WO2022210576A1

WO2022210576A1 - Adhesive agent and adhering method

Info

Publication number: WO2022210576A1
Application number: PCT/JP2022/015112
Authority: WO
Inventors: 誠芦内; 優一白米; 冬真大成
Original assignee: 国立大学法人高知大学
Priority date: 2021-03-31
Filing date: 2022-03-28
Publication date: 2022-10-06
Also published as: JPWO2022210576A1

Abstract

The purpose of the present invention is to provide an adhesive agent which is safe and has low environmental impact, and an adhering method which uses the adhesive agent. An adhesive agent according to the present invention is characterized by comprising, as active components, poly-γ-glutamic acid and a specific pyridinium compound. A method according to the present invention for adhering two adhesion targets is characterized by comprising: a step for either softening the adhesive agent according to the present invention on the surface of at least one of the adhesion targets, or adhering, onto the surface of at least one of the adhesion targets, the adhesive agent according to the present invention which has been softened; and a step for press-bonding, onto the softened adhesive agent on the surface of one of the adhesion targets, the other one of the adhesion targets.

Description

Adhesive and adhesion method

The present invention relates to an adhesive that is safe and has a low environmental impact, and a bonding method that uses the adhesive.

Adhesives are substances used to join two adherends, and in addition to natural products such as starch glue, casein, and gum arabic, many synthetic adhesives have been developed for various purposes. Naturally derived adhesives are generally applied to adherends in the form of an aqueous solution or a dispersion in water, exhibit adhesiveness when dried, and can be said to be highly safe. On the other hand, there is a problem that the adhesive strength of naturally derived adhesives is low.

Synthetic adhesives generally exhibit high adhesive strength, such as curing through reactions that form covalent bonds. On the other hand, many of them require an organic solvent as a solvent, such as being used as a solution or dispersion in an organic solvent, and there is concern about the impact on the environment.

Therefore, there is a demand for an adhesive that exhibits sufficient adhesiveness, yet is safe and has a low environmental impact.

For example, Patent Document 1 discloses a surgical adhesive containing a polyvalent metal salt of protein or polycarboxylic acid, and Patent Document 2 discloses a Ca ²⁺ -Na ⁺ mixed salt of polyaspartic acid or polyglutamic acid. and adhesive formulations containing quaternary ammonium cation salts. However, since the application of Patent Document 1 for surgical use, the adhesive force per unit area is several Pa, and the adhesive force of Patent Document 2 is several grams to ten and several grams, the adhesion of these adhesives Power is not considered sufficient.

By the way, the present inventors have proposed a PGA ion complex containing poly-γ-glutamic acid (PGA) and a quaternary ammonium ion compound (Patent Document 3) as a plastic material exhibiting antibacterial properties and biodegradability, and the PGA ion complex We have developed a fiber (Patent Document 4) consisting of The PGA ion complex can inactivate not only bacteria and fungi but also viruses (Non-Patent Documents 1 and 2).

Also, in recent years, attention has been focused on the problem of microplastics, in which plastic materials are miniaturized without being decomposed and pollute the environment. On the other hand, the PGA ion complex is decomposed into PGA and a quaternary ammonium ion compound in an environment of high ionic strength such as seawater (Non-Patent Document 3). PGA is originally biodegradable, and some quaternary ammonium ion compounds exhibit antibacterial properties, but their concentration drops sharply when separated from PGA. considered to be decomposed. Therefore, it can be said that the environmental load of the PGA ion complex is extremely low.

Japanese Patent Application Laid-Open No. 2004-113436 Japanese Patent Publication No. 2002-541285 Japanese Patent No. 5279080 Japanese Patent No. 5709158

Under the above circumstances, the object of the present invention is to provide an adhesive that is safe and has a low environmental load, and a bonding method that uses the adhesive.

The present inventors have made intensive studies to solve the above problems. As a result, the PGA ion complex that the present inventors have already developed is soluble in a specific organic solvent, but exhibits water insolubility, but surprisingly softens not only under heating but also under hydrothermal conditions, and is excellent. The inventors have found that it can be used as an adhesive because it exhibits adhesiveness, and completed the present invention.
The present invention is shown below.

[1] An adhesive comprising poly-γ-glutamic acid and a pyridinium compound represented by the following formula (I) as active ingredients.

[In the formula,
X represents a heteroaromatic ring group optionally having a substituent α and containing a pyridinium ring;
R ¹ represents a C _6-20 monovalent aliphatic hydrocarbon group or a group represented by the following formula (II),

(Wherein, Y represents a heteroaromatic ring group which may have a substituent β and contains a pyridinium ring, R ² represents a C _6-20 divalent aliphatic hydrocarbon group, and the substituent β represents one or more substituents selected from the group consisting of C _1-6 alkyl groups, C _1-6 alkoxy groups, hydroxyl groups, amino groups, halogeno groups, cyano groups, and nitro groups.)
Substituent α represents one or more substituents selected from the group consisting of a C _1-6 alkyl group, a C _1-6 alkoxy group, a hydroxyl group, an amino group, a halogeno group, a cyano group and a nitro group. ]
[2] R ¹ is a C _10-20 monovalent aliphatic hydrocarbon group, and the molar ratio of the pyridinium compound represented by the above formula (I) to glutamic acid constituting poly-γ-glutamic acid is 0.8 or more; The adhesive according to the above [1], which is 1.2 or less.
[3] R ¹ is a group represented by the above formula (II), and the molar ratio of the pyridinium compound represented by the above formula (I) to glutamic acid constituting poly-γ-glutamic acid is 0.4 or more, 0 .6 or less, the adhesive according to the above [1].
[4] The adhesive according to any one of [1] to [3], wherein X is a pyridinium group optionally having a substituent α.
[5] Any one of [1] to [4] above, wherein X is a quinolinium group optionally having a substituent α, and Y is a quinolinium group optionally having a substituent β. adhesive.

[6] A method for bonding two adherends, comprising:
softening the adhesive on the surface of at least one adherend or depositing the softened adhesive on the surface of at least one adherend; and
A step of crimping one adherend to the softened adhesive on the surface of the other adherend,
The method, wherein the adhesive contains poly-γ-glutamic acid and a pyridinium compound represented by the formula (I) as active ingredients.
[7] R ¹ is a C _10-20 monovalent aliphatic hydrocarbon group, and the molar ratio of the pyridinium compound represented by the above formula (I) to glutamic acid constituting poly-γ-glutamic acid is 0.8 or more; The method according to the above [6], which is 1.2 or less.
[8] R ¹ is a group represented by the above formula (II), and the molar ratio of the pyridinium compound represented by the above formula (I) to glutamic acid constituting the poly-γ-glutamic acid is 0.4 or more, 0 .6 The method according to the above [6].
[9] The method according to any one of the above [6] to [8], wherein X is a pyridinium group optionally having a substituent α.
[10] Any one of the above [6] to [9], wherein X is a quinolinium group optionally having a substituent α, and Y is a quinolinium group optionally having a substituent β. the method of.
[11] The method according to any one of [6] to [10], wherein the adhesive is softened under hydrothermal conditions.
[12] The method according to [11] above, wherein the adhesive is softened by steam or steam.

In the present disclosure, “C _6-20 monovalent aliphatic hydrocarbon group” refers to a linear or branched monovalent aliphatic hydrocarbon group having 6 or more and 20 or less carbon atoms, such as C ₆ Mention may be made of _-20 alkyl groups, _C6-20 alkenyl groups and _C6-20 alkynyl groups. Examples of C _6-20 alkyl groups include n-hexyl, isohexyl, n-octyl, n-decyl, n-dodecyl, n-tetradecyl, n-hexadecyl, n-octadecyl and n-icosyl. _{A C8-18} alkyl group is preferred, and a straight chain alkyl group is preferred. The C6-20 alkenyl group includes, for example, hexenyl, octenyl, decenyl, dodecenyl, tetradecenyl, hexadecenyl, octadecenyl, _icosenyl and the like, preferably a _C8-18 alkenyl group. The C6-20 alkynyl group includes, for example, hexynyl, _octynyl , decynyl, dodecynyl, tetradecynyl, hexadecynyl, octadecynyl, icosinyl and the like, preferably a _C8-18 alkynyl group.

"C _6-20 divalent aliphatic hydrocarbon group" refers to a divalent group corresponding to the above C _6-20 monovalent aliphatic hydrocarbon group, such as C _6-20 alkanediyl group, C _6- Mention may be made of ₂₀ alkenediyl groups and C _6-20 alkynediyl groups. Examples of C _6-20 alkanediyl groups include n-hexanediyl, isohexanediyl, n-octanediyl, n-decanediyl, n-dodecanediyl, n-tetradecanediyl, n-hexadecanediyl, n-octadecanediyl, n - includes icosandiyl. _{A C8-18} alkanediyl group is preferred, and a linear alkanediyl group is preferred. The C _6-20 alkenediyl group includes, for example, hexenediyl, octenediyl, decenediyl, dodecenediyl, tetradecenediyl, hexadecenediyl, octadecenediyl, icosenediyl and the like, preferably a C _8-18 alkenediyl group. The C _6-20 alkynediyl group includes, for example, hexynediyl, octynediyl, decynediyl, dodecynediyl, tetradecynediyl, hexadecynediyl, octadecynediyl, icosynediyl, etc., preferably a C _8-18 alkynediyl group.

A "C _1-6 alkyl group" refers to a linear or branched monovalent saturated aliphatic hydrocarbon group having 1 or more and 6 or less carbon atoms. Examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, n-hexyl and the like. It is preferably a C _1-4 alkyl group, more preferably a C _1-2 alkyl group, and even more preferably methyl.

A "C _1-6 alkoxy group" refers to a linear or branched saturated aliphatic hydrocarbonoxy group having 1 or more and 6 or less carbon atoms. For example, methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, t-butoxy, n-pentoxy, n-hexoxy and the like, preferably C _1-4 alkoxy groups, more preferably C _{1 -2} alkoxy group.

The “amino group” includes an unsubstituted amino group (—NH ₂ ), a mono C _1-6 alkylamino group substituted with one C _1-6 alkyl group and two C _1- A di-C _1-6 alkylamino group substituted by a ₆ -alkyl group shall be included. Examples of such amino groups include unsubstituted amino; C _1-6 alkylamino; dimethylamino, diethylamino, di(n-propyl)amino, diisopropylamino, di(n-butyl)amino, diisobutylamino, di(n-pentyl)amino, di(n-hexyl)amino, Di-C _1-6 alkylamino such as ethylmethylamino, methyl(n-propyl)amino, n-butylmethylamino, ethyl(n-propyl)amino and n-butylethylamino can be mentioned. An unsubstituted amino group is preferred.

When the heteroaromatic ring group containing a pyridinium ring has a substituent α or a substituent β, the number of substituents is not particularly limited as long as it can be substituted. The following are preferred, and 1 or 2 is more preferred. When the number of substituents is 2 or more, a plurality of substituents α or substituents β may be the same or different.

Since the active ingredient of the adhesive according to the present invention is a complex of poly-γ-glutamic acid, which constitutes the thread of natto, and a pyridinium compound used as an antibacterial agent, it can be said to be extremely safe. .
In addition, the adhesive according to the present invention, although it is composed of naturally derived components, exhibits extremely excellent adhesiveness, and it is possible to adjust the adhesive strength by selecting a pyridinium compound.
Furthermore, the adhesive according to the present invention is decomposed into poly-γ-glutamic acid and pyridinium compounds in an environment of high ionic strength such as seawater, and poly-γ-glutamic acid is a polyester of amino acids, so it exhibits biodegradability. On the other hand, pyridinium compounds are also used as antibacterial agents, but if they are released into the environment and become low in concentration, they cannot exhibit antibacterial properties and can also be biodegraded. Moreover, since the adhesive according to the present invention is softened under hydrothermal conditions, it is not necessary to use an organic solvent as a solvent. Therefore, it can be said that the environmental load of the adhesive according to the present invention is small.
As described above, the adhesive according to the present invention is safe and has a small burden on the environment, and is therefore industrially excellent.

FIG. 1 is a photograph showing the problem-free use of a cut porcelain pestle after gluing it with the adhesive according to the invention. FIG. 2 is a graph showing adhesion durability of commercially available cyanoacrylate-based general working adhesives. FIG. 3 is a graph showing adhesion durability of the PGA-DEQ ion complex according to the present invention. FIG. 4 is a graph showing adhesion durability of the PGA-HDP ion complex according to the present invention.

The adhesive according to the present invention contains poly-γ-glutamic acid and a pyridinium compound represented by formula (I) as active ingredients. Hereinafter, poly-γ-glutamic acid is abbreviated as "PGA", the pyridinium compound represented by formula (I) is abbreviated as "pyridinium compound (I)", and the complex of PGA and pyridinium compound (I) is abbreviated as " It may be abbreviated as "PGA ion complex".

In PGA, unlike general polypeptides, the α-carboxy group and the α-amino group do not form a peptide bond, but the γ-carboxy group and the α-amino group form an amide bond as shown in the following formula. It has a unique chemical structure and is known as the main component of natto threads.

The type of PGA is not particularly limited. For example, there are those consisting only of L-glutamic acid, those consisting only of D-glutamic acid, and those containing both, and any of them can be used. However, the higher the proportion of one of them, the better the stereoregularity and the higher the strength. This melting point becomes clearer by forming an ionic complex by forming an ionic bond with a pyridinium compound as in the present invention. Furthermore, since those composed of L-glutamic acid are superior in biodegradability, those containing 90 mol % or more of L-glutamic acid are preferably used. The ratio is preferably 95 mol % or more, more preferably 98 mol % or more, and even more preferably 99 mol % or more or 99.5 mol % or more. The upper limit of the proportion is 100 mol %, in which case PGA consists only of L-glutamic acid.

The molecular size of PGA to be used is also not particularly limited, but one with an average molecular mass of 10 kD or more is suitable. In general, the larger the molecular size, the higher the performance such as strength. On the other hand, PGA, which has an excessively large molecular size, is expensive to manufacture and may be technically difficult to manufacture, so it is usually 1,000 kD or less. For the average molecular mass, if there is a catalog value for the PGA product to be used, it may be referred to, but if there is no catalog value, it may be measured by a conventional method such as size exclusion chromatography.

Any commercially available PGA may be used, or it may be manufactured separately. However, since poly-α-glutamic acid can be obtained by polymerizing glutamic acid under normal conditions, biosynthesis using microorganisms is preferred. Microorganisms capable of producing PGA with a large molecular size include Natrialba aegyptiaca, which is a hyperhalophilic archaea.

The pyridinium compound (I) used in the present invention has a hydrophilic group called a pyridinium group and a hydrophobic group called a long-chain alkyl group in its molecule, and is generally used as a surfactant or the like. It is also used as an antifungal agent and an antiviral agent. The pyridinium group of the pyridinium compound (I) ionically bonds with the carboxyl group of PGA to form a PGA ion complex, which is a complex exhibiting at least water insolubility.

In the pyridinium compound (I), the heteroaromatic ring group containing a pyridinium ring includes, in addition to the pyridinium group itself, a quinolinium group, an isoquinolinium group, a naphthyridinium group, a phenanthridinium group, an acridinium group, a benzene ring and a pyridine ring on the pyridinium ring. A heteroaromatic ring group in which a ring or a pyridinium ring is condensed can be mentioned, and a pyridinium group or a quinolinium group is preferable.

In the adhesive according to the present invention, the adhesive strength can be adjusted by selecting the pyridinium compound (I). For example, an adhesive containing an ion complex of PGA and a pyridinium compound (I) in which R ¹ is a C _6-20 monovalent aliphatic hydrocarbon group as an active ingredient has relatively weak adhesive strength, so it must be unsealed. It can be used as a dismantling adhesive that can be peeled off as needed, and can be used as an adhesive for packaging bags. For example, since the adhesive according to the present invention is safe, it can be used for bonding food packaging bags. In addition, since it can be decomposed in a high-salt environment such as high-salt water, it can be applied to industrial applications such as manufacturing of products that assume recycling and temporary fixing of objects to be processed. In addition, in an adhesive containing an ion complex of PGA and a pyridinium compound (I) in which R ¹ is group (II) as an active ingredient, PGA is probably crosslinked two-dimensionally or three-dimensionally, so that the adhesive strength is reduced. Relatively high.

Pyridinium compounds (I) in which R ¹ is a C _6-20 monovalent aliphatic hydrocarbon group include, for example, n-hexylpyridinium, isohexylpyridinium, n-octylpyridinium, n-decylpyridinium, n-dodecylpyridinium, Mention may be made of n-tetradecylpyridinium, n-hexadecylpyridinium, n-octadecylpyridinium, n-icosylpyridinium. In particular, hexadecylpyridinium (cetylpyridinium) is used as an antibacterial agent.

Examples of pyridinium compounds (I) in which R ¹ is group (II) include decalinium (1,1′-decamethylenebis(4-aminoquinaldinium)) and N,N′-hexamethylenebis(4 -carbamoyl-1-decylpyridinium).

The PGA ion complex according to the present invention is preferably one in which PGA is sufficiently modified with pyridinium compound (I) in order to overcome the drawbacks of PGA such as excessive hydrophilicity. More specifically, when the pyridinium compound (I) has a C _6-20 monovalent aliphatic hydrocarbon group as R ¹ , the ratio of the pyridinium compound (I) in the PGA ion complex is is preferably at least 0.5 mol times, more preferably at least 0.6 mol times, even more preferably at least 0.8 mol times, and preferably 1.0 mol times or less. . When the pyridinium compound (I) has the group (II) as R ¹ , the proportion of the pyridinium compound (I) in the PGA ion complex is preferably 0.25 times or more by mol relative to the glutamic acid constituting the PGA, It is more preferably 0.3-fold or more by mol, still more preferably 0.4-fold or more by mol, and preferably 0.5-fold or less by mol.

In particular, a PGA ion complex containing equimolar or substantially equimolar glutamic acid constituting PGA and a pyridinium ring constituting pyridinium compound (I) is preferable. PGA is originally extremely hydrophilic, and continues to absorb water endlessly, gels, and becomes an aqueous solution. In addition, conventional techniques for modifying the side chain carboxyl groups of PGA have been known, but since it is not possible to sufficiently modify the many carboxyl groups present in the structure, even if modified, gelation and aqueous solution do not occur. It was inevitable. On the other hand, in the present invention, the side chain carboxyl groups of PGA can be modified very easily and sufficiently. . On the other hand, if the pyridinium rings constituting the pyridinium compound (I) in the PGA ion complex are equimolar or substantially equimolar with the glutamic acid constituting PGA, that is, the side chain carboxy groups, PGA can be sufficiently modified. Here, "substantially equimolar" means that the number of moles of both is approximately equal. Specifically, the amount of the pyridinium ring constituting the pyridinium compound (I) is 0.8 or more times the amount of glutamic acid constituting PGA. , 1.2 mol times or less, particularly 0.9 mol times or more and 1.1 mol times or less. Specifically, when the pyridinium compound (I) has a C _6-20 monovalent aliphatic hydrocarbon group as R ¹ , the ratio of the pyridinium compound (I) in the PGA ion complex is It is preferably 0.8 or more and 1.2 or less, and when pyridinium compound (I) has group (II) as R ¹ , the proportion of pyridinium compound (I) in the PGA ion complex is glutamic acid constituting PGA is preferably 0.4 or more and 0.6 or less.

The pyridinium compound (I) may be used alone or in combination of two or more.

The PGA ion complex, which is the active ingredient of the adhesive according to the present invention, can be produced extremely easily by simply mixing PGA and pyridinium compound (I) in a solvent.

Water is suitable as the solvent used here. This is because the raw material PGA can be dissolved satisfactorily, and since the PGA ion complex is insoluble in water, it is convenient for isolating and purifying the target product after the reaction. However, depending on the water solubility of the pyridinium compound (I), alcohols such as methanol and ethanol; ethers such as diethyl ether and THF; amides such as dimethylformamide and dimethylacetamide; of water-miscible organic solvents may be added to the reaction solution. However, considering separation of the PGA complex after completion of the reaction, it is preferable to use only water as the solvent.

Its salt may be used as the raw material PGA. Examples of the salt include alkali metal salts such as sodium salts and potassium salts; alkaline earth metal salts such as calcium salts and magnesium salts; Moreover, even when a salt is used, not all the carboxy groups need to be in the form of salt, and only a part of them may be in the form of salt. However, since polyvalent metal salts such as alkaline earth metal salts may have low solubility in water, it is preferable to use free PGA or monovalent metal salts of PGA.

The pyridinium compound (I) usually exists as a halide salt. Therefore, in the present invention, the salt of pyridinium compound (I) may be directly added to the reaction solution, or the salt may be dissolved in an aqueous solvent and then added. Since the pyridinium compound (I) sufficiently modifies PGA, it is preferable to use a sufficient amount with respect to PGA.

Since the PGA ion complex of the present invention is water-insoluble, it can be easily separated from the aqueous solvent, so the concentration of each component in the reaction solution is not particularly limited. For example, the concentration of PGA in the reaction solution is about 0.5 w/v% or more and 10 w/v% or less, and the concentration of pyridinium compound (I) is about 1.0 w/v% or more and 10 w/v% or less. can.

It is preferable to heat the reaction solution moderately in order to promote the formation of the PGA complex. The heating temperature can be, for example, approximately 40° C. or higher and 80° C. or lower. The reaction time may be adjusted as appropriate, but it can generally be about 1 hour or more and 20 hours or less.

Since the PGA ion complex of the present invention is water-insoluble, it can be easily separated from the aqueous solvent by filtration, centrifugation, or the like. The separated PGA ion complex can be washed with water to remove excess PGA, pyridinium compound (I), and other salts. Also, the water solvent can be easily removed by washing with acetone or the like.

The separated PGA ion complex is preferably dried by a conventional method such as vacuum drying or freeze drying.

The PGA ion complex according to the present invention is useful as an active ingredient for adhesives. Specifically, the PGA ion complex according to the present invention is softened on the surface of the adherend, or the softened PGA ion complex is applied to the surface of the adherend.

The present inventors have unexpectedly found that the PGA ion complex according to the present invention softens under hydrothermal conditions, although it is insoluble in water. For example, the PGA ion complex of the present invention can be softened by immersion in water at a temperature of about 60° C. or higher and 100° C. or lower, or by applying water vapor or steam.

More specifically, the adhesive of the present invention is placed on the surface of at least one of the adherends, and is softened by heating, steam or steam, or by heating, warm water, hot water, steam or steam. After the adhesive of the present invention is softened and adhered to the surface of at least one adherend, the softened adhesive is pressure-bonded to the other adherend and allowed to stand. Alternatively, the adhesive of the present invention is placed on the surface of at least one adherend, another adherend is superimposed on the adhesive, the adhesive is softened by heating or the like, and then allowed to stand. good.

The material of the adherend is not particularly limited, for example, wood; ceramics such as pottery and porcelain; metals such as iron, copper, zinc, aluminum, gold, silver, and alloys; glass; polyethylene terephthalate (PET), polyamide (PA ), polycarbonate (PC), polyvinyl chloride (PVC), polyethylene (PE), and polypropylene (PP). Moreover, the adhesive according to the present invention may be capable of bonding not only the same type of adherends but also different types of adherends.

After the adherend is crimped via the adhesive according to the present invention, the conditions for standing may be adjusted as appropriate. For example, the standing temperature can be 0° C. or higher and 50° C. or lower, and may be normal temperature. Moreover, the standing time can be 1 hour or more and 48 hours or less, preferably 12 hours or more and 24 hours or less.

The adhesive strength of the adhesive according to the present invention can be adjusted mainly by selecting the pyridinium compound (I). For example, an adhesive containing an ion complex of PGA and a pyridinium compound (I) in which R ¹ is a C _6-20 monovalent aliphatic hydrocarbon group as an active ingredient has relatively weak adhesive strength, so it must be unsealed. It can be used as a dismantling adhesive that can be peeled off as needed, and can be used as an adhesive for packaging bags. Also, an adhesive containing as an active ingredient a composite of pyridinium compound (I) in which R ¹ is group (II) and PGA can be used as an adhesive exhibiting high adhesive strength.

The PGA ion complex, which is the active ingredient of the adhesive according to the present invention, is a complex of PGA constituting the thread of natto and a pyridinium compound used as an antibacterial agent. For example, it can be used for food and its packaging. Moreover, the adhesive strength can be adjusted by selecting the pyridinium compound. Furthermore, the adhesive according to the present invention is decomposed in an environment of high ionic strength such as seawater, PGA exhibits biodegradability, and low-concentration pyridinium compounds can also be biodegraded. Moreover, since the adhesive according to the present invention is softened under hydrothermal conditions, it is not necessary to use an organic solvent as a solvent. Therefore, the environmental load of the adhesive according to the present invention is very small.

This application claims the benefit of priority based on Japanese Patent Application No. 2021-59214 filed on March 31, 2021. The entire contents of the specification of Japanese Patent Application No. 2021-59214 filed on March 31, 2021 are incorporated herein by reference.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples, and can be modified appropriately within the scope that can conform to the gist of the above and later descriptions. It is of course possible to implement them, and all of them are included in the technical scope of the present invention.

Example 1: Production of PGA-DEQ Ion Complex 1 g of dequalinium chloride (DEQ) hydrate powder was added to 100 mL of distilled water and dissolved by heating to about 80 to 100° C. to obtain an aqueous DEQ solution. 100 mL of a 0.5% by mass PGA aqueous solution was heated to about 80° C., and the DEQ aqueous solution was added while stirring. At this time, the amount of DEQ added was 1/2 mol with respect to the carboxy groups contained in the total amount of PAG. After confirming that a PGA-DEQ ion complex, which is a white substance, was formed in the mixed solution, suction filtration was performed, and the obtained PGA-DEQ ion complex was washed with warm water of about 80 to 100°C.
The resulting PGA-DEQ ion complex was frozen at −80° C. overnight, then transferred to a freeze dryer and dried until no weight loss occurred.

Example 2: Production of PGA-HDP Ion Complex 3 g of hexadecylpyridinium (HDP) bromide hydrate powder was added to 100 mL of distilled water and dissolved by heating to about 60 to 100°C to obtain an aqueous HDP solution. rice field. 100 mL of a 1% by mass PGA aqueous solution was heated to about 60° C., and an HDP aqueous solution was added while stirring. At this time, the amount of HDP added is equimolar to the carboxy groups contained in the total amount of PAG. After confirming that a PGA-HDP ion complex, which is a white substance, was formed in the mixed solution, suction filtration was performed, and the obtained PGA-DEQ ion complex was washed with warm water of about 60 to 100°C.
The resulting PGA-DEQ ion complex was frozen at −80° C. overnight, then transferred to a freeze dryer and dried until no weight loss occurred.

Test Example 1: Adhesiveness Test to Wood Using a tensile tester, the adhesive strength of the PGA-DEQ ion complex powder produced in Example 1 and the PGA-HDP ion complex powder produced in Example 2 was measured. Specifically, the PGA-DEQ ion complex is softened by adding hot water at 90° C. that is double the mass and heating for 15 minutes, then applying it to the wood material and overlapping it with another wood material. , 90° C. and 0.1 MPa for 5 minutes. It was then allowed to stand for 48 hours.
The PGA-HDP ion complex was added as a solid to the surface of the wooden material to be adhered, overlapped with another wooden material, and heat-pressed in the same manner. After that, it was allowed to stand still for 48 hours.
The wooden material adhered as described above was fixed to a tensile tester, and the adhesion strength was measured. Table 1 shows the results.

As shown in Table 1, the PGA-DEQ ion complex according to the present invention exhibited adhesive strength equivalent to that of vinyl acetate resin-based emulsion adhesives, which are commercially available synthetic adhesives.
On the other hand, since the adhesive strength of the PGA-HDP ion complex according to the present invention was relatively low, it is conceivable to apply it to adhesion such as food packaging where peeling is assumed.

Test Example 2: Adhesion Test to Ceramics A porcelain pestle with a length of about 18 cm ("Product number: 6-549-04" manufactured by AS ONE, SiO ₂ : about 67%, Al ₂ O ₃ : about 21%) was pressed with a blunt instrument. It was cut at the central portion by applying an impact using a tool (FIG. 1(1)). The PGA-DEQ ion complex powder (0.1 g) produced in Example 1 was softened by exposure to hot water for 30 seconds, and applied to one of the broken surfaces of a pestle at a rate of 20 mg/cm ² (Fig. 1 (1 )). Then, both fractured surfaces were manually crimped and allowed to stand at room temperature for 24 hours (FIG. 1(2)).
When 5.0 g of activated carbon was placed in a mortar and pulverized with a pestle attached thereto, fine particles were obtained without any problem (Fig. 1 (3)).

Test Example 3: Adhesion Durability Test 30 mg of a cyanoacrylate-based general work adhesive (“Aron Alpha” manufactured by Toagosei Co., Ltd., JIS S 6040 Type 6 A) was applied to a cross section of about 1 cm ² of the combination of adherends shown in FIG. Dropped and adhered. Note that the adhesive was dropped or applied to the cross section of X of the combination "X/Y" of the adherends shown in FIGS. Five adhesive samples were prepared for each combination.
The obtained adhesive sample was placed in a small environmental tester (“SH-262” manufactured by Espec Co., Ltd.), incubated at a temperature of 85° C. and a humidity of 95%, taken out every day, and tested for durability. Specifically, the number of samples in which only one adherend was grasped and lifted, and the other adherend was peeled off and dropped was determined, and the adhesion retention rate was calculated by the following formula. The results are shown in FIG.
Adhesion maintenance rate (%) = 100 - [(number of peeled samples) / 5] x 100

In addition, a similar test was performed using a PGA-DEQ ion complex or a PGA-HDP ion complex instead of the cyanoacrylate-based general working adhesive.
Specifically, hot water at 60 to 100° C. was added to 30 mg of each ion complex, and heated for 20 to 60 seconds until softened. After softening, it was applied to a cross section of 1 cm ² of the adherend X in the combination X/Y of the adherends shown in FIG. 3 or FIG. Then, the adhesion retention rate was calculated. The results for the PGA-DEQ ion complex are shown in FIG. 3, and the results for the PGA-HDP ion complex are shown in FIG. 2 to 4, "PET" represents polyethylene terephthalate, "PC" represents polycarbonate, and "wood" represents cypress (Chamaecyparis obtusa).

As the results shown in FIG. 2, in the case of the commercially available cyanoacrylate-based general work adhesive, peeling of the adhesive sample began to be observed in more than half of the combinations of adherends two or three days after the start of the test. Some adhesive samples had all 5 peeled off after ~5 days.
On the other hand, as shown in the results shown in FIG. 3, in the case of the PGA-DEQ ion complex, no peeling was observed in any of the adhesive samples until the third day, and finally all five adhesive samples were peeled off. It was only a combination of wood.
As the results shown in FIG. 4, in the case of the PGA-HDP ion complex, no peeling was observed in any of the adhesive samples.
From the above results, it was clarified that the adhesive according to the present invention is remarkably superior in adhesion durability to the commercially available cyanoacrylate-based general working adhesive.

Claims

An adhesive comprising poly-γ-glutamic acid and a pyridinium compound represented by the following formula (I) as active ingredients.

[In the formula,
X represents a heteroaromatic ring group optionally having a substituent α and containing a pyridinium ring;
R 1 represents a C 6-20 monovalent aliphatic hydrocarbon group or a group represented by the following formula (II),

(Wherein, Y represents a heteroaromatic ring group which may have a substituent β and contains a pyridinium ring, R 2 represents a C 6-20 divalent aliphatic hydrocarbon group, and the substituent β represents one or more substituents selected from the group consisting of C 1-6 alkyl groups, C 1-6 alkoxy groups, hydroxyl groups, amino groups, halogeno groups, cyano groups, and nitro groups.)
Substituent α represents one or more substituents selected from the group consisting of a C 1-6 alkyl group, a C 1-6 alkoxy group, a hydroxyl group, an amino group, a halogeno group, a cyano group and a nitro group. ]
R 1 is a C 10-20 monovalent aliphatic hydrocarbon group, and the molar ratio of the pyridinium compound represented by the above formula (I) to glutamic acid constituting poly-γ-glutamic acid is 0.8 or more and 1.2 The adhesive according to claim 1, wherein:
R 1 is a group represented by the above formula (II), and the molar ratio of the pyridinium compound represented by the above formula (I) to glutamic acid constituting poly-γ-glutamic acid is 0.4 or more and 0.6 or less. The adhesive according to claim 1, wherein
The adhesive according to any one of claims 1 to 3, wherein X is a pyridinium group optionally having a substituent α.
The adhesive according to any one of claims 1 to 4, wherein X is a quinolinium group optionally having a substituent α, and Y is a quinolinium group optionally having a substituent β.
A method for bonding two adherends comprising:
softening the adhesive on the surface of at least one adherend or depositing the softened adhesive on the surface of at least one adherend; and
A step of crimping one adherend to the softened adhesive on the surface of the other adherend,
A method, wherein the adhesive contains poly-γ-glutamic acid and a pyridinium compound represented by the following formula (I) as active ingredients.

[In the formula,
X represents a heteroaromatic ring group optionally having a substituent α and containing a pyridinium ring;
R 1 represents a C 6-20 monovalent aliphatic hydrocarbon group or a group represented by the following formula (II),

(Wherein, Y represents a heteroaromatic ring group which may have a substituent β and contains a pyridinium ring, R 2 represents a C 6-20 divalent aliphatic hydrocarbon group, and the substituent β represents one or more substituents selected from the group consisting of C 1-6 alkyl groups, C 1-6 alkoxy groups, hydroxyl groups, amino groups, halogeno groups, cyano groups, and nitro groups.)
Substituent α represents one or more substituents selected from the group consisting of a C 1-6 alkyl group, a C 1-6 alkoxy group, a hydroxyl group, an amino group, a halogeno group, a cyano group and a nitro group. ]
R 1 is a C 10-20 monovalent aliphatic hydrocarbon group, and the molar ratio of the pyridinium compound represented by the above formula (I) to glutamic acid constituting poly-γ-glutamic acid is 0.8 or more and 1.2 7. The method of claim 6, wherein:
R 1 is a group represented by the above formula (II), and the molar ratio of the pyridinium compound represented by the above formula (I) to glutamic acid constituting poly-γ-glutamic acid is 0.4 or more and 0.6 or less. 7. The method of claim 6, wherein
The method according to any one of claims 6 to 8, wherein X is a pyridinium group optionally having a substituent α.
The method according to any one of claims 6 to 9, wherein X is a quinolinium group optionally having a substituent α, and Y is a quinolinium group optionally having a substituent β.
The method according to any one of claims 6 to 10, wherein the adhesive is softened under hydrothermal conditions.
The method according to claim 11, wherein the adhesive is softened by steam or steam.