Polyurethane foam and its manufacturing method

Abstract

To provide a polyurethane foam which is suitable as a soundproof material and offers high soundproofing capability.SOLUTION: A polyurethane foam having a coating layer on a surface thereof is provided. The coating layer exhibits a breathability (as per JIS K6400-7:2012A) of 7 L / min or less and a portion on the inner side the coating layer exhibits a breathability greater than that of the coating layer. Preferably, difference between the breathability (as per JIS K6400-7:2012A) of the coating layer and breathability (as per JIS K6400-7:2012A) of the portion on the inner side of the coating layer is 15 L / min or greater. Sound insulation (as per JIS A1441-1:2007) should preferably be 11 dB or greater in average in a frequency range of 400 Hz to 4 kHz.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to polyurethane foams and methods for producing the same. [Background technology]

[0002] 2. Description of the Related Art Conventionally, in automobiles, soundproofing materials are placed in gaps in the sound transmission path around the fenders, instrument panel, cowl, etc. to reduce the transmission of noise into the vehicle interior.

[0003] Conventional soundproofing materials are difficult to achieve both sound insulation and sound absorption properties with a single material, so some are made up of an integrated product that combines a high-density sound-insulating sheet to ensure sound insulation with polyurethane foam to ensure sound absorption (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 02-151899 Summary of the Invention [Problem to be solved by the invention]

[0005] However, soundproofing materials made of a sound-insulating sheet and polyurethane foam have the problem of being heavy. Also, when the surface on which the soundproofing material is installed is uneven, the presence of the sound-insulating sheet can impair the shape-following ability of the soundproofing material, resulting in gaps between the surface on which the soundproofing material is installed and the soundproofing material itself, which can result in poor sound insulation.

[0006] The present invention has been made in view of the above points, and an object of the present invention is to provide a polyurethane foam having high sound insulation properties suitable for use as a soundproofing material. [Means for solving the problem]

[0007] A first aspect of the present invention is a polyurethane foam having a coating layer on its surface, The coating layer has an air permeability (JIS K6400-7:2012A method) of 7 L / min or less, and the air permeability inside the coating layer is higher than the air permeability of the coating layer.

[0008] The second aspect of the invention is characterized in that, in the first aspect of the invention, the difference between the air permeability of the coating layer (JIS K6400-7:2012A method) and the air permeability inside the coating layer (JIS K6400-7:2012A method) is 15 L / min or more.

[0009] A third aspect of the invention is characterized in that, in the first or second aspect of the invention, the average sound transmission loss (JIS A1441-1:2007) in the frequency range of 400 to 4 kHz is 11 dB or more.

[0010] A fourth aspect of the invention is a method for producing a polyurethane foam, characterized in that a release agent having two melting peaks, one at 70 to 90°C and the other at 100 to 130°C, is applied to the inner surface of a foam molding die, and polyurethane foam raw material is poured into the foam molding die and foamed, thereby forming a polyurethane foam having a coating layer on its surface. [Effects of the Invention]

[0011] According to the present invention, a polyurethane foam having high sound insulation properties suitable for use as a soundproofing material can be obtained. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a table showing the results of density, breathability, and sound insulation for each example and each comparative example. [Figure 2] 1 is a table showing the formulation of polyurethane foam raw materials used in each example and each comparative example. [Figure 3] 1 is a graph showing measurement results of transmission loss for some examples and some comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described. The polyurethane foam of the present invention has a coating layer on its surface, and the breathability of the coating layer (JIS K6400-7:2012A method) is 7 L / min or less, preferably 6 L / min or less, more preferably 5 L / min or less, and even more preferably 4 L / min or less, and the breathability of the interior side is higher than that of the surface coating layer.

[0014] The surface coating layer is the surface portion where the polyurethane foam cells are compressed, resulting in a layer that is denser than the inner (center) portion of the polyurethane foam. The thickness of the coating layer is usually about 0.001 to 3 mm.

[0015] In the present invention, the inner side of the surface coating layer refers to the inner (central) part away from the surface coating layer, specifically the part 3 mm or more away from the surface of the polyurethane foam. The air permeability (JIS K6400-7:2012A method) on the inside is 15 L / min or more, preferably 18 L / min or more, and more preferably 20 L / min or more.

[0016] By increasing the air permeability of the polyurethane foam on the inner side relative to the surface coating layer, good sound insulation can be achieved. The difference between the air permeability of the surface coating layer and the air permeability of the inner side is preferably 15 L / min or more, more preferably 18 L / min or more, and even more preferably 20 L / min or more. The greater the difference between the air permeability of the surface coating layer and the air permeability of the inner side, the higher the sound insulation.

[0017] The density of polyurethane foam (JIS K7222:2005) is 170 kg / m 3 less than 160 kg / m 3 less than 130 kg / m 3 less than 80 to 40 kg / m 3The density range of the polyurethane foam can be changed by varying the blending ratio of the polyurethane foam raw materials (mainly the blending amount of the blowing agent) and the amount of polyurethane foam raw materials injected into the foam molding die. By setting the density of the polyurethane foam within the above range, the polyurethane foam can be made lightweight.

[0018] The polyurethane foam of the present invention is produced by molding, in which a polyurethane foam raw material is injected into a foam mold and foamed. Molding is a widely used method for producing polyurethane foam, and by pre-forming the inner surface of the foam mold into the desired product shape, polyurethane foam can be obtained in the desired product shape without any post-processing.

[0019] The polyurethane foam raw materials include polyol, catalyst, crosslinking agent, blowing agent, and polyisocyanate. Polyols are compounds with two or more hydroxyl groups in one molecule, and are produced by addition polymerization of alcohols with two or more functional groups (polyhydric alcohols), or by using these as initiators with ethylene oxide or propylene oxide. The polyol may be any of polyether polyol, polyester polyol, and polymer polyol, and the polyol is not limited to one type, but may be a mixture of multiple types. The polyol preferably has 2 to 4 functional groups and a molecular weight of 3,000 to 7,000.

[0020] Examples of the catalyst include amine catalysts and metal catalysts used for polyurethane foams. Examples of the amine catalyst include N,N-dimethylcyclohexylamine, N,N-dimethylbenzylamine, N,N-dimethylaminoethanol, N,N',N'-trimethylaminoethylpiperazine, and triethylenediamine. Examples of the metal catalyst include tin catalysts such as stannous octoate and dibutyltin dilaurate, phenylmercury propionate, and lead octenate. The amount of catalyst is preferably about 0.1 to 8.0 parts by weight per 100 parts by weight of the polyol.

[0021] Examples of crosslinking agents include polyhydric alcohols such as ethylene glycol, diethylene glycol, glycerin, butanetetraol, and polyoxypropylene glycol, as well as diethanolamine and polyamine. The crosslinking agent is not limited to one type, and multiple types may be used in combination. The amount of crosslinking agent is preferably about 0.3 to 5 parts by weight per 100 parts by weight of polyol. If the amount of crosslinking agent is less than the above range, the effect of film formation tends to be reduced, and if it is more, the polyurethane foam tends to be too hard.

[0022] Examples of blowing agents include water, hydrocarbons, halogenated compounds, etc., and one or more of these may be used. Examples of hydrocarbons include cyclopentane, isopentane, and normal pentane. Examples of halogenated compounds include methylene chloride, trichlorofluoromethane, dichlorodifluoromethane, nonafluorobutyl methyl ether, nonafluorobutyl ethyl ether, pentafluoroethyl methyl ether, and heptafluoroisopropyl methyl ether. Among these, water is particularly suitable as a blowing agent. The amount of water used as a blowing agent is preferably about 1 to 10 parts by weight, more preferably about 1 to 7 parts by weight, per 100 parts by weight of polyol, which allows adjustment of the density of the polyurethane foam.

[0023] The polyisocyanate is not particularly limited as long as it is a compound having two or more isocyanate groups, and those for polyurethane foams can be used. The polyisocyanate is not limited to one type, and two or more types may be used in combination. Examples of polyisocyanates include aromatic, aliphatic, and alicyclic isocyanate compounds, and modified products thereof.

[0024] Examples of aromatic isocyanate compounds include diphenylmethane diisocyanate (MDI), crude diphenylmethane diisocyanate, tolylene diisocyanate (TDI), naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethyl xylene diisocyanate (TMXDI), and tolidine isocyanate (TODI). Examples of aliphatic isocyanate compounds include hexamethylene diisocyanate (HDI), lysine diisocyanate (LDI), and lysine triisocyanate (LTI). Examples of alicyclic isocyanate compounds include isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI), hydrogenated XDI (H6XDI), and hydrogenated MDI (H 12 Examples of modified isocyanate compounds include urethane-modified isocyanate compounds, dimers, trimers, carbodiimide-modified isocyanate compounds, allophanate-modified isocyanate compounds, biuret-modified isocyanate compounds, urea-modified isocyanurate-modified isocyanate compounds, oxazolidone-modified isocyanate compounds, and isocyanate-terminated prepolymers.

[0025] The amount of polyisocyanate blended is preferably an amount that results in an isocyanate index of 70 to 110. If the isocyanate index is less than 70, the polyurethane foam will have too low strength and poor durability, or it will be difficult for gas to escape, resulting in shrinkage and poor molding quality. On the other hand, if the isocyanate index exceeds 110, the polyurethane foam will have high hardness and will be difficult to deform into the shape of the mating surface. The isocyanate index is a value that indicates, as a percentage, the equivalent ratio of isocyanate groups in polyisocyanate to the total active hydrogen groups in the polyurethane foam raw materials (e.g., hydroxyl groups in polyols, active hydrogen groups such as water used as a blowing agent), and is an index used in the field of polyurethane foam.

[0026] In addition, additives may be added to the polyurethane foam raw materials as needed, such as a foam stabilizer, a foam opener, a flame retardant, and a colorant.

[0027] The foam stabilizer may be any foam stabilizer that is used in polyurethane foams, and examples thereof include silicone-based foam stabilizers, fluorine-containing compound-based foam stabilizers, and known surfactants.

[0028] The cell opener has the effect of destroying bubbles (gas bubbles) during foaming of polyurethane foam. The types of cell openers include hydrocarbon-based, ester-based, silicone-based, and polyol-based, and are not limited to one type, but two or more types may be used. Examples of hydrocarbon-based cell openers include oils such as polybutene. Examples of ester-based cell openers include dimer acid diesters. Examples of silicone-based cell openers include cyclopentasiloxane. Examples of polyol-based cell openers include polyether polyols with a high addition amount of ethylene oxide (EO ratio of 50% or more, preferably 60 to 100%).

[0029] When a cell opener is used, the amount is preferably about 0.01 to 15 parts by weight per 100 parts by weight of polyol. If the amount of cell opener is too large, it becomes difficult to achieve good foaming of the polyurethane foam.

[0030] The flame retardant may be a powder flame retardant such as a phosphorus-based flame retardant or ammonium polyphosphate, or a liquid flame retardant such as a phosphate ester-based flame retardant, either of which may be used alone or in combination. The coloring agent to be used may be one that is suited to the location where the polyurethane foam is to be used.

[0031] When molding polyurethane foam, a mold release agent is first applied to the inner surface of the foam mold. The foam mold is composed of a split mold that can be separated into upper and lower molds, and the inner surface of the mold is shaped to match the outer shape of the polyurethane foam product. The foam mold also has a heating means such as an electric heater or a heat transfer medium circulating pipe embedded in it, and the mold temperature can be controlled to a predetermined value using hot water or heated oil flowing through the electric heater or heat transfer medium circulating pipe. The mold temperature is preferably around 50 to 70°C. A mold temperature lower than 50°C results in poor curing and reduced productivity. Conversely, a mold temperature higher than 70°C results in excessive reactivity of the polyurethane foam raw materials, which reduces the flowability of the polyurethane foam raw materials and may result in underfill and a rough exterior surface.

[0032] The release agent used contains a solid component (wax component) that has two melting peaks: one at 70 to 90°C and the other at 100 to 130°C. The melting peaks are values ​​measured by a differential scanning calorimeter (DSC) on the solid component remaining after evaporating the liquid components of the release agent. When the release agent has two melting peaks, one at 70 to 90°C and the other at 100 to 130°C, a polyurethane foam with a good surface coating layer can be obtained.

[0033] The release agent having two melting peaks, one between 70 and 90°C and the other between 100 and 130°C, preferably contains a branched-chain wax-based release agent. Examples of branched-chain wax-based release agents include those that use a branched-chain wax, such as modified polyethylene wax, microcrystalline wax, or hydrocarbon wax, as the main component, dissolved in an organic solvent, or dispersed in water using an emulsifier. The branched-chain wax-based release agent facilitates the formation of a coating layer on the surface of the polyurethane foam.

[0034] The release agent having two melting peaks, one at 70 to 90°C and the other at 100 to 130°C, is preferably a mixed release agent containing a wax component having a weight-average molecular weight of 1000 or more and a wax component having a weight-average molecular weight of 600 or less.

[0035] The release agent can be applied to the inner surface of the foam molding mold by brush or spray. The amount of release agent applied is 10 to 100 g / m. 2 is preferred.

[0036] After applying a mold release agent to the inner surface of the foam molding mold, the polyurethane foam raw material is mixed and injected into the foam molding mold, and the foam molding mold is closed. The amount of polyurethane foam raw material injected into the foam molding mold is set so that the density of the resulting polyurethane foam (JIS K7222:2005) is 170 kg / m 3 (0.16g / cm 3 ) is considered to be an amount less than that.

[0037] After foaming the polyurethane foam raw material, the foaming mold is opened and the polyurethane foam is demolded. The resulting polyurethane foam has a coating layer on the surface and the above-mentioned physical properties. [Example]

[0038] The inner surface of the mold is a rectangular parallelepiped foam molding mold with inner dimensions of 500 x 500 x 20 mm (mold volume: 5000 cm). 3 ) and a foam molding mold with inner dimensions of 500 x 250 x 40 mm (mold volume 5000 cm 3 The release agent selected from the following release agents A, B, and C according to each example and comparative example shown in FIG. 1 was sprayed onto the inner surface of the mold (approximately 25 g / m 2 The polyurethane foam raw material having the composition shown in Figure 2, which was made up of the following raw materials, was mixed and poured into a foam molding die in an amount that would give the density set for each Example and Comparative Example, and foaming was carried out while maintaining the die temperature at 60°C. The polyurethane foam for each Example and Comparative Example was then demolded to obtain it.

[0039] Release agent A: Branched wax-based release agent, first melting peak 81.0°C, second melting peak 110.2°C, product name: FRX-C8, manufactured by Neos Co., Ltd. Release agent B: Branched wax-based release agent, melting point 106.9°C, product name: M975, manufactured by Chukyo Yushi Co., Ltd. Release agent C: Straight chain wax-based release agent, first melting peak 93.2°C, second melting peak 108.3°C, product name: T-626, manufactured by Chukyo Yushi Co., Ltd. Polyol A: Polyether polyol, molecular weight 7000, functionality 3, EO content 14%, product name: KC-737, manufactured by Sanyo Chemical Industries, Ltd. Polyol B: Polyether polyol, molecular weight 5000, functionality 3, EO content 14%, product name: FA-703, manufactured by Sanyo Chemical Industries, Ltd. Polyol C: Polymer polyol, molecular weight 5000, functional group 3, product name: FA-728R, manufactured by Sanyo Chemical Industries, Ltd. Catalyst A: Amine catalyst, product name: DABCO BL-11, manufactured by Evonik Catalyst B: Amine catalyst, product name: DABCO 33LSI, manufactured by Evonik Catalyst C: Amine catalyst, product name: TOYOCAT D-60, manufactured by Tosoh Corporation Crosslinking agent: Diethanolamine Foam stabilizer: Silicone foam stabilizer, product name: B8738LF2, manufactured by Evonik Foam opener: Polyether polyol, molecular weight 4800, functionality 3, PO / EO = 30 / 70 (EO ratio 70%), product name: CP1421, manufactured by Dow Chemical Company Foaming agent: water Polyisocyanate: Polymeric MDI, NCO%: 31.5%, Product name: 600B, manufactured by BASF INOAC Polyurethanes Co., Ltd.

[0040] The polyurethane foams of each example and comparative example were measured for density (JIS JIS K7222:2005), air permeability of the surface coating layer (JIS K6400-7:2012A method), and air permeability of the interior side (JIS K6400-7:2012A method).

[0041] The breathability of the coating layer was measured by cutting a 10 mm portion from the surface of a polyurethane foam molded with dimensions of 500 × 250 × 40 mm to obtain a 51 × 51 × 10 mm test piece for the coating layer. On the other hand, the breathability of the inner side was measured by cutting a central portion in the thickness direction of the molded polyurethane foam (10 to 20 mm away from the surface) to prepare an inner test piece of the same dimensions (51 × 51 × 10 mm) for use in the measurements.

[0042] When the breathability of the coating layer was 4 L / min or less, the breathability of the coating layer was evaluated as "◎", when it was between 4 and 7 L / min, the breathability of the coating layer was evaluated as "〇", and when it was more than 7 L / min, the breathability of the coating layer was evaluated as "▲". When the difference in breathability between the coating layer and the inner side was 20 L / min or more, the breathability difference was evaluated as "◎", when the difference in breathability was 15 L / min or more but less than 20 L / min, the breathability difference was evaluated as "〇", and when the difference in breathability was less than 15 L / min, the breathability difference was evaluated as "▲". An overall judgment of breathability was made based on the breathability evaluation and breathability difference evaluation of the coating layer according to the following criteria: When both the breathability evaluation and breathability difference evaluation of the coating layer were "◎", the overall breathability judgment was "◎", when either the breathability evaluation or the breathability difference evaluation of the coating layer was "◎" and the other was "〇", or when both were "〇", the overall breathability judgment was "〇", and when either or both of the breathability evaluation and the breathability difference evaluation of the coating layer were "▲".

[0043] Also, density 50kg / m 3 Example 1, Comparative Example 1, Comparative Example 5, density 150 kg / m 3 The polyurethane foams of Example 5 and Comparative Example 9 were evaluated for sound insulation. Sound insulation was evaluated by measuring sound transmission loss (JIS A1441-1:2007 / ISO 15186-1:2000) in a 1 / 3 octave band and calculating the average sound transmission loss (average sound transmission loss) over the frequency range of 400 Hz to 4 kHz. This average sound transmission loss is preferably 12 dB or more, more preferably 14 dB or more, and even more preferably 16 dB or more. If the average value of the transmission loss (average transmission loss) between 400 and 4 kHz was 16 dB or more, it was marked as "◎", if it was 12 dB or more and less than 16 dB, it was marked as "〇", if it was 8 dB or more and less than 12 dB, it was marked as "△", and if it was less than 8 dB, it was marked as "×". It is preferable to judge the sound insulation by comparing at the same density. The sound source reverberation chamber used for the measurement of transmission loss was 36m 3 , the anechoic chamber is 20m 3 , measurement area is 400 × 400 mm (0.16 m 2 ) The soundproofing material, made of polyurethane foam and measuring 500mm square and 20mm thick (with a surface coating layer), was fixed in a 50mm wide frame around the periphery, and the gaps were further sealed with clay. Sound was incident from the reverberation chamber (the sound source side), and measurements were taken from the anechoic receiving chamber (the non-sound source side) at 25 locations (80mm pitch) 215mm away from the surface of the soundproofing material over the range of 250Hz to 10kHz, and the average value from 400Hz to 4kHz was calculated. The measurement results are shown in Figure 3.

[0044] In Examples 1 and 2, release agent A was used, the isocyanate index was set to 80, and the density of the polyurethane foam was set to 50 kg / m 3 (Example 1) and 70 kg / m 3 This is an example that is different from (Example 2).

[0045] Example 1 (density 50 kg / m 3 ) had an internal air permeability of 56.6 L / min, an internal air permeability of 3.0 L / min, and an evaluation of "◎." The difference in air permeability between the surface coating layer and the internal side was 53.6 L / min, and an evaluation of "◎." The overall air permeability rating was "◎." The average transmission loss at 400 Hz-4 kHz was 14.3 dB, which was higher than the average transmission loss at 400 Hz-4 kHz of 10.9 dB for Comparative Example 1, which had the same density but a different release agent, and was evaluated as "good." Example 1 has the advantage of being lightweight, making it suitable for use as a soundproofing material for automobiles and other vehicles, where lightweight is required.

[0046] Example 2 (density 70 kg / m 3) had an internal breathability of 22.0 L / min, an internal breathability of 3.5 L / min for the surface coating layer, and a rating of "◎." The difference in breathability between the surface coating layer and the internal side was 18.5 L / min, and a rating of "〇." Overall breathability was judged to be "〇."

[0047] In Examples 3 and 4, release agent A was used, the isocyanate index was set to 100, and the density of the polyurethane foam was set to 50 kg / m 3 (Example 3) and 70 kg / m 3 This is an example that is different from (Example 4).

[0048] Example 3 (density 50 kg / m 3 ) had an internal breathability of 55.0 L / min, an internal breathability of 3.7 L / min for the surface coating layer, and a rating of "◎." The difference in breathability between the surface coating layer and the internal side was 51.2 L / min, and a rating of "◎." Overall breathability was judged to be "◎."

[0049] Example 4 (density 70 kg / m 3 ) had an internal breathability of 24.1 L / min, an external coating layer breathability of 3.9 L / min, and a rating of "◎." The difference in breathability between the external coating layer and the internal side was 20.3 L / min, and a rating of "◎." Overall breathability was judged to be "◎."

[0050] In Comparative Examples 1 and 2, release agent B was used, the isocyanate index was set to 80, and the density of the polyurethane foam was set to 50 kg / m 3 (Comparative Example 1) and 70 kg / m 3 This is an example that is different from (Comparative Example 2).

[0051] Comparative example 1 (density 50kg / m 3 ) had an internal air permeability of 58.6 L / min, an internal air permeability of 26.9 L / min for the surface coating layer, and a rating of "▲." The difference in air permeability between the surface coating layer and the internal side was 31.7 L / min, and a rating of "◎." Overall air permeability was judged to be "▲." The average transmission loss at 400 Hz-4 kHz was 10.9 dB, and the sound insulation was lower than that of Example 1 with the same density, and the sound insulation was judged to be "△."

[0052] Comparative example 2 (density 70kg / m 3) had an internal breathability of 22.1 L / min, an internal breathability of 9.2 L / min for the surface coating layer, and a rating of "▲". The difference in breathability between the surface coating layer and the internal side was 12.9 L / min, and a rating of "▲". Overall breathability was judged to be "▲".

[0053] In Comparative Examples 3 and 4, release agent B was used, the isocyanate index was set to 100, and the density of the polyurethane foam was set to 50 kg / m 3 (Comparative Example 3) and 70 kg / m 3 This is an example that is different from (Comparative Example 4).

[0054] Comparative example 3 (density 50kg / m 3 ) had an internal breathability of 68.6 L / min, an internal breathability of 14.0 L / min for the surface coating layer, and a rating of "▲." The difference in breathability between the surface coating layer and the internal side was 54.6 L / min, and a rating of "◎." Overall breathability was judged to be "▲."

[0055] Comparative example 4 (density 70kg / m 3 ) had an internal breathability of 35.1 L / min, an internal breathability of 14.7 L / min for the surface coating layer, and a rating of "▲." The difference in breathability between the surface coating layer and the internal side was 20.5 L / min, and a rating of "〇." The overall breathability rating was "▲."

[0056] In Comparative Examples 5 and 6, release agent C was used, the isocyanate index was set to 80, and the density of the polyurethane foam was set to 50 kg / m 3 (Comparative Example 5) and 70 kg / m 3 This is an example that is different from (Comparative Example 6).

[0057] Comparative example 5 (density 50kg / m 3 ) had an internal air permeability of 47.3 L / min, an internal air permeability of 14.7 L / min for the surface coating layer, and was rated as "▲." The difference in air permeability between the surface coating layer and the internal side was 32.6 L / min, and was rated as "◎." Overall air permeability was judged as "▲." The average transmission loss at 400 Hz-4 kHz was 7.5 dB, and the sound insulation was lower than that of Example 1 and Comparative Example 1 of the same density, and the sound insulation was judged as "×."

[0058] Comparative example 6 (density 70kg / m3 ) had an internal breathability of 21.3 L / min, an internal breathability of 7.3 L / min for the surface coating layer, and a rating of "▲". The difference in breathability between the surface coating layer and the internal side was 14.0 L / min, and a rating of "▲". Overall breathability was rated as "▲".

[0059] In Comparative Examples 7 and 8, release agent C was used, the isocyanate index was set to 100, and the density of the polyurethane foam was set to 50 kg / m 3 (Comparative Example 7) and 70 kg / m 3 This is an example that is different from (Comparative Example 8).

[0060] Comparative example 7 (density 50kg / m 3 ) had an internal breathability of 54.4 L / min, an internal breathability of 18.9 L / min for the surface coating layer, and a rating of "▲." The difference in breathability between the surface coating layer and the internal side was 35.5 L / min, and a rating of "◎." Overall breathability was judged to be "▲."

[0061] Comparative example 8 (density 70kg / m 3 ) had an internal breathability of 26.1 L / min, an internal breathability of 11.5 L / min for the surface coating layer, and a rating of "▲". The difference in breathability between the surface coating layer and the internal side was 14.6 L / min, and a rating of "▲". Overall breathability was rated as "▲".

[0062] In Example 5, release agent A was used, the isocyanate index was set to 100, and the density of the polyurethane foam was set to 150 kg / m 3 This is an example. Example 5 had an internal air permeability of 34.3 L / min, an internal air permeability of 2.6 L / min for the surface coating layer, and was rated as "◎." The difference in air permeability between the surface coating layer and the internal side was 31.7 L / min for the same evaluation, and was rated as "◎." The overall air permeability rating was "◎." The average transmission loss at 400 Hz-4 kHz was 20.9 dB, which was higher in sound insulation than the average transmission loss at 400 Hz-4 kHz of 15.8 dB in Comparative Example 9 of the same density, and the sound insulation rating was "◎." Since Example 5 has a higher density than Example 1, it has higher sound insulation than Example 1.

[0063] In Comparative Example 9, release agent B was used, the isocyanate index was set to 100, and the density of the polyurethane foam was set to 150 kg / m 3 This is an example. In Comparative Example 9, the air permeability on the inner side was 24.8 L / min, the air permeability of the surface coating layer was 7.8 L / min, and the evaluation was "▲". The difference in air permeability between the surface coating layer and the inner side was 17.0 L / min, and the evaluation was "〇". The overall air permeability evaluation was "▲". The average transmission loss from 400 Hz to 4 kHz was 15.8 dB. Since release agent B, which is different from the release agent of the present invention, was used, the sound insulation was lower than that of Example 5 of the same density, and the sound insulation evaluation was "〇".

[0064] In Comparative Example 10, release agent C was used, the isocyanate index was set to 100, and the density of the polyurethane foam was set to 150 kg / m 3 This is an example. In Comparative Example 10, the air permeability on the inner side was 31.8 L / min, the air permeability of the surface coating layer was 30.2 L / min, and the rating was "▲". The difference in air permeability between the surface coating layer and the inner side was 1.6 L / min, and the rating was "▲". The overall air permeability rating was "▲".

[0065] As described above, according to the present invention, a polyurethane foam with high sound insulation properties suitable for use as a soundproofing material can be obtained. Note that the present invention is not limited to the examples, and modifications can be made without departing from the spirit and scope of the invention.

Claims

1. A polyurethane foam having a coating layer on its surface, the coating layer having a release agent having two melting peaks of 70 to 90°C and 100 to 130°C, The density (JIS K7222:2005) is 40 to 80 kg / m 3 , The coating layer has an air permeability (JIS K6400-7:2012A method) of 7 L / min or less, A polyurethane foam characterized in that the air permeability of the inner side of the coating layer is higher than the air permeability of the coating layer.

2. A method for producing a polyurethane foam, comprising applying only a mold release agent having only two melting peaks, one at 70 to 90°C and the other at 100 to 130°C, to the inner surface of a foam molding die, and then injecting a polyurethane foam raw material into the foam molding die and foaming it, thereby forming a polyurethane foam having a coating layer on its surface.

3. A method for producing a polyurethane foam, comprising: applying a mold release agent having two melting peaks, one at 70 to 90°C and the other at 100 to 130°C, to the inner surface of a foam molding die; and then injecting a polyurethane foam raw material containing diphenylmethane diisocyanate into the foam molding die and foaming the material, thereby forming a polyurethane foam having a coating layer on its surface.

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