Flame-retardant sound-insulating material for vehicle

Abstract

This flame-retardant sound-insulating material for vehicles is provided with a polyurethane foam obtained by foam-molding a urethane resin composition. The urethane resin composition comprises (A) an isocyanate component, (B) a polyol component, (C) a flame-retardant plasticizer, and (D) an antioxidant. The isocyanate component (A) comprises a mixture of 2, 4 '-diphenylmethane diisocyanate and 4, 4'-diphenylmethane diisocyanate, and at least one type of modified body selected from a carbodiimide modified body and a uretonimine modified body in the mixture.

Description

Technical Field

[0001] The present disclosure relates to a flame-retardant sound insulating material for a vehicle used in an engine room or the like of a vehicle. Background Art

[0002] In vehicles such as motor vehicles, various countermeasures are implemented to reduce the noise leaking to the outside of the vehicle and the vehicle interior. For example, in the engine room of the vehicle, in order to achieve the reduction of the radiated sound from the engine as a noise source, sound insulation materials such as engine hoods, side covers, and oil pan covers are arranged around the engine. In recent years, in order to further improve the sound insulation, attempts have been made to arrange sound insulation materials around fuel piping, transmissions, etc. For example, in the sound insulation material arranged near the rotating body constituting the transmission, in order to avoid deformation and interference with the rotating body, the desired rigidity is required. In particular, rigidity at high temperatures is important, and it is required that deformation such as sagging does not occur even at high temperatures (sag resistance). In addition, in such a use environment around the engine, flame retardancy is required in addition to sound insulation.

[0003] For example, Patent Document 1 describes a flame-retardant sound-insulating and vibration-proofing material for a vehicle using a soft polyurethane foam obtained by reacting an isocyanate component with a polyol component and foaming the foam. Patent Document 1 describes that the heat degradation resistance and flame retardancy of the polyurethane foam are improved by making the main component of the isocyanate component a monomer MDI containing diphenylmethane diisocyanate and its carbodiimide modified product and / or uretonimine modified product.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2003-97645

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 5-105811 Summary of the invention

[0008] Problems to be solved by the invention

[0009] In the polyurethane foam described in patent document 1, as isocyanate component, one or more modified bodies selected from carbodiimide modified bodies and uretonimine modified bodies are used. If modified bodies are used, the intermolecular cohesion is improved, so the rigidity of polyurethane foam is improved. However, if the rigidity becomes high, the foam is difficult to melt during combustion, so the combustion continues and the flame retardancy is reduced. In this way, the improvement of rigidity is in a contradictory relationship with the improvement of flame retardancy.

[0010] The present disclosure has been made in view of such actual circumstances, and an object of the present disclosure is to provide a flame-retardant sound-insulating material for a vehicle having desired rigidity and flame retardancy in addition to sound insulation.

[0011] Means used to solve problems

[0012] (1) In order to solve the above problems, the flame-retardant sound-insulating material for vehicles disclosed herein is a flame-retardant sound-insulating material for vehicles comprising a polyurethane foam obtained by foaming a urethane resin composition, characterized in that the urethane resin composition comprises (A) an isocyanate component, (B) a polyol component, (C) a flame-retardant plasticizer, and (D) an antioxidant, and the (A) isocyanate component comprises a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, and at least one of the modified forms of the mixture selected from a carbodiimide modified form and a uretonimine modified form.

[0013] In the flame-retardant sound-insulating material for a vehicle disclosed herein, a polyurethane foam having desired sound-insulating properties, rigidity, and flame retardancy is achieved by using a specific isocyanate component as a raw material and a flame-retardant plasticizer and an antioxidant in combination. With respect to the isocyanate component, diphenylmethane diisocyanate is appropriately referred to as "MDI", 2,4'-diphenylmethane diisocyanate is appropriately referred to as "2,4'-MDI", and 4,4'-diphenylmethane diisocyanate is appropriately referred to as "4,4'-MDI".

[0014] By using a modified body as an isocyanate component, the intermolecular cohesive force is improved, so that a polyurethane foam with high rigidity not only at room temperature but also at high temperature can be obtained. The modified body is manufactured by a carbodiimidization reaction in which the NCO groups of two MDIs are condensed with each other, and then a uretonimide reaction of further adding a molecule of MDI to the generated carbodiimide (carbodiimide modified body). As a secondary reaction of the carbodiimidization reaction of MDI, a uretonimide (uretonimine modified body) is also generated in a chemically balanced reactive manner. It is generally believed that by the progress of the carbodiimidization reaction, most of the reaction products are uretonimine modified bodies. In this specification, in order to include all of the products obtained by the carbodiimidization reaction of either or both of 2,4'-MDI and 4,4'-MDI in the modified body, it is referred to as "a modified body selected from one or more of the carbodiimide modified body and the uretonimine modified body". This may also be expressed as “carbodiimide-modified product and / or uretonimine-modified product.” Carbodiimide-modified products and uretonimine-modified products can be obtained by a known method, for example, by reacting a single component MDI or a plurality of components including isomers using a catalyst such as a phosphoric acid ester.

[0015] The polyurethane foam constituting the flame-retardant sound insulation material for vehicles of the present disclosure (hereinafter appropriately referred to as "the polyurethane foam of the present disclosure") has a flame-retardant plasticizer. The flame-retardant plasticizer enters between the crystals of polyurethane at high temperatures, softening the polyurethane foam and making it easy to melt. For example, if a simple plasticizer without flame retardancy is used, although the polyurethane foam can be easily melted during combustion, there is a risk that the polyurethane foam itself will also burn and the fire will become larger. In this regard, in the polyurethane foam of the present disclosure, since a flame-retardant plasticizer is used, there is no such risk. In this way, in the polyurethane foam of the present disclosure, by using a modified body as the isocyanate component, even if the rigidity of the foam is increased, the foam is easy to melt during combustion due to the addition of a flame-retardant plasticizer, and the reduction in flame retardancy can be suppressed.

[0016] If a flame retardant plasticizer is added, the flame retardancy of the polyurethane foam is improved, but if the amount added is increased from the viewpoint of improving the flame retardancy, there is a hidden danger that the polyurethane foam softens and the rigidity is reduced. In this regard, in the polyurethane foam disclosed in the present invention, an antioxidant is used in combination to ensure flame retardancy while maintaining the rigidity of the polyurethane foam. The effect of the antioxidant is as follows. If polyurethane is thermally decomposed, the molecules are cut and low molecular weight components are generated. Low molecular weight components are easy to ignite, thus promoting the continuation of combustion. If an antioxidant is added, the thermal decomposition of polyurethane can be suppressed, and the generation of low molecular weight components can be suppressed, so the ignition components can be reduced. That is, in the polyurethane foam disclosed in the present invention, by adding an antioxidant to preventively reduce the components that are easy to ignite, flame retardancy can be imparted even if the flame retardant plasticizer is not added in excess. As a result, a balance between rigidity and flame retardancy that was previously difficult to achieve is achieved.

[0017] Incidentally, a flame retardant composition for liquid polyurethane composed of 50 to 99% by weight of a flame retardant organophosphorus compound and 50 to 1% by weight of tribromoneopentyl alcohol (TBNPA) is described in Patent Document 2. A method of further adding antioxidants such as hydroquinone compounds and trivalent organophosphorus compounds to a mixture of a flame retardant organophosphorus compound and TBNPA is described in Patent Document 2. In Patent Document 2, the purpose is to provide a composition that can impart flame retardancy using TBNPA with a low viscosity liquid. Therefore, the use of an antioxidant is not necessary, and there is no record of the effect exerted by the combined use with a flame retardant organophosphorus compound. In addition, for the polyurethane foam used, only the method in which the isocyanate component is toluene diisocyanate (TDI) is recorded, and there is no technical idea of ​​improving the rigidity of the polyurethane foam in Patent Document 2.

[0018] (2) In the above configuration, the modified product of the (A) isocyanate component may be contained in an amount of 19% by mass or more, when the total amount of the urethane resin composition is 100% by mass. Alternatively, the modified product may be contained in an amount of 30% by mass or less. With these configurations, it is easy to achieve a balance between the rigidity and flame retardancy of the polyurethane foam.

[0019] (3) In any of the above configurations, the content of the flame retardant plasticizer (C) may be 3.7% by mass or more, when the total weight of the urethane resin composition is 100% by mass. Alternatively, the content of the flame retardant plasticizer may be 6.5% by mass or less. With these configurations, it is easy to achieve a balance between the rigidity and flame retardancy of the polyurethane foam.

[0020] (4) In any of the above configurations, the flame retardant plasticizer (C) may include a phosphoric acid ester. According to this configuration, the polyurethane foam can be softened with a relatively small amount, and moldability is also good.

[0021] (5) In any of the above-mentioned structures, the following structure can be adopted: when the total amount of the polyurethane resin composition is 100% by mass, the content of the (D) antioxidant is 1.6% by mass or more. In addition, the following structure can be adopted: the content of the antioxidant is 2.4% by mass or less. According to these structures, the generation of low molecular weight components caused by the thermal decomposition of polyurethane can be effectively suppressed. As a result, even if the amount of the flame retardant plasticizer is small, the desired flame retardancy can be imparted. For example, when this structure is combined with the above-mentioned structures (2) and (3), it is effective in imparting the desired rigidity and flame retardancy to the polyurethane foam.

[0022] (6) In any of the above configurations, the antioxidant (D) may be a hindered phenol compound. According to this configuration, the effect of inhibiting the thermal decomposition of polyurethane can be improved. For example, if this configuration is combined with the configuration of (4), the rigidity and flame retardancy of the polyurethane foam can be further improved. Furthermore, it is more preferable to combine the configurations of (2), (3), and (5).

[0023] Effects of the Invention

[0024] The flame-retardant sound-insulating material for a vehicle disclosed in the present invention has desired rigidity and flame retardancy in addition to sound insulation. DETAILED DESCRIPTION

[0025] Hereinafter, embodiments of the flame-retardant sound-insulating material for a vehicle of the present disclosure will be described. In addition, the embodiments are not limited to the following embodiments, and can be implemented in various modified and improved forms that can be performed by those skilled in the art.

[0026] In the flame-retardant sound-insulating material for a vehicle disclosed in the present invention, the composition other than the polyurethane foam is not particularly limited. The flame-retardant sound-insulating material for a vehicle disclosed in the present invention may be composed of only the polyurethane foam, or may be composed of a combination of the polyurethane foam and other components. For example, in the case where the flame-retardant sound-insulating material for a vehicle disclosed in the present invention is embodied as an engine hood, the engine hood may be a single-layer structure of polyurethane foam, or may be a multi-layer structure having a sound insulation layer composed of polyurethane foam and a skin layer covering the surface thereof. In addition, the "vehicle" as a use includes, in addition to motor vehicles, airplanes, trams, etc.

[0027] <Composition of polyurethane foam>

[0028] The polyurethane foam disclosed herein is a foamed molded product of a urethane resin composition having (A) an isocyanate component, (B) a polyol component, (C) a flame retardant plasticizer, and (D) an antioxidant.

[0029] (A) Isocyanate component

[0030] The isocyanate component has a mixture of 2,4'-MDI and 4,4'-MDI, and at least one of the mixture selected from one or more modified bodies of carbodiimide modified bodies and uretonimine modified bodies. The content ratio of 2,4'-MDI and 4,4'-MDI in the mixture can be appropriately determined in consideration of rigidity and formability. As described above, the modified body includes a product obtained by carbodiimidization reaction of 2,4'-MDI or 4,4'-MDI, and a product obtained by carbodiimidization reaction of 2,4'-MDI and 4,4'-MDI.

[0031] From the viewpoint of improving the rigidity of the polyurethane foam, it is preferred to increase the content of the modified body in the isocyanate component as much as possible. For example, when the entire urethane resin composition is set to 100% by mass, the content of the modified body is preferably 19% by mass or more. More preferably, it is 21% by mass or more. On the other hand, if the content of the modified body is too large, it is difficult for the foam to melt during combustion, and it is difficult for the fire to fall. In view of this, the content of the modified body is preferably 30% by mass or less. More preferably, it is 28% by mass or more.

[0032] The isocyanate component can also have a prepolymer formed by the reaction of MDI and a polyol on the basis of a mixture and a modified body. In the case of having a prepolymer, compared with the case of not having a prepolymer, the viscosity of the carbamate resin composition becomes higher and the formability improves. When the entirety of the carbamate resin composition is set to 100% by mass, the prepolymer content ratio is preferably 18% by mass or more and 30% by mass or less. For example, if MDI is reacted with a polyol having a functional group number of 3, a prepolymer having three carbamate bonds can be obtained. Among them, it is preferably a prepolymer of isocyanate ends obtained by reacting MDI with a bifunctional polyether polyol. Here, as a bifunctional polyether polyol, a polyether polyol having a molecular weight of about 1000 can be cited.

[0033] As isocyanate components, mixtures, modified bodies, and prepolymers are described, but as long as the polyurethane foam of the present disclosure can be achieved without hindering the effects brought about by these components, isocyanate compounds other than these components are not excluded. As the isocyanate compound, for example, polymeric MDI (multinuclear body) having three or more isocyanate groups and benzene rings in one molecule can be cited. However, if polymeric MDI is contained, a cross-linked structure is formed in the polyurethane foam, so the foam is difficult to melt during combustion. As a result, there is a hidden danger of reducing flame retardancy, so it is not preferred.

[0034] (B) Polyol component

[0035] As the polyol component, there are known polyols, 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, etc. In the case of manufacturing the polyurethane foam of the present disclosure, polyether polyols are used as the main component. "Main component" refers to a component that accounts for more than 60% by mass when the entirety of the polyol component is set to 100% by mass. Thus, as the polyol component, only polyether polyols are used, or polyether polyols are used as the main component and other polyols are used in appropriate combination. For example, from the viewpoint of improving formability, polyester polyols are preferably used in combination. In addition, in the case of using only polyether polyols, a variety of polyether polyols with different functional group numbers, molecular weights, compatibility, etc. can also be used in combination.

[0036] The number of functional groups of the polyether polyol is preferably 2 or more and 4 or less. When the number of functional groups is less than 2, the chain reaction with the isocyanate component is easily interrupted, and it is difficult to polymerize, so the formability is reduced. For example, a polyether polyol with a functional group number of 2 does not form a cross-linked structure, so it is easy to make the fire fall during combustion and improve the flame retardancy, which is suitable in this respect. The polyether polyol with a functional group number of 3 or more forms a cross-linked structure, which hardens the polyurethane foam and improves the rigidity, which is suitable in this respect. However, if the number of functional groups is greater than 4, the elongation of the polyurethane foam decreases, resulting in a reduction in sound insulation.

[0037] In addition, the mass average molecular weight of the polyether polyol is preferably 5000 to 8000. When the mass average molecular weight is less than 5000, the polyurethane foam becomes hard, resulting in a decrease in sound insulation. When the mass average molecular weight is greater than 8000, the viscosity of the urethane resin composition becomes too high, and the reaction with the isocyanate component and the foaming operation become difficult.

[0038] (C) Flame retardant plasticizer

[0039] As flame retardant plasticizers, halogen or non-halogen phosphorus compounds used as flame retardants can be cited. Halogen phosphorus compounds lack plasticity, so it is necessary to increase the amount of compounding, and there is also a hidden danger of reducing foaming formability. Therefore, non-halogen phosphorus compounds are preferred. Flame retardant plasticizers can be liquid or solid, and are preferably liquid from the viewpoint of mixing with liquid materials such as isocyanate components. As flame retardant plasticizers, for example, phosphoric acid esters such as trimethyl phosphate and tributyl phosphate are preferred.

[0040] From the viewpoint of fully exerting the effect of suppressing the decrease in flame retardancy, when the entire urethane resin composition is set to 100% by mass, the content of the flame retardant plasticizer is preferably 3.7% by mass or more. More preferably, it is 4.0% by mass or more. On the other hand, from the viewpoint of avoiding the decrease in rigidity caused by the addition of the flame retardant plasticizer, the content of the flame retardant plasticizer is preferably 6.5% by mass or less. More preferably, it is 6.0% by mass or less.

[0041] (D) Antioxidants

[0042] As antioxidants, hindered phenol compounds, hindered amine compounds, etc. can be cited. Among them, hindered phenol compounds have a high effect of inhibiting the thermal decomposition of polyurethane, so they are preferred. Hindered phenol compounds are phenol compounds having a substituent showing steric hindrance at one or both ortho positions of the phenolic hydroxyl group. The antioxidant can be liquid or solid, but the molecular weight of the liquid antioxidant is relatively small, and it is easy to volatilize if heated, so there is a hidden danger of self-combustion and making the fire bigger. Therefore, from the viewpoint of improving flame retardancy, the antioxidant is preferably solid.

[0043] In order to fully exert the effect of inhibiting the thermal decomposition of polyurethane and reducing the low molecular weight components that become ignition components, the content of the antioxidant is preferably 1.6% by mass or more, when the entire urethane resin composition is set to 100% by mass. More preferably, it is 1.8% by mass or more. On the other hand, from the viewpoint of avoiding the reduction of flame retardancy caused by the combustion of the antioxidant itself, the content of the antioxidant is preferably 2.4% by mass or less. More preferably, it is 2.2% by mass or less.

[0044] (E) Other ingredients

[0045] In addition to the above (A) to (D), the urethane resin composition may also appropriately contain known materials used in the production of polyurethane foam, such as catalysts, foaming agents, foam stabilizers, crosslinking agents, antistatic agents, viscosity reducing agents, stabilizers, fillers, pigments, etc. Among them, as the catalyst, tetramethylethylenediamine, bis(2-dimethylaminoethyl)ether, triethylenediamine, triethylamine, N,N,N',N'-tetramethylhexane-1,6-diamine, N,N,N',N",N"-pentamethyl-diethylenetriamine, N,N,N',N",N"',N"'-hexamethyltriethylene-tetraamine, N,N',N'-trimethylaminoethylpiperazine and other amine catalysts, formic acid, citric acid, butyric acid, 2-ethylhexanoic acid and other acids, tin laurate, tin octoate and other organic metal catalysts can be listed. As the foaming agent, water is preferred. In addition to water, dichloromethane, CO2 gas and the like can be listed. As the foaming agent, a silicone foaming agent is preferred, and as the crosslinking agent, diethylene glycol, triethanolamine, diethanolamine and the like are preferred.

[0046] <Characteristics of polyurethane foam>

[0047] (1) Rigidity

[0048] The rigidity of the polyurethane foam disclosed in the present invention is preferably, for example, an Asker C hardness of 63 or more. More preferably, it is 65 or more. The Asker C hardness can be measured based on the spring hardness test type C specified in JIS K7312-1996 using an "Asker rubber hardness tester type C" manufactured by Kobunsu Keiki Co., Ltd.

[0049] (2) Flame retardancy

[0050] The flame retardancy of polyurethane foam can be determined by, for example, a horizontal burning test according to the UL94 standard. The horizontal burning test is performed as follows: a sample is fixed and kept horizontal at one end, and the flame of a gas burner is brought into contact with the free end for 30 seconds. If the sample continues to burn after leaving the flame, its burning rate is measured. The polyurethane foam disclosed herein preferably has a flame retardancy of the HB level according to the UL94 standard. The criteria for determining whether it has a flame retardancy of the HB level are as follows. (1) For samples with a thickness of 3.05 mm or more, the burning rate does not exceed 38.1 mm per minute. (2) For samples with a thickness of 3.05 mm or less, the burning rate stops when the burning rate does not exceed 76.2 mm per minute, or before the flame reaches a point 102 mm from the end of the sample. The polyurethane foam disclosed herein preferably has a flame retardancy of the HB level according to the UL94 standard not only in a normal state, i.e., in the same state as after manufacture, but also in a state after heat aging at 135°C for 168 hours. Furthermore, it is preferred that the flame retardancy of the HB level of the UL94 standard be maintained even after heat aging for 336 hours at 135° C., and further after heat aging for 600 hours at 135° C. The heat aging may be performed by placing the sample in an oven at 135° C. for a predetermined period of time.

[0051] <Method for producing polyurethane foam>

[0052] The polyurethane foam disclosed in the present invention is manufactured by foaming a urethane resin composition. First, an antioxidant and a catalyst, a foaming agent, a foam stabilizer and other components are pre-mixed in a polyol component to prepare a premixed polyol. Then, an isocyanate component and a flame retardant plasticizer are mixed in the prepared premixed polyol and foamed. For example, after mechanically stirring the premixed polyol with the isocyanate component and the flame retardant plasticizer using a propeller, the premixed polyol is injected into a molding mold for foaming. Alternatively, a mixed raw material mixed with an isocyanate component and a flame retardant plasticizer can be prepared in advance, and a high-pressure injection machine can be used to discharge the premixed polyol and the mixed raw material under high pressure, respectively, so that the two components collide and mix, and foaming is performed (collision stirring method). According to the collision stirring method, continuous production can be carried out. Therefore, it is suitable for mass production. In addition, according to the collision stirring method, compared with the mechanical stirring method, the cleaning process of the container required for each mixing is not required, and the yield rate is also improved. Therefore, the manufacturing cost can be reduced.

[0053] The premixed polyol and isocyanate component are preferably blended so that the isocyanate index (equivalent ratio of isocyanate group / active hydrogen group) is 1.0 or more and 1.5 or less, preferably 1.0 or more and 1.2 or less. When the isocyanate index is less than 1.0, the flame retardancy is reduced. In addition, when it is greater than 1.5, the moldability is reduced.

[0054] Example

[0055] Next, the present disclosure will be described in more detail with reference to examples.

[0056] <Production of Polyurethane Foam Samples>

[0057] First, with respect to 100 parts by mass of a polyether polyol ("SBU Polyol 0248" manufactured by Sumika Covestro Urethane Co., Ltd., average molecular weight 6000, number of functional groups 3) as the (B) polyol component, a hindered phenol compound ("IRGANOX (registered trademark) 1010" manufactured by BASF) as an antioxidant was appropriately blended, and further 3 parts by mass of diethanolamine as a crosslinking agent, 5 parts by mass of water as a foaming agent, 0.6 parts by mass of an amine catalyst A ("KAOLIZER (registered trademark) No. 31" manufactured by Kao Corporation), 0.4 parts by mass of an amine catalyst B ("TOYOCAT (registered trademark) MR" manufactured by Tosoh Corporation), 0.3 parts by mass of a silicone foam stabilizer ("VORASURF (registered trademark) SZ-1336" manufactured by DOW TORAY Co., Ltd.), and 0.3 parts by mass of a pigment ("FT-T" manufactured by Dainichi Seika Industries, Ltd.) were added. 1576BLACK") 2 parts by mass were mixed to prepare a premixed polyol.

[0058] Next, as the isocyanate component (A), an isocyanate raw material is prepared by appropriately mixing modified MDI ("SBU isocyanate 0632" manufactured by Sumika Covestro Urethane Co., Ltd.) including a mixture of 2,4'-MDI and 4,4'-MDI and a modified product obtained by carbodiimidizing 4,4'-MDI and an MDI prepolymer ("SBU isocyanate S234" manufactured by the same company).

[0059] Next, the prepared premixed polyol and isocyanate raw material are mixed in such a manner that the isocyanate index is 1.0 to 1.1, and further (C) a phosphate ester of a flame retardant plasticizer ("ADKSTAB (registered trademark) PFR" manufactured by ADEKA Co., Ltd.) is appropriately added and mixed to prepare a carbamate resin composition. The amount of each component in the carbamate resin composition is shown in Table 1 described below. Then, the carbamate resin composition is injected into the cavity of a molding die and sealed, and foamed for 5 minutes at a molding die temperature of 50°C to produce 13 samples of polyurethane foam. The density of the polyurethane foam of the samples is 0.12 g / cm 3 .

[0060] <Evaluation of polyurethane foam>

[0061] The manufactured samples were evaluated for rigidity, flame retardancy, and sound insulation.

[0062] [Evaluation method]

[0063] (1) Rigidity

[0064] The Asker C hardness of the sample was measured using an "Asker Rubber Hardness Tester Type C" manufactured by Kobunsu Keiki Co., Ltd.

[0065] (2) Flame retardancy

[0066] A strip-shaped test piece (normal test piece) with a length of 127 mm, a width of 12.7 mm, and a thickness of 12.7 mm was made from the manufactured sample. First, the horizontal combustion test specified in the UL94 standard was implemented on the normal test piece. Next, the normal test piece was placed in an oven at 135°C and kept for 168 hours, so that it was heat-aged (first heat aging), and the test was implemented. Separately, the normal test piece was placed in an oven at 135°C and kept for 336 hours, so that it was heat-aged (second heat aging), and the test was implemented. Furthermore, the normal test piece was placed in an oven at 135°C and kept for 600 hours, so that it was heat-aged (third heat aging), and the test was implemented. Then, the case where the HB level judgment standard (burning rate does not exceed 38.1 mm per minute) is met is evaluated as high flame retardancy (in Table 1, indicated by ○ mark), and the case where it is not met is evaluated as insufficient flame retardancy (in the table, indicated by × mark).

[0067] (3) Sound insulation

[0068] The cross section of the polyurethane foam was observed using a microscope, and if open cells were formed, it was evaluated as having the desired sound insulation. In the evaluation column of Table 1, the case where open cells were formed was indicated as "yes" for sound insulation.

[0069] [Evaluation results]

[0070] Table 1 summarizes the components of the urethane resin composition and the evaluation results of the polyurethane foam.

[0071]

[0072] As shown in Table 1, samples 1 to 7 have high rigidity in addition to sound insulation. In addition, they have flame retardancy at the HB level of the UL94 standard not only under normal conditions but also after heat aging. As for samples 8 to 13, although they have sound absorption, they are inferior to samples 1 to 7 in either rigidity or flame retardancy. Specifically, the flame retardancy of sample 8, which has a large content ratio of the modified body, is reduced compared to samples 1 to 7. On the contrary, the rigidity of sample 9, which has a small content ratio of the modified body, is reduced. Compared to samples 1 to 7, the rigidity of sample 10, which has a large content ratio of the flame retardant plasticizer, is low. On the contrary, the flame retardancy of sample 11, which has a small content ratio of the flame retardant plasticizer, is reduced. Compared to samples 1 to 7, sample 12, which has a large content ratio of the antioxidant, has high flame retardancy after heat aging, but the flame retardancy under normal conditions is reduced. On the contrary, sample 13, which has a small content ratio of the antioxidant, has high flame retardancy under normal conditions and after 168 hours of heat aging, but the thermal decomposition inhibition effect of polyurethane is insufficient, and the flame retardancy after heat aging for more than 336 hours is reduced.

[0073] Industrial Applicability

[0074] The flame-retardant sound insulating material for a vehicle of the present disclosure is useful as a sound insulating material disposed around a fuel pipe, a transmission, and the like in addition to an engine hood, a side cover, and an oil pan cover.

Claims

1. A flame-retardant sound-insulating material for a vehicle, comprising a polyurethane foam obtained by foaming a urethane resin composition, wherein: The urethane resin composition comprises (A) an isocyanate component, (B) a polyol component, (C) a flame retardant plasticizer, and (D) an antioxidant. The isocyanate component (A) comprises a mixture of 2,4′-diphenylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate and at least one modified form of the mixture selected from a carbodiimide-modified form and a uretonimine-modified form.

2. The flame-retardant sound-insulating material for a vehicle according to claim 1, wherein: When the entire urethane resin composition is taken as 100% by mass, the content ratio of the modified form of the (A) isocyanate component is 19% by mass or more and 30% by mass or less.

3. The flame-retardant sound-insulating material for a vehicle according to claim 1, wherein: When the entire urethane resin composition is taken as 100 mass %, the content ratio of the (C) flame retardant plasticizer is 3.7 mass % or more and 6.5 mass % or less.

4. The flame-retardant sound-insulating material for a vehicle according to claim 1, wherein: The (C) flame retardant plasticizer includes a phosphoric acid ester.

5. The flame-retardant sound-insulating material for a vehicle according to claim 1, wherein When the entire urethane resin composition is taken as 100 mass %, the content ratio of the (D) antioxidant is 1.6 mass % or more and 2.4 mass % or less.

6. The flame-retardant sound-insulating material for a vehicle according to claim 1, wherein: The (D) antioxidant includes a hindered phenol compound.

7. The flame-retardant sound-insulating material for a vehicle according to claim 1, wherein: The (C) flame retardant plasticizer includes a phosphate ester, and the (D) antioxidant includes a hindered phenol compound.

8. The flame-retardant sound-insulating material for a vehicle according to claim 1, wherein When the entire urethane resin composition is taken as 100% by mass, The content ratio of the modified product in the (A) isocyanate component is 19 mass % or more and 30 mass % or less, The content of the flame retardant plasticizer (C) is 3.7% by mass or more and 6.5% by mass or less, The content of the (D) antioxidant is 1.6% by mass or more and 2.4% by mass or less.

9. The flame-retardant sound-insulating material for a vehicle according to claim 8, wherein: The (C) flame retardant plasticizer includes a phosphate ester, and the (D) antioxidant includes a hindered phenol compound.

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