Cleaning and liquid contact with solids – Processes – Including regeneration – purification – recovery or separation...
Reexamination Certificate
2000-07-28
2002-10-15
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including regeneration, purification, recovery or separation...
C134S002000, C134S019000, C134S025100, C134S030000, C134S032000, C134S034000, C430S105000, C430S111300, C430S111310, C430S111320, C430S111340, C430S111350, C427S142000, C427S154000, C427S155000, C427S156000, C427S220000, C427S331000
Reexamination Certificate
active
06464797
ABSTRACT:
BACKGROUND
1. Field
This patent specification relates to a method of recycling two-components electrostatic image developers for use in electrophotography and electrostatic recording, capable of separating carrier coating materials from core materials of a carrier composite which includes at least metal containing magnetic materials and resinous materials, to subsequent recycling as a carrier, through processes benign to the environment and without affecting the properties of the core materials.
2. Discussion of the Background
In electrophotography, developers are used to render a latent image visible. The developed image is then transferred to paper and fixed to create resulting copy. Of these developers, two-component dry developers are known, which contain both toner and carrier.
Minute particles of the toner are held on the surface of the carrier particles of relatively large sizes. In addition to the magnetic force, which acts between the carrier particles themselves and is utilized for carrying toner particles, there are electrostatic and adhesive forces in the two-component development.
The adhesive force between the charged toner and the oppositely charged carrier bead is overcome by the development force produced on the toner by the photoreceptor surface charge distribution of a latent image. As a result, the toner particles are transferred selectively onto the photoreceptor to form the developed electrostatic image. Subsequently, the electrostatic image is fixed as indicated above.
The carrier for use in two-component dry developers of the present disclosure is made of at least magnetic particles and resinous materials. Examples of the carrier structure may also include, among others, layers of resinous materials coated on top of magnetic particles having relatively large sizes, and magnetic particles with a relatively small sizes, dispersed uniformly in the resinous materials.
The carrier particles are not intended to be consumed in use and generally are used repeatedly, with toner particles added to replenish those used up in producing copies. Therefore, it is desirable for the carrier to maintain its capability to impart, through frictional charging, an appropriate polarity and a sufficient amount of charge to toner particles throughout the repeated usage.
Previously known developers, however, tend to change their charging characteristics, due to factors such as collision with either toner particles themselves or walls of the developer housing. This can result in carrier surface changes such as cracks, fracturing and abrasion of carrier coatings, and compression of toner particles, thereby leading to so-called ‘spent’ toner. Such deteriorating effects reveal themselves in progressive loss of image quality with time in use and may ultimately require the replacement of the total developer package.
In order to alleviate these deteriorating effects, a variety of improvements have been made. For example, the selection of resinous materials and/or adhesion between the surface of the magnetic materials and the coating resins have been examined so as to improve mechanical strength, to thereby reduce cracks, fracture and abrasion of carrier coatings.
Among numerous proposals made regarding resinous materials, resins of crosslinking type have been proposed that are particularly capable of increasing the mechanical strength. In general, these resins include, but are not limited to, acrylic resins, polyester resins and silicone resins, used in combination with a variety of cross linking agents and appropriate additives.
Illustrative examples of the proposed resins and methods include one using crosslinking polycarbodiimide resins discussed in Japanese Laid-Open Patent Application No. 5-127432, a method of crosslinking acrylic resins having specific properties and structure, discussed in Japanese Laid-Open Patent Applications Nos. 5-216282 and 5-216283; a method of forming a composite crosslinking structure consisting of urethane and urea bonds, discussed in Japanese Laid-Open Patent Application No. 5-197211; a method using a silicone resin having specified silane coupling agents, discussed in Japanese Laid-Open Patent Application No. 7-114221; and a method of crosslinking a alcohol hydroxy group containing resin with a phenolic hydroxy group containing resin, discussed in Japanese Laid-Open Patent Application No. 8-87137.
A further method is also proposed for polymerizing resinous materials directly onto the surface of magnetic materials. This is exemplified by a method of interfacially polymerizing and subsequently cross-linking resinous materials coated on the surface of carrier core materials, discussed in Japanese Laid-Open Patent Application No. 6-194881.
The resultant coated materials formed by these methods, however, have drawbacks such as difficulties in separating resinous materials from the core, since their mechanical strength and stability against thermal stress are increased by these methods.
Furthermore, a method is proposed for coating various resinous materials on the surface of magnetic materials to prevent spent toner particles. For example, in a method discussed in Japanese Laid-Open Patent Application No. 62-61948, the hardness of coated silicone resin is said to be increased.
As described hereinabove, many carriers for use in two-component dry developers are formed with cross-linked resinous materials as the coating resin so as to increase mechanical strength and thus to reduce spent toners. As a result, a strong bond is generally formed between the resinous materials and core materials.
The aforementioned degraded developers have been collected to be subsequently discarded. Along with the recent increase in industrial waste and concomitant environmental destruction, recycling of the developers is one of the problems awaiting solution.
As for recovering these developers, two methods have been proposed, one is to remove spent toner from the carrier surface so as to restore developer characteristics, and the other is to remove resinous materials previously coated on carrier to thereby recover core materials for recycled use.
The former method is exemplified by Japanese Laid-Open Patent Application No. 6-149132, in which spent toner particles compressed onto the carrier surface are removed by either heating or cleansing with solvents so as to recycle core materials. In this method, previously coated resin materials are retained and used as a portion of recycled toner. According to this method, therefore, toners themselves which are once spent or degraded, may be recovered for recycled use.
However, the degradation in the above-noted developer characteristics are often caused to some extent not only by spent toners but also by cracking, fracture and abrasion of carrier coatings, to a certain extent. In such a case, carrier properties can not be restored by removing spent toners alone for cycled use. In addition, there are some spent toners which are difficult to remove by the above method. Therefore, further methods are awaited which are more effective for removing the toners. Furthermore, since solvents are used during cleansing processes in the above method and these solvents may necessitate after treatments, methods are again awaited which are more benign to the environment.
The other method is exemplified by Japanese Laid-Open Patent Application No. 47-12286, in which resinous materials previously coated on carrier are removed so as to recover core materials for recycled use. In this process, collected developers are recycled after heating at a relatively high temperature (10000° F.). When this method is applied to carriers coated with thermoplastic resins such as, for example, acrylic resin, even coated resin material can be removed. Therefore, even developers previously degraded not only by spent toners but also by cracking, fracture and abrasion of the coating, can be recoated to be used as core materials for forming recycled carriers.
However, when the above method is applied to a carrier which contains ferrite materials as its core, comprising metal
Ajiri Tadafumi
Arai Kunio
Itoh Yoshihiko
Santoh Hideyuki
Sugiyama Kunitoshi
Cooper & Dunham LLP
Gulakowski Randy
Kornakov M.
Ricoh & Company, Ltd.
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