CN1256278A - Process for preparing low degree of substitution hydroxypropyl cellulose - Google Patents
Process for preparing low degree of substitution hydroxypropyl cellulose Download PDFInfo
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- CN1256278A CN1256278A CN99122859A CN99122859A CN1256278A CN 1256278 A CN1256278 A CN 1256278A CN 99122859 A CN99122859 A CN 99122859A CN 99122859 A CN99122859 A CN 99122859A CN 1256278 A CN1256278 A CN 1256278A
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- low degree
- hydroxypropyl cellulose
- substitution hydroxypropyl
- cellulose
- substitution
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B11/00—Preparation of cellulose ethers
- C08B11/02—Alkyl or cycloalkyl ethers
- C08B11/04—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals
- C08B11/08—Alkyl or cycloalkyl ethers with substituted hydrocarbon radicals with hydroxylated hydrocarbon radicals; Esters, ethers, or acetals thereof
Abstract
The cleaning power of a hydroxypropylcellulose having a low degree of substitution can be increased during the production process therefor, particulary by lowering the water content thereof upon completion of reaction and after the cleaning refining process, while reducing the necessary amount of heat during the subsequent drying process is proceeded. The present invention provides a process for preparing a hydroxypropylcellulose having a low degree of substitution characterized by dissolving and neutralizing the reaction product at 60 DEG C or higher during dissolution neutralization process.
Description
The present invention relates in order to make preparations such as medicine and food have the preparation method of the low degree of substitution hydroxypropyl cellulose that slaking or binding property add.
Solid preparations such as granule in fields such as medicine and food or tablet, if only make preparation,, can not give full play to drug effect even administration can not obtain sufficient slaking with the main ingredient composition, and because also there is problems such as can not keeping the preparation shape in poor adhesion.In order to solve this class problem, when preparation,, make it have slaking or binding property by adding low degree of substitution hydroxypropyl cellulose.In order to reach this purpose, except that above-mentioned low degree of substitution hydroxypropyl cellulose, for example can also use carboxymethyl cellulose and calcium salt thereof, croscarmellose sodium, cross-linked polyvinylpyrrolidone, carboxymethyl starch etc.Wherein the advantage of low degree of substitution hydroxypropyl cellulose is that it is a nonionic, so seldom interact with ionic medicine etc. and take place rotten.
Therefore, preparations such as granule or tablet utilize above-mentioned advantage, and hydropropyl cellulose powder with low substitution with after effective ingredient and other vehicle dry type are mixed, is adopted and beats sheet, comes preparation with the aqueous solution of water or the water-soluble binder process for granulating of mixing afterwards.
Like this, be to make in its preparation process when preparation with low degree of substitution hydroxypropyl cellulose that slaking and binding property add, after at first former slip being soaked in aqueous sodium hydroxide solution, extruding is reacted the alkali cellulose and the propylene oxide that obtain; Perhaps add aqueous sodium hydroxide solution in the Powdered slurry in organic solvents such as Virahol, the trimethyl carbinol, hexane, the soda cellulose and the propylene oxide that obtain are reacted.Secondly, the crude reaction product that obtains is dispersed in the water, after the dissolving, with the residual alkali of acid neutralization.
In addition, carry out before the above-mentioned neutralization reaction,, can adjust the apparent density (with reference to special public clear 57-53100 communique) of low degree of substitution hydroxypropyl cellulose by adding a part of residual alkali of acid neutralization dissolving in advance.
At last, in order to remove salt and other impurity that side reaction generates in the aforesaid operations step, water or hot water wash refining, the refining resultant that obtains of extruding, after removing moisture,, can obtain low degree of substitution hydroxypropyl cellulose at last through operations such as super-dry, pulverizing.
But this low degree of substitution hydroxypropyl cellulose is water-insoluble, can carry out disintegration by water-swelling, has the good ins and outs of water-retentivity (character of holding moisture).Therefore, among the preparation method of former low degree of substitution hydroxypropyl cellulose, the product water ratio after water or hot wash are refining uprises, and needs more heat in the drying process afterwards, so there is the low problem of production performance.
In view of the foregoing, the objective of the invention is to when the preparation low degree of substitution hydroxypropyl cellulose, after particularly reaction finishes, the water ratio of low degree of substitution hydroxypropyl cellulose after the reduction washing purification operations.
To achieve these goals, a kind of preparation method of low degree of substitution hydroxypropyl cellulose can be provided according to one embodiment of the present invention, it is characterized in that in the reaction product dissolving N-process of preparation during low degree of substitution hydroxypropyl cellulose, in its dissolving and the time temperature more than 60 ℃.Adopt method of the present invention,, can reduce institute's heat requirement afterwards in the drying process, improve the rate of ash reduction of the per unit water yield simultaneously because the water ratio of low degree of substitution hydroxypropyl cellulose reduces.In addition, owing to can shorten the detergency of filtration time, raising low degree of substitution hydroxypropyl cellulose, thereby can reduce production cost.
Below, embodiments of the present invention are described.In addition, the present invention has more than and is confined to following embodiment.
The replacement mole number of the propoxyl on each anhydrous grape sugar monomer of low degree of substitution hydroxypropyl cellulose of the present invention is preferably 0.1～0.5.If the replacement mole number of propoxyl is lower than 0.1, then can not show required binding property; On the other hand,, then can not show required slaking, may cause preparation disintegration times such as the granule of moulding or tablet too to prolong if the replacement mole number of propoxyl surpasses 0.5.
Describe the preparation method of low degree of substitution hydroxypropyl cellulose of the present invention below in detail.At first, after former slip soaked in 10～50% aqueous sodium hydroxide solution, extruding made the alkali cellulose that obtains and propylene oxide reaction 2～8 hours under 20～90 ℃.Perhaps, Powdered slurry is dissolved in the organic solvents such as Virahol, the trimethyl carbinol, hexane, adds aqueous sodium hydroxide solution and prepare alkali cellulose, in this alkali cellulose, add propylene oxide and make it to react.Can obtain crude reaction product like this.
Then, fill it up with the hot water more than 60 ℃ in known dissolvers such as kneading type mixing machine or longitudinal type mixing machine, above-mentioned crude reaction product is remained on more than 60 ℃, certain hour dissolving back neutralizes with acid.Here, by under the hot conditions more than 60 ℃, handling the low degree of substitution hydroxypropyl cellulose alkaline solution, therefore low degree of substitution hydroxypropyl cellulose can be separated out with the dehydration form, and the highly finished product water ratio that obtains of dehydration is low, and owing to has improved during washing and remove water-based and can improve detergency.
In the above-mentioned dissolving and the time temperature be preferably more than 60 ℃ preferred 60～100 ℃.If in the dissolving and the time 60 ℃ of temperature less thaies, the highly finished product water ratio height that dehydration obtains, it is poor to remove water-based during washing.On the other hand, if in the dissolving and the time temperature surpass 100 ℃, probably can have the problems such as polymerization degree reduction, the finished product variable color of low degree of substitution hydroxypropyl cellulose.
Employed water or hot water amount were 2～20 weight parts with respect to anhydrous Mierocrystalline cellulose 1 weight part when low degree of substitution hydroxypropyl cellulose of the present invention dissolved, preferred especially 4～10 weight parts.If quantity not sufficient 2 weight parts of this dissolving water, because reactant solution viscosity uprises, low degree of substitution hydroxypropyl cellulose is difficult to the homogeneous dissolving; On the other hand, if the amount of dissolving water surpasses 20 weight parts, the problem that the water ratio of dehydration gained highly finished product increases when existing the required device of dissolving to become Datong District.
In addition, carry out before the above-mentioned dissolving neutralization, add the residual alkali of an acid neutralization dissolving part in advance in addition, also can adjust the solubleness of low degree of substitution hydroxypropyl cellulose.
Employed acid in the above-mentioned N-process is not particularly limited, can uses any acid, for example mineral acid such as organic acid such as acetic acid, formic acid, propionic acid and hydrochloric acid, sulfuric acid.This sour working concentration is not particularly limited, can freely selects, but the scope of preferred 10～50 weight %.
Afterwards, the precipitate that water or hot water dilution above-mentioned steps obtain obtains mashed prod, adopts ordinary methods such as filtration under diminished pressure or pressure filtration to wash this mashed prod.The employing ordinary method will be washed the highly finished product extruding that obtains, dry, pulverizing like this.That is to say, carry out extrusion dehydration, after dryings such as formula baking oven or flowing-type drying machine are left standstill in use, use pulverizing such as impact grinder, ball mill, can obtain the final product hydropropyl cellulose powder with low substitution by the pressurization compression.
Mixes with dry types such as effective ingredient and other vehicle by the hydropropyl cellulose powder with low substitution that will obtain and then to beat sheet, perhaps, can make preparations such as granule or tablet with the granulation of mixing of the aqueous solution of water or water-soluble binder.
Below in conjunction with embodiment and the present invention of comparative example more detailed description, but the present invention also not only is confined to these embodiment.(embodiment 1)
After of the sodium hydroxide solution immersion of former slip with 43 weight %, push, obtain consisting of the alkali cellulose of sodium hydroxide 22.2 weight %, Mierocrystalline cellulose 44.8 weight %, moisture 33.0 weight %.At volume is to add the alkali cellulose that is scaled 350g with Mierocrystalline cellulose in 50 liters the reaction vessel, feeds nitrogen in this reaction vessel.After being full of nitrogen, in reaction vessel, add propylene oxide 79g (is 0.226 weight part with respect to Mierocrystalline cellulose), 45 ℃ of reactions 2 hours, 65 ℃ of reactions 30 minutes, obtain propoxyl on each anhydrous grape sugar monomer and replace the crude reaction product 860g that mole number is 0.25 low degree of substitution hydroxypropyl cellulose.
Afterwards, in kneader, add 65 ℃ hot water 1925g (is 5.5 weight parts with respect to Mierocrystalline cellulose), behind the adding Glacial acetic acid 52g (is 0.2 mole with respect to alkali), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 65 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 631g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement following dehydration test and washing test for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.1. dehydration test
With 60 ℃ hot water dilution gained low degree of substitution hydroxypropyl cellulose, make it to become the mashed prod of 4 weight %, 1t condition lower compression 1 minute, carry out dehydration operation with strength testing machine (preceding river make produce).Afterwards, the drying and dehydrating product is 4 hours under 105 ℃ of conditions, calculates water ratio after the product dehydration according to its changes in weight.2. washing test
With 60 ℃ hot water dilution gained low degree of substitution hydroxypropyl cellulose, make it to become the mashed prod of 4 weight %, use pressure filter to apply the pressure of 49kPa, this mashed prod is taken off the liquid operation.Afterwards, add 80 ℃ hot water 50g, carry out the same liquid that takes off and operate.Thisly take off liquid operation and carry out 3 times, obtain average filtration time of taking off for these 3 times in the liquid operation and, estimate detergency with respect to the ash amount of the 3rd highly finished product.(embodiment 2)
Adopt the method identical with embodiment 1, embodiment 1 employed alkali cellulose and propylene oxide are reacted, the replacement mole number that obtains propoxyl on each anhydrous grape sugar monomer is 0.25 low degree of substitution hydroxypropyl cellulose.Afterwards, in wing mixer, add 55 ℃ hot water 1925g (is 5.5 weight parts with respect to Mierocrystalline cellulose), behind the adding Glacial acetic acid 52g (is 0.2 mole with respect to alkali), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 70 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 631g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.(embodiment 3)
Adopt the method identical with embodiment 1, embodiment 1 employed alkali cellulose and propylene oxide are reacted, the replacement mole number that obtains propoxyl on each anhydrous grape sugar monomer is 0.25 low degree of substitution hydroxypropyl cellulose.Afterwards, in kneader, add 80 ℃ hot water 1925g (is 5.5 weight parts with respect to Mierocrystalline cellulose), behind the adding Glacial acetic acid 52g (is 0.2 mole with respect to alkali), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 80 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 631g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.(embodiment 4)
After of the sodium hydroxide solution immersion of former slip with 43 weight %, push, obtain consisting of the alkali cellulose of sodium hydroxide 24.1 weight %, Mierocrystalline cellulose 40.9 weight %, moisture 35.0 weight %.At volume is to add the alkali cellulose that is scaled 350g with Mierocrystalline cellulose in 50 liters the reaction vessel, feeds nitrogen in this reaction vessel.After being full of nitrogen, in reaction vessel, add propylene oxide 41g (is 0.116 weight part with respect to Mierocrystalline cellulose), 45 ℃ of reactions 2 hours, 65 ℃ of reactions 30 minutes, obtain propoxyl on each anhydrous grape sugar monomer and replace the crude reaction product 896g that mole number is 0.14 low degree of substitution hydroxypropyl cellulose.Afterwards, in kneader, add 65 ℃ hot water 2520g (is 7.2 weight parts with respect to Mierocrystalline cellulose), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 65 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 937g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.(embodiment 5)
The embodiment 1 employed alkali cellulose of packing in volume is 5 liters reaction vessel, its amount is scaled 350g according to Mierocrystalline cellulose, feeds nitrogen in this reaction vessel.After being full of nitrogen, in reaction vessel, add propylene oxide 56g (is 0.116 weight part with respect to Mierocrystalline cellulose), 45 ℃ of reactions 2 hours, 65 ℃ of reactions 30 minutes, obtain propoxyl on each anhydrous grape sugar monomer and replace the crude reaction product 837g that mole number is 0.17 low degree of substitution hydroxypropyl cellulose.Afterwards, in the vane-type kneader, add 65 ℃ hot water 2450g (is 7.0 weight parts with respect to Mierocrystalline cellulose), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 65 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 937g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.(embodiment 6)
The embodiment 1 employed alkali cellulose of packing in volume is 5 liters reaction vessel, its amount is scaled 350g according to Mierocrystalline cellulose, feeds nitrogen in this reaction vessel.After being full of nitrogen, in reaction vessel, add propylene oxide 118.3g (is 0.338 weight part with respect to Mierocrystalline cellulose), 45 ℃ of reactions 2 hours, 65 ℃ of reactions 30 minutes, obtain propoxyl on each anhydrous grape sugar monomer and replace the crude reaction product 899g that mole number is 0.394 low degree of substitution hydroxypropyl cellulose.Afterwards, in kneader, add 80 ℃ hot water 1750g (is 5.0 weight parts with respect to Mierocrystalline cellulose), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 80 ℃ of solubilizing reaction products after 30 minutes, kept the hydrochloric acid 778g of uniform temp with 30 minutes interpolation 20 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.(comparative example 1)
Adopt the method identical with embodiment 1, embodiment 1 employed alkali cellulose and propylene oxide are reacted, the replacement mole number that obtains propoxyl on each anhydrous grape sugar monomer is 0.25 low degree of substitution hydroxypropyl cellulose.Afterwards, in kneader, add 30 ℃ hot water 1925g (is 5.5 weight parts with respect to Mierocrystalline cellulose), behind the adding Glacial acetic acid 52g (is 0.2 mole with respect to alkali), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 30 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 631g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.(comparative example 2)
Adopt the method identical with embodiment 1, embodiment 1 employed alkali cellulose and propylene oxide are reacted, the replacement mole number that obtains propoxyl on each anhydrous grape sugar monomer is 0.25 low degree of substitution hydroxypropyl cellulose.Afterwards, in kneader, add 40 ℃ hot water 1925g (is 5.5 weight parts with respect to Mierocrystalline cellulose), behind the adding Glacial acetic acid 52g (is 0.2 mole with respect to alkali), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 40 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 631g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.(comparative example 3)
Adopt the method identical with embodiment 4, embodiment 4 employed alkali celluloses and propylene oxide are reacted, the replacement mole number that obtains propoxyl on each anhydrous grape sugar monomer is 0.14 low degree of substitution hydroxypropyl cellulose.Afterwards, in kneader, add 25 ℃ hot water 2520g (is 7.2 weight parts with respect to Mierocrystalline cellulose), behind the adding Glacial acetic acid 52g (is 0.2 mole with respect to alkali), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 25 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 937g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.(comparative example 4)
Adopt the method identical with embodiment 5, embodiment 5 employed alkali celluloses and propylene oxide are reacted, the replacement mole number that obtains propoxyl on each anhydrous grape sugar monomer is 0.17 low degree of substitution hydroxypropyl cellulose.Afterwards, in pinching machine, add 25 ℃ hot water 2450g (is 7.0 weight parts with respect to Mierocrystalline cellulose), above-mentioned reaction product all is dispersed in wherein.Secondly, temperature remained on 25 ℃ of solubilizing reaction products after 30 minutes, kept the acetic acid 937g of uniform temp with 30 minutes interpolation 33 weight %, neutralized and separated out.Implement dehydration test and the washing test identical with embodiment 1 for the low degree of substitution hydroxypropyl cellulose of separating out, its outcome record is in table 1.
Table 1
Test-results
| Dehydration test | Washing test | ||
| Water ratio (weight %) | Filtration time (second) | Ash content (weight %) | |
| Embodiment 1 | ????69.2 | ????32 | ????0.33 |
| Embodiment 2 | ????68.8 | ????25 | ????0.28 |
| Embodiment 3 | ????67.4 | ????23 | ????0.26 |
| Embodiment 4 | ????64.7 | ????5 | ????0.13 |
| Embodiment 5 | ????66.5 | ????8 | ????0.19 |
| Embodiment 6 | ????69.9 | ????10 | ????0.41 |
| Comparative example 1 | ????80.8 | ????140 | ????3.82 |
| Comparative example 2 | ????79.7 | ????138 | ????1.22 |
| Comparative example 3 | ????75.3 | ????60 | ????0.65 |
| Comparative example 4 | ????76.8 | ????80 | ????0.89 |
By above-mentioned table 1 as can be known among the embodiment 1～6 because in the dissolving and the time under comparatively high temps reaction treatment, dehydration property and detergency two aspects of comparing final product with comparative example are all good.
From above-mentioned explanation as can be seen, since according to the present invention in preparation during low degree of substitution hydroxypropyl cellulose, after particularly reaction finishes, can reduce the water ratio of low degree of substitution hydroxypropyl cellulose after the washing purification operations, thereby can reduce institute's heat requirement in the drying process afterwards.In addition, the ash amount of the per unit water yield can be reduced,, production cost can be reduced by shortening the detergency of filtration time, raising low degree of substitution hydroxypropyl cellulose.
More than recorded and narrated embodiment of the present invention, but the present invention is not limited to above-mentioned form of implementation.
Also can carry out various changes or change according to technological thought of the present invention.
Claims (2)
1. the preparation method of low degree of substitution hydroxypropyl cellulose is characterized in that in the reaction product dissolving N-process when the preparation low degree of substitution hydroxypropyl cellulose, in its dissolving and the time temperature more than 60 ℃.
2. the method for claim 1, in the low degree of substitution hydroxypropyl cellulose on each anhydrous grape sugar monomer the replacement mole number of propoxyl be 0.1～0.5.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP34640998A JP4044689B2 (en) | 1998-12-07 | 1998-12-07 | Method for producing low substituted hydroxypropylcellulose |
| JP346409/1998 | 1998-12-07 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1256278A true CN1256278A (en) | 2000-06-14 |
| CN1120175C CN1120175C (en) | 2003-09-03 |
Family
ID=18383234
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN99122859A Expired - Fee Related CN1120175C (en) | 1998-12-07 | 1999-12-07 | Process for preparing low degree of substitution hydroxypropyl cellulose |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JP4044689B2 (en) |
| KR (1) | KR100482722B1 (en) |
| CN (1) | CN1120175C (en) |
| TW (1) | TW576840B (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1886428B (en) * | 2003-12-16 | 2010-12-01 | 三星精密化学株式会社 | Method for preparation of fine powdered cellulose ethers |
| CN101555285B (en) * | 2008-12-19 | 2010-12-01 | 浙江中维药业有限公司 | Preparation method of low-substituted hydroxypropyl cellulose |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5163927A (en) * | 1974-11-28 | 1976-06-02 | Shinetsu Chemical Co | Ketsugoseiryokonajozaihokaizaino seizohoho |
| JPS609521B2 (en) * | 1977-12-26 | 1985-03-11 | 信越化学工業株式会社 | Method for producing hydroxypropyl cellulose |
| JP2994956B2 (en) * | 1994-05-31 | 1999-12-27 | 信越化学工業株式会社 | Low-substituted hydroxypropylcellulose, composition thereof and tablet thereof |
| JP3212534B2 (en) * | 1997-04-08 | 2001-09-25 | 信越化学工業株式会社 | Low substituted hydroxypropylcellulose powder |
| JP3718341B2 (en) * | 1998-05-12 | 2005-11-24 | 信越化学工業株式会社 | Low substituted hydroxypropylcellulose and process for producing the same |
-
1998
- 1998-12-07 JP JP34640998A patent/JP4044689B2/en not_active Expired - Fee Related
-
1999
- 1999-12-04 TW TW088121262A patent/TW576840B/en not_active IP Right Cessation
- 1999-12-06 KR KR10-1999-0055080A patent/KR100482722B1/en not_active IP Right Cessation
- 1999-12-07 CN CN99122859A patent/CN1120175C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1886428B (en) * | 2003-12-16 | 2010-12-01 | 三星精密化学株式会社 | Method for preparation of fine powdered cellulose ethers |
| CN101555285B (en) * | 2008-12-19 | 2010-12-01 | 浙江中维药业有限公司 | Preparation method of low-substituted hydroxypropyl cellulose |
Also Published As
| Publication number | Publication date |
|---|---|
| JP4044689B2 (en) | 2008-02-06 |
| JP2000169501A (en) | 2000-06-20 |
| CN1120175C (en) | 2003-09-03 |
| KR100482722B1 (en) | 2005-04-13 |
| TW576840B (en) | 2004-02-21 |
| KR20000062186A (en) | 2000-10-25 |
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