JP4781694B2 - Aqueous emulsion - Google Patents

Description

  The present invention relates to an aqueous emulsion which has a low viscosity despite its high solid content concentration, is excellent in sedimentation stability, and is excellent in mechanical stability and skin resistance.

Conventionally, an aqueous emulsion using a vinyl alcohol polymer (PVA) as a dispersant is used for various applications such as adhesives and paints. These water-based emulsions have been awarded for using PVA as a dispersant because they have extremely good stability, excellent miscibility with inorganic substances, and high viscosity. Is.
In general, it is well known that an aqueous emulsion using PVA as a dispersant has a lower solid content concentration than an emulsion using various surfactants (emulsifiers). From another viewpoint, this means that the emulsion viscosity is high while having a low solid content concentration, which is one of the characteristics of an aqueous emulsion using PVA as a dispersant.
When these aqueous emulsions are used for adhesives, etc., it is natural that removal by evaporation of water contained in the aqueous emulsion affects the setting speed in the adhesive treatment, and the water content in the aqueous emulsion is low. That is, a high solid content concentration is extremely important in terms of improving the setting speed. In applications other than adhesives, reducing the amount of water in aqueous emulsions as much as possible has become an increasingly important issue in recent years as the need for energy saving in the manufacturing process of final products is increasing. In the sense of responding, technical development regarding high solid content concentration of emulsion is awaited.
However, usually when PVA is used as a dispersant, the viscosity of the emulsion becomes too high even if various efforts are made to increase the solid content concentration of the aqueous emulsion, so that the solid content concentration is only about 40 to 50%. I can't get it.
In addition, there is a method (Patent Document 1) for obtaining an emulsion having a high solid content by setting the polymerization degree of PVA to a low polymerization degree of 20 to 300. However, this method can improve the stability during polymerization and the aqueous emulsion. The strength of the film obtained by drying was insufficient.
Further, an aqueous emulsion having a polymer (A) having a vinyl ester unit as a dispersoid and PVA (B) having a 1,2-glycol bond of 1.9 mol% or more as a dispersant (Patent Documents 2 to 3) However, it does not disclose an aqueous emulsion having a solid content concentration of 55% or more and a viscosity of 2000 mPa · s or less.
JP 58-111181 (Claims) JP 2001-220484 A (Claims) JP 2004-346182 A (Claims)

  The present invention eliminates these disadvantages of the prior art, has a low viscosity despite its high solid content concentration, excellent sedimentation stability, mechanical stability and skin resistance. The object is to obtain an excellent aqueous emulsion.

The above object is to provide a vinyl alcohol polymer ( polyvinyl acetate (A) as a dispersoid and having a 1,2-glycol bond of 1.9 mol% or more, a polymerization degree of 300 or more, and a saponification degree of 70 mol% or more) B) as a dispersant, the weight ratio (B) / (A) is 1.3 / 100 to 2.7 / 100, the solid content concentration is 59.1% by weight or more, the emulsion viscosity is 1850 mPa · s or less, It is achieved by an aqueous emulsion having an average particle size of 1 to 2 μm.

  According to the present invention, although the solid content concentration is high, the viscosity is low, so the setting speed of the adhesive and the like is fast, the workability is excellent, the sedimentation stability is also excellent, and the mechanical stability An aqueous emulsion excellent in skin resistance can be obtained.

  There is no restriction | limiting in particular as a manufacturing method of PVA (A) which has 1.9 mol% or more of 1, 2- glycol bonds used as a dispersing agent of the aqueous | water-based emulsion which comprises this invention, A well-known method can be used. As an example, a method in which vinylene carbonate is copolymerized with a vinyl ester so that the 1,2-glycol bond amount falls within the above range, and the polymerization temperature of the vinyl ester is higher than normal conditions, for example, 75 to 200 ° C. And a method of polymerizing under pressure. In the latter method, the polymerization temperature is preferably 95 to 190 ° C, particularly preferably 100 to 180 ° C. Moreover, it is important to select the pressurizing condition such that the polymerization system is lower than the boiling point, preferably 0.2 MPa or more, and more preferably 0.3 MPa or more. The upper limit is preferably 5 MPa or less, and more preferably 3 MPa or less. The above polymerization can be carried out by any method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization in the presence of a radical polymerization initiator, but solution polymerization, particularly solution polymerization using methanol as a solvent. Legal is preferred. High vinyl 1,2-glycol bond-containing PVA is obtained by saponifying the vinyl ester polymer thus obtained by a conventional method. The PVA 1,2-glycol bond content is suitably 1.9 mol% or more, more preferably 1.95 mol% or more, still more preferably 2.0 mol% or more, optimally 2 More than 1 mol%. When the content of 1,2-glycol bond is less than 1.9 mol%, there is a concern that the mechanical stability of the resulting aqueous emulsion is lowered, and further, the polymerization stability is also lowered. The 1,2-glycol bond content is preferably 4 mol% or less, more preferably 3.5 mol% or less, and most preferably 3.2 mol% or less. Here, the content of 1,2-glycol bonds is determined from analysis of NMR spectra.

  Here, examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate and the like, but generally vinyl acetate is preferably used.

  The dispersant may be a copolymer of an ethylenically unsaturated monomer that can be copolymerized within a range that does not impair the effects of the present invention. Examples of such ethylenically unsaturated monomers include ethylene, acrylic acid, methacrylic acid, fumaric acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and trimethyl. -(3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropanesulfonic acid or its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, N-vinylamides such as vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinylsulfonate, sodium allylsulfonate, N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide And the like. It is also possible to use a terminal-modified product obtained by copolymerizing a vinyl ester monomer such as vinyl acetate with ethylene in the presence of a thiol compound such as thiol acetic acid or mercaptopropionic acid and saponifying it. it can.

  The saponification degree of PVA having 1,2-glycol bond of 1.9 mol% or more used as a dispersant for the aqueous emulsion of the present invention is 70 mol% or more, preferably 75 mol% or more, more preferably 80 mol% or more. It is. When the degree of saponification is less than 70 mol%, there is a concern that water solubility, which is the original property of PVA, is lowered. The degree of polymerization of the PVA is 300 or more, usually in the range of 300 to 8000, more preferably 300 to 3000. When the degree of polymerization is 300 or less, the characteristics of PVA as a protective colloid are not exhibited, and when it exceeds 8000, there is a problem in industrial production of the PVA.

  The aqueous emulsion of the present invention has a conventionally known anionic, nonionic or cationic surfactant, hydroxyethyl cellulose, and 1,2-glycol bond amount of 1.7 as long as the object of the present invention is not impaired. PVA less than mol% can be used in combination.

There are various types of polymers of ethylenically unsaturated monomers that are dispersoids in the aqueous emulsion of the present invention. Preferred examples of ethylenically unsaturated monomers that are raw materials for these polymers include ethylene. , Olefins such as propylene and isobutylene, halogenated olefins such as vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride, vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl versatic acid, acrylic acid, methacrylic acid Acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid 2 -Ethylhe Methacrylic acid esters such as syl, dodecyl methacrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate or quaternized products thereof, acrylamide, methacrylamide, N-methylolacrylamide, N, Acrylamide monomers such as N-dimethylacrylamide, acrylamide-2-methylpropanesulfonic acid or sodium salts thereof, styrene such as styrene, α-methylstyrene, p-styrenesulfonic acid or sodium salts or potassium salts thereof Monomers, other N-vinyl pyrrolidone and the like, and diene monomers such as butadiene, isoprene, chloroprene and the like may be used alone or in combination of two or more.
The polymer of ethylenically unsaturated monomers, especially vinyl ester (co) polymer, such as vinyl ester polymer, a copolymer of ethylene and vinyl esters are preferred.

Regarding the use amount of PVA having a 1,2-glycol bond of 1.9 mol% or more and a saponification degree of 70 mol% or more used as a dispersant for the aqueous emulsion of the present invention, the above ethylenically unsaturated monomer unit is used. It is important that the weight ratio (B) / (A) of the dispersoid (A) to the PVA (B) is in the range of 1.3 / 100 to 2.7 / 100 . When the amount used exceeds 2.7 / 100 , the average particle size of the emulsion obtained becomes apparently 1 μm or less, as shown in Comparative Examples 6 to 8, which will be described later. Can not. When the ratio is less than 1.3 / 100 , the polymerization stability may be lowered, and the average particle size of the emulsion is large and the mechanical stability is lowered. In addition, it is important that the average particle size of the aqueous emulsion of the present invention is 1 to 2 μm. By satisfying this condition, the aqueous emulsion targeted by the present invention can be obtained.

In the present invention, it is extremely important that the solid content concentration is 59.1% by weight or more and the viscosity is 1850 mPa · s or less. If the concentration is less than 59.1% by weight, the setting speed of the adhesive or the like cannot be improved, and if the viscosity exceeds 1850 mPa · s even at a high concentration, the workability of the aqueous emulsion is deteriorated. . In this way, a high-concentration and low-viscosity aqueous emulsion can be obtained, thereby improving the setting speed of adhesives and the like, and further providing an aqueous emulsion with excellent workability, as well as sedimentation stability and mechanical stability. The industrial value of having obtained an aqueous emulsion excellent in heat resistance and skin resistance is extremely large.
The upper limit of the solid content concentration is preferably 65% by weight or less, and the lower limit of the viscosity is preferably 500 mPa · s or more. In addition, solid content concentration represents weight% of the total amount of a dispersoid and a dispersing agent with respect to the total amount of water, a dispersoid, and a dispersing agent.

  As a method for producing the aqueous emulsion of the present invention, for example, a specific amount of PVA having a 1,2-glycol bond of 1.9 mol% or more, a polymerization degree of 300 or more, and a saponification degree of 70 mol% or more is used as a dispersant. Add the unsaturated unsaturated monomer temporarily or continuously, add polymerization initiators such as azo polymerization initiators, peroxide polymerization initiators such as hydrogen peroxide, ammonium persulfate and potassium persulfate, and emulsify The method of superposing | polymerizing is mentioned. The polymerization initiator may be used in combination with a reducing agent and used in a redox system. In that case, hydrogen peroxide is usually used together with tartaric acid, sodium tartrate, L-ascorbic acid, Rongalite and the like. Ammonium persulfate and potassium persulfate are used for sodium bisulfite, sodium hydrogencarbonate and the like.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Here, Examples of the present invention are 1 to 5, and Example 6 is described for reference. In the following examples, “%” and “part” mean “% by weight” and “part by weight” unless otherwise specified. Moreover, the average particle diameter, solid content concentration, viscosity measurement, sedimentation stability, mechanical stability, and skin resistance of the obtained aqueous emulsion were evaluated as follows.

(Average particle size)
The aqueous emulsion was diluted to a concentration of 0.2%, and the average particle size was measured by a dynamic light scattering method (manufactured by Otsuka Electronics Co., Ltd .; laser data potential system ELS-8000).

(Solid content concentration)
About 3 g of the aqueous emulsion was placed in an aluminum dish, precisely weighed, and then dried for 24 hours with a dryer at 105 ° C. to volatilize water. Thereafter, the weight of the dried product was measured, and the solid content concentration was calculated from the weight ratio.
(viscosity)
The viscosity at 30 ° C. and 20 rpm was measured with a B-type viscometer.
(Sedimentation stability)
Aqueous emulsion was filled into a test tube with a diameter of 22 mm to a height of 150 mm, sealed, and allowed to stand in an atmosphere of 20 ° C. for 4 weeks. The solid content concentration was measured, and the sedimentation stability was evaluated by the ratio of the upper solid content concentration / the lower solid content concentration.
(Mechanical stability)
The aqueous emulsion was tested for 10 minutes under the conditions of 20 ° C., load 0.5 kg / cm ² , 1000 rpm using a Maron mechanical stability measuring machine, and then a 60 mesh (ASTM standard fluid) stainless steel wire mesh was attached. And the ratio (%) of the weight of the filtration residue to the solid content weight of the emulsion was measured. It shows that mechanical stability is excellent, so that the ratio of the filtration residue weight is small.
The measurement of the solid content concentration and the filtration residue weight is as follows.
* Measurement method of filtration residue weight The filtration residue was dried with a dryer at 105 ° C. for 24 hours to evaporate water, and the weight of the dried product was defined as the filtration residue weight.
(Skin resistance)
Depth at which the surface of the glass plate is exposed with a 1000-point needle tip every 20 minutes at a temperature of 20 ° C. and 65% RH. Then, a trajectory was created by completely traversing a width of 50 mm over about 1 second, and the time until a partially minute skin was completely recognized around the trajectory was measured.

  Next, the contents of the vinyl alcohol polymers (PVA-1 to PVA-6) used in the following Examples and Comparative Examples are as follows.

PVA-1
A 5 L pressure reactor equipped with a stirrer, nitrogen inlet, and initiator inlet was charged with 2940 g of vinyl acetate, 60 g of methanol and 0.088 g of tartaric acid, and the reactor pressure was 2.0 MPa while bubbling with nitrogen gas at room temperature. The system was increased to 1, left for 10 minutes, and then the operation of releasing the pressure was repeated three times to purge the system with nitrogen. A concentration of 0.2 g / L solution in which 2,2′-azobis (cyclohexane-1-carbonitrile) (V-40) was dissolved in methanol as an initiator was prepared, and nitrogen substitution was performed to perform bubbling with nitrogen gas. Next, the temperature inside the polymerization tank was raised to 120 ° C. The reaction vessel pressure at this time was 0.5 MPa. Then, 2.5 ml of the above initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 120 ° C., and the polymerization was carried out by continuously adding V-40 at 10.0 ml / hr using the above initiator solution. The reactor pressure during the polymerization was 0.5 MPa. After 3 hours, the polymerization was stopped by cooling. The solid concentration at this time was 24%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration 33%). Methanol was added to the obtained polyvinyl acetate solution to adjust the concentration to 25% to 400 g of a polyvinyl acetate methanol solution (100 g of polyvinyl acetate in the solution), and 3.72 g (polyacetic acid at 40 ° C.). Saponification was performed by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.008) to vinyl acetate units in vinyl. After about 2 minutes after the addition of the alkali, the gelled product was pulverized with a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration, and the mixture was left to wash at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-1). The degree of saponification of the obtained PVA (PVA-1) was 88 mol%. In addition, a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization was saponified at an alkali molar ratio of 0.5, and the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. It was 1700 when the average degree of polymerization of this PVA was measured according to JISK6726 of the usual method. When the amount of 1,2-glycol bonds in the purified PVA was determined from measurement with a 500 MHz proton NMR (JEOL GX-500) apparatus, it was 2.2 mol%.

PVA-2
PVA-2 was obtained in the same manner except that the amount of the alkali solution added was changed to 11.6 g in the production method of PVA-1. As a result of measuring this in the same manner as PVA-1, the average polymerization degree was 1700, the saponification degree was 98 mol%, and the 1,2-glycol bond amount was 2.2 mol%.

PVA-3
A 5 L pressure reactor equipped with a stirrer, nitrogen inlet, and initiator inlet was charged with 2850 g of vinyl acetate, 150 g of methanol and 0.086 g of tartaric acid, and the reactor pressure while bubbling with nitrogen gas at room temperature. The pressure was raised to 2.0 MPa, left for 10 minutes, and then the pressure was released three times to replace the system with nitrogen. A solution of 2,2′-azobis (N-butyl-2-methylpropionamide) dissolved in methanol as an initiator was prepared at a concentration of 0.1 g / L, and was purged with nitrogen by bubbling with nitrogen gas. Next, the polymerization tank internal temperature was raised to 150 ° C., ethylene was introduced, and the reaction tank pressure was set to 20 MPa. Next, 15.0 ml of the above initiator solution was injected to initiate polymerization. During the polymerization, the polymerization temperature was maintained at 150 ° C., and 2,2′-azobis (N-butyl-2-methylpropionamide) was continuously added at 15.8 ml / hr using the above initiator solution. Carried out. The reactor pressure during the polymerization was 20 MPa. After 4 hours, the polymerization was stopped by cooling. The solid concentration at this time was 35%. Subsequently, unreacted vinyl acetate monomer was removed while adding methanol occasionally under reduced pressure at 30 ° C. to obtain a methanol solution of polyvinyl acetate (concentration 33%). 4.40 g (polyacetic acid) at 40 ° C. was added to 400 g of a polyvinyl acetate methanol solution (100 g of polyvinyl acetate in the solution) adjusted to a concentration of 25% by adding methanol to the obtained polyvinyl acetate solution. Saponification was performed by adding an alkaline solution (NaOH in 10% methanol) having a molar ratio (MR) of 0.01) to vinyl acetate units in vinyl. After about 3 minutes after the addition of the alkali, the gelled material was pulverized with a pulverizer and allowed to stand for 1 hour to allow saponification to proceed, and then 1000 g of methyl acetate was added to neutralize the remaining alkali. After confirming the end of neutralization using a phenolphthalein indicator, 1000 g of methanol was added to the white solid PVA obtained by filtration, and the mixture was left to wash at room temperature for 3 hours. After the above washing operation was repeated three times, the PVA obtained by centrifugal drainage was left in a dryer at 70 ° C. for 2 days to obtain dry PVA (PVA-3). The degree of saponification of the obtained PVA (PVA-3) was 88 mol%. Further, after saponification of a methanol solution of polyvinyl acetate obtained by removing unreacted vinyl acetate monomer after polymerization at an alkali molar ratio of 0.5, the pulverized product was allowed to stand at 60 ° C. for 5 hours to promote saponification. After that, Soxhlet washing with methanol was carried out for 3 days, followed by drying under reduced pressure at 80 ° C. for 3 days to obtain purified PVA. It was 1000 when the average degree of polymerization of this PVA was measured according to JISK6726 of the conventional method. The amount of 1,2-glycol bonds in the purified PVA was determined as described above from measurement with a 500 MHz proton NMR (JEOLGX-500) apparatus, and was 2.5 mol%. The ethylene unit content was 4.0 mol%.

PVA-4
In the production method of PVA-3, the polymerization temperature was controlled to obtain PVA-4. As a result of measuring this in the same manner as PVA-3, the average degree of polymerization was 1000, the degree of saponification was 88 mol%, and the amount of 1,2-glycol bonds was 1.6 mol%. The ethylene unit content was 4.0 mol%.

PVA-5
Product name: PVA-217 (saponification degree 88 mol%, average polymerization degree 1700, 1,2-glycol bond 1.6 mol%)

PVA-6
Product name: PVA-117 (saponification degree 98 mol%, average polymerization degree 1700, 1,2-glycol bond 1.6 mol%)

  In a 1 liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, a nitrogen inlet, and a squid type stirring blade, 320 g of ion-exchanged water, PVA-1 (polymerization degree 1700, saponification degree 88 mol%, 1, 2 -Glycol bond amount 2.2 mol%) 10 g was charged and completely dissolved at 95 ° C. Next, this PVA aqueous solution was cooled, purged with nitrogen, charged with 48 g of vinyl acetate while stirring at 140 rpm, heated to 60 ° C., and then polymerization was initiated in the presence of a hydrogen peroxide / tartaric acid redox initiator system. . From 15 minutes after the start of the polymerization, 432 g of vinyl acetate was continuously added over 3 hours to complete the polymerization. A polyvinyl acetate emulsion having a solid content concentration of 59.1%, a viscosity of 1400 mPa · s, and an average particle size of 1.7 μm was obtained.

  In the same manner as in Example 1 except that PVA-2 (polymerization degree 1700, saponification degree 98 mol%, 1,2-glycol bond amount 2.2 mol%) was used instead of PVA-1 in Example 1, A polyvinyl acetate emulsion having a solid content of 60.0%, a viscosity of 1100 mPa · s, and an average particle size of 1.8 μm was obtained.

  Other than using PVA-3 (polymerization degree 1000, saponification degree 88 mol%, 1,2-glycol bond amount 2.5 mol%, ethylene content 4.0 mol%) instead of PVA-1 in Example 1 Was polymerized in the same manner as in Example 1 to obtain a polyvinyl acetate emulsion having a solid content of 59.8%, a viscosity of 1300 mPa · s, and an average particle size of 1.6 μm.

  Polymerization was conducted in the same manner as in Example 1 except that the amount of PVA-1 used in Example 1 was changed to 13 g. Polyvinyl acetate having a solid content of 59.8%, a viscosity of 1850 mPa · s, and an average particle size of 1.3 μm. An emulsion was obtained.

  Polymerization was conducted in the same manner as in Example 1 except that the amount of PVA-1 used in Example 1 was changed to 6 g. Polyvinyl acetate having a solid content of 59.2%, a viscosity of 1000 mPa · s, and an average particle size of 1.9 μm. An emulsion was obtained.

8.5 g of PVA-1 was dissolved in 255 g of ion-exchanged water by heating and charged into a pressure-resistant autoclave equipped with a nitrogen inlet and a thermometer, and then charged with 368 g of vinyl acetate, and then ethylene up to 45 kg / cm ² The pressure was increased (the copolymerization amount of ethylene was equivalent to 74 g). After raising the temperature to 60 ° C., polymerization was initiated with a hydrogen peroxide / Longalite redox initiator. After 2 hours, the polymerization was terminated when the residual vinyl acetate concentration reached 0.6%, and a poly (ethylene-vinyl acetate) copolymer having a solid content of 63.4%, a viscosity of 1900 mPa · s, and an average particle size of 1.9 μm. An emulsion was obtained.

Comparative Example 1
Polymerization was conducted in the same manner as in Example 1 except that the amount of PVA-1 used in Example 1 was changed to PVA-5 (polymerization degree 1700, saponification degree 88 mol%, 1,2-glycol bond amount 1.6 mol%). However, it was blocked due to lack of stability.

Comparative Example 2
Polymerization was performed in the same manner as in Example 1 except that PVA-1 was changed to PVA-6 (polymerization degree 1700, saponification degree 98 mol%, 1,2-glycol bond amount 1.6 mol%) in Example 1. However, it was blocked due to lack of stability.

Comparative Example 3
Except that PVA-1 was changed to PVA-4 (polymerization degree 1700, saponification degree 88 mol%, 1,2-glycol bond content 1.6 mol%, ethylene content 4.0 mol%) in Example 1. Polymerization was carried out in the same manner as in Example 1, but blocked due to lack of stability.

Comparative Example 4
Polymerization was carried out in the same manner as in Example 1 except that the amount of PVA-1 used in Example 1 was changed to 4.3 g, but it was blocked due to lack of stability.

Comparative Example 5
Polymerization was carried out in the same manner as in Example 6 except that PVA-1 was changed to PVA-5 (polymerization degree 1700, saponification degree 88 mol%, 1,2-glycol bond amount 1.6 mol%) in Example 6. A poly (ethylene-vinyl acetate) copolymer emulsion having a solid content of 62.3%, a viscosity of 2500 mPa · s, and an average particle size of 3.0 μm was obtained.

Comparative Example 6
In Example 6, 27 g of PVA-2 (polymerization degree 1700, saponification degree 98 mol%, 1,2-glycol bond amount 2.2 mol%) was used instead of PVA-1, and ion-exchanged water and vinyl acetate. Polymerization was conducted in the same manner as in Example 6 except that 345 g and 280 g were used, respectively, and a poly (ethylene-vinyl acetate) copolymer having a solid content of 50.1%, a viscosity of 20000 mPa · s, and an average particle diameter of 0.5 μm. An emulsion was obtained.

Comparative Example 7
In Example 6, polymerization was performed in the same manner as in Example 6 except that 15 g of PVA-1, 315.5 g of ion-exchanged water, and 315 g of vinyl acetate were used, and the solid content was 54.4%, the viscosity was 3400 mPa · s, A poly (ethylene-vinyl acetate) copolymer emulsion having an average particle size of 0.8 μm was obtained.

Comparative Example 8
Polymerization was conducted in the same manner as in Example 1 except that the amount of PVA-1 used in Example 1 was changed to 16 g, and a polymer having a solid content of 58.5%, a viscosity of 10,000 mPs · s, and an average particle size of 0.9 μm was obtained. A vinyl acetate emulsion was obtained.

Comparative Example 9
The polymerization reaction was carried out in the same manner as in Comparative Example 5 except that PVA-1 was changed to PVA-5 (polymerization degree 1700, saponification degree 88 mol%, 1,2-glycol bond amount 1.6 mol%) in Comparative Example 5. I went there, but it was blocked because of lack of stability.

  The experimental results are summarized in Table 1.

  The aqueous emulsion of the present invention has low viscosity despite its high solid content, and has excellent mechanical stability and skin resistance as well as sedimentation stability. Suitable as an admixture.

Claims (1)

Disperse vinyl alcohol polymer (B) having polyvinyl acetate (A) as dispersoid and having 1,2-glycol bond of 1.9 mol% or more, polymerization degree of 300 or more, and saponification degree of 70 mol% or more. The weight ratio (B) / (A) is 1.3 / 100 to 2.7 / 100, the solid content concentration is 59.1% by weight or more, the emulsion viscosity is 1850 mPa · s or less, and the average particle size Is an aqueous emulsion of 1 to 2 μm.