JP3313319B2 - Recycling method of printing substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing base material for erasing a printed portion formed on the surface of a printing base material such as paper or an OHP sheet when necessary after using a printed material. Reproduction method.

[0002]

2. Description of the Related Art In recent years, jet ink printers have become very popular as home printers and office printers. As a result, printed materials such as paper and OHP sheets have increased, and as a result, their waste has been reduced. It has increased.

Further, as a method of recycling these printed materials, a method of performing a chemical treatment with a deinking agent or the like, then dissolving, making paper, and reusing it as recycled paper has been required, and some methods have been implemented.

[0004]

However, according to the conventional recycling method, the printed portion cannot be decolored without a chemical treatment with a deinking agent or the like, the process becomes complicated, the cost is high, and the printed matter which is sufficiently satisfactory can be obtained. At present, no recycling law has been obtained.

SUMMARY OF THE INVENTION The present invention solves the problems of the conventional printed matter recycling method.
A method for regenerating a printing base material that easily and quickly erases a printed portion formed on the surface of a printing base material such as a sheet, and a method for printing on a printing base material such as an OHP sheet by printing on a printing base material such as an OHP sheet. It is an object of the present invention to provide a method of recycling a printing base material in which a printed portion is erased when necessary after use to make it reusable as a printing base material.

[0006]

According to the present invention, there is provided a dye which can be decolorized by applying a clear paint containing titanium oxide having a photocatalytic action onto a substrate and irradiating it with ultraviolet rays as a colorant. The present inventors have found that printing can be performed easily and in a short time by irradiating ultraviolet rays after printing using the contained ink composition and using the printed matter, and have reached the present invention.

According to the invention: (i) an average particle size of 0.05
~0.2μm photocatalytic titanium oxide particles, (ii) a hydrolyzable silicon compound or a partial condensate of the hydrolyzate and / or a hydrolyzable silicon compound of該珪containing compounds and, clear coating composition comprising (iii) a solvent Printing on a substrate coated with a dye using an ink composition composed of a dye in which the color of the printed portion is decolorized by irradiation with ultraviolet light, and the printed portion thus obtained is irradiated with ultraviolet light to decolor the printed portion. There is provided a method for regenerating a printing substrate characterized by the following.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for recycling a printing substrate and a method for recycling a printing substrate according to the present invention will be described in detail.

The clear coating composition used in the present invention comprises: (i) photocatalytic titanium oxide fine particles having an average particle diameter of 0.05 to 0.2 μm; (ii) a hydrolyzable silicon compound or a hydrolyzate of the silicon compound; partial condensate of / or hydrolyzable silicon compounds and consists of (iii) a solvent.

[0010] The titanium oxide used in the clear coating composition is a substance which exhibits a catalytic action on the oxidation-reduction of organic substances by irradiation with light having a specific energy, and in addition to pure titanium oxide, hydrous titanium oxide and water. Includes those called so-called titanium oxide, metatitanic acid, orthotitanic acid, and titanium hydroxide. Titanium dioxide or those in a lower oxidation state than this are particularly preferably used. The crystal form of titanium dioxide may be any of anatase type, rutile type and flukite type, and may be a mixture thereof.

These titanium dioxides are in the form of fine powder and have a particle size of 0.05 to 0.2 μm in view of the photocatalytic activity.
m can be used. This fine powder may be used as a dry powder, but it is desirable that the fine powder is previously dispersed in a dispersion medium in order to uniformly disperse the silica binder derived from the hydrolyzable silicon compound described later. In the present invention, whether or not titanium dioxide is well dispersed greatly affects the photocatalytic function when a coating film is formed. Platinum, gold, silver, copper, palladium, rhodium,
A metal such as ruthenium or a metal oxide such as ruthenium oxide or nickel oxide may be coated.

These titanium oxides are used by being highly dispersed in a solvent such as water. In order to uniformly disperse the ultrafine particles of titanium oxide in a solvent such as water without secondary aggregation, it is preferable to store the titanium oxide as acidic or alkaline. When placed under acidic pH 0.5 ~
4, particularly preferably 1 to 3.5. As a dispersion medium, a mixture of water and alcohol may be used in addition to water.

The hydrolyzable silicon compound used in the present invention includes alkyl silicates, silicon halides and partial hydrolysates thereof. As the alkyl silicate, methyl, ethyl, isopropyl silicate and the like are used. Each of these silicates is used in the form of a monomer or an oligomer formed by partial hydrolysis, and the oligomer is represented by the general formula SinO _n-1 (OR)
_{2n + 2} (where n is 2 to 6, R is C1 to C4 alkyl group)
The alkyl silicate condensate represented by the formula is particularly preferred. These oligomers can also be used in a mixture.

As the catalyst for the partial hydrolysis,
Either acid or alkali can be used. When the titanium oxide dispersion is acidic, an alkyl silicate hydrolyzed with an acid is preferred. Water or an alcohol having 1 to 4 carbon atoms is used as a dispersion solvent for the hydrolysis solution. Esters such as ethyl acetate are not preferred because they make the composition liquid unstable. Since the silicon compound and its partial hydrolyzate and / or its partial condensate used in the present invention are used for the purpose of binding with titanium oxide, they are hereinafter referred to as silica binder.

The mixing of the titanium oxide and the silica binder can be carried out arbitrarily. As an example, a predetermined amount of an aqueous dispersion of titanium dioxide under acidic conditions is stored at a liquid temperature of 10 to 50 ° C. and weighed. When the alkyl silicate or the partial hydrolyzate is added, the hydrolysis catalyst may be added at the same time, or the hydrolysis may be promoted by utilizing the acid component present in the titanium dioxide dispersion. When an alcohol-based medium is used as a dispersion medium, an alkyl silicate or a partial hydrolyzate is dispersed in a water / alcohol mixed medium dispersion liquid of titanium dioxide and an alcohol medium in an amount of 50 to 1500.
% Hydrolyzed liquid can be mixed with stirring to obtain a clear coating composition.

The ratio between titanium and silica in the clear coating composition must be 85/15 to 30/70 in terms of the weight ratio (TiO ₂ / SiO ₂ ) in terms of titanium dioxide and silicon dioxide, respectively. . If the mixing ratio of silica is less than 15%, the adhesion strength between titanium oxides is not sufficient, and the titanium oxides easily fall off by touch or vibration, which is not preferable. 70% conversely
If it exceeds, the photocatalytic function of titanium oxide will decrease,
Poor practicality. This seems to increase the proportion of silica covering the surface of the titanium oxide particles, which would hinder contact between the titanium oxide and the substance to be oxidatively decomposed.
Preferably, 80 _{(TiO 2 / SiO 2) /} 20~5
Those in the range of 0/50 are preferred.

The solid content in the clear coating composition is not more than 30% by weight. Here, the solid content refers to the total amount of titanium oxide and silica in the entire composition, titanium oxide being titanium dioxide, and silica being silicon silicate in the alkyl silicate or oligomer thereof in the composition being SiO _2.
The value converted to is used.

The other components are mainly water and / or an organic solvent, and should be substantially removed by drying after the composition is applied to the surface of the substrate. The preferred solid content concentration is 5 to 30% by weight. When the solid content concentration is less than 5%, the adhesion to the substrate becomes strong, but the thickness of the coating film, that is, the amount of titanium dioxide is insufficient and the photocatalyst is insufficient. It is not preferable because it is impossible to form a coating film capable of sufficiently exhibiting the function. Conversely, when the solid content exceeds 30%, the dispersibility of the solid content in the composition is deteriorated, the storage stability of the composition is significantly reduced, and gelation easily occurs in a few days. In addition, when the concentration is such a high concentration, the film-forming property is poor, the adhesiveness to the base material is greatly reduced, and the film is easily peeled off with a finger, which is not preferable.

Small amounts of titanium alkoxide and titanium tetrachloride may be added to the clear coating composition. Further, titanium or a silane coupling agent may be added. Further, various surfactants may be added to ensure the stability of the composition and improve the wetting properties. Further, a compound of alkoxysilane or hydrosilane containing two or more alkoxy groups is added to the conversion of silica when calculating the solid content.

The clear coating composition is applied to the surface of a substrate,
It is dried and, if necessary, fired at a low temperature to form a coating film. As an application method, spin coating, spray coating, bar coating, dipping, or the like is appropriately used depending on the shape of the substrate to be applied. The thickness of the coating is 0.1-3 μm,
In particular, 0.3 to 2 μm is appropriate. The photocatalytic activity of titanium dioxide is related to the amount of titanium dioxide that can be contacted with the compound to be oxidatively decomposed by exposure to the surface, so the thickness of the coating is not related to the coating thickness. There is non-uniformity, and the dispersion of the particles does not always achieve the ideal uniformity. If the thickness is too small, the amount of titanium dioxide on the surface of the coating film is small, and the photocatalytic activity is not sufficient. . With such a thickness, the coating film can be made transparent, and a photoactive coating film can be formed on the surface of the substrate without impairing various configurations and designs of the substrate.

The clear coating film can be dried at 100 ° C. to form a fairly strong film that is not easily peeled off even when rubbed with a nail, but the silica binder can be dried at a temperature of 100 ° C. or more to obtain a more firm coating. Since a film can be formed, the film may be dried or fired at a low temperature of 100 to 300 ° C. as necessary. However, the catalytic activity of ultrafine titanium dioxide starts to gradually decrease by drying at 150 ° C or higher,
If the temperature exceeds 400 ° C., the temperature may rapidly decrease. Therefore, it is necessary to appropriately select a drying temperature according to the necessity of the coating film strength. In any case, drying at 480 ° C. or lower or firing at a low temperature is preferable.

The colorant used in the present invention comprises a dye which loses its color when irradiated with ultraviolet rays. I. Solvent Black 22,
C. I. Solvent Black 27, C.I. I. S
solvent Black 28, C.I. I. Solven
t Black29, C.I. I. Solvent Red
83-1, C.I. I. Solvent Red 125,
C. I. Solvent Red 132, C.I. I. Sol
vent Blue 47, C.I. I. Solvent B
lue48, C.I. I. Solvent Blue 70,
C. I. Solvent Yellow 88, C.I. I.
Solvent Yellow 89, C.I. I. Basi
c Violet1, C.I. I. Basic Violet
t3, C.I. I. Basic Red1, C.I. I. Bas
ic Red8, C.I. I. Basic Black2,
And Basic Blue 5, Basic Blue
7, Basic Violet 1, Basic Vio
let10, Basic Orange 22, Basi
c Red1: 1, Basic Yellow1, Ba
sic Yellow2, Basic Yellow3
Dyes used in ordinary inks, such as basic dyes, are not limited thereto.

Examples of the solvent for the ink composition used in the present invention include ketones such as acetone, methyl ethyl ketone and cyclohexanone; alcohols such as methanol, ethanol and isopropanol; ethers such as cellosolve and butyrocellosolve; Alkylene glycols such as diethylene glycol, triethylene glycol, propylene glycol and hexylene glycol; alkyls of polyhydric alcohols such as ethylene glycol methyl ether, diethylene glycol methyl ether, triethylene glycol monomethyl ether, diethylene glycol ethyl ether and triethylene glycol monoethyl ether Ethers; polyalkylene glycols such as glycerin, polyethylene glycol and polypropylene glycol Nitrogen-containing heterocyclic ketones such as N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone; ion-exchanged water; and mixtures of two or more of these. It is also possible to use.

The ink composition used in the present invention is a dye which can be decolored by irradiating the above ultraviolet rays.
% By weight and from 99.9 to 80% by weight of the abovementioned solvents. The ink composition used in the present invention further includes, if necessary, an electric power adjusting material, a surfactant, a quencher,
Additives such as dispersants and preservatives can be included.

Examples of the above-mentioned conductivity adjusting agent which can be used in the present invention include lithium nitrate, lithium nitrite, ammonium sulfite, ammonium formate, ammonium acetate, lithium halide, sodium thiocyanate and the like. Further, the above-mentioned surfactants, quenchers, dispersants, preservatives and the like which can be used in the present invention are those commonly used in ink compositions. The ink composition used in the present invention may contain these additives in an amount of 0.1 to 5% by weight of the ink composition.

The ink composition used in the present invention has characteristics suitable for an ink printing method. Therefore, the composition has a viscosity of 1 to 10 centipoise (20
° C), surface tension of 20-60 dynes / cm, specific resistance of 2
Desirably, the specific gravity is in the range of 0.00 to 3000 Ωcm and 0.8 to 1.2.

In preparing the ink composition of the present invention,
After mixing and stirring each component using a jet printer,
The mixture is filtered and purified using a filter having a pore size of, for example, about 1/10 or less of the nozzle diameter of the jet printer to be used.

The ink composition used in the present invention can be printed on a printing substrate using a conventionally known jet printer. Examples of such a jet printer include a charge amount control system, an ink-on-demand system, a bubble jet system, and a system in which ink is ejected by a thermal head. The ink-jet printed ink forms a dry film by drying at room temperature to several hundred degrees Celsius.

A printed material using an ink composition comprising only a dye whose colorant is decolored by irradiating ultraviolet rays on a printed portion is a printed material printed by means other than a jet printer, Even when handwritten using an ink composition containing a colorant consisting of only a dye which is decolored by irradiation and a solvent, the printed portion can be decolorized by irradiating ultraviolet rays.

The printing substrate used in the present invention includes plain paper, high quality paper, PP film, low quality paper, art paper, OHP sheet, postcard and the like.

In the present invention, when necessary, the printed matter is irradiated with ultraviolet light after use, and the printed portion is decolorized so that the printed material can be reused as a printing substrate, and the printing base is recycled. .

Ultraviolet light refers to light having a wavelength in the range of about 100 nm to 400 nm. In the present invention, light having a wavelength in the range of 300 nm to 400 nm is particularly preferable for decoloring a printed portion. Light sources include mercury lamps, xenon lamps,
There are a carbon arc, a plasma arc, a metal halide lamp and the like, and a high-pressure mercury lamp and a metal halide lamp are particularly useful from the viewpoint of decoloring efficiency. It is also possible with sunlight.

In the present invention, the reason why the printed portion is decolorized by irradiating ultraviolet rays for a certain period of time is as follows. It is easy to separate from the structure. Also, by applying the clear coating material having a photocatalytic action to the lower layer of the ink layer, it became possible to erase the printed portion more quickly.

[0034]

The present invention will be described in more detail with reference to the following examples. In the examples, “parts” and “%” are shown on a weight basis.

<Preparation of Clear Paint a> Stirrer, thermometer,
In a separable flask equipped with a reflux condenser, 10 parts of a hydrolyzed condensate solution of tetraalkoxysilicate and 60 parts of isopropyl alcohol are charged, and the mixture is stirred uniformly.
Maintain at 0 ° C. A predetermined amount of an aqueous dispersion of TiO ₂ having a particle size of 5 nm was added thereto, and the ratio of TiO ₂ / SiO ₂ was adjusted to 80/20.
(Weight ratio) and stirred at 40 ° C. for 1 hour. The solid concentration was adjusted to 10%, and a clear paint a was prepared.

<Preparation of Clear Paint b> Stirrer, thermometer,
A separable flask equipped with a reflux condenser was charged with 10 parts of a hydrolyzed condensate solution of an organoalkoxysilane and 60 parts of isopropyl alcohol, and the mixture was stirred uniformly.
Maintain at ° C. A predetermined amount of an aqueous dispersion of TiO ₂ having a particle size of 5 nm was added thereto, and the ratio of TiO ₂ / SiO ₂ was adjusted to 60/40.
(Weight ratio) and stirred at 40 ° C. for 1 hour. The solid content concentration was adjusted to 10%, and a clear paint b was prepared.

<Preparation of Clear Coating c>
In the same manner as the preparation, the ratio of TiO ₂ / SiO ₂ 20 /
80 (weight ratio) to prepare a clear paint c.

Examples 1 to 5 and Comparative Examples 1 to 4 The colorants shown in Table 1 were used in the amounts (parts by weight) shown in Table 1.
In addition, the solvents shown in Table 1 were used in the amounts (parts by weight) shown in Table 1, and they were blended and uniformly mixed, and then purified by filtration through a membrane filter having a pore size of 1.0 μm. Was prepared. The obtained ink composition was jetted or written in a predetermined image by hand using a jet printer, and printed on plain paper (PPC), an OHP sheet, and a white PP film, respectively. A decoloring test of the printed portion was performed as follows.

<Decoloring test of printed portion> After printing with an ink jet printer, the decoloring condition of the ink after irradiation for one hour with a fade meter (corresponding to one year of sunlight) was visually observed according to the following criteria. evaluated.

：: Decolored and recyclable ×: No decolored, remaining on substrate The results are as shown in Table 2.

[0041]

[Table 1]

[0042]

[Table 2] As is clear from Table 2, according to Examples 1 to 5 of the present invention, the decoloring effect was good in any of the low, white PP film and the transparent OHP sheet. On the other hand, Comparative Example 1 in which the clear paint was not applied, Comparative Example _{2 in which} the weight ratio of TiO ₂ / SiO ₂ of the clear paint did not belong to the predetermined range, and Comparative Example 3 in which the pigment was used instead of the dye were all decolorized. It was bad.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tsuneo Shirota 1-18-3 Nakazato, Minato-ku, Yokohama-shi, Kanagawa Pref. 31102 Belsche 31102 (56) References JP-A-11-61692 (JP, A) JP-A-11 -48627 (JP, A) JP-A-2-28683 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41M 7/00 B41M 5/00

Claims (3)

(57) [Claims] 1. (i) titanium oxide fine particles having an average particle diameter of 0.05 to 0.2 μm; (ii) a hydrolyzable silicon compound or a hydrolyzate of the silicon compound and / or a portion of the hydrolyzable silicon compound. condensate and, on a substrate coated with the clear coating composition consisting of (iii) a solvent, and printed using an ink composition colorants printed portion is made of dyes decolored by irradiation with ultraviolet rays, thus obtained A method for regenerating a printing substrate, comprising irradiating a printed material with ultraviolet light to erase a printed portion. 2. The weight ratio of titanium oxide and silicon in the clear coating composition is 85 in terms of TiO ₂ and SiO ₂ , respectively.
The method for regenerating a printing substrate according to claim 1, wherein the ratio is from / 15 to 30/70. 3. TiO ₂ and S in the clear paint
The method of reproduction printing base material according to claim 1, wherein the solid concentration of the total amount of converted titanium oxide and silica is 5 to 30 wt% as iO _2.