JPH0559143A - Production of polyurethane elastic foam - Google Patents

Abstract

(57) [Abstract] [Purpose] To produce foams with high elasticity. [Structure] Acrylonitrile polymer-containing hydroxyl value 28,
Polyoxyalkylene triol having a total degree of unsaturation of 0.02 to 0.10, and an alumina sol having a solid content of 0.3 to 0.8% by weight (particle diameter: 5 to 10 mμ, length: 50 to 100)
(mμ), a system liquid comprising a polyol, water, a catalyst, a foaming agent and a cross-linking agent (hydroxyl value 450, sorbitol-propylene oxide adduct), and a mixture of tolylene diisocyanate and polyphenyl polymethylene polyisocyanate are reacted, Allow to cure and produce an elastic foam. [Effect] It has an extremely remarkable effect in preventing foam shrinkage.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a polyurethane elastic foam.

[0002]

2. Description of the Related Art It is known to use a high molecular weight polyol blended with finely divided silica (fine silica) or silica sol in the production of a flexible polyurethane foam. The former is disclosed in JP-A-54-154498.
The latter is described in JP-A-58-13620.

One of the purposes of using high molecular weight polyols containing finely divided silica is to prevent shrinkage during the production of high resilience foams.

[0004]

Heretofore, in order to prevent shrinkage during the production of high-elasticity foam, finely particulate silica or finely particulate alumina may be used in addition to the polymer polyol and the highly reactive polyol. When finely divided silica or finely divided alumina is used as a mixture with polyoxyalkylene polyol, a relatively small amount may be effective in preventing shrinkage of the foam, but in most cases, the foam is unstable,
Cracks are easy to insert and sometimes collapse.

Further, the polyoxyalkylene polyol mixed with fine particle silica or fine particle alumina has a problem of storage stability that fine particle silica or fine particle alumina easily precipitates after long-term storage.

[0006]

The present invention has been made to solve the above-mentioned problems, in which a polyol and a polyisocyanate are reacted in the presence of an auxiliary agent such as a foaming agent, a foam stabilizer and a catalyst. In the method for producing a polyurethane elastic foam, a polyol having a hydroxyl value of 5 to 34 and a total unsaturation degree of 0.2 or less is used as a high molecular weight polyoxyalkylene polyol or a polymer polyol based on the same as a solid content of 0.01 to Using a polyol containing 2% by weight of alumina sol, and using as a polyisocyanate a mixture of tolylene diisocyanate or a modified product thereof and polyphenylpolymethylene polyisocyanate or a modified product thereof and / or a modified product obtained by modifying the mixture. In the method for producing a polyurethane elastic foam, which is characterized by That.

In a preferred embodiment of the present invention, the particle shape of the alumina sol has a length / diameter of 2 or more.

The alumina sol in the present invention is a dispersion of finely divided alumina in a dispersion medium.

"Stable" means that the fine particle alumina does not practically separate from the dispersion medium even when it is allowed to stand. The fine-grained alumina in this alumina sol has a fibrous shape with a length of 1 to 200 mμ, a diameter of 1 to 50 mμ, preferably a length of 10 to 200 mμ and a diameter of 5 to 20 mμ.
And the length / diameter is 2 or more.

An example in which silica gel stably dispersed in a dispersion medium is applied to a thermal cure foam has been reported (see JP-A-60-163912), but the silica gel has a spherical particle shape and is a cold cure type elastic foam. For manufacturing, the effect of preventing shrinkage is extremely small.

For preventing the shrinkage of the elastic foam, the effect of the polyol obtained by dispersing the fibrous alumina sol as in the present invention is remarkable.

The dispersion medium in the alumina sol is usually water. Other monohydric alcohols, polyhydric alcohols, ketones,
Esters and the like are used.

One of the preferred dispersion media for the alumina sol used in the present invention is water, and the other is a hydrophilic organic solvent such as a monohydric or polyhydric alcohol.
Particularly preferable alcohols are methanol, ethanol, n-propanol, isopropanol, and other alcohols having 4 or less carbon atoms.

Even if this alumina sol is simply added to the dispersion medium and dispersed, the dispersion stability is low, and both are easily separated over time. In order to stably disperse the alumina sol in the dispersion medium, an organic acid or an inorganic acid is added as a stabilizer to adjust the pH of the system to 5-7. If the pH is greatly deviated, the dispersion stability of the particles is poor and precipitates or gelation occur.

The method of blending the alumina sol with the polyoxyalkylene polyol is not particularly limited. A method of mixing the alumina sol and the polyoxyalkylene-based polyol and then removing the dispersion medium of the alumina sol is also possible.

In the present invention, the amount of alumina sol blended is small, so that it is not always necessary to remove the dispersion medium. For example, when alcohol is the dispersion medium, the presence of a small amount of alcohol has little influence on the foaming and curing behavior of the foamable mixture and the physical properties of the resulting flexible polyurethane foam.

On the other hand, when water is the dispersion medium, a small amount of water acts as a foaming agent, which has a great influence. However, in the production of flexible polyurethane foams, water is often used alone or in combination with other blowing agents. Therefore, when a silica sol containing water as a dispersion medium is blended, it is unnecessary to remove water unless the amount of water in the dispersion medium exceeds the amount of water required as a foaming medium. That is, when the amount of water in the dispersion medium is equal to the amount of water as the foaming agent, it can be used as it is, and when the amount is small, a difference amount of water can be added and used.

It is essential that the amount of alumina sol mixed with the polyoxyalkylene polyol is 0.01 to 2% by weight based on the solid content of the polyoxyalkylene polyol, and a more preferable amount is about 0.1. ~ 1.2
% By weight. If the blending amount is less than this range, the air permeability of the polyurethane elastic foam does not reach the intended level or a stable foam cannot be obtained.

In the present invention, the polyol may be one or more polyoxyalkylene polyols. In addition to polyoxyalkylene polyols, polyester-based polyols, hydroxyl-containing polydiene-based polymers, and other polyols having 2 to 8, particularly 2 to 4 hydroxyl groups can be used in combination.

In particular, one of polyoxyalkylene polyols
It is preferable to use only one kind or more, or to use it together with a small amount (usually 30% by weight or less) of a polyester-based polymer or a hydroxyl group-containing polydiene-based polymer as the main component.

Examples of the polyoxyalkylene polyol include polyhydric alcohols, saccharides, alkanolamines, polyhydric phenols and other initiators, and cyclic ethers, particularly polyoxyalkylene polyols obtained by adding propylene oxide alone or ethylene oxide. preferable.

The hydroxyl value of these high molecular weight polyoxyalkylene polyols must be 5 to 34 and the total degree of unsaturation must be 0.2 or less. In particular, the hydroxyl value is 5 to 30, and the total degree of unsaturation is 0. It is preferably 15 or less.

Alkali catalysts are generally used as catalysts for synthesizing polyoxyalkylene polyols. Polyoxyalkylene polyols having a low degree of unsaturation and a low hydroxyl value can be used for diethyl zinc, iron chloride, metal porphyrins other than alkali catalysts. It can be obtained by using a complex metal cyanide complex or the like as a catalyst. In particular, a good polyoxyalkylene polyol can be obtained by using a complex metal cyanide complex.

The polyol mixture has a hydroxyl value of 34.
The following are preferred. Further, a so-called polymer polyol in which fine particles such as an addition polymerization type polymer and a condensation polymerization type polymer are dispersed can be used as the high molecular weight polyol. This polymer polyol can also be used in combination with the above high molecular weight polyol.

The polymer polyol preferably contains 3 to 40% by weight of fine particles of homo- or copolymer such as acrylonitrile and styrene. The hydroxyl value of the polymer polyol or a mixture of the polymer polyol and other high molecular weight polyol is required to be 5 to 34, and the total degree of unsaturation is 0.2 or less, preferably 0.15 or less. Particularly preferred is a polymer polyol produced by using a polyoxyalkylene polyol having a hydroxyl value of 5 to 30 and a total degree of unsaturation of 0.12 or less as a base polyol.

The hydroxyl value is "mgKOH / g",
The total degree of unsaturation is expressed by "milliequivalent / g".

In these high molecular weight polyols, the hydroxyl groups are preferably hydroxyl groups having a high proportion of primary hydroxyl groups. As such a high molecular weight polyoxyalkylene polyol, a polyoxyalkylene polyol having an oxyethylene group block chain at the terminal is preferable.

The content ratio of the terminal oxyethylene group is 2 to 25 with respect to the molecular weight of the polyoxyalkylene polyol.
%, Especially 5 to 20% by weight is preferred.

In the present invention, the above low hydroxyl value (that is,
Only high molecular weight polyols (except water as a blowing agent) can be reacted with isocyanate compounds, but it is also possible to use polyfunctional compounds capable of reacting with lower molecular weight isocyanate groups together with high molecular weight polyols. it can.

This polyfunctional compound has a molecular weight of 600 or less, particularly 300 or less, per isocyanate-reactive group having two or more isocyanate-reactive groups such as hydroxyl group, primary amino group, or secondary amino group. Compounds are suitable.

Such compounds include compounds usually called cross-linking agents or chain extenders. Such compounds include, for example, polyhydric alcohols, alkanolamines, polyamines, and polyhydric alcohols, alkanolamines, sugars, polyamines, monoamines, polyhydric phenols, etc., which have low molecular weight and are obtained by adding a small amount of alkylene oxide. There are polyether polyols. Furthermore, low molecular weight polyester polyols, castor oil-based polyols and the like can also be used.

Preferred are polyhydric alcohols such as ethylene glycol, propylene glycol, 1,4-butanediol, glycerin and sorbitol, alkanolamines such as diethanolamine and triethanolamine, and polyether polyols having a hydroxyl value of 200 or more. Used.

The amount of the polyfunctional compound used is preferably about 10 parts by weight or less, and more preferably 5 parts by weight or less based on 100 parts by weight of the high molecular weight polyol. There is no lower limit to the amount used,
When used, about 0.2 parts by weight is sufficiently effective.

As the polyisocyanate compound, a mixture of tolylene diisocyanate or a modified product thereof and polyphenylpolymethylene polyisocyanate or a modified product thereof and / or a modified product obtained by modifying the mixture is used. The mixing weight ratio is such that the ratio of tolylene diisocyanate (or its modified product) / polyphenylpolymethylenene polyisocyanate (or its modified product) is 97/3 to 3/97, particularly 90/10.
A ratio of 5/95 is preferable.

2,4 as tolylene diisocyanate
-Body and / or 2,6-body are used, in particular 2,4
An isomer mixture in which the weight ratio of -form / 2,6-form is 95/5 to 50/50, particularly 90/10 to 65/35 is preferable.

The polyphenyl polymethylene polyisocyanate is obtained by condensing aniline and formaldehyde in the presence of a catalyst and hydrochloric acid to obtain a polyphenyl polymethylene polyamine mixture, which is further phosgenated.

Further, those obtained by removing a part or all of diphenylmethane diisocyanate from this can also be used. Further, a target polyphenyl polymethylene polyisocyanate mixture can be obtained from polymethylene polyphenyl isocyanate obtained by decomposing a condensate obtained by condensing N-phenylcarbamic acid ester and formaldehyde by thermal decomposition or the like. ..

The number of isocyanate groups per molecule must exceed 2 on average, and 2.1 to 4 is particularly preferable.

A modified product thereof can be used as a part or all of the above-mentioned tolylene diisocyanate. Similarly, a modified product of polyphenyl polymethylene polyisocyanate can be used. Further, a modified product of the polyisocyanate mixture can also be used.

The polyisocyanate as a whole preferably contains at least 10% by weight of isocyanate groups, and particularly preferably contains at least 15% by weight of isocyanate groups, including the case where these modified products are contained.

Examples of the modified products of the above polyisocyanates include prepolymer type modified products obtained by modifying with polyol or polyol and polycarboxylic acid, carbodiimide type modified products obtained by modifying with a phosphoric acid catalyst, and nurate modified products. Is appropriate.

Examples of the modifying polyol include polyhydric alcohols, polyoxyalkylene polyols having a relatively low molecular weight, polyester polyols, polyoxyalkylene polyols having a high molecular weight and a low degree of unsaturation, and mixtures of two or more thereof.

The polycarboxylic acid may be used in combination with a polyol in an excess equivalent amount than that, or one obtained by previously reacting both may be used. As a relatively low molecular weight polyoxyalkylene polyol, a molecular weight of 400-
1500 diols and triols are suitable and the degree of unsaturation may be 0.2 or less.

As the polycarboxylic acid, an aliphatic or aromatic dicarboxylic acid having 4 to 8 carbon atoms is suitable. Examples of the dicarboxylic acid used for modification include succinic acid, glutaric acid, pimelic acid, adipic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, phthalic acid and terephthalic acid. As the polyhydric alcohol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene glycol, tripropylene glycol, 1,4-butanediol, 1,6
-Hexanediol, 1,10-decanediol, trimethylolpropane, ethylene glycol, diethylene glycol, triethanolamine and the like can be used alone and / or in a mixture of two or more kinds.

In the present invention, the reaction between the polyol and polyisocyanate is carried out in the presence of a foaming agent. As the foaming agent, only water is preferable, but a low boiling point organic compound, an inert gas and the like may be used together in a small amount. For example 1,
1-dichloro-2,2,2-trifluoroethane (hereinafter referred to as R-123) or 1,1-dichloro-1-
Fluoroethane (hereinafter referred to as R-141b) and the like can be used together.

Conventionally widely used low-boiling halogenated hydrocarbons such as trichlorofluoromethane have recently been restricted in use due to ozone problems. R above
-123 and R-141b are alternative foaming agents with less risk of ozone layer destruction.

When reacting the polyol and the polyisocyanate compound, it is usually necessary to use a catalyst. As the catalyst, a metal compound catalyst such as an organic tin compound that promotes a reaction between an active hydrogen-containing group and an isocyanate group or a tertiary amine catalyst such as triethylenediamine is used.

Further, a multimerization catalyst for reacting isocyanate groups with each other, such as a carboxylic acid metal salt, is used depending on the purpose. Further, foam stabilizers for forming good bubbles are often used. Examples of the foam stabilizer include a silicone type foam stabilizer and a fluorine-containing compound type foam stabilizer. In addition, as a compounding agent which can be optionally used, there are, for example, a filler, a stabilizer, a coloring agent, a flame retardant and the like.

When an aqueous foaming agent is used as the foaming agent, part of the polyisocyanate compound reacts with water to generate carbon dioxide gas. Therefore, the amount of the polyisocyanate compound used is based on the total amount of the high-molecular-weight polyol and the low-molecular-weight polyfunctional compound to which an aqueous foaming agent is added, and 0.8 to 1. It is preferable to use 3 equivalents. 100 times the equivalent number of this polyisocyanate compound is usually called the (isocyanate) index. Therefore, the index of the polyisocyanate compound is preferably 80 to 130.

[0050]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Tables 1-3
The foaming evaluation in the present invention was carried out using the above polyols and the like.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

[Example 1] 70 parts of polyol B (same as below for weight parts), 30 parts of polymer polyol A1, 3.5 parts of water, 0.7 parts of amine catalyst Dabco-33LV.
Part, silicone foaming agent SRX274-C (manufactured by Toray Silicone) 1.0 part, and cross-linking agent (hydroxyl value 450, sorbitol-propylene oxide adduct) 3.0 parts in a polyol system liquid containing isocyanate G (index 1).
05) was added and stirred, then 350 mm × 350 mm × 100 mm
It was poured into a mold (mold temperature 60 ° C.) and cured at room temperature for 6 minutes. Table 4 shows the appearance, breathability (air flow), apparent density (core), 25% ILD, impact resilience, elongation and wet heat compression set of the obtained foam.

Example 2 Instead of polyol B, polymer polyol A1 and isocyanate G, polyol D, polymer polyol C1 and isocyanate F, respectively.
The same procedure as in Example 1 was performed except that was used. Table 4 shows the physical properties of the obtained foam.

Example 3 The same procedure as in Example 1 was carried out except that polyol E and polymer polyol C1 were used instead of polyol B and polymer polyol A1, respectively. Table 4 shows the physical properties of the obtained foam.

Comparative Example 1 The procedure of Example 1 was repeated except that the polyol A was used in place of the polyol B. Table 4 shows the physical properties of the obtained foam.

Comparative Example 2 The procedure of Example 2 was repeated except that the polyol C was used instead of the polyol D. Table 4 shows the physical properties of the obtained foam.

Comparative Example 3 The procedure of Example 3 was repeated except that the polyol C was used in place of the polyol E. Table 4 shows the physical properties of the obtained foam.

[0060]

[Table 4]

[0061]

INDUSTRIAL APPLICABILITY The present invention has a very remarkable effect in preventing the shrinkage of foam.

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Claims (2)

[Claims] 1. A method for producing a polyurethane elastic foam by reacting a polyol and a polyisocyanate in the presence of an auxiliary agent such as a foaming agent, a foam stabilizer and a catalyst, wherein the polyol has a hydroxyl value of 5 to 34 and total unsaturation. The polymer polyoxyalkylene polyol having a degree of 0.2 or less or a polymer polyol based on it has a solid content of 0.0
Using a polyol containing 1-2 wt% alumina sol,
Use of a mixture of tolylene diisocyanate or a modified product thereof and polyphenylpolymethylene polyisocyanate or a modified product thereof and / or a modified product obtained by modifying the mixture as a polyisocyanate, to produce a polyurethane elastic foam. Method. 2. The particle shape of alumina sol has a length / diameter of 2
The manufacturing method according to claim 1, which is as described above.