JP2006199869A - Polyurethane foam having continuous cell structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyurethane foam having a continuous cell structure, wherein temperature of heat released at expansion and curing can be lowered within a shorter time and coloring caused by scorch can be inhibited. <P>SOLUTION: The polyurethane foam having the continuous cell structure is obtained by compounding a hydrogencarbonate with a polyurethane foam material containing polyols, polyisocyanates, a foaming agent and a catalyst and reacting, expanding and curing the polyurethane foam material. The hydrogencarbonate is preferably sodium hydrogencarbonate or potassium hydrogencarbonate. The amount of the hydrogencarbonate compounded is preferably 10-100 pts.mass per 100 pts.mass. polyols. The hydrogencarbonate is decomposed through heating during the production of the polyurethane foam to produce a carbonate which preferably has a specific gravity of 2-3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyurethane foam having an open-cell structure used for a cushion material forming, for example, furniture, bedding, automobile seats and the like.

Conventionally, when a flexible polyurethane foam having a density of 25 kg / m ³ or less is produced as a polyurethane foam having an open-cell structure, if only the foaming agent is water, it is necessary to increase the amount of water added. And the exothermic temperature at the time of hardening reaches 170 degreeC or more. Therefore, there is a possibility of self-ignition based on oxidative deterioration (scorch) of polyurethane, and discoloration occurs in the obtained flexible polyurethane foam by the scorch. In order to avoid such a situation, it is known that methylene chloride or liquefied carbon dioxide gas is added as a foaming aid with the conventional amount of water added.

However, methylene chloride is one of the substances that adversely affect the environment and its use is regulated. On the other hand, foaming with liquefied carbon dioxide requires special equipment for supplying the liquefied carbon dioxide at a high pressure. In order to perform foaming smoothly, the production conditions are limited and the production cost also increases. Then, the technique of adding polyolefin powder, such as polyethylene powder, for the purpose of endothermic is known (for example, refer patent document 1 and patent document 2).
Japanese translation of PCT publication No. 2002-532596 (2nd page) JP-A-6-199973 (pages 2 and 3)

  However, in the conventional technology of adding polyolefin powder, an effect is observed against a decrease in heat generation temperature during foaming and curing, but in order to effectively suppress the heat generation amount, it is necessary to increase the amount of polyolefin powder. is necessary. In that case, due to the increased amount of polyolefin powder, the density of the resulting flexible polyurethane foam becomes too high, and physical properties such as tensile strength are lowered. In order to prevent such deterioration of physical properties, polyolefin powder cannot be blended sufficiently, so the heat generation temperature during foaming and curing cannot be reduced in a short time, and as a result, discoloration due to scorch is suppressed. There was a problem that could not.

  The present invention has been made paying attention to such problems existing in the prior art. An object of the invention is to provide a polyurethane foam having an open cell structure capable of lowering the heat generation temperature during foaming and curing in a shorter time and suppressing discoloration due to scorch.

  In order to achieve the above object, a polyurethane foam having an open-cell structure according to claim 1 is provided with a hydrogen carbonate to a polyurethane foam raw material containing polyols, polyisocyanates, a blowing agent and a catalyst. It is obtained by blending a salt, reacting the polyurethane foam raw material, foaming and curing.

  The polyurethane foam having an open-cell structure according to claim 2 is the invention according to claim 1, wherein the bicarbonate is decomposed by heating in the process of producing the polyurethane foam to produce carbonate, The specific gravity of the carbonate is 2 to 3.

  The polyurethane foam having an open-cell structure according to claim 3 is the invention according to claim 1 or 2, wherein the bicarbonate is sodium bicarbonate or potassium bicarbonate. Is.

  The polyurethane foam having an open-cell structure according to claim 4 is the invention according to any one of claims 1 to 3, wherein the amount of the hydrogen carbonate is 10 to 10 parts by weight per 100 parts by weight of polyols. It is 100 mass parts.

According to the present invention, the following effects can be exhibited.
The polyurethane foam having an open-cell structure according to claim 1 is obtained by blending a hydrogen carbonate with a polyurethane foam raw material, reacting the polyurethane foam raw material, and foaming and curing the polyurethane foam raw material. . Hydrogen carbonate is heated and decomposed in the production process of the polyurethane foam to produce water, and evaporation of the water removes latent heat of vaporization (heat of vaporization), thereby suppressing heat generation due to the reaction of the polyurethane foam raw material. Moreover, since the decomposition reaction of the bicarbonate is an endothermic reaction, heat generation due to the reaction of the polyurethane foam raw material can be suppressed. Therefore, the heat generation temperature during foaming and curing can be reduced in a shorter time, and discoloration due to scorch can be suppressed.

  In the polyurethane foam having an open-cell structure according to claim 2, the bicarbonate is decomposed by heating during the production process of the polyurethane foam to produce carbonate, and the carbonate has a specific gravity of 2 to 2. 3. Thus, since the specific gravity of the carbonate remaining in the polyurethane foam is larger than the specific gravity of 0.93 of the conventional polyethylene powder, the influence on the physical properties of the polyurethane foam such as density and hardness is small. In addition to the effect of the invention according to claim 1, it is possible to suppress changes in physical properties of the polyurethane foam.

  In the polyurethane foam having an open-cell structure according to the third aspect of the present invention, the hydrogen carbonate is sodium hydrogen carbonate or potassium hydrogen carbonate. These sodium hydrogen carbonate or potassium hydrogen carbonate has a low decomposition start temperature and can be decomposed along with the formation of the polyurethane foam to exert its function. For this reason, the effect of the invention which concerns on Claim 1 or Claim 2 can be improved.

  In the polyurethane foam having an open-cell structure according to claim 4, the amount of hydrogen carbonate is set to 10 to 100 parts by mass per 100 parts by mass of polyols, and decomposition of hydrogen carbonate is excessive or It is done moderately without shortage. Therefore, the effect of the invention according to any one of claims 1 to 3 can be further improved.

Hereinafter, embodiments of the present invention will be described in detail.
The polyurethane foam having an open cell structure in the present embodiment (hereinafter also simply referred to as a foam) is obtained as follows. That is, the foam is obtained by blending a hydrogen carbonate with a polyurethane foam raw material containing polyols, polyisocyanates, a foaming agent and a catalyst, reacting the polyurethane foam raw material, and foaming and curing. . Here, the polyurethane foam having an open-cell structure means that the foam (cell) present in the foam has a continuous structure, is flexible and exhibits resilience to a compressive load, and is a flexible polyurethane. Examples include foams and semi-rigid polyurethane foams.

  In addition, the heat generated during the production of the foam is suppressed by the latent heat of vaporization of water generated by decomposition, and the decomposition reaction of the hydrogen carbonate is an endothermic reaction, thereby suppressing heat generation due to foaming and curing. It is thought that the function that can be expressed. When the temperature during foaming and curing rises to, for example, 160 ° C. or higher, further 170 ° C. or higher, the foam undergoes oxidative degradation, that is, scorch, and discoloration occurs in the foam. This phenomenon is suppressed by utilizing decomposition of bicarbonate. The foam of this embodiment is foamed and cured in a mold by injecting a polyurethane foam raw material (reaction mixture) into a slab foam obtained by foaming and curing at room temperature and atmospheric pressure and a mold, and clamping the mold. It may be produced by any method of the molded foam obtained. In this case, since the slab foam is generally formed into a bulky of about 1 m in height by continuous production, it is easy to store heat and easily yellow, so the manufacturing method of this embodiment is a countermeasure against yellowing by a scorch. It is valid.

First, the polyurethane foam raw material will be described.
Polyether polyols or polyester polyols are used as the polyols. Of these, polyether polyols are preferable because they are excellent in reactivity with polyisocyanates and do not hydrolyze like polyester polyols. Examples of the polyether polyol include polypropylene glycol, polytetramethylene glycol, polyether polyol made of a polymer obtained by addition polymerization of propylene oxide and ethylene oxide to a polyhydric alcohol, and modified products thereof. Examples of the polyhydric alcohol include glycerin and dipropylene glycol.

  Specific examples of polyether polyols include triols obtained by addition polymerization of propylene oxide to glycerin and addition polymerization of ethylene oxide, diols obtained by addition polymerization of propylene oxide to dipropylene glycol, and addition polymerization of ethylene oxide. . The polyethylene oxide unit in the polyether polyol is about 10 to 30 mol%. When the content of the polyethylene oxide unit is high, the hydrophilicity is higher than when the content is low, and the miscibility with highly polar molecules, polyisocyanates and the like is improved. As a result, the reactivity increases. These polyols can change the number of functional groups and the hydroxyl value of the hydroxyl group by adjusting the type, molecular weight, condensation degree, and the like of the raw material components.

  Polyester polyols include condensation polyester polyols obtained by reacting polycarboxylic acids such as adipic acid and phthalic acid with polyols such as ethylene glycol, diethylene glycol, propylene glycol, and glycerin, as well as lactone polyester polyols and polycarbonates. Polyols are used.

  The polyisocyanates to be reacted with the polyols are compounds having a plurality of isocyanate groups, specifically, tolylene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI). ), Triphenylmethane triisocyanate, xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate, isophorone diisocyanate (IPDI), and modified products thereof. The isocyanate index of the polyisocyanates may be 100 or less or more than 100, but is usually in the range of about 90 to 130. Here, the isocyanate index represents the equivalent ratio of the isocyanate group of the polyisocyanate to the hydroxyl group of the polyol and water as a blowing agent in percentage.

The foaming agent is for foaming a polyurethane resin to form a polyurethane foam having an open cell structure. For example, pentane, cyclopentane, hexane, cyclohexane, dichloromethane, carbon dioxide gas, etc. are used in addition to water. When the blowing agent is water, the density of the polyurethane foam is preferably 25 kg / m ³ or less, more preferably 15 to 20 kg / m ³ , so that the blending amount is 5 to 100 parts by mass of polyols. It is preferable to set it as 13 mass parts. When the amount of water is less than 5 parts by mass, the amount of foaming is small and the density of the polyurethane foam tends to exceed 25 kg / m ³ , and when it exceeds 13 parts by mass, the temperature tends to rise during foaming and curing. It becomes difficult to reduce.

  The catalyst is for accelerating the urethanization reaction between polyols and polyisocyanates. Specifically, tertiary catalysts such as triethylenediamine, dimethylethanolamine, N, N ′, N′-trimethylaminoethylpiperazine, etc. Examples include amines, organometallic compounds such as tin octylate (tin octoate), acetates, alkali metal alcoholates, and the like.

  In addition to the polyurethane foam raw material, a foam stabilizer, a crosslinking agent, a filler, a stabilizer, a colorant, a flame retardant, a plasticizer, and the like are blended as necessary. Examples of the foam stabilizer include silicone compounds, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate, polyether siloxane, and phenolic compounds.

Next, the bicarbonate added to the polyurethane foam raw material is a compound that is decomposed by heating. For example, sodium hydrogen carbonate (NaHCO ₃ ) is decomposed based on the following reaction formula (1) to generate sodium carbonate (Na ₂ CO ₃ ), water (H ₂ O), and carbon dioxide (CO ₂ ).

2NaHCO ₃ → Na ₂ CO ₃ + H ₂ O + CO ₂ (1)
Further, potassium hydrogen carbonate (KHCO ₃ ) is decomposed based on the following reaction formula (2) to generate potassium carbonate (K ₂ CO ₃ ), water (H ₂ O) and carbon dioxide (CO ₂ ).

2KHCO ₃ → K ₂ CO ₃ + H ₂ O + CO ₂ (2)
As the hydrogen carbonate, sodium hydrogen carbonate or potassium hydrogen carbonate, which is an alkali metal hydrogen carbonate, is preferable because it has a low decomposition start temperature and can be decomposed along with the formation of the polyurethane foam to exert its function. In addition, the decomposition start temperature of the hydrogen carbonate is preferably 50 to 100 ° C. from the viewpoint that the decomposition of the hydrogen carbonate is started along with the temperature rise during the production of the polyurethane foam and the function can be exhibited. . The decomposition start temperature of sodium hydrogen carbonate is 50 ° C., and the decomposition start temperature of potassium hydrogen carbonate is 100 ° C. When this decomposition start temperature is less than 50 ° C., the decomposition start time is too early and water, which is a decomposition product of bicarbonate, functions as a foaming agent, or the balance of foaming is disrupted by carbon dioxide. It is not preferable. On the other hand, when the decomposition start temperature exceeds 100 ° C., the decomposition start time is too late, and the effect of the decomposition reaction cannot be sufficiently obtained.

  As the bicarbonate, a powder having an average particle diameter of preferably about 10 to 50 μm is used. When the average particle size of the bicarbonate is less than 10 μm, the powder becomes too fine and easily becomes dusty, which is inconvenient to handle, and when it exceeds 50 μm, the dispersibility with respect to the polyurethane foam raw material deteriorates and the bicarbonate The function of will not be fully demonstrated. In addition, when blending the bicarbonate into the polyurethane foam raw material, it is preferable to blend in a polyol rather than blending with water as a foaming agent. When the hydrogen carbonate is mixed with water and blended, the foaming state changes, and its control becomes difficult.

  The blending amount of the bicarbonate is preferably 10 to 100 parts by mass per 100 parts by mass of the polyols in order to appropriately perform the decomposition of the bicarbonate without excessive or insufficient. When the amount of the bicarbonate is less than 10 parts by mass, the amount of water that is a decomposition product of the bicarbonate is small, the endothermic amount due to the decomposition reaction is small, and the bicarbonate functions sufficiently. become unable. On the other hand, when the amount exceeds 100 parts by mass, a large amount of water is generated, and excessive water functions as a foaming agent, or the physical properties of the foam change due to foaming based on excessive carbon dioxide, which is not preferable.

  As described above, the bicarbonate is decomposed by heating in the production process of the polyurethane foam to produce a carbonate, and the specific gravity of the produced carbonate is usually 2 to 3. Thus, since the specific gravity of the carbonate remaining in the polyurethane foam is larger than the specific gravity of 0.93 of the conventional polyethylene powder and its volume is reduced, the influence on the physical properties of the polyurethane foam is small. Further, since hydrogen carbonates such as sodium hydrogen carbonate and potassium hydrogen carbonate dissolve in water and show an alkalinity of about pH 8 to 9, it functions as a catalyst for promoting the urethanization reaction between polyols and polyisocyanates. Demonstrate. For this reason, the amount of a catalyst such as a tertiary amine for promoting the urethanization reaction can be reduced. As a result, generation of a volatile organic compound (VOC) by a catalyst such as a tertiary amine can be suppressed.

  Then, a polyurethane foam having an open cell structure is produced by reacting the polyurethane foam raw material to foam and cure, but the reaction at that time is complicated, and basically the following reaction is mainly performed. It has become. That is, addition polymerization reaction (polyurethanation reaction) between polyols and polyisocyanates, foaming (foaming) reaction between polyisocyanates and water as a blowing agent, and crosslinking between these reaction products and polyisocyanates ( Curing) reaction. When producing a polyurethane foam, a one-shot method in which a polyol and a polyisocyanate are directly reacted or a polyol and a polyisocyanate are reacted in advance to obtain a prepolymer having an isocyanate group at the terminal, Any of the prepolymer methods in which polyols are reacted therewith can be employed.

In the polyurethane foam having an open-cell structure obtained in this way, the maximum exothermic temperature based on foaming and curing can be 160 ° C. or less, and the time to drop 10 ° C. from the maximum temperature can be 10 minutes or less. The color difference between the high part and the low temperature part can be made 5 or less. Here, the color difference is the difference (ΔYI) between the yellow index at the high temperature portion and the low temperature portion during foaming and curing. Furthermore, the polyurethane foam can make the density prescribed in JIS K6400 as low as 15 to 20 kg / m ³ .

  As described above, the polyurethane foam has a low density, has a good cushioning property, is lightweight, has a small color difference, and has no problem in terms of discoloration. Moreover, it is preferable that the hardness prescribed | regulated by JISK6400 is 110-130N. When the hardness is less than 110N, the polyurethane foam becomes too soft, and when it sits on it, the sinking becomes large. When it exceeds 130N, the polyurethane foam becomes too hard and cushioning May decrease. In the polyurethane foam, carbonate formed by decomposition of bicarbonate remains, but the carbonate has a specific gravity of 2 to 3 as described above, and its volume is small, which gives the properties of the polyurethane foam. There is little influence. Polyurethane foam having such physical properties forms furniture such as chairs and sofas, bedding such as beds, mattresses and pillows, automobile seats, door lining materials, automobile interior materials such as ceiling materials, etc. It is suitably used as a cushion material or the like.

  In the case of producing a polyurethane foam having an open cell structure, for example, a hydrogen carbonate such as sodium hydrogen carbonate with respect to a polyurethane foam raw material containing polyols, polyisocyanates, water as a blowing agent and an amine catalyst. The salt is blended in an amount of 10 to 100 parts by mass per 100 parts by mass of polyols. And while making polyols and polyisocyanate react, it is made to foam by making polyisocyanate and water react, and a polyurethane foam is manufactured.

  In this production process, during foaming and curing, the bicarbonate is decomposed by being heated to 50 ° C. or more to produce water, and the produced water evaporates. The evaporation of the water removes latent heat of vaporization and suppresses heat generation of the foam based on foaming and curing. At the same time, the heat generation by the decomposition reaction of the bicarbonate suppresses the heat generation of the foam. Due to their synergistic action, the exothermic temperature during foaming and curing can be reduced in a short time. The temperature of the foam during foaming and curing can be suppressed to 160 ° C. or lower, compared with the temperature during foaming and curing exceeding 160 ° C. when no bicarbonate is added. Accordingly, it is possible to suppress the scorch of the foam generated by being exposed to a high temperature of 160 ° C. or higher.

The effects exhibited by the above embodiment will be described collectively below.
-The polyurethane foam having an open-cell structure according to this embodiment is obtained by blending a hydrogen carbonate with a polyurethane foam raw material, reacting the polyurethane foam raw material, and foaming and curing. In that case, the bicarbonate is heated and decomposed to produce water, the evaporation of the water takes away latent heat of evaporation, and the endothermic effect of the decomposition reaction of the bicarbonate suppresses heat generation during foaming and curing. it can. Therefore, the heat generation temperature during foaming and curing can be reduced in a shorter time, and discoloration due to scorch can be suppressed.

  In addition, the bicarbonate is decomposed by heating in the process of producing the polyurethane foam to produce a carbonate, and the produced carbonate remains in the polyurethane foam. The specific gravity of the carbonate is 2 to 3, which is larger than the specific gravity of 0.93 of the conventional polyethylene powder, so the influence on the physical properties of the polyurethane foam such as density, hardness, tensile strength and elongation is small. The change in physical properties of the polyurethane foam can be suppressed.

  -Furthermore, by using sodium hydrogen carbonate or potassium hydrogen carbonate as the hydrogen carbonate, these sodium hydrogen carbonate or potassium hydrogen carbonate have a low decomposition start temperature and are decomposed along with the formation of polyurethane foam to exert their functions. can do.

  Moreover, by setting the blending amount of the bicarbonate to 10 to 100 parts by mass per 100 parts by mass of the polyols, the decomposition of the bicarbonate can be appropriately performed without being excessive or insufficient.

-The polyurethane foam having an open-cell structure obtained as described above suppresses excessive heat generation when foaming and curing, resulting in less oxidative degradation of the portion that has conventionally become a high-temperature part. The color difference between the high temperature part and the low temperature part during foaming and curing can be suppressed to 5 or less. Therefore, even when the product extends over both the high-temperature interior and the low-temperature surface portion, it is possible to prevent problems due to discoloration. In addition, the density specified in JIS K6400 can be as low as 15 to 20 kg / m ³ , and the physical properties such as hardness, tensile strength, and elongation can be used for furniture, bedding, automobile interior materials, etc. It can be adapted to the cushioning material to be formed.

  It is assumed that the carbon dioxide produced by the decomposition of the hydrogen carbonate suppresses the production of amine compounds and further urea compounds by the foaming reaction, and tends to lower the hardness of the foam. However, since the amount of hydrogen carbonate is large, the content of carbonate, which is a decomposition product of hydrogen carbonate, increases in the polyurethane foam, and the carbonate acts as a filler and the hardness of the foam is low. As a result, the hardness of the foam can be prevented from greatly changing.

Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples, but the invention is not limited to these examples.
(Examples 1-4 and Comparative Examples 1-3)
First, the polyethylene powder and bicarbonate used in each example and comparative example are shown below.

Polyethylene powder: Low density polyethylene powder having a specific gravity of 0.93 and an average particle size of 40 μm, manufactured by Mitsui Chemicals.
Sodium bicarbonate: Sodium bicarbonate having an average particle size of 40 μm.

Potassium bicarbonate: potassium bicarbonate having an average particle size of 20 μm.
The heat of evaporation of water is 2259 J / g, the latent heat of fusion of polyethylene powder is 198 J / g, and it can be seen that the endothermic effect of water is far superior to that of polyethylene powder.

  And the said polyethylene powder or hydrogencarbonate was mixed with the polyurethane foam raw material which consists of polyols, polyisocyanates, a foaming agent, a foam stabilizer, and a catalyst shown in Table 1 and Table 2, and the mixture was prepared. However, the bicarbonate was blended and dispersed in polyols. Here, in Comparative Example 1, an example in which no additive such as bicarbonate was added, and in Comparative Example 2 and Comparative Example 3, an example in which the blending amount of polyethylene powder was changed was shown.

A soft slab foam is prepared by injecting these mixtures into foam containers of 500 mm in length, width and depth, foaming them at room temperature and atmospheric pressure, and then allowing them to pass through a heating furnace to be heated (reacted). Got. The obtained soft slab foam was cut out to produce a sheet-like polyurethane foam. With respect to this polyurethane foam, the density, hardness, tensile strength, elongation, maximum exothermic temperature, time until the temperature decreased by 10 ° C. from the maximum exothermic temperature, and color difference were measured according to the following measurement methods. The results are shown in Tables 1 and 2. The meanings of the abbreviations in Table 1 and Table 2 are as follows.
(Measuring method)
Density (kg / m ³ ), hardness (N), tensile strength (kPa) and elongation (%): Performed according to JIS K6400.

Maximum exothermic temperature (° C.): A thermocouple was inserted in the center of the foaming container, and the highest temperature increased during foaming and curing.
Time until the maximum exothermic temperature falls by 10 ° C .: After measuring the maximum exothermic temperature (° C.), the time (minutes) until the maximum exothermic temperature (° C.) was lowered by 10 ° C. was measured.

Color difference: For the foamed part (center part) and the low-temperature part (side part) at the time of foaming and heating reaction, the color difference meter [SM color computer SM-4, manufactured by Suga Test Instruments Co., Ltd.] The degree of change (whiteness) was measured and indicated by their color difference (ΔYI).
(Abbreviations in Table 1 and Table 2)
Polyol GP3000: Polyether polyol, manufactured by Sanyo Chemical Industries, Ltd., hydroxyl value 56 (mgKOH / g)
Amine catalyst LV33: Amine catalyst manufactured by Chukyo Yushi Co., Ltd. Silicone foam stabilizer B8110: Gold schmitt stannic octylate MRH110: Johoku Chemical Co., Ltd. Polyisocyanate T-80: Nippon Polyurethane Industry Co., Ltd. Tolylene diisocyanate (mixture of 2,4-tolylene diisocyanate 80% by mass and 2,6-tolylene diisocyanate 20% by mass)

表１及び表２に示したように、実施例１〜４においては、発泡及び硬化時における最高発熱温度を１４４℃以下に抑えることができ、その最高温度より１０℃下がるまでの時間を９分以下に抑えることができるとともに、色差を３．０以下に抑制することができた。そして、得られた軟質ポリウレタン発泡体は、密度が１７．１〜１９．８（kg／m³）という低密度、硬さが１１７〜１３０（Ｎ）で比較的低く、引張強度が１１７〜１３３（ｋＰａ）及び伸びが１４０〜１８３％で十分な性能であった。一般に、マットレス等の家具類に用いられる軟質ポリウレタン発泡体では色差の目安が５以下とされ、そのような基準を十分に満たすことができた。

As shown in Table 1 and Table 2, in Examples 1 to 4, the maximum exothermic temperature at the time of foaming and curing can be suppressed to 144 ° C. or less, and the time until the temperature falls 10 ° C. from the maximum temperature is 9 minutes. While being able to suppress to below, the color difference was able to be suppressed to 3.0 or less. The obtained flexible polyurethane foam has a low density of 17.1 to 19.8 (kg / m ³ ), a hardness of 117 to 130 (N) and a relatively low tensile strength of 117 to 133. (KPa) and elongation of 140 to 183% were sufficient performance. In general, a soft polyurethane foam used for furniture such as mattresses has a color difference standard of 5 or less, and can sufficiently satisfy such a standard.

  Thus, the reason why the heat generation temperature can be suppressed low, the color difference can be sufficiently suppressed, and a low-foaming flexible polyurethane foam can be obtained is estimated as follows. That is, water generated by decomposition of hydrogen carbonate due to heat generation during foaming and curing evaporates, and the latent heat of vaporization is lost along with the evaporation, and at the same time, the heat generation temperature decreases, and the decomposition reaction of hydrogen carbonate is an endothermic reaction. Therefore, it is presumed that the endothermic effect is expressed and the exothermic temperature is lowered.

  In Example 3, since a large amount of potassium hydrogen carbonate was used, the potassium hydrogen carbonate functioned as a catalyst for the urethanization reaction, and foaming could be performed without adding LV33, which was an amine catalyst.

  On the other hand, as shown in Table 2, when an additive such as bicarbonate is not included (Comparative Example 1), the maximum exothermic temperature is as high as 187 ° C. and is 10 ° C. higher than the maximum exothermic temperature. It took a long time of 22 minutes to go down. For this reason, the color difference was as high as 12.1. When 30 parts by mass of polyethylene powder is added (Comparative Example 2), the time until the temperature is lowered by 10 ° C. from the maximum exothermic temperature is as long as 18 minutes, that is, because the time of exposure to high temperature is long, the color difference is 5. A high value of 1 was shown. As described above, the standard of the color difference is 5 or less, and the standard cannot be satisfied. Furthermore, when 100 parts by mass of polyethylene powder was blended (Comparative Example 3), the polyurethane foam raw material became a paste and foaming was impossible.

In addition, this embodiment can also be changed and embodied as follows.
-Multiple types of bicarbonates can be combined, and their blending amounts can be adjusted for use. For example, by using equal amounts of sodium hydrogen carbonate and potassium hydrogen carbonate, when the temperature exceeds 50 ° C. in the process of producing a polyurethane foam, sodium hydrogen carbonate decomposes to produce water, and when the temperature exceeds 100 ° C., hydrogen carbonate. Since potassium decomposes to produce water, the action of the bicarbonate can be fully exerted.

- as bicarbonate, potassium bicarbonate magnesium (KMgH (CO _{3) 2)} or the like can also be used.
As the hydrate of the inorganic compound, magnesium sulfate heptahydrate (MgSO ₄ · 7H ₂ O, specific gravity 1.68, decomposition temperature 70 to 116 ° C), calcium sulfate dihydrate (CaSO ₄ · 2H) ₂ O, dihydrate gypsum, specific gravity 2.32, decomposition temperature 130-148 ° C., iron sulfate monohydrate to pentahydrate (FeSO ₄ .H ₂ O to FeSO ₄ .5H ₂ O, specific gravity 2. 97, decomposition temperature 100 to 130 ° C.), sodium acetate trihydrate (CH ₃ COONa · 3H ₂ O, specific gravity 1.44, decomposition temperature 100 to 120 ° C.), and the like.

  A water-absorbing material that swells by absorbing water and absorbs heat by absorbing the absorbed water during heating, for example, a water-insoluble (mainly composed of (meth) acrylic acid units or (meth) acrylate units) A (meth) acrylic water-absorbing resin can also be blended in a state containing water.

A porous inorganic material that absorbs water, such as hemihydrate gypsum, zeolite, diatomaceous earth, activated carbon, etc., can also be blended in a state containing water.
Further, the technical idea that can be grasped from the embodiment will be described below.

The polyurethane having an open-cell structure according to any one of claims 1 to 4, which contains carbonate and has a density based on JIS K6400 of 15 to 20 (kg / m ³ ). Foam. When comprised in this way, in addition to the effect of the invention which concerns on any one of Claims 1-4, the change of physical properties, such as hardness, can be suppressed at low density.

  An open cell structure characterized by blending a hydrogen carbonate with a polyurethane foam raw material containing polyols, polyisocyanates, a foaming agent and a catalyst, and reacting and foaming and curing the polyurethane foam raw material. A method for producing a polyurethane foam. According to this manufacturing method, the heat generation temperature during foaming and curing can be reduced in a shorter time, and a polyurethane foam in which discoloration due to scorch is suppressed can be easily manufactured.

Claims (4)

Open cell characterized in that it is obtained by blending a hydrogen carbonate with a polyurethane foam raw material containing polyols, polyisocyanates, a foaming agent and a catalyst, and reacting the polyurethane foam raw material with foaming and curing. A polyurethane foam having a structure. 2. The open cell structure according to claim 1, wherein the bicarbonate is decomposed by heating in the process of producing a polyurethane foam to produce a carbonate, and the specific gravity of the carbonate is 2 to 3. Polyurethane foam having. The polyurethane foam having an open-cell structure according to claim 1 or 2, wherein the hydrogen carbonate is sodium hydrogen carbonate or potassium hydrogen carbonate. The polyurethane foam having an open-cell structure according to any one of claims 1 to 3, wherein the amount of the bicarbonate is 10 to 100 parts by mass per 100 parts by mass of polyols. .