JPH09286805A - Production of aqueous resin dispersion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous resin dispersion which has excellent resistances to water and solvents, and also is excellent with respect top stability during storage for a long period. SOLUTION: This method comprises subjecting to micro-dispersion of a monomer component prepd, by mixing γ-methacryloyloxypropyltrimethoxysilane with butyl (meth)acrylate and the like in the presence of a surfactant having a critical micelle concentration in an aqueous medium of 1×10<-4> mol/liter of less, a representative example of which is sodium stearate soap, to thereby obtain a monomer dispersion having average particle diameter of 5 to 500nm; and subsequently adding a radical polymerization initiator thereto followed by mixing, to effect a polymerization.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing an aqueous resin dispersion, which contains an arbitrary amount of a functional group having a room temperature crosslinkable function, and whose particle size is easily controlled. The present invention relates to a method for producing an aqueous resin dispersion useful as a binder or additive for paper processing, textile processing, adhesives, civil engineering and other coating applications.

[0002]

2. Description of the Related Art In recent years, attention has been paid to an aqueous resin dispersion with the use of a synthetic resin as a solvent-free organic solvent, and extensive studies have been made on the functionalization of resin particles dispersed in water. Among them, when using a water-dispersible resin as a binder, research on a reactive resin that leads to improvement in water resistance and the like is active, and a resin aqueous dispersion having a hydrolyzable silyl group is one of the reactive resins. Are known.

As such an aqueous resin dispersion, for example, in JP-A-61-9463, an organic silicon monomer having a polymerizable unsaturated group and a hydrolyzable group directly bonded to a silicon atom in the molecule is used. : 0.1 to 40% by weight, (meth) acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms: 50 to 99.9% by weight and other polymerizable monomers: 0 to 40% by weight An aqueous resin dispersion having a hydrolyzable silyl group, which contains an aqueous copolymer obtained by emulsion polymerization of the following monomer mixture as an essential component, is proposed.

[0004]

However, the resin aqueous dispersion obtained by such ordinary emulsion polymerization does not have sufficient storage stability, and is obtained when the resin aqueous dispersion is stored for a long period of time. There was a problem that the physical properties such as solvent resistance and water resistance of the coating film were considerably inferior to those of the coating film immediately after synthesis.

The problem to be solved by the present invention is that a coating film having excellent physical properties such as solvent resistance and water resistance can be obtained, and the physical properties of these coating films are deteriorated even when used after long-term storage. It is to provide a resin aqueous dispersion that does not have such a problem.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have decided that a radically polymerizable unsaturated monomer having an alkoxysilyl group as a room temperature crosslinkable group is an essential component. A strong coating film is formed by dispersing a monomer in an aqueous medium as a monomer particle of 5 to 500 nm using a surfactant, adjusting the pH to 5 to 7, and then polymerizing the monomer. In addition, they have found that an aqueous resin dispersion can be obtained which can maintain the physical properties of the coating film immediately after synthesis even after storage for several months in the state of the aqueous resin dispersion, and completed the present invention.

That is, according to the present invention, the radical-polymerizable unsaturated monomer component (a) containing a radical-polymerizable unsaturated monomer having an alkoxysilyl group as an essential component is added to an aqueous medium in the presence of a surfactant. A method for producing an aqueous resin dispersion, which is characterized by finely dispersing it in a monomer dispersion liquid having an average particle diameter of the dispersed monomer of 5 to 500 nm, and then adding a radical polymerization initiator to the polymerization. .

As described above, the production method of the present invention comprises a radically polymerizable unsaturated monomer component (a) containing a radically polymerizable unsaturated monomer having an alkoxysilyl group as an essential component.
Is finely dispersed in an aqueous medium in the presence of the above-mentioned surfactant, and it is important to rapidly finely disperse the average particle size of the dispersed monomer in the range of 5 to 500 nm.
By adding a radical polymerization initiator and polymerizing, the particle size of the resulting resin aqueous dispersion particles can be adjusted to 5 to 500 nm with almost no change as compared with the monomer dispersion particles.

The radical-polymerizable unsaturated monomer having an alkoxysilyl group contained as an essential component in the above-mentioned radical-polymerizable unsaturated monomer component (a) is one whose structure is particularly specified. However, for example, vinylmethyldimethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxyethoxy) silane, γ
-Methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxypropyltriethoxysilane and the like.

Of these, γ-methacryloxypropyltrimethoxysilane is particularly preferable because the water resistance and solvent resistance of the finally obtained coating film are remarkably good.

In the present invention, as the radically polymerizable unsaturated monomer component (a), in addition to the radically polymerizable unsaturated monomer having an alkoxysilyl group as a monomer component,
Other radically polymerizable unsaturated monomers can be used. As other radically polymerizable unsaturated monomer,
There is no particular limitation as long as it is commonly used for emulsion polymerization, and examples thereof include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. Acrylic acid esters; Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate; acrylic acid, methacrylic acid, maleic acid Acids, fumaric acid, itaconic acid, crotonic acid, etc .; Maleic acid, fumaric acid, itaconic acid, crotonic acid esters; vinyl acetate, vinyl propionate, tertiary carboxylic acid vinyl compounds, heterocyclic compounds such as vinylpyrrolidone Vinyl compound; chloride Cycloalkenyl, acrylonitrile, vinyl ethers, vinyl ketones, vinyl amides, and the like; styrene, alpha
-Methylstyrene, etc .; vinylidene halide compounds such as vinylidene chloride, vinylidene fluoride; α-olefins such as ethylene and propylene; dienes such as butadiene and isoprene; α, β-, such as acrylamide, methacrylamide, maleic amide, etc. Amides of ethylenically unsaturated acids; glycidyl group-containing monomers such as glycidyl methacrylate and allyl glycidyl ether; hydroxyl group-containing monomers such as 2-hydroxyethyl methacrylate; unsaturated carboxylic acids such as N-methylol acrylamide or methacrylamide, diacetone acrylamide Substituted amides; amino group-containing monomers such as dimethylaminoethyl methacrylate; diallyl phthalate, divinylbenzene, allyl acrylate, trimethylolpropane trimethacrylate, etc. 1 Such as a monomer having two or more unsaturated bonds in the child and the like.

Among these, acrylic acid esters and methacrylic acid esters are preferable from the viewpoint of water resistance, and particularly, the number of carbon atoms of the alkyl group constituting the ester is 4
Those having a hardness of 8 to 8 are particularly preferred because they have good water resistance.

Containing a radical-polymerizable unsaturated monomer having an alkoxysilyl group in the monomer component (a), and other radical-polymerizable unsaturated monomer and other radical-polymerizable unsaturated monomer The ratio is not particularly limited,
Specifically, the content of the radically polymerizable unsaturated monomer having an alkoxysilyl group in 100 parts by weight of the monomer component (a) is 0.1 to 50 parts by weight,
It is preferable because the average particle diameter of the dispersed monomer can be easily adjusted to 5 to 500 nm, and the storage stability of the resin aqueous dispersion, the water resistance of the coating film, and the solvent resistance become good.

In order to make the above-mentioned monomer component (a) have an average particle diameter of 5 to 500 nm in an aqueous medium, the conditions may be appropriately selected and adjusted, and the method is not particularly limited, For example, as the surfactant, one having a critical micelle concentration of 1 × 10 ⁻⁴ mol / liter or less in an aqueous medium is used, or an anionic surfactant having a polypropylene oxide skeleton in its molecule is used. It is preferable because the adjustment can be facilitated.

Among these surfactants, those having a critical micelle concentration of 1 × 10 ⁻⁴ mol / liter or less in an aqueous medium include, for example, icosyl sulfate sodium salt and n-octadecyl-α. -Sulfo fatty acid propyl ester sodium salt, sodium oleate soap, sodium stearate soap, α-phosphonostearic acid, hexadecyldimethylbenzylammonium chloride, octadecyldimethylbenzylammonium chloride and the like.

The critical micelle concentration in the aqueous medium is 1
Even greater surfactant than × 10 ^{over 4} mol / l, fine dispersion is facilitated if the following 1 × 10 ^{over 4} mol / l by combining two or more surfactants. Furthermore, the critical micelle concentration is 1 × 10 ^-4 mo
NaC even with surfactants larger than 1 / l
The critical micelle concentration can be reduced to 1 × 10 ⁻⁴ mol / liter or less by adding an electrolyte such as 1, KCl, CaCl ₂ or the like, or a middle or higher alcohol such as n-hexanol, n-octanol or n-octadecanol. For example, the particle size of the monomer-dispersed particles can be adjusted to 5 to 500 nm.
That is, the critical micelle concentration of the surfactant in the present invention refers to the critical micelle concentration in the aqueous medium used for polymerization.

The preferable value of the critical micelle concentration of the surfactant in the aqueous medium is 1 × 10 ⁻⁴ mol / liter or less, and there is no problem even if the value is infinitely close to 0 mol / liter. No, but above all 1 × ^10-7
It is preferably 1 × 10 ⁻⁴ mol / liter.

On the other hand, examples of the anionic surfactant having a polypropylene oxide skeleton in its molecule include:
Polypropylene skeleton-containing anionic surfactant such as polypropylene methacrylic acid polypropylene oxide sodium sulfate, acrylic acid polypropylene oxide sodium sulfate, polypropylene oxide such as polypropylene oxide-polyethylene oxide block copolymer sodium sulfonate, polypropylene oxide-polyethylene oxide block copolymer ammonium sulfate -Polyethylene oxide block copolymer skeleton-containing anionic surfactants and the like can be mentioned. Among them, the anionic surfactant having a polypropylene oxide skeleton and a (meth) acryloyl group atomizes the radically polymerizable unsaturated monomer. It is particularly preferable from the viewpoint of doing, especially polypropylene methacrylic acid polypropylene oxide sodium sulfate, acrylic acid polypropylene oxide sodium sulfate Distributed, from the viewpoint of excellent storage stability of the resin aqueous dispersion.

As the aqueous medium, water or water /
An organic solvent composite medium may be mentioned, but water alone or a water / organic solvent having a water content of 50% by weight or more from the viewpoint of ease of production of an aqueous resin dispersion and storage stability of the aqueous resin dispersion. Complex media are preferred. Here, the organic solvent is not particularly limited, but methanol, ethanol, n-propanol, i-propanol, n-
Lower alcohols such as butanol, n-hexanol, n
Examples thereof include middle or higher alcohols such as -octanol and n-octadecanol.

The amount of the surfactant used in the present invention is 100 in terms of the radically polymerizable unsaturated monomer 100 from the viewpoints of easily making the monomer particles fine, polymerization stability and the obtained resin viscosity.
2 to 5000 parts by weight, especially 5 to 20 parts by weight
It is preferably 0 part by weight.

Further, the radical polymerization initiator used in the present invention is not particularly limited, but potassium persulfate, sodium persulfate, ammonium persulfate, azobisisobutyronitrile and its hydrochloride, and peroxide. Examples thereof include hydrogen, tertiary butyl hydroperoxide, cumene hydroperoxide, benzoyl peroxide and the like.

The production method of the present invention can be carried out by using each of the components described in detail, but a preferable method is, specifically, the following method.

That is, first, 100 parts by weight of the radical-polymerizable unsaturated monomer composition (a) is added in an amount of 50 to 3000 parts by weight of the aqueous medium to 2 to 5000 parts by weight, preferably 5 to 200 parts by weight of the surfactant. Is mixed with the dissolved aqueous surfactant solution. Add an appropriate amount of pH adjuster and stir to add p
A monomer dispersion of H5-7 can be obtained. At this time, a mechanical shearing device such as a homomixer may be used.

The thus-obtained monomer dispersion has an average particle diameter of 5 to 500 nm. Among them, dispersion stability and storage stability, and further, coating film performance such as water resistance and solvent resistance. It is preferably from 10 to 200 nm.

Then, the obtained monomer fine particles are polymerized with a radical polymerization initiator to obtain an alkoxysilyl group-containing resin dispersion liquid. The alkoxysilyl group in the resin dispersion may be hydrolyzed and may exist as a hydroxysilyl group.

In the present invention, resin-dispersed particles having a small change in particle size can be obtained by emulsion polymerization under any conditions. Therefore, the polymerization conditions are set to the conditions of emulsion polymerization generally performed. You can, for example,
0.1 to 5 parts by weight of the radical polymerization initiator is used per 100 parts by weight of the radically polymerizable unsaturated monomer, and the aqueous medium is 50 to 50 parts by weight.
A method in which the content is adjusted to 3000 parts by weight and polymerization is performed at 0 to 100 ° C. is preferable.

In addition to the above-mentioned polymerization method, redox polymerization using 0.1 to 5 parts by weight of a reducing agent may also be used. At this time, a compound that produces a polyvalent metal ion such as iron or copper can be used together as an accelerator. At this time, examples of the reducing agent that can be used in combination with these radical polymerization initiators include sodium sulfoxylate formaldehyde, sodium pyrosulfite, and L-ascorbic acid.

It is also possible to use a chain transfer agent such as lauryl mercaptan together, if necessary, regardless of the type of polymerization method.

Further, in the resin aqueous dispersion obtained by the present invention, not only the solid content concentration can be set to a low range, but it is also possible to set it to a relatively high concentration in order to improve productivity. Specifically, the solid content concentration of the final resin dispersion is preferably 10 to 70% by weight. Further, the radically polymerizable unsaturated monomer, the radical polymerization initiator, and the reducing agent to the reaction system can be carried out by any known method such as batch charging, continuous dropping, and divided addition.

The resin aqueous dispersion in the present invention can also be obtained by preparing a monomer aqueous dispersion and then performing photopolymerization or radiation polymerization as in the case of thermal polymerization and redox polymerization.

Although a curing agent is not particularly required, it is possible to obtain a stronger coating film by adding the curing agent. The curing agent used is not particularly limited, and specifically,
Organic tin compounds such as dibutyltin dilaurate, dibutyltin dimaleate, dioctyltin dilaurate, dioctyltin dimaleate, dibutyltin diacetate, dibutyltin dimethoxide, tributyltin sulfite, dibutyltin thioglycate, tin octylate; aluminum isopropylate, aluminum Organoaluminum compounds such as tris (ethylacetoacetate), aluminum tris (acetylacetonate), and ethylacetoacetate aluminum diisopropylate; isopropyltristearoyl titanate, tetraisopropylbis (dioctylphosphite) titanate, bis (dioctylpyrophosphate) oxy Organic titanium compounds such as acetate titanate; tetra-n-butoxydyl Chloride, organometallic compound in the organic zirconium compounds such as octyl acid zirconyl sulfate,
Acidic compounds such as paratoluene sulfonic acid, basic compounds such as sodium hydroxide and potassium hydroxide, isopropyl acid phosphate, butyl acid phosphate,
Examples thereof include acidic phosphoric acid esters such as octyl acid phosphate, and these can be used alone or in combination of two or more kinds. The compounding amount of the curing agent is 0.001 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total resin solid content.

As described above, the resin aqueous dispersion obtained in the present invention contains a radical-polymerizable unsaturated monomer containing a radical-polymerizable unsaturated monomer having an alkoxysilyl group as an essential component, using a surfactant. 5 of body component (a) in an aqueous medium
It is obtained by dispersing as droplets of ~ 500 nm and then emulsion-polymerizing it.
The difference in particle size before and after the polymerization can be made extremely small, and specifically, the rate of change can be adjusted to within 30%.

The aqueous resin dispersion of the present invention is useful as a binder having excellent weather resistance, adhesive resistance, water resistance and solvent resistance for paints, paper processing, fiber processing, adhesives and the like. It can also be used as an additive, and by adding the resin aqueous dispersion of the present invention to a general-purpose binder, it becomes possible to improve the above physical properties.

[0034]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. In addition, all the following parts and% are values based on weight.

Examples 1 to 3 and Comparative Examples 1 to 3 The monomer mixture shown in Table 1 and a surfactant aqueous solution were mixed and finely dispersed in ion exchange water, and the pH was adjusted with a small amount of 25% ammonia water. A monomer aqueous dispersion liquid adjusted to 7 was prepared. The critical micelle concentrations of the surfactants used in each Example and Comparative Example in ion-exchanged water are as follows.

Sodium stearate soap 5.0 × 10-5 mol / L polypropylene methacrylate sodium oxide sulfate 7.0 × 10-4 mol / L nonylphenyl polyethylene oxide sodium sulfate 2.0 × 10-4 mol / L Next, stirrer, temperature 192 parts of the pre-emulsion was charged into a 1-liter reaction vessel equipped with a meter, a cooler and a dropping funnel, and the temperature inside the kettle was adjusted to 5 while stirring while feeding nitrogen gas.
The temperature was raised to 0 ° C. After the temperature was raised, 20% of those in which 2 parts of t-butyl hydroperoxide was dissolved in 20 parts of ion-exchanged water and 20% of those in which 2 parts of sodium pyrosulfite were dissolved in 15 parts of ion-exchanged water, 0.75 % Ferric chloride aqueous solution (1 part) was added, and the mixture was maintained at 50 ° C. for 30 minutes, and then the remaining monomer aqueous dispersion, t-butyl hydroperoxide aqueous solution, and sodium pyrosulfite aqueous solution were added dropwise. The dropping time was 2 hours for the aqueous monomer dispersion and 2 hours 15 minutes for the t-butyl hydroperoxide aqueous solution and sodium pyrosulfite aqueous solution. During the dropping, the temperature inside the kettle is maintained at 50 ° C and, at the same time, the pH is adjusted to 6 by appropriately dropping aqueous ammonia.
Adjusted to ~ 7. After the dropping was completed, the temperature was kept at 50 ° C. for 2 hours. Then, it cooled and the resin aqueous dispersion was obtained.

[0037]

[Table 1] First

[0038]

[Table 2] Table 2

[0039]

[Table 3] Table 3

The test method for each evaluation item shown in Table 3 is shown below. Emulsion state: The degree of sedimentation of particles was visually evaluated according to the following criteria.

◯: No sedimentation Δ: Partial sedimentation ×: Almost sedimentation

Film state: The degree of film formation at 25 ° C. was evaluated with the naked eye, and the transparency and the degree of film formation were evaluated according to the following criteria. ○: No cracks △: Fine cracks ×: No film formed

Solvent resistance: Acetone rubbing test (load 0.5 kg × 20 times) evaluated the remaining degree of the film in 5 levels according to the following criteria.

5: 100% remains 4: 80% or more and less than 100% 3: 50% or more and less than 80% 2: 20% or more and less than 50% 1: 0% (all peeled off) or less than 20%

Water resistance: Ion-exchanged water 25 ° C. ×
The degree of whitening of the film after immersion for 1 week was evaluated. 5: no whitening (colorless and transparent) 4: pale bluish 3: bluish white 2: bluish white part and whitening part mixed 1: completely whitening

[0046]

EFFECTS OF THE INVENTION According to the present invention, an alkoxysilyl group can be stably encapsulated in particles, and an aqueous resin dispersion having good long-term storage stability can be obtained.
A coating film having excellent physical properties such as solvent resistance and water resistance can be obtained, and even when used after being stored for a long period of time, the coating film can be formed without deteriorating the physical properties of these coating films. Moreover, the particle size of the resin particles can be strictly controlled.

Therefore, the composition obtained by the present invention is used for coating, coating agent, adhesive, primer, paper processing, textile processing, etc. coating water resistance, weather resistance, solvent resistance,
It can be effectively used not only as a binder for improving the adhesion resistance and chemical resistance but also as an additive thereof.

Claims (4)

[Claims] 1. A radically polymerizable unsaturated monomer component (a) containing a radically polymerizable unsaturated monomer having an alkoxysilyl group as an essential component is finely dispersed in an aqueous medium in the presence of a surfactant. The average particle size of the dispersed monomer is 5 to 50.
A method for producing an aqueous resin dispersion, which comprises forming a 0 nm monomer dispersion, and then adding a radical polymerization initiator to the polymerization. 2. The critical micelle concentration of the surfactant is 1 × 10.
^-4 mol / l or less is used, The manufacturing method of Claim 1 characterized by the above-mentioned. 3. The method according to claim 1, wherein an anionic surfactant having a polypropylene oxide skeleton in the molecule is used as the surfactant. 4. A radically polymerizable unsaturated monomer component (a)
The content of the radically polymerizable unsaturated monomer having an alkoxysilyl group therein is 0.1 to 50% by weight.
4. The production method according to 2 or 3.