JP2000159804A - Preparation of carboxypolysaccharide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering and reusing ruthenium in preparing a carboxypolysaccharide by a combination of ruthenium and an oxidizing agent. SOLUTION: A method for oxidizing a polysaccharide by a combination of a ruthenium compound and an oxidizing agent to prepare a carboxypolysaccharide which comprises (1) adding an oxidizing agent to a mixed solution after reaction to render ruthenium in a higher oxidation state, (2) extracting the ruthenium with a water-insoluble organic solvent, (3) extracting the ruthenium from the organic solvent with an alkaline solution, and (4) reusing the recovered ruthenium in the oxidation of a polysaccharide.

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]

Acrylic acid polymers or acrylic acid / maleic acid copolymers are manufactured industrially 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. Polycarboxylic acid produced by oxidative carboxylation of polysaccharide,
It is expected that this problem will be solved as a biodegradable builder.

[0003] Japanese Patent Application Laid-Open No. Hei 9-71601 discloses a method of carboxylating starch using hypochlorite in the presence of a ruthenium catalyst. Here, since ruthenium is a very expensive transition metal, the loss of ruthenium in the carboxypolysaccharide production process is severely restricted, and its recovery and reuse are strongly desired.

In the above publication, it is described that a precipitate is formed by treating a reaction solution with a reducing agent such as a sulfite and the color tone of a product polycarboxylic acid obtained by filtering the precipitate is improved. However, there is no specific description of ruthenium recovery and reuse.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a carboxy polysaccharide by oxidizing a polysaccharide, wherein a transition metal used in combination with an oxidizing agent is simply and effectively recovered from a reaction mixture solution. And a method for industrially producing a carboxypolysaccharide by reusing it.

[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 ruthenium compound in an organic solvent can be recovered by extracting it with an alkaline solution and reused. The invention has been completed.

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. (1) An oxidizing agent is added to the mixed solution after the reaction to highly oxidize ruthenium. (2) extracting ruthenium with an organic solvent insoluble in water, (3) extracting ruthenium from the organic solvent with an alkaline solution, and (4) reusing the ruthenium in the recovered alkaline solution for the oxidation of polysaccharides. And a method for producing a carboxy 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, pectic acid and β-linked polysaccharides such as cellulose. Starch is preferred because of the ease of reaction and availability. As starch,
Examples thereof include corn starch, potato starch, tapioca starch, wheat starch, sweet potato starch, rice starch, and the like, and low molecular weight water-soluble starch can also be used as a raw material. Here, these raw materials are 0.1 to 80% by weight, preferably 1 to 80% by weight in the reaction solution.
Used in the range of 50% by weight.

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
Is a tricarboxypolysaccharide having an average molecular weight of 1,000 to 100,000 and having a structure in which a 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. This highly oxidized ruthenium compound can be formed with a ruthenium compound and an oxidizing agent. The ruthenium compounds used in the present invention include ruthenium metal; ruthenium oxides such as ruthenium dioxide and ruthenium tetroxide; ruthenates such as sodium ruthenate; ruthenium halides such as ruthenium chloride; ruthenium nitrate; ruthenium sulfate; ruthenium acetate Ruthenium carboxylate such as ammonium hexachlororuthenate, potassium hexachlororuthenate, ammonium pentachloroaquaruthenate, potassium pentachloroaquaruthenate, hexaammineruthenium chloride, hexaammineruthenium bromide, hexaammineruthenium iodide, nitrosylpentaammine Ruthenium chloride, hydroxonitrosyltetraammineruthenium nitrate, ruthenium ethylenediaminetetraacetate, ruthenium Ruthenium complexes such as beam dodecacarbonyl and the like. The amount of the ruthenium compound used is 0.00001 to 1.0 times mol, preferably 0.000 mol, per mol of the structural unit of the raw material polysaccharide.
The catalyst amount is in the range of 1 to 0.1 times mol.

The oxidizing agent used in combination with the ruthenium compound in the reaction of the present invention and the oxidizing agent converted into the oxidized reaction solution 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 monoxide, chlorine dioxide and dibromine monoxide; perhalic acids such as periodic acid and perchloric acid and salts thereof; bromic acid and chloric acid Halogen acid and salts thereof, such as bromic acid and chlorite; hypohalous acid and salts thereof, such as hypobromous acid and hypochlorous acid; oxygen, formic acid, peracetic acid , Peroxy acids such as perbenzoic acid; hydroperoxides such as cumene hydroperoxide and benzyl hydroperoxide; peroxides such as tert-butylbenzyl oxide and dibenzoyl; persulfuric acid such as peroxydisulfuric acid and its salts; caloic acid; potassium ferricyanide; And ferricyanide salts such as sodium iodide. Among these oxidizing agents, water-soluble halogen acids and salts thereof are preferred. The amount of these oxidizing agents to be used is, in the oxidation reaction, in the range of 1.0 to 10 moles per mole of the raw material, preferably
It is 1.5 to 8 times mol.

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 the reaction solvent stable to the 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; paraffin-based hydrocarbons such as cyclohexane. Is mentioned. Among these solvents, organic acids, halogenated hydrocarbons, and paraffinic saturated hydrocarbons are preferred. In the case where the mixed solvent becomes non-uniform with water, the reaction rate can be increased by sufficiently performing stirring.

In the reaction of the present invention, the oxidizing agent is gradually added to a mixture of a polysaccharide, ruthenium and a water solvent or a mixed solvent of water and a solvent stable to the oxidizing agent while stirring, whereby ruthenium in a highly oxidized state is converted. While generating, temperature 0-100
The reaction is carried out at a temperature of 1 to 13C. The reaction mixture contains the generated carboxypolysaccharide, a ruthenium compound, a solvent, and the like.

The recovery of ruthenium in the present invention is based on a combination of extraction with an organic solvent and back extraction with an alkaline solution. Specifically, the solution after the reaction is completed is 1) a step of adding ruthenium to a highly oxidized state by adding an oxidizing agent, 2) a step of extracting ruthenium in a highly oxidized state with an organic solvent insoluble in water, 3) extracting the extracted ruthenium. It consists of a step of extraction with an alkaline solution, and the resulting alkaline aqueous solution of ruthenium is reused for the oxidation of polysaccharides. 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 type 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 it is preferable to use the same oxidizing agent in consideration of the treatment after the reaction. The amount used is in the range of 1.0 to 10 moles, preferably 1.2 to 5 moles, relative to the amount of ruthenium contained. The pH at the time of adding the oxidizing agent after the reaction can be used as it is at pH 1 to 13 at the end of the reaction. However, from the viewpoint of the stability of the oxidizing agent to be added and the generated ruthenium tetroxide, the pH is preferably 2 to 13. It is desirable to add the oxidizing agent after adjusting the pH to more preferably 4 to 10.

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. It is necessary that the extraction solvent be a solvent that is stable to the generated ruthenium tetroxide and insoluble in water. Specifically, fluorinated carbon such as perfluoroheptane, perfluoropentane, and perfluoromethylcyclohexane; halogenated hydrocarbons such as chlorinated carbon such as carbon tetrachloride, chloroform, and dichloromethane; and methane-based saturated solvents such as pentane and hexane. hydrocarbon;
Paraffinic hydrocarbons such as cyclohexane and liquid paraffin are preferred. These extraction solvents can be used for both purified and unpurified products. In addition, the extraction temperature is higher at a higher temperature, but the extraction speed is higher, but from the physical properties such as the volatility of ruthenium tetroxide, it is usually 0 to 100 ° C. at normal pressure,
Preferably, it is 10 to 80 ° C.

Third Step In this step, ruthenium tetroxide extracted in the organic solvent is back-extracted with an alkaline solution and recovered. The recovered ruthenium solution is reused as it is for the reaction of the polysaccharide. Here, the aqueous solution used for the extraction is not particularly limited as long as it is an aqueous solution having a pH of 9 or more, preferably pH 10 or more, and includes sodium hydroxide, potassium hydroxide, lithium hydroxide, aqueous ammonia, alkylamine and the like. General alkaline solutions such as sodium hydroxide and potassium hydroxide are industrially advantageous and preferred. The extraction temperature is higher at a higher temperature, but the extraction speed is higher. However, the extraction temperature is usually 0 to 100 ° C, preferably 10 to 80 ° C at normal pressure, due to the physical properties such as volatility of ruthenium tetroxide. A known extraction device such as a single-stage or multi-stage mixer settler or extraction tower can be used for mixing and separating the organic solvent and the alkali solution.

Further, in order to recover and reuse the ruthenium remaining in the raffinate after the extraction in the second step, a step of heating the raffinate is performed, and then the first step to the third step is repeated.
Perform the process. The obtained aqueous solution of the ruthenium compound is reused for oxidizing the polysaccharide. The above-mentioned heat treatment step will be specifically described.

Heating Step This step is a step for subjecting the solution after extraction separation to 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 carboxyl polysaccharide is decomposed. The pH of the reaction solution to be heated is
Since it is easily decomposed on the acidic side, the pH is usually adjusted to 7 to 13, preferably 8 to 10. 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. There is no particular limitation on the heating method, heating by heat exchange with steam or hot water, heater heating, infrared heating,
Normal heating methods such as 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 and the first to third steps may be further repeated. Alternatively, the first to third steps may be performed after the mixed solution after the reaction is subjected to heat treatment.

According to the above method, it is possible to recover a ruthenium compound from an organic solvent as an aqueous solution without using a reducing agent, and it is possible to industrially produce a tricarboxypolysaccharide by recovering and reusing the ruthenium compound. Become.

[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, 14% by weight was added to 453 g of the reaction solution.
13 g of an aqueous solution of sodium hypochlorite and 130 g of n-heptane were added, and the mixture was shaken, centrifuged, and allowed to stand at room temperature, and then the n-heptane phase was separated from the aqueous solution. This operation was performed four times at room temperature. The extract contains 2N-NaOH 20 g
(PH 13 or more) and stirred at room temperature. A clear n-heptane phase and a reddish-brown alkaline aqueous solution phase were obtained. Two times the volume of methanol was added to the raffinate to produce a white precipitate. The precipitate was separated by filtration, further dissolved in water, and precipitated by adding methanol, followed by vacuum drying at 60 ° C. for 5 hours to obtain 23.9 g of a product A.

The product A was analyzed by ¹³ C-NMR, IR and XRF. As a result, it was found that the primary alcohol at the C6-position of the glucopyranose unit constituting the raw corn starch was oxidized to 100 mol% carboxyl group and at the same time C2- 99.1% (92.3% yield) of tricarboxystarch sodium salt in which the C3-position is cleaved and the C2 and C3-position secondary alcohols are oxidized to 75 mol% carboxyl groups.
%) And 0.9% sodium chloride. When the ruthenium concentration of the product A was measured by ICP, it was 140 ppm.
(Removal rate 99.1%).

(Second reaction / reuse of ruthenium) Corn starch was added to an aqueous solution of a ruthenium compound obtained by alkali extraction, and the reaction, extraction, and separation of ruthenium were performed in the same manner as in the first reaction. In addition, as in the first reaction, the raffinate was added with methanol, precipitated,
Filtration, re-dissolution and drying gave 23.3 g of product B. When the product B was analyzed by ¹³ C-NMR, IR and XRF, the same sodium salt of tricarboxystarch as the product A obtained in the first reaction was 99.3% (yield 9).
3.1%) and 0.7% sodium chloride.

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, and the raffinate (reaction liquid) was placed in a 1-L round bottom Pyrex equipped with a thermometer and a cooling pipe, and was then placed in an oil bath for 98 hours.
The mixture was refluxed for 1 hour. After cooling, the heat-treated solution was extracted four times with n-heptane, and then precipitated and dried in the same manner as in Example 1 to obtain a product C. Extract contains 2N-N
20 g of aOH was added and the mixture was stirred at room temperature. As in Example 1, a transparent n-heptane phase and a reddish-brown alkaline aqueous solution phase were obtained.

When the product C was analyzed by ¹³ C-NMR, IR and XRF, the same tricarboxystarch sodium salt as that of the product A was obtained at 99.6% (yield 93.2%).
%) And 0.4% of sodium chloride. The ruthenium concentration in the product C was measured by ICP and found to be 5 ppm (removal rate 99.96%).

(Second reaction / reuse of ruthenium) Al
Tow is added to the aqueous solution of the ruthenium compound obtained by potassium extraction.
Add sorghum starch and react similarly to the first reaction.
The reaction, extraction, and separation of ruthenium were performed. Also, the raffinate
Performed heat treatment and extraction in the same manner as in the first reaction.
After addition of methanol, precipitation, filtration, re-dissolution and drying
23.4 g of product D were obtained. Product D ¹³C-NMR,
When analyzed by IR and XRF, the first reaction
The same tricarboxy starch nato as the obtained product C
99.4% (92.6% yield) of lithium salt and sodium chloride
Was 0.6%. Ruthenium concentration in product D
4 ppm (removal rate 99.96) as measured by ICP.
%)Met.

[0030]

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

Claims (2)

[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) extracting ruthenium with an organic solvent insoluble in water, (3) extracting ruthenium from the organic solvent with an alkaline solution, and (4) reusing the recovered ruthenium for oxidation of polysaccharides. A method for producing a polysaccharide. 2. The method according to claim 1, wherein the alkaline solution used in the step (3) is p
2. The method according to claim 1, wherein the temperature is H9 or higher.