JPH11181105A - Lignocellulose molding and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain a molding of an arbitrary shape while abridging the production process by molding a cellulose or hemicellulose to which lignin having a specified molecular weight range has been bonded in a specified ratio. SOLUTION: The lignin used has a peak top molecular weight of 8,000-20,000 as measured by gel permeation chromatography. A molding of a cellulose or hemicellulose to which 3-40 wt.% this lignin has been bonded is obtained. The lignin-bonded pulp, namely, a low-rank pulp such as a thermomechanical pulp, a semichemical pulp, or an unbleached kraft pulp is treated with about 10-40 wt.% aqueous alkali solution and xanthated with a 0.8-1.5 fold amount of carbon disulfide. This is dissolved in a 6-10 wt.% aqueous NaOH solution to form a viscose. This viscose is molded into a sheet or the like by casting, extrusion, or the like. When the molding is a porous one, it can be used as an adsorbent for metals and proteins in an aqueous system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded product made of lignocellulose bound with lignin and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, cellulose, which is a main component of plants,
Among hemicellulose and lignin, cellulose and hemicellulose polysaccharides are often used,
Despite its ability to adsorb metals and proteins and its antibacterial activity, lignin has hardly been used effectively except as a fuel. This is because the lignin is extracted from the waste liquid produced during pulping of wood, and most of the lignin has been modified into a water-soluble and less reactive structure. However, lignin is an organic substance which is present in a large amount in nature and is a renewable resource. Therefore, studies have been conducted on the effective use of lignin.

[0003] For example, since lignin is a phenolic substance, of the lignin contained in pulp waste liquid,
A method has been proposed in which a phenol resin is co-condensed with lignin sulfonic acid to obtain a modified phenol resin (see JP-A-55-137120).

Further, a method has been disclosed in which lignin is crosslinked with other biological substances to produce a material for a printed wiring board or the like (see Japanese Patent Application Laid-Open No. 9-143305).

Further, in order to increase the reactivity of lignin itself, a method of converting lignin into a lignin alkenyl derivative has been studied (see Japanese Patent Publication No. 195559/1993).

On the other hand, as a method of utilizing lignin in combination with a material such as cellulose, a multilayer body comprising cellulose and hemicellulose is impregnated with lignin to strengthen the original structure of lignin which plays a role in plants ( Japanese Patent Application Laid-Open No. 6-198811) and a lignin complex in which lignin is bonded and fixed to porous solid polymer particles made of cellulose or the like by chemical means have been proposed (see Japanese Patent No. 2548240).

As a method for molding wood flour or low-grade pulp containing a large amount of lignin into a desired shape, for example, acetic acid digested pulp is mixed in a mixed solvent of tertiary amine-N-oxide and water. A method of directly dissolving and molding into an arbitrary shape has been proposed (see JP-A-6-220213).

Further, as a method via a derivative, a method of obtaining an absorbent material in a form in which lignin is left by carboxymethylating wood flour or high yield pulp (Japanese Patent Publication No. 2-5689)
No. 7), a method in which hydroxyl groups in wood are partially substituted with acetyl groups or the like, a wood solution is prepared and molded into an arbitrary shape (see Japanese Patent Publication No. 63-1992). An ultraviolet-absorbing lignocellulose membrane obtained by solidifying a melt to form a membrane has been proposed (JP-A-4-339).
No. 86).

[0009]

However, in the above-mentioned method using lignin in pulp waste liquid, lignin obtained is water-soluble and has a low concentration, so that it is necessary to carry out concentration. In addition, in the method of producing a modified phenol resin using ligninsulfonic acid, in order to increase the reactivity of ligninsulfonic acid, after lowering the molecular weight by oxidative decomposition or hydrogenolysis, the one having a large amount of carboxyl groups is fractionated. Or
Further oxidation is required. Furthermore, kraft lignin obtained by the currently mainstream kraft pulp method has poor reactivity in the side chain structure, and it is necessary to increase the reactivity so as to convert it into an alkenyl derivative, but this is economically disadvantageous.

Further, in the method of combining lignin with an existing material, since lignin is water-soluble, lignin is eluted by contact with water simply by coating or impregnating the existing material with lignin. . In order to prevent this, there is a method of fixing by chemical bonding, but it is economically disadvantageous because an expensive cross-linking agent must be used, and if the reaction does not proceed sufficiently, lignin or The cross-linking agent is eluted.

Further, in the method of molding by dissolving wood flour or low-grade pulp, it is considered that lignin is less likely to be deteriorated in a solution with a mixed solvent of tertiary amine-N-oxide and water. Is limited to those obtained by the acetic acid digestion method, so that the versatility is poor. In the method of obtaining an absorbent material by carboxymethylation, it is difficult to form the material into an arbitrary shape, and thus the method is limited to use in a fibrous form. In addition, in a method in which wood is subjected to acetylation, acylation, etc. to prepare a wood solution and form a film, etc., it is necessary to increase the degree of substitution. There is a possibility that the mechanical strength of the molded article itself is significantly reduced. In the method of solidifying and forming a mutual solution of lignin and cellulose, blasted pulp is made into viscose, which is then formed into a film to obtain lignocellophane. However, in this method, the amount of carbon disulfide to be added is about 0.3 to 0.5 times the pulp as in the case of a general viscose production method using α-cellulose of high purity. For this reason, a large amount of lignin contained in the pulp hinders xanthetization, making it difficult to perform sufficient xanthation. Therefore, the obtained viscose tends to be non-uniform, and insoluble components are also generated. Therefore, in the method described in JP-A-4-33986, a method of removing insoluble components by centrifugation or the like is employed.

Therefore, an object of the present invention is to concentrate, react,
The process of removing insoluble components and the like is reduced as much as possible, thereby simplifying the production process, increasing the economic efficiency, increasing the moldability of lignin-bound cellulose, and easily obtaining a lignocellulose molded article of any shape. Is to do so.

[0013]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention relating to the lignocellulose molded article is characterized in that a lignin having a peak-top molecular weight of 8,000 to 20,000 in gel permeation chromatography is used.
Consists of ~ 40% by weight bound cellulose or hemicellulose.

Further, according to the invention relating to the method for producing a lignocellulose molded article, the molecular weight at the peak top in gel permeation chromatography is 8,000 to 200.
The pulp to which 3 to 40% by weight of lignin of 00 is bound is pretreated with an aqueous alkali solution, and carbon disulfide is added to the pulp in an amount of 0.8 to 1.5 times the amount of the pulp to xanthate and dissolved in the aqueous alkali solution. To prepare viscose and coagulate and regenerate it.

Further, the pulp may be any one or a mixture of two or more of thermomechanical pulp, semi-chemical pulp and unbleached kraft pulp.

This lignocellulose molded article is obtained by converting lignin-bonded pulp into viscose to form a solution, forming it into a predetermined shape, and then coagulating and regenerating, so that a lignocellulose molded article of any shape can be obtained. .

In addition, since the amount of carbon disulfide added to the pulp at the time of viscose preparation is 0.8 to 1.5 times, which is more than 0.3 to 0.5 times the usual amount, a large amount of lignin is added. Can be sufficiently xantated. Therefore, uniform viscose can be obtained without generating any insoluble components.

[0018]

Embodiments of the present invention will be described below. The lignocellulose molded article according to the present invention is made of lignin-bound cellulose or hemicellulose. This lignocellulose molded article is manufactured by the following method.

First, pulp to which lignin is bound is pretreated with an aqueous alkali solution, and carbon disulfide is added to form a xanthate.

The pulp is not particularly limited as long as it is a low-grade pulp bound with lignin. Examples include thermomechanical pulp (TMP), semi-chemical pulp (SCP), unbleached kraft pulp (UKP). Among these, it is preferable to use low-grade pulp to which lignin is bound in a large amount, because it can utilize the ability of lignin to adsorb metals and proteins.

The lignin is a phenolic substance,
Along with cellulose and hemicellulose, it is one of the main components of woody plants such as wood. The lignin is bound to cellulose or hemicellulose by a stable covalent bond close to the binding mode in wood. This lignin is composed of a large number of compounds, and shows a spread close to a normal distribution when the molecular weight distribution is taken.

This lignin has a peak-top molecular weight (hereinafter referred to as "peak-top molecular weight") of 8,000 to 20,000 in the molecular weight measurement by gel permeation chromatography after acetylation, and is 3 to 3 in pulp. 40% by weight are bound. If the peak top molecular weight of lignin is less than 8000, it is difficult to sufficiently exhibit the adsorptivity of lignin itself, which is not preferable. Although it may exceed 20,000, it is difficult to isolate such lignin by the method of the present invention.

Further, when the lignin is less than 3% by weight of the pulp, it may be difficult to sufficiently exhibit the adsorptivity of the lignin itself. Although it may exceed 40% by weight, pulp that binds lignin in a large amount rarely binds lignin having the above-mentioned molecular weight in excess of 40% by weight.

Since this lignin is bonded to cellulose or hemicellulose by a stable covalent bond close to the bonding mode in wood, it can not be separated simply by immersing pulp or lignocellulose molded article in water. In order to isolate the pulp or lignocellulose molded product, it is necessary to enzymatically decompose the surrounding cellulose or hemicellulose with cellulase or the like. This indicates that lignin and cellulose or hemicellulose constituting the pulp, lignocellulose molded article and the like are firmly bound. Therefore, lignin is unlikely to be decomposed or separated by viscose or the like.

The above pulp is pretreated with an aqueous alkali solution, and xanthetized by adding carbon disulfide. The pretreatment is performed to generate alkali cellulose, and the concentration of the aqueous alkali solution to be used is not particularly limited.
If it is 0 to 40% by weight, the pretreatment can be sufficiently performed. The alkaline aqueous solution is not particularly limited, and as an example,
Examples include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide.

The carbon disulfide is added to the pulp at 0.8 to 1.
5 times the amount is added. If the amount added is less than 0.8 times,
The viscose obtained tends to be non-uniform. Also, 1.
If the amount exceeds 5 times, it may be separated into two layers. In this case, not only the reaction becomes non-uniform, but also the reaction occurs only at the interface, so that the reaction efficiency decreases.

Xanthetized pulp is dissolved in an aqueous alkali solution to form viscose. The concentration of the aqueous alkali solution is preferably 6 to 10% by weight as sodium hydroxide. If it is lower than 6% by weight, undissolved matter in viscose increases. If it is higher than 10% by weight, the concentration of the acid bath at the time of coagulation / regeneration needs to be high, which is not preferable.
The alkaline aqueous solution is not particularly limited. For example,
Examples include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide.

Next, the obtained viscose is formed into a predetermined shape. For example, when forming into a film or sheet, a film or sheet having a predetermined thickness can be obtained by a casting method, an extrusion method, or the like. Also, if viscose is injected into a mold having a predetermined shape, it can be formed into an arbitrary shape. Further, when the particles are formed into particles, the particles can be obtained by dropping from a nozzle having a predetermined pore diameter or by suspending the particles in a medium having low compatibility.

Although viscose is viscous, it must be solidified immediately after molding because it is liquid. The coagulation is performed by using a coagulant such as an acid such as heating and hydrochloric acid or sulfuric acid. Thereafter, the cellulose is regenerated with an acid such as hydrochloric acid or sulfuric acid to obtain lignin-bound cellulose, that is, lignocellulose. If an acid such as hydrochloric acid or sulfuric acid is used during coagulation, coagulation and regeneration can be performed simultaneously, which is efficient.

The obtained lignocellulose molded article binds lignin having the same molecular weight at the same ratio as the pulp used. That is, the peak top molecular weight is 800
When pulp bound with 3 to 40% by weight of lignin of 0 to 20,000 is used, the peak top molecular weight is 8%.
A lignocellulose molded article in which lignin of 000 to 20,000 is bound by 3 to 40% by weight is obtained. This is because, as described above, since lignin and cellulose and hemicellulose are bonded by a stable covalent bond close to the bonding mode in wood, lignin is hardly decomposed and separated in the xanthetization reaction.

In the production of the lignocellulose molded article of the present invention, high-grade pulp, that is, viscose produced from pulp having a small amount of lignin bond, may be blended at any ratio in order to improve moldability. . As the viscose for blending, industrial viscose used for producing cellophane is preferable. As the properties of the viscose for blending, the cellulose concentration is usually 3 to 1
It is preferably 5% by weight, more preferably 4 to 12% by weight.
The alkali concentration in the viscose is preferably 2 to 15% by weight as sodium hydroxide, more preferably 5 to 13% by weight. Further, the ammonium chloride value is 3 to 12
Is preferable, and 4-9 are more preferable.

When the lignocellulose molded article of the present invention is used as an adsorbent or the like, a porogen such as calcium carbonate may be added to the viscose solution before molding.
Thereby, when the molded article is regenerated after the molding, the molded article is made porous and a porous body can be obtained.

[0033]

Next, an embodiment of the present invention will be described. In the following, “%” indicates “% by weight”.

EXAMPLE 1 10 g of unbleached softwood kraft pulp (NUKP) to which 5% of lignin was bound was placed in a beaker, and 150 m of a 17.5% aqueous sodium hydroxide solution was added.
1 and shaken at 25 ° C. for 2 hours. Excess sodium hydroxide aqueous solution was removed by filtration under reduced pressure, squeezed to three times the original dry weight, crushed and placed in a jar (200 ml), and shaken at 25 ° C. for 18 hours. After degassing for 30 minutes, 10 g of carbon disulfide was added, sealed and shaken at 25 ° C. for 2 hours to form xanthate. Thereto, 70 ml of a 6% aqueous sodium hydroxide solution was added, and the mixture was stirred at 25 ° C. for 18 hours to prepare NUKP viscose. It was dropped into a 2N sulfuric acid from a nozzle having a pore diameter of 1.8 mm and solidified and regenerated to prepare a spherical lignocellulose molded article having a particle diameter of 3 mm.

The amount of lignin bound and the peak top molecular weight, the adsorption rate of bovine serum albumin (hereinafter, referred to as “BSA”) in the obtained lignocellulose molded article, and the metallic aluminum (hereinafter, referred to as “Al”). ) Was measured by the following method. Table 1 shows the results. Also,
The saccharides contained in lignin isolated from the obtained lignocellulose compact were examined by the following method. As a result, lignin contained 10.8% of glucose and 3.8% of xylose.

Lignin binding in lignocellulose compacts
The sample for measuring the amount and the peak top molecular weight was treated with cellulase in an acetate buffer (pH = 4.5) (40 ° C., 96 hours) and centrifuged. After repeating this operation twice, the resultant was dissolved in a 1N aqueous sodium hydroxide solution, precipitated by adding hydrochloric acid, and the obtained suspension was dialyzed and freeze-dried. The weight was measured, and this was defined as the amount of lignin binding.

After pyridine / acetic anhydride was added to the obtained lignin and left overnight, acidified with hydrochloric acid, and the solvent was extracted with dichloromethane to isolate acetylated lignin.

The molecular weight of the acetylated lignin thus obtained was measured by gel permeation chromatography to determine the peak top molecular weight.

To a 500 mg sample of BSA adsorption rate, 2 ml of 1.0 mg / ml BSA acetate buffer solution (pH = 4.5) was added, shaken at 20 ° C. for 1 hour, and 50 μl aliquots were collected. Kit II (Nippon Bio-Rad Laboratories) Staining Solution 5
ml was added. After leaving it for 30 minutes at room temperature, 59
The absorbance at 5 nm was measured, and BS was determined from the calibration curve obtained in advance.
The A concentration was determined, and the BSA adsorption rate was calculated as a value per 1 g of the lignin contained.

1 g of a sample for measuring the Al adsorption rate was taken, and 100 ml of a standard solution containing 50 ppm of aluminum ions was added thereto. 25 ℃
After shaking for 3 hours, the metal ion concentration of the supernatant was determined by ICP emission spectrometry, and the Al adsorption rate was calculated as a value per 1 g of the lignin contained.

Measurement of Lignin-Containing Sugars Lignin isolated by the above method was added with 72% sulfuric acid, allowed to stand overnight, added with a little water, and autoclaved at 121 ° C. for 1 hour. added. Further, after adding inositol as an internal standard thereto, a portion was taken, and sodium borohydride was added thereto to add 4 parts.
The reaction was performed at 0 ° C. for 90 minutes. Acetic acid and 1-methylimidazole were added to the reaction solution, and the mixture was allowed to stand at room temperature for 10 minutes to acetylate. Then, water was added, extracted with dichloromethane, and analyzed by gas chromatography.

Example 2 NUKP was converted to lignin-binding amount 2
TM in the same manner as in Example except that the TMP was changed to 0%.
P viscose was prepared. It was blended with cellophane production viscose at a ratio of 3: 1, degassed for 30 minutes, cast to a thickness of 2 mm, and solidified with 2N sulfuric acid.
The sheet was regenerated to obtain a sheet-like lignocellulose molded article.

The amount of lignin bound in the obtained lignocellulose molded article, the peak top molecular weight, the BSA adsorption rate,
And the adsorption rate of Al were measured. Table 1 shows the results.
The saccharides contained in lignin isolated from the obtained lignocellulose compact were 3.2% glucose and 3.8% xylose.

Comparative Example 1 Kraft lignin having a peak top molecular weight of 2500 was mixed with 50% of the viscose for producing cellophane used in Example 2 and the mixed viscose was passed through a nozzle having a pore diameter of 1.8 mm in 2N sulfuric acid. To form a lignin-containing spherical cellulose molded article.

The lignin content and the peak top molecular weight in the obtained lignin-containing spherical cellulose molded article, BS
The A adsorption rate and the Al adsorption rate were measured. Table 1 shows the results.
Shown in Lignin isolated from the obtained cellulose molded product did not contain saccharides.

Comparative Example 2 For the kraft lignin used in Comparative Example 1, the peak top molecular weight, BSA adsorption rate, and Al adsorption rate were measured. Table 1 shows the results.

[Comparative Example 3] The viscose for producing cellophane used in Example 2 was passed through a nozzle having a hole diameter of 1.8 mm through a 2N nozzle.
By coagulating and regenerating by dropping into sulfuric acid, cellulose beads were prepared.

The lignin binding amount and the peak top molecular weight in the obtained cellulose beads, the BSA adsorption rate, and A
1 was measured. Table 1 shows the results.

[0049]

[Table 1]

[0050]

According to the present invention, a lignocellulose molded article having an arbitrary shape can be obtained.

Further, since viscose is prepared using an amount of carbon disulfide added to the pulp larger than usual, the cellulose to which a large amount of lignin such as low-grade pulp is bound is sufficiently xantated. be able to. For this reason, uniform viscose with very little insoluble content can be obtained, various moldings can be easily performed, and an arbitrary lignocellulose molded article can be obtained.

Further, since the lignocellulose molded article has a large amount of lignin having a high molecular weight, this molded article is
Has high adsorption capacity for proteins and metal ions.

Furthermore, the lignin bound to the pulp is almost uniformly compounded with the pulp. For this reason, when a lignocellulose molded article is obtained by using lignin-bound pulp as it is, lignin is uniformly compounded also in the obtained lignocellulose molded article, but due to the high hydrophilicity of cellulose, metals and proteins in aqueous systems are produced. Does not impair the adsorption capacity of In addition, since the molecular weight of lignin is maintained in a high state, the above-mentioned adsorption ability is maintained in a high state.

Claims (3)

[Claims] 1. The molecular weight at the peak top in gel permeation chromatography is 8,000 to 20,000.
A lignocellulose molded article comprising cellulose or hemicellulose having 3 to 40% by weight of lignin bound thereto. 2. The molecular weight at the peak top in gel permeation chromatography is 8,000 to 20,000.
The pulp bound with 3 to 40% by weight of lignin is pretreated with an aqueous alkali solution, carbon disulfide is added to the pulp in an amount of 0.8 to 1.5 times the amount of the pulp to xantate, and dissolved in an aqueous alkali solution. A method for producing a lignocellulose molded article by preparing viscose and coagulating and regenerating it. 3. The pulp is a thermomechanical pulp,
3. The method for producing a lignocellulose molded product according to claim 2, wherein the lignocellulose molded product is one or a mixture of two or more of semi-chemical pulp and unbleached kraft pulp.