Toner compositions and image forming method

Abstract: A toner composition comprised of a polyester resin with hydrophobic end groups, pigment, optional wax, optional charge additive, and optional surface additives.

Description: The invention is generally directed to toner and developer compositions. EP-A-606 873 discloses a toner for developing an electrostatic image, comprising a binder resin and a colorant, wherein said binder resin contains a polyester resin at least part of which has been modified with a compound which has a long-chain alkyl group having 22 to 102 carbon atoms and has a hydroxyl group or a carboxyl group at its terminal. The compound capable of modifying the polyester may include an alkyl alcohol represented by the Formula CH 3 (CH 2 ) x CH 2 OH wherein x represents a number from 22 to 100. DE-A-4228157 describes a toner for electrophotography comprising a polyester resin obtained from carboxylic acids containing an aromatic monomer in an amount of 80 mol% or more, relative to the total carboxylic acid component and alcohols containing aliphatic diols with 2 to 4 carbon atoms in an amount of 70 to 100 mol% relative to the total alcohol component and alicyclic alcohols in an amount of 0 to 30 mol% relative to the total alcohol component as a binder resin having a specific weight of 1.3 or above, a glass transition temperature of not less than 58°C and a number average molecular weight between 1000 and 6000. There is a need for toners having low relative humidity sensitivity, such as from 1.0 to 2.8 and preferably of from 1.0 to 2.5 as calculated by Equation 1, and wherein low minimum fixing temperatures are obtained, such as from 120°C to 140°C with broad fusing latitude such as from 30°C to 45°C wherein the fusing latitude is considered the difference between the minimum fixing temperature and the temperature at which the toner offsets to the fusing member. Preferably, such toners should have desirable admix properties of 15 seconds to 60 seconds as determined by the charge spectrograph, and preferably 15 to 30 seconds; triboelectric properties with low humidity sensitivity with low minimum fixing temperatures such as from about 120°C to about 140°C or triboelectric properties with low humidity sensitivity with broad fusing latitude, such as from about 30°C to about 45°C; and should be useful in a variety of electrostatic imaging and printing processes, including color xerography, and wherein the admix charging times are less than or equal to about 60 seconds. This object has been achieved by the toner composition according to claim 1. Another object of the present invention is to provide a method of imaging according to claim 4. Polyester resins are known to contain acid and hydroxyl groups of from about 20 to about 1,000 milliequivalents per gram of polyester, usually present as end groups. It is believed that these hydrophilic end groups cause the toner composites to have tribocharging performance that is humidity sensitive. The ratio of the triboelectric charge of the toner composites at low humidity to that at high humidity is of from 2.8 to 4.5, and usually from 3.0 to 3.5. To reduce the relative humidity sensitivity of polyester based toners, the present invention minimizes the hydrophilic end groups, such as hydroxyl or acid moieties on the polyester resin, by capping the ends of the polyester with hydrophobic groups, such as alkyl moieties, hence resulting in toners with low humidity sensitivity such as from 1.0 to 2.8 and preferably from 1.0 to 2.5. In the preparation of the aforementioned polyester resin with hydrophobic end groups, the concentration of the monofunctional hydrophobic monomers is from 0.1 mole percent to 4.0 mole percent based on the starting diacid or diester used to make the resin, thereby controlling the weight average molecular weight of from 4,000 grams per mole to 250,000 grams per mole, especially when monofunctional monomers with a carbon chain length of from 4 to 24 are selected. The aforementioned toner composition and developer thereof, that is toner mixed with a carrier, display a low relative humidity sensitivity for the toners thereof, which is desired such that the triboelectric charge is stable to changes in environmental humidity conditions. Copiers and printers equipped with two component developers, that is a toner as one component mixed with the carrier as the other component, can exhibit a positive or negative triboelectric charge with a magnitude of from 5 microcoulombs per gram to 40 microcoulombs per grams. This triboelectric charge permits the toner particles to be transferred to the latent image of the photoreceptor with an opposite charge, thereby forming a toned image on the photoreceptor, which is subsequently transferred to a paper or a transparency substrate, and thereafter subjected to fusing or fixing processes. In these development systems, it is important for the triboelectric charge to be stable under differing environmental humidity conditions such that the triboelectric charge does not change by more than from 5 to 10 microcoulombs per gram. A change of more than from 5 microcoulombs per gram to 10 microcoulombs per gram in triboelectric charge of the toner developer can cause nonuniform toned images or result in no toning of the photoreceptor, thus unbalanced density or gray scale is observed in the developed images, or no developed images at all result. Generally, humidity ranges may differ from less than 20 percent in dry regions to more than 80 percent in humid regions, and some geographical regions may exhibit fluctuations of up to from 50 to 80 percent humidity level within the same day. In such climates, it is important that the developmental triboelectric charge does not change by more than from 5 microcoulombs per gram to 10 microcoulombs per gram. As toner resins generally represent from 80 percent to 98 percent by weight of toner, the resin sensitivity to moisture or humidity conditions should be minimized thereby not adversely affecting the triboelectric charge thereof. Additionally, the aforementioned toner compositions of the present invention may contain waxes so that fuser stripping failure is avoided or minimized. The present invention in embodiments is directed to polyesters with hydrophobic end groups, wherein specifically the hydrophobic end groups are from 4 carbon atoms to 24 carbon atoms. Furthermore, the presence of the hydrophobic end group monomers provide an improved process for obtaining the aforementioned polyesters. Specifically, the concentration of the monofunctional monomer provides molecular weight control of the polyester product, and its reproducibility. The process for the preparation of the polyester resins of the present invention is known as a condensation process or step polymerization. The condensation process involves the addition of bifunctional monomers which result in dimers, followed by the reaction of dimers with dimers to form tetramers, or dimers with monomers to form trimers. The reaction sequence then continues in that these dimers, trimers and tetramers react with each other to form multiples thereof and known in the art to be oligomers, which in turn react with other oligomers to form the polyester. In this aforementioned kinetic scheme, the degree of polymerization is achieved by terminating the reaction at the desired point, hence it is time dependent It is known that obtaining a specific degree of polymerization by relying on the time of the polymerization of the step reaction polymerization process is very difficult. A method for controlling the degree of polymerization is to adjust the composition of the reaction mixture away from stoichiometric equivalence, by adding a nonvolatile monofunctional reagent in the amount from 0.1 mole percent to 4.0 mole percent based on the starting diacid or diester used to make the resin. In the present invention, the monofunctional monomers employed are the hydrophobic monomers. The degree of polymerization can further be controlled by the amount of monofunctional monomer utilized, hence limiting the degree of polymerization as determined by its concentration such that the total amount of end groups is proportional to the amount of monofunctional monomer employed. This aids in the reproducibility of the product by adjusting the amount of monofunctional monomer to the desired limit of degree of polymerization, hence avoiding total dependence on time of polymerization. The polyester resins with hydrophobic end groups display a number average molecular weight of trom 2,000 grams per mole to 100,000 grams per mole, a weight average molecular weight of from 4,000 grams per mole to 250,000 grams per mole, and polydispersity of from 1.8 to 17, as measured by gel permeation chromatography. The polyester resin with the hydrophobic end groups selected for the toner compositions of the present invention, such as the poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate, can be prepared by charging a 1 liter Parr reactor equipped with a mechanical stirrer and side condenser, a mixture of from 0.9 to 0.95 mole of diester, such as dimethylterephthalate, from 1.75 moles to 1.85 moles of a diol, such as 1,2-propanediol or diethylene glycol or a mixture of the diols, containing from 0.15 to 0.3 mole of diethylene glycol, from 0.01 to 0.1 mole percent of stearic acid, and from 0.001 mole to 0.05 of a condensation catalyst such as butyltin oxide. The reactor is subsequently heated to 170°C for a duration of from 360 minutes to 720 minutes with stirring at from 10 revolutions per minute to 200 revolutions per minute. During this time, from 1.7 moles to 1.9 moles of methanol byproduct can be collected through the condenser. The reactor temperature is then raised to 220°C and the pressure is reduced to 133 Pa (1 torr) over a period of from 2 hours to 3 hours. The polymeric resin comprised of poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate is then discharged through the bottom of the reactor and cooled to room temperature. In a specific embodiment, a polyester resin comprised of poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate can be obtained by charging a one liter Parr reactor equipped with a bottom drain valve, double turbine agitator and distillation receiver with a cold water condenser with from 0.95 mole to 1.05 mole of diester, such as dimethylterephthalate, from 0.60 to 2.05 moles of diol such as 1,2-propanediol, from 0.01 to 0.40 mole of a second diol such as diethylene glycol, from 0.001 to 0.04 mole of monofunctional monomer such as stearic acid, and from 0.001 to 0.05 mole of a catalyst such as tetrabutyl titanate. The reactor is then heated to from 150°C to 187°C with stirring for a duration of from 3 hours to 20 hours. Five tenths (0.5) to 1 mole of alcohol byproduct is collected in the distillation receiver comprised of from 80 percent to 100 percent by volume of methanol and from 0 percent to 20 percent by volume of 1,2-propanediol as measured by an ABBE refractometer available from American Optical Corporation. The mixture is then heated from 180°C to 220°C and vacuum applied slowly. While raising the reaction temperature from 180°C to 220°C, the pressure is reduced from atmospheric pressure (101.08 kPa (760 torr)) to 1.33 Pa (0.01 torr). This stepwise increase in temperature and reduction in pressure takes place over the course of from 1 to 9 hours while collecting distillate. Approximately 0.8 to 1.5 mole of distillate are collected in the distillation receiver comprised of a mixture of methanol and glycol. The reactor is then purged with nitrogen to atmospheric pressure. The resulting linear polyester resin is then discharged through the bottom drain onto a container cooled with dry ice to yield poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate. Variations of the above synthesis can be used by those skilled in the art, such as introducing the monofunctional monomer after the initial esterification. Toners prepared with the polyester resins as defined in claim 1 can be obtained by admixing and heating the polyester resin particles such as poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate, pigment particles such as magnetite, carbon black, or mixtures thereof, and preferably from 0.20 percent to 5 percent of optional charge enhancing additives, or mixtures of charge additives, and optionally wax in a melt mixing device, such as the ZSK53 extruder available from Werner Pfleiderer. After cooling, the toner composition is subjected to grinding utilizing, for example, a Sturtevant micronizer for the purpose of achieving toner particles with a volume median diameter of less than 25 µm (microns), and preferably from 6 to 12 µm (microns), as determined by a Coulter Counter. The toner particles can be classified by utilizing, for example, a Donaldson Model B classifier for the purpose of removing fines, that is toner particles less than 4 µm (microns) volume median diameter. Specific examples of diols utilized in preparing the aforementioned polyesters invention include as diols or glycols 1,2-propylene glycol and these glycols are employed in various effective amounts of, for example, from 45 to 55 mole percent of the polyester product resin. Specific examples of diacids or diesters utilized in preparing the aforementioned polyesters include terephthalic acid, and dialkyl esters thereof and dianhydrides, wherein the alkyl groups of the dialkyl ester are of one carbon atom to 5 carbon atoms and mixtures thereof, and which component is employed, for example, in amounts of from 45 to 55 mole percent of the resin. Specific examples of polycondensation catalysts can include tetraalkyl titanates, dialkyltin oxide such as dibutyltin oxide, tetraalkyltin such as dibutyltin dilaurate, dialkyltin oxide hydroxide such as butyltin oxide hydroxide, aluminum alkoxides, alkyl zinc, dialkyl zinc, zinc oxide, stannous oxide, or mixtures thereof; and which catalysts are selected in effective amounts of from 0.01 mole percent to 5 mole percent based on the starting diacid or diester used to make the resin. Examples of monofunctional hydrophobic monomers which can be utilized in preparing the aforementioned polyesters include monofunctional alcohols such as dodecanol, hexadecanol and octadecanol, and monofunctional acids such as stearic acid, lauric acid and palmitic acid; and which components can be employed in effective amounts of from 0.1 mole percent to 4.0 mole percent based on the starting diacid or diester used to make the resin. Numerous well known suitable pigments or dyes can be selected as the colorant for the toner particles including, for example, carbon black like REGAL 330® , nigrosine dye, aniline blue, phthalocyanines, magnetite, or mixtures thereof. Generally, the pigment particles are present in amounts of from 1 percent by weight to 20 percent by weight, and preferably from 2 to 10 weight percent based on the total weight of the toner composition. When the pigment particles are comprised of magnetites, thereby enabling single component magnetic toners in some instances, which magnetites are a mixture of iron oxides (FeO-Fe 2 O 3 ) including those commercially available as MAPICO BLACK® , they are present in the toner composition in an amount of from 10 percent by weight to 80 percent by weight, and preferably in an amount of from 10 percent by weight to 50 percent by weight. Mixtures of carbon black and magnetite with from 1 to 15 weight percent of carbon black, and preferably from 2 to 6 weight percent of carbon black, and magnetite, such as MAPICO BLACK® , in an amount of, for example, from 5 to 60, and preferably from 10 to 50 weight percent can be selected. Charge additive examples include those as illustrated in US-A-4,338,390, which additives can impart a positive charge to the toner composition; the alkyl pyridinium compounds as disclosed in US-A-4,298,672, and the charge control additives as illustrated in US-A-3,944,493; 4,007,293; 4,079,014; 4,394,430, and 4,560,635, which illustrates a toner with a distearyl dimethyl ammonium methyl sulfate charge additive. Negative charge additives can also be selected, such as zinc or aluminum complexes, like an aluminum compound of a hydroxy carboxylic acid (BONTRON E-88® from Orient Chemical Company), the zinc complex of 3,5-ditertiary butyl salicylate (BONTRON E-84® from Orient Chemical Company) and hydroxy bis (3,5-ditertiary butyl salicylic) aluminate monohydrate (Alohas). There can be included in the toner compositions of the present invention low molecular weight waxes, or mixtures thereof, such as polypropylenes and polyethylenes such as EPOLENE N-15™ commercially available from Eastman Chemical Products, Inc., VISCOL 550-P™, a low weight average molecular weight polypropylene available from Sanyo Kasei K.K., and similar materials. There can also be blended with the toner compositions of the present invention other toner additives, such as external additive particles including flow aid additives, which additives are usually present on the surface thereof. Examples of these additives include metal oxides, such as aluminum oxide, titanium oxide, tin oxide and cerium oxide mixtures thereof, colloidal fumed silicas, such as AEROSIL® , or Cabosil® , metal salts and metal salts of fatty acids including zinc stearate, magnesium stearate, polymeric particles of from 0.2 to 5 microns such as polyvinylidene fluoride which is obtainable from ATOCHEM North America, Inc, polytetrafluoroethylene that is available from ICI Advanced Materials, or polymeric microspheres of from 0.1 to 2.0 µm (microns), such as those obtainable from Nippon Paint, Osaka, Japan, and mixtures thereof, which additives are generally present in an amount of from 0.1 percent by weight to 5 percent by weight, and preferably in an amount of from 0.1 percent by weight to 3 percent by weight. Several of the aforementioned additives are illustrated in US-A-3,590,000 and 3,800,588. Encompassed within the scope of the present invention are colored toner and developer compositions comprised of toner resin particles illustrated herein, and optional carrier particles, and as pigments or colorants red, blue, green, brown, magenta, cyan and/or yellow particles, as well as mixtures thereof. For the formulation of developer compositions, there are mixed with the toner particles carrier components, particularly those that are capable of triboelectrically assuming an opposite polarity to that of the toner composition. Illustrative examples of carrier particles include iron powder, steel, nickel, iron, ferrites, including copper zinc ferrites. Polymer coatings not in close proximity in the triboelectric series can also be selected, reference US-A-4,937,166 and 4,935,326 including, for example, KYNAR® and polymethylmethacrylate mixtures like 40/60. Coating weights can vary as indicated herein; generally, however, from 0.3 to 2, and preferably from 0.5 to 1.5 weight percent coating weight is selected. Furthermore, the diameter of the carrier particles, preferably spherical in shape, is generally from about 35 µm (microns) to 1,000 and preferably from 50 to 200 µm (microns) in diameter, thereby permitting them to, for example, possess sufficient density and inertia to avoid adherence to the electrostatic images during the development process. The carrier component can be mixed with the toner composition in various suitable combinations, such as from 1 to 5 parts per toner to 100 parts to 200 parts by weight of carrier, are selected. The toner and developer compositions of the present invention may be selected for use in electrostatographic imaging apparatuses containing therein conventional photoreceptors providing that they are capable of being charged negatively. Thus, the toner and developer compositions of the present invention can be used with layered photoreceptors that are capable of being charged negatively, or positively, such as those described in U.S. Patent 4,265,990. Illustrative examples of inorganic photoreceptors that may be selected for imaging and printing processes include selenium; selenium alloys, such as selenium arsenic and selenium tellurium; halogen doped selenium substances; and halogen doped selenium alloys. Other similar photoreceptors can be selected providing the objectives of the present invention are achievable. The toner compositions are usually jetted and classified subsequent to preparation to enable toner particles with a preferred average diameter of from 5 to 25 µm (microns), and more preferably from 6 to 12 µm (microns). Also, the toner compositions of the present invention preferably possess a triboelectric charge of from 5 to 40 microcoulombs per gram in embodiments thereof as determined by the known charge spectograph. Admix time for the toners of the present invention are preferably from 15 seconds to 1 minute, and more specifically, from 15 to 30 seconds in embodiments thereof as determined by the known charge spectograph. These toner compositions with rapid admix characteristics enable, for example, the development of latent electrostatographic images in electrophotographic imaging apparatuses, which developed images have substantially no background deposits thereon, even at high toner dispensing rates in some instances, for instance exceeding 20 grams per minute; and further, such toner compositions can be selected for high speed electrophotographic apparatuses, that is those exceeding 70 copies per minute. The following Examples are being supplied to further define various species of the present invention, it being noted that these Examples are intended to illustrate and not limit the scope of the present invention. Parts and percentages are by weight unless otherwise indicated. EXAMPLE I Poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate with an average molecular weight of 10,500 grams per mole and having a diethylene/1,2-propylene molar ratio of 15:85, respectively, and end blocked with a stearate group was prepared as follows. A 7.6 liter Parr reactor equipped with a bottom drain valve, double turbine agitator and distillation receiver with a cold water condenser was charged with 3,250 grams of dimethylterephthalate, 2,369 grams of 1,2-propanediol, 267.91 grams of diethylene glycol, 51 grams of stearic acid, and 4.7 grams of butyltin oxide catalyst obtained as FASCAT 4100™ from Elf Atochem North America, Inc. The reactor was then heated to 165°C with stirring at 150 revolutions per minute and then heated to 200°C over a duration of 6 hours, wherein the methanol byproduct (890 grams) was collected via the distillation receiver to a container, and was comprised of about 98 percent by volume of methanol and 2 percent by volume of 1,2-propanediol as measured by the ABBE refractometer available from American Optical Corporation. The mixture was then maintained at 200°C, and the pressure was reduced from atmospheric to about 26.6 Pa (0.2 torr) over a duration of about 3 hours. During this time, there were further collected approximately 1,172 grams of glycol with about 97 percent by volume of 1,2-propanediol and 3 percent by volume of methanol as measured by the ABBE refractometer. (The theoretical yield of methanol is 1,072 grams, and usually the transesterification is accomplished until about 980 to 1,000 grams of methanol, 93 percent conversion). The reactor was then purged with nitrogen to atmospheric pressure, and the polymer discharged through the bottom drain onto a container cooled with dry ice to yield 3.65 kilograms of poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate resin. The aforementioned resin product glass transition temperature was measured to be 57°C (onset) utilizing the 910 Differential Scanning Calorimeter available from E.I. DuPont operating at a heating rate of 10°C per minute. The number average molecular weight of the polyester product resin was measured to be 6,000 grams per mole and the weight average molecular weight was measured to be 10,500 grams per mole using tetrahydrofuran as the solvent and obtained with the 700 Satellite WISP gel permeation chromatograph available from Waters Company equipped with a styrogel column. 1.8 Grams of the poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate resin were then pressed into a pellet of about 1 centimeter in diameter and about 10 centimeters in length using a press and die set supplied by Shimadzu with the Flowtester 500 series. The pressed sample pellet was then loaded in the flowtester and subjected to standard Shimadzu conditions using 20 kilograms/cm 2 load, and barrel temperature heated from 20°C to 130°C at a rate of 10°C per minute. For the polyester resin of this Example, a softening point of 78°C, beginning of flow temperature T 1 of 90°C, and flow temperature T 2 of 104°C were obtained. The melt index of the resin of this Example was found to be 9.3 grams per 10 minutes at 117°C with a loading of 2.16 kilograms. The acid number of the polyester resin was found to be less than 1 milliequivalent per gram of potassium hydroxide. EXAMPLE II Poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate with an average molecular weight of 15,600 grams per mole and having a diethylene/1,2-propylene molar ratio of 15:85, respectively, and end blocked with a stearate group was prepared as follows. A 7.6 liter Parr reactor equipped with a bottom drain valve, double turbine agitator and distillation receiver with a cold water condenser was charged with 3,250 grams of dimethylterephthalate, 2,369 grams of 1,2-propanediol (1 equivalent excess), 267.91 grams of diethylene glycol, 51 grams of stearic acid, and 4.7 grams of butyltin oxide catalyst obtained as FASCAT 4100™ from Elf Atochem North America, Inc. The reactor was then heated to 165°C with stirring at 150 revolutions per minute and then heated to 200°C over a duration of 6 hours, wherein the methanol byproduct (805 grams) was collected via the distillation receiver to a container comprised of about 98 percent by volume of methanol and 2 percent by volume of 1,2-propanediol as measured by the ABBE refractometer available from American Optical Corporation. The mixture was then maintained at 200°C, and the pressure was reduced from atmospheric to about 26.6 Pa (0.2 torr) over a duration of about 3 hours. During this time, there was further collected approximately 1,237 grams of glycol with about 97 percent by volume of 1,2-propanediol and 3 percent by volume of methanol as measured by the ABBE refractometer. The reactor was then purged with nitrogen to atmospheric pressure, and the polymer discharged through the bottom drain onto a container cooled with dry ice to yield 3.65 kilograms of poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearate resin. The resin glass transition temperature was measured to be 61°C (onset) utilizing the 910 Differential Scanning Calorimeter available from DuPont operating at a heating rate of 10°C per minute. The number average molecular weight was measured to be 7,700 grams per mole and the weight average molecular weight was measured to be 15,600 grams per mole using tetrahydrofuran as the solvent and obtained with the 700 Satellite WISP gel permeation chromatograph available from Waters Company equipped with a styrogel column. The melt index of the resin of this Example was found to be 2.0 grams per 10 minutes at 117°C with a loading of 2.16 kilograms. The acid number of the polyester resin was found to be less than 1 milliequivalent per gram of potassium hydroxide. EXAMPLE III Poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) end blocked with stearate with an average molecular weight of 41,700 grams per mole and having a diethylene/1,2-propylene molar ratio of 25:75, respectively, trimethylolpropane as branching agent and end blocked with a stearate group was prepared as follows. A 7.6 liter Parr reactor equipped with a bottom drain valve, double turbine agitator and distillation receiver with a cold water condenser was charged with 3,250 grams of dimethylterephthalate, 2,228.8 grams of 1,2-propanediol (1 equivalent excess), 443.1 grams of diethylene glycol, 47.5 grams of stearic acid, 44.8 grams of trimethylol propane and 4.7 grams of butyltin oxide catalyst obtained as FASCAT 4100™ from Elf Atochem North America, Inc. The reactor was then heated to 165°C with stirring at 150 revolutions per minute and then heated to 200°C over a duration of 6 hours, wherein the methanol byproduct (800 grams) was collected via the distillation receiver to a container comprised of about 98 percent by volume of methanol and 2 percent by volume of 1,2-propanediol as measured by the ABBE refractometer available from American Optical Corporation. The mixture was then maintained at 200°C, and the pressure was reduced from atmospheric to about 0.2 torr over a duration of about 3 hours. During this time, there were further collected approximately 1,300 grams of distillate in the distillation receiver comprised of approximately 97 percent by volume of 1,2-propanediol and 3 percent by volume of methanol as measured by the ABBE refractometer. The pressure was then further maintained at about 26.6 Pa (0.2 torr), and the temperature of the reaction mixture increased to 210°C for an additional 2 hours, wherein an additional 27 grams of 1,2-propanediol were collected. The reactor was then purged with nitrogen to atmospheric pressure, and the polymer discharged through the bottom drain onto a container cooled with dry ice to yield 3.7 kilograms of poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) end blocked with stearate resin. The resin glass transition temperature was measured to be 58°C (onset) utilizing the 910 Differential Scanning Calorimeter available from E.I. DuPont operating at a heating rate of 10°C per minute. The number average molecular weight was measured to be 10,900 grams per mole and the weight average molecular weight was measured to be 41,700 grams per mole using tetrahydrofuran as the solvent and obtained with the 700 Satellite WISP gel permeation chromatograph available from Waters Company equipped with a styrogel column. 1.8 Grams of the poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) end blocked with stearate resin were then pressed into a pellet of about 1 centimeter in diameter and about 10 centimeters in length using a press and die set supplied by Shimadzu with the Flowtester 500 series. The pressed sample pellet was then loaded in the flowtester and subjected to standard Shimadzu conditions using 20 kilograms/cm 2 load, and barrel temperature heated from 20°C to 130°C at a rate of 10°C per minute. For the resin of this Example, a softening point of 80°C, beginning of flow temperature T 1 of 97°C, and flow temperature T 2 of 105°C were obtained. The melt index of the resin of this Example was found to be 10.1 grams per 10 minutes at 117°C with a loading of 16.6 kilograms. The acid number of the polyester resin was found to be less than 1 milliequivalent per gram of potassium hydroxide. EXAMPLE IV Poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) end blocked with stearate with an average molecular weight of 38,300 grams per mole and having a diethylene/1,2-propylene molar ratio of 25:75, respectively, trimethylolpropane as branching agent and terminated with a stearyl end group was prepared as follows. A 7.6 liter Parr reactor equipped with a bottom drain valve, double turbine agitator and distillation receiver with a cold water condenser was charged with 3,250 grams of dimethylterephthalate, 2,228.8 grams of 1,2-propanediol (1 equivalent excess), 443. grams of diethylene glycol, 47.5 grams of stearic acid, 44.8 grams of trimethylol propane and 4.7 grams of butyltin oxide catalyst obtained as FASCAT 4100™ from Elf Atochem North America, Inc. The reactor was then heated to 165°C with stirring at 150 revolutions per minute and then heated to 200°C over a duration of 6 hours, wherein the methanol byproduct (809 grams) was collected via the distillation receiver to a container comprised of about 98 percent by volume of methanol and 2 percent by volume of 1,2-propanediol as measured by the ABBE refractometer available from American Optical Corporation. The mixture was then maintained at 200°C, and the pressure was reduced from atmospheric to about 26.6 Pa (0.2 torr) over a duration of about 3 hours. During this time, there were further collected approximately 1,350 grams of distillate in the distillation receiver comprised of approximately 97 percent by volume of 1,2-propanediol and 3 percent by volume of methanol as measured by the ABBE refractometer. The pressure was then further maintained at about 0.2 torr and the temperature of the reaction mixture increased to 210°C for an additional 2 hours, wherein an additional 27 grams of 1,2-propanediol were collected. The reactor was then purged with nitrogen to atmospheric pressure, and the polymer discharged through the bottom drain onto a container cooled with dry ice to yield 3.7 kilograms of poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) end blocked with stearate resin. The resin glass transition temperature was measured to be 57.5°C (onset) utilizing the 910 Differential Scanning Calorimeter available from DuPont operating at a heating rate of 10°C per minute. The number average molecular weight was measured to be 10,000 grams per mole and the weight average molecular weight was measured to be 38,300 grams per mole using tetrahydrofuran as the solvent and obtained with the 700 Satellite WISP gel permeation chromatograph available from Waters Company equipped with a styrogel column. 1.8 Grams of the poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) end blocked with stearate resin were then pressed into a pellet of about 1 centimeter in diameter and about 10 centimeters in length using a press and die set supplied by Shimadzu with the Flowtester 500 series. The melt index of the resin of this Example was found to be 20.3 grams per 10 minute at 117°C with a loading of 16.6 kilograms. The acid number of the polyester resin was found to be less than 1 milliequivalent per gram of potassium hydroxide. COMPARATIVE EXAMPLE V Poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) resin with an average molecular weight of 34,000 grams per mole and having a diethylene/1,2-propylene molar ratio of 25:75, respectively, and note that with no hydrophobic end groups are present, was prepared as follows. A 7.6 liter Parr reactor equipped with a bottom drain valve, double turbine agitator and distillation receiver with a cold water condenser was charged with 3,250 grams of dimethylterephthalate, 2,228.8 grams of 1,2-propanediol (1 equivalent excess), 443.1 grams of diethylene glycol, 44.8 grams of trimethylol propane and 4.7 grams of butyltin oxide catalyst obtained as FASCAT 4100™ from Elf Atochem North America, Inc. The reactor was then heated to 165°C with stirring at 150 revolutions per minute and then heated to 200°C over a duration of 6 hours, wherein the methanol byproduct (809 grams) was collected via the distillation receiver to a container comprised of about 98 percent by volume of methanol and 2 percent by volume of 1,2-propanediol as measured by the ABBE refractometer available from American Optical Corporation. The mixture was then maintained at 200°C, and the pressure was reduced from atmospheric to about 26.6 Pa (0.2 torr) over a duration of about 3 hours. During this time, there were further collected approximately 1,240 grams of distillate in the distillation receiver comprised of approximately 97 percent by volume of 1,2-propanediol and 3 percent by volume of methanol as measured by the ABBE refractometer. The pressure was then further maintained at about 0.2 torr and the temperature of the reaction mixture increased to 210°C for an additional 2 hours, wherein an additional 30 grams of 1,2-propanediol were collected. The reactor was then purged with nitrogen to atmospheric pressure, and the polymer discharged through the bottom drain onto a container cooled with dry ice to yield 3.7 kilograms of poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) resin. The resin glass transition temperature was measured to be 57.2°C (onset) utilizing the 910 Differential Scanning Calorimeter available from DuPont operating at a heating rate of 10°C per minute. The number average molecular weight was measured to be 10,100 grams per mole and the weight average molecular weight was measured to be 34,000 grams per mole using tetrahydrofuran as the solvent and obtained with the 700 Satellite WISP gel permeation chromatograph available from Waters Company equipped with a styrogel column. 1.8 Grams of the poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) resin were then pressed into a pellet of about 1 centimeter in diameter and about 10 centimeters in length using a press and die set supplied by Shimadzu with the Flowtester 500 series. The melt index of the resin of this Example was found to be 17 grams per 10 minute at 117°C with a loading of 16.6 kilograms. The acid number of the polyester resin was found to be 16 milliequivalent per gram of potassium hydroxide. EXAMPLE VI A toner composition comprised of 95 percent by weight of the polyester resin of Example II and 5 percent by weight of REGAL 330® pigment was prepared as follows. The polyester resin of Example II was ground to about 500 µm (microns) average volume diameter in a Model J Fitzmill equipped with an 850 micrometer screen. After grinding, 950 grams (95 percent by weight of toner) of the polyester polymer were mixed with 50 grams of REGAL 330® carbon black pigment (5 percent by weight of toner). The two components were dry blended first on a paint shaker and then on a roll mill. A Davo twin screw extruder was then used to melt mix the aforementioned mixture at a barrel temperature of 140°C, screw rotational speed of 50 rpm and at a feed rate of 20 grams per minute. The extruded strands were broken into coarse particles utilizing a coffee bean grinder available from Black and Decker. An 20.3 cm (8 inch) Sturtevant micronizer was used to reduce the particle size further. After grinding, the toner was measured to display an average volume diameter particle size of 9.1 µm (microns) with a geometric distribution of 1.43 as measured by the Coulter Counter. The resulting toner was then utilized without further classification. A developer composition was prepared by roll milling the aforementioned toner, 3 parts by weight, with 100 parts by weight of a 90 µm (micron) diameter ferrite carrier core with a coating, 0.55 percent by weight of a polymer of methylmethacrylate (80.4 percent), vinyl triethoxysilane (5 percent) and styrene (14.1 percent). The tribo data was obtained using the known blow-off Faraday Cage apparatus. Toner developer was subjected to 80 percent humidity in a chamber for 48 hours at 27°C (80°F) to result in a triboelectric charge of -15 microcoulombs per gram, and at 20 percent humidity level in a chamber for 48 hours at 16°C (60°F) to result in a triboelectric charge of -33 microcoulombs per gram. The ratio of the corresponding triboelectric charge at 20 percent RH to 80 percent RH as given by Equation 1 was measured to be 2.2. Unfused copies were then produced using a custom made imaging apparatus similar to the Xerox Corporation 9200 imaging apparatus with the fusing system disabled. The unfused copies were then fused in the 1075 fuser. Fusing evaluation of the toner indicated a minimum fixing temperature of about 129°C, and hot-offset temperature of 170°C. EXAMPLE VII A toner composition comprised of 91 percent by weight of the polyester resin of Example III, 5 percent by weight of REGAL 330® pigment, and 4 percent by weight of 660P wax available from SANYO KASEI K.K. was prepared as follows. The polyester resin of Example III was ground to about 500 µm (microns) average volume diameter in a Model J Fitzmill equipped with an 850 micrometer screen. After grinding, 910 grams of polymer were mixed with 50 grams of REGAL 330® pigment and 40 grams of 660P polypropylene wax. The three components were dry blended first on a paint shaker and then on a roll mill. A Davo twin screw extruder was then used to melt mix the aforementioned mixture at a barrel temperature of 140°C, screw rotational speed of 50 rpm and at a feed rate of 20 grams per minute. The extruded strands were broken into coarse particles utilizing a coffee bean grinder available from Black and Decker. An 20.3 cm (8 inch) Sturtevant micronizer was used to reduce the particle size further. After grinding, the toner was measured to display an average volume diameter particle size of 8.5 µm (microns) with a geometric distribution of 1.43 as measured by the Coulter Counter. The resulting toner was then utilized without further classification. A developer composition was prepared by roll milling the aforementioned toner, 3 parts by weight with 100 parts by weight of the carrier of Example VI. The tribo data was obtained using the known blow-off Faraday Cage apparatus, and the toner developer was subjected to 20 percent humidity in a chamber for 48 hours at 16°C (60°F) to result in a triboelectric charge of -37 microcoulombs per gram, and at 80 percent humidity level in a chamber for 48 hours at 27°C (80°F) to result in a triboelectric charge of -17 microcoulombs per gram. The ratio of the corresponding triboelectric charge at 20 percent RH to 80 percent RH as given by Equation 1 was measured to be 2.18. Unfused copies were then produced with the imaging apparatus of Example VI with the fusing system disabled. The unfused copies were then fused with a Xerox Corporation 1075 fuser. Fusing evaluation of the toner indicated a minimum fixing temperature of about 133°C, and hot-offset temperature of 165°C. EXAMPLE VIII A toner composition comprised of 95 percent by weight of the polyester resin of Example IV and 5 percent by weight of REGAL 330® pigment was prepared as follows. The polyester resin of Example IV was ground to about 500 µm (microns) average volume diameter in a Model J Fitzmill equipped with an 850 micrometers screen. After grinding, 950 grams (95 percent by weight of toner) of polymer were mixed with 50 grams of REGAL 330® pigment (5 percent by weight of toner). The two components were dry blended first on a paint shaker and then on a roll mill. A Davo twin screw extruder was then used to melt mix the aforementioned mixture at a barrel temperature of 140°C, screw rotational speed of 50 rpm and at a feed rate of 20 grams per minute. The extruded strands were broken into coarse particles utilizing a coffee bean grinder available from Black and Decker. An 8 inch Sturtevant micronizer was used to reduce the particle size further. After grinding, the toner was measured to display an average volume diameter particle size of 8.5 µm (microns) with a geometric distribution of 1.45 as measured by the Coulter Counter. The resulting toner was then utilized without further classification. A developer composition was prepared by roll milling the aforementioned toner, 3 parts by weight with 100 parts by weight of the carrier of Example VI. The tribo data was obtained using the known blow-off Faraday Cage apparatus, and the toner developer was subjected to 20 percent humidity in a chamber for 48 hours at 16°C (60°F) to result in a triboelectric charge of -30 microcoulombs per gram, and at 80 percent humidity level in a chamber for 48 hours at 27°C (80°F) to result in a triboelectric charge of -15 microcoulombs per gram. The ratio of the corresponding triboelectric charge at 20 percent RH to 80 percent RH as given by Equation 1 was measured to be 2.0. Unfused copies were then produced with the imaging apparatus of Example VI with the fusing system disabled. The unfused copies were subsequently fused in a Xerox Corporation 1075 fuser. Fusing evaluation of the toner indicated a minimum fixing temperature of about 129°C, and hot-offset temperature of 165°C COMPARATIVE EXAMPLE IX A toner composition comprised of 91 percent by weight of the polyester resin of Comparative Example V, 5 percent by weight of REGAL 330® pigment, and 4 percent by weight of 660P polypropylene wax was prepared as follows. The polyester resin of Example V was in the form of a large chunk. The resulting polymer was ground to about 500 µm (microns) average volume diameter in a Model J Fitzmill equipped with an 850 micrometer screen. After grinding, 910 grams of polymer were mixed with 50 grams of REGAL 330 ⊗ pigment and 40 grams of 660P wax. The three components were dry blended first on a paint shaker and then on a roll mill. A Davo twin screw extruder was then used to melt mix the aforementioned mixture at a barrel temperature of 140°C, screw rotational speed of 50 rpm and at a feed rate of 20 grams per minute. The extruded strands were broken into coarse particles utilizing a coffee bean grinder available from Black and Decker. An 8 inch Sturtevant micronizer was used to reduce the particle size further. After grinding, the toner was measured to display an average volume diameter particle size of 7.9 microns with a geometric distribution of 1.39 as measured by the Coulter Counter. The resulting toner was then utilized without further classification. A developer composition was prepared by roll milling the aforementioned toner, 3 parts by weight with 100 parts by weight of the carrier of Example VI. The tribo data was obtained using the known blow-off Faraday Cage apparatus, and the toner developer was subjected to 20 percent humidity in a chamber for 48 hours at 16°C (60°F) to result in toner triboelectric charge of -60 microcoulombs per gram, and at 80 percent humidity level in a chamber for 48 hours at 27°C (80°F) to result in toner triboelectric charge of -15 microcoulombs per gram. The ratio of the corresponding triboelectric charge at 20 percent RH to 80 percent RH as given by Equation I was measured to be 4.0. In comparison to the toner compositions of Examples VI, VII, and VIII, the RH sensitivity of this Example was much higher because no hydrophobic end group was present. Unfused copies were then produced with the imaging apparatus with the fusing system disabled. The unfused copies were then subsequently fused with the Xerox Corporation 1075 fuser. Fusing evaluation of the toner indicated a minimum fixing temperature of about 135°C, and hot-offset temperature of 170°C. EXAMPLE X A toner composition comprised of 98 percent by weight of the polyester resin of Example I and 2 percent by weight of PV FAST BLUE™ pigment was prepared as follows. The polyester resin of Example I was to about 500 µm (microns)average volume diameter in a Model J Fitzmill equipped with an 850 micrometer screen. After grinding, 980 grams (98 percent by weight of toner) of polymer were mixed with 20 grams of PV FAST BLUE™ pigment (2 percent by weight of toner). The two components were dry blended first on a paint shaker and then on a roll mill. A Davo twin screw extruder was then used to melt mix the aforementioned mixture at a barrel temperature of 120°C, screw rotational speed of 50 rpm, and at a feed rate of 25 grams per minute. The extruded strands were broken into coarse particles utilizing a coffee bean grinder available from Black and Decker. An 20.3 cm (8 inch) Sturtevant micronizer was used to reduce the particle size further. After grinding, the toner was measured to display an average volume diameter particle size of 6.9 µm (microns) with a geometric distribution of 1.37 as measured by the Coulter Counter. The resulting toner was then utilized without further classification. A developer composition was prepared by roll milling the aforementioned toner, 3 parts by weight, with 100 parts by weight of the carrier of Example VI. The tribo data was obtained using the known blow-off Faraday Cage apparatus, and the toner developer was subjected to 20 percent humidity in a chamber for 48 hours at 16°C (60°F) to result in a triboelectric charge of 16 microcoulombs per gram, and at 80 percent humidity level in a chamber for 48 hours at 27°C (80°F) to result in a triboelectric charge of 8 microcoulombs per gram. The ratio of the corresponding triboelectric charge at 20 percent RH to 80 percent RH as given by Equation 1 was measured to be 2.0. Unfused copies were then produced with the imaging apparatus of Example VI with the fusing system disabled. The unfused copies were then subsequently fused with the Xerox Corporation MAJESTIK™ color fuser. Fusing evaluation of the toner indicated a minimum fixing temperature of about 135°C, and hot-offset temperature of 170°C.

Claims: A toner composition comprising a polyester resin with hydrophobic end groups and a colorant, characterized in that the polyester resin with hydrophobic end groups is poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearyl or stearate, poly(1,2-propylene terephthalate-co-diethylene terephthalate-co-1,1,1-trimethylene propane terephthalate) end blocked with stearyl or stearate, poly(1,2-propylene terephthalate) end blocked with stearyl or stearate, poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with lauryl or laurate, poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked'with cetyl or palmitate, poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with octoate, poly(1,2-propylene terephthalate-co-diethylene terephthalate) end blocked with stearyl, lauryl, palmitate, stearate, or laurate; and mixtures thereof. The toner composition according to claim 1, further containing at least one of the components selected from the group consisting of a wax, a charge additive and surface additives. The toner composition according to claims 1 or 2 wherein said colorant is a pigment. A method of imaging which comprises formulating an electrostatic latent image on a negatively charged photoreceptor, affecting development thereof with the toner composition as claimed in any one of claims 1 to 3, and thereafter transferring the developed image to a suitable substrate.

Inventors: BAYLEY ROBERT D, FOX CAROL A, GRUSHKIN BERNARD, HOFFEND THOMAS R, SACRIPANTE GUERINO G, BAYLEY, ROBERT D., FOX, CAROL A., GRUSHKIN, BERNARD, HOFFEND, THOMAS R., SACRIPANTE, GUERINO G.
Applicants: XEROX CORP, XEROX CORPORATION
Application year: 1996
Main classification: G03G9
IPC codes: C08G63, G03G9