JP2002018848A - Method for recovering cellulose lower fatty acid ester resin base material, and resin base material recovered thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of recovering a cellulose lower fatty acid ester resin base material in a quality capable of being recycled from a resin waste material such as a polarizing plate or the like. SOLUTION: The method for recovering the cellulose lower fatty acid ester resin base material comprises at least two steps of treating a polarizing plate resin waste material containing a polarizing film of a cellulose lower fatty acid ester as a base material by an aqueous solution containing a peroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cellulose lower fatty acid ester resin base material having a reusable quality from a waste of a polarizing film, a polarizing plate or a liquid crystal display using the cellulose lower fatty acid ester resin base material. The present invention relates to a method for recovering and a resin substrate recovered by this method.

[0002]

2. Description of the Related Art With the development of the information society, display devices of OA equipment are converting from CRTs to liquid crystal display elements.
A polarizing member is used for a so-called LCD device, a liquid crystal cell, a liquid crystal film or a liquid crystal display panel. A polarizing film or a polarizing plate (hereinafter, collectively referred to as a “polarizing plate”) is also used for other display bodies and display devices.
With the increase in the use of polarizing plates, the amount of waste materials has rapidly increased, and this is becoming a social and environmental problem.

[0003] Cellulose resins, particularly cellulose lower fatty acid esters represented by cellulose triacetate, depend on natural resources. Cellulose lower fatty acid esters have excellent optical properties and physical strength, and are therefore used as a support or protective film in a polarizing plate by being attached to the polarizing film. The bonding is performed by applying an acryl adhesive or a pressure-sensitive adhesive on one or both sides of the polarizing plate. In addition, the protective film itself may be undercoated, or the surface thereof may be saponified to improve the bonding and prevent the peeling. Further, a cellulose acetate-based film used as a protective film may be provided with a vapor-deposited layer of magnesium oxide, SiO ₂ , TiO ₂ , ZrO ₂ for improving storage stability. Also, a polyester film or the like is stuck as a release film to protect the adhesive layer,
Silicone or the like may be applied to the surface. PET, cellulose diacetate (DAC), polysulfone film (PSE), polyarylate film (PAR), etc. are bonded to the liquid crystal cell polarizing plate via an adhesive layer.

As a binder for a polarizing film, PVA and its derivatives such as polyvinyl formal and polyvinyl acetal, as well as cellulose films and saponified products thereof are used. Iodine or a dichroic dye is absorbed and adsorbed to these binders, and stretched and arranged in a certain direction to form a polarizing film. In a polarizing plate or a liquid crystal resin waste material, a cellulose lower fatty acid ester resin base material is in an extremely complicated heterogeneous film configuration, and its surface is often subjected to a surface treatment, such as vapor deposition of metal oxide, an adhesive or the like. Since it is coated with an adhesive containing a curing cross-linking agent, it is extremely difficult to remove and remove foreign substances compared to photosensitive materials such as photographic films. is there.

An apparatus for peeling a protective film from a polarizing film is described in JP-A-11-174229, and means for easily separating and removing the components is disclosed in JP-A-09-30494.
7, No. 09-90124 and No. 11-281964. Japanese Patent Application Laid-Open Nos. 10-15429 and 10-15430 disclose a wet type separation apparatus for separating foreign matter.
No. etc. A method for cleaning electronic materials is described in JP-A-11-297657. As described above, there is no description that a cellulose lower fatty acid ester resin base material was recovered from a polarizing plate having a complicated layer structure and a liquid crystal resin waste material and reused.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for recovering a cellulose lower fatty acid ester resin base material from waste resin materials such as a polarizing plate with a reusable quality.

[0007]

The above objects to be solved by the present invention have been attained by the following means. (1) A cellulose lower fatty acid ester resin base material comprising: subjecting a polarizing plate resin waste material containing a polarizing film to a cellulose lower fatty acid ester base material to at least two steps of treatment with an aqueous solution containing a peroxide. Collection method,
(2) A polarizing plate resin comprising a cellulose lower fatty acid ester as a base material and a polarizing film provided on the base material further protected by a protective film made of a cellulose lower fatty acid ester, and an adhesive layer provided on the protective film. Waste material,
(1) After performing at least two-stage treatment with an aqueous solution containing a peroxide, (2) treating with an organic solvent that easily dissolves the adhesive used in the adhesive layer and hardly dissolves the cellulose resin base material. (3) A method of recovering a cellulose lower fatty acid ester resin base material, and (3) a polarizing plate resin waste material comprising a cellulose lower fatty acid ester base material and provided with a polarizing film and an adhesive layer is sequentially (1) peroxidized At least two-stage treatment with an aqueous solution containing a substance, (2)
A cellulose lower fatty acid ester resin group comprising: a step of washing with an aqueous alkali solution containing a halogen oxide compound; and (3) a step of treating the cellulose resin base material with an organic solvent that is easy to dissolve the pressure-sensitive adhesive used and hard to dissolve the cellulose resin base material. (4) (2) or (3), a method of recovering a cellulose lower fatty acid ester resin base material in which the organic solvent is toluene, (5) (1) to (4)
A cellulose lower fatty acid ester resin base material recovered by the recovery method according to any one of the above.

[0008] The recovery method of the present invention is a treatment with an aqueous solution containing a peroxide, or an organic solvent in which the pressure-sensitive adhesive to be used is easily dissolved and the cellulose resin base material is hardly dissolved (hereinafter also referred to as "specific organic solvent"). ) Is performed in a plurality of stages. Therefore, the recovery method of the present invention also includes a recovery method of performing three or more steps in addition to the two steps using an aqueous solution containing a peroxide, and a step of washing three or more steps in addition to the two steps with a specific organic solvent. Including.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The waste material of a polarizing plate resin includes an intermediate product, a defective product, a used product, and the like from a manufacturing process thereof. The present invention is directed to a waste material containing a cellulose lower fatty acid ester resin base material in advance. Preferably, it is a separated waste such as a polarizing plate that has been peeled off from the liquid crystal device material or from which the release film has been peeled off. It is easier to handle in processing if it is crushed in advance to a size of 1 mm to 10 cm square, preferably about 1 mm to 10 mm square before entering the recovery washing step. It is preferable to use wet crushing for this crushing.

[0010] The lower fatty acid of the cellulose lower fatty acid ester base material of the present invention means a fatty acid having 6 or less carbon atoms. Specific examples of the lower fatty acid ester of cellulose include cellulose acetate and cellulose butyrate. Cellulose acetate is mono,
Di, and triacetate. As the cellulose lower fatty acid ester of the present invention, cellulose triacetate is preferred. The present invention can be applied to a resin in which a lower fatty acid ester of cellulose and a lower alkyl ether (often less than 50% by mass) are combined. Before entering into the recovery and washing step, preferably before entering into crushing, it is better to separate the cellulose resin according to the cellulose resin used.

The peroxide of the present invention includes a metal oxide having a polyvalent valence and having an -OO- bond. For example, hydrogen peroxide and its salts, ozone, persulfuric acid and its salts, and perborate can be mentioned. Particularly, hydrogen peroxide and a salt thereof are preferred. The treatment of an aqueous solution containing a peroxide decomposes iodine and a dye used in the polarizing element, and also causes foaming in addition to decomposing and separating the adhesive film, thereby separating the cellulose resin substrate of the present invention from the other. There are features. The concentration of the peroxide used is preferably 1 to 25% by mass, and particularly preferably 5 to 20% by mass, which is higher than that used when recovering cellulose triacetate from general photosensitive materials. The processing temperature is relatively high
0 ° C to 100 ° C is preferable, and more preferably 75 ° C
To 100 ° C. The treatment step is preferably at least a two-stage treatment. Surprisingly, the two-stage treatment remarkably promotes the decomposition bleaching of the polarizing element and the removal of the pressure-sensitive adhesive. The aqueous solution containing hydrogen peroxide is preferably
It is preferable to use under acidic conditions of pH 5 or less or alkaline conditions of pH 8 or more. It is considered that hydrogen peroxide is accompanied by reductive foaming under weakly acidic conditions, and that hydrogen peroxide is accompanied by oxidative foaming under weakly alkaline conditions.

The halogen oxide compound used in the present invention is an oxyacid composed of halogen and oxygen or a salt thereof. For example, hypochlorous acid and its salt, chlorous acid and its salt, perchloric acid and its salt, For example, bromic acid and its salts. Preferred are sodium hypochlorite, potassium hypochlorite and sodium chlorite. The concentration of the active halogen is preferably 0.5 to 10% by mass as an aqueous alkali solution. The aqueous solution is preferably used at pH 8 or higher, preferably 9 or higher, and pH 11 or lower. Processing temperature is 60 ° C to 100 ° C, preferably 75 ° C to 95 ° C
Is preferred. As described in JP-A-05-045837, an amine compound, particularly a compound having an amino group and a sulfo group, may be added to the aqueous alkali solution containing a halogen oxide compound, as described in JP-A-05-045837. it can.

In the treatment with an aqueous solution of a peroxide or a halogen oxide compound, a reaction accelerator described in Japanese Patent Application No. 11-197497 can be used in combination. Examples of the reaction accelerator include a transition metal compound such as sodium tungstate for an aqueous solution containing a peroxide, and an alkali aqueous solution containing sodium hypochlorite. And bromide or iodide such as potassium bromide and sodium iodide. The treatment with an alkali aqueous solution of a halogen oxide compound is useful for removing a cross-linkable pressure-sensitive adhesive, an adhesive, and an undercoat layer from a cellulose resin substrate or decomposing and dissolving and removing a pressure-sensitive adhesive layer. The treatment step using the organic solvent of the present invention is described in
It is completely different from the aqueous solution of a water-soluble organic solvent described in the specification of -281686, and is for dissolving and removing a water-insoluble adhesive foreign substance or a decomposition product thereof. Therefore, as the organic solvent to be used, a solvent which easily dissolves the pressure-sensitive adhesive, and which easily dissolves its decomposed product similarly to the pressure-sensitive adhesive, and hardly dissolves the cellulose lower fatty acid ester resin, may be used. Preferred are oil-soluble organic solvents free of oil. Aromatic solvents are generally preferred, although different depending on the adhesive used, and for example, benzene or benzenes substituted with a lower alkyl group (an alkyl group having 4 or less carbon atoms) is more preferable.
Toluene is particularly preferred. Also, an alkyl ketone solvent having 5 to 7 carbon atoms is preferable, and hexanone is particularly preferable. A small amount of an alcohol-based solvent such as 3
0 mass% or less can be mixed and used.

By performing the treatment with the organic solvent of the present invention at least in two steps, the adhesive substance adhering to the cellulose resin substrate can be more efficiently peeled off, and the mixed adhesive substance and its decomposed product and its microfloat The substance can be dissolved and removed. In the case of two or more stages, the processing temperature and time of the former stage (first stage) and the latter stage (second stage or subsequent stages) or each stage, and the organic solvent to be used can be changed as necessary. The processing temperature is preferably from room temperature to about 60 ° C. 5
When the temperature is 0 ° C. or more, particularly more than 60 ° C., additives such as a plasticizer and a UV absorber previously contained in the cellulose resin substrate tend to elute into the organic solvent. If necessary, an appropriate amount of a plasticizer or a UV absorber can be added to an organic solvent in advance to suppress elution. It is preferable to add the plasticizer or the like to the organic solvent used in the subsequent (second or subsequent) treatment. Foreign matter separated during the treatment step can be separated by a specific gravity separation method, if necessary. The combined use of the hydrocyclone method and the specific gravity difference method is preferred. The specific gravity of the lower fatty acid ester base material of cellulose is about 1.1 to 1.3.

[0015] An aqueous solution of peroxide can be added to the final processing step. In this case, it is effective for decomposing and removing a small amount of the organic solvent used in the previous stage.

When the surface of the cellulose lower fatty acid ester resin substrate has undergone saponification, a corresponding treatment can be performed. That is, when the surface portion is saponified by treatment with an aqueous solution containing a peroxide or an alkaline aqueous solution, it is preferable to perform treatment with an aqueous solution of cellulase. The concentration of the cellulase is preferably 0.01 to 10 g / l, and the pH of the aqueous solution is adjusted to a predetermined value between 2 and 8 to adjust to the activity of the cellulase, and the treatment temperature is preferably normal temperature to 70 ° C. The washed substrate is dried at a temperature between 50 ° C and 150 ° C, preferably between 80 ° C and 125 ° C. The regenerated chips of the cellulose lower fatty acid ester resin which have been washed and dried for recovery can be evaluated for quality by external visual inspection and inspection in a dope state shown below. The regenerated chip is dissolved in an organic solvent (for example, a mixed solvent of methylene chloride and methanol at a mass ratio of 9: 1) used for the film-forming dope to adjust the dope (for example, 15% by mass). By examining the spectral transmittance of the dope, the presence or absence of cloudy or gel-like substances, or the presence or absence of suspended matter, the utility of the recovered resin can be evaluated. A regenerated chip obtained by the recovery method of the present invention, a cellulose resin substrate re-formed using a chip evaluated as good was stored under high-temperature and high-humidity conditions, and when compared with virgin resin, it was completely stable. Met.

[0017]

EXAMPLES Examples of the present invention will be specifically described. However, it is not limited to this.

(Example 1) A cellulose triacetate (TAC) resin base material was recovered from a waste material of a polarizing film.
A TAC film is provided as a protective film on both surfaces of the polarizing film, and an adhesive layer is coated thereon. The polarizing film was a mixture of a binder PVA containing iodine and a PVA containing a dichroic dye. The waste material (semi-finished product) of this polarizing film was crushed into chips of 0.5 to 3 cm square by wet cutting.

When a peeling film was provided, the film was peeled before wet cutting. At a solid-to-liquid weight ratio of 1: 1, the cut chips were put into the treatment liquid, and a stirring treatment was performed. [I Polarizing Film Removal Treatment; Cleaning with Hydrogen Peroxide-Containing Solution] [First-Step Treatment with Hydrogen Peroxide Solution] Hydrogen peroxide (3
10 to 17.5% by mass (5% by mass)
4% by mass) of an aqueous solution containing 0.06% by mass of a polyoxyethylene derivative (Emulgen A-500, manufactured by Kao Corporation) while stirring at 90 ° C.
Treated for 0 minutes. Subsequently, the solution was drained and post-stage treatment was performed. [Second Stage Treatment with Hydrogen Peroxide Solution] An aqueous solution having the same composition as that used in the first stage treatment with hydrogen peroxide and a polyoxyethylene derivative is used at a temperature of 90 ° C. for 30 minutes to 6 minutes.
Treated for 0 minutes. After the solution was drained and washed with water, the following treatment was performed. The primary decomposition of the adhesive layer proceeded concurrently with the removal of the TAC film and the removal of the polarizing film. [II Removal of adhesive, peeling off of adhesive layer; treatment with alkaline aqueous solution of hypochlorous acid] Using a 1% by mass aqueous alkaline solution of sodium hypochlorite (active chlorine) at a temperature of 90 ° C with stirring. Treated for 15 minutes. After the liquid was drained and washed with water, the following treatment was performed.

[III Dissolution of the pressure-sensitive adhesive layer and its fine particles, removal of adhesive, etc .; treatment with organic solvent] [First-stage treatment with toluene] Toluene at 50 ° C.
At 60 ° C. for 60 minutes while stirring, drained the solution, and performed the next process. [Second Stage Treatment with Toluene] The same treatment was performed for about 30 minutes using toluene, the liquid was drained, and after washing with water, the following treatment was performed. The adhesive layer on the chip surface, its decomposed foreign substances and the adhesive were completely removed, and the adhesive layer and its decomposed foreign substances floating in the processing solution were dissolved and removed. The reduction in the amount of the plasticizer, UV absorber and the like contained in the resin substrate is larger as the treatment temperature is higher, and is remarkable when the treatment temperature is higher than 50 ° C., for example. This reduction can be suppressed, if necessary, by including an appropriate amount of a plasticizer or a UV absorber in toluene in advance. [IV finishing treatment; washing with a solution containing hydrogen peroxide] An aqueous solution containing 0.03% by mass of sodium alkylbenzenesulfonate in a 10% by mass aqueous solution of hydrogen peroxide was stirred at a temperature of 90 ° C. After washing for 30 minutes while draining the solution, the plate was further washed with water. The remaining organic solvent, a part of the pressure-sensitive adhesive and the treatment chemicals permeating into the substrate were decomposed and removed. [Drying] Drain water and at a temperature of 80 ° C to 125 ° C,
Sample No. of the recovered cleaning chip of the TAC resin substrate dried by the usual method. 1 was obtained. [Quality Evaluation] The quality of the obtained collected chips of the base material was evaluated as follows, and those of acceptable quality could be used without any problem.

(1) External appearance: The degree of coloring was visually observed and compared with a standard sample (virgin resin) and a practically usable comparative sample (slightly yellowish). (2) Dope properties: A sample chip was prepared using a mixed solvent of methylene chloride and methanol at a mass ratio of 9: 1.
A mass% dope was prepared and visually determined. (2-1) Transparency: When the transmittance at 555 nm was in the range of 84 to 93%, it was judged as acceptable since it was equivalent to the standard sample. (2-2) Presence or absence of gel generation: A test was judged to be acceptable if it was equal to or more than the standard sample. (2-3) Presence or absence of foreign matter: A sample was judged to be acceptable if it was equal to or more than the standard sample.

In the sample No. of the present invention, The quality of No. 1 was as follows. (1) Appearance… good (2-1) Transparency… good (2-2) Gel generation… good (2-3) Presence or absence of foreign matter… less than standard sample and “good”

(Comparative Example) The waste of the polarizing film used in Example 1 was similarly cut into chips, and the chips were treated similarly under the conditions shown in Table 1. The quality of the collected chip samples A, B and C was evaluated, and the results shown in Table 1 were obtained. In Table 1, ○ indicates that the test was performed, and X indicates that the test was omitted.

[0024]

[Table 1]

(Example 2) Using the chip for recovery obtained from the waste of the polarizing film used in Example 1, washing for recovery was performed under the conditions shown in Table 2. The first stage treatment of the cleaning with the hydrogen peroxide solution was performed while changing the temperature and the time. Further, the cleaning time was changed with the treatment time with an organic solvent. Others were performed as described in Example 1, and the following results were obtained.

[0026]

[Table 2]

The following can be understood from the above results. (1) The efficiency of removing the polarizing film with the aqueous solution containing hydrogen peroxide is inferior in process efficiency, but it has been found that by performing the two-stage treatment, the cleaning efficiency is improved and particularly preferable results are obtained. did. Of course, the cleaning effect can be further improved by a multi-stage treatment of three or more stages. (2) The removal of the adhesive and the pressure-sensitive adhesive by an organic solvent can be performed in a single step, and by extending the processing time and selecting an organic solvent, the same quality as that of the two-step treatment with toluene can be obtained. Multi-step processing such as step processing is preferred.

[0028]

According to the recovery method of the present invention, the desired lower fatty acid ester base material of cellulose is removed from the waste material of the polarizing plate without accompanying other foreign substances and the quality of the base material is impaired. High quality can be collected without any trouble By performing a two-stage treatment of an aqueous solution containing hydrogen peroxide at a relatively high concentration, the polarizing film can be efficiently peeled and removed. By performing the treatment with an alkaline aqueous solution containing a halogen oxide compound, adhesion or residual The adhesive layer can be completely removed. Furthermore, floating decomposed products and remaining adhesive products can be dissolved and removed by the treatment with the specific organic solvent. By using the treatment with the specific organic solvent and the washing with the peroxide-containing aqueous solution together, the remaining treating agent can be more completely inactivated and removed. The recovered lower fatty acid ester base material of cellulose can be reused as a raw material for a polarizing film or plate. Cellulose resins are obtained from valuable natural resources, and the effect of the present invention is great from the viewpoint of environmental protection.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view schematically illustrating a layer configuration of an example of a polarizing plate resin waste material according to the present invention.

[Explanation of symbols]

Reference Signs List 1 polarizing film 2 cellulose lower fatty acid ester (substrate or protective film) 3 adhesive layer 4 release film (peeling film) 5 surface protective layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Ota 392 Hiromachi, Minamiashigara-shi, Kanagawa Pref. (72) Inventor Nobuyuki Ito 392 Hiromachi, Minamiashigara-shi, Kanagawa Pref. (72) Inventor Akira Nakazawa 392 Hiromachi, Minamiashigara-shi, Kanagawa Pref. F-term (reference) in Panac Industries, Ltd.

Claims (5)

[Claims] 1. A cellulose lower fatty acid ester resin base material, comprising subjecting a polarizing plate resin waste material comprising a cellulose lower fatty acid ester as a base material and including a polarizing film to at least two-stage treatment with an aqueous solution containing a peroxide. Material collection method. 2. A polarized light comprising a cellulose lower fatty acid ester as a base material, a polarizing film provided on the base material further protected by a protective film made of a cellulose lower fatty acid ester, and an adhesive layer provided on the protective film. After the plate resin waste material is subjected to (1) at least two-stage treatment with an aqueous solution containing a peroxide, (2) an organic solvent that easily dissolves the adhesive used in the adhesive layer and hardly dissolves the cellulose resin base material A method for recovering a cellulose lower fatty acid ester resin base material, wherein the base material is treated with a resin. 3. A polarizing plate resin waste material comprising a cellulose lower fatty acid ester as a base material and provided with a polarizing film and an adhesive layer,
In sequence, (1) at least 2
(2) washing with an alkali aqueous solution containing a halogenated oxide compound, and (3) treating with an organic solvent that easily dissolves the adhesive used and hardly dissolves the cellulose resin substrate. A method for recovering a cellulose lower fatty acid ester resin base material, which is characterized by the following. 4. The method for recovering a cellulose lower fatty acid ester resin base material according to claim 2, wherein the organic solvent is toluene. 5. A cellulose lower fatty acid ester resin base material recovered by the recovery method according to any one of claims 1 to 4.