Polyvinyl alcohol film and preparation method thereof

Abstract

The invention relates to the technical field of polymer film processing, and discloses a polyvinyl alcohol film and a preparation method thereof. The polyvinyl alcohol film contains polyvinyl alcohol resin, a plasticizer and a surfactant, the hydrophilic-lipophilic balance value HLB of the surfactant is 8-16, the foaming volume Vf of the surfactant in a polyvinyl alcohol aqueous solution is smaller than or equal to 5 mL, and the apparent half-life period t1 / 2 is smaller than or equal to 100 s. The polyvinyl alcohol film has few bubble defects and is conveniently applied to thin electronic display devices subsequently.

Description

Technical Field

[0001] This invention relates to the field of polymer film processing technology, specifically to a polyvinyl alcohol film and its preparation method. Background Technology

[0002] Polyvinyl alcohol (PVA) film, as the core substrate of polarizers, directly affects the color rendering effect and product yield of polarizers due to its optical uniformity, mechanical strength, and appearance quality. During the manufacturing process, the PVA film undergoes dyeing, high-ratio stretching, and boric acid crosslinking. If the PVA film itself contains air bubbles, these defects will be amplified in subsequent processes, severely impacting the final optical and tensile properties.

[0003] Currently, polyvinyl alcohol (PVA) films are manufactured through processes such as dissolving, extruding, casting, and drying. During the dissolving and stirring process, high-speed stirring entrains gas into the high-viscosity solution. As the polymer dissolves, the system viscosity rises sharply, and bubbles remain trapped due to insufficient buoyancy. Ultimately, the PVA solution contains a large number of bubbles, which remain on the PVA film after extrusion and casting. These bubble defects are extended into linear defects during subsequent stretching processes, leading to abnormal local light transmittance in polarizers and the formation of visible bright and dark stripes. In particular, as electronic display devices become increasingly thinner, optical-grade PVA films are also trending towards thinner designs. However, in this process, the aforementioned bubble defect problem becomes increasingly prominent, and bubble defects are a key issue restricting the quality of PVA films (especially thinner PVA films).

[0004] Therefore, developing a polyvinyl alcohol film with fewer bubble defects and its preparation method to solve the problem of bubble defects in polyvinyl alcohol films is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of bubble defects in polyvinyl alcohol (PVA) films in the prior art, and to provide a PVA film and its preparation method. This PVA film has fewer bubble defects, making it convenient for subsequent application in thin electronic display devices.

[0006] To achieve the above objectives, a first aspect of the present invention provides a polyvinyl alcohol film, wherein the polyvinyl alcohol film contains a polyvinyl alcohol-based resin, a plasticizer, and a surfactant, wherein the hydrophilic-lipophilic balance value of the surfactant is 8-16, and the foaming volume V of the surfactant in a polyvinyl alcohol aqueous solution is... f ≤5mL, apparent half-life t 1 / 2 ≤100s.

[0007] A second aspect of the present invention provides a method for preparing a polyvinyl alcohol film, the method comprising: mixing a polyvinyl alcohol resin, a plasticizer, a surfactant and a solvent to obtain a polyvinyl alcohol solution, and degassing and casting the polyvinyl alcohol solution into a film; The hydrophilic-lipophilic balance value of the surfactant is 8-16, and the foaming volume V of the surfactant in the polyvinyl alcohol solution is... f ≤5mL, apparent half-life t 1 / 2 ≤100s.

[0008] Through the above technical solution, the hydrophilic-lipophilic balance (HLB) value of the surfactant in the polyvinyl alcohol film is controlled to be 8-16, and the foaming volume V in the polyvinyl alcohol aqueous solution is... f The apparent half-life t in polyvinyl alcohol aqueous solution is controlled to be less than or equal to 5 mL. 1 / 2 By controlling the time to less than or equal to 100 seconds, the generation of bubbles can be suppressed at the source and their collapse can be accelerated, resulting in a significant reduction in the bubble content of the PVA solution and fundamentally eliminating the bubble defect problem that is difficult to avoid in traditional processes. Detailed Implementation

[0009] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0010] As previously stated, the first aspect of this invention provides a polyvinyl alcohol film, the polyvinyl alcohol film containing a polyvinyl alcohol-based resin, a plasticizer, and a surfactant, characterized in that the hydrophilic-lipophilic balance (HLB) value of the surfactant is 8-16, and the foaming volume V of the surfactant in a polyvinyl alcohol aqueous solution is... f ≤5mL, apparent half-life t 1 / 2 ≤100s.

[0011] During their research, the inventors discovered that controlling the hydrophilic-lipophilic balance (HLB) value of the surfactant in the polyvinyl alcohol film to 8-16 resulted in a foaming volume V of the surfactant in the polyvinyl alcohol aqueous solution. f The volume should be controlled to be less than or equal to 5 mL, and the apparent half-life t 1 / 2 By controlling the time to less than or equal to 100 seconds, the generation of bubbles can be suppressed at the source and their collapse can be accelerated, resulting in a significant reduction in the bubble content of the PVA solution and fundamentally eliminating the bubble defect problem that is difficult to avoid in traditional processes.

[0012] According to the present invention, the aforementioned polyvinyl alcohol aqueous solution is an aqueous solution with a polyvinyl alcohol degree of polymerization of 2100±100 and a concentration of 8wt%. Specifically, the foaming volume V of the surfactant in the polyvinyl alcohol aqueous solution with a concentration of 8wt% and a degree of polymerization of 2100±100 is... f ≤5mL, apparent half-life t 1 / 2 ≤100s, wherein the surfactant is added at 0.05% of the dry weight of polyvinyl alcohol.

[0013] HLB values ​​are determined using the Griffin emulsification method: surfactants are mixed and emulsified with standard oils, and HLB is measured according to the critical ratio of the stable emulsion.

[0014] Foaming volume V f and apparent half-life t 1 / 2 The determination method is as follows: (1) Prepare an 8wt% aqueous solution of polyvinyl alcohol (PVA) with a degree of polymerization of 2100±100 as the test medium; (2) Add the surfactant to be tested at 0.05% of the dry weight of PVA to the above PVA solution, and mechanically stir at 500 rpm for 60 minutes at 90°C to ensure complete dissolution, and obtain the mixture to be tested; (3) Take 50.0 mL (V0) of the mixture and place it in a 100 mL double-glass jacketed graduated cylinder, and maintain the solution temperature at 80 °C; (4) Use a four-blade agitator and stir at 1500 rpm for 60 seconds; (5) Immediately after stopping stirring, read the total volume of the mixture in the graduated cylinder and record it as V. total Foaming volume V f =V total -V0; (6) Immediately afterwards, the graduated cylinder was transferred to a high-speed camera to record the changes in the macroscopic morphology of the bubble swarm; the time required for the projected area of ​​the bubble swarm to decay to 50% was recorded as the apparent half-life t. 1 / 2 .

[0015] The method for determining the apparent half-life of bubble clusters is as follows: Move the measuring cylinder under the high-speed camera, turn on the high-speed camera (frame rate ≥ 500fps, resolution ≥ 1920×1080), and take a top-down shot from directly above the measuring cylinder to ensure that the field of view covers the entire liquid surface; Record a 300-second video, ensuring the light source illuminates the cylinder evenly from the bottom or side to guarantee high contrast between the bubbles and the solution; The video is processed frame by frame using image analysis software (such as ImageJ), and the total projected area of ​​the liquid surface bubble group in each frame is calculated by threshold segmentation. Plot the "projected area - time" curve, defining the projected area at time zero as A0. Apparent half-life t. 1 / 2 Defined as the time (in seconds) required for the projected area to decay to 0.5×A0.

[0016] According to the present invention, the hydrophilic-lipophilic balance value of the surfactant can be 8, 10, 12, 14, 16, or any value within any two of the above ranges. The foaming volume of the surfactant in the polyvinyl alcohol aqueous solution can be 1 mL, 2 mL, 3 mL, 4 mL, 5 mL, or any value within any two of the above ranges. The apparent half-life of the surfactant in the polyvinyl alcohol aqueous solution can be 10 s, 20 s, 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, or any value within any two of the above ranges.

[0017] Preferably, the hydrophilic-lipophilic balance value of the surfactant is 10-14, and the foaming volume V of the surfactant in the polyvinyl alcohol aqueous solution is... f ≤4mL, apparent half-life t 1 / 2 ≤60s. By controlling the hydrophilicity-philicity balance value, foaming volume, and apparent half-life of the surfactant within the above range, the number and volume of bubbles in the polyvinyl alcohol film can be further reduced.

[0018] Specifically, the foaming volume V of the surfactant in an aqueous solution of polyvinyl alcohol with a concentration of 8 wt% and a degree of polymerization of 2100 ± 100 is... f ≤4mL, apparent half-life t 1 / 2 ≤60s, wherein the surfactant is added at 0.05% of the dry weight of polyvinyl alcohol.

[0019] Preferably, the surfactant is selected from at least one of polyoxyethylene ether, oleic acid diethanolamide, lauryl polyoxyethylene ether, octadecyltrimethylammonium chloride, lauryl diethanolamide, cocoyl monoisopropanolamide, sodium 1,2-bis(N-lauroylaminoethyl)sulfosuccinate, and potassium salt of polyether phosphate. Using the above surfactant can control the foaming volume of the surfactant in the polyvinyl alcohol aqueous solution to ≤5 mL and the apparent half-life t 1 / 2 ≤100s, which can further reduce the number and volume of bubbles in the polyvinyl alcohol film. From the perspective of further reducing the number and volume of bubbles in polyvinyl alcohol, at least one of oleic acid diethanolamide, cocoyl monoisopropanolamide, and potassium salt of polyether phosphate is preferred.

[0020] The plasticizer is selected from at least one of glycerol, triacetin, polyglycerol, ethylene glycol, polyethylene glycol, propylene glycol, citric acid, and dimethyl sulfate. Using the above plasticizer allows for controlling the foaming volume of the surfactant in a polyvinyl alcohol aqueous solution to be ≤5 mL and the apparent half-life t... 1 / 2 ≤100s, which can further reduce the number and volume of bubbles in the polyvinyl alcohol film. From the perspective of further reducing the number and volume of bubbles in polyvinyl alcohol, glycerol is preferred.

[0021] Preferably, the degree of polymerization of the polyvinyl alcohol-based resin is 1700-3200, which can be 1700, 2000, 2300, 2600, 2900, 3200, or any value within any two of the above ranges; the degree of hydrolysis is 80-99.99 mol%, which can be 80 mol%, 84 mol%, 88 mol%, 92 mol%, 96 mol%, 99.99 mol%, or any value within any two of the above ranges. Controlling the degree of polymerization of the polyvinyl alcohol-based resin to 1700-3200 and the degree of hydrolysis to 80-99.99 mol% enables control of the foaming volume of the surfactant in the polyvinyl alcohol aqueous solution to be ≤5 mL and the apparent half-life t. 1 / 2 ≤100s, which further reduces the number and volume of bubbles in the polyvinyl alcohol film. Considering the ability to further reduce the number and volume of bubbles in polyvinyl alcohol, the polymer of the polyvinyl alcohol-based resin is 2100-2700, and the degree of alcoholysis is 99.75-99.99 mol%.

[0022] Preferably, relative to 100 parts by weight of the polyvinyl alcohol-based resin, the content of the surfactant is 0.005-0.1 parts by weight, and the content of the plasticizer is 5-30 parts by weight. More preferably, relative to 100 parts by weight of the polyvinyl alcohol-based resin, the content of the surfactant is 0.01-0.03 parts by weight, and the content of the plasticizer is 5-20 parts by weight. Controlling the amounts of surfactant and plasticizer within the above ranges can further reduce the number and volume of bubbles in the polyvinyl alcohol film. More preferably, relative to 100 parts by weight of the polyvinyl alcohol-based resin, the content of the plasticizer is 5-15 parts by weight.

[0023] Preferably, the thickness of the polyvinyl alcohol film is 10-70 μm. More preferably, the thickness of the polyvinyl alcohol film is 20-60 μm.

[0024] A second aspect of the present invention provides a method for preparing a polyvinyl alcohol film, the method comprising: mixing a polyvinyl alcohol resin, a plasticizer, a surfactant and a solvent to obtain a polyvinyl alcohol solution, and degassing and casting the polyvinyl alcohol solution into a film; The surfactant has a hydrophilic-lipophilic balance value of 8-16, and the foaming volume V of the surfactant in an aqueous solution of polyvinyl alcohol with a concentration of 8 wt% and a degree of polymerization of 2100±100 is... f ≤5mL, apparent half-life t 1 / 2 ≤100s, wherein the surfactant is added at 0.05% of the dry weight of polyvinyl alcohol.

[0025] During their research, the inventors discovered that controlling the hydrophilic-lipophilic balance (HLB) value of the surfactant in the polyvinyl alcohol film to 8-16 resulted in a foaming volume V of 8 wt% polyvinyl alcohol aqueous solution with a degree of polymerization of 2100±100 (the surfactant was added at 0.05% of the dry weight of the polyvinyl alcohol). f The volume should be controlled to be less than or equal to 5 mL, and the apparent half-life t 1 / 2 By controlling the time to less than or equal to 100 seconds, the generation of bubbles can be suppressed at the source and their collapse can be accelerated, resulting in a significant reduction in the bubble content of the PVA solution and fundamentally eliminating the bubble defect problem that is difficult to avoid in traditional processes.

[0026] Preferably, the surfactant has a hydrophilic-lipophilic balance value of 10-14, and the foaming volume V of the surfactant in an aqueous solution of polyvinyl alcohol with a concentration of 8 wt% and a degree of polymerization of 2100±100 (the surfactant is added at 0.05% of the dry weight of polyvinyl alcohol) is... f ≤4mL, apparent half-life t 1 / 2 ≤60s. By controlling the hydrophilicity-philicity balance value, foaming volume, and apparent half-life of the surfactant within the above range, the number and volume of bubbles in the polyvinyl alcohol film can be further reduced.

[0027] Preferably, the surfactant is selected from at least one of polyoxyethylene ether, oleic acid diethanolamide, lauryl polyoxyethylene ether, octadecyltrimethylammonium chloride, lauryl diethanolamide, cocoyl monoisopropanolamide, sodium 1,2-bis(N-lauroylaminoethyl)sulfosuccinate, and potassium salt of polyether phosphate. Using the above surfactant can control the foaming volume of the surfactant in the polyvinyl alcohol aqueous solution to ≤5 mL and the apparent half-life t 1 / 2 ≤100s, which can further reduce the number and volume of bubbles in the polyvinyl alcohol film. From the perspective of further reducing the number and volume of bubbles in polyvinyl alcohol, at least one of oleic acid diethanolamide, cocoyl monoisopropanolamide, and potassium salt of polyether phosphate is preferred.

[0028] Preferably, the plasticizer is selected from at least one of glycerol, triacetin, polyglycerol, ethylene glycol, polyethylene glycol, propylene glycol, citric acid, and dimethyl sulfate. Using the above plasticizer allows for controlling the foaming volume of the surfactant in the polyvinyl alcohol aqueous solution to be ≤5 mL and the apparent half-life t... 1 / 2 ≤100s, which can further reduce the number and volume of bubbles in the polyvinyl alcohol film. From the perspective of further reducing the number and volume of bubbles in polyvinyl alcohol, glycerol is preferred.

[0029] Preferably, the degree of polymerization of the polyvinyl alcohol-based resin is 1700-3200, which can be 1700, 2000, 2300, 2600, 2900, 3200, or any value within any two of the above ranges; the degree of hydrolysis is 80-99.99 mol%, which can be 80 mol%, 84 mol%, 88 mol%, 92 mol%, 96 mol%, 99.99 mol%, or any value within any two of the above ranges. Controlling the degree of polymerization of the polyvinyl alcohol-based resin to 1700-3200 and the degree of hydrolysis to 80-99.99 mol% enables control of the foaming volume of the surfactant in the polyvinyl alcohol aqueous solution to be ≤5 mL and the apparent half-life t. 1 / 2 ≤100s, which further reduces the number and volume of bubbles in the polyvinyl alcohol film. Considering the ability to further reduce the number and volume of bubbles in polyvinyl alcohol, the polymer of the polyvinyl alcohol-based resin is 2100-2700, and the degree of alcoholysis is 99.75-99.99 mol%.

[0030] Preferably, relative to 100 parts by weight of the polyvinyl alcohol-based resin, the amount of surfactant is 0.005-0.1 parts by weight, and the amount of plasticizer is 5-30 parts by weight. More preferably, relative to 100 parts by weight of the polyvinyl alcohol-based resin, the amount of surfactant is 0.01-0.03 parts by weight, and the amount of plasticizer is 5-20 parts by weight. Controlling the amounts of surfactant and plasticizer within the above ranges can further reduce the number and volume of bubbles in the polyvinyl alcohol film.

[0031] Preferably, the mixing conditions include: a temperature of 80-150℃, which can be 80℃, 100℃, 120℃, 140℃, 150℃, or any value within any two of the above ranges; and a time of 4-36h, which can be 4h, 8h, 12h, 16h, 20h, 24h, 28h, 32h, 36h, or any value within any two of the above ranges. Polyvinyl alcohol films prepared from polyvinyl alcohol solutions obtained under the above conditions have a smaller number and volume of bubbles.

[0032] Preferably, the degassing conditions include: a temperature of 90-150℃, which can be 90℃, 100℃, 120℃, 140℃, 150℃, or any value within any two of the above values; a rotation speed of 1-6 rpm, which can be 1 rpm, 2 rpm, 4 rpm, 6 rpm, or any value within any two of the above values; and a time of 8-32h, which can be 4h, 8h, 12h, 16h, 20h, 24h, 28h, 32h, 36h, or any value within any two of the above values.

[0033] According to a particularly preferred embodiment of the present invention, a method for preparing a polyvinyl alcohol (PVA) film is provided. A PVA solution is obtained by mixing a PVA-based resin, a plasticizer, a surfactant, and a solvent. The solution is then dissolved at 80-150°C for 4-36 hours to achieve homogeneity, resulting in a PVA solution. Subsequently, the PVA solution is defoamed in a dissolving tank at a defoaming temperature of 90-150°C, a defoaming speed of 1-6 rpm, and a defoaming time of 8-32 hours. After secondary filtration, the defoamed PVA solution is formed in a die and then dried using a drying roller at a speed of 1-1.1 and a temperature of 70-90°C. Finally, it is dried in a 70-90°C oven to obtain the finished PVA film.

[0034] The surfactant has a hydrophilic-lipophilic balance value of 8-16, and the foaming volume V of the surfactant in an aqueous solution of polyvinyl alcohol with a concentration of 8 wt% and a degree of polymerization of 2100±100 (the surfactant is added at 0.05% of the dry weight of polyvinyl alcohol) is... f ≤5mL, apparent half-life t 1 / 2 ≤100s; the plasticizer is selected from at least one of glycerol, triacetin, polyglycerol, ethylene glycol, polyethylene glycol, propylene glycol, citric acid, and dimethyl sulfate; the amount of the surfactant is 0.01-0.03 parts by weight relative to 100 parts by weight of the polyvinyl alcohol resin; the amount of the plasticizer is 5-20 parts by weight.

[0035] The polyvinyl alcohol film prepared by the above preferred embodiment has fewer bubble defects.

[0036] The present invention will be described in detail below through examples. In the following examples, the bubble defect parameters in the polyvinyl alcohol film were measured by cutting the obtained polyvinyl alcohol film (thickness 45 μm) into sizes TD0.5m × MD1000m, observing and detecting them using an online defect detector, and counting the number of bubbles and their average diameter. The polyvinyl alcohol (PVA) resin raw material was purchased from Inner Mongolia Shuangxin Energy Chemical Co., Ltd., and is a commercially available product with product number SG-01.

[0037] Example 1 1 kg of polyvinyl alcohol resin, 0.1 kg of glycerol, 0.1 g of oleic acid diethanolamide, and 2.4 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded in a die. It was then dried using a drying roller at a speed of 1.05 and a drying temperature of 85°C, and finally dried in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect situation of the polyvinyl alcohol film is shown in Table 1.

[0038] Example 2 1 kg of polyvinyl alcohol resin, 0.1 kg of glycerol, 0.1 g of octadecyltrimethylammonium chloride, and 2.4 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded in a die. It was then dried using a drying roller at a speed of 1.05 and a drying temperature of 85°C, followed by drying in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect characteristics of the polyvinyl alcohol film are shown in Table 1.

[0039] Example 3 1 kg of polyvinyl alcohol resin, 0.1 kg of glycerol, 0.2 g of cocoyl isopropanolamide, and 2.4 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded in a die. It was then dried using a drying roller at a speed of 1.05 and a drying temperature of 85°C, followed by drying in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect characteristics of the polyvinyl alcohol film are shown in Table 1.

[0040] Example 4 1 kg of polyvinyl alcohol resin, 0.12 kg of glycerol, 0.1 g of potassium polyether phosphate, 0.05 g of cocoyl diethanolamide, and 2.4 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded in a die. It was then dried using a drying roller at a speed of 1.05 and a drying temperature of 85°C, followed by drying in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect situation of the polyvinyl alcohol film is shown in Table 1.

[0041] Example 5 1 kg of polyvinyl alcohol resin, 0.11 kg of glycerol, 0.15 g of potassium polyether phosphate, and 2.4 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded in a die. It was then dried using a drying roller at a speed of 1.05 and a drying temperature of 85°C, followed by drying in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect characteristics of the polyvinyl alcohol film are shown in Table 1.

[0042] Example 6 1 kg of polyvinyl alcohol resin, 0.08 kg of glycerol, 0.14 g of lauryl alcohol polyoxyethylene ether, and 2.4 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded in a die. It was then dried using a drying roller at a speed of 1.05 and a drying temperature of 85°C, and finally dried in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect characteristics of the polyvinyl alcohol film are shown in Table 1.

[0043] Comparative Example 1 1 kg of polyvinyl alcohol resin, 0.09 kg of glycerol, 0.1 g of sodium lauryl polyoxyethylene ether sulfate, and 2.4 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded in a die. It was then dried using a drying roller at a speed of 1.05 and a drying temperature of 85°C, and finally dried in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect characteristics of the polyvinyl alcohol film are shown in Table 1.

[0044] Comparative Example 2 1 kg of polyvinyl alcohol resin, 0.1 kg of glycerol, 0.15 g of aminoethylaminopropyl polysiloxane, and 2.4 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded in a die. It was then dried using a drying roller at a speed of 1.05 and a drying temperature of 85°C, followed by drying in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect characteristics of the polyvinyl alcohol film are shown in Table 1.

[0045] Comparative Example 3 1 kg of polyvinyl alcohol resin, 0.1 kg of glycerol, 0.1 g of sodium dodecylbenzenesulfonate, and 2.40 kg of water were added to a dissolving tank and stirred until dissolved. The solution was dissolved at 110°C for 30 hours to obtain a homogeneous PVA solution. Defoaming was then performed in the dissolving tank at a defoaming temperature of 100°C, a defoaming speed of 3 rpm, and a defoaming time of 10 hours. After defoaming, the PVA solution was filtered twice and then molded. It was then dried using a drying roller at a speed of 1.05 and a drying roller temperature of 85°C, followed by drying in an 80°C oven to obtain the finished polyvinyl alcohol film. The bubble defect characteristics of the polyvinyl alcohol film are shown in Table 1.

[0046] Table 1

[0047] As can be seen from the results in Table 1, the number and diameter of bubbles in the final film formed using Examples 1-6 of the present invention are far superior to those in the comparative examples. This indicates that the polyvinyl alcohol film preparation method of the present invention, through comprehensive screening and compatibility of surfactants, controls the HLB of the surfactant to be 8-16, controls the foaming volume to be less than or equal to 5 mL, and controls the apparent half-life to be less than or equal to 100 s, which can effectively suppress the generation of bubble defects and obtain polyvinyl alcohol films with fewer bubble defects.

[0048] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A polyvinyl alcohol film, said polyvinyl alcohol film comprising a polyvinyl alcohol-based resin, a plasticizer, and a surfactant, characterized in that, The hydrophilic-lipophilic balance value of the surfactant is 8-16, and the foaming volume V of the surfactant in a polyvinyl alcohol aqueous solution is... f ≤5mL, apparent half-life t 1 / 2 ≤100s.

2. The polyvinyl alcohol film according to claim 1, characterized in that, The hydrophilic-lipophilic balance value of the surfactant is 10⁻¹⁴, and the foaming volume V of the surfactant in a polyvinyl alcohol aqueous solution is... f ≤4mL, apparent half-life t 1 / 2 ≤60s.

3. The polyvinyl alcohol film according to claim 1 or 2, characterized in that, The surfactant is selected from at least one of polyoxyethylene ether, oleic acid diethanolamide, lauryl polyoxyethylene ether, octadecyltrimethylammonium chloride, lauryl diethanolamide, cocoyl monoisopropanolamide, sodium 1,2-bis(N-lauroylaminoethyl)sulfosuccinate, and potassium phosphate polyether ester, preferably at least one of oleic acid diethanolamide, cocoyl monoisopropanolamide, and potassium phosphate polyether ester; and / or, The plasticizer is selected from at least one of glycerol, triacetin, polyglycerol, ethylene glycol, polyethylene glycol, propylene glycol, citric acid, and dimethyl sulfate, preferably glycerol; and / or, The polyvinyl alcohol-based resin has a degree of polymerization of 1700-3200 and a degree of alcoholysis of 80-99.99 mol%. Preferably, the polymer of the polyvinyl alcohol-based resin is 2100-2700 and the degree of alcoholysis is 99.75-99.99 mol.

4. The polyvinyl alcohol film according to claim 1 or 2, characterized in that, Relative to 100 parts by weight of the polyvinyl alcohol-based resin, the content of the surfactant is 0.005-0.1 parts by weight, preferably 0.01-0.03 parts by weight; the content of the plasticizer is 5-30 parts by weight, preferably 5-20 parts by weight.

5. The polyvinyl alcohol film according to claim 1 or 2, characterized in that, The thickness of the polyvinyl alcohol film is 10-70 μm, preferably 20-60 μm.

6. A method for preparing a polyvinyl alcohol film, characterized in that, The preparation method includes: mixing polyvinyl alcohol resin, plasticizer, surfactant and solvent to obtain polyvinyl alcohol solution, and degassing and casting the polyvinyl alcohol solution into a film; The surfactant has a hydrophilic-lipophilic balance value of 8-16, and the foaming volume V is calculated based on 0.05% of the surfactant by dry weight in an aqueous solution of polyvinyl alcohol with a concentration of 8 wt% and a degree of polymerization of 2100 ± 100. f ≤5mL, apparent half-life t 1 / 2 ≤100s.

7. The preparation method according to claim 6, characterized in that, The surfactant has a hydrophilic-lipophilic balance value of 10⁻¹⁴, and the foaming volume V of the surfactant at 0.05% of the dry weight of polyvinyl alcohol in an aqueous solution of polyvinyl alcohol with a concentration of 8 wt% and a degree of polymerization of 2100 ± 100 is... f ≤4mL, apparent half-life t 1 / 2 ≤60s.

8. The preparation method according to claim 6 or 7, characterized in that, The surfactant is selected from at least one of polyoxyethylene ether, oleic acid diethanolamide, lauryl polyoxyethylene ether, octadecyltrimethylammonium chloride, lauryl diethanolamide, cocoyl monoisopropanolamide, sodium 1,2-bis(N-lauroylaminoethyl)sulfosuccinate, and potassium phosphate polyether ester, preferably at least one of oleic acid diethanolamide, cocoyl monoisopropanolamide, and potassium phosphate polyether ester; and / or, The plasticizer is selected from at least one of glycerol, triacetin, polyglycerol, ethylene glycol, polyethylene glycol, propylene glycol, citric acid, and dimethyl sulfate, preferably glycerol; and / or, The polyvinyl alcohol resin has a degree of polymerization of 1700-3200 and a degree of alcoholysis of 80-99.99 mol, with the preferred degree of polymerization being 2100-2700 and the preferred degree of alcoholysis being 99.75-99.99 mol.

9. The preparation method according to claim 6 or 7, characterized in that, The amount of surfactant used relative to 100 parts by weight of the polyvinyl alcohol-based resin is 0.005-0.1 parts by weight, preferably 0.01-0.03 parts by weight; the amount of plasticizer used is 5-30 parts by weight, preferably 5-20 parts by weight.

10. The preparation method according to claim 6 or 7, characterized in that, The mixing conditions include: a temperature of 80-150℃ and a time of 4-36 hours; and / or, The degassing conditions include: a temperature of 90-150℃, a rotation speed of 1-6 rpm, and a time of 8-32 hours.

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