JP2001300939A - Method for recovering cellulose ester and cellulose ester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recycled cellulose ester film by recycling a recovered cellulose ester to provide a method for covering the cellulose ester in a high yield and high purity from a film laminate for polarizing plate. SOLUTION: The method for recovering the cellulose ester from the film laminate for polarizing plate having the cellulose ester film comprises the steps of crushing or cutting the laminate for the polarizing plate, and then separating the cellulose ester film from the other films by an electrostatic separator.

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 a cellulose ester from a film laminate used for a polarizing plate, and more particularly to a method for recovering a cellulose ester using an electrostatic separator. The present invention relates to a cellulose ester and a cellulose ester film obtained by reusing the cellulose ester.

[0002]

2. Description of the Related Art Conventionally, waste plastic processing has been carried out by landfilling or incineration. However, as environmental awareness has increased in recent years, it has become difficult to secure landfill sites and increase the number of incineration plants. I have. In addition, the depletion of petroleum resources and the reduction of carbon dioxide emissions have made it necessary to reuse and recycle used articles from the standpoint of resource protection and environmental conservation.

[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 tends to rely on wood pulp because of the small amount of linter pulp that can be obtained from the linter part of the cotton, the production amount is easily affected by the weather, and the cost.

A cellulose triacetate film is used for a polarizing plate for a liquid crystal image display device, a silver halide photographic light-sensitive material, and the like because it is transparent and mechanically strong.

In a film laminate including a polarizing plate for a liquid crystal display device, a cellulose triacetate film as a protective film for a polarizing film, the surface of which is saponified in advance with an alkaline solution, is attached to both sides of a uniaxially stretched polyvinyl alcohol-based polarizing film. A polarizing plate, and a surface 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 further laminated on both sides of the polarizing plate. With silver halide photographic light-sensitive materials, the yield in the production of cellulose triacetate film is fairly good, and most of the production remains at the photographer. On the other hand, for a cellulose triacetate film for a liquid crystal display device, a work is required because a polarizing plate having a highly hygroscopic uniaxially stretched polarizing film adhered thereto, and the above-described constituent layers are further laminated on both surfaces thereof. At present, the final yield is quite low because it is difficult to easily generate losses and large areas are used to avoid dust and defects.Each time, waste film is discarded in each of these work processes. Was.

Heretofore, the recovery of a cellulose ester film has been found only a few times in a cellulose triacetate film for a silver halide photographic light-sensitive material, but there is almost no description of a polarizing plate. As a technique for collecting a cellulose triacetate film for a silver halide photographic light-sensitive material, for example, Japanese Patent Application Laid-Open No. 5-281686 discloses a method of treating with hypochlorous acid and then treating with an aqueous solution, as described in U.S. Pat. No. 2,688,614. The patent discloses an acidic treatment containing potassium permanganate, British Patent 1,087,038 describes an alkaline treatment containing an oxidizing agent, and Patents 2,640,394 and 2,817,020 describe , Cellulase treatment and water-soluble organic solvent treatment, respectively. Further, in the silver halide photographic light-sensitive material, there is no mixture which is mostly composed of a polyethylene terephthalate film and a cellulose triacetate film separately as a support, but when discarded, it is composed of a polyethylene terephthalate film. And a film composed of a cellulose triacetate film may be mixed. In the case of such coexistence, a method of separating and recovering each film by an underwater floating separation method is disclosed in Japanese Patent Application Laid-Open No. 50-874.
Nos. 69, 50-87470 and 52-97738
No. pp. 147-64.

[0007]

However, the cellulose triacetate film recovered by the above-described method for recovering with a chemical is difficult to reuse in quality as a film for a liquid crystal display device, and the above-mentioned underwater floating separation is difficult. In the method, the foaming of the film pieces is unstable, the recovery rate is low, and the separation of the surface protective film component and the cellulose ester film component of the polarizing plate film laminate having the cellulose ester film and the surface protective film is not possible. Was enough. Further, with these methods, it was impossible to separate a laminate such as a film laminate for a polarizing plate.

An object of the present invention is to recover a cellulose ester from a film laminate for a polarizing plate and reuse it to obtain a cellulose ester.
It is intended to provide a method for obtaining a cellulose ester film.

[0009]

The present invention has the following constitution.

(1) In the method for recovering cellulose ester from a polarizing plate film laminate having a cellulose ester film, the cellulose ester film is crushed or cut, and then the cellulose ester film is separated by an electrostatic separation device. A method for recovering a cellulose ester, wherein the cellulose ester is separated from the film.

(2) In the method for recovering cellulose ester from a polarizing plate film laminate having a cellulose ester film, the polarizing plate film laminate is crushed or cut, then treated with an aqueous solution, dried, and further statically treated. A method for recovering a cellulose ester, comprising separating a cellulose ester film from other films by an electric separator.

(3) In the method for recovering a cellulose ester from a polarizing plate film laminate having a cellulose ester film, the polarizing plate film laminate is crushed or cut, then treated with an aqueous solution, dried, and dried. A method for recovering a cellulose ester, comprising separating a cellulose ester film from other films by a separator, and further dissolving and purifying the cellulose ester film with an organic solvent having a dissolving ability for the cellulose ester.

(4) The collection of cellulose ester according to any one of (1) to (3), wherein the polarizing plate film laminate has at least a surface protective film as a film other than the cellulose ester film. Method.

(5) The method for recovering a cellulose ester according to any one of (1) to (4), wherein the electrostatic separation device is based on triboelectric charging.

(6) A cellulose ester recovered by the method according to any one of (1) to (5).

(7) A cellulose ester film formed by a solution casting method using a dope obtained by recycling the cellulose ester according to (6).

The present invention will be described in detail. The film laminate for a polarizing plate referred to in the present invention is obtained by laminating various functional layers and films on a polarizing plate used for a liquid crystal image display device.
Specifically, for example, a laminate (this is referred to as a polarizing plate) in which a cellulose ester film (a protective film for a polarizing film) is adhered to at least one side of a polarizing film, an adhesive layer is provided on the cellulose ester film of the polarizing plate, Glare layer, antireflection layer, cured transparent layer, hard coat layer, antistatic layer and / or
Alternatively, a surface protection film or the like is appropriately laminated and laminated. The layer configuration as a completed product is exemplified as a layer configuration such as a surface protective film / antireflection layer / antiglare layer / cellulose ester film / polyvinyl alcohol polarizing film / cellulose ester film / adhesive layer / surface protective film. It is a laminate. Depending on the manufacturer, purpose, specifications, and the like, the types of these layers and the order of lamination are more complicated. In addition, in the present invention, the object to be recovered is a defective product or a cut-off edge which is formed by laminating an anti-reflection layer or an anti-glare layer as described above, but is not incorporated in the liquid crystal image display device as a completed product. A material obtained by laminating the above-mentioned layers and films, for example, a surface protective film, a cured transparent layer, etc., on a cellulose ester film before bonding to a polarizing film is also referred to as a polarizing plate film laminate (hereinafter simply referred to as a laminate). Body). In addition, the polarizing plate film laminate according to the present invention includes all of the above-described various films and layers, such as semi-finished products or scraps in the manufacturing process, but all the constituent layers are laminated. Various film laminates produced in each step of the process, for example, two layers, three layers, and a four-layer structure,
Some are discharged as waste in the form of a layered component, and are not limited to the above. In the present invention, what is most frequently collected is a laminate having at least a cellulose ester film and a surface protective film, and is preferably collected.

As described above, the present invention relates to recovering valuable cellulose ester films from the above-mentioned rejects and wastes such as scraps and reusing them.

The object to be recovered in the present invention is the cellulose ester used in the polarizing plate film laminate. The cellulose ester of interest in the present invention 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. Are reacted, and acetyl group, propionyl group and butyryl group are substituted and introduced into cellulose. Examples of the cellulose ester include cellulose triacetate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate propionate butyrate. Such a cellulose ester film is useful for a film laminate for a polarizing plate. In many cases, the cellulose ester film contains a plasticizer, an ultraviolet inhibitor, an oxidant inhibitor, and the like. The cellulose ester film according to the present invention is formed by a usual solution casting method. That is, a cellulose ester is dissolved in an organic solvent capable of dissolving the cellulose ester 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. The web is peeled off from the metal support before the metal support makes one rotation, and dried. The thickness of the cellulose ester film is preferably 30 to 150 μm.

In 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 a cellulose ester film having a surface saponified as described above on at least one surface of the polarizing film as described above, and is usually a laminate of two saponified cellulose ester films. . The polarizing plate is coated with an adhesive solution on one side of the saponified cellulose ester film, and on that surface, the above uniaxially stretched polyvinyl alcohol film is immersed in an iodine solution, and further uniaxially stretched, and a polarizing film is attached thereto. It is made. 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 a polyvinyl alcohol aqueous solution, particularly, a completely saponified polyvinyl alcohol aqueous solution is preferably used.

The antireflection layer (low refractive index layer and high refractive index layer, etc.) and antiglare layer of the polarizing plate film laminate according to the present invention are:
It is a material obtained by laminating substances with different refractive indexes by sputtering or mixing with a binder.Since these materials are only weak against external force such as abrasion, a hard coat layer that is strong against scratches or the like can be provided or specified. There are various forms such as curing the anti-reflection layer or the anti-glare layer itself containing a compound having a refractive index to form a film having high film strength. For example, the anti-glare 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 a similar polymerizable compound as a curable resin, the film is cured by heat, ultraviolet rays or electron beams to form a scratch-resistant film. These are naturally insoluble films after the cross-linking polymerization.

In addition to the above, a cured transparent layer may be provided. The compound having a curable group and the curable resin used therein are a polymerizable compound having an epoxy group and an ethylenically unsaturated group. It is a monomer having two or more polymerizable groups in the molecule, or an acrylate resin such as urethane acrylate, polyester acrylate, or epoxy acrylate, or a prepolymer or oligomer such as a siloxane resin, an epoxy resin, or an allyl resin. These form a layer with good transparency after polymerization. Hard coat layer,
This is a layer in which a film having high hardness is formed by the same method as described above, and is also an insoluble film.

In addition, the antistatic layer includes a layer in which a conductive metal compound is mainly contained in a binder and a layer in which a conductive metal compound is deposited 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.

The surface protective film according to the present invention includes various plastic films such as a polyethylene terephthalate film, a polyethylene film, a polypropylene film, a polyvinyl chloride film, and a polyamide film. It is a polyethylene film. The surface protective film constituting the polarizing plate film laminate according to the present invention, which protects the surface of the polarizing plate, an adhesive or a releasable adhesive substance or a release film on the cellulose ester film, Are provided, and
As a release agent, polydimethylsiloxane or a fluororesin is used. In many cases, the film laminate for a polarizing plate has a polyethylene terephthalate film provided with an adhesive or a release agent attached to the outermost surface thereof. When a film laminate is incorporated into a liquid crystal image display device as a final product, it is performed after the polyethylene terephthalate film is peeled off. However, most of rejected products, offcuts and semi-finished products are made by laminating cellulose ester film and polyethylene terephthalate film, and when collected as crushed or cut chips, chips of cellulose ester film and polyethylene terephthalate film are mixed. Therefore, it is necessary to separate them.

The film laminate for a polarizing plate at the time of recovery in the present invention is first formed into an amorphous or small square chip by crushing or cutting. The size of the tip (length of one side or span) is from 0.1 to min.
About 20 mm is suitable for processing, especially 0.5 to 10 m
m is preferred.

As described above, the polarizing plate is a laminate obtained by laminating a saponified cellulose ester film and a polarizing film. In the present invention, after the laminate is formed into chips, these are separated and collected. . As a separation method, a method of immersing in an aqueous solution is preferable. 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 performed 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 peeled off almost without 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 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, 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 peeled from the laminate chip with the aqueous liquid, the polyvinyl alcohol or the like used for the polarizing film or the adhesive is separated by ordinary filtration to obtain a cellulose ester film or a polarizing film. The unlaminated laminate or other surface protection film is washed with water and dried.

Next, the dried chip is separated and separated from the cellulose ester film and another surface protective film by an electrostatic separator.

The static electricity separator used in the present invention and its technology will be described. This electrostatic separation device is a device and technology for separating plastic from a mixture of plastics such as PET bottles based on differences in electrical characteristics, for example, conductivity, easiness of charging, and the like. The method of applying static electricity is not limited as long as static electricity occurs, but frictional electrification, which is a cost-effective and simple method, is preferred. If the electrification by friction is weak, the subsequent separation and separation cannot be sufficiently performed, and the recovery yield after the separation decreases. Therefore, a means for efficiently causing triboelectric charging is important. In the present invention, as means for efficiently causing frictional charging on plastic,
As long as it is efficient, it can be used without limitation, but JP-A-09-299829, JP-A-10-24251, and
-245252, 10-323580, 11-
The frictional charging device used for the electrostatic separation device described in 114451 and 11-114452 can also be used in the present invention. Further, the apparatus and method for separating and separating plastics are also described in the above-mentioned publications, but are disclosed in JP-A-09-299828 and JP-A-09-299.
No. 830, No. 10-263437, No. 10-2634
No. 38, No. 10-277530 and No. 11-1233
No. 46 publication.

The means for selecting and separating a mixed plastic by triboelectric charging useful in the present invention will be described with reference to FIG.
FIG. 1 is a schematic diagram of a triboelectric plastic sorting / separating apparatus. The triboelectric plastic sorting / separating apparatus includes a triboelectric charging apparatus 1, a supply tray 2, a metal rotating drum electrode 3 as an anode, a counter electrode 4, a high voltage power supply (+ output power supply) 5, a cathode ground 6, and a separation / separation container 7, 8. And 9 roughly. First, chips are continuously charged into the frictional charging device 1, and positively and negatively charged plastics are supplied from the supply tray 2 onto the metal rotary drum electrode 3 serving as the anode. The positively charged plastic is separated from the anode rotating drum electrode by the counter electrode 4 and attracted to the cathode counter electrode 4, thereby separating and collecting the container 7.
Is dropped and accommodated. On the other hand, the negatively charged plastic is scraped off by the scraper 10 while being attached to the anode metal rotating drum electrode 3, and is stored in another sorting and separating container 9 and separated. Another sorting and separating vessel 8 includes 7 and 9
This is a container for receiving the items that fall in the middle of the container. In this way, the positively charged plastic is placed in the separation container 7 and
The charged plastics are collected in a separation / separation container 9 and can be separated / separated.

The charging property of the mixed plastic can be known in advance by the charging sequence of the plastic itself.
The charging column is described in Electrostatics Handbook, p. 59, (1981, Ohmsha), edited by the Electrostatics Society of Japan.
As a result of the experiments conducted by the inventors of the present invention, the following order was confirmed: + charge: cellulose ester such as cellulose triacetate>polyethylene> polyethylene terephthalate> polyvinyl chloride: −charge. Since the electrostatic separation apparatus and method can separate even a small difference in the charging sequence, it was found that such a charging sequence can separate and separate cellulose ester and polyethylene terephthalate.

In the present invention, the cellulose ester is +
, And the polyethylene terephthalate is negatively charged and separated into the separation containers 7 and 9, respectively. In addition,
Separation is possible even with a functional layer such as an adhesive layer or a cured transparent layer.

In order to further purify the cellulose ester chip obtained by the recovery method of the present invention, the chip is immersed in an organic solvent in which the cellulose ester is dissolved, and the chip is dissolved.
The solution is filtered to remove impurities, and then the solution is poured into a large amount of a non-solvent that does not dissolve the cellulose ester, and the solution is precipitated to remove the cellulose ester. This is a method of dissolving and separating a cellulose ester film formed into chips using an organic solvent capable of dissolving cellulose ester. Organic solvents having the ability to dissolve cellulose esters include methylene chloride, ethylene chloride, chloroform, methyl acetate, 1,3-
Dioxolan, 1,4-dioxane, nitromethane, epichlorohydrin, N-methylpyrrolidone, dimethylsulfoxide, fluoroalcohol and the like can be mentioned, but the dissolving method may be different depending on the type and substitution degree of the acyl group of the cellulose ester. The usual dissolution method is to dissolve at around normal pressure. M. G. FIG. Co
Wie et al., Die Makromolekulare
Chemie, 143, 105-114 (1971).
Acetate) (Acetification degree 60.1% ~)
61.3%) in acetone, cooled to −80 to −70 ° C., and then heated to obtain a dilute solution in which 0.5 to 5% by mass is 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. A cooling dissolution method of dissolving by cooling at a temperature below zero degree as described in JP-A-11-0213
9.8 × 10 ^5-
A high-pressure dissolution method of dissolving in a high-pressure state where a pressure of 4.9 × 10 ⁸ Pa is applied can also 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.

For separating the other layer from the cellulose ester solution, a method by filtration is preferable. 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.Next, filtration by a sintered metal wire filter such as sintering a stainless wire, and finally filtration by a filter press combining a filter cloth and filter paper. This is the preferred method.

The filtered cellulose ester solution is dissolved in a non-solvent insoluble in cellulose ester, for example,
The mixture is poured into methanol, ethanol, hexane, cyclohexane, or the like with stirring, precipitated, taken out and dried to recover flaky or fibrous cellulose esters.

When the solvent-soluble adhesive layer is present in the laminate to be subjected to the recovery treatment, a solvent which is soluble in the adhesive and which does not dissolve the cellulose ester at room temperature before and after dissolving the cellulose ester. It is preferable to perform the pretreatment with a solvent capable of dissolving the adhesive layer.

[0042]

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

The following laminate is a cellulose triacetate film having an acetyl substitution degree of 2.88,
A cellulose acetate propionate film having an acyl substitution degree of 8 was used.

Example 1 A film laminate for a polarizing plate (manufactured by Sumitomo Chemical Co., Ltd.) composed of [cellulose triacetate film / polarizing film / cellulose triacetate / adhesive layer / polyethylene terephthalate surface protective film] has a minimum to maximum length of 0. 0.5-1
A chip having a size of 0 mm was crushed into an amorphous or square shape with a crushing machine, and 100 parts by mass of the chip was mixed with a mixed organic solvent of water / ethanol (30/70 by mass ratio) at 60 ° C.
100 parts by mass and stirred for 60 minutes to peel off the polarizing film,
The liquid part containing the polarizing film in the supernatant was scooped with a wire mesh, and after the polarizing film disappeared, the remaining solution containing insoluble matter was filtered with a wire mesh, and the insoluble matter was washed with water and dried. The chips were separated and separated using an electrostatic separation device as shown in FIG. A chip is charged by charging the chip into a frictional charging device as described in JP-A-10-24251, dropped on a metal rotating drum of an anode through a supply tray, and a positively charged cellulose triacetate chip is provided on the counter electrode side of the cathode. It was sucked and separated from the drum, collected in a lower sorting / separating container, and the polyethylene terephthalate chip attached to the metal rotary drum was scraped off with a scraper and collected in another sorting / separating container. 50 parts by mass of the collected cellulose triacetate chip with an adhesive layer was immersed in 500 parts by mass of an organic solvent of acetone / ethyl acetate (50/50 by mass), the adhesive layer was peeled off, and the insoluble matter was scooped with a wire mesh. Washed with some acetone and dried. Dissolve 2 parts by mass of the collected cellulose triacetate chip in 20 parts by mass of methylene chloride, pour into 200 parts by mass of methanol while filtering with filter paper, precipitate, take out 2-3 times of washing with methanol, and dry, and regenerate cellulose triacetate. Got flakes. Further, the recovered cellulose triacetate 10
Parts by mass, Tinuvin 326 (manufactured by Ciba Specialty Chemicals), 0.05 parts by mass, Tinuvin 171 (Ciba
0.05 parts by mass of Specialty Chemicals, Aerosil 200V (manufactured by Nippon Aerosil Co., Ltd.) 0.01
Parts by mass, 0.2 parts by mass of ethyl phthalylethyl glycolate, 1 part by mass of trimethyl phosphate, 45 parts by mass of methylene chloride and 5 parts by mass of ethanol are charged into a pressure-closed container, heated to 60 ° C., and placed in the container. The pressure is 2 atm,
While stirring, the cellulose triacetate was completely dissolved to obtain a dope. This dope was prepared using Azumi Filter Paper No. The solution was filtered using 244, and produced by a solution casting film forming apparatus to obtain a cellulose triacetate film usable as a protective film for a polarizing film.

Example 2 A film laminate for a polarizing plate comprising [cellulose acetate propionate film / polyvinyl alcohol polarizing film / cellulose acetate propionate film / adhesive layer / polyethylene terephthalate surface protective film] was prepared in the same manner as in Example 1. Then, 100 parts by mass of this chip is immersed in 2000 parts by mass of water at 80 ° C. for 100 minutes, and the polarizing film is dissolved and peeled off. The supernatant liquid containing the polarizing film is scooped with a wire mesh, and the polarizing film disappears. After that, the remaining solution containing the insoluble matter was filtered with a wire mesh, and the insoluble matter was washed with water and dried. 80 parts by mass of the chip was separated into a cellulose acetate propionate chip and a polyethylene terephthalate chip by an electrostatic separator in the same manner as in Example 1. 50 parts by mass of the separated cellulose acetate propionate chip with an adhesive layer was mixed with acetone / ethyl acetate /
The adhesive layer was peeled off by immersion in 500 parts by mass of a mixed organic solvent of cyclohexanone (30/30/40 in mass) for 100 minutes, and the insoluble chips were scraped off with a wire mesh, and the same solvent was used to remove
Washed twice and dried. Dissolve 2 parts by mass of the collected cellulose acetate propionate chip in 20 parts by mass of methyl acetate, pour into 200 parts by mass of methanol while filtering with filter paper, precipitate, take out and wash with methanol 2 to 3 times, and dry. A regenerated cellulose acetate propionate flake was obtained. Further, 10 parts by mass of this cellulose acetate propionate flake, 0.05 parts by mass of Tinuvin 326 (manufactured by Ciba Specialty Chemicals), 0.05 parts by mass of Tinuvin 171 (manufactured by Ciba Specialty Chemicals), and Aerosil 200V ( 0.01 parts by mass of Nippon Aerosil Co., Ltd., 0.2 parts by mass of ethyl phthalylethyl glycolate, 1 part by mass of trimethyl phosphate, 45 parts by mass of methyl acetate and 5 parts by mass of ethanol are charged into a pressurized airtight container. The mixture was heated to 60 ° C., the pressure in the vessel was adjusted to 2 atm, and the cellulose acetate propionate was completely dissolved with stirring to obtain a dope. This dope was prepared using Azumi Filter Paper No. The solution was filtered using 244, and produced by a solution casting film forming apparatus to obtain a cellulose acetate propionate film usable as a protective film for a polarizing film.

Example 3 [Polyethylene terephthalate surface protective film / cured transparent layer / cellulose triacetate film / polarizing film /
Cellulose triacetate film] and a film laminate for polarizing plate (manufactured by Sumitomo Chemical Co., Ltd.) made into a chip in the same manner as in Example 1, and 80 parts by mass of the chip was water / ethanol (30/70 by mass) 2000 Stir in the mass part for 2 hours, separate the polarizing film and the polyethylene terephthalate surface protective film chip, scoop up the supernatant liquid containing the polarizing film with a wire mesh, and after the polarizing film has disappeared, use the wire mesh to remove the remaining insoluble matter. Was filtered and the remaining chips were washed with water and dried. The chips were separated and separated using an electrostatic separation device as shown in FIG. The chip is charged by charging it into a triboelectric charging device as described in JP-A-10-24251, dropped on a metal rotating drum of an anode through a supply tray, and has a positively charged hardened transparent layer on the counter electrode side of the cathode. The cellulose triacetate chip was sucked and separated from the drum, collected in a lower separation / separation container, and the polyethylene terephthalate chip attached to the metal rotating drum was scraped off with a scraper and collected in another separation / separation container. Dissolve 20 parts by mass of the collected cellulose triacetate chip with a cured transparent layer in 100 parts by mass of methylene chloride, filter and separate the insoluble cured transparent layer with a filter paper, pour the solution into 1000 parts by mass of methanol, precipitate, and take out. After washing with methanol two or three times and drying, a regenerated cellulose triacetate flake was obtained. Further, 10 parts by mass of the collected cellulose triacetate and Tinuvin 326 (manufactured by Ciba Specialty Chemicals) were added.
05 parts by mass, Tinuvin 171 (Ciba Specialty
Chemicals) 0.05 parts by mass, Aerosil 200V
0.01 parts by mass (manufactured by Nippon Aerosil Co., Ltd.), 0.2 parts by mass of ethyl phthalylethyl glycolate, 1 part by mass of trimethyl phosphate, 45 parts by mass of methylene chloride and 5 parts by mass of ethanol are charged into a pressure-tight container. And 60 ° C
Then, the pressure in the container was increased to 2 atm, and the cellulose triacetate was completely dissolved with stirring to obtain a dope.
This dope was prepared using Azumi Filter Paper No. 244
Then, the mixture was filtered using a solution casting method, and produced using a solution casting film forming apparatus to obtain a cellulose triacetate film usable as a protective film for a polarizing film.

Comparative Example 1 A polarizing plate film laminate (Sumitomo Chemical Co., Ltd.) composed of [cellulose triacetate film / polarizing film / cellulose triacetate film / polyethylene terephthalate surface protective film] was crushed in the same manner as in Example 1. 80 parts by mass of the chips were put into 2000 parts by mass of water and stirred at 45 ° C. for 2 hours to separate the polarizing film and the polyethylene terephthalate surface protective film chip.
The supernatant liquid containing the polarizing film was scooped with a wire mesh, and after the polarizing film was removed, the remaining solution containing insolubles was filtered with a wire mesh, and the remaining chips were washed with water. These chips 5
0 parts by mass is again charged into a container containing 4000 parts by mass of water at 60 ° C., and bubbles are introduced into the water from the bottom of the container for 5 minutes, and the polyethylene terephthalate chips floating with bubbles and bubbles do not adhere. The cellulose triacetate chip submerged at the bottom of the container was separated, dried and taken out. However, the chips floating in the middle were separated separately.

Comparative Example 2 A polarizing plate laminate (Sumitomo Chemical Co., Ltd.) composed of [cellulose triacetate film / polarizing film / cellulose triacetate film / polyethylene terephthalate surface protective film] was crushed in the same manner as in Example 1. 80 parts by mass of the chips were put into 2000 parts by mass of water and stirred at 45 ° C. for 2 hours to separate the polarizing film and the polyethylene terephthalate surface protective film chip.
The supernatant liquid containing the polarizing film was scooped with a wire mesh, and after the polarizing film was removed, the remaining solution containing insolubles was filtered with a wire mesh, and the remaining chips were washed with water. These chips 5
0 parts by mass is added again to a container containing 4000 parts by mass of water at 60 ° C. and 0.05 part by mass of tannic acid as a wetting agent, and bubbles are introduced into the water from below the container for 10 minutes. The cellulose triacetate chips that floated and the polyethylene terephthalate chips that settled at the bottom of the container without bubbles were separated. However, the chips floating in the middle were separated separately.

The purity and recovery of the cellulose ester chips recovered in Examples 1 to 3 and Comparative Examples 1 and 2, and the original cellulose ester film used for the polarizing plate film laminate and the cellulose recovered and regenerated to form a film Table 1 shows a comparison (below) of the mechanical properties of the ester films.

<< Purity >> The purity is expressed as a percentage of the mass ratio of the pure cellulose ester film chips in the chips finally recovered as the cellulose ester film chips.

<< Recovery rate >> It is expressed as a percentage obtained by multiplying the purity by the mass ratio of the finally recovered cellulose ester film chip to the mass of the cellulose ester film chip used in the polarizing plate film laminate. .

<< Mechanical Properties >> The breaking strength, breaking elongation and elastic modulus of the original cellulose ester film used for the polarizing plate film laminate and the cellulose ester film formed after recovery were measured using a Tensilon type tensile tester. The mechanical properties of each of the films formed after collection with respect to the original film were expressed as ratios.

[0053]

[Table 1]

(Results) As can be seen from Table 1, the cellulose ester film of the polarizing plate film laminate was easily recovered at a high yield by an electrostatic separator and a separating method. In addition, the cellulose ester film produced by the solution casting film forming method of the recovered cellulose ester has no coloring, and the mechanical properties and light transmittance of the film formed after the recovery are almost the same as the original film, and the deterioration is recognized. Did not. On the other hand, the separation by the flotation method using air bubbles has a low yield and a low purity.

[0055]

According to the present invention, from the waste of the polarizing plate film laminate,
By recovering the cellulose ester whose quality does not change at all from the original, resources can be saved and the environment can be preserved without waste or incineration.

[Brief description of the drawings]

FIG. 1 is a schematic view of a triboelectric plastic sorting / separating apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Friction electrification apparatus 2 Supply tray 3 Metal rotating drum electrode of anode 4 Counter electrode 5 High voltage power supply (+ output power) 6 Cathode ground 7, 8, 9 Sorting separation container 10 Scraper

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08J 11/08 C08J 11/08 // B29K 1:00 B29K 1:00 105: 26 105: 26 C08L 1: 10 C08L 1:10 F term (reference) 4D054 GA01 GA09 GB01 4F071 AA09 AF35 AG31 AH19 BB02 BC01 4F205 AA01 AA50 AG01 GA07 GB02 GC07 GF24 GF52 GW45 4F301 AA02 AC02 BA17 BA21 BE21 BE31 BE32 BE44 BF08 BF12 BF12 BF12 BF12 BF12

Claims (7)

[Claims] 1. A method for recovering a cellulose ester from a polarizing plate film laminate having a cellulose ester film, wherein the polarizing film laminate is crushed or cut, and then the cellulose ester film is separated by an electrostatic separator. A method for recovering a cellulose ester, which is separated from a film. 2. A method for recovering a cellulose ester from a film laminate for a polarizing plate having a cellulose ester film, comprising: crushing or cutting the film laminate for a polarizing plate; A method for recovering a cellulose ester, comprising separating a cellulose ester film from other films by a separating device. 3. A method for recovering a cellulose ester from a film laminate for a polarizing plate having a cellulose ester film, wherein the film laminate for a polarizing plate is crushed or cut, treated with an aqueous solution, dried, and subjected to electrostatic separation. A method for recovering a cellulose ester, comprising separating a cellulose ester film from other films by an apparatus, and further dissolving and purifying the film with an organic solvent having a dissolving ability for the cellulose ester. 4. The method for recovering a cellulose ester according to claim 1, wherein the polarizing plate film laminate has at least a surface protective film as a film other than the cellulose ester film. 5. The method for recovering a cellulose ester according to claim 1, wherein the electrostatic separation device is based on triboelectric charging. 6. A cellulose ester recovered by the method according to any one of claims 1 to 5. 7. A cellulose ester film formed by a solution casting method using the dope obtained by recycling the cellulose ester according to claim 6.