Straw core-based composite membrane, and preparation method and use thereof

Abstract

A kind of straw core-based composite film, including nanocellulose, polyethylene oxide, straw core particles, nanocellulose is connected by hydrogen bond and is intertwined with nanocellulose, nanocellulose and polyethylene oxide, polyethylene oxide and polyethylene oxide between, and network structure is formed, straw core particles are uniformly distributed in network structure, including steps: 1) take straw core, after drying, crush and sieve, obtain straw core particles;2) configuration PEO aqueous solution, CNF dispersion, polyphenol functional compound dispersion;3) CNF dispersion, PEO aqueous solution, straw core particles are mixed evenly, add polyphenol functional compound dispersion, mix evenly;4) the solution mixed evenly is transferred to mould, is formed by flow casting film, and the composite film is obtained.The present application uses straw core as raw material, can effectively improve the utilization value of straw core, the composite film has excellent strength and tenacity, and antibacterial, antioxidant, anti-ultraviolet and water vapor barrier performance, has broad application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of materials, in particular to a straw core-based composite film and a preparation method and application thereof. BACKGROUND

[0002] Straw is a kind of natural and widely-sourced biodegradable material. As it contains certain nutrients, it has long been used as one of the feed materials for livestock, resulting in great waste of straw.

[0003] Therefore, how to effectively utilize straw core is a problem to be solved by those skilled in the art. SUMMARY

[0004] One of the purposes of the present application is to provide a straw core-based composite film, which utilizes straw core as raw material to effectively improve the utilization value of straw core. In addition, the composite film has excellent strength and toughness, as well as antibacterial, antioxidant, ultraviolet and water vapor barrier properties, and has broad application prospects.

[0005] The second purpose of the present application is to provide a preparation method of the above-mentioned straw core-based composite film, which is simple in process, green and environmentally friendly, and can realize the purpose of low-cost mass production.

[0006] The technical solution for achieving one of the purposes of the present application is: a straw core-based composite film, comprising nanocellulose, polyethylene oxide and straw core particles, the nanocellulose, the nanocellulose, the polyethylene oxide and the polyethylene oxide are connected by hydrogen bonds and are intertwined with each other to form a network structure, the straw core particles are uniformly distributed in the network structure, and the combination constitutes the straw core-based composite film.

[0007] Further, the mass ratio of the nanocellulose, the polyethylene oxide and the straw core particles is 2-3:1-2:3-4.

[0008] Preferably, the straw core particles are corn straw core and / or sunflower straw core and / or sesame straw core, the particle size is 20-70um, the diameter of the nanocellulose is 3-5nm, the aspect ratio is >1000, and the molecular weight of the polyethylene oxide is 1000000-10000000.

[0009] Further, it further comprises a polyphenolic functional compound, and the volume-mass ratio of the polyphenolic functional compound to the straw core particles is 0.1-5:100, and the polyphenolic functional compound is a verbenalin polyphenol.

[0010] The technical solution for achieving the second purpose of the present application is: a preparation method of any of the above-mentioned straw core-based composite films, comprising the following steps:

[0011] 1) Take the straw core, dry and crush it, and sieve it to obtain straw core particles for standby;

[0012] 2) Prepare PEO aqueous solution, CNF dispersion, and polyphenol functional compound dispersion for standby;

[0013] 3) Mix the CNF dispersion, PEO aqueous solution, and straw core particles, and add the polyphenol functional compound and mix them;

[0014] 4) Transfer the mixed solution to a mold, and cast it into a film to obtain a straw core-based composite film.

[0015] Preferably, the drying in step 1) is drying in a blast drying oven for more than 24 hours.

[0016] Further, the preparation method of the PEO aqueous solution in step 2) is as follows:

[0017] Dissolve PEO powder in deionized water, heat and stir, then stir at room temperature until transparent, the concentration of the PEO aqueous solution is 1wt%, heat to 50-80℃ and stir at 600rpm for 3h, and stir at room temperature for 24h.

[0018] Further, the preparation method of the polyphenol functional compound dispersion in step 2) is as follows:

[0019] Take the polyphenol functional compound, rinse it with water, soak it with a mixed solvent, filter it, the mixed solvent is a mixture of ethanol and deionized water in a volume ratio of 4:1, and the volume ratio of the mixed solvent to the polyphenol functional compound is 5:1.

[0020] Further, the casting film in step 4) is evaporating the solvent to form a film at an environment of 60-65℃.

[0021] The application also provides the use of any of the above-mentioned straw core-based composite films for ventilation, water vapor resistance, further for food-grade packaging, mask lining, printing paper, and writing paper.

[0022] The above technical solution has the following beneficial effects:

[0023] 1. The composite film of the application uses straw core particles, nanocellulose (CNF), and polyethylene oxide (PEO) as raw materials, and through CNF reinforcement and PEO toughening, the network structure is formed by the hydrogen bond interaction and winding action between CNF and CNF, CNF and PEO, and PEO and PEO, the straw core particles are uniformly distributed in the network structure, and the network structure also fills between the gaps of the straw core particles, solving the problems of the straw core that cannot be formed into a film, low strength, and poor toughness. The composite film prepared has a smooth micro-surface of the straw core particles, and water vapor is difficult to penetrate from the surface, so it has the properties of ventilation and water vapor resistance.

[0024] 2、The composite film of the present application also adds a polyphenol functional compound. The polyphenol compound strengthens the binding force between the straw core particles, CNF and PEO, improves the structural strength of the composite film, and also avoids the polyphenol functional compound from falling off during the processing into a film and the use process, ensures that the polyphenol functional compound on the composite film plays a corresponding function for a long time, and makes it become a nano composite film with wide application scenarios and practical popularization value. This composite film not only provides a new idea for the high-value utilization of plant straw cores, but also conforms to the concept and policy of green environmental protection and carbon neutralization.

[0025] 3、The composite film of the present application limits the corn straw core to have a particle size of 20-70um, the nanocellulose has a diameter of 3-5nm and an aspect ratio >1000, and the polyethylene oxide has a molecular weight of 1000000-10000000. The mass ratio of the nanocellulose, the polyethylene oxide and the straw core particles is limited to be 2:1:1. The reasons are as follows: firstly, if the corn straw core particles are too large or too small, the gaps between the particles will increase or increase, which is not conducive to the retention of water vapor; secondly, the nanocellulose is the basis for providing mechanical strength, and too short nanocellulose can easily cause a decrease in strength; the selection of PEO is also the same, because it has good water solubility, too small molecules can easily flow away with water, and cannot provide considerable toughness; the purpose of limiting the proportion of each component is to reduce the cost as much as possible under the condition of improving the performance, and the change of the amount range has a great influence on the performance and cost of the material.

[0026] 4、The preparation method of the present application adopts sieving, blending and casting to obtain a straw core-based composite film, and has simple preparation process, green environmental protection and low cost for large-scale industrial application. The concentration of the PEO water solution is controlled to be 0.5wt%~1.5wt%, and needs to be heated and stirred, because the solubility of PEO at room temperature is poor, and increasing the temperature is beneficial to the dissolution. The drying temperature is 50-60℃, and the drying time is 5-8h. Since the materials are natural and have biodegradability, they are not suitable for long-time drying under high temperature conditions, and a relatively mild condition is needed to remove the solvent.

[0027] Through the test verification of the applicant, the tensile strength of the straw core-based composite film prepared by the present application is 24-40MPa, the water vapor barrier coefficient can reach 10 -14 , the DPPH free radical scavenging rate is more than 80%, and it has obvious anti-ultraviolet and antibacterial effects.

[0028] The following will be further described in combination with the drawings and specific embodiments. DRAWINGS

[0029] Figure 1 It is a comparison chart of the water vapor transmission coefficient of the composite film material.

[0030] Figure 2 UV-vis transmittance spectrum of the composite film;

[0031] Figure 3 DPPH free radical scavenging rate (%) of the composite film;

[0032] Figure 4 FTIR spectrum of the composite film and VAE;

[0033] Figure 5 Antibacterial test results of the composite film;

[0034] Figure 6 Time required for the composite film to be applied to milk to be contaminated by bacteria. DETAILED DESCRIPTION

[0035] In the present application, the corn straw core is from Daxin Village, Xiajiaying Town, Jiaocheng County, Lüliang City, Shanxi Province; the cellulose nanofiber slurry (CNF) (diameter 3-5 nm, aspect ratio >1000, solid content 1.137%) is purchased from Tianjin Muxingling Biological Technology Co., Ltd.; polyethylene oxide (PEO) is purchased from Shanghai Aladdin Biochem Technology Co., Ltd., CAS No. 68441-17-8, molecular weight 4000000; and the verbena is purchased from a Chinese medicine shop. Of course, all raw materials can also be purchased from other places (no commercial reagent).

[0036] Example 1

[0037] Preparation according to the following steps:

[0038] 1) The corn straw core is placed in a forced air drying oven for drying for more than 24 h to ensure that the water in the straw core is evaporated as much as possible, and then the dried straw core is crushed by a crusher and passed through a 200 mesh sieve. The corn straw core powder after passing through the sieve is stored in a dry place for standby use;

[0039] 2) 1 g of PEO powder is dissolved in 99 g of deionized water, heated to 80°C, stirred at 600 rpm for 3 h, and then cooled to room temperature and continue to stir for 3 h until transparent;

[0040] 3) The verbena is washed with deionized water, then soaked and extracted with ethanol and deionized water for 48 h, the volume ratio of ethanol to deionized water is 4:1, and the volume to mass ratio of deionized water to verbena is 1:1. The soaking and extraction liquid is vacuum filtered to obtain a VAE solution;

[0041] 4) Take 100 mg of corn stalk core powder into a beaker, measure 5 ml of 1 wt% PEO aqueous solution into the above beaker, continue to take 5 g of CNF slurry into the above beaker; add deionized water and dilute to 20 ml (the purpose here is to control the mass and volume, too large volume will not be able to control in a mold to form a film, of course, the thinner concentration is conducive to dispersion); set the temperature to 50°C, adjust the rotation speed to 600 rad / min and stir for 2 h; take 0.2 mL of VAE solution into a beaker, continue to stir at room temperature for 24 h; pour into a PTFE mold, put into a 60°C air drying oven until film formation; then, place the prepared film in a special mold, cold press at 3 MPa pressure for 5 min at room temperature. At the end of the experiment, the sample is recorded as CCP-VAE-0.2.

[0042] Example 2

[0043] The difference from Example 1 is that step 5) takes 100 mg of corn stalk core powder into a beaker, measures 5 ml of 1 wt% PEO aqueous solution into the above beaker, continues to take 5 g of CNF slurry into the above beaker; adds deionized water and dilutes to 20 ml; sets the temperature to 50°C, adjusts the rotation speed to 600 rad / min and stirs for 2 h; takes 0.5 mL of VAE solution into a beaker, continues to stir at room temperature for 24 h; pours into a PTFE mold, puts into a 60°C air drying oven until film formation; then, places the prepared film in a special mold, cold press at 3 MPa pressure for 5 min at room temperature. At the end of the experiment, the sample is recorded as CCP-VAE-0.5.

[0044] Example 3

[0045] The difference from Example 1 is that step 5) takes 100 mg of corn stalk core powder into a beaker, measures 5 ml of 1 wt% PEO aqueous solution into the above beaker, continues to take 5 g of CNF slurry into the above beaker; adds deionized water and dilutes to 20 ml; sets the temperature to 50°C, adjusts the rotation speed to 600 rad / min and stirs for 2 h; takes 1 mL of VAE solution into a beaker, continues to stir at room temperature for 24 h; pours into a PTFE mold, puts into a 60°C air drying oven until film formation; then, places the prepared film in a special mold, cold press at 3 MPa pressure for 5 min at room temperature. At the end of the experiment, the sample is recorded as CCP-VAE-1.

[0046] Example 4

[0047] The difference from Example 1 is that in step 5), 100 mg of corn stalk core powder is weighed into a beaker, 5 ml of 1 wt% PEO aqueous solution is measured and poured into the beaker, and then 5 g of CNF slurry is weighed and poured into the beaker; deionized water is added and diluted to 20 ml; the temperature is set to 50°C, the stirring speed is adjusted to 600 rad / min, and stirring is continued for 2 h; 1.5 mL of VAE solution is taken out and placed in a beaker, and stirring is continued at room temperature for 24 h; it is poured into a PTFE mold, and placed in a 60°C air drying oven until a film is formed; then, the prepared film is placed in a special mold, and cold pressed at 3 MPa for 5 min at room temperature. At the end of the experiment, the sample is recorded as CCP-VAE-1.5.

[0048] Example 5

[0049] The difference from Example 1 is that in step 5), 100 mg of corn stalk core powder is weighed into a beaker, 5 ml of 1 wt% PEO aqueous solution is measured and poured into the beaker, and then 5 g of CNF slurry is weighed and poured into the beaker; deionized water is added and diluted to 20 ml; the temperature is set to 50°C, the stirring speed is adjusted to 600 rad / min, and stirring is continued for 2 h; 2 mL of VAE solution is taken out and placed in a beaker, and stirring is continued at room temperature for 24 h; it is poured into a PTFE mold, and placed in a 60°C air drying oven until a film is formed; then, the prepared film is placed in a special mold, and cold pressed at 3 MPa for 5 min at room temperature. At the end of the experiment, the sample is recorded as CCP-VAE-2.

[0050] Comparative Example 1

[0051] 10 ml of 1 wt% PEO aqueous solution is measured and poured into a beaker; deionized water is added and diluted to 20 ml; the temperature is set to 50°C, the stirring speed is adjusted to 600 rad / min, and stirring is continued for 2 h; it is poured into a PTFE mold, and placed in a 60°C air drying oven until a film is formed, and the experiment is ended, and the sample is recorded as PEO, which is too strong in solubility and does not have the necessity of testing.

[0052] Comparative Example 2

[0053] 5 ml of 1 wt% PEO aqueous solution is measured and poured into a beaker; 5 g of CNF slurry is weighed and poured into the beaker; deionized water is added and diluted to 20 ml; the temperature is set to 50°C, the stirring speed is adjusted to 600 rad / min, and stirring is continued for 2 h; it is poured into a PTFE mold, and placed in a 60°C air drying oven until a film is formed, and the experiment is ended, and the sample is recorded as CNF / PEO, which is only an observation sample of CNF and PEO compatibility, and has a large difference from the components of the experimental group, and does not have the necessity of testing.

[0054] Comparative Example 3

[0055] Take 100 mg of corn stalk core powder into a beaker, measure 5 ml of 1 wt% PEO aqueous solution into the above beaker, continue to take 5 g of CNF slurry into the above beaker; add deionized water and dilute to 20 ml; set the temperature to 50℃, adjust the speed to 600 rad / min and stir for 2h; pour into a PTFE mold, put into a 60℃ air drying oven until film formation, the experiment is over, the sample is recorded as CSC / CNF / PEO.

[0056] Test results:

[0057] Using infrared spectroscopy (FTIR), ultraviolet spectroscopy (UV-vis), using a moisture cup to test the water vapor transmission coefficient (P wv )

Using the test method in GB / T 1037-2021 Plastic Film and Sheet Water Vapor Transmission Performance Test Cup Weight Gain and Loss Method, through the water vapor transmission coefficient (P wv / g*cm*cm- 2 *s -1 *Pa -1 ) to indicate the barrier effect of the composite film

[0058] Table 1: Test results of water vapor transmission rate of corn stalk core-based antibacterial and antioxidant composite film

[0059]

[0060]

[0061] Table 2: Test results of antioxidant activity of corn stalk core-based antibacterial and antioxidant composite film

[0062]

[0063] The results in Table 1 and Figure 1 show that the stalk core-based composite film has good water vapor barrier performance, and when the VAE content is greater than 1.5 mL, the water vapor transmission coefficient is lower than that of the popular biodegradable materials PBAT and PLA on the market. Figure 2 The results show that the addition of VAE makes the ultraviolet resistance of the stalk core-based composite film reach the best state, and all samples except the CSC / CNF / PEO sample are almost completely isolated from ultraviolet light. Table 2 and Figure 3 ​The results show that the addition of VAE makes the composite film have strong DPPH free radical scavenging capacity, and can reach more than 95% at a content of 0.2 mL, in addition, the free radical scavenging rate of all samples is basically more than 80%. Figure 4 The results show that VAE mainly forms hydrogen bonds with CSC, CNF and PEO, and the improvement of mechanical properties is also based on this. Figure 5 The results show that the addition of VAE makes the sample have good self-antibacterial performance, from the contact surface with escherichia coli and staphylococcus aureus, the sample contains little soluble antibacterial substance, the addition of VAE mainly makes it have good antibacterial property. Figure 6 The results show that in the actual packaging test, the composite film shows excellent comprehensive performance, especially when the content of VAE is 1.5 mL.

Claims

1. A method for preparing a straw core-based composite film, characterized in that, The straw-core composite membrane comprises nanocellulose, polyethylene oxide, straw core particles, and polyphenolic functional compounds. The mass ratio of nanocellulose, polyethylene oxide, and straw core particles is 2-3:1-2:3-4. The straw core particles are corn straw cores and / or sunflower straw cores and / or sesame straw cores, with a particle size of 20-70 μm. The nanocellulose has a diameter of 3-5 nm and an aspect ratio >1000. The polyethylene oxide has a molecular weight of 1,000,000-10,000,000. The nanocellulose particles are interconnected by hydrogen bonds, entangled with each other to form a network structure, and the straw core particles are uniformly distributed within this network structure, thus forming a straw core-based composite membrane. The preparation process includes the following steps: 1) Take straw cores, dry them, crush them, and sieve them to obtain straw core granules for later use; 2) Prepare PEO aqueous solution, CNF dispersion, and polyphenol functional compound dispersion for later use. The preparation method of polyphenol functional compound dispersion is as follows: Take the insect-repellent chrysanthemum, rinse it with water, soak it in a mixed solvent for 48 hours and then filter it. The mixed solvent is a mixture of ethanol and deionized water in a volume ratio of 4:1 and the volume-to-mass ratio of the mixed solvent to the insect-repellent chrysanthemum is 5:

1. 3) Mix CNF dispersion, PEO aqueous solution and straw core particles, add polyphenol functional compound dispersion and mix well, wherein the volume-to-mass ratio of polyphenol functional compound dispersion to straw core particles is 0.1-5 ml: 100 mg; 4) Transfer the mixed solution to a mold and cast it into a film to obtain a straw core-based composite film.

2. The preparation method according to claim 1, characterized in that, The drying process described in step 1) involves drying in a forced-air drying oven for more than 24 hours.

3. The preparation method according to claim 1, characterized in that, Step 2) The method for preparing the PEO aqueous solution is as follows: Dissolve PEO powder in deionized water, heat and stir, then stir at room temperature until clear. The concentration of the PEO aqueous solution is 1 wt%. Heat to 50-80℃ and stir at 600 rpm for 3 hours, then stir at room temperature for 24 hours.

4. The preparation method according to claim 1, characterized in that, Step 4) The film casting process involves evaporating the solvent at 60-65°C until a film is formed.

5. The use of the straw core-based composite membrane prepared by any of the preparation methods of claims 1-4 in the application of ventilation and water vapor blocking.

6. The use according to claim 5, the straw core-based composite film is used in food-grade packaging, mask linings, printing paper, and writing paper.

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