Flame-retardant soundproofing material for vehicles

Abstract

To provide a flame-retardant sound insulating material for a vehicle having desired rigidity and flame retardancy in addition to sound insulation property.SOLUTION: A flame-retardant sound insulating material for a vehicle includes a polyurethane foam obtained by foam molding of a urethane resin composition. The urethane resin composition has (A) an isocyanate component, (B) a polyol component, (C) a flame-retardant plasticizer, and (D) an antioxidant. (A) The isocyanate component has a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, and one or more kinds of modified bodies selected from a carbodiimide modified body and a urethoneimine modified body of at least one of the mixture.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a flame-retardant soundproofing material for vehicles used in the engine compartment of a vehicle, etc. [Background technology]

[0002] In vehicles such as automobiles, various measures are taken to reduce noise leaking outside the vehicle or into the passenger compartment. For example, in the engine compartment of a vehicle, soundproofing materials such as engine covers, side covers, and oil pan covers are placed around the engine to reduce noise radiated from the engine, which is a noise source. In recent years, attempts have been made to further improve soundproofing by placing soundproofing materials around fuel pipes, transmissions, and other components. For example, soundproofing materials placed near rotating bodies that make up a transmission must have a desired rigidity to prevent deformation and interference with the rotating bodies. Rigidity at high temperatures is particularly important, and they must not sag or deform even at high temperatures (droop resistance). Furthermore, in the operating environment around the engine, flame retardancy is also required in addition to soundproofing.

[0003] For example, Patent Document 1 describes a flame-retardant soundproofing and vibration-proofing material for vehicles that uses a flexible polyurethane foam obtained by reacting and foaming an isocyanate component and a polyol component. Patent Document 1 also describes that by using monomeric MDI containing diphenylmethane diisocyanate and its carbodiimide-modified and / or uretonimine-modified derivatives as the main component of the isocyanate component, the heat degradation resistance and flame retardancy of the polyurethane foam are improved. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-97645 [Patent Document 2] Japanese Patent Application Publication No. 5-105811 Summary of the Invention [Problem to be solved by the invention]

[0005] The polyurethane foam described in Patent Document 1 uses one or more modified compounds selected from carbodiimide modified compounds and uretonimine modified compounds as the isocyanate component. The use of modified compounds increases intermolecular cohesion, improving the rigidity of the polyurethane foam. However, as the rigidity increases, the foam becomes less soluble during combustion, which prolongs combustion and reduces flame retardancy. Thus, improving rigidity and improving flame retardancy are in a trade-off relationship.

[0006] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a flame-retardant soundproofing material for vehicles that has desired rigidity and flame retardancy in addition to soundproofing properties. [Means for solving the problem]

[0007] (1) In order to solve the above-mentioned problems, the present disclosure provides a flame-retardant soundproofing material for vehicles, which comprises a polyurethane foam obtained by foam molding a urethane resin composition, and 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 one or more modified products selected from a carbodiimide-modified product and a uretonimine-modified product of at least one of the mixtures.

[0008] In the flame-retardant soundproofing material for vehicles disclosed herein, a polyurethane foam with desired soundproofing properties, rigidity, and flame retardancy is realized by using a specific isocyanate component as a raw material and by using a flame-retardant plasticizer and an antioxidant in combination. Regarding the isocyanate component, hereinafter, diphenylmethane diisocyanate will be referred to as "MDI," 2,4'-diphenylmethane diisocyanate will be referred to as "2,4'-MDI," and 4,4'-diphenylmethane diisocyanate will be referred to as "4,4'-MDI."

[0009] The use of a modified product as an isocyanate component enhances intermolecular cohesion, enabling the production of polyurethane foams with high rigidity not only at room temperature but also at high temperatures. The modified product is produced by a carbodiimidation reaction in which the NCO groups of two MDIs condense with each other, followed by a uretonimination reaction in which one molecule of MDI is added to the resulting carbodiimidized product (carbodiimide-modified product). As a secondary reaction of the carbodiimidation reaction of MDI, a uretonimin-modified product (uretonimine-modified product) is also produced in a chemical equilibrium reaction. It is generally believed that as the carbodiimidation reaction progresses, most of the reaction product is the uretonimine-modified product. In this specification, the term "modified product" refers to "one or more modified products selected from carbodiimide-modified products and uretonimine-modified products," so as to include all products obtained by the carbodiimidation reaction of either 2,4'-MDI or 4,4'-MDI, or both. This can also be expressed as a “carbodiimide-modified product and / or uretonimine-modified product.” The carbodiimide-modified product and uretonimine-modified product can be obtained by a known method, for example, by reacting a single-component MDI or a multi-component MDI including isomers using a catalyst such as a phosphoric acid ester.

[0010] The polyurethane foam constituting the flame-retardant soundproofing material for vehicles of the present disclosure (hereinafter referred to as "polyurethane foam of the present disclosure") contains a flame-retardant plasticizer. The flame-retardant plasticizer penetrates between polyurethane crystals at high temperatures, softening the polyurethane foam and making it more soluble. For example, if a simple plasticizer without flame retardancy is used, it can make the polyurethane foam more soluble during combustion, but there is a risk that it may burn and increase the size of the fire. In this regard, the polyurethane foam of the present disclosure uses a flame-retardant plasticizer, so this risk is eliminated. Thus, in the polyurethane foam of the present disclosure, even if the rigidity of the foam is increased by using a modified isocyanate component, the incorporation of the flame-retardant plasticizer makes the foam more soluble during combustion, thereby suppressing a decrease in flame retardancy.

[0011] The incorporation of a flame-retardant plasticizer improves the flame retardancy of a polyurethane foam. However, increasing the amount of the additive from the viewpoint of improving flame retardancy may soften the polyurethane foam and reduce its rigidity. In this regard, the polyurethane foam of the present disclosure uses an antioxidant in combination to ensure flame retardancy while maintaining the rigidity of the polyurethane foam. The antioxidant has the following effect: When polyurethane thermally decomposes, its molecules are cleaved, generating low-molecular-weight components. Low-molecular-weight components are easily ignited, promoting sustained combustion. The incorporation of an antioxidant inhibits the thermal decomposition of polyurethane and the generation of low-molecular-weight components, thereby reducing ignition components. In other words, the polyurethane foam of the present disclosure can be imparted with flame retardancy without the incorporation of an excessive amount of flame-retardant plasticizer by incorporating an antioxidant to preventively reduce ignition-prone components. This achieves both rigidity and flame retardancy, which was previously difficult to achieve.

[0012] Incidentally, Patent Document 2 describes a liquid flame-retardant composition for polyurethanes, comprising 50 to 99% by weight of a flame-retardant organophosphorus compound and 50 to 1% by weight of tribromoneopentyl alcohol (TBNPA). Patent Document 2 also describes a formulation in which an antioxidant, such as a hydroquinone compound or a trivalent organophosphorus compound, is further added to a mixture of the flame-retardant organophosphorus compound and TBNPA. Patent Document 2 aims to provide a low-viscosity liquid composition that can impart flame retardancy using TBNPA. Therefore, the use of an antioxidant is not essential, and the effects of using the composition in combination with a flame-retardant organophosphorus compound are not described. Furthermore, the only polyurethane foams described are those in which the isocyanate component is toluene diisocyanate (TDI), and Patent Document 2 does not include the technical idea of ​​increasing the rigidity of the polyurethane foam.

[0013] (2) In the above configuration, the content of the modified isocyanate component (A) may be 19% by mass or more, based on 100% by mass of the entire urethane resin composition. Alternatively, the content of the modified isocyanate component may be 30% by mass or less. These configurations make it easier to achieve a balance between the rigidity and flame retardancy of the polyurethane foam.

[0014] (3) In any of the above configurations, the content of the flame-retardant plasticizer (C) may be 3.7% by mass or more, based on 100% by mass of the entire urethane resin composition. Alternatively, the content of the flame-retardant plasticizer may be 6.5% by mass or less. These configurations make it easier to achieve a balance between the rigidity and flame retardancy of the polyurethane foam.

[0015] (4) In any of the above configurations, the flame-retardant plasticizer (C) may contain a phosphate ester. This configuration allows the polyurethane foam to be softened with a relatively small amount of the flame-retardant plasticizer, and also provides good moldability.

[0016] (5) In any of the above configurations, the content of the antioxidant (D) may be 1.6% by mass or more, based on 100% by mass of the entire urethane resin composition. Alternatively, the content of the antioxidant may be 2.4% by mass or less. These configurations effectively suppress the generation of low-molecular-weight components due to thermal decomposition of polyurethane. As a result, desired flame retardancy is imparted even with a small amount of flame-retardant plasticizer. For example, combining this configuration with the above configurations (2) and (3) is effective in imparting desired rigidity and flame retardancy to a polyurethane foam.

[0017] (6) In any of the above configurations, the antioxidant (D) may contain a hindered phenol compound. This configuration can enhance the effect of inhibiting thermal decomposition of polyurethane. For example, combining this configuration with the above configuration (4) can further enhance the rigidity and flame retardancy of the polyurethane foam. Furthermore, combining the above configurations (2), (3), and (5) is even more preferable. [Effects of the Invention]

[0018] The flame-retardant soundproofing material for vehicles of the present disclosure has desired rigidity and flame retardancy in addition to soundproofing properties. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the flame-retardant soundproofing material for vehicles 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.

[0020] In the flame-retardant soundproofing material for vehicles of the present disclosure, the components other than the polyurethane foam are not particularly limited. The flame-retardant soundproofing material for vehicles of the present disclosure may be composed of polyurethane foam alone, or may be composed of a combination of polyurethane foam and other components. For example, when the flame-retardant soundproofing material for vehicles of the present disclosure is embodied in an engine cover, the engine cover may have a single-layer structure of polyurethane foam, or a multi-layer structure having a soundproofing layer made of polyurethane foam and a skin layer covering the surface thereof. Furthermore, the term "vehicle" as used herein includes not only automobiles but also airplanes, trains, and the like.

[0021] <Polyurethane foam components> The polyurethane foam of the present disclosure is a foam-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.

[0022] (A) Isocyanate component The isocyanate component contains a mixture of 2,4'-MDI and 4,4'-MDI and one or more modified forms selected from a carbodiimide-modified form and a uretonimine-modified form of at least one of the mixtures. The ratio of 2,4'-MDI to 4,4'-MDI in the mixture may be determined appropriately taking into consideration rigidity, moldability, etc. As described above, the modified form includes a product obtained by the carbodiimidization reaction of 2,4'-MDI or 4,4'-MDI, and a product obtained by the carbodiimidization reaction of 2,4'-MDI and 4,4'-MDI.

[0023] From the viewpoint of increasing the rigidity of the polyurethane foam, it is desirable to maximize the content of the modified substance in the isocyanate component. For example, the content of the modified substance is desirably 19% by mass or more, where the entire urethane resin composition is taken as 100% by mass. 21% by mass or more is more preferable. On the other hand, if the content of the modified substance is too high, the foam will not melt easily during combustion, making it difficult for embers to fall. Taking this into consideration, the content of the modified substance is desirably 30% by mass or less, and 28% by mass or more is more preferable.

[0024] In addition to mixtures and modified products, the isocyanate component may also contain a prepolymer obtained by reacting MDI with a polyol. When the prepolymer is contained, the viscosity of the urethane resin composition increases and moldability improves compared to when the prepolymer is not contained. The prepolymer content is preferably 18% by mass or more and 30% by mass or less, with the entire urethane resin composition taken as 100% by mass. For example, reacting MDI with a polyol having three functional groups produces a prepolymer having three urethane bonds. Of these, an isocyanate-terminated prepolymer obtained by reacting MDI with a bifunctional polyether polyol is preferred. Here, examples of bifunctional polyether polyols include polyether polyols with a molecular weight of approximately 1,000.

[0025] Although mixtures, modified compounds, and prepolymers have been described as isocyanate components, the inclusion of other isocyanate compounds is not excluded as long as the polyurethane foam of the present disclosure can be realized without impairing the effects of these components. Examples of such isocyanate compounds include polymeric MDI (polynuclear compounds) containing three or more isocyanate groups and three or more benzene rings per molecule. However, the inclusion of polymeric MDI forms a crosslinked structure in the polyurethane foam, making it less likely to melt during combustion. This is undesirable because it may result in a decrease in flame retardancy.

[0026] (B) Polyol component Known polyol components include 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, and phenol-modified polyols. When producing the polyurethane foam of the present disclosure, polyether polyols are used as the main component. The term "main component" refers to a component that accounts for 60% by mass or more, assuming that the entire polyol component is 100% by mass. Therefore, the polyol component may be polyether polyol alone, or may be used in combination with other polyols as the main component. For example, from the viewpoint of improving moldability, it is desirable to use polyester polyols in combination. Even when using only polyether polyols, multiple types with different functional groups, molecular weights, compatibility, etc. may be used in combination.

[0027] 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 easily interrupted, making it difficult to polymerize, resulting in reduced moldability. For example, a polyether polyol with a functionality of 2 is suitable because it does not form a crosslinked structure, making it easier to extinguish the fire during combustion and improving flame retardancy. A polyether polyol with a functionality of 3 or more is suitable because it forms a crosslinked structure, making the polyurethane foam harder and increasing its rigidity. However, if the number of functional groups exceeds 4, the polyurethane foam will have less elongation, resulting in reduced soundproofing.

[0028] 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 becomes hard, resulting in reduced soundproofing. If the mass-average molecular weight exceeds 8,000, the viscosity of the urethane resin composition becomes too high, making it difficult to react with the isocyanate component and to foam.

[0029] (C) Flame-retardant plasticizer Examples of flame-retardant plasticizers include halogenated or non-halogenated phosphorus compounds used as flame retardants. Halogenated phosphorus compounds have poor plasticity and therefore require a large amount to be added, which may reduce foam moldability. Therefore, non-halogenated phosphorus compounds are preferred. Flame-retardant plasticizers may be liquid or solid, but liquid is preferable from the perspective of mixing with liquid materials such as isocyanate components. Suitable flame-retardant plasticizers include, for example, phosphoric acid esters such as trimethyl phosphate and tributyl phosphate.

[0030] From the viewpoint of fully suppressing the decrease in flame retardancy, the content of the flame-retardant plasticizer is preferably 3.7% by mass or more, and more preferably 4.0% by mass or more, based on 100% by mass of the entire urethane resin composition. On the other hand, from the viewpoint of avoiding a decrease in rigidity due to the addition of the flame-retardant plasticizer, the content of the flame-retardant plasticizer is preferably 6.5% by mass or less, and more preferably 6.0% by mass or less.

[0031] (D) Antioxidants Examples of antioxidants include hindered phenol compounds and hindered amine compounds. Among them, hindered phenol compounds are preferred because they are highly effective in suppressing thermal decomposition of polyurethane. Hindered phenol compounds are phenol compounds having a substituent exhibiting steric hindrance at one or both ortho positions of the phenolic hydroxyl group. The antioxidant may be liquid or solid, but liquid antioxidants have a relatively small molecular weight and tend to volatilize when heated, which may result in the risk of burning and causing a fire. Therefore, from the viewpoint of improving flame retardancy, it is preferable that the antioxidant be solid.

[0032] To fully exert the effects of suppressing thermal decomposition of polyurethane and reducing low-molecular-weight components that can become ignition components, the content of the antioxidant is desirably 1.6% by mass or more, and more preferably 1.8% by mass or more, based on 100% by mass of the entire urethane resin composition. On the other hand, from the viewpoint of avoiding a decrease in flame retardancy due to combustion of the antioxidant itself, the content of the antioxidant is desirably 2.4% by mass or less, and more preferably 2.2% by mass or less.

[0033] (E) Other ingredients In addition to the above (A) to (D), the urethane resin composition may contain, as appropriate, known materials used in producing polyurethane foams, such as catalysts, blowing agents, foam stabilizers, crosslinking agents, antistatic agents, viscosity reducers, stabilizers, fillers, and pigments. Examples of catalysts include amine catalysts such as 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'''-hexamethyltriethylenetetraamine, and N,N',N'-trimethylaminoethylpiperazine; acids such as formic acid, citric acid, butylic acid, and 2-ethylhexanoic acid; and organometallic catalysts such as tin laurate and tin octoate. Water is a preferred blowing agent. Other examples include methylene chloride and CO2 gas. As the foam stabilizer, a silicone-based foam stabilizer is preferred, and as the crosslinking agent, diethylene glycol, triethanolamine, diethanolamine, etc. are preferred.

[0034] <Properties of polyurethane foam> (1) Rigidity The rigidity of the polyurethane foam of the present disclosure is preferably, for example, an Asker C hardness of 63 or more, and more preferably 65 or more. The Asker C hardness may be measured using an "Asker Rubber Hardness Tester Type C" manufactured by Kobunshi Keiki Co., Ltd., based on the spring hardness test type C specified in JIS K7312-1996.

[0035] (2) Flame retardancy The flame retardancy of polyurethane foams can be determined, for example, by conducting a horizontal flame test according to the UL94 standard. The horizontal flame test involves holding a sample horizontally at one end and applying a gas burner flame to the free end for 30 seconds. If the sample continues to burn after the flame is removed, the burning rate is measured. The polyurethane foams of the present disclosure preferably have HB level flame retardancy according to the UL94 standard. The criteria for determining whether or not a sample has HB level flame retardancy are as follows: (1) For samples with a thickness of 3.05 mm or more, the burning rate must not exceed 38.1 mm per minute. (2) For samples with a thickness of 3.05 mm or less, the burning rate must not exceed 76.2 mm per minute, or the flame must cease before reaching a point 102 mm from the edge of the sample. The polyurethane foams of the present disclosure preferably have HB level flame retardancy according to the UL94 standard, not only in their normal state (i.e., the same state as when they were manufactured) but also after heat aging at 135°C for 168 hours. It is also desirable 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 even after heat aging for 600 hours at 135°C. Heat aging can be carried out by placing the sample in an oven at 135°C and holding it there for a specified period of time.

[0036] <Method of manufacturing polyurethane foam> The polyurethane foam of the present disclosure is produced by foam molding a urethane resin composition. First, a polyol component is premixed with an antioxidant and other components, such as a catalyst, a blowing agent, and a foam stabilizer, to prepare a premix polyol. Next, the prepared premix polyol is mixed with an isocyanate component and a flame-retardant plasticizer, followed by foam molding. For example, the premix polyol, isocyanate component, and flame-retardant plasticizer may be mechanically stirred using a propeller or the like, and then injected into a mold for foam molding. Alternatively, a mixed raw material containing the isocyanate component and the flame-retardant plasticizer may be prepared in advance, and the premix polyol and the mixed raw material may be discharged at high pressure using a high-pressure injector or the like, causing the two components to collide and mix, resulting in foam molding (impingement stirring method). The impingement stirring method enables continuous production, making it suitable for mass production. Furthermore, compared to mechanical stirring methods, the impingement stirring method eliminates the need for a container cleaning step required after each mixing, improving yield. Therefore, the manufacturing cost can be reduced.

[0037] The premix polyol and isocyanate component are desirably blended so that the isocyanate index (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, flame retardancy decreases. If it exceeds 1.5, moldability decreases. [Example]

[0038] Next, the present disclosure will be described more specifically with reference to examples.

[0039] <Production of polyurethane foam samples> First, 100 parts by mass of polyether polyol (B) as the polyol component (SBU Polyol 0248, manufactured by Sumika Covestro Urethane Co., Ltd., average molecular weight 6,000, number of functional groups 3) was appropriately blended with a hindered phenol compound (D) as the antioxidant (IRGANOX® 1010, manufactured by BASF), and then 3 parts by mass of diethanolamine as the crosslinking agent, 5 parts by mass of water as the blowing agent, 0.6 parts by mass of amine catalyst A (Kao Corporation, Kao Raiser® No. 31), 0.4 parts by mass of amine catalyst B (Tosoh Corporation, TOYOCAT® MR), 0.3 parts by mass of a silicone foam stabilizer (VORASURF® SZ-1336, manufactured by Dow-Toray Industries, Inc.), and 2 parts by mass of a pigment (FT 1576 Black, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) were added and mixed to prepare a premix polyol.

[0040] Next, as the isocyanate component (A), an isocyanate raw material was prepared by appropriately mixing a mixture of 2,4'-MDI and 4,4'-MDI, modified MDI containing a modified product obtained by carbodiimidizing 4,4'-MDI ("SBU Isocyanate 0632" manufactured by Sumika Bayer Urethane Co., Ltd.), and an MDI prepolymer ("SBU Isocyanate S234" manufactured by the same company).

[0041] Next, the prepared premix polyol and an isocyanate raw material were mixed so that the isocyanate index was 1.0 to 1.1, and then (C) a phosphate ester of a flame-retardant plasticizer ("ADEKA STAB (registered trademark) PFR" manufactured by ADEKA Corporation) was added appropriately and mixed to prepare a urethane resin composition. The blending amounts of each component in the urethane resin composition are as shown in Table 1 below. The urethane resin composition was then injected into the cavity of a mold, sealed, and foam-molded at a mold temperature of 50°C for 5 minutes to produce 13 types of polyurethane foam samples. The density of the polyurethane foam samples was 0.12 g / cm. 3 It was decided.

[0042] <Evaluation of polyurethane foam> The produced samples were evaluated for stiffness, flame retardancy and sound insulation.

[0043] [Evaluation method] (1) Rigidity The Asker C hardness of the sample was measured using an Asker Rubber Hardness Tester Type C manufactured by Kobunshi Keiki Co., Ltd.

[0044] (2) Flame retardancy From the manufactured samples, strip-shaped test pieces (normal test pieces) measuring 127 mm in length, 12.7 mm in width, and 12.7 mm in thickness were prepared. First, the normal test pieces were subjected to the horizontal flame test specified in the UL94 standard. Next, the normal test pieces were placed in an oven at 135°C and subjected to heat aging for 168 hours (first heat aging), and then the same test was conducted. Separately, normal test pieces were placed in an oven at 135°C and subjected to heat aging for 336 hours (second heat aging), and then the same test was conducted. Furthermore, normal test pieces were placed in an oven at 135°C and subjected to heat aging for 600 hours (third heat aging), and then the same test was conducted. The HB level criteria (burning rate not exceeding 38.1 mm per minute) were evaluated as high flame retardancy (indicated by a circle in Table 1), and those that did not meet the criteria were evaluated as insufficient flame retardancy (indicated by an x ​​in Table 1).

[0045] (3) Soundproofing The cross section of the polyurethane foam was observed under a microscope, and if open cells were formed, it was evaluated as having the desired soundproofing properties. In the evaluation column of Table 1, cases where open cells were formed are indicated as having soundproofing properties.

[0046] [Evaluation results] Table 1 shows the components of the urethane resin composition and the evaluation results of the polyurethane foam. [Table 1]

[0047] As shown in Table 1, Samples 1 to 7 had high soundproofing properties and high rigidity. Furthermore, they had UL94 HB level flame retardancy not only in the normal state but also after heat aging. Samples 8 to 13 had sound absorption properties, but were inferior to Samples 1 to 7 in either rigidity or flame retardancy. Specifically, Sample 8, which contained a higher proportion of modified substance than Samples 1 to 7, had reduced flame retardancy. Conversely, Sample 9, which contained a lower proportion of modified substance, had reduced rigidity. Sample 10, which contained a higher proportion of flame-retardant plasticizer than Samples 1 to 7, had reduced rigidity. Conversely, Sample 11, which contained a lower proportion of flame-retardant plasticizer, had reduced flame retardancy. Sample 12, which contained a higher proportion of antioxidant than Samples 1 to 7, had high flame retardancy after heat aging but reduced flame retardancy in the normal state. Conversely, sample 13, which contained a small amount of antioxidant, had high flame retardancy both at room temperature and after 168 hours of heat aging, but the effect of inhibiting the thermal decomposition of polyurethane was insufficient, and the flame retardancy decreased after heat aging for 336 hours or more. [Industrial Applicability]

[0048] The flame-retardant soundproofing material for vehicles of the present disclosure is useful as a soundproofing material to be placed around engine covers, side covers, oil pan covers, as well as fuel pipes, transmissions, etc.

Claims

[Claim 1] A flame-retardant soundproofing material for vehicles comprising 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, (A) the isocyanate component comprises a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate, and one or more modified products selected from a carbodiimide-modified product and a uretonimine-modified product of at least one of the mixtures; (C) The flame-retardant plasticizer has a phosphate ester, (D) The antioxidant has a hindered phenol compound, When the entire urethane resin composition is taken as 100% by mass, The content of the modified product in the isocyanate component (A) is 19% by mass or more and 30% by mass or less, (C) The content of the flame-retardant plasticizer is 3.7% by mass or more and 6.5% by mass or less, (D) A flame-retardant soundproofing material for vehicles, characterized in that the content of the antioxidant is 1.6 mass % or more and 2.4 mass % or less.

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