JP4689428B2 - Seat cushion - Google Patents

Description

The present invention is, for example, good cushioning feeling in seat for a vehicle such as an automobile, but about the no bottoming feeling seat cushion down.

  In automobiles, vibration transmission prevention means such as suspension systems and engine mounts that absorb engine vibrations are provided to reduce transmission of vibrations due to vehicle running, engine vibrations, etc., and to ensure passenger comfort. ing. Furthermore, since a good feeling when seated is also necessary, a flexible polyurethane foam has been conventionally used for the seat cushion. This type of flexible polyurethane foam has high cushioning properties and excellent seating feeling.

By the way, there are various types of automobiles such as passenger cars and trucks, and passenger cars also include types of ordinary passenger cars, sports cars, wagon cars and the like. And according to those kinds, the device which reduces the discomfort given to a passenger | crew by transmission of the vibration based on vehicle travel, the vibration of an engine, etc. is given. For example, a seat made of polyurethane foam, comprising a cushion main body constituting a seating portion, and a sheet-like low air-permeable foam integrally provided on the bottom surface of the cushion main body, and having a resonance magnification of 4.0 or less A pad is known (see, for example, Patent Document 1). Also, a sheet comprising a polyurethane foam having a skin layer and a core layer, having a single layer structure, a resonance magnification at a frequency of 2 to 4 Hz of 4 or less, and a core layer having a rebound resilience of 45 to 75%. A cushion pad is known (see, for example, Patent Document 2).
Japanese Patent Laying-Open No. 2005-177171 (page 2, page 7 and page 8) Japanese Patent Laying-Open No. 2005-124867 (pages 2 and 12)

  However, in the conventional seat pads described in Patent Documents 1 and 2, since the resonance magnification of the seat pad is 4.0 or less, the cushion feeling of the seat pad is weak, and when the seat pad becomes thin, the bottom feeling is felt. There was a problem that it was easy to feel. The thickness of the seat pad is specifically 115 mm in Patent Document 1 (experimental examples on pages 7 and 8 of Patent Document 1) and 125 mm in Patent Document 2 (implemented on page 11 of Patent Document 2). Examples 1 to 8) were thick, and the seat pad was heavy and required a space for the seat pad.

  In addition, since the seat pad described in Patent Document 1 is composed of two members, a cushion main body and a low-breathing foam, it is necessary to produce two members and integrate those members. There was a problem that it was complicated.

The present invention has been made paying attention to the above-mentioned conventional problems, and its purpose is that the cushioning feeling is good, there is no bottoming feeling, and the weight reduction and space saving are achieved by thinning. It is to provide a seat cushion down as possible.

In order to achieve the above object, the seat cushion of the invention according to claim 1 is a polyurethane foam containing a polyol, a polyisocyanate, a foaming agent, a catalyst, a crosslinking agent, a foam stabilizer and a foam breaker. A seat cushion made of polyurethane foam obtained by reacting raw materials, foamed and cured, and having a thickness of 50 to 60 mm, wherein the polyols are composed of a polyether polyol and a polymer polyol, and the polyether polyol Is 45-60% by mass in the polyols, the content of the polymer polyol is 55-40% by mass in the polyols, and the foam stabilizer is a silicone-based foam stabilizer. The content is 0.35 to 0.45 parts by mass per 100 parts by mass of the polyols, and the content of the foam breaker Is 1.15 to 1.45 parts by weight per 100 parts by weight the polyol, the a hardness measured according to JIS K 6400 of the seat cushion 216～245N, the resonance frequency is 4.2 Hz As described above , the resonance frequency is 4.9 Hz or less, and the resonance magnification at a frequency of 2.0 to 4.0 Hz is 4.1 or more and 4.9 or less.

The seat cushion of the invention according to claim 2 is characterized in that, in the invention according to claim 1 , the apparent density measured in accordance with JIS K 7222 is 35 to 40 kg / m ³ .

Seat cushion down of the invention described in claim 3 is the invention according to claim 1 or claim 2, wherein the polyurethane foam has a communication structure which the cell is communicated, the molecular weight of the polyols 6500-8000 The isocyanate index of the polyisocyanates is 98 to 104.

According to the present invention, the following effects can be exhibited.
The seat cushion of the invention according to claim 1 is made of a polyurethane foam, has a thickness of 50 to 60 mm, a resonance frequency of more than 4.0 Hz and 5.0 Hz or less, and a frequency of 2.0 to 4. The resonance magnification at 0 Hz exceeds 4.0 and is 5.0 or less. Since the thickness of the seat cushion is 50 to 60 mm, the seat cushion is sufficiently thinned as compared with the conventional thickness of 100 mm or more, thereby reducing the weight and saving the space. Even with such a thin seat cushion, by setting the resonance frequency to more than 4.0 Hz and not more than 5.0 Hz, the resonance frequency (around 6 Hz) that people feel uncomfortable can be avoided and resonance can be achieved. When the magnification exceeds 4.0 and is set to 5.0 or less, resonance can be suppressed and vertical shaking can be suppressed. Therefore, the seat cushion has a good cushion feeling and can eliminate the bottom sensation.

Moreover, since the hardness measured based on JISK6400 is 216-245N, in addition to the said effect, sufficient hardness can be exhibited and transmission of a vibration can be suppressed.

In the seat cushion of the invention according to claim 2 , since the apparent density measured in accordance with JIS K 7222 is 35 to 40 kg / m ³ , in addition to the effect of the invention according to claim 1 , the conventional (apparent) The density is lower than 50 to 65 kg / m ³ ), and the weight can be further reduced.

In the following, embodiments that are considered to be the best of the present invention will be described in detail.
The seat cushion in the present embodiment is made of a polyurethane foam (hereinafter also simply referred to as a foam) and has a thickness of 50 to 60 mm. As the polyurethane foam, a soft polyurethane foam is preferable, and the flexible polyurethane foam generally refers to a cell (cell) having a communication structure, elasticity, and resilience. When the seat cushion is used as a vehicle seat or the like, it is preferable that the seat cushion has a thickness of at least 50 to 60 mm. Since the thickness of the seat cushion is 50 to 60 mm, the seat cushion is light in weight and requires only a small amount of space.

  The vibration characteristics of the seat cushion are that the resonance frequency (resonance frequency) exceeds 4.0 Hz and 5.0 Hz or less, and the resonance magnification at the frequency (frequency) 2.0 to 4.0 Hz exceeds 4.0 Hz. , 5.0 or less. The resonance frequency is a frequency at which the ratio of the amplitude of the output to the amplitude of the vibration input is the highest in accordance with JASO B 408 (a performance test method for the pad material of an automobile seat). By setting this resonance frequency within the above range, a resonance frequency (around 6 Hz) that people feel uncomfortable can be avoided. When the resonance frequency is 4.0 Hz or less, the elasticity of the foam is weak and the cushion feeling tends to be lowered, which is not appropriate. On the other hand, if it exceeds 5.0 Hz, it approaches the resonance frequency at which a person feels uncomfortable, which increases the discomfort and is inappropriate.

  The resonance magnification is a ratio of the amplitude of the vibration output to the amplitude of the vibration input at the resonance frequency in the frequency range of 2 to 4 Hz in accordance with JASO B 408 (performance test method for the pad material of an automobile seat). By setting this resonance magnification within the above range, elasticity can be exhibited, resonance can be suppressed, and vertical shaking can be suppressed. When the resonance magnification is 4.0 or less, the resilience of the seat cushion is lowered and the cushion feeling is deteriorated. On the other hand, when the resonance magnification exceeds 5.0, the cushion feeling of the seat cushion becomes too high, which increases discomfort and is inappropriate.

  The polyurethane foam is preferably a mold foam. Mold foam is made by injecting a polyurethane foam material containing polyols, polyisocyanates, foaming agent, catalyst, cross-linking agent, foam stabilizer and foam breaker into the mold, reacting, foaming and curing. Manufactured by a molding method.

Next, raw materials for the polyurethane foam will be described in order.
The polyols are composed of polyether polyol and polymer polyol. Polyether polyols include polypropylene glycol and polytetramethylene glycol in addition to compounds obtained by addition polymerization of alkylene oxide to polyhydric alcohols. As the polyhydric alcohol, glycerin, dipropylene glycol, trimethylolpropane and the like are used. As the alkylene oxide, ethylene oxide, propylene oxide or the like is used.

  Specific examples of the polyether polyol include a triol obtained by addition polymerization of glycerin with propylene oxide, a triol obtained by addition polymerization of ethylene oxide, and a diol obtained by addition polymerization of propylene oxide with dipropylene glycol. When addition polymerization of ethylene oxide is performed, the content is about 5 to 15 mol%. When the content of the polyethylene oxide unit is large, the hydrophilicity becomes high, the miscibility with highly polar molecules, polyisocyanates and the like is improved, and the reactivity becomes high.

  The polyether polyol may be a polyether ester polyol. The polyether ester polyol is a compound obtained by reacting a polyoxyalkylene polyol with a polycarboxylic acid anhydride and a compound having a cyclic ether group. Examples of polyoxyalkylene polyols include polyethylene glycol, polypropylene glycol, and propylene oxide adducts of glycerin. Examples of polycarboxylic acid anhydrides include anhydrides such as succinic acid, adipic acid, and phthalic acid. Examples of the compound having a cyclic ether group (alkylene oxide) include ethylene oxide and propylene oxide. The polyether polyol is preferable from the viewpoint that it has excellent reactivity with polyisocyanates and does not hydrolyze as compared with the polyester polyol.

  On the other hand, the polymer polyol is a polyol obtained by graft polymerization of a vinyl monomer to a polyether polyol. The polyether polyol for forming the polymer polyol is obtained by addition polymerization of an alkylene oxide to a polyhydric alcohol. As the polyhydric alcohol, glycerin, dipropylene glycol, trimethylolpropane and the like are used. As the alkylene oxide, ethylene oxide, propylene oxide or the like is used. As the vinyl monomer, acrylonitrile, styrene, methyl methacrylate or the like is used. The content of the vinyl monomer unit (graft portion) in the polymer polyol is preferably 10 to 40% by mass in the total amount with the polyether polyol. In the polymer polyol, the graft portion has a solid content by crystallization.

  The content of the polyether polyol is 45 to 60% by mass in the polyol, and the content of the polymer polyol is preferably 55 to 40% by mass in the polyol. When the content of the polyether polyol is less than 45% by mass or the content of the polymer polyol exceeds 55% by mass, the viscosity of the polyol becomes too high, and the progress of the resinification reaction and the foaming reaction is suppressed, which is good. It becomes difficult to obtain a foam. On the other hand, when the content of the polyether polyol exceeds 60% by mass or when the content of the polymer polyol is less than 40% by mass, the ratio of the polymer polyol to the polyether polyol is reduced and the balance is lost. It shows a tendency to decrease the feeling.

  In addition, polyester polyol can also be included as polyols. Polyester polyols include condensed polyester polyols obtained by reacting polycarboxylic acids such as adipic acid and phthalic acid with polyols such as ethylene glycol, propylene glycol and glycerin, as well as lactone polyester polyols and polycarbonate polyester polyols. Is used. The molecular weight of the polyols is preferably 6500 to 8000. When the molecular weight is less than 6500, sufficient hardness cannot be obtained in the foam, and when it exceeds 8000, the foam becomes too hard and the elasticity tends to decrease. The above polyols can change the functional group number and hydroxyl value of a hydroxyl group by adjusting the kind of raw material component, molecular weight, polymerization degree, condensation degree and the like.

  In addition, it is preferable that the polyurethane foam raw material further contains a crosslinking agent having a plurality of hydroxyl groups in one molecule in order to increase the crosslinking density of the foam and improve the physical properties such as hardness and tensile strength. . This crosslinking agent reacts with polyisocyanates to form a crosslinked structure in the foam. Specifically, ethylene glycol, butanediol, hexanediol, diethylene glycol, dipropylene glycol, 2,2-bis (4- Hydroxyphenyl) propane, glycerin, trimethylolpropane, triethanolamine, pentaerythritol and the like are used.

  Next, 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), and 1,5-naphthalene. Diisocyanate (NDI), triphenylmethane triisocyanate, xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate, isophorone diisocyanate (IPDI), modified products thereof and the like are used.

  The isocyanate index (isocyanate index) of the polyisocyanates may be 100 or less or more than 100, but is preferably 98 to 104. If the isocyanate index is less than 98, the content of polyisocyanates is small and it becomes difficult to obtain a foam having good mechanical properties such as hardness and tensile strength. On the other hand, if it exceeds 104, the exothermic temperature during foaming increases. , The flexibility of the foam is reduced. Here, the isocyanate index represents the equivalent ratio of the isocyanate group of the polyisocyanate to the active hydrogen group such as polyols, crosslinking agent, water as a foaming agent, foam breaker and the like as a percentage. Therefore, an isocyanate index of 100 or less means that polyols are in excess of polyisocyanates.

  The catalyst is mainly for accelerating the urethanization reaction between polyols and polyisocyanates. Specific examples of the catalyst include triethylenediamine, dimethylethanolamine, tertiary amines such as N, N ′, N′-trimethylaminoethylpiperazine, organometallic compounds such as tin octylate (tin octoate), acetates, Alkali metal alcoholates are used. A plurality of these catalysts can be used in combination. The catalyst content is preferably 0.1 to 2.0 parts by mass per 100 parts by mass of polyols. When the catalyst content is less than 0.1 parts by mass, the urethanation reaction or the like is not sufficiently promoted, and when it exceeds 2.0 parts by mass, the urethanation reaction or the like proceeds excessively and the reaction is not successful. It is not preferable because it becomes uniform and side reactions occur.

The foaming agent is for foaming a polyurethane resin to form a polyurethane foam. For example, pentane, cyclopentane, hexane, cyclohexane, dichloromethane (methylene chloride) and the like are used in addition to water. As the foaming agent, water that is highly reactive in the foaming reaction and easy to handle is preferable. When the foaming agent is water, the content is preferably 2 to 6 parts by mass per 100 parts by mass of polyols in order to make the apparent density of the foam 35 to 40 kg / m ³ . When the water content is less than 2 parts by mass, the amount of foaming is small, and the apparent density of the foam tends to exceed 40 kg / m ³ , and when it exceeds 6 parts by mass, the temperature tends to rise during reaction and foaming. It becomes difficult to reduce.

  The raw material of the polyurethane foam preferably contains a foam stabilizer to facilitate foaming. As the foam stabilizer, those generally used in the production of foams can be used. Specific examples of the foam stabilizer include silicone compounds, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium lauryl sulfate, polyether siloxane, and phenolic compounds. The content of the foam stabilizer is preferably 0.35 to 0.45 parts by mass per 100 parts by mass of polyols. When this content is less than 0.35 parts by mass, the foam regulating action during foaming of the foam raw material is not sufficiently exhibited, and it becomes difficult to obtain a good foam. On the other hand, when it exceeds 0.45 parts by mass, the foam regulating action becomes strong, and the cell connectivity tends to be lowered, and the cushion feeling of the foam is lowered.

  The foam breaker is a substance that inhibits foam formation during foaming, increases the cell diameter, or communicates the cells to promote the open cell structure of the foam. Specific examples of such foam breakers include silicone compounds, oils such as polybutene, polybutadiene polyols, acidic compounds having a fluoroalkyl group or salts thereof such as polyfluorocarboxylic acid, polyfluorosulfonic acid, Examples thereof include phosphoric acid monoesters of polyfluoroalcohol, phosphoric acid diesters of polyfluoroalcohol, and polyoxyalkylene polyols (highly hydrophilic).

  The content of the foam breaker is preferably 1.15 to 1.45 parts by mass per 100 parts by mass of polyols. When this content is less than 1.15 parts by mass, the foam breaking action at the time of foaming of the foam raw material is not sufficiently exhibited, the connectivity of the cell is lowered, and the cushion feeling of the foam is lowered. On the other hand, when the amount exceeds 1.45 parts by mass, the bubble breaking action becomes stronger, the cell diameter becomes larger, and the cell connectivity becomes higher and the mechanical properties such as tensile strength and elongation tend to decrease. Show. In addition to the raw material of the polyurethane foam, a filler, a colorant, a plasticizer, a flame retardant, a stabilizer, an antioxidant, an ultraviolet absorber, an antioxidant, and the like are blended as necessary.

  And the foam is manufactured by reacting the raw material of the said polyurethane foam, and making it foam and harden | cure, but the reaction in that case is complicated, Basically, the following reactions are mainly. That is, addition polymerization reaction of polyols and polyisocyanates (urethanization reaction, resinification reaction), foaming (foaming) reaction of polyisocyanates with water as a blowing agent, and reaction products of these and polyisocyanates And crosslinking (curing) reaction. When producing a 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 is employed.

The polyurethane foam thus obtained has good elasticity, and even when it is a thin sheet, it does not feel a bottom sensation when seated. That is, the foam preferably has an apparent density based on JIS K 7222: 1999, preferably 35 to 40 kg / m ³ , preferably a hardness based on JIS K 6400-2: 2004, and 216 to 245 N, and JIS K 6400-3: The rebound resilience based on 2004 is preferably 78% or more, more preferably 78-80%.

  Now, the operation of the present embodiment will be described. The seat cushion formed of the polyurethane foam is formed as thin as 50 to 60 mm in thickness. In the seat cushion, as a vibration characteristic, a resonance frequency and a resonance magnification at a frequency of 2.0 to 4.0 Hz are set in the above numerical range. For this reason, even with a thin seat cushion as described above, by setting the resonance frequency to more than 4.0 Hz and not more than 5.0 Hz, a resonance frequency of around 6 Hz that people feel uncomfortable can be avoided. . In addition, by setting the resonance magnification to be greater than 4.0 and less than or equal to 5.0, resonance can be suppressed and vertical shaking can be suppressed. Due to the synergistic action of the resonance frequency and the resonance magnification, the cushion feeling of the thin seat cushion can be improved and the bottom sensation can be eliminated.

The effects exhibited by the above embodiment will be described collectively below.
The seat cushion in the present embodiment is formed from a thin polyurethane foam, the resonance frequency is set to be over 4.0 Hz and 5.0 Hz or less, and the resonance magnification at a frequency of 2.0 to 4.0 Hz is 4.0. Is set to 5.0 or less. Since the thickness of the seat cushion is 50 to 60 mm, the seat cushion is sufficiently thinned as compared with the conventional thickness of 100 mm or more, thereby reducing the weight and saving the space. Even with such a thin seat cushion, an uncomfortable resonance frequency can be avoided by setting the resonance frequency to more than 4.0 Hz and not more than 5.0 Hz, and the resonance magnification is set to 4.0. By setting over and below 5.0, the vibration due to resonance can be regulated. Therefore, the seat cushion has a good cushion feeling and can eliminate the bottom sensation. In addition, the seat cushion has a good bending feeling (stroke feeling) and excellent durability (stress maintenance). Therefore, the seat cushion can be suitably used as a member for reducing vibration transmission such as a seat for a vehicle such as an automobile.

  Furthermore, when the hardness measured in accordance with JIS K 6400 is 216 to 245N, the seat cushion can exhibit sufficient hardness, and vibration transmission can be suppressed.

- In addition, by the apparent density is measured according to JIS K 7222 is 35~40kg / ^{m 3,} a conventional (apparent density 50~65kg / ^{m 3)} of the more a lower density than the lighter Can be achieved.

  In such a seat cushion manufacturing method, the polyol is composed of a polyether polyol and a polymer polyol, the content of the polyether polyol is 45 to 60% by mass in the polyol, and the content of the polymer polyol is It is set to 55 to 40% by mass in the polyols. In this case, almost the same amount of polymer polyol is added to the polyether polyol, the viscosity of the polyol is increased, the progress of the resinification reaction and foaming reaction is suppressed, and the physical properties such as elasticity of the foam are improved. To do. Therefore, the seat cushion obtained from such a foam has a good cushion feeling and can eliminate the bottom sensation. Moreover, a seat cushion can be easily manufactured only by setting the kind and compounding quantity of polyols, and manufacturing a foam according to a conventional method.

  In the production method, the foam stabilizer is a silicone-based foam stabilizer, and the content thereof is 0.35 to 0.45 parts by mass per 100 parts by mass of polyols, and the content of the foam breaker is polyols. The amount is 1.15 to 1.45 parts by mass per 100 parts by mass. Therefore, the tendency for the cells of the foam to communicate with each other increases, and the above effect can be improved.

Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.
(Examples 1-9 and Comparative Examples 1-6)
First, the raw material of the polyurethane foam used by each Example and the comparative example is shown below.

  Polyether polyol: A product obtained by addition polymerization of propylene oxide and ethylene oxide to glycerin, molecular weight 7000, number of functional groups 3 regarding hydroxyl group, manufactured by Mitsui Takeda Chemical Co., Ltd., PPG EP-901.

Polymer polyol: Modified polyol in which vinyl polymer fine particles are dispersed in polyether polyol, molecular weight 7000, manufactured by Mitsui Takeda Chemical Co., Ltd., POP-36 / 90.
Crosslinking agent 1: Diethanolamine Crosslinking agent 2: Glycerin Crosslinking agent 3: Trimethylolpropane polyol, hydroxyl value 920 (mg KOH / g), manufactured by Mitsui Takeda Chemical Co., Ltd., IR-94.

Catalyst 1: A mixture of triethylenediamine and propylene glycol in a mass ratio of 1: 2, Chukyo Yushi Co., Ltd., LV33.
Catalyst 2: A mixture of tertiary amine and glycol.

Foaming agent: water Foam stabilizer: silicone foam stabilizer.
Anti-foaming agent: polyoxyalkylene polyol, manufactured by Mitsui Takeda Chemical Co., Ltd., MF-19.

Polyisocyanate: A mixture of 80% by mass of tolylene diisocyanate and 20% by mass of 4,4-diphenylmethane diisocyanate (MDI).
And the raw material of a polyurethane foam was prepared with content of each component shown in Table 1 and Table 2. Content of each component in Table 1 and Table 2 represents a mass part. Here, in Comparative Example 1, the foam becomes too hard and the resonance magnification exceeds 5.0, and in Comparative Example 2, the foam becomes too soft and the resonance magnification is 4.0 or less and the resonance frequency is 5. An example of exceeding zero is shown. Comparative Example 3 shows an example in which the content of the foam stabilizer is too small and the resonance magnification exceeds 5.0. In Comparative Example 4, the content of the foam stabilizer is excessive and the resonance magnification is 4.0 or less. An example will be shown. Comparative Example 5 shows an example in which the content of the foam breaker is too large and the resonance magnification exceeds 5.0. In Comparative Example 6, the content of the foam breaker is too small and the resonance magnification is less than 4.0. An example is shown.

The polyurethane foam (soft mold foam) is obtained by injecting these polyurethane foam raw materials into a mold whose inner surface forms the outer shape of the seat cushion, reacting the raw materials according to a conventional method, and foaming and curing. It was. The thickness of the seat cushion was set to the thickness shown in Table 1 and Table 2. About the obtained seat cushion, apparent density, hardness, vibration characteristics (resonance frequency and resonance magnification), cushion feeling, and bottom sensation were measured according to the following measurement methods. The results are shown in Tables 1 and 2.
(Measuring method)
Apparent density (kg / m ³ ): Measured according to JIS K 7222: 1999.

Hardness (N): Measured according to JIS K 6400-2: 2004.
Rebound resilience (%): Measured according to JIS K 6400-3: 2004.
Vibration characteristics Resonant frequency (Hz): Based on JASO B 408 (performance test method of pad material for automobile seats), the resonance frequency was calculated as the frequency at which the ratio of the vibration output amplitude to the vibration input amplitude becomes the highest. .

  Resonance magnification: Based on JASO B 408 (performance test method for automobile seat pad material), the ratio of the amplitude of the output to the amplitude of the vibration input at the resonance frequency in the frequency range of 2 to 4 Hz was calculated as the resonance magnification.

Cushion feeling: The cushioning property when seated on a seat cushion was evaluated according to the following criteria.
A: Cushioning property is very good, B: Cushioning property is good, B: Cushioning property is strong, it jumps too much, or cushioning property is insufficient.

Bottom sensation: The sensation of hitting the bottom when seated on the seat cushion was evaluated according to the following criteria.
A: There is no feeling that hits the bottom, and it is very good, ○: There is no feeling that hits the bottom, and it is good, Δ: A feeling that hits the bottom, is uncomfortable.

表１に示したように、実施例１〜９においては、厚さが５３〜５４ｍｍであることから、従来の１００ｍｍ以上の厚さに比べて十分に薄肉化され、それにより軽量化とスペースの節約を図ることができた。そのような薄肉のシートクッションであっても、共振周波数が４．０Ｈｚを越え、５．０Ｈｚ以下であり、かつ周波数２．０〜４．０Ｈｚにおける共振倍率が４．０を越え、５．０以下であることから、クッション感及び底突き感がいずれも良好であった。

As shown in Table 1, in Examples 1 to 9, since the thickness is 53 to 54 mm, the thickness is sufficiently reduced as compared with the conventional thickness of 100 mm or more, thereby reducing weight and space. I was able to save money. Even in such a thin seat cushion, the resonance frequency exceeds 4.0 Hz and is 5.0 Hz or less, and the resonance magnification at a frequency of 2.0 to 4.0 Hz exceeds 4.0, and 5.0 Since it was the following, both the cushion feeling and the bottom sensation were good.

  On the other hand, as shown in Table 2, in Comparative Example 1, since the foam became too hard and the resonance magnification exceeded 5.0, the cushion feeling of the seat cushion was lowered. In Comparative Example 2, the foam became too soft, the resonance magnification was 4.0 or less, and the resonance frequency exceeded 5.0, so that the cushion feeling was lowered and the bottom sensation was generated. In Comparative Example 3, the cushioning feeling deteriorated because the content of the foam stabilizer was too small and the resonance magnification exceeded 5.0. In Comparative Example 4, since the content of the foam stabilizer was too large and the resonance magnification was 4.0 or less, the cushion feeling and the bottom sensation were deteriorated. In Comparative Example 5, since the content of the foam breaker was too large and the resonance magnification exceeded 5.0, the feeling of cushioning deteriorated. In Comparative Example 6, since the content of the foam breaker was too small and the resonance magnification was less than 4.0, both the cushion feeling and the bottom sensation were deteriorated.

In addition, the said embodiment can also be changed and implemented as follows.
・ Range of vibration transmissibility etc. can be specified as vibration characteristics.
-It is also possible to define ranges such as air permeability and hardness reduction rate as the characteristics of the polyurethane foam.

Further, the technical idea that can be grasped from the embodiment will be described below.
-The said seat cushion characterized by the impact resilience measured based on JISK6400 being 78% or more. When comprised in this way, in addition to the effect of the invention which concerns on Claim 1 , a cushion feeling can be improved about a thin seat cushion.

Claims (3)

A polyurethane foam obtained by reacting, foaming and curing a raw material of a polyurethane foam containing a polyol, a polyisocyanate, a foaming agent, a catalyst, a crosslinking agent, a foam stabilizer and a foam breaker, and having a thickness of A seat cushion of 50-60 mm,
The polyol is composed of a polyether polyol and a polymer polyol, the content of the polyether polyol is 45 to 60% by mass in the polyol, and the content of the polymer polyol is 55 to 55% in the polyol. 40% by weight,
The foam stabilizer is a silicone foam stabilizer, and the content thereof is 0.35 to 0.45 parts by mass per 100 parts by mass of the polyols, and the content of the foam breaker is 100 parts by mass of the polyols. 1.15 to 1.45 parts by mass per part,
The hardness is measured according to JIS K 6400 of the seat cushion is 216～245N, the resonance frequency is 4.2 Hz or more and 4.9 Hz or less, the resonance at the frequency 2.0~4.0Hz A seat cushion having a magnification of 4.1 or more and 4.9 or less. 2. The seat cushion according to claim 1 , wherein an apparent density measured in accordance with JIS K 7222 is 35 to 40 kg / m < ³ >. The polyurethane foam has a communication structure in which cells communicate with each other,
The molecular weight of the polyols is from 6500 to 8000, the seat cushion according to claim 1 or claim 2 isocyanate index of the polyisocyanate compound is characterized by a 98 to 104.