JP3972545B2 - Method for recovering cellulose ester, regenerated cellulose ester and regenerated cellulose ester film - Google Patents

Description

【００３９】
ここで、ＴＡＣはセルローストリアセテート、ＣＡＰはセルロースアセテートプロピオネートである。ＴＡＣ＊は住友化学（株）製偏光板のものである。界面活性剤はノニオン界面活性剤として、Ｔｗｅｅｎ２０を用いた。ＰＶＡ分解酵素としては第２級アルコールオキシダーゼとβ−ジケトンヒドラーゼを使用した。また、超音波処理はシャープ（株）製ＵＴ−２０５型を使用し、処理容器を超音波洗浄漕に直接投入し、処理時間を通して行った。
【００４０】
（結果）
本発明の水系液で処理した偏光板は、容易にセルロースエステルフィルムが剥離した。また黄色の着色もほとんどないか、全くなかった。特に少なくとも一つの水酸基を有し、且つ炭素原子数１〜６の水と相溶性を有する化合物を使用した水系液処理では黄色の着色が全くなく、きれいなセルロースエステルを回収することが出来た。還元剤、また、ＰＶＡ分解酵素を添加使用したものも、着色のないセルロースエステルフィルムが回収出来た。市販の偏光板、セルロースアセテートプロピオネートフィルムから作製した偏光板、コニカ製のセルローストリアセテートフィルムから作製した偏光板、何れも同様にフィルムが剥離し、回収が出来た。少なくとも一つの水酸基を有し、且つ炭素原子数１〜６の水と相溶性を有する化合物だけの処理液では剥離することが出来なかった。
【００４１】
実施例２
実施例１で回収精製したセルロースエステルチップをメチレンクロライド９５質量部、メタノール５質量部の混合溶媒に濃度が２０質量％になるように溶解してドープを形成し、充分に濾過した後、溶液流延製膜装置を用いて製膜した。即ち、鏡面を有する無端のステンレスベルトの上にコートハンガーダイから流延し、ベルト上で溶媒を４０℃で蒸発させ、ベルトが１周する前に、ドープ膜をベルトから剥離し、テンター式乾燥機で幅を保持しながら６０℃乾燥し、更に多数のロールを有する乾燥機で１００〜１２０℃で乾燥して、冷却後、巻き取りセルロースエステルフィルムを作製し、回収後製膜したセルロースエステルフィルム及び偏光板作製前のフィルムの機械的性質（破断強さ、破断伸び、弾性率）及び透明度を測定し、測定値の比（回収後／偏光板作製前）で劣化の程度を示した。結果を表２に示す。
【００４２】
【表２】

【００４３】
（結果）
これらのセルロースエステルフィルムの機械的性質及び透明度の比は、ほとんど偏光板作製前と回収後で変わりがなく、再び偏光板に使用することが出来た。
【００４４】
【発明の効果】
偏光板から、元のものと品質が全く変わらないセルロースエステルを回収することにより、資源の節約、廃棄物や焼却等がなく環境保全が出来る。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering valuable cellulose ester from a polarizing plate comprising a cellulose ester film and a polarizing film, etc., a recovered regenerated cellulose ester and a regenerated cellulose ester film.
[0002]
[Prior art]
As conventional waste plastic processing methods such as landfilling and incineration are becoming increasingly difficult, it is becoming difficult to secure a landfill site and increase the number of incineration plants with the recent increase in environmental awareness. Furthermore, depletion of petroleum resources and reduction of carbon dioxide emissions are recent environmental issues, and recycling such as reuse and recycling of used articles is no longer essential from the standpoint of resource protection and environmental protection.
[0003]
Cellulose esters are plastics obtained by chemically treating pulp from natural resources such as linter and wood, but their reuse is an issue from the standpoint of forest protection. Linter pulp can be taken from the linter part of cotton, and its quantity is small, production is easily affected by the weather, and it tends to depend on wood pulp from the viewpoint of cost.
[0004]
Cellulose triacetate films are transparent and mechanically strong, and are used for photographic films, polarizing plates for liquid crystal image display devices, and the like.
[0005]
The polarizing plate is obtained by laminating a cellulose triacetate film whose surface is previously saponified with an alkaline solution on both surfaces of a uniaxially stretched polyvinyl alcohol polarizing film. Furthermore, a protective film of a polyester film, an adhesive layer, an antiglare layer, an antireflection layer, a hard coat layer, an antistatic layer and the like are laminated on both sides of the polarizing plate and incorporated into a liquid crystal image display device. In photographic film, the production yield is quite good, and most of the production remains at the photographer, while the polarizing plate is bonded with a highly uniaxially stretched polarizing film. Is difficult, the yield is likely to decrease, and the final yield is considerably low due to avoiding dust and defects and taking a large area, and the polarizing plate is discarded as waste film each time. It was.
[0006]
Conventionally, the recovery of the cellulose ester film is only to some extent in the photographic cellulose triacetate film, but the description of the polarizing plate is hardly found. As a recovery technique for photographic film, for example, a method of treating with aqueous liquid after hypochlorous acid treatment is disclosed in JP-A-5-281686, and potassium permanganate is disclosed in US Pat. No. 2,688,614. In the UK Patent No. 1,087,038, an alkaline treatment containing an oxidizing agent, and in Japanese Patent Publication Nos. 2640394 and 2817020, cellulase treatment and water-solubility. Each of the organic solvent treatments is described. However, none of these techniques are suitable for recovering cellulose ester from a polarizing plate.
[0007]
[Problems to be solved by the invention]
This invention is made | formed in view of said subject, and the 1st objective is to collect | recover a cellulose ester film from a polarizing plate, and to provide the method of reproducing | regenerating a high quality cellulose ester. The second object is to provide a regenerated cellulose ester film that reuses the regenerated cellulose ester.
[0008]
[Means for Solving the Problems]
The present invention is a method for recovering a cellulose ester film from a polarizing plate, and is a method for recovering a valuable cellulose ester film with good efficiency, good yield, environmental friendliness and low energy.
[0009]
The present invention has the following configuration.
(1) The polarizing plate is stirred at 20 to 100 ° C. in a mixed solution of water or a compound having water or at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms and water. A method for recovering cellulose ester.
[0010]
(2) The method for recovering a cellulose ester according to (1), wherein the liquid to be treated (hereinafter, this liquid is also referred to as an aqueous liquid) is water.
[0011]
(3) The cellulose ester according to (1), wherein the aqueous liquid is a mixed liquid of a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms and water. Recovery method.
[0012]
(4) The method for recovering a cellulose ester according to any one of (1) to (3), wherein the aqueous liquid contains a reducing agent.
[0013]
(5) The method for recovering a cellulose ester according to any one of (1) to (4), wherein the aqueous liquid contains a polyvinyl alcohol-degrading enzyme.
[0014]
(6) The method for recovering a cellulose ester according to any one of (1) to (5), wherein the polarizing plate is processed by being crushed or cut into an amorphous shape or a square.
[0015]
(7) A regenerated cellulose ester recovered by the method according to any one of (1) to (6).
[0016]
(8) A regenerated cellulose ester film formed using the regenerated cellulose ester according to (7).
[0017]
The present invention will be described in detail.
The collection object of this invention is the cellulose ester used for the polarizing plate.
[0018]
The cellulose ester used in the recovery of the present invention is obtained by acylating a lower fatty acid to a hydroxyl group of cellulose. Cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate propionate buty It is at least one selected from rates. The substitution degree of the acyl group substituted by the hydroxyl group of cellulose is preferably 2.4 to 3.0, and the degree of polymerization is preferably 300 or more, more preferably 400 or more.
[0019]
The cellulose ester film used in the polarizing plate according to the present invention is formed by dissolving a cellulose ester in a solvent, for example, methylene chloride to form a dope, and forming it by a solution casting film forming method such as a normal cellulose triacetate film. Further, the surface is saponified with an alkali solution so that the polarizing film can be easily adhered. An example of the saponification conditions of the cellulose ester film according to the present invention is as follows: after being immersed in a 2 mol / l NaOH aqueous solution at 40 to 60 ° C. for about 30 to 150 seconds, washed with room temperature water for about 30 to 60 seconds, Further, it is a condition of neutralizing with 1 to 5% by mass HCl for about 30 to 60 seconds, then washing with normal temperature water for about 30 to 60 seconds and drying at about 80 ° C., but is not limited thereto.
[0020]
The polarizing film according to the present invention is a film obtained by forming an aqueous solution of a polyvinyl alcohol polymer such as polyvinyl alcohol or ethylene-vinyl alcohol copolymer, and uniaxially stretching the film and dyeing it with iodine or a dichroic dye. After uniaxial stretching, water resistance treatment is performed with a crosslinking agent such as a boron compound.
[0021]
As described above, the polarizing plate according to the present invention is obtained by laminating a saponified cellulose ester film on both surfaces of the polarizing film.
[0022]
An example of how to prepare a polarizing film according to the present invention and how to laminate the polarizing film is as follows. A saponified cellulose ester film is coated with an aqueous polyvinyl alcohol solution as an adhesive solution on one side of each film. On the surface, a uniaxially stretched polyvinyl alcohol film is immersed in an iodine solution, and then a uniaxially stretched polarizing film is sandwiched and bonded. Examples of the adhesive liquid include a polyvinyl alcohol adhesive liquid such as a polyvinyl alcohol aqueous solution and a polyvinyl butyral solution, a vinyl polymerization latex such as butyl acrylate, and the like, and a completely saponified polyvinyl alcohol aqueous solution is preferable.
[0023]
At present, polarizing plate is manufactured separately from the manufacturer that produces the cellulose ester film and the manufacturer that attaches the polarizing film, and each waste is individually disposed of, etc., but these resources are collected consistently. As a result, the recovery amount is increased, the recovery rate is improved, and the cellulose ester can be reused advantageously.
[0024]
The polarizing plate at the time of collection in the present invention is convenient for collection in the form of an amorphous or small square chip by pulverization or cutting, and the minimum to maximum length of the chip is 0.00. About 1-20 mm is suitable for a process, and 0.5-10 mm is especially preferable. In the cellulose ester recovery method of the present invention, the cellulose ester film and the polarizing film are peeled and separated by treating a chip of the above size with an aqueous liquid.
[0025]
The aqueous liquid used in the present invention may be water alone, but may be a mixed liquid of water and a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms. Examples of the compound having at least one hydroxyl group and compatible with water having 1 to 6 carbon atoms include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s- Butanol, t-butanol, ethylene glycol, 1,3-trimethylene glycol, 1,4-tetramethylene glycol, diethylene glycol, glycerin, trimethanol ethane, trimethanol propane, pentaerythritol, cyclohexanol, glucose, pentose, xylitol, xylitol However, it is not limited to these. The content rate of the said compound in an aqueous liquid is 0.1-99.9 mass%, Preferably it is 10-90 mass%, More preferably, it is 30-80 mass%. However, these numerical values may differ depending on the solubility of these compounds in water.
[0026]
Although the treatment temperature in the aqueous liquid treatment of the present invention varies depending on the type and mixing ratio of water and the above compound, it is preferably 20 to 100 ° C, more preferably 35 to 80 ° C. Further, the treatment pH of the aqueous liquid is preferably near neutral, preferably 6.0 to 8.0, and more preferably 7.0 to 8.0.
[0027]
The state in which the polarizing film is separated from the cellulose ester film by the aqueous liquid treatment of the present invention is various, such as the polyvinyl alcohol film being dissolved, swollen or non-swelled. In particular, when a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms is used, the compound is often separated without swelling.
[0028]
Since the polarizing film is dyed with iodine or a dichroic dye, coloring may remain on the cellulose ester film side when it is treated with the above aqueous liquid, and a reducing agent is used in the present invention to decolor the coloring. Is preferred. The reducing agent can be used without limitation as long as it can be decolored, and examples thereof include sodium thiosulfate, ascorbic acid, ferrous chloride and the like. The amount used is 0.1 to 100 g, preferably 1 to 20 g, and more preferably 4 to 10 g in 1 kg of the aqueous liquid.
[0029]
Depending on the manufacturer, the polarizing film may be obtained by crosslinking a polyvinyl alcohol polymer with a crosslinking agent such as boric acid, or a polyvinyl alcohol having a high degree of saponification, and these are difficult to dissolve in an aqueous liquid. There is a case. In such a case, in the present invention, it is preferable to add a polyvinyl alcohol-degrading enzyme capable of decomposing a polyvinyl alcohol polymer to the aqueous liquid. Moreover, the polyvinyl alcohol film peeled off by the aqueous liquid treatment is dissolved or swollen in the aqueous liquid, and if it is discharged as it is, there is a risk of fouling the river, and an enzyme capable of decomposing the polyvinyl alcohol polymer is also used for the waste liquid treatment. It is preferable. Polyvinyl alcohol degrading enzymes are described in Yoshiharu Doi's “Biodegradable Plastic Handbook” edited by Biodegradation Research Group (published by NTS), Section 7 Polyvinyl alcohol degrading enzymes (pages 466-476). The degradation enzyme currently used can be used. Conditions suitable for the degradation of polyvinyl alcohol by the degrading enzyme vary depending on the degrading enzyme, but the temperature is 30 to 65 ° C. and the pH is 6.5 to 9.0. As a polyvinyl alcohol to be decomposed, a wide range of polyvinyl alcohols can be easily decomposed from those having a high degree of polymerization to those having a low degree of polymerization, and those having a complete saponification to those having a low saponification degree.
[0030]
A surfactant may be used to rapidly penetrate the aqueous liquid into the interface between the cellulose ester film and the polarizing film of the polarizing plate. The surfactant may be any of anionic, cationic, amphoteric and nonionic. Examples of anionic surfactants include alkyl carboxylates, alkyl sulfonates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfates, alkyl phosphates, N-acyl-N-alkyl taurines. , Sulfosuccinic acid esters, sulfoalkyl polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl phosphoric acid esters, etc., having a carboxy group, a sulfo group, a phospho group, a sulfuric acid ester group, a phosphoric acid ester group, etc. Compounds are preferred. Examples of the cationic surfactant include alkylamine salts, aliphatic or aromatic quaternary ammonium salts, heterocyclic quaternary ammonium salts such as pyridinium and imidazolium, and phosphonium or sulfonium salts containing aliphatic or heterocyclic rings. Is preferred. As the amphoteric surfactant, for example, amino acids, aminoalkylsulfonic acids, aminoalkylsulfuric acid or phosphate esters, alkylbetaines, amine oxides and the like are preferable. Nonionic surfactants include, for example, saponins (steroidal), alkylene oxide derivatives (for example, polyethylene glycol, polyethylene glycol / polypropylene glycol condensates, polyethylene glycol alkyl ethers or polyethylene glycol alkyl aryl ethers, polyethylene glycol esters, polyethylene Alkyl esters such as glycol sorbitan esters, polyalkylene glycol alkyl amines or amides, silicone polyethylene oxide adducts), glycidol derivatives (eg, alkenyl succinic acid polychloride, alkyl phenol polyglycerides), polyhydric alcohol fatty acid esters, etc. preferable.
[0031]
In the present invention, it is preferable to apply ultrasonic treatment in order to accelerate the peeling of the cellulose ester film from the polarizing plate. The ultrasonic treatment is preferably performed at a frequency of 20 to 50 Hz and an output of 30 to 900 W, depending on the size of the container or the amount of treatment.
[0032]
In the present invention, the quality of the recovered cellulose ester is completely the same as that at the time of manufacture, and the film formed from this can be reused as a photographic film support or a polarizing plate film.
[0033]
【Example】
The present invention is illustrated in detail in the following examples, but is not limited thereto.
[0034]
Example 1
A 80 μm-thick cellulose triacetate film (Konicatak KC80UVN) manufactured by Konica Corporation was alkali-treated with a 2.5 mol / l sodium hydroxide aqueous solution at 40 ° C. for 60 seconds, further washed with water and dried to saponify the surface. A cellulose triacetate film was prepared. Separately, the polyvinyl alcohol film is immersed in an aqueous solution containing 1 part by mass of iodine, 2 parts by mass of potassium iodide, and 4 parts by mass of boric acid, and stretched in the longitudinal direction by 4 times at 50 ° C. to give a polyvinyl alcohol film having a thickness of 120 μm. A polarizing film was produced. Further, the saponified surface of the cellulose triacetate film was bonded to both surfaces of the polarizing film as a 5% by mass aqueous solution of completely saponified polyvinyl alcohol as an adhesive to produce a polarizing plate.
[0035]
Further, cellulose acetate propionate (total average substitution degree 2.5, acetyl group substitution degree 1.9, propionyl group 0.6) was formed in the same manner as cellulose triacetate, and a polarizing film was prepared in the same manner as described above. Furthermore, a polarizing plate manufactured by Sumitomo Chemical Co., Ltd. was also used.
[0036]
The above polarizing plate is pulverized with a pulverizer to a size of minimum to maximum length of 0.5 to 10 mm to form chips, and 12 g thereof is put into 2 kg of an aqueous liquid described in Table 1 below, and for a predetermined time under the conditions of Table 1. The mixture was heated and stirred, and the peeling state of the cellulose ester film was observed. Separate the polarizing film from the cellulose ester film (if the polarizing film does not dissolve and float in the swollen or non-swelled state, separate using the density difference), filter the cellulose ester only, and then add 90 ° C hot water They were washed with water, washed with water, drained and dried at 65 ° C. These samples were evaluated for yellow coloration.
[0037]
[Evaluation]
<Colored state>
Aqueous solution treatment, put dry chips in a beaker, evaluate the degree of coloring as follows,
A: Not colored at all and not different from the color tone of the raw cellulose ester film B: Feeling slightly yellowish C: Very slightly yellow D: Light yellow E: Yellow slightly dark F: The result is quite yellow.
[0038]
[Table 1]

[0039]
Here, TAC is cellulose triacetate, and CAP is cellulose acetate propionate. TAC * is a polarizing plate manufactured by Sumitomo Chemical Co., Ltd. As the surfactant, Tween 20 was used as a nonionic surfactant. Secondary alcohol oxidase and β-diketone hydrolase were used as PVA degrading enzymes. In addition, the ultrasonic treatment was performed using a UT-205 type manufactured by Sharp Corporation, and the treatment container was directly put into an ultrasonic cleaning bowl, and the treatment time was performed.
[0040]
(result)
The cellulose ester film was easily peeled off from the polarizing plate treated with the aqueous liquid of the present invention. There was little or no yellow coloration. In particular, in the aqueous liquid treatment using a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms, there was no yellow coloration and a clean cellulose ester could be recovered. A cellulose ester film having no coloring could be recovered from those using a reducing agent or a PVA-degrading enzyme. A commercially available polarizing plate, a polarizing plate made from a cellulose acetate propionate film, and a polarizing plate made from a Konica cellulose triacetate film were all peeled off and recovered. It could not be peeled off with a treatment solution containing only a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms.
[0041]
Example 2
The cellulose ester chip recovered and purified in Example 1 was dissolved in a mixed solvent of 95 parts by mass of methylene chloride and 5 parts by mass of methanol so as to have a concentration of 20% by mass to form a dope, sufficiently filtered, It formed into a film using the film-forming apparatus. That is, cast from a coat hanger die on an endless stainless steel belt having a mirror surface, evaporate the solvent at 40 ° C. on the belt, peel off the dope film from the belt before the belt makes one turn, and dry by a tenter type The cellulose ester film was dried at 60 ° C. while maintaining the width with a machine, and further dried at 100 to 120 ° C. with a dryer having a large number of rolls. The mechanical properties (breaking strength, breaking elongation, elastic modulus) and transparency of the film before the production of the polarizing plate were measured, and the degree of deterioration was indicated by the ratio of the measured values (after recovery / before the production of the polarizing plate). The results are shown in Table 2.
[0042]
[Table 2]

[0043]
(result)
The ratio of mechanical properties and transparency of these cellulose ester films was almost unchanged before and after the production of the polarizing plate, and could be used again for the polarizing plate.
[0044]
【The invention's effect】
By recovering cellulose ester from the polarizing plate, the quality of which is completely the same as the original one, it is possible to preserve the environment without saving resources, waste or incineration.

Claims (6)

Cellulose characterized by stirring a polarizing plate at 20 to 100 ° C. in a mixed solution of water or water having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms and water Ester recovery method. The method for recovering a cellulose ester according to claim 1, wherein the liquid to be treated is water. 2. The cellulose ester according to claim 1, wherein the liquid to be treated is a mixed liquid of a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms and water. Collection method. The method for recovering a cellulose ester according to any one of claims 1 to 3, wherein the liquid to be treated contains a reducing agent. The method for recovering a cellulose ester according to any one of claims 1 to 4, wherein the liquid to be treated contains a polyvinyl alcohol-degrading enzyme.   The method for recovering a cellulose ester according to any one of claims 1 to 5, wherein the polarizing plate is processed by being pulverized or cut into an amorphous or square shape.