JPH0349757B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is generally non-carbon (carbonless).
Back coating (CB) of pressure-sensitive recording material called copy paper
Regarding ingredients. The invention more particularly relates to high solids content sodium carboxymethylcellulose (CMC) based formulations with efficient coating viscosities and to papers coated with such formulations. BACKGROUND OF THE INVENTION Non-carbon paper has two or more superimposed sheets. These sheets often have a paint containing a color forming substance on their back side, often referred to as a backcoat or "CB". This paint consists of a continuous matrix or microcapsules containing a color-forming substance. A composition containing a color developer component that reacts with the color-forming substance is applied to the upper surface of the receiving sheet, which is brought into contact with the back surface of the stacked sheets during use. When partial pressure is applied to the top sheet, the paint film containing the color former is ruptured and the color former is released and reacts with the co-reactant or developer paint on the receiver sheet. Ru. A visible colored image is produced in the area corresponding to where the pressure was applied and the colored substance was released. Therefore, the pressure applied to the top sheet produces a corresponding mark on the top surface of each of the other sheets. In the prior art, color-forming substances (also called color-forming precursors or leuco dyes) are dispersed in a solvent.
Disclosed is the production of a paint comprising: Prior patents such as US Pat. Nos. 4,397,483 and 4,082,668 and British Patent No. 1,280,769 disclose CB paints for pressure-sensitive recording materials consisting of a carboxymethyl cellulose precipitate containing an oily solvent and a color-forming substance. The oil containing the color-forming reactants is emulsified in an aqueous solution of sodium carboxymethylcellulose, and metal salts are added to precipitate the cellulose as a separate phase with the droplets of oily dye solution contained therein. The obtained emulsion is applied to the back side of the uppermost sheet of the non-carbon copy system and dried. Crosslinked resins are often added to this emulsion to strengthen the resulting coating. Although these coatings have been commercially successful, high solids content CB compositions based on previous embodiments of this technology have poor stability and are not currently in use. The viscosity is uncontrollable and too high for the coating equipment and methods currently available. CB paint with low solids content (e.g. 20% non-aqueous component)
requires high energy consumption and long drying times. It is therefore desirable to provide a CB paint with a high solids content that has an efficient coating viscosity. It is not possible to increase the intrinsic content of coating compositions of known CMC substrates by mere water reduction because significant viscosity problems arise.
CMC aqueous solutions have the characteristic that their viscosity increases exponentially as the CMC concentration increases. Therefore, even if the advantage of producing a coating composition that dries more quickly is obtained simply by increasing the CMC content, this may be due to the fact that the viscosity of such composition becomes too high, impairing workability. It ends up being canceled out. It is an object of the present invention to provide improved CB paints with low viscosity and high solids content for better application to paper and other substrates. Another objective is to increase drying efficiency by providing coating compositions with higher solids content and lower water content. Yet another objective is to increase labor and energy savings by producing coating compositions with low moisture content. Another object is to provide a CB paper with improved chromophore release efficiency, thereby obtaining improved images for computers and dot matrix printers using pressure sensitive paper. Another objective is to create a CB paint that has a white appearance. Yet another objective is to reduce distortion of the paper substrate due to fiber wetting. A further object is to provide a CB paint that can be applied to paper machines. [Means for solving the problem] High solids content CB paint with efficient and stable coating viscosity and improved
It has been discovered that CB products are produced by using certain types of CMC with acrylic resins, organic crosslinkers, and metal salts that can cause precipitation of the CMC. By using the formulations of the present invention, the formulations contain high solids content, i.e., greater than about 30% by weight of non-aqueous materials, and can
A CB paint composition is obtained that has an efficient coating viscosity that can reduce many of the problems encountered with CB paint compositions. The paintable formulation consists of an emulsion of an oil containing one or more color-forming reactants in an aqueous solution of CMC, preferably sodium CMC with a degree of substitution ranging from 0.65 to 1.8, a wall-forming acrylic resin, a polyvalent metal salts, organic crosslinking agents and other optional components present, which increase the total solids content in the formulation to at least 30% by weight, preferably at least
35% by weight and sufficient to provide a Burckffield viscosity in the range of about 50 to about 5000 centipoise (cps), set as needed for the particular coating equipment used and coating at the selected web speed. It is contained in a large amount. As used herein, weight percentage solids includes all components in the formulation other than water, ie, the oil in the paint and the dissolved dye or dyes. In a preferred embodiment, the wall-forming acrylic resin is a carboxylated polyethyl acrylate/methyl methacrylate copolymer with a most preferred ratio of ethyl acrylate to methacrylate of about 2:1. Organic crosslinking agent
Preferred are polyamide-epichlorohydrin and other resins that can crosslink both CMC and carboxylated acrylic resins. In the presently preferred embodiment, the CMC used
has a low viscosity (60-170 cps as a 6% aqueous solution) and a high degree of substitution, e.g. 1.1-1.5. In another aspect, the present invention includes an improved CB sheet consisting of a web having an adhesive and dried paint of the type described above that releases color formers upon application of pressure. This CB sheet features improved image density, low threshold pressure, and low cost. DESCRIPTION OF EMBODIMENTS According to the present invention, low viscosity CMC with a degree of substitution between about 0.65 and 1.8 is dissolved in water. CMC is an anionic, water-soluble polymer derived from cellulose. The degree of substitution is the average number of carboxymethyl groups that are substituted per anhydroglucose unit. A high degree of substitution improves the compatibility of CMC with other water-soluble compounds. The CMC used according to the invention is an alkali metal CMC, such as a sodium CMC group, with a degree of substitution of 1.1 to 1.5, ie an average of 1.1 to 1.5 carboxymethyl groups per anhydroglucose unit. A wall-forming acrylic resin is added to this aqueous solution. A preferred resin, Carbset 514H from BFGoodrich, is a polyethyl acrylate/
Preferably about a 2:1 ratio of carbosylated copolymers of methyl methacrylate. other resins,
For example, Rohm & Haas
ACRYSOL (WS) from Hass)
A carboxylated copolymer of polybutyl acrylate and styrene available as No. 24 may also be used. A solution of the dye in an oil solvent is then added to the acrylic resin-CMC solution. Suitable dyes and oil solutions are well known in the art. A preferred oil-dye solution consists of a basic color-forming lactone or phthalide dye that is colorless or light-colored and develops color on contact with acidic substances, dissolved in an effective solvent such as an alkyl biphenyl. The particular dye(s) and oil(s) used do not themselves form part of the invention. However, in a preferred embodiment, the dye(s) used are dissolved in the active oil at a concentration of 3 to 12% by weight. A crosslinking agent, such as a cationic water-soluble polyamide-epichlorohydrin resin that crosslinks the carboxymethyl cellulose and the water-soluble wall-forming carboxylated acrylic resin, is added to the resulting two-phase mixture. Other useful crosslinking agents include formaldehyde resins or formaldehyde-providing resins such as melamine formaldehyde resins. Hercules
Kymene 557H, available from Co., Ltd., is a preferred crosslinking agent. Kimene 557H is a highly efficient cationic, high wet strength resin that functions in acidic or alkaline conditions. The combination of CMC, acrylic resin, and such crosslinking materials produces a highly flexible and strong water-insoluble film. According to research reported by Herkyul, chimene reacts with hydroxyl and carboxyl groups, and primarily with carboxyl groups. An aluminum nitrate solution (eg, 5% by weight or less) is then added to the emulsion. Aluminum nitrate is CMC in this CB formulation.
It is used to insolubilize. Finally, a starch dispersion or other particle dispersion, which acts as a spacer material, is added to this mixture. The resulting coating formulation is at least 30%
It has a large solid content. The viscosity can vary widely and can be easily adjusted for specific applications by reducing water and/or using higher viscosity CMC. For air knife painting, go to Burdskfield.
The viscosity of the composition measured using an RVF viscometer (44 spindle) at 100 rpm is between 50 and 250, preferably 60
Set to ~100cps. Regarding roll coating,
The viscosity should normally range from 50 to 120 cps, for rod coatings between 50 and 600 cps, and for blade coatings between 300 and 5000 cps. The particular viscosity used will necessarily vary depending on the coating equipment used and the coating speed. In preferred embodiments, the ratio of oil and dye internal phase to CMC and organic crosslinker external phase is increased compared to the prior art. For example, in the preferred CB papers of the present invention, the amount of internal phase is increased by about 35% relative to prior art coating compositions. The formulation is applied and dried to the backside of paper or other substrates, typically at a coating weight of about 3.00 grams per square meter (dry weight) or more for non-carbon copy paper applications. When pressure is applied to the substrate, the color forming material is transferred by the oil to the underlying sheet containing material that reacts with the dye, producing a colored image corresponding to the location where pressure is applied. The essential components of the paint of the present invention have a degree of substitution of 0.65 to 1.8.
Including CMC, wall-forming carboxylated acrylic resin, organic crosslinker and metal salt. Generally this composition is used at 100 parts each (dry weight) of CMC
About, between about 50 and 200 parts of acrylic resin, 10
It should contain between 300 and 1000 parts of oil and dye and between 4.4 and 12.2 parts of salt. For each 100 parts of CMC used, the wall-forming resin is present at about 60-100 parts, the cross-linking agent at 60-100 parts, the oil and dye at 600-800 parts and the metal salt at 5-6 parts. It is preferable. If spacer particles are preferably used, they are present in the range of 100 to 500 parts, preferably 200 to 300 parts per 100 parts of CMC. The practice of the present invention provides significant advantages over conventional formulations. CB coatings with higher solids content and lower viscosity can be applied and dried at higher sprayer speeds and with significant energy savings. Productivity in coating preparation is increased by the ability to obtain fewer batches while maintaining the same dry coat weight.
This paint has greater whiteness than traditional CMC-based CB compositions. Images can also be formed with lower pressures due to improved ejection efficiency. In the compositions of the present invention, the CMC, the carboxylated acrylic resin, and the crosslinking agent work together to produce an aqueous coating composition with controllable and stable viscosity properties at any one point within a wide viscosity range. enable. The invention will be further understood by the following examples, which are given by way of illustration only and are non-limiting. Example 1 A CB coating composition for blue marks with a large solids content was prepared by the following method. All ratios are given by weight. The following solutions were prepared. Parts by weight of substance Formulation A H ₂ O 920.00 Carboxymethylcellulose (1.2DS, low viscosity) 1 / solids content of the resulting solution 80.0 Formulation B Oil and dye 2 / dye content of the resulting solution 4.7%
1820.0 Formulation C Starch Spacer Dispersion 3 / Solids content of the resulting solution 32.48% 1000.0 1 / Na-CMC obtained from Harkyul
12 UL 2 /820 parts deodorized kerosene, preferably obtained from Penreco, and 100 parts alkyl biphenyl [Koch
Suresol 290] and Crystal Violet Lactone and Copichem
[Obtained from Hilton Davis]. 3 /preferably water; CMC-7H available from Hercule; and starch particles (particle size approximately 10
~25 microns). 120 parts of carboxylated polyethyl acrylate/methyl methacrylate copolymer (preferably Carbocet 514H) are added to 1300 parts of Formulation A. To the resulting mixture, 600 parts of Formulation B are added with stirring. Stirring is continued until this emulsification is completed. 100 parts of a polyamide-epichlorohydrin crosslinker (preferably Chimene 557H) is then added to this emulsion. Next, 170 parts of an aqueous aluminum nitrate solution containing 1.4% solids is gradually added to 1200.0 parts of the emulsion. At this point, the solids content of the paint is 31% and the Bruckffield viscosity at 100 rpm [temperature approx.
25.6℃(78〓)PH5.9〕 is 250cps. The oil droplet size is 2-10 microns. Finally, 300 parts of Formulation C are added to give a coating composition with a solids content of 32% and a Bruckfield viscosity of 200 cps. Example 2 A CB paint with a high solids content was prepared by the following method. Formulations A-C are prepared according to Example 1. 670
120 parts of polyethyl acrylate/methyl methacrylate copolymer are added to 1 part of Formulation A. 600 parts of Formulation B are added to the resulting mixture with stirring. Next, 480 parts of polyamide-epichlorohydrin crosslinker are added. then 1200
Gradually add 190 parts of aluminum nitrate containing 1.4% solids to 1 part emulsifier. At this point, the temperature of the paint formulation is 78°, the pH is 5.6, and the solids content is 35%. The Burckfield viscosity is 100 cps, and the oil droplet size is between 2 and 10
It is micron. Finally 340 for the paint composition
When Part C of Formulation C is added, the solids content is 35.4%.
And the Burckfield viscosity is 90 cps. 5
After stirring for ~10 minutes, the viscosity is 120 cps. Example 3 To 765 parts of Formulation A, 125 parts of carboxylated polyethyl acrylate/methyl methacrylate copolymer are added. For the resulting mixture
Add 900 parts of Formulation B with stirring. then 400
Add part of polyamide-epichlorohydrin crosslinking agent. Then, 160 parts of aluminum nitrate solution (1.4% solids) are gradually added to 1200 parts of this emulsion. At this point, the solids content of the paint was 42%.
The viscosity is 160 cps, the pH is 5.8, and the temperature is 78〓.
The particle size of the oil droplets is 2-10 microns. Finally, 220 parts of Formulation C are added to the coating composition, resulting in a solids content of 41% and a viscosity of 130 cps. The coating composition described in each of the above Examples was applied to a white paper substrate using a laboratory air knife coater.
Target coat weights ranging from ~5.2 g/m ² were carried out and tested against similar coats at coat weights within the same range of coating compositions representative of the prior art. By way of example, the results obtained by applying the composition of Example 3 are compared with those according to the prior art. 1 Chromogen release efficiency A sheet strip containing the test paint was provided so that the test paint was superimposed on the developer coating of the sheet strip. The two strips thus assembled were then run between steel calender rolls under constant pressure. Read the non-imaging area of the receiving sheet using a densitometer and reflectance meter, and then calender 60
After a second, the imaged area of the receiving sheet was similarly read. The image density for each case was then calculated as follows: Image density = reading of imaged area/reading of non-imaged area x 100 (the lower the "image density" value, the darker or denser the image is) ) Results are as follows: Image Density Conventional Coating 50.0 Coating of “Example 3” 45.6 n=4 2 Paint Fading The reflectance readings of the uncoated paper substrate and the test paint were measured using a Minolta Chromameter ( Chroma
meters). In each case a six-sheet stack was placed below the measuring chip, with the sheets of each stack facing the measuring chip with the relevant side of the sheet. The results obtained are as follows.

[Table] The obtained values "a" and "b" are shown in the attached drawing. In the figure, circular symbols indicate uncoated paper, square symbols indicate the case of the prior art, and triangular symbols indicate the coated product of "Example 3". The accompanying drawings are graphs showing reflectance readings for uncoated paper substrates, paper substrates coated with prior art low solids coating compositions, and coating compositions formulated in accordance with the present invention. It is. The graph shows the improved whiteness of CB paper made according to the present invention. These data show that the "Example 3" coating is much closer in color to the white paper substrate (preferably) than the coatings representing the prior art. The invention may be embodied in other specific forms without departing from its spirit or scope. Accordingly, other embodiments are also within the scope of the claims.

[Brief explanation of drawings]

The figure is a graph showing the improved whiteness of CB paper according to the present invention in comparison with coated paper according to the prior art.

Claims (1)

Claims: 1. A paintable aqueous formulation with a high solids content for application to a substrate to produce a pressure-releaseable colorant, said formulation having a degree of substitution between 0.65 and 1.8. and carboxymethyl cellulose, having a viscosity of 170 centipoise or less as a 6% aqueous solution and present in an amount of 100 parts by weight, a salt of a polyvalent metal, present in an amount ranging from 4.4 to 12.2 parts by weight, 50 to a wall-forming carboxylated acrylic resin present in an amount ranging from 200 parts by weight; an organic crosslinking agent present in an amount ranging from 100 to 500 parts by weight; spacer particles, and a color-forming dye dissolved in an oil-based solvent, wherein the color-forming dye is present in an amount within the range of 300 to 1000 parts by weight, and the color-forming dye is present in an amount within the range of 3 to 12% in the oil-based solvent. wherein said material has a total non-aqueous content of at least
30% by weight and present in an amount sufficient to provide a Bruckfield viscosity at 25.6°C (78°C) in the range of 50 to 5000 cps. 2. A formulation according to claim 1, wherein the organic crosslinking agent is polyamide-epichlorohydrin. 3. A formulation according to claim 1, wherein the wall-forming acrylic resin is a carboxylated copolymer of polyethyl acrylate/methyl methacrylate. 4. A formulation according to claim 1, wherein the Bruckfield viscosity is in the range of 50 to 250 cps. 5. The material has a total non-aqueous content of at least 35% by weight and a Bruckfield viscosity of 60 to
A formulation as claimed in claim 1 for air knife painting present in an amount sufficient to provide within 100 cps. 6 Substitution degree of carboxymethyl cellulose is 1.1
~1.5 and its viscosity as a 6% aqueous solution is 170 cps or less
Preparations as described in Section. 7. Claim 1 comprising the following materials in the following parts by weight : metal salt 5-6 CMC 100 acrylic resin 60-100 cross-linking agent 60-100 dye and oil 600-800 spacer particles 200-300 Preparations as described in Section. 8 Paintable aqueous formulations with a high solids content for application to substrates to produce pressure-releaseable color bodies, with a degree of substitution of 0.65 to 1.8 and 170 as a 6% aqueous solution by weight. carboxymethylcellulose having a viscosity of less than or equal to centipoise and present in an amount of 100 parts by weight; a salt of a polyvalent metal present in an amount ranging from 4.4 to 12.2 parts by weight; an amount ranging from 50 to 200 parts by weight; a wall-forming carboxylated acrylic resin present in an amount ranging from 10 to 150 parts by weight, an organic crosslinking agent present in an amount ranging from 100 to 500 parts by weight, and a spacer particle present in an amount ranging from 300 to 500 parts by weight. 1000 parts by weight, and the color dye is present in the oil solvent in an amount ranging from 3% to 12%, wherein said material is completely free. At least aqueous content
A coating weight of not less than 3.00 g per square meter of said formulation at 30 wt. A coated sheet for pressure-sensitive recording members that releases a color-forming substance when pressure is applied, and includes a base material on which a coating film is formed by adhering and drying the coating. 9. The coated sheet for a pressure-sensitive recording member according to claim 8, wherein the organic crosslinking agent is polyamide-epichlorohydrin. 10. The coated sheet for a pressure-sensitive recording member according to claim 8, wherein the wall-forming acrylic resin is a carboxylated copolymer of polyethyl acrylate/methyl methacrylate. 11 The Bruckfield viscosity is 50 to 250 cps
A coated sheet for a pressure-sensitive recording member according to claim 8, which falls within the scope of claim 8. 12 The material has a total non-aqueous content of at least 35
wt%, and the Burckfield viscosity is 60
9. A coated sheet for a pressure sensitive recording member according to claim 8, wherein the air knife coating formulation is present in a sufficient amount to provide a pressure sensitive recording material in the range of .about.100 cps. 13 The degree of substitution of carboxymethyl cellulose is
1.1 to 1.5 and has a viscosity of 170 cps or less as a 6% aqueous solution. 14. Claim 8 comprising the following materials in the following parts by weight : metal salt 5-6 CMC 100 acrylic resin 60-100 cross-linking agent 60-100 dye and oil 600-800 spacer particles 200-300 Coated sheet for pressure-sensitive recording members as described in Section 1.