JPH03202136A - Emulsifier for preparing microcapsule, microcapsule using same emulsifier and its preparation and carbonless pressure-sensitive copy paper using same microcapsule - Google Patents

Abstract

PURPOSE:To obtain a high strength microcapsule using a small amount of a film material by forming the microcapsule using an amino-aldehyde condensate as a wall material in an aqueous medium containing a water-soluble polymer composed of a copolymer of a plurality of specific monomers. CONSTITUTION:Benzyl (meth)acrylate, styrene, maleic anhydride and anhydrous maleate are copolymerized in an org. solvent by emulsion or suspension polymerization to synthesize a water-soluble and high molecular substance being a multicomponent copolymer. A microcapsule is formed in an aqueous medium containing the water-soluble and high molecular substance using an aminoaldehyde condensate as a wall film material. A coating solution is prepared by compounding the microcapsule including an electron donating color former, a buffering agent and a binder and applied to a support such as neutral paper and dried to obtain carbonless pressure-sensitive copy paper.

Description

Detailed Description of the Invention (A) Industrial Field of Application The present invention relates to an emulsifier for manufacturing microcapsules, a method for manufacturing microcapsules using the emulsifier, microcapsules obtained by the manufacturing method, and a method for manufacturing microcapsules using the emulsifier. This invention relates to carbonless pressure-sensitive copying paper.

(8) Prior Art Microcapsules contain liquid, solid, or gas as fine particles ranging in size from 1 μm to several micrometers, and are uniformly covered with a thin film. Specifically, Microcapsules for colorless and colored dyes, pharmaceuticals, agricultural chemicals, fragrances, samples, etc. have been commercialized industrially.

The most common application is to pressure-sensitive copying paper, in which (1) a colorless electron-donating dye is dissolved in an organic solvent such as diphenylalkane, contained in microcapsules, and placed on a support. (2) So-called clay paper, which is coated with an electron-accepting color developer on another support. as well as,(
3) A combination of microcapsules containing a colorless end-donating dye on one side of the support, inner paper coated with a color developer on the ground, etc. is used. When using a combination of soil paper and bottom paper, top paper, middle paper, and bottom paper, applying pressure locally so that the microcapsule layer and color developer layer are in contact with each other will cause When the microcapsules are destroyed, the colorless dye and developer react, producing color in the developer layer.

Applications to pressure-sensitive copying paper other than Section E include (4) those in which the above microcapsules and a color developer are coated on the same side of a support, or (5) those in which the above microcapsules and a color developer are coated on the same side of a support. There are some that contain one color developer and coated with the other. Even when these sheets are used alone, the pressed portion develops color and can be used as recording paper, and it is also possible to copy and record a plurality of sheets by stacking them.

In this way, by forming a thin film on the outside of a substance with a certain characteristic, microcapsules can also incorporate that characteristic at the same time, and if the film is destroyed when necessary, the encapsulated substance cannot be removed. It is something that can be done.

Conventionally known methods for making Miccoco capsules include (1) Acervation method using an ionic complex of gelatin and anionic protective colloid.

(2) An interfacial polymerization method that utilizes a film-forming reaction at the interface between the internal and external phases.

(3) 1n-3itU method (Japanese Patent Publication No. 60-210
0, JP 53-8488, JP 54-25277, JP 54-49984, JP 55-47139, JP 56-51
238, 59-177129) is known.

The above encapsulation method yields microcapsules with a dense film that has excellent protection for the contained substances, and is widely applied industrially, but there are many problems in terms of production and quality. It is also true that there are points.

That is, in the coacervation method, (1)
The pH, temperature, and operations involved in the reaction are complicated.

(2) Since it is difficult to obtain a microcapsule slurry with a concentration of 20% or more, a large amount of water must be evaporated when used for pressure-sensitive copying paper, so the working speed is low.
There is a lot of room for improvement in terms of energy costs.

(3) Since the membrane material is a natural product, there are large fluctuations in quality and price.

(4) It cannot withstand long-term storage because it tends to rot and agglomerate.

It has the following problems.

Regarding the interfacial polymerization method, although the problem with the coacervation method has been improved to some extent, it is not suitable for encapsulating unstable substances because the highly reactive film base material is reacted (at a relatively high temperature). .

Further, there are still points to be improved regarding solvent resistance and water resistance.

In the 1n-8itt+ method, encapsulation with various amino resins has been proposed and is currently widely applied industrially, but it is also true that it has the following problems.

(1) Since the water-soluble polymer substance that emulsifies the hydrophobic liquid into microdroplets has a relatively high viscosity, the obtained microcapsule dispersion inevitably has a high viscosity, and a good solid content of 50% or more is obtained. It is virtually difficult to obtain a microcapsule slurry with good flowability.

(2) In contrast to (1), when a low-viscosity water-soluble polymer substance or a water-soluble polymer whose viscosity has been lowered by diluting it with an appropriate solvent is used as an emulsifier, the emulsion stability of the hydrophobic liquid will decrease. As a result, agglomeration or coagulation of hydrophobic liquids occurs.

(3) In order to obtain high physical and chemical film strength and stability, it is necessary to use high temperature reaction conditions or to add a large amount of film material. If an encapsulation method that is sensitive to such fluctuations in conditions is adopted, in industrial manufacturing, it is easy to produce defective products due to slight errors in setting conditions or unexpected changes in conditions, which limits the scope of industrial application. is narrowed down.

Furthermore, when microcapsules obtained by conventionally known manufacturing methods are used in carbonless pressure-sensitive copying paper, static pressure color staining and heat resistance are not sufficient.

(C) Problems to be Solved by the Invention The present invention aims to solve the problems in conventionally known microencapsulation methods shown in section (Is). An object of the present invention is to provide a water-soluble polymer emulsifier suitable for a method for producing microcapsules by the +n-5ttu method, which contains a liquid as a core substance. Furthermore, the above emulsifier is used, and 1n
- By adopting the in-situ method, the purpose is to obtain a microcapsule slurry with a high solid content concentration and low viscosity, and to provide microcapsules that can have a stronger film even when using a small amount of film agent. .

A further object of the present invention is to provide a carbonless pressure-sensitive copying paper which is excellent in resistance to static pressure staining and heat, using microcapsules produced by an improved manufacturing method.

(D) Means for Solving the Problems The present invention provides an emulsifier for microcapsules containing a water-soluble polymeric substance as an active ingredient, wherein the water-soluble polymeric substance is (A) benzyl (meth)acrylate, (B) An emulsifier for microcapsules characterized in that it is a multicomponent copolymer formed by copolymerizing monomers containing a threadin, (C) maleic anhydride, and (D) a maleic anhydride ester, more preferably the multicomponent copolymer. The monomer composition of the copolymer is (A) benzyl (meth)acrylate 0.1 to 5
0 mol%, (B) styrenes 5 to 57.9 mol%, (
It is an emulsifier for producing microcapsules composed of monomers containing C) 30 to 50 mol% of maleic anhydride and (D) 2 to 20 mol% of maleic anhydride ester.

The styrenes (B) used in the present invention include styrene, α- or (β-methylstyrene), vinyltoluene,
Examples include nuclear alkyl-substituted α-alkylstyrene.

Nuclear alkyl-substituted α-alkylstyrenes include nuclear methyl-substituted α-methylstyrene, nuclear ethyl-substituted α-methylstyrene, isopropyl-substituted α-methylstyrene, etc. (D-form, m-form, and 0-form can all be used). . These styrenes can be used alone or in combination. (D) Maleic anhydride ester is obtained by a synthetic reaction of maleic anhydride and alcohol. - It is known through analysis that most of the monoesters present in boat fishing are in the form of monoesters. In addition, as an ester residue, the number of carbon atoms is 1 to 1.
The alkyl group or aralkyl group having 0 is suitable for emulsification,
From the viewpoint of microcapsule production, preferred examples include methyl, ethyl, propyl, butyl, octyl, decyl, and benzyl groups, with methyl being preferred. The composition ratio (mol %) of the maleic anhydride is preferably in the range of 2 to 20%. A ratio higher than this is not preferable because it causes a decrease in the strength of the microcapsule film.

Furthermore, the present invention provides, in an aqueous medium containing a water-soluble polymer substance,
In a method for producing microcapsules using an aminoaldehyde condensation product as a wall material, the water-soluble polymer substance includes (A) benzyl (meth)acrylate, (B) styrenes, (C) maleic anhydride, and (D) Regarding a method for producing microcapsules characterized by using a multi-component copolymer obtained by copolymerizing monomers containing maleic anhydride, more preferably the monomer composition of the multi-component copolymer is 1 (A) benzyl ( meth〉acrylates from 0.1 to 50 mol%, CB) styrenes from 5 to 57.9 mol%, (C
) using an emulsifier for producing microcapsules composed of monomers containing 30 to 50 mol % of maleic anhydride and (D) 2 to 20 mol % of maleic anhydride ester, and using aminoaldehyde as a wall material. The present invention relates to a method for manufacturing microcapsules using VJ.

The method for producing the multi-component copolymer is not particularly limited, and various known methods can be appropriately selected and employed, such as emulsion polymerization, suspension polymerization, solution polymerization, and the like. Preferably, it is obtained by copolymerizing each monomer component in a suitable organic solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and then removing the organic solvent. Various known polymerization initiators can be used without particular limitation. In the case of the above solution polymerization method, organic peroxides such as benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy 2-ethylhexylinoate, azobisisobutyronitrile, dimethyl-2, 2
Organic azo compounds such as '-azobisisobutyrate and the like can be suitably used. In order to use the obtained copolymer as an emulsifier for producing microcapsules of the present invention, the copolymer may be suitably neutralized with a suitable neutralizing agent, and then diluted and dissolved in water.

There is no particular problem as long as the composition ratio of each component monomer varies within the above range, but if even one of them deviates from this range, unfavorable phenomena will occur for the microcapsule manufacturing process and quality obtained. .

Specifically, when the composition ratio of (C) maleic anhydride exceeds 50%, not only does it become difficult to carry out periodic copolymerization reactions of each component, but even if rawhide is used as an emulsifier aqueous solution, during the emulsification process. Separation of the hydrophobic liquid, or the presence of giant hydrophobic liquid particles. Furthermore, when the composition ratio of maleic anhydride is 30% or less, the copolymerization reaction proceeds relatively smoothly, but the product becomes insoluble in water or a severe increase in viscosity occurs, which may cause unfavorable phenomena in the emulsification process. 3. Furthermore, if the ratio of styrenes is higher than this range (if the benzyl (meth)acrylate content is small), it will not be possible to obtain a strong film as described in the present invention, and conversely, if the ratio of benzyl (meth)acrylate is high, the water-soluble The viscosity of the polyester polymer tends to increase, which is undesirable as it may interfere with the emulsification process or result in the formation of incomplete capsules.Furthermore, if the ratio of maleic anhydride ester is higher than this range, the emulsion stability will be poor. This is undesirable as it causes a decrease in the strength of the microcapsule film and causes discoloration.The effect of using maleic anhydride is that a microcapsule slurry with a high solid content concentration and low viscosity can be stably obtained. In addition, the copolymer also prevents liquid coloring of the microcapsule slurry, and this is thought to be because the maleic anhydride compound exhibits a weak desensitizing pressure effect. The effect is particularly remarkable when the composition ratio of the maleic anhydride ester is 2 mol % or more.

The molecular end of the water-soluble polymer used in the present invention is preferably 1,000,000 or less in terms of borisdylene, and the viscosity measured by a B-type viscometer is 10%, pH 4, 0, 25°C. 20~ in aqueous solution
A range of 2000 cps is preferred.

The method for producing microcapsules in the present invention basically consists of the following four steps.

(1. Preparation process of water-soluble polymer (Preparation process of 2-core substance (3. Preparation process of aminoaldehyde initial condensate (4-aminoaldehyde resin formation process 1) The concentration of the solution is determined by its viscosity and emulsion stability, but is preferably in the range of 3 to 15%.

The pl+ of the aqueous solution is usually set in an acidic range of 7 or less, but is preferably used at 6 or less.

In order to adjust the pH, a base such as mono-lithium hydroxide, potassium hydroxide, or ammonia, or an acid such as acetic acid, hydrochloric acid, or oxalic acid is used.

Specifically, various dyes, pharmaceuticals, agricultural chemicals, liquid crystals, fragrances, pigments, etc. are used as the core substance (2) after being dissolved or dispersed. Toriwa () When used as microcapsules for pressure-sensitive copying paper, an electron-donating coloring agent (organic colorless dye) is used as the core material, and its solvents include diarylalkane, alkylnaphthalene, and dibenzylbenzene. derivatives, alkylbenzenes, paraffins,
Examples include cycloparaffin, chlorinated paraffin, various esters, mineral oil, vegetable oil, and the like.

As the aminoaldehyde resin (3), urea-formalin resin, melamine-formalin resin, benzoguanamine resin, butylated melamine resin, and butylated urea resin are known, and melamine-formalin resin is particularly preferred.

The initial materials of these resins used in (3) can be easily obtained by reacting the corresponding monomers with each other under appropriate humidity and pH 1 temperature conditions, but ready-made commercial products may also be used.

Generally, the weight ratio of these aminoaldehyde initial condensates and the oil-soluble liquid serving as the core substance 6 is 1:3 to 1:4.
It is added and used within the range of 0, but it is not necessarily limited to this. Single substances (monomers) may be used together.
This step (3) may be omitted depending on the raw materials used and is not essential.

(4) The resin formation process of aminoaldehyde resin, that is, the reaction process, is generally carried out in a humidity range of 50 to 90°C, and the resin formation reaction is usually completed in 1 to 3 hours. a catalyst that accelerates the reaction during the resin formation, and after the reaction is complete;
There is no problem in using a processing agent containing excessive formaldehyde.

The microcapsule slurry obtained by the method of the present invention has a high concentration, low viscosity, and a rough and tough film. Toriwa (when used as microcapsules for horn carbon paper) had extremely good working properties and enabled higher concentration and higher speed smearing.

The carbonless pressure-sensitive copying paper of the present invention is obtained by applying the capsule containing the electron-donating coloring agent, the buffer, and the binder of the present invention onto a support. The buffering agent of the present invention is added for the purpose of preventing destruction of microcapsules, and generally wheat starch, potato starch, fine cellulose powder, synthetic plastic pigments, etc. are used, but the type and amount thereof are is not particularly limited. Binders generally include latex, soluble starch, casein,
Gelatin, gum arabic, polyvinyl alcohol, methyl cellulose, etc. are used alone or in combination for the purpose of fixing the capsule and buffer on the support, but the type and amount thereof are not particularly limited. As the support, acidic paper or neutral paper mainly composed of cellulose fibers is usually used, but synthetic paper may also be used.

(E) Example Examples of the present invention are shown below.

Note that all parts in the examples indicate parts by weight.

8 Example I Production Example 1 of Water-Soluble Polymer F 198 g (1 mol) of anhydrous maleic and 10 g of methyl isobutyl ketone were charged into a 11-size colben equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and a dropping funnel, and the mixture was heated under a nitrogen stream. 60℃
6.4 g (D, 2 mol) of methanol at the same temperature.
was added dropwise over 30 minutes, and the temperature was further kept for 1 hour to obtain a maleic anhydride. This was used as a raw material for maleic anhydride and maleic anhydride ester.

Reflux condenser, thermometer, nitrogen introduction stage, dropwise addition [Methyl isobutyl ketone 200 m
After charging 9 and raising the temperature to 110-115°C, at the same temperature, 59 g (D, 5 mol) of α-methylstyrene, 88 g (D, 5 mol) of benzyl methacrylate, the above maleic anhydride, and maleic anhydride were added. A monomer solution consisting of all esterified raw materials and 190 g of methyl isobutyl ketone,
A 9 initiator solution consisting of 2.29 g of tertiary-butyl peroxybenzoate and 100 g of methyl isobutyl ketone was added dropwise from a separate dropping funnel over 2 hours, and the mixture was kept warm for an additional 2 hours. Tert-butylperoxy 2-ethylhexanoate 2. is then added to complete the polymerization.
An initiator solution consisting of 29 and 5 (l) of methyl isobutyl ketone was added dropwise over 30 minutes and held for 1 hour. After the polymerization solution was cooled to below 100°C, 150 g of water and 75 g of 48% caustic soda (D, 9 mol) were added dropwise. ) was added thereto, and then steam was blown in using a conventional method to remove methyl isobutyl ketone.

Next, water was added to adjust the solid content concentration to 8% to obtain a water-soluble polymer. The properties were as follows.

p11=4.8B type packing (25°C) -60cps [Microcapsulation] 3 parts of crystal violet lactone (CVL) was added as the core material of the microcapsules to Hysol SAS N-
A solution dissolved in 96 parts of 296 (aromatic solvent manufactured by Nippon Petrochemical) was prepared.

Water-soluble polymer solution 1 obtained in the above production example as an emulsified aqueous solution
To 80 parts, 220 parts of the above hydrophobic liquid was gradually added under strong stirring, and the stirring was continued until the volume average particle diameter became 5 microns to obtain an emulsion.

Separately, 11 parts of melamine, 2 parts of 37% formaldehyde aqueous solution
1.2 parts and 28.2 parts of water were mixed, sodium hydroxide was added to adjust the pH to 9, and the mixture was heated to obtain an aqueous solution.

The melamine-formaldehyde initial condensate aqueous solution was added to the emulsion, and the mixture was stirred for 2 hours at a temperature of 70°C, and the U reaction was completed.

After TMI to generate microcapsules, the mixture was cooled to room temperature and the pll was raised to 9.0 with a caustic soda aqueous solution to complete the microencapsulation.

To 100 parts of the solid microcapsule liquid thus obtained, 30 parts of wheat starch particles and 100 parts of a 10% polyvinyl alcohol aqueous solution were added. The coating liquid was applied to a 40 g/m2 high-quality paper so that the dry coating amount was 5 g/TrL2 to obtain carbonless pressure-sensitive recording paper (CB). When this was combined with commercially available carbonless pressure-sensitive recording paper bottom paper (Mitsubishi NCR Paper Shimokawa Paper 40.40g/TrL2 base bottom paper) and printed on a typewriter, the no-force 1-bon paper with good color development was obtained. Obtained.

Example 2 In the production example in Example 1, the monomer composition was changed to 98 g (1 mol) of maleic anhydride, and the amount of methanol added during the production of the ester was 3.2 g (D, 1 mol) per 98 g (1 mol) of maleic anhydride. mole), styrene 10.4g (mol), styrene 10.4g (
D, 1 mol>, nuclear methyl substituted α-methylstyrene 13.
2 g (D, 1 mol), benzyl methacrylate 140.
The water-soluble polymer was prepared in the same manner except that 8 g (D, 8 mol) was added.

The properties of the obtained water-soluble polymer are as follows: solid content concentration -7.5%
, Type B packing degree (25℃) -100cps, pH-5
,1.

Using this water-soluble polymer as an emulsified aqueous solution, encapsulation and production of a CB sheet were carried out in the same manner as in Example 1.

Example 3 In the production example in Example 1, the monomer composition was changed to 198 g (1 mol) of maleic anhydride, and the amount of methanol added during production was changed to 98 g (1 mol) of maleic anhydride.
9.6 g (D, 3 mol), styrene 93
．． 69 (D, 9 mol), α-methylstyrene 11.4
59 (D, 097 mol), benzyl methacrylate 0
．． The water-soluble polymer was prepared in the same manner except that 525 g (D, 003 mol) was added.

The properties of the obtained water-soluble polymer are as follows: solid content concentration -8.0%
, Type B packing degree (25°C) -68CDS, pH -4.
It was 9.

Encapsulation and creation of a CB sheet were carried out in the same manner as in Example 1 using this water-soluble polymer as an emulsifier aqueous solution.

Example 4 Urea 14 was added to the hydrophobic liquid emulsion obtained in Example 1.
42 parts of a 37% aqueous formaldehyde solution and 29 parts of a 37% formaldehyde aqueous solution were added thereto, and the mixture was stirred at a temperature of 60° C. for 2 hours to complete the reaction.

After confirming the formation of microcapsules, the mixture was cooled to room temperature and the pH was raised to 9.0 with an aqueous sodium chloride solution.3 Microencapsulation was completed. Next, a CB sheet was prepared in the same manner as in Example 1.

Comparative Example 1 [Production of α-methylstyrene-maleic anhydride copolymer] In the production example in Example 1, maleic anhydride l! The procedure of Example 1 was repeated except that 59 g (D, 5 mol) of α-methylstyrene was used instead of 98 g (1 mol) of benzyl methacrylate (D, 5 mol). -Methylstyrene-maleic anhydride copolymer The properties of the water-soluble polymer are as follows: solid content = 8%
, Type B packing degree (25℃) -250cps, pH=4
．． It was 8.

E Microencapsulation] Using this water-soluble polymer as an emulsifier aqueous solution, Example 1
Water added with melamine-formaldehyde of 28.2
Encapsulation and production of a CB sheet were carried out in the same manner as in Example 1 except that 130.6 parts of water was used instead of 130.6 parts of water.

4 Comparative Example 2 D) As a water-soluble polymer solution, 180 parts of an 8.0% aqueous solution of an ethylene-maleic anhydride binary copolymer (trade name EM/131, manufactured by Monzant Co., Ltd., USA) adjusted to l = 3.5 was added. 220 parts of the hydrophobic liquid of Example 1 was added and emulsified in the same manner.

Next, 13 parts of melamine and 2 parts of 37% formaldehyde aqueous solution
A melamine-formaldehyde initial condensate was obtained by heating and dissolving 5.1 parts and 132 parts of water at PL+=9.0, which was added to the emulsion and stirred for 2 hours at a temperature of 70 DEG C., and the reaction was then completed.

The obtained microcapsule slurry was treated in the same manner as in Example 1 to obtain a carbonless pressure-sensitive copying paper (D8>).

The microcapsules and pressure-sensitive copy paper sheets obtained in the Examples and Comparative Examples were evaluated by the following method and used as criteria for evaluation.

・Solid content: 105°C, solid content concentration of capsules after dry heat treatment for 3 hours: 5 ・Viscosity: Viscosity of capsule emulsion at 20°C using a B-type viscometer.

・Dilute Blue Spot Capsule Emulsion with water so that the solid content of 11% becomes 20%, apply it directly to the developer-coated image of CF palm so that the dried smear fu6g/m2, and after drying,
Count the number of spots per aR2. The worse the encapsulation, the higher the number of points, and for practical purposes, 5 or less is preferable.

- The liquid coloring of the liquid-colored capsule emulsion was determined by visually observing the appearance.

○No coloring, 0 slightly colored, △ slightly more colored, X
Severe coloration/static pressure coloring stains CB sheet and C sheet are stacked so that the coated surfaces face each other, and static pressure is applied for 30 seconds at a pressure of 20 KI/cts2. Reflectance of the CF sheet surface. Measure.

The larger the value, the stronger the microcapsule film. to show that

・Heat-resistant CB sheet and CF sheet were overlapped so that the coated surfaces were symmetrical, a light load of 50 g/m2 was applied, and the reflectance of the CF sheet was measured after being left in an atmosphere of 140°C for 3 hours. . The larger the value, the better the heat resistance and the stronger the film.

The reflectance measurement of the static pressure colored stain and heat-resistant treated OF sheets 1 to 1 was carried out using a color difference meter ND101DP manufactured by Nippon Heavy Industries Ltd., and the display shows the reflectance of the colored part/untreated part (background surface). Part) reflectance x 100 (%)
It was shown in The results of the evaluation based on the above measurement methods are shown below.
Shown below.

7 Table 1 (F) Effect of the Invention As is clear from the results of the Examples, the present invention was able to obtain high strength capsules with low viscosity and high solid content even with a small amount of membrane material. .

In particular, when the method of the present invention is applied to the production of pressure-sensitive copying parts, it is possible to obtain pressure-sensitive paper with excellent coating suitability due to its low viscosity, as well as excellent color development and stain resistance. .

Furthermore, an unexpected effect obtained with the present invention is that the emulsification time is shortened, and the time required to prepare the hydrophobic liquid to a desired size is significantly shortened compared to conventionally known methods. You can get the same effect.

Claims (8)

[Claims] (1) An emulsifier for producing microcapsules containing a water-soluble polymeric substance as an active ingredient, wherein the water-soluble polymeric substance is (A) benzyl (meth)acrylate, (B) styrenes, (C) maleic anhydride and (D) An emulsifier for producing microcapsules, which is a multicomponent copolymer obtained by copolymerizing monomers containing maleic anhydride. (2) The monomer composition of the multi-component copolymer obtained by copolymerizing monomers containing (A) benzyl (meth)acrylate, (B) styrenes, (C) maleic anhydride, and (D) maleic anhydride ester is , (A) 0.1 to 50 mol% of benzyl (meth)acrylate, (B) 5 to 57.9 mol% of styrenes, , (C) 30 to 50 mol% of maleic anhydride
50 mol%, (D) maleic anhydride esterified product is 2~
The emulsifier for producing microcapsules according to claim 1, wherein the emulsifier is 20 mol%. (3) In a method for producing microcapsules having an aminoaldehyde condensation product as a wall material in an aqueous medium containing a water-soluble polymer substance, the water-soluble polymer substance (A
) benzyl (meth)acrylate, (B) styrenes,
A method for producing microcapsules, comprising using a multicomponent copolymer obtained by copolymerizing monomers containing (C) maleic anhydride and (D) a maleic anhydride ester. (4) The monomer composition of a multicomponent copolymer obtained by copolymerizing monomers containing (A) benzyl (meth)acrylate, (B) styrenes, (C) maleic anhydride, and (D) maleic anhydride ester is , (A) 0.1 to 50 mol% of benzyl (meth)acrylate, (B) 5 to 57.9 mol% of styrenes, , (C) 30 to 50 mol% of maleic anhydride
50 mol%, (D) maleic anhydride esterified product is 2~
The method for producing microcapsules according to claim 3, wherein the content is 20 mol%. (5) The emulsifier for producing microcapsules according to claim 1, wherein the ester residue of the maleic anhydride (D) is a methyl ester. (6) The method for producing microcapsules according to claim 3, wherein the ester residue of the maleic anhydride (D) is a methyl ester. (7) Microcapsules obtained by the method for producing microcapsules according to claim 3 or 4, wherein the wall material is an aminoaldehyde condensation product. (8) A carbonless pressure-sensitive copying paper comprising, on a support, a coating layer containing the microcapsules according to claim 7 containing an electron-donating coloring agent, a buffer agent, and a binder.