JPH03109409A - Resin aqueous emulsion - Google Patents

Abstract

PURPOSE:To obtain the subject emulsion, having resin particles prepared by carrying out emulsion copolymerization of a monomer mixture having a specific composition in an aqueous medium, excellent in polymerization stability and dispersion stability of the resin particles and usable in a state of the resin particles stably dispersed in the aqueous medium. CONSTITUTION:The objective emulsion containing resin particles prepared by carrying out emulsion copolymerization of a monomer mixture composed of (A) 30-98.8wt.% acrylic acid ester derivative expressed by the formula CH2= CR<1>COOR<2> (R<1> is H or lower alkyl; R<2> is 1-8C alkyl), (B) 0.1-30wt.% acrylic acid derivative expressed by the formula R<3>CH=CR<4>COOH (R<3> is R<1> or carboxyl; R<4> is R<1>), (C) 0.1-20wt.% sulfone group-containing vinyl monomer and (D) 1-20wt.% polyfunctional monomer for internal crosslinking in an aqueous medium. The aforementioned resin particles have 0.05-2mum average particle diameter and carboxyl groups at 0.7X10<-6> to 60X10<-6>mol/m<2> density.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous resin emulsion for use in a state in which resin particles are stably dispersed in an aqueous medium. An aqueous acrylic acid alkyl ester resin that maintains a stable dispersion state of fine particles in an aqueous medium and has excellent dispersion stability, especially when dispersed in buffer solutions, physiological saline, aqueous solutions containing polymeric solutes, etc. Regarding emulsions.

A typical conventional resin aqueous emulsion is produced by emulsion copolymerization of a sparingly water-soluble radically polymerizable monomer, such as styrene, in the presence of an emulsifier and a water-soluble radical polymerization initiator. Here, the emulsifier ensures polymerization stability during emulsion copolymerization and also contributes to stabilizing the resulting aqueous resin emulsion. The stabilizing effect of this emulsion is not necessarily clear, but in general, a part of the emulsifier is adsorbed to the emulsion particles, and the remainder exists in the emulsion in the free form B, and in this way, in the emulsion. It is said that an adsorption-desorption equilibrium exists between the emulsifier adsorbed on these resin particles and the free emulsifier, and as a result of this equilibrium, stabilization of the emulsion is achieved. Therefore, when an aqueous emulsion containing an emulsifier is dispersed in a buffer solution or physiological saline, the above-mentioned adsorption-desorption equilibrium of the emulsifier in the resin emulsion is disrupted, and as a result, the stability of the resin emulsion is impaired. As a result, resin particles tend to aggregate or settle. Furthermore, since the resin particles of polystyrene emulsion are hydrophobic, they easily aggregate when dispersed in a buffer solution or physiological saline containing an organic solute.

In addition, methacrylic acid ester is emulsion copolymerized with hydrophilic methacrylic acid, 2-hydroxyethyl methacrylate, and a polyfunctional monomer for internal crosslinking in the presence of an emulsifier using a water-soluble radical polymerization initiator to create a resin. Although methods for obtaining aqueous emulsions are already known (Polyme
r, Vol, 19. August+867-871
(197B)) Since the emulsion obtained by this method also contains an emulsifier, it has the same problems as above, and furthermore, since the obtained copolymer particles have hydroxyl groups, it is especially difficult to disperse them in a buffer solution etc. There is a tendency for the resin particles to easily aggregate when

To this end, a method of obtaining an acrylic ester emulsion in the absence of an emulsifier has recently been proposed (Kagaku Gijutsu Kenkyusho Report Vol. 75, No. 8, p. 341 (1980)).
), resin emulsions produced by this method also do not have sufficient dispersion stability and, in particular, easily aggregate under mechanical shear stress.

The present invention has been made to solve the above-mentioned problems, and in its production, it can be produced without using any emulsifier.
It has excellent polymerization stability during emulsion polymerization, and the resulting resin particles maintain a stable dispersion state in an aqueous medium. Therefore, the resin particles can be preferably used in a stable state dispersed in an aqueous medium. The present invention relates to an acrylic acid ester derivative and an aqueous resin emulsion containing the acrylic acid derivative as a main monomer component.

The resin aqueous emulsion for use in which the resin particles according to the present invention are stably dispersed in an aqueous medium has the following formula: represents an alkyl group of 1 to 8) 30 to 98.8% by weight of an acrylic acid alkyl ester derivative
, (blGeneral formula%Formula% (However, R3 represents hydrogen, a lower alkyl group or a carboxyl group, R4 represents hydrogen or a lower alkyl group, R3
When is hydrogen or a lower alkyl group, R4 may be a carbo-lower alkoxy group. ) 0.1 to 30% by weight of an acrylic acid derivative represented by (C) 0.1 to 20% of a vinyl monomer having a sulfonic acid group
% by weight, and (d) 1 to 20% by weight of a polyfunctional internal crosslinking monomer, the resin particles are formed by emulsion copolymerizing in an aqueous medium, and the resin particles have an average Particle size 0.05
~2 μm and a carboxyl group density of 0.7
It is characterized by having xlO-' to 60X10-6 mol/d.

In the present invention, the acrylic acid alkyl ester derivative has the general formula % (where R1 represents hydrogen or a lower alkyl group, preferably hydrogen or a methyl group, and R2 represents an alkyl group having 1 to 8 carbon atoms). ), for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,
Examples include butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, and the like.

In the present invention, in order to obtain an emulsion copolymer emulsion of an acrylic ester derivative having excellent dispersion stability in an aqueous medium, in addition to the acrylic ester derivative, an acrylic ester having a carboxyl group is added as a monomer component. A vinyl monomer having an acid derivative and a sulfonic acid group is used, as well as a polyfunctional internal crosslinking monomer. By emulsion copolymerizing a mixture of such monomer components at a predetermined ratio, the emulsion copolymerization is carried out stably without the generation of aggregates, and the dispersion state is stably maintained in an aqueous medium, such as Tris buffer. Using pns,.

It is possible to obtain an aqueous resin emulsion that is stable over time, non-staining, and non-swellable even when maintained at alkalinity.

The above acrylic acid derivative has the general formula % (where R3 represents hydrogen, a lower alkyl group or a carboxyl group, preferably hydrogen or a methyl group, and R4 represents hydrogen or a lower alkyl group, preferably hydrogen or a methyl group). , when R3 is hydrogen or a lower alkyl group, R4 may be a carbo-lower alkoxy group.) For example, (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, Preferred examples include monoalkyl maleic acid, monoalkyl fumaric acid, and monoalkyl itaconic acid, and in particular, one or a mixture of two or more of (meth)acrylic acid and itaconic acid is preferably used.

Next, in the present invention, as the vinyl monomer having a sulfonic acid group, vinyl sulfonic acid, its metal salt or ammonium salt, 10 formula % formula % (However, R5 is hydrogen or a lower alkyl group, preferably hydrogen or represents a methyl group, Rh represents an alkylene group having 1 to 6 carbon atoms, preferably an alkylene group having 2 to 3 carbon atoms,
M represents hydrogen, alkali metal or ammonium. ) Sulfoalkyl acrylates, such as sulfopropyl (meth)acrylate and its alkyl metal salts, general formula (where R7 represents hydrogen or a lower alkyl group, preferably hydrogen or a methyl group, and M is the same as above) Styrene sulfonic acid, its derivatives, alkyl metal salts thereof, such as sodium styrene sulfonate, represented by the general formula % (where Ra represents hydrogen or a lower alkyl group, preferably hydrogen or a methyl group) , R9 represents an alkylene group having 1 to 6 carbon atoms, preferably an alkylene group having 3 to 4 carbon atoms,
M is the same as above. ) 2-acrylamidoalkanesulfonic acid, derivatives thereof, and alkyl metal salts thereof, such as 2-acrylamido-2-methylpropanesulfonic acid, are used.

The internal crosslinking polyfunctional monomer is particularly effective in non-swelling the resin particles and increasing the dispersion stability of the resulting resin particles in an aqueous medium. Examples of polyfunctional internal crosslinking monomers include aliphatic polyhydric alcohol poly(
Meth)acrylates are preferably used. Specific examples include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, triethylene glycol diacrylate, trimethylolpropane trimethacrylate, and trimethylol. Propane triacrylate, tetramethylolmethanetetraacrylate, etc. are preferably used. Also,
Divinylbenzene, N,N''-methylenebisacrylamide, and the like can also be used as polyfunctional internal crosslinking monomers.

In producing the aqueous resin emulsion according to the present invention,
The monomer composition for emulsion copolymerization is 30 to 98.8% by weight, preferably 50% by weight of the acrylic acid alkyl ester derivative.
~98% by weight, acrylic acid derivative 0.1-30% by weight,
Preferably 0.5 to 20% by weight, vinyl monomer having sulfonic acid group 0.1 to 20% by weight, preferably 0.5 to 20% by weight.
15% by weight, 1-20% by weight of polyfunctional monomer for internal crosslinking
, preferably 1 to 15% by weight.

Both the acrylic acid derivative and the vinyl monomer having a sulfonic acid group are essential monomers for the polymerization stability during emulsion copolymerization of acrylic acid alkyl ester and the stability of the resulting emulsion, and these effects In order to effectively express these, the monomer composition should contain at least 0.
1% by weight is required. However, if too much of the copolymerized monomer component is used, the polymerization stability and the stability of the resulting emulsion are adversely affected, so they are used in a range of 30% by weight or less and 20% by weight or less, respectively.

In addition, as described above, the polyfunctional monomer for internal crosslinking is
A monomer necessary for stably proceeding polymerization, maintaining a stable dispersion state of the resulting resin particles, and making the resin particles non-swellable, and contains at least 1% by weight in the monomer composition. However, it is not preferable to use too much because it will actually impair polymerization stability and emulsion stability.

Further, although it depends on the use of the resulting aqueous resin emulsion, the specific types of individual monomers are selected so that the glass transition point of the resulting copolymer is 0° C. or higher, preferably room temperature or higher. . When the glass transition point of the resin particles is lower than 0°C, mutual fusion and aggregation of the resin particles tend to occur.
This is because the dispersion stability of the emulsion tends to decrease.

In the present invention, a water-insoluble acrylic ester copolymer is obtained by emulsion copolymerizing each of the monomers described above in an aqueous medium using a water-soluble radical polymerization initiator in a conventional manner. It is possible to obtain an aqueous emulsion of a polymer resin, but when the emulsifier is present in the resulting aqueous emulsion in a free state or in a state adsorbed to resin particles, there are various limitations on its use, as mentioned above. It is preferable not to use emulsifiers during emulsion copolymerization because of the deleterious effects that may occur.

The monomer composition according to the present invention is characterized in that stable copolymerization can be carried out without particularly using an emulsifier, and the dispersed state of the resulting resin emulsion can be stably maintained. However, as mentioned above, even when dispersed in a buffer solution or physiological saline, it is possible to use an emulsifier as long as the emulsion particles do not aggregate or settle. If necessary, an emulsifier may be used if it does not have any effect.

In the emulsion copolymerization according to the present invention, the concentration of the monomer component mixture in the aqueous medium is also related to the average particle size of the resin particles in the resulting emulsion, but is usually 0.
It ranges from 1 to 40% by weight.

As the polymerization initiator, a water-soluble radical polymerization initiator is used. Usually, persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate, these persulfates and thiosulfates such as sodium thiosulfate, potassium thiosulfate, sodium hydrogen thiosulfate, etc., or sodium sulfite, potassium sulfite. Redox polymerization initiators with sulfites such as sodium hydrogen sulfite and the like are preferably used, but are not limited thereto. The amount of these polymerization initiators used is preferably in the range of 0.01 to 1% by weight based on the monomer mixture. The atmosphere for polymerization is also not particularly limited, but preferably an inert gas atmosphere excluding oxygen is used. Further, the polymerization temperature is not particularly limited, but is usually in the range of 20 to 100°C, preferably 50 to 90°C.

In the resin aqueous emulsion according to the present invention, the average particle size of the resin particles must be in the range of 0.05 to 2 μm, preferably in the range of 0.1 to 1 μm.

If the particle size is too small, it will be difficult to recover it after use, while if the particle size is too large, it will be difficult to maintain a stable dispersion state. .

Moreover, it is preferable that the specific gravity of the resin particles is in the range of 0.9 to 1.3. When the specific gravity is smaller than 0.9, the resin particles float on the surface of the emulsion aqueous medium, resulting in poor dispersion stability, whereas when the specific gravity is larger than 1.3,
This is because the resin particles are likely to settle in the emulsion aqueous medium and cause aggregation as well.

Furthermore, in the present invention, it is necessary that the resin particles have carboxyl groups at a density in the range of 0.7 x 10-6 to 60 x 10-' mol/i. When the carboxyl group possessed by the resin particles is less than 0.7X10-6 mole/(, the water dispersion stability is insufficient; on the other hand, 60X10"
This is because when the amount is more than 6 mol/M, the resin particles become particularly swellable in an alkaline aqueous solution and tend to have poor water dispersibility.

As described above, according to the present invention, it is possible to perform emulsion copolymerization of an acrylic acid alkyl ester derivative while ensuring polymerization stability without using an emulsifier, and to obtain copolymer particles obtained. is non-swellable and non-staining, and not only maintains its dispersion state stably in aqueous media, but also maintains a stable dispersion state when dispersed in buffer solutions and physiological saline. Therefore, the aqueous resin emulsion according to the present invention can be suitably used in applications where resin particles are required to remain stably dispersed in an aqueous medium.

The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Equal weight ratio mixture of methyl methacrylate and isobutyl methacrylate 91% by weight, 5% by weight of acrylic acid, 0.5% by weight of sulfopropyl acrylate sodium salt and 3.5% by weight of triethylene glycol dimethacrylate
Add 60g of the monomer mixture consisting of the following to 330g of distilled water,
A polymerization initiator aqueous solution prepared by dissolving 0.3 g of potassium persulfate in 10 ml of water was added at a temperature of 75°C under a nitrogen stream, and 120
Polymerization was carried out for 6 hours while stirring at ppm, and the polymerization rate was 98.8.
%, an aqueous emulsion of resin particles having an average particle diameter of 0.34 μm was obtained. Polymerization was very stable and there were no aggregates. This emulsion was centrifuged to remove the resin.
．． After making it into an acid form with 01N hydrochloric acid, it was washed with distilled water and dispersed in distilled water. This emulsion was subjected to conductivity titration with a 0.05N aqueous potassium hydroxide solution to determine the amount of carboxyl groups. Separately, the particle size of the emulsion particles was measured using an electron microscope, and the amount of carboxyl groups possessed by the resin particles was determined from these measurements, and was found to be 9.8×10 −6 mol/d.

In addition, the emulsion obtained above was centrifuged, washed with distilled water, redispersed in distilled water, and adjusted to pH 7.0 with 0.0 IN sodium hydroxide aqueous solution to produce 1 ml of a resin emulsion with a solid content of 5%. in 1M calcium chloride aqueous solution (
When dispersed in 10 ml (pH 7.0), a stable dispersion state was maintained even after one month.

In addition, in the following, when 1 ml of such an emulsion is dispersed in 10 ml of IM calcium chloride aqueous solution,
The dispersibility is considered to be good when a stable dispersion state is maintained even after one month, and the dispersibility is considered to be poor when the resin particles coagulate and settle within several hours.

Comparative Example 1 As shown in Table 1, emulsion copolymerization was carried out in the same manner as in Example 1 using a monomer mixture containing no polyfunctional internal crosslinking monomer. The results are shown in Table 1.

Comparative Example 2 As shown in Table 1, emulsion copolymerization was carried out in the same manner as in Example 1 using a monomer mixture containing 25% by weight of triethylene glycol methacrylate.

The results are shown in Table 1.

Comparative Example 3 The monomer mixture shown in Table 1 was emulsion copolymerized in the same manner as in Example 1. The obtained emulsion particles had carboxyl groups at a density of 82.5xlO-6 mol/M and had poor dispersibility.

Comparative Example 4 As shown in Table 1, emulsion copolymerization was carried out in the same manner as in Example 1 using a monomer mixture that did not contain a vinyl monomer having a sulfonic acid group. The results are shown in Table 1.

Comparative Example 5 As shown in Table 1, emulsion copolymerization was carried out in the same manner as in Example 1 using a monomer mixture that did not contain a polyfunctional internal crosslinking monomer. The results are shown in Table 1.

Comparative Example 6 As shown in Table 1, emulsion copolymerization was carried out in the same manner as in Example 1 using a monomer mixture containing no acrylic acid derivative.

The results are shown in Table 1.

In addition, in Table 1, the abbreviations indicating monomers have the following meanings.

MMA Methyl methacrylate IBMA Isobutyl methacrylate SP Sulfopropyl acrylate sodium salt 70M Triethylene glycol dimethacrylate A Acrylic acid AA Methacrylic acid

Claims (1)

[Claims] (1) (a) General formula CH_2=CR^1COOR^2 (However, R^1 represents hydrogen or a lower alkyl group, and R^
2 represents an alkyl group having 1 to 8 carbon atoms. ) Acrylic acid alkyl ester derivative 30-
98.8% by weight, (b) General formula R^3CH=CR^4COOH (wherein R^3 represents hydrogen, a lower alkyl group, or a carboxyl group, and R^4 represents hydrogen or a lower alkyl group,
When R^3 is hydrogen or a lower alkyl group, R^4 may be a carbo-lower alkoxy group. ) 0.1 to 30% by weight of an acrylic acid derivative represented by (c) 0.1 to 20% of a vinyl monomer having a sulfonic acid group
% by weight, and (d) 1 to 20% by weight of a polyfunctional internal crosslinking monomer, the resin particles are formed by emulsion copolymerizing in an aqueous medium, and the resin particles have an average Particle size 0.05
~2 μm and a carboxyl group density of 0.7
An aqueous resin emulsion for use in a state in which resin particles are stably dispersed in an aqueous medium, characterized in that the resin particles have an amount of 10^-^6 to 60*10^-^6 mol/m^2.