JPH1135769A - Vinyl resin emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an emulsion excellent in long-term storage stability and adhesiveness and the water resistance of a coating film formed therefrom by selecting an emulsion containing an acetoacetyl-containing PVA resin and having a specified or smaller vinyl monomer content. SOLUTION: There is provided an emulsion containing desirably 0.1-30 wt.% acetoacetyl-containing PVA resin, desirably the one having an average degree of saponification of 68-100 mol.% as measured on the starting PVA), an acetoacetyl content of 0.05-15 mol.% and an average degree of polymerization of 200-3,000 and having a vinyl monomer content of at most 0.4 wt.%, desirably 0.01-0.3 wt.%, more desirably 0.01-0.2 wt.%. It is desirable that the pH is adjusted to 3-8 by the addition of e.g. a metal salt of an organic or inorganic acid or an amine and/or that desirably 0.05-2 wt.% reducing agent (e.g. sulfite) is added and/or that desirably 0.01-4 wt.% alkali metal silicate is added.

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 water resistance of a formed coating film.

[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 inventor has conducted intensive studies, and as a result, it has been found that a polyvinyl alcohol resin containing an acetoacetyl group is contained and a vinyl monomer content is 0.4 wt. % Or less, and when the pH is 3 to 8, it exhibits sufficient stability even at high or low temperatures in summer or winter, and when used as a film strength or adhesive after long-term storage. The inventors have found that an emulsion capable of maintaining the adhesive force or the like can be obtained, and have completed the present invention.

[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 AA-PVA by directly contacting PVA with diketene gas or liquid diketene, or adding an acid catalyst such as sulfuric acid to a saponified slurry of an alcohol solvent of PVA, transesterifying acetoacetate ester, and subjecting AA
A method of obtaining VA can be employed.

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, it is preferably in the range of 80 to 100 mol%, and the AA-PVA obtained when the average saponification degree is less than 68 mol% is obtained.
Is not preferred because it becomes insoluble in water. Furthermore, AA-PVA
Acetoacetyl group content (AA degree) of 0.05 to
When the AA degree is less than 0.05 mol%, the water resistance when the emulsion is formed into a coating film tends to decrease. If it exceeds mol%, the emulsion viscosity is too high and the storage stability tends to decrease, which is not preferred.

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 10% 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, tartaric acid, formic acid,
One or more of a reducing agent such as oxalic acid, a water-soluble azobis such as 2,2-azobis (2-amidinopropane) diacid salt, ammonium persulfate, potassium persulfate and the like, or two or more thereof are preferably used. A persulfate-based catalyst such as ammonium persulfate or potassium persulfate is used.

Various surfactants such as nonionic surfactants and anionic surfactants can be used in combination with AA-PVA.
Still other emulsifiers such as cellulose derivatives (carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, etc.), polyvinyl alcohols, polyacrylic acid derivatives, maleic anhydride-vinyl ether copolymer, maleic anhydride-vinyl acetate copolymer And a saponified product of vinyl acetate- (meth) allylsulfonic acid (salt) copolymer and the like can also be appropriately used.

According to the present invention, the amount of residual (acetic acid) vinyl monomer in the (Acetate) vinyl resin emulsion containing AA-PVA as described above is 0.4% by weight or less (furthermore, the amount is preferably 0.1% or less).
The most characteristic feature is that the reaction between AA-PVA and acetaldehyde generated by hydrolysis of residual monomers is controlled by adjusting the amount to 01 to 0.3% by weight, particularly 0.01 to 0.2% by weight. In the method for controlling the amount of the monomer is not particularly limited, for example,
A method in which isopropyl alcohol is allowed to coexist during the emulsion polymerization of the (acetic acid) vinyl compound as described above, and butyl alcohol is added after the addition of the polymerization catalyst is completed.
A method of removing the residual (acetic acid) vinyl monomer in the (acetic acid) vinyl resin emulsion containing the A-PVA by adding an alkali metal salt of silicic acid, a method of increasing the polymerization temperature during emulsion polymerization, and the like. However, the method is industrially useful, and such a method will be described in more detail.

In the above method, the coexisting 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.

Thus, the (acetic acid) vinyl resin emulsion of the present invention containing the acetoacetyl group-containing polyvinyl alcohol resin and having a vinyl monomer content of 0.4% by weight or less can be obtained. In the present invention, the pH of such an emulsion is 3 to 8, more preferably 4 to 8.
It is particularly preferred to be 7, and the control and effect of the pH can remarkably obtain the effects of the present invention.
As a specific method of such a control, it may be adjusted by adding various organic or inorganic acid metal salts or amines, and more specifically, sodium acetate, sodium phosphate, sodium carbonate, aluminum acetate. , Magnesium acetate or the like is added to the emulsion in an amount of about 0.01 to 5% by weight (based on the emulsion) (the timing of addition may be either during or after polymerization, and is not particularly limited. It is preferable to control the addition.

Further, in the present invention, the (aceto) vinyl resin-based emulsion of the present invention containing the obtained acetoacetyl group-containing polyvinyl alcohol-based resin and having a vinyl monomer content of 0.4% by weight or less, It is more preferable to include a reducing agent in terms of storage stability of the emulsion, and such a reducing agent is selected from sulfites, thiosulfates, bisulfites, metabisulfites, L-ascorbic acid, and hydrazines. At least one kind can be mentioned, and specifically, sodium sulfite, potassium sulfite, ammonium sulfite, sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, sodium bisulfite, ammonium bisulfite, sodium metabisulfite, potassium metabisulfite , L-ascorbic acid, hydrazine sulfate, hydrazine hydrochloride, Examples thereof include acid hydrazine, substituted hydrazine, hydrazine phosphate, and methyl hydrazine. Preferably, sodium bisulfite is used, and its content is 0.05 to 2% by weight (further 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, while if it exceeds 2% by weight, the water resistance and adhesion of the film are reduced. Not preferred. The addition of these reducing agents may be during or after polymerization, but preferably after polymerization, and may be in a solid state upon addition.
It is preferably added as an aqueous solution.

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 useful for the stability of the emulsion. The amount is preferably 0.01 to 5% by weight, more preferably 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 is lowered, which is preferable. Not properly.

A plasticizer such as dibutyl phthalate, dioctyl phthalate, or butyl carbitol may be added for adjusting the minimum film forming temperature and the like, and adipoi for improving the water resistance of the emulsion film. 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 it is also useful for applications (adhesives, paints, coating agents, etc.) for coating or impregnating wood or the like to supplement formaldehyde in the wood.

[0018]

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 A mixed solution composed of 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 was 1400, average degree of saponification was 99 mol%, and degree of AA was 5.5 mol. % AA PVA 10% aqueous solution 120 parts, 0.6% sodium acetate aqueous solution 10 parts, water 37 parts, 0.96% ammonium persulfate aqueous solution 5 parts equipped with a stirrer, reflux condenser, dropping funnel and thermometer Then, the temperature in the flask was set to 70 ° C. while stirring, and the initial polymerization was performed for 1 hour.

Next, 99 parts of the remaining mixed solution was added dropwise over 3 hours, 5 parts of a 0.96% ammonium persulfate aqueous solution was added, and the mixture was further added three times every hour. Butyl alcohol 0.3
The polymerization was terminated by adding 1 part of a 1% aqueous solution of hydroquinone 1 hour later. Finally, 2 parts of 40% aqueous sodium bisulfite solution and 15% aqueous sodium acetate solution 1
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 0.2%, a polymerization rate of 99.4%, and a pH of 9%.
4.4, viscosity 25,000 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 formed 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 one year are measured to determine how many times the viscosity before standing (the same method as above) (viscosity after standing / viscosity before standing). Was. In addition, the measurement of the viscosity was all performed at 25 degreeC. (Water resistance) The above-mentioned vinyl acetate resin emulsion left for one year at room temperature is coated on a glass plate, dried and heat-treated at 40 ° C. for 3 minutes, and air-dried for 24 hours to prepare a coating film of about 100 μm. Immersing the coating film in hot water of 90 ° C. for 3 hours,
The elution residue of the coating film was measured. (Low-temperature stability) The obtained vinyl acetate resin emulsion was sealed in a 450 ml mayonnaise bottle, left in a thermostat at 0 ° C. for 3 hours, the viscosity immediately after being taken out was measured, and the emulsion was further thermostated at 0 ° C. The container was left for one month, and the viscosity was measured in the same manner to determine how many times the viscosity before standing for one month (viscosity after standing for one month / viscosity after standing for three hours).

Example 2 Polymerization was started in the same manner as in Example 1 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 4.7). After one hour, the polymerization was terminated.
Two parts of an aqueous sodium hydrogen sulfite solution were added to obtain a vinyl acetate resin emulsion of the present invention. The amount of residual vinyl acetate monomer in the obtained vinyl acetate resin emulsion was 0.2
%, Polymerization rate 99.4%, pH 4.3, viscosity 23000
mPa · s (same as above). Evaluation was performed in the same manner as in Example 1 using the above-mentioned vinyl acetate resin emulsion.

Example 3 Polymerization was carried out in the same manner as in Example 1 except that 10 parts of a 30% aqueous solution of carbonic acid was used instead of the 15% aqueous sodium acetate solution added last, and the amount of residual vinyl acetate monomer was 0.1%. 2%, polymerization rate 99.4%, pH 7.2, viscosity 240
A vinyl acetate resin emulsion of 00 mPa · s (same as above) was obtained and evaluated in the same manner.

Example 4 In Example 1, 0.024 parts of butyl mercaptan was allowed to coexist at the time of the initial polymerization.
The polymerization was carried out in the same manner except that sodium bisulfite was not added after the polymerization was completed. The amount of the remaining vinyl acetate monomer was 0.3%, the conversion was 99.2%, and the pH was 4.
A vinyl acetate resin emulsion having a viscosity of 4.50 mPa · s (same as above) was obtained and evaluated in the same manner.

Example 5 Polymerization was carried out in the same manner as in Example 1 except that isopropyl alcohol and butyl alcohol were not added and 5 parts of a 10% aqueous sodium silicate solution was added instead of the 15% aqueous sodium acetate solution after the polymerization was completed. The amount of residual vinyl acetate monomer was 0.4%, the conversion was 98.9%, and the pH was 5.
1. A vinyl acetate resin emulsion having a viscosity of 25,000 mPa · s (same as above) was obtained and evaluated in the same manner.

Example 6 Polymerization was carried out in the same manner as in Example 1 except that the last added 15% aqueous solution of sodium acetate was changed to 0.6 part.
Residual vinyl acetate monomer amount 0.2%, polymerization rate 99.4
%, PH 3.2, and viscosity 26000 mPa · s (same as above) to obtain a vinyl acetate resin emulsion, which was similarly evaluated.

Example 7 Polymerization was carried out in the same manner as in Example 1 except that sodium bisulfite was not added. The amount of the remaining vinyl acetate monomer was 0.2%, the conversion was 99.4%, the pH was 4.2, and the viscosity was 20
A vinyl acetate resin emulsion of 000 mPa · s (same as above) was obtained and evaluated in the same manner.

Comparative Example 1 The procedure of Example 1 was repeated, except that isopropyl alcohol and butyl alcohol were not added. The remaining amount of vinyl acetate monomer was 0.5%, the polymerization rate was 98.6%, and the pH was 9%.
4.9, 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.

[0028]

[Table 1] Storage stability Water resistance Storage stability 70 ° C × 7 days Room temperature × 1 year (%) Example 1 1.0 1.0 97.4 1.2 〃 2 1.0 1.0 97.2 1.2 〃 3 1.1 1.1 96.5 1.3 〃 4 1.1 1.2 97.2 1.3 〃 5 1.2 1.2 96.8 1.4 ６ 6 1.3 1.2 97.1 1.5〃7 2.8 2.0 95.5 2.0 Comparative Example 1 3.2 Gelation Unmeasurable 3.5

[0029]

EFFECT OF THE INVENTION The (acetic acid) vinyl resin emulsion of the present invention contains an acetoacetyl group-containing polyvinyl alcohol resin and the amount of the residual monomer is adjusted to a specific amount. The resulting coating film has excellent water resistance and the like, and is particularly useful for applications such as woodworking adhesives and paper tube adhesives that require water resistance / hot water resistance.

Claims (9)

[Claims] 1. A vinyl resin emulsion comprising an acetoacetyl group-containing polyvinyl alcohol resin and a vinyl monomer content of 0.4% by weight or less. 2. The vinyl resin emulsion according to claim 1, wherein the pH is 3 to 8. 3. The vinyl resin emulsion according to claim 1, further comprising a reducing agent. 4. The vinyl according to claim 3, wherein the reducing agent is at least one selected from sulfites, thiosulfates, bisulfites, metabisulfites, L-ascorbic acid, and hydrazines. Resin-based emulsion. 5. The vinyl resin emulsion according to claim 3, wherein the content of the reducing agent is 0.05 to 2% by weight. 6. The vinyl resin emulsion according to claim 1, further comprising an alkali salt of silicic acid. 7. The vinyl resin emulsion according to claim 6, wherein the content of silicic acid is 0.01 to 4% by weight. 8. The vinyl resin emulsion according to claim 1, wherein a vinyl acetate monomer is emulsion-polymerized in the presence of isopropyl alcohol, and butyl alcohol is added after completion of the dropwise addition of the polymerization catalyst. . 9. The vinyl resin emulsion according to claim 1, which is used for coating or impregnating wood to capture formaldehyde in the wood.