Abstract: A seat pad is made of a flexible polyurethane foam, wherein when the seat pad is divided into five equal parts in a direction of a thickness and the five equal parts are termed from a first layer, to a fifth layer, starting from a front surface side, the equal parts are ranked in the following order of decreasing hardness: the fifth layer, the fourth layer, the third layer, and the second layer. The hardness of the fourth layer is set larger than the hardness of the first layer. A midportion of the seat pad that is a portion other than the front surface and an underside surface is set at a density of 45 to 55 kg/m3.

Abstract: A seat pad is made of a flexible polyurethane foam, wherein when the seat pad is divided into five equal parts in a direction of a thickness and the five equal parts are termed from a first layer, to a fifth layer, starting from a front surface side, the equal parts are ranked in the following order of decreasing hardness: the fifth layer, the fourth layer, the third layer, and the second layer. The hardness of the fourth layer is set larger than the hardness of the first layer. A midportion of the seat pad that is a portion other than the front surface and an underside surface is set at a density of 45 to 55 kg/m3.

Abstract: A polyurethane forming composition is for producing a flexible polyurethane foam by reaction with an isocyanate component and contains a polyol component, a foaming agent, a cross-linking agent, and a foam stabilizer. In the polyurethane forming composition, the cross-linking agent is contained in a proportion of 0.3 to 1.5 parts by mass relative to 100 parts by mass of the polyol component and the foam stabilizer having a weight-average molecular weight of 4000 to 6000 is contained in a proportion of 0.05 to 0.1 parts by mass relative to 100 parts by mass of the polyol component.

Abstract: A polyrotaxane is blended into a polyol composition, which can reduce the tensile stress of a flexible polyurethane foam. A vertical compressive stress due to the weight of a sitting user and a tensile stress due to the input of lateral vibrations act on a urethane pad. However, by reducing the tensile stress of the flexible polyurethane foam, the direction (inclination) of a resultant force obtained by combining the compressive stress and the tensile stress can be brought close to the vertical direction. Thus, the angle of inclination of the user's hip (ischium) on the urethane pad to the vertical direction due to the input of lateral vibrations can be reduced, so that the sense of wobble of the urethane pad can be reduced.

Abstract: A polyrotaxane is blended into a polyol composition, which can reduce the tensile stress of a flexible polyurethane foam. A vertical compressive stress due to the weight of a sitting user and a tensile stress due to the input of lateral vibrations act on a urethane pad. However, by reducing the tensile stress of the flexible polyurethane foam, the direction (inclination) of a resultant force obtained by combining the compressive stress and the tensile stress can be brought close to the vertical direction. Thus, the angle of inclination of the user's hip (ischium) on the urethane pad to the vertical direction due to the input of lateral vibrations can be reduced, so that the sense of wobble of the urethane pad can be reduced.

Abstract: A polyrotaxane is blended into a polyol composition, which can reduce the tensile stress of a flexible polyurethane foam. A vertical compressive stress due to the weight of a sitting user and a tensile stress due to the input of lateral vibrations act on a urethane pad. However, by reducing the tensile stress of the flexible polyurethane foam, the direction (inclination) of a resultant force obtained by combining the compressive stress and the tensile stress can be brought close to the vertical direction. Thus, the angle of inclination of the user's hip (ischium) on the urethane pad to the vertical direction due to the input of lateral vibrations can be reduced, so that the sense of wobble of the urethane pad can be reduced.

Abstract: A polyrotaxane is blended into a polyol composition, which can reduce the tensile stress of a flexible polyurethane foam. A vertical compressive stress due to the weight of a sitting user and a tensile stress due to the input of lateral vibrations act on a urethane pad. However, by reducing the tensile stress of the flexible polyurethane foam, the direction (inclination) of a resultant force obtained by combining the compressive stress and the tensile stress can be brought close to the vertical direction. Thus, the angle of inclination of the user's hip (ischium) on the urethane pad to the vertical direction due to the input of lateral vibrations can be reduced, so that the sense of wobble of the urethane pad can be reduced.