GB2107480A - Encapsulated electrostatographic toner material - Google Patents

Abstract

An electrostatographic toner material comprising encapsulated toner particles having an average particle size in the range from about 0.5 to about 1,000 microns, in which the toner particle comprises a pressure fixable adhesive core material containing a colorant and a pressure rupturable shell enclosing the core material, said shell being composed of a double layer comprising a polyurethane, polyurea and/or polythiourethane layer and a polyamide layer.

Description

SPECIFICATION Electrostatographic toner material This invention reiates to an electrostatographic toner material, and more particularly relates to a pressure fixable electrostatographic toner material comprising encapsulated toner pa rticles.

There is known the electrostatography which comprises developing a tone electrostatic latent image contained on a photoconductive or dielectric surface with a toner material containing colorant and a fixing aid to produce a visible toner image, and transferring and fixing the visible toner image onto a surface of a support medium such as a sheet of pauper.

The development of the latent image to produce a visible toner image is carried out by the use of either a developing agent consisting of a combination of toner material with carrier particles, or a developing agent consisting of toner material only. The developing process utilizing the combination of toner material with carrier particles is named "two component developing process", while the developing process utilizing only the toner material is named "one component developing process".

The toner image formed on the latent image is then transferred onto a surface of a support medium and fixed thereto. The process for fixing the toner image to the support medium can be done through one of three fixing processes, that is, a heat fixing process (fusion process), a solvent fixing process end a pressure fixing process.

The pressure fixing process which involves fixing the loner material onto the surface of a support medium under application of pressure thereto is described, for instance, in United States Patent No.

3,269,626. The pressure fixing process involving the use of neither the heating procedure nor the solvent produces no such troubles as inherently attached to either the heat fixing process or the solvent fixing process. Moreover, the pressure fixing process can be employed with a high speed automatic copying and duplicating process, and the access time is very short in the pressure fixing process. Accordingly, the pressure fixing process is said to be an advantageous fixing process inherently having a variety of preferable features.

However, the pressure fixing process also has a variety of inadvantageous features. For instance, the pressure fixing process generally provides poorer fixabilitythan the heat fixing process does, whereby the toner image fixed onto a paper is apt to rub off easily. Further, the pressure fixing process requires very high pressure forthe fixing, and such a high pressure tends to break the cellulose fibers of the support medium such as paper and also produces glossy surface on the support medium. Moreover, the pressing roller requires to have relatively greater size, because the roller necessarily imparts very high pressure to the toner image on the support medium.

Accordingly, reduction of the size of a copying and duplicating machine cannot exceed a certain limit defined by the size of the pressing roller.

There has been previously proposed an encapsu Sated toner material which comprises toner particles enclosed with micro-capsules, so as to overcome the above-fixing process. The encapsulated toner material is prepared by enclosing core particles (containing colorant such as carbon black) with shells which are rupturable by the application of pressure. The so-prepared encapsulated toner material has various advantageous features; for instance, the fixing of the encapsulated toner material does not require very high pressure, and the fixability is excellent. Accordingly, the encapsulated toner material is viewed as suitable for the use in the pressure fixing process.

However, the encapsulated toner materials proposed up to now appear unsatisfactory in practical use, because they are not able to satisfy all of the characteristics required for providing smooth copying and duplicating operation and for accomplishing excellent toner image fixability and quality.

More in detail, it is required for the toner material for the use as a dry type developing agent in the electrostatography to have excellent powder characteristics (or, powder flow properties) to provide high development quality, and to be free from staining the surface of the photosensitive material on which the latent image is formed. The term "powder characteristics" particularly means resistance to agglomeration and blocking of the toner particles. In the process for the preparation of an encapsulated toner material, the toner material is generally separated from a toner dispersed solution and dried through a spray-drying procedure. The previously known encapsulated toner material is apt to undergo agglomeration either in the spray-drying process, or in the storage period after the spray-drying.The so agglomerated toner material markedly degrades the resolution of the visible toner image produced on the electrostatographic latent image, thereby markedly decreasing the sharpness of the visible toner image fixed onto the support medium.

Further, a toner material employed for the two component developing process is also required not to stain the surfaces of the carrier particles. The toner material for the use as a developing agent in the pressure fixing process is furthermore required to be satisfactory in the fixability under pressure and not to undergo off-setting against the roller surface, that is, phenomenon in which the toner adheres to the roller surface so as to stain it.

The encapsulated toner materials proposed until now are not satisfactory, at least, on one of these requirements for the developing agent to be employed for the pressure fixing process.

It is, accordingly, an object of the invention to provide an encapsulated toner material suitably employed for the pressure fixing process and free from the drawbacks described above.

It is a further object of the invention to provide an encapsulated toner material suitably employed for the pressure fixing process and free from the drawbacks described above.

It is a further object of the invention to provide an encapsulated toner material suitable employed for the pressure fixing process, whose powder characteristics are remarkably improved.

It is a still further object of the invention to provide an encapsulated toner material having improved pressure fixability in addition to the improved powder characteristics.

It is a still further object of the invention to provide an encapsulated toner material having improved resistance to the off-setting in addition to the improved powder characteristics and the improved pressure fixability.

It is a still further object of the invention to provide an encapsulated toner material which is resistant to rupture prior to the pressing operation in the pressure fixing process, while which is readily rupturable in the pressure fixing operation.

It is a still further object of the invention to provide a process for the preparation of the electrostatog raphictoner material having the above-described advantageous characteristics.

The above-described objects and others objects which will be apparent from the hereinafter-given description are accomplished by the present invention, that is, an electrostatographic toner material comprising encapsulated toner particles having an average particle size in the range from about 0.5 to about 1,000 microns, in which the toner particle comprises a pressure fixable adhesive core material containing a colorant and a pressure rupturable shell enclosing the core material, said shell being composed of a double layer comprising a polyurethane, polyurea and/or polythiourethane layer and a polyamide layer.

In the present invention, the term "polyurethane, polyurea and/or polythiourethane" means a polymer produced by the polymerization reaction between polyisocyanate and/or polythioisocyanate and one or more of the counterpart compounds such as polyol, polythiol, water, polyamine and piperazine.

Accordingly, the term "polyurethane" means either a simple polyurethane comprising substantially the urethane bondings only or a polymer comprising the urethane bondings and a relatively small number of the urea and/orthiourethane bondings. The term "polyurea" means either a simple polyurea comprising substantially the urea bondings only or a polymer comprising the urea bondings and a relatively small number of the urethane and/or thiourethane bondings. In the same way, the term "polythiourethane" means either a simple polythiourethane comprising substantially the thiourethane bondings only or a polymer comprising the thiourethane bondings and a relatively small number ofthe urethane and/or urea bondings.

The electrostatographictoner material of the invention is preferably prepared by a process which comprises encapsulating very small droplets of the pressure fixable adhesive core material containing a colorant dispersed in an aqueous medium with the pressure rupturable double layer shell comprising a polyurethane, polyurea and/or polythiourethane layer and a polyamide layer to prepare encapsulated particles, and separating the encapsulated particles from the aqueous medium to obtain dry toner materials.

The encapsulation of the droplets of the core material with the shell material can be preferably done by the interfacial polymerization process as described in Japanese Patent Publications No.

38(1963)-19,574, No. 42(1967)-446 and No.

42(1976)-771, British Patents No.989,264, No.

950,443, No.867,797, No. 1,069,140 and No. 1,046, under some modifications. For instance, the encapsulation is preferably carried out as follows: In a hydrophobic liquid comprising core materials such as a colorant, a pressure fixable adhesive material (binder), and, if desired, magnetizable particles, are dissolved an acid chloride (Substance A) and a polyisocyanate (Substance B). This solution is then dispersed in an aqueous medium comprising a polyamine or piperazine (Substance C) and a dispersing agent to produce fine droplets of the core material having an average diameter in the range from about 0.5 to about 1,000 microns in the aqueous medium.

The dispersion produced as above is then neutralized or made weak-alkaline by addition of an alkaline substance, resulting in the formation of a polyamide resin shell (the polyamide substantially is a reaction product of the acid chloride with the polyamine) around the hydrophobic droplet. The dispersion was subsequently heated to a temperature between 40 and 90"C, resulting in the formation of a polyurea resin shell (the polyurea substantially is a reaction product of the polyisocyanate and the polyamine) on the inner surface of the polyamide resin shell. Thus, a double layer shell in which the outer layer is composed substantially of polyamide and the inner layer is composed substantially of polyurea is produced around the hydrophobic core material droplet to give an encapsulated particle.

If a polyol (Substance D) is further added to the hydrophobic liquid in the above, there is produced around the hydrophobic core material droplet a double layer shell in which the outer layer is composed substantially of polyamide and the inner layer is composed substantially of polyurethane (a reaction product of polyisocyanate with polyol).

Alternatively, if the polyisocyanate (Substance B) is replaced with a polyisothiocyanate (Substance E) and a polyol (Substance D) is added to the hydrophobic liquid, there is produced around the hydrophobic core material droplet a double layer shell in which the outer layer is composed substantially of polyamide and the inner layer is composed substantially of polythiourethane (a reaction product of polyisothiocyanate with polyol).

In the latter two procedures, the inner layer composed of a mixture of polyurethane and polyurea or a mixture of polythiourethane and polyurea can be produced, if the polyamine is introduced into the reaction system in an amount exceeding the amount required to react the introduced acid chloride.

The shell of the so produced particle is, as described above, a double layer shell. However, the term "double layer shell" is not intended to mean only a shell in which the two layers are completely separated by a simple interface, but include a shell in which one side, particularly the outer side, of the shell is composed mainly of polyamide, and, another side, particularly the inner side, of the shell is composed mainly of another polymer of other polymers such as polyurethane, polyurea, polythiourethane or a mixture of two or three of these polymers.

Examples of the Substances A, B, C, D and E are as follows: Examples of Substance A (acid chloride) include adipoyl chloride, sebacoyl chloride, phthaloyl chlor- ide, isophthaloyl chloride, terephthaloyl chloride, fumaloyl chloride,1,4 - cyclohexamedicarbonyl chloride, - biphenyidicarbonyl chloride,4,4' - sulfonyldibenzoyl chloride, phosgene, polyesters containing acid chloride groups, and polyamides containing acid chloride groups.

The acid chloride of Substance A can be replaced with a dicarboxylic acid or its acid anhydride.

Examples of the dicarboxylic acids include adipic acid, sebacic acid, phthalic acid, terephthalic acid, fumaric acid,1,4 - cyclohexanedicarboxylic acid and 4,4' - biphenyidicarboxylic acid. Examples of the acid anhydrides include phthalic anhydride.

Examples of Substance B (polyisocyanate containing at least two isocyanate groups) include m phenylenedi isocyanate, p - phenylenediisocyanate, p - phenylenediisocyanate, - tolylenediBsocyan- ate,2,4 - tolylenediisocyanate, naphthalene - 1,4 - diisocyanate, diphenylmethane 4,4' - diisocyanate, diphenylmethane - 4,4' -diisocyanate, - - dimethoxy - 4,4' - biphenyldiisocyanate, - dimethyl - diphenylmethane - 4,4' - diisocyanate, xylylene-1,4- diisocyanate, xylylene-1,3- diisocy anate, - diphenylpropane - diisocyanate, trimethylenediidocyanate, hexamethylenediisocyan- ate, propylene - 1,2 - diisocyanate, butylene - 1,2 - diisocyanate, ethylidynediisocyante, cyclohexylene - 1,2 - diisocyanate, cyclohexylene - 1,4 - diisocyante, 4,4',4" - triphenylmethanetriisocyante, toluene 2,4,6-triisocyante, 4,4' - dimethyidiphenylmethane - 2,2',5,5'-tetraisocyante, hexamethylenediisocyante - hexanetriol adduct,2,4 - tolylenediisocyante - catechol adduct, tolylenediisocyanate - trimethylol- propane adduct, and xylylenediisocyanate trimethylolpropane adduct.

Examples of Substance C (polyamine or piperazine) include ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, p-pheny lenediamine, m-phenylenediamine,2 - hydroxy- trimethyienediamine, diethylenetriamine, triethylene - tetraamine, diethylaminopropylamine, tetraethylenepenta - amine, epoxy compound amine compound adduct, piperazine,2 - methylpiperazine, and 2,5 - dimethylpiperazine.

Examples of Substance D (polyol) include water, ethylene glycol,1,4- butanediol, catechol, resorci nol, hydroquinone,1,2 - dihydroxy - 4 - methylbenzene,1,3 - dihydroxy - 5 - methylbenzene,3,4 - dihydroxy - 1 - methylbenzene, 3,5 - dihydroxy - 1 - methylbenzene,2,4 - dihydroxy - 1 - ethylbenzene, 1,3 - naphthalenediol,1,5 - naphthalenediol,2,3 - naphthalenediol,2,7 - naphthalenediol, o,o' - biphe- nol, p,p' - biphenol, 1,1' - bi - 2 - naphthol, bisphenol A,2,2' - bis(4- hydroxyphenyl)butane,2,2' - bis(4- hydroxyphenyl) - isopentane, - bis(4 - hydorx- yphenyl) - cyclopentane, - bis(4 - hydroxyphenyl) -cyclohexane, - bis(4 - hydroxy - 3 - methyl- phenyl) - propane, bis(2 - hydroxyphenyl) - methane, xyiylenediol, ethylene glycol,1,3 - propylene giycol, 1,4- butylene glycol,1,5 - pentanediol,1,6 - hep tanediol,1,7 - heptanediol,1,8 - octanediol, trimethy- lolpropane, hexanetriol, pentaerythritol, glycerol, and sorbitol.

Examples of Substance E (polyisothiocyanate) include tetramethylenediisothiocyanate, hexamethylenediisothiocyanate, p - pheny- lenediisothiocyanate, xylylene - 1,4 - diisothiocyanate, and ethylidynediisothiocyanate.

In the preparation of the dispersion of the very small hydrophobic droplets containing Substances for the formation of shell and the core material, the hydrophobic liquid to be dispersed preferably contains a low-boiling solvent of a polar solvent. These solvents serve for acceleration formation of the shell. Examples of these solvents include methyl alcohol, ethyl alcohol, diethyl ether, tetrahydrofuran, dioxane, methyl acetate, ethyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyc lohexanone,n-pentane,n-hexane,benzene,pe roleum ether, chloroform, carbon tetrachloride, methylene chloride, ethylene chloride, carbon disulfide and demethylformamide.

As forthe other aspects of the interfacial polymerization method and the other processes for the preparation of micro-capsules containing an oiiy liquid, there are given descriptions in United States Patent No.2,726,804, which is introduced hereinto as the reference.

The core material of the invention contains a colorant for producing a visible image from the latent image. The colorant generally is a dye or a pigment, but a certain agent providing no directly visible image such as a fluorescent substance can be employed as the colorant, if desired.

The colorant is generally selected from a variety of the dye, pigment and the like employed generally in the conventional electrostatographic copying and duplicating process. Generally the colorant is a black toner or a chromatic toner. Examples of the black towers include carbon black. Examples of the achromatic toners include blue colorants such as copper phthalocyanine and a sulfonamide derivative dye; yellow colorants such as a benzidine derivative colorant, that is generally called Diazo Yellow; and red colorants such as Rhodamine B Lake that is a double salt of zanthin dye with phosphorus wolframate and molybdate, Carmine 6B belonging to Azo pigment, and a quinacridone derivative.

The core material of the invention further contains a binder for keeping the colorant within the core and assisting the fixing of the colorant onto the surface of a support medium such as paper. The binder is generally selected from high-boiling liquids conventionally employed or proposed for employment for finely dispersing an oil-soluble photographic additive within an aqueous medium to incorporate the additive into a silver halide color photosensitive material, and/or selected from polymers proposed for employment as the binders for the pressu re fixable encapsulated toner materials.

Examples of the high-boiling liquids include the following compound having the boiling point of higher than 180 C: (1) Phthalic esters dibutyl phthalate, dihexyl phthalate, diheptyl phthalate, dioctyl phthalate, dininyl phthalate, dodecyl phthalate, butyl phthalyl butyl glycolate, dibutyl monofluorophthalate; (2) Phosphoric acid esters tricresyl phosphate, trixylenyl phosphate, tris (isopropyiphenyl) phosphate, tributyl phosphate, trihexyl phosphate, trioctyl phosphate, trininyl phosphate, tridecyl phosphate, trioleyl phosphate, tris (butoxyethyl) phosphate, tris (chloroethyl) phosphate, tris (dichloropropyl) phosphate;; (3) Citric acid esters O-acetyl triethyl citrate, O-acetyl tributyl citrate, O-acetyl trihexyl citrate, O-acetyl trioctyl citrate, O-acetyl trinonyl citrate, O-acetyl tridecyl citrate, triethyl citrate, tributyl citrate, trihexyl citrate, trioctyl citrate, trinonyl citrate, tridecyl citrate; (4) Benzoic acid esters butyl benzoate, hexyl benzoate, heptyl benzoate, octyl benzoate, nonyl benzoate, decyl benzoate, dodecyl benzoate, tridecyl benzoate, tetradecyl benzoate, hexadecyl benzoate, octadecyl benzoate, oleyl benzoate, pentyl o-methylbenzoate, decyl p-methylbenzoate, octyl o-chlorobenzoate, lauryl p-chlorobenzoate, propyl 2,4-dichlorobenzoate, octyl 2,4-dichlorobenzoate, stearyl 2,4-dichlorobenzoate, oleyl 2,4-dichlorobenzoate, octyl p-methoxybenzoate;; (5) Aliphatic acid esters hexadecyl myristate, dibutoxyethyl succinate, dioctyl adipate, dioctyl azelate, decamethylene - 1,10 - diol diacetate, triacetin, tributin, benzyl caprate, pentaerythritol tetracaproate, isosorbitol dicaprilate; (6) Alkylnaphthalenes methylnaphthalene, dimethylnaphthalene, trimethylnaphthalene, tetramethylnaphthalene, ethylnaphthalene, diethylnaphthalene, triethylnaphthalene, monoisopropylnaphthalene, diisopropylnaphthalene, tetraisopropyinaphthalene, monomethylethylnaphthalene, isooctylnaphthalene; (7) Dialkylphenyl ethers di-o-methylphenyl ether, di-m-methyldiphenyl ether, di-p-methylphenyl ether; (8) Amides of fatty acids and aromatic su Ifonic acid N,N - dimethyllauroamide, N,N - diethylcaprylamide, N - butylbenzenesulfonamide;; (9) Trimellitic acid esters trioctyl trimellitate; (10) Diarylalkanes diarylmethanes, e.g., dimethylphenylphenyimethane, diarylethanes, e.g., 1 - methyl phenol - 1 - phenylethane, 1 - dimethylphenyl - 1 - phenylethane, 1 - ethylphenyl - 1 - phenylethane.

The above-listed high-boiling liquids and examples of other high-boiling liquids employable in the invention are described in detail in the following publications: Japanese Patent Publications No. 46(1971)-23,233 and No. 49(1974)-29,461; Japanese Patent Provisional Publications No. 47(1972)-1,031, No.

50(1975)-62,632, No. 50(1975)-82,078, No.

51(1976)-26,035, No. 51(1976)-26,036, No.

51(1976)-26,037, No. 51(1976)-27,921, and No.

51(1976)-27,922; United States Patents No.

2,322,027, No. 2,353,262, No. 2,533,514, No.

2,835,579, No. 2,852,383, No. 3,287,134, No.

3,554,755, No. 3,676,137, No. 3,676,142, No.

3,700,454, No.3,748,141, No.3,837,863, and No.

3,936,303; British Patents No. 958,441, No. 1,222,753, No. 1,346,364, and No. 1,389,674; and West Germany Offenlegungsschrift No. 2,538,889.

For the purpose of the invention, the high-boiling liquid is preferably selected from the phthalic acid esters, phosphoric acid esters and alkylnaphthalenes.

Examples of the polymers include the following polymers: Polyolefins, olefin copolymers, polystyrene, styrene-butadiene copolymer, epoxy resins, polyesters, natural and synthetic rubbers, polyvinylpiroiidone, polyamides, cumarone-indene copolymer, methyl vinyl ethermaleic anhydride copolymer, maleic acid-modified phenol resin, phenol-modified terpene resin, silicone resins, epoxy-modified phenol resin, amino resins, polyurethane elastomers, polyurea elastomers, homopolymers and copolymers of acrylic acid ester, homopolymers and copolymers of methacrylic acid ester, acrylic acid-long chain alkyl methacrylate copolymer oligmer, poly (vinyl acetate), and poly(vinyl chloride).

The above-listed polymers and examples of other polymers employable in the invention are described in detail in the following publications: Japanese Patent Publications No.48(1973)-30,499, No. 49(1974)-1,588 and No. 54(1979)-8,104; Japanese Patent Provisional Publications No.

48(1973)-75,032, No. 48(1973)-78,931, No. 49(1974), -17,739, No. 51(1976)-132,838, No. 52(1977)-98,531, No. 52(1977)-108,134, No. 52(1977)-119,937, No.

53(1 978)-1,028, No. 53(1978)-36,243, No.

53(1978)-118,049, No. 55(1980)-89,854 and No.

55(1980)-166,655; and United States Patents No.

3,788,994 and No. 3,893,933.

The core material can further contain other agents such as a releasing agent amd magnetizable particles.

The releasing agent serves for keeping the ruptured shell and the released core material from adhering to the surface of the pressing roller. The releasing agent can be chosen from those proposed for employment in the previously reported encapsulated toners. Examples of the releasing agents include a florine-containing resin described in Japanese Patent Provisional Publications No.

55(1 980)-1 42,360 and No. 55(1980)-142,362.

The magnetizable particles are included in the core material where a magnetizable toner material for the two components developing process is desired. As for the magnetizable particles, there are descriptions, for instance, in Japanese Patent Provisional Publications No. 53(1978)-118,053, No.

53(1978)-1,028 and No. 55(1980)-166,655. Examples of materials of the magnetizable particles preferably employed in the invention include metals such as cobalt, iron and nickel; metal alloys or metal compositions comprising aluminum, cobalt, copper, iron, lead, magnesium, nickel, tin, zinc, gold, silver, antimony, beryllium, bismuth, cadmium, calcium manganese, titanium, tungsten, vanadium and/or zirconium; metallic compounds including metal oxides such as aluminium oxide, ferric oxide, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide and magnesium oxide; refractory metal nitrides such as chromium nitride; metal carbides such as tungsten carbide and silica carbide; ferro-magnetic ferrite; and their mixtures.

As mentioned hereinbefore, the process for the preparation of the encapsulated toner particles includes a stage for dispersing or emulsifying very small droplets of the hydrophobic liquid containing Substance (A) and the core material in the aqueous medium. For the preparation of the homogeneous dispersion (or, emulsion) of the very small droplets of the hydrophobic liquid, it is preferred to incorporate into the reaction liquid a hydrophilic protective colloid and/or an emulsifying surface active agent which assist the production of the homogeneous dispersion (or, emulsion) of the hydrophobic droplets and prevention of agglomeration of the so-produced hydrophobic droplets. The hydrophilic protective colloid and the surface active agent can be employed alone or in combination.

Examples of the preferred hydrophilic protective colloids include proteins such as gelatin, graft polymers of gelatin with other polymers, carboxylated gelatin, sulfonylated gelatin, isocyanated gelatin, albumin, and casein; cellulose derivatives such as hydroxyethylcelluiose, carboxymethylcellulose, and cellulose sulfuric acid ester; saccharide derivatives such as sodium alginate and starch derivatives; and a variety of synthetic hydrophilic homopolymers and copolymers such as polyvinyl alcohol, partially acetalized polyvinl alcohol, poly-N-vinyl pyrolidone, polyacrylic acid, polyacrylic amide, polyvinylimidazole and polyvinylpyrazole.

In the above-listed examples, the gelatin can be a lime-treated gelatin, an acid-treated gelatin, a hydrolyzed gelatin, and an enzymically decomposed gelatin. The graft polymers of gelatin and other polymers can be gelatins carrying graft chains consisting of homopolymers or copolymers of vinyl monomers such as acrylic acid, methacrylic acid, their derivatives, e.g., esters and amides, acrylonitrile, and styrene. Examples of the gelatin graft polymers are those miscible with gelatin such as the gelatins carrying the graft chains consisting of polymers of acrylic acid, methacrylic acid, acrylamide, methacrylamide and hydroxyalkyl methacrylate.

Details of these preferred gelatin graft polymers are described in United States Patents No. 2,763,625, No. 2,831,767, and No.2,956,884.

Representative examples of the synthetic hydrophilic polymers are described, for instance, in West German Offenlegungsschrift No.2,312,708, United States Patents No. 3,620,751 and 3,879,205, and Japanese Patent Pubiication No. 43(1978)-7,561.

The surface active agents for dispersing or emulsifying the hydrophobic liquid in the hydrophilic liquid medium can be incorporated into either or both of the hydrophobic liquid and the hydrophilic liquid medium.

Examples of the surface active agents include non-ionic surface active agents, for instance, saponin (steroidetype), alkylene oxide derivatives such as polyethylene glycol, polyethylene glycol/polypropylene glycol condensation product, alkyl- or alkylarylether of polyethylene glycol, polyethylene glycol esters, polyethylene glycol sorbitol ester, alkylamine or amide of polyalkylene glycol, polyethylene oxide adduct of silicone polymer, glycidol derivatives such as polyglyceride alkenyl-succinate and alkylphenol polyglyceride, fatty acid esters of polyhydric alcohols, alkylesters of saccharide, urethanes and ethers; and anionic surface active agents having acidic groups such as carboxy, sulfo, phospho, sulfate ester and phosphate ester groups, for instance, triterpenoide-type saponin, alkylcarboxylic acid salts, alkylsulfonic acid salts, alkylbenzenesulfonic acid salt, alkylnaphthalenesulfonic salts, alkylsulfate esters, alkylphosphate esters, N-acyl-N-alkyl-taurines, sulfosuccinic acid esters, sulfoalkyl-polyoxyethylene alkyl phenyl ethers, and polyoxyethylene alkylphosphate esters.

Particularly preferred surface active agents are anionic surface active agents belonging to the sulfonic acid type and the sulfate ester type, namely, compounds having in the molecular structure both of hydrophobic groups containing 8 - 30 carbon atoms and hydrophilic groups of-SO3M or-OSO3M (in which M is Na or K). These preferred anionic surface active agents belonging to the above-mentioned types are described in detail in "Surface Active Agents" (A. W. Perry; Interscience Publication Inc., New York).

Representative examples of the preferred anionic surface active agents are as follows: sodium dodecy Isulfate, sodium tetradecylsulfate, Turkey red oil, sodium dodecylcarboxyamidoethylsulfate, sodium dodecylsulfonate, sodium tetradecylsulfonate, sodium polyoxyethylene-octyl phenyl-ethersulfonate, sodium salt of sulfosuccinic acid dioctylester, sodium dodecyibenzenesulfonate, sodium tetradecylamidophenylsulfonate, and sodium tri-isopropylnaphthalenesulfonate.

Dispersing or emulsifying the reaction liquid can be carried out by means of a known homogenizer such as one belonging to the stirring type, the high pressure injecting type, the ultrasonic vibrating type and the kneader type. Particularly preferred homogenizers are a colloid mill, a conventional homozenizer, and electromagnetic distortion inducing ultrasonic homogenizer.

The encapsulated toner is then produced, for instance, by heating the emulsified reaction liquid in the presence of an appropriate catalyst, as described hereinbefore, so as to form shells around the core material droplets. Subsequently, the encapsulated toner is separated from the aqueous reaction medium and dried to obtain a dry encapsulated toner. The encapsulated toner is preferably washed with water after the separation from the aqueous reaction medium and priortothedrying procedure.

The drying procedure can be carried out by a known process such as the spray-drying process or the freeze-drying process. The spray-drying process is preferred.

The so-produced dry encapsulated toner can be admixed with an insulating material and/or a charge controller such as a metal-containing dye or Nigrosine dye.

The dry encapsulated toner can be admixed with a flow lubricant such as hydrophobic silica powder so that the flow lubricant can be dispersed over the surface of the encapsulated toner. The encapsulated toner having the flow lubricant such as hydrophobic silica powder over the toner surface shows particularly improved powder quality and property, and accordingly is very advantageous in the practical use.

The encapsulated toner obtained as above can be introduced into the electrostatographic copying and duplicating machine to develop an electrostatographically produced latent image so as to produce a visible toner image on the surface of the photoconductive material. The visible image is then fixed'onto a support medium such as paper by means of an appropriate pressure fixing apparatus. There is no limitation on the pressure fixing apparatus for fixing the encapsulated toner of the invention, and any known apparatus can be applied to the fixing of the encapsulated toner of the invention. Examples of the pressure fixing apparatuses include those illustrated in Japanese Patent Publications No. 44(1969)-9,880, No. 44(1969)-12,797, and No. No.46(1971 )-1 5,876; and Japanese Patent Provisional Publications No.

49(1 974)-62,143, No.49(1974)-77,641, No.

50(1975)-51,333, No. 5111976)-31,235, No.

51(1976)-40,351, No. 52(1977)-15,335, No.

52(1977)-102,743, No. 54(1979)-28,636, No.

54(1979)-32,326, No. 54(1979)-41,444, and No.

54(1979)-48,251.

The electrostatographic toner material comprising the encapsulated toner particles of the invention has improved powder characteristics, and is resistant to the mechanical shock and abrasion in the developing apparatus of the electrostatographic copying and duplicating machine. Further, the electrostatog raphictoner material of the invention is easily rupturable in the pressure fixing apparatus to produce a visible toner image well fixed onto the support medium such as paper. Furthermore, the toner material of the invention hardly undergoes off-setting to a pressing roller and hardly undergoes the so-called filming on the surfaces of the carrier particles, the developing sleeves and the photoconductive material.

The electrostatographic toner material having the double layer shell comprising an inner polyurethane, polyurea and/or polythiourethane layer and an outer polyamide layer, the preferred embodiment of the invention, particularly shows remarkably improved powder characteristics, that is, almost free form agglomeration. Moreover, the powder characteristics of this toner material can be further improved by deposition of a flow lubricant such as hydrophobic silica on the surface even in a small amount. These remarkable powder characteristics ofthetoner material are thought to stem from the outer polyamide surface easily releases water and moisture therefrom in the spray-drying procedure and that the flow lubricant can be deposited on the surface more efficiently and evenly.The present toner material shows no blocking even when stored under conditions of high temperature and high humidity such as 50"C and 90 %RH, for one day.

In the employment for the two component developing process, the toner material of the invention can be appropriately charged to carry an electron charge in the range of 10 - 20,uc/g (plus or minus) in combination with an adequate carrier or with an adequate charge controller, so as to provide a visible image fixed on a support medium with high quality such as high resolution and high sharpness with substantially no fog. The development characteristics and the pressure fixability of the toner material of the invention are kept at an excellent level even after copying and duplicating procedure is repeated to a certain extent.

Even in the employment for the one component developing process, the toner material of the invention is well qualified in the developing characteristics, the pressure fixing characteristics and the resistance to the off-setting. Moreover, no filming is produced on the surfaces of the development sleeve and the photo-sensitive material.

Other features of the electrostatographic copying and duplicating process employing an encapsulated toner material are described in United States Patent No.3,788,994, which is introduced hereinto as the reference.

The present invention will be illustrated by the following examples which are by no means intended to introduce any restriction into the invention. In the examples, the term "part(s)" means "part(s) by weight".

Example 1 Four parts of carbon black were mixed with 46 parts of castor oil to produce a primary liquid.

Separately, 25 parts of tolylenediisocyanate-hexanetriol adduct (3:1 molar ratio adduct) and 2 parts of terephthaloyl chloride were dissolved in 25 parts of ethyl acetate to produce a secondary liquid.

A mixture of the primary liquid and the secondary liquid was dispersed in 200 parts of pre-cooled aqueous gum arabic solution (10% by weight solution) to produce an oil-in-water emulsion containing oily droplets having average diameter of 10 - 1511.

Ten parts of an aqueous hexamethylenediamine solution (10% by weight solution) were added to the emulsion. The mixture was stirred for 30 minutes and adjusted to pH 9.0 by addition of an aqueous 10% sodium carbonate solution. The mixture was then heated to 70"C for 2 hours stirring, so as to complete the encapsulated reaction.

The dispersion containing the encapsulated oily particles was subjected to centrifugal separation at 5,000 r.p.m. to separate the encapsulated particles from the aqueous gum arabic solution. The so separated encapsulated particles were again dispersed in 100 ml. of water, and the dispersion was dried in a spray-drying apparatus to obtain a powdery encapsulated toner material.

The encapsulated toner material obtained above was composed of a core containing the carbon black and castor oil and a double layer shell in which the outer layer was made substantially of polyamide (reaction productoftetphthaloyl chloride with hexamethylenediamine) and the inner layer was made substantially of polyurea/urethane (reaction product of the tolylenediisocyanatehexanetriol adduct with water). Microscopic observation of the encapsulated toner indicated that most of the toner particles were present independently and that no bulky agglomerated particles were formed.

The evaluation of the encapsulated toner was carried out as follows.

The encapsulated toner was well admixed with 0.5% by weight of hydrophobic silica fine powder to place the silica powder on the surface of the toner.

Five parts by weight of the so treated toner were admixed with 95 parts by weight of powdery iron carrier in a shaking apparatus to prepare a developing agent. It was confirmed through microscopic observation that the developing agent contained no ruptured toner particles.

A conventional electrostatographic copying and duplicsting process was carried out using the above developing agent. The visible toner image produced on a latent image was then converted onto a paper.

The paper carrying the toner image was treated under a pressing roller at a pressure of 350 kg/cm2.

There was obtained a toner image with high sharpness and well fixed on to the paper. Further, the off-setting of the toner was at a very low level.

Example 2 The procedures described in Example 1 were repeated except that the aqueous hexamethylenediamine solution (10% by weight solution) was added in 20 parts amount in place of the 10 parts amount. As a result, there was obtained an encapsulated toner material composed of a core containing the carbon black and castor oil and double layer shell in which the outer layer was made substantially of polyamide (reaction product of terephthaloyl chloride with hexamethylenediamine) and the inner layer was made substantially of polyurea (reaction product of the tolylenediisocyanate-hexanetriol with hexamethylenediamine and water). Microscopic observation of the encapsulated toner indicated that most of the toner particles were present independently and that no bulky agglomerated particles were formed.

The evaluation of the encapsulated toner as the developing agent was carried out in the same manner as described in Example 1. It was confirmed that substantially no ruptured toner particles were seen upon mixing with the powdery iron carrier.

Also confirmed was that a toner image with sharpness was well fixed onto a paper. The off-setting of the toner was kept at a very low level.

Example 3 The procedures described in Example 1 were repeated except that the secondary liquid was replaced with a solution of 25 parts of the tolylenediisocyanate-hexanetriol adduct (3:1 molar ratio adduct), 2 parts ofterephthaloyl chloride, and 1 part of ethylenediamine-propylene oxide adduct (Adekakadorol, trade name of Asahi Denka Co., Ltd., Japan) in 25 parts of ethyl acetate. As a result, there was obtained an encapsulated toner material composed of a core containing the carbon black and castor oil and a double layer shell in which the outer layer was made substantially of polyamide (reaction product of terephthaloyi chloride with hexamethylenediamine) and the inner layer was made substantially of polyurethane (reaction product of the tolylene diisocyanate - hexanetriol adduct with ethylene diamine - propylene oxide adduct).Microscopic observation of the encapsulated toner indicated that most of the toner particles were present independently and that no bulky agglomerated particles were formed.

The evaluation of the encapsulated toner as the developing agent was carried out in the same manner as described in Example 1. It was confirmed that substantially no ruptured toner particles were seen upon mixing with the powdery iron carrier.

Also confirmed was that a toner image with sharpness was well fixed onto a paper. The off-setting of the toner was kept at a very low level.

Example 4 The procedures described in Example 3 were repeated except that 25 parts of the tolylenediisocyanate-hexanetriol adduct was replaced with 22 parts of tolylenediisothiocyanate. As a result, there was obtained encapsulated toner material composed of a core containing the carbon black and castor oil and a double layer shell in which the outer layer was made substantially of polyamide (reaction product of terephthaloyl chloride with hexamethylenediamine) and the inner layer was made substantially of polythiourethane (reaction product of tolylenediisothiocyanate with ethylenediamine-propylene oxide adduct). Microscopic observation of the encapsulated toner indicated that most of the toner particles were present independently and that no bulky agglomerated particles were formed.

The evaluation of the encapsulated toner as the developing agent was carried out in the same manner as described in Example 1. It was confirmed that substantially no ruptured toner particles were seen upon mixing with the powdery iron carrier.

Also confirmed was that a toner image with sharpness was well fixed onto a paper. The off-setting of the toner was kept at a very low level.

Claims (14)

1. An electrostatographictoner material comprising encapsulated toner particles having an average particle size in the range from about 0.5 to about 1,000 microns, in which the toner particle comprises a pressure fixable adhesive core material containing a colorant and a pressure rupturable shell enclosing the core material, said shell being composed of a double layer comprising a polyurethane, polythiourea and/or polythiourethane layer and a polyamide layer.

2. The electrostatographictoner material as claimed in Claim 1, in which the double layer shell comprises an inner polyurethane, polyurea and/or polythiourethane layer and an outer polyamide layer.

3. The electrostatographictoner material as claimed in Claim 2, in which the inner layer of the shell is made substantially of a polymerization reaction product of polyisocyanate, polyol and wa ter.

4. The electrostatographictoner material as claimed in Claim 2, in which the inner layer of the shell is made substantially of a polymerization reaction product of polyisocyanate, polyol and polyamine.

5. The eiectrostatographic toner material as claimed in any of Claims 1 through 4, in which the core material further contains magnetizable particles.

6. The electrostatographictoner material as claimed in any of Claims 1 through 5, in which the pressure fixable adhesive core material is a liquid medium boiling at a temperature of higher than 180cm.

7. The electrostatographic toner material as claimed in any of Claims 1 through 6, in which a flow lubricant is provided onto the surface of the shell.

8. The electrostatographic toner material as claimed in Claim 7, in which the flow lubricant is hydrophobic silica powder.

9. A process for the preparation of an electrostatographic toner material comprising encapsulated particles having an average particle size in the range from about 0.5 to about 1,000 microns which comprises: encapsulating droplets with an average droplet size in the range from about 0.5 about 1,000 microns of pressure fixable adhesive core material containing a colorant dispersed in an aqueous medium with a pressure rupturable double layer shell comprising a polyurethane, polyurea and/or polythiourethane layer and a polyamide layer to prepare encapsulated particles; and separating the encapsulated particles from the aqueous medium to obtain dry toner materials.

10. The process for the preparation of an elec trostatographic toner material as claimed in Claim 9, in which the double layer shell comprising an inner polyurethane, polyurea and/or polythiourethane layer and an outer polyamide layer.

11. The process for the preparation of an elec trostatgraphictoner material as claimed in Claim 10, in which the inner layer of the shell is made substantially of a polymerization reaction product of polyisocyanate, polyol and water.

12. The process for the preparation of an electrostatographic toner material as claimed in Claim 10, in which the inner layer of the shell is made substantially of a polymerization reaction product of polyisocyanate, polyol and polyamine.

13. Electrostatographictonermaterialsubstan- tially as hereinbefore described.

14. A process for the preparation of electrostatographic toner material substantially as hereinbefore described.