JPH0159118B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a dispersion, and more particularly to a method for producing a color developer dispersion useful for pressure-sensitive recording paper applications. It is well known that coloring occurs when a coloring agent such as crystal violet lactone comes into contact with a coloring agent such as acid clay, phenols, salicylic acid, or benzoic acid. Recording materials that specifically utilize this phenomenon include, for example, U.S. Pat.
No. 2550471, No. 2548366, No. 2712507, No.
No. 2730456, No. 2730457, No. 3418250, JP-A-Sho
Pressure-sensitive copying paper described in Japanese Patent Publication No. 49-28411 and Japanese Patent Publication No. 50-44009, for example, heat-sensitive recording paper described in Japanese Patent Publication No. 43-4160 and U.S. Patent No. 2939009,
and electrically conductive recording paper. In the form of these recording materials, for example, a color former is dissolved in a suitable oil, and the oil droplets are encapsulated in minute capsules and applied to one side of a base sheet, while a color developer is applied to one side of a base sheet. Examples include systems that are applied to one side of the sheet. When writing with the coated surfaces of the two facing each other, the capsule in the pressurized part breaks down, and the oil containing the color former transfers to the developer surface, causing a reaction between the color former and the developer. , and a colored image appears. As an example of another form, the color forming agent and the color developing agent are made into fine particles, and they are separated by a binder, etc., and applied onto the base sheet, and one or both of them are melted by heating, and the two come into contact and develop the color. There are things that cause a reaction. The present invention relates to a method for producing a color developer dispersion used in these recording materials. The first object of the present invention is to provide a color developer dispersion in which sedimentation is prevented. Second, it provides a dispersion with improved abrasion properties. Third
Another object of the present invention is to provide a dispersion for coated paper with improved whiteness. Fourthly, the present invention provides a dispersion liquid for coated paper with improved color developing ability. Fifth,
The present invention provides a dispersion for coated paper with improved ink receptivity. These objects of the present invention are to add 0.5 to 2 parts of zinc oxide, 2 to 20 parts of calcium carbonate, and 0.01 to 1 part of sodium hexametaphosphate to one part of the metal salt of a salicylic acid derivative at a pH of 7.5 to 10.5 and a solid content of A step of pre-dispersing at a concentration of 30 to 60 wt%, followed by a step of processing with a dispersion machine using media, and a mixed binder of carboxy-modified styrene-butadiene latex and water-soluble polymer becomes 15 to 25 wt% of the total solid content. This can be achieved by preparing a color developer dispersion having a volume average particle size of 3 μm or less, which consists of a step of mixing as follows. The metal salts of salicylic acid derivatives used in the present invention include those that cause a coloring reaction when they come into contact with crystal violet, and among them, those with low water solubility are desirable. Among such metal salts of salicylic acid derivatives, compounds represented by the following general formula are particularly preferred. general formula [In the formula, R ₁ , R ₂ , R ₃ , R ₄ , and R ₅ are each a hydrogen atom, a halogen atom, a hydroxy group, an amino group,
Represents a group having 28 or less carbon atoms, such as an alkylamino group, a nitro group, a formyl group, an alkyl group, a cycloalkyl group, an aryl group, an alkylaryl group, an aralkyl group, and an alkoxy group. Adjacent groups may be ring-closed with each other to form a five- or six-membered ring. ] Among the compounds of the above general formula, particularly useful compounds are:
R ₁ is a hydroxy group, and relative to the hydroxy group, o- and/or p-3,5-di-t-butylsalicylic acid, 3-phenyl-5-butylsalicylic acid, 3-methyl-5-t- Octylsalicylic acid, 3,5-di-tert-aminosalicylic acid, 3-
Cyclohexyl-5-butylsalicylic acid, 5-cyclohexyl-3-t-octylsalicylic acid, 3
-butyl-5-isoamylsalicylic acid, 5-isoamyl-3-α-methylbenzylsalicylic acid,
3,5-di-t-octylsalicylic acid, 5-nonyl-3-benzylsalicylic acid, 5,5-isopropylidenebissalicylic acid, (3,5-di-α-ethylbenzyl)salicylic acid, 5-(3'-carboxylic acid) -4'-Hydroxybenzyl)salicylic acid (methylenebissalicylic acid), 3-tertiarybutyl-
5-(3′,5′-ditertyabutyl-4-hydroxybenzyl)salicylic acid, 3-(α,α-dimethylbenzyl)-5-(3′,5′-di(α,α-dimethylbenzyl) -4'-hydroxybenzyl)salicylic acid, 3-tertiarybutyl-5-(α,α-
Dimethyl-3',5'-dithyabutyl-4'-hydroxybenzyl)salicylic acid, 5-dodecylsalicylic acid, 3,5-didodecylsalicylic acid, 4-
Pentadecylsalicylic acid, 5-(α,α-dimethyl-3′-carboxy-4′-hydroxybenzyl)
Salicylic acid, 5-(α,α-dimethyl-4′-hydroxybenzyl) salicylic acid, 3-(2′-hydroxyphenoxy) salicylic acid, 3-(2′-hydroxy-3′-carboxyphenoxy) salicylic acid,
3-(α-methyltolyl)-5-dimethylbenzylsalicylic acid, 3-(2'-hydroxy-3'-carboxy-5'-tertiarybutylphenoxy)-5-
tertiarybutylsalicylic acid, 3-(2'-hydroxy-3',5'-tertiarybutylphenoxy)
-5-tertiarybutylsalicylic acid, 3-{2'-
Hydroxy-3′-carboxy-5′-(α,α-dimethylbenzyl)phenoxy}-5-(α,α-dimethylbenzyl)salicylic acid, 3-{2′-hydroxy-3′,5′-di(α , α-dimethylbenzyl)
phenoxy}salicylic acid, 3-(2'-hydroxy-3',5'-dicyclohexylphenoxy)-5-
Examples include cyclohexylsalicylic acid. As the salt, a single salt or a mixture of salts such as aluminum, zinc, calcium, and magnesium can be used. Particularly preferred salts are zinc salts. or,
The combined use of about 10 to 30% resin with respect to these salts is effective in reducing the water solubility of the salts. Examples of these resins include homopolymers and copolymers of aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyltoluene, and sulfonated products thereof. There are also copolymers with monomers having acidic groups, such as acrylic acid, methacrylic acid and maleic anhydride, and vinyl monomers having 2 to 8 carbon atoms. As a vinyl monomer,
Examples include olefins such as ethylene, propylene, and isobutylene, esters such as vinyl acetate, ethers such as methyl vinyl ether, aromatic vinyl compounds such as styrene and α-methylstyrene, and acrylic compounds such as butyl acrylate and hexyl methacrylate. As zinc oxide, common commercially available products such as Zinc White No. 1 and Zinc White No. 3 are used. Zinc oxide is used in an amount of 0.5 to 2 parts per 1 part of the metal salt of the salicylic acid derivative. If it is less than 0.5 parts, the stabilization of the metal salt of the salicylic acid derivative is impaired and the color developing ability is reduced, and if it is more than 2 parts, the oil absorption is reduced and the ink receptivity is deteriorated, which is not preferable. As calcium carbonate, precipitated calcium carbonate is preferable, and those for coated paper and for internal filling are preferable. Preferably, calcium carbonate accounts for at least 50% by weight of the solids in which it is predispersed. In addition to improving ink receptivity, aging activity, and whiteness when coated paper is used, calcium carbonate is also used as a mechanochemical agent for metal salts of salicylic acid derivatives during the pre-dispersion or dispersion process. It has the effect of promoting finer processing and bringing out color developing ability. Calcium carbonate is a metal salt of salicylic acid derivative1
5 to 20 parts are used for each part. If it is less than 5 parts, the above effect will be small, and if it is more than 20 parts, the color developing ability of the metal salt of the salicylic acid derivative will be inhibited, resulting in a decrease in color density. As the dispersant, sodium hexametaphosphate is suitable. Conventionally, sulfonate salts have been generally used for dispersing metal salts of salicylic acid derivatives, but when calcium carbonate is used as in the present invention, secondary aggregation of the liquid occurs, which is undesirable. Sodium hexametaphosphate is used in an amount of 0.01 to 1 part per part of the metal salt of the salicylic acid derivative. If it is less than 0.01 part, the force between the dispersed particles will be insufficient, and if it is more than 1 part, dispersion stability will be impaired, making them more likely to aggregate, resulting in larger dispersed particles and insufficient color developing ability. I can't perform. The pH during pre-dispersion or treatment with a dispersion machine is preferably about 7.5 to 10.5, particularly 8 to 10.5. In the process of the present invention, if the process is carried out under conditions where the pH is lower than this, there is a drawback that color developing ability is difficult to obtain and aggregation is likely to occur. Furthermore, if the pH is higher than this, undesirable coloring called water immersion coloring will increase when finished into coated paper. The solid content concentration is 25 to 60 wt%, preferably 35 to 50 wt%, and if it is lower than this, there are disadvantages such as requiring a long processing time for fine dispersion and accelerating wear of the dispersion machine. . Also, 60wt%
If the temperature is exceeded, the viscosity of the liquid during dispersion will increase significantly due to temperature rise, making smooth processing difficult.
Further, at this time, it is advantageous to add an acetylene glycol antifoaming agent from the viewpoint of improving the color development rate and preventing foam suppression. There are various types of dispersion machines that use media, such as sand mills, dyno mills, attritors, and ball mills, but among these, the types that use high-speed rotation for dispersion and are capable of continuous processing, such as sand mills and dyno mills, are It is most advantageous in that it is possible to sufficiently bring out the color developing ability in a short treatment time, and the reaction mixture can be continuously treated and sent as it is to the tank. Various media are used during dispersion, but usually flint stones, Otsutawa sand, steel balls, ceramics, high alumina balls, zircon, glass beads, etc. are used. Among these materials, spherical ones, especially glass beads, are excellent in ease of handling and maintenance. Furthermore, it is desirable to perform the treatment with a dispersion machine at a temperature of 30°C or lower in order to prevent the reaction product from sticking. It is very important to control the volume average particle size during these treatments. Especially for aggregates larger than 20μ.
By pulverizing the particles to a size of 3μ or less, favorable performance, color development ability, color development speed, and water immersion color development can be improved, which cannot be explained by mere prevention of agglomeration. 3μ
If it is more than that, the coating solution will tend to aggregate and settle, resulting in a significant decrease in workability. In addition to the above-mentioned calcium carbonate, an inorganic pigment can also be used in combination. Regarding the ratio of these combinations, it is important that the total solid content of calcium carbonate in the pre-dispersion liquid exceeds 50%.
Examples of such inorganic pigments include barium sulfate, barium carbonate, aluminum hydroxide, gypsum, clay, silica, diatomaceous earth, basic magnesium carbonate,
Examples include calcium silicate, acid clay, activated clay, and magnesium carbonate. Preferred among these inorganic pigments are basic pigments such as aluminum hydroxide and lime carbonate. A mixed binder of carboxy-modified styrene-butadiene latex and a water-soluble polymer is added to the finely dispersed liquid, and the mixture is sent to the coating process as a color developer dispersion. The binder is selected from the viewpoints of adhesion between the recording layer and the support, surface strength of the recording layer, and maintenance of color developing ability. Carboxy-modified latex contains 10% or less of unsaturated acids, especially acrylic acid, methacrylic acid,
Those modified with an acid such as maleic acid are preferred. Among these, a carboxy-modified latex in which a nonionic compound is stabilized, as disclosed in JP-A-53-64578, is most suitable. Water-soluble binders include proteins (e.g., gelatin, albumin, casein, etc.), cellulose (e.g., carboxymethyl cellulose, hydroxyethyl cellulose, etc.), sutucarose (e.g., agar, sodium alginate, carboxymethyl starch, gum arabic, etc.), polyvinyl alcohol. , polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, etc., but polyvinyl alcohol is the best in terms of maintaining film surface strength without reducing color developing ability. The combined ratio of the water-soluble binder and the synthetic polymer compound is about 1/3 to 3/1. The mixed binder of carboxy-modified styrene-butadiene latex and water-soluble polymer is mixed in an amount of 15 to 25 wt% based on the total solid content. If the mixed binder is less than 15 wt%, sufficient film strength cannot be obtained, and if it is more than 25 wt%, the color density will decrease. In addition, in order to obtain sufficient film surface strength using latex alone, the color developing ability is greatly reduced. If polyvinyl alcohol is used alone, sufficient film surface strength can be obtained, but the water resistance when finished into coated paper is insufficient. Dispersants, stabilizers, etc. are added to these liquids. They are also applied to the support by the coating methods described in the above-mentioned patents, such as dip coating, air knife coating, blade coating, roller bead coating, curtain coating, and gravure coating. For example, a normal neutral size paper is used as the support. It is desirable that the color developer layer be smooth, and for this purpose, it is once compressed and smoothed using a calender or the like to have a smoothness of 30 seconds to 120 seconds. Next, the coloring agent will be described. The coloring agent is dissolved in a solvent and used after being encapsulated. Specific examples of solvents include chlorinated compounds and aromatic compounds, such as chlorinated paraffin, (degree of chlorination approximately 15 to 60), alkyl or aralkylbenzene, or naphthalene (depending on the number of carbon atoms in the alkyl group). 5 or less), such as triphenylmethane,
Diphenyltolylmethane, xylylphenylethane, benzylxylylene, α-methylbenzyltoluene, monoisopropyl diphenylethane, diisopropylnaphthalene, isobutylbiphenyl, tetrahydronaphthalene, hydrogenated terphenyl, di-α-methylbenzyl, xylene, tert−
Examples include butyl diphenyl ether and hydrogenated styrene dimer. Auxiliary solvents such as alkanes, alkylenes, ethers, esters, fatty acids, etc. having a boiling point of about 80°C to 250°C may be added to these solvents in an amount of about 30% by weight or less. The coloring agent includes a compound that imparts absorption in the visible region upon contact with a metal salt of a salicylic acid derivative. For example, it has a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide, etc.
The compound is usually almost colorless. Specifically, triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds,
There are spiropyran compounds, such as crystal violet lactone, benzoyl leucomethylene blue, malachite green lactone,
p-Nitrobenzoylleucomethylene blue, 3
-Dialkylamino-7-dialkylaminofluorane, 3-methyl-2,2'-spirobi(benzo-f-chromene), 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethyl Aminophenyl)-3-(1,2-dimethylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-methylindol-3-yl)phthalide, 3- (p-dimethylaminophenyl)-3-(2-phenylindole-
3-yl)phthalide, 3,3-bis-(1,2-
dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis-(1,2-dimethylindol-3-yl)-6-dimethylaminophthalide, 3,3-bis-(9- Ethylcarbazol-3-yl)-5-dimethylaminophthalide, 3,3-bis-(2-phenylindole-
3-yl)-5-dimethylaminophthalide, 3-
p-dimethylaminophenyl-3-(1-methylpyrrol-2-yl)-6-dimethylaminophthalide, 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl leukoolamine , N-2,4,5-trichlorophenylleucoauramine, rhodamine-B-anilinolactam, rhodamine-(p-nitroanilino)
Lactam, rhodamine B (p-chloroanilino)
Lactam, 3-dimethylamino-6-methoxyfluoran, 3-diethylamino-7-methoxyfluoran, 3-diethylamino-7-chloro-6
-Methylfluorane, 3-diethylamino-7-
(acetylmethylamino)fluoran, 3-diethylamino-7-(dibenzylamino)fluoran, 3-diethylamino-7-(methylbenzylamino)fluoran, 3-diethylamino-7-
(chloroethylmethylamino)fluoran, 3-
Diethylamino-7-(diethylamino)fluoran, 3-methyl-sprodinaphthopyran, 3
-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(3-methoxy-benzo)-spiropyran, 3-
Examples include propyl-spiro-dibenzodipyran. One or more of these color formers may be used. Color formers dissolved in one or more of the solvents mentioned above are encapsulated. For example, capsule manufacturing methods include a method using coacelvation as seen in U.S. Patent Nos. 2800457 and 2800458, a method using an interfacial polymerization method as seen in British Patent No. 990443 and U.S. Patent No. 3287154, and a method using an interfacial polymerization method as seen in U.S. Patent No. 3418250. ,same
There are methods such as polymer precipitation as seen in No. 3,660,304 and Japanese Patent Publication No. 47-23,165, and reactant polymerization from inside oil droplets as shown in US Pat. No. 3,726,804. In particular, the method of forming a capsule wall outside the oil droplets is advantageous in terms of atomization of highly concentrated oil droplets. These techniques reduce the average capsule size to approximately
Form capsules (volume average capsule size) of approximately 2 μ or more with a size of 10 μ or less. The color former-containing capsules thus obtained are coated on the opposite side of the color developer layer to produce a recording material for copying. Regarding various additives, binders, antioxidants, anti-smearing agents, surfactants, coating methods, usage methods, etc. when coating the capsule layer, see US Patent Nos. 2711375 and 3625736, British Patent No. 1232347,
JP-A No. 50-44012, No. 50-50112, No. 50-
No. 127718, No. 50-30615, U.S. Patent No. 3836383,
It is well known in No. 3846311, etc. In the present invention, the amount of coloring agent used is 0.05 to
It is convenient to use ^about 0.5 g/m2, especially about 0.08 to 0.3 g/ ^m2 , and the color developer should be about 0.2 to 1.2 g/m2.
About g/m ² is used. The method for producing the color developer dispersion of the present invention will be described in detail below with reference to Examples. Example: 25 parts of activated clay, 75 parts of calcium oxide, zinc oxide
10 parts of zinc 3,5-di-α-methylbenzylsalicylate and 1 part of sodium hexametaphosphate were dispersed in 200 parts of water using a KD mill. (PH
9.1) This dispersion was processed with a sand grinder (type 32G manufactured by Igarashi Kikai Co., Ltd.) at a discharge rate of 300/hr. The obtained dispersion was stirred and mixed into a mixed binder consisting of 125 parts of an 8% aqueous solution of polyvinyl alcohol (PVA-11a (manufactured by Kuraray)) and 10 parts (as solid content) of carboxy-modified SBR latex (SN-304 manufactured by Sumitomo Naugatatsu). Add it while keeping the solid concentration.
Water was added to adjust the concentration to 20 wt% to obtain a coating solution (volume average particle size 2.5 μm). Apply this coating liquid to 40g/ ^m2 of neutral size base paper.
A recording sheet was obtained by coating and drying using an air knife coater so that a solid content of g/m ² was coated. Comparative example: 70 parts of activated clay, 30 parts of calcium carbonate, zinc oxide
10 parts of zinc 3,5-di-α-methylbenzylsalicylate and 1 part of ammonium salt of oligostyrene sulfonic acid were dispersed in a K-day mill using 200 parts of water. (PH7.3) This dispersion was discharged at a rate of 300 using a sand grinder (32G type manufactured by Igarashi Kikai).
/hr was processed. The obtained dispersion was stirred and mixed in a mixed binder consisting of 125 parts of an 8% aqueous solution of polyvinyl alcohol (PVA-11a (manufactured by Kuraray)) and 10 parts (as solid content) of carboxy-modified SBR latex (SN-304 manufactured by Sumitomo Naugatux). Add it while keeping the solid concentration.
Water was added to adjust the concentration to 20 wt% to obtain a coating liquid (volume average particle size 3.9 μm). Apply this coating liquid to 40g/ ^m2 of neutral size base paper.
A recording sheet was obtained by coating and drying using an air knife coater so that a solid content of g/m ² was coated. Comparative tests were conducted on the following items in the above Examples and Comparative Examples. (a) Developing ability Microcapsule sheet containing the crystal violet lactone mentioned above (patent application 1972-
No. 159548, prepared according to Example 1) and the recording sheet obtained in the above example or comparative example. DB type). (b) Whiteness The whiteness of the coated paper was measured using a Hunter colorimeter (manufactured by Toyo Tester). 【table】

Claims (1)

[Claims] 1 0.5 to 2 parts of zinc oxide, 1 part of a metal salt of a salicylic acid derivative, 5 to 20 parts of calcium carbonate, and 0.01 to 1 part of sodium hexametaphosphate at pH 7.5
to 10.5, a step of pre-dispersing at a solid content concentration of 25 to 60 wt%, a subsequent step of processing with a dispersion machine using media, and a mixed binder of carboxy-modified styrene-butadiene latex and water-soluble polymer based on the total solid content. A method for producing a color developer dispersion having a volume average particle size of 3 μm or less, which comprises a step of mixing so that the concentration is 15 to 25 wt%.