Foamable urethane resin composition, polyurethane foam, and method for producing the same

Abstract

To provide a foamable urethane resin composition capable of producing a polyurethane foam with excellent moldability by employing light energy in a curing reaction.SOLUTION: A foamable urethane resin composition comprises an isocyanate component, a polyol component, a foaming agent, and a catalyst, wherein the catalyst includes a photobase generator that generates a base upon light irradiation and a base amplifier that generates a base by the action of the base generated from the photobase generator, the photobase generator and the base amplifier each being a compound having a carbamate structure or a carboxylic acid compound composed of a carboxylic acid and a basic compound, and the base generated from the photobase generator and the base amplifier being an amine or a guanidine.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a polyurethane foam suitable for use as a sound absorbing material or vibration damping material in vehicles, buildings, etc., and a method for producing the same. [Background technology]

[0002] In vehicles such as automobiles, sound-absorbing materials, vibration-proofing members, etc. are placed in areas that are sources of vibration and noise to reduce the transmission of vibration and the diffusion of noise. Foams such as polyurethane foam, which are lightweight and have high soundproofing and vibration-absorbing properties, are used for sound-absorbing materials and vibration-proofing members. Polyurethane foam, as described in Patent Document 1, for example, is produced by injecting a urethane foam resin composition containing an isocyanate component, a polyol component, a catalyst, a blowing agent, etc. into a mold and foaming it. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-80585 [Patent Document 2] International Publication No. 2009 / 019979 [Patent Document 3] International Publication No. 2020 / 045458 Summary of the Invention [Problem to be solved by the invention]

[0004] In the production of polyurethane foam, the foaming reaction and curing reaction begin immediately after mixing the isocyanate component, polyol component, catalyst, blowing agent, etc. During this process, the curing reaction may proceed faster than the foaming reaction, resulting in insufficient foaming, or the curing reaction may complete before the urethane foam resin composition has reached the corners and fine parts of the mold, resulting in molding defects.

[0005] Incidentally, as described in Patent Document 2 and the like, photocurable compositions that use light energy for the curing reaction are known. This type of photocurable composition contains a photobase generator and a curable compound. In the photocurable composition, the photobase generator generates a base upon irradiation with light, and the generated base promotes the curing reaction of the curable compound. A basic catalyst such as an amine is typically used in the production of polyurethane foam. Therefore, if the base generated upon irradiation with light could be used as a catalyst for producing polyurethane foam, it may be possible to control the start time and reaction rate of the curing reaction.

[0006] However, for polyurethane foam to exhibit soundproofing and vibration absorption properties, a certain thickness is required. Therefore, when foam molding is performed using light energy, the light irradiated from the surface of the composition does not penetrate deep into the composition, preventing the curing reaction from proceeding sufficiently. Furthermore, polyurethane foams are sometimes blended with black fillers to improve thermal conductivity, weather resistance, and other properties depending on the application. In this case, the irradiated light may be absorbed by the black filler, resulting in the curing reaction proceeding only in the surface layer.

[0007] In an attempt to improve the curing properties of a photobase generator, for example, Patent Document 3 describes a photocurable composition containing a photobase generator, a base amplifier, a polyfunctional isocyanate compound, and a polyhydric alcohol. The base amplifier is a compound that decomposes under the action of a base in the system and generates a new base. When a photobase generator and a base amplifier are used in combination, bases are generated in a chain reaction upon irradiation with light, accelerating the curing reaction (urethane bond formation reaction) of the composition.

[0008] However, the conventional photocurable compositions described in Patent Documents 2 and 3 do not undergo a foaming reaction when cured. Therefore, the effects of a photobase generator or a base multiplier on the foaming reaction, or the balance between the rates of the foaming reaction and the curing reaction, have not been considered. Furthermore, the case where a black filler is blended into the composition has not been considered.

[0009] The present disclosure has been made in view of the above circumstances, and aims to provide a urethane foam resin composition that uses light energy in the curing reaction and that can produce a polyurethane foam with good moldability. Another aim is to provide a polyurethane foam with excellent moldability using the urethane foam resin composition, and a method for producing the same. [Means for solving the problem]

[0010] (1) In order to solve the above problems, the urethane foam resin composition of the present disclosure comprises an isocyanate component, a polyol component, a blowing agent, and a catalyst. The catalyst comprises a photobase generator that generates a base upon irradiation with light, and a base multiplier that generates a base through the action of the base generated from the photobase generator. The photobase generator and the base multiplier are either compounds having a carbamate structure or carboxylic acid compounds composed of a carboxylic acid and a basic compound, and the base generated from the photobase generator and the base multiplier is an amine or guanidine.

[0011] The urethane foam resin composition of the present disclosure uses a photobase generator and a base amplifier as catalysts. The photobase generator has a structure in which a base (amine or guanidine) that serves as a catalyst for forming urethane bonds is protected by a carbamate structure or a carboxylic acid. When the photobase generator is irradiated with light, the protective structure is removed, releasing the base. The base amplifier also has a structure in which a base (amine or guanidine) that serves as a catalyst for forming urethane bonds is protected by a carbamate structure or a carboxylic acid. The base amplifier's protective structure is removed by the action of the base generated from the photobase generator, generating additional base. By selecting a combination of protective structure and base for the photobase generator and base amplifier that is less likely to affect the foaming reaction and achieves the desired curing reaction rate, the foaming reaction and curing reaction can be progressed in a balanced manner, improving moldability.

[0012] According to the urethane foam resin composition of the present disclosure, the catalyst does not act until light is irradiated, making it possible to adjust the timing of the start of the curing reaction. This allows the composition to be distributed to the corners and fine details of the mold after preparation, before the curing reaction progresses and the composition thickens. As a result, insufficient filling is suppressed, improving moldability. Therefore, the urethane foam resin composition of the present disclosure allows for the production of products with good moldability, even those with complex shapes. Furthermore, the urethane foam resin composition can be prepared in advance, improving workability.

[0013] The urethane foam resin composition of the present disclosure uses both a photobase generator and a base amplifier as catalysts. The base amplifier generates bases in a chain reaction, resulting in a larger amount of base being generated than when a photobase generator is used alone. This allows the curing reaction to proceed deep into the product, even when a thick product is manufactured. Furthermore, the curing reaction can proceed sufficiently even when a black filler is blended into the urethane foam resin composition.

[0014] (2) In the above configuration, the photobase generator is a compound having a carbamate structure, and may be one or more compounds selected from an o-nitrobenzene type compound, a dimethylbenzyloxy type compound, an o-acyloxime type compound, and a benzoin derivative, and the base generated from the photobase generator may be guanidine.

[0015] According to this configuration, guanidine can be released from the photobase generator using ultraviolet light as the irradiated light. According to this configuration, the foaming reaction and the curing reaction can proceed in a balanced manner without inhibiting the foaming reaction, thereby producing a polyurethane foam with good moldability. Furthermore, in the photobase generator of this configuration, the guanidine and the protective structure are bonded by a covalent bond. Therefore, the photobase generator remains stable until irradiated with light of a specific wavelength.

[0016] (3) In any of the above configurations, the base multiplier is a compound having a carbamate structure and is one or more compounds selected from the compounds represented by the following general formula (I), and the base generated from the base multiplier may be guanidine. [ka] [In formula (I), at least one of R1 and R2 is an electron-withdrawing group, R3 and R4 are hydrogen atoms or methyl groups, and Z is guanidine.] According to this configuration, guanidine is generated from the base amplifier by the action of the base generated from the photobase generator. According to this configuration, the foaming reaction and the curing reaction are allowed to proceed in a balanced manner without inhibiting the foaming reaction, thereby enabling the production of a polyurethane foam with good moldability. Furthermore, in the photobase amplifier of this configuration, the guanidine and the protective structure are bonded by a covalent bond. Therefore, the photobase amplifier remains stable until the base generated from the photobase generator acts on it.

[0017] (4) In any of the above configurations, the guanidine may be 1,1,3,3-tetramethylguanidine (TMG). TMG is a non-nucleophilic strong base that coordinates with water and isocyanate to promote the foaming reaction. Furthermore, because TMG is a strong base, it also promotes the reaction between isocyanate and polyol.

[0018] (5) In the above configuration (1), the photobase generator may be a carboxylic acid compound having a xanthone structure, and the base generated from the photobase generator may be a tertiary amine. According to this configuration, ultraviolet light can be used as the irradiated light to release the tertiary amine from the photobase generator. According to this configuration, the foaming reaction and the curing reaction can proceed in a balanced manner without inhibiting the foaming reaction, thereby producing a polyurethane foam with good moldability. The generated tertiary amine is strongly nucleophilic and easily coordinates with isocyanate and polyol. Therefore, it has a high effect of promoting the urethane bond formation reaction. Furthermore, even a small amount of tertiary amine can remove the protective structure of the base amplifier.

[0019] (6) In the above configuration (1) or (5), the base amplifier may be a carboxylic acid compound having a 9-fluorenylmethyloxycarbonyl group, and the base generated from the base amplifier may be a tertiary amine. According to this configuration, the tertiary amine is generated from the base amplifier by the action of the base generated from the photobase generator. According to this configuration, the foaming reaction and the curing reaction can proceed in a balanced manner without inhibiting the foaming reaction, thereby producing a polyurethane foam with good moldability. As mentioned above, the generated tertiary amine is strongly nucleophilic and easily coordinates with isocyanate and polyol. Therefore, even a small amount of base amplifier promotes the urethane bond formation reaction.

[0020] (7) In the above (1), (5), or (6), the tertiary amine may be triethylenediamine. This configuration allows the urethane bond-forming reaction to be promoted even with small amounts of the photobase generator and base amplifier. Therefore, the amounts of the photobase generator and base amplifier can be reduced, minimizing their impact on the physical properties of the polyurethane foam produced.

[0021] (8) In any of the above configurations, the content of the photobase generator may be 0.5 parts by mass or more and 4.0 parts by mass or less per 100 parts by mass of the polyol component. This configuration allows for the generation of a sufficient amount of base as a catalyst for the curing reaction and the base multiplier.

[0022] (9) In any of the above configurations, the content of the base multiplier may be 2.0 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the polyol component. With this configuration, a sufficient amount of base is generated by the action of the base generated from the photobase generator, allowing the foaming reaction and the curing reaction to proceed in a well-balanced manner.

[0023] (10) In any of the above configurations, the base generated by the photobase generator and the base multiplier may be the same. When the base is guanidine, the phototriggerability is excellent, and when the base is a tertiary amine, the effect of promoting the urethane bond formation reaction is high.

[0024] (11) In any of the above configurations, the urethane foam resin composition of the present disclosure may further contain a black pigment. This configuration allows production of a polyurethane foam excellent in weather resistance, soundproofing, and the like.

[0025] (12) The polyurethane foam of the present disclosure is obtained by foaming and curing a urethane foam resin composition having any of the above configurations. The polyurethane foam of the present disclosure has good moldability, and the foaming reaction and curing reaction proceed in a well-balanced manner, thereby achieving a desired cell (air bubble) structure. As a result, the desired properties of the foam are exhibited, and if a black pigment is contained, the properties of the black pigment are also exhibited.

[0026] (13) In the configuration of (12) above, the polyurethane foam may have a thickness of 5.0 mm or more. As described above, the urethane foam resin composition of the present disclosure allows the curing reaction to proceed sufficiently even when a thick polyurethane foam is produced. The polyurethane foam of this configuration is suitable for applications requiring a thick foam.

[0027] (14) The method for producing a polyurethane foam according to the present disclosure is one embodiment of the method for producing a polyurethane foam according to the above (12) or (13), and is characterized by comprising a step of irradiating a urethane foam resin composition according to any one of the above (1) to (11) with ultraviolet light to foam-mold it. According to the production method according to the present disclosure, a polyurethane foam can be produced with good moldability by the practical method of irradiating ultraviolet light. Furthermore, since the urethane foam resin composition can be prepared in advance, workability can be improved. [Effects of the Invention]

[0028] According to the urethane foam resin composition of the present disclosure, a curing reaction is initiated by light irradiation, and the foaming reaction and the curing reaction are allowed to proceed in a well-balanced manner, thereby enabling the production of a polyurethane foam with excellent moldability. The polyurethane foam of the present disclosure has good moldability and achieves a desired cell structure. According to the method for producing a polyurethane foam of the present disclosure, the polyurethane foam of the present disclosure can be produced with good moldability by a practical method. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a graph showing the change over time in viscosity of a urethane foam resin composition in the foam molding process of each sample produced in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, embodiments of the urethane foam resin composition, polyurethane foam, and method for producing the same according to the present disclosure will be described. Note that the embodiments are not limited to the following embodiments, and various modifications and improvements that can be made by those skilled in the art can be made.

[0031] <Urethane foam resin composition> The urethane foam resin composition of the present disclosure includes an isocyanate component, a polyol component, a blowing agent, and a catalyst.

[0032] [Isocyanate component] The isocyanate component is not particularly limited as long as it forms a urethane bond upon reaction with the polyol component. For example, it may be appropriately selected from tolylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate (MDI), triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, naphthalene diisocyanate, and derivatives thereof. Examples of derivatives include prepolymers obtained by reacting isocyanate with polyol, modified polyisocyanates, and polymeric MDI (polynuclear compounds) having three or more isocyanate groups and three or more benzene rings per molecule.

[0033] [Polyol component] The polyol component may be appropriately selected from polyhydric hydroxy compounds, polyether polyols, polyester polyols, polyether polyamines, polyester polyamines, alkylene polyols, urea-dispersed polyols, melamine-modified polyols, polycarbonate polyols, acrylic polyols, polybutadiene polyols, phenol-modified polyols, and the like.

[0034] For example, it is desirable to use polyether polyol as the main component. A "main component" is a component that accounts for 60% by mass or more when the entire polyol component is taken as 100% by mass. That is, as the polyol component, only polyether polyol may be used, or polyether polyol may be used as the main component in appropriate combination with other polyols. For example, from the viewpoint of improving moldability, it is desirable to use polyester polyol in combination. Furthermore, even when only polyether polyol is used, multiple types with different functional groups, molecular weights, compatibility, etc. may be used in combination.

[0035] The number of functional groups of the polyether polyol is preferably 2 or more and 4 or less. If the number of functional groups is less than 2, the chain reaction with the isocyanate component is likely to be interrupted, making it difficult to polymerize, which may result in reduced moldability. For example, polyether polyols with 2 functional groups are suitable because they do not form a crosslinked structure, making it easier to extinguish fire during combustion and improving flame retardancy. Polyether polyols with 3 or more functional groups are suitable because they form a crosslinked structure, thereby hardening the polyurethane foam and increasing its rigidity. However, if the number of functional groups exceeds 4, the polyurethane foam may have reduced elongation and reduced soundproofing properties. Furthermore, the mass average molecular weight of the polyether polyol is preferably 5,000 or more and 8,000 or less. If the mass average molecular weight is less than 5,000, the polyurethane foam may become hard and the soundproofing properties may be reduced. If the mass average molecular weight exceeds 8,000, the viscosity of the urethane foam resin composition becomes too high, making it difficult for the reaction with the isocyanate component and the foaming reaction to proceed.

[0036] [Foaming agent] The foaming agent is preferably water, but other foaming agents include methylene chloride and carbon dioxide (carbon dioxide gas).

[0037] [catalyst] The catalyst comprises a photobase generator that generates a base upon irradiation with light, and a base multiplier that generates a base by the action of the base generated from the photobase generator.

[0038] (1) Photobase generator The photobase generator is a compound having a carbamate structure or a carboxylic acid compound (carboxylate) composed of a carboxylic acid and a basic compound. The photobase generator has a structure in which a base, which serves as a catalyst for forming a urethane bond, is protected by a carbamate structure or a carboxylic acid. When the photobase generator is irradiated with light, the protective structure is removed and the base, amine or guanidine, is released. If carbon dioxide (CO2) is generated during the decomposition of the photobase generator, it also acts as a foaming agent. The compound used as the photobase generator may be one type or two or more types.

[0039] The carbamate structure is a structure in which O-C=O and N are bonded together. Examples include structures represented by the following general formulas (II) and (III). In formulas (II) and (III), R5 is preferably a structure having a benzene ring. [ka] [ka]

[0040] Compounds having a carbamate structure suitable as photobase generators include o-nitrobenzene type compounds, dimethylbenzyloxy type compounds, o-acyloxime type compounds, benzoin derivatives, etc. The general formulas of each are shown in order in the following formulas (IV) to (VII). [ka] [ka] [ka] [ka]

[0041] The base released from a compound having a carbamate structure is an amine or guanidine. Among these, guanidine is preferred because the photobase generator remains stable until irradiated with light of a specific wavelength and has excellent phototriggerability. Examples of guanidine include 1,1,3,3-tetramethylguanidine (TMG), diphenylguanidine (DPG), and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). A preferred photobase generator made of a compound having a carbamate structure is a TMG-based photobase generator, which is an o-nitrobenzene-type compound in which the base released upon irradiation with light is TMG. One example of a TMG-based photobase generator is 1-nitro,3,4-methyletherbenzenecarbamate-TMG, whose chemical formula is shown in Formula (VIII) below. [ka]

[0042] Examples of the carboxylic acid compound include 2-(3-benzoylphenyl)propanoic acid, 2-xanthone acetate, (E)-8-ethylidene-2-methoxy-5,6,7,8-tetrahydronaphthalene-1-carboxylic acid, etc. The general formulas of these compounds are shown in the following formulae (IX) to (XI), respectively. [ka] [ka] [ka]

[0043] The basic compound of the carboxylic acid compound is an amine or guanidine that is released as a base upon irradiation with light. Tertiary amines are particularly preferred due to their high urethane bond-forming reaction acceleration effect. Examples of tertiary amines include triethylenediamine (TEDA, also known as 1,4-diazabicyclo[2.2.2]octane), N,N-dimethyldodecylamine, and bis(2-dimethylaminoethyl) ether. A preferred photobase generator made of a carboxylic acid compound is an amine-based photobase generator that has a xanthone structure and releases a tertiary amine base upon irradiation with light. One example of an amine-based photobase generator is di(2-(2-xanthone)propanoic acid)-TEDA, whose chemical formula is shown in Formula (XII) below. [ka]

[0044] The content of the photobase generator is desirably 0.5 parts by mass or more per 100 parts by mass of the polyol component from the viewpoint of generating a sufficient amount of base as a catalyst for the curing reaction and the base multiplier. Conversely, if the amount of the photobase generator is too much, the amount of components that react with visible light increases, and there is a risk that the base release reaction will proceed before light irradiation. Therefore, the content is desirably 4.0 parts by mass or less per 100 parts by mass of the polyol component.

[0045] (2) Base multiplier The base amplifying agent is a compound having a carbamate structure or a carboxylic acid compound (carboxylate) composed of a carboxylic acid and a basic compound. The carbamate structure is as described above. The base amplifying agent has a structure in which a base, which serves as a catalyst for forming a urethane bond, is protected by a carbamate structure or a carboxylic acid. The base amplifying agent's protective structure is removed by the action of a base generated from a photobase generator, and an amine or guanidine base is additionally generated. The base generated from the base generator not only functions as a catalyst for the base amplifying agent but also activates the hydroxyl groups of the polyol component. The reaction in which a base is generated from the base amplifying agent is an acid-base equilibrium reaction. For example, when a base coordinates to a polyol as a catalyst, the equilibrium reaction shifts toward base generation. This promotes base generation from the base amplifying agent. If carbon dioxide is generated during the decomposition of the base amplifying agent, it also acts as a foaming agent. The compound used as the base amplifying agent may be one type or two or more types. The bases generated from the photobase generator and the base amplifying agent may be the same or different.

[0046] Compounds having a carbamate structure suitable as base amplifiers include compounds represented by the above-mentioned general formula (I). Examples of electron-withdrawing groups for R1 and R2 include fluorenyl groups, organic sulfoxide groups, cyano groups, nitro groups, ester groups, carbonyl groups, amide groups, and pyridyl groups. Furthermore, when R1 or R2 is not an electron-withdrawing group, R1 or R2 may be a hydrogen atom or a methyl group.

[0047] As a base multiplier consisting of a compound having a carbamate structure, a TMG-based base multiplier having a tert-butyl,9-fluorenylmethyloxycarbonyl group and in which the base released by the action of the base generated from the photobase generator is TMG is suitable. As an example of a TMG-based base multiplier, the chemical formula of 2,7-di-tert-butyl,9-fluorenylmethyloxycarbonyl-TMG is shown in the following formula (XIII). [ka]

[0048] As the base amplifier made of a carboxylic acid compound, an amine-based base amplifier having a 9-fluorenylmethyloxycarbonyl group and a tertiary amine as the base released by the action of the base generated from the photobase generator is suitable. As an example of an amine-based base amplifier, the chemical formula of di(2-ene-3-(9-fluorenylmethyloxycarboxylic acid)butanoic acid)-TEDA is shown in the following formula (XIV). [ka]

[0049] The content of the base multiplier is preferably 2.0 parts by mass or more per 100 parts by mass of the polyol component from the viewpoint of generating a sufficient amount of base by the action of the base generated from the photobase generator. Conversely, if the amount of the base multiplier is too large, precipitation may occur, so the content is preferably 10.0 parts by mass or less per 100 parts by mass of the polyol component.

[0050] [Other ingredients] In addition to the above-mentioned materials, the urethane foam resin composition of the present disclosure may contain, as appropriate, known materials used in the production of polyurethane foam, such as chain extenders, foam stabilizers, crosslinkers, antistatic agents, viscosity reducers, stabilizers, fillers, and colorants. Furthermore, a flame retardant may be added to impart flame retardancy to the polyurethane foam. Examples of chain extenders include ethylene glycol, diethylene glycol, propylene glycol, 3-methyl-1,5-pentanediol, and 1,9-nonanediol. Examples of foam stabilizers include polyether-modified silicone compounds and polyester-modified silicone compounds. Various pigments can be used as colorants, and black pigments in particular can improve the weather resistance and soundproofing properties of the polyurethane foam.

[0051] <Polyurethane foam> The polyurethane foam of the present disclosure is a foamed and cured product obtained by foaming and curing the urethane foam resin composition of the present disclosure. The size, shape, color, and the like of the polyurethane foam may be appropriately determined depending on the application. The urethane foam resin composition of the present disclosure allows the curing reaction to proceed not only on the surface but also deep within, making it possible to produce polyurethane foams with a relatively large thickness. For example, the thickness of the polyurethane foam can be 5.0 mm or more, 7.0 mm or more, or even 10 mm or more. Furthermore, the urethane foam resin composition of the present disclosure is less likely to cause insufficient filling of the molding die, making it possible to produce polyurethane foams with various shapes depending on the application. Furthermore, the urethane foam resin composition of the present disclosure allows the curing reaction to proceed even when a black filler is blended, making it possible to produce black polyurethane foams.

[0052] <Method of manufacturing polyurethane foam> The polyurethane foam of the present disclosure is produced by irradiating the urethane foam resin composition of the present disclosure with light and foaming it. The urethane foam resin composition may be prepared, for example, as follows: First, a premix polyol is prepared by premixing a polyol component with a blowing agent other than the isocyanate component, a catalyst, and the like. Next, the isocyanate component is mixed with the prepared premix polyol. The premix polyol and the isocyanate component may be mixed by mechanical stirring using a stirring blade or by spraying the two materials at high pressure using a high-pressure jet injection foaming device or the like, causing them to collide and mix (impingement stirring method). Compared to mechanical stirring methods, the impingement stirring method eliminates the need for a container cleaning step required after each mixing, improving yield and thereby reducing production costs. The premix polyol and the isocyanate component are desirably blended so that the isocyanate index (the equivalent ratio of isocyanate groups to active hydrogen groups) is 1.0 to 1.5, preferably 1.0 to 1.2. If the isocyanate index is less than 1.0 or more than 1.5, moldability may decrease.

[0053] The prepared urethane foam resin composition is then poured into a mold or the like and irradiated with light to foam-mold it. The mold may or may not be sealed. The illuminance and dose of light may be adjusted depending on the type of photobase generator and base amplifier so that the desired curing reaction proceeds. For example, when the illuminance of light is set to 30 mW / cm 2 More than 100mW / cm 2 Below, the light irradiation dose is 800mJ / cm 2 More than 8000mJ / cm 2 The following is recommended: The light irradiation should be carried out continuously during the foam molding.

[0054] Examples of light include X-rays, ultraviolet light, and visible light. For example, ultraviolet light is preferably used because it is possible to easily irradiate light of a single wavelength using an LED lamp or the like. In this case, a preferred embodiment of the method for producing a polyurethane foam of the present disclosure includes a step of irradiating a urethane foam resin composition with ultraviolet light to form a foam. The wavelength of the ultraviolet light may be 10 nm or more and 400 nm or less, and preferably 200 nm or more. An LED, a halogen lamp, or the like may be used as the light source.

[0055] The foam molding may be carried out at room temperature or under heating. When the foam molding is carried out under heating, the temperature of the urethane foam resin composition may be set to 30°C or higher and 100°C or lower. The method for producing a polyurethane foam of the present disclosure may include other steps in addition to the foam molding step. For example, the foam molding step may be preceded by a cooling step of cooling the urethane foam resin composition, or the foam molding step may be followed by a heating step of heating the resulting polyurethane foam. The temperature in the cooling step may be set to -20°C or higher and 20°C or lower. The temperature in the heating step may be set to 30°C or higher and 100°C or lower.

[0056] As an example of the curing reaction in the foam molding process, the reaction process when a TMG-based photobase generator (TMG-PBG) and a TMG-based base multiplier (TMG-BA) are used is shown in the following formulas (i) to (iii). [ka]

[0057] First, as shown in formula (i), when TMG-PBG (1-nitro, 3,4-methyl ether benzene carbamate-TMG) is irradiated with light, it decomposes, releasing CO2, to produce the base TMG. Next, as shown in formula (ii), TMG-BA (tert-butyl, 9-fluorenylmethyloxycarbonyl-TMG) decomposes, releasing CO2, using the generated TMG as a catalyst, to produce the base TMG in a chain reaction. Then, as shown in formula (iii), TMG generated from TMG-PBG and TMG-BA functions as a catalyst for the urethane bond-forming reaction between the isocyanate component (MDI) and the polyol component (polypropylene glycol). Separately, a foaming reaction also occurs due to the gas generated by the reaction of the isocyanate component with water, producing a polyurethane foam, which is a foamed and cured product. [Example]

[0058] Next, the present disclosure will be described more specifically with reference to examples. <Sample production> First, 100 parts by mass of polypropylene glycol (PPG) (DOW Corporation's "VORANOL® CP 6001," average molecular weight 6000, number of functional groups 3) serving as the polyol component was mixed with 1 part by mass of diethylene glycol (chain extender), 1.3 parts by mass of water (blowing agent), the catalyst shown in Table 1 below, 1 part by mass of a silicone-based foam stabilizer (Dow-Toray Industries, Inc.'s "VORASURF® SZ-1333"), and 2 parts by mass of a carbon-based black pigment (Dainichiseika Color & Chemicals Mfg. Co., Ltd.'s "FT 1576 BLACK") to prepare a premix polyol. Furthermore, a polymeric MDI-containing isocyanate agent (Tosoh Corporation's "Millionate MR-200") was prepared as the isocyanate component. Next, the premix polyol and isocyanate agent were mixed by stirring with a stirring blade to prepare a urethane foam resin composition. The urethane foam resin composition was then injected into the cavity of the mold, and measurement of the viscosity of the urethane foam resin composition was initiated using a vibration viscometer. Then, 60 or 180 seconds after the start of stirring, irradiation with ultraviolet light at a wavelength of 365 nm was initiated, and foam molding was carried out at room temperature with the top of the mold open. UV irradiation was continued throughout the foam molding process. Five types of polyurethane foam samples were produced in this manner. Samples 1 and 2, shown in Table 1 below, are included in the concept of polyurethane foams of the present disclosure. Samples 1 and 2 had a thickness of 10 mm.

[0059] The constituent materials and blending amounts of the urethane foam resin composition are shown in Table 1. Details of the catalysts used are as follows. Catalyst A: TMG-based photobase generator (TMG-PBG in the above formula (i)) Catalyst B: TMG-based base multiplier (TMG-BA in the above formula (ii)) Catalyst C:TMG Catalyst D: a solution of triethylenediamine (TEDA) dissolved in dipropylene glycol (DPG) at a concentration of 33% by mass ("TEDA-L33" manufactured by Tosoh Corporation). [Table 1]

[0060] <Sample evaluation> The change in viscosity of the urethane foam resin composition over time during the foam molding process for each sample is shown in Figure 1. The produced samples were evaluated for demoldability and moldability as follows.

[0061] [Evaluation method] (1) Demovability For samples in which the viscosity of the urethane foam resin composition reached 30 Pa·s within 300 seconds from the start of ultraviolet irradiation, the curing reaction was determined to have progressed sufficiently and the demoldability was good.

[0062] (2) Formability For samples in which the viscosity of the urethane foam resin composition was 10 Pa·s or less within 60 seconds after the start of ultraviolet irradiation, the urethane foam resin composition filled the cavity of the mold without leaving any voids, and the moldability was determined to be good.

[0063] [Evaluation results] The evaluation results of demoldability and moldability are summarized in Table 1. In the evaluation results column of Table 1, good demoldability is indicated by a circle, and poor demoldability is indicated by an x. Good moldability is indicated by a circle, and poor moldability is indicated by an x.

[0064] As shown in Figure 1 and Table 1, in Samples 1 and 2, which used a photobase generator and a base amplifier catalyst in which the base was protected by a specific structure, the curing reaction proceeded after UV irradiation, resulting in a viscosity curve (curing curve) that was well balanced with the foaming reaction, and both demoldability and moldability were good. In contrast, in Samples 3 and 4, which used TMG and TEDA catalysts in which the base was not protected, the demoldability was good, but the curing reaction proceeded before UV irradiation and the viscosity increase rate was high, resulting in insufficient foaming and filling, and poor moldability. Furthermore, in Sample 5, which used only a photobase generator as a catalyst, the viscosity increase rate was slow and the curing reaction did not proceed sufficiently, so the desired polyurethane foam could not be obtained. [Industrial Applicability]

[0065] Polyurethane foams using the urethane foam resin composition of the present disclosure are suitable for use as sound absorbing materials, vibration damping materials, etc. in vehicles, buildings, etc.

Claims

1. The composition comprises an isocyanate component, a polyol component, a blowing agent, and a catalyst; The catalyst comprises a photobase generator that generates a base upon irradiation with light, and a base multiplier that generates a base by the action of the base generated from the photobase generator; the photobase generator and the base amplifier are a compound having a carbamate structure or a carboxylic acid compound composed of a carboxylic acid and a basic compound, The urethane foam resin composition is characterized in that the base generated from the photobase generator and the base multiplier is an amine or guanidine.

2. The urethane foam resin composition according to claim 1, wherein the photobase generator is a compound having a carbamate structure and is at least one selected from the group consisting of an o-nitrobenzene-type compound, a dimethylbenzyloxy-type compound, an o-acyloxime-type compound, and a benzoin derivative, and the base generated from the photobase generator is guanidine.

3. The urethane foam resin composition according to claim 1, wherein the base multiplier is a compound having a carbamate structure and is one or more compounds selected from the group consisting of compounds represented by the following general formula (I), and the base generated from the base multiplier is guanidine: 【Chemistry 1】 [In formula (I), R １ and R ２ At least one of R is an electron withdrawing group, ３ and R ４ is a hydrogen atom or a methyl group, and Z is guanidine.

4. 4. The urethane foam resin composition according to claim 2, wherein the guanidine is 1,1,3,3-tetramethylguanidine (TMG).

5. 2. The urethane foam resin composition according to claim 1, wherein the photobase generator is a carboxylic acid compound having a xanthone structure, and the base generated from the photobase generator is a tertiary amine.

6. 2. The urethane foam resin composition according to claim 1, wherein the base multiplier is a carboxylic acid compound having a 9-fluorenylmethyloxycarbonyl group, and the base generated from the base multiplier is a tertiary amine.

7. 7. The urethane foam resin composition according to claim 5, wherein the tertiary amine is triethylenediamine.

8. 2. The urethane foam resin composition according to claim 1, wherein the content of the photobase generator is 0.5 parts by mass or more and 4.0 parts by mass or less per 100 parts by mass of the polyol component.

9. 2. The urethane foam resin composition according to claim 1, wherein the content of the base multiplier is 2.0 parts by mass or more and 10.0 parts by mass or less per 100 parts by mass of the polyol component.

10. 2. The urethane foam resin composition according to claim 1, wherein the base generated from the photobase generator and the base multiplier are the same.

11. The urethane foam resin composition according to claim 1, further comprising a black pigment.

12. A polyurethane foam obtained by foaming and curing the urethane foam resin composition according to claim 1.

13. 13. The polyurethane foam according to claim 12, having a thickness of 5.0 mm or more.

14. A method for producing a polyurethane foam, comprising a step of irradiating the urethane foam resin composition according to claim 1 with ultraviolet light to foam-mold it.

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