JP2000080101A - Preparation of carboxy polysaccharide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for recovering and reusing ruthenium in the preparation of carboxy polysaccharides using a combination of ruthenium and an oxide. SOLUTION: In a process for preparing carboxy polysaccharides by oxidizing polysaccharides using a combination of a ruthenium compound and an oxidizing agent, (1) after the reaction is over, a mixed solution is added with an oxidizing agent to bring ruthenium to a highly oxidized state, (2) ruthenium is extracted with a water-insoluble organic solvent, (3) the extracted solution is added with a reducing agent to recover ruthenium, and (4) the recovered ruthenium is reused in oxidization of polysaccharides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a carboxy polysaccharide or a salt thereof by oxidizing the polysaccharide. The carboxypolysaccharide or salt thereof obtained according to the present invention can be suitably used as a scale adhesion inhibitor, a pigment dispersant, a sizing agent, a concrete admixture, and a detergent builder.

[0002]

2. Description of the Related Art Conventionally, acrylic acid polymers or acrylic acid / maleic acid copolymers have been industrially produced as detergent builders. However, since these synthetic polycarboxylic acids have a vinyl polymer structure that is not common as a chemical structure of a natural polymer, there is a known problem that biodegradability by microorganisms is extremely low. It is expected that polycarboxylic acids produced by oxidative carboxylation of polysaccharides will help solve this problem as biodegradable builders.

Japanese Patent Application Laid-Open No. Hei 9-71601 discloses a method of carboxylating starch using a hypochlorite and a reaction pH under basic conditions in the presence of a ruthenium catalyst. Since ruthenium used here is an extremely expensive transition metal, the loss of ruthenium in the process of producing tricarboxystarch is severely limited, and its recovery and reuse are strongly desired.

In the above publication, a precipitate is formed by treating an oxidation reaction product with a reducing agent such as a sulfite,
Although it is described that the color tone of the resulting product polycarboxylic acid is improved by filtering the solution, it does not describe specific reduction of ruthenium content, recovery and reuse of the ruthenium catalyst.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a carboxy polysaccharide by oxidizing the polysaccharide, wherein the carboxy polysaccharide obtained by collecting and reusing ruthenium used in combination with an oxidizing agent is used. It is to provide an industrial production method.

[0006]

Means for Solving the Problems As a result of studying a method for solving the above problems, the present inventors have found that a reducing agent is added to an extract obtained by extraction with an organic solvent or a combination of extraction and heat treatment. As a result, they found that ruthenium can be recovered and reused, and completed the present invention.

That is, the present invention relates to a method for producing a carboxy polysaccharide by oxidizing a polysaccharide with a combination of a ruthenium compound and an oxidizing agent, wherein (1) an oxidizing agent is added to the mixed solution after the reaction to increase ruthenium. Oxidized state, (2)
Carboxy characterized by extracting ruthenium with a water-insoluble organic solvent, (3) adding a reducing agent to the extract to recover ruthenium, and (4) reusing the recovered ruthenium for oxidation of polysaccharides. The present invention relates to a method for producing a polysaccharide, and furthermore, the raffinate of the step (2) is heated at 50 ° C.
Heat at the boiling point temperature, further add an oxidizing agent to make ruthenium highly oxidized, extract ruthenium with an organic solvent insoluble in water, add a reducing agent to the extract to recover ruthenium,
The present invention relates to a method for producing a carboxy polysaccharide in which recovered ruthenium is reused for oxidizing the polysaccharide.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polysaccharides used in the present invention are α-linked polysaccharides such as starch, amylose, amylopectin, pectin, protopectin and pectic acid, and β-linked polysaccharides such as cellulose. Starch is preferred because of the ease of reaction. Examples of the starch include corn starch, potato starch, tapioca starch, wheat starch, sweet potato starch, rice starch, and the like. Water-soluble starch obtained by using these as a raw material and having a reduced molecular weight can also be used. Here, these raw materials are used in a concentration of 0.1 to 80% by weight, preferably 1 to 50% by weight in the reaction solution.

The carboxypolysaccharide of the present invention is converted into a carboxyl group or a salt thereof by oxidizing or hydrolyzing the primary alcohol or ester at the C6 position of the monosaccharide pyranose ring constituting the polysaccharide at an average of 10 mol% or more. The C2 and C3 positions of the pyranose ring are cleaved and C2 and C3
A tricarboxy polysaccharide having an average molecular weight of 1,000 to 100,000 and having a structure in which the secondary alcohol is converted to a carboxyl group or a salt thereof oxidized by 10 mol% or more.

[0010] The oxidation of the present invention is carried out by a combination of a ruthenium compound and an oxidizing agent. The ruthenium compound includes a ruthenium compound in a high oxidation state. This ruthenium compound in a highly oxidized state can be generated by a ruthenium compound and an oxidizing agent. The ruthenium compound used in the present invention includes ruthenium metal; ruthenium oxide such as ruthenium dioxide and ruthenium tetroxide;
Ruthenates such as sodium ruthenate; ruthenium halides such as ruthenium chloride and ruthenium bromide; ruthenium nitrate; ruthenium sulfate; ruthenium carboxylate such as ruthenium acetate; ammonium hexachlororuthenate, potassium hexachlororuthenate;
Potassium pentachloroaquaruthenate, ammonium pentachloroaquaruthenate, potassium pentachloronitrosylruthenate, hexaammineruthenium chloride, hexaammineruthenium bromide, hexaammineruthenium iodide, nitrosylpentaammineruthenium chloride, hydroxonitrosyltetraamineruthenium nitrate And ruthenium complexes such as ruthenium ethylenediaminetetraacetate and ruthenium dodecacarbonium. The amount of these ruthenium compounds used is
0.0000 per mole of monosaccharide unit constituting polysaccharide raw material
1 to 1.0 times mol, preferably 0.0001 to 0.1
The amount of catalyst is in the range of twice the molar amount.

The oxidizing agent to be combined with the ruthenium compound in the reaction of the present invention and the oxidizing agent added to the reaction solution after oxidation include halogen, halogen acid and salts thereof,
At least one selected from the group consisting of oxygen, peracid, hydrogen peroxide, persulfuric acid and salts thereof, and ferricyanide salts is used. Specifically, halogen molecules such as chlorine and bromine; halogen oxides such as dichlorine dichloride, chlorine dioxide, dibromobromide, and bromine dioxide; perhalic acids such as periodic acid and perchloric acid and salts thereof; bromate Halogen acids and salts thereof, such as bromic acid and bromic acid; halogen acids and salts thereof, such as bromic acid and chlorite; hypohalous acids and salts thereof, such as hypobromous acid and hypochlorous acid; oxygen, formic acid , Peracetic acid,
Peracids such as perbenzoic acid; hydroperoxides such as cumene hydroperoxide and benzyl hydroperoxide;
peroxides such as tert-butylbenzyl oxide and dibenzoyl oxide; persulfuric acid and salts thereof such as peroxydisulfuric acid; caloic acid; potassium ferricyanide;
And ferricyanide salts such as sodium ferricyanide. Among these oxidizing agents, water-soluble halogen acids and salts thereof are preferred. The amount of these oxidizing agents used is in the range of 1.0 to 10 moles, preferably 1.5 to 8 moles, per mole of the raw material in the oxidation reaction.

As the reaction solvent of the present invention, an aqueous solvent or a mixed solvent of water and a solvent stable to an oxidizing agent is usually used. Specific examples of a reaction solvent stable to an oxidizing agent include organic acids such as acetic acid; halogenated carbons such as carbon tetrachloride, chloroform and dichloromethane; methane-based saturated hydrocarbons such as pentane and hexane; and paraffin-based hydrocarbons such as cyclohexane. Is mentioned. Among these solvents, organic acids, halogenated hydrocarbons, and paraffinic saturated hydrocarbons are preferred. When the mixed solvent becomes non-uniform with water, the reaction rate can be increased by sufficiently stirring.

In the reaction of the present invention, the oxidizing agent is gradually added with stirring to a polysaccharide, ruthenium and a mixture of a water solvent or a mixed solvent of water and a solvent stable to the oxidizing agent to convert ruthenium in a highly oxidized state. While generating, temperature 0-100
The reaction is carried out at a temperature of 1 to 13C. In the reaction mixture, in addition to the generated carboxy polysaccharide, a ruthenium compound, a solvent,
Includes trace amounts of unreacted raw materials.

In the present invention, ruthenium is separated by a combination of extraction with an organic solvent and reduction treatment.
Specifically, the solution after completion of the reaction is 1) a step of adding ruthenium to a highly oxidized state by adding an oxidizing agent, 2) an extraction step of extracting ruthenium in a highly oxidized state with an organic solvent insoluble in water, and 3) extraction. It comprises a step of adding a reducing agent to ruthenium to form ruthenium oxide in a low oxidation state, and the obtained ruthenium oxide is reused for oxidizing the polysaccharide. The above steps will be specifically described.

First step In this step, prior to the extraction step of the second step, near the end of the reaction, an oxidizing agent is further added to convert as many ruthenium species as possible into ruthenium tetroxide in a highly oxidized state. This is a process for improving efficiency. The kind of the oxidizing agent used here may be the same as or different from the oxidizing agent used in the reaction. There is no particular limitation, but the use of the same kind of oxidizing agent is preferable in consideration of the treatment after the reaction. In addition, the amount used is 1.0 to 1.0% based on the amount of ruthenium contained.
It is in the range of 10-fold mol, preferably in the range of 1.2- to 5-fold mol. The pH at the time of adding the oxidizing agent after the reaction
Can be used as it is at the end of the reaction, but from the viewpoint of the stability of the oxidizing agent to be added and the generated ruthenium tetroxide, the pH is preferably adjusted to 2 to 13, more preferably 4 to 10, and then the oxidizing agent is adjusted. Is desirably added.

Second step This is a step of extracting ruthenium tetroxide generated in the first step with an organic solvent. The extraction is performed by mixing the aqueous solution of the first step and the organic solvent and then separating the mixture. For the mixing and separation of the aqueous solution and the organic solvent, a known extraction device such as a single-stage or multi-stage mixer settler or an extraction tower can be used. The extraction solvent must be a solvent that is stable to the generated ruthenium tetroxide and insoluble in water. Specifically, halogenated hydrocarbons such as fluorinated carbon such as perfluoroheptane, perfluoropentane and perfluoromethylcyclohexane, chlorinated carbon such as carbon tetrachloride, chloroform and dichloromethane; methane-based saturated such as pentane and hexane hydrocarbon;
Examples include paraffinic hydrocarbons such as cyclohexane and liquid paraffin. Of these solvents, halogenated hydrocarbons and paraffinic saturated hydrocarbons are preferred. These extraction solvents can be used for both purified and unrefined products. In addition, the extraction temperature, the higher the temperature, the faster the extraction speed, but from the physical properties such as the volatility of ruthenium tetroxide,
0 to 100 ° C. at normal pressure, preferably 10 to 80 ° C.
° C.

Third Step In this step, the ruthenium tetroxide extracted in the organic solvent is reduced with a reducing agent to form a precipitate of ruthenium oxide in a low oxidation state, separated and recovered. As reducing agents, sulfites,
Hydrazine and its salts, hydroxylamine and its salts, hydrogen peroxide, quinones, methanol, ethanol,
General reducing agents such as lower alcohols such as 2-propanol can be used. The amount of the reducing agent to be used is 1 to 100 times, preferably 1 to 50 times, the molar amount of the ruthenium-containing mole.

For separation of the ruthenium precipitated in the organic solvent, filtration or a centrifugal separator such as a sedimentation separator or a liquid cyclone can be used, and it can be recovered as a solid or a slurry. The obtained solid or slurry can be further recovered as a dried product by drying under reduced pressure using an evaporator or the like. Alternatively, a dried product may be obtained by directly drying under reduced pressure from the state of precipitation in an organic solvent. The obtained slurry, solid and dried ruthenium can be reused as it is or after being dispersed in a solvent such as water for the next oxidation of the polysaccharide.

Further, in order to collect and reuse the ruthenium present in the raffinate after the extraction in the second step, 1) a step of heat-treating the raffinate, and 2) the ruthenium is added by adding an oxidizing agent. 3) a step of extracting ruthenium in a high oxidation state with an organic solvent insoluble in water; 4) a step of adding a reducing agent to the extracted ruthenium to form a ruthenium oxide in a low oxidation state. The resulting ruthenium oxide is reused for the oxidation of polysaccharides. The above steps will be specifically described.

Heating Step This step is a step for subjecting the solution after the extraction separation to a heat treatment to facilitate removal of ruthenium remaining in the solution.
The heat treatment temperature is 50 ° C. to the boiling point at normal pressure. If the temperature is low, it takes a long time to increase the ruthenium removal rate, and if the temperature is too high, the carboxypolysaccharide is decomposed. The pH of the reaction solution to be subjected to the heat treatment is usually adjusted to pH 7 to 13, preferably 8 to 10, since it is easily decomposed on the acidic side. The heat treatment time varies depending on conditions and the like, but is from 5 minutes to 24 hours, preferably 3 minutes.
0 minutes to 10 hours. In performing the heat treatment, the temperature, the treatment time, and the like can be changed by changing the pressure. The heating method is not particularly limited, and a normal heating method such as heating with a heat exchanger using steam or hot water, heater heating, infrared heating, or high-frequency heating can be used.

The steps after the heating step are the first to third steps.
A process similar to the process is performed. In the present invention, the heat treatment, the oxidizing agent addition treatment, and the solvent extraction treatment may be further repeated. After the heat treatment of the mixed solution after the reaction,
The third to third steps may be performed.

[0022]

The present invention will be described below in detail with reference to examples.
The ruthenium concentration in the product tricarboxy starch is I
The measurement was performed using a CP (inductively coupled plasma emission spectrometry, 1200 VR analyzer manufactured by Seiko Instruments Inc.). The sodium chloride content is determined by XRF (X-ray fluorescence analysis,
It was measured using Rigaku Denki RIX3100).

Example 1 (First reaction) 1 equipped with stirrer, thermometer and pump
50 ml of water, 15 g of corn starch (manufactured by Shikishima Starch) and 0.70 g of ruthenium chloride (ruthenium content 43%, ruthenium 2.8 mmol) were placed in an L-volume round bottom Pyrex flask, and stirred in a cold water bath.
Cooled to 0 ° C. To this mixture, an aqueous solution of 12.9% by weight of sodium hypochlorite in a molar amount of 5 times the amount of starch was added over 3 hours. The pH of the reaction solution was controlled at 9.0 with a 2N aqueous sodium hydroxide solution.

After completion of the reaction, 12.9 g of an aqueous solution of 12.9% by weight of sodium hypochlorite and 130 g of n-heptane were added to 452 g of the reaction solution, and the mixture was shaken at room temperature (1 minute), centrifuged (2,000 pm, After 1 minute) and standing (1 minute), the n-heptane layer in which ruthenium tetroxide was dissolved and extracted was separated from the aqueous solution. This extraction operation was performed four times at room temperature. The extract was treated with 1.5 g of 2-propanol, and dried under reduced pressure with a rotary evaporator to obtain ruthenium oxide. To the raffinate, twice the volume of methanol was added to form a white precipitate. The precipitate was separated by filtration, dissolved in water, and precipitated by adding methanol.
C. for 5 hours to obtain 23.9 g of product A.

When the product A was analyzed by ¹³ C-NMR, IR and XRF, it was found that the primary alcohol at the C6-position of the glucopyranose unit constituting the starting corn starch was oxidized to 100 mol% carboxyl group. The C2-C3 position is cleaved and the secondary alcohol at C2 and C3 positions is
99.5% (yield 94.4%) of tricarboxystarch sodium salt in which
%) And 0.5% sodium chloride. When the ruthenium concentration of the product A was measured by ICP, it was 126 ppm.
(Removal rate 99.2%).

(Second reaction / reuse of ruthenium) Ruthenium oxide obtained by drying under reduced pressure was dispersed in 45 g of water.
Reaction, extraction, and ruthenium separation were performed in the same manner as in the first reaction. Further, as in the first reaction, the raffinate was added with methanol, precipitated, separated by filtration, redissolved and dried to obtain a product B2.
3.5 g were obtained. The product B was analyzed by ¹³ C-NMR, IR, XR
As a result of analysis by F, 99.4% (yield 92.7%) of the same sodium salt of tricarboxystarch as the product A obtained in the first reaction and 0.6% of sodium chloride were obtained.
%Met.

Example 2 (First reaction) Instead of ruthenium chloride, 0.600 g of ruthenium oxide (ruthenium content 47% by weight, 2.
The reaction was carried out in the same manner as in Example 1 except that 8 mmol) was used. After the reaction, the mixture was extracted four times with n-heptane in the same manner as in Example 1, then put into a 1 L round bottom reaction Pyrex flask equipped with a thermometer and a cooling tube, and placed in an oil bath at 98 ° C.
The mixture was heated under reflux for an hour. After cooling, heat-treated solution
After extraction with heptane four times, precipitation and drying were carried out in the same manner as in Example 1 to obtain 23.6 g of a product C.

The product was subjected to ¹³ C-NMR, IR, XRF
99.5% of the same sodium salt of tricarboxystarch as the product A (93.2% yield).
%) And 0.5% sodium chloride. The ruthenium concentration in the product C was measured by ICP and found to be 5 ppm (removal rate 99.96%). The n-heptane extract is
After adding 2 g of 30% hydrogen peroxide in the same manner as in Example 1, it was dried under reduced pressure with a rotary evaporator to obtain ruthenium oxide.

(Second reaction / reuse of ruthenium) The ruthenium oxide obtained in the first reaction was dispersed in 45 g of water, and the reaction, extraction and ruthenium separation were carried out in the same manner as in the first reaction. Further, the raffinate was subjected to addition of methanol, precipitation, filtration, re-dissolution and drying in the same manner as in the first reaction to obtain 23.8 g of a product D. The product D was analyzed by ¹³ C-NMR, IR,
When analyzed by XRF, the same tricarboxystarch sodium salt as the product C obtained in the first reaction was 99.4% (yield 93.9%) and sodium chloride 0.6%.

Example 3 A reaction and a post-treatment were carried out in the same manner as in Example 1 except that 10% by weight of hydrazine hydrochloride was used instead of 2-propanol, and 23.3 g of a product E of the first reaction was formed. 23.5 g of product F were obtained. Products E and F were analyzed by ¹³ C-NMR,
When analyzed by IR and XRF, the same tricarboxystarch sodium salt as in Example 1 was found to be 9
9.6% (yield 92.1%), 99.5% (yield 92.0%).
8%) and 0.4% and 0.5% of sodium chloride.

Example 4 A reaction G and a post-treatment were carried out in exactly the same manner as in Example 1 except that 10% by weight of hydroxyamine hydrochloride was used instead of 2-propanol, and a product G of the first reaction and a product of the second reaction were used. H
Was obtained in an amount of 23.4 g. Products G and H were converted to ¹³ C-NM
Analyzed by R, IR, XRF, the same sodium salt of tricarboxystarch as in Example 1 99.3%
(Yield 92.2%), 99.5% (yield 92.4%), and sodium chloride 0.7% and 0.5%.

Example 5 The first reaction was carried out in the same manner as in Example 1 to obtain the product I in the form of 23.
5 g were obtained. After the reaction, 1.5 g of 2-propanol was added to the extract.
After stirring and standing, 10 g of a ruthenium black slurry was obtained by decantation. 50 ml of water and corn starch were added to the obtained ruthenium slurry, and the reaction and post-treatment were carried out in the same manner as in the first reaction to obtain 23.3 g of a product J. Products I and J were analyzed by ¹³ C-NMR, I
When analyzed by R and XRF, the same sodium salt of tricarboxystarch as that of the product A was found to be 99.0% (94.0% yield), 99.5% (93.0% yield), and 1.0% sodium chloride. 0% and 0.5%.

[0033]

According to the present invention, the ruthenium used for oxidizing the polysaccharide can be recovered and effectively reused in the reaction.

Claims (4)

[Claims] 1. A method for producing a carboxy polysaccharide by oxidizing a polysaccharide with a combination of a ruthenium compound and an oxidizing agent, wherein (1) an oxidizing agent is added to the mixed solution after the reaction to make ruthenium highly oxidized; (2) Ruthenium is extracted with an organic solvent insoluble in water, (3) Ruthenium is recovered by adding a reducing agent to the extract, and (4) Recovered ruthenium is reused for oxidation of polysaccharides. A method for producing a carboxy polysaccharide. 2. The extraction residue in the step (2) is 5
Heated at 0 ° C. to the boiling point, further added an oxidizing agent to make ruthenium highly oxidized, extracted ruthenium with an organic solvent insoluble in water, added a reducing agent to the extract to recover ruthenium, and recovered The production method according to claim 1, wherein ruthenium is reused for oxidizing the polysaccharide. 3. The method according to claim 1, wherein the reducing agent is at least one selected from sulfites, hydrazine and its salts, hydroxylamine and its salts, hydrogen peroxide, quinones, methanol, ethanol, and 2-propanol.
The manufacturing method as described. 4. The method according to claim 1, wherein the ruthenium recovered in the step (4) is a dried product or a slurry.