JP2928369B2 - Aqueous emulsion type adhesive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aqueous emulsion type adhesive having excellent initial adhesiveness.

[Prior Art and Problems to be Solved by the Invention] Conventionally, various aqueous emulsion-type adhesives such as polyvinyl acetate-based and acrylic-based adhesives have been used as adhesives for paper such as corrugated cardboard and wood. . Unlike the organic solvent-based adhesive, these aqueous emulsion-based adhesives have advantages in that they are excellent in handling accuracy and that there is no risk of environmental pollution.
However, since the adhesive strength of the emulsion adhesive is developed through an aggregation process in which the polymer particles in the emulsion are aggregated, it is difficult to perform high-speed bonding when bonding paper or the like using an aqueous emulsion adhesive. is there. In particular, cardboard with large repulsion, such as cardboard,
Using an aqueous emulsion adhesive, under high speed, for example,
In the case of bonding at a speed of about 300 sheets / minute, the bonding surface is easily peeled off, so that high-speed processing cannot be performed and productivity is reduced.

As a method of increasing the initial adhesiveness, it is conceivable to increase the solid content of the aqueous emulsion. In this case, although the initial adhesiveness is slightly improved, it is still insufficient, and it is difficult to bond thick paper or the like having a large repulsive force at a high speed.

Accordingly, an object of the present invention is to provide an aqueous emulsion type adhesive which is excellent in initial adhesiveness and can bond a material to be joined at a high speed, despite being an aqueous emulsion.

[Constitution of the Invention] In order to achieve the above object, the present invention relates to an aqueous emulsion containing vinyl acetate-based polymer particles, wherein the average particle diameter is 1.5 to 3.5 μm, and the particles having a particle diameter of 2 to 3 μm are all contained. An aqueous emulsion type adhesive comprising 15 to 40% by volume of particles is provided.

The feature of the aqueous emulsion type adhesive of the present invention is that the particle size distribution of the polymer particles is wide. The average particle size of the polymer particles may be in the range of 1.5 to 3.5 μm, but is preferably about 2 to 3 μm. Further, the polymer particles are usually distributed within a range of about 0.01 to 10 μm, preferably about 0.1 to 5 μm. Then, the polymer particles of 2 to 3 μm account for 15 to 40% by volume, preferably 20 to 35% by volume, of all the particles.
Occupy. When the proportion of the polymer particles having a particle size of 2 to 3 μm is out of the above range, the initial adhesiveness is low in any case.

As a monomer forming the polymer particles, at least a vinyl acetate monomer is used, and other conventional monomers, for example, a vinyl monomer; a styrene monomer;
Acrylates, methacrylates; acetic acid monomers; monomers having a hydroxy or alkoxy group; monomers having an amide group; monomers having an amino group; monomers having a glycidyl group; monomers having an N-methylol group or an N-alkoxymethyl group; Monomers can also be used.

Examples of the vinyl monomer include a vinyl monomer generally called VeoVa, such as vinyl chloride, vinyl caproate, vinyl propionate, and vinyl versatate, and methyl vinyl ketone.

Examples of the styrene-based monomer include styrene, α
-Methylstyrene, p-methylstyrene, m-methylstyrene, p-chlorostyrene, m-chlorostyrene, p
-Methoxystyrene and the like. A preferred styrenic monomer is styrene.

Examples of the acrylate and methacrylate include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate ,
Examples include acrylates such as stearyl acrylate, α-chloroethyl acrylate, cyclohexyl acrylate, and phenyl acrylate, and methacrylates corresponding thereto. Preferred acrylates and methacrylates are alkyl (meth) acrylates.

Examples of the acidic monomer include monomers having a carboxy group, such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid half ester, maleic acid, and maleic acid half ester, and monomers having a sulfonic acid group. Preferred acidic monomers are acrylic acid and methacrylic acid.

Examples of the monomer having a hydroxy group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and methacrylate corresponding to these acrylates. Examples of the monomer having an alkoxy group include methoxyethyl acrylate, ethoxyethyl acrylate, methoxypropyl acrylate, ethoxypropyl acrylate, and methacrylate corresponding to these acrylates.

Examples of the monomer having an amide group include acrylamide, methacrylamide, and maleamide.

Examples of the monomer having an amino group include 2-aminoethyl acrylate, 3-aminopropyl acrylate, dimethylaminoethyl acrylate, methacrylate and vinyl pyridine corresponding thereto.

Examples of the monomer having a glycidyl group include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether.

Examples of the monomer having an N-methylol group or an N-alkoxymethyl group include N-methylol acrylamide,
Examples include N-methoxymethylacrylamide, N-ethoxymethylacrylamide, N-propoxymethylacrylamide, N-isopropoxymethylacrylamide, N-butoxymethylacrylamide, and methacrylamide corresponding thereto.

Other monomers include, for example, acrylonitrile, methacrylonitrile, acrolein, crotonaldehyde, diethyl malate, dipropyl malate, dibutyl malate, dihexyl malate, di (2-ethylhexyl) malate, dioctyl malate, diethyl fumarate Rate, dipropyl fumarate, dibutyl fumarate,
Di (2-ethylhexyl) fumarate, ethylene, propylene, butadiene, isoprene and the like.

By appropriately selecting these other conventional monomers and conducting emulsion polymerization, a vinyl acetate-based aqueous emulsion can be obtained.

The type of the polymer particles can be selected according to the use of the adhesive. When the use of the adhesive is for paper, the polymer particles are preferably a vinyl acetate-based polymer containing vinyl acetate. This vinyl acetate polymer is not limited to polyvinyl acetate alone, but may be a copolymer with a copolymerizable monomer,
For example, it may be a copolymer with at least one monomer such as alkyl acrylate; alkyl methacrylate; vinyl caproate; vinyl propionate; VeoVa; ethylene; dialkyl malate and dialkyl fumarate. Preferred polymer particles are polyvinyl acetate, vinyl acetate-alkyl acrylate copolymer, vinyl acetate-
A vinyl propionate copolymer, a vinyl acetate-VeoVa copolymer, a vinyl acetate-dialkyl fumarate copolymer, and an ethylene-vinyl acetate copolymer. Particularly preferred polymer particles are polyvinyl acetate, ethylene-vinyl acetate copolymer.

Note that different types of polymer particles may be present in the aqueous emulsion.

The homogeneity of polymer particles obtained by emulsion polymerization varies depending on the monomer composition. Even if the monomer composition is the same, the glass transition temperature, the minimum film forming temperature, and the like change depending on the emulsion polymerization method and the like. Therefore, although the monomer composition cannot be determined unconditionally, Tobols (Tobols)
ky) 1 / Tg = Wa / Tga + Wb / Tgb +... + Wn / Tgn [where Ws, Wb,... Wn are copolymer components a, b,.
n, Tga, Tgb,... Tgn are the respective copolymer components a,
b,... n indicate the glass transition temperature (K) of the homopolymer] in the range where the glass transition temperature of the polymer and the minimum film formation temperature of the emulsion are -10 to 40 ° C., preferably about -5 to 30 ° C. You can choose.

In selecting a monomer, a hard component monomer and a soft component monomer are usually used in combination in order to adjust the glass transition temperature, minimum film forming temperature, water resistance, and the like of the polymer particles.

The particle size distribution of the polymer particles in the aqueous emulsion may be controlled by an emulsion polymerization method, or may be controlled by mixing a plurality of emulsions having different particle sizes at an appropriate ratio.

The aqueous emulsion can be prepared by a conventional method, for example, a batch charging method in which monomers are charged into a reaction system in a lump; a continuous feeding method in which monomers having the same composition are continuously fed to the reaction system to be polymerized; Multi-stage polymerization method of feeding and polymerizing separately: power feed polymerization method of feeding and polymerizing while continuously changing the monomer composition; obtained by emulsion polymerization of monomers according to a seed polymerization method or the like. In the emulsion polymerization method, the polymerization of some monomers is preceded, and the remaining monomers are emulsified with water and an emulsifier, and then added and polymerized as an emulsion, or all the monomers are emulsified with water and an emulsifier to form an emulsion. In the case of addition and polymerization, an emulsion having a wide particle size distribution is usually obtained.

Emulsion polymerization may be carried out at normal pressure or under pressure depending on the type of monomer.

Emulsion polymerization is carried out by using conventional components such as anionic surfactants, nonionic surfactants, cationic surfactants, surfactants such as amphoteric surfactants, and water-soluble polymers such as polyvinyl alcohol and hydroxyethyl cellulose. At least one emulsifier selected from protective colloids such as water-soluble oligomers and the like; a polymerization initiator such as a redox polymerization initiator such as potassium persulfate, ammonium sulfate or hydrogen peroxide-Fe [III]. . At the time of emulsion polymerization, a buffer, a chain transfer agent and the like may be used.

When a plurality of emulsions having different particle diameters of polymer particles are mixed to control the particle size distribution of the polymer particles, the mixing ratio of each emulsion is determined according to the average particle size and the particle size distribution of the polymer particles in each emulsion. You can choose. Also, in this case, the glass transition temperature of the polymer particles of the emulsion, the average glass transition temperature after mixing,
What is necessary is just to be in the said range.

The solid content of the emulsion is not particularly limited, but usually,
It is about 30 to 70% by weight, preferably about 40 to 60% by weight.

In the case where the polymer particles have a crosslinkable functional group, the aqueous emulsion-type adhesive is prepared by adding a conventional crosslinking agent, for example, a metal salt, hydrazine, an aziridine compound, an isocyanate compound, an epoxy compound, or the like. ,
A one-component or two-component crosslinking system that can be cured at room temperature or by heating may be used.

Aqueous emulsion adhesives include conventional film forming aids, plasticizers, defoamers, tackifiers, preservatives, fungicides, antifreeze agents, fillers, clay regulators, rust inhibitors, fillers, etc. And various water-soluble organic solvents such as ethanol and isopropanol. Further, the aqueous emulsion type adhesive may contain an organic solvent such as an aliphatic hydrocarbon, an alicyclic hydrocarbon, an aromatic hydrocarbon, a halogenated hydrocarbon, an ester, an ether, and a ketone. The aqueous emulsion adhesive containing such an organic solvent is useful when the surface of the material to be bonded is subjected to a hydrophobic treatment, for example, a coating treatment with a hydrophobic material such as wax.

The application amount of the aqueous emulsion type adhesive to the adhesive is usually about ²⁰ to 70 g / m ² .

The aqueous emulsion type adhesive of the present invention has a high initial adhesiveness, so that various kinds of adherends, for example, films, woven fabrics,
Although it can be used as an adhesive for wood and the like, it is useful as an adhesive for paper, preferably a cardboard having a large repulsive force, particularly an adhesive for cardboard.

[Effect of the Invention] The aqueous emulsion type adhesive of the present invention has a high initial adhesiveness and can bond an adherend at a high speed irrespective of the aqueous emulsion.

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples.

The following four types of emulsions A and B having different particle size distributions,
C and D were used.

Emulsion A (manufactured by Daicel Chemical Industries, Ltd., trade name: Sebian 114, vinyl acetate, solid content: 60% by weight) Emulsion B (manufactured by Daicel Chemical Industries, Ltd., trade name: Sebian 117, vinyl acetate, solid content: 55 weight%) %) Emulsion C (manufactured by Daicel Chemical Industries, Ltd., trade name: Sebian 522, vinyl acetate, solid content: 45% by weight) Emulsion D (manufactured by Denki Kagaku Kogyo, trade name: Denka # 65, ethylene-vinyl acetate based) , Solid content: 65% by weight) The properties of each emulsion are shown in Table 1, and the particle size distribution measurement results are shown in FIGS. 2 (A) to (D).

In addition, the value of clay is measured by a BL viscometer at 30 ° C. and a rotation speed of 12 rpm (centipoise). The average particle diameter (μm) of the polymer particles was determined using a particle analyzer (manufactured by HORIBA, CAPA-500) at a density of 1.0 g / solvent.
The measurement was performed under the conditions of cc, a sample density of 1.1 g / cc, and a particle size width of 0.5 μm. Emulsion B was measured under the condition of a particle size width of 0.2 μm.

Example 1 An aqueous emulsion adhesive containing the above four emulsions A, B, C and D was prepared according to the following formulation.

(1) 10.7 parts by weight of emulsion A, (2) 45.3 parts by weight of emulsion B, (3) 6.0 parts by weight of emulsion C, (4) 23.1 parts by weight of emulsion D, (5) 9.1 parts by weight of dibutyl phthalate, ( 6) 0.9 parts by weight of xylene, (7) 2.7 parts by weight of trichlorethylene, (8) 0.2 parts by weight of an antifoaming agent, and (9) 2.0 parts by weight of a filtrate of 10% soda ash The average particle size of the mixed emulsion in Example 1 was 2.50
μm. FIG. 1 shows the measurement results of the particle size distribution of the mixed emulsion.

Comparative Example 1 Instead of the four types of mixed emulsions of Example 1,
Example 1 except that the emulsion A was used in an amount of 85.1 parts by weight.
An aqueous emulsion-type adhesive was prepared in the same manner as described above.

Comparative Example 2 Instead of the four types of mixed emulsions of Example 1,
Example 1 except for using 85.1 parts by weight of the emulsion B
An aqueous emulsion-type adhesive was prepared in the same manner as described above.

Comparative Example 3 Instead of the four types of mixed emulsions of Example 1,
Example 1 except that 85.1 parts by weight of the emulsion C was used.
An aqueous emulsion-type adhesive was prepared in the same manner as described above.

Comparative Example 4 Instead of the four types of mixed emulsions of Example 1,
Example 1 except that the emulsion D was used in an amount of 85.1 parts by weight.
An aqueous emulsion-type adhesive was prepared in the same manner as described above.

The initial adhesiveness of the aqueous emulsion adhesive obtained in Example 1 and each comparative example was examined as follows.

Humidity adjusted to a temperature of 20 ° C and a humidity of 65%, and a width of 2 at 5mm intervals
Kraft paper K liner with a series of 0mm strips (basis weight 200
g / m ² ). Then, each aqueous emulsion type adhesive was applied using a bar coater (No. 30) on a kraft paper K liner (basis weight 200 g / m ² ) conditioned in the same manner as above, and Were laminated by the weight of a rubber roller (self-weight: about 600 g). After lamination, each strip is peeled off sequentially with the passage of time. The time required for the paper to tear for the first time is defined as the initial paper break, and the time required for 50% and 100% of the total area of the strip to be broken is 50%. The initial adhesion was evaluated as paper breakage and 100% paper breakage. The above test was conducted at temperatures of 2 ° C. and 20 ° C.

The results are shown in Table 2 together with the particle size characteristics of the mixed emulsion in Example 1 and the emulsion used in each comparative example.

As shown in the table, the aqueous emulsion type adhesives of the examples develop adhesiveness earlier than the aqueous emulsion type adhesives of the respective comparative examples.

Example 2 Using a corrugated pole manufacturing apparatus for producing corrugated cardboard at a speed of 300 sheets / min, a coating amount of 40 g / m ² after drying on a joint portion of corrugated cardboard.
Under the conditions described above, the aqueous emulsion type adhesive of the example was applied, and the joints were bonded. As a result, there was no peeling at the joints, and a cardboard could be produced at a high speed.

[Brief description of the drawings]

FIG. 1 is a graph showing the particle size distribution of the mixed emulsion in Example 1, and FIGS. 2 (A) to 2 (D) are graphs showing the particle size distribution of the emulsion used in Examples and Comparative Examples, respectively.

Claims (1)

(57) [Claims] 1. An aqueous emulsion containing vinyl acetate polymer particles, having an average particle size of 1.5 to 3.5 μm,
And particles having a particle diameter of 2 to 3 μm account for 15 to 40% by volume of all particles
Aqueous emulsion type adhesive.