JP2675618B2 - Emulsifier for producing microcapsule, microcapsule using the emulsifier, method for producing the same, and carbon-free pressure-sensitive copying paper using the microcapsule - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention provides an emulsifier for producing microcapsules, a method for producing microcapsules using the emulsifier, microcapsules obtained by the production method, and microcapsules. It relates to a carbon-free pressure-sensitive copying paper used.

(B) Prior Art A microcapsule is a microcapsule that encloses a liquid, a solid, or a gas as fine particles with a size of 1 μm to several hundreds of μm, and coats the surroundings with a thin film uniformly.
Microcapsules such as colorless and blue dyes, pharmaceuticals, pesticides, fragrances, and feeds have been industrially commercialized.

The most common of these is application to pressure-sensitive copying paper. That is, top paper coated with microcapsules containing a hydrophobic liquid in which a colorless electron-donating dye is dissolved is coated on the back surface of a support, and bottom paper coated with a colorless electron-accepting developer on the surface of another support. When the writing pressure is applied, the microcapsules are destroyed and the inclusions are released, the coloring agent and the color developer come into contact with each other, and the coloring substance is attached to the lower paper by chemical reaction. It is formed on the surface and is obtained as copy paper.

In this way, by forming a thin film on the outside of a material with certain characteristics, the microcapsules can also contain the characteristics at the same time, and if the film is destroyed when necessary, the encapsulated material can be taken out Things.

The conventionally known methods for producing microcapsules include (1) a coacervation method using an ionic coplex of gelatin and an anionic protective colloid.

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

(3) An in-situ method for forming a water-insoluble resin film on the surface of oil droplets from the outer phase (water phase) (Japanese Patent Publication No. 60-2100, JP-A No. 53-
84881, 54-25277, 54-49984, 55-47139, 56
-51238 and 59-177129) are known.

In the above-mentioned encapsulation method, microcapsules having a dense film with excellent protection of inclusions can be obtained and are widely applied industrially, but various problems still remain in production and quality. It is also true that

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

(2) Since it is difficult to obtain a microcapsule slurry having a concentration of 20% or more, a large amount of water must be evaporated when used in pressure-sensitive copying paper, so there is much room for improvement in working speed and energy cost. thing.

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

(4) Since it has a tendency to corrode and aggregate, it cannot withstand long-term storage.

And the like.

Regarding the interfacial polymerization method, the problem with the coacervation method is that although it is improved to some extent, it reacts with a highly reactive coating substrate (at a relatively high temperature), so it is an unstable substance or a substance that is easily deformed by heat. Not suitable for encapsulation of.

In addition, there are still points to be improved in solvent resistance and water resistance.

In the in-situ 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 in the form of microdroplets has a relatively high viscosity, the obtained microcapsule dispersion liquid also inevitably has a high viscosity and has a solid content of 50% or more. It is practically difficult to obtain a flowable microcapsule slurry.

(2) In contrast to (1), when a low-viscosity water-soluble polymer diluted with an appropriate solvent or a low-viscosity water-soluble polymer is used as an emulsifier, the emulsification stability of a hydrophobic liquid is reduced. As a result, agglomeration or aggregation of the hydrophobic liquids occurs.

(3) In order to obtain physically and chemically high film strength and stability, it is necessary to introduce high-temperature reaction conditions or a large amount of film material. It is not preferable to change the conditions as described above in order to adopt the encapsulation method that is sensitive to condition fluctuations.In particular, in industrial manufacturing, defective products may occur due to slight errors in setting conditions or unexpected fluctuations in conditions. Therefore, the industrial application range is extremely limited.

Further, when microcapsules obtained by a conventionally known manufacturing method are used for carbonless pressure-sensitive copying paper, they cannot be said to be sufficient in terms of prevention of static pressure coloring stains and heat resistance.

(C) Problems to be Solved by the Invention The present invention aims to solve the problems in the conventionally known microencapsulation method described in the section (B), and in particular, a method in which a hydrophobic liquid is used as a core. It is an object of the present invention to provide a water-soluble polymer-based emulsifier suitable for a method for producing microcapsules by an in-situ method containing the substance as a substance. Furthermore, by using the emulsifier and adopting the in-situ method, a high solid content concentration, a microcapsule slurry having a low viscosity is obtained, and a tough film is provided even with a small amount of the film agent used. It is intended to provide microcapsules that can be obtained.

Still another object of the present invention is to provide a carbonless pressure-sensitive copying paper excellent in prevention of static pressure coloring stains and heat resistance by using microcapsules by an improved production method.

(D) Means for Solving the Problems The present invention relates to an emulsifier for producing microcapsules containing a water-soluble polymer as an active ingredient, wherein the water-soluble polymer is (A) benzyl (meth) acrylate,
An emulsifier for producing microcapsules, which is a quaternary copolymer composed of (B) diisobutylene, (C) styrene, and (D) maleic anhydride, and more preferably a monomer of the quaternary copolymer. The composition is (A) + (B) +
(C) + (D) = 100 mol%, the total amount of (A) benzyl (meth) acrylate and (B) diisobutylene is 0.1 to 50 mol%, (C) styrene is 5 to 59.9 mol%,
(D) An emulsifier for producing microcapsules, which comprises 40 to 50 mol% of maleic anhydride.

Furthermore, the present invention provides a method for producing microcapsules using an aminoaldehyde condensation polymer as a wall membrane material in an aqueous medium containing a water-soluble polymer, wherein (A) benzyl (meth) acrylate is used as the water-soluble polymer. , (B) diisobutylene, (C) styrene, and (D) a quaternary copolymer of maleic anhydride are used, and more preferably, a monomer of the quaternary copolymer is used. The composition is (A) + (B) + (C) +
(D) = 100 mol%, the total amount of (A) benzyl (meth) acrylate and (B) diisobutylene is 0.1 to 50
Using an emulsifier for producing microcapsules composed of 5% to 59.9% by mole of (C) styrene and 40 to 50% by mole of (D) maleic anhydride, and using an aminoaldehyde condensate as a wall film material. It relates to a method for producing microcapsules, which is characterized by being used.

The method for producing the quaternary copolymer is not particularly limited,
Various known methods can be appropriately selected and used, and examples thereof include 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 the like, and then removing the organic solvent. There are no particular restrictions on the polymerization initiator, and various known initiators can be used. In the case of the above solution polymerization method,
Benzoyl peroxide, tertiary butyl peroxybenzoate, tertiary butyl peroxy 2-
Organic peroxides such as ethyl hexanoate and organic azo compounds such as azobisisobutyronitrile and dimethyl-2,2'-azobisisobutyrate 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 appropriately neutralized with a suitable neutralizing agent and then diluted and dissolved in water.

The composition ratio of each constituent monomer is not particularly problematic if it fluctuates within the above range, but if any one of them is out of this range, undesirable phenomena occur in the production process and quality of the obtained microcapsules. Come.

Specifically, if the composition ratio of (D) maleic anhydride is 50% or more, not only the regular copolymerization reaction of the respective components becomes difficult, but also the produced product is used as an emulsifier aqueous solution during the emulsification process. The separation of the hydrophobic liquid, or huge hydrophobic liquid particles become present. Further, when the composition ratio of maleic anhydride is 40% or less, the copolymerization reaction proceeds relatively smoothly, but the product becomes insoluble in water or a sharp increase in viscosity occurs, which causes an unfavorable phenomenon in the emulsification step. . If the ratio of styrene is higher than this range (the amount of benzyl (meth) acrylate and diisobutylene is small), a tough film as described in the present invention cannot be obtained.
On the other hand, if the ratio of benzyl (meth) acrylate and diisobutylene is high, the viscosity of the water-soluble polymer tends to be high, which is not preferable because it hinders the emulsification process or results in incomplete capsules.

The molecular weight of the water-soluble polymer used in the present invention measured by gel permeation chromatography is preferably 1,000,000 or less in terms of polystyrene, and the viscosity measured by a B-type viscometer is 10
It is preferably in the range of 20 to 2000 cps in an aqueous solution having a pH of 4.0 and 25 ° C.

The method for producing microcapsules according to the present invention basically comprises the following four steps: (1) a water-soluble polymer preparation step, (2) a core material preparation step, (3) an aminoaldehyde precondensate Preparation process and (4) Aminoaldehyde resin formation process.

In the process (1) for preparing the water-soluble polymer, the concentration of the water-soluble polymer solution is determined by its viscosity and emulsion stability, but is preferably in the range of 3 to 15%. The pH of the aqueous solution is usually set in the acidic region of 7 or less, preferably 6 or less.

To adjust the pH, a base such as sodium hydroxide, potassium hydroxide or ammonia, or an acid such as acetic acid, hydrochloric acid or oxalic acid is used.

As the core substance of (2), various dyes, pharmaceuticals, agricultural chemicals, liquid crystals, fragrances, pigments, and the like are specifically used by being dissolved or dispersed. In particular, when used as a microcapsule for pressure-sensitive copying paper, an electric donative color former (organic colorless dye) is used as a core substance, and as a solvent thereof,
Examples thereof include diallyl alkane, alkylnaphthalene, dibenzylbenzene derivative, alkylbenzene, paraffin, cycloparaffin, chlorinated paraffin, and various esters, mineral oil, vegetable oil and the like.

As the amino aldehyde resin used in the present invention,
Urea-formalin resin, melamine-formalin resin, benzoguanamine resin, butylated melamine resin, butylated urea resin are known, and melamine-formalin resin is mentioned as a preferable resin.

The initial condensate of these resins used in (3) can be easily obtained by reacting corresponding monomers under appropriate concentrations, pH and temperature conditions, but ready-made commercial products may be used.

These aminoaldehyde initial condensates and the oil-soluble liquid that serves as the core substance are generally added and used in a weight ratio in the range of 1: 3 to 1:40, but not necessarily limited to this, the core substance, the membrane material. It may be used by appropriately changing it depending on the kind or the application. Simple substances (monomers) corresponding to the above initial condensates may be used. The process of (3) is
It may be omitted depending on the raw materials used and is not essential.

(4) The resin forming process of the aminoaldehyde resin, that is, the reaction process is generally performed in a temperature range of 50 to 90 ° C., and usually the resin forming reaction is completed in 1 to 3 hours. There is no problem in using a catalyst for accelerating the reaction at the time of forming the resin and using an excess formaldehyde treating agent after the reaction is completed.

The microcapsule slurry obtained by the method of the present invention is prepared at a high concentration, has a low viscosity, and has a tough film. In particular, when it is used as a microcapsule for carbonless paper, the coating workability is extremely good, and higher density and high-speed smearing are possible.

The carbonless pressure-sensitive copying paper of the present invention is obtained by smearing the capsule of the present invention containing the electron-donating color former, the buffer, and the binder on a support. The buffer used in the present invention is added for the purpose of preventing the destruction of microcapsules, and generally, wheat starch, potato starch, cellulose fine powder, synthetic plastic pigment, etc. are used. And the amount are not particularly limited.

As the binder, latex, soluble starch, casein, gelatin, gum arabic, polyvinyl alcohol, methylcellulose and the like are used alone or in combination, and are used for the purpose of fixing capsules and buffers on a support. The type and amount are not particularly limited.

As the support, acid paper or neutral paper mainly containing cellulose fibers is usually used, but synthetic paper may be used at all.

(E) Examples Examples of the present invention will be shown below.

 In addition, the number of parts in the examples all indicates parts by weight.

Example 1 [Production Example of Water-Soluble Polymer] 200 g of methyl isobutyl ketone was charged into 2 Kolben equipped with a reflux condenser, a thermometer, a nitrogen introducing tube, and two dropping funnels, and the temperature was raised to 110 to 115 ° C. , Styrene 52 at the same temperature
g (0.5 mol), benzyl methacrylate 44 g (0.25 mol), diisobutylene (2,4,4-trimethylpentene-
(1 is 76% by weight) 36.9 g (0.25 mol of 2,4,4-trimethylpentene-1), 98 g (1 mol) of maleic anhydride and 200 g of methyl isobutyl ketone, and a monomer solution of tert-butyl peroxybenzoate 2.2. g
An initiator solution consisting of 100 g of methyl isobutyl ketone and 2 g of each was added dropwise from separate dropping funnels over 2 hours, and the above temperature was maintained for 2 hours. Then, in order to complete the polymerization, an initiator solution consisting of 2.2 g of tert-butyl peroxy 2-ethylhexanoate and 50 g of methyl isobutyl ketone was added dropwise over 30 minutes and kept at the above temperature for 1 hour. After cooling the polymerization liquid to 100 ° C. or lower, 150 g of water and 48
After adding 75 g (0.9 mol) of% caustic soda, steam is blown by a conventional method to remove methyl isobutyl ketone, and then water is added to adjust the solid content concentration to 8% to obtain a water-soluble polymer. It was The properties were as follows.

pH = 4.7 B type viscosity (25 ° C) is 70 cps.

[Microencapsulation] As a core substance of microcapsules, a solution was prepared by dissolving 3 parts of crystal bio-leptlactone (CVL) in 96 parts of Hisol SASN-296 (aromatic solvent manufactured by Nippon Petrochemical).

220 parts of the above hydrophobic liquid was gradually added to 180 parts of the water-soluble polymer solution obtained in the above Preparation Example as an emulsifier aqueous solution with vigorous stirring, and stirring was continued until the volume average particle size became 5 microns to obtain an emulsifier. .

Separately, 11 parts of melamine, 37% formaldehyde aqueous solution 21.2
And 28.2 parts of water are mixed and sodium hydroxide is added to adjust the pH to 9 to dissolve to obtain an aqueous solution of the melamine-formaldehyde initial condensate, which is added to the emulsion and kept at 70 ° C. for 2 hours. Stirring was continued to complete the reaction.

After confirming the formation of microcapsules, the mixture was cooled to room temperature, the pH was increased to 9.0 with an aqueous sodium hydroxide solution, and the encapsulation was completed.

100 parts of the solid part of the microcapsule liquid thus obtained contains 30 parts of wheat starch particles and 100% aqueous 10% polyvinyl alcohol solution.
Then, the mixture was coated on a high quality paper of 40 g / m ^{2 so} that the dry coating amount was 5 g / m ² , to obtain a carbon-free pressure-sensitive recording paper (CB). This is a commercially available carbonless pressure-sensitive recording paper under paper (Mitsubishi
When combined with NCR paper under paper (N-40, paper under 40 g / m ² ) and type writer printing, carbonless paper with good color development was obtained.

Example 2 In the production example of Example 1, the amount of styrene added was 2
0.8 g (0.2 mol), benzyl methacrylate 70.4 g (0.
4 mol) and diisobutylene (containing 76% by weight as 2,4,4-trimethylpentene-1) of 59.0 g (0.4 mol as 2,4,4-trimethylpentene-1) were used in the same manner as above except that water was used. The polymer was prepared.

The properties of the obtained water-soluble polymer are as follows: solid content concentration 7.5%,
It had a B-type viscosity (25 ° C.) of 120 cps and a pH of 5.0.

Using this water-soluble polymer as an emulsifier solution, encapsulation and preparation of a CB sheet were performed in the same manner as in Example 1.

Example 3 In the production example of Example 1, 80 g of styrene (0.77
52.8 g (0.30 mol) of benzyl methacrylate, diisobutylene (2,4,4-trimethylpentene-
A water-soluble polymer was prepared in the same manner except that 14.7 g (containing 1,7 wt% as 1) (0.1 mol as 2,4,4-trimethylpentene-1) was used.

The properties of the obtained water-soluble polymer are as follows: solids concentration 8.0%,
The B-type viscosity (25 ° C.) was 70 cps, and the pH was 4.8.

Example 1 using this water-soluble polymer as an aqueous emulsifier solution
Encapsulation and CB sheet production were performed in the same manner as in.

Example 4 The urea 14 was added to the hydrophobic liquid emulsion obtained in Example 1.
42 parts of an aqueous solution containing 37 parts of a 37% formaldehyde aqueous solution
29 parts was added and stirring was continued at a temperature of 60 ° C. for 2 hours to complete the reaction.

After confirming the formation of the microcapsules, the mixture was cooled to room temperature, raised to pH 9.0 with an aqueous sodium hydroxide solution, and the microcapsulation was completed. A CB sheet was produced in the same manner as in Example 1.

Comparative Example 1 [Production of Styrene-Maleic Anhydride Copolymer Aqueous Solution] In the production example of Example 1, benzyl methacrylate 44 g (0.25 mol) and diisobutylene (2,4,4-trimethylpentene-1 as 76% by weight) In the same manner as in Example 1 except that 52 g (0.5 mol) of styrene was used instead of 36.9 g (0.25 mol as 2,4,4-trimethylpentene-1). The properties of the obtained styrene-maleic anhydride copolymer water-soluble polymer were as follows: solid content 8%, B-type viscosity (25 ° C.) 250 cps, pH 4.8.

[Microencapsulation] Using this water-soluble polymer as an aqueous emulsifier solution, water added together with the melamine-formaldehyde of Example 1
Encapsulation and preparation 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 parts.

Comparative Example 2 Ethylene adjusted to pH 3.5 as a water-soluble polymer solution
220 parts of the hydrophobic liquid of Example 1 was added to 180 parts of an 8.0% aqueous solution of a maleic anhydride binary copolymer (trade name: EMA-31 manufactured by Monsanto, USA) and emulsified in the same manner.

Next, 13 parts of melamine and 25.1% 37% formaldehyde solution
Parts and 132 parts of water were dissolved by heating at pH 9.0 to obtain a melamine formaldehyde initial condensate, which was added to the above emulsion and stirred at a temperature of 70 ° C. for 2 hours to complete the reaction.

The obtained microcapsule slurry was treated in the same manner as in Example 1 to obtain a carbon-free pressure-sensitive copying paper on paper (CB).

The microcapsules and pressure-sensitive copying paper obtained in the above Examples and Comparative Examples were evaluated by the following methods and used as criteria.

・ Solid content 105 ° C, solid content concentration of capsules after dry heat treatment for 3 hours ・ Viscosity Viscosity of capsule emulsion at 20 ° C by B-type viscometer ・ Blue spot Capsule emulsion diluted with water to 20% solid content concentration Then, the amount of dry smear on the surface of the CF sheet coated with the developer is 6 g / m
Apply directly to ² and dry, then count the number of spots per 100 cm ³ . The poorer the encapsulation, the higher the score and the practically preferable number is 5 or less.

・ Static pressure coloring stain The CB sheet and the CF sheet are superposed on each other so that the coating surfaces face each other, and the reflectance of the CF sheet surface is measured after applying a static pressure at a pressure of 20 kg / cm ² for 30 seconds. The larger the value, the stronger the microcapsule coating.

Heat resistance The CB sheet and the CF sheet were overlapped so that the coated surfaces faced, a light load of 50 g / m ² was applied, and the reflectance of the CF sheet surface was measured after being left for 3 hours in an atmosphere of 140 ° C. The larger the value, the better the heat resistance and the stronger the film.

A color difference meter ND101DP manufactured by Nippon Denshoku Industries Co., Ltd. was used for the evaluation of the static pressure coloring stain and the heat resistance. The evaluation results were expressed as reflectance of the color-developed portion / reflectance of the untreated portion (background portion) × 100 (%). Table I shows the results of evaluation based on the above measurement methods.

(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 film material.

In particular, when the method of the present invention for the production of pressure-sensitive copying paper is applied, it is possible to obtain a pressure-sensitive copying paper excellent in coating suitability because of its low viscosity, and excellent in color development and stain resistance. can get.

Further, as an unexpected effect obtained by the present invention, the emulsification time is shortened, that is, the time required for aligning the hydrophobic liquid with a desired size is significantly shortened as compared with those conventionally known. Is obtained.

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Claims (6)

(57) [Claims] 1. An emulsifier for producing microcapsules containing a water-soluble polymer as an active ingredient, wherein the water-soluble polymer is (A) benzyl (meth) acrylate,
An emulsifier for producing microcapsules, which is a quaternary copolymer composed of (B) diisobutylene, (C) styrene, and (D) maleic anhydride. 2. (A) benzyl (meth) acrylate,
The monomer composition of the quaternary copolymer consisting of (B) diisobutylene, (C) styrene and (D) maleic anhydride is
(A) + (B) + (C) + (D) = 100 mol%,
The total amount of (A) benzyl (meth) acrylate and (B) diisobutylene is 0.1 to 50 mol%, and (C) styrene is 5
The emulsifier for producing microcapsules according to claim 1, wherein the content of maleic anhydride (D) is 40 to 50 mol%. 3. A method for producing microcapsules using an aminoaldehyde polycondensation product as a wall membrane material in an aqueous medium containing a water-soluble polymer substance, wherein (A) benzyl (meth) acrylate is used as the water-soluble polymer substance. A method for producing microcapsules, which comprises using a quaternary copolymer consisting of, (B) diisobutylene, (C) styrene, and (D) maleic anhydride. 4. (A) benzyl (meth) acrylate,
The monomer composition of the quaternary copolymer consisting of (B) diisobutylene, (C) styrene and (D) maleic anhydride is
(A) + (B) + (C) + (D) = 100 mol%,
The total amount of (A) benzyl (meth) acrylate and (B) diisobutylene is 0.1 to 50 mol%, and (C) styrene is 5
4. The method for producing microcapsules according to claim 3, wherein the content of maleic anhydride (D) is 5 to 59.9 mol%, and the content of maleic anhydride is 40 to 50 mol%. 5. The microcapsule obtained by the method for producing a microcapsule according to claim 3 or 4, wherein the wall membrane material is an aminoaldehyde condensation polymer. 6. A carbonless pressure-sensitive copying paper having a coating layer containing a microcapsule according to claim 5 containing an electron-donating color developing agent, a buffer and a binder on a support.