JP2865311B2 - Emulsifier for microcapsule, microcapsule using the emulsifier, method for producing the same, and carbonless pressure-sensitive copying paper using the microcapsule - Google Patents

Description

The present invention relates to an emulsifier for microcapsules, a method for producing microcapsules using the emulsifier, a microcapsule obtained by the production method, and a microcapsule obtained by the method. The present invention relates to a carbonless pressure-sensitive copying paper to be used.

(B) Prior art A microcapsule contains liquid, solid, and gas as fine particles having a size of 1 μm to several hundred μm, and is uniformly covered with a thin film around it.
Microcapsules for colorless and colored dyes, pharmaceuticals, agricultural chemicals, flavors, feeds, and the like have been industrially manufactured.

The most common of these is application to pressure-sensitive copying paper. That is, an upper paper in which a microcapsule containing a hydrophobic liquid in which a colorless electron-donating dye is dissolved is applied to the back surface of a support, and a lower paper in which a colorless electron-accepting developer is applied to the surface of another support. When the application pressure is applied, the microcapsules are destroyed and the inclusions are released, the color former and the developer come into contact, and the coloring substance is brought into contact with the lower paper by a 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.

Conventionally known methods for producing microcapsules include: (1) a coacervation method using an ionic complex 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 external phase (aqueous phase) (JP 60-2100, JP-A 53-848)
81, 54-25277, 54-49984, 55-47139, 56-5123
8, ibid. 59-177129).

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) pH, temperature, time and operation relating to 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) It has a tendency to rot and agglomerate, and cannot withstand long-term storage.

And the like.

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

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 now widely applied industrially, but it is also true that it has the following problems.

(1) Since a water-soluble polymer substance that emulsifies a hydrophobic liquid into microdroplets has a relatively high viscosity, the resulting microcapsule dispersion also necessarily has a high viscosity, and a solid content of 50% or more is excellent. It is practically difficult to obtain a fluid 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. However, it is not preferable to change the conditions as described above for the encapsulation method which is sensitive to the condition fluctuation.In particular, in the case of industrial production, a defective product may be generated due to a slight error in setting conditions or unexpected fluctuation in conditions. And the industrial scope is very 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). An object of the present invention is to provide a water-soluble polymer-based emulsifier which is suitable for a method for producing microcapsules by an in-situ method containing a substance. Furthermore, by using the emulsifier and adopting the in-situ method, a high solid content, a low-viscosity microcapsule slurry can be obtained, and a tougher 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 provides an emulsifier for microcapsules containing a water-soluble polymer as an active ingredient, wherein the water-soluble polymer is (A) benzyl (meth) acrylate, (B) )
A terpolymer comprising styrene and (C) maleic anhydride, wherein the monomer composition of the terpolymer is (A) +
(B) + (C) = 100 mol%, (A) 0.1-2 mol% of benzyl (meth) acrylate, (B) 48-59.9 mol% of styrene, and (C) 40-50 mol of maleic anhydride. Mol%, and when (A) is 2 mol%,
(B) is an emulsifier for microcapsules characterized by being constituted in an amount exceeding 50 mol%.

Further, the present invention relates to a method for producing microcapsules using an aminoaldehyde polycondensate as a wall film 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 terpolymer comprising (B) styrene and (C) maleic anhydride, and wherein the monomer composition of the terpolymer is (A)
+ (B) + (C) = 100 mol%, (A) 0.1 to 2 mol% of benzyl (meth) acrylate, (B) 48 to 59.9 mol% of styrene, and (C) 40 to 40 mol% of maleic anhydride. When it is composed of 50 mol% and (A) is 2 mol%,
(B) relates to a method for producing microcapsules, which comprises using an emulsifier for microcapsules constituted in an amount exceeding 50 mol% and using an aminoaldehyde condensate as a wall film material.

The method for producing the terpolymer is not particularly limited, and various known methods can be appropriately selected and employed, and examples thereof include emulsion polymerization, suspension polymerization, and solution polymerization. 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. Various known polymerization initiators can be used without any particular limitation. In the case of the above solution polymerization method, organic peroxides such as benzoyl peroxide, tertiary butyl peroxybenzoate, tertiary butyl peroxy 2-ethylhexanoate, azobisisobutyronitrile, dimethyl-2,2 Organic azo compounds such as' -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.

(A) 2 to 50 mol% of benzyl (meth) acrylate, (B) 5 to 50 mol% of styrene, and (C) 40 to 50 mol% of maleic anhydride. A microcapsule using an emulsifier, a method for producing the microcapsule, and a carbonless pressure-sensitive copying paper using the microcapsule have already been disclosed in Japanese Patent Application No. 63-26374.
No. 5, proposed by the present inventors, and in the above-mentioned patent application invention, one having excellent characteristics as compared with the prior art is obtained.

As a result of further studies by the present inventors, even if the benzyl (meth) acrylate content is further reduced to prepare an emulsifier, the emulsifier has the same characteristics as the invention described in Japanese Patent Application No. 63-263745. Are obtained, and the present invention has been completed.

The molecular weight measured by gel permeation chromatography of the water-soluble polymer used in the present invention is preferably 1,000,000 or less in terms of polystyrene.
% Aqueous solution at pH 4.0 and 25 ° C. is preferably in the range of 20 to 2000 cps.

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

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 an acidic region of 7 or less, but is preferably 6 or less.

In order 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 electron-donating color former (organic colorless dye) is used as a core substance.
Diallylalkane, 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 resins, melamine-formalin resins, benzoguanamine resins, butylated melamine resins, and butylated urea resins are known, and melamine-formalin resins are particularly preferred.

The precondensate of these resins used in (3) can be easily obtained by reacting the corresponding monomers under appropriate concentration, pH and temperature conditions, but an off-the-shelf commercially available product may be used.

These aminoaldehyde precondensates and the oil-soluble liquid serving as the core substance are generally added and used in a weight ratio of 1: 3 to 1: 40.However, the present invention is not necessarily limited to this. What is necessary is just to change and use suitably according to a kind or a use. 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 the resin forming reaction is usually 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 used as a microcapsule for carbonless paper, the coating workability is extremely good, and higher density and higher speed smearing become 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 and the like are used. And the amount is 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 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 described 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 a 2 l corbene equipped with a reflux condenser, a thermometer, a nitrogen inlet tube, and two dropping funnels, and then heated to 110 to 115 ° C. Styrene at the same temperature.
7 g (0.997 mol), benzyl methacrylate 0.525 g (0.0
03 mol), 98 g (1 mol) of maleic anhydride and 200 g of methyl isobutyl ketone, and an initiator solution consisting of 2.2 g of tertiary butyl peroxybenzoate and 100 g of methyl isobutyl ketone were each added to another dropping funnel for 2 hours. Then, the temperature was maintained for 2 hours. Then, in order to complete the polymerization, tertiary butyl peroxy 2-ethylhexanoate 2.
An initiator solution consisting of 2 g and 50 g of methyl isobutyl ketone was added dropwise over 30 minutes and kept at the above temperature for one hour. The polymerization solution is
After cooling to below 100 ℃, water 150g and 48% caustic soda 75g
(0.9 mol), steam was blown in according to a conventional method to remove methyl isobutyl ketone, and then water was added.
The concentration of the solid content was adjusted to 8% to obtain a water-soluble polymer. The properties were as follows.

pH = 4.2 B type viscosity (25 ° C) is 300cps.

[Microencapsulation] A solution prepared by dissolving 3 parts of crystal violet lactone (CVL) in 96 parts of Hisol SASN-296 (aromatic solvent manufactured by Nippon Petrochemical) as a core substance of the microcapsules was prepared.

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 aqueous emulsifier under vigorous stirring, and stirring was continued until the volume average particle size became 5 μm to obtain an emulsion. Was.

Separately, 11 parts of melamine, 37% formaldehyde aqueous solution 21.2
And 28.2 parts of water, and sodium hydroxide was added to adjust pH to 9.
And dissolved by heating to obtain an aqueous solution of a melamine-formaldehyde precondensate, added to the emulsion,
Stirring was continued at a temperature of ° C for 2 hours 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 commercially available under carbon-free pressure-sensitive recording 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 preparation example in Example 1, 101.9 g of styrene (0.
98 mol), 3.5 g (0.02 mol) of benzyl methacrylate
A water-soluble polymer was prepared in the same manner except that it was used.

The properties of the obtained water-soluble polymer are as follows: solids concentration 8.0%,
Type B viscosity (25 ° C.) was 350 cps, pH 4.2.

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.

Comparative Example 1 [Production of styrene-maleic anhydride copolymer aqueous solution] In the production example in Example 1, 0.312 g of styrene was used instead of 0.525 g (0.003 mol) of benzyl methacrylate.
(0.003 mol), except that all were the same as in Example 1. The properties of the obtained styrene-maleic anhydride copolymer water-soluble polymer are as follows: solid content 8%, B-type viscosity (25 ° C.)
It was 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
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).
220 parts were added and emulsified in the same manner.

Next, 13 parts of melamine and 25.1% 37% formaldehyde solution
Of water and 132 parts of water were heated and dissolved at pH 9.0 to obtain a melamine formaldehyde precondensate, which was added to the emulsion and stirred at 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 of capsule after dry heat treatment at 105 ° C for 3 hours ・ Viscosity ・ Viscosity of capsule emulsion at 20 ° C by B-type viscometer ・ Blue spot Capsule emulsion with water so that the solid content of emulsion becomes 20% Dilute and dry smear 6 g / m on the developer coated surface of CF sheet
After applying directly and drying to obtain ² , the number of spots per 100 cm ³ is counted. The poorer the encapsulation, the higher the score and the practically preferable number is 5 or less.

・ Static pressure coloring stains The CB sheet and the CF sheet are superposed so that the coated 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 CB sheet and CF sheet coated surface was is superimposed as opposed added a light load of 50 g / m ^2, the reflectance was measured in the CF sheet surface after leaving 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 is applied to the production of pressure-sensitive copying paper, the effect of obtaining a pressure-sensitive copying paper excellent in coating suitability due to low viscosity and excellent in color development and stain resistance is obtained. can get.

Furthermore, as an unexpected and unexpected effect obtained in the present invention, the emulsification time is shortened, that is, the time required to adjust the hydrophobic liquid to a desired size is significantly shortened as compared with conventionally known ones. Is obtained.

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Claims (2)

(57) [Claims] 1. An emulsifier for microcapsules containing a water-soluble polymer as an active ingredient, wherein the water-soluble polymer is (A) benzyl (meth) acrylate, and (B)
A terpolymer comprising styrene and (C) maleic anhydride, wherein the monomer composition is (A) + (B) +
(C) = 100 mol%, (A) benzyl (meth) acrylate is 0.1 to 2 mol%, and (B) styrene is 48 to 59.
9 mol%, (C) 40 to 50 mol% of maleic anhydride and (A) 2 mol%, (B) is 50 mol%
Emulsifier for microcapsules, characterized in that the amount is more than. 2. A method for producing microcapsules using an aminoaldehyde polycondensate as a wall film material in an aqueous medium containing a water-soluble polymer substance, wherein (A) benzyl (meth) acrylate is used as the water-soluble polymer substance. Terpolymer comprising styrene, (B) styrene and (C) maleic anhydride, the monomer composition of which is (A) + (B) + (C) = 10
(A) 0.1 to 2 mol% of benzyl (meth) acrylate, (B) 48 to 59.9 mol% of styrene,
(C) A method for producing microcapsules, wherein when maleic anhydride is 40 to 50 mol% and (A) is 2 mol%, (B) is more than 50 mol%. .