JP3484080B2 - How to recycle paper - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of recycling pulp by making pulp from paper on which an image is formed using an erasable image forming material.

[0002]

2. Description of the Related Art In recent years, as office automation has advanced, the amount of various information has increased remarkably, and the output of information by hard copy has also increased accordingly. Hardcopy output is the most basic means of displaying information,
It has excellent versatility and storability. However, in hard copy output, as the amount of information increases, a large amount of paper is used as a recording medium, which leads to an increase in felling of wood, which is a raw material of paper. Forest resources are very important in terms of maintaining the global environment and suppressing the greenhouse effect of carbon dioxide. For this reason, the cutting of new timber is minimized,
The efficient use of the paper resources that we already have is a major issue.

Conventionally, the reuse (recycling) of paper resources is
It is carried out by treating a paper on which an image forming material is printed with a large amount of a bleaching agent and water, and re-filtering the paper fibers to produce a recycled paper of poor quality. Such a method not only raises the cost of recycled paper, but also causes new environmental pollution associated with the treatment of waste liquid.

On the other hand, the present inventors contain a color-developing compound (leuco dye), a color developer and a decoloring agent compatible with these compounds, and the image is formed in the same manner as an ordinary image-forming material. We are developing an image-forming material that can form an image and can erase an image by treating with heat or a solvent. By using such an erasable image forming material, paper that has been erased and returned to a blank state can be reused over and over again while preventing deterioration of paper quality as much as possible.
can do. Then, since the paper may be recycled when the deterioration of the paper quality due to the reuse becomes remarkable, the utilization efficiency of the paper resources is dramatically improved. In this way, the amount of paper used can be substantially reduced, so that the felling of wood can be minimized. Moreover, the high cost of recycled paper and environmental pollution due to waste liquid treatment, which are problems in the current recycling system, can be avoided as much as possible.

However, a specific method for efficiently recycling the paper on which an image is formed using an erasable image forming material has not been studied so far. Further, when recycling the paper using the erasable image forming material, it is preferable to be able to use the equipment used in the existing recycling system.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to efficiently recycle paper on which an image is formed using an erasable image forming material by utilizing the equipment used in the existing paper recycling system. To provide a way to do it.

[0007]

The method for recycling paper according to the present invention is directed to a paper on which an image is formed using an erasable image-forming material containing a color-developing compound, a developer and a decolorizer,
It is characterized in that pulp is produced by simultaneously performing decoloring and pulping using hot water .

In the method of the present invention, pulp is prepared from paper imaged with an erasable image forming material using equipment (eg, pulper) used in an existing recycling system, Paper can be recycled efficiently, and the pulp produced does not develop color again. At this time, it is preferable that the heating temperature is not lower than the softening point of the resin contained in the image forming material and not higher than 200 ° C. In addition, if the decoloring and pulping are performed at the same time with hot water in the pulper, the recycling efficiency is improved. When hot water is used in the pulper, it is preferable to raise the temperature of the hot water by applying pressure.

Further, the pulp produced by the above method is mixed with the pulp produced by deinking and pulping the paper on which an image is formed by using an ordinary image forming material to prepare recycled paper. If manufactured, a paper-dedicated subsystem using an erasable image forming material can be incorporated into the conventional paper recycling system to recycle the paper as in the conventional case. Further, since the pulp produced from the paper using the erasable image forming material has a high whiteness, the whiteness of the finally obtained recycled paper can be increased.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The erasable image forming material according to the present invention can be used in various forms such as electrophotographic toner, ink for inkjet printers, ink for ink ribbons and ink for writing instruments. Therefore, the erasable image forming material can be used as a substitute for usual toners and inks used in these applications.

The image forming material of the present invention is capable of developing and decoloring by using a color developable compound, a developer and a decolorizer. In the present invention, the color-forming compound is a precursor compound of a dye that forms coloring information such as characters and figures, and the color-developing agent is colored by interaction with the color-forming compound (mainly transfer of electrons). It is a compound that colors a volatile compound. The color-developing compound and the color-developing agent develop color when the interaction between them increases, and decolorize when the interaction between them decreases. The decoloring agent means that when the image-forming material is melted or softened by heating, or when the erasing solvent penetrates into the image-forming material, the decoloring agent is preferentially compatible with the color-developing compound-developing agent. It is a substance that has the effect of reducing interaction and decoloring.

The erasable image-forming material according to the present invention can be erased by heating or contact with an organic solvent or a basic aqueous solution. When the erasable image forming material of the present invention is heated for erasing, the erasing is performed according to the following principle. At room temperature, the state in which the phase of the color-developing compound and the developer and the phase of the decolorizer are phase-separated is close to the equilibrium state. In this case, the color-developing compound and the color-developing agent interact with each other to form a color. From this state, when the composition system is heated to the melting point or higher, the color developer is preferentially dissolved in the fluid decoloring agent and loses the interaction with the color developable compound, so that the decoloring state occurs. When the composition system in the molten state is forcibly solidified by cooling, the decolorizing agent takes in a developer in an amount exceeding the equilibrium solubility, becomes amorphous, and becomes colorless at room temperature. The amorphous composition system is relatively in a non-equilibrium state, but has a sufficiently long life at a temperature below the glass transition point Tg, and easily equilibrates from the amorphous state if Tg is room temperature or higher. It never goes into a state.

Also in the method of bringing the erasable image forming material of the present invention into contact with an organic solvent, erasing can be carried out according to the following principle almost in the same manner as the method by heating. That is, when the image forming material in the color-developed state on the paper is brought into contact with the solvent, the resin swells or partially dissolves the resin such as the binder. As a result, the color developer and the color erasing agent are allowed to move relatively freely, the color developing agent is mixed with the color erasing agent, and the interaction between the color developing agent and the color developing compound is lost, so that the image forming material. Disappears. Then, when the solvent is removed from the paper, the decolorizing agent becomes amorphized in a state where the decoloring agent has taken in an amount exceeding the equilibrium solubility, so that the erasing state of the image forming material is fixed. This erased state is very stable at room temperature.

The method of erasing by heating is the most environmentally friendly method because no waste liquid is produced. The heating method is not particularly limited as long as it does not damage the paper or damage the fibers of the paper. Suitable heating methods include heating with hot air, heating with infrared rays, heating by contact with a heat source,
Heating by contact with hot water can be mentioned. The temperature of the heat treatment is preferably in the range of 200 ° C. or higher above the softening point of the resin such as the binder contained in the image forming material. This is because the paper fibers and the image-forming material are likely to deteriorate when heated at a temperature higher than 200 ° C. In addition,
When heating above 200 ° C., the heating time is preferably within 1 minute.

In the method of decoloring by contact with an organic solvent, the paper may be dipped in a solvent tank, or the organic solvent may be sprayed onto the paper from a nozzle. The treatment with the organic solvent may be performed at room temperature or while heating.

In the present invention, the paper on which the image is formed using the erasable image forming material may be subjected to the erasing by heating or contact with an organic solvent and the pulping in separate steps. , You may go at the same time. When the erasing and the pulping are performed in separate steps, the order of both steps is not limited, and either step may be performed first.

Pulping of paper is performed by agitating the paper in a liquid using a pulper, which is also used in the conventional paper recycling system, to loosen the fibers of the paper.
Pulper is a low-concentration pulper (pulp concentration 5-6%),
It is classified into medium density pulper (pulp density 8 to 12%), high density pulper (pulp density 15% or more), spoiled paper pulper, secondary pulper and secondary disintegrator. The stirring speed is appropriately adjusted depending on the pulper method, paper quality and amount.

At this time, the paper may be pulped while being strongly stirred in hot water to loosen the fibers of the paper. Pressurization is applied to bring the temperature of hot water to 100 ° C or higher. The pressure range is 1 to
It is preferably set to 30 kg / cm ² , and more preferably ² to 10 kg / cm ² .

Alternatively, the paper may be strongly agitated in an organic solvent to loosen the fibers of the paper for pulping. Also in this case, the organic solvent may be heated. In addition, when the organic solvent is heated using an organic solvent having a low boiling point at normal pressure, pressure may be applied. The pressure range is preferably set to ¹ to ²⁰ kg / cm ² , more preferably ² to 10 kg / cm ² .

In the present invention, in order to control the decolored state, the reflection density of paper or pulp is monitored by a detector. The detector may be one that detects the reflection density online, or one that extracts a sample and detects the reflection density offline. If the reflection density does not meet the set value, the paper or pulp is returned to the erasing step.

When the paper is treated with pulper, a basic compound, an anionic or nonionic surfactant, a peroxide, etc. may be added to water, hot water or an organic solvent, if necessary. .

The basic compound is an additive for weakening the action of the color-developing compound and the color developer and enhancing the effect of the decoloring agent, and also for breaking the hydrogen bond which is a factor of bonding between fibers. As a result, the fibers are swollen and the contaminants such as toner scraps and dust taken into the fibers are solubilized. The basic compound is not particularly limited as long as it does not damage the fiber, but alkali such as caustic soda and water glass is preferable. The amount of the basic compound added is preferably adjusted such that the pH of the treatment liquid with pulper is in the range of 7 to 12, preferably 9 to 12, and specifically in the range of 1 to 10%.

The surfactant has a function of peeling off the image forming material attached to the fiber from the fiber. The surfactant has a hydrophilic group and a lipophilic group. Typical lipophilic groups are skeletons of hydrocarbons, alkylbenzenes, higher alcohols, alkylamines, ethylene oxide, propylene oxide, etc., and typical hydrophilic groups are carboxylates, sulfonates, sulfates, phosphates. , Quaternary ammonium salts and the like. The amount of surfactant added is
It is preferably 0.5% or less, more preferably 0.1 to 0.3%.

Hydrogen peroxide is a typical example of a peroxide that functions as a bleaching agent. The amount of peroxide added is
It is preferably 1% or less, more preferably 0.5 to 0.8%.
In the present invention, the pulp produced by decoloring and pulping is preferably washed with water to remove impurities and attached chemicals. The pulp may be squeezed to squeeze out the liquid, or may be dried to a solid state by heating or depressurization.

Pulp made from paper using an erasable image forming material according to the method of the present invention is made by deinking and pulping paper that has been imaged using conventional image forming materials. It is preferable to produce a recycled paper by mixing with the pulp. In this case, both pulps may be mixed in any of a state of being dispersed in water, a state of being pressed and squeezed out of water, or a state of being dried solid, but finally, a state of being dispersed in water. Recycled paper is manufactured by making paper from paper.

By this method, a paper-dedicated subsystem using an erasable image forming material can be incorporated into the conventional paper recycling system to recycle the paper as in the conventional case. Further, since the pulp produced from the paper using the erasable image forming material has a high whiteness, the whiteness of the finally obtained recycled paper can be increased. Further, as the replacement of the ordinary image-forming material with the erasable image-forming material is promoted, the frequency of use of the conventional paper recycling system for producing pulp from the normal image-forming material is reduced, so that the deinking process is accompanied. The problem of environmental pollution can be reduced.

The various components used in the present invention will be described in more detail below. Examples of the color-forming compound used in the present invention include electron-donating organic substances such as leuco auramine, diaryl phthalide, polyaryl carbinol, acyl auramine, aryl auramine, rhodamine B lactam, indoline, spiropyran, and fluoran. To be Specifically, crystal violet lactone (CVL), malachite green lactone, 2-
Anilino-6- (N-cyclohexyl-N-methylamino) -3-methylfluorane, 2-anilino-3-methyl-6- (N-methyl-N-propylamino) fluorane, 3- [4- (4 -Phenylaminophenyl) aminophenyl] amino-6-methyl-7-chlorofluorane, 2-anilino-6- (N-methyl-N-isobutylamino) -3-methylfluorane, 2-anilino-6-
(Dibutylamino) -3-methylfluorane, 3-chloro-6- (cyclohexylamino) fluorane, 2-chloro-6- (diethylamino) fluorane, 7- (N,
N-dibenzylamino) -3- (N, N-diethylamino) fluorane, 3,6-bis (diethylamino) fluorane, γ- (4′-nitroanilino) lactam, 3-
Diethylaminobenzo [a] -fluorane, 3-diethylamino-6-methyl-7-aminofluorane, 3-diethylamino-7-xylidinofluorane, 3- (4-
Diethylamino-2-ethoxyphenyl) -3- (1-
Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3-
(1-Ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino-7-chloroanilinofluorane, 3-diethylamino-7,8-benzofluorane, 3,3-bis (1-n- Butyl-2-methylindol-3-yl) phthalide, 3,6-dimethylethoxyfluorane, 3-diethylamino-6-methoxy-7-
Aminofluorane, DEPM, ATP, ETAC, 2-
(2-chloroanilino) -6-dibutylaminofluorane, crystal violet carbinol, malachite green carbinol, N- (2,3-dichlorophenyl) leuco auramine, N-benzoyl auramine, rhodamine B lactam, N-acetyl aura Min, N-phenyl auramine, 2- (phenyliminoethanedilidene) -3,3-dimethylindoline, N, 3,3-trimethylindolinobenzospiropyran, 8'-methoxy-N, 3,3-trimethylindoline Rinobenzospiropyran, 3-diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-6-benzyloxyfluorane, 1,2-benzo-6-diethylaminofluorane,
3,6-di-p-toluidino-4,5-dimethylfluorane, phenylhydrazide-γ-lactam, 3-amino-5-methylfluorane and the like can be mentioned. These may be used alone or in combination of two or more.
Since a colored state of various colors can be obtained by appropriately selecting a color-developing compound, multi-color compatibility is possible.

As the color developer used in the present invention, phenol, phenol metal salt, carboxylic acid metal salt, benzophenone, sulfonic acid, sulfonic acid salt, phosphoric acid, phosphoric acid metal salt, acidic phosphoric acid ester, acidic phosphoric acid. Acidic compounds such as ester metal salts, phosphorous acid, and metal phosphite salts can be mentioned.

The decoloring agent used in the present invention may be a low molecular weight organic material such as a sterol compound, a cyclic sugar alcohol and its derivative, or a high molecular weight decoloring agent.
Examples of the sterol compound include cholesterol, stegmasterol, pregnenolone, methylandrostenediol, estradiol benzoate, epiandrostene, stenolone, β-sitosterol, pregnenolone acetate, 5,16-pregnadien-3β-ol-20-one, 5α-pregnene. -3β-all-
20-one, 5-pregnene-3β, 17-diol-
20-one 21-acetate, 5-pregnene-3
β, 17-diol-20-one 17-acetate, 5
-Pregnene-3β, 21-diol-20-one 2
1-acetate, 5-pregnene-3β, 17-diol diacetate, locogenin, tigogenin, esmiragenin, hecogenin, diosgenin and the like can be mentioned.
These may be used alone or in combination of two or more.

The decoloring agents also include cholic acid, lithocholic acid, testosterone and cortisone, and their derivatives, which have a very high compatibility with the color developer. Specific examples include cholic acid, cholic acid methyl ester, sodium cholic acid, lithocholic acid, lithocholic acid methyl ester, sodium lithocholic acid, hyodeoxycholic acid, hyodeoxycholic acid methyl ester, testosterone, methyltestosterone, 11α-hydroxymethyl. Testosterone, hydrocortisone, cholesterol methyl carbonate, α-cholestanol may be mentioned. Among these, those having two or more hydroxyl groups are particularly preferable.

As the decoloring agent, a cyclic sugar alcohol and a derivative thereof which are compounds having a high amorphous property and having an action of suppressing phase separation of a composition system (phase separation suppressing agent) can also be mentioned.
Specific examples include D-glucose, D-mannose, D
-Galactose, D-fructose, L-sorbose,
L-rhamnose, L-fucose, D-ribodesource, α
-D-glucose = pentaacetate, acetoglucose, diacetone-D-glucose, D-glucuronic acid,
D-galacturonic acid, D-glucosamine, D-fructosamine, D-isosugaric acid, vitamin C, ertorubic acid,
Examples thereof include trehalose, saccharose, maltose, cellobiose, gentiobiose, lactose, melibiose, raffinose, gentianose, melezitose, stachyose, methyl = α-glucopyranoside, salicin, amygdalin, euxanthic acid, white sala sugar, granulated sugar, and white sugar. One or more of these may be used.

As a decoloring agent, a non-aromatic cyclic compound having a hydroxyl group other than the cyclic sugar alcohol, which is a phase separation inhibitor having a low amorphous property, and a non-aromatic cyclic compound having a 5-membered ring or more, or a derivative of the cyclic sugar alcohol may also be used. Can be mentioned. Specific examples include alicyclic monohydric alcohols such as cyclododecanol, hexahydrosalicylic acid, menthol, isomenthol, neomenthol, neoisomenthol, carbomenthol,
α-carbomenthol, piperitol, α-terpineol, β-terpineol, γ-terpineol, 1-
p-menthen-4-ol, isopulegol, dihydrocarbeol, carveol; alicyclic polyhydric alcohol,
For example, 1,4-cyclohexanediol, 1,2-cyclohexanediol, phloroglucitol, quercitol, inositol, 1,2-cyclododecanediol, quinic acid, 1,4-terpine, 1,8-terpine, pinol hydrate. , Betulin; polycyclic alcohol derivatives such as borneol, isoborneol, adamantanol, norborneol, fenchol, camphor, isosorbide; derivatives of cyclic sugar alcohols such as 1,2: 5,6-diisopropylidene-D- Mannitol is mentioned. One or more of these may be used. The phase separation inhibitor having low amorphousness is used together with the phase separation inhibitor having high amorphousness.

Since the decoloring agent has a polar group in common with the above-mentioned low-molecular decoloring agent and preferably has a high boiling point and is non-volatile, it is a high molecular decoloring agent (polymer or oligomer).
Can also be used. For example, the polymer decolorizer includes a polymer (or oligomer) having a total number of electron-donating groups of more than 15% of the total number of carbon atoms. Examples of the electron donating group include a hydroxyl group, an ether group, an acyl group, a carbonyl group, a hydroxycarbonyl group and a thiol group. Suitable polymer decolorizing agents include cellulose; cellulose derivatives (nitrocellulose, ethyl cellulose,
Acetyl cellulose etc.), polyacrylic acid, polymethacrylic acid, polyacrylate, polymethacrylate, polyacrylamide, polymethacrylamide, polyvinyl ester (polyvinyl acetate etc.), polyether sulfone, polyether ketone, polyamide, polyphenylene sulfide, starch (plant) Carbohydrates produced from) and the like. The polymer decolorizer may be used alone or in combination with a low molecular decolorizer.

The erasable image-forming material of the present invention contains a resin such as a binder or wax in order to fix each of the above components on paper and to retain each component during heat treatment or solvent treatment. May be. The binder resin preferably has a Tg or softening point lower than that of the polymer decoloring agent by 20 ° C. or more, more preferably 50 ° C. or more. Examples of the binder resin include polystyrene, styrene-acrylate copolymer, styrene-methacrylate copolymer, polyester, and epoxy resin. The wax is not particularly limited as long as it is used in ordinary image forming materials.

When the image-forming material of the present invention is contacted with a solvent to erase it, the following solvents are preferably used. That is, it is preferable that (A) has a property of assisting the formation of a hydrogen bond between the color developing agent and the decoloring agent, and further (B) has a high affinity with the binder resin and the wax and even inside the image forming material. It is preferable to have a property of easily penetrating. The solvent satisfying the above property (A) can be used alone. Two or more kinds of solvents may be mixed to satisfy the above two properties.

Examples of the solvent (first group) having both the above properties (A) and (B) include ethers, ketones and esters. Specific examples are saturated ethers such as ethyl ether, ethyl propyl ether, ethyl isopropyl ether, isopentyl methyl ether, butyl ethyl ether, dipropyl ether, diisopropyl ether, ethyl isopentyl ether, dibutyl ether, dipentyl ether, diisopentyl ether. Unsaturated ethers such as ethyl vinyl ether, allyl ethyl ether, diallyl ether, ethyl propargyl ether; ethers of dihydric alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 1,2-dimethoxy. Ethane, 1,2-diethoxyethane, 1,2-dibutoxyethane; cyclic ethers such as oxetane, tetrahydrofuran, tetrahydr Pyran, dioxolane, dioxane, trioxane; saturated ketones such as acetone, methylethylketone, methylpropylketone, diethylketone, isopropylmethylketone, butylmethylketone, ethylpropylketone, isobutylmethylketone, pinacolone, methylpentylketone, butylethylketone, diketone. Propyl ketone,
Diisopropyl ketone, hexyl methyl ketone, isohexyl methyl ketone, heptyl methyl ketone, dibutyl ketone; unsaturated ketones such as ethylidene acetone,
Allylacetone, mesityl oxide; Cyclic ketones such as cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone; Esters such as ethyl formate, propyl formate, butyl formate, isobutyl formate, pentyl formate, isopentyl formate, ethyl acetate, acetic acid Isopropyl, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, sec-amyl acetate, hexyl acetate, allyl acetate, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 1,2-
Diacetoxyethane, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, butyl propionate, pentyl propionate,
Isopentyl propionate, sec-amyl propionate, 2-methoxypropyl acetate, 2-ethoxypropyl acetate, methyl butyrate, ethyl butyrate, propyl butyrate, isopropyl butyrate, butyl butyrate, pentyl butyrate,
Isopentyl butyrate, sec-amyl butyrate, methyl isobutyrate, ethyl isobutyrate, propyl isobutyrate, isopropyl isobutyrate, butyl isobutyrate, pentyl isobutyrate, isopentyl isobutyrate, sec-amyl isobutyrate, methyl valerate, ethyl valerate, Propyl valerate, isopropyl valerate, butyl valerate, methyl valerate, ethyl valerate, propyl valerate, isopropyl valerate, butyl valerate, methyl hexanoate, ethyl hexanoate, propyl hexanoate, isopropyl hexanoate, etc. . Other solvents than the above include methylene chloride, γ-butyrolactone, β-propiolactone, n-methylpyrrolidinone, dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like. These may be used alone or in combination of two or more. When a mixed solvent is used, the mixing ratio can be set arbitrarily.

The solvent (second group) having the above-mentioned property (A) and having a low affinity with a general binder resin is, for example, water, methyl alcohol, ethyl alcohol, propyl alcohol or isopropyl. Alcohol, butyl alcohol, isobutyl alcohol, pentyl alcohol, 2-pentyl alcohol, 3-pentyl alcohol, isopentyl alcohol, 1-hexanol, 2-hexanol, 3-hexanol, cyclopentanol, cyclohexanol, ethylene glycol,
Examples include propylene glycol, butylene glycol, and glycerin.

Solvents (third group) which do not have the property (A) but have a high affinity for the binder resin include, for example, toluene, ethylbenzene, propylbenzene, cumene,
Butylbenzene, isobutylbenzene, sec-butylbenzene, pentylbenzene, diethylbenzene, mesitylene, xylene, cresol, ethylphenol, dimethoxybenzene, dimethoxytoluene, benzyl alcohol, tolylcarbinol, cumyl alcohol, acetophenone, propiophenone, hexane, Pentane,
Heptane, octane, cyclohexane, cyclopentane, cycloheptane, cyclooctane, petroleum fractions (petroleum ether, benzine, etc.).

As mentioned above, the first group of solvents can be satisfactorily used alone. The second group of solvents may be used alone or may be mixed with the first group of solvents. In this case, the solvents of both groups have the scavenging ability, so that they can be used at any mixing ratio. When a mixed solvent of the second group solvent and the third group solvent is used, the mixing ratio of the two is not particularly limited as long as sufficient scavenging ability is obtained, but the third group solvent should be 20 to 80 wt%. Is preferred. The solvent of the third group may be used as a mixture with the solvent of the first group. In this case, the solvent of the third group may be 90 wt% or less. Further, the solvents of the first group to the third group may be mixed and used.
In this case, it is preferable that the solvent of the third group is 80 wt% or less.

If a natural material such as ethyl butyrate (pineapple oil) that has a very low impact on the environment is used as the solvent, no problem will occur at the time of disposal even if the solvent remains.

[0041]

EXAMPLES Examples of the present invention will be described below. As the paper to be recycled in the examples, the paper printed with the erasable image forming material shown below was prepared.

1 part by weight of crystal violet lactone (CVL) as a color-forming compound, 1 part by weight of propyl gallate as a developer, and 17 parts by weight of cholic acid as a decolorizer.
1 part by weight of a charge control agent (LR-147, Nippon Carlit Co., Ltd.) was mixed, and a styrene / n-butyl methacrylate copolymer having a molecular weight of 85,000 (n-butyl methacrylate content 6 wt%) 79 was added to the mixture as a binder resin.
Parts by weight were added and kneading was sufficiently performed using a kneader. This kneaded material was pulverized with a pulverizer to obtain a powder having an average particle size of 10 μm. Toner was prepared by externally adding 1 wt% of hydrophobic silica to this powder. The softening point of the binder resin used is 120 to 125 ° C.

This toner was put in a toner cartridge of a copying machine (manufactured by Toshiba, Plimage 380), and a solid image was formed on a copy paper (manufactured by Neusiedler, pH 9.4). The reflection density of this paper was measured with a Macbeth densitometer. The reflection density of the background without toner is 0.07, and the reflection density of a solid image is 1.05.
Met.

Images were erased on the paper on which the solid image was printed in this manner as shown in the following examples, and the reflection density after the erasure and the stability of the erased state were evaluated. Example 1 An infrared heat source (Siliconit) capable of heating up to 600 ° C. was used, and a fan produced a wind speed of 10 m / sec on each sheet of paper.
Sent hot air. At this time, the hot air temperature is 120 ° C., 15
The paper was exposed to hot air for 30 minutes set at 0 ° C, 180 ° C, or 200 ° C. The hot air treatment is completed. Further, after pulping these papers, the papers were remade to obtain 7 papers. Of these, the reflection densities of arbitrary 3 sheets (A, B, C) were measured. The results are shown in Table 1.

[0045]

[Table 1]

Even when these papers were left in an environment of 80 ° C. and humidity of 90% for 90 days, no color was developed and the decolored state was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

Example 2 Using high-concentration pulper (manufactured by Mitsubishi Heavy Industries, Ltd.), water was added so that the pulp concentration would be 20% with respect to 5000 sheets of printed paper (4 g per sheet, total 20 kg), and the mixture was allowed to stand at room temperature for 3 After stirring for a while to loosen the fibers of the paper, it was squeezed to squeeze out the water.

Hot air was sent to the pulp at a wind speed of 10 m / sec by a fan using an infrared heat source (Siliconit).
At this time, the hot air temperature is 120 ° C, 150 ° C, 180 ° C,
Alternatively, it was set at 200 ° C. and the pulp was exposed to hot air for 30 minutes. Then, this pulp was put in water and paper was remade to obtain 7 sheets of paper, and the reflection density was measured on any 3 sheets (A, B, C). The results are shown in Table 2.

[0049]

[Table 2]

Even when these pulps were left in an environment of 80 ° C. and humidity of 90% for 90 days, no color was developed and the decolored state was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

Example 3 Using high-concentration pulper, water was added so that the pulp concentration became 20% with respect to 20 kg of printed paper, and the mixture was stirred for 5 hours at the temperature shown in Table 3 while loosening the fibers of the paper. Decolorization processing was performed. After that, the paper was remade to obtain 7 sheets of paper, and then the reflection density of any 3 sheets (A, B, C) was measured.
The results are shown in Table 3.

[0052]

[Table 3]

Even when these pulps were left in an environment of 80 ° C. and a humidity of 90% for 90 days, no color was developed and the decolored state was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

Example 4 A bundle of 100 printed papers was dipped in the organic solvent shown in Table 4 for 5 minutes, squeezed to remove the solvent, dipped in a washing bath and left for 1 hour. , Squeezed again to remove water. Then, using an infrared heat source (Siliconeit), a bundle of paper was blown by a fan at a wind speed of 10 m / sec for 150
It was dried by sending hot air at ℃ for 10 minutes. After pulping these papers, the papers were remade to obtain 7 papers, and the reflection density was measured on any 3 papers (A, B, C). The results are shown in Table 4.

[0055]

[Table 4]

Even when these papers were left in an environment of 80 ° C. and humidity of 90% for 90 days, no color was developed and the decolorized state was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

Example 5 Using a high-concentration pulper, diethoxyethane was added so that the pulp concentration was 20% with respect to 20 kg of printed paper, and the temperature shown in Table 5 was applied while applying a pressure of 5 kg / cm ^2. The mixture was stirred for 5 hours, and the decoloring treatment was performed while loosening the fibers of the paper. Then, the pulp was squeezed to squeeze out the solvent, dispersed in a water washing tank, stirred for 1 hour, and squeezed again to squeeze out water. Next, infrared heat source (Siliconit)
Using a fan, blow it into the pulp with a wind speed of 10 m / sec 1
It was dried by sending hot air at 50 ° C. for 10 minutes. This pulp was put in water and re-paper-made to obtain 7 sheets of paper, and the reflection density was measured on any 3 sheets (A, B, C). The results are shown in Table 5.

[0058]

[Table 5]

Even when these pulps were left in an environment of 80 ° C. and a humidity of 90% for 90 days, no color was developed and the decolored state was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

Example 6 Using a high-concentration pulper, water was added so that the pulp concentration became 20% with respect to 20 kg of printed paper, and 5 kg / c.
While applying a pressure of m ² , stirring was carried out for 5 hours at the temperature shown in Table 7, and the decoloring treatment was carried out while loosening the fibers of the paper. After that, the pulp was squeezed, put in water again, re-made into paper to obtain 7 sheets of paper, and the reflection density was measured on any 3 sheets (A, B, C). The results are shown in Table 6.

[0061]

[Table 6]

Even when these pulps were left in an environment of 80 ° C. and a humidity of 90% for 90 days, no color was developed and the decolorized state was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

Example 7 Using a high-concentration pulper, water was added to 20 kg of paper so that the pulp concentration was 20%, 3% of sodium carbonate was added, and the mixture was stirred at a pressure of 5 kg / cm ² and a temperature of 180 ° C. for 5 hours. Then, the color erasing treatment was performed while loosening the fibers of the paper. On the other hand, pulp was prepared by deinking with a newspaper deinking system (manufactured by EBARA CORPORATION) and dispersed in water. Both pulps were mixed in water in a ratio of 1: 1 to produce recycled paper.

The reflection density of the obtained recycled paper was 0.07. Even when this recycled paper was left in an environment of 80 ° C. and a humidity of 90% for 90 days, discoloration did not occur, and the color tone (hue) was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

Example 8 Using high-concentration pulper, methyl ethyl ketone was added so that the pulp concentration was 20% with respect to 20 kg of paper, and the mixture was stirred for 5 hours at a pressure of 5 kg / cm ² and a temperature of 150 ° C. to loosen the fibers of the paper. Meanwhile, the color erasing process was performed. After squeezing the pulp to squeeze out the solvent, the pulp was dispersed in a washing tank and washed for 1 hour, squeezed again to squeeze out water, and again dispersed in water. On the other hand, deinking process with newspaper deinking system,
A pulp dispersed in water was prepared. Both pulps were mixed in water in a ratio of 1: 1 to produce recycled paper.

The reflection density of the obtained recycled paper was 0.07. Even when this recycled paper was left in an environment of 80 ° C. and a humidity of 90% for 90 days, discoloration did not occur, and the color tone (hue) was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

Example 9 With respect to 5000 printed sheets (20 kg), an infrared heat source (Siliconit) was used, and a wind speed of 10 m /
The hot air of 180 ° C. was blown for 30 minutes. Using a high-concentration pulper, add water so that the pulp concentration becomes 20% with respect to 20 kg of paper after hot air treatment, add 0.5% of polyoxyethylene alkylallyl ether-based surfactant, and pressurize at 5 kg / The fibers of the paper were loosened by stirring for 5 hours at a temperature of 150 ° C. and cm ² . The pulp was squeezed to squeeze out water, then dispersed in a washing tank and washed for 1 hour, squeezed again to squeeze out water, and again dispersed in water. On the other hand, pulp which was deinked by a newspaper deinking system and dispersed in water was prepared. Both pulps were mixed in water in a ratio of 1: 1 to produce recycled paper.

The reflection density of the obtained recycled paper was 0.08. Even when this recycled paper was left in an environment of 80 ° C. and a humidity of 90% for 90 days, discoloration did not occur and the color tone was very stable. Further, no color development occurred even when an aqueous solution having a pH of 1 to 14 was sprayed or a 20% isopropyl alcohol solution of propyl gallate used as a color developer was sprayed.

In Examples 8 to 10, both the pulp prepared from paper printed with an erasable image forming material and the pulp prepared from paper (newspaper) printed with an ordinary image forming material were dispersed in water. However, as long as the latter deinking step is completed, both pulps may be mixed in any form.

[0070]

As described above in detail, according to the method of the present invention, an image can be formed using an erasable image forming material by utilizing equipment such as a pulper used in an existing paper recycling system. The formed paper can be efficiently recycled. Further, pulp made from paper using an erasable image forming material and pulp made by performing deinking and pulping on paper using an ordinary image forming material are mixed to prepare recycled paper. If manufactured, a paper-dedicated subsystem using an erasable image forming material can be incorporated into the conventional paper recycling system to recycle the paper as in the conventional case. Since the pulp produced from the paper using the erasable image forming material has a high whiteness, the whiteness of the recycled paper finally obtained can also be increased.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-27739 (JP, A) JP-A-4-108197 (JP, A) JP-A-4-333682 (JP, A) JP-A-10- 88046 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) D21C 5/02 D21B 1/00-1/40 G03G 9/06-9/10

Claims (3)

(57) [Claims] 1. A paper on which an image is formed using an erasable image-forming material containing a color-developing compound, a color-developing agent and a decoloring agent, is simultaneously decolorized and pulped using hot water, A method for recycling paper, which comprises producing pulp. 2. The method for recycling paper according to claim 1, wherein the temperature of the hot water is set to not less than the softening point of the resin contained in the image forming material and not more than 200 ° C. by applying pressure. 3. A color-developing compound, a color-developing agent, (a) a sterol compound, (b) cholic acid, lithocholic acid, testosterone and cortisone and derivatives thereof,
(C) a non-aromatic cyclic compound having a hydroxyl group other than (c1) cyclic sugar alcohol and (c2) cyclic sugar alcohol and having a 5-membered ring or a derivative of a cyclic sugar alcohol,
And (d) a polymeric decolorizer (a), (b),
A paper imaged with an erasable image forming material containing at least one decoloring agent selected from the group consisting of (c) and (d) is contacted with an organic solvent and
And a method of recycling paper, which comprises decoloring by heating at 120 to 200 ° C. and pulping to produce pulp.