JP2001181440A - Method for recovering cellulose ester, regenerated cellulose ester and regenerated cellulose ester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recovering a cellulose ester film from a polarizing plate to regenerate a high quality cellulose ester, and to provide a regenerated cellulose ester film recycled from the regenerated cellulose ester. SOLUTION: This method for recovering the cellulose ester, characterized by treating a cellulose ester film processed article recovered from a polarizing plate in an aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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]

2. Description of the Related Art With the recent increase in environmental consciousness, it has become difficult to secure landfill sites and increase incineration plants, as landfills and incineration, etc., as conventional methods for treating waste plastic. Further, depletion of petroleum resources and reduction of carbon dioxide emissions are environmental issues in recent years, and from the standpoint of resource protection and environmental conservation, the recycling and reuse of used articles is no longer essential.

[0003] Cellulose ester is originally a plastic obtained by chemically treating linter or pulp from wood, which is a natural resource, but its reuse has been an issue from the standpoint of forest protection. Linter pulp can be obtained from the linter part of cotton, and the quantity is small, the production is easily affected by the weather, and the cost, etc.
It tends to depend on wood pulp.

[0004] Cellulose triacetate films are used for photographic films, polarizing plates for liquid crystal image display devices, and the like because they are transparent and mechanically strong.

[0005] The polarizing plate is obtained by laminating a cellulose triacetate film whose surface has been saponified in advance with an alkali solution on both sides of a uniaxially stretched polyvinyl alcohol-based polarizing film. Further, the polarizing plate is laminated on both sides with 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, and is incorporated in a liquid crystal image display device. For photographic film, the production yield is fairly good, and most of the production remains at the photographer.On the other hand, for polarizing plates, a uniaxially stretched polarizing film with high hygroscopicity is attached, so the work is done. However, the yield is likely to decrease, and the final yield will be considerably lower due to the fact that a large area is used to avoid dust and defects.In each case, the polarizing plate is discarded as a waste film. I was

Heretofore, the recovery of a cellulose ester film has been found only occasionally in a cellulose triacetate film for photography, but there is almost no description of a polarizing plate. As a collection technique for a photographic film, for example, Japanese Unexamined Patent Publication No. 5-28
No. 1686 describes a method of treating with an aqueous liquid after hypochlorous acid treatment, and US Pat. No. 2,688,614 discloses an acid treatment containing potassium permanganate and a British patent 1,0.
No. 87,038 describes an alkaline treatment containing an oxidizing agent, and Japanese Patent Publication Nos. 2,640,394 and 2,817,020 describe a cellulase treatment and a water-soluble organic solvent treatment, respectively. However, none of these techniques is suitable for recovering cellulose ester from a polarizing plate.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object of the present invention is to provide a method for recovering a cellulose ester film from a polarizing plate to regenerate a high quality cellulose ester. To provide. A second object is to provide a regenerated cellulose ester film in which the regenerated cellulose ester is reused.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for recovering a cellulose ester film from a polarizing plate, which comprises recovering a valuable cellulose ester film efficiently, with good yield, environmentally friendly, and with low energy. How to

The present invention has the following constitution. (1) A method for recovering a cellulose ester, comprising treating a polarizing plate in an aqueous solution.

(2) The method for recovering cellulose ester according to (1), wherein the aqueous liquid is water.

(3) The aqueous liquid according to (1), wherein the aqueous liquid is a mixture of water and a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms. Method for recovering cellulose ester.

(4) The method for recovering a cellulose ester according to any one of (1) to (3), wherein the aqueous liquid contains a reducing agent.

(5) The method for recovering a cellulose ester according to any one of (1) to (4), wherein the aqueous liquid contains a polyvinyl alcohol decomposing enzyme.

(6) The method for recovering cellulose ester according to any one of (1) to (5), wherein the polarizing plate is pulverized or cut into an amorphous shape or a square and processed.

(7) A regenerated cellulose ester recovered by the method according to any one of (1) to (6).

(8) A regenerated cellulose ester film formed by using the regenerated cellulose ester according to (7).

The present invention will be described in detail. The object of recovery of the present invention is a cellulose ester used for a polarizing plate.

The cellulose ester used in the recovery of the present invention is obtained by subjecting a hydroxyl group of cellulose to an acylation reaction of a lower fatty acid. Cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate and cellulose acetate proteate are used. It is at least one selected from pionate butyrate. 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 3
It is preferably at least 00, more preferably at least 400.

The cellulose ester film used in the polarizing plate according to the present invention is obtained by dissolving a cellulose ester in a solvent, for example, methylene chloride to form a dope.
It is formed by a solution casting method such as a usual cellulose triacetate film. The surface is further saponified with an alkali solution and treated so that the polarizing film is easily adhered. An example of the saponification treatment conditions of the cellulose ester film according to the present invention is as follows: 2 mol of 40 to 60 ° C.
/ L of NaOH aqueous solution for about 30 to 150 seconds, washed with water at room temperature for about 30 to 60 seconds, and further added with 1 to 5% by mass HCl.
And neutralize for about 30-60 seconds, then with normal temperature water for about 30-60
The condition is that it is washed with water for 2 seconds and dried at about 80 ° C., but is not limited thereto.

The polarizing film according to the present invention is formed, for example, by forming an aqueous solution of a polyvinyl alcohol-based polymer such as polyvinyl alcohol or an ethylene-vinyl alcohol copolymer, stretching the film uniaxially, and dyeing it with iodine or a dichroic dye. The product was further uniaxially stretched and subjected to a water-resistant treatment with a crosslinking agent such as a boron compound.

As described above, the polarizing plate according to the present invention is obtained by laminating a cellulose ester film having a saponified surface on both sides of the polarizing film.

One example of the production of the polarizing film according to the present invention and the method of bonding the polarizing film to the polarizing film is shown below. One side of each of two saponified cellulose ester films is coated with an aqueous solution of polyvinyl alcohol as an adhesive liquid. Then, a uniaxially stretched polyvinyl alcohol film is immersed in an iodine solution, and then a uniaxially stretched polarizing film is sandwiched and bonded to the surface. Examples of the adhesive solution include a polyvinyl alcohol-based adhesive solution such as a polyvinyl alcohol aqueous solution and a polyvinyl butyral solution, and a vinyl polymerized latex such as butyl acrylate. A completely saponified polyvinyl alcohol aqueous solution is preferable.

At present, there are separate manufacturers of cellulose ester films and those that attach the polarizing film to the polarizing plate, and the waste is individually disposed of and treated separately. By doing so, the recovery amount is increased, the recovery rate is improved, and the cellulose ester can be advantageously reused.

In the present invention, the polarizing plate at the time of recovery is conveniently formed into an amorphous or small rectangular chip by pulverization or cutting, and has a minimum to maximum length of the chip. About 0.1 to 20 mm is suitable for the treatment, and particularly preferably 0.5 to 10 mm. The cellulose ester recovery method of the present invention is to separate and separate a cellulose ester film and a polarizing film by treating a chip having the above size with an aqueous liquid.

The aqueous solution used in the present invention may be water alone, or may be a mixture of water and a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms. Having at least one hydroxyl group and having 1 carbon atom
Examples of the compounds having compatibility with water of 6 to 6 include methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, s-butanol, t-butanol, ethylene glycol, 1,3-
Examples include, but are not limited to, trimethylene glycol, 1,4-tetramethylene glycol, diethylene glycol, glycerin, trimethanol ethane, trimethanol propane, pentaerythritol, cyclohexanol, glucose, pentose, xylitose, xylitol, and the like. The content of the above compound in the aqueous liquid is 0.1 to 99.9% by mass, preferably 10 to 90% by mass, and more preferably 30 to 80% by mass. However, these values may vary depending on the solubility of these compounds in water.

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.
-100 ° C is preferred, and 35-80 ° C is more preferred.
The treatment pH of the aqueous solution is preferably around neutral, preferably 6.0 to 8.0, and more preferably 7.0 to 8.0.

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 a state in which the polyvinyl alcohol film is dissolved, swollen, or not swollen. In particular, in the case where a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms is used, in many cases, separation is performed without almost swelling.

Since the polarizing film is dyed with iodine or a dichroic dye, when treated with the above-mentioned aqueous solution, coloring may remain on the cellulose ester film side. It is preferred to use The reducing agent can be used without limitation as long as it can be decolorized, and examples thereof include sodium thiosulfate, ascorbic acid, ferrous chloride and the like. The amount to be used is 0.1 to 100 g, preferably 1 to 20 g per 1 kg of the aqueous liquid.
g, more preferably 4 to 10 g.

Depending on the manufacturer, the polarizing film may be a polyvinyl alcohol-based polymer cross-linked with a cross-linking agent such as boric acid, or a polyvinyl alcohol having a high degree of saponification. It may be difficult to dissolve. In such a case, in the present invention,
It is preferable to add a polyvinyl alcohol-decomposing enzyme capable of decomposing a polyvinyl alcohol-based polymer to the aqueous solution. In addition, the polyvinyl alcohol film peeled off in the aqueous liquid treatment is dissolved or swelled in the aqueous liquid,
If discharged as it is, there is a risk that the river will be polluted, and it is preferable to use an enzyme capable of decomposing the polyvinyl alcohol-based polymer also in the waste liquid treatment. Description of the enzyme for degrading polyvinyl alcohol is described in Section 7, Polyvinyl Alcohol Degrading Enzyme (pp. 466-476) edited by Yoshiharu Dohi, “Biodegradable Plastic Handbook”, edited by Biodegradation Study Group (NTS Inc.). Degradative enzymes that have been used can be used. Conditions suitable for the decomposition of polyvinyl alcohol by the decomposing enzyme vary depending on the decomposing enzyme, but the temperature is 30 to 65 ° C and the pH is 6.5 to 9.0.
It is. As the 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 from complete saponification to those having a low degree of saponification.

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 the anionic surfactant include alkyl carboxylate, alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, alkyl sulfates, alkyl phosphates, and N-acyl-N-alkyltaurines. , Sulfosuccinates, sulfoalkylpolyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl phosphates, etc., which have a carboxy group, a sulfo group, a phospho group, a sulfate group, a phosphate 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 an aliphatic or heterocyclic ring. Is preferred. As the amphoteric surfactant, for example, amino acids, aminoalkyl sulfonic acids, aminoalkyl sulfates or phosphoric esters, alkyl betaines, amine oxides and the like are preferable. Nonionic surfactants include, for example, saponins (steroids), alkylene oxide derivatives (eg, polyethylene glycol, polyethylene glycol / polypropylene glycol condensates, polyethylene glycol alkyl ethers or polyethylene glycol alkyl aryl ethers, polyethylene glycol esters, polyethylene) Glycol sorbitan esters, polyalkylene glycol alkylamines or amides, polyethylene oxide adducts of silicone), glycidol derivatives (eg, alkenyl succinic acid polycerides, alkylphenol polyglycerides), and alkyl esters such as polyhydric alcohol fatty acid esters. preferable.

In the present invention, it is preferable to apply an 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 processing.

In the present invention, the quality of the recovered cellulose ester does not change at all from that at the time of manufacture, and the film formed from the cellulose ester can be reused as a photographic film support or a polarizing plate film.

[0033]

The present invention will be described in detail in the following examples.
It is not limited to these.

Example 1 An 80 μm-thick cellulose triacetate film (Konica Cat KC80UVN) manufactured by Konica Corporation at 40 ° C.
Was treated with a 2.5 mol / l aqueous sodium hydroxide solution for 60 seconds, washed with water and dried to prepare a cellulose triacetate film having a surface saponified. Separately, 1 part by mass of iodine,
It was immersed in an aqueous solution containing 2 parts by mass of potassium iodide and 4 parts by mass of boric acid, and stretched 4 times in the longitudinal direction at 50 ° C.
A 0 μm polyvinyl alcohol film polarizing film was produced. Further, a saponified surface of the cellulose triacetate film was bonded to both surfaces of the above-mentioned polarizing film with a 5% by mass aqueous solution of completely saponified polyvinyl alcohol as an adhesive to prepare a polarizing plate.

Further, a cellulose acetate propionate (total average degree of substitution 2.5, degree of acetyl group substitution 1.9, propionyl group 0.6) was formed into a film in the same manner as cellulose triacetate, and a polarizing film was formed in the same manner as described above. did. Further, a polarizing plate manufactured by Sumitomo Chemical Co., Ltd. was also used.

The above polarizing plate is provided with a minimum to maximum length of 0.5 to 1
Pulverized to a size of 0 mm with a pulverizer to obtain chips.
g was placed in 2 kg of an aqueous solution described in Table 1 below, and heated and stirred under the conditions of Table 1 for a predetermined time, and the state of peeling 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 a swelling or non-swelling state, use a density difference to separate). And washed them with water, drained and dried at 65 ° C. These samples were evaluated for yellow coloring.

[Evaluation] <Colored state> The aqueous liquid-treated and dried chips were placed in a beaker, and the degree of coloring was evaluated as follows. A: No coloring, no change in color tone of unprocessed cellulose ester film B: Felt very yellowish C: Very slightly yellowish D: Light yellow E: Yellow is slightly deeper F: Fairly yellow The results are shown in Table 1.

[0038]

[Table 1]

Here, TAC is cellulose triacetate, and CAP is cellulose acetate propionate. TAC * is a polarizing plate manufactured by Sumitomo Chemical Co., Ltd.
The surfactant is a nonionic surfactant, Tween 2
0 was used. Secondary alcohol oxidase and β-diketone hydrolase were used as PVA-degrading enzymes. The ultrasonic treatment was performed using a UT-205 model manufactured by Sharp Corporation, and the treatment container was directly charged into the ultrasonic cleaning tank, and the treatment was performed throughout the treatment time.

(Results) The polarizing plate treated with the aqueous liquid of the present invention easily peeled off the cellulose ester film. Also, there was little or no yellow coloring. In particular, in an aqueous liquid treatment using a compound having at least one hydroxyl group and having compatibility with water having 1 to 6 carbon atoms, yellow cellulose was not at all colored, and a clear cellulose ester could be recovered. In the case of using a reducing agent and a PVA-decomposing enzyme, a cellulose ester film without coloring could be recovered. Films were similarly peeled and collected from 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. Having at least one hydroxyl group and having 1 carbon atom
6 could not be peeled off using only a treatment liquid having a compound compatible with water.

Example 2 A cellulose ester chip recovered and purified in Example 1 was dissolved in a mixed solvent of methylene chloride (95 parts by mass) and methanol (5 parts by mass) to a concentration of 20% by mass to form a dope. After filtration, a film was formed using a solution casting film forming apparatus. That is, it is cast from a coat hanger die onto an endless stainless steel belt having a mirror surface, the solvent is evaporated at 40 ° C. on the belt, and the dope film is peeled off from the belt before the belt makes one round, and a tenter type drying is performed. Drying at 60 ° C. while maintaining the width with a machine, and further drying at 100 to 120 ° C. with a dryer having a number of rolls, cooling, producing a wound cellulose ester film, and collecting and forming a cellulose ester film The mechanical properties (rupture strength, elongation at break, 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 producing the polarizing plate). Table 2 shows the results.

[0042]

[Table 2]

(Results) The mechanical properties and the transparency ratio of these cellulose ester films were almost the same before and after the production of the polarizing plate, and could be used again for the polarizing plate.

[0044]

According to the present invention, by recovering a cellulose ester whose quality is not changed from the original one at all from the polarizing plate, it is possible to conserve resources and to protect the environment without waste or incineration.

Claims (8)

[Claims] 1. A method for recovering a cellulose ester, comprising treating a polarizing plate in an aqueous solution. 2. The method according to claim 1, wherein the aqueous liquid is water. 3. The liquid according to claim 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. Method for recovering cellulose ester. 4. The method for recovering a cellulose ester according to claim 1, wherein the aqueous liquid contains a reducing agent. 5. The method for recovering a cellulose ester according to claim 1, wherein the aqueous liquid contains a polyvinyl alcohol-decomposing enzyme. 6. The method for recovering a cellulose ester according to claim 1, wherein the polarizing plate is processed by being crushed or cut into an amorphous or square shape. 7. A regenerated cellulose ester recovered by the method according to any one of claims 1 to 6. 8. A regenerated cellulose ester film obtained by forming a film using the regenerated cellulose ester according to claim 7.