JPS5824445B2 - Polyurethane emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyurethane emulsions.

Polyurethane emulsions have traditionally been used for applications such as adhesives and fiber impregnating agents, and their usefulness has been increasingly recognized in recent years as they do not contain harmful solvents.

Methods for producing polyurethane emulsions include introducing hydrophilic groups such as carboxyl groups, sulfonic acid groups, and tertiary amino groups into polyurethane resins, and using hydrophilic polyols such as polyethylene glycol to make them self-emulsifying. methods, methods using emulsifiers, etc. are known.

However, polyurethane emulsions produced by these conventional methods have various drawbacks, so
It has not yet been widely used for dipping products, coatings, etc.

That is, this is because they lack emulsion stability, contain a small amount of solvent during production, and the physical properties of the resulting dry coatings, particularly water resistance and solvent resistance, are often poor.

The present inventors completed the present invention as a result of various studies aimed at improving the drawbacks of conventional polyurethane emulsions.

That is, in the present invention, an incyanate-terminated urethane prepolymer containing a carboxyl group is emulsified with an alkaline compound and water, and the chain length of the prepolymer is extended.
This is a method for producing a polyurethane emulsion characterized by adding a polyamine containing two or more grade amino groups.

The inocyanate-terminated urethane prepolymers containing carboxyl groups used in the process of the present invention can be prepared in a variety of ways.

For example, polyoxypropylene triol and acid anhydride (
For example, a half ester containing a hydroxyl group and a carboxyl group synthesized from maleic anhydride (maleic anhydride), an alkyl group having 1 to 3 carbon atoms produced by an oxidation reaction from aldehydes, or an alkyl group having 1 to 3 carbon atoms.

) and one of the compounds produced by a copolymerization reaction from an active hydrogen-containing vinyl monomer, a vinyl monomer, and a carboxyl group-containing vinyl monomer, and two or more terminals. Examples include a method of reacting with a polyincyanate compound containing an isocyanate group.

Examples of polyisocyanate compounds include diincyanates such as tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and hexamethylene diisocyanate, polyisocyanates such as polymethylene polyphenylisocyanate, and polyoxyalkylene polyols, polyester polyols, and other polyols. Incyanate prepolymers having two or more inocyanate groups at the end, prepared from a hydroxy compound and the above-mentioned isocyanates, are used individually and in mixtures.

Next, examples of alkaline compounds include sodium hydroxide, potassium hydroxide, sodium carbonate, and sodium bicarbonate.

The amount of the alkaline compound used varies depending on the equivalent amount of carboxyl groups in the incyanate-terminated urethane prepolymer, but the ratio of alkali equivalent/carboxyl equivalent is 1/1 to 1.
A range of /4 is preferred.

Furthermore, examples of polyamines containing two or more primary or secondary amine groups include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenediamine, xylylenediamine, metaphenylenediamine, piperazine, and maleic hydrazide. etc. are used.

The amount of polyamine added is used in the range of 0.1% to 3.0%, preferably in the range of 0.3% to 1.3%, based on the solid content of the polyurethane emulsion of the present invention.

To carry out the method of the present invention, an aqueous solution of an alkaline compound having a predetermined concentration is maintained at room temperature to 40° C., and the carboxy group-containing isocyanate-terminated urethane prepolymer is gradually separated into the solution while stirring.

At this time, while generating carbon dioxide gas by the reaction between the incyanate group and water, the chain length is extended by the urea bond, and a uniform emulsion of the urethane resin is formed.

After the separation of the urethane prepolymer is completed, stirring is continued for several hours, and after the generation of carbon dioxide gas is completed, a predetermined amount of polyamine is added thereto while stirring.

The solids content of the polyurethane emulsion thus obtained can be up to 70%, but
It is preferably 5% or less.

The polyurethane emulsion produced by the method of the present invention forms a transparent and smooth film even at room temperature, but by heat treatment,
The effect of the polyamine addition is significantly exhibited, and in particular, the water resistance and solvent resistance are superior to films made from conventional polyurethane emulsions.

The heat treatment conditions are 70°C to 120°C, 2 to 3°C.
0 minutes is preferable.

According to the method of the present invention, water resistance and solvent resistance, which are major drawbacks of conventional polyurethane emulsions, can be improved, and polyurethane emulsions having a wide range of excellent physical properties can be produced.

This polyurethane emulsion can be used in paints, fabrics,
It can be widely applied to paper, leather, wood, metal coatings, impregnation agents, binders, adhesives, adhesives, immersion products, cast products, etc.

Next, the present invention will be specifically explained with reference to Examples.

Note that parts in the examples are parts by weight unless otherwise specified.

Example 1 A semi-esterified product produced from 400 parts of polypropylene polyether triol with an average molecular weight of 400 and an OH value of 420 and 98 parts of maleic anhydride (OH value of 225 and acid value of 113)
, average molecular weight 498, viscosity 1500CP/25°C)
20 parts of isocyanate prepolymer (NCO content 11.2%, average molecular weight 748
) and reacted to obtain an incyanate-terminated urethane prepolymer containing carboxyl groups (C00H content 1-24%, NGO content 7.4%).

This was added to 868 parts of an aqueous solution containing 9.1 parts of caustic soda, and 5.5 parts of tetraethylenepentamine was added and mixed to the polyurethane emulsion obtained by emulsification and chain length extension to obtain a polyamine-added polyurethane emulsion. .

This milky white emulsion has a viscosity of 65CP/20℃,
Solid content 50%, pH value 8.2, surface tension 45.8 dy
n 7 cm, and the physical properties of the film obtained from this are as follows.

However, the film was obtained by heating at 100°C for 10 minutes after 16 hours at 20°C and 75% humidity.

Example 2 The isocyanate prepolymer (NCO content 8.1%, average molecular weight 1048) prepared from 700 parts of polypropylene polyether glycol having an average molecular weight of 700 and an OH value of 160 and 348 parts of tolylene diisocyanate was used in Example 1. 100 parts of half-esterified product was added.

Incyanate-terminated urethane prepolymer containing carboxy groups (COOH-containing OH0,78
%, NCO group content 5.83%) was added to 1148 parts of an aqueous solution containing 6.5 parts of caustic soda for emulsification and chain length extension.

6.2 parts of hexamethylene diamine was added and mixed to the obtained polyurethane emulsion to obtain a polyamine-added polyurethane emulsion.

This milky white emulsion has a viscosity of 520 cP/20°C.
, solid content 50.3%, pH value 8.2, surface tension 42-3
With a dyn of 7 cm, the physical properties of the film obtained from this are as follows.

The film was obtained by heating at 100°C for 30 minutes after 16 hours at 20°C and 75% humidity.

Example 3 6.0 parts of dimethylolpropionic acid was added to an incyanate prepolymer prepared from 200 parts of polypropylene polyether glycol with an average molecular weight of 2000 and OHHSO 31 and 34.8 parts of tolylene diincyanate.
The inocyanate-terminated urethane prepolymer containing carboxyl groups (C00H content 0.83%,
NCO content of 5.4%) was obtained.

This was added to 250 parts of an aqueous solution containing 1.6 parts of caustic soda, and 1.1 parts of xylylene diamine was added and mixed to the polyurethane emulsion obtained by emulsification and chain lengthening.
A polyamine-added polyurethane emulsion was obtained.

This milky white emulsion has a viscosity of 150CP/20℃
, solid content 51.5%, pHHBO2, and the film obtained from this has good stretch and excellent water resistance without clouding or swelling even after immersion in water.

The film was obtained by heat treatment at 100°C for 20 minutes after 16 hours at 20°C and 75% humidity.

Claims (1)

[Claims] 1. After emulsifying an incyanate-terminated urethane prepolymer containing a carboxyl group with an alkaline compound and water to extend the chain, a polyamine containing two or more of 7 primary or secondary amide groups is added thereto. A method for producing a polyurethane emulsion.