JP7795764B2 - Soundproofing material and its manufacturing method - Google Patents

Description

The present invention relates to soundproofing materials and methods for manufacturing them.

Traditionally, in automobiles, soundproofing materials have been placed in gaps in the sound transmission path around the fenders, instrument panel, cowl, etc. to prevent noise from being transmitted inside the vehicle.

Conventional soundproofing materials are difficult to achieve both sound insulation and sound absorption properties with a single material, so some are made from 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).

Japanese Patent Application Publication No. 02-151899

However, soundproofing materials made from a sound-insulating sheet and polyurethane foam have the problem of being heavy. Furthermore, if the surface on which the soundproofing material is installed is uneven, the presence of the sound-insulating sheet can impair the soundproofing material's ability to conform to the shape of the surface, resulting in gaps between the surface on which the soundproofing material is installed and the soundproofing material, which can prevent good sound insulation.

The present invention has been developed in consideration of the above points, and aims to provide a lightweight soundproofing material with high sound insulation properties.

A first aspect of the invention is a soundproofing material made of polyurethane foam, characterized in that the polyurethane foam has a coating layer on its surface, the coating layer has an air permeability (JIS K6400-7:2012A method) of 10 L/min or less, the inner side of the coating layer has an air permeability (JIS K6400-7:2012A method) of 15 L/min or more, and the density (JIS K7222:2005) is less than 130 kg/ ^m3 .

A second aspect of the invention is a method for producing a soundproofing material made of polyurethane foam, characterized in that a release agent having two melting peaks, one between 70 and 90°C and the other between 100 and 130°C, is applied to the inner surface of a foam molding die, polyurethane foam raw material is injected into the foam molding die and foamed, and polyurethane foam having a coating layer on its surface is molded, thereby producing a soundproofing material made of polyurethane foam having a coating layer on its surface.

A third aspect of the present invention is characterized in that, in the second aspect of the present invention, the release agent having two melting peaks is a mixed release agent containing a wax component having a weight-average molecular weight of 1,000 or more and a wax component having a weight-average molecular weight of 600 or less.

A fourth aspect of the present invention is the polyurethane foam according to the second or third aspect of the present invention, characterized in that the coating layer has an air permeability (JIS K6400-7:2012A method) of 10 L/min or less, an air permeability (JIS K6400-7:2012A method) of 15 L/min or more on the inner side than the coating layer, and a density (JIS K7222:2005) of less than 130 kg/ ^m3 .

The present invention provides a lightweight soundproofing material with high sound insulation properties.

1 is a table showing the results of density, breathability, and sound insulation for each example and each comparative example. 1 is a table showing the formulation of polyurethane foam raw materials used in each example and each comparative example. 1 is a graph showing measurement results of transmission loss for some examples and some comparative examples.

An embodiment of the present invention is described below. The soundproofing material of the present invention is made of polyurethane foam.

The polyurethane foam that makes up the soundproofing material has a coating layer on the surface, and the breathability of the coating layer (JIS K6400-7:2012A method) is 10 L/min or less, preferably 8 L/min or less, and more preferably 5 L/min or less, while the breathability (JIS K6400-7:2012A method) on the inner side of the surface coating layer is 15 L/min or more, preferably 18 L/min or more, and more preferably 20 L/min or more.

The surface coating layer is a surface portion where the cells of the polyurethane foam 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.
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 at least 3 mm away from the surface of the polyurethane foam.

By setting the air permeability of the surface coating layer and the air permeability of the inner side of the polyurethane foam within the above ranges and making the air permeability of the surface coating layer lower than the air permeability of the inner side, good sound insulation properties can be obtained.
The difference in air permeability between the surface coating layer and the inner side is preferably 10 L/min or more, more preferably 15 L/min or more, and even more preferably 20 L/min or more.

The density (JIS K7222:2005) of the polyurethane foam constituting the soundproofing material is less than 130 kg/ ^m3 , preferably less than 100 kg/ ^m3 , and more preferably 80 to 40 kg/ ^m3 . The density range of the polyurethane foam can be changed by varying the blending of the polyurethane foam raw materials (mainly the blending amount of the blowing agent) and the injection amount of the polyurethane foam raw materials into the foam molding die.
By setting the density of the polyurethane foam constituting the soundproofing material within the above range, the soundproofing material can be made lightweight.

The soundproofing material of the present invention is manufactured by molding, in which polyurethane foam raw materials are injected into a foam mold and allowed to foam. Molding is a widely used method for molding polyurethane foam, and by pre-setting the inner surface of the foam mold to the desired product shape, polyurethane foam can be obtained in the desired product shape without any post-processing.

The polyurethane foam raw materials include polyol, catalyst, crosslinking agent, blowing agent, and polyisocyanate.
Polyols are compounds that have two or more hydroxyl groups in one molecule, and are produced by addition polymerization of alcohols (polyhydric alcohols) that have two or more functional groups, or by addition polymerization of these with ethylene oxide or propylene oxide using these as initiators.
The polyol may be any of polyether polyol, polyester polyol, and polymer polyol. The polyol is not limited to one type, and 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.

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

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 approximately 0.3 to 5 parts by weight per 100 parts by weight of polyol. If the amount of crosslinking agent is less than this range, the film-forming effect tends to be reduced, and if the amount is more, the polyurethane foam tends to be too hard.

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 approximately 1 to 10 parts by weight, more preferably approximately 1 to 7 parts by weight, per 100 parts by weight of polyol, which allows adjustment of the density of the polyurethane foam.

The polyisocyanate is not particularly limited as long as it is a compound with two or more isocyanate groups, and those used 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, as well as modified versions of these.

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), tetramethylxylene 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 (H ₆ XDI), and hydrogenated MDI (H ₁₂ MDI). 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.

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 little strength and durability, or it will be difficult for gas to escape, resulting in shrinkage and poor molding. On the other hand, if the isocyanate index exceeds 110, the polyurethane foam will be too hard, making it difficult for the soundproofing material to deform to the shape of the mating surface. The isocyanate index is a value expressed as a percentage, representing 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 indicator used in the polyurethane foam field.

Additives may also be added to the polyurethane foam raw materials as needed. Examples of additives that may be added as needed include foam stabilizers, foam breakers, flame retardants, and colorants.

The foam stabilizer may be any foam stabilizer used in polyurethane foams, including silicone-based foam stabilizers, fluorine-containing compound-based foam stabilizers, and known surfactants.

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, and 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 amount of ethylene oxide added (EO ratio of 50% or more, preferably 60 to 100%).

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 too much cell opener is used, it will be difficult to achieve good foaming of the polyurethane foam.

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, and either one or both may be used in combination.
The coloring agent to be used may be selected depending on the location where the soundproofing material is to be used.

When molding soundproofing material, a release agent is first applied to the inner surface of the foam molding mold. The foam molding 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 soundproofing material. The foam molding mold also has heating means such as an electric heater or heat transfer medium circulating pipe embedded in it, and the mold temperature can be controlled to a predetermined level using hot water or heated oil flowing through the electric heater or heat transfer medium circulating pipe. A mold temperature of around 50 to 70°C is preferable. If the mold temperature is lower than 50°C, curing will be poor and productivity will be reduced. Conversely, if the mold temperature is higher than 70°C, the reactivity of the polyurethane foam raw materials will be too high, reducing the flowability of the polyurethane foam raw materials and potentially resulting in underfill and a rough exterior surface.

The release agent used contains a solid component (wax component) with two melting peaks: one between 70 and 90°C and one between 100 and 130°C. The melting peak is a value measured by a differential scanning calorimeter (DSC) on the solid component remaining after evaporating the liquid component of the release agent. A release agent with two melting peaks, one between 70 and 90°C and one between 100 and 130°C, allows for the production of polyurethane foam with an excellent surface coating layer.

Preferably, the release agent, which has two melting peaks, one between 70 and 90°C and the other between 100 and 130°C, 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. Branched-chain wax-based release agents facilitate the formation of a coating layer on the surface of polyurethane foam.

Preferably, the release agent having two melting peaks, one between 70 and 90°C and the other between 100 and 130°C, is a mixed release agent containing a wax component with a weight-average molecular weight of 1,000 or more and a wax component with a weight-average molecular weight of 600 or less.

The release agent can be applied to the inner surface of the foam molding mold by brushing or spraying, etc. The amount of release agent applied is preferably 10 to 100 g/ ^m2 .

After applying a mold release agent to the inner surface of the foam molding mold, a mixture of polyurethane foam raw materials is 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 such that the density of the resulting polyurethane foam (JIS K7222:2005) is less than 130 kg/ ^m3 (0.13 g/ ^cm3 ).

After the polyurethane foam raw material has expanded, the foam mold is opened and the soundproofing material made of polyurethane foam is demolded. The polyurethane foam that makes up the resulting soundproofing material has a coating layer on its surface and possesses the physical properties described above.

A release agent selected from the following release agents A, B, and ^{C according to each example and comparative example shown in Figure 1 was sprayed onto the inner surface of a foam molding mold (mold volume: 5000 cm3 )} having an inner rectangular parallelepiped shape and inner dimensions of 500 x 500 x 20 mm, and another foam molding mold (mold volume: 5000 cm3) having inner dimensions of 500 x 250 x 40 mm, at a rate of approximately 25 g/ ^m2 . A polyurethane foam raw material having the formulation shown in Figure 2 and made up of the following ingredients was mixed and injected into the foam molding mold in an amount to achieve the density set for each example and comparative example. The mold temperature was maintained at 60°C and foamed. The mixture was then demolded to obtain the polyurethane foam soundproofing materials of each example and comparative example.

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 Corporation. Release agent B: Branched wax-based release agent, melting peak 106.9°C, product name: M975, manufactured by Chukyo Yushi Co., Ltd. Release agent C: Linear 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, number of functional groups 3, EO content 14%, product name: KC-737, manufactured by Sanyo Chemical Industries, Ltd. Polyol B: Polyether polyol, molecular weight 5000, number of functional groups 3, EO content 14%, product name: FA-703, manufactured by Sanyo Chemical Industries, Ltd. Polyol C: polymer polyol, molecular weight 5000, number of functional groups 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 breaker: polyether polyol, molecular weight 4800, number of functional groups 3, PO/EO=30/70 (EO ratio 70%), product name: CP1421, manufactured by Dow Chemical Company. Blowing agent: water. Polyisocyanate: Polymeric MDI, NCO %: 31.5%, product name: 600B, manufactured by BASF INOAC Polyurethanes Co., Ltd.

The polyurethane foam (soundproofing material) of each example and comparative example was measured for density (JIS JIS K7222:2005), breathability of the surface coating layer (JIS K6400-7:2012A method), and breathability of the interior (JIS K6400-7:2012A method).

To measure the breathability of the coating layer, a 10 mm section was cut from the surface of a polyurethane foam molded to dimensions of 500 x 250 x 40 mm to create a 51 x 51 x 10 mm test piece for the coating layer. To measure the breathability of the interior side, a section was cut from the center of the thickness of the molded polyurethane foam (10-20 mm from the surface) to prepare an interior test piece of the same dimensions (51 x 51 x 10 mm), which was then used for the measurements.

When the breathability of the coating layer was 5 L/min or less, the breathability of the coating layer was evaluated as "◎", when it was more than 5 L/min but less than 10 L/min, the breathability of the coating layer was evaluated as "◯", and when it was more than 10 L/min, the breathability of the coating layer was evaluated as "▲".
When the difference in air permeability between the coating layer and the inner side was 20 L/min or more, the air permeability difference evaluation was "◎", when the difference in air permeability was 15 L/min or more but less than 20 L/min, the air permeability difference evaluation was "◯", and when the difference in air permeability was less than 15 L/min, the air permeability difference evaluation was "▲".
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 "▲".

Further, the sound insulation properties were evaluated for the soundproof materials of Example 1, Comparative Example 1, and Comparative Example 5, each having a density of 50 kg/m ³ , and Comparative Example 9, each having a density of 150 kg/m ³ .
The sound insulation was evaluated by measuring the 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 transmission loss) at frequencies from 400 Hz to 4 kHz. This average transmission loss is preferably 12 dB or more, more preferably 14 dB or more, and even more preferably 16 dB or more.
When the average value of the transmission loss (average transmission loss) between 400 Hz and 4 kHz was 16 dB or more, it was marked with "◎", when it was 12 dB or more and less than 16 dB, it was marked with "◯", when it was 8 dB or more and less than 12 dB, it was marked with "△", and when it was less than 8 dB, it was marked with "X". It is preferable to judge the sound insulation by comparing at the same density.
The sound transmission loss measurements were performed using a 36 ^m sound source reverberation chamber, a 20 ^m sound receiving anechoic chamber, and a measurement area of 400 x 400 mm (0.16 ^m ). A 500 mm square x 20 mm thick polyurethane foam soundproofing material (with a surface coating layer) was secured in a 50 mm wide frame around its periphery, and any gaps were sealed with clay. Sound was introduced from the reverberation chamber (sound source side), and measurements were taken at 25 locations (80 mm pitch) 215 mm away from the surface of the soundproofing material from the non-sound source side of the anechoic chamber at 250 Hz - 10 kHz, and the average value from 400 Hz - 4 kHz was calculated. The measurement results are shown in Figure 3.

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 (Example 2).

In Example 1 (density 50 kg/m ³ ), the air permeability on the inner side was 56.6 L/min, the air permeability of the surface coating layer was 3.0 L/min, and the rating was "◎", the difference in air permeability between the surface coating layer and the inner side was 53.6 L/min, and the rating was "◎", the overall air permeability rating was "◎", the average transmission loss at 400 Hz-4 kHz was 14.3 dB, and the sound insulation rating was "◎". Note that Example 1 had higher sound insulation than Comparative Example 1, which had the same density but had an average transmission loss at 400 Hz-4 kHz of 10.9 dB, and the sound insulation rating was "◯".

In Example 2 (density 70 kg/m ³ ), the air permeability of the inner side was 22.0 L/min, the air permeability of the surface coating layer was 3.5 L/min, and the evaluation was "◎". The difference in air permeability between the surface coating layer and the inner side was 18.5 L/min, and the evaluation was "〇". The overall air permeability was "〇".

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 varied to 50 kg/m ³ (Example 3) and 70 kg/m ³ (Example 4).

In Example 3 (density 50 kg/m ³ ), the air permeability of the inner side was 55.0 L/min, the air permeability of the surface coating layer was 3.7 L/min, and the rating was "◎". The difference in air permeability between the surface coating layer and the inner side was 51.2 L/min, and the rating was "◎". The overall air permeability rating was "◎".

In Example 4 (density 70 kg/m ³ ), the air permeability of the inner side was 24.1 L/min, the air permeability of the surface coating layer was 3.9 L/min, and the rating was "◎". The difference in air permeability between the surface coating layer and the inner side was 20.3 L/min, and the rating was "◎". The overall air permeability rating was "◎".

Comparative Examples 1 and 2 are examples in which 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 (Comparative Example 2).

In Comparative Example 1 (density 50 kg/m ³ ), the air permeability on the inner side was 58.6 L/min, the air permeability of the surface coating layer was 26.9 L/min, and the rating was "▲". The difference in air permeability between the surface coating layer and the inner side was 31.7 L/min, and the rating was "◎". The overall air permeability rating was "▲". 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 rating was "△".

In Comparative Example 2 (density 70 kg/m ³ ), the air permeability of the inner side was 22.1 L/min, the air permeability of the surface coating layer was 9.2 L/min, and the evaluation was "Good." The difference in air permeability between the surface coating layer and the inner side was 12.9 L/min, and the evaluation was "▲." The overall air permeability was judged to be "▲."

Comparative Examples 3 and 4 are examples in which release agent B was used, the isocyanate index was set to 100, and the density of the polyurethane foam was varied to 50 kg/m ³ (Comparative Example 3) and 70 kg/m ³ (Comparative Example 4).

In Comparative Example 3 (density 50 kg/m ³ ), the air permeability of the inner side was 68.6 L/min, the air permeability of the surface coating layer was 14.0 L/min, and the rating was "▲". The difference in air permeability between the surface coating layer and the inner side was 54.6 L/min, and the rating was "◎". The overall air permeability rating was "▲".

In Comparative Example 4 (density 70 kg/m ³ ), the air permeability of the inner side was 35.1 L/min, the air permeability of the surface coating layer was 14.7 L/min, and the rating was "▲". The difference in air permeability between the surface coating layer and the inner side was 20.5 L/min, and the rating was "〇". The overall air permeability rating was "▲".

Comparative Examples 5 and 6 are examples in which 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 (Comparative Example 6).

In Comparative Example 5 (density 50 kg/m ³ ), the air permeability on the inner side was 47.3 L/min, the air permeability of the surface coating layer was 14.7 L/min, and the rating was "▲". The difference in air permeability between the surface coating layer and the inner side was 32.6 L/min, and the rating was "◎". The overall air permeability rating was "▲". 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 rating was "×".

In Comparative Example 6 (density 70 kg/m ³ ), the air permeability of the inner side was 21.3 L/min, the air permeability of the surface coating layer was 7.3 L/min, and the evaluation was "Good." The difference in air permeability between the surface coating layer and the inner side was 14.0 L/min, and the evaluation was "▲." The overall air permeability was "▲."

Comparative Examples 7 and 8 are examples in which 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 (Comparative Example 8).

In Comparative Example 7 (density 50 kg/m ³ ), the air permeability of the inner side was 54.4 L/min, the air permeability of the surface coating layer was 18.9 L/min, and the rating was "▲". The difference in air permeability between the surface coating layer and the inner side was 35.5 L/min, and the rating was "◎". The overall air permeability rating was "▲".

In Comparative Example 8 (density 70 kg/m ³ ), the air permeability of the inner side was 26.1 L/min, the air permeability of the surface coating layer was 11.5 L/min, and the rating was "▲". The difference in air permeability between the surface coating layer and the inner side was 14.6 L/min, and the rating was "▲". The overall air permeability rating was "▲".

Comparative Example 9 is an example in which 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 .
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 "good." The difference in air permeability between the surface coating layer and the inner side was 17.0 L/min, and the evaluation was "good." The overall air permeability was judged to be "good." The average transmission loss at 400 Hz-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 was judged to be "good."
Comparative Example 9 had a high density of 150 kg/m ³ , and therefore had good sound insulation properties, but was heavy in weight.

Comparative Example 10 is an example in which 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 .
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 "▲".

As such, the present invention provides a lightweight soundproofing material with excellent sound insulation. Note that the present invention is not limited to the examples and can be modified within the scope of the invention.

Claims (3)

A method for producing a soundproofing material made of polyurethane foam, comprising:
A method for producing a soundproofing material, 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; injecting polyurethane foam raw material into said foam molding die and foaming it; and molding a polyurethane foam having a coating layer on its surface, thereby producing a soundproofing material composed of polyurethane foam having a coating layer on its surface. 2. The method for producing a soundproofing material according to claim 1 , wherein the release agent having two melting peaks is a mixed release agent containing a wax component having a weight-average molecular weight of 1,000 or more and a wax component having a weight-average molecular weight of 600 or less. 3. The method for producing a soundproofing material according to claim 1, wherein the polyurethane foam having a coating layer on its surface has an air permeability (JIS K6400-7:2012A method) of 10 L/min or less through the coating layer, an air permeability (JIS K6400-7: 2012A method) of 15 L/min or more on the inner side than the coating layer, and a density (JIS K7222:2005) of less than 130 kg/ ^m3 .