JPH10195101A - Method for producing polycarboxylic acid or salt thereof from polysaccharide having anhydrous glucose as a constituent unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polycarboxylic acid having a high carboxyl group content or a salt thereof from a polysaccharide having anhydrous glucose as a constituent unit without mixing of by-products. SOLUTION: When producing a polycarboxylic acid or a salt thereof by oxidizing a polysaccharide, a manganese oxide or a salt thereof is used as an oxidizing agent, and the acid type polycarboxylic acid is subjected to neutralization titration. The alkali required for this is 43% per g of the polycarboxylic acid in terms of sodium hydroxide.
A method for producing a polycarboxylic acid or a salt thereof of 5 mg or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polycarboxylic acid or a salt thereof from a polysaccharide having anhydrous glucose as a constituent unit.

[0002]

2. Description of the Related Art Polyacrylic acid and copolymers of acrylic acid and maleic acid are used as water-soluble polycarboxylic acids or salts thereof as dispersants, chelating agents or flocculants. When these carboxylic acids are used as a chelating agent, the effect is affected by the content and molecular weight of the carboxyl group, and the larger the content and the larger the molecular weight of the carboxyl group, the better the effect is exhibited. Is generally known. However,
These polycarboxylic acids obtained by polymerizing a monomer having a vinyl group, such as polyacrylic acid or a copolymer of acrylic acid and maleic acid, are extremely difficult to biodegrade by microorganisms. It is also well known to have points. Therefore, there has been an attempt to obtain a polycarboxylic acid or a salt thereof, which is expected to be biodegradable, by oxidizing a polysaccharide which is a natural polymer, aiming at a chelating agent useful for a detergent builder or the like. ing.

[0003] Japanese Patent Publication No. Sho 49-1281,
JP-A-226502 discloses that a polycarboxylic acid can be obtained from various polysaccharides by a two-step oxidation method using periodic acid and chlorite or a one-step oxidation method using hypochlorite. However, the content of carboxyl groups in the polycarboxylic acids obtained by this disclosed method is on average less than 2 per monosaccharide. Further, in the two-step method, the aldehyde form must be once isolated and further oxidized to a carboxyl form, which is industrially disadvantageous and harmful when performing the second step reaction using chlorous acid. When a large amount of gas is generated and synthesis is attempted in large quantities, there are many disadvantages. In addition, in the one-step method, a large amount of sodium chloride is by-produced in the product of the hypochlorite, and removal of this is costly from an industrial point of view.

Japanese Patent Laid-Open Publication No. 62-247837 discloses that P
A method of oxidizing a polysaccharide to obtain a polycarboxylic acid by using a metal catalyst such as d and a promoter such as Bi in combination has been disclosed. This method oxidizes the reducing end of the polysaccharide. And the carboxyl group content is less than 2 per monosaccharide.

Japanese Patent Application Laid-Open No. 4-175301 discloses a method for oxidizing a polysaccharide in the presence of hypobromite or hypoiodite, but this method also involves a large amount of by-products. It is mixed and is industrially disadvantageous.

[0006] JP-A-4-233901, JP-T-Hei-5
JP-A-5050685 discloses a method in which an enzyme hydrolyzate of starch or dextrin or inulin is used as a raw material, but the oxidation reaction is also carried out using periodate or hypochlorite. However, as already mentioned, industrial realization is considered to be a very difficult method.

On the other hand, in a method for producing a polycarboxylic acid or a salt thereof obtained by oxidizing a polysaccharide having anhydrous glucose as a constitutional unit, a manganese oxide or a salt thereof is used as an oxidizing agent and the content of a carboxyl group is reduced. There is no known method for producing more than two polycarboxylic acids or their salts per glucose unit.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a method for producing a polycarboxylic acid or a salt thereof having a high carboxyl group content from a polysaccharide having anhydrous glucose as a constitutional unit without mixing of by-products. Is the task.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention.

According to the present invention, a polysaccharide is oxidized using a specific oxidizing agent, so that no by-products are mixed in one step.
This is based on the finding that a polycarboxylic acid or a salt thereof having a high carboxyl group content can be obtained without generating harmful substances. That is, the present invention is characterized in that when producing a polycarboxylic acid or a salt thereof by oxidizing a polysaccharide, a manganese oxide or a salt thereof is used as an oxidizing agent. The alkali required for titration is calculated as sodium hydroxide,
The present invention provides a method for producing a polycarboxylic acid or a salt thereof in an amount of 435 mg or more per 1 g of the polycarboxylic acid.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The oxidizing agent used in the present invention is selected from manganese oxides and salts thereof, and is preferably a manganate or a permanganate. The amount of these oxidizing agents depends on the content of carboxyl groups in the polycarboxylic acid to be finally obtained,
It is usually 3-fold to 12-fold mol, preferably 3-fold to 10-fold mol, per monosaccharide unit of the polysaccharide. The reaction is carried out by adding these oxidizing agents to the aqueous dispersion of the polysaccharide. The method of adding the oxidizing agents may be added as a powder at once or in divided portions, or the aqueous solution may be added dropwise. The dropping speed is not particularly limited. The reaction time is not particularly limited, but is usually 2 hours to 24 hours. Although the reaction temperature is not particularly limited, it is usually 5 ° C to 7 ° C.
0 ° C.

The pH of the solution at the time of the reaction is generally kept in the range of 3 to 14, preferably 7 to 13. The pH can be adjusted using a hydroxide of an alkali metal such as sodium hydroxide, potassium hydroxide, or lithium hydroxide or an amine such as ammonia, an alkylamine, or an alkanolamine. Sodium or potassium hydroxide is used.

By reacting the manganese oxide or its salt with the polysaccharide in this way, the hydroxyl group of the polysaccharide is efficiently oxidized, and the polycarboxylic acid or its salt can be easily produced. The product by-produced from the oxidizing agent in this reaction is manganese dioxide, which can be easily removed by filtration without toxicity and can be converted to manganate or permanganate by a known method. It can be reused and is industrially advantageous.

In the polycarboxylic acid or its salt produced according to the present invention, examples of the salt include alkali metals such as Na, K and Li, and amines such as ammonia, alkylamine and alkanolamine. Na or K is preferable for ease. Further, only a part of the carboxyl group may be converted to a salt. In the present invention, as a method for determining the content of the carboxyl group, a neutralization titration method is used as described later. When it is necessary to obtain an acid-type polycarboxylic acid at the time of the neutralization titration, it is carried out by a method of treating with a cation exchange resin described later.

The polysaccharide used in the present invention is not particularly limited, and may be starch, dextrin, cellulose, mannan, inulin or a hydrolyzate thereof, or amylose, amylopectin or konjac obtained by fractionating starch. And these may be used in a mixture of two or more. And the origin of these polysaccharides is not particularly limited, for example, in the case of starch, corn starch, wheat starch, rice starch, potato starch, sweet potato starch, tapioca starch, etc. Cellulose obtained from hardwood, cotton and the like is used. Among these polysaccharides, use of starch or cellulose is preferred from the viewpoint of availability and economy, and starch is particularly preferably used.

Under the above reaction conditions, since the hydroxyl group of the polysaccharide is efficiently oxidized, sodium hydroxide required for neutralizing and titrating the target acid-form polycarboxylic acid is as follows:
It is possible to obtain a polycarboxylic acid or a salt thereof in an amount of 435 mg or more per 1 g of the polycarboxylic acid. Since this polycarboxylic acid or a salt thereof has a high content of carboxyl groups, it has a high chelating power against polyvalent cations such as Ca and Mg, and is a builder or an anti-scum agent for clothing detergents or automatic dishwasher detergents. And the like.

Next, a method for measuring the carboxyl group content and Ca ion chelating ability (CEC) of the polycarboxylic acid or its salt obtained in the present invention will be described below.

[Measurement of Carboxyl Group Content] Approximately 0.2 g (absolute dry weight) of acid-type polycarboxylic acid was precisely weighed,
Weigh out into a 0 ml conical beaker, add about 50 ml of ion-exchanged water to dissolve, titrate with 1/10 normal sodium hydroxide standard solution using phenolphthalein as an indicator, and add 1 g of acid type polycarboxylic acid. The carboxyl group content is indicated as mg of sodium hydroxide required for neutralization. When it is clear that a part or all of the polycarboxylic acid whose carboxyl group content is to be measured is in the form of a salt, the polycarboxylic acid is converted into an acid-form polycarboxylic acid and taken out by the following method. That is, an aqueous solution of about 1% by weight of a polycarboxylate is prepared, and the resulting solution is passed through a column filled with a cation exchange resin (DOWEX50W-X8), and is subjected to cation exchange to be converted into an acid-type polycarboxylic acid. The cation exchange resin is used in an amount of 10 ml per 1 g of a 1 wt% aqueous solution of a polycarboxylate. The eluate is freeze-dried or dried under reduced pressure (40 ° C. or lower) to obtain an acid-type polycarboxylic acid in powder form.

[Measurement of Ca ion chelating ability (CEC)] 0.1 mol / l CaC manufactured by Orion Research
By diluting the l ₂ standard solution 100 times, CaCO ₃
, A Ca ion solution corresponding to 100 ppm was prepared. On the other hand, the polycarboxylic acid to be tested was dissolved in ion-exchanged water to prepare an aqueous solution containing exactly 1% by weight of sodium polycarboxylate to prepare a test solution. After taking 100 ml of the Ca solution and adding 2 ml of a 4 mol / l KCl solution, the pH was adjusted to 10 with 1/10 N NaOH. While stirring this aqueous solution, the initial concentration of Ca ions was measured using a Ca ion electrode. Next, 2 ml of the test solution was accurately added, the pH was adjusted to 10 again, and the Ca ion concentration was measured using a Ca ion electrode. The Ca ion concentration after the addition of the test solution was subtracted from the initial concentration of Ca ions, and this amount was calculated as the chelated Ca ions,
The amount of ions was expressed as mg of CaCO ₃ .

Hereinafter, the present invention will be described in more detail by way of examples.

[0021]

【Example】

Example 1 300 m equipped with a stirrer, an oxidizing agent dropping funnel, a sodium hydroxide aqueous solution dropping port, a pH controller, and a thermometer
5 g of corn starch and 100 g of ion-exchanged water are added to a 1-liter separable flask in an absolute dry weight.
The mixture was stirred while being cooled in a water bath at ℃. After the internal temperature reached a constant temperature, 32.6 g of potassium permanganate (6.7 times mol based on anhydrous glucose units of starch) was dissolved in 500 g of ion-exchanged water and added over 6 hours.
During this period, a 2N aqueous sodium hydroxide solution was added using a pH controller to control the pH of the system to 12. After the addition of potassium permanganate, add 2 more
After continuing stirring for an hour, unreacted potassium permanganate was reduced with sodium sulfite, and manganese dioxide as a by-product was filtered off. The filtrate was purified by performing diffusion dialysis with ion-exchanged water for 5 days, and then freeze-dried to obtain a polycarboxylate powder. About the obtained polycarboxylate,
Its carboxyl group content was 542 mg, and Ca ion chelating ability (CEC) was 315 mg / g.

Example 2 300 m equipped with a stirrer, an oxidizing agent dropping funnel, a sodium hydroxide aqueous solution dropping port, a pH controller, and a thermometer.
5 g of corn starch and 100 g of ion-exchanged water are added to a 1-liter separable flask in an absolute dry weight.
The mixture was stirred while being cooled in a water bath at ℃. After the internal temperature reached a constant temperature, 32.6 g of potassium permanganate crystals (6.7 times the molar amount of anhydrous glucose units of starch) were added all at once, and the pH was adjusted to 8.8 using a pH controller. 5
The stirring was continued while adding a 2N aqueous sodium hydroxide solution so that 6 from the addition of potassium permanganate
After an hour, unreacted potassium permanganate was reduced with sodium sulfite, and manganese dioxide as a by-product was filtered off.
The filtrate was purified by performing diffusion dialysis with ion-exchanged water for 5 days, and then freeze-dried to obtain a polycarboxylate powder. The carboxyl group content of the obtained polycarboxylate was 546 mg, and its CEC was 308 mg / g.

Comparative Example 1 In Example 1, a 12 wt% aqueous solution of sodium hypochlorite was used instead of the aqueous solution of potassium permanganate.
The same operation was performed except that g (6.7 times the mol of the anhydrous glucose unit) was used. The carboxyl group content of the obtained polycarboxylate is 96 mg, and its CEC
Was 63 mg / g.

Example 3 A polycarboxylate was obtained in the same manner as in Example 1 except that sodium permanganate was used instead of potassium permanganate. The carboxyl group content of the obtained polycarboxylate was 458 mg, and its CEC was 305 m.
g / g.

Example 4 A polycarboxylate was obtained in the same manner as in Example 1, except that cellulose powder (reagent) was used instead of corn starch. Of the resulting polycarboxylate,
The carboxyl group content is 440 mg and its CEC is 30
It was 0 mg / g.

Example 5 300 m equipped with a stirrer, an oxidizing agent dropping funnel, a sodium hydroxide aqueous solution dropping port, a pH controller, and a thermometer.
5 g of amylopectin in absolute dry weight and 100 g of ion-exchanged water were added to a l-volume separable flask, and the mixture was stirred while cooling in a 30 ° C. water bath. After the internal temperature reached a constant temperature, 48.8 g of potassium permanganate crystals (10-fold mol based on anhydrous glucose units) were added all at once, and p was added.
Stirring was continued while adding a 2N aqueous solution of sodium hydroxide so that the pH became 10 using an H controller. Six hours after the addition of potassium permanganate, unreacted potassium permanganate was reduced with sodium sulfite, and manganese dioxide as a by-product was filtered off. The filtrate was purified by performing diffusion dialysis with ion-exchanged water for 5 days, and then freeze-dried to obtain a polycarboxylate powder. The carboxyl group content of the obtained polycarboxylate was 555 mg, CE
C was 347 mg / g.

Example 6 In Example 5, instead of potassium permanganate,
The same operation was performed except that 60.8 g of potassium manganate (10-fold mol with respect to anhydrous glucose units) was used. The carboxyl group content of the obtained polycarboxylate was 459 mg, and the CEC was 301 mg / g.

Example 7 300 m equipped with a stirrer, an oxidizing agent dropping funnel, a sodium hydroxide aqueous solution dropping port, a pH controller, and a thermometer.
5 g of amylopectin in absolute dry weight and 100 g of ion-exchanged water were added to a l-volume separable flask, and the mixture was stirred while cooling in a 30 ° C. water bath. After the internal temperature reached a constant temperature, 16.3 g of potassium permanganate crystals (3.3 times the mol of anhydrous glucose units) were replaced with deionized water 2
Dissolved in 50 g and added over 5 hours. During this time,
Stirring was continued while adding a 2N aqueous sodium hydroxide solution so that the pH became 10 using a pH controller. After the completion of the addition of potassium permanganate, unreacted potassium permanganate was reduced with sodium sulfite, and manganese dioxide as a by-product was filtered off. The filtrate was purified by performing diffusion dialysis with ion-exchanged water for 5 days, and then freeze-dried to obtain a polycarboxylate powder. The carboxyl group content of the obtained polycarboxylate was 442 mg, and its CE
C was 200 mg / g.

Comparative Example 2 In Example 7, 1 was used in place of potassium permanganate.
The same operation was performed except that 64 g of a 2 wt% aqueous solution of sodium hypochlorite (3.3 times the mol of the anhydrous glucose unit) was used. The carboxyl group content of the obtained polycarboxylate is 125 mg, and its CEC is 90 m.
g / g.

[0030]

According to the present invention, a polysaccharide is used as a raw material, from which a polycarboxylic acid having a high carboxyl group content or a salt thereof can be industrially advantageously produced.

Claims (2)

[Claims] 1. An alkali required for neutralizing and titrating an acid-type polycarboxylic acid, wherein a polysaccharide having an anhydrous glucose as a structural unit is oxidized using a manganese oxide or a salt thereof. A method for producing a polycarboxylic acid or a salt thereof, which is 435 mg or more per 1 g of the polycarboxylic acid in terms of sodium oxide. 2. The method according to claim 1, wherein the amount of the manganese oxide or a salt thereof is 3 to 12 moles per anhydroglucose unit of the polysaccharide, and the pH during the reaction is 7 to 13.