JP2889237B2 - Method for producing aqueous dispersion of developer for pressure-sensitive copying paper - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a process for producing an aqueous dispersion of a color developer for a pressure-sensitive copying paper having a high concentration and improved handleability and storage stability, and particularly to a dispersant. The present invention provides a method for producing a color developer aqueous dispersion which can significantly improve the color developability, printability, and light resistance of a color developer sheet by using a specific polyvinyl alcohol as a colorant. [Prior Art] Novolak-type phenolic resins and metal salts of substituted salicylic acids are called organic developers with respect to inorganic developers such as activated clay, and are widely used for pressure-sensitive copying paper ( No. 42-20144 and No. 51-25174). These color developing agents are usually finely pulverized or finely dispersed in water, mixed with an inorganic pigment, an adhesive, and the like, and then applied to the paper (Japanese Patent Publication No. 48-16341, Japanese Patent Application Laid-Open No. −14332
No. 2). By the way, the metal salt of substituted salicylic acid used as a developer for pressure-sensitive copying paper (hereinafter simply referred to as a developer) usually consists of an amorphous solid. Since this color developer is generally dispersed in water and applied to the paper surface, it is most desirable that the color developer be supplied as an aqueous dispersion which is thick and has excellent handleability and stability. However, when the coarse particles of the developer are finely pulverized in water containing a dispersant to a size suitable for application by a ball mill or a sand grinder, the dispersion becomes remarkably thixotropic. Poor fluidity makes handling difficult. In order to make it more or less fluid, it is necessary to lower the concentration of the developer in the dispersion or to use a large amount of the dispersant to such an extent that foaming is remarkable. On the other hand, when this developer is dissolved in an organic solvent and emulsified and dispersed in an aqueous solution containing a dispersing agent by vigorous stirring means, an emulsified dispersion having good fluidity even at a high concentration can be obtained. Since the droplets contain a solvent, during storage for a long period of time, a phenomenon occurs in which the size of the particles becomes large or the emulsification is destroyed near the wall of the container, resulting in a lack of stability. Therefore, the inventors of the present invention have conducted intensive studies on the development of a developer aqueous dispersion having a high concentration and excellent handleability and storage stability. As a result, the softening point containing a specific substituted salicylate as a main component was determined.
A developer at 30 ° C. or higher is emulsified and dispersed in water containing a dispersant at a temperature at least 30 ° C. higher than the softening point of the developer, and then cooled, or the developer is dissolved in an organic solvent. The resulting solution was emulsified and dispersed in water containing a dispersant,
Subsequently, a method of dispersing the color developing agent in water as true spherical particles by heating this dispersion and distilling off the organic solvent was found, and was previously filed as Japanese Patent Application No. 62-5129. The aqueous dispersion of the developer obtained by this method is excellent in handleability and storage stability even at a high concentration, and has an extremely large industrial effect. However, when a developer sheet for pressure-sensitive copying paper is manufactured using the obtained aqueous dispersion of the developer, there is still room for improvement in various quality characteristics to be provided by the developer sheet. Have been. [Problems to be Solved by the Invention] An object of the present invention is to provide a developer which is excellent in handleability and storage stability at a high concentration and which can remarkably improve the color developing property, printability and light fastness of a developer sheet. An object of the present invention is to provide a method for producing an aqueous dispersion. [Means and Actions for Solving the Problems] The aqueous developer dispersion of the present invention has the general formula [I] (In the general formula [I], R ₁ , R ₂ , R ₃ , and R ₄ may be the same or different, and may be a hydrogen atom, a halogen atom, an alkyl group having 1 to 9 carbon atoms, an alkylene group, a cycloalkyl group. , A cycloalkylene group, a phenyl group, a nucleus-substituted phenyl group, an aralkyl group or a nucleus-substituted aralkyl group, wherein two of R ₁ , R ₂ , R ₃ , and R ₄ are adjacent to each other to form a ring When at least _one of R ₁ , R ₂ , R ₃ , and R ₄ is an alkylene group, a nucleus-substituted aralkyl group or a cycloalkylene group, one molecule contains two or more salicylic acid skeletons. N is a number of 1 or more, and M is magnesium, calcium, zinc, aluminum, iron, cobalt,
Indicates nickel or their basic ions. ) Softening point 30 mainly composed of substituted salicylate represented by
C. or higher, in an aqueous solution of polyvinyl alcohol having a degree of polymerization of 1,000 or more and a saponification degree of 70% or more, melt-emulsify and disperse at a temperature at least 30 ° C. higher than the softening point of the developer. Then, it is manufactured by a cooling method. Further, a developer having a softening point of 30 ° C. or higher containing the substituted salicylate represented by the general formula [I] as a main component is dissolved in an organic solvent, and this solution has a degree of polymerization of 1,000 or more. It is also manufactured by emulsifying and dispersing in a polyvinyl alcohol aqueous solution having a degree of 70% or more with or without heating, and then heating the dispersion to distill and remove the organic solvent. It is considered that the surface of the fine particles of the color developer containing a substituted salicylate as a main component is strongly charged in water. It is known that when strongly charged non-spherical particles are dispersed in water, a partial non-uniform charge on the surface of the particles forms a structure and restricts free movement of the particles. In an aqueous dispersion of such particles, the smaller the size of the particles, the denser the structure is formed, and the more the dispersion becomes remarkably thixotropic, and the greater the tendency to lose fluidity. If the developer of the present invention is pulverized as it is to a preferable particle size, it almost loses fluidity. On the other hand, the surface charge of the spherical particles is the most uniform, and the aggregate of these particles only repels each particle evenly and does not hinder the movement of the particles. The viscosity is small. In fact, when preparing the respective aqueous dispersions of the non-spherical particles and the true spherical particles of the developer under the same other conditions of the present invention, the fluidity is remarkably different, and it must be surprising. . To prepare a non-spherical dispersion of a developer containing a substituted salicylate having a softening point of 30 ° C or higher as a main component, a coarse particle of the developer is dissolved in water containing a dispersant using a ball mill or a sand grinder. It is preferable that the powder is pulverized and dispersed in a pulverizer at a temperature at least about 20 ° C. lower than its softening point. This dispersion has the advantage that it does not settle, even if it contains coarse particles, but has the disadvantage that it has poor fluidity and that the particles fuse and solidify at temperatures near the softening point. On the other hand, the developer dispersion obtained by the two methods of the present invention contains almost only spherical particles, and is highly fluid even at a dispersoid content of about 55% by weight. Then, even if these are stored for a long period of time, the dispersed state is not destroyed. Each of the substituted salicylates represented by the general formula [I] has a large color developing ability for pressure-sensitive copying paper, and typical examples thereof include zinc 3-methyl-5- (α-methylbenzyl) salicylate and 3 Zinc 3,5-ditertiarybutylsalicylate, zinc 3-tert-butyl-5-phenylsalicylate, zinc 3,5-ditertiaryamylsalicylate, zinc 3,5-dicyclohexylsalicylate, 3-cyclohexyl-
Zinc 5- (α-methylbenzyl) salicylate, zinc 3-phenyl-5- (α-methylbenzyl) salicylate, 3
Zinc-phenyl-5- (α, ∽-dimethylbenzyl) salicylate, zinc 3- (α-methylbenzyl) -5-phenylsalicylate, zinc 3,5-di (α-methylbenzyl) salicylate, 3- (α- Methylbenzyl) -5- (α,
zinc α-dimethylbenzyl) salicylate, zinc 3- (α-methylbenzyl) -5-bromosalicylate, 3- (α
-Methylbenzyl) -4-methylsalicylate, 3-
(Α-methylbenzyl) -6-methylsalicylate zinc,
Zinc 3-nonyl-5-phenylsalicylate, 5- (4-
Mesitylmethylbenzyl) zinc salicylate, zinc pinenated salicylate, zinc 3-hydroxy-2-naphthoate,
3-hydroxy-7- (α, α-dimethylbenzyl)-
Zinc 2-naphthoate and the zinc of these substituted zinc salicylates are replaced with magnesium, calcium, aluminum,
Salicylates in place of iron, cobalt or nickel may, for example, be mentioned. Some of these substituted salicylates are crystalline by themselves, and their softening points also vary. In order to prepare a non-crystalline developer having a preferable softening point, many of them must be properly mixed and adjusted to obtain desired physical properties. If the softening point of the developer is too low, the developer applied and dried on the paper surface will penetrate and transfer between the paper fibers, causing a loss of the color developing effect, and the aqueous dispersion of the color developer will also solidify. And it is not sufficiently stable over a long period of time. On the other hand, even if the softening point of the color developer is too high, it hardly exhibits self-adhesion when it is applied and dried on the paper surface, so a large amount of adhesive is used to fix this to the paper surface. In that case, the adhesive becomes a film to prevent migration of the dye solution in the microcapsules, resulting in a loss of color developing effect. For these reasons, the lower limit and the upper limit of the preferable softening point range of the developer are determined. The softening point of the developer is preferably 30 ° C. or higher, more preferably 35 ° C.
To 85 ° C. As a method of adjusting the softening point of the developer to a preferable temperature, first, a developer having a different softening point is mixed, and second, the softening point is lowered to a developer having a too high softening point. Substances such as metal salts of fatty acids, trialkylphenols, triaralkylphenols or styrene oligomers, and thirdly, substances that increase the softening point to a developer having a softening point that is too low, such as Addition of polystyrene, poly-α-methylstyrene, petroleum resin, or the like is included. The softening point referred to in the present invention refers to a softening temperature in a state where the developer contains equilibrium moisture in water. Normally 50 from the softening point in the dry state
It is as low as about ° C. In addition, the term “spherical” refers to a state in which a droplet naturally becomes spherical due to the effect of its surface tension and solidifies. In the method of the present invention, a color developer comprising a substituted salicylate as described above, in water containing a dispersant, at a temperature higher than the softening point of the color developer by 30 ° C. or higher, more preferably at a temperature higher by 50 ° C. or higher, Preferably, a method in which the organic solvent is removed by melting and emulsifying and dispersing by a strong stirring means or the like and then cooling, or by emulsifying and dispersing a developer dissolved in an organic solvent in water containing an emulsifier and then heating the dispersion. An aqueous dispersion of a color developer is produced, but when a polyvinyl alcohol with a polymerization degree of 1,000 or more and a saponification degree of 70% or more is selected as a dispersant to be contained in water, a very important feature is obtained. Have Usually, as a dispersant for dispersing the organic developer in water, for example, an alkali salt of an alkyl sulfate, an alkali salt of an alkylbenzene sulfonic acid, an alkali salt of an alkyl naphthalene sulfonic acid, an alkali salt of an oleic acid amide sulfonic acid, Anionic surfactants such as alkali salts of dialkylsulfosuccinic acids, nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene fatty acid esters, natural polymer substances such as gum arabic, sodium alginate, agar, gelatin, and carboxy Methyl cellulose, hydroxyethyl cellulose,
Semi-synthetic polymer substances such as carboxymethylated starch, phosphorylated starch, sodium ligninsulfonate, methyl vinyl ether, maleic anhydride copolymer, ethylene / maleic anhydride copolymer, styrene / maleic anhydride copolymer, acrylic Polymers such as acid polymers, acrylic acid / methyl methacrylate copolymers, acrylic acid / acrylamide copolymers, vinylbenzenesulfonic acid polymers, and alkali polymers of copolymers, and synthetic polymers such as polyvinyl alcohol and polyacrylamide Substances and the like can be mentioned. In the method of the present invention, among them, polyvinyl alcohol is particularly selected, and a specific polyvinyl alcohol having a polymerization degree of 1.000 or more and a saponification degree of 70% or more is used as a dispersant. is there. The selective use of such a specific polyvinyl alcohol further facilitates emulsification of the developer in water, and increases the particle size of emulsified particles generated when the organic solvent is removed from the dispersion by using an organic solvent. Also, the formation of a resin mass does not occur, and a developer aqueous dispersion having extremely improved storage stability can be easily produced. Moreover, the obtained developer aqueous dispersion is prepared as a developer coating solution for pressure-sensitive copying paper, and the resulting developer sheet obtained by coating or impregnating a suitable support such as paper, film, etc. Compared with the case where other dispersants are used, the coloring properties are excellent, the printability such as surface strength is good, and the light resistance is also excellent. As described above, the polyvinyl alcohol used in the method of the present invention is a polyvinyl alcohol having a degree of polymerization of 1,000 or more and a degree of saponification of 70% or more.
If the polyvinyl alcohol is less than 000, the emulsifying ability of the color developer becomes insufficient, and a water dispersion of the color developer with improved storage stability cannot be obtained. Therefore, polyvinyl alcohol having a degree of polymerization of 1000 or more is used. However, when the degree of polymerization exceeds 5,000, the viscosity of the aqueous polyvinyl alcohol solution becomes high, and handling becomes difficult, so the degree of polymerization is 50.
It is desirable to keep it at about 00 or less. The saponification degree is 70%
Polyvinyl alcohol having a degree of saponification of 70% or more, more preferably 80% or more, is used because the emulsifying ability becomes insufficient with a polyvinyl alcohol less than the above. The amount of polyvinyl alcohol used is appropriately adjusted depending on the size of the target dispersed particles, but is preferably adjusted at a ratio of about 1 to 30 parts by weight with respect to 100 parts by weight of the developer. It was also found that when an anionic surfactant was used as a dispersant in addition to polyvinyl alcohol, an aqueous dispersion having further improved emulsifying ability and more improved storage stability was obtained. Examples of the anionic surfactants used in combination include low molecular weight anionic surfactants such as alkali salts of alkyl sulfates, alkali salts of alkylbenzene sulfonic acids, and alkali salts of oleic amide sulfonic acids, gum arabic, and sodium alginate. Such as anionic natural polymers, carboxymethylcellulose, phosphorylated starch, anionic semi-synthetic polymers such as sodium ligninsulfonate, acrylic acid polymer, vinylbenzenesulfonic acid polymer, acrylic acid / methyl methacrylate copolymer, Examples include alkali salts of anionic synthetic polymers such as acrylic acid / acrylamide copolymer and ethylene / maleic anhydride copolymer. It is necessary to pay attention to the combination ratio of these anionic surfactants, and if a large amount of the anionic surfactant is used, the resulting coloring sheet will have a lowering of the color developing performance and surface strength. It is desirable to adjust it in the range of about 2 to 50% by weight of polyvinyl alcohol. In the preparation of the developer dispersion, the size of the developer particles should be determined by judging from the applicability of the developer to the paper surface or the color developing effect thereof. Generally, the color developing agent of the present invention is applied only at a rate of 1 g or less per square meter of the paper surface. Therefore, when the size exceeds 5 microns, the distribution on the paper surface becomes uneven upon application and recording is performed. There are disadvantages such as loss of images and a reduction in the speed of developing recorded images in cold regions. The size is 0.3
If the particle size is smaller than a micron, the particles easily penetrate between the paper fibers, causing a loss of the color developing effect. Even if the particles are made finer than that, there is no advantage. Therefore, the preferred range of developer particle size is 0.3 to 5 microns in average particle size,
A more preferred range is 0.6 to 3 microns. The relationship between the shape of the color developer particles and the properties of the aqueous dispersion is as described above. One of the objects of the present invention is to provide a color developer having a high concentration and good handleability and good long-term storage stability. Because it is intended to provide an aqueous dispersion, it is preferable that the majority of the particles are spherical particles, but if non-spherical particles coexist to such an extent that the fluidity is not reduced, the liquid becomes thixotropic. In this way, sedimentation of large particle diameters is prevented. One method of adjusting the ratio of the spherical particles is to mix a dispersion of the spherical particles and a dispersion of the non-spherical particles separately prepared, and the other is a method of mixing the prepared spherical particles. A method of further finely pulverizing the aqueous dispersion of the particles with a sand grinder or the like at a temperature lower than the softening point of the particles by 20 ° C. or more, which is particularly preferable when coarse particles are mixed in spherical particles, and the coarse particles Are also preferentially refined to have a narrower particle size distribution, and also have the advantage of being more preferable as a color developer. The concentration of the developer in the aqueous dispersion of the present invention is usually a high concentration of 10% or more, and a preferable upper limit is 55%. With such a high concentration, not only the transportation cost can be reduced, but also a high-concentration coating solution can be prepared, and the drying efficiency in the coating step can be increased and the effect of improving the quality of the obtained color developing sheet can be expected. In the present invention, the organic solvent used in the method of dissolving a color developer in an organic solvent has relatively low solubility in water, good solubility of the color developer, low boiling point, or preparation of a dispersion. Various properties such as being less susceptible to chemical changes are required. Specific examples are benzene,
Toluene, xylene, chloroform, carbon tetrachloride, trichloroethane, trichloroethylene, chlorobenzene,
Examples include methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, butanol, amyl alcohol, and methyl tert-butyl ether. The amount of the organic solvent used is also appropriately adjusted according to the size of the intended dispersed particles, but 500 parts per 100 parts of the developer.
It is desirable to adjust in the range of not more than parts. EXAMPLES Next, the present invention will be described more specifically with reference to examples. Example 1 100 g of zinc 3,5-di (α-methylbenzyl) salicylate (softening point: 72 ° C.) and 100 g of toluene are mixed and dissolved at 70 ° C. to prepare a toluene solution. Separately, polymerization degree 17
00, 300 g of water containing 6 g of polyvinyl alcohol having a saponification degree of 98% is placed in a stainless steel beaker with an internal volume of 500 ml, and a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) is rotated and stirred at 3,000 times per minute. While adding the above toluene solution to this. When the addition of the toluene solution is completed, the number of revolutions is increased to 10,000 times per minute, and the mixture is stirred for 2 minutes. The dispersion is transferred to a 500 ml hard glass three-necked flask equipped with a stirrer, thermometer and distillation port. The flask is heated while slowly rotating the stirrer so that toluene and water are distilled off from the distillation port. Ten
If this operation is continued for about 1 hour at 0 ° C., the dispersion contains almost no toluene. Upon cooling, an aqueous dispersion containing about 33 percent of the developer is obtained. The average particle size of the dispersed particles is 1.0 micron. This aqueous dispersion was placed in a 500 ml measuring cylinder and allowed to stand for 48 hours, and then settled particles were examined, but hardly any settling was observed. Example 2 100 g of powder of zinc 3,5-di (α-methylbenzyl) salicylate (softening point 72 ° C.), polymerization degree 1000, saponification degree 8
200 grams of water containing 10 grams of 8% polyvinyl alcohol was charged into a 1,000 milliliter stainless steel autoclave having the homomixer of Example 1 modified and hermetically sealed to allow airtight sealing. The autoclave is heated while rotating at a rate of 3,000 revolutions per minute to bring the temperature of the contents to 160 ° C. Increase the number of revolutions to 13,000 times per minute, stir for 5 minutes, then increase the number of revolutions per minute
Cool down the autoclave immediately to 3,000 times. When the temperature of the contents drops below 30 ° C, open the autoclave and take out the contents. The content contained only true spherical particles having an average particle diameter of 1.2 μm. After settling for 48 hours in the same manner as in Example 1, the settled particles were examined, but hardly any settling was observed. Examples 3 to 6, Comparative Examples 1 to 8 In Example 1, the polyvinyl alcohol used as a dispersant was polyvinyl alcohol having a polymerization degree and a saponification degree as shown in Table 1, and various dispersants and surfactants. In the same manner as in Example 1 except that the above was replaced with Example 12, 12 types of developer aqueous dispersions were prepared. The emulsifying ability, emulsifying stability, and desolvation stability of each dispersant were evaluated as follows together with Examples 1 and 2, and the results are shown in Table 1. Example 7 Instead of 100 grams of zinc 3,5-di (α-methylbenzyl) salicylate and 100 grams of toluene, 50 grams of zinc 3,5-di-tert-butylsalicylate, 40 grams of toluene and 40 grams of 1-butanol were used. A developer aqueous dispersion was prepared in the same manner as in Example 1 except that the dispersion was used. First result
It is shown in the table. (Emulsifying ability) It was shown by the average particle diameter (μm) of emulsified particles. The smaller the particle size, the better the emulsifying ability. (Emulsification stability) The emulsion was left as it was for 48 hours, and evaluated according to the following evaluation criteria. A: The particle size of the emulsified particles does not change. B: Coarse particles gradually increase. C: Oil droplets float on the surface. (Solvent Removal Stability) The following evaluation criteria were used to determine the state of the aqueous dispersion obtained by removing toluene by heating. A: There is no generation of coarse particles. B: coarse particles of about 5 μm are observed. C: Coarse particles of 20 μm or more are observed. D: A lump of resin is generated. In Comparative Examples 6 and 7, the emulsion stability of the developer toluene solution in water was poor, coarse particles were generated in the emulsion, and the developer was removed by heating in an aqueous dispersion of the developer. Produced many resin lumps. Therefore, the subsequent quality confirmation test could not be performed as it was. Further, in Comparative Example 8, the emulsion stability of the developer toluene solution in water was extremely poor, and an emulsion could not be prepared. (Quality Confirmation Test) Using the 12 kinds of aqueous developer dispersions obtained in Examples and Comparative Examples, developer application liquids for pressure-sensitive copying paper each having the following composition were prepared. Developer aqueous dispersion (concentration 33%) 30 parts by weight Light calcium carbonate 100 parts by weight Sodium polyacrylate (concentration 20%) 5 parts by weight Oxidized modified starch (concentration 10%) 50 parts by weight styrene / butadiene Latex (concentration 50%)… 40 parts by weight Water… 230 parts by weight The obtained developer coating solution is applied 6.0 g on dry paper on dry paper.
/ m ² were applied and dried to prepare 12 types of developer sheets, and the following quality confirmation tests were performed. The results are shown in Table 1. (Color-forming ability) After the carbon-free paper (top paper) manufactured by Kanzaki Paper Co., Ltd. and the above-mentioned developer sheet are opposed to each other, a color image obtained by applying a pressure of 600 kg / cm ² for 1 minute is left for 24 hours. The density was measured with a Macbeth RD914 reflection densitometer. The higher the value, the better the coloring ability. (Adhesive ability) The developer sheet was printed with a RI II printing machine manufactured by Meiji Seisakusho and the surface strength was relatively evaluated. A: Good. B: Somewhat inferior. C: No commercial value. [Effects of the Invention] As is clear from the results in Table 1, the aqueous dispersions of the developers obtained in Examples of the present invention are all excellent in handleability and storage stability. The produced developer sheet was excellent in color developability and printability, and had extremely high commercial value.

Continued on the front page (72) Inventor Toranosuke Saito 1-10-24, Itokaichi, Ibaraki-shi, Osaka Co., Ltd. Inside Sanko Development Research Institute (72) Inventor Shoichi Murata 1-110-24, Itokaichi, Ibaraki-shi, Osaka (72) Inventor Eiji Kawabata 1-10-24, Itokaichi, Ibaraki-shi, Osaka, Japan Incorporated Sanko Development Research Institute (56) Reference JP-A-57-191087 (JP, A) 63-98483 (JP, A) Patent 2580144 (JP, B2) Published by the Society of Polymer Publishing, “Poval” P. 137-141 (1981) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/124-5/165

Claims (1)

(57) [Claims] General formula [I] (In the general formula [I], R ₁ , R ₂ , R ₃ and R ₄ may be the same or different, and may be a hydrogen atom, a halogen atom, an alkyl group having 1 to 9 carbon atoms, an alkylene group, a cycloalkyl group. , A cycloalkylene group, a phenyl group, a nucleus-substituted phenyl group, an aralkyl group or a nucleus-substituted aralkyl group, wherein two of R ₁ , R ₂ , R ₃ , and R ₄ are adjacent to each other to form a ring When at least _one of R ₁ , R ₂ , R ₃ , and R ₄ is an alkylene group, a nucleus-substituted aralkyl group, or a cycloalkylene group, two or more salicylic acid skeletons are contained in one molecule. N is a number of 1 or more, and M is magnesium, calcium, zinc, aluminum, iron, cobalt,
Indicates nickel or their basic ions. ) Softening point 30 mainly composed of substituted salicylate represented by
C. or higher, in an aqueous solution of polyvinyl alcohol having a degree of polymerization of 1,000 or more and a saponification degree of 70% or more, melt-emulsify and disperse at a temperature at least 30 ° C. higher than the softening point of the developer. A method for producing an aqueous dispersion of a color developer for pressure-sensitive copying paper, which is followed by cooling. 2. The method according to claim 1, wherein the degree of polymerization of the polyvinyl alcohol is 1,000 or more, and the degree of saponification is 80% or more. 3. The method according to claim 1, wherein 1 to 30 parts by weight of polyvinyl alcohol is used per 100 parts by weight of the developer. 4. The method according to claim 1, wherein the aqueous polyvinyl alcohol solution contains an anionic surfactant in a proportion equal to or less than that of polyvinyl alcohol. 5. General formula [I] (In the general formula [I], R ₁ , R ₂ , R ₃ and R ₄ may be the same or different, and may be a hydrogen atom, a halogen atom, an alkyl group having 1 to 9 carbon atoms, an alkylene group, a cycloalkyl group. , A cycloalkylene group, a phenyl group, a nucleus-substituted phenyl group, an aralkyl group or a nucleus-substituted aralkyl group, wherein two of R ₁ , R ₂ , R ₃ , and R ₄ are adjacent to each other to form a ring When at least _one of R ₁ , R ₂ , R ₃ , and R ₄ is an alkylene group, a nucleus-substituted aralkyl group, or a cycloalkylene group, two or more salicylic acid skeletons are contained in one molecule. N is a number of 1 or more, and M is magnesium, calcium, zinc, aluminum, iron, cobalt,
Indicates nickel or their basic ions. ) Softening point 30 mainly composed of substituted salicylate represented by
Dissolve the color developer above ℃ in the organic solvent, the polymerization degree is 1,000
The above-mentioned method is characterized in that the dispersion is emulsified and dispersed in a polyvinyl alcohol aqueous solution having a saponification degree of 70% or more with or without heating, and then the dispersion is heated to distill and remove the organic solvent. A method for producing an aqueous dispersion of a color developer for pressure copying paper. 6. The method according to claim 5, wherein the degree of polymerization of polyvinyl alcohol is 1,000 or more, and the degree of saponification is 80% or more. 7. The method according to claim 5, wherein 1 to 30 parts by weight of polyvinyl alcohol is used per 100 parts by weight of the developer. 8. The method according to claim 5, wherein the aqueous polyvinyl alcohol solution contains an anionic surfactant in a proportion equal to or less than that of polyvinyl alcohol.