JPH0780971B2 - Method for producing highly concentrated reactive microgel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention comprises a monomer having an ethylenic double bond such as acrylates as a main component, and can be further copolymerized with 1 to 5% by weight thereof. N-methylol acrylamide, 2
-Emulsion copolymerization of a functional monomer such as hydroxyethyl (meth) acrylate or glycidyl (meth) acrylate in an aqueous medium, wherein two or more (meth) acryloyl groups in one molecule and a phosphate ester Using a reactive emulsifier consisting of a (meth) acrylic acid ester compound having a structure, ultrafine particles with a particle size of 50 nm or less, and a reactive microgel having a three-dimensional network structure within the particles at high concentration with good dispersion stability The present invention relates to a manufacturing method.

(Prior Art) According to a recent theory, a durable coating film such as a lacquer film, an unsaturated polyester resin, an alkyd resin coating film, etc. undergoes a curing reaction while forming a microgel during the coating film formation process, and has a low crosslinking density. It is considered to have a stone wall structure with a non-uniform mesh structure having a contour structure in which a high crosslink density portion is embedded in the polymer. Therefore, reactive microgels are considered to be ideal as coating materials.

However, it has been very difficult to obtain a stable dispersion of a highly-concentrated reactive microgel without gelling the whole system in the synthesis of such reactive microgel by the conventional technique. In particular, a method for synthesizing ultrafine reactive microgel having a particle size of 50 nm or less at a high concentration is not known.

Conventionally, reactive microgels have been produced by cross-linking by irradiation or by polymerizing a cross-linking monomer having a functionality of 4 or more, such as divinylbenzene, diallyl phthalate, ethylene glycol dimethacrylate, triacrylate, and allyl acrylate. Alternatively, a method of copolymerization is known.

(Problems to be solved by the invention) However, when these crosslinkable monomers are used, polymerization stability is improved even when a large amount of anionic surfactant having good performance such as sodium dodecyl sulfate is used as an emulsifier. It had a defect that the property was poor and a high concentration dispersion could not be obtained. This is a polymer latex (microgel) in which unreacted pendant vinyl groups remain because a tetrafunctional crosslinking monomer such as divinylbenzene is used.
This is because the surface of the particles is highly reactive, so that the system undergoes macroglomerization and the entire system gels, or white aggregated particles are generated. Therefore, the polymer concentration has a drawback that the polymerization must be stopped at a low concentration of 8 to 16% by weight in terms of solid content, and it is very difficult to produce a reactive microgel having a high concentration of 40% by weight or more, which is practically necessary. Met.

In addition, polyfunctional monomers such as divinylbenzene are difficult to copolymerize, the polymerization rate is remarkably slow and it takes 10 to 30 hours, and since an emulsifier is used in a remarkably large amount, side effects of the emulsifier become a serious problem. There was a big problem in practical application.

(Means for Solving Problems) Since the above-mentioned conventional method is a method of polymerizing or copolymerizing a crosslinkable monomer such as divinylbenzene, the present inventors not only perform intra-particle cross-linking but also simultaneously form a particle surface. Also has the advantage of being able to impart reactivity, but on the other hand, it has the drawback of significantly promoting the aggregation of the reactive microgel produced by the highly reactive pendant vinyl group, which is this advantage, and therefore these crosslinkable monomers are As a result of earnest research to develop a method capable of introducing a cross-linking structure into polymer latex particles without using, a certain special chemical structure was used instead of a known cross-linkable monomer such as divinylbenzene. By using a reactive emulsifying agent and specifying the polymerization conditions such as polymerization initiator, monomer composition ratio, polymerization temperature, etc., the polymer solid content concentration should be 30 to 50% by weight. It was found that transparent ultrafine particles having a particle size of 50 nm or less can be formed without agglomeration even at a high concentration and a three-dimensional network structure can be formed in the particles, and the present invention has been completed based on this finding. .

That is, the present invention further provides a monomer comprising a mixture of a monomer selected from lower alkyl esters of acrylic acid or methacrylic acid and another polymerizable monomer copolymerizable with these monomers. When emulsifying and copolymerizing a monofunctional reactive monomer in an amount of 5% by weight or less based on the total amount of the monomer in an aqueous medium, the concentration in the system is 10 ^-8 mol / l to 10 ^-6 mol / From a (meth) acrylic acid ester compound having a phosphoric acid ester structure and a redox catalyst in the presence of divalent copper ions in the range of 1 and having two or more (meth) acryloyl groups in one molecule as an emulsifier The present invention provides a method for producing a high-concentration reactive microgel, which comprises reacting with the following reactive emulsifier.

The reactive microgel produced by the present invention is an aqueous medium dispersion of polymer fine particles obtained by further improving the performance of a polymer latex produced by a usual emulsion polymerization method, and the appearance of the ordinary polymer latex is milky white to white. Unlike that, it is a transparent, slightly viscous, ultrafine particle water dispersion that appears bluish white to reflected light and yellowish red to transmitted light. This reactive microgel has a reactive functional group such as a hydroxyl group, an amide group and an epoxy group on the surface of the particle, and has a three-dimensional network structure inside the particle, which is a so-called ultrafine particle of a reactive pre-crosslinked polymer latex. The morphology is shown.

In the present invention as a polymerization initiator 1.0 × 10 ^-3 ~ 1.0 × 10
Known redox catalysts such as potassium persulfate and sodium thiosulfate with an equimolar concentration of ^-2 mol / l are used, but in order to produce transparent ultrafine polymer latex, a system as a polymerization accelerator is used. Medium concentration 5.0 × 10 ^-8 ~ 7.5
It is indispensable to add a small amount of × 10 ^-6 mol / l divalent copper ion.

The polymerization temperature can be used within a temperature range that activates the polymerization catalyst, but at 80 ° C. or higher, the stability of the produced polymer dispersion deteriorates, and the deactivation of the initiator occurs, so that the polymerization temperature must be controlled. It is preferable to carry out the polymerization at 50 to 70 ° C. while continuously dropping the monomer little by little.

The reactive emulsifying agent used in the present invention is a reactive emulsifying agent composed of two or more (meth) acryloyl groups in one molecule and a (meth) acrylic acid ester compound having a phosphoric acid ester structure. (R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkylene group such as ethylene and a methylene group.) (New Frontier A as a commercially available product)
-229E (trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.). ).

There are a large number of reactive emulsifiers containing such a (meth) acrylic acid ester compound having a phosphoric acid ester structure as a main component, depending on the raw materials and the synthetic method, and it is difficult to obtain them as a single compound. Many are produced as a mixture of various compounds, and it is widely practiced to treat the mixture as a single compound.
In the method of the present invention, the commercially available New Frontier A-229E is used.
A known emulsifying agent, such as a long-chain α-olefinsulfonic acid sodium salt or alkyldiphenyloxy, which is generally used for emulsion polymerization, is a reactive emulsifier composed of a (meth) acrylic acid ester compound having a phosphoric acid ester structure. Ethylene alkyl allyl ether sulfate ester salt, more preferably anionic reactive emulsifier Eleminol JS-2 (trade name, manufactured by Sanyo Chemical Co., Ltd.); structural formula is as follows.

(R is an alkyl group having 12 or less carbon atoms), Latemur S-180 (trade name, manufactured by Kao Corporation); structural formulas are as follows.

(R is an alkyl group having 16 or 18 carbon atoms) and the like are used in combination with a sulfosuccinic acid-based reactive emulsifier, and the weight composition ratio thereof is preferably 1: 3 to 3: 1. The concentration of the emulsifiers alone or mixed is 0.5 to 20% by weight, preferably 2 to 10% by weight, based on the aqueous medium.
It is good to use in the range of.

The reactive microgels produced by polymerization in the process of the invention are insoluble in acetone and form a low viscosity microgel dispersion in acetone. The naturally dried film is insoluble in benzene, and the degree of crosslinking depends on the type and concentration of the reactive emulsifier, the abundance ratio of the functional monomer such as N-methylolacrylamide in the monomer composition, and the addition as a polymerization accelerator. The crosslinking density can be freely controlled by the polymerization conditions such as the concentration of divalent copper ions (copper sulfate aqueous solution).

As the monomer used in the present invention, acrylic vinyl monomers having a polymerizable ethylene bond, methyl methacrylate, acrylic vinyl monomers such as butyl methacrylate, acrylonitrile, vinyl acetate, and styrene are industrially widely used. There are used monomers and the like, and examples of the monomer that copolymerizes with the above-mentioned monomer to give reactivity to the produced microgel include N-methylol (meth) acrylamide, 2-hydroxy (meth) acrylate, ( Examples of the commonly used monofunctional reactive monomer such as (meth) acrylic acid, maleic anhydride, acrylamide, and glycidyl (meth) acrylate.

(Effect of the invention) The reactive microgel obtained by the method of the present invention is an ultrafine particle having a particle size of 50 nm or less and a solid content concentration in an aqueous medium of 40.
Dispersion stability is remarkably good even at up to 45% by weight, and the polymerization rate is also remarkably fast, and a wide range can be obtained by controlling the polymerization conditions such as the monomer composition ratio, emulsifier concentration, combination of emulsifiers, and copper (II) ion concentration. Since it is possible to easily synthesize a reactive microgel having the above hardness and crosslink density, it is suitable as an industrial method for producing a reactive microgel.

Further, the method of the present invention is characterized in that the degree of crosslinking and hardness of the reactive microgel can be arbitrarily controlled, and when the hardness is low, the particles are fused to each other by natural drying to form a continuous film, and the initial modulus value A large elastic film can be formed. In addition, when the hardness and the crosslink density become high, the film-forming property becomes poor and a lot of mesh-like streaks and cracks occur. However, by using a film-forming aid (such as diethylene glycol monoethyl ether acetate) together or increasing the drying temperature. A uniform flat film can be produced.

The reactive microgel produced by the method of the present invention can be used as a vehicle for an emulsion paint to form a coating film as it is, but it is preferably mixed with an aminoplast resin such as a methylolated melamine resin for baking and curing. Used as a material for water-based baking coatings. Also,
Powdered reactive microgel is useful for improving blocking property and coating film physical properties by adding to powder coating, and also useful as high solid coating material because it has low viscosity even if dispersed in organic solvent. Is. It can also be mixed with existing solvent-based paints, water-soluble paints and emulsion paints to improve the performance of the paints.

The reactive microgel obtained by the method of the present invention can also be used as a filler and a binder having good permeability. Further, by mixing an aminoplast resin such as hexakis methoxymethylol melamine, the performance of an adhesive or the like can be remarkably improved by crosslinking between particles by baking and curing.

The reactive microgel produced by the method of the present invention comprises
Since it is an ultrafine particle with a particle size of 50 nm or less, it has excellent adhesion to fine uneven surfaces such as metal surfaces and permeability to concrete, wood, etc.Aminoplast resin, which was a drawback of conventional polymer latex Mixing with a curing agent such as is more uniformly performed in a form close to a solution type molecular dispersion.

In addition, since the reactive microgel particles have a three-dimensional network structure inside, the entire coating film can have a higher three-dimensional network structure with less crosslinking reaction, so that it has solvent resistance and an initial modulus value. A peculiar film having a large size can be easily formed.

Furthermore, in the reactive microgel produced by the method of the present invention, a three-dimensional network can be formed between the reactive groups on the surface of the particles, or by a cross-linking between the reactive groups and the curing agent, and durability and thermal stability, It has the characteristics that a film with excellent impact strength can be obtained.

(Example) Next, the present invention will be described in more detail with reference to Examples.

Examples 1 to 17 Using a 1000 ml four-neck separable flask equipped with a gas inlet tube reflux condenser, a pH measuring composite gas electrode and a stirring device, 400 ml of distilled water was used as an emulsifier and the concentration in the system in terms of the solid content was used. Corresponding to 1.0-5.0 (g / 100 ml) New Frontier A229E (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) alone or by dissolving a mixture with a reaction-produced emulsifier, Eleminol JS-2 (manufactured by Sanyo Kasei Co., Ltd.) in 50 Keep at ℃. Mixed monomer of ethyl acrylate and methyl methacrylate as polymerization monomer
Polymerization flask containing 300g (mixing ratio 60:40) to which 3g to 15g of N-methylol acrylamide (N-MAM or 2-hydroxyethyl acrylate (2-HEMA) or glycidyl methacrylate (GMA) was added at first about 50g. A small amount of copper sulfate (concentration in the system 2.5 × 10 ^-6 or 5.0 × 10 ^-7 mol /
l) in the presence of an equimolar amount of potassium persulfate-sodium thiosulfate, a redox initiator (concentration in the system: 3.0 x 10
^-3 mol / l) to initiate polymerization at 50-60 ° C and pH 4-7. Then, about 250 g of the remaining mixed monomer was gradually added dropwise to carry out polymerization while preventing a temperature rise due to heat of polymerization.

If the viscosity of the system increases with the progress of polymerization and it becomes difficult to disperse or agitate the monomers, add 2-4 ml of 28% aqueous ammonia little by little before increasing the viscosity of the polymerization system. Before the start of polymerization, about 0.5 g of diammonium phosphate is added to adjust the viscosity.

Polymerization was completed in about 30 minutes, and a transparent dispersion of ultrafine particles of a polymer that appeared bluish white in reflected light and yellowish red in transmitted light was obtained.

Table 1 shows the results of experiments conducted by changing the composition ratio of the monomers and the type and concentration of the emulsifier.

Dispersion pair of generated polymer particles (reactive microgel)
The appearance transparency of the spectrophotometer is 800nm light transmittance 1
It is shown by the value measured in a glass cell of cm. The average particle diameter is the number average particle diameter measured by Nanosizer N-4G by the photon correlation method of Coulter Inc., which is the hydrodynamic radius including the hydrated layer, and is 1.5 to more than the dry particle diameter obtained by electron microscopy.
The value is twice as large.

The transparency of the film obtained by naturally drying the reactive microgel on a glass plate was generally good, and in the case of a flat film, the gloss was also very good.

When the hardness of the film is high and the degree of cross-linking is high, the film permeability is poor under natural drying conditions, and a uniform flat film is formed when a film-forming aid that causes network streaks and cracks is added to the entire film. Was found to be formed.

All the films formed by natural drying were insoluble in benzeneacetone, and the gel fractions were all 95% or more. The degree of swelling of the film with respect to benzene is 100 g for a film of about 0.1 g.
The swelling ratio was calculated from the increase in polymerization after being placed in a wire mesh basket with a mesh and immersed in benzene for 48 hours or more. When the swelling ratio was 20 times or less, the morphology of the film was retained, and when the swelling ratio was 30 times or more, the film was deformed and became a fluid gel mass.

(Note) * 1 A299E; Reactive emulsifier consisting of a (meth) acrylic acid ester compound having a phosphoric acid ester structure, which falls within the scope of the present invention. Commercial product Daiichi Kogyo Seiyaku New Frontier A-229E JS-2; Sulfocohaku Acid reactive emulsifier Commercial product Sanyo Kasei Eleminol JS-2 * 2 Concentration in water phase Eleminol JS-2 is calculated as solid component * 3 EA; Ethyl acrylate MMA; Methyl methacrylate N-MAM; N-methylol acrylamide 2- HEMA; 2-hydroxyethyl methacrylate GMA; glycidyl methacrylate * 4 5.0E-7 in the system has a concentration of 5.0 x 10 ^-7 mol / l * 5. 800 nm wavelength (1
cm light cell transmittance) * 6 Hydrodynamic radius measured by Coulter Nanosizer N4G * 7 Appearance of clear film naturally dried on glass plate Mesh line; Flat with 2 to 3 mm mesh line : Uniform and smooth high-gloss transparent film * 8 About 0.1 g of the film was put in a 100-mesh wire net basket and immersed in benzene for 48 hours or more, and the weight ratio before and after the immersion was compared.

* 9 Time required for a 5mm x 20mm film to be soaked in water and whitened to make it difficult to read newspaper type letters. In general, if it was 20 days or longer, there was almost no change after that, and no change was observed even if left for 6 months or more. .

Claims (1)

[Claims] 1. A monomer comprising a mixture of a monomer selected from lower alkyl esters of acrylic acid or methacrylic acid and another polymerizable monomer copolymerizable with these monomers. When emulsifying and copolymerizing a monofunctional reactive monomer in an amount of 5% by weight or less based on the total amount of the monomer in an aqueous medium, the concentration in the system is 10 ^-8 mol / l to 10 ^-6 mol / 2 of l range
Using a redox catalyst in the presence of divalent copper ions, and using as a emulsifier a reactive emulsifier consisting of two or more (meth) acryloyl groups in one molecule and a (meth) acrylic acid ester compound having a phosphoric acid ester structure. A method for producing a high-concentration reactive microgel, which comprises reacting by a reaction.