JPH10287722A - Production of aqueous resin dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production process whereby an aq. resin dispersion contg. a vinyl polymer and a self-emulsifiable polyurethane can be easily obtd. SOLUTION: This process comprises the first step wherein a polyisocyanate, a monovalent amine salt of a carboxylated polyhydric alcohol, and other polyhydric alcohols are reacted in a molar ratio of NCO/OH higher than 1 in a vinyl monomer having a solubility parameter of 8.5-9.5 and having no active hydrogen atom. giving a vinyl monomer soln. of a self-emulsifiable polyurethane prepolymer; the second step wherein the vinyl monomer soln. obtd. in the former step is mixed with a chain extender and emulsified in an aq. medium, or the soln. is emulsified in an aq. medium and mixed with a chain extender, giving an aq. emulsion of a vinyl monomer soln. of a self-emulsifiable polyurethane; and the third step wherein the vinyl monomer in the aq. emulsion obtd. in the second step is polymerized.

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 an aqueous resin dispersion by polymerizing a vinyl monomer in the presence of a self-emulsifying polyurethane.

[0002]

2. Description of the Related Art Self-emulsifying polyurethane emulsions that can be stably emulsified and dispersed in an aqueous medium without using an emulsifier are superior in storage stability and mechanical strength to other polyurethane emulsions using an emulsifier. It is suitably used for many uses including agents. A general method for producing a self-emulsifying polyurethane emulsion comprises the following first step and second step (for example, Japanese Patent Publication No. Sho 42
-24192). First step: an organic solvent solution of a polyurethane prepolymer having an anionic group by reacting a polyhydric alcohol having an anionic group such as polyvalent isocyanate and dimethylolpropanoic acid and other polyhydric alcohols in an organic solvent. Manufacturing process. Second step: After neutralizing an anionic group in the polyurethane prepolymer with a base, the prepolymer is emulsified and dispersed in an aqueous medium, and a urethane chain extender (hereinafter simply referred to as a chain extender) is added. Then, the prepolymer is made into polyurethane. Thereafter, if necessary, a step of removing an organic solvent contained in the aqueous dispersion by distillation or the like.

In contrast to the self-emulsifying polyurethane emulsion, a self-emulsifying emulsion comprising a vinyl polymer and polyurethane (hereinafter sometimes referred to as a modified polyurethane emulsion) has a low production cost and has excellent properties of a polyurethane emulsion. Has been put to practical use. Conventionally, such a modified polyurethane emulsion is prepared by using a vinyl monomer in place of an organic solvent in the first step of the above-mentioned method for producing a self-emulsifying polyurethane emulsion, and further polymerizing the vinyl monomer after the second step. It was manufactured by the method. However, in the first step of the above-mentioned production method, the polyhydric alcohol having an anionic group such as powdered dimethylolpropionic acid at room temperature is hardly dissolved in the reaction system composed of the polyurethane prepolymer and vinyl monomer to be produced. In addition, it was difficult to introduce a necessary amount of carboxyl groups into the polyurethane prepolymer for self-emulsification.

In order to increase the solubility of dimethylolpropionic acid or the like in a reaction solution, the amount of a vinyl monomer which also acts as a solvent in the reaction for synthesizing the polyurethane prepolymer in the first step is increased, or the amount of vinyl monomer is increased. Although the means of using an organic solvent together with the body has been adopted, new problems have arisen in each case. That is, when the amount of the vinyl monomer used was excessively increased, the physical properties of the resulting modified polyurethane decreased, while when an organic solvent was used in combination, the yield of the modified polyurethane per batch was reduced by the amount of the organic solvent used.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a modified aqueous polyurethane dispersion having excellent physical properties without lowering 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 is a method for producing an aqueous resin dispersion comprising the following steps (1), (2) and (3). Step (1): In a vinyl monomer having a solubility parameter of 8.5 to 9.5 and having no active hydrogen atom, a polyvalent isocyanate, a monovalent amine salt of a polyhydric alcohol having a carboxyl group and other polyvalents A step of reacting an alcohol with an isocyanate group in an excess ratio to a hydroxyl group to obtain the vinyl monomer solution (a) of a self-emulsifying polyurethane prepolymer. Step (2): After adding a chain extender to the vinyl monomer solution (a) obtained in step (1), emulsify and disperse in an aqueous medium, or convert the vinyl monomer solution (a) to an aqueous medium. A step of obtaining an aqueous emulsified dispersion (b) of a vinyl monomer solution of a self-emulsifying polyurethane by emulsifying and dispersing in a medium and then adding a chain extender. Step (3): a step of polymerizing a vinyl monomer in the aqueous emulsified dispersion (b) obtained in step (2). Hereinafter, the present invention will be described in more detail.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The vinyl monomer used in the present invention (hereinafter referred to as the “monomer of the present invention”) is as described above.
A solubility parameter (hereinafter referred to as SP value) of 8.5 to
A vinyl monomer having no active hydrogen atom at 9.5,
Specifically, methyl acrylate (9.38; SP value of the monomer; the same applies hereinafter), methyl methacrylate (9.
25), ethyl acrylate (8.81), n-butyl acrylate (8.63), isobutyl acrylate (8.50), 2-ethylhexyl acrylate (8.8.
53), vinyl acetate (9.05) and styrene (9.
32) and the like. In the present invention, a vinyl monomer having an SP value outside the range of 8.5 to 9.5, for example, lauryl methacrylate (SP value: 8.34), methoxyethyl acrylate (SP value: 9.80) and acrylonitrile (SP value: 11.57) can also be used, in which case a vinyl monomer having an SP value of 8.5 to 9.5 is used in combination, and the SP value of the entire monomer mixture is 8.5 to 9.5. Need to be adjusted. In the case of a vinyl monomer having an SP value of less than 8.5, the solubility of a monovalent amine salt of a polyhydric alcohol having a carboxyl group in a vinyl monomer is too low, which makes it difficult to introduce a carboxyl group into polyurethane. The aqueous emulsified dispersion (b) comprising the polyurethane and the vinyl monomer obtained in the step (2) cannot maintain the emulsion state and has a high viscosity. On the other hand, when the vinyl monomer has an SP value of more than 9.5, aggregation and precipitation of emulsified particles occur in the aqueous emulsified dispersion (b).

In the present invention, the polyvalent isocyanate (hereinafter referred to as component (A)) includes ethylene diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane-1,4-diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate. , P-xylylene diisocyanate, 1,
4-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate,
4,4′-diphenylmethane diisocyanate, 2,
Examples thereof include 4'-diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanate, and 1,5-naphthylene diisocyanate, and a mixture thereof can also be used. Also, urethane, allophanate,
Bifunctional isocyanates modified with urea, burette, carbimide, urethaneimine or isocyanurate residues can also be used.

The monovalent amine salt of a polyhydric alcohol having a carboxyl group [hereinafter referred to as component (B)] includes 2,2
Examples thereof include monovalent amine salts of polyhydric alcohols having a carboxyl group, such as 2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid. As a monovalent amine,
Dimethylamine, trimethylamine, diethylamine,
Triethylamine, tributylamine, N-ethylmorpholine and the like. Preferably, trimethylamine, triethylamine, tributylamine and N-
It is a monovalent tertiary amine represented by ethylmorpholine and the like.

[0010] Other polyhydric alcohol [the following component (C)
Is preferred as a high molecular weight polyhydric alcohol having a number average molecular weight of 500 to 5,000, specifically, polyester polyol, polyester polyamide polyol, polyether polyol, polythioether polyol, polycarbonate polyol, polyacetal polyol, polyolefin polyol and And polysiloxane polyols. Also, if necessary,
Ethylene glycol, propylene glycol, 1,4-
Low molecular weight polyhydric alcohols such as butanediol, diethylene glycol, neopentyl glycol, cyclohexanedimethanol, glycerol, trimethylolpropane and pentaerythritol can also be used.

The above components (A), (B) and (C)
The molar ratio of isocyanate groups to hydroxyl groups is 100: (40 to
95). When the molar ratio of the hydroxyl group to the isocyanate group exceeds 0.95, the molecular weight of the obtained prepolymer becomes too high and the viscosity of the vinyl monomer solution of the prepolymer increases, so that it is difficult to obtain a stable aqueous emulsion dispersion. , While the molar ratio is 0.4
When it is less than 0, it is difficult to obtain physical properties such as tensile strength based on polyhydric alcohol, particularly component (C). Furthermore, component (B)
The preferred amounts of the components (A), (B) and (C)
5 to 50 mol% based on the total amount of When the amount of the component (B) is less than 5 mol%, the obtained polyurethane prepolymer or polyurethane hardly exhibits self-emulsifiability, while when it exceeds 50 mol%, the viscosity of the obtained aqueous resin dispersion becomes extremely high. And handling workability is inferior.

In the reaction of each component, component (A),
(B) and (C) may be reacted at once, or the components (A) and (C) may first be reacted in a molar ratio of isocyanate group to hydroxyl group of preferably 100: 5 to 100: 70. And then reacting the component (B). The preferred amount of the monomer of the present invention used in the reaction for synthesizing the polyurethane prepolymer is as follows: the produced polyurethane prepolymer: the monomer of the present invention = (50 to 9)
0): (50 to 10) (weight ratio). When the ratio of the polyurethane prepolymer is less than 50, a carboxyl group can be easily introduced into the polyurethane prepolymer without using the component (B) in the present invention. In this case, a self-emulsifying polyurethane prepolymer can be produced by a conventional technique, that is, a method using a polyhydric alcohol having a carboxyl group as a raw material for producing a polyurethane prepolymer. On the other hand, when the proportion of the polyurethane prepolymer exceeds 90, the viscosity of the reaction solution in the synthesis reaction of the polyurethane prepolymer is too high, and it becomes difficult to react the component (B) with other components. The reaction 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.

By the above method, the above-mentioned vinyl monomer solution (a) of the self-emulsifying polyurethane prepolymer is obtained. In the present invention, a dispersion in which the self-emulsifying polyurethane and the vinyl monomer of the present invention are emulsified and dispersed in an aqueous medium is produced in the following step. Specifically, water is added dropwise to the solution (a) while stirring the solution (a) to produce an aqueous emulsified dispersion of a prepolymer and a vinyl monomer. After the method of making the polymer polyurethane, or after adding a chain extender to the solution (a) to make the prepolymer polyurethane,
Solution of the obtained polyurethane monomer (b) of the polyurethane of the present invention
And the like can be adopted. The prepolymer is rapidly polyurethaneized by the addition of a chain extender.

Examples of the chain extender include polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, butylenediamine and hexamethylenediamine. The amount of the polyamine used in the polyurethane chain extension reaction is the amount used in a general polyurethane chain extension reaction, that is, based on the isocyanate group in the polyurethane prepolymer, The amount is such that the ratio (molar ratio) is 25 to 80 mol%.

Next, the vinyl monomer of the present invention in the aqueous emulsion dispersion obtained in the above step is subjected to radical polymerization. At this time, the coexisting self-emulsifying polyurethane serves as a dispersant for the vinyl monomer of the present invention, and the polymerization has a reaction mechanism substantially similar to that of emulsion polymerization. A radical-generating compound can be used as the polymerization initiator, and specifically, is composed of a peroxide such as azobisisobutyronitrile, t-butylhydroxyperoxide, or t-butylhydroxyperoxide and a reducing agent such as sodium sulfite. Redox initiators and the like can be mentioned. The time when the polymerization initiator is added to the reaction system is preferably after step (2) in the present invention. Specifically, the aqueous emulsified dispersion obtained in step (2) is heated to a predetermined temperature. It is preferable that an aqueous solution of the polymerization initiator is added dropwise while stirring.

By the above polymerization, a self-emulsifying polyurethane emulsion modified with a vinyl polymer, that is, an aqueous resin dispersion of the present invention is obtained. To the aqueous resin dispersion, if necessary, an ultraviolet absorber, an antioxidant, an antifoaming agent, a leveling agent, a thickener, and the like can be added in a usual amount. The main use of aqueous resin dispersions is as coatings, but they can also be used, for example, in adhesives, texture finishes, foams or inks. When used as a coating agent, preferable materials for the support include metal, wood, stone, glass, cloth, leather, paper, and plastic.

[0017]

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
A polycarbonate diol having a molecular weight of 2,000 [Carbodiol D-2000, manufactured by Toagosei Co., Ltd.]
After adding 40.78 g and raising the temperature to 60 ° C., stirring was started. Then, 77.49 g of isophorone diisocyanate
Is added, and then dibutyltin dilaurate 0.03
2 g was added and reacted at a temperature of 60 ° C. for 60 minutes. In a mixed solution consisting of 50.30 g of methyl methacrylate and 54.49 g of butyl acrylate, 24.45 g of dimethylolpropionic acid and 11.68 g of triethylamine were added and mixed by stirring to obtain a solution (hereinafter referred to as solution A).

Solution A and 0.032 g of dibutyltin dilaurate were added to a reactor, and the temperature of the solution was increased to 70 ° C.
It was maintained for 0 minutes to complete the reaction of synthesizing the polyurethane prepolymer. 1.50 g of a 70% butyl hydroperoxide aqueous solution was added to the obtained reaction solution, and then cooled to room temperature. Next, the stirring speed was increased to 250 rpm, and 539.90 g of water was dropped into the reaction solution over 7 minutes. 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. By adding a mixture of 59.99 g of distilled water and 1.80 g of diethylenetriamine to the emulsion,
The prepolymer chain was extended. At this time, the color of the reaction solution changed from bluish white to white.

Next, while blowing nitrogen gas into the emulsion, maintaining the temperature inside the reactor at 65 ° C., the sodium sulfite / formaldehyde complex 1.78 was obtained.
g of water in 3.85 g of water was dropped into the reactor over 60 minutes, and after the dropping was completed, the reaction solution was further cooled to 65 for 30 minutes.
The polymerization was completed by maintaining the temperature in ° C. The aqueous resin dispersion obtained by the above method had a solid content of 40.
8% by weight, pH 6.8 and viscosity at 25 ° C. 80 cps
And the average particle size of the dispersed particles was 75 nm.

[0020]

Comparative Example 1 Instead of the solution A in Example 1, 24.45 g of dimethylolpropionic acid was added to a mixed solution consisting of 50.30 g of methyl methacrylate and 54.49 g of butyl acrylate, and the mixture was sufficiently stirred. The procedure was basically the same as that of Example 1 except that the solution (hereinafter referred to as solution B) was added to the reactor. Solution B together with 0.033 g of dibutyltin dilaurate was added to a reactor containing polycarbonate and isophorone diisocyanate, etc.
After operating in the same manner as in Example 1, it was confirmed that a considerable amount of unreacted powder (dimethylolpropionic acid) remained in the cooled reaction solution, and 11.68 g of triethylamine was added to the reaction solution. In addition, it was neutralized. The stirring speed of the reactor was increased to 250 rpm, and 457.9 distilled water was added to the reaction solution.
An attempt was made to add 1 g, but the operation was interrupted because the viscosity of the system increased during the operation and a white gel-like mass was generated, which made stirring impossible.

[0021]

According to the present invention, an aqueous resin dispersion comprising a vinyl polymer and a self-emulsifying polyurethane can be easily obtained.

Claims (1)

[Claims] 1. A method for producing an aqueous resin dispersion comprising the following steps (1), (2) and (3). Step (1): In a vinyl monomer having a solubility parameter of 8.5 to 9.5 and having no active hydrogen atom, a polyvalent isocyanate, a monovalent amine salt of a polyhydric alcohol having a carboxyl group and other polyvalents A step of reacting an alcohol with an isocyanate group in an excess ratio to a hydroxyl group to obtain the vinyl monomer solution (a) of a self-emulsifying polyurethane prepolymer. Step (2): After adding a chain extender to the vinyl monomer solution (a) obtained in step (1), emulsify and disperse in an aqueous medium, or convert the vinyl monomer solution (a) to an aqueous medium. A step of obtaining an aqueous emulsified dispersion (b) of a vinyl monomer solution of a self-emulsifying polyurethane by emulsifying and dispersing in a medium and then adding a chain extender. Step (3): a step of polymerizing a vinyl monomer in the aqueous emulsified dispersion (b) obtained in step (2).