JPH1192611A - Vinyl resin emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject emulsion that is excellent in shelf stability, the stability of water-resistant adhesion of the coated layer before and after long-term storage of the emulsion and is useful as wood-working adhesive or bobbin adhesive by admixing a polyvinyl alcohol resin and an organic sulfide thereto. SOLUTION: The objective vinyl resin emulsion is prepared by using an acetoacetyl group-containing polyvinyl alcohol resin and an organic sulfide as dibutyl disulfide, diacetyl disulfide or diethyl dithioglycolate, preferably in an amount of 0.05-4 wt.%, preferably in addition, a reducing agent as sulfite, thiosulfate or bisulfite salt in an amount of 0.05-2 wt.%. In a preferred embodiment, a vinyl monomer is polymerized in isopropanol, as the monomer is added dropwise and butyl alcohol is added after completion of dropping of the polymerization catalyst. The residual vinyl monomer in this emulsion is preferably <=0.4 wt.% and the pH is adjusted to 3-8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vinyl resin emulsion, and more particularly to a vinyl resin emulsion excellent in long-term storage stability and stability of water-resistant adhesive strength of a formed coating film before and after long-term storage of the emulsion. .

[0002]

2. Description of the Related Art Conventionally, (vinyl acetate) -based emulsions have been widely used for adhesives, paints, textile / textile processing agents, paper / leather processing agents, binders for various materials, and cement / mortar admixtures. It is used for various purposes. Among them,
(Acetic acid) vinyl resin emulsion containing acetoacetylated polyvinyl alcohol-based resin can be used as an adhesive for woodworking by using various cross-linking agents to further improve the water resistance, and to cut the adhesive. It has advantages such as not damaging the blade sometimes, and is therefore used for the above-mentioned applications. However, when an acetoacetylated polyvinyl alcohol-based resin is added, the stability of the emulsion decreases (increase in viscosity, generation of a gel, etc.), and thus various additives have been used in combination. For example,
JP-A-36218 discloses the combination use of sulfites, thiosulfates, bisulfites, metabisulfites and the like, and JP-A-7-3102 discloses the combination use of a hydroxyl group-containing compound represented by a specific formula. In Japanese Patent Application Laid-Open No. 8-113687, a combined use of a water-soluble organic amine and a water-soluble hydrazine is proposed, and the applicant of the present invention also used a combined use of ketones, keto acid esters, malonic acids, etc. JP-A-7-138305), combined use of sodium acid sulfite (JP-A-7-138305), combined use of mercaptans (JP-A-7-138306)
And so on.

[0003]

However, Japanese Patent Publication No. 60-36218 and Japanese Patent Application Laid-Open No.
JP-B-3-50772, JP-A-7-138306
In the combined use of the additives described in Japanese Patent Publication No. 1993, although a certain degree of storage stability can be expected, the stability at high and low temperatures in summer and winter is not sufficient, and it was used as a film strength or adhesive after long-term storage. Poor adhesiveness at the time, still unsatisfactory, and with the use of the additive described in JP-A-8-113687, gelling can be prevented, but the emulsion causes an increase in viscosity and is used in an adhesive or the like. However, there is a drawback that a stable adhesive force cannot be obtained depending on the time of use, and a new improvement is desired.

[0004]

In view of the above circumstances, the present inventors have conducted intensive studies. As a result, acetoacetyl group-containing polyvinyl alcohol-based resins and vinyl resin-based emulsions containing sulfides have been developed in summer and winter. The present invention has been found to be an emulsion that exhibits sufficient stability even at high and low temperatures, and that can maintain the film strength after long-term storage and the adhesive strength when used as an adhesive. I came to.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
Acetoacetylated polyvinyl alcohol resin used in the present invention (hereinafter sometimes abbreviated as AA-PVA)
Can be obtained by reacting a polyvinyl alcohol-based resin (hereinafter sometimes abbreviated as PVA) with diketene by a known method. For example, PVA is dispersed in an acetic acid solvent, and diketene is added thereto. In this method, PVA is previously dissolved in a solvent such as dimethylformamide or dioxane, and diketene is added thereto. Also, a method of obtaining an AA-PVA by directly contacting PVA with diketene gas or liquid diketene, and a method of preparing PVA DM
A method of obtaining an AA-PVA by adding an acid catalyst such as sulfuric acid to an organic solvent such as F, DMSO and acetate to transesterify the acetoacetate to obtain an AA-PVA.

The average degree of polymerization of the AA-PVA is not particularly limited, but is preferably from 200 to 3,000, more preferably from 40 to 3,000.
If the average degree of polymerization is less than 200, it is difficult to obtain a protective colloid as an emulsifier described later, and the emulsion has poor stability during emulsion polymerization. Conversely, if it exceeds 3,000, an emulsion obtained when used as an emulsifier The viscosity increases, which is not preferable. Also, a raw material P for AA-PVA
The average degree of saponification of VA is preferably 68 to 100 mol%,
Further, the content is preferably in the range of 75 to 100 mol%, particularly 80 to 100 mol%. If the average saponification degree is less than 68 mol%, the resulting AA-PVA becomes insoluble in water, which is not preferable. Further, the acetoacetyl group content (AA conversion degree) of the AA-PVA is preferably 0.05 to 15 mol%, more preferably 1 to 10 mol%, and the AA-degree is 0.05 mol%. If the amount is less than 15%, the water resistance of the emulsion formed into a coating tends to decrease. On the other hand, if the amount exceeds 15% by mole, the emulsion viscosity tends to be too high and the storage stability tends to decrease.

In the present invention, the AA-P
It is possible to use not only VA alone, but also other PVAs, and furthermore, two or more kinds of A having different degrees of saponification and the like.
It is also possible to use A-PVA. Such AA-P
The content of VA is preferably selected from the range of 0.1 to 30% by weight (more preferably 1 to 15% by weight) based on the whole of the vinyl resin emulsion of the present invention. When the amount is less than 30% by weight, the water resistance of the emulsion when formed into a coating film is reduced. On the other hand, when the amount is more than 30% by weight, the emulsion viscosity is too high and the storage stability is undesirably reduced.

The vinyl acetate resin emulsion of the present invention containing the AA-PVA as described above is usually obtained by emulsion polymerization of a vinyl compound. Examples of such a vinyl compound include vinyl acetate, vinyl propionate, and ( Meta)
Acrylic acid ester, vinyl chloride, vinylidene chloride,
Examples thereof include (meth) acrylonitrile, styrene, ethylene, propylene, and an acetoacetyl group-containing acrylic monomer. These are homopolymerization or copolymerization, or copolymerization with a diene monomer such as butadiene. In particular, vinyl acetate alone or a copolymer mainly composed of vinyl acetate is preferred.

As the emulsion polymerization catalyst, a radical generator, in particular, a water-soluble catalyst is preferably used. For example, peroxides such as hydrogen peroxide, reducing agents such as tartaric acid, formic acid and oxalic acid, and 2,2-azobis (2-amidinopropane)
One or more of water-soluble azobis such as diacid salt, ammonium persulfate, potassium persulfate and the like are used, and a persulfate catalyst such as ammonium persulfate and potassium persulfate is preferably used. Various surfactants such as nonionic surfactants and anionic surfactants are also used as AA-P
Can be used in combination with VA. Still other emulsifiers such as cellulose derivatives (carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, etc.), polyvinyl alcohols, polyacrylic acid derivatives, maleic anhydride-vinyl ether copolymer, maleic anhydride-
A vinyl acetate copolymer, a saponified vinyl acetate- (meth) allylsulfonic acid (salt) copolymer, and the like can also be appropriately used.

In the present invention, the AA-PV as described above is used.
The most characteristic feature is that the sulfides are further contained in the vinyl resin emulsion containing A.
Such sulfides include dibutyl disulfide,
Diacetyl disulfide, diethyl dithioglycate,
Examples thereof include 2-methylthioethanol and 2,2′-thiodiethanol, and preferably, 2-methylthioethanol and 2,2′-thiodiethanol are used.

The content of such sulfides in the vinyl emulsion is preferably 0.05 to 4% by weight, more preferably 0.05 to 2% by weight, and the content is less than 0.05% by weight. In this case, the storage stability of the emulsion is lowered, and when it exceeds 4% by weight, the water resistance of the emulsion is slightly lowered, which is not preferable. The method for adding such sulfides is not particularly limited, and may be any time during polymerization, such as after polymerization, but is preferably after polymerization in order to obtain better water resistance of the film, and may be in a solid state upon addition. Although it is good, it is preferable to add it as an aqueous solution.

In the present invention, thiourea, sulfite,
It is also preferable to include a reducing agent such as thiosulfate, bisulfite, metabisulfite, L-ascorbic acid, hydrazines, etc. Specific examples of such a reducing agent include sodium sulfite, potassium sulfite, ammonium sulfite, and thiosulfate. Sodium, potassium thiosulfate, ammonium thiosulfate, sodium bisulfite, ammonium bisulfite, sodium metabisulfite, potassium metabisulfite, L-ascorbic acid, hydrazine sulfate, hydrazine hydrochloride, hydrazine carbonate, substituted hydrazine, hydrazine phosphate, methylhydrazine Preferably, sodium bisulfite is used, and its content is 0.05 to 2% by weight.
(More preferably 0.1 to 1% by weight). If the content is less than 0.05% by weight, the storage stability of the emulsion cannot be expected to be much improved. Is unfavorable because the water resistance and the adhesive strength of the polymer decrease.
The addition of these reducing agents may be during or after the polymerization, but is preferably performed after the polymerization. The addition may be performed in a solid state, but is preferably performed as an aqueous solution.

Thus, the (acetic acid) vinyl resin emulsion of the present invention containing the acetoacetyl group-containing polyvinyl alcohol resin and the (hypo) phosphite is obtained. The residual amount of the vinyl monomer of 0.4% by weight or less, more preferably 0.3% by weight or less, particularly 0.2% by weight or less, and the pH of such an emulsion is 3-8, more preferably 4-7. Is also preferred. The method for controlling the residual amount of the vinyl monomer in the emulsion to 0.4% by weight or less is not particularly limited. For example, during the emulsion polymerization of the (acetic acid) vinyl compound as described above, isopropyl alcohol is allowed to coexist. A method of adding butyl alcohol after the addition of the polymerization catalyst, a method of adding an alkali metal salt of silicic acid to a residual (acetic acid) vinyl monomer in a (acetic acid) vinyl resin emulsion containing AA-PVA, In particular, a method of raising the polymerization temperature (for example, to 80 ° C. or higher) immediately before the end of the polymerization may be mentioned.
This will be described in more detail.

In the above method, the coexistence amount of isopropyl alcohol is 0.1 to 100 parts by weight of the vinyl compound.
The amount is preferably from 2 to 2 parts by weight (more preferably from 0.5 to 1.5 parts by weight). If the amount is less than 0.2 part by weight, the effect of reducing the amount of the monomer is not sufficient. Exceeding the weight part is not preferred because the viscosity stability of the emulsion decreases. Further, the addition amount of butyl alcohol to be added after the completion of the dropwise addition of the polymerization catalyst is preferably 0.05 to 0.3 parts by weight (more preferably 0.1 to 0.2 parts by weight) based on 100 parts by weight of the vinyl compound. If the amount is less than 0.05 part by weight, the effect of reducing the amount of the monomer is not sufficient, and if the amount exceeds 0.3 part by weight, it does not contribute to the reduction of the residual monomer.

In the above method, sodium silicate (sodium metasilicate, sodium orthosilicate, sodium disilicate, sodium tetrasilicate, etc.), potassium silicate (potassium metasilicate, potassium hydrogen disilicate, etc.), silicate Lithium (lithium metasilicate, lithium orthosilicate, etc.) and hydrates thereof can be mentioned. Preferably, the content (addition) of an alkali metal salt of silicic acid such as sodium silicate or potassium silicate is used. The content may be set to 0.01 to 4% by weight (further 0.02 to 2% by weight). When the content is less than 0.01% by weight, the effect of reducing the residual monomer is poor. Exceeding this is undesirable because the stability of the emulsion and the strength of the film decrease.

The method for controlling the pH of the emulsion is not particularly limited, and may be adjusted, for example, by adding various metal salts of organic or inorganic acids or amines. , Sodium phosphate, sodium carbonate, aluminum acetate, magnesium acetate, dibasic sodium phosphate, calcium carbonate, sodium bicarbonate and the like are added to the emulsion in an amount of about 0.01 to 5% by weight (based on the emulsion) Either during or after the polymerization may be performed, and is not particularly limited.
It is preferable to add at the time when the polymerization rate is 90% or more.)
Can be controlled by

In the above-mentioned polymerization, various additives used in ordinary emulsion polymerization can be used. In the present invention, polyethylene glycol, mercaptans (alkyl mercaptan, aromatic mercaptan), sulfides ( Use of a chain transfer agent such as dibutyl disulfide, diacetyl disulfide, diethyl dithioglycate) or a nitrogen-containing compound (methyl cyanoacetate, nitromethane, benzyl cyanide) is more useful for the stability of the emulsion. Is preferably from 0.01 to 5% by weight, more preferably from 0.02 to 2% by weight, based on the vinyl monomer. When the amount is less than 0.01% by weight, the storage stability of the emulsion is hardly obtained. If it exceeds 5% by weight, the water resistance of the emulsion film decreases. Unfavorable.

A plasticizer such as dibutyl phthalate, dioctyl phthalate, or butyl carbitol may be added to adjust the minimum film forming temperature and the like. Modified by adding a water-soluble aliphatic dihydrazide such as rudihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, or by mixing a phenolic resin initial condensate or resorcinol initial condensate. It can be handled as a vinyl acetate emulsion.

As described above, AA-PVA is used as an emulsifier,
(Acetate) AA
It is of course possible to obtain a (acetic acid) vinyl resin-based emulsion of the present invention by post-adding AA-PVA to the (acetic acid) vinyl resin-based emulsion. . Thus, the obtained (acetic acid) vinyl resin emulsion of the present invention is obtained on paper,
It is used as an adhesive, binder, coating agent and paint for wood, plastics, textiles, wallpaper, etc., especially for high-speed mechanization of woodworking and paper bonding, and it has excellent water resistance. It is useful for applications and the like, and is also useful for applications (adhesives, paints, coating agents, etc.) for coating or impregnating wood or the like to supplement formaldehydes in the wood.

[0020]

Next, the present invention will be described more specifically with reference to examples. In the examples, “parts” and “%” are based on weight unless otherwise specified. Example 1 10.8 parts of a vinyl acetate monomer and an average degree of polymerization of 1400,
AA having an average saponification degree of 99 mol% and an AA degree of 5.5 mol%
120 parts of a 10% aqueous PVA solution, 10 parts of a 0.6% aqueous sodium acetate solution, 37 parts of water, and 5 parts of a 0.96% aqueous ammonium persulfate solution were stirred with a stirrer, a reflux condenser, a dropping funnel,
The mixture was charged into a separable flask equipped with a thermometer, and the temperature in the flask was increased to 70 ° C. with stirring to perform initial polymerization for 1 hour. Next, 97.2 parts of a vinyl acetate monomer was added dropwise over 3 hours, 5 parts of a 0.96% ammonium persulfate aqueous solution was added, and the same amount of a 0.96% ammonium persulfate aqueous solution was added three times every hour. did.
One hour after the completion of the addition of the vinyl acetate monomer, 1 part of a 1% aqueous solution of hydroquinone was added to terminate the polymerization. Finally 4
2 parts of a 0% 2-methylthioethanol aqueous solution was added to obtain a vinyl acetate resin emulsion of the present invention. The obtained vinyl acetate resin emulsion had a residual vinyl acetate monomer content of 0.4%, a polymerization rate of 98.9%, a pH of 2.5, and a viscosity of 2
It was 7000 mPa · s (BH type rotational viscometer, rotor rotation speed 10 rpm, 25 ° C.). Using the above-mentioned vinyl acetate resin emulsion, the stability of standing and the water resistance of the resulting coating film were evaluated as follows.

(Stability on standing) The obtained vinyl acetate resin emulsion was sealed in a 450 ml mayonnaise bottle,
The viscosities after standing at 70 ° C. for 7 days and after standing at room temperature for 6 months were measured to determine how many times the viscosity before standing (the same method as above) (viscosity after standing / viscosity before standing). . In addition, the measurement of the viscosity was all performed at 25 degreeC. (Stability of water-resistant adhesive strength) Rawan material (25 mm x 50 m
m, thickness 10 mm), and apply the obtained vinyl acetate emulsion to a surface of 100 g / m ^2.
Half of the area (25m)
mx 25mm), 10kg
/ Cm ² at 20 ° C for 1 hour.
The specimen was cured at 48 ° C. and 65% RH for 48 hours.
Next, the obtained specimen was boiled for 4 hours, dried at 60 ° C. for 3 hours, and measured at 20 ° C. for compression shear adhesive strength at a compression speed of 10 mm / min, and evaluated as follows.
The measured value was an average value of n = 10, and the vinyl acetate emulsion left at room temperature for 6 months was similarly evaluated. ○ --- 30kg / cm ² or more △ --- 1~30kg / cm ² less × --- 1kg / cm ^2, or less than peeling the specimen before the measurement was observed (low-temperature stability) The obtained acetate The vinyl resin emulsion was sealed in a 450 ml mayonnaise bottle, left in a 0 ° C. thermostat for 3 hours, and the viscosity immediately after being taken out was measured. The emulsion was further left in a 0 ° C. thermostat for 1 month, and The viscosity was measured to determine how many times the viscosity before standing for one month (viscosity after standing for one month / 3 viscosity after standing for 3 hours).

Example 2 The procedure of Example 1 was repeated except that 2 parts of a 40% aqueous sodium bisulfite solution was further added. The amount of the remaining vinyl acetate monomer was 0.4%, the polymerization rate was 98.9%, and the pH was 2.0.
5. A vinyl acetate resin emulsion having a viscosity of 26000 mPa · s (same as above) was obtained and similarly evaluated.

Example 3 The procedure of Example 1 was repeated, except that 5 parts of a 10% aqueous sodium silicate solution was added simultaneously with the 40% aqueous 2-methylthioethanol solution. Rate 99.1%, pH 5.2, viscosity 25
A vinyl acetate resin emulsion of 000 mPa · s (same as above) was obtained and evaluated in the same manner.

Example 4 The procedure of Example 1 was repeated except that the amount of the 40% aqueous 2-methylthioethanol solution was changed to 10 parts. The amount of the remaining vinyl acetate monomer was 0.4%, the polymerization rate was 98.8%, p
A vinyl acetate resin emulsion having an H of 3.5 and a viscosity of 25,000 mPa · s (same as above) was obtained and evaluated similarly.

Example 5 The procedure of Example 1 was repeated, except that 1 part of a 15% aqueous sodium acetate solution was added simultaneously with a 40% aqueous 2-methylthioethanol solution. 9.9%, pH 5.0, viscosity 260
A vinyl acetate resin emulsion of 00 mPa · s (same as above) was obtained and evaluated in the same manner.

Example 6 A mixed solution comprising 108 parts of vinyl acetate monomer and 2 parts of isopropyl alcohol was prepared in advance, 11 parts of the mixed solution, average degree of polymerization of 1400, average degree of saponification of 99 mol%, and degree of AA of 5 120 parts of a 10% aqueous solution of 0.5 mol% AA-PVA, 120 parts of a 0.6% aqueous sodium acetate solution, 37 parts of water, and 5 parts of a 0.96% aqueous ammonium persulfate solution were stirred with a stirrer, a reflux condenser, a dropping funnel, and a temperature. The mixture was charged into a separable flask equipped with a meter, and the temperature in the flask was increased to 70 ° C. with stirring to carry out initial polymerization for 1 hour. Next, 99 parts of the remaining liquid mixture was added dropwise over 3 hours,
5 parts of a 6% ammonium persulfate aqueous solution was added, and the same amount of a 0.96% ammonium persulfate aqueous solution was further added three times every hour. At the same time as vinyl acetate monomer dropping,
0.3 parts of butyl alcohol was added, and one hour later, 1 part of a 1% aqueous solution of hydroquinone was added to terminate the polymerization.
Finally, 2 parts of a 40% aqueous 2-methylthioethanol solution, 1
One part of a 5% aqueous sodium acetate solution was added to obtain a vinyl acetate resin emulsion. The obtained vinyl acetate resin emulsion had a residual vinyl acetate monomer content of 0.2%, a polymerization rate of 99.4%, a pH of 4.8, and a viscosity of 25,000 mPa · s.
(Id.)

Example 7 Polymerization was started in the same manner as in Example 6, and butyl alcohol 0.3
At the time of addition, 1 part of a 15% aqueous solution of sodium acetate was added (at this time, the polymerization rate was 96%, and the pH was 5.2). After one hour, the polymerization was terminated.
After adding 2 parts of 2-methylthioethanol aqueous solution, the amount of residual vinyl acetate monomer was 0.2%, and the conversion was 99.4.
%, A pH of 4.6, and a viscosity of 23,000 mPa · s (same as above), and evaluated in the same manner.

Example 8 The procedure of Example 6 was repeated, except that the aqueous sodium acetate solution was replaced with 3
Polymerization was carried out in the same manner except that 10 parts of a 0% aqueous sodium carbonate solution was used. The amount of the remaining vinyl acetate monomer was 0.2%, the polymerization rate was 99.4%, the pH was 7.1, and the viscosity was 24000 mPa · s.
s (same as above) was obtained and similarly evaluated.

Example 9 In Example 6, finally, 1 part of a 40% aqueous solution of 2-methylthioethanol and 1 part of a 40% aqueous solution of sodium bisulfite 1
A vinyl acetate resin emulsion having a residual vinyl acetate monomer amount of 0.2%, a polymerization rate of 99.4%, a pH of 4.9, and a viscosity of 23,000 mPa · s (same as above) was obtained in the same manner except for adding An evaluation was performed.

Comparative Example 1 The procedure of Example 1 was repeated except that a 40% aqueous solution of 2-methylthioethanol was not used. The amount of the remaining vinyl acetate monomer was 0.4%, the conversion was 98.9%, and the pH was 2.0.
5. A vinyl acetate resin emulsion having a viscosity of 27,000 mPa · s (same as above) was obtained and similarly evaluated. Table 1 shows the evaluation results of the examples and the comparative examples.

[0031]

[Table 1] Leaving stability Stability of water-resistant adhesive strength Low temperature stability 70 ° C × 7 days Room temperature × 6 months Initial room temperature × 6 months Example 1 2.5 2.8 ○ △ 1.5 〃 2 2.5 2 1.8 △ 1.6 １．２ 3 1.2 1.3 ○ 1.3 ４ 4 2.4 2.5 △ 1.4 〃 5 2.3 2.4 △ 1.3 〃 6 1. 0 1.0 ○ １．０ 1.0 〃 7 1.0 1.0 ○ １．１ 1.1 〃 8 1.9 2.0 △ 1.4 ○ 9 1.2 1.2 ○ 1.2 Comparative example 1 Gelation Gelation ○ × 3.5

[0032]

Since the (acetic acid) vinyl resin emulsion of the present invention contains an acetoacetyl group-containing polyvinyl alcohol resin and sulfides, it is possible to maintain the storage (storage) stability and to form the emulsion before and after long-term storage. It is excellent in the stability of the water-resistant adhesive strength of the coating film, and is particularly useful for applications such as woodworking adhesives and paper tube adhesives requiring water resistance / hot water resistance.

Claims (11)

[Claims] 1. A vinyl resin emulsion comprising an acetoacetyl group-containing polyvinyl alcohol resin and a sulfide. 2. The sulfides are dibutyl disulfide,
Diacetyl disulfide, diethyl dithioglycate,
The vinyl resin emulsion according to claim 1, wherein the emulsion is one of 2-methylthioethanol and 2,2'-thiodiethanol. 3. The vinyl resin emulsion according to claim 1, wherein the content of the sulfide is 0.05 to 4% by weight. 4. The method according to claim 1, further comprising at least one reducing agent selected from the group consisting of sulfites, thiosulfates, bisulfites, metabisulfites, L-ascorbic acid and hydrazines. 4. The vinyl resin emulsion according to any one of claims 1 to 3. 5. The vinyl resin emulsion according to claim 4, wherein the content of the reducing agent is 0.05 to 2% by weight. 6. The residual amount of the vinyl monomer is 0.4% by weight.
The vinyl resin emulsion according to any one of claims 1 to 5, wherein: 7. The method according to claim 6, wherein a vinyl monomer is dropped and polymerized in the presence of isopropyl alcohol, and butyl alcohol is added after dropping the polymerization catalyst.
The vinyl resin emulsion according to the above. 8. The vinyl resin emulsion according to claim 6, further comprising an alkali salt of silicic acid. 9. The content of an alkali salt of silicic acid is 0.01
The vinyl resin emulsion according to claim 8, wherein the amount is from 4 to 4% by weight. 10. The vinyl resin emulsion according to claim 1, wherein the pH is 3 to 8. 11. The vinyl resin emulsion according to claim 1, which is used for coating or impregnating wood to supplement formaldehydes in the wood.