US3526533A - Coated carrier particles - Google Patents

Description

Sept. 1, 1910 B.B.JAcKNow TA 3,52 ,53

COATED CARRIER PARTICLES Filed Aug. 10. 1966 RESOLUTION [8 .a- (LINES/MM) las- 20 40 6'0 80 Too RELATIVE HUMIDITY (%y INVE TOR. BURTON B. JfiCKNOW AZ'TORNE) United States Patent US. Cl. 117-100 6 Claims ABSTRACT OF THE DISCLOSURE A carrier for electrostatographic developers comprising a core surrounded by a thin coating of a solid polymeric addition reaction product of at least one polym erizable unsaturated silicon free organic composition and an organo silane, silanol or siloxane having from 1 to 3 hydrolyzable groups and an organic group attached directly to a silicon atom containing an unsaturated carbon-to-carbon linkage; the reaction product having a weight-average molecular weight of at least 5,000 and a glass transition temperature of at least 55 C. This carrier is used with smaller finely-divided toner particles to develop electrostatic latent images.

This invention relates in general to imaging systems and, more particularly, to improved developing materials, their manufacture and use.

The formation and development of images on the surface of photoconductive materials by electrostatic means is well known. The basic xerographic process, as taught by C. F. Carlson in US. Pat. 2,297,691, involves placing a uniform electrostatic charge on a photoconductive insulating layer, exposing the layer to a light and shadow image to dissipate the charge on the areas of the layer exposed to the light and developing the resulting latent electrostatic image by depositing on the image a finelydivided electroscopic material referred to in the art as toner. The toner will normally be attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the latent electrostatic image. This powder image may then be transferred to a support surface such as paper. The transferred image may subsequently be permanently affixed to the support surface as by heat. Instead of latent image formation by uniformly charging the photoconductive layer and then exposing the layer to a light and shadow image, one may form the latent image by directly charging the layer in image configuration. The powder image may befixed to the photoconductive layer if elimination of the powder image transfer step is desired. Other suitable fixing means such as solvent or overcoating treatment may be substituted for the foregoing heat fixing step.

Many methods are known for applying the electroscopic particles to the latent electrostatic image to be developed.

One development method, as disclosed by E. N. Wise in US. Pat. 2,618,552. is :known as cascade development. In this method, a developer material comprising relatively large carrier particles having finely-divided toner particles electrostatically clinging to the surface of the carrier particles is conveyed to and rolled or cascaded across the latent electrostatic image-bearing surface. The composition of the toner particles is so chosen as to have a triboelectric polarity opposite that of carrier particles. As the mixture cascades or rolls across the image-bearing surface, the toner particles are electrostatically de- 3,526,533 Patented Sept. 1, 1970 than between the toner and the discharged background. The carrier particles and unused toner particles are then recycled. This technique is extremely good for the development of line copy images. The cascade development process is the most widely used commercial xero graphic development technique. A general purpose office copying machine incorporating this technique is described in US. Pat. 3,099,943.

Another technique for developing electrostatic images is the magnetic brush process as disclosed, for example, in U.S. Pat. 2,874,063. In this method, a developer material containing toner and magnetic carrier particles is carried by a magnet. The magnetic field of the magnet causes alignment of the magnetic carriers in a brush-like configuration. This magnetic brush is engaged with an electrostatic-image bearing surface and the toner particles are drawn from the brush to the electrostatic image by electrostatic attraction.

While ordinarily capable of producing good quality images, conventional developing materials suffer serious deficiencies in certain areas. The developing materials must fiow freely to facilitate accurate metering and even distribution during the development and developer recycling phases of the electrostatographic process. Some developer materials, though possessing desirable properties such as proper triboelectric characteristics, are unsuitable because they tend to cake, bridge and agglomerate during handling and storage. Adherence of carrier particles to reusable electrostatographic imaging surfaces causes the formation of undesirable scratches on the surfaces during image transfer and surface cleaning steps. The tendency of carrier particles to adhere to imaging surfaces is aggravated when the carrier surfaces are rough and irregular. The coatings of most carrier particles deteriorate rapidly when employed in continuous processes which require the recycling of carrier particles by bucket conveyors partially submerged in the developer supply such as disclosed in US. Pat. 3,099,943. Deterioration occurs when portions of or the entire coating separates from the carrier core. The separation may be in the form of chips, flakes or entire layers and is primarily caused by fragile, poorly adhering coating materials which fail upon impact and abrasive contact with machine parts and other carrier particles. Carriers having coatings which tend to chip and otherwise separate from the carrier core must be frequently replaced thereby increasing expense and consuming time. Print deletion and poor print quality occur when carrier having damaged coatings are not replaced. Fines and grit formed from carrier disintegration tend to drift and form unwanted deposits on critical machine parts. Many carrier coatings having high compressive and tensile strength either do not adhere well to the carrier core or do not possess the desired triboelectric characteristics. The triboelectric and flow characteristics posited and secured to the charged portion of the latent require carriers having stable and predictable triboelectric values. Another factor affecting the stability of carrier triboelectric properties is the susceptibility of carrier coatings to toner impaction. When carrier particles are employed in automatic machines and recycled through many cycles, the many collisions which occur between the carrier particles and other surfaces in the machine cause the toner particles carried on the surface of the carrier particles to be welded or otherwise forced into the carrier coatings. The gradual accumulation of permanently attached toner material on the surface of the carrier particles causes a change in the triboelectric value of the carrier particles and directly contributes to the =3 degradation of copy quality by eventual destruction of the toner carrying capacity of the carrier. Thus, there is a continuing need for a better system for developing latent electrostatic images.

It is, therefore, an object of this invention to provide developing materials which overcome the above noted deficiencies.

It is another object of this invention to provide developing materials which flow freely.

It is a further object of this invention to provide carrier coating materials which tenaciously adhere to carrier cores.

It is a still further object of this invention to provide carrier coatings which are more resistant to chipping, flaking and the like.

It is yet another object of this invention to provide carrier coatings having stable triboelectric values.

It is a further object of this invention to provide carrier coatings having high tensile and compressive strength.

It is still another object of this invention to provide toner impaction resistant carrier coatings.

It is another object of this invention to provide developers having physical and chemical properties superior to those of known developer materials.

The above objects and others are accomplished, generally speaking, by providing novel polymeric organo silicon carrier coating materials having improved properties. In general, the carrier coating materials of this invention are the products of an addition polymerization reaction between monomers or prepolymers of: (1) organo silanes, silanols or siloxanes having from 1 to 3 hydrolyzable groups and an organic group attached di rectly to the silicon atom containing an unsaturated carbon to carbon linkage capable of addition polymerization, and (2) one or more silicon free types of unsaturated polymerizable organic compounds. The resinous polymers of this invention have a weight average molecular weight of at least about 5,000 and a glass transition temperature (T of at least about 55 C. Optimum results have been obtained with polymers having a weight average molecular weight ranging from about 50,000 to about 1,250,000 and a T of at least about 60 C. because maximum durability and impaction resistance are achieved. The second order glass transition temperatures (T may, of course, be determined by measuring the dynamic modulus of a resin against its temperature and plotting the two as by the torsion pendulum method. As most polymer molecules are heated they first exist in a glassy state and the dynamic modulus remains fairly constant as temperature increases until it reaches the second order or glass transition temperature (T 'where a sharp increase and peak occurs in the dynamic modulus. Beyond this temperature, the polymer exists in a rubbery condition at a lower dynamic modulus than the peak and remains at this level as the temperature is increased over another relatively wide range until it reaches the melting point or first order transition temperature (T where a second and generally much larger peak occurs in the dynamic modulus. Beyond this peak, the resin is in a viscous fiow condition. The weight-average molecular weight, M is simply the total products of the square of the molecular weight of the molecules of a specific size, Mi, is multiplied by the number of that size Ni divided by the weight of all the molecules and may be represented by the formula:

Preferably, the organo silicon constituent of the polymer should be present in an amount at from about 0.5 percent to about 50 percent, by weight, for maximum adhesion and stable triboelectric properties. The polymers of this invention may comprise random, block or graft copolymers, terpolymers and high mixed polymer systems.

Excellent results are obtained with a carrier coating containing the solid polymeric reaction product of monomers or prepolymers of: (1) styrene; (2) acrylate or methacrylate esters and (3) organo-silanes, silanols or siloxanes having from 1 to 3 hydrolyzable groups and an organic group attached directly to the silicon atom containing an unsaturated carbon to carbon linkage capable of addition polymerization.

Preferably, the solid terpolymer should comprise from about 5 to about 94.5 percent, by weight, of a styrene composition; from about 94.5 to about 5 percent, by weight, of an acrylate or methacrylate ester and from about 0.5 to about percent, by Weight, of the polymerizable organo silicon composition because optimum. impaction resistance is achieved. However, satisfactory results are obtained with solid terpolymers comprising from about 0.5 to about 99 percent, by weight, of a styrene composition; from about 99 to about 0.5 percent, by weight, of an acrylate or methacrylate ester; and from about 0.5 to about 50 percent, by weight, of the polymerizable organo silicon composition. These reaction products have a Weight average molecular weight of at least about 5,000 and a T of at least about C. Optimum results are achieved with a terpolymer formed from the addition polymerization reaction between monomers or prepolymers of: styrene, methylmethacrylate and unsaturated organo silanes, silanols or siloxanes having from 1 to 3 hydrolyzable groups and an organic group attached directly to the silicon atom containing an unsaturated carbon to carbon linkage capable of addition polymerization. These reaction products have a weight average molecular weight of at least about 5,000 and a T of at least about 55 C. These polymers are preferred because they possess especially good triboelectric stability and excellent resistance to physical and chemical degradation. Good results are obtained with other addition reaction products of an unsaturated organo silicon compound and an unsaturated silicon free compound.

The unsaturated organic group attached to a silicon atom contains the unsaturation is a non-benzoid group and is preferably an unsaturated hydrocarbon group or derivatives thereof. Typical unsaturated organic groups include: vinyl, chlorovinyl, divinyl, styryl, distyryl, allyl, diallyl, triallyl, allylphenyl, dimethallyl and methacryloxypropyl groups and derivatives thereof. Typical hydrolyzable groups include: ethoxy, methoxy, chloro, bromo, propyloxy, acetoxy, and amino groups. Examples of typical unsaturated organo silanes having hydrolyzable groups attached to a silicon atom include: vinyltriethoxy silane, vinyltrimethoxy silane, vinyl-tris (beta-methoxyethoxy) silane, gamma methacryloxypropyltrimethoxy silane, vinyl trichlorosilane, vinyl triacetoxy silane, divinyl dichloro silane, and dimethylvinylchloro silane. Suitable corresponding polymerizable hydrolysis products and the corresponding siloxanes may be substituted for the foregoing unsaturated organo silanes. If more than one organic group is attached to a silicon atom, only one of the organic groups need be unsaturated to enter into a polymerization reaction with other unsaturated monomers. Hence, compounds such as dimethyl vinyl chlorosilane are suitable. When more than one unsaturated group attached to the silicon atom is present, these unsaturated groups need not be identical. For example, vinyl allyl silicon chlorides and bromides may be employed. Partially condensed siloxanes in the liquid state having reactive unsaturated organic groups attached to a silicon atom may be employed as a component of the polymers of this invention.

Suitable silicon free monomers or prepolymers with which the above organo silicon compounds are particularly adapted to react to form the improved carrier coatings of this invention include the unsaturated compounds which normally form resinous polymers by ad dition type polymerization. Monomers or prepolymers containing the unsaturation in a non-benzoid group may be employed, such unsaturated monomers or prepolymers include those having an ethylenic or acetylenic linkage. Thus, there are included olefins, diolefins, acetylenes and their derivatives, particularly derivatives having substituents such as halogen, alkyl, aryl, unsaturated alicyclic and other types of substituent groups including, for example, nitrile or nitro groups. The unsaturated organic monomers containing the unsaturation is a non-benzoid group also include unsaturated hydrocarbons, aliphatic, carbocyclic, and heterocyclic compounds including unsaturated alcohols, aldehydes, ketones, quinones, acids, acid anhydrides, esters, nitriles or nitro compounds. Typical unsaturated monomers include: ethylene, propylene, butenes, isobutylene, pentenes, hexenes, methyl methacrylate, methyl acrylate, vinyl chloride, vinylidene chloride, acrylonitrile, chlorovinyl acetate, styrene, butadiene, chloroprene, cyclopentadiene, divinylbenzene, cyclohexadiene, ethyl methacrylate, vinyl acetate, vinyl toluene, acetylene, phenylacetylene, ethylvinyl benzene, allyl chloride, allyl benzene, maleic anhydride, ethyl acrylate, diethyl-maleate, butyl acrylate, butyl methacrylate, isobutyl methacrylate, methacrylic anhydride, vinyl formate, and mixtures thereof.

The polymerizable unsaturated monomers or prepolymers of this invention are mixed with any free-radical initiator or catalyst capable of polymerizing the monomers or prepolymers. By a free-radical initiator or catalyst is meant a compound which is capable of producing free-radicals under the polymerization conditions employed, such as compounds having an OO or an N=N linkage. Examples of the more commonly employed free-radical initiators or catalysts include: alkyl peroxides, such as tert-butyl hydroperoxide, and di-tertbutyl peroxide; acyl and aroyl peroxides, such as dibenzoyl peroxide, perbenzoic acid, dilauroyl peroxide, perlauric acid and acetyl benzoyl peroxide, azo compounds, such as azo-bis-isobutyro nitrile, dimethylazodiisobutyrate, azo-bis-l-phenylethane and alkali metal azodisulfonates; and the like. In general, the free radical initiators or catalysts are employed in an amount from about 0.0001 to about 5.0 percent based on the combined weight of the polymerizable ingredients.

The polymerization temperature to be employed is generally dependent on the batch size, the amount of catalyst present, the molecular weight to be attained, and the activation energy of the polymerization reaction. The rate of polymerization increases with an increase in temperature. Because greater exothermic reactions occur at high temperatures and increase the danger of uncontrollable reactions, high temperatures are preferably employed in processes where the heat of polymerization may be removed under controlled conditions, e.g., in jacketed tubes through which the polymerizable or partially polymerized material is continuously passed and in stirred kettles. The polymerization temperature employed is usually within the range of about 60 C. to about the reflux temperatures of the monomer mixture at atmospheric pressure. However, economy and operating conditions such as the use of pressure or a vacuum may determine the use of higher or lower temperatures. Polymerization may be effectuated by suitable methods such as by bulk or solvent polymerization techniques. If a solvent is employed, it can be any suitable true organic solvent, i.e., a liquid unreactive to the system but capable of dissolving the reactive components. Typical well known solvents include the chlorinated, ketone, ester and hydrocarbon solvents such as, for example, xylene, benzene, toluene, hexane, cyclopentane, 1,1,l-trichloroethylene, ethyl acetate, methyl ethyl ketone, and the like. When the weight average molecular weight of the polymer or prepolymer is sufiicient, as controlled by the reaction conditions including time, temperature, catalyst and type of monomer, the polymer or prepolymer may, if necessary, be dissolved in any suitable solvent and applied by conventional coating methods, e.g., spraying, dipping, or fluidized bed coating. Typical solvents for the polymers include the solvents described immediately above.

Any suitabl coating thickness may be employed. However, a coating having a thickness at least sufficient to form a continuous film is preferred because the carrier coating will then possess sufiicient thickness to resist abrasion and prevent pinholes which adversely affect the triboelectric properties of the coated carrier particles. If a partially polymerized linear or cross-linked prepolymer is to be used as the coating material, polymerization is completed in situ on the surface of the carrier by further application of heat. To achieve further variation in the properties of the final resinous product, well known additives such as plasticizers, reactive or non-reactive resins, dyes, pigments, wetting agents and mixtures thereof may be mixed with the resin. Hydrolysis of the hydrolyzable groups attached to the silicon atoms may be promoted by pretreating the carrier core with any suitable hydrolyzing medium such as a dilute solution of acetic acid or sodium hydroxide, or by mixing the hydrolyzing material with the polymer prior to the coating operation.

Any suitable well known coated or uncoated carrier material may be employed as the core of the carriers of this invention. Typical carrier materials inculde sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacrylate, glass, silicon dioxide, flintshot, iron, steel, ferrite, nickel, carborundum and mixtures thereof. Many of the foregoing and other typical carriers are described by L. E. Walkup in US. Pat. 2,618,551; L. E. Walkup et al. in US. Pat. 2,638,416 and E. N. Wise in US. Pat. 2,618,552. An ultimate coated carrier particle diameter between about 50 microns to about 600 microns is preferred because the carrier particle then possesses sufiicient density and inertia to avoid adherence to the electrostatic images during the cascade development process. Adherence of carrier beads to an electrostatographic drum is undesirable because of the formation of deep scratches on the drum surface during the image transfer and drum cleaning steps, particularly where cleaning is accomplished by a web cleaner such as the Web disclosed by W. P. Graff, Jr. et al. in US. Pat. 3,186,838. The surprisingly better results obtained from the employment of polymeric carrier coating materials containing the reaction product of unsaturated organo silicon compounds and silicon free unsaturated monomers may be due to many factors. For example, the marked durability of the carrier may be due to the fact that these organo silicon polymers adhere extremely Well to the carrier cores tested. Outstanding adhesion is obtained when the organo silicon compounds of this invention are applied to glass or similar siliceous particles. The organo silicon carrier coatings of this invention possess a smooth outer surface which is highly resistant to chipping and flaking. The smooth tough surface enhances the rolling action of the carrier particles across the electrostatographic surfaces and reduces the tendency of the carrier particles to adhere to the surfaces. Employment of organo silicon terpolymers in the carrier coatings unexpectedly extends carrier life, particularly in respect to toner impaction resistance. Additionally, the hydrophobic properties of the resins of this invention appear to contribute in some unknown manner to the stability of the triboelectric properties of the coated carrier over a wide relative humidity range.

The various features, advantages, and limitations of the invention Will be further understood by reference to the drawing which shows a diagrammatic representation of the variations in image resolution obtained when various carrier coating materials are subjected to changing humidity conditions.

In the drawing, the average resolution obtained with an organo silicon terpolymer carrier coating of this invention represented by curve A is compared with the average image resolution obtained with a polycarbonate carrier coating represented by curve B and a vinyl chloride-vinyl acetate copolymer carrier coating represented by curve C under various relative humidity conditions. The technique employed to obtain the comparative data is set forth in detail in Example XXXVI below. As can be seen from the drawing, the average resolution obtained by carriers coated with a terpolymer of this invention is both substantially constant and extremely high under varying relative humidity conditions compared to the average resolution obtained with the coated carriers represented by curves B and C under substantially identical conditions.

The following examples further define, describe and compare methods of preparing the carrier materials of the present invention and of utilizing them to develop electrostatic latent images. Parts and percentages are by weight unless otherwise indicated.

In the following, Examples I through XXIII are carried out by washing the silicon free unsaturated monomers with a caustic solution to remove inhibitors and then washing with deionized water. The siliceous unsaturated monomers and solvent, if any, are dried with anhydrous magnesium sulfate for 10 to 24 hours and then filtered. The unsaturated organo silicon compositions, unless otherwise indicated, are distilled at reduced pressures prior to polymerization. The silicon free monomers and the organo silicon monomers are placed in a reactor with or without a solvent and purged with an inert gas such as argon or dry nitrogen for approximately 30 to 45 minutes. The inert gas introduced below the level of the reactants as the reactants are stirred. After the catalyst is added to the mixture, the reactor is maintained at atmospheric pressure and at a constant polymerization temperature for the desired time interval unless otherwise indicated. All the terpolymers formed have a weight-average molecular weight of at least about 5000.

Parts Temp. Time Example Reactor charge by wt. 0.) (hrs.)

I Styrene 65 n-Butyl meth aerylate. 35 93 48 Di-tert-butyl peroxide 2. 5 II Styrene 65 n-Butyl methacrylat 35 93 48 Vinyl triethoxy-silan 2. 5 Di-tert-butyl peroxid 2. 5 III Styrene 15 Methyl methacryla 85 93 48 Di-tert-hntyl peroxide... 2. 5 1V Styrene 15 Methyl methacrylate... 85 93 48 Vinyltriethoxy silane.-.. 5 Di-tert-butyl peroxide-.. 5 V Styrene 55 Isobutyl methacrylate... 35 Gamma-methacryl- 5 85 24 oxypropyltrimethoxy silane. Azobisisobutyro nitrile.. 1 VI Styrene 65 Isobutyl methacrylate.. 35 85 24 Azobisisobutyre nitrilc- 0.5 VII yert1ei. .fi 60 so u y met acrylate..- 40 Vinyltriethoxy-silane. 5 93 48 Di-tert-butyl peroxide... 5 VIII Styrene 5 Methyl methacrylate. 85 Vinyltriethoxy-silane. 5 90 81 Di-tert-butyl peroxide... 2v 5 Toluene (slvent).. 100 IX Styrene 60 Isobutyl methacrylate-.. 40 Gamma-methacryloxyso 94 propyltrimethoxysilane. Azobisisobutyronitrile.. 0. 5 X Styrene 50 Isobutyl methacrylate... 50 Gamma-methacryloxy- 1O 80 24 p ropyl-trimethoxys1 ne. Azobisisobutyronitrile..- 0. 5 XI Styrene 55 Ethyl methacrylate 35 Gamma-methaeryloxy- 5 80 24 propyl-trimethoxysilane. Azobisisobutyronitrile..- 0. 5 K11 Styrene 75 Ethyl methacrylate. 25 Gamma-methacryloxy- 5 8O 24 propyltrimethoxysilane. Azobisisobutyronitrilc..- 0. 5

Parts Temp. Time Example Reactor charge by wt. 0.) (hrs.)

XIII--. Styrene 15 MethyLmethacrylat Vinyltrietliwry-silane... 5 100 26 Di-tert-butyl peroxide-.. 1 Toluene (solvent)- 106 XIV stlyreneluutfinfli 74 nuty me acry ate.. 40 Vinyltriethexy-silane. 5 42 Di-tert-butyl peroxid 3 XV Styrene 65 n-Butyl me 35 Vinyltriethoxy-silane 5 93 48 (non-distilled). Di-tert-butyl peroxide 2. 5 XVI S5 5 Vinyltriethoxy-silane... 5 48 Di-tert-butyl peroxide-. 2. 5 XVII.. lSutytrienleuflfiuui 15 e y met acry ate. 85 Vinyltriethoxysilane.- 5 93 48 Di-tert-butyl peroxide... 2. 5 XVIIL- 1\(lintyll rlzhlortilglenn1 e y me acry ate.

Vinyl triethoxy silane. 5 l 93 48 Di-tert-butyl peroxide-.. 2. 5 XIX Styrene 15 Methyl methacrylate... 8 Vinyl .triethoxy silane. 5 100 12 Di-tert-butyl peroxide... 1 Toluene (solvent). 90 XX Styrene 65 Methyl methacrylate. 25 n-Butyl mcthacrylate. 10 93 48 Vinyltriethoxysilaneu 5 Di-tert-butyl peroxide-.. 5 XXI Vinyl acetate 25 Styrene 75 75 48 Vinyltriethoxy-s1lane.. 5 Di-tert-butyl peroxide... 2 XXII Isobornyl acrylate 100 Vinyltriethoxy-silane.. 5 93 48 Di-tert-butyl peroxide-.. 2. 5 XXIII Sgylienle ..1 15 l at y Inethacry ate. 85 Vinyltriethoxy-silane 5 85 24 Benzoyl peroxide-.. 2 XX1V. Styrene 15 Methyl methacrylate. 85 Vinyltriethoxy-silane 5 100 26 Di-tert-butyl peroxide..- 1 1,4-di0xane 106 XXV..-.. Styrene 100 Vinyltriethoxy-silane 5 93 48 Di-tert-butyl peroxide-.. 2. 5 XXVI. Styrene 100 Gammaqnethacryloxy- 5 propyltrimethoxy- 80 24 silane. Azobisisobutyronitrile.-. 1 XXVII... Aciylonitrile 100 Vinyltriethoxy-silane.. 5 75 48 Di-tert-butyl peroxide... 2. 5

1 Pressurized reactor.

EXAMPLE XXVIII A control sample containing one part colored toner particles having an average particle size of about 10 to about 20 microns and 99 parts coated carrier particles available in the Xerox 813 Developer sold by the Xerox Corporation, Rochester, NY. is cascaded across an electrostatic image-bearing surface. The resultant developed image is transferred by electrostatic means to a sheet of paper whereon it is fused by heat. The residual powder is removed from the electrostatic imaging surface by a cleaning web of the type disclosed by W. P. Grafl, Jr. et al. in U.S. Pat. 3,186,838. After the copying process is repeated 8,000 times, the developer mix is examined for the presence of carrier coating chips and flakes. Numerous carrier chips and flakes are found in the developer mix.

EXAMPLE XXIX A coating solution containing 10 percent, by weight, of the silicon free polymeric material of Example VI dissolved in toluene is applied to 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 20 grams of polymeric material is applied to about 2500* grams of glass cores. The developing procedure of Example XXVIII is repeated with the foregoing coated carriers substituted for th Xerox 813 carrier. An examination of the developer mix after test termination reveals numerous carrier chips or flakes in the developer mix.

9 EXAMPLE xxx A coating solution containing 10 percent, by weight, of the silicon free polymeric material of Example I dissolved in toluene is applied to 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 2500 grams of polymeric material is applied to about grams of glass cores. The developing procedure of Example XXVIII is repeated with the foregoing coated carrier substituted for the Xerox 813 carrier. An examination of the developer mix after test termination reveals numerous carrier coating chips and flakes.

EXA MPLE XXXI A coating solution containing 10 percent, by weight, of the polymeric material of Example XIV dissolved in toluene is applied to 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 20 grams of polymeric material is applied to about every 2500 grams of glass cores. The developing procedure of Example XXVIII is repeated with the foregoing coated carrier substituted for the Xerox 813 carrier. However, the copying process is repeated 21,000 times rather than 8,000 times. An examination of the developer mix after test termination reveals substantially no carrier coating chips or flakes.

EXAMPLE XXXII A solution containing 10 percent, by Weight, of the polymeric material of Example XV dissolved in toluene is applied to 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 20 grams of polymeric material is applied to about every 2500 grams of glass cores. The developing procedure of Example XXVIII is repeated with the foregoing coated carriers substituted for the Xerox 813 cartimes rather than 8,000 times. An examination of the developer mix after the test termination reveals substantially no carrier coating chips or flakes.

EXAMPLE XXXIII A coating solution containing 10 percent, by weight, of a polymeric material of Example XVI dissolved in toluene is applied to 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 20 grams of polymeric material is applied to about every 2500 grams of glass cores. The developing procedure of Example XXVIII is repeated With the foregoing coated carrier substituted for the Xerox 813 carrier. However, the copying process is repeated 21,000 times rather than 8,000 times. An examination of the developer mix after test termination reveals substantially no carrier coating chips nor flakes.

EXAMPLE XXXIV A coating solution containing 10 percent, by weight, of the polymeric material of Example XVIII dissolved in dioxane is applied 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 20 grams of polymeric material is applied to about 2500 grams of glass cores. The developing procedure of Example XXVIII is repeated with the foregoing coated carrier substituted for the Xerox 813 carrier. An examination of the developer mix after the test termination reveals relatively few carrier coating chips and flakes.

EXAMPLE XXXV A coating solution containing 10 percent, by weight, of a polymeric material of Example XIX dissolved in trichloroethylene is applied to 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 20 grams of polymeric material is applied to about 2500 grams of glass cores. The developing procedure of Example XXVIII is repeated with the foregoing coated carrier substituted for the.

1 0 Xerox 813 carrier. An examination of the developer mix after test termination reveals very few carrier coating chips and flakes.

EXAMPLE XXXVI Three different coating solutions, A, B, and C, containing 10 percent, by weight, of polymeric material dissolved in appropriate solvents are prepared. Solution A contains the polymeric material of Example XIV. Solution B contains a polycarbonate resin (Lexan sold by the General Electric Corporation) dissolved in ethylene dichloride. Solution C contains a copolymer of 87 percent vinylchloride and 13 percent vinylacetate dissolved in a mixture of methyl ethyl ketone and toluene. The coating solutions are sprayed onto three different batches of 450 micron glass carrier cores and the resulting coated cores heated to drive off the solvent. About 20 grams of polymeric material is applied to about 2500 grams of glass cores. About 99 parts of each carrier sample is mixed with 1 part colored styrene copolymer toner particles having an average particle size of about 10 to 20 microns and cascaded across an electrostatic image-bearing surface. The developed image is then electrostatically transferred to a receiving sheet. The development and transfer steps are repeated at different relative humidities in 10 percent increments from 20 percent to 8-0 percent. The resolution in lines per millimeter of each of the transferred images is plotted on a graph against the corresponding percent relative humidity. The change in resolution between 20 and percent relative humidity for samples B and C are more than 4 times greater than the change in resolution for sample A.

EXAMPLE XXXVII A control sample containing one part pigmented toner particles having an average particle size of about 10 to about 20 microns and 99 parts coated carrier particles available in the Xerox 813 Developer sold by the Xerox Corporation, Rochester, NY. is tumbled in a rotating cylindrical jar having an inside diameter of about 2.25 and a surface speed of 140 feet per minute. Toner impaction along with coating chips and flakes are observed within about 50 hours after the test is initiated.

EXAMPLE XXXVIII A coating solution containing 10 percent, by weight, of the polymeric material of Example XVII dissolved in toluene and applied to 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 20 grams of polymeric material is applied to about 2500 grams of glass cores. The impaction testing procedure of Example XXXVII is repeated with the foregoing coated carrier substituted for the Xerox 813 carrier. Toner impaction is discovered after about 100 hours after the test was initiated. No chips or flakes are found.

EXAMPLE XXXIX A coating solution containing 10 percent, by weight, of the polymeric material of Example XXII dissolved in toluene is applied to 600 micron glass carrier cores which are simultaneously heated and suspended in a vibrating drum. About 20 grams of polymeric material is applied to about 2500 grams of glass cores. The impaction 1 1 test procedure of Example XXXVII is repeated with the foregoing coated carrier substituted for the Xerox 813 carrier. Toner impaction is observed at about 100 hours after the test was initiated. No chips or flakes are found.

Although specific materials and conditions were set forth in the above exemplary processes in making and using the developer material of this invention, these are merely intended as illustrations of the present invention. Various other toners, carrier cores, substituents and processes such as those listed above may be substituted for those in examples with similar results.

Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

1. A carrier for electrostatographic developer mixtures comprising a core particle surounded by a thin outer layer, said outer layer comprising a solid terpolymer of (1) from about 5 to about 94.5 percent by weight, of a polymerizable styrene composition, '(2) from about 94.5 to about 5 percent, by weight, of a composition selected from the group consisting of polymerizable acrylate and methacrylate esters and (3) from about 0.5 to about 50 percent, by weight of a polymerizable organosilicon composition selected from the group consisting of organosilanes, silanols and siloxanes having from 1 to 3 hydrolyzable groups and an organic group attached directly to a silicon atom containing an unsaturated carbon-to-carbon linkage, said solid terpolymer having a weight-average molecular weight of at least about 5,000 and a glass transition temperature of at least about 5 5 C.

2. A carrier for electrostatographic developer mixtures comprising a core particle surrounded with a thin outer layer said outer layer comprising a solid polymeric addition reaction product of (1) from about 99.5 to about 50 percent, by weight, of at least one polymerizable unsaturated silicon free organic composition and (2) from about 0.5 to about 50 percent, by weight, of a polymerizable organosilicon composition selected from the group consisting of silanes, silanols, and siloxanes having from 1 to 3 hydrolyzable groups and an organic group attached directly to a silicon atom containing an unsaturated carbon to carbon linkage, said solid polymeric addition reactor product having a Weight-average molecular weight of at least about 5,000 and a glass transition temperature of at least about 55 C.

3. A carrier for electrostatographic developer mixtures according to claim 2 wherein said solid polymeric addition reaction product is a copolymer of said polymerizable unsaturated silicon free organic composition and said polymerizable organosilicon composition.

4. A carrier for electrostatographic developer mixtures comprising a core particle having an average particle size between about 50 and about 600 microns surrounded with a thin outer layer, said outer layer comprising a solid polymeric addition reaction product of (1) from about 99.5 to about 50 perecnt, by weight, of at least one polymerizable unsaturated silicon free organic composition and (2) from about 0.5 to about 50 percent, by weight, of a polymerizable organosilicon composition selected from the group consisting of silanes, silanols, and siloxanes having from 1 to 3 hydrolyzable groups and an organic group attached directly to a silicon atom containing an unsaturated carbon to carbon linkage, said solid polymeric addition reaction product having a weight-average molecular weight of at least about 5,000 and a glass transition temperature of at least about 55 C.

5. A carrier for electrostatographic developer mixtures comprising a core particle surrounded by a thin outer layer, said outer layer comprising a solid terpolymer of (1) from about 5 to about 94.5 percent, by weight, of a polymerizable styrene composition, (2) from about 94.5 to about 5 percent, by Weight, of a polymerizable methacrylate composition selected from the group consisting of methyl, propyl, ethyl, and butyl methacrylates and (3) from about 0.5 to about 50 percent, by weight, of a polymerizable organosilicon composition selected from the group consisting of silanes, silanols and siloxanes having from 1 to 3 hydrolyzable groups and an organic group attached directly to a silicon atom containing an unsaturated carbon-to-carbon linkage, said solid terploymer having a weight-average molecular weight of at least about 5,000 and a glass transition temperature of at least about 55 C. and said carrier having a diameter between about 50 microns to about 600 microns.

6. A carrier for electrostatographic developer mixtures comprising a core particle surrounded with a thin outer layer, said outer layer comprising a solid terploymer of (1) from about 5 to about 94.5 percent, by weight, of a first polymerizable unsaturated silicon free organic composition, (2) from about 94.5 to about 5 percent, by weight, of a second polymerizable unsaturated silicon free organic composition different from said first polymerizable unsaturated silicon free organic composition, and .(3) from about 0.5 to about 50 percent by weight, of a polymerizable organosilicon composition selected from the group consisting of silanes, silanols, and siloxanes having from 1 to 3 hydrolyzable groups and an organic group attached directly to a silicon atom containing an unsaturated carbon to carbon linkage, said solid terpolymer having a weight-average molecular weight of at least about 5,000 and a glass transition temperature of at least about 55 C.

References Cited UNITED STATES PATENTS 2,874,063 Q/1959 Greig 252621 3,046,242 7/1962 Santelli 1l7l00 X 3,410,614 11/1963 DeVries 117100 X 3,177,083 4/1965 DeVries 117100 X 3,291,633 12/1966 Wissinger 117l00 3,427,339 2/1969 Plueddemann 26046.5 vX 3,427,340 '2/ 1969 Plueddemann 26046.5 X

WILLIAM D. MARTIN, Primary Examiner M. R. PERRO'NE, JR., Assistant Examiner US. Cl. X.R.

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