JP3557858B2 - Method for producing aqueous polyurethane resin dispersion - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing an aqueous polyurethane resin dispersion. The water-water dispersible polyurethane resin obtained by the present invention includes various binders such as paints, magnetic paints, printing inks, artificial leather, plastic, glass, metal, wood, paper, floor, concrete, rubber, woven fabric and nonwoven fabric. And the like, or as an adhesive for various materials such as artificial leather, plastic, glass, metal, wood, paper, floor, concrete, rubber, woven fabric and non-woven fabric.
[0002]
[Prior art]
Polyurethane resins have excellent flexibility and a wide range of adhesiveness to various substrates, and are widely used as various binders, various coating agents or various adhesives. Conventionally, such polyurethane resins have been mainly of the solvent type dissolved in an organic solvent, but in recent years, in order to respond to social trends such as resource saving, environmental protection, and tightening of regulations on organic solvents, aqueous polyurethane resins have been used. In recent years, aqueous polyurethane resin dispersions have been put to practical use.
[0003]
The aqueous polyurethane resin dispersion currently in practical use is, for example, a solution obtained by dissolving a urethane prepolymer in an organic solvent inert to isocyanate groups such as acetone and methyl ethyl ketone by dispersing in water and elongating the chain. Being manufactured. However, since organic solvents such as acetone and methyl ethyl ketone do not preferably remain in the final product, they are removed by a reduced pressure or the like at the final stage of production. Therefore, such a manufacturing method has problems such as a longer manufacturing process, a lower yield, and a higher cost than a method of manufacturing a solvent-type polyurethane resin.
[0004]
Also, a method of producing an aqueous dispersion of a polyurethane resin without using any organic solvent has been proposed (JP-A-4-31439). However, such a production method requires a special reactor completely different from the conventional reactor, and the conditions for stably obtaining an aqueous polyurethane resin dispersion are considerably restricted. With difficulties.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for easily producing a polyurethane resin aqueous dispersion without using an organic solvent such as acetone or methyl ethyl ketone.
[0006]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, when performing a neutralization step, an aqueous dispersion step, and a chain extension step on a specific urethane prepolymer, the urethane prepolymer was once treated with a monoalcohol-based solvent. It has been found that the above problem can be solved by diluting and then performing an aqueous dispersion step, and further, under specific reaction conditions, any molecular design such as increasing the molecular weight of a water-dispersible polyurethane resin is possible. Thus, the present invention has been completed.
[0007]
That is, the present invention provides a isocyanate group-terminated urethane prepolymer comprising a diol compound and a diisocyanate compound containing a polymer polyol and containing a carboxyl group, and then neutralizing the carboxyl group with a basic compound in the urethane prepolymer. In the method for producing a polyurethane resin aqueous dispersion by performing the step (1) and the aqueous dispersion step (2) and the chain extension step (3) performed sequentially or simultaneously, before performing the aqueous dispersion step (4) , and wherein said that the urethane prepolymer is provided a step of diluting the secondary or tertiary mono-alcohol solvent (4), and provided further the neutralization step (1) prior to the dilution step (4) The present invention relates to a method for producing an aqueous polyurethane resin dispersion.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, first, an isocyanate group-terminated urethane prepolymer comprising a diol compound containing a polymer polyol and a diisocyanate compound and containing a carboxyl group is produced.
[0009]
Examples of the polymer polyol component include polyether polyols such as polyethylene glycol, polypropylene glycol, and polyoxytetramethylene ether glycol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, and tetrahydrofuran; ethylene glycol, diethylene glycol, triethylene glycol, 2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol Or unsaturated known low-molecular glycols such as octanediol, 1,4-butynediol, dipropylene glycol, bisphenol A, hydrogenated bisphenol A, and adipic acid Dibasic acids such as maleic acid, 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 corresponding acids Polyester polyols obtained by dehydration condensation of anhydrides and the like; polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone and β-methyl-δ-valerolactone; other polycarbonate polyols and polybutadiene glycols And various known polymer polyols generally used in the production of polyurethane. Among these high molecular polyols, polyether polyols that can lower the viscosity of the urethane prepolymer and can be rapidly dispersed in water as a dispersion medium in the aqueous dispersion step (2) are suitable. In addition, up to 5 mol% of the low molecular weight glycol component is used for various polyols such as glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, pentaerythritol and sorbitol. Can be replaced.
[0010]
The number average molecular weight of the high molecular polyol is not particularly limited, but from the viewpoint of the flexibility of the obtained polyurethane resin film, it is usually about 500 or more, preferably 700 or more, and the water dispersibility of the urethane prepolymer is also high. From the viewpoint of the drying property of the obtained polyurethane resin, it is about 10,000 or less, preferably 5000 or less.
[0011]
In the present invention, a carboxyl group-containing diol is usually used as a diol compound in order to introduce a carboxyl group into the urethane prepolymer. Examples of the carboxyl group-containing diol include α, α′-dimethylolalkanoic acid (glyceric acid, dimethylolpropionic acid, dimethylolbutanoic acid, 2,2-dimethylolpentanoic acid, etc.), dioxymaleic acid, dioxyfumaric acid, tartaric acid , 2,6-dioxybenzoic acid, 4,4-bis (hydroxyphenyl) valeric acid, 4,4-bis (hydroxyphenyl) butyric acid, etc., and ε-caprolactone, γ-butyrolactone using these carboxyl group-containing diols as initiators. And lactones such as γ-valerolactone obtained by ring-opening polymerization. Such a carboxyl group-containing diol is usually used as a diol component for producing a urethane prepolymer together with the above-mentioned polymer polyol. However, such a carboxyl group-containing diol as obtained by ring-opening polymerization of a lactone is used. In the case where the diol itself can be used as a polymer polyol, only the carboxyl group-containing diol can be used as the diol compound.
[0012]
As the diisocyanate compound, various known aromatic, aliphatic, or alicyclic diisocyanates can be used. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3- Phenylene diisocyanate, 1,4-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 Carboxyl groups of isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate and dimer acid were converted to isocyanate groups. Dimer isocyanate is a typical example.
[0013]
In the production of the isocyanate group-terminated urethane prepolymer containing a carboxyl group, the diol compound and the diisocyanate compound are reacted so that the isocyanate group equivalent of the diisocyanate compound is greater than the hydroxyl equivalent of the diol compound. The reaction is usually performed in the absence of a solvent, and the reaction temperature, the reaction time, and the presence or absence of the urethanization catalyst may be appropriately determined according to the reactivity. The amount of the carboxyl group-containing diol in the diol compound is not particularly limited, but the acid value in 1 g of the resin solid content of the polyurethane resin is 5 or more in order to obtain an aqueous dispersion of the polyurethane resin having good dispersion stability. It is preferable that the acid value be 100 or less from the viewpoint of water resistance of the obtained polyurethane resin.
[0014]
Next, the obtained urethane prepolymer is subjected to a step (1) of neutralizing a carboxyl group with a basic compound, an aqueous dispersion step (2) and a chain elongation step (3) to be carried out sequentially or simultaneously, respectively, to give a polyurethane resin water. Although the production of dispersions, a step (4) diluting the secondary or tertiary mono-alcohol solvent of the urethane prepolymer before applying said aqueous dispersion step (2) is provided in the present invention, and, the dilution The neutralization step (1) is further provided before the step (4) .
[0015]
The diluting step (4 ) was performed before the water dispersing step (2) was performed on the urethane prepolymer because the urethane prepolymer having a remarkably high viscosity in a solventless state was reduced in viscosity, and the monoalcohol-based solvent was used. This is because the dispersion in water, which is a dispersion medium, in the water dispersion step (2) is rapidly performed by utilizing the hydrophilicity. Further, the monoalcohol-based solvent does not need to be removed from a final product using a polyurethane resin obtained like an organic solvent such as acetone or methyl ethyl ketone. It should be noted that a very high-viscosity urethane prepolymer using no mixture of water and a monoalcohol solvent as a dispersion medium in the aqueous dispersion step (2) without the dilution step (4) before the aqueous dispersion step (2) . And water are not promptly and uniformly mixed, resulting in a partial increase in the molecular weight due to the reaction between water and isocyanate groups, and a stable aqueous polyurethane resin dispersion cannot be obtained.
[0016]
Various solvents can be used as the monoalcohol solvent used in the dilution step (4) , but those having a solubility in water at 25 ° C. of 5% by weight or more are preferable for prompt dispersion in water.
[0017]
Further, a secondary or tertiary monoalcohol solvent is preferable because the reaction rate with the terminal isocyanate group in the urethane prepolymer is low. Further, as the secondary or tertiary monoalcohol-based solvent, those not having an active hydrogen which is reactive to an isocyanate group in addition to an alcoholic hydroxyl group are preferable. According to such a secondary or tertiary monoalcohol solvent, the consumption of terminal isocyanate groups in the urethane prepolymer in the dilution step (4) is small, and the prepolymers can be linked to each other to increase the molecular weight. Therefore, any molecular design such as increasing the molecular weight of the polyurethane resin in the chain elongation step (3) is possible, and the dispersion in water in the water dispersing step (2) can be performed promptly. An aqueous resin dispersion can be obtained.
[0018]
Examples of the secondary or tertiary monoalcohol solvents satisfying the above conditions include isopropyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, sec-amyl alcohol, diacetone alcohol and the like.
[0019]
The monoalcohol-based solvent used in the dilution step (4) can be used alone or in combination of two or more, and the amount of use is not particularly limited, but is usually about 3% by weight or more, preferably about 3% by weight, based on the urethane prepolymer. Uses 10% by weight or more. Further, in order to suppress the reaction between the terminal isocyanate group of the urethane prepolymer and the hydroxyl group of the alcohol solvent, about 30% by weight or less, preferably about 25% by weight or less based on the urethane prepolymer is used. The temperature of the dilution step (4) is not particularly limited, but is preferably 50 ° C. or lower in order to reduce the reaction rate between the isocyanate group in the urethane prepolymer and the alcoholic hydroxyl group of the alcoholic solvent. The temperature of the dilution step (4) is usually equal to or higher than normal temperature.
[0020]
In this way the present invention, is carried out dilution step (4) prior to applying the aqueous dispersion step (2), a urethane prepolymer rapidly dispersed in water dispersion step (2), to obtain a stable aqueous polyurethane dispersion Preferably, the neutralization step (1) is performed before the water dispersion step (2) . When the dilution step (4) is performed after the neutralization step (1) , the reactivity between the isocyanate group in the urethane prepolymer and the alcoholic hydroxyl group of the alcoholic solvent tends to be slow, which is preferable.
[0021]
In the neutralization step (1) , examples of the basic compound used for neutralizing the carboxyl group in the urethane prepolymer include alkali metals such as potassium hydroxide and sodium hydroxide, ammonia or trimethylamine, triethylamine, and triisopropylamine. And tertiary amines such as tributylamine, triethanolamine, N-alkyldiethanolamine, and N, N'-dialkylmonoethanolamine. These basic compounds can be used alone or in combination of two or more. In the neutralization of the carboxyl group, a basic compound is used in an amount of about 0.5 to 1.5 equivalents relative to 1 equivalent of the carboxyl group contained in the prepolymer (hereinafter, the neutralization ratio is 50 to 150%. Is preferred). When the neutralization ratio is lower than 50%, the dispersion stability of the obtained polyurethane resin aqueous dispersion is not sufficient, and when it is higher than 150%, the viscosity of the system at the time of aqueous dispersion tends to increase. The temperature at which the neutralization is performed is not particularly limited, but is usually about 20 to 70 ° C.
[0022]
The aqueous dispersion step (2) is not particularly limited, for example, a method of adding and dispersing water to a urethane prepolymer diluted with an alcohol solvent, or a method of adding and dispersing a urethane prepolymer diluted in water. Etc. can be adopted.
[0023]
In addition, the chain elongation step (3) is carried out with a chain elongation agent and a chain length terminator used as needed. Examples of the chain extender include various known low molecular weight glycols listed in the description of the polyester diol; ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4 Examples include amines such as' -diamine and water. In addition, in a molecule such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine. Diamines having a hydroxyl group; dimer diamines obtained by converting a carboxyl group of a dimer acid into an amino group are also typical examples. Examples of the chain terminator include monoamines such as monobutylamine and dibutylamine; monoamines having a hydroxyl group such as monoethanolamine and diethanolamine; monoalcohols having a primary alcoholic hydroxyl group such as ethanol and n-butanol.ル, and the like.
[0024]
Since the water dispersing step (2) and the chain elongation step (3) are performed sequentially or simultaneously, the chain extender and the chain terminator used as necessary are added in advance to the water used for dispersing the urethane prepolymer in water. Or may be added after the urethane prepolymer is dispersed in water. The chain terminator can be added at the time of or after the aqueous dispersion of the urethane prepolymer, or may be added before or after the neutralization step (1) or the dilution step (4) .
[0025]
The average molecular weight of the water-dispersible polyurethane resin thus obtained can be appropriately determined according to the use of the resin. However, when the resin is used in a field where the film strength of the resin is required, the weight average molecular weight should be 5000 or more. preferable.
[0026]
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 and the like. Usually, it is practically preferable to adjust the solid concentration to 15 to 60% by weight and the viscosity to 10 to 100000 cps / 25 ° C.
[0027]
When the aqueous polyurethane resin dispersion of the present invention is provided for various uses, for example, water, various pigments and the like are added to the aqueous polyurethane resin dispersion of the present invention, and then mixed or dispersed according to a known method. Then, if necessary, additives such as an antiblocking agent and a plasticizer are appropriately blended to prepare the binder, coating agent and adhesive composition.
[0028]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, a polyurethane resin aqueous dispersion can be easily manufactured, without going through an inefficient solvent removal process. Further, by setting specific conditions in each step, an arbitrary molecular design such as increasing the molecular weight of the polyurethane resin is possible, and the production method is excellent in reproducibility. By setting specific conditions in each step, a polyurethane resin aqueous dispersion having excellent stability can be obtained.
[0029]
【Example】
Hereinafter, the present invention will be described specifically 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.
[0030]
Example 1
25.3 parts of dimethylolbutanoic acid and 334.5 parts of polytetramethylene ether glycol having a number average molecular weight of 2,000 were charged into a reaction vessel equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen gas inlet pipe, and then charged under a nitrogen stream. Dimethylolbutanoic acid was completely dissolved at 1 ° C. for 1 hour. Then, after cooling to 85 ° C, 120.2 parts of isophorone diisocyanate was charged and reacted at 85 ° C for 5 hours to obtain 480 parts of a urethane prepolymer having an isocyanate group end. This urethane prepolymer was neutralized by adding 17.3 parts of triethylamine at 50 ° C. (neutralization ratio: 100%), and then 84.7 parts of isopropyl alcohol was charged to obtain a uniform urethane prepolymer isopropyl alcohol solution. Then, 1078 parts of water was added with stirring at 40 ° C, and after dispersion, 23.2 parts of isophoronediamine was added and reacted at 40 ° C for 3 hours to obtain an aqueous dispersion A of a polyurethane resin. This aqueous dispersion A had a resin solid content of 30%, a viscosity of 25 cps / 25 ° C., and a pH of 8.2, and the dried resin had a resin acid value of 20.
[0031]
Example 2
In a reaction vessel similar to that of Example 1, 128.3 parts of Praxel 205BA (adduct of dimethylolbutanoic acid with ε-caprolactone: number average molecular weight 500; manufactured by Daicel Chemical Industries, Ltd.) and 128.3 parts of polypropylene glycol 221 having a number average molecular weight of 2000 .2 parts and 130.5 parts of isophorone diisocyanate were charged and reacted at 85 ° C. for 5 hours under a nitrogen stream to obtain 480 parts of an isocyanate group-terminated urethane prepolymer. The urethane prepolymer was neutralized by adding 25.9 parts of triethylamine at 50 ° C. (neutralization ratio: 100%), and then 120.0 parts of isopropyl alcohol was charged to obtain a uniform prepolymer isopropyl alcohol solution. Then, a mixture of 1147 parts of water, 18.5 parts of isophoronediamine, and 1.9 parts of diethylenetriamine was added at 35 ° C. with stirring, and after dispersion, the mixture was reacted at 35 ° C. for 3 hours to obtain an aqueous dispersion of a polyurethane resin. B was obtained. The aqueous dispersion B had a resin solid content of 28%, a viscosity of 380 cps / 25 ° C., and a pH of 8.3, and the dried resin had a resin acid value of 29.
[0032]
Example 3
In a reaction vessel similar to that in Example 1, 38.0 parts of dimethylolbutanoic acid, 149.1 parts of polypropylene glycol having a number average molecular weight of 3,000, and 149.1 parts of polybutylene adipate having a number average molecular weight of 2,000 were charged. Dimethylolbutanoic acid was completely dissolved at 1 ° C. for 1 hour. Then, after cooling to 85 ° C., 143.8 parts of isophorone diisocyanate was charged and reacted at 85 ° C. for 5 hours under a nitrogen stream to obtain 480 parts of an isocyanate group-terminated urethane prepolymer. This prepolymer was neutralized by adding 25.9 parts of triethylamine at 50 ° C. (neutralization ratio: 100%), and then 53.3 parts of tert-butyl alcohol was charged to obtain a uniform tert-butyl alcohol solution of the prepolymer. . Then, a mixture of 1106 parts of water, 21.1 parts of isophoronediamine, and 3.6 parts of diethylenetriamine was added at 45 ° C. with stirring, and after dispersion, the mixture was reacted at 45 ° C. for 3 hours to obtain an aqueous dispersion of a polyurethane resin. C was obtained. The aqueous dispersion C had a resin solid content of 30%, a viscosity of 110 cps / 25 ° C., and a pH of 8.0, and the dried resin had a resin acid value of 29.
[0033]
Comparative Example 1
In Example 3, after neutralization with triethylamine, tert-butyl alcohol was mixed with water, isophoronediamine and diethylenetriamine and added without diluting the prepolymer with tert-butyl alcohol before dispersing in water. Except for this, an attempt was made to produce an aqueous dispersion of the polyurethane resin in the same manner as in Example 3, but the dispersion was not uniform during the aqueous dispersion, and immediately separated when the stirring was stopped and allowed to stand.
[0034]
Comparative Example 2
In Example 2, after neutralization with triethylamine, 1163 parts of water was added under stirring at 40 ° C. without dilution with isopropyl alcohol before water dispersion, and an aqueous dispersion of a polyurethane resin was produced. When the stirring was stopped and the mixture was allowed to stand without being uniformly dispersed, the mixture immediately separated.
[0035]
The following items were evaluated for the aqueous dispersions of the polyurethane resins obtained in Examples 1 to 3 above. Table 1 shows the results of the above evaluation.
[0036]
Weight average molecular weight: measured by GPC in terms of polystyrene.
[0037]
Stability: After the aqueous dispersion of the polyurethane resin was allowed to stand at 40 ° C. for 30 days, a change in state was evaluated according to the following criteria.
：: No change.
×: Separation or precipitation has occurred.
[0038]
[Table 1]

Claims (4)

After producing an isocyanate group-terminated urethane prepolymer comprising a diol compound and a diisocyanate compound containing a high molecular polyol, and containing a carboxyl group, the urethane prepolymer is subjected to a neutralization step of a carboxyl group with a basic compound (1) . , sequentially or simultaneously performing water dispersion step (2) and chain elongation step (3) a process for preparing the polyurethane resin water dispersion by subjecting each, the urethane prepolymer before applying said aqueous dispersion step (2) Is provided with a step (4) of diluting with a secondary or tertiary monoalcohol solvent, and the neutralization step (1) is further provided before the dilution step (4). Liquid production method. The method for producing an aqueous polyurethane resin dispersion according to claim 1, wherein the solubility of the secondary or tertiary monoalcohol solvent in water at 25 ° C is 5% by weight or more. The method for producing an aqueous polyurethane resin dispersion according to claim 1 or 2 , wherein the amount of the secondary or tertiary monoalcohol solvent used is 3 to 30% by weight based on the urethane prepolymer. The process according to claim 1, 2 or 3 polyurethane resin water dispersion according temperature is 50 ° C. the following dilution step (4).