CA2352222A1 - Process for oxidising starch - Google Patents
Process for oxidising starch Download PDFInfo
- Publication number
- CA2352222A1 CA2352222A1 CA002352222A CA2352222A CA2352222A1 CA 2352222 A1 CA2352222 A1 CA 2352222A1 CA 002352222 A CA002352222 A CA 002352222A CA 2352222 A CA2352222 A CA 2352222A CA 2352222 A1 CA2352222 A1 CA 2352222A1
- Authority
- CA
- Canada
- Prior art keywords
- carbohydrate
- starch
- process according
- hydrogen peroxide
- viscosity
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B31/00—Preparation of derivatives of starch
- C08B31/18—Oxidised starch
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Biochemistry (AREA)
- Engineering & Computer Science (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- General Health & Medical Sciences (AREA)
- Molecular Biology (AREA)
- Polysaccharides And Polysaccharide Derivatives (AREA)
Abstract
The viscosity of starch and other carbohydrates can be lowered inexpensively, rapidly and without residual streams by treatment with hydrogen peroxide and a catalyst, in particular an organic acid or acid anhydride. After carbohydrate, hydrogen peroxide and catalyst have been brought together, the material is, if necessary, pre-dried at a temperature below 60 ~C and the dried material is then treated at a temperature of 80 - 140 ~C. The lowered viscosity is stable.
Description
21-09-2000 B~l9g$ CA 02352222 2001-05-24 ~~J~J72649 EPO - DG 1 Prrnn.~
- Process for oxidising starch 21. 09. 2000 The invention relates to a process for lowering the viscosity of carbohydrates by oxidative degradation.
Starch must be subjected to a treatment to lower the viscosity before it can be uscd industrially. To this end the starch is generally subjected to oxidative treatrnent at elevated temperature (40-60 °C) in an alkaline medium. For example, if hypochlorite is used as oxidising agent at 40 °C, the reaction takes 4 -15 hours. The disadvantage of this method is the amount of salt formed and the extensive degradation of starch, accompanied by incorporation of chlorine. According to DE 738909, virtually dry potato starch can be gelled by treatment with hydrogen peroxide at 45 °C for 6 hours. Such a treatrnent is suitable for the preparation of blancmange, but the viscosity is too high and not stable for other applications.
According to another method, hydrogen peroxide is used with a transition metal as catalyst. However, the catalyst, which is usually toxic, is difficult to remove afterwards, even with the use of compounds such as EDTA. A further disadvantage is the discolouration of the product.
US-A 5,362,868 discloses a method according to which the viscosity of (hydroxy ethyl)starch is lowered by oxidation with a per-acid. The per-acid used is, for example, peroxysulphuric acid (HzS05) or peracetic acid. The peroxysulphuric acid has to be prepared in situ from hydrogen peroxide and sulphuric acid. The reactivity of peracetic acid is lower and leads to longer reaction times. It is also described in US-A
5,362,868 that reaction with hydrogen peroxide leads to unacceptable reaction times.
According to WO 97/31951 the viscosity of starch and other carbohydrates can be lowered by treatment with hydrogen peroxide in the presence of an acylated carbohydrate.
CS Patent 143708 (CA 77:166487) discloses the treatment of starch with 0.1-0.3 aqueous hydrochloric acid, 0.2-0.5% hydrogen peroxide 40% and about 2% water at 70-90°C for 4-7 h, resulting in a depolymerised product for use as textile sizes and finishes.
The aim of the invention is to provide a method for lowering the viscosity of starch and other carbohydrates using simple reagents, without the use of heavy metals and salt-forming reagents, and without organic by-products. In this context it is desirable that a stable viscosity is obtained, that is to say a stability which does not increase further at ambient temperature.
Said aim is achieved by means of a method wherein the carbohydrate is oxidised with hydrogen peroxide in the presence of a catalyst and, after it has been brought into contact with the hydrogen peroxide, the carbohydrate is, if necessary, dried at a temperature below 60 °C and is then treated at a temperature of 80 - 140 °C.
AMENDED SHEET
B~19g5 CA 02352222 2001-05-24 P~,~S~.v 99972649 The process according to the invention is an inexpensive method with short reaction times and with low consumption of hydrogen peroxide, consumption being approximately times as low as with the method according to WO 97/31951. There is also no salt burden or other waste stream worthy of mention. The method leads in high yield and with little loss 5 to a soluble or dispersible carbohydrate, the solution or dispersion of which has a low and stable viscosity.
Any polysaccharide that is completely or partially soluble in water can be used as the carbohydrate that can be treated in accordance with the process according to the invention.
Such polysaccharides include, firstly, starch and fractions and derivatives thereof, such as amylose, ethoxylated starch and carboxymethylstarch. Furthermore, the solubility of cellulose and chitin and derivatives thereof can be improved, or the viscosity thereof can be lowered, by means of the method according to the invention.
The quantity of hydrogen peroxide to be used is entirely dependent on the desired degree of oxidation. By virtue of the higher efficiency of the method according to the invention, a limited quantity of hydrogen peroxide can suffice. In general a solution of 0.1 -% (m/m) hydrogen peroxide, preferably of 1 - 10 % (m/m), is used. Preferably the quantity and concentration of hydrogen peroxide taken is such that the carbohydrate does not dissolve to a significant extent and, in the case of starch, remains in granular form. The catalyst can be an organic acid, such as acetic acid, formic acid, propionic acid, lactic acid, 20 oxalic acid, citric acid, succinic acid or an anhydride such as acetic anhydride, and in particular a cyclic anhydride of a dicarboxylic acid such as succinic anhydride, malefic anhydride or citraconic anhydride, or possibly a lactone or lactide.
Phosphoric acid can also be used. The quantity of catalyst is, for example, 0.1 - 4 % (m/m), in particular 0.5 - 2 (m/m), with respect to the carbohydrate.
After hydrogen peroxide and catalyst have been added and mixed, the undissolved carbohydrate is filtered off if necessary. The water content must not be too high for the following step. If the water content is more than 20 or 25 % (with respect to the mass of the carbohydrate and water), the carbohydrate is then dried to a water content of 25 or lower, especially between 10 and 20%, with respect to the mass of the carbohydrate and water.
Drying is carried out at a temperature of at most 60, and in particular below 55 °C, down to, for example, ambient temperature, preferably 20°C or higher, preferably to a water content of at most 25 % (m/m), in particular of 15-20 % (m/m), with respect to the carbohydrate, corresponding to at most 20 % and 13-17 %, respectively, on the basis of the total mass of carbohydrate and water. In the case of starch, drying must be carried out under conditions such that the starch does not gelatinise or barely gelatinises. Drying drums can optionally be used for drying on a large scale.
The dried carbohydrate is then kept at a temperature above 80 °C, in particular AMENDED SHEET
B0419B5 PCTINL9~_. _ _ . __ above 100 °C, up to about 140 °C, preferably between 100 and 130°C, for a period of at least 10 minutes, in particular for a period of 1 -10 hours, during which period the actual oxidation takes place. At higher temperature, for example 120 °C, use can be made of fluidised beds, microwave ovens and the like. It is important that an open reactor is used, so that any residual water released can be removed easily. If the residual water is not adequately removed, the carbohydrate, in the case of starch, can then still gelatinise.
The viscosity of the carbohydrate of reduced viscosity that is obtained using the method according to the invention can be determined using a Brabender viscometer.
According to the measurement method, a 25 % (m/m) solution or suspension is heated from 40 °C at a rate of 1.5 °C/min; during this heating the viscosity initially rises to a maximum (peak viscosity); on further heating the viscosity falls again; at 90 °C the temperature is not raised further and the viscosity reaches a minimum (valley viscosity); after 30 min at 90 °C
cooling is carried out, again at a rate of 1.5 °C/min, to a final temperature of 40 °C; the viscosity at this end point is termed the final viscosity. The product according to the invention preferably has a peak, valley and final viscosity of 4,000, 200 and 2,000, respectively, with 2,000, 100 and 500 Brabender units, respectively, being most preferred, with a minimal reduction in the molecular weight. The treated starch product preferably has a molecular weight between 0.2 and 1 Mda, and a final viscosity which rises by less than 100 %, in particular by less than 50 % (in Brabender units) at 40°C
within one hour of completion of the treatment. The product of reduced viscosity can serve as the basis for various applications. One important application is in paper making, where it can be used to increase the initial wet strength of the paper and to obtain improved printability, better adhesion of cationic agents and improved reception of adhesive.
Example 1 A quantity of potato starch (100 - 1000 g) is suspended in a solution of 5 %
or 2.5 hydrogen peroxide in water. Acetic acid or malefic anhydride is optionally added. After filtration, the material filtered off contains 30-40 % water; the hydrogen peroxide content is therefore about 1 % (m/m) at 2.5 % H20z. The filter cake is dried in air for three days.
Instead of this it is also possible to dry for a few hours under a stream of air at approximately SO °C. The powder obtained is then kept at 120 °C
in an oven for a number of hours (reaction time). The material obtained is white and has retained its granular structure. The number of carboxylic acid groups is approximately 1 per 57 anhydroglucose units. Brabender curves were recorded for the materials (25 % in water) at pH
7Ø The results are summarised in the following table.
AMENDED SHEET
- Process for oxidising starch 21. 09. 2000 The invention relates to a process for lowering the viscosity of carbohydrates by oxidative degradation.
Starch must be subjected to a treatment to lower the viscosity before it can be uscd industrially. To this end the starch is generally subjected to oxidative treatrnent at elevated temperature (40-60 °C) in an alkaline medium. For example, if hypochlorite is used as oxidising agent at 40 °C, the reaction takes 4 -15 hours. The disadvantage of this method is the amount of salt formed and the extensive degradation of starch, accompanied by incorporation of chlorine. According to DE 738909, virtually dry potato starch can be gelled by treatment with hydrogen peroxide at 45 °C for 6 hours. Such a treatrnent is suitable for the preparation of blancmange, but the viscosity is too high and not stable for other applications.
According to another method, hydrogen peroxide is used with a transition metal as catalyst. However, the catalyst, which is usually toxic, is difficult to remove afterwards, even with the use of compounds such as EDTA. A further disadvantage is the discolouration of the product.
US-A 5,362,868 discloses a method according to which the viscosity of (hydroxy ethyl)starch is lowered by oxidation with a per-acid. The per-acid used is, for example, peroxysulphuric acid (HzS05) or peracetic acid. The peroxysulphuric acid has to be prepared in situ from hydrogen peroxide and sulphuric acid. The reactivity of peracetic acid is lower and leads to longer reaction times. It is also described in US-A
5,362,868 that reaction with hydrogen peroxide leads to unacceptable reaction times.
According to WO 97/31951 the viscosity of starch and other carbohydrates can be lowered by treatment with hydrogen peroxide in the presence of an acylated carbohydrate.
CS Patent 143708 (CA 77:166487) discloses the treatment of starch with 0.1-0.3 aqueous hydrochloric acid, 0.2-0.5% hydrogen peroxide 40% and about 2% water at 70-90°C for 4-7 h, resulting in a depolymerised product for use as textile sizes and finishes.
The aim of the invention is to provide a method for lowering the viscosity of starch and other carbohydrates using simple reagents, without the use of heavy metals and salt-forming reagents, and without organic by-products. In this context it is desirable that a stable viscosity is obtained, that is to say a stability which does not increase further at ambient temperature.
Said aim is achieved by means of a method wherein the carbohydrate is oxidised with hydrogen peroxide in the presence of a catalyst and, after it has been brought into contact with the hydrogen peroxide, the carbohydrate is, if necessary, dried at a temperature below 60 °C and is then treated at a temperature of 80 - 140 °C.
AMENDED SHEET
B~19g5 CA 02352222 2001-05-24 P~,~S~.v 99972649 The process according to the invention is an inexpensive method with short reaction times and with low consumption of hydrogen peroxide, consumption being approximately times as low as with the method according to WO 97/31951. There is also no salt burden or other waste stream worthy of mention. The method leads in high yield and with little loss 5 to a soluble or dispersible carbohydrate, the solution or dispersion of which has a low and stable viscosity.
Any polysaccharide that is completely or partially soluble in water can be used as the carbohydrate that can be treated in accordance with the process according to the invention.
Such polysaccharides include, firstly, starch and fractions and derivatives thereof, such as amylose, ethoxylated starch and carboxymethylstarch. Furthermore, the solubility of cellulose and chitin and derivatives thereof can be improved, or the viscosity thereof can be lowered, by means of the method according to the invention.
The quantity of hydrogen peroxide to be used is entirely dependent on the desired degree of oxidation. By virtue of the higher efficiency of the method according to the invention, a limited quantity of hydrogen peroxide can suffice. In general a solution of 0.1 -% (m/m) hydrogen peroxide, preferably of 1 - 10 % (m/m), is used. Preferably the quantity and concentration of hydrogen peroxide taken is such that the carbohydrate does not dissolve to a significant extent and, in the case of starch, remains in granular form. The catalyst can be an organic acid, such as acetic acid, formic acid, propionic acid, lactic acid, 20 oxalic acid, citric acid, succinic acid or an anhydride such as acetic anhydride, and in particular a cyclic anhydride of a dicarboxylic acid such as succinic anhydride, malefic anhydride or citraconic anhydride, or possibly a lactone or lactide.
Phosphoric acid can also be used. The quantity of catalyst is, for example, 0.1 - 4 % (m/m), in particular 0.5 - 2 (m/m), with respect to the carbohydrate.
After hydrogen peroxide and catalyst have been added and mixed, the undissolved carbohydrate is filtered off if necessary. The water content must not be too high for the following step. If the water content is more than 20 or 25 % (with respect to the mass of the carbohydrate and water), the carbohydrate is then dried to a water content of 25 or lower, especially between 10 and 20%, with respect to the mass of the carbohydrate and water.
Drying is carried out at a temperature of at most 60, and in particular below 55 °C, down to, for example, ambient temperature, preferably 20°C or higher, preferably to a water content of at most 25 % (m/m), in particular of 15-20 % (m/m), with respect to the carbohydrate, corresponding to at most 20 % and 13-17 %, respectively, on the basis of the total mass of carbohydrate and water. In the case of starch, drying must be carried out under conditions such that the starch does not gelatinise or barely gelatinises. Drying drums can optionally be used for drying on a large scale.
The dried carbohydrate is then kept at a temperature above 80 °C, in particular AMENDED SHEET
B0419B5 PCTINL9~_. _ _ . __ above 100 °C, up to about 140 °C, preferably between 100 and 130°C, for a period of at least 10 minutes, in particular for a period of 1 -10 hours, during which period the actual oxidation takes place. At higher temperature, for example 120 °C, use can be made of fluidised beds, microwave ovens and the like. It is important that an open reactor is used, so that any residual water released can be removed easily. If the residual water is not adequately removed, the carbohydrate, in the case of starch, can then still gelatinise.
The viscosity of the carbohydrate of reduced viscosity that is obtained using the method according to the invention can be determined using a Brabender viscometer.
According to the measurement method, a 25 % (m/m) solution or suspension is heated from 40 °C at a rate of 1.5 °C/min; during this heating the viscosity initially rises to a maximum (peak viscosity); on further heating the viscosity falls again; at 90 °C the temperature is not raised further and the viscosity reaches a minimum (valley viscosity); after 30 min at 90 °C
cooling is carried out, again at a rate of 1.5 °C/min, to a final temperature of 40 °C; the viscosity at this end point is termed the final viscosity. The product according to the invention preferably has a peak, valley and final viscosity of 4,000, 200 and 2,000, respectively, with 2,000, 100 and 500 Brabender units, respectively, being most preferred, with a minimal reduction in the molecular weight. The treated starch product preferably has a molecular weight between 0.2 and 1 Mda, and a final viscosity which rises by less than 100 %, in particular by less than 50 % (in Brabender units) at 40°C
within one hour of completion of the treatment. The product of reduced viscosity can serve as the basis for various applications. One important application is in paper making, where it can be used to increase the initial wet strength of the paper and to obtain improved printability, better adhesion of cationic agents and improved reception of adhesive.
Example 1 A quantity of potato starch (100 - 1000 g) is suspended in a solution of 5 %
or 2.5 hydrogen peroxide in water. Acetic acid or malefic anhydride is optionally added. After filtration, the material filtered off contains 30-40 % water; the hydrogen peroxide content is therefore about 1 % (m/m) at 2.5 % H20z. The filter cake is dried in air for three days.
Instead of this it is also possible to dry for a few hours under a stream of air at approximately SO °C. The powder obtained is then kept at 120 °C
in an oven for a number of hours (reaction time). The material obtained is white and has retained its granular structure. The number of carboxylic acid groups is approximately 1 per 57 anhydroglucose units. Brabender curves were recorded for the materials (25 % in water) at pH
7Ø The results are summarised in the following table.
AMENDED SHEET
Table 1 Reaction Catalyst HzOz Viscosity time (h) Type' %z %z Peak Valley Final 3 - - 2.5 5480 300 7080 3 AA I _ 3 3 3 AA 1 2.5 3760 148 3400 4 AA 1 2.5 3160 132 2680 3 AA+MA 1+1 2.5 32 32 32 3 MA 0.5 2.5 1010 40 984 35 MA 0.5 2.5 850 64 104 ' AA = acetic acid; MA = malefic anhydride S z percentage by weight in water 3 viscosity too high to be able to be measured 4 after 30 minutes at 40 °C: 108 wheat starch Example 2 A quantity of potato starch ( 100 - 1000 g) is dried to a moisture content of at most 10 %. 2.5 % HZOz (2.5 gram per 100 gram dry starch, 100 % solids), 1 % or 0.5 % or 0.25 % acetic acid (with respect to dry starch) and 1.0 % or 0.5 % malefic anhydride (with respect to dry starch) are then added to the starch. The peroxide, acetic acid and malefic anhydride are all dissolved in water. The total quantity of water (water already present in the starch plus water added via the chemicals) is, however, no greater than 20 % (solids content of 80 %). The whole is mixed well in order then to react for 3 hours at 120 °C.
The material obtained is white and has retained its granular structure.
Brabender curves were recorded for the materials (25 % in water) at pH 7Ø The results are given in Table 2 below.
The material obtained is white and has retained its granular structure.
Brabender curves were recorded for the materials (25 % in water) at pH 7Ø The results are given in Table 2 below.
Table 2 Quantity Catalyst Viscosity of water (%) HzOz(%) AA(%) MA{%) Peak Valley Final 20 2.5 1 0.5 367 9 500 6 I .0 0.5 0.5 501 i 6 480 16 I.0 0.5 I.0 610 6 250(S) S = Stable
Claims (9)
1. A process for lowering the viscosity of polymer carbohydrates by treatment with hydrogen peroxide in the presence of a catalyst, characterised in that the carbohydrate is brought into contact with the hydrogen peroxide and an organic acid, an organic acid anhydride, lactone or lactide or phosphoric acid as the catalyst and then, if necessary, dried at a temperature below 60 °C to a water content of at most 25 % with respect to the total of carbohydrate and water, and the dried carbohydrate is treated at a temperature of 80-140 °C.
2. A process according to Claim 1, wherein the carbohydrate is brought into contact with a solution of 0.1-20 %, in particular 1-10 % (m/m), hydrogen peroxide.
3. A process according to Claim 1 or 2, wherein the catalyst is an organic acid or an organic acid anhydride.
4. A process according to Claim 3, wherein the catalyst is an anhydride of an organic dicarboxylic acid.
5. A process according to one of Claims 1 - 4, wherein the carbohydrate is dried to a water content of 10-20 % (m/m), with respect to the total of carbohydrate and water.
6. A process according to one of Claims 1- 5, wherein drying is carried out at a temperature of 20 - 55 °C and treatment is then carried out at a temperature of 100 - 130 °C.
7. A process according to one of Claims 1 - 6, wherein the carbohydrate is starch.
8. A process according to Claim 7, wherein the average molecular weight of the treated starch is 0.2 - 1 MDa.
9. A process according to Claim 7 or 8, wherein the final viscosity rises by less than 100 %, in particular by less than 50 % (in Brabender units) within one hour of completion of gelatination, at 40 °C.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL1010660A NL1010660C2 (en) | 1998-11-26 | 1998-11-26 | Method for oxidizing starch. |
| NL1010660 | 1998-11-26 | ||
| PCT/NL1999/000726 WO2000031145A1 (en) | 1998-11-26 | 1999-11-26 | Process for oxidising starch |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2352222A1 true CA2352222A1 (en) | 2000-06-02 |
Family
ID=19768210
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002352222A Abandoned CA2352222A1 (en) | 1998-11-26 | 1999-11-26 | Process for oxidising starch |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP1133524A1 (en) |
| JP (1) | JP2002530487A (en) |
| CN (1) | CN1328572A (en) |
| AU (1) | AU1417200A (en) |
| CA (1) | CA2352222A1 (en) |
| NL (1) | NL1010660C2 (en) |
| PL (1) | PL347895A1 (en) |
| WO (1) | WO2000031145A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10146069A1 (en) * | 2001-09-19 | 2003-04-03 | Degussa | Starch oxidation process |
| US6887496B2 (en) | 2001-12-20 | 2005-05-03 | Kimberly-Clark Worldwide, Inc. | Products for controlling microbial organic compound production |
| CN102212143A (en) * | 2011-05-17 | 2011-10-12 | 东华大学 | Pollution-free preparation method for oxidized phosphated double-modified starch |
| EP3205673B1 (en) * | 2016-02-12 | 2018-05-23 | Coöperatie Avebe U.A. | Oxidation of starch |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3975206A (en) * | 1974-11-18 | 1976-08-17 | A. E. Staley Manufacturing Company | Method of peroxide thinning granular starch |
| NL1002494C2 (en) * | 1996-02-29 | 1997-09-01 | Inst Voor Agrotech Onderzoek | Method for oxidizing starch. |
-
1998
- 1998-11-26 NL NL1010660A patent/NL1010660C2/en not_active IP Right Cessation
-
1999
- 1999-11-26 CN CN99813802A patent/CN1328572A/en active Pending
- 1999-11-26 CA CA002352222A patent/CA2352222A1/en not_active Abandoned
- 1999-11-26 WO PCT/NL1999/000726 patent/WO2000031145A1/en not_active Application Discontinuation
- 1999-11-26 EP EP99972649A patent/EP1133524A1/en not_active Withdrawn
- 1999-11-26 JP JP2000583969A patent/JP2002530487A/en active Pending
- 1999-11-26 AU AU14172/00A patent/AU1417200A/en not_active Abandoned
- 1999-11-26 PL PL99347895A patent/PL347895A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| NL1010660C2 (en) | 2000-05-30 |
| EP1133524A1 (en) | 2001-09-19 |
| CN1328572A (en) | 2001-12-26 |
| PL347895A1 (en) | 2002-04-22 |
| JP2002530487A (en) | 2002-09-17 |
| WO2000031145A1 (en) | 2000-06-02 |
| AU1417200A (en) | 2000-06-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP0946598B1 (en) | Superabsorbent material and method for producing said material | |
| WO1996038484A1 (en) | Oxidized polymeric carbohydrate ethers for use as sequestering agent, and methods for the preparation thereof | |
| US4112222A (en) | Method of preparing hydroxypropylated starch derivatives | |
| TW583189B (en) | Process for producing high molecular weight oxidized cellulose, oxidized cellulose and process for producing a superabsorbent material comprising oxidized cellulose | |
| JP4356289B2 (en) | Polysaccharide complex and method for producing the same | |
| US20020072598A1 (en) | High molecular weight oxidized cellulose | |
| US4097667A (en) | Hydroxyalkyl cellulose ethers | |
| AU723782B2 (en) | Process for oxidising starch | |
| CA2352222A1 (en) | Process for oxidising starch | |
| JP5331994B2 (en) | Process for preparing polyanhydroglucuronate | |
| KR20010052494A (en) | Method for manufacturing high-cationic starch solutions | |
| JP2901176B2 (en) | Low viscosity chitosan and method for producing the same | |
| CA2126126A1 (en) | Thinning of granular starch | |
| JPH061801A (en) | Process for cationing nongranular polysaccharide | |
| US6008345A (en) | Process for making polycarboxylic acid derived from polysaccharide composed of anhydrous glucose units and salts thereof | |
| EP0885245B1 (en) | Catalyst-free ozone oxidation of starch | |
| EP0920874A1 (en) | Superabsorbent material and method for producing said material | |
| Hebeish et al. | Oxidation of maize and rice starches using potassium permanganate with various reductants | |
| JP4457554B2 (en) | Polyuronic acid | |
| JP2006507373A (en) | Depolymerization of water-soluble polysaccharides. | |
| US8552178B2 (en) | Process for modification of biopolymers | |
| KR100252704B1 (en) | Method of making n,o-carboxy methyl chitosan with high purity crystallization and a method of controlling a molecular weight of water-soluble chitosan | |
| GB2029431A (en) | Method of Preparing Hydroxypropylated Starch Derivatives | |
| MXPA98007046A (en) | Process to oxidate almi |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued | ||
| FZDE | Discontinued |
Effective date: 20031126 |