JP2008031241A - Method for producing flexible polyurethane foam - Google Patents

Abstract

Provided is a method capable of stably producing a flexible polyurethane foam having excellent low resilience, excellent durability, little hardness change with respect to temperature change, and air permeability without using a plasticizer.
A polyol (A) having an average number of hydroxyl groups of 2 to 3 and a hydroxyl value of 10 to 90 mgKOH / g, obtained by ring-opening addition polymerization of alkylene oxide to an initiator using a double metal cyanide complex catalyst, and A polyol mixture containing a polyol (B) having an average hydroxyl number of 2 to 3 and a hydroxyl value of 15 to 250 mgKOH / g and a polyisocyanate compound in the presence of a urethanization catalyst, a foaming agent and a foam stabilizer with an isocyanate index of 90 or more A process for producing a flexible polyurethane foam, comprising: a step of mixing 2) and a step of starting to blow an inert gas 2 to 15 minutes after mixing, and blowing an inert gas for 2 minutes or more.
[Selection figure] None

Description

  The present invention relates to a method for producing a low resilience flexible polyurethane foam.

  Conventionally, a soft polyurethane foam having a low impact resilience, that is, a low resilience, has been used as an impact absorber, a sound absorber, and a vibration absorber. Further, when used for a cushion material, a mattress or the like of a chair, it is known that the body pressure distribution becomes more uniform and the feeling of fatigue, bed slipping, and the like are reduced. As an example, a low resilience polyurethane foam described in Patent Document 1 is known.

  The low resilience polyurethane foam is a low resilience polyurethane foam obtained by reacting a polyurethane foam raw material composition containing a polyol, a polyisocyanate, a catalyst, and a foaming agent, and has a temperature of -70 ° C to -20 ° C. As a peak value of tan δ obtained when dynamic viscoelasticity measurement is performed at a frequency of 10 Hz, each having a glass transition point in a range and a temperature range of 0 ° C to 60 ° C. When expressed, the peak value of tan δ in the temperature range of −70 ° C. to −20 ° C. is 0.15 or more, and the peak value of tan δ in the temperature range of 0 ° C. to 60 ° C. has a value of 0.3 or more. It is described.

Since the low resilience polyurethane foam has a glass transition point in a temperature range of 0 ° C. to 60 ° C., the low resilience polyurethane foam has excellent low resilience at room temperature and a glass transition point in a temperature range of −70 ° C. to −20 ° C. Therefore, it is said that there is little increase in hardness at low temperatures.
However, a low resilience polyurethane foam having a glass transition point near room temperature has a so-called temperature-sensitive problem that the hardness changes and the low resilience is not stable as the operating temperature moves away from the glass transition point.

  In recent years, the level of durability required for flexible polyurethane foams has increased. Furthermore, development of a low-repulsive flexible polyurethane foam having a low rebound and a rebound resilience of 5% or less has been demanded.

  By the way, the resilience (rebound resilience) of the flexible polyurethane foam can usually be lowered by blending a plasticizer in the flexible polyurethane foam. Therefore, by adding an appropriate amount of plasticizer, a desired low resilience flexible polyurethane foam can be obtained to some extent. However, the added plasticizer may be eluted by washing the flexible polyurethane foam, and for example, it is difficult to maintain the low resilience of the flexible polyurethane foam after repeated washing.

  In addition, low resilience flexible polyurethane foam usually has low air permeability. That is, it is known that the breathability of the flexible polyurethane foam decreases as the resilience decreases. When the low resilience flexible polyurethane foam is applied particularly to bedding, if the air permeability is low, moisture (mainly released from the human body) is difficult to dissipate, so that it is in a state of being easily stuffy. There is a need for a soft polyurethane foam with low resilience for bedding that improves this sultry condition and does not accumulate heat and moisture. In consideration of the use state of the bedding, since the flexible polyurethane foam is used in a compressed state, the breathability test measured in an uncompressed state is required to exhibit a considerably high breathability. Furthermore, considering that compression is performed in a state that is easily stuffy, durability during humidification is required. As an index of durability during humidification, wet heat compression set can be mentioned.

The following methods have been proposed as a method for solving the above problems and improving the air permeability of the low-resilience flexible polyurethane foam.
(1) A method using a low molecular weight polyhydric alcohol as a raw material polyol (Patent Documents 2 and 3).
(2) A method using a polyether polyester polyol and a phosphorus-containing compound (Patent Document 4).
(3) A method of using monool together (Patent Document 5).
(4) A method using a polyol composition containing a specific monool (Patent Documents 6 and 7).

However, the low resilience flexible polyurethane foam obtained by the method (1) has a problem in durability, and the restoring performance tends to deteriorate gradually.
Since the phosphorus-containing compound used in the method (2) exhibits the same behavior as a plasticizer, it may be eluted from the flexible polyurethane foam, and it is expected that it is difficult to maintain performance after repeated washing.
The method (3) has a problem that it is inferior in durability during humidification.
In the method (4), the temperature sensitivity problem is still not solved.
JP-A-11-286666 JP 2004-2594 A JP 2004-43561 A JP-A-9-151234 JP 2004-3000352 A Special table 2003-522235 gazette JP-T-2004-530767

  Further, polyol (A) having an average number of hydroxyl groups of 2 to 3 and a hydroxyl value of 10 to 90 mgKOH / g and an average hydroxyl group obtained by ring-opening addition polymerization of alkylene oxide to an initiator using a double metal cyanide complex catalyst A polyol mixture containing a polyol (B) having a number of 2 to 3 and a hydroxyl value of 15 to 250 mgKOH / g and a polyisocyanate compound are used in the presence of a urethanization catalyst, a foaming agent and a foam stabilizer in an isocyanate index of 90 or more. In the case of producing a soft polyurethane foam having low resilience by mixing with a slab, if a relatively large slab foam (free form) having a distance from the center to the side of the foam of 200 mm or more is produced, a dent is generated on the surface portion. Problems arise. This is thought to be because the resin forming the foam cannot support the surface of the slab foam due to an increase in the internal temperature of the foam due to heat generation during the foaming process. If the distance from the center of the foam to the side is less than 200 mm, the dent on the surface is not a problem due to the side effect, but if a foam with a distance from the center of the foam to the side of 200 mm or more is produced, the phenomenon of the dent Appears prominently and adversely affects density uniformity, feel, breathability and product yield.

  The object of the present invention is a foam having excellent air permeability, low resilience without using a plasticizer, excellent durability, little hardness change with respect to temperature change (temperature sensitivity is suppressed), Even a flexible polyurethane foam having a large size (for example, the distance from the center to the side of the foam is 200 mm or more) has a good appearance with no dents on the surface of the flexible polyurethane foam. As a result, the density is uniform and the touch is good. It is an object of the present invention to provide a method for stably producing a flexible polyurethane foam having high air permeability.

The method for producing a flexible polyurethane foam according to the present invention comprises a polyol mixture containing the following polyol (A) and the following polyol (B) and a polyisocyanate compound having an isocyanate index of 90 or more, a urethanization catalyst, a foaming agent, and a foam stabilizer. 2 to 15 minutes after mixing the polyol mixture and the polyisocyanate compound, the process of mixing in the presence of the agent is started, and an inert gas is blown into the reaction product of the polyol mixture and the polyisocyanate compound. And a step of blowing gas.
However, the polyol (A) is obtained by ring-opening addition polymerization of alkylene oxide to an initiator using a double metal cyanide complex catalyst, the average number of hydroxyl groups is 2 to 3, and the hydroxyl value is 10 to 90 mgKOH / g. It is a certain polyether polyol, and the polyol (B) is a polyether polyol having an average number of hydroxyl groups of 2 to 3, a hydroxyl value of 15 to 250 mgKOH / g, and excluding the polyol (A).

In the method for producing a flexible polyurethane foam of the present invention, the pressure of the inert gas (gauge pressure) is preferably 0.01 to 0.8 MPa.
In the method for producing a flexible polyurethane foam of the present invention, it is preferable to make a cut on the upper surface of the reaction product of the polyol mixture and the polyisocyanate compound, and to blow an inert gas from the side or bottom of the reaction product.

It is preferable that a polyol (A) is 5-50 mass% among the sum total (100 mass%) of a polyol (A) and a polyol (B).
The polyol (A) is preferably a polyoxypropylene polyol obtained by ring-opening addition polymerization of only propylene oxide as an initiator.

The polyol mixture preferably further contains 10% by mass or less of the following polyol (C) in the polyol mixture (100% by mass).
However, the polyol (C) is a polyol having an average number of hydroxyl groups of 2 to 6 and a hydroxyl value of 300 to 1830 mgKOH / g.

The polyol mixture preferably further contains the following monool (D).
However, monool (D) is a polyether monool having a hydroxyl value of 10 to 200 mgKOH / g.
The monool (D) is preferably 1 to 10 parts by mass with respect to 100 parts by mass in total of the polyol (A) and the polyol (B).
The monool (D) is preferably a polyoxypropylene monool obtained by ring-opening addition polymerization of only propylene oxide as an initiator.

  According to the method for producing a flexible polyurethane foam of the present invention, it has excellent low resilience without using a plasticizer, excellent durability, little hardness change with respect to temperature change (temperature sensitivity is suppressed), and high air permeability. Even a soft polyurethane foam having a relatively large size (for example, a distance from the center to the side of the foam of 200 mm or more) has a good appearance with no dents on the surface of the flexible polyurethane foam. Can be stably produced with a flexible polyurethane foam that is uniform, feels good, and has high air permeability.

The method for producing a flexible polyurethane foam according to the present invention comprises a polyol mixture containing polyol (A) and polyol (B) and a polyisocyanate compound, wherein the isocyanate index is 90 or more, the urethanization catalyst, the foaming agent and the foam stabilizer. 2 to 15 minutes after mixing the polyol mixture and the polyisocyanate compound after mixing in the presence (hereinafter, mixing step), and starting to blow an inert gas into the reaction product of the polyol mixture and the polyisocyanate compound, And a step of blowing an inert gas for 2 minutes or longer (hereinafter referred to as a blowing step).
In addition, in this invention, an inert gas means the gas which does not react substantially with the reaction material of a polyol mixture and a polyisocyanate compound. Examples of the inert gas include air, carbon dioxide, nitrogen, and the like.

<Mixing process>
(Polyol (A))
The polyol (A) is obtained by ring-opening addition polymerization of alkylene oxide using a double metal cyanide complex catalyst (DMC catalyst) as an initiator, and has an average hydroxyl number of 2 to 3, and a hydroxyl value of 10 to 90 mgKOH. Polyether polyol (polyoxyalkylene polyol) which is / g. That is, polyol (A) is a polyether polyol having a polyoxyalkylene chain obtained by ring-opening addition polymerization of alkylene oxide using a double metal cyanide complex catalyst. When a double metal cyanide complex catalyst is used, a by-product monol can be reduced and a polyol having a narrow molecular weight distribution can be produced. A polyol with a narrow molecular weight distribution has a low viscosity compared to a polyol with a broad molecular weight distribution in the same molecular weight region (polyol having the same hydroxyl value), so it is excellent in the mixing of reactive raw materials. Increases foam stability.

  As the double metal cyanide complex catalyst, for example, those described in JP-B-46-27250 can be used. Specific examples include a complex mainly composed of zinc hexacyanocobaltate, and an ether and / or alcohol complex thereof is preferable. Examples of ethers include ethylene glycol dimethyl ether (glyme), diethylene glycol dimethyl ether (diglyme), ethylene glycol mono-tert-butyl ether (METB), ethylene glycol mono-tert-pentyl ether (METP), diethylene glycol mono-tert-butyl ether (DETB), Tripropylene glycol monomethyl ether (TPME) and the like are preferable. As the alcohol, tert-butyl alcohol or the like is preferable.

  Examples of the alkylene oxide include ethylene oxide, propylene oxide, 1,2-epoxybutane, and 2,3-epoxybutane. Among these, propylene oxide or a combination of propylene oxide and ethylene oxide is preferable, and only propylene oxide is particularly preferable. That is, as the polyol (A), polyoxypropylene polyol obtained by ring-opening addition polymerization of only propylene oxide as an initiator is preferable. It is preferable to use only propylene oxide because durability during humidification is improved.

  As the initiator, a compound having 2 or 3 active hydrogen atoms in the molecule is used alone or in combination. Specific examples of the compound having 2 active hydrogens include ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, and dipropylene glycol. Specific examples of the compound having 3 active hydrogens include glycerin and trimethylolpropane. Further, it is preferable to use a high hydroxyl group polyether polyol obtained by ring-opening addition polymerization of alkylene oxide, preferably propylene oxide, to these compounds. Specifically, it is preferable to use a high hydroxyl value polyether polyol (preferably a polyoxypropylene polyol) having a molecular weight per hydroxyl group of about 200 to 500, that is, a hydroxyl value of 110 to 280 mgKOH / g.

  The average number of hydroxyl groups of the polyol (A) is 2 to 3. The average number of hydroxyl groups means the average value of the number of active hydrogens in the initiator. By setting the average number of hydroxyl groups to 2 to 3, it is possible to avoid a problem that the physical properties such as dry heat compression set of the obtained flexible polyurethane foam are remarkably lowered, and the hardness of the obtained flexible polyurethane foam is reduced. It is possible to avoid problems such as an increase in physical properties such as tensile strength. As the polyol (A), it is preferable to use a polyether diol having 2 hydroxyl groups in an amount of 50 to 100% by mass in the polyol (A) from the viewpoint of easily suppressing the temperature sensitivity.

  The hydroxyl value of the polyol (A) is 10 to 90 mgKOH / g. By setting the hydroxyl value to 10 mgKOH / g or more, it is possible to stably produce a flexible polyurethane foam while suppressing collaps etc. By setting the hydroxyl value to 90 mgKOH / g or less, the flexibility of the produced flexible polyurethane foam is not impaired and the rebound resilience can be kept low. The hydroxyl value of the polyol (A) is particularly preferably 15 to 60 mgKOH / g.

  The degree of unsaturation of the polyol (A) is preferably 0.05 meq / g or less, more preferably 0.01 meq / g or less, and particularly preferably 0.006 meq / g or less. By setting the degree of unsaturation to 0.05 meq / g or less, it is possible to avoid the disadvantage that the durability of the obtained flexible polyurethane foam deteriorates. The lower limit of the degree of unsaturation is ideally 0 meq / g. The degree of unsaturation is measured by a method based on JIS K 1557 (1970 edition).

  The polyol (A) may be a polymer-dispersed polyol. The polyol (A) being a polymer-dispersed polyol means a dispersion system in which polymer fine particles (dispersoid) are stably dispersed using the polyol (A) as a base polyol (dispersion medium).

  Examples of the polymer of the polymer fine particles include addition polymerization polymers and condensation polymerization polymers. The addition polymerization polymer can be obtained by homopolymerizing or copolymerizing monomers such as acrylonitrile, styrene, methacrylic acid ester, acrylic acid ester and the like. Examples of the polycondensation polymer include polyester, polyurea, polyurethane, and polymethylol melamine. The presence of polymer fine particles in the polyol is effective in improving mechanical properties such as the hydroxyl value of the polyol being kept low and the hardness of the flexible polyurethane foam being increased. Moreover, the content ratio of the polymer fine particles in the polymer-dispersed polyol is not particularly limited, but is preferably 0 to 5% by mass with respect to the entire polyol (A). The various properties (unsaturation, hydroxyl value, etc.) of the polymer-dispersed polyol as a polyol are considered for the base polyol excluding the polymer fine particles.

(Polyol (B))
The polyol (B) is a polyether polyol having an average number of hydroxyl groups of 2 to 3, a hydroxyl value of 15 to 250 mgKOH / g, and excluding the polyol (A). That is, it is a polyether polyol obtained by ring-opening addition polymerization of alkylene oxide using an alkylene oxide ring-opening addition polymerization catalyst as an initiator. Here, the polyether polyol produced using the double metal cyanide complex catalyst as the alkylene oxide ring-opening addition polymerization catalyst is not included in the polyol (B).

  As the alkylene oxide ring-opening addition polymerization catalyst, a phosphazene compound, a Lewis acid compound or an alkali metal compound catalyst is preferable, and among these, an alkali metal compound catalyst is particularly preferable. Examples of the alkali metal compound catalyst include potassium hydroxide (KOH) and cesium hydroxide (CsOH).

  Examples of the alkylene oxide include ethylene oxide, propylene oxide, 1,2-epoxybutane, and 2,3-epoxybutane. Among these, propylene oxide or a combination of propylene oxide and ethylene oxide is preferable, and only propylene oxide is particularly preferable. That is, as the polyol (B), a polyoxypropylene polyol obtained by ring-opening addition polymerization of only propylene oxide as an initiator is preferable. It is preferable to use only propylene oxide because durability during humidification is improved.

  As the initiator, a compound having 2 or 3 active hydrogen atoms in the molecule is used alone or in combination. Specific examples of the compound having 2 or 3 active hydrogens include polyhydric alcohols such as ethylene glycol, propylene glycol, 1,4-butanediol, diethylene glycol, dipropylene glycol, glycerin and trimethylolpropane; bisphenol A and the like And polyamines such as monoethanolamine, diethanolamine, triethanolamine, and piperazine. Of these, polyhydric alcohols are particularly preferred. Further, it is preferable to use a high hydroxyl group polyether polyol obtained by ring-opening addition polymerization of alkylene oxide, preferably propylene oxide, to these compounds.

  The average number of hydroxyl groups of the polyol (B) is 2 to 3. By setting the average number of hydroxyl groups to 2 to 3, it is possible to avoid a problem that the physical properties such as dry heat compression set of the obtained flexible polyurethane foam are remarkably lowered, and the hardness of the obtained flexible polyurethane foam is reduced. It is possible to avoid problems such as an increase in physical properties such as tensile strength.

  The hydroxyl value of the polyol (B) is 15 to 250 mgKOH / g. By setting the hydroxyl value to 15 mgKOH / g or more, it is possible to stably produce a flexible polyurethane foam while suppressing collapse and the like. Moreover, by making a hydroxyl value into 250 mgKOH / g or less, the softness | flexibility of the flexible polyurethane foam manufactured is not impaired, and a resilience elastic modulus is restrained low. The hydroxyl value of the polyol (B) is particularly preferably 30 to 200 mgKOH / g.

  The polyol (B) may be a polymer-dispersed polyol. Examples of the polymer of the polymer fine particles include those described in the section of the polyol (A). Moreover, the content ratio of the polymer fine particles in the polymer-dispersed polyol is not particularly limited, but is preferably 0 to 10% by mass with respect to the entire polyol (B).

(Polyol (C))
The polyol (C) is a polyol having an average number of hydroxyl groups of 2 to 6 and a hydroxyl value of 300 to 1830 mgKOH / g. Examples of the polyol used as the polyol (C) include polyhydric alcohols, amines having 2 to 6 hydroxyl groups, polyester polyols, polyether polyols, and polycarbonate polyols. When the polyol (C) is used, it acts as a cross-linking agent, and mechanical properties such as hardness are improved. In the present invention, the polyol (C) also has a bubble-breaking effect, and the addition of the polyol (C) is effective in improving air permeability. Particularly when a low density (light weight) flexible polyurethane foam is to be produced using a large amount of a foaming agent, the foaming stability is good.

Examples of the polyhydric alcohols include ethylene glycol, propylene glycol, 1,4-butanediol, dipropylene glycol, glycerin, diglycerin, pentaerythritol and the like.
Examples of amines having 2 to 6 hydroxyl groups include diethanolamine and triethanolamine.

Examples of the polyether polyol include polyether polyols obtained by ring-opening addition polymerization of an alkylene oxide as an initiator.
As an initiator, the initiator used for manufacture of the polyhydric alcohol which may be used as a polyol (C), or a polyol (B) can be illustrated.

  Examples of the alkylene oxide include ethylene oxide, propylene oxide, 1,2-epoxybutane, and 2,3-epoxybutane. Among these, propylene oxide or a combination of propylene oxide and ethylene oxide is preferable, and only propylene oxide is particularly preferable. That is, the polyol (C) that is a polyether polyol is preferably a polyoxypropylene polyol obtained by ring-opening addition polymerization of only propylene oxide as an initiator. As the polyol (C), among the above, polyether polyol is preferable, and polyoxypropylene polyol polyol is particularly preferable. It is preferable to use only propylene oxide because durability during humidification is improved. As a polyol (C), only 1 type may be used or 2 or more types may be used together.

  The average number of hydroxyl groups of the polyol (C) is 2-6, preferably 3-4. Moreover, the hydroxyl value of a polyol (C) is 300-1830 mgKOH / g, and 300-600 mgKOH / g is preferable.

(Monoall (D))
Monool (D) is a polyether monool having a hydroxyl value of 10 to 200 mgKOH / g. That is, it is a polyether monool obtained by ring-opening addition polymerization of alkylene oxide using an alkylene oxide ring-opening addition polymerization catalyst to an initiator having 1 active hydrogen.

  As the alkylene oxide ring-opening addition polymerization catalyst, a composite metal cyanide complex catalyst, a phosphazene compound, a Lewis acid compound or an alkali metal compound catalyst is preferable, and among these, a composite metal cyanide complex catalyst is particularly preferable. That is, the monool (D) is preferably a polyether monool having a polyoxyalkylene chain obtained by ring-opening addition polymerization of alkylene oxide using a double metal cyanide complex catalyst.

  Examples of the alkylene oxide include ethylene oxide, propylene oxide, 1,2-epoxybutane, and 2,3-epoxybutane. Among these, propylene oxide or a combination of propylene oxide and ethylene oxide is preferable, and only propylene oxide is particularly preferable. That is, the monool (D) is preferably a polyoxypropylene monool obtained by subjecting only propylene oxide to ring-opening addition polymerization to an initiator. It is preferable to use only propylene oxide because durability during humidification is improved.

  As the initiator, a compound having only one active hydrogen atom is used. Specific examples thereof include monools such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol and tert-butyl alcohol; monohydric phenols such as phenol and nonylphenol; 2 such as dimethylamine and diethylamine. Examples thereof include polyether monools obtained by ring-opening addition polymerization of alkylene oxides to primary amines and the like and these initiators.

  The average number of hydroxyl groups of monool (D) is 1. Moreover, the hydroxyl value of monool (D) is 10-200 mgKOH / g, and 10-120 mgKOH / g is preferable.

(Polyol mixture)
The polyol mixture is a mixture containing polyol (A) and polyol (B), and preferably further contains polyol (C) and / or monool (D).

  The ratio of the polyol (A) and the polyol (B) is the ratio of the polyol (A) in the total (100% by mass) of the polyol (A) and the polyol (B), and is preferably 5 to 50% by mass. 10-30 mass% is more preferable. By setting the ratio of the polyol (A) in the polyol mixture within the above range, a flexible polyurethane foam having low rebound and small change in resilience modulus and hardness with respect to temperature change (low temperature sensitivity) can be obtained.

  The total ratio of the polyol (A) and the polyol (B) in the polyol mixture (100% by mass) is preferably 75% by mass or more, more preferably 85% by mass or more, and particularly preferably 90% by mass or more. By setting the total ratio of the polyol (A) and the polyol (B) in the polyol mixture within the above range, a flexible polyurethane foam excellent in low resilience and durability and excellent in air permeability can be obtained.

  The proportion of monool (D) is preferably 1 to 10 parts by mass and more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the total of polyol (A) and polyol (B). By setting the proportion of monool (D) within the above range, a flexible polyurethane foam excellent in low resilience and durability and having good air permeability can be obtained.

  The proportion of the polyol (C) is preferably 10% by mass or less, more preferably 0 to 5% by mass, and particularly preferably 0.5 to 2 parts by mass in the polyol mixture (100% by mass). By setting the ratio of the polyol (C) within the above range, the air permeability can be improved while lowering the low resilience of the flexible polyurethane foam.

  The polyol mixture may contain other polyol (E) that is not classified as any of polyol (A), polyol (B), polyol (C), and monool (D). The proportion of the other polyol (E) is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 0% by mass in the polyol mixture (100% by mass). The ratio of the other polyol (E) is 0% by mass. The polyol mixture contains the polyol (A) and the polyol (B), and if necessary, the polyol (C) and / or the monool (D). Contains but does not contain other polyols (E).

  Specific examples of suitable compositions of the polyol mixture (100% by mass) include polyol (A) 10-30% by mass, polyol (B) 60-90% by mass, polyol (C) 0-5% by mass, monool ( D) 2-8 mass% is mentioned.

(Polyisocyanate compound)
Examples of the polyisocyanate compound include aromatic, alicyclic and aliphatic polyisocyanates having two or more isocyanate groups; mixtures of two or more of the above polyisocyanates; modified polyisocyanates obtained by modifying these, etc. Is mentioned.

  Polyisocyanates include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), polymethylene polyphenyl polyisocyanate (common name: crude MDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HMDI). Etc. Examples of the modified polyisocyanate include a prepolymer modified product, a nurate modified product, a urea modified product, and a carbodiimide modified product of the above polyisocyanate. Of these, TDI, MDI, crude MDI, or modified products thereof are preferred. Further, among these, use of TDI, crude MDI, or a modified product thereof (especially a prepolymer modified product) is preferable in terms of improving foaming stability and improving durability. In particular, it is preferable to use a polyisocyanate compound having a relatively low reactivity among TDI, crude MDI, or a modified product thereof because air permeability is improved. Specifically, a TDI mixture having a high ratio of 2,6-TDI (30% by mass or more is particularly preferable) is preferable.

  The amount of the polyisocyanate compound used is represented by an isocyanate index. The isocyanate index is 100 times the value obtained by dividing the equivalent of the isocyanate group of the polyisocyanate compound by the total equivalent of all active hydrogens such as polyol and water. In the manufacturing method of the flexible polyurethane foam of this invention, the ratio of a polyol mixture and a polyisocyanate compound shall be 90 or more by an isocyanate index. If the isocyanate index is less than 90, the polyol is used excessively, the influence as a plasticizer becomes large, and the washing durability tends to deteriorate, which is not preferable. In addition, the urethanization catalyst is easily dissipated, and the produced flexible polyurethane foam is easily discolored. The isocyanate index is preferably 90 to 130, more preferably 95 to 110, and particularly preferably 100 to 110.

(Urethane catalyst)
As the urethanization catalyst, any catalyst that promotes the urethanation reaction can be used, for example, triethylenediamine, bis (2-dimethylaminoethyl) ether, N, N, N ′, N′-tetramethylhexamethylenediamine, etc. And carboxylic acid metal salts such as potassium acetate and potassium 2-ethylhexanoate; organometallic compounds such as stannous octoate and dibutyltin dilaurate.

(Foam stabilizer)
Examples of the foam stabilizer include silicone foam stabilizers and fluorine foam stabilizers. Of these, silicone-based foam stabilizers are preferred. Of the silicone foam stabilizers, silicone foam stabilizers based on polyoxyalkylene / dimethylpolysiloxane copolymers are preferred. The foam stabilizer may be a polyoxyalkylene / dimethylpolysiloxane copolymer alone or a mixture containing other combined components. Examples of other combined components include polyalkylmethylsiloxane, glycols, polyoxyalkylene compounds and the like. As the foam stabilizer, a foam stabilizer mixture containing a polyoxyalkylene / dimethylpolysiloxane copolymer, a polyalkylmethylsiloxane and a polyoxyalkylene compound is particularly preferred from the viewpoint of foam stability. Examples of the foam stabilizer mixture include trade name: SZ-1328 manufactured by Toray Dow Corning Silicone. Two or more types of foam stabilizers may be used in combination, or a foam stabilizer other than the specific foam stabilizer may be used in combination.

  0.01-2 mass parts is preferable with respect to 100 mass parts of a polyol mixture, and, as for the usage-amount of a foam stabilizer, 0.1-0.5 mass part is more preferable.

(Foaming agent)
Examples of the foaming agent include known foaming agents such as water, inert gas, and fluorinated hydrocarbon. As the foaming agent, water or an inert gas is preferable. Examples of the inert gas include air, nitrogen, carbon dioxide gas and the like. Of these, water is preferred. That is, in the present invention, it is particularly preferable to use only water as a foaming agent.

  When water is used, the amount of the blowing agent is preferably 10 parts by mass or less, more preferably 0.1 to 4 parts by mass with respect to 100 parts by mass of the polyol mixture.

(Other auxiliaries)
In producing the flexible polyurethane foam of the present invention, desired additives can be used in addition to the urethanization catalyst, foaming agent and foam stabilizer described above. Additives include fillers such as potassium carbonate and barium sulfate; surfactants such as emulsifiers; anti-aging agents such as antioxidants and ultraviolet absorbers; flame retardants, plasticizers, colorants, anti-fungal agents, and foam breaking Agents, dispersants, discoloration inhibitors and the like.

(Mixing method)
As a method of mixing each component, a method of injecting each component into a closed mold and foaming the reactive mixture (molding method) is a method of mixing each line segment in an open system and foaming the reactive mixture. (Slab method) may be used, and the slab method is preferable. Specifically, it can be performed by a known method such as a one-shot method, a semi-prepolymer method, or a prepolymer method. For production of the flexible polyurethane foam, a commonly used production apparatus can be used.

<Blowing process>
When a polyol mixture and a polyisocyanate compound are mixed in the presence of a urethanization catalyst, a foaming agent and a foam stabilizer, the polyol mixture and the polyisocyanate compound react to obtain a reaction product of the polyol mixture and the polyisocyanate compound. . Since the reaction involves foaming, the reaction product becomes a polyurethane foam.

  The present invention is characterized in that an inert gas is blown into the reactant to lower the heat generation temperature inside the foam, and at the same time, the cell film in the reactant is broken by the pressure of the inert gas. That is, by blowing an inert gas into the reaction product, a flexible polyurethane foam having high air permeability can be obtained. In addition, by blowing inert gas, the temperature inside the reactant is suppressed, the depression (dent) at the top of the reactant caused by the softening inside the reactant is suppressed, and defects in appearance and density distribution caused by depression are suppressed. Uniformity is suppressed, and the desired flexible polyurethane foam can be stably obtained.

  The timing at which the inert gas starts to be blown into the reaction product is 2 to 15 minutes after mixing the polyol mixture and the polyisocyanate compound, and preferably 2 to 10 minutes. If the timing to start blowing the inert gas into the reactant is too early, the solidification of the reactant is insufficient, and the foam gas itself may be damaged by the pressure of the blown inert gas, causing cracks and depressions. . If the timing at which inert gas starts to be blown into the reactant is too late, the temperature inside the reactant will rise too much and the urethane resin strength will decrease, and there will not be enough strength to support the foam surface. ) Goes on. The internal temperature of the foam is desirably limited to 130 ° C.

  The inert gas blowing time into the reactant is preferably 2 minutes or more, and can be appropriately selected depending on the shape of the foam, the inert gas blowing pressure, and the number of blowing nozzles. By setting the inert gas blowing time to the reactants to 2 minutes or more, the excessive temperature rise inside the reactants is suppressed, and the urethane resin softens and cannot support the foam surface. (Dent) is prevented from progressing.

  The pressure of the inert gas is preferably 0.01 to 0.8 MPa, more preferably 0.05 to 0.5 MPa. By setting the pressure of the inert gas to 0.01 MPa or more, a sufficient inert gas can be supplied into the urethane foam, and an excessive increase in temperature inside the reaction product can be suppressed. By setting the pressure of the inert gas to 0.8 MPa or less, the foam breakage and the bubble breakage due to the pressure of the blown inert gas can be suppressed. The pressure of the inert gas is a gauge pressure (relative pressure when the atmospheric pressure is 0). The gauge pressure is the pressure in the piping that supplies the inert gas.

The inert gas is preferably blown into the reactant so that the inert gas reaches the entire inside of the reactant. For example, as shown in FIG. 1, a notch 12 is made on the upper surface of the reactant 10, and an inert gas supply nozzle 14 is inserted into the side surface of the reactant 10 to inject inert gas. The inert gas blown in reaches the entire inside of the reactant and is then exhausted from the notch 12.
The inert gas is preferably blown from two or more locations. The position where the inert gas supply nozzle 14 is inserted is preferably the side or bottom of the reactant in order to allow the inert gas to reach the entire inside of the reactant, and more preferably the side as close as possible to the bottom of the reactant 10.

  The notch 12 is preferably a ten-letter notch cut in the vertical and horizontal directions so as to cross the upper surface of the reactant 10. The depth of the notch 12 is preferably 1 to 2 cm. By setting the depth of the notch 12 to 1 cm or more, the inert gas blown from the side surface and passed through the inside of the reactant 10 is released from the upper surface without difficulty. By making the depth of the notch 12 2 cm or less, when the surface of the reaction product 10 is cut and commercialized, the removal ratio can be kept low, and the amount of urethane foam to be discarded is reduced, which is preferable.

<Soft polyurethane foam>
The core rebound elastic modulus of the flexible polyurethane foam obtained as described above is preferably 15% or less, more preferably 12% or less, and particularly preferably 10% or less. By setting the core rebound resilience to 15% or less, sufficient low resilience is exhibited. The lower limit is usually 0%. The core rebound modulus is measured by a method based on the JIS K6400A method (1997 version). The “core” is a portion obtained by removing the skin portion from the central portion of the flexible polyurethane foam.

  The air permeability of the flexible polyurethane foam is preferably 30 to 100 L / min, and more preferably 70 to 100 L / min. The air permeability within the above range means that a certain amount of air permeability is secured even in a compressed state. That is, it is difficult to be stuffy when applied to bedding. The air permeability is measured by a method based on the JIS K6400B method (1997 version).

  The durability of the flexible polyurethane foam is expressed by dry heat compression set and wet heat compression set. The wet heat compression set is an index of durability in a steamed state. Both dry heat compression set and wet heat compression set are measured by a method based on JIS K6400 (1997 edition). The dry heat compression set of the flexible polyurethane foam is preferably 5% or less, more preferably 4% or less, and particularly preferably 3.5% or less. The wet heat compression set of the flexible polyurethane foam is preferably 5% or less, more preferably 4% or less, and particularly preferably 3.5% or less.

The density of a flexible polyurethane foam (core density) is preferably from ^{40~110kg / m 3, 40~80kg / m} 3 and more preferably. The production method of the present invention is characterized in that it can be stably foamed and produced even at a low density and is excellent in durability. The density is measured by a method based on JIS K6400 (1997 edition).

  In the present invention, when the polyol (A) has a hydroxyl number of 2 and a hydroxyl value of 10 to 90 mgKOH / g, a polyol that is completely straight without branching and has an extremely long molecular chain is used. The low repulsion property derived from the polyol (A) that is linear and has an extremely long molecular chain is exhibited, and has a sufficiently low repulsion property, specifically, a core rebound elastic modulus of 15% or less. A flexible polyurethane foam having Further, when the polyol (A) has a hydroxyl number of 3 and a hydroxyl value of 10 to 90 mgKOH / g, low repulsion can be achieved by selectively combining a polyol having a hydroxyl number of 2 in the polyol (B). Demonstrated.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by the following example. “Parts” in Examples and Comparative Examples represents “parts by mass”.

(material)
Polyol A1: Using a potassium hydroxide catalyst, propylene oxide was subjected to ring-opening addition polymerization to a molecular weight of 700 using dipropylene glycol as an initiator, and then purified with magnesium silicate. Thereafter, the average number of hydroxyl groups obtained by ring-opening addition polymerization of propylene oxide using a zinc hexacyanocobaltate-tert-butyl alcohol complex catalyst using the compound as an initiator was 2, the hydroxyl value was 20 mgKOH / g, and the degree of unsaturation. Of 0.005 meq / g.

Polyol B1: Polyoxypropylene polyol having an average number of hydroxyl groups of 2 and a hydroxyl value of 160 mgKOH / g obtained by ring-opening addition polymerization of propylene oxide using dipropylene glycol as an initiator using a potassium hydroxide catalyst.
Polyol B2: Polyoxypropylene polyol having an average number of hydroxyl groups of 3 and a hydroxyl value of 168 mgKOH / g, obtained by ring-opening addition polymerization of propylene oxide using glycerol as an initiator using a potassium hydroxide catalyst.

  Monool D1: The average number of hydroxyl groups obtained by ring-opening addition polymerization of propylene oxide using a zinc hexacyanocobaltate-tert-butyl alcohol complex catalyst with n-butyl alcohol as an initiator and a hydroxyl value of 16. 7 mg KOH / g polyoxypropylene monool.

Foaming agent: water.
Catalyst A: Amine catalyst (manufactured by Air Products and Chemicals, trade name: Niax A-230).
Catalyst B: Tin 2-ethylhexanoate (manufactured by Air Products and Chemicals, trade name: DABCO T-9).
Foam stabilizer A: Silicone foam stabilizer (manufactured by Toray Dow Corning Silicone, trade name: SZ-1328).

  Polyisocyanate compound a: TDI-80 (mixture of 2,4-TDI / 2,6-TDI = 80/20% by mass), isocyanate group content 48.3% by mass (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate) T-80).

[Example 1]
Among the raw materials and compounding agents shown in Table 1, the liquid temperature of the mixture of all raw materials other than the polyisocyanate compound (polyol system) is adjusted to 23 ° C. ± 1 ° C., and the polyisocyanate compound is adjusted to the liquid temperature 22 ± 1 ° C. did. Add a predetermined amount of polyisocyanate compound to the polyol system, mix for 5 seconds with a mixer (3000 revolutions per minute), and place a vinyl sheet inside at 600 mm in length, 600 mm in width and 600 mm in height with the top open at room temperature. It was poured into a wooden box.

  Five minutes after mixing the polyol system and the polyisocyanate compound, the reaction product (polyurethane foam) was taken out of the wooden box to obtain a flexible polyurethane foam having a length of 600 mm, a width of 600 mm, and a height of 380 mm. The obtained flexible polyurethane foam was allowed to stand for 24 hours or more in a room adjusted to room temperature (23 ° C.) and humidity 50%, and various physical properties were measured. The measurement results are shown in Table 1.

(Dent)
About the flexible polyurethane foam which was left to stand for 24 hours or more after production, the depth of the concave portion at the center of the upper surface was measured.
(density)
The density was measured by a method based on JIS K6400 (1997 edition). A central portion of the flexible polyurethane foam was cut out, and further, cut into a size of 100 mm in length and width and 50 mm in height, excluding the skin from the upper, middle and lower portions of the central portion, was used for the measurement.
(Breathable)
The air permeability was measured by removing the epidermis from the center of the foam by a method based on the method B of JIS K6400B method (1997 edition).

(25% hardness)
The 25% hardness (ILD) was measured by a method based on JIS K6400 (1997 edition). A central portion of the flexible polyurethane foam was cut out, and further cut into a size of 300 mm in length and width and 50 mm in height, excluding the skin from the upper, middle and lower portions of the central portion, was used for the measurement.
(Tensile strength, elongation, dry heat compression set, wet heat compression set)
Tensile strength, elongation, dry heat compression set, and wet heat compression set were measured by methods based on JIS K6400 (1997 edition).

(Core rebound resilience)
The core rebound resilience was measured by a method based on the JIS K6400A method (1997 version). What was cut out into a size of 100 mm in length and width and 50 mm in height excluding the skin part from the center part of the foam was used for the measurement.

[Example 2]
Among the raw materials and compounding agents shown in Table 1, the liquid temperature of the mixture of all raw materials other than the polyisocyanate compound (polyol system) is adjusted to 23 ° C. ± 1 ° C., and the polyisocyanate compound is adjusted to the liquid temperature 22 ± 1 ° C. did. Add a predetermined amount of polyisocyanate compound to the polyol system, mix for 5 seconds with a mixer (3000 revolutions per minute), and place a vinyl sheet inside at 600 mm in length, 600 mm in width and 600 mm in height with the top open at room temperature. It was poured into a wooden box.

  120 seconds after mixing the polyol system and the polyisocyanate compound, the reaction product (polyurethane foam) was taken out of the wooden box to obtain a flexible polyurethane foam having a length of 600 mm, a width of 600 mm, and a height of 380 mm. A cross-shaped notch having a depth of 1 cm as shown in FIG. 1 was made on the upper surface of the flexible polyurethane foam, and air supply nozzles were inserted on both sides. Three minutes after mixing the polyol system and the polyisocyanate compound, 0.05 MPa (gauge pressure) of air was started to be blown into the reaction product. Thereafter, air was continuously blown for 2 minutes and 30 seconds to obtain a flexible polyurethane foam. The obtained flexible polyurethane foam was allowed to stand in a room adjusted to room temperature (23 ° C.) and humidity of 50% for 24 hours or more, and various physical properties were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[Example 3]
A flexible polyurethane foam was obtained in the same manner as in Example 2 except that the air blowing time was changed to 5 minutes. Various physical properties were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[Example 4]
A flexible polyurethane foam was obtained in the same manner as in Example 2 except that the gas to be blown was changed to nitrogen gas. Various physical properties were measured in the same manner as in Example 1. The measurement results are shown in Table 1.

[Examples 5 to 7]
Example 2 except that the start of air blowing was changed to 5 minutes after mixing the polyol system and the polyisocyanate compound [Example 5], 10 minutes after [Example 6], and 15 minutes after [Example 7]. Similarly, a flexible polyurethane foam was obtained. Various physical properties were measured in the same manner as in Example 1. The measurement results are shown in Table 1.
In addition, Example 1 is a comparative example and Examples 2-7 are Examples.

  As shown in Table 1, the flexible polyurethane foams of Examples 2 to 7 in which an inert gas was blown under specific conditions had high air permeability, and the upper surface had a small dent and density distribution. On the other hand, in Example 1, since the inert gas was not blown, the air permeability was low, and the dents on the upper surface and the density distribution were large.

  The flexible polyurethane foam obtained by the production method of the present invention is suitable as an impact absorber, a sound absorber, and a vibration absorber, and is also suitable as a bedding, mat, cushion, and seat. It is particularly suitable for bedding (mattress, pillow, etc.).

It is a perspective view which shows the mode of the blowing of the inert gas to a reaction material.

Explanation of symbols

10 reactant 12 notch

Claims (9)

Mixing a polyol mixture containing the following polyol (A) and the following polyol (B) and a polyisocyanate compound in the presence of a urethanization catalyst, a foaming agent and a foam stabilizer at an isocyanate index of 90 or more;
2-15 minutes after mixing the polyol mixture and the polyisocyanate compound, a flexible polyurethane foam having a process of starting to blow an inert gas into a reaction product of the polyol mixture and the polyisocyanate compound and blowing the inert gas for 2 minutes or more Manufacturing method.
However, the polyol (A) is obtained by ring-opening addition polymerization of alkylene oxide to an initiator using a double metal cyanide complex catalyst, the average number of hydroxyl groups is 2 to 3, and the hydroxyl value is 10 to 90 mgKOH / g. A polyether polyol,
The polyol (B) is a polyether polyol having an average number of hydroxyl groups of 2 to 3, a hydroxyl value of 15 to 250 mgKOH / g, and excluding the polyol (A).   The method for producing a flexible polyurethane foam according to claim 1, wherein the pressure (gauge pressure) of the inert gas is 0.01 to 0.8 MPa.   The method for producing a flexible polyurethane foam according to claim 1 or 2, wherein a cut is made in the upper surface of the reaction product of the polyol mixture and the polyisocyanate compound, and an inert gas is blown from the side surface or the bottom of the reaction product.   The method for producing a flexible polyurethane foam according to any one of claims 1 to 3, wherein the polyol (A) is 5 to 50 mass% of the total (100 mass%) of the polyol (A) and the polyol (B). .   The method for producing a flexible polyurethane foam according to any one of claims 1 to 4, wherein the polyol (A) is a polyoxypropylene polyol obtained by ring-opening addition polymerization of only propylene oxide in an initiator. The method for producing a flexible polyurethane foam according to any one of claims 1 to 5, wherein the polyol mixture further contains 10% by mass or less of the following polyol (C) in the polyol mixture (100% by mass).
However, the polyol (C) is a polyol having an average number of hydroxyl groups of 2 to 6 and a hydroxyl value of 300 to 1830 mgKOH / g. The method for producing a flexible polyurethane foam according to any one of claims 1 to 6, wherein the polyol mixture further contains the following monool (D).
However, monool (D) is a polyether monool having a hydroxyl value of 10 to 200 mgKOH / g.   The method for producing a flexible polyurethane foam according to claim 7, wherein the monool (D) is 1 to 10 parts by mass with respect to 100 parts by mass in total of the polyol (A) and the polyol (B). The method for producing a flexible polyurethane foam according to claim 7 or 8, wherein the monool (D) is a polyoxypropylene monool obtained by ring-opening addition polymerization of only propylene oxide as an initiator.

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