An irradiation cross-linked high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel and a preparation method thereof

Abstract

The application belongs to the technical field of high polymer materials, and specifically discloses a kind of irradiation crosslinking high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel and preparation method thereof, the method comprises the following steps: nanocellulose dispersion liquid and polyvinyl alcohol solution are mixed uniformly according to mass ratio 2:3, obtain mixed solution, mixed solution is added to mould, and is placed at 30 DEG C~80 DEG C for 2h~48h, eliminate air bubble in mixed solution, then the mixed solution after defoaming is carried out radiation treatment, and high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel is obtained.The application also provides a kind of high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel prepared by the preparation method, and the high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel has good mechanical property and excellent light transmittance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular materials, in particular to a kind of high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel crosslinked by irradiation and a preparation method thereof. BACKGROUND

[0002] Hydrogel is a kind of three-dimensional network structure of polymer swelling body, with strong water absorption and water retention and biocompatibility, etc., has been widely studied in the field of biology and medical engineering. Polyvinyl alcohol (PVA) as a kind of biodegradable hydrophilic polymer, with good biocompatibility, low price and other advantages in the field of hydrogel is widely used. The preparation method of polyvinyl alcohol hydrogel mainly includes physical crosslinking, chemical crosslinking and radiation crosslinking. Physical crosslinking method is to realize physical crosslinking by repeated freeze-thaw cycle, the PVA hydrogel prepared by this method has good mechanical properties, but the process is complicated, the crosslinking degree is difficult to control, and the transparency is poor. The hydrogel prepared by chemical crosslinking method usually remains crosslinking agent and initiator, etc., which has the risk of causing inflammation or cytotoxicity. Radiation crosslinking is to use high-energy ray to irradiate PVA solution to form covalent crosslinking network directly, the product has high purity, good light transmittance and easy to control crosslinking degree, which has obvious advantages in medical field. However, the polyvinyl alcohol hydrogel prepared by radiation method has the problems of poor mechanical properties and easy to break.

[0003] In order to solve the problem of poor mechanical properties of polyvinyl alcohol hydrogel prepared by radiation crosslinking, many researchers have devoted to the development of composite hydrogel dressing. For example, CN101337086A discloses a hydrogel dressing, which is composed of a polyvinyl alcohol layer prepared by freeze-thaw cycle and a mixed layer of polyvinyl alcohol and carboxymethyl cellulose prepared by radiation method; CN110898251A discloses a composite hydrogel dressing with pH responsiveness and internal grafting porous through network structure, which is prepared by radiation crosslinking of a mixture of polyvinyl alcohol, polyethylene oxide and carboxymethyl chitosan; CN206026746U discloses a hydrogel, which includes a functional layer of hydrogel prepared by physical, chemical or radiation crosslinking method from a water solution of a mixture of polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, glycerol and deacetylated chitosan, and adding antibacterial drugs. Although these hydrogels can enhance the mechanical properties of hydrogel to some extent, harmful substances such as chemical crosslinking agent or initiator are introduced in the synthesis, which limits the application of hydrogel in medical field. SUMMARY

[0004] In view of the problems and deficiencies in the prior art, the purpose of the present application is to provide a kind of high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel crosslinked by radiation and a preparation method thereof.

[0005] To achieve the purpose of the application, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a preparation method of a high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel crosslinked by radiation, comprising the following steps: uniformly mixing a nanocellulose dispersion liquid and a polyvinyl alcohol solution according to a mass ratio of 2:3 to obtain a mixed liquid, adding the mixed liquid into a mold, standing and treating at 30-80°C for 2-48h to eliminate air bubbles in the mixed liquid, and then performing radiation treatment on the defoamed mixed liquid to obtain the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel.

[0007] The nanocellulose can be commercial TEMPO-oxidized cellulose nanofiber or cellulose nanocrystal obtained by concentrated sulfuric acid hydrolysis.

[0008] According to the preparation method of the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel, preferably, the nanocellulose dispersion liquid is prepared by dispersing nanocellulose in water, and the mass fraction of nanocellulose in the nanocellulose dispersion liquid is 0.25-3.75%, more preferably, the nanocellulose is derived from natural wood fiber resources.

[0009] According to the preparation method of the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel, preferably, the polyvinyl alcohol solution is prepared by dissolving polyvinyl alcohol in water, and the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 10%-25%, more preferably, the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 20%.

[0010] According to the preparation method of the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel, preferably, the radiation dose of the radiation treatment is 15-50kGy.

[0011] According to the preparation method of the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel, preferably, the radiation treatment is performed by using 60 Co γ -ray or high-energy electron beam radiation.

[0012] The present application also provides a high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel prepared by using the above preparation method.

[0013] Compared with the prior art, the present application has the following positive and beneficial effects:

[0014] (1) The present application uses nanocellulose derived from natural wood fiber resources as a "green" modifier of polyvinyl alcohol hydrogel, and prepares a high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel by radiation crosslinking method. Compared with the prior art, the present application does not introduce harmful substances such as chemical crosslinking agents and initiators during the preparation process, and does not generate other harmful substances, thereby widening the application of hydrogel in the medical field.

[0015] (2) The nanocellulose can be divided into cellulose nanofibril and cellulose nanocrystal, the surface of which is rich in hydroxyl groups, and has nanoscale diameter, high aspect ratio, high specific surface area, high modulus, and good biocompatibility and biodegradability. The nanocellulose is added to the polyvinyl alcohol hydrogel to prepare a composite hydrogel which has good biocompatibility, environmental protection and mechanical properties, and also maintains high light transmittance.

[0016] (3) The high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel of the application is prepared by 60Co γ-ray or high-energy electron beam irradiation, which can prevent bacteria, prolong preservation time, and ensure the quality of the hydrogel.

[0017] (4) The preparation method is simple and easy to operate, does not require expensive equipment, and has wide raw material sources and low cost, which is conducive to reducing production cost and realizing industrial transformation of technology. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the tensile property parameter diagram of examples 1-5 and comparative example 1;

[0019] Figure 2 is the compressive strength diagram of examples 10-14;

[0020] Figure 3 is the tensile property parameter diagram of examples 10-14;

[0021] Figure 4 is the performance parameter diagram of example 14 and example 15. DETAILED DESCRIPTION

[0022] The application will be further described below through specific examples, but the scope of the application is not limited.

[0023] (I), discussion on the mass fraction of nanocellulose in the nanocellulose dispersion

[0024] In order to explore the influence of the mass fraction of nanocellulose on the transparency, haze, tensile strength and elongation at break of the prepared high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel, the inventors made the following experiments, namely examples 1-5 and comparative example 1.

[0025] Example 1

[0026] A preparation method of a high light transmittance nanocellulose / polyvinyl alcohol composite hydrogel, comprising the following steps:

[0027] (1) 30 g of gel-state nanocellulose (nanocellulose content 5%) was added into a flask, and stirred at room temperature until it became homogeneous and translucent, to obtain a nanocellulose dispersion with a mass fraction of 0.75%;

[0028] (2) 50 g of polyvinyl alcohol and 250 mL of pure water were added into a flask, and stirred at 90°C for 4 h to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 16.67% of polyvinyl alcohol; 60 Co γ -ray radiation, with a radiation dose of 30 kGy, to obtain the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel.

[0029] Examples 2-5

[0030] Examples 2-5

[0031] Comparative Example 1

[0032] Comparative Example 1

[0033] The above examples 1-5 and comparative example 1 were subjected to transparency test and tensile property test, and the test methods were as follows:

[0034] 1. Transparency test method: the hydrogels prepared in examples 1-5 and comparative example 1 were cut into squares with a side length of 5 cm, and the light transmittance thereof was tested by SUGA HZ-V3 haze.

[0035] Tensile property test method: the hydrogels prepared in examples 1-5 and comparative example 1 were made into dumbbells (middle part width 4 mm, length 40 mm), and the tensile property thereof was tested by an electronic universal testing machine, with a tensile rate of 50 mm / min.

[0036] Compression property test method: the hydrogels prepared in examples 1-5 and comparative example 1 were cut into circles with a diameter of 1.6 cm, and the compression thereof was tested by an electronic universal testing machine, with a compression rate of 1 mm / min.

[0037] The results of the above performance tests are shown in Table 1.

[0038]

[0039] From Table 1, it can be seen that the mass fraction of nanocellulose in the nanocellulose dispersion mainly affects the tensile strength and elongation at break of the composite hydrogel. When the mass fraction of nanocellulose in the nanocellulose dispersion is 3.75%, the tensile strength and elongation at break of the obtained composite hydrogel are optimal. If the mass fraction of cellulose is continuously increased, the viscosity of the solution after mixing with polyvinyl alcohol is too large, resulting in that the bubbles generated by stirring cannot be small, and the performance of the product is reduced.

[0040] (II) Investigation of the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution

[0041] In order to investigate the influence of the mass fraction of polyvinyl alcohol on the transparency, compressive strength, tensile strength and elongation at break of the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel prepared, the inventors carried out the following experiments, i.e., Examples 6-9.

[0042] Example 6

[0043] A preparation method of a high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel, comprising the following steps:

[0044] (1) 10 g of gel-state nanocellulose (nanocellulose content of 5%) and 190 mL of pure water are added to a flask, and strong stirring is carried out at room temperature until a uniform translucent state is obtained, to obtain a nanocellulose dispersion with a mass fraction of 0.25%;

[0045] (2) 40 g of polyvinyl alcohol and 260 mL of pure water are added to a three-necked flask, and stirring is carried out at 90°C for 4 h, to obtain a polyvinyl alcohol aqueous solution with a mass fraction of 13.33% of polyvinyl alcohol;

[0046]

[0047] (3) The nanocellulose dispersion and the polyvinyl alcohol aqueous solution obtained in (1) and (2) are uniformly mixed, and then transferred to a mold, and the mold is vertically placed in an oven at a temperature of 60°C and left to stand for 24 h, wherein the mold is a parallel glass mold with a size of 30*18*2 mm, and finally subjected to γ-ray irradiation with a radiation dose of 30 kGy, to obtain the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel. 60

[0048] Examples 7-9

[0049] Examples 7-9 are basically the same as Example 6, except that the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 16.67%, 20.00% and 25.00%, respectively. ​​

[0050] The above examples 6-9 were tested for transparency and tensile properties, the testing method is as above, and the test results are shown in Table 2.

[0051]

[0052] From Table 2, it can be seen that the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution mainly affects the tensile strength, compressive strength and elongation at break, and the optimal mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 20%.

[0053] (Three), the discussion of the radiation dose of radiation treatment:

[0054] In order to explore the influence of radiation dose in the process of radiation treatment on the transparency, compressive strength, tensile strength and elongation at break of the prepared high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel, the inventors conducted the following experiments, namely examples 10-14.

[0055] Example 10

[0056] (1) 90 g of gel-state nanocellulose (5%) and 110 mL of pure water were added to a flask, and stirred at room temperature until a homogeneous translucent state was obtained, obtaining a nanocellulose dispersion with a mass fraction of 2.25%;

[0057] (2) 50 g of polyvinyl alcohol and 250 mL of pure water were added to a three-necked flask, and stirred at 90°C for 4 h, obtaining a polyvinyl alcohol aqueous solution with a mass fraction of 16.67% of polyvinyl alcohol;

[0058] (3) The nanocellulose dispersion and polyvinyl alcohol aqueous solution obtained in (1) and (2) were uniformly mixed, then transferred to a mold, and the mold was placed vertically in an oven at a temperature of 60°C for 24 h, wherein the mold was a parallel glass mold with a size of 30*18*2mm, and finally subjected to 60 Co γ -ray irradiation with a radiation dose of 20 kGy, to obtain the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel.

[0059] Examples 11-14

[0060] Examples 11-14 are basically the same as Example 10, except that the radiation dose is 30 kGy, 40 kGy, 50 kGy and 60 kGy, respectively.

[0061] The above examples 10-14 were tested for transparency, tensile and compressive properties, the testing method is as above, and the test results are shown in Table 3.

[0062]

[0063] From Table 3, it can be seen that the radiation dose of the radiation treatment mainly affects the compressive strength, tensile strength and elongation at break. Considering the cost and time factors, the optimal radiation dose of the radiation treatment is 50 kGy.

[0064] (4) Discussion on the radiation treatment mode

[0065] In order to investigate the influence of the radiation treatment mode on the transparency, haze, tensile strength and elongation at break of the prepared high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel, the inventors carried out the following experiments, i.e. Example 15, the corresponding radiation treatment modes of which are 60Co γ-rays and high-energy electron beams, respectively. The experimental results are shown in Table 4.

[0066] Example 15

[0067] (1) 90 g of gel-state nanocellulose (5%) and 110 mL of pure water were added into a flask, and stirred at room temperature until a homogeneous translucent state was obtained, to obtain a nanocellulose dispersion with a mass fraction of 2.25%;

[0068] (2) 50 g of polyvinyl alcohol and 250 mL of pure water were added into a three-necked flask, and heated and stirred at 90°C for 4 h to obtain a polyvinyl alcohol aqueous solution with a polyvinyl alcohol mass fraction of 16.67%;

[0069] (3) The nanocellulose dispersion and the polyvinyl alcohol aqueous solution obtained in (1) and (2) were uniformly mixed, then transferred into a mold, and the mold was vertically placed in an oven at a temperature of 60°C for 24 h, wherein the mold was a parallel glass mold with a size of 30*18*2 mm, and finally subjected to high-energy electron beam irradiation with a radiation dose of 50 kGy, to obtain the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel.

[0070] The above Example 15 was subjected to transparency test, tensile and compression performance test, and the test methods were as above, and the test results are shown in Table 4.

[0071]

[0072] From Table 4, it can be seen that the tensile performance of the hydrogel prepared by the electron accelerator is poor, and therefore the optimal radiation treatment mode is 60 Co-γ-ray irradiation.

Claims

1. A method for preparing a radiation-crosslinked, high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel, characterized in that, The preparation method is as follows: a nanocellulose dispersion and a polyvinyl alcohol solution are mixed evenly at a mass ratio of 2:3 to obtain a mixed solution. The mixed solution is added to a mold and allowed to stand at 30℃~80℃ for 2h~48h to eliminate air bubbles in the mixed solution. Then, the defoamed mixed solution is subjected to radiation treatment to obtain a high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel. The nanocellulose is cellulose nanofiber oxidized by TEMPO or cellulose nanocrystals obtained by hydrolysis with concentrated sulfuric acid. The nanocellulose dispersion is prepared by dispersing nanocellulose in water, and the mass fraction of nanocellulose in the nanocellulose dispersion is 0.75%~3.75%. The polyvinyl alcohol solution is prepared by dissolving polyvinyl alcohol in water, and the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 10.00%~25.00%.

2. The method for preparing the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel according to claim 1, characterized in that, The radiation dose for the radiation treatment is 15–50 kGy.

3. The method for preparing the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel according to claim 2, characterized in that, The radiation treatment is performed using 60Co γ-rays or a high-energy electron beam.

4. A high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel prepared by the preparation method of the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel according to any one of claims 1 to 3; wherein the high-transmittance nanocellulose / polyvinyl alcohol composite hydrogel has a transmittance of 91.1-94.1%, a compressive strength of 586.8-1533 kPa, a tensile strength of 65.6-195.4 kPa, and an elongation at break of 110.9-252.9%.

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