JP2000355603A - Production of aqueous resin dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an aqueous resin dispersion which enables the formation of a coating film excellent in water resistance. SOLUTION: This method comprises the initial polymerization step wherein a part of a polymerizable monomer component consisting of a polymerizable monomer having an acidic group and other polymerizable monomers copolymerizable therewith are fed in the presence of an emulsifier and at least 80 wt.% of the monomer component is polymerized and the main polymerization step wherein the rest of the monomer component is polymerized provided that: the total amount of the monomer having an acidic group used in the method is 0.1-5 wt.% of the total amount of the monomer component; 5-30 wt.% of the total amount of the monomer component is used in the initial polymerization step; the total amount of the emulsifier used in the method is 1-3.5 wt.% of the total amount of the monomer component: and 35-95 wt.% of the total amount of the emulsifier is used in the initial polymerization step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous resin dispersion used for paints and coatings requiring water resistance.

[0002]

2. Description of the Related Art In recent years, paints for coating, surface protective agents for structures,
As a coating agent for substrates with low water and weather resistance,
Aqueous paints containing an aqueous resin dispersion are widely used. The aqueous resin dispersion is usually obtained by emulsion polymerization that requires an emulsifier that is a hydrophilic substance, and furthermore, in order to ensure the stability of the obtained aqueous resin dispersion, an emulsifier is often used, Generally, a monomer having an acidic group is copolymerized. However, a hydrophilic component such as an emulsifier or a monomer having an acidic group has a drawback that the water resistance of a coating film, specifically, the water resistance, the water absorption resistance, the water absorption resistance, the water whitening resistance, and the like are reduced.

[0003] In order to improve the water resistance of the coating film,
Various studies have been made on aqueous resin dispersions. As one of the methods, reduction of the emulsifier which is a hydrophilic component and the component having an acidic group, and reduction of the particle diameter of the aqueous resin dispersion can be considered. That is, by reducing the hydrophilic component, forming a dense coating film by reducing the particle size, reducing the amount of water permeating into the coating film, and finely dispersing interparticle gaps by reducing the particle size. This is expected to prevent whitening caused by localization of the intruded water.

However, when the amount of the hydrophilic component is simply reduced, the stability of the aqueous resin dispersion during polymerization, the mechanical stability,
A problem arises in that the chemical stability is significantly reduced. Even in such a case, if the particle size is increased, a stable aqueous resin dispersion can be obtained, but if the particle size is increased, the water resistance decreases. Regarding reducing the particle size of the aqueous resin dispersion, see, for example, JP-A-10-1827.
No. 06 proposes a method for producing a water-dispersed resin composition having a small particle size and a small amount of residual monomers. However, the method proposed in the publication discloses a large amount of a water-soluble polymer having an emulsifying activity in its production. Therefore, water resistance cannot be expected. JP-A-9-302006 proposes a method for producing a polymer latex which is ultrafine particles having an average particle diameter of 1 to 50 nm and has a small emulsifier content. , There is a problem that economic efficiency is low and practicability is low. JP-A-8-48705 proposes a copolymer latex having a high polymerization stability by a seed polymerization method and a narrow particle size distribution.
Since it is necessary to prepare the seed particles in a separate reaction vessel during production, the process is complicated and takes time,
It was hard to say that it was an industrially simple method.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the amounts of a hydrophilic component, an emulsifier, and a polymerizable monomer having an acidic group in order to obtain an aqueous resin dispersion having excellent water resistance. Another object of the present invention is to provide an industrially simple production method of an aqueous resin dispersion having a small particle size and a resin solid content sufficient for practical use.

[0006]

Means for Solving the Problems In view of the above-mentioned problems, the present inventor has proposed that in a coating film formed by a conventional aqueous resin dispersion, a hydrophilic component contained in the aqueous resin dispersion is added to the coating film. Various methods of emulsion polymerization were examined, paying attention to the fact that water is infiltrated and that water localized between the particle intervals causes whitening of the coating film. As a result, after setting the amount of the polymerizable monomer having an acidic group and the emulsifier used in all the steps in a specific range, the emulsion polymerization is divided into the initial polymerization and the main polymerization, and in the initial polymerization step, The specific ratio of the total amount of the polymerizable monomer component used in all the steps and the specific ratio of the amount of the emulsifier used in all the steps are charged and reacted at once, and the polymerization is almost completed once. After that, in the main polymerization step, by reacting the remaining polymerizable monomer component and the emulsifier, it is possible to achieve both reduction in the hydrophilic component and reduction in the particle size, and furthermore, it can be put to practical use. It has been found that an aqueous resin dispersion having a sufficient resin solid content can be obtained, and the present invention has been completed.

That is, the method for producing an aqueous resin dispersion of the present invention comprises a polymerizable monomer having an acidic group and a polymerizable monomer component containing another polymerizable monomer copolymerizable therewith. Part of the polymerizable monomer component charged in the presence of an emulsifier, and an initial polymerization step of polymerizing 80% by weight or more of the polymerizable monomer component, and a main polymerization step of polymerizing the remaining polymerizable monomer component. And a total amount of the polymerizable monomer having an acidic group used in all the steps of 0.1 to 5% by weight based on all the polymerizable monomer components. 5 to 30% by weight of the total polymerizable monomer component
The total amount of the emulsifier used in all the steps is adjusted to 1 to 3.5% by weight based on all the polymerizable monomer components, and 35 to 95% by weight of the total emulsifier in the initial polymerization step.
Is used.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing an aqueous resin dispersion of the present invention is based on a multistage emulsion polymerization comprising an initial polymerization and a subsequent main polymerization. The initial polymerization refers to a polymerization initiated by adding a polymerization initiator in a state where an aqueous medium, an emulsifier, and a part of all polymerizable monomer components are mixed. In the initial polymerization,
80% by weight or more, preferably 90% by weight of the charged monomer component
By polymerizing at least weight%, a core of the polymer particles is formed. In the initial polymerization, polymerization may be started by adding a polymerizable monomer component to be used as a pre-emulsion emulsified by mechanical stirring, or polymerization may be started from a simple mixed state of an aqueous medium, an emulsifier, and a polymerizable monomer. You may start.

In the main polymerization, after the initial polymerization is once completed,
Specifically, it refers to polymerization performed by polymerizing 80% by weight or more, preferably 90% by weight or more of the charged polymerizable monomer component, and then adding a new polymerizable monomer component. The main polymerization may be performed in one stage, or may be performed in a multi-stage polymerization divided into multiple stages. When the main polymerization is carried out by multi-stage polymerization, at least 80% by weight, preferably 90% by weight or more of the polymerizable monomer components used up to the previous stage are polymerized, and then a new polymerizable monomer component is added and reacted. Let it. The method of adding the monomer in the main polymerization may be selected as appropriate, such as batch addition in a monomer or pre-emulsion, divided addition, continuous dropping, or the like. It may be different.

The polymerizable monomer component, which is the main raw material of the aqueous resin dispersion of the present invention, comprises a polymerizable monomer having an acidic group and another polymerizable monomer copolymerizable with the acidic group-containing polymerizable monomer. And a polymerizable monomer. In the present invention, it is important to use 5 to 30% by weight, preferably 10 to 20% by weight, of all the polymerizable monomer components in the initial polymerization step. When the amount of the polymerizable monomer component used in the initial polymerization step is less than 5% by weight, the resulting aqueous resin dispersion tends to have a large particle diameter. On the other hand, if the amount of the polymerizable monomer component used in the initial polymerization step exceeds 30% by weight, heat generation in the initial stage of polymerization is large, and a problem occurs in safety.

Specific examples of the polymerizable monomer having an acidic group include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; fumaric acid,
Unsaturated polycarboxylic acids such as itaconic acid; polymerizable monomers having a carboxyl group such as partially esterified ethylenically unsaturated polycarboxylic acids such as monoethyl maleate and monoethyl itaconate; vinyl sulfonic acid, styrene sulfone Polymerizable monomers having a sulfonic acid group such as acid and sulfo (meth) acrylate; 2- (meth) acryloyloxyethyl acid phosphate, 2- (meth) acryloyloxypropyl acid phosphate, 2- (meth) acryloyloxy- Acidic phosphoric acid ester-based polymerizable monomers such as 3-chloropropyl acid phosphate and 2-methacryloyloxyethylphenylphosphoric acid; and the like. In particular, among the polymerizable monomers having an acidic group described above, a polymerizable monomer having a carboxyl group is preferable, and an ethylenically unsaturated monocarboxylic acid such as (meth) acrylic acid is more preferable. Only one type of polymerizable monomer having an acidic group may be used, or two or more types may be used in combination. The polymerizable monomer having an acidic group may be used in only one of the initial polymerization and the main polymerization, or may be used in both.

In the present invention, the total amount of the polymerizable monomer having an acidic group used in all the steps is 0.1 to 5% by weight based on the total amount of the polymerizable monomer component. Is important, and preferably 0.5 to 2.5% by weight. By setting the total amount of the polymerizable monomer having an acidic group in the above range, the content of the hydrophilic component can be reduced, and an aqueous resin dispersion having excellent water resistance can be obtained. If the total amount of the polymerizable monomer having an acidic group is less than 0.1% by weight, the mechanical stability and chemical stability of the emulsion will be reduced. Will be impaired.

Specific examples of other polymerizable monomers copolymerizable with the polymerizable monomer having an acidic group include the following. In addition, only one type of the polymerizable monomer exemplified below may be used, or two or more types may be used in combination. For example, as main polymerizable monomers, methyl (meth) acrylate, ethyl (meth) acrylate, (meth)
(Meth) acrylic acid esters synthesized by an ester forming reaction of (meth) acrylic acid such as n-butyl acrylate, neopentyl (meth) acrylate, isobornyl (meth) acrylate and an alcohol having 1 to 18 carbon atoms; Aromatic vinyl monomers such as styrene, vinyltoluene and α-methylstyrene; vinyl esters such as vinyl acetate; vinyl ethers such as methyl vinyl ether;

For example, polymerizable monomers having a functional group other than an acidic group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, (meth) acrylic acid and polyethylene. Monoester with glycol or polypropylene glycol, α-
Monomers having a hydroxyl group such as (hydroxymethyl) methyl acrylate; monomers having an epoxy group such as glycidyl (meth) acrylate; monomers having a nitrile group such as (meth) acrylonitrile; N-monomethyl Monomers having an amide group such as (meth) acrylamide, N-monoethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, diacetone acrylamide, N-methylol (meth) acrylamide; dimethyl (meth) acrylate Monomers having an amino group such as aminoethyl and aminostyrene; monomers having other functional groups such as isopropenyloxazoline and vinylpyrrolidone; and the like.

For example, polyfunctional polymerizable monomers include (meth) acrylic acid and ethylene glycol, propylene glycol, 1,3-butylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, trimethylolpropane, pentaerythritol (Meth) acrylates of polyhydric alcohols such as esters with polyhydric alcohols such as dipentaerythritol; polyfunctional vinyl monomers such as divinylbenzene; (meth) acrylic acids such as allyl (meth) acrylate Allyl ester; and the like.

For example, other polymerizable monomers include:
Monomers having a halogen component, such as vinyl chloride, vinylidene chloride, chlorostyrene, vinyl fluoride, vinylidene fluoride, and perfluorooctylethyl (meth) acrylate; and the like. In order to efficiently reduce the particle diameter in the present invention, among the polymerizable monomer components used in the initial polymerization, a polymerizable monomer having a strong hydrophobicity of 5% by weight or more,
Preferably, it is used in an amount of 10% by weight or more. Examples of highly hydrophobic polymerizable monomers include acrylic acid esters having an alkyl group having 6 or more carbon atoms, such as 2-ethylhexyl acrylate, normal octyl acrylate, and cyclohexyl acrylate; n-butyl methacrylate, methacrylic acid Methacrylic acid esters having an alkyl group having 4 or more carbon atoms, such as t-butyl, 2-ethylhexyl methacrylate, and cyclohexyl methacrylate; aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene, and divinylbenzene; And the like. These highly hydrophobic polymerizable monomers may be used alone in the initial polymerization, or may be used in combination so that the total amount thereof becomes a specific amount or more.

In the present invention, in order to impart good weather resistance to the aqueous resin dispersion, a specific (meth) acrylate, a monomer having an ability to stabilize ultraviolet light, It is preferable to use a monomer having an absorbing ability and a monomer having an alkoxysilane group. Specifically, an esterified product of (meth) acrylic acid and an alcohol having a cycloalkyl group such as cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, and cyclododecyl (meth) acrylate; Esterified product of tertiary alcohol such as t-butyl acid and (meth) acrylic acid; vinyltrimethoxysilane, γ
-(Meth) acryloxypropyltrimethoxysilane,
A polymerizable monomer having an alkoxysilane group such as allyltriethoxysilane and trimethoxysilylallylamine;
2,4-dihydroxybenzophenone, or 2,
2-hydroxy-4- [3- (meth) acryloxy-2-hydroxypropoxy] benzophenone obtained by reacting 2 ', 4-trihydroxybenzophenone with glycidyl (meth) acrylate, 2,2'-dihydroxy- Benzophenone monomers such as 4- [3- (meth) acryloxy-2-hydroxypropoxy] benzophenone and 2- [2′-hydroxy-5′-
(Methacryloyloxymethyl) phenyl] -2H-benzotriazole, 2- [2′-hydroxy-5′-
(Methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-
(Methacryloyloxypropyl) phenyl] -2H-
Benzotriazole, 2- [2'-hydroxy-5'-
(Methacryloyloxyhexyl) phenyl] -2H-
Benzotriazole, 2- [2'-hydroxy-3'-
t-butyl-5 '-(methacryloyloxyethyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-5'-t-butyl-3'-(methacryloyloxyethyl) phenyl] -2H-benzotriazole 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-chloro-2H-benzotriazole, 2- [2'-hydroxy-5'-(methacryloyloxyethyl) phenyl] -5- Methoxy-
2H-benzotriazole, 2- [2′-hydroxy-
5 '-(methacryloyloxyethyl) phenyl] -5
UV-absorbing ability of benzotriazole monomers such as -cyano-2H-benzotriazole, 2- [2'-hydroxy-5 '-(methacryloyloxyethyl) phenyl] -5-t-butyl-2H-benzotriazole A monomer having the formula: 4- (meth) acryloyloxy-2,2,
6,6-tetramethylpiperidine, 4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2
6,6-pentamethylpiperidine, 4- (meth) acryloylamino-1,2,2,6,6-pentamethylpiperidine, 4-cyano-4- (meth) acryloyloxy-2,2,6,6- Tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acrylamino-2,
2,6,6-tetramethylpiperidine, 4-crotoyloxy-2,2,6,6-tetramethylpiperidine,
-Crotoylamino-2,2,6,6-tetramethylpiperidine, 1-crotoyl-4-crotoyloxy-
Monomers having an ability to stabilize ultraviolet light, such as piperidine monomers such as 2,2,6,6-tetramethylpiperidine; and at least one of these monomers is used. Is preferred.

In the present invention, it is important that the total amount of the emulsifier used in all the steps is 1 to 3.5% by weight based on the total amount of the polymerizable monomer components used in all the steps. And preferably 1.5 to 3% by weight. If the total amount of the emulsifier is less than 1% by weight, the emulsion stability such as polymerization stability, mechanical stability, and chemical stability tends to decrease, and the particle size increases and the water resistance decreases. . On the other hand, the total amount of the emulsifier used was 3.5.
If the amount is more than 10% by weight, water resistance will decrease.

Furthermore, it is important that the amount of the emulsifier used in the initial polymerization is 35 to 95% by weight, preferably 40 to 80% by weight, based on the total amount of the emulsifier used in all the steps. Good. By setting the amount of the emulsifier used in the initial polymerization in the above range, it is possible to effectively reduce the particle size in the present invention, although the amount of the emulsifier used in all the steps is small. If the amount of the emulsifier used in the initial polymerization is less than 35% by weight, the particle size increases, while if it exceeds 95% by weight, the polymerization stability in the main polymerization step is undesirably reduced.

The emulsifier that can be used in the present invention is not particularly limited, and examples thereof include an anionic surfactant,
All surfactants such as nonionic surfactants, cationic surfactants, amphoteric surfactants, and polymeric surfactants can be used. Further, in order to further improve the water resistance of the coating film, it is preferable to use a polymerizable surfactant having one or more polymerizable carbon-carbon unsaturated bonds in the molecule.

Examples of the anionic surfactant include, for example, alkali metal alkyl sulfates such as sodium dodecyl sulfate and potassium dodecyl sulfate; ammonium alkyl sulfates such as ammonium dodecyl sulfate; sodium dodecyl polyglycol ether sulfate; Hoshinoate; alkali metal salt of sulfonated paraffin,
Alkyl sulfonates such as ammonium salts of sulfonated paraffins; fatty acid salts such as sodium laurate, triethanolamine oleate and triethanolamine aviate; alkyl aryl sulfonates such as sodium dodecylbenzene sulfonate and alkali metal sulfate of alkali phenol hydroxyethylene;
High alkyl naphthalene sulfonate; naphthalene sulfonic acid formalin condensate; dialkyl sulfosuccinate;
Polyoxyethylene alkyl sulfate salts; polyoxyethylene alkyl aryl sulfate salts; and the like.

Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether; polyoxyethylene alkyl aryl ether; sorbitan fatty acid ester; polyoxyethylene sorbitan fatty acid ester; and fatty acids such as glycerol monolaurate. Monoglycerides; polyoxyethyleneoxypropylene copolymers; condensation products of ethylene oxide with aliphatic amines, amides or acids; and the like can be used.

As the polymer surfactant, specifically,
For example, polyvinyl alcohol; sodium poly (meth) acrylate, potassium poly (meth) acrylate, ammonium poly (meth) acrylate, polyhydroxyethyl (meth) acrylate; polyhydroxypropyl (meth) acrylate; or a polymer thereof And copolymers of two or more polymerizable monomers, which are constituent units, and copolymers with other monomers. In addition, phase transfer catalysts such as crown ethers exhibit surface activity and may be used as a surfactant.

As the polymerizable surfactant, specifically,
For example, sodium propenyl-2-ethylhexylbenzenesulfosuccinate, sulfate of polyoxyethylene (meth) acrylate, ammonium salt of polyoxyethylene alkylpropenyl ether sulfate, phosphate of polyoxyethylene (meth) acrylate, polyoxyethylene Anionic polymerizable surfactants such as compounds having the structure of an alkylaryl sulfate salt and having an isopropenyl group or an allyl group; polyoxyethylene alkylbenzene ether (meth) acrylate, polyoxyethylene alkyl ether (meth) Nonionic polymerizable surfactants such as compounds having an acrylate or polyoxyalkylaryl ether structure and having an isopropenyl group or an allyl group; That.

As the emulsifier of the present invention, particularly, the emulsifier used in the main polymerization, a polymerizable surfactant which is an emulsifier having a polymerizable group among the surfactants exemplified above is suitably used. By using an emulsifier having a polymerizable group in the main polymerization step, an aqueous resin dispersion having excellent water resistance of a dried coating film can be obtained. Further, as the emulsifier in the present invention, only one of the above-described surfactants may be used, or two or more of the surfactants may be used in combination, and the same type may be used in the initial polymerization and the main polymerization. Or different types may be used.

The emulsion polymerization in the present invention is carried out by using, in addition to the polymerizable monomer component and the emulsifier, an aqueous medium serving as a medium for emulsification and a polymerization initiator for initiating the polymerization. is there. As the aqueous medium, water is usually used, and if necessary, a hydrophilic solvent such as a lower alcohol or ketone can be used in combination. The preparation of the aqueous medium is not particularly limited, and the preparation can be carried out step by step with the initial polymerization step and the main polymerization step, if necessary. The amount of aqueous medium used is
The solid content of the aqueous resin dispersion finally obtained is 35 to
Preferably, it is 60% by weight.

The polymerization initiator is not particularly restricted but specifically includes, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-amidinopropane) .dihydrochloride Salts, water-soluble azo compounds such as 4,4'-azobis (4-cyanopentanoic acid); persulfates such as potassium persulfate; hydrogen peroxide, peracetic acid, benzoyl peroxide, di-t-butyl peroxide and the like Peroxide; and the like.

The amount of the polymerization initiator used is not particularly limited, but is preferably 0.05 to 1% by weight, more preferably 0.1 to 1% by weight, based on the total amount of the polymerizable monomer components.
It is preferably 0.5% by weight. If the amount of the polymerization initiator is too large, the water resistance of the coating film is reduced. On the other hand, if the amount is too small, the polymerization rate becomes slow, and unreacted monomers are apt to remain. The polymerization initiator may be used alone or in combination of two or more. Further, in order to increase the polymerization rate, a reducing agent such as sodium hydrogen sulfite or a metal salt such as ferrous sulfate can be used in combination with the polymerization initiator, if necessary.

The polymerization initiator is added in an amount of 40 to 40% of the total amount used in the initial polymerization step in order to make the obtained polymer particles fine.
It is preferred to add 100% by weight. The addition method is not particularly limited, and may be any method such as batch charging, divided charging, and continuous dropping. In order to accelerate the completion of the polymerization, a part of the polymerization initiator may be further added before and after the addition of the polymerizable monomer component in the main polymerization step.

In the present invention, in addition to the polymerization initiator, a chain transfer agent can be added, if necessary, during the polymerization. For example, a compound having a thiol group such as t-dodecyl mercaptan can be added. Can be. In the present invention, after the polymerization is completed, a part or all of the acidic groups of the polymer having an acidic group may be neutralized with an alkaline substance, or may be left unneutralized.

The neutralizing agent is not particularly limited.
Conventionally known various neutralizing agents can be used. Specifically, for example, alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine And water-soluble organic amines such as monopropylamine, dimethylpropylamine, monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine. One of the above-described neutralizing agents may be used alone, or two or more may be used in combination. As the neutralizing agent, a low-boiling amine such as aqueous ammonia or monoetamolamine is preferable in consideration of odor and water resistance.

The polymerization conditions for the emulsion polymerization are not particularly limited in both the initial polymerization step and the main polymerization step, and may be appropriately selected. Specifically, the polymerization temperature is
Preferably 0-100 ° C, more preferably 40-95 ° C
Is good. The polymerization temperature may be the same or different in the initial polymerization step and the main polymerization step. Also,
The polymerization time can be appropriately selected depending on the progress of the reaction for the initial polymerization and the main polymerization, and is preferably in the range of 2 to 8 hours from the start to the end of the reaction. Further, the emulsion polymerization is preferably performed in an atmosphere of an inert gas such as a nitrogen gas. In the present invention, a hydrophilic solvent or other known additives may be further added as long as the physical properties of the obtained coating film are not deteriorated.

The aqueous resin dispersion obtained in the present invention has a solid content of 35 to 60% by weight, preferably 40 to 55% by weight.
% By weight, and the volume average particle diameter of the resin particles is 50%.
１１０110 nm, preferably 70-100 nm. If the solid content of the aqueous resin dispersion is less than 35% by weight, the aqueous resin dispersion is uneconomical and unpractical when applied as a paint or the like, while the solid content is 60% by weight.
If it exceeds, the polymerization stability will be impaired,
Not preferred. Further, the volume average particle diameter of the resin particles is 50.
If it is less than nm, the polymerization stability will be impaired, while if it exceeds 110 nm, it will be difficult to obtain good water resistance when the aqueous resin dispersion is applied as a paint or the like.

In the present invention, as described above, an aqueous resin dispersion obtained by using a UV-stable polymerizable monomer or a UV-absorbing polymerizable monomer as another polymerizable monomer. Although it is possible to impart weather resistance to the body, it is also possible to impart weather resistance by adding a substance having an ultraviolet light stabilizing ability or a substance having an ultraviolet absorbing ability to the obtained aqueous resin dispersion. . For example, a low molecular weight UV stabilizer or UV absorber without a polymerizable group,
It may be added to the aqueous resin dispersion obtained in the present invention, or may be added together with the polymerizable monomer at the time of polymerization of the aqueous resin dispersion, or the ultraviolet-stable polymerizable monomer or ultraviolet light A high-molecular-weight water-soluble resin or water-dispersible resin obtained by separately polymerizing an absorbent polymerizable monomer may be added.

The aqueous resin dispersion obtained in the present invention may be used as it is, or may be used by adding a curing agent such as polyfunctional isocyanate or polyfunctional hydrazine. Further, if necessary, further known additives, for example, a film-forming aid, a pigment, a dispersant, a thickener, a preservative, a filler, an antistatic agent, a matting agent and the like may be used. Is also good. The aqueous resin dispersion obtained according to the present invention is widely used for coating agents and the like for protection of structures exposed to the elements, such as protection of structures exposed to wind and rain, and protection of low water-resistant substrates such as wood and paper. Can be Further, the aqueous resin dispersion having weather resistance obtained by the present invention is suitable for coating applications in which maintenance of a long-term beauty and protection of the substrate are required, and can be used with or without pigment. Also, drying conditions can be appropriately selected from room temperature drying to heating drying according to the application.

The aqueous resin dispersion obtained according to the present invention comprises
As a water resistance improver, it can be used by blending with another aqueous resin dispersion or a water-soluble resin. In particular, it is an effective usage to combine with a weather-resistant resin such as an acrylic resin, a urethane-based resin, a silicon-based resin, or a fluorine-based resin, or a corrosion-resistant resin such as an epoxy resin or an alkyd resin.

[0037]

EXAMPLES The present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. The aqueous resin dispersions obtained in Examples and Comparative Examples were measured for physical properties by the following measurement methods and calculation methods, and were subjected to evaluation tests.

<Solid Content> 1 g of a precisely weighed sample was dried in a hot air drier at 110 ° C. for 60 minutes, and the ratio of the remaining amount as a solid to the weight before drying was expressed in terms of% by weight. <Particle size> Particle size measuring device by dynamic light scattering method (HIAC / R
It was measured using OYCO INSTRUMENTS DIVISION NICOMP Model 370). The particle diameter was indicated by a volume average particle diameter.

Preparation of Test Plate A test solution was prepared by adding 5.8 parts by weight of a 75% aqueous solution of butyl cellosolve (a film forming aid) to 100 parts by weight of a sample aqueous resin dispersion. Using an applicator, a test solution was applied on a glass plate so that the film thickness after drying was about 60 μm, and the glass plate was dried in a hot-air dryer at 100 ° C. for 10 minutes to prepare a test plate.

<Water Resistance Whitening Test> The test plate was immersed in deionized water and kept at room temperature for 7 days. The test plate subjected to the immersion test for 7 days was visually observed to evaluate the degree of whitening. The test results were classified by symbols as follows, and ◎, △ and △ were accepted. ：: No abnormality, ○: Slightly fluorescent color, Δ: Fluorescent color, ×: Whitening <Water resistant whitening test> Except for holding for 24 hours in 60 ° C. hot water for 24 hours, A test was conducted in the same manner to evaluate the degree of whitening of the film. ◎, △ and △ were accepted.

Example 1 Initial polymerization step: dropping funnel, stirrer, nitrogen gas inlet tube,
In a flask equipped with a thermometer and a reflux condenser, 82.65 g of deionized water, 48.0 g of a 15% aqueous solution of Hytenol N-08 (manufactured by Daiichi Kogyo Seiyaku), and Nonipol 200
15.4 g of a 25% aqueous solution (manufactured by Sanyo Chemical Industries), 47.7 g of methyl methacrylate, and 40.000 g of butyl acrylate.
5 g and 1.8 g of acrylic acid were charged, and the temperature was raised to 75 ° C. with stirring while gently blowing nitrogen gas.
After the temperature was raised, 54.0 g of a 5% aqueous solution of potassium persulfate was added to initiate polymerization. After maintaining the inside of the reaction system at 80 ° C. for 10 minutes, the initial polymerization was once terminated. At this time, it was confirmed from the solid content that 80% by weight or more of the added monomer had reacted.

Main polymerization step: After completion of the initial polymerization reaction, 31.8 g of a 15% aqueous solution of hytenol N-08 (manufactured by Daiichi Kogyo Seiyaku) and Nonipol 200 (Sanyo Chemical Co., Ltd.) 9.7 g of 25% aqueous solution, 228.5 g of deionized water, and methyl methacrylate 42
A pre-emulsion consisting of 9.3 g, 364.5 g of butyl acrylate and 16.2 g of acrylic acid was added to 18
The solution was uniformly dropped over 0 minutes. After dripping, deionized water 2
The dropping funnel was washed with 0 g, and the washing solution was added to the flask. Thereafter, the inside of the reaction system was maintained at 80 ° C. for 60 minutes to terminate the polymerization.

Next, the inside of the reaction system was cooled to 50 ° C.
14.1 g of 5% aqueous ammonia was added, and the mixture was stirred at the same temperature for 10 minutes. After stirring, the mixture was cooled to room temperature and filtered through a 100-mesh wire net to obtain an aqueous resin dispersion. Solids,
Table 1 shows the particle diameter and the results of the water whitening resistance test and the warm water whitening resistance test. [Examples 2 to 5] and [Comparative Examples 1 to 4] Dispersion of the aqueous resin in the same manner as in Example 1 except that the types of the polymerizable monomer component and the emulsifier were changed as shown in Tables 1 and 3. I got a body. In each case, it was confirmed from the solid content that 80% by weight or more of the monomer added in the initial polymerization step was reacted. Tables 1 and 3 show the solid content, the particle size, and the results of the water whitening test and the hot water whitening test.

Example 6 Initial polymerization step: dropping funnel, stirrer, nitrogen gas inlet tube,
826.9 g of deionized water, 28.8 g of a 25% aqueous solution of Aqualon HS-10 (Daiichi Kogyo Seiyaku), and Aqualon RN-2 were placed in a flask equipped with a thermometer and a reflux condenser.
0 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), 14.4 g of an aqueous solution, 69.3 g of methyl methacrylate, 19.8 g of 2-ethylhexyl acrylate, and 0.9 g of acrylic acid were charged and stirred while gently blowing nitrogen gas. 7 below
The temperature was raised to 5 ° C. After the temperature was raised, 54.0 g of a 5% aqueous solution of potassium persulfate was added to initiate polymerization. 8 in the reaction system
After holding at 0 ° C. for 10 minutes, the initial polymerization was once terminated.
At this time, it was confirmed from the solid content that 80% by weight or more of the added monomer had reacted.

Main polymerization step: After completion of the initial polymerization reaction, while maintaining the inside of the reaction system at 80 ° C., 13.4 g of a 25% aqueous solution of Aqualon HS-10 (Daiichi Kogyo Seiyaku) and Aqualon RN-20 (No. 6.7% of 25% aqueous solution
g, deionized water 99.8 g, methyl methacrylate 259.2 g, and 2-ethylhexyl acrylate 7
A pre-emulsion consisting of 9.2 g, 3.6 g of acrylic acid, and 18.0 g of 2-hydroxyethyl methacrylate was uniformly dropped over 80 minutes. After the addition, the dropping funnel was washed with 20 g of deionized water, and the washing liquid was added to the flask. Then, for 8 minutes,
The temperature was maintained at 0 ° C. to complete the polymerization. At this time, it was confirmed from the solid content that 80% by weight or more of the added monomer had reacted.

Next, while maintaining the inside of the reaction system at 80 ° C., 25% of Aqualon HS-10 (Daiichi Kogyo Seiyaku) was used.
5.8 g of an aqueous solution, 2.9 g of a 25% aqueous solution of Aqualon RN-20 (manufactured by Daiichi Kogyo Seiyaku), and 139 g of deionized water.
2 g, methyl methacrylate 162.0 g, 2-ethylhexyl acrylate 256.5 g, acrylic acid 4.5 g, and 2-hydroxyethyl methacrylate 9.
A pre-emulsion composed of 0 g and 18.0 g of glycidyl methacrylate was uniformly dropped over 100 minutes. After the addition, the dropping funnel was washed with 20 g of deionized water, and the washing liquid was added to the flask. Then 60
The inside of the reaction system was maintained at 80 ° C. for minutes, and the polymerization was terminated.

Next, the inside of the reaction system was cooled to 50 ° C.
7.1 g of 5% aqueous ammonia was added, and the mixture was stirred at the same temperature for 10 minutes. After stirring, the mixture was cooled to room temperature and filtered through a 100-mesh wire net to obtain an aqueous resin dispersion. Table 2 shows the solid content, the particle size, and the results of the water whitening resistance test and the warm water whitening resistance test. Example 7 An aqueous resin dispersion was obtained in the same manner as in Example 6, except that the types of the polymerizable monomer component and the emulsifier were changed as shown in Table 2. Note that 80% by weight or more of the monomer added in the initial polymerization step has reacted,
Confirmed from solids. Table 2 shows the solid content, the particle size, and the results of the water whitening resistance test and the warm water whitening resistance test.

[0048]

[Table 1]

[0049]

[Table 2]

[0050]

[Table 3]

In the tables, polymerizable monomer components and emulsifiers are indicated by the following abbreviations. MMA: methyl methacrylate, 2EHA: 2-ethylhexyl methacrylate, AA: acrylic acid, St: styrene, CHMA: cyclohexyl methacrylate, H
EMA: 2-hydroxyethylhexyl methacrylate, GMA: glycidyl methacrylate, BA: butyl acrylate As is clear from Table 1, Examples 1 to 5 have compositions in which the polymerizable monomer component satisfies the range of the present invention. As a result, an aqueous resin dispersion having a small particle size, good water whitening resistance and hot water whitening resistance, and a sufficiently high solid content was obtained. As is clear from Table 2, Examples 6 and 7 were particularly excellent in water whitening resistance and hot water whitening resistance because the main polymerization was carried out in two stages by the dropping method. Was.

On the other hand, as is clear from Table 3, Comparative Example 1
Is, since the amount of the total emulsifier used is higher than the range of the present invention,
It was poor in water whitening resistance and warm water whitening resistance. In Comparative Example 2, since the amount of the emulsifier used in the initial polymerization step was smaller than the range of the present invention, the particle diameter was large, and the whitening resistance and the hot water whitening resistance were poor. Comparative Example 3
Since the content of the polymerizable monomer having an acidic group was larger than the range of the present invention, the whitening resistance and the hot water whitening resistance were poor. In Comparative Example 4, the amount of the polymerizable monomer component used in the initial polymerization step was smaller than the range of the present invention, and the amount of the total emulsifier used was small, so that the particle size was large, and the water whitening resistance and hot water whitening resistance Was inferior.

[0053]

According to the present invention, the amount of the water-soluble emulsifier and the polymerizable monomer having an acidic group is small, the particle diameter is small, and the resin is sufficient for practical use. An industrially simple method for producing an aqueous resin dispersion having a solid content can be provided.

The aqueous resin dispersion obtained by the present invention is used as a coating agent for protecting structures exposed to wind and rain, and for protecting low water-resistant substrates such as ceramic building materials, wood, and paper. Widely used for applications.

Continued on the front page (72) Inventor Akio Ito 5-8 Nishiburi-cho, Suita-shi, Osaka F-term (reference) 4J011 KA02 KA03 KA04 KA05 KA06 KA12 KA15 KA16 KA19 KB13 KB16 KB29 4J100 AB02Q AB03Q AB04Q AB07P AB07Q AB08Q AB16Q AC03Q AC04Q AC23Q AC24Q AE03Q AG04Q AJ01P AJ02P AJ08P AJ09P AL03Q AL08P AL08Q AL09Q AL36P AL44P AL62Q AL63Q AM02Q AM17Q AM19Q AP01P BA31Q BA56P BA65P BB07FA01 BC01 FA01

Claims (4)

[Claims] 1. A polymerizable monomer prepared by charging a part of a polymerizable monomer component containing a polymerizable monomer having an acidic group and another polymerizable monomer copolymerizable therewith in the presence of an emulsifier. A method for producing an aqueous resin dispersion comprising an initial polymerization step of polymerizing 80% by weight or more of a monomer component and a main polymerization step of polymerizing the remaining polymerizable monomer component. The total amount of the polymerizable monomer having an acidic group is 0.1 to 5% by weight based on the total polymerizable monomer component, and 5 to 30% of the total polymerizable monomer component in the initial polymerization step. % By weight, and the total amount of the emulsifier used in all the steps is 1 to 3.5% by weight based on the total polymerizable monomer components, and 35 to 95% by weight of the total emulsifier is used in the initial polymerization step. A method for producing an aqueous resin dispersion, which is used. 2. The method for producing an aqueous resin dispersion according to claim 1, wherein an emulsifier having a polymerizable group is used as an emulsifier used in the main polymerization step. 3. A polymerizable monomer component used in the initial polymerization step is an acrylic ester having an alkyl group having 6 or more carbon atoms, a methacrylic ester having an alkyl group having 4 or more carbon atoms, or an aromatic vinyl monomer. And at least one hydrophobic monomer selected from the group consisting of: and the total amount of the hydrophobic monomer is 5% by weight based on the amount of the polymerizable monomer component used in the initial polymerization step. % Of the aqueous resin dispersion according to claim 1. 4. A solid content of 35 to 60% by weight, and
The method for producing an aqueous resin dispersion according to any one of claims 1 to 3, wherein an aqueous resin dispersion having a volume average particle diameter of the resin particles of 50 to 110 nm is obtained.