seat pad

Abstract

This seat pad comprises a polyurethane foam, wherein the polyurethane foam exhibits a compressive residual strain ε1 of not more than 5.0% and a wet heat compressive residual strain ε2 of not more than 5.0%. The "compressive residual strain ε1" is a value measured in conformance with JIS K 6400-4 (with a temperature of 70°C and a compression ratio of 50%). The "wet heat compressive residual strain ε2" is a value measured in conformance with JIS K 6400-4 (with a temperature of 50°C, a humidity of 95% RH, and a compression ratio of 50%). The polyurethane foam preferably has a 25% hardness of not less than 150 N.

Description

Technical Field

[0001] The present invention relates to a seat pad, and more particularly to a seat pad made of a polyurethane foam having both small compression residual strain and wet heat compression residual strain.

Background Art

[0002] Automobile seats are of two types: those in which the seat cushion (seating surface) and the seat back (backrest) are separated, and those in which the two are integrated. In addition, automobile seats generally (a) a seat pad for receiving the load of a passenger when the passenger is seated, (b) a frame for supporting the seat pad, (c) a trim cover for covering the outer surface of the seat pad are provided. Generally, polyurethane foam is used for the seat pad.

[0003] When a passenger sits on an automobile seat provided with a seat pad, the seat pad is compressed in the load direction in proportion to the magnitude of the load applied to the seat pad. The magnitude of the load applied to the seat pad varies depending on the shape of the automobile seat, the inclination of the seat back, the part of the human body contacting the automobile seat, the posture of the passenger, the unevenness of the road surface on which the automobile travels, and the like. Therefore, even when the shape of the seat pad is optimized when not in use, residual strain (compression residual strain, wet heat compression residual strain) may occur in the seat pad due to sweating, temperature, compression stress, etc. during use, resulting in a seat with poor sitting comfort.

[0004] Therefore, various proposals have been made heretofore to solve this problem. For example, Patent Document 1 discloses a seat pad having different hardnesses along the thickness direction, although it is not intended to reduce compression residual strain and / or wet heat compression residual strain. The document states that by varying the hardness of the seat pad along its thickness, it is possible to reduce the weight of the seat pad while suppressing wobbling.

[0005] Patent Document 2 discloses a flexible polyurethane foam obtained by reacting raw materials containing a polymer polyol (N), a polyether polyol (A1), and a polyisocyanate component (B) that satisfy predetermined conditions. The same document states that, using this method, the 25% compression hardness is 250-280 (N / 314cm²). 2 It is stated that this method yields a flexible polyurethane foam with a moderate hysteresis loss rate and reduced stress relaxation.

[0006] Patent Document 3 discloses a polyol composition comprising a polyether polyol (a1) that satisfies predetermined conditions, a vinyl polymer (p), and a foam stabilizer consisting of a low molecular weight siloxane (c1). The document states that using such a polyol composition can yield an elastic polyurethane foam with a low moist heat residual strain.

[0007] Patent Document 4 discloses a polyol component (a) comprising a polyether polyol (a1) that satisfies predetermined conditions and a vinyl polymer (p). The document states that when 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 with a low moist heat residual strain is obtained.

[0008] Patent documents 3 and 4 describe that when manufacturing polyurethane foam, using a polyol that satisfies certain conditions reduces the moist heat residual compressive strain. However, generally, reducing either the moist heat residual compressive strain or the compressive strain tends to increase the other. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2018-048246 [Patent Document 2] Japanese Patent Publication No. 2019-031666 [Patent Document 3] Japanese Patent Application Publication No. 09-100336 [Patent Document 4] Japanese Patent Application Publication No. 10-025328 [Overview of the project] [Problems that the invention aims to solve]

[0010] The problem that this invention aims to solve is to provide a sheet pad made of polyurethane foam that exhibits low compression set and low moist heat compression set. Another problem that the present invention aims to solve is to provide a sheet pad made of polyurethane foam that has low compression set and moist heat compression set, and has appropriate hardness. [Means for solving the problem]

[0011] To solve the above problems, the seat pad according to the present invention Equipped with polyurethane foam, The aforementioned polyurethane foam The compressive residual strain ε1 is 5.0% or less, and, The moist thermal compression residual strain ε2 is 5.0% or less. however, The aforementioned "compression residual strain ε1" refers to the value measured in accordance with JIS K 6400-4 (however, temperature: 70°C, compressibility: 50%). The aforementioned "moist heat compression residual strain ε2" refers to the value measured in accordance with JIS K 6400-4 (where temperature: 50°C, humidity: 95%RH, compressibility: 50%).

[0012] The polyurethane foam is preferably one with a 25% hardness of 150N or higher.

[0013] The polyurethane foam is obtained by reacting a raw material mixture containing a polyol component and a polyisocyanate component. The polyol component (a) has an EO content of 50 mol% or more, (b) has a functionality of 2.0 or more and 3.0 or less, (c) has a weight average molecular weight of 3000 or more and contains one or more polyether polyols A, The polyisocyanate component preferably contains carbodiimide-modified MDI. However, it excludes the case where the polyol component contains only those which, as the polyether polyol A, (a) have an EO content of 50 mol% or more, (b) have a functionality of 2.0, (c) have a weight average molecular weight of 3000 or more (c) have a weight average molecular weight of 3000 or more are included.

Advantages of the Invention

[0014] When producing a polyurethane foam, by using a raw material mixture containing a polyether polyol A satisfying predetermined conditions and carbodiimide-modified MDI, a polyurethane foam with both small compression residual strain ε1 and wet heat compression residual strain ε2 can be obtained. Furthermore, when the production conditions are optimized, a polyurethane foam with a 25% hardness of 150 N or more can be obtained.

[0015] It is considered that the reduction of the compression residual strain ε1 is due to the increased rigidity of the polyurethane foam because a polyether polyol A with a large functionality and a large weight average molecular weight is used. It is considered that the reduction of the wet heat compression residual strain ε2 is due to the increased water absorption and the increased restoring force by the absorbed water because a polyether polyol A with a high EO content is used. Furthermore, the moderately increased hardness is thought to be due to the use of polyether polyol A, which has a large number of functional groups, resulting in an increased number of crosslinking points. [Modes for carrying out the invention]

[0016] One embodiment of the present invention will be described in detail below. [1. Seat pad] The sheet pad according to the present invention consists of a polyurethane foam obtained by reacting a raw material mixture containing a polyol component and a polyisocyanate component. The raw material mixture typically further includes a crosslinking agent, a foaming agent, and a catalyst.

[0017] [1.1. Polyurethane foam] The polyurethane foam that makes up the seat pad is obtained by foaming and reacting a raw material mixture that meets predetermined conditions. Details of the manufacturing method for polyurethane foam will be described later.

[0018] [1.2. Characteristics] [1.2.1. Compression Residual Strain ε1] "Compression residual strain ε1" refers to the value measured in accordance with JIS K 6400-4 (temperature: 70°C, time: 22 hours, compressibility: 50%).

[0019] The sheet pad according to the present invention consists of a polyurethane foam obtained by reacting a raw material mixture that satisfies predetermined conditions. Therefore, the polyurethane foam according to the present invention has a small compression set ε1. By optimizing the manufacturing conditions, the ε1 of the polyurethane foam becomes 5.0% or less. By further optimizing the manufacturing conditions, the ε1 becomes 4.0% or less, or 3.5% or less.

[0020] [1.2.2. Moisture-heat compression residual strain ε2] "Moist heat compression residual strain ε2" refers to the value measured in accordance with JIS K 6400-4 (temperature: 50°C, humidity: 95%RH, time: 22 hours, compressibility: 50%).

[0021] The sheet pad according to the present invention consists of a polyurethane foam obtained by reacting a raw material mixture that satisfies predetermined conditions. Therefore, the polyurethane foam according to the present invention has a small humid heat compression set ε2. When the manufacturing conditions are optimized, the ε2 of the polyurethane foam becomes 5.0% or less. When the manufacturing conditions are further optimized, the ε2 becomes 4.0% or less, 3.5% or less, 3.0% or less, or 2.0% or less.

[0022] [1.2.3. Distortion ratio ε2 / ε1] The "strain ratio ε2 / ε1" refers to the ratio of the moist heat compression residual strain ε2 to the compression residual strain ε1.

[0023] In conventional polyurethane foams, a decrease in either the compression set ε1 or the moist heat compression set ε2 often leads to an increase in the other. Therefore, conventional polyurethane foams often have a strain ratio ε2 / ε1 of 1.0 or higher. In contrast, the sheet pad according to the present invention consists of a polyurethane foam obtained by reacting a raw material mixture that satisfies predetermined conditions. As a result, both ε1 and ε2 are small in the polyurethane foam according to the present invention. In particular, the polyurethane foam according to the present invention has the characteristic that the moist heat compression set ε2 is smaller than the compression set ε1. As a result, ε2 / ε1 is less than 1.0. Further optimization of the manufacturing conditions results in ε2 / ε1 being between 0.03 and 0.8.

[0024] [1.2.4. 25% hardness] "25% hardness" refers to the value measured in accordance with JIS K 6400-2 Method D (with a pressure plate diameter of 200 mm).

[0025] Traditionally, soft polyurethane foams with good vibration absorption properties tend to have high density. However, using such soft polyurethane foams as seat pads sometimes increased the vehicle's weight. To solve this problem, simply reducing the density of the soft polyurethane foam would decrease its hardness. As a result, the rebound modulus would become excessively low, sometimes leading to a decrease in cushioning. In contrast, the seat pad according to the present invention is made of polyurethane foam obtained by reacting a raw material mixture that satisfies predetermined conditions. Therefore, the polyurethane foam according to the present invention has a moderate hardness. By optimizing the manufacturing conditions, the 25% hardness of the polyurethane foam becomes 150N or more. By further optimizing the manufacturing conditions, the 25% hardness becomes 170N or more, or even 190N or more. This hardness allows the seat pad to be thinner than conventional seat pads, while still providing excellent vibration absorption, a comfortable seating experience, and reducing weight. On the other hand, if the 25% hardness of the polyurethane foam becomes too high, the seat's comfort may deteriorate. Therefore, a 25% hardness of 350N or less is preferable.

[0026] [1.2.5. Hysteresis Loss] "Hysteresis loss" refers to the value measured in accordance with JIS K 6400-2 E method.

[0027] The sheet pad according to the present invention consists of a polyurethane foam obtained by reacting a raw material mixture that satisfies predetermined conditions. Therefore, the polyurethane foam according to the present invention exhibits a moderate hysteresis loss. When the manufacturing conditions are optimized, the hysteresis loss of the polyurethane foam becomes 5-30%.

[0028] [1.2.6. Deflection coefficient] The "deflection coefficient" refers to the value measured in accordance with JIS K 6400-2:2012. More specifically, the "deflection coefficient" is the force (F) at 65% compression when compressed to 75% at a constant speed after a 75% pre-compression. 65% ) with a force (F) at 25% compression25% The value obtained by dividing by (=F 65% / F 25% ) refers to.

[0029] The sheet pad according to the present invention is made of polyurethane foam obtained by reacting a raw material mixture that satisfies predetermined conditions. Therefore, the polyurethane foam according to the present invention has a small deflection coefficient. By optimizing the manufacturing conditions, the deflection coefficient of the polyurethane foam becomes 2.8 or less. By further optimizing the manufacturing conditions, the deflection coefficient becomes 2.7 or less, 2.6 or less, or 2.5 or less.

[0030] [1.2.7. Stress Relaxation] "Stress relaxation" refers to the value measured in accordance with JIS K 6400-2 (load 196N, 5 minutes).

[0031] The sheet pad according to the present invention consists of a polyurethane foam obtained by reacting a raw material mixture that satisfies predetermined conditions. Therefore, the polyurethane foam according to the present invention exhibits low stress relaxation. When the manufacturing conditions are optimized, the stress relaxation of the polyurethane foam becomes 2-20%.

[0032] [1.2.8. Density] "Density" refers to the value measured in accordance with JIS K 7222. To lighten the seat pad, the density of the polyurethane foam should be 68 kg / m³. 3 The following is preferable. The density is more preferably 66 kg / m³. 3 The following applies:

[0033] [2. Method for manufacturing polyurethane foam] The polyurethane foam that makes up the seat pad is (a) Prepare a raw material mixture containing a polyol component and a polyisocyanate component, (b) React the raw material mixture It is obtained by doing so. The raw material mixture typically further includes a crosslinking agent, a blowing agent, and a catalyst.

[0034] [2.1. Main raw materials] [2.1.1. Polyol components] Polyol components are one of the main raw materials for polyurethane foam. In the present invention, the polyol component is (a) The EO content is 50 mol% or more, (b) The number of functional groups is 2.0 or more and 3.0 or less, (c) The weight-average molecular weight is 3000 or more. Contains polyether polyol A.

[0035] The polyol component may contain one type of polyether polyol A that satisfies these conditions, or it may contain two or more types of polyether polyol A that satisfy these conditions. However, if the polyol component is as the polyether polyol A, (a) The EO content is 50 mol% or more, (b) The number of functional groups is 2.0, (c) The weight-average molecular weight is 3000 or more. Except when it includes only objects.

[0036] The polyol component is, (a) The EO content is 30 mol% or less, (b) The number of functional groups is 2.0 or greater. It may also contain polyether polyol B.

[0037] The polyol component may contain one type of polyether polyol B that satisfies these conditions, or it may contain two or more types of polyether polyol B that satisfy these conditions.

[0038] [A. Polyether polyol A] [A.1. EO content] The "EO content (mol%)" of polyether polyol A refers to the ratio of moles of ethylene oxide (EO) units to the total number of moles of alkylene oxide units contained in polyether polyol A. Polyether polyol A may contain alkylene oxide units other than EO units. In this case, the type of alkylene oxide unit other than EO units is not particularly limited, but propylene oxide (PO) units are preferred.

[0039] The EO content of polyether polyol A primarily affects the moist thermal compression residual strain ε2. Generally, as the EO content increases, ε2 decreases. This is because (a) Because EO units are hydrophilic, the higher the EO content, the better the water absorption of the polyurethane foam, and the easier it is for the polyurethane foam, which has been compressed and deformed by the absorbed water, to return to its original shape, and (b) Unlike polyester polyols, polyether polyols are less susceptible to hydrolysis in high humidity environments and their ε2 is less likely to deteriorate. It is thought that...

[0040] To obtain such effects, the EO content of polyether polyol A is preferably 50.0 mol% or higher. More preferably, the EO content is 60.0 mol% or higher, 70.0 mol% or higher, 80.0 mol% or higher, or 90.0 mol% or higher. The EO content of polyether polyol A may even be 100.0 mol%.

[0041] [A.2. Functional Cardinality] The number of functional groups in polyether polyol A affects the compressive residual strain ε1. Generally, as the number of functional groups increases, ε1 decreases. This is thought to be because as the number of functional groups increases, the number of crosslinking points increases, and the rigidity of the polyurethane foam increases. To obtain this effect, the number of functional groups in polyether polyol A is preferably 2.0 or more. More preferably, the number of functional groups is 2.1 or more, or 2.2 or more.

[0042] On the other hand, if the number of functional groups in polyether polyol A becomes excessive, the hardness of the polyurethane foam may become excessively high. Therefore, the number of functional groups is preferably 3.0 or less. More preferably, the number of functional groups is 2.9 or less, or 2.8 or less.

[0043] [A.3. Weight average molecular weight] If the weight-average molecular weight of polyether polyol A becomes too low, the compressive residual strain ε1 and / or the moist thermal residual strain ε2 may deteriorate. Therefore, a weight-average molecular weight of 3000 or more is preferable. More preferably, the weight-average molecular weight is 4000 or more, or 5000 or more.

[0044] On the other hand, if the weight-average molecular weight of polyether polyol A becomes too high, the viscosity of the raw material mixture may become excessively high, potentially reducing manufacturability. Furthermore, the reactivity of the raw material mixture may decrease, potentially lowering the tear strength of the polyurethane foam. Therefore, a weight-average molecular weight of 12,000 or less is preferable. More preferably, the weight-average molecular weight is 10,000 or less, or 8,000 or less.

[0045] [A.4. Hydroxyl Value] If the hydroxyl value of polyether polyol A becomes too high, the seating comfort may deteriorate when used as a seat pad. Therefore, a hydroxyl value of 70 mgKOH / g or less is preferable. More preferably, the hydroxyl value is 60 mgKOH / g or less, or 55 mgKOH / g or less. On the other hand, if the hydroxyl value of polyether polyol A becomes too low, the polyurethane foam may become too hard, and when used as a seat pad, it may not be able to maintain a good seating comfort. Therefore, a hydroxyl value of 10 mg KOH / g or higher is preferable. More preferably, the hydroxyl value is 15 mg KOH / g or higher, or 20 mg KOH / g or higher.

[0046] [B. Polyether Polyol B] [B.1. EO content] The "EO content (mol%)" of polyether polyol B refers to the ratio of moles of ethylene oxide (EO) units to the total number of moles of alkylene oxide units contained in polyether polyol B. Polyether polyol B may contain alkylene oxide units other than EO units. In this case, the type of alkylene oxide unit other than EO units is not particularly limited, but propylene oxide (PO) units are preferred.

[0047] If the EO content of polyether polyol B becomes too high, the reactivity of the raw material mixture may decrease. Furthermore, the foam state and foam air permeability may deteriorate. Therefore, an EO content of 30 mol% or less is preferable. More preferably, the EO content is 20 mol% or less, 10 mol% or less, or 5 mol% or less. The EO content may even be zero.

[0048] [B.2. Number of functional groups] The number of functional groups in polyether polyol B should be 2.0 or greater. However, if the number of functional groups in polyether polyol B becomes too large, the elongation of the polyurethane foam may decrease. Therefore, the number of functional groups is preferably 4.0 or less. More preferably, the number of functional groups is 3.8 or less, or 3.6 or less.

[0049] [B.3. Weight average molecular weight] The weight-average molecular weight of polyether polyol B is not particularly limited, and an optimal value can be selected depending on the purpose. Generally, if the weight-average molecular weight of polyether polyol B is too low, it may impair the elongation and flexibility of the polyurethane foam. Therefore, a weight-average molecular weight of 1000 or more is preferable. More preferably, the weight-average molecular weight is 2000 or more, or even 3000 or more.

[0050] On the other hand, if the weight-average molecular weight of polyether polyol B becomes too high, the viscosity of the raw material mixture may increase excessively, potentially reducing manufacturability. Therefore, a weight-average molecular weight of 12,000 or less is preferable. More preferably, the weight-average molecular weight is 10,000 or less, or 8,000 or less.

[0051] [2.1.2. Polyisocyanate components] Polyisocyanate is another main ingredient in polyurethane foam. In the present invention, the polyisocyanate component includes at least carbodiimide-modified MDI. The polyisocyanate component may include only carbodiimide-modified MDI, or it may further include a polyisocyanate other than carbodiimide-modified MDI (hereinafter also referred to as "polyisocyanate B").

[0052] [A. Carbodiimide-modified MDI] Carbodiimide (-N=C=N-) modified MDI consists of diphenylmethane diisocyanate (MDI) produced by condensation involving CO2 generation between the -NCO groups in the presence of a catalyst. When carbodiimide-modified MDI is used as the polyisocyanate component, the cushioning properties of the polyurethane foam are increased, its elasticity is enhanced, its hysteresis loss is reduced, its deflection coefficient is reduced, or stress relaxation is reduced.

[0053] [B. Polyisocyanate B] In the present invention, the type of polyisocyanate B is not particularly limited, and the most suitable type can be selected depending on the purpose. Polyisocyanate B specifically includes bifunctional aromatic isocyanates, bifunctional alicyclic isocyanates, bifunctional aliphatic isocyanates, and isocyanates with more than two functional groups. The polyisocyanate component may contain one of these polyisocyanate B types, or it may contain two or more types.

[0054] Examples of bifunctional aromatic isocyanates include, 2,4-Tolylene diisocyanate, 2,6-Tolylene diisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, 4,4'-Diphenylmethane diisocyanate (4,4'-MDI), 2,4'-Diphenylmethane diisocyanate (2,4'-MDI), 2,2'-Diphenylmethane diisocyanate (2,2'-MDI), Xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylenediisonate, Examples include 3,3'-dimethoxy-4,4'-biphenylenediisocyanate, and mixtures thereof may also be used.

[0055] Examples of bifunctional alicyclic isocyanates include, Cyclohexane-1,4-diisocyanate, isophorone diisocyanate, Dicyclohexylmethane-4,4'-diisocyanate, Examples include methylcyclohexanediisocyanate.

[0056] Examples of bifunctional aliphatic isocyanates include, Butane-1,4-diisocyanate, hexamethylene diisocyanate, Isopropyl diisocyanate, methylene diisocyanate, lysine isocyanate These include isocyanates with two or more functions, such as polymeric MDI and isocyanates with three or more functions.

[0057] Examples of isocyanates with three or more functionalities include, 1-Methylbenzol-2,4,6-triisocyanate, 1,3,5-trimethylbenzol-2,4,6-triisocyanate, Biphenyl-2,4,4'-triisocyanate, Diphenylmethane-2,4,4'-triisocyanate, Methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'tetraisocyanate, Triphenylmethane-4,4',4"-triisocyanate, These are some examples.

[0058] [C. NCO group content (NCO%)] "NCO group content (NCO%)" refers to the ratio of the mass of NCO groups to the total mass of the polyisocyanate component. The NCO% of the polyisocyanate component is preferably less than 35%, more preferably less than 30%, and even more preferably 29.5% or less.

[0059] [2.1.3. Crosslinking agents] The raw material mixture may also contain a crosslinking agent. The crosslinking agent is preferably a compound having at least three functional groups and containing a functional group with an active hydrogen atom (e.g., a hydroxyl group, an amino group, etc.). The crosslinking agent may consist only of compounds with three or more functional groups, or it may further contain compounds with two functional groups in addition to compounds with three or more functional groups.

[0060] The number of functional groups in the crosslinking agent affects the compression set ε1. To obtain a polyurethane foam with a low compression set ε1, it is preferable that the number of functional groups in the crosslinking agent be 3 or more. On the other hand, if the number of functional groups in the crosslinking agent becomes too large, the hardness of the polyurethane foam may become excessively high. Therefore, it is preferable that the number of functional groups in the crosslinking agent be 6 or less.

[0061] The molecular weight of the crosslinking agent is not particularly limited, and an optimal value can be selected depending on the purpose. Preferably, the molecular weight of the crosslinking agent is 1000 or less, 700 or less, or 500 or less. Furthermore, the molecular weight of the crosslinking agent is preferably 60 or higher, 90 or higher, or 120 or higher.

[0062] Examples of crosslinking agents include glycerin, diethanolamine (DEA), and polyfunctional polyols. The raw material mixture may contain one of these crosslinking agents, or it may contain two or more of them.

[0063] [2.1.4. Foaming agents] A "foaming agent" is an additive used to generate bubbles in a liquid raw material mixture during the resinification process. In the present invention, the foaming agent is (a) A physical foaming agent that generates gas by pressure reduction or heating, or (b) Chemical blowing agents that generate gas by thermal decomposition or chemical reaction Either of these is acceptable.

[0064] Examples of physical blowing agents include, (a) hydrocarbons such as cyclopentane, isopentane, and n-pentane, (b) Halogen compounds such as methylene chloride, trichlorofluoromethane, dichlorodifluoromethane, nonafluorobutyl methyl ether, pentafluoroethyl methyl ether, and pentafluoroisopropyl methyl ether. These are some examples.

[0065] Examples of chemical blowing agents include, (a) Water that reacts with an isocyanate group to produce CO2, (b) Azodicarbonamides that generate nitrogen, carbon monoxide, carbon dioxide, or ammonia gas by thermal decomposition. These are some examples.

[0066] The raw material mixture may contain one of these blowing agents, or it may contain two or more of them. Among these, water is preferred as the foaming agent. When water is used as the foaming agent, the CO2 gas generated by the reaction of water with isocyanate groups promotes foaming. In addition, the heat of reaction between water and isocyanate groups accelerates the curing of the resin.

[0067] [2.1.5. Catalyst] "Catalyst" refers to a catalyst that has a strong effect in promoting the resin formation reaction, and / or a catalyst that has a strong effect in promoting the foaming reaction. Furthermore, if a chemical blowing agent (water) is not used as the blowing agent, it is preferable to use a catalyst that has a strong effect in promoting the resinification reaction.

[0068] Examples of catalysts include amine-based catalysts and metal catalysts. Amine-based catalysts are highly effective in promoting both the resinification reaction and the foaming reaction. Metal catalysts are highly effective in promoting the resinification reaction. The raw material mixture may contain one of these catalysts, or two or more.

[0069] Examples of amine-based catalysts include, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, N,N-dimethylaminoethanol, N,N',N'-trimethylaminoethylpiperazine, triethylenediamine These are some examples.

[0070] Examples of metal catalysts include, (a) Tin catalysts such as stanus octoate and dibutylthin dilaurate, (b) Mercury catalysts such as phenylmercurypropionate, (c) Lead catalysts such as lead octonate These are some examples.

[0071] [2.2. Auxiliary raw materials] The raw material mixture may also contain, in addition to the main raw materials mentioned above, one or more of the following auxiliary raw materials. Specifically, the auxiliary raw materials include the following:

[0072] [2.2.1. Foam stabilizers] A "foam stabilizer" is an additive that helps to equalize the size and distribution of bubbles. By adding a foam stabilizer to the raw material mixture, a polyurethane foam with uniform bubble size and distribution can be obtained. Examples of foam stabilizers include silicone-based foam stabilizers, fluorine-containing compound-based foam stabilizers, and known surfactants.

[0073] [2.2.2. Flame retardants] A "flame retardant" is an additive that makes polyurethane foam flame-retardant. Examples of flame retardants include halogen-based flame retardants, phosphorus-based flame retardants, metal hydroxide-based flame retardants, and antimony-based flame retardants.

[0074] [2.3. Amount and content] [2.3.1. Amount and content of main ingredients] [A. Amount of polyether polyol A] "Amount of polyether polyol A (parts by mass)" refers to the total mass of polyether polyol A in the polyol components, when the total mass of the polyol components is set to 100.

[0075] Generally, the higher the amount of polyether polyol A added, the lower the humid thermal compression set ε2 of the polyurethane foam. To obtain this effect, the amount of polyether polyol A added is preferably 50 parts by mass or more. More preferably, the amount added is 60 parts by mass or more, or 70 parts by mass or more.

[0076] The amount of polyether polyol A may be 100 parts by mass. However, if the amount of polyether polyol A is excessive, the moldability of the foam may decrease. Therefore, the amount of polyether polyol A is preferably 90 parts by mass or less.

[0077] [B. Content of carbodiimide-modified MDI] "Carbodiimide-modified MDI content (mass%)" refers to the ratio of the mass of carbodiimide-modified MDI to the total mass of polyisocyanate components.

[0078] Generally, the higher the content of carbodiimide-modified MDI, the lower the stress relaxation and hysteresis loss of the polyurethane foam. To obtain such effects, the content of carbodiimide-modified MDI is preferably 50% by mass or more. More preferably, the content is 60% by mass or more, or 70% by mass or more.

[0079] The content of carbodiimide-modified MDI may be 100% by mass. Preferably, the content of carbodiimide-modified MDI is 90% by mass or less, or 80% by mass or less. The NCO content of carbodiimide-modified MDI is preferably 40% or less, 35% or less, or 32% or less, and particularly preferably 30% or less. Furthermore, the NCO content is preferably 15% or more, 20% or more, 25% or more, or 27% or more.

[0080] [C. Amount of crosslinking agent A] "Amount of crosslinking agent A (parts by mass)" refers to the mass of crosslinking agent A when the total mass of the polyol components is set to 100.

[0081] Generally, the higher the content of crosslinking agent A, the smaller the compression set ε1 of the polyurethane foam. To obtain this effect, it is preferable that the amount of crosslinking agent A is greater than 0 parts by mass. More preferably, the amount is 1.0 part by mass or more, or 2.0 parts by mass or more.

[0082] On the other hand, if the amount of crosslinking agent A is excessive, the hardness of the polyurethane foam may become excessively high. Therefore, the amount of 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.

[0083] [D. Amount of polyether polyol B] "Amount of polyether polyol B (parts by mass)" refers to the total mass of polyether polyol B in the polyol components, when the total mass of the polyol components is set to 100.

[0084] Generally, when the amount of polyether polyol B is excessive, the amount of polyether polyol A decreases relatively. As a result, the moist heat compression set ε2 of the polyurethane foam may increase. Therefore, the amount of polyether polyol B is preferably less than 50 parts by mass. More preferably, the amount is 40 parts by mass or less, or 30 parts by mass or less.

[0085] [E. Isocyanate Index] The "isocyanate index" is the value obtained by multiplying the ratio of the equivalent amount of isocyanate groups in the polyisocyanate in the raw material mixture to the equivalent amount of active hydrogen groups in the raw material mixture by 100.

[0086] In the present invention, the isocyanate index is not particularly limited, and an optimal value can be selected depending on the purpose. Generally, as the isocyanate index increases, the number of crosslinking points increases, and therefore the compressive residual strain ε1 of the polyurethane foam decreases. For this reason, an isocyanate index of 90 or higher is preferred. More preferably, the isocyanate index is 95 or higher. On the other hand, if the isocyanate index becomes too high, the hardness of the polyurethane foam may become excessively high. Therefore, an isocyanate index of 115 or less is preferable.

[0087] [2.3.2. Amount of auxiliary ingredients] In this invention, the amount of auxiliary ingredients is not particularly limited, and the optimal amount can be selected according to the purpose.

[0088] [2.4. Reaction of the raw material mixture] In the method for producing polyurethane foam according to the present invention, either slab foaming or mold foaming can be employed for foaming. Slab foaming is a method in which a polyurethane foam manufacturing composition (raw material for polyurethane foam) is mixed, extruded onto a belt conveyor, and foamed under atmospheric pressure and at room temperature.

[0089] On the other hand, mold foaming is a method in which raw materials for polyurethane foam production (raw materials for polyurethane foam) are mixed and injected into the cavity of a mold, and foamed into the shape of the cavity. Mold foaming is preferable because it can produce polyurethane foam that has a shape close to that of a sheet pad. Furthermore, when using mold molding, polyisocyanates with low viscosity are preferred; for example, prepolymer-type polyisocyanates are not preferred.

[0090] [3. Effect] When manufacturing polyurethane foam, using a raw material mixture containing polyether polyol A that meets predetermined conditions and carbodiimide-modified MDI yields a polyurethane foam with low compressive set ε1 and moist heat compressive set ε2. Furthermore, optimizing the manufacturing conditions allows for the production of a polyurethane foam with a 25% hardness of 150N or higher.

[0091] The decrease in compressive residual strain ε1 is thought to be due to the increased rigidity of the polyurethane foam, resulting from the use of polyether polyol A, which has a large number of functional groups and a high weight-average molecular weight. The reason the moist thermal compression set ε2 is small is thought to be because the use of polyether polyol A with a high EO content increases water absorption, and thus increases the restorative force due to absorbed water. Furthermore, the moderately increased hardness is thought to be due to the use of polyether polyol A, which has a large number of functional groups, resulting in an increased number of crosslinking points. [Examples]

[0092] (Examples 1-3, Comparative Examples 1-2) [1. Sample Preparation] A mixture (hereinafter also referred to as "component A") was obtained by blending polyether polyol, a crosslinking agent, a foaming agent, a catalyst, a foam stabilizer, and a flame retardant in predetermined ratios. Furthermore, MDI containing TDI-80, polymeric MDI, and carbodiimide-modified MDI (NCO content: 29%, carbodiimide-modified MDI content: 75% by mass) was blended in a predetermined ratio to obtain a mixture (hereinafter also referred to as "component B"). Furthermore, component A and component B were mixed so that the isocyanate index reached a predetermined value, thereby obtaining a raw material mixture. Table 1 shows the composition of component A and component B.

[0093] [Table 1]

[0094] In addition, in Examples 1 and 2, polyether polyol A is used as follows: (a) Polyether polyol 2 (molecular weight: 4000, number of functional groups: 2, EO content: 80 mol%), (b) Polyether polyol 3 (molecular weight: 5000, number of functional groups: 3, EO content: 80 mol%) and This is an example using a mixture of the two. Furthermore, Example 3 is an example in which only polyether polyol 4 (molecular weight: 3500, number of functional groups: 3, EO content: 75 mol%) was used as polyether polyol A.

[0095] The resulting raw material mixture was poured into a 400mm x 400mm x 100mm mold and allowed to foam and harden at a mold temperature of approximately 60°C. The curing time was 5 minutes.

[0096] [2. Test Method] [2.1. Core Density] The skin layer was removed from the obtained foam to prepare a sample for core density measurement. The core density was measured using the obtained sample in accordance with JIS K 7222.

[0097] [2.2. 25% hardness] The 25% hardness was measured in accordance with JIS K 6400-2 Method D.

[0098] [2.3. Hysteresis Loss] Hysteresis loss was measured in accordance with JIS K 6400-2 Method E.

[0099] [2.4. Deflection coefficient] The deflection coefficient was measured in accordance with JIS K 6400-2 Method E. The deflection coefficient was determined by dividing the 65% compressive load by the 25% compressive load.

[0100] [2.5. Stress Relaxation] Stress relaxation was sought in accordance with JIS K 6400-4. The load was set to 196 N, and the pressurization time was 5 minutes.

[0101] [2.6. Compression Residual Strain ε1] The compression set ε1 was measured in accordance with JIS K 6400-4. The test temperature was 70°C, the test duration was 22 hours, and the compressibility was set to 50%.

[0102] [2.7. Moist heat compression residual strain ε2] The moist thermal compression set ε2 was measured in accordance with JIS K 6400-4. The test temperature was 50°C, the humidity was 95%RH, the test duration was 22 hours, and the compressibility was 50%.

[0103] [3. Results] Table 2 shows the results. Table 2 also shows the test piece size and the evaluation test method for each physical property. From Table 2, the following can be seen: (1) Comparative Example 1 had a moist heat compression residual strain ε2 exceeding 5.0%. This is thought to be because the raw material mixture did not contain polyether polyol A with an EO content of 50 mol% or more. (2) In Comparative Example 2, the compressive residual strain ε1 exceeded 5.0%. This is thought to be because the raw material mixture did not contain polyether polyol A with more than 2.0 functional groups.

[0104] (3) In all of Examples 1 to 3, ε1 was 5.0% or less and ε2 was 5.0% or less. This is thought to be because the raw material mixture contains polyether polyol A that satisfies the specified conditions. In addition, the density of Examples 1 to 3 was 68 kg / m³. 3 It is lightweight, and exhibits excellent deflection coefficient and hysteresis loss. (4) In Examples 1 and 2, ε1 and ε2 were lower compared to Example 3.

[0105] [Table 2]

[0106] Although embodiments of the present invention have been described in detail above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. [Industrial applicability]

[0107] The seat pad according to the present invention can be used as a seat pad for seats in automobiles, aircraft, and railway vehicles, as well as for sofas, mattresses, and cushioning materials thereof.

Claims

1. A seat pad made of polyurethane foam, The aforementioned polyurethane foam Compression residual strain ε 1 is 5.0% or less, and Moist heat compression residual strain ε 2 The percentage is 5.0% or less. The polyurethane foam is obtained by reacting a raw material mixture containing a polyol component and a polyisocyanate component. The aforementioned polyol component is (a) The EO content is 50 mol% or more, (b) The number of functional groups is 2.0 or more and 3.0 or less, (c) The weight-average molecular weight is 3000 or more. Containing one or more types of polyether polyol A, The polyisocyanate component includes carbodiimide-modified MDI. Seat pad. however, The aforementioned "compression residual strain ε 1 " refers to the value measured in accordance with JIS K 6400-4 (however, temperature: 70°C, compressibility: 50%). The aforementioned "moist heat compression residual strain ε 2 " refers to a value measured in accordance with JIS K 6400-4 (where temperature: 50°C, humidity: 95% RH, compressibility: 50%). The polyol component is, as the polyether polyol A, (a) The EO content is 50 mol% or more, (b) The number of functional groups is 2.0, (c) The weight-average molecular weight is 3000 or more. Except when it includes only objects.

2. The sheet pad according to claim 1, wherein the polyurethane foam has a 25% hardness of 150 N or more. However, the aforementioned "25% hardness" refers to the value measured in accordance with JIS K 6400-2 Method D.

3. The aforementioned polyol component is (a) The EO content is 30 mol% or less, (b) The number of functional groups is 2.0 or more. The sheet pad according to claim 1, further comprising one or more types of polyether polyol B.

4. A seat pad comprising polyurethane foam, The aforementioned polyurethane foam The compressive residual strain ε1 is 5.0% or less, and, The moist thermal compression residual strain ε² is 2.0% or less. The polyurethane foam is obtained by reacting a raw material mixture containing a polyol component and a polyisocyanate component. The aforementioned polyol component is (a) The EO content is 50 mol% or more, (b) The number of functional groups is 2.0 or more and 3.0 or less, (c) The weight-average molecular weight is 3000 or more. Containing one or more types of polyether polyol A, The polyisocyanate component includes carbodiimide-modified MDI. Seat pad. however, The aforementioned "compression residual strain ε1" refers to the value measured in accordance with JIS K 6400-4 (however, temperature: 70°C, compressibility: 50%). The aforementioned "moist heat compression residual strain ε²" refers to the value measured in accordance with JIS K 6400-4 (where temperature: 50°C, humidity: 95% RH, compressibility: 50%).

5. A seat pad comprising polyurethane foam, The aforementioned polyurethane foam The compressive residual strain ε1 is 5.0% or less. The moist thermal compression residual strain ε² is 5.0% or less, and, ε² / ε¹ is between 0.03 and 0.8, The polyurethane foam is obtained by reacting a raw material mixture containing a polyol component and a polyisocyanate component. The aforementioned polyol component is (a) The EO content is 50 mol% or more, (b) The number of functional groups is 2.0 or more and 3.0 or less, (c) The weight-average molecular weight is 3000 or more. Containing one or more types of polyether polyol A, The polyisocyanate component includes carbodiimide-modified MDI. Seat pad. however, The aforementioned "compression residual strain ε1" refers to the value measured in accordance with JIS K 6400-4 (however, temperature: 70°C, compressibility: 50%). The aforementioned "moist heat compression residual strain ε²" refers to the value measured in accordance with JIS K 6400-4 (where temperature: 50°C, humidity: 95% RH, compressibility: 50%).

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