CN112142862B - Method for preparing sulfonated cellulose - Google Patents
Method for preparing sulfonated cellulose Download PDFInfo
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Abstract
The invention relates to a preparation method of sulfonated cellulose, which comprises the step of preparing the sulfonated cellulose by the addition reaction of dialdehyde cellulose and a sulfonating agent, wherein the reaction medium of the addition reaction contains ethanol. The invention has the following effects: the method selects the reaction medium containing ethanol for the addition reaction of the dialdehyde cellulose and the sulfonating agent, and can easily separate the sulfonated cellulose from the reaction system even if the highly hydrophilic sulfonated cellulose is prepared by adopting the dialdehyde cellulose with higher aldehyde group content. Furthermore, the inventors have found that sulfonated cellulose is obtained in high yield by using a reaction medium containing ethanol.
Description
Technical Field
The invention relates to the technical field of cellulose modification, in particular to a preparation method of sulfonated cellulose.
Background
Cellulose is oxidized by periodate to generate dialdehyde cellulose which has active aldehyde groups, and carboxyl cellulose, glycol cellulose, ammoniated cellulose and sulfonated cellulose can be generated by modification. The sulfonated cellulose is prepared by addition reaction of bisulfite and dialdehyde cellulose, and sulfonic acid groups are introduced into the carbon at the 2-position and the 3-position of a cellulose glucose unit after sulfonation. The continuous sodium periodate oxidation and sodium bisulfite sulfonation reaction of cellulose is shown as the following formula:
sulfonated cellulose prepared by continuous sodium periodate oxidation and bisulfite sulfonation, the sulfonated cellulose characterized by: (1) the water absorption of the sulfonic acid group is strong, and the water absorption and water retention value of the fiber can be obviously improved by adopting periodate oxidation and bisulfite sulfonation to treat the paper pulp. (2) Sulfonated nano-microfibrillar cellulose (NFC) can be separated by combining continuous periodate oxidation and bisulfite sulfonation with homogenization mechanical treatment, and sulfonated nano-microfibrillar cellulose suspension is stable due to negative charges of sulfonic acid groups and electrostatic repulsion of the negative charges, so that the sulfonated nano-microfibrillar cellulose can be prepared into a film for serving as a packaging material, and can also be prepared into aerogel for oil-water separation. It can also be used as flocculant for inorganic filler particles such as kaolin. (3) Sulfonated cellulose has anticoagulant properties and is used as an immunoadsorbent in the field of biological medicine for extracorporeal blood treatment.
For the convenience of subsequent utilization, after the sulfonated cellulose is produced by the above reaction formula, it is often necessary to separate the sulfonated cellulose from the reaction system. Conventional separation means are for example: dialysis, which typically uses dialysis membranes (e.g., 5000Da or 14000Da), tends to lose low molecular weight sulfonated cellulose, reducing yield, and consumes large amounts of deionized water, which is time and labor intensive. And the part of dissolved sulfonated cellulose can be removed along with the supernatant by centrifugation, so that the yield is low and the energy consumption is high. Ion exchange methods rely on electrostatic removal of only charged ions from reactants and ion exchange resins are expensive. The filtering method saves time and labor, and the equipment has simple structure and easy operation.
However, if the dialdehyde cellulose is sulfonated by bisulfite using water as a reaction medium according to the conventional operation, when the aldehyde group content of the dialdehyde cellulose is high, the sulfonated cellulose is highly hydrophilic due to introduction of sulfonic acid groups into the molecular chain of the cellulose and a large amount of hydroxyl groups in the cellulose. In addition, sulfonated cellulose consists of dissolved sulfonated cellulose and sulfonated nanocrystalline cellulose. The nano microcrystalline cellulose has large specific surface area and contains a large amount of hydroxyl and sulfonic acid group hydrophilic groups, so that the reaction product (sulfonated cellulose suspension) is very difficult to filter water. At this time, even if the sulfonated cellulose can be produced, it is difficult to separate it from the reaction medium (i.e., water) by a conventional separation means. The following phenomena tend to occur during the separation process: no filtrate is filtered out even if medium-speed filter paper is adopted under the vacuum degree of 0.08-0.10MPa, and no filtrate is filtered out by adopting other filter membranes, such as an aqueous mixed fiber microporous filter membrane, an organic nylon microporous filter membrane or a polytetrafluoroethylene microporous filter membrane.
Disclosure of Invention
Based on this, the main object of the present invention is to provide a method for preparing sulfonated cellulose. When the sulfonated cellulose is prepared by the preparation method, even if the dialdehyde cellulose with higher aldehyde group content and the bisulfite are subjected to addition reaction to prepare the sulfonated cellulose, the sulfonated cellulose can be easily separated from a reaction system.
The purpose of the invention is realized by the following technical scheme:
the preparation method of the sulfonated cellulose comprises the step of carrying out addition reaction on dialdehyde cellulose and a sulfonating agent to prepare the sulfonated cellulose, wherein a reaction medium of the addition reaction contains ethanol.
In one embodiment, the reaction medium is ethanol or an aqueous solution of ethanol.
In one embodiment, the reaction medium contains ethanol in an amount not less than 70% by volume.
In one embodiment, the conditions of the addition reaction include: the reaction temperature is 20-30 ℃, and the reaction time is 6-24 h.
In one embodiment, the mass ratio of the dialdehyde cellulose to the sulfonating agent is 1: (1-1.6).
In one embodiment, the sulfonating agent is selected from at least one of bisulfite, metabisulfite, and metabisulfite.
In one embodiment, the preparation method further comprises the step of isolating the sulfonated cellulose.
In one embodiment, the separation is by filtration.
In one embodiment, the filtration membrane used for filtration has a pore size of 0.8-1.2 μm.
In one embodiment, the material of the filter membrane used for filtration is selected from at least one of organic nylon, pyrosulfite and pyrosulfite.
In one embodiment, the preparation method further comprises a step of drying the sulfonated cellulose obtained through the separation.
In one embodiment, the drying is performed by vacuum drying.
In one embodiment, the aldehyde group content of the dialdehyde cellulose is not less than 4.32 mmol/g.
The invention has the following beneficial effects:
the method selects the reaction medium containing ethanol for the addition reaction of the dialdehyde cellulose and the bisulfite, and can easily separate the sulfonated cellulose from the reaction system even if the highly hydrophilic sulfonated cellulose is prepared by adopting the dialdehyde cellulose with higher aldehyde group content. Furthermore, the inventors have found that sulfonated cellulose is obtained in high yield by using a reaction medium containing ethanol.
Drawings
FIG. 1 is a flow diagram of the preparation of sulfonated cellulose;
FIG. 2 is a filter cake-sulfonated cellulose (A), which forms a gel (B) immediately upon addition of water to the filter cake, and which is not sonicated and centrifuged to a 0.2% suspension (C);
FIG. 3 is a sulfonated cellulose suspension (A) at a concentration of about 0.2% after filtration, sonication and centrifugation, exhibiting the Tyndall effect by laser irradiation at 560nm, indicating the presence of nanocrystalline cellulose (B);
FIG. 4 is an infrared spectrum of sulfonated cellulose.
Detailed Description
In order that the invention may be more fully understood, reference will now be made to the following description. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The preparation method of the sulfonated cellulose comprises the step of carrying out addition reaction on dialdehyde cellulose and a sulfonating agent to prepare the sulfonated cellulose, wherein a reaction medium of the addition reaction contains ethanol.
At present, in most cases, when sulfonated cellulose is prepared by addition reaction of dialdehyde cellulose and a sulfonating agent, water is selected as a reaction medium. However, the inventors found that: when water is used as a reaction medium, if the aldehyde group content of the dialdehyde cellulose is low, the correspondingly prepared sulfonated cellulose has no high hydrophilicity, and at the moment, the obtained sulfonated cellulose can be easily separated from the reaction system by a conventional separation method (such as filtration and the like) and can be easily purified for subsequent use. However, if the aldehyde group content of the dialdehyde cellulose is high, the prepared sulfonated cellulose has strong hydrophilicity, and at this time, the highly hydrophilic sulfonated cellulose cannot be separated from the reaction system at all by a conventional separation method (such as filtration, etc.), and purification is difficult to achieve.
The inventors found that, in the course of the preparation of sulfonated cellulose, a transparent sulfonated cellulose suspension produced a white flocculent precipitate after adding ethanol to the sulfonated cellulose suspension, indicating that sulfonated cellulose separated out. This is probably because the polarity of ethanol is low, and according to the principle of similar solubility, the polarity of the mixed solution is reduced with the increase of the dosage of ethanol in the sulfonated cellulose, so that the sulfonated cellulose is precipitated and precipitated, and the more the ethanol content in the mixed solvent is, the more the sulfonated cellulose is precipitated. Based on the discovery, the invention tries to put dialdehyde cellulose and sulfonating agent into a reaction medium containing ethanol for addition reaction, and the generated sulfonated cellulose is easy to separate, thereby overcoming the problem that the sulfonated dialdehyde cellulose is difficult to separate in the reaction medium of water. And moreover, the reaction medium containing ethanol is adopted, so that the yield of the sulfonated cellulose is high. The sulfonated cellulose prepared by the embodiment of the invention is filtered into powder, and the powder is dissolved in water after being filtered, so that the sulfonated cellulose can be prepared into films, hydrogel or aerogel.
Preferably, the reaction medium is ethanol or aqueous ethanol.
Further preferably, the reaction medium is ethanol aqueous solution. The solubility of the sulfonating agent, such as bisulfite, in water is greater than in ethanol, and if water is present in the reaction medium, the dissolution of the sulfonating agent and thus the addition reaction is facilitated. Meanwhile, after the reaction is finished, the sulfonating agent which does not participate in the reaction and other soluble substances in the reaction system are easier to remove along with the filtrate in the subsequent filtering step, and the adoption of the ethanol water solution is also beneficial to improving the purity of the finally obtained sulfonated cellulose.
Preferably, the ethanol aqueous solution contains ethanol with a volume percentage of not less than 70%, for example, 70% (ethanol and water in a volume ratio of 7: 3).
Preferably, the conditions of the addition reaction include: the reaction temperature is 20-30 ℃, and the reaction time is 6-24 h.
Further preferably, the conditions of the addition reaction include: the reaction temperature is 23-28 ℃, and the reaction time is 20-24 h. For example, the reaction may be carried out at ordinary temperature for 24 hours.
Preferably, the mass ratio of the dialdehyde cellulose to the sulfonating agent is 1: (1-1.6). For example, the mass ratio of the dialdehyde cellulose to the sulfonating agent is 1:1, 1:1.6, etc.
It is understood that the sulfonating agents described in the embodiments of the present invention include, but are not limited to, bisulfite, metabisulfite, pyrosulfite, and the like. Wherein: the bisulfite such as sodium bisulfite and the like; pyrosulfite such as sodium pyrosulfite and the like; such as potassium metabisulfite and the like. The following examples illustrate the technical solution of the present invention in detail by using bisulfite, specifically sodium bisulfite.
It is understood that after the addition reaction of dialdehyde cellulose and sulfonating agent is finished, sulfonated cellulose is generated in the whole system, and other substances, including but not limited to impurities, reaction medium, unreacted dialdehyde cellulose or sulfonating agent, exist in the system. For convenience, preferably, the preparation method further comprises a step of separating the sulfonated cellulose.
Preferably, the separation is by filtration. It is understood that filtration herein includes, but is not limited to, suction filtration and the like.
Preferably, the filter membrane used for filtration has a pore size of 1-6.5 μm. The pore size of the filter membrane can be 1 μm, 4.5 μm or 6.5 μm, and the smaller the pore size, the higher the yield of the sulfonated cellulose.
It is understood that the sulfonated cellulose obtained by separation may be purified for subsequent use, and the purification method includes but is not limited to: in the process of separating the sulfonated cellulose, filtering and washing by using a washing solution containing ethanol; or filtering and washing by using a washing solution containing ethanol after the sulfonated cellulose is obtained by separation. The washing liquid containing ethanol adopted by the invention can further separate out the sulfonated cellulose so as to improve the yield, and can also make the impurities dissolved in the sulfonated cellulose flow out along the filtrate so as to play a role in removing the impurities. It is understood that the ethanol content of the ethanol-containing washing solution used in the purification of the embodiment of the present invention is not less than 70% by volume. Preferably, the ethanol-containing washing solution used in the embodiment of the present invention is an ethanol aqueous solution, more preferably an ethanol aqueous solution with ethanol content of not less than 70% by volume, for example, an ethanol aqueous solution with ethanol content of 80% by volume.
It is understood that the material of the filter membrane used for filtration is not particularly limited, and includes, but is not limited to, organic nylon, polytetrafluoroethylene, polyvinylidene fluoride, etc.
Further, the preparation method of the present invention further comprises a step of drying the sulfonated cellulose separated from the reaction system for the purpose of preservation, easy utilization, etc.
Preferably, the drying mode is vacuum drying.
It can be understood that the dialdehyde cellulose described in the embodiment of the invention is prepared by oxidizing cellulose with periodate, and the aldehyde content of the dialdehyde cellulose is different in different conditions in the oxidation reaction.
Preferably, the aldehyde group content of the dialdehyde cellulose is not less than 4.32 mmol/g. The preparation of the dialdehyde cellulose comprises but is not limited to the following steps:
the cellulose and periodate are put in water and hydrochloride environment to generate oxidation reaction.
It can be understood that: the oxidation reaction is carried out in water bath, the temperature of the oxidation reaction is 45-55 ℃, and the time of the oxidation reaction is 2.5-3.5 h. The cellulose species include, but are not limited to, microcrystalline cellulose.
Preferably, the hydrochloride salt includes, but is not limited to, sodium chloride, lithium chloride, calcium chloride, and the like. The following examples illustrate the technical solution of the present invention in detail by selecting sodium chloride.
Preferably, the molar ratio of the periodate to the AGU of the cellulose is 1: (A)0.4-1.2). For example 1:1.
Preferably, the molar ratio of the chloride salt to the AGU of the cellulose is 7:(1-4). Such as 7: 3.
Preferably, after the oxidation reaction is finished, ethylene glycol is further added into the reaction system, and the reaction is continued. Preferably, the reaction is continued for a period of 5 to 30min, for example 10 min.
Example 1
This example provides a method for preparing sulfonated cellulose, the preparation scheme is shown in fig. 1, and the method comprises the following steps:
step one, preparing dialdehyde cellulose.
(1) 4g of microcrystalline cellulose was weighed into a 250ml Erlenmeyer flask, 200ml of distilled water, 5.28g of NaIO were added4(molar ratio NaIO)4AGU 1:1) and 3.364g sodium chloride (molar ratio NaCl: AGU 7:3) and the flask was covered with aluminum foil to prevent photocatalytic decomposition of periodic acidAnd (3) salt.
(2) The reaction was stirred in a water bath at 50 ℃ for 3 hours.
(3) After the reaction, 3ml of ethylene glycol was added and the reaction was continued for 10 min.
(4) Filtering and washing for several times by using deionized water until the conductivity is less than 50 mu S/cm, washing for 2 times by using ethanol, and then drying in vacuum to prepare the oven-dried dialdehyde cellulose.
And step two, preparing sulfonated cellulose.
70ml of ethanol and 30ml of deionized water were transferred to a conical flask (volume ratio of ethanol to deionized water: 7:3), and 0.5g of the oven-dried dialdehyde cellulose prepared in the first step and 0.5g of sodium bisulfite were added (mass ratio of dialdehyde cellulose to sodium bisulfite: 1). After a reaction time of 24 hours under stirring at room temperature, the reaction was terminated.
(2) Then, the mixture is filtered and washed by 400ml of ethanol and deionized water (volume ratio is 80:20) in a rapid filtering device for 4 times, the used filtering material is an organic nylon filtering film with the aperture of 1 mu m, the reaction product is easy to separate, and the filtering liquid is smooth during filtering.
Due to the rapid evaporation of ethanol, the resulting filter cake was a powdered sulfonated cellulose, see fig. 2A. The sulfonated cellulose has strong water absorption, and is added dropwise with deionized water to obtain hydrogel, as shown in FIG. 2B.
When in use: dispersing sulfonated fiber, adding 200ml of water into sulfonated cellulose to obtain transparent suspension, performing ultrasonic treatment on the sulfonated cellulose at an ultrasonic power of 650W, an amplitude of 60% and a frequency of 20-25KHz for 2 seconds every 2 seconds, performing ultrasonic treatment for 5min in total, and performing ultrasonic treatment in an ice bath to prevent the temperature from rising in the ultrasonic process. After ultrasonic treatment, in order to remove impurities such as fiber bundles in the sulfonated cellulose, the suspension is subjected to centrifugal treatment at the rotating speed of 10000rpm for 10 min. After the centrifugation is finished, the supernatant is the prepared sulfonated cellulose, and the lower part is precipitated as fiber bundle impurities. After the supernatant was treated by sonication and centrifugation, the sulfonated cellulose became a clear transparent suspension, and a clear light beam was observed by irradiating the suspension with 560nm laser, as shown in FIG. 3. Indicating that a significant amount of nanocrystalline particles of sulfonated cellulose were present in the suspension. Namely, the sulfonated cellulose suspension consists of sulfonated cellulose molecular chains and sulfonated cellulose nano-microcrystals. The ir spectrum of the sulfonated cellulose also shows the generation of sulfonic acid groups, see fig. 4.
The sulfonation yield is calculated by measuring the concentration of the supernatant. The surface charge density of the sulfonated cellulose was measured to evaluate the sulfonation degree of the sulfonation reaction.
(1) Determination of aldehyde group content of dialdehyde cellulose
According to the literature method, 25mL of 0.25M hydroxylamine hydrochloride was adjusted to pH 3.2 with acetic acid, 100mg (oven dry mass) of undried dialdehyde cellulose was added, and the mixture was stirred at room temperature for 2 hours and filtered. The filtrate was titrated with 0.01M sodium hydroxide solution and the number of volumes of sodium hydroxide solution consumed was recorded at a pH of 3.2. The aldehyde group content (mmol/g) was calculated as follows:
the aldehyde group content is (V multiplied by M)/M; in the formula:
v is the volume of the sodium hydroxide solution used for titrating the dialdehyde cellulose, mL;
m is the molar concentration of sodium hydroxide, 0.01M/L;
m is the oven dry mass of dialdehyde cellulose, g.
(2) Determination of the content of sulfonic acid groups
The sulfonic acid group content was evaluated by using the surface charge density, and the surface charge density of the sulfonated cellulose was measured using a particle charge analyzer (PCD-05travel, Sweden). During the determination, firstly, the suspension of the sulfonated cellulose is diluted by 10 times, 10ml of the diluted suspension is taken to be put into a measuring cell, and then, the diluted suspension is titrated by 0.001N poly dimethyl diallyl ammonium chloride solution (PDADMAC) until the flow potential reaches 0 mV. The PDADMAC volume consumed was recorded. The surface charge density (ueq/g) is:
q ═ Vp × c × 1000/w; in the formula:
q is the surface charge density, ueq/g;
vp is the volume, mL, used to titrate sulfonated cellulose consumed PDADMAC;
c is the concentration of PDADMAC, mol/L;
w is the oven dry mass of the sulfonated cellulose, g.
(3) The yield of the sulfonated cellulose is measured, and the yield (%) of the sulfonated cellulose is as follows:
the yield (%) ═ V × c/m,
wherein V is the volume of the supernatant, mL,
c is the concentration of the supernatant, g/mL,
m is the mass of dialdehyde cellulose, g.
The yield of the sulfonated cellulose obtained under the conditions of this example was 121.8%, and the surface charge density was 0.984 meq/g. The sulfonation is an addition reaction of sodium bisulfite and aldehyde group. The aldehyde group is converted to a hydroxyl group and a sulfonic acid group, and thus, a yield of more than 100% may occur under some reaction conditions.
Example 2
This example is a modification of example 1, and compared with example 1, the modification is only that: in the second step, the ratio (volume ratio) of ethanol to water is 10: 0. specifically, the steps of this embodiment include:
step one, preparing dialdehyde cellulose.
(1) 4g of microcrystalline cellulose are weighed into a 250ml Erlenmeyer flask, 200ml of distilled water and 5.28g of NaIO are added4(molar ratio NaIO)4AGU 1:1) and 3.364g sodium chloride (molar ratio NaCl: AGU 7:3) and the flask was covered with aluminum foil to prevent photocatalytic decomposition of periodate.
(2) The reaction was stirred in a water bath at 50 ℃ for 3 hours.
(3) After the reaction, 3ml of ethylene glycol was added and the reaction was continued for 10 min.
(4) Filtering and washing for several times by using deionized water until the conductivity is less than 50 mu S/cm, washing for 2 times by using ethanol, and then drying in vacuum to prepare the oven-dried dialdehyde cellulose.
And step two, preparing sulfonated cellulose.
(1) 100ml of ethanol was transferred to an Erlenmeyer flask (without water, volume ratio of ethanol to deionized water was 10: 0), and 0.5g of the oven-dried dialdehyde cellulose prepared in the first step and 0.5g of sodium bisulfite were added (mass ratio of dialdehyde cellulose to sodium bisulfite was 1: 1). After a reaction time of 24 hours under stirring at room temperature, the reaction was terminated.
(2) Then, the mixture is filtered and washed by 400ml of ethanol and deionized water (volume ratio is 80:20) in a rapid filtering device for 4 times, the used filtering material is an organic nylon filtering film with the aperture of 1 mu m, the reaction product is easy to wash, and the filtering liquid is smooth during filtering. The remaining subsequent processing steps are also referred to example 1.
Example 3
This example is a modification of example 1, and is modified from example 1 only in that the mass ratio of dialdehyde cellulose to sodium bisulfite in step two is 1: 1.6. Specifically, the steps of this embodiment include:
step one, preparing dialdehyde cellulose.
(1) 4g of microcrystalline cellulose are weighed into a 250ml Erlenmeyer flask, 200ml of distilled water and 5.28g of NaIO are added4(molar ratio NaIO)4AGU 1:1) and 3.364g sodium chloride (molar ratio NaCl: AGU 7:3) and the flask was covered with aluminum foil to prevent photocatalytic decomposition of periodate.
(2) The reaction was stirred in a water bath at 50 ℃ for 3 hours.
(3) After the reaction, 3ml of ethylene glycol was added and the reaction was continued for 10 min.
(4) Filtering and washing for several times by using deionized water until the conductivity is less than 50 mu S/cm, washing for 2 times by using ethanol, and then drying in vacuum to prepare the oven-dried dialdehyde cellulose.
And step two, preparing sulfonated cellulose.
(1) 70ml of ethanol and 30ml of deionized water were transferred to an Erlenmeyer flask (volume ratio of ethanol to deionized water: 7:3), and 0.5g of the oven-dried dialdehyde cellulose prepared in the first step and 0.8g of sodium bisulfite were added (mass ratio of dialdehyde cellulose to sodium bisulfite: 1.6). After a reaction time of 24 hours under stirring at room temperature, the reaction was terminated.
(2) Then, the mixture is filtered and washed by 400ml of ethanol and deionized water (volume ratio is 80:20) in a rapid filtering device for 4 times, the used filtering material is an organic nylon filtering film with the aperture of 1 mu m, the reaction product is easy to wash, and the filtering liquid is smooth during filtering. The remaining subsequent processing steps are also referred to example 1.
Example 4
This example is a modification of example 1, and is modified only in that the sulfonation reaction time in step two is 12 hours, as compared with example 1. Specifically, the present embodiment includes the following steps:
step one, preparing dialdehyde cellulose.
(1) 4g of microcrystalline cellulose was weighed into a 250ml Erlenmeyer flask, 200ml of distilled water, 5.28g of NaIO were added4(molar ratio NaIO)4AGU 1:1) and 3.364g sodium chloride (molar ratio NaCl: AGU 7:3) and the flask was covered with aluminum foil to prevent photocatalytic decomposition of periodate.
(2) The reaction was stirred in a water bath at 50 ℃ for 3 hours.
(3) After the reaction, 3ml of ethylene glycol was added and the reaction was continued for 10 min.
(4) Filtering and washing for several times by using deionized water until the conductivity is less than 50 mu S/cm, washing for 2 times by using ethanol, and then drying in vacuum to prepare the oven-dried dialdehyde cellulose.
And step two, preparing sulfonated cellulose.
(1) 70ml of ethanol and 30ml of deionized water were transferred to a conical flask (volume ratio of ethanol to deionized water: 7:3), and 0.5g of the oven-dried dialdehyde cellulose prepared in the first step and 0.5g of sodium bisulfite were added (mass ratio of dialdehyde cellulose to sodium bisulfite: 1). After a reaction time of 12 hours with stirring at room temperature, the reaction was terminated.
(2) Then, the mixture is filtered and washed by 400ml of ethanol and deionized water (volume ratio is 80:20) in a rapid filtering device for 4 times, the used filtering material is an organic nylon filtering film with the aperture of 1 mu m, the reaction product is easy to wash, and the filtering liquid is smooth during filtering. The remaining subsequent processing steps are also referred to example 1.
The reaction conditions and test results of the above examples 1 to 4 are shown in Table 1.
TABLE 1 reaction conditions, reaction yields and charge densities of sulfonated cellulose
Example 5
This example is a modification of example 1, and compared with example 1, the modification is only to prepare dialdehyde cellulose having aldehyde group content of 6mmol/g with reference to the first step. Procedure for preparation of sulfonated cellulose reference is made to procedure two of example 1.
As a result: the product obtained by the addition reaction has smooth filtrate flow during filtration, and the sulfonated cellulose is easy to separate, and the yield is 112.4 percent.
Example 6
This example is a modification of example 1, and compared with example 1, the modification is only to prepare dialdehyde cellulose having aldehyde group content of 8mmol/g with reference to the first step. Procedure for preparation of sulfonated cellulose reference is made to procedure two of example 1.
As a result: the product obtained by the addition reaction has smooth filtrate when being filtered, and the sulfonated cellulose is easy to separate, and the yield is 106.3 percent.
Example 7
This example is a variation of example 1, compared to example 1, only in that in step two, the volume ratio of ethanol to water in the reaction medium is 8: 2.
as a result: the product obtained by the addition reaction has smooth filtrate flow during filtration, and the sulfonated cellulose is easy to separate, and the yield is 113.5 percent.
Example 8
This example is a variation of example 1, compared to example 1, only in that in step two, the volume ratio of ethanol to water in the reaction medium is 1:1.
as a result: the addition reaction has the filtrate exudation under the vacuum degree of-0.08 MPa, but the filtration speed is slow, and the sulfonated cellulose is not easy to purify.
Comparative example 1
This comparative example is that of example 1, compared to example 1 only in that the sulfonation reaction medium is pure water. As a result, the aqueous suspension of the sulfonated cellulose as a reaction product was not filtered, and no filtrate was leaked out at a vacuum degree of 0.08 to 0.1 MPa.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (11)
1. The preparation method of the sulfonated cellulose is characterized by comprising the step of carrying out addition reaction on dialdehyde cellulose and a sulfonating agent to prepare the sulfonated cellulose, wherein a reaction medium of the addition reaction is ethanol or an ethanol aqueous solution with the volume percentage content of the ethanol not less than 70%.
2. The method for preparing sulfonated cellulose according to claim 1, wherein the conditions of the addition reaction include: the reaction temperature is 20-30 ℃, and the reaction time is 6-24 h.
3. The method for preparing sulfonated cellulose according to claim 1, wherein the mass ratio of the dialdehyde cellulose to the sulfonating agent is 1: (1-1.6).
4. The method for producing the sulfonated cellulose according to any one of claims 1 to 3, wherein the sulfonating agent is at least one selected from the group consisting of a bisulfite and a metabisulfite.
5. The method for preparing sulfonated cellulose according to any one of claims 1 to 3, further comprising a step of isolating sulfonated cellulose.
6. The method of claim 5, wherein the separation is by filtration.
7. The method for preparing sulfonated cellulose according to claim 6, wherein the filtration membrane used for filtration has a pore size of 1 to 6.5 μm.
8. The method for preparing sulfonated cellulose according to claim 6, wherein the material of the filter membrane used for filtration is at least one selected from the group consisting of organic nylon, polytetrafluoroethylene and polyvinylidene fluoride.
9. The method of claim 5, further comprising drying the sulfonated cellulose obtained by the separation.
10. The method for preparing sulfonated cellulose according to claim 9, wherein the drying is performed by vacuum drying.
11. The method for producing the sulfonated cellulose according to any one of claims 1 to 3 and 6 to 10, wherein the aldehyde group content of the dialdehyde cellulose is not less than 4.32 mmol/g.
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| CN113087924B (en) * | 2021-04-13 | 2022-04-05 | 华纺股份有限公司 | Method for preparing nano cellulose suspension by low-temperature hydrothermal method |
| CN114874342A (en) * | 2022-05-20 | 2022-08-09 | 齐鲁工业大学 | Preparation method and asymmetric catalytic hydrogenation application of DAC-BINAP (DAC-BINAP) bio-based chiral ligand |
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