JP2010241887A - Method for producing carboxyalkylcellulose derivative - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a carboxyalkylcellulose derivative, industrially simple and of high reaction selectivity, that produces a carboxyalkyl group-introducing cellulose derivative efficiently from a powdered cellulose of low crystallinity. <P>SOLUTION: This method for producing the carboxyalkylcellulose derivative includes reacting the powdered cellulose of low crystallinity, in the presence of a basic catalyst, with α,β-unsaturated carboxylate ester represented by Formula (1): R<SP>1</SP>-(R<SP>2</SP>-)C=C(-R<SP>3</SP>)-R<SP>4</SP>(wherein R<SP>1</SP>and R<SP>2</SP>are each independently a hydrogen atom or a substituted group represented by -COOR<SP>5</SP>, however both are not to be a hydrogen atom; R<SP>3</SP>and R<SP>4</SP>are each independently a hydrogen atom or a methyl group; R<SP>5</SP>is a 1-17C hydrocarbon group, a hydrogen atom or an alkali metal atom, however in the molecule at least one R<SP>5</SP>is a hydrocarbon group, and when two R<SP>5</SP>s are present in the molecule, both may be the same or different, however the total carbon number of the compound represented by Formula (1) is 4-20). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a carboxyalkyl cellulose derivative, particularly a carboxyethyl cellulose derivative.

Carboxyalkylcelluloses such as carboxymethylcellulose and carboxyethylcellulose are useful as thickeners, dispersants, emulsifiers, protective colloid agents, and stabilizers. In addition to the above uses, carboxyethyl cellulose has uses as a raw material for sponges and the like.
When producing these carboxyalkyl celluloses, the cellulose that is the raw material generally has very poor reactivity with various reagents. For example, carboxymethyl cellulose once generates alkali cellulose using a large excess of alkali relative to cellulose. In this way, it is activated and then industrially produced by a stoichiometric reaction with chloroacetic acids. Patent Document 1 discloses a method for producing carboxyethyl cellulose by treating cellulose with an aqueous alkali solution and carbon disulfide to obtain viscose, then reacting with acrylonitrile, and further hydrolyzing with acid or alkali. .

JP-A-7-242767

  The reaction using the alkali cellulose is not industrially used for the production of carboxyalkyl cellulose except for carboxymethyl cellulose using chloroacetic acid which is highly reactive and relatively inexpensive. Moreover, since the method using this alkali cellulose and the method disclosed in Patent Document 1 both use at least 1 mol or more, usually 1 to 3 mol of alkali per glucose unit constituting cellulose, decomposition of the reactants. There is a problem that the purification load is high because a large amount of salt is generated after neutralization and neutralization of the reaction. Furthermore, the method disclosed in Patent Document 1 has a problem that the product is limited to carboxyethyl cellulose.

  It is an object of the present invention to provide a method for producing a carboxyalkyl cellulose derivative that is industrially simple, has high reaction selectivity, and is efficient.

  When the present inventors use powdered cellulose with reduced crystallinity as a raw material, the reaction with a specific α, β-unsaturated carboxylic acid ester, preferably an acrylic acid ester, is carried out in the presence of a catalytic amount of a base. It has been found that it proceeds efficiently. The product obtained by the reaction with the acrylate ester can be easily converted into a carboxyethyl cellulose derivative by hydrolysis of the ester group with an acid or alkali.

  That is, in the present invention, low crystalline powdery cellulose is represented by the following general formula (1) in the presence of a base catalyst.

(In the formula, R ¹ and R ² each independently represent a hydrogen atom or a substituent represented by —COOR ⁵ , but they are not hydrogen atoms, and R ³ and R ⁴ are each independently Represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrocarbon group having 1 to 17 carbon atoms, a hydrogen atom or an alkali metal atom. In the molecule, at least one R ⁵ is a hydrocarbon group, and 2 in the molecule If there is One of R ^5, it may be different even in the same, but the total number of carbon atoms of the compound represented by the general formula (1) is 4 to 20.)
The manufacturing method of the carboxyalkyl cellulose derivative made to react with the (alpha), (beta)-unsaturated carboxylic acid ester represented by these is provided.

  According to the present invention, an industrially simple, highly selective and efficient method for producing a carboxyalkyl cellulose derivative can be provided.

[Preparation of low crystalline powdered cellulose]
In general, cellulose has several known crystal structures, and is defined as the crystallinity from the ratio of the amorphous part and the crystal part present in a part. The “crystallinity” in the present invention is natural. The degree of crystallinity of type I derived from the crystal structure of cellulose is shown, and is defined by the degree of crystallinity represented by the following formula (1) obtained from the powder X-ray crystal diffraction spectrum.
Crystallinity (%) = [(I _22.6 −I _18.5 ) / I _22.6 ] × 100 (1)
[I _22.6 is the diffraction intensity of the lattice plane (002 plane) (diffraction angle 2θ = 22.6 °) in X-ray diffraction, and I _18.5 is the diffraction intensity of the amorphous portion (diffraction angle 2θ = 18.5 °). Show

The “low crystallinity” of the low crystalline powdery cellulose in the present invention indicates a state in which the ratio of the amorphous part is large in the crystal structure of the cellulose, and the crystallinity obtained from the above calculation formula (1) is 0% Including the case of
Since the generally known powdered cellulose also has a very small amount of amorphous part, the crystallinity thereof is included in the range of approximately 60 to 80% according to the calculation formula (1) used in the present invention. These are so-called crystalline celluloses, and the reactivity in synthesis of ordinary cellulose derivatives is extremely low.
Therefore, the “low crystallinity” of the low crystalline powdery cellulose in the present invention indicates a state in which the ratio of the amorphous portion is large in the crystal structure of the cellulose, and preferably the crystallization obtained from the calculation formula (1). The degree is preferably in the range of 0 to 50%. Within this range, the reaction with the α, β-unsaturated carboxylic acid ester by the base catalyst proceeds very well. In this respect, the crystallinity is more preferably in the range of 0 to 40%, and further preferably in the range of 0 to 30%. In particular, in the present invention, it is most preferable to use a so-called amorphous cellulose that is completely amorphized, that is, the crystallinity obtained from the above formula (1) is approximately 0%.

  The low crystalline powdery cellulose used in the present invention can be prepared very easily from a sheet-like or roll-like pulp having a high cellulose purity obtained as a general-purpose raw material. The method for preparing the low crystalline cellulose is not particularly limited. For example, as described in Japanese Patent No. 4160109, a chip-like pulp obtained by roughly pulverizing a cellulose pulp sheet is used. It can be easily prepared by treating with an extruder and further with a pulverizer such as a ball mill. By this method, it is possible to prepare a low-crystalline powdery cellulose having a high molecular weight, that is, a degree of polymerization.

As the extruder used in this method, a single-screw or twin-screw extruder can be used, and from the viewpoint of applying a strong compressive shear force, a so-called kneading disk portion is provided in any part of the screw. There may be. Although there is no restriction | limiting in particular as a processing method using an extruder, The method of throwing a chip-form pulp into an extruder and processing continuously is preferable.
As a pulverizer such as a ball mill, a rod mill can be used in addition to a known vibration ball mill, medium stirring mill, rolling ball mill, planetary ball mill, and the like. There is no restriction | limiting in particular in the material of a ball | bowl or a rod used as a medium, For example, iron, stainless steel, an alumina, a zirconia etc. are mentioned. The diameter of a medium such as a ball or a rod is preferably 0.1 to 100 mm, more preferably 0.5 to 50 mm, and still more preferably 1 to 30 mm, from the viewpoint of efficiently amorphizing cellulose. A tube-shaped medium can also be used as the medium. The filling rate of a medium such as a ball or a rod is usually 10 to 97%, preferably 20 to 90% from the viewpoint of grinding efficiency, although it depends on the model. Here, the filling rate refers to the apparent volume of the medium relative to the volume of the stirring unit of the pulverizer.

Since the crystallinity of cellulose can be efficiently reduced, the treatment time for the ball mill or the like is preferably 5 minutes to 72 hours, and more preferably 5 minutes to 50 hours. In this treatment, in order to minimize denaturation and deterioration due to the generated heat, it is preferably carried out in the range of 5 to 250 ° C., more preferably 5 to 200 ° C. Furthermore, it is preferable to perform the treatment under an inert gas atmosphere such as nitrogen as necessary.
Moreover, as a polymerization degree of the low crystalline powder cellulose in this invention, 100-2000 are preferable from the viewpoint of operativity at the time of carrying out industrial pulp or industrial implementation, and 100-1000 are more preferable.
The average particle size of the low crystalline powder cellulose is not particularly limited as long as it can maintain a good fluidity as a powder, but is preferably 300 μm or less, more preferably 150 μm or less, and particularly preferably 50 μm or less. However, from the viewpoint of operability when carried out industrially, 20 μm or more is preferable, and 25 μm is particularly preferable.

(Method for producing carboxyalkyl cellulose derivative)
In the method for producing a carboxyalkyl cellulose derivative of the present invention, low crystalline powdered cellulose is converted into the following general formula (1) in the presence of a base catalyst.

(In the formula, R ¹ and R ² each independently represent a hydrogen atom or a substituent represented by —COOR ⁵ , but they are not hydrogen atoms, and R ³ and R ⁴ are each independently Represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrocarbon group having 1 to 17 carbon atoms, a hydrogen atom or an alkali metal atom. In the molecule, at least one R ⁵ is a hydrocarbon group, and 2 in the molecule If there is One of R ^5, it may be different even in the same, but the total number of carbon atoms of the compound represented by the general formula (1) is 4 to 20.)
And an α, β-unsaturated carboxylic acid ester represented by:

The α, β-unsaturated carboxylic acid ester used in the present invention is an α, β-unsaturated carboxylic acid ester having a total carbon number of 4 to 20 represented by the general formula (1).
The α, β-unsaturated carboxylic acid ester having a total carbon number of 4 to 20 represented by the general formula (1) includes a α, β-unsaturated carboxylic acid ester having a total carbon number of 4 to 20, and a carboxyl at the β-position. An α, β-unsaturated carboxylic acid ester substituted with a group or an alkali metal salt thereof may be mentioned.

When R ⁵ in the general formula (1) is a hydrocarbon group having 1 to 17 carbon atoms, the hydrocarbon group may be linear, branched, or cyclic, and includes an unsaturated bond. Also good. As the hydrocarbon group having 1 to 17 carbon atoms in R ^5, a linear or branched saturated or unsaturated hydrocarbon having 1 to 8 carbon atoms is preferable from the viewpoint of reactivity, and a straight chain having 1 to 4 carbon atoms is preferred. A chain or branched chain saturated hydrocarbon, specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, or a tert-butyl group is more preferable.
When R ⁵ in the general formula (1) is an alkali metal atom, the alkali metal atom is preferably sodium or potassium.
Show R ³ and R ⁴ each independently represent a hydrogen atom or a methyl group in the general formula (1), it is preferable that at least one is a hydrogen atom.

Examples of the α, β-unsaturated carboxylic acid ester include acrylic acid or methacrylic acid methyl ester, ethyl ester, n-propyl ester, isopropyl ester, n-butyl ester, sec-butyl ester, tert-butyl ester, In addition to pentyl ester, hexyl ester, heptyl ester, octyl ester, 2-ethylhexyl ester, etc., mono or dimethyl ester of maleic acid, mono or diethyl ester, mono or diisopropyl ester, mono or di-tert-butyl ester, mono or dioctyl Examples thereof include polyvalent carboxylic acid esters such as esters, mono- or di-2-ethylhexyl esters and similar fumaric acid esters, or alkali metal salts thereof. Examples of alkali metal salts include sodium salts or potassium salts. Salt and the like.
Among these, from the viewpoint of reactivity and solubility in a solvent, an ester of acrylic acid or methacrylic acid is preferable, and an acrylic ester is more preferable.

In the present invention, the addition reaction of α, β-unsaturated carboxylic acid ester to cellulose proceeds satisfactorily. Therefore, α, β-unsaturated carboxylic acid ester is large relative to the planned introduction amount of carboxyalkyl group. It is not necessary to use excessively, and it is also possible to adjust to a desired substitution degree per glucose unit constituting cellulose.
The amount of α, β-unsaturated carboxylic acid ester used is 0.1 to 5 moles per glucose unit in the cellulose molecule as carboxyalkyl cellulose from the viewpoint of suppressing performance and aggregation during the reaction. It is preferable to use 0.2 to 2.5 moles.

In the production method of the present invention, the base used as a catalyst is, for example, an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide or lithium hydroxide, an alkaline earth metal hydroxide such as magnesium hydroxide or calcium hydroxide, Alkali metal alkoxides such as sodium methoxide, sodium tert-butoxide, potassium tert-butoxide and the like can be mentioned. Of these, alkali metal alkoxides are preferable from the viewpoint of suppressing the decomposition of the α, β-unsaturated carboxylic acid ester. In addition, from the viewpoint of suppressing the effect of transesterification with an α, β-unsaturated carboxylic acid ester, the following general formula (2)
R ⁶ -OH (2)
(In the formula, R ⁶ has the same meaning as the hydrocarbon group having 1 to 17 carbon atoms represented by R ⁵ in the general formula (1).)
An alkali metal alkoxide of an alcohol represented by or an alkali metal alkoxide of a tertiary alcohol is particularly preferred.
As a usage-amount of a base catalyst, it is preferable to use 1-50 mass% with respect to low crystalline powdered cellulose, and it is more preferable to use 2-20 mass%.

These base catalysts are preferably added and dispersed in advance to low crystalline powdered cellulose, and then the α, β-unsaturated carboxylic acid ester is dropped and reacted.
The method for adding this base catalyst is not particularly limited, but when an alkali metal hydroxide or alkaline earth metal hydroxide such as sodium hydroxide, potassium hydroxide, lithium hydroxide or the like is added as an aqueous solution as a base catalyst. From the viewpoint of avoiding hydrolysis before the α, β-unsaturated carboxylic acid ester reacts, the reaction system is heated in advance under reduced pressure before adding the α, β-unsaturated carboxylic acid ester. It is preferable to perform a dehydration operation to reduce the amount of water in the inside.

In the present invention, it is also possible to use an organic solvent during the reaction. Specific examples of the organic solvent include diglyme such as dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, non-reactive polar solvent such as triglyme ether solvent, dimethyl sulfoxide, toluene, benzene, hexane, and other hydrocarbons. Non-reactive low polarity or non-polar solvents such as oils may be mentioned, but non-reactive polar solvents are preferred from the viewpoint of satisfactorily dispersing the low crystalline powdered cellulose and the base catalyst.
Moreover, as the usage-amount of these solvents, it is preferable to use 1 to 20 weight times with respect to low crystalline powdered cellulose.

The reaction temperature in the present invention is preferably from 30 to 100 ° C., particularly preferably from 40 to 80 ° C., from the viewpoint of suppressing the reaction rate and coloring of the product.
The carboxyalkyl group in the product of the present invention may be bonded to the hydroxyl group at any position in the glucose unit in the cellulose molecule.
In the present invention, a dicarboxyalkyl group such as a carboxyethyl group, a carboxypropyl group, a dicarboxyethyl group, a dicarboxypropyl group, a dicarboxybutyl group or the like is added to cellulose depending on the type of α, β-unsaturated carboxylic acid ester used. It can be introduced into the molecule. Among them, it is preferable to introduce a carboxyethyl group into a cellulose molecule since a product having performance equivalent to that of carboxymethylcellulose widely used can be obtained.
The degree of substitution per glucose unit constituting the cellulose in the carboxyalkylcellulose derivative obtained in the present invention (average added mole number of carboxyalkyl group) is the reaction time, reaction temperature, α, β-unsaturated carboxylic acid ester, base catalyst And it can adjust arbitrarily by adjusting reaction conditions, such as the usage-amount of an organic solvent. For example, a carboxyalkyl cellulose derivative having a substitution degree of 0.1 to 2.5, preferably 0.6 to 2.0 can be efficiently produced.

In the following Examples and Comparative Examples, the crystallinity of cellulose, the degree of polymerization, the average particle size, and the degree of substitution in carboxyalkyl cellulose derivatives were calculated by the following methods.
(1) Crystallinity The crystallinity of cellulose is calculated from the peak intensity of the powder X-ray diffraction spectrum measured using the “Rigaku RINT 2500VC X-RAY diffractometer” manufactured by Rigaku Corporation under the following conditions ( 1).
Measurement conditions: X-ray source: Cu / Kα-radiation, tube voltage: 40 kv, tube current: 120 mA, measurement range: 2θ = 5-45 °, measurement sample: compressed 320 mm ² × 1 mm thick pellet , X-ray scanning speed: 10 ° / min
(2) Degree of polymerization The degree of polymerization of cellulose was measured by the copper ammonia method described in ISO-4312 method.
(3) Average Particle Size The average particle size of cellulose was measured using a laser diffraction / scattering particle size distribution measuring device “LA-920” manufactured by Horiba, Ltd. The refractive index used is 1.2.

(4) Calculation of substitution degree A substitution degree shows the average addition mole number of the carboxyalkyl group per glucose unit which comprises a cellulose. As the calculation method, first, methoxyacetylation of the unreacted hydroxyl groups in the products obtained in Examples and Comparative Examples was performed using methoxyacetyl chloride in a pyridine solvent, and a ¹ H-NMR spectrum of the methoxyacetylated product was obtained. The integration of the methyl proton and methylene proton signals derived from the methoxyacetyl group and the proton signal derived from the introduced carboxyalkyl group observed at 3.2 to 4.6 ppm (in deuterated chloroform solvent, TMS standard) Calculated from the ratio. For NMR measurement, “Unity Inova300” manufactured by Varian was used.

Production Example 1 (Production of Amorphized Powdered Cellulose)
Amorphized powdered cellulose was prepared according to the method described in Japanese Patent No. 4160109. That is, first, a commercially available wood pulp sheet (Boreguard's pulp sheet, crystallinity 74%) was applied to a shredder (manufactured by Meiko Shokai Co., Ltd., “MSX2000-IVP440F”) to form a 1 cm square chip. Next, the obtained chip-like pulp was charged at 2 kg / hr into a twin-screw extruder ("EA-20" manufactured by Suehiro EPM Co., Ltd.) equipped with a kneading disk at the center of the screw, and a shear rate of 660 sec. ^-1 and powdered by one pass treatment with cooling water flowing from outside under the condition of screw rotation speed of 300 rpm. Next, 100 g of the powdered cellulose was put into a batch-type medium stirring ball mill (“Attritor” manufactured by Mitsui Mining Co., Ltd .: a container volume of 800 mL, 1400 g of 6 mmφ steel balls filled, a stirring blade diameter of 65 mm). did. While passing cooling water through the container jacket, pulverization was performed at a stirring rotational speed of 600 rpm for 3 hours to obtain powdered cellulose (crystallinity 0%, polymerization 600, average particle size 40 μm). A sieved product (90% by mass of the charged amount) obtained by further sieving this powdered cellulose with a sieve having an opening of 32 μm was used for the reaction described later.

Example 1
In a 500 ml eggplant flask, 10 g of the amorphous powdered cellulose (crystallinity 0%, polymerization degree 600) obtained in Production Example 1 above, 0.6 g of potassium tert-butoxide, and 150 ml of triethylene glycol dimethyl ether were added at room temperature. Dispersed. Next, the temperature was raised to 50 ° C. in a nitrogen atmosphere, 16 g of tert-butyl acrylate was added all at once, and the mixture was stirred as it was at 50 ° C. for 24 hours. After completion of the reaction, the reaction mixture was neutralized with acetic acid, further washed with 500 ml of methanol, and dried under reduced pressure to obtain 11 g of a reaction product. From ¹ H-NMR analysis after methoxyacetylation, the degree of substitution per glucose unit was 0.94.

Example 2
In a 500 ml eggplant flask, 10 g of the amorphous powdered cellulose (crystallinity 0%, polymerization degree 600) obtained in Preparation Example 1, potassium tert-butoxide 0.6 g, and dimethyl sulfoxide 150 ml are added and dispersed at room temperature. It was. Next, the temperature was raised to 50 ° C. in a nitrogen atmosphere, 16 g of tert-butyl acrylate was added all at once, and the mixture was stirred at 50 ° C. for 24 hours. After completion of the reaction, the reaction mixture was neutralized with acetic acid, the unreacted ester was distilled off, and then dried under reduced pressure to obtain 18 g of a crude reaction product. The degree of substitution determined from ¹ H-NMR analysis after methoxyacetylation was 1.25 per glucose unit.

Comparative Example 1
The reaction was conducted in the same manner as in Example 1 except that 10 g of crystalline commercially available cellulose (KC-Flock W400G manufactured by Nippon Paper Chemical Co., Ltd., crystallinity 74%) was used. As a result, 9.6 g of reaction product was produced. objects are obtained, the degree of substitution of determined by ¹ H-NMR analysis after methoxy acetylation was 0.51 per glucose unit.

Claims (4)

A low crystalline powdery cellulose in the presence of a base catalyst is represented by the following general formula (1)

(In the formula, R ¹ and R ² each independently represent a hydrogen atom or a substituent represented by —COOR ⁵ , but they are not hydrogen atoms, and R ³ and R ⁴ are each independently Represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrocarbon group having 1 to 17 carbon atoms, a hydrogen atom or an alkali metal atom. In the molecule, at least one R ⁵ is a hydrocarbon group, and 2 in the molecule If there is One of R ^5, it may be different even in the same, but the total number of carbon atoms of the compound represented by the general formula (1) is 4 to 20.)
The manufacturing method of the carboxyalkyl cellulose derivative made to react with the (alpha), (beta)-unsaturated carboxylic acid ester represented by these.   The method for producing a carboxyalkyl cellulose derivative according to claim 1, wherein the α, β-unsaturated carboxylic acid ester represented by the general formula (1) is an acrylic acid ester.   The method for producing a carboxyalkyl cellulose derivative according to claim 1 or 2, wherein the crystallinity of the low-crystalline powdery cellulose is 50% or less.   The method for producing a carboxyalkyl cellulose derivative according to any one of claims 1 to 3, wherein the base catalyst is an alkali metal hydroxide or an alkaline earth metal hydroxide.