CN110818839A - Method for preparing super absorbent resin by using waste corn straws - Google Patents
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Abstract
The invention is suitable for the technical field of water-absorbent resin preparation, and provides a method for preparing super water-absorbent resin by using waste corn straws, wherein the waste corn straws are used as raw materials, carboxymethyl cellulose straw powder with a certain degree of substitution is prepared after alkalization and etherification treatment, and then the carboxymethyl cellulose straw powder is dissolved and mixed with acrylic acid, sodium hydroxide, an initiator and a cross-linking agent to prepare the super water-absorbent resin; the initiator is a mixture of potassium persulfate and sodium bisulfite. Therefore, the invention can reasonably utilize the waste corn straws, reduce the raw material cost, reduce the reaction temperature, improve the product quality of the super absorbent resin, save the heat energy and have wider application range.
Description
Technical Field
The invention relates to the technical field of preparation of water-absorbent resin, in particular to a method for preparing high water-absorbent resin by using waste corn straws.
Background
According to statistics, the yield of agricultural straws is 9 hundred million tons every year in China, the processing by-products are only 5.8 hundred million tons, the utilization rate of the processing by-products is lower than 40 percent, most agricultural waste plant fibers are randomly stacked, burned and buried, fibers in wastes are not reasonably utilized, a large amount of waste of resources is caused, and environmental problems are also caused. If the waste plant straws are deeply processed into the super absorbent resin with the water retention and absorption functions, the resource waste and the environmental problem can be greatly reduced.
The high water absorption resin is a novel functional high molecular compound which has high molecular weight, low crosslinking degree and is insoluble in water, and usually adopts hydrophilic monomers containing carboxyl, hydroxyl, amino or amido and the like to carry out chemical reactions such as polymerization, crosslinking and the like under the action of an initiator and a crosslinking agent to form a three-dimensional network polymer which is insoluble in water but can be highly swelled in water. The super absorbent resin has the capability of absorbing hundreds of times or even thousands of times of water by self weight, has good stability to heat, light, acid and alkali, has high water absorption rate and good water retention performance, and is difficult to separate water out even if pressurized. With the rapid development of economy, the improvement of the quality of life of people and the enhancement of environmental awareness, the application range of the super absorbent resin is continuously expanded, the market demand is increasing day by day, and the super absorbent resin is widely applied to the fields of industrial production, agricultural production, food processing, medical treatment and health, daily chemical industry, environmental protection and the like.
The patent with publication number CN109456451A discloses a corn straw-based super absorbent resin, which is prepared from the following raw materials, wherein the corn straw accounts for 20-35 parts; 100 parts of acrylic acid; 0.01-0.05 part of a crosslinking agent; 0.45-1.65 parts of an initiator; wherein, the initiator comprises a single photoinitiator or a mixed initiator consisting of the photoinitiator and a thermal initiator. Although the patent technology fully utilizes the corn straw resource, the water absorption capacity of the prepared water-absorbent resin is still relatively low by using the photoinitiator or the mixed initiator consisting of the photoinitiator and the thermal initiator.
In addition, the temperature of the initiator used in the prior art for preparing the super absorbent resin generally reaches 60-70 ℃, the heat energy demand ratio is increased, and the cost is relatively high.
In view of the above, the prior art is obviously inconvenient and disadvantageous in practical use, and needs to be improved.
Disclosure of Invention
Aiming at the defects, the invention aims to provide a method for preparing super absorbent resin by using waste corn straws, which can reasonably use the waste corn straws, reduce the raw material cost, reduce the reaction temperature, improve the product quality of the super absorbent resin, save heat energy and have a wider application range.
In order to achieve the purpose, the invention provides a method for preparing super absorbent resin by using waste corn straws, which comprises the following steps:
step one, preparing carboxymethyl corn straw fiber
A1, crushing waste corn straws, and grinding the waste corn straws into particles to obtain particles;
a2, dissolving a sodium hydroxide solid in deionized water to prepare a sodium hydroxide solution with the mass fraction of 15-25%;
a3, soaking the particles in the deionized water to obtain a material I; slowly dripping the sodium hydroxide solution into the first material for continuous soaking to obtain a second material;
continuously and slowly dripping the sodium hydroxide solution into the material II to perform alkalization treatment to obtain a material III;
a4, dissolving chloroacetic acid solid in the deionized water to prepare a chloroacetic acid solution with the mass fraction of 15-25%;
a5, slowly adding the chloroacetic acid solution into the material III to carry out etherification reaction to obtain a material IV;
a6, drying the material IV, taking out and crushing to obtain a material V;
a7 washing the material five with 95% ethanol to obtain pure carboxymethyl corn stalk fiber powder;
step two preparation of super absorbent resin
B1, pouring acrylic acid into a neutral alumina chromatographic column to remove a polymerization inhibitor, and then slowly dropwise adding the sodium hydroxide solution into the acrylic acid to perform a neutralization reaction to obtain an intermediate product I;
b2, dissolving and mixing the carboxymethyl corn straw fiber powder, the intermediate product I, the initiator and the cross-linking agent by using the deionized water to obtain an intermediate product II; the initiator is a mixture of potassium persulfate and sodium bisulfite;
b3, filling nitrogen into the intermediate product II, slowly heating the intermediate product II in a water bath, continuing to heat after water is boiled, reacting the intermediate product II in the boiling water bath for 1.5-2.5h, and stopping introducing the nitrogen to obtain an intermediate product III;
b4 cooling the intermediate product III to room temperature, cutting into small pieces, drying and crushing to obtain the super absorbent resin.
According to the method for preparing the super absorbent resin by using the waste corn stalks, the mass ratio of the carboxymethyl corn stalk fiber powder, the intermediate product I, the potassium persulfate, the sodium bisulfite, the cross-linking agent and the total deionized water of the system is 1: 3-23: 0.04-0.36: 0.04-0.21: 0.018-0.042: 45-85.
According to the method for preparing the super absorbent resin by using the waste corn stalks, the mass ratio of the carboxymethyl corn stalk fiber powder, the intermediate product I, the potassium persulfate, the sodium bisulfite, the cross-linking agent and the total deionized water of the system is 1: 9-18.5: 0.08-0.20: 0.08-0.16: 0.02-0.035: 60-80.
According to the method for preparing the super absorbent resin by using the waste corn straws, the total deionized water of the system comprises the steps of preparing the sodium hydroxide solution, preparing the chloroacetic acid solution, and dissolving the carboxymethyl corn straw fiber powder, the intermediate product I, the initiator and the deionized water required by the cross-linking agent.
According to the method for preparing the super absorbent resin by using the waste corn straws, the cross-linking agent is N, N-methylene bisacrylamide.
According to the method for preparing the super absorbent resin by using the waste corn stalks, in the first step, the mass ratio of the particles to the sodium hydroxide solid and the chloroacetic acid solid is 1: 0.2-0.7: 0.4 to 0.7.
According to the method for preparing the super absorbent resin by using the waste corn stalks, in the step B2, in the process of dissolving and mixing the carboxymethyl corn stalk fiber powder, the intermediate product I, the initiator and the cross-linking agent by using the deionized water, the reaction temperature is 25-45 ℃.
According to the method for preparing the super absorbent resin by using the waste corn stalks, in the step B1, the mass ratio of the acrylic acid to the sodium hydroxide solid in the sodium hydroxide solution is 3-23: 1 to 7.
According to the method for preparing the super absorbent resin by using the waste corn stalks, the maximum substitution degree of hydrogen on hydroxyl on a glucose residue in the carboxymethyl corn stalk fiber powder by carboxymethyl is 0.36.
According to the method for preparing the super absorbent resin by using the waste corn straws, the water absorption rate of the super absorbent resin is 2100-2350 g/g.
The invention aims to provide a method for preparing super absorbent resin by using waste corn straws, which takes the waste corn straws as raw materials, has low cost, prepares carboxymethyl cellulose straw powder with certain degree of substitution after alkalization and etherification treatment of the raw materials, and the carboxymethyl corn straw fiber has better solubility and can be dissolved in cold water, thereby avoiding the complex step of starch gelatinization when starch is used as the raw material in the traditional preparation of the super absorbent resin, leading the synthesis process to be simple and greatly reducing the synthesis cost; then, the high-water-absorption resin is dissolved and mixed with acrylic acid, sodium hydroxide, an initiator and a cross-linking agent to prepare the high-water-absorption resin, wherein the high-water-absorption resin has a high water absorption rate which can reach 2100-2350 g/g; the initiator used in the invention is a redox initiator formed by potassium persulfate and sodium bisulfite, which can obviously reduce the reaction temperature, save heat energy, prevent implosion in the polymerization process and improve the quality of the water-absorbent resin; meanwhile, the reaction is mild, the requirement on production equipment is reduced, and the cost is saved. In conclusion, the beneficial effects of the invention are as follows: the waste corn straws are reasonably utilized, the raw material cost is reduced, the reaction temperature is reduced, the product quality of the super absorbent resin is improved, meanwhile, the heat energy can be saved, and the application range is wide.
Drawings
FIG. 1 is a graph showing the effect of the degree of neutralization of acrylic acid on the water absorption of a super absorbent resin;
FIG. 2 is a graph showing the effect of the amount of the crosslinking agent on the water absorption of the super absorbent resin;
FIG. 3 is a graph showing the effect of the amount of initiator on the water absorption of a super absorbent resin;
FIG. 4 is a graph showing the effect of the water content of the system on the water absorption of a super absorbent resin.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a method for preparing super absorbent resin by using waste corn straws, which comprises the following steps:
step one, preparing carboxymethyl corn straw fiber
A1 smashing the waste corn straws, and grinding the smashed waste corn straws into particles with the particle size of 100-200 meshes to obtain particles.
A2 sodium hydroxide solid is dissolved in deionized water to prepare a sodium hydroxide solution with the mass fraction of 15-25%.
A3, soaking the particles in deionized water for 0.5-1 h to fully swell and extend cellulose chains in the particles to obtain a first material; slowly dropwise adding the sodium hydroxide solution into the first material for continuously soaking for 1.5-2 hours to obtain a second material; in the process of dropwise adding the sodium hydroxide solution, stirring is carried out while dropwise adding, so that the local temperature is prevented from being overhigh; dripping sodium hydroxide solution to continue soaking to promote the swelling of the cellulose chain;
continuously and slowly dripping the sodium hydroxide solution into the material II to perform alkalization treatment to obtain a material III; the temperature of the alkalization treatment is 30-35 ℃, and the time is 1.5-2.5 h; the alkalization treatment activates the hydroxyl groups on the glucose residues on the cellulose chain.
The inventor proves through multiple tests that if the concentration of the sodium hydroxide solution in the first material at the early stage is too high, side reaction is generated, and the etherification reaction at the later stage is influenced; in the invention, the sodium hydroxide solution is dripped in two steps, so that the etherification reaction can be promoted.
A4 dissolving chloroacetic acid solid in deionized water to prepare a chloroacetic acid solution with a mass fraction of 15-25%.
And A5, slowly adding the chloroacetic acid solution into the material III to perform etherification reaction, wherein the time of the etherification reaction is 1.5-2 h, the temperature of the etherification reaction is 70-80 ℃, and the material IV is obtained after the reaction is completed.
A6, drying the material IV in an oven at 70-80 ℃, taking out after 48-60 hours, crushing, grinding, and sieving with a 100-200-mesh sieve to obtain a material V. And the material V is a mixture of carboxymethyl corn straw fiber powder, sodium hydroxide solid and sodium chloride solid.
A7 washing the material V with 95% ethanol for 2-3 times, and then filtering to remove sodium hydroxide solids and sodium chloride solids in the material V to obtain pure carboxymethyl corn straw fiber powder.
In the first step, the mass ratio of the particles to the sodium hydroxide solid to the chloroacetic acid solid is 1: 0.2-0.7: 0.4 to 0.7; the preferable mass ratio is 1: 0.3-0.5: 0.5 to 0.6. The maximum substitution degree of the hydrogen on the hydroxyl on the glucose residue in the obtained carboxymethyl corn straw fiber powder by the carboxymethyl is 0.36.
Step two preparation of super absorbent resin
B1, pouring acrylic acid into a neutral alumina chromatographic column to remove polymerization inhibitors such as benzoquinone and the like, and then slowly dropwise adding the sodium hydroxide solution into the acrylic acid for neutralization reaction to obtain an intermediate product I; the neutralization reaction is carried out in a cold water bath to prevent the acrylic acid from polymerizing into small molecules to generate oligomer.
In the above step, the mass ratio of acrylic acid to sodium hydroxide solid in the sodium hydroxide solution is 3-23: 1-7; the intermediate product I is a mixture of acrylic acid solution and sodium acrylate solution; the acrylic acid is neutralized into sodium acrylate, so that the solubility of the acrylic acid in the reaction can be improved, and meanwhile, as the acrylic acid has stronger volatility, the reaction for preparing the water-absorbent resin is exothermic, the volatilization of the acrylic acid can be promoted, so that the utilization rate of the acrylic acid is low, the production cost is high, the environment is polluted, the volatility is reduced after the acrylic acid is neutralized into the sodium acrylate, the utilization rate of the acrylic acid is improved, the production cost is reduced, and the environmental pollution is reduced.
And B2, dissolving and mixing the carboxymethyl corn straw fiber powder, the intermediate product I, the initiator and the cross-linking agent by using deionized water, and stirring at room temperature for 1.5-3 hours to fully and uniformly mix the materials to obtain an intermediate product II.
B3, filling nitrogen into the intermediate product II, heating slowly in a water bath, stirring while heating, stopping stirring when the temperature reaches 30-45 ℃, gradually raising the temperature of the water bath, continuing heating after water boils, enabling the intermediate product II to react in the boiling water bath for 1.5-2.5h, removing water in the intermediate product II, and stopping introducing nitrogen to obtain an intermediate product III; the intermediate product III is in a gel state.
B4 cooling the intermediate product III to room temperature, cutting into small pieces, drying in an oven at 50-70 ℃ for 36-48 h to constant weight, and crushing to obtain the super absorbent resin.
In the invention, the initiator is a mixture of potassium persulfate and sodium bisulfite, and the mass ratio of the carboxymethyl corn straw fiber powder, the intermediate product I, the potassium persulfate, the sodium bisulfite, the cross-linking agent and the total deionized water of the system is 1: 3-23: 0.04-0.36: 0.04-0.21: 0.018-0.042: 45-85 parts; the preferable mass ratio is 1: 9-18.5: 0.08-0.20: 0.08-0.16: 0.02-0.035: 60-80. The total deionized water of the system comprises deionized water required for preparing a sodium hydroxide solution, preparing a chloroacetic acid solution and dissolving carboxymethyl corn straw fiber powder, an intermediate product I, an initiator and a cross-linking agent. The cross-linking agent is N, N-methylene bisacrylamide.
The inventor proves through multiple tests that the potassium persulfate is used as the initiator alone, the reaction temperature is higher than 70 ℃, the potassium persulfate and the urea are used as the initiator, the reaction temperature is higher than 55 ℃, the potassium persulfate and the sodium sulfite are used as the initiator, the reaction temperature is higher than 50 ℃, the potassium persulfate and the vitamin are used as the initiator, and the reaction temperature is about 60 ℃; the initiator used in the invention is a redox initiator formed by potassium persulfate and sodium bisulfite, so that the reaction temperature can be obviously reduced, generally 25-45 ℃, the heat energy demand is low, and the production cost can be reduced; meanwhile, the low reaction temperature can prevent the polymerization reaction between cellulose chains from imploding, and the quality of the prepared super absorbent resin is improved; in addition, the initiator used in the invention can make the reaction stable, the controllability of the cellulose chain polymerization reaction is good, and the molecular weight range of the prepared super absorbent resin is relatively uniform.
According to the invention, 1g of super absorbent resin is prepared, and when the water absorption capacity of the super absorbent resin is maximum, the dosage of each reagent is 55-63% of acrylic acid neutralization degree, 118-125 mg of initiator, 35-43 mg of N, N-methylene bisacrylamide and 67-75 ml of deionized water (see figure 1, figure 2, figure 3 and figure 4). Because the contents of cellulose, hemicellulose and lignin in different raw materials or substances are different, in the process of preparing the super absorbent resin, the dosage of reagents such as acrylic acid, an initiator (potassium persulfate and sodium bisulfite), a cross-linking agent (N, N-methylene bisacrylamide), deionized water and the like is different, and the difference of the water absorption capacity of the prepared super absorbent resin is very large due to the dosage difference of the reagents; therefore, in the invention patent publication No. CN104072669B, potassium persulfate and sodium bisulfite are used as the initiator, but the amounts of potassium persulfate, sodium bisulfite and other agents are different depending on the cellulose raw material, and the amounts of these agents cause a large difference in the amount of water absorbed by the super absorbent resin.
According to the curve shown in FIG. 3, the mass ratio of potassium persulfate to sodium bisulfite in the initiator is 1: 0.80.
The super absorbent resin prepared by utilizing the waste corn straws is mainly applied to agriculture, forestry and flower industry, can be used for water and soil conservation, changes the granular structure of soil, increases the water permeability and the air permeability of the soil, and can also be used for water conservation and desert control of the soil in arid regions.
In order to verify the water absorption performance of the super absorbent resin of the present invention, the present invention is provided with the following examples.
Example one
Step one, preparing carboxymethyl corn straw fiber
A1 waste corn stalks are crushed and ground into particles to obtain the particles.
A2 sodium hydroxide solid is dissolved in deionized water to prepare sodium hydroxide solution with mass fraction of 16%.
A3, soaking the particles in the deionized water to obtain a material I; slowly dripping the sodium hydroxide solution into the first material for continuous soaking to obtain a second material;
and continuously and slowly dripping the sodium hydroxide solution into the material II to perform alkalization treatment to obtain a material III.
A4 chloroacetic acid solid is dissolved in the deionized water to prepare 16% chloroacetic acid solution by mass fraction.
And A5, slowly adding the chloroacetic acid solution into the material III to carry out etherification reaction to obtain a material IV.
And A6, drying the material IV, taking out and crushing to obtain a material V.
A7 washing the material five with 95% ethanol to obtain pure carboxymethyl corn stalk fiber powder.
The mass ratio of the particles to the sodium hydroxide solid to the chloroacetic acid solid is 1: 0.3: 0.4.
step two preparation of super absorbent resin
B1, pouring acrylic acid into a neutral alumina chromatographic column to remove a polymerization inhibitor, and then slowly dropwise adding the sodium hydroxide solution into the acrylic acid to perform a neutralization reaction to obtain an intermediate product I; the mass ratio of the acrylic acid to the sodium hydroxide solid in the sodium hydroxide solution is 5: 1.
b2, dissolving and mixing the carboxymethyl corn straw fiber powder, the intermediate product I, the initiator and the cross-linking agent by using the deionized water to obtain an intermediate product II; the initiator is a mixture of potassium persulfate and sodium bisulfite; the mass ratio of the carboxymethyl corn straw fiber powder to the intermediate product I to the total deionized water is 1: 4: 0.04: 0.05: 0.018: 50.
b3, filling nitrogen into the intermediate product II, slowly heating the intermediate product II in a water bath, continuing to heat after the water is boiled, reacting the intermediate product II in the boiling water bath for 1.5h, and stopping introducing the nitrogen to obtain an intermediate product III.
B4 cooling the intermediate product III to room temperature, cutting into small pieces, drying and crushing to obtain the super absorbent resin.
The water absorption of the super absorbent resin prepared by the above steps was 2135 g/g.
Example two
Step one, preparing carboxymethyl corn straw fiber
A1 waste corn stalks are crushed and ground into particles to obtain the particles.
A2 sodium hydroxide solid is dissolved in deionized water to prepare sodium hydroxide solution with mass fraction of 20%.
A3, soaking the particles in the deionized water to obtain a material I; slowly dripping the sodium hydroxide solution into the first material for continuous soaking to obtain a second material;
and continuously and slowly dripping the sodium hydroxide solution into the material II to perform alkalization treatment to obtain a material III.
A4 chloroacetic acid solid is dissolved in the deionized water to prepare 20% chloroacetic acid solution by mass fraction.
And A5, slowly adding the chloroacetic acid solution into the material III to carry out etherification reaction to obtain a material IV.
And A6, drying the material IV, taking out and crushing to obtain a material V.
A7 washing the material five with 95% ethanol to obtain pure carboxymethyl corn stalk fiber powder.
The mass ratio of the particles to the sodium hydroxide solid to the chloroacetic acid solid is 1: 0.4: 0.6.
step two preparation of super absorbent resin
B1, pouring acrylic acid into a neutral alumina chromatographic column to remove a polymerization inhibitor, and then slowly dropwise adding the sodium hydroxide solution into the acrylic acid to perform a neutralization reaction to obtain an intermediate product I; the mass ratio of the acrylic acid to the sodium hydroxide solid in the sodium hydroxide solution is 19: 5.
b2, dissolving and mixing the carboxymethyl corn straw fiber powder, the intermediate product I, the initiator and the cross-linking agent by using the deionized water to obtain an intermediate product II; the initiator is a mixture of potassium persulfate and sodium bisulfite; the mass ratio of the carboxymethyl corn straw fiber powder to the intermediate product I to the total deionized water is 1: 18: 0.21: 0.15: 0.022: 62.
b3, filling nitrogen into the intermediate product II, slowly heating the intermediate product II in a water bath, continuing to heat after the water is boiled, reacting the intermediate product II in the boiling water bath for 2 hours, and stopping introducing the nitrogen to obtain an intermediate product III.
B4 cooling the intermediate product III to room temperature, cutting into small pieces, drying and crushing to obtain the super absorbent resin.
The water absorption rate of the super absorbent resin prepared by the steps is 2283 g/g.
EXAMPLE III
Step one, preparing carboxymethyl corn straw fiber
A1 waste corn stalks are crushed and ground into particles to obtain the particles.
A2 sodium hydroxide solid is dissolved in deionized water to prepare sodium hydroxide solution with mass fraction of 24%.
A3, soaking the particles in the deionized water to obtain a material I; slowly dripping the sodium hydroxide solution into the first material for continuous soaking to obtain a second material;
and continuously and slowly dripping the sodium hydroxide solution into the material II to perform alkalization treatment to obtain a material III.
A4 chloroacetic acid solid is dissolved in the deionized water to prepare a 24% chloroacetic acid solution by mass fraction.
And A5, slowly adding the chloroacetic acid solution into the material III to carry out etherification reaction to obtain a material IV.
And A6, drying the material IV, taking out and crushing to obtain a material V.
A7 washing the material five with 95% ethanol to obtain pure carboxymethyl corn stalk fiber powder.
The mass ratio of the particles to the sodium hydroxide solid to the chloroacetic acid solid is 1: 0.7: 0.7.
step two preparation of super absorbent resin
B1, pouring acrylic acid into a neutral alumina chromatographic column to remove a polymerization inhibitor, and then slowly dropwise adding the sodium hydroxide solution into the acrylic acid to perform a neutralization reaction to obtain an intermediate product I; the mass ratio of the acrylic acid to the sodium hydroxide solid in the sodium hydroxide solution is 20: 7.
b2, dissolving and mixing the carboxymethyl corn straw fiber powder, the intermediate product I, the initiator and the cross-linking agent by using the deionized water to obtain an intermediate product II; the initiator is a mixture of potassium persulfate and sodium bisulfite; the mass ratio of the carboxymethyl corn straw fiber powder to the intermediate product I to the total deionized water is 1: 22: 0.35: 0.21: 0.04: 80.
b3, filling nitrogen into the intermediate product II, slowly heating the intermediate product II in a water bath, continuing to heat after the water is boiled, reacting the intermediate product II in the boiling water bath for 2.5h, and stopping introducing the nitrogen to obtain an intermediate product III.
B4 cooling the intermediate product III to room temperature, cutting into small pieces, drying and crushing to obtain the super absorbent resin.
The water absorption rate of the super absorbent resin prepared by the steps is 2350 g/g.
In conclusion, the waste corn straws are used as the raw material, the cost is low, the carboxymethyl cellulose straw powder with a certain degree of substitution is prepared after alkalization and etherification treatment of the raw material, the carboxymethyl corn straw fiber has better solubility and can be dissolved in cold water, the complex step of starch gelatinization when starch is used as the raw material in the traditional preparation of the super absorbent resin is omitted, the synthesis process is simple, and the synthesis cost is greatly reduced; then, the high-water-absorption resin is dissolved and mixed with acrylic acid, sodium hydroxide, an initiator and a cross-linking agent to prepare the high-water-absorption resin, wherein the high-water-absorption resin has a high water absorption rate which can reach 2100-2350 g/g; the initiator used in the invention is a redox initiator formed by potassium persulfate and sodium bisulfite, which can obviously reduce the reaction temperature, save heat energy, prevent implosion in the polymerization process and improve the quality of the water-absorbent resin; meanwhile, the reaction is mild, the requirement on production equipment is reduced, and the cost is saved. In conclusion, the beneficial effects of the invention are as follows: the waste corn straws are reasonably utilized, the raw material cost is reduced, the reaction temperature is reduced, the product quality of the super absorbent resin is improved, meanwhile, the heat energy can be saved, and the application range is wide.
The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it should be understood that various changes and modifications can be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method for preparing super absorbent resin by using waste corn straws is characterized by comprising the following steps:
step one, preparing carboxymethyl corn straw fiber
A1, crushing waste corn straws, and grinding the waste corn straws into particles to obtain particles;
a2, dissolving a sodium hydroxide solid in deionized water to prepare a sodium hydroxide solution with the mass fraction of 15-25%;
a3, soaking the particles in the deionized water to obtain a material I; slowly dripping the sodium hydroxide solution into the first material for continuous soaking to obtain a second material;
continuously and slowly dripping the sodium hydroxide solution into the material II to perform alkalization treatment to obtain a material III;
a4, dissolving chloroacetic acid solid in the deionized water to prepare a chloroacetic acid solution with the mass fraction of 15-25%;
a5, slowly adding the chloroacetic acid solution into the material III to carry out etherification reaction to obtain a material IV;
a6, drying the material IV, taking out and crushing to obtain a material V;
a7 washing the material five with 95% ethanol to obtain pure carboxymethyl corn stalk fiber powder;
step two preparation of super absorbent resin
B1, pouring acrylic acid into a neutral alumina chromatographic column to remove a polymerization inhibitor, and then slowly dropwise adding the sodium hydroxide solution into the acrylic acid to perform a neutralization reaction to obtain an intermediate product I;
b2, dissolving and mixing the carboxymethyl corn straw fiber powder, the intermediate product I, the initiator and the cross-linking agent by using the deionized water to obtain an intermediate product II; the initiator is a mixture of potassium persulfate and sodium bisulfite;
b3, filling nitrogen into the intermediate product II, slowly heating the intermediate product II in a water bath, continuing to heat after water is boiled, reacting the intermediate product II in the boiling water bath for 1.5-2.5h, and stopping introducing the nitrogen to obtain an intermediate product III;
b4 cooling the intermediate product III to room temperature, cutting into small pieces, drying and crushing to obtain the super absorbent resin.
2. The method for preparing the super absorbent resin by using the waste corn stalks according to claim 1, wherein the mass ratio of the carboxymethyl corn stalk fiber powder, the intermediate product I, the potassium persulfate, the sodium bisulfite, the cross-linking agent and the total deionized water in the system is 1: 3-23: 0.04-0.36: 0.04-0.21: 0.018-0.042: 45-85.
3. The method for preparing the super absorbent resin by using the waste corn stalks as claimed in claim 2, wherein the mass ratio of the carboxymethyl corn stalk fiber powder, the intermediate product I, the potassium persulfate, the sodium bisulfite, the cross-linking agent and the total deionized water of the system is 1: 9-18.5: 0.08-0.20: 0.08-0.16: 0.02-0.035: 60-80.
4. The method for preparing super absorbent resin from waste corn stover according to claim 3, wherein the total deionized water in the system comprises the sodium hydroxide solution, the chloroacetic acid solution, and deionized water required for dissolving the carboxymethyl corn stover fiber powder, the first intermediate product, the initiator, and the crosslinking agent.
5. The method for preparing the super absorbent resin by using the waste corn stalks as claimed in claim 2, wherein the cross-linking agent is N, N-methylenebisacrylamide.
6. The method for preparing the super absorbent resin by using the waste corn stalks as claimed in claim 5, wherein in the first step, the mass ratio of the particles to the sodium hydroxide solid and the chloroacetic acid solid is 1: 0.2-0.7: 0.4 to 0.7.
7. The method for preparing super absorbent resin from waste corn stalks according to claim 5, wherein in the step B2, the reaction temperature is 25-45 ℃ in the process of dissolving and mixing the carboxymethyl corn stalk fiber powder, the intermediate product I, the initiator and the cross-linking agent by using the deionized water.
8. The method for preparing super absorbent resin from waste corn stalks according to claim 5, wherein in the step B1, the mass ratio of the acrylic acid to the sodium hydroxide solid in the sodium hydroxide solution is 3-23: 1 to 7.
9. The method for preparing super absorbent resin using waste corn stover according to claim 5, wherein the maximum degree of substitution of the carboxymethyl group for the hydrogen on the hydroxyl group on the glucose residue in the carboxymethyl corn stover fiber powder is 0.36.
10. The method for preparing the super absorbent resin from the waste corn stalks according to any one of claims 1 to 9, wherein the water absorption rate of the super absorbent resin is 2100 to 2350 g/g.
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