seat pad

Abstract

This seat pad comprises a polyurethane foam. The polyurethane foam has a deflection coefficient of 2.8 or less, with a displacement rate (t1×100 / t0) of 30% or greater. t0 refers to the thickness of a plate-shaped sample cut from the polyurethane foam, and t1 is the maximum value for the displacement (sinking quantity) of an iron test plate with which the plate-shaped sample is used to measure attenuation characteristics in accordance with JASO B408. It is preferable that the displacement rate of the seat pad for when t0 is 50 mm be 45% or greater.

Description

Technical Field

[0001] The present invention relates to a seat pad, and more particularly to a seat pad provided with a polyurethane foam having a small deflection coefficient and a large displacement rate.

Background Art

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

[0003] When an occupant 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 occupant, the unevenness of the road surface on which the automobile travels, and the like. Therefore, if the deflection coefficient or the amount of deflection (or displacement rate) of the seat pad is inappropriate, the seat may be uncomfortable to sit on.

[0004] Therefore, various proposals have been made conventionally to solve this problem. For example, in Patent Document 1, (a) 60 parts by mass of polyol A obtained by reacting a compound (initiator 1) having a hydroxyl value of 168 mgKOH / g obtained by adding propylene oxide to glycerin with an ethylene oxide / propylene oxide mixture containing 8% by mass of ethylene oxide; (b) Polyol K: 40 parts by mass, in which polymer particles are dispersed in polyol G5 obtained by reacting initiator 1 with propylene oxide, (c) TDI-80 (NOC content: 44.8% by mass): an amount equivalent to an isocyanate index of 105 A flexible polyurethane foam for automotive seats obtained by reacting raw materials containing is disclosed.

[0005] The document states: (A) By this method, a soft polyurethane foam with an X value (= static spring constant at a load of 883N / static spring constant at a load of 98N) of 2.94 can be obtained, and (B) When such soft polyurethane foam is applied to car seats, the feeling of bottoming out after sitting down is eliminated. It is stated.

[0006] Patent Document 2 contains: The cushion body that makes up the seating area, A low-breathability foam is integrally provided on the bottom surface of the cushion body. A seat pad consisting of the following is disclosed. The document states that by integrally incorporating a low-breathability foam on the bottom surface of the cushion, vibrations that worsen ride comfort can be absorbed.

[0007] Patent Document 3 contains: (a) 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: 90 parts by weight, (b) 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%: 10 parts by weight, (c) A linear silicone-based foam stabilizer with a viscosity of 7280 mPa·s (25℃) and a surface tension of 20.08 mN / m (25℃): 0.5 parts by weight, (d) A mixture of TDI (80% by weight) and MDI (20% by weight) (NCO = 44.8%): an amount equivalent to 100 on the isocyanate index and A polyurethane foam obtained by reacting raw materials containing is disclosed. The document describes how this method makes it possible to obtain a polyurethane foam that is less prone to bottoming out even when thinner than conventional foams, and that also has high breathability.

[0008] Patent Document 4 discloses a deformation analysis method for simulating the nonlinear viscoelastic behavior of a compressible material having nonlinear viscoelastic behavior, although it is not a sheet pad. The document states that by using a model that has both a linear viscoelastic portion based on a generalized Maxwell model and a compressible elastoplastic portion with a yield condition dependent on hydrostatic stress, the damping behavior of urethane foam when slowly compressed can be analyzed with high accuracy.

[0009] Patent Document 5 contains: (a) A three-dimensional mesh material is placed inside a mold, and polyurethane is foamed inside the mold to form a seat back portion in which the three-dimensional mesh material is incorporated into a polyurethane foam cushioning material. (b) With tension applied to the net material protruding from both sides of the seat back, the net material is fixed to the frame. An automotive seat obtained by this method is disclosed.

[0010] The document states: (A) By this method, a seat back section can be obtained in which a three-dimensional net material is integrally incorporated into a cushioning material made of polyurethane foam, and (B) The parts of the net material that are impregnated with polyurethane have high surface rigidity, which allows them to dampen the impact when an impact is applied from behind the occupants. It is stated.

[0011] The hardness and elasticity of a seat pad affect the sitting comfort when sitting. To increase the cushioning feeling, it is preferable to bend more in the high load region, that is, the bending coefficient is small. Also, to reduce the feeling of having a bottom when sitting, it is preferable that the displacement rate is large. However, there has been no example of a seat pad that achieves both a small bending coefficient and a large displacement rate in the past.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0013] The problem to be solved by the present invention is to provide a seat pad made of polyurethane foam, having a small bending coefficient and a large displacement rate.

Means for Solving the Problems

[0014] In order to solve the above problems, the seat pad according to the present invention includes polyurethane foam, the polyurethane foam has a bending coefficient of 2.8 or less, and the displacement rate represented by the following formula (1) is 30% or more.

[0015] Displacement rate = t1 × 100 / t0…(1) however, t0 is the thickness of the flat plate-shaped sample cut from the polyurethane foam. t1 is the maximum displacement (sinking amount) of the iron grinding plate when the damping characteristics are measured in accordance with JASO B408 using the aforementioned flat plate sample.

[0016] 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) Weight-average molecular weight is greater than 3500 Contains one or more types of polyether polyol A The aforementioned polyisocyanate component includes carbodiimide-modified MDI. I prefer that. [Effects of the Invention]

[0017] When manufacturing polyurethane foam, using a raw material mixture containing polyether polyol A that satisfies predetermined conditions and carbodiimide-modified MDI yields a polyurethane foam with a deflection coefficient of 2.8 or less and a displacement rate of 30% or more.

[0018] The reason the deflection coefficient is 2.8 or less is thought to be because the use of polyether polyol A with a high EO content results in a relatively smaller number of side chains in the polymer chain, leading to less entanglement between polymer chains. This also makes the molecular chains more flexible, imparting elasticity to the polyurethane foam. The displacement rate exceeding 30% is thought to be due to the use of polyether polyol A, which has a large weight-average molecular weight. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic diagram of a damping test machine. [Figure 2] These are the FS curves of the polyurethane foams obtained in Examples 1-4 and Comparative Examples 1-2. [Figure 3] These are the results of the damping tests on the polyurethane foam (100 mm thick) obtained in Examples 1-4 and Comparative Examples 1-2. [Figure 4] These are the results of the damping tests on the polyurethane foam (50 mm thick) obtained in Examples 1-4 and Comparative Examples 1-2. [Modes for carrying out the invention]

[0020] 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 contains a crosslinking agent, a foaming agent, and a catalyst.

[0021] [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.

[0022] [1.2. Characteristics] [1.2.1. Deflection coefficient] The "deflection coefficient" refers to the value measured in accordance with JIS K 6400-2:2012. 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% compression 25% The value obtained by dividing by (=F 65% / F 25% ) refers to.

[0023] As described later, the polyurethane foam according to the present invention uses polyether polyol A with a high EO content as one of its raw materials. When polyether polyol A with a high EO content is used, the deflection coefficient of the polyurethane foam becomes relatively small. This is thought to be because the number of side chains contained in the polymer chain is relatively small, resulting in less entanglement between polymer chains, and as a result the molecular chain becomes more flexible, imparting elasticity to the polyurethane foam. In general, the smaller the deflection coefficient, the greater the deflection in the high-load range, resulting in a greater cushioning effect.

[0024] To maximize cushioning, the deflection coefficient of the polyurethane foam needs to be 2.8 or less. Optimizing the manufacturing conditions results in a deflection coefficient of 2.7 or less, 2.6 or less, or 2.5 or less. On the other hand, if the deflection coefficient becomes too small, the amount of deflection may become too large, and the feeling of bottoming out may increase. Therefore, a deflection coefficient of 2.0 or higher is preferable. More preferably, the deflection coefficient is 2.1 or higher, or 2.2 or higher.

[0025] [1.2.2. Displacement Rate] "Displacement rate" refers to the value expressed by the following equation (1). Displacement rate = t1 × 100 / t0 ... (1) however, t0 is the thickness of the flat plate-shaped sample cut from the polyurethane foam. t1 is the maximum displacement (sinking amount) of the iron grinding plate when the damping characteristics are measured in accordance with JASO B408 using the aforementioned flat plate sample.

[0026] The displacement rate strictly depends on the thickness t0 of the flat plate-shaped sample. The polyurethane foam according to the present invention only needs to satisfy the following conditions when multiple displacement rates are measured using multiple flat plate-shaped samples with different thicknesses t0.

[0027] Generally, the greater the displacement rate, the greater the cushioning when seated. To achieve this effect, the displacement rate needs to be 30% or higher. Preferably, the displacement rate is 35% or higher, 40% or higher, 45% or higher, 50% or higher, or 55% or higher.

[0028] In the polyurethane foam according to the present invention, when the manufacturing conditions are optimized, the displacement rate when t0 = 50 mm is 45% or more. Further optimization of the manufacturing conditions results in a displacement rate of 55%, 60% or more, or 65% or more when t0 = 50 mm. Similarly, in the polyurethane foam according to the present invention, optimizing the manufacturing conditions results in a displacement rate of 50% or more when t0 = 100 mm. Further optimizing the manufacturing conditions results in a displacement rate of 55% or more when t0 = 100 mm.

[0029] [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.

[0030] [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) Weight-average molecular weight is greater than 3500 Contains polyether polyol A.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] [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.

[0035] The EO content of polyether polyol A primarily affects the coefficient of deflection. Generally, the higher the EO content of polyether polyol A, the lower the coefficient of deflection. This is thought to be because, as the EO content increases, the number of side chains (-CH3) in the polymer chain decreases relatively, reducing entanglement between polymer chains. This, in turn, makes the molecular chains more flexible, imparting elasticity to the polyurethane foam. 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%.

[0036] [A.2. Functional Cardinality] The number of functional groups in polyether polyol A affects the deflection coefficient. Generally, the larger the number of functional groups in polyether polyol A, the higher the rigidity of the polyurethane foam and the smaller the compressive residual strain. To obtain such effects, the number of functional groups in polyether polyol A is preferably 2.0 or higher. More preferably, the number of functional groups is 2.1 or higher, or 2.2 or higher.

[0037] On the other hand, if the number of functional groups in polyether polyol A becomes excessive, the stiffness of the polyurethane foam may become excessively high, and the coefficient of deflection may increase. 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.

[0038] [A.3. Weight average molecular weight] As the weight-average molecular weight of polyether polyol A increases, the hardness of the polyurethane foam decreases, and it becomes more flexible. To obtain this effect, the weight-average molecular weight of polyether polyol A is preferably greater than 3500. More preferably, the weight-average molecular weight is 4000 or more, or even 5000 or more.

[0039] 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.

[0040] [A.4. Hydroxyl Value] If the hydroxyl value of polyether polyol A becomes too high, the seating comfort when used as a seat pad may deteriorate. 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 sitting 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.

[0041] [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.

[0042] 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.

[0043] [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.

[0044] [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.

[0045] 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.

[0046] [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").

[0047] [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 elasticity of the polyurethane foam increases, resulting in greater deflection under high load conditions.

[0048] [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 raw material mixture may contain one of these polyisocyanate B types, or it may contain two or more types.

[0049] 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.

[0050] Examples of bifunctional alicyclic isocyanates include, Cyclohexane-1,4-diisocyanate, isophorone diisocyanate, Dicyclohexylmethane-4,4'-diisocyanate, Examples include methylcyclohexanediisocyanate.

[0051] 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.

[0052] Examples of isocyanates with more than two functional groups 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.

[0053] [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.

[0054] [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.

[0055] The number of functional groups in the crosslinking agent affects the compression set. To obtain a polyurethane foam with low compression set, 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.

[0056] 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.

[0057] 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.

[0058] [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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] [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.

[0063] 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.

[0064] Examples of amine-based catalysts include, N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, N,N-dimethylaminoethanol, N,N',N'-trimethylaminoethylpiperazine, triethylenediamine These are some examples.

[0065] 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.

[0066] [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:

[0067] [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.

[0068] [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.

[0069] [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.

[0070] Generally, the greater the amount of polyether polyol A added, the smaller the coefficient of deflection 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.

[0071] 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.

[0072] [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.

[0073] Generally, the higher the content of carbodiimide-modified MDI, the lower the deflection coefficient and the higher the displacement rate of the polyurethane foam. To obtain these 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.

[0074] 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.

[0075] [C. Amount of crosslinking agent] "Amount of crosslinking agent (parts by mass)" refers to the mass of the crosslinking agent when the total mass of the polyol components is set to 100.

[0076] Generally, the higher the amount of crosslinking agent added, the lower the compression set of the polyurethane foam. To achieve this effect, it is preferable that the amount of crosslinking agent be greater than 0 parts by mass. More preferably, the amount is 1 part by mass or more, or 2 parts by mass or more.

[0077] On the other hand, if the amount of crosslinking agent is excessive, the hardness of the polyurethane foam may become excessively high. Therefore, the amount of 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.

[0078] [D. Amount of polyether polyol B] "Amount of polyether polyol B (parts by mass)" refers to the mass of polyether polyol B in the polyol components, when the total mass of the polyol components is set to 100.

[0079] Generally, when the amount of polyether polyol B is excessive, the amount of polyether polyol A decreases relatively. As a result, the deflection coefficient of the polyurethane foam may increase, or the displacement rate may decrease. 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.

[0080] [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.

[0081] In the present invention, the isocyanate index is not particularly limited, and an optimal value can be selected depending on the purpose. Generally, the higher the isocyanate index, the lower the compressive residual strain. To obtain such an effect, an isocyanate index of 90 or higher is preferable. 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.

[0082] [2.3.2. Amount of auxiliary ingredients] In this invention, the amount of auxiliary ingredients is not particularly limited, and the optimal content can be selected according to the purpose.

[0083] [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.

[0084] 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.

[0085] [3. Effect] When manufacturing polyurethane foam, using a raw material mixture containing polyether polyol A that satisfies predetermined conditions and carbodiimide-modified MDI yields a polyurethane foam with a deflection coefficient of 2.8 or less and a displacement rate of 30% or more. When such polyurethane foam is used as a seat pad, it exhibits excellent deflection coefficient and superior damping characteristics, as well as deflection (displacement rate), even at thin walls (e.g., 50 mm or less).

[0086] The reason the deflection coefficient is 2.8 or less is thought to be because the use of polyether polyol A with a high EO content results in a relatively smaller number of side chains in the polymer chain, leading to less entanglement between polymer chains. This also makes the molecular chains more flexible, imparting elasticity to the polyurethane foam. The displacement rate exceeding 30% is thought to be due to the use of polyether polyol A, which has a large weight-average molecular weight. [Examples]

[0087] (Examples 1-4, Comparative Examples 1-2) [1. Sample Preparation] A mixture (hereinafter also referred to as "component A") was obtained by blending a polyether polyol, a crosslinking agent, a foaming agent, a catalyst, and a foam stabilizer in predetermined ratios. Furthermore, polymeric MDI, MDI containing carbodiimide-modified MDI (NCO content: 29%, carbodiimide-modified MDI content: 75% by mass), and MDI prepolymer (NCO content: 28.5%) were blended in predetermined ratios 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.

[0088] In Example 1, only polyether polyol 2 (molecular weight: 4000, number of functional groups: 2, EO content: 80 mol%) was used as polyether polyol A. Examples 2 and 3 use polyether polyol A 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. Example 4 is an example in which only polyether polyol 3 is used as polyether polyol A.

[0089] [Table 1]

[0090] 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.

[0091] [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.

[0092] [2.2. 25% hardness] The 25% hardness was measured in accordance with JIS K 6400-2 Method D.

[0093] [2.3. Hysteresis Loss] Hysteresis loss was measured in accordance with JIS K 6400-2 Method E.

[0094] [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.

[0095] [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.

[0096] [2.6. Damping Characteristics] Figure 1 shows a schematic diagram of the damping test machine. A 50 kg iron grinding plate was placed 20 mm above the sample. The iron grinding plate was then dropped from that position towards the sample. The vibration characteristics of the sample were evaluated from the displacement of the iron grinding plate after the drop and the time it took for the vibration to stop.

[0097] [3. Results] Table 2 shows the results. Table 2 also shows the test piece size and the evaluation test method for each physical property. Figure 2 shows the FS curves of the polyurethane foam obtained in Examples 1-4 and Comparative Examples 1-2. Figure 3 shows the results of the decay test for the polyurethane foam (100 mm thick) obtained in Examples 1-4 and Comparative Examples 1-2. Figure 4 shows the results of the decay test for the polyurethane foam (50 mm thick) obtained in Examples 1-4 and Comparative Examples 1-2. From Table 2 and Figures 2-4, the following can be seen.

[0098] (1) In Comparative Example 1, the displacement rate at t0=50mm and the displacement rate at t0=100mm were both less than 30%. This is thought to be because it does not contain polyether polyol A with a weight-average molecular weight exceeding 3500. (2) Comparative Example 2 had a large displacement ratio, but its deflection coefficient exceeded 2.8. This is thought to be due to an excessively low content of polyether polyol A. (3) In all of Examples 1 to 4, the deflection coefficient was 2.8 or less. Also, regardless of the thickness t0 of the sample, the displacement rate was 50% or more in all cases.

[0099] [Table 2]

[0100] 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]

[0101] 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 The deflection coefficient is 2.8 or less. The displacement ratio expressed by the following equation (1) is 30% or more, 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 greater than 3500. Contains one or more types of polyether polyol A The polyisocyanate component includes carbodiimide-modified MDI. Seat pad. Change rate = t 1 ×100 / t 0 …(1) however, t 0 The thickness of the flat plate-shaped sample cut from the polyurethane foam, t 1 This is the maximum value of the displacement (sinking amount) of the iron grinding plate when the damping characteristics are measured in accordance with JASO B408 using the aforementioned flat plate sample.

2. t 0 The seat pad according to claim 1, wherein the displacement rate when the displacement is 50 mm is 45% or more.

3. t 0 The seat pad according to claim 1, wherein the displacement rate when the displacement is 100 mm is 50% or more.

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

Images