JP2004155856A - Method for producing polyurethane foam - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain polyurethane foam which has excellent reactivity and adhesiveness to a material to be bonded such as a steel plate, concrete, etc., even in the case of using a hydrofluoroalkane having excellent environmental protection as a blowing agent. <P>SOLUTION: The method for producing the polyurethane foam comprises reacting a polyol component with an isocyanate component in the presence of a catalyst containing an N-substituted imidazole compound and 1,4-azabicyclo[2,2,2]octane and the blowing agent containing water and the hydrofluoroalkane. The polyurethane foam is obtained by the method. <P>COPYRIGHT: (C)2004,JPO

Description

【００５６】
表１に示された結果から、各実施例においては、発泡剤として環境保全面に優れているヒドロフルオロアルカンが用いられた場合であっても、反応時間が短いことから反応性が高く、モールドへの付着量が少ないことから、接着性に優れたポリウレタンフォームが得られることがわかる。
【００５７】
【発明の効果】
本発明によれば、発泡剤として環境保全に優れたヒドロフルオロアルカンを使用した場合であっても、反応性に優れ、かつ鋼板やコンクリート等の被着材との接着性に優れたポリウレタンフォームが得られる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polyurethane foam and a method for producing the same. More specifically, the present invention relates to a polyurethane foam that can be suitably used as a heat insulating material for building materials, electric refrigerators, freezing warehouses, bathtubs, and the like, and a method for producing the same.
[0002]
[Prior art]
In recent years, from the viewpoint of avoiding destruction of the ozone layer and global warming in the stratosphere, reduction of hydrochlorofluoroalkane, which is the most common foaming agent for polyurethane foam, has been called for. Regarding HCFC-141b, in Japan, It will be banned from use in 2004. Under such circumstances, hydrofluoroalkanes such as HFC-245fa and HFC-365mfc have been studied as foaming agents for polyurethane foams. However, when they are used, not only does the reactivity decrease due to the deterioration of the compatibility with the raw materials, but also the density of the polyurethane foam near the skin decreases, so that the adhesive strength to the adherend such as steel plate or concrete is reduced. Is reduced.
[0003]
For example, a rigid polyurethane foam has been proposed in which, when an imidazole-based compound is used as a catalyst and water and hydrofluorocarbon are used in combination as a foaming agent, the compounding solution is prevented from deteriorating and storage stability is enhanced (for example, see Patent Document 1). . However, this rigid polyurethane foam has a drawback that it not only does not sufficiently satisfy the adhesiveness to an adherend such as a steel plate or concrete but also has poor reactivity.
[0004]
[Patent Document 1]
JP, 2002-220429, A
[Problems to be solved by the invention]
The present invention provides a polyurethane foam having excellent reactivity and excellent adhesion to adherends such as steel plates and concrete, even when a hydrofluoroalkane excellent in environmental protection is used as a foaming agent. As an issue.
[0006]
[Means for Solving the Problems]
The present invention relates to a method for preparing a polyol component and an isocyanate component in the presence of a catalyst containing an N-substituted imidazole compound and 1,4-diazabicyclo [2.2.2] octane, a blowing agent containing water and a hydrofluoroalkane. The present invention relates to a method for producing a polyurethane foam to be reacted.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention has one significant feature in that an N-substituted imidazole compound and 1,4-diazabicyclo [2.2.2] octane are used in combination as a catalyst. As described above, since the N-substituted imidazole compound and 1,4-diazabicyclo [2.2.2] octane are used in combination, when a hydrofluoroalkane is used as a blowing agent in the production of a polyurethane foam, Even if it is used, it is superior in reactivity to the case where N-substituted imidazole compound is used alone or 1,4-diazabicyclo [2.2.2] octane is used alone, and it can be applied to steel sheets and concrete. An excellent effect of being able to obtain a polyurethane foam having excellent adhesiveness to the adhesive is exhibited.
[0008]
The reason why such a remarkably excellent effect is exhibited is not clear, but probably, when the N-substituted imidazole compound and 1,4-diazabicyclo [2.2.2] octane are used in combination, Is used alone, the resinification reaction between the polyol component and the isocyanate component at the center of the polyurethane foam is accelerated, that is, not only the reactivity of both is increased, but also the polyurethane foam having a low surface temperature. It is considered that this is based on the fact that excellent curability can be exhibited even in the vicinity of the surface.
[0009]
Examples of the N-substituted imidazole compound include 1,2-dimethylimidazole, 1-methylimidazole, 1-isobutyl-2-methylimidazole, 1-n-butyl-2-methylimidazole, 1-ethylimidazole, and 1-ethyl- 2-methylimidazole, 1-benzylimidazole, 1-phenylimidazole, 1-hydroxyethylimidazole, 1-hydroxyethyl-2-methylimidazole, and the like, each of which is used alone or in combination of two or more. be able to. Among these, from the viewpoint of catalytic activity per unit weight and handleability, at least one selected from the group consisting of 1,2-dimethylimidazole, 1-methylimidazole and 1-isobutyl-2-methylimidazole is preferred. And 1,2-dimethylimidazole are more preferred.
[0010]
Since the amount of the N-substituted imidazole compound varies depending on the type of the polyurethane foam, it cannot be unconditionally determined. Usually, the amount of the N-substituted imidazole compound is preferably from 0.3 to 100 parts by weight of the polyol component, from the viewpoint of increasing the reactivity between the polyol component and the isocyanate component and improving the adhesion to the adherend. It is at least 0.5 part by weight, more preferably at least 0.5 part by weight, and preferably at most 7 parts by weight, more preferably at most 5 parts by weight from the viewpoint of maintaining the strength of the polyurethane foam. Therefore, from these viewpoints, the amount of the N-substituted imidazole compound is preferably 0.3 to 7 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polyol component.
[0011]
The amount of 1,4-diazabicyclo [2.2.2] octane cannot be determined unconditionally because it depends on the type of polyurethane foam. Usually, the amount of 1,4-diazabicyclo [2.2.2] octane is preferably at least 0.3 part by weight from the viewpoint of increasing the reactivity between the polyol component and the isocyanate component with respect to 100 parts by weight of the polyol component. And more preferably 0.5 part by weight or more, and from the viewpoint of maintaining the strength of the polyurethane foam, preferably 7 parts by weight or less, more preferably 5 parts by weight or less. Accordingly, from these viewpoints, the amount of 1,4-diazabicyclo [2.2.2] octane is preferably from 0.3 to 7 parts by weight, more preferably from 0.5 to 7 parts by weight, based on 100 parts by weight of the polyol component. 5 parts by weight.
[0012]
The catalyst may be composed of an N-substituted imidazole compound and 1,4-diazabicyclo [2.2.2] octane, but other catalysts may be contained as long as the object of the present invention is not impaired. May be.
[0013]
Other catalysts include, for example, 2-methyl-1,4-diazabicyclo [2.2.2] octane, N-methylmorpholine, N-ethylmorpholine, N- (dimethylaminoethyl) morpholine, N, N, N ', N'-tetramethylethylenediamine, N, N, N', N'-tetramethylpropylenediamine, N, N, N ', N'-tetramethyl-1,6-hexanediamine, N, N-dimethylpiperazine , N, N ', N'-trimethylaminoethylpiperazine, tris (3-dimethylaminopropyl) amine, N, N-dimethylcyclohexylamine, N, N-dimethylbenzylamine, N, N, N', N ", N "-pentamethyldiethylenetriamine, bis (2-dimethylaminoethyl) ether, 1,8-diazabicyclo [5.4.0] undecene-7, N N ', N "-tris (3-dimethylaminopropyl) hexahydro-s-triazine, 6-dimethylamino-1-hexanol, 5-dimethylamino-3-methyl-1-pentanol, N, N-dimethylethanolamine N, N-dimethylaminoethoxyethanol, N, N-dimethylaminoethoxyethoxyethanol, N- (3-dimethylaminopropyl) -N-methylaminoethanol, N- (2-dimethylaminoethyl) -N-methylamino Tertiary amine catalysts such as ethanol and derivatives thereof, and salts thereof with acids such as carboxylic acid and carbonic acid; tin dibutyl diacetate, tin dibutyl dilaurate, tin di (2-ethylhexyl) dilaurate, di (2- Organic tin compounds such as tin (ethylhexanoate) and lead represented by lead di (2-ethylhexanoate) Metal catalyst, and the like. These may be used alone or used in combination of two or more.
[0014]
When a polyurethane foam is produced by spraying, the catalyst preferably contains an organometallic catalyst in order to rapidly foam and cure the polyol component and the isocyanate component. In this case, suitable organometallic catalysts include tin dibutyl diacetate, tin dibutyl dilaurate, tin di (2-ethylhexyl) dilaurate, tin di (2-ethylhexanoate) and lead di (2-ethylhexanoate) At least one selected from the group consisting of
[0015]
Further, the catalyst may contain a potassium salt such as potassium acetate or potassium 2-ethylhexanoate, or a quaternary ammonium salt, which is a trimerization (isocyanurate) catalyst for isocyanate. These catalysts can be used alone or in combination of two or more.
[0016]
Since the amount of the other catalyst cannot be determined unconditionally because the reaction mechanism and reaction characteristics vary depending on the type of the catalyst, it is preferable to appropriately adjust the amount according to the type of the catalyst and the isocyanate index.
[0017]
The foaming agent may be composed of water and a hydrofluoroalkane, and may contain other foaming agents in addition to the above as long as the object of the present invention is not hindered.
[0018]
The amount of water is preferably 0.5 to 5 parts by weight, more preferably 1 to 4 parts by weight, based on 100 parts by weight of the polyol, from the viewpoint of imparting strength to the polyurethane foam and maintaining flexibility.
[0019]
Examples of the hydrofluoroalkane include 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1-difluoroethane (HFC-152a), 1,1,1,2,3,3,3- Heptafluoropropane (HFC-227ea), 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,3,3-pentafluorobutane (HFC-365mfc), 1,1 , 2,3,3-pentafluoropropane (HFC-245ea), 1,1,2,2,3-pentafluoropropane (HFC-245ca), 1,1,1,2,2-pentafluoropropane (HFC -245cb), 1,1,2,2,3,3-hexafluoropropane (HFC-236ca), 1,1,1,4,4,4-hexafluorobutane (H C-356mffm) such hydrofluoroalkane may be mentioned, these can be used alone or in admixture of two or more thereof. Among these, 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1,3,3- Pentafluoropropane (HFC-245fa) and 1,1,1,3,3-pentafluorobutane (HFC-365mfc) are preferred.
[0020]
The amount of the hydrofluoroalkane is preferably from 10 to 50 parts by weight, more preferably from 10 to 40 parts by weight, based on 100 parts by weight of the polyol, from the viewpoint of improving the thermal conductivity of the polyurethane foam and economical efficiency.
[0021]
Other foaming agents may be used as long as they do not inhibit the object of the present invention. From the viewpoint of protection of the global environment, low-boiling hydrocarbons such as cyclopentane, normal pentane, isopentane, normal butane, and isobutane, air, carbon dioxide, and the like are preferable as other blowing agents.
[0022]
Since the amount of the other foaming agent differs depending on the type and the density of the intended polyurethane foam, it cannot be unconditionally determined. Therefore, it is preferable to appropriately adjust the amount according to these.
[0023]
Examples of the polyol component include polyester polyols, polyether polyols, phenolic resin-based polyols, Mannich polyols, and the like, and these can be used alone or in combination of two or more.
[0024]
The polyester polyol can be produced by a condensation reaction between a dicarboxylic acid and a polyhydric alcohol.
[0025]
Examples of the dicarboxylic acid used in the polyester polyol include, for example, a saturated aliphatic dicarboxylic acid such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid; a saturated aliphatic dicarboxylic acid such as cyclohexanedicarboxylic acid; phthalic acid Aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid; unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; halogen-containing dicarboxylic acids such as tetrabromophthalic acid; Acid anhydrides and the like can be mentioned, and these can be used alone or in combination of two or more. The dicarboxylic acid may optionally contain a tribasic or higher polybasic acid such as trimellitic acid or pyromellitic acid.
[0026]
Examples of the polyhydric alcohol constituting the polyester polyol include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6- Hexanediol, trimethylolpropane, glycerin, pentaerythritol, diglycerin, dextrose, sorbitol and the like can be mentioned, and these can be used alone or in combination of two or more.
[0027]
Polyether polyols use a compound having two or more active hydrogen-containing groups as a starting material compound, and ring-opening of an alkylene oxide such as ethylene oxide, propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, and styrene oxide. It can be produced by an addition reaction.
[0028]
Compounds having two or more active hydrogen-containing groups include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, and 1,6-hexanediol; Trihydric or higher polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, diglycerin, dextrose, sorbitol, and sucrose; polyhydric phenols such as resorcinol, hydroquinone, and bisphenol A; ethylenediamine, tolylenediamine, and 1,3-propane Polyamines such as diamine and isophorone diamine; alkanolamines such as diethanolamine and triethanolamine; and modified products thereof. These may be used alone or in combination of two or more. It can be used.
[0029]
A phenolic resin-based polyol is a compound having two or more active hydrogen-containing groups determined in the molecule by the Tsuerevichinoff method. Examples of phenolic resin-based polyols include novolak-type phenolic resin-based polyols, resol-type phenolic-based polyols, and benzylic ether-type phenolic-based polyols obtained by subjecting phenols and aldehydes to a condensation reaction in the presence of a catalyst. And modified phenolic resin-based polyols obtained by ring-opening addition of alkylene oxide or alkylene carbonate to some or all of the phenolic hydroxyl groups of the phenolic resin.
[0030]
Mannich polyols can be obtained by subjecting phenols, aldehydes, alkanolamines, and the like to a condensation reaction and, if necessary, performing a ring-opening addition reaction of an alkylene oxide such as ethylene oxide or propylene oxide.
[0031]
For example, when manufacturing a rigid polyurethane foam used for heat insulating materials such as building materials, among the polyol components, aromatic dicarboxylic acid-based polyester polyols, polyhydric phenol-based polyether polyols and Mannich polyols have heat resistance and flame retardancy. From the viewpoint of phthalic acid, terephthalic acid, and isophthalic acid, and more preferably at least one selected from the group consisting of phthalic acid-based polyester polyols, Mannich polyols and alkylene oxide adducts of bisphenol A.
[0032]
The content of at least one selected from the group consisting of aromatic dicarboxylic acid-based polyester polyol, polyhydric phenol-based polyether polyol, and Mannich polyol in the polyol component is preferable from the viewpoint of imparting heat resistance and flame retardancy. Is 20 to 100% by weight, more preferably 30 to 100% by weight, still more preferably 40 to 100% by weight.
[0033]
Examples of the isocyanate component include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, and polymethylene polyphenylene. Aromatic polyisocyanates such as polyisocyanate, xylylene diisocyanate and naphthylene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate and lysine diisocyanate; alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate and isophorone diisocyanate Urethane bond, carbodiimide bond, uretoimine bond, allophanate bond, urea bond, buret If the polyisocyanate modified product, etc. containing one or more such isocyanurate bond and the like, which may be used alone or in admixture of two or more thereof.
[0034]
For example, when manufacturing rigid polyurethane foam used for heat insulating materials such as building materials, among these, from the viewpoint of reactivity, foam strength, heat resistance and flame retardancy, polymethylene polyphenylene polyisocyanate, urethane bond, carbodiimide A modified polyisocyanate having at least one bond such as a bond, a uretimine bond, an allophanate bond, a urea bond, a burette bond, an isocyanurate bond, or the like is preferable.
[0035]
The ratio between the polyol component and the isocyanate component may be adjusted according to the physical properties required for the desired polyurethane foam. Usually, the ratio between the two is adjusted so that the isocyanate index is 80 to 500.
[0036]
In the present invention, when producing a polyurethane foam, a foam stabilizer can be used if necessary. Any foam stabilizer may be used as long as it is generally used when producing a polyurethane foam.
[0037]
Representative examples of foam stabilizers include silicone surfactants such as dimethylpolysiloxane and polyoxyalkylene-modified dimethylpolysiloxane, and anionic surfactants such as fatty acid salts, sulfate esters, phosphate esters, and sulfonates. These can be used alone or in combination of two or more.
[0038]
Since the amount of the foam stabilizer differs depending on its type and the density of the intended polyurethane foam, it cannot be unconditionally determined. Therefore, it is preferable to appropriately adjust the amount according to the kind of the foam stabilizer.
[0039]
In addition, besides the foam stabilizer, for example, it is possible to use optional components such as a cross-linking agent, a flame retardant, a stabilizer, a pigment, a filler, a viscosity reducing agent, and a compatibilizer within a range in which an object of the present invention is not hindered. it can.
[0040]
For example, flame retardants include tricresyl phosphate, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate And the like, and these can be used alone or in combination of two or more.
[0041]
A polyurethane foam can be produced by reacting a polyol mixture with an isocyanate component.
[0042]
The polyol mixture can be prepared by mixing optional components such as a polyol component, a catalyst, a foaming agent and, if necessary, a foam stabilizer.
[0043]
The polyurethane foam can be produced, for example, by mixing and stirring a polyol mixture and an isocyanate component with a molding machine or the like, injecting the obtained mixture into a molding die, and foaming. More specifically, for example, after adjusting the temperature of the polyol mixture to about 5 to 15 ° C. using a tank or the like, an isocyanate component is used with a foaming machine such as an automatic mixing injection type foaming machine and an automatic mixing injection foaming machine. By mixing and reacting, a polyurethane foam can be produced.
[0044]
In the method for producing a polyurethane foam of the present invention, a blowing agent containing water and hydrofluoroalkane is used, but since a catalyst having a specific composition is used, adhesion to an adherend such as a metal is used. Polyurethane foam with improved properties can be produced quickly.
[0045]
Accordingly, the polyurethane foam obtained by the production method of the present invention can be used as a heat insulating material, a panel or board for building materials, an electric refrigerator, etc., formed by directly spraying on a wall or ceiling of a house or a building. It can be suitably used as a heat insulating material for refrigeration and stockers.
[0046]
【Example】
Examples 1 to 9 and Comparative Examples 1 and 2
A polyol component, a flame retardant, a foam stabilizer, a catalyst, and a foaming agent were mixed by a laboratory mixer so that the composition shown in Table 1 was obtained, to obtain a polyol mixture.
[0047]
Next, the obtained polyol mixture and an isocyanate component (manufactured by Sumika Bayer Urethane Co., Ltd., trade name: Sumidur 44V20, NCO: 31.4%) are subjected to a lab at 10 ° C. so that the isocyanate index becomes 110. The resulting mixture was mixed and stirred by a mixer, and 250 g of the obtained mixture was poured into a mold (inner size: 150 × 150 × 300 (height) mm) to form a rigid polyurethane foam free foam.
[0048]
The reactivity at the time of producing the rigid polyurethane foam and the adhesiveness of the obtained rigid polyurethane foam were examined based on the following methods. Table 1 shows the results.
[0049]
(Reactivity)
Cream time (hereinafter, referred to as CT), gel time (hereinafter, referred to as GT) and rise time (hereinafter, referred to as "free time") of 40 g of the mixture stirred in a 300 mL polycup (trade name, manufactured by Teraoka Co., Ltd.). RT).
[0050]
〔Adhesiveness〕
The mixture is poured into a vertical mold (internal size: 200 × 200 × 50 mm, where a polypropylene sheet is stuck on the entire inner wall of the mold) adjusted to 25 ° C. so that the pack ratio becomes 110% to form a polyurethane foam. It was molded and released after 10 minutes. The adhesion rate of the polyurethane foam to the mold (the ratio of the adhesion area of the polyurethane foam to the surface area inside the mold. The same applies hereafter; the unit is area%) was determined, and the adhesiveness of the foam was evaluated based on the following evaluation criteria.
In addition, the smaller the adhesion rate of the polyurethane foam to the mold, the smaller the brittleness of the polyurethane foam and the higher the adhesiveness.
[0051]
〔Evaluation criteria〕
：: No polyurethane foam adhered to the mold or a small amount of the polyurethane foam adhered (the polyurethane foam adhered to the mold was less than 5%)
Δ: When there is little adhesion of the polyurethane foam to the mold (the adhesion rate of the polyurethane foam to the mold is 5% or more and less than 30%)
×: When the amount of the polyurethane foam adhered to the mold is large (the adhesion rate of the polyurethane foam to the mold is 30% or more)
[0052]
In addition, each component used for the polyol mixture shown in Table 1 is as follows.
(1) Polyol component / polyol A: ethylene glycol-terephthalic acid polyester polyol (manufactured by OXID, trade name: Terol 250, hydroxyl value: 250 mgKOH / g)
Polyol B: Tolylenediamine propylene oxide-added polyol [manufactured by Asahi Glass Co., Ltd., trade name: Exenol 455AR, hydroxyl value: 450 mg KOH / g]
Polyol C: propylene oxide-added polyol of ethylenediamine [Mitsui Takeda Polyurethane Co., Ltd., trade name: polyol AE-300, hydroxyl value: 760 mgKOH / g]
Polyol D: a propylene oxide-added polyol of bisphenol A [manufactured by NOF Corporation, trade name: Uniol DA-400, hydroxyl value: 280 mgKOH / g]
-Polyol E: Mannich polyol (manufactured by OXID, trade name: Sanol R-350-X, hydroxyl value: 530 mgKOH / g)
[0053]
(2) Flame retardant / TCPP: tris (2-chloropropyl) phosphate (3) Silicone foam stabilizer / Nihon Unicar Co., Ltd., trade name: L-5340
(4) Blowing agent / HFC-245fa: 1,1,1,3,3-pentafluoropropane / HFC-365mfc: 1,1,1,3,3-pentafluorobutane
(5) Catalyst / KL-31: 1,4-diazabicyclo [2.2.2] 33% dioctane glycol solution of octane [manufactured by Kao Corporation, trade name: Kaolyzer No. 31]
KL-300: 1,2-dimethylimidazole / 1-methylimidazole = 50/50 (parts by weight) mixed solution [manufactured by Kao Corporation, trade name: Kaorizer No. 300]
DMI: 1,2-dimethylimidazole KL-120: 1-isobutyl-2-methylimidazole [manufactured by Kao Corporation, trade name: Kaolyzer No. 120]
Tin octoate: tin di (2-ethylhexanoate)
[Table 1]

[0056]
From the results shown in Table 1, in each of the examples, even when hydrofluoroalkane, which is excellent in environmental protection, was used as the foaming agent, the reactivity was high because of the short reaction time, It can be seen from the fact that the polyurethane foam excellent in adhesion can be obtained from the small amount of adhering to polyurethane.
[0057]
【The invention's effect】
According to the present invention, even when a hydrofluoroalkane excellent in environmental protection is used as a foaming agent, a polyurethane foam excellent in reactivity and excellent in adhesion to an adherend such as a steel plate or concrete can be obtained. can get.

Claims (5)

Polyurethane foam in which a polyol component and an isocyanate component are reacted in the presence of an N-substituted imidazole compound and a 1,4-diazabicyclo [2.2.2] octane-containing catalyst, water and a blowing agent containing hydrofluoroalkane. Manufacturing method. The method according to claim 1, wherein the N-substituted imidazole compound is at least one selected from the group consisting of 1,2-dimethylimidazole, 1-methylimidazole and 1-isobutyl-2-methylimidazole. The catalyst is further selected from the group consisting of tin dibutyl diacetate, tin dibutyl dilaurate, tin di (2-ethylhexyl) dilaurate, tin di (2-ethylhexanoate) and lead di (2-ethylhexanoate). 3. The process according to claim 1, wherein the process comprises one or more organometallic catalysts. The method according to any one of claims 1 to 3, wherein the polyol component contains at least 20% by weight of at least one selected from the group consisting of an aromatic dicarboxylic acid-based polyester polyol, a polyhydric phenol-based polyether polyol, and a Mannich polyol. . A polyurethane foam obtained by the production method according to claim 1.