JPH10225631A - Emulsifier for producing fine capsule, and production of fine capsule by using the emulsifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emulsifier improved in the uniformity of grain size of a urea-formaldehyde resin based fine capsule for pressure sensitive recording paper and the heat resistance of a film and to produce a fine capsule by using the emulsifier. SOLUTION: In this emulsifier for producing fine capsule containing a water soluble high polymer material as an active principle and forming the urea-formaldehyde resin film around a hydrophobic core material, the water soluble high polymer material is composed of (A) a partially neutralized matter of isobutylene-maleic anhydride copolymer and (B) an acryl based copolymer containing 75-100wt.% acrylic acid or its alkali metallic salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an emulsifier for producing microcapsules and a method for producing microcapsules using the emulsifier. More particularly, the present invention relates to a microcapsule comprising a urea-formaldehyde resin film for pressure-sensitive recording paper and having a particle size. The present invention relates to an emulsifier for producing microcapsules having excellent uniformity and heat resistance of a membrane, and a method for producing microcapsules using the emulsifier.

[0002]

2. Description of the Related Art A microcapsule is a microcontainer in which a core substance such as liquid or solid is covered with a membrane substance such as gelatin, urea-formaldehyde resin, urethane resin or the like.
m. Examples of a method for producing a microcapsule include a coacervation method, an interfacial polymerization method, and an in-site method.
The u method and the like are known.

One common use of microcapsules is in pressure sensitive recording paper. The pressure-sensitive recording paper is coated on one side of a base paper with a color former microcapsule composition mainly composed of a microcapsule containing an oily substance in which an electron-donating almost colorless organic compound (hereinafter referred to as a color former) is dissolved. And a developer composition containing as a main component an electron-accepting compound (hereinafter referred to as a color developer) that exhibits a color when it comes into contact with the color former on one side of the base paper, and the other side. It consists of a medium paper having a color former microcapsule composition applied on one side and a lower paper having a developer composition applied on one side of a base paper. Generally, upper paper-lower paper or upper paper-middle paper-lower paper are used in this order in such a manner that the surface coated with the colorant microcapsule composition and the surface coated with the developer composition are in contact with each other. The microcapsules are destroyed by the pressure, and the oil in which the color former is dissolved is transferred to the color developer layer, and the color is developed by reacting with the color developer. As described above, the pressure-sensitive recording paper is designed so that the capsule can be destroyed when necessary and its function can be exhibited.

[0004] Microencapsulation of a pressure-sensitive recording paper by forming an in-situ urea-formaldehyde resin film has been widely known and many patents have been filed. Among them, JP-A-53-84882, JP-A-53-84883, and JP-A-54-8518.
No. 4 discloses a technique in which a urea-formaldehyde-based isobutylene-maleic anhydride copolymer is used as an emulsifier. Similarly, Japanese Patent Application Laid-Open No. 57-13 / 1982
Japanese Patent No. 5038 discloses an example in which an isobutylene-maleic anhydride copolymer or the like is used as an emulsifier in a polyvalent amine-glutaraldehyde system. However, in any of these cases, when pressure-sensitive recording paper is used, there is a problem in that giant particles called spot contamination are generated. Furthermore, the heat resistance of the capsule membrane was not sufficient.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a urea-formaldehyde resin-based microcapsule for a pressure-sensitive recording paper when an isobutylene-maleic anhydride copolymer, which has not been conventionally satisfactory, is used as an emulsifier. It is an object of the present invention to provide an emulsifier for producing microcapsules which is excellent in uniformity of particle diameter and heat resistance of a film, and a method for producing microcapsules using the emulsifier.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above problems, and as a result, have found that a partially neutralized isobutylene-maleic anhydride copolymer and a specific acrylic copolymer are microencapsulated. The present inventors have found that a microcapsule having excellent uniformity of particle diameter and excellent heat resistance of a film can be obtained by using it as an emulsifier for production.

That is, 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) a partially neutralized product of an isobutylene-maleic anhydride copolymer. And (B) an emulsifier for producing microcapsules, comprising an acrylic copolymer containing 75 to 100% by weight of acrylic acid or an alkali metal salt thereof, and a method for producing microcapsules using the emulsifier It is about.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The isobutylene-maleic anhydride copolymer used in the present invention is a partially neutralized product. As a method of obtaining a partially neutralized product, the amount of alkali added when dissolving the isobutylene-maleic anhydride copolymer is calculated stoichiometrically and added. That is, when the maleic anhydride portion in the copolymer is completely converted into a maleate, the degree of neutralization is defined as 1.0, and the amount of alkali added in the case of partial neutralization is determined. The details are described in, for example, a catalog of Isovan (isobutylene-maleic anhydride copolymer) manufactured by Kuraray Co., Ltd.

In the present invention, a partially neutralized isobutylene-maleic anhydride copolymer provides a favorable uniform particle size result. The neutralization degree is suitably from 0.1 to 0.7, and more preferably from 0.1 to 0.5. When the degree of neutralization is larger than 0.7, the generation of giant particles increases. On the contrary, when the degree of neutralization is smaller than 0.1, it becomes difficult to dissolve the isobutylene-maleic anhydride copolymer. The reason why a favorable result is obtained at a specific degree of partial neutralization is not clear, but it is assumed that the balance between hydrophilicity and hydrophobicity during emulsification changes.

The molecular weight of the isobutylene-maleic anhydride copolymer used in the present invention is preferably 50,000 to 500,000.

The present invention is characterized in that a specific acrylic copolymer is used together with a partially neutralized isobutylene-maleic anhydride copolymer. That is, in the acrylic copolymer containing 75 to 100% by weight of acrylic acid or an alkali metal salt thereof, a preferable uniform particle size result is obtained. More preferably, those containing 80 to 100% by weight of acrylic acid or an alkali metal salt thereof are preferred. When the content of acrylic acid or an alkali metal salt thereof is lower than 75% by weight, the generation of giant particles increases and a favorable result cannot be obtained. The reason for this is not clear, but is presumed to be due to a change in the emulsifying ability.

The monomer component other than acrylic acid or its alkali metal salt in the acrylic copolymer is not particularly limited as long as it is acrylic, but may be any other derivative of acrylic acid or methacrylic acid, such as an ester, amide, or nitrile. A derivative having a sulfonic acid group, such as 2-acrylamide-2-methylpropanesulfonic acid, or a vinyl-based monomer can be added as long as the physical properties aimed at by the present invention are not impaired. In addition, examples of the alkali metal salt of acrylic acid include salts such as sodium and potassium, and a sodium salt is preferable.

The molecular weight of the acrylic copolymer is 1
It is preferably from 100,000 to 1,000,000, and more preferably from 300,000 to 1,000,000. When the molecular weight is less than 100,000, the heat resistance of the formed capsule membrane is reduced. On the other hand, when the molecular weight is 1,000,000 or more, the viscosity of the acrylic copolymer itself is increased, and the workability is reduced.

The ratio of the partially neutralized isobutylene-maleic anhydride copolymer (A) and the specific acrylic copolymer (B) used in the present invention is (A) / (B) = 2. 7, and within this range, it is possible to obtain a capsule having an excellent balance between uniformity of the particle diameter and heat resistance of the film. Among them, (A) / (B) = 2 to 5 is more preferable. (A) /
When the ratio of (B) is smaller than 2, the heat resistance of the film is reduced, and when it is larger than 7, the generation of giant particles is increased.

The addition amount of the emulsifier according to the present invention is preferably 0.5 to 10%, more preferably 1 to 6% as the concentration in the aqueous phase.

The emulsifier of the present invention is used in a urea-formaldehyde type membrane substance reaction system. As a so-called core substance, a hydrophobic oily substance can be used. As the oily substance, in the case of pressure-sensitive recording paper, a synthetic oil such as an alkyl-substituted aromatic compound in which an electron-donating color former is dissolved is usually used. In addition, an oil-soluble auxiliary agent and the like can be added to this oily substance, if necessary, in addition to the color former.

The ratio of urea-formaldehyde is as follows:
The amount of formaldehyde is 1 to 4 mol, preferably 1.5 to 3.0 mol, per 1 mol of urea. Substances present in the aqueous phase producing the membrane substance include urea-formaldehyde, emulsifiers, phenols that polymerize as the membrane substance, pH
There are acids or alkalis added for adjustment. The pH of the aqueous phase is preferably from 2 to 5, more preferably from 3 to
4. The temperature for performing the polymerization reaction is preferably 40 to
90 ° C, more preferably 50 to 80 ° C. The microcapsules for pressure-sensitive recording paper have a particle size of 1 to 10 μm, preferably 2 to 8 μm.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. Unless otherwise specified, parts and% described below indicate parts by weight and% by weight, respectively.

Example 1 Powder 10 of a 1: 1 molar ratio copolymer of isobutylene-maleic anhydride having a molecular weight of 160,000 to 170,000 (Isoban 10: trade name of Kuraray Co., Ltd.)
Parts, sodium acetate trihydrate 10.6 parts, water 179.4
The resulting mixture was heated and dissolved to obtain a dissolved product A having a degree of neutralization of 0.6. On the other hand, in 400 parts of water, 80 parts of acrylic acid and 20 parts of ethyl acrylate were subjected to radical polymerization to obtain a reactant B having a molecular weight of 1,000,000. 80 parts of a 5% (active ingredient) solution of A, 20 parts of B
% (Active ingredient) solution 10 parts (A / B = 2), urea 10
, 1 part of resorcinol and 60 parts of water were added and dissolved by stirring, and the pH of the system was adjusted to 3.6 with 3.5% hydrochloric acid. 3.5
% Of crystal violet lactone was dissolved in the aqueous solution and vigorously stirred and emulsified to obtain an O / W type emulsion having an average oil droplet diameter of 5 μm. After adding 22 parts of a 37% aqueous formaldehyde solution to this emulsion under stirring, the temperature of the system was reduced to 55 ° C.
And maintained at this temperature for 2 hours with stirring. Thereafter, the temperature was returned to room temperature to obtain a capsule slurry.

Example 2 Isoban 1 in Example 1
10.6 parts of sodium acetate trihydrate at the time of heating and dissolving 0
1.0 part of sodium hydroxide instead of 179.4 parts of water,
189 parts of water was used to obtain dissolved product C having a degree of neutralization of 0.2, which was used in place of dissolved product A. On the other hand, polyacrylic acid (manufactured by Wako Pure Chemical, molecular weight 150,000, concentration 25%) D was used in place of the acrylic copolymer B, and 98 parts of a 5% (active ingredient) solution of C was used.
A capsule slurry was obtained in exactly the same manner as in Example 1, except that 2.8 parts of a 25% solution of D (C / D = 7) and 48 parts of water were used.

Example 3 Isoban 1 in Example 1
10.6 parts of sodium acetate trihydrate at the time of heating and dissolving 0
179.4 parts of water were used as 7.1 parts and 182.9 parts, respectively, to obtain a dissolved product E having a neutralization degree of 0.4. On the other hand, in 400 parts of water, 90 parts of acrylic acid and 10 parts of butyl acrylate are radically polymerized to obtain a reactant F having a molecular weight of 300,000, and substitute for the acrylic copolymer B.
A capsule slurry was prepared in exactly the same manner as in Example 1 except that 100 parts of a 5% (active ingredient) solution of E, 5 parts of a 20% (active ingredient) solution of F (E / F = 5), and 30 parts of water were used. Obtained.

Example 4 Instead of the acrylic copolymer B in Example 1, sodium polyacrylate (Modicol VD-S: trade name, manufactured by San Nopco, molecular weight 800,000, concentration 12%) G was used. , 60 parts of a 5% (active ingredient) solution of A, 25 parts of a 12% solution of G (A / G =
1) Except for using 65 parts of water, a capsule slurry was obtained in exactly the same manner as in Example 1.

Example 5 Isoban 1 in Example 1
10.6 parts of sodium acetate trihydrate at the time of heating and dissolving 0
Capsules were prepared in exactly the same manner as in Example 1 except that 179.4 parts of water was used as 14.1 parts and 175.9 parts, respectively, to obtain dissolved product H having a degree of neutralization of 0.8 and to substitute for dissolved product A. A slurry was obtained.

Example 6 The amounts of A and G added in Example 4 were changed to 108 parts of A solution and 5 parts of G solution (A / G =
9) A capsule slurry was obtained in exactly the same manner as in Example 1, except that water was 37 parts.

Example 7 Instead of the acrylic copolymer D in Example 2, sodium polyacrylate (Nopcosanto R: trade name, manufactured by San Nopco Co., Ltd., molecular weight 8)
Using I, 98 parts of a 5% (active ingredient) solution of C, 1.8 parts of a 40% solution of I (C / I = 7), water 4
A capsule slurry was obtained in exactly the same manner as in Example 2 except that the amount was 9 parts.

Comparative Example 1 In 400 parts of water, 70 parts of acrylic acid and 30 parts of butyl acrylate were radically polymerized to obtain a reactant J having a molecular weight of 400,000, which was obtained by reacting the acrylic copolymer B in Example 1. A capsule slurry was obtained in exactly the same manner as in Example 1 except for using a substitute.

Comparative Example 2 Isoban 1 in Example 1
10.6 parts of sodium acetate trihydrate at the time of heating and dissolving 0
Capsule slurry was obtained in exactly the same manner as in Example 1 except that 179.4 parts of water was changed to 18 parts and 172 parts, respectively, to obtain dissolved product K having a degree of neutralization of 1.0 and to substitute for dissolved product A. .

Comparative Example 3 A capsule slurry was obtained in exactly the same manner as in Example 1 except that the acrylic copolymer B in Example 1 was not used, and that the amount of water to be added was 65 parts.

After adjusting the capsule slurry obtained in the above Examples and Comparative Examples to a concentration of 25%, 400 parts were collected,
200 parts water, 20 parts starch granules, 40% latex 7.5
, 10 parts of polyvinyl alcohol (110 parts) were sequentially mixed with stirring, and water was further added to prepare 18% of a colorant layer coating. This paint was applied to 50 g / m ² base paper so that the solid content was 3.5 g / m ² and dried to obtain a capsule-coated sheet.

On the other hand, 3,5-
50 parts of a 20% dispersion of zinc di (α-methylbenzyl) salicylate, 50% dispersion of light calcium carbonate 200
, 25 parts of a 20% solution of oxidized starch, 50 parts of a 10% solution of polyvinyl alcohol, 25 parts of a 40% latex, and 25% of a paint by adding water to a base paper of 50 g / m ^{2 to} apply a solid content of 6 g / m ^2. And dried to obtain a developer-coated sheet.

Evaluation of the physical properties of the capsule was performed as follows. Table 1 shows the evaluation results. (1) Heat resistance The change in the coloring ability of the capsule-coated sheet when left in an atmosphere of 105 ° C. for 24 hours is examined. The coloring ability is
The capsule-coated sheet and the colorant-applied sheet are pressed together at a pressure of 100 kg / cm ² , with the applied surfaces thereof together, and evaluated. The color density was measured by measuring the cyan density with a Macbeth densitometer, and the rate of change before and after the heat treatment was evaluated. ：: 95% or more △: 90% or more and less than 95% ×: less than 90%

(2) Giant Particles The capsule slurry was filtered through a 625 mesh screen and evaluated in terms of the residual amount ratio and the size of the giant particles as follows. ◎: Almost no residue ：: The residue is small and the particles are not extremely large. ：: The residue is small and the particles are huge. X: The residue is considerably large.

[0033]

[Table 1] Table 1

[0034]

The emulsifier of the present invention improves the uniformity of the particle size of urea-formaldehyde resin-based microcapsules for pressure-sensitive recording paper and the heat resistance of the film.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshifumi Nishikubo 1-30-6 Kamiochiai, Shinjuku-ku, Tokyo Japan Paper Manufacturing Co., Ltd.

Claims (10)

[Claims] 1. An emulsifier for producing microcapsules, comprising a water-soluble polymer as an active ingredient and forming a urea-formaldehyde resin film around a hydrophobic core material, wherein the water-soluble polymer is (A) isobutylene -An emulsifier for producing microcapsules, comprising a partially neutralized product of a maleic anhydride copolymer and (B) an acrylic copolymer containing 75 to 100% by weight of acrylic acid or an alkali metal salt thereof. 2. The emulsifier according to claim 1, wherein the degree of neutralization of the partially neutralized product of the isobutylene-maleic anhydride copolymer is 0.1 to 0.7. 3. The ratio of (A) the partially neutralized isobutylene-maleic anhydride copolymer to the (B) acrylic copolymer is (A) / (B) = 2-7. Item 1 or 2
An emulsifier for producing microcapsules according to the above. 4. The emulsifier according to claim 1, wherein the alkali metal salt of acrylic acid is a sodium salt. 5. The acrylic copolymer having a molecular weight of 10
5. The emulsifier for producing microcapsules according to claim 1, wherein the amount is from 10,000 to 1,000,000. 6. A method for producing a microcapsule in which urea and formaldehyde are polymerized in an acidic aqueous system to form a urea-formaldehyde resin film around a hydrophobic core substance, wherein (A) an isobutylene-maleic anhydride copolymer And (B) a water-soluble polymer material comprising an acrylic copolymer containing 75 to 100% by weight of acrylic acid or an alkali metal salt thereof. . 7. The method for producing microcapsules according to claim 6, wherein the degree of neutralization of the partially neutralized product of the isobutylene-maleic anhydride copolymer is 0.1 to 0.7. 8. The method according to claim 1, wherein the ratio of the (A) partially neutralized isobutylene-maleic anhydride copolymer to the (B) acrylic copolymer is (A) / (B) = 2 to 7. Item 6 or 7
A method for producing the microcapsule according to the above. 9. The method for producing microcapsules according to claim 6, wherein the alkali metal salt of acrylic acid is a sodium salt. 10. The acrylic copolymer having a molecular weight of 1
10. The method for producing a microcapsule according to claim 6, wherein the amount is from 10,000 to 1,000,000.