Polyurethane foam and seat cushions

Abstract

To provide a polyurethane foam having a large bending feeling even when thinned, and a seat cushion using the same.SOLUTION: A polyurethane foam includes a large diameter cell having a diameter of 1000 μm or more and a small diameter cell having a diameter of less than 1000 μm, and a Mlarge / Msmall ratio is 5.0 or more. When choosing 100 or more cells at random from all cells included in the polyurethane foam to calculate the cumulative distribution of diameter number standard of the cells, Msmall is the arithmetic average diameter of the cells having a cumulative value of 0-10% in the cumulative distribution; and Mlarge is the arithmetic average diameter of the cells having a cumulative value of 90-100% in the cumulative distribution.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a polyurethane foam and a seat cushion, and more particularly to a polyurethane foam that provides a high cushioning feel even when made thin, and a seat cushion that uses such a polyurethane foam as a seat pad. [Background technology]

[0002] Automobile seats are classified into two types: one in which the seat cushion (seat portion) and the seat back (back portion) are separate, and one in which the two are integrated. In addition, automobile seats generally: (a) a seat pad for receiving the weight of an occupant when the occupant is seated; (b) a frame for supporting a seat pad; (c) A trim cover that covers the outer surface of the seat pad and It is equipped with: The seat pad is generally made of flexible polyurethane foam.

[0003] When an occupant sits in an automobile seat equipped with a seat pad, the seat pad is compressed in the direction of the load 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 that comes into contact with the automobile seat, the posture of the occupant, etc. Therefore, if the hardness of the seat pad is constant regardless of the location, the seat may become uncomfortable to sit on.

[0004] Therefore, various proposals have been made in the past to solve this problem. For example, Patent Document 1 discloses a method for producing a flexible polyurethane foam product by foam molding a foaming raw material containing two types of foam stabilizers (a silicone surfactant or a fatty acid ester compound). The same document states: (a) By this method, a flexible polyurethane foam molded article can be obtained in which the cell diameter gradually increases from the surface (seating surface) toward the thickness direction, and (b) The cell diameter can be changed by changing the amount of two types of foam stabilizer added. is stated.

[0005] Patent Document 2 discloses a method for producing a flexible polyurethane foam by foam molding a foaming raw material containing a foam stabilizer and SiO2 (a foam opener), although the method is not intended to improve the comfort of seats. The same document states: (a) By this method, a soft polyurethane foam having a spongy cell structure (a double cell structure in which coarse cells and fine cells are mixed), low density, and soft like a sponge can be obtained; and (b) SiO2 has the effect of roughening the cells formed during foaming. is stated.

[0006] Patent Document 3 discloses a method for producing a coarse-celled flexible urethane foam by foam molding a foaming raw material containing a trifunctional polyol for flexible foams, a hydrophilic polyol, and a polyoxyalkylene-modified polysiloxane (a foam-breaking silicone for hard foams), although the method is not intended to improve the comfort of the seat. The document describes that this method makes it possible to obtain a coarse-cell flexible urethane foam having coarse cells of 5 to 10 mmφ.

[0007] Patent Document 4 does not aim to improve the comfort of the seat, but (a) A mixed solution containing a polyol, a crosslinking agent, a foaming agent (distilled water), a catalyst, and an antifoaming agent (polybutene) is prepared; (b) Add isocyanate to this and stir. (c) The mixture is poured into a mold and foamed. A method for producing a molded urethane foam article is disclosed. The same document states: (a) By this method, a molded urethane foam product having a high density surface layer can be obtained without using a halogenated hydrocarbon blowing agent; and (b) When no antifoaming agent is added, the density difference between the high-density surface layer and the middle foam layer is not as large as when an antifoaming agent is used. is stated.

[0008] Patent Document 5 discloses a method for producing a flexible polyurethane foam, which is not intended to improve the comfort of seats, but is characterized in that a reactive mixture containing a polyol, a polyisocyanate compound, a catalyst, and a blowing agent is reacted to foam and harden, and a polyoxyalkylene polyol obtained by a predetermined production method is used as the polyol. The same document states: (A) When flexible polyurethane foams are produced using polyols synthesized by conventional methods using composite metal cyanide complex catalysts, the foams produced by foam molding may shrink and the desired shape may not be obtained; and (B) When a polyoxyalkylene polyol obtained by a predetermined manufacturing method is used as the polyol, foam shrinkage can be improved and a flexible polyurethane foam having excellent mechanical properties can be produced. is stated.

[0009] Recently, there has been a trend toward thinner rear cushions for automobile seat cushions in order to improve fuel efficiency or to secure space for battery installation in hybrid vehicles. However, when a thin seat pad is made using conventional polyurethane foam in which fine cells are uniformly dispersed, (a) Small deflection, (b) When the deflection becomes large, you feel a sense of bottoming out. (c) Little cushioning Problems specific to thinning occur, such as:

[0010] On the other hand, Patent Document 1 describes that a seat with good riding comfort can be obtained by gradually increasing the cell diameter from the surface (seating surface) toward the thickness direction. However, the method described in Patent Document 1 cannot solve the above-mentioned problems specific to thinning. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 2019-205613 [Patent Document 2] Patent No. 4898322 [Patent Document 3] Special Publication No. 02-057808 [Patent Document 4] Japanese Patent Application Publication No. 06-087945 [Patent Document 5] Patent No. 5549945 Summary of the Invention [Problem to be solved by the invention]

[0012] The problem to be solved by the present invention is to provide a polyurethane foam that has a large sense of flexibility even when made thin-walled. Another object of the present invention is to provide a seat cushion using such polyurethane foam. [Means for solving the problem]

[0013] In order to solve the above problems, the polyurethane foam according to the present invention comprises: A large-diameter cell having a diameter of 1000 μm or more; Small diameter cells with a diameter of less than 1000 μm Including, M large / M small The gist is that the ratio is 5.0 or more. however, M smallis the arithmetic mean of the diameters of the cells whose integrated value in the integrated distribution is in the range of 0% to 10% when 100 or more cells are randomly selected from all the cells contained in the polyurethane foam and the integrated distribution of the diameters of the cells is calculated based on the number of the cells; M large is the arithmetic mean of the diameters of the cells whose cumulative value in the cumulative distribution is in the range of 90% to 100%.

[0014] Furthermore, the seat cushion according to the present invention uses the polyurethane foam according to the present invention as a seat pad. [Effects of the Invention]

[0015] In polyurethane foam with a structure in which large-diameter cells and small-diameter cells are mixed (double cell structure), large / M small By optimizing the ratio, a polyurethane foam with a large degree of deflection can be obtained even when the wall is thin. This is thought to be because, in the low load range, the large cells are mainly deformed, and in the high load range, after the large cells are completely crushed, the small cells deflect further. [Brief explanation of the drawings]

[0016] [Figure 1] 1(A) to 1(C) are optical microscope photographs of the cross sections of the polyurethane foams obtained in Examples 6 to 8, respectively. [Figure 2] 2(A) to 2(C) show the diameters of 100 cells randomly selected from the cells appearing in the cross sections of the polyurethane foams obtained in Examples 6 to 8, respectively.

[0017] [Figure 3] FS characteristics of polyurethane foams obtained in Examples 6 to 9 and Comparative Example 1. [Figure 4] FS characteristics of the polyurethane foams obtained in Examples 1 to 5. [Figure 5] 1 shows vibration curves of the polyurethane foams obtained in Examples 6 to 9 and Comparative Example 1. [Figure 6] 1 shows vibration curves of the polyurethane foams obtained in Examples 1 to 5. [Figure 7] 1 shows the results of a free drop test of the polyurethane foams obtained in Examples 6 to 9 and Comparative Example 1. [Figure 8] 1 shows the results of a free drop test of the polyurethane foams obtained in Examples 1-2 and 4-5. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will be described in detail below. [1. Polyurethane foam] The polyurethane foam of the present invention can be obtained by the method described below, and therefore has the following characteristics.

[0019] [1.1. Cell Structure] Generally, polyurethane foams are (a) An open-cell structure in which most of the cells are interconnected; (b) a closed-cell structure in which most of the cells are closed cells, or (c) A structure with properties intermediate between an open-cell structure and a closed-cell structure It can be broadly divided into: Using the method described below, (a) a flexible polyurethane foam containing closed cells, or (b) Polyurethane foam with few or no closed cells is obtained.

[0020] [1.2. Cell size distribution] "Large cells" refer to cells with a diameter of 1000 μm or more. "Small cells" refer to cells with a diameter of less than 1000 μm. The "diameter of a cell" refers to the length in the direction in which the length of the cell is smallest (for example, in the case where the cell is irregular and elliptical, the minor axis of the ellipse).

[0021] Antifoaming agents have the effect of increasing the cell diameter of polyurethane foam. Furthermore, using a raw material mixture containing an antifoaming agent can produce polyurethane foam with a structure in which large and small cells coexist (hereinafter referred to as a "double cell structure"). Controlling the composition of the raw material mixture can change the cell size distribution.

[0022] [1.2.1. M large / M small ratio] "M small " means the arithmetic mean of the diameters of cells whose cumulative value in the cumulative distribution is in the range of 0% to 10% when 100 or more cells are randomly selected from all cells contained in polyurethane foam and the cumulative distribution of the cell diameters is calculated based on the number of cells. "M large " refers to the arithmetic mean of the diameters of cells in the cumulative distribution whose cumulative value is in the range of 90% to 100%.

[0023] M large / M small The ratio is the ratio of the diameters of the large and small cells, and is an index of the non-uniformity of the cells. In the case of polyurethane foam with a double cell structure, the skeleton of the polyurethane between the large cells is itself made of a foam containing small cells. large / M small The smaller the ratio, the more difficult it becomes to obtain the structure characteristic of the double cell structure (a structure in which the skeleton between the large diameter cells is made of a foam containing small diameter cells). large / M small The smaller the ratio, the closer the physical property values ​​become to those of a foam with a uniform cell structure. The small cells in the skeleton may be interconnected or closed.

[0024] On the other hand, M large / M smallThe larger the ratio, the smaller the deflection coefficient, allowing for greater deflection in the high load region. This is because the large diameter cells deform in the initial stage of deflection, and the small diameter cells deform further in the high load region. In order to keep the deflection coefficient at 2.8 or less, M large / M small The ratio is preferably 5.0 or more. large / M small The ratio is more preferably 6.0 or greater, and even more preferably 8.0 or greater. On the other hand, M large / M small If the ratio is too large, the hardness (25% ILD) becomes too low and it is not suitable as a seat pad. large / M small The ratio is preferably 40.0 or less. large / M small More preferably, the ratio is 30.0 or less.

[0025] 1.2.2. Coefficient of variation of diameter of all cells Coefficient of variation (CV) of the diameter of all cells total ) is the average diameter of all cells (m total ) versus the standard deviation of the diameter of all cells (σ total ) ratio (=σ total ×100 / m total ) "Average diameter of all cells (m total )" refers to the average diameter of 100 or more cells randomly selected from all cells contained in the polyurethane foam. "Standard deviation of the diameter of all cells (σ total )" refers to the standard deviation of the diameters of 100 or more cells randomly selected from all cells contained in a polyurethane foam.

[0026] The polyurethane foam of the present invention has a double cell structure, so CV total is relatively large. Generally, CV total The smaller the CV, the more difficult it becomes to obtain the unique structure of the double cell structure, and the larger the deflection coefficient. totalCV is preferably 50% or more. total is more preferably 70% or more, and even more preferably 90% or more. On the other hand, CV total If CV becomes too large, the hardness (25% ILD) becomes too low and the material becomes unsuitable as a seat pad. total The CV is preferably 500% or less. total is more preferably 400% or less, and even more preferably 300% or less.

[0027] 1.2.3. Coefficient of variation of small cell diameter Coefficient of variation (CV) of the diameter of small cells small ) is the average diameter of the smallest cells (m small ) versus the standard deviation of the diameter of the small cells (σ small ) ratio (=σ small ×100 / m small ) Average diameter of small cells (m small )" refers to the average diameter of small cells contained in 100 or more cells randomly selected from all cells contained in polyurethane foam. The standard deviation of the diameter of the small cells (σ small )" refers to the standard deviation of the diameter of small cells contained in 100 or more cells randomly selected from all cells contained in polyurethane foam.

[0028] CV small is an index showing the stability of the diameter of small diameter cells. small The smaller the CV, the easier it is to obtain a structure in which small cells of uniform size are uniformly dispersed in the framework between large cells. As a result, the tensile strength increases. small The CV is preferably 70% or less. small is more preferably 60% or less, and even more preferably 50% or less. On the other hand, CV small If CV is too small, the tensile strength may be low. small is preferably 10% or more.small is more preferably 20% or more, and even more preferably 30% or more.

[0029] [1.2.4. Mean diameter of small cells] In the present invention, the average diameter of the small cells (m small ) is not particularly limited, and an optimum value can be selected depending on the purpose. By using the method described later, m small The polyurethane foam has a particle size of 300 μm or more and 500 μm or less.

[0030] 1.2.5. Coefficient of variation of large cell diameter Coefficient of variation (CV) of the diameter of large cells large ) is the average diameter of the large cells (m small ) versus the standard deviation of the diameter of the large cells (σ large ) ratio (=σ large ×100 / m large ) Average diameter of large cells (m large )" refers to the average diameter of large cells contained in 100 or more cells randomly selected from all cells contained in polyurethane foam. The standard deviation of the diameter of the large cells (σ large )" refers to the standard deviation of the diameter of large cells contained in 100 or more cells randomly selected from all cells contained in polyurethane foam.

[0031] CV large is an index showing the stability of the diameter of large cells. large If CV becomes too large, the large-diameter cells tend to become excessively coarse. As a result, the cell diameter varies widely from part to part, and the hardness and deflection also vary. The hardness (25% ILD) also decreases. Therefore, CV large The CV is preferably 80% or less. large is more preferably 70% or less, and even more preferably 60% or less. On the other hand, CV largeIf CV becomes too small, the variation in cell diameter for each part will become small, and the variation in hardness and deflection will also become small, resulting in a feeling of bottoming out when the wall is thinned. large is preferably greater than 0%. large is more preferably 10% or more.

[0032] [1.2.6. Mean diameter of large cells] The average diameter of the large cells (m large ) affects the flexibility and moldability of polyurethane foam. large If m becomes too small, the flexural modulus approaches that of a conventional polyurethane foam with a uniform cell structure. large is preferably 1400 μm or more. On the other hand, m large If m becomes too large, the moldability of the polyurethane foam deteriorates. large If m becomes too large, the ratio of the cell volume to the volume of the polyurethane foam becomes excessively large. As a result, the hardness (25% ILD) decreases excessively, and the cushioning feeling decreases. Therefore, m large is preferably 5000 μm or less.

[0033] [1.2.7. Difference in coefficient of variation ΔCV] "Difference in coefficient of variation ΔCV (%)" means CV large -CV small This refers to ΔCV affects the 400N static spring constant. If ΔCV becomes too small, the 400N static spring constant becomes excessively large. As a result, the amount of deflection in the high load range decreases. Therefore, ΔCV is preferably -30% or more. ΔCV is more preferably -20% or more, and even more preferably -10% or more. On the other hand, if ΔCV becomes too large, the static spring constant of 400 N will become too large. Therefore, ΔCV is preferably 60% or less. ΔCV is more preferably 50% or less, and even more preferably 40% or less.

[0034] [1.3. FS (Force-Strain) characteristics] 1.3.1. Flexibility coefficient "Deflection coefficient" is a value measured in accordance with JIS K6400-2:2012, and is the force at 65% compression (F) when compressed to 75% at a constant speed after pre-compression to 75%. 65% ) at 25% compression (F 25% ) divided by (=F 65% / F 25% )

[0035] The polyurethane foam of the present invention has a double-cell structure and therefore a smaller deflection coefficient than polyurethane foams without a double-cell structure. Generally, the smaller the deflection coefficient, the greater the deflection and the greater the cushioning feel in the high load range. To achieve this effect, the deflection coefficient is preferably 2.8 or less. The deflection coefficient is preferably 2.7 or less, and more preferably 2.4 or less. On the other hand, if the deflection coefficient is too small, the amount of deflection becomes too large, resulting in a strong feeling of bottoming out. Therefore, the deflection coefficient is preferably 2.0 or more. The deflection coefficient is more preferably 2.1 or more, and even more preferably 2.2 or more.

[0036] [1.3.2. 400N static spring constant] "400N static spring constant (N / mm)" refers to the slope of the tangent to the FS (Force-Strain) curve when the load is 400N.

[0037] Because the polyurethane foam of the present invention has a double-cell structure, it has a smaller 400N static spring constant than polyurethane foams that do not have a double-cell structure. Generally, the smaller the 400N static spring constant, the softer the foam feels when sitting on it, and the greater the cushioning effect. To achieve this effect, the 400N static spring constant is preferably 9.0 N / mm or less. The 400N static spring constant is more preferably 8.0 N / mm or less. On the other hand, if the 400N static spring constant is too small, the resilience of the polyurethane foam will be excessively small. Therefore, the 400N static spring constant is preferably 5.0N / mm or more. The 400N static spring constant is preferably 6.0N / mm or more, and more preferably 7.0N / mm or more.

[0038] 1.4. Vibration characteristics [1.4.1. Resonance magnification] "Resonance magnification" refers to a value measured in accordance with JASO B407. Specifically, a Tekken-type pressure platen with a mass of 50 kgf was used, and the absolute displacement of the pressure platen was measured when the vibration table was vibrated up and down with a total width of 5 mm, and the resonance magnification was calculated from the absolute displacement. The excitation frequency ranged from 1 Hz to 11 Hz.

[0039] The polyurethane foam of the present invention has a double-cell structure, and therefore has a higher resonance magnification than polyurethane foams that do not have a double-cell structure. Generally, the higher the resonance magnification, the greater the cushioning feel. To achieve this effect, the resonance magnification is preferably 2.3 or higher. The resonance magnification is more preferably 2.8 or higher, and even more preferably 3.0 or higher. On the other hand, if the resonance magnification is too high, the polyurethane foam will transmit vibrations and cause large amplitudes. As a result, the foam will bounce too much when you sit on it, making the seating comfort worse. Therefore, the resonance magnification is preferably 6.0 or less. The resonance magnification is more preferably 5.5 or less, and even more preferably 5.0 or less.

[0040] [1.4.2. Resonant frequency] The "resonance frequency" is a value calculated when measuring the resonance magnification, and refers to the frequency at which the polyurethane foam resonates.

[0041] Generally, the lower the resonant frequency, the higher the elastic modulus of the urethane foam resin, making it easier to feel the cushioning effect. To achieve this effect, the resonant frequency is preferably 3 Hz to 4 Hz.

[0042] [1.4.3. 6Hz magnification] The "6 Hz magnification" is a value calculated when measuring the resonance magnification, and refers to the ratio of the amplitude A3 of the pressure platen to the amplitude A0 (= A3 / A0) when the polyurethane foam is vibrated at 6 Hz.

[0043] The resonant frequency of the human internal organs is approximately 6 Hz. Therefore, when a seat cushion is manufactured using the polyurethane foam of the present invention, the smaller the 6 Hz magnification of the polyurethane foam, the smaller the vibrations that the internal organs of the occupant will be. To achieve this effect, the 6 Hz magnification is preferably 1.0 or less. The 6 Hz magnification is preferably 0.9 or less, and more preferably 0.8 or less. The smaller the 6 Hz magnification, the better.

[0044] 1.5. Attenuation characteristics: logarithmic decay rate "Logarithmic decrement (λ)" refers to a value measured in accordance with JASO B408 and expressed by the following formula (1): λ=log e (1 / n)(a0 / a1+a1 / a2+…+a n-1 / a n ) …(1) Here, a: amplitude, n: The number of waveforms read, which is read until it becomes less than 10% of the amplitude (a0) of the first waveform.

[0045] The polyurethane foam of the present invention has a double-cell structure and therefore has a smaller logarithmic decrement (λ) than polyurethane foams without a double-cell structure. Generally, the smaller λ, the greater the cushioning feel. To achieve this effect, λ is preferably 3.5 or less. λ is more preferably 2.5 or less, and even more preferably 1.5 or less.

[0046] 1.6. Core Density When a raw material mixture containing polyol and isocyanate is poured into a mold and foamed, the area near the contact surface with the mold becomes a layer with a low foaming ratio (skin layer), while the center becomes a layer with a high foaming ratio (core layer). "Core density" refers to the apparent density of the core layer, measured in accordance with JASO B408.

[0047] Generally, if the core density is too high, the weight of the polyurethane foam increases. Therefore, the core density should be 80 kg / m 3 The core density is preferably 75 kg / m or less. 3 More preferably, 70 kg / m or less 3 The following is the result. On the other hand, if the core density is too low, the cushioning effect will be reduced, and the riding comfort will be worse when applied to a seat. Also, the core will be prone to wear and tear after long-term use. Therefore, the core density should be 35 kg / m 3 The core density is preferably 40 kg / m or more. 3 More preferably, 45 kg / m 3 That's all.

[0048] 1.7. Air permeability "Air permeability (method A)" ​​refers to a value measured in accordance with JIS K6400-7 method A (sample size: 51 x 51 x 25 mm). "Air permeability (Method B)" refers to a value measured in accordance with JIS K6400-7 Method B (sample thickness: 10 mm).

[0049] The air permeability (Method A) of polyurethane foam affects the resonance magnification, resilience, cushioning, etc. Generally, the higher the air permeability (Method A), the better the resilience. To achieve this effect, the air permeability (Method A) is preferably 10 L / min or more. The air permeability (Method A) is more preferably 20 L / min or more, and even more preferably 30 L / min or more. However, if the air permeability (Method A) is too high, production may become difficult. Therefore, the air permeability (Method A) is preferably 100 L / min or less. The air permeability (Method A) is more preferably 80 L / min or less.

[0050] Similarly, the air permeability (B method) of polyurethane foam affects the resonance rate, resilience, cushioning, etc. Generally, the higher the air permeability (B method), the better the resilience. To achieve this effect, the air permeability (B method) should be set to 10cm 3 / cm 2 / s or more is preferable. The air permeability (B method) is more preferably 15 cm 3 / cm 2 / s or more, more preferably 20cm 3 / cm 2 / s or more. However, if the air permeability (Method B) is too high, it may be difficult to manufacture. Therefore, the air permeability (Method B) is set to 150 cm 3 / cm 2 The air permeability (method B) is preferably 100 cm 3 / cm 2 / s or less. The polyurethane foam according to the present invention may satisfy either one of the above-mentioned conditions regarding air permeability (method A) or air permeability (method B), or may satisfy both of them.

[0051] [2. Application] The polyurethane foam according to the present invention can be used for various purposes. Examples of uses of the polyurethane foam according to the present invention include: (a) a seat pad for a seat cushion of an automobile seat; (b) a seat pad for a seat back of a motor vehicle seat; (c) Mattresses, chairs, sofas, car wash sponges, cleaning sponges, scrubbing brushes, etc.

[0052] The polyurethane foam of the present invention has a large deflection in the high load range, so that the required amount of deflection can be ensured even if the thickness is thin. Therefore, when this foam is used as a seat pad for a seat cushion, a seat cushion with a large sense of deflection can be obtained despite its relatively thin thickness.

[0053] [3. Polyurethane foam manufacturing method] The method for producing a polyurethane foam according to the present invention comprises the steps of: A first step of obtaining a raw material mixture containing an isocyanate, a polyol, a foaming agent, a catalyst, and an antifoaming agent, and which may or may not further contain a silicone-based foam stabilizer; a second step of reacting the raw material mixture; It is equipped with:

[0054] [3.1. 1st step] First, a raw material mixture containing an isocyanate, a polyol, a foaming agent, a catalyst, and an antifoaming agent, and which may or may not contain a silicone-based foam stabilizer, is obtained (first step).

[0055] [3.1.1. Raw materials] [A. Isocyanate] In the present invention, the type of isocyanate is not particularly limited. The isocyanate may be any of aromatic, alicyclic, and aliphatic. The isocyanate may be a bifunctional isocyanate having two isocyanate groups in one molecule, or a trifunctional or higher isocyanate having three or more isocyanate groups in one molecule. Furthermore, any one of these isocyanates may be used as a starting material, or two or more may be used in combination.

[0056] Examples of bifunctional aromatic isocyanates include: 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 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, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, etc., and a mixture of these may also be used.

[0057] Examples of bifunctional alicyclic isocyanates include: Cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, Examples include methylcyclohexane diisocyanate.

[0058] Examples of bifunctional aliphatic isocyanates include: Butane-1,4-diisocyanate, hexamethylene diisocyanate, Isopropylene diisocyanate, methylene diisocyanate, lysine isocyanate Examples of difunctional or higher isocyanates include polymeric MDI and trifunctional or higher isocyanates.

[0059] Examples of tri- or higher functional isocyanates include: 1-methylbenzol-2,4,6-triisocyanate, 1,3,5-trimethylbenzene-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, etc.

[0060] [B. Polyol] In the present invention, the type of polyol is not particularly limited. The polyol may be an ether polyol or an ester polyol. Furthermore, as a starting material, any one of these polyols may be used alone, or two or more of them may be used in combination.

[0061] Examples of ether polyols include: (a) ethylene glycol, diethylene glycol, propylene glycol, Dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, Polyhydric alcohols such as pentaerythritol, trimethylolpropane, sorbitol, and sucrose; (b) Polyether polyols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to polyhydric alcohols etc.

[0062] Examples of ester polyols include: (a) polyester polyols obtained by polycondensation of aliphatic carboxylic acids such as malonic acid, succinic acid, and adipic acid, or aromatic carboxylic acids such as phthalic acid, with aliphatic glycols such as ethylene glycol, diethylene glycol, and propylene glycol; (b) Phthalate ester polyol etc.

[0063] [C. Foaming Agent] The blowing agent is used to generate bubbles in the polyurethane. (a) a chemical blowing agent that generates gas by thermal decomposition or chemical reaction (e.g., water reacting with isocyanate groups to generate CO2); (b) Physical blowing agents that generate gas when pressure is reduced or heated (e.g., pentane, cyclopentane, methylene chloride, carbon dioxide, etc., dissolved in resin under high pressure). etc. Among these, water is preferred as the blowing agent, because carbon dioxide gas generated by the reaction of water with isocyanate promotes foaming, while heat generated by the reaction of water with isocyanate promotes curing of the resin.

[0064] [D. Catalyst] In order to synthesize polyurethane, it is preferable to add a catalyst (resinification catalyst) to the raw materials in order to promote the reaction between isocyanate and polyol. When a chemical foaming agent, particularly water, is used as the foaming agent, it is preferable to add a catalyst (foaming catalyst) to the raw material to promote the reaction between water and isocyanate and generate gas. In the present invention, the type of catalyst is not particularly limited.

[0065] Resinification catalysts include, for example, 1,2-dimethylimidazole, 1-methylimidazole, N·(N',N'-dimethylaminoethyl)-morpholine, tetramethylguanidine, Dimethylaminoethanol, triethylenediamine, N-methyl-N'-(2hydroxyethyl)-piperazine, N,N,N',N'-tetramethylpropane 1,3-diamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N",N"-pentamethyl-(3-aminopropyl)ethylenediamine, N,N'-dimethylpiperazine, N,N,N',N'-tetramethylhexane-1,6-diamine, N,N,N',N",N"-pentamethyldipropylene-triamine, N-(2-hydroxyethyl)morpholine, ethylene glycol bis(3-dimethyl)-aminopropyl ether, N,N-dimethylcyclohexylamine, N-methyl-N'-(2-dimethylamino)ethylpiperazine and other amine catalysts. When the blowing agent is water, examples of the foaming catalyst include amine catalysts such as triethylamine, N,N,N',N",N"-pentamethyldiethylenetriamine, triethylenediamine, diethanolamine, bis(2-dimethylaminoethyl)ether, dimethylaminomorpholine, N-ethylmorpholine, and tetramethylguanidine.

[0066] [E. Antifoaming Agent] When a silicone-based foam stabilizer and an antifoaming agent are simultaneously added to a raw material mixture, by optimizing the composition of the raw material mixture, it is possible to obtain a polyurethane foam containing closed cells and having a double-cell structure. On the other hand, if a silicone-based foam stabilizer is not added to the raw material mixture and an antifoaming agent is added, a polyurethane foam having few or no closed cells and a double-cell structure can be obtained. The antifoaming agent is not particularly limited as long as it performs this function.

[0067] Examples of antifoaming agents include fatty acid esters, petrolatum, etc. Any one of these may be used as the antifoaming agent, or two or more of them may be used in combination. Among these, fatty acid esters are preferred as antifoaming agents because they tend to cause cells to coalesce, resulting in foam with large cell diameters and the formation of a double-cell structure.

[0068] [F. Foam stabilizer] Generally, foam stabilizers are said to have the functions of increasing the compatibility of the raw materials used to produce polyurethane, adjusting the surface tension of the mixed raw materials, and stabilizing the bubbles generated by the blowing agent. (a) nonionic surfactants such as polyethylene glycol alkyl ethers and sorbitan fatty acid esters; (b) silicone surfactants such as polyether siloxanes; etc.

[0069] As described above, when a silicone-based foam stabilizer and an antifoaming agent are simultaneously added to a raw material mixture, by optimizing the composition of the raw material mixture, it is possible to obtain a polyurethane foam containing closed cells and having a double-cell structure. On the other hand, when a silicone-based foam stabilizer is not added to the raw material mixture and an antifoaming agent is added, by optimizing the composition of the raw material mixture, it is possible to obtain a polyurethane foam having few or no closed cells and a double-cell structure.

[0070] [3.1.2. Amount added] [A. Isocyanate Index] "Isocyanate index" refers to the ratio of the number of moles of isocyanate groups in raw materials (polyol, blowing agent, etc.) to the number of moles of active hydrogen groups in the raw materials (= (NCO equivalent / active hydrogen equivalent) × 100).

[0071] If the isocyanate index is too small, resin formation is not promoted, resulting in reduced hardness and strength, or foaming may become difficult. Therefore, the isocyanate index is preferably 70 or more. The isocyanate index is preferably 80 or more, and more preferably 90 or more. On the other hand, if the isocyanate index is too high, the urethane foam will be too hard. Therefore, the isocyanate index is preferably 120 or less. The isocyanate index is preferably 115 or less, and more preferably 110 or less.

[0072] [B. Foaming Agent] The amount of foaming agent to be added is preferably selected to be optimal depending on the type of foaming agent. For example, when the blowing agent is water, if the amount of the blowing agent added is too small, the amount of bubbles generated will be insufficient and the desired foam structure will not be obtained. Therefore, the amount of the blowing agent added is preferably 1.0 part by mass or more per 100 parts by mass of polyol. The amount of the blowing agent added is preferably 2.0 parts by mass or more, more preferably 3.0 parts by mass or more. On the other hand, if the amount of foaming agent added is excessive, it is necessary to increase the amount of isocyanate added to maintain the isocyanate index. As a result, the reaction between the foaming agent and the isocyanate may proceed excessively, resulting in an excessively high exothermic temperature. Furthermore, if the amount of foaming agent added is excessive, the pressure inside the mold may become too high. Therefore, the amount of foaming agent added is preferably 10 parts by mass or less per 100 parts by mass of polyol. The amount of foaming agent added is preferably 6 parts by mass or less, more preferably 5 parts by mass or less.

[0073] [C. Catalyst] One or more catalysts are used in a total amount of preferably 0.1 to 5.0 parts by mass, more preferably 0.3 to 3.0 parts by mass, per 100 parts by mass of polyol.

[0074] [D. Antifoaming Agents] If the amount of antifoaming agent added is too small, the cells become smaller, the difference between the large-diameter cells and the small-diameter cells disappears, and the properties of the double-cell structure cannot be satisfied. Therefore, the amount of antifoaming agent added is preferably 0.5 parts by mass or more per 100 parts by mass of polyol. The amount of antifoaming agent added is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more. On the other hand, if the amount of antifoaming agent added is excessive, the cells become too large and the hardness decreases. Therefore, the amount of antifoaming agent added is preferably 15 parts by mass or less per 100 parts by mass of polyol. The amount of antifoaming agent added is preferably 12 parts by mass or less, more preferably 10 parts by mass or less.

[0075] [F. Foam stabilizer] When a foam stabilizer is added, if the amount of foam stabilizer added is too small, the cells in the foam may become non-uniform. Therefore, the amount of foam stabilizer added is preferably 0.01 parts by mass or more per 100 parts by mass of polyol. The amount of foam stabilizer added is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more. On the other hand, if the amount of foam stabilizer added is excessive, the cells may become closed cells, causing the foam to shrink. Therefore, the amount of foam stabilizer added is preferably 2.0 parts by mass or less per 100 parts by mass of polyol. The amount of foam stabilizer added is preferably 1.8 parts by mass or less, more preferably 1.5 parts by mass or less.

[0076] [3.2. 2nd process] Next, the resulting raw material mixture is poured into an appropriate mold and reacted (second step), thereby obtaining the polyurethane foam according to the present invention.

[0077] [4. Effect] Silicone foam stabilizers have the effect of stabilizing the bubbles generated by foaming. Therefore, adding a silicone foam stabilizer to the raw material mixture used to produce polyurethane foam results in a polyurethane foam with uniformly dispersed fine bubbles. However, the polyurethane foam obtained in this manner has little deflection under high loads, so it feels less deflected when made thinner.

[0078] In contrast, when polyurethane foam is produced using a raw material mixture containing a defoaming agent and with or without a silicone-based foam stabilizer, a double-cell structure is obtained, with large cells with diameters of 1000 μm or more and small cells with diameters of less than 1000 μm. Such polyurethane foams have a large deflection under high loads, and therefore a large sense of deflection even when thin-walled. [Example]

[0079] (Examples 1 to 9, Comparative Examples 1 and 2) 1. Sample Preparation For polyols, (a) Main polyol 1 (KC737, manufactured by Sanyo Chemical Industries, Ltd.), (b) Main Polyol 2 (Sanyo Chemical Industries, Ltd., No. 38), and (c) Polymer polyol (FM5704, manufactured by Sanyo Chemical Industries, Ltd.) was used.

[0080] The isocyanate used was K645 (modified MDI) manufactured by Covestro and having an isocyanate content (NCO%) of 28%. The resinification catalyst used was an amine catalyst (33LSI) manufactured by EVONIK. Water was used as the blowing agent, and an amine catalyst (BL-19) manufactured by EVONIK was used as the foaming catalyst. The antifoaming agent used was a fatty acid ester manufactured by EVONIK. The defoamer used was S240 manufactured by Covestro. Furthermore, as the foam stabilizer, a silicone foam stabilizer (B8738LF2) manufactured by EVONIK was used.

[0081] The blending ratios (parts by mass) of the raw materials are shown in Table 1. A raw material mixture for producing flexible polyurethane foam was obtained by blending the raw materials according to the blending ratios shown in Table 1. This raw material mixture was poured into a mold measuring 40 cm x 40 cm x 10 cm in diameter and foamed at a mold temperature of approximately 60°C.

[0082] [Table 1]

[0083] 2. Test Method 2.1. Cell size distribution A 100 mm thick molded polyurethane foam was sliced ​​horizontally at positions 45 mm and 60 mm from the surface to obtain a 15 mm thick plate. A 100 x 100 x 15 mm cut sample was prepared from the center of the plate to serve as the core layer. An optical microscope photograph was taken of the horizontal surface (100 x 100 mm) of the core layer. 100 cells were randomly selected from those appearing on the horizontal surface, and the diameter of each cell was measured. If each cell was irregular and elliptical, the minor axis of the cell was measured and this was taken as the "diameter."

[0084] 2.2 Hardness The hardness (25% ILD) of the polyurethane foam was measured in accordance with JIS K6400-2:2012 (Method D). [2.3. FS characteristics] For the obtained polyurethane foam, an FS curve was obtained in the load range of 0 N to 980 N. Furthermore, the hysteresis loss, 400 N static spring constant, and deflection coefficient were calculated from the FS curve in accordance with JIS K6400-2.

[0085] 2.4. Vibration characteristics The vibration characteristics of the polyurethane foam were measured in accordance with JASO B407. The frequency was 1 to 10 Hz. The resonance magnification, resonance frequency, 10 Hz magnification, and 6 Hz magnification were calculated from the obtained vibration curve. 2.5. Damping characteristics A free drop test was conducted on polyurethane foam in accordance with JASO B408. The logarithmic decay rate and decay time were calculated from the obtained decay curve.

[0086] 2.6. Core Density The core density of the flexible polyurethane foam was measured in accordance with JASO B408. 2.7. Breathability The air permeability (Method A) was measured in accordance with JIS K6400-7 Method A (sample size: 51 × 51 × 25 mm), and the air permeability (Method B) was measured in accordance with JIS K6400-7 Method B (sample thickness: 10 mm).

[0087] [3. Results] 3.1. Cell size distribution Figures 1(A) to 1(C) show optical microscope photographs of the cross sections of the polyurethane foams obtained in Examples 6 to 8, respectively. Figures 2(A) to 2(C) show the diameters of 100 cells randomly selected from the cells appearing in the cross sections of the polyurethane foams obtained in Examples 6 to 8, respectively. Figures 1 and 2 show that the proportion of large-diameter cells increases and the diameters of the large-diameter cells increase as the amount of antifoaming agent added increases.

[0088] Table 2 shows the cell size distribution, deflection coefficient, and 400N static spring constant of the large and small cells contained in the polyurethane foams obtained in Examples 1 to 9 and Comparative Examples 1 and 2. Table 2 reveals the following. (1) M large / M small When the ratio was 5.0 or more, the deflection coefficient was 2.8 or less. large / M small When the ratio was 6.0 or more, the deflection coefficient was 2.7 or less. large / M small When the ratio was 8.0 or more, the deflection coefficient was 2.4 or less. (2) When both a silicone-based foam stabilizer and an antifoaming agent were added, the 400N static spring constant was 9N / mm or less when the amount of antifoaming agent added was 6 parts by mass or more. (3) When only antifoaming agent was added, the 400N static spring constant was 9N / mm or less, regardless of the amount of antifoaming agent added.

[0089] (4) CV total When the CV is 50% or more, the deflection coefficient is 2.8 or less. total When the CV is 70% or more, the deflection coefficient is 2.7 or less. total When the strain rate was 90% or more, the deflection coefficient was 2.4 or less. (5) When ΔCV was between -30% and 60%, the 400N static spring constant was 10N / mm or less. Furthermore, when ΔCV was between -5% and 40%, the 400N static spring constant was 9N / mm or less.

[0090] [Table 2]

[0091] [3.2. FS characteristics] Figure 3 shows the FS properties of the polyurethane foams obtained in Examples 6 to 9 and Comparative Example 1. Figure 4 shows the FS properties of the polyurethane foams obtained in Examples 1 to 5. Figures 3 and 4 show that the amount of deflection in the high load range increases as the amount of antifoaming agent added increases, regardless of the presence or absence of a silicone-based foam stabilizer.

[0092] [3.3. Vibration characteristics] Figure 5 shows the vibration curves of the polyurethane foams obtained in Examples 6 to 9 and Comparative Example 1. When no silicone-based foam stabilizer was added, there was no significant change in the resonance frequency even when the amount of antifoaming agent added was increased. On the other hand, as the amount of antifoaming agent added increased, the resonance magnification decreased, but since it was still 2.3 or higher, the resonance magnification was good. Note that the breathability tends to decrease as the amount of antifoaming agent added increases.

[0093] Figure 6 shows the vibration curves of the polyurethane foams obtained in Examples 1 to 5. When a silicone foam stabilizer was added, the resonance frequency shifted to a higher frequency when the amount of antifoaming agent added was 4 to 8 parts by mass. This is thought to be because the polyurethane foam had a closed-cell structure, reducing the breathability of the polyurethane foam.

[0094] [3.4. Damping characteristics] Figure 7 shows the results of the free drop test of the polyurethane foams obtained in Examples 6 to 9 and Comparative Example 1. When no silicone-based foam stabilizer was added, the logarithmic decrement increased as the amount of antifoaming agent added increased. This is thought to be due to a decrease in breathability. In particular, Examples 6 and 7, in which the amount of antifoaming agent added was 2 parts or 4 parts, had a logarithmic decrement of 1.5 or less, which was very excellent, and a moderate cushioning feeling was obtained.

[0095] Figure 8 shows the results of the free drop test of the polyurethane foams obtained in Examples 1-2 and 4-5. When a silicone foam stabilizer and an antifoaming agent were added simultaneously, the resilience was reduced compared to when only an antifoaming agent was added. This is thought to be because the polyurethane foam had a closed-cell structure, reducing the breathability of the polyurethane foam.

[0096] [3.5. Overall Evaluation] Table 3 shows a list of the various test results.

[0097] [Table 3]

[0098] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the present invention. [Industrial Applicability]

[0099] The polyurethane foam according to the present invention can be used as an interior material for automobiles and aircraft, a vibration-damping material or a sound-proofing material for office automation equipment and electrical appliances, and the like.

Claims

1. A large-diameter cell having a diameter of 1000 μm or more; A small diameter cell having a diameter of less than 1000 μm; Including, M large / M small The ratio is 10.96 or more, Coefficient of variation (CV) of the diameter of all cells total ) is 107% or more. however, M small is the arithmetic mean of the diameters of the cells whose integrated value in the number-based cumulative distribution is in the range of 0% to 10% when 100 or more cells are randomly selected from all the cells contained in the polyurethane foam and the cumulative distribution of the diameters of the cells is calculated; M large is the arithmetic mean of the diameters of the cells whose integrated value in the integrated distribution is in the range of 90% to 100%; CV total =s total ×100 / m total 、 m total is the average value of the diameters of 100 or more cells randomly selected from all the cells contained in the polyurethane foam, σ total is the standard deviation of the diameters of 100 or more cells randomly selected from all the cells contained in the polyurethane foam.

2. 2. The polyurethane foam according to claim 1, having a coefficient of deflection of 2.0 or more and 2.4 or less.

3. 3. The polyurethane foam according to claim 1, having a 400 N static spring constant of 9.0 N / mm or less.

4. A seat cushion using the polyurethane foam described in any one of claims 1 to 3 as a seat pad.

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