JPH06128443A - Aqueous emulsion - Google Patents

Abstract

PURPOSE:To provide an aqueous emulsion having excellent polymerization stability and extremely excellent mechanical stability, stability in a state left standing at high temperature, stability in freezing and thawing and water- resistance. CONSTITUTION:The aqueous emulsion contains a polyvinyl alcohol polymer having a mercapto group on a molecular terminal and having specific polymerization degree and saponification degree as a dispersion stabilizer and an acrylic acid ester polymer and/or a methacrylic acid ester polymer as a disperse phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous emulsion, and more particularly to an aqueous emulsion excellent in polymerization stability, mechanical stability, high temperature storage stability, freeze-thaw stability and water resistance.

[0002]

2. Description of the Related Art Generally, anionic surfactants have been conventionally used for emulsion (co) polymerization of radically polymerizable unsaturated monomers such as ethylenically unsaturated monomers or diene monomers. The nonionic surfactants have been used alone or in combination of two or more. Emulsions produced by such a method are useful in a wide range of applications such as paints, adhesives and paper processing agents, but have many problems due to the use of surfactants.
That is, (1) when the emulsion is left for storage, mechanical stability, freeze-thaw stability and pigment miscibility are insufficient, and (2) when the emulsion has a low viscosity, it is used as an adhesive. It is necessary to increase the viscosity by some method, and the operation is complicated. (3) As the thickening method, addition of a thickener or alkali thickening by copolymerization of unsaturated acid is currently used. However, all of them have various problems such as a change in viscosity with time and an adverse effect on the physical properties of the thickener for end use.
Further, the inhibition of adhesion due to migration of the surfactant to the resin surface often causes troubles in the application of the tacky adhesive.

In order to solve the above problems of the conventional emulsion polymerization method using a surfactant, (1) using a copolymerizable emulsifier, (2) performing soap-free polymerization, and further (3) ) Various ideas have been proposed, such as using a water-soluble polymer as an emulsion dispersion stabilizer. However, (1) above
For, the emulsifier is chemically bound to the particle surface, which may improve stability or eliminate the problem of migration of the emulsifier to the resin surface, but it is also related to the reactivity with the target unsaturated monomer. However, it cannot be applied to all emulsions. Even if it can be applied, an emulsion with high viscosity cannot be obtained, and post-thickening is still necessary to obtain a desired viscosity, and in this case also, as described above, there is a problem that the thickened substance changes with time. There is.

The above (2) is the polarity of the initiator segment of persulfate used as an initiator for copolymerizing a polar unsaturated monomer such as unsaturated carboxylic acid or its salt or unsaturated sulfonate. The base is to stabilize the emulsion. This may be effective for the problem of migration of the emulsifier to the resin surface and the problem of deterioration of water resistance of the emulsion film due to the presence of the emulsifier, but the stability of the emulsion is generally decreased. Moreover, since the viscosity of the emulsion is low as in the emulsion of (1), a thickening operation is necessary to obtain a desired viscosity.

Regarding (3), it is true that in emulsion polymerization of vinyl acetate or vinyl chloride, an emulsion produced by using polyvinyl alcohol (PVA), which is a water-soluble polymer, as an emulsion dispersion stabilizer is mechanically stable. Since it has excellent dispersion stability such as stability, freeze-thaw stability, and pigment miscibility, an emulsion of the desired viscosity can be obtained by the polymerization formulation.
Since PVA does not require post-thickening, PVA is characterized in that it migrates to the resin surface less than a low molecular weight emulsifier. Among the water-soluble polymers, PVA is a useful emulsion-dispersion stabilizer which gives an emulsion having the above-mentioned characteristics in a relatively small amount. However, in this case, the graft reaction to PVA is considered to be related to the stability of the emulsion, and the target is limited to vinyl acetate and vinyl chloride, which have large radical reactivity, and the radical reactivity is small. A stable emulsion cannot be obtained even if PVA is used for the acrylic acid ester monomer and the methacrylic acid ester monomer. However, if PVA and a surfactant are used together, a relatively stable emulsion can be obtained, but compared to an emulsion in which PVA is used alone, it has the above-mentioned problems due to the use of a low molecular weight emulsifier. There is.

For the above-mentioned reasons, the P
Using VA alone to obtain a stable emulsion
The current situation is strongly desired in the industry. In this regard, some improvement measures have been taken so far. For example, from the viewpoint of devising the formulation of emulsion polymerization,
In JP-B-45-15033, a specific allyl compound is allowed to coexist, and in JP-A-57-158252, an organic initiator that is both monomer-soluble and partially water-soluble is used as an initiator. It is proposed to use. From the viewpoint of modifying PVA, for example, Japanese Patent Publication No. 54-34425 discloses sulfonated PV.
A, and JP-A-53-44419 propose to use a so-called modified PVA in which a hydrophobic group and a hydrophilic group are introduced.

In the former case, not only the stability does not reach a sufficient level, but also the manufacturing conditions are limited to an extremely narrow range. On the other hand, when the latter modified PVA is used, an emulsion having several steps higher stability than the conventional unmodified PVA can be obtained, but it is not yet sufficient. Further, in order to obtain a more stable emulsion by using PVA alone, for example, JP-B-3-24481 proposes to use a PAV polymer having a mercapto group as a dispersion stabilizer. In this case, from the viewpoint of polymerization stability, it is certainly practically sufficient, and it has a much higher stability than not only the unmodified PVA but also the modified PVA. However, with the expansion of applications of aqueous emulsions due to the tendency toward aqueousization in recent years, those having both polymerization stability and performance such as water resistance and adhesiveness are required, and in that sense, they are not always satisfactory. That was the current situation.

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems in the prior art and provides an aqueous emulsion containing a polymerization stabilizer and PVA as a dispersion stabilizer having both performances such as water resistance and adhesiveness. The purpose is to do.

[0008]

Means for Solving the Problems The inventors of the present invention have made extensive studies in view of the above object, and as a result, P having a mercapto group at the molecular end and a specific degree of polymerization and saponification
It has been found that an aqueous emulsion in which a certain amount of a VA polymer is used as a dispersion stabilizer and an acrylic acid ester polymer or a methacrylic acid ester polymer is a dispersoid is suitable for the purpose. The present invention has been completed based on such findings. That is, the present invention uses a polyvinyl alcohol polymer having a mercapto group at the molecular end and having a degree of polymerization of 200 to 700 and a degree of saponification of 80 to 95 mol% as a dispersion stabilizer, and an acrylic ester polymer and And / or a methacrylic acid ester polymer as a dispersoid, and the dispersion stabilizer is used in an amount of 2 to 5.5 parts by weight based on 100 parts by weight of the dispersoid.

The aqueous emulsion of the present invention contains the dispersoid and the dispersion stabilizer as described above, and the dispersoid is composed of an acrylic acid ester polymer and / or a methacrylic acid ester polymer. Here, there are various monomer units constituting the acrylic acid ester-based polymer and the methacrylic acid ester-based polymer, but preferably monomer units having an alkyl group having 1 to 12 carbon atoms, for example, Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacryl Butyl acid, 2-ethylhexyl methacrylate,
Units derived from decyl methacrylate, dodecyl methacrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and quaternary products thereof, as well as acrylamide, methacrylamide, N-methylolacrylamide, Examples include units derived from N, N-dimethylacrylamide, acrylamido-2-methylpropanesulfonic acid and its sodium salt. Among them, acrylic acid ester units or methacrylic acid ester units having an alkyl group having 1 to 8 carbon atoms are particularly preferable.

In the aqueous emulsion of the present invention, an acrylic acid ester-based polymer and / or a methacrylic acid ester-based polymer is used as the dispersoid, but other ethylenically unsaturated monomers or diene-based unsaturated monomers are used. It is also possible to contain a (co) polymer having one or more kinds of monomers as a constitutional unit. Examples of such an ethylenically unsaturated monomer include olefins such as ethylene, propylene and isobutylene, halogenated olefins such as vinyl chloride, vinyl fluoride, vinylidene chloride and vinylidene fluoride, vinyl formate, vinyl acetate and vinyl propionate. , Vinyl ester such as vinyl versatate, styrene-based monomers such as styrene, α-methylstyrene, p-styrenesulfonic acid and its sodium and potassium salts, and N-vinylpyrrolidone. Further, examples of the diene unsaturated monomer include butadiene, isoprene, and chloroprene. However, in the aqueous emulsion of the present invention, it is desirable that at least 20% by weight, preferably at least 30% by weight, of the entire dispersoid is composed of an acrylic acid ester polymer and / or a methacrylic acid ester polymer. This is because the higher the content of the acrylic acid ester-based polymer or the methacrylic acid ester-based polymer, the higher the weather resistance and hydrolysis resistance of the film obtained by forming the emulsion.

On the other hand, the dispersion stabilizer in the aqueous emulsion of the present invention comprises a PVA polymer having a mercapto group at the molecular end as described above. This PVA polymer is
A polymer having a mercapto group in the main chain of the molecule also has a sufficient effect, but in this case, the PVA polymer itself may oxidize to form a disulfide bond and become insolubilized. A product having a mercapto group bonded only to is convenient for handling without concern about insolubilization. PVA-based polymers having a mercapto group only at one end of such a molecule can be produced by various methods. For example, vinyl monomers mainly composed of vinyl esters are polymerized in the presence of thiol acid. It can be obtained by saponifying the obtained polyvinyl ester polymer by a conventional method. The thiol acid used in this production method includes an organic thiol acid having a -COSH group. Examples include thiol acetic acid, thiol propionic acid, thiol butyric acid, and thiol valeric acid.
Of these, thiolacetic acid is the most preferable because it is highly degradable.

Various vinyl esters may be used as long as they are radically polymerizable vinyl esters.
For example, vinyl formate, vinyl acetate, vinyl propionate,
Examples thereof include vinyl versatate, vinyl laurate, vinyl stearate, vinyl pivalate, vinyl valerate, vinyl caprate, vinyl benzoate and the like. Among them, vinyl acetate is the most preferable because it is most polymerizable. It is also possible to copolymerize these vinyl esters with a copolymerizable monomer. For example, ethylene, propylene, isobutylene, acrylic acid, methacrylic acid, maleic acid, itaconic acid or salts thereof or alkyl esters thereof, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, trimethyl-
(3-Acrylamido-3-dimethylpropyl) -ammonium chloride, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, vinyl sulfonic acid. Examples thereof include sodium and sodium allyl sulfonate.

The polymerization of vinyl monomers mainly composed of vinyl esters such as vinyl acetate in the presence of thiol acid is carried out in the presence of a radical polymerization initiator in the bulk polymerization method, the solution polymerization method,
Although any method such as pearl polymerization method and emulsion polymerization method can be used, the solution polymerization method using methanol as a solvent is the most industrially advantageous. There is no particular limitation on the amount of addition of the thiol acid present in the polymerization to the polymerization system, and the addition method,
It should be appropriately determined according to the physical properties of the intended polyvinyl ester polymer. As the polymerization method, a known method such as a batch method, a semi-continuous method, or a continuous method can be adopted.

As the radical polymerization initiator, 2,2'-
Known radical polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, and carbonate carbonate can be used, but azo initiators such as 2,2′-azobisisobutyronitrile are easy to handle and preferred. Radiation, electron beam, etc. can also be used. Although it is desirable to adopt an appropriate temperature as the polymerization temperature depending on the kind of the initiator used, it is usually selected from the range of 30 to 90 ° C. After polymerizing for a predetermined time, unpolymerized vinyl esters are removed by a usual method to obtain a polyvinyl ester polymer having a thiol ester group at the terminal.

The polyvinyl ester-based polymer thus obtained is saponified by a conventional method, but it is usually advantageous to carry out the polymer as an alcohol solution, especially a methanol solution. As the alcohol, not only an anhydride but also a small amount of a water-containing alcohol may be used according to the purpose, and an organic solvent such as methyl acetate or ethyl acetate may be optionally contained. The saponification temperature is usually selected from the range of 10 to 70 ° C. As the saponification catalyst, alkaline catalysts such as sodium hydroxide, potassium hydroxide, sodium methylate and potassium methylate are preferable, and the amount of the catalyst used is appropriately determined depending on the degree of saponification and the amount of water. The molar ratio is 0.001 or more, preferably
It is desirable to use 0.002 or more.

On the other hand, when the amount of the alkali is too large, it becomes difficult to remove the residual alkali from the polymer, and an undesirable phenomenon such as coloring of the polymer occurs. Therefore, the molar ratio is preferably 0.2 or less. . When the polyvinyl ester-based polymer contains a component that reacts with an alkali catalyst and consumes an alkali, such as a carboxyl group or its ester group, it is desirable to use an amount of the alkali catalyst added. This saponification reaction saponifies the terminal thiolate ester of the polyvinyl ester-based polymer having a thiolate ester group at the end and the vinyl ester bond of the main chain, and the polymer end becomes a mercapto group, and the main chain becomes vinyl alcohol, The saponification degree of the vinyl ester unit of the main chain is 80 to 9 depending on the purpose of use.
It may be appropriately selected within the range of 5 mol%. After the saponification reaction,
The precipitated polymer can be usually obtained as a white powder by purification by a known method such as washing with methanol, removing impurities such as residual alkali and an alkali metal salt of acetic acid, and drying.

The PVA-based polymer having a mercapto group at the molecular end used in the present invention is produced, for example, as described above. The degree of polymerization of this PVA-based polymer is 200 to
It is selected in the range of 700. Here, when the degree of polymerization is less than 200, the mechanical stability of the emulsion is lowered, and conversely, when the degree of polymerization is more than 700, the polymerization stability is lowered and the coagulated product is increased. The degree of polymerization of this PVA-based polymer is
It is the viscosity average degree of polymerization (P) obtained by the following equation from the intrinsic viscosity number [η] of the PVA polymer in water at 30 ° C. P = ([η] × 10 ³ /7.51) ^{(1 / 0.64) The} PVA polymer having a mercapto group at the molecular end has a saponification degree of 80 to 95 mol%. If the degree of saponification is less than 80 mol% or more than 95 mol%, the polymerization stability will decrease and the coagulated product will increase.

As described above, the aqueous emulsion of the present invention uses a PVA polymer having a mercapto group at the molecular end as a dispersion stabilizer, and an acrylic ester polymer and / or
Alternatively, the methacrylic acid ester-based polymer is used as the dispersoid, and the amount of the dispersion stabilizer used here should be selected within the range of 2 to 5.5 parts by weight with respect to 100 parts by weight of the dispersoid. Is. Here, if the amount of the dispersion stabilizer used is less than 2 parts by weight, the polymerization stability and the dispersion stability decrease, which is not preferable in practice. On the other hand, if it exceeds 5.5 parts by weight, polymerization stability and dispersion stability are good, but water resistance and adhesive performance are deteriorated, which is not practical.

By the way, the aqueous emulsion of the present invention is
It can be prepared by various methods, for example, in the presence of water, a dispersion stabilizer comprising a PVA-based polymer having a mercapto group at the molecular end and a polymerization initiator, A usual emulsion polymerization method in which a methacrylic acid ester-based monomer and, if necessary, another monomer are temporarily or continuously added and heated and stirred can be used. Alternatively, a method may be used in which a mixture of the above monomers with an aqueous solution of a dispersion stabilizer and emulsification is added continuously. Alternatively, it may be carried out by dispersion polymerization in a non-aqueous solvent. As the polymerization initiator used at this time, various ones can be used, for example, a mercapto group at the terminal of the PVA-based polymer and a water-soluble oxidizing agent such as potassium bromate, potassium persulfate, ammonium persulfate, and hydrogen peroxide. A redox system is also possible, and among these, potassium bromate does not generate a radical alone under ordinary polymerization conditions, but decomposes only by a redox reaction with a mercapto group at the end of a PVA polymer, and generates a radical. Therefore, it is a particularly preferable initiator because it effectively produces a block copolymer with a PVA-based polymer and thereby enhances the stabilizing effect. It is also possible to use potassium bromate at the start of the polymerization, and then to add another oxidizing agent, so that the oxidizing agent can be used in combination.

Emulsification (co) using the dispersion stabilizer of the PVA polymer having a mercapto group at the molecular end of the present invention.
In carrying out the polymerization, it is important and desirable that the polymerization system is acidic. This is because the mercapto group, which shows an extremely active reaction in radical polymerization, under basic conditions has a large rate of ionic addition to and disappearance from the double bond of the monomer, resulting in a marked decrease in polymerization efficiency. Depending on the type of unsaturated monomer, all polymerization operations were performed at pH 6
Hereafter, it is desirable to carry out at pH 4 or less. The average particle size of the dispersoid of the aqueous emulsion in the present invention is not particularly limited, but is preferably 0.2 to 2.0 μm,
More preferably, it is 0.3 to 1.5 μm. Further, the concentration of the dispersoid in this aqueous emulsion may be appropriately selected according to various situations, but is preferably 30 to 70% by weight, more preferably 40 to 60% by weight.

The dispersion stabilizer comprising a PVA-based polymer having a mercapto group at the molecular end of the present invention is preferably used alone as described above, but if necessary, conventionally known anionic and nonionic agents are used. Alternatively, a cationic surfactant can be used in combination.

[0022]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. In the examples, "part" and "%" mean weight basis. Reference Example (Synthesis of PVA-based polymer having mercapto group at molecular end) According to the method described in JP-A-59-187003, P having a mercapto group at the end of a molecule shown below is used.
A VA polymer was synthesized. PVA No. 1: degree of polymerization 230, degree of saponification 88.0 mol% PVA No. 2: degree of polymerization 500, degree of saponification 94.0 mol% PVA No. 3: degree of polymerization 350, degree of saponification 84.0 mol%

Example 1 A PVA No. 1 (polymerization degree: 230, polymerization degree: 230, obtained by the above-mentioned reference example) was placed in a 1 liter glass-made polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen blowing port, after purging with nitrogen. Saponification degree 8
210.5 g of a 5.7% aqueous solution (8.0 mol%) was charged and the pH was adjusted to 3.5 with dilute sulfuric acid. Then, with stirring at 140 rpm, 120 g of styrene and 1 part of n-butyl acrylate.
After charging 20 g and raising the temperature to 60 ° C., 10 cc of 5% ammonium persulfate aqueous solution was added to initiate polymerization. The polymerization rate reached 99.7% in 5 hours, and then cooled. The produced emulsion was pH-adjusted and then filtered through a 100-mesh wire net, but no coagulation was observed. The obtained emulsion has a solid content concentration of 49.4% and a viscosity of 1600 m.
It was Pa · sec (millipascal · second). The following items were evaluated for this emulsion. The results are shown in Table 1.

(1) Mechanical Stability Using a Marron type mechanical stability measuring device, a sample of 50 g,
After testing under the condition of a load of 20 kg for 10 minutes, the test liquid was filtered through an 80-mesh wire net, the amount of coagulated material on the wire net was measured, and the coagulation rate was determined by the following formula. Coagulation rate (%) = [coagulated product weight (dry content) / (50 × solid content of emulsion)] × 100 (2) High temperature storage stability After 50 g of emulsion was left in a constant temperature bath at a temperature of 60 ° C. for 5 days, 3 After cooling for a period of time, the appearance was observed and evaluated as follows: excellent, good, good, and bad. Excellent: Appearance and no change in viscosity Good: Slightly thickening tendency Possible: Fluidity but large thickening tendency Not possible: Coagulated product is formed (3) Freeze-thaw stability 50 g of emulsion After keeping at −15 ° C. for 16 hours, freezing, and thawing at 30 ° C. for 1 hour, the state of appearance was observed and evaluated as excellent, good, good, and bad as in the above (2).
The evaluation criteria are the same as in (2). (4) Water Absorption of Film An emulsion was cast on a Teflon sheet and dried at 50 ° C. to prepare a film (thickness: about 500 μm). The water absorption rate after immersing the film in water at 20 ° C. for 7 days was determined by the following equation. Water absorption rate (%) = (Ww−Wd) / Wd × 100 Ww: Indicates the film weight (wet state) after immersion. Wd: Shows the film weight after dipping (absolutely dry state).

Example 2 A PVA No. 2 (polymerization degree: 500, degree of polymerization: 500, obtained in the above-mentioned reference example was placed in a 1-liter glass polymerization container equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen blowing port, after purging with nitrogen. Saponification degree 9
(8.5 mol%) of 5.7% aqueous solution (18.5 g) was added and the pH was adjusted to 3.0 with dilute sulfuric acid. Then, while stirring at 140 rpm, 48 g of styrene and 48 g of n-butyl acrylate were charged and the temperature was raised to 60 ° C., then 10 cc of 2.0% potassium bromate was added to initiate polymerization. When the polymerization rate reached 85% in 1 hour, 72 g of styrene and 72 g of n-butyl acrylate were sequentially added in 2 hours, and then,
Polymerization was completed by adding 5 g of 5% ammonium persulfate. The polymerization rate was 99.9%, and the pH of the produced emulsion was adjusted and then filtered through a 100-mesh wire net, but no coagulation was observed. The resulting emulsion had a solid content concentration of 50.2% and a viscosity of 1200 mPa · sec. The above substances were measured for the emulsion in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 1 In Example 2, 25% of a 5.7% aqueous solution of PVA No. 2 was added.
An emulsion was obtained in the same manner as in Example 2 except that 2.6 g was used. The obtained emulsion has a solid content concentration of 47.5%, a viscosity of 1850 mPa · sec, and a pH of
After the adjustment, the product was filtered through a 100-mesh wire mesh, but no coagulated product was observed. The above substances were measured for the emulsion in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 2 In Example 2, 24% of a 1.5% aqueous solution of PVA No. 2 was used.
An emulsion was obtained in the same manner as in Example 2 except that 0 g was used. The obtained emulsion had a solid content concentration of 42.0% and a viscosity of 320 mPa · sec. After pH adjustment, it was filtered through a 100-mesh wire net to give 13.5%
A coagulated substance (in terms of dry weight) was observed. The above substances were measured for the emulsion in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 3 In Example 1, instead of PVA No. 1, unmodified PV
A (manufactured by Kuraray Co., Ltd., trade name: PVA205, degree of polymerization 5
00, a 5.7% aqueous solution with a saponification degree of 88.2 mol%)
Polymerization was carried out in the same manner as in Example 1 except that 5 g was used, but after 30 minutes, coarse particles of a few mm were generated at a polymerization rate of 15%, making it difficult to continue the polymerization.

Example 3 In Example 1, PVA No. 1 was used instead of PVA No. 1.
An emulsion was obtained in the same manner as in Example 1, except that 20.5 g of a 5.7% aqueous solution having a polymerization degree of 350 and a saponification degree of 84.0 mol% was used. The obtained emulsion has a solid content concentration of 49.7% and a viscosity of 2200 mPa · sec.
After adjusting the pH, the product was filtered through a 100-mesh wire net, and no coagulated product was observed. The above substances were measured for the emulsion in the same manner as in Example 1, and the results are shown in Table 1.

Example 4 Instead of PVA No. 2 in Example 2, PVA No.
An emulsion was obtained in the same manner as in Example 2 except that 240 g of a 2.0% aqueous solution having a polymerization degree of 230 and a saponification degree of 88.0 mol% was used. The emulsion obtained is
The solid content concentration was 48.0%, the viscosity was 180 mPa · sec, and after adjusting the pH, filtration with a 100-mesh wire net revealed 0.1% (dry weight conversion) of a solidified product. The above substances were measured for the emulsion in the same manner as in Example 1, and the results are shown in Table 1.

Example 5 In Example 1, 120 g of styrene and n-acrylic acid were used.
An emulsion was obtained in the same manner as in Example 1 except that 240 g of 2-ethylhexyl acrylate was used instead of 120 g of butyl. The obtained emulsion had a solid content concentration of 48.0% and a viscosity of 1800 mPa · sec, and after adjusting the pH, it was filtered through a 100-mesh wire net, and no coagulation was observed. The above substances were measured for the emulsion in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 4 In Example 1, PVA No. 1 was replaced with sodium allylsulfonate-modified PVA (SAS PVA) (polymerization degree 300, saponification degree 90.2%, sodium allylsulfonate 3 mol% modification). An emulsion was obtained in the same manner as in Example 1 except that 2110.5 g of the above 5.7% aqueous solution of was used. The obtained emulsion has a solid content of 39.9.
%, Viscosity is 300 mPa · sec, and after pH adjustment 1
When filtered through a wire mesh of 00 mesh, 17.2% (dry weight conversion) of a solidified product was recognized. The above substances were measured for the emulsion in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Example 5 A 1 liter glass-made polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet was charged with 120 ion-exchanged water.
g, styrene 24 g, n-butyl acrylate 24 g, alkyl diphenyl ether disulfonic acid sodium salt (manufactured by Sanyo Kasei Co., Ltd., trade name: Sandet BL) 0.6 g
And polyoxyethylene 40 mol addition nonyl phenyl ether (manufactured by Sanyo Kasei Co., Ltd., trade name: Nonipol 40
0) was charged with 6.0 g, and stirred at 140 rpm for 60
The temperature was raised to ° C. Then 5% ammonium persulfate aqueous solution 1
After 0 cc was added to initiate polymerization, 0.6 g of Sandet BL and 6.0 g of Nonipol 400 were added to 120 g of ion-exchanged water, 96 g of styrene and 96 g of n-butyl acrylate, and the mixture was emulsified in advance for 3 hours. Was added. After 5 hours, the polymerization rate was 99.5%, and the mixture was cooled. After the pH of the emulsion was adjusted and filtered through a 100-mesh wire net, 0.2% (dry weight conversion) of a solidified product was observed. The resulting emulsion has a solids content of 49.
The viscosity was 8% and the viscosity was 30 mPa · sec. The above substances were measured for the emulsion in the same manner as in Example 1, and the results are shown in Table 1.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

As is apparent from the above description, the aqueous emulsion of the present invention is excellent in polymerization stability and is extremely excellent in various properties such as mechanical stability, high temperature storage stability, freeze-thaw stability and water resistance. It is excellent. Therefore, the emulsion of the present invention can be used for various purposes as it is or by blending conventionally known additives. For example, it is widely and effectively used in paints, adhesives, fiber processing agents, paper processing agents, inorganic binders, cement admixtures, mortar primers and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C09D 133/06 PGF 7921-4J C09J 133/08 JDD 7921-4J D06M 15/333 D21H 19/20

Claims (1)

[Claims] 1. A polyvinyl alcohol-based polymer having a mercapto group at the molecular end and having a degree of polymerization of 200 to 700 and a degree of saponification of 80 to 95 mol% is used as a dispersion stabilizer, and an acrylic ester polymer and And / or a methacrylic acid ester-based polymer as a dispersoid, and the dispersion stabilizer is used in an amount of 2 to 5.5 parts by weight based on 100 parts by weight of the dispersoid.