JP2024014696A - Sound absorbing material for vehicles - Google Patents

Abstract

The present invention provides a sound absorbing material for a vehicle that has a thin base material and high performance in a wide frequency range when used as a sound absorbing material, a foam laminate, and a method for manufacturing the same. [Solution] A sound absorbing material for a vehicle is made of a flexible polyurethane foam containing a polyol component and a polyisocyanate component as constituent components, wherein the polyol component contains a catalyst, a foam stabilizer, and a blowing agent, and the polyol component or At least one of the isocyanate components contains a foam-breaking agent, the surface tension of the foam-stabilizing agent is 22 to 28 mN/m @ 23°C, and the content of the foam-breaking agent is 0.0% relative to the total amount of the polyol component and polyisocyanate component. It is 1 to 7.5% by mass. [Selection diagram] None

Description

The present invention relates to a sound absorbing material for vehicles.

Noise has a long history in people's lives, and has long been a source of major trouble in Japan, including noise problems at airports and military bases. Furthermore, the Basic Environmental Law stipulates that noise pollution is one of the seven typical types of pollution, along with air pollution, water pollution, soil pollution, vibration, ground subsidence, and bad odors. Against this background, for example, in the automobile industry, there is a strong demand for lower noise levels in vehicle components due to stricter regulations on noise levels outside the vehicle and the fact that quieter interior noise is directly linked to the value of the car. expensive. Therefore, it is essential to further reduce noise by improving the performance of soundproof materials such as sound absorbing materials. In particular, there is an urgent need to reduce engine transmitted sound and tire radiated sound, and there is a growing need for sound-absorbing materials that can address this issue. In response to these demands, it is relatively easy to increase the sound absorption performance and vibration absorption performance by increasing the thickness of the base material, but if the base material is thick, it is necessary to ensure sufficient space in the vehicle interior. There are concerns that it may not be possible. Therefore, it is necessary to improve the sound absorption performance and reduce the thickness of the base material.

Various efforts have been made to improve this sound absorption performance. For example, Patent Document 1 describes a method of increasing the sound absorption of 1000 Hz to 2000 Hz by increasing the cell diameter of a rigid foam as a soundproofing member for a dash panel. However, since the base material is a rigid foam, it is difficult to follow the shape when attached to a vehicle, and it is difficult to restore the shape when compressed, which limits the locations where it can be used. Further, since the average sound absorption coefficient at 1000 to 2000 Hz is 45% or more when the thickness of the base material is 15 mm, it cannot be said that the thinning of the base material and the sound absorption performance are sufficient.

JP2006-017983A

The present invention has been made in view of the above-mentioned background art, and an object of the present invention is to provide a sound absorbing material for vehicles that has a thin base material and has high performance in a wide frequency range when used as a sound absorbing material.

That is, the present invention includes the embodiments shown below.

[1] A sound absorbing material for vehicles made of a flexible polyurethane foam containing a polyol component (A) and a polyisocyanate component (B), wherein the polyol component (A) is a catalyst (C), a foam stabilizer ( D) and a foaming agent (E), at least one of the polyol component (A) or the polyisocyanate component (B) contains a foam-breaking agent (F), and the foam stabilizer (D) has a surface tension of 22 to 28 mN/m@23°C, and the content of the foam-breaking agent (F) is 0.1 to 7.5% by mass based on the total amount of the polyol component (A) and polyisocyanate component (B). A sound absorbing material for vehicles.

[2] The foam-breaking agent (F) is a silicone oil, and the polysiloxane component contained in the silicone oil has a number average molecular weight of 10,000 to 50,000. Sound absorbing material for vehicles.

[3] The sound absorbing material for a vehicle as described in [1] or [2] above, wherein the foam-breaking agent (F) is contained in the polyol component (A).

[4] The polyisocyanate component (B) contains diphenylmethane diisocyanate in a range of 50 to 85% by mass, and the total amount of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate contained in the diphenylmethane diisocyanate is The sound absorbing material for a vehicle according to any one of [1] to [3] above, wherein the amount of diphenylmethane diisocyanate is 10 to 50% by mass based on the total amount of diphenylmethane diisocyanate.

[5] The density is 25 to 200 kg/m ³ , the Asker C hardness measured according to JIS K7312 is 20 to 100 points, and the air permeability is 0.1 to 100 cm ³ /cm ² /sec. The sound absorbing material for a vehicle according to any one of [1] to [4] above, characterized by:

[6] The vehicle according to any one of [1] to [5] above, wherein the average cell diameter is 2000 μm or more, and the area ratio occupied by cells with a diameter of 5000 μm or more is 20% or more. sound absorbing material.

[7] The sound absorbing material for a vehicle according to any one of [1] to [6] above, characterized in that the thickness of the thinnest part is 5.0 to 50 mm.

[8] A vehicle comprising the sound absorbing material for a vehicle according to any one of [1] to [7] above and a film, wherein at least one film is arranged with respect to a sound source in the order of the film and the sound absorbing material for a vehicle. A foam laminate characterized by:

[9] The foam laminate according to [8] above, wherein the film is coated on a surface of a sound absorbing material for a vehicle.

[10] The foam laminate according to [8] or [9] above, wherein the film is a polyurethane resin film.

[11] The foam laminate according to [10] above, wherein the polyurethane resin film is made of an aqueous polyurethane resin emulsion.

[12] The foamed laminate as described in [11] above, wherein the polyol component used as a raw material for the aqueous polyurethane resin emulsion has a carbonate skeleton.

[13] The foamed laminate according to [12] above, wherein the polyol component having a carbonate skeleton has an average number of functional groups of 2.1 or more.

[14] The film has a thickness of 0.1 to 250 μm, a porosity of 0 to 2.0%, and an average pore diameter of 300 to 1000 μm when the porosity exceeds 0%. The foam laminate according to any one of [8] to [13] above.

[15] A method for producing a foam laminate, characterized in that the film is coated on the surface of the sound absorbing material by integral molding with the sound absorbing material for a vehicle according to the above [1].

By using the sound absorbing material for vehicles of the present invention, the base material can be thin and have high sound absorbing performance in a wide frequency range.

The present invention will be explained in more detail.

The sound absorbing material for vehicles in the present invention comprises the following polyol component (A), polyisocyanate component (B), catalyst (C), foam stabilizer (D), foaming agent (E), and foam-breaking agent (F). Consists of flexible polyurethane foam obtained from

The polyol component (A) is polyadded with the polyisocyanate component (B) to form polyurethane, and in the present invention, it is at least one selected from the group consisting of polyether polyols and polyester polyols. preferable. Furthermore, the number average molecular weight is preferably 1,000 to 10,000, more preferably 3,000 to 8,000, and most preferably 4,000 to 8,000. Furthermore, those having a nominal number of functional groups of 2 or more are more preferable. When the number average molecular weight is less than the lower limit, the resulting foam tends to lack flexibility, and when it exceeds the upper limit, the hardness of the foam tends to decrease. In addition, when the number of nominal functional groups is less than 2, the impact resilience of the foam is significantly reduced, causing a problem that the foam does not return to its original shape when compressed. In addition. The nominal number of functional groups refers to the theoretical average number of functional groups (the number of active hydrogen atoms per molecule) assuming that no side reactions occur during the polymerization reaction of the polyol.

As the polyether polyol, for example, polypropylene ether polyol, polyethylene polypropylene ether polyol (hereinafter referred to as PPG), polytetramethylene ether glycol (hereinafter referred to as PTG), etc. can be used, and as the polyester polyol, for example, polycondensation Polyester polyols consisting of adipic acid and diol, which are type polyester polyols, and polycaprolactone polyols, which are lactone type polyester polyols, can be used.

In the present invention, from the viewpoint of improving the heat resistance of the foam, at least one polyol selected from the group consisting of castor oil and castor oil-modified polyols can be used in combination with the polyol component (A). At least one polyol selected from the group consisting of castor oil and castor oil-modified polyols includes, for example, refined castor oil, semi-refined castor oil, unrefined castor oil, hydrogenated castor oil with added hydrogen, etc. Examples include derivatives.

Further, in the present invention, the polyol component (A) contains a polyether polyol having a polyoxyalkylene chain made of a copolymer of oxyethylene and oxypropylene for the purpose of promoting communication of the flexible polyurethane foam. It is preferable. The number average molecular weight is preferably 3,000 to 8,000, and the nominal number of functional groups is preferably 2 to 4. Furthermore, the amount of oxyethylene units in the polyether polyol is preferably 60 to 90% by mass, more preferably 60 to 80% by mass. By controlling the content of oxyethylene units to 60 to 90% by mass, the durability of the foam can be improved. Further, from the viewpoint of storage stability at low temperatures, the copolymer made of oxyethylene and oxypropylene is preferably a random copolymer.

The amount of the polyether polyol added is preferably 0.5 to 5.0% by mass based on the polyol component (A). If it is less than the lower limit, the moldability of the foam may deteriorate, and if it exceeds the upper limit, the elongation rate of the foam may decrease.

In the polyol component (A) of the present invention, a polymer polyol obtained by polymerizing a vinyl monomer in a polyol by a conventional method can be used in combination for the purpose of hardness adjustment. Examples of such polymer polyols include those obtained by polymerizing and stably dispersing a vinyl monomer in a polyalkylene polyol such as the above-mentioned PPG in the presence of a radical initiator. Examples of vinyl monomers include acrylonitrile, styrene, vinylidene chloride, hydroxyalkyl methacrylate, and alkyl methacrylate, with acrylonitrile and styrene being preferred. Examples of such polymer polyols include EL-910 and EL-923 manufactured by AGC, and FA-728R manufactured by Sanyo Chemical Industries.

The polyisocyanate component (B) in the present invention includes 4,4'-diphenylmethane diisocyanate (hereinafter referred to as 4,4'-MDI), 2,4'-diphenylmethane diisocyanate (hereinafter referred to as 2,4'-MDI), 2,2 It is preferable to use diphenylmethane diisocyanate (hereinafter referred to as MDI) such as '-diphenylmethane diisocyanate (hereinafter referred to as 2,2'-MDI), and polyphenylene polymethylene polyisocyanate (hereinafter referred to as P-MDI) as the isocyanate source. In the present invention, various modified products such as the above-described MDI, a mixture of MDI and P-MDI, a urethane modified product, a urea modified product, an allophanate modified product, a nurate modified product, a biuret modified product, etc. can also be used.

The MDI content of the polyisocyanate component (B) according to the present invention is preferably in the range of 50 to 85% by mass. If the MDI content exceeds 85% by mass, the storage stability at low temperatures of the resulting polyisocyanate composition and the durability of the resulting flexible foam may decrease, while if it is less than 50% by mass, the crosslinking density may increase. Accordingly, the elongation of the flexible polyurethane foam may decrease, making it difficult to obtain sufficient foam strength.

Further, the total content of 2,2'-MDI and 2,4'-MDI (hereinafter referred to as isomer content) relative to the total amount of MDI is preferably 10 to 50% by mass.

If the content of 2,2'-MDI and 2,4'-MDI with respect to the total amount of MDI according to the present invention is less than 10% by mass, the storage stability at low temperatures of the obtained polyisocyanate composition may be impaired, It may be necessary to constantly heat the isocyanate storage area, piping, and inside the foam molding machine. Furthermore, the molding stability of the flexible polyurethane foam may be impaired, and the foam may collapse during foaming. On the other hand, if it exceeds 50% by mass, the reactivity decreases, which may cause problems such as lengthening of the molding cycle, high cell foam ratio, and shrinkage after molding.

As the catalyst (C), various urethanation catalysts known in the art can be used, such as triethylamine, tripropylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine, dimethylbenzylamine, N,N, N',N'-tetramethylhexamethylenediamine, N,N,N',N',N''-pentamethyldiethylenetriamine, bis-(2-dimethylaminoethyl)ether, triethylenediamine, 1,8-diaza- Bicyclo[5.4.0]undecene-7,1,2-dimethylimidazole, dimethylethanolamine, N,N-dimethyl-N-hexanolamine, and organic acid salts thereof, stannous octoate, zinc naphthenate, etc. Also included are organometallic compounds. Also preferred are amine catalysts having active hydrogen such as N,N-dimethylethanolamine and N,N-diethylethanolamine.

The amount of catalyst added is preferably 0.01 to 10% by mass based on the polyol component (A). If it is less than the lower limit, curing tends to be insufficient, and if it exceeds the upper limit, moldability may deteriorate.

As the foam stabilizer (D), ordinary surfactants are used, and silicone-based surfactants are preferably used. The surface tension of the foam stabilizer is preferably 22 to 28 mN/m @ 23°C, more preferably 23 to 27 mN/m @ 23°C. Examples of the foam stabilizer include Y-10366J, L-3646J, L-5309J, and L-3639LF manufactured by Momentive, and B-4113LF and B-8715LF2 manufactured by Evonik. The amount of these foam stabilizers added is preferably 0.1 to 3.0% by mass based on the polyol component (A).

Water is mainly used as the blowing agent (E). Water reacts with isocyanate groups to form highly hard urea groups and also generates carbon dioxide gas, which can cause foaming. Additionally, any blowing agent may be used in addition to water. For example, a small amount of a low boiling point organic compound such as cyclopentane or isopentane may be used in combination, or air, nitrogen gas, or liquefied carbon dioxide may be mixed and dissolved in the stock solution using a gas loading device to cause foaming. The amount of the blowing agent added is usually 0.5 to 10% by mass based on the polyol composition, but when obtaining a low density flexible polyurethane foam with an apparent density of 25 kg/m ³ , it is 4.0 to 7.0% by mass. It is preferably 4.0 to 6.5% by mass, and more preferably 4.0 to 6.5% by mass. If the upper limit is exceeded, foaming may become difficult to stabilize, and if it is less than the lower limit, the density of the foam may not be sufficiently lowered.

The foam-breaking agent (F) in the present invention is used for the purpose of coarsening the cells of the flexible polyurethane foam. By making the cells coarser, a resonator-type sound absorption mechanism is developed within the flexible polyurethane foam, making it possible to enhance the sound absorption effect at specific frequencies. Components of the foam-breaking agent (F) include, for example, silicone-based, oil-based, fatty acid-based, fatty acid ester-based, and phosphoric acid ester-based foam-breakers, and foam-breakers whose structures are partially modified. Examples include things such as These may contain only one type or two or more types. In addition, if two or more types are contained, silicone-based, alcohol-based, ether-based, polyol-based, metal soap-based, nonionic surfactant-based, oil-based, fatty acid-based, fatty acid ester-based, and phosphate ester-based It may be a combination of any of the foam-breaking agent components. Moreover, this foam-breaking agent component is particularly preferably a silicone-based foam-breaking agent. Examples of the silicone foam-breaking agent include oil type, oil compound type, solution type, emulsion type, self-emulsifying type, and powder type, and any of them can be suitably used. Silicone foam-breaking agents have a polysiloxane structure like the silicone-based foam stabilizers mentioned above, but in order to exhibit foam-breaking properties, the polysiloxane chain is relatively long, and the polyol component (A) or polyisocyanate component ( It differs in that it is insoluble in B). The number average molecular weight of the polysiloxane component is preferably 10,000 to 50,000, more preferably 10,000 to 30,000. If the number average molecular weight is less than 10,000, it may be difficult to obtain a foam breaking effect, and if the number average molecular weight exceeds the upper limit, the dispersibility of the foam breaking agent may decrease and separation may occur.

Examples of silicone-based foam breakers include dimethyl silicone oil [(CH ₃ ) ₃ Si-[OSi(CH ₃ ) ₂ ]n-O-Si(CH ₃ ) ₃ ], methylphenyl silicone oil [(CH ₃ ) ₃ Si-[OSi(CH ₃ ) ₂ ]m-[OSi(CH ₃ )(C ₆ H ₅ )]n-O-Si(CH ₃ ) ₃ , (CH ₃ ) ₃ Si-[OSi(CH ₃ ) ₂ ]m-[OSi(C ₆ H ₅ ) ₂ ]n-O-Si(CH ₃ ) _3, etc.], methyl hydrogen silicone oil [(CH ₃ ) ₃ Si-[OSi(CH ₃ ) ₂ ]m-[ OSi(CH ₃ )(H)] n-O-Si(CH ₃ ) ₃ , etc.], and the like.

The content of the foam-breaking agent (F) is preferably 0.1 to 7.5% by mass, and 0.1 to 7.0% by mass based on the total amount of the polyol component (A) and the polyisocyanate component (B). Mass% is more preferred. If the content is less than 0.1% by mass, the cells may not be sufficiently coarsened and adequate sound absorption performance may not be obtained, and if the content exceeds 7.5% by mass, foaming may be difficult to stabilize. There is a risk that it will happen.

The sound absorbing material for vehicles made of flexible polyurethane foam in the present invention requires fillers such as calcium carbonate and barium sulfate, and various known additives and auxiliaries such as flame retardants, plasticizers, colorants, and antifungal agents. It can be used according to your needs.

According to the present invention, the thickness of the thinnest part is 5.0 to 50 mm, the density is 25 to 200 kg/ ^m3 , the C hardness of the foam test piece is 20 to 100 points, and the sound absorption coefficient is 1000 Hz to 3500 Hz. A vehicle made of flexible polyurethane foam with a simple average value (hereinafter referred to as average sound absorption coefficient) of 0.6 or more, an average sound absorption coefficient of 0.5 or more between 1000Hz and 2000Hz, and an air permeability of 0.1 to 100cm ³ /cm ² /sec. A sound absorbing material for use can be suitably obtained.

Here, sound absorption refers to the prevention of sound reflection, and is a completely different concept from sound insulation, which blocks the transmitted sound with walls and roofs. In addition, the average sound absorption coefficient from 1000Hz to 3500Hz is the simple average value of the normal incidence sound absorption coefficient at 1000Hz, 1250Hz, 1600Hz, 2000Hz, 2500Hz, 3150Hz, and 3500Hz measured based on the method described in JIS A1405-2:2007. mean do. A sound absorption coefficient of 0.6 or more means that 60% or more of sound is absorbed. Furthermore, the average sound absorption coefficient from 1000Hz to 2000Hz means a simple average value of normal incidence sound absorption coefficients at 1000Hz, 1250Hz, 1600Hz, and 2000Hz measured based on the method described in JIS A1405-2:2007.

The sound absorbing material for vehicles in the present invention includes engine room interior materials (hood liner, dash outer, oil pan, engine head cover, engine capsule, intake duct, air conditioner compressor cover), engine undercover, floor undercover, floor carpet, dash It can be suitably used for inner parts, front fender liners, rear fender liners, pillars, console door panels, instrument panels, headliners, trunk liners, inside air cleaner systems, inside tires, etc.

Next, the method for manufacturing the flexible polyurethane foam of the present invention will be explained.

The flexible polyurethane foam of the present invention contains a mixed solution of a polyol component (A), a polyisocyanate component (B), a catalyst (C), a foam stabilizer (D), a blowing agent (E), and a foam-breaking agent (F). It can be produced by reaction foaming. The foam-breaking agent (F) is preferably added to the polyol component (A) from the viewpoint of ensuring dispersion stability.

NCO INDEX (100 times the molar ratio of NCO to active hydrogen) when all the isocyanate groups in the polyisocyanate composition of the present invention and all the active hydrogen groups in the active hydrogen group-containing compound containing water are mixed and foamed. It is preferably 70 to 140, and more preferably 70 to 120 as a good range for molding cycles.

If NCO INDEX is less than 70, the closed-cell property of the foam will increase excessively, and if it is higher than 120, unreacted isocyanate will remain for a long time, which will lengthen the molding cycle, and the foam will collapse during foam expansion due to a delay in increasing the molecular weight. There is a possibility that this may occur.

The method for producing flexible polyurethane foam includes mixing the polyol component (A), polyisocyanate component (B), catalyst (C), foam stabilizer (D), foaming agent (E), and foam-breaking agent (F). Flexible polyurethane molded foam (hereinafter referred to as "flexible molded foam"), in which a liquid foaming stock solution is injected into a mold and then foamed and hardened; and flexible polyurethane, which is foamed by supplying a mixed solution into a foaming container or continuously on a belt conveyor. A method for manufacturing slab foam (hereinafter referred to as flexible slab foam) can be used.

In the production of flexible molded foam, the temperature of the mold when the foaming stock solution is injected into the mold is usually 30 to 80°C, preferably 45 to 70°C. If the mold temperature when injecting the above foaming stock solution into the mold is less than 30°C, there is a risk that the reaction rate will decrease and the production cycle will be extended. On the other hand, if it is higher than 80°C, the reaction between polyol and isocyanate will occur. On the other hand, if the reaction between water and isocyanate is excessively promoted, the foam may collapse during foaming.

The curing time when foaming and curing the above-mentioned foaming stock solution is preferably 10 minutes or less, more preferably 7 minutes or less, considering the production cycle of general flexible molded foams.

When producing a flexible molded foam, the above-mentioned components can be mixed using a high-pressure foaming machine, a low-pressure foaming machine, etc., as in the case of ordinary flexible molded foams.

It is preferable that the isocyanate component and the polyol component are mixed immediately before foaming. Other components can be mixed in advance with the isocyanate component or polyol component within a range that does not affect the storage stability of the raw material or changes in reactivity over time. These mixtures may be used immediately after mixing, or may be stored and then used in the required amount as appropriate. In the case of a foaming device that can simultaneously introduce more than two components into the mixing section, polyols, blowing agents, isocyanates, catalysts, foam stabilizers, foam breakers, etc. can also be introduced individually into the mixing section.

Further, the mixing method may be either dynamic mixing in which mixing is performed in the mixing chamber of the machine head of the foaming machine, or static mixing in which mixing is performed within the liquid feeding pipe, or both may be used in combination. Mixing of a gaseous component such as a physical foaming agent and a liquid component is often performed by static mixing, and mixing of components that can be stably stored as a liquid is often performed by dynamic mixing. The foaming device used in the present invention is preferably a high-pressure foaming device that does not require solvent cleaning of the mixing section.

The liquid mixture obtained by such mixing is injected into a mold, foamed and hardened, and then demolded. In order to perform the above-mentioned demolding smoothly, it is also suitable to apply a mold release agent to the mold in advance. As the mold release agent to be used, a mold release agent commonly used in the field of molding processing may be used.

Furthermore, in the production of flexible molded foam, the surface of the foam can be coated with a film by integral molding for the purpose of enhancing the sound absorption effect of a specific frequency. The sound absorbing film according to the present invention absorbs sound passing through the film from the outside by converting relatively low frequency sound of 1000 to 2000 Hz into vibration energy.

Integrated mold molding is a method in which a film is placed in advance in at least one of the lower mold or upper mold in a shape that follows the inner surface shape, the mixed liquid is injected into the mold, and the mold is removed after foaming and hardening. be. At least one film is placed in the order of the film and the flexible polyurethane foam with respect to the sound source, but may also be placed on the opposite side of the sound source in order to increase the sound absorption coefficient.

As the film laminated on the flexible polyurethane foam, a non-breathable resin film is preferably used. Examples of the resin include polyurethane resin, acrylic resin, polyethylene resin, polypropylene resin, vinyl chloride resin, EVA resin, PBT resin, silicone rubber, 6-nylon, 6,6-nylon, 11-nylon, 12-nylon, etc. Examples include polyamide resin.

The thickness of the film is preferably 0.1 to 250 μm. If the thickness of the film is less than 0.1 μm, the moldability during molding may deteriorate, and if it exceeds 250 μm, the sound absorption performance may deteriorate. Further, the density of the film is preferably 0.8 to 1.8 g/cm ³ . If the film density is less than 0.8 g/cm ³ , a sufficient sound absorption effect may not be obtained in the low frequency range, and if it exceeds the upper limit, the weight of the sound absorbing material will increase.

As a method of forming a film layer on the surface of flexible polyurethane foam, it is also possible to perform in-mold coat molding, in which the polyurethane foam is molded after applying an in-mold coat paint to at least one of the lower mold or upper mold in advance. .

The paint for in-mold coating can suitably be used in both water-based and solvent-based systems, and may be either a one-component curing type or a two-component curing type. Examples of the resin for in-mold coating paints include known paints such as polyurethane resins, acrylic resins, and polyester resins, among which polyurethane resins are preferred, and furthermore, from the viewpoint of being able to increase the softening temperature. An aqueous polyurethane resin emulsion using a polyol component having a carbonate skeleton is preferred. The polyol component having a carbonate skeleton may contain an ester group other than the carbonate skeleton, and an aqueous polyurethane resin emulsion using a polyol component having a carbonate skeleton, and an aqueous polyurethane resin emulsion using a polyol component having an ester group. It may be a mixture of. The average number of functional groups in the polyol component having a carbonate skeleton is preferably 2.1 or more. When the average number of functional groups is less than 2.1, the heat resistance of the resulting film layer is likely to be impaired.

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

The hardness of the flexible polyurethane foam obtained by the above manufacturing method is preferably 20 to 100 points, preferably 40 to 100 points in C hardness measured using a rubber hardness meter (Asker C type) according to JIS K7312. It is more preferable that there be. If the C hardness is less than 20 points, there is a possibility that sufficient sound absorption properties cannot be obtained. Further, the air permeability of the flexible polyurethane foam obtained by the above manufacturing method is preferably 0.1 to 100 cm ³ /cm ² /sec, and preferably 0 to 80 cm ³ /cm ² /sec, as measured in accordance with JIS K6400. Something is better. If the air permeability exceeds the upper limit, there is a risk that sufficient sound absorption may not be obtained.

Furthermore, the thickness of the thinnest part of the flexible polyurethane foam obtained by the above manufacturing method is preferably 5.0 to 50 mm, more preferably 5.0 to 30 mm. If the thickness of the thinnest part is less than 5.0 mm, it may not be possible to obtain sufficient sound absorption effect in the low and medium frequency range, and if the thickness exceeds the upper limit, there is a risk that it will not be possible to secure sufficient space in the passenger compartment. be.

After demolding, the soft molded foam is subjected to needle punching or hot needle processing on the surface skin layer or laminated film in order to effectively input sound wave energy into the internal porous layer and increase the sound absorption effect on the high frequency side. It can be used after being subjected to hole-opening treatment such as laser irradiation. The porosity is preferably 0 to 2.0%. If the porosity exceeds 2.0%, the sound absorption effect on the low frequency side may be reduced. Furthermore, when the porosity ratio exceeds 0%, the average pore diameter is preferably 300 μm to 1000 μm, more preferably 300 μm to 900 μm. If the average opening diameter is less than 300 μm, there is a risk that the hole will be blocked by burrs generated during drilling, and if it exceeds 1000 μm, there is a risk that the sound absorption effect on the low frequency side will decrease.

By the above-described manufacturing method of flexible polyurethane foam, the thickness is 5.0 to 50 mm, the density is 25 to 200 kg/ ^m3 , the C hardness of the foam test piece is 20 to 100 points, and the average sound absorption coefficient is 1000 Hz to 3500 Hz. It is possible to obtain a flexible polyurethane foam having an average sound absorption coefficient of 0.6 or more, an average sound absorption coefficient of 0.5 or more at 1000 Hz to 2000 Hz, and an air permeability of 0.1 to 100 cm ³ /cm ² /sec.

[Mechanism of obtaining high sound absorption effect by coarsening cells]
In the flexible polyurethane foam according to the present invention, a high sound absorption effect can be obtained by coarsening the cells using a foam-breaking agent. This is thought to be because as the cells become coarser, a Helmholtz resonator-type sound absorption mechanism is developed within the flexible polyurethane foam, increasing the sound absorption effect at specific frequencies. In a Helmholtz resonator, the air inside a container with an opening acts as a spring and resonates with vibrations at a specific frequency determined by the internal volume of the container and the area of the opening. The resonance phenomenon causes the air introduced into the container to violently vibrate, and the noise energy is dissipated due to friction loss, thereby absorbing the sound.

In the present invention, the Helmholtz resonator is constructed by using coarse cells as containers, relatively small cells other than coarse cells, holes existing in the foam skin layer formed during manufacturing, or openings in the film as container openings. It is thought that a high sound absorption effect can be exhibited by adjusting the coarse cell size (inner volume of the container) so that the resonance frequency is between 1000 Hz and 3500 Hz.

Furthermore, although a flexible polyurethane foam is used in the present invention, if a rigid polyurethane foam is used, it may be difficult to obtain a high sound absorption coefficient in a high frequency region of 3000 Hz or higher. Further, rigid polyurethane foam is difficult to conform to its shape when attached to a vehicle, and its shape is difficult to restore when compressed, which limits the locations where it can be used.

EXAMPLES Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples. In addition, unless otherwise specified, "part" and "%" in the text are based on mass.

(Examples 1 to 10, Comparative Examples 1 to 3)
[Preparation of polyol composition]
After purging the reactor equipped with a stirrer, a cooling tube, a nitrogen introduction tube, and a thermometer with nitrogen, add 50 g of polyol 1, 50 g of polyol 2, 2.5 g of crosslinking agent 1, 3.0 g of crosslinking agent 2, and catalyst 1. By preparing 0.4 g of , 0.06 g of catalyst 2, 1.0 g of foam stabilizer 1, 2.5 g of foam breaking agent 1, and 3.0 g of water, and stirring at 23 ° C. for 0.5 hour, A polyol composition (P-1) was obtained. As shown in Table 1, other polyol compositions (P-2 to P-9) were also prepared in the same manner as P-1.

[Preparation of isocyanate composition]
After purging the reactor equipped with a stirrer, a cooling tube, a nitrogen introduction tube, and a thermometer with nitrogen, 100 g of isocyanate 1 and 2.8 g of foam-breaking agent 1 were charged, and the mixture was stirred at 23° C. for 0.5 hours. An isocyanate composition (I-2) was obtained.

[Synthesis of polycarbonate polyol]
31.3 g of trimethylolpropane, 413.8 g of 1,6-hexanediol, 454.9 g of diethyl carbonate, and lithium acetylacetonate were placed in a 1L two-necked glass reactor equipped with a stirrer, thermometer, heating device, and cooler. 0.045 g were mixed and reacted at 100 to 150° C. for 8 hours under normal pressure while removing low-boiling components. Further, the reaction temperature was set to 150°C, the pressure inside the flask was reduced to 1 kPa, and the reaction was further carried out for 8 hours to obtain polycarbonate polyol (PCP-1) with a number average molecular weight of 1790 g/mol and a hydroxyl value of 90.7 mgKOH/g. Ta.

[Preparation of water-based polyurethane resin emulsion]
・PUD-1
In a reactor with a capacity of 1 L equipped with a stirrer, a thermometer, a nitrogen seal tube, and a condenser, N-980N (manufactured by Tosoh Corporation: number average molecular weight 2000; hydroxyl value 56.11 mgKOH/g; 1,6-hexanediol 77.6 g of polycarbonate diol), 3.04 g of 1,6-hexanediol, 26.9 g of PCP-1, 75 g of acetone, 5.29 g of 2,2-dimethylolpropanoic acid, 31.2 g of isophorone diisocyanate. After charging, heating to 60° C. and stirring at the same temperature for 30 minutes, 0.12 g of Neostane U-600 was added and reacted for 5 hours. Next, 3.99 g of triethylamine was charged to neutralize the carboxyl groups, and then 320 g of water was charged and emulsified while stirring. After emulsification, 0.18 g of KL-245 was added, and within 30 minutes, amine water (30 g of water and 1.99 g of isophorone diamine were blended) was charged, and the amine chain extension reaction was carried out at 40° C. for 12 hours. Stirring was stopped when the presence of isocyanate groups was no longer confirmed by FT-IR. Thereafter, the reaction solution was transferred to a 2 L eggplant flask and distilled under reduced pressure to remove 75 g of acetone and 50 g of water to obtain an aqueous polyurethane resin emulsion composition (PUD-1).

・PUD-2
In a reactor with a capacity of 1 L equipped with a stirrer, a thermometer, a nitrogen seal tube, and a condenser, N-980N (manufactured by Tosoh Corporation: number average molecular weight 2000; hydroxyl value 56.11 mgKOH/g; 1,6-hexanediol 51.8 g of polycarbonate diol), 1.99 g of 1,6-hexanediol, 53.8 g of PCP-1, 75 g of acetone, 5.29 g of 2,2-dimethylolpropanoic acid, and 31.2 g of isophorone diisocyanate. After heating to 60°C and stirring at the same temperature for 30 minutes, 0.12g of U-600 was added and reacted for 5 hours. Next, 3.99 g of triethylamine was charged to neutralize the carboxyl groups, and then 320 g of water was charged and emulsified while stirring. After emulsification, 0.18 g of KL-245 was added, and within 30 minutes, amine water (30 g of water and 1.99 g of isophorone diamine were blended) was charged, and the amine chain extension reaction was carried out at 40° C. for 12 hours. Stirring was stopped when the presence of isocyanate groups was no longer confirmed by FT-IR. Thereafter, the reaction solution was transferred to a 2 L eggplant flask and distilled under reduced pressure to remove 75 g of acetone and 50 g of water to obtain an aqueous polyurethane resin emulsion composition (PUD-2).

The raw materials used to obtain PUD-1 and PUD-2 are as follows.
・Trimethylolpropane: Sigma-Aldrich ・1,6-hexanediol: BASF-JAPAN ・2,2-dimethylolpropionic acid: Tokyo Kasei Co., Ltd. ・Isophorone diisocyanate: Evonik Co., Ltd. ・Acetone: KH Neochem Co., Ltd. - Triethylamine: Kishida Kagaku Co., Ltd. - Isophoronediamine: Tokyo Kasei Co., Ltd. - Neostan U-600: Nitto Kasei Co., Ltd. - KL-245: Evonik Co., Ltd. - Water: City water.

Among the raw materials shown in Table 1, the liquid temperature of the isocyanate composition and the mixture of all raw materials other than the isocyanate composition (polyol composition) was adjusted to 24° C. to 26° C., respectively. A predetermined amount of the polyisocyanate component was added to the polyol composition, mixed for 7 seconds using a mixer (7000 revolutions per minute), and then poured into a mold to foam a flexible polyurethane foam. Thereafter, it was taken out from the mold and the physical properties of the obtained flexible polyurethane foam were measured.

[Foaming conditions]
Mold temperature: 60-70℃
Mold shape: 200 mm x 200 mm x 10 mm (Example 8 is 200 x 200 x 30 mm)
Mold material: Aluminum Cure time: 5 minutes Mold integral molding: Place the film on the lower mold (Example 2, Example 3, Example 6)
: Spraying in-mold coat paint on the lower mold (Examples 9 and 10)

[Raw materials used]
・Polyol 1: Polyoxyethylene polyoxypropylene polyol with average functional group number = 3.0 and hydroxyl value = 33 (mgKOH/g), Excenol 823 (trade name) manufactured by AGC Corporation
・Polyol 2: Polymer polyol with average functional group number = 3.0 and hydroxyl value = 24 (mgKOH/g), Excenol 923 (trade name) manufactured by AGC Corporation
・Polyol 3: Unrefined castor oil with average functional group number = 2.7 and hydroxyl value = 160 (mgKOH/g), URIC H-24 (trade name) manufactured by Ito Oil Co., Ltd.
・Polyol 4: average number of functional groups = 4.0, hydroxyl value = 28 (mgKOH/g), polyoxyethylene polyoxypropylene polyol with 80% by mass of oxyethylene units in polyether polyol, NEF-024 manufactured by Tosoh Corporation ( Product name)
・Crosslinking agent 1: Diethanolamine (manufactured by Mitsui Chemicals)
・Crosslinking agent 2: Triethanolamine (manufactured by Mitsui Chemicals)
・Catalyst 1: 33% dipropylene glycol solution of triethylenediamine (manufactured by Tosoh Corporation, product name: TEDA L-33)
・Catalyst 2: 70% dipropylene glycol solution of bis(2-dimethylaminoethyl) ether (manufactured by Tosoh Corporation, product name: TOYOCAT ET)
・Foam stabilizer 1: Silicone foam stabilizer (manufactured by Momentive, trade name: L-5309J)
・Foam stabilizer 2: Silicone foam stabilizer (manufactured by Momentive, product name: L-3639LF)
・Foam stabilizer 3: Silicone foam stabilizer (manufactured by Momentive, trade name: L-3646J)
・Foam stabilizer 4: Silicone foam stabilizer (manufactured by Dow Toray Industries, product name: SRX-280A)
・Foam-breaking agent 1: GC-302SS (trade name) Silicone-based foam-breaking agent manufactured by Nissin Kagaku Kenkyusho Co., Ltd. ・Isocyanate 1: Polyphenylene polymethylene polyisocyanate with an MDI content of 70% by mass and an isomer content of 17.7% by mass (Manufactured by Tosoh Corporation, product name: CEF-507)
・Film: Thermoplastic polyurethane elastomer film with a film thickness of 30 μm (manufactured by Okura Kogyo Co., Ltd., trade name Silkron ET85)
・PUD-1, PUD-2: In-mold coat paint.

[Moldability evaluation]
In Table 1, an evaluation of formability of "○" means that the urethane foam does not collapse significantly after reaching its maximum height, or that the generated urethane foam shrinks immediately after foaming or after curing, and is soft. It means that the polyurethane foam was molded, and an evaluation of "x" means that phenomena such as collapse and shrinkage occurred in the urethane foam.

[Apparent density]
It was determined by the method described in JIS K6400.

[C hardness]
It was measured using a rubber hardness meter (Asker C type) according to JIS K7312.

[Air permeability]
It was measured by the method described in JIS K6400.

[Sound absorption coefficient]
Based on the method described in JIS A1405-2:2007, the normal incidence sound absorption coefficient at 500 to 6400 Hz was measured using a Brüel & Kjær Japan 4206 sound tube. The sound absorption coefficient was measured by placing a urethane foam with a diameter of 28.8 mm and a thickness of 10 mm so that the lower molding surface of the mold faced the sound source side, and with no air layer provided behind the urethane foam.

[Average cell diameter]
The average cell diameter of each polyurethane foam molded product was determined by hollowing out a 10 mm thick molded product into a disc shape with a diameter of 28.8 mm, and measuring the side surface of the foam vertically using a microscope equipped with a Moritex lens MTL5518C-034-01. An image with a field of view of 10 mm and a width of 16.3 mm was taken, the cell diameters of a predetermined number of cells present in the field of view were measured, and the cell diameters were simply averaged.

[Area ratio occupied by cells with a diameter of 5000 μm or more]
The area ratio occupied by cells with a diameter of 5,000 μm or more in each polyurethane foam molded product is determined by hollowing out a 10 mm thick molded product into a disc shape with a diameter of 28.8 mm, and equipping the foam cross section with a Moritex lens MTL5518C-034-01. Using a microscope, an image with a field of view of 10 mm in length and 16.3 mm in width was photographed, and the area of cells with a diameter of 5000 μm or more existing in the field of view was measured and calculated based on the following calculation formula.
Area ratio occupied by cells with a diameter of 5000 μm or more =
(Total area of cells with a diameter of 5000 μm or more/viewing area)×100 (formula).

As shown in Comparative Example 1 in Table 1, when no foam-breaking agent is used, the average sound absorption coefficient at 1000 to 3500 Hz and 1000 to 2000 Hz is extremely small. In this case, the average cell diameter is smaller than in the example. As shown in Comparative Example 2, even when a foam-breaking agent was used, if the amount used was too large compared to the specified amount, the molding stability of the foam decreased significantly and the foam could not be molded. As shown in Comparative Example 3, when the surface tension of the foam stabilizer was smaller than the specified value and no foam breaker was used, the molded foam shrank.

By comparing the above Examples and Comparative Examples, it is clear that in the present invention, when used as a sound absorbing material for vehicles, a molded article with a thin base material and high sound absorbing performance in a wide frequency range can be obtained. Therefore, the significance and remarkable excellence of the configuration of the present invention can be understood.

Claims (15)

A sound absorbing material for a vehicle made of a flexible polyurethane foam containing a polyol component (A) and a polyisocyanate component (B), wherein the polyol component (A) is a catalyst (C), a foam stabilizer (D), and a foaming agent (E), a foam-breaking agent (F) is contained in at least one of the polyol component (A) or the polyisocyanate component (B), and the surface tension of the foam stabilizer (D) is 22 to 28 mN/m. @23°C, and the content of the foam-breaking agent (F) is 0.1 to 7.5% by mass based on the total amount of the polyol component (A) and the polyisocyanate component (B), Sound absorbing material for vehicles. The sound absorbing material for a vehicle according to claim 1, wherein the foam-breaking agent (F) is a silicone oil, and the number average molecular weight of the polysiloxane component contained in the silicone oil is 10,000 to 50,000. . The sound-absorbing material for a vehicle according to claim 1 or 2, wherein the foam-breaking agent (F) is contained in the polyol component (A). The polyisocyanate component (B) contains diphenylmethane diisocyanate in a range of 50 to 85% by mass, and the total amount of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate contained in the diphenylmethane diisocyanate is 50 to 85% by mass. The sound absorbing material for a vehicle according to claim 1, characterized in that the amount of diisocyanate is 10 to 50% by mass based on the total amount of diisocyanate. It is characterized by having a density of 25 to 200 kg/m ³ , an Asker C hardness of 20 to 100 points measured according to JIS K7312, and an air permeability of 0.1 to 100 cm ³ /cm ² /sec. The sound absorbing material for a vehicle according to claim 1. The sound absorbing material for a vehicle according to claim 1, wherein the average cell diameter is 2000 μm or more, and the area ratio occupied by cells with a diameter of 5000 μm or more is 20% or more. The sound absorbing material for a vehicle according to claim 1, wherein the thickness of the thinnest part is 5.0 to 50 mm. A foam laminate comprising the sound absorbing material for a vehicle according to claim 1 and a film, wherein at least one film is arranged in the order of the film and the sound absorbing material for a vehicle with respect to a sound source. . The foam laminate according to claim 8, wherein the film is coated on a surface of a sound absorbing material for a vehicle. The foam laminate according to claim 8, wherein the film is a polyurethane resin film. The foam laminate according to claim 10, wherein the polyurethane resin film is made of an aqueous polyurethane resin emulsion. The foamed laminate according to claim 11, characterized in that a polyol component used as a raw material for the aqueous polyurethane resin emulsion has a carbonate skeleton. The foamed laminate according to claim 12, wherein the polyol component having a carbonate skeleton has an average number of functional groups of 2.1 or more. Claim 8, wherein the film has a thickness of 0.1 to 250 μm, a porosity of 0 to 2.0%, and an average pore diameter of 300 to 1000 μm when the porosity exceeds 0%. 14. The foam laminate according to any one of 13 to 13. A method for manufacturing a foam laminate, characterized in that the film is coated on the surface of the sound absorbing material by integral molding with the sound absorbing material for a vehicle according to claim 1.