JPH0431425A - Preparation of aqeous polyurethane dispersion - Google Patents

Abstract

PURPOSE:To prepare the title dispersion having excellent applicability and giving a good coating film without using a defoaming agent in a short time by adding a specific compd. to an aq. polyurethane dispersion contg. an org. solvent and distilling the dispersion under reduced pressure. CONSTITUTION:At least one compd. selected from the group consisting of an alcohol and a glycol ether (e.g. hexylcellosolve) is added to an aq. polyurethane dispersion (e.g. an aq. polyurethane dispersion obtd. from a 1,6-hexanediol- neopentyl glycol-adipic acid polyester polyol, 4,4'-diphenylmethane diisocyanate, dimethylolpropionic acid, and piperazine) contg. an org. solvent (e.g. methyl ethyl ketone), and the dispersion is distilled under reduced pressure.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for producing an aqueous dispersion of a high molecular weight polyurethane resin useful for paints, fiber treatment, and adhesives. More specifically, since the content of organic solvents is extremely low, it is sufficient in terms of resource saving, low pollution, and safety and hygiene, and also has excellent performance in workability such as various coatings and spray painting. The present invention relates to a method for producing an aqueous dispersion of a polyurethane resin.

(Prior Art) Various methods for producing aqueous dispersions of high molecular weight polyurethane resins have been proposed. For example, the special public service 1977-907
No. 6 and Japanese Patent Publication No. 44-27904 disclose compounds having a basic tertiary amino group that can be neutralized with acid or can be quaternized, and carboxylic acid groups and sulfonic acid groups that have salt-forming ability. A method is disclosed for making a polyurethane material water-soluble or water-dispersible by incorporating a compound having a group into the polyurethane material to form a salt before or during the addition of water to the polyurethane material. .

In addition, by using an emulsifier in combination, a hydrophobic prepolymer is dispersed in water using mechanical shearing force and polymerized, and after a polyurethane resin solution of polymer H is synthesized in advance, the emulsifier is dissolved. There is also known a method of phase inversion emulsification from a water-in-oil type to an oil-in-water type by subsequently adding water dropwise.

However, in either method, it is essential to use an organic solvent in order to facilitate condensation polymerization or emulsification and dispersion.

As a result, the resulting resin dispersion contains a considerable amount of organic solvent, which is a resource-saving solution that is currently strongly demanded by society.
However, it has the drawback of not being able to fully satisfy the following questions in terms of low pollution, safety and hygiene, etc.

In order to eliminate such drawbacks, it is very effective to reduce the amount of organic solvent by removing the solvent under reduced pressure from the resulting aqueous polyurethane resin dispersion containing organic solvent.

However, in this case, problems occur such as significant foaming during solvent removal, resulting in a significant decrease in yield and the need for an extremely long time.

There is a method of using an antifoaming agent to suppress this foaming.

However, when an antifoaming agent is used, even if the amount is extremely small, the obtained polyurethane resin aqueous dispersion can cause cissing, pinholes, etc. when applied to plastic films, metal surfaces, etc., resulting in significant limitations in terms of application. It had been.

For this reason, aqueous polyurethane resin dispersions for sprays and roll feet, which need to be used at low viscosity levels where conventional antifoaming agents cannot be used, foam when desolventized under reduced pressure, so they cannot be desolventized and cannot be used with organic solvents. Could not be reduced. Therefore, hydrophilic organic solvents with low flammability and high boiling points (e.g. N-methylpyrrolidone, dimethylformamide, etc.)
Only types containing a large amount of can be manufactured industrially.

(Problems to be Solved by the Invention) As mentioned above, it is not possible to reduce the organic solvent content by removing solvents because antifoaming agents cannot be used for polyurethane resin aqueous dispersions that need to be coated with low viscosity. However, as a result of intensive studies to overcome this drawback, the inventor of the present invention found that
The present invention was completed by discovering a method that allows solvent removal under reduced pressure in a short period of time without using conventional antifoaming agents.

(Means for Solving the Problems) That is, the present invention involves adding one or more compounds selected from alcohols and glyfuryl ethers to an aqueous polyurethane dispersion containing an organic solvent, and subjecting the mixture to vacuum distillation. A method for producing an aqueous polyurethane dispersion, characterized in that the above-mentioned compound is a compound having a solubility in water in the range of 0.01 to 10 g per 100 g of water. This is a manufacturing method.

The aqueous polyurethane dispersion of the present invention prepared by this method substantially contains almost no highly flammable organic solvent,
In addition, it is an aqueous dispersion of high molecular weight polyurethane resin that does not have coating problems such as repellency and pinholes in applied processing.

Conventionally, some of the above-mentioned low-molecular-weight alcohol or ether compounds have been added to acrylic and epoxy systems, but in the synthesis of polyurethane resins, most of the above compounds are not reacted during urethanization. Since it acts as a terminator, it is common sense to remove it in advance before the urethanization reaction, and even more so, it is completely contrary to common sense to add the above compounds during the synthesis of polyurethane resin. .

The configuration of the present invention will be explained in more detail below.

The polyurethane aqueous dispersion of the present invention is not particularly limited, and any of anionic, cationic, and nonionic types can be applied.

The feature of the present invention is that one or two selected from alcohols and glycol ethers are removed under reduced pressure in order to remove organic solvents from an aqueous polyurethane resin dispersion containing organic solvents.
The process involves adding more than one type of compound to an aqueous polyurethane dispersion and distilling it.

That is, it is characterized in that alcohols and glycol ethers are added in order to remove the organic solvent in the aqueous polyurethane resin dispersion under reduced pressure.

In this case, if the solubility in water is lower than 0.01 g, the above compound will not dissolve in water and the antifoaming effect will be reduced. In addition, if the solubility in water is 10 g or more, for example, alcohols and glycol ethers that can be mixed with water arbitrarily, in extreme cases, when painted on metal or plastic surfaces, the paint will be repelled and form water droplets. This results in a scattered state.

Therefore, alcohols and the like whose solubility in water is in the range of 0.01 to 10 g per 100 g of water are preferred.

Examples of alcohols include n-butanol, n-hexanol, and octanol, and examples of glycol ethers include hexyl cellosolve. Among these, a particularly preferred compound is hexyl cellosolve from the viewpoint of antifoaming properties, odor, volatility, and the like. The amount used is within the range of 0.5 to 10% (apparent weight ratio) based on the aqueous dispersion of the urethane resin containing an organic solvent and dispersed in water.

In this case 0. If it is less than 5%, the defoaming effect during desolvation will be reduced, and there will be problems such as a very long time being required for desolventizing or the desolvation not being possible, which is not preferable. In addition, if the amount used exceeds 10%, the defoaming effect during solvent removal will not improve even if the amount used is increased further, making it uneconomical, and the boiling point of these alcohols and glyfur ethers is that of water. Since it is more expensive and less likely to volatilize, the rate of coating film formation becomes slow, which is undesirable. In particular, a usage amount of 1 to 7% is preferable.

According to the method of the present invention, solvent removal can be carried out in a short time, and the resulting low-solvent polyurethane aqueous dispersion has excellent coating properties, and when solvent removal is carried out using a conventional antifoaming agent, It has an extremely excellent feature of eliminating problems such as the occurrence of cissing and binholes.

Examples of methods for producing the aqueous polyurethane dispersion include the following.

That is, it has at least two active hydrogen atoms reactive with isocyanate groups in its molecule and has an average molecule j! 1300～
20,000 active hydrogen-containing compound and an organic polyisocyanate compound to prepare a prepolymer having an isocyanate group at the end, and then dispersing the prepolymer in water. An aqueous polyurethane dispersion is produced by elongation followed by solvent removal. At that time, in order to disperse the prepolymer in water, a salt forming group is included in the prepolymer or an emulsifier is used in combination.

Here, the molecule has at least two active hydrogen atoms reactive with isocyanate groups, and has an average molecular weight of 300 to 300.
The active hydrogen-containing compound of 20,000 is generally linear and has an average molecular weight of preferably 500 to 400 degrees.

Such compounds include polyhydroxy compounds, such as polyesters, polyacetals, polyethers, polythioethers, polyamides and polyesteramides, which contain terminal hydrobosyl, carboquinyl, amine or mercapto groups. I can do it.

Among these, polyester polyols include ethylene glycol, propylene glycol, 1°3-propanediol, 1,4-butanediol, 1,5-bentanediol, 3-methyl-1,5-bentanediol, 1,
6-hexanediol, neopentylglyfur, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (molecular weight 30
0-6000), dipropylene glycol, tripropylene glycol, bishydroxyethoxybenzene, 1
, 4-cyclohexane diol, 1,4 cyclohexane dimetatool, bisphenol A, water $1 bisphenol A1 Glycol components such as hydroquinone and their alkylene oxide adducts, succinic acid, adipic acid, azelaic acid, sebacic acid , dodecanedicarboxylic acid, maleic anhydride, fumaric acid, 1. 3-cyclopentanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2.5-+7taledicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid acids, biphenyldicarboxylic acid, 1,2-bis(phenoxy)ethane-p, p-dicarboxylic acid, anhydrides or ester-forming derivatives of these dicarboxylic acids; p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid It is obtained by a dehydration condensation reaction from an acid and an acid component such as an ester-forming derivative of these dihydroxycarboxylic acids.

In addition to these, it can also be obtained by ring-opening polymerization reaction of cyclic ester compounds such as ε-caprolactone, and copolyesters thereof can also be mentioned.

Examples of polyether include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, glycerin, and trimethylol. Ethane, trimethylolpropane, sorbitol, sucrose, aconite sugar, trimellitic acid, hemimellitic acid, phosphoric acid, ethylenediamine, diethylenetriamine, triisopropane, pyrogallol, dihydroxybenzoic acid, hydroxybenzoic acid, II2.3-
At least 2 active hydrogen atoms such as propane trithiol
Using one or more compounds as an initiator,
Examples include those obtained by addition polymerization of one or more monomers such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, tetrahydrofuran, and cyclohexylene by a conventional method.

Examples of polycarbonate polyols include compounds obtained by reacting glycols such as 1,4-butanediol, 1,6-hesanodiol, and diethylene glycol with diphenyl carbonate, phosgene, and the like.

In addition, polyhydroxy compounds containing urethane groups or urea groups, and natural polyols such as castor oil and carbohydrates can also be used.

The active hydrogen-containing compound of the present invention having an average molecular weight J of 1,300 to 20,000 is obtained by mixing a polyol of polymer I with a low molecular weight compound having a molecular weight of 300 or less to obtain an average molecular weight of 300 to 200.
Of course, it is also possible to set it to 00.

As the low molecular weight compound, a compound containing at least two or more active hydrogens in the molecule with a molecular fi of 300 or less is suitable, for example, a glycol component used as a raw material for polyester polyol; glycerin, trimethylolethane, trimethylolpropane. , sorbitol, pentaerythritol, and other polyhydroxy compounds.

Next, as the organic polyisocyanate compound, for example, 2.4-1-lylene diisocyanate, 2.6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4. 4'-diphenylmethane diisocyanate, 2. 4'-diphenylmethane diisocyanate, 2.2'-diphenylmethane diisocyanate, 3.3'-dimethyl-4,
4'-biphenylene diisocyanate, 3. 3'
-dimethquine-4,4'-biphenylene diisocyanate, 3°3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1°6-hexocyanate Methylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate,
1,3-cyclohexylene diisocyanate, 1,4-
Cyclohexylylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4゜4'
-dicyclohexylmethane diisocyanate, 3.3'
-dimethyl-4,4'-dicyclohexylmethane diisocyanate and the like.

Particularly advantageous are 9 eg dimers of toluylene diisocyanate, or phenols, tertiary phthanols,
There are partially blocked polyisocyanates which themselves have the ability to form crosslinked polyurethanes, such as polyisocyanates partially reacted with phthalimide or caprolactam.

In order to disperse the prepolymer in water, a salt-forming group that becomes a hydrophilic group is contained in the prepolymer, or an emulsifier is used in combination.

A method for introducing a hydrophilic group into a hydrophilic group-containing isocyanate-terminated prepolymer is one that has at least one active hydrogen atom in the molecule and contains a carboxyl group, a sulfonic acid group, a sulfosate group, or a repeating unit of ethylene oxide. It can be obtained by copolymerizing at least one hydrophilic group-containing compound during the production of a prepolymer.

Such hydrophilic group-containing compounds include, for example, 2-oxyethanesulfonic acid, phenolsulfonic acid, sulfobenzoic acid, sulfoconophosphoric acid, 5-sulfoisophthalic acid, sulfanilic acid, 1,3-phenylenediamine-4,6-disulfone. acid, sulfonic acid-containing compounds such as 2,4-diaminotoluene-5-sulfonic acid, derivatives thereof, or polyester polyols obtained by copolymerizing these; 2
, 2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dioxymaleic acid, 2. Carboxylic acid-containing compounds such as 6-dioxybenzoic acid and 3°4-diaminobenzoic acid, derivatives thereof, or polyester polyols obtained by copolymerizing these; at least 30 repeating units of ethylene oxide
% by weight or more, and a nonionic group-containing compound such as a polyethylene-polyaldehylene copolymer with a molecular weight of 300 to 10,000 containing a small amount (both one or more active hydrogen atoms) in the polymer, or a copolymer of these. Examples of the hydrophilic group-containing compound of the present invention include carboxyl group-containing compounds and derivatives thereof, or polyester polyols obtained by copolymerizing these.They may be used alone or in combination. is preferable.Also, as an emulsifier to be used in combination, H
/ionic emulsifiers such as polyethylene nonylphenol ether and polyoxyethylene-oxypropylene block copolymers with LB of 16 to 18; anionic emulsifiers such as sodium lauryl sulfate and sodium dodecylbenzenesulfonate; preferable.

Examples of the polyamine chain extender used in the present invention include ethylenediamine, 1,2-propanediamine, l
, 6-hexamethylene diamine, piperazine, 2,5-
Dimethylpiperazine, inphorondiamine, 4. 4'
-dicyclohexylmethanediamine, 3,3'-dimethyl-4,4'dicyclohexylmethanediamine, 1
, 4-cyclohexanediamine; polyamines such as diethylenetriamine, dipropylenetriamine, triethylenetetramine; hydrazines; acid hydrazides and water, which may be used alone or in combination.

In the present invention, the polyurethane aqueous dispersion contains an active hydrogen atom-containing compound having an active hydrogen atom reactive with at least two isocyanate groups in the molecule and having an average molecular weight of 300 to 20,000, and an organic polyisocyanate compound. The reaction is carried out to prepare a prepolymer having an isocyanate group at the end. At this time, the amount of the organic polyinsyanate compound used is preferably 1.3:2.5 in an equivalent ratio to the amount of the active hydrogen atom-containing compound used. is 1.5:2.
Used at a rate of 0.

In preparing the prepolymer, an organic solvent inert toward isocyanate groups, such as dioxane, acetone, methyl ethyl ketone, acetonitrile, ethyl acetate, tetrahydrofuran, toluene, and xylene, is used in order to uniformly carry out the reaction. The amount used is usually 20 to 100% by weight based on the solid content of the prepolymer.

Next, water is added to prepare an aqueous dispersion of the prepolymer, and chain extension is performed by adding a polyamine compound to this aqueous dispersion. The amount of the polyamine chain extender to be used in the prepolymer is 0.00% per equivalent of the terminal incyanate group of the prepolymer. An amount of 7 to 1,1 equivalents is preferred.

- The amount of water used to water-disperse the prepolymer is not particularly limited, but after water-dispersion, the weight percentage of the prepolymer (excluding organic solvents, if any) is approximately An amount of 20-40% is generally preferred.

As a method for dispersing the prepolymer in water, water may be added dropwise to the prepolymer while stirring to effect phase inversion emulsification, or a heprepolymer in water may be added dropwise to the prepolymer while stirring well. In order to minimize the reaction between the isocyanate groups of the prepolymer and water, water is quickly added to the prepolymer for water dispersion, or water dispersion is performed while applying mechanical shearing force using a homogenizer, colloid mill, etc. The preferred method is to Furthermore, a method using ultrasonic waves during water dispersion is also preferred.

The aqueous polyurethane dispersion containing the organic solvent thus obtained is then azeotroped with water under reduced pressure conditions in order to remove the organic solvent. In the present invention, in order to remove the organic solvent in the polyurethane resin aqueous dispersion containing the organic solvent, one or more compounds selected from alcohols and glycol ethers, especially water, are added under reduced pressure. A compound having a solubility in the range of 0.01 to 1° per 100 g of water is added to the aqueous polyurethane dispersion and distilled.

(Effects of the Invention) The aqueous polyurethane dispersion obtained by the method of the present invention has excellent coating workability, and produces a good coating film, especially in spray coatings that are used at very low viscosity, coatings that use roll coach inks, etc. You can get it.

It also has excellent coating properties on metals and plastics, and can be used in many applications that conventional aqueous polyurethane dispersions cannot be used for.

Examples include inks, vehicles for automobile paints and household paints, coatings for plastics, textiles, paper, leather, wood, and metals, thin film coatings for fibers and textiles, surface fluting for fur, various adhesives, and many more. It can be used in a wide range of applications, including household aerosol paints.

(Examples) The present invention will be explained in detail below using Examples, but the present invention is not limited to these Examples.

Example 1 First, 550 parts of 1.6 hexanediol-neobentyl glycol adipic acid-polyester (OH value 102) was added to a 4-tubular flask equipped with a thermometer, a stirrer, and a reflux condenser, and the mixture was heated to 120 to 130 parts under reduced pressure. Dehydration was performed at °C, then cooled to 50'C, 500 parts of methyl ethyl ketone (hereinafter referred to as "MEK") was added, and after thorough stirring and mixing, 250 parts of 4.4'-diphenylmethane diisocyanate was added, and the mixture was heated to 70'C. The mixture was heated and reacted at this temperature for 2 hours to obtain a prepolymer solution having terminal isocyanate groups. After the reaction is completed, the mixture is cooled to 40°C, 33 parts of dimethylolpropionic acid is added, and stirring is continued at this temperature for 2 hours. Next, while stirring at high speed with a homomixer, 1000 parts of water containing 25 parts of triethylamine were added to prepare an aqueous dispersion of the prepolymer12, and then 218 parts of an aqueous solution in which 45 parts of piperazine hexahydrate were dissolved was added over about 3 minutes. drip. 500 parts of the white emulsion thus obtained was added with hexyl Sorosolve (solubility 0.9 in 100 g of water).
MEK was removed at 55° C. under reduced pressure while stirring. There was very little foaming during desolvation, and MEK desolvation was completed in about 30 minutes. When the concentration was adjusted by adding water, the nonvolatile content was 40.5%, the viscosity was 155 eps, the pH was 7.3, and the remaining amount of MEK was 0.5%. A 2% aqueous polyurethane dispersion was obtained.

When the resulting aqueous polyurethane dispersion was applied to an untreated steel plate with an air spray to a thickness of 20 microns (dry film thickness), an extremely good glossy film with no repellents or pinholes was obtained. It was done. The coating film also had good drying properties and became tank-free in 20 minutes at room temperature.

The results obtained by changing the type and amount of the compound used in combination are shown in the table.

Example 2-5 Comparative Example 1-2 A resin was synthesized in the same manner as in Example 1, and the solvent was removed*1) N-phytanool solubility in 100 g of water was 7.08.
g*2) Silicone antifoaming agent - insoluble in water *3) Phylcellosophyl = solubility in 100g of water ■Example 6 515 parts of polyoxypropylene glycol with a molecular weight of 515 was added to the same apparatus as in Example 1, and the amount of 120-130 °C
Dehydration was carried out at
After adding 0.07 parts, 175 parts of tolylene diisocyanate (2,4/2.6 isomer ratio = 80720) was added,
The mixture was heated to 0.09C and reacted at this temperature for 2 hours to obtain a prepolymer solution having terminal isocyanate groups. After the reaction was completed, it was cooled to 40'C, and without stirring, 1075 parts of water in which 35 parts of polyoxyethylene nonylphenol ether with an HLB of 17 was dissolved was added, and stirred for about 3 minutes with a homomixer, resulting in a milky white water dispersion of the prepolymer. can get.

154 parts of an aqueous solution containing 24 parts of ethylenediamine is added dropwise to the prepolymer aqueous dispersion. Add 25 parts of hexyl cellosolve to 500 parts of the white emulsion thus obtained.
The toluene was removed under reduced pressure at 60°C. There was almost no foaming during the solvent removal, and the solvent removal was completed in about 25 minutes, yielding an aqueous polyurethane dispersion with a nonvolatile content of 41.9%, a viscosity of 470 cps, and a pH of 7.8. When this material was used to coat a glass plate with an airless sprayer, a strong elastic coating film with excellent gloss and no pinholes was formed. When removing the solvent by adding 100 parts of isopropyl calpitol (solubility φ in 100 g of water) instead of hexyl cellosolve, foaming was severe and removal of the solvent was difficult. Also, mineral oil-based antifoaming agent (insoluble in water)
0. Solvent removal was possible when 5 parts were added, but
When the obtained aqueous polyurethane dispersion was applied onto a glass plate by airless spraying, scorch appeared on the entire surface and was not usable.

Agent Patent Attorney Katsutoshi Takahashi

Claims (1)

[Claims] 1. A polyurethane characterized by adding one or more compounds selected from alcohols and glycol ethers to an aqueous polyurethane dispersion containing an organic solvent and performing vacuum distillation. Method for producing an aqueous dispersion. 2. The method for producing an aqueous polyurethane dispersion according to claim 1, wherein a compound having a solubility in water of 0.01 to 10 g per 100 g of water is used as the alcohol or glycol ether. 3. The amount of alcohols and glycol ethers used is 0 for the polyurethane resin aqueous dispersion containing organic solvents.
．． The method for producing an aqueous polyurethane dispersion according to claim 1 or 2, wherein the polyurethane aqueous dispersion is 5 to 10% (apparent weight ratio). 4. The method for producing an aqueous polyurethane dispersion according to any one of claims 1 to 3, wherein the alcohol is one or more of butanol, pentanol, hexanol, and octanol. 5. The method for producing an aqueous polyurethane dispersion according to any one of claims 1 to 4, wherein the glycol ether is hexyl cellosolve. 6. The aqueous polyurethane dispersion according to any one of claims 1 to 5, wherein the organic solvent is one or more of dioxane, acetone, methyl ethyl ketone, acetonitrile, ethyl acetate, tetrahydrofuran, toluene, and xylene. manufacturing method.