Polyvinyl alcohol water transfer printing film and preparation method thereof

Abstract

The invention discloses a polyvinyl alcohol water transfer printing film and a preparation method thereof, and belongs to the technical field of water transfer printing film preparation, the polyvinyl alcohol water transfer printing film comprises the following components: polyvinyl alcohol, a cross-linking agent, a plasticizer, a surfactant and water; wherein the addition amount of the cross-linking agent is 0.1%-2% of the mass of the polyvinyl alcohol, and the addition amount of the surfactant is 0.2%-1% of the mass of the polyvinyl alcohol; in addition, the invention also comprises nanoparticles with the addition amount being 0.5%-3% of the mass of the polyvinyl alcohol. The polyvinyl alcohol water transfer printing film prepared through the preparation method is excellent in water solubility and mechanical property, simple in forming process, small in elongation on water and not prone to curling, and can be applied to the laundry condensate bead industry and various water-soluble packaging industries, especially the field of water transfer printing films.

Description

Technical Field

[0001] This invention relates to the field of water transfer printing film preparation technology, and particularly to a polyvinyl alcohol water transfer printing film and its preparation method. Background Technology

[0002] Water transfer printing is a widely used transfer process for decorating complex curved surfaces, with a water-soluble transfer film as its core carrier. Polyvinyl alcohol (PVA) has become a common material for water transfer printing films due to its excellent water solubility, film-forming properties, emulsifying properties, and mechanical properties. The dissolution process of PVA film in water typically includes three stages: initial curling, stretching and swelling, and final dissolution. Currently, PVA water transfer printing films have some shortcomings in application. For example, PVA water transfer printing films are prone to excessive curling and swelling in the first and second stages, leading to deformation, distortion, and even overlap of the transferred pattern, seriously affecting the transfer accuracy and product quality.

[0003] Currently, a common practice to improve the performance of PVA water transfer films is to add starch-based substances to adjust the tensile strength, moisture content, and elongation at water. However, starch is prone to gelatinization, aging, and even carbonization and discoloration under high-temperature processing conditions, such as during blown film production. This not only limits the process window but also affects the appearance and performance consistency of the film, making it difficult to meet the requirements of continuous industrial production. Furthermore, existing PVA water transfer films still have shortcomings in balancing dissolution rate, swelling control, mechanical strength, and surface properties, necessitating a water transfer film solution with superior overall performance.

[0004] Therefore, there is an urgent need to develop a PVA water transfer film with low swelling, rapid disintegration, high mechanical strength and good printability. Summary of the Invention

[0005] The purpose of this invention is to provide a polyvinyl alcohol water transfer film to solve the problems of excessive curling and unfolding and large deformation during dissolution in the prior art.

[0006] The present invention also aims to provide a method for preparing a polyvinyl alcohol water transfer film, which is used to prepare a polyvinyl alcohol water transfer film.

[0007] In a first aspect, the present invention provides a polyvinyl alcohol water transfer film, comprising the following components: Polyvinyl alcohol, crosslinking agent, plasticizer, surfactant, deionized water; The amount of crosslinking agent added is 0.1% to 2% of the mass of polyvinyl alcohol; The amount of surfactant added is 0.2% to 1% of the mass of polyvinyl alcohol; The polyvinyl alcohol water transfer film also includes nanoparticles added at a concentration of 0.5% to 3% of the mass of polyvinyl alcohol.

[0008] By adopting the above technical solution, the polyvinyl alcohol (PVA) water transfer film of the present invention contains a crosslinking agent. On the one hand, the swelling degree of the PVA water transfer film can be reduced by a low degree of crosslinking; on the other hand, the water solubility can be adjusted by reducing the degree of hydrogen bonding between PVA molecules. Therefore, the amount of crosslinking agent is crucial in the present invention. The present invention selects to add 0.1% to 2% of the mass of PVA as the crosslinking agent because the molecular weight will not increase sharply during mild crosslinking, and the viscosity of the system will not become uncontrollable due to the crosslinking reaction. However, when the amount of crosslinking agent is too large, the degree of crosslinking of the system increases, and a three-dimensional crosslinked network is formed within the system, which reduces the water solubility of the PVA film. Adding 0.1% to 2% of the mass of PVA as the crosslinking agent can produce a micro-crosslinked structure. The presence of this micro-crosslinked structure makes the chain segments of the PVA material more ordered and the structure more stable, which is beneficial to improving the mechanical properties of PVA.

[0009] This invention improves the water solubility of polyvinyl alcohol (PVA) water transfer film by compounding plasticizers. Adjusting the type and ratio of plasticizers can disrupt the regularity of the PVA molecular structure. The groups in the added plasticizers can form hydrogen bonds with the hydroxyl groups of PVA molecules and also form complexes with PVA molecules, effectively disrupting the internal structure of PVA molecules and improving the water solubility of PVA films.

[0010] Furthermore, the surface tension of the transfer film is crucial in the water transfer printing process. Excessive surface tension can lead to poor adhesion of the substrate and cause the film to curl up in water and fail to unwind, resulting in overlapping images and transfer failure. Therefore, this invention adjusts the surface tension of the film by adding a surfactant. The amount of surfactant added is also critical, as excessive addition can reduce surface tension and increase the number of hydrophilic groups on the film surface, potentially causing the film to dissolve completely in water before the transfer process is complete. This results in premature ink detachment and incomplete adhesion to the product. Therefore, this invention selects to add 0.1% to 1% (by weight of polyvinyl alcohol) of surfactant, which not only adjusts the surface tension of the film but also has minimal impact on its solubility.

[0011] The degree of swelling of the water transfer film directly affects the size and distortion of the transferred image. The polyvinyl alcohol (PVA) water transfer film of this invention incorporates nanoparticles, which inhibit the curling and stretching of the PVA water transfer film. The nanoparticles of this invention have a particle size of 30–100 μm. Nanoparticles of this size can be uniformly distributed within the PVA water transfer film without affecting the film's surface smoothness. Furthermore, they can exist as small functional groups, providing dissolution points within the film and hindering curling and stretching during the dissolution process, thus ensuring the printing quality of the product as a water transfer film.

[0012] Furthermore, nanoparticles can work synergistically with other components in the polyethylene glycol water transfer film. First, nanoparticles can work with crosslinking agents to improve the overall stability of the crosslinked network, inhibiting swelling from both chemical and physical dimensions. Specifically, the physical barrier of nanoparticles can prevent uneven local swelling, while the chemical crosslinking of the crosslinking agent controls the overall degree of swelling, jointly stabilizing the swelling degree within a range that does not affect the image size, while avoiding excessive crosslinking that leads to a decrease in water solubility. Second, nanoparticles can work synergistically with surfactants to prevent excessive hydrophilicity that could lead to transfer failure. Nanoparticles control the dissolution site, while surfactants control the dissolution rate, ensuring that the film's dissolution process in water is synchronized with the image transfer steps.

[0013] Preferably, the degree of polymerization of polyvinyl alcohol is 1500-2000 and the degree of alcoholysis is 88%-92%.

[0014] Preferably, the crosslinking agent comprises one or more of the following: polybasic acids, polybasic aldehydes, divalent metal salts, and boric acid.

[0015] More preferably, the polyacid includes one or more of citric acid, malic acid and oxalic acid.

[0016] More preferably, polyaldehydes include glyoxal and glutaraldehyde.

[0017] More preferably, the divalent metal salt includes one or a combination of magnesium chloride, magnesium sulfate and calcium chloride.

[0018] Preferably, the amount of plasticizer added is 15% to 35% of the mass of polyvinyl alcohol; the plasticizer includes one or more of amides, alkanolamines, small molecule alcohols and polyols.

[0019] More preferably, the amides include one or more of formamide, acetamide and caprolactam.

[0020] More preferably, alkanolamines include diethanolamine and triethanolamine.

[0021] More preferably, the small molecule alcohols include one or more of glycerol, ethylene glycol, butanediol, pentanediol and pentaerythritol; More preferably, the polyols include sorbitol and polyethylene glycol.

[0022] Preferably, the surfactant comprises a complex of an ionic surfactant and a nonionic surfactant in a mass ratio of (0.1~0.9):(0.1~0.9).

[0023] Preferably, the ionic surfactant includes one or more of sodium dodecyl sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, and potassium dodecyl phosphate.

[0024] Preferably, the nonionic surfactant includes one or a combination of several of AEO-9, Tween 80, OP-10, diglycerol, triglycerol, tetraglycerol, hexaglycerol and decaglycerol.

[0025] Preferably, the nanoparticles include one or more of the following: silicon dioxide, titanium dioxide, calcium stearate, magnesium stearate, calcium carbonate, barium sulfate, zinc oxide, microcrystalline cellulose, talc, and bentonite.

[0026] Secondly, the present invention provides a method for preparing a polyvinyl alcohol water transfer film, comprising the following steps: S1. Polyvinyl alcohol, crosslinking agent, nanoparticles, plasticizer and surfactant are added to deionized water and mixed to obtain polyvinyl alcohol powder; S2. The polyvinyl alcohol powder is granulated and melt blown to obtain a polyvinyl alcohol film.

[0027] Preferably, in step S1, the moisture content of the polyvinyl alcohol powder is 20% to 40%.

[0028] Preferably, in step S2, granulation is carried out at a temperature of 100–180°C; melt blow molding is carried out at a temperature of 100–180°C.

[0029] Preferably, in step S2, the equipment used for melt blow molding is equipped with an internal cooling air ring.

[0030] Preferably, the thickness of the polyethylene water transfer film is 10–40 μm.

[0031] By adopting the above technical solutions, this invention uses extrusion blow molding to prepare films. Compared to the dissolution and defoaming process of solution casting, solid mixing takes less time and has higher production efficiency. Furthermore, during the film inflation process, the blow molding method stretches the film to varying degrees in both the longitudinal and transverse directions. This bidirectional stretching results in a more balanced molecular chain orientation, leading to relatively uniform internal stress. Simultaneously, the presence of a relaxation time during inflation and traction allows the polymer chains to fully extend, resulting in a film with lower internal stress after formation. Moreover, the blow molding equipment used in this invention is equipped with a cooling air ring, accelerating gas flow within the film bubble and avoiding differences in cooling caused by varying contact between the inside and outside of the bubble and the air, which could lead to different degrees of molecular chain relaxation and thus thermal stress. This invention further improves the water solubility of the prepared film by improving the film processing heating process and significantly reduces production costs compared to the casting method.

[0032] The beneficial effects of this invention are: 1. This invention effectively improves the problem of film curling when exposed to water during the use of water transfer film by adopting a combination of polyvinyl alcohol, surfactant, crosslinking agent, and compound plasticizer. At the same time, the addition of crosslinking agent and nanoparticles effectively inhibits the increase of water elongation in the second stage of film dissolution.

[0033] 2. The polyvinyl alcohol water transfer film prepared by the preparation method of the present invention has excellent water solubility and mechanical properties, and the molding process is simple. The prepared film has low elongation in water and is not easy to curl. It can be used in the laundry detergent pod industry, various water-soluble packaging industries, especially in the field of water transfer film. Attached Figure Description

[0034] Figure 1 A microscope image of a polyvinyl alcohol water transfer film prepared in Example 1 of the present invention; Figure 2 This is a microscope image of a polyvinyl alcohol water transfer film prepared in Comparative Example 1 of the present invention. Figure 3 This is a microscope image of a polyvinyl alcohol water transfer film prepared in Comparative Example 4 of the present invention. Detailed Implementation

[0035] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0036] Example

[0037] Example 1: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 8 parts of butanediol, 10 parts of polyethylene glycol, 5 parts of acetamide, and 1 part of titanium dioxide (by weight of polyvinyl alcohol) to a vertical mixer. Then add 0.4 parts of sodium fatty alcohol polyoxyethylene ether sulfate, 0.1 parts of 10-polyglycerol, 0.5 parts of glutaraldehyde, and 3 parts of deionized water (by weight of polyvinyl alcohol) after thorough mixing to the vertical mixer. The resulting polyvinyl alcohol powder mixture has a moisture content of 23%.

[0038] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0039] Example 2: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of hydrolysis 88%), 5 parts of caprolactam, 10 parts of glycerol, 10 parts of sorbitol, and 0.5 parts of microcrystalline cellulose (based on the mass of polyvinyl alcohol) to a vertical mixer. Then add 0.1 parts of OP-10, 0.1 parts of sodium dodecyl sulfate, 0.1 parts of magnesium chloride, and 4 parts of deionized water (based on the mass of polyvinyl alcohol) after thorough mixing to the vertical mixer. The resulting polyvinyl alcohol powder mixture has a moisture content of 30%.

[0040] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0041] Example 3: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of hydrolysis 88%), 5 parts of triethanolamine, 10 parts of glycerol, 10 parts of formamide, and 3 parts of calcium stearate (based on the mass of polyvinyl alcohol) to a vertical mixer. Then add 0.6 parts of Tween 10, 0.4 parts of sodium dodecyl sulfate, 2 parts of citric acid, and 2 parts of deionized water (based on the mass of polyvinyl alcohol) after thorough mixing to the vertical mixer. The resulting polyvinyl alcohol powder mixture has a moisture content of 25%.

[0042] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0043] Example 4: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of hydrolysis 92%), 5 parts of caprolactam, 10 parts of glycerol, 10 parts of sorbitol, and 3 parts of silica (by weight of polyvinyl alcohol) to a vertical mixer. Then add 0.2 parts of OP-10, 0.7 parts of tetraglycerol, 0.3 parts of boric acid, and 3 parts of deionized water (by weight of polyvinyl alcohol) after thorough mixing to the vertical mixer. The resulting polyvinyl alcohol powder mixture has a moisture content of 27%.

[0044] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0045] Example 5: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 5 parts of glycerol, 5 parts of polyethylene glycol, 10 parts of caprolactam, and 0.5 parts of talc (based on the mass of polyvinyl alcohol) to a vertical mixer. Then add 0.4 parts of sodium fatty alcohol polyoxyethylene ether sulfate, 0.1 parts of 6-polyglycerol, 0.5 parts of Tween, 0.4% sodium dodecyl sulfate, 0.1 parts of boric acid, and 3 parts of deionized water (based on the mass of polyvinyl alcohol) after thorough mixing to the vertical mixer. The resulting polyvinyl alcohol powder mixture has a moisture content of 27%.

[0046] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0047] Example 6: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 10 parts of glycerol, 5 parts of polyethylene glycol, and 3 parts of talc (based on the mass of polyvinyl alcohol) to a vertical mixer. Then add 0.3 parts of AEO-9, 0.2% of sodium dodecyl sulfate, 1 part of glyoxal, and 3 parts of deionized water (based on the mass of polyvinyl alcohol) after thorough mixing to the vertical mixer. The resulting polyvinyl alcohol powder mixture has a moisture content of 27%.

[0048] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0049] Comparative Example

[0050] Comparative Example 1: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 8 parts of butanediol, 10 parts of polyethylene glycol, and 5 parts of acetamide (by weight of polyvinyl alcohol) to a vertical mixer. Then add 3 parts of deionized water (by weight of polyvinyl alcohol). The resulting polyvinyl alcohol powder mixture has a moisture content of 23%.

[0051] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0052] Comparative Example 2, a polyvinyl alcohol water transfer film, was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 8 parts of butanediol, 10 parts of polyethylene glycol, 5 parts of acetamide, and 1 part of titanium dioxide (by weight of polyvinyl alcohol) to a vertical mixer. Then add 3 parts of water (by weight of polyvinyl alcohol). The resulting polyvinyl alcohol powder mixture has a moisture content of 23%.

[0053] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0054] Comparative Example 3: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 8 parts of butanediol, 10 parts of polyethylene glycol, and 5 parts of acetamide (by weight of polyvinyl alcohol) to a vertical mixer. Then add 3 parts of deionized water and 0.5 parts of glutaraldehyde (by weight of polyvinyl alcohol). The resulting polyvinyl alcohol powder mixture has a moisture content of 23%.

[0055] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0056] Comparative Example 4: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 8 parts of butanediol, 10 parts of polyethylene glycol, and 5 parts of acetamide (by weight of polyvinyl alcohol) to a vertical mixer. Then add 3 parts of deionized water (by weight of polyvinyl alcohol), 0.4 parts of sodium fatty alcohol polyoxyethylene ether sulfate (by weight of polyvinyl alcohol), and 0.1 parts of 10-polyglycerol. The resulting polyvinyl alcohol powder mixture has a moisture content of 23%.

[0057] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0058] Comparative Example 5: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 8 parts of butanediol, 10 parts of polyethylene glycol, 5 parts of acetamide, and 1 part of titanium dioxide (by weight of polyvinyl alcohol) to a vertical mixer. Then add 3 parts of deionized water (by weight of polyvinyl alcohol), 0.4 parts of sodium fatty alcohol polyoxyethylene ether sulfate (by weight of polyvinyl alcohol), and 0.1 parts of 10-polyglycerol. The resulting polyvinyl alcohol powder mixture has a moisture content of 23%.

[0059] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0060] Comparative Example 6: A polyvinyl alcohol water transfer film was prepared according to the following method: S1. Add 100 parts of polyvinyl alcohol (average degree of polymerization 1700, average degree of alcoholysis 88%), 8 parts of butanediol, 10 parts of polyethylene glycol, and 5 parts of acetamide (by weight of polyvinyl alcohol) to a vertical mixer. Then add 3 parts of deionized water, 0.5 parts of glutaraldehyde, 0.4 parts of sodium fatty alcohol polyoxyethylene ether sulfate, and 0.1 parts of 10-polyglycerol (by weight of polyvinyl alcohol). The resulting polyvinyl alcohol powder mixture has a moisture content of 23%.

[0061] S2. The material is extruded and granulated using a single-screw extruder at an extrusion temperature of 150°C. The granules are then fed into a blown film machine for blown film production at an extrusion temperature of 150°C, thus obtaining a polyvinyl alcohol water transfer film.

[0062] Performance testing

[0063] 1. Moisture content test: Place the weighing bottle in a forced-air drying oven for 0.5 hours, remove it and weigh it (m0). Add 1g of polyvinyl alcohol water transfer film, and weigh the weighing bottle again (m1). Place the weighing bottle containing 1g of polyvinyl alcohol water transfer film in a forced-air drying oven at 105℃ for 3 hours. After drying, place the sample in a desiccator, cool it for 0.5 hours, and weigh it (m2). The moisture content is calculated using the following formula: W 含水率 = % 2. Water solubility test: The polyvinyl alcohol water transfer film was equilibrated in a constant temperature and humidity chamber for 24 hours (25℃, 50%RH). The moisture content after equilibration was measured, and then it was cut into 8 pieces. 8cm 2 The size of the film is fixed on the clamp, and it is submerged in water and timed synchronously. When a corner of the water-soluble film falls off or the middle is damaged, it is considered to have disintegrated. The disintegration time and the time of complete dissolution are recorded. 3. Mechanical property testing, refer to GB / T 1040.3-2006 Determination of tensile properties of plastics Part 3: Test methods for films and sheets; 4. Swelling test (i.e., elongation at sea level): After equilibrating the polyvinyl alcohol water transfer film in a constant temperature and humidity chamber for 24 hours (23℃, 55%RH), cut the film into 10mm pieces. 10cm 2 The sample is laid flat on a glass plate, and its initial length is measured using a digital caliper. It is then immersed in a 10°C water bath for 20 seconds, removed, and laid flat on the glass plate again. The flow direction is determined through a small opening, and the length after immersion is measured. The degree of swelling is calculated using the following formula: Swelling degree = (Length after soaking / Initial length) × 100% 5. Water curling test: After equilibrating the polyvinyl alcohol water transfer film in a constant temperature and humidity chamber for 24 hours (23℃, 55%RH), the film is cut into 15mm pieces. 15cm 2 The sample was laid flat in a constant temperature water bath at 10℃. The time when the film began to curl was recorded by a stopwatch, and the area of ​​the film spread out on the water surface was recorded and calculated by taking pictures and measuring with vernier calipers.

[0064] 6. Transparency and haze test: Cut the polyvinyl alcohol water transfer film into 5cm pieces. For a 5cm sample, fix the sample in the magnetic clamp. Ensure the film is free of creases and fingerprints. Place it on the sample holder and use a transmittance / haze meter. After calibration, click to test and record the transparency and haze values. 7. Group analysis detection: Observe the polyvinyl alcohol water transfer film under a microscope to see if there is group analysis.

[0065] The polyvinyl alcohol water transfer films obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were subjected to the above performance tests. The performance test results are shown in Table 1. Table 1 Performance test results

[0066] According to Table 1, and in conjunction with Example 1 and Comparative Examples 1 and 4, it can be seen that no "oil spots" appeared in Example 1. Microscopic images are attached. Figure 1 As shown, both Comparative Example 1 and Comparative Example 4 exhibited "oil spots," and microscope images are attached. Figure 2 and attached Figure 3As shown, the specific components of the "oil flowers" may be the precipitation of plasticizers or surfactants. The reason is that neither Comparative Example 1 nor Comparative Example 4 added a crosslinking agent, so the lack of micro-crosslinking structure generated by the crosslinking agent led to the instability of the film's chain segment structure, thereby causing the plasticizer or surfactant to precipitate.

[0067] Combining Example 1 and Comparative Example 5, it can be seen that Comparative Example 5 exhibits increased dissolution time, decreased mechanical properties, increased swelling degree, and increased curling degree. After 48 hours of exposure to 98% RH, the haze increased, and microscopic observation revealed the appearance of "oil spots." The reason for this is that the difference between Comparative Example 5 and Example 1 is that Comparative Example 5 did not add a crosslinking agent. The lack of a crosslinking agent prevented the formation of a micro-crosslinked structure, resulting in a longer dissolution time, weakened mechanical properties, increased swelling degree and curling degree, and increased haze after exposure to high humidity. Furthermore, the lack of a crosslinking agent caused the precipitation of plasticizers or surfactants, manifesting as the "oil spot" phenomenon.

[0068] Combining Example 1 and Comparative Example 6, it can be seen that the dissolution time of Comparative Example 6 is increased, the mechanical properties are decreased, and the swelling degree and curling degree are increased. The reason is that the difference between Comparative Example 6 and Example 1 is that Comparative Example 6 does not add nanoparticles. The lack of nanoparticles leads to the lack of internal dissolution points and physical reinforcement support, resulting in decreased dissolution efficiency, reduced mechanical strength, and increased swelling degree and curling degree.

[0069] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A polyvinyl alcohol water transfer film, characterized in that, Includes the following components: Polyvinyl alcohol, crosslinking agent, plasticizer, surfactant, deionized water; The amount of crosslinking agent added is 0.1% to 2% of the mass of polyvinyl alcohol; The amount of surfactant added is 0.2% to 1% of the mass of polyvinyl alcohol; The polyvinyl alcohol water transfer film also includes nanoparticles added at a concentration of 0.5% to 3% of the mass of polyvinyl alcohol.

2. The polyvinyl alcohol water transfer film according to claim 1, characterized in that, The degree of polymerization of the polyvinyl alcohol is 1500-2000, and the degree of hydrolysis is 88%-92%.

3. The polyvinyl alcohol water transfer film according to claim 1, characterized in that, The crosslinking agent includes one or more of the following: polybasic acids, polybasic aldehydes, divalent metal salts, and boric acid.

4. The polyvinyl alcohol water transfer film according to claim 1, characterized in that, The amount of plasticizer added is 15% to 35% of the mass of polyvinyl alcohol; the plasticizer includes one or more of amides, alkanolamines, small molecule alcohols and polyols.

5. The polyvinyl alcohol water transfer film according to claim 1, characterized in that, The surfactant comprises a complex of an ionic surfactant and a nonionic surfactant in a mass ratio of (0.1 to 0.9): (0.1 to 0.9).

6. The polyvinyl alcohol water transfer film according to claim 5, characterized in that, The ionic surfactant includes one or more of sodium dodecyl sulfonate, sodium fatty alcohol polyoxyethylene ether sulfate, and potassium dodecyl phosphate; the nonionic surfactant includes one or more of AEO-9, Tween 80, OP-10, diglycerol, triglycerol, tetraglycerol, hexaglycerol, and decaglycerol.

7. The polyvinyl alcohol water transfer film according to claim 1, characterized in that, The nanoparticles include one or more of the following: silicon dioxide, titanium dioxide, calcium stearate, magnesium stearate, calcium carbonate, barium sulfate, zinc oxide, microcrystalline cellulose, talc, and bentonite.

8. A method for preparing a polyvinyl alcohol water transfer film, using the components of the polyvinyl alcohol water transfer film as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Polyvinyl alcohol, crosslinking agent, nanoparticles, plasticizer and surfactant are added to deionized water and mixed to obtain polyvinyl alcohol powder; S2. The polyvinyl alcohol powder is granulated and melt blown to obtain a polyvinyl alcohol film.

9. In the method for preparing polyvinyl alcohol water transfer film according to claim 8, in step S1, the water content of the polyvinyl alcohol powder is 20% to 40%.

10. The method for preparing polyvinyl alcohol water transfer film according to claim 8, wherein in step S2, the granulation is carried out at a temperature of 100-180°C; and the melt blow molding is carried out at a temperature of 100-180°C.

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