JPH10338730A - Production of urethane emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for rapidly and stably producing a urethane emulsion capable of giving a high-molecular weight urethane polymer. SOLUTION: This method for producing a urethane emulsion comprises that a urethane prepolymer A bearing carboxyl group and/or sulfonic acid group and also bearing isocyanate group is dispersed in water, a chain extender B consisting of a compound bearing two or more amino groups is then added to the resulting dispersion to carry out a chain extension reaction, and then a desolvation is conducted; wherein the chain extender consists of the compound bearing two or more amino groups in an amount corresponding to 0.9-0.98 equivalent of the remaining isocyanate group in the urethane prepolymer A, the chain extension reaction is carried out via an aging process at 45-80 deg.C, and the desolvation is conducted under the agitation of an agitating blade at a circumferential rate of 0.2-1.0 m/s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a urethane emulsion capable of rapidly and stably obtaining a high molecular weight urethane polymer.

[0002]

2. Description of the Related Art Urethane emulsions are widely used as paints, adhesives, adhesives, coatings and the like. Various methods have been proposed for producing urethane emulsions, for example, Japanese Patent Application Laid-Open No. 5-320321.
There is a prepolymer mixing method as disclosed in Japanese Patent Application Laid-Open Publication No. H10-260, 1988. In this prepolymer mixing method, in the presence of an organic solvent, a urethane prepolymer having an isocyanate group is dispersed in water, and then a chain extender is added to perform a chain extension reaction, and thereafter, the solvent is removed. This is a method for obtaining a urethane emulsion.

[0003] In the prepolymer mixing method, a compound having two or more amino groups is used as a chain extender. Since a compound having two or more amino groups is much more reactive than a water molecule or the like which can be a chain extender, the compound can perform a chain extension reaction in a short time.

[0004] However, in the prepolymer mixing method, since water molecules exist as a dispersion medium, the water molecules react with isocyanate groups, thereby causing a chain extension reaction with low reactivity. .
For this reason, a chain extension reaction by a compound having two or more amino groups and a chain extension reaction by a water molecule become a competitive reaction.

Therefore, if a compound having two or more amino groups as a chain extender is added in an amount equivalent to the remaining isocyanate groups in the urethane prepolymer, a part of the remaining isocyanate groups will react with water molecules. Eventually, the amino groups of the compound having two or more amino groups are left by the remaining isocyanate groups that have reacted with the water molecules. If the amino group remains in this way, it is theoretically considered that the urethane prepolymer continues to undergo a chain extension reaction and becomes higher in molecular weight.
The resulting urethane polymer has a low molecular weight.

Therefore, the amount of the compound having two or more amino groups is reduced to 0.90 to 0.98 equivalents of the remaining isocyanate groups of the urethane prepolymer, and the remaining remaining isocyanate groups are reduced by water molecules. It has been attempted to increase the molecular weight of the obtained urethane polymer as much as possible by performing a chain extension reaction.

However, also in this case, carbon dioxide molecules are produced as a by-product during the chain extension reaction between the water molecules and the remaining isocyanate groups, so that vigorous foaming occurs in the subsequent solvent removal step such as distillation under reduced pressure. As a result, it has been difficult to obtain a urethane emulsion from which the solvent has been stably removed.

[0008]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a rapid and stable method for producing a urethane emulsion from which a high molecular weight urethane polymer can be obtained.

[0009]

According to the present invention, a urethane prepolymer (A) having at least one of a carboxyl group and a sulfonic acid group and having an isocyanate group is dispersed in water, and then the two A method for producing a urethane emulsion, in which a chain extender (B) comprising a compound having an amino group as described above is added to carry out a chain extension reaction, and thereafter the solvent is removed, wherein the chain extender (B) comprises The urethane prepolymer (A) comprises a compound having two or more amino groups in an amount equivalent to 0.9 to 0.98 equivalents of the remaining isocyanate groups in the urethane prepolymer (A). This is a method for producing a urethane emulsion in which a solvent is passed through an aging step at a temperature of 0 ° C., and the solvent is removed under stirring with a stirring blade having a peripheral speed of 0.2 to 1.0 m / sec. Hereinafter, the present invention will be described in detail.

In the present invention, first, the urethane prepolymer (A) is dispersed in water. The urethane prepolymer (A) is, for example, a compound (a) having at least one of a carboxyl group and a sulfonic acid group and having at least two functional groups having active hydrogen capable of reacting with an isocyanate group. , Polyisocyanate compound (b)
And a compound (c) having two or more functional groups having active hydrogen capable of reacting with an isocyanate group.

As the compound (a), for example, a polyhydroxy compound having at least one of a carboxyl group and a sulfonic acid group in the molecule can be used. Such polyhydroxy compounds are not particularly limited, and include, for example, 2,2-dimethylol lactic acid, 2,2
-Dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, 3,4-diaminobutanesulfonic acid, 3,
6-diamino-2-toluenesulfonic acid and the like.

At least one of a carboxyl group and a sulfonic acid group introduced into the urethane prepolymer (A) by the compound (a) is at least 5 mmol per 100 g of the solid content of the urethane prepolymer (A). Is preferred. When the amount is less than 5 mmol, it is difficult to disperse the urethane prepolymer (A) in water, and the resulting urethane emulsion has poor physical properties such as adhesiveness.

As the compound (b), for example, an organic polyisocyanate used in the production of a usual urethane resin can be used. The organic polyisocyanate may be either aliphatic or aromatic.
Such organic polyisocyanate is not particularly limited, and examples thereof include 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate,
2,4-trimethylhexamethylene diisocyanate,
3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexyl-2,4-diisocyanate, methylcyclohexyl-
2,6-diisocyanate, xylylene diisocyanate, 1,3-bis (isocyanate) methylcyclohexane, tetramethylxylylene diisocyanate, transcyclohexane-1,4-diisocyanate, lysine diisocyanate, 2,4-toluylene diisocyanate, 2,6 -Toluylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 1,5-naphthene diisocyanate, tolidine diisocyanate, diphenylmethylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, etc. Diisocyanates; lysine ester triisocyanate, triphenylmethane triisocyanate, 1,6,1, - Un de Country isocyanate,
Examples thereof include triisocyanates such as 1,8-diisocyanate-4,4-isocyanatomethyloctane, 1,3,6-hexamethylene triisocyanate, and bicycloheptane triisocyanate. These may be used alone or in combination of two or more.

The above compound (c) can be arbitrarily designed in terms of physical properties such as hardness and adhesiveness of the obtained urethane polymer by appropriately selecting the compound according to the intended purpose or use of the obtained urethane emulsion. As the compound (c), for example, polyols, polyamines and the like can be used, but since the reaction can be easily controlled,
Polyols are preferably used.

The above polyols are not particularly restricted but include, for example, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol,
Polyether polyols such as glycerin, polyethylene glycol and polypropylene glycol; adipic acid,
Sebacic acid, itaconic acid, maleic anhydride, phthalic acid,
Dicarboxylic acids such as isophthalic acid and ethylene glycol, triethylene glycol, propylene glycol,
Tripropylene glycol, 1,4-butanediol,
Polyester polyol composed of glycols such as 1,6-hexanediol and neopentyl glycol; polycaprolactone polyol, tetramethylene ether glycol, polybutadiene polyol, polycarbonate polyol, polythioether polyol and the like. These may be used alone or in combination of two or more.

The compound (c) has a molecular weight of 500 to 3
10,000 is preferred. If it is less than 500, the resulting urethane emulsion has a too dry dried film, and if it exceeds 30,000, the viscosity of the urethane prepolymer (A) before dispersion in water becomes too high, and it is difficult to perform a dispersion operation during dispersion in water. Becomes More preferably, it is 800 to 10,000.

If necessary, the compound (c) may have a functional group having a low molecular weight of less than 500 and having an active hydrogen capable of reacting with an isocyanate group.
Compounds having two or more compounds can be used as a mixture.
Examples of such a material include ethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

The method for obtaining the urethane prepolymer (A) by polymerizing the compound (a), the compound (b) and the compound (c) is not particularly limited, and examples thereof include bulk polymerization and solution polymerization. However, solution polymerization is preferred because the reaction can be easily controlled.
As the organic solvent used in the solution polymerization, a hydrophilic organic solvent having a boiling point of 100 ° C. or lower, which is inert to isocyanate groups and can be efficiently removed from the system at the time of removing the solvent, is preferable. Such a hydrophilic organic solvent is not particularly limited, and examples thereof include acetone, methyl ethyl ketone, tetrahydrofuran, and ethyl acetate.

The temperature of the above polymerization is preferably from 50 to 150 ° C. When the temperature is lower than 50 ° C., the polymerization reaction rate is reduced, and 1
If the temperature exceeds 50 ° C., gelation tends to occur during the polymerization reaction.

The urethane prepolymer (A) obtained by the above polymerization has a residual isocyanate group,
The equivalent ratio represented by the following formula is preferably from 1.1 to 2.0. If it is less than 1.1, the molecular weight is high, so that the dispersibility in water is inferior. If it exceeds 2.0, the molecular weight is too low. [Isocyanate equivalent in compound (b)] / [Active hydrogen equivalent in compound (a) and compound (c)]

The above urethane prepolymer (A) is prepared according to JI
The content of the residual isocyanate group measured according to 5.3 of SK1603-1985 is preferably 2.0 to 12% by weight based on the solid content of the urethane prepolymer (A). If the content is less than 2.0% by weight, the molecular weight becomes high, so that the dispersibility in water is poor. If the content exceeds 12% by weight, the chain extension reaction due to the residual isocyanate group becomes violent, and aggregation and solidification easily occur.

In the polymerization of the urethane prepolymer (A), a tin-based or amine-based catalyst may be used in combination to promote the reaction. However, it is preferable to minimize the use of a substance that also acts as a catalyst for a chain extension reaction to be performed later.

In the present invention, the modifier is mixed with the urethane prepolymer (A) and then dispersed in water, whereby the modifier is contained in the particles of the obtained urethane emulsion, and the tackiness is improved. And other characteristics can be improved. In this case, the treatment is performed on the basis of the residual isocyanate groups calculated per solid content of the entire dispersion including the modifier.

The above-mentioned modifier is not particularly restricted but includes, for example, rosin-based resins such as gum rosin, tall oil rosin, wood rosin, polymerized rosin, hydrogenated rosin, disproportionated rosin ester, rosin-modified phenolic resin; Tackifying resins such as phenolic resins, terpene phenolic resins, xylene resins, ketone resins, aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, coumarone resins, styrene resins; styrene resins, (meth) acrylic Resin, vinyl acetate resin, epoxy resin, phenoxy resin,
Thermoplastic resins such as vinyl chloride resin, urethane resin and acrylonitrile resin; rubbers such as acrylonitrile-butadiene copolymer rubber (NBR), chloroprene, acrylic rubber and urethane rubber; paraffin wax, microcrystalline wax, low molecular weight polyethylene wax,
Waxes such as oxidized polyethylene wax; antioxidants or ultraviolet absorbers such as hindered phenol, hindered amine, benzotriazole and phosphorus; phthalic acid plasticizers such as dioctyl phosphate, dihexyl phthalate, dicyclohexyl phthalate; trioctyl Phosphorus plasticizers such as phosphate and triphenyl phosphate; benzoate plasticizers; inorganic fillers; dyes;

In the present invention, when the urethane prepolymer (A) is dispersed in water, at least 5 mmol of the carboxyl groups and sulfonic acid groups contained per 100 g of the urethane prepolymer (A) are neutralized. Is preferably performed. If less than 5 mmol,
The dispersibility of the urethane prepolymer (A) is too low, resulting in coarse particles, and a stable urethane emulsion cannot be obtained. More preferably, it is 7 to 13 mmol. However, after the urethane prepolymer (A) is completely dispersed in water to obtain particles having an appropriate particle size, the urethane prepolymer (A) may be further neutralized to increase the stability of the obtained urethane emulsion.

The neutralization method is not particularly limited.
For example, a method of adding a neutralizing agent to the urethane prepolymer (A) and the like can be mentioned. By adding the neutralizing agent, the carboxyl group and the sulfonic acid group in the urethane prepolymer (A), and the hydrophilic group in the modifying agent added as desired are neutralized. Can be easily ionized and the state of dispersion in water can be stabilized.

The neutralizing agent is not particularly restricted but includes, for example, ammonia, trimethylamine, triethylamine and the like. The neutralization may be performed on all or a part of the hydrophilic groups such as the carboxyl group and the sulfonic group contained in the urethane prepolymer (A). The neutralizing agent may be added directly to the urethane prepolymer (A) before dispersion in water, or may be added to water.

The viscosity of the entire dispersion to be formed of the urethane prepolymer (A) is preferably 10,000 cP or less. If it exceeds 10,000 cP, dispersibility in water becomes poor. More preferably, it is 5000 cP or less. More preferably, it is 2000 cP or less. In order to reduce the viscosity, the material to be dispersed comprising the urethane prepolymer (A) may be heated or heated. However, since the reaction rate of the chain extension reaction to be performed later also increases, it is preferable to minimize the reaction rate. When heating or heating the material to be dispersed comprising the urethane prepolymer (A), the water in which the urethane prepolymer (A) is dispersed is also set to a temperature close to the urethane prepolymer (A), It is preferable to avoid sudden temperature changes.

In the present invention, in order to obtain good dispersibility in water, it is preferable to use an organic solvent. If the amount of the organic solvent is too large, a large amount of energy is required in the solvent removal step, resulting in poor economic efficiency. In addition, the particle size of the obtained urethane emulsion becomes too small and the viscosity increases. On the other hand, if the amount of the organic solvent is too small, the amount of the organic solvent dissolved in water becomes insufficient, and it becomes difficult to obtain a urethane emulsion having a small particle size.

The organic solvent is inert to isocyanate groups and has a boiling point of 100 ° C. or less,
Those which can be efficiently removed from the system at the time of solvent removal are preferable. Such an organic solvent is not particularly limited, and examples thereof include a hydrophilic organic solvent such as acetone, methyl ethyl ketone, tetrahydrofuran, and ethyl acetate that can be used in the above solution polymerization. The organic solvent may be used for adjusting the viscosity of the dispersion. The organic solvent may be used as a mixture in the dispersion, or may be dissolved in water before dispersing the dispersion in water.

As the organic solvent, a hydrophilic organic solvent such as methyl isobutyl ketone having a boiling point of 100 ° C. or more for increasing the dispersibility of the urethane prepolymer (A) and improving the physical properties of the obtained urethane emulsion is used. May be used. Further, a hydrophobic organic solvent such as toluene and hexane may be used. However, its use is preferably kept to a minimum.

At the time when the urethane prepolymer (A) is dispersed in water, the amount of the organic solvent is preferably not more than 100% by weight of the amount of water to be dispersed. If the content exceeds 100% by weight, a large amount of energy is required in the solvent removal step, so that economic efficiency is poor. More preferably, it is 40 to 90% by weight.

In the present invention, in order to obtain a urethane emulsion having good drying properties, at the time when the urethane prepolymer (A) is dispersed, the solid content of the substance to be dispersed is 40 to 40% of the water to be dispersed. Preferably it is 185% by weight. If it is less than 40% by weight,
Since the solid content of the urethane emulsion obtained by performing the chain extension reaction and desolvation is low, the dehydration and concentration operation described below is required, which is inferior in economical efficiency. It occurs in large quantities and is difficult to manufacture. More preferably, it is 65 to 170% by weight.

The method for dispersing the urethane prepolymer (A) in water is not particularly limited, and any conventionally known means can be used. For example, mechanical shearing force can be reduced by a disperser such as a homomixer or a disper. A method of dispersing while adding water to the organic phase containing the urethane prepolymer (A) while the application is being performed, a method of adding the organic phase containing the urethane prepolymer (A) to the aqueous phase, and the like are employed. can do. The urethane prepolymer (A) may be dispersed in water by a batch method or a continuous dispersion method such as a rotor-stator method, a line mill method, a static mixer method, a vibration method, an ultrasonic method, and a high-pressure method. It may be performed by a method. When a batch system or a continuous system is employed, two or more types of facilities may be connected. Further, the apparatus for performing the dispersion may have only one dispersion unit for dispersing the substance to be dispersed in water,
It may have more than one.

The temperature at which the urethane prepolymer (A) is dispersed in water is preferably from 0 to 60 ° C., since the chain extension reaction between the isocyanate group and the dispersion water does not proceed more than necessary. Lower temperatures are more stable, but temperatures below 0 ° C. can freeze the emulsion. From an energy efficiency point of view, if there is no particular safety concern,
More preferably, it is carried out at ambient temperature.

In the present invention, after the urethane prepolymer (A) is dispersed in water, a chain extension reaction is then carried out with a chain extender (B) comprising a compound having two or more amino groups, Increase the molecular weight.

The compound having two or more amino groups constituting the chain extender (B) is not particularly limited. Examples thereof include ethylenediamine, 1,2-propanediamine, and 1,6-hexamethylenediamine. Aliphatic polyamine compounds such as hydrazine, diethylenetriamine, 1,3-bis (aminomethyl) cyclohexane,
1,4-cyclohexanediamine, 3-aminomethyl-
3,5,5-trimethylcyclohexylamine, piperazine, 2-methylpiperazine, 2,5-dimethylpiperabine, cis-2,6-dimethylpiperazine, N, N'-
Bis (3-aminopropane) piperazine, isophoronediamine, 4,4'-cyclohexylmethanediamine, triethylenetetramine, 1- (2-aminoethyl) piperazine, 4,4'-diaminodiphenylmethane, 3,
3'-dimethyl-4,4'-diaminodiphenylmethane, m-xylylenediamine, o-phenylenediamine, p-phenylenediamine, m-phenylenediamine, 1,5-naphthylenediamine, toluene-2,4-
Examples thereof include polyamine compounds such as diamine, toluene-2,6-diamine and o-tolidine. These may be used alone or in combination of two or more.

The chain extender (B) may contain a chain extender other than the compound having two or more amino groups. Such chain extenders are not particularly limited, and include, for example, polyalkylene glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, and polyethylene glycol.

In the present invention, the above chain extender (B)
Is used in an amount of 0.90 to 0.98 equivalents of the remaining isocyanate groups in the urethane prepolymer (A).
It comprises a compound having at least two amino groups.
If the amount is less than 0.90 equivalents, the chain elongation reaction due to low-reactivity water molecules and the like increases, so that it takes a very long time to complete the reaction, the efficiency is poor, and if it exceeds 0.98 equivalents, Since the isocyanate group that is to react with the compound having two or more amino groups is consumed by the chain extension reaction with water molecules or the like, the amino group of the compound having two or more amino groups remains. As a result, the molecular weight of the obtained urethane polymer becomes low, so that it is limited to the above range.

In the case where the above-mentioned modifier is mixed with the urethane prepolymer (A) and then dispersed in water, the modifier has a reactive functional group of the urethane prepolymer (A), In the case of dispersing in water after reacting with an isocyanate group, the compound having two or more amino groups is used in an amount of 0.2 or more with respect to the effective remaining isocyanate group as a base of the chain extension reaction of the dispersion. 90 ~
0.98 equivalents.

The addition of the chain extender (B) is carried out after the urethane prepolymer (A) is uniformly dispersed in water.
It is preferable to start during 10 minutes. If the time is longer than 10 minutes, an unnecessarily long chain extension reaction between the remaining isocyanate groups in the urethane prepolymer (A) and water molecules proceeds.

The temperature at which the chain extender (B) is added is preferably from 0 to 60 ° C. If the temperature is lower than 0 ° C., the emulsion may freeze. If the temperature is higher than 60 ° C., the chain extension reaction proceeds rapidly, and it is difficult to obtain an emulsion stably such as generation of aggregates. From the viewpoint of energy efficiency, if there is no particular problem in stability, the atmospheric temperature is more preferable.

When the above chain extender (B) is added,
It is preferable to dilute the above chain extender (B) such as water or an organic solvent with a diluent capable of diluting, and then to add it as a chain extender solution. The concentration of the chain extender solution is 30 to 8
0% by weight is preferred. However, in this case, it is preferable to minimize the use of a hydrophobic solvent which is difficult to remove at the time of solvent removal or an organic solvent having a boiling point of 100 ° C. or more as a diluent.

By performing a chain extension reaction of 0.90 to 0.98 equivalents of the remaining isocyanate group with the compound having two or more amino groups, the chain extension reaction
Done quickly. Further, a chain extender other than the compound having two or more amino groups completes the chain elongation reaction for 0.02 to 0.10 equivalents of the remaining isocyanate slowly later, so that the molecular weight of the urethane polymer obtained is Becomes larger.

In the present invention, the above-mentioned chain extension reaction goes through an aging step. That is, the chain elongation reaction between a chain extender other than the compound having two or more amino groups or a water molecule and the remaining isocyanate group in the urethane prepolymer (A) has low reactivity. Mature. Through the aging step, the chain extension reaction proceeds rapidly.

The above-mentioned heating for aging is performed at a temperature of 45 to 80 ° C. When the temperature is lower than 45 ° C., the progress of the reaction is slow, so that it is not efficient. When the temperature is higher than 80 ° C., the emulsion particles may be broken or skin burrs may be generated. Preferably, 50 to 65
° C.

The heating for aging is preferably started 5 to 60 minutes after the addition of the entire amount of the chain extender (B) is completed. If the reaction time is less than 5 minutes, the reactivity between the compound having two or more amino groups and the residual isocyanate group is insufficient, and there is a risk that the chain elongation reaction may proceed at a stretch by heating, and is stable. It becomes difficult to obtain an emulsion. Heating for the above aging,
It is preferably performed for 30 to 120 minutes.

When the above-mentioned chain extender (B) is added and when the chain extension reaction is matured, it is preferable to carry out stirring to produce a urethane emulsion more stably. In this case, the strength of the stirring is controlled by the mechanical force applied when the urethane prepolymer (A) is dispersed in water during the period from the addition of the chain extender (B) to the heating for aging. A strength close to the shearing force is preferable for stably performing the chain extension reaction. In addition, it is preferable that the period during which the heating for the ripening is performed is set to be weaker than the above period in order to prevent foaming as much as possible. However, in any period, it is important that the stirring is performed so as not to impair the stability of the emulsion.

In the present invention, after the chain elongation reaction including the aging step, the organic solvent is distilled off by a method such as heating and reduced pressure to remove the solvent. Further, the water may be removed by distillation by heating or reduced pressure to be concentrated. The solvent removal is 45
It is preferably carried out at a temperature of ７０70 ° C. If the temperature is lower than 45 ° C., it takes time to remove the organic solvent,
When it exceeds, skin burrs and particle aggregation occur. More preferably, it is 45 to 60 ° C. The solvent removal is 50 mmH
g is preferably performed at a reduced pressure of not more than 50 gHg.

The chain extension reaction between the remaining isocyanate groups in the urethane prepolymer (A) and the water molecules generates carbon dioxide gas, so that foaming is caused by heating and pressure reduction. However, in the present invention, since the solvent is removed after the chain extension reaction by water molecules is aged, newly generated carbon dioxide gas is small and foaming can be suppressed with a small amount. Therefore, the solvent can be removed at a low degree of reduced pressure, and the time required for the solvent removal can be shortened.

In the present invention, the desolvation is carried out under stirring by a stirring blade having a peripheral speed of 0.2 to 1.0 m / sec. If it is less than 0.2 m / sec, the emulsion stability is impaired due to skin burrs and agglomeration of particles, and if it is more than 1.0 m / sec, bubbling occurs violently, so it is limited to the above range. More preferably, it is 0.3 to 0.7 m / sec. The peripheral speed is a value represented by the following equation.

Peripheral speed = 1/60 × D × π × n In the above equation, D represents the diameter of the stirring blade (m), π represents the circular constant, and n represents the rotation speed of the stirring blade (rpm).

In the above solvent removal, an antifoaming agent may be added for the purpose of reducing foaming. The defoaming agent is not particularly limited, and examples thereof include silica silicon, silicon, metal soap, amide, ester, polyether, organic phosphoric acid, and higher alcohols. However, it is preferable that the addition of the defoaming agent be kept to the minimum necessary in view of the physical properties of the dried film from the obtained urethane emulsion.

The solid concentration of the urethane emulsion obtained by the production method of the present invention is preferably 30 to 70% by weight. If the amount is less than 30% by weight, the energy and time required for drying become large, so that the economic efficiency is poor. If the amount exceeds 70% by weight, the viscosity of the obtained urethane emulsion becomes remarkably high, the coating property is poor, and Coating becomes difficult. More preferably, it is 40 to 65% by weight. In addition,
The above-mentioned solid content concentration means a non-volatile content in a vinyl acetate resin emulsion test method specified in JIS K 6828.

The viscosity of the urethane emulsion obtained by the production method of the present invention is 10 to 10 as apparent viscosity at 60 rpm at 23 ° C. using a B-type viscometer.
000 cP is preferred. When the viscosity is less than 10 cP, the viscosity is too low, and it becomes difficult to secure the coating thickness.
If it exceeds 00 cP, the coatability will be poor, and uniform coating will be difficult. More preferably, 10 to 5000 cP
It is.

The average particle size of the urethane emulsion obtained by the production method of the present invention is the median value of the particle size distribution (d5
0), and preferably 0.03 to 5 μm. If it is less than 0.03 μm, the viscosity becomes too high and good coatability cannot be maintained. If it exceeds 5 μm, the storage stability will be poor. More preferably, it is 0.05 to 3 μm, and still more preferably 0.1 to 1 μm.

In the present invention, if necessary, polymer emulsions such as vinyl acetate, acrylic, epoxy and ethylene-vinyl acetate; acrylonitrile-
Rubber emulsions such as butadiene copolymer rubber (NBR) and chloroprene; rosin resins such as gum rosin, tall oil rosin, wood rosin, polymerized rosin, hydrogenated rosin, disproportionated rosin ester, rosin modified phenol resin; terpene resin, phenol Resin, terpene phenol resin, xylene resin, ketone resin, aliphatic petroleum resin, aromatic petroleum resin, alicyclic petroleum resin, tackifier resin emulsion such as coumarone resin, styrene resin; carbon black, aluminum hydroxide, etc. , A plasticizer, a pigment, a film thickening aid, a crosslinking agent, and the like.

In the method for producing a urethane emulsion of the present invention, the input amount of the compound having two or more amino groups is set to 0.9 to 0.98 equivalents of the remaining isocyanate groups in the urethane prepolymer (A). As a result, the reaction is quick and efficient, and the reaction is carried out without leaving any amino group, so that the molecular weight of the obtained urethane polymer is increased.

In the method for producing urethane of the present invention, the chain elongation reaction is aged, and stirring is performed by a stirring blade at the time of solvent removal, so that foaming at the time of solvent removal is suppressed to a low level. Therefore, a urethane emulsion can be obtained stably and quickly. Therefore, a dried film obtained from the urethane emulsion obtained according to the present invention has excellent physical properties.

[0060]

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

Synthesis of Urethane Prepolymer A urethane prepolymer was synthesized by the following procedure. In a reactor equipped with a reflux condenser, polycaprolactone polyol (PLACCEL L220AL, OH number:
57, manufactured by Daicel Chemical Industries, Ltd.) 100 parts by weight, 2,2-
6.7 parts by weight of dimethylolbutanoic acid (manufactured by Mitsubishi Chemical Corporation)
And 37.3 parts by weight of methyl ethyl ketone and 9
Stir at 0 ° C. until uniform.

Next, after confirming the reflux of the solvent, 42.7 parts by weight of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (VESTANT IPDI, manufactured by Huls Co.) was added, and polymerization was carried out. A urethane prepolymer having a ratio of 6.2% by weight (isocyanate group / urethane prepolymer solid content) was synthesized.

Example 1 A urethane emulsion was obtained using the composition shown in Table 1 and the following operation procedure. Predetermined amounts of triethylamine (manufactured by Mitsubishi Gas Chemical Company) and methyl ethyl ketone were added to the urethane prepolymer and uniformly mixed. Then, 2
Under a temperature condition of 3 ° C., a methyl ethyl ketone solution of the urethane prepolymer was stirred at a peripheral speed of 1.3 m / sec using a batch type homogenizer, and a predetermined amount of ion-exchanged water was added thereto.

Further, the whole amount of a chain extender solution of ethylenediamine (manufactured by Sumitomo Seika Co., Ltd.) having the composition shown in Table 1 was dropped at 90 ° C. under a temperature condition of 23 ° C., and stirring was continued for further 45 minutes. Subsequently, the temperature was set to 50 ° C., and the peripheral speed was set to 0.
Stirring was further continued at 42 m / sec. Then, at 55 ° C, 50
The solvent was removed and dewatered while stirring at a peripheral speed of 0.42 m / sec under the condition of mmHg to obtain a urethane emulsion.

COMPARATIVE EXAMPLE 1 With respect to the composition shown in Table 1, the whole amount of the aqueous solution of the chain extender was dropped in 90 seconds and stirred at a peripheral speed of 0.42 m / sec for 45 minutes. An attempt was made to obtain a urethane emulsion in the same manner as in Example 1 except that the solvent was removed and dewatered while stirring at a peripheral speed of 0.42 m / sec. However, foaming occurred violently during solvent removal, and it was difficult to continue the solvent removal operation.

Comparative Example 2 For the composition shown in Table 1, the entire amount of the aqueous solution of the chain extender was dropped in 90 seconds, and the mixture was further stirred for 45 minutes.
An attempt was made to obtain a urethane emulsion in the same manner as in Example 1, except that the solvent was removed and dewatered while stirring at a peripheral speed of 1.3 m / sec under the conditions of 50 ° C and 50 mmHg.
However, foaming occurred violently during solvent removal, and it was difficult to continue the solvent removal operation.

Comparative Example 3 An attempt was made to obtain a urethane emulsion in the same manner as in Example 1 for the composition shown in Table 1. However, foaming occurred violently during solvent removal, and it was difficult to continue the solvent removal operation.

Comparative Example 4 A urethane emulsion was obtained in the same manner as in Example 1 for the composition shown in Table 1.

Evaluation of Urethane Emulsion The obtained urethane emulsion was evaluated by the following method. The results are shown in Table 2. (1) Degree of foaming at the time of performing the solvent removing operation The degree of foaming of the emulsion at the time of performing the solvent removing operation was visually confirmed. (2) Solid Content Concentration of Urethane Emulsion The solid content concentration of the urethane emulsion at the time when the solvent removal operation was completed was determined according to JIS K 6828 (Testing method for vinyl acetate resin emulsion). (3) Viscosity of urethane emulsion Using a B-type viscometer “BM” (manufactured by Tokyo Keiki Co., Ltd.), 23
The viscosity was measured at 60 ° C. and 60 ° C.

(4) Particle Size Distribution of Urethane Emulsion The obtained urethane emulsion was diluted with ion-exchanged water, and the particle size distribution was measured using a particle size distribution analyzer (laser diffraction type particle size distribution analyzer HORIBA LA-910, manufactured by HORIBA, Ltd.). The particle size distribution was measured, and the median (d50) was obtained. (5) Stability of Urethane Emulsion The obtained urethane emulsion was visually evaluated, and those having no aggregate were evaluated as ◎, and those having aggregates were evaluated as x. (6) Molecular weight distribution of urethane polymer The obtained urethane emulsion was dried to form a film, and the molecular weight of the urethane polymer was measured using a liquid chromatograph LC-10A (manufactured by Shimadzu Corporation).

[0071]

[Table 1]

[0072]

[Table 2]

[0073]

The method for producing a urethane emulsion of the present invention is as described above, so that the chain extension reaction can be carried out quickly and reliably, and foaming during solvent removal can be suppressed. Therefore, a high molecular weight urethane polymer can be stably obtained.

Claims (1)

[Claims] 1. After dispersing a urethane prepolymer (A) having at least one of a carboxyl group and a sulfonic acid group and having an isocyanate group in water,
A method for producing a urethane emulsion in which a chain extender (B) comprising a compound having two or more amino groups is added, a chain extension reaction is performed, and then the solvent is removed, wherein the chain extender (B) is And a compound having two or more amino groups in an amount of 0.9 to 0.98 equivalents of the remaining isocyanate groups in the urethane prepolymer (A), Through an aging step at -80 ° C.
A method for producing a urethane emulsion, which is carried out under stirring by a stirring blade of 1.0 to 1.0 m / sec.