CA1111168A - Two stage method for polymerizing to form toner - Google Patents
Two stage method for polymerizing to form tonerInfo
- Publication number
- CA1111168A CA1111168A CA279,727A CA279727A CA1111168A CA 1111168 A CA1111168 A CA 1111168A CA 279727 A CA279727 A CA 279727A CA 1111168 A CA1111168 A CA 1111168A
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- toner
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Abstract
ABSTRACT OF THE DISCLOSURE
A method of forming toner utilizing a two stage process wherein monomer containing pigment is sized by high shear mixing in a first stage then polymerized during slow speed agitation in the second stage to form toner particles.
A method of forming toner utilizing a two stage process wherein monomer containing pigment is sized by high shear mixing in a first stage then polymerized during slow speed agitation in the second stage to form toner particles.
Description
1116~
_I~C:E~GP~ D OF THE I~;IVEMTION
This invention relates to electrophotography and more particularly to improved electrosta-tographic developiny ma,erials, their manufacture and use.
The Eormatioll and development of images on the surface of photoconductor materials by elec-trostatic means is well known. The basic xerographic process, as taught by C. F. Carlson in U. S. Patent 2,297,691, involves placing a uniform electro-static charge on a photoconductive insulating layer, e~posiny 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 electro-static image. This powder image may then be transferred to a support surface such as paper. The transEerred image may subsequently be permanently afixed to the support surface as by heat. Instead o latent lmage 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 foregoincJ heat fixing steps.
'' ' .' :
Several methods are kno~n for applying the electroscopic particles to the latent elec-trostatic image to be developed. One development method, as disclosed by E. N. Wise in U. S. Patent 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 conve~ed -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 backyroun~. The carrier and exc~3ss toner are then recycled. This techni~ue is e~tremely good for the development of line copy images.
Another method of developing electrostatic images is the "magnetic brush" process as disclosed, for e~ample, in U. S. Patent No. 2,87~,063. In this method, a developer material con-taining toner and magnetic carrier particles are carried by a magnet. The magnetic fie]d of the magnet causes alignment oE the magnet:ic carrier into a brush-like configuration. This "magnetic brush" is engaged with the elec-trostatic image-bearing suxface and the tOneL par~icles 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. Patent No. 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. Patent No. 3,166,~32, may be used where suitable.
Toners have generally been prepared by thoroughly mixing the softened resin and pigment to form a uniform dis~
persion as by blending these ingredients in a rubber mill or the like and then pulverizing this material to form it into small particles. Most frequently, this division of the resin pigment dispersion has been made by jet pulverization of the material. Although this technique of toner manufacture has produced some very excellent toners, it does tend to have certain shortcomings. For example, it generally produces a rather wide range of particle sizes in the toner particles.
Although the average particle size of toner made according to this technique generally ranges between about 5 and about 10 microns, individual particles ranging from sub micron in size to above 20 microns are not infrequently produced. Furthermore, this is a batch process which tends to be slow, expensive, noisy .~
and dusty. In addition, this technique of toner production imposes certain limitations upon the material selested for -the toner because the resin-pigment dispersion must be sufficiently friable so that it can be pulverizecl at an economically feasible rate of production. The pxoh]em which arises from this require-men-t is that when the resin-pig~lent dispersion is sufficien-tly friable for really high speed pulveriz.ing, it tends to form an even wider range of particle sizes during pulverization including relatively large percentages of fines. In addition, such highly friable materials are ~requently subject to further pulverization or powdering when they are employed for developing in xerographic copying apparatus. All other requirements of xerographic developers or toners including the requirements that they be stable in storage, non-agglomerative, have the proper triboelectric properties for developing, form good images, do no-t film or soil the selenium xerograph.ic plate and have a low melting point for heat fusing are only compounded by the additional requirements imposed by this toner forming process.
Anothe:r method of toner format.ion consists of bl.endi.ng a water latex o:E the desired toner resin with a colorant and then spray drying this combined system to the desired particle size. The spray drying step consists of atomizing the colorant-water latex blend into sma].l dropl.ets, mixing these with a gas, and holding the droplets in suspension in the gas until evaporation drives off the liquid in the droplets and heat and surface tension forces cause the resin particles in each droplet to coalesce encasing the colorant included in that droplet.
Most frequently, spray drying utilizes air as the gas for the drying step. The gas is heated to raise the temperature of the 111~1~;8 resin partic]es to a poin-t where they coalesce so that -the many small paLticles oriyina-ting in any one droplet formed during atomization come toge-ther to form a small, hard spherical toner particle which entraps any colorant initially included within the droplet. The colorant used may be either water soluble in which case it may be merely added and dissolved into the resin latex or water insoluble dye in which case it may first be placed in an aqueous suspension and then added to the resin latex. Spray dried toners are not totally satisfactory as it is difficult to completely remove all the solvent and the solvent which remains in the toner particles acts to eEfect triboelectric properties and contribute to bloc~ing of -the toner when in use.
In U. S. Patent 3,391,0~2 to Maclay, it is proposed that toner be formed directly from an emulsion polymerization system.
~owever, this method i.s not totally satisfactory as the toner comprises agglomerates of the small latex (.03 to .25 micron) particles the total drying of the system is difficult leading to blocking problems and also voids in the particles may cause structural wea~ness and uneven triboe:L~ctric proper-ties.
It has been proposed in United Kingdom Patent 1,319,815 that toner be prepared directly from the monomer by polymerization of the monomer in toner sized particles containing a colorant.
The method of the British patent comprises preparing a kneaded oil phase component made up of one or more liquid resin monomers, coloring material, the polymerization initiator and a finely-divided inorganic dispersion stabilizer such as a metal powder or inoryanic salt or oxide and a polar resinous ac1di-tive which is soluble in a monomer. ~fter suspension polymerization of the monomer, i' recluired, the finely-divided dispersion stabilizer is removed by dissolution in an aci.d and -the polymer particles are removed from the aqueous phase and dr:ied to produce toner. However, this process is not totally successful as it requires a high ra-~io of inorganic stabilizer which needs to be removed or it affects the quality of the toner. Further the par-ticles recovered contain an unacceptably great number of particles which are either larger or smaller than the size range preferred for electrophoto-graphic use. Further, the removal of the inorganic stabilizer adds a process step thereby minimizing the advantage of forming a toner in one operati.on from the monomer. The process in any case often resùlts in incomplete polymerization that leaves residual monomer that affects the triboelectric, blocking and fixing properties of the toner. This incomplete polymerization of the monomer i5 theorized as caused by the pigment inhibiting polymerization. The similar type Maeda et al process, U. S.
3,63~,251, also entails the removal of the inorganic component and problems of incomplete polymerlzation.
A method of producing small methyl methacrylate beads is disclosed in U. S. Patent 2,701,2~5 to Lynn. This process uses large amounts of wetting agent, a short period of mixing to size the monomer and does not agitate during polymerization.
However, this process does not produce colored beads and the large amount of wetting agents required leave impurities very undesirable in toners and further the toner has a wide range of particle sizes.
A Jour.nal of Applied Polymer Science article at Volume 16, pages 1867 and 1868 (1972), discloses that polymerization of small partiale size polymers may be carried out after sizing by high speed stirring of a paddle stirrer. However, the article indicates that control of si.zin~ is difficult and does not 6~
c~eal ~`7i th the complications caused by introduction of colorant into the system.
It has also been proposed that a suspension polymerization p.rocess si~ilar to the above referenced British patent but not making use of an inorganic stabilizer be carried out to produce an encapsulat~d -toner. This process is performed generally hy mixing a monomer, a colorant and an initiator to form an oil soluble organic phase; dispersing this oil soluble phase in controlled size between 5 to 20 microns in a water phase, employing a sus-pending agent, for example polyvinyl alcohol; polymerizing, employing convent.ional suspension polymerization techniques;
introducing a second monomer which is allowed to diffuse into the first polyrner and consequently swells the polymer; introducing a water soluble initiator; and heating this reaction mixture to effect a polymerization of the second monomer and form the desired toner. It is found that the second initiator, the water soluble initiator, generates a free radical which attacks the surface of the swollen polymer particle and promotes polymerization at the surface by reacting with monomer at the surface thereby decreasing the monomer concentrakion and causing the transport of monomer to the surface by diffusion. The process is found to be self terminating when the total amount of sorbed monomer has been converted to polymer at the surface, thus providing an encapsulated toner. ~Iowever, while this process may be used to produce encapsulated toners, it still does not provide an acceptable method for producing toners which are not encapsulated and which may withstand the abrasion, ~tress and humidity variation to which toners are subject in ordinary development systems.
A dlffi.culty with suspension polymerization processes is that it is difficult to maintain the toner particle size .
~, _ ~L111~68 particles of about 5 to 30 microns in large suspension polymeri-zation equipment. To obtain particle sizes in the 10 microns range requires stirrer speeds in excess of 1,000 r.p.m. In view of the high stirring speeds, the design of large reactors becomes increasingly difficult as size increases. Large high speed reactors are much more expensive to design and operate than a normal suspension polymerization reactor that operates at the normal about 75 to 100 r.p.m. stirring speed. The form-ing of toner size particles at slow speeds by utilizing large amounts of suspending agents creates difficulties as set forth above as suspending agents in large amounts must be removed from the particles in order for them to operate effectively as toner particles. The conventional reactors with paddle blade stirrers when operating at high speeds produce a broad range of particle sizes.
As can be seen, there remains a need for a process of producing toners which would not involve extensive processing steps of polymer formation, colorant addition, mixing and particle formation. There remains a need for a process which would produce toner particles directly from monomer that have good triboelectric properties, abrasive resistance, blocking resistance, narrow size variation, and good colorant loading capability. Since the prior forming methods are deficient in one or more of the above areas, there is a continuing need for an improved method of formation of toners for use in electro-photographic development.
SU~MA~Y OF THE INVENTION
_ It is therefore an object of an aspect of this invention to provide a toner overcoming the above noted deficiencies.
It is an object of an aspect of this invention to ~1~1168 provide a method of producing a toner which overcomes the above noted deficiencies in processes of toner production.
It is an object of an aspect of this invention to provide a toner of low cost.
It is an object of an aspect of this in~ention to provide a method of direct polymerization of colored toners.
It is an object of an aspect of this invention to provide simplified equipment for toner production.
It is an object of an aspect of this invention to provide a process of producing low cost toner.
It is an object of an aspect of this invention to provide a method of forming a toner size monomer suspension to form toners.
It is an object of an aspect of the invention to allow the use of less carbon in a toner particle.
It is an object of an aspect of this invention to produce toner size particles utilizing slow speed stirring of a monomer suspension.
It is an object of an aspect of this invention to produce toner part:icles having a narrow size range.
It is an object of an aspect of this invention to provide a direct polymerization process of forming pigmented toner.
In accordance with one aspect of this invention there is provided a method of toner formation comprising dispersion of pigment in monomer, high shear treatment of the pigment con-taining monomer in an aqueous medium to form toner size monomer in suspension, agitation of said monomer during polymerization and recovery of toner particles.
By way of added explanation, the foregoing and other objects of the instant invention may be accomplished, generally, by providing a process for dispersing in water the monomer containing pigment in one stage to the toner particle size of between about 5 and about 30 microns. Such pigmented monomer particles after initial suspension and sizing are stable such that they may be transferred to a reactor and stirred at relatively low speeds of between about 75 and 100 r.p.m. and will remain in suspension during polymerization to form toner.
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BRIEF DESCRIPTION OF THE DRAWINGS
Flgure 1 is a view of a rotor stator mixer.
Figure 2 is a view of the static element of a rotor stator mixer.
Figure 3 is a view of the rotating element of the mixer.
Figure 4 illustrates a base construction for a rotor stator mixer.
DETAILED DESCRIPTION OF THE INVENTION
. ., The toner formation process of the invention is carried out in one instance by the use of a styrene monomer to which is added lauroyl peroxide and Molacco-H carbon black that has been treated with an active silane dispersion agent such as tri-ethoxy silane ("Siliclad"), a reactive silane. The carbon particles are coated with the silane by suspension of the carbon in water followed by addition of the triethoxy silane ("Siliclad"~ Clay Adams Division of Becton Dickinson Co.). The mixture of silane and carbon is agitated to allow the silane to form a coat on the surface of the carbon particles. The treated (cladded) carbon is dispersed in a styrene monomer with lauroyl peroxide.
Then, utilizing a short period of mixing in a high speed and high shear mixer, the monomer is suspended in an aqueous medium and toner size particles are formed. The suspension of toner size pigmented monomer is then transferred to a reactor which is agitated by a stirrer at about 75 r.p.m. as polymerization takes place. After polymerization is complete, the particles are recovered and found to be suitable for use as toner materials without further processing.
Any polymeric material which may be formed by dispersion polymerization and which has a meIting point within the range suitabIe for use as a toner may be used in the toner forming 6~
process of the instant invention. Typical monomeric units which may be employed to form polymers include: styrene, 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 alphamethylene 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 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 isopropanyl 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. 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 styrene resins are typically 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 ~1~116~
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 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 ~etone and the like; vinylidene halides such as vinylidene chloride, vinylidene chlorofluoride and the 'ike; and N-vinyl compounds such as N~vinyl pyrrole, N-vinyl carbazole, N-viny]. indole, N-vinyl pyrrolidene and the like; and mixtures thereof. 'rhe styrene resins may also be formecl 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 radical, anionic and cationic polymerization processes. Monomers forming polystyrene and copolymers of styrene and n-butylmethacrylate have been found to be particularly ~suitable for the polymerization process of the invention as they result in good yields oE completely polymerized monomer which are suitable for use as toner material as they possess good triboeIectric and fusing properties.
.
~1~1168 Any suitable pigment material may be used in the process of the invention. A pigment generally should be capable of being dispersed in a monomer, be insoluble in the water used in the cladding and polymerization processes and give strong, clear, permanent colors when used as toner. Typical of such pigments are phthalocyanines, lithols, toluidene and inorganic pigments such as TiO2 and dyes. Typical of phthalocyanine pigments are copper phthalocyanine, mono-chlor copper phthalocyanine, hexadecachlor copper phthalocyanine, metal-free phthalocyanine, mono-chIor metal-free phthalocyanine, and hexadecachlor metal-free phthalocyanines; anthraquinone vat pigments such as: vat yellow 6 GL CI 1127, quinone yellow 18-1, indanthrone CI 1106, pyranthrone CI 1096; brominated pyranthrones such as: dibromo-pyranthrone, vat brilliant orange RK, anthrimide brown CI 1151, dibenzanthrone green CI 1101, flavanthrone yellow CI 1118;
thioindigo pigments such as: thioindigo red and pink FF; azo pigments such as: toluidine red CI 69 and hansa yellow; and metalized pigments such as: azo yellow (green gold) and permanent red. Carbon black has been found to be a preferred colorant as it is low in cost, may be completely cladded so as not to inhibit polymerization, and provides strong black images at relatively low loading of the colorant. The carbon black may be of any of the known types such as channel black or furnace black.
The furnace black is preferred as it is lower in cost. The amount of carbon black necessary in the toner typically is between about 1 and about 20 percent. A loading of between about 5 and about 10 percent in the toner has been found to be suitable for the process of the invention.
If necessaryl a reactive material which allows the coating (cladding) o the pigments to prevent their inhibition 1~L116~
of or :reactio~ /i th tne mOllOmer durirlg L ~S polyrneriza-tion Inay be used in the inven-tion. Coating is not necessary in the case of most dyes and inorganic pigmen-ts. Typical of such cladding materials are water soluble monomers that precipitate onto carbon black or other pigments such as neutralize~ poly-acrylic acid and reactive silanes such as amine silicate-organosi.lane copolymers. ~crylonitri].e monomer has been found to be a suitable water soluble monomer which will precipita-te onto carbon. The react.ive silanes of water emulsified or water soluble types have been found to be sui~able for the cladding process.
Typical of suitable oryanofunctional silanes are aminofunctional silane, methacrylake-functional silane, epoxide-functional silane, polyaminofunctional silane, mercaptofunctional silane, vinyl-functional silane, and chloroalkyl-functional silane; typical of suitable alkoxysilanes are methyltrimethoxysilane/ phenyltri-methoxysilane, methylphenyldimethoxysilane, diphenyldimethoxy~
silane and typical of suitable silizanes is hexamethyldisilozane.
A preferred silane is triethoxy silane (C18-Si(C2H50)3) marketed as "Siliclad" by the Clay Adams Division of Becton, Dickinson and Company, which gives a good poly~ner:ic coating on carbon black that prevents hydrophilic and other types of reaction.
A system containing cladded carbon will polymerize in about the ; same time as one not containing carbon.
The cladding agent when utilized is provided in any amount which provides a covering of the pigment sufficient to prevent the pigment inhibiting complete polymerization to form the toner. Generally, the claclding agent is used in an amount that is the minimum whlch will give complete coverage as this keeps the expense and -time of claddinc3 low. rlypically, an amount of . -15-. .
. . . .
, 6t~
cladding agent from about .05 to 10 percent by weight of the pigment may be utilized. A suitable range has been found to be .1 to 4 percent by weight of the pigment. A preferred range in the case of triethoxy silane is from about .3 percent to about 1 percent for complete coverage at low cost.
Any initiator which is compatible with the particular monomer being used may be utilized in the process of the invention. Typical of initiators for polymeriæation are the peroxide and azo initiators. Among those found suitable for use in the process of the invention are azobis(2-methylpropionitrile) and lauroyl peroxide which result in complete polymerization with-out leaving detrimental residual materials or requiring high temperatures or pressures.
The initiator may be added to the monomer during dispersion of the carbon black or may be mixed in after the carbon black dispersion. It is preferred that the polymerization initiator, treated carbon black and monomer be mixed in high shear agitation to produce a stable dispersion of the carbon black in the monomer. The carbon in stable dispersion is separated into sub-micron size particles evenly distributed throughout the monomer. The mixture may be heated during dispersion. Generally, the initiator is used in the amount necessary to achieve complete polymerization without waste of the initiator. An amount of about
_I~C:E~GP~ D OF THE I~;IVEMTION
This invention relates to electrophotography and more particularly to improved electrosta-tographic developiny ma,erials, their manufacture and use.
The Eormatioll and development of images on the surface of photoconductor materials by elec-trostatic means is well known. The basic xerographic process, as taught by C. F. Carlson in U. S. Patent 2,297,691, involves placing a uniform electro-static charge on a photoconductive insulating layer, e~posiny 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 electro-static image. This powder image may then be transferred to a support surface such as paper. The transEerred image may subsequently be permanently afixed to the support surface as by heat. Instead o latent lmage 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 foregoincJ heat fixing steps.
'' ' .' :
Several methods are kno~n for applying the electroscopic particles to the latent elec-trostatic image to be developed. One development method, as disclosed by E. N. Wise in U. S. Patent 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 conve~ed -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 backyroun~. The carrier and exc~3ss toner are then recycled. This techni~ue is e~tremely good for the development of line copy images.
Another method of developing electrostatic images is the "magnetic brush" process as disclosed, for e~ample, in U. S. Patent No. 2,87~,063. In this method, a developer material con-taining toner and magnetic carrier particles are carried by a magnet. The magnetic fie]d of the magnet causes alignment oE the magnet:ic carrier into a brush-like configuration. This "magnetic brush" is engaged with the elec-trostatic image-bearing suxface and the tOneL par~icles 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. Patent No. 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. Patent No. 3,166,~32, may be used where suitable.
Toners have generally been prepared by thoroughly mixing the softened resin and pigment to form a uniform dis~
persion as by blending these ingredients in a rubber mill or the like and then pulverizing this material to form it into small particles. Most frequently, this division of the resin pigment dispersion has been made by jet pulverization of the material. Although this technique of toner manufacture has produced some very excellent toners, it does tend to have certain shortcomings. For example, it generally produces a rather wide range of particle sizes in the toner particles.
Although the average particle size of toner made according to this technique generally ranges between about 5 and about 10 microns, individual particles ranging from sub micron in size to above 20 microns are not infrequently produced. Furthermore, this is a batch process which tends to be slow, expensive, noisy .~
and dusty. In addition, this technique of toner production imposes certain limitations upon the material selested for -the toner because the resin-pigment dispersion must be sufficiently friable so that it can be pulverizecl at an economically feasible rate of production. The pxoh]em which arises from this require-men-t is that when the resin-pig~lent dispersion is sufficien-tly friable for really high speed pulveriz.ing, it tends to form an even wider range of particle sizes during pulverization including relatively large percentages of fines. In addition, such highly friable materials are ~requently subject to further pulverization or powdering when they are employed for developing in xerographic copying apparatus. All other requirements of xerographic developers or toners including the requirements that they be stable in storage, non-agglomerative, have the proper triboelectric properties for developing, form good images, do no-t film or soil the selenium xerograph.ic plate and have a low melting point for heat fusing are only compounded by the additional requirements imposed by this toner forming process.
Anothe:r method of toner format.ion consists of bl.endi.ng a water latex o:E the desired toner resin with a colorant and then spray drying this combined system to the desired particle size. The spray drying step consists of atomizing the colorant-water latex blend into sma].l dropl.ets, mixing these with a gas, and holding the droplets in suspension in the gas until evaporation drives off the liquid in the droplets and heat and surface tension forces cause the resin particles in each droplet to coalesce encasing the colorant included in that droplet.
Most frequently, spray drying utilizes air as the gas for the drying step. The gas is heated to raise the temperature of the 111~1~;8 resin partic]es to a poin-t where they coalesce so that -the many small paLticles oriyina-ting in any one droplet formed during atomization come toge-ther to form a small, hard spherical toner particle which entraps any colorant initially included within the droplet. The colorant used may be either water soluble in which case it may be merely added and dissolved into the resin latex or water insoluble dye in which case it may first be placed in an aqueous suspension and then added to the resin latex. Spray dried toners are not totally satisfactory as it is difficult to completely remove all the solvent and the solvent which remains in the toner particles acts to eEfect triboelectric properties and contribute to bloc~ing of -the toner when in use.
In U. S. Patent 3,391,0~2 to Maclay, it is proposed that toner be formed directly from an emulsion polymerization system.
~owever, this method i.s not totally satisfactory as the toner comprises agglomerates of the small latex (.03 to .25 micron) particles the total drying of the system is difficult leading to blocking problems and also voids in the particles may cause structural wea~ness and uneven triboe:L~ctric proper-ties.
It has been proposed in United Kingdom Patent 1,319,815 that toner be prepared directly from the monomer by polymerization of the monomer in toner sized particles containing a colorant.
The method of the British patent comprises preparing a kneaded oil phase component made up of one or more liquid resin monomers, coloring material, the polymerization initiator and a finely-divided inorganic dispersion stabilizer such as a metal powder or inoryanic salt or oxide and a polar resinous ac1di-tive which is soluble in a monomer. ~fter suspension polymerization of the monomer, i' recluired, the finely-divided dispersion stabilizer is removed by dissolution in an aci.d and -the polymer particles are removed from the aqueous phase and dr:ied to produce toner. However, this process is not totally successful as it requires a high ra-~io of inorganic stabilizer which needs to be removed or it affects the quality of the toner. Further the par-ticles recovered contain an unacceptably great number of particles which are either larger or smaller than the size range preferred for electrophoto-graphic use. Further, the removal of the inorganic stabilizer adds a process step thereby minimizing the advantage of forming a toner in one operati.on from the monomer. The process in any case often resùlts in incomplete polymerization that leaves residual monomer that affects the triboelectric, blocking and fixing properties of the toner. This incomplete polymerization of the monomer i5 theorized as caused by the pigment inhibiting polymerization. The similar type Maeda et al process, U. S.
3,63~,251, also entails the removal of the inorganic component and problems of incomplete polymerlzation.
A method of producing small methyl methacrylate beads is disclosed in U. S. Patent 2,701,2~5 to Lynn. This process uses large amounts of wetting agent, a short period of mixing to size the monomer and does not agitate during polymerization.
However, this process does not produce colored beads and the large amount of wetting agents required leave impurities very undesirable in toners and further the toner has a wide range of particle sizes.
A Jour.nal of Applied Polymer Science article at Volume 16, pages 1867 and 1868 (1972), discloses that polymerization of small partiale size polymers may be carried out after sizing by high speed stirring of a paddle stirrer. However, the article indicates that control of si.zin~ is difficult and does not 6~
c~eal ~`7i th the complications caused by introduction of colorant into the system.
It has also been proposed that a suspension polymerization p.rocess si~ilar to the above referenced British patent but not making use of an inorganic stabilizer be carried out to produce an encapsulat~d -toner. This process is performed generally hy mixing a monomer, a colorant and an initiator to form an oil soluble organic phase; dispersing this oil soluble phase in controlled size between 5 to 20 microns in a water phase, employing a sus-pending agent, for example polyvinyl alcohol; polymerizing, employing convent.ional suspension polymerization techniques;
introducing a second monomer which is allowed to diffuse into the first polyrner and consequently swells the polymer; introducing a water soluble initiator; and heating this reaction mixture to effect a polymerization of the second monomer and form the desired toner. It is found that the second initiator, the water soluble initiator, generates a free radical which attacks the surface of the swollen polymer particle and promotes polymerization at the surface by reacting with monomer at the surface thereby decreasing the monomer concentrakion and causing the transport of monomer to the surface by diffusion. The process is found to be self terminating when the total amount of sorbed monomer has been converted to polymer at the surface, thus providing an encapsulated toner. ~Iowever, while this process may be used to produce encapsulated toners, it still does not provide an acceptable method for producing toners which are not encapsulated and which may withstand the abrasion, ~tress and humidity variation to which toners are subject in ordinary development systems.
A dlffi.culty with suspension polymerization processes is that it is difficult to maintain the toner particle size .
~, _ ~L111~68 particles of about 5 to 30 microns in large suspension polymeri-zation equipment. To obtain particle sizes in the 10 microns range requires stirrer speeds in excess of 1,000 r.p.m. In view of the high stirring speeds, the design of large reactors becomes increasingly difficult as size increases. Large high speed reactors are much more expensive to design and operate than a normal suspension polymerization reactor that operates at the normal about 75 to 100 r.p.m. stirring speed. The form-ing of toner size particles at slow speeds by utilizing large amounts of suspending agents creates difficulties as set forth above as suspending agents in large amounts must be removed from the particles in order for them to operate effectively as toner particles. The conventional reactors with paddle blade stirrers when operating at high speeds produce a broad range of particle sizes.
As can be seen, there remains a need for a process of producing toners which would not involve extensive processing steps of polymer formation, colorant addition, mixing and particle formation. There remains a need for a process which would produce toner particles directly from monomer that have good triboelectric properties, abrasive resistance, blocking resistance, narrow size variation, and good colorant loading capability. Since the prior forming methods are deficient in one or more of the above areas, there is a continuing need for an improved method of formation of toners for use in electro-photographic development.
SU~MA~Y OF THE INVENTION
_ It is therefore an object of an aspect of this invention to provide a toner overcoming the above noted deficiencies.
It is an object of an aspect of this invention to ~1~1168 provide a method of producing a toner which overcomes the above noted deficiencies in processes of toner production.
It is an object of an aspect of this invention to provide a toner of low cost.
It is an object of an aspect of this in~ention to provide a method of direct polymerization of colored toners.
It is an object of an aspect of this invention to provide simplified equipment for toner production.
It is an object of an aspect of this invention to provide a process of producing low cost toner.
It is an object of an aspect of this invention to provide a method of forming a toner size monomer suspension to form toners.
It is an object of an aspect of the invention to allow the use of less carbon in a toner particle.
It is an object of an aspect of this invention to produce toner size particles utilizing slow speed stirring of a monomer suspension.
It is an object of an aspect of this invention to produce toner part:icles having a narrow size range.
It is an object of an aspect of this invention to provide a direct polymerization process of forming pigmented toner.
In accordance with one aspect of this invention there is provided a method of toner formation comprising dispersion of pigment in monomer, high shear treatment of the pigment con-taining monomer in an aqueous medium to form toner size monomer in suspension, agitation of said monomer during polymerization and recovery of toner particles.
By way of added explanation, the foregoing and other objects of the instant invention may be accomplished, generally, by providing a process for dispersing in water the monomer containing pigment in one stage to the toner particle size of between about 5 and about 30 microns. Such pigmented monomer particles after initial suspension and sizing are stable such that they may be transferred to a reactor and stirred at relatively low speeds of between about 75 and 100 r.p.m. and will remain in suspension during polymerization to form toner.
- lOa -~
- - .
BRIEF DESCRIPTION OF THE DRAWINGS
Flgure 1 is a view of a rotor stator mixer.
Figure 2 is a view of the static element of a rotor stator mixer.
Figure 3 is a view of the rotating element of the mixer.
Figure 4 illustrates a base construction for a rotor stator mixer.
DETAILED DESCRIPTION OF THE INVENTION
. ., The toner formation process of the invention is carried out in one instance by the use of a styrene monomer to which is added lauroyl peroxide and Molacco-H carbon black that has been treated with an active silane dispersion agent such as tri-ethoxy silane ("Siliclad"), a reactive silane. The carbon particles are coated with the silane by suspension of the carbon in water followed by addition of the triethoxy silane ("Siliclad"~ Clay Adams Division of Becton Dickinson Co.). The mixture of silane and carbon is agitated to allow the silane to form a coat on the surface of the carbon particles. The treated (cladded) carbon is dispersed in a styrene monomer with lauroyl peroxide.
Then, utilizing a short period of mixing in a high speed and high shear mixer, the monomer is suspended in an aqueous medium and toner size particles are formed. The suspension of toner size pigmented monomer is then transferred to a reactor which is agitated by a stirrer at about 75 r.p.m. as polymerization takes place. After polymerization is complete, the particles are recovered and found to be suitable for use as toner materials without further processing.
Any polymeric material which may be formed by dispersion polymerization and which has a meIting point within the range suitabIe for use as a toner may be used in the toner forming 6~
process of the instant invention. Typical monomeric units which may be employed to form polymers include: styrene, 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 alphamethylene 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 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 isopropanyl 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. 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 styrene resins are typically 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 ~1~116~
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 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 ~etone and the like; vinylidene halides such as vinylidene chloride, vinylidene chlorofluoride and the 'ike; and N-vinyl compounds such as N~vinyl pyrrole, N-vinyl carbazole, N-viny]. indole, N-vinyl pyrrolidene and the like; and mixtures thereof. 'rhe styrene resins may also be formecl 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 radical, anionic and cationic polymerization processes. Monomers forming polystyrene and copolymers of styrene and n-butylmethacrylate have been found to be particularly ~suitable for the polymerization process of the invention as they result in good yields oE completely polymerized monomer which are suitable for use as toner material as they possess good triboeIectric and fusing properties.
.
~1~1168 Any suitable pigment material may be used in the process of the invention. A pigment generally should be capable of being dispersed in a monomer, be insoluble in the water used in the cladding and polymerization processes and give strong, clear, permanent colors when used as toner. Typical of such pigments are phthalocyanines, lithols, toluidene and inorganic pigments such as TiO2 and dyes. Typical of phthalocyanine pigments are copper phthalocyanine, mono-chlor copper phthalocyanine, hexadecachlor copper phthalocyanine, metal-free phthalocyanine, mono-chIor metal-free phthalocyanine, and hexadecachlor metal-free phthalocyanines; anthraquinone vat pigments such as: vat yellow 6 GL CI 1127, quinone yellow 18-1, indanthrone CI 1106, pyranthrone CI 1096; brominated pyranthrones such as: dibromo-pyranthrone, vat brilliant orange RK, anthrimide brown CI 1151, dibenzanthrone green CI 1101, flavanthrone yellow CI 1118;
thioindigo pigments such as: thioindigo red and pink FF; azo pigments such as: toluidine red CI 69 and hansa yellow; and metalized pigments such as: azo yellow (green gold) and permanent red. Carbon black has been found to be a preferred colorant as it is low in cost, may be completely cladded so as not to inhibit polymerization, and provides strong black images at relatively low loading of the colorant. The carbon black may be of any of the known types such as channel black or furnace black.
The furnace black is preferred as it is lower in cost. The amount of carbon black necessary in the toner typically is between about 1 and about 20 percent. A loading of between about 5 and about 10 percent in the toner has been found to be suitable for the process of the invention.
If necessaryl a reactive material which allows the coating (cladding) o the pigments to prevent their inhibition 1~L116~
of or :reactio~ /i th tne mOllOmer durirlg L ~S polyrneriza-tion Inay be used in the inven-tion. Coating is not necessary in the case of most dyes and inorganic pigmen-ts. Typical of such cladding materials are water soluble monomers that precipitate onto carbon black or other pigments such as neutralize~ poly-acrylic acid and reactive silanes such as amine silicate-organosi.lane copolymers. ~crylonitri].e monomer has been found to be a suitable water soluble monomer which will precipita-te onto carbon. The react.ive silanes of water emulsified or water soluble types have been found to be sui~able for the cladding process.
Typical of suitable oryanofunctional silanes are aminofunctional silane, methacrylake-functional silane, epoxide-functional silane, polyaminofunctional silane, mercaptofunctional silane, vinyl-functional silane, and chloroalkyl-functional silane; typical of suitable alkoxysilanes are methyltrimethoxysilane/ phenyltri-methoxysilane, methylphenyldimethoxysilane, diphenyldimethoxy~
silane and typical of suitable silizanes is hexamethyldisilozane.
A preferred silane is triethoxy silane (C18-Si(C2H50)3) marketed as "Siliclad" by the Clay Adams Division of Becton, Dickinson and Company, which gives a good poly~ner:ic coating on carbon black that prevents hydrophilic and other types of reaction.
A system containing cladded carbon will polymerize in about the ; same time as one not containing carbon.
The cladding agent when utilized is provided in any amount which provides a covering of the pigment sufficient to prevent the pigment inhibiting complete polymerization to form the toner. Generally, the claclding agent is used in an amount that is the minimum whlch will give complete coverage as this keeps the expense and -time of claddinc3 low. rlypically, an amount of . -15-. .
. . . .
, 6t~
cladding agent from about .05 to 10 percent by weight of the pigment may be utilized. A suitable range has been found to be .1 to 4 percent by weight of the pigment. A preferred range in the case of triethoxy silane is from about .3 percent to about 1 percent for complete coverage at low cost.
Any initiator which is compatible with the particular monomer being used may be utilized in the process of the invention. Typical of initiators for polymeriæation are the peroxide and azo initiators. Among those found suitable for use in the process of the invention are azobis(2-methylpropionitrile) and lauroyl peroxide which result in complete polymerization with-out leaving detrimental residual materials or requiring high temperatures or pressures.
The initiator may be added to the monomer during dispersion of the carbon black or may be mixed in after the carbon black dispersion. It is preferred that the polymerization initiator, treated carbon black and monomer be mixed in high shear agitation to produce a stable dispersion of the carbon black in the monomer. The carbon in stable dispersion is separated into sub-micron size particles evenly distributed throughout the monomer. The mixture may be heated during dispersion. Generally, the initiator is used in the amount necessary to achieve complete polymerization without waste of the initiator. An amount of about
2 percent up to about 10 percent by weight initiator to monomer has been found to be suitable. A preferred range i.5 about 2 to about 5 percent by weight of initiator to monomer to give complete polymerization without waste at low cost. The optimum amount in the instance of lauroyl peroxide with styrene monomer systems is about 2 percent as this gives complete polymerization at low cost and results in good toner properties.
. . .
~ ny suitable carrier may be used in the -toner of the instant invention to form a developer. Suitable coated and uncoated carrier materia]s for cascade and magnetic bru~h develop-ment are well known in the art. The carrier particles may be electrically conduc-tive, insulating, mac~netic or nonmagnetic provided that the carrier partic]es acquire a charge having an opposite polarity to that of the toner particles when brought in close contact with the toner particles so tha-t the toner particles adhere to and surround the carrier particles. ~len a positive reproduction of an electrostatic image is desired, the carrier particle is selected so that the toner particles acquire a charge having a polarity opposite to that oE the electrostatic latent image. Alternatively, if a reversal reproduction of the electrostatic image is desired, the carriers are 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 their tribo-electric 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 ne~atively if the other component is above the first component in the tribo-electric 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 oE carrier particles and also adhere to that portion of the electrostatic image bearing surfaces having a greater attraction for the toner thal- do the carrier particles. Typical carriers i.nclude sodium chloride, ammonium - ~,'.... ,' :
;8 chloride, c~lunlin~lm ~)o~assiuml chlorid~, Pocll~lle s-ai., s~ m nitrate, alumlrlum nitra-te, potassium chlorate, granular zircon, yranular silicon, met:hyl methacrylate, glass, steel, nickel, iron, -ferri-tes, ferromacJnetic materials, silicon dioxide and the like. The carriers may be employed with or without a coating.
Many of the foregoiny and typical carriers are described by L. E. Walkup in U. S. Patent No. 2,618,55I; I,. E. Walkup et al in U. S. Patent No. 2,638,416; E. N. Wise in U. S. Patent No.
2,618,552; R. J. Hagenbach et al in U. S. Patent No. 3,591,503 and U. S. Patent No. 3,533,835; and B. J. Jacknow et al in U. S.
Patent No. 3,526,533. Suitable carriers for use with the toners of the instant invention include nickel berry, coated ferrites and methyl terpolymer coated steel. Nickel berry is a nodular nickel particle disclosed in U. S. Patent No. 3,767,568 having a pebbled surface. Methyl texpolymer coated steel carrier is a steel core coated with a composition such as that of Example XI~I of U. S. Patent No. 3,526,533. An ultimate coated carrier particle diameter between about 50 microns to about 1,000 microns is suitable because the carrier partic].es then po~3se5s suEEicient density and inertia to avoid adherence to the elcctrostcltic imacJes during the cascade development process~ A range o-f about 75 to about 400 microns is generally preferred to give clear~ sharp images.
Adherence of carrier beads to xerographic drum surfaces is undesirable because of the formation of deep scratches on the surface during the image transfer and drum cleaning s-teps, particularly where cleaning is accomplished by a web cleaner such as the web disclosed by W. P. GrafE, Jr. et al in U. S.
Patent No. 3,186,838. ALso, print deletion occurs when carrier beads adhere to electrostatographic imaging surfaces.
~illl68 It is generaLly desirabLe to utilize a stabilization agent other than the monomer itself in the solution. Such an a~ent aids the formation of particles which will remain dispersed in -the water ~uring polymerization. The stabilization agent stabilizes the particles so they remain dispersed and do not agglomerate during polymerization. Polymers pass through tacky stages when they have a strong tendency to agglomerate during polymerization. Any suitable stabilization agent may be used.
Typical of such stabilizers are both non-ionic and ionic water soluble polymeric stabilizers such as methyl cellulose, ethyl cellulose, sodium salt of carbo~yl methyl cellulose, polyacrylate acids and their salts, polyvinyl alcohol gelatins, starchs, ~ums, algimates, zein and casin. Suitable stabilization agents are polyacrylic acid, polymethacrylic acid, polyacrylamide and polyethylene o~ide. Stabilized agents found to be preferred for this invention are polyethylene oxide - polypropylene block copolymers and polyvinyl alcohols, which give good suspension at low concentration and narrow particle range. The stabilizer i~
generally added in a ratio based on the amount of watex. An amount of about .2 to about 5 percent by weiyht stabilizer to water is suitable. An amount of about .2 to about 1.5 percent is preferred to give good suspension at low cost and low impurity in the toner. An optimum amount for use in formation of tonexs is about .75 to about 1 percent to give low materials cost and narrow size distribution. The preferred polyvinyl alcohol contains from about 1 to abGut 20 mole percent of polyvinyl acetate groups. The optimum amount oE polyvinyl acetate is about 16 mole percent to yive good dispersion at low concentration and narrow particle size range. The molecular weiyht of suitable polyvinyl alcohols is between about 10,000 and about 125,000 , , - - , . - - - -, , .
.. . ~ . , ., , , . . . : . ... . . ~
number average molecular weight. A preferred polyvinyl alcohol is Monsanto 20-60 of about 90,000 weight average molecular weight.
The preferred polyethylene oxide - polypropylene (PEO-PPO) block copolymers comprise about 40 to about 80 weight percent ethylene oxide. Suitable molecular weights of the (PEO-PPO~ block copolymer are between about 3,000 and about 27,000 weight average molecular weight. A preferred range of molecular weight is between about 10,000 and 15,000 weight average to give good dispersion at low concentration.
The dispersing of pigment containing monomer may be carried out in any suitable type of mixer which results in toner particles of narrow size distribution in stable suspension in less than about 3 minutes. The mixer may be of either the batch or in line type. Suitable for the process of the invention are reed type ultrasonic mixers such as the Dispersonic mixers. A preferred type mixer for the process is the rotor stator type mixer such as the Polytron or ~ispac in which one element is stationary and the other rotates in close tolerance therewith while the liquid is drawn through appertures in the static element. The shear rate should be greater than 103 sec 1. ~n axial turbine agitator that comprises an arrangement of discs and paddles is the other preferred type of mixer. The axial turbine mixers are found to form stable dispersions of naxrow particle siæe distribution at speed ranges of about 200 to about 3,000 r.p.m.
The drawings illustrate a preferred type of rotor stator mixer. The mixer comprises a static element 22 as shown in Figure 2. The static element comprises raised elements 15 separated by slots having a bottom 12. The static element is mounted on base 21 supported by mounting element 24. Gaskets such as 23 are used in mounting of the element. Figure 3 i! lust~al~s Ihe .ro~at:ing eL. ~.inen-L 3.L 0~, trl mi~.er. 'l`n~ rC)tatiiicJr elelnen-t has blades 34 ~7hicrl corYesyond in height to -the depth of the slots in the s-tatic element. The rotor i5 provided with a base 32 having an indented portion for attachment to suitable drive means, not shown, SUC}l as a high speed blender. Fiyure 1 illustrates the rotor and static elemen-t assembled to -the mixing unit 11. The rotor is in close clearance with the static element and rotates around center 14. Figure 4 illustrates attachmen-t means for the mixer wherein a collar 42 is placed over base 24 of static element 22. The static element is secured with nut 42, keyed washer 44 and rubber shim ~5. The indented portions of the rotor allow better flow oE the material being treated.
The shear applied by the sizing mixer is the amount which results in narrow size range distribution. The preferred rotor stator mixer applies a high shear mixing of greater than 103 sec 1 for about 10 seconds to 2 minutes to achieve a size ranye between about 2 and 30 microns with about 95 percent between about 5 and about 20 microns. The volume average particle siæe is about 12 to about 13 microns.
The time of h:igh shear ~lixi.ng ln part varies with the viscosity of the aqueous medium in which the pigmented monomer is suspended. Generally, the stabilization agent changes the vis-cosity of -the aqueous suspension medium. A sui-tab]e viscosity range generally is between about 1 and 100 centipoises (cps).
The preferred viscosity of the aqueous suspension medium is between about 1 and about 10 centipoises (cps) to give low cos-t and rapid mixincJ. An optimum range is abou-t 1 to about 3 cps to give a stabLe d:ispersion of rnonomer ~,~7ith short mixing time, low cost and Little impurity in the toner.
rne :~:ot.or ~tator I~J~JIl .~;2i~e~ J`n ~he,~r ~ er is ca~ah],e of producincJ narrow toner pa~-ticle rdnges. The size range of particles is affected by t~le vi,scosity o~ -the aqueous solution, viscosity of the rnonomer arlc'l ratio of monomer to aqueous suspendinc3 medium. ~ suitable mixture ,is wnen the pigment containing monomer forms from about .2 to abou-t 40 pexcerlt of the total volume o:E the monorner and water mix-ture. l'he ~ize ranc3e produced may suitably be between about 2 and 30 microns. However, for best toner per-formance, it is preferred that the range of par-ticles be between about 5 and 20 microns.
P~EFERRE'D EM.BO~IMENTS
The following examples further define, describe, and compare methods of preparing developers of the instant invention and of utilizing them i.n electrophotographic applications. Parts and pe.rcentages are by weight unless otherwise indicated.
EX~MPLE I
To lO0 grams of styrene are added 5 grams of lauroyl peroxide which are mixed until dissolved. To this mixturo i5 added 7 grams of a cladded carbon b.lac]c, Molacco-H, which has been treated with triethoxy silane, Siliclad, in an about 2 percent solution with water in a stirred beaker for about 5 minutes to prevent interference with the polymerization. This mixture is heated with mixing in a Waring Blender to about 70C for about 5 minutes to provide a good dispersion of carbon blac~ in the monomer mix. The pigmented monomer mix is then poured into a Waring Blender jar equipped with a Polytron mixinc3 head along with about 500 cc.
of an about 1.25 percent polyvinyl alcohol water solution. The two phase mixture i.s then s-tirred at about 3,000 r.p.m. for about 30 seconds to produce a pigrnented droplet dispersion with an average size of about 12 microns.
2~
qne siæed dispersioll is transferred to a reac-tor vessel consisting of a l,000 ml. round bottomed flask equipped with a paddle blade stirrer. With s-,irring speed of 60 to ~0 r.p.m. the flask is heated to about 70C and controlled at that tempera-ture by m~ans of a constant temperature water bath.
The progress of the polymerization is followed by injecting samples at various time intervals into a gel permeation chrom~tograph. The rate of disappearance of both monomer and catalyst is thus determined. After six hours, the polymerization is complete and the suspension of 12 micron sized pigmented par~icles is poured into three liters of cold water. The resulting diluted suspension is centrifuged 15 minutes at l,000 r.p.m in a bucket type centrifuge. The supernatent liquid consisting of the diluted polyvinyl alcohol is decanted, fresh water is added and the mixture is shaken for 5 minutes to disperse the particles. This washing procedure is repeated three times.
After the final wash, the sedimented slurry is poured into a stainless steel tray and allowed to air dry. The resulting cake is very friable and can be broken down to individual particles by tumbling on a roll mill. The particles have an average particle size between about 8 and about 12 microns. The divided particles are utilized in a Model D processor and found to produce good images.
EX~MPLh II
lO0 parts monomer consisting of a 65:35 ratio of styrene and n-butyl methacrylate, 10 parts carbon black treated as in Example I, 1 part ethyl cellulose, Z parts azobisisobutyronitrile were mixed in a Waring Blender to give a well dispersed carbon black. This mixture was added to 500 parts of 0.5 percent poly-vin~l alcohol solution in a Waring Blender jar equipped with a . .
. .
-?~,-~11168 Pol~rtron mi~.ing hecld. lrhe mi~-~ur~ was agita-ted at about 3,000 r.p.m.
for 30 seconds to disperse the pi~mented monomer phase in the water phase. The resultin~ dispersion was further stabilized by the addition of sufficien-t 5 percent polyvinyl alcohol solution to yield a 2.6 percent concentration of polyvinyl alcohol. The s-tabilized dispersion was then transferred to a 1,000 ml. poly-merization flask e~uipp~d with an argon purge and paddle stirrer, and heated -to 65C while stirring at 60 r.p.m. After eight hours, the resulting polymer dispersion was cooled by pouring into three liters oE cold water. The particles were recovered by sedimentation and consisted of uniformly black spheres with an average particle diameter of 10 microns. These particles utilized in a Model D
processor produce images of good quality.
EXAMPLE III
-The process of Example I is repeated except that the TiO2 is substituted for the carbon black and is not cladded. The particles formed exhibit good xerographic properties and are completely polymerized. The particles are operable in a xerographic reproduction process utili7ing a Model D processor and have a size between 5 and 15 microns.
XAMPLE IV
The process of Example I is repeated except that Dow Corning reactive silane DC~Z-6020 is substituted for the Siliclad. This is found to produce toner which has good xero-graphic properties.
F.XAMPIE V
The process of Example II runs 7 and 8 oE British patent 1,319,815, which is hereby incorporated by reference, is performed utilizing Molacco-H carbon blac~. which has been --? 1-cladded in accordance with the process of Example I in place of the No. 35 Asahi Carbon of the patent. Further, dispersion is carried out first in a high speed blender of Example I, then by slow speed agitation. The toner recovered is found to be completely polymerized, exhihits good copying qualities and is not sub~ect to blocking. Further, the size range is that 95 percent of the particles are between about 5 and about 20 microns.
EXAMPLE VI
The process of Example I was performed except that an axial turbine agitator at 2,000 r.p.m. is substituted for the rotor stator (Polytron) mixer. The particles that result have a particle range of about 95 percent between about 5 and about 30 microns. The particles are operable as toner when utilized in a Model D processor.
EX~MPLE VII
As a control, the process of Example I is performed with particle sizing taking place by high speed stirring of the paddle blade stirrer at about 1,000 r.p.m. for about 15 minutes. The paddle stirrer is then slowed to about 75 r.p.m.
for completion of polymerization. The particles recovered have a size range of 95 percent between about 5 and about lO0 microns and are operable as toner.
EXAMPLE VIII
The process of Example I is performed utilizing acrylonitrile monomer in an amount of about 1.7 percent with water as the cladding agent. The toner produced is of good quality.
EXAMPLE IX
. . .
The process of Example I is repeated except after 2.5 percent by weight acrylonitrile monomer is substituted for ,. ~
..
-. , , , : , : - , . - :
.
the triethoxy silane. The toner has good triboelectric properties, is not subject to blocking and is completely polymerized.
EXAMPLE_X
The process of Example II is repeated except about
. . .
~ ny suitable carrier may be used in the -toner of the instant invention to form a developer. Suitable coated and uncoated carrier materia]s for cascade and magnetic bru~h develop-ment are well known in the art. The carrier particles may be electrically conduc-tive, insulating, mac~netic or nonmagnetic provided that the carrier partic]es acquire a charge having an opposite polarity to that of the toner particles when brought in close contact with the toner particles so tha-t the toner particles adhere to and surround the carrier particles. ~len a positive reproduction of an electrostatic image is desired, the carrier particle is selected so that the toner particles acquire a charge having a polarity opposite to that oE the electrostatic latent image. Alternatively, if a reversal reproduction of the electrostatic image is desired, the carriers are 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 their tribo-electric 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 ne~atively if the other component is above the first component in the tribo-electric 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 oE carrier particles and also adhere to that portion of the electrostatic image bearing surfaces having a greater attraction for the toner thal- do the carrier particles. Typical carriers i.nclude sodium chloride, ammonium - ~,'.... ,' :
;8 chloride, c~lunlin~lm ~)o~assiuml chlorid~, Pocll~lle s-ai., s~ m nitrate, alumlrlum nitra-te, potassium chlorate, granular zircon, yranular silicon, met:hyl methacrylate, glass, steel, nickel, iron, -ferri-tes, ferromacJnetic materials, silicon dioxide and the like. The carriers may be employed with or without a coating.
Many of the foregoiny and typical carriers are described by L. E. Walkup in U. S. Patent No. 2,618,55I; I,. E. Walkup et al in U. S. Patent No. 2,638,416; E. N. Wise in U. S. Patent No.
2,618,552; R. J. Hagenbach et al in U. S. Patent No. 3,591,503 and U. S. Patent No. 3,533,835; and B. J. Jacknow et al in U. S.
Patent No. 3,526,533. Suitable carriers for use with the toners of the instant invention include nickel berry, coated ferrites and methyl terpolymer coated steel. Nickel berry is a nodular nickel particle disclosed in U. S. Patent No. 3,767,568 having a pebbled surface. Methyl texpolymer coated steel carrier is a steel core coated with a composition such as that of Example XI~I of U. S. Patent No. 3,526,533. An ultimate coated carrier particle diameter between about 50 microns to about 1,000 microns is suitable because the carrier partic].es then po~3se5s suEEicient density and inertia to avoid adherence to the elcctrostcltic imacJes during the cascade development process~ A range o-f about 75 to about 400 microns is generally preferred to give clear~ sharp images.
Adherence of carrier beads to xerographic drum surfaces is undesirable because of the formation of deep scratches on the surface during the image transfer and drum cleaning s-teps, particularly where cleaning is accomplished by a web cleaner such as the web disclosed by W. P. GrafE, Jr. et al in U. S.
Patent No. 3,186,838. ALso, print deletion occurs when carrier beads adhere to electrostatographic imaging surfaces.
~illl68 It is generaLly desirabLe to utilize a stabilization agent other than the monomer itself in the solution. Such an a~ent aids the formation of particles which will remain dispersed in -the water ~uring polymerization. The stabilization agent stabilizes the particles so they remain dispersed and do not agglomerate during polymerization. Polymers pass through tacky stages when they have a strong tendency to agglomerate during polymerization. Any suitable stabilization agent may be used.
Typical of such stabilizers are both non-ionic and ionic water soluble polymeric stabilizers such as methyl cellulose, ethyl cellulose, sodium salt of carbo~yl methyl cellulose, polyacrylate acids and their salts, polyvinyl alcohol gelatins, starchs, ~ums, algimates, zein and casin. Suitable stabilization agents are polyacrylic acid, polymethacrylic acid, polyacrylamide and polyethylene o~ide. Stabilized agents found to be preferred for this invention are polyethylene oxide - polypropylene block copolymers and polyvinyl alcohols, which give good suspension at low concentration and narrow particle range. The stabilizer i~
generally added in a ratio based on the amount of watex. An amount of about .2 to about 5 percent by weiyht stabilizer to water is suitable. An amount of about .2 to about 1.5 percent is preferred to give good suspension at low cost and low impurity in the toner. An optimum amount for use in formation of tonexs is about .75 to about 1 percent to give low materials cost and narrow size distribution. The preferred polyvinyl alcohol contains from about 1 to abGut 20 mole percent of polyvinyl acetate groups. The optimum amount oE polyvinyl acetate is about 16 mole percent to yive good dispersion at low concentration and narrow particle size range. The molecular weiyht of suitable polyvinyl alcohols is between about 10,000 and about 125,000 , , - - , . - - - -, , .
.. . ~ . , ., , , . . . : . ... . . ~
number average molecular weight. A preferred polyvinyl alcohol is Monsanto 20-60 of about 90,000 weight average molecular weight.
The preferred polyethylene oxide - polypropylene (PEO-PPO) block copolymers comprise about 40 to about 80 weight percent ethylene oxide. Suitable molecular weights of the (PEO-PPO~ block copolymer are between about 3,000 and about 27,000 weight average molecular weight. A preferred range of molecular weight is between about 10,000 and 15,000 weight average to give good dispersion at low concentration.
The dispersing of pigment containing monomer may be carried out in any suitable type of mixer which results in toner particles of narrow size distribution in stable suspension in less than about 3 minutes. The mixer may be of either the batch or in line type. Suitable for the process of the invention are reed type ultrasonic mixers such as the Dispersonic mixers. A preferred type mixer for the process is the rotor stator type mixer such as the Polytron or ~ispac in which one element is stationary and the other rotates in close tolerance therewith while the liquid is drawn through appertures in the static element. The shear rate should be greater than 103 sec 1. ~n axial turbine agitator that comprises an arrangement of discs and paddles is the other preferred type of mixer. The axial turbine mixers are found to form stable dispersions of naxrow particle siæe distribution at speed ranges of about 200 to about 3,000 r.p.m.
The drawings illustrate a preferred type of rotor stator mixer. The mixer comprises a static element 22 as shown in Figure 2. The static element comprises raised elements 15 separated by slots having a bottom 12. The static element is mounted on base 21 supported by mounting element 24. Gaskets such as 23 are used in mounting of the element. Figure 3 i! lust~al~s Ihe .ro~at:ing eL. ~.inen-L 3.L 0~, trl mi~.er. 'l`n~ rC)tatiiicJr elelnen-t has blades 34 ~7hicrl corYesyond in height to -the depth of the slots in the s-tatic element. The rotor i5 provided with a base 32 having an indented portion for attachment to suitable drive means, not shown, SUC}l as a high speed blender. Fiyure 1 illustrates the rotor and static elemen-t assembled to -the mixing unit 11. The rotor is in close clearance with the static element and rotates around center 14. Figure 4 illustrates attachmen-t means for the mixer wherein a collar 42 is placed over base 24 of static element 22. The static element is secured with nut 42, keyed washer 44 and rubber shim ~5. The indented portions of the rotor allow better flow oE the material being treated.
The shear applied by the sizing mixer is the amount which results in narrow size range distribution. The preferred rotor stator mixer applies a high shear mixing of greater than 103 sec 1 for about 10 seconds to 2 minutes to achieve a size ranye between about 2 and 30 microns with about 95 percent between about 5 and about 20 microns. The volume average particle siæe is about 12 to about 13 microns.
The time of h:igh shear ~lixi.ng ln part varies with the viscosity of the aqueous medium in which the pigmented monomer is suspended. Generally, the stabilization agent changes the vis-cosity of -the aqueous suspension medium. A sui-tab]e viscosity range generally is between about 1 and 100 centipoises (cps).
The preferred viscosity of the aqueous suspension medium is between about 1 and about 10 centipoises (cps) to give low cos-t and rapid mixincJ. An optimum range is abou-t 1 to about 3 cps to give a stabLe d:ispersion of rnonomer ~,~7ith short mixing time, low cost and Little impurity in the toner.
rne :~:ot.or ~tator I~J~JIl .~;2i~e~ J`n ~he,~r ~ er is ca~ah],e of producincJ narrow toner pa~-ticle rdnges. The size range of particles is affected by t~le vi,scosity o~ -the aqueous solution, viscosity of the rnonomer arlc'l ratio of monomer to aqueous suspendinc3 medium. ~ suitable mixture ,is wnen the pigment containing monomer forms from about .2 to abou-t 40 pexcerlt of the total volume o:E the monorner and water mix-ture. l'he ~ize ranc3e produced may suitably be between about 2 and 30 microns. However, for best toner per-formance, it is preferred that the range of par-ticles be between about 5 and 20 microns.
P~EFERRE'D EM.BO~IMENTS
The following examples further define, describe, and compare methods of preparing developers of the instant invention and of utilizing them i.n electrophotographic applications. Parts and pe.rcentages are by weight unless otherwise indicated.
EX~MPLE I
To lO0 grams of styrene are added 5 grams of lauroyl peroxide which are mixed until dissolved. To this mixturo i5 added 7 grams of a cladded carbon b.lac]c, Molacco-H, which has been treated with triethoxy silane, Siliclad, in an about 2 percent solution with water in a stirred beaker for about 5 minutes to prevent interference with the polymerization. This mixture is heated with mixing in a Waring Blender to about 70C for about 5 minutes to provide a good dispersion of carbon blac~ in the monomer mix. The pigmented monomer mix is then poured into a Waring Blender jar equipped with a Polytron mixinc3 head along with about 500 cc.
of an about 1.25 percent polyvinyl alcohol water solution. The two phase mixture i.s then s-tirred at about 3,000 r.p.m. for about 30 seconds to produce a pigrnented droplet dispersion with an average size of about 12 microns.
2~
qne siæed dispersioll is transferred to a reac-tor vessel consisting of a l,000 ml. round bottomed flask equipped with a paddle blade stirrer. With s-,irring speed of 60 to ~0 r.p.m. the flask is heated to about 70C and controlled at that tempera-ture by m~ans of a constant temperature water bath.
The progress of the polymerization is followed by injecting samples at various time intervals into a gel permeation chrom~tograph. The rate of disappearance of both monomer and catalyst is thus determined. After six hours, the polymerization is complete and the suspension of 12 micron sized pigmented par~icles is poured into three liters of cold water. The resulting diluted suspension is centrifuged 15 minutes at l,000 r.p.m in a bucket type centrifuge. The supernatent liquid consisting of the diluted polyvinyl alcohol is decanted, fresh water is added and the mixture is shaken for 5 minutes to disperse the particles. This washing procedure is repeated three times.
After the final wash, the sedimented slurry is poured into a stainless steel tray and allowed to air dry. The resulting cake is very friable and can be broken down to individual particles by tumbling on a roll mill. The particles have an average particle size between about 8 and about 12 microns. The divided particles are utilized in a Model D processor and found to produce good images.
EX~MPLh II
lO0 parts monomer consisting of a 65:35 ratio of styrene and n-butyl methacrylate, 10 parts carbon black treated as in Example I, 1 part ethyl cellulose, Z parts azobisisobutyronitrile were mixed in a Waring Blender to give a well dispersed carbon black. This mixture was added to 500 parts of 0.5 percent poly-vin~l alcohol solution in a Waring Blender jar equipped with a . .
. .
-?~,-~11168 Pol~rtron mi~.ing hecld. lrhe mi~-~ur~ was agita-ted at about 3,000 r.p.m.
for 30 seconds to disperse the pi~mented monomer phase in the water phase. The resultin~ dispersion was further stabilized by the addition of sufficien-t 5 percent polyvinyl alcohol solution to yield a 2.6 percent concentration of polyvinyl alcohol. The s-tabilized dispersion was then transferred to a 1,000 ml. poly-merization flask e~uipp~d with an argon purge and paddle stirrer, and heated -to 65C while stirring at 60 r.p.m. After eight hours, the resulting polymer dispersion was cooled by pouring into three liters oE cold water. The particles were recovered by sedimentation and consisted of uniformly black spheres with an average particle diameter of 10 microns. These particles utilized in a Model D
processor produce images of good quality.
EXAMPLE III
-The process of Example I is repeated except that the TiO2 is substituted for the carbon black and is not cladded. The particles formed exhibit good xerographic properties and are completely polymerized. The particles are operable in a xerographic reproduction process utili7ing a Model D processor and have a size between 5 and 15 microns.
XAMPLE IV
The process of Example I is repeated except that Dow Corning reactive silane DC~Z-6020 is substituted for the Siliclad. This is found to produce toner which has good xero-graphic properties.
F.XAMPIE V
The process of Example II runs 7 and 8 oE British patent 1,319,815, which is hereby incorporated by reference, is performed utilizing Molacco-H carbon blac~. which has been --? 1-cladded in accordance with the process of Example I in place of the No. 35 Asahi Carbon of the patent. Further, dispersion is carried out first in a high speed blender of Example I, then by slow speed agitation. The toner recovered is found to be completely polymerized, exhihits good copying qualities and is not sub~ect to blocking. Further, the size range is that 95 percent of the particles are between about 5 and about 20 microns.
EXAMPLE VI
The process of Example I was performed except that an axial turbine agitator at 2,000 r.p.m. is substituted for the rotor stator (Polytron) mixer. The particles that result have a particle range of about 95 percent between about 5 and about 30 microns. The particles are operable as toner when utilized in a Model D processor.
EX~MPLE VII
As a control, the process of Example I is performed with particle sizing taking place by high speed stirring of the paddle blade stirrer at about 1,000 r.p.m. for about 15 minutes. The paddle stirrer is then slowed to about 75 r.p.m.
for completion of polymerization. The particles recovered have a size range of 95 percent between about 5 and about lO0 microns and are operable as toner.
EXAMPLE VIII
The process of Example I is performed utilizing acrylonitrile monomer in an amount of about 1.7 percent with water as the cladding agent. The toner produced is of good quality.
EXAMPLE IX
. . .
The process of Example I is repeated except after 2.5 percent by weight acrylonitrile monomer is substituted for ,. ~
..
-. , , , : , : - , . - :
.
the triethoxy silane. The toner has good triboelectric properties, is not subject to blocking and is completely polymerized.
EXAMPLE_X
The process of Example II is repeated except about
3 percent by weight of hexamethyldisilozane is substituted for the diethoxy silane. The toner is completely polymeriæed and has good triboelectric properties. The particles have a particle size of about 95 percent between about 5 and 20 microns.
EXAMPLE XI
As a control, the process of Example I is repeated except the dispersion of treated carbon black and monomer is transferred directly into the reactor vessel. The reactor vessel contains about 600 cc of a 1.5 percent by weight solution of Pluronic F-127 a 70/30 polyethylene oxide - polypropylene block copolymer. The paddle is rotated at about 800 r.p.m. for 5 minutes and then slowed to about 85 r.p.m. for polymerization. The particles have a size range of 95 percent of the particles between about 5 to about 85 microns. The particles develop good images when used in a Model D processor. The particles are completely polymerized.
This illustrates the wider particle ranye obtained without the high shear, h:igh speed mixing step.
EXAMPLE XII
The process of Example I is repeated substituting Monsanto 2060 a polyvinyl alcohol of about 90,000 weight average molecular weight having about 16 mole percent polyvinyl acetate groups for the polyvinyl alcohol of Example I~ The toner exhibits excellent xerographic properties and has 95 percent of the particles between about 5 and 25 microns.
'~
. .
~.X~ P LE XIII
The process of l.~ample I is repeated about 2 percent.
me-thyl-trimethoxysilane is substitu-ted for the reac-tive silane of Example I. The part:icles are found to be completely polymerized, satisfactory in xeroyraphic prop rties and of a size range of 95 percent hetween abou-t 5 and ~0 microns.
EXAMPLES_XIV-XV
The processes of Examples I and II are repeated .substituting about 1 percent by weiyht di.phenyldimethoxy silane for thc reactive silanes of Examples I and II. The toners produced have good properties and are completely polymerized.
The particles have a size range of about 95 percent between about 5 and about 20 microns.
Although specific materials and conditions were set forth in the above exemplary processes in the formation of the toner of the invention, these are merely intended as illustrations of the present invention. Various other subst.ituents and processes such as those :listed above, may be substituted :Eor those in the Examples with similar results. In addit:ion to the steps used to prepare the toner of the present invention, other steps or modifications may be used if desired. In addition, other materials may be incorporated into the toner of the invention which will enhance, synergize or otherwise desirabl.y effect the properties of these materials for their present use. For example, additives to increase resistance to moi.sture absorption or to effect triboelectric properties, could be added to the surface of the particles.
Other modif:i.cations of the present invention will occur to those skilled in the ar-t upon a readiny of the present dis-closu:re . For ins tance, magne-tic p:i.qmen s coul.c~ be used in -tne pxo-cess if it was desired that magnetic toner be produced. Further, if toner for use in developin~ processes other than magnetic or cascade were desired, the particle size could be regulated to be sma]ler such as 1 to 5 microns for use in powder cloud develop-ment processes. E`urther the sizing may be performed as a thru put or in line process rather than the batch process illustrated.
If desired~ any suitable chain transfer agents or erosslinking agent may be used in the invention to modify the polymeric toner to produce partieularly desired properties.
Typieal of erosslinking agents of the invention are aromatie divinyl eompounds sueh as divinylbenzene, divinylnaphthalene or derivatives thereof; diethyleneearboxylate esters sueh as diethyleneglycol methaerylate, diethyleneglyeol aerylate; any other divinyl eompounds sueh as divinyl sulfide or divinyl sulfone eompounds provided with three or more vinyl radieals;
or mixtures of the foregoing eompounds. Chain transfer agents aet to eontrol moleeular weight by inhibiting chain growth.
Typical of chain transfer agents of the invention are mercaptans such as laurylmercaptan, phenylmercaptan, bukylmercaptan, dodeeylmereapkan; or halogenated earbons sueh as carbon tetrachlo-ride or earbon tetrabromide. Also, examples of materials which become effective when used in a mueh larger amount sueh as solvents for the vinyl monomer are substituted aromatie eompounds sueh as toluene or isopropylbenzene; or substituted fa-tty aeids such as triehloroaeetie aeid or tribromoaeetie acid. Also, examples of materials whieh can be added as a monomer to be incorporated in the resulting polymer and simultaneously effect molecular weight eo~trol are ethylenic unsaturated rnonoolefins with radicals such as propylene or isobutylene; allyl compounds sueh as allyl benzene, allyl aeetate or allylidene chloride.
~ 2~
EXAMPLE XI
As a control, the process of Example I is repeated except the dispersion of treated carbon black and monomer is transferred directly into the reactor vessel. The reactor vessel contains about 600 cc of a 1.5 percent by weight solution of Pluronic F-127 a 70/30 polyethylene oxide - polypropylene block copolymer. The paddle is rotated at about 800 r.p.m. for 5 minutes and then slowed to about 85 r.p.m. for polymerization. The particles have a size range of 95 percent of the particles between about 5 to about 85 microns. The particles develop good images when used in a Model D processor. The particles are completely polymerized.
This illustrates the wider particle ranye obtained without the high shear, h:igh speed mixing step.
EXAMPLE XII
The process of Example I is repeated substituting Monsanto 2060 a polyvinyl alcohol of about 90,000 weight average molecular weight having about 16 mole percent polyvinyl acetate groups for the polyvinyl alcohol of Example I~ The toner exhibits excellent xerographic properties and has 95 percent of the particles between about 5 and 25 microns.
'~
. .
~.X~ P LE XIII
The process of l.~ample I is repeated about 2 percent.
me-thyl-trimethoxysilane is substitu-ted for the reac-tive silane of Example I. The part:icles are found to be completely polymerized, satisfactory in xeroyraphic prop rties and of a size range of 95 percent hetween abou-t 5 and ~0 microns.
EXAMPLES_XIV-XV
The processes of Examples I and II are repeated .substituting about 1 percent by weiyht di.phenyldimethoxy silane for thc reactive silanes of Examples I and II. The toners produced have good properties and are completely polymerized.
The particles have a size range of about 95 percent between about 5 and about 20 microns.
Although specific materials and conditions were set forth in the above exemplary processes in the formation of the toner of the invention, these are merely intended as illustrations of the present invention. Various other subst.ituents and processes such as those :listed above, may be substituted :Eor those in the Examples with similar results. In addit:ion to the steps used to prepare the toner of the present invention, other steps or modifications may be used if desired. In addition, other materials may be incorporated into the toner of the invention which will enhance, synergize or otherwise desirabl.y effect the properties of these materials for their present use. For example, additives to increase resistance to moi.sture absorption or to effect triboelectric properties, could be added to the surface of the particles.
Other modif:i.cations of the present invention will occur to those skilled in the ar-t upon a readiny of the present dis-closu:re . For ins tance, magne-tic p:i.qmen s coul.c~ be used in -tne pxo-cess if it was desired that magnetic toner be produced. Further, if toner for use in developin~ processes other than magnetic or cascade were desired, the particle size could be regulated to be sma]ler such as 1 to 5 microns for use in powder cloud develop-ment processes. E`urther the sizing may be performed as a thru put or in line process rather than the batch process illustrated.
If desired~ any suitable chain transfer agents or erosslinking agent may be used in the invention to modify the polymeric toner to produce partieularly desired properties.
Typieal of erosslinking agents of the invention are aromatie divinyl eompounds sueh as divinylbenzene, divinylnaphthalene or derivatives thereof; diethyleneearboxylate esters sueh as diethyleneglycol methaerylate, diethyleneglyeol aerylate; any other divinyl eompounds sueh as divinyl sulfide or divinyl sulfone eompounds provided with three or more vinyl radieals;
or mixtures of the foregoing eompounds. Chain transfer agents aet to eontrol moleeular weight by inhibiting chain growth.
Typical of chain transfer agents of the invention are mercaptans such as laurylmercaptan, phenylmercaptan, bukylmercaptan, dodeeylmereapkan; or halogenated earbons sueh as carbon tetrachlo-ride or earbon tetrabromide. Also, examples of materials which become effective when used in a mueh larger amount sueh as solvents for the vinyl monomer are substituted aromatie eompounds sueh as toluene or isopropylbenzene; or substituted fa-tty aeids such as triehloroaeetie aeid or tribromoaeetie acid. Also, examples of materials whieh can be added as a monomer to be incorporated in the resulting polymer and simultaneously effect molecular weight eo~trol are ethylenic unsaturated rnonoolefins with radicals such as propylene or isobutylene; allyl compounds sueh as allyl benzene, allyl aeetate or allylidene chloride.
~ 2~
Claims (34)
1. A method of toner formation comprising dispersion of pigment in monomer, high shear treatment of the pigment con-taining monomer in an aqueous medium to form toner size monomer in suspension, agitation of said monomer during polymerization and recovery of toner particles.
2. The method of Claim 1 wherein said pigment is carbon black.
3. The method of Claim 1 wherein said high shear treatment utilizes a rotor stator type mixer.
4. The method of Claim 1 wherein said monomer comprises styrene.
5. The method of Claim 1 wherein said agitation is carried out for longer than about 3 hours.
6. The method of Claim 1 wherein said toner particles range in size from about 2 to about 30 microns.
7. The method of Claim 6 wherein about 95 percent of said particles are between about 5 and about 20 microns.
8. The method of Claim 9 wherein said pigment containing monomer forms about .2 to about 40 percent of the total volume of the monomer and water mixture.
9. The method of Claim 1 wherein an initiator is present during pigment dispersion in the monomer.
10. The method of Claim 9 wherein said initiator is present in an amount between about 2 percent and about 10 percent of said monomer.
11. The method of Claim 9 wherein said initiator is lauroyl peroxide.
12. The method of Claim 1 wherein an effective amount of stabilizer is present during said high shear treatment.
13. The method of Claim 12 wherein said stabilizer is polyvinyl alcohol.
14. The method of Claim 12 wherein said stabilizer is present in an amount between about .2 and about 5 percent by weight of said aqueous medium.
15. The method of Claim 12 wherein said stabilizer is present in about .75 to about 1 percent by weight of the water.
16. The method of Claim 12 wherein said stabilizer comprises a material selected from the group consisting of polyethylene oxide, polyacrylic acid, polymethacrylic acid, polyacrylamide and mixtures thereof.
17. The method of Claim 1 wherein the high shear treatment is carried out for about 10 seconds to 2 minutes.
18. The method of Claim 1 wherein said particles are spherical.
19. The method of Claim 17 wherein said high shear comprises a greater than 103 sec-1 shear rate.
20. The method of Claim 1 wherein said pigment, said monomer and a polymerization initiator are subjected to high shear mixing for said dispersion of pigment in monomer.
21. The process of Claim 20 wherein heat is applied during said dispersing of said pigment in said monomer.
22. The method of Claim 1 wherein heat is applied to aid in initiating and carrying out said polymerization.
23. The method of Claim 1 wherein polymerization is complete in about 6 hours.
24. The method of Claim 2 wherein said pigment is treated prior to dispersion in monomer by a method comprising suspension of the pigment in a solution of water and a reactive water soluble monomer.
25. The method of Claim 24 wherein said reactive monomer comprises a reactive silane.
26. The method of Claim 25 wherein said silane is selected from the group comprising organofunctional silanes, alkoxysilanes and silizanes.
27. The method of Claim 24 wherein said reactive monomer comprises an acrylonitrile monomer.
28. The method of Claim 24 wherein treating pigment comprises forming a coating on the pigment.
29. The method of Claim 24 wherein said reactive monomer is present in about .1 to about 4 percent by weight of the pigment.
30. The method of Claim 1 wherein said high shear mixing utilizes an axial turbine mixer.
31. The method of Claim 1 wherein the viscosity of said aqueous medium is between about 1 and about 10 centipoises.
32. The method of Claim 1 wherein the viscosity of said aqueous medium is between about 1 and about 100 centipoises.
33. The method of Claim 1 wherein said monomer further comprises a material selected from the group consisting of crosslinking agents, chain transfer agents and mixtures thereof.
34. The method of Claim 1 wherein said toner size monomer in suspension is transferred to a reactor for said agitation comprising low speed stirring at 85 to 100 r.p.m.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US71100676A | 1976-08-02 | 1976-08-02 | |
| US711,006 | 1985-03-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111168A true CA1111168A (en) | 1981-10-20 |
Family
ID=24856411
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA279,727A Expired CA1111168A (en) | 1976-08-02 | 1977-06-02 | Two stage method for polymerizing to form toner |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1111168A (en) |
-
1977
- 1977-06-02 CA CA279,727A patent/CA1111168A/en not_active Expired
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