Cold-resistant, freeze-resistant, breathable polyvinyl alcohol hydrogel film and preparation method and application thereof

Abstract

The present application relates to a kind of preparation method of cold-proof anti-freezing breathable polyvinyl alcohol hydrogel film, including the preparation of hydrogel precursor solution and the preparation steps of polyvinyl alcohol hydrogel film.The present application also provides the cold-proof anti-freezing breathable polyvinyl alcohol hydrogel film obtained by the preparation method and the application of the film in the field of medical and skin care instruments.The present application is the porous structure of polyvinyl alcohol film prepared by repeated freeze-thaw, ice template method in the ternary solvent system of polyethylene glycol / ethylene glycol / water, the pore size thereof can be controlled by the method of the present application, and the obtained film has good air permeability and biocompatibility, and can be used as covering film in low-temperature surgery, medical dressing, air-permeable protective mask and other scenes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hydrogel and its preparation method, and particularly relates to a method for manufacturing a cold-proof and anti-freezing breathable hydrogel film. BACKGROUND

[0002] Hydrogel is a composite material composed of a large amount of water and a three-dimensional polymer network. In recent years, the demand for multifunctional hydrogels has been growing. However, current research on hydrogels mainly aims to improve the mechanical properties and functionality of the material, ignoring the shortcomings of hydrogels in practical application environments, especially their specific material properties under extreme conditions. Traditional hydrogels will inevitably lose water due to evaporation until they dry out in normal working environments, and the loss of water at high temperatures will accelerate, reducing their stability, which limits their use in air and high-temperature environments. In addition, hydrogels will freeze at low temperatures, losing their breathability and stretchability. Although hydrogels can be temporarily relieved of water loss by encapsulating them with materials such as PDMS and VHB, they cannot permanently solve the problem of slow evaporation and freezing. These defects greatly limit the application fields and use environments of hydrogels.

[0003] Ethylene glycol is used as an effective freezing inhibitor in industry. By changing the concentration of ethylene glycol, the freezing point of the ethylene glycol / H2O binary solution can be reduced to below -40℃. The anti-freezing property of ethylene glycol is attributed to its tendency to break the hydrogen bonds between H2O molecules in the binary solution. The freezing temperature of pure ethylene glycol is about -12℃, and when mixed with H2O, ethylene glycol can form various molecular clusters with H2O molecules, thus greatly reducing the saturated vapor pressure of water. It is also well known that a polyvinyl alcohol aqueous solution can be converted into a hydrogel by repeated freeze-thaw cycles to crystallize polyvinyl alcohol. The mechanical strength of polyvinyl alcohol hydrogel is closely related to its crystallinity, which can be adjusted by the number of freeze-thaw cycles.

[0004] Although the above-mentioned methods can achieve the functions of anti-freezing and water retention of hydrogels, there are the following deficiencies: if biological-related applications are required, hydrogels with good biocompatibility are needed, so it is necessary to design and synthesize hydrogels with good biocompatibility, in addition, traditional hydrogel films do not have breathability, and for related applications that require good breathability (masks), the breathability of the material is required.

[0005] Therefore, it is of great significance to develop and design a cold-proof and anti-freezing breathable hydrogel film with good biocompatibility for related applications in extreme environments. SUMMARY

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by providing a cold-resistant, cold-resistant, breathable polyvinyl alcohol hydrogel film with water retention, antifreeze, and breathability, and good biocompatibility, as well as its preparation method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a method for preparing a cold-resistant, antifreeze, and breathable polyvinyl alcohol hydrogel film, comprising the following steps:

[0008] Step 1: Preparation of the hydrogel precursor solution:

[0009] Three types of polyvinyl alcohol powder with molecular weights of 25,000~40,000, 120,000~150,000, and 250,000~300,000 were added to a mixed solution of ethylene glycol, ultrapure water, and polyethylene glycol with a molecular weight of 200~2000. After heating and stirring, a uniform hydrogel precursor solution was obtained.

[0010] The mass ratio of the three polyvinyl alcohol powders is 1~10:1~20:1~10; the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1~20:1~10:1~20, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and to enable the hydrogel to have antifreeze properties at a temperature of 0 to -40°C and moisturizing properties at a temperature of 40°C to 60°C.

[0011] As can be seen from step one, this invention uses polyvinyl alcohol powders of three different molecular weights—high, medium, and low—to prepare hydrogel films. When only medium and low molecular weight polyvinyl alcohol powders are used, the polymer solution is in a sol state. However, when high molecular weight polyvinyl alcohol powder is added, the degree of crosslinking increases, and gelation occurs quickly. By adjusting the ratio of the three different molecular weight polyvinyl alcohol powders, the modulus change of the hydrogel film can be further controlled between 100 and 1000 kPa.

[0012] Simultaneously, a ternary solvent system of polyethylene glycol / ethylene glycol / water is used to improve the biocompatibility of polyvinyl alcohol. A hydrogen bond network is formed between the ethylene glycol, polyvinyl alcohol molecular chains, and water molecules, significantly improving the mechanical properties of the hydrogel. Furthermore, it enhances the water-locking effect, enabling the prepared hydrogel film to exhibit antifreeze properties at low temperatures and excellent moisture retention at high temperatures. Also, by adjusting the ratio of polyethylene glycol, ethylene glycol, and water solvent, the freezing point of the hydrogel film can be further adjusted to achieve optimal antifreeze performance.

[0013] Step 2: Preparation of polyvinyl alcohol hydrogel film:

[0014] The temperature of the hydrogel precursor solution is reduced to -80℃ to 0℃ by using a single ice template method, ice particles are added and uniformly dispersed in the solution, and then the solution is poured into a mold to form shaped ice crystals with a size of 50μm to 800μm, the shaped ice crystals are subjected to at least one repeated freezing and thawing at a melting temperature of 10 to 40℃ and a freezing temperature of -80℃ to 0℃, and thus a polyvinyl alcohol hydrogel film with a thickness of 100μm to 500μm is obtained.

[0015] In the method, the mass ratio of the hydrogel precursor solution to the ice particles is 1:1 or 2:1.

[0016] In the second step, a porous structure with orientation and adjustable pore size is prepared by using a single ice template method, the size of the ice crystals is adjusted by adjusting the freezing temperature, so as to control the pore size and wall thickness, and thus the hydrogel film has good air permeability.

[0017] Further, in the first step, the stirring temperature in the heating and stirring reaction is 30 to 100℃, and the time is 1 to 10h.

[0018] Further, in the second step, the particle size of the ice particles is 50 to 800μm, and the number of repeated freezing and thawing is 1 to 10 times.

[0019] Further, the method comprises the following steps:

[0020] Three polyvinyl alcohol powders with molecular weights of 40,000, 120,000 and 250,000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with a molecular weight of 200, and the solution is subjected to a heating and stirring reaction at a stirring temperature of 95℃ for 2h, and thus a uniform hydrogel precursor solution is obtained.

[0021] The mass ratio of the three polyvinyl alcohol powders is 1:2:1, and the mass ratio of the polyethylene glycol, the ethylene glycol and the ultrapure water is 2:1:2, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and to make the hydrogel have anti-freezing properties at a temperature condition of 0℃ to -40℃ and moisturizing properties at a temperature condition of 40℃ to 60℃.

[0022] The temperature of the hydrogel precursor solution is reduced to 0℃, ice particles are added and uniformly dispersed in the solution, and then the solution is frozen at a temperature of -20℃ to form shaped ice crystals with a size of 200μm, the shaped ice crystals are subjected to three repeated freezing and thawing at a melting temperature of 10 to 40℃ and a freezing temperature of -80℃ to 0℃, and thus a polyvinyl alcohol hydrogel film with a thickness of 100μm to 250μm is obtained.

[0023] Further, the method comprises the following steps:

[0024] The three kinds of polyvinyl alcohol powder with molecular weight of 30000, 130000, 260000 are added into the mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 400, and after heating and stirring reaction under the condition of stirring temperature of 95℃ and time of 4h, a uniform hydrogel precursor solution is obtained;

[0025] The mass ratio of the three kinds of polyvinyl alcohol powder is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1:1:1, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and make the hydrogel have the anti-freezing property under the temperature condition of-50℃ to-70℃ and the moisturizing property under the temperature condition of 40℃ to 50℃;

[0026] The hydrogel precursor solution is cooled to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 100μm are frozen under the temperature condition of-60℃. After 5 times of repeated freezing and thawing of the shaped ice crystals under the melting temperature of 10 to 40℃ and the freezing temperature condition of-80℃ to 0℃, a polyvinyl alcohol hydrogel film with a thickness of 50μm to 150μm is obtained.

[0027] Further, the specific steps include:

[0028] The three kinds of polyvinyl alcohol powder with molecular weight of 40000, 140000, 300000 are added into the mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 600, and after heating and stirring reaction under the condition of stirring temperature of 95℃ and time of 1h, a uniform hydrogel precursor solution is obtained;

[0029] The mass ratio of the three kinds of polyvinyl alcohol powder is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 2:1:4, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and make the hydrogel have the anti-freezing property under the temperature condition of-30℃ to-50℃ and the moisturizing property under the temperature condition of 40℃ to 50℃;

[0030] The hydrogel precursor solution is cooled to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 50μm are frozen under the temperature condition of-20℃. After 2 times of repeated freezing and thawing of the shaped ice crystals under the melting temperature of 10 to 40℃ and the freezing temperature condition of-80℃ to 0℃, a polyvinyl alcohol hydrogel film with a thickness of 50μm to 100μm is obtained.

[0031] Further, the specific steps include:

[0032] The three kinds of polyvinyl alcohol powders with molecular weight of 40000, 150000 and 280000 are added into a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 600, and after heated stirring reaction under the condition of stirring temperature of 95℃ and time of 5h, a uniform hydrogel precursor solution is obtained;

[0033] The mass ratio of the three kinds of polyvinyl alcohol powders is 1:2:2, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1:1:2, so as to improve the biocompatibility and mechanical properties of the hydrogel, and make the hydrogel have the anti-freezing property under the temperature condition of-40℃ to-60℃ and the moisturizing property under the temperature condition of 40℃ to 55℃.

[0034] The hydrogel precursor solution is reduced to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 300μm are frozen under the temperature condition of-80℃, and after 4 times of repeated freezing and thawing under the melting temperature of 10 to 40℃ and the freezing temperature condition of-80℃ to 0℃, the polyvinyl alcohol hydrogel film with a thickness of 200μm to 300μm is obtained.

[0035] Further, the method specifically comprises the following steps:

[0036] The three kinds of polyvinyl alcohol powders with molecular weight of 30000, 120000 and 260000 are added into a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 500, and after heated stirring reaction under the condition of stirring temperature of 95℃ and time of 5h, a uniform hydrogel precursor solution is obtained;

[0037] The mass ratio of the three kinds of polyvinyl alcohol powders is 1:1:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1:2:1, so as to improve the biocompatibility and mechanical properties of the hydrogel, and make the hydrogel have the anti-freezing property under the temperature condition of-50℃ to-80℃ and the moisturizing property under the temperature condition of 40℃.

[0038] The hydrogel precursor solution is reduced to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 400μm are frozen under the temperature condition of-80℃, and after 6 times of repeated freezing and thawing under the melting temperature of 10 to 40℃ and the freezing temperature condition of-80℃ to 0℃, the polyvinyl alcohol hydrogel film with a thickness of 250μm to 350μm is obtained.

[0039] The application further provides a polyvinyl alcohol hydrogel film prepared by the method, and the pore size of the polyvinyl alcohol hydrogel film is 20μm to 450μm, the air permeability is 1000 g / m² / day to 5000 g / m² / day, the elongation at break is 350% to 550%, and the tensile strength is 5 to 55 MPa.

[0040] The present application also provides the use of the polyvinyl alcohol hydrogel film in medical and skin care devices requiring air permeability and cold resistance and anti-freezing functions.

[0041] The present application has the following advantages: the present application provides a method for preparing a cold-resistant and anti-freezing air-permeable hydrogel film, and a polyvinyl alcohol film prepared in a polyethylene glycol / ethylene glycol / water ternary solvent system by repeated freeze-thaw and ice template method. The film has a freezing point as low as -70℃, good flexibility (500% breaking strain), and good transparency at -50℃. In addition, the film can still maintain 80% of its weight after long-term (at least two weeks) outdoor storage at room temperature.

[0042] On this basis, a film with oriented porous structure is prepared by using a unidirectional ice template method, and the size of the ice crystals is adjusted by adjusting the freezing temperature, so as to control the pore size and wall thickness, and a film with a pore size of 40 μm and a thickness of 250 nm is constructed, and the film has good air permeability.

[0043] The film has good biocompatibility, and the extract of the film is used to culture cells for one week, and the results show that the cell survival rate is higher compared with the normal cultured cells.

[0044] Since the polyvinyl alcohol, ethylene glycol and polyethylene glycol used in the film all have good biocompatibility, the film is expected to be used in the biomedical field, especially in medical devices or auxiliary materials requiring air permeability and cold resistance and anti-freezing functions. For example, the material can be used for covering films in low-temperature surgery, medical dressings, air-permeable protective masks and other scenes, which helps to protect the skin and tissues in extreme environments. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a cytotoxicity experiment of a polyvinyl alcohol hydrogel film;

[0046] Figure 2 is the mass change of a polyvinyl alcohol hydrogel film;

[0047] Figure 3 is a tensile test of a polyvinyl alcohol hydrogel film. DETAILED DESCRIPTION

[0048] The principles and characteristics of the present application are described below in combination with the drawings, and the examples are only used to explain the present application and are not used to limit the scope of the present application.

[0049] In order to achieve the above-mentioned purpose, the present application provides the following specific embodiments:

[0050] Example 1: a method for preparing a cold-resistant and anti-freezing air-permeable polyvinyl alcohol hydrogel film, comprising the following steps:

[0051] Step one, preparation of hydrogel precursor solution:

[0052] Three kinds of polyvinyl alcohol powders with molecular weight of 25000-40000, 120000-150000, 250000-300000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 200-2000, and heated and stirred at a stirring temperature of 30-100℃ for 1-10h to obtain a uniform hydrogel precursor solution;

[0053] The mass ratio of the three kinds of polyvinyl alcohol powders is 1-10:1-20:1-10, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1-20:1-10:1-20, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and to make the hydrogel have anti-freezing property under temperature condition of 0℃ to -40℃ and moisturizing property under temperature condition of 40℃ to 60℃;

[0054] Step two, preparation of polyvinyl alcohol hydrogel film:

[0055] The temperature of the hydrogel precursor solution is reduced to -80℃ to 0℃ by using a unidirectional ice template method, ice particles are added and uniformly dispersed, and then poured into a mold to form shaped ice crystals with a size of 50μm to 800μm. The shaped ice crystals are subjected to at least one repeated freeze-thaw at a melting temperature of 10 to 40℃ and a freezing temperature of -80℃ to 0℃, thereby obtaining a polyvinyl alcohol hydrogel film with a thickness of 100μm to 500μm;

[0056] The mass ratio of the hydrogel precursor solution and the ice particles is 1:1 or 2:1, the particle size of the added ice particles ranges from 50μm to 800μm, and the number of repeated freeze-thaw is 1-10 times.

[0057] Example 2: The same as example 1, except that:

[0058] Step one, preparation of hydrogel precursor solution:

[0059] Three kinds of polyvinyl alcohol powders with molecular weight of 40000, 120000 and 250000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 200, and heated and stirred at a stirring temperature of 95℃ for 2h to obtain a uniform hydrogel precursor solution;

[0060] The mass ratio of the three kinds of polyvinyl alcohol powders is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 2:1:2, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and to make the hydrogel have anti-freezing property under temperature condition of 0℃ to -40℃ and moisturizing property under temperature condition of 40℃ to 60℃;

[0061] Step two, preparation of polyvinyl alcohol hydrogel film:

[0062] The hydrogel precursor solution is cooled to 0°C, ice particles are added and uniformly dispersed, and then shaped ice crystals with a size of 200 μm are frozen at a temperature of -20°C. After 3 cycles of repeated freezing and thawing at a melting temperature of 10 to 40°C and a freezing temperature of -80°C to 0°C, a polyvinyl alcohol hydrogel film with a pore size of 200 μm to 400 μm, a thickness of 100 μm to 250 μm, a gas permeability of 3000 g / m² / day to 5000 g / m² / day, an elongation at break of 500%, and a tensile strength of 20 to 50 MPa is obtained.

[0063] Example 3: The same as Example 1, except that:

[0064] Step one, preparation of hydrogel precursor solution:

[0065] Three polyvinyl alcohol powders with molecular weights of 30,000, 130,000, and 260,000 are added to a mixed solution of ethylene glycol, ultrapure water, and polyethylene glycol with a molecular weight of 400. After heating and stirring at a temperature of 95°C for 4 hours, a uniform hydrogel precursor solution is obtained.

[0066] The mass ratio of the three polyvinyl alcohol powders is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol, and ultrapure water is 1:1:1, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and to make the hydrogel have anti-freezing properties at a temperature of -50°C to -70°C and moisturizing properties at a temperature of 40°C to 50°C.

[0067] Step two, preparation of polyvinyl alcohol hydrogel film:

[0068] The hydrogel precursor solution is cooled to 0°C, ice particles are added and uniformly dispersed, and then shaped ice crystals with a size of 200 μm are frozen at a temperature of -20°C. After 3 cycles of repeated freezing and thawing at a melting temperature of 10 to 40°C and a freezing temperature of -80°C to 0°C, a polyvinyl alcohol hydrogel film with a pore size of 200 μm to 400 μm, a thickness of 100 μm to 250 μm, a gas permeability of 3000 g / m² / day to 5000 g / m² / day, an elongation at break of 500%, and a tensile strength of 20 to 50 MPa is obtained.

[0069] Example 4: The same as Example 1, except that:

[0070] Step one, preparation of hydrogel precursor solution:

[0071] The three kinds of polyvinyl alcohol powder with molecular weight of 40000, 140000, 300000 are added into the mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 600, and after heating and stirring reaction under the condition of stirring temperature of 95℃ and time of 1h, a uniform hydrogel precursor solution is obtained;

[0072] The mass ratio of the three kinds of polyvinyl alcohol powder is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 2:1:4, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and make the hydrogel have the anti-freezing property under the temperature condition of-30℃ to-50℃ and the moisturizing property under the temperature condition of 40℃ to 50℃;

[0073] Step two, preparation of polyvinyl alcohol hydrogel film:

[0074] The hydrogel precursor solution is cooled to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 50μm are frozen at a temperature condition of-20℃. After 2 times of repeated freezing and thawing at a melting temperature of 10 to 40℃ and a freezing temperature condition of-80℃ to 0℃, the polyvinyl alcohol hydrogel film with a pore size of 200μm to 350μm, a thickness of 50μm to 100μm, a gas permeability of 2000 g / m² / day to 4000 g / m² / day, an elongation at break of 350% and a tensile strength of 5 to 30 MPa is obtained.

[0075] Example 5: the same as example 1, except that:

[0076] Step one, preparation of hydrogel precursor solution:

[0077] The three kinds of polyvinyl alcohol powder with molecular weight of 40000, 150000, 280000 are added into the mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 600, and after heating and stirring reaction under the condition of stirring temperature of 95℃ and time of 5h, a uniform hydrogel precursor solution is obtained;

[0078] The mass ratio of the three kinds of polyvinyl alcohol powder is 1:2:2, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1:1:2, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and make the hydrogel have the anti-freezing property under the temperature condition of-40℃ to-60℃ and the moisturizing property under the temperature condition of 40℃ to 55℃;

[0079] Step two, preparation of polyvinyl alcohol hydrogel film:

[0080] The hydrogel precursor solution is cooled to 0°C, ice particles are added and uniformly dispersed, and then the solution is frozen into shaped ice crystals with a size of 300 μm at a temperature of -80°C. After 4 cycles of repeated freezing and thawing at a melting temperature of 10 to 40°C and a freezing temperature of -80°C to 0°C, a polyvinyl alcohol hydrogel film with a pore size of 100 μm to 250 μm, a thickness of 200 μm to 300 μm, a gas permeability of 1000 g / m² / day to 2000 g / m² / day, an elongation at break of 450%, and a tensile strength of 25 to 55 MPa is obtained.

[0081] Example 6: The same as example 1, except that:

[0082] Step 1: Preparation of a hydrogel precursor solution:

[0083] Three polyvinyl alcohol powders with molecular weights of 30,000, 120,000, and 260,000 are added to a mixed solution of ethylene glycol, ultrapure water, and polyethylene glycol with a molecular weight of 500. After heating and stirring at a temperature of 95°C for 5 hours, a uniform hydrogel precursor solution is obtained.

[0084] The mass ratio of the three polyvinyl alcohol powders is 1:1:1, and the mass ratio of polyethylene glycol, ethylene glycol, and ultrapure water is 1:2:1. This is used to improve the biocompatibility and mechanical properties of the hydrogel, and to give the hydrogel anti-freezing properties at a temperature of -50°C to -80°C and moisturizing properties at a temperature of 40°C.

[0085] Step 2: Preparation of a polyvinyl alcohol hydrogel film:

[0086] The hydrogel precursor solution is cooled to 0°C, ice particles are added and uniformly dispersed, and then the solution is frozen into shaped ice crystals with a size of 400 μm at a temperature of -80°C. After 6 cycles of repeated freezing and thawing at a melting temperature of 10 to 40°C and a freezing temperature of -80°C to 0°C, a polyvinyl alcohol hydrogel film with a pore size of 20 μm to 400 μm, a thickness of 250 μm to 350 μm, a gas permeability of 2000 g / m² / day to 4000 g / m² / day, an elongation at break of 550%, and a tensile strength of 35 to 45 MPa is obtained.

[0087] Example 7: Figure 3 As shown in the table, the present application also provides a polyvinyl alcohol hydrogel film prepared by the method described in examples 1-5. The pore size of the polyvinyl alcohol hydrogel film is 20 μm to 450 μm, the gas permeability is 1000 g / m² / day to 5000 g / m² / day, the elongation at break is 350% to 550%, and the tensile strength is 5 to 55 MPa.

[0088] Figure 3 The tensile test results of the polyvinyl alcohol hydrogel film prepared according to Example 2 are shown in the figure. The film exhibits an elongation at break of 500% and a tensile strength of 20-50 MPa, indicating that the film has excellent elasticity and toughness.

[0089] Example 8: As shown in Figure 1 , Figure 2 , Figure 3 The present application also provides the use of the polyvinyl alcohol hydrogel film in medical and skin care devices that require air permeability and cold resistance and anti-freezing functions.

[0090] Figure 1 : Cytotoxicity test results of the film in vitro cell culture, verifying the safety and biocompatibility of the film prepared by the present application, confirming whether the film produces toxicity when contacting cells, and thus verifying its safety in the biomedical field. The experiment shows that the film has no significant toxicity to cells and exhibits good biocompatibility, making it suitable for use in medical and skin care fields.

[0091] Figure 2 : Film mass change graph, three samples of the film provided by the present application are taken to show the durability of the film prepared by the present application under normal temperature and open-air conditions. The experiment shows that the film can still maintain 80% of its original weight within two weeks, indicating its good moisturizing performance and suitability for use in medical and skin care fields.

[0092] Figure 3 : Tensile test graph, used to show the mechanical properties of the film prepared by the present application. The results show that the film has high ductility and tensile strength, making it suitable for high-strength application scenarios. These characteristics make it suitable for use in application scenarios that require strong mechanical properties, such as motion protection or weather-resistant protective materials in medical devices.

[0093] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of a cold-weather, freeze resistant, breathable polyvinyl alcohol hydrogel film, characterized in that, The method comprises the following steps: Step one, preparation of hydrogel precursor solution: Three kinds of polyvinyl alcohol powders with molecular weight of 25000-40000, 120000-150000 and 250000-300000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 200-2000, and after heating and stirring reaction, a uniform hydrogel precursor solution is obtained; The mass ratio of the three kinds of polyvinyl alcohol powders is 1-10:1-20:1-10, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1-20:1-10:1-20, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and to make the hydrogel have anti-freezing property under temperature condition of 0- -40℃ and moisturizing property under temperature condition of 40-60℃; Step two, preparation of polyvinyl alcohol hydrogel film: The temperature of the hydrogel precursor solution is reduced to -80-0℃, ice particles are added and uniformly dispersed, and then poured into a mold to form a shaped ice crystal with a size of 50-800μm, and the shaped ice crystal is subjected to at least one repeated freeze-thaw at a melting temperature of 10-40℃ and a freezing temperature of -80-0℃, thereby obtaining a polyvinyl alcohol hydrogel film with a thickness of 100-500μm; The mass ratio of the hydrogel precursor solution and the ice particles is 1:1 or 2:

1.

2. The method for preparing the cold-resistant, antifreeze, and breathable polyvinyl alcohol hydrogel film as described in claim 1, characterized in that, The stirring temperature in the heating and stirring reaction in step one is 30-100℃, and the time is 1-10h.

3. The method for preparing the cold-resistant, antifreeze, and breathable polyvinyl alcohol hydrogel film as described in claim 1, characterized in that, The particle size of the ice particles added in step two is 50-800μm, and the number of repeated freeze-thaw is 1-10 times.

4. Process for the preparation of cold-resistant, frost-resistant, breathable polyvinyl alcohol hydrogel films according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: Three kinds of polyvinyl alcohol powders with molecular weight of 40000, 120000 and 250000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 200, and after heating and stirring reaction at a stirring temperature of 95℃ for 2h, a uniform hydrogel precursor solution is obtained; The mass ratio of the three kinds of polyvinyl alcohol powders is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 2:1:2, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and to make the hydrogel have anti-freezing property under temperature condition of 0- -40℃ and moisturizing property under temperature condition of 40-60℃; The temperature of the hydrogel precursor solution is reduced to 0℃, ice particles are added and uniformly dispersed, and then frozen at a temperature of -20℃ to form a shaped ice crystal with a size of 200μm, and the shaped ice crystal is subjected to 3 times of repeated freeze-thaw at a melting temperature of 10-40℃ and a freezing temperature of -80-0℃, thereby obtaining a polyvinyl alcohol hydrogel film with a thickness of 100-250μm.

5. The method for preparing the cold-resistant, antifreeze, and breathable polyvinyl alcohol hydrogel film according to any one of claims 1-3, characterized in that, The method comprises the following steps: Three kinds of polyvinyl alcohol powders with molecular weight of 30000, 130000 and 260000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 400, and after heating and stirring reaction at a stirring temperature of 95℃ for 4h, a uniform hydrogel precursor solution is obtained; The mass ratio of the three kinds of polyvinyl alcohol powders is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 2:1:2, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and to make the hydrogel have anti-freezing property under temperature condition of 0- -40℃ and moisturizing property under temperature condition of 40-60℃; The mass ratio of the three polyvinyl alcohol powders is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1:1:1, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and the hydrogel has the properties of anti-freezing under the temperature condition of-50℃ to-70℃ and moisturizing under the temperature condition of 40℃ to 50℃; The hydrogel precursor solution is cooled to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 100μm are frozen at a temperature condition of-60℃, and the shaped ice crystals are subjected to 5 times of repeated freezing and thawing at a melting temperature of 10 to 40℃ and a freezing temperature condition of-80℃ to 0℃, so that the polyvinyl alcohol hydrogel film with a thickness of 50μm to 150μm is obtained.

6. The method of claim 1-3, wherein the cold-resistant, freeze- resistant, breathable polyvinyl alcohol hydrogel film is prepared by the steps of: Specifically comprising the following steps: The three polyvinyl alcohol powders with molecular weights of 40000, 140000 and 300000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with a molecular weight of 600, and heated and stirred under the condition of a stirring temperature of 95℃ and a stirring time of 1h, so that a uniform hydrogel precursor solution is obtained; The mass ratio of the three polyvinyl alcohol powders is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1:1:1, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and the hydrogel has the properties of anti-freezing under the temperature condition of-50℃ to-70℃ and moisturizing under the temperature condition of 40℃ to 50℃; The hydrogel precursor solution is cooled to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 100μm are frozen at a temperature condition of-60℃, and the shaped ice crystals are subjected to 5 times of repeated freezing and thawing at a melting temperature of 10 to 40℃ and a freezing temperature condition of-80℃ to 0℃, so that the polyvinyl alcohol hydrogel film with a thickness of 50μm to 150μm is obtained.

7. A process for the preparation of cold weather frost resistant, breathable polyvinyl alcohol hydrogel film according to any one of claims 1 to 3, wherein, Specifically comprising the following steps: The three polyvinyl alcohol powders with molecular weights of 40000, 140000 and 300000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with a molecular weight of 600, and heated and stirred under the condition of a stirring temperature of 95℃ and a stirring time of 1h, so that a uniform hydrogel precursor solution is obtained; The mass ratio of the three polyvinyl alcohol powders is 1:2:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1:1:1, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and the hydrogel has the properties of anti-freezing under the temperature condition of-50℃ to-70℃ and moisturizing under the temperature condition of 40℃ to 50℃; The hydrogel precursor solution is cooled to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 100μm are frozen at a temperature condition of-60℃, and the shaped ice crystals are subjected to 5 times of repeated freezing and thawing at a melting temperature of 10 to 40℃ and a freezing temperature condition of-80℃ to 0℃, so that the polyvinyl alcohol hydrogel film with a thickness of 50μm to 150μm is obtained.

8. A process for the preparation of cold weather frost resistant, breathable polyvinyl alcohol hydrogel film according to any one of claims 1 to 3, wherein, Specifically comprising the following steps: The three polyvinyl alcohol powders with molecular weights of 40000, 140000 and 300000 are added to a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with a molecular weight of 600, and heated and stirred under the condition of a stirring temperature of 95℃ and a stirring time of 1h, so that a uniform hydrogel precursor solution is obtained; Three kinds of polyvinyl alcohol powders with molecular weight of 30000, 120000, 260000 are added into a mixed solution of ethylene glycol, ultrapure water and polyethylene glycol with molecular weight of 500, and after heated and stirred at a temperature of 95℃ for 5 hours, a uniform hydrogel precursor solution is obtained; The mass ratio of the three kinds of polyvinyl alcohol powders is 1:1:1, and the mass ratio of polyethylene glycol, ethylene glycol and ultrapure water is 1:2:1, which is used to improve the biocompatibility and mechanical properties of the hydrogel, and make the hydrogel have the anti-freezing property under the temperature condition of-50℃ to-80℃ and the moisturizing property under the temperature condition of 40℃; The hydrogel precursor solution is reduced to 0℃, ice particles are added and uniformly dispersed, and then the shaped ice crystals with a size of 400μm are frozen at a temperature condition of-80℃, and after 6 times of repeated freezing and thawing at a melting temperature of 10 to 40℃ and a freezing temperature condition of-80℃ to 0℃, a polyvinyl alcohol hydrogel film with a thickness of 250μm to 350μm is obtained.

9. A polyvinyl alcohol hydrogel film prepared according to the method of any one of claims 1 to 3, characterized in that, The polyvinyl alcohol hydrogel film has a pore size of 20 μm to 450 μm, a gas permeability of 1000 g / m 2 / day to 5000 g / m 2 / day, an elongation at break of 350% to 550%, and a tensile strength of 5 to 55 MPa.

10. Use of a polyvinyl alcohol hydrogel film according to claim 9, characterized in that, The application in the preparation of medical devices and skin care devices which need air permeability and cold resistance and anti-freezing function.

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