US3515572A - Transfer sheet for obliterating typed character - Google Patents

Description

United States Patent US. Cl. 117-36.1 6 Claims ABSTRACT OF THE DISCLOSURE A material for obliterating erroneously typed characters from typed paper. The material comprises a relatively dense base sheet and a covering layer composition. The covering layer is microporous and not substantially penetrated into the base sheet. The covering layer com: position is weakly adherent to the base sheet, detachable therefrom by pressure of a typewriter key, and compressible and transferable thereby in substantially the thickness of the covering layer and with substantially sharp contours of the typewriter key. The composition is a barrier for oils, polyhydric alcohols and water and is free from hygroscopic substances and those which are liquid below 50 C. The composition comprises substantially a particulate mixture of about 75-98% by weight of a lightcolored pigment not soluble in or swellable in the composition constituents; about 120% by weight of a hard wax or hard parafiin, both having a molecular Weight above 400 and a melting point not lower than 70 C., or an aluminum soap; and 0.510% by weight of a macromolecular soft resin having a molecular weight of at least 3000.

This application is a continuation-in-part of my prior application, Ser. No. 562,473, filed July 5, 1966, which, in turn, is a continuation-in-part of my prior application Ser. No. 303,172, filed Aug. 19, 1963, which, in turn, is a continuation-in-part of my prior application Ser. No. 854,008, filed Nov. 19, 1959, all three now abandoned, corresponding to German application filed Nov. 26, 1958, and priority is claimed thereon.

This invention relates to means for covering up characters which have been typed in error by means of an ordinary typewriter or the like, and which permits another character to be typed thereover for correcting mistakes or making changes while the typewriter sheet is still in the machine. More specifically, the invention relates to a sheet, film or ribbon coated on the surface with a coating layer of colored material matching the color of the paper (usually white) which coating layer can be brought into contact with the erroneously typed character to be removed and struck upon the reverse side with the same key that printed the erroneous character to provide a covering layer to cover the erroneous character with the light colored coating.

It is among the objects of the invention to provide correction material for correcting by obliterating a mistakenly-placed typed character on a copy by permanently covering the mistakenly-placed character with an opaque covering layer of the color of the copy sheet, which covering layer permanently adheres to the copy.

It is also among the objects to provide means to simultaneously correct the ribbon copy and/or the carbon copies while in a typewriter.

It is still among the objects to provide a composition having discrete pigment particles and which is compres- 3,515,572 Patented June 2, 1970 sible when struck by a typewriter key to adhere to erroneously typed characters.

In the prior art, the general method of removing erroneously-typed characters by means of a covering material has been mentioned in the literature, German Pat. No. 268,837; Swiss Pat. No. 209,866; and French Pat. No. 849,868. Until now, no practical means in the form of a suitable coating on a base sheet has existed which would enable corrections to be made in offices in a practical manner. The patents referred to above have not made any significant contribution to the art since they have merely formulated a problem without reaching how means could be produced for solving the problem in a practical manner.

According to the invention, the correction material consists of a base carrier sheet of paper or similar material, coated with a not-strongly coherent relatively thick lightcolored coating layer of suitable cohesive and adhesive strength. The material may be supplied in the form of small sheets. One sheet is held in front of the type with the coating layer in contact with the erroneously typed character so the portion of the coating layer corresponding to the erroneously typed character is transferred to the copy in substantially the thickness of the covering layer and wtih substantially sharp contours, when the uncoated surface of the said one sheet is struck with the type of the erroneous character compressing the coating layer into a covering layer over the erroneous character on the type.

The inventive material for obliterating erroneously typed characters from typed paper comprises a relatively dense base sheet and a cOVering layer composition, said composition being weakly adherent to said base sheet and detactable therefrom by the pressure of a typewriter key, and compressible and transferable thereby in substantially the thickness of the covering layer and with substantially sharp contours of the typewriter key, said composition being a barrier for oils, polyhydric alcohols and water, being free from hygroscopic substances 'and those liquid below about 50 C. and comprising substantially a particulate mixture of (1) about -98% by weight of a light-colored pigment not soluble in or capable of swelling in the constituents of said composition, (2) about 120% by weight of a member of the group of hard waxes and hard paraflins both having a molecular weight of about 400 and a melting point not lower than 70 C., and polyvalent metal soaps and (3) 05-10% by weight of a macromolecular soft resin having a molecular weight of at least 3,000, said covering layer being microporous and not substantially penetrated into said base sheet.

The light-colored coating includes a light-colored pigment, a binding agent and an adhesive agent which are applied suspended or dissolved respectively in a liquid dispersing agent. Other ingredients or additional agents such as wetting agents may be included. All the ingredients are ground together in a ball mill and coated on the base sheet which may be paper or finished fabric, a film, or similar material, and then dried.

A new feature in the method of applying the transfer coating layer to the carrier base sheet is that the binding agent, which is by all means essential in one form or another, is preferably not applied to the base sheet in dissolved form so that it remains in a microporous condition until the coating layer is transferred by the pressure of the type which, at the same time, compresses it with the pigment into a compact clinging covering layer.

The binding agents make the coating layer a coherent layer instead of a loose powder without cohesion and abrasion strength. The binding agents also cause the coating layer, after separation, to adhere as a covering layer to the typewritten paper sheet over the erroneous character and give the layer sufiicient strength so that the covering in turn may be written upon with the typewriter. Furthermore, the binding agents must make the coating layer and the resulting covering layer durable and capable of withstanding changing climatic conditions, including high tropical temperatures and humidity. Important for the transferability of the covering layer composition is the ratio of adhesion of the composition on the paper sheet to which it shall be transferred to the cohesion of the particles of the composition. If the cohesion is too strong and the adhesion is too weak, the composition is transferred not satisfactorily.

Binding agent combinations of the type used in carbon paper were found to be unsuitable because they include vegetable *and/ or mineral oils in admixture with natural and artificial waxes or Wax-like materials. The presence of the oils in the light-colored covering layer of the present invention would permit the black dye from. the typewritten character to bleed through or penetrate the covering layer so that it would not effectively cover up the mistake. It was therefore soon obvious that the problem could not be simply solved by merely using the binding agent combinations known to be suitable for carbon paper. If the pigment could be applied over the erroneously typed character without any binding agent at all, the black dye from the typetwritten character would also penetrate the pigment and darken it. Usual components of a typetwriter ribbon are oils, polyhydric alcohols and water, and thus the covering layer composition of the present materials shall be a barrier for such substances, because otherwise said substances would penetrate the transferred covering layer composition and carry black dye into it.

Nonoily hard waxes and/or paraffins (i.e., waxes without additions of oil or oil-like substances) can be used as the binding agent. For example, hard ceresin wax, cleaned montan wax, synthetic waxes, chlorinated naphthalene (chlornaphthalin) or polyethylene may be used. When this type of binding agent is used, one can vary the proportion of pigment and increase or decrease the thickness of the coating layer accordingly in order to control the separation properties (obtain the desired cohesion and adhesion) and to control the abrasion strength of the coating layer and the resulting covering layer.

In the'present invention, the molecules of a suspended or partly-soaked or gelatinized binding agent form, after drying, a microporous weakly-coherent coating layer in which the fine particles of the pigment are imbedded and which is therefore plastically workable. The partial soaking results in a coherence within the layer so that it can be transferred in coherent form, but the layer is not strongly bound to the base sheet because the gelatinized binding agent does not penetrate the base sheet. Thus sufficient cohesive strength is obtained Without getting too great adhesion to the base sheet.

A preferred class of suspended binding agents is the polyvalent metal soaps of fatty'acids (twelve or more carbon atoms). The aluminum soaps are particularly suitable and probably the best example is aluminum stearate. Such binding agents compared to the waxes and paraflins require only a small addition of an adhesive agent.

The following properties of binding agents make them particularly suitable:

(1) High adhesive power in dry form; i.e., without the addition of any substance which would be liquid below 50-60 C. A good test to determine if such a binding agent hase sufiicient adhesive power is to rub it between two finger tips. It should have an ability to agglomerate. This ability is especially found in the aluminum soaps presumably due to the valence of the aluminum atom.

(2) Fluid repulse. All polyvalent metal soaps repel not only water but also oils and polyhydric alcohols such as glycerine. They therefore help greatly in the prevention of penetration by ink from typewriter'ribbon (which contains glycerine) as well as images formed from carbon paper which, as previously pointed out, contains oils.

(3) Ability to gelatinize or to be soluble only partly when soaked in the suspension liquids for the pigments used. This makes it possible to gelatinize all or part of the binding agent in a liquid heated up to 60 C. before the pigment is added. This affords a method of controlling the cohesion of the coating layer so that a true-to-shape transfer to the writing paper can be obtained to cover the erroneously typed character without incorporating larger amounts of other addition agents which may have other disadvantages.

(4) Or ability for fine grain precipitation forming a uniform microporous coating layer on the base or carrier sheet and having desired properties of cohesion and adhesion.

Waxes and parafiins can be used in partly or entirely undissolved form, for example, by dissolving them in a hot liquid and then cooling the liquid down so that it will no longer hold all the wax in solution. These waxes should have a melting point not lower than 70 C. and preferably below C. But due to the poor ability of waxes to form gels, an addition of a polyvalent metal soap may be useful, thus improving the transferring properties of the dry covering layer. Those combinations are suitable for specific requirements.

The most suitable pigment of high covering power for use in the covering layer is titanium dioxide. This exists in the rutile and anatase forms of which the rutile is most suitable. Zinc sulfide may also be used but this requires an increase in thickness of the covering layer by about 30% because of its lower covering power. For special purpose, e.g., the correction of copies only, it is possible to use an organic pigment such as pulverized cellulose or its derivatives. This is useful because, due to the trans parency of most copy and airmail papers, a really opaque covering is not desirable. However, the same result can be achieved by reducing the thickness of the layer to about .008 mm., perhaps with a simultaneous increase in the proportion of the binding agent.

To compensate the lack of adhesive strength brought about by the absence of oils as adhesive agents macromolecular soft resins having a molecular Weight of at least 3,000 are added. Their function is to increase cohesion within the covering layer to a degree and secondly, to help the covering layer to cling to the writing paper. Especially suitable are resins of the polyvinyl type since they do not permit penetration of the dyes present in the typewriter ink. Preferably, polyvinyl type resins are used which are plasticized by a plasticizer usual for said type of resins. For improving the adhesion properties of the covering layer composition additionally other additives, such as colophony or derivatives thereof can be incorporated. Also, the aluminum salt of albertic acid which is the addition product of phenol-resol with abietic acid can be admixed. Examples for the macromolecular soft resins useful according to the present invention and which may be natural or synthetic resins are polyvinyl isobutyl ether, chloroprene polymers, chlorosulphonated polyethylene, butyl rubber, polyisobutylene and other rubbery resins.

Additional preferred additives are lecithine and derivatives of montmorillonite, for example Bentone which is a reaction product of organic ammonium bases and montmorillonite.

The choice of the suspension liquid depends on the choice of the binding agent. It should not be a good solvent for the binding agent. If the binding agent is soluble in the solvent, the amount of solvent must be limited or the conditions under which it is used are controlled so that very little of the binder can be dissolved in the solvent. Organic solvents as well as Water can be considered. The addition of highly superficial solvents, for example, dichloroethylene to the amount of 10% of the total solvent mixture, causes a reduction of adhesion of the coating layer to the base sheet due to the faster drying which results in an easier separation.

The base sheet or carrier sheet for the light-colored microporous not strongly coherent coating layer has to be chosen very carefully. Dissolved agents in the suspension tend to penetrate the carrier base sheet and thereby anchor it to the coating layer. For example, when waxes as binding agents are used, the dissolved portion of the wax may act in this manner. This is, however, a disadvantage for the proper disengagement of the colored transfer coating layer from the base sheet.

To avoid this disadvantage, relatively dense (heavily sized) papers should be used as the base sheet, particularly when wax or parafiin binding agents are used. For this purpose, the base sheet should be a smooth, heavilysized but not too hard paper, with low absorbability, such as a paper-like half-vellum or chromopaper. In fact, such papers have been found best for the coatings including wax or wax-like binding agents. A vellum paper of about 35 to 70 grams per square meter has been found suitable.

The following glossary defines some of the terms used in this application:

Bentone grade 34 (Abbey Chemicals Ltd.).Bentone and zincum stearate have the function to stabilize and to homogenize the wax or paraifin suspension or metal soapsuspension, resp. the coloring matter; (Bentone is a reaction product of alkyl substituted amines and alkali earth silicates of the type of montmorillonite; very fine scalelike powder, manufactured by Abbey Chemicals Ltd.).

Behenz'c acid.A fatty acid with 22 carbon atoms lecithine (oil free) are used as wetting agents. Its proportion can decrease in some cases, since several kinds of resins have a specific wetting effect, e.g., Albertol (colophonyl); (The proposed hard ceresin is a product of Ceresinfabrik Georg Schiitz, Weiskirchen am Taunum, Germany).

Colophony.-A tacky solid resin of natural origin.

Neoprene FB.A stabilized chloroprene polymer having a low molecular weight; a liquid elastomer becoming gradually slightly crystalline according to Du Pont Reports No. 586.

Oppanol B10.A soft resin of poly isobutylene having an average molecular weight of 10,000, sold by Badische Anilin- & Soda-Fabrik, Ludwigshafen.

Oppanol B50.A polyiso-butylene having a molecular weight of about 50,000.

Staybelite Ester 10.-A glycerol ester of hydrogenated colophony manufactured by Hercules Powder Company.

The milling time is dependent on the milling intensity, which is difiierent for each ball Inill. The optimal time can be found by systematic variation. When using another milling system, e.g., a colloid mill, the proportion of the adhesive agent as well as of the suspended binding agent must be considerably decreased in some cases.

The following examples are given to show a few specific forms of the invention. Many variations within the spirit and scope of the invention are possible.

EXAMPLE 1 38 parts solution of polyvinyl isobutyl ether in trichloroethylene 4 parts lecithine 12 parts hard paraffin Ruhrwachs SP1002 (Scholven- Chemie, Gelsenkirchen-Buer), M.P. about 90 C.

8 parts Bentone 160 parts titanium dioxide rutile 200 parts trichloroethylene The mixture of the above components is ground in a ball mill with the suspension liquid trichloroethylene. It is coated immediately on a base sheet of a wood-free, satin-finished vellum or half-vellum and the solvent evaporated to form a dry layer of about .016 mm. thickness.

EXAMPLE 2 105 g. solution 25%. of Oppanol B10 in perchloroethyl- 6 20 g. Bentone grade 34 (not dissolved) 10 g. behenic acid (C22) 10 g. Staybelite Ester 10 are dissolved or finely dispersed in 500 g. trichloroethylene In this solution or dispersion a hot solution or dispersion of the following is added: 30 g. hard ceresin in 1 00 g. trichloroethylene with a rapid mixer, thus obtaining a Wax-emulsion, in which 800 g. titanium dioxide rutile and/or paste.

Said paste is ground in a ball mill about minutes and then diluted with 1,200 g. trichloroethylene and ground again about 10 minutes.

The finished coating is applied on vellum or half-vellum in a (wet) thickness of about 0.05 mm. and immediately dried.

EXAMPLE 3 200 g. solution 8% of Oppanol B50 in perchloroethylene 20 g. zincum stearate (not dissolved) 25 g. Albertol are dissolved or finely divided in 400 g. trichloroethylene by means of a rapid mixer 2 g. aluminum stearate or myristicate are gelatinized by heating in g. trichloroethylene; the gel is stirred up with a rapid mixer in the solution above; into the resulting solution a hot solution of the following is added:

20 g. hard ceresin in 200 g. trichloroethylene with a rapid mixer, thus obtaining a wax-emulsion, in which is given 800 g. titanium dioxide rutile and/or anatase to form a paste.

Said paste is ground in a ball mill about 90 minutes and then diluted with 800 g. trichloroethylene and ground again about 10 minutes. Coating as in Example 1.

EXAMPLE 4 40 g. solution 25% of Oppanol B10 in perchloroethylene 25 g. Albertol 30 g. zincum stearate 800 g. titanium dioxide rutile and/or anatase and 450 g. trichloroethylene are mixed together to form a paste, which is ground in a ball mill about 70 minutes and then diluted with 600 g. trichloroethylene and ground again about 5 minutes. The thickness of the (wet) coating is about 0.04

mm. This composition is preferably coated on vellum paper of about 40 g./sq. m.

The following Examples 5 and 6 are particularly suitable for correcting carbon copies, so the covering layer on the erroneous character on the copy sheet does not adhere to the carbon coating in the carbon paper.

The principal difference in these examples (5 and 6) is the very high proportion of the undissolved but finely suspended binding agent (wax, paraffin or aluminum soap), combined with a considerable decrease of the white pigment proportion. By this the layer obtains maximal density and cohesion without becoming brittle under the pressure of the typewriter type. This is necessary, because the relatively high adhesion power of the carbon color would cause white pigment particles to cling to the carbon layer of the carbon paper rather than to the black color of the copy paper at the correction place on the copy paper. The consequence would be a white-spotted carbon paper, so that a clear character would no longer be produced on a copy sheet at such spots of the carbon paper. The general aim is to make the structure of the covering layer as much as possible similar to the structure of the copy paper, after the correction is made While maintaining the microporous character in the coating on the carrier sheet. Waxes and aluminum soaps are entirely equivalent in the effect; but the use of the waxes "has the great advantage, that a wax-emulsion can much more easily be kept stable than a suspension of an aluminum soap; the latter is very sensitive in respect to variations of the room temperature and storing time of the fluid coating.

EXAMPLE 100 g. solution of Neoprene FB (Du Pont) in trichloroethylene 25 g. Albertat 20 g. Bentone grade 34 4 g. lecithine (free of oil) 2 g. soot-coal 100 g. aluminum-monobehenate 500 g. titanium dioxide rutile and/ or anatase 1,200 g. trichloroethylene, are mixed together with a rapid mixer to form a paste. Said paste is ground in a ball mill about 90 minutes and then diluted with 900 g. trichloroethylene and ground again about 10 minutes. The thickness of the (wet) coating is about 0.03 mm.; coated to vellum or half-vellum of about 3050 g./sq. rn.

EXAMPLE 6 30 g. solution 25% of Oppanol B10 in perchloroethylene 10 g. behenic acid (dissolved) 10 g. Albertat (dissolved) 10 g. zincum stearate (suspended) 2 g. soot-coal 600 g. trichloroethylene are thoroughly mixed with a rapid mixer. Into this solution a hot solution of the following is added:

90 g. hard ceresinin 300 g. trichloroethylene and thoroughly mixed by means of a rapid mixer, to form a stable wax-emulsion or suspension. Then are added:

400 g. titanium dioxide rutile and/or anatase or other white pigment, to form a paste, which is ground in a ball mill about 90 minutes and then diluted with 1,800 g. trichloroethylene and then ground again 10 minutes. The finished coloring matter is coated in a thickness of about 0.03 mm. to vellum or half-vellum of 3050 g./sq. m.

In each of the examples it will be observed that a microporous coating is provided by the plastic encasement of each pigment particle so that each plastic encased particle contacts the adjacent plastic encased particles in limited areas of contact, leaving appreciable voids resulting in a microporous structure which is relatively thick in the coating on the base carrier sheets. After the uncoated surface of the correction material is struck with a type forcing the coating against the copy, the coating is compressed and securely attached to the copy covering the area of the copy corresponding to the shape of the type with which it is struck.

The coating layer on the base carrier sheets is only loosely bound to such base carrier sheets and under some circumstances the liquid suspending the binder may slightly dissolve the binder, but the extent of solution of the binder is accurately controlled and must be very limited so that the bond between the base carrier sheet is not suflicient to cause the coating layer to be attached to the base carrier sheet stronger than the covering layer is attached to the copy to secure proper transfer of the coating from the base carrier sheet to the copy to effectively obliterate the erroneous character. The impact of the type also causes the plastic binder and pigment to compress to a substantial nonporous solid which is strongly adherent to the copy and strongly coherent to adjacent coated particles to prevent abrading of the covering layer from the copy.

It will thus be apparent that applicant has provided a new and eflicient correction material of a suitable sheet base with a microporous transfer coating layer on one surface thereof for correcting mistakes in typing by applying he Coating layer over the erroneous typed character and transferring such coating layer to the erroneous character on the copy sheet covering the erroneously typed character with a single strike of the erroneous type thereby covering the erroneously typed character. After removal of the correction material, the correct type is struck over the covering layer making a permanent correction which is not adversely affected by ordinary conditions of humidity and temperature, thereby simplifying and speeding up the correction of typing copies.

The ribbon copy and all of the carbon copies can be corrected simultaneously with the single strike of the erroneous type by inserting the carbon copy correction material sheets between each carbon paper and its copy and inserting a ribbon correcting sheet between the type and the ribbon copy and restriking the erroneous character. After removal of the correction material sheets the correct type is struck, making the corrected copies simultaneously.

What is claimed is:

1. A material for obliterating erroneously typed characters from typed paper which comprises a relatively dense base sheet and a covering layer composition, said composition being weakly adherent to said base sheet and detachable therefrom by the pressure of a typewriter key, and compressible and transferable thereby in substantially the thickness of the covering layer and with substantially sharp contours of the typewriter key, said composition being a barrier for oils, polyhydric alcohols and water, being free from hygroscopic substances and those liquids below about 50 C. and comprising substantially a particulate mixture of (1) about 7598% by weight of a light-colored pigment not soluble in or capable of swelling in the constituents of said composition, (2) about 120% by weight of a binding agent selected from the group consisting of hard Waxes and hard paraffins both having a molecular weight of above 400 and a melting point not lower than 70 C., and aluminum soaps and (3) 05-10% by weight of a macromolecular soft resin adhesive agent for making the covering layer composition cling to the erroneously typed characters on the typed paper, said soft resin having a molecular weight of at least 3000, said covering layer being microporous and not substantially penetrated into said base sheet.

2. A material in accordance with claim 1 in which this pigment is essentially titanium dioxide.

3. A material in accordance with claim 1 in which said aluminum soap is aluminum stearate.

4. A material in accordance with claim 1 in which said macromolecular soft resin is one of the polyvinyl type.

5. A material in accordance with claim 1 which contains additionally lecithine or derivatives of montrnorillonite.

6. A material in accordance with claim 1 which contains additionally colophony or derivatives thereof.

References Cited UNITED STATES PATENTS 852,191 4/ 1907 McFadden. 1,783,442 12/1930 Mayer et al. 2,313,808 3/1963 Dalton. 2,313,810 3/1943 Dalton. 2,572,871 10/1951 Kline. 2,665,262 1/1954 Rolle. 2,872,340 2/ 1959 Newman et al. 2,931,752 4/ 1960 Newman. 3,025,180 3/ 1962 Dalton.

FQREIGN PATENTS 25 ,602 1913 Great Britain. 528,589 1940 Great Britain.

MURRAY KATZ, Primary Examiner U.S. Cl. X.R. I 106-230; 1l72, 150, 26023, 41, 285