KR20210148129A - water-based adhesive - Google Patents

Abstract

An aqueous adhesive comprising a copolymer obtainable by polymerizing a plurality of monomers including (meth)acrylic acid ester is described, wherein the aqueous adhesive is applied to a paper tube. Also disclosed is a paper tube coated with an aqueous adhesive for use in paper straws.

Description

water-based adhesive

The present invention relates to a paper tube used for a paper straw and an aqueous adhesive applied to the paper tube.

Usually, most straws are made of plastic, and although a single straw is not bulky, the number of straws used per day is enormous. So, huge amounts of straw waste are generated around the world every day.

Plastic straws cannot be degraded naturally and are difficult to dispose of. When plastic straws are incinerated, dioxins are released, which can cause air pollution. Recently, plastic straws flow into the sea and decompose into fine fragments, which can be consumed by fish in the sea, but there is a problem that the fish can be eaten by humans.

To solve this problem, repeatable stainless steel straws or glass straws have appeared on the market. However, these straws are expensive, can be used repeatedly only after washing and sterilization, and since they are inconvenient as portable straws, it is difficult to use them as a substitute for plastic straws.

In consideration of these problems, studies on paper straws that are easy to discard have been made (see Patent Documents 1 and 2).

The straw of Patent Document 1 is a paper tube made of a paper material, and the paper tube is made of an inner paper material spirally wound therein and an outer paper material wound around the outer surface of the inner paper material. The inner paper material and the outer paper material are adhered to each other with a coating agent (for example, a solution obtainable by dissolving polyvinyl alcohol resin in paraffin) in a slightly misaligned state (Patent Documents 1, [0007], [0012], [Fig. 1], [see Fig. 2]).

Patent Document 2 discloses a straw made by winding a paper sheet by overlapping it several times (see Patent Document 2, [Claim 1], [0026], [Fig. 1], and [Fig. 2]).

When manufacturing a paper straw, in consideration of safety, it is necessary to use a resin excellent in water resistance as an adhesive to bond the paper materials together. As shown in Patent Documents 1 and 2, the paper material of the paper straw is coated with a polyvinyl alcohol resin or a vinyl acetate resin as a resin that is difficult to dissolve in water and has high safety (Patent Document 1, [Claim 1], [0007] ], and see Patent Document 2, [0024]).

JP H06-133840 A JP U3218847

However, it cannot be said that the paper straws of Patent Documents 1 and 2 sufficiently meet the recent strict safety requirements. In particular, in the food industry, customers' demands for safety are increasing year by year, and there is a tendency to eliminate factors that adversely affect the human body and environment, such as dishes and straws, as much as possible.

Therefore, as a resin composition applied to a paper straw, it is judged that a water-based adhesive is preferable to the solvent-based adhesive disclosed in Patent Document 1, and the resin composition has a higher level of water resistance and excellent stability of the polymer in an aqueous medium (i.e. , emulsion safety).

In view of this situation, the present invention has been made, and an object thereof is to provide an aqueous pressure-sensitive adhesive having excellent water resistance and stability applied to a paper tube, and a paper tube useful for the human body and the environment used for a paper straw.

As a result of continuous intensive research, the present inventors found that an emulsion containing a copolymer obtainable by polymerizing a number of specific monomers has excellent water resistance and stability, and an aqueous adhesive containing the copolymer emulsion and a paper tube coated with an aqueous adhesive Found that this problem can be solved, the present invention has been completed.

The present invention includes the following embodiments.

1. An aqueous adhesive comprising a copolymer obtainable by polymerizing a plurality of monomers,

The plurality of monomers include (meth)acrylic acid ester,

Water-based adhesive is a water-based adhesive that is applied to a paper tube.

2. The aqueous adhesive of clause 1, wherein the plurality of monomers further comprises styrene.

3. The water-based adhesive according to item 2, wherein the content of styrene is 20 to 50 parts by mass based on 100 parts by mass of the monomer.

4. The water-based adhesive according to any one of items 1 to 3, wherein the copolymer has a glass transition temperature of 30° C. or less.

5. The aqueous adhesive according to any one of items 1 to 4, wherein the copolymer is obtainable by polymerizing a plurality of monomers in the presence of a polymer having a carboxyl group as a stabilizer.

6. The water-based adhesive according to item 5, which contains the stabilizer in an amount of 10 to 50 parts by mass based on 100 parts by mass of the total mass of the monomers.

7. The water-based adhesive according to item 5 or 6, wherein the stabilizer has an acid value of 100 to 300 mgKOH/g.

8. The water-based adhesive according to any one of items 5 to 7, wherein the stabilizer has a chemical structure derived from a (meth)acrylic resin.

9. A paper tube coated with the water-based adhesive according to any one of Items 1 to 8.

The aqueous adhesive according to an embodiment of the present invention includes a copolymer emulsion obtainable by polymerizing a plurality of monomers and is applied to a paper tube, wherein the plurality of monomers include (meth)acrylic acid ester, and thus excellent water resistance and stability give

A paper tube coated with a water-based adhesive is used for paper straws, and thus the paper tube produced is safe for the human body, is easy to dispose of, and is environmentally friendly.

1 is a perspective view systematically showing a paper straw as a paper tube according to an embodiment of the present invention.

The aqueous adhesive according to an embodiment of the present invention is an aqueous adhesive comprising a copolymer emulsion obtainable by polymerizing a plurality of monomers, and is applied to a paper tube, for example, a paper straw.

In an embodiment of the present invention, the plurality of monomers comprises a (meth)acrylic acid ester.

In the present specification, "(meth)acrylic acid" means both acrylic acid and methacrylic acid, and means including at least one of acrylic acid and methacrylic acid.

"(meth)acrylic acid ester" means an ester of (meth)acrylic acid, ie a (meth)acrylate. (Meth) acrylate refers to both acrylate and methacrylate, and means to include at least one of acrylate and methacrylate.

Vinyl esters having a structure in which a vinyl group and oxygen are bonded, for example, vinyl acetate, etc. are not included in (meth)acrylates herein.

Specific examples of (meth)acrylate include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth) Acrylate, 2-ethylhexyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, dodecyl syl (meth)acrylate, tridecyl (meth)acrylate, octadecyl (meth)acrylate, behenyl (meth)acrylate and docosyl (meth)acrylate; and

(meth)acrylic acid hydroxyalkyl esters such as 2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

These (meth)acrylates may be used independently, or may be used combining 2 or more types of (meth)acrylates.

In an embodiment of the present invention, the (meth)acrylic acid ester is preferably a (meth)acrylic acid alkyl ester. More specifically, it is preferable to include methyl (meth)acrylate, butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate, and it is preferable to include n-butyl acrylate or 2-ethylhexyl acrylate Especially preferred. Homopolymers of n-butyl acrylate and 2-ethylhexyl acrylate have a low glass transition temperature (hereinafter referred to as Tg).

The copolymer is preferably obtainable by polymerizing n-butyl acrylate or 2-ethylhexyl acrylate with other monomers. In this case, the Tg of the copolymer can be adjusted at a low temperature, and the water resistance of the water-based adhesive can be improved.

In an embodiment of the present invention, the monomer may include other monomers than the (meth)acrylic acid ester. Other monomers are not particularly limited as long as the aqueous adhesive according to the embodiment of the present invention can be obtained. It is preferable that styrene is contained as another monomer. The Tg of the homopolymer of styrene is 100°C. Polymerizing a (meth)acrylic acid ester with a low Tg (for example, the Tg of a homopolymer of n-butyl acrylate is -54°C, and the Tg of a homopolymer of 2-ethylhexyl acrylate is -70°C) with styrene In the copolymer emulsion obtainable, the Tg is easily adjusted to the amount of blended styrene, thereby facilitating control of the water resistance of the water-based adhesive.

The content of the other monomers is not particularly limited, and for example, the content of styrene is preferably 20 to 50 parts by mass based on 100 parts by mass of the total mass of the monomers. When the content of styrene is within the above range, the Tg of the copolymer is easily controlled, so that it is easy to control the water resistance of the water-based adhesive.

The Tg of the copolymer is preferably 30°C or lower, particularly preferably -40°C to 15°C, more preferably -40°C to 0°C, most preferably -35°C to -20°C. When the Tg of the copolymer is within the above range, the water-based adhesive according to the embodiment of the present invention has better water resistance and stability.

In the present specification, the glass transition temperature of the copolymer is calculated from the glass transition temperature of the homopolymer obtainable by homopolymerizing a monomer used as a raw material of the copolymer (hereinafter also referred to as "homopolymer Tg"). In consideration of the mixing ratio (parts by mass) of the homopolymer Tg and each monomer, Tg is determined. Specifically, the Tg of the copolymer can be determined by calculating using the following formula (1):

Equation (1)

In the above formula (1), Tg is the theoretical Tg of the copolymer, C _n is the mass percentage of the nth monomer n contained in the monomer mixture, Tg _n is the homopolymer Tg of the nth monomer n, and n is the air It is a positive integer as the number of monomers constituting the coalescence.

As homopolymer Tg, it is possible to use the values described in the literature. Literature includes, for example, "POLYMER HANDBOOK" (4th edition; published by John Wiley & Sons, Inc.). As an example, the homopolymer Tg of the monomers mentioned in POLYMER HANDBOOK is shown below.

methyl methacrylate (“MMA”, Tg = 105° C.)

n-Butyl acrylate ("n-BA", Tg = -54°C)

2-ethylhexyl acrylate ("2EHA", Tg = -70°C)

Styrene ("St", Tg = 100°C)

Acrylic acid ("AA", Tg = 106°C)

methacrylic acid ("MAA", Tg = 130°C)

n-Butyl methacrylate (“BMA”, Tg = 20° C.)

In the present specification, in addition to the Tg of the homopolymer obtainable by homopolymerizing the above monomers, the glass transition temperature (Tg) of the homopolymer obtainable by homopolymerizing other monomers may be applied to the formula (1).

In an embodiment of the present invention, the copolymer is preferably a copolymer obtainable by polymerizing at least one of n-butyl acrylate and 2-ethylhexyl acrylate with styrene. When the copolymer includes the above component, the Tg can be easily adjusted to 30° C. or less, thereby improving the water resistance of the water-based adhesive according to the embodiment of the present invention.

In an embodiment of the present invention, the copolymer may be prepared in the form of an emulsion. The concentration of the solid component of the copolymer emulsion is not particularly limited, but is preferably 5 to 70% by mass of the copolymer emulsion component. The solid component of the emulsion means a solid component obtainable by drying the emulsion at 105° C. for 3 hours.

The copolymer emulsion of an embodiment of the present invention can be obtained by emulsion polymerization of a plurality of monomers. Emulsion polymerization is carried out in water or an aqueous medium using an emulsifier, and a known method can be used.

The emulsifier is fixed to the surface of the polymer particles during or after polymerization to promote particle dispersion stability. Examples of emulsifiers include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymer surfactants, and the like.

In order to improve water resistance, alkali resistance and water resistance, it is preferable to use a "reactive surfactant" having a radically polymerizable double bond in one molecule of the emulsifier.

It is preferable that the copolymer emulsion according to the embodiment of the present invention can be obtained by emulsion polymerization of a plurality of monomers in the presence of a stabilizer (eg, a polymer having a carboxyl group, a polymer having a hydroxyl group) in an aqueous medium. . The stabilizer has an effect of stabilizing the solid component of the emulsion in an aqueous medium to disperse the solid component, and a polymer having a carboxyl group is preferable.

Here, "aqueous medium" refers to general water such as tap water, distilled water, or ion-exchanged water, but is soluble in an aqueous medium and has poor reactivity with the raw material (eg, monomer) of the copolymer according to the embodiment of the present invention. organic solvents such as acetone and ethyl acetate and the like, and may further include monomers, oligomers, prepolymers and/or resins soluble in aqueous media. The aqueous medium may include an emulsifier, a polymerizable emulsifier, a polymerization initiator, a chain extender, and/or various additives commonly used in the preparation of an aqueous resin or a water-soluble resin, as will be described later.

In an embodiment of the present invention, the polymer having a carboxyl group as a stabilizer preferably has a chemical structure derived from a (meth)acrylic resin, which is a modified (meth)acrylic resin.

In an embodiment of the present invention, the modified (meth)acrylic resin is a synthetic resin having a carboxyl group obtainable by polymerizing at least one selected from (meth)acrylic acid and (meth)acrylic acid ester. In the present specification, the modified (meth)acrylic resin is a copolymer obtainable by copolymerizing at least one selected from (meth)acrylic acid and (meth)acrylic acid ester with another monomer.

Examples of the modified acrylic resin include a styrene/acrylic acid copolymer, a styrene/acrylic acid/acrylic acid ester copolymer, a styrene/methacrylic acid copolymer, and a styrene/methacrylic acid/methacrylic acid ester copolymer. When a modified acrylic resin is used as a stabilizer, the water-based adhesive according to the embodiment of the present invention has better water resistance and stability.

In an embodiment of the present invention, the stabilizer is preferably blended in an amount of 10 to 50 parts by mass relative to 100 parts by mass of the total mass of the monomers. When the amount of the stabilizer is in the above range, the particles (solid component) of the copolymer emulsion can be stably dispersed in the aqueous medium. When the dispersion of the copolymer emulsion becomes stable, the water-based adhesive according to the embodiment of the present invention has better water resistance and stability.

The acid value of the polymer having a carboxyl group according to an embodiment of the present invention is preferably 100 to 300 mgKOH/g, more preferably 150 to 250 mgKOH/g, particularly preferably 180 to 220 mgKOH/g, 190 to 210 mgKOH/g is most preferred. When the acid value of the polymer having a carboxyl group is within the above range, the water resistance of the water-based adhesive is further improved.

The "acid value" of the copolymer having a carboxyl group according to an embodiment of the present invention is a calculated value of the number of milligrams of potassium hydroxide required to neutralize the acid, assuming that all acid groups contained in 1 g of the copolymer are free acids. Thus, although present as a base in the system, it is considered a free acid.

This corresponds to the acid group possessed by the monomer (hereinafter referred to as "raw material monomer") serving as a raw material of the polymer having a carboxyl group. In an embodiment of the present invention, "acid value" can be determined by the following formula (2).

Equation (2):

Acid value = ((mass of raw material monomer/molecular weight of raw material monomer) × number of moles of acid groups contained in 1 mole of raw material monomer × chemical formula weight of KOH × 1,000/mass of polymer (A) having a carboxyl group)

The aqueous adhesive according to an embodiment of the present invention has an emulsion form, which may include a copolymer in an emulsion form, and may include a stabilizer, and the stabilizer may include a polymer having a carboxyl group. The aqueous adhesive may further include, as an additive, a crosslinking agent, a viscosity modifier, a plasticizer, an antifoaming agent, a preservative, a colorant, and the like. These additives may be blended after synthesizing the copolymer emulsion, pre-blended with a monomer serving as a raw material of the copolymer emulsion, or added to the aqueous adhesive in the form of an emulsion. Those mentioned above in the copolymer emulsion may be referred to as an aqueous adhesive in the form of an emulsion according to an embodiment of the present invention.

Examples of the crosslinking agent include zinc acetate, zinc oxide, zirconium acetate, zirconium ammonium carbonate, and the like. These crosslinking agents may be used alone or in combination.

Examples of the viscosity modifier include nitrogen-containing substances such as urea, urea compounds and dicyandiamide; calcium hydroxide, calcium oxide, sodium carbonate, trisodium phosphate, diammonium hydrogen phosphate, borax, sodium fluoride, water glass, aqueous ammonia and the like.

Examples of plasticizers include glycerin; polyhydric alcohols such as ethylene glycol and propylene glycol; sugars such as sucrose and sorbitol; and organic solvents such as cellosolve.

Examples of anti-foaming agents include:

silicone-based antifoaming agents such as dimethylpolysiloxane, polyoxyalkylene-modified silicone, organic modified polysiloxane and fluorine silicone;

oil and fat-based antifoaming agents such as castor oil, sesame oil, linseed oil and animal and vegetable oils;

fatty acid-based antifoaming agents such as stearic acid, oleic acid and palmitic acid;

Fatty acid ester-based antifoaming agents such as isoamyl stearate, diglycolauric acid, distearylsuccinic acid, distearic acid, sorbitan monolauric acid, glycerin fatty acid esters, polyoxyethylene sorbitan, butyl stearate monolaurate, water cross fatty acid esters, ethyl acetate alkyl esters of sulfonated ricinoleic acid, and natural waxes;

alcohol-based antifoaming agents such as polyoxyalkylene glycol and its derivatives, polyoxyalkylene alcohol hydrate, diamylphenoxy ethanol, 3-heptanol and 2-ethylhexanol;

etheric antifoaming agents such as 3-heptylcellosolve and nonylcellosolve-3-heptylcarbitol;

phosphate ester-based antifoaming agents such as tributyl phosphate, sodium octyl phosphate and tris(butoxyethyl)phosphate;

amine-based antifoaming agents such as diamyl amine;

amide-based antifoaming agents such as polyalkyleneamides, acylate polyamines and dioctadecanoyl piperidine;

metal soap-based antifoaming agents such as aluminum stearate, calcium stearate, potassium oleate and calcium salts of wool olein; and

Antifoaming agents based on sulfonate esters, such as sodium lauryl sulfonate and sodium dodecyl sulfonate.

A paper tube may be manufactured using the water-based adhesive according to an embodiment of the present invention. Such a paper tube is obtainable by winding a paper material and coating the surface of the paper material with an aqueous pressure-sensitive adhesive according to an embodiment of the present invention.

1 is a paper tube according to an embodiment of the present invention, for example, schematically shows a paper straw. As shown in Fig. 1, a paper tube (paper straw) 1 has an inner paper material 2 spirally wound therein, and an outer paper material 3 wound around the outer surface of the inner paper material 2 . The inner paper material 2 and the outer paper material 3 are adhered in a slightly shifted state by a water-based adhesive (not shown).

The paper straw 1 according to the embodiment of the present invention may take various forms other than the form shown in FIG. 1 , and may take a form by repeatedly winding a paper sheet several times.

The paper tube according to the embodiment of the present invention has excellent water resistance, so it can be used in the core of toilet paper, photo paper, calendar, film, tape, carpet, and packaging material for replacing corrugated cardboard in addition to paper straws.

[Example]

The present invention will be explained below by way of Examples and Comparative Examples. It should be noted that these examples are for illustrating the embodiments of the present invention, and the present invention is not limited thereto. In the examples, unless otherwise specified, parts by weight (or parts by mass) and percentages by weight (or percentages by mass) are based on the part in which no solvent is considered.

Aqueous adhesives according to embodiments of the present invention were prepared from (A) a stabilizer, (B) a monomer (a polymerizable monomer having an ethylenic double bond) and (C) an ethylene vinyl acetate (EVA) copolymer emulsion.

Water-based adhesives of Examples 1 to 5 and Comparative Examples 1 to 2 were prepared using component (A), component (B) and component (C) according to the formulations shown in Table 1. Details of components (A) to (C) are shown below.

(A) Stabilizer

(A-1) Polymer having a carboxyl group (JONCRYL679 (trade name), manufactured by BASF Japan Ltd.) and having an acid value of 200 mgKOH/g

(A-2) Polymer having a carboxyl group (SOLURYL 820 (trade name), manufactured by Hanwha Chemical Corporation) and having an acid value of 205 mgKOH/g

(A-3) Polymer having a hydroxyl group (OKS-8041 (trade name), manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.) and having an acid value of 0 mgKOH/g

(A-4) Polymer having a hydroxyl group (DENKA POVAL B-17 (trade name), manufactured by Denka Company Limited) and having an acid value of 0 mgKOH/g

(A-5) Polymer having a hydroxyl group (DENKA POVAL B-24T (trade name), manufactured by Denka Company Limited) and having an acid value of 0 mgKOH/g

(B) a monomer (a polymerizable monomer having an ethylenic double bond)

(B-1) butyl acrylate (n-butyl acrylate)

(B-2) 2-ethylhexyl acrylate

(B-3) Styrene

(B-4) methyl methacrylate

(B-5) vinyl acetate

(C) Ethylene vinyl acetate copolymer (EVA) emulsion

(C-1); Sumikaflex 408HQE (manufactured by Sumitomo Chemical Company, Limited)

Preparation of water-based adhesive of Example 1

100 parts by mass of distilled water, 40 parts by mass of (A-1) and 7 parts by mass of 25% ammonia water were charged to a four-necked flask equipped with a stirring blade, a thermometer and a reflux condenser. After stirring while blowing nitrogen gas into the four-necked flask, the liquid temperature was maintained at 70°C.

On the other hand, a mixture of 75 parts by mass of (B-1) and 25 parts by mass of (B-2) and an aqueous solution of 1.3 parts by mass of sodium persulfate and 19 parts by mass of water were prepared.

A mixture of about 4% by volume and an aqueous solution of about 30% by volume were respectively filled in a four-necked flask. After stirring to initiate the emulsion polymerization, the remaining (about 96% by volume) mixture and the remaining (about 70% by volume) aqueous solution were simultaneously added dropwise to the four-necked flask over about 4 hours.

After completion of the dropping, stirring was continued for about 1 hour and 30 minutes while maintaining the liquid temperature at 70° C., and then the obtained reaction mixture was cooled to room temperature. Ammonia water was added to adjust the reaction mixture to pH 8 to obtain an aqueous adhesive. This water-based adhesive is an emulsion because of its turbidity and is therefore an emulsion composition. The glass transition temperature of the copolymer of (B) shown in Table 1 is a value theoretically calculated based on the Tg of the homopolymer of the monomer (B).

The test results of the water-based adhesive thus obtained are shown in Table 1.

Preparation of water-based adhesives of Examples 2 to 5

As shown in Table 1, water-based adhesives of Examples 2 to 5 were prepared in the same manner as in Example 1, except that each component was changed. The test results of the water-based adhesive thus obtained are shown in Table 1.

Comparative Example 1

Using each component changed as shown in Table 1, a vinyl acetate emulsion containing polyvinyl alcohol as a stabilizer was prepared in a conventional manner. Specifically, Henkel Japan Ltd. 225-1025 manufactured by the company was used.

Comparative Example 2

As the ethylene vinyl acetate copolymer (EVA) emulsion, Sumikaflex 408HQE manufactured by Sumitomo Chemical Company, Limited was used as it was.

The aqueous adhesive thus obtained was evaluated by the following procedure.

1. Stability

Samples were prepared by dispensing each of the synthesized aqueous adhesives into 100 ml aliquots, followed by dilution with 100 ml of distilled water. After storage at room temperature for 24 hours, the state of each sample was visually observed. The evaluation criteria are as follows.

A: Coagulation, precipitation and separation of the copolymer of (B) were not observed in all samples, and the samples were found to be uniform emulsions.

B: Coagulation, precipitation or separation of the copolymer of (B) was observed in less than 30% of the samples.

C: Coagulation, precipitation or separation of the copolymer of (B) was observed in more than 30% of the samples.

2. Water resistance

Using a bar coater, apply a water-based adhesive to general high-quality (or wood-free) paper, and immediately after application, adhere high-quality paper and uncoated high-quality paper to each other, and then dry at 105° C. for 5 minutes to prepare a laminated sample did. After this laminated sample was cut into pieces of 2.5 cm length, it was immersed in 50 ml of distilled water at 60° C., and the state after immersion was further observed. The evaluation criteria are as follows.

A: Peeling does not occur from the adhesive surface after 1 hour, and high-quality paper causes the material to rupture when peeled off by hand.

B: Peeling does not occur on the adhesive surface after 1 hour, and high-quality paper peels off from the adhesive interface when peeling by hand.

C: Peeling occurs on the adhesive surface after 1 hour.

[Table 1]

As shown in Table 1, the aqueous adhesives of Examples 1 to 5 are copolymers having a chemical structure derived from (meth)acrylic acid ester, and include copolymers of a plurality of monomers, and thus both stability and water resistance are excellent.

The water-based adhesive of Comparative Example 1 contained a homopolymer of vinyl acetate and did not contain a copolymer having a chemical structure derived from (meth)acrylic acid ester. The aqueous adhesive of Comparative Example 2 contained a commercially available ethylene-vinyl acetate copolymer, but did not have a chemical structure derived from (meth)acrylic acid ester.

Therefore, the water-based adhesives of Comparative Examples 1 and 2 were remarkably poor in water resistance. The water-based adhesive of Comparative Example 2 also had poor stability.

As can be seen from the comparison of the water-based adhesive of Examples and the water-based adhesive of Comparative Examples, the water-based adhesive of Examples has a chemical structure derived from a polymer of (meth)acrylic acid ester, and thus is excellent in both stability and water resistance.

[Industrial Applicability]

According to the present invention, it is possible to provide an aqueous adhesive applied to a paper tube. The water-based adhesive according to an embodiment of the present invention is applied to a paper material, and a paper tube (eg, a paper straw, etc.) is prepared from the paper material.

[Cross-Reference to Related Applications]

This application claims priority under the Paris Convention to Japanese Patent Application No. 2019-63985, filed on March 28, 2019, which is hereby incorporated by reference in its entirety.

1. Paper tube (paper straw)
2...inner paper material
3...outer paper material

Claims (5)

An aqueous adhesive comprising a copolymer obtainable by polymerizing a plurality of monomers, the aqueous adhesive comprising:
The plurality of monomers include (meth)acrylic acid ester,
Water-based adhesive is a water-based adhesive that is applied to a paper tube. The aqueous adhesive of claim 1 , wherein the plurality of monomers further comprises styrene. The water-based adhesive according to claim 2, wherein the content of styrene is 20 to 50 parts by mass based on 100 parts by mass of the monomer. 4. The water-based adhesive according to any one of claims 1 to 3, wherein the copolymer has a glass transition temperature of 30 °C or less. A paper tube coated with the water-based adhesive according to any one of claims 1 to 4.

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