Water-based adhesive

Abstract

To provide a water-based adhesive that has an excellent water resistance and stability and is applied to a paper tube, and to provide a paper tube used for paper straw or the like that is useful for the human body and the environment.SOLUTION: Provided is a water-based adhesive, which is a water-based adhesive containing a copolymer obtained by polymerizing multiple kinds of monomers, and in which the monomer contains a (meth)acrylic acid ester, and that is applied to paper tube. A paper tube to which the water-based adhesive is applied and used for paper straws and the like.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a paper tube used for paper straws and the like, and a water-based adhesive applied to such a paper tube. [Background technology]

[0002] Generally, most straws are made of plastic and each straw does not have a large volume, but a large number of them are used each day, so a huge amount of straw waste is generated every day in the world.

[0003] Plastic straws cannot be decomposed naturally and are difficult to dispose of. When plastic straws are incinerated, dioxins are produced, which may pollute the air. In recent years, discarded plastic straws may enter the ocean and turn into microscopic garbage, which is then eaten by fish in the ocean, and the possibility that these fish may then be eaten by humans has become an issue.

[0004] To solve these problems, reusable stainless steel or glass straws have appeared on the market, but these straws are expensive, cannot be used repeatedly without cleaning and disinfection, and are inconvenient to carry, so they are not useful as a substitute for plastic straws.

[0005] In consideration of such problems, paper straws that are easy to dispose of have been studied (see Patent Documents 1 and 2). The straw in Patent Document 1 is a paper tube made of paper, and is formed of an inner paper material wound in a spiral shape on the inside 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 bonded together in a slightly misaligned state by a coating agent (for example, a solution of polyvinyl alcohol resin dissolved in paraffin) (see Patent Document 1

[0007]

[0012] [Figure 1] [Figure 2]). Patent Document 2 discloses a straw formed by winding a single paper sheet in multiple layers (see Patent Document 2 [Claim 1]

[0026] [Figures 1 and 2]).

[0006] When manufacturing paper straws, it is necessary to use a resin with excellent water resistance as an adhesive to bond the paper materials together, taking safety into consideration. As shown in Patent Documents 1 and 2, the paper material of paper straws is coated with polyvinyl alcohol resin or vinyl acetate resin, which is a resin that is difficult to dissolve in water and is highly safe (Patent Document 1 [Claim 1]

[0007] , Patent Document 2

[0024] ). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-133840 [Patent Document 2] Utility Model Registration No. 3218847 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the paper straws of Patent Documents 1 and 2 do not fully meet the recent stringent safety requirements. In the food industry in particular, customer safety requirements are increasing year by year, and there is a trend to eliminate factors that have adverse effects on the human body and the environment as much as possible from tableware and straws. Therefore, it is considered that the resin composition to be applied to the paper straws should preferably be a water-based adhesive rather than the solvent-based adhesive disclosed in Patent Document 1, and it is desirable for the resin composition to have a higher level of water resistance and excellent polymer stability in an aqueous medium (i.e., emulsion stability).

[0009] The present invention has been made to solve the above problems, and aims to provide a paper tube that has excellent water resistance and stability and can be used for water-based adhesives applied to paper tubes, and for paper straws that are useful for the human body and the environment. [Means for solving the problem]

[0010] As a result of extensive research conducted by the present inventors in order to solve the above-mentioned problems, the present inventors discovered that an emulsion containing a copolymer obtained by polymerizing multiple types of specific monomers has excellent water resistance and stability, and that an aqueous adhesive containing this copolymer emulsion and a paper tube coated with this aqueous adhesive can solve the above problems, thereby completing the present invention.

[0011] The present specification includes the following aspects. 1. An aqueous adhesive comprising a copolymer obtained by polymerizing multiple types of monomers, the monomer comprises a (meth)acrylic acid ester, A water-based adhesive that is applied to the paper tube. 2. The water-based adhesive according to 1, wherein the monomer further comprises styrene. 3. The aqueous adhesive according to 2, wherein the styrene content is 20 to 50 parts by mass per 100 parts by mass of the total monomer mass. 4. The aqueous adhesive according to any one of 1 to 3, wherein the copolymer has a glass transition temperature of 30°C or lower. 5. The aqueous adhesive according to any one of 1 to 4, wherein the copolymer is obtained by polymerizing a plurality of types of monomers in the presence of a polymer having a carboxyl group as a stabilizer. 6. The aqueous adhesive according to 5, comprising 10 to 50 parts by mass of a stabilizer per 100 parts by mass of the total monomer mass. 7. The aqueous adhesive according to 5 or 6, wherein the acid value of the stabilizer is 100 to 300 mg KOH / g. 8. The aqueous adhesive according to any one of 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 described in any one of 1 to 8. Effect of the Invention

[0012] The aqueous adhesive of an embodiment of the present invention contains a copolymer emulsion obtained by polymerizing multiple types of monomers, and is applied to a paper tube. The monomers contain (meth)acrylic acid esters, which gives the adhesive excellent water resistance and stability. The paper tubes coated with the water-based adhesive can be used for paper straws, etc., and are safe for the human body, easy to dispose of, and environmentally friendly. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic perspective view of a paper straw as a paper tube according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The aqueous adhesive according to an embodiment of the present invention contains a copolymer emulsion obtained by polymerizing a plurality of types of monomers, and is an aqueous adhesive that is applied to paper tubes, such as paper straws. In an embodiment of the invention, the monomer comprises a (meth)acrylic acid ester.

[0015] In this specification, the term "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid, and is meant to include at least one of acrylic acid and methacrylic acid. The term "(meth)acrylic acid ester" refers to an ester of (meth)acrylic acid, that is, a (meth)acrylate. The term "(meth)acrylate" refers to both an acrylate and a methacrylate, and is meant to include at least one of an acrylate and a methacrylate. In addition, vinyl esters having a structure in which a vinyl group is bonded to oxygen, such as vinyl acetate, are not included in the (meth)acrylates in this specification.

[0016] Specific examples of (meth)acrylates 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 (meth)acrylate, tridecyl (meth)acrylate, octadecyl (meth)acrylate, behenyl (meth)acrylate, and docosyl (meth)acrylate; Examples include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. These can be used alone or in combination of two or more.

[0017] In the 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 particularly preferable to include n-butyl acrylate or 2-ethylhexyl acrylate. The glass transition temperature (hereinafter, Tg) of the homopolymers of n-butyl acrylate and 2-ethylhexyl acrylate is low.

[0018] It is preferable to obtain the copolymer by polymerizing n-butyl acrylate or 2-ethylhexyl acrylate with other monomers. In this case, the Tg of the copolymer can be adjusted to a low value, and the water resistance of the water-based adhesive can be improved.

[0019] In an embodiment of the present invention, the monomer may contain other monomers in addition to the (meth)acrylic acid ester. As long as the aqueous adhesive of the embodiment of the present invention can be obtained, the other monomers are not particularly limited. It is preferable to contain styrene as the other monomer. The Tg of a homopolymer of styrene is 100°C. The Tg of a copolymer emulsion obtained by polymerizing styrene with a (meth)acrylic acid ester having 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) can be easily adjusted by the amount of styrene blended, which makes it easy to control the water resistance of the aqueous adhesive.

[0020] The content of other monomers is not particularly limited, but for example, the styrene content is preferably 20 to 50 parts by mass per 100 parts by mass of the total monomer mass. By having the styrene content within the above range, the Tg of the copolymer can be easily adjusted, and the water resistance of the water-based adhesive can be easily controlled.

[0021] The Tg of the copolymer is preferably 30° C. or less, particularly preferably −40° C. to 15° C., more preferably −40° C. to 0° C., and most preferably −35° C. to −20° C. When the Tg of the copolymer is within the above range, the aqueous adhesive of the embodiment of the present invention becomes more excellent in stability and water resistance and stability.

[0022] In this specification, the glass transition temperature of a copolymer is calculated from the glass transition temperature of a homopolymer (hereinafter also referred to as "homopolymer Tg") obtained when the monomers that are raw materials of the copolymer are homopolymerized. It is determined in consideration of this homopolymer Tg and the mixing ratio (parts by mass) of each monomer. Specifically, the Tg of a copolymer can be calculated using the following formula (1).

[0023] Formula (1): 1 / Tg=C1 / Tg1+C2 / Tg2+···+C n / Tg n [In the calculation formula (1), Tg is the theoretical Tg of the copolymer, C n is the mass fraction of the nth monomer in the monomer mixture, Tg n is the homopolymer Tg of the nth monomer, n is the number of monomers constituting the copolymer and is a positive integer.

[0024] For the homopolymer Tg, values ​​described in literature can be used. For example, "POLYMER HANDBOOK" (4th edition; published by John Wiley & Sons, Inc.) is one such literature. As an example, the homopolymer Tg of the monomers described in POLYMER HANDBOOK is shown below.

[0025] Methyl methacrylate ("MMA", Tg=105°C) n-Butyl acrylate ("n-BA", Tg=-54℃) 2-Ethylhexyl acrylate ("2EHA", Tg=-70℃) Styrene ("St", Tg=100°C) Acrylic acid ("AA", Tg=106℃) Methacrylic acid ("MAA", Tg=130℃) n-Butyl methacrylate ("BMA", Tg=20°C)

[0026] In this specification, in addition to the Tg of the homopolymer obtained by homopolymerization of the above-mentioned monomers, the glass transition temperature (Tg) of a homopolymer obtained by homopolymerization of another monomer is also applicable to formula (1).

[0027] In an embodiment of the present invention, the copolymer is preferably one obtained by polymerizing at least one of n-butyl acrylate and 2-ethylhexyl acrylate with styrene. By including the above component, the copolymer can easily adjust the Tg to 30° C. or less, thereby improving the water resistance of the aqueous adhesive of the embodiment of the present invention.

[0028] In the embodiment of the present invention, the copolymer can be produced in the form of an emulsion. The solid content of the copolymer emulsion is not particularly limited, but is preferably 5 to 70 mass% in the copolymer emulsion components. The solid content of the emulsion refers to the solid content obtained by drying the emulsion at 105°C for 3 hours.

[0029] The copolymer emulsion according to the embodiment of the present invention is obtained by emulsion polymerization of a plurality of types of monomers. The emulsion polymerization is a radical polymerization using water or an aqueous medium as a medium and an emulsifier, and a known method can be used.

[0030] The emulsifier is fixed to the surface of the polymer particles during or after polymerization to stabilize the dispersion of the particles. Examples of the emulsifier include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and polymeric surfactants. In order to improve water resistance, alkali resistance and waterproofing, it is preferable to use a "reactive surfactant" having a radically polymerizable double bond in one molecule of the emulsifier.

[0031] The copolymer emulsion according to the embodiment of the present invention is preferably obtained by emulsion polymerization of a plurality of types of monomers in the presence of a stabilizer (e.g., a polymer having a carboxyl group, a polymer having a hydroxyl group) in an aqueous medium. The stabilizer has the effect of stably dispersing the solid content of the emulsion in the aqueous medium, and is preferably a polymer having a carboxyl group.

[0032] Here, the term "aqueous medium" refers to common water such as tap water, distilled water, or ion-exchanged water, but may also include an organic solvent that is soluble in the aqueous medium and has poor reactivity with the raw materials of the copolymer of the embodiment of the present invention, such as monomers, such as acetone and ethyl acetate, and may further include monomers, oligomers, prepolymers, and / or resins that are soluble in the aqueous medium, and may also include emulsifiers, polymerizable emulsifiers, polymerization initiators, chain extenders, and / or various additives that are commonly used in producing aqueous resins or water-soluble resins, as described below.

[0033] In an embodiment of the present invention, the polymer having a carboxyl group, which serves as a stabilizer, preferably has a chemical structure derived from a (meth)acrylic resin, and is preferably 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 obtained by polymerizing at least one selected from (meth)acrylic acid and (meth)acrylic acid esters. That is, in this specification, the modified (meth)acrylic resin is a copolymer obtained by copolymerizing at least one selected from (meth)acrylic acid and (meth)acrylic acid esters with other monomers.

[0034] Examples of modified acrylic resins include styrene / acrylic acid copolymers, styrene / acrylic acid / acrylic acid ester copolymers, styrene / methacrylic acid copolymers, and styrene / methacrylic acid / methacrylic acid ester copolymers. When the modified acrylic resins are used as stabilizers, the aqueous adhesive of the present invention has better stability and water resistance.

[0035] In an embodiment of the present invention, the stabilizer is preferably blended in an amount of 10 to 50 parts by mass per 100 parts by mass of the total monomer mass. By blending the amount of the stabilizer in the above range, the particles (solid portion) of the copolymer emulsion can be stably dispersed in the aqueous medium. When the dispersion of the copolymer emulsion is stable, the aqueous adhesive of the embodiment of the present invention has excellent stability and water resistance.

[0036] The acid value of the polymer having a carboxyl group according to the 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, and most preferably 190 to 210 mgKOH / g. When the acid value of the polymer having a carboxyl group is within the above range, the water resistance of the aqueous adhesive is further improved.

[0037] The "acid value" of the copolymer having a carboxyl group according to the embodiment of the present invention is expressed as the calculated value of the amount of potassium hydroxide required to neutralize the acid groups contained in 1 g of the copolymer, assuming that all of the acid groups are free acids. Therefore, even if the acid groups exist as bases in the actual system, they are considered as free acids.

[0038] This corresponds to the acid group contained in a monomer (hereinafter, "raw material monomer") that is a raw material for a polymer having a carboxyl group. In the embodiment of the present invention, the "acid value" can be calculated by the following formula (2).

[0039] Formula (2): Acid value = ((mass of raw material monomer / molecular weight of raw material monomer) x number of moles of acid group contained in 1 mole of raw material monomer x formula weight of KOH x 1000 / (A) mass of polymer having carboxyl group)

[0040] The aqueous adhesive of the embodiment of the present invention has an emulsion form, which may contain a copolymer in the form of an emulsion, may contain a stabilizer, the stabilizer may contain a polymer having a carboxyl group, and may further contain a crosslinking agent, a viscosity adjuster, a plasticizer, a defoamer, a preservative, a colorant, etc. as additives. These additives may be mixed after the copolymer emulsion is synthesized, may be mixed in the monomer that is the raw material of the copolymer emulsion, or may be added to the aqueous adhesive in emulsion form. The description of the copolymer emulsion can be referred to the aqueous adhesive in emulsion form of the embodiment of the present invention.

[0041] Examples of the crosslinking agent include zinc acetate, zinc oxide, zirconium acetate, ammonium zirconium carbonate, etc. These crosslinking agents can be used alone or in combination.

[0042] Examples of the viscosity adjuster include urea, urea compounds, nitrogen-containing substances such as dicyandiamide, calcium hydroxide, calcium oxide, sodium carbonate, trisodium phosphate, diammonium hydrogen phosphate, borax, sodium fluoride, water glass, and aqueous ammonia. Examples of the plasticizer include glycerin; polyhydric alcohols such as ethylene glycol and propylene glycol; sugars such as sucrose and sorbitol; and organic solvents such as cellosolves.

[0043] As an antifoaming agent, for example, Silicone-based defoamers such as dimethylpolysiloxane, polyoxyalkylene-modified silicone, organic modified polysiloxane, and fluorine silicone; Oil-based defoamers such as castor oil, sesame oil, linseed oil, animal and vegetable oils; Fatty acid-based defoamers such as stearic acid, oleic acid, palmitic acid, etc.; Fatty acid ester-based defoaming agents such as isoamyl stearic acid, diglycol laurate, distearyl succinic acid, distearic acid, sorbitan monolaurate, glycerin fatty acid esters, polyoxyethylene sorbitan, monolaurate butyl stearate, sucrose fatty acid esters, ethyl acetate alkyl esters of sulfonated ricinoleic acid, and natural waxes; Alcohol-based defoamers such as polyoxyalkylene glycol and its derivatives, polyoxyalkylene alcohol hydrate, diamylphenoxyethanol, 3-heptanol, and 2-ethylhexanol; Ether-based defoamers such as 3-heptyl cellosolve and nonyl cellosolve-3-heptyl carbitol; Phosphate ester-based defoamers such as tributyl phosphate, sodium octyl phosphate, and tris(butoxyethyl) phosphate; Amine-based defoamers such as diamylamine; Amide-based defoamers such as polyalkylene amides, acylated polyamines, and dioctadecanoylpiperidine; Metal soap-based defoamers such as aluminum stearate, calcium stearate, potassium oleate, and calcium salts of wool olein; Examples of the antifoaming agents include sulfonate esters such as sodium lauryl sulfonate and sodium dodecyl sulfonate.

[0044] The aqueous adhesive of the embodiment of the present invention can be used when manufacturing a paper tube. The paper tube is obtained by winding a paper material and applying the aqueous adhesive of the embodiment of the present invention to the surface of the paper material. Fig. 1 shows a schematic diagram of a paper straw, for example, as a paper tube according to an embodiment of the present invention. As shown in Fig. 1, the paper tube (paper straw) 1 includes an inner paper material 2 wound in a spiral shape on the inside, and an outer paper material 3 wound around the outer surface of the inner paper material 2, and the inner paper material 2 and the outer paper material 3 are bonded together with a water-based adhesive (not shown) in a state where they are slightly misaligned.

[0045] The paper straw 1 according to the embodiment of the present invention may have various forms other than that shown in FIG. 1, for example, a form in which a single sheet of paper material is wound in multiple layers. Furthermore, since the paper tube of the embodiment of the present invention has excellent water resistance, in addition to paper straws, it can also be used for toilet paper, information paper, calendars, film, tape, carpet cores, packaging materials as an alternative to cardboard, etc. EXAMPLES

[0046] The present invention will be specifically and in detail explained below with reference to examples and comparative examples. However, these examples are merely one embodiment of the present invention, and the present invention is not limited to these examples in any way. In the description of the examples, unless otherwise specified, parts by mass and % by mass are based on the parts not taking into account the solvent.

[0047] A water-based adhesive according to an embodiment of the present invention was 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.

[0048] Components (A), (B), and (C) were used in the proportions shown in Table 1, and Examples 1 to 4, Reference example 5 The aqueous adhesives of Comparative Examples 1 and 2 were also produced. 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.) Acid value: 200 mg KOH / g (A-2) Polymer having a carboxyl group (SOLURYL 820 (trade name) manufactured by Hanwha Chemical Co.) Acid value: 205 mg KOH / g (A-3) Polymer having hydroxyl groups (OKS-8041 (product name) manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) Acid value 0 mg KOH / g (A-4) Polymer having hydroxyl groups (Denka Poval B-17 (product name) manufactured by Denka Co., Ltd.) Acid value: 0 mg KOH / g (A-5) Polymer having hydroxyl groups (Denka Poval B-24T (product name) manufactured by Denka Co., Ltd.) Acid value: 0 mg KOH / g

[0049] (B) Monomer (polymerizable monomer having an ethylenic double bond) (B-1) Butyl acrylate (n-butyl acrylate) (B-2) 2-Ethylhexyl acrylate (2-ethylhexyl acrylate) (B-3) Styrene (B-4) Methyl methacrylate (methyl methacrylate) (B-5) Vinyl acetate

[0050] (C) Ethylene vinyl acetate copolymer (EVA) emulsion (C-1): Sumikaflex 408HQE (manufactured by Sumitomo Chemical Co., Ltd.)

[0051] Preparation of the Water-Based Adhesive of Example 1 Into a four-neck flask equipped with a stirring blade, a thermometer, and a reflux condenser, 100 parts by mass of distilled water, 40 parts by mass of (A-1), and 7 parts by mass of 25% aqueous ammonia were added. The mixture was stirred while blowing nitrogen gas into the four-neck flask, and the liquid temperature was maintained at 70°C. Separately, an aqueous solution containing a mixture of 75 parts by mass of (B-1) and 25 parts by mass of (B-2), as well as 1.3 parts by mass of sodium persulfate and 19 parts by mass of water was prepared. Approximately 4 volume % of the above mixture and approximately 30 volume % of the above aqueous solution were each added to the above four-neck flask and stirred to initiate emulsion polymerization, and then the remainder of the mixture (approximately 96 volume %) and the remainder of the aqueous solution (approximately 70 volume %) were simultaneously added dropwise to the four-neck flask over a period of approximately 4 hours. After the dropwise addition, the mixture was stirred for about 1.5 hours while maintaining the liquid temperature at 70°C, and then cooled to room temperature. Ammonia water was added to adjust the pH to 8 to obtain an aqueous adhesive. This aqueous adhesive is an emulsion because it is turbid, and therefore an emulsion composition. The glass transition temperatures of the copolymers (B) listed in Table 1 are theoretically calculated values ​​based on the Tg of the homopolymers of the monomers (B). The test results of the resulting water-based adhesive are shown in Table 1.

[0052] Example 2 4 Manufacture of water-based adhesives Examples 2 to 4 were prepared in the same manner as in Example 1, except that the components were changed as shown in Table 1. 4 The test results of the resulting water-based adhesive are shown in Table 1.

[0053] Comparative Example 1 A vinyl acetate emulsion stabilized with polyvinyl alcohol was produced by a conventional method using each component as shown in Table 1. Specifically, 225-1025 manufactured by Henkel Japan Co., Ltd. was used.

[0054] Comparative Example 2 As an ethylene vinyl acetate copolymer (EVA) emulsion, Sumikaflex 408HQE manufactured by Sumitomo Chemical Co., Ltd. was used as it is.

[0055] The resulting water-based adhesive was evaluated as follows. 1. Stability The synthesized water-based adhesive was divided into 100 mL portions and diluted with 100 mL of distilled water to prepare samples. The condition was visually observed after storing at room temperature for 24 hours. The evaluation criteria are as follows: ⊚: No aggregation, precipitation, separation, or the like of the (B) copolymer was observed in any of the samples, and the samples were homogeneous emulsions. ◯: Aggregation, precipitation, separation, etc. of copolymer (B) was observed in less than 30% of the samples. ×: Aggregation, precipitation, separation, etc. of copolymer (B) was observed in 30% or more of the samples.

[0056] 2. Water resistance A water-based adhesive was applied to ordinary wood-free paper using a bar coater, and immediately after that, uncoated wood-free paper was laminated on top of it, and then the laminated sample was dried for 5 minutes at 105°C. The laminated sample was cut into pieces of 2.5 cm each, immersed in 50 ml of distilled water at 60°C, and the state was observed after that. The evaluation criteria are as follows. ○: The adhesive surfaces did not separate after one hour, and when peeled off by hand, the wood-free paper was destroyed. △: The adhesive surfaces did not peel off after 1 hour, but when peeled off by hand, the wood-free paper peeled off at the adhesive interface. ×: The adhesive surfaces peeled off after 1 hour.

[0057] [Table 1]

[0058] As shown in Table 1, Examples 1 to 4 The water-based adhesive of the present invention has a copolymer of multiple types of monomers, and since this copolymer contains a chemical structure derived from a (meth)acrylic acid ester, it has excellent both stability and water resistance.

[0059] The aqueous adhesive of Comparative Example 1 contains a homopolymer of vinyl acetate and does not contain a copolymer containing a chemical structure derived from a (meth)acrylic acid ester. The aqueous adhesive of Comparative Example 2 contains a commercially available ethylene-vinyl acetate copolymer but does not contain a chemical structure derived from a (meth)acrylic acid ester. Therefore, the water resistance of the water-based adhesives of Comparative Examples 1 and 2 is extremely poor. The water-based adhesive of Comparative Example 2 is also poor in stability.

[0060] As is clear from the aqueous adhesives of the Examples and the Comparative Examples, it has been demonstrated that the aqueous adhesives of the Examples have excellent both stability and water resistance due to their chemical structure derived from a (meth)acrylic acid ester polymer. [Industrial Applicability]

[0061] The present invention can provide a water-based adhesive to be applied to a paper tube. The water-based adhesive of the embodiment of the present invention is applied to a paper material, and a paper tube (e.g., a paper straw, etc.) is produced from the paper material. [Explanation of symbols]

[0062] 1...Paper tube (paper straw) 2…Internal paper material 3…External paper material

Claims

1. An aqueous adhesive comprising a copolymer obtained by polymerizing a plurality of types of monomers in the presence of a copolymer having a carboxyl group as a stabilizer, The copolymer having a carboxyl group, which is a stabilizer, is a styrene-α-methylstyrene-acrylic acid copolymer having an acid value of 100 to 300 mgKOH / g, the plurality of monomers include at least one selected from n-butyl acrylate and 2-ethylhexyl acrylate, and styrene; the content of styrene is 20 to 50 parts by mass relative to 100 parts by mass of the total mass of the plurality of monomers, A water-based adhesive that is applied to paper stock to produce paper tubes from the paper stock.

2. The aqueous adhesive according to claim 1, further comprising 10 to 50 parts by mass of a stabilizer per 100 parts by mass of the total mass of the plurality of monomers.

3. 3. The aqueous adhesive according to claim 1, wherein the copolymer obtained by polymerizing the plurality of monomers in the presence of a stabilizer has a glass transition temperature of -40 to 0°C.

4. A paper tube having a paper material coated with the water-based adhesive according to any one of claims 1 to 3.

Images