SET FOR CARBONLESS COPYING

Abstract: A color-former sheet or set for carbonless copying con­ sisting essentially of microcapsules, a capsule protective agent, and a binder, characterized in that there is included in the sheet coating a surface active agent in an amount of from 0.1 to 4% based on the weight of the microcapsules, thereby im­ proving glued-sef separability.

Description: The invention relates to carbonless copy paper sets. Specifically, the invention concerns non-carbon copying paper with improved glued-set separability layered in sets each comprising one color forming upper sheet and one color developing lower sheet, and optionally one or more intermediate sheets each serving as both a color Forming sheet and a color developing sheet between the upper sheet and the lower sheet, said color-forming sheet(s) being coated with a coating color basically composed of color former-containing synthetic resin micro-capsules, a capsule protective agent and an adhesive, the cut face of the no-carbon copying paper layered in sets having been covered in manufacture with an aqueous edge-padding adhesive composition. The invention may be presented as no-carbon copying paper as above, in which for the purpose of giving improved glued set separability, use is made in said coating color of a nonionic surface active agent having a hydrophilicliphophilic balance (HLB) of 10 or above in an amount of 0.1 to 2% by weight based on the microcapsules, or as a method of manufacture of such no-carbon copying paper wherein, for such purpose, use is made in the coating color of such kind and amount of surface active agent. So presented, the invention may be thought of as the no-carbon copying paper or method of making it or primarily as the use of the surface active agent for such purpose in such paper or method. The microcapsules are of melamine-formaldehyde resin. Known carbonless copying paper usually comprises a combination of an upper sheet (color former) coated on its back surface with microcapsules containing an electron-donative colorless organic compound and an organic solvent of a high boiling point, a capsule protective agent, and a binder and a lower sheet (color developer) coated on its front surface with an electron-acceptive acid substance which enables the colorless organic compound to generate a color. When it is necessary to produce a multiplicity of copies, one or more intermediate sheets coated on both front and back surfaces may be interposed between the upper and lower sheets. "Glued-set separability" is known in the field of carbonless copying paper. When multiple sets of slips, for instance n in number, are prepared, printed carbonless copying sheets consisting of a single upper sheet, ( n - 2) intermediate sheets and a single lower sheet are put together in the order named and severed. A plurality of such sets of sheets are superimposed one on another and an edge-padding glue is applied to the cut edges of the sheets to bond them edgewise together in each set, while allowing the lower sheet in each set to remain unglued from the upper sheet in a succeeding set, so that a particular set of n slips can easily be separated from the rest of slip sets. The ease with which such glued sets can be separated as desired is called "glued-set separability." Since the respective coated faces of the color-former and color-developer sheets are held in confronting relation in each set with their respective non-coated surfaces confronting with each other between each set, the glued-set separability has been considered variable with the property of an edge-padding glue applied to the sheets. It is important to attain a desired degree of glued-set separability in preparing carbonless copying paper. However, the prior practice has been disadvantageous in that the slips or sheets in each set are not strongly enough bonded and objectionable bonding often occurs between the slip sets. A marked progress has recently been made in the microcapsulization technology. Interfacial polymerization and in situ processes have found extensive use besides the conventional coarcervation process using gelation. A wide application is found of microcapsules formed with a film of a synthetic resin such as polyurethane, epoxy resin, polyurea, urea-formalin resin, or melamine-formalin resin. Researches have been directed mainly to the edge-padding glue for improveing the glued-set separability. Such attempts are described in Japanese Patent Publication No. 50-7634 which discloses a mixture of gelatin derivatives and aqueous resinous emulsions. Japanese Patent Publications Nos. 53-12347, 53-12846, 53-21414, 54-21415, and 53-21416 disclose the use of naphthalenesulfonic acids and formalic condensates. Japanese Patent Publications Nos. 53-12845 and 53-12844 disclose adding a surface active agent to an edge-padding glue. All of such attempts have been centered on studying edge-padding glues, but no satisfactory results have however been so far found. It is an object of the present invention to improve glued-set separability by modifying color-former sheets. An aqueous edge padding adhesive when applied is attracted by the surface active agent, enhancing binding within, but not between, the sets. It has been known to use various additives for color-former sheets for the purpose of improving water-resisting property and preventing color fogging and static electricity (see, for example, Japanese Patent Publications Nos. 52-24449, 50-34510, 54-5328 and 53-28028). It has however not been known to add a surface active agent for the improvement of glued-set separability. Japanese Laid-Open Patent Publications Nos. 50-89111 and 55-113592 disclose including a desensitizer but are directed to objects and advantages different from those of the present invention. Further, DE-A-2 457 897 discloses the use of a cationic surfactant-containing desensitizing agent in the microcapsule layer, but the purpose is to prevent undesired colour formation and copy paper sets with improved glued set separability are not the aim. Another use of a surface active agent against undesirable early color formation is FR-A-2 338 143 and there is also FR-A-1 341 737 with color transfer and color receiving (developing) layers, where a non-ionic surface active agent is present in the color receiving 1a to facilitate absorption of transferred color. Both purposes again are different from those of the present invention, and neither show the claimed sets nor touch the problem lying behind them. Microcapsules made from a melamin-formalin resin are advantageous for the reason that the melamin-formalin resin is considered to give less wetting with respect to the edge-padding glue than other substances that the film of the microcapsules is to be made from. A capsule protective agent typically includes cellulose powder, starch powder or synthetic-resin emulsions commonly used in the art. Any capsule protective agent may be eligible provided that it is a particulate form slightly larger than the microcapsule. The binder used in the present invention should not be limited to any particular kind, but may be selected from any known binders. As noted above, a surface active agent is added in an amount of from 0.1 to 2% based on the weight of the microcapsules used. No satisfactory results can be obtained with less than 0.1% surface active agent. Greater amounts than just specified would result in reduced water-resistance of color-former sheets. It has now been found that the addition of the above specified amounts of surface active agents to a coating liquid composed of a capsule protective agent and a binder will provide improved fluidity and eliminate "kicks" and irregularities of the coated surface finish. Surface active agents under contemplation require no further description as there are many pertinent references available. Hydrophilic surface active agents are used because glued-set separability is attributable to the wetting property of such agents, and must be nonionic surface active agents which have a hydrophilic-lipophilic balance (HLB) of 10 or more. Cationic and amino surface active agents are not as good, as they may make the coated paper yellowish, deteriorate the properties of the coating liquid and have adverse effect on the microcapsules. Likewise, while anionic surface active agents improve glued-set separability and fluidity of the coating liquid, they are less advantageous than the nonionic surface active agents. The anionic surface active agent is inferior to the nonionic surface active agent in that the former may be found to be adversely affected when the coated layer of microcapsules grow acidic in pH over a period of time under the influence of the web of paper which is normally acidic. The nonionic surface active agent should preferably have a relatively large molecular weight of 200 or more, or preferably 400 or more. The surface active agent used in the present invention may have but should preferably have little or no desensitization effect, a feature which is common in chemical materials and additives for carbonless copying paper. Microcapsules made for a melamin-formalin resin as used in the present invention can be conveniently prepared by an in situ process as described in detail in Japanese Laid-Open Patent Publications Nos. 53-84881 and 54-49984. The coating liquid according to the present invention which consists essentially of microcapsules, a capsule protective agent, a binder and a surface active agent may be applied to paper by an ordinary process such as air-knife coating, blade coating or roll coating, and then dried. The present invention will be further illustrated by the following examples. EXAMPLE 1 In 200 parts of an oil of a high boiling point (KMC-113, produced by Kureha Chemical Industry Co., Ltd.) were dissolved 5 parts by weight of Crystal Violet Lactone (CVL). The oil was emulsified in a 5% solution (pH 5.0) of a styrene-maleic anhydride copolymer to produce an emulsion having an average particle size of 6 microns. To the emulsion were added 20 parts of a 40% solution of a melamin-formalin pre-condensate, Sumilet, resin produced by Sumitomo Chemical Co., Ltd., and the reaction was continued for 2 hours at a temperature of 75°C. The pH was adjusted to 9.0 by adding caustic soda. The admixture was cooled to complete encapsulation. The resulting capsules and other additives were applied to a sheet of paper of 42 g/m² as follows: 200 upper sheets thus prepared and 200 commercially available lower sheets (Mitsubishi NCR paper, resinous lower sheets, N-40) were superimposed alternately on one another to form 200 sets of sheets and were severed by a guillotine cutter. 8% aqueous solution of a commercially available latex (Polysol) (produced by Showa Kobunshi K.K was applied to the cut edges of the sheets and then dried. Thereafter, the sets of sheets were inspected for glued-set separability. Separation between the sheet sets was complete, and the sheets in each individual set were glued strongly together. COMPARATIVE EXAMPLE 1 The procedure of Example 1 was followed except that no polyoxyethylene nonylphenol ether was used. Separation between adjacent sets of sheets was poor, and there were several sets bonded together. EXAMPLE 2 Employing the procedure of Example 1 substituting 2 parts of polyoxyethylene stearate (HLB 16.9) for 1 part of polyoxyethylene nonylphenol ether, the same good results were obtained as in Example 1 with respect to glued-set separability. EXAMPLE 3 Employing the procedure of Example 1 sustituting 0.5 part of polyoxyethylene sorbitan mono-laurate (HLB 14.9) for 1 part of polyoxyethylene nonylphenol ether, the same good results as in Example 1 were obtained.

Claims: 1. No-carbon copying paper layered in sets each comprising one color forming upper sheet, one color developing lower sheet and optionally one or more intermediate sheets each serving as both a color forming sheet and a color developing sheet between the upper sheet and the lower sheet, said color-forming sheet(s) being coated with a coating color basically composed of color former-containing synthetic resin microcapsules, a capsule protective agent and an adhesive and the cut face of the no-carbon copying paper layered in sets having been covered in manufacture with an aqueous edge-padding adhesive composition, whereby for the purpose of giving improved glued set separability, use is made in said coating color of a nonionic surface active agent having a hydrophilic-lipophilic balance (HLB) of 10 or above in an amount of 0.1 to 2% by weight based on the microcapsule, which are of melamine formaldehyde resin. 2. A method of manufacture of no-carbon copying paper layered in sets each comprising one color forming upper sheet, one color developing lower sheet and optionally one or more intermediate sheets each serving as both a color forming sheet and a color developing sheet between the upper sheet and the lower sheet, said color-forming sheet(s) being coated with a coating color basically composed of color former-containing synthetic resin microcapsules, a capsule protective agent and an adhesive and the cut face of the no-carbon copying paper layered in sets having been covered in manufacture with an aqueous edge-padding adhesive composition, wherein for the purpose of giving improved glued set separability, use is made in said coating color of a nonionic surface active agent having a hydrophilic-lipohpilic balance (HLB) of 10 or above, in an amount of 0.1 to 2% by weight based on the microcapsules, which are of melamine formaldehyde resin. 3. No-carbon copying paper according to claim 1, wherein the nonionic surface active agent is polyoxyethylene nonylphenol ether, polyoxyethylene stearate or polyoxyethylene sorbitan monolaurate. 4. No-carbon copying paper according to claim 1 or 3, wherein the nonionic surface active agent has a molecular weight of above 200. 5. No-carbon copying paper according to claim 4, wherein the surface active agent has a molecular weight of above 400. 6. Method according to claim 2, wherein the nonionic surface active agent is polyoxyethylene nonylphenol ether, polyoxyethylene stearate or polyoxyethylene sorbitan monolaurate. 7. Method according to claim 2 or 6, wherein the nonionic surface action agent has a molecular weight of above 200. 8. Method according to claim 7, wherein the surface active agent has a molecular weight of above 400.

Inventors: FUCHIGAMI, MITSURU, ISHIGURO, MAMORU, OHYE, HIDEO
Applicants: MITSUBISHI PAPER MILLS, LTD.
Application year: 1981
Main classification: B41M5
IPC codes: B41M5