Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1998-01-27
2001-04-24
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S105000, C536S110000, C536S119000, C536S128000
Reexamination Certificate
active
06222031
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for oxidizing an &agr;-bonding type polysaccharide, and more specifically, it relates to a process for preparing a water-soluble tricarboxypolysaccharide by oxidizing an &agr;-bonding type polysaccharide with a high valence ruthenium oxide produced by the use of a ruthenium compound and an oxidizing agent. The water-soluble tricarboxypolysaccharide which can be obtained by the present invention can be utilized as any of a scale deposition inhibitor, a pigment dispersant, a sizing agent, a concrete blending agent, a detergent builder and the like.
2. Description of the Related Art
Heretofore, various methods for preparing a dicarboxypolysaccharide by oxidizing an &agr;-bonding type polysaccharide are known. For example, in Japanese Patent Publication No. 1281/1974, there has been described a method for oxidizing an &agr;-bonding type polysaccharide by the use of a combination of periodic acid and a chlorite, or a hypochlorite, and it has also been disclosed therein that a dicarboxystarch obtained by oxidizing the C
2
and C
3
positions of the &agr;-bonding type polysaccharide is an excellent detergent builder.
Furthermore, Japanese Patent Application Laid-open No. 2187/1985 has described a process for preparing a dicarboxypolysaccharide from an &agr;-bonding type polysaccharide in the presence of sodium hypochlorite, chlorine, or a combination of periodic acid and a halogen. In Japanese Patent Application Laid-open No. 175301/1992, a method for preparing a dicarboxypolysaccharide by the use of a hypochlorite and/or a hypoiodite has been disclosed.
On the other hand, with regard to a process for preparing a tricarboxypolysaccharide by oxidizing an &agr;-bonding type polysaccharide, for example, Czechoslovakian Patent No. 235576 has described a method for preparing a tricarboxystarch from starch in the presence of a combination of a periodate and dinitrogen tetroxide. From EP-A-O 542496, there is known a process for preparing a tricarboxystarch from starch in the presence of a combination of a vanadium salt and a nitrite in a concentrated nitric acid-concentrated sulfuric acid solvent. Japanese Patent Application Laid-open No. 71601/1997 has described a process for preparing a polycarboxylic acid derived from a polysaccharide having anhydrous glucose as a constitutional unit.
However, in Czechoslovakian Patent No. 235576 mentioned above, a long process of two steps is required, and the oxidizing agent which is expensive and is available through a complicated route must be used. In addition, the obtained tricarboxystarch is not water-soluble, which is inconvenient for its use. Moreover, in the process described in EP-A-O 542496, a post-treatment of the mixed acids having the high concentrations which is to be done after reaction is not easy, and another problem such as the removal/disposal of the used metal salt are also present. For these reasons, the disclosed process is not desirable as an industrial manufacturing technique. Furthermore, these methods described above are insufficient to easily and inexpensively manufacture a water-soluble tricarboxypolysaccharide having a high carboxyl group content in a high yield which is intended by the present invention. Additionally, even by the process disclosed in Japanese Patent Application Laid-open No. 71601/1997, sufficiently satisfactory results have not been obtained so far.
SUMMARY OF THE INVENTION
The present invention has been developed to solve the above-mentioned problems of the conventional techniques, and an object of the present invention is to provide an industrial process for easily and inexpensively preparing a conveniently usable water-soluble tricarboxypolysaccharide having a high carboxyl group content in a high yield without any problem of a post-treatment after a reaction.
The present inventors have investigated on a process for preparing a water-soluble tricarboxypolysaccharide from an &agr;-bonding type polysaccharide as a raw material, and as a result, the present invention has now been completed.
That is to say, the present invention is directed to a process for easily and inexpensively preparing a conveniently usable water-soluble tricarboxypolysaccharide having a high carboxyl group content in a high yield without any problem of a post-treatment after a reaction which comprises the step of oxidizing an &agr;-bonding type polysaccharide, in an aqueous solvent or a mixed solvent stable to water and an oxidizing agent, in the presence of a high valence ruthenium oxide produced from a catalytic amount of a ruthenium compound with an oxidizing agent.
DETAILED DESCRIPTION OF THE INVENTION
A water-soluble tricarboxypolysaccharide referred to in the present invention means a water-soluble tricarboxypolysaccharide in which the C
2
and C
3
positions of a saccharic pyranose ring constituting an &agr;-bonding type polysaccharide are cleaved and 10 mol % or more of secondary alcohols at the C
2
and C
3
positions and 10 mol % or more of a primary alcohol at the C
6
position are simultaneously oxidized into carboxyl groups, or a water-soluble tricarboxypolysaccharide in which 10 mol % or more of secondary alcohols at the C
2
and C
3
positions is oxidized into carboxyl groups and 10 mol % or more of an ester at the C
6
position is simultaneously hydrolyzed, or a mixture thereof.
A raw material which can be used in the present invention is the &agr;-bonding type polysaccharide, and typical examples of the &agr;-bonding type polysaccharide include starch, amylose, amylopectin, pectin, protopectin and pectinic acid. Examples of the starch include corn starch, potato starch, tapioca starch, wheat starch, sweet potato starch and rice starch, and above all, corn starch, potato starch and tapioca starch are particularly preferable. Furthermore, a water-soluble starch obtained by decreasing the molecular weight of any of these starches is also preferable. The above-mentioned raw material can be used at a concentration in the range of 1 to 80% by weight, preferably 5 to 50% by weight.
A high valence ruthenium oxide which can be used in the present invention means a ruthenium oxide in which a ruthenium atom has a valence of +6, +7 or +8. This high valence ruthenium oxide can be produced by the use of a ruthenium compound and an oxidizing agent. Examples of the ruthenium compound which can be used in the present invention include ruthenium metal and various kinds of ruthenium compounds. Typical examples of the ruthenium compounds include ruthenium oxides such as ruthenium dioxide and ruthenium tetroxide; ruthenium hydroxide; ruthenium sulfate; ruthenium halides such as ruthenium chloride and ruthenium bromide; and ruthenium complexes such as ruthenium dodecacarbonium.
In addition, a ruthenium metal supporting material obtained by supporting the ruthenium metal on any of various carriers can also be used. Typical examples of the ruthenium metal supporting material include ruthenium metal-alumina, ruthenium metal-carbon, ruthenium metal-silica-alumina and ruthenium metal-titania. The amount of the ruthenium compound to be used is a catalytic amount in the range of 0.00001 to 1 mol, preferably 0.0001 to 0.1 mol per mol of the &agr;-bonding type polysaccharide which is the raw material. Here, 1 mol of the &agr;-bonding type polysaccharide as the raw material means the number of mols of a glucopyranose unit or a methyl galacturonate ester pyranose unit.
Examples of the oxidizing agent for the ruthenium compound which can be used in the present invention include halogens, halogenic acids and their salts, oxygen, ozone, peracids, hydrogen peroxide, persulfuric acid and its salts, and ferricyanides. Typical examples of the oxidizing agent include halogen molecules such as chlorine and bromine; halogen oxides such as dichlorine monoxide, chlorine dioxide, dibromine monoxide and bromine dioxide; perhalogenic acids such as periodic acid and perchloric acid as well as their salts; halogenic acids such as bromic acid and chloric
Sakamoto Masaru
Sano Rieko
Takahashi Toru
Wakabayashi Hidechika
Antonelli Terry Stout & Kraus LLP
Mitsubishi Gas Chemical Company Inc.
Owens Howard
Wilson James O.
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