US2073528A - Method of making printing rolls - Google Patents

Description

Marh 9, 1937." M, M AFF RD 2,073,528

METHOD OF MAKING PRINTING ROLLS Original Filed Sept. 11, 1931 b Wm H is .Attm ne Patented Mar. 9, 1937 UNITED STATES amaze PATENT oFFlca to General Electric Company,

New York a corporation of Original application September 11, 1931, Serial No. 562,353. Divided and this application May 27, 1932, Serial No. 613,853

' Claims.

The present invention relates to printing rolls and method of making the same, and constitutes a division of my copending application, Serial No. 562,353, filed Sept. 11, 1931 and assigned to 5 the same assignee as the present invention.

A principal object of the invention is to produce an improved printing roll which will be oil resistant, will not cause distortion of the characters being printed and have longer life than the present printing roll constructions.

Other and further objects of the invention will be more apparent as the description thereof proceeds.

In the printing industry it is often required to transfer printing from an-embossed metal roll to a rubber covered roll which in turn transfers it to paper or some other material. After these rubber rolls have been in use for a short period of time they absorb oil from the ink causing distortion which in turn causes inaccurate printing. The rubber covered rolls or rolls made of glycerine and glue compositions which are also used in the printing industry are particularly affected in hot weather and by friction. The rolls must be kept 2;, resilient and of the proper consistency suitable to the season so that rolls made for winter use cannot be successfully used in warm weather and vice versa. Present types of rolls have short life and in industries where considerable printing is;

done, as for example in the newspaper industry, frequent changing of rolls especially in hot weather is necessary in order to prevent delay in operations.

In accordance with' the present invention a printing roll has been constructed wherein the surface is'made of a material, which like rubber,

is resilient and flexible, but unlike it does not,

The drawing illustrates somewhat diagrammatically the various steps in the process of making the printing roll' as well as the finished product. In the drawing, Fig. 1 is a view in perspective showing the roll in a preliminary stage of construction carrying a surface sheet of alkyd resin. and ready for the mold.

Fig. 2 is a perspective view partly broken away showing the mold containing the roll illustrated in Fig. 1.

Fig. 3 is a view partly in elevation and partly in section showing the roll held in place by specially constructed means to permit proper curing of the same, and ready for the oven treatment which follows.

Fig. 4 is a perspective view of the finished product, and.

Fig. 5 is a view in perspective of a slightly mod ified form of the roll.

In carrying the invention into practice a roll 'is constructed wherein the surface is of a flexible type of alkyd resin. As is known, alkyd resins include all those complexes resulting primarily from the interreaction of a polyhydric alcohol such as glycerine, and a polybasic acid or its anhydride, such-as phthalic anhydride. These resins may be prepared in various degrees of flexibility, the flexibility being permanent in character. Such resins are more fully described and. claimed in the copending application. of R. H. Kienle and H. C. Rohlfs, Serial No. 393,119, filed Sept. 16, 1929 (now Patent Number 1,897,260 dated Feb. 14, 1933) and assigned to the same assignee as the present invention. Briefly, the resins are prepared by reacting suitable proportions of dibasic aliphatic acid, for example succinic or adipic acid, and dihydric alcohol, for example, ethylene glycol, with the usual alkyd resin ingredients, namely, a polyhydric alcohol having pref erably three or more hydroxyl groups in. the molecule, for example, glycerine, and a polybasic aromatic acid or its anhydride for example, phthalic anhydride. By varying the ratio of dibasic aliphatic acid-dihydric alcohol ester to polyhydric alcohol-polybasic acid ester the de= gree of flexibility of the resinous compositions may be varied. Increasing, for example, the ra= tio of the former to the latter increases the flex= ibility of the resulting resin. v

As an example of the preparation of a resin suitable for use in the construction of the printing roll of the present invention the following is given.

Glycerine, phthalic anhydride, ethylene glycol and succinic acid are taken in proportions such that the ratio of glycol succinate to glycerol phthalate is 4: 1.. The ingredients are heated together in an aluminum vessel to a temperature of 180-200 C. until there is ew'dence of gelation. The melt is then poured into shallow amalgamated tins and cured at about C. or higher from about three to five weeks. The cured resin is tough, resilient and exceedingly flexible under all conditions.

In constructing the printing roll a suitable body portion or core I is first taken. This body portion may be of any material suitable as a core v material for receiving the alkyd resin layer. For example, it may be constructed of steel. On this core is placed a layer or sheet ll of the flexible resin, the resin being wrapped around the core and joined at the meeting edges. In order to prepare this sheet of resin the following procedure is satisfactory:

A composition which is by weight 75% completely cured, 4:1 resin prepared as outlined above is broken down on ordinary rubber compounding rolls into a fine flour consistency and is mixed with of twenty-four hour cured 4:1 resin. After working the mixture on the compounding rolls for a period of time the mass 20 is'formed into a rubber-like sheet. Such fillers as cork, wood fiour, cotton flock, lamp-black, titanium dioxide and the like may be incorporated with the resin, although the pure resin is entirely satisfactory. In order to have a dense 5 material for molding the composition is next placed between fiat steel chromium plated plates and pressed under heat into a fiat sheet of about thickness. The plates are then cooled and the sheet removed. This is the sheet ll enveloping the core Ill.

The mold l2 shown in Fig. 2 is an aluminum split mold provided with end plates I3 removably secured thereto as by screws H. The mold is lined with brass tubing (not shown) and is chromium plated on its inner surfaces. It is designed to hold the core III of the printing roll and the sheet of resin ll wrapped thereon as clearly shown in Fig. 2. After the core wrapped with the alkyd resin has been inserted in the 'mold the mold is closed and allowed to heat,

then pressure is applied. Holes I5 are provided in the end plates of the mold through which excess resin may extrude as a pressure is applied.

Pressure is applied very slowly until the mold has been closed. A pressure of for example 1500-2000 pounds per square inch at a temperature of about 150 C. is satisfactory. After a short time, about 10 minutes, under heat and pressure, the mold is cooled, preferably under pressure, after which the roll is removed. At this stage the roll is considerably over size and the layer of resin is still not totally cured. It is well to mentionthat the inner surfaces of the mold should beadequately covered with a material such as a mixture of soap and mica powder to prevent sticking upon extraction of the roll therefrom. The roll is now ready for the curing operation.

This operation is an important step in the proc- 1 l8 passing through the center of the core ill.

The rod I8 is fixed to the end plates by nuts I9 70 and 20, screwed on the threaded ends thereof.

As will be apparent later, the object of these end plates is to prevent the resin which is still in the plastic stage from being forced over the ends when wound with tape and wire.

" .The end plates being in place and the roll clamped therebetween, a single layer 2| of medium weight cloth tape is wound as tightly as possible over the whole roll. The purpose of this tape is to allow gases generated during curing of the resin to be expelled and at the same time to prevent the layer of cord or wire which will cover the surface from sinking into the roll.

After the roll has been covered with tape it is then wound tightly with a single layer 22 of strong cord or wire, preferably wire, and of say 40 mil dimension. The unit is now placed in a suitable oven,'preferably one which is electrically heated, and maintained at a temperature of 140 C. for a period of twenty-four to ninetysix hours depending on the degree of hardness desired in the resin surface. After ninety-six hours composition has reached the maximum hardness for a 4:1 type of composition.

When the roll has been cured for the requisite period of time it is removed from the oven and allowed to cool slowly. The surface is then machined to size on a lathe using preferably a cutting speed of about 250 revolutions per minute and a feed of about 100 turns per inch. A pointed nose tool having a large rake is satisfactory for this purpose. A smooth surface is thus obtained. An extremely smooth surface can be obtained by providing the surface while machining with emery flour and water.

In Fig. 4 the finished roll 23 is shown, em-

bodying the core I0, and the finished alkyd resin surface 24 on the core.

Fig. 5 shows a slightly modified form of construction wherein there is interposed between the core l0 and alkyd resin layer, a sheet or layer 25 of a resilient material adapted to increase the cushioning orresiliency of the roll. In some cases such a construction may be desirable, as for example in the construction of the cushioning roll in the impression type of rolls. Among suitable resilient materials for this purpose may be mentioned rubber, compositions of cork, gelatin, or oxidized oils, or suitable compositions of such materials. In some cases where an intermediate layer of resilient material is employed it may be practical to provide the layer with a surface of flexible alkyd resin by applying thereto a suitable lacquer embodying such resin or a layer of the fiexible resin may be directly cast either on the core itself or on the intermediate layer 25. At present, however, I prefer the construction shown in Fig. 4 made as described in detail in the foregoing specification. While the preferred resin composition is on wherein the ratio of dibasic aliphatic acid- W dihydric alcohol ester to polyhydric alcohol-K polybasic acid'e'ster is 4:1, this ratio is not the only one which may be employed. Successful combinations for the purpose intended may be made by varying the ratio between the limits 2:1 to 8: 1.

What I claim as new and desire to secure by molecule, a dibasic aliphatic acid and a dihydric I alcohol; and converting the resin to airesilient state. a

2. The method of making a printing roll which comprises providing a core with a; surface layer of flexible alkyd resin containiugthe proqict o! reaction of glycerine, phthalic anhydride, ethylene glycol and dibasic aliphatic acid in the uncured state and curingvsaid resin on said core until a resilient surface results.

3. The method-of making a printing roll which comprises forming a sheet of flexible alkyd resin containing the product of reaction of glycerine, phthalic anhydride, ethylene glycol and dibasic aliphatic acid in the uncured state, wrapping said sheet on a core, molding said core and resin sheet and curing the resin under conditions permitting the escape of gases generated during molding.

4. The method of making a resilient inkresistant printing roll which comprises providing the surface of a steel core with a cushioning layer, wrapping on said layer another layer com-' prising cured and uncured flexible alkyd resins, and curing the latter.

'5. The method of making an oil and inkresistant printing roll which comprises wrapping on a metallic core a sheet .of flexible alkyd resin containing the uncured product of reaction of glycerlne, phthalic anhydride, dihydric alcohol and dibasic aliphatic acid, heating said wrapped core in a mold under pressure, removing the same from the mold, wrapping a porous covering over the surface of the resin and providing the covering with means to keep it in position while permitting the escape of gases during baking, baking the covered core until the desired hardness in the resin surface is obtained, cooling and machining the surface to size.

7 MOYER M. SAFFORD;

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