JP7575753B2 - Ion composite material containing lignosulfonic acid, ε-polylysine and a compound having an aldehyde group - Google Patents

Description

The present invention relates to an ionic composite material that combines lignin sulfonic acid, an anionic polymer derived from wood, ε-polylysine (hereinafter sometimes referred to as ε-PL), and a compound having an aldehyde group.

Conventionally, in order to effectively utilize plant biomass, attempts have been made to utilize lignin or its derivatives, which are one of the main components constituting a plant body, as a moldable material. For example, Patent Document 1 describes the composite of lignin and a polystyrene resin, and Patent Document 2 describes a moldable ion-complexed clay composition consisting of lignin sulfonic acid, which is a cation-exchange type (i.e., anionic) polymer, and an anion-exchange type (i.e., cationic) clay mineral. In addition, Patent Document 3 describes an electrostatic complex composed of a naturally derived polymer compound capable of forming an organogel containing an organic solvent, and an ion complex containing ε-PL and an anionic surfactant having a sulfonic acid group, which has a water content of 2.0 mass% or less, with the aim of providing an organogel formed from the electrostatic complex.
The present inventors have found that a water-soluble or water-suspendable ion complex formed by mixing lignosulfonic acid, a lignin-derived compound that can be obtained during the production of pulp by the sulfite method or by the sulfuric acid treatment of lignin, with a cationic polymer in an aqueous solvent can be used to obtain an ion composite material that can be molded into various shapes, is highly elastic, and has excellent self-repairing ability (Patent Document 4). Furthermore, the inventors have found that a combination of ε-PL, a cationic polymer produced by a microorganism, and lignosulfonic acid exhibits superior strength and toughness compared to the ion composite material of the combination described in the examples of Patent Document 4 (Patent Document 5).

Japanese Patent Application Laid-Open No. 11-152410 JP 2006-133299 A JP 2018-159064 A JP 2019-112526 A Patent Application No. 2019-013942

Green Chemistry;2016;18(20);5607-5620 Progress in Polymer Science;2014;39(7);1266-1290 Chemical Science;2015;6(11); 6385-6391

The present invention aims to solve the problem of dramatically improving the strength, Young's modulus, and water resistance of a new ionic composite material described in Patent Document 5, which is made of lignosulfonic acid and ε-PL, can be molded into a variety of shapes, and has flexibility and elasticity.

In the course of conducting research into Patent Document 5, the present inventors discovered that a combination of lignosulfonic acid and a compound having an aldehyde group in ε-PL exhibits superior strength, Young's modulus, and water resistance compared to the ionic composite material having the combination described in the examples of Patent Document 5.
The present invention was made based on these findings by the present inventors.

That is, this application provides the following inventions.
[1] An ionic composite material comprising lignin sulfonic acid, a derivative thereof, or a salt thereof, ε-polylysine, a derivative thereof, or a salt thereof, and a compound having an aldehyde group.
[2] The ionic composite material according to [1], characterized in that it has elasticity.
[3] The ionic composite material according to [1] or [2], wherein the salt of lignin sulfonic acid or a derivative thereof is a metal salt.
[4] The ionic composite material according to [3], wherein the metal salt is selected from the group consisting of sodium salts, calcium salts, and magnesium salts.
[5] The ionic composite material according to any one of [1] to [4], wherein the ε-polylysine has a weight average molecular weight of 500 to 1,000,000.
[6] The ionic composite material according to any one of [1] to [5], wherein the compound having an aldehyde group is a saccharide exhibiting reducing property or an aldehyde.
[7] The ionic composite material according to [6], wherein the saccharide exhibiting reducing properties is fructose, arabinose, glucose, lactose, maltose, ribose, xylose, mannose or galactose.
[8] The ionic composite material according to [6], wherein the aldehyde is an aliphatic dialdehyde or an aliphatic aldehyde.
[9] The ionic composite material according to [8], wherein the aliphatic dialdehyde is glutaraldehyde.
[10] A method for producing an ionic composite material according to any one of [1] to [9], comprising: a step of mixing lignin sulfonic acid, a derivative thereof, or a salt thereof, ε-polylysine, a derivative thereof, or a salt thereof, and a compound having an aldehyde group in a solvent to form an ionic composite material in the solvent; and a step of removing the solvent from the solvent or suspension containing the ionic composite material.
[11] A solution or suspension containing an ion complex formed from lignin sulfonic acid, a derivative thereof, or a salt thereof, ε-polylysine, a derivative thereof, or a salt thereof, a compound having an aldehyde group, and a solvent.
[12] The solution or suspension according to [11], wherein the solvent is water.
[13] An ion composite material formed of lignin sulfonic acid, a derivative thereof, or a salt thereof, ε-polylysine, a derivative thereof, or a salt thereof, and a compound having an aldehyde group, the material further containing an organic solvent.
[14] An adhesive comprising the ion composite material according to any one of [1] to [9] or the material according to [13].

Specifically, it was confirmed that the combination of lignosulfonic acid, ε-PL and a compound having an aldehyde group exhibited excellent strength, Young's modulus and water resistance.

A photograph of a test specimen punched into the shape of a dumbbell (No. 8, JIS K 6251) obtained from a composite consisting of sodium lignosulfonate, ε-PL, and lactose is shown. The photographs show the results of a water resistance test of a composite consisting of sodium lignosulfonate, ε-PL, and reducing sugar. Photographs showing the results of elasticity evaluation of a composite composed of lignosulfonic acid sodium salt, ε-PL, and fructose are shown.

Lignosulfonic acid is derived from lignin, which is one of the main components constituting plants along with polysaccharides such as cellulose, and is produced as a by-product by sulfonation of lignin when pulp is produced from plants by the sulfite method, for example. In the present invention, the lignosulfonic acid is not particularly limited, and may be the lignosulfonic acid itself produced as a by-product in this manner, or it may be modified lignosulfonic acid or partially desulfonated lignosulfonic acid, which are lignosulfonic acid that has been modified or partially desulfonated.
The modified lignosulfonic acid may be, for example, lignosulfonic acid in which the content of functional groups has been changed by treating lignosulfonic acid with an acid or alkali.
Partially desulfonated lignosulfonic acid refers to lignosulfonic acid in which some of the sulfo groups ( _-SO3H or _-SO3- ⁾ of the lignosulfonic acid have been desulfonated. It is preferable that the desulfonation of the lignosulfonic acid in the entire ionic composite material is the desulfonation of 1% or more of the total sulfo groups in the ionic composite material when it is assumed that partial desulfonation has not occurred.

In the present invention, examples of lignin sulfonic acid derivatives include, but are not limited to, lignin sulfonic acid derivatives obtained by applying the method of modifying the hydroxyl groups of lignin with polyethylene glycol described in Non-Patent Document 1, lignin sulfonic acid derivatives obtained by applying the method of modifying the hydroxyl groups of lignin with an epoxy group-containing compound described in Non-Patent Document 2, and lignin sulfonic acid derivatives obtained by applying the method of modifying the phenolic hydroxyl groups of lignin with a fatty acid or aromatic carboxylic acid described in Non-Patent Document 2.

In the present invention, the salt of lignin sulfonic acid or its derivative is preferably a metal salt, and from the viewpoint of water solubility, the metal salt is preferably selected from the group consisting of sodium salts, calcium salts, and magnesium salts.

The ε-PL used in the present invention is not particularly limited, and may be, for example, one produced by a microorganism or one obtained by chemical synthesis.
The production method using a microorganism is not particularly limited as long as it can produce ε-PL, but for example, a production method using ε-PL-producing bacteria belonging to Streptomyces alblus or Streptomyces noursei can be used, and ε-PL can be isolated and purified from the culture medium of these bacteria. As a chemical synthesis method, for example, the chemical synthesis method described in Non-Patent Document 3 can be used, and ε-PL can be obtained by this chemical synthesis method. In addition, ε-PL can be obtained by using ε-PL synthase derived from ε-PL-producing bacteria.

In addition, ε-PL may have some of its amino groups or carboxyl groups chemically modified via covalent bonds or the like.
Examples of chemically modified compounds include compounds in which the amino group of ε-PL is modified via an amide bond with a carboxyl group-containing compound such as a carboxylic acid or an amino acid, and compounds in which the carboxyl group at the terminal of ε-PL is modified via an amide bond with an amino group-containing compound such as an amine or an amino acid, or compounds in which the carboxyl group at the terminal of ε-PL is modified via an amide bond with a hydroxyl group-containing compound such as an alcohol, or both.
An example of a derivative of ε-PL is ε-PL having a higher molecular weight obtained by dehydration condensation of ε-PL molecules.
From the viewpoint of water solubility, the ε-PL used in the present invention may be an inorganic acid salt such as a hydrochloride or an organic acid salt such as an acetate of the above-mentioned ε-PL.

The structure of lysine forming ε-PL is not particularly limited, and may be any of those consisting of only L-lysine, those consisting of only D-lysine, and those containing both. In addition, the ratio of L-lysine to D-lysine is not particularly limited.
The degree of polymerization of ε-PL is not particularly limited, but is preferably a pentamer or more, and the weight average molecular weight is preferably 500 to 1,000,000, and more preferably 1,000 to 10,000.

The compound having an aldehyde group used in the present invention is not particularly limited as long as it has an aldehyde group, but examples include sugars and aldehydes that exhibit reducing properties.

Examples of reducing sugars include fructose, arabinose, glucose, lactose, maltose, ribose, xylose, mannose, galactose, dihydroxyacetone, ribulose, psicose, erythrose, and oligosaccharides and polysaccharides containing these sugars. Preferred are fructose, arabinose, glucose, lactose, maltose, ribose, xylose, mannose, or galactose, more preferred are fructose, arabinose, glucose, or lactose, and particularly preferred are fructose or arabinose.
In the present invention, oligosaccharides refer to oligosaccharides, which are formed by linking 2 to 10 monosaccharides via glycosidic bonds, but are not limited thereto, and polysaccharides are formed by linking at least two monosaccharides via glycosidic bonds. Oligosaccharides are included in the category of polysaccharides.

Aldehydes include, for example, aliphatic dialdehydes, aliphatic aldehydes, or aromatic aldehydes.
An example of the aliphatic dialdehyde is glutaraldehyde.
Examples of aliphatic aldehydes include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, pentanal, hexanal, heptanal, octanal, nonanal, decanal, undecanal, dodecanal, glyceraldehyde, isovaleric aldehyde, and crotonaldehyde.
Examples of aromatic aldehydes include salicylaldehyde, cinnamaldehyde, furfural, methylfurfural, naphthaldehyde, phenylbenzaldehyde, acetoxybenzaldehyde, methoxybenzaldehyde, tolualdehyde, and syringaldehyde.
The aldehyde is preferably glutaraldehyde or butyraldehyde.

"Containing lignosulfonic acid, its derivatives, or their salts, ε-PL, its derivatives, or their salts, and a compound having an aldehyde group" can further include any other components other than "lignosulfonic acid, its derivatives, or their salts, ε-PL, its derivatives, or their salts, and a compound having an aldehyde group." It can also consist only of "lignosulfonic acid, its derivatives, or their salts, ε-PL, its derivatives, or their salts, and a compound having an aldehyde group."

The composition ratio of lignosulfonic acid, its derivatives, or salts thereof to ε-PL, its derivatives, or salts thereof in the ion composite material is not particularly limited, but the weight ratio of the weight of lignosulfonic acid or the weight of a derivative of lignosulfonic acid, a salt of lignosulfonic acid, or a salt of a derivative of lignosulfonic acid in lignosulfonic acid equivalent to the weight of ε-PL or the weight of a derivative of ε-PL, a salt of ε-PL, or a salt of a derivative of ε-PL in ε-PL equivalent is preferably 1:10 to 10:1, and more preferably 1:4 to 4:1.
The weight of the compound having an aldehyde group in the ionic composite material is preferably 1/100 to 1/2, and more preferably 1/100 to 1/10, of the total weight of lignosulfonic acid, or the weight of a derivative of lignosulfonic acid, a salt of lignosulfonic acid, or the weight of a salt of a derivative of lignosulfonic acid in terms of lignosulfonic acid, and the weight of ε-PL, or the weight of a derivative of ε-PL, a salt of ε-PL, or the weight of a salt of a derivative of ε-PL in terms of ε-PL.

The water content in the ionic composite material is 3 to 95% by weight, preferably 5 to 40% by weight, and more preferably 10 to 30% by weight of the entire ionic composite material. This water content allows the ionic composite material to have elasticity.
The moisture content is adjusted by holding a solution or suspension containing an ionic complex formed by lignosulfonic acid, its derivatives, or their salts, ε-PL, its derivatives, or their salts, and a compound having an aldehyde group in the atmosphere or under controlled humidity conditions. In this case, evaporation of moisture may be promoted by heating using a thermostatic bath or a hot plate. Alternatively, the solution or suspension containing this ionic complex may be dropped into an organic solvent to obtain a complex precipitation, and the obtained complex may be held in the atmosphere or under controlled humidity conditions as necessary to adjust the moisture content.

In the present invention, "having elasticity" refers to a property in which, when a dumbbell-shaped test piece (No. 8, JIS K 6251) is cut out from a material, tension is applied to the test piece, and the dumbbell-shaped test piece is deformed to a degree that does not break, or is deformed until it breaks, and then the tension is completely removed and the test piece is left to stand for a specified time, the amount of deformation after standing is 50% or less of the maximum deformation when tension is applied. It is preferable that the amount of deformation after standing is 30% or less of the maximum deformation when tension is applied. The specified standing time from when tension is completely removed until the deformation of the test piece is measured is not particularly limited, but it is preferable to leave it to stand for at least about 1 hour in order to properly evaluate the elasticity. Specifically, it may be 1 hour, 72 hours, or longer.

The ionic composite material of the present invention has excellent toughness. Here, toughness is an index of the tenacity of a material and is expressed by the area under the stress-strain curve.

The ionic composite material of the present invention can be processed into, for example, a sheet. The thickness of the sheet is not particularly limited, but is preferably 1 to 10 mm.

Another aspect of the present invention is a method for producing an ionic composite material, comprising the steps of mixing lignosulfonic acid, a derivative thereof, or a salt thereof, ε-PL, a derivative thereof, or a salt thereof, and a compound having an aldehyde group in a solvent to form an ionic composite in the solvent, and removing the solvent from a solution or suspension containing the ionic composite.
The step of forming an ion complex is not particularly limited, and may be, for example, a step of forming an ion complex by mixing lignosulfonic acid, a derivative thereof, or a salt thereof, ε-PL, a derivative thereof, or a salt thereof, and a compound having an aldehyde group in a solvent, or a step of forming an ion complex by mixing a solution containing lignosulfonic acid, a derivative thereof, or a salt thereof, a solution containing ε-PL, a derivative thereof, or a salt thereof, and a solution containing a compound having an aldehyde group.
In the step of forming an ion complex, the order in which the components are mixed and the mixing conditions for the components, such as temperature, humidity, and time, are not particularly limited as long as a significantly non-uniform composition is not formed.
The step of removing the solvent is, for example, a step of removing the solvent from a solution or suspension containing the ion complex by volatilization, or, in the case where the solvent is water, a step of introducing the aqueous solution or aqueous suspension into an organic solvent to precipitate the ion complex in the organic solvent and then removing the solvent.

The solvent used in the present invention is preferably water or an organic solvent miscible with water, such as methanol, ethanol, isopropyl alcohol, ethylene glycol, glycerin, polyethylene glycol, formic acid, acetic acid, propionic acid, acetone, acetonitrile, tetrahydrofuran, dimethylsulfoxide, dimethylformamide, or dioxane, with water being particularly preferred.

Another embodiment of the present invention is a solution or suspension containing an ionic complex formed in a solvent by mixing lignosulfonic acid, a derivative thereof, or a salt thereof, ε-PL, a derivative thereof, or a salt thereof, and a compound having an aldehyde group in the solvent.
The solution or suspension containing the ion complex can be prepared, for example, by mixing aqueous solutions of lignosulfonic acid, its derivatives, or their salts, ε-PL, its derivatives, or their salts, and a compound having an aldehyde group, or by mixing powder of lignosulfonic acid, its derivatives, or their salts with an aqueous solution of ε-PL, its derivatives, or their salts, and a compound having an aldehyde group.
The solution or suspension containing the ion complex thus prepared is placed on a flat plate such as a petri dish, and the solvent is then evaporated to obtain a sheet-like ion complex.

In addition, when the solvent is water, the ion complex can be recovered as a precipitate by adding an aqueous solution or aqueous suspension containing the ion complex prepared in this manner to an organic solvent.

By conducting a tensile test on the obtained ionic complex, the maximum stress (breaking strength) and Young's modulus (elastic modulus) can be measured. In addition, based on the results of the tensile test, the toughness, which is expressed as the area under the stress-strain curve, can be calculated.

The level of water resistance of the ion complex can be determined by conducting a water resistance test on the obtained ion complex. That is, a test piece of a given mass is cut out from the ion complex, immersed in pure water, and shaken for a given period of time. The less coloring of the supernatant after the given period of time, the less the amount of sodium lignosulfonate dissolved from the ion complex, which indicates that the ion complex has a high water resistance.

Another aspect of the present invention is an adhesive comprising an ionic composite material containing lignosulfonic acid, a derivative thereof, or a salt thereof, ε-PL, a derivative thereof, or a salt thereof, and a compound having an aldehyde group.

The moisture content in the adhesive is not particularly limited, but is usually 0.1 to 95% by weight, preferably 2 to 30% by weight.

The adhesive of the present invention can be a one-component adhesive or an adhesive consisting of a single agent. By using a one-component adhesive or an adhesive consisting of a single agent, there is less uneven application during bonding compared to two-component adhesives, and more stable and strong bonding can be achieved.

The adhesive of the present invention containing lignosulfonic acid, its derivatives, or their salts, ε-PL, its derivatives, or their salts, and a compound having an aldehyde group can be prepared by mixing these by an appropriate method. There are no particular limitations on the order in which the components are mixed, or on the mixing conditions for the composition, such as temperature, humidity, or time, as long as a significantly non-uniform composition is not formed.

The adhesive can be used, for example, by placing or applying the ionic complex prepared by the above method on the substrate to be bonded, and then sandwiching the ionic complex between the substrates to bond them together. The substrate is not particularly limited, and examples of the substrate that can be used include stainless steel plates, aluminum plates, polypropylene plates, and wood plates.
Preferably, bonding can be performed by applying pressure while heating using a device such as a hot press, which allows strong bonding to be achieved more quickly. In the hot press device, the heating temperature is not particularly limited, but is, for example, 50 to 110°C. The pressure is not particularly limited, but is, for example, 0.01 to 10 MPa, or 0.05 to 0.5 MPa. The heating and pressurizing time is not particularly limited, but is, for example, 30 seconds to 3 minutes.
Furthermore, after sandwiching the ion complex between the substrates, or after heating and pressurizing with a hot press device, an operation for volatilizing the solvent may be performed. In the operation for volatilizing the solvent, the temperature is not particularly limited, but is, for example, 10 to 90°C or ambient temperature. The humidity is not particularly limited, but is, for example, 20 to 80%. The time for volatilizing the solvent is not particularly limited, but is, for example, 1 hour or more.

The adhesive strength test is not particularly limited, but can be carried out, for example, by the following method.
A 9 mg complex of lignosulfonic acid sodium salt, ε-PL, and a compound having an aldehyde group is sandwiched between two substrates (length 5 cm, width 1 cm, thickness 2 mm) so that the overlapping area is 1 ^cm2 . This substrate is heated in a hot press at 80°C and 0.2 MPa for 2 minutes. After cooling the heated substrate in the air, the solvent is evaporated in a thermo-hygrostat at 30°C and 50% humidity for more than 24 hours.
The resulting bonded substrate is subjected to a tensile test to measure the tensile shear adhesive strength (maximum stress), which can be used as an index of adhesive strength.

Next, the present invention will be explained in more detail using examples, but the present invention is not limited to these examples.

Example 1 Preparation of a Complex Consisting of Sodium Lignosulfonate, ε-PL, and Lactose 2 g of Pearlex NP (high-purity, high-molecular-weight sodium lignosulfonate, manufactured by Nippon Paper Industries Co., Ltd.) powder and ε-PL solution (JNC Corporation, 25-35 mer (weight average molecular weight approximately 3,200-4,
500), Lot No. 2160204, 25 wt% aqueous solution) (12 mL) was mixed uniformly. 253 mg of lactose monohydrate (Wako Pure Chemical Industries, Ltd., special grade) was mixed with the resulting homogeneous mixture and stirred until the lactose was completely dissolved. This mixture was transferred to a fluororesin petri dish (size: 6 cm x 6 cm) and the solvent was evaporated to obtain a sheet-like composite with a thickness of 1 mm or more. The obtained sheet-like composite was punched into the shape of a dumbbell-shaped test piece (No. 8, JIS K 6251) and a photograph of the test piece is shown in Figure 1.

Example 2 Preparation of a complex consisting of sodium lignosulfonate, ε-PL, and glucose Using 2 g of the Pearlex NP powder used in Example 1, 12 mL of ε-PL solution, and 240 mg of D-glucose (Wako Pure Chemical Industries, Ltd., special grade), a complex was prepared in the same manner as in Example 1, and a sheet-like complex was obtained. The appearance of the obtained complex was almost the same as that of the complex obtained in Example 1.

Example 3 Preparation of a Complex Consisting of Sodium Lignosulfonate, ε-PL, and Arabinose Using 2 g of the Pearlex NP powder used in Example 1, 12 mL of ε-PL solution, and 240 mg of D-(-)-arabinose (Tokyo Chemical Industry Co., Ltd.), a complex was prepared in the same manner as in Example 1 to obtain a sheet-like complex. The appearance of the obtained complex was almost the same as that of the complex obtained in Example 1.

Example 4 Preparation of a Complex Consisting of Lignosulfonic Acid Sodium Salt, ε-PL, and Fructose Using 2 g of the Pearlex NP powder used in Example 1, 12 mL of ε-PL solution, and 240 mg of D-(-)-fructose (Wako Pure Chemical Industries, Ltd., special grade), a complex was prepared in the same manner as in Example 1 to obtain a sheet-like complex. The appearance of the obtained complex was almost the same as that of the complex obtained in Example 1.

Example 5 Preparation of a composite consisting of lignosulfonic acid sodium salt, ε-PL, and glutaraldehyde 7.68 mL of a 25 wt% aqueous solution of Pearlex NP used in Example 1 and 192 μL of an aqueous solution of glutaraldehyde (50% solution, Polysciences) were mixed uniformly. 11.52 mL of a 25 wt% aqueous solution of ε-PL used in Example 1 was added to this solution and mixed uniformly. This mixture was transferred to a fluororesin petri dish (size: 6 cm x 6 cm) and the solvent was volatilized to obtain a sheet-like composite with a thickness of 1 mm or more. The appearance of the obtained composite was almost the same as that of the composite obtained in Example 1.

Example 6 Preparation of a composite consisting of lignosulfonic acid sodium salt, ε-PL, and butyraldehyde 7.68 mL of a 25 wt% aqueous solution of Pearlex NP used in Example 1 and 240 μL of butyraldehyde (Wako Pure Chemical Industries, Ltd., special grade) were mixed uniformly. 11.52 mL of a 25 wt% aqueous solution of ε-PL used in Example 1 was added to this solution and mixed uniformly. This mixture was transferred to a fluororesin petri dish (size: 6 cm x 6 cm) and the solvent was volatilized to obtain a sheet-like composite with a thickness of 1 mm or more. The appearance of the obtained composite was almost the same as that of the composite obtained in Example 1.

Comparative Example 1 Preparation of a composite consisting of sodium lignosulfonate and ε-PL 2 g of the Pearlex NP powder used in Example 1 and 12 mL of the ε-PL solution were mixed uniformly. This mixture was transferred to a fluororesin petri dish (size: 6 cm x 6 cm) and the solvent was evaporated to obtain a sheet-like composite with a thickness of 1 mm or more. The appearance of the obtained composite was almost the same as that of the composite obtained in Example 1.

Comparative Example 2 Preparation of a Complex Consisting of Lignosulfonic Acid Sodium Salt, ε-PL, and Sucrose (Non-reducing Sugar) Using 2 g of the Pearlex NP powder used in Example 1, 12 mL of ε-PL solution, and 240 mg of sucrose (Wako Pure Chemical Industries, Ltd., special grade), a complex was prepared in the same manner as in Example 1 to obtain a sheet-like complex. The appearance of the obtained complex was almost the same as that of the complex obtained in Example 1.

Example 7 Tensile test of composites consisting of lignosulfonic acid sodium salt, ε-PL and a compound having an aldehyde group The sheet-like composites prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were left to stand for 5 days in a thermohygrostat at 30°C and a relative humidity of 50%, and then punched out into the shape of dumbbell-shaped test pieces (No. 8, JIS K 6251) to prepare test pieces for evaluation. The results of tensile tests (in air, tensile speed 50 mm/min) using these test pieces are shown in Table 1 (average value of 3 to 5 tests).
As shown in Table 1, it was confirmed that the maximum stress of the test pieces of Examples 1 to 6 was improved by 1.5 to 5.2 times compared to the test piece of Comparative Example 1. In other words, it was shown that the ion complex mixed with the compound having an aldehyde group has a significantly improved breaking strength.
Moreover, it was confirmed that the Young's modulus of the test pieces of Examples 1 to 6 was improved by 1.4 to 7.3 times compared to the test piece of Comparative Example 1. In other words, it was shown that the Young's modulus of the ionic complex mixed with a compound having an aldehyde group is significantly improved.
On the other hand, in Comparative Example 2, there was a slight improvement in toughness compared to the sample in Comparative Example 1 (1.
1x) but no improvement in maximum stress or Young's modulus was confirmed. In other words, it was confirmed that the ionic complex mixed with non-reducing sugar does not have a significant effect on improving physical properties such as breaking strength or Young's modulus, unlike the ionic complex mixed with reducing sugars or aldehydes.

Example 8 Water resistance test of complexes composed of sodium lignosulfonate, ε-PL and reducing sugar A 60 mg test piece was cut out from the sheet-like complexes prepared in Examples 2 to 4 and Comparative Examples 1 and 2. The test piece was immersed in 1.2 mL of pure water and shaken at room temperature for 6 hours to carry out a water resistance test. The less colored the supernatant, the less the amount of sodium lignosulfonate dissolved in the ionic complex, i.e., the higher the water resistance of the ionic complex.
The results of the water resistance test are shown in Figure 2. After shaking in pure water for 6 hours, the ionic complexes of Comparative Examples 1 and 2 were completely dissolved, whereas the ionic complexes of Examples 2 to 4 were not completely dissolved. In other words, it was found that the use of fructose, arabinose or glucose, which are reducing sugars, showed a remarkable effect in terms of the water resistance of the ionic complexes.

Example 9: Elasticity evaluation of a composite of sodium lignosulfonate, ε-PL, and fructose. The composite of sodium lignosulfonate, ε-PL, and fructose that broke in the tensile test in Example 7 was left to stand for 72 hours or more, and the morphology of the composite was compared with that of a sample that had not been subjected to a tensile test. In the tensile test, the sample broke within 50% (fixture distance).
Although a strain of more than 35 mm × 50% = 17.5 mm) was applied to the portion between the jigs, causing deformation, the amount of deformation of the portion between the jigs of the sample after it was left to rest was less than 10% (3.5 mm) of the distance between the jigs of the sample before the tensile test. In other words, the length of the sample left to rest after the tensile test spontaneously recovered to the same length as the sample before the tensile test, demonstrating that this composite has elasticity.

Example 10: Adhesion of stainless steel plates by a complex of lignosulfonic acid sodium salt, ε-PL and fructose 0.6 mL of a 25 wt% aqueous solution prepared by dissolving Pearlex NP used in Example 1 in pure water, 1.4 mL of a 25 wt% aqueous solution of ε-PL used in Example 1 and 50 mg of D-(-)-fructose used in Example 4 were mixed. This mixture was transferred to a fluororesin petri dish and heated on a hot plate at 150°C to remove moisture, thereby obtaining a viscous complex. Approximately 9 mg of the obtained complex was sandwiched between two stainless steel plates (length 5 cm, width 1 cm, thickness 2 mm) so that the overlapping area was 1 ^cm2 . The stainless steel plates were heated at 80°C and 0.2 MPa for 2 minutes in a hot press. After cooling the heated stainless steel plates in the air, the solvent was volatilized in a constant temperature and humidity chamber at 30°C and 50% humidity for more than 24 hours, thereby adhering the stainless steel plates to each other. After bonding, a tensile test was conducted (in air, tensile speed 10 mm/min) using the stainless steel plate, and the tensile shear adhesive strength was measured, which was 7.06±0.47.
MPa (average value of three measurements).

Comparative Example 3 Adhesion of stainless steel plate with a complex of lignosulfonic acid sodium salt and ε-PL 0.6 mL of a 25 wt% aqueous solution of Pearlex NP used in Example 10 and 1.4 mL of a 25 wt% aqueous solution of ε-PL were mixed, and the mixture was heated on a hot plate at 150°C in the same manner as in Example 10 to obtain a viscous complex. Approximately 9 mg of the resulting complex was used to bond a stainless steel plate in the same manner as in Example 10. A tensile test (in air, tensile speed 10 mm/min) was performed using the stainless steel plate after bonding, and the tensile shear adhesive strength was measured, which was 5.80 ± 0.40 MPa (average value of three tests).

From the results of Example 10 and Comparative Example 3, it was confirmed that the test piece of Example 10 had an approximately 1.2-fold improvement in tensile shear adhesive strength compared to the test piece of Comparative Example 3. In other words, it was shown that the composite obtained by mixing lignosulfonic acid sodium salt and ε-PL with fructose had improved tensile shear adhesive strength compared to the composite made of lignosulfonic acid sodium salt and ε-PL.

The ionic composite material of the present invention can be molded into a variety of shapes, is highly elastic, and has excellent strength, toughness, and water resistance, so it can be used as a material for molded products for a variety of applications where such properties are required.

Claims (12)

(1) lignosulfonic acid, a derivative thereof, or a salt thereof; (2) ε-polylysine;
(3) an ion complex material containing a saccharide or an aldehyde exhibiting reducing properties ,
An ion complex material, wherein the reducing saccharide is fructose, arabinose, glucose, or lactose. The ionic composite material according to claim 1, characterized by having elasticity. The ionic composite material according to claim 1 or 2, wherein the salt of lignosulfonic acid or a derivative thereof is a metal salt. The ionic composite material of claim 3, wherein the metal salt is selected from the group consisting of sodium salts, calcium salts, and magnesium salts. The ionic complex according to any one of claims 1 to 4, wherein the ε-polylysine has a weight average molecular weight of 500 to 1,000,000. The ionic composite material according to any one of claims 1 to 5, wherein the aldehyde is an aliphatic dialdehyde or an aliphatic aldehyde. 7. The ionic composite material of claim 6, wherein the aliphatic dialdehyde is glutaraldehyde. A method for producing the ionic composite material according to any one of claims 1 to 7, comprising the steps of: mixing (1) lignin sulfonic acid, a derivative thereof, or a salt thereof; (2) ε-polylysine, a derivative thereof, or a salt thereof; and (3) a saccharide or an aldehyde exhibiting reducing properties in a solvent to form an ionic composite material in the solvent; and removing the solvent from the solvent or suspension containing the ionic composite material. (1) lignosulfonic acid, a derivative thereof, or a salt thereof; (2) ε-polylysine;
A solution or suspension containing an ion complex formed by the above-mentioned compound or a derivative thereof or a salt thereof, (3) a sugar or an aldehyde exhibiting reducing properties , and (4) a solvent ,
A solution or suspension, wherein the reducing sugar is fructose, arabinose, glucose, or lactose. The solution or suspension of claim 9, wherein the solvent is water. (1) lignosulfonic acid, a derivative thereof, or a salt thereof; (2) ε-polylysine;
(3) a saccharide or aldehyde exhibiting reducing properties, and (4) an organic solvent ,
The material, wherein the reducing sugar is fructose, arabinose, glucose, or lactose. An adhesive comprising an ionic composite material according to any one of claims 1 to 7 or a material according to claim 11.

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