Composition for molding polyurethane foam, polyurethane foam, and sound-absorbing material

Abstract

To provide a composition for molding polyurethane foam that enables the formation of polyurethane foam having superior sound-absorbing properties in the low frequency range even with a small thickness.SOLUTION: The present invention provides a composition for molding polyurethane foam, comprising a polyol (A), a polyisocyanate (B), a blowing agent (C), a foam stabilizer (D), a catalyst (E), and a defoamer (F), wherein the defoamer (F) contains a sugar alcohol, and the content of the defoamer (F) is 1 to 8 pts.mass relative to 100 pts.mass of the polyol (A).SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a composition for forming a polyurethane foam, a polyurethane foam, and a sound-absorbing material.

Background Art

[0002] Sound-absorbing materials having a polyurethane foam (polyurethane foam) are widely used, for example, as building materials and interior materials of vehicles. As related prior art documents, Patent Documents 1 to 5 can be cited.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] In vehicles such as automobiles, it is required to reduce noise in the low frequency band (500 to 1000 Hz), typified by the transmission sound of the engine and the road noise from the tires. However, according to the findings of the present inventors, conventional porous sound-absorbing materials generally have significantly low sound absorption in the low frequency band as shown in FIG. 9. Therefore, in order to enhance the sound absorption in the low frequency band, usually, the polyurethane foam is formed thick (the thickness t is increased).

[0005] However, if the thickness of the sound-absorbing material increases, the space inside the vehicle will become narrow. Furthermore, there is also a risk that the weight of the sound-absorbing material will increase and the fuel efficiency will deteriorate. Therefore, there is a demand for a sound-absorbing material that has excellent sound absorption in the low-frequency band even if it is thin (for example, 10 mm or less).

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a polyurethane foam having excellent sound absorption in the low-frequency band even if the thickness is thin, a sound-absorbing material having the same, and a composition for forming a polyurethane foam capable of realizing these.

Means for Solving the Problems

[0007] The present invention includes the following [1] to

[12] . 〔1〕A composition for forming a polyurethane foam, comprising a polyol (A), a polyisocyanate (B), a blowing agent (C), a foam stabilizer (D), a catalyst (E), and a foam breaker (F), wherein the foam breaker (F) contains a sugar alcohol, and the blending ratio of the foam breaker (F) is 1 part by mass or more and 8 parts by mass or less when 100 parts by mass of the polyol (A) is used. 〔2〕The composition for forming a polyurethane foam according to [1], wherein the sugar alcohol contains a monosaccharide alcohol. 〔3〕The composition for forming a polyurethane foam according to [1], wherein the sugar alcohol has a multi-layer structure coated with a silicone compound and further coated with a surfactant on the outside thereof, and is in the state of emulsion particles. 〔4〕A polyurethane foam obtained by reacting and foaming the composition for forming a polyurethane foam according to any one of [1] to [3]. 〔5〕A molded body having a core layer and a skin layer thinner than the core layer, having a thickness of 10 mm or less, and having a reverberation chamber sound absorption rate at a frequency of 1000 Hz measured by the reverberation chamber method in accordance with ISO354 of 0.6 or more at a thickness of 10 mm, the polyurethane foam according to [4]. 〔6〕The ratio (Dc / Ds) of the average bubble diameter Dc of the core layer to the average bubble diameter Ds of the skin layer is 5 or more and 20 or less, the polyurethane foam according to 〔5〕. 〔7〕The average bubble diameter Dc of the core layer is 200 μm or more and 600 μm or less, the polyurethane foam according to 〔6〕. 〔8〕The number of bubbles per 1 mm 2 of the core layer is 10 or less, and the average bubble diameter Dc of the core layer is 200 μm or more and 600 μm or less, the polyurethane foam according to 〔5〕 or 〔6〕. 〔9〕The average aspect ratio of the bubbles in the core layer is 1.5 or more and 3 or less, the polyurethane foam according to any one of 〔5〕 to 〔8〕. 〔10〕The number of bubbles per 1 mm 2 of the skin layer is 10 or less, and the average bubble diameter Ds of the skin layer is 10 μm or more and 100 μm or less, the polyurethane foam according to any one of 〔5〕 to 〔9〕. 〔11〕A sound-absorbing material having the polyurethane foam according to 〔4〕. 〔12〕A sound-absorbing material having the polyurethane foam according to 〔5〕.

[0008] As a result of intensive studies, the present inventors have found that the above problems can be solved by blending a defoaming agent (F) containing a sugar alcohol in a polyurethane foam-forming composition at a predetermined ratio. By using the polyurethane foam-forming composition disclosed herein, a polyurethane foam excellent in sound absorption in the low frequency band (500 to 1000 Hz) can be suitably obtained even with a thin thickness. Further, according to the polyurethane foam and the sound-absorbing material having the same disclosed herein, noise in the low frequency band (for example, engine noise and road noise) can be reduced even with a thin thickness, so that the sound absorption can be enhanced while achieving space saving. As a result, weight reduction can also be realized.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than those specifically mentioned in this specification, which are necessary for the implementation of the present invention, can be grasped as design matters of those skilled in the art based on the prior art. The present invention can be implemented based on the matters disclosed in this specification and the drawings and the common general knowledge in the art. In addition, the notation "X to Y" indicating a range in this specification includes the meanings of "greater than X" and "less than Y" as well as the meaning of "X or more and Y or less".

[0011] ≪Composition for Molding Polyurethane Foam≫ The composition for molding a polyurethane foam according to the present embodiment essentially contains a polyol (A), a polyisocyanate (B), a foaming agent (C), a foam stabilizer (D), a catalyst (E), and an anti-foaming agent (F), and may further contain optional components such as an additive (G) as needed.

[0012] The polyol (A) reacts with the polyisocyanate (B) to form a polyurethane. The polyol (A) is not particularly limited as long as it is a compound having two or more hydroxy groups in one molecule, and one or more compounds conventionally used in this type of composition can be appropriately used. Specific examples include polyether polyols, polyester polyols, polyether ester polyols, and the like. Among them, it is preferably included polyether polyol because of its excellent reactivity with the polyisocyanate (B), and it is more preferable that the polyether polyol is the first component (the component with the highest blending ratio by mass. The same shall apply hereinafter).

[0013] Examples of the polyether polyol include polypropylene glycol (PPG), polymer polyol (POP) obtained by copolymerizing acrylonitrile or styrene in PPG and dispersing polymer particles, polytetramethylene glycol, polyether polyol composed of a polymer obtained by addition polymerization of propylene oxide and ethylene oxide to a polyhydric alcohol, and modified products thereof. Examples of the polyhydric alcohol include glycerin and dipropylene glycol. Among them, it is preferably included polyether polyol of polypropylene glycol type produced by adding a propylene oxide group to a polyhydric alcohol.

[0014] In some embodiments, it is preferable that the polyol (A) contains both polypropylene glycol (PPG) and polymer polyol (POP). Thereby, a polyurethane foam with appropriate hardness can be preferably produced. Further, for example, during mold molding, the swelling of the polyurethane foam can be suppressed, and demolding can be easily performed. In the polyol (A), PPG may be the first component, or POP may be the first component. Although not particularly limited, the mixing ratio of PPG and POP is preferably PPG:POP = 30:70 to 70:30, more preferably PPG:POP = 40:60 to 60:40 on a mass basis. By setting the ratio of POP to a predetermined value or more, the bubbles inside the foam tend to communicate after demolding, and the shrinkage of the polyurethane foam can be preferably suppressed.

[0015] Although not particularly limited, the polyol (A) preferably has a number average molecular weight of 500 or more, more preferably 1,000 or more, and preferably 15,000 or less, more preferably 10,000 or less. By setting it within the above range, a polyurethane foam excellent in flexibility and durability can be easily obtained. In this specification, the "number average molecular weight" is a value measured by gel permeation chromatography (GPC) method and determined in terms of standard polystyrene.

[0016] The polyisocyanate (B) is not particularly limited as long as it is a compound having two or more isocyanate groups in one molecule, and one or more compounds conventionally used in this type of composition can be appropriately used. Specific examples include 4,4-diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), 1,5-naphthalene diisocyanate (NDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate, and modified products thereof. Among them, MDI is preferred. Thereby, it has appropriate hardness during demolding and is less likely to deform, so it becomes easier to mold a polyurethane foam having a desired shape. Therefore, it is particularly suitable when producing a thin-walled (for example, 10 mm or less) polyurethane foam. In addition, since the polyurethane foam is less likely to sag, the durability can be improved.

[0017] It is preferable that MDI is the first component in the polyisocyanate (B), more preferably occupying 80% by mass or more of the entire polyisocyanate (B), and particularly preferably consisting substantially of (95% by mass or more of the entire polyisocyanate (B)) MDI. It is preferable that the polyisocyanate (B) does not substantially contain TDI which is particularly widely used in this type of composition (for example, TDI is 1% by mass or less of the entire polyisocyanate (B)).

[0018] The foaming agent (C) is for foaming the polyurethane into a foam shape. As the foaming agent (C), water is preferred. Water forms high-hardness urea groups and generates carbon dioxide gas in the reaction between the polyol (A) and the polyisocyanate (B). Thereby, the polyurethane can be foamed. It is preferable that water is the first component in the foaming agent (C), and particularly preferably consists substantially of (95% by mass or more of the entire foaming agent (C)) water. However, the foaming agent (C) may contain an arbitrary foaming agent together with water. Examples of the arbitrary foaming agent include low-boiling organic compounds such as cyclopentane and isopentane.

[0019] Although not particularly limited, the blending ratio of the foaming agent (C) is generally 0.5 to 10 parts by mass, preferably 2 to 5 parts by mass, when the polyol (A) is 100 parts by mass. This makes it easier to obtain a polyurethane foam having the properties (for example, air permeability) described later.

[0020] The foam stabilizer (D) is for smoothly advancing the foaming performed by the foaming agent (C) and homogenizing the bubbles (cells) of the polyurethane foam. The foam stabilizer (D) is not particularly limited, and one or more compounds conventionally used in this type of composition can be appropriately used. Specific examples include silicone compounds, polyether siloxanes, surfactants such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate. Among them, silicone compounds are preferred.

[0021] Although not particularly limited, the blending ratio of the foam stabilizer (D) is generally 0.1 to 5 parts by mass, preferably 0.2 to 2 parts by mass, when the polyol (A) is 100 parts by mass. The blending ratio of the foam stabilizer (D) is preferably less than that of the foaming agent (C). This makes it easier to obtain a polyurethane foam having good properties.

[0022] The catalyst (E) is not particularly limited, and one or more urethanization catalysts conventionally used in this type of composition can be appropriately used. Specific examples include amine compounds such as triethylamine, triethylenediamine, tripropylamine, tributylamine, bis-(2-dimethylaminoethyl) ether, N-methylmorpholine, N-ethylmorpholine, triethylenediamine, and organic acid salts thereof; tin compounds such as stannous octoate and dibutyltin dilaurate. Among them, amine compounds are preferred. The catalyst (E) preferably consists substantially of (95% by mass or more of the whole catalyst (E)) amine compounds.

[0023] Although not particularly limited, the blending ratio of the catalyst (E) is generally 0.1 to 5 parts by mass, preferably 0.35 to 2 parts by mass, when the polyol (A) is 100 parts by mass. The blending ratio of the catalyst (E) is preferably less than that of the foaming agent (C). This makes it easier to obtain a polyurethane foam with good properties.

[0024] The foam breaker (F) is for entering the foam, destroying the cells, and coarsening the cells of the polyurethane foam. The foam breaker (F) essentially contains a sugar alcohol. Thereby, a polyurethane foam having the following properties (for example, the number of cells, average cell diameter, average aspect ratio) can be preferably obtained. Sugar alcohol is a carbohydrate produced by the reduction reaction of the carbonyl group of a saccharide. The sugar alcohol is not particularly limited, and for example, one or more compounds as described below can be appropriately used. Specific examples of sugar alcohol include monosaccharide alcohols obtained by reducing monosaccharides, disaccharide alcohols obtained by reducing disaccharides, oligosaccharide alcohols obtained by reducing oligosaccharides, and the like. Among them, it is preferable to contain a monosaccharide alcohol.

[0025] Examples of monosaccharide alcohols include tetritols such as erythritol and threitol; pentitols such as arabinitol, xylitol, and ribitol; hexitols such as sorbitol, mannitol, and galactitol; heptitols such as volemitol; octitols such as D-erythro-D-galactooctitol; nonitols; and decitols. There is no restriction on the configuration of these sugar alcohols, and the sugar alcohol may be in the D form, L form, or a mixture of the D form and L form. Examples of disaccharide alcohols include sucrose, maltitol, and lactitol. Oligosaccharide alcohols are sugar alcohols of trisaccharides to decasaccharides, that is, trisaccharide alcohols to decasaccharide alcohols. Specific examples include maltotriitol, maltotetraitol, maltopentaitol, and maltohexitol.

[0026] The sugar alcohol preferably has a monosaccharide alcohol as the first component, more preferably occupies 80% by mass or more of the total sugar alcohol, and particularly preferably consists substantially of (95% by mass or more of the total sugar alcohol) monosaccharide alcohol. Further, in some embodiments, the monosaccharide alcohol preferably contains a plurality of types (the above-mentioned types) of monosaccharide alcohols having different numbers of hydroxy groups. For example, it is preferable to contain both tetritols and pentitols.

[0027] Although not particularly limited, the sugar alcohol preferably has a number average molecular weight of 100 or more, more preferably 120 or more, and preferably 2000 or less, more preferably 1000 or less, still more preferably 500 or less, for example 300 or less. This makes it easier to obtain a polyurethane foam with good properties.

[0028] The sugar alcohol is typically water-soluble. In some embodiments, from the perspective of improving the affinity or solubility / dispersibility with the various components described above, the defoaming agent (F) preferably contains a sugar alcohol, a silicone compound, and a surfactant (emulsifier), and is more preferably in the state of emulsion particles containing a sugar alcohol, a silicone compound, and a surfactant (emulsifier). In particular, it is preferably in the state of emulsion particles having a multilayer structure in which a water-soluble sugar alcohol is coated with a hydrophobic silicone compound and further coated with a surfactant on the outside. The emulsion particles are more preferably oil-in-water (O / W type) emulsions. Examples of such commercially available products include Paracool ID-8, IDC-1,4 manufactured by Ohara Palladium Chemical Co., Ltd.

[0029] The emulsion particles preferably have a volume-based diameter based on laser diffraction / scattering particle size distribution measurement in the sub-micro order. For example, it is more preferable that the diameter of 95% or more of the particles is 0.1 μm (100 nm) to 0.9 μm (900 nm), and still more preferable that it is 0.2 μm (200 nm) to 0.5 μm (500 nm).

[0030] As the silicone compound constituting the emulsion particles, there is no particular limitation as long as it is a compound having a siloxane bond in the molecule, and one or more conventionally known compounds can be appropriately used. Specific examples include silicone oil, methylhydrogenpolysiloxane, silicone resin, etc. Examples of silicone oil include amino-modified silicone oil, epoxy-modified silicone oil, carbonyl-modified silicone oil, polyether-modified silicone oil, dimethyl silicone oil, etc. The content of the silicone compound is preferably 0.1 to 10 times, more preferably 0.5 to 2 times the content of the sugar alcohol on a mass basis.

[0031] The surfactant constituting the emulsion particles is not particularly limited, and one or more conventionally known compounds can be appropriately used. Specific examples include nonionic surfactants, anionic surfactants, etc. Examples of nonionic surfactants include polyoxyethylene secondary alcohol ether, polyoxyethylene tridecyl ether, polyoxyethylene isodecyl ether, etc.

[0032] The defoaming agent (F) preferably has a sugar alcohol as the first component and more preferably occupies 80% by mass or more of the entire defoaming agent (F). The defoaming agent (F) may substantially consist of a sugar alcohol (95% by mass or more of the entire defoaming agent (F)). However, the defoaming agent (F) may further contain components other than the sugar alcohol as long as it does not significantly reduce the effects of the technology disclosed herein. As an example, saccharides other than sugar alcohol, such as monosaccharides, disaccharides, oligosaccharides (e.g., trisaccharides to decasaccharides), and compounds known to be usable as the defoaming agent (F) conventionally, such as silicone-based defoaming agents, etc. can be mentioned.

[0033] The blending ratio of the foam breaker (F) needs to be 1 to 8 parts by mass when the polyol (A) is 100 parts by mass. If the blending ratio is less than 1 part by mass, the core layer cannot be properly foamed. Conversely, if the blending ratio exceeds 8 parts by mass, the foaming progresses too much and the bubbles become too large, and appropriate sound absorption cannot be obtained. The blending ratio of the foam breaker (F) is preferably 2.5 to 8 parts by mass, and more preferably 5 to 8 parts by mass.

[0034] The blending ratio of the foam breaker (F) is preferably higher than that of the foaming agent (C). Although not particularly limited, the ratio (F / C) of the blending ratio of the foam breaker (F) to the blending ratio of the foaming agent (C) is preferably more than 1, for example, 1.1 to 2. The blending ratio of the foam breaker (F) is preferably higher than that of the foam stabilizer (D). Although not particularly limited, the ratio (F / D) of the blending ratio of the foam breaker (F) to the blending ratio of the foam stabilizer (D) is preferably more than 1, for example, 2 to 10. The blending ratio of the foam breaker (F) is preferably higher than that of the catalyst (E). The blending ratio of the foam breaker (F) is preferably less than that of the polyisocyanate (B). Although not particularly limited, the ratio (F / B) of the blending ratio of the foam breaker (F) to the blending ratio of the polyisocyanate (B) is preferably less than 1, for example, 0.01 to 0.9, preferably 0.1 to 0.2. By satisfying at least one (preferably two or more) of these, it becomes easier to obtain a polyurethane foam having the properties (for example, the number of bubbles, average bubble diameter, average aspect ratio) described later.

[0035] Examples of the additive (G) include a linking agent, a crosslinking agent, a flame retardant, a filler, a stabilizer, a colorant, a plasticizer, a release agent, and the like. Examples of the linking agent include polyhydric alcohols such as polypropylene glycol, ethylene glycol, glycerin, trimethylolpropane, and pentaerythritol. The additive (G) is not particularly limited as long as it is blended according to a conventional method. For example, the blending ratio of the linking agent is generally 1 to 10 parts by mass, preferably 2 to 8 parts by mass, when 100 parts by mass of the polyol (A) is used. Further, from the viewpoint of facilitating the production of the polyurethane foam having the properties (for example, the number of bubbles, the average bubble diameter, and the average aspect ratio) described later, a compound that functions as a crosslinking agent is not included, or for example, when 100 parts by mass of the polyol (A) is used, it is preferably suppressed to less than 0.1 part by mass, more preferably less than 0.01 part by mass.

[0036] ≪Method for producing polyurethane foam≫ The polyurethane foam can be produced by reacting and foaming each component (raw material) of the polyurethane foam composition as described above according to a conventional method. The production method may be a one-shot method or a prepolymer method. The polyurethane foam having the properties described later can be preferably produced by a production method including, for example, a composition preparation step S1 and a mold forming step S2.

[0037] In the preparation step S1, first, a first raw material (resin premix) containing, as essential components, a polyol (A), a foaming agent (C), a foam stabilizer (D), a catalyst (E), and an antifoaming agent (F), and further containing various other additives as optional components, is prepared. Also, a second raw material containing a polyisocyanate (B) as an essential component and further containing various other additives as optional components is prepared. Although not particularly limited, the ratio of the polyisocyanate (B) is generally 25 to 80 parts by mass, preferably 30 to 50 parts by mass, when 100 parts by mass of the first raw material (resin premix) is used.

[0038] In the mold forming step S2, the polyurethane raw material is injected into the mold, clamped, and the polyurethane raw material is reacted and foamed in the mold. Specifically, the first raw material and the second raw material prepared in the above preparation step S1 are mixed and injected into the mold body (lower mold), and the lid body (upper mold) is closed. Thereby, polyol (A) and polyisocyanate (B) are chemically reacted in the mold, and the polymer obtained with the carbon dioxide gas generated simultaneously with the reaction is foam-molded. Note that the conditions for foam molding (such as molding temperature) may be the same as those in the prior art. The molding temperature may be, for example, 40 to 90°C. As described above, the polyurethane foam disclosed herein can be manufactured.

[0039] Figures 1(A) and (B) are curves (rise curves) showing changes in foam height during the rise time from the start of foaming to the end of foaming when polyisocyanate (B) is mixed with the resin premix. The horizontal axis represents time, and the vertical axis represents foam height. Figure 1(A) is a schematic diagram of the rise curve when the defoaming agent (F) disclosed herein is not included, and Figure 1(B) is a schematic diagram of the rise curve when the defoaming agent (F) disclosed herein is included. Note that the conditions for foam molding (such as molding temperature) are the same. As shown in Figure 1(A), when the defoaming agent (F) is not included in the polyurethane raw material, gas does not escape during the rise, and gas escape occurs at the final point, so fine bubbles (cells) are maintained inside the core layer. On the other hand, as shown in Figure 1(B), when the defoaming agent (F) is included in the polyurethane raw material, the reaction proceeds while destroying the bubbles, and is rapidly cured by the heat of the molding die before the foam skeleton collapses, so coarse bubbles (cells) are formed inside the core layer. Thereby, it is considered that the core layer becomes coarser than before.

[0040] ≪Polyurethane Foam≫ The polyurethane foam of this embodiment is obtained by reacting and foaming the above-described composition for producing a polyurethane foam. The thickness (average thickness) T of the polyurethane foam (see Figure 2) is preferably 10 mm or less. Thereby, space saving and weight reduction can be achieved. From the viewpoint of stably exhibiting the effects of the technology disclosed herein at a high level, the thickness T of the polyurethane foam is preferably 1 mm or more, more preferably 2 mm or more, still more preferably 3 mm or more, and particularly preferably 5 mm or more. The apparent density of the polyurethane foam measured in accordance with JIS K6400 is preferably 70 kg / m 3 or more, and more preferably 80 kg / m 3 or more. The resilience modulus of the polyurethane foam measured in accordance with JIS K6400 is preferably less than 50%, and more preferably less than 45%.

[0041] The polyurethane foam preferably has a reverberation chamber sound absorption rate of 0.6 or more, more preferably 0.7 or more, at a frequency of 1000 Hz measured by the reverberation chamber method in accordance with ISO354 at a thickness of 10 mm. The reverberation chamber sound absorption rate indicates that the closer the value is to 1, the better the sound absorption performance. By setting the reverberation chamber sound absorption rate at a thickness of 10 mm to a predetermined value or more, for example, noise in the low frequency band (such as engine noise and road noise) can be reduced at a high level, so that sound absorption can be enhanced while achieving space saving. Consequently, weight reduction can also be realized. The measurement method of the reverberation chamber sound absorption rate will be described in detail in the Examples section.

[0042] FIG. 2 is a cross-sectional view schematically showing a polyurethane foam 10 according to an embodiment. The polyurethane foam 10 of this embodiment is a molded body including a core layer 11 and a skin layer (surface layer) 12. The skin layer 12 is typically the layer on the side facing the noise source (the layer disposed on the sound incident side). The skin layer 12 is formed here on the first surface (front surface) and the second surface (back surface) of the core layer 11, respectively. The skin layer 12 is typically a layer formed substantially simultaneously with the core layer 11 by mold molding. Therefore, in the polyurethane foam 10, the boundary between the core layer 11 and the skin layer 12 can be relatively unclear compared to the case where the skin layer 12 is formed later on the surface of the core layer 11 by, for example, a spraying method or the like. When the skin layer 12 is formed by mold molding, the thickness ts of the skin layer 12 is thinner than the thickness tc of the core layer 11. The thickness ts of the skin layer 12 is typically 500 μm or less, and here is about 10 to 200 μm.

[0043] The core layer 11 has a plurality of bubbles (cells) P1. The skin layer 12 has a plurality of bubbles (cells) P2. The core layer 11 and the skin layer 12 each have a porous structure. The apparent density of only the skin layer 12 may be higher than that of the core layer 11.

[0044] In some embodiments, the average bubble diameter (cell diameter) Dc of the bubbles P1 in the core layer 11 is preferably 200 to 600 μm, more preferably 250 to 500 μm. By setting the average bubble diameter Dc to a predetermined value or more, the core layer 11 becomes coarser, and it becomes easier to entangle noise (especially noise in the low frequency band) when passing through the core layer 11, so that the sound absorption effect is easily obtained. Also, by setting the average bubble diameter Dc to a predetermined value or less, it is possible to suppress the core layer 11 from becoming too coarse and sound from escaping. As a result, noise (especially noise in the low frequency band) is less likely to pass through the core layer 11, so that the sound absorption effect is easily obtained. In this specification, the "average bubble diameter Dc" refers to a value obtained by measuring the bubbles P1 of the core layer 11 with a cell structure distribution analyzer Porescan (manufactured by Goldlucke Ingenieurleistungen) from the cross-sectional side (lamination direction) of the polyurethane foam 10.

[0045] In some embodiments, the average bubble diameter (cell diameter) Ds of the bubbles P2 in the skin layer 12 is preferably 10 to 100 μm, more preferably 15 to 50 μm. By setting the average bubble diameter Ds to a predetermined value or more, noise (especially noise in the low frequency band) easily penetrates into the polyurethane foam 10, so that the sound absorption effect is easily obtained. Further, by setting the average bubble diameter Ds to a predetermined value or less, the skin layer 12 becomes film-like and ventilation on the surface can be suppressed, so that the sound insulation effect is easily obtained. In this specification, the "average bubble diameter Ds" refers to the value obtained by measuring the bubbles P2 in the skin layer 12 with a cell structure distribution analyzer Porescan (manufactured by Goldlucke Ingenieurleistungen) from the surface side of the polyurethane foam 10.

[0046] In some embodiments, the average bubble diameter Dc of the core layer 11 is larger than the average bubble diameter Ds of the skin layer 12. The ratio (Dc / Ds) of the average bubble diameter Dc of the core layer 11 to the average bubble diameter Ds of the skin layer 12 is preferably 2 or more, more preferably 3 or more, further preferably 5 or more, for example 7 or more, and even more preferably 9 or more. Thereby, ventilation on the surface of the skin layer 12 can be suppressed and the sound insulation effect is easily obtained, and the core layer 11 becomes rough and it becomes easy to entangle noise (especially noise in the low frequency band) in the core layer 11, so that the sound absorption effect is particularly easily obtained. Further, the above ratio (Dc / Ds) is preferably 50 or less, more preferably 30 or less, and further preferably 20 or less. Thereby, it is possible to prevent the core layer 11 from becoming too rough, or the skin layer 12 becomes film-like and ventilation on the surface is suppressed to obtain a sound insulation effect.

[0047] In some embodiments, the unit area of the core layer 11 (1 mm 2)The number of bubbles P1 per hit is preferably 20 or less, more preferably 10 or less, and more preferably 1 to 10 or 3 to 10, for example. By setting the number of bubbles P1 to a predetermined value or more, the average bubble diameter Dc of the core layer 11 can be relatively increased, and it becomes easier to trap noise (especially noise in the low frequency band) when passing through the core layer 11, so that the sound absorption effect is easily obtained. In the present specification, the "number of bubbles P1" refers to the value obtained by measuring the bubbles P1 in the core layer 11 with a cell structure distribution analyzer Porescan (manufactured by Goldlucke Ingenieurleistungen) from the cross-sectional side (lamination direction) of the polyurethane foam 10.

[0048] In some embodiments, the number of bubbles P2 per unit area (1 mm 2 ) of the skin layer 12 is preferably 20 or less, more preferably 10 or less, and more preferably 1 to 10 or 4 to 10, for example. By setting the number of bubbles P2 to a predetermined value or less, the skin layer 12 becomes film-like and ventilation on the surface of the skin layer 12 can be suppressed, so that the sound insulation effect is easily obtained. The number of bubbles P2 per unit area of the skin layer 12 is preferably larger than the number of bubbles P1 per unit area of the core layer 11. In the present specification, the "number of bubbles P2" refers to the value obtained by measuring the bubbles P2 in the skin layer 12 with a cell structure distribution analyzer Porescan (manufactured by Goldlucke Ingenieurleistungen) from the surface side of the polyurethane foam 10.

[0049] In some embodiments, the average aspect ratio of the bubbles P1 in the core layer 11 is preferably 1 to 10, more preferably 1.5 to 5, still more preferably 1.5 to 3, and particularly preferably 1.5 to 2. Thereby, the core layer 11 becomes coarser, and it becomes easier to trap noise (especially noise in the low frequency band) when passing through the core layer 11, so that the sound absorption effect is easily obtained. In the present specification, the "average aspect ratio" refers to the ratio (L / W) of the major axis L to the minor axis W when measuring the bubbles P1 in the core layer 11 with a cell structure distribution analyzer Porescan (manufactured by Goldlucke Ingenieurleistungen) from the cross-sectional side (lamination direction) of the polyurethane foam 10.

[0050] In some embodiments, the polyurethane foam 10 has a thickness of 10 mm, and the air permeability of the core layer 11 measured in accordance with JIS L 1096 A method is 1 to 10 cm 3 / cm 2 ·s, preferably 2 to 5 cm 3 / cm 2 ·s. This makes it easier to obtain a sound absorption effect and can also achieve weight reduction.

[0051] Preferably, in addition to reducing noise in the low-frequency band, the polyurethane foam 10 can also reduce noise in the high-frequency band exceeding 1000 Hz. For example, the polyurethane foam 10 preferably has a reverberation room absorption coefficient at a frequency of 2000 Hz measured by the reverberation room method in accordance with ISO354 of 0.8 or more, more preferably 0.9 or more, at a thickness of 10 mm. For example, the polyurethane foam 10 preferably has a reverberation room absorption coefficient at a frequency of 4000 Hz measured by the reverberation room method in accordance with ISO354 of 0.6 or more, more preferably 0.7 or more, at a thickness of 10 mm. The maximum value of the reverberation room absorption coefficient measured in the frequency range of 400 to 5000 Hz of the polyurethane foam 10 is preferably in the frequency band of 1000 to 2000 Hz. Thereby, excellent sound absorption can be exhibited in a wide frequency band.

[0052] The polyurethane foam 10 disclosed herein is excellent in absorbing sound (sound absorption property) in the low-frequency band. The polyurethane foam 10 preferably has a vibration transmissibility at a frequency of 1000 Hz measured by a vibration test of 0.2 (G’ / G) or less, more preferably 0.1 (G’ / G) or less, at a thickness of 10 mm. Note that the smaller the value of the vibration transmissibility, the better the sound absorption property. The vibration test will be described in detail in the Examples section.

[0053] ≪Applications of Polyurethane Foam≫ The polyurethane foam 10 can be suitably used for various applications as a sound-absorbing material. Since the polyurethane foam 10 is particularly excellent in sound absorption in the low-frequency band, it can be suitably used as an interior member of a vehicle such as an automobile, for example, a ceiling material, a floor under cover, a transmission insulator, a hood insulator, a dash outer insulator, an engine cover, a wheel house liner, etc. Further, the use of the polyurethane foam 10 is not limited to a sound-absorbing material, and it may be used as, for example, a sound-insulating material, a vibration-proof material, etc.

[0054] Hereinafter, examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples.

[0055] ≪Test Example I: Examination on the presence or absence of a blowing agent≫ As Example 1 and Comparative Examples 1 and 2, polyurethane foams were produced by mold-molding polyurethane raw materials prepared with the following components. Specifically, first, the following components were mixed in the blending amounts shown in Table 1 to prepare a resin premix. 〇Polyol (A) ·PPG1: Actocol (registered trademark) EP-828 (manufactured by Mitsui Chemicals, Inc.) ·PPG2: A mixture of the above PPG1, Actocol (registered trademark) T-1000 (manufactured by Mitsui Chemicals, Inc.), and Sunnex (registered trademark) GP-3000 (manufactured by Sanyo Chemical Industries, Ltd.) ·POP: Sunnex (registered trademark) KC-900 (manufactured by Sanyo Chemical Industries, Ltd.) 〇Blowing agent (C): Water 〇Foam stabilizer (D) ·Foam stabilizer 1: VORASURF (registered trademark) SZ-1346E (manufactured by Dow Corning Toray Co., Ltd.) ·Foam stabilizer 2: VORASURF (registered trademark) SZ-3601 (manufactured by Dow Corning Toray Co., Ltd.) ·Foam stabilizer 3: TEGOSTAB (registered trademark) B8736LF2 (manufactured by Evonik Degussa Japan Co., Ltd.) 〇Catalyst (E) ·Catalyst 1: TD-33A (manufactured by Huntsman) · Catalyst 2: ZF-22 (manufactured by Huntsman) 〇 Foaming agent (F): Paracol ID-8 (manufactured by Okihara Palladium Chemical Co., Ltd.) 〇 Additive (G) · Crosslinking agent: Actocol (registered trademark) EP-505S (manufactured by Mitsui Chemicals, Inc.) In addition, each part by mass in Table 1 is a blending ratio with the total of polyol (A) being 100 parts by mass.

[0056] Next, the above-prepared resin premix and 4,4-diphenylmethane diisocyanate (MDI) as the polyisocyanate (B) were mixed at the mass ratio shown in Table 1 and molded by molding. Thereby, polyurethane foams (Example 1 and Comparative Examples 1 and 2, thickness 10 mm) made of molded products were produced.

[0057] <Evaluation of bubbles> A part of the produced polyurethane foam was cut out and prepared as a flat foam test piece with a length of 110 mm × width of 110 mm × thickness (t) of 10 mm. Figure 3 is a perspective view schematically showing the foam test piece. Then, using a cell structure distribution analyzer Porescan (manufactured by Goldlucke Ingenieurleistungen), the properties of the bubbles (cell diameter (average bubble diameter), cell number (number of bubbles), average aspect ratio of cells) in the core layer and the skin layer were measured. Note that Porescan includes a CCD camera and software components, and is an automatic cell size analyzer that can separate cells (bubbles) and cell septa from the images taken by the CCD camera. Therefore, after measurement with software incorporating a unique algorithm, image analysis and statistical processing are performed to obtain the above values. As shown in Figure 3, the measurement surface of the core layer was set as one side surface (cross-section) side of the foam test piece, and the measurement surface of the skin layer was set as one surface side of the foam test piece. Also, for each test piece, at least 5000 bubbles (cells) were subjected to image analysis and statistical processing. The CCD observation images of the skin layer and the core layer are shown in Figure 4. Also, the measurement results of the core layer and the skin layer are shown in Table 1.

[0058] As shown in Table 1, the skin layer of Example 1 had a significantly smaller average bubble diameter Ds and a significantly smaller number of bubbles P2 compared to Comparative Examples 1 and 2. As a result, as shown in Fig. 4, the skin layer of Example 1 was formed in a thin film shape on the surface of the foam test piece. Also, the core layer of Example 1 had a larger average bubble diameter Dc and a smaller number of bubbles P1 compared to Comparative Examples 1 and 2. As a result, as shown in Fig. 4, the cells of the core layer of Example 1 were coarser. Due to these reasons, in the foam test piece of Example 1, the ratio (Dc / Ds) of the average bubble diameter Dc of the core layer to the average bubble diameter Ds of the skin layer was significantly larger compared to Comparative Examples 1 and 2.

[0059] <Evaluation of Reverberation Room Sound Absorption Coefficient> A flat polyurethane foam with a length of 1 m, a width of 1 m, and a thickness of 10 mm was prepared as a measurement sample. Then, the reverberation room sound absorption coefficient was measured by the reverberation room method in accordance with ISO 354. Specifically, on the floor surface of a reverberation room (Ab-Loss, manufactured by Nippon Acoustics Engineering Co., Ltd., internal volume of the reverberation room: 9 m 3 ), the measurement sample was placed so that the core layer was on the upper side (sound incidence side), and the reverberation room sound absorption coefficient was measured in the frequency range of 400 to 5000 Hz. Fig. 5 shows a graph of the reverberation room sound absorption coefficient (horizontal axis: frequency, vertical axis: sound absorption coefficient) in Example 1 and Comparative Example 2. Also, Table 1 shows the reverberation room sound absorption coefficients at frequencies of 1000 Hz and 4000 Hz. Note that the reverberation room sound absorption coefficient indicates that the closer the value is to 1, the better the sound absorption performance.

[0060] As shown in Fig. 5 and Table 1, in the polyurethane foam of Example 1, the sound absorption performance in the low-frequency band of 1000 Hz was significantly improved compared to Comparative Example 2, and it was found to be effective in reducing noise in the low-frequency band. Also, the sound absorption performance in the high-frequency band of 4000 Hz was significantly improved, and it was found that it can reduce noise in a wide range of frequency bands. Although not intended to be construed in a particularly limited manner, for this reason, it is considered that the Helmholtz resonator type sound absorption mechanism effectively acted because the skin layer was formed in a thin film shape and the bubbles in the skin layer were coarsened like a kettle. In addition, it is considered that the ventilation on the surface of the skin layer was suppressed to obtain a sound insulation effect, and because the core layer was rough, the bubble partitions were easily membrane-vibrated, and the porous type sound absorption mechanism or the membrane vibration type sound absorption mechanism effectively acted. These effects indicate the significance of the technology disclosed herein.

[0061] <Evaluation of vibration transmission rate> The prepared polyurethane foam was cut into a flat plate shape with a length of 400 mm × width of 400 mm × thickness of 10 mm and prepared as a measurement sample. Then, as shown in Fig. 6, the measurement sample was placed on a vibration table, and the center of the measurement sample was pressed with a disk-shaped weight (iron anvil, 20 kg). In this state, the vibration table was sweep-vibrated at a constant acceleration (0.2G) to apply vibration G with a frequency of 0 to 2000 Hz. Then, the vibration G' of the measuring element when vibration G was applied was measured, and the vibration transmission rate (G' / G) was obtained. The graphs of the vibration transmission rates (horizontal axis: vibration frequency, vertical axis: vibration transmission rate) in Example 1 and Comparative Examples 1 and 2 are shown in Fig. 7. Also, the resonance frequency and the vibration transmission rate at a frequency of 1000 Hz are shown in Table 1. Note that the smaller the value of the vibration transmission rate, the better the sound absorption performance, indicating that vibration (sound wave) can be converted into thermal energy to absorb sound.

[0062] As shown in Fig. 7 and Table 1, in the polyurethane foam of Example 1, the resonance frequency shifted to the low-frequency band compared to Comparative Examples 1 and 2, and the vibration transmission rate at 1000 Hz was significantly improved, and it was found that the sound absorption performance in the low-frequency band was also excellent.

[0063]

Table 1

[0064] ≪Test Example II: Examination of Blowing Agent Blending Ratio, etc.≫ In Examples 2 and 3 and Comparative Example 3, the blending ratio of the blowing agent was varied between 1.5 and 10 parts by mass, and polyurethane foam was produced by molding the polyurethane raw material according to Example 1. Then, together with the polyurethane foam obtained in Example 1, the moldability and foamability were evaluated visually and simply. The results are shown in Table 2. The evaluation results in Table 2 are based on the following criteria. (Moldability) ·〇: The produced sample forms a shape and has no cracks or chips. ·×: The produced sample does not form a shape due to poor molding, or has cracks or chips. (Foamability) ·◎: The properties of the bubbles (number and bubble diameter) are equivalent to those in Example 1. ·〇: The properties of the bubbles (number and bubble diameter) are slightly different from those in Example 1, but acceptable. ·×: The properties of the bubbles (number and bubble diameter) are significantly different from those in Example 1, there are many gaps in the layer, or the layer is too dense.

[0065]

Table 2

[0066] As shown in Table 2, in Example 2 where the blending ratio of the blowing agent was 2.5 parts by mass, the foam breaking in the core layer was less than that in Example 1, and the number of small bubbles was large. Also, in Comparative Example 3 where the blending ratio of the blowing agent was 10 parts by mass, the edge of the produced sample was chipped and the moldability was not sufficient. Furthermore, both the skin layer and the core layer were foamed too much, the bubbles were significantly large, and the layer was sparse. From the above, it was found that the appropriate blending ratio of the blowing agent is 1 to 8 parts by mass, more preferably 2.5 to 8 parts by mass, and even more preferably 5 to 8 parts by mass.

[0067] ≪Test Example III: Examination of Blowing Agent Types≫ As Comparative Examples 4 and 5, a defoaming agent that does not contain a sugar alcohol (here, a silicone-based defoaming agent) was used, and the blending ratios were 5 parts by mass and 10 parts by mass. A polyurethane foam was produced by molding a polyurethane raw material according to Example 1. Then, together with the polyurethane foam obtained in Example 1, the moldability and defoaming property were simply evaluated visually. The results are shown in Table 3. The evaluation results in Table 3 are based on the same criteria as those in Table 2 of Test Example II. In addition, cross-sectional photographs of the polyurethane foams of Example 1 and Comparative Examples 3, 4 are shown in FIGS. 8(A) to (C).

[0068]

Table 3

[0069] As shown in Table 3 and FIG. 8(B), in Comparative Example 4 using a silicone-based defoaming agent, only the skin layer was defoamed, and the core layer was not sufficiently defoamed and became excessively dense. Also, in Comparative Example 5 where the blending ratio was increased to 10 parts by mass, the defoaming of the core layer did not progress, and no significant change was observed. From this, it was found that the effects of the technology disclosed herein are not exhibited by a defoaming agent that does not contain a sugar alcohol, in other words, they are specifically expressed by a defoaming agent that contains a sugar alcohol.

[0070] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

Explanation of Reference Numerals

[0071] 10 Polyurethane foam 11 Core layer 12 Skin layer

Claims

1. A polyurethane foam forming composition comprising a polyol (A), a polyisocyanate (B), a blowing agent (C), a foam stabilizer (D), a catalyst (E), and a foam breaker (F), wherein the foam breaker (F) contains a sugar alcohol, and the blending ratio of the foam breaker (F) is 1 part by mass or more and 8 parts by mass or less when the polyol (A) is 100 parts by mass. A polyurethane foam forming composition.

2. The sugar alcohol contains a monosaccharide alcohol. The polyurethane foam forming composition according to Claim 1.

3. The sugar alcohol is in the state of emulsion particles having a multilayer structure coated with a silicone compound and further coated with a surfactant on the outside. The polyurethane foam forming composition according to Claim 1.

4. A polyurethane foam obtained by reacting and foaming the polyurethane foam forming composition according to any one of Claims 1 to 3.

5. A molded body having a core layer and a skin layer thinner than the core layer, with a thickness of 10 mm or less, and having a reverberation chamber sound absorption rate of 0.6 or more at a frequency of 1000 Hz measured by the reverberation chamber method in accordance with ISO 354 at a thickness of 10 mm. The polyurethane foam according to Claim 4.

6. The ratio (Dc / Ds) of the average bubble diameter Dc of the core layer to the average bubble diameter Ds of the skin layer is 5 or more and 20 or less. The polyurethane foam according to Claim 5.

7. The average bubble diameter Dc of the core layer is 200 μm or more and 600 μm or less. The polyurethane foam according to Claim 6.

8. 1 mm of the core layer ２ the number of bubbles per hit is 10 or less, and The average bubble diameter Dc of the core layer is 200 μm or more and 600 μm or less. The polyurethane foam according to Claim 5.

9. The average aspect ratio of the bubbles in the core layer is 1.5 or more and 3 or less. The polyurethane foam according to Claim 5.

10. 1 mm of the skin layer ２ the number of bubbles per hit is 10 or less, and The average bubble diameter Ds of the skin layer is 10 μm or more and 100 μm or less. The polyurethane foam according to Claim 5.

11. A sound absorbing material having the polyurethane foam according to Claim 4.

12. A sound absorbing material having the polyurethane foam according to Claim 5.

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