JP2002241411A - Production method of vinyl ester resin emulsion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vinyl ester resin emulsion which is excellent in hot water adhesion resistance and storage stability, and which is excellent in transparency and film forming property when formed into a film. SOLUTION: The ethylene unit is 0.5 mol% or more, 20
A method for producing a vinyl ester-based resin emulsion, comprising: using a vinyl alcohol-based polymer containing at most mol% as a dispersant, and emulsion-polymerizing a vinyl ester-based monomer in the presence of a compound containing a mercapto group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl ester resin emulsion which is excellent in hot water adhesion and storage stability, and which is excellent in film forming property and transparency when formed into a film.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter referred to as PV)
A may be abbreviated as A) is an ethylenically unsaturated monomer,
Particularly, it is widely used as a protective colloid for emulsion polymerization of a vinyl ester monomer represented by vinyl acetate, and a vinyl ester aqueous emulsion obtained by emulsion polymerization using this as a protective colloid is for paper and woodwork. It is widely used in various fields such as adhesives for plastics and the like, binders for impregnated papers and non-woven products, admixtures, jointing materials, paints, paper processing and textile processing. Such an aqueous emulsion generally has a low viscosity by adjusting the degree of saponification of the PVA-based polymer,
It has a viscosity close to Newtonian flow and has relatively good water resistance, and generally has high viscosity and relatively low temperature dependence of emulsion viscosity. It has been. For example, as a woodworking adhesive, a higher-viscosity emulsion is preferable, and a vinyl ester-based aqueous emulsion using so-called partially saponified PVA as a protective colloid is widely used. A vinyl ester-based aqueous emulsion using partially saponified PVA as a protective colloid has excellent low-temperature stability and is easily obtained with high viscosity, but has a problem of poor water resistance. On the other hand, vinyl ester-based aqueous emulsions using completely saponified PVA as a protective colloid have a problem that, although excellent in water resistance, they are inferior in low-temperature storage stability. For the purpose of solving such problems, 3-methyl-3-methoxybutanol and compounds having a water-soluble and alcoholic OH group have been disclosed in JP-A-63-46252, JP-A-64-62347 and the like. It has been proposed that water-resistant compounds have been improved in water resistance and storage stability.However, since water-soluble compounds are incorporated, their water resistance is limited, and is essential for vinyl acetate emulsions. Poor plasticizing effect,
At present, it is necessary to add some plasticizer. Furthermore, when such a compound is added,
By causing chain transfer during the polymerization, the dispersoid of the emulsion, that is, the degree of polymerization of the polyvinyl ester is reduced. For this reason, there was a defect that the adhesive strength when immersed in warm water or the like was poor. Further, it is proposed to use a vinyl alcohol-based polymer containing an ethylene unit as a dispersant (JP-A-11-21529, JP-A-11-21380).
JP-A-10-226774), and the water resistance and the low-temperature storage stability have been greatly improved. However, when the vinyl alcohol-based polymer containing ethylene units is also a completely saponified product, the surface activity is lower than that of conventional partially saponified PVA, and the particle size of the obtained emulsion is large. When the emulsion is formed into a film due to an increase in the particle diameter, there is a problem that its transparency is inferior.

[0003]

SUMMARY OF THE INVENTION Under such circumstances, the present invention is excellent in hot water adhesion resistance and standing stability,
It is another object of the present invention to provide a vinyl ester resin emulsion having excellent film forming properties and transparency when forming a film.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop a vinyl ester resin emulsion having the above-mentioned preferable properties. A vinyl ester-based resin emulsion obtained by emulsifying and polymerizing a vinyl ester-based monomer in the presence of a compound containing a mercapto group with a vinyl alcohol-based polymer contained below as a dispersant satisfies the above object. The inventors have found that the present invention has been completed.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION A vinyl alcohol polymer containing 0.5% by mole or more and 20% by mole or less of ethylene units used in the present invention (hereinafter, the polymer of the present invention is referred to as a low ethylene-modified PVA-based polymer). There is no particular limitation on the production method of the above-mentioned compounding, and it can be obtained by saponifying a copolymer of vinyl ester and ethylene by a known method.

[0006] Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate. In general, vinyl acetate is preferably used.

The dispersant may be a copolymer of an ethylenically unsaturated monomer copolymerizable within a range not to impair the effects of the present invention. Examples of such an ethylenically unsaturated monomer include, for example, propylene, acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, itaconic acid, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, trimethyl- (3 -Acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamido-2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N-vinyl pyrrolidone, vinyl chloride,
N-vinylamides such as vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate, sodium allyl sulfonate, N-vinyl pyrrolidone, N-vinyl formamide, N-vinyl acetamide No. Further, in the presence of a thiol compound such as thiolacetic acid or mercaptopropionic acid, a terminal-modified product obtained by copolymerizing ethylene and a vinyl ester-based monomer such as vinyl acetate and saponifying it can also be used. .

[0008] The degree of saponification of the low ethylene-modified PVA polymer used as a dispersant in the present invention is not particularly limited, but is usually 80 mol% or more, preferably 85 mol% or more, more preferably 95 mol% or more. % Or more is used. If the degree of saponification is less than 80 mol%, there is a concern that the water solubility, which is an intrinsic property of PVA, is reduced. Although the degree of polymerization (viscosity average degree of polymerization) of the low ethylene-modified PVA polymer is not particularly limited, it is usually from 100 to 80.
A range of 00 is used, and 300 to 3000 is more preferably used. When the degree of polymerization is less than 100,
When the characteristic of the low ethylene-modified PVA-based polymer as a protective colloid is not exhibited, and when it exceeds 8,000, there is a problem in industrial production of the low ethylene-modified PVA-based polymer. It is important that the ethylene content in the low ethylene-modified PVA-based polymer is 0.5 mol% or more and 20 mol% or less. If the ethylene content does not satisfy this range, the above object of the present invention cannot be achieved.

The amount of the low ethylene-modified PVA-based polymer is not particularly limited.
Parts by weight, preferably 1 to 10 parts by weight, more preferably 1.5 to 7 parts by weight. If the amount of the low ethylene-modified PVA-based polymer is less than 0.5 part by weight, polymerization stability may be reduced. On the other hand, if it exceeds 15 parts by weight, there is a concern that the water resistance of the obtained vinyl ester resin emulsion is reduced.

The vinyl ester monomer constituting the dispersoid of the vinyl ester resin emulsion of the present invention includes vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like. In general, vinyl acetate is preferred. Used.

In one preferred embodiment of the present invention, an ethylene-vinyl ester resin emulsion is obtained by copolymerizing a vinyl ester monomer with ethylene. In that case, the ethylene content of the ethylene-vinyl ester resin emulsion is not particularly limited, but usually,
Those having 3 to 35% by weight are used. Use of an ethylene-vinyl ester resin emulsion having such an ethylene content may further improve performance such as hot water adhesion.

The above-mentioned dispersoid may be copolymerized with another ethylenically unsaturated monomer or diene monomer which can be copolymerized as long as the effects of the present invention are not impaired. At least one monomer unit selected from ethylenically unsaturated monomers and diene monomers includes olefins such as propylene and isobutylene, and halogenated compounds such as vinyl chloride, vinyl fluoride, vinylidene chloride and vinylidene fluoride. Olefins, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, acrylates such as 2-hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate,
Methacrylates such as butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and quaternized products thereof, further, acrylamide,
Methacrylamide, N-methylolacrylamide,
N, N'-dimethylacrylamide, acrylamide-2-
Acrylamide monomers such as methylpropanesulfonic acid and its sodium salt, styrene, α-methylstyrene, p-styrenesulfonic acid and sodium, styrene monomers such as potassium salt, and other N-vinylpyrrolidone, Diene monomers such as butadiene, isoprene and chloroprene; furthermore, divinylbenzene, tetraallyloxyethane, N, N'-methylenebis-acrylamide, 2,2'-bis (4-acryloxypolyethoxyphenyl) propane, 1 1,3-butylene glycol diacrylate, 1,5-pentanediol diacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate Acrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate,
Pentaerythritol tetraacrylate, allyl methacrylate, 1,4-butanediol diacrylate, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol dimethacrylate, Triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, Aluminum methacrylate, zinc methacrylate, calcium methacrylate, methacrylate Magnesium lylate, N,
N'-m-phenylene bismaleimide, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl chlorendate, polyfunctional monomers such as ethylene glycol diglycidyl ether acrylate and the like. These may be used alone or as a mixture of two or more.

The compound containing a mercapto group used in the emulsion polymerization of the vinyl ester monomer of the present invention is not particularly restricted but includes, for example, 2-mercaptoethanol, 3-mercaptopropionic acid, n-dodecylmercaptan, Phenol, thioglycerol, 2-aminothiophenol, allyl mercaptan, 2-naphthalene thiol, 4-mercaptophenol, cysteine,
-Mercaptobenzimidazole, thioacetic acid, furfuryl mercaptan, benzyl mercaptan, thiosalicylic acid, 2-aminothiophenol, and the like.
-Mercaptoethanol, 3-mercaptopropionic acid, n-dodecylmercaptan and the like are preferably used.

The amount of the compound containing a mercapto group is not particularly limited, but may be 0.01 to 1 part by weight, preferably 0.02 to 0.5 part by weight, per 100 parts by weight of the solid content of the vinyl ester resin emulsion. Parts by weight. If the addition amount is less than 0.01 part by weight, the particle size of the obtained emulsion becomes large, and a transparent film may not be obtained. On the other hand, when it exceeds 1 part by weight, there is a concern that the polymerization stability may be reduced.

The average particle size of the vinyl ester resin emulsion of the present invention is not particularly limited, but usually the value measured by a dynamic light scattering method is preferably 1.3 μm or less, more preferably 1 μm or less. When the average particle diameter is in this range, the transparency of the film obtained from the emulsion becomes more excellent. The measurement by the dynamic light scattering method can be performed by, for example, a laser zeta potentiometer ELS-8000 manufactured by Otsuka Electronics Co., Ltd.

The solid content of the vinyl ester resin emulsion of the present invention is not particularly limited, but usually 30 to 70% by weight, preferably 40 to 65% by weight. If the solid content is less than 30% by weight, the emulsion may have poor storage stability and may be separated into two phases. When the amount exceeds 70% by weight, there is a concern that the production of the vinyl ester resin emulsion becomes difficult.

The method for producing the vinyl ester resin emulsion of the present invention is not particularly limited, except that the compound containing a mercapto group of the present invention is contained in the emulsion polymerization of a vinyl ester monomer. For example, in a reaction vessel, using an aqueous solution of a PVA-based polymer as a dispersant,
In the presence of the compound containing a mercapto group, a vinyl ester-based monomer is added temporarily or continuously, and an azo-based polymerization initiator, hydrogen peroxide, ammonium peroxide and potassium persulfate start polymerization of a peroxide. A conventional method in which a polymerization initiator such as an agent is added and emulsion polymerization is performed. In the case of an ethylene-vinyl ester resin emulsion, a method in which an aqueous solution of a low ethylene-modified PVA polymer is used as a dispersant in an autoclave, ethylene is pressed, and emulsion polymerization is performed in the presence of a compound containing a mercapto group. No. 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, L-ascorbic acid, Rongalit and the like. Further, ammonium persulfate and potassium persulfate are used together with sodium hydrogen sulfite, sodium hydrogen carbonate and the like.

As the vinyl ester resin emulsion of the present invention, the emulsion obtained by the above method can be used as it is, but if necessary, various conventionally known emulsions can be used as long as the effects of the present invention are not impaired. It can be added and used. Further, commonly used additives can be added to the vinyl ester resin emulsion of the present invention. Examples of the additive include organic solvents (aromatics such as toluene and xylene, alcohols, ketones, esters, and halogen-containing solvents).
Plasticizers, suspending agents, thickeners, flow improvers, preservatives,
Examples include rust inhibitors, defoamers, fillers, wetting agents, coloring agents, and the like. It is also possible to add aluminum chloride, aluminum nitrate and its hydrate, aluminum sulfate (sulfuric acid band) and the like.

The vinyl ester resin emulsion of the present invention is excellent in hot water adhesion resistance and storage stability, particularly in high temperature storage stability, and when formed into a film, has excellent film forming properties and transparency. Adhesives for paperwork, adhesives for paperwork, adhesives for plywood / PVC, binders for impregnated paper, non-woven products, admixtures, jointing materials, paints, paper and textile processing, coatings, etc. Are suitably used in the field of

[0020]

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following Examples and Comparative Examples, “parts” and “%” mean on a weight basis unless otherwise specified.

Example 1 A 1-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer and a nitrogen inlet was charged with 279.
2 parts, polyvinyl alcohol (hereinafter abbreviated as PVA)
-1 (polymerization degree: 2000, saponification degree: 97 mol%, ethylene modification amount: 3 mol%) 19.5 parts were charged and completely dissolved at 95 ° C. Next, after cooling this PVA aqueous solution, 0.52 parts of n-dodecyl mercaptan was added. After replacing with nitrogen and stirring at 200 rpm, the temperature was raised to 60 ° C., 4.4 parts of a 10% aqueous solution of tartaric acid and 3 parts of a 5% aqueous hydrogen peroxide solution were added, and 26 parts of vinyl acetate was charged and polymerized. Started. 30 minutes after the start of the polymerization, completion of the initial polymerization was confirmed. 0.9 parts and 5% of a 10% aqueous solution of tartaric acid
After adding 3 parts of hydrogen peroxide shot, vinyl acetate 234 was added.
Parts were added continuously over 2 hours to complete the polymerization and then cooled. Thereafter, the mixture was filtered using a 60-mesh stainless steel wire mesh. As a result, the solid content concentration was 47.
A 6% polyvinyl acetate emulsion was obtained. Various physical properties of this emulsion were measured by the following methods. Table 1 shows the results. (1) Hot water adhesive strength (adhesion of birch material);
g / m2, and put together with a load of 7 kg / m2.
It was pressed for 6 hours, then released, and cured at 20 ° C. and 65% RH for 5 days. This test piece was immersed in 70 ° C. hot water for 6 hours, and the compressive shear strength was measured in a wet state.
It was left in a dryer for 24 hours, and the compression shear adhesive strength immediately after the standing was measured at 20 ° C. and 65% RH. (2) Leaving stability: The emulsion was left at 60 ° C. for one month, and the state after the standing was observed. The results of the evaluation are indicated by な し, no change after standing, Δ, slight increase in viscosity, and × gelation. (3) Transparency of the film: A 500 μm-thick film obtained by casting the emulsion at 20 ° C. was observed, and the transparency was evaluated. The evaluation results were as follows: ○ almost transparent, Δ slightly cloudy, ×
Completely cloudy, indicated by (4) Film-forming property: At 5 ° C., 0.5 g of the emulsion was dropped on a slide glass, and after 24 hours, the state of the dried film was observed and evaluated according to the following criteria. ○ Transparency, Δ slightly cloudy, × completely cloudy (5) Emulsion particle size: The average particle size of the emulsion by dynamic light scattering was measured using ELS-8000 manufactured by Otsuka Electronics. (6) Degree of polymerization of dispersoid: The degree of polymerization of polyvinyl acetate obtained by extracting a 500 μm-thick film obtained by casting the emulsion at 20 ° C. with acetone was measured by JISK6726. (7) Emulsion viscosity: measured at 30 ° C.

Example 2 Example 1 was repeated except that 2-mercaptoethanol was used instead of n-dodecyl mercaptan used in Example 1.
Emulsion polymerization was carried out in the same manner as in Example 1 to obtain a polyvinyl acetate emulsion having a solid content of 48%. This emulsion was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 Emulsion polymerization was carried out in the same manner as in Example 1 except that n-dodecyl mercaptan used in Example 1 was not used, and a polyvinyl acetate emulsion having a solid content of 47.5% was obtained. Was. This emulsion was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2 Emulsion polymerization was carried out in the same manner as in Example 1 except that the n-dodecyl mercaptan used in Example 1 was blended after the emulsion polymerization instead of being used during the emulsion polymerization.
A 7.6% polyvinyl acetate emulsion was obtained.
This emulsion was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3 Example 1 was repeated except that 2.6 parts of 3-methyl-3-methoxybutanol (manufactured by Kuraray Co., Ltd.) was used instead of using n-dodecylmercaptan used in Example 1. Emulsion polymerization was carried out in the same manner as in Example 1 to obtain a polyvinyl acetate emulsion having a solid content of 47.8%. This emulsion was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3 Instead of using PVA-1 used in Example 1, PVA-
Emulsion polymerization was carried out in the same manner as in Example 1 except that 2 (degree of polymerization: 1000, degree of saponification: 99.2 mol%, ethylene modification amount: 8 mol%), and polyvinyl acetate having a solid content of 47.9% was used. A system emulsion was obtained. This emulsion was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4 In a pressure-resistant autoclave equipped with a nitrogen inlet, a thermometer and a stirrer, 72.7 parts of a 5.5% aqueous solution of PVA-2, n-
After 0.16 parts of dodecyl mercaptan was charged and the temperature was raised to 60 ° C., the atmosphere was replaced with nitrogen. After charging 80 parts of vinyl acetate, ethylene is pressurized to 40 kg / cm ² ,
2 parts of a 0.5% hydrogen peroxide aqueous solution and 0.3 part of a 2% Rongalite aqueous solution were injected under pressure to initiate polymerization. When the residual vinyl acetate concentration became 10%, ethylene was released,
The ethylene pressure was set to 20 kg / cm ^2, and 0.3 parts of a 3% aqueous hydrogen peroxide solution was injected to complete the polymerization. No aggregation during polymerization, excellent polymerization stability, solid concentration 5
An ethylene-vinyl acetate resin emulsion having 5.1% and an ethylene content of 20% by weight was obtained. This emulsion was evaluated in the same manner as in Example 1. Table 1 shows the results.
Shown in

Comparative Example 4 Emulsion polymerization was carried out in the same manner as in Example 6 except that the same amount of ion-exchanged water was used instead of using n-dodecyl mercaptan used in Example 4, and the solid content concentration was 55.2. %, An ethylene-vinyl acetate resin emulsion having an ethylene content of 20% by weight was obtained. This emulsion was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 5 In Example 1, PVA-1 was used instead of PVA-1.
Emulsion polymerization was carried out in the same manner as in Example 1 except that A-3 (PVA-217 manufactured by Kuraray Co., Ltd .; polymerization degree 1700, saponification degree 88 mol%) was used, and polyvinyl acetate having a solid content of 48% was used. A system emulsion was obtained. This emulsion was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 6 In Example 1, PV was replaced with PVA-1.
Emulsion polymerization was carried out in the same manner as in Example 1 except that A-4 (PVA-117 manufactured by Kuraray Co., Ltd .; polymerization degree 1700, saponification degree 98.5 mol%) was used, and the solid content concentration was 47.9%. Was obtained. This emulsion was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0031]

[Table 1]

PVA-1; polymerization degree 2000, saponification degree 97 mol%, ethylene unit content 3 mol% PVA-2; polymerization degree 1000, saponification degree 99.2 mol%, ethylene unit content 8 mol% PVA-3 A degree of polymerization of 1700 and a degree of saponification of 88 mol% (manufactured by:
Kuraray PVA-217) PVA-4; degree of polymerization 1700, degree of saponification 98.5 mol%
(PVA-117 manufactured by Kuraray Co., Ltd.)

[0033]

EFFECT OF THE INVENTION The vinyl ester resin emulsion obtained by the method of the present invention is excellent in hot water adhesion resistance and shelf stability, and is also excellent in film forming property and transparency when formed into a film. It is particularly useful as an adhesive, and is further suitably used in the fields of binders for impregnated paper and non-woven products, admixtures, jointing materials, paints, paper processing and fiber processing.

Claims (3)

[Claims] An ethylene unit having a content of 0.5 mol% or more,
A method for producing a vinyl ester-based resin emulsion, comprising: using a vinyl alcohol-based polymer containing at most mol% as a dispersant, and emulsion-polymerizing a vinyl ester-based monomer in the presence of a compound containing a mercapto group. 2. The method for producing a vinyl ester resin emulsion according to claim 1, wherein the vinyl ester resin emulsion is a copolymer emulsion of a vinyl ester monomer and ethylene. 3. An adhesive comprising a vinyl ester resin emulsion obtained by the method according to claim 1.