JPS646040B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improvements in color developer sheets for pressure-sensitive copying paper. Pressure-sensitive copying paper is well known and consists of a sheet coated with microcapsules of a non-volatile organic solvent containing a substantially colorless electron-donating or proton-accepting organic compound (hereinafter referred to as a coloring agent) and an electron-accepting or proton-accepting sheet. A sheet coated with a donor compound (hereinafter referred to as a color developer) along with a binder, etc. was placed so that the coated surfaces of each sheet faced each other, and the microcapsules were destroyed by printing pressure from a ballpoint pen, pencil, typewriter, etc., and leaked out. The color forming agent solution comes into contact with the color developer and develops a color. Color formers used in pressure-sensitive copying paper include crystal violet lactone, malachite green lactone, benzoyl leucomethylene blue,
Rhodamine B lactam, 3-diethylamino-7
-Methylaminofluorane, spiropyran compounds, etc. are known. On the other hand, various substances have been proposed as color developers, but in reality, (1) inorganic solid acids such as acid clay and attapulgite disclosed in USP 2712507 are used.
(2) p-substituted phenol formaldehyde resin disclosed in Japanese Patent Publication No. 42-20144 (3) Japanese Patent Publication No. 1973
Substituted salicylic acid and its metal salts disclosed in -10856, Japanese Patent Publication No. 52-1327, etc. (4) Japanese Patent Application Publication No. 1983-
Metal-modified phenol-formaldehyde resins, which were introduced in JP-A No. 14409 and JP-A No. 48-25744, are used. Among these color developers, p-substituted phenol-
Formaldehyde resin More specifically, p-phenylphenol-formaldehyde resin has excellent coloring performance, storage stability of colored images, processability during coating, etc., and also contains no metal elements, has low pollution, and is inexpensive. It meets many of the requirements for isosensitive copying paper and is widely used. However, there is selectivity in the combination with a color former, and hardly any color develops even when it comes into contact with, for example, benzoylleucomethylene blue. Another disadvantage is that when stored indoors or exposed to sunlight, nitrogen oxides and the like in the atmosphere are adsorbed, causing the developer-coated paper surface to turn yellow. On the other hand, clay minerals such as activated clay have no selectivity to color formers and develop color with most color formers at high concentrations. Although the water resistance and storage stability of the resulting colored image are not necessarily sufficient, the storage stability and the like against solvents are excellent. In order to compensate for the drawbacks of the above color developers,
17888, phenol-formaldehyde resin and solid acids such as activated clay have been used together, and in fact, pressure-sensitive copying using p-phenylphenol-formaldehyde resin and clay minerals in combination has been carried out. Compared to using paper alone,
The above drawbacks have been significantly improved. However, when the above two types of color developers are used in combination, serious drawbacks that are not observed when they are used alone arise. That is, when used in combination, the yellowing of the developer-coated paper surface during storage is significantly promoted, and the commercial value of the pressure-sensitive copying paper is significantly reduced. Originally, p-phenylphenol-formaldehyde resin is easily oxidized by light, heat, or oxidizing substances in the atmosphere, causing yellowing and discoloration.
When used in combination with clay minerals, it is presumed that the oxidation reaction is promoted by the oxidizing action, adsorption action, or catalytic action of the clay mineral itself. To improve this drawback, various proposals have been made to add inorganic pigments such as zinc oxide and titanium oxide, ultraviolet absorbers or antioxidants, or to change or improve the latex or water-soluble polymer substances used as adhesives. However, the effect is not sufficient. In addition, in order to improve the yellowing during storage of color developer sheets using p-phenylphenol-formaldehyde resin, for example, modification (cocondensation) with alkyl-substituted phenols as disclosed in Japanese Patent Publication No. 50-29364, or special 1977-149409, 1977 Japanese Patent Publication
Methods such as blending or containing a polyfunctional phenol resin such as bisphenol A disclosed in Japanese Patent No. 59518 have been considered, but the improvements achieved by these methods are still insufficient and the differences are small. In order to meet the demands of increasingly sophisticated pressure-sensitive copy paper consumers, the present inventors have developed clay minerals and p-phenylphenol-formaldehyde resins that can reduce yellowing during storage without losing their respective excellent performance. The present invention was completed as a result of intensive studies on improving the performance of phenol-formaldehyde resin with the aim of providing a color developer sheet for pressure-sensitive copying paper that has improved and overall excellent performance. The color developer sheet of the present invention is prepared by primary condensation of (1) activated clay or acid clay and (2) p-phenylphenol and formaldehyde as a color developer in the presence of an acidic catalyst, and then the following formula () (In the formula (), R represents an alkyl group or an aralkyl group) A product characterized by containing a phenol-formaldehyde resin obtained by adding and secondary condensation of p-substituted phenol and formaldehyde. It is. The color developer sheet of the present invention has significantly improved the yellowing behavior during storage, which was considered a drawback of color developer sheets using activated clay or acid clay and phenol-formaldehyde resin, especially p-phenylphenol-formaldehyde resin. It has excellent performance that meets the demands of customers. Clay minerals used in the present invention include activated clay, acid clay, similar clays, and chemically and physically treated products thereof. In order to produce the phenol-formaldehyde resin used in the present invention (hereinafter referred to as the phenolic resin of the present invention), the condensation reaction of phenols and formaldehyde is preferably carried out in water or an organic solvent in the presence of an acidic catalyst. is carried out in a hydrophobic organic solvent that is azeotropic with water. Examples of hydrophobic organic solvents include aromatic hydrocarbons such as benzene, toluene, and xylene, pentane, heptane,
Aliphatic or alicyclic hydrocarbons such as hexane or cyclohexane, or halogenated hydrocarbons are used alone or in combination of two or more. In the method for producing the phenolic resin of the present invention, p-phenylphenol and formaldehyde are first condensed in the presence of an acidic catalyst. In this primary condensation, the amounts of p-phenylphenol and formaldehyde used are:
The proportion is 0.3 to 1.2 mol, preferably 0.5 to 0.8 mol. Outside these ranges, it is unfavorable in terms of coating performance and paper surface properties due to the softening point of the color-forming resin. Examples of the acidic catalysts used include inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as oxalic acid and p-toluenesulfonic acid. The acidic catalyst may be added in the entire amount required for both the primary condensation and the subsequent secondary condensation, or may be divided appropriately between the primary condensation and the secondary condensation. The amount of acidic catalyst used is 0.05 to 10% by weight based on the phenols, and when added all at once for primary condensation, p-
The amounts within the above ranges are used based on the total amount of phenylphenol and p-substituted phenol used. Further, the formaldehyde used is a compound that generates formaldehyde such as formalin, paraformaldehyde, trioxane, and polyoxymethylene. p-phenylphenol, formaldehyde and an acidic catalyst in the amounts used as described above in water and/or a hydrophobic organic solvent at 50-200°C, preferably 70-150°C, generally under reflux of the reaction solvent; The condensation reaction is carried out for several tens of minutes to several hours. This condensation reaction is usually carried out until most of the formalin used is consumed. Next, the p-substituted phenol represented by the formula () and formaldehyde are added to the reaction product of the above first condensation to perform second condensation. Specifically, the p-substituted phenol of formula () is:
For example, p-cresol, p-ethylphenol, p-tert-butylphenol, p-sec-butylphenol, p-tertoctylphenol,
p-2-ethylhexylphenol, p-nonylphenol, p-cyclohexylphenol, p
Compounds such as -dodecylphenol and p-cumylphenol may be mentioned. In the secondary condensation, the amount of p-substituted phenol of the formula () used is p-phenylphenol 1
0.05 to 2 moles, preferably 0.1 to 2 moles
A suitable amount is 0.8 mol; if it is less than this range, the effect of improving yellowing will be insufficient, and if it exceeds this range, coloring performance (coloring density and coloring speed) will decrease, making it undesirable for use in pressure-sensitive copying paper. The amount of formaldehyde used is 0.3 to 2.0 mol, preferably 0.6 to 2.0 mol, per 1 mol of p-substituted phenol.
The proportion is 1.2 moles. Outside these ranges, color development performance, coating performance due to the softening point of the resin, and paper surface properties deteriorate. When adding an acidic catalyst in stages during primary condensation,
From 0.05 to 10% by weight, based on p-substituted phenol, is used. These p-substituted phenols, formaldehyde, and acidic catalysts are added to the reaction product after the primary condensation, but there are no particular limitations on the addition temperature, addition method, etc., and they are usually cooled to below the reaction temperature. After that, the p-substituted phenol is added and dissolved, followed by the addition of formaldehyde and optionally an acidic catalyst. The secondary condensation reaction is similar to the primary condensation reaction, at a temperature of 50 to 200°C, preferably 70 to 150°C,
Generally, the condensation reaction is carried out for several tens of minutes to several hours while the reaction solvent is refluxed. Note that this secondary condensation reaction was carried out using separately produced p-
To obtain a phenol-formaldehyde resin that can be used in the present invention by using a phenylphenol resin and treating it with p-substituted phenol and formaldehyde in water and/or a hydrophobic organic solvent in the presence of an acidic catalyst. I can do it. The phenolic resin of the present invention is obtained by a conventional method from the secondary condensation reaction product reacted as described above. The method for preparing the color developer sheet for pressure-sensitive copying paper of the present invention is as follows: (1) A method of applying a water-based paint using an aqueous suspension of a color developer to a support such as paper; (2) A method of applying a color developer to a support such as paper; an organic solvent,
For example, methods known in the industry can be used, such as applying a solution or suspension in acetone, methyl ethyl ketone, ethyl acetate, etc. to the support, or (3) adding a color developer during paper making.
Generally, method (1) or (2), particularly method (1), is advantageous from the viewpoint of safety or productivity associated with solvent volatilization. The water-based paint is produced by thoroughly dispersing and mixing clay minerals such as activated clay, the phenolic resin of the present invention, and various additives such as pigments, dispersants, binders, and others for adjusting the paper properties of the color developer sheet. There are no particular limitations on the method of dispersion and mixing, and any method may be used as long as it allows sufficient dispersion and mixing to exhibit the properties of the color developing sheet. Practically speaking, an aqueous suspension obtained by dispersing the phenolic resin of the present invention in the presence of a dispersant using a sand grinding mill, a ball mill, an attritor, etc. is separately prepared, and then dispersed with other components. It is common to mix them. In water-based paints, examples of pigments include kaolin talc, bentonite, calcium carbonate, aluminum oxide, silicon oxide, titanium oxide, zinc oxide, polystyrene emulsion, urea-formaldehyde resin, and the like. Dispersants include phosphates such as sodium metaphosphate, sodium hexametaphosphate, and sodium tripolyphosphate, or polycarboxylate salts such as sodium polyacrylate, and binders include starch or modified starch, casein, gelatin, polyvinyl alcohol, and carboxylic acid. Methyl cellulose, styrene butadiene latex (SBR), methyl methacrylate butadiene latex (MBR), vinyl acetate (co)polymer, etc. Various additives include fluorescent brighteners, antifoaming agents, clay regulators, and lubricants. agents etc. are used. In the color developing sheet of the present invention, it is preferable to use 1 part by weight or more of the phenolic resin of the present invention, preferably 5 to 100 parts by weight, per 100 parts by weight of activated clay or acid clay. The color developing sheet of the present invention is prepared by applying the above water-based paint onto a support such as paper and drying it. The amount of paint to be applied is 0.5 g/m2 ^or more in terms of dry weight, preferably 1
~10g/ ^m2 . A coating amount of 10 g/m ² or more has little effect on improving color performance and is economically disadvantageous. Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. The method for preparing the water-based paint, the method for creating the color developer sheet, and the method for measuring color development and yellowing during storage in Examples and Comparative Examples are as follows. (1) Preparation method of water-based paint 100g of phenol-formaldehyde resin,
Anionic dispersant (Orotan 731SD; Rohm &
(manufactured by Haas) and 150 g of water were dispersed using a sand grinding mill to obtain an aqueous suspension. A water-based paint having the following composition is prepared using this aqueous suspension and other paint components. Parts by weight Aqueous suspension 2 Activated clay 5 Kaolin 5 Calcium carbonate 3 Oxidized starch 8 (20% aqueous solution) Styrene-butadiene latex
1.5 (50% dispersion) Sodium metaphosphate 0.1 Water 15 Total 39.6 (2) How to make a color developer sheet The above water-based paint was coated on high-quality paper (50 g/m ² ) so that the dry coating amount was 6 g/m ² It was coated using a Mayer bar and dried to obtain a color developing sheet. (3) Color development density Commercially available pressure-sensitive copying paper (Mitsubishi NCR paper, top paper containing crystal violet as a blue pigment and One Dye Black as a black pigment) and the above-mentioned color developer sheet. Place both coated surfaces facing each other and apply pressure using an electric typewriter to develop the color. Measure the reflectance using a TSS type Hunter colorimeter (manufactured by Toyo Seiki) using an amber filter. The color density was measured 24 hours after the color development, and the color density was measured before and 24 hours after the color development.
Color density [J] = I ₀ − I ₂₄ / I ₀ ×100 using the time reflectance I ₀ and I ₂₄ . The higher the color density, the better. Replace the upper paper and measure the two types of color development: blue and black. (4) Yellowing Yellowing was determined by (1) NOx yellowing, (2) photo yellowing, and (3) storage yellowing. (4-1) NOx yellowing Color developer sheets using phenol-formaldehyde resin turn yellow when stored in an oxidizing atmosphere.
-1055 (Nitric oxide gas fastness test method for dyed products and dyes), the degree of yellowing after exposing undeveloped color developing sheets to nitrogen oxide gas for 45 minutes in a closed container was compared. For yellowing, the reflectance after the test was measured using a blue filter, and this was taken as the whiteness. The larger the value, the smaller the degree of yellowing under the oxidizing agent (NOx) atmosphere, indicating that it is better. (4-2) Photoyellowing After irradiating the uncolored developing sheet with a fuedometer (carbon arc lamp) for 2 hours, the reflectance after the test was measured using a blue filter, and this was taken as whiteness. . The larger the value, the less yellowing caused by light and the better. (4-3) Yellowing due to storage An uncolored developer sheet was attached to a wall in a room not exposed to direct sunlight, and the reflectance after storage for 3 months was measured, and this was taken as the whiteness. The higher the value, the less yellowing occurs during storage and the better the quality. Example 1 P-phenylphenol was added to a glass flask.
136g (0.8mol), 80% paraformaldehyde
18.75g (0.5mol), p-toluenesulfonic acid 1.7
g and 204 ml of benzene, and heat while stirring. The distilled benzene-water azeotrope is cooled and separated, and the benzene layer is reacted for 4 hours while refluxing in the flask to effect primary condensation. Next, add 41.2 (0.2 mol) of p-tert-octylphenol and completely dissolve it, then add 6 g (0.16 mol) of 80% paraformaldehyde and react for an additional 3 hours while refluxing benzene to perform primary condensation. . Next, add 200g of 0.2% caustic soda aqueous solution,
The temperature was raised to 140°C under reduced pressure to remove benzene and water to obtain a pale solid resin with a softening point of 94°C. Using the obtained resin, a color developing sheet was prepared by the method described above. The results of performance evaluation of this color developing sheet are shown in Table 1. Examples 2 to 4 Resins were obtained in the same manner as in Example 1, except that the amounts of p-phenylphenol and paraformaldehyde and the type or amount of alkyl-substituted phenol were changed as shown in Table 1. A color developing sheet was prepared using the obtained resin in the manner described above. Table 1 shows the results of performance evaluation of these color developing sheets. Comparative example 1 p-phenylphenol in a glass flask
170g (1 mole), 80% paraformaldehyde 22.5
(0.6 mol), 1.7 g of p-toluenesulfonic acid and 204 ml of benzene, and heated while stirring. The distilled benzene-water azeotrope is cooled and separated, and the benzene layer is reacted at 70 to 80°C for 5 hours while refluxing in the flask. Next, 200g of 0.2% caustic soda aqueous solution was added, the temperature was raised to 140℃ under reduced pressure, benzene and water were removed, and the softening point was 88℃.
A light and colored solid resin was obtained. A color developing sheet was prepared using the obtained resin in the manner described above. Table 2 shows the results of performance evaluation of the color developer sheet. Comparative Example 2 p-phenylphenol 170 in Comparative Example 1
22.5 g of 80% paraformaldehyde were replaced with 212 g of p-cumylphenol and 30 g of 80% paraformaldehyde, respectively, and a pale colored solid resin with a softening point of 92.5° C. was obtained by the same experimental procedure. The obtained resin and the resin obtained in Comparative Example 1 were mixed in a ratio of 5:5.
A color developing sheet was obtained by the above-mentioned method. The performance evaluation results of the color developer sheet are shown below.
Shown in 2. Comparative example 3 p-phenylphenol in a glass flask
136g (0.8mol), p-tert-octylphenol
41.2g (0.2mol), 80% paraformaldehyde
24.75g (0.66mol), p-toluenesulfonic acid 1.7
g and 204 ml of benzene and heat while stirring. The distilled benzene-water azeotrope is cooled and separated, and the benzene layer is reacted at 70 to 80°C for 5 hours while refluxing in the flask. then 0.2
Add 20g of % caustic soda aqueous solution and heat to 140℃ under reduced pressure.
The softening point is reached by removing benzene and water.
A light and colored solid resin was obtained at 89°C. Using the obtained resin, a color developing sheet was prepared by the method described above. Table 2 shows the performance evaluation results of the color developer sheet.

[Table] Phenol 2 0.7 0.42 p〓tert〓Butylph 0.3
0.24 95 51.6 47.2 71.2 77.5 77.0
enol

3 0.5 0.3 p〓cumylphenol 0.5
0.4 100 49.0 48.9 75.9 78.5 78.5

le

4 0.7 0.385 p〓Cresol 0.3
0.3 106 51.9 50.5 70.6 79.5 78.0

Claims (1)

[Claims] 1. (1) Activated clay or acid clay and (2) p-phenylphenol and formaldehyde are primary condensed in the presence of an acidic catalyst, and then the following formula () (In the formula, R represents an alkyl group or an aralkyl group.) It is obtained by secondary condensation of p-substituted phenol represented by the formula (wherein, R represents an alkyl group or an aralkyl group) and formaldehyde. 1. A color developer sheet for pressure-sensitive copying paper, characterized in that it contains a phenol-formaldehyde resin obtained by secondary condensation using 0.05 to 2.0 moles per mole of p-phenylphenol.