JP2002194044A - Method for preparing polyurethane resin aqueous dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily and safely preparing a polyurethane resin having required properties without using such a harmful solvent as ketone, based aromatic, ester-based solvents and also, suppressing a side reaction to its isocyanate group. SOLUTION: A urethane prepolymer having carboxy groups in the molecule and isocyanate groups at the terminals, is dispersed into an aqueous solution containing an alcoholic solvent, a neutralizer and a chain extender.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a novel method for producing an aqueous dispersion of a polyurethane resin.

[0002]

2. Description of the Related Art Polyurethane resins are rich in flexibility and excellent in various properties such as adhesion, and are therefore suitably used for various binders, coating agents, adhesives and the like. When producing a polyurethane resin, a solvent is used from the viewpoint of adjusting the viscosity of the reaction system, but the solvent does not have a side reaction with the urethane prepolymer and sufficiently dissolves a highly polar polyurethane resin. Organic solvents that can be used (for example, ketone-based, aromatic-based, ester-based solvents) are used. With the demand for water-based polyurethane resins being promoted due to social demands such as environmental protection and stricter regulations on organic solvents, the use of organic solvents that are harmful to the human body and have a large environmental load as described above is considered unsuitable.

Under such a background, for example, Japanese Unexamined Patent Publication No.
Japanese Patent No. 31439 discloses a method for producing an aqueous dispersion of a polyurethane resin without using an organic solvent. According to the method, there is an advantage that there is no need to use an organic solvent, but a special dispersing apparatus for forcibly dispersing the polyurethane resin in water is required, such as equipment, a manufacturing process,
There are considerable disadvantages in economics and other aspects.

As a method for easily producing an aqueous dispersion of a polyurethane resin, for example, a urethane prepolymer is synthesized in the above-mentioned organic solvent, and then a reaction is carried out by adding a neutralizing agent, a chain extender, an alcohol-based solvent and the like. A method is known in which a polyurethane resin is used, and then the polyurethane resin is dispersed in water. However, since a harmful organic solvent is used during the synthesis of the prepolymer, a step of removing the solvent from the final product is required. Therefore, such a method is disadvantageous in terms of safety and health, a manufacturing process, economy, and the like.

[0005] Further, without using the above harmful solvents,
Moreover, a method for easily producing an aqueous polyurethane resin dispersion has been already practiced. That is, a urethane prepolymer is synthesized in the absence of a solvent, and after diluting the same with an alcohol-based solvent, a neutralizing agent, a chain extender and the like are added and reacted to form a polyurethane resin, and then the resin is dispersed in water. Is the way. This method has the advantage that the solvent removal step can be omitted because no harmful solvent is used, but when an isocyanate group in the urethane prepolymer undergoes a chain extension reaction with a chain extender,
As a result of a side reaction with an alcohol-based solvent, neutralizing agent, or water (dispersion medium), it becomes difficult to control the original chain extension reaction, or unreacted chain extender remains. It is difficult to obtain a polyurethane resin having the following molecular weight and molecular structure. In addition, various performances when used for various applications such as printing inks, paints, and adhesives are also unsatisfactory.

[0006]

SUMMARY OF THE INVENTION The present invention does not use the harmful solvent as described above and reduces the side reaction to the isocyanate group, whereby the polyurethane resin having the target property can be easily and safely produced. The purpose is to provide.

[0007]

That is, the present invention provides a urethane prepolymer having a carboxyl group in a molecule and an isocyanate group at a molecular terminal, comprising an aqueous solution containing an alcohol solvent, a neutralizing agent and a chain extender. The present invention relates to a method for producing an aqueous dispersion of a polyurethane resin, characterized by being dispersed therein.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, first, a urethane prepolymer having a carboxyl group in a molecule and an isocyanate group at a molecular terminal (hereinafter, simply referred to as "urethane prepolymer") is produced. Such a urethane prepolymer is produced by reacting a diol compound containing a high molecular polyol with a polyisocyanate compound.

As the diol compound containing a high molecular polyol, high molecular weight polyol compounds such as polyether polyols, polyester polyols, polycarbonate polyols, and polybutadienes can be used. Specific examples of the polyether polyols include polyethylene glycol, polypropylene glycol, and polyoxytetramethylene ether glycol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, and the like. Specific examples of the polyester polyols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-
Propanediol, 1,3-propanediol, 1,3
-Butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,
Saturated or unsaturated low molecular weight glycols such as 5-pentanediol, 1,6-hexanediol, octanediol, 1,4-butynediol, dipropylene glycol, bisphenol A, hydrogenated bisphenol A and adipic acid, maleic acid Dibasic acids such as fumaric acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, suberic acid and the corresponding acid anhydrides And the like obtained by dehydration-condensation. In addition, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol,
Trihydric alcohols such as 1,2,4-butanetriol,
A low-molecular-weight polyol compound having three or more valences such as a tetrahydric alcohol such as pentaerythritol and a hexahydric alcohol such as sorbitol can be used in combination. Further, as the polyester polyols, ε-caprolactone,
Compounds obtained by ring-opening polymerization of lactones such as β-methyl-δ-valerolactone can also be used. These high molecular weight polyol compounds may be used alone or in combination of two or more.

The number average molecular weight of the diol compound containing the high molecular weight polyol is generally about 500 to 10,000, preferably 700 to 5,000. If the value is too small, the resulting polyurethane resin film tends to be inferior in flexibility.If the value is too large, the urethane prepolymer is not rapidly dispersed in an aqueous solution containing a neutralizing agent and a chain extender, and is obtained. The drying property of the polyurethane resin film tends to be poor.

As the diol compound containing a high molecular weight polyol, a diol compound containing a carboxyl group in the molecule is used. Specifically, α, α′-dimethylolalkanoic acid (glyceric acid, dimethylolpropionic acid, dimethylolbutanoic acid, 2,2-dimethylolpentanoic acid, etc.), dioxymaleic acid, dioxyfumaric acid,
Examples thereof include tartaric acid, 2,6-dioxybenzoic acid, 4,4-bis (hydroxyphenyl) valeric acid, and 4,4-bis (hydroxyphenyl) butyric acid. Further, these carboxylic compounds containing a carboxyl group are used as initiators to form ε-
Compounds obtained by ring-opening polymerization of lactones such as caprolactone, γ-butyrolactone, and γ-valerolactone, and high molecular weight compounds obtained by ring-opening polymerization of lactones can also be used.

As the polyisocyanate compound, various known aromatic, aliphatic or alicyclic polyisocyanate compounds can be used. Specifically, 1,
5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, , 4-
Phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane- 1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate,
Examples include dimer isocyanate in which a carboxyl group of dimer acid is converted into an isocyanate group.

The urethane prepolymer required in the present invention is obtained by converting a diol compound containing a high molecular polyol and a polyisocyanate compound into a total equivalent of hydroxyl groups contained in the diol compound containing the high molecular polyol in the absence of a solvent. On the other hand, it is obtained by reacting the polyisocyanate compound so that the isocyanate group equivalent becomes excessive. The reaction temperature, reaction time, reaction conditions such as the urethane-forming catalyst, etc. in the production of the urethane prepolymer may be determined as appropriate. Although the amount of the carboxyl group in the urethane prepolymer is not particularly limited, the acid value of the polyurethane resin should be 5 to 1 in order to obtain a polyurethane resin aqueous dispersion having excellent stability.
It is preferable to be in the range of about 00 mgKOH / g. When the value is smaller than the above range, the stability of the obtained aqueous dispersion of the polyurethane resin tends to be inferior. When the value is larger than the range, the water resistance of the polyurethane resin film tends to be inferior. The urethane prepolymer thus obtained is usually 1,000 to 10,000,000 mPa.
・ High viscosity of about s (70 ° C).

Next, the urethane prepolymer obtained as described above is dispersed in an aqueous solution containing an alcoholic solvent, a neutralizing agent and a chain extender (hereinafter, simply referred to as “aqueous solution”). At this time, it is necessary to disperse under conditions that the total equivalent of the active hydrogen contained in the chain extender in the aqueous solution always becomes excessive with respect to the equivalent of the isocyanate group in the urethane prepolymer. Under these conditions, the chain extension reaction between the urethane prepolymer and the chain extender proceeds faster than the side reaction between the urethane prepolymer and the alcohol-based solvent. A dispersion can be easily obtained. The specific dispersing method is not particularly limited as long as the above conditions are satisfied. After production in a container, the urethane prepolymer is allowed to stand, and then the aqueous solution is supplied to the isocyanate groups in the urethane prepolymer until the active hydrogen in the chain extender in the aqueous solution becomes excessive, Thereafter, a method in which stirring in the reaction system is started to mechanically disperse the urethane prepolymer in the aqueous solution may be mentioned. The conditions such as the reaction temperature and pressure during dispersion are not particularly limited, but are usually room temperature or higher and normal pressure.

In the present invention, an alcohol-based solvent is allowed to coexist in the aqueous solution. This has the advantage that the urethane prepolymer can be rapidly dispersed in the aqueous solution. Further, in the production method of the present invention, since the urethane prepolymer and the chain extender can be preferentially reacted,
Since almost no side reaction occurs between the urethane prepolymer and the alcohol-based solvent, neutralizing agent, water, or the like, there is an advantage that various known alcohol-based solvents can be used. As the alcohol-based solvent, a solvent that does not particularly contain a reactive hydrogen for an isocyanate group (excluding an alcoholic hydroxyl group) in the molecule is preferable. Specific examples include ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-
Examples thereof include butyl alcohol, sec-amyl alcohol, and diacetone alcohol, and these can be used alone or in combination of two or more. Also,
The amount used is not particularly limited, but is usually about 3 to 40% by weight, preferably 10 to 35% by weight based on the urethane prepolymer.
% By weight. If the used amount is smaller than the above numerical range, the urethane prepolymer tends to be difficult to be rapidly dispersed in the aqueous solution. If the value is larger than the range,
The resulting polyurethane resin aqueous dispersion tends to have poor stability.

Examples of the neutralizing agent include ammonia, alkali metals such as potassium hydroxide and sodium hydroxide, tertiary amines such as trimethylamine, triethylamine, triisopropylamine and tributylamine, triethanolamine, triisopropanolamine, N- Alkyldiethanolamine, N, N′-dialkylmonoethanolamine, N-alkyldiisopropanolamine,
Basic compounds such as alkanolamines such as N, N'-dialkylmonoisopropanolamine can be used, and these can be used alone or in combination of two or more. The neutralizing agent is usually used to form a carboxyl group 1 in the prepolymer.
It is preferable to set the equivalent to about 0.5 to 2.0 equivalents. If it is lower than the above range, the storage stability of the obtained aqueous dispersion of polyurethane resin tends to decrease, and if it is higher than this range, the viscosity of the system tends to increase when the prepolymer is dispersed in water.

As the chain extender, ethylenediamine,
Aliphatic diamines such as propylene diamine, hexamethylene diamine, diethylene triamine, triethylene tetramine, isophorone diamine, dicyclohexylmethane-4,4′-diamine; 2-hydroxyethyl ethylene diamine, 2-hydroxyethyl propylene diamine;
Di-2-hydroxyethylethylenediamine, di-2-
Diamines having a hydroxyl group in a molecule such as hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine; alkylenedihydrazines such as methylenedihydrazine, ethylenedihydrazine, propylenedihydrazine, and adipic acid Saturated or unsaturated dihydrazines such as dihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, phthalic acid dihydrazide and itaconic acid dihydrazide; dimer diamines in which a carboxyl group of dimer acid is converted to an amino group; These chain extenders are preferred in that they react quickly with isocyanate groups in the urethane prepolymer. .
In addition, these chain extenders can be used as chain terminators by using an excess of isocyanate groups in the prepolymer. In addition, a chain length terminator can be used if necessary. For example, monoamines such as monobutylamine and dibutylamine are exemplified.

The number-average molecular weight of the aqueous polyurethane resin dispersion thus obtained can be appropriately determined depending on the intended use. However, printing inks, paints and the like which require a resin film strength are required.
When used in the field of adhesives and the like, it is preferably 5000 or more.

The solid content concentration and viscosity of the aqueous polyurethane resin dispersion of the present invention are not particularly limited, and may be appropriately determined in consideration of workability during use. Usually, the solid concentration is 10 to 60% by weight, and the viscosity is 10 to 100,000 mPa ·
Adjustment to the range of s / 25 ° C. is practically preferable.

The aqueous polyurethane resin dispersion obtained by the method of the present invention can be suitably used for various applications. For example, by adding water and, if necessary, various pigments and the like to the aqueous polyurethane resin dispersion and mixing or dispersing them, and further appropriately adding additives such as an antiblocking agent and a plasticizer as necessary, a binder is obtained. , Coating agents and adhesive compositions can be prepared.

[0021]

According to the production method of the present invention, side reactions with isocyanate groups in the urethane prepolymer can be reduced even when an alcohol-based solvent is used, so that the target design (for example, molecular weight and molecular structure) is close. An aqueous polyurethane resin dispersion can be easily and economically produced. Further, since the aqueous polyurethane resin dispersion obtained by the method of the present invention is excellent in various properties such as adhesion, various binders such as paints and printing inks, artificial leather, plastic, glass, metal,
It can be suitably used for coatings and adhesives for various substrates such as wood, paper, floor, concrete, rubber, woven fabric and non-woven fabric.

[0022]

EXAMPLES The present invention will be specifically described below with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples. All parts and percentages are based on weight.

Example 1 A reaction vessel equipped with a stirrer, thermometer, cooling pipe and nitrogen gas inlet pipe was charged with 74.4 parts of dimethylolbutanoic acid and 615.6 parts of polytetramethylene ether glycol having a number average molecular weight of 2,000. The dimethylolbutanoic acid was completely dissolved at 100 ° C. for 1 hour under a nitrogen stream. Then, after cooling to 85 ° C., 250.0 parts of isophorone diisocyanate was charged, and the reaction was carried out at 85 ° C. for 5 hours.
0 parts were obtained. This urethane prepolymer was cooled to 70 ° C. 2140 parts of water, 14 isopropyl alcohol
The urethane prepolymer was added and dispersed in an aqueous solution comprising 0.0 parts, 50.8 parts of triethylamine and 58.9 parts of adipic dihydrazide with stirring, and reacted at 50 ° C. for 3 hours. The aqueous polyurethane resin dispersion thus obtained had a resin solid content concentration of 30% and a viscosity of 50 mPa ·
s / 25 ° C, pH 8.0, acid value of resin solids is 30mg
KOH / g. Also, as a result of GPC measurement, the number average molecular weight (polystyrene conversion) of the solid content of the polyurethane resin was determined.
Was 42,000, which was in good agreement with the theoretical value of 45,000.

Example 2 Into the same reaction vessel as in Example 1, dimethylolbutanoic acid 7 was added.
615.6 parts of polytetramethylene ether glycol having 4.4 parts and a number average molecular weight of 2,000 were charged, and dimethylolbutanoic acid was completely dissolved at 100 ° C. for 1 hour under a nitrogen stream. Then, after cooling to 85 ° C., 250.0 parts of isophorone diisocyanate was charged and reacted at 85 ° C. for 5 hours to obtain 940 parts of an isocyanate group-terminated urethane prepolymer. The urethane prepolymer was cooled to 70 ° C., the stirring was stopped, and the urethane prepolymer was allowed to stand. Then, 2140 parts of water, 140.0 parts of isopropyl alcohol, 50.8 parts of triethylamine, adipic acid dihydrazide 5
After adding 8.9 parts of an aqueous solution, stirring was started to disperse, and the mixture was reacted at 50 ° C. for 3 hours. The aqueous polyurethane resin dispersion thus obtained had a resin solid content concentration of 30.
%, Viscosity 100 mPa · s / 25 ° C., pH 8.0, acid value of resin solids was 30 mg KOH / g. G
As a result of the PC measurement, the measured value of the number average molecular weight (polystyrene conversion) of the polyurethane resin solid content was 42,000,
This was in good agreement with the theoretical value of 45000.

Comparative Example 1 Into the same reaction vessel as in Example 1, dimethylolbutanoic acid 7 was added.
615.6 parts of polytetramethylene ether glycol having 4.4 parts and a number average molecular weight of 2,000 were charged, and dimethylolbutanoic acid was completely dissolved at 100 ° C. for 1 hour under a nitrogen stream. Then, after cooling to 85 ° C., 250.0 parts of isophorone diisocyanate was charged and reacted at 85 ° C. for 5 hours to obtain 940 parts of an isocyanate group-terminated urethane prepolymer. The urethane prepolymer was cooled to 70 ° C., and then 2140 parts of water, 140.0 parts of isopropyl alcohol, 50.8 parts of triethylamine
And an aqueous solution consisting of 58.9 parts of adipic dihydrazide was added to the urethane prepolymer with stirring and dispersed.
The reaction was performed at 0 ° C. for 3 hours. The aqueous polyurethane resin dispersion thus obtained had a resin solid content concentration of 30% and a viscosity of 50%.
mPa · s / 25 ° C., pH 8.0, acid value of resin solid content was 30 mgKOH / g. As a result of GPC measurement, the actually measured value of the number average molecular weight (in terms of polystyrene) of the polyurethane resin solid was 35,000, which was 4 theoretical values.
It was devastating to 5000.

With respect to the aqueous dispersions of the polyurethane resins obtained in Examples 1 and 2 and Comparative Example 1, the following items were evaluated. Table 1 shows the results.

Adhesion: Each polyurethane resin aqueous dispersion was
Corona treated polypropylene film (OP
P), polyethylene terephthalate film (PE
T) and a nylon film (NY) treated surface using a bar coder (No. 4), followed by drying with a heat gun for 1 minute to obtain a polyurethane resin coating film. Then, an adhesive tape was applied to the coated surface, and the remaining state of the coating film when peeled off in a direction perpendicular to the coated surface was visually evaluated. ：: No peeling at all. Δ: 50% or more remained. X: Less than about 50% remained.

[0027]

[Table 1]

Continued on front page F-term (reference) 4J034 BA08 CA02 CA03 CA04 CA05 CA15 CA17 CA22 CC03 CC15 CC23 CC26 CC61 CC62 DA01 DB04 DF02 DF11 DF12 DF16 DF20 DF22 DG03 DG04 DG06 DG14 GA06 GA33 HA01 HA07 HC03 HC09 HC12 HC13 HC17 HC18 HC18 HC67 HC71 JA42 RA07 RA08

Claims (2)

[Claims] 1. A polyurethane comprising a urethane prepolymer having a carboxyl group in a molecule and an isocyanate group at a molecular terminal dispersed in an aqueous solution containing an alcohol solvent, a neutralizing agent and a chain extender. A method for producing an aqueous resin dispersion. 2. The method for producing a polyurethane resin aqueous dispersion according to claim 1, wherein the alcohol-based solvent does not contain active hydrogen for reacting with isocyanate groups (excluding alcoholic hydroxyl groups).