JPH07258372A - Production of low-density high-hardness flexible polyurethane foam - Google Patents

Abstract

PURPOSE: To obtain a flexible polyurethane foam low in density and high in hardness without generating scorch by reacting two kinds of specific polyether polyols and a polyfunctional isocyanate in the presence of a blowing agent or the like.

CONSTITUTION: A mixture of 70-99 wt.% of (A) an OH terminated polyetherf polyol with an average functionality of 2-4 and an OH value of 26-60 mgKOH/g and 1-30 wt.% of (B) a polyether polyol with an average functionality of 4-6 and an OH value of 130-160 mgKOH/g is used to be reacted in the presence of a polyfunctional isocyanate, a blowing agent, a foam stabilizer and a catalyst to prepare a flexible polyurethane foam. By this method, a polyurethane foam low in density and high in hardness, having a density of 20 kg/m³ or less is obtained without generating scorch (discoloration caused by internal heating). As the component A, a polyoxypropylene ether polyol with an average functionality of 3 and an OH value of 56 mgKOH/g is pref. and, as the component B, a compd. wherein propylene oxide is added to an alkylene glycol is pref.

COPYRIGHT: (C)1995,JPO

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a flexible polyurethane foam and a foam produced by the method. More specifically, the present invention relates to a method for producing a flexible polyurethane foam having low density and high hardness.

[0002]

2. Description of the Related Art Flexible polyurethane foam is used for molding a very wide range of molded articles such as automobiles, furniture and bedding. Conventional flexible polyurethane foam has a density of 10-5
Products in the range of 0 kg / m ³ are produced, especially 14-25
The mainstream is a foam having a JIS hardness of 5.5 to 13.5 kg / m ³ .

A flexible polyurethane foam is produced by reacting a polyfunctional isocyanate with a polyol in the presence of a blowing agent containing water. In such a reaction, carbon dioxide gas and chlorofluorocarbon generated by the reaction between the polyfunctional isocyanate and water, Foaming is achieved by the action of a physical blowing agent such as dichloromethane. Usually, in order to produce a flexible polyurethane foam suitable for the use of the molded product, the types and amounts of the polyol and polyfunctional isocyanate used in the reaction, molding conditions, etc. are adjusted. In recent years, in order to save raw materials for the purpose of cost reduction, reduction in density of flexible polyurethane foam has been an issue, and the amount of carbon dioxide gas generated by the reaction of water and a polyfunctional isocyanate and a physical blowing agent is compounded. Is adjusted to lower the density of the flexible polyurethane foam.

Generally, the density and hardness of a flexible polyurethane foam are in a proportional relationship, and the lower the density, the lower the hardness. In particular, in the production of flexible slab stock foam, low density foam having a density of 20 kg / m ³ or less is mainly used in terms of cost. In the case of the soft slab stock foam manufactured by reducing the density as described above, the hardness is not sufficient, and higher hardness is demanded. A method of using a polymer polyol is known as a method for producing a high-hardness flexible polyurethane foam, but in the case of this method, a high viscosity cannot be achieved unless the addition amount is increased, and the mixer has a high viscosity. However, there are drawbacks such as difficulty in controlling the flow rate and increase in cost. Especially when manufacturing low density and high hardness flexible polyurethane foam, scorch (burning or discoloration caused by internal heat generation) is likely to occur. The problem arises. Also,
There is also a method of producing a foam with higher hardness by increasing the amount of isocyanate added to the theoretical amount,
Not only is it prone to scorch, but internal heat generation is also large, which can lead to a fire.

The above scorch can be prevented by adding an anti-scorch agent, but the addition of an anti-scorch agent is not preferable because it causes a decrease in reactivity, a decrease in hardness and an increase in cost.

[0006]

However, the conventional methods of increasing the amount of polymer polyol or isocyanate to improve hardness have problems such as scorch and are difficult to industrially use. .

An object of the present invention is to provide a method for producing a flexible polyurethane foam having a low density and a high hardness.

Another object of the present invention is to provide a method for producing a flexible polyurethane foam having a low density and a high hardness while maintaining other physical properties without causing scorch inside the foam.

[0009]

Means for Solving the Problems The present invention has conducted extensive studies in order to solve the above-mentioned problems, and as a result, a polyol and a polyfunctional isocyanate are reacted in the presence of a foaming agent, a foam stabilizer and a catalyst to give a flexible polyurethane. When producing a foam, the average number of functional groups is 4 to 6, and the OH value is 13 as a polyol component.
The above object is achieved by blending a polyether polyol having 0 to 160 mgKOH / g, more preferably a specific polyol obtained by adding propylene oxide to sorbitol to a conventional polyether polyol for flexible polyurethane foam. The inventors have found that they have gained the invention and have reached the present invention.

Therefore, the method for producing a low-density and high-hardness flexible polyurethane foam provided by the present invention comprises reacting a polyol and a polyfunctional isocyanate in the presence of a foaming agent, a foam stabilizer and a catalyst. As the polyol, (1) an average number of functional groups of 2 to 4 and an OH value of 26 to
70-99% by weight of a polyether polyol having terminal OH groups having 60 mg KOH / g, and (2) a polyether polyol having an average number of functional groups of 4-6 and an OH value of 130-160 mg KOH / g, preferably sorbitol, with propylene oxide. It is characterized in that a mixture of 1 to 30% by weight of added polyether polyol is used.

For each raw material used in the method of the present invention,
The details will be described below.

Polyol component (1) Average number of functional groups 2-4 and OH number 26-60 mg KOH / g
Any commercially available polyether polyol known to be used in the production of conventional flexible polyurethane foams can be used as long as it has a OH group and has a terminal OH group.
The preferred average number of functional groups and OH value are 3 to 4 and 3, respectively.
6 to 58 mg KOH / g. Especially, the average functionality 3
Polyoxypropylene ether polyols or polyoxyethylene propylene ether polyols having an OH number of 56 mg KOH / g are preferred.

It is also possible to use two or more of these polyether polyols.

Polyol component (2) Average number of functional groups 4-6 and OH number 130-160 mgKOH
Is a polyether polyol having a / g. Examples of the polyether polyol include polyfunctional alcohols having 4 or more OH groups, preferably 4 to 6 OH groups (for example, diglycerin, methyl glucoside,
Tetrahydric alcohols such as pentaerythritol, mesoerythritol and threitol, pentahydric alcohols such as adonitol, arabitol and xylitol, hexahydric alcohols such as sorbitol, dulcitol and mannitol), monosaccharides such as glucose, mannose, fructose and sorbose, sucrose Examples thereof include oligosaccharides and polysaccharides such as crehalose, lactose, and raffinose, and particularly preferably polyether polyol obtained by adding propylene oxide to sorbitol.

While the specific polyether polyols are prepared by well known methods, the specific polyether polyols used in the Examples below were prepared as follows: Generally, the polyether polyols start with an alkylene glycol. As an agent, it can be obtained by an ionic continuous addition reaction of alkylene oxide in the presence of an alkali catalyst. Here, the molecular weight is extended to a predetermined molecular weight by ring-opening addition polymerization of propylene oxide into a polyhydric alcohol which is an active hydrogen compound in a temperature range of 80 to 140 ° C. by using a small amount of KOH as an alkali catalyst, and thus a target molecular weight is obtained. Then, the alkaline catalyst in the polyether polyol which reached the temperature was removed by neutralization to obtain the target polyether polyol. In the process of increasing the molecular weight of the polyether polyol during propylene oxide addition polymerization, the average number of functional groups generated because the transfer reaction of propylene oxide to allyl alcohol, which is a side reaction, becomes more active than the addition reaction of propylene oxide, which is the main reaction In order to avoid the problem that is lower than the value of the initiator, in the present invention, sorbitol was used as the initiator and propylene oxide was reacted as described above.

The reactivity of active hydrogen is remarkably increased in the polyether polyol in which ethylene oxide is added to sorbitol, and the reactivity of active hydrogen is significantly decreased in the polyether polyol in which butylene oxide is added to sorbitol. This is not preferable because it deteriorates the stability.

The specific polyether polyol has an average number of functional groups of 4 to 6, preferably 4.8 to 5.6 and an OH value of 13.
0 to 160 mg KOH / g, more preferably 135 to 1
It has 55 mg KOH / g.

It is also possible to use two or more of these specific polyether polyols.

The particular polyether polyol should comprise 1 to 30% by weight of the polyol mixture. If it is less than 1% by weight, a flexible polyurethane foam having high hardness cannot be obtained. If it exceeds 30% by weight, the proportion of open cells in the obtained foam decreases, and the soft texture of the flexible polyurethane foam is lost. A preferable blending amount is 5 to 25% by weight, particularly 5 to 20% by weight.

Polyfunctional Isocyanate All known polyfunctional isocyanates can be used as long as they are bifunctional or more. Aromatic polyfunctional isocyanates are particularly suitable, for example 2,4- and 2,6-tolylene diisocyanate (TDI) or TDI-80.
[80% by weight of 2,4-tolylene diisocyanate and 2,
6-Tolylene diisocyanate 20% by weight mixture] or an isomer mixture such as TDI-65, crude tolylene diisocyanate (crude TDI), orthotoluidine isocyanate (TODI), naphthylene diisocyanate (NDI), xylene diisocyanate (XDI). ,
4,4'-diphenylmethane diisocyanate (MD
I) and carbondiimide-modified MDI, polymethylene polyphenyl isocyanate (PAPI), and polymeric polyisocyanate can be used alone or in combination.

The polyfunctional isocyanate is usually 100 to 1
Used in an amount to give an Isocyanate Index of 30. Here, the isocyanate index is
It is the percentage of the stoichiometric amount of isocyanate required to react with all active hydrogens in the formulation. That is,
Isocyanate index 110 is 110% of the stoichiometric amount required for reaction with all active hydrogen.
Means that the above isocyanates are used. Since the hardness decreases as the isocyanate index decreases, the isocyanate index can be appropriately increased or decreased according to the desired hardness.

Blowing agent Water and / or readily volatile inorganic or organic compounds can be used. Suitable organic blowing agents include acetone,
Ethyl acetate, halogen-substituted alkanes (for example, chloroform, ethylidene chloride, vinylidene chloride, chlorodifluoromethane, trichloromonofluoromethane, trichlorotrifluoroethane, dibromotetrafluoroethane, dichlorotetrafluoroethane, dichloromethane), butane, n-pentane, Examples thereof include i-pentane, n-hexane, i-hexane, heptane and diethyl ether. Further, examples of suitable inorganic foaming agents include air, carbon dioxide gas and N ₂ O. It is also possible to use it as a mixture of two or more kinds.

The amount of the foaming agent used is usually 100 polyols.
1 to 30 parts by weight are used relative to parts by weight. The amount used varies depending on the density and hardness of the foam to be sought, but it is more preferably 5 to 15% by weight.

Foam Stabilizer Suitable foam stabilizers are organosilicon surfactants. For example, L-520, L532, L-580 manufactured by Nippon Unicar Co., Ltd.
L-582, Toray Dow Corning Silicon SH1
90, SH192, SRX253, XF2961, F114, F121, F122 manufactured by Shin-Etsu Silicon Co., TFA-4200, TFA-4202 manufactured by Toshiba Silicon Co., B4113, BF2370 manufactured by Gold Schmidt, and the like.

The amount of the foam stabilizer used is usually 100 polyols.
0.01 to 5 parts by weight, preferably 0.1
~ 2 parts by weight.

[0026] The known catalysts which are conventionally used for the preparation of the catalyst flexible polyurethane foams can be used. Suitable catalysts include amine catalysts such as triethylamine, tripropylamine,
Triisopropanolamine, tributylamine, hexadecyldimethylamine, N-methylmorpholine, N-
Ethylmorpholine, N-octadecylmorpholine, monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N, N-dimethylethanolamine, N, N, N ', N'-tetramethylethylenediamine, N, N, N ', N'-tetramethylpropylenediamine, N, N, N', N'-tetramethylbutanediamine, N, N, N ', N'-tetramethyl-1,3-butanediamine, N, N, N ', N'
-Tetramethylhexamethylenediamine, bis [2-
(N, N-Dimethylamino) ethyl] ether, N, N
-Dimethylbenzylamine, N, N-dimethylcyclohexylamine, N, N, N ', N', N ", N"-
Pentamethyldiethylenetriamine, triethylenediamine, salts of triethylenediamine, oxyalkylene adducts of amino groups of primary and secondary amines, azacyclo compounds such as N, N-dialkylpyrazines, various N, N ', N' Examples thereof include'-trialkylaminoalkylhexahydrotriazines. Other suitable catalysts include metal catalysts such as tin acetate, tin octylate, tin oleate, tin laurate, dibutyl lead dichloride, lead naphthenate, nickel naphthenate and cobalt naphthenate.

It is also possible to use two or more catalysts.

The amount of the catalyst used is usually 0.001 to 10 parts by weight, preferably 0.001 part by weight per 100 parts by weight of the polyol.
01 to 2 parts by weight.

Optional components Further, known fillers, stabilizers, colorants and the like can be added as required.

The low-density and high-hardness flexible polyurethane foam of the present invention is manufactured by a conventional slab manufacturing method, in which all raw materials are sufficiently mixed and then foamed on a belt conveyor. Alternatively, it may be manufactured in a batch system. The conditions during mixing and molding are not particularly limited.

[0031]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Details of each component in the formulation are as follows.

Polyol Polyol A: Carador SC56-01, Shell Co. (average number of functional groups 3, average OH value 56 mgKOH / g) Polyol B: Carador SC56-02, Shell Co. (average number of functional groups 3, average OH value 56 mgKOH / g) Polyol C: Average number of functional groups 5.2, average OH value 145
mgKOH / g polyether polyol Polyol D: average number of functional groups 5.2, average OH value 155
mg KOH / g polyether polyol Polyol E: average number of functional groups 3, average OH value 155 mg
KOH / g polypropylene polyol.

Method for producing foam 100% by weight of a mixture of polyether polyols was placed in a beaker and the temperature was adjusted to 20 ° C., amine catalyst: DAB.
CO33LV (manufactured by Japan Air Products Co., Ltd.) 0.1% by weight, water, dichloromethane, and foam stabilizer: L582 (manufactured by Nippon Unicar Co., Ltd.) 1.2% by weight were added, and the mixture was stirred for 30 seconds.
Then, tin catalyst: T-9 (manufactured by Air Products Co.) 0.2
After adding wt% and stirring for 10 seconds, the isocyanate:
Add Karadate 80 (made by Shell) and stir for 10 seconds,
It was allowed to foam freely in a 35 × 35 × 20 cm container. The obtained foam was heated in an air circulation oven at 70 ° C. for 10 minutes and left at room temperature for 24 hours to obtain a flexible polyurethane foam.

The properties of the polyurethane foams produced in the examples were measured as follows.

Density Measured according to JIS-K6401 (kg / m ³ ) Hardness Measured according to JIS-K6401 (kg) Tensile strength Measured according to ASTM-D3754 (kPa) Elongation Measured according to ASTM-D3754 ( %).

Examples 1 to 12 and Comparative Examples 1 to 6 Foaming was carried out in an amount 4 times the amount shown in Tables 1 and 2.

[0038]

[Table 1]

[0039]

[Table 2]

Effects of the Invention (1) From Table 1, the flexible polyurethane foams produced in Examples 1 to 8 have the same density as those produced in Comparative Examples 1 to 2, but the hardness Is significantly improved,
It is clear that low density and high hardness flexible polyurethane foams can be produced by the method of the present invention.

(2) From Table 2, it is clear that even when the isocyanate index is high, a low-density and high-hardness flexible polyurethane foam can be produced, and when the OH values are the same, a decrease in the number of functional groups causes a decrease in hardness. Is.

According to the method of the present invention, in the method for producing a low-density flexible polyurethane foam having a density of 20 kg / m ³ or less, which is a drawback of the conventional method, the defect that the hardness becomes lower as the density becomes lower is eliminated. The method of the invention is useful as an industrial method for producing a flexible polyurethane foam.

Claims (3)

[Claims] 1. A method comprising reacting a polyol and a polyfunctional isocyanate in the presence of a foaming agent, a foam stabilizer and a catalyst, wherein the polyol has (1) an average functional group number of 2 to
4 and OH with an OH number of 26-60 mg KOH / g
70 to 99% by weight of a polyether polyol having a group, and (2) an average number of functional groups of 4 to 6 and an OH value of 130 to 160 m.
Polyether polyols 1 to 30 having gKOH / g
A method for producing a flexible polyurethane foam having a low density and a high hardness, which comprises using a mixture in a weight percentage. 2. The method according to claim 1, wherein the polyol (2) is a polyether polyol obtained by adding propylene oxide to alkylene glycol. 3. A flexible polyurethane foam having a density of 20.
The method according to claim 1 or 2, which is not more than kg / m ³ .