US3740334A

US3740334A - Process of preparing solid developer for electrostatic latent images

Info

Publication number: US3740334A
Application number: US00196700A
Authority: US
Inventors: B Jacknow; J Moriconi
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1970-08-28
Filing date: 1971-11-08
Publication date: 1973-06-19
Anticipated expiration: 1990-06-19

Abstract

A PROCESS FOR THE PREPARATION OF A SOLID ELECTROSTATOGRAPHIC DEVELOPER MATERIAL COMPRISING PROVIDING TONER PARTICLES CAPABLE OF BEING ELECTROSTATICALLY COATED ON A CARRIER SURFACE, THE TONER PARTICLES HAVING A BLOCKING TEMPERATURE OF AT LEAST ABOUT 110*F., A MELT VISCOSITY LESS THAN ABOUT 2.5X10**-4 POISE AT TEMPERATURES UP TO ABOUT 450*F., THE TONER PARTICLES INCLUDING A COLORANT, A THERMOPLASTIC RESIN, A SOLID ADDITIVE HAVING A MELTING POINT BETWEEN ABOUT 115*F. AND 270*F., FORMING THE TONER PARTICLES INTO PARTICLES HAVING A SIZE RANGE OF UP TO ABOUT 30 MICRONS, AND THERE AFTER TUMBLING THE PARTICLES WITH FROM ABOUT 0.002 PERCENT TO ABOUT 20 PERCENT BY WEIGHT, BASED ON THE WEIGHT OF THE PARTICLES, OF AT LEAST ONE SOLID, STABLE HYDROPHOBIC METAL SALT OF A FATTY ACID UNTIL THE METAL SALT IN UNIFORMLY MIXED WITH AND IS AVAILABLE AT THE EXTERNAL SURFACES OF THE PARTICLES.

Description

United States Patent Ofice 3,740,334 Patented June 19, 1973 3,740,334 PROCESS OF PREPARING SOLID DEVELOPER FOR ELECTROSTATIC LATENT IMAGES Burton B. Jacknow and Joseph H. Moriconi, Rochester, N.Y., assignors to Xerox Corporation, Rochester, N .Y.

No Drawing. Original application Aug. 28, 1970, Ser. No.

68,019, now Patent No. 3,653,893. Divided and this application Nov. 8, 1971, Ser. No. 196,700

Int. Cl. G03g 9/02 U.S. Cl. 252-621 8 Claims ABSTRACT OF THE DISCLOSURE A process for the preparation of a solid electrostatographic developer material comprising providing toner particles capable of being electrostatically coated on a carrier surface, the toner particles having a blocking temperature of at least about 110 F., a melt viscosity less than about 2.5 10' poise at temperatures up to about 450 F., the toner particles including a colorant, a thermoplastic resin, a solid additive having a melting point between about 115 F. and about 270 F.; forming the toner particles into particles having a size range of up to about 30 microns, and thereafter tumbling the particles with from about 0.002 percent to about 20 percent by weight, based on the Weight of the particles, of at least one solid, stable hydrophobic metal salt of a fatty acid until the metal salt is uniformly mixed with and is available at the external surfaces of the particles.

This is a division of application Ser. No. 68,019, filed Aug. 28, 1970, now U.S. Pat. No. 3,653,893.

BACKGROUND OF THE INVENTION This invention relates to imaging systems, and more particularly, to improved xerographic developing materials, their manufacture and use.

The formation and development of images on the surface of photoconductor materials by electrostatic means is well known. The basic xerographic process, as taught by C. F. Carlson in U.S. 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 finely divided 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 be fixed 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 steps.

Several 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 U.S. 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 coated thereon is conveyed to and rolled or cascaded across the electrostatic latent image bearing surface. The composition of the carrier particles is so selected as to'triboelectrically charge the toner particles to the desired polarity. As the mixture cascades or rolls across the image bearing surface, the toner particles are electrostatically deposited and secured to the charged portion of the latent image and are not deposited on the uncharged or background portions of the image. Most of the toner particles accidentally deposited in the background are removed by the rolling carrier, due apparently, to the greater electrostatic attraction between the toner and the carrier than between the toner and the discharged background. The carrier and excess toner are then recycled. This technique is extremely good for the development of line copy images.

Another method of 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 are carried by a magnet. The magnetic field of the magnet causes alignment of the magnetic carrier into a brush-like configuration. This magnetic brush is engaged with the electrostatic image-bearing surface and the toner particles are drawn from the brush to the latent image by electrostatic attraction.

Still another technique for developing electrostatic latent images is the powder cloud process as disclosed, for example, by C. F. Carlson in U.S. P'at. 2,221,776. In this method, a developer material comprising electrically charged toner particles in a gaseous fluid is passed adjacent the surface bearing the latent electrostatic image. The toner particles are drawn by electrostatic attraction from the gas to the latent image. This process is particularly useful in continuous tone development.

Other development methods such as touchdown development as disclosed by R. W. Gundlach in U.S. Pat. 3,166,432 may be used where suitable.

Although some of the foregoing development techniques are employed commercially today, and most Widely used commercial xerographic development technique is the technique known as' cascade development. A general purpose oflice copying machine incorporating this development process is described in U.S. Pat. 3,099,943. The cascade technique is generally carried out in a commercial apparatus by cascading a developer mixture over the upper surface of an electrostatic latent image-bearing drum having a horizontal axis. The developer is transported from a trough or sump to the upper portion of the drum by means of an endless belt conveyor. The developer is cascaded downward along a portion of the surface of the drum into the sump and is subsequently recycled through the developing system to develop additional electrostatic latent images. Small quantities of toner are periodically added to the developing mixture to compensate for the toner depleted by development. This process is then repeated for each copy produced by the machine and is ordinarily repeated many thousands of times during the usable life of the developer.

Thus, it is apparent from the description presented above as well as in other development techniques, that the toner is subjected to mechanical attrition which tends to break down the particles into undesirable dust fines. Toner fines are detrimental to machine operation because they are extremely difficult to remove from reusable imaging surfaces and also because they tend to drift to other parts of the machine and deposit on critical machine parts such as optical lenses. The formation of fines is retarded when the toner contains a tough, high molecular weight resin which is capable of withstanding the shear and impact forces imparted to the toner in the machine. Unfortunately, many high molecular weight materials cannot be employed in high speed automatic machines because they cannot be rapidly fused during a powder image heat fixing step. Attempts to rapidly fuse a high melting point toner by means of oversized high capacity heating units have been confronted with the problems of preventing the charring of paper receiving sheets and of adequately dissipating the heat evolved from the fusing unit or units. Thus, in order to avoid charring or combustion, additional equipment such as complex and expensive cooling units are necessary to properly dispose of the large quantity of heat generated by the fuser. Incomplete removal of the heat evolved will result in operator discomfort and damage to heat sensitive machine components. Further, the increased space occupied by and the high operating cost of the heating and cooling units, often outweigh the advantages achieved by the increased machine speed. On the other hand, low molecular weight resins which are easily heat fused at relatively low temperatures are often undesirable because these materials tend to form thick films on reusable photoconductor surfaces. These films tend to cause image degradation and contribute to machine maintenance down time. In addition, low molecular weight resins tend to form tacky images on the copy sheet which often offset to other adjacent sheets. Further, toner particles containing low molecular weight resins tend to bridge, cake and block in the shipping container as well as in the xerographic machine. Also, the toner material must be capable of accepting a charge of the correct polarity when brought into rubbing contact with the surface of carrier materials in cascade, magnetic brush or touchdown development systems. Some resinous materials which possess many properties which would be desirable in xerographic toners dispense poorly and cannot be used in automatic copying and duplicating machines. Other resins dispense well but form images which are characterized by low density, poor resolution, or high background. Further, some resins are unsuitable for processes where electrostatic transfer is employed. Since most thermoplastic materials are deficient in one or more of the above areas, there is a continuing need for improved toners and developers.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a toner overcoming the above noted deficiencies.

It is another object of this invention to provide a toner which is resistant to film formation when employed in conventional xerographic copying and duplicating devices.

It is another object of this invention to provide a xerographic toner which forms images having reduced background.

It is another object of this invention to provide a free flowing toner which is resistant to agglomeration.

It is another object of this invention to provide a xerographic toner which can be fused at higher rates with less heat energy.

It is another object of this invention to provide a xerographic toner which forms high resolution images.

It is another object of this invention to provide a xerographic toner which is resistant to mechanical attrition during the development process.

It is another object of this invention to provide a xerographic toner having improved dispensing characteristics.

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

The above objects and others are accomplished by providing a finely-divided low melting toner comprising a colorant, a thermoplastic resin comprising a vinyl resin, a solid metal salt of a fatty acid and a solid additive having a melting point between about 115 F. to about 270 F. and having the general structures 1) r TI) -o l'l wherei n p se ts a pqsitivs i t g twin 3 to 7 i c usive and R represents an organic moiety having from 3 to 12 carbon atoms,

Cllnl wherein n represents a positive integer from 0 to 3 inclusive and m has an average value from 0.5 to 2.5 inclusive. For optimum operation in high speed xerographic machines employing paper receiving webs, the toner should have a melting range between about F. to about 300 F. and a melt viscosity of less than about 2.0 l0- poise up to temperatures of about 300 F. Toner melting temperatures below about 300 F. are preferred because heat dissipation and paper degradation problems are avoided. The developers of this invention contain from about 0.02 percent to about 20 percent by weight, based on the weight of the toner in the final developer mixture, of the solid hydrophobic metal salt of a higher fatty acid. Preferably, the developers of this invention contain from about 0.05 to about 4 percent by weight of the metal salt because maximum reduction of background deposits, improved image density and higher image character resolution are achieved. Without the presence of a solid stable hydrophobic metal salt of a higher fatty acid in the developer, extremely rapid degradation of reusable imaging surfaces, untenably high background, reduced toner image density, poor toner image transfer, reduced carrier particle life, increased difficulty in removing residual toner material from reusable imaging surfaces, and reduced electrical stability occurs. Although the initial electrostatic imaging surface potential may be reduced and abrasion resistance improved when the proportion of metal salt present is increased above about 10 percent, undesirable background deposits increase noticeably. If the charge voltage is reduced to compensate for the presence of metal salt in excess of about 10 percent, the images begin to acquire a washed out appearance. It is not essential that the entire surface of each toner particle be coated with the metal salt, e.g., sufficient metal salt is present when about 10 to about 16 percent of the toner particle surfaces are coated with a metal salt. When the metal salt is dispersed in rather than coated on a toner or carrier particle, proportionately more metal salt is necessary in order to maintain a sufficient quantity of the exposed salt at the surface of the toner or carrier particle. The additional amount of metal salt necessary depends to a large extent on the surface area of the developer particles, hence upon the particle diameter selected. Any suitable stable solid hydrophobic metal salt of a fatty acid having a melting point greater than about 57 C. may be employed. Optimum results are obtained when about 0.05 to about 4 percent by weight, based on the weight of the toner, of zinc stearate is available at the outer surfaces of the particles in the developing material. The developers of this invention containing zinc stearate are preferred because the resulting mixture is characterized by outstanding fusing rates, high cleanability from electrostatic imaging surfaces, greater triboelectric stability, denser toner images and increased resistance to mechanical attrition. Unexpectedly, both the fire hazard and excessive power consumption problems encountered in high speed xero- R @1111 also be more than 1 substltuen uch. a 2 chlcrlnes e 6' y graphic development processes are obviated when toners containing the above described polymeric esterification product and metal salt are employed.

Any suitable vinyl resin having a melting point of at least about 110 F. may be employed in the toners of this invention. The vinyl resin may be a homopolymer or a copolymer of two or more vinyl monomers. Typical monomeric units which may be employed to form vinyl polymers include: styrene, p-chlorostyrene; vinyl naphthalene; ethylenically unsaturated mono-olefins such as ehtylene, propylene, butylene, isobutylene and the like; vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and the like; esters of alphamethylene aliphatic monocarboxylic acids such as methyl acrylate, ethyl acrylate, nbutylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methylalpha-chloroacrylate, methyl methacrylate, ethyl meth acrylate, butyl methacrylate and the like; acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, and the like; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone and the like; vinylidene halides such as vinylidene chloride, vinylidene chlorofiuoride and the like; and N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N- vinyl pyrrolidene and the like; and mixtures thereof. Generally, suitable vinyl resins employed in the toner have a weight average molecular weight between about 3,000 to about 500,000.

Toner resins containing a relatively high percentage of a styrene resins are preferred. The presence of a styrene resin is preferred because a greater degree of image definition is achieved with a given quantity of additive material. Further, denser images are obtained when at least about 25 percent by weight, based on the total weight of resin in the toner, of a styrene resin is present in the toner. The styrene resin may be a homopolymer of styrene or styrene homologues or copolymers of styrene with other monomeric groups containing a single methylene group attached to a carbon atom by a double bond. Thus, typical monomeric materials which may be copolymerized With styrene by addition polymerization include: p-chlorostyrene; vinyl naphthalene; ethylenically unsaturated mono-olefins such as ethylene, propylene, butylene, isobutylene and the like; vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and the like; esters of alpha-methylene aliphatic monocarboxylic acids such as methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl alpha-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl meth acrylate and the like; acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, and the like; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone and the like; vinylidene halides such as vinylidene chloride, vinylidene chlorofluoride and the like; and N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidene and the like; and mixtures thereof. The styrene resins may also be formed by the polymerization of mixtures of two or more of these unsaturated monomeric materials with a styrene monomer. The expression addition polymerization is intended to include known polymerization techniques such as free radical, anionic and cationic polymerization processes.

The vinyl resins, including styrene type resins, may also be blended with one or more other resins if desired. When the vinyl resin is blended with another resin, the added resin is preferably another vinyl resin because the resulting blend is characterized by especially good triboelectric stability and uniform resistance against physical degradation. The vinyl resins employed for blending with etc the styrene type or other vinyl resin may be prepared by the addition polymerization of any suitable vinyl monomer such as the vinyl monomers described above. Other thermoplastic resins may also be blended with the vinyl resins of this invention. Typical non-vinyl type thermoplastic resins include: rosin modified phenol formaldehyde resins, oil modified epoxy resins, polyurethane resins, cellulosic resins, polyether resins and mixtures thereof. When the resin component of the toner contains styrene coypolymerized with another unsaturated monomer or a blend of polystyrene and another resin, a styrene component of at least about 25 percent, by weight, based on the total weight of the resin present in the toner is preferred because denser images are obtained and a greater degree of image definition is achieved with a given quantity of additive material.

The combination of the resin component, colorant and additive, whether the resin component is a homopolymer, copolymer or blend, should have a blocking temperature of at least about F and a melt viscosity of less than about 2.5 X 10" poise at temperatures up to about 450 F. When the toner is characterized by a blocking temperature less than about 110 F. the toner particles tend to agglomerate during storage and machine operation and also form undesirable films on the surface of reusable photoreceptors which adversely affect image quality. If the melt viscosity of the toner is greater than about 2.5 10" poise at temperatures above about 450 F., the toner material of this invention does not adhere properly to a receiving sheet even under conventional xerographic machine fusing conditions and may easily be removed by rubbing.

The solid toner additives of this invention may be selected from three different groups of organic compounds. In the first group, the compounds have the general structure:

ROO

wherein n represents a positive integer from 3 to 7 inclusive and R represents an organic moiety having from 3 to 12 carbon atoms. Typical compounds represented by this formula include: pentaerythritol tetrabenzoate, sucrose benzoate, triethylene glycol dibenzoate, glyceryl tribenzoate, neopentylglycol dibenzoate, trimethylolethane tribenzoate, and the like. Outstanding results have been obtained when the additive is pentaerythritol tetrabenzoate. When the additive is pentaerythritol tetrabenzoate, the advantages obtained in blocking resistance, lower tendency to film and optimum fusing temperatures are supplemented by sharp, high-contrast copies having little or no background deposits. The negligible background deposits in the ultimate copy appear to be due to a markedly reduced tendency of the toner to adhere to the background areas of a photoconductor during development. Thus, toners containing pentaerythritol tetrabenzoate are the preferred toners in this invention. Compounds in the second group having the general structure:

ill. Q 4;

2 R can also be more than 1 substituent, such as 2 chlorines sulfonamide, o-toluene sulfonamide, p-toluene sulfonamide, N,N-di-p-hydroxyethyl-p-toluene sulfonamide, N, N-dimethyl benzene sulfonamide, N-cyclohexyl benzene sulfonamide, N-cyclohexyl 3,4 dichlorobenzene sulfonamide, N-allyl p-toluene sulfonamide, N,N-di-p-hydroxyethyl p-toluene sulfonamide, N-cyclohexyl p-toluene sulfonamide and the like. Compounds representative of the third group having the general structure:

wherein n represents a positive integer from to 3 inelusive and in has an average value from 0.5 to 2.5 inclusive. Typical polychlorinated polyphenyl compounds represented by this formula include: p,p-dichloro biphenyl; 2,4,7,9-tetrachloro biphenyl; 1,4 bis (p-chlorophenyl)-2 chlorobenzene; 2,2 dichloro-4,4' (p-chlorophenyl) biphenyl and the like. Some of these compounds are sold under the Aroclor trademark by the Monsanto Company, St. Louis, Mo., and under the Halowax trademark by the Koppers Company, Inc., Pittsburgh, Pa., for example, Aroclor 2565, Aroclor 4465, Aroclor 5442, Aroclor 5460 and Halowax 0077. Preferably, the additive is employed in an amount from about 5 percent to about 55 percent, by weight, based on the total weight of the resinous component of the toner. As the relative quantity of additive in the toner is increased above about 65 percent, the mechanical strength, creep resistance and permanency of the ultimate fused toner image begins to decrease rapidly. Thus, when brittle, non-polymeric compounds such as the compounds disclosed in US. Pat. 3,272,644 are employed in automatic copying and duplieating machines, extensive toner dust is formed and the fused toner images tend to crumble and flake off receiving sheets when the sheets are folded Further, some solid non-polymeric materials tend to vaporize or sublime and form toxic or flammable fumes. When less than about 3 percent of the additive is employed in the toner, the toner fusing, flow and triboelectric properties are substantially the same as a toner which does not contain the additives. If desired, mixtures of additives may be employed in the toner. An increase in the relative quantity of additive tends to reduce the melt viscosity of the ultimate toner.

It is to be understood that the specific formulas given for the units contained in the additives and resins of this invention represent the vast majority of the units present, but do not exclude the presence of other monomeric units or reactants than those which have been shown. For example, some commercial materials such as polystyrenes, and polychlorinated polyphenyl compounds contain trace amounts of homologues or unreacted or partially reacted monomers. Any minor amount of such substituents may be present in the materials of this invention.

Any suitable stable solid hydrophobic metal salt of a fatty acid having a melting point greater than about 57 C. may be employed with the toner resin of this invention. The metal salt should be substantially insoluble in Water. Water soluble metal salts lack the proper electrical properties and are adversely affected by humidity changes normally occurring in the ambient atmosphere. However, a large proportion of salts commonly regarded as insoluble, actually dissolve to a slight extent. To effectively carry out the purposes of this invention, the solubility of the salt should be negligible. The salts having the desired specific characteristics include many salts of linear saturated fatty acids, unsaturated fatty acids, partially hydrogenated fatty acids and substituted fatty acids and mixtures thereof. The metal salts may be tumbled or milled with the toner or carrier particles or intimately dispersed in each toner or carrier particle. However, the latter embodiment is less desirable than the tumbled or milled mixtures because a greater q y f metal salt is required to provide a suflicient quantity of metal salt, exposed at the surface of the developer particles. The metal salts are preferably mixed with toner material by tumbling preformed finely divided metal salt particles with preformed finely divided toner particles. The tumbling process is continued until the preformed metal salt particles are uniformly distributed throughout the mass of toner particles. Excellent toner mixtures are obtained when the preformed toner particles are tumbled with preformed metal salt particels having a size range between about 0.5 to about 50 microns. The tumbled mixtures are preferred because the resulting treated toners exhibit extremely stable imaging characteristics under widely fluctuating humidity conditions.

Typical fatty acids from which stable solid hydrophobic metal salts may be derived include: caproic acid, enanthylic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, nondecylic acid, arachidic acid, beh'enic acid, stillingic acid, palmitoleic acid, oleic acd, ricinoleic acid, petroselinic acid, vaccenic acid, linoleic acid, linolenic acid, eleostearic acid, licanic acid, parinaric acid, gad-oleic acid, arachidonic acid, cetoleic acid and mixtures thereof. Typical stable solid metal salts of fatty acids include: cadmium stearate, barium stearate, lead stearate, iron stearate, nickel stearate, cobalt stearate, copper stearate, strontium stearate, calcium stearate, cadmium stearate, magnesium stearate, zinc oleate, manganese oleate, iron oleate, cobalt oleate, copper oleate, lead oleate, magnesium oleate, zinc palmitate, cobalt palmitate, copper palmitate, magnesium palmitate, aluminum palmitate, calcium palmitate, lead caprylate, lead caproate, zinc linoleate, cobalt linoleate, calcium linoleate, zinc ricinoleate, cadmium ricinoleate and mixtures thereof.

Where the solid hydrophobic metal salt of a higher fatty acid is to be physically mixed with or applied as a coating on toner or carrier particles, the metal salt is preferably present in an amount from about 0.02% to about 10% based on the weight of the toner in the final developer mixture. Optimum results are obtained with about 0.05 to about 4% of the metal salt. Although the initial electrostatic imaging surface potential may be reduced and abrasion resistance improved when the proportion of metal salt present is increased above about 10%, undesirable background deposits increase noticeably. If the charge voltage is reduced to compensate for the presence of metal salt in excess of about 10%, the images begin to acquire a washed out appearance. It is not essential that the entire surface of each toner particle be coated with the metal salt, e.g., suflicient metal salt is present when 10 to 16% of the toner particle surfaces are coated with' a metal salt. When the metal salt is dispersed in rather than coated on a toner or carrier particle, proportionally more metal salt is necessary in order to maintain a sufficient quantity of exposed salt at the surface of the toner or carrier particle. The additional amount of metal salt necessary depends to a large extent on the surface area of the particles, hence upon the particle diameter selected. The use of small quantities of calcium stearate as a pigment wetting agent in zinc oxide developing powders is known as disclosed by Greig in US. Pat. 3,053,688 at column 5, line 41 and Greig et al. in Canadian Pat. 633,- 458 at column 9, line 8. However, the quantity of calcium stearate used by Greig and Greig et al. to facilitate the wetting of pigments dispersed in zinc oxide developing powders is insufficient to provide an effective quantity of exposed calcium stearate at the surface of the toner particle for the purposes of the instant invention. When less than about 0.02% metal salt based on the Weight of the toner is actually available at the surface of the toner particle, its triboelectric, flow, abrasion, transfer and image forming properties are substantially the same as a toner or carrier which does not contain a metal salt of a fatty acid. Obviously, with a given quantity of metal salt based on the weight of the toner, a greater volume of the salt is available at the surface of the toner or carrier when the metal salt is added to a mixture of preformed colored toner particles or carriers than when it is intimately dispersed Within each toner particle or carrier. If the concentration of metal salt is increased to the point where the toner consists essentially of 100% metal salt, the metal salt will form slippery films on the electrostatic image-bearing surface and carrier particles which interfere with powder image transfer, background removal and cleaning. US. Pat. 3,083,117 discloses a method of applying reactive toners containing 100% iron stearate to an electrostatic image and then transferring the developed image to a transfer sheet wet with an alcoholic solution of gallic acid. The iron stearate reacts with the gallic acid to form a black reaction product. In addition to the problems encountered when toner containing 100% metal salt is employed, electrostatic development methods of the foregoing type require liquid pre-treatment of the receiving sheet with an attendant increase in cost and inconvenience. Further, curling, image bleeding, and offset, often occur when moistened receiving sheets are used. Additional equipment to dispose of toxic and inflammable fumes may also be necessary.

Excellent results have been obtained with zinc stearate. When the toner and developer particles of this invention are treated with Zinc stearate, particularly in the range of about 0.05 to about 4 percent by weight based on the total weight of toner, better flow, less background, higher density images at lower initial charging voltages, and higher machine speeds with less power are achieved. Drum Wear is markedly reduced.

Any suitable pigment or dye may be employed as the colorant for the toner particles. Toner colorants are well known and include, for example, carbon black, nigrosine dye, aniline blue, Calco Oil Blue, chrome yellow, ultra marine blue, Du Pont Oil Red, Quinoline Yellow, methylene blue chloride, phthalocyanine blue, Malachite Green Oxalate, lamp black, Rose Bengal and mixtures thereof. The pigment or dyes should be present in the toner in a suflicient quantity to render it highly colored so that it will form a clearly visible image on a recording member. Thus, for example, where conventional xerographic copies of typed documents are desired, the toner may comprise a black pigment such as carbon black or a black dye such as Amaplast Black dye, available from the National Aniline Products, Inc. Preferably, the pigment is employed in an amount from about 3 percent to about 20 percent, by weight, based on the total weight of the colored toner. If the toner colorant employed is a dye, substantially smaller quantities of colorant may be used.

The toner compositions of the present invention may be prepared by any well known toner mixing and comminution technique. For example, the ingredients may be thoroughly mixed by blending, mixing and milling the components and thereafter micropulverizing the resulting mixture. Another well known technique for forming toner particles is to spray-dry a ball-milled toner composition comprising a colorant, a resin and a solvent.

Generally, the degree of quality of toner fix at a given fuser temperature decreases with an increase in toner melt viscosity. As discussed above, if the melt viscosity of the toners of this invention is greater than about 2.5 poise at temperatures above about 450 F., the toner materials do not adhere properly to a receiving sheet even under conventional xerographic machine fusing conditions. Thus, the melt viscosity value of the toners of this invention aids in the determination of the degree of flow and penetration of the toner into the surface of a receiving substrate such as paper during the heat fixing step. The expression melt viscosity, as employed herein, is a measure of the ratio of shear stress to shear rate in poise at a given temperature. All viscosity measurements are determined with an Instron Capillary Rheometer, Model TTC.

When the toner mixtures of this invention are to be employed in a cascade development process, the toner should have an average particle size by weight percent less than about 30 microns and preferably between about 4 and about 20 microns for optimum results. For use in powder cloud development methods, particle diameters of slightly less than 1 micron are preferred.

Suitable coated and uncoated carrier materials for cascade development are well known in the art. The carrier particles comprise any suitable solid material, provided that the carrier particles acquire a charge having an opposite polarity to that of the toner particles when brought in close contact with the toner particles so that the toner particles adhere to and surround the carrier particles. When a positive reproduction of the electrostatic images is desired, the carrier particle is selected so that the toner particles acquire a charge having a polarity opposite to that of the electrostatic image. Alternatively, if a reversal reproduction of the electrostatic image is desired, the carrier is selected so that the toner particles acquire a charge having the same polarity as that of the electrostatic image. Thus, the materials for the carrier particles are selected in accordance with its triboelectric properties in respect to the electroscopic toner so that when mixed or brought into mutual contact one component of the developer is charged positively if the other component is below the first component in the triboelectric series and negatively if the other component is above the first component in a triboelectric series. By proper selection of materials in accordance with their triboelectric effects, the polarities of their charge when mixed are such that the electroscopic toner particles adhere to and are coated on the surfaces of carrier particles and also adhere to that portion of the electrostatic image-bearing surface having a greater attraction for the toner than the carrier particles. Typical carriers include sodium chloride, ammonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, aluminum nitrate, potassium chlorate, granular zircon, granular silicon, methyl methacrylate, glass, silicon dioxide and the like. The carriers may be employed with or without a coating. Many of the foregoing and other typical carriers are described by L. 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 1,000 microns is preferred because the carrier particles then possess sufiicient density and inertia to avoid adherence to the electrostatic images during the cascade development process. Adherence of carrier beads to xerographic drums is undesirable because of the formation of deep scratches on the surface during the imaging 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. Also print deletion occurs when carrier beads adhere to xerographic imaging surfaces. Generally speaking, satisfactory results are obtained when about 1 part toner is used with about 10 to 200 parts by weight of carrier.

The toner compositions of the instant invention may be employed to develop latent electrostatic images on any suitable electrostatic latent image-bearing surface including conventional photoconductive surfaces. Well known photoconductive materials include vitreous selenium, organic or inorganic photoconductors embedded in a nonphotoconductive matrix, organic or inorganic photoconductors embedded in a photoconductive matrix, or the like. Representative patents in which photoconductive materials are disclosed include U.S. Pat. 2,803,542 to Ullrich, US. Pat. 2,970,906 to Bixby, U.S. Pat. 3,121,006 to Middleton, US. Pat. 3,121,007 to Middleton, and US. Pat. 3,151,982 to Corrsin.

DESCRIPTION OF PREFERRED EMBODIMENTS The following examples further define, describe and compare methods of preparing the toner materials of the 1 1 present invention and of utilizing them to develop electrostatic latent images. Parts and percentages are by weight unless otherwise indicated.

Example I A sample of Xerox 813 Toner particles sold by the Xerox Corporation, Rochester, N.Y. is employed as a control. Copies of a standard test pattern are made with the toner in a modified 813 Xerox copying machine. The fuser temperature is regulated with a proportional temperature controller and is monitored by means of a thermocouple mounted in the center of the upper fuser plate. The fuser plates are mounted about 0.75 inch apart. The toner images on 8 inch by 13 inch copy sheets are trans ported through the fuser at the rate of 11 sheets per minute which is twice the normal rate. Since the standard Xerox 813 copy machine drive motor stalls and overheats when the machine is operated at twice the normal operating speed, a motor having twice the power output is employed. After passage through the fuser, the copy sheets are fastened to a full page abrading cylinder having a diameter of about 4.75 inches. A conventional 813 cleaning web is pressed against the copy sheet by a spring loaded roller under a spring tension of about 40 pounds. By rotating the cylinder bearing the copy sheet, the entire toner image on the copy sheet is abraded by frictional contact with the web. A minimum fuser temperature is established when all the test characters are legible after an abrasion run of revolutions of the abrading cylinder. Xerox 813 carrier beads are employed with the toner during the development step. The minimum fuser temperature at which legible copies are obtained with the 813 toner is found to be about 610 F. Many of the copies leaving the fuser contain glowing embers and in some instances live flames. Micrograph studies of the reusable imaging surface after 5,000 cycles reveals considerable wear and degradation of the surface.

Example II A toner mixture is prepared comprising about 7.5 parts by weight of a copolymer of about 65 parts by weight of styrene and 35 parts by weight of butyl methacrylate; about 1.5 parts by weight of pentaerythritol tetrabenzoate; and about 1 part by weight of carbon black (Neo Spectra Mark II). The additive is a hard, dry solid having a melting range of about 201 to about 204 F. The toner mixture has an Instron Capillary Rheometer melt viscosity of about .5 poise at 255 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight percent of about 10 to about 20 microns. About 1 part by weight of the pulverized toner particles are mixed with about 0.01 part by weight of zinc stearate particles having a size range from about 0.5 to about 35 microns and about 99 parts by weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and high resolution images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 510 F. This is a reduction of about 100 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser. No blocking is observed after a sample of this toner is stored in an air circulating oven maintained at a temperature of about 110 F. for 24 hours.

1 2 Example III A toner mixture is prepared comprising about 8.5 parts by weight of a copolymer of about 65 parts, by weight of styrene and about 35 parts by weight of butyl methacrylate; about 0.5 part by weight of a mixture of ortho and para toluene sulfonamide; and about 1 part by Weight of carbon black (Regal 300). The additive is available from the Monsanto Co. under the trademark Santicizer 9 and is a hard, dry solid having a melting point of about 221 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight percent of about 7 to about 12 microns. About 2 parts by weight of the pulverized toner particles are mixed with about 0.05 part by weight of zinc stearate having a size range from about 0.5 to about 35 microns and about 98 parts by weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and high resolution images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 550 F. This is a reduction of about 60 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser. Micrograph studies of the reusable imaging surface after 10,000 cycles reveals less wear and degradation of the surface than the imaging surface of Example 1.

Example IV A toner mixture is prepared comprising about 6.5 parts by weight of polystyrene; about 2 parts by weight of a polychlorinated polyphenyl and about 1.5 parts by weight of carbon black. The additive is available from the Monsanto Co. under the trademark Aroclor 5460 and is a hard, dry solid having a melting range of about 208 F. to about 221 F., a specific gravity (25 C./25 C.) of about 1.67 and a chlorine content of about 58.5 to 60.6

, percent by weight. After melting and preliminary mixing,

the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight percent of about 10 to about 18 microns. About 1.5 parts by weight of the pulverized toner particles are mixed with about 0.015 part by weight of iron oleate having a size range from about 5 to about 40 microns and about 98.5 parts by weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and high resolution images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 550 F. This is a reduction of 60 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example V A toner mixture is prepared comprising about 7.5 parts by weight of a copolymer of about 70 parts by weight styrene and about 30 parts by weight of hexylmethacrylate; about 1.5 parts by weight of pentaerythritol tetrabenzoate and about 1 part by weight of carbon black (Super Carbobar). The additive is a hard, dry solid having a melting range of about 201 to about 204 F. After melting and preliminary mixing, the composition is fed into a rubber, mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight percent of about 10 to about 20 microns. About 1 part by weight of the pulverized toner particles are mixed With about 0.025 part by weight of cobalt palmitate having a size range from about 1 to about 30 microns and about 99 parts by weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and high resolution images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of revolutions of the abrading cylinder is about 490 F. This is a reduction of 120 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example VI A toner mixture is prepared comprising about 7 parts by weight of a copolymer of 80 parts by weight of styrene and about 20 parts by weight of isobutyl methacrylate and about 2 parts by weight of pentaerythritol tetrabenzoate and about 1 part by weight of carbon black (Black Pearls L). The additive is a hard, dry solid having a melting range of about 201 F. to about 204 F. The toner mixture has an Instron Capillary Rheometer melt viscosity of about .5 poise at 260 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverized to yield toner particles having an average particle size by weight percent of about 10 to about 20 microns. About 1 part by weight of the pulverized toner particles are mixed with about 0.01 part by weight of zinc stearate having a size range from about 0.04 to about 40 microns and about 99 parts by weight of glass beads having an average diameter of about 500 microns and coated with a silicone terpolymer reaction product of butyl methacrylate, styrene and vinyl triethoxy silane and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses extremely well and very high resolution images having negligible background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 520 F. This is a reduction of 90 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser. Micrograph studies of the reusable imaging surface after 10,000 cycles reveals less wear and degradation of the surface than the imaging surface of Example I. No blocking is observed after a sample of this toner is stored in an air circulating oven maintained at a temperature of about 110 F. for about 24 hours. Both the quality of images formed by this toner and its handling characteristics are superior to all the other toners tested.

Example VII A toner mixture is prepared comprising about 7 parts by weight of isopropyl methacrylate resin; about 2 parts by weight of glyceryl tribenzoate; and about 1 part by weight of carbon black. The additive is a hard, dry solid having a melting point of about F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastc resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight percent of about 0.5 to about 1 micron. About 1 part by weight of the pulverized toner particles are mixed with about 0.05 part by weight of zinc linoleate having a size range from about 0.8 to about 25 microns and about 99 parts by weight of uncoated glass carrier beads having an average particle size of about 500 microns and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and good images low in background are obtained. Under substantially identical test conditions, it is found the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 570 F. This is a reduction of about 40 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser. Micrograph studies of the reusable imaging surface after 10,000 cycles reveals less wear and degradation of the surface than the imaging surface of Example I.

Example VIII A toner mixture is prepared comprising about 7 parts by weight of a copolymer of about 50 parts, by weight of propyl methacrylate and about 50 parts by weight of methacrylonitrile; about 2 parts by Weight of a mixture of ortho and para toluene sulfonamide; and about 1 part by weight of carbon black (Neo Spectra Mark II). The additive is available from the Monsanto Co. under the trademark Santicizer 9 and is a hard, dry solid having a melting point of about 221 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by Weight percent of about 5 to about 16 microns. About 1 part by weight of the pulverized toner particles are mixed with about 0.06 part by weight of zinc stearate having a size range from about 0.5 to about 20 microns and about 99 parts by weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and good resolution images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 580 F. This is a reduction of about 30 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser. Micrograph studies of the reusable imaging surface after 10,000 cycles reveals less wear and degradation of the surface than the imaging surface of Example I.

Example IX A toner mixture is prepared comprising about 7.5 parts by weight of a copolymer of about 20 parts by weight of vinyl acetate and about '80 parts by Weight of vinyl chloride; about 1.5 parts by Weight of pentaerythritol tetrabenzoate; and about 1 part by weight of carbon black. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a tSzegvari attritor to yield toner particles having an average particle size by weight of about 10 to about 20 microns. About 2 parts by weight of the pulverized toner particles are mixed with about 0.1 part by weight of zinc stearate having a size range from about 0.5 to about 20 microns and about 98 parts by weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 560 F. This is a reduction of about 50 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example X A toner mixture is prepared comprising about 9 parts by weight of an ethyl methacrylate polymer; about 1 part by weight of pentaerythritol tetrabenzoate and about 1 part by weight of carbon black. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight of about 5 to about 10 microns. About 1.5 parts by weight of the pulverized toner particles are mixed with about 0.01 part by weight of zinc stearte having a size range from about 0.5 to about 40 microns and about 98.5 parts by weight of uncoated glass beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motar can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 540 F. This is a reduction of about 70 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XI A toner mixture is prepared comprising about 8 parts by weight of a copolymer of about 35 parts by weight vinyl acetate and about 65 parts by weight of acrylonitrile; about 1 part by weight of trimethylolethane tribenzoate and about 1 part by weight of carbon black. The additive is a hard, dry solid having a melting point of about 163 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight of about 7 to about 12 microns. About 1 part by weight of the pulverized toner particles are mixed with about 0.04 part by weight of zinc stearate having a size range from about '0.5 to about 20 microns and about 99 parts by weight of glass beads having an average diameter of about 500 microns and coated with a silicone terpolymer reaction product of butyl methacrylate, styrene and vinyl triethoxy silane and substituted for the 815 developer in the testing machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 560 F.

This is a reduction of about 50 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XII A toner mixture is prepared comprising 7.5 parts by weight of a copolymer of about 25 parts of n-butyl methacrylate resin and about 75 parts by weight of acrylonitrile resin; about 1.5 parts by weight of glyceryl tribenzoate; and about 1 part by weight of carbon black. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive and pigment in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a high speed attritor to yield a toner particle size by Weight of about 5 to about 10 microns. About 99 parts by weight of 813 Xerox carrier beads is mixed with about 1 part by weight of toner and about 0.05 part by weight of zinc stearate having a size range from about 0.5 to about 40 microns and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under substantially identical conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 545 F. This is a reduction of about 65 F. from the fuser temperature required for the control example of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XIII A toner mixture is prepared comprising about 5.5 parts by weight of a copolymer of about parts by weight of styrene and 10 parts by weight of isobutyl methacrylate, about 3.5 parts by weight of pentaerythritol tetrabenzoate and about 1 part by weight of carbon black. The additive is a hard, dry solid having a melting range of about 201 to about 204 F. After melting and preliminary mixing in a Banbury Mixer, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight percent of about 10 to 20 microns. About 1 part by weight of the pulverized toner particles is mixed with about 0.01 part by weight of zinc stearate having a size range from about 0.5 to about 20 microns and about 99 parts by weight of 500 microns uncoated glass carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and high resolution images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 510 F. This is a reduction of about 100 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XIV A toner mixture is prepared comprising of about 5.5 parts by weight of copolymer of about 80 parts by weight styrene and about 20 parts by weight of ethyl acrylate, and about 3.5 parts by weight of a mixture of ortho and para toluene sulfonamide, and about 1.0 by weight of carbon black. The additive is available from the Monsanto Co. under the trademark Santicizer 9 and is a hard, dry s l d having a melting point of 221 F. After milling and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by Weight of about 10 to about 20 microns. About 1 part by weight of the pulverized toner particles are mixed with about 0.02 part by Weight of lead stearate having a size range from about 10 to about 35 microns and about 99 parts by Weight of 81.3 carrier in the testing machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 500 F. This is a reduction of about 110 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XV A toner mixture is prepared comprising about 7.5 parts of copolymer of about 80 parts by Weight of styrene and about 20 parts by weight isobutyl methacrylate and about 1.5 parts glyceryl tribenzoate and 1.0 part by weight carbon black. Glyceryl tribenzoate is a dry solid manufactured by Velsicol Chemical Corporation with a molecular weight of 404 and a melting point about 160 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight of about 8 to 22 microns. About 1 part by weight of the pulverized toner particles are mixed with about 0.01 part by weight of zinc stearate having a size range from about 0.4 to about 40 microns and about 99 parts by weight of 813 Xerox carrier and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses Well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after abrasion of 5 revolutions of the abrading cylinder is about 540 F. This is a reduction of 70 F. from the fuser temperature required for the con trol sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XVI A toner mixture is prepared comprising about 8.0 parts by weight of a copolymer of about 70 parts by weight styrene and 30 parts by weight of vinyl acetate, about 1.0 part by weight of trimethylolethane tribenzoate and about 1.0 part by weight of carbon black. The additive is a hard, white crystalline solid having a melting point of about 163 F. and a molecular weight of 432. After melting and mixing in a Banbury mixer and thoroughly rubber milling to yield a uniformly dispersed composition of the additive in the thermoplastic resin body, the mixed composition is cooled and then pulverized in a Szegvari attritor to yield toner particles having an average particle size of about 10 to microns. About 1 part by weight of the pulverized toner particles are mixed with about 0.03 part by weight of zinc stearate having a size range from about 0.4 to about 40 microns and about 99 parts by weight of 813 carrier in the test machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under' substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 550 F. This is a reduction of about 60 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XVI'I A toner mixture is prepared comprising about 8.0 parts by Weight of a copolymer of about 85 parts by weight styrene and about 15 parts by weight vinylidene chloride copolymer and about 1.0 part by weight of ethylene glycol dibenzoate and about 1.0 part by weight carbon black. The additive is available from the C. P. Hall Co. under the trademark Hallco 870 and is a hard, dry solid having a melting range of about 156 F. to about 164 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight of about 8 to 14 microns. About 1 part by Weight of the pulverized toner particles are mixed with about 0.01 part by Weight of zinc stearate having a size range from about 0.4 to about 40 microns and about 99 parts by weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 540 F. This is a reduction of 70 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XVIII A toner mixture is prepared comprising about 6.0 parts by weight of a copolymer of about 20 parts by weight styrene and about parts by weight of vinyl alcohol; and about 3.0 parts by Weight of n-cyclohexyl p-toluene sulfonamide, and about 1.0 part by Weight of carbon black. The additive is available from the Monsanto C0. under the trademark Santicizer 1H and is a hard water insoluble crystalline solid, heat stable to about 300 F. with a crystalline melting point of 186 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed com-position of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverizer to yield toner particles having an average particle size by weight percent of about 10 to 20 microns. About 2 parts by weight of the pulverized toner particles are mixed with about 0.02 part by Weight of zinc palmitate having a size range from about 0.5 to about 35 microns and about 98 parts by Weight of a coated carrier comprising glass beads coated with ethyl cellulose coating and having an average diameter of about 600 microns and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses Well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at Which-legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 560 F. This is a reduction of 50 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XIX A toner mixture is prepared comprising about 6.0 parts by weight of a copolymer of about 80 parts by Weight styrene, about 20 parts by weight acrylonitrile and about 3.0 parts by Weight of n-ethyl-p-toluene sulfonamide and about 1.0 part by weight of carbon black. The additive is available from the Monsaonto Co. under the trademark Santicizer 3 and is a hard, white solid with a melting point of about 139 F. After melting and initial mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pul verizer to yield toner particles having an average particle size by weight of 10 to 20 microns. About 1 part by weight of the pulverized toner particles are mixed with about 0.04 part by wegiht of zinc stearate having a size range from about 0.4 to about 40 microns and about 99 parts by Weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 560 F. This is a reduction of 50 F. from the fuser temperature required for the control sample of Example I. 'No live embers or flames are observed on copies emerging from the fuser.

Example XX A toner mixture is prepared comprising about 7.5 parts copolymer of about 80 parts by weight styrene and about 20 parts by Weight of isobutyl methacrylate and about 1.5 parts by Weight of pentaerythritol tetrabenzoate and about 1.0 part by weight carbon black (Super Carbobar). The toner has a melt viscosity as measured on the Instron Capillary Rheometer of .5 poise at a temperature of about 280 F. The additive is a dry solid having a melting range of about 201 to about 204 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a Szegvari attritor to yield toner particles having an average particle size of about 10 to 20 microns. About one part of the toner is mixed with,

about 0.03 part by weight of zinc stearate having a size range from about 0.5 to about 40 microns and about 99 parts of a coated carrier comprising glass beads coated with an ethyl cellulose coating and having an average diameter of about 600 microns and is substituted for the 813 developer in the testing machine described in Example I. The treated toner dispenses well and images substantially free from background are obtained. Under substantially identical test conditions, it is found that the original standard Xerox 813 drive motor can be used and that the minimum fuser temperature at which legible copies are obtained after an abrasion run of 5 revolutions of the abrading cylinder is about 550 F. This is a reduction of about 60 F. from the fuser temperature required for the control sample of Example I. No live embers or flames are observed on copies emerging from the fuser.

Example XXI A sample of the treated toner and carrier described in Example V is employed in the 813 Xerox copying machine described in Example I to make copies of a standard test image. Although the 813 machine is again operaated at 11 copies per minute, the fuser temperature is set at about 490 F. The quality of fix of the toner image is tested in a Taber Abraser, Model 174, available from the Welch Scientific Co. About 20 cycles of the abraser is required to obtain an image density reduction of about 20 percent as measured on a Densichrom reflection unit.

Example XXII A sample of the control toner and carrier described in Example I is employed to form toner images. The imaging and testing procedure used is substantially identical to the procedure described in Example XXI. Less than about 2 cycles of the abraser is required to obtain an image density reduction of about 20 percent as measured on the Densichrom reflection unit. The deposited toner image is easily destroyed by rubbing the images With a finger or thumb.

Example XXIII A control toner mixture is prepared comprising about 9 parts by Weight of a mixture of ortho and para toluene sulfonamide and 1 part by weight of Nigrosine SSB dye. The sulfonamide mixture is available under the trademark Santicizer 9 and is a hard, dry solid having a melting point of about 221 F. After melting a preliminary mixing, the composition is thoroughly milled to yield a uniform dispersion of dye and sulfonamide. The resulting mixed composition is cooled and finely subdivided in a Szegvari attritor to yield an average particle size by Weight percent of about 8 to about 15 microns. The resulting toner is mixed with coated glass carrier beads and cascaded across a negatively charged latent electrostatic image bearing surface. The deposited toner image is transferred to a paper sheet and fused at about 305 -F. When the imaged paper sheet is folded, it is found that the toner images located along the crease tended to crack and crumble. When an imaged sheet formed by the processes described in Example III is folded, no cracking or crumbling of the toner images located along the crease is observed.

Example XXIV A control sample containing 1 part toner particles containing Santicizer 9 dyed with Amplast Black and having an average particle size of about 10 to about 20 microns and about 99 parts Xerox 813 carrier particles is tumbled in a rotating cylindrical jar having an inside diameter of about 2.25 and a surface speed of about 140 feet per minute. An inspection of the developer mixture after about 50 hours after the test is initiated reveals a large quantity of undesirable fine powder.

Example XXV A toner mixture containing about 7.5 parts by weight of a copolymer of about parts by weight of styrene and about 20 parts by Weight of isobutyl methacrylate and about 1.5 parts by Weight Santicizer 9 and about 1 part by weight of carbon black, and having an average particle size of about 10 to about 20 microns is mixed with about 99 parts by weight of Xerox 813 carrier particles. The resulting developer is tumbled in the rotating cylindrical jar described in Example XXIV. An inspection of the developer mixture 50 hours after the test is initiated reveals substantially no undesirable powder.

Example XXVI A control toner mixture is prepared comprising about 7.5 parts by weight of a copolymer of about 65 parts by weight of styrene and 35 parts by Weight of butylmethacrylate; about 1.5 parts by weight of polyethylene Wax; and about 1 part by Weight of carbon black (Neo Spectra Mark II). The Wax is available under the trademark Tenite 812A, sold by Eastman Kodak and is a dry solid having a melting range of about 220 to about 230 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the wax in the thermoplastic resin body. The resulting mixed composition is cooled with liquid nitrogen and then finely subdivided in a Szegvari Attritor to yield toner particles 21 having an average particle size of about to about 20 microns. Cooling below room temperature was necessary to avoid filming of the toner material on the attritor parts. About one part of the toner is mixed with about 99 parts of a coated carrier comprising glass beads coated with an ethyl cellulose coating and having an average diameter of about 600 microns. The resulting developer is used to make 8,000 copies in an 813 Xerox copying machine. The copies, particularly the copies made near the termination of the test, are characterized by very low density images and high background. An examination of the xerographic drum after the termination of the test reveals a heavy film of toner over the surface of the drum.

Example XXVII A control toner mixture is prepared comprising about 7 parts by weight of a compolymer of about 80 parts by weight styrene and about 20 parts by weight of isobutyl methacrylate and about 2.0 parts by weight of polyethylene sebacate and about 1.0 part by weight of carbon black. The additive is a dry solid having a melting point of about 167 F. After melting and preliminary mixing, the composition is fed into a rubbermill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a jet pulverized to yield toner particles having an average particle size by weight of about 10 to about 20 microns. About 1 part by weight of the pulverized toner particles are mixed with about 99 parts by weight of 813 Xerox carrier beads and substituted for the 813 developer in the testing machine described in Example I. The resulting developer is used to make 10,000 copies in an 813 Xerox copying machine. The copies made near the termination of the test are characterized by very low density images and high background. An examination of the xerographic drum after the termination of the test reveals a heavy film of the toner over the surface of the drum resulting from poor toner cleanability.

' Example XXVIII A toner mixture is prepared comprising about 8 parts by weight of a copolymer of about 65 parts by weight of styrene and 35 parts by weight of butylmethacrylate; about 1 part by weight of pentaerythritol tetrabenzoate and about 1 part by weight of carbon black (Neo Spectra Mark II). The toner mixture has an Instron Capillary Rheometer melt viscosity of about .5 10- at 265 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the additive in the thermoplastic resin body. The resulting mixed composition is cooled and then finely subdivided in a Szegvari attritor to yield toner particles having an average particle size of about 10 to about 20 microns. About one part of the toner is mixed with about 0.01 part by weight of zinc stearate having a size range from about 0.4 to about 40 microns and about 99 parts of a coated carrier comprising glass beads coated with an ethyl cellulose coating and having an average diameter of about 600 microns. The resulting developer is used to make 8,000 copies in an 813 Xerox copying machine. Substantially, all the copies are characterized by sharp, high density images and low background deposits. An examination of the xerographic drum after the termination of the test reveals substantially imperceptible film of the toner over the surface of the drum.

Example XXIX A control toner sample substantially identical to the toner described in Example VI is tested for its blocking temperature. The test procedure involves the steps of initially heating the toner particles in an air circulating oven at about 100 F. for a 24 hour period and, thereafter, increasing the temperature in 5 increments every 22 24 hours. The blocking temperature is that temperature at which a mild crushing action with a spatula is required to restore any toner agglomerates formed to the original finely divided particulate form. The blocking temperature of the control sample is about 125 F.

Example XXX A control toner mixture is prepared comprising about 7 parts by weight of a copolymer of about parts by weight of styrene and 20 parts by Weight of isobutyl methacrylate; about 2 parts by weight of ethyl phthalyl ethyl glycolate; and about 1 part by weight of carbon black (Black Pearls L). The ethyl phthalyl ethyl glycolate is available under the trademark S'anticizer E-15 and is a liquid. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the wax in the thermoplastic resin body. The resulting mixed composition is cooled with liquid nitrogen and then finely subdivided in a Szegvari attritor to yield toner particles having an average particle size of about 10 to about 20 microns. The toner particles are then tested according to the procedure described in Example XIV. The toner particles blocked at the initial test temperature of F.

Example XXXI A control toner mixture is prepared comprising about 7 parts by weight of a copolymer of about 80 parts by weight of styrene and 20 parts by weight of isobutyl methacrylate; about 2 parts by Weight of paraffin; and about 1 part by weight of carbon black (Black Pearls L). The parafiin is available under the trademark 4312 and is a dry solid having a melting range of about to about 143 F. After melting and preliminary mixing, the composition is fed into a rubber mill and thoroughly milled to yield a uniformly dispersed composition of the wax in the thermoplastic resin body. The resulting mixed composition is cooled with liquid nitrogen and then finely subdivided in a Szegvari attritor to yield toner particles having an average particle size of about 10 to about 20 microns. The toner particles are then tested according to the procedure described in Example XIV. The toner particles blocked at the initial test temperature of 100 F.

Example XXXII A control sample containing one part colored preformed toner particles of the type described in Example VI having an average particle size of about 10 to about 20 microns is mixed with about 99' parts by weight of glass beads having an average particle diameter of about 400 microns and coated With ethyl cellulose and then cascaded across an electrostatic image-bearing drum surface. The developed image is then 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. Graft, Jr., et al. in US. Pat. 3,186,838. After the copying process is repeated 25,000 times, the copies and electrostatic image-bearing surface are examined for quality and Wear, respectively. The copies possess sharp line contrast and minimal background deposition. However, an examination of the imaging surface reveals numerous scratches and the effects of erosive conditions.

Example XXXIII About 0.1 part of zinc stearate having a particle size distribution from 0.75 micron to about 40 microns is gently folded into one part of a colored preformed toner particle of the type described in Example VI. The resulting developer mixture is then thoroughly milled in a Szegvari attritor for about 10 minutes. The developing procedure of Example XXXII is repeated with a new drum and with the foregoing milled mixture substituted for the toner of Example XXXII at a relative humidity of about 5 0 percent at 70 F. and at a relative humidity of 80 percent at 80 F. Copies prepared with the milled sample possess higher density solid area coverage and cleaner background than copies prepared with the control sample. Further, visual examination of the electrostatic image-bearing surface reveals less wear than on the scratched image-bearing surface of Example XXXII. Considerably less torque is necessary to drive the drum when the stearate additive is employed and a lower voltage is required to transfer the toner images to a receiving sheet.

Example XXXIV About 0.025 part of zinc stearate having a particle size distribution from about 0.75 micron to about 40 microns is gently folded into about parts of a colored preformed toner particle of the type described in Example VI. The resulting mixture is then tumbled in a sealed contaner for minutes. About one part of the tumbled mixture is mixed with 99 parts of ethyl cellulose coated carrier beads having an average particle size of about 400 microns. The resulting developer mixture is employed in a cascade developing process as described in Example XXXII at a relative humidity of 50 percent at 70 F. and at a relative humidity of 80 percent at 80 F. The resulting fused toner images are denser under both humidity conditions than the images obtained in Example XXXIII.

The expression developer material as employed herein is intended to include electroscopic toner material or combinations of toner material and carrier material.

Although specific materials and conditions are set forth in the foregoing examples, these are merely intended as illustrations of the present invention. Various other suitable thermoplastic toner resin components, additives, colorants, and development processes such as those listed above may be substituted for those in the examples with similar results. Other materials may also be added to the toner or carrier to sensitize, synerize or otherwise improve the fusing properties or other desirable properties of the system.

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 process for the preparation of a solid electrostatographic developer material comprising providing finely-divided toner particles uniformly electrostatically coated on a carrier surface capable of retaining said toner particles by electrostatic attraction, said toner particles having a blocking temperature of at least about 110 F., a melt viscosity less than about 2.5 10- poise at temperatures up to about 450 F., and comprising a colorant selected from the group consisting of a pigment and a dye, a thermoplastic resin consisting essentially of a vinyl polymer having a melting point of at least about 110 F., and about 3 percent to about 65 percent by weight, based on the total weight of said vinyl polymer, of a solid additive having a melting point between about 115 F. and about 270 F. and selected from the group of organic compounds having the general structures wherein R is selected from the group consisting of hydrogen, chlorine, bromine, aryl radicals, and alkyl radicals having from 1 to 6 carbon atoms and R and R" are 24 selected from the group consisting of hydrogen, aryl radicals, and alkyl radicals having from 1 to 12 carbon atoms,

and

Gi Cl 01m l wherein n represents a positive integer from 0 to 3 inclusive and in has an average value from 0.5 to 2.5 inclusive and mixtures thereof; forming said finely-divided toner particles into particles having a size range of up to about 30 microns, and thereafter tumbling said particles with from about 0.02 percent to about 20 percent by weight, based on the weight of said particles, of at least one solid, stable hydrophobic metal salt of a fatty acid having a melting point greater than about 57 C. until said metal salt is uniformly mixed with and is available at the external surfaces of said particles.

2. A process according to claim 1 wherein said additive is pentaerythritol tetrabenzoate.

3. A process according to claim 1 wherein said finelydivided toner particles contain at least about 25 percent by weight, based on the total weight of said thermoplastic resin in said toner, of a styrene resin.

4. A process according to claim 1 wherein said solid, stable hydrophobic metal salt of a fatty acid is zinc stearate.

5. A process according to claim 1 wherein said finelydivided low melting toner particles are uniformly electrostatically coated on the surface of carrier particles having an average particle diameter between about 50 to about 1000 microns.

6. A process according to claim 1 wherein said developer material comprises about 1 part by weight of said finely-divided toner particles and from about 10' to about 200 parts by weight of said carrier particles.

7. A process for the preparation of a treated solid electrostatographic toner material comprising providing toner particles having a blocking temperature of at least about F., a melt viscosity less than about 2.5 10 poise at temperatures up to about 450 F., and comprising a colorant selected from the group consisting of a pigment and a dye, a thermoplastic resin consisting essentially of a vinyl polymer having a melting point of at least about 110 F., and from about 3 percent to about 65 percent, based on the weight of said vinyl polymer, of a solid additive having a melting point between about F. and about 270 F. and selected from the group of organic compounds having the general structure o Riot wherein n represents a positive integer from 3 to 7 inclusive and R represents an organic moiety having from 3 to 12 carbon atoms;

wherein R is selected from the group consisting of hydrogen, chlorine, bromine, aryl radicals, and alkyl radicals having from 1 to 6 carbon atoms and R and R" are selected from the group consisting of hydrogen, aryl radicals, and alkyl radicals having from 1 to 12 carbon atoms,

sive and in has an average value from 0.5 to 2.5 inclusive, and mixtures thereof; forming said toner particles into particles having a size range of up to about 30 microns, and thereafter tumbling said particles with from about 0.002 percent to about 20 percent by weight, based on the Weight of said toner particles, of at least one solid, stable hydrophobic metal salt of a fatty acid until said metal salt is uniformly mixed with and is available at the external surfaces of said particles.

8. A process according to claim 7 wherein said solid additive is pentaerythritol tetrabenzoate and said metal salt is zinc stearate.

References Cited 5 UNITED STATES PATENTS 3,653,893 4/1972 Jacknow et a1. 252-62.1 3,417,019 12/1968 Beyer 252,'62.1 3,931,374 1/1966 Serambi 25262.1

NORMAN G. TORCHIN, Primary Examiner J. P. BRAMMER, Assistant Examiner