Resin foam and seat

Abstract

To provide a resin foam and a seat that can achieve both a good sense of touch at the initial stage where a load starts being applied and a good sense of support in the state of the load reaching the bottom.SOLUTION: A resin foam includes a first bubble group in which a bubble radius r is less than a predetermined value and a second bubble group in which a bubble radius r is not less than a predetermined value, wherein as a result of structural analysis, integrated values of bubble volume rates calculated by dividing a product of the number of bubbles having the radius r and a volume of the bubbles having the radius r by a volume of all the bubbles are plotted with respect to radius sections rn (a radius range larger than rn-1 and not larger than rn) obtained by dividing the range from a maximum bubble radius to 0 into 20 sections, and a scatter diagram thus obtained provides two approximate straight lines, the two approximate straight lines being a first approximate straight line obtained from plots of the first bubble group and a second approximate straight line obtained from plots of the second bubble group, the first approximate straight line and the second approximate straight line having different slopes, and a sum of bubble volume rates of the bubbles forming the second bubble group ranging from 10% to 80% of a whole bubble volume rate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a resin foam and a sheet. [Background technology]

[0002] Flexible foams have been used as resin foams with excellent shock-absorbing properties. Such resin foams are used as cushioning materials for furniture such as sofas and beds, and seats for automobiles, etc. Cushioning materials play an important role in appealing to the five senses and providing comfort, such as comfort when sitting, sleeping, and touching.

[0003] The feel of a resin foam is evaluated by physical indices such as the feel when the resin foam is compressed, the support feeling, and the push-back feeling after compression. The feel is, for example, the feel at the beginning of a load being applied to the resin foam, and softness is required. The support feeling is, for example, the feel when the resin foam is compressed by a load and no longer has any room for deformation, that is, when it bottoms out, and firm elasticity that can support the load is required.

[0004] To obtain a good tactile feel, resin foams have been manufactured using various methods. For example, changing the resin composition to obtain a resin foam with a lower elastic modulus or changing molding conditions to obtain a larger cell diameter has been proposed. Patent Document 1 also discloses a flexible polyurethane foam in which the proportion of cells present is controlled, and the ratio obtained by dividing the arithmetic mean of the diameters of cells with an integrated value of 90% to 100% in the integrated distribution by the arithmetic mean of the diameters of cells with an integrated value of 0% to 10% is 5.0 or greater. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-008067 Summary of the Invention [Problem to be solved by the invention]

[0006] By changing the resin type or composition, it is possible to reduce the elastic modulus of a resin foam and achieve a softer feel. However, while this method can improve the feel of touch, it requires a short stroke to reach the bottoming out state, and does not provide a good sense of support. Increasing the proportion of large bubbles can lengthen the stroke, but the cell walls formed between the bubbles become thinner, reducing their function as pillars to support the load, and therefore, a good sense of support cannot be achieved. Reducing the void ratio can improve the sense of support, but this results in the problem of increased weight. Patent Document 1 also focuses on increasing the deflection of flexible polyurethane foam in the high-load range, which improves the sense of support but does not improve the sense of touch.

[0007] Therefore, an object of the present disclosure is to provide a resin foam and a sheet that can provide both a good touch feeling when a load is first applied and a good support feeling when the base is touching the ground. [Means for solving the problem]

[0008] In order to solve the above problems, one embodiment of the resin foam according to the present disclosure is A resin foam comprising a first group of cells having a bubble radius r less than a predetermined value and a second group of cells having a bubble radius r equal to or greater than the predetermined value, As a result of the structural analysis, The integrated value of the bubble volume ratio, calculated by multiplying the number of bubbles of radius r by the volume of bubbles of radius r by the volume of all bubbles, is calculated as the bubble volume ratio in the radius range r, which is divided into 20 ranges from the maximum bubble radius to 0. n (r n-1 Larger than r n The scatter plot obtained by plotting the radius range below gives two approximate straight lines. the two approximate straight lines are a first approximate straight line obtained from the plot of the first bubble group and a second approximate straight line obtained from the plot of the second bubble group, and the first approximate straight line and the second approximate straight line have different slopes; The sum of the volume fractions of the bubbles constituting the second bubble group is 10% or more and 80% or less of the total volume fraction of the bubbles.

[0009] According to the above configuration, the resin foam has cells that are at least divided into a first group of small cells and a second group of large cells. For example, a histogram with the volume fraction on the vertical axis and the radius on the horizontal axis results in a multi-peak histogram. Furthermore, the volume fractions of the first and second groups of cells are distributed apart, and the cell walls between the large cells are formed by small cells. This structure allows the cell walls between the small cells to form multiple skeletons, and the skeletons of the small cells absorb loads, improving the touch feeling. This structure also maintains a sufficient sense of support. Therefore, the above configuration achieves both a good touch feeling and a good sense of support.

[0010] In one embodiment, the predetermined value is 0.5 mm or more and 1.2 mm or less, that is, 25% or more and 75% or less of the maximum bubble radius, preferably 30% or more and 70% or less, and more preferably 40% or more and 65% or less.

[0011] According to this, in a histogram showing the air bubble volume ratio on the vertical axis and the air bubble radius range on the horizontal axis, there are two distribution peaks for the first and second air bubble groups, with the air bubble diameter between 0.5 mm and 1.2 mm, i.e., between 25% and 75% of the maximum air bubble radius, as the boundary. A resin foam with this configuration can easily achieve both a good touch feeling and a good support feeling.

[0012] In one embodiment, the resin foam has a maximum cell radius within a structural analysis range of less than 2000 μm.

[0013] According to this, bubbles larger than 2000 μm can be excluded as voids caused by molding defects, and the structure of resin foam can be evaluated without considering their influence.

[0014] In one embodiment, the resin foam has communication holes provided in cell walls between adjacent cells, which communicate between the cells.

[0015] This makes it possible to improve sound absorption performance. Furthermore, a resin foam having such a structure is suitable for use as a cushioning material for seats in passenger cars and the like.

[0016] In one embodiment, the resin foam is formed from a resin composition containing a crosslinkable polymer.

[0017] This makes it possible to easily obtain a resin foam that can provide both a good touch feeling and a good support feeling.

[0018] In one embodiment, the resin foam has the crosslinkable polymer having a urethane bond.

[0019] In one embodiment, the resin foam is a flexible polyurethane foam.

[0020] In one embodiment, the porosity is 90% or greater.

[0021] This makes the resin foam suitable for use as a cushioning material for seats in passenger cars and the like.

[0022] Furthermore, one aspect of the sheet disclosed herein is characterized in that the above-mentioned resin foam is used as a cushioning material.

[0023] In a seat of this configuration, a resin foam that combines a sense of touch and a sense of support is used as the cushioning material. Therefore, for example, when this seat is applied to the seat of a passenger car, there will be areas where a relatively large load is applied by the buttocks and areas where a relatively small load is applied by the thighs, but both areas will have a good feel to them, making it possible to provide a comfortable sitting experience. [Effects of the Invention]

[0024] As described above, the present disclosure provides a resin foam and a sheet that can achieve both a good touch feeling when a load is first applied and a good support feeling when the base is touching the ground. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a scatter plot showing the integrated values ​​of the bubble radius and bubble volume fraction contained in the resin foam of Example 1. FIG. [Figure 2] 1 is a scatter plot showing the integrated values ​​of the bubble radius and bubble volume fraction contained in the resin foam of Example 2. FIG. [Figure 3] 10 is a scatter plot showing the integrated values ​​of the bubble radius and bubble volume fraction contained in the resin foam of Example 3. FIG. [Figure 4] 1 is a scatter plot showing the integrated values ​​of the bubble radius and bubble volume fraction contained in the resin foam of Example 4. FIG. [Figure 5] 1 is a scatter diagram showing the integrated values ​​of the bubble radius and bubble volume fraction contained in the resin foam of Comparative Example 1. FIG. [Figure 6] 10 is a scatter diagram showing the integrated values ​​of the bubble radius and bubble volume fraction contained in the resin foam of Comparative Example 2. FIG. [Figure 7] 10 is a scatter plot showing the integrated values ​​of the bubble radius and bubble volume fraction contained in the resin foam of Comparative Example 3. FIG. [Figure 8] 1 is a histogram showing the radius and volume fraction of bubbles contained in the resin foam of Example 1. [Figure 9] 10 is a histogram showing the radius and volume fraction of bubbles contained in the resin foam of Example 2. [Figure 10] 10 is a histogram showing the radius and volume fraction of bubbles contained in the resin foam of Example 3. [Figure 11] 10 is a histogram showing the radius and volume fraction of bubbles contained in the resin foam of Example 4. [Figure 12] 1 is a histogram showing the radius and volume fraction of bubbles contained in the resin foam of Comparative Example 1. [Figure 13] 10 is a histogram showing the radius and volume fraction of bubbles contained in the resin foam of Comparative Example 2. [Figure 14] 10 is a histogram showing the radius and volume fraction of bubbles contained in the resin foam of Comparative Example 3. [Figure 15] 1 is a graph showing the results of measuring the elastic modulus of the resin foams of Example 2 and Comparative Example 2. [Figure 16] 1 is a graph showing the results of measuring the elastic modulus of the resin foams of Example 2 and Comparative Example 2. [Figure 17] 1 shows three-dimensional images of resin foams of Example 2 and Comparative Examples 2 and 3. DETAILED DESCRIPTION OF THE INVENTION

[0026] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The description is merely exemplary in nature and is not intended to limit the disclosure, its application, or its uses. There is nothing to illustrate.

[0027] <Resin foam> The resin foam of the present disclosure has a cell structure. The cell structure may be a closed-cell structure, an open-cell structure, or the like. A closed-cell structure is a structure in which cells exist independently of each other. An open-cell structure is a structure in which the cell walls between adjacent cells have communicating holes that connect the cells. The resin foam of the present disclosure may have a closed-cell structure, an open-cell structure, or a cell structure in which a closed-cell structure and an open-cell structure are mixed. A cell structure having an open-cell structure is preferred.

[0028] The resin foam of the present disclosure is a resin foam comprising a first group of cells having a cell radius r less than a predetermined value and a second group of cells having a cell radius r equal to or greater than a predetermined value. The predetermined value of the radius r, which forms the boundary between the first group of cells and the second group of cells, is not limited to, but is, for example, 0.5 mm to 1.2 mm, and is 25% to 75% of the maximum cell radius, preferably 30% to 70%, and more preferably 40% to 65%.

[0029] As will be described in detail later, the resin foam of the present disclosure is obtained by capturing a three-dimensional transmission image and analyzing the three-dimensional structure, and excluding minute bubbles that may be noise, the volume fraction of bubbles with a radius r is calculated for all bubbles present in the resin foam within the analysis range. n (r n-1 Larger than r n A histogram showing the distribution for each radius range (below) can be obtained. This histogram is a multi-modal histogram in which multiple distribution peaks appear, and preferably a bimodal histogram. This histogram has multiple distribution peaks with a predetermined value of radius r as the boundary. In the case of a bimodal histogram, the first and second bubble groups appear as two distribution peaks with the predetermined value as the boundary. The predetermined value of radius r, which corresponds to the valley between the two peaks, is the radius that forms the boundary between the first and second bubble groups, and is, for example, 0.5 mm to 1.2 mm, i.e., 25% to 75% of the maximum bubble radius, preferably 30% to 70%, and more preferably 40% to 65%.

[0030] As will be described in detail later, the resin foam of the present disclosure is obtained by taking a three-dimensional transmission image and analyzing the three-dimensional structure, and the integrated value of the bubble volume ratio is calculated by dividing the product of the number of bubbles with a radius r and the volume of the bubbles with a radius r by the volume of all the bubbles, for all the bubbles present in the resin foam within the analysis range .... n (r n-1 Larger than r n A scatter plot can be obtained in which the radius of each bubble is plotted against the radius range below. Two approximate lines are obtained from this scatter plot. The two approximate lines are a first approximate line obtained from the plot of the first group of bubbles and a second approximate line obtained from the plot of the second group of bubbles. The first approximate line and the second approximate line have different slopes. The predetermined value of the radius r at the boundary between the first and second approximate lines is the radius that forms the boundary between the first and second groups of bubbles, and is, for example, 0.5 mm to 1.2 mm, that is, 25% to 75% of the maximum bubble radius, preferably 30% to 70%, and more preferably 40% to 65%.

[0031] The sum of the volume fractions of the bubbles constituting the second group of bubbles is preferably 10% to 80% of the total volume fraction of the bubbles, and the sum of the volume fractions of the bubbles constituting the first group of bubbles is preferably more than 20% to less than 90% of the total volume fraction of the bubbles.

[0032] The structural analysis involves imaging the resin foam using an X-ray CT imaging device, then converting the image into 3D data using 3D data conversion software, and analyzing the bubble structure using cell structure analysis software, thereby allowing the bubble radius, volume fraction, etc. to be calculated. While devices commonly used for 3D structural analysis and commercially available analysis software can be used, for example, a 3D stereoscopic image can be captured using an X-ray CT imaging device (nano3DX) manufactured by Rigaku Corporation, and calculations can be performed based on the stereoscopic image using 3D data conversion software (ExFact® VR) and analysis software (ExFact® Analysis for Porous / Particles) manufactured by Nippon Visual Science Co., Ltd.

[0033] In the resin foam of the present disclosure, in order to exclude voids caused by molding defects from the range of structural analysis, the maximum radius of the cells to be subjected to structural analysis is preferably less than 2000 μm.

[0034] When the resin foam of the present disclosure is used as a cushioning material for forming a seat portion such as a passenger car seat, the porosity thereof is preferably 90% or more.

[0035] The porosity can be determined by a known method. For example, the apparent volume Vd is determined from the true volume Vc and the outer dimensions of the test piece, and the porosity can be calculated using the following formula: porosity (%) = [(Vd - Vc) / Vd] × 100. Alternatively, the porosity can be measured using a porosity meter (PHI-X, manufactured by Mecanum).

[0036] The resin foam of the present disclosure is generally obtained by foaming a resin composition. The resin contained in the resin composition is not particularly limited as long as it can be molded into a flexible foam used in a cushioning material, and examples thereof include acrylic resins, silicone resins, urethane resins, ester resins, and polyolefin resins. One type of resin may be used alone, or two or more types may be used in combination.

[0037] The resin foam of the present disclosure preferably contains a crosslinkable polymer, and more preferably, the crosslinkable polymer has a urethane bond.

[0038] An example of the resin foam of the present disclosure is a flexible polyurethane foam. Flexible polyurethane foams are produced by foaming a resin composition containing a polyol, an isocyanate, a crosslinking agent, a catalyst, a foam stabilizer, a blowing agent, and the like. The raw materials constituting the resin composition may be any known materials used in the production of flexible polyurethane foams. Other additives, such as colorants, stabilizers, compatibilizers, fillers, and flame retardants, may also be added as needed.

[0039] Examples of polyols include polyether polyols, polyester polyols, polymer polyols, etc. One type of polyol may be used alone, or two or more types may be used in combination.

[0040] Examples of polyether polyols include polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol.

[0041] Examples of polyester polyols include those obtained by a condensation polymerization reaction between a polycarboxylic acid such as phthalic acid, isophthalic acid, terephthalic acid, oxalic acid, or adipic acid and a polyol such as ethylene glycol, propanediol, propylene glycol, or glycerin.

[0042] Examples of polymer polyols include those obtained by polymerizing butadiene, acrylonitrile, styrene, or the like in the presence of a catalyst, and those obtained by dispersing polymer components such as vinyl acetate or polyacrylonitrile in polyether polyol. Examples of isocyanates include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), modified MDI, naphthylene diisocyanate, biphenylene diisocyanate, diphenyl ether diisocyanate, etc. One type of isocyanate may be used alone, or two or more types may be used in combination.

[0043] Examples of crosslinking agents include water, glycerin, 1,4-butanediol, diethylene glycol, ethanolamines, polyethylene polyamines, etc. One type of crosslinking agent may be used alone, or two or more types may be used in combination.

[0044] Examples of the catalyst include amine catalysts such as triethylenediamine (TEDA) and triethylamine, and metal catalysts such as organotin compounds, organoiron compounds, organozinc compounds, and organonickel compounds. One type of catalyst may be used alone, or two or more types may be used in combination.

[0045] Examples of the foam stabilizer include silicone compounds, surfactants, phenolic compounds, etc. One type of foam stabilizer may be used alone, or two or more types may be used in combination.

[0046] Examples of blowing agents include water, carbon dioxide gas, ammonia, hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), hydrochlorofluoroolefins (HCFOs), etc. One type of blowing agent may be used alone, or two or more types may be used in combination.

[0047] When the resin foam is a flexible polyurethane foam, the minimum spring constant at a compression rate of 10% or more is preferably 10 to 20 N / mm, more preferably 3 to 15 N / mm, and even more preferably 5 to 10 N / mm. [Example]

[0048] <Preparation of resin foam> Next, a specific method for producing a resin foam will be described.

[0049] To prepare the base blend polyol, polyol and additives (crosslinking agent, catalyst, foam stabilizer, and blowing agent) were mixed in the following proportions. Polyol 100 parts: A polyether polyol (average molecular weight: 5000, functionality 3) to which polymer polyol has been added. Crosslinking agent 3.5 parts: Triethanolamine Catalyst 0.9 parts: 33% triethylenediamine (67% dipropylene glycol), N,N-dimethylaminohexanol, bis(dimethylaminoethyl) ether Foam stabilizer 0.6 parts: Dow (formerly Nippon Unicar) SZ-1302 and SZ-1342 Foaming agent 3.5 parts: water In each example and comparative example, additives were added to the blend polyol (no additives were added in Comparative Example 2), and then mixed with isocyanate in a predetermined ratio to prepare a resin composition serving as a raw material for a resin foam. Immediately after preparation, the resin composition was poured into a mold adjusted to 65°C and the lid was closed. The mold used was an aluminum mold measuring 400 mm x 400 mm x 100 mm, the surface of which had been coated with a wax-based mold release agent. Foaming was completed within the mold in approximately 6 minutes, and a flexible polyurethane foam serving as a resin foam was removed from the mold.

[0050] Next, the resin compositions of the examples and comparative examples will be described.

[0051] [Example 1] 1.0 part of a cell opener was added to the above blend polyol, and a resin foam was obtained according to the above production method.

[0052] [Example 2] 2.0 parts of a cell opener was added to the above blend polyol, and a resin foam was obtained according to the above production method.

[0053] [Example 3] 3.0 parts of a cell opener was added to the above blend polyol, and a resin foam was obtained according to the above production method.

[0054] [Example 4] 5.0 parts of a cell opener was added to the above blend polyol, and a resin foam was obtained according to the above production method.

[0055] [Comparative Example 1] 7.0 parts of a cell opener was added to the above blend polyol, and a resin foam was obtained according to the above production method.

[0056] Comparative Example 2 A resin foam was obtained according to the above-mentioned production method without adding anything to the above-mentioned blend polyol.

[0057] [Example 3] 0.5 parts of a foam stabilizer was added to the above blend polyol, and a resin foam was obtained according to the above production method.

[0058] The compressive modulus and porosity were measured and evaluated for Examples 1 to 4 and Comparative Examples 1 to 3. The results are shown in Table 1.

[0059] [Table 1]

[0060] <Evaluation> -Structural analysis- A 10 mm × 10 mm × 10 mm evaluation sample was taken from a position 10 mm or more inward from the surface of each of the 400 mm × 400 mm × 100 mm resin foam test blocks produced in Examples 1 to 4 and Comparative Examples 1 to 3. Next, the evaluation sample was imaged using an X-ray CT imaging device (Rigaku Corporation, nano3DX). The measurement area was 5424.3 μm × 5424.3 μm × 5424.3 μm. The resin portion of the imaged data was extracted and converted into 3D data using 3D data conversion software (Nihon Visual Science Co., Ltd., ExFact® VR). Finally, the 3D data was used to analyze the cell structure using cell structure analysis software (Nihon Visual Science Co., Ltd., ExFact® Analysis for Porous / Particles). The bubble radius was calculated by first analyzing the volume of the bubble and then assuming that the bubble was spherical.

[0061] From the results of the structural analysis, bubbles with a bubble radius of 0.1 mm or more were extracted, and the bubble radius and volume fraction of bubbles with that radius contained in the resin foam were calculated, and Figures 1 to 14 were created. Figures 1 and 8 show the resin foam of Example 1. Figures 2 and 9 show the resin foam of Example 2. Figures 3 and 10 show the resin foam of Example 3. Figures 4 and 11 show the resin foam of Example 4. Figures 5 and 12 show the resin foam of Comparative Example 1. Figures 6 and 13 show the resin foam of Comparative Example 2. Figures 7 and 14 show the resin foam of Comparative Example 3.

[0062] 1 to 7 show the vertical axis of the graph, which shows the cumulative bubble volume ratio (cumulative bubble volume ratio) calculated by dividing the product of the number of bubbles of radius r and the volume of bubbles of radius r by the total volume of bubbles. The cumulative bubble volume ratio is calculated by accumulating the bubble volume ratio in ascending order of radius r. The vertical axis shows the cumulative bubble volume ratio, which is the cumulative bubble volume ratio ... n (r n-1 Larger than r nThe scatter diagrams are obtained by plotting the radius range (below) on the horizontal axis. In the scatter diagrams (FIGS. 1 to 6) of Examples 1 to 4 and Comparative Examples 1 and 2, the plot range of the first group of bubbles was examined so that the coefficient of determination of the first approximation line obtained by the least squares method from the point where the cumulative bubble volume fraction is 100% is 0.965 or more (i.e., 0.97 or more when rounded to the third decimal place). The radius interval r of the plot range of the first group of bubbles derived from the examination results is n (r n-1 Larger than r n The maximum value of r n was obtained as the boundary radius, i.e., the predetermined value of the bubble radius r. Next, a second approximate line consisting of the plot of the second bubble group was obtained by the least squares method in the range from the predetermined value of the bubble radius to the point where the cumulative bubble volume fraction is 0%. Similarly, in Comparative Example 3, one approximate line was obtained. The two approximate lines shown by dashed lines in Figures 1 to 6 are the first approximate line obtained from the plot of the first bubble group and the second approximate line obtained from the plot of the second bubble group. The first approximate line and the second approximate line have different slopes. In Figure 7, only one approximate line was obtained.

[0063] 8 to 14 are histograms showing the volume fraction of bubbles with a radius r on the vertical axis and the radius r on the horizontal axis. The histograms (FIGS. 8 to 13) for Examples 1 to 4 and Comparative Examples 1 and 2 were bimodal, with two distribution peaks appearing for the small-radius bubble group and the large-radius bubble group. The peak on the small-radius side represents the first bubble group, and the peak on the large-radius side represents the second bubble group. The histogram for Comparative Example 3 (FIG. 14) was a unimodal histogram with only one distribution peak appearing.

[0064] The radius of the boundary between the two approximate lines in Figures 1 to 6 is equal to the radius of the boundary between the two mountains in Figures 8 to 13, and this boundary radius is the boundary between the first and second cell groups. From the results in Figures 1 to 4 and 8 to 11, the cell radius of the boundary between the first and second cell groups in the resin foam of this embodiment is 0.5 mm to 1.2 mm, that is, 25% to 75% of the maximum cell radius, preferably 30% to 70%, and more preferably 40% to 65%.

[0065] -Porosity- The porosity was measured using a porosity / density meter (PHI-X, manufactured by Mecanum, Canada). The measurement method was the isothermal constant volume change method, and the measurement environment temperature was 15°C to 30°C.

[0066] -Compression modulus- Evaluation samples (100 mm thick) measuring 400 mm × 400 mm × 100 mm were taken from a position at least 10 mm inward from the surface of each of the 400 mm × 400 mm × 100 mm resin foam test blocks prepared in Examples 1 to 4 and Comparative Examples 1 to 3. A compression tester (Aiko Engineering Co., Ltd., Model-1840-TS, Load Cell: MODEL-3200 (2KN)) was used as the testing device, and the test conditions were a compression speed of 200 mm / min and a load range of 0 N to 980 N. Each evaluation sample was allowed to stand for at least 22 hours in an environment of 23°C and 50% humidity before testing. The evaluation samples were placed at intervals of approximately 20 mm on a flat plate with approximately 6 mm diameter ventilation holes. Compression was initiated at a rate of 200 mm / min, and data on the compressed height (displacement) and compressed force (compression load) were collected. When the compressive load reached 980 N, the compressive pressure was released and the sample was opened twice.

[0067] The measurement results were obtained by plotting the change in compression load (N) and the change in spring constant (N / mm) against the displacement (mm) based on the displacement and compression load recorded during the compression test. Evaluation was performed using a B / A ratio, where A represents the maximum spring constant at a compression rate of 10% or less, and B represents the minimum spring constant at a compression rate of 10% or more. The smaller the difference between the maximum and minimum spring constants (the larger the B / A ratio), the better the touch and support feel are considered to be compatible. In Table 1 above, if the B / A ratio is less than 25%, the touch and support feel are not compatible and the evaluation is given as ×, while if the B / A ratio is 25% or more, the touch and support feel are compatible and the evaluation is given as ○.

[0068] Examples of measurement results of compressive modulus are shown in FIGS. 15 and 16. FIG. 15 is a graph showing the compressive load versus displacement, showing the measurement results for the resin foams of Example 2 (solid line) and Comparative Example 2 (dashed line). FIG. 16 is a graph showing the change in spring constant versus displacement, showing the measurement results for the resin foams of Example 2 (solid line) and Comparative Example 2 (dashed line). As shown in FIG. 16, in Example 2, in the initial state when the load begins to be applied (compression rate of 10% or less), the rise of the peak was slightly delayed and the maximum spring constant was suppressed. This indicates an excellent touch. In the resin foam of Example 2, the load is concentrated on the skeleton of the small cells between the large cells, causing bending with a small amount of displacement, resulting in this change in spring constant. In Comparative Example 2, the rise of the peak spring constant was rapid and the maximum spring constant was also large at compression rates of 10% or less. This indicates that the touch is inferior to that of Example 2. Furthermore, in Example 2, the large bubbles ensure a sufficient stroke length until bottoming out, and improve the support feeling when bottoming out. In Example 2, the minimum spring constant at a compression rate of 10% or more is a good value, indicating that an excellent support feeling can be obtained. Compared to Comparative Example 2, Example 2 significantly reduces the difference between the maximum and minimum spring constants, achieving both a good touch feeling and a good support feeling.

[0069] FIG. 17 shows three-dimensional images of the resin foams of Example 2 and Comparative Examples 2 and 3. In the image of Example 2, small cell groups (first cell groups) are seen between large cell groups (second cell groups), with wide spacing between the large cells and numerous skeletons formed by the cell walls of the small cell groups. Example 2 has a cell structure that can provide both a sense of touch and a sense of support. In the images of Comparative Examples 2 and 3, many small to medium-sized cells are seen, with little difference in cell size and narrow spacing between the cells. With such a structure, it is difficult to provide both a sense of touch and a sense of support.

[0070] <Other Comparative Examples> As another comparative example, the properties were compared with those of the resin foam of the present disclosure using the data disclosed in Patent Document 1. Specifically, using the data from Examples 6 to 8 of Patent Document 1 (see Patent Document 1, Figure 3), the maximum spring constant A at a compression rate of 10% or less and the minimum spring constant B at a compression rate of 10% or more were determined, and evaluation was performed using B / A.

[0071] Patent Document 1, Example 6: B / A=14% (A: 32.5 N / mm, B: 4.7 N / mm) Patent Document 1, Example 7: B / A=14% (A: 32.5 N / mm, B: 4.7 N / mm) Patent Document 1, Example 8: B / A=15% (A: 32.5 N / mm, B: 5.0 N / mm) In all cases, B / A was less than 25%, and it is believed that both the touch feeling and the support feeling were not achieved. [Industrial Applicability]

[0072] INDUSTRIAL APPLICABILITY The resin foam of the present disclosure is used in furniture such as sofas and beds, and seats for passenger cars, etc., and is extremely useful as a cushioning material with an excellent tactile feel that combines a sense of touch and a sense of support.

Claims

1. A resin foam comprising a first group of cells having a cell radius less than a predetermined value and a second group of cells having a cell radius equal to or greater than the predetermined value, As a result of the structural analysis, The integrated value of the bubble volume ratio calculated by dividing the product of the number of bubbles of radius r and the volume of the bubbles of radius r by the volume of all bubbles is calculated as the radius interval r, which is divided into 20 intervals from the maximum bubble radius to 0. ｎ (r ｎ－１ Larger than r ｎ The scatter plot obtained by plotting the radius of the sample against the radius range below gives two approximate straight lines. the two approximate straight lines are a first approximate straight line obtained from the plot of the first gas bubble group and a second approximate straight line obtained from the plot of the second gas bubble group, and the first approximate straight line and the second approximate straight line have different slopes; A resin foam in which the sum of the volume fractions of the cells constituting the second cell group is 10% or more and 80% or less of the total volume fraction of the cells.

2. In claim 1, A resin foam, wherein the predetermined value is 25% or more and 75% or less of the maximum bubble radius.

3. In claim 1, A resin foam in which the maximum bubble radius within the structural analysis range is less than 2000 μm.

4. In claim 1, A resin foam having communicating holes formed in the cell walls between adjacent cells, which communicate between the cells.

5. In claim 1, A resin foam formed from a resin composition containing a crosslinkable polymer.

6. In claim 5, The resin foam, wherein the crosslinkable polymer has a urethane bond.

7. In claim 1, A resin foam that is a soft polyurethane foam.

8. In claim 1, A resin foam characterized by having a porosity of 90% or more.

9. A sheet using the resin foam according to claim 1 as a cushioning material.

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