JP7844862B2 - Flexible polyurethane foam-forming composition and flexible polyurethane foam - Google Patents

Description

This disclosure relates to a flexible polyurethane foam-forming composition and a flexible polyurethane foam.

Flexible polyurethane foam is widely used in furniture cushioning materials and automotive seats due to its excellent cushioning properties. Various characteristics are required for this flexible polyurethane foam, including foam properties, moldability, and surface curing properties.

Here, Patent Document 1 discloses a polyisocyanate composition for flexible polyurethane foam obtained by urethane-forming pure MDI (a) with an equivalent or less amount of polyol (b), and then mixing it with polymeric MDI (c). The composition contains a total of 60 to 85% by mass of 2,2'-MDI and 2,4'-MDI in the total amount of MDI components derived from (a) and (c); the content of MDI components derived from (a) and (c) relative to the total amount of (a) and (c) is 50 to 85% by mass; and (b) is a polyether polyol having a specific number-average molecular weight, a specific average number of functional groups, and a specific amount of oxyethylene groups. Furthermore, Patent Document 1 discloses that such a polyisocyanate composition for flexible polyurethane foam yields a flexible polyurethane foam with high storage stability, good moldability, and excellent mechanical properties, moist heat compression set, and rebound elasticity.

Furthermore, MDI is an abbreviation for diphenylmethane diisocyanate (hereinafter referred to as MDI), polymeric MDI is an abbreviation for polymethylene polyphenylene polyisocyanate (hereinafter referred to as p-MDI), and pure MDI is a general term for 2,2'-MDI, 2,4'-MDI, and 4,4'-MDI.

International Publication No. 2008/136179

However, in the composition described in Patent Document 1, the isocyanate component is modified with a polyol, resulting in high viscosity and low NCO content. Therefore, obtaining a low-density, flexible polyurethane foam with excellent elasticity was extremely difficult. Furthermore, when producing polyurethane foam, carbon dioxide is generated by reacting the NCO groups of the isocyanate with water to induce foaming. However, adding a large amount of water to reduce density leads to the formation of many highly cohesive urea bonds, resulting in excessively high foam hardness.

Therefore, one aspect of this disclosure is aimed at providing a flexible polyurethane foam-forming composition that contributes to the production of a flexible polyurethane foam having low density, moderate softness, strong mechanical properties, and durability. Another aspect of this disclosure is aimed at providing a flexible polyurethane foam having low density, moderate softness, strong mechanical properties, and durability.

Each aspect of this disclosure provides the following (1) to (6):
(1) Polyol component (A),
Catalyst (B),
Foam stabilizer (C),
Foaming agent (D),
It contains polyisocyanate component (E),
The ratio of the foaming reaction rate constant to the resinification reaction rate constant of the catalyst (B) (foaming reaction rate constant / resinification reaction rate constant) is 0.090 or less.
The aforementioned polyisocyanate component (E) is
Diphenylmethane diisocyanate (E-1) and,
It contains the optional component polymethylene polyphenylene polyisocyanate (E-2),
In the aforementioned polyisocyanate component (E),
The content of the diphenylmethane diisocyanate (E-1) is 75% by mass or more and 100% by mass or less, relative to the total amount of the polyisocyanate component (E).
A flexible polyurethane foam-forming composition wherein the content of the polymethylene polyphenylene polyisocyanate (E-2) is 0% by mass or more and 25% by mass or less, relative to the total amount of the polyisocyanate component (E).

(2) The flexible polyurethane foam-forming composition according to (1), wherein the total content of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate in the diphenylmethane diisocyanate (E-1) is 20% by mass or more and 60% by mass or less based on the total amount of the diphenylmethane diisocyanate (E-1).

(3) The flexible polyurethane foam-forming composition according to (1) above, wherein the total content of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate in the diphenylmethane diisocyanate (E-1) is 30% by mass or more and 50% by mass or less based on the total amount of the diphenylmethane diisocyanate (E-1).

(4) A flexible polyurethane foam that is a foamed molded article of a flexible polyurethane foam-forming composition described in any one of items (1) to (3) above.

(5) The apparent density is 25 kg/ ^m³ or more and 40 kg/ ^m³ or less,
The flexible polyurethane foam described in (4) above, wherein the 25% compression hardness of a skinned foam test specimen measured according to Method B described in JIS K6400 is 100 N/314 ^cm² or less.

(6) The elongation rate measured according to the method described in JIS K6400 is 100% or more.
The tear strength is 4.5 N/cm or more.
A flexible polyurethane foam as described in (4) or (5) above, wherein the moist heat compression strain is 25% or less.

According to one aspect of this disclosure, a flexible polyurethane foam-forming composition can be provided that contributes to the production of a flexible polyurethane foam having low density, moderate softness, strong mechanical properties, and durability. Furthermore, according to one aspect of this disclosure, a flexible polyurethane foam having low density, moderate softness, strong mechanical properties, and durability can be provided.

The following describes in detail exemplary embodiments for carrying out each aspect of this disclosure.
<Flexible polyurethane foam-forming composition>
A flexible polyurethane foam-forming composition according to one aspect of this disclosure is:
Polyol component (A),
Catalyst (B),
Foam stabilizer (C),
Foaming agent (D),
It contains polyisocyanate component (E).
The ratio of the foaming reaction rate constant to the resinification reaction rate constant of catalyst (B) (foaming reaction rate constant / resinification reaction rate constant) is 0.090 or less.
The aforementioned polyisocyanate component (E) is
Diphenylmethane diisocyanate (E-1) and,
It contains the optional component polymethylene polyphenylene polyisocyanate (E-2),
In the aforementioned polyisocyanate component (E),
The content of the diphenylmethane diisocyanate (E-1) is 75% by mass or more and 100% by mass or less, relative to the total amount of the polyisocyanate component (E).
The content of the aforementioned polymethylene polyphenylene polyisocyanate (E-2) is 0% by mass or more and 25% by mass or less, relative to the total amount of the polyisocyanate component (E).

<<Polyol component (A)>>
The polyol component (A) polyaddition with the polyisocyanate component (E) to form polyurethane. Preferably, the polyol component (A) is at least one selected from the group consisting of polyether polyols and polyester polyols.
The number-average molecular weight of the polyol component (A) is preferably between 1,000 and 10,000. If the number-average molecular weight is 1,000 or more, the flexibility of the resulting foam is further improved. If the number-average molecular weight is 10,000 or less, the hardness of the foam is further improved.
The nominal number of functional groups in the polyol component (A) is preferably two or more. When the nominal number of functional groups is two or more, the moist heat compressive strain, which is an indicator of durability, becomes even better. The nominal number of functional groups refers to the theoretical average number of functional groups (number of active hydrogen atoms per molecule) assuming that no side reactions occur during the polymerization reaction of the polyol.

Examples of polyether polyols include polypropylene ether polyol, polyethylene polypropylene ether polyol (hereinafter referred to as PPG), and polytetramethylene ether glycol (hereinafter referred to as PTG). Examples of polyester polyols include polycondensation-type polyester polyols composed of adipic acid and a diol, and lactone-type polyester polyols such as polycaprolactone polyol.

From the viewpoint of improving the durability of the resulting foam, it is preferable that the polyol component (A) contains a polyoxyalkylene polyol (A-1) having a total unsaturation degree of 0.001 meq./g or more and 0.04 meq./g or less. A higher total unsaturation degree of polyol (A-1) means that there are more monool components, etc., that have unsaturated groups at the terminals. For this reason, when the total unsaturation degree of polyoxyalkylene polyol (A-1) is 0.04 meq./g or less, the crosslinking density of the resulting foam becomes higher, and the durability is further improved. In addition, when the total unsaturation degree of polyoxyalkylene polyol (A-1) is 0.001 meq./g or more, the manufacturing time can be shortened and productivity can be improved, making it economical.
For polyoxyalkylene polyol (A-1), it is preferable that the polymerization catalyst is at least one selected from a complex metal cyanide catalyst, a phosphazene catalyst, and an imino group-containing phosphazenium salt.

The polyol component (A) preferably contains a polyether polyol (A-2) having a polyoxyalkylene chain made of a copolymer of oxyethylene and oxypropylene, as this promotes the breaking of bubbles in the flexible polyurethane foam. The polyether polyol (A-2) preferably has a nominal number of 2 to 4 functional groups.

The oxyethylene units in polyether polyol (A-2) are preferably 60% to 90% by mass, and more preferably 60% to 80% by mass. Having 60% to 90% by mass of oxyethylene units further improves durability. Furthermore, from the viewpoint of storage stability at low temperatures, it is preferable that the copolymer of oxyethylene and oxypropylene in polyether polyol (A-2) is a random copolymer.

The content of polyether polyol (A-2) is preferably 0.5% by mass or more and 5.0% by mass or less relative to the polyol component (A). A content of 0.5% by mass or more further improves the moldability of the foam. A content of 5.0% by mass or less further improves the elongation of the resulting foam.

For polyol component (A), it is preferable to use a polymer polyol obtained by polymerizing vinyl monomers in a polyol using a conventional method, for the purpose of adjusting hardness. Examples of such polymer polyols include those obtained by polymerizing vinyl monomers in a polyalkylene polyol such as PPG in the presence of a radical initiator and stably dispersing them. Examples of vinyl monomers include acrylonitrile, styrene, vinylidene chloride, hydroxyalkyl methacrylate, and alkyl methacrylate, with acrylonitrile and styrene being preferred. Examples of such polymer polyols include EL-910 and EL-923 from AGC Corporation, and FA-728R from Sanyo Chemical Industries, Ltd.

<<Catalyst (B)>>
Examples of catalyst (B) include various urethane catalysts known in the field. For example, triethylamine, tripropylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine, dimethylbenzylamine, N,N,N',N'-tetramethylhexamethylenediamine, N,N,N',N',N''-pentamethyldiethylenetriamine, bis-(2-dimethylaminoethyl) ether, triethylenediamine, 1,8-diazabicyclo[5.4.0]undecene-7, 1,2-dimethylimidazole, dimethylethanolamine, N,N-diethylethanolamine, N,N-dimethyl-N-hexanolamine, and their organic salts; organometallic compounds such as stanus octoate and zinc naphthenate; and so on.
These may be a single type or a combination of two or more types.

The content of catalyst (B) is preferably 0.01% by mass or more and 10% by mass or less relative to the polyol component (A). A content of 0.01% by mass or more further suppresses curing deficiency, while a content of 10% by mass or less further improves moldability.

The ratio of the foaming reaction rate constant to the resinification reaction rate constant of catalyst (B) (foaming reaction rate constant / resinification reaction rate constant) is 0.090 or less, preferably 0.005 to 0.080, and more preferably 0.010 to 0.080.
The resin formation reaction rate constant is the reaction rate constant used when an isocyanate group and a hydroxyl group react to form a urethane bond.
Furthermore, the foaming reaction rate constant is the reaction rate constant for the formation of a urea bond through the reaction of an isocyanate group with water.
The inventors speculate that when the ratio of the foaming reaction rate constant to the resin formation reaction rate constant (foaming reaction rate constant / resin formation reaction rate constant) is 0.090 or less, the formation of urethane bonds is promoted, and the molecular weight increase proceeds sufficiently, thereby suppressing the deterioration of moldability.

The resin formation reaction rate constant (k1w) is a parameter calculated by the following method. Specifically, toluene diisocyanate and diethylene glycol are charged so that the [isocyanate group]/[hydroxyl group] (molar ratio) is 1.0, a fixed amount of catalyst component (the target for k1w calculation) is added, the reaction is carried out in a benzene solvent at a constant temperature, and the amount of unreacted isocyanate is measured. Here, assuming that the reaction between toluene diisocyanate and diethylene glycol is first-order at their respective concentrations, the following equation holds.
dx/dt=k(ax) ² (1)
x: Concentration of reacted NCO group (mol/L)
a: Initial concentration of NCO group (mol/L)
k: Reaction rate constant (L/mol·h)
t: reaction time (h)

Substituting the initial conditions t=0 and X=0 into equation (1) and integrating, we obtain the following equation.
1/(ax)=kt+1/a (2)
k=ko+KcC (3)
ko: Reaction rate constant without catalyst (L/mol·h)
Kc: Catalytic constant (L ² /g・mol・h)
C: Catalyst concentration in the reaction system (mol/L)

The reaction rate constant k is determined from equation (2), and the catalyst constant Kc is determined by substituting it into equation (3).
The calculated catalyst constant Kc is divided by the molecular weight (mc) of the catalyst to determine the resinification reaction rate constant k1w ( ^L² /g·mol·h), which can be considered as the activity per unit mass.
Kc/mc=k1w (4)
Furthermore, if catalyst (B) is a combination of n types (n≧2), the resin formation reaction rate constant k1w ( ^L² /g·mol·h) can be calculated using equation (5).

W: Mass of catalyst (g)

On the other hand, the foaming reaction constant (k²w) can be determined in the same manner as described above by reacting toluene disisocyanate with water in a benzene solvent under the same conditions as the resin formation reaction.

<<Foam stabilizer (C)>>
As the foam stabilizer (C), a conventional surfactant can be used, and organosilicon-based surfactants are preferably used. Examples include SZ-1327, SZ-1325, SZ-1336, SZ-3601 from Toray Dow Corning, Y-10366, L-5309 from Momentive, and B-8724LF2, B-8715LF2 from Evonik.
The content of the foam stabilizer (C) is preferably 0.1% by mass or more and 3.0% by mass or less relative to the polyol component (A).

<<Foaming agent (D)>>
Water is preferred as the foaming agent (D). Water reacts with isocyanate groups to form high-hardness urea groups and generates carbon dioxide. The carbon dioxide causes foaming in the flexible polyurethane foam-forming composition, thus forming urethane foam.

The solution may contain other foaming agents along with water. Examples of other foaming agents include small amounts of low-boiling point organic compounds such as cyclopentane or isopentane. Alternatively, foaming may be induced by mixing and dissolving air, nitrogen gas, or liquefied carbon dioxide into the stock solution using a gas loading device.

The content of the foaming agent (D) is preferably 0.5% by mass or more and 10% by mass or less relative to the polyol component (A). When obtaining a low-density flexible polyurethane foam with an apparent density of less than 40 kg/ ^m³ , it is preferably 3.0% by mass or more and 7.0% by mass or less, and more preferably 3.0% by mass or more and 5.5% by mass or less. If it exceeds the upper limit, foaming may become unstable, and if it is below the lower limit, the density of the foam may not be sufficiently reduced.

<<Polyisocyanate component (E)>>
The polyisocyanate component (E) is
Diphenylmethane diisocyanate (E-1) and,
It contains the optional component polymethylene polyphenylene polyisocyanate (E-2),
In the polyisocyanate component (E),
The content of diphenylmethane diisocyanate (E-1) is 75% by mass or more and 100% by mass or less, relative to the total amount of the polyisocyanate component (E).
The content of polymethylene polyphenylene polyisocyanate (E-2) is 0% by mass or more and 25% by mass or less, relative to the total amount of the polyisocyanate component (E).

Examples of the polyisocyanate component (E) include 4,4'-diphenylmethane diisocyanate (hereinafter, 4,4'-MDI), 2,4'-diphenylmethane diisocyanate (hereinafter, 2,4'-MDI), 2,2'-diphenylmethane diisocyanate (hereinafter, 2,2'-MDI), and other diphenylmethane diisocyanates (hereinafter, MDI), as well as polymethylene polyphenylene polyisocyanate (hereinafter, p-MDI); and various modified compounds using these as isocyanate sources. These may be used individually or in combination of two or more. Examples of modified compounds include urethane modified compounds, urea modified compounds, allophanate modified compounds, nurate modified compounds, and biuret modified compounds.

The MDI (E-1) content of the polyisocyanate component (E) is 75% by mass or more and 100% by mass or less. If the MDI content is less than 75% by mass, the elongation of the flexible polyurethane foam decreases as the crosslinking density increases, and sufficient foam strength cannot be obtained.

Furthermore, the total content of 2,2'-MDI and 2,4'-MDI in MDI(E-1) (hereinafter referred to as the isomer content) is preferably 20% to 60% by mass, and more preferably 30% to 50% by mass, relative to the total amount of MDI(E-1). A content of 60% by mass or less further improves reactivity, allows for further shortening of the molding cycle, and further suppresses the increase in the foam's cell-locking ratio, thereby reducing problems such as shrinkage after molding.

<<Molar ratio (NCO group/active hydrogen group)>>
In a flexible polyisocyanate-forming composition, the molar ratio (NCO groups/active hydrogen groups) of total isocyanate groups to total active hydrogen groups in an active hydrogen group-containing compound containing water is preferably 0.5 to 1.4 (isocyanate index (NCO INDEX) = 50 to 140), and more preferably 0.7 to 1.2 (NCO INDEX = 70 to 120). Within this range, the resulting foam exhibits good durability and molding cycles.
If the NCO INDEX is 50 or higher, durability is further improved, and excessive increases in cell locking can be suppressed. If the NCO INDEX is 140 or lower, high molecular weight formation proceeds rapidly, and foam collapse during foam foaming is more effectively suppressed.

<<Other ingredients>>
The flexible polyurethane foam-forming composition may optionally contain various known additives and auxiliary agents such as fillers like calcium carbonate and barium sulfate, flame retardants, plasticizers, colorants, and antifungal agents.

<Flexible polyurethane foam, and its manufacturing method>
A flexible polyurethane foam according to one aspect of this disclosure is a foamed molded article of the flexible polyurethane foam-forming composition described above. This flexible polyurethane foam provides a comfortable ride when used, for example, as a cushioning material.
The apparent density of the flexible polyurethane foam is preferably 25 kg/ ^m³ or more and 40 kg/ ^m³ or less.
The skinned foam test specimen of the flexible polyurethane foam (details will be described later) preferably has a 25% compression hardness of 100 N/314 ^cm² or less.
The elongation rate of the flexible polyurethane foam is preferably 100% or more.
The tear strength of the flexible polyurethane foam is preferably 4.5 N/cm or higher.
The moist thermal compression set of the flexible polyurethane foam is preferably less than 25%.

Next, we will explain the manufacturing method of flexible polyurethane foam.
A method for manufacturing flexible polyurethane foam according to one aspect of this disclosure is:
The process involves mixing a polyol component (A), a catalyst (B), a foam stabilizer (C), a blowing agent (D), and a polyisocyanate component (E) to obtain a mixed solution.
The method comprises reacting and foaming the mixture to obtain a flexible polyurethane foam.

Here, each component (A) to (E) may be added one by one in sequence, or two or more may be mixed beforehand and then all components may be mixed together at the end.
In the former case, there are no restrictions on the order in which components (A) to (E) are added; any order is acceptable. Furthermore, two or more components from (A) to (E) may be added separately or simultaneously.
In the latter case, for example,
The first liquid is obtained by the first pre-mixing,
The second liquid is obtained through a second pre-mixing,
The method includes mixing the first liquid and the second liquid to obtain a mixed solution.
Here, for example, the first liquid may contain a polyol component (A), a catalyst (B), a foam stabilizer (C), and a blowing agent (D), while the second liquid may consist only of an isocyanate component (E). In this case, the second pre-mixing can be omitted.

It is preferable to inject the mixed liquid (foaming concentrate) into the mold, and then allow it to react, foam, and harden.
The mold temperature when injecting the above mixture into the mold is usually 30°C to 80°C, preferably 45°C to 65°C. If the mold temperature when injecting the above mixture into the mold is 30°C or higher, the reaction rate is improved and the production cycle can be shortened. If the mold temperature is 80°C or lower, the reaction between water and isocyanate is further suppressed in relation to the reaction between polyol and isocyanate, thereby further suppressing the collapse of the foam during foaming.

When the above foaming concentrate is allowed to harden, the hardening time is preferably 10 minutes or less, and more preferably 7 minutes or less, considering the typical production cycle of flexible mold foam.

When manufacturing flexible molded foam, the above components can be mixed using high-pressure or low-pressure foaming machines, similar to the process for conventional flexible molded foam.

It is preferable to mix the isocyanate component (E) and the polyol component (A) immediately before foaming. Components (B) to (D) and other components can be pre-mixed with the isocyanate component (E) or polyol component (A) to the extent that it does not affect the storage stability or reactivity of the raw materials over time. The resulting mixture may be used immediately after mixing, or it may be stored and used as needed. In the case of a foaming apparatus capable of simultaneously introducing more than two components into the mixing section, each component (A) to (E), and additives, etc., can also be introduced into the mixing section individually.

Furthermore, the mixing method may be either dynamic mixing, performed within the mixing chamber of the foaming machine's machine head, or static mixing, performed within the liquid delivery piping, or a combination of both. While static mixing is often used for mixing gaseous components such as physical foaming agents with liquid components, and dynamic mixing is often used for mixing components that can be stably stored as liquids, this is not the only method. For the production of flexible polyurethane foam, a high-pressure foaming apparatus that does not require solvent cleaning of the mixing section is preferable.

The mixture obtained through this mixing process is dispensed into a mold, reacted, foamed, and cured, and then demolded. To facilitate the demolding process, it is preferable to apply a release agent to the mold beforehand. Examples of release agents used include those commonly used in the molding industry.

While the demolded product can be used as is, it is preferable to break the foam's cell membrane under compression or reduced pressure using conventionally known methods to stabilize the product's appearance and dimensions.

By the method for manufacturing the flexible polyurethane foam described above,
Apparent density 25 kg/ ^m³ or more and 40 kg/ ^m³ or less.
The 25% compression hardness of the skinned foam test specimen is 100 N/314 ^cm² or less.
Tear strength of 4.5 N/cm or more,
Moist heat compressive strain is less than 25%.
A flexible polyurethane foam can be easily obtained.

The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, "parts" and "%" in this text refer to mass.

[Preparation of Polyol Compositions]
(Examples 1-4, Comparative Examples 1-3)
After purging a reactor equipped with a stirrer, condenser, nitrogen inlet tube, and thermometer with nitrogen, 97 g of polyol 1, 3.0 g of polyol 2, 1.2 g of catalyst 1, 1.0 g of foam stabilizer 1, and 5.4 g of water were charged and stirred at 23°C for 0.5 hours to obtain polyol composition (P-1). Other polyol compositions (P-2 to P-7) were prepared in the same manner as P-1.

The liquid temperatures of the isocyanate component (E) and the mixture of all other raw materials (polyol compositions (P-1) to (P-7)) shown in Table 1 were adjusted to 24°C to 26°C. A predetermined amount of polyisocyanate component (E) was added to polyol compositions (P-1) to (P-7), mixed for 5 seconds in a mixer (7000 rpm), and then injected into a mold to foam flexible polyurethane foam. Afterward, the foam was removed from the mold, and its physical properties were measured. The NCO Index in Table 1 represents the ratio of moles of NCO groups to moles of active hydrogen atoms present in the flexible polyurethane foam-forming composition.

[Foaming conditions]
Mold temperature: 60-70°C
Mold shape: 400mm x 400mm x 100mm
Mold material: Aluminum

[Raw materials used]
Isocyanate 1: MDI content 89%, isomer content 38%, polyphenylene polymethylene polyisocyanate content 11%
Isocyanate 2: Diphenylmethane diisocyanate with 100% MDI content and 55% isomer content. Isocyanate 3: 70% MDI content, 29% isomer content, and 30% polyphenylene polymethylene polyisocyanate content.
Polyol 1: Polyoxyethylene polyoxypropylene polyol (manufactured by Tosoh Corporation, product name: NEF-693) with an average number of functional groups of 3.0, a hydroxyl value of 24 (mg KOH/g), a primary terminal rate of 84 mol%, an oxyethylene unit ratio of 14.6% by mass, and a total unsaturation degree of 0.03 meq./g.
• Polyol 2: Polyoxyethylene polyoxypropylene polyol (manufactured by Sanyo Chemical Industries, Ltd., product name: Sannix FA-159) with an average number of functional groups of 3.0, a hydroxyl value of 24 (mg KOH/g), a terminal primary status of 51 mol%, an oxyethylene unit ratio of 70% by mass, and a total unsaturation degree of 0.03 meq./g.
• Polyol 3: Polyoxyethylene polyoxypropylene polyol (manufactured by Toho Chemical Industry Co., Ltd., product name: Toho Polyol QB-8000) with average functional group count = 4.0, hydroxyl value = 28 (mg KOH/g), terminal primary status = 79 mol%, oxyethylene units = 80 mass%, and total unsaturation degree of 0.01 meq./g.
Catalyst 1: 1,2-dimethylimidazole, [foaming reaction rate constant / resin formation reaction rate constant] = 0.076
Catalyst 2: 33% triethylenediamine dipropylene glycol solution, [foaming reaction rate constant / resin formation reaction rate constant] = 0.132
• Foam stabilizer 1: Silicone-based foam stabilizer (manufactured by Momentive, product name: L-3641LF)
• Foam stabilizer 2: Silicone-based foam stabilizer (manufactured by Momentive, product name: L-3627)
• Foam stabilizer 3: Silicone-based foam stabilizer (manufactured by Momentive, product name: Y-10366)

[Moldability Evaluation]
In the moldability evaluation in Table 1, A means that the soft polyurethane foam was molded without shrinkage or roughness occurring on the surface or inside of the foam after demolding, while B means that shrinkage, surface roughness, or other phenomena occurred in the polyurethane mold foam.

[Apparent Density]
The results were obtained using the method described in JIS K6400.

[25% Compression Hardness (25% ILD) of Skinned Foam Test Specimens]
The results were obtained using Method B described in JIS K6400. Note that the skinned foam test specimens are molded foam produced using the method described above, and refer to foam with the skin still attached without being cut or otherwise altered.

[Tear strength]
The measurement was performed according to the method described in JIS K6400.

[Moist heat compressive strain]
The measurement was performed according to the method described in JIS K6400.

[Growth Rate]
The measurement was performed according to the method described in JIS K6400.

As shown in Table 1, according to Examples 1 to 4, a flexible polyurethane foam is obtained in which the [foaming reaction rate constant / resinification reaction rate constant] value is 0.090 or less, the 25% compression hardness is 100 N/314 cm² or ^less , the tear strength is 4.5 N/cm or more, the elongation is 100% or more, and the moist heat compression strain is 25% or less. On the other hand, according to Comparative Examples 1 and 2, when the [foaming reaction rate constant / resinification reaction rate constant] value exceeds 0.090, the stability of the cells in the foam decreases significantly, and moldability deteriorates, resulting in roughness on the surface and inside the polyurethane foam. Furthermore, according to Comparative Example 3, the tear strength is less than 4.5 N/cm and the moist heat compression strain exceeds 25%.
As is clear from comparing the above examples and comparative examples, a molded article can be obtained that has a hardness that provides good ride comfort when used, for example, as a seat back material, and possesses desirable physical properties.

Claims (6)

Polyol component (A),
Catalyst (B),
Foam stabilizer (C),
Foaming agent (D),
It contains polyisocyanate component (E),
The ratio of the foaming reaction rate constant to the resinification reaction rate constant of the catalyst (B) (foaming reaction rate constant / resinification reaction rate constant) is 0.090 or less.
The aforementioned polyisocyanate component (E) is
Diphenylmethane diisocyanate (E-1) and,
It contains the optional component polymethylene polyphenylene polyisocyanate (E-2),
In the aforementioned polyisocyanate component (E),
The content of the diphenylmethane diisocyanate (E-1) is 75% by mass or more and 100% by mass or less, relative to the total amount of the polyisocyanate component (E).
The content of the aforementioned polymethylene polyphenylene polyisocyanate (E-2) is 0% by mass or more and 25% by mass or less, relative to the total amount of the polyisocyanate component (E).
A flexible polyurethane foam-forming composition wherein the total content of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate in the diphenylmethane diisocyanate (E-1) is 20% by mass or more and 60% by mass or less based on the total amount of the diphenylmethane diisocyanate (E-1) . The aforementioned flexible polyurethane foam-forming composition has an apparent density of 25 kg/m³ as measured under the following conditions (1) to (4). ³ More than 40kg/m ³ The following is the flexible polyurethane foam-forming composition according to claim 1.
(1) The polyol component (A), the catalyst (B), the foam stabilizer (C), and the blowing agent (D) are each adjusted to 24°C to 26°C.
(2) Mix the polyisocyanate component (E) with the mixture for 5 seconds in a mixer that rotates at 7,000 revolutions per minute.
(3) The material is injected into a mold with a mold temperature of 60-70°C, a mold shape of 400 mm x 400 mm x 100 mm, and made of aluminum, and then foamed.
(4) Remove from the mold and determine the apparent density according to the method described in JIS K6400. The flexible polyurethane foam-forming composition according to claim 1, wherein the total content of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate in the diphenylmethane diisocyanate (E-1) is 30% by mass or more and 50% by mass or less based on the total amount of the diphenylmethane diisocyanate (E-1). A flexible polyurethane foam, which is a foamed molded article of a flexible polyurethane foam-forming composition according to any one of claims 1 to 3. The apparent density is between 25 kg/ ^m³ and 40 kg/ ^m³ .
The flexible polyurethane foam according to claim 4, wherein the 25% compression hardness of a skinned foam test specimen measured according to Method B described in JIS K6400 is 100 N/314 ^cm² or less. The elongation rate measured according to the method described in JIS K6400 is 100% or more.
The tear strength is 4.5 N/cm or more.
The flexible polyurethane foam according to claim 4 or 5, wherein the moist heat compression strain is 25% or less.