JP2797960B2 - Manufacturing method of microcapsules - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyurethane and / or
Also, the present invention relates to a method for producing microcapsules having a polyurea wall and having excellent solvent resistance, heat resistance and pressure resistance.

[0002]

2. Description of the Related Art Microcapsules are used for recording materials such as pressure-sensitive recording paper, fragrances, pharmaceuticals, pesticides, adhesives, adhesives, foods,
Investigations have been made in the fields of dyes, solvents, liquid crystals, etc., and various ones have reached the stage of practical use or practical use.

[0003] In general, microcapsule production methods include:
A physical method, a mechanical method, a physicochemical method, and a chemical method are known, and these methods are appropriately selected and used depending on the use of the microcapsule. Use of the microcapsules produced by these methods is limited because the capsules obtained by the physical method and the mechanical method have a large particle size and the denseness of the wall film is insufficient.
In contrast, in the physicochemical method and the chemical method, the capsule particle size is arbitrarily controlled, a small one of about several μm can be easily produced, and a dense capsule having a high wall film can be obtained. Used in range.

As a physicochemical method, a coacervation method (phase separation method) using gelatin is known. This method has been applied in a wide range of fields.
Due to the use of natural gelatin, there are large fluctuations in quality and price, and it has a tendency to rot, agglomerate and cannot withstand long-term storage, and the capsule has poor water resistance, In addition, it has the drawback that it is difficult to obtain a high-concentration capsule slurry and that the encapsulation step is complicated.

As a chemical method, in addition to an in-situ polymerization method in which a reaction proceeds from a continuous aqueous phase to form a wall film such as an amino resin around a core substance, both an aqueous phase and an oil phase are used. There is an interfacial polymerization method in which a reaction material is made to exist and a polymerization or condensation reaction is carried out at the interface between the two, that is, at the surface of the core material to form a polymer microcapsule wall film.

[0006] In-situ polymerization method (for example,
No. -27452, Japanese Patent Publication No. 5-51339, Japanese Patent Publication No. 5-53538, Japanese Patent Publication No. 5-53539, etc.) can use an inexpensive amino resin and have excellent heat resistance. The wall film is brittle, and there is a limit in increasing the particle size of the microcapsule, and there are disadvantages such as generation of formaldehyde. In contrast, the interfacial polymerization method uses polyamide, which forms an elastic body, as a film material.
Polyester or polyurethane or the like can be used, and has the advantage that microcapsules excellent in strength can be prepared (for example, JP-B-63-33474, JP-A-63-107741, and JP-A-64 -7288
No. 6, JP-A-2-2057, etc.). In particular, a method using a polyurethane or polyurea obtained by reacting a polyvalent isocyanate with water, a polyvalent amine or a polyhydric alcohol is excellent in that a high-concentration microcapsule solution is obtained and the obtained microcapsules have excellent water resistance. And that microencapsulation can be performed in a short time. However, the microcapsules using the polyvalent isocyanate, under an atmosphere in which an organic solvent is present, the oil contained therein is gradually extracted, and at a high temperature, the core material of the microcapsules leaks,
It has the disadvantage of being destroyed by relatively weak pressure.

[0007]

SUMMARY OF THE INVENTION The present invention overcomes the above-mentioned drawbacks of the conventional method for producing microcapsules, does not generate formaldehyde, and is excellent in solvent resistance, heat resistance and pressure resistance. The purpose is to provide.

[0008]

As a result of various studies, the present inventors have found that a hydrophobic liquid in which a polyvalent isocyanate is dissolved can be used to convert acrylic acid, methacrylic acid, (meth) acrylonitrile, hydroxyethyl (meth) acrylate And emulsified in an aqueous solution containing a water-soluble polymer whose main component is a multi-component copolymer of (meth) acrylamide, and then reacted and microencapsulated. Solvent resistance,
Heat resistance and pressure resistance are found to be significantly improved,
The object of the present invention has been achieved.

That is, the present invention provides a method for producing microcapsules, which comprises emulsifying a hydrophobic liquid in which a polyvalent isocyanate is dissolved in an aqueous solution containing an emulsifier, and then forming a film on the interface between the hydrophobic liquid and water. The present invention relates to a method for producing microcapsules, wherein a multi-component copolymer of acrylic acid, methacrylic acid, (meth) acrylonitrile, hydroxyethyl (meth) acrylate, and (meth) acrylamide is used as a main component of the emulsifier.

The microcapsule of the present invention is a microcapsule composed of a polyurethane and / or polyurea wall. In microencapsulation, acrylic acid, methacrylic acid, (meth) acrylonitrile, hydroxyethyl (meth) acrylate and It is characterized by using a water-soluble polymer whose main component is a multi-component copolymer composed of (meth) acrylamide.

The multi-component copolymer of acrylic acid, methacrylic acid, (meth) acrylonitrile, hydroxyethyl (meth) acrylate and (meth) acrylamide used in the present invention has a viscosity of 50 to 2 in terms of the viscosity of an aqueous solution.
000 cps is preferred, preferably 100 to 10,
000cps is good. However, the viscosity mentioned here is a value measured by using a B-type viscometer at 30 ° C. for a multicomponent aqueous copolymer solution having a solid content of 21% by weight and a pH of 2 to 4. If the viscosity is less than 50 cps, the emulsifying and dispersing power and the protective action during capsule formation are insufficient, and if it is more than 20,000 cps, handling becomes difficult, and the resulting capsule slurry also has a high viscosity, which is not preferable.

The copolymerization ratio of the multicomponent copolymer is as follows: acrylic acid: 21 to 48 mol%, methacrylic acid: 9 to 27 mol%,
(Meth) acrylonitrile is preferably 2 to 28 mol%, hydroxyethyl (meth) acrylate is preferably 15 to 32 mol%, and (meth) acrylamide is preferably 5 to 32 mol%, and more preferably acrylic acid is 25 to 40 mol%. , Methacrylic acid is 15 to 25 mol%, (meth) acrylonitrile is 10 to 20 mol%, hydroxyethyl (meth) acrylate is 20 to 28 mol%, and (meth)
Acrylamide is 10 to 25 mol%.

When the copolymerization ratio of acrylic acid in the multi-component copolymer is less than 21 mol%, the emulsifying and dispersing power and stability of the emulsified particles are lacking, and when it is more than 48 mol%, the obtained capsule slurry has a high viscosity. Would. If the amount of (meth) acrylonitrile is less than 2 mol%, the emulsifying and dispersing power and the stability of the emulsified particles are lacking. If the amount is more than 28 mol%, the multicomponent copolymer becomes insoluble in water. When the amount of methacrylic acid is less than 9 mol%, the resulting capsule lacks heat resistance, and when it exceeds 27 mol%, the obtained capsule slurry has a high viscosity. If the amount of hydroxyethyl (meth) acrylate is less than 15 mol%, the emulsifying and dispersing power and the stability of the emulsified particles are lacking. If the amount exceeds 32 mol%, the viscosity of the capsule slurry becomes high. If the amount of (meth) acrylamide is less than 5 mol%, the capsules lack heat resistance, and if the amount is more than 32 mol%, the obtained capsule slurry has a high viscosity.

Acrylic acid and methacrylic acid may be free acids, or some of the carboxyl groups in the molecule may form salts. Representative salts include, for example, sodium salts, potassium salts, ammonium salts and the like.

The multi-component copolymer of acrylic acid, methacrylic acid, (meth) acrylonitrile, hydroxyethyl (meth) acrylate and (meth) acrylamide used in the present invention can be prepared, for example, by mixing these monomers in water with hydrogen peroxide, It is produced by a known method of radical polymerization using an initiator such as potassium persulfate, ammonium persulfate, benzoyl peroxide, cumene hydroperoxide, methyl ethyl ketone peroxide, azobisisobutyronitrile and the like. When the copolymerization ratio of (meth) acrylonitrile is high, the aqueous solution sometimes becomes cloudy, but can be used without any problem in the production of microcapsules, and the desired effect can be obtained. Also, the multi-component copolymer can be mixed with water at any ratio.

The amount of the multi-component copolymer in the hydrophilic encapsulating medium is 1 to 100 parts by weight of the hydrophobic liquid.
The amount is generally 30 parts by weight, but it is appropriately selected depending on the concentration, viscosity, capsule particle size and the like of the capsule slurry to be produced. However, if the amount used is small, agglomeration occurs during the encapsulation step, or if the amount used is large, the viscosity of the obtained capsule slurry becomes high, and it becomes difficult to obtain good capsules. Parts by weight are preferred.

In the present invention, another emulsifier can be used in combination with the above-mentioned multi-component copolymer. Specific examples of other emulsifiers (surfactants) include ionic ones such as alkylbenzene sulfonates, polyoxyethylene sulfates, and funnel oils, and nonionic ones such as polyoxyethylene alkyl ethers and polyoxyethylene sorbitan fatty acid esters. Are given. The amount of other emulsifiers used is at most 50% by weight, preferably at most 10% by weight, of the total emulsifiers.
It is.

The polyvalent isocyanate used in the present invention is
There is no particular limitation, and aromatic polyisocyanates, aliphatic polyisocyanates, and combinations thereof can be used.

Examples of the aromatic polyvalent isocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, 4,4'-diphenylmethane diisocyanate, and 1,3. -Xylene diisocyanate, triphenylmethane triisocyanate,
And polymethylene polyphenyl isocyanate.

Examples of the aliphatic polyisocyanate include:
Hexamethylene diisocyanate, propylene-1,2
-Diisocyanate, butylene-1,2-diisocyanate, ethylidine diisocyanate, isophorone diisocyanate, biuret of hexamethylene diisocyanate, isocyanurate of hexamethylene diisocyanate, and the like.

The amount of the polyvalent isocyanate used is 10 to 50 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the hydrophobic liquid. If the amount of the polyvalent isocyanate used is less than 10 parts by weight, the resulting capsule membrane is thin and the capsule strength is weak, so that it cannot be used. If the amount is more than 50 parts by weight, the system gels and a safe capsule cannot be obtained.

Examples of the hydrophobic liquid to be encapsulated include animal oils such as fish oil and lard oil, and vegetable oils such as soybean oil, castor oil and linseed oil, petroleum, kerosene, paraffin oil, toluene, xylene and the like. And hydrophobic oils such as synthetic oils such as alkylated naphthalene, diphenylethane, dibutyl phthalate and the like. These hydrophobic liquids are used for microcapsule applications,
Pharmaceuticals, agricultural chemicals, flavors, foods, dyes, catalysts and the like can be appropriately mixed and dissolved according to the purpose and used.

The microcapsule of the present invention is obtained by emulsifying a hydrophobic liquid in which the above-mentioned polyvalent isocyanate is dissolved into an aqueous solution containing the above-mentioned multi-component copolymer in the form of fine particles. Alternatively, it can be easily produced by forming a polymer film of Pourea. The pH at the time of emulsifying the hydrophobic liquid is as follows:
It may be in the acidic range of 2 to 7. For this purpose, if necessary, the pH is adjusted with a suitable acid or alkali.

[0024]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.
Although the embodiment describes the case of carbonless paper in which microcapsules are most frequently used, the present invention is not limited to the embodiment alone, and capsules for other uses can be similarly manufactured. All parts and percentages in the examples are on a weight basis.

Example 1 Production of pentacopolymer aqueous solution 529 parts of water was charged into a five-necked flask equipped with a stirrer, a thermometer and a reflux condenser, and the temperature was raised to 80 ° C. Next, 109 parts of acrylic acid aqueous solution (80%), acrylonitrile 23
209 parts of water, and 39 parts of methacrylic acid, 57 parts of hydroxyethyl acrylate and 57 parts of an aqueous acrylamide solution (40%) were added to obtain 20% of a uniform aqueous monomer solution.
Was charged into the flask. Then, 3% of potassium persulfate
39 parts of an aqueous solution were added. The temperature inside the flask rises,
When the temperature reached 84 ° C., the remainder of the monomer aqueous solution (80% of the whole) was continuously dropped into the flask over 2 hours. At the end of the dropping, and 30 minutes after that, 15 parts of a 3% aqueous solution of potassium persulfate was charged into the flask. The temperature inside the flask was kept at 82 to 85 ° C. After cooling, 13 parts of a 20% aqueous sodium hydroxide solution was added.

The obtained acrylic acid, acrylonitrile,
The analysis values of the aqueous methacrylic acid, hydroxyethyl acrylate, and acrylamide terpolymer solution were as follows: solid content: 21.0%; viscosity: 210 cps (30 ° C., B-type viscometer); pH: 3.20. 38 parts of acrylic acid, 10 parts of acrylonitrile, 17 parts of methacrylic acid, 25 parts of hydroxyethyl acrylate thus obtained.
Pentacopolymer water-soluble polymer composed of 10 parts of acrylamide and 10 parts of acrylamide (copolymerization ratio is 40.5: 14.
5: 15.2: 19.1: 10.7) 30 parts of an aqueous solution was added to 70 parts of water while stirring, and the pH was adjusted to 4.3 to obtain an encapsulated hydrophilic medium.

On the other hand, 4 parts of crystal violet lactone (CVL) were added to 100 parts of diisopropylnaphthalene, and dissolved by heating at 90 ° C. for 2 hours with stirring, and hexamethylene diisocyanate was used as an aliphatic polyvalent isocyanate. 17 parts were mixed and dissolved. A mixture of 100 parts of the oily core material and 100 parts of the encapsulated hydrophilic medium is mixed with a homomixer (Special Kika Co., Ltd.)
T. K. 10,0 using an auto homomixer)
After emulsification at 00 rpm for 10 minutes, an o / w emulsion containing particles having an average particle size of 8.0 μm was obtained. The temperature of the emulsion was raised to 80 ° C., and this temperature was maintained for 2 hours to perform microencapsulation.

Example 2 40 parts of acrylic acid, 5 parts of acrylonitrile, 17 parts of methacrylic acid, 25 parts of hydroxyethyl acrylate, and 13 parts of acrylamide 13 prepared in the same manner as in Example 1
Parts with a solid content of 20.9% and a viscosity of 250 cps (3
0 ° C., B-type viscometer), pentacopolymer water-soluble polymer having a pH of 3.18 (copolymerization ratio: 43.4: 7.4: 1 in mol%)
5.4: 19.5: 14.3) An encapsulation reaction was carried out in the same manner as in Example 1 except that an aqueous solution was used.
A capsule slurry was obtained.

Example 3 30 parts of acrylic acid, 10 parts of acrylonitrile, 30 parts of methacrylic acid, 20 parts of hydroxyethyl acrylate and acrylamide 1 prepared in the same manner as in Example 1
0 parts, 21.0% solids, 200 cps viscosity
(30 ° C., B-type viscometer), pentacopolymer water-soluble polymer having a pH of 3.42 (copolymerization ratio is 32.2: 14.
6: 26.9: 15.4: 10.9) An encapsulation reaction was performed in the same manner as in Example 1 except that an aqueous solution was used, to obtain a capsule slurry.

Example 4 25 parts of acrylic acid, 10 parts of acrylonitrile, 20 parts of methacrylic acid, 35 parts of hydroxyethyl acrylate, and acrylamide 1 prepared in the same manner as in Example 1
0 parts, 20.5% solids, 175 cp viscosity
s, pH: 3.55 copolymer water-soluble polymer having a pH of 3.55 (copolymerization ratio is 28.7: 15.6: 19.3: 24.
8: 11.6) An encapsulation reaction was performed in the same manner as in Example 1 except that an aqueous solution was used, to obtain a capsule slurry.

Example 5 28 parts of acrylic acid, 10 parts of acrylonitrile, 17 parts of methacrylic acid, 25 parts of hydroxyethyl acrylate and 25 parts of acrylamide 2 prepared in the same manner as in Example 1
0 parts, solid content 20.6%, viscosity 335 cps,
Five-component copolymer water-soluble polymer having a pH of 3.50 (copolymerization ratio is 29.7: 14.4: 15.1: 19.1: 1 in mol%)
21.6) An encapsulation reaction was performed in the same manner as in Example 1 except that an aqueous solution was used, to obtain a capsule slurry.

Example 6 A capsule slurry was obtained in the same manner as in Example 2 except that 2,4-tolylene diisocyanate was used instead of hexamethylene diisocyanate. .

Example 7 An encapsulation reaction was carried out in the same manner as in Example 5 except that 2,4-tolylene diisocyanate was used instead of hexamethylene diisocyanate to obtain a capsule slurry. .

Comparative Example 1 A solid content of 20.5% and a viscosity of 75 cps consisting of 48 parts of acrylic acid, 10 parts of acrylonitrile, 17 parts of methacrylic acid and 25 parts of hydroxyethyl acrylate produced in the same manner as in Example 1. The encapsulation reaction was performed in the same manner as in Example 1 except that a quaternary copolymer water-soluble polymer having a pH of 2.86 was used.
A capsule slurry could not be obtained.

Comparative Example 2 In Example 1, instead of 10.7 parts of the pentacopolymer (acrylic acid-acrylonitrile-methacrylic acid-hydroxyethyl acrylate-acrylamide) contained in 100 parts of the encapsulated hydrophilic medium, 6.2 parts of polyvinyl alcohol and 4.5 of carboxymethylcellulose
And 5.8 parts of carbodiimide-modified diphenylmethane diisocyanate, 5.8 parts of a biuret of hexamethylene diisocyanate and butylene of ethylenediamine instead of 14.1 parts of hexamethylene diisocyanate contained in 100 parts of the oily core material. Oxide adduct (addition mole of butylene oxide to ethylenediamine 16.8 mole, molecular weight 1267)
An encapsulation reaction was performed in the same manner as in Example 1 except that 2.5 parts were used, to obtain a capsule slurry. The average particle size was 7.0 μm.

Comparative Example 3 An encapsulation reaction was carried out in the same manner as in Comparative Example 2 except that carboxy-modified polyvinyl alcohol (10.7 parts) was used instead of the polyvinyl alcohol and carboxymethyl cellulose of Comparative Example 2. A slurry was obtained.

With respect to the capsules obtained in the above Examples and Comparative Examples, various characteristics were evaluated for the following items. (1) Particle size: Microtrac particle size analyzer (9240)
The average particle size of the capsule measured by a mold (manufactured by Nikkiso Co., Ltd.) was shown as a particle size at a 50% volume point. (2) Viscosity: The viscosity of the capsule slurry at 30 ° C. was measured with a B-type viscometer. (3) Color development: 50 parts of water was added to 50 parts of the capsule slurry, and 5 parts of cellulose powder and 10 parts of a 10% aqueous starch oxide solution were mixed and dispersed to prepare a capsule coating liquid. This capsule coating solution was applied to a 60 g / m ² base paper with a wire bar so that the dry coating amount was 4 g / m ² , and dried to prepare a pressure-sensitive copying paper top sheet. The upper sheet was superimposed on a commercially available lower sheet and printed with an electric typewriter, and the color development was evaluated. (4) Pressure resistance: An upper sheet is prepared in the same manner as in the above (3), superimposed on a commercially available lower sheet, and a pressure is applied by an IGT tester at a setting condition of 30 kg to thereby obtain a lower sheet developer surface. Were compared. When the film strength of the capsule is weak, or the capsule particle size distribution is poor, and the coarse particles are present, the capsule is broken, and the coated surface of the lower paper developer is colored blue, indicating that the pressure resistance is poor. (5) Heat resistance: After applying the capsule slurry to the paper under carbonless paper and drying it, leave it in a dryer at 140 ° C. for 2 hours, and evaluate the degree of color development thereafter. That is, the obtained capsule slurry was applied to a lower sheet with a 0.05 mm applicator, dried, and the color of the coated surface after 2 hours at 140 ° C. was compared. If the coated surface is white, the core material does not leak out and the heat resistance of the capsule film is evaluated as good, but if it becomes slightly blue, the core material is slightly leaking and the heat resistance is poor Will be. Table 1 shows the results of the above evaluation.

[0038]

[Table 1]

As is clear from Table 1, all of the capsules according to the present invention had an average particle size of about 8 μm, and the viscosity of the capsule slurry was as low as 300 to 500 cps. Further, the color development, pressure resistance and heat resistance of the capsule were also good. On the other hand, the capsules according to Comparative Examples 2 and 3 had good coloring properties and pressure resistance, but were inferior in heat resistance.
It was not good. In Comparative Example 1, even a good capsule slurry was not obtained.

[0040]

According to the present invention, a stable emulsion of a hydrophobic liquid can be obtained, and the formation of a highly efficient and dense capsule wall film can be promoted in a short period of time. Capsules having excellent heat resistance can be obtained, which is extremely useful in industry. Such excellent effects are achieved by the acrylic acid, methacrylic acid, (meth) acrylonitrile,
Hydroxyethyl (meth) acrylate, (meth) acrylamide multi-component copolymer itself has high emulsifying and dispersing power,
It is also considered that it has an excellent protective colloid ability and has the ability to form a crosslinked film with a polyvalent isocyanate on the surface of the core material.

Claims (5)

(57) [Claims] 1. A method for producing microcapsules, wherein a hydrophobic liquid in which a polyvalent isocyanate is dissolved is emulsified in an aqueous solution containing an emulsifier, and then a film is formed on an interface between the hydrophobic liquid and water. A method for producing microcapsules, wherein a multicomponent copolymer of acrylic acid, methacrylic acid, (meth) acrylonitrile, hydroxyethyl (meth) acrylate, and (meth) acrylamide is used as a component. 2. The acrylic copolymer as claimed in claim 1, wherein
-48 mol%, 9-27 mol% of methacrylic acid, 2-28 mol% of (meth) acrylonitrile, 15-32 mol% of hydroxyethyl (meth) acrylate, and 5-32 mol% of (meth) acrylamide. The method for producing microcapsules according to claim 1, wherein 3. The use amount of the multi-component copolymer is 1 to 30 parts by weight based on 100 parts by weight of a hydrophobic liquid.
Or the method for producing a microcapsule according to 2. 4. The method according to claim 1, wherein the viscosity of the aqueous multi-component copolymer solution (solid content: 21% by weight) is 50 to 20,000 cps (30 ° C., B-type viscometer). Production method of microcapsules. 5. The method for producing microcapsules according to claim 1, wherein the polyvalent isocyanate is an aromatic polyvalent isocyanate or an aliphatic polyisocyanate.