JP2002129071A - Decolorable composition and method for producing the same and decolortable coloring agent thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decolorable composition which enables it to decolor easily by decoloring treatment such as heating or bringing it to contact with an organic solvent or the like after using it to such uses that printing, typing, etc., giving a good and stable colored-state as an image-forming material, and it, also, retains a stable decolored-state. SOLUTION: The decolorable composition is characterized in that it contains, essentially, a matrix material, a color developer, a colorable compound and decoloring agent, and in the composition, the decoloring agent exists in a shape of a fine particle having an average diameter which does not exceed the diameter of the composition when its shape is spherically approximated, or in a state of separated microphase, and the color developer exists under the condition of intermolecularly interacting with the colorable compound in a colored-state and under adsorption on the surface of the particle of the decoloring agent in a decolored-state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an erasable composition capable of changing a color-forming compound in a colored state to a colorless erasable state, a method for producing the same, and an erasable colorant.

[0002]

2. Description of the Related Art In recent years, with the spread of computers, printers, copiers, facsimiles, and the like, the output of information on paper has increased. Although there is a call for "paperless by digitizing information" in order to reduce output on paper, hard copy to paper is required because of its features such as good visibility, high portability, and easy information retrieval by turning pages. Demands are endless. As a result, protection of natural resources as a raw material for paper, reduction of refuse disposal, and reduction of carbon dioxide emission have become issues to be solved. “Recycling and reuse of paper” is a very contemporary issue in each of the aspects of protecting natural resources, reducing garbage disposal, and reducing carbon dioxide emissions.

Under these circumstances, the technology of making image forming materials (various printing inks, toners, jet inks, etc.) for printing and printing on paper colorless after printing and printing promotes the recycling and reuse of paper. It is extremely important in doing so. That is, in the conventional paper recycling method, a method in which the recovered paper is deflocculated with water and then the ink portion is floated and separated in a so-called "deinking step" or a method of decolorizing using a bleaching agent is used. However, these are factors that make the process cost higher than in the case of newly producing paper. Therefore, paper printed with an image forming material using an erasable colorant capable of changing a color-forming compound in a color-developing state to a colorless erasing state requires a time-consuming deinking process as in the related art. It is expected that it will be possible to reuse or reproduce without going through.

In recent years, various studies have been conducted on erasable colorants, and erasable colorants that can be erased by applying heat are disclosed in, for example, JP-A-7-81236 and JP-A-Hei.
No. 0-88046. In the former publication, a coloring compound such as a leuco dye, a developer,
An erasable colorant containing an organic phosphoric acid compound having a decolorizing action, and the latter publication discloses, in combination with a color developing compound such as a leuco dye and a developer, a heat dissipating agent. A discolorable colorant using a sterol compound such as cholic acid, lithocholic acid, testosterone, cortisone or the like as a decoloring agent exhibiting a decoloring effect by adding a colorant is disclosed.

Further, an erasable colorant which can be erased by contact with an organic solvent is disclosed in, for example, JP-A-2000-109.
No. 896. This erasable colorant is composed of a color developing compound such as a leuco dye, a color developer, and a color erasing agent, and physically or chemically adsorbs the color developing agent as the color erasing agent. It is characterized by using a polymer compound having an electron-donating group capable of being used (eg, starch, starch derivative, cellulose derivative, etc.). The method for producing an erasable colorant includes polystyrene as a binder resin. A method is disclosed in which a mixture of a color former, a color developer, and a decolorizer is kneaded using a kneader, and the kneaded material is pulverized with a pulverizer.

[0006]

While such conventional erasable colorants have their respective features, it is not easy to achieve both good coloring and good erasing properties, or as a printed matter. However, there are drawbacks such as poor durability under actual use conditions and high cost, and further improvement in performance is desired for full-scale practical use. Accordingly, an object of the present invention is to provide a decolorizable, good and stable color-forming state under actual use conditions as a printed matter, and to use it for heating or contact with an organic solvent after being used for printing or printing as an image forming material. It is an object of the present invention to provide an erasable composition which can be easily erased by an erasing process such as the above and can stably maintain the erased state, and a method for producing the same. The present inventor, in the prior art, as a result of various studies on the cause of insufficient coloring and decoloring of the erasable colorant, the existence form and color development of the decolorable agent in the erasable colorant The inventors have found that intermolecular interaction with an agent is an important controlling factor, and have completed the present invention based on this finding.

[0007]

The above object is achieved by the present invention described below. That is, the present invention is based on at least a matrix material, a color developer, a color developing compound that develops a color by an intermolecular interaction with the color developer, and a molecular interaction between the color developer and the color developing compound. (1) When the composition is used as a particulate erasable colorant, the erasable composition comprises a erasable agent that interacts with the color developer. In the particulate decolorizable colorant, the decolorant is always fine particles having a size whose average diameter when the shape is approximated by a sphere does not exceed the diameter of the particulate decolorable colorant. Exists as a microphase separated state,
(2) When the composition is used as a thin-film image forming material, in the thin-film image forming material, the decoloring agent always has an average diameter when the shape approximates a sphere. (3) When the composition is used as a fibrous colorant, the colorant is present in the form of fine particles or microphase separated in a size not exceeding the film thickness of the image forming material. The agent always exists as a fine particle or microphase separated state whose average diameter when its shape is approximated by a sphere does not exceed the diameter of the fiber cross section of the fibrous colorant, and in any of the above cases. In the color-developed state, the color developer is present in the matrix material through intermolecular interaction with the color former, and in the decolored state, the color developer is present between the color former and the molecule. Without interaction, It is allowed decolorizable composition characterized present in the interaction between the decoloring agent molecules are adsorbed on the surface of the decoloring agent present as a phase separation state.

[0008] The present invention also provides at least a matrix material, a color developer, a color-forming compound which develops a color by an intermolecular interaction with the color developer, and an intermolecular structure between the color developer and the color-formable compound. Stronger than the interaction, a method for producing an erasable composition comprising a decoloring agent that interacts with the color developing agent, wherein the matrix material, the color developing agent, the color developing compound, and In the kneading step of kneading the mixture comprising the erasing agent, the average diameter of the decolorizing agent in the mixture when the shape thereof is approximated by a sphere is from the following groups (1) to (3). A process for producing an erasable color composition, which comprises dispersing so as to exist as fine particles or a microphase separated state having a size not exceeding a selected value. (1) when the composition is used as a particulate erasable colorant, the average diameter of the particulate erasable colorant approximated by a sphere; (2) the composition is a thin film (3) when the composition is used as a fibrous discolorable colorant, when the composition is used as a fibrous discolorable colorant, Fiber cross section diameter.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention. When the erasable composition of the present invention is processed and used as a particulate erasable colorant, the size of the particles is selected to be an optimal size according to the use as the colorant. For example, when used as a poster color for writing characters of several cm to several tens of centimeters or when coated on the entire surface of the poster, the average diameter when the shape is approximated by a sphere is several tens μm.
It can be used even if it has a relatively large size of about 100 to several tens of μm. When the particulate erasable colorant of the present invention is used as a toner for copying machines or printers, the average diameter of the particles when approximated by a sphere is preferably about 10 μm to about 7 μm. . When the particulate erasable colorant of the present invention is dispersed and used as an aqueous ink for writing implements or an ink for an ink jet printer (jet ink), the average diameter of particles approximated by a sphere is used for writing implements. Preferably, the thickness is 8 μm or less for aqueous inks and 2 μm or less for jet inks.

When the erasable composition of the present invention is processed and used as a thin-film erasable image forming material, the thickness of the thin film has an optimum value according to the use as a colorant. Selected. For example, when it is used as an image forming material for a large-sized notice, it can be used even if the thickness as a thin film is a relatively large value of several tens μm to one hundred and several tens μm. On the other hand, when used as an ink ribbon for a thermal transfer printer, the thickness as a thin film is several μm to several tens μm.
m is preferable. Therefore, when the erasable composition of the present invention is processed and used as a fibrous erasable colorant, the diameter of the fiber cross section is an optimal value selected according to the use as the colorant. You. For example, in the case where paper is mixed and erasable coloring is applied to paper, the diameter of the fiber cross section is preferably several μm to several tens μm.

Hereinafter, the matrix material, the color forming compound, the color developer, and the color erasing agent which constitute the color erasable composition of the present invention will be sequentially described in detail. [Matrix Material] As a matrix material used in the erasable composition of the present invention, an organic high molecular compound or a low molecular compound can be used. Hereinafter, a matrix material composed of an organic polymer compound is referred to as a polymer matrix material, and a matrix material composed of a low molecular compound is referred to as a low molecular matrix material, as required.

The polymer matrix material used in the erasable composition of the present invention may be the same as the binder resin usually additionally used when the erasable composition is used as an image forming material. , May be different. For example, in the case of an image forming material in which a particulate erasable colorant is directly dispersed in a solvent (water or an organic solvent) such as a jet ink (ink for an ink jet printer), it is additionally used. The binder resin or dispersant must be soluble in the solvent, while the matrix material used in the erasable composition must be insoluble and swellable in the solvent.

When a particulate erasable colorant is dispersed in a varnish, such as an offset ink, the matrix material used in the erasable composition is a varnish solvent. It must be insoluble and non-swellable in linseed oil, soybean oil, high boiling petroleum solvents and the like. Further, for example, when the erasable composition of the present invention is used for a crayon, a craper, a thermal transfer ink, and a toner for a copying machine, the matrix material used for the erasable composition is the present erasable composition. It may be the same as the binder resin additionally used when the product is used as an image forming material.

The polymer matrix material may be selected from known thermoplastic resins and thermosetting resins according to the use form of the erasable composition of the present invention such as ink jet inks and printing inks. In the temperature range in which the composition is used in a color-developed state as a pigment, the color former and the developer can be solid-solved (dissolve and molecularly dispersed),
In addition, a resin capable of dispersing the decoloring agent in the form of fine particles or microphase separated with the above-mentioned size and further maintaining the form as particles can be appropriately selected and used, and is not particularly limited.

Specifically, for example, when a leuco dye is used as a color-forming compound, a phenol compound is used as a color developer, and a starch is used as a decolorant, the following organic polymer compound is preferably used as a matrix material. be able to. That is, for example, ketone resin, norbornene resin, polystyrene, poly (α-methylstyrene), polyindene, poly (4-methyl-1-pentene), polyvinylpyridine, polyoxymethylene, polyvinylformal,
Polyvinyl acetal, polyvinyl butyral, polyvinyl acetate, polyvinyl propionate, polyvinyl alcohol, polyethylene, polypropylene, polybutadiene, polymethylpentene, polyvinyl chloride, chlorinated polyvinyl chloride, chlorinated polyethylene, chlorinated polypropylene,

Polyvinylidene chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl methyl ether, polyvinyl ethyl ether, polyvinyl benzyl ether, polyvinyl methyl ketone, poly (N-vinyl carbazole),
Poly (N-vinylpyrrolidone), polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polyacrylonitrile, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polybenzyl methacrylate, polyhexyl methacrylate, Polymethacrylic acid, polymethacrylamide, polymethacrylonitrile, polyacetaldehyde, polychloral, polyethylene oxide, polypropylene oxide, polyethylene terephthalate, polybutylene terephthalate,
Polycarbonates (bisphenols + carbonic acid), polysulfone, polyethersulfone, polyphenylene sulfide, poly (diethylene glycol bisallyl carbonate),

6-nylon, 6,6-nylon, 12-
Nylon, 6,12-nylon, polyethyl aspartate, polyethylglutamate, polylysine, polyproline, poly (γ-benzyl-L-glutamate), methylcellulose, ethylcellulose, benzylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, acetylcellulose, Cellulose triacetate, cellulose tributyrate, alkyd resin (phthalic anhydride + glycerin), fatty acid modified alkyd resin (fatty acid + phthalic anhydride + glycerin), unsaturated polyester resin (maleic anhydride + phthalic anhydride + propylene glycol), epoxy Resin (bisphenols + epichlorohydrin), epoxy resin (cresol novolak + epichlorohydrin), polyurethane resin, phenol resin, urea resin Melamine resin, xylene resin,
Resins such as toluene resin, furan resin, guanamine resin and diallyl phthalate resin, organic polysilanes such as poly (phenylmethylsilane), organic polygermanes, and copolymers / copolycondensates thereof can be suitably used.

Further, for example, the decolorizable composition of the present invention obtained by using a leuco dye as a color-forming compound, a phenol compound as a color developer, and starch as a decolorant is used for a copier or printer. When used in a toner, as a matrix material of the erasable composition and a binder resin of the image forming material, for example, polystyrene, a blend polymer of polystyrene and an acrylic resin, a styrene-acrylic copolymer, polyester, An epoxy resin or the like can be particularly preferably used. Here, as the acrylic monomer constituting the styrene-acrylic copolymer,
N-butyl methacrylate, isobutyl methacrylate, ethyl acrylate, n-butyl acrylate, methyl methacrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate,
Examples thereof include diethylaminopropyl acrylate, 2-ethylhexyl acrylate, butyl acrylate-N- (ethoxymethyl) acrylamide, ethylene glycol methacrylate, and 4-hexafluorobutyl methacrylate. One or more of these (meth) acrylate monomers can be used. The proportion of styrene in the copolymer is preferably at least 50% by weight.
Further, in addition to styrene and acrylic monomers, butadiene, maleic ester, chloroprene, and the like may be copolymerized, but the content of these components is preferably 10% by weight or less. Here, when using a blend polymer of polystyrene and acrylic resin as a matrix,
As the acrylic resin, one or more of those exemplified for the above copolymerization can be used. Incidentally, a copolymer containing butadiene, maleic ester, chloroprene or the like at a ratio of 10% by weight or less may be used. The proportion of polystyrene in the matrix is preferably at least 50% by weight.

Further, a polyester synthesized from a carboxylic acid and a polyhydric alcohol can also be used. As the carboxylic acid, for example, terephthalic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, pimelic acid,
Suberic acid, azelaic acid, sebacic acid, brassic acid,
Examples include pyromellitic acid, citraconic acid, glutaconic acid, mesaconic acid, itaconic acid, terraconic acid, phthalic acid, isophthalic acid, hemimellitic acid, melophanic acid, trimesic acid, planitic acid, trimellitic acid, and the like. One or more of these can be used. Examples of the polyhydric alcohol include bisphenol A, hydrogenated bisphenol A, ethylene glycol, propylene glycol, butanediol, neopentyldiol, hexamethylenediol, heptanediol, octanediol, pentaglycerol, pentaerythritol, cyclohexanediol, and cyclopentane Examples include diol, pinacol, glycerin, etherified diphenol, catechol, resorcinol, pyrogallol, benzenetriol, phloroglucinol, benzenetetraol and the like. One or more of these can be used. Further, a blend polymer of two or more polyesters may be used.

An epoxy resin synthesized from epichlorohydrin and a compound having a polyhydric phenolic hydroxyl group can also be used. Examples of the polyhydric phenol compound include bisphenol A, hydrogenated bisphenol A, bisphenol S, etherified diphenol, catechol, resorcin, pyrogallol, benzenetriol, phloroglucinol, benzenetetraol, and the like. One or more of these are used.
Further, a phenol resin, a urea resin, a melanin resin, an alkyd resin, an acrylic resin, a polyester, a polyamide, a polyurethane, or the like may be blended with the epoxy resin at a ratio of 15% by weight or less.

As the low molecular matrix material, a low molecular compound such as a low molecular plasticizer, a low molecular lubricant or a low molecular wax can be used. That is, in the temperature range in which the decolorizable composition is used in a colored state as a dye, the color former and the developer can be solid-solved (dissolved and molecularly dispersed), and A low molecular compound that can be dispersed as fine particles or a microphase separated state and that can maintain the form as particles can be appropriately selected and used as a low molecular matrix material.
Specifically, for example, a leuco dye as a coloring compound,
When a crayon is prepared using a phenol compound as a color developer and starch as a decolorizer, for example, 1-docosanol can be suitably used as a low-molecular compound (wax).

[Color-forming compound] Examples of the color-forming compound used in the present invention include leuco auramines, diaryl phthalides, polyaryl carbinols, acyl auramines, aryl auramines, and rhodamines. B
Organic compounds such as lactams, indolines, spiropyrans, and fluorans can be given. Specific color-forming compounds include, for example, crystal violet lactone (CVL), malachite green lactone,
-Anilino-6- (N-cyclohexyl-N-methylamino) -3-methylfluoran, 2-anilino-3-methyl-6- (N-methyl-N-propylamino) fluoran, 3- [4- ( 4-phenylaminophenyl) aminophenyl] amino-6-methyl-7-chlorofluoran, 2-anilino-6- (N-methyl-N-isobutylamino) -3-methylfluoran, 2-anilino-6
(Dibutylamino) -3-methylfluoran, 3-chloro-6- (cyclohexylamino) fluoran,

2-chloro-6- (diethylamino) fluoran, 7- (N, N-dibenzylamino) -3-
(N, N-diethylamino) fluoran, 3,6-bis (diethylamino) fluoran-γ- (4′-nitroanilino) lactam, 3-diethylaminobenzo [a]-
Fluoran, 3-diethylamino-6-methyl-7-aminofluoran, 3-diethylamino-7-xylidinofluoran, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methyl Indole-3-yl) -4-azaphthalide, 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3-diethylamino-7
-Chloroanilinofluoran, 3-diethylamino-
7,8-benzofluoran,

3,3-bis (1-n-butyl-2-methylindol-3-yl) phthalide, 3,6-dimethylethoxyfluoran, 3-diethylamino-6-methoxy-7-aminofluoran, -(2-chloroanilino) -6-dibutylaminofluoran, crystal violet carbinol, malachite green carbinol, N- (2,3-dichlorophenyl) leuco auramine, N-benzoyl auramine, rhodamine B lactam, N-acetyl Auramine, N-phenyl auramine, 2- (phenyliminoethanedylidene) -3,3-
Dimethylindoline, N, 3,3-trimethylindolinobenzospiropyran, 8'-methoxy-N, 3,3-
Trimethylindolinobenzospiropyran,

3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-6-benzyloxyfluoran, 1,2-benzo-6-diethylaminofluoran, 3 , 6-Di-p-toluidino-4,5-dimethylfluoran, phenylhydrazide-γ-lactam, 3-
Amino-5-methylfluoran and the like can be suitably used. These can be used alone or in combination of two or more. Needless to say, if a color-forming compound is appropriately selected, a color-developed state of various colors can be obtained, and multicoloring can be realized.

These color-forming compounds are, for example, tautomeric compounds which can take both a colorless form and a colored form, as shown by the chemical formula below.

Embedded image

[Developer] It is known that, in the above-mentioned chemical formula showing tautomerism, the chemical structure of the inner salt type shown at the lower side corresponds to the "color-forming type". A compound capable of stabilizing the chromogenic type by stabilizing such an ionic inner molecular salt type structure by transfer of protons or formation of hydrogen bonds, or formation of a metal complex salt is a so-called color developing compound. Agent. As the developer used in the present invention, for example, phenol and phenol derivatives, metal salts of phenol derivatives, metal salts of carboxylic acid derivatives, salicylic acid and salicylic acid metal salts, benzophenone and benzophenone derivatives, sulfonic acids, sulfonates, phosphorus Acids, metal phosphates, acid phosphates, acid phosphate metal salts, phosphorous acid, metal phosphites, zinc halides and the like can be mentioned. These can be used alone or in combination of two or more. Specific examples of phenol derivatives that can be used as a color developer are shown below by chemical formulas.

[0028]

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These phenol derivatives, for example, interact with the carboxylic acid residues of the color-forming color forming compound between the molecules to form hydrogen bonds as shown by the following chemical formula, thereby stabilizing the color-forming state. Can be Such an intermolecular interaction between the color-forming compound and the developer can occur even when both are solid-solved (dissolved and molecularly dispersed) in the matrix material.

[0030]

Embedded image

As exemplified in the above chemical formula, in a system in which a color former and a color developer interact with each other in a matrix material in a matrix material, and the color former becomes a color-forming type, as described later, Decoloring agent ”is (1) amorphous (amorphous)
When it is present in the matrix material in the form of microphase-separated fine particles, and (2) when it is crystalline and is dispersed as microcrystals in the matrix material, it may be heated or treated with a decolorizing aid. Without activation, the intermolecular interaction between the color developer and the decolorant (which is stronger in chemical equilibrium than the interaction between the color former and the color developer) is controlled by kinetic control. It is virtually impossible to "freeze" and the color developing compound stabilizes the color developing form with the developer.

[Color Decoloring Agent] The color decoloring agent in the erasable composition of the present invention is stronger than the intermolecular interaction between the color developing compound and the color developing agent, Fine particles (in which the decoloring agent is a crystalline compound) are present in the matrix material in the color-developing state of the decolorizable composition and in the melted, swollen or dissolved mixture in the decolored state. Compound) or a compound that can be dispersed and present as a microphase separated state (when the decoloring agent is in an amorphous state). Hydrogen bonding, ionic bonding, hydrophobic bonding, stereochemical inclusion, and the like can be used as the intermolecular interaction that can function between the decoloring agent and the developer. That is, from among compounds having one or more alcoholic hydroxyl groups, free carboxylic acid groups, carboxylate residues, cyclic saturated hydrocarbon residues, etc. in the molecule, the solubility in the matrix material used and Based on the temperature dependency, a material usable as a decoloring agent can be selected.

Specific examples of the decoloring agent used in the present invention include, for example, starch such as corn starch, tapioca starch and potato starch, and cereal powder containing starch as a main component (eg, flour, barley flour, rye flour, Rice starch), starch derivatives (eg, methylated starch, ethylated starch, acetylated starch, nitrated starch, etc.), cellulose, cellulose derivatives (eg, cellulose acetate, methylated cellulose, ethylated cellulose,
Nitrated cellulose), polysaccharides and derivatives thereof (eg, dextrin, dextran, mannan, amylopectin, amylose, xylan, glycogen, inulin, lichenin, chitin, hemicellulose, pectin, vegetable gum, agarose, carrageenan, saponin, etc.) and the like are suitable. Can be used.

The decolorizable composition of the present invention comprises at least a matrix material, a color former, a color developer, and a decolorizer having a controlled particle size. It is. The matrix material is used in an amount of usually 0.1 to 1000 parts by weight, preferably 0.5 to 100 parts by weight, more preferably 1 to 20 parts by weight, based on 1 part by weight of the coloring compound. The developer is usually 0.1 to 10 parts by weight with respect to 1 part by weight of the color-forming compound.
Preferably, the ratio is 1 to 2 parts by weight. The developer is 0.
When the amount is less than 1 part by weight, the color development of the erasable composition becomes insufficient due to the interaction between the color former and the developer. When the amount of the developer exceeds 10 parts by weight, it is difficult to sufficiently reduce the interaction between the two. The decoloring agent is used in an amount of usually 1 to 200 parts by weight, preferably 10 to 100 parts by weight, based on 1 part by weight of the coloring compound. When the amount of the decoloring agent is less than 1 part by weight, it becomes difficult to cause a state change between the colored state and the decolored state of the erasable composition. When the amount of the decoloring agent exceeds 200 parts by weight, the color of the erasable composition becomes insufficient.

In the erasable composition of the present invention, irrespective of the state of color development or the state of erasure,
The decoloring agent is always dispersed and present as fine particles or microphase separated. The size of the decoloring agent in the form of fine particles or microphase separation is such that the average diameter when its shape is approximated by a sphere does not exceed the diameter of the decolorizable composition having a predetermined size. is necessary. Assuming that the size of the decoloring agent in the state of fine particles or microphase separation in the decolorizable composition exceeds the diameter of the decolorizable composition as an average diameter when its shape is approximated by a sphere. The particles are substantially composed of only the decoloring agent. That is, in producing the erasable composition, the matrix material, the coloring compound, the color developer, and the coarse particulate erasing agent are prepared with the above composition without paying attention to the particle size of the erasing agent. And only kneading, pulverizing and classifying results in "particles comprising a matrix material, a color former, and a developer and substantially free of a decolorizer" and "substantially a decolorizer." A mixture of "particles consisting solely". The erasable colorant composed of such a particle mixture has no problem in terms of the color density in a color-developed state, but is used as an image forming material as compared with the erasable composition obtained by the production method of the present invention. If the ink is used, the resolution is poor, the decoloring characteristics are poor, and the fluidity and long-term storage stability when used as an ink are problematic.

In the erasable composition of the present invention, irrespective of the state of color development or the state of erasure,
It is preferable that the decoloring agent is always present in a state of fine particles or micro phase separation and dispersed with a non-smooth surface.
Here, the “erasing agent having a non-smooth surface” means an erasing agent in a fine particle or microphase separated state having a surface area larger than the surface area of a sphere having the same weight due to the unevenness of the surface. The erasing agent having such a non-smooth surface exhibits excellent decoloring characteristics because the surface for interacting with the color developer has a large surface area. Incidentally, the erasable composition of the present invention, as long as the function is not impaired, if necessary, a plasticizer comprising a low molecular compound,
Additives such as waxes, lubricants, release agents, light stabilizers, antioxidants, and charge control agents can be contained in appropriate amounts.

The method for producing the erasable composition of the present invention will be described below. [Method for producing an erasable composition] The method for producing an erasable composition according to the present invention includes a step of kneading a mixture of a matrix material, a color developer, a color former, and an erasing agent. It is characterized in that the decoloring agent is dispersed in the mixture so as to exist as fine particles or a microphase separated state whose average diameter when the shape is approximated by a sphere does not exceed a predetermined value. In producing the erasable composition of the present invention, a kneading apparatus having 15 strong shearing force such as a Banbury mixer is preferably used. That is, the decoloring agent is literally torn off by the strong shearing force of the kneading device, and is dispersed so as to exist as fine particles having a predetermined size or a microphase separated state.

The strength of the "kneading" in the kneading step can be defined as the amount of energy (power) applied per unit time per unit weight of the kneaded material. As a result of intensive studies, the average power applied per unit weight of the kneaded material over a period until the kneaded material (mixture) having the above composition reaches a molten / fluid state due to heat generated by frictional heat is 2 to 30 kW / kg, the decolorizing agent in the mixture, the average diameter when its shape is approximated by a sphere, as fine particles having a size not exceeding the diameter of the decolorizable composition or a microphase separated state, It has been found that it can be dispersed to have (with a non-smooth surface). Here, the “average power” is a value obtained by averaging the power over a period until the kneaded material (mixture) having the above composition reaches a molten / fluid state due to heat generated by frictional heat. Although depending on the type and structure of the kneading apparatus, the peak value of the power may reach twice or more the average power. The average power applied per unit weight of the kneaded material is 2 kW / kg
If it is less than 1, the rate at which the decoloring agent is torn off by the shearing force decreases, and the proportion of the decoloring agent dispersed and present in the form of particles when charged as a raw material increases, with the result that the decoloring properties deteriorate. On the other hand, when the average power applied per unit weight of the kneaded material exceeds 30 kW / kg, a local temperature rise due to frictional heat becomes remarkable, and a part of the erasable colorant is thermally decomposed or carbonized. It is not preferable. Since the local temperature rise due to frictional heat occurs in an extremely short time, it is not easy to prevent thermal decomposition even when cooling from the outer wall portion or the rotor portion of the kneading device.

To process the erasable composition of the present invention to produce a particulate erasable colorant, a thin film erasable image forming material, or a fibrous erasable colorant A known method can be appropriately applied and is not particularly limited. However, it goes without saying that various conditions need to be set during the manufacturing process so that the frozen decoloring effect does not appear.

The fact that the decoloring agent is present in the erasable composition in the form of fine particles having the above-mentioned size or in a microphase-separated state with a non-smooth surface can be obtained by various analysis means as described below. Can be used to confirm. For example,
Processing the decolorizable dye composition as it is into a thin film, and observing the thin film with an optical microscope, a confocal laser microscope, or the like, to confirm the size of the decolorant as fine particles or a microphase separated state. Can be. At this time, the fact that the observed “fine particle or microphase separation state” is attributed to the decoloring agent means that the coloring compound / matrix material, the developing agent / matrix material, the coloring compound and the color developing compound Agent / matrix material, decolorant / matrix material,
And when other additives are used, the composition of the combination of the other additives / matrix material is processed into a thin film under the same conditions as above, and compared with an optical microscope or a confocal laser microscope. Can be confirmed by Whether the decoloring agent is present as fine particles (crystal) or in a microphase separated state (amorphous) can be confirmed by X-ray diffraction.

When the size of the main component of the decoloring agent dispersed and present in the form of fine particles or microphase separation is less than 0.1 μm as an average diameter when approximated by a sphere, (1) X-ray Small-angle scattering method, (2) Observation of a thin film sample by a transmission electron microscope (using a technique such as osmium tetroxide staining as necessary to clarify the image), or (3) Scanning type of thin film sample surface The size of the fine particles or the microphase separated state can be confirmed by electron microscopic observation (in combination with a method of dissolving only the decoloring agent from the sample surface using an appropriate solvent). Also in this case, the attribution of the observed fine particles or microphase separation state can be confirmed by comparison with a sample containing no decoloring agent. The non-smooth surface of the decoloring agent present as dispersed in the form of fine particles or microphase separation means that (A) components other than the decoloring agent of the erasable composition are dissolved in an appropriate solvent, A method of taking out only the decolorizing agent and observing the surface with a scanning electron microscope, or (B) dissolving only the decoloring agent with a suitable solvent from the surface of the thin film in which the erasable composition is melted Can be confirmed by a method of observing the trace with a scanning electron microscope.

[Solvent System Containing Water] The erasable color composition of the present invention can be used as an erasable aqueous colorant.
Examples of the aqueous medium include water and a mixed solvent of water and an organic solvent compatible with water. Specific examples of the organic solvent compatible with water include, for example, methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, 1-pentanol, 2-pentanol, 3-pentanol, isopentyl alcohol, and the like. Solvents having an alcoholic hydroxyl group, such as -hexanol, 2-hexanol, 3-hexanol, cyclopentanol, cyclohexanol, ethylene glycol, propylene glycol, butylene glycol, and glycerin. The preferred proportion of water in a mixed solvent of water and an organic solvent compatible with water is 10 to 99% by weight. If the water content is less than 10% by weight, the organic solvent component may damage the matrix resin. Also, if the water content ratio is 99
If the amount is more than 10% by weight, the effect of mixing the organic solvent, for example, the effect of improving volatility or the effect of preventing drying cannot be exhibited.

[Binder] When the erasable composition of the present invention is used as an erasable aqueous colorant as a coating liquid, a printing ink, a jet ink, or an ink for a writing implement, the film forming property is required. Alternatively, in order to impart printability, a binder is required as one component of the erasable aqueous colorant. still,
Except when the binder itself acts as a dispersant,
It is used in combination with a dispersant described below. In the erasable aqueous colorant, the binder is used as a solution or an emulsion.
As the binder for the decolorable aqueous colorant, a binder that satisfies the following conditions among known binders can be appropriately selected and used. It is not necessary that all of the following conditions be satisfied at the same time.

(1) Particulate erasable colorant components (matrix resin, coloring compound,
And a developer or a low-molecular compound that can be dispersed while maintaining a color-developed state to impart film formability or printability. (2) A resin or a low-molecular compound that melts when subjected to a heat treatment for forming an erasable colorant into a decolored state after forming an image. (3) After forming an image, when the decolorizable colorant is treated with a decolorization aid to make it in a decolored state, it is swollen by the decolorization aid, or permeation and penetration of the decolorization aid. Resin or low molecular weight compound that does not hinder (4) A resin or a low-molecular compound that dissolves in the color erasing aid when the color erasable colorant is subjected to a color erasing aid treatment to bring the color erasable colorant into a color erasing state after the image is formed.

As a specific example of the binder, a fine powder comprising polystyrene as a matrix resin, a leuco dye as a color-forming compound, and n-propyl gallate as a color developer is used as an erasable colorant. When starch is used as the decolorizing agent, when the binder is used, for example, an aqueous emulsion of an acrylic acid or methacrylic acid ester copolymer; polyvinyl alcohol; a water-soluble cellulose derivative such as hydroxyethyl cellulose, hydroxypropyl cellulose, or methyl cellulose; acrylonitrile −
Acrylonitrile-butadiene copolymer rubber latex such as butadiene copolymer rubber and carboxylated acrylonitrile-butadiene copolymer rubber; methyl methacrylate-butadiene copolymer rubber such as methyl methacrylate-butadiene copolymer rubber and carboxylated methyl methacrylate-butadiene copolymer rubber Rubber latex; styrene-butadiene copolymer rubber, carboxylated styrene
Styrene-butadiene copolymer rubber latex such as butadiene copolymer rubber; acrylate rubber latex;
A vinyl chloride rubber latex, a vinyl pyridine-styrene-butadiene copolymer rubber latex, a polychloroprene rubber latex, and the like can be suitably used.

[Dispersant] A dispersible aqueous colorant is coated with a coating solution,
When used as printing ink, jet ink, or ink for writing instruments, a dispersant may be used in combination with a binder as a component of the erasable aqueous colorant in order to impart dispersion stability. preferable. As the dispersing agent for the decolorable aqueous colorant, a dispersing agent which satisfies all of the following conditions at the same time among known ones can be appropriately selected and used. (1) Dispersing the particulate erasable colorant component (comprised of a matrix resin, a color former, and a color developer) in the erasable aqueous colorant while maintaining the color-developed state, and dispersion stable A resin or a low-molecular compound capable of imparting properties. (2) When the decoloring agent is solvent-soluble, do not dissolve the decoloring agent. (3) The developer is not dissolved at all. (4) Do not dissolve or swell the matrix resin. (5) The dispersant itself does not act as a decoloring agent.

As a specific example of the dispersant, a fine powder composed of polystyrene as a matrix resin, leuco dye as a color-forming compound, and n-propyl gallate as a color developer is used as an erasable aqueous colorant. When a starch is used as a decolorizing agent and an aqueous emulsion of acrylic acid or methacrylic acid ester copolymer is used as a binder, for example, a nonionic interface such as a polyethylene oxide derivative having an aromatic ring group at a terminal is used. Activators can be suitably used.

The compositional ratio of the erasable aqueous colorant comprising the above-mentioned components is not particularly limited as long as the compositional ratio in the case of producing an ordinary wet colorant can be referred to. In addition, in order to produce an erasable aqueous colorant having such a composition, a usual coating liquid, printing ink, jet ink,
Alternatively, a method for producing ink for a writing instrument can be used. When the erasable composition of the present invention is used as an erasable aqueous colorant, other additives can be used, if necessary, in addition to the above essential components. However, needless to say, these additives must be selected so as not to adversely affect the coloring and decoloring of the erasable aqueous colorant. Specifically, humectants such as glycerin and urea; preservatives such as sodium benzoate, sodium dehydroacetate, potassium sorbate and 1,2-benzoisothiazolin-3-one; benzotriazole, tolyltriazole,
Rust inhibitors such as ethylenediaminetetraacetic acid; lubricants such as potassium linoleate and sodium oleate; ultraviolet absorbers and pH adjusters can be added. Furthermore, when applying the erasable aqueous colorant of the present invention to an aqueous ballpoint pen having a simple structure without an ink flow control member inside the pen body, polysaccharides such as xanthan gum, welan gum and succinoglycan are added. The ink is used as a viscous ink to which thixotropy is imparted. The amount of these polysaccharides to be added is preferably in the range of 0.1 to 0.8% by weight in the erasable aqueous colorant composition.

[Color erasing method] In order to bring the color erasable composition into a color erasable state, that is, to erase the color, the color is erased by heating and melting the color erasable composition; There is a method in which a part or all of the erasable composition is brought into contact with a liquid or gaseous erasing aid which dissolves or swells the color to erase the color. By heating and melting the decolorizable composition, the molecular motion of the developer that has been kinetically frozen becomes active, and moves through the molten state mixture of the composition to separate fine particles or microphase. Adsorbs on the non-smooth surface of the erasable composition present in the state,
The interaction between the color former and the color developer is stronger than that between the color developer and the color developer, and a stronger molecular interaction between the color developer and the color erasing agent occurs. It stabilizes and becomes a decolored state. Since the decolored state as described above is stable in terms of equilibrium, it continues even if the heating is stopped.

The heating means for decolorizing the erasable composition may be in any form, for example, a thermal printer head (TPH), a thermal bar, a hot stamp,
A heat roller or the like can be used. Further, heating may be performed by an infrared lamp or hot air. When a large amount of paper on which characters and images are formed by the image forming material using the erasable composition of the present invention is subjected to a large amount of color erasing at a time, a box-shaped warm air dryer or a blown thermostat is preferable. Can be used for

The heating temperature at the time of decolorizing the erasable composition by heating is the temperature at which the erasable composition becomes a mixed and molten state as the composition ("degradation of the melting point due to mixing"). The temperature is lower than the melting point or the softening point of the coloring composition component alone). The upper limit of the heating temperature when decolorizing the decolorizable composition by heating,
It is the lowest temperature among the thermal decomposition onset temperatures of the decolorable composition component. Note that, depending on the type or combination of the color-forming compound, the color developer, the decoloring agent, and the matrix material, the component thermally decomposes by heating, or causes an undesired side reaction to produce a non-decolorable colored compound. Or may be formed. In such a case, it is preferable to apply a method using a color erasing aid described below as the color erasing method.

When decoloring is carried out by bringing a part or all of the decolorizable composition in a colored state into contact with a liquid decoloring aid (organic solvent) for dissolving or swelling, the composition is kinetically frozen. The molecular motion of the developer which has been activated by the color erasing aid, moves in the dissolved or swollen composition, and moves to the surface of the erasable composition present in the state of fine particles or microphase separation. It absorbs and is stronger than the molecular interaction between the color developing compound and the color developer, and causes a strong molecular interaction between the color developing compound and the color erasing agent. As a result, the color of the color developing compound is developed. The state becomes unstable and becomes a decolored state. Since the decoloring state as described above is equilibrium-stable, it continues even if the liquid decoloring aid is removed. As is apparent from such a decoloring mechanism, it is extremely effective to carry out this method at a temperature higher than room temperature, for example, at 50 ° C. to 80 ° C.

When decoloring is performed by contacting a gas decolorizing auxiliary (organic gas) that swells the color-developing decolorizable composition, the molecules of the developer that have been kinetically frozen are also used. The movement is activated by the color erasing aid, moves through the swollen or dissolved composition, and is adsorbed on the surface of the erasable composition present in the state of fine particles or microphase separation, thereby forming a color forming compound. Is stronger than the intermolecular interaction between the developer and the developer, and causes a strong intermolecular interaction between the developer and the decolorant. As a result,
The coloring state of the coloring compound is destabilized and becomes a decolored state. Since the decoloring state as described above is equilibrium-stable, it continues even after the gas decoloring aid is removed and the swelling state is removed. As is apparent from such a decoloring mechanism, it is extremely effective to carry out this method at a temperature higher than room temperature, for example, at 50 ° C. to 80 ° C.

The gas used as the color erasing aid in the method of decoloring by contacting the gas with the color erasing aid that swells the colored state of the color erasable composition contains the gas inside the erasable composition. It is necessary to have the property of easily penetrating to the swelling.
Specifically, organic compounds which are gaseous at normal temperature and pressure, such as ethylene, acetylene, and dimethyl ether, and naphthalene, p
-An organic compound, such as dichlorobenzene, which sublimates at normal temperature and normal pressure to become a gas, can be suitably used.

The organic solvent used as the color erasing aid in the method of erasing by contacting the liquid erasable composition in a colored state with a liquid erasing aid for swelling or dissolving the color developing agent is (A) a color developer. It preferably has a property of assisting the formation of a hydrogen bond between the dye and the decoloring agent, and further has a property of having high affinity with the matrix material (B) and easily penetrating into the interior of the decolorizable composition. It is preferred to have. The solvent satisfying the above property (A) can be used alone. Further, two or more solvents may be mixed to satisfy the above two properties.

The first type of solvent, ie, a solvent having both the properties (A) and (B), includes ether,
Examples include ketones and esters. Specifically, for example, ethyl ether, ethyl propyl ether, ethyl isopropyl ether, isopentyl methyl ether,
Saturated ethers such as butyl ethyl ether, dipropyl ether, diisopropyl ether, ethyl isopentyl ether, dibutyl ether, dipentyl ether, diisopentyl ether and dihexyl ether; unsaturated ethers such as ethyl vinyl ether, allyl ethyl ether, diallyl ether and ethyl propargyl ether Saturated ethers; ethers of dihydric alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane; oxetane; Cyclic ethers such as tetrahydrofuran, tetrahydropyran, dioxolan, dioxane, and trioxane; acetone, methyl ethyl ketone,

Methyl propyl ketone, diethyl ketone,
Isopropyl methyl ketone, butyl methyl ketone, ethyl propyl ketone, isobutyl methyl ketone, pinacolone, methyl pentyl ketone, butyl ethyl ketone, dipropyl ketone, diisopropyl ketone, hexyl methyl ketone, isohexyl methyl ketone, heptyl methyl ketone, dibutyl ketone, etc. Unsaturated ketones such as ethylidene acetone, allyl acetone and mesityl oxide; cyclic ketones such as cyclopentanone, cyclohexanone, cycloheptanone and cyclooctanone; ethyl formate, propyl formate, butyl formate, isobutyl formate and formic acid Pentyl, isopentyl formate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, acetic acid sec
-Amyl, 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, butyric acid Butyl, pentyl butyrate, isopentyl butyrate, sec-butyrate, amyl, methyl isobutyrate, ethyl isobutyrate, propyl isobutyrate, isopropyl isobutyrate, butyl isobutyrate, pentyl isobutyrate, isopentyl isobutyrate, sec-isobutyrate
Amyl, methyl valerate, ethyl valerate, propyl valerate, isopropyl valerate, butyl valerate, methyl valerate, ethyl valerate, propyl valerate, isopropyl valerate, butyl valerate, methyl hexanoate, ethyl hexanoate, Esters such as propyl hexanoate and isopropyl hexanoate. Solvents other than the above include dichloromethane, γ-butyrolactone, β-propiolactone, N-methylpyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-dimethylisoindolinone, dimethyl sulfoxide and the like. is there. These may be used alone or as a mixture of two or more. When using a mixed solvent, the mixing ratio can be set arbitrarily.

Examples of the solvent of the second kind, that is, a solvent having the property of the above (A) but having low affinity for the matrix, include, for example, water, methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and the like. 1-pentanol, 2-pentanol, 3
-Pentanol, isopentyl alcohol, 1-hexanol, 2-hexanol, 3-hexanol, cyclopentanol, cyclohexanol, ethylene glycol, propylene glycol, butylene glycol, glycerin and the like.

A solvent of the third kind, that is, a solvent (B) which does not have the properties of the above (A) but has a high affinity for the matrix
As, for example, toluene, ethylbenzene, propylbenzene, cumene, butylbenzene, isobutylbenzene, sec-butylbenzene, pentylbenzene, diethylbenzene, mesitylene, xylene, cresol,
Ethylphenol, dimethoxybenzene, dimethoxytoluene, benzyl alcohol, tolyl carbinol, cumyl alcohol, acetophenone, propiophenone,
Hexane, pentane, heptane, octane, cyclohexane, cyclopentane, cycloheptane, cyclooctane, petroleum fractions (petroleum ether, benzine, etc.) and the like can be mentioned.

As mentioned above, the first solvent can be used singly and favorably. The second type of solvent may be used alone or may be mixed with the first type of solvent. In this case, any kind of solvent has a decoloring ability, so that it can be used at an arbitrary mixing ratio. When a mixed solvent of the second type solvent and the third type solvent is used, the mixing ratio of the two is not particularly limited as long as a sufficient decoloring ability can be obtained. Is preferred. The third type of solvent may be used as a mixture with the first type of solvent. In this case, the content of the third type solvent may be 90% by weight or less. or,
A mixture of the first to third solvents may be used. In this case, the content of the third type solvent is preferably 80% by weight or less.

In order to efficiently decolor the erasable colorant, the solvent may be heated in advance. In this case, it is preferable to heat the temperature of the solvent to 40 ° C. or higher within a range not exceeding the boiling point of the solvent. When a decoloring method using a solvent is used, a decoloring agent can be added to the solvent.

[0063]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples.

Example 1 Commercially available corn starch (particle outer diameter of about 9 to 15 μm) was used as a starch as a decolorizing agent. The particle size of starch was determined by measuring a sample obtained by ultrasonically dispersing in water containing an electrolyte using sodium dodecylbenzenesulfonate as a dispersant with a Coulter Counter TA-II (manufactured by Coulter Corporation). . FIG. 1 shows a scanning electron micrograph of the used starch. As is evident from FIG. 1, the surface of the commercially available starch particles is non-smooth.

The heat-sensitive dye PSD-18 is used as a color-forming compound.
4 (manufactured by Nippon Soda Co., Ltd.), 2 parts by weight of propyl gallate as a color developer, 17 parts by weight of starch (a number average particle diameter of 9 μm and a volume average particle diameter of 15 μm) as a decolorizer, 79 as a matrix material Parts by weight of polystyrene and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge controlling agent are mixed in advance, and a total of 1.2 k
g of the mixture was kneaded using a Banbury mixer, and the mixture became molten and fluid in about 2 minutes due to frictional heat.
During this time, the average power applied per unit time per unit weight of the mixture (hereinafter simply referred to as the average power) is 6.67 kW / kg, and the peak value is 8.33 k.
W / kg. The kneaded product was cooled to obtain a black kneaded product (erasable composition) of Example 1.

About 10 mg of the erasable composition of Example 1 was placed on a slide glass heated to 100 ° C. on a hot plate, and another slide glass heated to 100 ° C. was overlaid, pressed and cooled. Then, a thin film sample having a thickness of about 20 μm sandwiched between glass plates was prepared. When melted at 100 ° C., it was confirmed that the erasable colorant of Example 1 maintained black. When the thin film produced by melting was observed under a microscope, particles belonging to the decoloring agent starch could hardly be observed.

Therefore, about 10 parts of the erasable composition of Example 1 were used.
g was dissolved in 100 ml of tetrahydrofuran, and the insoluble matter (starch) was filtered off using a membrane filter made of ethylene tetrafluoride (pore size: 0.1 μm), and sufficiently washed with 200 ml of tetrahydrofuran. It was confirmed by an infrared absorption spectrum that the obtained grayish insoluble matter was starch. The obtained insoluble matter (starch) was dispersed in tetrahydrofuran, applied to a conductive substrate for scanning electron microscope observation, dried, carbon was deposited, and observed with a scanning electron microscope. Although coarse particles having a diameter of about 5 μm were also observed in the visual field, it was confirmed that most of the starch was present as fine particles having a diameter of less than 2 μm as shown in FIG. From the comparison between FIG. 1 and FIG. 2, it can be seen that the starch particles were torn off and made finer by the strong shearing force during kneading using a Banbury mixer.

Next, in order to perform decoloring by heating, the above-mentioned thin film sample of the erasable composition of this example was heated at 200 ° C. for 1 hour.
Upon heating for 0 minutes and cooling to room temperature, the black color development was erased and the thin film became milky white. The reason why the decolored thin film does not become transparent and looks milky white is that starch fine particles are dispersed in the matrix material. For comparison, a kneaded product consisting of a color former, a color developer, a charge controlling agent, and a matrix material was produced in the same manner as in this example except that starch of the decoloring agent was not included,
This was sandwiched between glass plates and melt-formed at 100 ° C. to obtain a black thin film, which was further heated at 200 ° C. for 10 minutes and cooled to room temperature, but no decoloration occurred.

From the above observations, the mechanism of decoloring when starch is used as a decolorizing agent is that the developer, which has been hydrogen-bonded to the color forming compound, moves through the matrix material by heating, and It is presumed that the particles reach the surface of the starch fine particles, which are adsorbed there, and interact with each other. As a result, the coloring state of the color former is destabilized and the color is erased.

The kneaded material of Example 1 was roughly pulverized to a particle outer diameter of 1 mm by a rotary cutter with a cutter blade, and then reduced to a maximum particle diameter of 20 μm or less by a circulating air jet pulverizer equipped with a cyclone classifier. Crushed and further classified using another cyclone classifier to obtain a number average particle diameter of 8 μm.
m, and the particulate erasable colorant of Example 1 was obtained as fine particles having a volume average particle size of 12 μm (yield: 81%).
The particle diameter was measured in the same manner as described above. The yield of the pulverization / classification process is a loss, which is a portion that remains in the apparatus and cannot be taken out (constant regardless of the charged amount) and a portion that cannot be collected by the cyclone classifier (proportional to the charged amount).
The above value is an example because it is affected by
Reasonable values can be achieved for the yield of the classification process.

The particulate erasable colorant of Example 1 produced as described above (number-average particle diameter 8 μm and volume-average particle diameter 12 μm; internal starch particles are less than 2 μm in diameter)
The toner of Example 1 was prepared by adding 1 part by weight of hydrophobic silica to 100 parts by weight. The obtained toner is put into a toner cartridge of an electrophotographic copying machine, and a test image (test chart) is printed on neutral paper for a copying machine (reflectance: 0.1).
08). The obtained copy image has a sufficient image density, the resolution is standard as a toner image of the above particle size, shows high durability under normal use conditions, and is heated at 100 ° C. for 30 minutes. Even the image was maintained. Incidentally, since the heat fixing process of the toner composed of the erasable composition is performed at a speed on the order of seconds including the completion of cooling, the mass transfer of the erasing agent or the developer in the erasable composition and Intermolecular interaction between the decoloring agent and the developer is kinetically suppressed, and as a result, an image having a sufficient density can be formed. This copy image can be erased by heating to 190 ° C. or higher, or by contacting it with a liquid or gaseous erasing aid.

A 100-sheet paper sheet on which a copy image was formed with the toner comprising the erasable composition of Example 1 was bundled, and the temperature was adjusted to 190 ° C. in a blast type thermostat (Yamato Type DN83). And left at the same temperature for 12 hours, and then taken out. As a result, all the copy images formed on 100 sheets of paper were erased, and could not be confirmed with the naked eye. The reflection density of each of the erasable image recording papers after erasing was measured and found to be 0.10. That is, it was confirmed that excellent decoloring characteristics were exhibited. The paper on which the copy image had been erased by heating was erased and left at 60 ° C. for 300 hours, but the image did not reappear.

The paper on which a copy image was formed with the toner comprising the erasable composition of Example 1 was immersed in methyl isobutyl ketone (MIBK). As a result, the image copied on the paper was erased and could not be confirmed with the naked eye. The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited. When the numerical values of the reflection density of the paper after erasing were compared between the erasing by heating and the erasing by solvent treatment, the values in the case of solvent treatment were slightly better. This is because, in the case of decolorization by solvent treatment, the erasable colorant is decolorized and soaks into the paper at the same time and disappears from the paper surface, whereas in the case of heat decoloration,
This is because the erased colorant melt that has been erased remains on the paper surface and slightly affects the reflection density measurement, and there is no problem in reusing the erased paper.

In order to confirm the decoloring process by the solvent treatment,
When the toner was brought into contact with MIBK, it swelled and dissolved instantaneously. Apply this liquid thinly on a glass plate and at room temperature,
Evaporate the solvent and add a vacuum of 0.001 Pa
The solvent was completely removed by heating at 00 ° C. for 24 hours.
The decolored state was maintained even when the solvent was removed. From the above observations, even when the color was decolorized using a solvent, the developer which had been hydrogen-bonded to the color-forming compound was activated by the solvent and moved through the dissolved or swollen mixture, causing the starch, which is a decolorizer, to be starch. The particles reach the surface of the microparticles, are adsorbed there, and interact with each other. As a result, the coloring state of the coloring compound becomes unstable,
It is assumed that the color will be erased.

The paper whose copy image was erased by the solvent treatment was left at 60 ° C. for 300 hours, but the image did not reappear. Thereafter, another image was transferred to paper whose image was erased by the solvent treatment, and the process of erasing the image by the solvent treatment was repeated nine times. The 10th image transferred after that is 1
The quality was the same as the first image. Further, copying and decoloring were repeated up to 50 times. As a result, the paper was mechanically damaged, but the quality of the copied image and the quality of the erased state were good.

COMPARATIVE EXAMPLE 1 Instead of the Banbury mixer in Example 1, kneading was performed using a pressurized kneader of the same capacity while adjusting the pressurizing pressure.
It became a fluid state. During this time, the average power applied to the mixture was 1.25 kW / kg and the peak value was 2.
It was 5 kW / kg. When the pressure of the pressure kneader is increased, the average power applied to the mixture becomes a large value. The obtained kneaded material was cooled to obtain the erasable composition of Comparative Example 1.

A thin film of the erasable composition of Comparative Example 1 was prepared in the same manner as in Example 1. It was confirmed that the thin film kept black. When this molten thin film was observed under a microscope,
Particles attributed to the quencher starch were clearly observed. Next, the insoluble matter (confirmed to be starch in the infrared absorption spectrum) was separated from the erasable composition of Comparative Example 1 in the same manner as in Example 1, and observed with a scanning electron microscope. Spherical starch particles as shown in FIG. 1 were observed in most of the visual field. Figure 3
It was confirmed that spherical starch particles having a diameter of about 10 μm were broken into several pieces as shown in FIG. From the comparison between FIG. 1 and FIG. 3, in the kneading using the pressurized kneader (the average power applied to the mixture is 1.25 kW / kg),
Although a shearing force of such a degree that the starch particles are broken into several pieces acts, when the Banbury mixer is used (average power in Example 1 is 6.67 kW / kg), the starch particles are finely divided. It turns out that it did not reach. Therefore, the experiment of increasing the average power applied to the mixture by gradually increasing the pressurizing pressure of the pressurized kneader was repeated. When the average power applied to the mixture was 2 kW / kg or more, It was confirmed that the fineness of the decoloring agent / starch particles progressed smoothly.

In the same manner as in Example 1 except that the erasable composition of Comparative Example 1 was used, the composition was roughly pulverized to a particle outer diameter of 1 mm, and then circulated air equipped with a cyclone classifier. The powder is crushed by a jet crusher to a maximum particle diameter of 20 μm or less, and further classified using another cyclone classifier, and the number average particle diameter is 8 μm and the volume average particle diameter is 12 μm.
Was obtained in a yield of 80%. The particle diameter was measured in the same manner as in Example 1. Microscopic observation of the thin film (using the composition before fine pulverization) and the molten thin film of the particulate erasable colorant of Comparative Example 1 revealed that starch particles having a diameter of several μm to 10 μm or more (electron microscope) Observation confirmed that many particles (corresponding to the particles in FIG. 3) were present. That is, since there was a region where the particle size as the particulate erasable colorant and the starch particle size were equal, Comparative Example 1 was used.
It is presumed that particles composed of only starch, which is a decoloring agent, are substantially mixed in the particulate decolorizable colorant. Also, when particles composed of substantially only starch are mixed in the particulate erasable colorant, the erasable agent is contained in other particulate erasable colorants that are not starch particles. The component (starch) will be less than the design value.

The particulate erasable colorant of Comparative Example 1 produced and analyzed as described above (number-average particle diameter 8 μm and volume-average particle diameter 12 μm; including particles consisting essentially of starch) 100 1 part by weight of hydrophobic silica was added to 1 part by weight to prepare a toner. The obtained toner is placed in a toner cartridge of an electrophotographic copying machine, and a test image (test chart) is printed on neutral paper for a copying machine (with a reflectance of 0.0).
8). Although the density of the obtained copy image was the same as that of Example 1, the resolution was inferior to that of the toner image having the above-mentioned particle diameter, and blurring was observed in places of fine lines. Further, when the color was erased by heating, the result was clearly inferior to the case of Example 1 using the toner comprising the erasable composition of Example 1. That is, 100 sheets of paper on which a copy image was formed with the toner composed of the erasable composition of Comparative Example 1 were treated at 190 ° C. for 1 sheet in the same manner as in Example 1.
After heating for 2 hours, it was taken out. As a result, all the copied images formed on 100 sheets of paper were erased, but afterimages were confirmed with the naked eye. When the reflection density of each of the erasable image recording paper after erasing was measured, it was about 0.25. That is, it was found that the color erasing property by heating was remarkably poor as compared with the copy image formed by the toner comprising the erasable composition of Example 1. These causes are as described above, since the erasable color composition of Comparative Example 1 does not contain fine particles of the starch particles as the raw material, and thus contains particles substantially consisting of starch only, and is smaller than the design value. This is presumed to be because the composition contains an erasable composition having a low content of the decoloring agent.

Example 2 The same commercially available corn starch (particle outer diameter of about 9 to 15 μm) as used in Example 1 was used as a decolorizing agent. 4 parts by weight of crystal violet lactone as a coloring compound, 2 parts by weight of propyl gallate as a color developer, 8 parts by weight of starch (number average particle diameter 9 μm and volume average particle diameter 15 μm) as a decolorizer, 85 as a matrix material Parts by weight of polystyrene and 1 part by weight of LR-147 (manufactured by Nippon Carlit Co., Ltd.) as a charge controlling agent were mixed in advance, and a total of 66 kg of the mixture was kneaded using a Banbury mixer. It became a molten and fluid state. During this time, the average power applied to the mixture was 2.44 kW / kg, and the peak value was 4.27 kW / kg. The kneaded material was cooled to obtain the kneaded material of Example 2 (erasable composition).

This erasable composition was heated to 100 ° C. and melted to form a thin film in the same manner as in Example 1. The composition was observed with an optical microscope, but very few starch particles were observed. An insoluble substance (starch was confirmed from an infrared spectrum) was separated from this composition in the same manner as in Example 1, and was observed with a scanning electron microscope. As a result, in the case of Example 1 (FIG. 2). It was confirmed that the particles were formed into fine particles in the same manner as described above. However, the diameter 5μ seen in the field of view
The number of particles around m was greater than in Example 1. This is presumed to reflect the difference in the value of the average power applied to the mixture.

A particle having a number average particle diameter of 8 μm and a volume average particle diameter of 12 μm (the internal starch particles are
μm or less) to produce the particulate erasable composition of Example 2. The yield was equivalent to that of Example 1. The particle diameter was measured in the same manner as in Example 1. A toner of Example 2 was prepared by adding 1 part by weight of hydrophobic silica to 100 parts by weight of the particulate erasable composition of Example 2. The obtained toner was placed in a toner cartridge of an electrophotographic copying machine, and a test image (test chart) was transferred to neutral paper for a copying machine (reflectance 0.08). The resulting blue-violet image had a sufficient image density, exhibited high durability under normal use conditions, and maintained the image even after heating at 100 ° C. for 30 minutes. Heat this image above 190 ° C or
Alternatively, the color can be erased by contact with a liquid or gaseous color erasing aid. When the paper on which the image was copied was immersed in methyl isobutyl ketone (MIBK), the image copied on the paper was erased and could not be visually confirmed.
The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited.

Example 3 The erasable composition of Example 1 was roughly pulverized to a particle outer diameter of 1 mm with a rotary cutter-type pulverizer, and then this was circulated with an air jet pulverizer equipped with a cyclone classifier. To a maximum particle diameter of 10 μm or less, and further classified using another cyclone classifier to obtain a number average particle diameter of 3.0 μm.
In addition, the particulate decolorizable composition of Example 3 was obtained as fine particles having a volume average particle diameter of 6.0 μm (the diameter of the internal starch fine particles was 2 μm or less). The particle diameter was measured in the same manner as in Example 1.

20 parts by weight of the particulate erasable composition of Example 3 were mixed with 20 parts by weight of a binder methyl methacrylate-butyl acrylate-acrylic acid (ammonium salt) copolymer and 2 parts by weight of a nonionic dispersant. The mixture was dispersed in a binder solution containing 10 parts by weight of propylene glycol and 48 parts by weight of water using a three-roll mill to prepare the erasable water-based colorant of Example 3.

The erasable water-based colorant was applied to the whole surface of one side of neutral paper for a copying machine (reflectance 0.08) using a bar coater and dried. This paper was immersed in methyl isobutyl ketone (MIBK). As a result, the decolorizable aqueous colorant was decolorized, and the color could not be confirmed with the naked eye.
The measured reflection density of the paper after erasing was 0.08. That is, it was confirmed that excellent decoloring characteristics were exhibited.

A pen body holder to which a pen body formed by binding a fiber bundle with a resin is fixed is made of an aluminum cylinder fitted to the tip via a valve mechanism. At the time of marking, the pen tip is pressed against the paper to open the valve. Prepare a pen body of a marking pen of the type that leads the ink in the cylinder to the pen tip,
The above-mentioned erasable water-based coloring agent was filled in the mixture, and a writing implement was prepared as an application example. Using this writing instrument, writing was performed on neutral paper for a copying machine (reflectance 0.08). The drawn lines had a sufficient concentration, exhibited high durability under ordinary use conditions, and were maintained even after heating at 100 ° C. for 30 minutes. This drawing line could be erased by heating it to 190 ° C. or higher, or by contacting it with a decolorizing aid.

That is, the paper written with this writing instrument was immersed in methyl isobutyl ketone (MIBK). As a result, the drawn line drawn with the erasable aqueous colorant using the erasable composition of Example 3 was erased and could not be confirmed with the naked eye. The paper whose drawing line was erased by the solvent treatment using the erasable aqueous colorant using the erasable composition of Example 3 was heated to 60 ° C.
For 300 hours, but the drawing did not appear again. Thereafter, the process of writing the drawing line on the paper with the drawing line erased with the above-mentioned writing implement and erasing the color by the solvent treatment was repeated 9 times. The tenth stroke drawn thereafter was of the same quality as the first stroke, and was not broken on the erased stroke. Further, writing and decoloring were repeated up to 50 times. As a result, the quality of the drawn lines and the quality of the decolored state were good.

In order to test the storage stability of the erasable aqueous colorant using the erasable composition of Example 3 of the present invention,
A long-term storage test at 50 ° C. was performed in a state in which (a) the glass bottle and (b) the writing implement of Example 3 were sealed. As a result, even after storage at 50 ° C. for 6 months, no change was observed in the color development state and dispersion state, and no deterioration was observed in the decoloring characteristics after coating or drawing on paper. .

Comparative Example 2 For the purpose of producing a pigment composition particle having a composition containing no decoloring agent for comparison, a leuco dye PSD-18 was used as a coloring compound.
4 (manufactured by Nippon Soda Co., Ltd.), 2 parts by weight of propyl gallate as a color developer, and 79 parts by weight of polystyrene as a matrix material are mixed in advance, and a temperature of not more than 100 ° C. is sufficiently determined using a kneader. After kneading, the mixture was cooled to produce a dye composition that developed black. The kneaded product (dye composition) is subjected to a particle outer diameter of 1 with a cutter blade rotary grinder.
mm, and then crushed by a circulating air jet pulverizer equipped with a cyclone classifier to a maximum particle size of 10 μm.
m, and then classified using another cyclone classifier to obtain pigment composition particles having a number average particle diameter of 3.0 μm and a volume average particle diameter of 6.0 μm.

To 83% by weight of this particulate pigment composition, finely ground starch (number average particle size 3.0) was used as a decolorizing agent.
μm and a volume average particle diameter of 6.0 μm) (leuco dye, color developer, and decolorant in the case of the erasable aqueous colorant of Example 3). 20 parts by weight of methyl methacrylate as a binder
To a binder solution containing 20 parts by weight of a butyl acrylate-acrylic acid (ammonium salt) copolymer, 2 parts by weight of a nonionic dispersant, 10 parts by weight of propylene glycol, and 48 parts by weight of water, using a three-roll mill By dispersing, an erasable aqueous colorant of Comparative Example 2 was prepared. This was filled in the same pen body as in Example 3 to produce a writing implement of Comparative Example 2.

The paper obtained by coating the erasable water-based colorant of Comparative Example 2 on paper and the drawing written on paper by using the writing implement of Comparative Example 2 were tested immediately after the preparation. Decoloring characteristics equivalent to those of the application example were exhibited. However, as a result of testing the storage stability of the erasable water-based colorant of Comparative Example 2 in the same manner as in Example 3, starch particles were aggregated only after storage at 50 ° C. for one week. It becomes difficult to apply the decolorizable aqueous colorant, while Comparative Example 2
Writing instrument is no longer writable. It is presumed that the cause of such an inconvenience is that the fine particles of starch as the decoloring agent are not protected by the matrix material.

[0092]

As described above in detail, according to the erasable composition of the present invention and the method for producing the same, a stable image is formed on paper, and the formed image has excellent erasing characteristics. Thus, an erasable composition that can be erased by the method can be efficiently produced.

[Brief description of the drawings]

FIG. 1 is a diagram obtained by observing a raw material starch used in Example 1 with a scanning electron microscope. The length of the white line inserted in the figure is 10 μm.

FIG. 2 is a diagram obtained by observing a starch taken out from the erasable composition of Example 1 with a scanning electron microscope. The length of the white line inserted in the figure is 5 μm.

FIG. 3 is a diagram obtained by observing a starch taken out of the erasable composition of Comparative Example 1 with a scanning electron microscope. The length of the white line inserted in the figure is 5 μm.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Mitsuo Noda 1-7-6 Nibashi-Bakucho, Chuo-ku, Tokyo Dainichi Seika Industry Co., Ltd. F-term (reference) 2H005 AA06 AA27 AB07 CA21 CA30 4J039 BE02

Claims (7)

[Claims] 1. At least a matrix material, a developer,
A color developing compound which develops a color by an intermolecular interaction with the color developer; and a decolorizing compound which is stronger than the molecular interaction between the color developing agent and the color developing compound and has an intermolecular interaction with the color developing agent. An erasable composition comprising a coloring agent, wherein (1) when the composition is used as a particulate erasable colorant, the erasable colorant is contained in the particulate erasable colorant. The agent always exists as fine particles or microphase-separated state whose average diameter when its shape is approximated by a sphere does not exceed the diameter of the particulate erasable colorant, and (2) the composition Is used as a thin film-like image forming material, in the thin film image forming material, the decoloring agent always has an average diameter when the shape is approximated by a sphere, and the film thickness of the thin film image forming material. Exists as fine particles or microphase separated in a size not exceeding
(3) When the composition is used as a fibrous colorant, in the fibrous colorant, the decolorant always has an average diameter when the shape is approximated by a sphere. Fine particles having a size not exceeding the diameter of the fiber cross section or exist in a microphase-separated state, and in any of the above cases, in the color-developing state, the color developer and the color-forming compound are contained in the matrix material. Present by intermolecular interaction, in the decolored state, the developer does not undergo intermolecular interaction with the color-forming compound, and on the surface of the decoloring agent present as fine particles or microphase separated state. A decolorizable composition characterized in that it is adsorbed and present in a molecular interaction with the decoloring agent. 2. The decolorizable composition according to claim 1, wherein the surface of the decoloring agent is non-smooth. 3. The erasable composition according to claim 2, which is in the form of particles. 4. At least a matrix material, a developer,
A color developing compound which develops a color by an intermolecular interaction with the color developer; and a decolorizing compound which is stronger than the molecular interaction between the color developing agent and the color developing compound and has an intermolecular interaction with the color developing agent. A method for producing an erasable color composition comprising a coloring agent, wherein in the kneading step of kneading a mixture comprising the matrix material, the developer, the coloring compound, and the erasing agent, When the shape of the decoloring agent is approximated by a sphere in the mixture, the average diameter is as follows (1) to (3).
A method for producing an erasable color composition, wherein the composition is dispersed so as to exist as fine particles having a size not exceeding a value selected from the group or a microphase separated state. (1) when the composition is used as a particulate erasable colorant, the average diameter of the particulate erasable colorant approximated by a sphere; (2) the composition is a thin film (3) when the composition is used as a fibrous discolorable colorant, when the composition is used as a fibrous discolorable colorant, Fiber cross section diameter. 5. In the kneading step, the average power per unit weight applied per unit time to the mixture per unit time is 2 to 30 kW over a period until the mixture reaches a molten / fluid state due to heat generated by frictional heat. The method for producing the erasable composition according to claim 4, wherein the composition is / kg. 6. A toner comprising the erasable composition according to claim 1 or 3. 7. An aqueous erasable colorant comprising fine particles of the erasable composition according to claim 1 or 3 dispersed in a solvent system containing water.