US3104173A - Eradicable carbon paper - Google Patents

Description

United States Patent This invention relates to a pressure-sensitive transfer paper commonly called carbon paper, and more particularly to such paper having a transfer medium which is capable of simple and easy eradication.

A simplified flow sheet of the method employed in producing the transfer paper is as follows:

Prepare aqueous solution of tannic acid, ferric chloride and potassium carbonate Filter and separate pigment residue Mix pigment thoroughly with cane wax binder and carrier of oleic acid and mineral oil Apply pigment mix conventionally to paper backing to produce pressure-sensitive transfer paper Carbon papers, of course, have been known for many years in the field of typewriter supplies. The transfer surface on such paper usually comprises an ink pigment in a suitable binder.

When carbon paper is employed to make additional copies of typewritten matter, there is little difiiculty in removing unwanted transfer material by erasing. However, recently carbon paper ribbons have been developed for use with typewriters, particularly electric typewriters, to make the ribbon or original copy. The carbon paper ribbon has gained in popularity because of the sharp and distinct imprint which is possible as a result of the relatively stiff paper backing as distinguished from the softer fabric ribbons. Further, the ink pigment on the conventional carbon paper ribbons is dispersed in a hard carnauba wax binder which contributes to the sharpness and clarity of the type imprint.

As is well known, removing the imprint from a fabric ribbon copy is considerably more difficult than removing the imprint from a carbon copy. The most common means for removing the ribbon copy imprint is the eraser. The chore of removing the transfer material from the ribbon copy when an electric typewriter is used is aggravated because the imprint is cut deeper into the paper. As a result, erasing has become tedious and the results of the erasure often distractful. The problem of erasing is further aggravated when carbon paper ribbon is employed, since the imprint is more bold and distinct than that produced by the fabric ribbon.

An attempt has been made to find an eradicator for the ink pigment in carnauba wax, however, solvents of the pigment and carnauba wax either damage or discolor the paper and are, therefore, unsatisfactory.

Accordingly, it is a primary object of the invention to provide a carbon paper having a novel transfer material which is capable of simple and easy eradication.

It is a further object of the invention to provide a carbon paper typewriter ribbon having a transfer surface which is amenable to eradication.

It is a feature of this invention to provide a novel liquid eradicator which eradicates the transfer material but which does not damage the "paper and which leaves the paper in condition for immediate use.

In accordance with a broad aspect of the invention, there is provided a paper backing faced with a layer of pressure-sensitive transfer material comprising ink pigment dispersed in a wax binder, the wax binder being characterized by having an acid number between 25 and 35, a saponification number between 55 and 70, a resin content less than 3%, and an oil content less than 5%.

In accordance with a further aspect of the invention, the ink pigment comprises a reaction product of tannic acid, ferric chloride and potassium carbonate.

The above mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention.

The paper backing and the techniques for applying the transfer material to the paper backing are conventional and will, therefore, not be described.

The novel transfer material which is applied as facing to a paper backing comprises an ink pigment consisting of a reaction product of tannic acid, ferric chloride and potassium carbonate. The constituents are thoroughly mixed in distilled water and the proportions are determined by observing the color of the filtrate during the removal of the water by filtering. Empirically, it has been found that the most satisfactory proportion of constituents is that which produces a clear filtrate. For example, a preferred composition comprises approximately the following parts by weight:

The pigment residue, in powder form, is mixed with a cane wax binder having the following characteristics: A melting point of 171 to 176 F., a penetration of 3 maximum, an acid number of between 25 and 35, a saponification number of between 55 and 70, an ash content of less than 0.5%, a resin content less than 3% and an oil content of less than 5%. The pigment and wax binder are mixed thoroughly at a temperature slightly higher than the melting temperature of the wax, and to this mixture is added a carrier comprising oleic acid commonly called red oil, and a mineral oil commonly called white oil. This mixture of pigment, binder and carrier is mixed thoroughly and applied in the conventional way to the paper backing.

-In accordance with a preferred composition, the ingredients which consist essentially of the pigment, carrier and binder are mixed together in approximately equal portions, the oleic acid constituting approximately 7% by weight of the carrier.

The novel eradicator which is capable of dissolving the wax and eradicating the pigment comprises an aqueous solution containing approximately 2% by volume of citric acid, and a separate solution of sodium hypochlorite. The sodium hypochlorite solution serves primarily as a bleach. Preferably, in eradicating the transfer material, the sodium hypochlorite is first applied in a small amount to the transfer material and then the diluted solution of citric acid is applied to the sodium hypochlorite. The dissolved wax and pigment are then removed from the paper by blotting in the conventional way.

While the foregoing description sets forth the principles of the invention in connection with specific materials, it is to be understood that this description is made only by way of example and not as a limitation of the scope of the invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. A pressure-sensitive transfer paper faced with a layer of transfer material amenable to eradication consisting essentially of an ink pigment formed of a reaction product of tannic acid, ferric chloride and potassium carbonate dispersed in a cane wax binder having an acid number ranging from about 25 to 35, a melting point of about 171 F. to 176 F., a penetration of 3 maximum, a saponification number ranging from about 55 to 70, an ash content of less than 0.5%, a resin content less than 3% and an oil content less than 5 said ink pigment and wax also having mixed therewith a carrier comprising oleic acid and mineral oil, the proportion of the pigment, the wax binder and the carrier being approximately equal.

2. A pressure-sensitive transfer paper faced witha layer of transfer material amenable to eradication consisting essentially of an ink pigment formed of a reaction product of approximately 3.79 parts by weight of tannic acid, 3.2 parts by weight of ferric chloride, and 2.36 parts by weight of potassium carbonate dispersed in a cane wax binder having an acid number ranging from about 25 to 35, a melting point of about 171 F. to 176 F., a penetration number of 3 maximum, a saponification number ranging from about 55 to 70, an ash content of less than 0.5%, a resin content less than 3% and an oil content less than 5%, said ink pigment and wax also having mixed therewith a carrier comprising oleic acid and mineral oil, the proportion of the pigment, the wax binder and the carrier being approximately equal,

the oleic acid constituting approximately 7% of the car- ,rier.

3. A method for treating a selected area of a surface containing an imprint of an ink pigment and remove the same, said ink pigment consisting essentially of a reaction product of tannic acid, ferric chloride and potassium carbonate dispersed through a cane wax binder having an acid number ranging from about 25 to 35, a melting point of about 171 F. to 176 F., a penetration of 3 maximum, a saponification number ranging from about to 70, a resin content less than 3% and an oil content less than 5%, said ink pigment and wax also having mixed therewith a carrier comprising oleic acid and mineral oil, the proportion of the pigment, the wax binder and the carrier being approximately equal, which comprises, treating the selected area containing said impressed ink pigment with a solution of sodium hypochlorite, contacting the treated selected area with a dilute aqueous solution of citric acid, and then blotting said area to remove the dissolved wax and pigment.

References Cited in the file of this patent UNITED STATES PATENTS 1,905,118 Nadell Apr. 25, 1933 2,559,608 Ehrlich July 10, 1951 2,589,306 Steiner Mar. 18, 1952 2,682,516 Wilder et al. June 29, 1954 2,824,812 Drautz Feb. 25, 1958 2,836,152 Rosenblum May 27, 1958 2,955,958 Brown Oct. 11, 1960 OTHER REFERENCES Karrer: Organic Chemistry, 2 ed., 1946, p. 530. Mosher: Specialty Papers, 1950, pp. 345-354.

Claims (1)

1. A PRESSURE-SENSITIVE TRANSFER PAPER FACED WITH A LAYER OF TRANSFER MATERIAL AMENABLE TO ERADICATION CONSISTING ESSENTIALLY OF AN INK PIGMENT FORMED OF A REACTION PRODUCT OOF TANNIC ACID, FERRIC CHLORIDE AND POTASSIUM CARBONATE DISPERSED IN A CANE WAX BINDER HAVING AN ACID NUMBER RANGING FROM ABOUT 25 TO 35, A MELTING POINT OF ABOUT 171*F. TO 176*F., A PENETRATION OF 3 MAXIMUM, A SAPONIFFICATION NUMBER RANGING FROM ABOUT 55 TO 70, AN ASH CONTENT OF LESS THAN 0.5%, A RESIN CONTENT LESS THAN 3% AND AN OIL CONTENT LESS THAN 5%, SAID INK PIGMENT AND WAX ALSO HAVING MIXED THEREWITH A CARRIER COMPRISING OLEIC ACID AND MINERAL OIL, THE PROPORTION OF THE PIGMENT, THE WAX BINDER AND THE CARRIER BEING APPROXIMATELY EQUAL.