Preparation method of konjac glucoside-based hydrophobic biomass film

Abstract

The application discloses a preparation method of konjac glucoside-based hydrophobic biomass film, and comprises the following steps: S1, purification: eluting konjac powder, drying, grinding and screening to obtain konjac glucoside; S2, modification: fully stirring and mixing the konjac glucoside obtained in the step S1 with an ethanol solution to configure a homogeneous solution, adding a sodium hydroxide solution to carry out a deacetylation reaction, and obtaining deacetylated konjac glucoside; and S3, film preparation: blending the deacetylated konjac glucoside with agar, pullulan and glycerol in a solvent, heating and stirring to form a film solution, removing bubbles, and drying to obtain the konjac glucoside-based hydrophobic biomass film formed by the deacetylated konjac glucoside, agar and pullulan; the konjac glucoside-based hydrophobic biomass film prepared by the method has good hydrophobic performance and mechanical performance, can help to reduce the dependence on fossil energy, promote the development of circular economy, and make contributions to environmental protection and sustainable development.

Description

A method for preparing a konjac glucomannan-based hydrophobic biomass film Technical Field

[0001] This invention belongs to the field of composite material preparation technology, specifically relating to a method for preparing a konjac glucomannan-based hydrophobic biomass film. Background Technology

[0002] Konjac glucomannan is a neutral, hydrophilic polysaccharide derived from konjac tubers. The genus *Amorphophallus* is rich in species, with over 163 confirmed species worldwide. As an excellent natural renewable resource, konjac glucomannan is abundant, easily degradable, and possesses excellent hydrophilicity, thickening properties, and stability, making it widely used in the food production industry. Its hydrosol can form films under appropriate conditions, showing great promise as a green packaging film.

[0003] Agar, also known as agarose, is extracted from the cell walls of red algae polysaccharides. It is a water-soluble polysaccharide with a polygalactosyl structure, making it a renewable and biodegradable green material. Agar has excellent gelling, film-forming, and thickening properties. It is widely used in food, medicine, chemical, and bioengineering industries.

[0004] Pullulan has high film-forming properties, adhesion, biocompatibility and biodegradability, certain mechanical strength, good film transparency, and good low oxygen permeability and oil resistance. Therefore, its products have a wide range of applications in food processing and packaging environmental protection, electronics, cosmetics and biomedicine.

[0005] In recent years, fossil resources have been dwindling. Therefore, the research and development of new materials based on natural polymers has become one of the cutting-edge directions in polymer science. Natural polymer materials are renewable and biodegradable, and are widely found in plants and animals. The development of new materials based on natural polymers can effectively reduce dependence on fossil resources, lower environmental pressure, and align with the concept of sustainable development.

[0006] Therefore, it is of great significance to develop an environmentally friendly composite film with high mechanical strength, good hydrophobicity, harmlessness, greenness, and environmental protection. Summary of the Invention

[0007] To address the aforementioned issues, this invention proposes a method for preparing a konjac glucomannan-based hydrophobic biomass film. The konjac glucomannan-based hydrophobic biomass film prepared by this method exhibits excellent hydrophobic and mechanical properties. This konjac glucomannan-based hydrophobic biomass film material uses biodegradable and biocompatible polymer materials as raw materials, which helps reduce dependence on fossil fuels, promotes the development of a circular economy, and contributes to environmental protection and sustainable development.

[0008] The present invention adopts the following technical solution:

[0009] A method for preparing a konjac glucomannan-based hydrophobic biomass film includes the following steps:

[0010] S1. Purification: Konjac flour is washed, dried, ground and sieved to obtain konjac glucomannan;

[0011] S2. Modification: The purified konjac glucomannan is thoroughly mixed with an ethanol solution to prepare a homogeneous solution. Sodium hydroxide solution is added to carry out a deacetylation reaction to obtain deacetylated konjac glucomannan.

[0012] S3. Membrane preparation: Deacetylated konjac glucomannan is mixed with agar, pullulan, and glycerol in a solvent, heated and stirred to form a membrane solution, defoamed, and dried to obtain a hydrophobic biomass film based on konjac glucomannan formed by deacetylated konjac glucomannan, agar, and pullulan.

[0013] Preferably, the konjac flour in step S1 is obtained by washing in 65% ethanol for 4 hours, repeating the washing process three times, drying in a 60°C forced-air oven, grinding, and then sieving through a 100-mesh sieve.

[0014] Preferably, the concentration of ethanol in step S2 is 50%, and the mixture is stirred at 40°C.

[0015] Preferably, the concentration of sodium hydroxide in step S2 is 0.025-0.15 mol / L.

[0016] Preferably, in step S2, the stirring speed is 600 rpm and the stirring time is 24 h.

[0017] Preferably, in step S3, the mass ratio of deacetylated konjac glucomannan to agar is 3:1, the mass fraction of pullulan is 10%, and the mass fraction of glycerol in the polysaccharide is 12.5%.

[0018] Preferably, in step S3, the mixture is stirred using an electric stirrer at a speed of 800 rpm for 120 minutes.

[0019] Preferably, the konjac glucomannan-based hydrophobic biomass film described in step S3 is formed by casting.

[0020] Preferably, the deacetylated konjac glucomannan, agar, pullulan, and glycerol described in step S3 are blended at 90°C.

[0021] Preferably, the membrane solution in step S3 is heated and dried in a forced-air drying oven at a temperature of 60°C to obtain a konjac glucomannan-based hydrophobic biomass film.

[0022] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0023] 1. The materials used in this invention, such as konjac glucomannan, agar, and pullulan, are all natural polymer materials with biodegradability and biocompatibility. After purification, konjac glucomannan exhibits more pronounced gelation and higher viscosity. The resulting konjac glucomannan-based hydrophobic biomass film is highly dense and possesses excellent hydrophobic and mechanical properties.

[0024] 2. This invention uses a casting method supplemented by vibration and temperature defoaming treatment to improve the uniformity of the composite film and reduce the impact of bubble leakage.

[0025] 3. This invention addresses the problems of excessive water solubility and poor mechanical properties in films made directly from konjac glucomannan in the traditional method. By altering the molecular structure of konjac glucomannan and removing these acetyl groups, the performance of the film is improved, expanding its possibilities in practical applications.

[0026] 4. The composite film prepared by this invention has high strength and good hydrophobicity, further expanding the application field of konjac glucomannan in blending with other materials. Attached Figure Description

[0027] Figure 1 shows the Fourier transform infrared spectra of deacetylated konjac glucomannan powder in Examples 1-6 and the comparative example of the present invention.

[0028] Figure 2 shows the tensile strength of the konjac glucomannan-based hydrophobic biomass films in Examples 1-6 and the comparative examples of the present invention.

[0029] Figure 3 shows the elongation at break of the konjac glucomannan-based hydrophobic biomass films in Examples 1-6 and the comparative examples of the present invention.

[0030] Figure 4 shows the water swelling rate of the konjac glucomannan-based hydrophobic biomass film in Examples 1-6 and the comparative example of the present invention.

[0031] Figure 5 shows the water solubility of the konjac glucomannan-based hydrophobic biomass films in Examples 1-6 and the comparative examples of the present invention.

[0032] Figure 6 shows the water vapor transmission rate of the konjac glucomannan-based hydrophobic biomass film in Examples 1-6 and the comparative example of the present invention.

[0033] Figure 7 shows the water contact angle of the konjac glucomannan-based hydrophobic biomass films in Examples 1-6 and the comparative examples of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] See Figures 1 through 7.

[0036] Raw materials to be prepared: konjac flour, agar, pullulan, glycerol, and sodium hydroxide. The purity of the konjac flour is 98% (Hubei Qiangsen Konjac Technology Co., Ltd.), the purity of the agar is 99.9% (Lanjieke Technology Co., Ltd.), the purity of the pullulan is 99.9% (Shanghai Maclean Biochemical Technology Co., Ltd.), the purity of the glycerol is 99% (Sinopharm Chemical Reagent Co., Ltd.), and the purity of the sodium hydroxide is 99.5% (Sinopharm Chemical Reagent Co., Ltd.).

[0037] Example 1

[0038] Purification: Konjac flour was eluted in 65% ethanol for 4 hours, repeated 3 times, and finally rinsed with anhydrous ethanol. It was then dried in an oven at 60℃, ground, and sieved through a 100-mesh sieve to obtain konjac glucomannan.

[0039] Modification: 15g of purified konjac glucomannan was added to 150ml of 50% ethanol solution and shaken at 40℃ and 600rpm for 30min. 7.5ml of 0.025mol / L sodium hydroxide solution was added to the suspension, and the mixture was stirred at 600rpm for 24h. After the reaction was complete, the solution was washed with 50%, 75%, and 95% ethanol, and finally with anhydrous ethanol. The solution was dried at 60℃ to prepare deacetylated konjac glucomannan with a degree of deacetylation of 17.29%.

[0040] Membrane preparation: Measure 0.675g of modified deacetylated konjac glucomannan, 2.025g of agar, 0.3g of pullulan, and 0.375g of glycerol into a three-necked flask, and add 200ml of deionized water. Prepare the membrane solution by stirring at 800rpm for 120min at 90℃. Pour the membrane solution into a beaker and sonicate for 5min to remove air bubbles. Pour 50ml of the sol into 90mm diameter glass petri dishes and allow to gel at room temperature. After gel formation, dry in a 60℃ oven to form a membrane.

[0041] Example 2

[0042] Purification: Konjac flour was eluted in 65% ethanol for 4 hours, repeated 3 times, and finally rinsed with anhydrous ethanol. It was then dried in an oven at 60℃, ground, and sieved through a 100-mesh sieve to obtain konjac glucomannan.

[0043] Modification: 15g of purified konjac glucomannan was added to 150ml of 50% ethanol solution and shaken at 40℃ and 600rpm for 30min. 7.5ml of 0.05mol / L sodium hydroxide solution was added to the suspension, and the mixture was stirred at 600rpm for 24h. After the reaction was complete, the solution was washed with 50%, 75%, and 95% ethanol, and finally with anhydrous ethanol. The solution was dried at 60℃ to prepare deacetylated konjac glucomannan with a degree of deacetylation of 10.07%.

[0044] Membrane preparation: Measure 0.675g of modified deacetylated konjac glucomannan, 2.025g of agar, 0.3g of pullulan, and 0.375g of glycerol into a three-necked flask, and add 200ml of deionized water. Prepare the membrane solution by stirring at 800rpm for 120min at 90℃. Pour the membrane solution into a beaker and sonicate for 5min to remove air bubbles. Pour 50ml of the sol into 90mm diameter glass petri dishes and allow to gel at room temperature. After gel formation, dry in a 60℃ oven to form a membrane.

[0045] Example 3

[0046] Purification: Konjac flour was eluted in 65% ethanol for 4 hours, repeated 3 times, and finally rinsed with anhydrous ethanol. It was then dried in an oven at 60℃, ground, and sieved through a 100-mesh sieve to obtain konjac glucomannan.

[0047] Modification: 15g of purified konjac glucomannan was added to 150ml of 50% ethanol solution and shaken at 40℃ and 600rpm for 30min. 7.5ml of 0.075mol / L sodium hydroxide solution was added to the suspension, and the mixture was stirred at 600rpm for 24h. After the reaction was complete, the solution was washed with 50%, 75%, and 95% ethanol, and finally with anhydrous ethanol. The solution was dried at 60℃ to prepare deacetylated konjac glucomannan with a degree of deacetylation of 22.91%.

[0048] Membrane preparation: Measure 0.675g of modified deacetylated konjac glucomannan, 2.025g of agar, 0.3g of pullulan, and 0.375g of glycerol into a three-necked flask, and add 200ml of deionized water. Prepare the membrane solution by stirring at 800rpm for 120min at 90℃. Pour the membrane solution into a beaker and sonicate for 5min to remove air bubbles. Pour 50ml of the sol into 90mm diameter glass petri dishes and allow to gel at room temperature. After gel formation, dry in a 60℃ oven to form a membrane.

[0049] Example 4

[0050] Purification: Konjac flour was eluted in 65% ethanol for 4 hours, repeated 3 times, and finally rinsed with anhydrous ethanol. It was then dried in an oven at 60℃, ground, and sieved through a 100-mesh sieve to obtain konjac glucomannan.

[0051] Modification: 15g of purified konjac glucomannan was added to 150ml of 50% ethanol solution and shaken at 40℃ and 600rpm for 30min. 7.5ml of 0.1mol / L sodium hydroxide solution was added to the suspension, and the mixture was stirred at 600rpm for 24h. After the reaction was complete, the mixture was washed with 50%, 75%, and 95% ethanol, and finally with anhydrous ethanol. The mixture was dried at 60℃ to prepare deacetylated konjac glucomannan with a degree of deacetylation of 28.56%.

[0052] Membrane preparation: Measure 0.675g of modified deacetylated konjac glucomannan, 2.025g of agar, 0.3g of pullulan, and 0.375g of glycerol into a three-necked flask, and add 200ml of deionized water. Prepare the membrane solution by stirring at 800rpm for 120min at 90℃. Pour the membrane solution into a beaker and sonicate for 5min to remove air bubbles. Pour 50ml of the sol into 90mm diameter glass petri dishes and allow to gel at room temperature. After gel formation, dry in a 60℃ oven to form a membrane.

[0053] Example 5

[0054] Purification: Konjac flour was eluted in 65% ethanol for 4 hours, repeated 3 times, and finally rinsed with anhydrous ethanol. It was then dried in an oven at 60℃, ground, and sieved through a 100-mesh sieve to obtain konjac glucomannan.

[0055] Modification: 15g of purified konjac glucomannan was added to 150ml of 50% ethanol solution and shaken at 40℃ and 600rpm for 30min. 7.5ml of 0.125mol / L sodium hydroxide solution was added to the suspension, and the mixture was stirred at 600rpm for 24h. After the reaction was complete, the mixture was washed with 50%, 75%, and 95% ethanol, and finally with anhydrous ethanol. The mixture was dried at 60℃ to prepare deacetylated konjac glucomannan with a degree of deacetylation of 35.28%.

[0056] Membrane preparation: Measure 0.675g of modified deacetylated konjac glucomannan, 2.025g of agar, 0.3g of pullulan, and 0.375g of glycerol into a three-necked flask, and add 200ml of deionized water. Prepare the membrane solution by stirring at 800rpm for 120min at 90℃. Pour the membrane solution into a beaker and sonicate for 5min to remove air bubbles. Pour 50ml of the sol into 90mm diameter glass petri dishes and allow to gel at room temperature. After gel formation, dry in a 60℃ oven to form a membrane.

[0057] Example 6

[0058] Purification: Konjac flour was eluted in 65% ethanol for 4 hours, repeated 3 times, and finally rinsed with anhydrous ethanol. It was then dried in an oven at 60℃, ground, and sieved through a 100-mesh sieve to obtain konjac glucomannan.

[0059] Modification: 15g of purified konjac glucomannan was added to 150ml of 50% ethanol solution and shaken at 40℃ and 600rpm for 30min. 7.5ml of 0.15mol / L sodium hydroxide solution was added to the suspension, and the mixture was stirred at 600rpm for 24h. After the reaction was complete, the mixture was washed with 50%, 75%, and 95% ethanol, and finally with anhydrous ethanol. The mixture was dried at 60℃ to prepare deacetylated konjac glucomannan with a degree of deacetylation of 42.41%.

[0060] Membrane preparation: Measure 0.675g of modified deacetylated konjac glucomannan, 2.025g of agar, 0.3g of pullulan, and 0.375g of glycerol into a three-necked flask, and add 200ml of deionized water. Prepare the membrane solution by stirring at 800rpm for 120min at 90℃. Pour the membrane solution into a beaker and sonicate for 5min to remove air bubbles. Pour 50ml of the sol into 90mm diameter glass petri dishes and allow to gel at room temperature. After gel formation, dry in a 60℃ oven to form a membrane.

[0061] Comparative Example

[0062] Purification: Konjac flour was eluted in 65% ethanol for 4 hours, repeated 3 times, and finally rinsed with anhydrous ethanol. It was then dried in an oven at 60℃, ground, and sieved through a 100-mesh sieve to obtain konjac glucomannan.

[0063] Membrane preparation: Measure 0.675g of modified deacetylated konjac glucomannan, 2.025g of agar, 0.3g of pullulan, and 0.375g of glycerol into a three-necked flask, and add 200ml of deionized water. Prepare the membrane solution by stirring at 800rpm for 120min at 90℃. Pour the membrane solution into a beaker and sonicate for 5min to remove air bubbles. Pour 50ml of the sol into 90mm diameter glass petri dishes and allow to gel at room temperature. After gel formation, dry in a 60℃ oven to form a membrane.

[0064] Performance testing:

[0065] (1) The dried deacetylated konjac glucomannan powder samples from the comparative example and Examples 1-6 were ground and mixed evenly with KBr powder, then dried in a forced-air oven for 5 minutes, and pressed into thin sheets in a mold. The temperature was maintained between 400 and 4000 cm⁻¹. -1 Within the wavenumber range, with air as the background, 32 scans were performed at room temperature with a resolution of 4 cm⁻¹. -1 Furthermore, baseline correction was performed on the data. The prepared sample was 1733 cm³. -1and 1614cm -1 The absorption peak at the point decreases with increasing degree of deacetylation, indicating a reduction in C=O stretching vibration and hydrogen bonding, and successful deacetylation modification, as shown in Figure 1. The degrees of deacetylation in the comparative example, Example 1, Example 2, Example 3, Example 4, Example 5, and Example 6 in Figure 1 are 0%, 10.07%, 17.29%, 22.91%, 28.56%, 35.28%, and 42.41%, respectively.

[0066] (2) The film samples obtained in the comparative examples and Examples 1-6 were placed in an environment of 25°C and 50% relative humidity for a period of time for constant temperature and humidity equilibrium. The films were then cut into rectangles of 10×100mm. The tensile strength and elongation at break of the composite films were measured using a universal testing machine. The prepared composite film exhibited the highest tensile strength (85.47 MPa) at a degree of deacetylation of 28.56%, as shown in Figure 2. The highest elongation at break (14.86%) was observed at a degree of deacetylation of 35.28%, as shown in Figure 3.

[0067] (3) Testing the water solubility and water swelling of the composite films obtained in the comparative examples and Examples 1-6: The equilibrium composite films were cut into 2×2cm pieces and dried at 60°C to constant weight, the mass of which was recorded as m1. The film pieces were soaked in water at room temperature for 24 hours, and then the water on the surface of the film was absorbed with filter paper, the mass of which was recorded as m2. The water swelling rate = (m2-m1) / m1. The swollen film pieces were dried in an oven at 50°C to constant weight, the mass of which was recorded as m3, and the water solubility rate = (m1-m3) / m1. The prepared composite film had the lowest swelling rate of 465.37% at a degree of deacetylation of 35.28%, as shown in Figure 4. The lowest water solubility of 15.90% was found at a degree of deacetylation of 28.56%, as shown in Figure 5.

[0068] (4) The film samples obtained in the comparative example and Examples 1-6 were covered on a 50mL Erlenmeyer flask containing anhydrous CaCl2 and sealed with glue. The flask was then placed in a desiccator containing 1000mL of saturated sodium chloride solution at 25°C and 75% RH. Weighing was performed every hour until mass equilibrium was reached. Every 24 hours, the Erlenmeyer flasks were removed and weighed sequentially according to a prescribed order. (The saturated water vapor pressure of the sodium chloride solution at 25°C is 2.63 kPa.) WVP=(Δm·d) / (A·Δt·ΔP). Where Δm is the weight gain per unit permeation time, d is the film thickness, A is the area of ​​the flask opening, Δt is the permeation time interval, and ΔP is the water vapor pressure difference across the film. The lowest water vapor permeability was observed at a degree of deacetylation of 28.56%, which was 0.9849 g·m. -1 h - 1 Pa -1 .

[0069] (5) The film samples obtained in the comparative examples and Examples 1-6 were cut into 5×50mm strips and placed on a horizontal movable stage. Water (5μL) was dropped onto the film surface using a 10μL microsyringe, and after waiting for 30s, the contact angle between the water and the film was measured. The composite film prepared had the highest water contact angle of 102.5° at a degree of deacetylation of 35.28%, as shown in Figure 7.

[0070] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a konjac glucomannan-based hydrophobic biomass film, characterized in that, The process includes the following steps: S1, Purification: Konjac flour is washed, dried, ground, and sieved to obtain konjac glucomannan; the konjac flour in step S1 is washed in 65% ethanol for 4 hours, repeated three times, dried in a 60℃ forced-air oven, ground, and then sieved through a 100-mesh sieve to obtain konjac glucomannan; S2, Modification: The purified konjac glucomannan is thoroughly mixed with an ethanol solution to prepare a homogeneous solution, sodium hydroxide solution is added, and a deacetylation reaction is carried out to obtain deacetylated konjac glucomannan; the concentration of ethanol in step S2 is 50%, and the mixture is stirred at 40℃; the concentration of sodium hydroxide in step S2 is 0.025-0.15 mol / L; the stirring speed in step S2 is 600... S3, Membrane Formation: Deacetylated konjac glucomannan, agar, pullulan, and glycerol are mixed in a solvent, heated and stirred to form a membrane solution, defoamed, and dried to obtain a konjac glucomannan-based hydrophobic biomass film. In step S3, the mass ratio of deacetylated konjac glucomannan to agar is 1:3, the mass fraction of pullulan is 10%, and the mass fraction of glycerol is 12.5%. In step S3, the mixture is stirred using an electric stirrer at 800 rpm for 120 min. In step S3, the deacetylated konjac glucomannan, agar, pullulan, and glycerol are mixed at 90 °C. The membrane solution in step S3 is heated and dried in a forced-air oven at 60 °C to obtain the konjac glucomannan-based hydrophobic biomass film.

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