Process for making flexible polyurethane foam having hardness gradient

Abstract

To provide a molded flexible polyurethane foam having a hardness gradient with the hardness increasing from the top to the bottom.SOLUTION: The hardness gradient in the foam is a result of a foam elasticity gradient arising from a polymer elasticity gradient and / or a density gradient. A method for producing a flexible foam having a hardness gradient, and a reactive mixture suitable for producing the flexible foam, are disclosed. Furthermore, the use of the flexible foam having a hardness gradient in mattresses, cushions for seating (more specifically for automotive seating), furniture, automotive under-carpets, and automotive dash insulators is disclosed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a molded flexible polyurethane foam having a hardness gradient that increases from the top to the bottom. The hardness gradient in the foam is caused by an elastic gradient of the polymer and / or a density gradient of the foam, which results in an elastic gradient of the foam.

[0002] Surprisingly, the present inventors have now found a method for producing a flexible foam having a hardness gradient and a reaction mixture suitable for producing said flexible foam.

[0003] The present invention further relates to the use of a flexible foam having a hardness gradient in a seat mattress or cushion, and more particularly to the use of said flexible foam in an automobile seat.

Background Art

[0004] Improving the comfort of the passenger compartment remains an important need in the global transportation industry. Since its introduction over 40 years ago, flexible molded polyurethane foam has successfully contributed to the comfort provided by all forms of transport seats. The comfort experience involves maintaining technical performance specifications (e.g., providing sufficient support duration that implies a much harder foam at the bottom of the foam), while having a tendency to reduce the foam density to provide a softer foam experience for the passenger. This is a combination of many different factors, including

[0005] This problem is currently solved by creating a multi-layer foam layup by adding a softer slabstock foam layer on top of a high-hardness foam sheet pad molded in the normal way. The current solution is not ideal as an additional process step and requires two different (foam) materials.

Summary of the Invention

[0006] According to a first aspect, there is disclosed a molded flexible polyurethane comprising a foam having a hardness gradient. The foam comprises at least: a top layer having a thickness (height) corresponding to about 25% of the total thickness (height) of the foam; a bottom layer having a thickness (height) corresponding to about 25% of the total thickness (height) of the foam; and the foam elasticity E f of the top layer of the foam is at least three times higher (preferably 3 to 10 times higher) than the foam elasticity E f of the bottom layer of the foam; wherein the foam elasticity is given by Equation [2]: E f = ω n 2 × mh / A [2] [where ω n is the natural frequency; m is the fixed mass; h is the thickness of the foam sample; and A is the cross-sectional area of the foam sample] corresponding thereto.

[0007] According to some embodiments, the molded flexible foam according to the present invention has a polymer elasticity E p of the top layer of the foam that is at least twice as high (preferably 2 to 8 times as high) as the polymer elasticity E p of the bottom layer of the foam, where the polymer elasticity is given by Equation [1]: E p = E f / R 2 [1] [where the relative density (R) defined as R is ρ f / ρ p ; ρ p which is the density of the polyurethane polymer is 1200 kg / m 3 ; and ρ f which is the density of the polyurethane foam is measured according to ISO845] corresponding thereto.

[0008] A molded flexible polyurethane comprising a foam having a hardness gradient, where the foam is , at least, an uppermost layer having a thickness (height) corresponding to about 25% of the total thickness (height) of the foam; a lowermost layer having a thickness (height) corresponding to about 25% of the total thickness (height) of the foam; and the foam elasticity E of the uppermost layer of the foam f at least three times higher (preferably 3 to 10 times higher) than the foam elasticity E of the lowermost layer of the foam f ; including, where the foam elastic ity is given by Equation [2]: E f = ω n 2 × mh / A [2] [where ω n is the natural frequency; m is the fixed mass; h is the thickness of the foam sample; and A is the cross-sectional area of the foam sample] corresponds to.

[0009] According to some embodiments, the molded soft foam of the present invention has a foam density of the lowermost layer of the foam that is 10 to 40% higher than that of the uppermost layer of the foam.

[0010] According to some embodiments, the molded soft foam of the present invention has a polymer elasticity E of the lowermost layer of the foam that is at least twice as high (preferably 2 to 8 times as high) as the polymer elasticity E of the uppermost layer of the foam, where the polymer elasticity corresponds to Equation [1] and the hardness gradient is such that the foam density ρ of the lowermost layer of the foam is 10 to 40% higher than that of the uppermost layer of the foam. p has, where the polymer elasticity corresponds to Equation [1] and the hardness gradient is such that the foam density ρ of the lowermost layer of the foam is 10 to 40% higher than that of the uppermost layer of the foam. p has. f has.

[0011] According to some embodiments, the molded soft foam of the present invention has an uppermost layer polymer elasticity E that is lower than the polymer elasticity E of the core (central part) of the foam. p has. p has.

[0012] According to some embodiments, the molded soft foam of the present invention has a foam density ρ of the lower half of the foam that is higher than the foam density ρ of the upper half of the foam. f has. f has.

[0013] According to some embodiments, the molded soft foam of the present invention has a polymer elasticity E of the foam central portion p lower than the top layer polymer elasticity E p , and a foam density ρ of the upper half of the foam f higher than the foam density ρ of the lower half of the foam f .

[0014] According to a second aspect, a reactive foam formulation for producing the foam of the present invention is disclosed . The formulation is prepared by mixing at least an isocyanate-reactive composition (a) and a polyisocyanate composition (b) at an isocyanate index in the range of 70 to 130 (preferably 75 to 110, more preferably 75 to 100), where the isocyanate-reactive composition (a) is ■ Polyether polyol (a1) having a propylene oxide (PO) content of 51 to 100% by weight and an ethylene oxide (E O) content of 0 to 49% by weight (preferably at most 20% by weight), an average nominal hydroxyl functionality of 2 to 4, and an average molecular weight of 2000 to 7000, based on the total weight of the polyether polyol (a1); ■ Optionally, a polyether polyol (a2) having an ethylene oxide content of 50 to 95% by weight, based on the weight of the polyether polyol (a2), where the weight ratio of the polyol (a2) in the isocyanate-reactive composition (a) is in the range of 0 to 20% by weight (preferably in the range of 0 to 10% by weight, more preferably in the range of 0 to 5% by weight) based on the total weight of the isocyanate-reactive composition (a); ■ Optionally, a filled polyether polyol (a3), also referred to as a polymer polyol, where the weight ratio of the polyol (a3) in the isocyanate-reactive composition (a) is in the range of 0 to 30% by weight (preferably 0 to 20% by weight) based on the total weight of the isocyanate-reactive composition (a); ■ Optionally, a catalyst, a surfactant, a foam stabilizer, a flame retardant, a colorant, and other additives as needed; ; comprising, and the polyisocyanate composition (b) has an NCO value in the range of 21 to 27% (preferably 23 to 2 5.5%).

[0015] According to some embodiments, the polyisocyanate composition (b) in the reactive foam formulation for producing the foam of the present invention is first pre-reacted with a polyol (i.e., prep olymerized), and at this time, the amount reacted with the polyol in the polyisocyanate composition (b) is in the range of 0 to 40% by weight (preferably in the range of 0 to 30% by weight, more preferably in the range of 0 to 20% by weight) based on the total weight of the polyisocyanate composition (b).

[0016] According to some embodiments, the polyisocyanate composition (b) is 0 to 12% by weight (preferably 0 to 10% by weight) of methylene diphenyl 2,4'-diisocyanate (2,4-MDI) and 2 1 to 27% (preferably 23 to 25.5%) of the NCO value based on the total weight of all polyisocyanate compounds in the polyisocyanate composition.

[0017] According to some embodiments, the polyisocyanate composition (b) is 0 to 12% by weight (preferably 0 to 10% by weight) of methylene diphenyl 2,4'-diisocyanate (2,4-MDI) and at least 40% by weight (preferably at least 50% by weight) of 4,4'-diphenylmethane diisocyanate (4,4-MDI) and 21 to 27% (preferably 23 to 25.5% range) of the NCO value based on the total weight of all polyisocyanate compounds in the polyisocyanate composition.

[0018] According to some embodiments, the polyisocyanate composition (b) has an NCO value in the range of 21 to 27% (preferably 23 to 25.5%).

[0019] According to some embodiments, the polyisocyanate composition (b) has an NCO value in the range of 20 to 25.5% ( preferably 23 to 25.5%).

[0020] According to some embodiments, the reactive foam formulation for producing the foam of the present invention further comprises additives such as a blowing agent, a catalyst, and a chain extender, as well as other additives (for example, a flame retardant and a surfactant, etc.).

[0021] According to some embodiments, the reactive foam formulation for producing the foam of the present invention further comprises a blowing agent, wherein the blowing agent contains at least water, and the amount of water used is 0.5 to 10% by weight (preferably 1 to 5% by weight) based on the total weight of all components present in the isocyanate-reactive composition (a) used to prepare the reactive foam formulation of the present invention. % by weight).

[0022] According to a third aspect, a method for producing a flexible foam of the present invention is disclosed, and the production method includes at least the following steps: (1) Mixing the polyisocyanate composition (b) and the isocyanate-reactive composition (a) at an isocyanate index in the range of 70 to 130 (preferably in the range of 75 to 110, more preferably in the range of 75 to 100) to obtain a reactive foam formulation as described in any one of claims 9 to 12; step; (2) Pouring the reactive foam formulation obtained in step (1) into a mold to obtain a flexible foam having a hardness gradient; (3) Demolding the obtained flexible foam having a hardness gradient; including, step (3) being carried out such that there is a temperature difference (ΔT) of at least 25 to 30 °C between the temperature (T chemicals ) of the reactive foam formulation and the temperature (T mold ) of the mold, characterized in that

[0023] According to some embodiments, the temperature difference (ΔT) between the temperature (T chemicals ) of the initial reactive foam formulation used and the temperature (T mold ) of the mold is in the range of at least 25 to 30 °C and more preferably in the range of at least 30 to 50 °C, and most preferably in the range of at least 35 to 55 °C.

[0024] According to some embodiments, the minimum temperature (T chemicals ) of the initial reactive foam formulation used is 10 to 15 °C, preferably, T chemicals is about room temperature, and the temperature of the mold (T mold ) is above 50 °C and less than 100 °C, preferably, T mold is in the range of 55 to 70 °C, and more preferably in the range of 60 to 70 °C.

[0025] According to a fourth aspect, the use of the molded flexible foam of the present invention as an automotive seat, mattress, furniture, automotive under-carpet, and automotive dash insulator is disclosed.

[0026] The independent claims and the dependent claims describe specific and preferred features of the present invention. The features from the dependent claims can be combined, if necessary, with the features of the independent claims or the features of other dependent claims.

[0027] The above characteristics, features, and advantages of the present invention, as well as other characteristics, features, and advantages, will become apparent upon consideration of the following detailed description in conjunction with the accompanying drawings that illustrate the principles of the present invention by way of example. The following description is by way of example only and does not limit the present invention thereby.

[0028] Meaning of Terms In the context of the present invention, the following terms have the meanings described below. (1) Isocyanate index or NCO index or index It is the ratio of the NCO groups to the isocyanate-reactive hydrogen atoms present in the formulation, and is expressed as a percentage value by [NCO]×100 / [reactive hydrogen atoms](%).

[0029] That is, the NCO index represents the percentage value of the isocyanate actually used in the formulation relative to the amount of isocyanate theoretically required to react with the amount of isocyanate-reactive hydrogen used in the formulation.

[0030] It should be noted that the isocyanate index used here is considered from the perspective of the actual polymerization process for producing a foaming material containing an isocyanate component and an isocyanate-reactive component. The isocyanate groups consumed in the preliminary process for producing a modified polyisocyanate (including isocyanate derivatives such as those called prepolymers in the industry) or the active hydrogen consumed in the preliminary process (for example, reacting with isocyanate to produce a modified polyol or modified polyamine) is not considered in the calculation of the isocyanate index. is not considered in the calculation of the isocyanate index. is not considered in the calculation of the isocyanate index.

[0031] (2) The term "isocyanate-reactive hydrogen atom" used herein to calculate the isocyanate index represents the sum of the active hydrogen atoms in the hydroxyl groups and amine groups present in the reactive composition; this means that for calculating the isocyanate index in the actual polymerization process, one hydroxyl group is regarded as containing one reactive hydrogen, and one primary amine group is regarded as containing one reactive hydrogen.

[0032] (3) As used herein, the terms "reaction system", "reactive foam formulation", and "reactive mixture" refer to a combination of reactive components used to produce polyurethane containing foam, where the polyisocyanate is typically held in one or more containers separate from the isocyanate-reactive components.

[0033] (4) The term "average nominal hydroxyl functionality" (i.e., "functionality") is used in this specification to indicate the number average functionality of a polyol or polyol composition (the number of hydroxyl groups per molecule), assuming that this is the number average functionality of the initiator used in the production (the number of active hydrogens per molecule). However, in reality, it is often somewhat lower due to some terminal unsaturation. In this specification, it is used to indicate the number average functionality of a polyol or polyol composition (the number of hydroxyl groups per molecule), assuming that this is the number average functionality of the initiator used in the production (the number of active hydrogens per molecule). However, in reality, it is often somewhat lower due to some terminal unsaturation. However, in reality, it is often somewhat lower due to some terminal unsaturation. However, in reality, it is often somewhat lower due to some terminal unsaturation.

[0034] (5) "Average" represents the number average unless otherwise specified.

[0035] (6) As used herein, "gradient" refers to the change in the value of a variable (e.g., temperature, hardness, elasticity, concentration, etc.) due to the change of a certain variable (especially, per unit distance in a specific direction). The gradient is expressed as a number in this specification, and this number is the difference between the maximum value and the minimum value observed for the said variable. For example, the foam of the present invention has a foam elasticity E gradient such that the foam elasticity E of the lowermost layer of the foam is 3 to 4 times higher than the foam elasticity E of the uppermost layer of the foam. For example, changes in temperature, hardness, elasticity, and concentration, etc.) (especially, per unit distance in a specific direction). The gradient is expressed as a number in this specification, and this number is the difference between the maximum value and the minimum value observed for the said variable. For example, the foam of the present invention has a foam elasticity E gradient such that the foam elasticity E of the lowermost layer of the foam is 3 to 4 times higher than the foam elasticity E of the uppermost layer of the foam. For example, the foam of the present invention has a foam elasticity E gradient such that the foam elasticity E of the lowermost layer of the foam is 3 to 4 times higher than the foam elasticity E of the uppermost layer of the foam. f For example, the foam of the present invention has a foam elasticity E gradient such that the foam elasticity E of the lowermost layer of the foam is 3 to 4 times higher than the foam elasticity E of the uppermost layer of the foam. f For example, the foam of the present invention has a foam elasticity E gradient such that the foam elasticity E of the lowermost layer of the foam is 3 to 4 times higher than the foam elasticity E of the uppermost layer of the foam. f For example, the foam of the present invention has a foam elasticity E gradient such that the foam elasticity E of the lowermost layer of the foam is 3 to 4 times higher than the foam elasticity E of the uppermost layer of the foam.

[0036] (7) When referring to the "uppermost layer" and "lowermost layer" in the form of the present invention, it describes a molded form that has a softer uppermost layer with a lower foam density at the uppermost layer of the form, while having a harder lowermost layer with a higher foam density at the lowermost layer of the form. In explaining the hardness gradient in the form of the present invention, the uppermost layer of the molded form is in contact with the lowermost part of the mold and corresponds to the layer formed at the start of the foaming process when considering the foaming process. The uppermost layer of the form may have a thickness (height) corresponding to a maximum of 25% of the total thickness (total height) of the form. The lowermost layer of the molded form is in contact with the uppermost part of the mold and corresponds to the layer formed at the end of the foaming process when considering the foaming process. The lowermost layer of the form may also have a thickness (height) corresponding to a maximum of 25% of the total thickness (total height) of the form.

[0037] (8) "Room temperature" represents a temperature of about 20°C and means representing a temperature in the range of 18°C to 25°C. Such temperatures include 18°C, 19°C, 20°C, 21°C, 22°C, 23°C, 24°C, and 25°C.

[0038] (9) Unless otherwise specified, the weight percentage (%) of a component in a composition (recorded as %wt or wt%) represents the weight of the component relative to the total weight of the composition in which the component is present and is expressed as a percentage value. carried) represents the weight of the component relative to the total weight of the composition in which the component is present and is expressed as a percentage value. value.

[0039] (10) Unless otherwise specified, the parts by weight (pbw) of a component in a composition represents the weight of the component relative to the total weight of the composition in which the component is present and is expressed as pbw.

[0040] (11) The foam density (ρ f ) represents the density measured for a foam sample by cutting out a parallelepiped of the foam, weighing it, and measuring its dimensions. The foam density is the weight-to-volume ratio measured in accordance with ISO845 and is expressed in kg / m 3 .

[0041] (12) The polymer density referred to in the present invention represents the density (ρ p ) of the polyurethane polymer, and is assumed to be 1200 kg / m 3 〔Randall, D. and Lee S., eds., (2002) The Polyurethanes Handbook, London: Wiley〕.

[0042] (13) The polymer elasticity (E p ) referred to in the present invention can be estimated from the Gibson and Ashby equation [Gibso, L. J. & Ashby, MF. (1988) Cellular Solids, Pergamon, Oxford〕 that describes the relationship between the foam elasticity, polymer elasticity, and relative density. . E p can be expressed as follows in Equation [1]: E p = E f / R 2 [1] [where the relative density (R) defined as R is ρ f / ρ p ; ρ p which is the density of the polyurethane polymer is 1200 kg / m 3 ; ρ f which is the density of the polyurethane foam is measured according to ISO845] (14) The foam elasticity (E f ) referred to in the present invention can be obtained from the natural frequency of a one-degree-of-freedom mass-spring damper system (referred to as a vibration transmissibility test, consisting of a fixed mass and a foam sample) (see Figure 1a). The natural frequency ω of the system is the frequency at which the transmissibility is maximum (see Figure 1b). E f is given by the following Equation [2]: E f = ω n2 ×mh / A [2] [where ω n is the natural frequency; m is the fixed mass; h is the thickness of the foam sample; A is the cross-sectional area of the foam sample] can be expressed as follows.

[0043] Detailed Description The present invention relates to a flexible polyurethane foam having a hardness gradient that changes from softer to harder from the top to the bottom of the foam. The hardness gradient in the foam occurs as a result of the foam elasticity gradient caused by the polymer elasticity gradient and / or density gradient. As a result of the hardness gradient, the foam has a softer top layer and a harder bottom layer, and thus the foam is suitable for producing a more comfortable foam sheet (for example, an automobile seat). Therefore, the foam thus obtained has a softer feel on the surface while ensuring sufficient support at the bottom of the foam.

[0044] Accordingly, the present invention discloses a molded flexible polyurethane comprising a foam having a hardness gradient, said foam being in contact with at least the bottom of the mold and corresponding to the layer formed at the start of the foaming process (start time) when considering the foaming process, the top layer having a thickness (height) corresponding to a maximum of 25% of the total thickness (height) of the foam; in contact with the top of the mold and corresponding to the layer formed at the end of the foaming process when considering the foaming process, the bottom layer having a thickness (height) corresponding to a maximum of 25% of the total thickness (height) of the foam; and the foam elasticity E f of the top layer of said foam is at least 3 times higher (preferably 3 to 10 times higher) than the foam elasticity E f of the bottom layer of said foam, said foam elasticity being given by the formula [2]: E f =ω n 2 ×mh / A [2] [where ω nis the natural frequency; m is the fixed mass; h is the thickness of the foam sample; A is the cross-sectional area of the foam sample corresponding to; having.

[0045] According to some embodiments, the molded flexible polyurethane comprising the foam of the present invention has a polymer elasticity E of the uppermost layer of the foam p at least twice as high as (preferably 2 to 8 times higher) than the polymer elasticity E of the lowermost layer of the foam p wherein the polymer elasticity is given by the formula 1]: E p =E f / R 2 [1] [wherein the relative density (R) defined as R is ρ f / ρ p and ρ is the density of the polyurethane polymer p is 1200 kg / m 3 and ρ is the density of the polyurethane foam f is measured according to ISO845 corresponding to.

[0046] According to some embodiments, the molded flexible polyurethane comprising the foam of the present invention has a foam density ρ of the uppermost layer of the foam f 10 to 40% higher than the foam density ρ of the lowermost layer of the foam f having.

[0047] According to some embodiments, the molded flexible polyurethane comprising the foam of the present invention has a polymer elasticity E of the uppermost layer of the foam p at least twice as high as (preferably 2 to 8 times higher) than the polymer elasticity E of the lowermost layer of the foam p wherein the polymer elasticity corresponds to the formula 1], and the hardness gradient is such that the foam density ρ of the uppermost layer of the foam f is 10 to 40% higher than the foam density ρ of the lowermost layer of the foam f having.

[0048] According to some embodiments, the molded flexible polyurethane comprising the foam of the present invention has a polymer elasticity E of the core (central portion) of the foam p and a lower top layer polymer elasticity Ep.

[0049] According to some embodiments, the molded flexible polyurethane comprising the foam of the present invention has a foam density ρ of the upper half of the foam f and a higher foam density ρ of the lower half of the foam f .

[0050] According to some embodiments, the molded flexible polyurethane comprising the foam of the present invention has a polymer elasticity E of the core (central portion) of the foam p and a lower top layer polymer elasticity E p , and a foam density ρ of the upper half of the foam f and a higher foam density ρ of the lower half of the foam f .

[0051] Surprisingly, it has been found that by combining a specific reactive foam formulation with specific process conditions, a soft foam of the present invention having a hardness gradient is obtained, and said hardness gradient occurs as a result of a foam elasticity gradient resulting from a polymer elasticity gradient and / or a density gradient.

[0052] The process conditions of the present invention used to produce a soft foam having a hardness gradient according to the present invention in a mold include using a specific temperature difference (ΔT) between the temperature (T chemicals ) of the reactive foam formulation used and the temperature (T ) of the mold mold ). To achieve said specific temperature difference ΔT, the mold may be heated, or the reactive foam formulation may be cooled, or the mold may be heated and the reactive foam formulation may be cooled at the same time.

[0053] According to some embodiments, the initial temperature (T of the reactive foam formulation usedchemicals ) and the temperature (T mold ) of the mold, the temperature difference ΔT therebetween is at least 25 to 30 °C, more preferably at least 30 to 50 °C, and most preferably at least 35 to 55 °C. The present invention deals with a much larger temperature difference ΔT between the initial temperature (T chemicals ) of the reactive foam formulation used and the temperature (T mold ) of the mold, compared with state-of-the-art processing conditions. State-of-the-art processing usually applies a temperature difference ΔT of 10 to 20 °C between the initial temperature (T ) of the reactive foam formulation used and the temperature (T chemicals ) of the mold, mold and preferably uses a ΔT of about 15 °C.

[0054] According to some embodiments, the minimum temperature (T chemicals ) of the initial temperature of the reactive foam formulation used is 10 to 15 °C, and T chemicals is preferably about room temperature. chemicals

[0055] According to some embodiments, the temperature (T mold ) of the mold is 50 °C or higher and less than 100 °C, preferably in the range of 55 to 70 °C, and most preferably in the range of 60 to 70 °C. The most preferred T mold is about 65 °C.

[0056] According to some embodiments, a specific temperature (T mold ) of the mold is achieved by heating at least the lowest part of the mold, and it is preferred to heat the entire mold.

[0057] The reactive foam formulation of the present invention used to produce the soft foam having a hardness gradient according to the present invention includes the use of a specific foam formulation comprising at least an isocyanate-reactive composition (a) and a polyisocyanate composition (b).

[0058] The polyisocyanate composition (b) of the present invention contains diphenylmethane diisocyanate (M DI) and its analogues (polymeric MDI) having an isocyanate functionality of 3 or more. At this time, the amount of methylene diphenyl 2,4'-diisocyanate is in the range of 0 to 12% by weight (preferably in the range of 0 to 10% by weight) based on the total weight of all polyisocyanate compounds in the polyisocyanate composition, and the remaining polyisocyanate compounds are polymeric MDI and methylene diphenyl 4,4'-diisocyanate (4,4-MDI). An example of a commercially available polyisocyanate composition is Suprasec (registered trademark) 4801 manufactured by Huntsman Corporation.

[0059] According to some embodiments, first, the polyisocyanate composition (b) of the present invention is pre-reacted (i.e., prepolymerized) with a polyol. At this time, the amount of this reactive polyol in the polyisocyanate composition (b) is in the range of 0 to 40% by weight (preferably in the range of 0 to 30% by weight, more preferably in the range of 0 to 20% by weight) based on the total weight of the polyisocyanate composition (b). The isocyanate-reactive composition (a) can be used as the polyol for producing the prepolymerized polyisocyanate composition (b). Separately, the polyol used for producing the prepolymerized polyisocyanate composition (b) is a selected polyol from similar polyols and / or polymers used in the isocyanate-reactive composition (a).

[0060] According to some embodiments, the polyisocyanate composition (b) contains diphenylmethane diisocyanate (MDI) and a free isocyanate-containing prepolymer made from said MDI ​​A composition comprising, and preferably the polyisocyanate composition (b) is a composition comprising at least 40% by weight (preferably at least 50% by weight) of 4,4'-diphenylmethane diisocyanate (4,4-MDI). The polyisocyanate composition (b) preferably has an NCO value in the range of 21 to 27% (preferably in the range of 23 to 25.5%).

[0061] According to some embodiments, the polyisocyanate composition (b) is a prepolymer composition obtained by pre-reacting (i.e., prepolymerizing) the polyisocyanate composition (b) of the present invention with a polyol. The prepolymer composition preferably contains 0 to 12% by weight (preferably 0 to 10% by weight) of methylene diphenyl 2,4'-diisocyanate (2,4-MDI) and at least 40% by weight (preferably at least 50% by weight) of 4,4'-diphenylmethane diisocyanate (4,4-MDI), based on the total weight of all polyisocyanate compounds in the polyisocyanate composition, and an NCO value in the range of 21 to 27% (preferably in the range of 23 to 25.5%).

[0062] According to some embodiments, the polyisocyanate composition (b) is a prepolymer composition obtained by pre-reacting (i.e., prepolymerizing) the polyisocyanate composition (b) of the present invention with a polyol. The prepolymer composition preferably contains 0 to 12% by weight (preferably 0 to 10% by weight) of methylene diphenyl 2,4'-diisocyanate (2,4-MDI), based on the total weight of all polyisocyanate compounds in the polyisocyanate composition, and an NCO value in the range of 21 to 27% (preferably in the range of 23 to 25.5%).

[0063] According to some embodiments, the polyisocyanate composition (b) is a polyisocyanate composition containing 0 to 12% by weight (preferably 0 to 10% by weight) of methylene diphenyl 2,4'-diisocyanate (2,4-MDI), based on the total weight of all polyisocyanate compounds in the polyisocyanate It is a composition containing an NCO value in the range of 21 to 27% (preferably in the range of 23 to 25.5%).

[0064] According to some embodiments, the polyisocyanate composition (b) has an NCO value in the range of 21 to 27% (preferably in the range of 23 to 25.5%).

[0065] According to some embodiments, the polyisocyanate composition (b) has an NCO value in the range of 20 to 25.5% (preferably in the range of 23 to 25.5%).

[0066] According to some embodiments, the isocyanate-reactive composition (a) according to the present invention comprises the following: (a) 51 to 100% by weight of oxypropylene ( PO) content and 0 to 49% by weight (preferably at most 20% by weight) of oxyethylene (EO) content , a polyether polyol (a1) having an average nominal hydroxyl functionality of 2 to 4 and an average molecular weight of 2000 to 7000; (b) Optionally, a polyether polyol (a2) having an oxyethylene content of 50 to 95% by weight based on the weight of the polyol (a2), wherein the weight ratio of the polyol (a2) in the isocyanate-reactive composition (a) is in the range of 0 to 20% by weight (preferably in the range of 0 to 10% by weight, more preferably in the range of 0 to 5% by weight) based on the total weight of the isocyanate-reactive composition (a); (c) Optionally, a filled polyether polyol (a3) also called a polymer polyol, wherein the weight ratio of the polyol (a3) in the isocyanate-reactive composition (a) is in the range of 0 to 30% by weight (preferably 0 to 20% by weight) based on the total weight of the isocyanate-reactive composition (a).

[0067] According to some embodiments, the isocyanate-reactive composition (a) according to the present invention contains more than 70% of primary hydroxyl groups.

[0068] The polyether polyols (a1), (a2) and (a3) used in producing the soft foam of the present invention are obtained by polymerizing propylene oxide and optional ethylene oxide, optionally in the presence of a polyfunctional initiator. The polyether polyols are also called polyoxyethylene polyoxypropylene polyols. Suitable initiator compounds used to produce the polyols contain a plurality of active hydrogen atoms. Suitable initiator compounds include water, butanediol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, ethanolamine, diethanolamine, triethanolamine, cyclohexanedimethanol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, and sorbitol. Mixtures of initiators and / or cyclic oxides can also be used. As described in detail in the prior art, polyoxyethylene polyoxypropylene polyols are obtained by the simultaneous addition or sequential addition of ethylene oxide and propylene oxide to the initiator.

[0069] The most preferred examples of the polyether polyol (a1) are polyoxypropylene polyols and polyoxyethylene polyoxypropylene polyols having an average nominal hydroxyl functionality of 2 to 4, an average molecular weight of 2000 to 7000, and an oxyethylene content of at most 20% by weight based on the weight of the polyol. Examples of commercially available polyols are Daltocel® F428 and Daltocel F435 commercially available from Huntsman, Alcupol® F4811 commercially available from Repsol, Voranol® CP3322, NC700 and HL400, Caradol® SC48-08 commercially available from Shell, and Arcol® 1374 commercially available from Bayer.

[0070] The most preferred examples of the polyether polyol (a2) are Daltocel F442, Daltocel F444, and Daltocel F555 commercially available from Huntsman Corporation.

[0071] According to some embodiments, the reactive foam formulation of the present invention further comprises additives such as a blowing agent, a catalyst, a chain extender, and other additives (e.g., flame retardants, fillers, surfactants, etc.). It is preferred that the additives are added to the isocyanate-reactive composition (a) before mixing the isocyanate-reactive composition (a) and the polyisocyanate composition (b).

[0072] According to some embodiments, the reactive foam formulation of the present invention contains a blowing agent, and it is preferred that the blowing agent contains water. In a preferred embodiment, the blowing agent is selected from water in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total weight of all components present in the isocyanate-reactive composition (a) used to prepare the reactive foam formulation of the present invention.

[0073] According to some embodiments, the reactive foam formulation of the present invention comprises a chain extender, and a preferred chain extender is an isocyanate-reactive chain extender having 2 to 8 reactive hydrogen atoms and a molecular weight of up to 999. Examples include butanediol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, ethanolamine, diethanolamine, triethanolamine, cyclohexanedimethanol, glycerol, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, sorbitol, and polyoxyethylene diol having an average molecular weight of 200 to 600, and mixtures of these compounds.

[0074] ​According to some embodiments, the reactive foam formulation of the present invention comprises a surfactant, and the surfactant is used in an amount of 0.1 to 5% by weight, preferably 0.2 to 2% by weight, based on the total weight of all components present in the isocyanate-reactive composition (a) used to prepare the reactive foam formulation of the present invention. The surfactant is preferably a polysiloxane polymer, more preferably a polyoxyalkylene polysiloxane polymer, and preferably has a molecular weight of 5000 to 60000.

[0075] According to some embodiments, the reactive foam formulation of the present invention comprises a catalyst. In a preferred embodiment, the catalyst is selected from known catalysts used in the field of polyurethane foams. Examples of known catalysts include amine-based catalysts and tin catalysts. The catalysts used to produce polyurethane flexible foams are generally classified into a gelling catalyst that promotes the resinification of polyurethane and a foaming catalyst that promotes the foaming of the polyisocyanate component. Preferred gelling catalysts are tertiary amine catalysts that particularly promote the reaction between polyisocyanate and polyol, and examples of these include triethylenediamine, 1,8-diazabicyclo[5.4.0]undecene-7, and imidazoles such as 1-methylimidazole (not limited thereto), and the reactive amine catalyst can promote the reaction between polyisocyanate and polyol and thereby form urethane bonds (this means that the above-mentioned catalyst can be chemically incorporated into the polyurethane matrix), and can be selected from the latest known tertiary amine catalysts. The tertiary amine catalyst preferably has at least one isocyanate-reactive hydrogen atom, and preferably has one or more primary amine groups and / or secondary amine groups, and / or one or more hydroxy groups. Examples of suitable reactive tertiary amine catalysts are as follows: N,N-3-dimethylaminopropylamine [Jeffcat (registered trademark) DMAPA commercially available from Huntsman] N,N-3-dimethylaminopropylamine [Jeffcat (registered trademark) DMAPA commercially available from Huntsman] ​​ N,N-dimethylethanolamine (Jeffcat DMEA commercially available from Huntsman), N,N-dimethylaminoethoxyethanol (Jeffcat ZR70 commercially available from Huntsman), N,N,N’-trimethyl-N’-hydroxyethyl-bisaminoethyl ether (from Huntsman or commercially available Jeffcat ZF10), N,N-bis-(3-dimethylaminopropyl)-N-isopropanolamine (Jeffcat ZR50 commercially available from Huntsman) N-(3-dimethylaminopropyl)-N,N-diisopropanolamine (Jeffcat DPA commercially available from Huntsman), N,N,N’-trimethyl-N’-(hydroxyethyl)ethylenediamine (Jeffcat Z110 commercially available from Huntsman), tetramethyliminobispropylamine (Jeffcat Z130 commercially available from Huntsman), N-[2-[2-(dimethylamino)ethoxy]ethyl]-N-methyl-1,3-propanediamine [Dabco (registered trademark) NE300 commercially available from Evonik], 2-(dimethylamino)-ethan-1-ol (Jeffcat TD20 commercially available from Huntsman), tetramethyliminobispropylamine (Jeffcat Z130 commercially available from Huntsman), 2-(2-(2-dimethylaminoethoxy)-ethylmethylamino)-ethanol (from Evonik or commercially available Dabco NE1061), bis(dimethylaminomethyl)-phenol (Dabco TMR30 commercially available from Evonik).

[0076] Furthermore, a foaming process for producing a soft foam having a hardness gradient according to the present invention is disclosed, and the foaming process comprises reacting a reactive foam formulation in a mold at a temperature in the range of 70 to 130 ​Reacting at an isocyanate index in the range of preferably 75 to 110, more preferably 75 to 100, and using the processing conditions of the present invention in the mold at this time.

[0077] According to some embodiments of the present invention, a method for manufacturing a soft foam having a hardness gradient according to the present invention includes at least the following steps: (1) A step of premixing the isocyanate-reactive composition (a) of the present invention with a chain extender, a catalyst, a foaming agent, and other additives; (2) Mixing the polyisocyanate composition (b) of the present invention with the premixed isocyanate-reactive composition (a) obtained in step 1 at an isocyanate index in the range of 70 to 130 (preferably in the range of 75 to 110, more preferably in the range of 75 to 100) to obtain a reactive foam formulation; (3) A step of casting the reactive foam formulation obtained in step 2 using the processing conditions of the present invention to obtain a soft foam having a hardness gradient; (4) A step of demolding the soft foam having a hardness gradient thus obtained.

[0078] According to some embodiments of the present invention, a method for manufacturing a soft foam having a hardness gradient according to the present invention includes at least the following steps: (1) Mixing the polyisocyanate composition (b) with the premixed isocyanate-reactive composition (a) obtained in step 1 at an isocyanate index in the range of 70 to 130 (preferably in the range of 75 to 110, more preferably in the range of 75 to 100) to obtain a reactive foam formulation; (2) Casting the reactive foam formulation obtained in step 2 to have a hardness gradient; (3) A step of demolding the soft foam having a hardness gradient thus obtained; comprising, wherein the isocyanate-reactive composition (a) comprises at least 50% by weight (preferably at least 70% by weight), based on the total weight of the isocyanate-reactive composition (a), of 51 to 100% by weight % oxypropylene (PO) content, 0 to 49% by weight ethylene oxide content, an average nominal hydroxyl functionality of 2 to 4, and a polyether polyol (a1) having an average molecular weight of 2000 to 7000; the polyisocyanate composition (b) comprises 0 to 12% by weight (preferably 0 to 10% by weight), based on the total weight of all polyisocyanate compounds in the polyisocyanate composition, of methylene diphenyl 2,4'-diisocyanate (2,4-MDI) and the balance of polymeric MDI and its variants as the polyisocyanate compound; step 3 is demolding such that there is a temperature difference (ΔT) of at least 25 to 30 °C between the temperature (T ) of the reactive foam formulation and the temperature (T chemicals ) of the mold; characterized in that. mold According to some embodiments, the isocyanate-reactive composition (a) is first premixed with a chain extender, a catalyst, a blowing agent, and other additives.

[0079] According to some embodiments, step 3 is such that there is a temperature difference ΔT of at least 25 to 30 °C

[0080] between the temperature (T chemicals ) of the initial reactive foam formulation and the temperature (T mold ) of the mold, more preferably such that there is a temperature difference ΔT of at least 30 to 50 °C, most preferably such that there is a temperature difference ΔT in the range of at least 35 to 55 °C.

[0081] ​​According to some embodiments, the isocyanate-reactive composition (a) in step 1 further comprises a polyether polyol (a2) having an oxyethylene content of 50 to 95% by weight based on the weight of the polyether polyol (a2), wherein the weight ratio of the polyether polyol (a2) in the isocyanate-reactive composition (a) is in the range of 0 to 20% by weight, preferably in the range of 0 to 10% by weight, and more preferably in the range of 0 to 5% by weight based on the total weight of the isocyanate-reactive composition (a).

[0082] According to some embodiments, the isocyanate-reactive composition (a) in step 1 further comprises a filled polyether polyol (a3), also referred to as a polymer polyol, wherein the weight ratio of the polyol (a3) in the isocyanate-reactive composition (a) is in the range of 0 to 30% by weight based on the total weight of the isocyanate-reactive composition (a) and preferably in the range of 0 to 20% by weight.

[0083] According to some embodiments of the present invention, the mixing of the isocyanate-reactive composition (a) premixed with the polyisocyanate composition (b) is carried out using a two-component high-pressure mixing system or a two-component dynamic mixing system.

[0084] According to some embodiments of the present invention, step 3 (the step of casting the reactive foam formulation obtained in step 2) is carried out such that the overpack degree in the mold is kept low and the overpack preferably has a calculated overpack ratio of the molding density to the free-rise density in the range of 1 to 1.5. This means that the molding (foaming) process occurs until the mold is filled exactly.

[0085] According to some embodiments of the present invention, step 3 (the reactive foam obtained in step 2 The step of casting the complex) is performed by inserting the reactive foam compound at an angle of about 30 degrees (with respect to the bottom plate of the mold), so that the foam flows down due to the inclination. This means that the mold surface is horizontal and the inlet of the reactive foam compound has an inclination of 30 degrees, thereby promoting the vertical rise of the foam.

[0086] The present invention further discloses the use of the molded soft foam of the present invention as an automotive seat, mattress, furniture, automotive under-carpet, and automotive dash insulator.

Brief Description of the Drawings

[0087]

Figure 1

Figure 2a

Figure 2b

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Example

[0088] Chemicals Used ■ Spurasak 2525: It comprises about 10% by weight of 2,4-MDI based on the total weight of all isocyanate compounds in Spurasak 2525 (the remaining isocyanate compounds are polymeric M DI and 4,4-MDI), and a polyisocyanate prepolymer composition having an NCO value of about 25.5%. ■ Spracsec 4801: A polyisocyanate composition comprising about 7% by weight of 2,4-MDI based on the total weight of all isocyanate compounds in Spracsec 4801 (the balance of the isocyanate compounds being polymeric MDI and 4,4-MDI), and having an NCO value of about 23%. ■ Spracsec 7007: Comprising about 15% by weight of 2,4-MDI based on the total weight of all isocyanate compounds in Spracsec 7007 (the balance of the isocyanate compounds being polymeric M DI and 4,4-MDI), and having an NCO value of about 29.5% polyisocyanate composition. ■ Daltocel F428: A polyoxyethylene polyoxypropylene polyol having a hydroxyl functionality of 3, a molecular weight of about 6000, and an ethylene oxide content of 15% by weight (all terminal tips). ■ Daltocel F526: A polyoxyethylene polyoxypropylene polyol having a hydroxyl functionality of 3, a molecular weight of about 6000, and an ethylene oxide content of 93% by weight. ■ Alcupol P-2321: A styrene-acrylonitrile graft-reactive polyether polymer having a solids content of 35%, a hydroxyl value of 23 mg KOH / g, and a molecular weight of 2680 g / mol. ■ Jeffcat DPA: A polyurethane catalyst. ■ Jeffcat DMEA: A polyurethane catalyst ■ Jeffcat LED204, 36%: A polyurethane catalyst ■ DELA: A crosslinking agent ■ Tegostab B8734LF: A surfactant ■ Tegostab B8745: A surfactant ■ Tegostab KE810L: A surfactant. ■ Tegostab B8738: A surfactant. ■ Water Examples 1-2 and Comparative Examples 1-2 According to the Present Invention Examples 1 and 2 of the soft polyurethane foam according to the present invention having a hardness gradient were prepared by mixing a polyisocyanate composition (b) and an isocyanate-reactive composition (a) to form a reactive foam according to the present invention. The reactive foam formulation at about room temperature was filled into a mold, and at this time, the temperature (T chemicals ) of the reactive foam formulation and the temperature (T ) of the mold mold ) The temperature difference (ΔT) between them is about 45 °C.

[0089] The same reactive foam formulation as in Example 1 was used, but the temperature (T chemicals ) of the reactive foam formulation not according to the present invention and the temperature (T mold ) of the mold ) When Example 1 was repeated using the temperature difference (ΔT chemicals ) between the temperature (T mold ) of the reactive foam formulation and the temperature of the mold, the resulting foam (Comparative Example 1) did not show the hardness gradient clearly obtained in the present invention. In Comparative Example 1, the temperature of the reactive foam formulation was 30 °C and the temperature of the mold was 45 °C. Therefore, the temperature difference (ΔT) between the temperature (T chemicals ) of the reactive foam formulation and the temperature (T mold ) of the mold was about 15 °C, and this The temperature difference is insufficient to obtain a soft foam having a hardness gradient according to the present invention.

[0090] Comparative Example 2 contained too much 2,4'-MDI in the polyisocyanate composition used to prepare the reactive foam formulation and did not provide a hardness gradient foam according to the present invention. In Comparative Example 2, the polyisocyanate composition contained 15% by weight of 2,4'-MDI based on the total weight of all isocyanate compounds in the polyisocyanate composition.

[0091] Table 1 shows the compositions of the reactive foam formulations used to produce the soft foams of Example 1, Example 2, Comparative Example 1, and Comparative Example 2.

[0092]

Table 1

[0093] Table 2 compares the foam elasticity ratios (foam elasticity / average foam elasticity) of the foam compartment layers. In Examples 1 and 2, the foam elasticity increases clearly from the top layer to the bottom layer. In Comparative Examples 1 and 2, the top and bottom layers have higher foam elasticity than the core layer.

[0094] Table 3 compares the foam density ratios (foam density / average foam density) of the foam compartment layers. In Examples 1 and 2, the bottom layer has a higher foam density than the other layers. In Comparative Examples 1 and 2, the top and bottom foam layers have a higher foam density than the foam core.

[0095] In Table 4, the polymer elasticity ratio (polymer elasticity / average polymer elasticity) of the foam compartment layers is The polymer elasticity of each layer is derived from the foam elasticity according to the formula in the definition of polymer elasticity. In Example 1, the top two layers have much lower polymer elasticity than the other two layers. In Example 2, the polymer elasticity of the top layer is much lower than the other layers. In Comparative Examples 1 and 2, the change in the polymer elasticity of each layer is limited. From these results, It can be seen that in Example 1, the change in foam elasticity arises primarily from the change in polymer elasticity in the foam, with density change being considered as a separate effect, whereas in Comparative Examples 1 and 2, the change in foam elasticity in the top and bottom layers arises from density change.

[0096] Figures 3a and 3b show the foam elasticity and polymer elasticity of the compartmentalization layers in the foams obtained from Example 1 and Comparative Example.

[0097] FIG. 4a shows the results of a foam according to the invention (Example 2) and a foam not according to the invention (Comparative Example 2). Foam elasticity E obtained by dividing layer f Shows.

[0098] Figure 4b shows the polymer elasticity E obtained in the separation layer of the foam according to the present invention (Example 2) and the foam not according to the present invention (Comparative Example 2). p

[0099] Figure 5a shows the foam density (ρ ) obtained in the separation layer of the foam according to the present invention (Example 1) and the foam of Comparative Example 1. f

[0100] Figure 5b shows the foam density (ρ ) obtained in the separation layer of the foam according to the present invention (Example 2) and the foam of Comparative Example 2 (Comparative Example 2). f

[0101] To examine the properties of the foam, the foam sample was divided into separation layers as shown in Figure 6.

[0102] [Table 2]

[0103] [Table 3]

[0104] [Table 4] [1] A molded flexible polyurethane foam having a foam with a hardness gradient, wherein the foam includes at least an uppermost layer having a thickness (height) corresponding to about 25% of the total thickness (height) of the foam; and a lowermost layer having a thickness (height) corresponding to about 25% of the total thickness (height) of the foam; and the foam elasticity E of the lowermost layer of the foam f is at least 3 times, preferably 3 to 10 times higher than the foam elasticity E of the uppermost layer of the foam, where the foam elasticity is given by the following formula [2]: f ​​​​​​E f = ω n 2 × mh / A [2] [where ω n is the natural frequency; m is the fixed mass; h is the thickness of the foam sample; A is the cross-sectional area of the foam sample] corresponds to the foam is produced using a reactive foam formulation, and the reactive formulation is prepared by mixing at least an isocyanate-reactive composition (a) and a polyisocyanate composition (b) at an isocyanate index in the range of 70 to 130, preferably 75 to 110, more preferably 75 to 100, a polyether polyol (a1) having an oxypropylene (PO) content of 51 to 100% by weight, based on the total weight of the polyether polyol (a1), and an oxyethylene (EO) content of 0 to 49% by weight, preferably at most 20% by weight, an average nominal hydroxyl functionality of 2 to 4, and an average molecular weight of 2000 to 7000; and, optionally, a polyether polyol (a2) having an oxyethylene content of 50 to 95% by weight, based on the weight of the polyether polyol (a2), where the weight ratio of the polyol (a2) in the isocyanate-reactive composition (a) is in the range of 0 to 20% by weight, preferably 0 to 10% by weight, more preferably 0 to 5% by weight, based on the total weight of the isocyanate-reactive composition (a); an isocyanate-reactive composition (a) comprising the polyisocyanate composition (b) is the above-mentioned molded flexible polyurethane having an NCO value in the range of 21 to 27%, preferably in the range of 23 to 25.5%. [2] the elasticity E of the bottom-layer polymer of the foam p is at least twice, preferably 2 to 8 times higher than the polymer elasticity E of the top layer of the foam p where the polymer elasticity is given by the following formula [1]: E p = E f / R 2 [1] [where the relative density (R) defined as R is ρ f / ρp is; ρ which is the density of the polyurethane polymer p is 1200 kg / m 3 is; ρ which is the density of the polyurethane foam f is measured according to ISO845] The molded flexible foam described in [1], corresponding to [3] The foam density ρ of the bottom layer of the foam f is such that the foam density ρ of the bottom layer of the foam f is 10 - 40% higher than that of the top layer of the foam, the molded flexible foam according to any one of [1] or [2]. [4] The polymer elasticity E of the bottom layer of the foam p is such that the polymer elasticity E of the bottom layer of the foam p is at least twice, preferably 2 - 8 times higher than that of the top layer of the foam, where the polymer elasticity corresponds to formula [1], and the foam density ρ of the bottom layer of the foam f is such that the foam density ρ of the bottom layer of the foam f is 10 - 40% higher than that of the top layer of the foam, having a hardness gradient, the molded flexible foam according to any one of [1] - [3]. [5] The polymer elasticity E of the core part of the foam, i.e., the central part of the foam p is lower than the polymer elasticity E of the top layer, the molded flexible foam according to any one of [1] - [4]. p having [6] The foam density ρ of the upper half of the foam f is such that the foam density ρ of the bottom layer of the foam f is higher, the molded flexible foam according to any one of [1] - [5]. [7] The polymer elasticity E of the top layer p is such that the polymer elasticity E of the top layer p is lower than that of the central part of the foam, and the foam density ρ of the lower half of the foam f is such that the foam density ρ of the lower half of the foam f is higher than that of the upper half of the foam, the molded flexible foam according to any one of [1] - [6]. [8] A reactive foam formulation for producing a molded flexible foam according to any one of [1] to [7], wherein the polyisocyanate composition (b) contains 0 to 12% by weight, preferably 0 to 10% by weight, of methylene diphenyl 2,4'-diisocyanate (2,4-MDI) based on the total weight of all polyisocyanate compounds in the polyisocyanate composition, said reactive foam formulation. [9] The reactive foam formulation further comprises a filled polyether polyol (a3), wherein the weight ratio of the polyol (a3) in the isocyanate-reactive composition (a) is in the range of 0 to 30% by weight, preferably 0 to 20% by weight, based on the total weight of the isocyanate-reactive composition (a), a reactive foam formulation for producing a molded flexible foam according to any one of [1] to [8].

[10] First, the polyisocyanate composition (b) and the polyol are pre-reacted, i.e., prepolymerized, wherein the amount of the isocyanate component reacting with the polyol in the polyisocyanate composition (b) is in the range of 0 to 40% by weight, preferably 0 to 30% by weight, more preferably 0 to 20% by weight, based on the total weight of the polyisocyanate composition (b), a reactive foam formulation for producing a molded flexible foam according to any one of [1] to [9].

[11] Further comprising additives such as a blowing agent, a catalyst, and a chain extender, and other additives such as a flame retardant, a filler, and a surfactant, a reactive foam formulation for producing a molded flexible foam according to any one of [1] to

[10] .

[12] Comprising a blowing agent, said blowing agent containing at least water, and the amount of water used is 0.5 to 10% by weight, preferably 1 to 5% by weight, based on the total weight of all components present in the isocyanate-reactive composition (a) used to prepare the reactive foam formulation according to the present invention, a reactive foam formulation for producing a molded flexible foam according to any one of [1] to

[11] .

[13] A method for manufacturing a molded soft foam according to any one of [1] to

[12] , (1) Mixing a polyisocyanate composition (b) and an isocyanate-reactive composition (a) at an isocyanate index in the range of 70 to 130, preferably in the range of 75 to 110, more preferably in the range of 75 to 100, to obtain a reactive foam formulation according to any one of [9] to

[12] ; (2) Casting the reactive foam formulation obtained in step 1 to obtain a soft foam having a hardness gradient; (3) Demolding the obtained soft foam having a hardness gradient; including at least, and step 3 being carried out such that there is a temperature difference (ΔT) of at least 25 to 30 °C between the temperature (T chemicals ) of the reactive foam formulation and the temperature (T mold ) of the mold, characterized in that the above method.

[14] The temperature difference ΔT between the temperature (T chemicals ) of the initial reactive foam formulation used and the temperature (T mold ) of the mold is in the range of at least 25 to 30 °C, more preferably in the range of at least 30 to 50 °C, and most preferably the temperature difference ΔT is in the range of at least 35 to 55 °C, the method according to

[13] .

[15] The lowest temperature (T chemicals ) of the initial reactive foam formulation used is 10 to 15 °C, preferably T chemicals is about room temperature, the temperature (T mold ) of the mold is above 50 °C and below 100 °C, preferably T mold is in the range of 55 to 70 °C, more preferably in the range of 60 to 70 °C, the method according to any one of

[13] or

[14] .

[16] Use of the molded soft foam according to any one of [1] to [7] as an automotive seat, mattress, furniture, automotive under-carpet, and automotive dash insulator.

Claims

1. A molded flexible polyurethane foam having a hardness gradient, comprising: The foam comprises at least a top layer having a thickness (height) corresponding to about 25% of the total thickness (height) of the foam; and a bottom layer having a thickness (height) corresponding to about 25% of the total thickness (height) of the foam; and the foam elasticity E of the bottom layer of the foam ｆ is the foam elasticity E of the top layer of the foam ｆ wherein the foam resilience is greater than or equal to three times the elasticity of the foam as defined by the following formula [2]: E ｆ =ω ｎ ２ ×mh / A [2] [In the formula, ω ｎ is the natural frequency; m is the fixed mass; h is the thickness of the foam sample; and A is the cross-sectional area of ​​the foam sample. is equivalent to The foam is produced using a reactive foam formulation, the reactive formulation being made by mixing at least an isocyanate-reactive composition (a) and a polyisocyanate composition (b) at an Isocyanate Index in the range of 70 to 130; isocyanate-reactive composition (a) comprises polyether polyol (a1) having an oxypropylene (PO) content of 51 to 100 weight percent and an oxyethylene (EO) content of 0 to 49 weight percent, based on the total weight of polyether polyol (a1), an average nominal hydroxyl functionality of 2 to 4, and an average molecular weight of 2000 to 7000; further, isocyanate-reactive composition (a) optionally comprises polyether polyol (a2) having an oxyethylene content of 50 to 95 weight percent, based on the weight of polyether polyol (a2), wherein the weight proportion of polyol (a2) in isocyanate-reactive composition (a) is in the range of 0 to 20 weight percent, based on the total weight of isocyanate-reactive composition (a); The above molded flexible polyurethane foam, wherein the polyisocyanate composition (b) comprises 0 to 12 weight % of 2,4'-MDI based on the total weight of all polyisocyanate compounds in the polyisocyanate composition and has an NCO value in the range of 21 to 27%.

2. Elasticity E of the bottom polymer of the foam ｐ However, the polymer elastic E of the foam top layer ｐ wherein the polymer elasticity is greater than or equal to two times the elasticity of the polymer, and E ｐ =E ｆ / R ２ [1] [wherein the relative density (R) defined as R is ρ ｆ / ρ ｐ ρ is the density of the polyurethane polymer ｐ is 1200 kg / m ３ ρ is the density of the polyurethane foam ｆ is measured according to ISO 845] 2. The molded flexible foam of claim 1, which corresponds to

3. Foam density ρ of the bottom layer of foam ｆ is the foam density of the top layer of foam, ρ ｆ The molded flexible foam according to claim 1 or 2, wherein the elastic modulus is 10 to 40% higher than that of the molded flexible foam according to claim 1 or 2.

4. Foam bottom layer polymer elastic E ｐ However, the polymer elastic E of the foam top layer ｐ where the polymer elasticity corresponds to formula [1] and the foam density ρ of the bottom layer of the foam is ｆ is the foam density of the top layer of foam, ρ ｆ 3. The molded flexible foam of claim 2, having a hardness gradient of 10 to 40% higher than the hardness gradient of claim 2.

5. The polymer elasticity E of the foam core, i.e., the central part of the foam ｐ Lower top layer polymer elastic E ｐ The molded flexible foam according to any one of claims 1 to 4, having

6. Foam density ρ of the upper half of the foam ｆ Higher foam density ρ of bottom layer ｆ The molded flexible foam according to any one of claims 1 to 5, having

7. Top layer polymer elastic E ｐ The polymer elasticity E of the foam core ｐ Lower, foam density ρ in the lower half of the foam ｆ is the foam density ρ ｆ The molded flexible foam according to any one of claims 1 to 6, wherein the elastic modulus is higher.

8. The molded flexible foam according to claim 1, wherein the polyisocyanate composition (b) has an NCO value of 25.5% or less.

9. A reactive foam formulation for producing the molded flexible foam of any one of claims 1 to 8, comprising: The reactive blend is made by mixing at least an isocyanate-reactive composition (a) and a polyisocyanate composition (b) with an Isocyanate Index in the range of 70 to 130; isocyanate-reactive composition (a) comprises polyether polyol (a1) having an oxypropylene (PO) content of 51 to 100 weight percent and an oxyethylene (EO) content of 0 to 49 weight percent, based on the total weight of polyether polyol (a1), an average nominal hydroxyl functionality of 2 to 4, and an average molecular weight of 2000 to 7000; further, isocyanate-reactive composition (a) optionally comprises polyether polyol (a2) having an oxyethylene content of 50 to 95 weight percent, based on the weight of polyether polyol (a2), wherein the weight proportion of polyol (a2) in isocyanate-reactive composition (a) is in the range of 0 to 20 weight percent, based on the total weight of isocyanate-reactive composition (a); The reactive foam formulation wherein the polyisocyanate composition (b) comprises 0 to 12 weight percent 2,4'-MDI, based on the total weight of all polyisocyanate compounds in the polyisocyanate composition, and has an NCO value in the range of 21 to 27 percent.

10. 10. The reactive foam formulation of claim 9, wherein the reactive foam formulation further comprises a filled polyether polyol (a3), wherein the weight percentage of polyol (a3) ​​in the isocyanate-reactive composition (a) ranges from 0 to 30 wt%, based on the total weight of the isocyanate-reactive composition (a).

11. 11. The reactive foam formulation of claim 9 or 10, wherein the polyisocyanate composition (b) and the polyol are first pre-reacted, i.e., prepolymerized, and wherein the amount of isocyanate component in the polyisocyanate composition (b) that reacts with the polyol ranges from 0 to 40 weight percent, based on the total weight of the polyisocyanate composition (b).

12. 12. The reactive foam formulation of any one of claims 9 to 11, further comprising: (1) an additive selected from blowing agents, catalysts, and chain extenders; and (2) an additive selected from flame retardants, fillers, and surfactants.

13. 13. The reactive foam formulation of any of claims 9 to 12, comprising a blowing agent, said blowing agent comprising at least water, the amount of water used being 0.5 to 10 wt.%, based on the total weight of all components present in the isocyanate-reactive composition (a) used to make the reactive foam formulation according to the present invention.

14. The reactive foam formulation of claim 9, wherein the NCO value of the polyisocyanate composition (b) is 25.5% or less.

15. Use of the molded flexible foam according to any one of claims 1 to 8 as an automobile seat, a mattress, furniture, an automobile undercarpet, and an automobile dash insulator.

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