JP2000109507A - Polyvinyl acetate emulsion and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject emulsion excellent in water resistance by reacting a copolymer comprising structural units respectively derived from an α-olefin, an α,β-unsaturated carboxyic acid and an acrylate- or a methacrylate-based monomer with a basic substance and using the resultant neutralized substance as a protective colloid. SOLUTION: A copolymer comprising (A) a structural unit derived from an g-olefin (e.g. isobutylene), (B) a structural unit derived from an α,β-unsaturated carboxylic acid or its anhydride (e.g. maleic anhydride) and (C) a structural unit derived from an acrylate- or a methacrylate-based monomer [e.g. lauryl (meth)acrylate] and represented by the formula (R1 is H or methyl; R2 is a 6-25C alkyl or a 3-12C cycloalkyl) is reacted with (D) a basic substance (e.g. sodium hydroxide) and the resultant neutralized substance is used as a protective colloid. The compositional ratio of the structural units of the components A to C in the above copolymer is preferably 1:(0.9-1.1):(0.01-0.3).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polyvinyl acetate emulsion and a method for producing the same. The polyvinyl acetate emulsion provided by the present invention comprises an adhesive,
It is useful as a paint, a papermaking paste and the like.

[0002]

2. Description of the Related Art Polyvinyl acetate emulsion is produced by emulsion polymerization of vinyl acetate, and is used for applications such as adhesives and paints. In the emulsion polymerization of vinyl acetate, a water-soluble polymer such as polyvinyl alcohol, sodium polyacrylate, polyvinylamine and casein is generally added as a protective colloid in addition to an emulsifier such as an anionic surfactant or a nonionic surfactant. Among them, when polyvinyl alcohol is used as a protective colloid, emulsion polymerization is easy, and an emulsion having an arbitrary viscosity can be obtained by adjusting the degree of saponification of the polyvinyl alcohol to be used and the degree of polymerization. is there. However, the obtained emulsion has a remarkable increase in viscosity at low temperatures and is inferior in film-forming properties at low temperatures. Further, when the emulsion is used as an adhesive, there is a problem in the heat resistance and water resistance of the obtained adhesive layer. It has been pointed out that there is. In order to solve such problems, it has been proposed to use an isobutylene-maleic anhydride copolymer as a protective colloid (see Japanese Patent Publication No. 51-20213).

[0003]

However, even when an emulsion containing isobutylene-maleic anhydride copolymer as a protective colloid, sufficient water resistance can be obtained when a polyvalent metal salt such as calcium carbonate is not used in combination. It cannot be achieved. Accordingly, an object of the present invention is to provide a polyvinyl acetate emulsion capable of overcoming the above-mentioned problems such as an increase in viscosity at low temperatures and water resistance when used as an adhesive, and a method for producing the same.

[0004]

According to the present invention, one of the above objects is to provide a structural unit (I) derived from an α-olefin, an α, β-unsaturated carboxylic acid or an anhydride thereof. Structural unit (II) and the following general formula (1)

[0005]

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Wherein R ¹ is a hydrogen atom or a methyl group,
R ² is an alkyl group having 6 to 25 carbon atoms or 3-1.
2 represents a cycloalkyl group)
The problem is solved by providing a polyvinyl acetate emulsion in which a neutralized product obtained by reacting a basic substance with the copolymer comprising I) is used as a protective colloid.

According to the present invention, another object of the present invention is to provide a structural unit (I) derived from an α-olefin, an α, β-unsaturated carboxylic acid or an anhydride thereof. Structural unit (II) and the following general formula (1)

[0008]

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(Wherein R ¹ is a hydrogen atom or a methyl group,
R ² is an alkyl group having 6 to 25 carbon atoms or 3-1.
2 represents a cycloalkyl group) (II)
The problem is solved by providing a method for producing a polyvinyl acetate emulsion, comprising emulsion-polymerizing vinyl acetate in the presence of a neutralized product obtained by reacting a basic substance with a copolymer comprising I).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, polyvinyl acetate, which is a dispersoid of an emulsion, contains not only a homopolymer of vinyl acetate but also a small amount of monomers copolymerizable with vinyl acetate such as olefins such as ethylene and propylene. It may be copolymerized.

The α-olefin constituting the structural unit (I) in the copolymer used in the present invention includes, for example, ethylene, propylene, 1-butene, isobutylene, 1-pentene, 2-methyl-1-butene , 1-hexene, 2-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-
Examples thereof include butene and diisobutylene. Of these, isobutylene is preferable.

The structural unit (II) in the copolymer used in the present invention is a structural unit derived from an α, β-unsaturated carboxylic acid or its anhydride. Examples of the α, β-unsaturated carboxylic acid or its anhydride include (meth)
Acrylic acid, maleic anhydride, maleic acid, citraconic acid, citraconic anhydride, itaconic acid, fumaric acid and the like can be mentioned, and among them, maleic anhydride is preferable.

The structural unit (III) in the copolymer used in the present invention is derived from a (meth) acrylate monomer represented by the following formula (2).

[0014]

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(In the above formula, R ¹ and R ² are as defined above.) In the above formula (2), examples of the alkyl group having 6 to 25 carbon atoms represented by R ² include n-hexyl Group, n-octyl group, 2-ethylhexyl group, stearyl group, lauryl group and the like. Further, the carbon number represented by R ² is 3 to
Examples of the 12 cycloalkyl groups include a cyclopropyl group and a cyclohexyl group.

As the (meth) acrylate monomer represented by the formula (2), for example, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl ( Examples thereof include (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate. Of these, lauryl (meth) acrylate and stearyl (meth) acrylate are preferable. As the (meth) acrylate-based monomer represented by the formula (2), one type may be used, or two or more types may be used in combination.

The structural units (I), (II) and (III) in the copolymer used in the present invention
Is usually [structural unit (I)]: [structural unit (II)]: [structural unit (III)] = 1: 0.9-1.
1: 0.01 to 0.3. If the proportion of the structural unit (III) is less than the above range, the resulting emulsion will have poor water resistance when used as an adhesive, while if the proportion of the structural unit (III) is greater than the above range. Stability during emulsion polymerization cannot be obtained. The composition molar ratio of each structural unit in the copolymer is [structural unit (I)]: [structural unit (II)]: [structural unit (III)] = 1: 1: 0.0
It is preferably from 5 to 0.2. The copolymer used in the present invention may contain an imide type structural unit such as a maleimide unit.

The number average molecular weight of the copolymer used in the present invention is usually from 1,000 to 500,000.
However, from the viewpoints of stability at the time of emulsion polymerization and viscosity of the obtained emulsion at low temperature, it is 1,000 to 30.
Preferably it is 000.

The copolymer used in the present invention is α
-Manufactured from olefins, α, β-unsaturated carboxylic acids or anhydrides thereof, and (meth) acrylate-based monomers represented by the formula (2) (hereinafter, abbreviated as raw material monomers) according to a conventional method. be able to. For example, it can be produced by charging a raw material monomer into a reaction vessel and copolymerizing it in a solvent by a solution polymerization method using a radical polymerization initiator.

As the radical polymerization initiator, those conventionally used can be used without particular limitation.
For example, di (dodecanoyl) peroxide, benzoyl peroxide, cumene hydroperoxide, t
Organic peroxides such as -butyl hydroperoxide;
2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), dimethyl-2,
An azo compound such as 2'-azobisisobutyrate can be used. The amount of the radical polymerization initiator used is not particularly limited, but usually, the amount of the starting monomer 10
It is in the range of 0.05 to 5 parts by weight with respect to 0 parts by weight.

Examples of the solvent used in the polymerization reaction include various solvents that do not inhibit radical polymerization, for example, ketones such as acetone and methyl ethyl ketone;
Aliphatic hydrocarbons such as hexane and n-octane; aromatic hydrocarbons such as benzene, toluene and ethylbenzene;
Esters such as ethyl acetate and isopropyl acetate; ethers such as diisopropyl ether, dioxane and tetrahydrofuran; chlorinated hydrocarbons such as methylene chloride and chloroform can be used. One of these solvents may be used, or two or more of them may be used as a mixture.

The molar ratio of the charged amounts of the starting monomers is substantially the same as the molar ratio of the structural units constituting the copolymer, that is, [α-olefin]: [α, β-unsaturated carboxylic acid or its anhydride. ]: [(Meth) acrylate monomer represented by formula (2)] = 1: 0.9 to 1.1:
It is preferably 0.01 to 0.3.

When the starting monomers are charged, a copolymer having a uniform composition can be obtained by charging the starting monomers in consideration of the difference in the polymerization reactivity of the starting monomers. For example, when the reactivity of the (meth) acrylate-based monomer represented by the formula (2) is low, it is possible to charge the (meth) acrylate-based monomer in the initial stage of the polymerization reaction so that the concentration of the (meth) acrylate-based monomer becomes high. preferable. When maleic anhydride is used as the α, β-unsaturated carboxylic acid or its anhydride, it is preferable that maleic anhydride is charged at a rate such that the concentration in the reaction system becomes constant throughout the polymerization reaction.

The polymerization temperature varies depending on the solvent and the radical polymerization initiator used, but is generally in the range of 0 to 200 ° C., preferably 20 to 150 ° C. The polymerization time is
It generally ranges from 1 to 50 hours, preferably from 2 to 20 hours. Further, the polymerization can be carried out under normal pressure or under pressure.

After completion of the polymerization reaction, the copolymer is separated and obtained from the reaction mixture by, for example, i) a method of filtering and removing the precipitated copolymer followed by drying, and ii) removing a solvent from the reaction mixture. Then, the obtained residue can be carried out according to a conventional method such as a method of drying.

The above-mentioned copolymer reacts with a basic substance to form a salt and become water-soluble. In the present invention, the copolymer is a neutralized product obtained by the reaction with the basic substance thus obtained,
That is, it is used as a salt form. Here, as the basic substance, for example, sodium hydroxide, potassium hydroxide,
Hydroxides of alkali metals such as lithium hydroxide; ammonia; carbonates of alkali metals such as sodium carbonate, potassium carbonate and lithium carbonate; acetates of alkali metals such as sodium acetate and potassium acetate; ammonium acetate and the like. Among them, sodium hydroxide, potassium hydroxide or ammonia is preferred. One of these basic substances may be used, or two or more of them may be used in combination.

The basic substance is used in such an amount that the degree of neutralization is usually in the range of 0.05 to 0.6, preferably 0.1 to 0.5, based on the copolymer. Here, the degree of neutralization indicates the ratio between the acid group and the basic substance in the copolymer. The number of moles of the carboxyl group in the copolymer is x (mol), and the basic substance used is Y / x when the amount of is y (gram equivalent)
Given by When an acid anhydride group is present in the copolymer, the calculation is performed on the assumption that the acid anhydride group corresponds to two carboxyl groups.

The reaction between the above-mentioned copolymer and a basic substance can be carried out according to a conventional method, but it is convenient to carry out the reaction in the presence of water to obtain a neutralized product of the copolymer as an aqueous solution.

The amount of the neutralized product used in the present invention is usually 5 to 40 per 100 parts by weight of vinyl acetate (monomer) to be subjected to emulsion polymerization, in terms of the amount of the above-mentioned copolymer to give it.
It is within the range of parts by weight. When the amount of the neutralized product is less than the above range, the obtained emulsion is not sufficiently water-resistant when used as an adhesive, and when the amount of the neutralized product is more than the above range, the emulsion polymerization is performed. , The viscosity of the dispersion becomes high, and the stability of emulsion polymerization cannot be achieved. The use amount of the neutralized product is preferably in the range of usually 15 to 40 parts by weight, per 100 parts by weight of vinyl acetate (monomer) to be subjected to emulsion polymerization, in terms of the amount of the copolymer to give the neutralized product. Further, in the present invention, in addition to the above neutralized product, polyvinyl alcohol, ethyl cellulose, isobutylene-maleic anhydride copolymer, and the like have been conventionally used as a protective colloid of a polyvinyl acetate emulsion within a range not to impair the gist of the invention. May be used in combination.

The polyvinyl acetate emulsion of the present invention may optionally contain a filler, a pigment, an ultraviolet absorber, a fungicide, and the like. Examples of the filler include calcium carbonate, clay, talc, diatomaceous earth, alumina, mica, alumina sulfate, barium sulfate, asbestos, graphite, glass beads, and the like. Is 3 to 100 parts by weight based on 100 parts by weight of a polyvinyl acetate emulsion not containing them. By incorporating this filler, the strength of the cured film of the polyvinyl acetate emulsion is improved. Examples of the pigment include an aqueous pigment such as titanium oxide and red iron oxide. These fillers, pigments and the like are usually added after the completion of the emulsion polymerization, but may be present in the system during the emulsion polymerization.

The polyvinyl acetate emulsion of the present invention comprises
It can be produced by emulsion polymerization of vinyl acetate and, if desired, a small amount of a comonomer according to a conventional method in the presence of a neutralized product of the above copolymer with a basic substance. The amount of the monomer such as vinyl acetate used is such that the concentration of polyvinyl acetate in the obtained emulsion is 30 to 60.
It is preferable that the amount is such that the amount becomes% by weight. Further, the neutralized product of the copolymer with a basic substance is usually used as an aqueous solution, but when performing emulsion polymerization, the concentration in the aqueous solution is 5 to 50.
% By weight. The temperature at which emulsion polymerization is carried out is
Generally 70-95 ° C. In the emulsion polymerization, an anionic surfactant or a nonionic surfactant may be used in combination.

As the polymerization catalyst, hydrogen peroxide, potassium peroxodisulfate, ammonium peroxodisulfate, sodium peroxoborate, cumene hydroperoxide and the like are used. The amount of the polymerization catalyst used is usually 0.3 to 1 part by weight based on 100 parts by weight of vinyl acetate.

The polyvinyl acetate emulsion of the present invention comprises:
Paper applications such as paper containers, paper tubes, corrugated cardboard, plywood, bookbinding, aluminum foil and paper lamination, labels, decorative paper plywood, furniture,
Adhesive bonding of chairs, natural wood decorative plywood, glued wood, plywood, etc., wood bonding applications such as mosaic parquet, gymnasium flooring boards, etc. Can be used for applications. The vinyl acetate emulsion of the present invention can also be used for applications such as paints, fiber treatment agents, and papermaking pastes.

[0034]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, various performances of the emulsion were evaluated by the following methods.

Viscosity of emulsion at low temperature 300 g of the emulsion was precisely weighed in a glass bottle with a lid,
Was measured using a B-type viscometer immediately after being allowed to stand for 7 days in the atmosphere described above.

Initial adhesive strength (tensile shear strength) "5.5.9 Adhesive rising strength" specified in "α-olefin-maleic anhydride resin wood adhesive" of Japan Adhesive Industry Association Standard (JAI-5). According to the test method
The amount of the emulsion (adhesive) applied to the bonding surface of the Lauan plywood was set to an amount of 200 g / m ^2, and the tensile shear strength was measured for a test piece prepared with a pressing time of 10 minutes.

Normal adhesive strength (compression shear strength) "5.5.1 Compressive shear strength" specified in "α-olefin-maleic anhydride resin wood adhesive" of the Japan Adhesive Industry Association Standard (JAI-5). according to the (normal) "test method, the coating amount of the emulsion (adhesive) to the adhesive surface of birch were measured compressive shear strength test pieces were prepared as 250 g / m ^2.

Water-resistant adhesive strength (compressive shear strength) "5.5.2 compressive shear adhesive strength" specified in "α-olefin-maleic anhydride resin wood adhesive" of Japan Adhesive Industry Association Standard (JAI-5). (Water resistance) "
The amount of emulsion (adhesive) applied to the bonding surface of birch is 2
The compressive shear strength of the test piece prepared at 50 g / m ² was measured.

Warm water adhesive strength (compression shear strength) "5.5.3 compression shear adhesion" specified in "α-olefin-maleic anhydride resin wood adhesive" of Japan Adhesive Industry Association Standard (JAI-5) Strength (warm water resistance) ", the compressive shear strength was measured for a test piece prepared with the amount of the emulsion (adhesive) applied to the bonding surface of birch wood at 250 g / m ² .

Reference Example 1 An autoclave having an internal volume of 1 liter equipped with a stirrer was prepared.
Under a nitrogen atmosphere, toluene 650 g, isobutylene 24 g
(0.43 mol), 41 g (0.42 mol) of maleic anhydride, 7 g (0.02 mol) of stearyl methacrylate
And 0.2 g of benzoyl peroxide at 70 ° C.
Polymerization was carried out for hours. After completion of the polymerization reaction, the reaction mixture in the autoclave was taken out, poured into methanol, and the obtained precipitate was dried at 100 ° C. under reduced pressure for 6 hours to obtain a copolymer A having a number average molecular weight of 47,000. ¹ H-NM
As a result of R analysis, isobutylene unit in the copolymer A,
The molar ratio of maleic anhydride units to stearyl methacrylate units was found to be 1: 1: 0.05.

REFERENCE EXAMPLE 2 In Reference Example 1, the amounts of isobutylene, maleic anhydride and stearyl methacrylate were changed to 21
The same operation as in Reference Example 1 was carried out except that g, 37 g and 14 g were used, to obtain a copolymer B having a number average molecular weight of 34000. As a result of ¹ H-NMR analysis, this copolymer B
The composition molar ratio of isobutylene units, maleic anhydride units, and stearyl methacrylate units in the composition was 1: 1: 0.1
It turned out to be.

Reference Example 3 In Reference Example 1, the amounts of isobutylene and maleic anhydride used were changed to 21 g and 36 g, respectively, and 16 g (0.09 mol) of n-hexyl methacrylate was used instead of 7 g of stearyl methacrylate. Other than the above, the same operation as in Reference Example 1 was performed, and the number average molecular weight was 630.
00 was obtained. As a result of ¹ H-NMR analysis, the composition molar ratio of isobutylene units, maleic anhydride units, and n-hexyl methacrylate units in the copolymer C was as follows:
It was found to be 1: 1: 0.2.

REFERENCE EXAMPLE 4 The procedure of Reference Example 1 was repeated except that the amounts of isobutylene and maleic anhydride were changed to 21 g and 37 g, respectively, and 13 g (0.09 mol) of n-butyl methacrylate was used instead of 7 g of stearyl methacrylate. Performs the same operation as in Reference Example 1 and has a number average molecular weight of 7500
0 was obtained. As a result of ¹ H-NMR analysis, the composition molar ratio of isobutylene units, maleic anhydride units, and n-butyl methacrylate units in the copolymer D was as follows:
It was found to be 1: 1: 0.2.

Example 1 30 g of the copolymer A obtained in Reference Example 1 was taken and distilled water 100
After dispersion in 5 g, 5 g of 25% aqueous ammonia (an amount at which the degree of neutralization becomes 0.4) was added, and the mixture was heated and dissolved. 0.3 g of ammonium persulfate was added to the resulting solution, and then 80 g of vinyl acetate was added dropwise over 3 hours. Emulsion polymerization was carried out at 85 ° C. with vigorous stirring to obtain a polyvinyl acetate having a solid content of 50.5% by weight. An emulsion was obtained. The viscosity at 30 ° C. of this emulsion was 12000 cps (centipoise) [measured using a B-type viscometer]. Various properties of the obtained emulsion were measured according to the methods described above. Table 1 shows the results.

Examples 2, 3 and Comparative Example 1 In Example 1, 30 g of copolymer B (Example 2) and 30 g of copolymer C were used instead of 30 g of copolymer A.
(Example 3), 30 g of copolymer D (Comparative Example 1) was used, and the amount of 5% aqueous ammonia used was 3.6 g each.
(Amount at which the degree of neutralization becomes 0.3, Example 2), 11.8 g
(Amount at which the degree of neutralization becomes 0.5, Example 3), 14.3 g
(Amount at which the degree of neutralization becomes 0.6, Comparative Example 1) A polyvinyl acetate emulsion was prepared in the same manner as in Example 1 except that the various properties of the obtained emulsion were measured by the above-mentioned method. It was measured according to. Table 1 shows the results.

Comparative Example 2 Polyvinyl alcohol (degree of polymerization: 1700, degree of saponification:
98.5%) was dispersed in 100 g of distilled water and then dissolved by heating. 0.3 g of ammonium persulfate was added to the obtained solution, and then 80 g of vinyl acetate was added dropwise over 3 hours, and emulsion polymerization was carried out at 85 ° C. with vigorous stirring to prepare a polyvinyl acetate emulsion.
Various properties of the obtained emulsion were measured according to the methods described above. Table 1 shows the results.

Comparative Example 3 A copolymer of isobutylene and maleic anhydride [Isoban 0
4 (trade name, manufactured by Kuraray Co., Ltd.), molecular weight Mw = 6500
0] was dispersed in 100 g of distilled water.
10.6 g of aqueous ammonia (an amount at which the degree of neutralization becomes 0.4) was added and heated to dissolve. 0.3 g of ammonium persulfate was added to the obtained solution, and then 80 g of vinyl acetate was added.
Was added dropwise over 3 hours, and emulsion polymerization was carried out at 85 ° C. with vigorous stirring to produce a vinyl acetate emulsion. Various properties of the obtained emulsion were measured according to the methods described above. Table 1 shows the results.

[0048]

[Table 1]

As is apparent from Table 1, the polyvinyl acetate emulsion of the present invention, when used as an adhesive,
It has excellent water resistance and excellent initial adhesive strength.
In the polyvinyl acetate emulsion of the present invention, the rate of increase in viscosity at low temperatures is small.

[0050]

According to the present invention, there is provided a polyvinyl acetate emulsion which is excellent in water resistance when used as an adhesive, has a small rate of increase in viscosity at low temperatures, and has good film-forming properties at low temperatures. You.

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Claims (2)

[Claims] 1. A structural unit (I) derived from an α-olefin, a structural unit (II) derived from an α, β-unsaturated carboxylic acid or an anhydride thereof, and the following general formula (1): (Wherein R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 6 to 25 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms). A polyvinyl acetate emulsion in which a neutralized product obtained by reacting a coalesced substance with a basic substance is used as a protective colloid. 2. A structural unit (I) derived from an α-olefin, a structural unit (II) derived from an α, β-unsaturated carboxylic acid or an anhydride thereof, and the following general formula (1): (Wherein R ¹ represents a hydrogen atom or a methyl group, and R ² represents an alkyl group having 6 to 25 carbon atoms or a cycloalkyl group having 3 to 12 carbon atoms). A method for producing a polyvinyl acetate emulsion, comprising emulsion-polymerizing vinyl acetate in the presence of a neutralized product obtained by reacting a coalesced substance with a basic substance.