JP2001213995A - Method of recovering cellulose ester, regenerated cellulose ester and cellulose ester film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of recovering cellulose esters from polarizing sheets of liquid crystal image displays, and further regenerated cellulose ester films with the reuse of the recovered cellulose esters. SOLUTION: The method of recovering cellulose esters comprises treating waste polarizing sheets of liquid crystal image displays having a cellulose ester film having a degree of substitution of acyl groups of 2.5-3.0 with an organic solvent capable of dissolving cellulose esters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recovering valuable cellulose ester from a polarizing sheet used in a liquid crystal image display device, a recovered regenerated cellulose ester, and a regenerated cellulose ester film.

[0002]

2. Description of the Related Art In the conventional disposal of waste plastics, such as landfilling and incineration, it is becoming difficult to secure landfill sites and to increase the number of incineration plants with the recent rise in environmental awareness. 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] A polarizing sheet for a liquid crystal image display device is obtained by laminating a cellulose triacetate film whose surface has been saponified in advance with an alkali solution to both sides of a uniaxially stretched polyvinyl alcohol-based polarizing film to form a polarizing plate. , Polyester film protective film, adhesive layer,
An antiglare layer, an antireflection layer, a hard coat layer, an antistatic layer and the like are laminated. For photographic film, the production yield is quite good, and most of the production remains at the photographer.On the other hand, for polarizing sheets for liquid crystal image display devices, a uniaxially stretched polarizing film with high hygroscopicity is laminated. Since the above-mentioned constituent layers are laminated on both sides of the polarizing plate, the operation is difficult, the yield is likely to be reduced, and the final yield is low because a large area is used to avoid dust and defects. At present, it is considerably low, and waste films are discarded in each of these work processes each time.

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.
Japanese Patent No. 87,038 discloses an alkali treatment containing an oxidizing agent, and Japanese Patent Nos. 2,640,394 and 281.
No. 7020 describes a cellulase treatment and a water-soluble organic solvent treatment, respectively.

[0007]

However, all of these techniques are not suitable for recovery from a polarizing plate or a polarizing sheet for a liquid crystal image display device.

A first object of the present invention is to provide a method for recovering a cellulose ester from a polarizing sheet for a liquid crystal image display, and a second object is to reuse the recovered cellulose ester to obtain a regenerated cellulose. An ester film is provided.

[0009]

The present invention comprises the following constitutions.

(1) The degree of acyl group substitution is 2.5 to 3.0.
A waste of a polarizing sheet for a liquid crystal image display device having a cellulose ester film according to (1), which is treated with an organic solvent capable of dissolving the cellulose ester.

(2) The degree of acyl group substitution is 2.5 to 3.0.
The waste of a polarizing sheet for a liquid crystal image display device having a cellulose ester film of the above is treated with an organic solvent capable of dissolving the cellulose ester to separate the insoluble member from the solution after removing the cellulose ester. A method for recovering a cellulose ester, which is a feature.

(3) The degree of acyl group substitution is 2.5 to 3.0.
The waste of the polarizing sheet for a liquid crystal image display device having a cellulose ester film is treated with an aqueous solution and separated, and then the member in which the cellulose ester film remains is treated with an organic solvent having a dissolving ability for cellulose ester. A method for recovering a cellulose ester, comprising:

(4) The degree of acyl group substitution is 2.5 to 3.0.
After treating the waste of the polarizing sheet for a liquid crystal image display device having a cellulose ester film with an aqueous solution and separating the same, an organic solvent having a dissolving ability for the cellulose ester film in the member in which the cellulose ester film remains is removed. A method for recovering a cellulose ester, comprising separating a solution treated with the method and an insoluble member, and then removing the cellulose ester from the solution.

(5) The degree of acyl group substitution is 2.5 to 3.0.
Waste of a polarizing sheet for a liquid crystal image display device having a cellulose ester film and an acrylic adhesive layer of
After treatment and separation with an organic solvent that is soluble in acrylic adhesive and insoluble in cellulose ester,
A method for recovering a cellulose ester, comprising treating the remaining waste having the cellulose ester film with an organic solvent capable of dissolving the cellulose ester.

(6) The cellulose ester according to any one of (1) to (5), wherein the polarizing sheet for a liquid crystal image display device is pulverized or cut into amorphous or square pieces and processed as chips. Collection method.

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

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

The present invention will be described in detail. The present invention recovers valuable cellulose esters from these wastes discharged from each step of producing a polarizing sheet for a liquid crystal image display device,
It is to reuse this.

The polarizing sheet for a liquid crystal image display device according to the present invention is a laminate having a polarizing function used for a liquid crystal image display device, and a laminate of a polarizing plate comprising a cellulose ester film and a polarizing film, and a polarizing plate. Before preparing a monolayer or multiple layers of an adhesive layer, an antiglare layer, an antireflection layer, a hard coat layer, an antistatic layer and / or a protective film on one surface of a cellulose ester film, A laminate obtained by laminating the above-mentioned layers in a single layer or a plurality of layers on a board is collectively referred to. In the present invention, in addition to the polarizing sheet for a liquid crystal display device, in the case of a form close to a polarizing plate, it may be referred to as a polarizing plate, or may be referred to as a polarizing plate with an antiglare layer. If the completed polarizing sheet for a liquid crystal image display device is described as an example, a polyester protective film / antireflection layer / antiglare layer / cellulose ester film / polyvinyl alcohol polarizing film / cellulose ester film / adhesive layer / polyester protective film With a laminate having the structure as described above, an antireflection layer, an adhesive layer, an antiglare layer, a hard coat layer, an antistatic layer, etc. are formed on a polarizing plate obtained by laminating a polarizing film on two cellulose ester films in a sandwich type. Are laminated in various arrangements, and a protective film or the like is further laminated on both sides thereof. Depending on the manufacturer, purpose, specifications, etc., the types of these layers, the order of lamination, and the like are more complicated, and various laminated products produced in each step until all the constituent layers are laminated, for example, two layers, three layers The waste is discharged as waste in the form of a four-layer structure, a five-layer structure, and the like stacked thereon, but is not limited thereto.

The waste of a polarizing sheet for a liquid crystal image display device is a member that is discharged in each step of manufacturing a polarizing sheet that has not become a product, and is a member that is discarded. Further, even if it is a finished product, a product not used as a liquid crystal image display device or a product after use is also included in the waste of the present invention.

The object to be recovered in the present invention is a cellulose ester used for a polarizing sheet for a liquid crystal image display device, and has a degree of acyl group substitution of 2.5 to 3.0. Cellulose esters are those obtained by reacting a cellulose-containing pulp with an acylating agent. As the acylating agent, acetic anhydride, propionic anhydride, and butyric anhydride are used. Reacts to substitute and introduce acetyl, propionyl and butyryl groups into cellulose. Examples of the cellulose ester include cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate, and are useful for the polarizing sheet for a liquid crystal image display device according to the present invention. In many cases, the cellulose ester film contains a plasticizer, an ultraviolet inhibitor, an oxidant inhibitor, and the like. The cellulose ester film is formed by a usual solution casting method. That is, a cellulose ester is dissolved in an organic solvent capable of dissolving the same to form a dope, and the dope is cast on a metal support having a mirror surface (for example, a stainless steel belt or an iron drum) to form a web. It is obtained by peeling the web from the metal support and drying it before the support makes one rotation. The thickness of the cellulose ester film is preferably 30 to 150 μm.

For the polarizing plate according to the present invention, a cellulose ester film whose surface has been saponified with an alkali solution is usually used in order to enhance the adhesion to the polarizing film after the film is formed. The saponification treatment of the cellulose ester film shows one example,
In a 2 mol / l NaOH aqueous solution at 40-60 ° C, about 3
After immersion for 0 to 150 seconds, rinse with normal temperature water for about 30 to 60 seconds,
Further, neutralization is carried out with 1 to 5% by mass of HCl for about 30 to 60 seconds, followed by washing with constant temperature water for about 30 to 60 seconds and drying at about 80 ° C. The polarizing film, for example, polyvinyl alcohol, an aqueous solution of a polyvinyl alcohol-based polymer such as an ethylene-vinyl alcohol copolymer is formed,
This is uniaxially stretched, dyed with iodine or a dichroic dye, further uniaxially stretched, and then subjected to a water-resistant treatment with a crosslinking agent such as a boron compound. The polarizing plate is obtained by laminating two cellulose ester films each having a surface saponified as described above on both sides of the polarizing film as described above. The polarizing plate is a polarizing film obtained by applying an adhesive solution to one surface of each of two saponified cellulose ester films, immersing a uniaxially stretched polyvinyl alcohol film in an iodine solution, and further uniaxially stretching the film. Are sandwiched and laminated. Examples of the adhesive liquid include a polyvinyl alcohol-based adhesive liquid such as an aqueous solution of polyvinyl alcohol and polyvinyl butyral, a vinyl polymer-based latex such as butyl acrylate, a polyester-based adhesive, a polyacryl-based adhesive, an epoxy-based adhesive, and a cyanoacrylate. Examples thereof include a system-based adhesive and a polyurethane-based adhesive, and are preferably aqueous polyvinyl alcohol solutions, and particularly preferably completely saponified polyvinyl alcohol aqueous solutions.

The antireflection layer (low-refractive-index layer and high-refractive-index layer, etc.) and antiglare layer of the polarizing sheet for a liquid crystal image display device according to the present invention are prepared by mixing substances having different refractive indices by sputtering or by mixing the binder. However, since these materials alone are weak against external forces such as abrasion, a hard coat layer strong against scratches or the like can be provided thereon, or an antireflection layer containing a compound having a specific refractive index or an antireflection layer can be used. There are various forms such as curing the glaze layer itself to form a film having high film strength. For example, the antireflection layer is a compound having a specific refractive index itself, by using a compound having a heat, ultraviolet ray or electron beam-curable polymerizable group, or a binder containing a compound having a specific refractive index. By using the same polymerizable compound as a curable resin, it may be cured by heat, ultraviolet light or electron beam to form a scratch-resistant film,
These are naturally insoluble films after the cross-linking polymerization. The compound having a curable group and the curable resin,
A polymerizable compound having an epoxy group or an ethylenically unsaturated group, a monomer having two or more polymerizable groups in one molecule, or an acrylate resin such as urethane acrylate, polyester acrylate, epoxy acrylate, a siloxane resin, or an epoxy resin. Prepolymers or oligomers such as resins and allyl resins. These form a layer with good transparency after polymerization. The hard coat layer is also a layer for forming a film having high hardness by the same method as described above, and is also an insoluble film.

In addition, the antistatic layer mainly exists as a layer containing a conductive metal compound in a binder or a layer formed by depositing a conductive metal compound by sputtering. In addition, an acrylic adhesive is mainly used as the adhesive resin of the adhesive layer, and has a carboxylic acid such as acrylic acid or methacrylic acid as a copolymer component.

Further, the protective film has an adhesive substance capable of peeling the film such as polyester, and a release film. As a release agent, polydimethylsiloxane or a fluororesin is used.

It is preferable that the polyester protective film be peeled off as much as possible before the treatment.

Therefore, when recovering the cellulose ester, it is preferable to recover the cellulose ester by a simple method which can be easily treated even if different laminated components are mixed.

In the present invention, the shape of the laminated component at the time of recovery may be conveniently obtained by pulverizing or cutting into an amorphous or small square chip. Maximum length is 0.1 ~
About 20 mm is suitable for processing, especially 0.5 to 10 m
m is preferred.

One of the recovering methods of the present invention is a method of dissolving and separating a cellulose ester film as a chip using an organic solvent having a dissolving ability for cellulose ester. Examples of the organic solvent capable of dissolving the cellulose ester include methylene chloride, ethylene chloride, chloroform, methyl acetate, 1,3-dioxolan, 1,4-dioxane, nitromethane, epichlorohydrin, N-methylpyrrolidone, dimethyl sulfoxide, Examples thereof include fluoroalcohol and the like, but the dissolving method may be different depending on the type of acyl group and the degree of substitution of the cellulose ester. The usual dissolution method is to dissolve at around normal pressure. M. G. FIG. Cowi
e, Die Makromolekulare Ch
emie, 143, 105-114 (1971)
Cellulose acetate (degree of acetylation 60.1% -6)
(1.3%) in acetone at −80 to −70 ° C., followed by heating to obtain a dilute solution in which 0.5 to 5% by mass was dissolved. Also, Kenji Ude et al. Dry spinning of cellulose acetate from acetone solution "(Journal of the Textile Society of Japan, vol. 34, pp. 57-61, 1981).
A method for obtaining a 25% by mass cellulose triacetate solution, and a method of applying -10 to -80 ° C as described in JP-A-9-95544, JP-A-9-95557, JP-A-9-95538, etc. Such a cooling dissolution method of cooling and dissolving at or below zero degree, and Japanese Patent Application No. Hei 9-17828.
9.8 × 10 ⁵ to 4.9 × as described in No. 4
A high-pressure dissolution method of dissolving under a high pressure of 10 ⁸ Pa can be used in the present invention. In the present invention, dissolution at around normal pressure and normal temperature is preferable, and methylene chloride and methyl acetate are preferable as the solvent used at around normal pressure and normal temperature.

The separation of the cellulose ester solution from the other layers is preferably carried out by filtration. For example, a method in which coarse filtration is performed first, followed by medium filtration, and finally fine filtration is preferable. Filtration in the final stage is preferably a wire mesh of various meshes, followed by filtration with a sintered metal wire filter such as a sintered stainless wire, and finally filtration with a filter press combining filter cloth and filter paper. This is the preferred method. The filtered cellulose ester solution may be applied as it is to a solution casting film forming method as a dope, directly formed into a film, and reused. Also, when impurities and the like are worried, the recovered cellulose ester solution is poured into a non-solvent having no dissolving ability for a large amount of cellulose ester, for example, methanol, ethanol, hexane, and cyclohexane while stirring. The flakes may be precipitated and dried to form flakes, which may be again dissolved and reused as a dope by a solution casting method.

The cellulose ester solution obtained by dissolution under pressure can be precipitated by reducing the pressure.

Another recovery method is to treat the chip with an aqueous solution to separate the polarizing film sandwiched between the cellulose ester films, and then dissolve the cellulose ester in an organic solvent having this dissolving ability. Then, it is a method of separating another laminated member. The aqueous liquid used in the present invention is water or a mixture 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 being compatible with water having 1 to 6 carbon atoms include, for example, methanol, ethanol, n-propanol and 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,
Examples include, but are not limited to, pentose, xylitol, and xylitol. The content of the compound in the aqueous solution is 0.1 to 99.5% by mass, preferably 10 to 90% by mass, and more preferably 30 to 90% by mass.
８０80% 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, but is preferably 20 to 100 ° C, more preferably 35 to 80 ° C. Further, the treatment pH of the aqueous solution is preferably around neutral, preferably 6.0 to 8.0.
0, more preferably 7.0 to 8.0.

In the aqueous treatment of the present invention, the treatment may be carried out by adding a reducing agent to the aqueous liquid. The state in which the cellulose ester film and the polarizing film are separated from the chip by the aqueous liquid treatment of the present invention is various, such as a state in which the polyvinyl alcohol film of the polarizing film is dissolved, swollen, or not swollen. In particular, it has at least one hydroxyl group and has 1 to 1 carbon atoms.
In the case where a compound compatible with water of No. 6 is used, there are many cases where the compound is separated 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 agents. 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 film cross-linked with a cross-linking agent such as boric acid, or the polyvinyl alcohol may have a high degree of saponification, or may be difficult to dissolve in an aqueous solution. There is. In such a case, in the present invention, it is preferable to add a polyvinyl alcohol degrading enzyme capable of decomposing the polyvinyl alcohol-based polymer to the aqueous liquid.
In addition, the polyvinyl alcohol film or adhesive 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 in order to promptly 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, pyridinium,
Examples thereof include heterocyclic quaternary ammonium salts such as imidazolium, and phosphonium or sulfonium salts containing an aliphatic or heterocyclic ring. Examples of the amphoteric surfactant include amino acids, aminoalkyl sulfonic acids, aminoalkyl sulfates or phosphoric esters, alkyl betaines, amine oxides, and the like. Nonionic surfactants include, for example, saponins (steroids), alkylene oxide derivatives (eg, polyethylene glycol, polyethylene glycol / polypropylene glycol condensate, 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 Can be mentioned.

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 aqueous liquid treatment of the present invention, after the polarizing film is separated from the laminated component chip with the aqueous liquid, the cellulose ester film or the laminated structure of the cellulose ester film is washed with water by ordinary filtration and further dried. Thereafter, the cellulose ester is dissolved in a solvent capable of dissolving the same, and subsequent treatments such as filtration, film formation, precipitation, purification, and re-dissolution may be performed in the same manner as described above.

In the case where a solvent-soluble adhesive layer is present in the laminated component to be subjected to the recovery treatment, a solvent such as acetone which does not dissolve the cellulose ester at room temperature before dissolving the cellulose ester is used before dissolving the cellulose ester. Is preferably performed with a solvent capable of dissolving the compound.

[0040]

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

The following laminated structure is a cellulose triacetate film having an acetyl group substitution degree of 2.88,
A cellulose acetate propionate film having an acyl substitution degree of 2.58 is used.

Example 1 Both sides of a polarizing sheet for a liquid crystal display device comprising [polyester protective film / anti-reflection layer / anti-glare layer / cellulose triacetate film / polyvinyl alcohol polarizing film / cellulose triacetate film / adhesive layer / polyester protective film] And the remaining [antireflection layer / antiglare layer / cellulose triacetate film / polyvinyl alcohol polarizing film / cellulose triacetate film / adhesive layer] having a minimum to maximum length of 0.5 to 10 mm The chips were pulverized with an crusher into amorphous and square shapes, and 10 parts by mass of the chips were mixed with 100 parts by mass of an acetone / ethyl acetate (50/50 by mass) organic solvent 100.
It was immersed in parts by mass, the adhesive layer was dissolved, the insolubles were scooped with a wire mesh, washed with a little acetone and dried. next,
The insoluble matter was immersed in 100 parts by mass of methylene chloride at room temperature for 180 minutes to dissolve the dissolved matter, the insoluble matter was scooped with a wire mesh, and filtered twice with a filter cloth. The solution was added to methanol 5
The mixture was gradually poured into 00 parts by mass to precipitate and coagulate the resin. The precipitate was washed with methanol three times and dried to collect cellulose triacetate. 10 parts by mass of the collected cellulose triacetate was dissolved in 50 parts by mass of methylene chloride / ethanol (90/10 by mass), and a cellulose triacetate film was prepared using a solution casting film forming apparatus.

Example 2 A polyester protective film was peeled off from the same polarizing sheet for a liquid crystal display device as in Example 1, and 10 parts by weight of the crushed sample 1 chip were placed in water / ethanol at 60 ° C. (30/7 by weight).
0) Immersion in 100 parts by mass for 60 minutes, peeling off the polarizing film, scooping the supernatant of the polarizing film-containing liquid portion with a wire mesh, and filtering the solution containing the remaining insoluble matter with the wire mesh after the polarizing film has disappeared. Then, the insoluble matter was washed with water and dried. 9 parts by mass of this insoluble matter is immersed in 100 parts by mass of an organic solvent of acetone / ethyl acetate (50/50 by mass) to dissolve the adhesive layer, scoop up the insoluble matter with a wire mesh, wash with a little acetone and dry. I let it. Next, methylene chloride 10
It was immersed in 0 parts by mass to dissolve the dissolved matter, and the insoluble matter was scooped out with a wire mesh, and filtered twice with a filter cloth. The solution was gradually poured into 500 parts by mass of methanol to coagulate and precipitate the resin, and the precipitate was washed with methanol three times and dried to collect cellulose triacetate. 10 parts by mass of the collected cellulose triacetate was dissolved in 50 parts by mass of methylene chloride / ethanol (90/10 by mass), and a cellulose triacetate film was prepared using a solution casting film forming apparatus.

Example 3 A polarizing sheet for a liquid crystal display comprising [Anti-reflective layer / Anti-glare layer / Cellulose triacetate film / Polyvinyl alcohol polarizing film / Cellulose triacetate film / Adhesive layer] A chip having a size of 10 mm was crushed into a chip of an amorphous shape and a square shape by a crusher, and 10 parts by mass of the chip were immersed in 100 parts by mass of an organic solvent of acetone / ethyl acetate (50/50 by mass) at 40 ° C. for 100 minutes and bonded. The agent layer was dissolved, the insolubles were scooped with a wire mesh, washed with a little acetone and dried. Next, this insoluble matter was immersed in 100 parts by mass of methylene chloride at room temperature for 180 minutes to dissolve the dissolved matter, the insoluble matter was scooped up with a wire mesh, and filtered twice with a filter cloth. The solution was gradually poured into 500 parts by mass of methanol to coagulate and precipitate the resin, and the precipitate was washed with methanol three times and dried to collect cellulose triacetate. 10 parts by mass of the recovered cellulose triacetate was added to methylene chloride / ethanol (90/1 by mass).
0) It was dissolved in 50 parts by mass, and a cellulose triacetate film was prepared using a solution casting film forming apparatus.

Example 4 A polarizing plate having an antiglare layer of [antiglare layer / cellulose triacetate film / polyvinyl alcohol polarizing film / cellulose triacetate film] was pulverized into chips in the same manner as in Example 3, and 10 parts by mass of the chips Dissolve the soluble part in methylene chloride at room temperature, scoop up the insoluble matter with a wire mesh, filter the solution with a filter cloth, slowly pour the solution into 500 parts by mass of methanol, coagulate and precipitate the resin. The precipitate was washed with methanol twice and dried to collect cellulose triacetate. 10 parts by mass of the collected cellulose triacetate was dissolved in 50 parts by mass of methylene chloride / ethanol (90/10 by mass), and a cellulose triacetate film was prepared using a solution casting film forming apparatus.

Example 5 A polarizing plate having an antiglare layer of [antiglare layer / cellulose triacetate film / polyvinyl alcohol polarizing film / cellulose triacetate film] was pulverized into chips in the same manner as in Example 3, and 10 parts by mass of the chips Immersed in 100 mass of water at 100 ° C for 100 minutes, swelled and peeled off the polarizing film, scooped the supernatant of the polarizing film-containing liquid with a wire mesh, and when the polarizing film disappeared, filtered the remaining solution containing insoluble matter with a wire mesh. Then, the insoluble matter was washed with water and dried. 9 parts by weight of the dried insoluble matter was immersed in 100 parts by weight of methylene chloride at room temperature to dissolve the dissolved matter, and the insoluble matter was scooped with a wire net, and filtered twice with a filter cloth. The solution was gradually poured into 500 parts by mass of methanol to coagulate and precipitate the resin, and the precipitate was washed three times with methanol.
The cellulose triacetate was recovered by drying. 10 parts by mass of the collected cellulose triacetate was dissolved in 50 parts by mass of methylene chloride / ethanol (90/10 by mass), and a cellulose triacetate film was prepared using a solution casting film forming apparatus.

Example 6 A polarizing plate with a hard coat of [hard coat layer / cellulose triacetate film / polyvinyl alcohol polarizing film / cellulose triacetate film] was pulverized in the same manner as in Example 3 to obtain a chip. Immerse in 100 parts by mass of methylene chloride for 180 minutes to dissolve the dissolved matter, scoop insoluble matter with a wire mesh, and remove with a filter cloth.
Filtered twice. The solution was gradually poured into 500 parts by mass of methanol to coagulate and precipitate the resin, and the precipitate was washed with methanol three times and dried to collect cellulose triacetate. 10 parts by mass of the recovered cellulose triacetate was added to methylene chloride / ethanol (90/10 by mass) 5
The solution was dissolved in 0 parts by mass, and a cellulose triacetate film was prepared using a solution casting film forming apparatus.

Example 7 A polarizing plate of [cellulose triacetate film / polyvinyl alcohol polarizing film / cellulose triacetate film] was used as a chip in the same manner as in Example 3, and 10 parts by mass of the chip was added to 100 parts by mass of methylene chloride at room temperature.
Then, the cellulose triacetate film portion was dissolved, and the polarizing film peeled off and floated on the upper side was scooped with a wire net, and washed with a little methylene chloride. The solution was filtered twice with a filter cloth and poured into 500 parts by mass of methanol to coagulate and precipitate the resin component. The precipitate was washed with methanol three times and dried to collect cellulose triacetate.
10 parts by mass of the collected cellulose triacetate was dissolved in 50 parts by mass of methylene chloride / ethanol (90/10 by mass), and a cellulose triacetate film was prepared using a solution casting film forming apparatus.

Example 8 A polarizing plate provided with an adhesive layer of [cellulose acetate propionate film / polyvinyl alcohol polarizing film / cellulose acetate propionate film / adhesive layer] was used as a chip in the same manner as in Example 3, and this chip was used. 10 parts by mass of the adhesive layer was immersed in 100 parts by mass of acetone / ethyl acetate / cyclohexane (40/30/30 by mass) at 40 ° C. for 100 minutes to dissolve the adhesive layer. Wash and dry twice. Next, the insoluble matter 9.5
A part by mass was immersed in 100 parts by mass of methyl acetate at 30 ° C. for 150 minutes to dissolve the film, the insoluble polarizing film was scooped with a wire mesh, and the solution was filtered with a filter cloth. Subsequently, the filtered solution was poured into 200 parts by mass of methanol to coagulate and precipitate the resin,
The precipitate was washed with methanol 20 times and dried. 20 parts by mass of the dried resin was dissolved in 100 parts by mass of methyl acetate / methanol (95/5 by mass), and a cellulose acetate propionate film was produced using a solution casting film forming apparatus.

Comparative Example 1 A polarizing plate having an anti-reflection layer and an anti-glare layer comprising [anti-reflection layer / anti-glare layer / cellulose triacetate film / polyvinyl alcohol polarizing film / cellulose triacetate film] was chipped in the same manner as in Example 3. 10 parts by mass of the chip was immersed in 100 parts by mass of methanol,
For 6 hours, no separation occurred and separation was not possible.

Comparative Example 2 The protective film was peeled off from the polarizing sheet for a liquid crystal display device comprising [protective film / antireflection layer / antiglare layer / cellulose triacetate film / polyvinyl alcohol polarizing film / cellulose triacetate / adhesive layer / protective film]. Then, a chip was formed in the same manner as in Example 3, and 10 parts by mass of the chip was immersed in 100 parts by mass of ethyl acetate, and treated at 40 ° C. for 6 hours. No delamination occurred.

Comparative Example 3 10 parts by mass of a polarizing plate chip composed of [cellulose acetate propionate film / polyvinyl alcohol polarizing film / cellulose acetate propionate film] was immersed in 100 parts by mass of ethanol and treated at 50 ° C. for 5 hours. However, the laminate did not peel off and could not be separated.

<Evaluation Method><< Colored State >> The dried chips after the treatment were put into 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.

<< Mechanical Properties >> The mechanical properties (rupture strength, rupture) of the original cellulose ester film used for producing the polarizing sheet for a liquid crystal image display device and the cellulose ester film formed to the same thickness as the original after recovery. Elongation, elastic modulus)
About the value measured by a Tensilon type tensile tester,
The degree of deterioration was represented by the ratio of (film formed after collection) / (original film).

<< Transmittance >> The value obtained by measuring the light transmittance at 500 nm of the original cellulose ester film used for producing the polarizing sheet for a liquid crystal image display device and the cellulose ester film formed to have the same original thickness after collection was measured. ,
The degree of deterioration is represented by the ratio of (film formed after collection) / (original film), and the results are shown in Table 1.

[0056]

[Table 1]

(Results) As can be seen from Table 1, in the method of the present invention, the cellulose ester film was separated from the polarizing sheet for a liquid crystal image display device, and the cellulose ester could be easily recovered. The cellulose ester film produced by the film-forming method was not colored, and the mechanical properties and light transmittance of the film formed after collection were almost the same as the original film, and no deterioration was observed.

[0058]

According to the present invention, by recovering the cellulose ester of the same quality as the original one from the waste of the polarizing sheet for the liquid crystal image display device, resources can be saved, and there is no waste or incineration, and environmental conservation is prevented. I can do it.

Claims (8)

[Claims] 1. A method for treating a waste liquid of a polarizing sheet for a liquid crystal image display device having a cellulose ester film having a degree of acyl group substitution of 2.5 to 3.0 with an organic solvent capable of dissolving cellulose ester. A method for recovering a cellulose ester. 2. A waste liquid of a polarizing sheet for a liquid crystal image display device having a cellulose ester film having a degree of acyl group substitution of 2.5 to 3.0 is treated with an organic solvent having a solubility in cellulose ester. A method for recovering a cellulose ester, comprising removing a cellulose ester from a solution after separating an insoluble member. 3. A waste liquid of a polarizing sheet for a liquid crystal image display device having a cellulose ester film having a degree of acyl group substitution of 2.5 to 3.0 is treated with an aqueous liquid and separated, and the cellulose ester film remains. A method for recovering a cellulose ester, wherein the member is treated with an organic solvent capable of dissolving the cellulose ester. 4. A waste of a polarizing sheet for a liquid crystal image display device having a cellulose ester film having a degree of acyl group substitution of 2.5 to 3.0 is treated with an aqueous liquid and separated, and the cellulose ester film remains. A method for recovering a cellulose ester, comprising separating a solution obtained by treating a member having been treated with an organic solvent capable of dissolving the cellulose ester from an insoluble member, and then removing the cellulose ester from the solution. 5. A liquid crystal display device comprising a polarizing sheet for a liquid crystal image display device having a cellulose ester film having a degree of acyl group substitution of 2.5 to 3.0 and an acrylic adhesive layer is soluble in an acrylic adhesive. And treating the remaining waste having the cellulose ester film with an organic solvent capable of dissolving the cellulose ester after treating and separating with an organic solvent insoluble in the cellulose ester. Ester recovery method. 6. The method for recovering a cellulose ester according to claim 1, wherein the polarizing sheet for a liquid crystal image display device is pulverized or cut into amorphous or square pieces and processed as chips. 7. A regenerated cellulose ester recovered by the method according to any one of claims 1 to 6. 8. A cellulose ester film formed by using the regenerated cellulose ester according to claim 7.