CN107722337B - Preparation method of cellulose-based foaming buffer packaging material in BmimCl/LiOH system - Google Patents
Preparation method of cellulose-based foaming buffer packaging material in BmimCl/LiOH system Download PDFInfo
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- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
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- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
- C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
- C08J3/075—Macromolecular gels
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
- C08J3/09—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids
- C08J3/091—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in organic liquids characterised by the chemical constitution of the organic liquid
- C08J3/096—Nitrogen containing compounds
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- C08J2201/00—Foams characterised by the foaming process
- C08J2201/04—Foams characterised by the foaming process characterised by the elimination of a liquid or solid component, e.g. precipitation, leaching out, evaporation
- C08J2201/048—Elimination of a frozen liquid phase
- C08J2201/0484—Elimination of a frozen liquid phase the liquid phase being aqueous
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- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/04—Oxycellulose; Hydrocellulose
Abstract
The invention belongs to the technical field of cellulose materials, and relates to a preparation method of a cellulose-based foaming buffer packaging material in a BmimCl/LiOH system. The method comprises the following steps: vacuum drying microcrystalline cellulose; taking a mixed solution of chlorinated-1-butyl-3-methylimidazole and a lithium hydroxide solution as a solvent, adding dry microcrystalline cellulose, and uniformly mixing; introducing protective gas to perform anti-oxidation decomposition treatment; stirring and heating to obtain a microcrystalline cellulose solution; dropping the mixture into water by a ball dropping method to prepare cellulose hydrogel; washing the cellulose hydrogel by a gradient washing method; vacuum freeze drying to obtain porous cellulose base foaming buffer packaging material; and filtering the residual solvent to remove impurities, performing rotary evaporation, and recovering the ionic liquid. The cellulose packaging material prepared by the invention is biodegradable and is an environment-friendly packaging material. Simplifies the preparation process of the cellulose-based foaming buffer packaging material, does not add chemical additives, and has the advantages of environmental protection and no pollution.
Description
Technical Field
The invention belongs to the technical field of cellulose materials, and relates to a preparation method of a cellulose-based foaming buffer packaging material in a BmimCl/LiOH system.
Background
With the rise and development of the packaging industry, the packaging material with the buffering and shockproof functions is subjected to foam plastics, pulp molding materials and plant fiber foaming packaging materials in sequence. The foamed plastic has the advantages of light weight, easy processing, good protective performance, wide applicability, low cost and the like, but the foamed plastic is difficult to recycle after being discarded, pollutes the environment by burning and has poor environmental protection performance. With the gradual recognition of the low-carbon economy and green packaging concepts, the development technology of environment-friendly packaging materials is increasingly emphasized.
Cellulose is a cheap renewable polymer resource generated by photosynthesis in the nature, has high yield, can be repeatedly used, is easy to degrade after being used without causing pollution problem, and can realize recycling. The cellulose fiber buffer packaging material has 100 percent of biodegradability and environment harmony, can be completely degraded and rotted, can be used as fertilizer when entering the soil, and completely overcomes the defects of chemical engineering foamed plastics.
However, the existing cellulose-based foaming material has a complex manufacturing process, and a large amount of chemical additives are added in the manufacturing process, so that the cellulose-based foaming material discharges some harmful gases in the production and use processes, and the environment pollution is caused; in addition, a plurality of wastes are generated in the traditional production process, the production cost is high, and the treatment process is complex.
Disclosure of Invention
A preparation method of a porous cellulose-based foaming buffer packaging material comprises the following steps:
(1) and (3) vacuum drying: vacuum drying the microcrystalline cellulose;
(2) mixing treatment: taking a mixed solution of 1-butyl-3-methylimidazole chloride and 10% lithium hydroxide solution as a solvent, adding the dried microcrystalline cellulose prepared in the step (1), and uniformly mixing to obtain a mixed solution a;
(3) protection treatment: introducing protective gas into the mixed solution a prepared in the step (2) to perform anti-oxidation decomposition treatment to obtain a mixed solution b;
(4) and (3) heat treatment: stirring and heating the mixed solution b in the step (3) to obtain a microcrystalline cellulose solution c;
(5) and (3) regeneration reaction: dripping the microcrystalline cellulose solution c prepared in the step (4) into water by a falling ball method to prepare cellulose hydrogel d;
(6) cleaning: washing residual solvent in the cellulose hydrogel d prepared in the step (5) by using a gradient washing method to obtain pure cellulose hydrogel e;
(7) and (3) freeze drying: and (4) carrying out vacuum freeze drying on the pure cellulose hydrogel e prepared in the step (6) to obtain the porous cellulose-based foaming and buffering packaging material f.
Preferably, the temperature of vacuum drying in the step (1) is 45-50 ℃, and the vacuum drying time is 24-36 h.
Preferably, in the step (2), the mass fraction of the 1-butyl-3-methylimidazole chloride in the solvent is 97.5-99%, and the mass fraction of the added microcrystalline cellulose in the mixed solution a is 3-10%.
Preferably, the protective gas in the step (3) is nitrogen.
Preferably, the heating temperature in the step (4) is 80-120 ℃, the stirring speed is 300-800 rpm, and the stirring heating time is 20-120 min.
Preferably, the gradient washing method in the step (6) comprises the following steps: firstly, washing for 4-6 h by using a mixed solution of chlorinated-1-butyl-3-methylimidazole and a lithium hydroxide solution in a mass ratio of 3: 1; then, washing for 2-3h by using a mixed solution of 1:1 mass ratio of chlorinated-1-butyl-3-methylimidazole and lithium hydroxide solution; then, washing for 1h by using a mixed solution of 1-butyl-3-methylimidazole chloride and lithium hydroxide solution in a mass ratio of 1: 3; finally, pure water is used for replacing for 3 times, and each time lasts for 1 hour.
Preferably, the temperature of the vacuum freeze drying in the step (7) is-55 ℃ to-45 ℃ and the time is 24-48 h.
Preferably, the method also comprises an ionic liquid recovery step, wherein the process comprises the steps of filtering the residual solvent to remove impurities and carrying out rotary evaporation; the temperature of the rotary evaporation is 99 ℃, and the rotating speed is 120-240 rpm.
Compared with the prior art, the invention has the advantages and positive effects that:
1. the cellulose hydrogel prepared by the invention is prepared by slowly replacing and washing a cellulose solution in an anti-solvent system, and regenerating cellulose in the anti-solvent system to obtain a complex space three-dimensional cellulose network structure with abundant cross-linking and crossing. The cellulose itself has good strength and rigidity, so that the cellulose molecules cross-linked with each other can absorb a large amount of impact and vibration generated by the package. The cellulose is a renewable and degradable natural polymer material, namely the obtained porous cellulose packaging material has 100 percent of biodegradability and is a real environment-friendly packaging material.
2. The invention uses the mixed solution of the chloride-1-butyl-3-methylimidazole ionic liquid and the lithium hydroxide solution with the mass fraction of 10 percent as a dissolving system, uses cellulose as a raw material to prepare the porous buffer packaging material, simplifies the preparation process of the cellulose-based foam buffer packaging material, does not add chemical additives, has excellent performance of the obtained product, does not need the investment of special equipment, and can recycle the ionic liquid for reuse, thereby having the advantages of environmental protection and no pollution.
Detailed Description
In order that the above objects, features and advantages of the present invention may be more clearly understood, the present invention will be further described with reference to specific embodiments. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and thus the present invention is not limited to the specific embodiments of the present disclosure.
In the following examples, the lithium hydroxide solutions used in examples 1 to 5 each had a lithium hydroxide mass fraction of 10%, unless otherwise specified.
Example 1: the embodiment provides a preparation method of a porous cellulose-based foaming and buffering packaging material, which comprises the following specific steps:
(1) and (3) vacuum drying: vacuum drying microcrystalline cellulose at 45 deg.C for 36 hr;
(2) mixing treatment: mixing chlorinated-1-butyl-3-methylimidazole with LiOH solution to prepare a solvent, wherein the mass fraction of the chlorinated-1-butyl-3-methylimidazole in the solvent is 97.5%, and then adding vacuum-dried microcrystalline cellulose into the solvent to obtain a mixed solution, wherein the mass fraction of the microcrystalline cellulose in the mixed solution is 5%;
(3) protection treatment: before the mixed solution is subjected to heat treatment, nitrogen is introduced into the mixed solution for protection, so that cellulose is prevented from being oxidized during the heat treatment;
(4) and (3) heat treatment: placing the mixed solution obtained after the mixing treatment in the step (2) and the protection of nitrogen introduced in the step (3) in a heat preservation device at 80 ℃, and carrying out isolated water treatment for 120 min at the stirring speed of 300 rpm;
(5) and (3) regeneration reaction: dropping the cellulose solution obtained after the heat treatment in the step (4) into purified water by using a ball dropping method, wherein the water temperature is 15 ℃, the temperature of the cellulose solution is 80 ℃, the dropping height is 10 cm, the dropping speed is 3mL/min, and washing out the ionic liquid in the mixed solution by using the principle of an anti-solvent to obtain cellulose hydrogel;
(6) fully cleaning: the method comprises the following steps of replacing ionic liquid and LiOH in a cellulose-based material by utilizing gradient washing, firstly washing for 4-6 hours by utilizing a mixed solution of chlorinated-1-butyl-3-methylimidazole and LiOH solution in a mass ratio of 3: 1; after substitution balance, washing for 2-3h by using a mixed solution of 1:1 mass ratio of 1-butyl-3-methylimidazole chloride and LiOH solution, and after substitution balance, washing for 1h by using a mixed solution of 1:3 mass ratio of 1:3 chloridized-1-butyl-3-methylimidazole and LiOH solution; finally, pure water is used for replacing for 3 times, and each time is 1 hour, so that pure cellulose hydrogel is obtained;
(7) and (3) freeze drying: carrying out vacuum freeze drying on the fully substituted cellulose hydrogel at the temperature of minus 55 ℃ for 24 hours to obtain a final product, namely a porous cellulose buffer packaging product;
(8) and (3) recovering the ionic liquid: filtering and removing impurities from a mixed solution of ionic liquid and water, putting the mixed solution into a rotary evaporator, setting the temperature at 99 ℃ and the rotation speed at 120 rpm until no liquid drops drop in a condensation reflux device, taking out the obtained ionic liquid, cooling to room temperature, and transferring the ionic liquid into a conical flask for recycling.
The porous cellulose cushioning packaging material prepared by the embodiment utilizes a gradient solvent substitution process to enable dissolved cellulose molecules to perform a regeneration reaction under a mild condition, so that the cellulose molecules are arranged more orderly, and have abundant pore structures which are uniformly distributed to form a three-dimensional network gap structure. The three-dimensional network gap structure can better absorb the packing materials in transitShock and vibration during transportation. And the density of the obtained product is 0.035 g/cm3And the compressive strength thereof was measured to be 25N. The ionic liquid used in the experiment can be recycled, and the cellulose buffering packaging material can be completely and naturally degraded in the natural environment and cannot generate any pollutant.
Example 2: the embodiment provides a preparation method of a porous cellulose-based foaming and buffering packaging material, which comprises the following specific steps:
(1) and (3) vacuum drying: vacuum drying microcrystalline cellulose at 45 deg.C for 36 hr;
(2) mixing treatment: mixing chlorinated-1-butyl-3-methylimidazole with LiOH solution to prepare a solvent, wherein the mass fraction of the chlorinated-1-butyl-3-methylimidazole in the solvent is 97.5%, and then adding vacuum-dried microcrystalline cellulose into the solvent to obtain a mixed solution, wherein the mass fraction of the microcrystalline cellulose in the mixed solution is 10%;
(3) protection treatment: before the mixed solution is subjected to heat treatment, nitrogen is introduced into the mixed solution for protection, so that the cellulose is prevented from being oxidized during the heat treatment.
(4) And (3) heat treatment: placing the mixed solution obtained after the mixing treatment in the step (2) and the protection of nitrogen introduced in the step (3) in a heat preservation device at 120 ℃, insulating water for treatment for 60 min, and stirring at 480 rpm;
(5) and (3) regeneration reaction: and (3) dripping the cellulose solution obtained after the heat treatment in the step (4) into purified water by using a falling ball method, wherein the water temperature is 15 ℃, the temperature of the cellulose solution is 110 ℃, the dripping height is 15 cm, the dripping speed is 2mL/min, and the ionic liquid in the mixed solution is washed out by using the principle of an anti-solvent to obtain the cellulose hydrogel.
(6) Fully cleaning: the method comprises the following steps of replacing ionic liquid and LiOH in a cellulose-based material by utilizing gradient washing, firstly washing for 4-6 hours by utilizing a mixed solution of chlorinated-1-butyl-3-methylimidazole and LiOH solution in a mass ratio of 3: 1; after substitution balance, washing for 2-3h by using a mixed solution of 1:1 mass ratio of 1-butyl-3-methylimidazole chloride and LiOH solution, and after substitution balance, washing for 1h by using a mixed solution of 1:3 mass ratio of 1:3 chloridized-1-butyl-3-methylimidazole and LiOH solution; finally, pure water is used for replacing for 3 times, and each time is 1 hour, so that pure cellulose hydrogel is obtained;
(7) and (3) freeze drying: carrying out vacuum freeze drying on the fully substituted cellulose hydrogel at the temperature of minus 50 ℃ for 24 hours to obtain a final product, namely a porous cellulose buffer packaging product;
(8) and (3) recovering the ionic liquid: filtering and removing impurities from a mixed solution of ionic liquid and water, putting the mixed solution into a rotary evaporator, setting the temperature at 99 ℃ and the rotation speed at 120 rpm until no liquid drops drop in a condensation reflux device, taking out the obtained ionic liquid, cooling to room temperature, and transferring the ionic liquid into a conical flask for recycling.
The porous cellulose buffering packaging material prepared by the embodiment can be dissolved in the mixed solution of the ionic liquid and the lithium salt only in a short time at a high temperature, and the obtained porous cellulose buffering packaging material has rich pore structures and uniform distribution of cut pore structures, forms a three-dimensional network pore structure and can better absorb shock. And the density of the obtained product is 0.075 g/cm3And the compressive strength thereof was measured to be 45N. The ionic liquid used in the experiment can be recycled, and the cellulose buffering packaging material can be completely degraded in the natural environment and cannot generate any pollutant.
Example 3: the embodiment provides a preparation method of a porous cellulose-based foaming and buffering packaging material, which comprises the following specific steps:
(1) and (3) vacuum drying: vacuum drying microcrystalline cellulose at 45 deg.C for 36 hr;
(2) mixing treatment: mixing chlorinated-1-butyl-3-methylimidazole and LiOH solution to prepare a solvent, wherein the mass fraction of the chlorinated-1-butyl-3-methylimidazole in the solvent is 99%, and then adding vacuum-dried microcrystalline cellulose into the solvent to obtain a mixed solution, wherein the mass fraction of the microcrystalline cellulose in the mixed solution is 7%;
(3) protection treatment: before the mixed solution is subjected to heat treatment, nitrogen is introduced into the mixed solution for protection, so that the cellulose is prevented from being oxidized during the heat treatment.
(4) And (3) heat treatment: placing the mixed solution obtained after the mixing treatment in the step (2) and the protection of nitrogen introduced in the step (3) in a heat preservation device at 100 ℃, insulating water for treatment for 60 min, and stirring at 600 rpm;
(5) and (3) regeneration reaction: and (3) dripping the cellulose solution obtained after the heat treatment in the step (4) into purified water by using a falling ball method, wherein the water temperature is 15 ℃, the temperature of the cellulose solution is 100 ℃, the dripping height is 10 cm, the dripping speed is 3mL/min, and the ionic liquid in the mixed solution is washed out by using the principle of an anti-solvent to obtain the cellulose hydrogel.
(6) Fully cleaning: the method comprises the following steps of replacing ionic liquid and LiOH in a cellulose-based material by utilizing gradient washing, firstly washing for 4-6 hours by utilizing a mixed solution of chlorinated-1-butyl-3-methylimidazole and LiOH solution in a mass ratio of 3: 1; after substitution balance, washing for 2-3h by using a mixed solution of 1:1 mass ratio of 1-butyl-3-methylimidazole chloride and LiOH solution, and after substitution balance, washing for 1h by using a mixed solution of 1:3 mass ratio of 1:3 chloridized-1-butyl-3-methylimidazole and LiOH solution; finally, pure water is used for replacing for 3 times, and each time is 1 hour, so that pure cellulose hydrogel is obtained;
(7) and (3) freeze drying: carrying out vacuum freeze drying on the fully substituted cellulose hydrogel at the temperature of minus 45 ℃ for 24 hours to obtain a final product, namely a porous cellulose buffer packaging product;
(8) and (3) recovering the ionic liquid: filtering and removing impurities from a mixed solution of ionic liquid and water, putting the mixed solution into a rotary evaporator, setting the temperature at 99 ℃ and the rotation speed at 120 rpm until no liquid drops drop in a condensation reflux device, taking out the obtained ionic liquid, cooling to room temperature, and transferring the ionic liquid into a conical flask for recycling.
The porous cellulose cushioning packaging material prepared by the embodiment has the advantages that the heat treatment time is prolonged along with the increase of the content of cellulose, the size of the pore structure of the prepared porous cellulose cushioning packaging material is reduced by 5%, and the cellulose inside the porous cellulose cushioning packaging material is formed by cross-linkingThe skeleton structure of (a) can be further enhanced, and the density of the skeleton structure can be improved to a certain extent, and is 0.05 g/cm3The pore structure is distributed uniformly to form a three-dimensional network pore structure, the compressive strength of the three-dimensional network pore structure is increased from 25N to 36N, the compressive and impact resistance of the three-dimensional network pore structure is obviously improved, and the pressure and the vibration of the packing material caused by the vibration in the transportation process can be better absorbed. The ionic liquid used in the experiment can be recycled, and the cellulose buffering packaging material can be completely degraded in the natural environment and cannot generate any pollutant.
Example 4: the embodiment provides a preparation method of a porous cellulose-based foaming and buffering packaging material, which comprises the following specific steps:
(1) and (3) vacuum drying: vacuum drying microcrystalline cellulose at 45 deg.C for 36 hr;
(2) mixing treatment: mixing chlorinated-1-butyl-3-methylimidazole with LiOH solution to prepare a solvent, wherein the mass fraction of the chlorinated-1-butyl-3-methylimidazole in the solvent is 98%, and then adding vacuum-dried microcrystalline cellulose into the solvent to obtain a mixed solution, wherein the mass fraction of the microcrystalline cellulose in the mixed solution is 8%;
(3) protection treatment: before the mixed solution is subjected to heat treatment, nitrogen is introduced into the mixed solution for protection, so that the cellulose is prevented from being oxidized during the heat treatment.
(4) And (3) heat treatment: placing the mixed solution obtained after the mixing treatment in the step (2) and the protection of nitrogen introduced in the step (3) in a heat preservation device at 90 ℃, insulating water for treatment for 120 min, and stirring at 480 rpm;
(5) and (3) regeneration reaction: and (3) dripping the cellulose solution obtained after the heat treatment in the step (4) into purified water by using a falling ball method, wherein the water temperature is 15 ℃, the temperature of the cellulose solution is 90 ℃, the dripping height is 15 cm, the dripping speed is 2mL/min, and the ionic liquid in the mixed solution is washed out by using the principle of an anti-solvent to obtain the cellulose hydrogel.
(6) Fully cleaning: the method comprises the following steps of replacing ionic liquid and LiOH in a cellulose-based material by utilizing gradient washing, firstly washing for 4-6 hours by utilizing a mixed solution of chlorinated-1-butyl-3-methylimidazole and LiOH solution in a mass ratio of 3: 1; after substitution balance, washing for 2-3h by using a mixed solution of 1:1 mass ratio of 1-butyl-3-methylimidazole chloride and LiOH solution, and after substitution balance, washing for 1h by using a mixed solution of 1:3 mass ratio of 1:3 chloridized-1-butyl-3-methylimidazole and LiOH solution; finally, pure water is used for replacing for 3 times, and each time is 1 hour, so that pure cellulose hydrogel is obtained;
(7) and (3) freeze drying: carrying out vacuum freeze drying on the fully substituted cellulose hydrogel at-48 ℃ for 48 hours to obtain a final product, namely a porous cellulose buffer packaging product;
(8) and (3) recovering the ionic liquid: filtering and removing impurities from a mixed solution of ionic liquid and water, putting the mixed solution into a rotary evaporator, setting the temperature at 99 ℃ and the rotation speed at 120 rpm until no liquid drops drop in a condensation reflux device, taking out the obtained ionic liquid, cooling to room temperature, and transferring the ionic liquid into a conical flask for recycling.
The porous cellulose cushioning packaging material prepared by the embodiment has the advantages that the heat treatment time is prolonged along with the increase of the content of cellulose, the size of the internal pore structure of the prepared porous cellulose cushioning packaging material is slightly reduced, the density is improved to 0.06 g/cm3However, the pore structure is uniformly distributed to form a three-dimensional network pore structure, the compressive strength of the three-dimensional network pore structure is obviously greatly improved by 5 percent and is almost doubled from 25N to 40N, and the three-dimensional network pore structure can better absorb shock. The ionic liquid used in the experiment can be recycled, and the cellulose buffering packaging material can be completely degraded in the natural environment and cannot generate any pollutant.
Example 5: the embodiment provides a preparation method of a porous cellulose-based foaming and buffering packaging material, which comprises the following specific steps:
(1) and (3) vacuum drying: vacuum drying microcrystalline cellulose at 45 deg.C for 36 hr;
(2) recovery and reuse of the solution: taking the ionic liquid recovered by rotary volatilization, and then preparing a new mixed solvent with 10% LiOH solution again.
(3) Mixing treatment: adding the microcrystalline cellulose subjected to vacuum drying into a mixed solution of 98% of chlorinated-1-butyl-3-methylimidazole and 2% of 10% of LiOH to obtain a mixed solution, wherein the mass fraction of the microcrystalline cellulose in the mixed solution is 8%;
(4) protection treatment: before the mixed solution is subjected to heat treatment, nitrogen is introduced into the mixed solution for protection, so that the cellulose is prevented from being oxidized during the heat treatment.
(5) And (3) heat treatment: placing the mixed solution obtained after the mixing treatment in the step (2) in a heat preservation device at 100 ℃, insulating water for treatment for 120 min, and stirring at 480 rpm;
(6) and (3) regeneration reaction: and (3) dripping the cellulose solution obtained after the heat treatment in the step (4) into purified water by using a falling ball method, wherein the water temperature is 15 ℃, the temperature of the cellulose solution is 100 ℃, the dripping height is 15 cm, the dripping speed is 2mL/min, and the ionic liquid in the mixed solution is washed out by using the principle of an anti-solvent to obtain the cellulose hydrogel.
(7) Fully cleaning: the method comprises the following steps of replacing ionic liquid and LiOH in a cellulose-based material by utilizing gradient washing, firstly washing for 4-6 hours by utilizing a mixed solution of chlorinated-1-butyl-3-methylimidazole and LiOH solution in a mass ratio of 3: 1; after substitution balance, washing for 2-3h by using a mixed solution of 1:1 mass ratio of 1-butyl-3-methylimidazole chloride and LiOH solution, and after substitution balance, washing for 1h by using a mixed solution of 1:3 mass ratio of 1:3 chloridized-1-butyl-3-methylimidazole and LiOH solution; finally, pure water is used for replacing for 3 times, and each time is 1 hour, so that pure cellulose hydrogel is obtained;
(8) and (3) freeze drying: carrying out vacuum freeze drying on the fully substituted cellulose hydrogel at the temperature of-52 ℃ for 48 hours to obtain a final product, namely a porous cellulose buffer packaging product;
(9) and (3) recovering the ionic liquid: filtering and removing impurities from a mixed solution of ionic liquid and water, putting the mixed solution into a rotary evaporator, setting the temperature at 99 ℃ and the rotation speed at 120 rpm until no liquid drops drop in a condensation reflux device, taking out the obtained ionic liquid, cooling to room temperature, and transferring the ionic liquid into a conical flask for recycling.
The present example is a porous cellulose cushioning packaging material prepared using a recovered ionic liquid, and it can be found from experimental results that the recovered ionic liquid and ionic liquid have no effect on dissolution of cellulose, and thus cellulose can be dissolved in a short time. The prepared porous cellulose buffer packaging material has the density of 0.05 g/cm3The pore structure is distributed uniformly to form a three-dimensional network pore structure, the compressive strength of the three-dimensional network pore structure is 36N, the three-dimensional network pore structure is consistent with the quality of a product prepared by common ionic liquid, and the three-dimensional network pore structure can better absorb the pressure and the vibration of a packing material caused by the vibration of the packing material in the transportation process.
The biodegradation study was performed on the porous cellulose-based foamed cushioning packaging materials prepared in examples 1-5, with the following steps:
(1) and (3) vacuum drying: the porous cellulose buffer packaging product is heated to a constant weight at 105 ℃.
(2) Mixing treatment: 0.05 mol/L citric acid buffer (pH = 4.8) was added to the cellulose at a solid-to-liquid ratio of 1/20(w/V), and the mixture was placed in a water bath shaker at a temperature of 50 ℃ and a rotation speed of 150 r/min for reaction.
(3) And (3) enzymolysis treatment: and adding 40 FPU/g cellulase into the sample reaction device, and carrying out shaking treatment in a constant-temperature water bath for 24 hours.
(4) And (3) inactivation treatment of cellulase: sampling, placing in boiling water, heating for 10 min, and inactivating enzyme.
(5) And (4) analyzing results: filtering the solution after enzyme deactivation through a filter membrane of 0.22 mu m, taking supernatant to perform constant volume in a volumetric flask of 100 ml, and detecting by an ion chromatograph to obtain the glucose release amount of the enzymolysis reaction so as to obtain the degradation rate.
TABLE 1 results of performance tests of porous cellulose cushioning packaging materials prepared in examples 1-5
From the test results, it can be seen that the prepared porous cellulose buffer packaging materials are subjected to enzymolysis, which confirms that the porous cellulose buffer packaging materials prepared in examples 1-5 can be completely biodegraded. The enzymolysis data can be obtained, the yield of glucose released by product enzymolysis reaches about 97.5%, and the cellulose can be proved to be completely dissolved, so that the porous cellulose buffer packaging material can be completely biodegraded. The porous cellulose buffer packaging material also has good physical properties, and the recycled ionic liquid and the ionic liquid have no influence on cellulose dissolution, so that the cellulose can be dissolved in a short time. The prepared porous cellulose buffer packaging material has uniform density and pore structure distribution, forms a three-dimensional network pore structure, has high compressive strength, is consistent with the product quality obtained by preparing common ionic liquid, and can better absorb the pressure and vibration of the packaging material caused by vibration during the transportation of the packaging material.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention in other forms, and any person skilled in the art may apply the above technical details to other fields by using the equivalent embodiments with equivalent variations or modifications, which may be changed or modified by the above technical details disclosed, but any simple modification, equivalent variation and modification made to the above embodiments according to the technical details of the present invention still fall within the protection scope of the technical solution of the present invention.
Claims (8)
1. The preparation method of the porous cellulose-based foaming buffering packaging material is characterized by comprising the following steps of:
(1) and (3) vacuum drying: vacuum drying the microcrystalline cellulose;
(2) mixing treatment: taking a mixed solution of 1-butyl-3-methylimidazole chloride and 10% lithium hydroxide solution as a solvent, adding the dried microcrystalline cellulose prepared in the step (1), and uniformly mixing to obtain a mixed solution a;
(3) protection treatment: introducing protective gas into the mixed solution a prepared in the step (2) to perform anti-oxidation decomposition treatment to obtain a mixed solution b;
(4) and (3) heat treatment: stirring and heating the mixed solution b in the step (3) to obtain a microcrystalline cellulose solution c;
(5) and (3) regeneration reaction: dripping the microcrystalline cellulose solution c prepared in the step (4) into water by a falling ball method to prepare cellulose hydrogel d;
(6) cleaning: washing residual solvent in the cellulose hydrogel d prepared in the step (5) by using a gradient washing method to obtain pure cellulose hydrogel e;
(7) and (3) freeze drying: and (4) carrying out vacuum freeze drying on the pure cellulose hydrogel e prepared in the step (6) to obtain the porous cellulose-based foaming and buffering packaging material f.
2. The method for preparing the porous cellulose-based foaming cushioning packaging material according to claim 1, wherein the temperature of the vacuum drying in the step (1) is 45-50 ℃ and the vacuum drying time is 24-36 h.
3. The method for preparing the porous cellulose-based foaming cushioning packaging material according to claim 1, wherein the mass fraction of the 1-butyl-3-methylimidazole chloride in the solvent in the step (2) is 97.5 to 99%, and the mass fraction of the added microcrystalline cellulose in the mixed solution a is 3 to 10%.
4. The method for preparing the porous cellulose-based foaming cushioning packaging material according to claim 1, wherein the shielding gas in the step (3) is nitrogen.
5. The method for preparing the porous cellulose-based foaming cushioning packaging material according to claim 1, wherein the heating temperature in the step (4) is 80-120 ℃, the stirring speed is 300-800 rpm, and the stirring heating time is 20-120 min.
6. The method for preparing the porous cellulose-based foaming cushioning packaging material according to claim 1, wherein the gradient washing method in the step (6) comprises the steps of: firstly, washing for 4-6 h by using a mixed solution of chlorinated-1-butyl-3-methylimidazole and a lithium hydroxide solution in a mass ratio of 3: 1; then, washing for 2-3h by using a mixed solution of 1:1 mass ratio of chlorinated-1-butyl-3-methylimidazole and lithium hydroxide solution; then, washing for 1h by using a mixed solution of 1-butyl-3-methylimidazole chloride and lithium hydroxide solution in a mass ratio of 1: 3; finally, pure water is used for replacing for 3 times, and each time lasts for 1 hour.
7. The method for preparing the porous cellulose-based foaming cushioning packaging material according to claim 1, wherein the temperature of the vacuum freeze-drying in the step (7) is from-55 ℃ to-45 ℃ and the time is from 24 to 48 hours.
8. The preparation method of the porous cellulose-based foaming cushioning packaging material according to claim 1, further comprising a ionic liquid recovery step, wherein the process comprises the steps of filtering the residual solvent to remove impurities and performing rotary evaporation; the temperature of the rotary evaporation is 99 ℃, and the rotating speed is 120-240 rpm.
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| CN103205015A (en) * | 2012-01-17 | 2013-07-17 | 中国科学院化学研究所 | Transparent and flexible cellulose aerogel and preparation method thereof |
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