Polyvinyl alcohol composition, polyvinyl alcohol film and method for producing the same and use thereof

Abstract

This invention relates to the field of polymer materials, and discloses a polyvinyl alcohol composition, a polyvinyl alcohol film, a method for preparing the same, and their applications. The polyvinyl alcohol composition comprises polyvinyl alcohol resin, a plasticizer, and a surfactant; the plasticizer comprises a polyol and a dihydrogen phosphate ionic liquid. The polyvinyl alcohol film can be stretched at high ratios, has a low dimensional swelling ratio in water and boric acid, and the polarizer prepared from this polyvinyl alcohol film has high polarization and transmittance.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, specifically to a polyvinyl alcohol composition, a polyvinyl alcohol film, and their preparation methods and applications. Background Technology

[0002] Currently, the production method of polyvinyl alcohol (PVA) optical films involves dissolving washed PVA resin, additives, and surfactants, followed by processes such as degassing, die casting, drying on drying rollers, heat treatment in an air flotation oven, and winding to obtain the finished PVA optical film. PVA optical films are mainly used in the production of polarizers, with the end product being various types of liquid crystal displays. The performance of the PVA optical film determines the optical properties of the polarizer, such as polarization degree and transmittance. PVA optical films are further swelled, dyed, stretched, and fixed, and then laminated with cellulose triacetate (TAC) films to form polarizers.

[0003] The optical properties of polarizers, such as polarization degree and transmittance, are closely related to the stretching ratio of the optical film. With the increasing demand for high polarization degree and high transmittance polarizers in the downstream display industry, higher requirements are needed for the stretching ratio of polyvinyl alcohol optical films. Summary of the Invention

[0004] To overcome the problem of plasticizer migration and leakage in existing technologies, the present invention provides a polyvinyl alcohol composition, a polyvinyl alcohol film, a method for preparing the same, and its application. The polyvinyl alcohol film can be stretched at a high ratio, thereby improving the polarization and transmittance of the polarizer prepared from the polyvinyl alcohol film.

[0005] To achieve the above objectives, a first aspect of the present invention provides a polyvinyl alcohol composition comprising a polyvinyl alcohol resin, a plasticizer, and a surfactant;

[0006] The plasticizer comprises a polyol and a dihydrogen phosphate ionic liquid.

[0007] A second aspect of the present invention provides a polyvinyl alcohol film prepared from the composition provided in the first aspect of the present invention.

[0008] Preferably, the ratio of the size swelling degree of the polyvinyl alcohol film in water to that in a 3wt% boric acid aqueous solution is 1.1-1.3:1.

[0009] A third aspect of this invention provides a method for preparing a polyvinyl alcohol film, comprising the following steps:

[0010] (1) The composition provided in the first aspect of the present invention is mixed with a solvent to obtain a casting solution;

[0011] (2) The casting solution is degassed, shaped, dried and heat-treated to obtain a polyvinyl alcohol film.

[0012] The fourth aspect of the present invention provides a composition provided in the first aspect of the present invention, or the application of a polyvinyl alcohol film provided in the second aspect of the present invention in a polarizer.

[0013] The beneficial technical effects of this invention are as follows:

[0014] In this invention, the dihydrogen phosphate ionic liquid can crosslink with polyvinyl alcohol, and the hydroxyl groups of the polyvinyl alcohol molecular chain can crosslink with dihydrogen phosphate ions to form a spatial cage structure, which reduces the precipitation of plasticizer during heat treatment, improves the elongation at break of the polyvinyl alcohol film, and also reduces the influence of boric acid on the polyvinyl alcohol molecular chain during the polarizer manufacturing process, so that the obtained polarizer has uniform dyeing and excellent optical performance. Detailed Implementation

[0015] 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.

[0016] A first aspect of the present invention provides a polyvinyl alcohol composition comprising a polyvinyl alcohol resin, a plasticizer, and a surfactant;

[0017] The plasticizer comprises a polyol and a dihydrogen phosphate ionic liquid.

[0018] In this invention, the dihydrogen phosphate ionic liquid can crosslink with polyvinyl alcohol, and the hydroxyl groups of the polyvinyl alcohol molecular chain can crosslink with dihydrogen phosphate ions to form a spatial cage structure, which reduces the precipitation of plasticizer during heat treatment, improves the elongation at break of the polyvinyl alcohol film, and also reduces the influence of boric acid on the polyvinyl alcohol molecular chain during the polarizer manufacturing process, so that the obtained polarizer has uniform dyeing and excellent optical performance.

[0019] The present invention allows for a wide range of selection of polyvinyl alcohol resins. When the degree of polymerization of the polyvinyl alcohol resin is 1600-2500 and the degree of hydrolysis is 95-99.9%, it is beneficial to improve the optical and mechanical properties of the obtained polyvinyl alcohol.

[0020] More preferably, the degree of polymerization of the polyvinyl alcohol resin is 1800-2400, and the degree of hydrolysis is 98-99.9%.

[0021] According to a preferred embodiment of the present invention, the mass ratio of the polyvinyl alcohol resin, plasticizer and surfactant is 100:10-30:0.05-1.

[0022] In this invention, when the mass ratio of the polyvinyl alcohol resin, plasticizer, and surfactant is within the above-mentioned range, the film prepared from the polyvinyl alcohol composition has better optical and mechanical properties.

[0023] More preferably, the mass ratio of the polyvinyl alcohol resin, plasticizer, and surfactant is 100:15-25:0.1-0.5.

[0024] According to a preferred embodiment of the present invention, the mass ratio of the polyol to the dihydrogen phosphate ionic liquid is 30-50:1.

[0025] In this invention, when the mass ratio of the polyol to the dihydrogen phosphate ionic liquid is within the above-mentioned range, the migration and precipitation of the polyol can be better suppressed, thereby further improving the optical and mechanical properties of the polyvinyl alcohol film.

[0026] The mass ratio of the polyol to the dihydrogen phosphate ionic liquid can be 30:1, 35:1, 40:1, 45:1, 50:1, or any range between the two.

[0027] More preferably, the mass ratio of the polyol to the dihydrogen phosphate ionic liquid is 35-45:1.

[0028] According to a preferred embodiment of the present invention, the cation of the dihydrogen phosphate ionic liquid is selected from... At least one of them, wherein R, R1 and R2 are each independently selected from H or alkyl.

[0029] The alkyl group can be a C1-C8 straight-chain, branched, cyclic aliphatic alkyl group or aralkyl group, preferably ethyl, n-propyl or phenyl.

[0030] In this invention, when the cation of the dihydrogen phosphate ionic liquid is selected from the above-mentioned range, it has better compatibility with polyols.

[0031] More preferably, the cation of the dihydrogen phosphate ionic liquid is

[0032] In this invention, the anion of the dihydrogen phosphate ionic liquid is:

[0033] According to a specific embodiment of the present invention, the dihydrogen phosphate ionic liquid is selected from 1-ethyl-3-methylimidazolium dihydrogen phosphate, 1-propyl-3-methylimidazolium dihydrogen phosphate and n-butylpyridine tetrafluoroborate.

[0034] According to a preferred embodiment of the present invention, the polyol is selected from C 10 The following polyols.

[0035] In this invention, when the polyol is selected from the above range, it has better compatibility with ionic liquids.

[0036] More preferably, the polyol is selected from at least one of ethylene glycol, propylene glycol, glycerol, and butanediol.

[0037] More preferably, the polyol is glycerol.

[0038] According to a preferred embodiment of the present invention, the surfactant comprises anionic surfactant and / or nonionic surfactant.

[0039] The anionic surfactant can be an ether sulfate and / or an acyl amino acid.

[0040] The nonionic surfactant may be fatty acid alcohol amide, fatty alcohol polyoxyethylene ether, and / or alkylphenol polyoxyethylene ether.

[0041] More preferably, the surfactant is lauric acid diethanolamide and / or sodium lauryl ether sulfate.

[0042] According to the present invention, preferably, the hydrophilic-lipophilic balance value of the surfactant is 10-14.

[0043] In this invention, when the hydrophilic-lipophilic balance value of the surfactant is within the above-mentioned range, the surfactant can make the polyol and dihydrogen phosphate ionic liquid more uniformly dispersed in the polyvinyl alcohol resin, while inhibiting the precipitation of polyol, thereby further improving the flexibility and optical properties of the polyvinyl alcohol film.

[0044] More preferably, the surfactant has a hydrophilic-lipophilic balance value of 10-12.

[0045] A second aspect of the present invention provides a polyvinyl alcohol film prepared from the composition provided in the first aspect of the present invention.

[0046] According to a preferred embodiment of the present invention, the ratio of the size swelling degree of the polyvinyl alcohol film in water to the size swelling degree in a 3wt% boric acid aqueous solution is 1.1-1.3:1.

[0047] The dimensional swelling degree of the polyvinyl alcohol (PVA) film is the arithmetic mean of the rate of change of the PVA film's dimensions in the width and mechanical stretching directions after immersion in water or a boric acid aqueous solution. The temperature of the water or solution is 45°C, the immersion time is 5 minutes, and the PVA film has not been stretched.

[0048] In this invention, when the ratio of the size swelling degree of the polyvinyl alcohol film in water to the size swelling degree in a 3wt% boric acid aqueous solution is within the above-mentioned range, the shrinkage of the PVA film during the color fixing process can be reduced, allowing the PVA film to be stretched at a higher ratio, thereby improving the transmittance and polarization rate of the obtained PVA polarizing film.

[0049] More preferably, the ratio of the size swelling degree of the polyvinyl alcohol film in water to the size swelling degree in a 3wt% boric acid aqueous solution is 1.15-1.25:1.

[0050] A third aspect of this invention provides a method for preparing a polyvinyl alcohol film, comprising the following steps:

[0051] (1) The composition provided in the first aspect of the present invention is mixed with a solvent to obtain a casting solution;

[0052] (2) The casting solution is degassed, shaped, dried and heat-treated to obtain a polyvinyl alcohol film.

[0053] In the above method, the dihydrogen phosphate ionic liquid can improve the crosslinking degree of the polyvinyl alcohol film, improve the stability of the polyvinyl alcohol film in different solution environments, and obtain a polyvinyl alcohol film with a size swelling ratio of 1.1-1.3:1 in water to 3wt% boric acid aqueous solution, thereby improving the mechanical properties of the polyvinyl alcohol film and the optical properties of the prepared polarizing film.

[0054] The present invention does not particularly limit the specific type of solvent, and those skilled in the art can choose conventionally. According to the present invention, preferably, the solvent is selected from at least one of water, ethanol, isopropanol, acetone, dimethyl sulfoxide, and N,N-dimethylformamide.

[0055] More preferably, the solvent is water.

[0056] According to a preferred embodiment of the present invention, the solvent content in the casting solution is 60-90 wt%.

[0057] More preferably, the solvent content in the casting solution is 65-85 wt%.

[0058] The present invention does not particularly limit the specific method of degassing, and those skilled in the art can choose conventional methods. For example, the degassing method can be vacuum degassing, ultrasonic degassing, static degassing, stirring degassing, or heating degassing.

[0059] According to the present invention, preferably, the mixing temperature in step (1) is 100-150°C and the time is 5-10h.

[0060] In this invention, when the mixing temperature and time in step (1) are within the above range, the mixing is more uniform and the plasticizing effect is better.

[0061] More preferably, the mixing temperature in step (1) is 120-140°C and the time is 6-8h.

[0062] According to the present invention, preferably, the drying temperature in step (2) is 50-100°C and the time is 5-30 min.

[0063] More preferably, the drying temperature in step (2) is 60-80°C and the time is 15-25 min.

[0064] According to the present invention, preferably, the heat treatment temperature in step (2) is 100-150°C and the time is 2-10 min.

[0065] In this invention, when the temperature and time of the heat treatment in step (2) are within the above range, the obtained PVA film has better crystallinity and better thermodynamic properties such as glass transition temperature.

[0066] More preferably, the heat treatment temperature in step (2) is 110-140°C and the time is 4-8 min.

[0067] The fourth aspect of the present invention provides a composition provided in the first aspect of the present invention, or the application of a polyvinyl alcohol film provided in the second aspect of the present invention in a polarizer.

[0068] The polyvinyl alcohol film provided by the present invention has an elongation at break of ≥500%, and the polarizer prepared by the polyvinyl alcohol film is uniformly dyed, with a polarization degree of ≥99.9% and a transmittance of ≥43.5%.

[0069] The present invention also provides a method for preparing a polarizer, the method comprising the following steps:

[0070] (1) Immerse the polyvinyl alcohol film in water for 10-30 seconds;

[0071] (2) Immerse the polyvinyl alcohol film treated in step (1) in an iodine / potassium iodide aqueous solution for 1-5 min, wherein the mass concentration ratio of iodine to potassium iodide in the iodine / potassium iodide aqueous solution is 1:50-200;

[0072] (3) The polyvinyl alcohol film treated in step (2) is uniaxially stretched to 4-8 times its original length in the first boric acid aqueous solution at a stretching rate of 8-15 m / min. The boric acid concentration in the first boric acid aqueous solution is 30-50 g / L.

[0073] (4) Immerse the polyvinyl alcohol film treated in step (3) in a potassium iodide aqueous solution for 3-10 min, wherein the potassium iodide concentration in the potassium iodide aqueous solution is 40-80 g / L;

[0074] (5) Immerse the polyvinyl alcohol film treated in step (4) in a second boric acid aqueous solution for 3-10 min;

[0075] (6) The polyvinyl alcohol film treated in step (5) is dried with hot air at a temperature of 50-60°C for 3-10 minutes. The boric acid concentration in the second boric acid aqueous solution is 30-50 g / L.

[0076] (7) Attach cellulose triacetate film to both sides of the polyvinyl alcohol film treated in step (6) to obtain a polarizer.

[0077] In the above method for preparing polarizers, the temperatures of water and aqueous solutions are each independently 25-40℃.

[0078] In the polarizer, preferably, the polyvinyl alcohol film has a thickness of 10-40 μm and the cellulose triacetate film has a thickness of 20-50 μm.

[0079] In this invention, the tensile strength and elongation at break of the polyvinyl alcohol film are as follows:

[0080] First, immerse the film in water at 35℃ for 5 minutes, then immerse it in 3.5wt% boric acid at 50℃ for 5 minutes. Then, measure the tensile properties of molded and extruded plastics according to GB-T 1040.1.2.2006 "Test for tensile properties of molded and extruded plastics", with a tensile spacing of 40 mm, a tensile speed of 150 mm / min, and a strip width of 15 mm.

[0081] The dimensional swelling degree of polyvinyl alcohol film was determined using the following method:

[0082] Cut the sample into 100mm × 100mm squares. Measure the lengths in the width direction (TD) and mechanical extension direction (MD) of the sample using vernier calipers. Then, immerse the sample in water or a solution at a constant temperature. Calculate the ratio of the lengths in the width direction and mechanical extension direction before and after immersion to obtain the dimensional change rates in the width direction and mechanical extension direction, i.e.:

[0083]

[0084] in:

[0085] χ - Dimensional change rate, %;

[0086] L1 - Length after soaking, mm;

[0087] L0 - Length before soaking, mm.

[0088] The dimensional swelling degree is the arithmetic mean of the rate of change of dimensions in the width direction and the mechanical extension direction of the sample.

[0089] The transmittance of the polarizer is determined as follows:

[0090] Using the stretching direction (i.e., optical axis) of the PVA film as the reference edge, the polarizer was cut into 40mm×40mm pieces along the 45° direction. The transmittance was calculated by using a Shimadzu UV 2200 spectrophotometer and referring to GB / T25275-2010, by averaging the values ​​in the 45° and -45° directions relative to the stretching axis of the polarizer.

[0091] The polarization degree of the polarizer is measured in the following manner:

[0092] Using the stretching direction (i.e., optical axis) of the PVA film as the reference edge, the polarizer is cut into two 40mm × 40mm pieces at a 45° angle. The two cut polarizer pieces are overlapped parallel to the polarization axis, and the transmittance of the overlapped polarizer is measured using a Shimadzu UV 2200 spectrophotometer, denoted as parallel transmittance Y1. The two cut polarizer pieces are then overlapped orthogonally to the polarization axis, and the transmittance of the overlapped polarizer is measured, denoted as orthogonal transmittance Y2. The polarization degree V of the polyvinyl alcohol polarizer is calculated using the following formula:

[0093]

[0094] The present invention will be described in detail below through embodiments.

[0095] Unless otherwise specified, all raw materials and reagents used in the following examples are commercially available.

[0096] The cellulose triacetate membrane was purchased from FIXFILM and was 40 μm thick.

[0097] The PVA resin has a degree of polymerization of 2200 and a degree of alcoholysis of 99.5%.

[0098] Examples 1-11

[0099] Following the feed amounts shown in Table 1, PVA resin, glycerol, 1-ethyl-3-methylimidazolium dihydrogen phosphate, and lauric acid diethanolamide were dissolved in ultrapure water to prepare a casting solution with a mass concentration of 15%. After the casting solution was allowed to stand for 7 hours to remove bubbles, it was cast using a die, dried for 10 minutes using 10 drying rollers at a surface temperature of 75°C. Then, it was heat-treated at 120°C for 5 minutes. Finally, it was wound up to obtain a PVA film.

[0100] Table 1

[0101]

[0102] Example 12

[0103] PVA films were prepared according to the raw materials and methods of Example 1, except that 1-ethyl-3-methylimidazolium dihydrogen phosphate was replaced with sodium dihydrogen phosphate of the same mass.

[0104] Example 13

[0105] PVA films were prepared according to the raw materials and methods of Example 2, except that polyoxyethylene laurate was used instead of lauric acid diethanolamide in the same mass.

[0106] Example 14

[0107] PVA films were prepared according to the raw materials and methods of Example 2, except that polyoxyethylene (10) stearate was used instead of lauric acid diethanolamide of the same mass.

[0108] Comparative Example 1

[0109] PVA films were prepared according to the raw materials and methods of Example 2, except that 1-ethyl-3-methylimidazolium dihydrogen phosphate was not added.

[0110] Comparative Example 2

[0111] PVA films were prepared according to the raw materials and methods of Example 1, except that 1-ethyl-3-methylimidazolium acetate was used instead of 1-ethyl-3-methylimidazolium dihydrogen phosphate in the same mass.

[0112] Comparative Example 3

[0113] PVA films were prepared according to the raw materials and methods of Example 2, except that lauric acid diethanolamide was not added.

[0114] Application examples

[0115] PVA films prepared in the above examples and comparative examples were pre-swelled by immersing in water at 30°C for 20 seconds, and then immersed in an I2 / KI aqueous solution (total I2 and KI concentration 3.5 g / L, I2 to KI mass ratio 1:100) at 35°C for 3 minutes for dyeing. The dyed PVA films were uniaxially stretched to 6 times their original length at a rate of 10 m / min in a 40 g / L boric acid aqueous solution at 50°C. The dyed and stretched PVA films were then immersed in a 60 g / L KI aqueous solution at 30°C for 5 minutes, followed by immersion in a 35 g / L boric acid aqueous solution at 30°C for 5 minutes. The PVA films were then removed and dried with hot air at 55°C for 6 minutes to obtain a PVA film with a thickness of 30 μm. Finally, a 40 μm thick cellulose triacetate film was attached to both sides of the PVA film to obtain a polarizer.

[0116] Test case

[0117] According to the method described in the specific embodiments of this invention, the elongation at break of the stretched and dyed PVA film and the dimensional swelling degree in water and 3wt% boric acid aqueous solution were determined, the swelling ratio was calculated, and the polarization and transmittance of the prepared polarizer were measured.

[0118] Table 2

[0119]

[0120] As can be seen from the results in Table 2, the PVA film provided by the present invention has a lower swelling ratio and a higher elongation at break, and the polarizer prepared by it has better optical performance.

[0121] 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 composition, characterized in that, It contains polyvinyl alcohol resin, plasticizer, and surfactant; The plasticizer comprises a polyol and a dihydrogen phosphate ionic liquid.

2. The composition according to claim 1, characterized in that, The mass ratio of the polyvinyl alcohol resin, plasticizer, and surfactant is 100:10-30:0.05-1.

3. The composition according to claim 1, characterized in that, The mass ratio of the polyol to the dihydrogen phosphate ionic liquid is 30-50:

1.

4. The composition according to claim 1, characterized in that, The cations of the dihydrogen phosphate ionic liquid are selected from... At least one of them, wherein R, R1 and R2 are each independently selected from H or alkyl.

5. The composition according to any one of claims 1-4, characterized in that, The polyol is selected from C 10 The following polyols; Preferably, the polyol is selected from at least one of ethylene glycol, propylene glycol, glycerol, and butanediol.

6. The composition according to any one of claims 1-4, wherein the surfactant comprises anionic surfactant and / or nonionic surfactant.

7. A polyvinyl alcohol film, characterized in that, Prepared from the composition according to any one of claims 1-6.

8. The polyvinyl alcohol film according to claim 7, characterized in that, The ratio of the size swelling of the polyvinyl alcohol film in water to that in a 3wt% boric acid aqueous solution is 1.1-1.3:

1.

9. A method for preparing a polyvinyl alcohol film, characterized in that, Includes the following steps: (1) Mix the composition according to any one of claims 1-6 with a solvent to obtain a casting solution; (2) The casting solution is degassed, shaped, dried and heat-treated to obtain a polyvinyl alcohol film.

10. The composition according to any one of claims 1-6, or the use of the polyvinyl alcohol film according to claim 7 or 8 in a polarizer.

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