JP3358733B2 - Aqueous emulsion type adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous emulsion type adhesive which is useful as an adhesive for office and industrial paper such as general consumers and offices. More specifically, the present invention relates to an aqueous emulsion-type adhesive which is water-based, does not wrinkle paper materials, and has a fast setting.

[0002]

2. Description of the Related Art Conventionally, aqueous adhesives for paper have often used water-soluble polymers such as polyvinyl alcohol, starch, dextrin, and gum arabic as main components, and contain water in an amount of 50% by mass or more. Are common. For this reason, when applied to paper, paper wrinkles due to moisture are generated, wrinkles remain on the paper even after drying, and there is a problem that the finish is poor. So, in order to solve such a problem,
Suppress paper wrinkles by blending polyhydric alcohols such as glycerin and sorbitol, and sugars such as glucose and sucrose into an aqueous solution of a water-soluble polymer such as polyvinyl alcohol, starch, and dextrin to increase the solids concentration and increase the solid content. Techniques have been proposed (JP-A-11-43663).

[0003] However, such a solution-type adhesive has a disadvantage that it is difficult to adhere to hardly-adhesive paper materials such as processed paper due to the adhesive properties of a water-soluble polymer as a main component. In addition, since the polymer solution is a homogeneous and high-concentration polymer solution, the viscosity is high, and stringing tends to occur. In addition, in the solution type adhesive, since a polyhydric alcohol or saccharide that is difficult to dry is mixed in the homogeneous solution, the setting speed after application is slow, and the resin concentration is limited due to the need to dissolve the water-soluble polymer. It is extremely difficult to eliminate paper wrinkles. further,
When stored for a long period of time, the viscosity increases with time due to hydrogen bonding or the like of the water-soluble polymer, so that workability deteriorates.

On the other hand, JP-A-10-158620 discloses an aqueous emulsion type adhesive in which polyvinyl alcohol and propylene glycol are blended in an emulsion of an acrylic ester copolymer. But,
This adhesive is not sufficiently satisfactory in terms of application workability such as low setting speed and stringing.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an aqueous emulsion type adhesive which does not wrinkle even when used as a paper material and has a high setting speed. Another object of the present invention is to provide a water-based emulsion-type adhesive exhibiting good adhesiveness even with a paper material such as processed paper that is difficult to bond. Still another object of the present invention is to provide an aqueous emulsion type adhesive which has low viscosity, does not have stringiness, and exhibits good coating workability. Another object of the present invention is to provide an aqueous emulsion type adhesive having excellent storage stability.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, blended two kinds of specific polymers, an acrylic polymer and a vinyl acetate polymer, with a polyhydric alcohol, Further, when a high-concentration aqueous emulsion having a water content of 36% by mass or less was prepared, it was found that all the above-mentioned problems of the conventional solution-type adhesive could be solved. In addition, in the case of an aqueous emulsion in which a polyhydric alcohol is simply blended with an acrylic polymer or an aqueous emulsion in which a polyhydric alcohol is blended with a vinyl acetate polymer, the generation of paper wrinkles cannot be sufficiently suppressed, and the setting speed is slow. As described above, it was found that when an acrylic polymer and a vinyl acetate polymer were used in combination and a polyhydric alcohol was added thereto, the occurrence of paper wrinkles was significantly suppressed, and the setting speed was significantly improved. Although the detailed reason for this is not clear, it is presumed that the interaction between the acrylic polymer particles and the vinyl acetate polymer particles greatly affects the morphology of the system. It is surprising that such a combination of two polymers produces a special effect that cannot be obtained with a single polymer. The present invention has been completed based on these findings.

That is, the present invention relates to an aqueous emulsion-type adhesive in which a polymer is dispersed in water, which contains an acrylic polymer, a vinyl acetate polymer and a polyhydric alcohol, and has a water content of 36% by mass or less. An aqueous emulsion-type adhesive is provided.

In this aqueous emulsion type adhesive,
The ratio of the acrylic polymer and the vinyl acetate polymer is, for example, the former / latter = 1/99 to 99/1.

Examples of the vinyl acetate polymer include an ethylene-vinyl acetate copolymer and the like, and sugar alcohol and the like can be used as the polyhydric alcohol. The content of the polyhydric alcohol is, for example, about 1 to 20% by mass.

The aqueous emulsion adhesive can be prepared by mixing an emulsion containing an acrylic polymer, an emulsion containing a vinyl acetate polymer, and a polyhydric alcohol.

In this specification, “acryl” and “methacryl” may be collectively referred to as “(meth) acryl”. In addition, the property that wrinkles do not occur in the paper material after the adhesive is applied may be referred to as “wrinkle-free property”, and the property that the setting speed is fast may be referred to as “high setting property”.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous emulsion adhesive of the present invention contains an acrylic polymer and a vinyl acetate polymer as polymer components.

[0013] The acrylic polymer is a water-dispersible polymer containing an acrylic monomer as a constituent monomer and which exhibits adhesiveness when the aqueous dispersion is applied to an adherend. There is no particular limitation so long as an acrylic polymer commonly used for an emulsion adhesive can be used.

The acrylic polymer includes one or more (meth) acrylic acid ester copolymers, and one or more (meth) acrylic acid esters and one or more copolymerizable monomers. Copolymers (polymerizable unsaturated compounds) with one or more kinds of other monomers are included.

Examples of the (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and the like.
Isobutyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate , Isononyl (meth) acrylate, (meth)
Decyl acrylate, dodecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, (meth)
And C _1-20 alkyl (meth) acrylates such as icosyl acrylate.

Other monomers copolymerizable with the (meth) acrylic acid ester include, for example, styrene monomers such as styrene, vinyltoluene and α-methylstyrene; olefins and dienes; vinyl acetate and the like. Vinyl esters such as methyl vinyl ether;
Carboxyl group-containing vinyl monomers such as (meth) acrylic acid, itaconic acid and maleic anhydride; cyano group-containing vinyl monomers such as acrylonitrile; hydroxyl group-containing vinyl monomers such as hydroxyethyl (meth) acrylate; Epoxy group-containing vinyl monomer such as glycidyl (meth) acrylate; amide group-containing vinyl monomer such as N-methylol (meth) acrylamide; amino group-containing vinyl monomer such as dimethylaminoethyl (meth) acrylate And the like.

Among acrylic polymers, acrylates such as butyl acrylate and 2-ethylhexyl acrylate (eg, C _4-12 alkyl acrylate) and methacrylates such as methyl methacrylate (eg, methacrylic acid) Acid C _1-4 alkyl ester and, if necessary, the other monomer such as a carboxyl group-containing vinyl monomer such as (meth) acrylic acid or a styrene monomer such as styrene as a constituent monomer Acrylic copolymers are preferred.

Further, the acrylic polymer may be siliconized. Such a siliconized polymer can be used, for example, as a chain transfer agent during polymerization.
It can be produced by using a silane coupling agent such as mercaptopropyltrimethoxysilane.

Examples of the vinyl acetate polymer include polyvinyl acetate, ethylene-vinyl acetate copolymer,
Vinyl acetate- (meth) acrylate copolymers [for example, vinyl acetate-methyl (meth) acrylate copolymer, vinyl acetate-ethyl (meth) acrylate copolymer] and the like can be mentioned.

In the aqueous emulsion type adhesive of the present invention, the ratio between the acrylic polymer and the vinyl acetate polymer may be in a wide range, for example, the former / latter = 1/99 to 99.
/ 1, but preferably the former / latter =
About 5/95 to 95/5, more preferably 20/80
About 80/20.

The aqueous emulsion type adhesive of the present invention includes:
As long as the effects of the present invention are not impaired, polymers other than acrylic polymers and vinyl acetate polymers may be contained.

The concentration of the polymer in the aqueous emulsion type adhesive can be appropriately selected in consideration of the amount of water and the amount of the polyhydric alcohol within a range that does not impair the adhesiveness and the coating workability, but is preferably 55% by mass. This is the above (for example, about 55 to 75% by mass).

The aqueous emulsion type adhesive of the present invention contains a polyhydric alcohol as an essential component. By blending the polyhydric alcohol, it is possible to greatly improve the wrinkle-free property, probably because the permeability of the adhesive into the paper is suppressed.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, glycerin, and sugar alcohols having 4 or more carbon atoms. Preferred polyhydric alcohols include sugar alcohols having 4 or more carbon atoms.

As sugar alcohols having 4 or more carbon atoms, for example, tetrits such as trait and erythrite; pentits such as arabbit, ribit, xylit; Octit; nonit; decit; dodecit; and other monosaccharide alcohols. In addition, as the sugar alcohol, oligosaccharide alcohols such as maltitol and lactitol, polysaccharide alcohols, and cyclic sugar alcohols such as inosit can be used.

Among these sugar alcohols, sugar alcohols having 6 carbon atoms (such as hexit) such as sorbite and mannitol are preferred, and sorbite is particularly preferred.

The content of the polyhydric alcohol in the aqueous emulsion type adhesive is, for example, about 1.5 to 17.5% by mass,
Preferably, it is about 5 to 10% by mass. When the content of the polyhydric alcohol is less than 1.5% by mass, the effect of improving wrinklelessness is reduced, and when the content exceeds 17.5% by mass,
It tends to impair high setting.

The water content of the aqueous emulsion type adhesive of the present invention is 36% by mass or less (for example, about 20 to 36% by mass), and preferably about 25 to 30% by mass.
If the water content exceeds 36% by mass, paper wrinkles are likely to occur, and the setting speed is slow.

The aqueous emulsion type adhesive of the present invention includes:
Depending on the purpose of use, commonly used additives such as fillers, fungicides, wetting promoters, viscosity improvers, coloring agents, fragrances and the like can be blended.

The aqueous emulsion type adhesive of the present invention is prepared, for example, by mixing an emulsion containing an acrylic polymer, an emulsion containing a vinyl acetate polymer and a polyhydric alcohol, and adjusting the water content to 36% by mass or less. Can be manufactured.

The emulsion containing the acrylic polymer can be obtained, for example, by subjecting one or more monomers to emulsion polymerization. Emulsion polymerization can be performed by a conventional method.

When the emulsion containing the acrylic polymer is a high-concentration emulsion having an acrylic polymer concentration of 65% by mass or more (for example, about 65 to 75% by mass), the adhesive of the present invention can be easily prepared. It is.
The emulsion having a high polymer concentration can be obtained, for example, by a so-called monomer emulsification method in which a slurry comprising a monomer, an emulsifier, and water is dropped into a reaction system and polymerized.

The emulsion containing the vinyl acetate polymer can be obtained, for example, by a conventional emulsion polymerization method. In addition, as an emulsion containing a vinyl acetate polymer, the vinyl acetate polymer concentration is about 65% by mass or more (for example, about 65 to 80% by mass, preferably 70 to 8% by mass).
It is preferable to use an emulsion having a high concentration (about 0% by mass).

In the above-mentioned production method, the adjustment of the water content can be carried out, for example, by adding water or distilling off water.

[0035]

According to the aqueous emulsion adhesive of the present invention, since the water-containing adhesive contains a specific plurality of polymer components and a polyhydric alcohol and the water content is adjusted to a specific range, the plurality of polymer Due to the interaction of the components, the wrinkle-free property and the high setting property are remarkably improved. Further, even a hardly-adhesive paper material such as processed paper shows good adhesiveness and has a wide range of application. Furthermore, since the water content is low, the viscosity is low and there is no stringing, so that the coating operation can be performed efficiently. It is also excellent in storage stability.

[0036]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following, unless otherwise specified, "parts"
Indicates "parts by mass" and "%" indicates "% by mass". The materials used in the examples and comparative examples are as follows.

(Acrylic copolymer) (1) HVC-3300 (trade name, manufactured by Toagosei Co., Ltd.)
(Solid content: 68%; acrylic emulsion obtained by emulsion polymerization) (2) Prototype A (solid content: 70%; monomer mixture of butyl acrylate, methyl methacrylate, and acrylic acid, anionic interface Acrylic copolymer obtained by emulsion polymerization using an activator and monomer emulsification method)

(Ethylene-vinyl acetate copolymer)
"Sumika Flex 74" manufactured by Sumitomo Chemical Co., Ltd.
00 "(solid content: 74%; ethylene-vinyl acetate copolymer emulsion obtained by emulsion polymerization)

(Dextrin) manufactured by Nisseki Chemical Co., Ltd., trade name "Amicol No. 1" (polyvinyl alcohol) manufactured by Kuraray Co., Ltd., trade name "Kuraray Poval 203" (polyhydric alcohol) Kyowa Hakko Kogyo Co., Ltd. Made, trade name "Sorbit Kyowa Powder 50M"

The method of evaluating the adhesive was as follows. In addition,
In the following evaluations, in the case of ◎ or ○, it is judged that there is practicality. (Paper wrinkle) The adhesive is applied to the copy paper, the copy paper is pasted immediately after that, and the state of the paper wrinkle when drying immediately after the application is determined based on the following criteria. A: Wrinkles do not occur immediately after application. ：: Wrinkles occur immediately after application, but disappear when dried. Δ: Wrinkles are formed immediately after application, but a little wrinkles remain when dried. ×: Wrinkles occur immediately after coating, and wrinkles remain even when dried.

(Setting property) [Setting property] An adhesive is applied to copy paper, immediately bonded, and peeled off after 30 seconds, and the state is determined according to the following criteria. A: The paper is completely torn (paper break). ：: Most of the paper is broken. Δ: There is no paper break, but there is resistance when peeled. ×: easily peeled off without resistance. [Setting properties] An adhesive is applied to copy paper, immediately bonded, and peeled off after 20 seconds, and the state is determined according to the following criteria. A: The paper is completely torn (paper break). ：: Most of the paper is broken. Δ: There is no paper break, but there is resistance when peeled. ×: easily peeled off without resistance.

(Adhesiveness) The processed paper is bonded using an adhesive, peeled off one week later, and the state is determined according to the following criteria. ：: Strongly adhered and the paper was torn. ：: Sufficiently adhered and floating or tearing occurs on the paper surface. Δ: There is resistance, but it is peeled off cleanly from the surface of the processed paper. X: There is no resistance and it is peeled off from the surface of the processed paper.

(Stringing property (coating workability)) An adhesive is put into a container for adhesive (“Sponge glue” manufactured by Konishi Co., Ltd.), and when the adhesive is applied to paper, it is removed from the container. The state of the adhesive and the state of application of the adhesive are determined based on the following criteria. ：: There is no stringing, and it can be applied very smoothly. ：: No stringing, can be applied without resistance. Δ: Short yarn is slightly generated, but can be applied without resistance. X: Stringing occurs and there is some resistance during coating.

Examples 1 to 6 and Comparative Examples 1 to 3 An acrylic copolymer, an ethylene-vinyl acetate copolymer, dextrin, polyvinyl alcohol, polyhydric alcohol (Sorbit) and water were mixed in the proportions shown in Table 1. And an adhesive composition was prepared. The obtained adhesive composition was evaluated by the above method, and the results are shown in Table 1.

Examples 7 to 10 and Comparative Examples 4 to 7 Acrylic copolymer, ethylene-vinyl acetate copolymer, dextrin, polyvinyl alcohol, polyhydric alcohol (Sorbit) and water were blended in the proportions shown in Table 2. And an adhesive composition was prepared. The obtained adhesive composition was evaluated by the above method, and the results are shown in Table 2.

[0046]

[Table 1]

[0047]

[Table 2]

As is clear from Tables 1 and 2, the water-based emulsion adhesives of Examples 1 to 10 corresponding to the present invention are water-based, but when applied to paper, In addition to preventing wrinkles from occurring, the setting speed is extremely high, and the adhesiveness and coating workability are excellent. On the other hand, Comparative Example 1, in which only an acrylic copolymer was used as the polymer, was inferior to the Examples in terms of setting properties. Comparative Example 2 using only the ethylene-vinyl acetate copolymer as the polymer has insufficient setting properties and adhesiveness, and Comparative Example 3 containing no polyhydric alcohol has insufficient wrinkle-free properties and setting properties. . Furthermore, in the adhesive compositions of Comparative Examples 4 and 5, which have a large water content, paper wrinkles occur and the setting speed is low.
In addition, the solution-type adhesive compositions of Comparative Examples 6 and 7 using dextrin or polyvinyl alcohol as the polymer were inferior in the setting properties and adhesiveness, and particularly in the case of Comparative Example 7, stringing occurred during application. Therefore, the coating operation cannot be performed smoothly. From the above results, it can be seen that the aqueous emulsion type adhesive of the present invention has extremely excellent features not found in the conventional adhesive.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-2-212542 (JP, A) JP-A-2-212573 (JP, A) JP-A-6-322347 (JP, A) JP-A-46-197 4132 (JP, A) JP-A-2-245081 (JP, A) JP-A-10-110149 (JP, A) JP-A-7-233357 (JP, A) JP-A-7-233358 (JP, A) JP-A-57-96071 (JP, A) JP-A-2001-72705 (JP, A) JP-A-2000-192003 (JP, A) JP-B-48-22327 (JP, B1) JP-B-47-44976 (JP, A) , B1) (58) Field surveyed (Int. Cl. ⁷ , DB name) C09J 4/00-201/10

Claims (6)

(57) [Claims] 1. An aqueous emulsion-type adhesive in which a polymer is dispersed in water, comprising an acrylic polymer, a vinyl acetate polymer and a polyhydric alcohol, and having a water content of 36% by mass or less. Aqueous emulsion adhesive. 2. The aqueous emulsion adhesive according to claim 1, wherein the ratio of the acrylic polymer and the vinyl acetate polymer is the former / the latter = 1/99 to 99/1. 3. The aqueous emulsion adhesive according to claim 1, wherein the vinyl acetate polymer is an ethylene-vinyl acetate copolymer. 4. The aqueous emulsion adhesive according to claim 1, wherein the polyhydric alcohol is a sugar alcohol. 5. The aqueous emulsion type adhesive according to claim 1, wherein the content of the polyhydric alcohol is 1 to 20% by mass. 6. The aqueous emulsion type adhesive according to claim 1, which is obtained by mixing an emulsion containing an acrylic polymer, an emulsion containing a vinyl acetate polymer, and a polyhydric alcohol.