Pineapple leaf fiber hydrogel and a preparation method thereof

Abstract

The present application relates to the technical field of pineapple leaf fiber processing technology, and particularly relates to a pineapple leaf fiber hydrogel and a preparation method thereof.The present application provides a preparation method of the pineapple leaf fiber hydrogel, which comprises the following steps: mixing epichlorohydrin, an antibacterial agent and cellulose derived from pineapple leaf fiber at-2 to 1 DEG C, and then performing cross-linking polymerization at 40 to 80 DEG C.The present application realizes a pineapple leaf fiber hydrogel with excellent antibacterial performance by optimizing a cross-linking system, and the pineapple leaf fiber hydrogel has strong cross-linking stability, high mechanical strength and good drug loading performance.

Description

Technical Field

[0001] This invention relates to the field of pineapple leaf fiber processing technology, and in particular to a pineapple leaf fiber hydrogel and its preparation method. Background Technology

[0002] Pineapple leaf fiber is a natural, environmentally friendly, and biodegradable tropical plant fiber extracted from discarded pineapple leaves. It is also a fiber with natural antibacterial and bacteriostatic properties, a large specific surface area, and a high content of surface hydroxyl groups, exhibiting excellent adsorption characteristics. Cellulose, derived from pineapple leaf fiber, is a rich natural organic polymer resource, possessing advantages such as low cost, easy availability, environmental friendliness, and good mechanical properties, offering vast potential for development and utilization. Cellulose contains a large number of hydroxyl groups, which, through a series of chemical or physical modifications, can be endowed with special properties to produce functional polymer materials.

[0003] Smart hydrogels, with their reversible volume phase transition response to minute changes in environmental stimuli such as temperature, magnetic fields, electric fields, pH, and ionic strength, are ideal carriers for antibacterial drugs. Loading soluble antibacterial active components onto appropriate carriers to prepare sustained-release antibacterial complexes allows for effective antibacterial action at the site of need without harming the surrounding environment. This will become an effective measure for controlling the harm of superbugs and other harmful microorganisms, demonstrating broad application potential in the controlled release of antibacterial drugs.

[0004] Currently, when existing technologies involve cross-linking and polymerizing hydrogels using monomers such as cellulose, it is often difficult to ensure cross-linking stability. This leads to problems such as poor drug loading capacity and low mechanical strength in practical applications. Summary of the Invention

[0005] This invention provides a pineapple leaf fiber hydrogel and its preparation method, which solves the defects of poor crosslinking stability, poor drug loading capacity and low mechanical strength of existing hydrogels, and realizes a pineapple leaf fiber hydrogel with high mechanical strength and strong crosslinking stability, thus prolonging the release of antibacterial properties.

[0006] This invention provides a method for preparing pineapple leaf fiber hydrogel, comprising: mixing epichlorohydrin, an antibacterial agent and cellulose derived from pineapple leaf fiber at -2 to 1°C, and then performing cross-linking polymerization at 40 to 80°C.

[0007] Pineapple leaf fiber is a fiber with natural antibacterial and bacteriostatic properties. Its cross-linking antibacterial agent can give it unique chemical properties. However, in the research and development of this invention, a large number of conventional cross-linking agents in the field were tried, but the cross-linking effect was poor. The cross-linking was easily destroyed after cross-linking, and the cross-linking stability was difficult to guarantee.

[0008] Subsequent research unexpectedly revealed that using epichlorohydrin as a crosslinking agent and mixing at low temperatures first allows for thorough mixing while preserving the activity of the antibacterial agent, facilitating the exposure of more free hydroxyl groups in cellulose. Then, crosslinking polymerization at higher temperatures significantly enhances the formation of covalent and hydrogen bonds between the polyhydroxyl groups of cellulose and the antibacterial agent, rapidly crosslinking and fixing the antibacterial agent onto the cellulose molecular chain. Ultimately, this results in a rapid crosslinking reaction that is not easily destroyed after crosslinking, significantly enhancing crosslinking stability and resulting in a tighter bond between the two, thus prolonging the antibacterial effect.

[0009] Preferably, the mixing time is 10–60 min and the crosslinking polymerization time is 2–5 h.

[0010] Preferably, the mass ratio of cellulose to epichlorohydrin is 1:1.5 to 1:3.

[0011] Preferably, the antibacterial agent is one or more of pineapple polyphenols, pineapple leaf polyphenols, and tea tree oil.

[0012] Preferably, the amount of antibacterial agent is 0.1 to 2 wt% based on the weight of the cellulose.

[0013] Preferably, the cellulose exists in the form of a cellulose solution, which is obtained by the following steps: pretreating pineapple leaf fibers, then mixing them with a 4-8 wt% NaOH aqueous solution and a 3-13 wt% urea aqueous solution in a weight ratio of 1:1 to 1:2, and then centrifuging to obtain a cellulose solution; wherein the concentration of cellulose in the cellulose solution is 1-6 wt%.

[0014] Preferably, the pretreatment includes: subjecting the pineapple leaf fibers to steam explosion treatment and oxidation treatment in sequence.

[0015] The steam explosion treatment achieves a synergistic effect of thermal degradation, mechanical-like fracture, hydrogen bond disruption, and structural rearrangement. After steam explosion treatment, pineapple leaf fibers are significantly affected in terms of pectin, lignin, and hemicellulose, but the cellulose content remains largely unchanged. Meanwhile, the electrolyte produced by electrolyzing sodium chloride solution contains HClO and ClO₂. - ,ClO 3- Multiple strong oxidizing active substances such as H2O2 and O3 can destroy the pectin and lignin structure on pineapple leaf fibers, while the cellulose is not lost.

[0016] This invention discovers that by controlling the order of steam explosion treatment and oxidation treatment, performing steam explosion treatment first and then oxidation treatment, cellulose with excellent mechanical properties and high specific surface area can be obtained, thereby improving the crosslinking stability of the final hydrogel.

[0017] Preferably, the moisture content of the pineapple leaf fiber is controlled at 40-60 wt% by soaking before the steam explosion treatment.

[0018] More preferably, the soaking solution used in the soaking process is water or a sodium hydroxide solution with a mass fraction of 0.1 to 1 wt%.

[0019] The pineapple leaf fibers after steam explosion treatment are relatively long and, due to their softness, are very difficult to crush. Existing techniques typically require cutting the long fibers after steam explosion treatment before crushing. However, this invention unexpectedly discovered that by controlling the moisture content of the pineapple leaf fibers before steam explosion treatment, the fiber length can be significantly shortened. When the moisture content of the pineapple leaf fibers is controlled within the aforementioned range, the average fiber length after steam explosion treatment is significantly shorter, greatly reducing the difficulty of crushing. Furthermore, when soaking in a sodium hydroxide solution within the aforementioned concentration range to control the moisture content to 40–60 wt%, the fiber length is even shorter.

[0020] Preferably, the steam explosion pressure during steam explosion treatment is 2.5–4.0 MPa, and the pressure holding time is 10–60 min.

[0021] Preferably, the oxidation treatment is: soaking the pineapple leaf fibers after steam explosion treatment in an electrolyte generated from an electrolytic sodium chloride solution.

[0022] Preferably, during the electrolysis process, the current intensity is 1-5A, the voltage is 3-11V, and the electrolysis time is 10s-60min.

[0023] More preferably, the concentration of the sodium chloride solution is 0.05 to 1 g / ml.

[0024] Preferably, the current density during electrolysis is 1–12 mA / cm². 2 ;

[0025] Preferably, the bath ratio in the electrolysis is 1:20 to 1:50.

[0026] Preferably, the soaking time is 10 to 60 minutes.

[0027] Preferably, the pretreatment further includes: pulverizing the pineapple leaf fiber after the oxidation treatment to obtain pineapple leaf fiber powder; the particle size of the pineapple leaf fiber powder is 80-120 mesh.

[0028] In practice, those skilled in the art can perform routine washing and drying operations on the treated pineapple leaf fibers according to actual needs.

[0029] As a preferred embodiment of the present invention, the preparation method includes the following steps:

[0030] (1) Soaking treatment

[0031] Soak pineapple leaf fibers in water or a sodium hydroxide solution with a mass fraction of 0.1–1 wt%.

[0032] (2) Steam explosion handling

[0033] Pineapple leaf fibers are placed in a steam explosion device for steam explosion treatment, and then the treated pineapple leaf fibers are washed and dried.

[0034] (3) Oxidation treatment

[0035] At room temperature, an aqueous solution of sodium chloride with a concentration of 0.05–1 g / ml is electrolyzed to obtain an electrolyte. Pineapple leaf fibers that have undergone steam explosion treatment are soaked and stirred in the electrolyte at a bath ratio of 1:20–1:50. Then, the oxidized pineapple leaf fibers are washed with water and dried.

[0036] (4) Crushing process

[0037] The pineapple leaf fibers after electrochemical treatment are crushed and passed through an 80-120 mesh sieve.

[0038] (5) Hydrogel preparation

[0039] The pineapple leaf fibers were dissolved in a mixture of 4-8 wt% NaOH aqueous solution and 3-13 wt% urea aqueous solution in a weight ratio of 1:1 to 1:2. The mixture was then centrifuged at 8000 r / min for 20 min at 15°C to obtain a cellulose solution. The cellulose solution, antibacterial agent, and epichlorohydrin were then stirred and mixed at -2 to 1°C and reacted at 40 to 80°C. Finally, the mixture was washed with water to obtain the pineapple leaf fiber hydrogel.

[0040] The present invention further provides a pineapple leaf fiber hydrogel, which is prepared by the above preparation method.

[0041] This invention provides a pineapple leaf fiber hydrogel and its preparation method. By optimizing the crosslinking system, a pineapple leaf fiber hydrogel with excellent antibacterial properties is achieved, exhibiting strong crosslinking stability, high mechanical strength, and good drug loading capacity. Furthermore, this invention uses natural polymer fibers as raw materials, employing a simple and efficient preparation process with mild and environmentally friendly conditions. The raw materials are widely available, inexpensive, and highly safe, making it a promising new technology for preparing high-performance, eco-friendly composite materials. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] Example 1

[0044] This embodiment provides a pineapple leaf fiber gel, the preparation method of which includes the following steps:

[0045] (1) Soak pineapple leaf fibers in water to obtain pineapple leaf fibers with a water content of 50%.

[0046] (2) Steam explosion handling

[0047] The soaked pineapple leaf fibers were placed in a steam explosion device for steam explosion treatment; then the treated fibers were washed with water and dried. The steam explosion pressure was 3 MPa, and the pressure holding time was 60 s. The average length of the treated pineapple leaf fibers was 4.81 ± 0.12 cm.

[0048] (3) Oxidation treatment

[0049] A sodium chloride electrolyte solution with a concentration of 0.05 g / ml was prepared at room temperature using a current intensity of 2 A and a voltage range of 8 V, with a current density of 2 mA / cm². 2 An aqueous solution for treating pineapple leaf fibers was prepared by electrolysis in an electrolytic cell for 30 minutes. The steam-exploded pineapple leaf fibers were then immersed in this aqueous solution with stirring for 30 minutes at a liquor ratio of 1:50. The treated fibers were then washed with water and dried.

[0050] (4) Crushing process

[0051] The pineapple leaf fibers after electrochemical treatment are crushed and passed through an 80-mesh sieve.

[0052] (5) Hydrogel preparation

[0053] The pineapple leaf fibers were dissolved in a 1:1 ratio of 6 wt% NaOH and 12 wt% urea aqueous solution. The solution was mechanically stirred for 10 min to ensure rapid dissolution, followed by high-speed centrifugation to remove air bubbles and impurities, yielding a cellulose solution with a concentration of 4 wt%. Then, 0.1 wt% tea tree oil (relative to the weight of cellulose) was added, with a cellulose to epichlorohydrin mass ratio of 1:2. The mixture was stirred and mixed at 0°C for 30 min, then reacted in a 70°C incubator for 5 h. Finally, the mixture was washed with water to obtain the pineapple leaf fiber hydrogel.

[0054] The pineapple leaf fiber hydrogel had an equilibrium swelling rate of 24.89 g / g, an elongation of 54.83%, and a porosity of 22.34% in distilled water. Its antibacterial rates against Escherichia coli and Staphylococcus aureus were 97.6% and 98.5%, respectively.

[0055] Example 2

[0056] This embodiment provides a pineapple leaf fiber gel, the preparation method of which includes the following steps:

[0057] (1) Pineapple leaf fibers were soaked in a sodium hydroxide solution with a mass fraction of 0.5 wt% to obtain pineapple leaf fibers with a water content of 60%.

[0058] (2) Steam explosion handling

[0059] The soaked pineapple leaf fibers were placed in a steam explosion device for steam explosion treatment; then the treated fibers were washed with water and dried. The steam explosion pressure was 4.0 MPa, and the pressure holding time was 10 minutes. The average length of the treated pineapple leaf fibers was 3.42 ± 0.15 cm.

[0060] (3) Oxidation treatment

[0061] A sodium chloride electrolyte solution with a concentration of 0.5 g / ml was prepared at room temperature using a current intensity of 2 A and a voltage of 5 V, with a current density of 4 mA / cm². 2 An aqueous solution for treating pineapple leaf fibers was prepared by electrolysis in an electrolytic cell for 60 minutes. The steam-exploded pineapple leaf fibers were then immersed in this aqueous solution with stirring for 40 minutes at a bath ratio of 1:20. The treated fibers were then washed with water and dried.

[0062] (4) Crushing process

[0063] The pineapple leaf fibers after electrochemical treatment are crushed and passed through a 100-mesh sieve.

[0064] (5) Hydrogel preparation

[0065] The pineapple leaf fibers were dissolved in a 7wt% NaOH / 12wt% urea aqueous solution at a weight ratio of 1:1. The solution was mechanically stirred for 8 minutes to ensure rapid dissolution. Afterward, high-speed centrifugation was used to remove air bubbles and impurities, yielding a cellulose solution with a cellulose concentration of 2wt%. Then, 0.5wt% pineapple polyphenols (relative to the weight of cellulose) were added, with a cellulose to epichlorohydrin mass ratio of 1:2.5. The mixture was stirred and mixed at -2℃ for 20 minutes, then placed in a 70℃ constant temperature oven for 4 hours. Finally, the mixture was washed with water to obtain the pineapple leaf fiber hydrogel.

[0066] The pineapple leaf fiber hydrogel had an equilibrium swelling rate of 35.27 g / g, an elongation of 60.21%, and a porosity of 32.57% in distilled water. Its antibacterial rates against Escherichia coli and Staphylococcus aureus were 98.3% and 97.6%, respectively.

[0067] Example 3

[0068] This embodiment provides a pineapple leaf fiber gel, the preparation method of which includes the following steps:

[0069] (1) Soak pineapple leaf fibers in water to obtain pineapple leaf fibers with a water content of 40%.

[0070] (2) Steam explosion handling

[0071] The soaked pineapple leaf fibers were placed in a steam explosion device for steam explosion treatment; then the treated fibers were washed with water and dried. The steam explosion pressure was 2.5 MPa, and the pressure holding time was 20 min. The length of the treated pineapple leaf fibers was 3.97 ± 0.09 cm.

[0072] (3) Oxidation treatment

[0073] A sodium chloride electrolyte solution with a concentration of 1 g / ml was prepared at room temperature using a current intensity of 2 A and a voltage range of 3 V, with a current density of 6 mA / cm². 2 An aqueous solution for treating pineapple leaf fibers was prepared by electrolysis in an electrolytic cell for 10 minutes. The pineapple leaf fibers after steam explosion treatment were then immersed in the above aqueous solution and stirred for 30 minutes at a bath ratio of 1:50. The treated fibers were then washed with water and dried.

[0074] (4) Crushing process

[0075] The pineapple leaf fibers after electrochemical treatment are crushed and passed through a 120-mesh sieve.

[0076] (5) Hydrogel preparation

[0077] The pineapple leaf fibers were dissolved in a 7wt% NaOH / 12wt% urea aqueous solution at a weight ratio of 1:1.5. The solution was mechanically stirred for 5 minutes to ensure rapid dissolution. Afterward, high-speed centrifugation was used to remove air bubbles and impurities, yielding a cellulose solution with a cellulose concentration of 6%. Then, 1wt% pineapple polyphenols (relative to the weight of cellulose) were added, with a cellulose to epichlorohydrin mass ratio of 1:2. The mixture was stirred and mixed at 1°C for 40 minutes, then placed in a 60°C incubator for 5 hours. Finally, the mixture was washed with water to obtain the pineapple leaf fiber hydrogel.

[0078] The pineapple leaf fiber hydrogel had an equilibrium swelling rate of 28.46 g / g, an elongation of 51.36%, and a porosity of 29.54% in distilled water. Its antibacterial rates against Escherichia coli and Staphylococcus aureus were 97.8% and 99.5%, respectively.

[0079] Example 4

[0080] This comparative example provides a pineapple leaf fiber gel, which is prepared using the same method as in Example 1, except that the moisture content of the pineapple leaf fiber before the steam explosion treatment is 20%. The average length of the treated pineapple leaf fiber is 10.24 ± 0.42 cm.

[0081] Comparative Example 1

[0082] This comparative example provides a pineapple leaf fiber hydrogel, prepared using the same method as in Example 1, except that its crosslinking agent is glutaraldehyde. The equilibrium swelling ratio of this pineapple leaf fiber hydrogel in distilled water is 16.24 g / g, the elongation is 19.87%, the porosity is 15.36%, and the inhibition rates against Escherichia coli and Staphylococcus aureus are 80.74% and 84.37%, respectively.

[0083] Comparative Example 2

[0084] This comparative example provides a pineapple leaf fiber gel, which is prepared in the same way as in Example 1, except that mixing and cross-linking are carried out simultaneously at a temperature of 20°C.

[0085] The pineapple leaf fiber hydrogel had an equilibrium swelling rate of 10.27 g / g, an elongation of 6.21%, and a porosity of 8.48% in distilled water. Its antibacterial rates against Escherichia coli and Staphylococcus aureus were 72.58% and 71.24%, respectively.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing pineapple leaf fiber hydrogel, characterized in that, include: Epichlorohydrin, an antibacterial agent, and cellulose derived from pineapple leaf fiber were mixed at -2 to 1°C, and then crosslinked polymerized at 40 to 80°C. The antibacterial agent is one or more of pineapple polyphenols, pineapple leaf polyphenols, and tea tree oil. The mass ratio of cellulose to epichlorohydrin is 1:1.5 to 1:3; Based on the weight of the cellulose, the amount of the antibacterial agent is 0.1–2 wt%. The cellulose exists in the form of a cellulose solution, which is obtained by the following steps: pretreating pineapple leaf fibers, then mixing them with a 4-8 wt% NaOH aqueous solution and a 3-13 wt% urea aqueous solution in a weight ratio of 1:1 to 1:2, and then centrifuging to obtain the cellulose solution; The concentration of cellulose in the cellulose solution is 1-6 wt%. The pretreatment includes: subjecting the pineapple leaf fibers to steam explosion treatment and oxidation treatment in sequence; Before steam explosion treatment, the moisture content of pineapple leaf fibers was controlled to 40-60 wt% by soaking. The oxidation treatment is as follows: soaking the pineapple leaf fibers after the steam explosion treatment in an electrolyte generated from an electrolytic sodium chloride solution; The concentration of the sodium chloride solution is 0.05~1g / ml.

2. The method for preparing pineapple leaf fiber hydrogel according to claim 1, characterized in that, The soaking solution used in the soaking process is water or a sodium hydroxide solution with a mass fraction of 0.1~1wt%.

3. The method for preparing pineapple leaf fiber hydrogel according to claim 1 or 2, characterized in that, The pretreatment further includes: pulverizing the pineapple leaf fiber after the oxidation treatment to obtain pineapple leaf fiber powder; the particle size of the pineapple leaf fiber powder is 80~120 mesh.

4. A pineapple leaf fiber hydrogel, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 3.