JPH04350856A - Method for recovering cellulose plastic - Google Patents

Abstract

PURPOSE:To recover and regenerate cellulose plastics in a short period of time from molded products of cellulose plastics as the base material to such degree of purity as high as that the regenerated plastics can be reused by treating the molded product with an aq. soln. containing manganese compd. and a halogen oxide compd. and then removing the manganese compd. adhering to the molded product from the molded product. CONSTITUTION:Cellulose plastic is recovered from a molded product of cellulose having such a structure that a surface layer is provided on a plastic base body comprising a lower fatty acid ester of cellulose. First, the molded product of cellulose is treated with an aq. soln. containing a manganese compd. and a halogen oxide compd. In this process, impurities in the product is forcedly oxidized by the synergestic effect of the manganese compd. and the halogen oxide compd. Then the manganese compd. adhering to the product is removed from the product. This treatment is preferably and easily performed by adding a reducing agent to the treating liquid containing a manganese compd. and then using this treating liquid to reduce the manganese compd.

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 cellulose plastic from molded articles based on cellulose plastic. In particular, the present invention relates to a method for recovering lower fatty acid esters of cellulose from molded articles containing nitrocellulose and plastics based on lower fatty acid esters of cellulose.

0002

BACKGROUND OF THE INVENTION In recent years, plastics have become widely used, and as a result, there has been a demand for the development of techniques for collecting and processing used plastics. On the other hand, the use of biodegradable plastics is also being considered, but biodegradable plastics have problems of increased production costs and deterioration in physical and chemical strength.

[0003] In general plastic recovery processing, consideration must be given to the sorting of various miscellaneous plastics, the selection of processing methods corresponding to each type of plastic, and the reduction of processing costs.

By the way, plastics are also used in the photographic industry. Among plastics, cellulose plastics, which have excellent optical properties and physical strength, are frequently used as supports for photographic films. In recent years, cellulose plastics have also been used in optical materials such as polarizing films.

Cellulose plastics are plastics based on cellulose derivatives such as cellulose esters and cellulose ethers. In the old days, plastics based on nitrocellulose, that is, celluloid, were representative. However, because celluloid is flammable and combustible, it is rarely used anymore. Currently, lower fatty acid esters of cellulose, which have excellent flame resistance, are mainly used instead. Since plastics based on lower fatty acid esters of cellulose have high added value, there is a demand for the development of recovery processing technology from an economic standpoint.

Photographic films, such as general black and white films, general color films, and motion picture films, are provided with an undercoat layer, a photosensitive layer (silver halide emulsion layer), an image layer, and a protective layer on a support. There is. The subbing layer typically includes a polymer such as nitrocellulose or polyacrylate. This polymer has the function of increasing the compatibility between the support and the photosensitive layer or image layer. Because of this function, the polymer firmly adheres to or penetrates into the support, which becomes an obstacle in the process of recovering lower fatty acid esters of cellulose contained in the support.

[0007] In a method for recovering lower fatty acid esters of cellulose from photographic film, a treatment for removing polymers such as nitrocellulose is described in US Pat.
88614, British Patent No. 1087038, and Research Disclosure RD-12629 and RD-19634. The treatment described in US Pat. No. 2,688,614 uses an acidic treatment solution containing potassium permanganate. British patent number 1
In the treatment described in No. 087038, an alkaline treatment solution containing an oxidizing agent (eg, permanganate, persulfate) is used. The process described in RD-12629 uses persulfates as oxidizing agents. In the treatment described in RD-19634, perborate is used as an oxidizing agent.

[0008]

[Problem to be Solved by the Invention] When the present inventor tried the recovery methods described in each of the above-mentioned documents, there were problems with the quality of the recovered plastic, processing time, and recovery cost, and the results were satisfactory. was not obtained.

[0009] An object of the present invention is to provide a method for recovering and recycling cellulose plastic from a molded article based on cellulose plastic to such a high degree of purity that it can be reused in a short processing time.

Another object of the present invention is to provide a method for recovering lower fatty acid esters of cellulose from a photographic film in which an undercoat layer is provided on a support made of lower fatty acid esters of cellulose to such a high purity that it can be reused. It is to provide.

[0011]

[Means for Solving the Problems] The object of the present invention is to provide a cellulose plastic molded article (hereinafter simply referred to as a cellulose plastic molded article) in which a surface layer is provided on a plastic based on a lower fatty acid ester of cellulose. This was achieved by a method for recovering cellulose plastic, which includes a step of treating the molded article with an aqueous liquid containing a manganese compound and a halogen oxide compound; and a step of subsequently removing the manganese compound adhering to the molded article from the molded article. The aqueous liquid containing the manganese compound and halogen oxide compound is weakly acidic or neutral, that is, has a pH of 5.0 to 8.0.
Preferably it is 0.

[0012] Through research conducted by the present inventors, it has been found that when a manganese compound and a halogen oxide compound are applied to a cellulose plastic molded article, highly pure plastic can be recovered in a very short time. Manganese compounds and halogen oxide compounds act synergistically to strongly oxidize and decompose polymers such as nitrocellulose, which have been an obstacle in the recovery process. Therefore, in the recovery method of the present invention, a significantly more significant effect can be obtained compared to the case where a manganese compound and a halogen oxide compound are used alone.

However, as the present inventor conducted further research, it was found that manganese compounds (including both residual compounds and compounds produced by the treatment) adhere to plastics during the above treatment process. In recycling cellulose plastic, the cellulose plastic is dissolved in a suitable solvent to form a dope. The attached manganese compounds cause the dope to become cloudy and colored. Therefore, a step of removing the manganese compound from the plastic is added after the above treatment step. This allows the method of the invention to recover plastics of very high quality.

The cellulose plastic recovery method of the present invention is preferably carried out in the following manner.

(1) A cellulose plastic molded article has a surface layer containing a polymer on a plastic based on a lower fatty acid ester of cellulose. In particular, the molded product of cellulose plastic is a photographic film in which a surface layer (undercoat layer) containing a polymer is provided on a support made of cellulose plastic.

(2) The lower fatty acid ester of cellulose is cellulose acetate (preferably cellulose triacetate).

(3) The molded article has a surface layer containing nitrocellulose on a plastic based on a lower fatty acid ester of cellulose.

(4) The cellulose plastic molded product is cut into chips of 1 mm to 10 cm square, and the chips are collected.

(5) Cellulose plastic molded product (
Preferably, the above chip (hereinafter the same) is immersed in an aqueous treatment solution containing a manganese compound, and then treated by adding an oxidized halogen compound (preferably an aqueous solution thereof) to the treatment solution. In this case, at the stage of adding the halogen oxide compound, the pH is adjusted to 5.0 to 8.0 as necessary.

(6) The pH value of the treatment liquid is 6.0 to 7.
．． It is 8.

(7) The manganese compound is permanganate.

(8) The treatment liquid contains 0.00 manganese compound.
Contains 1 mol to 0.1 mol.

(9) The oxidized halogen compound is hypochlorite or hypobromite.

(10) The treatment liquid contains an oxidized halogen compound in an active halogen content of 0.05% to 10%.

(11) The processing temperature is room temperature to 95°C.

(12) Processing time is 1 minute to 60 minutes.

(13) A step of adding a reducing agent to the treatment solution containing the manganese compound to reduce the manganese compound, thereby removing the manganese compound.

(14) Hydrogen peroxide (usually an aqueous solution) is used as the reducing agent. Hydrogen peroxide is preferably added to the above-mentioned treatment liquid under conditions of pH 5.0 or less. Hydrogen peroxide is preferably added to the treatment solution in an amount of 0.1 to 5%. Note that hydrogen peroxide also has a bleaching effect.

(15) The treatment liquid contains a surfactant.

(16) In addition to the treatment of the present invention, the following treatment steps or drying treatment may be performed. Note that after the treatment of the present invention and the following treatment, it is preferable to perform a treatment of washing the molded article with water.

"Swelling treatment" The molded product is treated with an alkaline aqueous solution (
The molded product is swollen by immersion in an acidic aqueous solution (pH 7 to 13) or an acidic aqueous solution (pH 2 to 7). Preferably, an alkaline aqueous solution is used.

"Gelatin Layer Removal Treatment" When the molded article is provided with a gelatin-containing layer such as a photosensitive layer in a photographic film, the molded article is treated with protease.

"Bleaching treatment" The molded article is bleached by treating it with peroxide.

"Cellulase treatment" By immersing a cellulose plastic molded article in an aqueous solution of cellulase, impurities generated by detachment of the derivative groups of the cellulose derivative are decomposed and removed.

Next, the present invention will be explained in detail.

As mentioned above, the cellulose plastic in the present invention is a plastic based on a lower fatty acid ester of cellulose. Lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 4 or less. Specific examples of lower fatty acid esters of cellulose include cellulose acetate and cellulose butyrate. Cellulose acetate includes mono-, di- and triacetates. Cellulose triacetate is commonly used in photographic film.

[0037] In this specification, molded products include not only finished products but also semi-finished products. For example, a so-called film base (having an undercoat layer provided on a support), which is a semi-finished product in the manufacturing process of photographic film, is also included in the molded article.

[0038] In the recovery method of the present invention, the cellulose plastic molded article is provided with a surface layer on a plastic based on a lower fatty acid ester of cellulose. The method of the invention is particularly effective when the surface layer comprises a polymer, especially nitrocellulose. As previously mentioned,
In photographic films, an undercoat layer (surface layer) containing a polymer such as nitrocellulose or polyacrylate is usually provided on a support.

When carrying out the recovery method of the present invention, it is preferable that the cellulose plastic molded product is cut into chips of 1 mm to 10 cm square, and the chips are subjected to the recovery process.

The recovery method of the present invention includes the steps of treating a cellulose plastic molded article as described above with an aqueous liquid containing a manganese compound and a halogen oxide compound, and removing the manganese compound adhering to the molded article from the molded article. Characterized by process. The aqueous liquid containing the manganese compound and halogen oxide compound preferably has a pH of 5.0 to 8.0.

[0041] The process of treating the molded article with an aqueous liquid containing a manganese compound and a halogen oxide compound is preferably carried out by immersing the molded article in the aqueous liquid because it is easiest. This process has the following three processing procedures. (I) A cellulose plastic molded article is treated by immersing it in an aqueous treatment solution containing a manganese compound, and then adding an oxidized halogen compound (preferably an aqueous solution thereof) to the treatment solution. In this case, at the stage of adding the halogen oxide compound, the pH is adjusted to 5.0 to 8.0 as necessary. (II) A cellulose plastic molded article is treated by immersing it in an aqueous treatment solution containing an oxidized halogen compound, and then adding a manganese compound (preferably an aqueous solution thereof) to the treatment solution. In this case, at the stage of adding the manganese compound, the pH is adjusted to 5.0 to 8.0 as necessary. (III) An aqueous treatment solution containing a halogen oxide compound and a manganese compound is prepared, and the pH is adjusted to 5.0 to 8.0 as necessary. A cellulose plastic molded product is immersed in the treatment solution.

[0042] Any of the above procedures can be implemented. Particularly preferred is procedure (I).

As shown in the above processing procedure, the p of the processing solution is
The H value is 5.0 to 8.0 when all of the molded article, manganese compound, and halogen oxide compound are present in the treatment solution.
It is preferable to adjust it to 0. Note that it is preferable to adjust the pH values of the liquid containing the manganese compound and the liquid containing the oxidized halogen compound in advance through a preliminary experiment or the like, so that a predetermined pH value can be achieved simply by mixing the two.

The pH value of the treatment liquid is more preferably 6.0 to 7.8, particularly preferably 6.5 to 7.8.

The manganese compound used in the present invention is preferably water-soluble. The valence of manganese may be any of II, IV and VII. Permanganic acid and its salts are preferred. As salts, preference is given to alkali metal salts, especially sodium and potassium salts. Preferably, the treatment liquid contains 0.001 mol to 0.1 mol of a manganese compound. The manganese compound is preferably used as an aqueous solution, particularly preferably as an acidic aqueous solution (pH 2 to 6).

[0046] The halogen oxide compound used in the present invention is:
Refers to acids consisting of oxygen and halogens and their salts. The halogen is preferably chlorine or bromine. Examples of acids consisting of oxygen and halogens include chlorine dioxide, chlorous acid,
Mention may be made of hypochlorous acid, bromine dioxide, bromic acid and hypobromous acid. As salts, preference is given to the alkali metal salts of these acids, especially the sodium and potassium salts. Particularly preferred are hypochlorites and hypobromites. The halogen oxide compound is preferably used as an aqueous solution, particularly preferably as an alkaline aqueous solution. The treatment liquid preferably contains an oxidized halogen compound in an active halogen content of 0.05% to 10%, particularly preferably 0.1 to 1%. The halogen oxide compound is preferably used as an approximately 10% aqueous solution and diluted to the above concentration by mixing it with a solution containing a manganese compound to prepare a treatment solution.

The step of treating the molded article with an aqueous liquid containing a manganese compound and a halogen oxide compound is preferably carried out in a closed container shielded from the working chamber. As the container, it is preferable to use a corrosion-resistant container made of glass, a processed ceramic product, stainless steel, or the like. It is convenient to provide the container with a stirring mechanism.

[0048] The processing temperature in the above steps is generally room temperature to 95°C. The temperature is preferably 35°C to 95°C, more preferably 50°C to 85°C,
Most preferably the temperature is between 70°C and 85°C. The treatment time is preferably 1 minute to 60 minutes, and preferably 15 minutes to 4 minutes.
Particularly preferred is 5 minutes. Note that the specific processing time is determined depending on the processing temperature. That is, when the treatment temperature is high, the reaction is completed in a short treatment time.

As described above, when a cellulose plastic molded article is treated with an aqueous liquid containing a manganese compound and a halogen oxide compound, the manganese compound and the halogen oxide compound act synergistically, and the impurities contained in the molded article (e.g. , polymers such as nitrocellulose contained in the surface layer) are strongly oxidized and decomposed.

[0050] The manganese compound oxidizes the molded article containing impurities, resulting in the deposition of manganese oxide. On the other hand, the oxidized halogen compound oxidizes the molded article and simultaneously oxidizes the manganese salt. Due to this strong oxidation effect, the pH of the processing solution
Values typically fall between 3.5 and 5.0.

Next, in the recovery method of the present invention, a process is performed to remove the manganese compound adhering to the molded product from the molded product. In this treatment, it is easiest and preferable to add a reducing agent to the treatment solution containing the manganese compound to reduce the manganese compound, thereby removing the manganese compound. By adding a reducing agent to the treatment solution, manganese compounds are reduced to Mn2+ ions, and halogen oxide compounds are reduced to halogen ions, so that manganese and halogen can be easily removed from the molded article. Furthermore, since the processing liquid that had a strong oxidizing effect is inactivated by the reducing agent, subsequent processing can be carried out safely. Furthermore, when enzymes (cellulase, etc.) are used in the subsequent treatment, it is necessary to use a reducing agent to prevent the enzymes from being inactivated by the strong oxidation effect of the remaining treatment solution.

[0052] Hydrogen peroxide is preferred as the reducing agent. Hydrogen peroxide is preferably added to the above-mentioned treatment liquid under conditions of pH 5.0 or less. Hydrogen peroxide is preferably added in the form of an aqueous solution to the treatment liquid in an amount of 0.1 to 5%. Hydrogen peroxide concentration in the treatment solution is 0.3% to 1%
It is more preferable that Note that hydrogen peroxide acts as a reducing agent for manganese compounds and halogen oxide compounds, but acts as an oxidizing agent for cellulose plastic, bleaching the cellulose plastic white. Therefore, when hydrogen peroxide is used as a reducing agent, there is no need to provide a particular bleaching step.

A surfactant may be added to the above treatment liquid. As the surfactant, nonionic surfactants are particularly preferred. Examples of nonionic surfactants include polyethylene glycol ether surfactants, specifically polyethylene glycol ethers of higher alcohols, polyethylene glycol ethers of alkylphenols, and polyethylene glycol ethers of sorbitan esters. The surfactant can be added to the treatment liquid in an amount of 0.001 to 5% by weight.

In the cellulose plastic recovery method of the present invention, in addition to the treatments described above, swelling treatment, gelatin layer removal treatment, bleaching treatment, cellulase treatment, drying treatment, etc. can be carried out. Each process will be explained below. When carrying out a plurality of treatment steps, it is preferable to carry out them in the following order. The treatment using the manganese compound and halogen oxide compound of the present invention is preferably carried out after the gelatin layer removal treatment. Note that it is preferable to perform a water washing treatment after each treatment step. In the water washing treatment, it is preferable to use warm water.

"Swelling Treatment" Alkali or acid treatment can be carried out for the purpose of swelling or softening the molded article. For alkaline or acid treatment, molded products are treated with an alkaline aqueous solution (pH 7 to 13) or an acidic aqueous solution (pH 2 to 7).
It is carried out by immersing it in pH 2-4 or pH 8-1
It is preferable to treat the cellulose plastic at a relatively low or relatively high pH, such as pH 3, for a short time to allow the acid or alkali to act on the surface of the cellulose plastic. Particular preference is given to using an alkaline aqueous solution.

[0056] The swelling treatment is carried out at room temperature to 70°C, especially at 30°C.
It is preferable to carry out the reaction at a temperature of 10 to 100 minutes at a temperature of 60° C. to 60° C. while stirring. This treatment swells or softens the surface layer provided on the molded article, such as the photosensitive layer, intermediate layer, undercoat layer, and back layer of a photographic film.

Examples of alkalis used in the alkaline aqueous solution include sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate and sodium hydroxide. The pH of the alkaline aqueous solution is preferably 8 to 13, particularly preferably 8 to 12. Preferably, the alkaline aqueous solution contains a surfactant. As the surfactant, nonionic surfactants are particularly preferred. Examples of the nonionic surfactant are the same as the treatment liquid containing the manganese compound and the halogen oxide compound described above. Surfactant: 0.001 to 5% by weight
It is preferable that the content of the alkaline aqueous solution be within the following range.

"Gelatin Layer Removal Treatment" When the molded article is provided with a gelatin-containing layer such as a photosensitive layer in a photographic film, the molded article is treated with protease. In addition,
If the surface of the molded product is contaminated with oil or fat, treat it with lipase in the same way.

[0059] There are no particular restrictions on the protease. Protease is usually prepared in an aqueous solution (0.001% by weight to 20% by weight).
(% by weight). The pH of the aqueous solution is preferably adjusted to the optimum pH for the protease. It is preferable that the protease aqueous solution also contains a surfactant (approximately 0.001 to 5% by weight).

[0060] The gelatin layer removal treatment is carried out at room temperature to 70°C.
In particular, it is preferable to carry out the reaction at a temperature of 30° C. to 60° C. for 10 minutes to 200 minutes while stirring.

"Bleaching treatment" The molded article is bleached by treating it with peroxide. Examples of peroxides include hydrogen peroxide and potassium permanganate. When using hydrogen peroxide, usually hydrogen peroxide solution (1 to 20% by weight)
Use as.

Bleaching treatment is carried out at room temperature to 90°C, especially at 70°C.
Preferably, the reaction is carried out at a temperature of 90°C to 90°C for 30 minutes to 150 minutes while stirring.

"Cellulase Treatment" The cellulase treatment is preferably carried out by immersing the cellulose plastic molded article in an aqueous solution of cellulase. The concentration of cellulose in aqueous solution is 0.01g to 10g/100
Preferably it is ml. Further, the pH of the aqueous solution is preferably adjusted to 2 to 8. The processing temperature is generally 2
Preferably from 0°C to 70°C, preferably from 30°C to 6°C
More preferably, the temperature is 0°C. It is preferable to stir after dipping. It is preferable to process for 10 minutes or more. The preferred treatment time is 10 minutes to 90 minutes, more preferably 10 minutes to 60 minutes.

[0064] The cellulase aqueous solution preferably contains a surfactant. Examples of surfactants and amounts used are:
This is the same as in the case of the treatment liquid containing the manganese compound and the halogen oxide compound described above. Cellulases are combined with other degrading enzymes (such as proteases, amylases and lipases)
, especially in combination with proteases. The conditions for using protease are almost the same as those used in the gelatin layer removal treatment described above.

"Drying process" The drying process is carried out at 50°C to 15°C.
It can be carried out by conventional methods at a temperature of 0°C, preferably 80°C to 125°C.

The recovery method of the present invention can be widely applied to cellulose plastic molded products used in various fields such as photographic films and polarizing films.

Quality inspection of recycled chips of recovered cellulose plastic, such as cellulose acetate, is carried out by completely dissolving the chips in an organic solvent used as a film-forming dope (for example, a mixed solvent of methylene chloride and methanol (9:1)). It can be evaluated by preparing a dope and inspecting the spectral transmittance of the dope and the presence of cloudiness or gel-like substances. According to the present invention, it is possible to recover high-quality chips in which no insoluble matter is observed by such an evaluation method. Therefore,
The cellulose derivatives recovered according to the present invention can be used in the production of cellulose plastic molded products such as photographic films, as well as new raw materials.

Next, embodiments of the present invention will be described.

[0069]

【Example】

[Example 1] Used color positive film (made by Eastman Kodak Company, in which an undercoat layer containing nitrocellulose is provided on a base film mainly made of cellulose triacetate) is 3c
It was cut into m square chips and used.

First step (gelatin layer removal treatment) 0.20 g of sodium carbonate and polyethylene glycol ether of higher alcohol (Emulgen 106, manufactured by Kao Corporation) 0
．． 50 g of chips were immersed in 150 ml of an aqueous solution prepared by dissolving 0.5 g in water and stirred at about 55° C. for 10 minutes. moreover,
Add 3 g of highly alkaline protease aqueous solution and
Stirred at 0°C for 40 minutes. The chips were taken out from the aqueous solution and drained, then immersed in 150 ml of an aqueous solution in which 0.20 g of sodium carbonate was dissolved in water, and stirred at about 70° C. for 20 minutes. The chips were rinsed with warm water.

Second step (treatment of the present invention) 8 ml of a 1% by weight sulfuric acid aqueous solution was diluted with 120 ml of water, the chip was immersed in this, and immediately 2 ml of a 0.2 M aqueous solution of potassium permanganate was added and stirred. 4 ml of an aqueous solution of sodium hypochlorite (active chlorine content: 10%) was added, the pH was adjusted to 7.0 using sulfuric acid, and the mixture was stirred at 80° C. for 20 minutes. Next, 5 ml of hydrogen peroxide (35%) was added and stirred for 10 minutes. Thereafter, the chips were washed with water.

Third step (cellulase treatment) Cellulase (
0.3 g of Cellulase Daiwa (prototype produced by Daiwa Kasei Co., Ltd.) was added to an acetic acid/sodium acetate 0.02N buffer solution (pH 4.
50) Added to 150ml. The treated chips were immersed in this, and 0.04 g of higher alcohol polyethylene glycol ether and 0.02 g of sodium nonylbenzenesulfonate were added, and the mixture was heated at 45°C to 50°C.
The mixture was stirred for 40 minutes. The treated chips were washed with water.

Fourth step (drying treatment) After washing the treated chip with water, the water was immediately drained and dried under hot air at about 105° C. for about 2 hours to obtain a regenerated chip sample.

[Example 2] A recycled chip sample was obtained in the same manner as in Example 1 except that the third step was omitted.

[Comparative Example 1] A chip sample for comparison was obtained in the same manner as in Example 1 except that the second and third steps were omitted.

[Comparative Example 2] A chip sample for comparison was obtained in the same manner as in Example 1 except that the addition of potassium permanganate was omitted in the second step.

[Comparative Example 3] A chip sample for comparison was obtained in the same manner as in Example 1 except that the addition of sodium hypochlorite was omitted in the second step.

The relationships among the above Examples 1 and 2 and Comparative Examples 1, 2 and 3 are shown in Table 1 below.

[0079]

[Table 1]

Evaluation of Chip Samples 10 g of each of the chip samples obtained in Examples 1, 2, Comparative Examples 1, 2, and 3 were added to 57 g of methylene chloride:methanol (9:1) mixed solvent, and the mixture was heated while rotating the container. It took 4 hours to dissolve. The dope solution was evaluated by visual observation. The results are shown in Table 2.

[0081]

[Table 2]

Next, a comparative experiment was carried out using sodium hypobromite instead of sodium hypochlorite, and results similar to those obtained when sodium hypochlorite was used as described above were obtained.

[Example 3] Used color positive film for projection (in which an undercoat layer, an image layer, and a protective layer are provided on a base film mainly made of cellulose triacetate, manufactured by Fuji Photo Film Co., Ltd.) ), about 0
．． It was cut into chips of 5 to 3 cm square and used.

First step (gelatin layer removal treatment) 0.20 g of sodium carbonate and polyethylene glycol ether of higher alcohol (Emulgen 106, manufactured by Kao Corporation) 0
．． 50 g of the chip was immersed in 150 ml of an aqueous solution prepared by dissolving 0.5 g of 0.05 g in water and stirred at about 55° C. for 5 minutes. Furthermore, 0.08 g of an aqueous solution of alkaline protease was added, and the mixture was stirred at about 50° C. for 20 minutes. After removing the chips from the aqueous solution and draining the water, add 150% of the above aqueous solution of polyethylene glycol ether of sodium carbonate and higher alcohol.
ml and stirred in the same manner as above. Furthermore, add 0.08 g of alkaline protease aqueous solution and
Stirred at 0°C for 20 minutes. After the chips were taken out of the aqueous solution and drained, they were immersed in 150 ml of an aqueous solution in which 1.5 g of sodium carbonate was dissolved in water, and stirred at about 70° C. for 20 minutes. The chips were rinsed with warm water.

Second step (treatment of the present invention) 4 ml of a 1% by weight sulfuric acid aqueous solution was diluted with 135 ml of water, the chip was immersed in this, and immediately 0.8 ml of a 0.2 M aqueous solution of potassium permanganate was added and stirred. Thereafter, 4 ml of an aqueous solution of sodium hypochlorite (active chlorine content 10%) was added, the pH was adjusted to 7.4 using sulfuric acid, and the mixture was stirred at 80° C. for 20 minutes. Next, 3 ml of hydrogen peroxide (35%) was added and stirred for 5 minutes. The chips were washed with water. When washing chips with water,
One wash treatment with a 0.1% aqueous solution of sodium sulfite was performed.

The third step (cellulase treatment) and fourth step (drying treatment) were carried out in the same manner as in Example 1 to obtain a regenerated chip sample. Yield was 45g (90%).

[Example 4] A recycled chip sample was obtained in the same manner as in Example 3 except that the third step was omitted.

[Comparative Example 4] A comparative chip sample was prepared in the same manner as in Example 3, except that the addition of potassium permanganate and sodium hypochlorite was omitted in the second step, and the third step was omitted. Obtained.

[Comparative Example 5] A comparative chip sample was obtained in the same manner as in Example 3, except that the addition of potassium permanganate was omitted in the second step.

[Comparative Example 6] A chip sample for comparison was obtained in the same manner as in Example 3 except that the addition of sodium hypochlorite was omitted in the second step.

[Comparative Example 7] A chip sample for comparison was obtained in the same manner as in Example 3 except that the addition of hydrogen peroxide was omitted in the second step.

The relationships among the above Examples 3 and 4 and Comparative Examples 4, 5, 6 and 7 are shown in Table 3 below.

[0093]

[Table 3]

Evaluation of Chip Samples 10 g each of the chip samples obtained in Examples 3 and 4 and Comparative Examples 4, 5, 6, and 7 were added to 57 g of a methylene chloride:methanol (9:1) mixed solvent, and the container was rotated. It took about 4 hours to dissolve the mixture. The dope solution was evaluated by visual observation. The results are shown in Table 4.

[0095]

[Table 4]

In Comparative Example 7 in which hydrogen peroxide was not used, chlorine odor and brown precipitates were observed in the chips. Furthermore, in Comparative Example 7, most of the cellulase was inactivated in the third step.

[0097]

Effects of the Invention: The method for recovering cellulose plastic based on low-fatty acid cellulose ester of the present invention can recover high-quality plastic in a short period of time even if impurities such as nitrocellulose are present, which impede recovery. It can be recovered and reused at low cost through processing.

Claims (3)

[Claims] Claim 1: A step of treating a cellulose plastic molded article, in which a surface layer is provided on a plastic based on a lower fatty acid ester of cellulose, with an aqueous liquid containing a manganese compound and an oxidized halogen compound; A method for recovering cellulose plastic that includes a step of removing manganese compounds attached to the molded product. 2. The method of claim 1, wherein the step of removing the manganese compound is carried out using hydrogen peroxide. 3. The method according to claim 1, wherein the aqueous liquid containing the manganese compound and the halogen oxide compound has a pH of 5.0 to 8.0.