US2453769A - Preparation of photosetting coating composition - Google Patents

Description

Patented Nov. 16, 1948 lTED s'r I PREPARATION OF PHOTOSETTING COATING COMPOSITION Gerald L. Wendt, New Yer-am. Y., assignor to Sun Chemical Corporation, a corporation of Delaware No Drawing. Original application April #7, 1944;

Serial No. 533,060. Divided and this applica- 1 tion August 21, 1946, Serial No. 692,150

, 8 Claims. E

This invention relates to the preparation of coating and impregnating compositions containing eleostearin, to the compositions so prepared, and tomethods for rapidly drying or setting these compositions.

While there are many industries in which quickdrying coating or impregnating compositions are desirable, the printing industry is one in which such compositions are of great importance. Modern high-speed press operations require inks which will dry quickly enough to avoid the difficulties of smudging, smearing and offsetting. Printing at these high speeds has been made possible by a number of developments, such as by modifying the compositionof the inksor the character of the surface to be printed upon, by heating the printed webs or sheets, or by other means. The present invention therefore is particularly applicable in the printing industry, although it is not limited thereto and may be used in other fields where rapidly-drying coating or impregnating compositions are desired-as in paints, varnishes, and the like.

This application is a division of applicant's copending application Serial No. 533,060, filed April 27, 1944, which has become abandoned, which in turn is a continuation of applica'nts earlier filed application Serial No. 266,682, filed April 7, 1939, which has become abandoned.

Illustrative of the need for rapid drying or setting. of the printed impression to non-offsetting condition before contact with a surface which can cause offsetting or smearing or smudging are the speeds of the traveling paper webs in present day high-speed printing operations. Thes web speeds range for example from 300 to 1800 feet per minute. Hence procedures have been adopted for drying in a very short time-say 3 or 4 seconds or less, and even down to fractions of a second. Because if an ink' were used which required say seconds to dry or set up sufllciently so that it would not oifset, smear or smudge, the

web would have to travel 50 to 300 feet before contacting its printed face in oflsetting relation with any object, e. g., before making a second impression or contacting with a smearing or smudging part of the press mechanism, or before backing up, rewinding, stacking. etc.

Ordinarily the time required for a printing ink to set up sufllciently to avoid offsetting is definitely' less than the time required for complete drying or setting of the same ink. Again, the conditions which contribute toward offsetting vary more or less-p-that is to say, the amount of offsetting,

smearing or smudging, of any given ink at any given point in its drying obviously depends upon the amount of pressure, slipping action. or the like applied to the ink impression.

It is, therefore, an object of the present invention to provide coating and impregnating compositions which can under proper photosetting conditions be dried or set up rapidly to be non-offsetting and non-smudging.

Another object is to provide such proper conditions for effecting rapid drying or setting of these compositions.

Another object is to provide inks, and means for setting them with sufllcient rapidity, which are particularly useful for high-speed printing purposes.

Other objects will be evident from the present disclosure.

In the practicing of the present invention, compositions are prepared which comprise as an essential a substance made up largel or wholly of eleostearin or keto eleostearin, and the said compositions also include such binders, pigments, solvents, or other materials as may be required to make them suitable for the use desired. The present invention comprises, briefly, the preparation of a suitable composition of such kind which is essentially responsive to light of certain limited wave lengths of such range as to photoset with the required and desired rapidity to give nonoifsetting o1- non-smudging or non-smearing condition as stated; taking suitable steps to accelerate appreciably the rapid set-up or drying of said composition under photosetting conditions subsequent to applying it to the object to be coated, impregnated, or impressed; coating, impregnating or impressing the object with the composition; and then subjecting the resulting object to light of suitable wave-length, with or without other accelerating means, to photoset rapidly the coating or impregnation.

It is found, in accordance with the present invention, that eleostearin and keto eleostearin are particularly susceptible to rapid photosetting under the influence of, or irradiation by, certain definite wave length bands of radiation which are severally in the ultraviolet region. The speed of this photosetting can be markedly accelerated by various means, as by adding promoters or by" removing inhibitors, or both, as will be discussed in greater detail below.

Eleostearin is a natural product, which is the glyceryl ester of eleostearic acid. It is found naturally, in the alpha form (i. e., as tri-c-eleostearin), in tung oil, and constitutes about to thereof. A small amount of the beta isomer aesaroo is present in eleostearin and may be made from the alpha isomer; and it is a solid. Both isomers are suitable for use in the present invention, and both are included herein under the term eleostearin.

Keto eleostearin is eleostearin in which all of the radicals of eleostearic acid are replaced by radicals of d-keto eleostearic' acid (licanic acid). These radicals are also known as the eleostearate radicals and the d-keto eleostearate or licanate radical respectively. Qiticica ,oil is largely keto eleostearin.

There are three conjugated double bonds in each of the acid radicals offeleostearin and keto eleostearin. This configuration is potentially extremely reactive and I have found that when initiated and affected by the procedure of the present invention the drying of either eleostearin or keto eleostearin proceeds very rapidly to form a solid three-dimensional molecular structure. In this manner the eieostearin-containing compositions of this invention are rapidly set or dried. For convenience, therefore, the term eleostearin" herein will include not only the isomers, as above stated, but keto eleostearin as well. The term eleostearin is also intended to include herein other closely related compounds of eleostearic acid or keto eleostearic acid which are characterized by containing at least two radicals of one or the other of these acids. Thus, esters of these acids with polyhydric alcohols (of which glycerine is one) are included.

This rapid setting or drying is efiected, as already stated, by the combined action of the accelerating means and of radiation of suitable wave length within the ultraviolet range.

While it is known that radiations within the ultraviolet and within the infrared ranges, as well as visible radiations, may have some physical or chemical efiects upon various materials, including some oils used in inks; no one before has known, as I have discovered, that waves within each of two, mutually exclusive, comparatively narrow wave bands and each of which is within the ultraviolet range, are particularly specific, but difierently so, to effectuate rapid setting of ink materials containing the type of conjugated double bond system in eleostearin. One of these specific bands is the range of waves within 2450-2600 A. and the other is within the 2800-3500 A. range, and the specific and particular efiectlveness of these two mutually exclusive, comparatively narrow wave bands, in the ultraviolet range, are both disclosed and claimed in my said copending application 8. N. 533,060, and the companion application Serial No. 692,151, filed of even date herewith as a division of said application S. N. 533,000 relates more particularly to my'invention with respect to the particular band of waves within the range 2450-2600 A;

" while the instant application, which is also a division of my said application S. N. 533,060, relates more particularly to my invention with respect to the particular band of waves within the range 2800-3500 A.

The range 2800-3500 ii. appears to be specific to ink materials having the type of conjugated double bond system in eleostearin when used to the exclusion of objectionable waves outside said band and particularly to the exclusion of waves within'the band 2450-2600 A, as set out in said copending application S. N. 533,060 and in mycompanion application filed of even date herewith as a division thereof and hereinabove re- 4 ferred to; while the range 2450-2000 is likewise specific in its own different way to ink materials having the type of conjugated double bond system.

in eleostearin, when used to the exclusion of objectionable waves outside said particular band and within the ultraviolet range, and particularly to the exclusion of waves within the other specific band'or range of 2800-3500 5., to which thisinstant application relates. The products which resuit from the use of said 2800-3500 A. wave band have a smooth, glossy surface; while, in contrast if waves within the band 2450-2600 A. are used the products which result have a /dull or matte dividing zone between the ultraviolet and, the

visible radiations) I have found nevertheless that each of these two wave bands, when free from objectionable inhibiting quantities of waves within the ultraviolet range and outside the specific narrow band being used, and particularly when substantially free from waves within the other specified and mutually exclusive band, will have a. very unusual and unexpected specific effect particularly upon materials having the characteristics such as the conjugated double bond system of eleostearin.

In accordance with the invention of themesent divisional application, therefore, I have found, as stated above, that radiation within the range of 2800-3500 A; is particularly'effective in causing rapid setting of such ink materials, containing the selectively afiected constituent such as eleostearin, to produce rapidly set imprints which have a dried oil film with the smooth, glossy surface referred to; and with the waves within such 2800-3500 A. band applied for the setting operation while substantially free of the mutually exclusive waves of the other specified band,-and free from objectionable quantities of other waves in the ultraviolet range.

Acceleration of the photosetting action of waves in this 2800-3500 A. band may be effected by the use of promoters or by the removal of inhibitors, or both. The degree or extent of acceleration will of course depend upon many factors, such as the type and quantity of promoters used, but I prefer to employ accelerating means which will reduce by at least 25%, and preferably by at least 50%, the time required for photosetting under otherwise identical conditinns.

Types of compounds suitable for promoters of the photosetting of eleostearin under the conditions in the present invention are those which are influenced by ultraviolet radiation to activate or release active Br, I, and/or 0.

tion) due to union with oxygen, probably inv cluding the formation of peroxides, together; with some polymerization. This blowing be carried out to a greater orless extent; as desired-that is, the eleostearin may be only partly blown. As is well known, these oils may be bodied by heat alone; however, a different product results from that obtainedby blowing. This resulting heat-bodied product has undergone extensive polymerization, without the formation of compounds with oxygen, and is definitely unsuited for use in the present process.

Alternatively, I may use an extraneous promoter having the foregoing characteristic of activating or releasing active Br, I, and/or under the conditions imposed. Typical of such promoters are the bromine, iodine, and nitro derivatives of methane whereinrat least three of the carbon bonds are attached to active groups, e. g., bromoform, bromal, iodoform carbon tetrabromide, and tetranitromethane. 'Also useful are some other halogen-containing compounds such as heptachloropropane and hexachlorophenol, and certain iodonium compounds and substances which are easily converted thereinto, e. g., iodosobenzene and phenyl iodonium chloride. I have found that the addition of promoters of this type to raw eleostearin accelerates quick setting as much as does the blowing of the eleostearin-or even more, if enough of such promoters is used. They may also be used to promote the setting of blown eleostearin.

A few of these extraneous promoters are so reactive that they will cause the eleostearin compositions containing them to set up even on standing in the dark. of those listed above, tetranitromethane is such a promoter. Tetranitromethane is more or less unstable and hence care should be taken to avoid explosive conditions. Hence such promoters as tetranitromethane would not be used when the composition is to be kept for any length of time before use. Such promoters are, however, entirely suitable if added to the composition immediately before use.

Alternatively to the procedure of adding extraneous promoters to the compositions containing eleostearin, it is ossible to incorporate these promoters in the paper or other surface or article to be coated or impregnated, whereupon these promoters are effective as soon as the composition is applied to such surface or article, and sub-' jected to radiation of appropriate'limited wave lengths as described herein. In following this ting of tung and oiticica oils, which method may be used with or without the promoters, is to remove substances which inhibit the photosetting mercial range of low pressures, or at least in Y heat-bodying the oil, and hencein considerable polymerization without formation of oxygencontaining promoting agents, which, as already stated, is to be avoided prior to subjecting the composition to the desired wave length radiation. A suitable method of distillation is that known as "shortpath molecular distillation," wherein the oil is flowed in a thin film over a heated surface in a chamber under extremely high vacuum, and as the molecules vaporize, they pass quickly to a cooled surface situated a relatively short distance from the heated surface. It is not necessary nor even desirable to distill the eleostearin itself; the important point is to distill off the inhibitors having a higher vapor pressure (lower boiling point). This type of distillation has been recently introduced commercially for the separation of the constituents of more or less complex natural mixtures which would be damaged or destroyed by attempts'to separate them by hitherto used distillation methods.

This procedure of removing inhibitors may be used in conjunction with promoters-promoters including both the blown eleostearin and the extraneous promoters such as carbon tetrabromide, etc, described above. 'Or it may be used without promoters. In ordinary commercial practice, elimination of inhibitors would not ordinarily be performed, because of the expense of doing so, although in some particular instances, as where an extremely rapid photosetting is-desired, such procedure may be advantageously used in addition to the use of promoters.

The procedure of this invention. may be con- I vcniently carried out as follows: A composition of the type desired ismade up, using tung or oiticica oil or mixtures thereof, together with such other materials as may be requirede. g., binders, solvents, other oils such as linseed, pigments, etc.- Means for promoting the photosetting is eifected-either by first blowing the tung or oiticica oil, or by adding an extraneous promoter of the type already described, or by removing inhibitors of photosetting,or by combinations of these. The composition is then applied to the object to be coated, impregnated or impressed-which object maybe glazed or unglazed paper, or wood, cloth, glass, metal, synthetic resin sheets, regenerated cellulosic sheets, etc-and the coated or impressed surface is subjected to a source of light rich in radiation in the 2800-3500A. range. The light source is placed as near as conveniently possible to the imprinted action. 'I'ung and oiticica oils characteristically contain about 10 to 15% of substances other than eleostearin. More or less of these substances can be removed as by the method described below, and those having a vapor pressure above (1. e, a boiling point below that of eleostearin appear to have an inhibiting effect on the photosetting. In other "words, for example, I have found' 'purifled eleostearin more susceptible to the photosetting action by radiation of 2800-3500 A. wave length than'are the raw oils. The, separation .of' these inhibitors from the raw oils may be performed in various ways. For example, it maybe performed by distillation, but most ordinary methods of distillation are not suitablefi as they result either in decomposition of the oil; ,due to the high heat required for distillation even at the ordinary comsurface and is preferably provided with a reflector to concentrate the effective radiations upon such imprinted surface. A distance of one-half to five inches between the imprinted surface and the light source may be used satisfactorily.

Heated air may sometimes be used to advantage to hasten the drying. In place of heated 'air, the paper or other surface to be coated or eleostearin may be exposed in thin films tothe action of radiation of thewave lengths preferred herein, prior to the application of the coating composition to the object and prior to the final photosetting operation. Such preliminary ex- Parts Raw tung oil 40.0 Gum varnish 22.5 Stearinpitch 5.5 Wax compound 3.0 Black pigment 17.0 Blue pigment 12.0

The gum varnish, stearin pitch, and wax compound are conventional substances for making printing inks, and serve their usual functions.

Thus, the stearin pitch assists in controlling length and flow characteristics, and the wax compound reduces tendency to offset. The wax compound may be carnauba or other suitable wax dispersed in an oil such as linseed oil.

To 90 parts of the foregoing ink composition add parts of promoter, e. g., carbon tetrabromide.

The ink thus prepared is-used for printing in high speed press operations in the usual manner. As the paper leaves the printing means, the imprinted surface is exposed to radiation from a source of ultraviolet light equipped with suitable reflecting means so that substantially all of the radiation from such source is directed upon the imprinted .paper. The radiation from the source is such that at least 50% of it falls within the range of 2800-3500 A.; and preferably the source of radiation is controlled, for example, by filters, so that substantially all radiation within the range 2450-2600 A. is effectively removed and is not directed upon the imprinted surface. As pointed out, the presence of such 2450-2600 A. radiation inhibits the action of the 2800-3500 A. radiation. By this procedure the ink is dried to non-offsetting condition in a very short time, of the order of a few seconds or less. The exact time depends upon thickness of the printed impression, surface or finish of the paper, and severity of ofiset conditions, but under average working conditions the drying time to non-offsetting condition will be definitely less than one second. This time can also be shortened still further by having a plurality of tubes, so arranged that the printed impression is subjected successively to the radiation from each of these several tubes, for example. Thus each tube may extend transversely the entire width of the web, and have its radiation portion substantially coextensive with said width, and a series of two or more of these tubes, each with its own reflector and associated mechanism, may be placed at suitable intervals along the line of travel of the web. The distance between these intervals will obviously depend upon the speed of the web, characteristics of ink and paper. and other factors,

and should therefore be determined for each particular set of conditions. The characteristics of some types of tubesmay prevent their extending the full width of the web, hence in such instances a series of shorter tubes may-be used. which series extends the full width. of the web. But with irradiation with the selected wave band drying to non-offsetting or non-smudging condition may be attained within the speed range stated by coordinating the controlling factors as stated.

. The amounts of the various ingredients given in the foregoing example may be varied considerably or replaced by others. in accordance with the characteristics desired in the composition. The raw tung oil may be replaced byoiticica oil; the amount used may be increased or decreased above or below the amount specified. However, it is preferable to use at least about 20% of raw or blown tung or oticica oils or mixtures thereof, in order to give a. composition which will photoset with sufllcient rapidity under the conditions of the procedure of the present invention.

The amount of extraneous promoter may vary considerably, depending upon the nature of the promoter, the results desired, the time the ink must be kept before use, and the presence or absence of inhibitors and of inherent promoter (in the form of the blown oils). In the foregoing example, for instance, the amount of carbon tetrabromide or its equivalent may range be-. tween 1 and 20 parts per 100 parts of the ink base, depending on the speed of drying or setting desired.

It is to be understood that the foregoing disclosure is for the .purpose of illustration of the present invention, and that various changes and modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

. What is claimed is:

1. Method of causing rapid setting of a coating composition which comprises applying a coating composition containing as an essential ingredient not less than 20% of a compound having in its ,molecule at least two radicals of the group consisting of eleostearate and keto eleostearate and subjecting such applied composition to radiation controlled to contain essentially not less than approximately 50% within the wave length band 2800-3500 A.

2. Method of causing rapid setting of a coating composition which comprises applying a coating composition containing as essential ingredients not less than 20% of a compound having in its molecule at least two radicals of the group consisting of the eleostearate and keto eleostearate radicals, and subjecting such applied composition to radiation controlled to contain essentially not less than approximately 50% within the wave length band 2800-3500 A., and to exclude any substantial proportion of a wave length of a band 2450-2600 A.

3. Method of causing rapid setting of a coating composition which comprises applying a coating composition containing a photosetting promoter and, as an essential ingredient, not less than 20 per cent of a compound having in its molecule at least two radicals of the groups consisting of eleostearate and keto eleostearate and subjecting such applied composition to radiation controlled to contain essentially not less than approximately 50 per cent within .the wave length band 2800-3500 A.

4. Method of causing rapid setting of a coating composition which comprises applying a coating composition containing, as an essential ingredient. not less than 20'per cent of a compound having in its molecule at least two radicals of the group consisting of eleostearate and keto eleostearate andfrom -which compound a substantial amount of substances having a vapor I aassnoa pressure above that oi! eleostearin have been removed and subjecting such applied composition to radiation controlled to contain essentially not less than approximately 50 per cent within the wave length band 2800-3500 A.

5. Method of causing rapid setting of a coating composition which comprises applying a coating composition containing a photosetting promoter and, as an essential ingredient, not less than per cent of a compound having in its molecule at least two radicals of the group consisting of eleostearate and keto eleostearate and from which compound a substantial amount of cals, and subjecting such applied composition to radiation controlled to-contain essentially not less than. approximately 50 per cent within the wave length band 2800-3500 A. and to exclude any substantial proportion of a wave length of a band 2450-2600 A.

7. Method of causing'rapid setting of a coating composition which comprises applying a coating composition containing, as an essential ingredient, not-less than 20 per cent of a compound having in its molecule at least two radicals of the group consisting of eleostearate and keto eleostearate and from which compound a. substantial amount of substances having a vapor pressure greater than eleostearin have been removed and subjecting such applied composition to radiation controlled to contain essentially not less than approximately per cent within the wave length band 2800-3500 A., and to exclude any substantial proportion of a wave length of a band 2450-2600 A. 8; Method of causing rapid setting of a coating composition which comprises applying a coat- .ing composition containing a photosetting proinoter and, as an essential ingredient, not less than 20 per cent of a compound having in its molecule at least two radicals of the group consisting of eleostearate and keto eleostearate radicalsand from which compound a substantial amount of substances having a. vapor pressure greater than that of eleostearin have been removed and subjecting such applied composition to radiation controlled to contain essentially not less than approximately 50 per cent within the wave length band 2800-3500 A., and to exclude any substantial proportion of a wave length of a band 2450-2600 A. v

- GERALD L. WENDT.

REFERENCES CITED The following references are of record in the file of this patent:

\ UNITED STATES PATENTS Number Name Date 1,179,414 Ellis Apr. 18, 1916 1,180,025 Ellis Apr. 18, 1916 2,109,774 1 Hooft Mar. 1, 1938 2,213,943 Auer Sep. 10, 1940 OTHER REFERENCES Chemical and Metallurgical Engineering, Sept. 17, 1923, page 533.

a, American Pressman, Sept. 1931, pages 27-30.