JP6903993B2 - Polyisocyanate composition for flexible polyurethane foam - Google Patents

Description

The present invention relates to a polyisocyanate composition for a flexible polyurethane foam and a flexible polyurethane foam obtained from the composition.

Since ancient times, flexible polyurethane foam for automobile seat cushions (hereinafter, also referred to as soft foam) has been required to have high durability so that the driver's viewpoint change due to thickness reduction is small even when riding for a long time from the viewpoint of safety. .. On the other hand, in recent seat cushions, in order to reduce vibration transmitted from the road surface, it is required to suppress the elastic modulus of the foam to a low level and to reduce the foam density as much as possible from the viewpoint of cost reduction. However, it is known that these low resilience and low density significantly deteriorate the foam durability, and it has been required to establish a technique for achieving both durability, ride quality and economy.

The polyisocyanate component is roughly divided into a TDI system containing a mixture of tolylene diisocyanate (hereinafter also referred to as TDI) and polyphenylpolymethylene polyisocyanate (hereinafter also referred to as p-MDI) as a main component and diphenylmethane diisocyanate (hereinafter referred to as MDI). There is an MDI system whose main component is a mixture of (also referred to as) and p-MDI. Since the TDI system has a high isocyanate group content and a large amount of carbon dioxide gas generated per unit weight due to the reaction with water, it is possible to reduce the density without increasing the blending amount of water so much. Since the isocyanate group content per unit weight (hereinafter, also referred to as NCO content) is high, the hydrogen bondability is high, and the mechanical properties such as elongation and strength at break are excellent. However, since TDI as a raw material has a high vapor pressure and high toxicity, it tends to deteriorate the working environment at the flexible polyurethane foam manufacturing site. Further, the obtained flexible polyurethane foam has a problem of low durability. Further, in the urethane foam using TDI, the density difference between the skin layer and the core layer of the foam is large, and even if the foam has the same 25% compression hardness and hysteresis loss rate, the surface feel is hard and the riding comfort performance is inferior.

On the other hand, the MDI-based flexible foam, which generally has a lower elastic modulus than the TDI-based flexible polyurethane foam, is relatively easy to achieve both vibration absorption and durability in a high-density region. However, in comparison NCO content is low MDI based isocyanate TDI, it is necessary to blend a large amount of water for the density-reducing, in the low density region of less than 55 kg / m ³ which is required in recent seat cushion, isocyanate and water There is a problem that the resilience from deformation of the resin is reduced due to the increase in the rigid urea bond generated by the reaction with the resin, the durability is deteriorated, and the good texture characteristic of the MDI-based flexible polyurethane foam is lost. ..

Patent Document 1 discloses a method of improving durability by reacting MDI with a polyether polyol having an oxyethylene unit. However, in the MDI-based flexible polyurethane foam using this method, the durability such as compression set is improved, but the mechanical properties such as the strength at break, the tear strength, and the elongation rate of the foam are deteriorated.

Patent Document 2 describes a method of reacting MDI with an aliphatic or aromatic alcohol to improve mechanical properties, but the MDI-based flexible polyurethane foam obtained by this method is inferior in durability. As described above, the mechanical properties of the MDI-based flexible polyurethane foam and the durability such as compression set have contradictory properties.

Special Table No. 10-501830 Japanese Unexamined Patent Publication No. 11-217420

The present invention is an isocyanate composition for producing a flexible polyurethane foam, which has good vibration absorption due to a low elastic modulus, and realizes high mechanical properties and low moist heat compression permanent strain even in a low density region of less than ^{55 kg / m 3.} , And a soft foam with high vibration absorption, high mechanical properties, and high durability using this isocyanate composition, and a vehicle seat that uses this soft foam to achieve both good ride comfort and high safety. The purpose is to provide cushions, seat backs and saddles.

As a result of diligent studies to solve the above-mentioned problems, the present invention has been found to be solved by a polyisocyanate composition containing an allophanate modified product composed of MDI and a specific polyoxyalkylene polyol, leading to the present invention. ..

That is, the present invention includes the following embodiments (1) to (5).

(1) A polyisocyanate composition containing an allophanate modified product of diphenylmethane diisocyanate and polyoxyalkylene polyol (A).
The hydroxyl value of the polyoxyalkylene polyol (A) is 25 to 120 mgKOH / g, the weight ratio of the oxypropylene unit to the oxyethylene unit is 30/70 to 100/0, and the isocyanate content of the polyisocyanate composition. A polyisocyanate composition in the range of 20 to 32% by weight.

(2) The diphenylmethane diisocyanate contains 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate, and 2,2'-diphenylmethane with respect to the total amount of diphenylmethane diisocyanate. The polyisocyanate composition according to (1) above, wherein the total content of diisocyanate and 2,4'-diphenylmethane diisocyanate is 10 to 50% by weight.

(3) The polyisocyanate composition according to (1) or (2) above, wherein the polyoxyalkylene polyol (A) has an average nominal hydroxyl functional value of 1.7 to 2.4.

(4) A mixed solution of the polyol (C), the catalyst (D), the foaming agent (E) and the foam stabilizer (F) and the polyisocyanate composition according to any one of (1) to (3) above. A method for producing a flexible polyurethane foam that is reacted and foamed.

(5) The apparent density of the flexible polyurethane foam is 50 to 70 kg / m ³ , the 25% compressive hardness of the foam test piece with skin is in ^{the range of 100 to 300 N / 314 cm 2} , and the elastic modulus is 23 to 53%. The mechanical properties are such that the elongation is 90 to 170%, the tear strength is 5 to 10 N / cm, and the moist heat compression permanent strain is 9% or less.
The method for producing a flexible polyurethane foam according to (4) above.

According to the composition for molding a flexible polyurethane foam containing the isocyanate composition for a flexible polyurethane foam of the present invention, it has good vibration absorption due to a low elastic modulus and low moist heat compression permanent strain even in a low density region. It is possible to obtain a flexible polyurethane foam that has high mechanical properties and thus prevents breakage of a molded product.

First, the polyisocyanate composition of the present invention will be described. The polyisocyanate composition of the present invention is a polyisocyanate composition containing an allophanate modified product of MDI and a polyoxyalkylene polyol (A), and the hydroxyl value of the polyoxyalkylene polyol (A) is 25 to 120 mgKOH / g. Polyisocyanate, which is characterized in that the weight ratio of the oxypropylene unit to the oxyethylene unit is 30/70 to 100/0, and the isocyanate content of the polyisocyanate composition is in the range of 20 to 32% by weight. It is a composition.

As the MDI in the present invention, a commercially available MDI can be used without particular limitation, but the total content of 2,2'-MDI and 2,4'-MDI (hereinafter, also referred to as isocyanate content) is high. , 10 to 50% by weight, more preferably 20 to 45% by weight, based on the total amount of MDI used in the polyisocyanate composition.

If the total content of 2,2'-MDI and 2,4'-MDI with respect to the total amount of MDI is less than 10% by weight, the storage stability of the obtained polyisocyanate composition at low temperature is impaired, and the storage location and piping of isocyanate are impaired. In addition to the constant heating inside the foam molding machine, the molding stability of the flexible polyurethane foam is impaired, and foam collapse during foaming is likely to occur. On the other hand, if it exceeds 50% by weight, the foam hardness decreases, sufficient hardness cannot be secured as a seat cushion, a seat back or a saddle, the reactivity decreases, the molding cycle is extended, and the foaming rate of the foam increases. Problems such as an increase in compression set are likely to occur.

The polyoxyalkylene polyol (A) of the present invention has a hydroxyl value of 25 to 120 mgKOH / g and a weight ratio of oxypropylene unit to oxyethylene unit of 30/70 to 100/0, preferably 50/50. ~ 70/30. If the weight ratio of the oxypropylene unit is less than 30%, the amount of highly hydrophilic oxyethylene unit becomes too large, and when water is used as the foaming agent, it is highly hydrophilic and therefore the molding stability of the flexible polyurethane foam. Is impaired, which causes foam collapse during foaming.

Further, the polyoxyalkylene polyol (A) is at least one selected from the group consisting of a copolymer of an oxypropylene unit and an oxyethylene unit, a copolymer of only an oxypropylene unit, and a copolymer of only an oxyethylene unit. Can be adjusted and used so as to have the above ratio.

The polyoxyalkylene polyol (A) of the present invention can realize good flexible polyurethane foam performance as long as the weight ratio of the oxypropylene unit to the oxyethylene unit and the hydroxyl value are within the above ranges. When the average nominal hydroxyl functional value is 1.7 to 2.4 and the hydroxyl value of the polyoxyalkylene polyol (A) is 35 to 80 mgKOH / g, a better flexible polyurethane foam can be obtained.

Further, in the polyoxyalkylene polyol (A) of the present invention, the CPR value (controlled polymerization rate) defined by JIS K 1557 is preferably 10 or less, and more preferably 5 or less. When the CPR value exceeds 10, in the urethane modification and allophanate modification of isocyanate, trimmerization reaction and dimerization reaction other than urethanization and allophanation reaction are promoted, and the isocyanate being synthesized is solidified or isocyanate. The viscosity tends to rise unexpectedly, making it unusable for practical use.

In the present invention, when a flexible polyurethane foam is formed using a polyisocyanate composition containing an allophanate-modified MDI allophanate with the above-mentioned polyoxyalkylene polyol (A), the allophanate group having the polyoxyalkylene polyol is flexible. It works as a cross-linking agent, and electrostatic interaction occurs between allophanate bond, urethane bond and urea bond in the resin, and by adopting a pseudo-cross-linking structure, low moist heat even in foam with low repulsive elasticity. It realizes compression set, high mechanical properties, and high durability.

As the allophanation catalyst that can be used in the present invention, conventionally known catalysts can be appropriately selected and used. For example, acetylacetone metal complex, carboxylate such as zirconium octylate, dimethylaminoethoxyethanol and the like 3 Secondary amines and the like can be used. The amount of the allophanate catalyst used is preferably 0.0005 to 1% by weight, more preferably 0.001 to 0.1% by weight, based on the total weight of the polyisocyanate and the polyoxyalkylene polyol (A).

Alofanation may be performed at the same time as urethanization or after urethanization. When urethanization and allophanation are carried out at the same time, the reaction may be carried out in the presence of an allophanization catalyst, and when allophanization is carried out after urethanization, the urethanization reaction is carried out for a predetermined time in the absence of the allophanization catalyst. After that, an allophanation catalyst may be added to carry out the allophanization reaction. After completion of the reaction, a reaction terminator such as benzoyl chloride, phosphoric acid, or a phosphate ester is added into the reaction system, and the terminating reaction is carried out at 30 to 100 ° C. for 1 to 2 hours to stop the allophanation reaction.

The isocyanate group content of the polyisocyanate composition containing the allophanate modified product obtained as described above is 20 to 32% by weight. If the NCO content is less than 20% by weight, the amount of carbon dioxide generated by the reaction between isocyanate and water is too small, and moldability in a low density region cannot be ensured. If it exceeds 32% by weight, the amount of allophanate structure containing the oxypropylene unit and the oxyethylene unit is small, the high mechanical characteristics of the present invention cannot be obtained, and the moist heat compression permanent distortion reduction effect cannot be obtained.

Next, the method for producing the flexible polyurethane foam of the present invention will be described.

As a method for producing the flexible polyurethane foam of the present invention, a foaming stock solution of a mixed solution of the polyisocyanate composition, a polyol (C), a catalyst (D), water (E) as a foaming agent, and a foam stabilizer (F). Can be preferably used by a method for producing a flexible polyurethane mold foam (hereinafter, also referred to as a soft mold foam), which is formed by injecting a foam into a mold and then foam-curing.

As the polyol (C) of the present invention, it is preferable to use a polyether polyol having a hydroxyl value of 20 to 40 mgKOH / g and an average number of functional groups of 2 to 4, which easily exhibits excellent performance as a flexible polyurethane foam.

If the hydroxyl value exceeds 40 mgKOH / g, the hardness of the flexible polyurethane foam becomes too high, and the flexibility may decrease. On the other hand, if the amount is less than 20 mgKOH / g, the hardness of the obtained polyurethane foam is too soft for the flexible polyurethane foam for vehicle seats, and mixing defects due to high viscosity are likely to occur.

Examples of the polyether polyol having a hydroxyl value of 20 to 40 mgKOH / g and an average number of functional groups of 2 to 4 include low molecular weight polyols having a number average molecular weight of less than 700, low molecular weight polyamines, low molecular weight amino alcohols and the like as an initiator. Examples thereof include alkylene oxides such as ethylene oxide and propylene oxide, and those obtained by adding cyclic ethers such as tetrahydrofuran.

Examples of the initiator include water, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 1,5. -Pentanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol , 2,2-Diethyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 2-ethyl- 1,3-Hexanediol, 2-n-hexadecane-1,2-ethylene glycol, 2-n-eicosan-1,2-ethylene glycol, 2-n-octacosane-1,2-ethylene glycol, diethylene glycol, dipropylene Glycol, 1,4-cyclohexanedimethanol, ethylene oxide or propylene oxide adducts of bisphenol A, hydrogenated bisphenol A, 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropionate, Examples thereof include low molecular weight polyols such as trimethylolpropane, glycerin, and pentaerythritol. In addition, low molecular weight amines such as aniline, ethylenediamine, propylenediamine, toluenediamine, metaphenylenediamine, diphenylmethanediamine, and xylylenediamine, and low molecular weight amino alcohols such as monoethanolamine, diethanolamine, triethanolamine, and N-methyldiethanolamine. And so on.

Polyether polyols that can be obtained by adding alkylene oxides such as ethylene oxide and propylene oxide and cyclic ethers such as tetrahydrofuran to these initiators can be used alone or in combination of two or more. When two or more kinds of polyether polyols are used in combination, it is preferable that the combined components as a whole have a hydroxyl value of 20 to 40 mgKOH / g and an average number of functional groups of 2 to 4.

A polymer polyol produced by polymerizing a vinyl-based monomer in a polyol by a usual method can be used in combination with the polyol (C) of the present invention for the purpose of adjusting the hardness. Examples of such a polymer polyol include those obtained by polymerizing a vinyl-based monomer in the presence of a radical initiator in a polyether polyol similar to the polyol (C) and stably dispersing it. Examples of the vinyl-based monomer include acrylonitrile, styrene, vinylidene chloride, hydroxyalkyl, methacrylate, and alkyl methacrylate, and acrylonitrile and styrene are preferable.

Further, as the polyol (C), a polyol such as a polyester polyol or a polycarbonate polyol can be used in combination as long as the performance is not deteriorated.

Examples of the polyester polyol include those obtained from dibasic acids such as adipic acid and phthalic acid and glycols such as ethylene glycol and 1,4-butylene glycol.

Examples of the polycarbonate polyol include those obtained from dialkyl carbonates such as dimethyl carbonate and diethyl carbonate and glycols such as 1,6-hexanediol.

As the catalyst (D) used in the present invention, various conventionally known urethanization catalysts and trimerization catalysts can be used. Examples of such a catalyst include triethylamine, tripropylamine, tributylamine, N-methylmorpholin, N-ethylmorpholin, dimethylbenzylamine, N, N, N', N'-tetramethylhexamethylenediamine, N, N. , N', N', N''-pentamethyldiethylenetriamine, triethylenediamine, bis- (2-dimethylaminoethyl) ether, 1,8-diaza-bicyclo [5.4.0] undecene-7, etc. Reactive tertiary amines such as amines, dimethylethanolamines, N-trioxyethylene-N, N-dimethylamines, N, N-dimethyl-N-hexanolamines or their organic acid salts, 1-methiimidazole, 2- Imidazole compounds such as methyl imidazole, 1,2-dimethyl imidazole, 2,4-dimethyl imidazole, 1-butyl-2-methyl imidazole, organic metal compounds such as stanas octoate, dibutyltin dilaurate, zinc naphthenate, 2, Examples thereof include 4,6-tris (dimethylaminomethyl) phenol, 2,4,6-tris (dialkylaminoalkyl) hexahydro-S-triazine, potassium acetate, potassium 2-ethylhexanoate and the like.

The type of catalyst is not particularly limited as long as it can realize an appropriate foaming rate and production cycle of the foam cell, but 0.1 to 5 parts by weight is added to the polyol (C) from the viewpoint of foam odor and the like. Is preferable.

The foaming agent (E) used in the present invention is preferably water, and the amount of water is preferably 2 to 15 parts by weight with respect to 100 parts by weight of the polyol (C). In addition to water, liquefied carbon dioxide gas can be added in the range of up to 6 parts by weight with respect to 100 parts by weight of the polyol (C) to increase the foaming ratio.

As the defoaming agent (F) used in the present invention, a conventionally known organic silicon-based surfactant can be used, and for example, SZ-1327, SZ-1325, SZ-1336 manufactured by Toray Dow Corning Co., Ltd., Examples thereof include SZ-3601, Y-10366 and L-5309 manufactured by Momentive, B-8724LF2 and B-8715LF2 manufactured by Evonik, and F-122 manufactured by Shin-Etsu Chemical. The amount of these foam stabilizers is preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the polyol (C).

Further, a cross-linking agent such as diethanolamine or triethanolamine can be added to the present invention for the purpose of improving molding stability and adjusting foam hardness. The preferable amount of the cross-linking agent added is up to 5 parts by weight with respect to 100 parts by weight of the polyol (C). If a cross-linking agent is added more than necessary, strong foaming property tends to occur, and the mechanical strength tends to deteriorate due to an increase in the cross-linking density.

In addition to the above, as additives, flame retardants, plasticizers, antioxidants, ultraviolet absorbers, colorants, various fillers, internal mold release agents, and other processing aids can be used. Among these auxiliaries, those having no active hydrogen group capable of reacting with isocyanate can be used by being mixed with polyisocyanate in advance.

The mold temperature at the time of injecting the foaming stock solution into the mold is usually 30 to 80 ° C, preferably 45 to 65 ° C. If the mold temperature at the time of injecting the foaming stock solution into the mold is less than 30 ° C., the production cycle is extended due to a decrease in the reaction rate, while if it is higher than 80 ° C., the reaction between the polyol and isocyanate is affected. When the reaction between water and isocyanate is excessively promoted, the foam collapses during foaming, the durability due to the local increase in urea bond, and the foam tactile sensation tend to deteriorate.

The curing time for foaming and curing the foam stock solution is preferably 10 minutes or less, more preferably 7 minutes or less, considering the production cycle of general vehicle seat pads, saddles, and the like.

When producing the soft mold foam of the present invention, each of the above components can be mixed using a high-pressure foaming machine, a low-pressure foaming machine, or the like, as in the case of a normal soft mold foam.

The polyisocyanate component and the polyol component are preferably mixed immediately before foaming. Other components can be premixed with the polyisocyanate component or the polyol component as long as they do not affect the storage stability of the raw material or the change in reactivity with time. The mixture may be used immediately after mixing, or may be stored and then used in the required amount as appropriate. In the case of a foaming apparatus having a structure capable of simultaneously introducing more than two components into the mixing portion, polyols, foaming agents, polyisocyanates, catalysts, defoaming agents, additives and the like can be individually introduced into the mixing portion.

Further, the mixing method may be either dynamic mixing in which mixing is performed in the machine head mixing chamber of the foaming machine or static mixing in which mixing is performed in the liquid feeding pipe, or both may be used in combination. In many cases, mixing of gaseous components such as physical foaming agents and liquid components is performed by static mixing, and mixing of components that can be stably stored as liquid is performed by dynamic mixing. The foaming device used in the present invention is preferably a high-pressure foaming device that does not require solvent cleaning of the mixing portion.

The mixed liquid obtained by such mixing is discharged into a mold (mold), foamed and cured, and then demolded.

In order to smoothly perform the above-mentioned demolding, it is also preferable to apply a mold release agent to the mold in advance. As the release agent to be used, a release agent usually used in the molding processing field may be used.

The product after demolding can be used as it is, but it is preferable to destroy the cell membrane of the foam under compression or reduced pressure by a conventionally known method to stabilize the appearance and dimensions of the subsequent product.

The molar ratio (NCO / NCO reactive group) at the time of mixed foaming of the total isocyanate group in the polyisocyanate composition of the present invention and the total isocyanate reactive group in the isocyanate reactive compound containing water is 0.7 to It is preferably 1.4 (isocyanate index (NCO INDEX) = 70 to 140), and more preferably 0.8 to 1.3 (NCO INDEX = 80 to 130) in consideration of foam durability and molding cycle.

If the isocyanate index is less than 70, the durability tends to decrease and the foaming property tends to increase excessively, and if it exceeds 140, the molding cycle is extended due to the long residual unreacted isocyanate, and the foam is foamed due to the delay in increasing the molecular weight. Cell collapse is likely to occur.

By using the polyisocyanate composition of the present invention, the apparent density measured by the method of JIS K6400 is 50 to 70 kg / m ³ , and 25% compression of the foam test piece with skin measured by the method B described in JIS K6400. The hardness is 100 to 300 N / 314 cm ² , the mechanical properties are 90 to 170% of elongation measured by the method described in JIS K6400, the tear strength is 5 to 10 N / cm, and the elastic modulus described in JIS K6400 is. A flexible polyurethane foam having a wet heat compression permanent strain of 23 to 53% and JIS K 6400 of 9% or less can be preferably obtained.

By using such a flexible polyurethane foam, it can be preferably used for a vehicle seat cushion, a seat back, a saddle, etc., which achieve both good ride comfort and high safety while ensuring viewpoint stability.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples. Unless otherwise specified, "parts" and "%" in the text are based on weight.

<Synthesis example of polyisocyanate composition>
MDI (M1) with an isomer content of 55.0% and MDI (M2) with an isomer content of 1.0% in a capacity: 1 L reactor with a stirrer, thermometer, cooler and nitrogen gas inlet tube. Was mixed at a weight ratio of 68.5 / 31.5, MDI (M3): 750 g adjusted to have an isomer content of 38.0% was charged, the temperature was raised to 55 ° C., and then a polyoxyalkylene polyol (polyoxyalkylene polyol) ( 100.0 g of polyol A-2) was charged, further 150.0 g of polyoxyalkylene polyol (polyol A-1) was charged, 0.07 g of acetylacetone zinc (Nasem zinc manufactured by Nippon Kagaku Sangyo Co., Ltd.) was charged as a reaction catalyst, and the temperature was 90 ° C. The temperature was raised to. The allophanization reaction was carried out for 1.5 hours while uniformly mixing with a stirring blade while maintaining the temperature. 0.14 g of benzoyl chloride was added to stop the allophanation reaction, and the mixture was cooled to room temperature to obtain a polyisocyanate composition (B1) (NCO content 23.0%).

Similarly, the polyisocyanate compositions shown in Table 3 using MDIs (M3 to M6) having an adjusted isomer content shown in Table 1, various polyoxyalkylene polyols (A) shown in Table 2, and a reaction catalyst. (B1 to B11) were obtained.

<Preparation of polyol premix>
In a mixer having a capacity of 100 L equipped with a stirrer, the polyol (C), the catalyst (D), the water as the foaming agent (E), and the foam stabilizer (F) are charged at the ratios shown in Table 4, and are uniform. Diol premix (P) was obtained by mixing with.

<Polyprethane (C)>
-Polyol C1: Polymerization initiator A polyoxyethylene polyoxypropylene polyol having an average number of functional groups of 3.0 and a hydroxyl value of 24 (mgKOH / g), Exenol 923 manufactured by Asahi Glass Co., Ltd.
-Polyol C2: Polyoxyethylene polyoxypropylene polyol having an average number of functional groups of the polymerization initiator = 3.0 and a hydroxyl value = 28 (mgKOH / g), Exenol 823 manufactured by Asahi Glass Co., Ltd.
-Polyol C3: Polyoxypropylene polyol having an average number of functional groups of the polymerization initiator = 3.0 and a hydroxyl value = 281 (mgKOH / g), Sanniks GP-600 manufactured by Sanyo Chemical Industries, Ltd.
<Catalyst (D)>
-Catalyst D1: 33% dipropylene glycol solution of triethylenediamine, TEDA-L33 manufactured by Tosoh Corporation.
-Catalyst D2: 70% dipropylene glycol solution of bis (2-dimethylaminoethyl) ether, TOYOCAT-ET manufactured by Tosoh Corporation
<Blowing agent (E)>
・ Water (city water)
<Foaming agent (F)>
-Foam conditioner F: Silicone-based defoamer, SZ-1325 manufactured by Toray Dow Corning.

<Foam molding>
The polyisocyanate compositions (B1 to B11) synthesized with the polyol premix (P) having the blending ratios shown in Table 4 were adjusted to a liquid temperature of 25 ± 1 ° C. The polyisocyanate composition (B1 to B11) is mixed with the polyol premix (P) at a ratio of the isocyanate index values shown in Tables 5 and 6, mixed with a mixer (7000 rpm) for 7 seconds, and placed in a mold. After injecting and foaming the soft foam, it was taken out from a mold, and after foaming by roller crushing, the physical properties of the obtained soft foam were measured.
[Foaming conditions]
Mold temperature: 55-60 ° C
Mold shape: 100 x 300 x 300 mm
Mold material: Aluminum cure Conditions: 55-60 ° C x 6 minutes.

<Measurement of foam physical characteristics>
Apparent density, tensile strength, elongation, tear strength, elastic modulus, moist heat compression residual strain is the method described in JIS K6400, and compression residual strain is the method A described in JIS K6400, which is 25% of the test piece foam with skin. The compressive hardness (25% ILD) was measured by the method B described in JIS K6400.

As is clear from the results shown in Table 5, the flexible polyurethane foam obtained by the method of the present invention has an apparent density of 50 to 70 kg / m ³ , and the 25% compression hardness of the skinned foam test piece is 100 to 300 N / 314 cm. It was confirmed that good mechanical properties and durability were exhibited in the range of ^2.

As shown in Table 6, in Comparative Example 1, the molecular weight of the denaturing agent was low and it could not act as a flexible cross-linking agent, resulting in a moist heat compression strain exceeding 9%. Further, even when a polyol other than the polyoxyalkylene polyol is used as in Comparative Examples 2 and 3, the result is that the wet heat compression strain exceeds 9% because the cross-linking point is not flexible. When the weight ratio of the oxyethylene unit in the polyoxyalkylene polyol exceeds 70% as in Comparative Examples 4 and 5, the affinity with water as a foaming agent is affected by the high ratio of the highly hydrophilic oxyethylene unit. The molding stability of the soft foam was impaired, and the foam collapsed during foaming, resulting in molding failure. In Comparative Example 6, the isomer content was low, the molding stability of the soft foam was impaired, and foam collapse occurred during foaming, resulting in molding failure.

From the above results, by using the polyisocyanate composition of the present invention, the apparent density of the flexible polyurethane foam is 50 to 70 kg / m ³ , and the 25% compression hardness of the foam test piece with skin is 100 to 300 N / 314 cm ² . Since it is possible to mold soft urethane foam having good mechanical properties and high durability in the range, it is extremely useful for vehicle seat cushions, seat backs and saddles that have both good riding comfort and high safety.

Claims (3)

A polyisocyanate composition containing an allophanate modified product of diphenylmethane diisocyanate and polyoxyalkylene diol (A).
A hydroxyl value of 25～120MgKOH / g of polyoxyalkylene diol (A), and the weight ratio of the oxypropylene units and oxyethylene units is 50 / 50-70 / 30, diphenylmethane diisocyanate, 2,2'- It contains diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate, and contains the total amount of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate with respect to the total amount of diphenylmethane diisocyanate. The amount is 10 to 50% by weight, and
A polyisocyanate composition characterized in that the isocyanate content of the polyisocyanate composition is in the range of 20 to 32% by weight. A method for producing a flexible polyurethane foam, which comprises reacting and foaming a mixed solution of the polyisocyanate composition, polyol (C), catalyst (D), foaming agent (E) and foaming agent (F) according to claim 1. The apparent density of the flexible polyurethane foam is 50 to 70 kg / m ³ , the 25% compressive hardness of the foam test piece with skin is in ^{the range of 100 to 300 N / 314 cm 2} , and the elastic modulus is 23 to 53%. The method for producing a flexible polyurethane foam according to claim 2 , wherein the mechanical properties are elongation of 90 to 170%, tear strength of 5 to 10 N / cm, and moist heat compression permanent strain of 9% or less. ..