Patent GB-1319787-A (GB)
Title: Electrostatographic developer mixture
IPC: G03G9/10
Filed: 1970-04-06
Abstract: 1319787 Coated particles XEROX CORP 6 April 1970 [8 April 1969] 16141/70 Heading B2E [Also in Divisions C1 and G2] A carrier for electrostatographic developer mixtures comprises a core surrounded by a first layer comprising an at least partially cured, hydrolysed ambi-functional silane, silanol or siloxane, and a second overlying layer comprising an unsaturated polyester resin, the first layer chemically coupling the second layer to the core. The carriers are produced by (1) hydrolysing an ambi-functional organosilane, silanol or siloxane containing 1-3 hydrolysable groups attached to the silicon atom and at least one functional organic group attached to the silicon atom, (2) before or after (1) applying the ambi-functional silicon material to carrier cores to obtain a uniform, continuous thin film pre-coating thereon, (3) at least partially curing the hydrolyzate to bond the pre-coat to the cores, (4) applying an unsaturated polyester forming monomer or prepolymer solution to the pre-coated cores, and (5) curing the multi-coated cores to chemically couple the over-coat to the core. Suitable carrier materials include sodium chloride, ammonium chloride, aluminium potassium choride, Rochelle salt, sodium nitrate, potassium chlorate, granular zircon, silicon, methyl methacrylate, glass, silicon dioxide, flint-shot, iron, steel, ferrite, nickel, carborundum. Suitable hydrolysable groups in the silicon compounds are alkoxy, halo, acetoxy, hydroxy and amino groups. Suitable organic groups are residues of amines, glycidyl ethers, acrylates, methacrylates, fibriles and unsaturated 2-8 C aliphatics. Examples of suitable ambifunctional silicon compounds are given. Hydrolysis given rise to siloxane polymers. Hydrolysis can be promoted by pre-heating the carrier core with a hydrolysing medium, or by mixing the hydrolysing medium with the compound prior to the coating operation, to obtain in situ hydrolysis. Preferably the unsaturated polyesters are those derived from the aryl esters of unsaturated organic acids or anhydrides or prepolymers thereof, especially diallylphthalate, diallyl isophthalate and diallyl isophthalate and diallyl chlorendate. The polyester-forming solution may also contain a free radical initiator, especially a peroxide initiator which is an active polymerization catalyst for both the silicon compound and the unsaturated polyester-forming solution. Promoters, activators, anti-oxidants can also be added to the polyester soltuion. The coatings may be applied by mixing, dipping, spraying. Electrostatographic developer mixtures comprise finely-divided toner particles electrostatically clinging to the surface of the carrier particles. The toner particles may consist of a carbon black dispersed in a resin. In a typical Example a coating solution of the hydrolysis product of gamma-methacryloxy propyl trimethoxy silane was admixed with 600 micron glass carrier cores and the resulting mixture heated. Thereafter an overcoating solution comprising diallyl phthalate polyester polymer was admixed with the pre-coated glass cores at 110‹C, and coated cores then cured.