Method for preparing regenerated cellulose / chitosan composite fiber / membrane by dissolving regenerated cellulose / chitosan with ionic liquid

Abstract

The invention provides a method for preparing regenerated cellulose / chitosan composite fibers / membranes by dissolving regenerated cellulose / chitosan with ionic liquid, and belongs to the technical field of regenerated cellulose / chitosan composite membranes. The preparation method comprises the following steps: (1) mixing an ionic liquid and an organic solvent according to a certain proportion to form a cosolvent, and dissolving regenerated cellulose and chitosan; (2) carrying out vacuum defoaming on the dissolved regenerated cellulose / chitosan-ionic liquid solution, filtering, and preparing regenerated cellulose / chitosan composite fibers by adopting a dry-jet wet spinning process, or preparing a regenerated cellulose / chitosan composite membrane by adopting a tape casting method; the process is simple, operation is convenient, the solvent is novel, rapid dissolution of regenerated cellulose / chitosan can be achieved, and the prepared regenerated cellulose / chitosan composite fiber / membrane has the excellent characteristics of cellulose and chitosan.

Description

Technical Field

[0001] The present invention relates to the technical field of regenerated cellulose / chitosan composite membranes, and particularly relates to a method for preparing regenerated cellulose / chitosan composite fibers / membranes by dissolving regenerated cellulose / chitosan in ionic liquids. Background Art

[0002] In recent years, with the increasing depletion of non-renewable fossil resources such as fossil fuels, it is an inevitable trend for the industrial development to replace petroleum-based polymers with abundant bio-based polymers in nature. Cellulose is widely used in low-value fields such as papermaking, textiles, and packaging due to its good renewable, degradable, and low-cost properties. With the progress of technology and the change of market demand, people pay more and more attention to the high-value utilization of cellulose. In the future, cellulose will be more widely used in high-end fields such as biomedicine, functional foods, and bioenergy. Chitosan, as the second most abundant natural polymer after cellulose, has a chemical structure similar to cellulose and is widely used in high-end fields such as medicine and cosmetics. However, chitosan materials have problems such as poor stability, easy deliquescence, and poor mechanical properties, which limit their application in some fields. If the preparation of cellulose / chitosan composites can be realized, it can not only promote the high-value application of cellulose, but also improve the problems of poor stability and poor mechanical properties of chitosan materials.

[0003] However, the complex hydrogen bond network existing in cellulose / chitosan molecules makes it difficult to dissolve in water and most organic solvents, which greatly limits the application of cellulose / chitosan. Traditional cellulose / chitosan dissolution methods include acid-base systems, organic solvent systems (N-methylmorpholine-N-oxide (NMMO) aqueous system), salt solvent systems (LiCl / DMAC), NaOH / urea systems, ultrasonic systems, etc. Among them, the NMMO aqueous system is prone to oxidation side reactions during dissolution and has poor thermal stability, with an explosion risk; the LiCl in the LiCl / DMAC system is expensive and difficult to recycle and reuse; the NaOH / urea system has high energy consumption and seriously corrodes equipment; the ultrasonic system has complex operation and high equipment cost.

[0004] As a green solvent, ionic liquids provide a new possibility for the efficient utilization of cellulose / chitosan due to their adjustable structure, excellent solubility, stability, and recyclability. Xie et al. (Green Chemistry, 2006, 8: 630 - 633) first studied the dissolution properties of chitosan and cellulose using [Bmim]Cl. [Bmim]Cl showed good dissolution properties for chitosan and cellulose, but chloride-containing ionic liquids are highly corrosive to equipment, which limits their industrial applications in dissolving cellulose / chitosan. Patent CN103183832A uses ionic liquids as solvents to dissolve cellulose and chitosan, but the dissolution rate is low and the dissolution conditions are harsh. Patent CN116284848A uses multi-functional acidic ionic liquids to dissolve cellulose / chitosan, but its complex ionic liquid preparation method is not conducive to industrial application promotion. Therefore, developing a new solvent system with a simple process, convenient operation, and capable of rapidly dissolving cellulose / chitosan is beneficial to promoting the green and low-carbon industrial application of cellulose / chitosan. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing regenerated cellulose / chitosan composite fibers / membranes by dissolving and regenerating cellulose / chitosan with ionic liquids, aiming to solve the technical problem of poor solubility of cellulose and chitosan.

[0006] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing regenerated cellulose / chitosan composite fibers / membranes by dissolving and regenerating cellulose / chitosan with ionic liquids, comprising the following steps:

[0008] 1) Sequentially dissolve chitosan and regenerated cellulose in a blend solvent of ionic liquid and organic solvent to obtain a regenerated cellulose / chitosan-ionic liquid solution;

[0009] 2) Vacuum degas the regenerated cellulose / chitosan-ionic liquid solution and then filter it. Prepare regenerated cellulose / chitosan composite fibers by dry-jet wet spinning process, or prepare regenerated cellulose / chitosan composite membranes by casting method;

[0010] The cation structure of the ionic liquid is:

[0011]

[0012] The anion structure of the ionic liquid is selected from one of the following structures:

[0013]

[0014] Wherein, R 1 , R 2 and R6 Independently for C m H 2n+1 , m and n are independently integers from 1 to 10, R 3 , R 4 , R 5 are independently methyl, ethyl, methoxy or ethoxy.

[0015] Furthermore, the organic solvent comprises one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and acetone.

[0016] Furthermore, the mass ratio of the ionic liquid to the organic solvent is 1:0.1 - 2.

[0017] Furthermore, the degree of polymerization of the regenerated cellulose is 200 - 700, the molecular weight of chitosan is 100 - 600 kDa, and the degree of deacetylation is 80%.

[0018] Furthermore, the mass ratio of chitosan to regenerated cellulose is 1 - 5:1 - 10;

[0019] The total mass percentage of chitosan and regenerated cellulose in the blend solvent is 1 - 10%.

[0020] Furthermore, the dissolution is carried out under stirring, the stirring speed is 100 - 200 rpm, the dissolution time is 0.5 - 2 h, and the dissolution temperature is 60 - 100 °C.

[0021] Furthermore, the vacuum degree of the vacuum degassing is 0.09 - 0.095 MPa.

[0022] Furthermore, the parameters of the dry-jet wet spinning process are: the temperature of the spinning pack is 60 - 90 °C, the coagulation bath is water or ethanol, and the temperature of the coagulation bath is 20 - 40 °C;

[0023] The parameters of the casting method are: the temperature of the casting die head is 60 - 90 °C, the coagulation bath is water or ethanol, and the temperature of the coagulation bath is 20 - 40 °C.

[0024] Furthermore, the breaking strength of the regenerated cellulose / chitosan composite fiber is 0.8 - 2.0 cN / dtex, and the elongation at break is 8.0 - 15.0%; the tensile strength of the regenerated cellulose / chitosan composite film is 50 - 100 MPa, and the elongation at break is 10.0 - 20.0%.

[0025] Advantages of the present invention:

[0026] (1) The blended solvent of the ionic liquid and the organic solvent provided by the present invention has a low viscosity, which improves the fluidity of the system and is conducive to mass transfer. Moreover, the synergistic effect between the organic solvent and the ionic liquid destroys the intramolecular or intermolecular hydrogen bond system of cellulose / chitosan, so that the blended solvent of the ionic liquid and the organic solvent has good dissolution ability for both cellulose and chitosan.

[0027] (2) The ionic liquids provided by the present invention are all synthesized by a one-step method, and the synthesis raw material cost is low, which is conducive to industrial application.

[0028] (3) The regenerated cellulose / chitosan composite fiber / membrane prepared by the present invention has excellent mechanical properties, biodegradability and antibacterial properties. Moreover, the ionic liquid can be recycled after recovery, which improves the economic benefits.

[0029] (4) The process of the present invention is simple and easy to operate, providing a new method for the application of cellulose / chitosan. Detailed Embodiments

[0030] The present invention provides a method for preparing a regenerated cellulose / chitosan composite fiber / membrane by dissolving regenerated cellulose / chitosan in an ionic liquid, comprising the following steps:

[0031] 1) Dissolve chitosan and regenerated cellulose in turn in a blended solvent of an ionic liquid and an organic solvent to obtain a regenerated cellulose / chitosan-ionic liquid solution;

[0032] 2) Vacuum degas and filter the regenerated cellulose / chitosan-ionic liquid solution, and prepare a regenerated cellulose / chitosan composite fiber by a dry-jet wet spinning process, or prepare a regenerated cellulose / chitosan composite membrane by a casting method;

[0033] The cation structure of the ionic liquid is:

[0034]

[0035] The anion structure of the ionic liquid is selected from one of the following structures:

[0036]

[0037] Wherein, R 1 , R 2 and R 6 are independently C m H 2n+1 , m and n are independently integers from 1 to 10, and R 3 , R 4 , R 5 are independently methyl, ethyl, methoxy or ethoxy.

[0038] In the present invention, the addition sequence of chitosan and regenerated cellulose is as follows: the chitosan is swollen in a blend solvent of an ionic liquid and an organic solvent and then regenerated cellulose is added to continue the dissolution.

[0039] In the present invention, after preparing the regenerated cellulose / chitosan composite fiber / membrane, the ionic liquid in the coagulation bath can be further recovered and recycled.

[0040] In the present invention, the ionic liquid is preferably one or more of 1-methyl-3-methylimidazolium methyl methylphosphonate, 1-ethyl-3-methylimidazolium diethyl phosphonoacetate, 1-methyl-3-methylimidazolium dimethyl phosphonoacetate, and 1-methyl-3-methylimidazolium ethyl methylphosphonoacetate.

[0041] In the present invention, the organic solvent includes one or more of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), and acetone, and is preferably dimethyl sulfoxide.

[0042] In the present invention, the mass ratio of the ionic liquid to the organic solvent is 1:0.1 - 2, preferably 1:0.5 - 1.5, and more preferably 1:1.

[0043] In the present invention, the degree of polymerization of the regenerated cellulose is 200 - 700, preferably 300 - 600, and more preferably 400 - 500; the molecular weight of chitosan is 100 - 600 kDa, preferably 200 - 500 kDa, and more preferably 300 - 400 kDa; the degree of deacetylation is 80%.

[0044] In the present invention, the mass ratio of chitosan to regenerated cellulose is 1 - 5:1 - 10, preferably 2 - 4:2 - 8, and more preferably 3 - 4:4 - 6.

[0045] In the present invention, the total mass percentage of chitosan and regenerated cellulose in the blend solvent is 1 - 10%, preferably 2 - 9%, and more preferably 3 - 7%.

[0046] In the present invention, the dissolution is carried out with stirring, the stirring speed is 100 - 200 rpm, preferably 200 rpm; the dissolution time is 0.5 - 2 h, preferably 1 h; the dissolution temperature is 60 - 100 °C, preferably 70 - 90 °C, and more preferably 80 °C.

[0047] In the present invention, the vacuum degree of the vacuum degassing is 0.09 - 0.095 MPa, preferably 0.095 MPa.

[0048] In the present invention, the parameters of the dry-jet wet spinning process are as follows: the temperature of the spinning pack is 60 to 90 °C, preferably 70 to 80 °C; the coagulation bath is water or ethanol, preferably ethanol; the temperature of the coagulation bath is 20 to 40 °C, preferably 30 °C.

[0049] In the present invention, the parameters of the casting method are as follows: the temperature of the casting die head is 60 to 90 °C, preferably 70 to 80 °C; the coagulation bath is water or ethanol, preferably ethanol; the temperature of the coagulation bath is 20 to 40 °C, preferably 30 °C.

[0050] In the present invention, the breaking strength of the regenerated cellulose / chitosan composite fiber is 0.8 to 2.0 cN / dtex, and the elongation at break is 8.0 to 15.0%; the tensile strength of the regenerated cellulose / chitosan composite film is 50 to 100 MPa, and the elongation at break is 10.0 to 20.0%.

[0051] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0052] Example 1

[0053] (1) 30 g of 1-methyl-3-methylimidazolium methyl phosphate ([Mmim]MMP), 20 g of 1-ethyl-3-methylimidazolium phosphonoethyl acetate ([Emim]MEPA) and 30 g of DMSO were uniformly mixed to form an ionic liquid co-solvent. 5 g of chitosan with a molecular weight of 600 kDa and a degree of deacetylation of 80% was added to the ionic liquid co-solvent, and it was swollen at room temperature for 30 min. Subsequently, 2 g of regenerated cellulose with a degree of polymerization of 600 was added, and the temperature was raised to 100 °C, and mechanical stirring was carried out for 1 h at a rotation speed of 100 rpm to obtain a regenerated cellulose / chitosan-ionic liquid solution;

[0054] (2) The regenerated cellulose / chitosan-ionic liquid solution obtained in (1) was vacuum degassed (vacuum degree 0.090 MPa) and then filtered, and dry-jet wet spinning was used for spinning. The spinning temperature was 80 °C, and it was solidified at 30 °C with water as the coagulation bath. The obtained fiber was dried at 150 °C for 20 s to obtain a regenerated cellulose / chitosan composite fiber. The breaking strength of the obtained regenerated cellulose / chitosan composite fiber was 1.4 cN / dtex, and the elongation at break was 8.0%.

[0055] (3) The ionic liquid co-solvent in the coagulation bath was recovered and could be recycled for use in step (1). The recovery steps were as follows: after the aqueous solution of the coagulation bath was filtered, the filtrate was subjected to vacuum distillation to remove water at 70 °C to recover the ionic liquid co-solvent therein. The breaking strength of the regenerated cellulose / chitosan composite fiber prepared by repeating steps (1) and (2) with the recovered ionic liquid co-solvent was 1.3 cN / dtex, and the elongation at break was 8.2%.

[0056] Example 2

[0057] (1) 50 g of diethyl 1-ethyl-3-methylimidazolium phosphonoacetate ([Emim]DEPA) and 50 g of DMAC were uniformly mixed to form an ionic liquid co-solvent. 3 g of chitosan with a molecular weight of 370 kDa and a deacetylation degree of 80% was added to the ionic liquid co-solvent and swollen at room temperature for 20 min. Subsequently, 5 g of regenerated cellulose with a degree of polymerization of 460 was added, and the temperature was raised to 90 °C, followed by mechanical stirring for 1.5 h at a rotation speed of 150 rpm to obtain a regenerated cellulose / chitosan-ionic liquid solution;

[0058] (2) The regenerated cellulose / chitosan-ionic liquid solution obtained in (1) was degassed under vacuum (vacuum degree 0.095 MPa) and then filtered. A film was prepared by the casting method, with the casting die head temperature at 80 °C, and solidified in a water coagulation bath at 25 °C. The obtained film was dried at 80 °C to obtain a regenerated cellulose / chitosan composite film. The tensile strength of the obtained regenerated cellulose / chitosan composite film was 60 MPa, and the elongation at break was 12.0%.

[0059] (3) The ionic liquid co-solvent in the coagulation bath was recovered and could be recycled for use in step (1). The recovery procedure was as follows: After the aqueous solution of the coagulation bath was filtered, the filtrate was subjected to vacuum distillation for water removal at 80 °C to recover the ionic liquid co-solvent therein. The tensile strength of the regenerated cellulose / chitosan composite film prepared by repeating steps (1) and (2) with the recovered ionic liquid co-solvent was 62 MPa, and the elongation at break was 13.0%.

[0060] Example 3

[0061] (1) 25 g of dimethyl 1-methyl-3-methylimidazolium phosphonoacetate ([Mmim]DMPA), 25 g of [Mmim]MMP, and 30 g of DMF were uniformly mixed to form an ionic liquid co-solvent. 3 g of chitosan with a molecular weight of 500 kDa and a deacetylation degree of 80% was added to the ionic liquid co-solvent and swollen at room temperature for 30 min. Subsequently, 6 g of regenerated cellulose with a degree of polymerization of 500 was added, and the temperature was raised to 100 °C, followed by mechanical stirring for 1.5 h at a rotation speed of 200 rpm to obtain a regenerated cellulose / chitosan-ionic liquid solution;

[0062] (2) The regenerated cellulose / chitosan-ionic liquid solution obtained in (1) was degassed under vacuum (vacuum degree 0.095 MPa) and then filtered. Spinning was carried out by the dry-jet wet-spinning method, with the spinning temperature at 75 °C, and solidified in a water coagulation bath at 25 °C. The obtained fibers were dried at 160 °C for 15 s to obtain regenerated cellulose / chitosan composite fibers. The breaking strength of the obtained regenerated cellulose / chitosan composite fibers was 1.8 cN / dtex, and the elongation was 12.0%.

[0063] (3) Recover the ionic liquid co-solvent in the coagulation bath and it can be recycled for use in step (1). The recovery steps are as follows: After the aqueous solution of the coagulation bath is filtered, the filtrate is subjected to vacuum distillation to remove water at 80 °C to recover the ionic liquid co-solvent therein. The recycled ionic liquid co-solvent is used to repeat steps (1) and (2). The breaking strength of the prepared regenerated cellulose / chitosan composite fiber is 1.9 cN / dtex, and the elongation at break is 12.5%.

[0064] Example 4

[0065] (1) Uniformly mix 30 g of 1-methyl-3-methylimidazolium ethyl methylphosphonoacetate ([Mmim]EMPA) with 60 g of DMSO to form an ionic liquid co-solvent. Add 2 g of chitosan with a molecular weight of 500 kDa and a degree of deacetylation of 80% to the ionic liquid co-solvent, and swell it at room temperature for 15 min. Then add 8 g of regenerated cellulose with a degree of polymerization of 640, raise the temperature to 100 °C, and mechanically stir for 1.5 h at a rotation speed of 200 rpm to obtain a regenerated cellulose / chitosan-ionic liquid solution.

[0066] (2) After vacuum degassing (vacuum degree 0.095 MPa) the regenerated cellulose / chitosan-ionic liquid solution obtained in (1), filter it, and use the casting method to prepare a film. The temperature of the casting die head is 85 °C, and it is solidified at 25 °C using water as the coagulation bath. The obtained film is dried at 75 °C to obtain a regenerated cellulose / chitosan composite film. The tensile strength of the obtained regenerated cellulose / chitosan composite film is 90 MPa, and the elongation at break is 16.0%.

[0067] (3) Recover the ionic liquid co-solvent in the coagulation bath and it can be recycled for use in step (1). The recovery steps are as follows: After the aqueous solution of the coagulation bath is filtered, the filtrate is subjected to vacuum distillation to remove water at 70 °C to recover the ionic liquid co-solvent therein. The recycled ionic liquid co-solvent is used to repeat steps (1) and (2). The tensile strength of the prepared regenerated cellulose / chitosan composite film is 87 MPa, and the elongation at break is 15.5%.

[0068] Comparative Example 1

[0069] Same as Example 1, except that only 30 g of 1-methyl-3-methylimidazolium methyl phosphate ([Mmim]MMP) and 20 g of 1-ethyl-3-methylimidazolium ethyl methylphosphonoacetate ([Emim]MEPA) are used as the ionic liquid co-solvent. The breaking strength of the obtained regenerated cellulose / chitosan composite fiber is 0.90 cN / dtex, and the elongation at break is 6.0%.

[0070] Comparative Example 2

[0071] Same as Example 2, except that only 50 g of DMAC was used as the solvent, and cellulose and chitosan could not be dissolved.

[0072] As can be seen from the above examples, the present invention provides a method for preparing regenerated cellulose / chitosan composite fibers / membranes by dissolving and regenerating cellulose / chitosan in an ionic liquid co-solvent. The regenerated cellulose / chitosan is dissolved in the ionic liquid co-solvent, degassed under vacuum, filtered, and the regenerated cellulose / chitosan composite fibers are prepared by a dry-jet wet spinning process, or the regenerated cellulose / chitosan composite film is prepared by a casting method. The process of the present invention is simple, easy to operate, and can achieve rapid dissolution of regenerated cellulose / chitosan.

[0073] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid, characterized in that: The following steps are involved: 1) dissolving chitosan and regenerated cellulose in a mixed solvent of an ionic liquid and an organic solvent in sequence to obtain a regenerated cellulose / chitosan-ionic liquid solution; 2) vacuum degassing the regenerated cellulose / chitosan-ionic liquid solution and filtering it, preparing the regenerated cellulose / chitosan composite fiber by dry-jet wet spinning process, or preparing the regenerated cellulose / chitosan composite film by casting method; The cationic structure of the ionic liquid is: The anion structure of the ionic liquid is selected from one of the following structures: Among them, R1, R2 and R6 are independently C m H 2n+1 , m and n are independently integers of 1 to 10, and R3, R4, and R5 are independently methyl, ethyl, methoxy, or ethoxy.

2. The method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid according to claim 1, characterized in that: The organic solvent comprises one or more of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide and acetone.

3. The method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid according to claim 1 or 2, characterized in that: The mass ratio of the ionic liquid to the organic solvent is 1:0.1-2.

4. The method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid according to claim 3, characterized in that: The polymerization degree of the regenerated cellulose is 200-700, the molecular weight of the chitosan is 100-600 kDa, and the deacetylation degree is 80%.

5. The method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid according to claim 1, 2 or 4, characterized in that: The mass ratio of chitosan to regenerated cellulose is 1-5:1-10; The total mass of the chitosan and the regenerated cellulose accounts for 1-10% of the mass of the blending solvent.

6. The method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid according to claim 5, characterized in that: The dissolution is carried out under stirring, the stirring speed is 100-200 rpm, the dissolution time is 0.5-2h, and the dissolution temperature is 60-100°C.

7. The method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid according to claim 1, characterized in that: The vacuum degree of the vacuum degassing is 0.09-0.095 MPa.

8. The method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid according to claim 1 or 7, characterized in that: The parameters of the dry-jet wet spinning process are: the temperature of the spinning assembly is 60-90°C, the coagulation bath is water or ethanol, and the temperature of the coagulation bath is 20-40°C; The parameters of the casting method are as follows: the temperature of the casting die is 60-90°C, the coagulation bath is water or ethanol, and the temperature of the coagulation bath is 20-40°C.

9. The method for preparing regenerated cellulose / chitosan composite fiber / film by dissolving regenerated cellulose / chitosan by ionic liquid according to claim 8, characterized in that: The regenerated cellulose / chitosan composite fiber has a breaking strength of 0.8-2.0 cN / dtex and an elongation of 8.0-15.0%; the regenerated cellulose / chitosan composite film has a tensile strength of 50-100 MPa and a breaking elongation of 10.0-20.0%.

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