US3515590A - Temperature stable ink transfer coating compositions - Google Patents

Description

United States Patent O US. Cl. 117235 19 Claims ABSTRACT OF THE DISCLOSURE An ink transfer coating composition of improved temperature stability comprising a pigment dispersed in a resin, a plasticizer and a solvent system compatible with the resin. Low viscosity resins are preferred. The pigment may be finely divided rnagnetizable particles. Specific resins, solvents, and plasticizers are included, as well as surfactants.

FIELD OF THE INVENTION Compositions of matter, having or not having structure, physical form or heterogeneous arrangements of components, including those designed for use as magnetic materials and for impact transfer printing.

PRIOR ART Physical image transfer media such as typewriter ribbons and duplicator stencils are commonly used to transfer a visual image from one medium to another. Each of these transfer media comprises a supporting base of paper or plastic foil, for example, carrying a coating of a pigmented material. For certain applications it is desirable that the coating composition contain a magnetizable medium so that the printed image in turn will be responsive to magnetic detecting means. With the increasing use of computers, for example, that have an ability to read printed matter by optical and by magnetic means, quality transfer coatings become of increasing importance.

Current image transfer coatings as commonly used in the form of typewriter ribbons, or print ribbons in high speed printers, suffer from various inherent disadvantages. It is not unusual for these coatings to contain 8 or 9 or more individual constituents. Many of these constituents are natural fats, oils, or greases, which are subject to the variations that are inherent to any product from a natural source. Many of these coatings show a degradation of print quality when exposed to environmental conditions exceed, for example, 120 F. for periods of longer than 24 hours. Thus storage of print medium utilizing such compositions often requires temperature and humidity control, both in storage and in shipment.

To compensate for some of these problems, the coating composition, which is usually applied to an inert backing, such as polypropylene, polyethylene, Mylar, or other plastics or paper backings, is often applied as a thick coating. This limits the number of feet of, for example, typewriter ribbon, that may be wound on a given reel. Further, the thicker the coating, the more expensive it is to use, as a given quantity coats less backing material. Current compositions also suffer from a lack of batch to batch uniformity, which reflects in part the use of natural materials. Handling of ink transfer coated tapes is often messy, resulting in a transfer of the coating composition onto the mechanical parts of the transfer unit, such as the rollers in a printing unit. This, of course, is clearly undesirable.

Thus it is desirable to produce an ink transfer coating ice composition that can be applied by current methods; on substrates currently in use; having better batch to batch uniformity; that are less expensive; are clean to handle; contain fewer components, and preferably of synthetic materials; and that offer a better print quality than is currently available. Such a composition should also lessen peeling or flaking problems from the environmental storage and use of such tapes, and have improved release characteristics, that is, the ease of transference from the backing to the object printed upon.

SUMMARY OF THE INVENTION The present invention overcomes these and other problems of the prior art by formulating ink transfer compositions having superior release characteristics and improved temperature stability when applied upon a plastic or paper backing material, for example. These compositions include, in one case, a cellulose acetate butyrate resin, a plasticizer, such as dioctyl azelate, a solvent, such as N-propyl acetate, and a pigment dispersed therein, such as carbon black or finely divided magnetizable iron oxide. Alcohol soluble butyrate and cellulose acetate propionate may also be used as the resin, with an appropriate plasticizer and solvent. Composition ranges and materials, and the advantages of these, will be evident from the following objects and general description.

It is an object of this invention to formulate ink tnansfor covering compositions of improved environmental stability that suffers no degradation of print quality in the temperature range of from --20 F. to at least F., even when stored under such conditions for a period exceeding five days.

Another object is to formulate ink transfer coating compositions having improved print quality over those compositions of the prior art.

A further object is to formulate ink transfer coating compositions that may be applied to an inert substrate in a thinner layer than is currently done, thus reducing the cost of the final product, and increasing the amount of such tape that may be stored on standard reels.

Still another object of this invention is to formulate ink transfer coating compositions comprised entirely of synthetic components, resulting in improved batch to batch uniformity.

A further object is to formulate ink transfer coating compositions of improved stability, resulting in a lessening of peeling or flaking of the composition from the backing than is found in the prior art.

A further object is to formulate magnetic ink transfer coating compositions incorporating the improvements of the aforementioned objects.

GENERAL DESCRIPTION We have found that the resins cellulose acetate butyrate, alcohol soluble butyrate, cellulose acetate propionate, or tenth-second butyrate, when combined with certain other materials, all synthetic in nature, results in an ink transfer coating composition that allows us to achieve the objects stated above. These compositions are mixed in the usual manner known in the art, and may be mixed in small or large quantities without any change in the resulting properties. The resulting compositions may then be applied to a backing material by any conventional coating technique, such as spraying, or screening, although we have found the preferred process is to use the well known reverse roll process for applying the composition to the backing material.

While many backing materials may be used, such as Mylar, or polypropylene, we have found it most desirable to use high density polyethylene. The coatings are generally, though not necessarily, applied to a backing of web form, and then cut into ribbons of any desired width by means of conventional slitting machinery. Thus the compositions of our invention have all the advantages of being able to be used with conventional and well known processes of manufacture.

The resins used contain varying percents of aectyl, butyryl, and hydroxyl, and are generally classified by their viscosity using the A.S.T.M. falling ball viscosity test.

The following table, Table I, lists the various resins we have used by the vendor code, in this case those products made by the Eastman Chemical Products Co., the constituents therein, and lastly, the maximum viscosities of each resin that We desire to use in keeping with our In some of our formulations, we have also found it desirable to use a surfactant or Wetting agent. We have found a surfactant comprising fatty amides plus polyethylene glycol ester, such as Tenlo '70, made by the Nopco Chemical Company, to be especially useful. However, other surfactants may be used.

Plasticizers are generally added to resins to impart flexibility and ease of processing. The plasticizers must, of course, be compatible with the resin with which they are to be used. Various plasticizers may be used in formulating the compositions of our invention.

Various solvents may also be used that meet the general requirements that the solvent or solvent system must dissolve the resin system used in the formulation, and the solvent to resin system, from a practical viewpoint, must evaporate at a rate which permits good coating techniques. The preferred solvents are listed with the preferred compositions, to follow.

Various pigments may be used within the compositions of our invention. These include, for example, non-magnetics such as carbon black and zinc oxide, and finely divided magnetizable particles, such as iron oxide, iron alloys, nickel alloys, ferrites, etc. These pigments, well known in the art, impart a color characteristic to the composition, as Well as, in some cases, magnetic properties. These pigments are dispersed within the combination of resin, plasticizer and solvent.

We have found that various iron oxides ranging in size to an average particle size of 2 microns may be advantageously used within the compositions of our invention. We prefer to use an alpha acicular iron oxide of an average particle size of one micron. One such material is known as IRN-IOO, manufactured by C. K. Williams and Co.

The following table, Table II, represents some of the general and preferred compositions within those ranges that we have discovered meet the objects of this invention. It is to be noted that in most cases there are but four constituents within each composition, and that all constituents are entirely synthetic materials, which allows excellent quality control, without the variations normally found in natural materials. Table II lists the compositions of our invention by ranges, and by preferred embodiment within each range.

TABLE II Preferred composition, pa 5 Parts by Wt. General materials Preferred materials by wt 4.5-7.5 EAB-SOO EAB-SOO-l 7 8-15. Plasticizer. Glyceryl trioleate. 10 Pigment. Iron oxide 16. 5 Solvent. Methyl ethyl ketone 50 EAB-171 EAB-l71-2 5 Plastieize 10 Pigment. 16. 5 Solvent N-propyl acetate 50 3-8 EAR-272 EAB-272-3 4. Plasticizer Dioctyl azelate 14 Pigment-.- Iron oxide 16. 5 Solvent N-propyl acetate 50 5-8 Tenth second butyr- Tenth second butyr- 6. 5

ate. ate. 10-18 Plasticizer Dioetyl azelate 14 18 Pigment--. Iron oxide 16. 5 Methyl ethyl ketone 40 EAB-381-1w- 6. 5 Dioctyl azela 12. 5 Iron oxide..- 16. 5 N-propyl acetate 50 5-8 Cellulose acetate pro- Half-second propio- 6 pionate. nate. 10-16 Plasticizer D ioctyl azelate 12 igmen Iron oxide 16. 5 30-60 Solvent Methyl ethyl ketone- 40 5-8 Alcohol soluble butyr- Alcohol soluble butyr- 6 ate. ate.

12 16. 5 40-80 Solvent- 60 The last single number following the vendor designation of the resin represents the falling ball viscosity of that resin. Thus, for example, EAB-SOO-l represents, by the numeral 1, a viscosity of 1 second.

Other pigments may be used in place of the preferred pigment, iron oxide, such as carbon black, iron alloys, etc.

The two most preferred compositions of this invention, used for magnetic ink transfer coatings, are as follows:

N-propyl acetate solvent Tenlo 7O surfacant Finely divided iron oxide pigment 16.5

These composition and those of Table II have been made and tested for environmental stability by placing them in temperature ranges from 20 F. to at least F. for a period exceeding five days, and then subjected to print testing, which has shown no degradation of print quality over this time period. This is in marked contrast to the temperature stability of current ink transfer compositions, shown in the prior art. This temperature stability thus results in a longer shelf life and greater ease of handling with image transfer mediums utilizing the ink transfer coating composition of our invention. This coating composition may be applied thinner than compositions currently in use, due to the temperature stability and uniformity of the compositions, thus allowing winding a greater amount of a tape onto a given reel. Thus .25 mil coatings, instead of current .35 mil thick coatings, may 'be used. The use of all synthetic materials, which have greater parameter control than natural materials,

and the use of as few as four constituents, which allows greater accuracy in mixing and blending, clearly allows better batch to batch uniformity. Further, these compositions, through temperature stability and uniformity of mixing, lessen peeling problems and flaking problems found in present print compositions. The increased temperature stability and uniformity of these compositions results in ribbons that exude very little oil, with the result that they are very clean to handle, and do not dirty the mechanical parts with which they come into contact in the course of use. The combination of the above helps result in improved print quality.

While coating compositions taught by our invention would most readily be applied to one Side of a substrate, and transfer effected by impacting the other side of the substrate, as in the usual typewriter or print system, it is clear that these compositions may be utilized wherever a high quality ink transfer coating composition is required.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

'1. A transfer sheet comprising a substrate having thereon the dried residue of a coating composition consisting essentially of, in parts by weight:

3 to 8 parts of a resin selected from the group consisting of cellulose acetate butyrate and cellulose acetate propionate;

3 to 16 parts of a plasticizer comparable with said resin, selected from the group consisting of dioctyl azelate, glyceryl mono ricinoleate, and glyceryl trioleate;

40 to 80 parts of a solvent system capable of dissolving said resin, selected from the group consisting of N-propyl acetate, methyl ethyl ketone, and ethanol; and

13 to 18 parts of a pigment capable of being dispersed within said resin, plasticizer, and solvent.

2. The transfer sheet of claim 1 wherein said pigment is finely divided magnetizable material.

3. The transfer sheet of claim 1 wherein said pigment is finely divided iron oxide material.

4. The transfer sheet of claim 1 wherein said composition includes a surfactant of the class consisting of fatty amides and polyethylene glycol ester.

5. The transfer sheet of claim 1 wherein the resin is cellulose acetate butyrate.

6. The transfer sheet of claim wherein said composition includes up to .25 part of a wetting agent of the class consisting of fatty amides and polyethylene glycol ester.

7. The transfer sheet of claim 5 wherein said pigment is finely divided magnetizable material.

8. The transfer sheet of claim 5 wherein said pigment is finely divided iron oxide material.

9. The transfer sheet of claim 5 wherein the cellulose acetate butyrate is alcohol soluble butyrate and wherein the plasticizer is dioctyl azelate and wherein the solvent is ethanol.

10. The transfer sheet of claim 9 wherein said pigment is finely divided magnetizable material.

11. The transfer sheet of claim 9 wherein said pigment is finely divided iron oxide material.

12. The transfer sheet of claim 5 wherein the cellulose acetate butyrate is tenth second butyrate, the plasticizer is dioctyl azelate, and the solvent is methyl ethyl ketone.

13. The transfer sheet of claim 12 wherein said pigment is a finely divided magnetizable material.

14. The transfer sheet of claim 12 wherein said pigment is a finely divided iron oxide material.

15. A transfer sheet comprising a substrate having thereon the dried residue of a coating composition consisting essentially of, in parts by weight:

5 to 8 parts cellulose acetate propionate;

10 to 16 parts of dioctyl azelate plasticizer;

30 to 60 parts of methyl ethyl ketone solvent;

13 to 18 parts of a pigment capable of being dispersed within said resin, plasticizer, and solvent.

16. The transfer sheet of claim 15 wherein said pigment is a finely divided magnetizable material.

17. The transfer sheet of claim 15 wherein said pigment is finely divided iron oxide material.

18. A transfer sheet comprising a substrate having thereon the dried residue of a coating composition consisting essentially of, in parts by weight:

6 parts cellulose acetate butyrate resin containing 13% acetyl, 37% butyryl, 2% hydroxyl, with a falling ball viscosity of substantially 0.5 second;

12.5 parts of dioctyl azelate plasticizer;

16.5 parts of a finely divided iron oxide material;

50 parts N-propyl acetate solvent;

0.2 part of a wetting agent of the class comprising fatty amides and polyethylene glycol ester.

19. A transfer sheet comprising a substrate having thereon the dried residue of a coating composition consisting essentially of, in parts by weight:

7.0 parts cellulose acetate butyrate resin containing 13% acetyl, 37 butyryl, 2% hydroxyl, with a falling ball viscosity of substantially 0.5 second;

14.0 parts dioctyl azelate plasticizer;

1.0 part glyceryl mono ricinoleate plasticizer;

50.0 parts N-propyl acetate solvent;

0.25 part of a wetting agent of the class comprising fatty amides and polyethylene glycol ester;

16.5 parts of a finely divided iron oxide material.

References Cited UNITED STATES PATENTS 3,062,676 11/1962 Newman et al.

FOREIGN PATENTS 947,219 1/1964 Great Britain.

MURRAY KATZ, Primary Examiner US. Cl. X.R. 106-26, '180; 11736.1, 138.8