JP4745671B2 - Method for producing polyurethane foam having open cell structure - Google Patents

Description

The present invention is, for example, a method for producing a polyurethane foam having an open cell structure used as materials for forming the cushion for automotive seating.

  In general, cushioning materials for seats (seats and backrests) for automobiles, cushioning materials for chairs, and the like are required to have various hardnesses according to each application. For example, it may be required to soften the seat portion and harden the backrest portion with a cushion material for an automobile seat. In such a case, a cushion material capable of changing only the hardness without changing physical properties other than the hardness as much as possible is required. Conventionally, methods for lowering the hardness of a flexible polyurethane foam include methods for lowering the amount of polyisocyanate relative to the polyol in the raw material, ie, the isocyanate index, and nonreactive auxiliary foaming agents such as methylene chloride (methylene chloride) and carbon dioxide There are known methods for increasing the usage ratio (see, for example, Patent Documents 1 and 2).

  However, in the former method, the hardness of the flexible polyurethane foam is lowered, but the crosslink density of the whole foam is lowered, so that physical properties such as tensile strength, elongation, and residual compressive strain of the foam are lowered. On the other hand, in the latter method, since a non-reactive auxiliary foaming agent such as methylene chloride has the property of dissolving the foam, cracks occur in the process of producing the foam, or the tensile strength of the obtained foam is low. There was a tendency to decrease. In addition, when carbon dioxide gas is used, the gas pressure suddenly rises and it is difficult to control the gas pressure, so that there is a problem that the cell size becomes uneven or cracks occur.

An inorganic-organic composite slab foam obtained by using a phosphoric acid aqueous solution, a metal carbonate, and a urethane prepolymer having an isocyanate group is also known (see, for example, Patent Document 3). In this technique, a metal carbonate reacts with phosphoric acid to form an inorganic skeleton in the foam, and at the same time, carbon dioxide is generated to cause foaming.
Japanese Laid-Open Patent Publication No. 6-221958 (pages 2 and 3) JP 2003-238642 A (pages 2 and 3) JP-A-11-279316 (pages 2 and 8)

  In the technique described in Patent Document 3, a mixed solution of phosphoric acid and a carbonate metal salt are reacted to generate carbon dioxide, and foamed with the carbon dioxide to obtain a low-density foam. . Furthermore, flame retardance can be exhibited by an inorganic skeleton formed by the reaction of a metal carbonate with phosphoric acid. However, since the generated carbon dioxide is an amount sufficient to form a foam structure, it has a great influence on the physical properties of the obtained foam. Therefore, such a technique has a problem that the hardness of the foam cannot be adjusted in a state where changes in physical properties other than the hardness are suppressed.

The present invention has been made in view of the above-described problems of the prior art, and its object is to have an open cell structure capable of adjusting hardness while suppressing changes in physical properties other than hardness. It is providing the manufacturing method of the polyurethane foam which has this.

In order to achieve the above object, the method for producing a polyurethane foam having an open-cell structure according to claim 1 is based on a polyurethane foam raw material containing polyols, polyisocyanates, a foaming agent and a catalyst. An aqueous solution in which a hydrogen carbonate salt is dissolved in water is blended, and the polyurethane foam raw material is reacted to be foamed and cured.

The method for producing a polyurethane foam having an open cell structure according to claim 2 is the invention according to claim 1 , wherein the hydrogen carbonate is sodium hydrogen carbonate or potassium hydrogen carbonate, and the hydrogen carbonate is decomposed. starting temperature is 50 to 100 ° C., the amount of pre-Symbol bicarbonate is characterized in that 0.005 to 0.5 parts by weight polyol per 100 parts.

According to the present invention, the following effects can be exhibited.
According to the method for producing a polyurethane foam having an open cell structure according to the first and second aspects of the invention, it is easy to obtain a polyurethane foam capable of adjusting the hardness while suppressing a change in physical properties other than the hardness. Can be manufactured.

Embodiments of the present invention are described in detail below.
The polyurethane foam having an open-cell structure according to the present embodiment (hereinafter also simply referred to as a foam) is obtained by using a hydrogen carbonate salt in water relative to a polyurethane foam raw material containing polyols, polyisocyanates, a foaming agent and a catalyst. It is obtained by blending a dissolved aqueous solution and reacting and foaming and curing the polyurethane foam raw material. 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.

  First, the polyurethane foam raw material will be described. As the polyols, polyether polyols or polyester polyols are used. Examples of polyether polyols include polypropylene glycol, polytetramethylene glycol, modified products thereof, and compounds obtained by adding alkylene oxide to glycerin. As polyester polyols, in addition to 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, lactone polyester polyols and polycarbonate systems A polyol is mentioned. These polyols can change the number of hydroxyl groups and the hydroxyl value by adjusting the kind of raw material components, the molecular weight, the degree of condensation, and the like.

  The hydroxyl value of the polyols is preferably less than 250 (mgKOH / g), more preferably 50 to 60 (mgKOH / g). By using a polyether polyol having such a hydroxyl value, it is possible to obtain a soft polyurethane foam that is excellent in reactivity with polyisocyanates and is appropriately crosslinked. When the hydroxyl value of the polyols is 250 (mgKOH / g) or more, the crosslinking density becomes too high, the foam becomes hard, and the touch is lowered. On the other hand, when the hydroxyl value is less than 50 (mgKOH / g), the hydroxyl value becomes too small, and the crosslinking density of the polyurethane foam tends to be low, and the foam tends to buckle.

  A crosslinking agent can be mix | blended with a polyurethane foam raw material. Such a crosslinking agent reacts with polyisocyanates and the like to form a crosslinked structure in the foam, and is, for example, a polyol having a hydroxyl value of 250 to 650 (mgKOH / g) and a molecular weight of 150 to 500. As such a polyol, polyethylene glycol, diethylene glycol, polypropylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol and the like are used. By using polyether diol, a structure in which the chain of the polymer forming the foam extends linearly is formed, and the flexibility of the foam can be improved.

  Subsequently, the polyisocyanate to be reacted with the polyol is a compound 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 the like are used.

  Here, it is preferable that the isocyanate index of a polyisocyanate compound is 100-120. That is, the isocyanate index represents the equivalent ratio of the isocyanate group of the polyisocyanate compound to the hydroxyl group of the polyol, the hydroxyl group of the polyol as the crosslinking agent, and the blowing agent (water), but the value exceeds 100. This means that the isocyanate group is in excess of the hydroxyl group. When the isocyanate index is less than 100, the reaction of the polyisocyanate with the polyol is insufficient, and the foam tends to be too soft. On the other hand, when the isocyanate index exceeds 120, the foam tends to be too hard and a soft feel cannot be obtained.

  Next, the catalyst is for accelerating the urethanization reaction between polyols and polyols as crosslinking agents and polyisocyanates. As such a catalyst, N, N ′, N′-trimethylaminoethylpiperazine, tertiary amines such as triethylenediamine and dimethylethanolamine, organometallic compounds such as tin octylate, acetates, alkali metal alcoholates and the like are used.

  The foaming agent is for foaming polyurethane into a polyurethane foam. As the foaming agent, water or an acid amide is used. The blending amount of the foaming agent is preferably 3 to 7 parts by mass per 100 parts by mass of polyols. When the blending amount of the foaming agent is less than 3 parts by mass, the foaming reaction becomes insufficient, and when it exceeds 7 parts by mass, the foaming reaction and the crosslinking reaction become excessive, and the foam tends to become hard. In addition to this foaming agent, auxiliary foaming agents such as carbon dioxide, methylene chloride, and fluorocarbon compounds (such as trichlorofluoromethane and dichlorodifluoromethane) can be used as necessary. By using carbon dioxide as the auxiliary foaming agent, the same effect as the hydrogen carbonate can be obtained. As a raw material of the polyurethane foam, a foam stabilizer such as a surfactant, a flame retardant such as a condensed phosphate ester, an antioxidant, a plasticizer, an ultraviolet absorber, a colorant and the like can be added.

Next, the bicarbonate added to the polyurethane foam raw material is an aqueous solution dissolved in water. By adding such an aqueous solution, it is considered that the bicarbonate is dispersed at the molecular level in the polyurethane foam raw material, and the bicarbonate prevents the formation of urea bonds and the formation of polyurethane hard segments. It is possible to sufficiently exhibit the function of suppressing the above. This is considered to be due to, for example, carbon dioxide (CO ₂ ) generated by decomposition of sodium hydrogen carbonate (NaHCO ₃ ) based on the following reaction formula (1).

2NaHCO ₃ → Na ₂ CO ₃ + CO ₂ + H ₂ O (1)
The hydrogen carbonate is preferably an alkali metal hydrogen carbonate because the decomposition start temperature is low and it can be decomposed along with the formation of the polyurethane foam to exert its function. Specific examples of the alkali metal hydrogen carbonate include sodium hydrogen carbonate and potassium hydrogen carbonate. The solubility in water is 10.6 g / 100 g (25 ° C.) for sodium hydrogen carbonate and 36.2 g / 100 g (25 ° C.) for potassium hydrogen carbonate. This alkali metal hydrogen carbonate is used as an aqueous solution in a state dissolved in water within the solubility range. Since potassium hydrogen carbonate has a higher solubility than sodium hydrogen carbonate, the blending amount can be increased, and the hardness of the resulting polyurethane foam can be lowered and softened. If the hydrogen carbonate powder is used in a state where it is dispersed in, for example, a polyol, the effect of the hydrogen carbonate is not exhibited in a stable state.

  Further, the decomposition start temperature of the bicarbonate is preferably 50 to 100 ° C. from the viewpoint that the decomposition of the bicarbonate can be 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 the decomposition start temperature is less than 50 ° C., the start of decomposition is too early, and the balance of foaming is lost due to carbon dioxide, which is a decomposition product of bicarbonate, or water, which is a decomposition product, is used as a foaming agent. It is not preferable because it functions. 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 product cannot be sufficiently obtained.

  The blending amount of the bicarbonate is preferably 0.005 to 0.5 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. As a compounding quantity of the aqueous solution of hydrogen carbonate, 0.1-1.5 mass parts is preferable per 100 mass parts of polyols. When the blending amount of the bicarbonate is less than 0.005 parts by mass, the amount of carbon dioxide that is a decomposition product of the bicarbonate is small, and the function of the bicarbonate cannot be sufficiently achieved. On the other hand, when it exceeds 0.5 parts by mass, the amount of carbon dioxide produced is large, and physical properties of the foam change due to excessive foaming, or excessive water as a decomposition product functions as a foaming agent. Absent.

By using the above-mentioned bicarbonate, the hardness of the resulting polyurethane foam can be reduced. This function is considered to be expressed as follows.
The polyurethane formation reaction (urethane bond formation reaction, resinification reaction) by the reaction of polyols and polyisocyanates proceeds based on the following reaction formula (2).

ROH + —R—NCO → —R—NH—CO—O—R (2)
Moreover, the foaming reaction by reaction of polyisocyanate and water proceeds according to the following reaction formula (3).

_{-R-NCO + H 2 O →} -R-NH 2 + CO 2 ··· (3)
Furthermore, the reaction in which the amine compound (—R—NH ₂ ) produced in the reaction formula (3) reacts with polyisocyanates to form a urea (urea) bond proceeds according to the following reaction formula (4).

_{-R-NCO + -R-NH 2} → -R-NH-CO-NH-R ··· (4)
The carbon dioxide produced by the decomposition of the bicarbonate increases the concentration of carbon dioxide on the right side in the reaction formula (3), so that the progress of the reaction represented by the reaction formula (3) is suppressed, and the amine compound (—R— Formation of NH ₂ ) is suppressed. Therefore, in reaction formula (4), the component on the left side is reduced and the progress of the reaction is restricted. Urea bonds have stronger cohesion due to hydrogen bonds than urethane bonds, and the presence of them makes the foam harder, but it is speculated that the formation of urea bonds can be restricted to reduce the hardness of the foam Is done.

  When the urethanization reaction between the polyols and the polyisocyanates is performed, a one-shot method or a prepolymer method is employed. The one-shot method is a method in which polyols and polyisocyanates are directly reacted. The prepolymer method is a method in which a part of a polyol and a polyisocyanate are reacted in advance to obtain a prepolymer having an isocyanate group or a hydroxyl group at a terminal, and the polyol and the polyisocyanate are reacted therewith. The one-shot method is a preferable method because the manufacturing process is one step compared to the prepolymer method, and there are few restrictions on the manufacturing conditions, and the manufacturing cost can be reduced.

  As a polyurethane foam, a slab polyurethane foam is preferable. Slab polyurethane foam is a polyurethane foam material mixed and stirred by the above-mentioned one-shot method. The polyurethane foam material is naturally foamed and cured at room temperature and atmospheric pressure while the belt conveyor moves. It is obtained by doing. Thereafter, it is cured (cured) in a drying furnace and cut into a predetermined shape. In addition, a polyurethane foam can be obtained by a molding method, an on-site spray molding method, or the like.

The obtained polyurethane foam has a density specified in, for example, JIS K6400 of 20 to 25 (kg / m ³ ), and the hardness can be adjusted in the range of 90 to 120 (N), and the tensile strength can be adjusted. It is possible to maintain 120 to 140 (kPa), elongation to 140 to 150 (%), and compression residual strain to 3 to 4 (%).

  Now, when producing a polyurethane foam, it is carried out by reacting a polyol and a polyisocyanate in the presence of a catalyst and water as a foaming agent to cause foaming and curing. At that time, by setting the isocyanate index of the polyisocyanate to 100 to 120, the reactivity of the polyisocyanate with respect to the polyol is enhanced, and the urethanization reaction (polymerization reaction) proceeds sufficiently, and the crosslinking reaction also proceeds. The foam is given a certain hardness. In this case, an aqueous solution in which bicarbonate is dissolved in water is added to the polyurethane foam raw material. The bicarbonate is thermally decomposed based on the above reaction formula (1) due to heat generation during the production of the polyurethane foam, and the progress of the reaction formula (3) is suppressed by the generated carbon dioxide. As a result, it is estimated that the formation of urea bonds based on the reaction formula (4) is suppressed, and the formation of polyurethane hard segments is suppressed.

  By the way, a polyurethane foam is comprised by the hard segment which consists of a urethane bond and a urea bond, and the soft segment which consists of an ether bond which has a methylene group. And generation | occurrence | production and aggregation of the hard segment which consists especially of a urea bond are inhibited, molecular weight distribution is disturbed and the hardness of a foam is suppressed. Furthermore, the foaming reaction and the cross-linking reaction are suppressed by the carbon dioxide produced by the decomposition of the hydrogen carbonate, and the foam is plasticized and softened. Together, these actions allow the polyurethane foam to exhibit softness, while suppressing changes in physical properties such as tensile strength, elongation, and compressive residual strain.

The effects exhibited by the above embodiment will be described collectively below.
In the polyurethane foam having an open cell structure according to this embodiment, an aqueous solution in which a hydrogen carbonate salt is dissolved in water is added to the polyurethane foam raw material. The added bicarbonate is thermally decomposed by the heat generated during the formation of the polyurethane foam, and the formation of urea bonds is suppressed by the generated carbon dioxide, and the formation of the hard segment of the polyurethane composed of the soft segment and the hard segment is suppressed. it is conceivable that. Therefore, the hardness of the polyurethane foam at the same density can be adjusted low by setting the blending amount and decomposition conditions of the bicarbonate. Moreover, decomposition products such as sodium carbonate (specific gravity 2.25) and potassium carbonate (specific gravity 2.43) produced by decomposition of hydrogen carbonate are more specific than organic substances such as polyethylene powder (specific gravity 0.93). Is big. For this reason, the influence which it has on the physical property change of the polyurethane foam which arises by being filled with a filler is small, and the change of physical properties other than the hardness of a polyurethane foam can be suppressed.

  In addition, since the hydrogen carbonate is an alkali metal hydrogen carbonate, the alkali metal hydrogen carbonate has a low decomposition start temperature and is decomposed along with the formation of the polyurethane foam, and can exhibit its function.

  Furthermore, when the decomposition start temperature of the hydrogen carbonate is 50 to 100 ° C., the decomposition of the hydrogen carbonate is started as the temperature rises during the production of the polyurethane foam, and the function can be exhibited.

  -In addition, when the blending amount of the bicarbonate is 0.005 to 0.5 parts by mass per 100 parts by mass of the polyol, the decomposition of the bicarbonate proceeds appropriately without being excessive or insufficient.

  In addition, based on the latent heat of vaporization of water produced by the decomposition of the bicarbonate, it is possible to suppress the temperature rise during the production of the polyurethane foam, and to suppress the scorch (coloring) of the polyurethane foam.

  -The polyurethane foam having such an open-cell structure can be suitably used as, for example, an automobile seat cushion material, a chair cushion material, or the like. In that case, since the hardness of the polyurethane foam is adjusted, for example, the seat can be softened with a cushion material for a seat of an automobile, and the backrest can be hardened. It becomes.

Hereinafter, the embodiment will be described more specifically with reference to examples and comparative examples.
(Examples 1-5 and Comparative Examples 1-3)
First, the mixture of bicarbonate used in each example and comparative example is shown below.

Mixture 1: A dispersion obtained by dispersing 1 part by mass of sodium hydrogen carbonate (powder) in 10 parts by mass of a polyether polyol.
Mixture 2: An aqueous solution in which 1 part by mass of sodium bicarbonate was dissolved in 10 parts by mass of water.

Mixture 3: An aqueous solution in which 1 part by mass of potassium hydrogen carbonate was dissolved in 10 parts by mass of water.
Mixture 4: An aqueous solution in which 1 part by mass of potassium hydrogen carbonate was dissolved in 3 parts by mass of water.
In addition, a part of water as a foaming agent was used for water for dissolving the hydrogen carbonate in the mixture 2, the mixture 3, and the mixture 4.

  And the mixture of the said hydrogen carbonate was added to the polyurethane foam raw material which consists of polyols, polyisocyanates, a foaming agent, a foam stabilizer, and a catalyst which are shown in Table 1 and Table 2, and the raw material was prepared. Here, Comparative Example 1 and Comparative Example 2 are examples in which no additive such as hydrogen carbonate is added, and Comparative Example 3 is an example in which mixture 1 in which sodium hydrogen carbonate is dispersed in polyether polyol (GP3000) is used. showed that.

These raw materials are poured into a foam container of 500 mm in length, width and depth, foamed at room temperature and atmospheric pressure, then temporarily stored in a heating furnace and heated and reacted (cured) to form a soft slab. A foam was obtained. The obtained soft slab foam was cut out to produce a sheet-like polyurethane foam. About this polyurethane foam, the density, hardness, tensile strength, elongation, and compression residual strain were measured according to the following measuring methods. The results are shown in Tables 1 and 2. The meanings of the abbreviations in Table 1 and Table 2 are shown below.
(Measuring method)
Density (kg / m ³ ), hardness (N), tensile strength (kPa), elongation (%) and compression residual strain (%): Performed according to JIS K6400.
(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に示したように、炭酸水素塩として炭酸水素ナトリウムを用いた実施例３、炭酸水素カリウムを用いた実施例４及び実施例５では、密度を２４（kg／m³）前後に維持した状態で、比較例１に比べてポリウレタン発泡体の硬さのみを１２８Ｎから１１３〜１１９Ｎに低下させることができた。実施例２及び実施例１では、炭酸水素ナトリウムの配合量を増加させることにより、ポリウレタン発泡体の硬さを１０９Ｎ、さらに９６Ｎにまで低下させることができた。

As shown in Table 1, in Example 3 using sodium bicarbonate as the bicarbonate, Example 4 and Example 5 using potassium bicarbonate, the density was maintained around 24 (kg / m ³ ). As compared with Comparative Example 1, only the hardness of the polyurethane foam could be reduced from 128N to 113 to 119N. In Example 2 and Example 1, the hardness of the polyurethane foam could be reduced to 109 N and further to 96 N by increasing the blending amount of sodium bicarbonate.

  Thus, in Examples 1-5, the hardness can be adjusted in the range of 96-119N, maintaining the density of the obtained flexible polyurethane foam in the range of 23.9-24.1. It was. Moreover, the tensile strength of the flexible polyurethane foam was 127 to 135 kPa, the elongation was 143 to 150%, and the compression residual strain was 3.1 to 3.9%.

  In general, a soft polyurethane foam used for automobile seat cushions, chair cushions, and the like has a compression residual strain of 5% or less, and can sufficiently satisfy such a standard.

  On the other hand, as shown in Table 2, when an additive such as sodium hydrogen carbonate was not included (Comparative Example 1), the hardness was 128 N, indicating a high value, and the elongation also tended to be high. . Comparative Example 2 is an example in which the isocyanate index was lowered to 100 in Comparative Example 1, but the density and compressive residual strain increased, but the hardness, tensile strength, and elongation tended to decrease. When a dispersion liquid in which sodium hydrogen carbonate was dispersed in a polyether polyol was used (Comparative Example 3), physical properties close to those of Comparative Example 1 were shown.

In addition, the said embodiment can also be changed and actualized 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 each time, when the temperature exceeds 50 ° C. in the process of producing a polyurethane foam, sodium hydrogen carbonate decomposes to produce carbon dioxide, and when the temperature exceeds 100 ° C. Since potassium hydrogen is decomposed to generate carbon dioxide, the action of the hydrogen carbonate can be sufficiently exerted.

- as bicarbonate, potassium bicarbonate magnesium _{(KMgH (CO 3) 2)} , ammonium bicarbonate (NH ₄ HCO ₃₎ and the like can also be used.
-The required amount of bicarbonate can be dissolved in water as a blowing agent.

  -It can also comprise so that the hardness of a foam may be changed by adding the compound which has hydroxyl groups, such as a propanol and a butanol, to a polyurethane foam raw material, and adjusting the isocyanate index of a polyisocyanate compound.

  ・ Blending polyurethane foam raw material with bifunctional polyether diol and trifunctional polyether triol or polyol with 4 or more functional groups as a crosslinking agent, adjusting the degree of crosslinking of the resulting polyurethane foam, It can also be configured to change.

-Polyurethane foam can also be used, for example, as a cushioning material such as an automobile door trim and a center pillar garnish, a damping material such as a sealing material, a mattress, and a pillow .

Claims (2)

A polyurethane foam raw material containing polyols, polyisocyanates, a foaming agent and a catalyst is blended with an aqueous solution obtained by dissolving a hydrogen carbonate salt in water, and the polyurethane foam raw material is reacted and foamed and cured. A method for producing a polyurethane foam having an open cell structure. The bicarbonate salt is sodium bicarbonate or potassium bicarbonate, the decomposition temperature of the bicarbonate is 50 to 100 ° C., the amount of pre-Symbol bicarbonate, polyols per 100 parts by 0.005 method for producing a polyurethane foam having an open cell structure according to claim 1, characterized in that the 0.5 parts by weight.