A PROCESS FOR PRODUCING A PRESSURE-SENSITIVE RECORD MATERIAL

Abstract: A process for producing a pressure-sensitive record material having a substrate (20) carrying on one surface thereof pressure rupturable microcapsules (24) containing a colorless chromogenic material capable of reacting with a color developer (22) to produce distinctive color marks, wherein an aqueous capsular dispersion including a binder material is coated on said one surface and dried. In accordance with the invention the capsular dispersion is intermixed, before coating, with an aqueous dispersion of a water-insoluble wax material. The wax (26) material forms a protective barrier between the color-forming reactants thereby to prevent or at least minimize unwanted precoloration of the record material.

Description: A PROCESS FOR PRODUCING A PRESSURE-SENSITIVE RECORD MATERIAL Technical Field This invention relates to a process for pro¬ ducing pressure-sensitive record material of the kind in which a colorless, chromogenic, ink held in microcapsules is reacted, upon rupturing the capsules, with a co- reactant material to form distinctive colored marks. Background Art Pressure-sensitive record materials of this kind are referred to as carbonless copying papers and are either of the "couplet" or the "manifold" types. The "couplet" type consists of a top transfer sheet carrying the capsular coating on the back side thereof and known as a "CB" ("coated back") sheet, and a bottom receiving sheet having the co-reactant or color former material coated on the front side thereof and known as a "CF" ("coated front") sheet. In the "manifold" type record material, the top sheet of a stack is a "CB" sheet and the bottom sheet of the stack is a "CF" sheet, with a number of transfer-receiving sheets therebetween, which are commonly called "CFB" ("coated front and back") sheets and are being coated both on the front and back with the co-reactant material and the capsules, respec¬ tively. It has been found that during handling or storage of a stack of "CFB" sheets or a roll of "CFB" paper inadvertent rupture of the capsules may occur causing the colorless dye to transfer to the adjacent sheet or to mix with the co-reactant and thereby to pre- color the paper. "CB" or capsular coating material of the prior art usually contained an aqueous capsular dispersion to which a binder material was added and the dispersion was then coated onto the back side of a sheet and dried. To produce a "CFB" sheet, the "CB" sheet was then processed in well-known manner through a solvent coating or print¬ ing press operation to apply the co-reactant material, usually a phenolic resin, on the other side thereof. The application of the "CF" coating to a capsule-coated sheet was also responsible for unwanted coloration of the paper. Disclosure of Invention It is an object of the present invention to provide a process for producing a pressure-sensitive record material in which unwanted precoloration is pre¬ vented or at least minimized. Thus according to the invention, there is pro^ vided a process for producing a pressure-sensitive record material having a substrate carrying on one sur- face thereof pressure-rupturable microcapsules contain¬ ing a colorless chromogenic material capable of reacting with a color developer material to produce distinctive colored marks, wherein an aqueous capsular dispersion including a binder material is coated on said one sur- face of said substrate and dried, characterized of intermixing said capsular dispersion, before coating, with an aqueous dispersion of a wax material. Brief Description of the Drawing Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawing, in which Fig. 1 is a diagrammatic view of a conven¬ tional coated, carbonless record sheet; Fig. 2 is a diagrammatic view of a coated carbonless record sheet produced according to the present invention; and Fig. 3 is a diagrammatic view of a plurality of coated carbonless record sheets produced according to the present invention. Best Mode for Carrying Out the Invention Fig. 1 shows a conventional construction of carbonless record media wherein a substrate 10 of paper or like material has a phenolic resin coating 12 on the front side thereof and a capsular coating 14 on the back side. The resin CF coating 12 and the capsular CB coating 14 on the paper 10 form a CFB sheet. As men¬ tioned above, handling and/or storage of a stack of CFB sheets or roll of CFB paper can and sometimes does result in a mixing of the reactant materials wherein the CF coating seeps into or penetrates the body of the paper and certain particles of the CF coating may contact capsules of the CB coating, which CB capsules have become inadvertently ruptured and thereby cause precolor of the paper. The CB coating capsules contain a dye ingredient which is released upon rupture of any of the capsules and contact of the colorless dye with particles of the CF coating causes the precolor condition. The two coatings react with each other to form a blue color in the paper 10 which is premature in the use of the paper and such blue color may be significant so as to prevent normal use of the paper. While a certain amount of capsule rupture is caused by handling and/or storage of the paper in stacks or rolls with resulting precolor, additional precolor can and does result from the printing press operation or like application of the CF coating on the paper. In this respect the oil used in the CF formulation is a non-volatile solvent or like vehicle that moves into or penetrates the paper and may cause precolor thereof. In the attempts to produce a satisfactory carbonless CFB paper, a printing press has been employed to apply the CF coating of phenolic resin material on the front of the paper which previously had been coated on the back side with the capsular CB coating. While there are numerous formulations used for the carbonless CB paper, two of the well-known stock materials include a CB paper as manufactured by Appleton Papers, Inc., of OMPI -4- Appleton, Wisconsin, and a CB paper as manufactured by The Mead Corporation, of Dayton, Ohio. The printing press has been used to apply spot or full sheet CF coating on the CB paper, however, the blue precolor may 5 be evident in the finished CFB product and, as such, the paper is not satisfactory for commercial use. The present invention is directed to prevent¬ ing or at least minimizing the chances of premature mixing of the reactive coatings and the resultant pre- 10 color condition by providing a barrier between the coatings on either side of the paper. Such precolor condition is unwanted and undesirable and greatly les¬ sens the quality and usefulness of the carbonless paper. Fig. 2 illustrates the arrangement of the present inven- 15 tion wherein a substrate 20 of paper or like material has a coating 22 on the front or top thereof and a capsular coating 24 on the back or bottom of the paper. The CF coating 22 and the CB coating 24 on the paper 20 form a CFB sheet. In accordance with the present inven- 20 tion, a wax dispersion 26 is mixed into or formulated with the CB coating 24 in manner and arrangement wherein the coating 22 and the coating 24 are protected and maintained in separate form or condition by the disper¬ sion 26 acting as a barrier between the particles or 25 ingredients of the two coatings 22 and 24. The preferred method of producing a carbonless CFB paper which is substantially immune to the blue precolor includes the step of incorporating wax, in the form of an aqueous wax dispersion, as an ingredient in 30 the CB capsule coating 24 to act in the finished pro¬ duct as a barrier, in the nature of a layer or film, between any CB colorless dye and phenolic resin material of the CF coating which may enter or penetrate the paper 20. The wax dispersion 26 contains particles of wax 35 which, in effect, replace at least a portion of the capsules in the CB coating 24. Through the use of such dispersion, the reduced CB capsular content provides good image transfer by being compensated with improved transfer efficiency of colorless dye solution from the CB capsules to an adjacent CF coating due to the wax acting as a barrier against such colorless dye solution entering or penetrating the supporting paper stock 20 after rupture of any of the CB capsules. Fig. 2 there¬ fore illustrates a CFB paper having the aqueous wax dispersion 26 intermixed in the CB coating 24 to elimi¬ nate or at least minimize any blue precoloring of the paper 20. Fig. 3 illustrates the arrangement of multiple sheets of CFB paper with the CF coating 22 on the one side and the CB coating 24 on the other side of the paper stock 20. The wax dispersion 26 provides a wax filler to protect the CB side of one CFB sheet from reacting with the CF side of a second CFB sheet. The addition of the wax dispersion 26 to the capsular coating 24 particularly lends protection from precolor condi¬ tions where either solvent CF or press-type CF coatings have been used to produce CFB paper. The addition of such wax dispersion 26 would also lend protection from precolor to the standard aqueous dispersion CF of stan¬ dard CFB paper, as illustrated in Fig. 1. It is thus seen that the wax dispersion 26 incorporated into the CB coating 24 of CFB paper pro¬ vides or gives in the finished product the effect of a barrier coating between the CF and CB reactants and that the wax dispersion particles substantially envelop the CB capsules. The procedure includes the step of re- placing a predetermined quantity of CB capsular solids with wax solids or particles which are added as an aqueous wax dispersion to the capsular formulation on a one-to-one basis. The optimum quantity of wax substi¬ tution for CB capsules is determined by the properties of the CB paper produced in meeting pertinent test specifications including print intensity, smudge, or other parameters of current commercial carbonless papers. While the wax particles are illustrated as individual -6- particles in the capsule wax dispersion 26, it is probable that such individual particles coalesce into a continuous film upon drying. Since the wax particles are appreciably smaller (approximately one micron in 5 diameter) than the capsules of the CB coating 24, it is predictable that such wax particles settle and concen¬ trate at or near the paper 20 interface to form a con¬ tinuous layer and barrier between the CB capsules and the CF material. 10 It is further seen that the incorporation of the aqueous wax dispersion 26 into the CB capsular coating 24 acts as a holding agent for the colorless dye solution contained in the CB capsules after rupture of the activated capsules, thereby keeping the colorless 15 dye solution from penetrating the paper stock 20 and, in turn, promoting dye transfer efficiency to adjacent CF paper. It has therefore been found that adding the prescribed amount of wax into the capsular coating 24 does not limit or detract from print quality. 20 Still further, it is seen that incorporation of the wax dispersion 26 into the CB coating 24 may effect a cost-savings by reason that the quantity of wax replaces an equal quantity of capsular solid material. The amount of savings, of course, depends on the rela- 25 tive costs of the wax and the CB capsular dispersion. The waxes which have been incorporated into the CB coating 24 have included Jonwax 120, a wax dis¬ persion of polyethylene and paraffin wax; Jonwax 26, a wax dispersion of polyethylene wax; and Jonwax 22, 30 described as a water-base ax_compound. Jonwax is a trademark of S. C. Johnson & Son, Inc., of Racine, Wisconsin. EXAMPLE I Example I is a CB coating formulation con- 35 taining 36% wax solids in the dry coating and applied on the back surface of a paper substrate having a CF coat¬ ing formulation available from Appleton Papers, Inc. ^ cTv5 B f ._OMP jK WIP CB COATING FORMULATION • Material Percent Dry Weight Capsule Batch (54.1% solids) 35.8 Jonwax 120 (35% solids) 36.0 Stayco S Starch (10% soluble) 6.1 Keystar 328 Starch (88% solids) 22.1 EXAMPLE II Example II is a CB coating formulation con¬ taining 22% wax solids in the dry coating and applied on the back surface of a paper substrate having a CF coat¬ ing formulation available from Appleton Papers, Inc. CB COATING FORMULATION Material Percent Dry Weight Capsule Batch (54.0% solids) 49.8 Jonwax 120 (35% solids) 22.0 Stayco S Starch (10% soluble) 6.1 Keystar 328 Starch (88% solids) 22.1 The procedure for formulating the CB capsular coating includes the steps of combining, by gentle agitation, the Stayco S water-soluble, starch solution, the capsular dispersion and the Jonwax 120. The Keystar 328 water-insoluble starch is then added to the above combination by stirring at moderate speed to uniformly disperse the particulate starch throughout the formu- lation. Stayco S Starch is available from A. E. Staley Manufacturing Company, of Decatur, Illinois 62525, and Keystar 328 Starch is available from Henkel Corporation, of Minneapolis, Minnesota, 55435. The capsule batch (54% solids) is prepared in the laboratory in accordance with procedures provided by Appleton Papers, Inc. The CF coating formulation to be applied to the front surface of the paper substrate by use of the printing press is as follows: CF COATING FORMULATION Material Percent Dry Weight Phenolic resin 28 Magie ink oil 535 29 Petrolatum 11 Kaolin clay 30 Fluorescent dye 2 The CF coating is prepared by mixing the phenolic resin and the ink oil at a temperature of 66°C. When a sample of this mixture shows a complete solution of the resin by visual inspection of the solution in a test tube, the kaolin clay (pigment) is added with vigorous agitation until further dispersion produces no further dispersing effect (approximately 10-15 minutes after last addition) . The petrolatum is then added to the solution and mixed until such petrolatum is fully dis¬ persed (approximately 10-15 minutes) . The mixture is then run over a three-roll mill to reduce all particu- lates to less than 25 microns. The final mixture is agitated with a mixer to obtain a uniform product. It is noted that the formulation of the ink coating is based on the use of a phenolic resin as the resin portion of a colorless ink and simultaneously as the color reactive portion of the coating formulation. The ink oil provides a solvent for the resin and a vehicle for the ink, and the amount of the ink oil controls the tack and flow characteristics of the ink. The petrolatum is used to adjust the body and the length of the ink, while the clay is provided as a filler and a pigment for the ink. The phenolic resin is available from Durez Division, Hooker Chemical and Plastic Corporation, of North Tonawanda, New York. The Magie ink oil 535 is available from Magie Brothers Oil Company, Division of Pennzoil, Franklin Park, Illinois, and the petrolatum is available from Witco Chemical Company, Inc., New York, New York, 10017. Further, the kaolin clay is available OMP from Georgia Kaolin Company, Elizabeth, New Jersey, 07207, and the fluorescent dye is available from Hilton- Davis Company, Cincinnati, Ohio. EXAMPLE III Example III is a CFB coating formulation containing 36% wax solids in the dry coating and applied on the back surface of a paper substrate and including the CF coating formulation as applied by the printing press on the front surface. CB COATING FORMULATION Material Percent Dry Weight Capsule Batch (54.1% solids) 35.8 Jonwax 120 (35% solids) 36.0 Stayco S Starch (10% soluble) 6.1 Keystar 328 Starch (88% solids) 22.1 CF COATING FORMULATION Material Percent Dry Weight Phenolic resin 28 Magie ink oil 535 29 Petrolatum 11 Kaolin clay 30 Fluorescent dye 2 EXAMPLE IV Example IV is a CFB coating formulation con- taining 22% wax solids in the dry coating and applied on the back surface of a paper substrate and including the CF coating formulation as applied by the printing press on the front surface. CB COATING FORMULATION Material Percent Dry Weight Capsule Batch (54.0% solids) 49 .8 Jonwax 120 (35% solids) 22 .0 Stayco S Starch (10% soluble) 6 . 1 Keystar 328 Starch (88% solids) 22 .1 ( OMPI CF COATING FORMULATION Material Percent Dry Weight Phenolic resin 28 Magie ink oil 535 29 Petrolatum - 11 Kaolin clay 30 Fluorescent dye 2 Each of the above CB coatings is sufficient to withstand the force or pressure of applying the asso- ciated CF coating on the paper substrate by means of the printing press to produce a carbonless CFB paper that develops minimal or no evidence of precolor in the finished product. It has been found that the amount of wax solids in the wax dispersion can range from 10% to 50% of the capsular coating, the lower percentage giving less precolor protection and better printing, and the higher percentage giving better precolor protection and lower print quality. It should be noted that the cap¬ sule batch portion of the CB coating formulation is in accordance with a formula provided by Appleton Papers, Inc. OMP "WI

Claims: CLAIMS : 1. A process for producing a pressure-sensi¬ tive record material having a substrate carrying on one surface thereof pressure-rupturable microcapsules con¬ taining a colorless chromogenic material capable of reacting with a color former material to produce dis¬ tinctive colored marks, wherein an aqueous capsular dispersion including a binder material is coated on said one surface of said substrate and dried, characterized by intermixing said capsular dispersion, before coating, with an aqueous dispersion of a wax material. 2. A process according to claim 1, charac¬ terized in that said wax material is water-insoluble. 3. A process according to claim 1, charac¬ terized in that said color former is coated on the other surface of said substrate. 4. A process according to claim 1, charac¬ terized in that said wax material includes a wax having a polyethylene base. 5. A process according to claim 1, charac¬ terized in that said wax material includes a wax having a polyethylene and paraffin base. 6. A process according to claim 1, charac¬ terized in that the dry capsular coating contains from 10 to 50%, by weight, preferably 35 to 40%, by weight, wax. 7. A process according to claim 1, charac¬ terized in that said binder material is a water-soluble starch. WIPO 8. A process according to claim 1, charac¬ terized in that said capsular dispersion has added thereto particles of a water-insoluble starch stilt material. 9. A process according to claims 7 and 8, characterized in that the dry capsular coating contains 6%, by weight, of said water-soluble starch binder, and 20%, by weight, of said water-insoluble starch stilt material. 10. A pressure-sensitive record material pro¬ duced according to the process claimed in claim 1.

Inventors: MARINELLI NICOLA, MARINELLI, NICOLA
Applicants: NCR CO, NCR CORPORATION
Application year: 1984
Main classification: B41M5
IPC codes: B41M5