JP2013124317A - Polyvinyl alcohol-based polymer and method for producing hydrolyzable cellulose using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide PVA which imparts a suitable viscosity to a mixture containing cellulosic biomass, or the like, on the production of the hydrolyzable cellulose from the cellulosic biomass as a raw material, whereby the decomposition of cellulosic biomass to a molecular level can be facilitated, and the hydrolyzable cellulose can consequently efficiently be produced.SOLUTION: The polyvinyl alcohol-based polymer is used for producing the hydrolyzable cellulose from cellulosic biomass as a raw material and having monomer units represented by formula (1) (wherein, Rand Rare each independently H, alkyl or acyl; and X is a 1-3C alkylene which may be single-bonded or bonded through an oxygen atom).

Description

  The present invention relates to a polyvinyl alcohol polymer used for producing hydrolyzable cellulose using cellulose biomass as a raw material, and a method for producing hydrolyzable cellulose using the same.

  Biomass refers to biologically-renewable resources, and can be defined as “renewable, biologically-derived organic resources excluding fossil resources”. Among the biomass, effective utilization of unused plant biomass such as wood from thinned wood, rice straw, straw, rice husk, stalks of starch-based crops such as corn and sugarcane, and oil palm empty bunch (EFB) is required. .

  Among such plant-based biomass components, many polysaccharides such as starch are easily decomposed into monosaccharides by enzymes and the like, and are used as energy sources, foods, and the like. Therefore, for effective utilization of plant-based biomass, it is important to break down cellulose, which has a high abundance ratio in plant cells, into methane and monosaccharides (glucose) and use them as an energy source, food, and the like. However, as can be seen from the fact that cellulose forms most of the cell wall, cellulose is not effectively utilized because it has a strong structure and is not easily decomposed.

  Specifically, cellulose has the following multiple structures in the cell wall. The cellulose that forms the cell wall has a quasicrystalline structure that adheres in a straight line, most often referred to as microfibrils. Celluloses (microfibrils) having this quasicrystalline structure are bonded to each other via non-cellulose components such as hemicellulose and lignin. These cellulose components (microfibrils) and non-cellulose components are arranged as a larger structure generally referred to as fibrils. These fibrils are usually laminated in a sheet form to constitute a cell wall. In cellulose (microfibril) having the above-described quasicrystalline structure, the polymer chains of cellulose are strongly bound by hydrogen bonding. This hydrogen bond causes the plant to have a strong cell wall.

  As a means for decomposing cellulose having such a structure into methane, there is a method by decomposing and digesting anaerobic microorganisms. However, the degradation of cellulose using microorganisms is not sufficiently practical due to the complex reaction control.

  On the other hand, it is also chemically possible to hydrolyze cellulose into monosaccharides using a catalyst or an enzyme. Monosaccharides obtained by chemical decomposition of cellulose are converted into ethanol by fermentation, for example, and can be used as an energy source for existing internal combustion engines and turbines. However, chemical direct hydrolysis of cellulosic biomass derived from plants is not efficient due to the molecular structure of cellulose in the cell wall as described above. This is considered to be because the strong structure of cellulose hinders the entry of water and enzymes into the quasicrystalline structure and greatly delays the action of the cellulolytic enzyme. That is, the enzyme cannot easily break into a glycosidic bond because it cannot easily enter the interior of the quasicrystalline structure that is strongly bound by hydrogen bonding. Therefore, since the enzyme can only be gradually decomposed from the surface of the quasicrystalline structure of cellulose, it is not efficient to directly hydrolyze the cellulosic biomass with the enzyme.

  In view of this, a method has been proposed in which cellulose-based biomass is finely divided in advance before hydrolysis with an enzyme or the like to produce cellulose that is easily hydrolyzed. In this method, basically, cellulose having a quasicrystalline structure is gradually hydrated, and this hydration weakens the hydrogen bond between the polymer chains of adjacent celluloses. The physical action of mechanically applying force by kneading or the like to break the cellulose polymer chain is utilized. As specific contents of this method, for example, (1) a cellulosic biomass particle is agitated in a container to produce a particle floating body, and then the temperature of the particle floating body is raised while continuing stirring and water is added. Technology for producing fine powder by gradually supplying and hydrating (see Patent Document 1), (2) Mechanical biomass produced by stirring by mixing cellulosic biomass particles with a viscous water-soluble polymer aqueous solution A technique for efficiently transmitting a strong force to a cellulose polymer chain and dividing the cellulose polymer chain so as to be separated from each other has been proposed (see Patent Document 2).

  However, in the technique (1), an apparatus for causing the fine particles of the cellulosic biomass to exist as a floating body becomes complicated. Moreover, since a great amount of energy is consumed when using this technology, it cannot be said that productivity is high. On the other hand, in the technique (2), a certain degree of easily hydrolyzable improvement of the cellulosic biomass is recognized by using a water-soluble polymer for imparting viscosity to the aqueous solution. However, in order to improve the hydrolyzability for practical use, further improvements are required.

Special Table 2004-526008 International Publication No. 2009/124072

  The present invention has been made based on such circumstances, and by providing a suitable viscosity to a mixture containing cellulosic biomass in the production of hydrolyzable cellulose using cellulosic biomass as a raw material, etc. In addition, it is possible to easily divide cellulosic biomass at a molecular level, and as a result, a polyvinyl alcohol polymer capable of efficiently producing hydrolyzable cellulose, and a hydrolyzate using this polyvinyl alcohol polymer. It aims at providing the manufacturing method of degradable cellulose.

The polyvinyl alcohol polymer of the present invention made to solve the above problems is
A polyvinyl alcohol polymer used for the production of hydrolyzable cellulose using cellulosic biomass,
It has a monomer unit represented by the following formula (1).

In formula (1), R ¹ and R ² each independently represent a hydrogen atom, an alkyl group or an acyl group, and X represents a C 1-3 alkylene group which may be via a single bond or an oxygen atom. .

  Since the polyvinyl alcohol-based polymer has a monomer unit represented by the above formula (1), it has a high affinity with water and cellulosic biomass and can increase the viscosity of this aqueous solution when it is used as an aqueous solution. In addition, when this aqueous solution is mixed with powdered or particulate cellulosic biomass, the uniform dispersibility (miscibility) of the cellulosic biomass in the resulting mixture can be enhanced.

  Accordingly, an appropriate shearing force can be applied to the cellulosic biomass by mixing the aqueous solution of the polyvinyl alcohol polymer and the cellulosic biomass particles. That is, in such an operation using the polyvinyl alcohol polymer, cellulose polymer chains are easily separated from each other by a viscous aqueous solution, and water and polyvinyl alcohol are contained inside the polymer chain having a quasicrystalline structure. As the polymer enters efficiently, hydrogen bonds between the polymer chains can be weakened. Furthermore, the re-quasi-crystallization of the polymer chain can be prevented by the polyvinyl alcohol polymer entering between the polymer chains thus torn. That is, according to the polyvinyl alcohol-based polymer, it is possible to effectively break the cellulose polymer chain in the cellulosic biomass at the molecular level and obtain cellulose that is easily hydrolyzed (saccharified) by an enzyme or the like.

  The polyvinyl alcohol polymer preferably has an average degree of polymerization of 100 or more and 4,000 or less. The polyvinyl alcohol polymer preferably has a saponification degree of 70 mol% or more and 99.9 mol% or less. Furthermore, the content of the monomer unit represented by the above formula (1) is preferably 0.2 mol% or more and 10 mol% or less. When the average degree of polymerization, the degree of saponification, and / or the content of the monomer units of the polyvinyl alcohol polymer are in the above range, the aqueous solution of the polyvinyl alcohol polymer and the cellulosic biomass are more suitable for viscosity. Thus, the polyvinyl alcohol polymer can be easily and uniformly mixed, and can easily enter between the torn cellulose polymer chains. Therefore, cellulose having higher hydrolyzability can be obtained by using such a polyvinyl alcohol polymer.

Another invention made to solve the above problems is as follows:
A method for producing hydrolyzable cellulose using cellulosic biomass as a raw material,
A mixing step of obtaining a mixture containing the aqueous solution of the polyvinyl alcohol polymer and the cellulose-based biomass;
And a dividing step of dividing the cellulosic biomass by applying a shearing force to the mixture.

  According to the method for producing hydrolyzable cellulose, a mixture having an appropriate viscosity can be obtained by mixing an aqueous polyvinyl alcohol polymer solution and cellulose biomass. Further, according to the production method, by applying a shearing force to the mixture, cellulose polymer chains are easily separated from each other by a viscous aqueous solution, and water and polyvinyl are contained inside the polymer chain having a quasicrystalline structure. The alcohol-based polymer can efficiently enter to weaken the hydrogen bond between the polymer chains. That is, according to the method for producing hydrolyzable cellulose, it is possible to effectively break the cellulose polymer chain in the cellulosic biomass at the molecular level and obtain cellulose that is easily hydrolyzed (saccharified) by an enzyme or the like.

  In the manufacturing method, the aqueous solution may be in a gel form. Thus, by using a polyvinyl alcohol polymer aqueous solution that is in the form of gel, the mixture can be made to have a suitable viscosity from the initial stage in the dividing step, and the viscosity can be maintained to a certain degree, so that the efficiency can be maintained. Good hydrolyzable cellulose can be produced. Furthermore, since the gel-like aqueous solution can enter and stay between the separated cellulose polymer chains due to the gel form, re-crystallization of the cellulose polymer chains can be prevented, and the fragmentation ability is improved. Will be.

Here, “hydrolyzable cellulose” refers to cellulose obtained by using cellulose-based biomass or the like as a raw material and physically dividing it, etc., and having higher hydrolyzability than the above raw materials. The “average degree of polymerization” is a value of viscosity average degree of polymerization (P) measured according to JIS-K6726. That is, when the saponification degree is less than 99.5 mol%, the polyvinyl alcohol polymer is re-saponified to a saponification degree of 99.5 mol% or more, purified, and then the intrinsic viscosity measured in water at 30 ° C η] (unit: deciliter / g) is a value obtained by the following formula (I).
P = ([η] × 1000 / 8.29) ^{(1 / 0.62)} (I)
The “saponification degree” is a value measured according to JIS-K6726. “Aqueous solution” refers to a solution using water as a solvent, and is a concept including a gel-like material that loses fluidity.

  As described above, according to the polyvinyl alcohol polymer of the present invention, when producing hydrolyzable cellulose using cellulosic biomass as a raw material, by imparting a suitable viscosity to the mixture containing cellulosic biomass, etc. In addition, the cellulosic biomass can be easily divided at a molecular level, and as a result, hydrolyzable cellulose can be efficiently produced. Moreover, according to the manufacturing method of the hydrolysable cellulose of this invention, a hydrolysable cellulose can be manufactured efficiently using cellulosic biomass as a raw material.

  Therefore, according to this invention, a plant-type biomass raw material can be utilized efficiently as a food or energy resource, and the feasibility of biomass utilization can be improved.

  Hereinafter, embodiments of the method for producing a polyvinyl alcohol polymer of the present invention and a hydrolyzable cellulose using the same will be described in detail.

[Polyvinyl alcohol polymer]
The polyvinyl alcohol polymer of the present invention (hereinafter also referred to as “PVA”) has a monomer unit represented by the formula (1). That is, the PVA is a copolymer containing a monomer unit represented by the above formula (1) and a vinyl alcohol unit (—CH ₂ —CHOH—), and further has other monomer units. You may do it.

  Since the PVA has a monomer unit represented by the above formula (1), it has a high affinity for water and cellulose. Therefore, the PVA can increase the viscosity of the aqueous solution when the aqueous solution is made into an aqueous solution, and the cellulosic biomass in the mixture obtained when the aqueous solution is mixed with the powdered or particulate cellulose biomass. Uniform dispersibility (miscibility) can be improved.

  Therefore, an appropriate shearing force can be applied to the cellulosic biomass by mixing the aqueous solution of PVA and the cellulosic biomass particles. That is, in such an operation using the PVA, cellulose polymer chains are easily separated from each other by a viscous aqueous solution, and water and PVA efficiently enter the polymer chain having a quasicrystalline structure. Can weaken hydrogen bonds between polymer chains. Furthermore, the re-crystallization of the polymer chain can be prevented by the PVA entering between the polymer chains thus torn. That is, according to the PVA, a cellulose polymer chain in cellulosic biomass can be effectively divided at a molecular level, and cellulose that is easily hydrolyzed (saccharified) by an enzyme or the like can be obtained.

In said formula (1), R < ¹ >, R < ² > is respectively independently a hydrogen atom, an alkyl group, or an acyl group. As an alkyl group, a C1-C10 alkyl group is preferable, and a methyl group, an ethyl group, a propyl group, a hexyl group etc. are mentioned specifically ,. Moreover, as an acyl group, a C1-C10 aliphatic acyl group is preferable, and a formyl group, an acetyl group, a propionyl group, a butyryl group etc. are mentioned specifically ,. Among these, R ¹ and R ² are each independently preferably a hydrogen atom, a methyl group, an ethyl group, or an acetyl group, more preferably a hydrogen atom or a methyl group, and further preferably a hydrogen atom from the viewpoint of productivity.

  In said formula (1), X shows a C1-C3 alkylene group which may be via the single bond or the oxygen atom. Among these, a single bond, a methylene group or an ethylene group is preferable, and a single bond is more preferable.

  The content of the monomer unit represented by the above formula (1) contained in the PVA of the present invention is preferably 0.2 mol% or more and 10 mol% or less, more preferably 0.5 mol% or more and 8 mol% or less. Preferably, it is 0.7 mol% or more and 5 mol% or less. In addition, the content rate of this unit is the ratio of the mole number of the monomer unit represented by the said Formula (1) which occupies for the mole number of all the structural units which comprise PVA. When this PVA is used as an aqueous solution and mixed with cellulosic biomass, it can be mixed efficiently and uniformly with a suitable viscosity. As a result, the cellulose polymer chain is efficiently divided and hydrolysis is facilitated. It can be in a state where it can be performed.

  When the content of the monomer unit having the group represented by the above formula (1) exceeds 10 mol%, the intramolecular interaction of PVA becomes too strong, the water solubility of the PVA is decreased, and the powdery A reduction in uniform dispersibility of the cellulose-based biomass in an aqueous solution tends to occur. On the other hand, when the content of the monomer unit is less than 0.2 mol%, the water-soluble PVA is excellent, but the interaction with the intramolecular and cellulosic biomass is not sufficiently exhibited, and the resulting mixture is obtained. The uniform dispersibility (miscibility) of the cellulosic biomass may decrease.

The content of the monomer unit represented by the above formula (1) may be obtained from PVA or from the precursor polyvinyl ester polymer, and both are obtained from proton NMR. For example, in the case of a polyvinyl ester polymer, specifically, the polyvinyl ester polymer is purified by reprecipitation with hexane-acetone to sufficiently remove unreacted monomers from the polymer, and then dried at 90 ° C. under reduced pressure. For 2 days and then dissolved in CDCl ₃ solvent for analysis.

  The production method of the PVA is not particularly limited and can be produced by several methods. For example, a vinyl ester monomer and a compound (monomer) represented by the following formula (2) Are copolymerized by various methods (bulk polymerization, solution polymerization using methanol as a solvent, emulsion polymerization, suspension polymerization, etc.), and the resulting polyvinyl ester polymer is obtained by a known method (alkali saponification, acid saponification, etc.). A saponification method can be employed.

In formula (2), the definitions of R ¹ and R ² are the same as in formula (1). The same applies to these preferred groups.

  Examples of the compound represented by the above formula (2) include 3,4-dihydroxy-1-butene, 3,4-dialkoxy-1-butene, 3,4-diasiloxy-1-butene, and 4,5-dihydroxy- 1-pentene, 4,5-dialkoxy-1-pentene, 4,5-diasiloxy-1-pentene, 5,6-dihydroxy-1-hexene, 5,6-dialkoxy-1-hexene, 5,6- Examples include diacyloxy-1-hexene, glycerin monoallyl ether, glycerin monovinyl ether, (2-hydroxy-3-alkoxy-propyl) allyl ether, and (2-hydroxy-3-alkoxy-propyl) vinyl ether. Among these, 3,4-diacyloxy-1-butene is preferable from the viewpoint of industrial productivity.

  Examples of the vinyl ester monomers include vinyl acetate, vinyl formate, vinyl propionate, vinyl versatate, vinyl pivalate and the like, and vinyl acetate is preferred from the viewpoint of polymerization controllability and availability.

  In the polymerization, an ethylenically unsaturated monomer copolymerizable within a range not impairing the gist of the present invention may be copolymerized. Examples of such ethylenically unsaturated monomers include olefins such as ethylene, propylene, 1-butene and isobutene, acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, Acrylic acid esters such as n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, methacryl Methacrylic acid esters such as i-propyl acid, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, methyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl Ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, dodecyl vinyl ether, vinyl ethers such as stearyl vinyl ether, nitriles such as acrylonitrile and methacrylonitrile, allyl compounds such as vinyl chloride and allyl chloride, fumaric acid, Carboxylic group-containing compounds such as maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimetic anhydride, itaconic anhydride and their esters and acid anhydrides, diacetone groups such as diacetone acrylamide, diacetone acrylate and diacetone methacrylate Examples thereof include isopropenyl acetate, 3-acrylamidopropyltrimethylammonium chloride, and 3-methacrylamidopropyltrimethylammonium chloride.

  In the polymerization, a chain transfer agent may be allowed to coexist for the purpose of adjusting the polymerization degree of the obtained PVA. Chain transfer agents include aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde and benzaldehyde; ketones such as acetone, methyl ethyl ketone, hexanone and cyclohexanone; mercaptans such as 2-hydroxyethanethiol; halogens such as trichlorethylene and perchloroethylene Hydrocarbons are mentioned, among which aldehydes and ketones are preferably used. The addition amount of the chain transfer agent is determined according to the chain transfer constant of the chain transfer agent to be added and the polymerization degree of the target PVA, but is generally 0.1% by mass or more and 10% by mass with respect to the vinyl ester monomer. % Or less is desirable.

  The average degree of polymerization of the PVA of the present invention is preferably from 100 to 4,000, more preferably from 200 to 3,500, further preferably from 300 to 3,000, particularly preferably from 400 to 2,500. By setting the average polymerization degree of the PVA in the above range, when this PVA is used as an aqueous solution and mixed with cellulosic biomass, it can be mixed efficiently and uniformly with a suitable viscosity. As a result, cellulose is obtained. The polymer chain can be efficiently divided so that hydrolysis can be easily performed. In addition, by using PVA having a high average degree of polymerization in this way, it can be gelled with a small amount of borate or the like.

  When the average degree of polymerization of the PVA is less than 100, the molecular weight is too small, so that it is difficult to impart sufficient viscosity to the aqueous solution, and the force to physically separate the cellulose polymer chains during kneading may be weakened. On the contrary, when this average degree of polymerization exceeds 4,000, the viscosity is too high and the workability and handling properties in the fragmentation process are likely to decrease, and the molecular weight is too large to enter between the cellulose polymer chains, There is a possibility that the action of weakening hydrogen bonds may be reduced.

  The saponification degree of the PVA of the present invention is preferably 70 mol% or more and 99.9 mol% or less, more preferably 75 mol% or more and 99 mol% or less, and further preferably 85 mol% or more and 98.5 mol% or less. . By setting the degree of saponification of the PVA in the above range, when this PVA is used as an aqueous solution and mixed with cellulosic biomass, it can be mixed efficiently and uniformly with a suitable viscosity. As a result, the cellulose polymer The chain can be efficiently divided so that hydrolysis can be easily performed.

  When the saponification degree of the PVA is less than 70 mol%, the water solubility is lowered and sufficient viscosity cannot be obtained, and the cellulose separating ability during kneading tends to be lowered. On the other hand, even when the degree of saponification exceeds 99.9 mol%, the fragmentation ability at the molecular level of the cellulose polymer chain reaches its peak and handling properties are lowered.

  The PVA of the present invention is used for producing hydrolyzable cellulose using cellulosic biomass as a raw material. Specifically, as will be described in detail later, an aqueous solution of PVA and cellulosic biomass are mixed to form a mixture, and a shearing force is applied by kneading the mixture to make the cellulosic biomass at a molecular level (quasi-level). It can be used for fine division at the crystal structure level. Under the present circumstances, the viscosity of the said mixture can be maintained in a suitable state by using the aqueous solution of the said PVA. As a result, according to the PVA, when the mixture is kneaded, the cellulose polymer chain is easily peeled off by a viscous aqueous solution, and water and polyvinyl alcohol polymer are contained inside the polymer chain having a quasicrystalline structure. By efficiently entering, hydrogen bonds between polymer chains can be weakened. Furthermore, the recrystallization of this structure can be prevented by the polyvinyl alcohol polymer entering between the polymer chains thus torn. In addition, the cellulose divided | segmented in this molecular level is easily decomposed | disassembled by a hydrolase etc.

[Method for producing hydrolyzable cellulose]
A method for producing hydrolyzable cellulose using cellulosic biomass as a raw material includes a mixing step of obtaining a mixture containing the above aqueous solution of PVA and cellulosic biomass, and dividing the cellulosic biomass by adding shearing force to the mixture. At least a process. Prior to the mixing step, the cellulosic biomass raw material is cut to obtain cellulosic biomass having an appropriate size, and the aqueous solution of the PVA is prepared prior to the mixing step. It is preferable to have a preparation process and the gelatinization process which makes the said PVA aqueous solution gel. Hereinafter, it demonstrates in order along the manufacturing process of a hydrolysable cellulose.

(1) Cellulosic biomass raw material cutting step In this step, in order to make the processing in the subsequent steps efficient, the cellulosic biomass raw material is cut into particles of an appropriate size. The cellulose-based biomass material used here is not particularly limited, and plant-derived biomass can be preferably used. Specifically, for example, wood such as thinned wood, rice straw, wheat straw, rice husk, bagasse, stalks of starch-based crops such as corn and sugarcane, oil palm waste (EFB, etc.), palm nut shell, etc. Can do. Such a cellulosic biomass raw material is reduced to particles by various cutting means such as shearing and beating after removing unnecessary components such as soil as much as possible. In this cutting step, for example, a breaker described in JP-T-2004-526008, an apparatus used when producing a pulp chip, and the like can be suitably employed.

  The size of the cellulosic biomass particles that have undergone this cutting step is preferably 2 mm or less, more preferably 1 mm or less, particularly preferably 100 μm or less, and particularly preferably 20 μm or more and 70 μm or less. By setting the average particle size of the cellulose-based biomass particles to 2 mm or less, the subsequent mixing step, particularly the dividing step can be efficiently performed, and cellulose having excellent hydrolyzability can be obtained in a short time.

(2) Aqueous solution preparation step In this step, the above PVA is dissolved in water to obtain an aqueous solution. Although it does not specifically limit as a density | concentration of this PVA aqueous solution, 3 mass% or more and 30 mass% or less are preferable, and 5 mass% or more and 20 mass% or less are more preferable. By setting the concentration of the PVA aqueous solution within the above range, an appropriate viscosity can be imparted to the aqueous solution. Therefore, by setting the concentration of the aqueous solution in the above range, during kneading, physical force is effectively transmitted to the cellulosic biomass through the aqueous solution, and as a result, the cellulose polymer chain is peeled off by this aqueous solution, Cellulosic biomass can be effectively divided at the molecular level. When the concentration of the PVA aqueous solution is less than 3% by mass, the aqueous solution does not have an appropriate viscosity, and there is a possibility that the dividing function due to physical action is not sufficiently exhibited. Conversely, when the concentration of the PVA aqueous solution exceeds 30% by mass, the viscosity of the aqueous solution is so high that it becomes difficult to knead, and the workability in the dividing step may be reduced.

  In addition, said PVA aqueous solution may further contain PVA other than PVA which has a monomer unit represented by the said Formula (1). When it contains other PVA, 50 mass% or more is preferable with respect to content of the whole PVA, and, as for the content rate of PVA of this invention, 70 mass% or more is more preferable. In this case, it is preferable that the density | concentration as the whole PVA containing other PVA is the said density | concentration range. Moreover, other compounds other than PVA may be dissolved or dispersed in the PVA aqueous solution.

(3) Gelation step Prior to mixing the cellulose-based biomass particles obtained by the cellulose-based biomass raw material cutting step described above and the PVA aqueous solution, the PVA aqueous solution is preferably gelled. By using such a gel-like PVA aqueous solution, the mixture has a high viscosity from the initial stage of kneading in the subsequent dividing step, so that the physical action of kneading is effectively transmitted to the cellulosic biomass. Can be efficiently divided at the molecular level. Furthermore, by using a gelled PVA aqueous solution, the gelled aqueous solution can enter and stay between the split cellulose polymer chains, so that re-crystallization of the cellulose polymer chains can be prevented, The splitting ability will be improved.

  Examples of the gelation method of the PVA aqueous solution include a method of adding a chemical substance such as borate, titanium acetate, and other metal salts to crosslink the PVA.

  When adding a borate to gelatinize an aqueous PVA solution, for example, 1 to 10 parts by mass of a saturated aqueous solution of sodium tetraborate is added to and mixed with 100 parts by mass of a 5% by mass PVA aqueous solution. Can be done. The gelled PVA aqueous solution has a suitable viscosity in the production, and is easy and efficient because the viscosity hardly increases (hardens) even if it is mixed with the cellulosic biomass and kneaded. Kneading can be performed. In addition, it is preferable that this gel-like PVA aqueous solution is acidic, and specifically, it is preferable that pH is 4-6.

(4) Mixing step Mixing the aqueous solution of PVA obtained in the above step, preferably the aqueous solution of PVA gelled in the gelation step, and the cellulosic biomass cut into a preferred size in the above step Thus, a mixture containing these is obtained.

The mixing amount of the cellulose-based biomass is not particularly limited, but the mixing amount of the cellulose-based biomass with respect to the entire mixture is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 40% by mass or less. When the mixing amount of the cellulosic biomass is less than 5% by mass, the viscosity of the mixture is low and there is a possibility that the function of dividing by the physical action may not be sufficiently exhibited. descend. On the other hand, when the mixing amount of the cellulosic biomass exceeds 50% by mass, the water absorption by the biomass is strong, the viscosity of the mixture is too high, and kneading becomes difficult, so that workability is lowered. The viscosity of the mixture is preferably, for example, from 5.0 × 10 ⁴ mPa · s to 1.0 × 10 ⁶ mPa · s.

(5) Splitting Step Cellulosic biomass is split at the molecular level (quasicrystalline structure level) by applying shearing force to the mixture obtained in the mixing step described above. That is, cellulose having a quasicrystalline structure is partially hydrated, PVA enters, hydrogen bonds between the cellulose molecules are weakened, and in addition, due to the physical force due to the addition of shear force, intermolecular Cellulose polymer chains are separated from each other in a weakened bond, so that the microscopic structure of the cell wall is disrupted.

  Here, by using an aqueous solution of PVA having a monomer unit represented by the above formula (1), an appropriate viscosity can be imparted to the mixture due to the high affinity between the PVA, water, and cellulose. Both the chemical action of lowering hydrogen bonds between cellulose molecules and the action of physically separating cellulose molecules by a mechanical operation of applying a shearing force can be effectively exhibited. Moreover, by using the PVA, the PVA effectively enters and adheres to the gaps between the physically separated cellulose polymer chains. Therefore, according to the production method using the above PVA, re-quasicrystallization of the cellulose polymer chain can be prevented, and hydrolyzable cellulose can be produced effectively.

  Furthermore, by using a gelled PVA aqueous solution, a mixture having a favorable viscosity can be obtained from the first stage of applying shearing force, and cell-based biomass can be efficiently divided at the molecular level. be able to.

  The method for applying a shearing force to the mixture in the dividing step is not particularly limited, and examples thereof include a method of kneading the mixture. In addition, the apparatus used in the dividing step is not particularly limited, but a twin screw extruder generally used for molding a thermoplastic resin or the like is preferably used. The time required for the dividing step is appropriately set according to the amount of the mixture and the like, and is, for example, about 30 minutes to 10 hours. In addition, when the viscosity decreases during the dividing step, the viscosity may be appropriately adjusted by adding a sodium tetraborate aqueous solution or the like.

  According to this method for producing hydrolyzable cellulose, the cellulosic biomass becomes cellulose that is easily hydrolyzed with the quasicrystalline structure divided by passing through the above-described steps.

(6) Post-process In addition, the hydrolysable cellulose obtained by doing in this way is easily saccharified by using a well-known hydrolase in a mixture, for example, and the produced glucose melt | dissolves in aqueous solution. Examples of the hydrolase include cellulase, pectinase, hemicellulase, β-glucanase, xylanase, mannase, amylase, mecerase, and acremonium cellulase (cellulase obtained from Acremonium cellulolyticus). Further, at the time of saccharification, hemicellulose-derived xylose and the like contained in the cellulosic biomass are also dissolved in the aqueous solution. At this time, the lignin contained in the cellulosic biomass may exist as insoluble particles, but this lignin can be separated by, for example, filtration or centrifugation. The saccharides such as soluble glucose thus obtained can be converted to ethanol by fermentation and can be suitably used as a fuel resource.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

[Synthesis Example 1] Production of PVA1 A reactor (6 L) equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with 1081 g of vinyl acetate, 1800 g of methanol, and 137.98 g of 3,4-diacetoxy-1-butene. The inside of the reactor was purged with nitrogen by bubbling gas. The temperature of the reactor was increased, and while maintaining the internal temperature at 60 ° C., 7.8 g of 2,2′-azobisisobutyronitrile was added to the reactor together with 19 g of methanol to initiate polymerization. During the polymerization, the temperature was maintained at 60 ° C., and when the polymerization rate reached 50%, 10.7 g of sorbic acid as a polymerization inhibitor was added together with 1000 g of methanol to terminate the polymerization. Subsequently, the unreacted vinyl acetate monomer was removed while adding methanol occasionally at 30 ° C. under reduced pressure. Further, the operation of adding methanol and distilling off under reduced pressure was repeated three times. A combined methanol solution was obtained.
A methanol solution of this polyvinyl acetate copolymer, methanol and distilled water were charged into a beaker, and the solution temperature was adjusted to 40 ° C. A methanol solution having a sodium hydroxide concentration of 9% by mass was added so that the alkali molar ratio (ratio of the number of moles of sodium hydroxide to the number of moles of vinyl acetate units in the polyvinyl acetate copolymer) was 0.0080. The saponification reaction of the polyvinyl acetate copolymer having vinyl acetate units and 3,4-diacetoxy-1-butene units was started. The addition amounts of methanol and distilled water were adjusted so that the concentration of the polyvinyl acetate polymer during the saponification reaction was 50% by mass and the water content of the saponification reaction system was 1.0% by mass. did. After the addition of sodium hydroxide, the gelled PVA was recovered and pulverized, and 1 hour after the addition of sodium hydroxide, the obtained PVA was immersed in methyl acetate and neutralized. After neutralization, the obtained PVA was dried at 60 ° C. for 1 day to obtain PVA1.
The average polymerization degree of PVA1 was 1,000, the saponification degree was 88.2 mol%, and the content of the monomer unit represented by the above formula (1) was 6.0 mol%. The content of the monomer unit represented by the above formula (1) ^is, 1 H-NMR (internal standard: tetramethylsilane, solvent: _{DMSO-d 6)} was calculated by measuring at.

[Example 1]
Distilled water was heated to 70 ° C., and PVA1 was added while stirring to prepare a 10% by mass PVA aqueous solution. This aqueous PVA solution was slightly more viscous than water. After cooling 100 g of this aqueous solution to room temperature, 2 mL of a saturated aqueous solution of boric acid (H ₃ BO ₃ ) was added and mixed. The pH of the obtained aqueous solution was 5.0. Further, 0.5 mL of a saturated aqueous solution of sodium tetraborate was added to and mixed with this aqueous solution, whereby the aqueous solution was made into a viscous gel. The gel-like body had a pH of 6.5. Next, 50 g of EFB (particles having a diameter of 20 to 70 μm) as cellulosic biomass particles was added to the gel, and kneaded using a mixer-type kneader at room temperature. This mixture had a relatively low viscosity at the beginning of kneading, but as the kneading continued, EFB (cellulosic biomass particles) absorbed water and the viscosity improved. This mixture could be easily stretched and kneaded with a roller. Each time kneading for a certain time, a part of the mixture was taken out and the particle size was confirmed by a microscope. It was observed that the particle size decreased and the cell structure was fragmented as the fragmentation process proceeded.

  It was confirmed with a microscope that the cellulose was sufficiently divided by kneading, and an aqueous solution of hydrolyzable cellulose was obtained. Thereafter, distilled water was added to the mixture to reduce the viscosity. In order to adjust to the optimum pH of the hydrolase, sodium hydroxide solution was further added to the mixture to adjust the pH to 6.0. This mixture was as viscous as melted chocolate. To this mixture, 0.5 parts by mass of Mecelase (manufactured by Meiji Seika Co., Ltd.) and Acremonium cellulase (cellulase obtained from Acremonium cellulolyticus): 100 parts by mass of EFB, respectively, as hydrolases Added and stirred in a reaction vessel at a temperature of 50 ° C. A few tens of minutes with the addition of enzyme, the viscosity of this mixture decreased markedly. This stirring was performed for 6 hours to obtain a glucose solution.

[Examples 2-4, Comparative Examples 1-2]
Except having changed PVA from PVA1 to other PVA of Table 1, it carried out similarly to Example 1, and performed Examples 2-4 and Comparative Examples 1-2, and obtained the hydrolysable cellulose aqueous solution, and finally A glucose solution was obtained. In addition, PVA5-6 does not contain the monomer unit represented by the said Formula (1).

[Evaluation]
(Saccharification efficiency)
After adding distilled water to the obtained glucose solution to 400 mL, 2 mL (0.5% of the total solution) of this glucose solution sample solution was collected and sterilized at 100 ° C. for 5 minutes. After cooling the sample solution, it is centrifuged at 3,000 rpm for 30 minutes using a centrifuge, filtered to remove solids, and then the filtrate is subjected to liquid chromatography to remove monosaccharides (such as glucose). Weighed. The mass ratio of cellulose and hemicellulose occupying EFB (50 g) used was determined to be 50%, and saccharification efficiency (%) was determined by the following calculation formula (II). The measurement results are shown in Table 1.
Saccharification efficiency = [mass of monosaccharide in sample solution (g) / {50 (g) × 0.005 × 0.5}] × 100 (%) (II)

(Miscibility)
In Examples 1 to 4 and Comparative Examples 1 and 2, EFB was added to the gel-like body, and after mixing for 1 hour using a mixer-type kneader at room temperature, a part of the mixture was taken out. Using a microscope, EFB aggregation in the extracted mixture was visually observed. If no aggregation was observed, it was determined as “very good”, and if the particles were hardly aggregated, “good” Was determined.

  As Table 1 shows, since Examples 1-4 use PVA which has a monomer unit represented by Formula (1), all have saccharification efficiency exceeding 80% and a cellulose is easy. It was found that it was divided into hydrolyzed states. On the other hand, since Comparative Examples 1-2 was PVA which does not have a monomer unit represented by Formula (1), it turned out that cellulose is not fully divided to the state where it is easily hydrolyzed. .

  As described above, the PVA of the present invention can be suitably used when producing hydrolyzable cellulose using cellulosic biomass as a raw material. Therefore, according to this invention, a plant-type biomass raw material can be efficiently utilized as a food or energy resource, and the feasibility of utilization of biomass can be improved.

Claims (6)

A polyvinyl alcohol polymer used for the production of hydrolyzable cellulose using cellulosic biomass,
A polyvinyl alcohol polymer having a monomer unit represented by the following formula (1).

(In Formula (1), R < ¹ >, R < ² > shows a hydrogen atom, an alkyl group, or an acyl group each independently, X is a C1-C3 alkylene group which may be via the single bond or the oxygen atom. Show.)   The polyvinyl alcohol polymer according to claim 1, wherein the average degree of polymerization is from 100 to 4,000.   The polyvinyl alcohol polymer according to claim 1 or 2, wherein the saponification degree is 70 mol% or more and 99.9 mol% or less.   The content rate of the monomer unit represented by the said Formula (1) is 0.2 mol% or more and 10 mol% or less, The polyvinyl alcohol-type polymer of any one of Claims 1-3. A method for producing hydrolyzable cellulose using cellulosic biomass as a raw material,
A mixing step of obtaining a mixture containing the aqueous solution of the polyvinyl alcohol polymer according to any one of claims 1 to 4 and cellulosic biomass,
The cutting method which adds a shearing force to the said mixture, and cut | disconnects cellulosic biomass.   The production method according to claim 5, wherein the aqueous solution is in a gel form.