Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-03-26
2004-04-20
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S176000, C528S302000, C528S304000, C525S444000, C430S109500
Reexamination Certificate
active
06723822
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a crystalline polyester which can be suitably used for a resin binder for toner for electrophotography and the like used for developing electrostatic latent images formed in electrophotography, electrostatic recording method, electrostatic printing, and the like; a polyester resin composition comprising the crystalline polyester; a resin binder for toner comprising the crystalline polyester or the polyester resin composition; and a toner for electrophotography comprising the resin binder for toner.
2. Discussion of the Related Art
One of the major problems to be solved in electrophotographical methods is improvement in low-temperature fixing ability. A strategy for improving low-temperature fixing ability includes the use of a resin binder comprising a crystalline polyester, and a resin binder comprising a crystalline polyester and an amorphous polyester is reported.
Japanese Examined Patent Publication No. Sho 62-39428 discloses a toner comprising a crystalline polyester comprising an aromatic polycarboxylic acid component as an acid component in an amount of 50% by mol or more, and an amorphous polyester comprising an aromatic polycarboxylic acid component as an acid component in an amount of 60% by mol or more. However, the above-mentioned crystalline polyester is classified as the amorphous polyester by the definition according to the present invention. Even if the above-mentioned polyester can be a crystalline polyester, the crystalline polyester and the amorphous polyester are so compatible that a dispersed domain cannot be observed because the structures of the both polyesters are too similar. As a result, an excellent property as a crystalline polyester is not at all exhibited.
On the other hand, a crystalline polyester comprising an aliphatic diol as a main component is known. However, such polyester is poor in the compatibility with an amorphous polyester having a bisphenol A backbone which has excellent fixing ability and triboelectric properties, so that a satisfactory, appropriate dispersibility cannot be obtained under usual kneading conditions.
An object of the present invention is to provide a crystalline polyester which is appropriately compatible with an amorphous resin, especially an amorphous polyester having a bisphenol A backbone, and which can be suitably used for a resin binder for toner and the like.
In addition, another object of the present invention is to provide a polyester resin composition comprising the crystalline polyester, a resin binder for toner comprising the crystalline polyester or the polyester resin composition, and a toner for electrophotography comprising the resin binder for toner.
The above object and other objects of the present invention will be apparent from the following description.
SUMMARY OF THE INVENTION
The present invention relates to:
(1) a crystalline polyester obtained by polycondensing monomers comprising 0.1 to 10% by mol of a divalent aromatic compound, wherein the crystalline polyester has a softening point of 85° to 150° C.;
(2) a polyester resin composition comprising the crystalline polyester, and an amorphous resin obtained by polycondensing monomers comprising an aromatic compound having a bisphenol A backbone, wherein the aromatic compound having a bisphenol A backbone is contained in an amount of 40% by mol or more of an alcohol component;
(3) a resin binder for toner comprising the crystalline polyester or the polyester resin composition; and
(4) a toner for electrophotography comprising the resin binder for toner.
DETAILED DESCRIPTION OF THE INVENTION
The crystalline polyester of the present invention is prepared, like conventionally known polyesters, by polycondensing monomers comprising an alcohol component comprising a dihydric or higher polyhydric alcohol and a carboxylic acid component comprising a dicarboxylic or higher polycarboxylic acid compound. However, the crystalline polyester of the present invention, which has a softening point of 85° to 150° C., is a totally novel polyester in that a divalent aromatic compound, preferably a diol compound having a bisphenol A backbone is contained in the entire monomers in an amount of from 0.1 to 10% by mol, preferably from 0.5 to 7.5% by mol, more preferably from 1 to 5% by mol. The crystalline polyester of the present invention comprises an aromatic compound, in a small amount though, so that it is appropriately compatible with an amorphous resin comprising 40% by mol or more of an aromatic compound having a bisphenol A backbone of an alcohol component. Therefore, a polyester resin composition obtained by mixing the both exhibits excellent properties as a resin binder for toner.
Here, in the present invention, the term “crystalline” means that a ratio of the softening point to the maximum peak temperature of heat of fusion (softening point/maximum peak temperature of heat of fusion) is from 0.6 or more and less than 1.1, preferably from 0.9 or more and less than 1.1, more preferably from 0.98 to 1.05. Also, the term “amorphous” means that a ratio of the softening point to the maximum peak temperature of heat of fusion (softening point/maximum peak temperature of heat of fusion) is from 1.1 to 4.0, preferably from 1.5 to 3.0.
The divalent aromatic compound used as an alcohol component is preferably a diol compound having a bisphenol A backbone represented by Formula (I):
wherein R represents an alkylene group having 2 or 3 carbon atoms; x and y are a positive number; and the sum of x and y is 1 to 16, preferably 1.5 to 5.0. Concretely, the diol compound having a bisphenol A backbone includes an alkylene oxide adduct of bisphenol A such as polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane and polyoxyethylene(2.2)-2,2-bis(4-hydroxyphenyl)propane, and the like.
Also, a divalent aromatic compound used as a carboxylic acid component includes phthalic acid, isophthalic acid, terephthalic acid, and the like.
The monomers which are usable other than the above-mentioned divalent aromatic compound are exemplified below.
It is preferable that the alcohol component comprises aliphatic diols having 2 to 6 carbon atoms, preferably 4 to 6 carbon atoms.
The aliphatic diol having 2 to 6 carbon atoms includes 1,4-butanediol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,6-hexanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol and the like, among which a, &ohgr;-linear alkyl diol is more preferable.
The crystalline polyester of the present invention is obtained using the divalent aromatic compound in an amount of 0.1 to 10% by mol in the monomers. The divalent aromatic compound is not limited to either the alcohol or the carboxylic acid compound, and the compound may be a mixture of both. Therefore, the content of the monomers other than the divalent aromatic compound in each of the component cannot be absolutely determined, but it is desirable that the aliphatic diols having 2 to 6 carbon atoms are contained in the alcohol component in a total amount of 80% by mol or more, preferably from 90 to 100% by mol. Especially, it is desirable that one of the aliphatic diols constitutes 70% by mol or more, preferably 80% by mol or more, of the alcohol component.
Other divalent alcohol components include diethylene glycol, triethylene glycol, 1,8-octanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hydrogenated bisphenol A, and the like.
The trihydric or higher polyhydric alcohol includes aromatic alcohols such as 1,3,5-trihydroxymethylbenzene; aliphatic alcohols such as sorbitol, 1,2,3,6-hexanetetrol, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane; cycloaliphatic alcohols such as 1,4-sorbitan; and the like.
As the carboxylic acid component, those comprising aliphatic dicarboxylic acid compounds having 2 to 6 carbon atoms, preferably 4 to 6 carbon ato
Aoki Katsutoshi
Maruta Masayuki
Shirai Eiji
Birch & Stewart Kolasch & Birch, LLP
Kao Corporation
Short Patricia A.
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