JP2981498B2 - 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 the use of the microcapsules. It relates to carbonless pressure-sensitive copying paper.

(B) Prior art Microcapsules contain liquids, solids, and gases as fine particles having a size of 1 μm to several hundred μm, and are uniformly covered with a thin film.
Microcapsules for colorless and colored dyes, pharmaceuticals, agricultural chemicals, flavors, feeds, and the like have been industrially manufactured.

Among them, the most common is application to pressure-sensitive copying paper. (1) A colorless electron-donating dye is dissolved in an organic solvent such as diphenylalkane and contained in microcapsules to form a support on a support. So-called upper paper coated on (2) lower paper in which an electron-accepting color developer is coated on many supports, and
(3) A combination of upper paper and lower paper in which microcapsules containing a colorless electron-donating dye are coated on one surface of the support and medium paper coated with a color developer on the other surface. When using in combination with paper, middle paper and lower paper, when the microcapsule layer and the color developer layer are brought into contact with each other and pressurized extremely, the microcapsules in that part are destroyed and the colorless dye And the color developer react to form a color in the color developer layer.

Other applications to pressure-sensitive copying paper include (4) the above-mentioned microcapsules and a developer coated on the same surface of a support, or (5) the above-mentioned microcapsules are developed in the support. For example, one in which one of the agents is contained and the other is applied. As for these, even a single sheet itself can form a recording sheet by coloring a pressurized portion, and a plurality of sheets can be copied and recorded.

In this way, microcapsules can form a thin film on the outside of a material with certain properties, so that the properties can also be encapsulated at the same time, and if necessary, the film can be broken to take out the encapsulated substance. Things.

Conventionally known methods for producing microcapsules include: (1) a coacervation method using an ion 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 of forming a water-insoluble resin film on the surface of oil droplets from the external phase (aqueous phase) (Japanese Patent Publication No. 60-2100, Japanese Patent Application Laid-Open No.
84881, 54-25277, 54-49984, 55-47139, 56
-51238, 59-177129).

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

That is, in the coacervation method, (1) pH, temperature, time, and operation related 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 in the coacervation method is that it is not suitable for encapsulation of unstable substances because it reacts (at a relatively high temperature) a highly reactive coating substrate, although it has been improved to some extent. .

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 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 the case of using a water-soluble polymer substance having a low viscosity with respect to (1) or a water-soluble polymer diluted with an appropriate solvent to reduce the viscosity, an emulsion stability of a hydrophobic liquid is used. And the aggregation or aggregation of the hydrophobic liquids occurs.

(3) In order to obtain physically and chemically high film strength and stability, high-temperature reaction conditions or a large amount of film material needs to be introduced. The adoption of the encapsulation method that is sensitive to such condition fluctuations leads to the possibility that defective products are easily formed in industrial manufacturing, especially due to slight errors in setting conditions and unexpected changes in conditions, thereby narrowing the industrial application range. Would be done.

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

(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 can be obtained even with a small amount of the film agent used. It is intended to provide a microcapsule that can be provided.

Still another object of the present invention is to provide a carbonless pressure-sensitive copying paper excellent in 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 microcapsules containing a water-soluble polymer as an active ingredient, wherein the water-soluble polymer is (A) benzyl (meth) acrylate, (B) An emulsifier for microcapsules, which is a multi-component copolymer obtained by copolymerizing styrenes having an alkyl substituent and a monomer containing (C) maleic anhydride,
More preferably, the monomer composition of the multi-component copolymer is (A)
Benzyl (meth) acrylate is 0.1 to 50 mol%,
(B) 5 to 59.9 mol% of styrenes having an alkyl substituent and (C) 40 to 50 mol% of maleic anhydride are emulsifiers for microcapsules.

Examples of (B) styrenes having an alkyl substituent used in the present invention include α-methylstyrene, β-methylstyrene, vinyltoluene, and alkyl-substituted α-alkylstyrene. As the core alkyl-substituted α-alkylstyrene, a core methyl-substituted α-methylstyrene,
Nuclear ethyl-substituted α-methylstyrene, nuclear isopropyl-substituted α-methylstyrene and the like (o-form, m-form, p-form)
Any body can be used). These styrenes having an alkyl substituent can be used alone or in combination of several kinds, and the most preferred monomer is α-methylstyrene.

Further, as the monomer composition of the multi-component copolymer of the present application,
Other monomers may be used within a range that does not deteriorate the performance as an emulsifier for microcapsules.
Examples include styrene, isobutylene, alkyl (meth) acrylate, acrylonitrile, acrylamide, and the like.

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. And (B) a method for producing microcapsules, characterized by using a multicomponent copolymer obtained by copolymerizing a styrene having an alkyl substituent and (C) a monomer containing maleic anhydride.
More preferably, the monomer composition of the multi-component copolymer,
(A) 0.1 to 50 mol% of benzyl (meth) acrylate, and (B) 5 to 5 styrenes having an alkyl substituent.
The present invention relates to a method for producing microcapsules, which comprises using an emulsifier for microcapsules containing 9.9 mol% and (C) maleic anhydride in an amount of 40 to 50 mol%, and using an aminoaldehyde condensation polymer as a wall film material.

The method for producing the above-mentioned multi-component copolymer 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, tert-butyl peroxybenzoate, tert-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 the emulsifier for microcapsules of the present invention, the copolymer may be appropriately neutralized with a suitable neutralizing agent and dissolved 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 is out of this range, an undesirable phenomenon occurs in the obtained microcapsule production process and quality. Come.

Specifically, when the constituent ratio of (C) maleic anhydride is 50 mol% or more, not only the regular copolymerization reaction of each constituent component becomes difficult, but also when the resulting product is used as an aqueous emulsifier solution, Separation of hydrophobic liquid, or large hydrophobic liquid particles are present in the liquid. When the maleic anhydride component ratio is 40 mol% or less, the copolymerization reaction proceeds relatively smoothly, but the product becomes insoluble in water or a sharp increase in viscosity occurs, which is an undesirable phenomenon in the emulsification process. Bring. On the other hand, if the ratio of styrenes is higher than this range (the amount of benzyl (meth) acrylate is small), a tough film as described in the present invention cannot be obtained. The viscosity of the polymer tends to be high, which hinders the emulsification step or results in incomplete capsules, which is not preferable.

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., preferably in the range of 20 to 2000 cps.

The method for producing a microcapsule according to the present invention basically includes the following four steps.

(1) Preparation process of water-soluble polymer (2) Preparation process of core substance (3) Preparation process of aminoaldehyde initial condensate (4) Formation process of aminoaldehyde resin In preparation process of water-soluble polymer in (1) 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 water-soluble pH is usually set in the acidic range of 7 or less, but is preferably used in the range of 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 electron-donating color former (organic colorless dye) is used as a core substance.
Examples include diarylalkanes, alkylnaphthalenes, dibenzylbenzene derivatives, alkylbenzenes, paraffins, cycloparaffins, chlorinated paraffins, and various esters, mineral oils, vegetable oils, 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. Melamine-formalin resin is particularly preferred. .

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

The aminoaldehyde precondensate 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, but the present invention is not necessarily limited to this. What is necessary is just to change and use suitably according to a material type or a use. Corresponding simple substances (monomers) may be used instead of the initial condensate. The step (3) 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 completed usually 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 adjusted to 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 was extremely good, and higher density and higher speed smearing were possible.

The carbonless pressure-sensitive copying paper of the present invention is obtained by smearing the capsule of the present invention containing an electron-donating color former, a buffer, and a binder on a support. The buffer of 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 a binder, generally latex, soluble starch, casein, gelatin, gum arabic, polyvinyl alcohol,
Methylcellulose or the like is used alone or as a mixture, and is used for the purpose of fixing the capsule and the buffer on the support, but the type and amount thereof 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 colben equipped with a reflux condenser, a thermometer, a nitrogen introduction tube, and two dropping funnels, and heated to 110 to 115 ° C. At the same temperature, α-methylstyrene 59 g (0.5 mol), benzyl methacrylate 88 g
(0.5 mol), a monomer solution consisting of 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 placed in separate dropping funnels. The mixture was added dropwise over a period of time, and the temperature was further maintained for 2 hours. Then, to complete the polymerization, 2.2 g of tert-butyl peroxy 2-ethylhexanoate and methyl isobutyl ketone
An initiator solution consisting of 50 g was dropped over 30 minutes and held for 1 hour. After cooling the polymerization solution to 100 ° C or lower, 150 g of water and 4 g
After adding 75 g (0.9 mol) of 8% caustic soda, steam was blown in according to 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 solution. The properties were as follows.

pH = 4.7 B type viscosity (25 ° C.) = 70 cps [Microencapsulation] 3 parts of crystal violet lactone (CVL) are used as the core material of the microcapsules, and Hisol SAS N-296 is used.
(Nippon Petrochemical's aromatic solvent) A solution dissolved in 96 parts was prepared.

Water-soluble polymer solution obtained in the above Preparation Example as an emulsified aqueous solution
To 180 parts, 220 parts of the above hydrophobic liquid was gradually added under vigorous stirring, and stirring was continued until the volume average particle size became 5 μm to obtain an emulsion.

Separately, 11 parts of melamine, 37% formaldehyde aqueous solution 21.2
Parts, 28.2 parts of water, and add sodium hydroxide to adjust pH 9
To obtain an aqueous solution. The melamine-
An aqueous formaldehyde precondensate solution was added to the emulsion, and the mixture was stirred at a temperature of 70 ° 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 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 10% aqueous solution of polyvinyl alcohol 10
0 parts were added. The coating solution on a high-quality paper 400 g / m ² dry coating amount
The solution was applied at 5 g / m ² to obtain a carbon-free pressure-sensitive copy paper (CB). This was printed typewriter in combination with a commercially available carbonless pressure-sensitive copying paper under the paper (Mitsubishi NCR paper under Paper N-40,40g / m ² based bottom sheet), chromogenic good carbonless paper is obtained Was.

Example 2 In the preparation example of Example 1, the monomer composition was changed to 10.4 g (0.1 mol) of styrene, and a methyl-substituted α-methylstyrene nucleus was used.
13.2 g (0.1 mol), benzyl methacrylate 140.8 g (0.
8 mol) and 98 g (1 mol) of maleic anhydride, except that the water-soluble polymer was prepared in the same manner.

The properties of the obtained water-soluble polymer were as follows: solids concentration = 7.5
%, B-type viscosity (25 ° C.) = 120 cps, pH = 5.0.

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

Example 3 In the production example in Example 1, the monomer composition was changed to 83.2 g (0.8 mol) of styrene and 23.25 g (0.19 g) of α-methylstyrene.
7 mol), and benzyl methacrylate was added to the mixture except that it was changed to 0.525 g (0.003 mol) and 98 g (1 mol) of maleic anhydride.

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

Example 1 using this water-soluble polymer as an aqueous emulsifier solution
In the same manner as described above, encapsulation and preparation of a CB sheet were performed.

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 were 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, the pH was increased to 9.0 with a sodium hydroxide aqueous solution, and the microcapsulation was completed. Next, a CB sheet was prepared in the same manner as in Example 1.

Comparative Example 1 [Production of aqueous solution of α-methylstyrene-maleic anhydride copolymer] In the production example in Example 1, 59 g of α-methylstyrene was used instead of 88 g (0.5 mol) of benzyl methacrylate.
(0.5 mol), except that all were the same as in Example 1. The properties of the resulting α-methylstyrene-maleic anhydride copolymer water-soluble polymer were as follows: solids = 8%, B-type viscosity (25 ° C.) = 250 cps, pH = 4.8.

[Microencapsulation] Encapsulation was performed in the same manner as in Example 1 except that this water-soluble polymer was used as an emulsifier aqueous solution, and 130.6 parts of water was used instead of 28.2 parts of water added together with melamine-formaldehyde of Example 1. And the CB sheet was created.

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

Next, 13 parts of melamine and 25.1% 37% formaldehyde solution
Parts, 132 parts of water were heated and dissolved at pH = 9.0 to obtain a melamine-formaldehyde initial condensate, and added to the above emulsion at 70 ° C.
Stirring was continued for 2 hours at a temperature of to terminate 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).

Comparative Example 3 A water-soluble polymer was prepared in the same manner as in Production Example 1 except that the monomer composition was changed to 104 g (1 mol) of styrene and 98 g (1 mol) of maleic anhydride. Done.

The properties of the obtained water-soluble polymer were as follows: solids concentration = 7.5
%, B-type viscosity (25 ° C.) = 120 cps, pH = 4.4.

Using this water-soluble polymer as an aqueous emulsifier solution, and using 79.4 parts of water instead of 28.2 parts of water added together with the melamine-formaldehyde of Example 1, all in the same manner as in Example 1 except for the encapsulation and preparation of a CB sheet. Was performed.

Evaluation Method The microcapsules and pressure-sensitive copy 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 of capsule after drying for 3 hours ・ Viscosity The viscosity of capsule emulsion at 20 ° C by B-type viscometer ・ Blue spot Diluted with water so that the solid content of capsule emulsion becomes 20% , 6g / m dry smear on CF sheet
After ² become as directly applied and dried, counting the number of 100 cm ² per spot. 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 each other, a slight load of 50 g / m ² was applied, and the reflectance of the CF sheet surface was measured after being left in an atmosphere at 140 ° C. for 3 hours. The larger the value, the better the heat resistance and the stronger the film.

The reflectance measurement of the CF sheet subjected to the static pressure coloring stain and the heat treatment was performed using a color difference meter ND101DP manufactured by Nippon Denshoku Industries Co., Ltd. The display was the reflectance of the coloring portion / the untreated portion (the background portion). ) × 100 (%). Table I shows the results of evaluation based on the above measurement methods.

(F) Effects 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 paper, the effect of obtaining a pressure-sensitive paper excellent in coating suitability due to low viscosity and excellent in color development and stain resistance can be obtained. .

Furthermore, as an unexpected effect obtained by 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. The effect is obtained.

Claims (1)

(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,
(B) Styrenes containing alkyl substituents and (C)
An emulsifier for microcapsules, which is a multi-component copolymer obtained by copolymerizing a monomer containing maleic anhydride.