US3139826A

US3139826A - Inking roller for printing machines

Info

Publication number: US3139826A
Application number: US118015A
Authority: US
Inventors: Claude H Rainwater
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1961-06-19
Filing date: 1961-06-19
Publication date: 1964-07-07
Anticipated expiration: 1981-07-07

Description

INKING ROLLER FOR PRINTING MACHINES Filed June 19, 1961 DAMPENING PLATE DAMPENING ROLLS CYI-lNDER N ROLLS PLATE CYLINDER PAPER OFFSET BLANKET CYLINDER IMPRESSION CYLINDER IMPRESSION CYLINDER INVENTOR. FIG. 6 I c. H. RAlNWATER BY AQLM ATTORNEYS United States Patent 3,139,826 MKL'NG ROLLER FOR PRINTING MACHlNES (Iiaude H. Rainwater, Nowata, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware Fiied June 19, 1961, Ser. No. 118,015 23 @laims. (Cl. 101348) This invention relates to an inking roller for a printing machine. In one aspect this invention relates to an inking roller for a lithographic printing machine. In another aspect this invention relates to an improved inking roller, made of certain plastic polymer materials (defined hereinafter), for a printing machine.

In lithographic printing, sometimes referred to as offset printing, photolithography, photo-offset printing, lithography, or planography, the printing plate is without appreciable relief or depression. The printing image on said plate is ink receptive and the non-image is water receptive. In the actual printing process the non-image area of the plate is first moistened with an aqueous solution by dampening rollers to make said non-image areas ink repellant. The printing image is then inked with the inking rollers, and the ink is finally transferred by pressure from said printing image to the receiving surface.

As is well known to those skilled in the art, there are a number of ways of preparing lithographic printing plates. Said plates can be made of metal, paper, certain plastics, or other materials capable of receiving a greasy image. One of the most common and widely employed of such plates is prepared by typing the printing image on a special paper using a special grease ribbon on an ordinary typewriter. Thus, the resulting printing image has a greasy surface.

The dampening rollers on a lithographic printing machine are made of cloth such as cotton flannel, called molleton, and are fed from a suitable fountain containing a special aqueous solution. Said aqueous solution contains a desensitizing gum and a small amount of an inorganic acid to keep the non-image area of the plate clean. As indicated above, in the printing process the dampening rollers are passed over the plate first and are followed by the inking rollers which apply ink to the printing image. The aqueous solution from said dampening rollers forms a continuous film on the non-image area of the plate and thus prevents adhesion of the ink thereto. However, the water film formed on the surface of the printing image is discontinuous (due to the greasy surface of said printing image) and does not prevent transfer of ink to said printing image by the inking rollers.

Lithographic inks are basically a concentrated dispersion of a suitable pigment, e.g. carbon black, in a viscous oil vehicle and also contain various additives to give the ink suitable working properties. An example of such an additive is a drier to cause hardening of the ink vehicle. Said additives contribute to the difficulties encountered with conventional hard rubber inking rollers, as described hereinafter.

Throughout the history of lithographic printing the inking rollers have been a source of much trouble and expense. Many different materials have been employed for fabricating said rollers. None of said materials have been completely satisfactory and all leave much to be desired. In recent years the most widely employed inking rollers have been made of a hard rubber. While such hard rubber inking rollers represented a distinct advance in the art, they also have left much to be desired.

Said hard rubber inking rollers have a limited life due to mechanical damage, swelling due to absorption of the ink vehicle, and the development on the surface thereof of a vitreous glaze which causes stripping.

The problem of glazing and the resultant stripping is 3,139,826 Patented July 7, 1964 most serious. So far as is now known, this problem exists with all presently commercially available inking rollers and all commercially available lithographic printing inks. The problem is particularly acute when colored inks are employed. Glazing is apparently caused by some form of oxidation reaction between components of the aqueous dampening solution and the additive components contained in the ink. An actual glaze of a vitreous nature forms on the surface of the prior art hard rubber inking rollers. This glaze prevents proper adhesion of the ink to the inking roller. This in turn results in improper application of the ink to the printing image with resultant stripping in the actual printing, i.e., strips of the printing image which do not print. The problem is so severe when employing the hard rubber inking rollers of the prior art that it is usually necessary to clean said rollers every 4 to 7 days. Said cleaning is done manually employing steel wool or some other suitable abrasive. This results in excessive wear to the roller and expensive down time on the printing machine while the rollers are being cleaned.

I have found that the above problems can be eliminated by providing an inking roller having a surface formed of certain plastic polymer material defined further hereinafter. Inking rollers fabricated in accordance with the invention do not glaze and do not require cleaning, other than the normal routine cleaning which is done during the routine overhauls of the printing machine. Even in said routine cleaning it is not necessary to remove glaze. Thus, broadly speaking, the present invention resides in a printing machine inking roller having a surface formed of certain plastic polymer materials as defined further hereinafter.

An object of this invention is to provide an improved inking roller for a printing machine. Another object of this invention is to provide an improved inking roller for a lithographic printing machine which. does not glaze. Another object of this invention is to provide an inking roller for a printing machine which does not need cleaning except for normal routine cleaning carried out during normal routine overhauls of the machine. Still another object of this invention is to provide an improved inking roller which readily takes ink and which naturally repels water. Still another object of this invention is to provide an improved inking roller which is less expensive than the presently commercially available inking rollers. Other aspects, objects, and advantages of the invention will be apparent to those skilled in the art in view of this disclosure.

Thus, according to the invention, there is provided an inking roller for a printing machine, said roller comprising: a cylindrical surface formed of a plastic material selected from the group consisting of homopolymers of l-olefins, copolymers of a l-olefin with another l-olefin as a comonomer, and blends of at least one of said copolymers with polyisobutylene; and shaft means for supporting said surface.

The preferred plastic polymer materials suitable for use in the practice of the invention are the normally solid polymers of aliphatic l-olefins having a density in the range of 0.940 to 0.980, preferably 0.949 to 0.963, grams per cubic centimeter, and a molecular weight in the range of about 35,000 to 250,000. As employed herein and in the claims, unless otherwise specified, the term polymer includes homopolymers of said l-olefins, copolymers of one of said l-olefins with another of said l-olefins as a comonomer, and blends of at least one of said copolymers with normally solid polyisobutylene. The l-olefins having from 2 to 4 carbon atoms per molecule are usually preferred for preparing the plastic polymer materials employed in the practice of the invention. However, any normally solid polymer of a l-olefin 3 having suitable properties as set forth herein can be used in the practice of the invention. Methods for preparing said normally solid polymers of said l-olefins are well known to those skilled in the art. A preferred method for preparing said normally solid polymers of l-olefins is that described and claimed in U.S. Patent 2,825,721 issued March 4, 1958 to I. P. Hogan et al. Polymers prepared in accordance with the method of said patent are known as linear polymers and are available commercially under the trademark Marlex.

A presently preferred plastic polymer material for use in the practice of the invention is a polymer of ethylene prepared in accordance with the method of said patent and having a density of at least 0.940 gram per cc. at 73-78 F., and a molecular weight of at least 35,000. This classification includes, in addition to homopolyrners of ethylene, copolymers of ethylene with higher monoolefins and diolefins, e.g., propylene and l-butene, the higher comonomer generally being incorporated into the copolymer molecule in small proportions as compared with the ethylene monomer. Any desired amount of said comonomer can be utilized to form said copolymer so long as the density of the resulting copolymer is at least 0.940 gram per cc. This classification also includes, in

7 addition to said homopolymers of ethylene and said copolymers of ethylene with said comonomers, blends of said copolymers with a normally solid polyisobutylene having a molecular Weight Within the range of 80,000 to 200,000, preferably 120,000 to 160,000. Preferably, the

polymers of ethylene according to this classification Which are utilized in the practice of the invention Will have a density in the range of about 0.949 to 0.963 grams per cc. and a molecular weight in the range of about 35,000

to about 250,000. Such polymers of ethylene are known in the art as high density polyethylenes.

The copolymers of ethylene with a higher monoolefin which are applicable for use in the practice of the invention are those containing ethylene and at least one higher olefin such as propylene, l-butene, l-pentene, l-hexene, 1-

heptene, l-octene, and the like. An example of such a copolymer suitable for use in the practice of the invention is a copolymer of ethylene with l-butene having a density fwithin the range of from 0.946 to 0.954 gram per cc.

Copolymers of ethylene with l-butene having from 1 to 10, preferably 1.5 to 5, more preferably 1 to 3 weight percent of the 1-butene comonomer incorporated into the copolymer molecule can be utilized in the practice of the invention; Preferably, the density of the copolymer is approximately 0.949 to 0.951 and the melt index is approximately 0.3. Copolymers of this type are preferably prepared by the copolymerization of a major amount of ethylene and a minor amount of l-butene in the presence of a catalyst consisting essentially of chromium oxide supported on a silica-alumina composite, the catalyst containing at least 0.1 Weight percent chromium in the hexavalent state. The total chromium content of the catalyst is generally, though not necessarily, Within the range of 1 to 10 Weight percent of the total catalyst. The copolymerization is frequently carried out at a tempera- Other suitable copolymers, though less preferred than those already described herein, can be obtained by the copolymerization of ethylene and l-butene at approximately the temperatures already described herein, in the presence of a catalyst prepared from or containing organometal compounds. Examples of such catalysts are those obtained by mixing, for example, triethylaluminum with titanium tetrachloride, a mixture of diethylaluminum monochloride and monoethylaluminum dichloride with titanium tetrachloride, a mixture obtained by admixing metallic aluminum with titanium tetrachloride, a mixture of ethylaluminum chloride with titanium tetrabutoxide, and similar catalysts, discussed in more detail in U.S. Patent 2,846,427, issued August 5, 1958, to R. A. Findlay, and U.S. Patent 2,827,447, issued March 18,

V 195 8, to Gene Nowlin and H. D. Lyons.

Blends of said copolymers with polyisobutylene which are suitable for use in the practice of the invention are those blends containing up to 35 Weight percent, preferably from 1 to 35 Weight percent of said polyisobutylene and from 99 to 65 weight percent of a copolymer of ethylene with one of said comonomers. One presently more preferred blend consists essentially of from 65 to 75 weight percent of a copolymer of ethylene and l-butene,

, said copolymer having a density in the range of 0.946 to 0.954, preferably 0.948 to 0.952, and from 35 to 25 percent, respectively, of a polyisobutylene having a molecular weight in the range of 80,000 to 200,000. The preferred polyisobutylene utilized in accordance with this aspect of the invention is a normally solid polymer of isobutylene having a molecular weight in the range of 120,000 to 160,000. Examples of this type of material and the preparation thereof are discussed in U.S. Patent 2,240,582.

The above-described preferred plastic polymer materials are superior to the commercially available low density polyethylenes which are made by what is commonly called the high pressure process, although in some instances said low density polyolefins are useful in the practice of the invention. Such low density high pressure polyethylenes typically have a density Within the range of about 0.910 to about 0.925, a hardness (Shore D) in the range of 40 to 50, a stiffness value, p.s.i., in the range of 10,000 to 25,000 and molecular Weights of less than 25,000.

The above-described preferred polymers of l-olefins will commonly have a stiffness value in the range of about 50,000 to about 155,000 p.s.i., and a Shore D hardness value in the range of about 58 to about 70. Conventional hard rubber inking rolls of the prior art commonly have a Shore D hardness value in the range of about to 85.

The environmental stress cracking value, sometimes referred to as stress-strain cracking value, is an important property of plastic polymer materials which can be utilized in the practice of the invention because it is a measure of the capacity of the polymer to resist stresses and strains which may develop during fabrication and use of articles made therefrom. Plastic polymer materials having low environmental stress cracking values are not desirable for the fabrication of inking rollers for printing machines because rollers made of such materials will frequently develop cracks in use. There is no upper limit on the environmental stress cracking value in the practice of the invention. Some of said preferred plastic polymer materials which can be utilized have an environmental stress cracking value greater than 1000 hours. It is preferred that plastic polymers utilized in the practice of the invention have an environmental stress cracking value of at least 50 hours.

There is a definite correlation between melt index value and environmental stress cracking value. For a given polymer as the melt index value increases the environmental stress cracking value decreases. Therefore, plastic polymer materials having the lowest practical value of melt index should be selected for use in the practice of the invention. The preferred solid polymers of l-olefins defined above which have a melt index of 0.1 to 0.5 are preferred although polymers having melt index values of as much as 1.5, and sometimes higher, are useful in the practice of the invention.

A valuable property of the plastic polymers preferred herein as suitable for utilization in the practice of the invention is their outstanding chemical inertness and nonpermeability. Said preferred plastic polymers are extremely resistant to attack by acids or acidic substances, bases or basic substances, resins, oils, hydrocarbons, etc. Thus, inking rollers made of said preferred plastic polymer materials are not penetrated by the ink and are not subject to swelling caused by the oil or similar material comprising the ink vehicle. In these respects, said preferred plastic polymers are much superior to the abovedescribed commercially available low density polyethylenes.

The following Table I sets forth data comparing the permeability of a typical high density (0.96 g./cc.) polyethylene (one of the above-described preferred polymers) with the permeability of a typical commercially available low density (0.92 g./ cc.) polyethylene. In the test, commercial 4-ounce bottles made of said high density polyethylene and said low density polyethylene were filled with various liquids, seal capped and stored at 80 F. Said bottles had a wall thickness of approximately 0.047 inch. The bottles were weighed periodically over a period of four months and the average rate loss of the contents per week was established. The average loss per year was ob tained by multiplying the average weekly value by 52 and expressing this change as a percent of the original weight Since the loss of the bottle contents was by diffusion through the bottle wall, the above test is considered a good comparison of the permeabilities of said high density polyethylene and said low density polyethylene with respect to the test liquids. It should be noted that in every instance the high density polyethylene is superior, i.e., lesspermeable, to the low density polyethylene.

Another property of said preferred plastic polymer materials which contributes to the superiority of inking rollers made therefrom in accordance with the invention is the self-lubricating property of said plastic polymers. The surface of said preferred plastic polymers has an oily feel, yet said surface is not oily. Said surface naturally repels water but attracts the printing ink. This attraction for ink results in superior ink adherence on rollers fabricated therefrom in accordance with the invention. It has been found that inking rollers made of said preferred plastic polymer materials in accordance with the invention will ink up, i.e., become satisfactorily covered with ink and ready for printing operations, in less than one-half the time normally required for inking rollers made of the conventional hard rubber materials.

Furthermore, once inked up, the inking rollers of the invention remain so with no glaze formation thereon and resulting stripping. While it is not intended to limit the invention by any theory of operation, it is presently believed that the outstanding superiority of the inking rollers of the invention is due, at least in part, to the unique surface properties of the plastic polymer materials used eliminate unnecessary Weight.

in fabricating said rollers. As mentioned above, in the lithographic printing process the non-image area of the printing plate is first moistened or dampened by the dampening rollers. The inking rollers are, of course, exposed to this moisture because they contact the plate after said dampening rollers have contacted said plate. However, since the surface of the inking rollers of the invention naturally repels water, the aqueous solution used for dampening the non-image area of the plate is not available on the roller for reacting with components in the ink to form the vitreous glaze which forms on the conventional inking rollers fabricated of hard rubber. In actual use of inking rollers fabricated from the above-described preferred plastic polymer materials in accordance with the invention, no glazing whatever occurred on the surface thereof, even after substantially continuous use for several months. By way of contrast, the conventional hard rubber rollers must be deglazed about every 4 to 5 days in order to prevent stripping and thus assure a first-class printing job.

Thus, among the more important advantages of the inking rollers of the invention over the conventional hard rubber inking rollers there can be stated (1) complete freedom from glazing and resultant stripping, (2) readily takes ink onto the surface resulting in faster ink up and superior adhesion of ink, (3) the surface naturally repels water, resulting in less contamination of the ink with the aqueous dampening solution, (4) longer life, and (5) less initial cost.

FIGURE 1 is a diagrammatic illustration in elevation of an inking roller fabricated in accordance with the invention.

FIGURE 2 is an enlarged cross-sectional view along the lines 2 2 of FIGURE 1.

FIGURE 3 is a cross-sectional view of another inking roller similar to that of FIGURE 1.

FIGURE 4 illustrates still another modification of an inking roller in accordance with the invention.

FIGURE 5 is a cross-sectional view of another inking roller similar to that of FIGURE 1 except that the portion of the shaft which is covered with the plastic polymeric material is triangular in shape.

FIGURE 6 is a schematic representation of the offset lithography process.

FIGURE 7 is a schematic representation of the direct lithography process.

Referring now to said drawings, the invention will be more fully explained. In FIGURE 1 there is illustrated an inking roller, designated generally by the reference numeral It), fabricated in accordance with the invention. Said inking roller comprises a shaft 11 having a cylinder 12 formed of a normally solid polymer of a l-olefin as described above mounted concentrically on and along a portion of said shaft. Said shaft is also provided with suitable driving gears 13 and 14 mounted thereon.

In FIGURE 3 the inking roller comprises a shaft 11, a cylinder 13 of hard rubber or other suitable base material mounted on said shaft, and a cylinder 14 of a normally solid polymer of a l-olefin as defined above mounted concentrically on said rubber cylinder.

The

shafts

11 and 11 described in FIGURES 1, 2, and 3 can be solid as is illustrated, but in some instances at least, it is preferred to make said shaft tubular so as to Such a tubular shaft is illustrated by the shaft 16 of FIGURE 4. Thus, the inking roller of FIGURE 4 comprises a cylindrical hollow shaft 16 provided with solid reduced end portions 16' which form the journals of the shaft and on which suitable driving gears can be mounted. A cylinder 17 of a normally solid polymer of a l-olefin as described above is mounted concentrically on the cylindrical or hollow portion of said shaft.

Other suitable shaft means can be employed to support the inking rollers of the invention depending upon the type of printing machine in which the roller is to be employed.

' on the non-image area thereof.

In the operation of a lithographic printing machine as represented schematically in FIGURE 6, the printing plate is mounted on the plate cylinder which rotates in the direction indicated by the arrow. As said plate cylinder rotates, the dampening rolls, which are fed from a fountain (not shown) containing a suitable aqueous dampening solution, contact said plate and deposit an aqueous film As the plate cylinder rotates further, it is contacted by the inking rollers which transfer ink from the ink fountain (not shown) to the printing image on the printing plate. Upon continued rotation of the plate cylinder, the now inked printing image contacts the offset blanket cylinder and ink is transferred from the printing image to the surface of said offset blanket cylinder which rotates in the direction indicated by the arrow. Paper is fed between said offset blanket cylinder and the impression cylinder, which rotates in the direction of the arrow as shown, and the ink is transferred by pressure from the offset blanket cylinder to the surface of said paper. Such a printing process is known as Olfset Lithography and the plate is referred to as reading right.

The printing process illustrated schematically in FIG- URE 7 is known as Direct Lithography and operates essentially like that of FIGURE 6 except for the omission of the offset blanket cylinder. In such a process the printing plate reads in reverse.

Any suitable method can be employed for fabricating the inking rollers of the invention. For example, in one method for fabricating a roller as illustrated in FIGURES 1 and 2, a solid bar of plastic polymer material can be drilled to form a bore therein having a diameter slightly less than the diameter of shaft 11, for example about 0.015 inch for a 0.5 inch diameter shaft, so as to form interference when the drilled bar of plastic polymer material is started onto said shaft. Cold pressing of such a drilled bar onto a shaft will result in a tight fit between said shaft and the plastic polymer material. If necessary, the thus assembled shaft and plastic polymer material can then be inserted in a lathe and the surface of the plastic polymer material machined to the desired true diameter.

In fabricating the type of roller illustrated in FIGURE 3, a base core of hard rubber or other suitable material is first mounted on the shaft 11' in any suitable manner. A relatively thin cylinder of plastic polymer material having an inside diameter when cold (room temperature 75- 80 F.) slightly less than the outside diameter of said core is then warmed to a temperature sufiicient to cause expansion but insnfiicient to cause deforming or melting, for

. example in the neighborhood of about 150 to about 200 F. The expanded cylinder is then slipped over the core of hard rubber and allowed to cool. This results in a shrink fit. If desired or necessary the outside surface of said cylinder can then be machined to the desired diameter. The above-described preferred polymers of 1- olefins have Vicat softening temperatures within the range of 240 to 260 F.

The above-described shrink fit method can also be employed in fabricating inking rollers of the type illustrated in FIGURES 1 and 2.

Said shrink fit method is advantageous in converting conventional hard rubber rollers. For example, a conventional roller can be machined in a lathe to the proper outside diameter and a cylinder of plastic polymer material mounted thereon as described.

In another method of fabricating the roller of FIG- URES 1-3 the cylinder of polymer plastic material can be drilled to have a close fitting bore slightly larger than the shaft diameter and then keyed to said shaft as by a spline or other suitable conventional method.

The inking roller of FIGURE 4 can be fabricated according to any of the above-described methods.

If desired, the inking rollers of the invention can be fabricated by placing a suitable shaft in a mold and then molding the plastic polymer material around said shaft.

Also, if desired, the inking rollers of the invention can be fabricated by extruding the plastic polymer material around a suitable shaft. Such a shaft instead of being round or cylindrical as in FIGURES 1 to 4 can be noncylindrical, i.e., polysided such as triangular or square in that portion covered with the plastic polymer material, but of course being provided with round end portions to form the journals for the shaft. Such a polysided shaft is particularly adapted to fabricating the roller by said molding or extrusion methods. Such a polysided shaft would need to be symmetrical as in an equilateral triangle or as in a square for purposes of balance. The polysided shafts can be solid as in FIGURES 1 to 3 or hollow as in FIGURE 4. FIGURE 5 illustrates an inking roller wherein the portion of the shaft 15 which is covered by the plastic polymer material is polysided in the shape of an equilateral triangle.

The following examples will serve to further illustrate the invention.

Example I An inking roller having a length of 10.25 inches and a diameter of 2.25 inches was fabricated from a normally solid commercially available copolymer prepared by the copolymerization of ethylene and l-butene in a cyclohexane slurry of chromium oxide catalyst according to the process described in said US. Patent 2,825,721. The feed to the copolymerization reaction comprised ethylene containing about 5 weight percent l-butene. The copolymer contained about 2.5 weight percent l butene. Typical properties of this commercially available copolymer are:

Density, g./cc. 0.95 .Melt index 0.3 Environmental stress cracking, hrs. 300-400 Vicat softening temperature, F 255 Stiffness, p.s.i 115,000 Hardness, Shore D 67 A solid bar of said copolymer having the proper length Was drilled to provide a bore therein having a tight sliding fit with a steel shaft having an outside diameter of 0.5 inch and a length of 16 inches. Said drilled bar of copolymer was slipped onto said shaft and pinned thereto by inserting a pin through the copolymer cylinder and the shaft. The thus assembled cylinder of copolymer and shaft was then placed in a lathe and the cylinder machined to a true 2.25 inch outside diameter.

Said roller was then installed as the oscillating roller in an Addressograph-Multigraph Model 1250 offset lithographic printing machine. Said machine was operated substantially continuously, except for shut downs at night and over weekends, over a period of several months using said roller in various printing operations with various different inks including the four types set forth below, various different fountain solutions, and various grades of paper. During all these operations no glazing whatsoever occurred on the surface of the roller, and the operation of the roller was completely satisfactory in every respect.

In contrast to this very sucessful operation, when using a conventional hard rubber inking roller in the same machine under essentially the same conditions it has been necessary to stop printing operations and de-glaze the roller every 4 to 5 days in order to avoid stripping.

Example II Subsequent to the successful test described in Example I above a set of four rollers for a Model 1250 Addressegraph-Multigraph offset lithograph printing machine was fabricated. Said rollers were fabricated from the same type of copolymer as described in Example I. Each roller was 11 inches long but each had a difierent diameter. Said diameters were 1.0"; 1.5"; 2.5"; and 2.625.

Each of said rollers comprised a cylinder of said copolymer mounted on a solid steel shaft having a length of about 16 inches and a diameter of about 0.5 inch, and each roller was fabricated as follows. The true diameter of said shaft was determined with a micrometer. A solid bar of said copolymer 12 inches in length was then drilled to provide a cylinder having an inside diameter 0.015 inch less than the diameter of said shaft. The resulting cylinder of copolymer was pressed (coldat room temperature, 7580 F.) onto said shaft. The thus assembled cylinder and shaft was then placed in a lathe and the cylinder machined to the required true outside diameter. Said cylinder was then cut to the 10.25 inch length.

The thus fabricated set of rollers was installed in said printing machine and operated under conditions similar to those described in Example I for several months. During said operation no glazing whatsoever occurred on any of said rollers and the operation of said rollers was satisfactory in every respect.

So far as is now known, inking rollers fabricated in accordance with the invention can be employed when using any of the known commercially available lithographic inks. Inking rollers fabricated in accordance with the invention have been successfully used over periods of several months with no glazing problems what soever with the following four commercially available inks.

(1) Slieght-Hellmuth #41804 Regular Black Offset Ink.

(2) Slieght-Hellmuth #M6427 Multi-Black Offset Ink.

(3) Flint Ink Company #TU1358 OflFset Black Ink.

(4) Slieght-Hellmuth #M5077 Phillips Special Red Offset Ink.

Said inking rollers of the invention have been tested with said inks when using several different aqueous dampening solutions. An example of such a solution is prepared as follows. First, mix Stock Solution A by mixing 1.5 ounces of ammonium dichromate and 0.75 ounces of 85 percent phosphoric acid with 32 ounces of water. Next, mix Stock Solution B by dissolving 16 ounces of magnesium nitrate in suflicient waterto make one gallon of solution. Finally, prepare the finished fountain solution by mixing 0.5 ounces of Stock Solution A, one ounce of Stock Solution B, one ounce of gum arabic (14 Be.), and one gallon of water.

The following test methods were employed in determining the properties of the plastic polymer materials described herein:

Density ASTM D 1505-57T Melt Index ASTM D 1238-57T Environmental Stress Cracking ASTM D 1693-59T Vicat Softening Temperature ASTM D 1525-58T Stiffness ASTM D 747-58T The molecular weight determination is based upon a measurement of the intrinsic viscosity of the polyethylene. The intrinsic viscosity is determined by measuring the time required for a filtered solution of 0.1000 gram of the polyethylene in 50 ml. of tetralin (measured at room temperature, i.e., about 75 F.) to run through the marked length on a size 50 (0.8-3.0 centistokes) Ostwald-Fenske viscosimeter at a temperature of 130 C. (the viscosimeter being immersed in a thermostatically controlled oil bath) and measuring also the time required for an equal volume of tetralin containing no polyethylene to run through the same distance on the same viscosimeter. The molecular weight is calculated in accordance with the following I Vr=time, in seconds, required for solution to run through viscosimeter divided by the corresponding time required for the polymer-free tetralin, both at 130 C.

10 A single determination of molecular weight ordinarily has a precision of :1000 molecular weight units.

While the invention has been described primarily in connection with lithographic printing processes, the inking rollers of the invention can also be employed in other printing processes such as typographic or letter press printing processes.

While certain embodiments of the invention have been described for illustrative purposes, the invention obviously is not limited thereto. Various other modifications will be apparent to those skilled in the art in view of this disclosure. Such modifications are within the spirit and scope of the invention.

I claim:

1. In a printing machine, an inking roller comprising a shaft having a cylindrical covering surface mounted concentrically on and along at least a portion thereof, said covering surface being characterized by freedom from glazing and consisting essentially of a normally solid polymer of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule.

2. An inking roller according to claim 1 wherein said polymer is a polymer of ethylene.

3. An inking roller according to claim 1 wherein said polymer is a polymer of ethylene having a density within the range of 0.940 to 0.980 grams per cubic centimeter, and a melt index within the range of 0.1 to 1.5.

4. An inking roller according to claim 1 wherein said polymer is a polymer of ethylene having a density within the range of 0.949 to 0.963 grams per cubic centimeter, a melt index within the range of 0.1 to 0.5, and an environmental stress cracking value of at least 50 hours.

5. An inking roller for a printing machine, said roller comprising: shaft means, and mounted concentrically thereon a cylindrical surface characterized by freedom from glazing and formed from and consisting essentially of a normally solid plastic material selected from the group consisting of homopolymers of l-olefin hydrocarbons having from 2 to 4 carbon atoms per molecule, copolymers of a l-olefin hydrocarbon having from 2-4 carbon atoms per molecule with another l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule as a comonomer, and blends of at least one of said copolymers with polyisobutylene.

6. An inking rollers according to claim 5 wherein said cylindrical surface is formed of a copolymer of ethylene with l-butene having a density within the range of 0.946 to 0.954 grams per cubic centimeter.

7. An inking roller for a printing machine, said roller comprising: shaft means, and mounted concentrically thereon a cylindrical surface formed from and consisting essentially of a normally solid plastic polymer material having a density in the range of 0.940 to 0.980 gram per cubic centimeter, a molecular weight in the range of 35,000 to 250,000, a stiffness value in the range of about 50,000 to about 155,000 p.s.i., a Shore D hardness value in the range of about 58 to about 70, an environmental stress cracking value of at least 50, and a melt index in the range of 0.1 to 0.5, said plastic polymer material being selected from the group consisting of homopolymers of l-olefin hydrocarbons having from 2 to 4 carbon atoms per molecule, copolymers of a l-olefin hy drocarbon having from 2 to 4 carbon atoms per molecule with another l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule as a comonomer, and blends of at least one of said copolymers with polyisobutylene; said surface being characterized by superior ink adherence and freedom from glazing during use.

8. An inking roller according to claim 7 wherein said cylindrical surface is formed of a copolymer of ethylene and l-butene having from 1 to 10 weight percent of l-butene incorporated into the copolymer molecule, and a density within the range of 0.946 to 0.954 gram per cubic centimeter.

9. A method of printing which comprises transferring ink from an ink supply to a printing surface on a printing plate by contacting said printing surface by rolling action with an ink coated inking roller having a surface formed from and consisting essentially of a normally solid polymer of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule.

10. A method according to claim 9 wherein said polymer is a polymer of ethylene having a density within the range of from 0.940 to 0.980 gram per cubic centimeter.

11. A method according to claim 9 wherein said polymer is a copolymer of ethylene and l-butene having from 1 to 10 weight percent of l-butene incorporated into the copolymer molecule, and a density within the range of from 0.946 to 0.954 gram per cubic centimeter.

12. In a method of printing wherein a printing image on a printing plate is contacted by rolling action with an ink coated inking roller to transfer ink from said roller to said image, and wherein glazing of said roller occurs with resultant stripping during said printing, the improvement comprising the step of contacting said printing image by rolling action with an ink coated inking roller having a non-glazing surface formed from and consisting essentially of normally solid polymer of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule.

13. In a method of printing wherein ink is transferred from an ink supply to a printing image on a printing plate by means including an ink coated inking roller which contacts said image, the improvement comprising trans ferring said ink by contacting said image by rolling action with an ink coated inking roller having a non-glazing surface formed from and consisting essentially of a normally solid polymer of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule.

14. In a method of lithographic printing wherein ink is transferred from an ink supply to a printing image on a printing plate by means including an inking roller which contacts said image, and wherein glazing of said roller occurs which prevents proper adhesion of ink to said roller and causes improper transfer of said ink with resultant stripping insaid printing, the improvement which comprises transferring said ink by means of an inking roller having a non-glazing surface formed from and consisting essentially of a normally solid polymer of ethylene having a density within the range of 0.940 to 0.980 gram per cubic centimeter.

15. A printing machine inking roller comprising a shaft means having a cylindrical covering surface formed with a uniformly true outer diameter mounted concentrically on and along at least a portion thereof, said covering surface being characterized by freedom from glazing and consisting essentially of a normally solid polymer of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule.

16. An inking roller for a printing machine, said roller comprising: a shaft means; and a cylindrical surface having a machine-finished true outer diameter throughout its length, characterized by freedom from glazing, and formed from and consisting essentially of a normally solid plastic material mounted concentrically along at least a portion of said shaft means, said plastic material being selected from the group consisting of homopolymers of 1- olefin hydrocarbons having from 2 to 4 carbon atoms per molecule, copolymers of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule with another 1- olefin hydrocrabon having from 2 to 4 carbon atoms per molecule as a comonomer, and blends of at least one of said copolymers with polyisobutylene.

17. An inking roller for a printing machine, said roller comprising: a cylindrical surface machined to a true outer diameter, characterized by freedom from glazing, and formed from and consisting essentially of a normally solid plastic material selected from the group consisting of homopolymers of l-olefin hydrocarbons having from 2 to 4 carbon atoms per molecule, copolymens of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule with another l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule as a comonomenand blends of at least one of said copolymers with polyisobutylene; 21nd shaft means for concentrically supporting said surace.

18. In a printing machine, an inking roller comprising: shaft means having a cylindrical covering surface mounted concentrically on and along a portion thereof, said covering surface being characterized by freedom from glazing and consisting essentially of a normally solid polymer of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule; and a gear means mounted on each extended end portion of said shaft means.

19. An inking roller for a printing machine, said roller having a surface characterized by freedom from glazing and comprising: a shaft; a cylinder of rubber mounted concentrically on and along a portion of said shaft; and a cylinder formed from and consisting essentially of a normally solid plastic material mounted concentrically on said rubber cylinder; said plastic material being selected from the group consisting of homopolymers of l-olefin hydrocarbons having from 2 to 4 carbon atoms per molecule, copolymers of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule with another l-olefin hydrocarbon having from 2 to 4 carbon atoms per mole cule as a comonomer, and blends of at least one of said copolymers with polyisobutylene.

20. In a printing machine, an inking roller comprising: a cylindrical surface characterized by freedom from glazing and formed from and consisting essentially of a normally solid plastic material selected from the group consisting of homopolymers of l-olefin hydrocarbons having from 2 to 4 carbon atoms per molecule, copolymers of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule with another l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule as a comonomer, and blends of at least one of said copolymers with polyisobutylene; and shaft means, journaled in bearings at each end thereof, for concentrically supporting said surface.

21. A method of fabricating a printing machine inking roller comprising a shaft means supporting a cylindrical covering surface consisting essentially of a normally solid polymer of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule, said method comprising: concentrically mounting a layer of said polymer on and around said shaft means; and machine-finishing said layer of polymer to form said surface with a uniformly true outer diameter.

22. A method of fabricating a printing machine inking roller comprising a shaft means having a cylindrical covering surface mounted thereon, said surface consisting essentially of a normally solid plastic material selected from the group consisting of homopolymers of l-olefin hydro carbons having from 2 to 4 carbon atoms per molecule, copolymers of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule with another l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule as a comonomer, and blends of at least one of said copolymers with polyisobutylene, said method comprising: concentrically mounting a substantially cylindrical layer of said polymer on said shaft means; and machine-finishing said layer of polymer to form said surface with a uniformly true outer diameter.

23. A method of fabricating a printing machine inking roller comprising a shaft means supporting a cylindrical covering surface consisting essentially of a normally solid polymer of a l-olefin hydrocarbon having from 2 to 4 carbon atoms per molecule, said method comprising: concentrically mounting a layer of said polymer on and around said shaft means; and turning said thus mounted layer of polymer in a lathe to form said surface with a uniformly true outer diameter.

(References on following page) 13 14 References Cited in the file of this patent 2,825,721 Hogan et a1. Mar. 4, 1958 2,983,990 Stevenson et a1 May 16, 1961 UNITED STATES PATENTS 2,988,803 Mohn June 24, 1961 2,027,962 Curne Jan. 14, 1936 2,278,982 Frolich Apr. 7, 1942 5 OTHER REFERENCES 2, Hallshalter 00L 1948 vulcanization and Elastomeric Properties of Ethylene 5 Go g 1951 Propylene Copolymers; Rubber and Plastic Age, vol. 42,

2,631,358 Hill Mar. 17, 1953 January 1961, p. 53.

Claims

1. IN A PRINTING MACHINE, AN INKING ROLLER COMPRISING A SHAFT HAVING A CYLINDRICAL COVERING SURFACE MOUNTED CONCENTRICALLY ON AND ALONG AT LEAST A PORTION THEREOF, SAID COVERING SURFACE BEING CHARACTERIZED BY FREEDOM FROM GLAZING AND CONSISTING ESSENTIALLY OF A NORMALLY SOLID POLYMER OF A 1-OLEFIN HYDROCARBON HAVING FROM 2 TO 4 CARBON ATOMS PER MOLECULE.