JP4015035B2 - Water-absorbing material and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the use of a lignin derivative obtained by introducing a phenol compound into lignin, and particularly to a hydrophilic lignin-based crosslinked product.About the use of.
[0002]
[Prior art]
Lignin is known as a plant polymer, but at present, it is only commercially available as a reagent or chemical product. Lignin is a generic name and circulated lignin is mainly kraft lignin and lignosulfonic acid which are lignin derivatives discharged from the pulp industry. In addition, lignin derivatives derived from pulping technology are extracted after decomposition of brown rot fungi (filamentous fungi), solvolisis lignin (treated lignin such as autohydrolysis, alcoholysis, acetic acid steaming, etc.), steamed pulverized lignin, and wood. And lignin derivatives. Furthermore, as a laboratory level thing, there exists lignin called a sulfate lignin (Klason lignin), a dioxane lignin, a millwood lignin (MWL), etc.
[0003]
It is well known that lignin is originally rich in diversity when it is present in the plant body, but the molecular characteristics of the lignin separated by the various separation methods for separating lignin from the plant body are also greatly different.
Since all lignin derivatives are phenolic polymers, their affinity for water is low, and research on their utilization technology has been focused on resination to infusible and insoluble giant polymers such as phenolic resins and urethane resins, and addition of these. Most of the research and development as an agent has not been realized yet. Of these lignin derivatives, lignosulfonic acid, which is a water-soluble derivative, is only used as a dispersant for cement or the like (Patent Document 1).
In addition, it has been reported that a crosslinked product of lignin acetate and polyethylene glycol diglycidyl ether constitutes a water-absorbing gel (Non-patent Document 1). However, the water absorption of this gel is very low, 2-5 times the weight of the crosslinked body.
Even in a three-dimensional network polymer using an aromatic compound in a chemically synthesized product typified by a phenol resin or an epoxy resin, it is recognized that its general characteristics are high durability, high water resistance, and the like.
[0004]
[Patent Document 1]
JP-A-10-53444
[Non-Patent Document 1]
45th Annual Meeting of Lignin (2000) p.139-p.142
[0005]
[Problems to be solved by the invention]
  In view of such circumstances, the present invention is a hydrophilic crosslinked body using a lignin-containing material derived from a lignocellulosic resource that is a renewable resource.To provide the use ofFor that purpose.
[0006]
[Means for Solving the Problems]
The present inventors have found that by using a specific lignin derivative, it is possible to construct a hydrophilic crosslinked body having high aromaticity and excellent characteristics, and completed the present invention.
The present inventors reduced the amount of low cross-linking by cross-linking a primary derivative of a specific lignin derived from a lignin-containing material using a phenol compound or a secondary derivative that is a further derivative of this primary derivative with a hydrophilic cross-linking compound. At times, it has been found that lignin derivatives are water-soluble, and excellent water absorption characteristics can be obtained during high crosslinking. That is, according to the present invention, the following means are provided.
[0007]
(1) A water absorbing material,
The following (a) to (d):
(A) The phenol compound is introduced at the α-position of the lignin arylpropane unit obtained by adding an acid to a lignin-containing material solvated with a phenol compound free of ortho-position and / or para-position and mixing. , A primary lignin derivative having a 1-bisarylpropane unit,
(B) A lignin secondary derivative in which one or more selected from a carboxyalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group are introduced to the lignin primary derivative of (a),
(C) The lignin primary derivative of (a), which has a 1,1-bisarylpropane unit in which the ortho-position carbon atom of the phenol compound is bonded to the α-position of the arylpropane unit, is alkali-treated. A lignin secondary derivative having an arylcoumaran unit,
(D) A lignin primary derivative of (a) having a 1,1-bisarylpropane unit in which the carbon atom at the ortho position of the phenol compound is bonded to the α-position of the arylpropane unit. Lignin secondary derivative subjected to alkali treatment and introduction reaction of one or more functional groups selected from a carboxylalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group,
One or two or more lignin derivatives selected from the group consisting of are obtained by crosslinking with a hydrophilic crosslinking compound in the presence of a crosslinking reaction medium containing water,
A water-absorbing material having a water absorption ratio of 20 times or more.
(2) The water absorbing material according to (1), wherein the phenol compound is p-cresol.
(3) The water-absorbing material according to (1) or (2), wherein the lignin derivative is a lignin derivative of (b) and a secondary derivative having a carboxyalkyl group introduced.
(4) The water-absorbing material according to any one of (1) to (3), wherein the hydrophilic crosslinkable compound is an ether compound having a glycidyl group having two or more functional groups.
(5) The water-absorbing material according to (4), wherein the hydrophilic crosslinkable compound is a polyalkylene glycol having a glycidyl group having two or more functional groups.
(6) The water-absorbing material according to any one of (1) to (5), wherein the lignin-containing material is a lignocellulosic material derived from a woody plant and / or a herbaceous plant.
(7) One or more lignin derivatives selected from the lignin derivatives described in (1), polysaccharides, oligosaccharides, and carboxyalkyl groups, hydroxyalkyl groups, and epoxy groups for these saccharides Formed by crosslinking with one or more saccharide compounds selected from the group consisting of saccharide derivatives obtained by introducing one or more selected from carboxyl groups with a hydrophilic crosslinkable compound Water absorbing material.
(8) The water-absorbing material according to any one of (1) to (7), wherein the crosslinking reaction medium contains an alkali.
(9) A method for producing a water-absorbing material,
The following (a) to (d):
(A) The phenol compound is introduced at the α-position of the lignin arylpropane unit obtained by adding an acid to a lignin-containing material solvated with a phenol compound free of ortho-position and / or para-position and mixing. , A lignin primary derivative having a 1-bisarylpropane unit,
(B) A lignin secondary derivative in which one or more selected from a carboxyalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group are introduced to the lignin primary derivative of (a),
(C) The lignin primary derivative of (a), which has a 1,1-bisarylpropane unit in which the ortho-position carbon atom of the phenol compound is bonded to the α-position of the arylpropane unit, is alkali-treated. Secondary derivatives of lignin obtained by
(D) A lignin primary derivative of (a) having a 1,1-bisarylpropane unit in which the carbon atom at the ortho position of the phenol compound is bonded to the α-position of the arylpropane unit. Lignin secondary derivative subjected to alkali treatment and introduction reaction of one or more functional groups selected from a carboxylalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group,
A method comprising the step of cross-linking one or more lignin derivatives selected from the group consisting of a hydrophilic cross-linkable compound in a cross-linking reaction medium containing water.
(10) The method according to (9), wherein the crosslinking reaction medium contains an alkali.
(11) The method according to (9) or (10), wherein the crosslinkable compound is an ether compound having a glycidyl group having two or more functional groups.
(12) The method according to (11), wherein the crosslinkable compound is a polyalkylene glycol having a glycidyl group having two or more functional groups.
(13) The method according to any one of (9) to (12), wherein an amount sufficient to crosslink the crosslinkable compound and the lignin derivative is supplied to form a gel-like crosslinked body.
(14) The method according to (13), wherein the water absorption ratio of the obtained crosslinked product is adjusted by adjusting the crosslinking reaction time when the gel-like crosslinked product is generated.
(15) The method according to (13) or (14), further comprising a step of supplying excess water to the gel-like crosslinked body separated from the reaction system to absorb water after the crosslinking reaction step.
(16) The method according to any one of (9) to (15), wherein the lignin-containing material is one or more lignocellulosic materials derived from woody plants and / or herbaceous plants. .
(17) A method for producing a water-absorbing material,
  One or more lignin derivatives selected from the lignin derivatives described in (1), polysaccharides, oligosaccharides, and carboxyalkyl groups, hydroxyalkyl groups, epoxy groups and carboxyl groups for these saccharides One or two or more saccharide compounds selected from the group consisting of saccharide derivatives obtained by introducing one or two or more functional groups selected from the above are crosslinked with a hydrophilic crosslinkable compound. A method for obtaining a crosslinked product.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described in detail.
The water-absorbing material of the present invention is obtained by crosslinking one or more lignin derivatives selected from the following lignin derivatives (a) to (d) with a hydrophilic crosslinkable compound.
(A)The ortho and / or para positions are freeObtained by adding and mixing acid to lignin-containing material solvated with phenolic compoundsA primary lignin derivative having a 1,1-bisarylpropane unit in which the phenol compound is introduced at the α-position of an arylpropane unit of lignin,
(B) A carboxyalkyl group, a hydroxyalkyl group, an epoxy group with respect to the lignin primary derivative of (a)AndLignin secondary derivatives introduced with one or more selected from ruboxyl groups,
(C) Lignin primary derivative of (a)And having a 1,1-bisarylpropane unit in which the carbon atom at the ortho position of the phenol compound is bonded to the α-position of the arylpropane unit.A lignin secondary derivative obtained by subjecting a lignin primary derivative to an alkali treatment and having an arylcoumaran unit,
(D) Lignin primary derivative of (a)A primary lignin derivative having a 1,1-bisarylpropane unit in which the carbon atom at the ortho position of the phenol compound is bonded to the α-position of the arylpropane unitFor alkali treatment, carboxyl alkyl group, hydroxyalkyl group, epoxy groupAndA lignin secondary derivative subjected to an introduction reaction of one or more functional groups selected from a ruboxyl group.
[0009]
OrThe water-absorbing material of the present invention is obtained by crosslinking one or more lignin derivatives selected from the following (e) and (f) with a hydrophilic crosslinkable compound, and has a water absorption capacity of 10 times or more. Material.
(E) One or more lignins selected from the group consisting of alkali lignin, organosolv lignin, lignosulfonic acid, solvolysis lignin, steamed pyrolysis lignin, filamentous fungus treated wood, sulfate lignin, dioxane lignin and milled wood lignin A primary derivative and a lignin secondary in which one or more selected from the group consisting of a carboxyalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group are introduced to the primary derivative and the lignin primary derivative of (e) (e) Derivative.
[0010]
Hereinafter, various lignin derivatives will be described, and then the crosslinked product will be described.
(Primary derivative of lignin)
One lignin primary derivative used in the present invention is a lignin derivative which is a phenol compound of lignin obtained by solvating a lignin-containing material with a phenol compound and then adding and mixing an acid (hereinafter, this lignin primary derivative, in particular, Lignophenol derivatives or lignophenol primary derivatives). Through this reaction process, a lignin derivative in which a phenol compound is grafted (introduced) to the benzyl position (side chain C1 position, hereinafter simply referred to as C1 position) of the arylpropane unit of lignin can be obtained. The phenol compound is bonded to the carbon atom at the C1 position in the ortho position or para position with respect to the phenolic hydroxyl group. As a result, 1,1-bis (aryl) propane units are formed in lignin. In this reaction, since the phenol compound is selectively introduced with respect to the C1 position, various bonds at the C1 position in the lignin-containing material as a starting material are released, reducing the diversity of the lignin matrix, and The molecular weight can be reduced. Furthermore, as a result, it is already known that various properties such as solubility in various solvents, thermal fluidity, and thermoplasticity, which were not found in conventional lignin, are exhibited.
Here, solvating with a phenol compound means solvating by immersing a lignin-containing material in a liquid phenol compound, or dissolving a liquid or solid phenol compound in a solvent in which the phenol compound is dissolved. This can also be achieved by sorbing a phenolic compound onto the lignin-containing material by distilling off the solvent after applying it to the lignin-containing material.
[0011]
The inventors of the present invention have previously studied that lignocellulosic materials are combined with the destruction of tissue structure based on the swelling of carbohydrates by concentrated acid and the solvation of lignin by phenolic compounds to suppress the inactivation of lignin. Has been developed for separating carbohydrate into a lignophenol derivative (Japanese Patent Application Laid-Open No. Hei 2-233701). As a method of utilizing the lignophenol derivative obtained by this method, for example, it has been reported that a molded body is produced by applying it to a molding material such as cellulose fiber (Japanese Patent Laid-Open No. 9-278904). Such a lignophenol derivative is a lignin-based polymer having 1,1-bis (aryl) propane as a high-frequency constituent unit, and has been found to have a high caking property (Japanese Patent Application Laid-Open No. Hei 9). -278904).
Furthermore, such lignophenol derivatives can be imparted with crosslinkability by methylolation, and can form a linear or network-like crosslinked structure, and at the same time, can be reduced in molecular weight and dissolved in a solvent by alkali treatment. It has been found by the present inventors (Japanese Patent Laid-Open No. 2001-261839).
In addition to these, more general description of lignophenol derivatives and the production process thereof can be found in International Publication No. WO99 / 14223, JP-A-2001-64494, JP-A-2001-261839, JP-A-2001-2001. No. 131201, JP-A No. 2001-342353, and JP-A No. 2002-105240 (the contents described in these patent documents are all incorporated herein by reference).
[0012]
An example of a structure conversion process in a system for obtaining a lignophenol derivative from a lignocellulosic material by this process is shown in FIG.
As shown in FIG. 1, this structure conversion process is performed by previously solvating a lignocellulosic material with a phenol compound, and then bringing the lignocellulosic material into contact with an acid so that the arylpropane unit of lignin The complex state of lignin is relaxed, and at the same time, the phenol derivative is selectively grafted to the C1 position (benzyl position) of the arylpropane unit of natural lignin to produce a lignophenol derivative, and at the same time, cellulose and lignophenol derivatives are converted into cellulose. Can be separated. An example of structural transformation in this process is shown in FIG.
[0013]
The lignophenol derivative itself is a mixture of lignin-derived polymers obtained by reaction and separation from a lignin-containing material such as a lignocellulosic material. For this reason, the amount and molecular weight of the introduced phenol derivative in the obtained polymer vary depending on the lignin structure and reaction conditions of the lignin-containing material as a raw material.
[0014]
(Lignin-containing material)
The lignin-containing material in the present invention includes a lignocellulosic material containing natural lignin. Lignocellulosic materials are woody materials, various materials that are mainly wood, such as wood flour, chips, agricultural waste and industrial waste associated with woody plant resources such as waste wood, scraps, and waste paper. Can be mentioned. Moreover, as a kind of woody tree to be used, any kind can be used, such as conifers such as cedar and cypress, and broad-leaved trees such as beech. Furthermore, various herbaceous plants such as kenaf, jute, rice, bamboo, and related agricultural and industrial wastes such as rice straw and rice straw can be used.
[0015]
(Phenol compound)
As the phenol compound, a monovalent phenol compound, a divalent phenol compound, a trivalent phenol compound, or the like can be used.
Specific examples of the monovalent phenol compound include phenol that may have one or more substituents, naphthol that may have one or more substituents, and one or more substituents. A good anthrol, an anthroquinone all optionally having one or more substituents, and the like can be mentioned.
Specific examples of the divalent phenol compound include catechol which may have one or more substituents, resorcinol which may have one or more substituents, and one or more substituents. Examples include good hydroquinone.
Specific examples of the trivalent phenol compound include pyrogallol, which may have one or more substituents.
In the present invention, one or more of monovalent phenol compounds, divalent phenol compounds and trivalent phenol compounds can be used. In order to increase the introduction ratio of the phenol compound, it is preferable to use a monocyclic phenol compound. P-cresol, phenol, and p-ethylphenol are preferable. Moreover, in order to improve the water affinity of the obtained lignin derivative, it is preferable to increase the introduction ratio of the phenol compound or to use a divalent or higher valent phenol compound. Preferably, catechol or pyrogallol can be used.
[0016]
The type of substituent that the monovalent to trivalent phenol compound may have is not particularly limited, and may have any substituent, but preferably an electron-withdrawing group (such as a halogen atom). A lower alkyl group-containing substituent having 1 to 4 carbon atoms, preferably 1 to 3 carbon atoms. Examples of the lower alkyl group-containing substituent include a lower alkyl group (such as a methyl group, an ethyl group, and a propyl group) and a lower alkoxy group (such as a methoxy group, an ethoxy group, and a propoxy group). Further, it may have an aromatic substituent such as an aryl group (such as a phenyl group). Further, it may be a hydroxyl group-containing substituent.
[0017]
In these phenol compounds, a 1,1-bis (aryl) propane unit is formed by bonding a carbon atom in the ortho-position or para-position to the C1-position carbon of the lignin arylpropane unit relative to the phenolic hydroxyl group. Will be. Therefore, in order to secure at least one introduction site, it is preferable that a substituent is not present in at least one of the ortho and para positions.
A unit formed by bonding the ortho-position carbon atom of the phenolic hydroxyl group of the phenol compound to the C1-position is called an ortho-position binding unit, and the para-position carbon atom of the phenolic hydroxyl group of the phenol compound is bonded to the C1-position. The formed unit is called a para unit. FIG. 3 shows units formed using p-cresol and 2,6-dimethylphenol, respectively, as phenol compounds as examples of ortho-position binding units and para-position binding units.
[0018]
From the above, in the present invention, in addition to the unsubstituted phenol derivative, at least one phenol derivative in various substituted forms having at least one unsubstituted ortho-position or para-position may be appropriately selected and used. it can.
[0019]
The ortho bond unit and the para bond unit express different functions in, for example, an alkali treatment step described later. The ortho-position binding unit eliminates the phenolic hydroxyl group in the phenolic compound introduced by mild alkali treatment and generates an aryl coumaran structure in the unit, and the molecular form is changed with the migration of the aryl group by strong alkali treatment. The In any case, the ortho-position binding unit contributes to efficient reduction of the molecular weight of the lignophenol derivative by alkali treatment.
On the other hand, the para-bonded unit does not cause an aryl coumaran structure or subsequent molecular morphology change by alkali treatment, and does not contribute to the reduction in molecular weight at the unit site. Therefore, it can be said that it has a function of imparting alkali treatment resistance.
[0020]
Moreover, in the lignophenol derivative, by selecting the type of phenol compound to be used, the position and frequency of introduction of the functional group in the subsequent secondary derivatization step to the obtained lignophenol derivative are adjusted, resulting in crosslinking. Structural control in the body is possible.
[0021]
In order to obtain a lignophenol derivative having an ortho-position binding unit, a phenol compound having no substituent at at least one ortho position (preferably all ortho positions) is used. In addition, a phenol compound (typically a 2,4-position substituted monohydric phenol derivative) in which at least one ortho position (position 2 or 6) has no substituent and has a substituent in the para position (position 4) ) Is preferred. Most preferably, it is a phenol compound (typically a 4-position substituted monohydric phenol compound) in which all the ortho positions do not have a substituent and has a substituent in the para position. Accordingly, the 4-position substituted phenol compound and the 2,4-position substituted phenol compound can be used alone or in combination of two or more.
[0022]
In order to obtain a lignophenol derivative having a para-linkage unit, a phenol compound having no substituent at the para-position (typically a 2-position (or 6-position) substituted monohydric phenol compound) is preferred, and more preferred. At the same time, a phenol compound having a substituent at the ortho position (preferably, all ortho positions) (typically 2,6-substituted monohydric phenol compound) is used. That is, it is preferable to use one or two or more of 2-position (or 6-position) substituted phenol compound and 2,6-position substituted phenol.
[0023]
Preferable specific examples of the phenol derivative include p-cresol, 2,6-dimethylphenol, 2,4-dimethylphenol, 2-methoxyphenol (Guaiacol), 2,6-dimethoxyphenol, catechol, resorcinol, homocatechol, pyrogallol And phloroglucinol. By using p-cresol, high introduction efficiency can be obtained.
[0024]
(acid)
The acid to be brought into contact with the lignin-containing material is not particularly limited, and various inorganic acids and organic acids can be used as long as the lignophenol derivative can be generated. Therefore, in addition to inorganic acids such as sulfuric acid, phosphoric acid and hydrochloric acid, p-toluenesulfonic acid, trifluoroacetic acid, trichloroacetic acid, formic acid and the like can be used. When a lignocellulosic material is used as the lignin-containing material, it preferably has an action of swelling cellulose. For example, 65 wt% or more sulfuric acid (preferably 72 wt% sulfuric acid), 85 wt% or more phosphoric acid, 38 wt% or more hydrochloric acid, p-toluenesulfonic acid, trifluoroacetic acid, trichloroacetic acid, formic acid, etc. Can be mentioned. The preferred acid is 85% by weight or more (preferably 95% by weight or more) phosphoric acid, trifluoroacetic acid or formic acid. In order to obtain a lignophenol derivative in a high yield, 65% by weight or more of sulfuric acid (preferably 72% by weight of sulfuric acid) is preferable.
[0025]
Various methods can be adopted as a method for converting and separating lignin in the lignin-containing material into a lignophenol derivative.
For example, as shown in FIG. 1, a lignin-containing material is infiltrated with a liquid phenol derivative (as described above, for example, p-cresol), lignin is solvated with the phenol derivative, and then lignocellulose is used. An acid (as described above, for example, 72% sulfuric acid) is added to the system material and mixed to dissolve the cellulose component. According to this method, lignin is reduced in molecular weight, and at the same time, a lignophenol derivative in which a phenol compound is introduced at the C1 position of the basic structural unit is generated in the phenol compound phase. A lignophenol derivative is extracted from this phenol compound phase. A lignophenol derivative is obtained as an aggregate of low molecular weight forms of lignin in which the benzyl aryl ether bond in lignin is cleaved to reduce the molecular weight. FIG. 2 shows that the lignophenol derivative in the present invention can be obtained by subjecting natural lignin having an arylpropane unit to phase separation.
[0026]
Extraction of the lignophenol derivative from the phenol compound phase can be performed, for example, by the following method. That is, the precipitate obtained by adding the phenol compound phase to a large excess of ethyl ether is collected and dissolved in acetone. The acetone insoluble part is removed by centrifugation, and the acetone soluble part is concentrated. The acetone soluble part is dropped into a large excess of ethyl ether, and the precipitate section is collected. The solvent is distilled off from this precipitation section to obtain a lignophenol derivative. The crude lignophenol derivative can be obtained by simply removing the phenol compound phase and the acetone-soluble fraction by distillation under reduced pressure.
[0027]
In addition, when the solvent (for example, ethanol or acetone) in which a solid or liquid phenol compound is dissolved is infiltrated into the lignin-containing material, the solvent is distilled off (sorption of the phenol derivative). Like, a lignophenol derivative is produced. In this method, the produced lignophenol derivative can be extracted and separated with a liquid phenol compound. Alternatively, the entire reaction solution is poured into excess water, the insoluble sections are collected by centrifugation, deacidified and then dried. The lignophenol derivative is extracted by adding acetone or alcohol to the dried product. Furthermore, the soluble segment can be dropped into excess ethyl ether or the like in the same manner as in the first method to obtain a lignophenol derivative as an insoluble segment. In the above, specific examples of the method for preparing the lignophenol derivative have been described. However, the present invention is not limited to these, and it can be prepared by a method in which these are appropriately improved.
[0028]
The general and general properties of lignophenol derivatives obtained from lignocellulosic materials are listed below. However, the lignophenol derivative in the present invention is not intended to be limited to those having the following properties.
(1) The weight average molecular weight is about 2000 to 20000.
(2) There is almost no conjugated system in the molecule, and the color tone is very light. Typically a pale pink white powder.
(3) It has a solid-liquid phase transition point at about 170 ° C. derived from conifers and at about 130 ° C. derived from hardwoods.
(4) Easily soluble in methanol, ethanol, acetone, dioxane, pyridine, tetrahydrofuran, dimethylformamide and the like.
In lignophenol derivatives, it is known that some phenol compounds are introduced into the C1 position via their phenolic hydroxyl groups. Moreover, in the obtained lignophenol derivative, an arylpropane unit to which no phenol compound is grafted usually remains.
[0029]
Secondary derivatives can be obtained by introducing any one or more of carboxyalkyl group, hydroxyalkyl group, epoxy group and carboxyl group into these primary derivatives. Hereinafter, secondary derivatization when the lignin primary derivative is the lignin primary derivative of the above (a) will be described.
[0030]
(Introduction of carboxyalkyl group)
The carboxyalkyl group is introduced into an alcoholic or phenolic hydroxyl group in the lignin primary derivative, and the primary derivative is a carboxyalkylated lignin secondary derivative. Carboxyalkylation can generally be achieved by reacting with a monohalogenoalkyl carboxylic acid in the presence of an alkali. Various conventionally known methods can be adopted as the carboxyalkylation method of the lignin derivative. Examples of the carboxyalkyl group include an acetyl group, a carboxyethyl group, a carboxypropyl group, and a carboxybutyl group.
For example, a lignin primary derivative is dispersed in an organic solvent such as isopropanol in which the derivative can be dispersed, an aqueous alkaline solution is added, and an organic solvent such as isopropanol is further added as necessary. Monohalogenoacetic acid (carboxyalkylating agent) such as acetic acid can be added and reacted while stirring. Moreover, after immersing a lignin primary derivative in an alkaline solution beforehand, this immersion thing can be disperse | distributed to the organic solvent and it can be made to react after that.
The alkali may be a commonly used alkali reagent, but a strong alkali such as an alkali metal compound such as sodium hydroxide or potassium hydroxide is preferably used. Examples of organic solvents for dispersing lignin primary derivatives and the like include alcohols such as methanol, ethanol, isopropanol and t-butanol, ketones such as acetone and methyl ethyl ketone, ethers such as diethyl ether, tetrahydrofuran and 1,4-dioxane. , Halides such as dichloromethane and chloroform, and hydrocarbons such as hexane, cyclohexane, benzene and toluene. These may be used alone or in admixture of two or more. Among these, 1 type, or 2 or more types of combinations of polar organic solvents, such as alcohol, ketones, ethers, are good, More preferably, isopropanol, acetone, 1, 4- dioxane is used.
[0031]
As the monohalogenoalkylcarboxylic acid, those represented by the following general formula [I] are preferably used.
XRCOOH [I]
(In the above formula, X and R represent the following, respectively.
X: a halogen atom such as F, Cl, Br, or I; R: an alkyl group having 1 to 12 carbon atoms and having a straight chain and a branch. )
Among the above compounds, those in which X is a Cl or Br atom and R is a linear or branched alkyl group having 1 to 5 carbon atoms are particularly preferred.
[0032]
The amount of the monohalogenoalkylcarboxylic acid used may be equal to or greater than the amount of hydroxyl group of lignin, and is preferably about 1 to 3 mol per hydroxyl group. As a method for adding the monohalogenoalkylcarboxylic acid, it may be added as a solid and / or as a solution of this organic solvent by batch or continuous dropping. The method of continuous dripping which took 0.5 to 3 hours as a solution of an organic solvent is preferable, and it is particularly preferable to continuously drop the solution in 1-2 hours. In addition, after completion of the addition of the monohalogenoalkylcarboxylic acid, it is preferable to continue the reaction at that temperature for 0.5 to 5 hours (more preferably 1 to 4 hours). In the reaction with the monohalogenoalkylcarboxylic acid, the reaction solution is preferably heated in the range of about 40 ° C to 60 ° C.
[0033]
The carboxyalkylated secondary derivative is obtained in a state in which a part of the solid product is dissolved. After completion of the reaction, the solid product was separated and collected by filtration or the like, and the solid product was dissolved in water and neutralized with an acid such as a dilute mineral acid such as dilute hydrochloric acid or dilute sulfuric acid. Thereafter, it can be obtained by desalting by electrodialysis and freeze-drying. The dissolved product can be recovered by distilling off the organic solvent in the filtrate, drying the dissolved product, and adding the dried product to the solid product before neutralization. it can.
[0034]
(Introduction of hydroxyalkyl group)
Hydroxyalkylated secondary derivatives are produced by reacting a primary derivative with a hydroxyalkylating agent under alkaline conditions to introduce a crosslinkable group at the ortho-position and / or para-position of the phenolic hydroxyl group in the lignin primary derivative. ,Obtainable.
That is, this secondary derivative can be obtained by mixing and reacting the primary derivative with a reaction reagent under the condition that the phenolic hydroxyl group of the primary derivative used can be dissociated. The state in which the phenolic hydroxyl group of the primary derivative can be dissociated is usually formed in a suitable alkaline solution. The kind, concentration and solvent of the alkali used are not particularly limited as long as the phenolic hydroxyl group of the primary derivative is dissociated. For example, a 0.1N sodium hydroxide aqueous solution can be used.
[0035]
Under such conditions, the hydroxyalkyl group is introduced at the ortho-position or para-position of the phenolic hydroxyl group, and the introduction position of this group is roughly determined by the type and combination of the phenol derivatives used. That is, when the ortho-position and the para-position are disubstituted, a crosslinkable group is not introduced into the introduced phenol nucleus, but is introduced into the phenolic aromatic nucleus on the lignin base side. Since the phenolic aromatic nucleus on the base side is mainly present at the polymer terminal of the primary derivative, a secondary derivative having a crosslinkable group introduced mainly at the polymer terminal is obtained.
In the case of 1 substitution or less at the ortho position and the para position, a crosslinkable group is introduced into the introduced phenol nucleus and the phenolic aromatic nucleus of the lignin matrix. Therefore, in addition to the end of the polymer chain, a crosslinkable group is introduced over its length, and a multifunctional secondary derivative is obtained.
[0036]
Therefore, crosslinkability can be adjusted by combining a 2-substituted phenol derivative and a phenol derivative having 1 or less substitution. In the present invention, when a disubstituted phenol compound typified by 2,4-dimethylphenol and / or 2,6-dimethylphenol is used, linear polymer-forming ability is imparted to the secondary derivative. Moreover, when the phenol compound below 1 substitution represented by p-cresol is used, network polymer formation ability is provided to a secondary derivative. By using a combination of a 2-substituted phenol derivative and a mono- or lower substituted phenol derivative, the network property can be adjusted.
[0037]
The kind of hydroxyalkyl group introduced into the primary derivative is not particularly limited. Any material that can be introduced into the aromatic nucleus of the lignin matrix or the aromatic nucleus of the introduced phenol derivative may be used. Examples of the group include a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, and a 1-hydroxyvaleraldehyde group. The hydroxyalkylating agent may be any one that is nucleophilic and can form a hydroxyalkyl group after bonding. For example, formaldehyde, acetaldehyde, propionaldehyde, glutaraldehyde, ethylene oxide, propylene oxide There may be mentioned oxides.
[0038]
From the viewpoint of efficiently introducing a hydroxyalkyl group when mixing the primary derivative and the reagent, the reagent is added at least 1 mole of the aromatic nucleus of the lignin arylpropane unit in the lignophenol derivative and / or the introduced phenol nucleus. It is preferable to do. More preferably, it is 10 mol times or more, More preferably, it is 20 mol times or more.
[0039]
Next, in the state where the lignophenol derivative and the present reagent are present in the alkaline solution, the solution is heated as necessary to introduce a hydroxyalkyl group into the phenol nucleus. The heating conditions are not particularly limited as long as the hydroxyalkyl group is introduced, but 40 to 100 ° C. is preferable. If the temperature is lower than 40 ° C., the reaction rate of the reagent is very low and is not preferable. More preferably, it is 50-80 degreeC, for example, about 60 degreeC is especially preferable. The reaction is stopped by cooling the reaction solution, acidified (approx. PH 2) with an appropriate concentration of hydrochloric acid, etc., and acid and unreacted reagents are removed by washing, dialysis and the like. Collect the sample by lyophilization after dialysis. If necessary, vacuum dry over diphosphorus pentoxide.
[0040]
The prepolymer thus obtained is crosslinkable at the ortho position and / or para position with respect to the phenolic hydroxyl group in the 1,1-bis (aryl) propane unit containing the first unit or the second unit or the arylpropane unit of lignin. Have a group.
[0041]
(Epoxidation)
An epoxidized lignin secondary derivative can be obtained by introducing an epoxy group into a phenolic hydroxyl group and / or an alcoholic hydroxyl group in the primary derivative. Epoxidation can impart high crosslinkability reactivity.
Epoxidation can be obtained by reacting with a glycidyl agent having one epoxy group such as epihalohydrin under alkali, and various conventionally known methods can be employed. As the glycidylating agent, epichlorohydrin, epibromohydrin, epiiodohydrin, etc., as well as β-methylepibromohydrin, β-methylepichlorohydrin, β-ethylepichlorohydrin, etc. can be used. . In addition, since the epoxidation by a glycidylating agent has high reactivity with respect to the phenolic hydroxyl group, the phenolic hydroxyl group is preferentially epoxidized.
[0042]
Epoxidation is performed by, for example, dissolving a lignin primary derivative in a glycidylating agent such as epichlorohydrin and refluxing under a reduced pressure of about 55 ° C. to 60 ° C. After completion of the reaction, the mixture is centrifuged, and the supernatant can be concentrated with a vacuum evaporator, dropped into an organic solvent such as cyclohexane and separated as a precipitate.
[0043]
(Carboxylation)
The carboxylated lignin secondary derivative reacts the primary derivative with a carboxylating agent to introduce a polyvalent carboxyl group into the phenolic hydroxyl group and / or alcoholic hydroxyl group in the lignin primary derivative and the conjugated double bond that is slightly present. Can be obtained. Carboxylation can provide high crosslinkability reactivity.
A polybasic acid anhydride etc. can be used for a carboxylating agent, and the kind of polybasic acid anhydride is not specifically limited. Preferably, succinic anhydride, octenyl succinic anhydride, maleic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, dibasic acid anhydride such as trimellitic acid, biphenyltetracarboxylic Acid dianhydride, naphthalene tetracarboxylic dianhydride, diphenyl ether tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride, pyromellitic anhydride, benzophenone tetracarboxylic dianhydride And polybasic acid anhydrides such as aliphatic or aromatic tetrabasic acid dianhydrides, and the like, and one or more of them can be used. The lignin primary derivative and the polybasic acid anhydride are preferably reacted with 0.5 to 1.5 mol of the polybasic acid anhydride with respect to the hydroxyl group in the lignin primary derivative at a temperature of 50 ° C to 170 ° C.
The carboxylated secondary derivative is, for example, a lignin primary derivative mixed well with maleic anhydride, reacted in a sealed container at about 90 ° C. for 2 hours, and after completion of the reaction, the reaction system was put into an organic solvent such as benzene, The precipitate can be washed and separated by centrifugation or the like.
[0044]
(Alkali treatment)
The alkali treatment is performed by bringing a lignin primary derivative or a secondary derivative into contact with an alkali. Preferably it heats. In the alkali treatment, the C2-position carbon is attacked by the phenoxide ion of the introduced phenol compound in the ortho-position binding unit. That is, once this reaction occurs, the C2 aryl ether bond is cleaved.
For example, in a mild alkali treatment, when the primary derivative has a first unit, the phenolic hydroxyl group of the introduced phenol derivative is cleaved, and the resulting phenoxide ion has an intramolecular C2 position constituting a C2 aryl ether bond. The nucleophilic reaction can be attacked to cleave the ether bond to reduce the molecular weight. Cleavage of the C2 aryl ether bond results in the formation of a phenolic hydroxyl group in the lignin nucleus, and the introduced phenol nucleus forms a coumaran skeleton with the phenylpropane unit into which it is introduced by the intramolecular nucleophilic reaction. The resulting structure (arylcoumaran unit) is expressed.
As a result, the phenolic hydroxyl group on the phenol derivative side is moved to the lignin mother nucleus side.
For this reason, in lignophenol derivatives having an ortho-position binding unit, (1) low molecular weight by cleavage of C2 aryl ether bond, (2) expression of arylcoumaran structure, (3) C2 aryl at the site of this unit A phenolic hydroxyl group on the lignin mother nucleus side that has been bonded by an ether bond is expressed.
[0045]
Specifically, the alkali treatment is performed by dissolving a cross-linked lignophenol derivative in an alkali solution, reacting for a predetermined time, and heating if necessary. The alkali solution that can be used in this treatment is not particularly limited as long as it can dissociate the phenolic hydroxyl group of the introduced phenol derivative in the lignophenol derivative, and the type and concentration of alkali and the type of solvent are not particularly limited. . This is because if the phenolic hydroxyl group is dissociated under an alkali, a coumaran structure is formed due to the effect of neighboring group participation. For example, in a lignophenol derivative into which p-cresol is introduced, a sodium hydroxide solution can be used. For example, the alkali concentration range of the alkaline solution can be 0.5 to 2 N, and the treatment time can be about 1 to 5 hours. The lignophenol derivative in the alkaline solution easily develops a coumaran structure when heated. Conditions such as temperature and pressure during heating can be set without any particular limitation. For example, by reducing the alkaline solution to 100 ° C. or higher (for example, about 140 ° C.), the molecular weight of the crosslinked product of the lignophenol derivative can be achieved. Furthermore, the molecular weight of the crosslinked product of the lignophenol derivative may be reduced by heating the alkaline solution to the boiling point or higher under pressure.
[0046]
It has been found that at the same concentration in the same alkaline solution, when the heating temperature is in the range of 120 ° C. to 140 ° C., the higher the heating temperature, the lower the molecular weight due to the cleavage of the C2-aryl ether bond. In addition, it has been found that the higher the heating temperature in this temperature range, the more phenolic hydroxyl groups derived from the aromatic lignin derived from the lignin matrix and the fewer phenolic hydroxyl groups derived from the introduced phenol derivative. Therefore, the degree of molecular weight reduction and the degree of conversion of the phenolic hydroxyl moiety from the C1-introduced phenol derivative side to the phenol nucleus of the lignin matrix can be adjusted by the reaction temperature. That is, a reaction temperature of about 80 to 140 ° C. is preferred in order to obtain an aryl coumaran body in which low molecular weight is promoted or more phenolic hydroxyl sites are converted from the C1-introduced phenol derivative side to the lignin matrix. .
[0047]
Although the cleavage of C2-aryl ether by participation of adjacent group of C1 phenol nucleus is accompanied by the formation of arylcoumaran structure as described above, the reduction of the molecular weight of the cross-linked lignophenol derivative is not necessarily generated efficiently by aryl claman. It is not necessary to carry out under conditions (around 140 ° C.), and it can be carried out at a higher temperature (for example, around 170 ° C.) depending on the material or purpose. In this case, once the generated claman ring is cleaved and the phenolic hydroxyl group is regenerated on the introduced phenol derivative side, a material having higher phenol activity than that of the 140 ° C. treated product can be induced.
[0048]
From the above, the heating temperature in the alkali treatment is not particularly limited, but is preferably 80 ° C. or higher and 200 ° C. or lower. This is because the reaction does not proceed sufficiently when the temperature is greatly below 80 ° C., and an undesirable side reaction tends to be easily induced when the temperature is greatly above 200 ° C.
[0049]
As a preferable example of the treatment for formation of the Kuraman structure and the accompanying reduction in molecular weight, a 0.5N sodium hydroxide aqueous solution is used as an alkaline solution, and a heating time of 60 minutes at 140 ° C. in an autoclave can be exemplified. . In particular, this treatment condition is preferably used for lignophenol derivatives derivatized with p-cresol or 2,4-dimethylphenol.
[0050]
By performing one or more of the above various functional group introduction reactions on the lignin primary derivative, a lignin secondary derivative having one or more functional groups can be obtained. Moreover, the lignin secondary derivative provided with an above-mentioned alkali treatment structure can be obtained by performing an alkali treatment with respect to a lignin primary derivative. In addition, a lignin secondary derivative having one or more functional groups and an alkali-treated structure is obtained by performing one or more of various functional group introduction reactions and an alkali treatment on the lignin primary derivative. Derivatives can be obtained.
[0051]
In addition, various industrial lignins etc. can also be used as a lignin primary derivative of this invention. These industrial lignins include the lignin primary derivatives of (e) above.
Such lignin primary derivatives include steamed crushed lignin obtained by processing with high-pressure saturated steam and instantaneously releasing the pressure to crush the wood. Kraft lignin obtained by digesting wood flour, alcohol-soluble lignin obtained by boiling wood flour with alcohol, lignin sulfonic acid obtained by cooking wood flour with neutral or weakly alkaline bisulfite solution at high temperature Milled Wood Lignin obtained by pulverizing wood powder with a vibrating ball mill and extracting with hydrous dioxane, Nitrolignin nitrated with nitrous acid at pH 2 and 100 ° C, and Browns Natural lignin, periodate lignin, sulfate lignin, hydrochloride lignin, copper ammo Arigunin, dioxane lignin, thioglycolic acid lignin, other lignin derived from wood, such as hydrolysis lignin include lignin obtained from plants of the rice and the like. Particularly preferable examples include alkali lignin, organosolv lignin, lignosulfonic acid, solvolysis lignin, steamed crushed lignin, filamentous fungus-treated wood, sulfate lignin, dioxane lignin, and milled wood lignin. These can be used alone or in combination of two or more.
In the present invention, these lignin primary derivatives can be subjected to the above-described carboxyalkylation, hydroxyalkylation, epoxidation and carboxylation to obtain lignin secondary derivatives. In particular, carboxyl alkylation is preferred. Introduction of various functional groups to these lignin primary derivatives can be carried out as it is or by appropriately modifying the method used for the above lignin primary derivatives.
[0052]
(Crosslinked product)
The crosslinked product of the present invention can be obtained by allowing a hydrophilic crosslinking compound to act on one or more of these lignin primary derivatives and secondary derivatives. In FIG. 4, an example of the crosslinked body manufacturing process of this invention is shown.
As the hydrophilic crosslinkable compound, a hydrophilic compound having two or more crosslinkable groups can be used. Preferably, the crosslinkable compound has sufficient solubility in water or an aqueous alkali solution. It is preferable to have water solubility that is at least soluble in water or an aqueous alkali solution supplied in the reaction system.
The crosslinkable group may be at least bifunctional, but may be a polyfunctional group having three or more functional groups. It is preferable to have an epoxy group, specifically, a glycidyl group. Further, the crosslinkable compound preferably has hydrophilicity in a portion other than the crosslinkable group, and preferably has a straight chain portion having two or more ether bonds as a crosslinkable group connecting portion. Such a hydrophilic linear moiety is preferably polyalkylene glycol. The alkylene group is preferably a lower alkylene group having 1 to 5 carbon atoms, and more preferably an alkylene group having 2 to 3 carbon atoms. The alkylene group may be branched but is preferably a straight chain.
The degree of polymerization of the polyalkylene group is preferably about 30 or less. Although the degree of polymerization varies depending on the type of alkylene group, for example, in the case of polyethylene glycol diglycidyl ether in which the alkylene group is an ethylene group, it is preferably 1 or more and 25 or less, more preferably 1 or more. Moreover, it is more preferable that it is 22 or less.
In the case of polypropylene glycol diglycidyl ether in which the alkylene group is a propylene group, it is preferably 1 or more and 10 or less, more preferably 1 or more, and preferably 3 or less.
[0053]
In the crosslinking reaction between the lignin derivative and the hydrophilic crosslinkable compound, the lignin derivative and the present crosslinkable compound are reacted in the presence of water. It is necessary that water be present in the reaction system. By cross-linking in the presence of water, the cross-linked product incorporating water appears from the reaction system as a gel.
The reaction medium may be distilled water or an aqueous acid solution, but is preferably an alkaline aqueous solution. This is because, in distilled water or an acid aqueous solution, although the crosslinking reaction proceeds, it is slow. In the case of an alkaline aqueous solution, the crosslinking reaction time varies depending on the alkali concentration, and the gelation time tends to be longer at a low concentration and shortened at a high concentration. Therefore, the crosslinking reaction time for obtaining an optimum gel can be adjusted according to the reaction system by the alkali concentration. As a result, there exists an advantage that a preferable gel (namely, gel with high water absorption) can be obtained easily.
[0054]
The concentration of the aqueous alkali solution to be used is not particularly limited, but is preferably about 0.1 N or more and 3 N or less, more preferably 0.2 N or more, and more preferably 2 N or less. If it is less than 0.1N, the crosslinking rate is too slow and the time until gelation is too long. If it exceeds 3N, the crosslinking rate is too fast and the time until gelation is too fast, and the gelation is rapid. This is because it is difficult to adjust the reaction stop timing to obtain a high water absorption rate or a stable water absorption rate. This is because if it is less than 0.2N, the time until gelation is long, and if it exceeds 2N, it is difficult to stop the reaction. More preferably, it is 0.5N or more and 1N or less. This is because a preferable gelation rate can be obtained with a wide concentration of the crosslinkable compound within the range. In addition, the kind of alkali to be used is not particularly limited, and a commonly used organic or inorganic alkali reagent can be used. Examples thereof include inorganic alkalis such as KOH and NaOH.
[0055]
The lignin derivative is preferably completely dissolved in the reaction medium to be used. However, it is not always necessary to completely dissolve the lignin derivative, and it may have an insoluble section. Moreover, the lignin density | concentration at the time of melt | dissolution may be high, and you may become a slurry form.
For example, 1 g of lignin derivative can be reacted with water, an acid aqueous solution, or an alkaline aqueous solution in an amount of 2 ml to 10 ml. Preferably, it is 3 ml or more, and preferably 7 ml or less. Most preferably, it is 4 ml or more and 6 ml or less.
[0056]
After the lignin derivative is dissolved or dispersed in a reaction medium such as water or an aqueous alkali solution, a crosslinkable compound is added, and the crosslinking reaction is allowed to proceed while stirring at a predetermined temperature. Although the reaction temperature is not particularly limited, the reaction proceeds even at about 20 ° C., and the reaction time becomes longer, but a water-absorbent crosslinked product can be obtained as a gel from the reaction system. On the other hand, when the temperature exceeds 80 ° C., the molecular weight of the lignin derivative is lowered particularly under alkaline conditions. Therefore, the cross-linking reaction and the low molecular weight reaction compete with each other, which may make it difficult to control the reaction. From the above, the reaction temperature is preferably 20 ° C. or higher and 80 ° C. or lower, and more preferably 40 ° C. or higher and 60 ° C. or lower.
[0057]
Depending on the length of the hydrophilic portion of the crosslinkable compound to be used, the water absorption rate of the crosslinked product varies. For example, the crosslinkable compound (diglycidyl group-containing) having a hydrophilic portion of polyethylene glycol has an increased water absorption as the degree of polymerization increases in the range of the degree of polymerization of 2 to 13. Therefore, it is considered that the hydrophilic part greatly contributes to water absorption.
Although the addition amount of the crosslinkable compound to be used is not particularly limited, the crosslinkable group in the crosslinkable compound to be used can be 0.5 times the molar amount or more with respect to the functional group contained in the lignin derivative. That is, when the reactive functional group contained in the lignin derivative is 2 mol, the crosslinkable compound may be supplied so as to supply 1 mol of the crosslinkable group. In the case of a bifunctional crosslinkable compound, 0.5 mol of compound may be supplied. The amount of the reactive group in the lignin derivative can be measured by NMR spectrum, IR spectrum, potentiometric titration and the like.
When the addition amount of the crosslinkable compound is large, the degree of crosslinking is high (resulting in a high recovery rate as a crosslinked product), and a crosslinked product having a low maximum water absorption rate tends to be obtained. When the amount is small, the degree of crosslinking is low (recovery rate as a crosslinked body is low), and a crosslinked body having a high maximum water absorption rate tends to be obtained.
It is preferable to add a crosslinkable compound having a crosslinkable group of 0.5 mol times or more and 30 mol times or less with respect to the reactive functional group contained in the lignin derivative. If it is less than 0.5 mol times, sufficient crosslinking is not achieved, and it is difficult to obtain a crosslinked product exhibiting water absorption. Conversely, when obtaining a water-soluble crosslinked product having no water absorption property, 0.5 mol is obtained. Less than double is preferable. On the other hand, when it exceeds 30 mole times, a new reactive functional group (such as a hydroxyl group) generated by ring-opening of the crosslinkable group in the crosslink reaction is frequently caused due to the presence of an excessive crosslinkable compound in the vicinity thereof. As a result, the recovery rate of the gel and the crosslink density are increased, and the voids for holding water absorption generated inside the cross-linked body molecules by the cross-linking are hardened tightly, resulting in a low water absorption rate. Because it becomes. A more preferable amount of the crosslinkable compound added is 0.65 mol or more and 14 or less with respect to the reactive functional group in the lignin derivative.
[0058]
As the cross-linking reaction between the lignin derivative and the cross-linking compound proceeds, the cross-linking density gradually increases, and at a certain point, gelation occurs and further cross-linking proceeds, and then the cross-linking reaction no longer proceeds. The crosslinked body can be separated by filtering the reaction solution at any point in the progress of the crosslinking reaction.The BookIn the reaction system of the invention, gelation occurs abruptly in the process of cross-linking. That is, in the progress of crosslinking, gelation clearly occurs at a certain reaction time, and the viscosity tends to increase rapidly. In general, such a phenomenon is often due to the high regularity of the form of introduction of the functional group that reacts with the crosslinkable compound. In the present invention, the regularity of the structure of the lignin derivative and the introduction of the functional group are often used. Presumably due to the high rate. Further, the water absorption rate takes a maximum value at a certain point in the progress of the crosslinking process, and then decreases. That is, a high maximum water absorption ratio is exhibited immediately after the start of gelation, and the water absorption ratio decreases with the progress of gelation and crosslinking. This is presumed to be because the network is coarse and water can be sufficiently retained at the start of gelation, but as the crosslinking proceeds, the network becomes dense and it becomes difficult to retain water. Therefore, a crosslinked product having high water absorption can be obtained by stopping the crosslinking reaction during or immediately after gelation. As already mentioned, the gel formation process in the process of cross-linking varies greatly depending on the amount of the crosslinkable compound. Therefore, in order to obtain a crosslinked product having a high water absorption capacity, it is preferable to adjust the gelation by paying attention to the addition amount of the crosslinking compound and the reaction stop time.
[0059]
The water-absorbing crosslinked product obtained in the present invention has a water absorption ratio of several tens to several hundreds of times, and easily obtains a water-absorbing crosslinked body having a higher water absorption ratio than conventional lignin-derived water-absorbing crosslinked bodies. be able to.
Here, the water absorption ratio can be obtained from the water absorption weight in a state where water absorption by the crosslinked body is balanced and the dry weight obtained by dehydration (drying). That is, the water absorption ratio is a numerical value obtained by dividing the equilibrium water absorption weight by the dry weight.
The water absorption magnification can be obtained, for example, by the following method. The reaction solution that has been cross-linked for a predetermined time and gelled is filtered through an 80-mesh nylon screen to separate the cross-linked product, and this separated cross-linked product is washed with water several times with water until it becomes neutral. After washing, soak again with a large excess of water, and after several hours, filter again with a mesh nylon screen, repeat this separation washing and soaking operation until the water absorption of the crosslinked body reaches parallel, and this water-absorbed crosslinking The body (gel) is weighed. Subsequently, this gel is dried by freeze-drying or the like, the dry weight is measured, and the gel weight relative to the dry weight can be used as the water absorption ratio. Moreover, the ratio of the dry weight with respect to the amount of lignin derivatives used can be made into a gelling rate (recovery rate).
[0060]
For example, using p-cresol as a phenolic compound, a lignin primary derivative obtained by using a lignocellulosic material (eg, defatted wood flour) such as beech as a lignin-containing material, the above water absorption ratio of 20 times or more can be easily obtained. be able to. In addition, a secondary derivative obtained by carboxyalkylating (typically carboxymethylating) this primary derivative can easily obtain a water absorption ratio of several tens to several hundreds times, at least 20 times to a maximum of 1000 times. it can. As a method for measuring the water absorption magnification, a method other than the method described here can be adopted as long as it is a water absorption magnification in a state in which the crosslinked body absorbs water until water absorption is balanced.
Therefore, the crosslinked product of the present invention has a water absorption ratio of at least 20 times. Furthermore, it can be preferably 100 times or more, more preferably 300 times or more. In addition, a particularly preferred water absorption ratio is 400 times or more and 600 times or less as the crosslinked product of the present invention.
[0061]
In addition, in order to obtain a high-strength cross-linked body (synonymous with a cross-linked body having a low water absorption ratio) or to increase the recovery rate of the cross-linked body, the amount of crosslinkable compound added or It is preferable to adjust the gelation by paying attention to the reaction stop time. In the presence of sufficient crosslinkable compound, the degree of crosslinking and recovery can be maximized by taking a sufficiently long crosslinking reaction time.
[0062]
In particular, a lignin secondary derivative having a carboxyalkyl group (particularly a carboxymethyl group) and / or a carboxyl group introduced has a high water solubility per se, and therefore a preferred water-absorbent crosslinked product can be obtained.
In addition, when p-cresol is used as a phenol compound, since the introduction efficiency of the phenol compound is high, the amount of the functional group introduced at the ortho-position or para-position of the phenolic hydroxyl group or the phenolic hydroxyl group also increases. High functional group introduction efficiency can be obtained. As a result, a secondary derivative having high cross-linking reactivity can be obtained. As a result, a gel having a high cross-linking density and a high strength can be obtained. Can do.
[0063]
In the cross-linking process before reaching gelation, this cross-linked product is present as a water-soluble cross-linked product because the cross-linking is rough and water cannot be restrained or retained. Further, when the final degree of crosslinking is low, gelation does not occur. The crosslinked product in the reaction system before gelation or not gelling can be obtained by dialysis of the reaction solution through a dialysis membrane and removing unreacted ethylene glycol diglycidyl ether and catalyst. After dialysis, the crosslinked product is dried by freeze-drying or the like, and the dry weight is measured. The recovery rate of the crosslinked product can be obtained as a ratio of the dry weight to the amount of the lignin derivative used.
[0064]
When the weight average molecular weight of the lignin derivative is about 700 to 1500, even if a sufficient crosslinking reaction time is ensured, a network structure that retains water is difficult to be constructed and may remain water-soluble. Such a low molecular weight lignin derivative can be easily obtained as a secondary derivative subjected to alkali treatment.
Further, such a water-soluble crosslinked product can be dissolved in an organic solvent such as dimethyl sulfoxide, dioxane, methanol, ethanol, chloroform, pyridine and a mixed solvent containing these organic solvents. For example, in the case of a lignin secondary derivative (lignin-containing material: beech wood flour, phenolic compound: p-cresol used) obtained by subjecting a lignophenol-based primary derivative to an alkali treatment at 170 ° C. (under 0.5N NaOH for 60 minutes), methanol is used. , Dissolved in chloroform, dimethyl sulfoxide, pyridine and the like.
[0065]
In addition to one or two or more lignin derivatives, the cross-linked product may be selected from polysaccharides, oligosaccharides, and one or more selected from carboxyalkyl groups, hydroxyalkyl groups, glycidyl ether groups, and carboxyl groups for these saccharides. It is also possible to mix with one or two or more saccharide compounds selected from the group consisting of saccharide derivatives obtained by introducing two or more functional groups and a crosslinked product obtained by crosslinking the crosslinking compound. According to this crosslinked body composition, it is possible to have both properties of a lignin-based crosslinked body and a crosslinked body of a saccharide compound. The various functional groups can be introduced into the polysaccharide and / or oligosaccharide by a conventionally known method.
[0066]
Moreover, a lignin derivative and a saccharide compound can be combined and crosslinked with the hydrophilic crosslinkable compound to obtain a crosslinked product. According to this copolymer-like cross-linked product, it is possible to combine both properties of a lignin-based cross-linked product and a saccharide compound cross-linked product.
[0067]
The crosslinked product thus obtained can be used as a conventionally known water-absorbing material in the case of a water-absorbed crosslinked product. Since the water-absorbing material is derived from plant resources, it is possible to promote the cyclic use of plant resources while suppressing adverse effects on the environment.
Further, by dehydrating the water-absorbed gel-like body, a crosslinked body that retains water absorption can be regenerated, and the crosslinked body can be used repeatedly for water-absorbing material applications, as well as further chemical modification (alkali treatment). , Various functional group introduction reactions) can be sequentially used for the next use.
[0068]
In particular, when the lignin derivative used for the cross-linked body has an ortho-position substitution unit, the gel-like body that has absorbed water is subjected to alkali treatment as it is to reduce the molecular weight of the lignin derivative that is a constituent part of the cross-linked body. It is also possible.
Furthermore, lignin derivatives have various adsorption performances and also function as adsorbents. Therefore, these adsorbed substances can be taken into the gel by gelling the lignin derivative adsorbed adsorbed substances including pollutants and harmful substances using the crosslinking agent. For example, the adsorbed substance in the aqueous medium can be separated and recovered in the gel by allowing the lignin derivative adsorbing the adsorbed substance to proceed in a crosslinking reaction in the aqueous medium.
Or the gel which hold | maintained the said useful substance can be obtained by gelatinizing the lignin derivative which adsorb | sucked the useful substance.
[0069]
According to the embodiment of the present invention described above, it is apparent that the present invention also includes the following aspects.
(1) A lignin-based crosslinked product,
The following (a) to (d):
(A) a lignin primary derivative of a phenolic compound of lignin obtained by adding an acid to a lignin-containing material solvated with a phenolic compound and mixing;
(B) A lignin secondary derivative in which one or more selected from the group consisting of a carboxyalkyl group, a hydroxyalkyl group, an epoxy group, and a carboxyl group are introduced to the lignin primary derivative of (a),
(C) a lignin secondary derivative obtained by alkali treatment of the lignin primary derivative of (a),
(D) The lignin derivative of (a) is subjected to an alkali treatment and one or more introduction reactions selected from the group consisting of a carboxylalkyl group, a hydroxyalkyl group, an epoxy group, and a carboxy group. Secondary lignin derivatives,
Secondary derivatives,
A lignin-based crosslinked product obtained by crosslinking one or more lignin derivatives selected from the above and a hydrophilic crosslinkable compound and having a water absorption ratio of 200 times or more.
(2) The lignin-based crosslinked product according to (1), wherein the water absorption ratio is 400 times or more and 600 times or less.
(3) A lignin-based crosslinked product,
The following (a) to (d):
(A) a primary derivative of a lignin phenolic compound obtained by adding an acid to a lignin-containing material solvated with a phenolic compound and mixing,
(B) A lignin secondary derivative in which one or more selected from the group consisting of a carboxyalkyl group, a hydroxyalkyl group, an epoxy group, and a carboxyl group are introduced to the lignin primary derivative of (a),
(C) a lignin secondary derivative obtained by alkali treatment of the lignin primary derivative of (a),
(D) The lignin derivative of (a) is subjected to an alkali treatment and one or more introduction reactions selected from the group consisting of a carboxylalkyl group, a hydroxyalkyl group, an epoxy group, and a carboxy group. Secondary lignin derivatives,
Secondary derivatives,
A hydrogel having a water absorption of 200 times or more obtained by crosslinking one or more lignin derivatives selected from the above and a hydrophilic crosslinkable compound.
(4) The hydrogel according to (3), wherein the lignin derivative holds an adsorbable substance.
[0070]
【Example】
Examples of the present invention will be described below. In addition, these Examples demonstrate this invention concretely, Comprising: This invention is not restrained.
Example 1
Preparation of primary lignin derivative (lignocresol)
3 mol-fold amount of p-cresol per lignin was sorbed on 25 g of acetone-defatted wood flour (beech, rice straw, rice bran, kenaf, bamboo). After adding 100 ml of 72% sulfuric acid to the total amount of this sorbed wood flour and reacting at 30 ° C. with stirring for 1 hour, the reaction system was poured into a large excess of water, and the insoluble precipitate was separated by centrifugation. The sample was thoroughly washed until sulfuric acid and unreacted cresol were removed, and dried on phosphorus pentoxide under reduced pressure. After adding 500 ml of acetone to this and stirring for a whole day and night, the insoluble matter is removed by centrifugation. After concentration by an evaporator, it is dropped into a large excess of diethyl ether, and the insoluble precipitate is centrifuged and washed. The phenolic primary derivative (lignocresol) was quantified after drying under reduced pressure on phosphorus pentoxide.
[0071]
(Example 2)
Preparation of lignin secondary derivatives by alkali treatment
The lignocresol prepared in Example 1 was used as a lignin primary derivative, 20 g of which was completely dissolved in 400 ml of a 0.5N aqueous sodium hydroxide solution, which was put into an autoclave, and 140 ° C. (0.25 MPa) and 170 ° C. (0 .68 MPa) for 1 hour. After completion of the reaction, the reaction mixture was cooled and neutralized with 1N hydrochloric acid. The precipitate was collected by centrifugation, washed with water, and freeze-dried to obtain an alkali-treated product.
[0072]
(Example 3)
Preparation of carboxyalkylated lignin secondary derivatives
1 g of lignocresol prepared in Example 1 was placed in a container, dispersed in advance with 4 g of isopropyl alcohol, added with 6.25 g of 40% aqueous sodium hydroxide solution, and allowed to stand sufficiently. 12 g of isopropyl alcohol was added thereto, and this heterogeneous mixed solution was maintained at 50 ° C. with stirring. A solution of monochloroacetic acid (approximately 1.3 mol per hydroxyl group in lignocresol) dissolved in 4 g of isopropyl alcohol was added over 1 hour. Then, the mixture was further stirred at 50 ° C. for 2 hours. After completion of the reaction, the reaction system is separated into an alcohol solution containing a precipitate of a lignin secondary derivative containing sodium hydroxide and a partially dissolved secondary derivative, and the precipitate and the alcohol solution are separated by filtration to obtain an alcohol solution. Was distilled off with an evaporator, and the dissolved product was dried. Next, the precipitate was dissolved in water, and a dry solid dissolved in a small amount of water was added thereto, and neutralized with 1N hydrochloric acid. The precipitate formed at this time was separated and washed by centrifugation, removed, and the supernatant and washings were collected, desalted by dialysis and freeze-dried to obtain a water-soluble carboxymethylated lignin secondary derivative.
[0073]
Example 4
Preparation of hydroxyalkylated lignin secondary derivatives
2.5 g of lignocresol prepared in Example 1 was placed in a container, and 6.25 ml of 1N aqueous sodium hydroxide solution was added and completely dissolved. While this was vigorously stirred in a 25 ° C. bath, 37.5 ml of propylene oxide was gradually added, the container was sealed, and the mixture was stirred for 1 hour. After completion of the reaction, the container was released, and the excess propylene oxide was volatilized at 48 ° C. to 50 ° C. for 1 hour or more. After cooling, the mixture was neutralized with 1N hydrochloric acid, and the precipitate was collected by centrifugation, washed with water until the precipitate was not separated, and lyophilized to obtain a hydroxypropylated lignin secondary derivative.
[0074]
(Example 5)
Preparation of epoxidized lignin secondary derivatives
2.5 g of lignocresol prepared in Example 1 was completely dissolved in 150 ml of epichlorohydrin and charged into a separable flask equipped with a thermometer, a dropping funnel and a water separator. The reaction vessel was depressurized using an aspirator and refluxed at 55 ° C to 60 ° C. At this time, the reaction system is 1.33 × 10 6.^-2The reduced pressure was adjusted to MPa. After the reflux was stabilized, 1.25 g of a 20% aqueous sodium hydroxide solution was added dropwise over 30 minutes from the dropping funnel. After the dropwise addition, reflux dehydration reaction was further performed for 1 hour 30 minutes. After completion of the reaction, the reaction system was cooled to room temperature and centrifuged to remove insoluble precipitates that were refreshed during the dropwise addition. The supernatant was concentrated with a vacuum evaporator and then dropped into a large excess of cyclohexane, and the resulting precipitate was centrifuged. Further, the precipitate was washed with cyclohexane using a centrifugal separation, and after the solvent was distilled off, the precipitate was dried under reduced pressure on phosphorus pentoxide to prepare glycidyl etherified lignocresol.
[0075]
(Examples 6 to 11)
Preparation of various cross-linked products
In the following examples, a crosslinked product was prepared under various conditions, and the recovery rate and water absorption ratio of the crosslinked product were measured. Hereinafter, the basic operation of the crosslinking reaction will be described, and individual conditions will be described in each example.
(Crosslinking reaction method)
The cross-linking reaction scheme is shown in FIG.
Water or an aqueous alkaline solution was added to the lignin derivative and completely dissolved. A hydrophilic crosslinkable compound was added to this solution and allowed to undergo a crosslinking reaction at a predetermined temperature with stirring. After the predetermined time, the sufficiently crosslinked product is crosslinked and gelled at this stage. In the case of gelation, water was absorbed and the swollen lignin cross-linked product was filtered through an 80 mesh nylon screen and separated. The separated crosslinked body was washed with water several times, then dipped again with a large excess of water, and after several hours, filtered again with a mesh nylon screen. This separation and washing operation was repeated until the water absorption of the crosslinked product reached a sufficient equilibrium. The weight of the crosslinked product in which water absorption reached a sufficient equilibrium was measured. Then, the lignin crosslinked body was dried by freeze-drying, and the water absorption capacity of the crosslinked body hydrogel was calculated. Moreover, the ratio of the dry weight with respect to the used lignin derivative was computed as a recovery rate. In addition, as already demonstrated, the water absorption magnification was a numerical value obtained by dividing the equilibrium water absorption weight by the dry weight of the crosslinked body.
On the other hand, if the lignin derivative is not cross-linked after completion of the reaction and no gel is formed, that is, if it cannot be filtered through a mesh nylon screen, the reaction solution is dialyzed through a dialysis membrane and unreacted cross-linkable compound. And the catalyst was removed. After completion of dialysis, the crosslinked product was dried by lyophilization, and the dry weight was measured. The ratio of the dry weight to the lignin derivative used was calculated as the recovery rate.
[0076]
(Example 6)
Influence of the type of lignin derivative in the crosslinking reaction
As the lignin derivative, the lignocresol prepared in Example 1 and the carboxymethylated lignin secondary derivative prepared in Example 3 were used, and various crosslinked products were prepared using ethylene glycol diglycidyl ether as the crosslinkable compound. Alkali lignin (manufactured by Aldrich, product number; 8068-05-1), carboxymethylated alkali lignin (manufactured by Aldrich, product number; 102962-28-7), organosolv lignin (manufactured by Aldrich, product number; 8068-03-9) and carboxymethylcellulose (manufactured by Wako Pure Chemical Industries, Ltd., product number: 039-01335) were also prepared. FIG. 6 shows the amount of lignin derivative used, the concentration and amount of alkaline aqueous solution, the amount of crosslinking compound used, the crosslinking reaction temperature, the crosslinking reaction time, the recovery rate, and the water absorption ratio.
In addition, the cross-linking reaction of each sample was performed 6 to 8 samples under the same reaction conditions (alkali addition concentration, cross-linking agent addition concentration, reaction temperature), respectively, and the condition reaction solution was visually observed and gelled (rapidly The reaction time was set at 10 minute intervals from the start, each reaction was stopped, and the separation and washing operation was performed immediately. The cross-linking reaction time of the sample in which the obtained cross-linked product showed the highest water absorption capacity was defined as the water absorption capacity by setting the cross-linking reaction time of each sample.
Each crosslinkable compound used was 10.2 × 10 5 as an epoxy equivalent in 1 ml.^-3(Eq / ml).
[0077]
As shown in FIG. 6, in addition to lignocresol, which is a primary derivative of lignin, and its carboxymethylated product, the carboxymethylated derivative of alkali lignin showed high water absorption. From this, it was found that carboxymethylation of the lignin primary derivative or this primary derivative and other lignin derivatives is effective for the preparation of a water-absorbing gel.
[0078]
(Example 7)
Influence of plants derived from lignin derivatives on cross-linking reaction
As the lignin derivative, various cross-linked products were prepared using the carboxymethylated lignin secondary derivative prepared in Example 3 for the various lignocresols prepared in Example 1 and ethylene glycol diglycidyl ether as the crosslinkable compound. FIG. 7 shows the amount of the lignin derivative used, the concentration and amount of the aqueous alkali solution, the amount of the crosslinking compound used, the crosslinking reaction temperature, the crosslinking reaction time, the recovery rate, and the water absorption ratio.
In addition, the cross-linking reaction of each sample was performed 6 to 8 samples under the same reaction conditions (alkali addition concentration, cross-linking agent addition concentration, reaction temperature), respectively, and the condition reaction solution was visually observed and gelled (rapidly The reaction time was set at 10 minute intervals from the start, each reaction was stopped, and the separation and washing operation was performed immediately. The cross-linking reaction time of the sample in which the obtained cross-linked product showed the highest water absorption capacity was defined as the water absorption capacity by setting the cross-linking reaction time of each sample.
Each crosslinkable compound used was 10.2 × 10 5 as an epoxy equivalent in 1 ml.^-3(Eq / ml).
[0079]
As shown in FIG. 7, not only lignin derivatives derived from woody plants such as beech but also lignin derivatives derived from agricultural by-products of herbaceous plants such as rice straw and rice straw, and lignin derivatives derived from herbaceous plants such as kenaf and bamboo were used. It was clear that even a cross-linked product exhibited a good recovery rate and water absorption capacity.
[0080]
(Example 8)
Influence of introduced functional groups on lignin derivatives in cross-linking reactions
As the lignin derivative, for the beech-derived lignocresol prepared in Example 1, and for the beech-derived lignocresol, various lignin secondary derivatives respectively obtained in Examples 2 to 5 were used, and ethylene glycol diglycidyl ether was used as a crosslinkable compound. Various cross-linked products were prepared by use. FIG. 8 shows the amount of the lignin derivative used, the concentration and amount of the alkaline aqueous solution, the amount of the crosslinkable compound used, the crosslinking reaction temperature, the crosslinking reaction time, the recovery rate, and the water absorption ratio.
In addition, the cross-linking reaction of each sample was performed 6 to 8 samples under the same reaction conditions (alkali addition concentration, cross-linking agent addition concentration, reaction temperature), respectively, and the condition reaction solution was visually observed and gelled (rapidly The reaction time was set at 10 minute intervals over time from the start, each reaction was stopped, and the separation and washing operation was immediately performed. The cross-linking reaction time of the sample in which the obtained cross-linked product showed the highest water absorption capacity was defined as the water absorption capacity by setting the cross-linking reaction time of each sample.
Each crosslinkable compound used was 10.2 × 10 5 as an epoxy equivalent in 1 ml.^-3(Eq / ml).
[0081]
As shown in FIG. 8, except for the lignin secondary derivative subjected to alkali low molecular weight treatment at 170 ° C., all gelled and exhibited high water absorption. Among them, it was clear that carboxymethylation was effective.
On the other hand, in the case of the lignin secondary derivative subjected to the alkali molecular weight reduction treatment, the crosslinked product was induced as water-soluble. This is also clear from the fact that absorption of methylene groups of the crosslinkable compound introduced with crosslinking and absorption derived from ether bonds are recognized from the IR spectrum. From these facts, the lignin primary derivative having a low molecular weight has a small molecule, so that the molecular weight does not increase to the extent that it becomes a gel even when the crosslinking proceeds. Furthermore, the cross-linking of the cross-linked product is such that the functional groups present in the same molecule of the lignin derivative cross-link via a cross-linkable compound, and the functional groups present in different lignin derivative molecules serve as a cross-linking point. There are two types of cross-linking forms of intermolecular cross-linking, and these cross-linking forms are mixed in the cross-linked body. Therefore, the low molecular weight lignin primary derivative has a small molecule and a small number of cross-linking points in the same molecule, and the resulting cross-linked form of the cross-linked product has a high frequency of inter-molecular cross-linking of the lignin derivative. That is, it can be said that the intramolecular cross-linking inside the lignin derivative molecule greatly contributes to the water absorption capacity of the cross-linked product because the cross-linked product of the lignin primary derivative having a low molecular weight with high intermolecular cross-linking frequency exhibits water solubility. By adjusting the frequency of this intramolecular crosslinking, the water absorption characteristics of the crosslinked product can be arbitrarily changed.
[0082]
Example 9
Effect of addition amount of crosslinkable compound
A carboxymethylated lignin secondary derivative prepared in Example 3 was used as the lignin derivative, and a crosslinked product was prepared using ethylene glycol diglycidyl ether as the crosslinkable compound. In addition, the usage-amount of a lignin derivative, the kind and quantity of aqueous alkali solution, the usage-amount of a crosslinking | crosslinked compound, crosslinking reaction temperature, crosslinking reaction time, a recovery rate, and a water absorption magnification are shown in FIG.
In addition, about each sample shown in FIG. 9, about the samples 1-4, several crosslinking reaction time was set, the recovery rate and water absorption factor in each crosslinking reaction time were measured, and the maximum obtained from these results The result about the crosslinking reaction time which shows the water absorption magnification of is shown. In addition, the result of the collection rate in each bridge | crosslinking reaction time about the samples 1-4 and a water absorption magnification is shown in FIG.
Samples 5 to 14 were each subjected to 6 to 8 samples under the same reaction conditions (alkali addition concentration, crosslinker addition concentration, reaction temperature), and the condition reaction solution was visually observed to form a gel (abrupt viscosity). (Increase) The reaction time was set at 10 minute intervals from the start, each reaction was stopped, and the separation and washing operation was performed immediately. The cross-linking reaction time of the sample in which the obtained cross-linked product showed the highest water absorption capacity was defined as the water absorption capacity by setting the cross-linking reaction time of each sample. The reaction solution was visually observed, and the time immediately after the start of gelation was taken as the crosslinking reaction time, and the separation and washing operation was performed immediately.
The crosslinkable compound used was 10.2 × 10 5 as an epoxy equivalent in 1 ml.^-3(Eq / ml).
[0083]
As shown in FIG. 10, when the amount of the crosslinkable compound was increased, the final recovery rate was increased, while the maximum water absorption ratio obtained was clearly decreased. Conversely, it was found that when the amount of the crosslinkable compound is decreased, the recovery rate is not high, but the maximum absorption rate to be obtained is increased and the crosslinking reaction time zone in which a certain water absorption rate can be secured is increased.
From these facts, it was found that adjustment of the amount of the crosslinkable compound added is important for obtaining a crosslinked product having a high water absorption capacity or for stably obtaining a crosslinked product having a certain water absorption capacity or more.
[0084]
Further, as shown in Samples 5 to 8 in FIG. 9, the addition amount of the crosslinkable compound is 0.05 ml, that is, about 0.5 times the mole of the functional group that can react with the epoxy group in the lignin derivative. It was found that gelation was possible with a corresponding addition amount.
According to the results of Samples 5 to 11, it was found that when the same crosslinkable compound was added, a higher water absorption ratio was obtained with a smaller amount of alkali (Samples 5 and 9, Samples 7 and 11). From comparison).
Moreover, according to the results of Samples 9 to 14, it was clear that setting the reaction temperature to 70 ° C. shortened the cross-linking reaction time until gelation as compared with the case of 50 ° C.
[0085]
(Example 10)
Influence of the type of crosslinkable compound in the crosslinking reaction
The carboxymethylated lignin secondary derivative prepared in Example 3 was used as the lignin derivative, polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether were used as the crosslinkable compounds, and the polymerization degree (n) of the polyalkylene glycol chain was determined. Various crosslinked products were prepared by differentiating them. FIG. 11 shows the amount of the lignin derivative used, the type and amount of the alkaline aqueous solution, the type and amount of the crosslinkable compound, the crosslinking reaction temperature, the crosslinking reaction time, the recovery rate, and the water absorption ratio.
In addition, the cross-linking reaction of each sample was performed 6 to 8 samples under the same reaction conditions (alkali addition concentration, cross-linking agent addition concentration, reaction temperature), respectively, and the condition reaction solution was visually observed and gelled (rapidly The reaction time was set at 10 minute intervals from the start, each reaction was stopped, and the separation and washing operation was performed immediately. The cross-linking reaction time of the sample in which the obtained cross-linked product showed the highest water absorption capacity was defined as the water absorption capacity by setting the cross-linking reaction time of each sample.
Each crosslinkable compound used was polyethylene glycol glycidyl ether as an epoxy equivalent in 1 ml: n = 1; 10.2 × 10^-3(Eq / ml), n = 2; 9.3 × 10^-3(Eq / ml), n = 4; 6.2 × 10^-3(Eq / ml), n = 9; 4.2 × 10^-3(Eq / ml), n = 13; 3.0 × 10^-3(Eq / ml), polypropylene glycol glycidyl ether: n = 1; 7.0 × 10^-3(Eq / ml), n = 2; 6.4 × 10^-3(Eq / ml), n = 3; 6.0 × 10^-3(Eq / ml).
[0086]
As shown in FIG. 11, any of polyethylene glycol diglycidyl ether and polypropylene glycol diglycidyl ether can be used as a crosslinking agent for lignin derivatives and can be gelled by selecting the degree of polymerization. It was found that the water absorption characteristics of the body can be changed arbitrarily.
Further, according to the results of Samples 15 to 19 (polyethylene glycol diglycidyl ether), the longer the chain length, the higher the gel water absorption capacity. That is, it has been found effective to adjust the degree of polymerization.
Further, according to the results of samples 20 to 22 (polypropylene glycol diglycidyl ether), when the degree of polymerization is 1, a gel having the highest water absorption is obtained. However, the recovery rate of Samples 20 to 22 was lower than that of Samples 15 to 19, and when the degree of polymerization was 3, the crosslinked product was water-soluble. Even when the degree of polymerization is 3, the IR spectrum of the cross-linked product shows that the methylene group absorption, ether bond, and ester bond absorption of the cross-linkable compound introduced with the cross-linking are recognized. The formation of a cross-linked product was obvious. The cross-linked product became water-soluble due to its increased hydrophilicity, but polypropylene glycol diglycidyl ether differs from polyethylene glycol diglycidyl ether in that the alkylene chain has a methyl group as a side chain, and the cross-linked product absorbs water. It is considered that the water absorption retention void formed by intramolecular crosslinking that contributes to the magnification has a highly hydrophobic void structure as compared with the crosslinked product of polyethylene glycol diglycidyl ether, and the water absorption retention capability is reduced. In other words, it was speculated that the cross-linked product exhibits higher water absorption by lengthening the hydrophilic chain of the cross-linkable compound and introducing a side difference that enhances the hydrophilic property.
[0087]
(Example 11)
Influence of alkali concentration in crosslinking reaction
Various cross-linked products were prepared using the carboxymethylated lignin secondary derivative prepared in Example 3 as the lignin derivative, ethylene glycol diglycidyl ether as the crosslinkable compound, and different alkali concentrations. FIG. 12 shows the amount of the lignin derivative used, the concentration and amount of the alkaline aqueous solution, the amount of the crosslinkable compound used, the crosslinking reaction temperature, the crosslinking reaction time, the recovery rate, and the water absorption rate.
In addition, the cross-linking reaction of each sample was performed 6 to 8 samples under the same reaction conditions (alkali addition concentration, cross-linking agent addition concentration, reaction temperature), respectively, and the condition reaction solution was visually observed and gelled (rapidly The reaction time was set at 10 minute intervals from the start, each reaction was stopped, and the separation and washing operation was performed immediately. The cross-linking reaction time of the sample in which the obtained cross-linked product showed the highest water absorption capacity was defined as the water absorption capacity by setting the cross-linking reaction time of each sample.
Each crosslinkable compound used was 10.2 × 10 5 as an epoxy equivalent in 1 ml.^-3(Eq / ml).
[0088]
As shown in FIG. 12, it was clear that as the alkali concentration in the reaction system increased, the cross-linking reaction time until gelation decreased. In Samples 23 to 26, although the alkali concentration greatly fluctuates, the water absorption ratio is within the range of about 400 to 650. Therefore, although the change in the reaction rate is large, the water absorption ratio is approximately It was found that a stable crosslinked product was obtained. On the other hand, in Sample 27, the water absorption ratio was significantly reduced, and it was found that a critical concentration of alkali concentration exists between Sample 26 and Sample 27 in this example.
[0089]
【The invention's effect】
According to the present invention, a highly aromatic and hydrophilic cross-linked product can be provided using a lignin-containing material derived from a lignocellulosic resource that is a renewable resource.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of a structure conversion process for obtaining a lignophenol derivative.
FIG. 2 is a diagram showing an example of structure conversion in the structure conversion process shown in FIG. 1;
FIG. 3 is a diagram showing an ortho-position binding unit and a para-position binding unit.
FIG. 4 is a diagram showing an example of a crosslinked body production process.
FIG. 5 shows an example of a cross-linking reaction scheme.
FIG. 6 is a diagram showing the influence of the type of lignin derivative in the crosslinking reaction.
FIG. 7 is a diagram showing the influence of a plant derived from a lignin derivative in a crosslinking reaction.
FIG. 8 is a diagram showing the influence of an introduced functional group on a lignin derivative in a crosslinking reaction.
FIG. 9 is a diagram showing the influence of the addition amount of a crosslinkable compound.
FIG. 10 is a diagram showing the results of the recovery rate and water absorption ratio in each cross-linking reaction time for samples 1 to 4;
FIG. 11 is a diagram showing the influence of the type of a crosslinkable compound in a crosslinking reaction.
FIG. 12 is a diagram showing the influence of alkali concentration in a crosslinking reaction.
FIG. 13 is a diagram showing the influence of temperature in a crosslinking reaction.

Claims (17)

A water-absorbing material,
The following (a) to (d):
(A) The phenol compound is introduced into the α-position of the arylpropane unit of lignin obtained by adding an acid to a lignin-containing material solvated with a phenol compound free of ortho-position and / or para-position and mixing 1 , A lignin primary derivative having a 1-bisarylpropane unit,
(B) A lignin secondary derivative in which one or more selected from a carboxyalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group are introduced to the lignin primary derivative of (a),
(C) The lignin primary derivative of (a), which has a 1,1-bisarylpropane unit in which the ortho-position carbon atom of the phenol compound is bonded to the α-position of the arylpropane unit, is alkali-treated. Secondary derivatives of lignin obtained by
(D) A lignin primary derivative of (a) having a 1,1-bisarylpropane unit in which the carbon atom at the ortho position of the phenol compound is bonded to the α-position of the arylpropane unit. Lignin secondary derivative subjected to alkali treatment and introduction reaction of one or more functional groups selected from a carboxylalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group,
One or two or more lignin derivatives selected from the group consisting of are obtained by crosslinking with a hydrophilic crosslinking compound in the presence of a crosslinking reaction medium containing water,
A water-absorbing material having a water absorption ratio of 20 times or more. The water-absorbing material according to claim 1, wherein the phenol compound is p-cresol. The water-absorbing material according to claim 1 or 2, wherein the lignin derivative is a lignin derivative of (b) and a secondary derivative having a carboxyalkyl group introduced therein. The water-absorbing material according to claim 1, wherein the hydrophilic crosslinkable compound is an ether compound having a glycidyl group having two or more functional groups. The water-absorbing material according to claim 4, wherein the hydrophilic crosslinkable compound is a polyalkylene glycol having a glycidyl group having two or more functional groups. The water-absorbing material according to any one of claims 1 to 5, wherein the lignin-containing material is a lignocellulosic material derived from a woody plant and / or a herbaceous plant. One or more lignin derivatives selected from the lignin derivatives according to claim 1 , polysaccharides, oligosaccharides, and carboxyalkyl groups, hydroxyalkyl groups, epoxy groups, carboxyl groups for these saccharides Formed by crosslinking with one or two or more saccharide compounds selected from the group consisting of saccharide derivatives obtained by introducing one or more selected from Water absorption material. The water-absorbing material according to any one of claims 1 to 7 , wherein the crosslinking reaction medium contains an alkali. A method of manufacturing a water absorbing material,
The following (a) to (d):
(A) The phenol compound is introduced into the α-position of the arylpropane unit of lignin obtained by adding an acid to a lignin-containing material solvated with a phenol compound free of ortho-position and / or para-position and mixing 1 , A lignin primary derivative having a 1-bisarylpropane unit,
(B) A lignin secondary derivative in which one or more selected from a carboxyalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group are introduced to the lignin primary derivative of (a),
(C) The lignin primary derivative of (a), which has a 1,1-bisarylpropane unit in which the ortho-position carbon atom of the phenol compound is bonded to the α-position of the arylpropane unit, is alkali-treated. Secondary derivatives of lignin obtained by
(D) A lignin primary derivative of (a) having a 1,1-bisarylpropane unit in which the carbon atom at the ortho position of the phenol compound is bonded to the α-position of the arylpropane unit. Lignin secondary derivative subjected to alkali treatment and introduction reaction of one or more functional groups selected from a carboxylalkyl group, a hydroxyalkyl group, an epoxy group and a carboxyl group,
A method comprising the step of cross-linking one or more lignin derivatives selected from the group consisting of a hydrophilic cross-linkable compound in a cross-linking reaction medium containing water. The method according to claim 9 , wherein the crosslinking reaction medium contains an alkali. The method according to claim 9 or 10 , wherein the crosslinkable compound is an ether compound having a glycidyl group having two or more functional groups. The method according to claim 11 , wherein the crosslinkable compound is a polyalkylene glycol having a glycidyl group having two or more functional groups. The method according to any one of claims 9 to 12 , wherein an amount sufficient to crosslink the crosslinkable compound and the lignin derivative is supplied to crosslink to form a gel-like crosslinked body. The method of Claim 13 which adjusts the water absorption rate of the crosslinked body obtained by adjusting crosslinking reaction time when producing | generating a gel-like crosslinked body. The method of Claim 13 or 14 provided with the process of supplying excess water to the gel-like crosslinked body isolate | separated from the reaction system after the said crosslinking reaction process, and making it water-absorb. The method according to any one of claims 9 to 15 , wherein the lignin-containing material is one or more lignocellulosic materials derived from woody plants and / or herbaceous plants. A method of manufacturing a water absorbing material,
One or more lignin derivatives selected from the lignin derivatives according to claim 1 , polysaccharides, oligosaccharides, and carboxyalkyl groups, hydroxyalkyl groups, epoxy groups and carboxyl groups for these saccharides One or two or more saccharide compounds selected from the group consisting of saccharide derivatives obtained by introducing one or two or more functional groups selected from the above are crosslinked with a hydrophilic crosslinkable compound. A method for obtaining a crosslinked product.

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