Seat cushion

Abstract

The seat cushion comprises polyurethane foam. The polyurethane foam has a deflection coefficient of 2.8 or less and a displacement rate of 30% or more (= t1 * 100 / t0). T0 is the thickness of the flat plate-shaped sample cut from the polyurethane foam, and t1 is the maximum value of the displacement (sinkage) of the iron test plate when the attenuation characteristic is measured according to JASO B408 by using the flat plate-shaped sample. It is preferable that the displacement rate of the seat cushion is 45% or more when t0 = 50 mm.

Description

Technical Field

[0001] The present invention relates to a seat cushion, and more particularly, to a seat cushion including a polyurethane foam having a small flexural coefficient and a high displacement rate. 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, an inappropriate deflection coefficient and deflection amount (or displacement rate) of the seat cushion may result 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 flexible polyurethane foam for automobile seats, which is obtained by reacting raw materials including the following:

[0011] (a) 60 parts by mass of a polyol A obtained by reacting an ethylene oxide / propylene oxide mixture containing 8% by mass of ethylene oxide with a compound having a hydroxyl value of 168 mgKOH / g obtained by adding propylene oxide to glycerol (initiator 1);

[0012] (b) 40 parts by mass of polyol K in which polymer particles are dispersed in polyol G5 obtained by reacting propylene oxide with initiator 1; and

[0013] (c) TDI-80 (NOC content: 44.8 mass %) in an amount corresponding to an isocyanate index of 105.

[0014] Patent Document 1 states:

[0015] (A) This method provides a flexible polyurethane foam having an X value (=static spring constant under a load of 883 N / static spring constant under a load of 98 N) of 2.94; and

[0016] (B) When this soft polyurethane foam is used for automobile seats, it is possible to eliminate the bottoming feeling after sitting down.

[0017] Patent document 2 discloses a seat cushion comprising:

[0018] A cushion main body constituting a seat portion; and

[0019] A low-air-permeable foam is integrally provided on the bottom surface of the seat cushion main body.

[0020] Patent Document 2 describes that when low-air-permeable foam is integrally provided on the bottom surface of a seat cushion body, vibrations that deteriorate riding comfort can be absorbed.

[0021] Patent Document 3 discloses a polyurethane foam obtained by reacting raw materials including:

[0022] (a) 90 parts by weight of a polyether polyol having a number average molecular weight of 7000, an average number of functional groups of 3 and a hydroxyl value of 26 mgKOH / g;

[0023] (b) 10 parts by weight of a polymer polyol having a number average molecular weight of 5000, an average number of functional groups of 3, a hydroxyl value of 25 mgKOH / g, and a solid content of 30%;

[0024] (c) 0.5 parts by weight of a linear silicone foam stabilizer having a viscosity of 7280 mPa·s (25° C.) and a surface tension of 20.08 mN / m (25° C.); and

[0025] (d) A mixture of TDI (80% by weight) and MDI (20% by weight) (NCO=44.8%) in an amount corresponding to an isocyanate index of 100.

[0026] Patent Document 3 describes that this method can provide a polyurethane foam that is less likely to bottom out even when it is thinner than before and has high air permeability.

[0027] Patent Document 4 discloses a deformation analysis technique for simulating the nonlinear viscoelastic behavior of a compressible material that is not a seat pad but has nonlinear viscoelastic behavior.

[0028] Patent Document 4 describes that when a model including a linear viscoelastic part according to a generalized Maxwell model and a compressive elastoplastic part having a yield condition equation depending on hydrostatic stress is used in parallel, the decay behavior when a polyurethane foam is slowly pressed can be analyzed with high accuracy.

[0029] Patent Document 5 discloses a car seat obtained by:

[0030] (a) disposing a mesh material having a three-dimensional structure in a die and foaming polyurethane in the die, thereby forming a seat back in which the mesh material having a three-dimensional structure is assembled in a cushion material made of polyurethane foam; and

[0031] (b) The net material is fixed to the frame while tension is applied to the net material protruding toward both side portions of the seat back portion.

[0032] Patent Document 5 states:

[0033] (A) This method provides a seat back in which a mesh material having a three-dimensional structure is integrally assembled in a seat cushion material made of polyurethane foam, and

[0034] (B) The portion of the mesh material impregnated with polyurethane has high surface rigidity, so that when an impact is applied from behind the occupant, the impact can be attenuated.

[0035] The hardness and elasticity of the seat cushion affect the riding comfort when sitting. In order to further increase the cushioning feeling, the seat cushion is made to be more flexible in a high load range, that is, preferably has a small flexibility coefficient. In addition, in order to reduce the bottoming feeling when sitting, a high displacement rate is preferred. However, in previous examples, no seat cushion that simultaneously achieves a small flexibility coefficient and a high displacement rate has been proposed.

[0036] Prior art literature

[0037] Patent Literature

[0038] Patent Document 1: JP 2003-119240 A

[0039] Patent Document 2: JP 2005-177171 A

[0040] Patent Document 3: JP 2019-194321 A

[0041] Patent Document 4: JP 2020-094980 A

[0042] Patent Document 5: JP 2002-102008 A Summary of the invention

[0043] Problem that the invention aims to solve

[0044] An object of the present invention is to provide a seat cushion which is composed of polyurethane foam and has a small flexural coefficient and a high displacement rate.

[0045] Solutions for solving problems

[0046] In order to achieve the above object, the seat cushion according to the present invention comprises:

[0047] Polyurethane foam, and

[0048] The polyurethane foam has:

[0049] A flexural coefficient of less than 2.8, and

[0050] The displacement rate expressed by the following formula (1) is 30% or more:

[0051] Displacement rate = t 1 ×100 / t 0 ...(1)

[0052] in

[0053] t 0 is the thickness of a flat plate sample cut out from the polyurethane foam, and

[0054] t 1 It is the maximum value of the displacement amount (sinking amount) of the iron disk when the attenuation characteristics are measured according to JASO B408 using a flat plate-like sample.

[0055] Preferably, the polyurethane foam is obtained by reacting a raw material mixture comprising a polyol component and a polyisocyanate component,

[0056] The polyol component comprises one or more polyether polyols A, wherein the polyether polyols A have:

[0057] (a) an EO content of 50 mol% or more,

[0058] (b) the number of functional groups is greater than 2.0 and less than 3.0, and

[0059] (c) a weight average molecular weight greater than 3500, and

[0060] The polyisocyanate component comprises carbodiimide-modified MDI.

[0061] Effects of the Invention

[0062] In the case of producing a polyurethane foam, use of a raw material mixture containing polyether polyol A and carbodiimide-modified MDI satisfying the prescribed conditions provides a polyurethane foam having a flexural coefficient of 2.8 or less and a displacement rate of 30% or more.

[0063] The flex coefficient is considered to be 2.8 or less because the use of polyether polyol A having a high EO content relatively reduces the number of side chains contained in the polymer chain, resulting in less entanglement between polymer chains and because the molecular chains are thus likely to expand and contract, thereby imparting elasticity to the polyurethane foam.

[0064] It is considered that the displacement rate is 30% or more because the polyether polyol A having a large weight average molecular weight is used. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a schematic diagram of the attenuation test machine;

[0066] Figure 2 is the FS curve of the polyurethane foam obtained in Examples 1 to 4 and Comparative Examples 1 to 2;

[0067] Figure 3 are the results of attenuation tests on the polyurethane foams (thickness: 100 mm) obtained in Examples 1 to 4 and Comparative Examples 1 to 2; and

[0068] Figure 4 These are the results of the attenuation test of the polyurethane foams (thickness: 50 mm) obtained in Examples 1 to 4 and Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0069] Hereinafter, embodiments of the present invention will be described in detail.

[0070] [1. Seat cushion]

[0071] 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. Typically, the raw material mixture further contains a crosslinking agent, a blowing agent, and a catalyst.

[0072] [1.1. Polyurethane foam]

[0073] 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.

[0074] [1.2 Features]

[0075] [1.2.1 Flexural coefficient]

[0076] The "flex coefficient" refers to a value measured according to JIS K 6400-2:2012. Specifically, the "flex coefficient" refers to the force (F) at 65% compression when the pre-compression is performed at a constant speed until 75% after 75%. 65％ ) divided by the force at 25% compression (F 25％) and the value obtained (=F 65％ / F 25％ ).

[0077] As described later, the polyurethane foam according to the present invention uses a polyether polyol A having a high EO content as one of the raw materials. The use of a polyether polyol A having a high EO content relatively reduces the flexural coefficient of the polyurethane foam. It is believed that this is because the use of a polyether polyol A having a high EO content relatively reduces the number of side chains contained in the polymer chain, resulting in less entanglement between the polymer chains, and because the molecular chains are therefore likely to expand and contract, thereby giving the polyurethane foam elasticity. Generally, as the flexural coefficient is smaller, the polyurethane foam is more flexed in a high load range, so that the cushioning feeling is increased.

[0078] In order to increase the cushioning feeling, the flexural coefficient of the polyurethane foam needs to be 2.8 or less. When the manufacturing conditions are optimized, the flexural coefficient is 2.7 or less, 2.6 or less, or 2.5 or less.

[0079] On the other hand, if the flex coefficient is too small, the flex amount may be excessively increased, resulting in a strong bottoming feeling. Therefore, the flex coefficient is preferably 2.0 or more. The flex coefficient is more preferably 2.1 or more or 2.2 or more.

[0080] [1.2.2. Displacement rate]

[0081] The "displacement rate" is a value represented by the following formula (1).

[0082] Displacement rate = t 1 ×100 / t 0 ...(1)

[0083] in

[0084] t 0 is the thickness of a flat plate sample cut out from the polyurethane foam, and

[0085] t 1 It is the maximum value of the displacement amount (sinking amount) of the iron disk when the attenuation characteristics are measured according to JASO B408 using a flat plate-like sample.

[0086] Strictly speaking, the displacement rate depends on the thickness t of the flat sample. 0 For the polyurethane foam according to the present invention, when using 0 When measuring multiple displacement rates of multiple flat-plate samples, it is sufficient as long as at least one displacement rate satisfies the following conditions.

[0087] Generally, as the displacement rate increases, the cushioning property when sitting increases. In order to obtain such an effect, the displacement rate needs to be 30% or more. The displacement rate is preferably 35% or more, 40% or more, 45% or more, 50% or more, or 55% or more.

[0088] In the polyurethane foam according to the present invention, when the manufacturing conditions are optimized, when t 0 =50mm, the displacement rate is more than 45%. When the manufacturing conditions are further optimized, when t 0 =50mm, the displacement rate is 55%, 60% or more, or 65% or more.

[0089] Likewise, in the polyurethane foam according to the present invention, when the manufacturing conditions are optimized, when t 0 =100mm, the displacement rate is more than 50%. When the manufacturing conditions are further optimized, when t 0 =100mm, the displacement rate is more than 55%.

[0090] [2. Method for producing polyurethane foam]

[0091] The polyurethane foam constituting the seat cushion is obtained by:

[0092] (a) preparing a raw material mixture comprising a polyol component and a polyisocyanate component; and

[0093] (b) reacting the raw material mixture.

[0094] Typically, the raw material mixture further comprises a crosslinking agent, a blowing agent and a catalyst.

[0095] [2.1. Main raw materials]

[0096] [2.1.1. Polyol component]

[0097] Polyol component is one of the main raw materials of polyurethane foam.

[0098] In the present invention, the polyol component comprises a polyether polyol A, wherein the polyether polyol A has:

[0099] (a) an EO content of 50 mol% or more,

[0100] (b) the number of functional groups is greater than 2.0 and less than 3.0, and

[0101] (c) a weight average molecular weight greater than 3500.

[0102] 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.

[0103] The polyol component may further comprise a polyether polyol B having:

[0104] (a) an EO content of 30 mol% or less, and

[0105] (b) The number of functional groups is greater than 2.0.

[0106] 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.

[0107] [A. Polyether polyol A]

[0108] [A.1.EO content]

[0109] 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.

[0110] 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.

[0111] The EO content of polyether polyol A mainly affects the flexural coefficient. Generally, as the EO content of polyether polyol A increases, the flexural coefficient decreases. This is believed to be because as the EO content increases, the side chains (-CH 3 ) is relatively reduced, resulting in less entanglement between polymer chains, and because the molecular chains are therefore likely to expand and contract, thus giving the polyurethane foam elasticity.

[0112] 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%.

[0113] [A.2. Number of functional groups]

[0114] The number of functional groups of polyether polyol A affects the flexural coefficient. Generally, as the number of functional groups of polyether polyol A increases, the rigidity of the polyurethane foam increases, and the compressive residual strain decreases. 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.

[0115] On the other hand, an excessive number of functional groups in polyether polyol A may excessively increase the hardness of the polyurethane foam and increase the flexural coefficient. Therefore, the number of functional groups in polyether polyol A is preferably 3.0 or less. More preferably, the number of functional groups is 2.9 or less or 2.8 or less.

[0116] [A.3. Weight average molecular weight]

[0117] As the weight average molecular weight of polyether polyol A increases, the hardness of the polyurethane foam decreases and the polyurethane foam is likely to bend. In order to obtain such an effect, the weight average molecular weight of polyether polyol A is preferably greater than 3500. The weight average molecular weight is more preferably 4000 or more or 5000 or more.

[0118] 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.

[0119] [A.4. Hydroxyl value]

[0120] If the hydroxyl value of 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.

[0121] 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.

[0122] [B. Polyether polyol B]

[0123] [B.1.EO content]

[0124] 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.

[0125] 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.

[0126] 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.

[0127] [B.2. Number of functional groups]

[0128] The number of functional groups of the polyether polyol B may be 2.0 or more.

[0129] However, if the number of functional groups of the polyether polyol B is too large, the elongation of the 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.

[0130] [B.3. Weight average molecular weight]

[0131] 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, a weight average molecular weight of polyether polyol B that is too small 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.

[0132] 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.

[0133] [2.1.2. Polyisocyanate component]

[0134] Polyisocyanate component is another main raw material of polyurethane foam.

[0135] 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").

[0136] [A. Carbodiimide-modified MDI]

[0137] Carbodiimide (-N=C=N-)-modified MDI is prepared by reacting the -NCO groups of diphenylmethane diisocyanate (MDI) in the presence of a catalyst to form a CO 2 The product produced by the condensation of .

[0138] The use of carbodiimide-modified MDI as the polyisocyanate component increases the elasticity of the polyurethane foam, resulting in increased deflection in the high load range.

[0139] [B. Polyisocyanate B]

[0140] 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.

[0141] 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 raw material mixture may contain any one of these polyisocyanates B, or may contain two or more thereof.

[0142] Examples of difunctional aromatic isocyanates include:

[0143] 2,4-Toluene diisocyanate, 2,6-Toluene diisocyanate,

[0144] Isocyanate, p-phenylene diisocyanate,

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

[0146] 2,4'-diphenylmethane diisocyanate (2,4'-MDI),

[0147] 2,2'-diphenylmethane diisocyanate (2,2'-MDI),

[0148] Xylylene diisocyanate,

[0149] 3,3'-dimethyl-4,4'-biphenyl diisocyanate, and

[0150] 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, and a mixture thereof may be used.

[0151] Examples of difunctional alicyclic isocyanates include:

[0152] Cyclohexane-1,4-diisocyanate, isophorone diisocyanate,

[0153] Dicyclohexylmethane-4,4'-diisocyanate, and

[0154] Methylcyclohexane diisocyanate.

[0155] Examples of difunctional aliphatic isocyanates include:

[0156] 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.

[0157] Examples of isocyanates having a functional group number greater than 2 include:

[0158] 1-Methylbenzene-2,4,6-triisocyanate,

[0159] 1,3,5-Trimethylbenzene-2,4,6-triisocyanate,

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

[0161] Diphenylmethane-2,4,4'-triisocyanate,

[0162] Methyl diphenylmethane-4,6,4'-triisocyanate,

[0163] 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, and

[0164] Triphenylmethane-4,4′,4″-triisocyanate.

[0165] [C. NCO group content (NCO%)]

[0166] The “NCO group content (NCO%)” refers to the ratio of the mass of the NCO group to the total mass of the polyisocyanate component.

[0167] The NCO% of the polyisocyanate component is preferably less than 35%, more preferably less than 30%, and still more preferably 29.5% or less.

[0168] [2.1.3. Cross-linking agent]

[0169] 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.

[0170] The number of functional groups of the crosslinking agent affects the compressive residual strain. In order to obtain a polyurethane foam having a small compressive residual strain, the number of functional groups of the crosslinking agent is preferably 3 or more.

[0171] 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.

[0172] 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.

[0173] The molecular weight of the cross-linking agent is preferably 60 or more, 90 or more, or 120 or more.

[0174] Examples of the cross-linking agent include glycerol, diethanolamine (DEA), and multifunctional polyols.

[0175] The raw material mixture may contain any one of these cross-linking agents, or may contain two or more thereof.

[0176] [2.1.4. Foaming agent]

[0177] 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.

[0178] In the present invention, the blowing agent may be:

[0179] (a) physical blowing agents that generate gas by reducing pressure or heating; or

[0180] (b) Chemical blowing agents that generate gas by thermal decomposition or chemical reaction.

[0181] Examples of physical blowing agents include:

[0182] (a) hydrocarbons such as cyclopentane, isopentane and n-pentane, and

[0183] (b) Halogen compounds such as dichloromethane, trichlorofluoromethane, dichlorodifluoromethane, nonafluorobutyl methyl ether, pentafluoroethyl methyl ether and pentafluoroisopropyl methyl ether.

[0184] Examples of chemical blowing agents include:

[0185] (a) Reaction with isocyanate groups to produce CO 2 of water, and

[0186] (b) Azodicarbonamides which generate nitrogen, carbon monoxide, carbon dioxide or ammonia by thermal decomposition.

[0187] The raw material mixture may contain any one of these foaming agents, or may contain two or more thereof.

[0188] Among them, the blowing agent is preferably water. When water is used as the blowing agent, CO generated by the reaction between water and isocyanate groups 2 The gas promotes foaming. The heat of reaction between water and isocyanate groups promotes curing of the resin.

[0189] [2.1.5. Catalyst]

[0190] 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.

[0191] 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.

[0192] Examples of the catalyst include amine catalysts and metal catalysts. Amine catalysts are catalysts that have a large effect of promoting both the resinification reaction and the foaming reaction. Metal catalysts are catalysts that have a large effect of promoting the resinification reaction. The raw material mixture may contain any one of these catalysts, or may contain two or more thereof.

[0193] Examples of amine-based catalysts include:

[0194] N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine,

[0195] N,N-dimethylaminoethanol,

[0196] N,N',N'-trimethylaminoethylpiperazine and triethylenediamine.

[0197] Examples of metal catalysts include:

[0198] (a) tin catalysts, such as stannous octoate and dibutyltin dilaurate,

[0199] (b) a mercury catalyst, such as phenylmercuric propionate, and

[0200] (c) Lead catalysts, for example lead octoate.

[0201] [2.2. Auxiliary materials]

[0202] 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.

[0203] [2.2.1. Foam stabilizer]

[0204] The term "foam stabilizer" refers to an additive that has the function of making the size and distribution of bubbles uniform.

[0205] 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.

[0206] [2.2.2. Flame retardant]

[0207] The "flame retardant" refers to an additive having a function of making polyurethane foam flame-retardant.

[0208] Examples of the flame retardant include halogen-based flame retardants, phosphorus-based flame retardants, metal hydroxide-based flame retardants, and antimony-based flame retardants.

[0209] [2.3. Compounding amount and content]

[0210] [2.3.1. Compounding amount and content of main raw materials]

[0211] [A. Compounding amount of polyether polyol A]

[0212] 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.

[0213] Generally, the flexural coefficient of the polyurethane foam decreases as the blending amount of the polyether polyol A increases. In order to obtain such an effect, the blending amount of the 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.

[0214] 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.

[0215] [B. Content of carbodiimide-modified MDI]

[0216] 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.

[0217] Generally, as the content of carbodiimide-modified MDI is higher, the flexural coefficient of polyurethane foam decreases and the displacement rate increases. 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.

[0218] 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.

[0219] 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.

[0220] [C. Amount of crosslinking agent blended]

[0221] The “amount of the cross-linking agent compounded (parts by mass)” refers to the mass of the cross-linking agent when the total mass of the polyol component is 100.

[0222] Generally, as the amount of the crosslinking agent is increased, the compressive residual strain of the polyurethane foam is reduced. In order to obtain such an effect, the amount of the crosslinking agent is preferably greater than 0 parts by mass. The amount is more preferably 1 part by mass or more or 2 parts by mass or more.

[0223] On the other hand, an excessive amount of the crosslinking agent may excessively increase the hardness of the polyurethane foam. Therefore, the amount of the crosslinking agent 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.

[0224] [D. Amount of polyether polyol B blended]

[0225] The “compounding amount (parts by mass) of the polyether polyol B” refers to the mass of the polyether polyol B in the polyol component when the total mass of the polyol component is 100.

[0226] Usually, the compounding amount of polyether polyol B is excessive, so that the compounding amount of polyether polyol A is relatively reduced. Therefore, the flexural coefficient of the polyurethane foam may increase, or the displacement rate may decrease. Therefore, the compounding amount of polyether polyol B is preferably less than 50 parts by mass. The compounding amount is more preferably less than 40 parts by mass or less than 30 parts by mass.

[0227] [E. Isocyanate index]

[0228] 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.

[0229] In the present invention, isocyanate index is not particularly limited, and can select optimum value according to purpose.Usually, as isocyanate index is larger, compression residual strain is reduced.In order to obtain such effect, isocyanate index is preferably more than 90.Isocyanate index is more preferably more than 95.

[0230] 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.

[0231] [2.3.2. Amount of auxiliary raw materials added]

[0232] In the present invention, the compounding amount of the auxiliary raw material is not particularly limited, and an optimum content can be selected according to the purpose.

[0233] [2.4. Reaction of raw material mixture]

[0234] As foaming in the method for producing the polyurethane foam according to the present invention, slab foaming or mold foaming may be adopted.

[0235] 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.

[0236] 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.

[0237] In the case of mold forming, the polyisocyanate preferably has a low viscosity, and, for example, a prepolymer type polyisocyanate is not preferred.

[0238] [3. Function]

[0239] In the case of producing a polyurethane foam, use of a raw material mixture containing polyether polyol A and carbodiimide-modified MDI satisfying the prescribed conditions provides a polyurethane foam having a flexural coefficient of 2.8 or less and a displacement rate of 30% or more.

[0240] When such a polyurethane foam is used as a seat pad, the seat pad has an excellent flexural coefficient even when the seat pad is thin (eg, 50 mm or less), and has an excellent flexural amount (displacement rate) in damping characteristics.

[0241] The flex coefficient is considered to be 2.8 or less because the use of polyether polyol A having a high EO content relatively reduces the number of side chains contained in the polymer chain, resulting in less entanglement between polymer chains and because the molecular chains are thus likely to expand and contract, thereby imparting elasticity to the polyurethane foam.

[0242] It is considered that the displacement rate is 30% or more because the polyether polyol A having a large weight average molecular weight is used.

[0243] [Example]

[0244] (Examples 1 to 4 and Comparative Examples 1 to 2)

[0245] [1. Sample preparation]

[0246] A polyether polyol, a crosslinking agent, a foaming agent, a catalyst, and a foam stabilizer are compounded in a prescribed ratio to obtain a mixed liquid (hereinafter, also referred to as "component A").

[0247] Separately, polymeric MDI, MDI including carbodiimide-modified MDI (NCO content: 29%, carbodiimide-modified MDI content: 75 mass %), and MDI prepolymer (NCO content: 28.5%) were blended at a prescribed ratio to obtain a mixed solution (hereinafter, also referred to as "component B").

[0248] 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.

[0249] Example 1 is an example in which only polyether polyol 2 (molecular weight: 4000, number of functional groups: 2, EO content: 80 mol %) is used as polyether polyol A.

[0250] Examples 2 and 3 are examples using a mixture of the following (a) and (b) as polyether polyol A.

[0251] (a) polyether polyol 2 (molecular weight: 4000, number of functional groups: 2, EO content: 80 mol%) and

[0252] (b) Polyether polyol 3 (molecular weight: 5000, number of functional groups: 3, EO content: 80 mol %)

[0253] Example 4 is an example in which only polyether polyol 3 is used as polyether polyol A.

[0254] [Table 1]

[0255] <Composition of Polyol Side Component A (Parts by Mass)>

[0256]

[0257] <Composition of isocyanate side component B (parts by mass)>

[0258] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Isocyanate Polymeric MDI 5 5 5 5 5 MDI containing carbodiimide-modified MDI 95 95 95 95 95 <![CDATA[MDI prepolymer (NCO%: 28.5%) * 1]]> 100 Total of isocyanate side component B 100 100 100 100 100 100

[0259] * 1) Prepolymer of MDI (MDI mixture with binuclear form ratio of more than 70%) and polyether polyol

[0260] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 index[-] 105 106 103 105 105 95 Amount of component B used relative to 100g of component A [g] 48.4 49.5 49.9 51.6 56.6 49.6

[0261] 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.

[0262] [2. Test method]

[0263] [2.1. Core density]

[0264] The surface layer was removed from the obtained foam to prepare a sample for measuring the core density. The obtained sample was used to measure the core density in accordance with JIS K 7222.

[0265] [2.2.25% hardness]

[0266] The 25% hardness is measured according to JIS K 6400-2D method.

[0267] [2.3. Hysteresis loss]

[0268] The hysteresis loss was measured according to JIS K 6400-2E method.

[0269] [2.4. Flexural coefficient]

[0270] The flexural coefficient was measured according to JIS K 6400-2E method. The flexural coefficient was determined by dividing the 65% compression load by the 25% compression load.

[0271] [2.5. Stress relaxation]

[0272] 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.

[0273] [2.6. Attenuation characteristics]

[0274] Figure 1 The schematic diagram of the attenuation test machine is shown. An iron plate with a mass of 50 kg is placed 20 mm above the sample. From this position, the iron plate falls freely toward the sample. The vibration characteristics of the sample are evaluated from the displacement of the iron plate after falling and the time until the vibration stops.

[0275] [3. Results]

[0276] 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. Figure 2 FS curves of the polyurethane foams obtained in Examples 1 to 4 and Comparative Examples 1 and 2 are shown. Figure 3 The results of the attenuation test of the polyurethane foams (thickness: 100 mm) obtained in Examples 1 to 4 and Comparative Examples 1 and 2 are shown. Figure 4 The results of the attenuation test of the polyurethane foams (thickness: 50 mm) obtained in Examples 1 to 4 and Comparative Examples 1 to 2 are shown. Figure 2 to Figure 4 The following can be seen.

[0277] (1) Comparative Example 1 shows that t 0 = Displacement rate and t when 50 mm 0 =100 mm, both displacement rates were less than 30%. This is considered to be because the polyether polyol A having a weight average molecular weight of more than 3,500 was not included.

[0278] (2) Comparative Example 2 showed a high displacement rate but a flexural coefficient greater than 2.8. This is considered to be because the content of polyether polyol A was too low.

[0279] (3) All Examples 1 to 4 showed a deflection coefficient of 2.8 or less. 0 However, the displacement rates in all the embodiments were above 50%.

[0280]

[0281] 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.

[0282] Industrial Applicability

[0283] 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 flexural coefficient of less than 2.8, and The displacement rate expressed by the following formula (1) is 30% or more: Displacement rate = t1 × 100 / t0...(1) in t0 is the thickness of a flat plate sample cut out from the polyurethane foam, and t1 is the maximum value of the displacement amount (sinking amount) of the iron disk when the attenuation characteristics are measured according to JASO B408 using the flat plate-like sample.

2. The seat pad according to claim 1, wherein the displacement rate when t0 = 50 mm is 45% or more.

3. The seat pad according to claim 1, wherein the displacement rate when t0 = 100 mm is 50% or more.

4. 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 greater than 3500, and The polyisocyanate component comprises carbodiimide-modified MDI.

5. The seat cushion according to claim 4, 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) Average number of functional groups greater than 2.0.

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