Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1999-06-08
2001-03-13
Seidleck, James J. (Department: 1711)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S110100, C430S135000, C430S137170, C430S633000, C525S061000, C525S058000, C525S069000, C524S503000, C524S504000, C524S537000, C524S557000, C524S558000, C526S202000
Reexamination Certificate
active
06200720
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a graft resin having a novel structure, a process for the production thereof and use thereof. More specifically, it relates to a graft resin having low-temperature moldability, a process for the production thereof and an electrostatic charge developing toner excellent in low-temperature fixing properties and developing properties.
PRIOR ART
Polymer alcohols typified by polyvinyl alcohol (called “PVA” for short hereinafter) are highly useful materials which have been and are widely used in industry. PVA having a highly reactive alcoholic hydroxyl group is widely used as a raw material for a formal resin and a butylal resin. Further, polyvinyl acetate as a precursor of PVA plays an important role in the fields of coating compositions and adhesives. In hydrous gel compositions containing PVA, further, there has been proposed a method in which PVA is dissolved in a highly polar solvent such as water or dimethylsulfoxide and a water-soluble monomer is grafted in a radical polymerization manner (J. Polym. Sci. Polym. Chem. Ed., 12, 1829 (1974) or a method in which a functional separation membrane is formed by grafting (Journal of Japan Chemical Society, 1995 (11)).
PVA is grade-classified with regard to polymerization degree, purity and saponification degree. Further, a variety of modified polyvinyl alcohols having thermal characteristics meeting with requirements, obtained by adjusting the saponification degree of polyvinyl acetate as a precursor, are commercially available, and used depending upon required characteristics. Many manufactures produce these modified polyvinyl alcohols, which are commercially available in the general name of “POVAL”.
Polyethylene vinyl alcohol, which has a similar structure to PVA, having lower crystallinity based on hydrogen bond than PVA, is easily melted by heating and easily molded. It is therefore used as a material for producing food packaging materials by film forming or injection molding. Polyethylene vinyl acetate which is a precursor of polyethylene vinyl alcohol is also applied to a modifier for polyvinyl chloride or an additive for special waxes.
However, the above PVA and polyethylene vinyl alcohol according to prior art techniques have very high melt initiation temperatures and therefore have a problem that they cannot be shaped or molded at a low temperature.
For decreasing the melt initiation temperature of PVA, it is required to decrease the saponification degree and decrease the polymerization degree to 200 or less. It is also required to decrease the polymerization degree of polyethylene vinyl alcohol as well. In this case, however, the heat absorption peak temperature measured with a differential scanning calorimeter (called “DSC” for short hereinafter) decreases, and there arises a shelf life problem that polymers are softened when stored at high temperatures such as high temperatures of summer seasons, etc. As other method, a monomer similar to vinyl acetate may be introduced as a comonomer. In this method, however, a vinyl acetate monomer and a long-chain fatty acid are converted to a vinyl ester monomer by an ester exchange reacttion in an organic solvent in the presence of a catalyst and then the copolymerization reaction is carried out. The production process is therefore complicated, and a less expensive end product is difficult to produce.
Further, it is known that for improving a polymer in shelf life while maintaining its melt initiation temperature at a decreased temperature, a vinyl ester monomer having an aromatic ring introduced into its main chain or a vinyl ester monomer having a tert-butyl group is used to increase the heat absorption peak temperature. However, the former aromatic vinyl ester monomer is liable to cause a side reaction based on a radical reaction, and the intended copolymerization is difficult to carry out. A bulk polymerization of the aromatic vinyl ester monomer is therefore carried out, while it is difficult to control the bulk polymerization so as to obtain the intended thermal characteristics. The latter permits the intended copolymerization, while it has the above problem of cost, and it is difficult to increase the amount ratio of the monomer. It is therefore difficult to improve the polymer in the low-temperature moldability while maintaining the excellent shelf life of the polymer.
Meanwhile, in an electrophotographic method, an electrostaic recording method and an electrostaic printing method, an image of electrostaic charge formed on a substrate (recording layer) is visualized with toner particles composed of a binder resin and a colorant as main components. The so-visualized image is fixed directly to the substrate, or it is transferred to a receptor such as a paper sheet and then fixed. Therefore, not only a toner for electrostatic charge development is naturally required to have excellent developing properties, but also it is required to have excellent transfer properties and excellent fixing properties. In recent years, further, copying machines and printers to which an electrophotographic method is applied are widely spreading and are beginning to be used as family use. Further, these machines and printers are being functionally multiplied, and it is therefore demanded to accomplish low-energy fixing for decreasing the consumption power and simplifying the fixing mechanism.
Recent copying machines and printers use a contact heating method using a heat roll. This method is advantageous in that it has a high heat efficiency so that the power for a fixing portion can be decreased and that the fixing portion can be decreased in size, as compared with a conventional method. As a binder resin for a toner used in this method, there are known a vinyl-like resin having a broad molecular weight distribution and a polyester resin having a crosslinked structure obtained by using a trihydric or higher alcohol or acid component as part of monomers, for preventing an offset phenomenon. An electrophotographic toner is prepared by adding a colorant, a lubricant (a releasing agent), a charge controller, etc., to the above binder resin. Generally, those resins which satisfy the shelf life requirement have a melt initiation temperature, measured with a “Koka” type flow tester (supplied by Simadzu Corporation), of 120° C. or higher, and they are not at all suitable for satisfying the low-energy fixing demand.
Further, in addition to the above binder resin, a graft resin and a block copolymer resin have been proposed. For example, JP-A-54-63831 discloses a developer containing a graft product of oxidized starches. JP-A-56-15740 discloses a toner containing a resin obtained by graft-polymerizing or copolymerizing 1 to 30 parts by weight of a vinyl compound and 100 parts by weight of a vinyl acetate monomer in the presence of crystalline polyethylene and polypropylene. JP-A-63-27855, JP-A-64-35456 and JP-A-2-93658 disclose a toner containing a resin obtained by graft-polymerizing or blocck-copolymerizing a crystalline polyester resin and an ion-crosslinked amorphous vinyl polymer having an Mw/Mn of at least 3.5. JP-A-2-108066 and JP-A-2-108067 disclose an electrophotographic toner containing a graft copolymer obtained from a fluorine-containing monomer. JP-A-3-122660 discloses a heat-fixing toner containing a polyolefin obtained by graft-modifying an &agr;,&bgr;-unsaturated polyolefin with an aromatic vinyl monomer, an unsaturated fatty acid or an unsaturated fatty acid ester. JP-A-3-9370 discloses a resin for a toner, obtained by grafting a crystalline polyester resin and an amorphous vinyl polymer having an Mw/Mn of at least 3.5 by a mechanochemical reaction. JP-A-4-274247 discloses a heat-fixing toner containing a polyethylene which is graft-modified with a styrene derivative or unsaturated fatty acid and has a number average molecular weight of 1,500 or less and an Mw/Mn of 4.0 or less and a polypropylene having a low molecular weight. However, all of the above prior art documents use a graft resin and other resin in combination, and do not use a
Asinovsky Olga
Seidleck James J.
Tomoegawa Paper Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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