JP2022162846A - Floor material - Google Patents

Abstract

To provide a floor material that reduces risk of femur fractures.SOLUTION: A floor material comprises an upper floor material having a cross-sectional secondary moment of 400 mm4 or more and 25000 mm4 or less, and a lower floor material provided below the upper floor material and having a lower cross-sectional secondary moment than the upper floor material. Bending rigidity of the upper floor material should be 100 Nm2/10 mm or more and 200 Nm2/10 mm or less. The lower floor material is formed by a foam with isolated cells, and a ratio of density after foaming to the density before foaming of the lower floor material is preferably between 0.067 or more and 0.143 or less.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to flooring, and more particularly to flooring capable of reducing the risk of femur fractures.

In recent years, falling fractures in the elderly have become a social problem, and falling fractures account for 10% of the factors that make elderly people need nursing care. Falling fractures account for 20% to 25% of medical accidents. Furthermore, falls and fractures account for more than 20% of the total accidents at childcare-related facilities such as kindergartens, nursery schools, and certified children's centers. For this reason, floor materials have been proposed that reduce the risk of bone fractures by absorbing the impact when falling (for example, Patent Documents 1 and 2).

Japanese Patent No. 3600726 Japanese Patent No. 5244927

Fracture sites due to falls as described above vary greatly depending on age, and the risk of femoral fracture increases sharply in people in their 60s and beyond. Femoral fractures require hospitalization for treatment, and the inability to walk continues for a long period of time. However, the performance of the above-described conventional flooring materials is evaluated based on the floor hardness test specified in the Japanese Industrial Standard "JIS A6519". However, since the above-mentioned test is based on the evaluation of head injury, it is difficult to say that the safety evaluation against femoral fractures is sufficiently secured for the floor materials whose performance was evaluated in this test.
This indication is made in view of such a problem, and an object of this indication is to provide the floor material which especially reduces the risk of a femoral bone fracture.

In order to solve the above-described problems, a flooring material according to an aspect of the present disclosure includes a flooring material having a geometrical moment of inertia of 400 mm ⁴ or more and 25000 mm ⁴ or less, and a flooring material provided below the flooring material, and having a cross section larger than that of the flooring material. and an underfloor member having a low secondary moment.

According to the present disclosure, it is possible to obtain a flooring that reduces the risk of femoral fracture.

FIG. 2 is a cross-sectional view showing a positional configuration example of a flooring material according to the present disclosure; Fig. 10 is a cross-sectional view showing a second state (plateau region) when pressure is applied to the underfloor material having a plurality of closed cells; FIG. 10 is a cross-sectional view showing a third state (densified region) when pressure is applied to the underfloor material having a plurality of closed cells; 4 is a graph schematically showing a displacement-load curve showing the relationship between the displacement of the underfloor material and the impact load applied to the underfloor material. FIG. 3 is a schematic diagram illustrating an impact test for obtaining impact load and displacement-load curve of flooring. It is a graph explaining plateau height.

Embodiments of the present disclosure will be described below with reference to the drawings. However, the embodiments described below are merely examples, and are not intended to exclude various modifications and application of techniques not explicitly described below. The present disclosure can be implemented in various modifications (for example, by combining each embodiment) without departing from the gist of the disclosure.

1. Flooring Material of the Present Disclosure The flooring material according to the present disclosure is, as described above, a flooring material capable of reducing the risk of bone fractures, particularly fractures of the femur.
In order to reduce the risk of femoral fracture, the flooring material according to the present disclosure suppresses the toes from being caught during walking and has high walkability. This reduces the risk of femoral fracture by making it less likely that the user will fall during walking. In order to obtain a floor material with a small impact load for suppression of bone fracture, the floor material is softened. When the floor material is softened, the weight of the pedestrian easily causes the floor material to sink under the feet of the pedestrian, resulting in poor walking performance.
In the present embodiment, a flooring material having high walkability while being a flooring material having a small impact load will be described.

In addition, the floor material according to the present disclosure is a floor material that can reduce the risk of femoral fracture by reducing the impact load of the floor material even if a pedestrian falls. is preferred. When the floor material is softened to prevent bone fractures, a foamed floor material is used, but when the underfloor material is hardened, it is necessary to lower the foaming ratio. In this case, the displacement of the flooring material until it reaches the densified region is insufficient, resulting in a decrease in the amount of energy absorbed when an impact is applied.
In the present embodiment, a flooring material that has high walkability and is highly effective in suppressing femoral fracture will be described.

2. Structure of Floor Material Hereinafter, a floor material 1 according to the present disclosure will be described with reference to FIG.
The floor material 1 includes an underfloor material 11 and an overfloor material 12 provided on the upper surface of the underfloor material 11 (the surface on the side closer to the surface of the floor material 1).

The underfloor material 11 has, for example, a plurality of closed cells that are not connected to each other, and has a function of absorbing the pressure applied to the floor material 1 during walking and enhancing the cushioning properties of the floor material 1 . Moreover, thereby, the underfloor material 11 can demonstrate the function which improves a cushioning performance, reducing the usage-amount of material.
In addition, the upper floor material 12 provided on the underfloor material 11 is less deformed by the pressure applied locally when a pedestrian walks on the floor material 1, and improves the walkability on the floor material 1. In addition, the upper floor material 12 disperses the pressure locally exerted on the floor material 1 during walking in the plane of the underfloor material 11, and disperses the energy at the time of impact application even at positions other than the position of the underfloor material 11 where the pedestrian walked. It has the function of increasing the absorption capacity and enhancing the cushioning properties of the flooring material 1 .
The floor material 1 is configured by laminating an underfloor material 11 and an upper floor material 12, thereby improving walkability and reducing the risk of fracture of the femur when falling.

The area of the flooring 1 is preferably adjusted so that the load in the plateau region of the compression characteristics (details will be described later) is less than the fracture load. Specifically, the area of the floor material 1 is preferably 100 cm ² or more and 900 cm ² or less, and more preferably 100 cm ² or more and 400 cm ² or less. When the floor material 1 is 100 cm ² or more, the area of the underfloor material 11 that absorbs the pressure during walking and deforms is large, so the pressure locally applied to the floor material 1 is dispersed and the cushioning performance of the floor material 1 is enhanced. be able to. Moreover, since the floor material 1 is 900 cm ² or less, the pressure is efficiently dispersed.

The impact load of the flooring 1 is preferably 2000N or more and 6000N or less, more preferably 2000N or more and 3600N or less. When the impact load of the floor material 1 is 2000 N or more, a suitable repulsive force is obtained from the entire floor when walking, and the sinking of the underfloor material is suppressed, so the risk of overturning itself is reduced. When the impact load of the floor material 1 is 6000 N or less, the risk of fracture of the femur when a pedestrian falls is reduced.

Here, the impact load of the floor material 1 corresponds to the height of the pedestrian's waist, which is based on the weight and shape of the impact applying body based on the pressure distribution applied to the trochanter of the femur when the pedestrian falls. This is the impact load F generated when the floor material 1 is dropped from a predetermined drop height and an impact is applied to the flooring material 1 through a cushioning material formed of a material simulating human soft tissue. The impact load F is measured under the conditions set so that the reference impact load Fs generated when impact is applied to the cushioning material is 6500N.
Below, the underfloor member 11 and the upper floor member 12 will be described in detail.

<Floor material>
A hard member that is rigid and less deformable is used for the floor covering member 12 . Specifically, the floor covering 12 is made of a material having a geometrical moment of inertia of 400 mm ⁴ or more and 25000 mm ⁴ or less. When the geometrical moment of inertia of the floor material 12 is 400 mm ⁴ or more and 25000 mm ⁴ or less, the floor material 12 has a very high rigidity, so the floor material 12 is hard to bend, and the entire surface of the floor material 11 can be deformed. , it is possible to suppress the sinking of the floor material 1 immediately below the position of the pedestrian, thereby enhancing the walkability. As a result, the risk of falls leading to femoral fractures can be reduced.

The bending rigidity of the floor covering 12 is preferably 100 Nm ² /10 mm or more and 300 Nm ² /10 mm or less, and preferably 100 Nm ² /10 mm or more and 200 Nm ² /10 mm or less. When the bending rigidity of the floor material 12 is 100 Nm ² /10 mm or more and 300 Nm ² /10 mm or less, the floor material 12 has a very high rigidity. can be dispersed over a wide surface to enhance the cushioning properties of the flooring material 1. As a result, the risk of falls leading to femoral fractures can be reduced.

The thickness of the floor covering 12 is preferably 15 mm or more and 40 mm or less. When the thickness of the upper floor material 12 is 15 mm or more and 40 mm or less, the deformation of the underfloor material 11 during walking does not easily progress to the densified region (details will be described later), and the tactile sensation during walking is less likely to decrease, resulting in improved walkability. improves. As a result, the risk of falls leading to femoral fractures can be reduced.

The bending elastic modulus of the floor covering 12 is preferably 8000 MPa or more. When the flexural modulus of the floor material 12 is 8000 MPa or more, the bending rigidity of the floor material 12 is increased, so that the pressure applied to the floor material 12 when falling is distributed over a wide surface of the floor material 11. Sinking can be suppressed and the risk of falling itself can be suppressed. Therefore, it is possible to further reduce the risk of falls leading to bone fractures.

Such a flooring material 12 preferably includes a layer formed of, for example, wood or a resin material mixed with a woody material. That is, the flooring material 12 may have at least one of a layer of wood and a layer formed of a resin material mixed with a wood material. The layer may be laminated. Further, the floor upper material 12 may be formed by laminating a metal layer such as stainless steel (SUS) on a layer formed of wood or a resin material mixed with a woody material.
When the flooring material 12 is a laminate formed of a plurality of layers, the physical properties of the entire laminate may be within the ranges described above.

<Underfloor material>
The underfloor member 11 is provided below the upper floor member 12 (on the side opposite to the surface of the upper floor member 12 ), and is made of a soft material having a lower geometrical moment of inertia than the upper floor member 12 . The underfloor material 11 is formed using polyethylene or vinyl chloride, for example. Thereby, the underfloor material 11 can absorb the pressure applied to the upper floor material 12 .

The underfloor material 11 is made of, for example, a foam having closed cells. Here, the impact absorption mechanism of the underfloor member 11 in which closed cells are formed will be described with reference to FIGS. 2A and 2B and FIG. FIG. 2A is a cross-sectional view showing a second state when pressure is applied to the underfloor material 11 having a plurality of closed cells 11A, and FIG. FIG. 11 is a cross-sectional view showing a third state when 3 is a graph schematically showing a displacement-load curve showing the relationship between the displacement of the underfloor member 11 and the impact load applied to the underfloor member 11. As shown in FIG. The energy absorption amount of the underfloor member 11 can be calculated from the area in the displacement-load curve due to the deformation of the underfloor member 11 .

The displacement-load curve of the underfloor material 11 having closed cells has, as shown in FIG. is doing. The load rising region of the displacement-load curve corresponds to the first state of the underfloor member 11, the plateau region corresponds to the second state of the underfloor member 11 shown in FIG. 2A, and the densified region corresponds to the underfloor shown in FIG. 2B. This corresponds to the third state of material 11 .

The underfloor material 11 is hard when the load in the plateau region is large, and is soft when the load in the plateau region is small. In the plateau region, the load increase due to energy absorption is small, so the impact load can be kept almost constant as long as the impact energy reaches the densified region. The magnitude of energy absorption in the plateau region contributes to the energy absorption characteristics of the underfloor material 11 . Therefore, the load in the plateau region and the displacement until reaching the densification region determine the energy absorption amount of the underfloor material 11 .
It should be noted that the ideal energy absorption characteristic is a characteristic in which the amount of displacement up to the densified region is large under the load in the plateau region within the allowable range, that is, the displacement that becomes the plateau region and the displacement that becomes the densified region. It is a characteristic that the difference between is large. A quasi-static compression test can be used to compare the impact absorption energy of the underfloor material 11 as described above.

It is considered that the bending and buckling of the cell walls accompanying the buckling of the independent cells 11A contribute to the load in the plateau region described above. That is, the lower the ratio (expansion ratio) of the post-foaming density (ρ*) to the pre-foaming density (ρ) of the underfloor material 11 and the thicker the cell walls surrounding the closed cells 11A, the higher the load in the plateau region. , the higher the expansion ratio and the thinner the cell wall thickness, the lower the load in the plateau region.
The displacement of the underfloor material 11 from the plateau area to the densified area depends on the expansion ratio and thickness of the underfloor material 11 . The underfloor material 11 with a low expansion ratio reaches the densified region with less displacement than the underfloor material 11 with a high expansion ratio.

When the load in the plateau region is within the permissible range, in order to increase the energy absorption of the underfloor member 11 with a low expansion ratio, the thickness of the underfloor member 11 should be increased to increase the displacement until it reaches the densified region. is effective for energy absorption. Further, in the underfloor material 11 with a high expansion ratio, as described above, the displacement until reaching the densified region is large, but the load in the plateau region is reduced. Therefore, by increasing the area where the underfloor member 11 deforms and increasing the load in the plateau region within the allowable range, the energy absorption amount in the plateau region can be increased.

From the above mechanism, the ratio (expansion ratio) of the post-foaming density (ρ*) to the pre-foaming density (ρ) in the underfloor material 11 is preferably 0.067 or more and 0.143 or less. By setting the expansion ratio within this range, the load in the plateau region of the underfloor material 11 can be increased. Therefore, even if you fall, the risk of femoral fracture is further reduced.
Here, the post-foaming density (ρ*) of the underfloor material 11 is lower than the pre-foaming density (ρ) of the underfloor material 11 due to the formation of closed cells. The density before foaming (ρ) and the density after foaming (ρ*) can be measured using a density measuring device such as a true densimeter. The pre-foaming density is obtained by performing high-pressure compression on the underfloor material to sufficiently break the foam, and then measuring the density.

Further, the thickness of the underfloor material 11 is preferably 3 mm or more and 10 mm or less. By setting the thickness of the underfloor material 11 within this range, the displacement up to the densified area can be increased, and the load in the plateau area of the underfloor material 11 can be increased.

Furthermore, the plateau height (plateau stress) of the underfloor material 11 at a strain rate of 200/s or more and 600/s is preferably 0.2 MPa or more and 1.6 MPa or less. Here, the plateau height is the minimum value after the upward convex peak corresponding to the transition from the load rising region to the plateau region in the first differential curve of the displacement-load curve described above. say power. When the plateau height is within the range described above, the underfloor material 11 becomes soft.

In addition, when a load is applied, the energy consumption (EI(x)) of the bending of the cell walls accompanying the buckling of the closed cells 11A of the underfloor material 11 is the energy consumption (EI(x)) due to the gas pressure rise of the cell walls of the closed cells 11A EΔP(x)), preferably 1.8 or more. This is because the underfloor member 11 can efficiently absorb the impact energy to the underfloor member 11 as the energy consumption (EI(x)) of the bending of the cell wall associated with the buckling of the independent cells 11A increases.
A method of measuring the energy consumption (EI(x)) for bending the cell wall accompanying the buckling of the closed cell 11A and the energy consumption (EΔP(x)) due to the gas pressure increase of the cell wall of the independent cell 11A will be described later.

3. Method for Measuring Characteristics of Flooring Material A method for measuring the characteristics of each part of the flooring material 1 will be described below.
<Impact load>
An impact test for acquiring the impact load and the displacement-load curve of the flooring 1 will be described with reference to FIG.
The impact load of the floor material 1 can be measured using the method specified in JP-A-2020-076764. That is, to measure the impact load, first, a cushioning material 20 made of a material that simulates the soft tissue of a human body is prepared on the flooring material (the surface of the flooring material). A laminate for evaluation (hereinafter referred to as a laminate) in which the cushioning material 20 is arranged on the surface of the flooring 1 is subjected to impact using an evaluation apparatus described in Japanese Patent Application Laid-Open No. 2020-076764. Then, the impact load generated in the laminate is obtained by measuring it with a load measuring device (load cell). Here, the evaluation device is a pendulum-type evaluation device provided with an integrated weight and a hitting part imitating the shape of a femur.

At this time, the impact load applied to the floor material is measured by, for example, dropping the impact part onto the laminate from a height of 50 cm, which corresponds to the average hip height of an adult (fall height). As the cushioning material 20, human skin gel, which is a super-soft urethane molding resin having a thickness of 15 mm, dimensions of 27 mm long and 27 mm wide, and an Asker C hardness of 7 (manufactured by Exseal) can be used.
Further, when measuring the impact load, the displacement of the laminate is measured with an accelerometer and a displacement meter, and the impact speed of the impact part is measured with a speedometer.
At this time, as described in Japanese Patent Application Laid-Open No. 2020-076764, the shape of the striking part is such that the surface integrated with the rectangular parallelepiped weight is flat, and the surface not integrated with the weight has a curvature of 115 mm. It has a curved surface.

The energy when the floor material 1 is subjected to the impact test is mainly absorbed by the deformation of the cushioning material 20 and the floor material 1 . The deformation of the floor material 1 can be decomposed into the deformation of the upper floor material 12 and the deformation of the underfloor material 11 . When an impact test is performed on the floor material 12, a compressive load is applied directly under the impact, while a force in the direction opposite to the compression is generated in areas other than the area directly under the impact due to the resistance to the compression of the underfloor material 11. - 特許庁At this time, since a compressive force is generated in the underfloor material 11 due to the bending moment of the floor material 12, when the geometrical moment of inertia of the overfloor material 12 is low, the deflection of the overfloor material 12 increases. local compression of the underfloor material 11 occurs.

On the other hand, in the flooring material 1, since the geometrical moment of inertia of the flooring material 12 is very high, the deflection of the flooring material 12 is very small, and the underfloor material 11 is approximately uniformly compressed over the entire flooring material 1. When the underfloor material 11 is uniformly compressed, the load required for compressing the underfloor material 11 increases due to the increase in the compression area. As will be described below, the area of the floor material 1 itself must be optimized so that the load in the plateau region of the compression characteristics (displacement-load curve) is less than the fracture load.

<Plateau height>
As shown in FIG. 5, the plateau height of the flooring 1 corresponds to the transition from the load rise region in the initial stage of pressurization to the plateau region by creating a first order differential curve of the displacement-load curve obtained in the impact test. Obtained from the test force at strain, which is the minimum after the convex peak.

<Energy consumption (EI(x)) for bending of the cell walls accompanied by buckling of the closed cells of the underfloor material and energy consumption (EΔP(x)) due to the pressure increase of the closed cells of the underfloor material>
The energy consumption (EI(x)) for the bending of the cell wall accompanied by the buckling of the closed cells of the underfloor material and the energy consumption (EΔP(x)) due to the pressure increase of the closed cells under the floor material are obtained from the displacement − It can be calculated by decomposing the load curve into elements. These energy consumptions can be compared using static compression test results to compare the energy absorption at a reference load (6500N).

(Measurement of displacement-load curve of laminate)
The displacement-load curve obtained in the impact test mainly shows the impact load to the cushioning material for displacement (x) in the impact test, the impact load to the floor material for displacement (x), and the underfloor for displacement (x). impact loads on the material. Here, since the floor material has a very high geometrical moment of inertia and little deformation, it is estimated that the deformation of the floor material hardly contributes to the displacement-load curve. Therefore, when the displacement-load curve of the cushioning material is G(x) and the displacement-load curve of the underfloor material is H(x), the displacement-load curve F(x) of the laminate is expressed by the following equation (1). Calculated by
F(x)≈G(x)+H(x) (1)

(Measurement of cushioning material displacement-load curve)
The impact load G(x) on the cushioning material is measured in the same manner as described above. That is, in the method described in the impact test, the laminate is replaced with a single layer of cushioning material, and the impact load of the cushioning material is measured. Further, when measuring the impact load, the displacement of the cushioning material is measured by an accelerometer and a displacement meter, and the impact velocity of the impact part is measured by a speedometer.

(Measurement of displacement-load curve of underfloor material)
Subsequently, a displacement-load curve G(x) of the cushioning material is created from the measured impact load to the cushioning material, the displacement of the cushioning material, and the impact speed of the impact part. From the displacement-load curve F(x) of the laminate and the displacement-load curve G(x) of the cushioning material, the displacement-load curve H(x) of the underfloor material is calculated by the following formula (2). .
H(x)≈F(x)-G(x) (2)

(Calculation of pressure rise effect due to compression of closed cells)
The displacement-load curve H(x) of the underfloor material 11 is divided into the contribution of the bending of the cell walls accompanied by buckling and the contribution of the pressure rise of the closed cells. Among them, the contribution of the pressure rise of closed cells can be roughly calculated by Boyle's law. That is, the compression of the underfloor material 11 causes the buckling deformation of the closed cells 11A, but the outflow of gas from the closed cells 11A is small, and the pressure of the internal gas rises with the volumetric compression inside the closed cells 11A. .
Such a pressure rise can be explained by the following equation (3) using Boyle's law. Here, the Poisson's ratio of the underfloor material 11 is assumed to be approximately zero.

式中、ΔＰはセル内部の気圧増加であり、Ｐ_０は面積を考慮した大気圧である。ここで、発泡倍率は、床下材１１の発泡前密度ρ及び発泡後の密度ρ*から、発泡倍率＝ρ＊/ρで表すことができる。

where ΔP is the pressure increase inside the cell and P ₀ is the atmospheric pressure considering the area. Here, the expansion ratio can be expressed as expansion ratio = ρ*/ρ from the pre-foaming density ρ and the post-foaming density ρ* of the underfloor material 11 .

(Calculation of contribution of bubble wall bending with buckling)
As shown in the equation (4), subtracting the curve of the contribution ΔP of the pressure rise of the closed cells 11A obtained by the equation (3) from the displacement-load curve H(x) of the underfloor member 11 yields the following equation: The cell wall bending contribution I(x) is obtained.
I(x)=H(x)-ΔP(x) (4)

(Calculation of each energy consumption)
The energy consumption EΔP(x) due to the pressure rise of the independent bubbles can be calculated by integrating the equation (3) as shown in the equation (5).
EΔP(x)=∫ΔP(x)dx (5)
Also, the energy consumption EI(x) for the bending of the cell wall with buckling can be calculated by integrating the equation (4) as shown in the equation (6).
EI(x)=∫I(x)dx (6)
Here, the integration in the equations (5) and (6) is the interval integration, and the interval from x=x1 to 0 is integrated when x1 is the displacement x at which F(x)=6500N. As described above, the energy consumption EI(x) for the bending of the cell wall accompanying the buckling of the closed cells 11A of the underfloor member 11 and the energy consumption EΔP(x) due to the pressure increase of the closed cells 11A of the underfloor member 11 can be obtained.

(Secondary moment of area)
The geometrical moment of inertia of the upper floor material 12 can be calculated by measuring the thickness of each layer constituting the upper floor material 12 and calculating with respect to the set width. Specifically, by performing image analysis on the cross section of the flooring material including the flooring material 12, the thickness of the flooring material 12 can be measured, and the geometric moment of inertia can be calculated with respect to a predetermined width. .

(bending rigidity)
The value of the flexural rigidity of the flooring material 12 in a unit width (10 mm) is obtained from the product (EI) of the Young's modulus E (flexural elasticity) obtained by a three-point bending test and the geometrical moment of inertia I. When the flooring material 12 is made of a composite material in which a plurality of materials with different hardness are laminated, the product (EI) of the Young's modulus E (flexural elasticity) and the geometrical moment of inertia I for each layer of each material is calculated. By calculating the sum of these values, the bending rigidity of the entire floor covering 12 can be obtained.

(Bending Young's modulus)
The bending Young's modulus of the flooring material 12 can be obtained by performing a three-point bending test as indicated by JIS K7171.

4. Effect of Floor Material According to Present Disclosure The floor material according to the present disclosure described above has the following effects.
(1) The floor material is composed of an upper floor material having a high geometrical moment of inertia and an underfloor material having a lower geometrical moment of inertia than the upper floor material.
As a result, the entire surface of the underfloor material can be deformed without the upper floor material sagging against its own weight when walking. It can reduce the risk of falls that lead to

(2) The floor material includes an underfloor material made of a foam having closed cells.
As a result, the floor material can exhibit high impact absorption and low impact load in the underfloor material. In addition, by having the above floor material, the entire surface of the underfloor material can be deformed without bending the floor material. Therefore, the compression area of the floor material can be increased, and the plateau height can be increased even with an underfloor material having a high expansion ratio and low stress in the plateau region during compression. Also, by increasing the impact absorption energy in the plateau region, it is possible to reduce the impact load against the impact energy at the time of falling.

(3) With the above-described configuration, the strain up to the densified region where the impact load rises sharply is large, so the thickness necessary for energy absorption can be easily secured, and the material for the underfloor material can be reduced.

Hereinafter, the flooring material according to the present disclosure will be described with reference to examples.

<Example 1>
A flooring material having a thickness of 30 mm, a flexural rigidity of 122 Nm ² , a flexural modulus of 12000 MPa, and a geometrical moment of inertia of 10139 mm ⁴ ; A flooring material having a thickness of 6.5 mm and a thickness of 0.125 was laminated to form a flooring material having an area of 100 cm ² (100 mm length × 100 mm width), which was used as the flooring material of Example 1. . At this time, since the underfloor material is made of polyethylene containing closed cells, the moment of inertia of area is smaller than that of the overfloor material made of wood having a thickness of 30 mm.

<Example 2>
A flooring material of Example 2 was formed in the same manner as in Example 1, except that an underfloor material having a density after foaming to a density before foaming of 0.1 was used.

<Example 3>
A flooring material having a thickness of 10 mm, a flexural rigidity of 10 Nm ² , a flexural modulus of 12000 MPa, and a geometric moment of inertia of 833 mm ⁴ , and a 5 mm thick flooring material having a flexural rigidity of 87 Nm ² and a flexural modulus of 205000 MPa. , a stainless steel plate having a geometric moment of inertia of 427 mm ⁴ , an upper floor material laminated so that the stainless steel plate is on the under floor material side, and an under floor material having a density after foaming density ratio of 0.067 to a density before foaming. A flooring material of Example 3 was formed in the same manner as in Example 1, except that it was used.

<Example 4>
An upper floor material having a thickness of 30 mm, a bending rigidity of 225 Nm ² , a bending elastic modulus of 10000 MPa, and a geometrical moment of inertia of 22500 mm ⁴ , and an underfloor material having a ratio of density after foaming to density before foaming of 0.050. A floor material of Example 4 was formed in the same manner as in Example 1, except that the area of the floor material was 225 cm ² (150 mm long×150 mm wide).

<Example 5>
An upper floor material having a thickness of 30 mm, a flexural rigidity of 225 Nm ² , a flexural modulus of 10000 MPa, and a geometrical moment of inertia of 22500 mm ⁴ , and an underfloor material having a ratio of density after foaming to density before foaming of 0.033. A floor material of Example 5 was formed in the same manner as in Example 1, except that the area of the floor material was 400 cm ² (200 mm long×200 mm wide).

<Example 6>
A flooring material having a thickness of 30 mm, a flexural rigidity of 225 Nm ² , a flexural modulus of 10000 MPa, and a geometrical moment of inertia of 22500 mm ⁴ ; A floor material of Example 6 was formed in the same manner as in Example 1 except that an underfloor material with a thickness of 10 mm was used and the area of the floor material was 900 cm ² (300 mm long x 300 mm wide).

<Example 7>
An upper floor material having a thickness of 30 mm, a bending rigidity of 225 Nm ² , a bending elastic modulus of 10000 MPa, and a geometrical moment of inertia of 22500 mm ⁴ , and an underfloor material having a ratio of density after foaming to density before foaming of 0.025. A floor material of Comparative Example 2 was formed in the same manner as in Example 1, except that the area of the floor material was 900 cm ² (300 mm long×300 mm wide).

<Example 8>
An upper floor material having a thickness of 30 mm, a bending rigidity of 225 Nm ² , a bending elastic modulus of 10000 MPa, and a geometrical moment of inertia of 22500 mm ⁴ , and an underfloor material having a ratio of density after foaming to density before foaming of 0.025. A floor material of Comparative Example 3 was formed in the same manner as in Example 1, except that the area of the floor material was 400 cm ² (200 mm long×200 mm wide).

<Example 9>
A floor of Comparative Example 4 was prepared in the same manner as in Example 1 except that an underfloor material having a density after foaming density ratio of 0.100 to a density before foaming was used and the floor material area was 225 cm ² (length 150 mm × width 150 mm). formed the material.

<Example 10>
The procedure was the same as in Example 1, except that the ratio of the post-foaming density to the pre-foaming density was 0.025, an underfloor material with a thickness of 3 mm was used, and the floor material area was 400 cm ² (length 200 mm × width 200 mm). A flooring material of Comparative Example 5 was formed.

<Comparative Example 1>
A flooring material having a thickness of 3 mm, a flexural rigidity of 0.23 Nm ² , a flexural modulus of 10000 MPa, and a geometric moment of inertia of 23 mm ⁴ , and a ratio of the density after foaming to the density before foaming is 0.025. A floor material of Comparative Example 1 was formed in the same manner as in Example 1, except that an underfloor material was used.

[Evaluation of flooring]
The following evaluations were performed using the floor materials of the above-described examples and comparative examples.
(Walkability)
Walkability is determined by the energy consumption (EI(x)) for the bending of the cell wall accompanying the buckling of the closed cells of the underfloor material, the energy consumption (EΔP(x)) due to the pressure increase of the closed cells, and the cross-sectional quadratic Evaluated based on moment. Specifically, the geometrical moment of inertia of the upper floor material is 400 mm ⁴ or more, and the energy consumption (EI(x)) of the bending of the cell wall accompanying the buckling of the independent cells of the underfloor material is the energy consumption due to the pressure rise of the closed cells ( EΔP(x)) is 1.8 or more, the walkability is marked as “◎”, the geometrical moment of inertia of the upper floor material is 400 mm ⁴ or more, and the energy consumption for bending the cell wall accompanied by the buckling of the closed cells of the underfloor material When (EI(x)) was less than 1.8 greater than the energy consumption (EΔP(x)) due to the pressure increase of closed cells, the walkability was evaluated as "good". In addition, the energy consumption (EI(x)) for the bending of the cell wall accompanied by the buckling of the independent cells of the underfloor material and the geometric moment of inertia of the upper floor material being 400 mm ⁴ or more is the energy consumption (EΔP(x ))), the walkability was evaluated as “△”, and when the geometrical moment of inertia of the floor material was less than 400 mm ⁴ , the walkability was evaluated as “×”.

Here, when the geometrical moment of inertia of the upper floor material is small, it becomes difficult to spread the local pressure applied to the floor material to the front surface of the underfloor material when walking, and the tactile sensation during walking deteriorates.
In addition, the larger the energy consumption (EI(x)) of the bending of the cell wall accompanying the buckling of the closed cells of the underfloor material than the energy consumption (EΔP(x)) due to the pressure increase of the closed cells, the more the floor material during walking. less subsidence. In addition, when the energy consumption (EI(x)) for bending of the cell wall accompanying the buckling of the closed cells in the underfloor material is similar to or smaller than the energy consumption (EΔP(x)) due to the pressure increase of the closed cells, the underfloor during walking Since the deformation of the material progresses to the densified area, the tactile sensation during walking becomes poor.

(shock absorption)
Impact absorption was evaluated based on the impact load of the floor material. Impact absorption is evaluated as “◎” when the impact load of the floor material is 3600N or less, “◯” when the impact load of the floor material is over 3600N and 6000N or less, and “×” when the impact load of the floor material is over 6000N. ” was evaluated.

As shown in Table 1, the floor material of each example having a very high geometrical moment of inertia of 400 mm ⁴ or more can suppress deterioration in walking ability. This is because the deformation of the floor material in each embodiment is small, and the local pressure applied to the floor material during walking is dispersed in the planar direction of the floor material. It is thought that this is because the subduction is small.

Further, as shown in Table 1, when the bending rigidity of the floor material is 100 Nm ² /10 mm or more, preferably 100 Nm ² /10 mm or more and 200 Nm ² /10 mm or less, the walkability is further improved. Further, when the floor material has a thickness of 15 mm or more and 40 mm, the moment of inertia of area tends to increase, which is preferable. As shown in Example 3, when a floor material having a remarkably high flexural modulus is used, high walkability can be obtained even if the thickness of the floor material is relatively thin.

When the energy consumption (EI(x)) of the bending of the cell wall accompanying the buckling of the closed cells of the underfloor material is greater than the energy consumption (EΔP(x)) due to the pressure increase of the closed cells, the walkability of the underfloor material is improved. Improved. It is considered that this is because the floor material is less likely to sink when walking. In particular, when the energy consumption (EI(x)) for the bending of the cell wall accompanied by the buckling of the closed cells is 1.8 or more greater than the energy consumption (EΔP(x)) due to the pressure increase of the closed cells, the walkability is remarkable. improved to

In addition, when the ratio of the density before foaming to the density after foaming of the underfloor material is 0.067 or more and 0.143 or less, the walkability is further improved, and this ratio is 0.100 or more and 0.143 or less. , improved shock absorption.
This is because the closed cells absorb the pressure during walking, but if the ratio of the density before foaming to the density after foaming is not too large (the number of closed cells is not too large), the strength of the underfloor material itself will not decrease. This is because it becomes easier to support the pressure during walking.
Furthermore, when the underfloor material had a thickness of 3 mm or more and 10 mm or less, the walkability was improved. It is believed that this is because the deformation of the underfloor material does not easily progress to the densified region, and the tactile sensation during walking is less likely to deteriorate.

A floor material having a smaller area (for example, 400 cm ² or less) is preferable because it tends to improve walkability and shock absorption. For example, even if the ratio of the density before foaming to the density after foaming is within a preferable range, if the area of the flooring material is large, the effect of dispersing the impact tends to weaken, so the area of the flooring material should be set appropriately. is particularly preferred.

Although the embodiments of the present disclosure have been described above, the above embodiments illustrate devices and methods for embodying the technical ideas of the present disclosure. It does not specify the material, shape, structure, arrangement, etc. Various modifications can be made to the technical idea of the present disclosure within the technical scope defined by the claims.

1 floor material 11 underfloor material 11A closed cell 12 overfloor material 20 cushioning material

Claims (12)

a flooring material having a geometrical moment of inertia of 400 mm ⁴ or more and 25000 mm ⁴ or less;
an underfloor material provided below the floor material and having a lower geometrical moment of inertia than the floor material;
flooring with The flooring material according to claim 1, wherein the flooring material has a bending rigidity of 100 Nm2/10 mm or ^more and ²⁰⁰ Nm2/10 mm or less. The flooring material according to claim 1 or 2, wherein the flooring material has a thickness of 15 mm or more and 40 mm or less. The floor material according to any one of claims 1 to 3, wherein the floor material has a bending elastic modulus of 8000 MPa or more. 5. The flooring material according to any one of claims 1 to 4, wherein the flooring material includes a layer formed of wood or a resin material mixed with a woody material. The flooring material according to any one of claims 1 to 5, wherein the underfloor material is formed of a foam having closed cells. 7. The flooring material according to claim 6, wherein the ratio of the post-foaming density to the pre-foaming density of the underfloor material is 0.067 or more and 0.143 or less. 8. The method according to claim 6 or 7, wherein when a load is applied, the energy consumption of bending of the cell walls associated with the buckling of the closed cells of the underfloor material is greater than the energy consumption due to an increase in gas pressure of the cell walls of the closed cells. Flooring as described. The flooring material according to any one of claims 6 to 8, wherein the plateau stress of the underfloor material at a strain rate of 200/s to 600/s is 0.2 MPa to 1.6 MPa. The floor material according to any one of claims 1 to 9, wherein the underfloor material has a thickness of 3 mm or more and 10 mm or less. The flooring material according to any one of claims 1 to 10, having an area of 100 cm ² or more and 900 cm ² or less. The flooring material according to any one of claims 1 to 11, wherein the impact load is 2000N or more and 6000N or less.

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