JPH10273513A - Production of self-emulsifiable polyurethane prepolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a self-emulsifiable polyurethane prepolymer with high production efficiency by reacting a polyisocyanate, a monovalent amine salt of a carboxylated polyhydric alcohol, and other polyhydric alcohol in the presence of a hydrophilic organic solvent having no active hydrogen atom. SOLUTION: The polyisocyanate (A) used comprises, e.g. ethylene diisocyanate. The monovalent amine salt (B) of a carboxylated polyhydric alcohol used comprises, e.g. dimethylamine salt of 2,2-dimethylolpropionic acid. The other polyhydric alcohol (C) used preferably comprises a high-molecular polyhydric alcohol, such as a polyester polyol, having a number-average molecular weight of 500 to 5,000. It is desirable to use components A, B and C at a ratio to provide a molar ratio of isocyanato groups to hydroxyl groups of 100:(40 to 95).a The suitable reaction temperature is 30-130 deg.C. The organic solvent comprising, e.g. acetone is used in an amount of 5-50 pts.wt. based on 100 pts.wt. polyurethane polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a polyurethane prepolymer having a property capable of being stably emulsified and dispersed in an aqueous medium, that is, a self-emulsifying property.

[0002]

2. Description of the Related Art As a means of solving the problem of environmental pollution, aqueous polymer emulsions have been used in many technical fields in place of solvent-based resins, and similar trends have been observed for polyurethanes having excellent properties as coating agents. There is.
Among aqueous polyurethane emulsions, anionic self-emulsifying polyurethane emulsions, i.e., polyurethane emulsions having an anionic group such as carboxylate and having self-emulsifying properties due to the action of the anionic group, have improved storage stability and mechanical strength. Are better.

[0003] Anionic self-emulsifying polyurethane emulsions are usually produced by obtaining an aqueous emulsion of a self-emulsifying polyurethane prepolymer and then adding a chain extender to the emulsion to form a polyurethane. Further, the aqueous emulsion of the polyurethane prepolymer is a polyhydric isocyanate, a polyhydric alcohol having an anionic group such as dimethylolpropanoic acid and other polyhydric alcohols are reacted in an organic solvent, and then the obtained prepolymer is obtained. It is manufactured by a method in which an anionic group in the prepolymer is neutralized with a base and emulsified and dispersed in an aqueous medium (for example, Japanese Patent Publication No. 42-24192).

[0004] However, in the above method, powdery raw materials such as dimethylolpropionic acid are hardly dissolved in a reaction system comprising a polyurethane prepolymer to be formed and an organic solvent as a diluent. There was a problem that the reaction itself for obtaining a polyurethane prepolymer having an appropriate amount of carboxyl groups did not proceed smoothly. In order to solve such a problem, in order to increase the solubility of dimethylolpropionic acid or the like in the reaction system, a means has been adopted in which a large amount of an organic solvent is added to lower the viscosity of the reaction system. However, when a large amount of the organic solvent is used, the yield of the polyurethane prepolymer per batch is reduced, and the cost of the step of removing the organic solvent is increased.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a self-emulsifying polyurethane prepolymer having an amount of carboxyl groups required for aqueous emulsification with high production efficiency.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above problems, and as a result, have completed the present invention. That is, the present invention provides a polyvalent isocyanate,
Production of a self-emulsifying polyurethane prepolymer characterized by reacting a monohydric amine salt of a polyhydric alcohol having a carboxyl group and another polyhydric alcohol in the presence of a hydrophilic organic solvent having no active hydrogen. Is the way. Hereinafter, the present invention will be described in more detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyvalent isocyanate (hereinafter sometimes referred to as component (A)) that can be used in the present invention includes ethylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, and the like.
Cyclohexane-1,4-diisocyanate, 4,4 ′
-Dicyclohexylmethane diisocyanate, p-xylylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6
-Toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanate, 1,5-naphthylene diisocyanate, and the like, and mixtures thereof can also be used. Also,
Bifunctional isocyanates modified with urethane, allophanate, urea, burette, carboimide, urethaneimine or isocyanurate residues can also be used.

The monovalent amine salt of a polyhydric alcohol having a carboxyl group [hereinafter sometimes referred to as component (B)] includes 2,2-dimethylolpropionic acid and 2,2 dimethylolpropionic acid.
A monovalent amine salt of a polyhydric alcohol having a carboxyl group such as dimethylolbutanoic acid. Examples of the monovalent amine include dimethylamine, trimethylamine, diethylamine, triethylamine, tributylamine and N-ethylmorpholine. Preferred monovalent amines are monovalent tertiary amines such as trimethylamine, triethylamine, tributylamine and N-ethylmorpholine.

[0009] Other polyhydric alcohol [the following component (C)
That the number average molecular weight is 500 to
Preferred are 5000 polyhydric alcohols, and specific examples include polyester polyols, polyester polyamide polyols, polyether polyols, polythioether polyols, polycarbonate polyols, polyacetal polyols, polyolefin polyols, and polysiloxane polyols. Also, if necessary, ethylene glycol, propylene glycol,
Low molecular weight polyhydric alcohols such as 1,4-butanediol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, glycerol, trimethylolpropane and pentaerythritol can also be used.

The above components (A), (B) and (C)
Molar ratio of isocyanate group to hydroxyl group is 100: 40-9
It is preferable to use them at a ratio of 5. The reaction temperature is
The temperature is suitably from 30 to 130 ° C, and a catalyst for a urethanization reaction such as dibutyltin dilaurate or stannous octoate may be added. In the reaction of each of the above components, the components (A), (B) and (C) may be reacted at a time, or the molar ratio of isocyanate group to hydroxyl group may be 10 or more.
The components (A) and (C) may be first reacted at a ratio of 0: 5 to 100: 70, and then the component (B) may be reacted. In any case, the ratio between the polyvalent isocyanate and the polyhydric alcohol is selected so that the obtained polyurethane prepolymer has a plurality of isocyanate groups. Furthermore, for the purpose of obtaining a self-emulsifying polyurethane prepolymer, the proportion of constituent units based on component (B) in the polyurethane prepolymer is from 5 to 50 based on the total amount of all constituent units of the prepolymer. Molar% is preferred. If the proportion of the structural unit based on the component (B) is less than 5 mol%, aqueous emulsification is difficult, while if it exceeds 50 mol%, the viscosity of the obtained aqueous dispersion of polyurethane becomes extremely high, and the workability decreases. easy.

The organic solvent which is hydrophilic and has no active hydrogen used in the reaction of components (A), (B) and (C) includes ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate and ethyl acetate; tetrahydrofuran And N-methylpyrrolidone. The preferred amount of the organic solvent is 5 to 100 parts by weight of the polyurethane prepolymer.
50 parts by weight.

By the above method, an organic solvent solution of a self-emulsifying polyurethane prepolymer is obtained. While stirring the organic solvent solution of the polyurethane prepolymer in a state where the carboxyl group in the polyurethane prepolymer is neutralized with a base, water is added dropwise thereto, or the organic solvent solution is dropped into the stirred water. As a result, an aqueous emulsion dispersion is obtained. Usually, after obtaining the above-mentioned aqueous emulsion dispersion, the polyurethane prepolymer is subjected to chain extension. As the chain extender, polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, butylenediamine and hexamethylenediamine are preferred. In the polyurethane chain extension reaction, the preferred amount of the polyvalent amine to be used may be the same as the amount used in a general polyurethane chain extension reaction. As a result of the chain extension reaction, a self-emulsifying polyurethane aqueous emulsion which is polymerized and has excellent physical properties can be obtained.

The main uses of the self-emulsifying polyurethane aqueous emulsions are as adhesives, texture finishes, foams, inks or coatings.
If necessary, an appropriate amount of an ultraviolet absorber, an antioxidant, an antifoaming agent, a leveling agent, a thickener, a rheology control agent and the like may be added. When used as a coating agent, preferable materials of the support include metal, wood, stone, glass, cloth, leather, paper, plastic, and the like.

[0014]

Examples and Comparative Examples Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1 1 having a stirrer and a reflux funnel
In a liter volume separable flask (hereinafter referred to as a reactor), a polycarbonate diol having a molecular weight of 2,000 [Carbodiol D-2000, manufactured by Toagosei Co., Ltd.] 2
55.59 g and 34.29 g of methyl ethyl ketone were added and stirring was started. Next, 70.10 g of isophorone diisocyanate was added, and the temperature of the reaction solution was adjusted to 60 ° C. Further, 0.009 g of dibutyltin dilaurate was added and reacted at a temperature of 75 ° C. for 60 minutes. 17.23 g of dimethylolpropionic acid and 12.9 of triethylamine
By reacting 7 g in 34.29 g of methyl ethyl ketone, a solution of the amine salt of dimethylolpropionic acid in methyl ethyl ketone (hereinafter referred to as solution A) was obtained.

Solution A and 0.033 g of dibutyltin dilaurate were added to a reactor, and the temperature of the solution was raised to 83 ° C.
Hold for 0 minutes to complete the reaction. The self-emulsifying polyurethane prepolymer thus obtained was made into an aqueous emulsion by the following operation. After cooling the reaction solution, the stirring speed was increased to 250 rpm, and 457.91 g of distilled water was added dropwise. On the way, the viscosity of the system once increased, but when distilled water was further added, the liquid color became bluish white and the viscosity rapidly decreased (phase inversion), and a low-viscosity emulsion was obtained. (Reference) A prepolymer chain was extended by adding a mixture of 114.48 g of distilled water and 1.63 g of diethylenetriamine to the above emulsion. At this time, the color of the reaction solution changed from bluish white to white. Then 70-80
The mixture was heated to ℃ and demethylethyl ketone was obtained to obtain a self-emulsifying aqueous polyurethane emulsion.

[0016]

Comparative Example 1 The procedure of Example 1 was basically repeated, except that a solution prepared by dissolving 17.23 g of dimethylolpropionic acid in 34.29 g of methyl ethyl ketone (hereinafter referred to as solution B) was added to the reactor in place of the solution A in Example 1. The same operation was performed. Solution B was added to the reactor together with 0.033 g of dibutyltin dilaurate, and the same operation as in Example 1 was carried out. After that, a considerable amount of unreacted powder (dimethylolpropionic acid) remained in the cooled reaction solution. However, 12.97 g of triethylamine was added to the reaction solution to neutralize it. The stirring rate of the reactor was increased to 250 rpm and an attempt was made to drop 457.91 g of distilled water into the reaction solution. However, the viscosity of the system increased during the operation, and a white gel-like mass was formed. It was interrupted.

[0017]

According to the present invention, a polyurethane prepolymer having a self-emulsifying property can be produced with high production efficiency.

Claims (2)

[Claims] 1. A polyisocyanate, a monovalent amine salt of a polyhydric alcohol having a carboxyl group and another polyhydric alcohol are reacted in the presence of a hydrophilic organic solvent having no active hydrogen. Of producing a self-emulsifying polyurethane prepolymer. 2. A polyhydric isocyanate, a monohydric amine salt of a polyhydric alcohol having a carboxyl group and another polyhydric alcohol are used in a molar ratio of isocyanate group to hydroxyl group of 100: 40 to 95. A method for producing a self-emulsifying polyurethane prepolymer of the above.