US2375660A

US2375660A - Method of printing

Info

Publication number: US2375660A
Application number: US424415A
Authority: US
Inventors: Wilbur L Jones
Original assignee: Interchemical Corp
Current assignee: Interchemical Corp
Priority date: 1941-12-26
Filing date: 1941-12-26
Publication date: 1945-05-08
Anticipated expiration: 1962-05-08

Description

Patented May 8, 1945 UNITED STATES 2,375,660 PATENT OFFICE 2,375,660 r ETHOD OF PRINTING Wilbur -L. Jones, New York, N. Y., assignor to Interchemical Corporation, New York, N. Y.,

a. corporation of Ohio No Drawing.

Application December 26, 1941, Serial No. 424,415

4 claims. (Cl. 101-170) tendency to offset and smudge than prints produced by former methods.

Printing with thermoplastic or hot melt inkshas certain obvious advantages over printing cold with conventional inks and has been receiving considerable attention recently. At present such inks have been printed both by the typographic and gravure methods. In printing by the latter method with inks that have lateraly been developed, commercially acceptable results have been obtained, but there nevertheless have been certain limitations, due primarily to the thickness of the film laid dow I have found, for example, that while the appearance of prints produced with an ordinary gravure cylinder is acceptable in the areas of half-tone, the areas of solid color contain noticeable mounds of ink where the flow-out has been incomplete before cooling and solidification of the ink. The film is also thick enough so that there is a pronounced tendency for the prints to offset if stored in a warm room or rewound before the web and ink are entirely cool. Furthermore, due to the thickness of the film, it is somewhat difl'icult to obtain drying or cooling quickly enough altogether to prevent oil'setting, and this obviously limits the ultimate speed at which the printing can be carried out.

I have now discovered that all of these difficulties or limitations in the gravure method of thermoplastic printing can be successfully over- 40 come, and at the same time the process can be rendered far more economical, by (1) printing with anintaglio or gravure cylinder in which the depth of the engraved cells is approximately one third to one half of that normally used and (2) employing an ink which has sufileient pigment to hide the paper properly and with suitable color efl'ect in film thicknesses of from 5 to 15 microns but in insuificient quantity to produce a yield value of over 100 dynes per square centimeter at 0 temperatures at which the ink is printable. The

term "yield value? as used herein refers to a tan.-

gential force (measured in dynes per square centimeter) equivalentto that acting upon an area of one square centimeter that will just produce a flow of a plastic at an infinitely slow rate relative to an area of one square centimeter parallel to the first area and spaced perpendicularly therefrom by a distance of one centimeter.

Thus, the practice of my improved method of to 'fore, produced and used cylinders which have a cell depth of 20 to 30 microns in the areas which produce solid color, as compared with conventional intaglio cylinders which have a cell depth,

in the areas which produce solid color, of from I 40 to microns. Cylinders etched in accordance with my invention are so shallow that solid colors cannot be deposited from them when conventional solvent intaglio inks are used.

However, it should-be understood that the reduction in the depth of the cells of the intaglio cylinder alone, with consequent reduction in the thickness or the applied film, for the attainment of my improved results. My experiments have shown that if the depth of the cells is reduced in the areas of solid color and ordinary thermoplastic inks are employed, proper coverage and colorintensity cannot be obtained. Therefore, it is necessary to increase the pigmentation of the thermoplastic inks to a point where proper coverage and color. intensity can be obtained with the reduced film thicknesses. I have found that if thermoplastic inks are very highly pigmented, so as to produce satisfactory prints in films of the order of 5 microns to 15.

microns in thickness, the tendency to transfer .in piles is substantially reduced. This is due to the fact that the very thin film hasa tendency to adhere to the paper on which it is printed, and

there is insufiicient film to produce an eifective transfer. However, there is a critical upper limit on the amount of pigment that may be addedsince too high a pigmentation may introduce undesirable yield value into the ink compositions and this will produce unsatisfactory fiow-out.

25% of iron blue may be used; and the limits the conventional is not suflicient rise't'o airange of from 30 to 50% for chrome yellow.

Thermoplastic inks of the general character disclosed in my copending application Serial No. 244,607, filed December 8, 1938, may be used in the practice of my improved method. Typical examples of such inks including the particular pigments referred to above are as follows:

EXAMPLE 1 Monotone yellow ink Parts by weight Chrome yellow 35 Hydrogenated castor oil: (M. P- 183 F.) 51

Grinding varnish comprising: Gum rosin (W. W. grade), 50% Raw linseed oil, 50%

The pigment is introduced into the ink by dis persion into the grinding varnish. This ink has a melting point of about 180 F., and at a temperature of 210 F. has a' viscosity of 0.8 poise and a yield value of about '7 dynes per square centimeter. When chilled, it is printable to about 170 F. -It is an excellent ink for printing of monotone yellows.

EXAMPLE 2 Process blue Parts by weight Iron blue 20.0 is ground in a varnish comprising Linseed oil and Alkyd resin (see below) and the paste is mixed with Hydrogenated castor oil 56.6

The alkyd resin in the above ink may be prepared by reacting, at 475 F., 150 parts by weight of the dfloasic acid obtained by reacting molar proportions of dipentene and maleic anhydride, 150 parts of the unsaturated fatty acids obtained by the dehydration of castor oil acids, '70 parts of glycerol, 3 parts of lauryl alcohol and 292 parts of modified rosin ester gum (modified with 20 per cent. of phenol aldehyde resin in known manner) to the point where the resin has an acid value of 9 to 10, and a melting point of 165 F.

This ink has a melting point of 185 F., and is printable at 170 to 175 F. At a temperature of 195 F., the ink has a viscosity of 1.0 poise and a yield value of 4 dynes per square centimeter. This is an excellent process blue, as I have found that best results are obtained when blue process inks have melting pointsabove 160 F., and are printable below 1'75" F.

EXAMPLE 3 Monotone black Parts by weight Carbon black 6.0 Gilsonite 6.8 Methyl violet toner 1.0 Zinc resinate 1.7 Petroleum base ink oil 14.0 Hydrogenated soya bean oil 10.0 Candelilla wax 60.5 F. At

This link has a melting point of 160 amount of pigment in the ink may vary from 6 to 25%; whereas, if the pigment has relatively poor hiding power and low tinctorial value, such as is he case with yellows and other light colors, the amount required in the thermoplastic ink may vary from 30 to50%.

What I claim is:

I l. A method of printing with thermoplastic inks which are solid at normal room temperatures and become liquid when heated to elevated temperatures between 150 and 300 F. which comprises applying to an intaglio printing cylinder, having engraved cells with a depth of from 20 to 30 microns in the areas of solid color, a thermoplastic printing'ink comprising a thermoplastic vehicle and pigment in sufficient quantity completely to hide paper in film thickness of from 5 to 15 microns but in insufiicient quantity to produce a yield value of over dynes per square centimeter at temperatures at which the ink is printable; and transferring such ink from said engraved cells of the printing cylinder to the material being printed.

2 A method of printing with thermoplastic inks which are solid at normal room temperatures and become liquid when heated to elevated temperatures between and 300 F. which comprises applying to an intaglio printing cylinder, having engraved cells with a depth of from 20 to 30 microns in the areas of solid color, a thermoplastic printing ink comprising a thermoplastic vehicle and from'8 to 50% of pigment, the ink having a yield value of less than 100 dynes per square centimeter at temperatures at which the ink is printable; and transferring such ink from said engraved cells of the printing cylinder to the material being printed.

3. A method of printing with thermoplastic ink which are solid at normal room temperatures and become liquid when heated to elevated temperatures between 150 and 300 F. which comprises applying to an intaglio printing cylinder, having-engraved cells wi h a depth of from 20 to 30 microns in the areas of solid color, a thermoplastic printing ink comprising a thermoplastic vehicle and from 6 to 25% of a pigment having good hiding power and high tinctorial value; and transferring such ink from said engraved cells of the printing cylinder to the material being printed.

l. A method of printing with thermoplastic inks which are solid at normal room temperatures and become liquid when heated to elevated temperature between 150 and 300 F. which comprises applying to an intaglio printing cylinder, having engraved cells with a depth of from 20 to 30 microns in the areas of solid color, a thermopla'itic printing ink comprising a thermoplastic vehicle and from 30 to 50% of a pigment having poor hiding power and low tinctorial value; and tlallSfBlILlg such ink from said engraved cells of the printing cylinder to the material being printed.

WILBUR L. JONES.