Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-09-18
2003-01-21
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S109400, C430S111400, C430S124300
Reexamination Certificate
active
06509129
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for electrophotography used for developing electrostatic latent images formed in electrophotography, electrostatic recording method, electrostatic printing, toner jetting and the like.
2. Discussion of the Related Art
In order to improve the offset resistance in the toner, a wax is usually added together with a resin binder, a colorant and the like during the kneading process. However, when the wax is poorly dispersed in a resin binder, the durability is deteriorated such that there arise filming of the toner on a photoconductor, heat-fusion of a toner to a carrier in a two-component development, or heat-fusion of a toner to a charged blade in a one-component development. In order to eliminate the problems mentioned above, there has been proposed a process for preparing a toner comprising previously pre-dispersing a wax in a resin binder with applying a high shearing force and kneading the resulting dispersion together with the same resin and a pigment (Japanese Patent Laid-Open No. Hei 5-188644).
However, even in this process, since the resin for pre-dispersing the wax and the resin for diluting the dispersed wax-containing resin have similar thermal properties, shearing force is insufficient during the kneading of a toner, so that the wax cannot be sufficiently finely dispersed. In addition, as another process for preparing toner, there has been proposed a process comprising dispersing a wax in a resin binder during the polymerization of the resin binder (Japanese Patent Laid-Open Nos. Hei 9-304966, Hei 10-312080 and Hei 11-352720, and the like). However, since only a single component of a wax-containing resin as a resin binder is subjected to kneading, the shearing force is insufficient so that the wax cannot be sufficiently finely dispersed.
An object of the present invention is to provide a toner for electrophotography with a well-dispersed wax, the toner having excellent offset resistance and durability.
These and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a toner for electrophotography comprising a toner for electrophotography comprising Resin is (A) and Resin (B), wherein Resin (A) comprises Resin (C) and a wax dispersed therein, wherein a difference between the softening point of Resin (C) and the melting point of the wax is within 20° C., and the softening point of Resin (B) is higher than the softening point of Resin (C).
DETAILED DESCRIPTION OF THE INVENTION
The toner of the present invention is a toner for electrophotography comprising Resin (A) and Resin (B) as the resin binders, wherein Resin (A) comprises Resin (C) and a wax dispersed therein, the wax having similar thermal properties to those of Resin (C). Therefore, the wax can be finely and homogeneously pre-dispersed in Resin (C) in a high concentration. Further, since Resin (B) having a higher softening point than that of Resin (C) is added and kneaded, kneading can be carried out under a high-shearing force, so that the dispersed state of the wax can be maintained or further improved.
Resin (C) includes, for instance, polyesters, epoxy resins, styrene-acrylate copolymers, polyurethanes, hybrid resins, and composite resins thereof In the present invention, a hybrid resin in which a condensation polymerization resin unit is chemically bonded with an addition polymerization resin unit is preferred. More preferred is a hybrid resin prepared by the steps comprising (a) preparing a mixture of raw material monomers for two polymerization resins each having an independent reaction path, i.e., a mixture of a raw material monomer for a condensation polymerization resin and a raw material monomer for an addition polymerization resin and, if necessary, a compound (dually reactive compound) capable of reacting with both of the raw material monomers for the two polymerization resins; and (b) carrying out the two polymerization reactions preferably in the same reaction vessel by the use of the mixture obtained in step (a).
Representative examples of the condensation polymerization resin include polyesters, polyester-polyamides, polyamides, and the like. Representative examples of the addition polymerization resin include vinyl resins obtained by radical polymerization, and other resins.
The raw material monomer for the polyester includes dihydric or higher polyhydric alcohols and dicarboxylic acid or higher polycarboxylic acid compounds.
The dihydric alcohol includes, for instance, alkylene oxide adducts of bisphenol A such as polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane and polyoxyethylene(2.0)-2,2-bis(4-hydroxyphenyl)propane, ethylene glycol, 1,2-propylene glycol, 1,4-butanediol, neopentyl glycol, polyethylene glycol, polypropylene glycol, bisphenol A, hydrogenated bisphenol A, and the like,
The trihydric or higher polyhydric alcohol includes, for instance, sorbitol, pentaerythritol, glycerol, trimethylolpropane, and the like.
In the present invention, these dihydric or higher polyhydric alcohols can be used alone or in admixture of two or more kinds.
In addition, the dicarboxylic acid compound includes, for instance, dicarboxylic acids such as maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid and succinic acid; a substituted succinic acid of which substituent is an alkyl group having 1 to 20 carbon atoms or an alkenyl group having 2 to 20 carbon atoms, such as n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isooctenylsuccinic acid and isooctylsuccinic acid; acid anhydrides thereof or lower alkyl(1 to 3 carbon atoms) esters thereof; and the like. Among them, maleic acid, fumaric acid, terephthalic acid and a substituted succinic acid of which substituent is an alkenyl group having 2 to 20 carbon atoms are preferably used.
The tricarboxylic or higher polycarboxylic acid compound includes, for instance, 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid, acid anhydrides, lower alkyl(1 to 3 carbon atoms) esters thereof, and the like. Among them, 1,2,4-benzenetricarboxyhc acid, i.e., trimellitic acid, and the anhydride thereof are particularly preferably used since they are inexpensive and the reaction is easily controlled.
In the present invention, these dicarboxylic or higher polycarboxylic acid compounds can be used alone or in admixture of two or more kinds.
In the formation of the polyester, an esterification catalyst such as dibutyltin oxide can be appropriately used.
In addition, the raw material monomer for forming the amide component of the polyester-polyamide or the polyamide includes various known polyamines, aninocarboxylic acids and amino alcohols, and hexamethylenediamine and &egr;-caprolactam are preferred.
Incidentally, the above-described raw material monomer also includes those usually classified as a monomer for ring-opening polymerization. Since these monomers are hydrolyzed in the presence of water generated by the condensation reaction of other monomers and then subjected to condensation, the monomers are considered to be included in the raw material monomer for condensation polymerization resins in a broad sense.
The raw material monomer for the vinyl resin includes styrenic compounds such as styrene and a-methylstyrene; ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate and vinyl propionate; esters of ethylenic monocarboxylic acids such as alkyl(1 to 18 carbon atoms) esters of (meth)acrylic acid, 2-hydroxyethyl (meth)acrylate, glycidyl (meth)acrylate, and dimethylaminoethyl (meth)acrylate; vinyl ethers such as vinyl methyl ether; vinylidene halides such as vinylidene chloride; N-vinyl compounds such as N-vinylpyrrolidone; and the like. It is desired that styrene and/or the alkyl ester of (meth)acrylic acid is contained in an amount of 50% by weight or more, prefe
Eida Akihiro
Kawaji Hiroyuki
Goodrow John
KAO Corporation
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