Polyvinyl alcohol film with high water dissolution rate and comprehensive performance and preparation method of polyvinyl alcohol film

Abstract

The invention discloses a polyvinyl alcohol film with high water dissolution rate and comprehensive performance and a preparation method thereof. The film is prepared from 100-120 parts by weight of polyvinyl alcohol resin, 5-20 parts by weight of a plasticizer and 2-8 parts by weight of a nonionic surfactant with a star-shaped structure or a linear alkyne diol structure. Through structural regulation and formula optimization of the surfactant, synergistic improvement of high water-soluble rate, excellent mechanical performance, high transparency and good storage stability of the film is realized, the problem that water solubility and comprehensive performance of a traditional polyvinyl alcohol film are difficult to consider at the same time is solved, and the film can be widely applied to multiple fields of packaging, agriculture, medicine and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, and in particular to a polyvinyl alcohol film with high water solubility and comprehensive performance, and its preparation method. Background Technology

[0002] Polyvinyl alcohol (PVA) films are widely used in water-soluble packaging, textile sizing, pharmaceuticals, and agriculture due to their excellent water solubility, biodegradability, film-forming properties, and non-toxicity. However, PVA films face a long-standing technical challenge in practical applications: how to significantly improve their water solubility without sacrificing their mechanical strength, transparency, and storage stability.

[0003] In existing technologies, two strategies are typically employed to accelerate the dissolution of polyvinyl alcohol (PVA) films: one is to use PVA resin with a low degree of polymerization, but this severely compromises the film's mechanical strength; the other is to add large amounts of small-molecule plasticizers (such as glycerol), which, while increasing the water-soluble rate by breaking the hydrogen bonds between PVA molecules, leads to a series of derivative problems, including: Significantly reduced mechanical strength: Excessive plasticizers act as "molecular lubricants," severely weakening the forces between PVA molecular chains. Decreased moisture resistance and increased sensitivity to environmental humidity: Small-molecule plasticizers are highly hydrophilic and easily absorb moisture from the environment, causing the film to soften and become sticky. Easy adhesion and poor storage stability: Plasticizers easily migrate to the film surface during storage, causing films to stick together, making them difficult to peel off, and their performance degrades over time. Reduced transparency: Plasticizer migration or poor compatibility with PVA may lead to phase separation, causing light scattering and reducing film transparency.

[0004] Therefore, in view of the problems existing in the prior art, there is an urgent need in the field to invent a high-performance polyvinyl alcohol film that can synergistically improve and solve the above-mentioned technical bottlenecks. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to overcome the shortcomings of the prior art and provide a polyvinyl alcohol film with high water solubility rate and comprehensive performance, as well as its preparation method, so as to solve the problem that polyvinyl alcohol films are difficult to balance water solubility rate with mechanical strength, transparency and storage stability.

[0006] The technical solution of the present invention: A high water-soluble rate polyvinyl alcohol film with comprehensive performance, wherein the raw materials of the high water-soluble rate polyvinyl alcohol film, by weight, include the following components: 100-120 parts polyvinyl alcohol resin, 5-20 parts plasticizer, and 2-8 parts nonionic surfactant with star-shaped or linear acetylenic diol structure.

[0007] In some specific embodiments, the star-shaped nonionic surfactant uses a rigid aromatic ring or alicyclic structure as the core rigid unit, and connects 3-4 identical molecular arms through covalent bonds. The structure of each molecular arm is -LH, wherein L is selected from -(CH2)2-, -(CH2)3- or -(CH2)4-; and H is a hydrophilic group containing at least two hydroxyl groups. In some specific embodiments, the linear acetylenic diol-based nonionic surfactant uses unsaturated acetylenic bonds as structural units, with hydrophilic groups attached to both ends of the molecular chain. Its general structural formula is HO-(RC≡CR′)-OH or HO-(EO). x -RC≡CR′-(EO) y -OH, where x and y are independent integers from 1 to 20, and R and R' are independently selected from -(CH2). n - where n is an integer between 2 and 6.

[0008] In some specific embodiments, the core of the star-shaped surfactant is selected from one of trimesoyl, pentaerythritol, or trimethylolpropane; the linear alkynyl diol nonionic surfactant is selected from 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, or 1,4-dihydroxy-2-butyne, or a polyoxyethylene modified product of the above alkynyl diols.

[0009] In some specific embodiments, the hydrophilic end group H of the star-shaped surfactant is a glycerol group, a diglycerol group, or a polyethylene glycol monoether group with a number average molecular weight of not more than 200 g / mol.

[0010] In some specific embodiments, the plasticizer is at least one of glycerol, ethylene glycol, and diethylene glycol.

[0011] In some specific embodiments, the degree of polymerization of the polyvinyl alcohol resin is 300-1500, and the degree of hydrolysis is 75%-99%.

[0012] This invention provides a method for preparing a polyvinyl alcohol film with high water solubility rate and comprehensive performance, characterized by comprising the following steps: S1. Preparation of nonionic surfactant solution: Dissolve the nonionic surfactant with the star structure or linear alkynyldiol structure in water or an alcohol-water mixture to prepare the nonionic surfactant solution with the star structure or linear alkynyldiol structure; S2. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in hot water at 85-95℃ to form a homogeneous solution, then add plasticizer and nonionic surfactant solution with star structure or linear alkynyl diol structure prepared in step S1, and stir continuously at 60-75℃ for 1-3 hours to obtain a uniformly mixed casting solution. S3. Degassing and film formation: The casting solution obtained in step S2 is degassed under vacuum and then cast onto a smooth substrate; S4. Drying and post-treatment: The casting liquid cast onto a smooth substrate is dried at 40-60°C and then peeled off from the substrate to obtain the polyvinyl alcohol film.

[0013] In some specific embodiments, the mass concentration of the star-shaped surfactant solution is 5%-20%. Too low a concentration (<5%) will result in an excessively large solution volume, diluting the casting solution concentration and affecting film formation efficiency; too high a concentration (>20%) will result in insufficient dissolution of the surfactant, easy aggregation, and inability to be uniformly dispersed in the polyvinyl alcohol system.

[0014] In some specific embodiments, the mass concentration of polyvinyl alcohol in the casting solution is 8%-15%. Too low a concentration (<8%) will result in a film that is too thin, lacks mechanical strength, and is easily damaged after drying; too high a concentration (>15%) will result in a casting solution with too high viscosity, making casting difficult and prone to defects such as bubbles and cracks.

[0015] In some specific embodiments, the drying process in step S4 reduces the moisture content of the cast liquid film to below 10 wt%. Excessive moisture content (≥10 wt%) will cause the film to absorb moisture, stick together, and experience performance degradation during storage; excessive moisture content (<3 wt%) will cause the film to become brittle and lose flexibility.

[0016] This invention achieves a balance between high water solubility and overall performance through the synergistic effect of a nonionic surfactant with a specific structure, polyvinyl alcohol resin, and plasticizer. Its core mechanism includes the following three aspects: Hydrogen bonding: The hydrophilic groups of polyhydroxyl groups in nonionic surfactant molecules form strong hydrogen bonds with the hydroxyl groups on the polyvinyl alcohol molecular chain. On the one hand, this replaces some of the hydrogen bonds between polyvinyl alcohol molecules, weakens the molecular chain aggregation, and reduces the water molecule permeation resistance. On the other hand, it forms a stable cross-linked network structure, which plays a "in-situ reinforcement" role and makes up for the loss of mechanical strength that may be caused by increasing water solubility.

[0017] Dynamic wetting: Nonionic surfactants with rigid or unsaturated alkyne bond structures can significantly reduce the contact angle between the film surface and water, achieving a dynamic wetting effect. When the film comes into contact with water, surfactant molecules rapidly migrate to the solid-liquid interface, reducing interfacial tension, promoting the rapid spreading and penetration of water molecules into the film interior, and accelerating the swelling and dissociation of polyvinyl alcohol molecular chains.

[0018] Construction of microscopic hydrophilic channels: The multi-molecular arms of star-shaped surfactants or the molecular chains of linear alkynyl diol surfactants are uniformly dispersed in the polyvinyl alcohol matrix, forming continuous microscopic hydrophilic channels. These channels provide a rapid transport path for water molecules, preventing slow diffusion of water molecules within the dense structure of polyvinyl alcohol and significantly improving the water solubility rate. Simultaneously, the spatial support provided by rigid units or unsaturated alkynyl bond structural units can inhibit excessive crystallization of the polyvinyl alcohol molecular chains, reducing the obstruction of water penetration by crystalline regions and further optimizing solubility.

[0019] Beneficial effects:

[0020] This invention provides a polyvinyl alcohol film with high water solubility rate and comprehensive performance, which has the following beneficial effects: 1. Significantly improved water solubility rate: Through the synergistic effect of hydrogen bonding, dynamic wetting and micro-hydrophilic channel construction, the water molecule penetration and polyvinyl alcohol dissolution rate are greatly accelerated. The complete dissolution time in deionized water at 25°C can be as low as 45 seconds, which is far superior to traditional polyvinyl alcohol films. 2. Balanced overall performance: While maintaining a high water solubility rate, it also maintains excellent mechanical strength, good flexibility and high transparency, thus resolving the contradiction between water solubility and mechanical properties and transparency in existing technologies; 3. Excellent storage stability: The rigid units or unsaturated alkyne bond structures of the nonionic surfactant provide good steric hindrance, inhibiting plasticizer migration and film adhesion. After storage at 60℃ and 85% relative humidity for 7 days, there is no obvious adhesion phenomenon, and the haze change rate is ≤0.09%. 4. Controllable moisture resistance: The hydrophilic-hydrophobic balance of the surfactant is reasonably controlled to avoid film softening caused by excessive water absorption. The water absorption rate is controlled at 27.8%-32.3% in 24 hours, taking into account both water solubility and morphological stability during use. 5. Wide range of applications: The preparation process is simple and controllable, and the raw materials have good compatibility. It is suitable for high-end water-soluble packaging, pharmaceutical packaging, agricultural films and other fields with high requirements for comprehensive performance. Detailed Implementation

[0021] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0022] Preparation method of star-shaped surfactants: Star-shaped surfactant SP-1 (with pentaerythritol as the core) In a three-necked flask equipped with a stirrer, thermometer, and reflux condenser, pentaerythritol (10 g) and epichlorohydrin (50 g), and tetrabutylammonium bromide catalyst (0.5 g) were added. The reaction was carried out at 65 °C for 6 hours under nitrogen protection. After the reaction was completed, excess epichlorohydrin was removed by vacuum distillation to obtain an epoxidized intermediate. The intermediate was dissolved in 50 mL of DMF, and glycerol (20 g) and 0.4 g of sodium hydroxide catalyst were added. The reaction was carried out at 80 °C for 8 hours. After the reaction was completed, the product was poured into a large amount of diethyl ether to precipitate, filtered, and vacuum dried to obtain a white waxy solid, which is the target star-shaped surfactant SP-1.

[0023] Star-shaped surfactant SP-2 (with pyromellitic trimethylol group as the core) In a three-necked flask equipped with a stirrer, 5 g of trimesoyl chloride and 50 mL of dry tetrahydrofuran (THF) were added. Under an ice-water bath and nitrogen protection, 100 mL of a THF solution containing 4.5 g of 3-amino-1,2-propanediol and 5.5 g of triethylamine was slowly added dropwise. After the addition was complete, the mixture was allowed to return to room temperature and reacted for 12 hours. After the reaction was complete, the salt was removed by filtration, and the filtrate was concentrated and poured into diethyl ether to precipitate, yielding a pale yellow solid, SP-2. This molecule has a rigid trimesoyl group as its core, with three propylene glycol molecular arms containing two hydroxyl groups connected by amide bonds.

[0024] The nonionic surfactant L-1 with a linear alkynyl diol structure is selected as 2,4,7,9-tetramethyl-5-decyn-4,7-diol (industrial grade, purity ≥98%).

[0025] Example 1 Raw material preparation (by weight): Polyvinyl alcohol resin: 100 parts, degree of polymerization 500, degree of alcoholysis 98%; Plasticizer: 15 parts glycerin; Star-shaped surfactant: 2 parts star-shaped surfactant SP-1; A method for preparing polyvinyl alcohol films with high water solubility rates and comprehensive performance includes the following steps: S1. Preparation of star-shaped surfactant solution: Dissolve star-shaped surfactant SP-1 in 10 times its mass of hot water at 70°C to prepare a star-shaped surfactant solution; S2. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in 10 times its mass of hot water at 90°C to form a homogeneous solution, then add plasticizer and star-shaped surfactant solution prepared in step S1, and stir continuously at 70°C for 2 hours to obtain a uniformly mixed casting solution. S3. Degassing and film formation: The casting solution obtained in step S2 is degassed under vacuum and then cast onto a smooth substrate; S4. Drying and post-treatment: The casting solution cast onto a smooth substrate is dried at 50°C with a water content of 5.2 wt%, and then peeled off from the substrate to obtain the polyvinyl alcohol film.

[0026] Example 2 Raw material preparation (by weight): Polyvinyl alcohol resin: 100 parts, degree of polymerization 500, degree of alcoholysis 98%; Plasticizer: 15 parts glycerin; Star-shaped surfactant: 5 parts star-shaped surfactant SP-1; A method for preparing polyvinyl alcohol films with high water solubility rates and comprehensive performance includes the following steps: S1. Preparation of star-shaped surfactant solution: Dissolve star-shaped surfactant SP-1 in 10 times its mass of hot water at 70°C to prepare a star-shaped surfactant solution; S2. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in 10 times its mass of hot water at 90°C to form a homogeneous solution, then add plasticizer and star-shaped surfactant solution prepared in step S1, and stir continuously at 70°C for 2 hours to obtain a uniformly mixed casting solution. S3. Degassing and film formation: The casting solution obtained in step S2 is degassed under vacuum and then cast onto a smooth substrate; S4. Drying and post-treatment: The casting solution cast onto a smooth substrate is dried at 50°C with a water content of 5.8 wt%, and then peeled off from the substrate to obtain the polyvinyl alcohol film.

[0027] Example 3 Raw material preparation (by weight): Polyvinyl alcohol resin: 100 parts, degree of polymerization 1500, degree of alcoholysis 99%; Plasticizer: 10 parts glycerin, 5 parts ethylene glycol; Star-shaped surfactant: 5 parts star-shaped surfactant SP-2; A method for preparing polyvinyl alcohol films with high water solubility rates and comprehensive performance includes the following steps: S1. Preparation of star-shaped surfactant solution: Dissolve star-shaped surfactant SP-2 in 10 times its mass of hot water at 70°C to prepare a star-shaped surfactant solution; S2. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in 10 times its mass of hot water at 95°C to form a homogeneous solution, then add plasticizer and star-shaped surfactant solution prepared in step S1, and stir continuously at 75°C for 2 hours to obtain a uniformly mixed casting solution. S3. Degassing and film formation: The casting solution obtained in step S2 is degassed under vacuum and then cast onto a smooth substrate; S4. Drying and post-treatment: The casting solution cast onto a smooth substrate is dried at 50°C with a water content of 5.3 wt%, and then peeled off from the substrate to obtain the polyvinyl alcohol film.

[0028] Example 4 Raw material preparation (by weight): Polyvinyl alcohol resin: 100 parts, degree of polymerization 500, degree of alcoholysis 98%; Plasticizer: 15 parts glycerin; Linear alkynyldiol-based nonionic surfactants: 5 parts of linear alkynyldiol-based nonionic surfactant L-1; A method for preparing polyvinyl alcohol films with high water solubility rates and comprehensive performance includes the following steps: S1. Preparation of star-shaped surfactant solution: Dissolve L-1, a nonionic surfactant with a linear alkynyldiol structure, in 70°C hot water at 10 times its mass to prepare a nonionic surfactant solution with a linear alkynyldiol structure; S2. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in 10 times its mass of hot water at 90°C to form a homogeneous solution. Then add plasticizer and nonionic surfactant solution with linear acetylenic diol structure prepared in step S1. Stir continuously at 70°C for 2 hours to obtain a uniformly mixed casting solution. S3. Degassing and film formation: The casting solution obtained in step S2 is degassed under vacuum and then cast onto a smooth substrate; S4. Drying and post-treatment: The casting solution cast onto a smooth substrate is dried at 50°C with a water content of 5.8 wt%, and then peeled off from the substrate to obtain the polyvinyl alcohol film.

[0029] Example 5 Raw material preparation (by weight): Polyvinyl alcohol resin: 100 parts, degree of polymerization 1800, degree of alcoholysis 99%; Plasticizer: 15 parts glycerin; Star-shaped surfactant: 5 parts star-shaped surfactant SP-1; A method for preparing polyvinyl alcohol films with high water solubility rates and comprehensive performance includes the following steps: S1. Preparation of star-shaped surfactant solution: Dissolve star-shaped surfactant SP-1 in 10 times its mass of hot water at 70°C to prepare a star-shaped surfactant solution; S2. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in 10 times its mass of hot water at 90°C to form a homogeneous solution, then add plasticizer and star-shaped surfactant solution prepared in step S1, and stir continuously at 70°C for 2 hours to obtain a uniformly mixed casting solution. S3. Degassing and film formation: The casting solution obtained in step S2 is degassed under vacuum and then cast onto a smooth substrate; S4. Drying and post-treatment: The casting solution cast onto a smooth substrate is dried at 50°C with a water content of 5.8 wt%, and then peeled off from the substrate to obtain the polyvinyl alcohol film.

[0030] Comparative Example 1 Raw material preparation (by weight): Polyvinyl alcohol resin: 100 parts, degree of polymerization 500, degree of alcoholysis 98%; Plasticizer: 15 parts glycerin; Surfactant: 5 parts Tween-80; A method for preparing polyvinyl alcohol films with high water solubility rates and comprehensive performance includes the following steps: S1. Preparation of surfactant solution: Dissolve the surfactant Tween-80 in 10 times its mass of hot water at 70°C to prepare a surfactant solution; S2. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in 10 times its mass of hot water at 90°C to form a homogeneous solution, then add plasticizer and surfactant solution prepared in step S1, and stir continuously at 70°C for 2 hours to obtain a uniformly mixed casting solution. S3. Degassing and film formation: The casting solution obtained in step S2 is degassed under vacuum and then cast onto a smooth substrate; S4. Drying and post-treatment: The casting solution cast onto a smooth substrate is dried at 50°C with a water content of 5.8 wt%, and then peeled off from the substrate to obtain the polyvinyl alcohol film.

[0031] Comparative Example 2 Raw material preparation (by weight): Polyvinyl alcohol resin: 100 parts, degree of polymerization 500, degree of alcoholysis 98%; Plasticizer: 10 parts glycerin; Surfactant: 10 parts of star-shaped surfactant SP-1; A method for preparing polyvinyl alcohol films with high water solubility rates and comprehensive performance includes the following steps: S1. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in 10 times its weight of hot water at 90°C to form a homogeneous solution, then add plasticizer and polyethylene glycol 400, and stir continuously at 70°C for 2 hours to obtain a uniformly mixed casting solution. S2. Degassing and film formation: The casting solution obtained in step S1 is degassed under vacuum and then cast onto a smooth substrate; S3. Drying and post-treatment: The casting solution cast onto a smooth substrate is dried at 50°C with a water content of 6.0 wt%, and then peeled off from the substrate to obtain a comparative polyvinyl alcohol film.

[0032] Comparative Example 3 Raw material preparation (by weight): Polyvinyl alcohol resin: 100 parts, degree of polymerization 500, degree of alcoholysis 98%; Plasticizer: 20 parts glycerin; Star-shaped surfactant: 0 parts; A method for preparing polyvinyl alcohol films with high water solubility rates and comprehensive performance includes the following steps: S1. Preparation of thin film casting solution: Dissolve polyvinyl alcohol resin in 10 times its mass of hot water at 85°C to form... The solution was prepared by adding a plasticizer and stirring continuously at 70°C for 2 hours to obtain a uniformly mixed casting solution. S2. Degassing and film formation: The casting solution obtained in step S1 is degassed under vacuum and then cast onto a smooth substrate; S3. Drying and post-treatment: The casting solution cast onto a smooth substrate is dried at 50°C with a water content of 5.4 wt%, and then peeled off from the substrate to obtain a comparative polyvinyl alcohol film.

[0033] The following performance tests were performed on Examples 1-4 and Comparative Examples 1-3: 1. Water dissolution rate test: Test conditions: Deionized water at 25℃ was used as the test medium. A 2cm×2cm film sample (thickness 0.05mm) was completely immersed in 500mL of deionized water (stirring speed 100r / min). A stopwatch was used to record the time from immersion to complete dissolution (no visible solid particles). The complete dissolution time is the total time it takes for the sample to be completely dispersed in water under the above conditions without any residual solids.

[0034] 2. Tensile strength and elongation at break test: Test method: According to GB / T 1040.3-2006 standard, dumbbell type I specimens (gauge length 25 mm, width 4 mm, thickness 0.05 mm) were prepared and tested using a universal tensile testing machine at a tensile rate of 50 mm / min; tensile strength is the maximum stress at which the specimen breaks, and elongation at break is the ratio of the elongation at break to the initial gauge length × 100%.

[0035] 3. Transparency (Haze) Test: Test method: According to GB / T 2410-2008 standard, a haze meter is used to select an area of ​​the film sample that is free of bubbles and impurities, and the haze value is tested at a wavelength of 550nm; haze is the ratio of scattered light flux to total transmitted light flux through the sample × 100%, which directly reflects the light transmission purity of the film.

[0036] 4. Storage stability test: Test conditions: The film sample was stored in a constant temperature and humidity chamber at 60℃ and 85% relative humidity for 7 days. After the sample was taken out, the surface was observed to see if there was adhesion or wrinkling. At the same time, the haze value before and after storage was tested, and the haze change rate was calculated (haze change rate = (haze after storage - haze before storage) / haze before storage × 100%).

[0037] 5. Water absorption rate test: Test method: According to GB / T 1034-2008 standard, take a film sample (2cm×2cm) dried to constant weight (mass m0), immerse it in deionized water at 25℃ for 24 hours, wipe off the surface moisture quickly and weigh it (mass m1); Water absorption rate = (m1-m0) / m0×100%.

[0038] Table 1: Test Results Table

[0039] As shown in Table 1, the high water solubility rate polyvinyl alcohol films prepared in Examples 1-4 of this invention achieve synergistic optimization of water solubility rate, mechanical strength, transparency, and storage stability. Specifically, comparing Example 2 and Example 5, Example 5 uses polyvinyl alcohol with a degree of polymerization of 1800, resulting in stronger intermolecular forces and a more significant hindrance to water penetration. This leads to a water solubility rate much higher than in Example 2, but the elongation at break is still low, the tensile strength is reduced, and the overall performance is not balanced. Comparing Example 2 and Comparative Example 1, Comparative Example 1 uses the traditional linear surfactant Tween-80, which lacks a rigid core with a star-shaped structure and multiple hydroxyl end groups, making it impossible to construct effective hydrophilic channels. This results in a slow water solubility rate, significantly reduced tensile strength and elongation at break, and a lack of steric hindrance to prevent adhesion, leading to slight adhesion after storage. Adhesion, increased haze, excessive water absorption, and overall performance degradation were observed in Example 2 compared to Comparative Example 2. Comparative Example 2 added 10 parts of SP-1 excessively, resulting in an unbalanced formulation ratio. Excessive hydrophilicity led to increased water absorption, causing severe adhesion after storage. Excessive surfactant disrupted the intermolecular forces of polyvinyl alcohol, resulting in a significant decrease in tensile strength and elongation at break. Simultaneously, surfactant aggregation caused a significant increase in haze. Although the water solubility rate (62s) was better than the traditional system, the overall performance deteriorated and could not meet the usage requirements. Compared to Comparative Example 3, Example 2 did not add star-shaped surfactants, resulting in no hydrophilic channels to guide water penetration, a slower water solubility rate, and a lack of hydrogen bond enhancement and steric hindrance. This led to a decrease in tensile strength and elongation at break, slight adhesion after storage, and increased haze. It was completely impossible to achieve a balance between high water solubility rate and overall performance.

[0040] This invention can also be implemented in various other ways. Without departing from the spirit and essence of this invention, those skilled in the art can make various corresponding changes and modifications according to this invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A high water-soluble rate, all-purpose polyvinyl alcohol film, characterized by, The raw material of the high water-soluble rate comprehensive performance polyvinyl alcohol film comprises the following components in parts by weight: 100-120 parts of polyvinyl alcohol resin, 5-20 parts of plasticizer, and 2-8 parts of non-ionic surfactant with star structure or linear acetylenic diol structure.

2. The high water-soluble rate, all-around polyvinyl alcohol film according to claim 1, characterized by, The star structure non-ionic surfactant takes rigid aromatic ring or alicyclic structure as the core of rigid unit, and is connected with 3-4 identical molecular arms through covalent bond, and the structure of each molecular arm is -L-H, wherein L is selected from -(CH2)2-, -(CH2)3- or -(CH2)4-, and H is a hydrophilic group containing at least two hydroxyl groups. The linear acetylenic diol type nonionic surfactant has unsaturated acetylenic bond as structural unit, and hydrophilic groups connected at both ends of the molecular chain, and its general structure is H-O-(R-C≡C-R')-O-H or H-O-(EO) x -R-C≡C-R'-(EO) y -O-H, wherein x, y are independently integers from 1 to 20, R and R' are independently selected from -(CH2) n -, and n is an integer from 2 to 6.

3. The high water-soluble rate, all-around polyvinyl alcohol film according to claim 2, characterized by, The core of the star structure surfactant is selected from one of trimesic acid group, pentaerythritol group or trimethylolpropane group; and the linear acetylenic diol structure non-ionic surfactant is selected from 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol or 1,4-dihydroxy-2-butynyl or polyoxyethylene modified product of the above acetylenic diols.

4. The high water-soluble rate, all-around polyvinyl alcohol film according to claim 2, characterized by, The hydrophilic end group H of the star structure surfactant is glycerol group, diglycerol group or polyethylene glycol monoether group with number average molecular weight not greater than 200 g / mol.

5. The high water-soluble rate, all-around polyvinyl alcohol film according to claim 1, characterized by, The plasticizer is at least one of glycerol, ethylene glycol or diethylene glycol.

6. The high water-soluble rate, all-around polyvinyl alcohol film according to claim 1, characterized by, The polyvinyl alcohol resin has a polymerization degree of 300-1500 and an alcoholysis degree of 75%-99%.

7. The method for preparing a high water solubility rate polyvinyl alcohol film according to any one of claims 1-6, characterized in that, The method comprises the following steps: S1. Preparing a non-ionic surfactant solution: dissolving the non-ionic surfactant with star structure or linear acetylenic diol structure in water or alcohol-water mixed solvent to prepare the non-ionic surfactant solution with star structure or linear acetylenic diol structure; S2. Preparing a film casting solution: dissolving polyvinyl alcohol resin in hot water at 85-95 ℃ to form a homogeneous solution, then adding plasticizer and the non-ionic surfactant solution with star structure or linear acetylenic diol structure prepared in step S1, and continuously stirring at 60-75 ℃ for 1-3 hours to obtain a uniformly mixed casting solution; S3. Defoaming and film forming: defoaming the casting solution obtained in step S2 under vacuum, and then casting on a smooth substrate; S4. Drying and post-treatment: drying the casting solution cast on the smooth substrate at 40-60 ℃, and then peeling off from the substrate to obtain the polyvinyl alcohol film.

8. The method for preparing a high water solubility rate and high-performance polyvinyl alcohol film according to claim 7, characterized in that, The mass concentration of the non-ionic surfactant solution with star structure or linear acetylenic diol structure is 5%-20%.

9. The method for preparing a high water solubility rate and high-performance polyvinyl alcohol film according to claim 7, characterized in that, The mass concentration of polyvinyl alcohol in the casting solution is 8%-15%.

10. The method for preparing a high water solubility rate and high-performance polyvinyl alcohol film according to claim 7, characterized in that, The drying in step S4 makes the cast liquid film have a water content of less than 10 wt%.

Images