JPH08109221A - Salt-water-resistant latex - Google Patents

Abstract

PURPOSE: To obtain a salt-water-resistant latex showing excellent stability against an electrolyte solution, especially a highly concentrated aqueous electrolyte solution and an aqueous polyvalent metal salt solution by using a specified polymeric emulsifier. CONSTITUTION: This latex is obtained by emulsion-polymerizing a hydrophobic radical-polymerizable monomer in the presence of a water-soluble (co)polymer of a zwitter-ionic vinyl monomer having a zwitter-ionic functional group of the formula (wherein R is 1-10C alkylene or (substituted)phenylene; and X is COO<-> or SO<-> 3 ) with optionally a water-soluble radical-polymerizable monomer and/or a hydrophobic radical-polymerizable monomer and optionally a water-soluble radical-polymerizable monomer as an emulsifier for the monomers. Examples of the zwitterionic a sulfobetaine monomer and a carboxybetaine monomer.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention uses a water-soluble (co) polymer containing a zwitterionic vinyl-based monomer having a Zwitter ionic functional group as a copolymerization component as a polymer emulsifier. Provided is a saltwater-resistant latex obtained by emulsion polymerization. This latex is particularly useful when the latex is used under the above conditions, because it can be stably dispersed in an aqueous electrolyte solution, particularly a polyvalent metal salt aqueous solution or a high-concentration aqueous electrolyte solution without agglomeration.

[0002]

2. Description of the Related Art In general, polymer fine particles in a latex have a markedly deteriorated dispersion stability due to addition of a salt having a specific concentration or more, and agglomerate, precipitate or float, so that latex should not be used in the presence of a salt. It is greatly limited. Therefore, industrial application under these conditions is hindered.

As a method for imparting salt water resistance to the latex, there is a method by emulsion polymerization using a nonionic surfactant or monomer as an emulsifier. It is considered that the latex obtained by such a method is stabilized mainly by steric repulsion due to the hydrated layer of the hydrophilic group of the emulsifier, and a certain degree of salt water resistance can be obtained.

However, such a latex is stable to an aqueous electrolyte solution having a low concentration of up to several% by weight, but it aggregates, precipitates or floats at a higher electrolyte concentration, so that the latex in an aqueous electrolyte solution having a high concentration is used. It cannot be an effective means for using latex.

[0005]

In order to overcome the above-mentioned problems, the present inventors have earnestly studied a latex having excellent dispersion stability in an aqueous electrolyte solution, and have reached the present invention. Is. To develop a latex having excellent dispersion stability in an electrolyte aqueous solution, particularly a high-concentration electrolyte aqueous solution, and a polyvalent metal salt aqueous solution,
It is possible to apply to fields where latex could not be used so far, and it has an extremely excellent use effect.

[0006]

SUMMARY OF THE INVENTION The present invention provides the chemical formula 6
R is a linear or branched alkyl group having 1 to 10 carbon atoms.
A len group or a substituted or unsubstituted phenylene group, X is
COO^-Or SO₃ ^-Shows)
Amphoteric vinyl group-containing monomer (A)
And, if necessary, a water-soluble radically polymerizable monomer (B)
And / or with a hydrophobic radically polymerizable monomer (C)
Water-soluble (co) polymer (D) (however, monomer (A),
(The total of (B) and (C) is 100% by weight), and if necessary
Water-soluble radically polymerizable monomer as a monomer emulsifier
In the presence of (B), at least one or more hydrophobic radicals
Salt-resistant water obtained by emulsion-polymerizing the cal-polymerizable monomer (E)
Can be achieved with a hydrophilic latex and
To provide a latex with excellent dispersion stability
it can. Here, the water-soluble (co) polymer (D) is generally
It is called a high molecular weight emulsifier, and has a surface activity in ordinary emulsion polymerization.
A water-soluble polymer is used as an emulsifier instead of the sexing agent.
In particular, the polymer emulsifiers are
Reactivity when covalently immobilized on the surface of particles
It is called a polymeric emulsifier. In addition, monomer emulsifier is surface active
A monomer used as an emulsifier instead of an agent. In addition,
Deterioration means that the solution is dissolved in water or other solvent and the solution is ionic
It is a substance that conducts electricity, and an electrolyte aqueous solution is
An aqueous solution in which one or more substances are dissolved.

[0007]

[Chemical 6]

The present invention will be described in detail below. First, the zwitterionic vinyl-based monomer (A) having a Zwitter ionic functional group is a zwitterionic monomer having both an anionic group and a cationic group in the same monomer unit. Good,
One or more of these monomers are used. The Zwitter ionic functional group is a functional group having an ionic group selected from a carboxyl group or a sulfonic acid group as an anionic group as shown in Chemical formula 6 and a quaternary ammonium group as a cationic group. The monomer (A) is a radical-polymerizable monomer having such a functional group in the molecule.

Examples of such a monomer (A) include the following chemical compounds 7 to 10 (wherein R ₁ is a hydrogen atom or a methyl group, and R ₂ is a straight-chain or branched C 0-6 carbon atom). An alkylene group or a hydroxyalkylene group, R ₃ and R ₄ each independently represent a methyl group or an ethyl group, R ₅ represents a linear or branched alkylene group or a hydroxyalkylene group having 1 to 10 carbon atoms, or a substituted or unsubstituted group Phenylene group, R ₆ is a linear or branched alkylene group or hydroxyalkylene group having 1 to 6 carbon atoms, X is —COO ⁻ or —SO ₃ ^— , Y is an ester group amide group or substituted or unsubstituted phenylene group, Z is shown -O- or -NH-. in addition, the substitution position of substituents (R ₁ and polymerizable substituents) relative to the pyridine ring of formula 9 and formula 10 is anywhere Monomer represented by the stomach) is preferably employed in the present invention.

[0010]

[Chemical 7]

[0011]

Embedded image

[0012]

[Chemical 9]

[0013]

[Chemical 10]

The monomer (A) in the present invention is generally known as a sulfobetaine type monomer and a carboxybetaine type monomer. Here, the monomer in which X in Chemical formulas 7 to 10 is a sulfobetaine-type monomer, and the monomer having a carboxyl group is called a carboxybetaine-type monomer.

In many cases, the sulfobetaine-type monomer is synthesized by reacting the corresponding tertiary amine-type monomer with a sultone. For example, by reacting N, N-dimethylaminoethyl methacrylate and 1,3-propane sultone in dimethylformamide at 30 ° C. for 7 days, N, N-dimethyl-N- (2-methacryloyloxyethyl) -N- An inner salt of (3-sulfopropyl) ammonium can be synthesized. In addition, a tertiary amine type monomer is reacted with a condensate of an aldehyde or a ketone and acidic sodium sulfite, or a reaction between the tertiary amine type monomer and a haloalkanesulfonic acid, and a hydroxyl group having a hydroxyl group
The sulfobetaine-type monomer can also be synthesized by a sulfuric acid esterification reaction of a quaternary ammonium-type monomer.

In addition, 1-vinyl-3- (3-sulfopropyl) imidazolium inner salt, 1-vinyl-2-methyl-3- (3-sulfopropyl) imidazolium inner salt, 1-vinyl-2-methyl -3- (4-sulfobutyl) imidazolium inner salt, 1-vinyl-3- (2-sulfobenzyl) imidazolium inner salt, 2-vinyl-1
-(3-Sulfopropyl) pyridinium inner salt, 2-methyl-5-vinyl-1- (3-sulfopropyl) pyridinium inner salt, 4-vinyl-1- (3-sulfopropyl) pyridinium inner salt, N, N -Diethyl-N- (2
-Methacryloyloxyethyl) -N- (3-sulfopropyl) ammonium inner salt, 3- {3- [2- (methacryloyloxy) ethoxycarbonyl] pyridinio}
Propane sulfonate inner salt, N, N-dimethyl-N-
(2-Acryloyloxyethyl) -N- (3-sulfopropyl) ammonium inner salt, N, N-dimethyl-N
The sulfobetaine-type monomer such as-(3-acrylaminopropyl) -N- (3-sulfopropyl) ammonium inner salt is the zwitterionic vinyl monomer (A) in the present invention.
Can be preferably used as.

On the other hand, the carboxybetaine type monomer can be synthesized by reacting the corresponding tertiary amine type monomer with a monohaloalkylcarboxylic acid. For example,
The N, N-dimethyl-N- (3-acrylamidopropyl) -N- (carboxymethyl) ammonium inner salt can be synthesized by reacting dimethylaminopropyl acrylamide with sodium monochloroacetate in methanol. The carboxybetaine-type monomer of the present invention can also be synthesized by reacting a tertiary amine-type monomer with a cyclic ester compound such as β-propiolactone. Further, there is a method in which after the reaction of a tertiary amine type monomer with a monohaloalkylcarboxylic acid alkyl ester such as ethyl monobromobutyrate, the ester group is hydrolyzed.

In addition, N, N-dimethyl-N- (2-methacryloyloxyethyl) -N- (carboxymethyl) ammonium inner salt, N, N-dimethyl-N- (2
-Methacryloyloxyethyl) -N- (carboxyethyl) ammonium inner salt, N, N-dimethyl-N-
(2-Acryloyloxyethyl) -N- (carboxymethyl) ammonium inner salt, N, N-dimethyl-N-
(2-Acryloyloxyethyl) -N- (carboxyethyl) ammonium inner salt, N, N-dimethyl-N-
The carboxybetaine-type monomer such as (3-acrylamidopropyl) -N- (carboxyethyl) ammonium inner salt is the zwitterionic vinyl-based monomer (A) in the present invention.
Can be preferably used as.

The zwitterionic vinyl-based monomer (A) having a Zwitter ionic functional group is preferably contained in an amount of 30% by weight or more.
By emulsion-polymerizing at least one or more hydrophobic radically polymerizable monomers (E) in the presence of a water-soluble (co) polymer (D) contained within a range of 90% by weight,
A latex that is stable with respect to the aqueous electrolyte solution, which is the subject of the present invention, can be obtained. If the composition of the monomer (A) in the (co) polymer (D) is less than 30% by weight, sufficient stability against an aqueous electrolyte solution cannot be obtained, so that the composition of the monomer (A) is 30%.
It is desirable that the content be not less than% by weight. If the composition of the monomer (A) exceeds 90% by weight, the water solubility may decrease in some cases and emulsion polymerization may not proceed well. Therefore, it is preferably 90% by weight or less.

In the present invention, the water-soluble radically polymerizable monomer (B) is added to the (co) polymer (D) together with the monomer (A).
It can also be used as a copolymerization component therein. That is,
In order to improve the dispersion stability, leaving stability, stirring stability, dilution stability, freezing stability, etc. of the produced latex, and to improve the physical properties of the film after film formation, a relatively expensive monomer (A In order to reduce the amount used of (1) or when used as a reactive polymer emulsifier, it may be introduced as an active site in a graft reaction or the like. Further, a homopolymer of a radically polymerizable monomer (A) having a Zwitter ionic functional group or a copolymer having a high monomer (A) composition does not dissolve in pure water, or dissolves in pure water. The sex may be extremely low. In such a case, for use as a polymer emulsifier, the water-soluble radically polymerizable monomer (B) is contained in the (co) polymer (D) as a copolymer component to improve water solubility. Alternatively, the use of the water-soluble radically polymerizable monomer (B) as a copolymerization component for controlling the water solubility does not cause any problem as long as it does not impair the stability of salt water. Further, when it is not necessary to use the monomer (B), it may not be used.

The water-soluble radically polymerizable monomer (B) is
It can be used together with the water-soluble (co) polymer (D) as an emulsifier. That is, it can be used together with the (co) polymer (D) as a monomer emulsifier in a usual emulsifier-free emulsion polymerization for the purpose of improving various properties of the latex produced. If it is not necessary to use it, it may not be used.

Since the monomer (B) is water-soluble, it must have a hydrophilic functional group in the molecule. As the hydrophilic functional group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amide group, a hydroxyl group, a polyether group,
There are primary, secondary and tertiary amino groups, quaternary ammonium groups and the like. The term "water-soluble" used herein means that the solubility in water in the standard state is 20% by weight or more.

Examples of the water-soluble radically polymerizable monomer (B) having such a hydrophilic functional group include acrylic acid and its salts, methacrylic acid and its salts, itaconic acid and its salts, acrylamide and methacryl. Amide, N-substituted alkyl acrylamide, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylamide, hydroxypropyl acrylamide, vinyl sulfonic acid and its salt, methallyl sulfonic acid and its salt, styrene sulfonic acid And salts thereof, 2-acrylamido-2-methylpropanesulfonic acid and salts thereof, 2-methacryloyloxyethanesulfonic acid and salts thereof, mono (2-acryloyloxyethyl) acid Sufeto, mono (2-methacryloyloxyethyl) acid phosphate, 3-methacrylamidopropyl dimethylamine and salts thereof, 2-methacryloyloxyethyl dimethyl amine and its salts,
Examples thereof include 3-methacrylamidopropyltrimethylammonium chloride, N-vinyl-2-pyrrolidone, polyethylene glycol acrylate, and polyethylene glycol methacrylate, and these monomers can be used alone or in combination of two or more.

In particular, by using a monomer selected from those having a carboxylic acid group and its salt and a sulfonic acid group and its salt as the monomer (B), the other water-soluble monomer (B) is obtained. It is possible to obtain a latex having stability superior to that obtained by using.

Examples of the monomer (B) include acrylic acid and its salts, methacrylic acid and its salts, styrenesulfonic acid and its salts, 2-acrylamido-2-methylpropanesulfonic acid and its salts, and 2-methacryloyloxyethane. Examples thereof include sulfonic acid and salts thereof.

The composition of the water-soluble radically polymerizable monomer (B) in the (co) polymer (D) is preferably 10% by weight.
Within the range of 70 wt%.

By controlling the degree of hydrophilicity of the water-soluble (co) polymer (D), the emulsifying action of the (co) polymer (D) can be controlled. As a method of controlling the hydrophilicity of a water-soluble polymer, it is possible to control the amount of hydrophilic and hydrophobic moieties in the polymer structure. The hydrophilicity can be controlled by controlling the monomer composition of the amphipathic polymer composed of the body. Also in the present invention, the hydrophilicity of the (co) polymer (D) is controlled by copolymerizing a hydrophobic radically polymerizable monomer (C) as a copolymerization component of the (co) polymer (D). It is possible to control the emulsifying action on the hydrophobic radically polymerizable monomer (E).

The hydrophobic radically polymerizable monomer (C) is
Any monomer may be used as long as it is a hydrophobic monomer that is basically insoluble in water. However, the produced (co) polymer (D)
Is dissolved in pure water and the stability of the produced latex is not impaired. In addition, the hydrophobic property here means
It has a solubility in water of 10% by weight or less in a standard state. Examples of the monomer (C) include styrene derivatives such as styrene, vinyltoluene, vinylbenzyl chloride and divinylbenzene, and methacrylates such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate and glycidyl methacrylate. Derivatives, acrylate derivatives such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate and glycidyl acrylate, diene compounds such as butadiene, isoprene and chloroprene, vinyl halides such as vinyl chloride and vinylidene chloride, and vinylidene halides. , Vinyl acetate, acrylonitrile, methacrylonitrile, vinylidene cyanide, etc. , Not of course limited to these monomers.

The composition of the monomer (C) in the water-soluble (co) polymer (D) is such that the (co) polymer (D) is water-soluble and the stability of the latex produced is not impaired. There is no particular limitation as long as this is satisfied, but it is preferably 30% by weight or less.

The (co) polymer (D) may be prepared by any method of radical polymerization, but is generally synthesized by solution polymerization using water as a polymerization solvent. When the hydrophobic monomer (C) is copolymerized to some extent, a solvent that dissolves the monomer mixture and the (co) polymer (D) is used. For example, a water-methanol mixed solvent system, a water-dimethylformamide mixed solvent system and the like can be exemplified. The polymerization initiator is not particularly limited as long as it can be dissolved in the polymerization solvent, and a commonly used radical polymerization initiator can be used. Examples thereof include persulfates such as ammonium persulfate and potassium persulfate, and redox initiators composed of a combination of these oxidizing agents and reducing agents such as acidic sulfites, and azobis initiators such as azobiscyanovaleric acid.

The molecular weight of the (co) polymer (D) is not particularly limited, but if a too high molecular weight is used, latex fine particles may aggregate during emulsion polymerization. Is good.

The composition of the (co) polymer (D) at the time of emulsion polymerization is preferably 3% by weight or more in order to exhibit the stability of the latex particles in the aqueous electrolyte solution. Further, if the charged composition of the (co) polymer (D) exceeds 20% by weight, it is not preferable because the physical properties of the film after film formation are deteriorated.

The hydrophobic radical-polymerizable monomer (E), which is the center of the latex particles, is a monomer that is hydrophobic and separates into an oil phase when mixed with water, and is generally emulsion polymerized. There is no particular limitation as long as it is used for
One or more kinds may be appropriately selected as necessary in consideration of the purpose of use of the latex, the performance of the latex, the physical properties of the film after film formation, and the like. The term "hydrophobic" as used herein means that the solubility in water in the standard state is 10% by weight or less, like the monomer (C).

As the monomer (E), the monomers exemplified in the section of the hydrophobic radically polymerizable monomer (C) can be used as they are.

The salt-water resistant latex of the present invention can be prepared by a conventional emulsification method using a high molecular weight emulsifier system using a water-soluble polymer as an emulsifier without using a conventional surfactant. . That is, an emulsion polymerization method is employed in which an aqueous medium is used as a polymerization medium, and a water-soluble polymer, optionally a water-soluble monomer, and a hydrophobic monomer are polymerized with a water-soluble radical polymerization initiator. .

Examples of the water-soluble radical polymerization initiator include oxidizing agents such as ammonium persulfate and potassium persulfate,
Further, there may be mentioned redox type initiators composed of a combination of these oxidizing agents and reducing agents such as sodium acid sulfite, and water-soluble azobis type initiators such as azobiscyanovaleric acid. The amount of the water-soluble radical polymerization initiator used is preferably within the range of 0.1% by weight to 5% by weight, and more preferably 0.3% by weight to 1.5% by weight, based on the total weight of the monomers. The polymerization operation is carried out by adding (co) polymer (D), each monomer, and
The initiator is mixed and the temperature is controlled under stirring as necessary.
At this time, the (co) polymer (D), each monomer, and the initiator may be added in the total amount in advance, but if necessary,
A continuous multi-step polymerization method or an intermittent multi-step polymerization method in which the (co) polymer (D), each monomer, and the initiator are added while changing them with time can also be adopted. The polymerization temperature may be appropriately set according to the type of monomer and initiator used. The solid content of the latex is generally about 20 to 50% by weight, but the (co) polymer (D) at the time of polymerization and the charged concentration of each monomer may be set according to the purpose.

The latex prepared as described above exhibits excellent salt water resistance without aggregation or separation even when added to a high-concentration aqueous electrolyte solution.

[0038]

The reason why the latex of the present invention has excellent stability with respect to an aqueous electrolyte solution has not been fully clarified, but it is considered to be generally as follows. That is,
The homopolymer of the radically polymerizable monomer (A) having a Zwitter ionic functional group not only exhibits high solubility in an aqueous electrolyte solution, but also a high concentration aqueous electrolyte solution, as compared with a general polymer electrolyte. Since it also exhibits high solubility, it is considered that it is stabilized in the aqueous electrolyte solution mainly by steric repulsion between latex fine particles having a copolymer having a Zwitter ionic functional group as a protective layer.

[0039]

EXAMPLES The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited to these examples.

Reference Example Synthesis of Water-Soluble (Co) Polymer (D) In this Reference Example, the radically polymerizable monomer (A) having a Zwitter ionic functional group is a sulfobetaine type monomer, , N-dimethyl-N- (2-methacryloyloxyethyl) -N- (3-sulfopropyl) ammonium internal salt (hereinafter abbreviated as DMEPS), N, N-dimethyl-N (3-acrylaminopropyl) -N -(3-
Sulfopropyl) ammonium inner salt (DAPPS),
1-vinyl-3- (3-sulfopropyl) imidazolium inner salt (VIPS), 4-vinyl-1- (3-sulfopropyl) pyridinium inner salt (VPPS)
MER, 1977, Vol. 18,1058. In the same manner as in the method described in 1 above, it was synthesized from the corresponding tertiary amine type monomer of each monomer and propane sultone. The crude product was purified by reprecipitation several times with methanol / ethyl acetate and vacuum dried to obtain a monomer. The carboxybetaine type monomer, N, N-dimethyl-N- (3-acrylamidopropyl) -N- (carboxymethyl) ammonium inner salt (DAPMB) is from Kojin Co., Ltd. N,
N-dimethyl-N- (2-methacryloyloxyethyl) -N- (carboxymethyl) ammonium inner salt (DMEMB) is prepared by reacting a corresponding tertiary amine type monomer with sodium monochloroacetate in methanol at 60 ° C. Was synthesized by.

In this reference example, methacrylic acid (MAA), acrylic acid (AA), sodium styrenesulfonate (SS) were used as the water-soluble radically polymerizable monomer (B).
Na) was used. Further, methyl methacrylate (MMA), butyl acrylate (BA), and styrene (St) were used as the hydrophobic radically polymerizable monomer (C). As the hydrophobic radically polymerizable monomer (E), methyl methacrylate (MMA), methyl acrylate (MA), styrene (St), vinyl acetate (VAc) were used. As the radical polymerization initiator, a redox initiator composed of azobiscyanovaleric acid (ACVA) and ammonium persulfate (APS) and sodium bisulfite (SBS) was used.

The (co) polymer (D) is pure water or water /
Dissolving a predetermined amount of various monomers (total monomer concentration is 20% by weight) and ACVA as an initiator in a mixed solvent of methanol,
It was obtained by polymerizing at 60 ° C. for 24 hours, dialysis with ion-exchanged water for 7 days, and drying under reduced pressure. As a comparative example, a copolymer containing no amphoteric vinyl-based monomer (A) was similarly synthesized. Table 1 shows the composition of the charged monomers and the polymerization conditions for each copolymer.

[0043]

[Table 1]

Among the (co) polymers (D) in Table 1, D
For MSSB-5, the standard polymer equivalent molecular weight is measured by GPC (standard polystyrene is sodium polystyrene sulfonate), and the elemental analysis (N%, S%) is also used.
The copolymer composition was calculated by
The copolymer composition is DMEPS: SSNa: BA = 56: 3.
It was determined to be 014 (wt%).

Example The emulsion polymerization operation was performed according to the following procedure. 80 g of distilled water was put into a 500 ml separable flask equipped with a cooling tube, a thermometer, and a stirrer, and placed in a constant temperature bath of 55 ° C. 1% by weight of the total monomer weight, APS, a predetermined amount of (co) polymer (D) and optionally a water-soluble radically polymerizable monomer (B) are dissolved, and a single amount is added with stirring. Body (E)
Was added (total monomer concentration = 20% by weight). Keep the stirring speed at about 300 rpm, and use 30 times 1.2 times the molar amount of APS.
A wt% SBS aqueous solution was added. After 2 hours, the water temperature in the constant temperature bath was raised to 65 ° C., and the mixture was further stirred for 3 hours, then cooled with tap water with stirring, and filtered with 200 mesh to obtain a latex. The polymerization rate was estimated from the solid content after drying the latex. The particle diameter of the latex particles was measured using an electrophoretic light scattering photometer ELS-800 manufactured by Otsuka Electronics Co., Ltd. Tables 2 and 3 show the charged composition of each monomer at the time of polymerization, the polymerization rate, and the weight average particle diameter.

[0046]

[Table 2]

[0047]

[Table 3]

No. 1 to 9 are DMEPS as a zwitterionic vinyl monomer (A), SSNa as a water-soluble radically polymerizable monomer (B), and BA as a hydrophobic radically polymerizable monomer (C). A latex obtained by emulsion-polymerizing DMSSB-5 as a (co) polymer (D) is shown. No. Nos. 10 to 14 represent latices using the (co) polymer (D) in which the charged composition of DMEPS and SSNA was changed. No. 15 and 16 are DMEPS and SSNa,
2 shows a latex using a composition in which the monomer (C) of the (co) polymer (D) including B and BA is changed. N
o. 17 to 26 were various kinds of monomers (co)
The latex which used the polymer (D) is shown. Incidentally, No. Two
No. 3 is a latex using a homopolymer of a zwitterionic vinyl monomer (A) as an emulsifier, No. 3 A latex 24 is a combination of a homopolymer of the amphoteric vinyl monomer (A) and a water-soluble radically polymerizable monomer (B). In addition, No. 27 and 28 show the latex of the comparative example.

To evaluate the stability of salt water, 5 ml of each latex obtained and 25 ml of various electrolyte aqueous solutions were mixed and allowed to stand still, and the state of the mixed solution after 24 hours was visually determined.
As the electrolyte aqueous solution, 10% Na ₂ SO ₄ and 10% C
aCl ₂ , 50% NaSCN, chromate solution for steel plate anticorrosion coating (chromate solution, composition: chromium trioxide = 20% by weight, phosphoric acid = 5% by weight, colloidal silica = 2.5% by weight, barium silicofluoride = 1% by weight) %) Was used. The results are shown in Table 4. The meanings of the salt water stability evaluation symbols in the table are as follows. ◯: Stable (no aggregation) Δ: Some aggregates present ×: Aggregation (or phase separation)

[0050]

[Table 4]

No. The latex of No. 1 has poor stability in a high-concentration electrolyte aqueous solution, but 10% Na ₂ SO ₄ ,
And stable to 10% CaCl ₂ . No.
The latex of No. 2 had some aggregation with respect to a high-concentration electrolyte aqueous solution, but had stability against a sufficiently high-concentration electrolyte aqueous solution as compared with the comparative example. No.
No. 14 has a relatively small charge composition of the zwitterionic vinyl-based monomer (A) in the copolymer (D), and is somewhat instable to a high-concentration aqueous electrolyte solution, but other It was stable with respect to the electrolyte aqueous solution. N
o. Reference numeral 16 is a latex using the (co) polymer (D) having a high charged composition of the hydrophobic radically polymerizable monomer (C) in the (co) polymer (D), which also has a high concentration of the electrolyte. Some aggregation was observed in the aqueous solution.

No. 3 to 13, 15, and 17 to 26 exhibited extremely excellent dispersion stability in various electrolyte aqueous solutions. In particular, it is surprising that the electrolyte solution stably exists without aggregation or phase separation even in an extremely high concentration aqueous electrolyte solution of 50% NaSCN. It also showed excellent stability against polyvalent metal salt aqueous solutions. The latex of the present invention is particularly useful when the latex is to be stably treated in such an extremely high-concentration electrolyte aqueous solution or polyvalent metal salt aqueous solution, which is an environment that cannot be treated originally.

No. which is a comparative example. Although 27 and 28 show salt water resistance to a low concentration electrolyte aqueous solution to some extent, they have no stabilizing effect because they agglomerate to a high concentration electrolyte aqueous solution and a polyvalent metal salt aqueous solution.
From this, it is clear that the presence of the (co) polymer (D) containing the amphoteric vinyl-based monomer (A) as a copolymerization component exhibits a high degree of salt water resistance.

[0054]

The salt-water resistant latex of the present invention described above has excellent dispersion stability especially in a high concentration aqueous electrolyte solution or polyvalent metal salt solution, and therefore is extremely effective when the latex is used in the aqueous solution. Demonstrate effective use. Therefore, the saltwater-resistant latex of the present invention provides an effective development strategy for the industrial application of latex under such an environment.

Claims (4)

[Claims] 1. A zwitterionic vinyl monomer (A) having a Zwitter ionic functional group (Chemical formula 1) and, if necessary, a water-soluble radically polymerizable monomer (B) and / or hydrophobic. Water-soluble (co) polymer (D) with a radically polymerizable monomer (C) (however, the total amount of the monomers (A), (B) and (C) is 100% by weight), Obtained by emulsion polymerization of at least one or more hydrophobic radically polymerizable monomers (E) in the presence of a water-soluble radically polymerizable monomer (B) as a monomer emulsifier, if necessary. Salt-resistant latex (wherein R is a linear or branched alkylene group having 1 to 10 carbon atoms or a substituted or unsubstituted phenylene group,
X represents COO ⁻ or SO ₃ ⁻ ). Embedded image 2. A zwitterionic vinyl-based monomer (A) has the formula
To 5 (provided that R ₁ is a hydrogen atom or a methyl group, R ₂ is a linear or branched alkylene group or hydroxyalkylene group having 0 to 6 carbon atoms, and R ₃ and R ₄ are each independently a methyl group or An ethyl group, R ₅ is a linear or branched alkylene group or a hydroxyalkylene group having 1 to 10 carbon atoms or a substituted or unsubstituted phenylene group, and R ₆ is a linear or branched chain having 1 to 6 carbon atoms. Alkylene group or hydroxyalkylene group, X
Is —COO ⁻ or —SO ₃ ^— , Y is an ester group amide group or a substituted or unsubstituted phenylene group, and Z is —O.
-Or -NH- is shown. It should be noted that one or more kinds of monomers selected from the monomers represented by the substituents (R ₁ and the polymerizable substituent) on the pyridine ring of Chemical formula 4 and Chemical formula 5 may be anywhere. The saltwater-resistant latex according to claim 1, which is characterized in that. Embedded image Embedded image [Chemical 4] Embedded image 3. The water-soluble (co) polymer (D) is a copolymer containing at least one water-soluble radical-polymerizable monomer (B) as an essential component. Item 1. A salt-water resistant latex according to item 1 or 2. 4. The water-soluble radically polymerizable monomer (B) is
The salt-water resistant latex according to any one of claims 1 to 5, which is selected from monomers having a carboxylic acid group and a salt thereof and a sulfonic acid group and a salt thereof.