among them, the blowing agent is preferably water. When water is used as the blowing agent, CO2 gas generated by the reaction between water and isocyanate groups promotes foaming. The reaction heat between water and isocyanate groups promotes the curing of the resin.

[0188] [2.1.5. Catalyst]

[0189] The "catalyst" refers to a catalyst having a large effect of accelerating the resinification reaction and / or a catalyst having a large effect of accelerating the foaming reaction.

[0190] When a chemical blowing agent (water) is not used as the blowing agent, it is preferred to use a catalyst having a large effect of accelerating the resinification reaction.

[0191] Examples of the catalyst include amine catalysts and metal catalysts. Amine catalysts are catalysts that have a large effect of promoting both resinification reaction and foaming reaction. Metal catalysts are catalysts that have a large effect of promoting resinification reaction. The raw material mixture may contain any one of these catalysts, or may contain two or more thereof.

[0192] Examples of amine-based catalysts include:

[0193] N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine,

[0194] N,N-dimethylaminoethanol,

[0195] N,N',N'-trimethylaminoethylpiperazine and triethylenediamine.

[0196] Examples of metal catalysts include:

[0197] (a) tin catalysts, such as stannous octoate and dibutyltin dilaurate,

[0198] (b) a mercury catalyst, such as phenylmercuric propionate, and

[0199] (c) Lead catalysts, for example lead octoate.

[0200] [2.2. Auxiliary materials]

[0201] The raw material mixture may further contain one or more of the following auxiliary raw materials in addition to the above main raw materials. Specific examples of the auxiliary raw materials are as follows.

[0202] [2.2.1. Foam stabilizer]

[0203] The term "foam stabilizer" refers to an additive that has the function of making the size and distribution of bubbles uniform.

[0204] Adding a foam stabilizer to the raw material mixture can provide a polyurethane foam having uniform size and distribution of bubbles. Examples of the foam stabilizer include silicone-based foam stabilizers, fluorine-containing compound-based foam stabilizers, and well-known surfactants.

[0205] [2.2.2. Flame retardant]

[0206] The "flame retardant" refers to an additive having a function of making polyurethane foam flame-retardant.

[0207] Examples of the flame retardant include halogen-based flame retardants, phosphorus-based flame retardants, metal hydroxide-based flame retardants, and antimony-based flame retardants.

[0208] [2.3. Compounding amount and content]

[0209] [2.3.1. Compounding amount and content of main raw materials]

[0210] [A. Compounding amount of polyether polyol A]

[0211] The “compounding amount (parts by mass) of the polyether polyol A” means the total mass of the polyether polyol A in the polyol component when the total mass of the polyol component is 100.

[0212] Generally, the wet heat compression residual strain ε2 of the polyurethane foam decreases as the blending amount of polyether polyol A increases. In order to obtain such an effect, the blending amount of polyether polyol A is preferably 50 parts by mass or more. The blending amount is more preferably 60 parts by mass or more, or 70 parts by mass or more.

[0213] The blending amount of polyether polyol A may be 100 parts by mass. However, an excessive blending amount of polyether polyol A may deteriorate the moldability of the foam. Therefore, the blending amount of polyether polyol A is preferably 90 parts by mass or less.

[0214] [B. Content of carbodiimide-modified MDI]

[0215] The “content (mass %) of the carbodiimide-modified MDI” refers to the ratio of the mass of the carbodiimide-modified MDI to the total mass of the polyisocyanate component.

[0216] Generally, as the content of carbodiimide-modified MDI is higher, the stress relaxation and hysteresis loss of the polyurethane foam are reduced. In order to obtain such an effect, the content of carbodiimide-modified MDI is preferably 50% by mass or more. This content is more preferably 60% by mass or more, or 70% by mass or more.

[0217] The content of the carbodiimide-modified MDI may be 100% by mass, but the content of the carbodiimide-modified MDI is preferably 90% by mass or less, or 80% by mass or less.

[0218] The NCO content of the carbodiimide-modified MDI is preferably 40% or less, 35% or less, or 32% or less, and particularly preferably 30% or less. The NCO content is preferably 15% or more, 20% or more, 25% or more, or 27% or more.

[0219] [C. Amount of crosslinking agent A blended]

[0220] The “compounding amount (parts by mass) of the crosslinking agent A” means the mass of the crosslinking agent A when the total mass of the polyol component is 100.

[0221] Generally, the compressive residual strain ε1 of the polyurethane foam decreases as the content of the crosslinking agent A increases. To obtain such an effect, the amount of the crosslinking agent A is preferably greater than 0 parts by mass. The amount is more preferably 1.0 parts by mass or more, or 2.0 parts by mass or more.

[0222] On the other hand, an excessive amount of the crosslinking agent A may excessively increase the hardness of the polyurethane foam. Therefore, the amount of the crosslinking agent A is preferably 10 parts by mass or less. More preferably, the amount is 8 parts by mass or less, or 6 parts by mass or less.

[0223] [D. Amount of polyether polyol B blended]

[0224] The “compounding amount (parts by mass) of the polyether polyol B” means the total mass of the polyether polyol B in the polyol component when the total mass of the polyol component is 100.

[0225] Generally, the amount of polyether polyol B added is excessive, so that the amount of polyether polyol A added is relatively reduced. Therefore, the wet heat compression residual strain ε2 of the polyurethane foam may increase. Therefore, the amount of polyether polyol B added is preferably less than 50 parts by mass. The amount is more preferably 40 parts by mass or less, or 30 parts by mass or less.

[0226] [E. Isocyanate index]

[0227] The "isocyanate index" refers to a value obtained by multiplying by 100 the ratio of the equivalent weight of isocyanate groups of the polyisocyanate in the raw material mixture to the equivalent weight of active hydrogen groups in the raw material mixture.

[0228] In the present invention, the isocyanate index is not particularly limited, and an optimal value can be selected according to the purpose. Generally, as the isocyanate index increases, the compressive residual strain ε1 of the polyurethane foam decreases due to the increase in the number of crosslinking points. Therefore, the isocyanate index is preferably 90 or more. The isocyanate index is more preferably 95 or more.

[0229] On the other hand, if the isocyanate index is too large, the hardness of the polyurethane foam may be excessively increased. Therefore, the isocyanate index is preferably 115 or less.

[0230] [2.3.2. Amount of auxiliary raw materials added]

[0231] In the present invention, the compounding amount of the auxiliary raw material is not particularly limited, and an optimum compounding amount can be selected according to the purpose.

[0232] [2.4. Reaction of raw material mixture]

[0233] As foaming in the method for producing the polyurethane foam according to the present invention, slab foaming or mold foaming may be adopted.

[0234] The slab foaming is a method in which a composition for producing polyurethane foam (raw material of polyurethane foam) is mixed, discharged onto a belt conveyor, and foamed at normal temperature and atmospheric pressure.

[0235] On the other hand, die foaming is a method of mixing and injecting raw materials for polyurethane foam production (raw materials of polyurethane foam) into a cavity of a mold (die) and foaming to form the cavity shape. From the viewpoint of obtaining a polyurethane foam having a shape close to that of a seat cushion, die foaming is preferred.

[0236] In the case of mold forming, the polyisocyanate preferably has a low viscosity, and, for example, a prepolymer type polyisocyanate is not preferred.

[0237] [3. Function]

[0238] In the case of producing polyurethane foam, using a raw material mixture containing polyether polyol A and carbodiimide-modified MDI satisfying specified conditions provides a polyurethane foam having both small compressive residual strain ε1 and wet heat compressive residual strain ε2. In addition, optimization of production conditions provides a polyurethane foam having a 25% hardness of 150N or more.

[0239] It is considered that the compressive residual strain ε1 is reduced because the rigidity of the polyurethane foam is improved due to the use of the polyether polyol A having a large number of functional groups and a large weight average molecular weight.

[0240] It is considered that the reason why the wet heat compression residual strain ε2 is reduced is that the use of the polyether polyol A with a high EO content improves the water absorption and thus improves the restoring force by the absorbed water.

[0241] Furthermore, it is considered that the hardness is moderately improved because the number of crosslinking points is increased due to the use of polyether polyol A having a large number of functional groups.

[0242] [Example]

[0243] (Examples 1 to 3 and Comparative Examples 1 and 2)

[0244] [1. Sample preparation]

[0245] A polyether polyol, a crosslinking agent, a foaming agent, a catalyst, a foam stabilizer, and a flame retardant are compounded in a prescribed ratio to obtain a mixed liquid (hereinafter, also referred to as "component A").

[0246] Separately, TDI-80, polymeric MDI, and MDI containing carbodiimide-modified MDI (NCO content: 29%, carbodiimide-modified MDI content: 75% by mass) were blended at a predetermined ratio to obtain a mixed solution (hereinafter also referred to as "component B").

[0247] Further, component A and component B are mixed so that the isocyanate index reaches a prescribed value to obtain a raw material mixture. Table 1 shows the compositions of component A and component B.

[0248] [Table 1]

[0249] <Composition of Polyol Side Component A (Parts by Mass)>

[0250]

[0251] <Composition of Isocyanate Side Component B (Parts by Mass)>

[0252] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Isocyanate TDI-80 80 Polymeric MDI 20 5 5 5 5 MDI containing carbodiimide-modified MDI 95 95 95 95 Total of isocyanate side component B 100 100 100 100 100

[0253] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 index[-] 85 105 105 105 105 Amount of component B used relative to 100g of component A [g] 496 47.6 48.9 49.3 56.6

[0254] Examples 1 and 2 are examples using a mixture of the following (a) and (b) as polyether polyol A.

[0255] (a) polyether polyol 2 (molecular weight: 4000, number of functional groups: 2, EO content: 80 mol%) and

[0256] (b) Polyether polyol 3 (molecular weight: 5000, number of functional groups: 3, EO content: 80 mol %).

[0257] Example 3 is an example in which only polyether polyol 4 (molecular weight: 3500, number of functional groups: 3, EO content: 75 mol%) is used as polyether polyol A.

[0258] The obtained raw material mixture was injected into a die of 400 mm×400 mm×100 mm, and foamed and cured at a die temperature of about 60° C. The curing time was set to 5 minutes.

[0259] [2. Test method]

[0260] [2.1. Core density]

[0261] The surface layer was removed from the obtained foam to prepare a sample for measuring the core density. The core density was measured in accordance with JISK 7222 using the obtained sample.

[0262] [2.2.25% hardness]

[0263] The 25% hardness was measured according to JIS K 6400-2 D method.

[0264] [2.3. Hysteresis loss]

[0265] The hysteresis loss was measured according to JIS K 6400-2 E method.

[0266] [2.4. Flexural coefficient]

[0267] The flexural coefficient was measured according to JIS K 6400-2 Method E. The flexural coefficient was determined by dividing the 65% compression load by the 25% compression load.

[0268] [2.5. Stress relaxation]

[0269] Stress relaxation was determined in accordance with JIS K 6400-4. The load was set to 196 N, and the pressurization time was set to 5 minutes.

[0270] [2.6. Compressive residual strain ε1]

[0271] The compressive residual strain ε1 was measured according to JIS K 6400-4. The test temperature was set to 70° C., the test time was set to 22 hours, and the compression ratio was set to 50%.

[0272] [2.7. Hygrothermal compression residual strain ε2]

[0273] The wet heat compressive residual strain ε2 was measured according to JIS K 6400-4. The test temperature was set to 50°C, the humidity was set to 95% RH, the test time was set to 22 hours, and the compression rate was set to 50%.

[0274] [3. Results]

[0275] The results are shown in Table 2. Table 2 also shows the test piece dimensions and the evaluation test methods of each physical property value. From Table 2, the following matters can be seen.

[0276] (1) Comparative Example 1 showed that the wet heat compression residual strain ε2 was larger than 5.0%. This is considered to be because the raw material mixture did not contain the polyether polyol A having an EO content of 50 mol% or more.

[0277] (2) Comparative Example 2 showed a compressive residual strain ε1 of more than 5.0%. This is considered to be because the raw material mixture did not contain the polyether polyol A having a functional group number of more than 2.0.

[0278] (3) All of Examples 1 to 3 showed that ε1 was 5.0% or less and ε2 was 5.0% or less. This is considered to be because the raw material mixture contains polyether polyol A that satisfies the specified conditions. Examples 1 to 3 showed a low ε1 of 68 kg / m 3 The density is below 100%, and it also has excellent flexural modulus and hysteresis loss.

[0279] (4) Compared with Example 3, ε1 and ε2 of Examples 1 and 2 are reduced.

[0280] [Table 2]

[0281] project unit Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Core density kg / m3 56.8 64.5 65.2 65.1 64.8 25% hardness N 224 223 206 194 227 Hysteresis loss ％ 18.6 14.1 15.2 15.1 27.7 Flexural coefficient - 2.99 2.36 2.65 2.61 2.41 Stress relaxation ％ 10.7 6.2 6.2 6.5 16.3 Compressive residual strain ％ 1.9 8.5 2.7 2.4 3.4 Hygrothermal compression residual strain ％ 7.2 0.2 0.4 0.6 1.6

[0282] project unit Evaluation test method Other / Detailed Information Test piece size mm (length x width x thickness) 400×400×100 Core density kg / m3 JIS K 7222 Measured on the core part with the skin removed 25% hardness N JIS K 6400-2D method 400×400×100 Hysteresis loss ％ JIS K 6400-2E method Flexural coefficient - JIS K 6400-2E method The value obtained by dividing 65% compressive load by 25% compressive load Stress relaxation ％ JIS K 6400-2 Load: 196N, 5 minutes Compressive residual strain ％ JIS K 6400-4 Hygrothermal compression residual strain ％ JIS K 6400-4

[0283] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments at all, and various modifications can be made within the scope not departing from the gist of the present invention.

[0284] Industrial Applicability

[0285] The seat cushion according to the present invention can be used as a seat cushion for seats of automobiles, airplanes, and railway vehicles, a sofa, a mattress, and a cushioning material thereof.

Claims

1. A seat cushion comprising polyurethane foam, The polyurethane foam has a compressive residual strain ε1 of 5.0% or less and a wet heat compressive residual strain ε2 of 5.0% or less, wherein the "compression residual strain ε1" refers to a value measured according to JIS K 6400-4 (temperature: 70°C, compression rate: 50%), and The “wet heat compressive residual strain ε2” refers to a value measured according to JIS K 6400-4 (temperature: 50° C., humidity: 95% RH, compression rate: 50%).

2. The seat cushion according to claim 1, wherein the polyurethane foam has a 25% hardness of 150N or more, The "25% hardness" mentioned herein refers to a value measured according to JIS K 6400-2D method.

3. The seat cushion according to claim 1, wherein The polyurethane foam is obtained by reacting a raw material mixture comprising a polyol component and a polyisocyanate component, The polyol component comprises one or more polyether polyols A, wherein the polyether polyols A have: (a) an EO content of 50 mol% or more, (b) the number of functional groups is greater than 2.0 and less than 3.0, and (c) a weight average molecular weight of 3000 or more, and The polyisocyanate component includes carbodiimide-modified MDI, Provided that the polyol component excludes the case where the polyol component contains only the polyether polyol having the following (a) to (c) as the polyether polyol A, (a) an EO content of 50 mol% or more, (b) the number of functional groups is 2.0, and (c) A weight average molecular weight of 3,000 or more.

4. The seat cushion according to claim 3, wherein the polyol component further comprises one or more polyether polyols B, wherein the polyether polyols B have: (a) an EO content of 30 mol% or less, and (b) The number of functional groups is greater than 2.0.

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