JP2007237696A - Microcapsule for pressure-sensitive recording material, its manufacturing method and pressure-sensitive recording material using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microcapsule for pressure-sensitive copy sheets using straight chain alkylbenzene as a solvent for dissolving an electron-donating color-developing agent equipped with an adequate color-developing property, its manufacturing method and a pressure-sensitive recording material obtained using the method and the microcapsule. <P>SOLUTION: The microcapsule for pressure-sensitive copy sheets contains a color-developing solution formed by dissolving an electron-donating color-developing agent in straight chain alkylbenzene represented by a formula C<SB>6</SB>H<SB>5</SB>C<SB>n</SB>H<SB>2n+1</SB>(n=9-14) wherein the diaphragm is formed of a polyurea film having an allophanate group. After the electron-donating color-developing agent dissolved in a mixture of polyisocyanate having the straight chain alkylbenzene and the allophanate group is emulsified and dispersed in an aqueous solution containing a polyvinyl alcohol dispersing agent, a polyurea film is formed in the emulsified particulate interface by undergoing a polymerization reaction with the addition of polyamine. The pressure-sensitive recording material is formed of the microcapsule and the electron-donating developer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a microcapsule for pressure-sensitive recording material, a method for producing the same, and a pressure-sensitive recording material using the same.

  Conventionally, a colorless or light-colored electron-donating color former (hereinafter referred to as “color former”) is incorporated in a microcapsule film in the form of a solution and applied to one side of the paper, and reacts with the color former on the other side of the paper. Apply an acid accepting material (hereinafter referred to as “developer”) such as an acidic inorganic material, polymer material, or aromatic carboxylic acid that has the property of developing a color, and face each other during use. A recording material of a type in which a copy record is obtained by overlapping and applying pressure, that is, a pressure-sensitive recording material is known. This type of recording material copying and recording mechanism uses a developer applied to the oppositely disposed paper surface to break the microcapsule film by pressure such as writing pressure, type pressure, etc., to release the color developer solution. The color is developed by contact. Also known is a recording material in which each coating material having such a coloring function is coated on one side of a sheet of paper.

  As a method for producing the microcapsules, a color former solution in which a color former is dissolved in a hydrophobic solvent is emulsified and dispersed in an aqueous emulsifying dispersant solution, and a melamine-formaldehyde initial condensate is added to the obtained emulsified dispersion and heated. In-situ polymerization method in which a resin film is formed by polycondensation is known (Patent Document 1). Also, natural or synthetic oil (specifically diisopropylnaphthalene or 1-phenyl-1-xylylethane) is used as a hydrophobic solvent for dissolving the color former, and polyisocyanate containing allophanate group and water or polyvalent amine. There has also been proposed a microcapsule based on an interfacial polymerization method in which an active hydrogen substance such as is reacted to form a wall film (Patent Document 2).

As the solvent for dissolving the color former, polycyclic aromatic solvents are mainly used. Specifically, diarylalkanes such as phenylxylylethane, phenylethylphenylethane and butyldiphenylethane; alkyls such as diisopropylnaphthalene. Examples include naphthalene; alkyl biphenyl such as monoisopropyl biphenyl. In addition, aliphatic hydrocarbon solvents such as normal paraffin and isoparaffin, alicyclic hydrocarbon solvents having a naphthene ring, alkylbenzene, and the like are also used as a diluting solvent or auxiliary solvent. In recent years, there has been a demand for highly biodegradable solvents that are more environmentally friendly, and it has been proposed to use natural oils such as vegetable oils. There are problems in terms of color development performance. On the other hand, linear alkylbenzene, which is particularly biodegradable among synthetic oils, is not used alone because of low solubility of the color former, but is only used in combination with the above polycyclic aromatic solvent (patent) Document 3 and Patent document 4).
JP-A-56-155636 Japanese Patent Laid-Open No. 8-52939 JP-A-2-47085 Japanese Patent Publication No. 60-232991

  The object of the present invention is to use a linear alkylbenzene that has been used only in combination with the above polycyclic aromatic solvent because it has a low biodegradability but low solubility of the color former. It is an object to provide a microcapsule for pressure-sensitive recording material having sufficient color development performance by using it as a main solvent for dissolving an electron-donating color former, a production method thereof, and a pressure-sensitive recording material using the same. .

In the first aspect of the present invention, a wall film is formed by encapsulating a color former solution obtained by dissolving an electron donating color former in a linear alkylbenzene represented by C ₆ H ₅ .C _n H _{2n + 1} (n = 9 to 14). Relates to a microcapsule for pressure-sensitive recording material comprising polyurea having an allophanate group.

In the second aspect of the present invention, an electron-donating color former is dissolved in a mixture of a linear alkylbenzene represented by C ₆ H ₅ .C _n H _{2n + 1} (n = 9 to 14) and a polyisocyanate having an allophanate group, thereby forming a color. A colorant solution is prepared, the colorant solution is emulsified and dispersed in an aqueous dispersant solution, a polyamine is added to the dispersion, and a polymerization reaction is performed to form a polyurea wall film including the emulsified particles of the colorant solution. The present invention relates to a method for producing a microcapsule for a pressure-sensitive recording material.

  A third aspect of the present invention relates to a method for producing a microcapsule for pressure sensitive recording material according to the second aspect of the present invention, wherein the emulsification dispersion and the polymerization reaction are each performed at 70 to 120 ° C.

  The fourth aspect of the present invention relates to a pressure-sensitive recording material comprising the first microcapsule of the present invention and an electron-accepting developer.

  By combining a film material made of polyurea having an allophanate group and linear alkylbenzene as a solvent for the color former, linear alkylbenzene, which has been used only as an auxiliary, although it is highly biodegradable, is colored. It can be used as the main solvent of the agent. The pressure-sensitive copying material using the microcapsules of the present invention is excellent in color development performance. Compared with pressure-sensitive recording materials using microcapsules using a polyurea film material composed of polyurea having an allophanate group and a polycyclic aromatic hydrocarbon solvent that has been widely used as a main solvent, Blueing) has been reduced.

Hereinafter, the present invention will be further described in detail.
The microcapsules for pressure-sensitive recording material of the present invention are obtained by encapsulating a color former solution in which a color former is dissolved in linear alkylbenzene with a film wall made of polyurea having an allophanate group.

As the linear alkyl benzene, a mono linear alkyl benzene represented by C ₆ H ₅ · C _n H _{2n + 1} (n = 9 to 14) is used. If the alkyl group has 8 or less carbon atoms, it is not preferable because the boiling point is low and the odor is strong, and if it is 15 or more, the solubility of the color former is lowered and the viscosity is increased and the color development is lowered. As the solvent, it is preferable to use only the linear alkylbenzene, but other various solvents, diluents, and auxiliary solvents may be appropriately mixed and used to the extent that the effect of the present invention is not adversely affected. it can. In general, polycyclic aromatic hydrocarbon solvents widely used as color former solvents have good compatibility with polyisocyanates containing allophanate groups, and the formed capsule wall film swells. Since the color former solution flows out and the contribution to color development is reduced, it is preferable not to use it as much as possible.

  The color former used in the present invention is not particularly limited as long as it can be used for a pressure-sensitive recording material, and known ones of various colors such as a blue color former and a black color former can be used. For example, triphenylmethane phthalide compounds, fluorane compounds, phenothiazine compounds, phenoxidine compounds, indolyl phthalide compounds, rhodamine lactam compounds, diphenylmethane compounds, triphenylmethane compounds, spirolane compounds and xanthene compounds Color formers such as compounds can be used in combination. Specifically, crystal violet lactone, benzoyl leucomethylene blue, a fluoran compound, an indolyl phthalide compound, and the like are preferable. These may be mixed as appropriate.

  The concentration of the color former in the color former solution is not particularly limited, but is usually 0.01 to 20% by mass, preferably 1 to 10% by mass with respect to the linear alkylbenzene. If the concentration is low, it is difficult to obtain sufficient color development, and if the concentration is high, dissolution in a solvent becomes difficult, which is not preferable.

A polyurea film having an allophanate group, which is a wall film of a microcapsule, is formed by reacting a polyisocyanate having an allophanate group with a polyvalent amine.
As polyisocyanate which has an allophanate group, if it melt | dissolves in a linear alkylbenzene in a microcapsule manufacturing process, it will not specifically limit, A commercially available thing can be used.

  The polyisocyanate having an allophanate group used in the present invention may be produced by any conventionally known method, but a polyisocyanate is produced by urethanizing a monomeric isocyanate compound and a hydroxyl group-containing compound. And then allophanatized with an allophanatization catalyst.

  Examples of the isocyanate compound monomer include saturated and unsaturated aliphatic, alicyclic, and aromatic monoisocyanate compound monomers such as n-hexyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, and isocyanato methacrylate, and hexamethylene diisocyanate. Aliphatic diisocyanate compound monomers, cycloaliphatic diisocyanate and other alicyclic diisocyanate compound monomers, phenylene diisocyanate, diphenyl diisocyanate, naphthalene diisocyanate and other aromatic diisocyanate compound monomers, and other aliphatic polyisocyanate compound monomers Body, alicyclic polyisocyanate compound monomer, aromatic polyisocyanate compound monomer, dimer, burette and isocyanate compound and low molecular weight And an isocyanate compound derivative, an adduct of a polyol. These isocyanate compound monomers may be used alone or in combination. From the viewpoint of wall film strength and compatibility with hydrophobic liquids, aliphatic diisocyanate compound monomers and aromatic diisocyanate compound monomers are preferred, and hexamethylene diisocyanate is suitably used as the aliphatic diisocyanate compound monomer.

  Examples of the hydroxyl group-containing compound used for urethanization of the isocyanate compound monomer include aliphatic monoalcohols such as hexanol, and divalent or trivalent or higher polyhydric alcohols such as hexanediol and glycerin. These hydroxyl group-containing compounds may be used alone or in combination. Polyisocyanate is a urethanization of the above polyisocyanate compound monomer and hydroxyl group-containing compound in an equivalent ratio (NCO group / OH group) of 2 to 100, a reaction temperature of about 20 to 160 ° C., and a reaction time of about 0.5 to 10 hours. It can be made to react. In this reaction, a conventionally known urethanization catalyst or the like may be used. The progress of the reaction can be followed by NCO% measurement or refractive index measurement of the reaction solution.

  The polyisocyanate is then subjected to an allophanatization reaction in the presence of an allophanatization catalyst. The allophanatization catalyst may be any conventionally known catalyst, for example, tetraalkylammonium hydroxides such as tetramethylammonium, tetraethylammonium, tetrabutylammonium, trimethylbenzylammonium, weak organic acid salts, trimethylhydroxypropylammonium, trimethyl. Hydroxyl ammonium of trialkylhydroxyalkylammonium such as hydroxyethylammonium, triethylhydroxypropylammonium, triethylhydroxyethylammonium and the like, organic weak acid salts, alkali metal salts of alkylcarboxylic acids such as acetic acid, caproic acid, octylic acid, myristic acid, the above alkyl Metal salts such as tin, zinc and lead of carboxylic acid, aminosilyl group-containing compounds such as hexamethylsilazane, Tertiary amines such as reethylamine, tributylamine and triethylenediamine, Mannich bases such as 2-dimethylaminomethylphenol, 2,4,6-tris (dimethylaminomethyl) phenol, β-like such as aluminum acetylacetone and lithium acetylacetone Examples include various metalorganic compounds such as diketone metal chelate compounds, Friedel-Crafts catalysts such as aluminum chloride and boron trifluoride, titanium tetrabutyrate, and tributylantimony oxide.

  The amount of the catalyst used varies depending on the type of catalyst and the like, but is usually in the range of 0.0001 to 1% by mass, preferably 0.001 to 0.1% by mass with respect to the polyisocyanate compound monomer. The allophanatization reaction is usually performed at a reaction temperature of about 0 to 160 ° C. and a reaction time of about 0.5 to 20 hours. When the reaction reaches the desired allophanate group content, for example, an allophanate catalyst deactivator such as phosphoric acid is added to the reaction system to stop the allophanate reaction. The desired allophanate group content is usually in the range of 0.1 to 10 mmol / g. As the reaction solvent, aromatic hydrocarbons such as toluene and xylene and esters such as ethyl acetate and butyl acetate can be used.

After stopping the reaction, the obtained polyisocyanate may be used as it is. However, if necessary, the deactivated catalyst is removed, and the unreacted polyisocyanate compound is further removed by a known method such as a thin film distillation method or a solvent extraction method. It is preferable to remove the monomer.
The polyisocyanate having an allophanate group thus obtained usually has an isocyanate group content of 1 to 50% and a viscosity in the range of 500 to 500,000 mPas (25 ° C.). Moreover, you may add antioxidants, such as hindered phenols, hindered amines, and organic phosphites, ultraviolet absorbers, such as benzotriazole, as needed. In the production of microcapsules, these polyisocyanates having allophanate groups can be used alone or in combination, or together with other known polyisocyanates.

Any polyvalent amine can be used as long as it has _two or more NH groups or NH ₂ groups in the molecule and is soluble in an aqueous dispersion agent solution in the emulsification dispersion step. Specific examples include aliphatic polyamines such as hexamethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, aromatic polyamines such as phenylenediamine and xylylenediamine, and trimethylolated melamine.
The amount of polyvalent amine used is appropriately determined depending on the type and amount of polyisocyanate having an allophanate group, and the ratio of isocyanate functional group equivalent / amine functional group equivalent is preferably 0.3 or more and 3 or less. Preferably it is 0.5 or more and 2 or less. When it is less than 0.3, the foaming phenomenon due to the reaction of the isocyanate group and water becomes remarkable, which is not preferable. On the other hand, if it exceeds 3, coloring due to the remaining amines and fading after coloring become remarkable, which is not preferable.

  The microcapsules of the present invention are prepared by a step of preparing a color former solution, a step of emulsifying and dispersing the color former solution in a dispersant aqueous solution, and an encapsulation step. The color former solution is preferably prepared by dissolving the color former in a mixed solution in which polyisocyanate having an allophanate group is dissolved in linear alkylbenzene. The dissolution amount of the polyisocyanate having an allophanate group in the linear alkylbenzene is usually 0.5 to 50% by mass, preferably 2 to 30% by mass. When the content is lower than 2% by mass, the strength of the formed wall film (polyurea film) is small and the capsule is likely to be broken. When the content is higher than 30% by mass, the strength of the wall film is excessively increased, leading to a decrease in color development. Absent. Dissolves polyisocyanate having allophanate groups in a mixed solution in which linear alkylbenzene is dissolved. Even when using a coloring agent that has low solubility compared to the case of using only linear alkylbenzene, it dissolves at a sufficient concentration. And sufficient color development can be obtained. That is, the amount of the color former to be dissolved is greater in the former when the polyisocyanate having an allophanate group is dissolved in a mixed solution in which it is dissolved in linear alkylbenzene and when it is directly dissolved in linear alkylbenzene.

Examples of the emulsifying dispersant used for emulsifying dispersion include natural hydrophilic polymer materials such as gelatin, gum arabic, casein, and starch, semi-synthetic hydrophilic polymer materials such as carboxymethyl cellulose, and synthetic hydrophilic polymer materials such as polyvinyl alcohol. Is mentioned. Along with these, surfactants can be used as appropriate. Of these, polyvinyl alcohol is preferred. As the polyvinyl alcohol, the average degree of polymerization is usually in the range of 300 to 2400, preferably 1000 to 1700. If the average degree of polymerization is less than 300, it is difficult to emulsify, and if it is more than 2400, the viscosity during emulsification dispersion becomes high and it becomes difficult to obtain the target emulsified particles.
The emulsifying dispersant is preliminarily dissolved in water to form a dispersant aqueous solution. The density | concentration of dispersing agent aqueous solution is 1-20 mass% normally, Furthermore, the range of 2-10 mass% is preferable. When the concentration is lower than 1% by mass, it is not preferable because it takes time for emulsification and dispersion, the production efficiency is lowered, and aggregation of the obtained capsule particles easily occurs. When the content is higher than 20% by mass, the viscosity of the aqueous dispersant solution is high, it becomes difficult to control the particle size, and the particle size distribution becomes wide, so that the decrease in color development becomes remarkable.

The emulsification dispersion is performed by stirring and mixing the color former solution and the aqueous dispersant solution. The mixing ratio of the two liquids is usually 40: 1 to 5: 1 as a mass ratio between the color former solution and the solid content of the emulsifying dispersant, and more preferably in the range of 20: 1 to 10: 1. preferable.
If the amount of the color former solution is larger than the ratio 40: 1, it takes time to emulsify and disperse, and the stability of the emulsified dispersion decreases. If the ratio is less than 5: 1, the emulsifying power becomes too large. It is not preferable because it is difficult to control the particle size, and the scale of the emulsifier is large and the cost increases.
The temperature during emulsification dispersion is preferably in the range of 70 to 120 ° C. When the temperature is less than 70 ° C, the color former is likely to be precipitated in the color former solution, and when it is higher than 120 ° C, it is dissolved in linear alkylbenzene. This is not preferable because the isocyanate thus easily reacts with water, and the wall film reaction is initiated to easily cause aggregation of particles. When the boiling point is higher than the boiling point of water, it is necessary to emulsify and disperse in an airtight container such as an autoclave.
A known homogenizer, ultrasonic homogenizer, homomixer, in-line mixer, or the like can be used as the agitator / mixer in the emulsification dispersion step. Among them, the homogenizer is easy to handle and is preferable. The stirring speed is preferably in the range of 10,000 to 15,000 rpm, and the emulsification time is preferably within 5 to 15 minutes.

  Encapsulation is performed by adding a polyvalent amine to the obtained emulsified dispersion. In general, the polyvalent amine is preferably diluted with water at a suitable amount such that the above-mentioned isocyanate functional group equivalent ratio / amine functional group equivalent ratio is diluted to 10%, for example. The polyvalent amine is preferably added gradually. The encapsulation reaction is usually performed by reacting for 3 to 6 hours. A polyurea film having an allophanate group is formed on the emulsified dispersion particle interface of the color former solution by a polymerization reaction between the polyisocyanate having an allophanate group and the polyvalent amine in the color former solution. Encapsulation is preferably carried out while maintaining the emulsified dispersion at 70 to 120 ° C. When the reaction temperature is less than 70 ° C., the color former is likely to be precipitated during film formation, and when it is higher than 120 ° C., capsule aggregation tends to occur, which is not preferable.

As described above, pressure-sensitive copying paper microcapsules are obtained as a dispersion.
The volume average particle size of the microcapsules is preferably 1 μm or more and 10 μm or less. A more preferable range is 3 μm or more and 8 μm or less. According to the production method of the present invention, desired microcapsules can be obtained. When the volume average particle diameter of the microcapsules is less than 1 μm, the color development of the recording material is lowered, and when the volume average particle diameter exceeds 10 μm, the recording material is likely to be stained, which is not preferable.

The resulting microcapsule dispersion is appropriately added with a binder, a protective agent, etc. by a conventional method, applied to the base paper of pressure-sensitive copying paper, and dried to give a microcapsule containing a color former solution. Pressure copy paper can be manufactured.
A water-soluble binder such as styrene-butadiene copolymer latex, starch, or carboxymethylcellulose can be used as the binder, and starch particles, cellulose powder, talc, or the like can be used as the capsule protective agent.

Furthermore, a pressure-sensitive recording material can be obtained by combining with an electron-accepting developer that develops color by contact with a color former.
In addition to clay, such as activated clay, acidic clay, kaolin, zeolite, bentonite as a developer, aromatic carboxylic acids, polymers thereof, metal salts thereof, or polyvalent metallized carboxy-modified terpene phenol resins or derivatives thereof, and Any one developer selected from the group consisting of these mixtures can be used.

  Here, the aromatic carboxylic acid is a compound in which a carboxyl group is directly bonded to an aromatic ring (which may be monocyclic or polycyclic), and examples of such aromatic carboxylic acid include 3,5- Di (α-methylbenzyl) salicylic acid, 3- (α-methylbenzyl) -5- (α, α′-dimethylbenzyl) salicylic acid, 3- (4′-α, α′dimethylbenzylphenyl-5- (α, α'-dimethylbenzyl) -salicylic acid, 3,5-di-tert-butylsalicylic acid, 3,5-di-tert-octylsalicylic acid, 3-cyclohexyl-5- (α, α'-dimethylbenzyl) salicylic acid, 3- Illustrative examples include phenyl-5- (α, α'-dimethylbenzyl) salicylic acid, 3,5-di (α, α'-dimethylbenzyl) salicylic acid, etc. Further, an aromatic carbo to which styrenes are added. Acids such as styrenated salicylic acid are also included, and particularly preferred aromatic carboxylic acids are aromatic carboxylic acids having a total carbon number of 15 or more when used as a co-condensation or copolymerization monomer described below. The number of carbon atoms is not particularly limited, and a condensation or cocondensation resin using an aromatic carboxylic acid, particularly salicylic acid as a condensation monomer, can also be used as the color developer of the present invention. Examples thereof include co-condensation resins with alkoxyxylene, condensation polymers of salicylic acid and aldehydes, etc. Trialkylbenzene can be further added as a co-condensation monomer, and aromatic carboxylic acids or polymers thereof can be added. Metal salts can also be used, such as zinc, aluminum, barium, tin, iron, calcium, etc. Umm, lead, and the like polyvalent metal salts, such as.

In addition, polyvalent metallized carboxy-modified terpene phenol resin or derivatives thereof are obtained by condensing cyclic monoterpenes and phenols in the presence of an acidic catalyst, and then converting the product into which carboxyl groups are introduced according to a conventional method to polyvalent metallization. The resulting polyvalent metallized carboxy-modified terpene phenol resin can be exemplified. Examples of cyclic monoterpenes include pinene, limonene, terpinene, mentadiene, gum turpentine oil, and dipentene. Examples of phenols include monophenols such as carboxylic acid (phenol), alkylphenols, alkoxyphenols, and halogenated phenols. Such as polyhydric phenols. For example, phenol as a phenol and α-pinene as a cyclic monoterpene are condensed by an acidic catalyst such as a boron trifluoride catalyst, and carbon dioxide is blown in the presence of an alkali metal compound such as sodium metal to form a carboxyl group. The carboxylated terpene phenol resin obtained by conducting is then polyvalent metalized with a polyvalent metal such as zinc chloride or a salt thereof by a known method to produce a polyvalent metallized carboxyl-modified terpene phenol resin.
Aromatic carboxylic acid as a developer, a polymer thereof, a metal salt thereof and a polyvalent metallized carboxyl-modified terpene phenol resin can also be used as a mixture. This mixing can be performed in a solvent, a dispersion medium, or by melt mixing.
Next, embodiments of the present invention will be described by way of examples.

Polyisocyanate containing 85 parts by mass of linear alkylbenzene (manufactured by Shin Nippon Petrochemical Co., Ltd., trade name: “alkene L”, alkyl group having 10 to 14 carbon atoms) and allophanate group (trade name “made by Asahi Kasei Chemicals Corporation” 2 parts by mass of crystal violet lactone as a color former were dissolved at 130 ° C. in a mixture of 10 parts by mass of “Duranate TSA-100” (NCO content = 20.7 mass%, viscosity = 451 mPa.s / 25 ° C.). Next, 10 parts by weight of polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: “PVA-217EE”) in 190 parts by weight of water was dissolved at 95 ° C. to obtain a dispersant aqueous solution. (Solution B) Set a homogenizer (trade name “TK Homomixer Mark II” manufactured by Tokushu Kika Kogyo Co., Ltd.) to the B solution maintained at 80 ° C. The liquid A was gradually added and emulsified and dispersed at 80 ° C. The obtained emulsified dispersion was stirred at 300 rpm, and 2.9 parts by mass of hexamethylenediamine was added to 20 parts by mass of water. The dissolved liquid was gradually added in a state of constant temperature at 80 ° C. to perform encapsulation (polymerization reaction), and the reaction was performed for 6 hours at 80 ° C. The average particle size of the microcapsules was measured by Coulter Counter (Coulter Co., Ltd.). Product, product name “Multisizer II”) was 5.2 μm, and the solid content in the microcapsule dispersion was 34.4% by mass. On the other hand, 27 parts by mass of a 5% by mass aqueous solution of carboxymethyl cellulose, 2.7 parts by mass of a 50% by mass aqueous solution of SBR latex, and 13.5 parts by mass of insoluble starch (average particle size 15 μm) were mixed. . Further, in order to adjust the coating amount, water was added 1100 parts by mass, it was applied using a Mayer bar coater on the 40 g / ^{m 2} base paper, pressure-sensitive dry weight 5.0 g / ^{m 2} copy paper (top Paper).

Example 1 except that Duranate TSR-100 (NCO content = 20.4 mass%, viscosity = 322 mPa.s / 25 ° C.) (manufactured by Asahi Kasei Chemicals Corporation) was used as the polyisocyanate containing allophanate groups. It is the same. The average particle diameter of the obtained microcapsules was 4.9 μm, and the solid content was 34.3 mass%. A pressure-sensitive copying paper (upper paper) having a dry mass of 5.0 g / m ² was obtained as a coated paper.

Example 1 except that Duranate TSS-100 (NCO content = 17.8 mass%, viscosity = 387 mPa.s / 25 ° C.) (manufactured by Asahi Kasei Chemicals Corporation) was used as the polyisocyanate containing allophanate groups. It is the same. The average particle size of the obtained microcapsules was 5.1 μm, and the solid content was 34.5% by mass. A pressure-sensitive copying paper (upper paper) having a dry mass of 5.0 g / m ² was obtained as a coated paper.

Instead of crystal violet lactone as a color former, 6 parts by mass of 3-isobutylethylamino-6-methyl-7-anilinofluorane (trade name “PSD-184” manufactured by Nippon Soda Co., Ltd.) is used as a black dye. Example 1 is the same as in Example 1. The obtained microcapsules had an average particle size of 5.2 μm and a solid content of 36.0% by mass. A pressure-sensitive copying paper (upper paper) having a dry mass of 6.0 g / m ² was obtained as a coated paper.

[Comparative Example 1]
2 parts by weight of crystal violet lactone as a color former is dissolved in 85 parts by weight of linear alkylbenzene (trade name: “Alken L”, manufactured by Nippon Petrochemical Co., Ltd.) at 130 ° C., and is kept at 80 ° C. to prepare solution A. did. Next, 44.6 parts by mass of a 22.4 mass% aqueous solution of methyl vinyl ether-maleic anhydride copolymer (manufactured by Nissho Kogyo Co., Ltd., trade name “MICRON 8020”) is added to 155.4 parts by mass of water as a dispersant aqueous solution. It melt | dissolved and the B liquid was adjusted by making constant temperature at 80 degreeC. A homogenizer (trade name “TK Homomixer Mark II” manufactured by Tokushu Kika Kogyo Co., Ltd.) was set in the liquid B kept at 80 ° C., and the liquid A kept at 80 ° C. was added and emulsified and dispersed. To this emulsified dispersion, 23.5 parts by mass of water and 23.5 parts by mass of an etherified trimethylolmelamine resin 80% by mass aqueous solution (manufactured by Sumitomo Chemical Co., Ltd., trade name “Smitex Resin M3”) were added. The reaction was held at 80 ° C. for 6 hours to complete the polymerization. As a result of observing the capsule slurry with a polarizing microscope after completion of the reaction, it was confirmed that a large amount of crystals of the color former were present.

[Comparative Example 2]
Instead of linear alkylbenzene (manufactured by Shin Nippon Petrochemical Co., Ltd., trade name: “Alken L”), 100 parts by mass of phenylxylylethane (manufactured by Shin Nippon Petrochemical Co., Ltd., trade name: “SAS-296”) The same procedure as in Example 1 was performed except that it was used.

[Comparative Example 3]
It carried out similarly to Example 1 except having used the biuret-type polyisocyanate (Sumitomo Bayer Urethane Co., Ltd. make, brand name "Desmodur N3200") of hexamethylene isocyanate instead of the polyisocyanate containing an allophanate group.

[Comparative Example 4]
Except for using polyisocyanate containing allophanate group, the same procedure as in Example 1 was performed except that hexamethylene isocyanate isocyanate polyisocyanate (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name “Desmodur N3300”) was used. It was.

[Comparative Example 5]
Example 1 is used except that 100 parts by mass of 1-phenylheptane (ALDRICH, purity 98%) is used instead of linear alkylbenzene (trade name: “Alken L”, manufactured by Nippon Petrochemical Co., Ltd.). The same was done. The average particle diameter of the obtained microcapsules was 5.0 μm, and the solid content was 34.3 mass%.

[Comparative Example 6]
The same procedure as in Example 1 was carried out except that 100 parts by mass of 1-phenylpentadecane (manufactured by Fluka, purity 97%) was used instead of linear alkylbenzene (manufactured by Nippon Petrochemical, trade name: “Alken L”). It was. The average particle size of the obtained microcapsules was 5.1 μm, and the solid content was 34.6% by mass. As the coated paper, a pressure-sensitive copying paper (upper paper) having a dry mass of 5.0 g / m ² was obtained.

The evaluation results of each example and comparative example are shown in Table 1 below.
1) Solubility of polyisocyanate The presence or absence of polyisocyanate dissolution in a hydrophobic liquid was visually evaluated.
◯: Almost dissolved Δ: Partially undissolved ×: Almost undissolved 2) Color former recrystallization The presence or absence of color former recrystallization released to the outside of the microcapsules was evaluated with a polarizing microscope.
○: Almost absent Δ: Partially present ×: Existent in large quantities 3) Blueing test Water was added to the microcapsule dispersion to adjust the solid content concentration to 20% by mass. 14 was applied to the coated surface of the lower paper coated with 3,5-di (α-methylbenzyl) salicylic acid zinc salt, and the colored state of the coated surface after drying was visually evaluated.
○: Almost not colored Δ: Lightly colored ×: Darkly colored 4) Color development The obtained upper paper and the lower paper coated with 3,5-di (α-methylbenzyl) salicylic acid zinc salt The coated surfaces were overlapped so as to face each other, and color was developed using an impact printing machine. The reflectance of the lower paper 60 minutes after the color development was measured with a reflectometer NDY-1D (manufactured by Nippon Denshoku Industries Co., Ltd.), and the color development intensity (%) was determined and compared using Formula-1. The higher the value, the better the color development.
Color intensity (%) = (I ₀ −I) × 100 / I ₀ (Formula-1)
(I ₀ : Reflectance of the lower paper before color development, I: Reflectance of the lower paper after color development)
5) Odor The capsule applied to the upper paper was broken, and the odor of the solvent was judged by the odor of the six panelists.
○: No odor △: Slight odor ×: Odor

Claims (4)

From a polyurea containing an allophanate group, including a color former solution in which an electron donating color former is dissolved in a linear alkylbenzene represented by C ₆ H ₅ · C _n H _{2n + 1} (n = 9 to 14) A microcapsule for pressure-sensitive recording material. A color former solution is prepared by dissolving an electron donating color former in a mixture of a linear alkylbenzene represented by C ₆ H ₅ .C _n H _{2n + 1} (n = 9 to 14) and a polyisocyanate having an allophanate group, Pressure sensitive, characterized in that a color former solution is emulsified and dispersed in a dispersant aqueous solution, and a polyurea wall film containing emulsified particles of the color former solution is formed by adding a polyvalent amine to the dispersion and performing a polymerization reaction. A method for producing microcapsules for recording materials.   The method for producing microcapsules for pressure-sensitive recording material according to claim 2, wherein the emulsification dispersion and the polymerization reaction are each carried out at 70 to 120 ° C.   A pressure-sensitive recording material comprising the microcapsule according to claim 1 and an electron-accepting developer.