US 3060853 A
Description (OCR text may contain errors)
R. K. REMER 3,060,853
Oct. 30, 1962 PRINTING 2 Sheets-Sheet 1 Filed July 16, 1958 I J m INVENIOR.
Oct. 30, 1962 R. K. REMER 3,060,853
PRINTING Filed July 16, 1958 2 Sheets-Sheet 2 INVENTOR.
BY Ads/. 42
United States Patent Ofi ice 3,060,853 Patented Oct. 30, 1962 3,660,853 PRlNTlNG Robert K. Rerner, Elgin, Ill., assignor to Tribune Comparry, Chicago, 1th, a corporation of lilinois Filed July 16, 1958, Ser. No. 748,863 19 Claims. (Cl. 101-426) My present invention relates, generally, to new and useful improvements in printing, particularly, direct, dry offset and rotogravure printing. It involves the combined use of electrically conductive, water-oil base inks (may alternatively be referred to as oil-water base inks), either black or colored, and low-friction fountain knives and rollers, the working surfaces of which are formed with, or carry, permanent solid type lubricants, and, depending on the type of printing one or more of the following: lowfriction press rollers formed of rubber or resilient rubberlike material the ink contacting or working surfaces of which are formed with or carry solid type lubricants; electrically conductive printing blanets; and, electrically conductive impression cylinders (such blankets and cylinders being suitably grounded).
While separate patent protection is being or will be sought by me on some or all of the foregoing features and innovations, the present invention is directed primarily to combinations of them, or certain of them, as improvements in printing processes and instrumentalities so as to obtain the combined, cooperative efiects and interaction thereof, as distinguished from merely independent or additive results.
In view of its greater commercial importance and the fact that it represents one most complete embodiment of the present invention, the process of direct printing (also referred to as relief and letter press printing) will be used as the principal ilustration of the present invention. However, the invention also applies importantly to offset and rotogravure printing and will also be described in connection with these other printing processes. The objects and nature of my invention Will better be understood by first briefly discussing the present status of direct, oflfset and rotogravure printing as commercially practiced, the major defects therein, and the manner in which the present invention overcome these defects and improves the processes.
Considering first the direct printing of newspapers (one of the most important uses of direct printing), news ink has been made according to substantially the same basic formulas for many years. In fact, no one has developed an ink for newsprint paper for use at newspaper printing speed, which improves materially on the conventional, prevailing formulas, based on finely divided carbon black suspended in mineral or petroleum oils. There have always been several glaring faults in news ink, each of which is well known and recognized in the printing industry.
The fact that ink (or rather carbon or other pigment from the ink) is pressed onto, and thereby offset onto, the second impression blanket from the side of the newspaper which has been printed first, when the impression is applied with which to print the second side of the sheet of newsprint, this creates so-called first impression offset. Since the impressions do not always hit at the exact same spot on each revolution, the offset pickup of carbon from the second impression blanket onto the first printed side of the paper shows alongside the printed dots in the shape of the design in the type of the page printed second (i.e. last). It shows particularly when type is printed on the second impression back of cuts (i.e. pictures) on the first impression side. Any show-through or strike-through of ink is increased by the amount of this carbon black offset, such increase appearing in the form of type. This fault has a tendency to spoil the printing on every other page of a newspaper. It has been accentuated in recent years due to the increase of pictures that are printed, whereas in former years the newspapers had printing mostly and fewer pictures.
This fault or problem of so-called first impression offset is considered perhaps the greatest printing problem that newspapers have. In addition to spoiling the appearance of many cuts (pictures) in each newspaper, it is the major cause of refunds and/ or free re-runs allowed to advertisers.
Another defect in newspaper printing which is closely related to first impression oifset is the black rub off from newspapers onto hands, gloves and clothing. This is an annoyance to the reader and undoubtedly has resulted in reduction in newspapers sales.
Still another fault with present news ink and printing processes arises from the fact that the oil in the ink soaks into the newsprint sheet and gives it a greasy appearance which is very undesirable. This fault is referred to as strike-through in the trade. The oily appearance is most noticeable on the reverse of a page when heavily inked large type or solids are printed.
Present news ink films split or separate during the printing process at high speeds and tend to fly over the press room as ink mist. This, together with the oily nature of the ink creates a difiicult and expensive housekeeping problem.
In ofiset (planographic) printing, the problems are much the same as in direct printing. Considerable static friction is created during operation of a printing press. This causes a number of problems, but the main one is that it causes accumulations of lint, fuzz and dust on the blankets and rollers, and such deposits (referred to by pressmen as hickies) may even work back into the inking mechanisms. The eifects of static friction are particularly troublesome in connection with dry ofiset print ing and, as a result, frequent stopping of presses tor clean up is necessary.
The third commerically important printing process is rotogravure or intaglio printing. One of the main difficulties of roto printing is the requirement of heat for drying. At the present time, steam drums and hot air are used on the presses to dry the ink. In addition to the cost of the heat, there is difficulty in getting good register, and the working conditions around the press are objectionable due to the heat and solvent vapors. Because of considerable static friction and tension difficulties there is trouble in the running of the web through the press and web breaks are frequent.
Another difficulty associated with the operation of present rotogravure presses is the deposit of considerable amounts of sediment in fountains and pumps from the present inks and this requires stirring and mixing of inks with frequent cleaning of the fountains and pumps.
Periodic addition of a volatile solvent such as naphtha is presently required for thinning of roto inks and this results in variation in the depth of the printing. Even with efficient recovery systems appreciable amounts of volatile solvent are lost. The cost of recovery and such losses materially add to the cost of rotor printing.
Still another difficulty associated with present roto inks is the necessity to treat the printed sheets with powder at the folders in order to keep sections from sticking together.
The principal object of my invention, generally stated, is the provision of innovations and improvements in printing processes and apparatus which substantially eliminate the foregoing difiiculties currently associated with direct, offset and rotogravure printing.
Another important object of the invention is the provision of such innovations and improvements in direct, offset and rotogravure printing processes inexpensively by using an electrically conductive ink which is on the same order of cost as, or cheaper than, black or colored commercial inks now used for direct, offset and rotogravure printing and by making certain relatively inexpensive changes in existing presses.
7 Another object of the invention is the attaining of the foregoing objects with a material simplification of the presses, i.e. a reduction in the number of press rollers required in direct and offset printing and elimination of drying drums and heat in rotogravure printing.
Certain other objects of the invention will in part be obvious and will in part appear hereinafter.
For a more complete understanding of the nature and scope of the invention reference may now be had to the following detailed description thereof, taken in connection with the accompanying drawings, wherein:
FIG. I- is a diagrammatic showing of a direct printing process such as may be used for printing newsprint;
FIG. 2 is an enlarged diagrammatic view of one type of direct printing unit which may be used in the processes illustrated in FIG. 1;
FIG. 3 is an enlarged fragmentary sectional view taken on line 3-3 of FIG. 2;
FIG. 4 is a side elevational view, partly diagrammatic, illustrating the manner in which one standard type of news press may be modified to incorporate and practice the present invention;
FIG. 5 is a diagrammatic view illustrating the application of the present invention to the dry ofiset printing process; and
FIG. 6' is a diagrammatic view illustrating the application of the present invention to a rotogravure printing process. I
Referring to FIG. -1 of the drawings a roll of newsprint 5 is mounted in known manner on a roll stand whereby the web of newsprint P may be withdrawn and passed in series through two direct printing press impression units so as tobe printed on opposite sides and then conducted to the folder on press delivery. Each of the printing press impression units will be suitably grounded in known manner so that no electrical charges will accumulate or build up on the electrically conductive printing blankets that are used. The web P is guided through the apparatus over a plurality of guide rollers designated at, 8-8. The first guide roller 8 over which the web passes after leaving the first printing unit may be in the form of a so-called potato grater roll, through which air may be discharged onto the freshly printed web from an air supply line as indicated. Each press unit in FIG. 1 comprises a fountain 10; a fountain roll 11; fountain knife 12; an oscillating or distributor roller 13; from rollers 1 1-14; a plate cylinder 15; and an impression cylinder or blanket roll :16.
In accordance with my invention, the ink used in each fountain 19 is a water-oil base, electrically conductive ink which will be described in detail below with illustrative examples under the heading Conductive Ink Formulations. Each fountain knife 12 has a knife blade the working surface of which (i.e. the surface that engages the fountain roll 11) is a low-friction type surface relative to the usual metal or steel blades, and carries a permanent solid type lubricant on the working surface. This element will also be described in detail hereinafter under the heading Fountain Knives. The fountain rolls '11, oscillating rollers 13 and the press or form rollers 14 are formed of rubber or resilient, rubber-like material the surfaces of which are low-friction surfaces as compared with those of conventional steel rollers or rubber or synthetic rubber rolls used for these parts. The working or ink contacting surfaces of rollers 11, 13 and 14 carry, or are provided with, a permanent, solid-type lubricant. The details of the oscillating rollers 13 and the form rollers .14 will also be described in detail hereinafter under the heading Press Rollers." The blankets used on the blanket cylinders 16 are electrically conductive and of special construction and will be described in detail below under the heading Printing Blankets.
Observing the direction of travel of the paper web P, in FIG. 1, it will be seen that when it passes through the left hand printing unit it is printedon one side by the plate cylinder 15. This printed side which has received the first impression then passes over the impression cylinder 16' in the right hand press unit wherein the opposite side of the sheet is printed by the plate cylinder 15.
Referring to FIG. 2, the fountain 10 is shown with a supply of electrically conductive ink indicated at 20. The bottom of the fountain roll 11 dips into the ink 20 in the usual manner. This roll ll may suitably be formed of rubber or rubber-like material as hereinafter described.
The blade 21 of the fountain knife assembly 12 is formed of such material that the friction between the blade and the ink on the fountain cylinder or roll 11 is greatly reduced and practically eliminated. To accomplish'this such blade 21 is made of a material which may be impregnated or otherwise formed to carry a permanent deposit of a solid type lubricant as will be described in detail below under 'the heading Fountain Knives. Preferably, a second fountain knife 19 is provided, also having a solid film lubricant. The knife 19 removes part of the ink on the fountain roll 11 and the blade 21 is carefully set to regulate the ink transferred to the press rollers.
The form rolls 1414 are each mounted for engagement with the distributor roll or ductor roller 13 and also for engagement with the printing cylinder 15 having a printing plate 22 fitted to and secured to its outer surface in known manner. This plate 22 may for example be a stereotype plate such as are commonly used in newspaper printing. The blanket cylinder 16 is provided with an electrically conductive blanket 2'3 which'is suitably secured in place on the exterior of the roll in known manner and the construction of which will 'be described in detail below in connection with FIG. 3. The press rolls, i.e. distributor roller 13 and form rollers 14, are formed in known manner on supporting shafts but differ from the ordinary rubber press rollers used in that they are low-friction rolls so as'to reduce the surface friction on the ink to a negligible value. This is accomplished by providing the surfaces of the press rollers with a permanent type solid lubricant as will be described below in detail under the heading Press Rollers.
It will be seen from the above description in connection with FIGS. 1-2 that in addition to having a wateroil base, electrically conductive ink in the fountain 10, the printing unit also makes use of the special low-friction fountain knives, the low-friction press rollers and the electrically conductive blanket. Each press unit will be grounded in known manner as mentioned.
In FIG. 4 there is illustrated, the manner in which a standard type of high speed news press may be converted to make use of the improvements in direct printing provided by this invention. The press shown has a generally U-shaped frame 25 and conventionally has more press rollers than are shown in FIG. 4. It will be suitably grounded, one ground being diagrammatically known. It has been found that in using the present invention the number of press rollers may be reduced and that as few as three ink transferring rollers may be sufiicient in each impression unit, i.e. a distributor or oscillating roller, and two form rollers. Reducing the number of press rollers is desirable since they require power to drive them, take up room, contribute to the original cost, and increase the maintenance of a press. In designing a new press on the basis of the present invention it could be made simpler, cheaper and lower by reducing the number of rollers. However, one important advantage of the invention is the fact that it may be readily practiced on existing presses.
In the press illustrated in FIG. 4 two fountains will be provided which are indicated diagrammatically at 26 and 27. It will be understood that these may be of the type described above in FIG. 2. The fountains have primary and secondary fountain knives 29 and 29' as shown therein and include the nonfriction rubber fountain rolls designated at 28 and 30 respectively. The fountain rolls 28 and 30 engage underneath or from the bottom side, the distributor rollers 31 and 32, respectively, which in turn engage sets of form rollers 33--33 and 3434, respectively. The form rollers 33 serve to transfer the ink film to the plate cylinder 35 while the form rollers 34 apply the ink film to the plate cylinder 36. The plate cylinder 35' cooperates with a blanket cylinder 37 while the plate cylinder 36 cooperates with a blanket cylinder 38. The web of paper P comes upwardly, in well known manner, from the bottom of the press over guide roller 40 and then into the right hand press unit where it runs between the plate cylinder 35 and the blanket cylinder 37. After passing over one or more additional guide rollers 41 (one shown), the web is return to the left hand side of the press where it passes between the plate cylinder 36 and the blanket cylinder 38 so that it is printed on the reverse side.
In this press unit in FIG. 4 it will be understood that the fountain knives, the press rollers, and the blankets have the construction to be described in detail below under the respective headings Fountain Knives, Press Rollers and Electrically Conductive Blankets.
All of the features of the present'invention described above in connection with the direct printing procms may also be used with the proved results in the dry offset printing process. Referring to FIG. 5, a dry offset press incorporating the principles of this invention is illustrated as comprising a fountain 50 having a low-friction fountain knife 51 (two if desired) and a low-friction fountain roll 52. The fountain roll 52 engages a distributor or oscillating roller 53 which in turn applies the ink film to the form rollers 54. The form rollers 54 engage a plate cylinder 55 which takes up the ink on the areas to be printed and then transfers it to the rubber blanket cylinder 56. The blanket cylinder 56 cooperates with a steel impression cylinder 57 and is covered with an electrically conductive printing blanket such as the blanket 23. The press unit will be suitably grounded so that electrical charges will not accumulate or build up on the blanket 23.
A web of paper or the like designated at P passes through the press from left to right being guided over the guide rollers 5858 so as to pass in between the blanket cylinder 56 and the impression cylinder 57.
The knife blade 51, the press rollers 52, 53 and 54 and the rubber blanket on the blanket cylinder 56 have the same construction, respectively, as described above for the corresponding elements in connection with FIGS.
1-3. That is, the fountain knives 51 and the press rollers 52, 53 and 54 are formed of low-friction material by hav- 5 ing their surfaces provided with deposits or quantities of solid film type lubricant as will be described in detail below. The rubber blanket on the blanket cylinder 56 is electrically conductive and grounded as mentioned above.
Referring to FIG. 6, there is illustrated diagrammatically therein a rotogravure press which utilizes the novel features of the present invention except for the low-fric tion press rollers. The press unit in FIG. 6 comprises a fountain 60 having an intaglio or etched cylinder 61 and a low-friction fountain knife 62. The impression cylinder 63 which cooperates with the etched cylinder 61 is made of rubber or rubber-like material which is compounded so as to be electrically conductive as in the case of the blankets for the blanket cylinders in the direct and offset printing units described above and as will be hereinafter described in detail under the heading Impression Cylinders. Likewise, the impression cylinder 63 is grounded so that static charges do not build up or accumulate thereon. A paper web P is passed through the printing unit in FIG. 6 between the etched cylinder 61 and the impression cylinder 63 by means of guide rollers 64. An electrically conductive ink of the type hereinafter described is utilized in the fountain 60.
CONDUCTIVE INKS As stated above one of the important features of the improvements in printing processes provided by this invention is the utilization of electrically conductive printing inks in conjunction with the other features. While I have formulated a number of such inks, the ten following preferred formulations will serve as illustrative. It will be understood that they are given by way of example only and that variations both as to materials and proportions may be made within normal ranges of equivalency and within the scope of the appended claims.
Example 1 An aqueous carbon black dispersion of the following composition is prepared:
Water kilograms-.. 45.4
Sodium lignosulfonate powder (partially desulfonat'ed if desired--e.g. Marasperse CB of Marathon Corp.) grams 1150 Carbon black (e.g. Raven 11 Channel Black) kilograms" 11.3
Sulphur black hydrosol-water dispersible grams 240 This aqueous dispersion is run for 30 minutes in a colloid mill, e.g. a Kady Colloid Mill, so as to obtain a fine grind, e.g. 7 on the Hedgeman Scale. Using the above carbon black dispersion the following ink formulation is made:
Grams Paraffin oil 800 Petroleum sulfonate (oil-soluble, soda soap obtained in the treatment of mineral oil with strong sulfuric acid, e.g. Amoco AA of Standard 1 (The soda soap may be replaced by petroleum sulfonates neutralized with other bases, e.g. calcium hydroxide or triethanolamine.)
Example 2 Same as Example 1 with 50 grams of glyoxal included in the carbon black dispersion.
Example 3 Same as Example 1 with 100 grams of polyvinylpyrrolidone (20% aqueous solution) or 100 grams of guar gum (20% aqueous solution) included in the carbon black dispersion.
Example 4 An aqueous carbon black dispersion prepared in accordance with Example 1 is used in the following ink formulation:
Grams Parafi'in oil 800 Petroleum sulfonate (Amoco AA) 200 Calcium lignosulfonate 50% solids, neutralized with moropholine 800 Ethofat 60/20 40 Carbon black dispersion 1400 Polyvinylpyrrolidone 20% solution (PVP 20%)-- 20 Procedure:
- (1) Heat paraflin oil to 200 F.
(2) Add petroleum sulfonate with stirring.
(3) Add Ethofat 60/ 20 with stirring.
(4) Add calcium lignosulfonate with stirring.
(5) Add polyvinylpyrrolidone with stirring.
(6) The temperature is increased to 220 F. and maintained at this temperature for 20 minutes.
(7) Cool to 150 F.
(8) Add carbon black dispersion.
(9) Homogenize (e.g. one pass at 4000 p.s.i. through a double-stroke Gaulin-Maton homogenizer).
(10) Chill to room temperature.
Example 5 A varnish of the following composition is prepared: Grams Mineral oil (news ink grade) 1020 Oleamide (e.g. Armid O-Armour Chemicals Co.) 10 Syrian asphalt: 106
l'lhis may be replaced by an equal amount of Gilsonite.
Procedure (a) Pour mineral oil in a three-neck reactor flask and heat to 200 F. with stirring.
(b) Add oleamide and bring temperature to 300 F.
(0) Add Syrian asphalt and react at 300 F. for one hour. A protective blanket, such as gaseous CO should be used to exclude oxygen from the surface. Cool to room temperature and pour into container.
This'varnish and an aqueous carbon black dispersion prepared in accordance with Example 1 are then used in the following ink formulation: 7
Grams Varnish 750 Polyoxyethylene sorbitan mono-oleate (e.g. Span 50 Polyoxyethylene tallow amine (e.g. Atlas G3763) 30 Carbon black dispersion 1100 Procedure:
(1) Heat varnish to F. (2) Add (Span 80 and G3763) with stirring. (3) Add carbon black dispersion with stirring. (4) Stir for 10 minutes. (5) Homogenize (as in Example 1).
Example 6 A varnish of the following composition is prepared:
' Grams Calcium lignosulfonate 50% solids neutralized with morpholine 2000 Direct deep black BAG 1 (Ciba Co.) 300 Dicyandiamide (cyanoguanidine-the dimer of cyanamide) 80 Formaldehyde30% 50 1 May be replaced by any one of the following dyestufis:
Color index number: DyestufE 581 Direct deep black EW extra.
582-..- Direct deep blackRW extra.
864""- Nlgrosine spirit solu'ble.
870 niline black.
878 Sulphur black T extra (the sodium salt of picramic acid).
1102 Anthra black B.
(a) Heat calcium lignosulfonate to 200 F. in a reactor.
(1)) Add black dye with stirring and react together for 20 minutes at 200 F.
(c) Add dicyandiamide.
(d) Add formaldehyde.
(2) React for 30 minutes at 200 F.
Using this varnish, the following ink formulation is made:
Grams Parafiin oil 800 Petroleum sulfonate (Amoco AA) 200 Ethofat 60/20 40 Polyvinylpyrrolidone 20% Q. 20
Calcium lignosulfonate 50% solids, neutralized with morpholine 800 Varnish (above) 1000 Procedure:
(1) Heat parafiin oil to 200 F.
(2) Add petroleum sulfonate with stirring.
(3) Add Ethofat 60/20 with stirring.
(4) Add calcium lignosulfonate with stirring.
(5) Add polyvinylpyrrolidone with stirring.
(6) Heat mixture to 220 F. and hold at this -temperature for 15 minutes.
(7) Discontinue heat and add Varnish with stirring.
(8) Homogenize as in Example 1.
The inks in the foregoing examples are all electrically conductive black inks. Electrically conductive color inks may be made according to the following examples:
Example 7 A pigment dispersion of the following composition is prepared:
Grams Water 700 Sodium lignosulfonate powder as in Example 1... 20 Benzidene yellow press cake 1100 Pigment extender (e.g. calcium carbonate, clay or calcium silicate-Mirocel) 200 Calcium lignosulfonate (as in Example 1) 200 Polyvinylpyrrolidon'e (20% solution) 10 Using this pigment dispersion, the following ink formulation is made:
Grams Paraifin oil (or mineral oil) 800 Petroleum sulfonate (Amoco AA) 30 Ethofat 60/20 120 Calcium lignosulfonate (as in Example 1) 400 Above yellow pigment dispersion 1700 Procedure:
(1) Heat the paraffin oil, petroleum sulfonate and Ethofat to 180 F.
(2) Add calcium lignosulfonate and heat for 10 minutes at 200 F.
(3) Add the yellow pigment dispersion with agitation.
(4) Run mixture through a homogenizer-one pass at 4000 p.s.i.
Example 8 T make a blue ink, follow Example 7 but substitute an equal amount of Milori Blue press cake for the Benzidene Yellow press cake.
Example 9 To make a red ink, follow Example 7 but substitute an equal amount of Barium Lithol Red press cake for the yellow pigment.
Example 10 Formulation:
Grams Calcium lignosulfonate (as in Example 1) 1200 Benzidene Yellow press cake 1200 Sodium silicate (SiO :Na O of 1.9-2.9:1) 200 The above materials are milled together for 30 minutes in a colloid mill (e.g. Kady Mill) and the milling continued with the addition of CO gas to the mill to bring about the formation of a co-precipitate of calcium carbonate and calcium silicate. The yellow pigment may be replaced by blue and red pigments as in Examples 8 and 9.
In the foregoing examples, the depth of the inks may be varied by increasing or decreasing the content of carbon black dye or color pigment.
Among the possible variations in the foregoing examples the sodium lignosulfonate powder may be replaced by the following lignosulfonates of Lignosol Chemicals, Ltd., Canada; calcium lignosulfonate (Lignosol BD); magnesium lignosulfonate (Lignosol ND); ammonium lignosulfonate (Lignosol TSD); and sugar-free sodium lignosulfonate (Lignosol SFX). Likewise, the calcium lignosulfonate 50% solids evaporate may be replaced with the 50% solids evaporates of the following: sodium base sulfite liquor (Lignosol X); magnesium base sulfite liquor (Lignosol N); and ammonium base sulfite liquor (Lignosol TS). The lignosulfonates may be replaced by other lignin materials such as the sodium salt of alkali lignin (e.g. Indulin C. of West Virginia Pulp & Paper).
Each of the foregoing inks is electrically conductive whereas regular news ink is electrically non-conductive. Thus, the resistance of ink made according to Example 1 measured, at 8 volts, 60 cycles A.C. through a sample 1" x 1" x 1" is 81 ohms. The resistance of the same 10 sample measured at 3 volts DC. is initially 125 ohms,
but increases to 400 ohms due to polarization at the PRESS R OLLERS The term press rollers is used herein to designate the fountain rolls, ductor rolls, form rollers and similar rollers which may be used in transferring ink from the fountain to a printing cylinder. Conventionally, some of these rollers are formed of steel, whereas others are formed of rubber or rubber-like plastics. In the present invention all of the press rollers are formed of rubber or of a resilient rubber-like plastic material. One feature that characterizes the press rollers of this invention from the conventional press rollers whether steel or ordinary rubber rollers, is the fact that the surfaces of my press rollers are relatively low-friction surfaces due to the presence of a solid film lubricant thereon to prevent skin friction which is detrimental to the ink. Consequently, friction detrimental to the ink cannot develop between adjacent press rollers or between the press rollers and the fountain knives or ductor knives when the latter are also formed of a low-friction material. If desired, the press rollers may have sufiicient electrical conductivity so that static charges cannot build up thereon.
Among the several formulations which may be used for the purpose of making press rollers for use in the present invention, the following examples are given as illustrative, parts referred to therein being parts by weight:
Example 1A To 75 parts of water are added, 5 parts of Duomeen T diacetate and 20 parts of a solid film lubricant, preferably molybdenum disulfide. This resulting aqueous mixture is dispersed for one hour in a high speed colloid mill and then vacuum dried. Duomeen T diacetate is obtainable commercially from Armour Chemical Co. and has the following structural formula parts of a vinyl-modified silicone rubber polymer, such as Vinyl Silicone W-96 made by Linde Air Products Company, 35 parts of the dried molybdenum disulfide colloidal dispersion as prepared above, and 2 parts of di-tertiary butyl peroxide are milled together. The resulting mixture is then used to make press rollers by making use of known molding equipment in which a steel shaft is supported and the mixture is mold cured onto the shaft at a temperature of approximately 300 F. under steam pressure equal to about lbs. per square inch. After mold curing the finish roll is removed from the mold and the surface is ground in known manner to an accurate dimension and finish. A suitable grinder and honing machine for this purpose is the so-called Micro Grinder of Curtin-Herbert Co., Inc., Gloversville, NY. When such a roll is covered with an electrically conductive ink of the type herein described, the ink is readily slidable on the surface of the roll which acts as if it were permanently lubricated. In other words, for practical purposes there is little or no friction when two such rolls are run together with my ink films wetting the same.
While the molybdenum disulfide is the preferred solid type lubricant for use in formulating the press rollers, it may be replaced in whole or in part with other solid type permanent lubricants such for example as graphite or mica. Also blends of the solid lubricants may be used such as 90 parts of molybdenum disulfide and 10 parts 1 l" of graphite. The proportion of the dried colloidal dispersion may range from 10 to 50 parts in the above formulation depending upon the hardness desiredthe higher amounts resulting in press rollers of increased hardness. The ditertiary butyl peroxide may be replaced by other known curing catalysts.
A press roller made with the rubber mix of this example, having a diameter of 2.75 inches with a steel core .or shaft of 1.25 inch diameter, had a resistance of 70 ohms measured between the outer surface and the shaft. A similar press roller formed of conventional rubber press roller stock was an insulator.
Example 2A To 100 parts of neoprene rubber is added, two parts of an accelerator (e.g. E. I. du Ponts Neozone-phenylalpha-naphthylamine), 4 parts of magnesia, 5 parts of zinc oxide, parts of hydrocarbon rubber oil (e.g. Circo light oil) and 10 to parts of molybdenum disulfide. The resulting mixture is milled on a rubber mill and thereafter is used in making press rollers, in this case being cured at a temperature of approximately 290 F. under steam pressure of approximately 110 lbs. per square inch.
Example 4A To 100 parts of butyl rubber there is added 2 parts of Neozone, 4 parts of magnesia, 5 parts of zinc oxide, 10 parts of hydrocarbon rubber oil and 10 to 20 parts of molybdenum disulfide. This mixture is milled on a rubber mill and then is used in making press rollers in known manner, being cured at a temperature of approximately 340 F. under steam pressure equal to about 110 lbs. per
Example 5A To 100 parts of depolymerized rubber is added, 5 parts of spider sulphur, 0.3 part of diphenyl guanidine, 0.8 part of methyl Tuads (tetramethyl thiuram disulfide), 0.5 part of zinc oxide, and 10 to 20 parts of molybdenum disulfide. The resulting mixture is milled on a rubber mill and then is ready for mold curing at a temperature of approximately 300 F. under steam pressure of approximately 110 lbs. per square inch.
Example 64 To 1000 parts of water are added, 100 parts of calcium lignosulfonate neutralized with an alkaline material such as ammonium hydroxide or morpholine, and 300 parts of a solid film type lubricant such as molybdenum disulfide, wet ground mica or graphite. However, molybdenum disulfide is preferred. The resulting aqueous mixture is ground for approximately 45 minutes in a high speed grinding mill such as a Kady Colloid Mill. The resulting dispersion is added to a latex or plastic polymer in such a proportion that the molybdenum disulfide will equal 10 to 20% by weight of the latex or plastic polymer. The rubberlatexes that may be used include: natural, fluocarbon rubber, butyl, acrylonitrile, neoprene, silicone and ThiokoL. Theplastic polymers that may be used include: nylon, polyvinyl chloride, polyesters, 'epoxy-polyamide combined resins, polyethylene, isocyanates, and combined polyesterv diisocyanate (e.g. VullcalonBayerMonsanto Mfg. Co.) I
The resulting molybdenum disulfide-latex (or plastic polymer) mixture is coagulated or polymerized in known manner and dried. The dried product is then compounded in known manner with rubber oil or plasticizers, molded, and cured in the form of press rollers.
The proportion of molybdenum disulfide or other solid film lubricant in the foregoing formulations is not highly critical. If there is too little the friction on the surface will not be sufiiciently low and the desired low-friction effect will not be obtained. On the other hand, when sufiicient of the lubricant material is incorporated so as to give a low-friction surface, there is no need to add more and it may impart undue hardness of the press rollers and cause compounding difliculties.
The molybdenum disulfide when use as the solid lowfriction material or lubricant, retains its low coefficient of friction over a wide temperature range extending well below and above press temperatures. The kinetic coefiicient of friction (i.e. ,u) for press rollers made according to the foregoing examples with molybdenum disulfide will desirably range between 0.02 and 0.1.
PRINTING BLANKETS Referring to FIG. 3, the blanket which is indicated generally at 23, may comprise an outer layer of rubber or rubberlike material which is formulated so as to be electrically conductive; a layer 76 of cork or cork paper which is also made so as to be electrically conductive; and layers of electrically conductive fabric 77-7 7 on opposite sides of the cork layer 76. A paper underlay 78, which is also treated so as to be electrically conductive, is separately applied to the outer surface of the steel cylinder 16 so as to build up the diameter of the blanket cylinder to the desired dimension for impression. In news presses of the type shown in FIG. 4 an underlay blanket is used instead of the paper underlay. Such an underlay blanket will desirably comprise a cork layer laminated in between fabric layers, all plies being rendered electrically conductive as in the case of the printing blanket 23.
Except for the fact that the various plies which constitute it, are electrically conductive, the printing blanket 23 corresponds, generally, to conventional printing blankets. Desirably, the cork layer 76 is used although satisfactory electrically conductive blankets have been made without this layer, as described in my co-pending ap plication Serial No. 627,467 filed December 10, 1956. Considering first the rubber layer 75, in general, any electrically conductive rubber or rubber-like material of suitable resilience may be used, several of which are commercially known. Preferably it consists basically of either natural or synthetic rubber, although certain plastic materials can be used. Among the various formulations which have been successfully used for the purpose of making the rubber ply or layer 75 of the blanket 23, the following examples are given, parts being by weight unless otherwise specified.
Example 1B To a coating composition comprising 500 grams of depolymerized natural rubber, 10 grams of Arquad S-2C (soy trimethylammonium chloride, 50% active in toluene Armour Chemical Co.) 5 grams of sulphur, 17.5 grams of methyl Tuads (tetramethyl thiuram disulfideR. T. Vanderbilt Co.), 1 gram of diphenyl guanadine, and 23 grams of zinc oxide, there was added 250 grams of acetylene black which was thoroughly dispersed therein by milling. This rubber base composition was then applied to the previously prepared frabric-cork-fabric laminate by calendaring, solution coating, knife coating, or in other suitable manner. The acetylene black serves to provide electrical conductivity to the rubber layer. In place of acetylene black, flaked or colloidal graphite grams) may be used, or certain of the super abrasion furnace (SAF) blacks could be used in substantially the same amount as the acetylene black. However, acetylene black is preferred since it has a molecular structure of linear configuration very similar to that of rubber and thus combines with the rubber in such manner that long chainlike aggregates persist in the compound not only during milling but also when the material is stretched, thereby constituting the most satisfactory filler for imparting electrical conductivity to the compound. After having been applied onto the fabric surface by a suitable method, the rubber layer is cured in known manner and then ground to final dimension and finish on a surface grinding or honing machine, such as the Micro Grinder of Curtin-Herbert Co., Inc. of Gloversville, N.Y.
The outer surface of the honed and ground rubber layer 75 is desirably treated to make it liquid repellent so that it resists pick-up of ink. This treatment helps materially to prevent first-impression offset without deleteriously affecting the electrical conductivity. For example organic solvent solutions of the following materials may be sprayed or brushed onto the surface of the conductive rubber: a mixture of dimethyldichlorosilane and methyl trichlorosilane (e.g. General Electric Companys Dri-Film); tetrafiuoroethylene polymer (du Ponts Teflon); and chromium complex of a long chain fluorocarbon (Minnesota Mining & Manufacturing Co.s Scotch- Guard). After application, the silicone material may be allowed to air dry over night or it may be oven-dried at 350 F. Only a small amount of the silicone material is required and it will wear for a long time before a re-treatment is required. The printing blanket made according to this example may to advantage be given a low-friction surface by incorporating therein a solid film lubricant such as molybdenum disulfide in the manner described above under Press Rollers.
Example 2B A base compound consisting of 100 parts of neoprene rubber, and 0.5 part of an accelerator (e.g. Neozone), to which there was added 100 parts of acetylene black, was milled. In this example the neoprene rubber could be replaced by copolymers of butadiene and styrene or butadiene and acrylonitrile and, if desired, one of the other electrically conductive fillers mentioned in Example 1 may be used in lieu of the acetylene black. 205 parts of the above described base compound was mixed with 0.5 part of an accelerator (e.g. Accelerator 552-piperidinium penta methylene dithiocarbmate), 201 parts of mixed solvents comprising 75% naphtha and 25% xylene, and parts of an antistatic agent such as Arquad S-2-C. The resulting compound after being applied to the fabric layer of the blanket is cured and ground as described.
Example 33 The rubber used in this example was formed by the reaction of sodium polysulfide with ethylene dichloride and is of the type commercially available as Thiokol rubber. To a base compound consisting of 100 parts of Thiokol rubber as the liquid polymer and 0.5 part of methyl Tuads was added 100 parts of acetylene black. The resulting mixture comprising 205 parts of base compound was then mixed with 10 parts of zinc oxide, 201 parts of mixed solvents (75% ethylene dichloride and N-methyl 2-pyrrolidone) and 10 parts of Arquad S-2-C. This mixture was applied to the fabric, and then cured and surface finished.
Example 4B In this example the rubber used was a vinyl-modified silicone rubber polymer (e.g. Vinyl Silicone W-96-Linde Air Products Company). The base compound consisted of 100 parts of vinyl-modified silicone rubber, 2 parts of ditertiary butyl peroxide (catalyst), and 100 parts of toluene, to which was added parts of acetylene black. This mixture was thoroughly mixed whereupon it was ready for application and curing as described above.
Example 5B The base compound in this example consisted of 230 parts chlorinated rubber (e.g. Parlon), and 230 parts of a copolymer of butadiene acrylonitrile (e.g. Paracril), 150 parts of a plasticizer (e.g. Abitol, a mixture of tetra, di, and dehydroabietyl alcohols made from rosin) 150 parts of a plasticizer, diallyl phthalate, 30 parts of a stabilizer (e.g. Deenax), ditertiary butyl-para-cresol), 20 parts of an antistatic agent Arquad S-2-C, 610 parts of methyl ethyl ketone, 1540 parts toluene, to which mixture was added 50 parts of acetylene black. The resulting mixture was mixed and applied and cured as described above in connection with Example 1.
Example 6B To 1000 parts of water are added, parts of calcium llgTlOSUlfOIlfi'tB neutralized with an alkaline material such as ammonium hydroxide or morpholine, 300 parts of acetylene black (for electrical conductivity) and 300 parts of molybdenum disulfide (for solid film lubrication). The resulting aqueous mixture is ground approximately 45 minutes in a high speed grinding mill, such as a Kady Colloid Mill. The resulting dispersion is added to a latex or plastic polymer in such proportion that the amount of molybdenum disulfide will equal 10 to 20% by weight of the latex or plastic polymer. Rubber latexes or plastic polymers of the type mentioned in Example 6 (Press Rollers) may be used. The resulting mixture (i.e. latex or plastic polymer) is coagulated or polymerized respectively, in knOWn manner, and dried. The dried product is then mixed with rubber oil or plasticizers, depending upon whether it has a latex or plastic polymer base, and the resulting mix is applied to one of the fabric layers 77, and then cured and surface finished as described. The resulting rubber layer 75 is electrically conductive, and has a low-friction surface by reason of its content of solid film lubricant.
The conductive cork layer 76 may be made by taking a sheet of cork of suitable thickness and running it between a pair of rollers which have been etched so as to have the surfaces thereof in the form of a multitude of sharp points. The rollers will be mounted in an impregnating mixture such as the liquid formulation described in Example 5 above prior to curing. The points should be long enough so that they extend approximately half way through the cork layer. After having received this impregnating treatment the cork layer with its content of electrically conductive rubber mix is cured. The cork will take up approximately 10% of its weight of the mix and this will be cured under heat and pressure. Another procedure is to disperse ground cork in the mix described in Example 6 above prior to curing. The coated ground cork is then sheeted and cured under heat and pressure.
The fabric plies or layers 77 may be formed of several different types of material such as airplane fabric, sail cloth, cotton duck, nylon, woven glass, Dacron, rayon, or polyester fabrics. I have found that airplane fabric serves very well. The fabric is treated so as to render it conductive by passing through a solution or dispersion of colloidal graphite in a textile paddling machine. Instead of graphite other forms of electrically conductive carbon may be used. While the strength of the dispersion may vary, and is not highly critical, a 28% aqueous dispersion has been found suitable to provide a normally satisfactory degree of conductivity. If desired, a small amount of stannous tin chloride, e.g. one-half percent, may be added to the graphite dispersion, to increase the conductivity. The fabric is passed through the dispersion two or three times so as to take up a maximum amount which will usually be approximately 10% of graphite dry basis based on the weight of the fabric.
After the fabric has been thus substantially saturated with the dispersion, it may be run between squeeze rollers to remove excess of the dispersion and then over drying 15 drums or cylinders. At this point a sample may be taken to measure the graphite pick-up which should be approximately and to measure the conductivity.
If desired, the fabric could be impregnated with a mix of the type described in Example 6 above, and then subjected to curing.
The paper underlay 78 must also be rendered electrically conductive. For this purpose a layer of paper, e.g. tissue paper (which may have a thickness of approximately .001 inch) is saturated with dispersion of colloidal graphite in alcohol. After being so saturated the paper is dried and it is electrically conductive. In place of graphite one of the other forms of electrically conductive carbon could be used such as acetylene black.
After the electrically conductive cork layer 76 and fabric layers 77 have been prepared they may be laminated in known manner using a suitable laminating adhesive such as methylene-bis-(4 phenyl isocyanate) in orthodichlorobenzene (50% concentration) or rubber cement (e.g. Marbon Chemical Companys Multiply Adhesive). The resulting lamination may be used as such as the underlay blanket, and it may also be used in making the printing blanket 23.
The surface of the rubber layer 75 which is contacted by the paper P will normally be hydrophobic as formed, and may be treated so as to make it hydrophilic. Since paper is naturally hydrophilic it will ordinarily be advantageous to so treat the rubber, although because the electrically conductive inks which are used and described above are hydrophilic-hydrophobic, it is not as important as if the inks are hydrophobic only. In order to render the surface of the rubber layer 77 hydrophilic it may be treated with an aqueous solution of a salt such as magnesium carbonate, odium hydroxide, ammonium hydroxide or ethyl silicate. applied with a brush for example.
By the term electrically conductive as used herein in connection with the printing blankets, it is meant to indicate that these blankets have such a degree of electrical conductivity as will be adequate to discharge through the grounding system of the press friction static charges which would otherwise build up during the operation of a press. For example, the resistance was measured between opposite sides of a piece of electrically conductive blanket made according to Example 5, one square inch on a side, at a potential of 4.5 volts at different pressures, with the following results:
Pressure on electrodes in Resistance in ohms pounds per square inch A strip of the same blanket material was taken one inch wide and 6 inches long and its resistance was measured at the potential of 4.5 volts without tension and with ten pounds stretch with the electrodes being on different or the same sides as brought out in the following table:
No tension on strip 16,000 10 pounds stretch 12,000
ONE ELECTRODE O'N RUBBER SIDE AND ONE EIJECTRODE ON FABRIC SIDE No tension on strip 14,000
'10 pounds stretch 10,000
By way of comparison ordinary rubber printing blankets are good electrical insulators.
Such an aqueous solution may be' 7 tion.
1 0 FOUNTAIN OR DUCTOR KNIVES The fountain or ductor knives are made of rigid material the working edge or surface of which is lubricated by a solid film lubricant, preferably molybdenum disulfide, but also either wet ground mica or graphite. While various techniques may be used to provide blades with solid film lubricated surfaces, I prefer to blend the solid lubricant into a plastic mass and then extrude it or use it in injection molding. Various plastics may be used for this purpose including nylon, fluocarbon rubber, silicone, polyesters, polyester diisocyanate (Vullcalon), or any structural plastic material which can be loaded withmolybdenum disulfide or other solid film lubricants to produce throughout an even film or deposit which eliminates fric- The following is a preferred embodiment of such a fountain knife or blade:
Example 1C To parts (by-weight) of nylon molding powder (e.g. du Ponts Zytel 101 or 31 nylon) is added 10 parts of extra fine molybdenum disulfide. The molybdenum was first colloidally dispersed in water and dried preferably in the presence of a material such as Duomeen T diacetate as described in Example 1A (Press Rollers). The resulting mixture is heated to melt the nylon and after blending the mixture is cooled and ground. It is now ready to be used as a molding powder either for extruding or injection molding.
After extruding or injection molding the knife stock is preferably annealed in mineral oil heated to about 350 F. with an inert gas such as nitrogen or carbon dioxide bubbling through the hot oil so as to prevent oxidation. After annealing the material is cooled. The injection molded product is preferred because of its greater dimensional stability and the fact that it does not require finishing other than to be cut to length. The extruded product must be finished and may be given a beveled edge by grinding and polishing, as on the Micro Grinder of Curtin Herbert Co., Inc.
In the above example the nylon may be replaced with du Ponts Delrin (polymerized formaldehyde) or with tetrafluoroethylene resin du Pout-Teflon) Example 2C To parts (by weight) of low viscosity depolymerized rubber are added: 1.5 parts of diphenylguanidine; 12 parts of calcium oxide; 50 parts of sulfur (spider); and 10 to 40 parts of molybdenum disulfide. If desired 10 to 20 parts of refined coaltar oil (Bardol-Barrett Co.) may also be added as a dispersing agent. The mixture is thoroughly blended, molded into the form of a fountain knife and then cured at 275 F. for 8 to 12 hours. The hard rubber-molybdenum disulfide loaded knife may then be ground and polished for use.
IMPRESSION CYLINDERS In rotogravure printing as illustrated in FIG. 6, the impression cylinder 63 is formed of rubber or a rubber-like material. As stated, in the present invention these cylinders are electrically conductive, and if desired, may also have solid film lubricants for giving a low-friction surface.
Any one of the rubber compositions of Examples lB-6B (Printing Blankets) used for the electrically conductive rubber layer 75 of the printing blanket may be used in making the impression cylinder., The rubber will be molded and cured on a steel axle and then the surface will be ground to finish and dimension as described under Press Rollers above.
While in order to obtain the fullest advantage of the present invention and the optimum results an electrically conductive ink, low-friction fountain knives and rollers,
' low-friction press rollers and electrically conductive print- 17 obtain partial, but significant, improvements and advantages in some instances by using less than the full or complete combinations. Specifically, in the direct and offset printing processes good and significantly improved results may be obtained by using electrically conductive inks, low-friction fountain knives and rollers, and low friction press rollers but without using an electrically conductive printing blanket. However, in all cases of direct or offset printing where an electrically conductive ink is used it is practically necessary that low-friction fountain knives, fountain rollers and press rollers also be employed, as otherwise the ink will soon burn up. That is, the friction breaks down or produces a separation of the hydrophilic and hydrophobic portions of the ink films molecular structure and a satisfactory ink film will not be obtained.
In the rotogravure printing process satisfactory printing may be obtained with improved results by using an electrically conductive ink and low-friction fountain knives but with a conventional non-conductive impression roller. However, to obtain the full and optimum results and benefits of this invention, the impression roller should also be electrically conductive.
Having fully described my invention and set forth a number of illustrative examples showing how it may best be practiced, it will be understood that certain changes and modifications may be made therein and other examples may be substituted without departing from the spirit and scope of the invention.
What is claimed as new is:
1. In printing the improvement which comprises using in combination, an electrically conductive ink, a nonmetallic fountain knife the ink contacting surface of which carries a solid film lubricant, and fountain and press rollers comprised of resilient rubber-like material the ink contacting surfaces of which carry a solid film lubricant.
2. In printing the improvement which comprises using in combination, an electrically conductive ink, a nonmetallic fountain knife the ink contacting surface of which carries a solid film lubricant, fountain and press rollers comprised of resilient rubber-like material the ink contacting surfaces of which carry a solid film lubricant, and a non-metallic electrically conductive printing blanket.
3. In printing the improvement which comprises using in combination, an electrically conductive water-oil base ink containing a substantial proportion of a lignin material selected from the group consisting of alkali lignin and lignosulfonate, a fountain knife the ink contacting surface of which carries molybdenum disulfide as a solid film lubricant, and fountain and press rollers comprised of resilient rubber-like material containing molybdenum disulfide as a solid film lubricant.
4. In the direct and dry oifset printing processes the improvement which comprises using in combination, an electrically conductive ink, a non-metallic fountain knife the ink contacting surface of which carries a solid film lubricant, and fountain and press rollers comprised of resilient rubber-like material the ink contacting surfaces of which carry a solid film lubricant.
5. In the direct and dry offset printing processes the improvement which comprises using in combination, an electrically conductive ink, a non-metallic fountain knife the ink contacting surface of which carries a solid film lubricant, fountain and press rollers comprised of resilient rubber-like material the ink contacting surfaces of which carry a solid film lubricant, and a non-metallic electrically conductive printing blanket having an outer surface of rubber rendered liquid-repellent by treatment with a silicone.
6. In the direct and dry olfset printing processes the improvement which comprises using in combination, an electrically conductive water-oil base ink containing a subtantial proportion of a lignin material selected from the group consisting of alkali lignin and lignosulfonate, a fountain knife the ink contacting surface of which carries 1 molybdenum disulfide as a solid film lubricant, and fountain and press rollers comprised of resilient rubber-like material containing molybdenum disulfide as a solid film lubricant.
7. In rotogravure printing the improvement which comprises, using in combination, an electrically conductive ink, a fountain knife the ink contacting surface of which carries a solid film lubricant, and an electrically conductive impression cylinder formed of a resilient rubber-like material.
8. In rotogravure printing the improvement which comprises using in combination, an electrically conductive water-base ink containing a substantial proportion of a lignin material selected from the group consisting of alkali lignin and lignosulfonate, a fountain knife the ink contacting surface of which carries molybdenum disulfide as a solid film lubricant, and an electrically conductive impression cylinder comprised of a resilient rubber-like material.
9. In printing the improvement which comprises using in combination an electrically conductive ink and a nonmetallic fountain knife, the ink contacting surface of which carries molybdenum disulfide as a solid film l-ubricant.
10. In a printing press in combination, a fountain roller, a distributor roller, and form rollers, all being comprised of resilient rubber-like material the ink contacting surfaces of which carry solid film lubricant, and a non-metallic fountain knife the ink contacting surface of which carries a solid film lubricant.
11. In a printing press in combination, a fountain roller, a distributor roller and form rollers, all being comprised of resilient rubber-like material containing molybdenum disulfide as a surface lubricant, and a fountain knife the ink contacting surface of which carries molybdenum disulfide as a solid film lubricant.
12. In a direct printing press, in combination, a fountain roller, a distributor roller, and form rollers, all being comprised of resilient rubber-like material the ink contacting surfaces of which carry solid film lubricant, a nonmetallic fountain knife the ink contacting surface of which carries a solid film lubricant, and a blanket cylinder having a non-metallic electrically conductive printing blanket thereon.
13. In an offset printing press, in combination, a fountain roller, a distributor roller, and form rollers, all being comprised of resilient rubber-like material the ink contacting surfaces of which carry solid film lubricant, a nonmetallic fountain knife the ink contacting surface of which carries a solid film lubricant, and a blanket cylinder having a non-metallic electrically conductive printing blanket thereon.
14. In a rotogravure printing press, in combination, a non-metallic fountain knife for the intaglio cylinder, the ink contacting surfaces of the knife having a solid film lubricant, and an impression cylinder comprised of electrically conductive resilient rubber-like material.
15. In a rotogravure printing press, in combination, a fountain knife the ink contacting surface of which carries molybdenum disulfide as a solid film lubricant, and an impression cylinder formed of electrically conductive resilient rubber-like material.
16. In a printing press, an ink fountain, a fountain roller and a fountain knife unit having a doctor blade with a working edge engaging said roller, said doctor blade being made of a molded, heat-treated low-friction plastic material containing molybdenum disulfide as a solid film lubricant.
17. In a printing press, an ink fountain, a fountain roller and a fountain knife unit having a doctor blade with a working edge engaging said roller, said doctor blade being made of nylon containing molybdenum disulfide as a solid film lubricant, and having been treated by annealing the same in hot mineral oil with an inert gas bubbling through said hot oil.
19 18. The method of making a non-metallic doctor blade for a printing press ink fountain knife which comprises preparing a blended mixture of a low-friction plastic material and molybdenum disulfide, molding the blade from said mixture, annealing the molded blade in hot mineral oil with an inert gas bubbling through said hot oil, and finishing the molded and annealed blade by grinding and polishing the same.
19. The method of claim 16 in which the plastic material is nylon. V
References Cited in the file of this patent UNITED STATES PATENTS 1,963,856 Lewis June 19, 1934 9 Wainwright et al Sept. 1, 1936 Smith Sept. 8, 1942 Lundbye Mar. 16, 1943 Lundbye Oct. 10, 1944 Irion Q. Sept. 14, 1948 Prentiss Ian. 15, 1952 Pyle June 10, 1952 Voet' Oct. 5, 1954 Ward Feb. 11, 1958 Coudriet Apr. 5, 1960 OTHER REFERENCES 15 relied on.
(Copy to be found in Div. 17.)