JP3792669B2 - Method for producing aqueous polyurethane resin dispersion and aqueous polyurethane resin dispersion - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an aqueous polyurethane resin dispersion and an aqueous polyurethane resin dispersion.
[0002]
[Prior art]
As a method for producing a water-based polyurethane resin dispersion, conventionally, a batch-type emulsifier such as a homomixer, a homogenizer, or an ultrasonic emulsifier is used to produce a dispersion for each batch, or a line mill, a colloid mill, or the like. A method for continuously producing a dispersion using a continuous emulsifier is known.
[0003]
However, in the method using a continuous emulsifier, the emulsified state of the dispersion is adjusted by the rotation speed, the slit interval, etc., but the emulsified state remains insufficient when the viscosity of the mixed liquid changes. May be discharged.
[0004]
Further, in the method using a batch emulsifier, it is necessary to add a large amount of an emulsifier and it is difficult to obtain a dispersion having a fine particle size.
[0005]
Therefore, as a method for obtaining a fine dispersion, a method of introducing a premixed mixture of water and a polyurethane resin solution into a chamber under pressure and causing the mixture to collide to emulsify (Patent Document 1) has been studied.
[0006]
[Patent Document 1]
JP-A-5-132567 [0007]
However, the method described in Patent Document 1 requires a device that can withstand high pressure, so that the device is expensive and it is difficult to scale up for mass processing.
[0008]
[Problems to be solved by the invention]
Therefore, in view of the above problems, the object of the present invention is to produce a dispersion while confirming a sufficient emulsified state, and to use a batch-type emulsifier that is easy to scale up, and to efficiently disperse a finer dispersion than before. It is an object of the present invention to provide a method for producing an aqueous polyurethane resin dispersion that can be produced, and a fine aqueous polyurethane resin dispersion obtained by the production method.
[0009]
[Means for Solving the Problems]
As a result of intensive studies in view of the above problems, the present inventors have rapidly increased the viscosity of the liquid at the phase inversion point when water is added to the polyurethane resin solution, and as a result, the stirring state in the stirring tank It is found that a dispersion with a fine particle size can be obtained by efficiently stirring the liquid mixture at this phase inversion point. The headline and the present invention were completed.
[0010]
That is, the method for producing a water-based polyurethane resin dispersion of the present invention is a method for producing a water-based polyurethane resin dispersion in which a mixed liquid containing water and a polyurethane resin solution is stirred in a stirring tank, and the polyurethane resin is emulsified and dispersed in water. In addition, stirring is performed while adding water to the polyurethane resin solution, and when stirring, a stirring blade having a diameter of 35 to 95% with respect to the inner diameter of the stirring tank has a depth of the mixed liquid in the stirring tank. On the other hand, it occupies a height of 40% or more.
In the present invention, the depth of the mixed liquid refers to the depth of the mixed liquid when emulsification is completed.
[0011]
When the mixing ratio of water with respect to the polyurethane resin solution is increased, the viscosity of the mixed solution increases rapidly immediately before emulsification (phase inversion point), and once the emulsification is completed, the viscosity decreases rapidly again. . Therefore, the phase inversion point is obtained by stirring in a state where a stirring blade having a diameter of 35 to 95% with respect to the inner diameter of the stirring tank occupies a height of 40% or more with respect to the depth of the mixed liquid in the stirring tank. In this case, even when the viscosity of the liquid mixture suddenly increases, the whole liquid mixture is efficiently stirred, so that it is easy to obtain finer emulsified particles.
[0012]
Further, the method for producing an aqueous polyurethane resin dispersion of the present invention is the method for producing an aqueous polyurethane resin dispersion, wherein the polyurethane resin solution is stirred while adding water, and the emulsification is completed during the stirring. The stirring resistance is measured in order to determine the timing.
[0013]
As described above, when the mixing ratio of water with respect to the polyurethane resin solution is increased, the viscosity of the mixed solution rapidly increases immediately before emulsification, and when the emulsification is completed, the viscosity decreases rapidly again. If stirring resistance is measured during stirring, the peak of stirring resistance can be detected, and the timing of completion of emulsification can be easily determined by detecting the peak.
[0014]
Further, the method for producing an aqueous polyurethane resin dispersion according to the present invention is the method for producing an aqueous polyurethane resin dispersion, wherein the polyurethane resin solution is stirred while adding water, and the temperature of the added water is adjusted from the mixed solution. Also, the temperature of the mixed liquid is controlled by lowering the temperature.
[0015]
As described above, since the viscosity of the mixed solution rapidly increases at the phase inversion point, it has been difficult to suppress local heat generation by the conventional cooling method, but the aqueous polyurethane resin dispersion of the present invention has According to the manufacturing method, since the temperature is controlled by adding water at a temperature lower than that of the mixed solution, local heat generation can be effectively prevented, and the temperature of the mixed solution can be easily controlled. Further, if local heat generation is prevented, it is possible to prevent the emulsion from reacting to cause aggregation and gelation of particles.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 schematically shows an embodiment of a stirring device used for stirring a mixed solution containing water and a polyurethane resin solution in one embodiment of the present invention. As shown in FIG. 1, the stirring device 1 includes a stirring tank 2 having an inner diameter D, and a stirring blade 3 immersed in a mixed solution (water and polyurethane resin solution) in the stirring tank 2.
The stirring blade 3 is a flat plate having a diameter d of 35 to 95% with respect to the inner diameter D of the stirring tank 2, and with respect to the depth H of the mixed solution charged into the stirring tank 2 when emulsification is completed. And occupies a height h of 40% or more. For example, as shown in FIG. 1, the flat stirring blade 3 has a large number of rectangular openings formed therein.
[0017]
The shaft of the stirring blade 3 is connected to a motor (not shown), and the motor is connected to the power supply device via a load measuring device (for example, an ammeter) capable of measuring a load required for rotation. It is connected. That is, the stirring resistance when stirring while adding water is configured so that it can be measured at any time by the load measuring device.
[0018]
A procedure for producing a water-based polyurethane resin dispersion using the stirring device 1 will be described. First, a predetermined amount of a polyurethane resin solution in which a polyurethane resin is dissolved in a solvent is charged into the stirring tank 2. The relationship between the depth H of the liquid 5 and the height h of the stirring blade 3 at this time is not particularly limited, but when the phase inversion point is reached, In order to satisfy the relationship, the range should be calculated backward from the approximate mixing ratio of water and polyurethane resin solution.
[0019]
Then, water is gradually added while stirring the solution by rotating the stirring blade 3. The temperature of the water to be added is preferably set to 10 to 40 ° C. lower than the temperature of the mixed solution in the stirring tank 2 and added while controlling the temperature of the mixed solution to be constant. For example, when the temperature of the liquid mixture tends to increase, the temperature of the liquid mixture tends to decrease by increasing the flow rate of the water to be added or further decreasing the temperature of the water to be added. Controls the temperature of the mixed liquid to be constant by reducing the flow rate of the water to be added or by increasing the temperature of the water to be added.
[0020]
Thus, when water is added to the polyurethane resin solution, the viscosity of the mixed solution suddenly increases when the ratio of water to the polyurethane resin solution is generally within a range of 0.3 to 1.5, and water is added to the polyurethane resin solution. Changes from a dispersed state (W / O type) to a dispersed state of polyurethane resin solution in water (O / W type) (also referred to as phase inversion). Further, by adding a small amount of water, the emulsification is completed, the polyurethane resin dispersion becomes stable, and the viscosity of the mixed solution rapidly decreases.
[0021]
FIG. 2 shows an example of the result of measuring the relationship between the ratio of water to the polyurethane resin solution and the viscosity of the mixed solution. As is clear from FIG. 2, the mixed solution of the polyurethane resin solution and water is in a low-viscosity state of less than 1000 mPa · s in almost the entire region except the vicinity of the phase inversion point. Although it is a narrow range, it can be seen that a high viscosity of about 9500 mPa · s has been reached.
[0022]
According to the method for producing the aqueous polyurethane resin dispersion of the present embodiment, the stirring blade having a diameter d of 35 to 95% with respect to the inner diameter D of the stirring tank 2 is 40% or more with respect to the depth H of the mixed solution. Since the mixture is stirred in a state of occupying a large amount of water, it is possible to efficiently stir the liquid mixture having a high viscosity in the vicinity of the phase inversion point. As a result, the emulsion particles of the polyurethane resin can be atomized. Is possible.
[0023]
In addition, in this embodiment, the viscosity of the mixed liquid suddenly increases and decreases (also referred to as a viscosity peak) in this embodiment, the peak of the stirring resistance of the stirring blade 3, that is, the load of the stirring motor. Therefore, the completion of emulsification can be easily detected by adding water while measuring the stirring resistance.
[0024]
Furthermore, in order to control the temperature by supplying water at a temperature lower than that of the mixed liquid in the stirring tank 3, when cooling by providing a jacket on the outer periphery of the stirring tank as in the prior art, a cooling pipe is provided in the stirring tank. Compared with the case where it cools, it becomes possible to cool a liquid mixture more directly. Therefore, even when the viscosity suddenly increases at the phase inversion point, local heat generation is effectively prevented in combination with the effect of using the stirring blade as described above.
In addition, although the method of cooling and adding a polyurethane resin solution is also considered, since the viscosity of a polyurethane resin solution increases and mixing with water becomes difficult, it is not preferable in this invention.
[0025]
The stirring blade used in the present invention may be a portion having a diameter of 35 to 95% with respect to the inner diameter of the stirring tank as long as it occupies 40% or more with respect to the depth of the mixed liquid when emulsification is completed. It is not necessarily limited to the stirring blade of the said embodiment.
Therefore, for example, in the blades separated vertically as shown in FIG. 3, the sum of the heights h1 and h2 of the portion having a diameter d of 35 to 95% with respect to the inner diameter of the stirring tank is the mixing at the time of completion of emulsification What is necessary is just to stir in the state which occupies 40% or more with respect to the depth H of a liquid.
[0026]
Further, the blade shape and angle of the stirring blade are not particularly limited, and when a plurality of stirring blades are provided with respect to the shaft, they may be provided at different angles.
[0027]
Further, as the stirring blade used in the present invention, a helical type (spiral type) can be adopted. That is, in the case of a helical stirring blade, the outer diameter of the helical blade is 35 to 95% with respect to the inner diameter of the stirring tank, and the helical blade occupies 40% or more with respect to the depth of the mixed liquid. What is necessary is just to be provided with the length of a certain axial direction, and to extend spirally.
[0028]
Moreover, as a commercially available stirring blade, a Max blend blade (manufactured by Sumitomo Heavy Industries, Ltd.), a full zone blade (manufactured by Shinko Pantec) or the like can be suitably used in the present invention.
[0029]
Examples of the aqueous polyurethane resin produced by applying the production method of the present invention include those in which an anionic, cationic or nonionic hydrophilic group is introduced into the urethane resin skeleton and self-emulsified and dispersed, or hydrophobic What is emulsified and dispersed by adding a surfactant to a urethane resin can be targeted.
[0030]
As the polyisocyanate constituting the polyurethane resin, conventionally used aromatic, aliphatic, and alicyclic polyisocyanates can be used. For example, naphthalene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, hydrogen Polyisocyanates such as added diphenylmethane diisocyanate, diphenylmethane diisocyanate, and tolylene diisocyanate can be used.
[0031]
Moreover, as a polyol which comprises the said polyurethane resin, a well-known thing can be used and it has two or more hydroxyl groups in molecules, such as polyether, polyester, polyetherester, polythioether, polyacetal, polybutadiene, polysiloxane. Compounds can be used.
[0032]
Examples of the polyol include ethylene glycol, diethylene glycol, butanediol, propylene glycol, hexanediol, bisphenol A, bisphenol B, bisphenol S, hydrogenated bisphenol A, dibromobisphenol A, 1,4-cyclohexanedimethanol, dihydroxyethyl. Polyhydric alcohols such as ethyl terephthalate, hydroquinone dihydroxyethyl ether, trimethylolpropane, glycerin and pentaerythritol; alkylene derivatives of these polyhydric alcohols; polyhydric alcohols or alkylene derivatives, polyhydric carboxylic acids, polyhydric carboxylic anhydrides Or an ester compound with a polycarboxylic acid ester; polycarbonate polyol, polytetramethylene glycol, polycap Lactone polyols, polybutadiene polyols, polythioether polyols, polyacetal polyols, fluorine polyol, silicon polyol, castor oil polyol, and acrylic polyol.
[0033]
The solvent constituting the polyurethane resin solution is an organic solvent (so-called reaction solvent) added mainly for the purpose of reaction control and viscosity reduction in polyurethane production, and is not particularly limited. Examples of the solvent include aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran, acetates such as ethyl acetate and butyl acetate, and amides such as dimethylformamide.
The solvent may be distilled off after obtaining the aqueous polyurethane resin dispersion according to the present invention.
[0034]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.
[0035]
Example 1
After dehydrating a mixture of 1.2 parts by weight of 1,2-polybutadiene polyol as a polyol and 2.5 parts by weight of a polyester polyol by a known method, 4.5 parts by weight of methyl ethyl ketone is added as a reaction solvent and sufficiently stirred. A polyurethane resin solution was prepared by adding naphthylene diisocyanate as a polyisocyanate in an equivalent ratio of 1: 2 with respect to the polyol and causing the reaction. When the polyurethane resin solution was cooled to 50 ° C., it was a solution containing 56% non-volatile content.
The polyurethane resin solution (2.0 kg) was charged into a stirring tank having an inner diameter D of approximately 18 cm, and a stirring blade (full zone manufactured by Shinko Pantec Co., Ltd., diameter: 14 cm) was stirred at 160 rpm, and the power required for stirring was measured. 2.4 kg of water cooled to ° C. was gradually added over 10 minutes. When the whole amount of water is added (when emulsification is completed), the stirring blade having a diameter of 35 to 95% with respect to the inner diameter of the stirring tank occupies a height of 80% with respect to the depth of the mixed liquid. It was in a state.
[0036]
As a result, the power required for stirring was 8 W before the addition of water, the maximum value was 33 W when the ratio of water to the polyurethane resin solution was 1.1, and the resistance rapidly increased when the ratio was 1.2. It decreased to 7W.
[0037]
Further, when the viscosity of the mixed solution was measured with a BM viscometer in each state, it was 830 mPa · s before the addition of water, 9400 mPa · s when the resistance was the highest, and 640 mPa · s after the emulsification.
[0038]
Thereafter, the resulting emulsified liquid mixture was further subjected to reduced pressure treatment to remove methyl ethyl ketone as a solvent, and the particle size was measured using a laser diffraction particle size distribution device (SALD-2100, manufactured by Shimadzu Corporation). It was confirmed that a fine polyurethane resin dispersion having a particle size of 0.20 μm was obtained.
[0039]
Comparative Example 1
When the full-zone blade is replaced with a paddle blade (diameter 9 cm) and all of the water is added, the stirring blade having a diameter of 35 to 95% with respect to the inner diameter of the stirring tank is 10% of the depth of the mixed liquid. A polyurethane resin dispersion was produced in the same manner as in Example 1 except that the height was occupied.
[0040]
As a result, the polyurethane resin and water were not sufficiently stirred and mixed, and could not be emulsified. The height h / H occupied by the stirring blade with respect to the depth of the mixed solution when the stirring resistance reached the maximum was 11%.
[0041]
Comparative Example 2
As a stirring device, a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd., TK homomixer MARK II 10) has a diameter of 35 to 95% with respect to the inner diameter of the stirring tank when all the water is added. Polyurethane in the same manner as in Example 1 except that the stirring blade occupies a height of 20% with respect to the depth of the mixed solution and that the water to be added is cooled at a room temperature with a jacket. A resin dispersion was prepared.
[0042]
As a result, the power required for stirring was 12 W before the addition of water, the maximum value was 60 W when the ratio of water to the polyurethane resin solution was 1.1, and the resistance rapidly increased when the ratio was 1.2. It decreased to 10W.
[0043]
Further, when the viscosity of the mixed solution was measured with a BM viscometer in each state, it was 830 mPa · s before the addition of water, 8200 mPa · s when the resistance was the highest, and 520 mPa · s after the emulsification.
[0044]
Thereafter, the obtained emulsified liquid mixture was further subjected to reduced pressure treatment to remove methyl ethyl ketone as a solvent. As a result, the obtained emulsion contained a gelled product of several mm. The particle diameter of the polyurethane resin dispersion was 0.32 μm.
[0045]
【The invention's effect】
As described above, according to the method for producing a water-based polyurethane resin dispersion according to the present invention, even when a batch type emulsifier is used, it is possible to efficiently produce a finer dispersion than before. .
[0046]
The aqueous polyurethane resin dispersion of the present invention is a polyurethane resin dispersed in a finer state than before.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a stirring device used in the present invention.
FIG. 2 is a graph showing an example of measurement results for the relationship between the mixing ratio of water to the polyurethane resin solution and the viscosity of the mixed solution.
FIG. 3 is a cross-sectional view showing another embodiment of the stirring device used in the present invention.
[Explanation of symbols]
1 Stirrer 2 Stirrer 3 Stirring Blade

Claims (1)

In the method for producing an aqueous polyurethane resin dispersion in which a mixed liquid containing water and a polyurethane resin solution is stirred in a stirring vessel, and the polyurethane resin is emulsified and dispersed in water.
While adding water of the polyurethane resin solution was stirred, during 攪拌is the depth of the mixture stirring blade of the stirring vessel having a 35% to 95% of the rotational diameter relative to the inner diameter of the stirring vessel On the other hand, the temperature of the liquid mixture is controlled by measuring the agitation resistance to determine the timing of completion of emulsification, and by setting the temperature of the water to be added to be lower than that of the liquid mixture. method of manufacturing an aqueous polyurethane resin dispersion which is characterized in that.

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