US2197145A - Drying printing inks - Google Patents

Description

April 16, 1940.

As. ENGLE DRYING PRINT-ING INKs Filed Sept. l1, 1937 INVENTOR ATTO EY desired temperature by Patented Apr. 16, 1940 PATENT OFFICE alarms DBYING PRINTING :Nxs

Loy S. Engle, Harrlngtonlark, N. J., assl'gnor to Interchemical Corporation, New York, N. Y., a

corporation o! Ohio Application septembeii1, 1937, serial No. 163,350

4 claims.` (on 3424) 'I-'his invention relates to printing-and has particular reference to a new and novel method of drying printing ink containing a diicultly volatilizable solvent. More particularly, my method 5 contemplates passing the prints through a hot bath of inert material, such as molten metal, to drive oif the solvents from the ink.

Recently, a new type of printing ink has been introduced into the printing art. These inks lo comprise dispersions of pigments in vehicles consisting of plastic to solid binders, dissolved in solvents which are substantially non-evaporating at ordinary press-room temperatures, but which evaporate at elevated temperatures. Prints of 16 these inks. are ordinarily dried either by passing them over a drum heated to a very high temperature orby subjecting them to very high tem-` peratures, of the' order of 1000 F. to 2000 F. for

ra few seconds. Flashing and burning of the ink vapors have likewise. been resorted to in order to improve the drying of such inks.

In order to obtain high press speeds with these methods, the heat applied to the paper must be considerably higher than. that actually required to dry the ink, since the paper passes the heat at such speeds that the prints neverattain maxil.

mum temperature. Because of the use of Such high heats, there is always danger that thel paperv vused will`scorch,`where unusual conditions pern mit of the/ development of too high aheat at some spot on the paper. This is particularly true with heat-sensitive stocks, such as bread wrapper paper, which scorches as low as 200 C.

I have discovered a new and novel method of printingpaper with such inks without danger of scorching,.which comprises passing the printed paper through a bath of inert fluid heated to a temperature suiciently high to cause rapid vaporization of the solvent, but below the scorchw ingpoint of the paper. The paper thus attains 'a maximum temperature above which it cannot rise, thus eliminating the danger of scorching.

'The huid must be substantially non-volatile at the high temperatures used (in the neighborhood o f 150 C. to 200 C.) must not affect the ink orA the paper, and preferably be cheapand easy to heat. The metals are particularly suitable fromall points of yview; and I prefer to use low melting metals and alloys, such as wood metal (1W. P.

65.5 C.) as the heating bath.

The diagrammatic drawing attached. hereto is A illustrative of the process. A. web of paper I, which bears a wet print, passes under a roller 2 into'a bath of molten metal I, maintained at the burners l. The molten scorching point of the paper,

, quires a minimum metal is kept at a uniform temperature by any known thermostatlc device, indicated at 5'. The paper web passes under roll `6 and nally out under roll 1, then over cooling rolls 8 and 9, to a rewind. As can be seen from the drawings, the I rollers 2, 0 and 1 are preferably journalled above the bath to prevent the possibility of contact between molten metal and the roll shaft bearings.

As the paper passes through the bath, 'it rapidly reaches the temlwxature"` of the bath, owing' l to the excellent heat transfer of the metal. The solvent evaporates into the bath, and rises to ifs surface, from whence it is exhausted up a stack I0.

. The metal is of the paper by a doctor blade I I, which wipes the back side clean just as it emerges from the bath. Anypmetal clinging to the printed sideof the paper is removed either by centrifugal force whilev passing about the roll 1 at a high speed, while 20 molten,or by gra ty and centrifugal force while going about the cooling roller 9, after the metal has set a solid. Such metal is collected in a box I2, placed under the roller.

By the use of my method, the bath may be 2B heated up to `temperatures within 10 C. of the with assurance that the paper will not be damaged. This heating re time, because of the high rate of heat transfer of the metal, so that' complete $0 drying maybe obtained with press-stable inks, by keeping the web immersed in the bath for as short a time as 2 to 3 seconds.

As indicated above, I prefer to operate at as high a temperature as possible, while running no a5 danger of scorching the paper. With more heatsensitive stocks, such as Scorch at 200 C to 220 C., I prefer to operate at 180 C. to 200 C.; with less Asensitive stocks (scorching at 250 C. to 300 C.), temperaturesl of225 C. to 240 C. may be o used. i

While my method is particularly applicable to printing inks containing diiiicultly volatilizable solvents, it is likewise applicable to printing inks containing polymerizable synthetic resins and 5 the like which are set largely by heat, as my method provides for the application of maximum heat to the prints without danger of scorching.

What YI claim is:

l. .The method of drying prints of prntinglm` inks containing solvents which are substantially non-volatile at 20 C. but which evaporate rapidly at 150 C., which comprises passing the prints through abath of an inert fluid heatedto a temperature of the order of 150 C. or higher the 5| removed from the unprinted side 13' passage through the bath being completed in a few seconds.

2. The method of drying wet mms containing solvents which are substantialiv non-volatile at 20 C. but which evaporate rapidly at temperatures of the order o1' 150 C. on paper carrying such lms, which comprises passing the paper through a bath of uid metal heated to a temperature of at least the order o1' 150 C., but below the scorching point of the paper, the passage through the bath being completed in a few seconds.

3. 'I'he method of frying wet ilims containing solvents which are substantially non-volatileat 20 C. but which evaporate rapidly at temperatures of the order of 150 C. on paper carrying such films, which comprises passing the paper through a. bath of iiuid metal heated to a tem-` perature of at least the order of 150 C., but be-l low the scorching point of the paper, the passage through the bath being in a few marked side of the, paper with after it emerges from the bath.

solvents which are. substantially non-volatile at seconds, and removing the metal from the unfY a doctor imite- 4. The method of -drying wet lms containing tures of the order of150 C. on papercarrymg such mms, which comprises passing the paper through a bath of fluid metal lheated to a temperature of at least theorder of 150 C.;

-low the scorching point of the the pssagq through the bath being completed'in a few seconds, removing the metal froxnthe side of the paper withY a Adoctor knife after it emerges Afrom the bath,` and from the marked Asideby4 gravity and 1 by centrifugal applied tothepapenr, 1

i f A LoY s'. Y20

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