JP7394573B2 - modified cellulose - Google Patents

Description

The present invention relates to modified cellulose. More specifically, the present invention relates to a modified cellulose that can be suitably incorporated as a filler into daily necessities, home appliance parts, automobile parts, resins for three-dimensional modeling, etc., and a method for producing the modified cellulose.

In the past, plastic materials derived from petroleum, which is a finite resource, were often used, but in recent years, technologies with less environmental impact have been in the spotlight, and against this technological background, biomass, which naturally exists in large quantities, has been used. Materials using cellulose are attracting attention.

For example, Patent Document 1 discloses a cellulose fiber in which a part of the hydroxyl groups of cellulose is substituted with at least one of a carboxyl group and an aldehyde group, for the purpose of providing a cellulose fiber with improved hygroscopicity and heat coloring. Disclosed is a modified cellulose fiber having a specific substituent structure, in which at least a portion of the unsubstituted hydroxyl residues of the cellulose are substituted with acetyl groups.

Japanese Patent Application Publication No. 2011-99064

The modified cellulose fiber specifically disclosed in Patent Document 1 is produced by a method in which the raw material cellulose having a carboxy group is formed into a film, and then the surface is acetylated and modified using modifiers such as acetic anhydride and sodium acetate. It is prepared. However, when the present inventors prepared modified cellulose fibers according to the method, the redispersibility was insufficient, and practical productivity may not be obtained in terms of production. The use of this technology is extremely limited, and further improvements are required from the perspective of reducing environmental impact and manufacturing costs.

In view of such matters, the present invention relates to a modified cellulose that can be stably dispersed and has excellent redispersibility when blended with various solvents, and a method for producing the same.

Therefore, as a result of intensive studies to solve the above problems, the present inventors have found that modified cellulose obtained by introducing ionic groups and nonionic substituents into cellulose has the ability to retain cellulose even after solvent removal. It has been found that it has excellent redispersibility without causing aggregation.

The present invention relates to the following [1] to [4].
[1] A modified cellulose having an ionic group and a nonionic substituent and having a cellulose I type crystal structure, wherein the nonionic substituent is bonded to the cellulose via an ether bond. .
[2] Modified cellulose having a cellulose type I crystal structure, which includes a step of introducing an ionic group into the raw material cellulose, and a step of introducing a nonionic substituent into the hydroxyl group of the cellulose via an ether bond. manufacturing method.
[3] The production method according to [2] above, which includes a step of introducing a nonionic substituent into the hydroxyl group of cellulose having an ionic group via an ether bond.
[4] The production method described in [2] or [3] above, which includes a step of introducing an ionic group into a hydroxyl group of cellulose having a nonionic substituent.

The modified cellulose of the present invention does not cause cellulose aggregation during the solvent removal process, has excellent redispersibility, and can be handled as a powder, making it easy to handle during production, distribution, and storage. This has the excellent effect of improving performance and expanding the range of applications.

<Modified cellulose>
The modified cellulose of the present invention is characterized in that cellulose has two types of substituents, namely, an ionic group and a nonionic substituent. Here, the nonionic substituent is bonded to cellulose via an ether bond, and in this specification, "bonded to cellulose via an ether bond" refers to the hydroxy group of cellulose and the etherification agent described below. This means a state in which the nonionic substituent of the etherifying agent is ether bonded to a group obtained by removing a hydrogen atom from a hydroxyl group of cellulose. Furthermore, the modified cellulose of the present invention is characterized by having a cellulose I type crystal structure.

Although the details are unknown, the presumed mechanism for the superior redispersibility of the modified cellulose of the present invention is that nonionic substituents are introduced into the hydroxyl groups of cellulose via ether bonds, resulting in some kind of It is considered that the effect is being realized. As used herein, "redispersibility" refers to the dispersibility when dry modified cellulose is suspended in a medium.

One preferred embodiment of the modified cellulose of the present invention has a structure represented by the following general formula (Ce).

(wherein each R is independently selected from the group consisting of a hydrogen atom, an ionic group, and a nonionic substituent, at least one of R is an ionic group, and at least one of R is a nonionic substituent) It is an ionic substituent. m is an integer from 20 to 3,000.)

In a more preferred embodiment of the present invention, the modified cellulose is such that a part or all of the hydroxyl group at the 6-position of glucose constituting the cellulose is substituted with a carboxy group, and a part or all of the carbon atoms at the 3- or 4-position are substituted with a carboxy group. It is a modified cellulose having a structure in which nonionic substituents are bonded to atoms via ether bonds.

[Ionic group]
Ionic groups include anionic groups and cationic groups. Examples of the anionic group include a carboxy group, a sulfonic acid group, and a phosphoric acid group, and examples of the cationic group include groups having onium in the group, such as ammonium, phosphonium, and sulfonium. From the viewpoint of introduction efficiency into cellulose, anionic groups are preferred, and carboxy groups are more preferred. The ionic groups may be introduced singly or in combination of two or more.

In the present invention, the cellulose containing an ionic group may be an anion-modified cellulose such that the cellulose contains an anionic group, that is, an anion-modified cellulose. A preferred embodiment of the anion-modified cellulose is one derived from TEMPO oxidation, which will be described later, in which the hydroxy group (-CH ₂ OH) at the C6 position of the cellulose structural unit is a carboxy group (-COOH or -COO ^- X ⁺ ; X ⁺ is a metal ions or organic cations) (herein, cellulose converted to such carboxy groups may be referred to as "oxidized cellulose"). Here, the metal ion is preferably an alkali metal ion from the viewpoint of redispersibility, and examples thereof include sodium ion and potassium ion. The organic cation is preferably a primary to quaternary ammonium cation from the viewpoint of redispersibility, and examples include ammonia, an alkylamine, and an alkylamine having a hydrocarbon group with a copolymerization moiety. Specific examples of alkyl amines include primary amines to tertiary amines and quaternary ammonium compounds described in paragraph 0055 of JP-A-2019-094388, which have a hydrocarbon group with a copolymerized part. Examples of the alkylamine include EOPO amines described in paragraphs 0069 to 0077 of JP 2019-094388A.

(Content of ionic groups)
From the viewpoint of redispersibility, the ionic group content in the modified cellulose is preferably 0.1 mmol/g-cellulose or more, more preferably 0.4 mmol/g-cellulose or more, and even more preferably 0.6 mmol/g. - More than cellulose. In addition, from the viewpoint of improving handling properties, it is preferably 3 mmol/g-cellulose or less, more preferably 2 mmol/g-cellulose or less, even more preferably 1.8 mmol/g-cellulose or less, and even more preferably 1.5 mmol/g-cellulose. It is lower than cellulose. In addition, "ionic group content" means the total amount of ionic groups in the modified cellulose, and when the ionic groups are anionic groups (carboxy groups), the anionic groups (carboxy groups) in the modified cellulose are means the total amount of Note that the above-mentioned carboxy group is defined as -COOH or -COO ^- X ⁺ ; X ⁺ is a metal ion or an organic cation. "g-cellulose" means "1 g of cellulose obtained by removing ionic groups and nonionic substituents from modified cellulose". When the ionic group is an anionic group, the anionic group content is measured by the method described in Examples below.

[Nonionic substituent]
The nonionic substituent is, for example, a monovalent hydrocarbon group that may have an oxygen atom. From the viewpoint of redispersibility, the number of carbon atoms in the nonionic substituent is preferably 2 or more, more preferably 4 or more, more preferably 6 or more, and even more preferably 10 or more. From the viewpoint of introduction efficiency, it is preferably 100 or less, more preferably 50 or less, more preferably 30 or less, and even more preferably 20 or less.

More specifically, one or more substituents selected from the group consisting of the following general formulas (1), (2), and (3) are preferable as the nonionic substituent. In addition, although there are a plurality of substituents corresponding to general formula (1), the substituents as general formula (1) introduced into cellulose may be the same or two or more types. This also applies to general formulas (2) and (3).
-R ¹ (1)
-CH ₂ -CH(OH)-R ² (2)
-CH ₂ -CH(OH)-CH ₂ -(OA) _n -O-R ³ (3)
(In the formula, R ¹ is a hydrocarbon group having 2 to 100 carbon atoms, R ² is a hydrocarbon group having 1 to 100 carbon atoms, and R ³ is a hydrocarbon group having 1 to 100 carbon atoms. (n is a number from 0 to 100, and A is a divalent hydrocarbon group having 1 to 6 carbon atoms.)

The number of carbon atoms in R ¹ in general formula (1) is preferably 3 or more, more preferably 4 or more from the viewpoint of redispersibility, and preferably 30 or less, more preferably from the viewpoint of availability and reactivity. is 25 or less, more preferably 20 or less. Preferred specific examples of R ¹ include a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a hexadecyl group, an octadecyl group, Saturated alkyl groups such as icosyl group and triacontyl group; unsaturated alkyl groups such as vinyl group, allyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, dodecenyl group, hexadecenyl group, octadecenyl group; Examples include substituents having a cyclic structure such as a cyclohexyl group, a phenyl group, a benzyl group, a naphthyl group, and a trityl group.

The number of carbon atoms in R ² in general formula (2) is preferably 2 or more, more preferably 3 or more, even more preferably 4 or more from the viewpoint of redispersibility, and from the viewpoint of availability and reactivity, it is preferable. is 30 or less, more preferably 25 or less, even more preferably 20 or less. Preferred specific examples of ^R2 include a methyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a 2-ethylhexyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a hexadecyl group, Saturated alkyl groups such as octadecyl, icosyl and triacontyl groups; unsaturated such as vinyl, allyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, hexadecenyl and octadecenyl groups Alkyl group: Examples include substituents having a cyclic structure such as cyclohexyl group, phenyl group, benzyl group, naphthyl group, and trityl group.

The preferable carbon number range and preferable specific examples of R ³ in general formula (3) are the same as those of R ² in general formula (2).

A in general formula (3) is a divalent saturated hydrocarbon group having 1 or more and 6 or less carbon atoms, and forms an oxyalkylene group with an adjacent oxygen atom. From the viewpoint of availability and cost, the number of carbon atoms in A is preferably 2 or more, and from the same viewpoint, preferably 4 or less, more preferably 3 or less. Preferred specific examples of A include methylene group, ethylene group, propylene group, butylene group, pentylene group, hexylene group, and the like.

n in general formula (3) represents the number of moles of alkylene oxide added. From the viewpoint of availability and cost, n is preferably 3 or more, more preferably 5 or more, even more preferably 10 or more, and from the same viewpoint, preferably 40 or less, more preferably 30 or less, even more preferably 20 or less. , more preferably 15 or less. Alternatively, an embodiment in which no alkylene oxide is added is also preferred, and in this case, n=0.

A preferred combination of n and A in the substituent represented by general formula (3) is that n is a number of 0 to 20, and A is a divalent saturated hydrocarbon group having 2 to 3 carbon atoms. .

(Introduction rate of nonionic substituent (molar degree of substitution))
In the modified cellulose of the present invention, the molar amount (molar substitution degree: MS) of nonionic substituents introduced per mole of anhydroglucose units of cellulose is preferably 0.001 or more from the viewpoint of redispersibility. It is more preferably 0.005 or more, more preferably 0.01 or more, and still more preferably 0.03 or more. On the other hand, from the viewpoint of cost, MS is preferably 1.5 or less, more preferably 1.0 or less, and still more preferably 0.75 or less. In addition, in this specification, anhydroglucose unit may be abbreviated as "AGU". Here, when the nonionic substituent is composed of multiple types of substituents, the MS of the nonionic substituent is the sum of the MS of each substituent. In this specification, the degree of molar substitution (MS) can be measured according to the method described in Examples below.

[Cellulose type I crystal structure and crystallinity]
The modified cellulose of the present invention has a cellulose type I crystal structure due to the use of natural cellulose as its raw material.
The degree of crystallinity of the modified cellulose of the present invention is preferably 10% or more, more preferably 15% or more, from the viewpoint of strength development of a molded product obtained when the modified cellulose is applied to a resin composition. It is more preferably 20% or more. Further, from the viewpoint of raw material availability, it is preferably 90% or less, more preferably 85% or less, still more preferably 80% or less, and still more preferably 75% or less.

In this specification, the crystallinity of cellulose is cellulose type I crystallinity calculated from the diffraction intensity value by X-ray diffraction, and can be measured according to the method described in Examples below. Cellulose type I is a crystalline form of natural cellulose, and cellulose type I crystallinity refers to the ratio of crystalline regions to the total cellulose. The presence or absence of a cellulose type I crystal structure can be determined by the presence of a peak at 2θ=22.6° in the X-ray diffraction measurement described in Examples below.

[Average fiber diameter]
The preferred range of the average fiber diameter of the modified cellulose of the present invention may be the same range as that of the raw material cellulose, and if necessary, the average fiber diameter of the modified cellulose may be refined from several nanometers to several hundred nanometers. It may be. In the latter case, the average fiber diameter of the modified cellulose is preferably 1 nm or more, more preferably 3 nm or more, still more preferably 10 nm or more, and even more preferably 20 nm or more, from the viewpoints of handling, availability, and cost. From the viewpoint of handleability, the diameter is preferably less than 1 μm, preferably 500 nm or less, more preferably 300 nm or less, and still more preferably 200 nm or less. The average fiber diameter of various celluloses such as modified cellulose is specifically measured by the method described in Examples below.

[Average fiber length]
The average fiber length of the modified cellulose is preferably 150 nm or more and 1,000 nm or less, for example, when the below-mentioned micronization treatment is performed. On the other hand, the average fiber length in the case where the micronization treatment is not performed is not particularly limited, and may be approximately the same as that of the raw material cellulose. The modified cellulose having an average fiber length within this range satisfies the condition "m is an integer of 20 or more and 3,000 or less" in the general formula (Ce). The average fiber length of modified cellulose can be measured by the method described in Examples below.

<Production method of modified cellulose>
The method for producing modified cellulose having a cellulose type I crystal structure of the present invention includes a step of introducing an ionic group into cellulose as a raw material, and a step of introducing a nonionic substituent into a hydroxyl group of cellulose through an ether bond. It has a process of In the production method of the present invention, either the step of introducing an ionic group or the step of introducing a nonionic substituent may be performed first.

Specifically, a method for producing a modified cellulose having a cellulose I type crystal structure (aspect 1), which includes a step of introducing a nonionic substituent into a hydroxyl group of cellulose having an ionic group via an ether bond; and a method for producing a modified cellulose having a cellulose type I crystal structure (aspect 2), which includes a step of introducing an ionic group into a hydroxyl group of cellulose having a nonionic substituent.

[Raw material cellulose]
The raw material cellulose used in the present invention is woody (coniferous and broad-leaved trees), herbaceous (grass, mallow, leguminous plant materials, non-woody palm material of palmaceous plants), and pulp (cotton seeds). (cotton linter pulp, etc. obtained from the surrounding fibers), papers (newspapers, cardboard, magazines, high-quality paper, etc.), and the like. Among these, woody plants and herbaceous plants are preferred from the viewpoint of availability and cost.

The shape of the raw material cellulose is not particularly limited, but from the viewpoint of ease of handling, fibrous, powder, spherical, chip, and flake shapes are preferable. Alternatively, a mixture of these may be used.

In addition, the raw material cellulose is subjected to at least one pretreatment selected from biochemical treatment, chemical treatment, and mechanical treatment described in paragraphs 0017 to 0018 of JP2018-145571 from the viewpoint of ease of handling. This can be done in advance.

The average fiber diameter of the raw material cellulose is preferably 5 μm or more, more preferably 7 μm or more, from the viewpoint of handleability and cost. Further, the upper limit is not particularly set, but from the viewpoint of handleability, it is preferably 10,000 μm or less, more preferably 5,000 μm or less. Note that, if necessary, fine cellulose having a fiber diameter of 1 to 200 nm, which has been subjected to a refinement treatment in advance, can also be used as the raw material cellulose. From the viewpoint of availability, the average fiber length of the raw material cellulose is preferably 1,000 μm or more and 10,000 μm or less. The average fiber diameter and average fiber length of the raw material cellulose fibers can be measured by the method described in Examples.

[Ionic group introduction step]
This step is a step of introducing ionic groups into cellulose. In Aspect 1, this step is carried out on cellulose as a raw material, and in Aspect 2, this step is carried out on cellulose in which a nonionic substituent has been introduced into the hydroxyl group, that is, after passing through the nonionic substituent introduction step. Performed on cellulose. By going through this step, cellulose having ionic groups is obtained in the case of aspect 1, and modified cellulose having ionic groups and nonionic substituents is obtained in the case of aspect 2.

(When the ionic group is a carboxy group)
When the ionic group introduced in the ionic group introduction step is a carboxy group, for example, 2,2,6,6,-tetramethyl-1-piperidine-N-oxyl (TEMPO) is used as a catalyst, and the following Carboxy groups can be introduced by oxidizing the hydroxy groups of cellulose using a combination of an oxidizing agent such as sodium chlorite and a bromide such as sodium bromide. More specifically, reference can be made to the method described in Japanese Patent Application Laid-open No. 2011-140632. By performing such oxidation of cellulose, the group (-CH ₂ OH) at the C6 position of the cellulose structural unit is selectively converted into a carboxy group.

In the case of Embodiment 1, TEMPO oxidation of cellulose as a raw material yields oxidized cellulose in which the hydroxy group at the C6 position of the cellulose structural unit is converted to a carboxy group.

(When the ionic group is a sulfonic acid group or a phosphoric acid group)
When introducing a sulfonic acid group or a phosphoric acid group as an anionic group into cellulose, examples of the method for introducing the sulfonic acid group include a method of adding sulfuric acid to cellulose and heating it. Examples of methods for introducing phosphoric acid groups into cellulose include a method of mixing dry or wet cellulose with a powder or aqueous solution of phosphoric acid or a phosphoric acid derivative.

From the viewpoint of redispersibility, the ionic group content in the cellulose having ionic groups is preferably 0.1 mmol/g-cellulose or more, more preferably 0.4 mmol/g-cellulose or more, and even more preferably 0.1 mmol/g-cellulose or more. 6 mmol/g-cellulose or more. In addition, from the viewpoint of improving handling properties, it is preferably 3 mmol/g-cellulose or less, more preferably 2 mmol/g-cellulose or less, even more preferably 1.8 mmol/g-cellulose or less, and even more preferably 1.5 mmol/g-cellulose. It is lower than cellulose. When the ionic group is an anionic group, the anionic group content is measured by the method described in Examples below.

After the reaction is completed, it is preferable to carry out an appropriate post-treatment in order to remove unreacted compounds, bases, and the like. As a method for the post-treatment, for example, an unreacted base can be neutralized with an acid (organic acid, inorganic acid, etc.), and then washed using a solvent in which the unreacted compound and base can be dissolved. If desired, further drying (vacuum drying, etc.) may be performed.

[Nonionic substituent introduction step]
This step is a step of introducing a nonionic substituent into the hydroxyl group of cellulose via an ether bond. In aspect 1, this step is performed on cellulose into which ionic groups have been introduced, that is, after the ionic introduction step, and in aspect 2, this step is performed on cellulose as a raw material. Specifically, this step can be achieved by mixing cellulose and an etherification agent for introducing the substituent, preferably in the presence of a base and a solvent. By going through this step, in the case of Aspect 1, a modified cellulose having an ionic group and a nonionic substituent is obtained, and in the case of Aspect 2, a cellulose having a nonionic substituent is obtained.

(etherification agent)
As used herein, the term "etherification agent" refers to a compound having a nonionic substituent that is used to introduce the nonionic substituent. The reaction between the hydroxyl group of cellulose and the etherification agent causes the nonionic substituent to bond to the cellulose through an ether linkage.

From the viewpoint of reactivity, the etherifying agent is preferably a compound having a reactive cyclic structural group and/or an organic halogen compound, and more preferably a compound having an epoxy group and/or a halogenated hydrocarbon group. Examples of etherifying agents for introducing the substituent represented by the general formula (1), (2), or (3) are shown below.

As the etherifying agent having a substituent represented by the general formula (1), for example, a compound having a nonionic halogenated hydrocarbon group represented by the following general formula (1A) is preferable. Such compounds may be prepared according to known techniques, or commercially available products may be used. In addition, the details of R ¹ in the following general formula (1A) are as explained in the above general formula (1).

X-R ¹ (1A)
(In the formula, X represents a halogen atom, and R ¹ is a hydrocarbon group having 2 to 100 carbon atoms.)

Specific examples of the compound represented by the general formula (1A) include chloroethane, 1-chloropropane and its isomers, 1-chlorobutane and its isomers, 1-chloropentane and its isomers, 1-chlorohexane and its isomers. , 1-chlorodecane and its isomers, 1-chlorododecane and its isomers, 1-chlorohexadecane and its isomers, 1-chlorooctadecane and its isomers, 1-chloroeicosane and its isomers, 1-chlorotria Examples include consan and its isomers, 1-chloro-5-hexene and its isomers, chlorocyclohexane, chlorobenzene, benzyl chloride, naphthyl chloride, trityl chloride, and compounds in which bromine or iodine replaces chlorine in the above compounds.

As the etherifying agent having a substituent represented by the general formula (2), for example, a nonionic alkylene oxide compound represented by the following general formula (2A) is preferable. Such compounds may be prepared according to known techniques, or commercially available products may be used. Note that the details of R ² in the following general formula (2A) are as explained in the above general formula (2).

(In the formula, ^R2 represents a hydrocarbon group having 1 to 100 carbon atoms.)

Specific examples of the compound represented by the general formula (2A) include propylene oxide, butylene oxide, 3,4-epoxy-1-butene, 1,2-epoxypentane, 1,2-epoxyhexane, 1,2-epoxy -5-hexene, 1,2-epoxyoctane, 1,2-epoxydecane, 1,2-epoxy-9-decene, 1,2-epoxydodecane, 1,2-epoxyhexadecane, 1,2-epoxyoctadecane, Examples include 1,2-epoxy-17-octadecene, 1,2-epoxyeicosane, styrene oxide and derivatives thereof.

As the etherifying agent having a substituent represented by the general formula (3), for example, a nonionic glycidyl ether compound represented by the following general formula (3A) is preferable. Such compounds may be prepared according to known techniques, or commercially available products may be used. In addition, the details of R ³ , A, and n in the following general formula (3A) are as explained in the above general formula (3).

(In the formula, ^R3 is a hydrocarbon group having 1 to 100 carbon atoms, n is a number of 0 to 100, and A is a divalent hydrocarbon group having 1 to 6 carbon atoms.)

Specific examples of the compound represented by the general formula (3A) include methyl glycidyl ether, ethyl glycidyl ether, propyl glycidyl ether, isoprenyl glycidyl ether, allyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, lauryl glycidyl ether, Stearyl glycidyl ether, isostearyl glycidyl ether, polyoxyalkylene alkyl ether, 5-hexenyl glycidyl ether, 9-decenyl glycidyl ether, 9-octadecenyl glycidyl ether, 17-octadecenyl glycidyl ether, phenyl glycidyl ether , trityl glycidyl ether, benzyl glycidyl ether and derivatives thereof.

(base)
In the method for producing modified cellulose of the present invention, from the viewpoint of promoting the etherification reaction, it is preferable to mix cellulose, etherification agent, etc. in the presence of a base.

From the viewpoint of advancing the etherification reaction, bases include alkali metal hydroxides, alkaline earth metal hydroxides, primary to tertiary amines, quaternary ammonium salts, imidazole and its derivatives, pyridine and its derivatives, and alkoxides. One or more selected from the group consisting of are preferred.

Examples of the alkali metal hydroxide and alkaline earth metal hydroxide include sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide, and the like.

Primary to tertiary amines refer to primary amines, secondary amines, and tertiary amines, and specific examples include ethylenediamine, diethylamine, proline, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, tris(3-dimethylaminopropyl)amine, Examples include N,N-dimethylcyclohexylamine and triethylamine.

Examples of quaternary ammonium salts include tetrabutylammonium hydroxide, tetrabutylammonium chloride, tetrabutylammonium fluoride, tetrabutylammonium bromide, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium fluoride, tetraethylammonium bromide, and water. Examples include tetramethylammonium oxide, tetramethylammonium chloride, tetramethylammonium fluoride, and tetramethylammonium bromide.

Examples of imidazole and its derivatives include 1-methylimidazole, 3-aminopropylimidazole, and carbonyldiimidazole.

Examples of pyridine and its derivatives include N,N-dimethyl-4-aminopyridine and picoline.

Examples of the alkoxide include sodium methoxide, sodium ethoxide, potassium-t-butoxide, and the like.

(solvent)
Mixing of cellulose, etherification agent, etc. may be performed in the presence of a solvent. The solvent is not particularly limited and includes, for example, water, isopropanol, t-butanol, dimethylformamide, toluene, methyl isobutyl ketone, acetonitrile, dimethyl sulfoxide, dimethyl acetamide, 1,3-dimethyl-2-imidazolidinone, hexane, 1,4-dioxane, and mixtures thereof.

(Etherification reaction and reaction conditions)
There are no particular restrictions on the mixing conditions for promoting the etherification reaction between cellulose and the etherification agent, as long as the cellulose, etherification agent, etc. are mixed uniformly and the reaction can proceed sufficiently, and continuous mixing treatment is possible. You may or may not do so.

From the viewpoint of production efficiency, the cellulose concentration in the mixture of all components in this step is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, while From the viewpoint of handling properties, the content is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 45% by mass or less, and even more preferably 40% by mass or less.

The amount of the etherification agent used is preferably 0.02 equivalent or more, more preferably 0.05 equivalent or more with respect to 1 unit of anhydroglucose unit of cellulose, from the viewpoint of introduction efficiency of nonionic substituent. and is more preferably 0.1 equivalent or more, still more preferably 0.3 equivalent or more, and even more preferably 1.0 equivalent or more. On the other hand, when the modified cellulose is applied to the resin composition, From the viewpoint of mechanical strength of the molded article of the resulting resin composition, the amount is preferably 10.0 equivalents or less, more preferably 8.0 equivalents or less, and Preferably it is 7.0 equivalents or less, more preferably 6.0 equivalents or less.

The amount of the base to be used is preferably 0.01 equivalent or more, more preferably 0.05 equivalent or more, and even more preferably 0.1 equivalent to 1 unit of anhydroglucose in cellulose from the viewpoint of advancing the etherification reaction. The amount is at least an equivalent, more preferably at least 0.2 equivalents, and from the viewpoint of production cost, it is preferably at most 10 equivalents, more preferably at most 8 equivalents, even more preferably at most 5 equivalents, and even more preferably at most 3 equivalents.

From the viewpoint of reactivity, the amount of the solvent used is preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 75 parts by mass or more, based on 100 parts by mass of cellulose. More preferably, it is 200 parts by mass or more, while from the viewpoint of productivity, it is preferably 10,000 parts by mass or less, more preferably 7,500 parts by mass or less, and even more preferably 5,000 parts by mass or less. , more preferably 2,000 parts by mass or less.

From the viewpoint of improving reactivity, the reaction temperature is preferably 25°C or higher, more preferably 30°C or higher, even more preferably 35°C or higher, even more preferably 40°C or higher, and still more preferably 45°C or higher. ℃ or higher, and on the other hand, from the viewpoint of suppressing thermal decomposition, the temperature is preferably 120℃ or lower, more preferably 110℃ or lower, still more preferably 100℃ or lower, still more preferably 90℃ or lower, The temperature is more preferably 80°C or lower, and even more preferably 70°C or lower. Further, a temperature raising/lowering process may be provided as appropriate.

From the viewpoint of reactivity, the reaction time is preferably 0.1 hour or more, more preferably 0.5 hour or more, still more preferably 1 hour or more, and even more preferably 2 hours or more, More preferably, the time is 4 hours or more, and from the viewpoint of productivity, the time is preferably 60 hours or less, more preferably 48 hours or less, and still more preferably 36 hours or less.

After the reaction is completed, it is preferable to carry out an appropriate post-treatment in order to remove unreacted compounds, bases, and the like. As a method for the post-treatment, for example, an unreacted base can be neutralized with an acid (organic acid, inorganic acid, etc.), and then washed using a solvent in which the unreacted compound and base can be dissolved. If desired, further drying (vacuum drying, etc.) may be performed.

By this production method, a modified cellulose preferably having a structure represented by the general formula (Ce) can be produced.

[Refining process]
The modified cellulose obtained by the method for producing modified cellulose of the present invention may be further subjected to a refining treatment. For example, it can be made fine by processing using a grinder such as a mass colloider or processing using a high-pressure homogenizer or the like in a solvent.
As appropriate, operations can be performed to change the solvent used in the previous step, and to wash by-products, residual reagents, etc. generated in the previous step.

Hereinafter, the present invention will be specifically explained by showing Examples, Comparative Examples, etc. It should be noted that these Examples and the like are merely illustrative of the present invention, and do not mean any limitation. Parts in the examples are parts by weight unless otherwise specified. Note that "normal pressure" refers to 101.3 kPa, and "normal temperature" refers to 25°C.

[Introduction rate of nonionic substituent (molar degree of substitution)]
First, the content% (mass%) of substituents contained in the cellulose to be measured is determined according to the Japanese Pharmacopoeia 15th Edition (Hydroxy It is calculated according to the Zeisel method, which is known as a method for analyzing the average number of added moles of alkoxy groups in cellulose ether, as described in "Propyl cellulose analysis method section)". The procedure is shown below.

(i) Add 0.1 g of n-tetradecane to a 200 mL volumetric flask and make up to the marked line with hexane to prepare an internal standard solution.
(ii) Accurately weigh 70 mg of purified and dried cellulose to be measured and 80 mg of adipic acid into a 10 mL vial, add 2 mL of hydroiodic acid, and seal the vial.
(iii) The mixture in the vial is heated with a block heater at 160° C. for 1 hour while stirring with a stirrer chip.
(iv) After heating, 2 mL of the internal standard solution and 2 mL of diethyl ether are sequentially poured into the vial and stirred for 1 minute at room temperature.
(v) Analyze the upper layer (diethyl ether layer) of the mixture separated into two phases in the vial using gas chromatography (manufactured by SHIMADZU, trade name: GC2010Plus).
(vi) Analyzes were conducted in the same manner as in (ii) to (v) except that the cellulose to be measured was changed to 5 mg, 10 mg, and 15 mg of the etherifying agent used to modify the cellulose. Create a calibration curve.
(vii) Quantify the substituents contained in the cellulose to be measured from the prepared calibration curve and the analysis results of the cellulose to be measured. The analysis conditions are as follows.

Column: Manufactured by Agilent Technologies, product name: DB-5 (12 m, 0.2 mm x 0.33 μm)
Column temperature: 30°C (10min Hold) → 10°C/min → 300°C (10min Hold)
Injector temperature: 300℃
Detector temperature: 300℃
Injection amount: 1μL
The content (% by mass) of substituents contained in the cellulose to be measured is calculated from the detected amount of the etherification agent used.

Next, from the obtained substituent content, the degree of molar substitution (MS) (the molar amount of substituents per mole of anhydroglucose unit) is calculated using the following mathematical formula (1).
Formula (1)
MS=(W/Mw)/((100-W)/162.14)
W: Content of substituents introduced in the nonionic substituent introduction step in the cellulose to be measured (% by mass)
Mw: Molecular weight (g/mol) of the etherification agent used in the nonionic substituent introduction step

[Confirmation of crystal structure of cellulose]
The crystal structure of various celluloses, such as raw material cellulose, anion-modified cellulose, and modified cellulose, is confirmed by measurement using a diffractometer (manufactured by Rigaku Corporation, trade name: MiniFlex II) under the following conditions.
Measurement pellet preparation conditions: A smooth pellet with an area of 320 mm ² × thickness of 1 mm is prepared by applying pressure to the target cellulose in a range of 10 to 20 MPa using a tablet press.
X-ray diffraction analysis conditions: step angle 0.01°, scan speed 10°/min, measurement range: diffraction angle 2θ = 5 to 40°
X-ray source: Cu/Kα-radiation, tube voltage: 15kv, tube current: 30mA
Peak division conditions: After removing background noise, fitting is performed using a Gaussian function so that the error between 2θ=13 and 23° is within 5%.

The crystal structure of each type of cellulose is confirmed by measurement using the above-mentioned diffractometer under the above-mentioned conditions.
The crystallinity of cellulose type I crystal structure is calculated based on the following formula (A) using the area of the X-ray diffraction peak obtained by the above-mentioned peak division.
Cellulose type I crystallinity (%) = [I _cr / (I _cr + I _am )] x 100 (A)
[In the formula, I _cr is the area of the diffraction peak of the lattice plane (002 plane) (diffraction angle 2θ = 22-23°) in X-ray diffraction, I _am is the area of the amorphous part (diffraction angle 2θ = 18.5°) The area of the diffraction peak is shown. ]

[Average fiber diameter and average fiber length of various celluloses]
(1) If the average fiber diameter of cellulose to be measured is expected to be from several nanometers to several hundred nanometers, determine the average fiber diameter of cellulose as follows.
A suitable solvent was added to the cellulose to be measured to prepare a dispersion liquid with a concentration of 0.0001% by mass, and the dispersion liquid was dropped onto mica (mica), dried, and used as an observation sample. Using a force microscope (AFM) (manufactured by Digital Instrument, Inc., Nanoscope III Tapping mode AFM, probe manufactured by Nanosensors, Inc., using Point Probe (NCH)), the height of the cellulose fibers (fiber height) in the observation sample was measured. Measure the difference in height between one place and the other. A suitable solvent may be any solvent that swells the cellulose to be measured, preferably water or ethanol in the case of cellulose, and dimethylformamide (DMF) or methyl ethyl ketone (MEK) in the case of modified cellulose or finely modified cellulose. , toluene, etc. are preferred. At that time, 100 or more cellulose fibers are extracted from a microscopic image in which the cellulose can be confirmed, and the average fiber diameter is calculated from the height of these fibers. The average fiber length is calculated from the distance in the fiber direction. The average aspect ratio is calculated from the average fiber length/average fiber diameter, and the standard deviation is also calculated. In general, the minimum unit of cellulose nanofibers prepared from higher plants is a 6 x 6 molecular chain packed in an almost square shape, so the height analyzed in an AFM image can be regarded as the width of the fiber. I can do it.

(2) If the average fiber diameter of the cellulose to be measured is expected to be from several hundred nanometers to several thousand micrometers, determine the average fiber diameter of cellulose as follows.
A medium is added to the cellulose to be measured to prepare a dispersion having a content of 0.01% by mass. The dispersion liquid was measured using a wet dispersion type image analysis particle size distribution analyzer (manufactured by Jusco International Co., Ltd., trade name: IF-3200), front lens: 2x, telecentric zoom lens: 1x, image resolution: 0.835 μm/pixel. , Syringe inner diameter: 6515 μm, Spacer thickness: 500 μm, Image recognition mode: Ghost, Threshold: 8, Analysis sample amount: 1 mL, Sampling: 15%. Measure 100 or more pieces of cellulose, use their average ISO fiber diameter as the average fiber diameter, and calculate the average ISO fiber length as the average fiber length. The average aspect ratio is calculated from the average fiber length/average fiber diameter, and the standard deviation is also calculated.

[Anionic group content of various celluloses]
Dry mass 0.5 g - Cellulose to be measured is taken into a 100 mL beaker, and deionized water or a mixed solvent of methanol/deionized water = 2/1 is added to make a total of 55 mL. Add 5 mL of 0.01M sodium chloride aqueous solution to this to prepare a dispersion. The dispersion is stirred until the cellulose to be measured is sufficiently dispersed. 0.1M hydrochloric acid was added to this dispersion to adjust the pH to 2.5-3, and a 0.05M aqueous sodium hydroxide solution was added using an automatic titrator (manufactured by DKK Toa Co., Ltd., trade name "AUT-701"). It is added dropwise to the dispersion with a waiting time of 60 seconds, and the conductivity and pH values are measured every minute. The measurement is continued until the pH reaches about 11, and a conductivity curve is obtained. The sodium hydroxide titer is determined from this conductivity curve, and the anionic group content of the cellulose to be measured is calculated using the following formula.
Anionic group content (mmol/g-cellulose) = sodium hydroxide titration x sodium hydroxide aqueous solution concentration (0.05M)/mass of cellulose to be measured (0.5g-cellulose)

When the cellulose to be measured is cellulose that has not undergone chemical modification or cellulose that has ionic groups, "mass of cellulose (g-cellulose)" = "mass of cellulose that has not undergone chemical modification or cellulose that has ionic groups" If the cellulose to be measured is cellulose with nonionic substituents, then "mass of cellulose (g - cellulose)" = "mass of cellulose with nonionic substituents (g)" ×162/[162+molecular weight of etherifying agent (g/mol)×molar substitution degree]”. In addition, when two or more types of etherification agents are used, the mass of cellulose is calculated in consideration of the molar ratio of each etherification agent.

[Preparation of anion-modified cellulose]
Preparation example 1
Bleached softwood kraft pulp (manufactured by West Fraser, trade name: Hinton) was used as the natural cellulose. As TEMPO, a commercially available product (manufactured by ALDRICH, Free radical, 98% by mass) was used. Commercially available products (manufactured by Wako Pure Chemical Industries, Ltd.) were used as sodium hypochlorite and sodium bromide.

First, 10 g of the bleached kraft pulp was thoroughly stirred with 990 g of deionized water, and then 0.13 g of TEMPO, 1.3 g of sodium bromide, and 27 g of a 10.5% by mass sodium hypochlorite aqueous solution were added to 10 g of the pulp. were added in this order. A 0.5M aqueous sodium hydroxide solution was added dropwise to the solution to maintain the pH at 10.5 using a pH-stat titration using an automatic titrator (manufactured by DKK Toa Co., Ltd., trade name: AUT-701). After the reaction was carried out at a stirring speed of 200 rpm for 120 minutes (20° C.), the dropping of the aqueous sodium hydroxide solution was stopped to obtain anion-modified cellulose (oxidized cellulose) having a carboxy group as an anionic group.

After neutralizing the obtained oxidized cellulose with 0.01M hydrochloric acid, the electrical conductivity of the filtrate was measured using deionized water using a compact electrical conductivity meter (Horiba, Ltd., LAQUAtwin EC-33B) for 200 μs. /cm or less. Then, by performing a dehydration treatment, acid-type oxidized cellulose was obtained. The carboxy group content of this acid type oxidized cellulose was 1.3 mmol/g-cellulose.

Example 1
The acid type oxidized cellulose obtained in Preparation Example 1 was solvent-substituted with dimethyl sulfoxide (DMF). To 3.0 g of the obtained dispersion (solid content 26.4% by mass), 1.21 g of acetonitrile and 0.74 g (1.00 equivalents) of N,N-dimethyl-4-aminopyridine (DMAP) as a catalyst were added. /AGU) and mixed uniformly. Next, 3.66 g of lauryl glycidyl ether (manufactured by Yokkaichi Gosei Co., Ltd., 2.5 equivalents/AGU) was added as an etherification agent, and the container was sealed. Next, the reaction was stirred at 70° C. for 24 hours using a block heater. After the reaction was completed, it was neutralized with 1M hydrochloric acid, and then ethanol was added to perform reprecipitation. The obtained precipitate was thoroughly washed with ethanol in a filtration operation to remove impurities, and vacuum dried at 70° C. overnight to obtain a modified cellulose having a cellulose I type crystal structure. The cellulose type I crystallinity of this modified cellulose was 65%, and the carboxy group content was 1.3 mmol/g-cellulose.

Example 2
A modified cellulose having a cellulose I type crystal structure was obtained in the same manner as in Example 1 except that the amount of lauryl glycidyl ether used was changed to 6.0 equivalents/AGU.

Comparative example 1
The acid-type oxidized cellulose obtained in Preparation Example 1 was used as the cellulose to be evaluated in the test examples described below.

Comparative example 2
The acid type oxidized cellulose obtained in Preparation Example 1 was solvent-substituted with DMF to obtain a dispersion (solid content 0.5% by mass). After adding 24 parts by mass (0.5 equivalent per carboxy group of oxidized cellulose) of laurylamine (manufactured by Kao Corporation, trade name: Firmin 20D) to 100 parts by mass of oxidized cellulose to the obtained dispersion, The reaction was allowed to proceed at room temperature for 1 hour. After the reaction was completed, it was filtered, and the cake was washed with DMF and vacuum dried at 70° C. overnight. Since the carboxy group content of the obtained modified cellulose was 1.3 mmol/g-cellulose, a part of the carboxy groups of the obtained modified cellulose was oxidized cellulose as shown in the following formula LA. It was presumed that the carboxyl group and the amino group of laurylamine were bonded through an ionic bond.

Comparative example 3
The acid type oxidized cellulose obtained in Preparation Example 1 was solvent-substituted with N-methylpyrrolidone (NMP) to obtain a dispersion (solid content 13.4% by mass). 1.5 g of acetic anhydride and 1.25 g of potassium carbonate were added to 37.3 g of the obtained dispersion, and the mixture was allowed to stand at 80° C. for 1.5 hours to carry out an acetylation reaction of hydroxyl groups in the oxidized cellulose. After the reaction was completed, it was filtered and thoroughly washed with water, and vacuum dried at 80° C. overnight to obtain modified cellulose in which the hydroxy groups were acetylated.

The degree of introduction of acetyl groups corresponding to nonionic substituents in the obtained modified cellulose is determined by the degree of chemical modification determined by the back titration method described in paragraphs 0249 to 0253 of JP-A-2016-176052. The values are listed in Table 1. Note that the degree of chemical modification can be adjusted by adjusting the amount of acetylating agent, reaction temperature, reaction time, etc. in the acetylation.

Test example 1 (dispersion stability)
The modified cellulose or anion-modified cellulose obtained in each Example and Comparative Example was subjected to a high-pressure homogenizer ("Nano Veita L-ES" manufactured by Yoshida Kikai Co., Ltd.) treatment 10 times in total using each medium shown in Table 1. A dispersion treatment was performed to obtain a dispersion (solid content: 0.5% by mass). Each dispersion was allowed to stand at room temperature for one day, and the transparency and presence of precipitates were visually confirmed and evaluated based on the following evaluation criteria. In addition, the amount of modified cellulose or anion-modified cellulose in the dispersion here is an amount in which the amount of cellulose obtained by removing ionic groups and nonionic substituents from modified cellulose or anion-modified cellulose is 0.5% by mass. It is.

Evaluation A: Transparent state or slightly cloudy state, and no precipitate was observed.
Evaluation B: Some precipitates were observed.
Evaluation C: Complete separation and the entire amount was precipitated.
Dispersion stability is evaluated in the order of A>B>C, with evaluation A indicating excellent dispersion stability, and evaluation B indicating dispersion stability that does not pose a problem in actual use. Indicates that there is a

Test example 2 (permeability of dispersion)
Using the dispersion prepared in Test Example 1 and obtained for each Example and Comparative Example, the permeability of the dispersion was evaluated as follows. The measurement of light transmittance was carried out at room temperature and pressure.

Specifically, 30 mL of each dispersion immediately after the dispersion treatment was transferred to a screw tube (No. 7 manufactured by As One), the dispersion was shaken together with the screw tube, and the sample, which was visually homogeneous, was transferred to a quartz tube with an optical path length of 10 mm. 3 mL was put into the cell. After the cell was allowed to stand for 1 minute, absorbance at a wavelength of 660 nm was measured using a double beam spectrophotometer (manufactured by Hitachi High-Tech Science Co., Ltd., "U-2910"). The medium used to prepare each dispersion was used as a blank (ie, transmittance 100%), and the transmittance was determined from the absorbance of each dispersion.
The results are summarized in Table 1.

From the above experimental results, it was found that the modified cellulose of the present invention had excellent dispersion stability and permeability when made into a dispersion (Examples 1 and 2).
On the other hand, according to Comparative Examples, it was found that dispersions of oxidized cellulose without nonionic substituents (Comparative Examples 1 and 2) had very poor evaluations of dispersion stability and permeability. Furthermore, it was found that a dispersion of modified cellulose (Comparative Example 3) in which nonionic substituents were bonded not through ether bonds but through ester bonds also had very poor evaluations of dispersion stability and permeability.

The modified cellulose of the present invention can be used as a material for various parts for industrial applications such as automobiles, aircraft, and ships, and for sports applications.

Claims (9)

Cellulose I having a carboxy group and one or more nonionic substituents selected from the group consisting of the following general formulas (1), (2) and (3) , and having a crystallinity of 10% or more and 90% or less A modified cellulose having a type crystal structure,
The content of the carboxy group is 0.1 mmol/g-cellulose or more and 3 mmol/g-cellulose or less,
The introduction rate of the nonionic substituent is 0.001 mol or more and 1.5 mol or less per 1 mol of anhydroglucose unit of cellulose,
Modified cellulose in which the nonionic substituent is bonded to cellulose via an ether bond.
-R ¹ (1)
-CH ₂ -CH(OH)-R ² (2)
-CH ₂ -CH(OH)-CH ₂ -(OA) _n -O-R ³ (3)
(In the formula, R ¹ is a hydrocarbon group having 2 to 100 carbon atoms, R ² is a hydrocarbon group having 1 to 100 carbon atoms, and R ³ is a hydrocarbon group having 1 to 100 carbon atoms. (n is a number from 0 to 100, and A is a divalent hydrocarbon group having 1 to 6 carbon atoms.) The modified cellulose according to claim 1, wherein the modified cellulose is represented by the following general formula (Ce).

(wherein each R is independently selected from the group consisting of a hydrogen atom, a carboxy group , and a nonionic substituent, at least one of R is a carboxy group , and at least one of R is a nonionic substituent) It is a substituent. m is an integer from 20 to 3,000.) The modified cellulose according to claim 1 or 2 , wherein the introduction rate of the nonionic substituent is 0.005 mol or more and 1.0 mol or less per 1 mol of anhydroglucose unit of cellulose. A step of introducing a carboxy group into the raw material cellulose, and one or more nonionic substituents selected from the group consisting of the following general formulas (1), (2) and (3) via an ether bond. A method for producing modified cellulose having a cellulose type I crystal structure with a crystallinity of 10% or more and 90% or less, the method comprising the step of introducing into the hydroxyl group of cellulose ,
The content of the carboxy group is 0.1 mmol/g-cellulose or more and 3 mmol/g-cellulose or less,
A method for producing modified cellulose, wherein the introduction rate of the nonionic substituent is 0.001 mol or more and 1.5 mol or less per 1 mol of anhydroglucose unit of cellulose .
-R ¹ (1)
-CH ₂ -CH(OH)-R ² (2)
-CH ₂ -CH(OH)-CH ₂ -(OA) _n -O-R ³ (3)
(In the formula, R ¹ is a hydrocarbon group having 2 to 100 carbon atoms, R ² is a hydrocarbon group having 1 to 100 carbon atoms, and R ³ is a hydrocarbon group having 1 to 100 carbon atoms. (n is a number from 0 to 100, and A is a divalent hydrocarbon group having 1 to 6 carbon atoms.) 5. The production method according to claim 4 , comprising a step of introducing a nonionic substituent into the hydroxyl group of cellulose having a carboxy group via an ether bond. 5. The production method according to claim 4 , comprising a step of introducing a carboxy group into a hydroxy group of cellulose having a nonionic substituent. The manufacturing method according to any one of claims 4 to 6 , wherein the modified cellulose is represented by the following general formula (Ce).

(wherein each R is independently selected from the group consisting of a hydrogen atom, a carboxy group , and a nonionic substituent, at least one of R is a carboxy group , and at least one of R is a nonionic substituent) It is a substituent. m is an integer from 20 to 3,000.) The production method according to any one of claims 4 to 7 , wherein the introduction rate of the nonionic substituent is 0.005 mol or more and 1.0 mol or less per 1 mol of anhydroglucose unit of cellulose. Any one of claims 4 to 8 , wherein n of the substituent represented by general formula (3) is a number of 0 to 20, and A is a divalent saturated hydrocarbon group having 2 to 3 carbon atoms. The manufacturing method described in section .