JP7250431B2 - Polyurethane foam and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a lightweight polyurethane foam having sound absorption properties and a method for producing the same.

Polyurethane foams obtained from polyurethane foam raw materials containing polyol, isocyanate, blowing agent and catalyst are widely used for furniture, building materials, vehicle interior materials and the like.

Polyurethane foams containing a large amount of water (7 to 17 parts by weight per 100 parts by weight of polyol) used as a blowing agent are known as lightweight polyurethane foams having sound absorbing properties. (Patent document 1, claim 7).

However, a polyurethane foam containing a large amount of water as a blowing agent generates heat at a high temperature during foaming, and scorches occur in the polyurethane foam, resulting in deterioration of quality.

Japanese Patent No. 5204754

SUMMARY OF THE INVENTION It is an object of the present invention to provide a sound-absorbing, lightweight and high-quality polyurethane foam and a method for producing the same.

The invention according to a first aspect provides a polyurethane foam obtained from a polyurethane foam raw material containing a polyol, an isocyanate, a blowing agent, and a catalyst, wherein the polyurethane foam raw material contains sodium hydrogen carbonate, and water as the blowing agent is the polyol. It is characterized by being 10 parts by weight or more per 100 parts by weight and having an isocyanate index of 100 or more.

An invention according to a second aspect is characterized in that, in the invention according to the first aspect , the sodium hydrogen carbonate is 5 to 30 parts by weight with respect to 100 parts by weight of the polyol.

An invention according to a third aspect is characterized in that, in the invention according to the first or second aspect , the polyurethane foam raw material contains an organic solid acid together with the sodium hydrogen carbonate.

The invention according to a fourth aspect is characterized in that in the invention according to the third aspect , the amount of the organic solid acid is 1/30 to 1/60 of the amount of the sodium hydrogen carbonate.

An invention according to a fifth aspect is characterized in that, in the invention according to the third or fourth aspect , the organic solid acid is citric acid and/or malic acid.

The invention according to a sixth aspect provides a method for producing a polyurethane foam by mixing and reacting polyurethane foam raw materials containing a polyol, an isocyanate, a blowing agent, and a catalyst, wherein the polyurethane foam raw material contains sodium hydrogen carbonate, and the foaming agent is A certain amount of water is 10 parts by weight or more with respect to 100 parts by weight of the polyol, and the isocyanate index is 100 or more.

In the present invention, the state of the polyurethane foam is such that it has cell regions (hereinafter referred to as "double cell regions") 11 in which cells (pores) aggregate as shown in FIG. A cell region other than the double cell region 11 of polyurethane foam is referred to as a matrix cell region 12 .

In general, sound transmitted through a porous region is regarded as a solid-borne wave propagating through the porous resin skeleton and an air-borne wave propagating through the voids in the bubbles. In the polyurethane foam of the present invention having double-cell regions, both solid-propagating waves and air-propagating waves are easily attenuated in the countless cells that are complicatedly convoluted, and sound is attenuated when it passes through the foam. Great sound absorption. On the other hand, in a polyurethane foam having a normal cell structure without double cell regions, a plurality of intricately arranged cells are not agglomerated. Low sound absorption.

In the present invention, since 10 parts by weight or more of water is used as a blowing agent, there is a concern that the reaction exothermic temperature may increase during the production of polyurethane foam. It is decomposed to produce water, and the latent heat of evaporation (heat of vaporization) of the water suppresses the temperature rise, so the inside of the polyurethane foam is not exposed to high temperatures, is less likely to scorch, is lightweight, and has little discoloration. A polyurethane foam of good quality is obtained.

The amount of sodium bicarbonate is preferably 5 to 30 parts by weight per 100 parts by weight of polyol. By setting the amount of sodium bicarbonate within this range, it is possible to effectively suppress the temperature rise due to heat generation and obtain a polyurethane foam of good quality.

Moreover, it is preferable that the polyurethane foam raw material contains an organic solid acid together with sodium hydrogen carbonate. Sodium hydrogen carbonate and an organic solid acid first cause an endothermic reaction in the first stage during the production of polyurethane foam, thereby suppressing temperature rise.

When the organic solid acid is citric acid, the endothermic reaction in the first stage is as shown in FIG. Absorption of heat suppresses temperature rise due to reaction of raw materials for polyurethane foam.

The sodium hydrogen carbonate not consumed in the endothermic reaction in the first stage undergoes the endothermic reaction in the second stage shown in FIG. The rise can be further suppressed. In the endothermic reaction of the second stage, the sodium hydrogen carbonate not consumed in the endothermic reaction of the first stage is thermally decomposed into sodium carbonate, water and carbon dioxide.

FIG. 3 shows the first-stage endothermic reaction and the second-stage endothermic reaction when the organic solid acid is malic acid.
In addition, water and carbon dioxide are generated as reaction decomposition products of sodium bicarbonate and an organic solid acid (e.g. citric acid or malic acid). form can be lightened.

It is the photograph which image|photographed the surface of the polyurethane foam of this invention with the microscope by 20 times. It is a figure which shows the endothermic reaction by sodium hydrogencarbonate and a citric acid. It is a figure which shows the endothermic reaction by sodium hydrogencarbonate and malic acid. 1 is a table showing formulations and measurement results of physical properties of examples and comparative examples. It is a table|surface which shows the measurement result of a 7-point average sound absorption coefficient.

The polyurethane foam of the present invention is produced by mixing and reacting polyurethane foam raw materials containing polyol, isocyanate, blowing agent, catalyst, sodium hydrogen carbonate, and preferably further an organic solid acid.

Polyols for polyurethane foams can be used as polyols, and for example, any of polyether polyols, polyester polyols, and polyether ester polyols can be used, and one or more of them can be used.

Examples of polyether polyols include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, neopentyl glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, sucrose, and ethylene oxide (EO ) and polyether polyols to which alkylene oxides such as propylene oxide (PO) are added.

Examples of polyester polyols include polycondensation from aliphatic carboxylic acids such as malonic acid, succinic acid and adipic acid, aromatic carboxylic acids such as phthalic acid, and aliphatic glycols such as ethylene glycol, diethylene glycol and propylene glycol. Polyester polyols obtained by
Examples of polyether ester polyols include those obtained by reacting the above polyether polyols with polybasic acids to form polyesters, and those having both polyether and polyester segments in one molecule.

As for the polyol, it is preferable to use one or a plurality of polyols having a hydroxyl value (OHV) of 20 to 300 mgKOH/g, a functional group number of 2 to 6, and a weight average molecular weight of 500 to 15,000.

As the isocyanate, aliphatic or aromatic polyisocyanates having two or more isocyanate groups, mixtures thereof, and modified polyisocyanates obtained by modifying them can be used. Examples of aliphatic polyisocyanates include hexamethylene diisocyanate, isophorone diisocyanate, and dicyclohexamethane diisocyanate. Examples of aromatic polyisocyanates include toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, xyloxy Examples include diisocyanate, polymeric MDI (crude MDI), and the like. In addition, other prepolymers can also be used.

The isocyanate index (INDEX) is preferably 100 or more, more preferably 120 or more, and the upper limit is 200 or less. A more preferred isocyanate index range is 140-160.

By the way, let's take a look at the temperature change over time that accompanies foaming and curing of polyurethane foam. In the initial reaction, the reaction between the polyol component and isocyanate, etc. is accelerated, and the temperature of the foam rises with an exothermic reaction. In particular, heat tends to accumulate inside the foam, and the temperature rises significantly. During this time, urethane bonds are predominantly generated by polyol and isocyanate, and matrix cell regions 12 are formed. Then, when the temperature rising inside the foam reaches the decomposition temperature of sodium hydrogen carbonate, the sodium hydrogen carbonate finally decomposes to produce carbon dioxide gas and water. This generated water reacts with the isocyanate. The isocyanate envisioned to react here is any isocyanate other than the isocyanate consumed by reacting with the polyol component to form urethane linkages in the initial reaction. That is, it is an isocyanate corresponding to an isocyanate index exceeding 100. Theoretically, it is assumed that when water generated from sodium hydrogencarbonate reacts with isocyanate, a urea bond is generated to form the double cell region 11 .
The isocyanate index is a value obtained by dividing the number of moles of isocyanate groups in isocyanate by the total number of moles of active hydrogen groups such as hydroxyl groups in polyol and multiplying this value by 100. Calculated.

Water is preferred as the blowing agent. Water generates carbon dioxide gas when polyol reacts with isocyanate, and the carbon dioxide gas causes foaming. The amount of water as a blowing agent is 10 parts by weight or more with respect to 100 parts by weight of polyol, and the preferred amount of water is 10 to 15 parts by weight.

As a catalyst, a known urethanization catalyst can be used in combination. For example, amine catalysts such as triethylamine, triethylenediamine, diethanolamine, dimethylaminomorpholine, N-ethylmorpholine and tetramethylguanidine; tin catalysts such as stannus octoate and dibutyltin dilaurate; phenylmercuric propionate and lead octoate. metal catalysts (also called organometallic catalysts) such as amine catalysts and metal catalysts, or both may be used in combination. The amount of amine catalyst is preferably 0.05 to 1.0 parts by weight with respect to 100 parts by weight of polyol. The amount of metal catalyst is preferably 0 or 0.05 to 0.5 parts by weight.

The amount of sodium bicarbonate is 5 to 30 parts by weight, more preferably 10 to 30 parts by weight, based on 100 parts by weight of the polyol. By setting the amount of sodium bicarbonate within the above range, the endothermic reaction can be favorably performed, and an exothermic temperature rise during the production of the polyurethane foam can be suppressed.

When the organic solid acid is used in combination with sodium hydrogencarbonate, the endothermic effect increases during the production of the polyurethane foam, and the increase in the exothermic temperature of the polyurethane foam can be suppressed more effectively. The amount of organic solid acid is preferably 1/30 to 1/60 of the amount of sodium hydrogen carbonate. Further, the amount of the organic solid acid with respect to 100 parts by weight of polyol is preferably 0.3 to 0.7 parts by weight with respect to 100 parts by weight of polyol.

Examples of organic solid acids include citric acid, fumaric acid, malonic acid, stearic acid, pyruvic acid, phthalic acid, malic acid, maleic acid, succinic acid, and polybasic carboxylic acids having hydroxy groups. The organic solid acid is not limited to one type, and two or more types may be used in combination. In particular, citric acid and malic acid (hydroxy acids) are more preferred organic solid acids in the present invention, and either or both of them are used. In particular, malic acid is a preferred organic solid acid in the present invention. Both hydrates and anhydrides of citric acid can be used.

Other auxiliary agents may be added to the polyurethane foam raw material. Examples of auxiliary agents include foam stabilizers and coloring agents. As the foam stabilizer, those known for polyurethane foam can be used. Examples thereof include silicone foam stabilizers, fluorine foam stabilizers and known surfactants. As the colorant, a carbon pigment or the like can be used according to the use of the polyurethane foam.

As a foaming method for producing polyurethane foam, a molding foaming method of casting into a mold or a slabstock foaming method can be employed, and among these, the slabstock foaming method is preferable for mass production. The slabstock foaming method is a method in which two liquid polyurethane foam raw materials are mixed with a stirrer, discharged onto a belt conveyor, and foamed at room temperature under atmospheric pressure. A one-shot method, a prepolymer method, or the like can be employed for the polyurethane raw material composition.

The following components were mixed according to the formulation shown in FIG. 4, reacted and foamed to produce polyurethane foams for each of Comparative Examples and Examples. The unit of the addition amount of each component is parts by weight.
Polyol: polyether polyol, molecular weight: 3000, functional number: 3, hydroxyl value: 56.1 mgKOH/mg, product number: GP-3000, manufactured by Sanyo Chemical Industries, Ltd. Blowing agent: water, amine catalyst; product number: 33LV, Air Products・Foam stabilizer: silicone foam stabilizer, product number: B8110, manufactured by Goldschmidt ・Metal catalyst: stannous octoate, product number: MRH110, manufactured by Johoku Chemical Industry Co., Ltd. ・Isocyanate: 2,4-TDI/2, 6-TDI = 80/20, product number: Coronate T-80, manufactured by Nippon Polyurethane Industry Co., Ltd. Gypsum dihydrate; Specific gravity 2.32, gypsum dihydrate having an average particle size of 40 μm Sodium hydrogen carbonate Citric acid Malic acid

The maximum exothermic temperature of each comparative example and each example was measured as follows. A wooden box of 38 cm×38 cm×24 cm without a lid was prepared in advance, and the thermocouple was set in the center of the wooden box. Then, two liquids, a polyol compounding component and an isocyanate component, are separately prepared, and after mixing and stirring the two liquids with a propeller mixer, the reaction mixture is poured into the wooden box to form a polyurethane foam at normal temperature and atmospheric pressure. Naturally foamed.

In addition, cream time and rise time were visually measured in order to determine the reactivity during production of the polyurethane foams of each comparative example and each example. The cream time is the time it takes for the polyurethane foam raw material to solidify from the state of the mixed reaction liquid at the time of mixing and casting and change color to a resin state. On the other hand, the rise time is the time from the time of mixing and casting until the foam expands and reaches the maximum foam height. A short cream time indicates that the initial reaction is rapid, and a long cream time indicates that the initial reaction is mild. On the other hand, the rise time is the time it takes to reach the maximum foaming height. If the value after the cream time is large, it indicates that the reaction after the cream time is gradual.

The density (JIS K7220) and air permeability (JIS K6400-7) were measured for the polyurethane foams of each comparative example and each example.
In addition, the surface of the polyurethane foam of each comparative example and each example was observed with a microscope to determine the presence or absence of double cell regions. When the double-cell region does not exist, it is indicated by "X", and when it exists, it is indicated by three levels of "Δ", "◯", and "⊚" according to the amount of the double-cell region. "△" is 1 or more but less than 10 on a surface of 5 cm x 5 cm, "○" is on a surface of 5 cm x 5 cm, and 10 or more but less than 20 is "◎" on a surface of 5 cm x 5 cm. shows the case of 20 or more.

Comparative Example 1 contains 100 parts by weight of polyol, 10 parts by weight of water as a foaming agent, 0.5 parts by weight of an amine catalyst, 1.5 parts by weight of a foam stabilizer, 0.15 parts by weight of a metal catalyst, 170 parts by weight of isocyanate, and an isocyanate index. 160 and 20 parts by weight of gypsum dihydrate, and neither sodium hydrogen carbonate nor citric acid and malic acid as organic solid acids are added. Comparative Example 1 had a maximum heat generation temperature of 178° C., a density of 11.2 kg/m ³ , an air permeability of 1.37 cc/cm ² /sec, and a double cell area of “x”.

Comparative Example 2 is Comparative Example 1 with 5 parts by weight of water, 0.35 parts by weight of a metal catalyst, 93 parts by weight of isocyanate, and 5 parts by weight of sodium hydrogen carbonate and 0.5 parts by weight of malic acid instead of gypsum dihydrate. The procedure is the same as in Comparative Example 1, except that some components were added. Comparative Example 2 has a maximum heat generation temperature of 139° C., a density of 27.5 kg/m ³ , an air permeability of 0.46 cc/cm ² /sec, and a double cell area of “×”. High density. Moreover, since the blending amount of water as a foaming agent is small, a double cell region cannot be obtained.

Comparative Example 3 is the same as Comparative Example 2 except that the citric acid used in Comparative Example 2 was 15 parts by weight. Comparative Example 3 has a maximum heat generation temperature of 136° C., a density of 26.4 kg/m ³ , an air permeability of 0.55 cc/cm ² /sec, and a double cell area of “×”. , the density is large. Moreover, since the blending amount of water as a foaming agent is small, a double cell region cannot be obtained.

Comparative Example 4 is the same as Comparative Example 2 except that the citric acid used in Comparative Example 2 was changed to 30 parts by weight. Comparative Example 4 has a maximum heat generation temperature of 126° C., a density of 19.5 kg/m ³ , an air permeability of 0.44 cc/cm ² /sec, and a double cell area of “×”. , the density is large. Moreover, since the blending amount of water as a foaming agent is small, a double cell region cannot be obtained.

Example 1 contains 100 parts by weight of polyol, 10 parts by weight of water as a foaming agent, 0.5 parts by weight of an amine catalyst, 1.5 parts by weight of a foam stabilizer, 0.15 parts by weight of a metal catalyst, 170 parts by weight of isocyanate, and an isocyanate index. 160 and 20 parts by weight of sodium hydrogen carbonate, and neither citric acid nor malic acid as the organic solid acid is blended. Example 1 had a maximum exothermic temperature of 183° C., a density of 14.8 kg/m ³ , an air permeability of 1.85 cc/cm ² /sec, and a double cell area of “◯”. Due to the double cell area, the sound absorption is good. Moreover, since the maximum exothermic temperature is not extremely high, the quality of the obtained polyurethane foam is good, and furthermore, the density is small and the weight is light.

Example 2 is the same as Example 1 except that the amount of sodium bicarbonate was reduced to 15 parts by weight and 0.5 parts by weight of malic acid was added. Example 2 had a maximum heat generation temperature of 165° C., a density of 10.8 kg/m ³ , an air permeability of 1.07 cc/cm ² /sec, and a double cell area of “⊚”. In Example 2, 15 parts by weight of sodium bicarbonate and 0.5 parts by weight of malic acid were used in combination, so the maximum exothermic temperature was lower than in Example 1, and the double cell region was rated as "⊚". Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 3 is similar to Example 2 except that the isocyanate was 149 parts by weight and the isocyanate index was 140. Example 3 had a maximum heat generation temperature of 160° C., a density of 11.6 kg/m ³ , an air permeability of 0.81 cc/cm ² /sec, and a double cell region of “◯”. In Example 3, the isocyanate index decreased from 160 in Example 2 to 140, so the double cell region changed from "⊚" in Example 2 to "◯". Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 4 is similar to Example 2 except that the isocyanate was 128 parts by weight and the isocyanate index was 120. Example 4 had a maximum heat generation temperature of 151° C., a density of 12.8 kg/m ³ , an air permeability of 1.25 cc/cm ² /sec, and a double cell area of “Δ”. In Example 3, the isocyanate index decreased from 160 in Example 2 to 120, so the double cell region changed from "⊚" in Example 2 to "Δ". Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 5 is the same as Example 2, except that 0.5 parts by weight of citric acid was added instead of malic acid. Example 5 had a maximum exothermic temperature of 162° C., a density of 13.6 kg/m ³ , an air permeability of 0.75 cc/cm ² /sec, and a double cell region of “◯”. In Example 5, by substituting citric acid for malic acid in Example 2, the double cell region changed from "⊚" in Example 2 to "◯". Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 6 is similar to Example 2, except that 0.25 parts by weight of citric acid and 0.25 parts by weight of malic acid were used together. Example 6 had a maximum exothermic temperature of 154° C., a density of 18.9 kg/m ³ , an air permeability of 4.45 cc/cm ² /sec, and a double cell area of “◯”. In Example 6, 0.25 parts by weight of 0.5 parts by weight of malic acid in Example 2 was replaced with citric acid, so that the double cell region changed from "⊚" in Example 2 to "○". Due to the double cell area, the sound absorption is good. Also, the density was slightly higher than that of the other examples.

Example 7 is similar to Example 2 except that the isocyanate was 106 parts by weight and the isocyanate index was 100. Example 7 had a maximum heat generation temperature of 132° C., a density of 15.8 kg/m ³ , an air permeability of 0.2 cc/cm ² /sec, and a double cell area of “Δ”. In Example 7, by lowering the isocyanate index to 100, the double cell region changed from "⊚" in Example 2 to "Δ". Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 8 is similar to Example 2 except that the isocyanate was 191 parts by weight and the isocyanate index was 180. Example 8 had a maximum exothermic temperature of 166° C., a density of 12.9 kg/m ³ , an air permeability of 2.01 cc/cm ² /sec, and a double cell area of “◯”. In Example 8, by increasing the isocyanate index to 180, the double cell region changed from "⊚" in Example 2 to "◯". Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 9 is similar to Example 2 except that the isocyanate was 212 parts by weight and the isocyanate index was 200. Example 9 had a maximum heat generation temperature of 167° C., a density of 13.1 kg/m ³ , an air permeability of 5.98 cc/cm ² /sec, and a double cell area of “◯”. In Example 9, by increasing the isocyanate index to 200, the double cell region changed from "⊚" in Example 2 to "◯". Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 10 is the same as Example 2, except that 30 parts by weight of sodium bicarbonate was used. Example 10 had a maximum heat generation temperature of 134° C., a density of 12.7 kg/m ³ , an air permeability of 0.97 cc/cm ² /sec, and a double cell area of “⊚”. In Example 10, the amount of sodium bicarbonate was increased from 15 parts by weight in Example 2 to 30 parts by weight, but the double cell region was "A" as in Example 2. Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 11 is similar to Example 2 except that the water is 15 parts by weight and the isocyanate is 247 parts by weight. Example 11 had a maximum heat generation temperature of 185° C., a density of 14.8 kg/m ³ , an air permeability of 12.3 cc/cm ² /sec, and a double cell region of “◯”. In Example 11, by increasing the amount of water from 10 parts by weight in Example 2 to 15 parts by weight, the exothermic temperature was higher than in Example 2, and the double cell region changed from "◎" in Example 2 to "○". became. Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 12 is the same as Example 11 except that 30 parts by weight of sodium bicarbonate was used. Example 12 had a maximum heat generation temperature of 145° C., a density of 11.9 kg/m ³ , an air permeability of 13.9 cc/cm ² /sec, and a double cell region of “◯”. In Example 12, the exothermic temperature was lower than in Example 11 by increasing the amount of sodium hydrogencarbonate to 30 parts by weight, but the double cell region was "O" as in Example 11. Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 13 is similar to Example 2, except that 0.3 parts by weight of malic acid was used. Example 13 had a maximum exothermic temperature of 182° C., a density of 15.0 kg/m ³ , an air permeability of 3.28 cc/cm ² /sec, and a double cell area of “◯”. In Example 13, the amount of malic acid was reduced from 0.5 parts by weight in Example 2 to 0.3 parts by weight, so that the double cell region changed from "⊚" in Example 2 to "○". Due to the double cell area, the sound absorption is good. Moreover, since the maximum exothermic temperature is not extremely high, the quality of the obtained polyurethane foam is good, and furthermore, the density is small and the weight is light.

Example 14 is similar to Example 2, except that 0.7 parts by weight of malic acid was used. Example 14 had a maximum exothermic temperature of 157° C., a density of 15.0 kg/m ³ , an air permeability of 2.05 cc/cm ² /sec, and a double cell region of “◯”. In Example 14, the amount of malic acid was increased from 0.5 parts by weight in Example 2 to 0.7 parts by weight. Due to the double cell area, the sound absorption is good. In addition, the density is small and the weight is light.

Example 15 is the same as Example 2, except that 5 parts by weight of sodium bicarbonate was used. Example 15 had a maximum exothermic temperature of 186° C., a density of 13.8 kg/m ³ , an air permeability of 2.85 cc/cm ² /sec, and a double cell area of “Δ”. In Example 15, the amount of sodium bicarbonate was reduced from 15 parts by weight in Example 2 to 5 parts by weight, so that the double cell region changed from "⊚" in Example 2 to "Δ". Also, although the maximum heat generation temperature was higher than that of Example 2, it was not extremely high, so the quality of the obtained polyurethane foam was good, and furthermore, it had a low density and a light weight.

Seven-point average sound absorption coefficients were measured at frequencies of 500-2000 Hz and 2500-10000 Hz for Example 2 having a double cell region and Comparative Examples A and B. Comparative Example A is a non-woven fabric sound absorbing and heat insulating material (Thinsulate TC, manufactured by 3M, basis weight: 300 g/m ² ), while Comparative Example B is a melamine resin foam (Basotect G+, manufactured by BASF, basis weight). : 300 g/m ² ). The test sample has a thickness of 20 mm and a basis weight of 300 g/m ² . The method for measuring the seven-point average sound absorption coefficient is JIS A1409:1998 (reverberation room method sound absorption coefficient measurement method).

The measurement results of the 7-point average sound absorption coefficient are as shown in FIG. In Comparative Example A, 500-2000 Hz was 76.0%, and in Comparative Example B, 500-2500 Hz was 86.4%.
As described above, the example has a double-cell region in the open-cell structure of the polyurethane resin, so that the sound absorption is better than that of the conventional non-woven fabric or the comparative example of the melamine resin foam.

INDUSTRIAL APPLICABILITY The polyurethane foam of the present invention has good sound absorbing properties, is lightweight and of good quality, and is suitable for furniture, building materials, vehicle interior materials, sound absorbing materials, and the like.

11: double cell region 12: matrix cell region

Claims (6)

In a polyurethane foam obtained from a polyurethane foam raw material containing a polyol, an isocyanate, a blowing agent and a catalyst,
The polyurethane foam raw material contains sodium hydrogen carbonate and an organic solid acid,
Water as the foaming agent is 10 parts by weight or more with respect to 100 parts by weight of the polyol,
A polyurethane foam having an isocyanate index of 100 or more and 200 or less . In a polyurethane foam obtained from a polyurethane foam raw material containing a polyol, an isocyanate, a blowing agent and a catalyst,
The polyurethane foam raw material contains sodium hydrogen carbonate,
Water as the foaming agent is 10 parts by weight or more with respect to 100 parts by weight of the polyol,
A polyurethane foam having an isocyanate index of 140 or more and 200 or less . In a polyurethane foam obtained from a polyurethane foam raw material containing a polyol, an isocyanate, a blowing agent and a catalyst,
The polyurethane foam raw material contains sodium hydrogen carbonate,
Water as the foaming agent is 10 parts by weight or more with respect to 100 parts by weight of the polyol,
The isocyanate index is 100 or more and 200 or less ,
A polyurethane foam having a density of 14.8 kg/m ³ or less. 4. The polyurethane foam according to claim 2, wherein the polyurethane foam raw material contains an organic solid acid together with the sodium hydrogen carbonate. 5. The polyurethane foam according to claim 1, wherein the amount of said organic solid acid is 1/30 to 1/60 of the amount of said sodium hydrogen carbonate. In a polyurethane foam obtained from a polyurethane foam raw material containing a polyol, an isocyanate, a blowing agent and a catalyst,
The polyurethane foam raw material contains sodium hydrogen carbonate,
Water as the foaming agent is 10 parts by weight or more with respect to 100 parts by weight of the polyol,
A sound absorbing material comprising a polyurethane foam having an isocyanate index of 100 or more and 200 or less .

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