JP2018165292A - Polyisocyanate composition for soft polyurethane foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyisocyanate composition for manufacturing a soft foam having good vibration absorption property with low rebound resilience, and achieving high mechanical physical property and low wet heat compressive permanent set even in a low density region of less than 55 kg/m.SOLUTION: The problem is solved by a polyisocyanate composition for soft polyurethane foam obtained by allophanatization of diphenylmethane diisocyanate in a specific component ratio range with a specific oxypropylene unit and polyoxyalkylene polyol having oxyethylene unit content width and specific initiator functional group number width.SELECTED DRAWING: None

Description

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

  For a long time, flexible polyurethane foam for automobile seat cushions (hereinafter also referred to as flexible foam) has been required to have high durability so that changes in the viewpoint of the driver due to reduced thickness are reduced even when riding for a long time. . On the other hand, in recent seat cushions, in order to reduce vibration transmitted from the road surface, it is required to suppress the resilience modulus of the foam low and to reduce the foam density as much as possible from the viewpoint of cost reduction. However, these low resilience and low density are known to significantly deteriorate foam durability, and establishment of a technology that achieves both durability, ride comfort and economy has been demanded.

  The polyisocyanate component is roughly divided into a TDI system mainly composed of a mixture of tolylene diisocyanate (hereinafter also referred to as TDI) and polyphenylpolymethylene polyisocyanate (hereinafter also referred to as p-MDI) and diphenylmethane diisocyanate (hereinafter referred to as MDI). MDI system mainly composed of a mixture of p-MDI). Since the TDI system has a high isocyanate group content and generates a large amount of carbon dioxide gas per unit weight due to reaction with water, the density can be reduced without increasing the 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 mechanical properties such as elongation and strength at break are excellent. However, TDI as a raw material has a high vapor pressure and strong toxicity, so that the working environment of the flexible polyurethane foam production site is likely to deteriorate. Moreover, the obtained flexible polyurethane foam has a problem of low durability. Furthermore, the urethane foam using TDI has a large density difference between the skin layer and the core layer of the foam, and even if the foam has the same 25% compression hardness and hysteresis loss rate, the surface feel is hard and the ride performance is poor.

On the other hand, compared with TDI-based flexible polyurethane foams, MDI-based flexible foams generally having a low impact elastic modulus are relatively easy to achieve both vibration absorption and durability in a high density region. However, MDI-based isocyanates, which have a lower NCO content than TDI, require a large amount of water to be added to reduce the density. In the low density region of less than 55 kg / m ³ that is required for seat cushions these days, isocyanate and water are required. Increased rigid urea bond generated by the reaction with the resin reduces the resilience from deformation of the resin, which deteriorates the durability and loses the good texture characteristic of the MDI flexible polyurethane foam. .

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

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

Japanese National Patent Publication No. 10-501830 Japanese Patent Laid-Open No. 11-217420

The present invention relates to an isocyanate composition for producing a flexible polyurethane foam, which has high mechanical properties and low wet heat compression set even in a low density region of less than 55 kg / m ³ , while having good vibration absorption due to low rebound resilience. , And a flexible foam having high vibration absorption, high mechanical properties, and high durability using the isocyanate composition, and further, a vehicle seat using the flexible foam that achieves both good riding comfort and high safety. The purpose is to provide cushions, seat backs and saddles.

  As a result of intensive 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 comprising MDI and a specific polyoxyalkylene polyol, and has led 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, and 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.

  (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 as described in (1) above, wherein the total content of diisocyanate and 2,4′-diphenylmethane diisocyanate is 10 to 50% by weight.

  (3) The polyisocyanate composition as described in (1) or (2) above, wherein the polyoxyalkylene polyol (A) has an average nominal hydroxyl functionality of 1.7 to 2.4.

  (4) A mixed liquid 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 the above (1) to (3). A process for producing a flexible polyurethane foam which is reacted and foamed.

(5) The apparent density of the flexible polyurethane foam is 50 to 70 kg / m ³ , the 25% compression hardness of the foamed test piece with skin is in the range of 100 to 300 N / 314 cm ² , and the impact resilience is 23 to 53%. The elongation as mechanical properties is 90 to 170%, the tear strength is 5 to 10 N / cm, and the wet heat compression set is 9% or less,
A process for producing a flexible polyurethane foam as described in (4) above.

  According to the flexible polyurethane foam molding composition containing the isocyanate composition for a flexible polyurethane foam of the present invention, it has good vibration absorption due to a low rebound resilience, and low wet heat compression set even in a low density region. It is possible to obtain a flexible polyurethane foam which has a high mechanical property and realizes prevention of 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 polyoxyalkylene polyol (A), and the hydroxyl value of the polyoxyalkylene polyol (A) is 25 to 120 mgKOH / g. A polyisocyanate having a weight ratio of oxypropylene unit to oxyethylene unit of 30/70 to 100/0 and an isocyanate content of the polyisocyanate composition of 20 to 32% by weight It is a composition.

  As MDI in the present invention, 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 isomer content). The amount of MDI used in the polyisocyanate composition is preferably 10 to 50% by weight, more preferably 20 to 45% by weight.

  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 resulting polyisocyanate composition at low temperatures is impaired, and the isocyanate storage location and piping In addition to constant heating in 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 will decrease and sufficient hardness as a seat cushion, seat back or saddle will not be secured, the reactivity will decrease, the molding cycle will be extended, and the foam foam rate will increase. 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. When the weight ratio of oxypropylene units is less than 30%, the amount of highly hydrophilic oxyethylene units increases too much. When water is used as the blowing agent, the molding stability of flexible polyurethane foam is high due to the high hydrophilicity. Is damaged, and foam collapse occurs during foaming.

  The polyoxyalkylene polyol (A) is at least one selected from the group consisting of a copolymer of oxypropylene units and oxyethylene units, a copolymer of oxypropylene units only, and a copolymer of oxyethylene units only. Can be used by adjusting to the above ratio.

  The polyoxyalkylene polyol (A) of the present invention can achieve 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 functionality is 1.7 to 2.4 and the hydroxyl value of the polyoxyalkylene polyol (A) is 35 to 80 mg KOH / g, a more excellent flexible polyurethane foam is obtained.

  Furthermore, 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, trimerization reaction and dimerization reaction other than urethanization and allophanate reaction are promoted, and the isocyanate during synthesis is solidified, Viscosity rises unexpectedly and tends to be unusable.

  In the present invention, when a flexible polyurethane foam is molded using a polyisocyanate composition containing an allophanate-modified product in which MDI is allophanate-modified with the polyoxyalkylene polyol (A), the allophanate group having the polyoxyalkylene polyol is flexible. It acts as a proper cross-linking agent, and electrostatic interaction occurs between allophanate bonds, urethane bonds and urea bonds in the resin, and by taking a pseudo-crosslinked structure, even in foams with low impact resilience, low moist heat It achieves compression set, high mechanical properties, and high durability.

  The allophanatization catalyst that can be used in the present invention can be appropriately selected from conventionally known catalysts. Examples thereof include acetylacetone metal complexes, carboxylates such as zirconium octylate, and dimethylaminoethoxyethanol. Secondary amines and the like can be used. In addition, the amount of the allophanatization 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).

  Allophanatization may be performed simultaneously with urethanization or after urethanization. When urethanization and allophanatization are performed simultaneously, the reaction may be performed in the presence of an allophanatization catalyst. When allophanatization is performed after urethanization, the urethanization reaction was performed for a predetermined time in the absence of the allophanatization catalyst. Thereafter, an allophanatization catalyst may be added to carry out the allophanatization reaction. After completion of the reaction, a reaction terminator such as benzoyl chloride, phosphoric acid, phosphoric acid ester or the like is added to the reaction system, and a termination reaction is performed at 30 to 100 ° C. for 1 to 2 hours to terminate the allophanatization reaction.

  The isocyanate group content of the polyisocyanate composition containing the allophanate modified product obtained as described above is 20 to 32% by weight. When 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 the moldability in the low density region cannot be ensured. When it exceeds 32% by weight, there are few allophanate structures containing oxypropylene units and oxyethylene units, the high mechanical properties of the present invention cannot be obtained, and the wet heat compression set reduction effect cannot be obtained.

  Next, the manufacturing method of the flexible polyurethane foam of this invention is demonstrated.

  As the method for producing the flexible polyurethane foam of the present invention, a foamed undiluted solution of the polyisocyanate composition, polyol (C), catalyst (D), water (E) as a foaming agent, and foam stabilizer (F) is used. Can be suitably used in the manufacturing method of a flexible polyurethane mold foam (hereinafter also referred to as a soft mold foam) in which is injected into a mold and then foam-cured.

  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 that easily exhibits excellent performance as a flexible polyurethane foam.

  When the hydroxyl value exceeds 40 mgKOH / g, the hardness of the flexible polyurethane foam becomes too high, and the flexibility may be lowered. On the other hand, if the polyurethane foam is less than 20 mgKOH / g, the hardness of the polyurethane foam obtained is too soft for a vehicle seat flexible polyurethane foam, and poor mixing due to high viscosity tends to occur.

  As a polyether polyol having a hydroxyl value of 20 to 40 mg KOH / g and an average functional group number of 2 to 4, for example, 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, Examples 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, 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-eicosane-1,2-ethylene glycol, 2-n Octacosane-1,2-ethylene glycol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol, ethylene oxide or propylene oxide adduct of bisphenol A, hydrogenated bisphenol A, 3-hydroxy-2,2-dimethylpropyl- Mention may be made of low molecular weight polyols such as 3-hydroxy-2,2-dimethylpropionate, trimethylolpropane, glycerin, pentaerythritol. Also, 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. Etc.

  The polyether polyols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to these initiators and cyclic ethers such as tetrahydrofuran can be used alone or in combination of two or more. When using 2 or more types of polyether polyol together, it is preferable that the hydroxyl value 20-40 mgKOH / g and the average number of functional groups are 2-4 as the whole component used together.

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

  Furthermore, polyols such as polyester polyols and polycarbonate polyols can be used in combination with the polyol (C) 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-methylmorpholine, N-ethylmorpholine, 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 amine, dimethylethanolamine, N-trioxyethylene-N, N-dimethylamine, N, N-dimethyl-N-hexanolamine, or organic acid salts thereof, 1-methimidazole, 2- Methylimidazole, 1,2-dimethylimidazole, 2,4-dimethylimidazole Imidazole compounds such as 1-butyl-2-methylimidazole, stannous octoate, dibutyltin dilaurate, organometallic compounds such as zinc naphthenate, 2,4,6-tris (dimethylaminomethyl) phenol, 2,4,6 -Tris (dialkylaminoalkyl) hexahydro-S-triazine, potassium acetate, potassium 2-ethylhexanoate and the like.

  The type of the catalyst is not particularly limited as long as it can realize a suitable foam cell foaming rate and production cycle, but is added in an amount of 0.1 to 5 parts by weight with respect to the polyol (C) in terms of foam odor and the like. It is preferable.

  The blowing agent (E) used in the present invention is preferably a carbon dioxide gas generated by a reaction between an isocyanate group and 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 a range of up to 6 parts by weight with respect to 100 parts by weight of polyol (C) to increase the expansion ratio.

  As the foam stabilizer (F) used in the present invention, a conventionally known organosilicon surfactant can be used. For example, SZ-1327, SZ-1325, SZ-1336, manufactured by Toray Dow Corning, SZ-3601, Momentive Y-10366, L-5309, Evonik B-8724LF2, B-8715LF2, Shin-Etsu Chemical F-122, and the like. 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).

  In addition, a crosslinking 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 preferred addition amount of the crosslinking agent is preferably up to 5 parts by weight per 100 parts by weight of the polyol (C). When the crosslinking agent is added more than necessary, strong foaming properties are produced, or the mechanical strength tends to deteriorate due to an increase in the crosslinking density.

  In addition to the above, flame retardants, plasticizers, antioxidants, ultraviolet absorbers, colorants, various fillers, internal mold release agents, and other processing aids can be used as additives. Of these auxiliaries, those that do not have an active hydrogen group capable of reacting with isocyanate can be mixed with polyisocyanate in advance and used.

  The mold temperature when the foaming stock solution is poured into the mold is usually 30 to 80 ° C, preferably 45 to 65 ° C. When the mold temperature at the time of pouring the foaming stock solution into the mold is less than 30 ° C., it leads to the extension of the production cycle due to a decrease in the reaction rate. When the reaction between water and isocyanate is excessively promoted, the foam collapses during foaming, and the durability due to local increase of urea bonds and the foam feel are likely to deteriorate.

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

  When the flexible mold foam of the present invention is produced, 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 flexible mold foam.

  The polyisocyanate component and the polyol component are preferably mixed immediately before foaming. Other components can be mixed in advance with the polyisocyanate component or the polyol component in such a range that does not affect the storage stability of the raw material and the change over time of the reactivity. These mixtures may be used immediately after mixing or may be used in appropriate amounts after storage. In the case of a foaming apparatus having a structure capable of simultaneously introducing more than two components into the mixing part, polyols, foaming agents, polyisocyanates, catalysts, foam stabilizers, additives and the like can be individually introduced into the mixing part.

  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. Mixing of a gaseous component such as a physical foaming agent and a liquid component is often performed by static mixing, and mixing of components that can be stably stored as a liquid is often performed by dynamic mixing. The foaming apparatus used in the present invention is preferably a high-pressure foaming apparatus that does not require solvent cleaning of the mixing part.

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

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

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

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

  If the isocyanate index is less than 70, the durability and self-foaming properties tend to increase excessively, and if it exceeds 140, the unreacted isocyanate remains long and the molding cycle is prolonged, while foam foaming is delayed due to the high 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 the 25% compression of the foamed test piece with skin measured by the method B of JIS K6400 The hardness is 100 to 300 N / 314 cm ² , the mechanical properties are 90 to 170% elongation measured by the method described in JIS K6400, the tear strength is 5 to 10 N / cm, and the rebound resilience described in JIS K6400 is A flexible polyurethane foam having a wet heat compression set of 23% to 53% and JIS K6400 of 9% or less can be suitably obtained.

  By using such a flexible polyurethane foam, it can be preferably used for vehicle seat cushions, seat backs, saddles and the like that achieve both good riding comfort and high safety while ensuring viewpoint stability.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. Unless otherwise specified, “part” and “%” in the text are based on weight.

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

  Similarly, the polyisocyanate composition described in Table 3 using MDI (M3 to M6) having the isomer content described in Table 1, various polyoxyalkylene polyols (A) described 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) were charged at the ratios shown in Table 4, respectively. To obtain a polyol premix (P).

<Polyol (C)>
Polyol C1: Polyoxyethylene polyoxypropylene polyol having a polymerization initiator average functional group number 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 a polymerization initiator average functional group number of 3.0 and a hydroxyl value of 28 (mgKOH / g), Exenol 823 manufactured by Asahi Glass Co., Ltd.
Polyol C3: polymerization initiator average functional group number = 3.0, hydroxyl value = 281 (mgKOH / g) polyoxypropylene polyol, Sanyo Chemical Industries, Ltd. Sannix GP-600
<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
<Foaming agent (E)>
・ Water (city water)
<Foam stabilizer (F)>
-Foam stabilizer F: Silicone foam stabilizer, SZ-1325 manufactured by Toray Dow Corning.

<Form molding>
The polyol premix (P) having the blending ratio shown in Table 4 and the synthesized polyisocyanate compositions (B1 to B11) 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, and mixed for 7 seconds with a mixer (7000 rpm) into the mold. After injecting and foaming the flexible foam, it was taken out from the mold, and after the foam was broken by roller crushing, the physical properties of the obtained flexible foam were measured.
[Foaming conditions]
Mold temperature: 55-60 ° C
Mold shape: 100 × 300 × 300mm
Mold material: Aluminum cure Conditions: 55-60 ° C. × 6 minutes.

<Measurement of physical properties of foam>
Apparent density, tensile strength, elongation, tear strength, impact resilience, wet heat compression residual strain are the methods described in JIS K6400, and compression residual strain is A method described in JIS K6400, 25% of the test piece foam with skin. The compression hardness (25% ILD) was measured by the B method described in JIS K6400.

As is apparent 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 foamed test piece with skin is 100 to 300 N / 314 cm. ^In the range of ² , it was confirmed that good mechanical properties and durability were exhibited.

  As shown in Table 6, in Comparative Example 1, the molecular weight of the modifier was low and it could not work as a flexible cross-linking agent, so the wet heat compression strain exceeded 9%. Further, when a polyol other than the polyoxyalkylene polyol was used as in Comparative Examples 2 and 3, the wet heat compression strain exceeded 9% because it was not a flexible crosslinking point. 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 blowing agent is high due to the high hydrophilic oxyethylene unit ratio. The molding stability of the flexible foam was impaired, and foam collapse occurred during foaming, resulting in poor molding. In Comparative Example 6, the isomer content was low, the molding stability of the flexible foam was impaired, foam collapse occurred during foaming, and molding failed.

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 foamed test piece with skin is 100 to 300 N / 314 cm ² . Since a flexible urethane foam having good mechanical properties and high durability in a range can be molded, it is extremely useful for a vehicle seat cushion, a seat back and a saddle that achieve both good riding comfort and high safety.

Claims (5)

A polyisocyanate composition comprising a modified allophanate of diphenylmethane diisocyanate and a polyoxyalkylene polyol (A),
The hydroxyl value of the polyoxyalkylene polyol (A) is 25 to 120 mg KOH / g, and the weight ratio of the oxypropylene unit to the oxyethylene unit is 30/70 to 100/0, and
A polyisocyanate composition having an isocyanate content in the range of 20 to 32% by weight.   The diphenylmethane diisocyanate contains 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, and 4,4′-diphenylmethane diisocyanate, and the total amount of diphenylmethane diisocyanate is 2,2′-diphenylmethane diisocyanate and 2 The polyisocyanate composition according to claim 1, wherein the total content of 4,4'-diphenylmethane diisocyanate is 10 to 50% by weight.   3. The polyisocyanate composition according to claim 1, wherein the polyoxyalkylene polyol (A) has an average nominal hydroxyl functionality of 1.7 to 2.4.   The flexible polyurethane foam which reacts the liquid mixture of the polyisocyanate composition in any one of Claims 1 thru | or 3, a polyol (C), a catalyst (D), a foaming agent (E), and a foam stabilizer (F), and makes it foam. Manufacturing method. The apparent density of the flexible polyurethane foam is 50 to 70 kg / m ³ , the 25% compression hardness of the foamed test piece with skin is in the range of 100 to 300 N / 314 cm ² , and the impact resilience is 23 to 53%. 5. The method for producing a flexible polyurethane foam according to claim 4, wherein the elongation as mechanical properties is 90 to 170%, the tear strength is 5 to 10 N / cm, and the wet heat compression set is 9% or less. .