US2393875A - Method of etching and dampening planographic printing plates and repellent solution t herefor - Google Patents

Description

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Q U Q Patented Jan. 29, 1946 onuoo summits METHOD OF ETCHING. AND DAMPENING .PLANOGRAPHIC PRINTING PLATES AND REPELLENT SOLUTlONTHEREFOR Charles H. Van Dusen, Jr.,- Willoughby, Ohio, as-

, signor to' Addressograph-Multigraph Corporation, Cleveland, Ohio, a corporation of Delaware No Drawing. Application May 29, 1944,

Serial No. 537,972 16 Claims. (01. 101-1492) Ihis invention relates to an etching and dampening or so-called repellent solution for use upon planographic printing plates. The uses and functions or purposes of such solutions are wellknown in the art and are disclosed, for example, in United States Patents Nos. 1,977,646 and 2,003,268, to which reference may disclosure of the general composition and purposes of such solutions. In general it may be said, however, that such solutions are of two types, namely, those which are applied directly to the plates as v a printing operation to renderthe non-printing areas of the plate repellent to greasy or fatty acid-containing printing inks and those which are employed for the same purpose as so-c alled fountain repellent solutions upon rotary offset duplicating machines. In the latter instance the repellent fountain solution in addition to serving as a dampening or repellent solution,

per se, keeps the plate moist and prevents it from scumming up when the machine is stopped temporarily during the printing of long editions.

It is customary to include in such planographic etching and dampening or so-called repellent fountain solutions a hygroscopic agent which has commonly been glycerine. This hygroscopic agent has been, intended purpose and especially when the solu tion is used upon or in conjunction with metal planographic printing plates and as a so-called fountain repellent solution for use upon rotary offset planographic printing or duplicating presses employing such metal plates. It has also been common practice to employ gum arabic in such solutions to increase the moisture-retaining or hydrophilic characteristics of the plates.

However, I have found that certain of the water-soluble glycols including diethylene glycol, ethylene glycol and propylene glycol may be used advantageously as hygroscopic agents in etching and dampening or fountain repellent solutions of the present invention and when so used have certain advantages over glycerine. Among these are that such glycerols are more volatile than glycerine so that when planographic printing plates moistened therewith are removed from the machine they dry rapidly. Howevenf the volatility of such glycols isnot suchas tof cause excessive evaporation when used as the hygroscopic agent in a repellent fountain s01ution for a rotary offset duplicating machine.

etching solutions at the start of,

in general, satisfactory for its be had for a Moreover, when suchglycol hygroscopic agents are used in repellent solutions in conjunction with planographic' printing plates which after use are stored and .onto which additional reproducible matter is added before reuse, it has been found that better results are realized than those attained when glycerine is used as the hygroscopic agent in the repellent solution. This is believed to be due to the factthat since glycerine is not as volatileas the glycols, it tends to remain .on the surface of the plate thereby rendering the same objectionably hydrophilic and this -may interfere with retention on the surface of the added reproducible matter but this is avoided when the glycols referred .to hereinv are used as hygroscopic agents in etching and dampening or fountain repellent solutions;

However, when diethylene glycol or one of the other glycols referred to above, is employed as the hygroscopic agent in such etching and dampening or repellent fountain solutions it has a tendency to cause the blankets used in the:

rotary offset lithographic duplicating presses with which such planographic printing plates and fountain repellent solutions therefor areused tobecome objectionably tacky after a relatively small number of copies or a short edition has.

been run off from the rotary offset duplicating machines or press with which such planographic printing plates and blankets are used. This is objectionable in that it tends to cause the paper sheets, which are run through the press to receive the image from the master plate to adhere printing plates is thus afforded.

A typical example of a suitable formula which ,may be followed in preparing the newcomposition especially for use as an etching solution, when diluted as described hereinafter, for direct SEARCH R00! following example in which all parts indicated are by weight:

Example 1 Parts by weight Monoammonium acid phosphate Water (distilled) (balance) 71.50

A typical example of a suitable formulawhichmay be followed in preparing the new composition especially for use as a fountain -repellent. solution, when diluted as described'hereinej'fter,

is shown in the following example in which all parts indicated are by weight:

Examplefl I-Partsby'wveight Monoammonium acid phosphate In .place of diethylene glycolspecifle'd in the foregoing examples equivalentQuantitiesofetliyI- ene glycol .or propylene gl'ycol, .or mixtures of such water-miscible gglycols, .may' be employed.

v.If desired, the ammonium .nitrate. maybe e'liminated entirely .from the -solutions ,prepared .ac-

. inexpensive and :readily and nompletely watersoluble and :is .free from any tendency :to .form any objectionable precipitate or colloidal suspension. inthe solution. Moreover, .the newsolution containing the .relative quantity .or ,percentage of formaldhydespecifie'd .in the foregoing ex- .amples inhibits mold growth but, .at the same time, is non-toxic and substantially odorlesswhile lhaving a desired.pH value of about4i0.

Thus, equivalent quantities of other water-soluble aldehydesmayibe employed in "Example :2 in place of'the relative quantity of the formaldehyde solution having the strength therein specified, as follows:

"Percent by weiht lPara-vformaldehyde 0.4

-Acetal'dehyde i .W OL-S'Izto 4.0

Benzaldehyde 0.3

percent solutioni s 0.1 33

In preparing the new solution, according to the foregoing examples, it is preferred to mix the formaldehyde directly with the monoammonium phosphate, ammonium nitrate, and nickelous ni- 5 trate, as the dry salts of these three substances. The water is then added, with stirring, so as to dissolve the mixture thus prepared. .The diethyL 'ene glycol, or other water-miscible glycol is then added slowly with continuous stirring. The mix- .ture is then allowed to stand for a few hours, as over night, after which it should be filtered,

"whereuponritma'y belputinto suitable glass bottles or like Lcontainer aand distributed for use.

It ispre'fer'red, however, that the solution be I .allowed to stand forabout a week before it is used -andtha'twhen .used as a fountain repellent soluitionitishould=be-diluted with water in the ratio of about 1 partnfethe solution, prepared as above, to about '7 parts of water, by volume.

.Irhave also found that in place of the glycols "hereinbefore referred to I may also employ as a. hygroscopic agent in such etching and dampening or so-called nt solutions certain water- 'soluble invert sugars sllclifiti example, "as that which is-known commercially "as GER? It -will thus be seen from the foregoing description that the present invention affords a novel 'and 'efli'cient etching and dampening'ands'o-called repellent fountain solution for use upon or in conjunction with planographic printing plates and rotary ofiset printing or duplicating presses employing such planographic"printing'plates. It will also thus be seen that the new solution prepared according to the present invention "accomplishes its intended objects and has the desirable advantages and characteristics including those hereinbefore pointed out and others which are inherent in the invention.

Iclaim:

40 *1. A composition for "etching and dampening *planographicprinting plates comprising'an aque- -ous'solutiono'f an acid phosphate, nickel nitrate, a water-miscible glycol, and 'a water-soluble alde- 'hyde.

2. A compositionfor etching and.dampening plan'ographic .printingpla'tes comprising anaqueous "solution :of an 'acidphosphate, nickel nitrate, a'water-miscible glycol, and formaldehyde.

"3. A "composition for etching and dampening 'planographic printingplates comprisingan aque- "oussolution of amm'onium'aci'diphosphate, nickel nitrate, diethylene .glycol, and -a wateresoluble aldehyde.

'4. A composition "for etching and dampenin ,iplan'ographic printing plates-comprising. anaqueous solution of monoammonium-acid phosphate, ammonium nitrate, nickelous .nitrate, .diethylene glycol, andformal'dehyde.

"5. A composition for etching and dampening 0 "planographic printing .plates comprising an aqueous solution of =an.acid phosphate, a watermiscible ,glycol', and .a wateresolublezalde'hyde.

6. A composition for etching .and .dampening "planographic printing plates .'comprising .an

aqueoussolution of ammonium acid phosphate,

nickel nitrate, ethylene glycol; and a .water solublea'ld'ehyde.

"I. A composition for etching and dampening "plano'graphic printing plates comprising "an 7 aqueous solution "ammonium 'acid phosphate,

nickel nitrate, propylene glycol, and 'a watersoliible aldehyde.

' 8. The improvementin the-art 'o'f printing from pianographic printingplates which c'omprisesthe 76 step 0: treating thenon-printing areas-of the plates with an aqueous solution of an acid phosphate, nickel nitrate, a water-soluble glycol and a water-soluble aldehyde.

9. The improvement in the art of printing from planographic printing plates which comprises the step of treating the non-printing areas of the plates with an aqueous solution of an acid phosphate, nickel nitrate, a water-miscible glycol and formaldehyde.

10. The improvement in the art of printing from planographic printing plates which comprises the step of treating the non-printing areas of the plates with an aqueous solution or" an acid phosphate, a water-miscible glycol, and a watersoluble aldehyde.

11. The improvement in the art of printing from planographic printing plates which comprises the step of treating the non-printing areas of the plates with an aqueous solution of ammonium acid phosphate, nickel nitrate, diethylene glycol and a water-soluble aldehyde.

12. The improvement in the art of printing from planographic printing plates which comprises the step of treating the non-printing areas of the plates with an aqueous solution of monoammonium acid phosphate, ammonium nitrate,

pawns, he: namiwn.

nickelous nitrate, diethylene glycol and formaldehyde.

13. The improvement in the art of printing from planographic printing plates which oomprises the step of treating the non-printing areas of the plates with an aqueous solution of ammonium acid phosphate, nickel nitrate, ethylene glycol and a water-soluble aldehyde.

14. The improvement in the art of printing from planographic printing plates which comprises the step of treating the non-printing areas of the plates with an aqueous solution of ammonium acid phosphate, nickel nitrate, propylene lycol and a water-soluble aldehyde.

15. A composition for etching and dampening planographic printing plates comprising an aqueous solution of a water-miscible glycol and a water-soluble aldehyde, said solution having a pH of approximately 4.

16. A composition for etching and dampening planographic printing plates comprising an aqueous solution of a water-miscible glycol, a watersoluble aldehyde, and an acid phosphate, said solution having a pH of approximately 4.

CHARLES H. VAN DUSEN, JR.