JPH0348955B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing an aqueous polyurethane resin varnish.

(Prior art) Water-based polyurethane resins have traditionally been used for applications such as paints, adhesives, and textile texturing agents, and have been recognized as useful because they contain no or only a small amount of harmful solvents. It's starting to get worse.

Conventionally, methods for producing aqueous polyurethane resins, particularly polyurethane emulsions, include methods for producing polyurethane resins by introducing hydrophilic groups such as carboxyl groups, sulfonic acid groups, tertiary amino groups, etc. A method of manufacturing using a hydrophilic polyol as a self-emulsifier, a method of manufacturing using an emulsifier, etc. are known. However, polyurethane emulsions produced by these methods have problems such as poor emulsion stability and the formation of precipitates over time depending on the mechanical dispersion conditions during emulsion production. Since the membrane was also an emulsion, many of the membranes were particularly poor in water resistance and solvent resistance.

In order to improve the drawbacks of these polyurethane emulsions, the present inventors conducted various studies on the production of water-soluble type water-based urethane resin varnishes, and arrived at the present invention.

That is, in the present invention, an isocyanate-terminated urethane prepolymer containing carboxyl groups is diluted by adding a water-soluble organic solvent, and then inorganic bases or tertiary amines are added to the isocyanate-terminated urethane prepolymer containing carboxyl groups per equivalent of carboxyl groups in the urethane prepolymer. After using the mixture in an amount of 0.25 to 1.5 equivalents, a mixture of water and a polyamine compound containing two or more primary or secondary amino groups is added in an amount of 0.2 to 1.5 equivalents per equivalent of isocyanate group in the urethane play polymer.
1. A method for producing an aqueous polyurethane resin varnish, characterized in that it is used in an amount of 1.0 equivalent and the proportion of the water-soluble organic solvent in water and the water-soluble organic solvent is 10 to 40% by weight.

In the present invention, the isocyanate-terminated urethane prepolymer containing carboxyl groups can be produced by various methods.

That is, a polyhydric alcohol having a carboxyl group, preferably a polyester polyol, a polyether polyol or a polyhydric alcohol having a molecular weight of 500 to 3000, and a polyisocyanate containing two or more isocyanate groups at the terminals are combined with an isocyanate group equivalent of hydroxyl. A common method is to carry out the reaction at 60 to 100°C for about 2 to 10 hours in a nitrogen stream under conditions larger than the base equivalent. At this time, the water-soluble organic solvent referred to in the present invention can be used as necessary. Examples of the polyhydric alcohol having a carboxyl group include dimethylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid,
Examples include dimethylolcaproic acid. Further, polyester polyols can be obtained, for example, by a condensation reaction between a polyhydric alcohol and a polyhydric carboxylic acid or an alkyl ester of a polyhydric carboxylic acid. In some cases, it can also be obtained by ring-opening polymerization of lactones such as caprolactone and butyl lactone. Examples of the polyhydric alcohols mentioned above include ethylene glycol, propylene glycol, 1.4.butanediol, 1.3.butanediol, 1.6.hexanediol,
Examples include neopentyl glycol. Examples of polycarboxylic acids include aliphatic polycarboxylic acids such as adipic acid, sebacic acid, and azelaic acid;
Examples include aromatic polycarboxylic acids such as isophthalic acid, terephthalic acid, phthalic anhydride, and phthalic acid, or alkyl esters thereof.

As the polyisocyanate compound containing two or more isocyanate groups at the terminal mentioned above,
Examples include diisocyanates such as triene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

Next, examples of polyamine compounds containing two or more primary or secondary amino groups include ethylenediamine,
Examples include hexamethylenediamine, diethylenetriamine, triethylenetetramine, xylylenediamine, isophoronediamine, 4,4'-dichlorohexylmethanediamine, piperazine, maleic dihydrazide, isophthalic dihydrazide, and the like.

In addition, the inorganic bases or tertiary amines used in the present invention include sodium hydroxide,
Examples include inorganic bases such as potassium hydroxide, and tertiary amines such as trimethylamine, triethylamine, triethylenediamine, N-methyldiethanolamine, N-methylmorpholine, and triethanolamine.
The use of grade amines is preferred. Further, the amount of these inorganic bases or tertiary amines used varies depending on the equivalent amount of carboxyl group in the isocyanate-terminated urethane prepolymer, but the ratio of base equivalent/carboxyl group equivalent is in the range of 0.25 to 1.5, more preferably. is preferably in the range of 0.85 to 1.2 for the production of aqueous polyurethane.

In the present invention, the water-soluble organic solvent refers to a solvent that forms a uniform state when mixed with water, and is preferably a solvent that can dissolve the polyurethane resin.

Examples of these water-soluble organic solvents include N-
pyrrolidone solvents such as methyl-2-pyrrolidone,
Examples include amide solvents such as dimethylformamide, lactone solvents such as α-butyl lactone, ketone solvents such as acetone and methyl ethyl ketone, and alcohol solvents such as tertiary butanol. Preference is given to using pyrrolidone and amide solvents.

In the present invention, the content ratio of the water-soluble organic solvent to water in the water-based polyurethane resin varnish is required to be in the range of 10 to 40% by weight. When the water-soluble organic solvent is less than 10% by weight, the storage stability of the water-based polyurethane resin varnish is poor, and when it is more than 40% by weight, there is no problem with storage stability, but the organic solvent is too large. Due to its presence, it is unfavorable from the standpoint of pollution prevention and resource conservation.

To carry out the method of the present invention, it is preferable to add a basic compound to the isocyanate-terminated urethane prepolymer containing carboxyl groups produced as described above after diluting it with a water-soluble organic solvent. Furthermore, water and a primary or secondary amino group are
A water-based polyurethane resin can be obtained by quickly adding a mixture of polyamine compounds containing at least 100% polyamine compounds dropwise while stirring while keeping the temperature in the system below 35°C.

The aqueous polyurethane resin varnish thus obtained can be dried as it is at room temperature and used as a resin coating, but it may be heated to shorten the drying time. The heating temperature may be below the temperature at which the resin decomposes, and at 100° C. or higher, the heating time may be 30 minutes or less. At this time, the ratio between the isocyanate group equivalent of the urethane prepolymer and the amino equivalent of the polyamine compound is: isocyanate equivalent/amino equivalent=
Preferably, the ratio is between 1.0/0.2 and 1.0.

(Function) According to the method of the present invention, water resistance and storage stability, which are major drawbacks of conventional polyurethane emulsions, can be improved, and water-based polyurethane resin varnishes having a wide range of excellent physical properties can be produced. can. This water-based polyurethane resin varnish can be used for paints, cloth, paper, leather, wood, metal coatings, impregnants, binders, adhesives, etc.
It can be applied to a wide range of applications such as adhesives and immersion products.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Note that parts and % in Examples and Comparative Examples indicate parts by weight and % by weight.

Example 1 80 parts of polytetramethylene ether glycol (number average molecular weight 1000), 143.7 parts of isophorone diisocyanate, 64.4 parts of dimethylolpropionic acid, and N were added to a four-necked flask equipped with a reflux condenser, a thermometer, and a stirring device. -Methyl-2-pyrrolidone
Charge 16.33 parts and react in a nitrogen atmosphere at a temperature of 80 to 100°C for 4 hours to determine the solid content equivalent NCO content =
2.9%, carboxyl group content (oxidized 93.8mg/
KOH) urethane prepolymer was obtained. The prepolymer was then cooled to room temperature, neutralized by adding 47 parts of triethylamine (0.96 equivalents of base per equivalent of carboxyl group), and 16 parts of isophoronediamine (1 equivalent of amine group per equivalent of isocyanate group). was gradually added together with distilled water, and the polymerization reaction was carried out while cooling the temperature inside the reactor to 35°C or less. A total of 490 distilled water by the end of the reaction
In addition, an aqueous polyurethane resin varnish was obtained.

The content ratio of distilled water and water-soluble organic solvent in this water-based polyurethane resin varnish was 75:25. This aqueous polyurethane resin varnish was a slightly cloudy liquid and remained stable without forming any precipitates during storage for 3 months. In addition, the temperature is 20℃ and the humidity is 60℃.
% water resistance test after drying in a constant temperature and humidity room for 7 days, that is, after soaking for 1 day at 50°C and 98% humidity, there was no whitening etc. even after taking it out and leaving it at room temperature for 1 hour. There were no symptoms and the condition was good.

Example 2 A reaction was carried out using 158 parts of polycaprolactone (number average molecular weight 1000), 109 parts of dicyclohexylmethane diisocyanate, 21 parts of dimethylolpropionic acid, and 240 parts of dimethylformamide in the same apparatus as in Example 1, and the reaction was carried out in terms of solid content. NCO content = 3.0
%, carboxyl group content (oxidized 30.5mg/KOH)
A urethane prepolymer was obtained.

Next, in the same manner as in Example 1, 16 parts of trimethylamine (1.0 equivalent of base per 1 equivalent of carboxyl group) and 16 parts of isophoronediamine (0.95 equivalent of amine group per equivalent of isocyanate group) were added to carry out a polymerization reaction. Ivy. A total of 444 parts of distilled water was added until the reaction was completed. The ratio of distilled water and water-soluble solvent in this water-based polyurethane resin varnish was 65:35. As a result of conducting the same test as in Example 1, the storage stability and water resistance were good.

Comparative Example A water-based polyurethane resin varnish was produced in the same manner and in the same amount as in Example 1. However, the ratio of N-methyl-2-pyrrolidone and distilled water is 7:
A water-based polyurethane resin varnish was produced by charging the solution to a concentration of 93%. The resulting aqueous polyurethane resin varnish was a milky-white dispersion, which produced a large amount of precipitate during storage for 3 months and had poor storage stability. Moreover, the resulting coating film did not turn white and become transparent again.

Claims (1)

[Claims] 1. An isocyanate-terminated urethane prepolymer containing carboxyl groups is diluted by adding a water-soluble organic solvent, and then inorganic bases or tertiary amines are added to 1 equivalent of carboxyl groups in the urethane prepolymer. After using the polyamine compound in an amount of 0.25 to 1.5 equivalents per equivalent of isocyanate group in the urethane prepolymer, a mixture of water and a polyamine compound containing two or more primary or secondary amino groups is added. A method for producing a water-based polyurethane resin varnish, characterized in that it is used in an amount of 0.2 to 1.0 equivalents, and the ratio of water-soluble organic solvent to water-soluble organic solvent is 10 to 40% by weight. . 2. The manufacturing method according to claim 1, wherein the water-soluble organic solvent is N-methyl-2-pyrrolidone or dimethylformamide.