JP2002088333A - Aqueous emulsion-type adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aqueous emulsion-type adhesive free from the generation of wrinkles on a paper material even when the adhesive is applied on the paper material and having a fast setting speed. SOLUTION: This aqueous emulsion-type adhesive is an aqueous emulsion-type adhesive in which a polymer is dispersed in water and which contains a>=4C sugar alcohol, and whose water content is <=36 mass%. The examples of the polymer include a vinyl acetate-based polymer, an acrylic copolymer and a rubber. The acrylic copolymer is, for example, a polymer obtained by emulsion polymerization using an anionic surfactant. The concentration of the polymer in the aqueous emulsion-type adhesive is, for example, >=55 mol%. Further, the sugar alcohol may contain a 6C sugar alcohol such as sorbitol. The content of the >=4C sugar alcohol is, for example, about 1.5-17.5 mass%.

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 saccharides such as glucose and sucrose into an aqueous solution of a water-soluble polymer such as polyvinyl alcohol, starch, and dextrin to increase the solid content concentration. 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 inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, formulated a specific component into the aqueous emulsion type adhesive and adjusted the water content to a specific value or less. Then, although it is water-based, the generation of paper wrinkles can be significantly suppressed, and the setting speed (adhesion speed) can be remarkably accelerated. It has been found that an exceptionally excellent effect of having a coating workability, which has never been seen before, can be obtained. The present invention has been completed based on these findings.

That is, the present invention is an aqueous emulsion type adhesive in which a polymer is dispersed in water, which contains a sugar alcohol having 4 or more carbon atoms and has a water content of 36% by mass or less. To provide an aqueous emulsion adhesive.

[0008] The polymers include, for example, vinyl polymers. Typical examples of the polymer include a vinyl acetate polymer, an acrylic copolymer, and rubber. As the acrylic copolymer, for example, a polymer obtained by emulsion polymerization using an anionic surfactant can be used.

The concentration of the polymer in the aqueous emulsion type adhesive is, for example, 55% by mass or more. Also,
The sugar alcohol includes a sugar alcohol having 6 carbon atoms such as sorbitol. The content of the sugar alcohol having 4 or more carbon atoms is, for example, about 1.5 to 17.5% by mass.

[0010] 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”.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer in the aqueous emulsion type adhesive of the present invention is a polymer which can be dispersed in water and which exhibits an adhesive property when the aqueous dispersion is applied to an adherend. The polymer is not particularly limited as long as it is a polymer, and a polymer usually used for an emulsion adhesive can be used. Such polymers are often vinyl polymers.

Representative examples of the polymer include vinyl acetate polymers, acrylic copolymers, and rubbers (including elastomers). Examples of the vinyl acetate polymer include polyvinyl acetate, ethylene-vinyl acetate copolymer, vinyl acetate- (meth) acrylate copolymer [eg, vinyl acetate-methyl (meth) acrylate copolymer, acetic acid Vinyl-ethyl (meth) acrylate copolymer) and the like.

The acrylic copolymer includes a copolymer of two or more (meth) acrylates, one or more (meth) acrylates, and one or more copolymerizable with them. Alternatively, a copolymer (polymerizable unsaturated compound) with two or more other monomers is 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 the acrylic copolymers, acrylates such as butyl acrylate and 2-ethylhexyl acrylate (eg, C _4-12 alkyl acrylate) and methacrylates such as methyl methacrylate (eg, A monomer comprising a C _1-4 alkyl ester of methacrylic acid 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. Is preferred.

Further, the acrylic copolymer may be siliconized. Such a siliconized polymer can be produced, for example, by using a silane coupling agent such as 3-mercaptopropyltrimethoxysilane as a chain transfer agent during polymerization.

A typical example of the rubber is styrene-
Butadiene rubber (SBR), isoprene rubber (IR),
Diene-based polymers such as chloroprene rubber (CR) are exemplified.

The polymer may be obtained by any known or conventional polymerization method. However, since the preparation of an aqueous emulsion type adhesive is easy, an emulsion type polymer obtained by emulsion polymerization is used. Preferably, a polymer is used. Further, for example, in the case of an acrylic copolymer or the like, the use of a surfactant obtained by emulsion polymerization using a surfactant, particularly an anionic surfactant, rather than polyvinyl alcohol as an emulsifier, the effect of the present invention can be obtained. Is further enhanced.

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 sugar alcohol within a range that does not impair the adhesiveness and the coating workability.
Preferably 55% by mass or more (for example, 55 to 75% by mass)
Degree).

The aqueous emulsion type adhesive of the present invention contains a sugar alcohol having 4 or more carbon atoms as an essential component. By blending a sugar alcohol having 4 or more carbon atoms, it is possible to significantly improve the wrinkle-free property, possibly because the permeability of the adhesive into the paper is suppressed.

When a polyhydric alcohol having 3 or less carbon atoms, such as propylene glycol, is blended, the setting speed is undesirably low. Further, when polyvinyl alcohol is blended, not only the setting speed is reduced, but also the adhesiveness is reduced, and stringing is likely to occur during application.

As the sugar alcohol having 4 or more carbon atoms,
Tetrits, such as traits, erythrits, etc .;
Pencils such as arabbits, rebits, xylits;
Monosaccharide alcohols such as sorbit, mannitol, idit, tarit, galactit (zulcit), hexit such as alit; heptit; octit; nonit; decit; dodecit. 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 sorbitol and mannitol are preferred, and sorbite is particularly preferred.

The content of the sugar alcohol having 4 or more carbon atoms in the aqueous emulsion type adhesive is, for example, 1.5 to 1
It is about 7.5% by mass, preferably about 5 to 10% by mass. When the content of the sugar alcohol is less than 1.5% by mass, the effect of improving the wrinkle-less property is reduced, and when it exceeds 17.5% by mass, the high setting property tends to be impaired.

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 adhesive of the present invention can be produced, for example, by mixing an aqueous polymer dispersion with a sugar alcohol having 4 or more carbon atoms and adjusting the water content to 36% by mass or less.

The aqueous polymer dispersion 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 polymer is rubber, rubber latex can be used as the polymer aqueous dispersion. Adjustment of water content
For example, it can be performed by adding water, distilling water, or the like.

In the above method, the polymer concentration of the polymer aqueous dispersion is 65% by mass or more (for example, 65 to 75%).
Mass%) of a high concentration aqueous polymer dispersion,
The advantage is obtained that the adhesive can be easily prepared only by adding and mixing the sugar alcohol and, if necessary, water.
The polymer aqueous dispersion 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.

[0031]

According to the aqueous emulsion type adhesive of the present invention, since the specific component is contained and the water content is adjusted to a specific range, wrinkles are generated in the paper material even when used as a paper material. And the setting speed is fast. 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.

[0032]

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) "HVC-3300" (trade name: 68, manufactured by Toagosei Co., Ltd.)
%; Acrylic emulsion obtained by emulsion polymerization using an anionic surfactant) (Dextrin) manufactured by Nisseki Chemical Co., Ltd., trade name “Amicol No. 1” (polyvinyl alcohol) manufactured by Kuraray Co., Ltd. Kuraray Povar 203 (sugar alcohol) manufactured by Kyowa Hakko Kogyo Co., Ltd., trade name “Sorbit Kyowa Powder 50M” (propylene glycol) Commercial reagent

The evaluation method of the adhesive was as follows. (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. ：: Wrinkles do not occur immediately after application, or wrinkles occur immediately after application, but disappear when drying. 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 properties) 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. ：: The paper was completely torn (paper break) or almost all the paper was 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, the paper is torn or sufficiently adhered, and the paper surface is lifted or torn. 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 an adhesive container [trade name "Sponge glue" manufactured by Konishi Co., Ltd.], and when the adhesive is applied to paper, the container 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. ：: 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 3 and Comparative Examples 1 to 6 An acrylic copolymer, dextrin, polyvinyl alcohol, sugar alcohol (sorbitol), propylene glycol and water were blended in the proportions shown in Table 1 to prepare an adhesive composition. Prepared. The obtained adhesive composition was evaluated by the above method, and the results are shown in Table 1.

Examples 4 to 8 Acrylic copolymers and sugar alcohols (sorbitol) were blended in the proportions shown in Table 2 to prepare adhesive compositions. The obtained adhesive composition was evaluated by the above method, and the results are shown in Table 2.

[0040]

[Table 1]

[0041]

[Table 2]

As is clear from Tables 1 and 2, the aqueous emulsion adhesives of Examples 1 to 8 corresponding to the present invention, when applied to paper, despite being water-based, Not only does it not cause wrinkles, but also the setting speed is extremely fast, and the adhesiveness and coating workability are excellent. On the other hand, in the adhesive composition of Comparative Example 1 having a large water content, paper wrinkles occur and the setting speed is low. Further, in the adhesive composition of Comparative Example 2 in which sorbite was not blended, many paper wrinkles occurred. Furthermore, the adhesive composition of Comparative Example 3 in which polyvinyl alcohol was blended in place of sorbite was inferior in setting properties, adhesiveness and application workability, and Comparative Example 4 in which propylene glycol was blended in place of sorbite was inferior in setting properties. . Further, the solution-type adhesive compositions of Comparative Examples 5 and 6 using dextrin or polyvinyl alcohol instead of the acrylic copolymer are inferior in setting properties and adhesiveness, and particularly in the case of Comparative Example 6, In addition, since stringing occurs during coating, 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.

Continued on the front page F term (reference) 4J040 BA142 CA081 CA091 CA141 DB061 DE021 DE031 DF011 DF041 DF051 GA07 JA03 KA38 LA11 MA09 PA35

Claims (8)

[Claims] 1. An aqueous emulsion type adhesive in which a polymer is dispersed in water, wherein the aqueous emulsion type adhesive contains a sugar alcohol having 4 or more carbon atoms and has a water content of 36% by mass or less. adhesive. 2. The method according to claim 1, wherein the polymer is a vinyl polymer.
The aqueous emulsion type adhesive according to the above. 3. The aqueous emulsion type adhesive according to claim 1, wherein the polymer is a vinyl acetate polymer, an acrylic copolymer or a rubber. 4. The aqueous emulsion adhesive according to claim 3, wherein the acrylic copolymer is a polymer obtained by emulsion polymerization using an anionic surfactant. 5. The aqueous emulsion type adhesive according to claim 1, wherein the polymer concentration is 55% by mass or more. 6. The aqueous emulsion type adhesive according to claim 1, wherein the sugar alcohol is a sugar alcohol having 6 carbon atoms. 7. The aqueous emulsion adhesive according to claim 1, wherein the sugar alcohol is sorbite. 8. The aqueous emulsion type adhesive according to claim 1, wherein the content of the sugar alcohol having 4 or more carbon atoms is 1.5 to 17.5% by mass.