US 3753909 A
Description (OCR text may contain errors)
United States Patent 3,753,909 XEROGRAPHIC TONER COMPOSITION Lauren L. Hulse, Saratoga, William K. Carlton, San Jose, and Elinor J. Tanck, Cupertino, Califl, assignors to Memorex Corporation No Drawing. Filed Nov. 1, 1971, Ser. No. 194,696 Int. Cl. G03g 9/02 US. Cl. 25262.1 1 Claim ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The essential steps in the operating cycle of a xero- 3,753,909 Patented Aug. 21, 1973 The resin is prepared by copolymerizing a mixture of two parts by weight of n-butylmethacrylate, l.8-2.2 parts by weight styrene and 0.8-1.2 parts by weight methylmethacrylate. The temperature, time and amount of initiator in the polymerization reaction are adjusted to produce a product having a melt index (ASTM D 1238-65T Condition Cl50 C. and 2.16 'kg.) in the range 9-11, :1 molecular weight in the range about 55,000 to 75,000, a glass transition temperature about 64 C. and a Gardner-Holt viscosity (35% in ethylne dichloride) in the range about 2.20 to 3.35.
As determined by the Kofler Hot Bench Test, the resins are free flowing at 6070 C., begin to exhibit tack at about 8090 C. and melt at about 95-105 C.
A representative preparation of the toner of the present invention is described in the following example:
Example The resin is prepared by suspension polymerization characterized by a two-phase system. Polymerization occurs in the organic phase; the aqueous phase acts as a heat-sink and controls the exotherm generated by the polymerization. Suspension polymerization yields a final product in the form of a free flowing bead.
The polyvinyl alcohol is the suspending agent and its graphic reproducing machine include imposing a uniform concentration affects the bead size of the resulting poly- Ingredients Type Amount Percent A Deionized water. 740 B Polyvinyl alcohol (DuPont, Elvanol 5042) 0.30 0.075 based on monomer (E, F, G). C Sodium nitrate 0. 12 0.03 based on monomer. D Benzoyl peroxlde 10.0 2.5 based on monomer.
Monomers E Styrene 160 40 of monomer F... n-Butyl methacrylate 160 do of total ingredients. G Methyl methacrylate 80 20 of monomer electrostatic charge on a photoconductive surface, exposing the surface to a light pattern which selectively dissipates the charge on the radiated areas of the surface, cascading a developer composition consisting of carrier particles coated with finely divided toner particles electrostatically bonded to the carrier particles over the photoconductive surface to deposit toner particles on the still charged areas of the photoconductive surface, electrostatically transferring the toner particles to an image surface and fusing the toner particles on that surface, cleaning the photoconductive surface to remove residual toner particles, and the cycle is then repeated.
The nature of the operating cycle inherently imposes severe physical and chemical property requirements on the toner. Its triboelectric properties must insure good adherence to the carrier, ready transfer to the still charged areas of the photoconductive surface and strong adherence to that surface; the toner particles must be readily transferra-ble to the image surface and adhere strongly to that surface; residual toner particles must be readily removable from the photoconductive surface to prevent film formation on that surface as operation continues; the toner particles must be free flowing and resistant to agglomeration; the toner particles must be readily and rapidly fusible; the particles must be resistant to attrition as they pass through the cycle; the particles should be of great uniformity in size and they should be resistant to agglomeration in storage under a wide variety of storage conditions. The toner composition of this invention meets all of these property requirements and is outstanding in strong adherence to the image surface and resistance to agglomeration during storage.
DETAILED DESCRIPTION OF THE INVENTION The toner composition of the present invention is a mixture of resinous particles having carbon black uniformly dispersed in the particles.
mer. If the polyvinyl alcohol concentration is too low, the reaction will lump during polymerization; if it is too high, the reaction will foam excessively. The sodium nitrite inhibits polymerization in the aqueous phase and prevents the formation of insoluble polymer gel. The benzoyl peroxide thermally decomposes to free radicals which initiate polymer chains. It controls the rate of polymerization and the average polymer chain length and melt index. The given monomer ratio yields a polymer with the desired melt properties.
If the total monomer concentration is too high, the exothermic reaction can get out of control. The temperature is limited to at atmospheric pressure because of the boiling point of the reaction mixture. The temperature also affects the decomposition rate and the polymer melt index.
A, B and C were placed in a two-liter resin kettle fitted with a heating mantle and equipped with a 0100 C. thermometer, mechanical stirrer, Friedrick condenser and nitrogen inlet, which extends to beneath the surface of the water. Nitrogen was bubbled below the surface to eliminate any oxygen, which inhibits polymerization, and the mixture was heated with moderate stirring to C. During the heatup period, D was dissolved in the mixture of E, F and G. The water was cooled to 90 C. and nitrogen injection was changed from below the surface to a nitrogen sweep over the surface. The mixture of D, E, F and G was added to the reaction and the temperature controlled at 90 C. The best method of temperature control is an automatic thermowatch. The stirring speed affects the bead size. Insufiicient stirring can cause the reaction to lump or cause formation of large beads. After four hours at 90 C., the temperature was increased to 95 C. and held for one hour. No reflux occurred. The reaction mix was cooled to room temperature, filtered and the beads constituting the filter cake were washed thoroughly with deionized water to remove the polyvinyl alcohol.
The polymer beads were dried for eighteen hours in vacuo at 40 C. The temperature should not exceed 40 or the beads may agglomerate.
This reaction gave 400 g. -100% yield) of a freefiowing polymer bead. The polymer had a melt index at 150 C., 2.16 kg. load, of about 11.0. This corresponds to a weight average molecular weight as measured by gel permeation chromatography of 64,600 :10%. A 35% solution of the polymer in ethylene dichloride contains no gel particles.
A change in the benzoyl peroxide concentration will change the melt index; to increase the melt index or decrease the molecular weight, increase the benzoyl peroxide; to lower the melt index and raise the molecular Weight, decrease the benzoyl peroxide.
The polymer product was then melted and 70 grams of finely divided carbon black (Regal 400-R supplied by Cabot Corp.) were intimately mixed with the molten polymer. The resulting mixture was cooled until it solidified and then jet pulverized to produce particles having, by Weight percent, an average maximum dimension in the range 10 to 20 microns.
The pulverized particles were then passed through a classifier to remove both fine and large particles. The final product contained less than 3% by weight of particles below 5 microns and less than 1% 40 microns or larger.
A number of preparations of toner were made generally following the procedure of the above example. The proportions of the monomers charged to the polymerization reaction were varied and the results indicated that the proportions must be held within the ranges 2 parts by weight n-butylmethacrylate, 21.8 to 2.2 parts by weight sty rene and 0.8 to 1.2 parts by weight methmethacrylate if uniform satisfactory resin properties were to be obtained.
Carbon black is the preferred colorant but other colorants may be dispersed in the resin if desired in the form of pigments, or dyes may be employed. Such other colorants are well known in the art as illustrated, for example, in US. Pat. 3,577,345.
The toner performed excellently in commercial xerographic reproduction machines. It exhibits very strong adherence to the image surface.
In addition to performing reliably in commercial machine operation, the toner of the present invention exhibits unusually resistant to thermal agglomeration. This property was measured by placing toner samples in aluminum dishes and exposing them to varying oven temperatures for 18 hour periods.
Samples of the toner produced pursuant to the above example showed essentially no agglomeration at F.
The toner of the present invention can be stored in any ordinary facility and in any climate without experiencing agglomeration loss.
1. A xerographic toner composition consisting essentially of:
(a) a major proportion of a polymer having a molecular weight in the range 55,000 to 75,000, said polymer being a terpolymer of 2 parts by weight n-bntylmethacrylate, 1.8 to 2.2 parts by weight styrene and 0.8 to 1.2 parts by weight methylmethacrylate, and
(b) finely divided carbon black in amount such that the carbon black constitutes 12-18% of the combined weights of resin and carbon black the carbon black being intimately dispersed in the resin and the resulting dispersion being predominantly in the form of 10-20 micron solid particles.
References Cited UNITED STATES PATENTS 3,391,082 7/ 1968 Maclay 25262.1 3,079,342 11/1963 Insalaco 252-621 2,940,934 6/ 1960 Carlson 25262.1 2,917,460 12/ 1959 Solar 252-621 2,321,048 6/ 1943 Schildknecht 26080.81
NORMAN G. TORCHIN, Primary Examiner I P. BRAMMER, Assistant Examiner US. Cl. X.R. 260-41, 88.1