CN110734508B - Method for disassembling natural rubber - Google Patents
Method for disassembling natural rubber Download PDFInfo
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- CN110734508B CN110734508B CN201911022046.2A CN201911022046A CN110734508B CN 110734508 B CN110734508 B CN 110734508B CN 201911022046 A CN201911022046 A CN 201911022046A CN 110734508 B CN110734508 B CN 110734508B
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- C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
- C08C19/00—Chemical modification of rubber
- C08C19/08—Depolymerisation
Abstract
The invention provides a method for disassembling natural rubber, and belongs to the technical field of natural rubber. The disassembling method provided by the invention comprises the following steps: dissolving natural rubber in an organic solvent to obtain a natural rubber solution; mixing the natural rubber solution with sodium methoxide under the conditions of protective atmosphere and light protection, then carrying out reflux reaction, neutralizing reaction liquid obtained by the reflux reaction, mixing with methanol, and refrigerating to finish the disassembly. In the invention, during the reflux reaction, sodium methoxide and terminal group-lipoid at one end of natural rubber molecular chain are subjected to ester exchange reaction, and lipoid connection points for generating molecular crosslinking are broken; and then neutralizing the reaction liquid obtained by the reflux reaction, and mixing the neutralized reaction liquid with methanol, wherein the methanol can break hydrogen bonds formed by natural rubber molecular chains and proteins, so that linear molecules are obtained.
Description
Technical Field
The invention relates to the technical field of natural rubber, in particular to a natural rubber disassembling method.
Background
The natural rubber is polyisoprene polymerized from monomer isoprene in a rubber tree, the inherent molecules of the polyisoprene are linear, however, due to the influence of the interaction of hydrogen bonds or chemical bonds and the like between molecular chain end groups and non-rubber substances (proteins and lipids) in the natural rubber, the molecular chains of the polyisoprene of the natural rubber are branched and crosslinked in the processes of biosynthesis, processing and storage to form a physical network structure, the physical network structure forms rubber gel on one hand, and when the molecular weight of the natural rubber is measured by adopting gel permeation chromatography, insoluble gel in a sample is filtered and removed, so that the test result cannot reflect the real molecular weight of the natural rubber; on the other hand, rubber molecules are branched and gradually increased in the processing and storage processes, so that the shape and position of a molecular weight distribution curve are dynamically changed, the inherent characteristics of the biosynthetic rubber molecules cannot be embodied, and the accurate analysis and evaluation of the molecular weight of the natural rubber are influenced. Therefore, in order to accurately analyze the inherent molecular structure (mainly, molecular weight and distribution thereof) characteristics of natural rubber, it is necessary to unravel the physical network structure in natural rubber.
In the prior art, natural latex (fresh latex or concentrated latex) is usually disassembled by a method of combining deproteinization and delipidization, wherein the deproteinization generally comprises an enzymatic hydrolysis method, a urea treatment method and a centrifugation method, the enzymatic hydrolysis method needs to add a large amount of surfactant, but the surfactant is difficult to remove, the urea treatment method has the problem of urea residue, and the centrifugation method cannot completely remove protein; the delipidation is generally performed by firstly using sodium hydroxide for ester exchange and then sequentially using ethanol and acetone for extraction, but the amount of the lipoid remaining is high, the extraction operation is complex, and the toxicity of the reagent is high. It can be seen that the prior art disassembly method is relatively complicated.
Disclosure of Invention
The invention aims to provide a natural rubber disassembling method which is simple to operate and can completely disassemble natural rubber.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a natural rubber disassembling method, which comprises the following steps:
dissolving natural rubber in an organic solvent to obtain a natural rubber solution;
mixing the natural rubber solution with sodium methoxide under the conditions of protective atmosphere and light protection, then carrying out reflux reaction, neutralizing the reaction solution obtained by the reflux reaction, mixing with methanol, and refrigerating to finish the disassembly of the natural rubber.
Preferably, the organic solvent is toluene, tetrahydrofuran or cyclohexane.
Preferably, the organic solvent contains an antioxidant, the antioxidant is at least one of 2, 6-di-tert-butyl-4-methylphenol, tert-butyl hydroquinone, an anti-aging agent 264, an antioxidant 1010 and an antioxidant 1076, and the concentration of the antioxidant is 50-250 ppm.
Preferably, the dosage ratio of the natural rubber to the organic solvent is 1-10 mg/mL.
Preferably, the dissolving is carried out under the condition of keeping out of the sun, the dissolving time is 3-7 days, the vibration is carried out for 0.5-2 hours every day, and the rotating speed of the vibration is 50-300 rpm.
Preferably, the sodium methoxide is added in the form of a sodium methoxide solution, the mass ratio of the sodium methoxide solution to the natural rubber is 1.5-2: 1, and the concentration of the sodium methoxide solution is 25-50 wt.%.
Preferably, the temperature of the reflux reaction is 60-85 ℃, and the time is 2-8 h.
Preferably, after neutralization, the reaction liquid obtained by neutralization is concentrated and then mixed with methanol, the concentration degree is 1/20-1/5 of the volume of the reaction liquid, and the volume ratio of the concentrated liquid to the methanol is 1: 5-10.
Preferably, the refrigeration temperature is 1-10 ℃, and the time is 16-24 h.
Preferably, the refrigeration temperature is 2-10 ℃ and the refrigeration time is 16-24 h.
The invention provides a natural rubber disassembling method, which comprises the following steps: dissolving natural rubber in an organic solvent to obtain a natural rubber solution; mixing the natural rubber solution with sodium methoxide under the conditions of protective atmosphere and light protection, then carrying out reflux reaction, neutralizing the reaction solution obtained by the reflux reaction, mixing with methanol, and refrigerating to finish the disassembly of the natural rubber. Dissolving natural rubber in an organic solvent, mixing the natural rubber solution with sodium methoxide and then carrying out reflux reaction under the conditions of protective atmosphere and light protection, wherein in the reflux reaction process, the sodium methoxide and the end group-lipoid at one end of a natural rubber molecular chain have ester exchange reaction, and lipoid connection points for generating molecular crosslinking are broken; and then neutralizing the reaction liquid obtained by the reflux reaction, mixing the neutralized reaction liquid with methanol, and refrigerating the mixture to break hydrogen bonds formed by natural rubber molecular chains and proteins by the methanol so as to obtain linear molecules and precipitate the linear molecules.
Drawings
FIG. 1 is a graph showing the molecular weight distribution of the natural rubber used in the example;
FIG. 2 is a graph showing the molecular weight distribution of the disassembled product obtained in example 1;
FIG. 3 is a graph showing the molecular weight distribution of the disassembled product obtained in example 2;
FIG. 4 is a graph showing the molecular weight distribution of the disassembled product obtained in example 3;
FIG. 5 is a graph showing the molecular weight distribution of the disassembled product obtained in example 1 and comparative example 1, in which the dotted line is the molecular weight distribution curve of the disassembled product obtained in example 1, and the solid line is the molecular weight distribution curve of the disassembled product obtained in comparative example 1.
Detailed Description
The invention provides a natural rubber disassembling method, which comprises the following steps:
dissolving natural rubber in an organic solvent to obtain a natural rubber solution;
mixing the natural rubber solution with sodium methoxide under the conditions of protective atmosphere and light protection, then carrying out reflux reaction, neutralizing the reaction solution obtained by the reflux reaction, mixing with methanol, and refrigerating to finish the disassembly of the natural rubber.
The invention dissolves natural rubber in organic solvent to obtain natural rubber solution.
In the present invention, the natural rubber is preferably 1mm or less in volume3Small pieces of (a).
In the present invention, the organic solvent is preferably toluene, tetrahydrofuran or cyclohexane. In the present invention, the above organic solvent is advantageous for sufficiently dissolving the natural rubber.
In the invention, the solvent preferably contains an antioxidant, the antioxidant is preferably at least one of 2, 6-di-tert-butyl-4-methylphenol, tert-butyl hydroquinone, an anti-aging agent 264, an antioxidant 1010 and an antioxidant 1076, and the concentration of the antioxidant is preferably 50-250 ppm, and more preferably 100-200 ppm. In the invention, the antioxidant is added to prevent the molecular chain of the natural rubber from being degraded in the dissolving process.
In the invention, the dosage ratio of the natural rubber to the organic solvent is preferably 1-10 mg/mL, and more preferably 3-8 mg/mL.
In the invention, the dissolving is preferably carried out under a dark condition, the dissolving time is preferably 3-7 days, the shaking is preferably carried out for 0.5-2 hours every day, and the rotating speed of the shaking is preferably 50-300 rpm; the dissolution time is more preferably 7 days, and the shaking time per day is more preferably 1 hour. In the present invention, the above dissolution process can ensure sufficient swelling of the natural rubber; and the light-shielding condition can avoid the degradation of the molecular chain of the natural rubber.
After the natural rubber solution is obtained, the reflux reaction is carried out after the natural rubber solution is mixed with sodium methoxide under the conditions of protective atmosphere and light shielding. In the invention, during the reflux reaction, sodium methoxide and terminal group-lipoid at one end of natural rubber molecular chain are subjected to ester exchange reaction, and lipoid connection points for generating molecular crosslinking are broken; the light-shielding condition can avoid the degradation of the molecular chain of the natural rubber.
In the present invention, the mass ratio of the sodium methoxide to the natural rubber is preferably 1.5 to 2: 1.
In the present invention, the sodium methoxide is preferably added in the form of a sodium methoxide solution, the solvent of which is preferably methanol, and the sodium methoxide solution is preferably a freshly prepared sodium methoxide solution; the concentration of the sodium methoxide solution is preferably 25-50 wt.%. The method for preparing the sodium methoxide solution is not particularly limited in the present invention.
The protective atmosphere is not particularly limited in the invention, and the conventional protective atmosphere such as nitrogen and argon can be adopted.
In the invention, the temperature of the reflux reaction is preferably 60-85 ℃, more preferably 65-70 ℃, and the time is preferably 2-6 hours, more preferably 3-4 hours.
After the reflux reaction is completed, the reaction solution obtained by the reflux reaction is preferably cooled to room temperature and then neutralized in the present invention.
In the present invention, the cooling is preferably natural cooling.
In the present invention, the acid solution used for the neutralization is preferably hydrochloric acid, an ether solution of hydrogen chloride or a methanol solution of hydrogen chloride, and the concentration of the acid solution is not particularly limited in the present invention.
After neutralization, the reaction solution obtained in the invention is mixed with methanol, and the natural rubber is disassembled after refrigeration. In the invention, the methanol is added and then refrigerated, and during the refrigeration process, the methanol can break the hydrogen bond formed by the natural rubber molecular chain and the protein, thereby obtaining the linear molecule.
In the invention, after neutralization, the reaction liquid obtained by neutralization is preferably concentrated and then mixed with methanol, the concentration degree is preferably 1/20-1/5 of the volume of the reaction liquid, and the volume ratio of the volume of the concentrated liquid to the volume of the methanol is preferably 1: 5-10.
In the invention, the refrigerating temperature is preferably 1-10 ℃, more preferably 2-10 ℃, most preferably 8-10 ℃, and the time is preferably 16-24 h.
After refrigeration is completed, the present invention preferably takes the resulting solids out and dries them to yield a disassembled product. In the present invention, the refrigeration enables sufficient precipitation of linear molecules.
In the present invention, the drying is preferably vacuum drying; the temperature of the vacuum drying is preferably room temperature. The vacuum drying time is not specially limited, and a product with constant weight can be obtained.
In the present invention, the obtained disassembled product can be used for measuring the inherent molecular weight of natural rubber, for studying the structure of natural rubber or for controlling the quality of natural rubber.
The method for disassembling natural rubber according to the present invention will be described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Weighing 10mg of natural rubber and cutting into about 1mm3To the small piece of (5), 10mL of a toluene solution of 2, 6-di-t-butyl-4-methylphenol was added, whereinThe concentration of the 2, 6-di-tert-butyl-4-methylphenol is 50ppm, the solution is dissolved for 5 days under the condition of keeping out of the sun, and the solution is vibrated for 1 hour every day at the rotating speed of 50rpm to obtain a natural rubber solution;
vacuumizing to completely exhaust air in the device, introducing argon, adding 60mg of a methanol solution of 25 wt.% sodium methoxide into the natural rubber solution, carrying out a light-shielding reflux reaction at 70 ℃ for 6 hours, naturally cooling the reaction solution to room temperature, neutralizing the solution by using an ether solution of hydrogen chloride, carrying out rotary evaporation on the neutralized solution until the volume of the neutralized solution is 10mL, adding 100mL of methanol, refrigerating the obtained mixed solution at 2 ℃ for 24 hours, taking out all solid matters by using tweezers, drying the mixed solution in a vacuum drying oven at room temperature to constant weight, and obtaining 9.933mg of disassembled products, wherein the recovery rate is 99.33%.
Example 2
60mg of natural rubber is weighed and cut to about 1mm3Adding 10mL of 2, 6-di-tert-butyl-4-methylphenol toluene solution, wherein the concentration of 2, 6-di-tert-butyl-4-methylphenol is 200ppm, dissolving for 7 days in a dark condition, shaking for 1h every day, and shaking at the rotating speed of 300rpm to obtain a natural rubber solution;
vacuumizing to exhaust air in the device, introducing nitrogen, adding 360mg of methanol solution of sodium methoxide with the concentration of 30 wt.% into the natural rubber solution, carrying out light-shielding reflux reaction for 4 hours at 70 ℃, neutralizing the solution by using the methanol solution of hydrogen chloride after the reaction solution is naturally cooled to room temperature, carrying out rotary evaporation on the neutralized solution until the volume of the neutralized solution is 20mL, adding 160mL of methanol, refrigerating the obtained mixed solution for 16 hours at 8 ℃, taking out all solid matters by using tweezers, drying the mixed solution in a vacuum drying oven at room temperature to constant weight, and obtaining 59.934mg of disassembled products, wherein the recovery rate is 99.89%.
Example 3
100mg of natural rubber is weighed and cut to about 1mm3Adding 10mL of 2, 6-di-tert-butyl-4-methylphenol toluene solution, wherein the concentration of 2, 6-di-tert-butyl-4-methylphenol is 250ppm, dissolving for 7 days in a dark condition, shaking for 0.5h every day, and obtaining natural rubber solution with the shaking rotating speed of 200 rpm;
vacuumizing to exhaust air in the device, introducing nitrogen, adding 400mg of methanol solution of sodium methoxide with the concentration of 50 wt.% into the natural rubber solution, carrying out light-shielding reflux reaction at 85 ℃ for 2 hours, neutralizing the solution by using hydrochloric acid solution after the reaction solution is naturally cooled to room temperature, carrying out rotary evaporation on the neutralized solution until the volume of the neutralized solution is 25mL, adding 125mL of methanol, refrigerating the obtained mixed solution at 10 ℃ for 24 hours, taking out all solid substances by using tweezers, and drying the solid substances in a vacuum drying oven at room temperature to constant weight to obtain 99.87mg of disassembled products, wherein the recovery rate is 99.87%.
The content of macrogel in the disassembled products obtained in examples 1-3 is tested by adopting a method disclosed by ISO 17278, and the disassembled products obtained by testing do not contain macrogel, which indicates that a physical network structure in natural rubber is damaged, and further, a solution used for testing the content of macrogel is filtered by using a polytetrafluoroethylene filter membrane with the pore diameter of 1 mu m, no precipitate is generated on the filter membrane, and the disassembly is complete.
The molecular weight distribution curves of the natural rubber and the disassembled products obtained in examples 1 to 3 were measured by the method of ISO 16564, and the results are shown in FIGS. 1 to 4, in which FIG. 1 is the molecular weight distribution curve of the natural rubber, FIG. 2 is the molecular weight distribution curve of the disassembled product obtained in example 1, FIG. 3 is the molecular weight distribution curve of the disassembled product obtained in example 2, and FIG. 4 is the molecular weight distribution curve of the disassembled product obtained in example 3. As can be seen from FIGS. 1 to 4, the molecular weight distribution curves of the disassembled products obtained in examples 1 to 3 showed significant double peaks, and the recovery rates of the disassembled products obtained in examples 1 to 3 were close to 100%, indicating that the disassembly was complete.
Comparative example 1
Taking 60g of natural latex, adding 1 wt% of dilute ammonia water to dilute the latex until the dry rubber content is 30%, adding 11.3mg of protease and 0.5mL of Rriton X-100, putting the latex into a constant-temperature water bath at 37 ℃ for curing for 16h to obtain deproteinized latex, centrifuging the latex at a rotating speed of 10000r/min for 40min, taking the upper layer of latex to disperse the latex in the dilute ammonia water, adding deionized water to dilute the dry rubber content to about 30%, centrifuging the latex again for 3 times, taking the upper layer of concentrated latex out, putting the latex into an oven and drying the latex at 40 ℃ until the mass is constant, and obtaining the deproteinized natural rubber;
weighing 6g of deproteinized natural rubber, dissolving the deproteinized natural rubber in 400mL of toluene at 40 ℃, adding 6mL of sodium methoxide solution after dissolving, reacting for 6h at 40 ℃, finally adding methanol for precipitation, taking out the precipitate, drying at 40 ℃ until the mass is constant, extracting for 10-24 h with acetone, and drying again at 40 ℃ until the mass is constant to obtain a disassembled product. The calculated recovery rate was 97.88%.
The macrogel content and molecular weight distribution curves of the disassembled sample were obtained by the methods disclosed in ISO 17278 and ISO 16564, respectively, and the distribution curves are shown in fig. 5, in which the dotted line is the molecular weight distribution curve of the disassembled product of example 1, and the solid line is the molecular weight distribution curve of the disassembled product of comparative example 1. The macrogel content was calculated to be 0, and further, the solution used for the macrogel content test was filtered using a polytetrafluoroethylene filter with a pore size of 1 μm, with no precipitate on the filter.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (5)
1. A natural rubber disassembling method is characterized by comprising the following steps:
dissolving natural rubber in an organic solvent to obtain a natural rubber solution;
mixing the natural rubber solution with sodium methoxide under the conditions of protective atmosphere and light protection, then carrying out reflux reaction, neutralizing reaction liquid obtained by the reflux reaction, mixing the reaction liquid with methanol, and refrigerating to finish the disassembly of the natural rubber;
the organic solvent is toluene, tetrahydrofuran or cyclohexane;
the dosage ratio of the natural rubber to the organic solvent is 1-10 mg/mL;
the dissolving is carried out under the condition of keeping out of the sun, the dissolving time is 3-7 days, the vibration is carried out for 0.5-2 hours every day, and the rotating speed of the vibration is 50-300 rpm;
the sodium methoxide is added in the form of a sodium methoxide solution, the mass ratio of the sodium methoxide solution to the natural rubber is 1.5-2: 1, and the concentration of the sodium methoxide solution is 25-50 wt.%;
the temperature of the reflux reaction is 60-85 ℃, and the time is 2-8 h.
2. The disassembling method according to claim 1, wherein the organic solvent contains an antioxidant, the antioxidant is at least one of 2, 6-di-tert-butyl-4-methylphenol, tert-butyl hydroquinone, an anti-aging agent 264, an antioxidant 1010 and an antioxidant 1076, and the concentration of the antioxidant is 50 to 250 ppm.
3. The disassembling method according to claim 1, wherein after the neutralization, the reaction liquid obtained by the neutralization is concentrated and then mixed with methanol, the concentration degree is 1/20-1/5 of the volume of the reaction liquid, and the volume ratio of the concentrated liquid to the methanol is 1: 5-10.
4. The dismantling method according to claim 1, wherein the temperature of the refrigeration is 1-10 ℃ and the time is 16-24 h.
5. The dismantling method according to claim 1, wherein the temperature of the refrigeration is 2 to 10 ℃ and the time is 16 to 24 hours.
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| CN201911022046.2A CN110734508B (en) | 2019-10-25 | 2019-10-25 | Method for disassembling natural rubber |
| AU2020102371A AU2020102371A4 (en) | 2019-10-25 | 2020-09-22 | Method for disintegrating natural rubber |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0584597A1 (en) * | 1992-08-05 | 1994-03-02 | Kao Corporation | Deproteinized natural rubber and process for producing the same |
| CN101240049A (en) * | 2008-03-17 | 2008-08-13 | 中国热带农业科学院农产品加工研究所 | Natural rubber latex imitation composition |
| CN102268106A (en) * | 2011-08-26 | 2011-12-07 | 中国热带农业科学院农产品加工研究所 | Preparation method of high-purity natural rubber |
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2019
- 2019-10-25 CN CN201911022046.2A patent/CN110734508B/en active Active
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- 2020-09-22 AU AU2020102371A patent/AU2020102371A4/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0584597A1 (en) * | 1992-08-05 | 1994-03-02 | Kao Corporation | Deproteinized natural rubber and process for producing the same |
| CN101240049A (en) * | 2008-03-17 | 2008-08-13 | 中国热带农业科学院农产品加工研究所 | Natural rubber latex imitation composition |
| CN102268106A (en) * | 2011-08-26 | 2011-12-07 | 中国热带农业科学院农产品加工研究所 | Preparation method of high-purity natural rubber |
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