JP2001316552A - Aqueous emulsion and adhesive for woodwork - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous emulsion which has a high viscosity but has excellent flowability, and further has excellent water resistance and excellent adhesivity to wood-based materials. SOLUTION: This aqueous emulsion, comprising polymer vinyl ester-based monomer units as a dispersion and a composition comprising (A) a vinyl alcohol- based polymer containing ethylene units of 0.5 to 10 mol.% of ethylene units and having a saponification degree of >=80 mol.% and (B) at least one water-soluble polymers selected from hydroxyethylcellulose, methylcellulose and carboxymethylcellulose having a 2% aqueous solution viscosity of 1,000 to 8,000 mPa.s as a dispersant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous emulsion having high viscosity, excellent fluidity, excellent adhesion to wood, and excellent water resistance, and an adhesive for woodwork using the aqueous emulsion.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter referred to as P
VA may be abbreviated) 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. As the woodworking adhesive, a higher viscosity emulsion is preferable, and a vinyl ester aqueous emulsion using so-called partially saponified PVA as a protective colloid is widely used. Divided PVA
A vinyl ester-based aqueous emulsion using 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 they are excellent in water resistance, but are inferior in low-temperature stability. Under such circumstances, vinyl alcohol-based polymers containing ethylene units have been proposed (JP-A-11-21529, JP-A-11-21380, JP-A-10-226774, etc.), and have improved water resistance and low-temperature storage stability. Significantly improved. However, the viscosity of the obtained emulsion is generally lower than that of an emulsion using partially saponified PVA as a protective colloid, and at present, it is insufficient as an adhesive for woodworking. Further, an emulsion using a vinyl alcohol polymer containing an ethylene unit as a protective colloid exhibits Newtonian viscosity as compared with an emulsion using a conventional vinyl alcohol polymer containing no ethylene unit as a protective colloid. When used as an adhesive for woodworking, there is a problem that the fluidity is not sufficient, especially when the viscosity is high, so that it is difficult to apply to the base material and the adhesive has poor "spread".

[0003]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides an aqueous emulsion which is excellent in low-temperature stability and water resistance, and has a high viscosity and excellent fluidity, and the use of the aqueous emulsion. It is an object of the present invention to provide a woodworking adhesive.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to develop an aqueous emulsion and a woodworking adhesive having the above-mentioned preferable properties, and as a result, have found that a polymer having a vinyl ester monomer unit has been obtained. Is a dispersoid, contains 0.5 to 10 mol% of ethylene units, and has a saponification degree of 80 mol%.
The vinyl alcohol polymer (A) described above and at least one water-soluble polymer selected from hydroxyethyl cellulose, methyl cellulose, and carboxymethyl cellulose having a 2% aqueous solution viscosity of 1,000 to 8,000 mPa · s
It has been found that an aqueous emulsion using the composition comprising (B) as a dispersant satisfies the above object. Also,
The present inventors have found that a woodworking adhesive comprising the aqueous emulsion satisfies the above object, and have completed the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing a vinyl alcohol polymer (A) containing 0.5 to 10 mol% of ethylene units and having a degree of saponification of 80 mol% or more is not particularly limited. Instead, it can be obtained by saponifying a copolymer of vinyl ester and ethylene by a known method.

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

Further, (A) may be obtained by copolymerizing an ethylenically unsaturated monomer copolymerizable within a range not to impair the effects of the present invention. Such ethylenically unsaturated monomers include, for example, acrylic acid, methacrylic acid, fumaric acid,
(Anhydride) maleic acid, itaconic acid, acrylonitrile,
Methacrylonitrile, acrylamide, methacrylamide, trimethyl- (3-acrylamido-3-dimethylpropyl) -ammonium chloride, acrylamide-
2-methylpropanesulfonic acid and its sodium salt, ethyl vinyl ether, butyl vinyl ether, N
-Vinylpyrrolidone, vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene, sodium vinyl sulfonate, sodium allyl sulfonate, N-vinyl pyrrolidone, N-
N such as vinylformamide and N-vinylacetamide
-Vinyl amides. Also, thiolacetic acid,
A terminal-modified product obtained by polymerizing a vinyl ester monomer such as vinyl acetate in the presence of a thiol compound such as mercaptopropionic acid and saponifying the same can also be used.

The ethylene unit used in the present invention is 0.5 to 1
The vinyl alcohol polymer (A) containing 0 mol% and having a degree of saponification of 80 mol% or more needs to have a saponification degree of 80 mol% or more, preferably 90 mol% or more, It is more preferably at least 95 mol%. When the saponification degree is less than 80 mol%, there is a concern that the water resistance of the obtained aqueous emulsion is reduced. The degree of polymerization of the vinyl alcohol-based polymer is not particularly limited.
Those having a range of 00 to 8000 are used, and 300 to 30
00 is more preferably used. It is important that the ethylene unit is contained in an amount of 0.5 to 10 mol%.
When the ratio exceeds the above, there is a concern that the water solubility, which is an intrinsic property of the vinyl alcohol polymer, is reduced.

The viscosity of a 2% aqueous solution used in the present invention is 10
At least one water-soluble polymer (B) selected from hydroxyethylcellulose, methylcellulose, and carboxymethylcellulose having a water content of 00 to 8000 mPa · s is produced by a known method. Hydroxyethyl cellulose, carboxymethyl cellulose 2% aqueous solution viscosity is 1
It is at least 2,000 mPa · s, preferably at least 1500 mPa · s, more preferably at least 2,000 mPa · s. If the 2% aqueous solution viscosity is less than 1000 mPa · s, the fluidity of the resulting aqueous emulsion may be reduced. Also 700
It is preferably 0 mPa · s or less.

The vinyl alcohol polymer used in the present invention
The ratio (A) / (B) of (A) and the water-soluble polymer (B) is 9.9 /
It is necessary to be 0.1 to 5/5, preferably 9.85 / 0.15 to 6/4, more preferably 9.8 /.
0.2 to 7/3. The ratio of (A) / (B) is 9.9 /
When it is larger than 0.1, the viscosity of the obtained emulsion may be low. Also, the ratio of (A) / (B) is 5 /
If it is smaller than 5, the fluidity of the obtained emulsion may be reduced.

The vinyl ester monomers constituting the dispersoid of the aqueous emulsion of the present invention include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like. In general, vinyl acetate is preferably used.

The dispersoid may be copolymerized with a copolymerizable ethylenically unsaturated monomer as long as the effects of the present invention are not impaired. As at least one monomer unit selected from ethylenically unsaturated monomers and diene monomers, ethylene, propylene, olefins such as isobutylene, vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride and the like Halogenated olefins, vinyl formate, vinyl acetate, vinyl propionate,
Vinyl esters such as vinyl versatate, acrylates such as acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, 2-hydroxyethyl acrylate, and methacrylic acid Methyl,
Ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, methacrylates such as 2-hydroxyethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and quaternized products thereof, and , Acrylamide, methacrylamide, N-methylolacrylamide, N, N-dimethylacrylamide,
Acrylamide monomers such as acrylamide-2-methylpropanesulfonic acid and its sodium salt, styrene monomers such as styrene, α-methylstyrene, p-styrenesulfonic acid, and sodium and potassium salts;
Others such as N-vinylpyrrolidone, butadiene,
Diene monomers such as isoprene and chloroprene, as well as divinylbenzene, tetraallyloxyethane, N, N '
-Methylenebis-acrylamide, 2,2'-bis (4-acryloxypolyethoxyphenyl) propane, 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, 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, methacrylic acid Zinc, calcium methacrylate, magnesium methacrylate, N, N'-m-phenylenebismaleimide, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, diallyl chlorendate, ethylene glycol diglycidyl ether Examples thereof include polyfunctional monomers such as acrylates, which may be used alone or as a mixture of two or more. Ethylene is preferably used as a monomer copolymerizable with these vinyl esters.

The method for producing the aqueous emulsion used in the present invention is not particularly limited.
Using the aqueous solution of (A) and (B) as a dispersant, a vinyl ester-based monomer is added temporarily or continuously, an azo-based polymerization initiator,
A method in which a polymerization initiator such as a peroxide polymerization initiator such as hydrogen peroxide, ammonium persulfate, and potassium persulfate is added and emulsion polymerization is performed.

The total amount of the vinyl alcohol-based polymer (A) and the water-soluble polymer (B) is not particularly limited,
The amount is preferably 3 to 20 parts by weight, more preferably 5 to 15 parts by weight, based on 100 parts by weight of the polymer containing the vinyl ester monomer. If the amount is less than 3 parts by weight, the polymerization stability may decrease. If the amount exceeds 20 parts by weight, the storage stability of the obtained emulsion may decrease.

As the aqueous emulsion and the woodworking adhesive of the present invention, the aqueous emulsion obtained by the above-mentioned method can be used as it is, but if necessary, various conventionally known aqueous emulsions can be used as long as the effects of the present invention are not impaired. An emulsion can be added and used. As the dispersant in the aqueous emulsion of the present invention, the above-mentioned vinyl alcohol-based polymer (A) and water-soluble polymer (B) are used.If necessary, conventionally known anionic, nonionic or A cationic surfactant can be used in combination, and a vinyl alcohol-based polymer other than the vinyl alcohol-based polymer (A) may be used in a range not to impair the object of the present invention.

The water-based emulsion and the woodworking adhesive of the present invention have excellent viscosity, high fluidity, and excellent water resistance and low-temperature stability, and are used for processing flash panels, laminated materials, wood boards, and plywood. Plywood secondary processing (kneading), general woodworking and other woodworking adhesives, various adhesives, impregnated paper, binders for non-woven products, admixtures, jointing materials, paints, paper processing and fiber processing It is suitably used in the field.

[0017]

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. In addition, the water resistance and storage stability of the obtained emulsion were evaluated in the following manner.

(Evaluation of Emulsion) (1) Emulsion Viscosity Using a BH type viscometer (manufactured by Tokimec Co., Ltd.), the viscosity of the obtained aqueous emulsion was measured at 30 ° C. at a rotation speed of 2 rpm and 20 rpm. Using the measured values, the fluidity of the emulsion was determined by the following equation. (Fluidity) = log (η2 rpm / η20 rpm) It is generally considered that the larger the value, the better the coating property. (2) Wood Adhesive Strength The obtained aqueous emulsion was applied to a birch material (straight grain) at 150 g / m 2 using a brush, and bonded together to obtain 7 kg / m.
2 was pressed for 16 hours. The coatability at that time was determined according to the following criteria. ：: easy to apply, Δ: slightly poor spread, ×: very difficult to apply The coating was then decompressed, cured at 20 ° C. and 65% RH for 5 days, and the compression shear strength was measured (normal adhesive strength) ). Also,
After curing, it was immersed in warm water of 60 ° C. for 3 hours, and the compressive shear strength was measured in a wet state (hot water adhesive strength). (3) Low-temperature stability The viscosity change after 14 days when the emulsion was left at 0 ° C. was observed. ○ Little change, slightly thickening, thickening / gelling

Example 1 300 ml of ion-exchanged water was placed in a 1-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet.
24.7 g of PVA-1 (polymerization degree 1000, saponification degree 99.2 mol%, ethylene unit content 6 mol%) and hydroxylethyl cellulose (Daicel Chemical Industries, Ltd.)
HEC SP-900, 2% aqueous solution viscosity 5000 mPa · s)
3 g was completely dissolved at 95 ° C. (PVA-1 / HEC = 9.5 / 0.5). Next, after cooling this PVA aqueous solution and replacing with nitrogen,
After the temperature was raised to 60 ° C. while stirring at 200 rpm, 4.4 g of a 10% aqueous solution of tartaric acid and 3 g of a 5% aqueous hydrogen peroxide solution (0.015 in a molar ratio with respect to vinyl acetate) were added, and acetic acid was added. 26 g of vinyl was charged and polymerization was started. 30 minutes after the start of the polymerization, completion of the initial polymerization was confirmed. 0.9 g of a 10% aqueous solution of tartaric acid and 5% hydrogen peroxide solution 3
After the addition of g, 234 g of vinyl acetate was continuously added over 2 hours to complete the polymerization, followed by cooling. Thereafter, the mixture was filtered using a 60-mesh stainless steel wire mesh. As a result, a polyvinyl acetate emulsion having a solid content of 48.3% was obtained. 5 parts of dibutyl phthalate was added to and mixed with 100 parts by weight of this emulsion. The physical properties of this emulsion (Em-1) were measured by the methods described above. Table 1 shows the results.

Example 2 Em-2 was obtained in the same manner as in Example 1 except that the ratio of PVA-1 / HEC was changed from 9.5 / 0.5 to 9/1. Table 1 also shows the physical properties of this emulsion.

Example 3 Instead of using HEC used in Example 1, methylcellulose (Metroze 90SH-400 manufactured by Shin-Etsu Chemical Co., Ltd.)
Em-3 was obtained in the same manner as in Example 1 except that a 0% and 2% aqueous solution viscosity of 4000 mPa · s) was used. Table 1 also shows the physical properties of this emulsion.

Example 4 Instead of using HEC used in Example 1, sodium carboxymethylcellulose (CM manufactured by Daicel Chemical Industries, Ltd.)
Em-4 was obtained in the same manner as in Example 1 except that C-22002% aqueous solution viscosity 6000 mPa · s) was used. Table 1 also shows the physical properties of this emulsion.

Comparative Example 1 Em-5 was obtained in the same manner as in Example 1 except that PVA-1 was used instead of HEC used in Example 1 (only PVA-1 was used). Table 1 also shows the physical properties of this emulsion.

Example 5 300 ml of ion-exchanged water was placed in a 1-liter glass polymerization vessel equipped with a reflux condenser, a dropping funnel, a thermometer, and a nitrogen inlet.
17.6 g of PVA-2 (degree of polymerization: 1700, degree of saponification: 98.2 mol%, ethylene unit content: 4 mol%) and hydroxyl ethyl cellulose (Daicel Chemical Industries, Ltd.)
HEC SP-900, 2% aqueous solution viscosity 5000 mPa · s)
9 g was charged (PVA-2 / HEC = 9/1) and completely dissolved at 95 ° C. Next, after cooling this PVA aqueous solution and replacing with nitrogen,
After the temperature was raised to 60 ° C. while stirring at 00 rpm, 4.4 g of a 10% aqueous solution of tartaric acid and 3% aqueous 5% hydrogen peroxide were added.
g (0.015 in molar ratio to vinyl acetate) was added, and 26 g of vinyl acetate was charged to initiate polymerization.
30 minutes after the start of the polymerization, completion of the initial polymerization was confirmed. After 0.9 g of a 10% aqueous solution of tartaric acid and 3 g of a 5% aqueous hydrogen peroxide solution were added in a shot, 234 g of vinyl acetate was continuously added over 2 hours to complete the polymerization, followed by cooling. Thereafter, the mixture was filtered using a 60-mesh stainless steel wire mesh. As a result, a polyvinyl acetate emulsion having a solid content of 47.2% was obtained. 10 of this emulsion
5 parts of dibutyl phthalate was added to and mixed with 0 parts by weight. Table 1 also shows the results of evaluating the physical properties of this emulsion (Em-6).

Comparative Example 2 Em-7 was obtained in the same manner as in Example 2 except that PVA-2 was used instead of HEC used in Example 5 (PVA-2 was used alone). Table 1 also shows the results of evaluating the physical properties of this emulsion.

Comparative Example 3 In place of using PVA-2 used in Example 5, PVA-3 containing no ethylene unit (polymerization degree 1700, saponification degree 98.5 mol%, Kuraray PVA-117) was used. In the same manner as in Example 5, Em-8 was obtained. Table 1 also shows the results of evaluating the physical properties of this emulsion.

Example 6 A pressure-resistant autoclave equipped with a nitrogen inlet, a thermometer and a stirrer was charged with 92.5 g of ion-exchanged water and 7.5 of PVA-1.
g and hydroxyl ethyl cellulose (manufactured by Daicel Chemical Industries, Ltd .; HEC SP-900, 2% aqueous solution viscosity 5000 m)
Pa · s) 0.83 g (PVA-1 / HEC = 9/1) 0.83
g was completely dissolved at 95 ° C. After that, the internal temperature was increased to 6
After adjusting to 0 ° C., nitrogen substitution was performed. Vinyl acetate 8
After charging 0 g, ethylene was pressurized to 45 kg / cm ² ,
2 g of a 0.5% aqueous hydrogen peroxide solution and 0.3 g of a 2% Rongalit 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 g of a 3% aqueous hydrogen peroxide solution was injected to complete the polymerization. No aggregation during polymerization, excellent polymerization stability, solid content concentration of 49.5
%, An ethylene-vinyl acetate copolymer emulsion (Em-9) having an ethylene content of 10% by weight was obtained. Evaluation was performed by the method described above. The results are shown in Table 1.

Comparative Example 4 Hydroxyethyl cellulose 0.8 used in Example 6
Em-10 was obtained in the same manner as in Example 6, except that 0.83 g of PVA-1 was used instead of 3 g. Table 1 also shows the results of evaluating the physical properties of this emulsion.

[0029]

[Table 1]

PVA-1; polymerization degree 1000, saponification degree 99.2 mol%, ethylene unit content 6 mol% PVA-2; polymerization degree 1700, saponification degree 98.2 mol%, ethylene unit content 4 mol% PVA-3; polymerization Degree 1700, saponification degree 98.5 mol% ｛manufactured by Kuraray Co., Ltd.
PVA-117｝

[0031]

The water-based emulsion and the woodworking adhesive of the present invention are excellent in fluidity while having a high viscosity, and are also excellent in water resistance and adhesion to wood materials. , For plywood processing, plywood secondary processing (kneading), general woodworking and other woodworking adhesives, various adhesives,
It is suitably used in fields such as binders for impregnated paper and non-woven products, admixtures, joining materials, paints, paper processing and fiber processing.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09J 201/00 C09J 201/00 F term (Reference) 4J002 AB033 BE032 BF011 BF021 BF031 FD312 FD313 GJ01 HA07 4J040 BA042 BA082 DD022 DE011 DE021 JA03 LA06 LA07 MA08

Claims (4)

[Claims] 1. A polymer having a vinyl ester monomer unit is used as a dispersoid, and an ethylene unit is contained in an amount of 0.5 to 10 mol%.
A vinyl alcohol-based polymer (A) having a degree of saponification of 80 mol% or more and a 2% aqueous solution viscosity of 1,000 to 800
An aqueous emulsion containing a composition of at least one water-soluble polymer (B) selected from hydroxyethylcellulose, methylcellulose, and carboxymethylcellulose having a dispersant of 0 mPa · s. 2. The aqueous solution according to claim 1, wherein the ratio (A) / (B) of the vinyl alcohol polymer (A) and the water-soluble polymer (B) is 9.9 / 0.1 to 5/5. Emulsion. 3. The aqueous emulsion according to claim 1, wherein the dispersoid is a polymer having a vinyl ester monomer and an ethylene unit. 4. A woodworking adhesive comprising the aqueous emulsion according to claim 1.