CN116135913A - Polyvinyl alcohol film, polarizing film comprising the same, and method for producing the same - Google Patents
Polyvinyl alcohol film, polarizing film comprising the same, and method for producing the same Download PDFInfo
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- CN116135913A CN116135913A CN202111351186.1A CN202111351186A CN116135913A CN 116135913 A CN116135913 A CN 116135913A CN 202111351186 A CN202111351186 A CN 202111351186A CN 116135913 A CN116135913 A CN 116135913A
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- polyvinyl alcohol
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- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 121
- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 119
- 238000004519 manufacturing process Methods 0.000 title abstract description 13
- 238000010521 absorption reaction Methods 0.000 claims abstract description 26
- 229920005989 resin Polymers 0.000 claims description 40
- 239000011347 resin Substances 0.000 claims description 40
- 238000005266 casting Methods 0.000 claims description 29
- 238000000034 method Methods 0.000 claims description 29
- 239000000243 solution Substances 0.000 claims description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- 238000002835 absorbance Methods 0.000 claims description 19
- 238000001035 drying Methods 0.000 claims description 19
- 238000007127 saponification reaction Methods 0.000 claims description 17
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical group CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 15
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 claims description 15
- 239000004327 boric acid Substances 0.000 claims description 15
- 239000007864 aqueous solution Substances 0.000 claims description 14
- 229920001567 vinyl ester resin Polymers 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 13
- 239000000178 monomer Substances 0.000 claims description 13
- 238000006116 polymerization reaction Methods 0.000 claims description 12
- 229920001577 copolymer Polymers 0.000 claims description 11
- 239000002904 solvent Substances 0.000 claims description 11
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 8
- 229910052796 boron Inorganic materials 0.000 claims description 8
- 238000003756 stirring Methods 0.000 claims description 8
- 229920001290 polyvinyl ester Polymers 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 5
- 230000000379 polymerizing effect Effects 0.000 claims description 5
- 238000004090 dissolution Methods 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 3
- 239000010408 film Substances 0.000 description 103
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 description 12
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 10
- 229910052739 hydrogen Inorganic materials 0.000 description 10
- 239000001257 hydrogen Substances 0.000 description 10
- 230000003287 optical effect Effects 0.000 description 9
- 239000012788 optical film Substances 0.000 description 8
- -1 olefin compounds Chemical class 0.000 description 7
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 6
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 6
- 238000004458 analytical method Methods 0.000 description 6
- 239000004014 plasticizer Substances 0.000 description 6
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- 238000005070 sampling Methods 0.000 description 4
- IAZDPXIOMUYVGZ-WFGJKAKNSA-N Dimethyl sulfoxide Chemical compound [2H]C([2H])([2H])S(=O)C([2H])([2H])[2H] IAZDPXIOMUYVGZ-WFGJKAKNSA-N 0.000 description 3
- 238000005481 NMR spectroscopy Methods 0.000 description 3
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 3
- 238000000862 absorption spectrum Methods 0.000 description 3
- 125000000218 acetic acid group Chemical group C(C)(=O)* 0.000 description 3
- XXROGKLTLUQVRX-UHFFFAOYSA-N allyl alcohol Chemical compound OCC=C XXROGKLTLUQVRX-UHFFFAOYSA-N 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 3
- 238000004043 dyeing Methods 0.000 description 3
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 3
- 238000002329 infrared spectrum Methods 0.000 description 3
- HVAMZGADVCBITI-UHFFFAOYSA-M pent-4-enoate Chemical compound [O-]C(=O)CCC=C HVAMZGADVCBITI-UHFFFAOYSA-M 0.000 description 3
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 2
- 239000005977 Ethylene Substances 0.000 description 2
- XPDWGBQVDMORPB-UHFFFAOYSA-N Fluoroform Chemical compound FC(F)F XPDWGBQVDMORPB-UHFFFAOYSA-N 0.000 description 2
- 238000004566 IR spectroscopy Methods 0.000 description 2
- BAPJBEWLBFYGME-UHFFFAOYSA-N Methyl acrylate Chemical compound COC(=O)C=C BAPJBEWLBFYGME-UHFFFAOYSA-N 0.000 description 2
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 2
- 150000001252 acrylic acid derivatives Chemical class 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- CZUYDSZPFGEDEQ-UHFFFAOYSA-N ethenyl 3,3,3-trifluoro-2-methyl-2-(trifluoromethyl)propanoate Chemical compound CC(C(=O)OC=C)(C(F)(F)F)C(F)(F)F CZUYDSZPFGEDEQ-UHFFFAOYSA-N 0.000 description 2
- 238000007667 floating Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 125000004435 hydrogen atom Chemical group [H]* 0.000 description 2
- 238000009616 inductively coupled plasma Methods 0.000 description 2
- 229920002521 macromolecule Polymers 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000004575 stone Substances 0.000 description 2
- AQSYHEKLGWEVDF-UHFFFAOYSA-N 1-n,3-n-bis[4-(4,5-dihydro-1h-imidazol-2-yl)phenyl]benzene-1,3-dicarboxamide;hydrochloride Chemical compound Cl.C=1C=CC(C(=O)NC=2C=CC(=CC=2)C=2NCCN=2)=CC=1C(=O)NC(C=C1)=CC=C1C1=NCCN1 AQSYHEKLGWEVDF-UHFFFAOYSA-N 0.000 description 1
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N 2-Propenoic acid Natural products OC(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- JIGUQPWFLRLWPJ-UHFFFAOYSA-N Ethyl acrylate Chemical compound CCOC(=O)C=C JIGUQPWFLRLWPJ-UHFFFAOYSA-N 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- UWHCKJMYHZGTIT-UHFFFAOYSA-N Tetraethylene glycol, Natural products OCCOCCOCCOCCO UWHCKJMYHZGTIT-UHFFFAOYSA-N 0.000 description 1
- KXKVLQRXCPHEJC-UHFFFAOYSA-N acetic acid trimethyl ester Natural products COC(C)=O KXKVLQRXCPHEJC-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- CQEYYJKEWSMYFG-UHFFFAOYSA-N butyl acrylate Chemical compound CCCCOC(=O)C=C CQEYYJKEWSMYFG-UHFFFAOYSA-N 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- MEGHWIAOTJPCHQ-UHFFFAOYSA-N ethenyl butanoate Chemical compound CCCC(=O)OC=C MEGHWIAOTJPCHQ-UHFFFAOYSA-N 0.000 description 1
- GFJVXXWOPWLRNU-UHFFFAOYSA-N ethenyl formate Chemical compound C=COC=O GFJVXXWOPWLRNU-UHFFFAOYSA-N 0.000 description 1
- QBDADGJLZNIRFQ-UHFFFAOYSA-N ethenyl octanoate Chemical compound CCCCCCCC(=O)OC=C QBDADGJLZNIRFQ-UHFFFAOYSA-N 0.000 description 1
- BLZSRIYYOIZLJL-UHFFFAOYSA-N ethenyl pentanoate Chemical compound CCCCC(=O)OC=C BLZSRIYYOIZLJL-UHFFFAOYSA-N 0.000 description 1
- UIWXSTHGICQLQT-UHFFFAOYSA-N ethenyl propanoate Chemical compound CCC(=O)OC=C UIWXSTHGICQLQT-UHFFFAOYSA-N 0.000 description 1
- 238000013213 extrapolation Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 229920001477 hydrophilic polymer Polymers 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 239000011630 iodine Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- PNJWIWWMYCMZRO-UHFFFAOYSA-N pent‐4‐en‐2‐one Natural products CC(=O)CC=C PNJWIWWMYCMZRO-UHFFFAOYSA-N 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- LYBIZMNPXTXVMV-UHFFFAOYSA-N propan-2-yl prop-2-enoate Chemical compound CC(C)OC(=O)C=C LYBIZMNPXTXVMV-UHFFFAOYSA-N 0.000 description 1
- PNXMTCDJUBJHQJ-UHFFFAOYSA-N propyl prop-2-enoate Chemical compound CCCOC(=O)C=C PNXMTCDJUBJHQJ-UHFFFAOYSA-N 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000008213 purified water Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 150000005846 sugar alcohols Polymers 0.000 description 1
- 230000008961 swelling Effects 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- ZIBGPFATKBEMQZ-UHFFFAOYSA-N triethylene glycol Chemical compound OCCOCCOCCO ZIBGPFATKBEMQZ-UHFFFAOYSA-N 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 230000037303 wrinkles Effects 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/12—Chemical modification
- C08J7/14—Chemical modification with acids, their salts or anhydrides
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
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- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- General Chemical & Material Sciences (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
Abstract
The invention relates to a polyvinyl alcohol film, a polarized film containing the same and a manufacturing method thereof, wherein the polyvinyl alcohol film has an IR absorption intensity ratio of 0.85<A1730cm ‑1 /A1710cm ‑1 <0.97. The polyvinyl alcohol film of the present invention has excellent hue characteristics.
Description
Technical Field
The invention relates to a polyvinyl alcohol (polyvinyl alcohol, PVA) film which can be used as an optical film, in particular to a polarizing film.
Background
Polyvinyl alcohol (polyvinyl alcohol, PVA) film is a hydrophilic polymer having transparency, mechanical strength, water solubility, processability, etc., and has been widely used for optical films, particularly polarizing films, of packaging materials or electronic products.
In the production of the PVA film into an optical film, functional groups may be optionally modified according to desired properties, followed by stretching. The manufacturing method can be divided into dry type and wet type, wherein the dry type is to stretch the PVA film in an inert gas environment under a fixed temperature and humidity, and then to dye; the wet method is to dye a PVA film and then stretch it in a solution. Since the PVA film produced in the dry process often has problems of uneven surface or uneven dyeing, the PVA film produced in the wet process has better performance (e.g., uniform color), so that the PVA film is generally produced in the wet process.
When the polarizing film is manufactured, the higher the stretching ratio is, the higher the obtainable optical performance is, so that the PVA film is stretched to the vicinity of the fracture critical point as much as possible during stretching, thereby obtaining the PVA film with better optical performance.
The good polarizing film has the characteristics of uniform color, less color spots, no wrinkles and the like, and can provide better optical properties. In order to improve the optical properties of the polarizing film, the prior art changes the viscosity or saponification degree by changing the structure of polyvinyl alcohol or adding functional groups (e.g., cationic groups), etc., thereby improving the optical properties.
Disclosure of Invention
However, residual acetic acid group distribution (Syndiotacticity) of conventional processes can have a significant effect on polarizer color.
The inventors found that the cause of leakage of red or blue light from the polarizing film is the relative amounts of I3-and I5-in the film. If I5-is less, the absorbance at 700nm is lower, and the appearance is reddish (Red leak); on the other hand, if I3-is small, 480nm absorption is low and the appearance is bluish (Blue leak). Boric acid can effectively crosslink with PVA, which is helpful for the generation of I5-complex or the prevention of I3-loss, therefore, if the crosslinking reaction amount of boric acid and PVA is insufficient, the phenomenon that the color of the polarizing film is reddish or bluish may occur. On the other hand, if the syndiotacticity is higher, the I5-complex is more likely to form, and Red leak is likely to be reduced. In addition to syndiotacticity, residual acetic acid group alignment, degree of boric acid mismatching, etc. also affect relative hue. The effect of uniform hue can be achieved only by controlling the color phase to be in a specific range.
Accordingly, in order to solve the above problems, the present invention provides a PVA film having excellent hue by controlling the ratio of non-hydrogen bond carbonyl groups/hydrogen bond carbonyl groups in the IR absorption spectrum, wherein the IR absorption intensity of the non-hydrogen bond carbonyl groups is A1730cm -1 IR absorption of hydrogen bond carbonyl groupsIntensity of A1710cm -1 。
The object of the present invention is to provide a polyvinyl alcohol (polyvinyl alcohol, PVA) film having an IR absorption intensity ratio of 0.85<A1730cm -1 /A1710cm -1 <0.97, wherein the IR absorption intensity is determined by immersing the polyvinyl alcohol film in pure water, stirring, taking out, drying at 105 ℃/1hr, and analyzing.
In a preferred embodiment, the PVA film has an acetate group absorption strength of 0.35<(A1710cm -1 +A1730cm -1 )/A1425cm -1 <0.55, wherein the acetate group absorption strength is determined by immersing the polyvinyl alcohol film in pure water, stirring, taking out, drying at 105 ℃/1hr, and analyzing.
In a preferred embodiment, the PVA film has a syndiotacticity of 52% to 56%.
In a preferred embodiment, 0.12g of the PVA film is treated with an aqueous solution of 0.2% by weight of boric acid and dissolved in water, the aqueous solution having a boron content of 16 to 19ppm.
It is another object of the present invention to provide an optical film comprising a PVA film as described above. In a preferred embodiment, the optical film is a polarizing film.
In a preferred embodiment, the ratio (A/B) of the absorbance (A) at 480nm wavelength to the absorbance (B) at 700nm wavelength of the polarizing film in the crossed nicols state is 1.40 to 1.70.
In a preferred embodiment, the ratio (A/B) of the absorbance (A) at 480nm wavelength to the absorbance (B) at 700nm wavelength of the polarizing film in the crossed nicols state is 1.51 to 1.65.
Another object of the present invention is to provide a method for producing a PVA film, comprising: (a) Polymerizing vinyl ester resin monomer to form polyvinyl ester resin, and then carrying out saponification reaction to obtain polyvinyl alcohol resin, wherein vinyl2,2-bis (trifluoromethyl) propionic acid (vinyl 2,2-bis (trifluoromethyl) propionate) copolymer is added during polymerization reaction, the addition ratio of the mole amount of the copolymer to the mole amount of the vinyl ester resin monomer is 1-3 mole percent, and solvent with saponification dielectric constant of 34-36 is added; (b) Heating and dissolving the polyvinyl alcohol resin to form a polyvinyl alcohol casting solution; (C) casting the casting solution to a casting drum; and (d) drying to form the PVA film.
In a preferred embodiment, steps (a) to (c) of the method for producing a PVA film are performed using an external heat-retaining device.
In a preferred embodiment, the external heat-insulating device is a metal heating wire or a jacket with liquid inside.
In a preferred embodiment, the method for preparing the PVA film further comprises adjusting the pH value in the step (a), or adding solvents with different dielectric constants to control the arrangement of residual acetate groups.
In a preferred embodiment, the method for preparing a PVA film further includes the step (a) of pulverizing and drying the polyvinyl alcohol resin obtained by the saponification reaction, and spraying steam in due time during the drying process to avoid excessive drying of the resin particles and skinning.
The invention has the effects of improving the process of the conventional PVA film and achieving the PVA film with excellent hue by regulating the proportion of non-hydrogen bond carbonyl groups/hydrogen bond carbonyl groups in an IR absorption spectrum.
Drawings
FIG. 1 shows that the C=0 absorption peak in the acetate group is divided into 1710cm -1 (linked to OH groups) 1730cm -1 Schematic representation of (non-hydrogen bonded carbonyl groups within the block).
Fig. 2 is a schematic diagram of a syndiotactic triad (Syndiotactic triad), an Isotactic triad (isotic triad), a hetero-syndiotactic triad (Heterotactic triad) according to one embodiment of the present invention.
Detailed Description
The following embodiments should not be construed as unduly limiting the invention. Modifications and variations of the embodiments discussed herein may be made by those skilled in the art without departing from the spirit or scope of the invention, and remain within the scope of the invention.
The terms "a" and "an" herein mean that there is one or more than one (i.e., at least one) of the grammatical object herein.
The present invention provides a PVA film, in particular, a PVA film having a specific IR absorption intensity ratio. In addition, the invention also provides an optical film comprising the PVA film.
The aforementioned "IR absorption intensity ratio" is obtained by using infrared spectroscopy (infrared spectroscopy), which is a technique for detecting the vibration energy (or frequency) of molecules, and uses the principle of infrared light and molecular vibration generated by molecular action to record the vibration mode (vibrational modes) of the molecules after absorbing infrared light, and record the graph of the relative intensity of the absorbed light to the wavelength (λ) of the infrared light, namely, the infrared spectrum, which can be used for specific molecular identification. The IR analysis method is as follows: 10 cm. Times.10 cm of PVA film was immersed in 2000ml of pure water at 30℃in accordance with JIS k 6726, stirred for 5 minutes by a magnet stirrer, and then taken out. The oven was preheated to 105 ℃, the soaked film was spread in a tray, dried at 105 ℃/1hr, and then the film was taken out for IR analysis. If the IR absorption value has a negative value, the data are translated appropriately, and a fixed constant is added to all the data, so that the lowest point of the full-range IR spectrum absorption value is 0.
Referring to FIG. 1, the absorption peak of C=0 in acetate group is divided into 1710cm -1 (linked to OH groups) 1730cm -1 (non-hydrogen bonded carbonyl groups within the block). According to at least one embodiment, the inventors found that the C=0 absorption peak in the acetate group was divided into 1710cm -1 (linked to OH groups) 1730cm -1 (in block) 1730cm -1 Absorption Strength (A1730 cm) -1 ) The higher the representative block, the more c=0, which has an effect on the hue of the polarizer. In a preferred embodiment, the polyvinyl alcohol film of the invention has an IR absorption intensity ratio of 0.85<A1730cm -1 /A1710cm -1 <0.97. Ranges between any two of the following values are specified but are not inclusive of the values, e.g.: 0.85, 0.86, & 0.97.
In addition and/or as found by the inventors, (A1710 cm) -1 +A1730cm -1 )/A1425cm -1 Represents the overall acetate residue, and the higher the value, the lower the bias brightness and the tendency for red light leakage. In a preferred embodiment, the present inventionThe clear polyvinyl alcohol film further had an acetate group absorption strength of 0.35<(A1710cm -1 +A1730cm -1 )/A1425cm -1 <0.55, specifically ranging between any two of the following values, although not inclusive of the recited values, e.g.: 0.35, 0.36,..0.55. A1730cm -1 The higher the absorption value, the more acetate groups (OAc groups) are in the block, which can be controlled by properly adjusting the pH during saponification or adding solvents of different dielectric constants to control the residual acetate group arrangement; in addition, basification of different solvents will control the alignment of the different residual acetic acid groups.
The PVA film of the present invention also has a specific syndication. "Syndiotacticity" as used herein refers to the stereoregularity of a molecular chain, meaning the configuration in which R groups appear alternately on either side of the chain. In a preferred embodiment, the PVA film of the present invention has a syndiotacticity of 52% to 56%. Specifically, the range between any two of the following values is exemplified by: 52%, 53%,. According to at least one embodiment, the degree of syndiotacticity may be adjusted during the polymerization reaction by the appropriate addition of specific copolymers, such as but not limited to: vinyl2,2-bis (trifluoromethyl) propionate, vinyl5H-octafluorovalerate, carbon trifluoride (CF) 3 ) Etc.; if the polymerization temperature is too high, the steric hindrance is overcome, the syndiotacticity is lowered, and branches (branches) are easily generated, so that the dyeability is affected.
In a preferred embodiment, the PVA film of the present invention is treated with an aqueous solution of 0.2wt% boric acid and dissolved in water, the aqueous solution having a boron content of 16 to 19ppm, specifically in a range between any two of the following values, for example: 16ppm, 16.5ppm, 19ppm. In the invention, the boron content measuring method comprises the following steps: about 0.12g of PVA film was cut and put into a 30ml glass sampling bottle, 20g of pure water was added so that the film was completely immersed below the level of pure water, and a stirring stone was added thereto at a stirring speed of 250rpm for 1.0 hour. Then pouring out pure water in the bottle, adding 0.2wt% boric acid aqueous solution, standing for 1.0 hour, pouring out the boric acid aqueous solution, and standing and curing the PVA film in the bottle for 16.0 hours. Then, the PVA film was taken out, rinsed with pure water, put into a 30ml glass sampling bottle, and 20g of pure water was added, and after it was sufficiently dissolved, the boron concentration in the solution was analyzed by an inductively coupled plasma optical emission spectrometer (ICP-OES).
The "optical film" as referred to herein refers to a polarizing film, a blue light resistant film, a filter, etc., and the present invention is not limited to these. Preferably, the PVA film of the present invention is used as a polarizing film.
The polarizing film has a ratio (A/B) of absorbance (A) at a wavelength of 480nm to absorbance (B) at a wavelength of 700nm in a specific crossed nicols state. As used herein, "orthogonal Ni Ke Er" refers to the transmission of orthogonal Nickels (Cross Nicol), a method used to analyze optical properties. The measurement wavelength range was set to 380nm to 780nm, and the transmittance when the vibration direction of the polarized light incident on the polarizing film through the gram-taylor polarizer was parallel to the transmission axis of the polarizing film was set to be parallel transmittance, and the case perpendicular to the transmission axis of the polarizing film was set to be orthogonal nicol transmittance. Then, using the "polarizing film evaluation program" (manufactured by japan spectroscopic corporation), the sensitivity correction in the visible light range of the C light source and the 2 ° field of view was performed using the above-described parallel transmittance and orthogonal nicol transmittance so as to comply with JIS Z8722 (measurement method of object color), and the individual transmittance and the polarization degree of the polarizing film were calculated, and these two values were obtained as the optical characteristics of the polarizing film.
In a preferred embodiment, the ratio (A/B) of the absorbance (A) at 480nm wavelength to the absorbance (B) at 700nm wavelength in the crossed nicols state of the polarizing film of the present invention is 1.40 to 1.70, and the ratio (A/B) is specifically in the range between any two of the following values, for example: 1.40, 1.41, & gt, 1.70. In a more preferred embodiment, the ratio (A/B) of the absorbance (A) at 480nm wavelength to the absorbance (B) at 700nm wavelength in the crossed nicols state of the polarizing film of the present invention is 1.51 to 1.65, and the ratio (A/B) is specifically in the range between any two of the following values, for example: 1.51, 1.52, & gt, 1.65.
In another aspect, the present invention also provides a method for producing the polyvinyl alcohol film, comprising the steps of: (a) Polymerizing vinyl ester resin monomer to form polyvinyl ester resin, and then carrying out saponification reaction to obtain polyvinyl alcohol resin, wherein vinyl2,2-bis (trifluoromethyl) propionic acid (vinyl 2,2-bis (trifluoromethyl) propionate) copolymer is added during polymerization reaction, the addition ratio of the mole amount of the copolymer to the mole amount of the vinyl ester resin monomer is 1-3 mole percent, and solvent with saponification dielectric constant of 34-36 is added; (b) Heating and dissolving the polyvinyl alcohol resin to form a polyvinyl alcohol casting solution; (c) casting the casting solution to a casting drum; and (d) drying to form the polyvinyl alcohol film.
In a preferred embodiment, the PVA film of the present invention is produced by the method wherein the ratio of the molar amount of the copolymer to the molar amount of the vinyl ester resin monomer in the (a) vinyl ester resin monomer polymerization step is 1 to 3mole%. Specifically, the range between any two of the following values, for example: 1. 1.2., 3mole% and the invention is not limited to these. In a preferred embodiment, the pH is adjusted in step (a), or solvents of different dielectric constants are added to control the residual acetate group alignment. In another preferred embodiment, in the step (a), the polyvinyl alcohol resin obtained by saponification is crushed and dried, and steam is sprayed in due time in the drying process, so that resin particles are prevented from being excessively dried to generate crust.
The solvent having a saponified dielectric constant of 34 to 36 in the step (a) is, for example: the more the amount of methyl acetate, the lower the saponification dielectric constant value, A1730cm -1 /A1710cm -1 The IR absorption intensity ratio will become high.
The polyvinyl alcohol resin is obtained by polymerizing a vinyl ester resin monomer to form a polyvinyl ester resin and then performing saponification reaction; the vinyl ester resin monomer includes vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, and vinyl caprylate, and the present invention is not limited to these, but vinyl acetate is preferable. In addition, copolymers of olefin compounds or acrylate derivatives copolymerized with the vinyl ester resin monomers mentioned above can also be used; the olefin compound may be, for example, ethylene, propylene, butene, etc., or an acrylate derivative such as allyl acetate, acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, etc., and a copolymer obtained by copolymerizing the above vinyl ester monomer may be used. Ethylene, allyl acetate, and allyl alcohol are preferable from the viewpoint of the production cost and the film quality. According to at least one embodiment, the ethylene, allyl acetate, allyl alcohol unit content is within 5mole%, preferably 2 to 3.5 mole%.
Specific copolymers may also be added appropriately during the polymerization to adjust syndiotacticity, such as vinyl2,2-bis (trifluoromethyl) propionate. The polymerization temperature is also adjusted slightly. Too high a polymerization temperature, a decrease in syndiotacticity, and branching (Branch) tend to occur, which affects dyeability.
In general, the degree of saponification of the polyvinyl alcohol resin is 90% or more, preferably 99% or more, to obtain preferable optical characteristics, specifically any of the following values, for example: 90%, 91%, 99%, or between any two of the foregoing. The pH value can be properly adjusted in the saponification process, or solvents with different dielectric constants can be added to control the arrangement of residual acetate groups.
The degree of polymerization of the polyvinyl alcohol is between 800 and 10000, and preferably between 2200 and 10000, for example: 800. 900, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000 or any value therebetween, and a degree of polymerization higher than 800 has preferable processing characteristics, but if the degree of polymerization is higher than 10000, dissolution is not favored.
In general, in the polyvinyl alcohol casting solution used, if the content of the polyvinyl alcohol resin is insufficient, the viscosity of the casting solution is too low, and the drying load is too large, resulting in poor film formation efficiency. On the other hand, if the content of the polyvinyl alcohol resin is too high, the polyvinyl alcohol resin is not easily dissolved and clusters are easily left. Thus, the polyvinyl alcohol casting solution used in this embodiment has a content of the polyvinyl alcohol resin of usually 10 to 60 wt%, preferably 15 to 40 wt%, more preferably 20 to 30 wt%, particularly 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60 wt%, etc.
The dissolution temperature of the polyvinyl alcohol casting solution is preferably 130 to 140 ℃, clusters are easy to remain when the temperature is too low, energy consumption is eliminated when the temperature is too high, and the cost is increased. Specific temperatures are, for example, 130 to 140 ℃, 133 to 140 ℃, 136 to 140 ℃, 139 to 140 ℃, 130 to 137 ℃, 130 to 134 ℃ or 130 to 131 ℃.
In addition to the polyvinyl alcohol resin, a plasticizer may be contained in the casting solution to enhance the film forming processability, and the plasticizer that may be used includes a polyhydric alcohol such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, or glycerol, and the like, and the present invention is not limited to these, but ethylene glycol and glycerol are preferable. The plasticizer is added in an amount of usually 3 to 30 parts by weight, preferably 7 to 20 parts by weight, relative to 100 parts by weight of the polyvinyl alcohol resin, specifically for example: 3. 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 parts by weight or between any two of the foregoing values. If the plasticizer content is insufficient, the formed PVA film is easy to crystallize and influence the dyeing efficiency of subsequent processing. Conversely, if the plasticizer content is too high, the mechanical properties of the PVA film may be deteriorated.
The equipment used in the method for manufacturing the PVA film comprises a dissolving tank, a filter, a coating machine and a conveying pipeline connected from the dissolving tank to the front of the coating machine, wherein the equipment is preferably coated with a heat preservation device, the heat preservation device can be a metal heating wire or a jacket filled with liquid, such as oil or water, by heating the liquid in the metal wire or the jacket, the dissolving tank, the filter, the coating machine and the pipeline connected from the dissolving tank to the coating machine maintain a uniformly heated heat preservation state, in particular to the surfaces of the equipment and the pipeline, so that the equipment or the pipeline can avoid the polyvinyl alcohol in the polyvinyl alcohol casting solution from forming gel due to the loss of temperature of the surface, and the filter is adhered or blocked, so that the process can not continue to operate. On the other hand, if the heating temperature is too high, a part of the solution is dehydrated or gelled to form a yellowish or black gel, which is also unfavorable for improving the quality and uniformity of the surface of the film formed by coating. In the method of the present invention, the polyvinyl alcohol is applied under the heating and heat-preserving condition of 80 to 120 ℃, preferably under the heating and heat-preserving condition of 90 to 110 ℃, more preferably under the heating and heat-preserving condition of 90 to 100 ℃, specifically for example: 80. 85, 90, 95, 100, 105, 110, 115, 120 ℃ or between any two of the foregoing values. In a preferred embodiment, steps (a) to (c) are performed with the use of an external heat-retaining device.
In the method disclosed above, after a polyvinyl alcohol resin and a plasticizer are dissolved in a solution to form a polyvinyl alcohol casting solution, the polyvinyl alcohol casting solution is filtered by a filter, and finally, the polyvinyl alcohol casting solution is cast to a casting drum by a gear pump (gear pump) and a T-type die coater, and the drum speed is too slow, so that the polyvinyl alcohol casting solution tends to be excessively dry and have phase difference and uneven melting point distribution; if the drying is too fast, the drying becomes insufficient and the peelability is lowered. If the drum temperature is raised, foaming is likely to occur. The rotation speed of the drum is thus preferably 3 to 7 m/min, preferably 4 to 6 m/min, and may be in particular in the range between any two of the following values, for example: 2 meters per minute, 3 meters per minute … meters per minute. The temperature is set between 85 to 90 ℃, for example, 85 to 90 ℃, 86 to 90 ℃, 87 to 90 ℃, 88 to 90 ℃, 89 to 90 ℃, 85 to 89 ℃, 85 to 88 ℃, 85 to 87 ℃, or 85 to 86 ℃. If the drum temperature is too high, the casting solution on the drum tends to foam.
The film was peeled off from the drum, further dried by a series of hot rolls, and then subjected to heat treatment to obtain a polyvinyl alcohol film. The heat treatment method includes, for example, (1) a polyvinyl alcohol film is carried out on a hot roll or (2) a floating dryer. The number of the heat roller and the floating dryer is not particularly limited. But is preferably 115 to 130 ℃, for example 115 to 130 ℃, 115 to 128 ℃, 115 to 126 ℃, 115 to 124 ℃, 115 to 122 ℃, 115 to 120 ℃, 115 to 118 ℃, 115 to 116 ℃, 117 to 130 ℃, 119 to 130 ℃, 121 to 130 ℃, 123 to 130 ℃, 125 to 130 ℃, 127 to 130 ℃, or 129 to 130 ℃. When the temperature is too high, the swelling degree is deteriorated, the dyeing property and the boric acid reactivity are affected, and when the temperature is too low, the PVA is eluted.
The PVA film is stretched and dyed in the manufacture of optical films, for example, polarizing films, because I-containing films are used in the polarizing film process 3 - 、I 5 - The PVA film is dyed by aqueous solution of boric acid of iodide ions, and the boric acid can be crosslinked with the area of the PVA which is not shaped (amorphlus), so that the iodide ions are fixed to avoid the dissolution of the iodide ions.
Examples
Hereinafter, the present invention will be described in further detail with reference to the detailed description and examples. However, it should be understood that these examples are only for helping to make the present invention more easily understandable and are not intended to limit the scope of the invention.
Manufacturing a PVA film: firstly preparing a polyvinyl alcohol casting solution, casting the polyvinyl alcohol casting solution to a casting roller, and drying to form a polyvinyl alcohol polymer film. Specifically, in the above-mentioned process for producing a polyvinyl alcohol polymer film, the polyvinyl alcohol casting solution mainly comprises polyvinyl alcohol obtained by polymerizing a vinyl ester resin monomer to obtain a polyvinyl ester resin, and then subjecting the polyvinyl ester resin to saponification.
Manufacturing a polarizing film: a polyvinyl alcohol film was immersed in water at 30℃to swell it and stretched to 2.0 times the original length in the Machine Direction (MD), then immersed in an aqueous solution at 30℃containing 0.03 mass% of iodine and 3 mass% of potassium iodide, stretched to 3.3 times the original length, then immersed in an aqueous solution at 30℃containing 3 mass% of potassium iodide and 3 mass% of boric acid, and further stretched to 3.6 times the original length. Then immersed in a 60 ℃ aqueous solution of 5 mass% potassium iodide and 4 mass% boric acid, and further extended to 6.0 times the original. The polarizing film was obtained by immersing in a 3 mass% aqueous potassium iodide solution for 15 seconds and then drying at 60℃for 4 minutes.
Referring to Table 1, the experimental control factors and the color uniformity measurement results of examples 1 to 4 and comparative examples 1 to 3 are shown below.
TABLE 1
In this embodiment, the IR analysis method includes: a10 cm by 10cm PVA film was immersed in 2000ml of pure water at 30℃and stirred for 5 minutes by a magnet stirrer, and then taken out. The oven was preheated to 105℃, the soaked film was spread in a tray, dried at 105℃/1hr, and the film was taken out for analysis. If the IR absorption value has a negative value, the data are translated appropriately, and a fixed constant is added to all the data, so that the lowest point of the full-range IR spectrum absorption value is 0.
In this embodiment, the boron content measuring method includes: about 0.12g of PVA film was cut and put into a 30ml glass sampling bottle, 20g of pure water was added so that the film was completely submerged under the pure water level, and a stirring stone was added thereto at a stirring speed of 250rpm for 1.0 hour. Then, pure water in the bottle was poured out, and 0.2wt% boric acid aqueous solution was additionally added thereto, and allowed to stand for 1.0 hour, and then the boric acid aqueous solution was poured out, and the PVA film was allowed to stand still and mature for 16.0 hours in the bottle with closure (close). Then, the PVA film was taken out, rinsed with pure water, put into a 30ml glass sampling bottle, and 20g of pure water was added thereto, and after it was sufficiently dissolved, the boron concentration in the solution was analyzed by ICP-OES.
In this embodiment, the ICP-OES analysis method comprises: firstly, preparing a detection line by an extrapolation method, absorbing 200ppm of ICP multi-element standard liquid (purchased from Merck company) by a micro-dispenser, placing the detection line in a 100ml measuring flask, and diluting the detection line to 100ml by deionized water to prepare the detection line with required concentration (such as 100, 200, 500 and 2000 ppb) for later use; the sample is directly analyzed on the machine without pretreatment. The analytical element selected in the method is boron (B, 249.773 nm).
In this embodiment, the method for analyzing syndication control includes: the test sample of 10 cm. Times.10 cm was immersed in 2000ml of purified water at 30℃and stirred for 5 minutes by a magnet stirrer, and then taken out. Preheating the oven to 105 ℃ in advance, and thinning the soaked filmThe films were spread in trays and dried at 105℃/1 hr. The film was taken out and then subjected to NMR analysis. The solvent used was deuterated dimethyl sulfoxide (dimethyl sulfoxide-d 6 ) The method comprises the steps of carrying out a first treatment on the surface of the The instrument is 1 H NMR. The analysis method is described in the journal of Macromolecules (Macromolecules, 5,577) of T.Moritani et al 1972, and the percentage (%) of triples (triads; mm/mr/rr) is determined by NMR with reference to FIG. 2, and then by the formula: syndication (dyads) =rr+mr/2.
In this example, the resin saponification degree and the average overlap ratio were measured by the JIS 6726 test method.
From Table 1, the ratio (A/B) of absorbance (A) at a wavelength of 480nm to absorbance (B) at a wavelength of 700nm in the crossed nicols state is preferably 1.40 or more from the viewpoint of uniformity of hue of the polarizing film produced by the PVA film of the present invention. On the other hand, if the ratio (A/B) is too high, the red light leakage tends to increase, and therefore, the ratio (A/B) is preferably 2.00 or less, more preferably less than 1.80. The absorbance (a) and the absorbance (B) can be obtained by using a spectroluminance meter.
In summary, the present invention has the effects of improving the process of conventional PVA films and achieving PVA films with excellent hue by controlling the ratio of non-hydrogen bond carbonyl groups/hydrogen bond carbonyl groups in the IR absorption spectrum.
All ranges provided herein are intended to include each specific range within the given range as well as combinations of sub-ranges between the given ranges. Moreover, unless otherwise indicated, all ranges provided herein include the endpoints of the ranges. Thus, ranges 1-5 specifically include 1, 2, 3, 4, and 5, as well as subranges such as 2-5, 3-5, 2-3, 2-4, 1-4, and the like.
All publications and patent applications cited in this specification are herein incorporated by reference and for any and all purposes, each individual publication or patent application is specifically and individually indicated to be incorporated by reference. In the event of a discrepancy between this document and any publication or patent application incorporated by reference herein, this document controls.
The terms "comprising," "having," "including," and "containing" are used herein in an open, non-limiting sense. The terms "a" and "an" are to be construed to cover both the plural and the singular. The term "one or more" means "at least one" and thus may include a single feature or a mixture/combination of features.
Except in the operating examples, or where otherwise indicated, all numbers expressing amounts of ingredients and/or reaction conditions can be modified in all instances by the term "about," meaning within + -5% of the indicated number. The term "substantially free" or "substantially free" as used herein refers to less than about 2% of a particular feature. All elements or features that are positively set forth herein are negatively excluded from the claims.
Claims (10)
1. A polyvinyl alcohol film having an IR absorption intensity ratio of 0.85<A1730cm -1 /A1710cm -1 <0.97, wherein the IR absorption intensity is determined by immersing the polyvinyl alcohol film in pure water, stirring, taking out, drying at 105 ℃/1hr, and analyzing.
2. The polyvinyl alcohol film according to claim 1, wherein it further has an acetate group absorption strength of 0.35<(A1710cm -1 +A1730cm -1 )/A1425cm -1 <0.55, wherein the acetate group absorption intensity is obtained by immersing the polyvinyl alcohol film in pure water, stirring, taking out, drying at 105 ℃/1hr, and analyzing.
3. The polyvinyl alcohol film according to claim 1 or 2, wherein it further has a syndiotacticity of 52% to 56%.
4. The polyvinyl alcohol film according to claim 3, wherein 0.12g of the polyvinyl alcohol film is treated with an aqueous solution of 0.2wt% boric acid and the boron content of the aqueous solution after dissolution with water is 16 to 19ppm.
5. A polarizing film comprising the polyvinyl alcohol film according to any one of claims 1 to 4.
6. The polarizing film according to claim 5, wherein a ratio (A/B) of absorbance (A) at a wavelength of 480nm to absorbance (B) at a wavelength of 700nm in a crossed nicols state is 1.40 to 1.70.
7. The polarizing film according to claim 6, wherein a ratio (A/B) of absorbance (A) at a wavelength of 480nm to absorbance (B) at a wavelength of 700nm in a crossed nicols state is 1.51 to 1.65.
8. A process for producing a polyvinyl alcohol film according to any one of claims 1 to 4, wherein the process comprises:
(a) Polymerizing vinyl ester resin monomer to form polyvinyl ester resin, and then performing saponification reaction to obtain polyvinyl alcohol resin, wherein vinyl2,2-bis (trifluoromethyl) propionic acid (vinyl 2,2-bis (trifluoromethyl) propionate) copolymer is added during polymerization reaction, the addition ratio of the mole amount of the copolymer to the mole amount of the vinyl ester resin monomer is 1-3, and solvent with saponification dielectric constant of 34-36 is added;
(b) Heating and dissolving the polyvinyl alcohol resin to form a polyvinyl alcohol casting solution;
(c) Casting the casting solution to a casting drum; and
(d) Drying to form the polyvinyl alcohol film;
wherein the steps (a) to (c) are carried out under a jacket which is provided with an external heat preservation device and is a metal heating wire or a liquid inside.
9. The method according to claim 8, wherein the residual acetate group alignment is controlled by further adjusting the pH in the step (a) or adding a solvent having a different dielectric constant.
10. The process according to claim 8, wherein in the step (a), the polyvinyl alcohol resin obtained by the saponification reaction is pulverized and dried, and steam is injected at a proper time during the drying process to avoid excessive drying of the resin particles and skinning.
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| CN202111351186.1A CN116135913A (en) | 2021-11-16 | 2021-11-16 | Polyvinyl alcohol film, polarizing film comprising the same, and method for producing the same |
| JP2022011777A JP7288526B2 (en) | 2021-11-16 | 2022-01-28 | POLYVINYL ALCOHOL FILM, POLARIZING FILM CONTAINING THE SAME, AND METHOD FOR MANUFACTURING THEM |
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