JP7673353B2 - Ion Complexes - Google Patents

Description

The present invention relates to an ion complex.

For the purpose of effective utilization of plant biomass, attempts have been made widely to use lignin or its derivatives, which are one of the main components constituting plants, as moldable materials. Lignosulfonic acid is a lignin-derived compound that can be obtained during pulp production using the sulfite method or by sulfuric acid treatment of lignin, and attempts have been made to use it as a moldable material like lignin. Lignosulfonic acid is an anionic polymer that has many sulfo groups, which are anionic functional groups, in the molecule, and has high hydrophilicity. In general, a method for using such ionic polymers as materials is to combine various anionic polymers with cationic polymers to form ionic complexes, and then prepare various materials depending on the properties of the complexes obtained.

Regarding the combination of lignin sulfonic acid and cationic polymers, for example, Patent Document 1 describes an ionic composite material that has moldability, flexibility, elasticity, and self-repairing ability by combining lignin sulfonic acid with a cationic polymer. Patent Document 2 describes an ionic composite clay composition that consists of lignin sulfonic acid, which is a cation exchange type (i.e., anionic) polymer, and an anion exchange type (i.e., cationic) clay mineral.

JP 2019-112526 A JP 2006-133299 A

The ion composite material described in Patent Document 1 is capable of forming a complex in an aqueous system, but the dried molded body has a high humidity response, absorbing moisture in the air and collapsing in shape under high humidity, making it difficult to use industrially as a molding material. The ion composite clay composition described in Patent Document 2 makes it possible to form a molded body and has excellent shape retention in water, but the molded body has poor flexibility and contains solvents such as PEG 400, posing safety issues.

The objective of the present invention is to provide an ion complex that has good moldability in a substantially solvent-free state, has good moisture resistance and shape retention after molding, and contains lignin sulfonic acid, which is a recyclable resource, as a constituent component.

That is, the present invention provides the following [1] to [6].
[1] (A) a lignosulfonic acid compound,
(B) a cationic polymer; and (C) an ionic complex formed from a polyanion.
[2] The ionic complex according to [1], wherein the weight average molecular weight of the polyanion is 3,000 to 1,000,000.
[3] The ionic complex according to [1] or [2], wherein the content of component (C) is 1 to 80% by weight.
[4] The ionic complex according to any one of [1] to [3], wherein the component (C) contains polyacrylic acid or polystyrene sulfonic acid.
[5] The ionic complex according to any one of [1] to [4], wherein the component (A) contains one or more selected from lignin sulfonic acid, polyethylene glycol-derivatized lignin sulfonic acid, and salts thereof.
[6] (A) lignosulfonic acid-based compound,
A method for producing an ionic complex, comprising a mixing step of mixing (B) a cationic polymer, and (C) a polyanion.

According to the present invention, an ion complex having good moldability can be provided, which can be molded into various shapes by removing the solvent by drying, etc. In the molded state, the ion complex can exhibit good moisture resistance and shape retention, and can also exhibit good flexibility.

1. Ion Complexes
The ionic complex is formed from components (A) to (C), which allows it to exhibit solubility or suspendability in a solvent. Each component will be described below.

[1.1 Component (A): Structural unit derived from lignosulfonic acid compound]
-Lignosulfonic acid compounds-
The lignin sulfonic acid compound is a compound having a skeleton in which a carbon atom at the α-position of the side chain of the hydroxyphenylpropane structure of lignin is cleaved to introduce a sulfo group. The structure of the skeleton is shown in formula (1).

The lignosulfonic acid compound may be a modified product of a compound having the skeleton represented by the above formula (1) (hereinafter, also referred to as a "modified lignosulfonic acid compound"). The modification method is not particularly limited, but examples include chemical modification methods such as hydrolysis, alkylation, alkoxylation, sulfonation, sulfonate esterification, sulfomethylation, aminomethylation, desulfonation, and polyethylene glycolation; and a method of molecular weight fractionation of the lignosulfonic acid compound by ultrafiltration. Of these, the chemical modification method is preferably one or more reactions selected from hydrolysis, alkoxylation, desulfonation, alkylation, and polyethylene glycolation.

In the case of lignosulfonic acid modified with polyethylene glycol (polyethylene glycol-derivatized lignosulfonic acid), the molecular weight of the polyethylene glycol used for modification is preferably 1000 to 5000, more preferably 1500 to 4000, and even more preferably 2000 to 3000. The ratio of polyethylene glycol in the polyethylene glycol-modified lignosulfonic acid (polyethylene glycol ratio) is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more. The upper limit is usually 70% or less.

The lignin sulfonic acid compound may be in the form of a salt. Examples of salts include monovalent metal salts, divalent metal salts, ammonium salts, and organic ammonium salts. Of these, calcium salts, magnesium salts, sodium salts, and mixed calcium-sodium salts are preferred.

There are no particular limitations on the manufacturing method or origin of lignosulfonic acid compounds, and either natural or synthetic products can be used. Lignosulfonic acid compounds are one of the main components of the waste liquor of sulfite pulp obtained by cooking wood under acidic conditions. For this reason, lignosulfonic acid compounds derived from sulfite pulp waste liquor can also be used.

Lignin sulfonic acid compounds (modified lignin sulfonic acid compounds) are abundantly contained in commercially available products, and such commercially available products may be used in the present invention. Examples of commercially available products include Sunex P252 (manufactured by Nippon Paper Industries Co., Ltd.), Sunex M (manufactured by Nippon Paper Industries Co., Ltd.), Pearlex NP (manufactured by Nippon Paper Industries Co., Ltd.), Sunflow RH (manufactured by Nippon Paper Industries Co., Ltd.), sodium lignin sulfonate (manufactured by Tokyo Chemical Industry Co., Ltd.), sodium lignin sulfonate (manufactured by Merck), and calcium lignin sulfonate (manufactured by Merck).

However, it is difficult to uniformly specify the chemical structure of lignosulfonic acid using a general formula or other method. This is because lignin, the backbone of lignosulfonic acid compounds, has an extremely complex molecular structure.

- Molecular weight of lignosulfonic acid compounds -
The weight average molecular weight of the lignin sulfonic acid compound is not particularly limited, but is preferably 5,000 to 300,000, more preferably 10,000 to 100,000. If the weight average molecular weight is less than 5,000, the complexability with the cationic polymer deteriorates, and the ionic complex becomes non-uniform. If the weight average molecular weight exceeds 300,000, the moldability of the ionic complex deteriorates. The weight average molecular weight in this specification can be measured by a known method using gel permeation chromatography (GPC) in terms of polyethylene glycol.

The measurement conditions for GPC are not particularly limited, but the following conditions can be exemplified.
Measurement equipment: Tosoh Columns used: Shodex Column OH-pak SB-806HQ, SB-804HQ, SB-802.5HQ
Eluent: 0.05 mM sodium nitrate/acetonitrile 8/2 (v/v)
Standard substance: polyethylene glycol (manufactured by Tosoh or GL Sciences)
Detector: Differential refractometer (manufactured by Tosoh)

Component (A) may be one type of lignin sulfonic acid compound, or a combination of two or more types that differ in molecular weight, production method, origin, etc.

--Content of component (A)--
The content of the (A) component is not particularly limited, and may be appropriately adjusted depending on the composition, type, and amount of the ionic complex. As an example, the content is preferably 5% by weight or more, more preferably 10% by weight or more, and even more preferably 15% by weight or more, based on 100% by weight of the ionic complex. The upper limit is preferably 70% by weight or less, more preferably 60% by weight or less, and even more preferably 50% by weight or less. This makes it possible to suppress a decrease in the moldability of the ionic complex. Therefore, the content of the (A) component is preferably 5 to 70% by weight, more preferably 10 to 60% by weight, and even more preferably 15 to 50% by weight.

[1.2 Component (B): Cationic polymer]
-Cationic polymer-
Examples of the cationic polymer used in the present invention include polymers having at least one functional group selected from the group consisting of primary, secondary, and tertiary amino groups, quaternary ammonium groups, and imino groups, and polymers consisting of structural units derived from a single monomer having at least one functional group selected from the group consisting of primary, secondary, and tertiary amino groups, quaternary ammonium groups, and imino groups are preferred. Examples of the cationic polymer include poly(ethyleneimine), poly(allylamine), poly(diallyldimethylammonium chloride), chitosan, cationized cellulose, cationized carboxymethylcellulose, cationized starch, cationized hyaluronic acid, cationized guar gum, α-polylysine, ε-polylysine, α-polyornithine, δ-polyornithine, lysine-containing proteins, poly(vinylpyridine), poly(vinyl N-methylpyridine), poly{[3-(methacryloylamino)propyl]trimethylcellulose}. ammonium}, poly[(3-acrylamidopropyl)trimethylammonium], poly{[2-(methacryloyloxy)ethyl]trimethylammonium}, poly{[2-(acryloyloxy)ethyl]trimethylammonium}; cationic polymers in which the primary, secondary, and tertiary amino groups are converted to quaternary ammonium; and cationic polymers having an imino group, such as polyarginine, poly(hexamethylene biguanide), polyhexamethylene guanidine, cyanophycin, and arginine-containing proteins. From the viewpoint of water solubility, the cationic polymer may be an inorganic acid salt such as a hydrochloride, or an organic acid salt such as an acetate, of the above-mentioned polymers.

- Molecular weight of cationic polymer -
The weight average molecular weight of the cationic polymer is not particularly limited, but is preferably 50,000 to 500,000, more preferably 100,000 to 450,000, and even more preferably 150,000 to 400,000.

Component (B) may be one type of cationic polymer, or a combination of two or more types with different molecular weights, structures, etc.

--Content of component (B)--
The content of the (B) component is not particularly limited, and may be appropriately adjusted depending on the composition, type, and amount of the ionic complex. As an example, the content is preferably 5% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more, based on 100% by weight of the ionic complex. The upper limit is preferably 70% by weight or less, more preferably 65% by weight or less, and even more preferably 60% by weight or less. This makes it possible to suppress a decrease in the moldability of the ionic complex. Therefore, the content of the (B) component is preferably 5 to 70% by weight, more preferably 15 to 65% by weight, and even more preferably 20 to 60% by weight.

[1.3 Component (C): Polyanion]
-Polyanion-
The polyanion used in the present invention is not particularly limited as long as it is other than the component (A). For example, a polymer containing an anionic functional group can be mentioned. Examples of the anionic functional group include a sulfo group, a carboxyl group, a phenolic hydroxy group, and a phospho group. The molecular weight of the polyanion is preferably 3,000 to 1,000,000, more preferably 5,000 to 500,000, but is not particularly limited. Examples of the polyanion include a compound having a carboxyl group (e.g., polyacrylic acid) and a compound having a sulfo group (e.g., polystyrene sulfonic acid). The polyanion used in the present invention may be a salt such as a sodium salt, a magnesium salt, a calcium salt, or an ammonium salt from the viewpoint of water solubility.

Component (C) may be one type of polyanion or a mixture of two or more types with different molecular weights, structures, etc.

--Content of component (C)--
The content of the (C) component is not particularly limited, and may be appropriately adjusted according to the composition, type, and amount of the ionic complex. As an example, the content is preferably 1% by weight or more, more preferably 5% by weight or more, relative to 100% by weight of the ionic complex. This can suppress the decrease in moisture resistance of the ionic complex. The upper limit is preferably 80% by weight or more, more preferably 60% by weight or more, even more preferably 50% by weight or more, and even more preferably 40% by weight or more. This can suppress the decrease in moldability of the ionic complex, and can suppress the molded product from becoming brittle. Therefore, the content of the (C) component is preferably 1 to 80% by weight, more preferably 5 to 60% by weight, even more preferably 5 to 50% by weight, and even more preferably 5 to 40% by weight.

[1.4 Optional Components]
The ionic complex may contain optional components other than the components (A) to (C) as necessary, such as antioxidants, preservatives, stabilizers, and solvents.

As the solvent, for example, water; organic solvents that are miscible with water, such as methanol, ethanol, isopropyl alcohol, ethylene glycol, glycerin, polyethylene glycol, formic acid, acetic acid, propionic acid, acetone, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and dioxane, are preferred, and among these, water is preferred from the viewpoint of safety.

1.5 Morphology of Ionic Complexes
The ionic complex may be formed from components (A) to (C) in a form in which the components are bonded together by ionic bonds, hydrogen bonds, or the like, or in a form in which the components are not bonded together.

The ionic complex may be in a liquid state, dissolved or suspended (dispersed) in a solvent (e.g., water), or may be substantially solvent-free (solid state).

2. Method for preparing ionic complexes
The method for preparing the ionic complex may be any method that includes at least a mixing step of mixing the components (A) to (C).

[2.1 Mixing process]
The components (A) to (C) in the mixing step may each be in any form of liquid, powder, or solid, but from the viewpoint of handling, the components are preferably in liquid form.

The order of mixing may be, for example, mixing components (A) and (B), then adding and mixing component (C) to the resulting mixture; mixing components (A) and (C), then adding and mixing component (B) to the resulting mixture; mixing components (B) and (C), then adding and mixing component (A) to the resulting mixture. The mixture may be in a solid or liquid state. Components (A) and (B) are preferably mixed with a solvent before mixing with other components. Addition to the system and mixing may be performed simultaneously (e.g., line mixing).

[2.2 Solvent removal step]
After the mixing step, a solvent removal step may be performed to remove the solvent from the system (from the resulting solution or suspension) as necessary. The solvent can be removed by, for example, drying or precipitation. The drying temperature when drying may be any temperature at which the solvent can be removed. In the case of water, the temperature is preferably 30 to 150° C. The humidity during drying can be appropriately set, for example, in the range of 30 to 70%. This allows humidity adjustment (for example, moisture content of 20% by weight or less, preferably 18% by weight or less, with a lower limit of, for example, 1% by weight or more, preferably 3% by weight or more) to be performed together with drying. As a method for removing the solvent by precipitation, for example, when the solvent is water, a method in which the solution or suspension is put into an organic solvent and the precipitate is collected as an ion complex can be mentioned.

[3. Uses of ion complexes]
The ion complex can exhibit good moisture resistance and shape retention even in a state substantially free of solvent, and also has good flexibility. Therefore, the ion complex can be used as a molded product for various applications. Such applications are suitable for applications where biodegradability is expected, such as agricultural mulch films, architectural cover sheets, planters, etc.

- Evaluation of physical properties -
The shape retention of the ion complex can be evaluated by the following method. The prepared sample is punched into the shape of a dumbbell-shaped test piece (No. 8, JIS K 6251), and a tensile test is performed to measure the maximum stress, Young's modulus, and toughness, and it is confirmed that these measured values are higher than those of a control sample prepared in advance or the target value. The moisture resistance can be confirmed by maintaining the sample under high humidity conditions and measuring the moisture absorption, and it is confirmed that the measured value is higher than those of a control sample prepared in advance or the target value.

The present invention will be explained in more detail below with reference to the following examples. However, the present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the spirit of the above and below descriptions, all of which are within the technical scope of the present invention. In the examples, "%" means % by weight unless otherwise specified. Furthermore, the measurement methods for physical properties, etc. are the same as those described above, unless otherwise specified.

[Ingredients used in the examples]
(1) Component (A): Lignin sulfonic acid compound Lignin 1: TCI reagent sodium lignin sulfonate (powder, lignin sulfonic acid, weight average molecular weight 11,200, manufactured by Tokyo Chemical Industry Co., Ltd.)
Lignin 2: Pearlex NP (powder, high-purity lignin sulfonic acid, weight-average molecular weight 16,100, manufactured by Nippon Paper Industries Co., Ltd.)
Lignin 3: Polyethylene glycol-derivatized lignosulfonic acid 1 (36% aqueous solution, polyethylene glycol-derivatized lignosulfonic acid, weight average molecular weight 38,000, molecular weight of polyethylene glycol 2200, polyethylene glycol ratio 60%, manufactured by Nippon Paper Industries Co., Ltd.)
Lignin 4: Polyethylene glycol derivatized lignosulfonic acid 2 (35% aqueous solution, polyethylene glycol derivatized lignosulfonic acid, weight average molecular weight 30,000, molecular weight of polyethylene glycol 2200, polyethylene glycol ratio 50%, manufactured by Nippon Paper Industries Co., Ltd.)
Lignin 5: Polyethylene glycol-derivatized lignosulfonic acid 3 (33% aqueous solution, polyethylene glycol-derivatized lignosulfonic acid, weight average molecular weight 56,000, molecular weight of polyethylene glycol 2200, polyethylene glycol ratio 40%, manufactured by Nippon Paper Industries Co., Ltd.)

(2) Component (B): Cationic polymer Cation 1: Poly(diallyldimethylammonium chloride) (20% aqueous solution, weight average molecular weight 200,000 to 350,000, manufactured by Merck)

(3) Component (C): Polyanion Anion 1: Polyacrylic acid 25000 (solid, weight average molecular weight 25,000, free acid type, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)
Anion 2: Sodium polystyrene sulfonate (powder, weight average molecular weight 70,000, Na salt type, manufactured by Merck)

[Examples 1 to 9 and Comparative Examples 1 to 6]
The lignin sulfonic acid compounds (lignins 1 to 5), cationic polymers (cations 1), and polyanions (anions 1 to 2) shown in Table 1 were each prepared into 20% by weight aqueous solutions, which were then uniformly mixed in the ratios shown in Table 1. The mixture was transferred to a fluororesin petri dish, dried at a temperature of 30° C. and a relative humidity of 50%, and humidified to a moisture content of 20% by weight or less, to obtain an ion complex. The moisture contents after drying and humidification in Examples 6 and 7 and Comparative Example 6 were 8.1% by weight, 12.2% by weight, and 6.6% by weight, respectively.

The blending ratios (%) in Table 1 are the blending percentages of solids relative to the total solid content of the ionic complex.

-Evaluation of mechanical properties of composites-
The mechanical properties of the samples obtained in each of the Examples and Comparative Examples were evaluated. The prepared samples were left to stand in a thermohygrostat at 30°C and 50% relative humidity for 5 days, and then punched out into the shape of a dumbbell-shaped test piece (No. 8, JIS K 6251) and subjected to a tensile test (in air, tensile speed 50 mm/min). In the tensile test, the maximum stress, Young's modulus, and toughness were measured. The results are shown in Table 2. The measurements were performed three times, and the average values and standard errors were recorded.

-Evaluation of morphology (hygroscopicity)-
The samples obtained in each Example and Comparative Example were evaluated for morphology. The prepared samples were homogenized under conditions of 70% and 80% relative humidity, respectively, and the hygroscopicity was evaluated by checking the morphology of the samples. The morphology was evaluated as follows: if the surface of the ion complex was not sticky and maintained its shape after peeling from the petri dish in which the complex sample was placed, it was marked "Good"; if only the surface was slightly liquefied and the shape collapsed after peeling from the petri dish, it was marked "Good"; if the entire sample was liquefied and difficult to peel from the petri dish, it was marked "Poor." The results are shown in Table 2.

The ionic complexes described in Examples 1 to 9 are found to have at least improved tensile stiffness such as maximum stress and Young's modulus, or resistance to breakage such as toughness, compared to the ionic complexes of the same composition ratio not containing polyanion described in Comparative Examples 1 to 6. Furthermore, in terms of hygroscopicity, the ionic complexes relatively maintain their shape even under conditions of relative humidity of 70% and 80%, and it is found that the addition of polyanion provides excellent resistance to humidity. On the other hand, the ionic complexes described in Comparative Examples 1 and 3 to 6 do not contain polyanion, and therefore absorb moisture in an environment of relative humidity of 80%, causing stickiness, making them difficult to handle as ionic complexes. Comparative Example 2 can be handled as an ionic complex, but is poor in shape retention and is not suitable for use under high humidity conditions.

Claims (6)

(A) a lignosulfonic acid compound,
(B) a cationic polymer; and (C) a polyanion.
(B) the cationic polymer comprises poly(diallyldimethylammonium chloride);
(C) the polyanion comprises polyacrylic acid or polystyrene sulfonic acid;
Ionic complexes. The ionic complex according to claim 1, wherein the weight average molecular weight of the polyanion is 3,000 to 1,000,000. The ionic complex according to claim 1 or 2, in which the content of component (C) is 1 to 80% by weight. The ionic complex according to any one of claims 1 to 3 , wherein the component (A) comprises at least one member selected from the group consisting of lignosulfonic acid, polyethylene glycol-derivatized lignosulfonic acid, and salts thereof. The ionic complex according to any one of claims 1 to 4 , wherein component (B) comprises poly(diallyldimethylammonium chloride). (A) a lignosulfonic acid compound,
(B) a cationic polymer; and (C) a polyanion ,
(B) the cationic polymer comprises poly(diallyldimethylammonium chloride);
(C) the polyanion comprises polyacrylic acid or polystyrene sulfonic acid ;
Method for producing ionic complexes.