JPH0454495B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Application Field The present invention relates to a method for producing microcapsule suspensions which are monodispersed in an organic solvent vehicle.
More specifically, microcapsules are monodispersed in an organic solvent vehicle to which an organophilic binder material and other auxiliary materials are added as necessary, for example, an organic solvent vehicle for forming a carbonless copying layer. The present invention relates to a method for producing a microcapsule suspension suitable for use in flexographic inks, etc. (B) Prior art A method for coating microcapsules containing various active ingredients as core materials on a planar support (hereinafter referred to as a substrate) such as paper or film involves coating an aqueous suspension of microcapsules on a substrate. The main method used has been to apply the microcapsule aqueous suspension to the entire surface of the substrate using various coating methods, but in recent years, methods have also been introduced in which the microcapsule aqueous suspension is applied only to the necessary areas on the substrate using various printing methods. It has started to be practiced in some places. This partial coating of microcapsules was born out of social demands for resource conservation and the diversification and sophistication of printed matter designs, and is thought to be a technique that will become more widespread in the future. (C) Problems to be Solved by the Invention However, when the existing method for coating microcapsules is carried out on a substrate such as paper, the paper expands and contracts during coating and drying because the vehicle is aqueous, resulting in a change in size. Problems such as deformation and wrinkles may occur, making it difficult to obtain a fully satisfactory result, and the above-mentioned problems occur particularly frequently with thin paper. Therefore, it has been considered to avoid the above-mentioned trouble by partially coating a paper substrate with a microcapsule suspension made of an organic solvent such as alcohol. The present inventors prepared an aqueous microcapsule suspension by a known method, and then removed most of the water by spray drying, for example, to obtain solid or powdered microcapsules. When attempting to obtain a non-aqueous suspension by adding it to an organic solvent vehicle, the following problems were discovered. (1) In gelatin wall microcapsules produced by the coacelvation method as described in U.S. Patent No. 2,800,457 or U.S. Pat. No. 3,041,289, the core substance easily leaches into the organic solvent vehicle. cannot be used. (2) Synthetic resins that can be subjected to in-situ polymerization methods as described in JP-A-51-9079, JP-A-53-84881, JP-A-54-49984, JP-A-56-51238, etc. Mural membrane microcapsules or Tokkosho
No. 38-19574, Special Publication No. 42-446, Special Publication No. 42-
No. 771, Special Publication No. 49-45133, Japanese Patent Publication No. 159990-1977
No., Japanese Patent Application Publication No. 56-15836, British Patent No. 1091077
It has been found that synthetic resin wall microcapsules using interfacial polymerization method as described in British Patent No. 1,091,141, etc. are suitable for the purpose of the present invention because the core substance is difficult to exude even in an organic solvent vehicle. However, the solid or powdered microcapsules from which most of the water has been removed are not monodispersed in organic solvents such as alcohol and form aggregates; When the coating was partially coated, the microcapsules were destroyed due to light friction and the coated surface became undesirably rough, making it unsuitable for practical use. The object of the present invention is to prepare a microcapsule aqueous suspension by a known method as described above;
The object of the present invention is to provide a method in which microcapsules in solid or powder form from which most of the water has been removed are difficult to exude core substances even in an organic solvent vehicle such as alcohol, and are monodispersed and do not form aggregates.
Thereby, when the microcapsule suspension monodispersed in an organic solvent vehicle such as an alcohol is partially coated on a substrate such as paper,
The object of the present invention is to provide a practically excellent method in which little destruction of microcapsules is observed with light friction, and no roughness is observed on the coated surface. (D) Means for Solving the Problems The present invention has solved the above problems and achieved the object by the following means. That is, in a method for producing a microcapsule suspension that is monodispersed in an organic solvent vehicle, (a) a hydrophobic substance is dispersed in a weakly acidic aqueous solution of an ammonium salt of an anionic polymer electrolyte so as to form discontinuous microparticles; emulsifying or dispersing the microparticles, and (b) forming a synthetic resin wall film around the microparticles by applying an in-situ polymerization method or an interfacial polymerization method to create an aqueous suspension of microcapsules with a hydrophobic substance as a core material. (c) removing most of the water from the aqueous suspension to form microcapsules containing a hydrophobic substance as a core substance in a solid or powder form; (d) placing the suspension in an organic solvent vehicle. By adding the solid or powdered microcapsules described above, a microcapsule suspension monodispersed in an organic solvent vehicle was obtained. In particular, ammonium salts of anionic polyelectrolytes are used when emulsifying or dispersing hydrophobic substances into discontinuous microparticles to prepare aqueous suspensions of microcapsules containing hydrophobic substances as core substances. By using this, the object of the present invention was achieved. More specifically, in the already exemplified known method for producing synthetic resin wall microcapsules, when emulsifying or dispersing a hydrophobic substance to form discontinuous microparticles, an alkali metal salt of an anionic polymer electrolyte is used. (for example, salts of sodium, potassium, lithium, etc.), but when an alkali metal salt of the electrolyte is used, the solid or powdered microcapsules prepared by the above method are On the other hand, when an ammonium salt of the electrolyte is used, the solid state prepared by the above method cannot be achieved because it is not monodispersed and forms aggregates in a solvent-based vehicle. The microcapsules in powder form were monodispersed in an organic solvent vehicle, and the object of the present invention was achieved. Examples of the ammonium salt of the anionic polymer electrolyte used in the present invention include ethylene-maleic anhydride copolymer, butadiene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, and propylene-maleic anhydride copolymer. Polymer, styrene-maleic anhydride copolymer, methyl vinyl ether
Groups such as maleic anhydride copolymer, polystyrene sulfonic acid, styrene sulfonic acid-methacrylic acid copolymer, isobutylene-maleic anhydride-polymethyl acrylate copolymer, polyacrylic acid, acrylic acid-acrylamide copolymer, etc. An ammonium salt of at least one anionic polymer electrolyte selected from the following. Among the ammonium salts of the anionic polymer electrolyte, particularly preferred are ammonium salts of maleic anhydride-containing copolymers such as styrene-maleic anhydride copolymers and ethylene-maleic anhydride copolymers. The key point of the present invention is that microcapsules are prepared using ammonium salts of anionic polymer electrolytes as emulsifiers or dispersants for hydrophobic substances instead of alkali metal salts, and this does not apply to any of the above-mentioned conventional techniques. There is nothing to do, and the method for producing microcapsule organic solvent suspension according to the present invention is a completely new technology that does not exist in the prior art. More specifically, the ammonium cation of the ammonium salt of the anionic polymer electrolyte used in the present invention is added to make the electrolyte a weakly acidic solution,
Particularly preferably, the ammonium cation is added to make the pH weakly acidic from 3.5 to 6.5, and although ammonium carbonate may be used as the ammonium cation, it is particularly preferable to use ammonium hydroxide. Furthermore, the substance forming the wall of the synthetic resin wall microcapsule used in the present invention is preferably an amino resin-based synthetic resin, and is composed of one or more amino compounds selected from melamine, guanamine, urea, and derivatives thereof and an organic aldehyde compound. Synthetic resins selected from the group consisting of polycondensation resins with one or more of the following, polyureas, and polyurethanes are recommended. The organic aldehyde compound is particularly preferably formaldehyde, but may also be acetaldehyde, and the present invention is not limited thereto. Further, as a method for forming a synthetic resin wall film, a conventionally known in-situ polymerization method or interfacial polymerization method is applied to form a wall film made of the above-mentioned synthetic resin. Furthermore, in the present invention, in order to remove most of the moisture from the aqueous suspension of microcapsules containing a hydrophobic substance as a core material, hot air drying, spray drying, flash drying, continuous fluidized bed drying, and infrared rays can be used. There are drying methods, high-frequency heating methods, freeze-drying methods, etc., and solid or powder microcapsules may be obtained by any method. Examples of the organic solvent vehicle used in the present invention include methyl alcohol, ethyl alcohol, n-
propyl alcohol, isopropyl alcohol,
Alcohols such as n-butyl alcohol are preferably used, and n-hexane,
Aliphatic hydrocarbons such as n-heptane,
Aromatic hydrocarbons such as toluene and xylene, glycol derivatives such as ethylene glycol monomethyl ether, esters such as ethyl acetate and isoamyl acetate, and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. It is often used by adding and mixing at least one kind selected from the group such as the following, but in some cases, it does not contain alcohol at all, and is used by selecting from a wide range of organic solvents. Of course, glycols such as ethylene glycol and high boiling point solvents may be added as necessary. Heat-molten wax and the like can also be considered as organic solvents, and fall under the category of organic solvent vehicles in the present invention. The main body of the vehicle used in the present invention has a boiling point of 120
It is preferable to use a low boiling point organic solvent such as the one mentioned above with a boiling point of about 80°C or less, and it is particularly preferable that alcohols with a boiling point of 80°C or less account for 50% (by weight) or more of the entire vehicle.
The present invention is not particularly limited to this. The hydrophobic substance used in the present invention may be liquid, solid, or gas at room temperature, as long as it can be emulsified or dispersed to form discontinuous fine particles, and as an application example, it is a color former or developer for forming a carbonless copying layer. Examples include microcapsules containing microcapsules, microcapsules containing adhesives, microcapsules containing fragrance, and the like.
More specifically, for example, in the case of forming a carbonless copying layer, a color former or developer is added to a high boiling point oily solvent such as an allylmethane solvent, an alkylnaphthalene solvent, an alkyl diphenyl solvent, a triphenyl solvent, or a chlorinated paraffin solvent. Examples include liquids in which agents are dissolved, but the present invention is not limited thereto. (E) Effect As mentioned above, when the ammonium salt of an anionic polymer electrolyte, which is the key point of the present invention, is used as an emulsifier or dispersant for hydrophobic substances, the resulting solid or powdered microcapsules can be No unwanted aggregation was observed during dispersion into a solvent vehicle, demonstrating a very effective effect on monodispersion. (F) Example As a typical example, a specific example will be described of a method for manufacturing a microcapsule suspension monodispersed in an organic solvent vehicle suitable for forming a carbonless copying layer. Suspensions can also be made in the same way and are not limited in any way. Note that "part" means "part by weight"
shall be shown. Example 1 As a hydrophobic substance, 5 parts of crystal violet lactone dissolved in 95 parts of KMC-113 (manufactured by Kureha Chemical Co., Ltd., high boiling point solvent for carbonless use) is used. A styrene-maleic anhydride copolymer with a molecular weight of approximately 100,000 is dissolved in water while adding 28% ammonium hydroxide to make a 5% aqueous solution with a pH of 4.5.
Emulsify 100 parts of a hydrophobic substance in 200 parts at 60°C. 10 parts melamine, 15 parts 37% formaldehyde, 70 parts water
Melamine-formalin initial condensate was prepared by heating and dissolving at pH 9, added to the emulsion, and heated at 60℃ for 1 hour.
The mixture was stirred at 80° C. for 2 hours to obtain an aqueous suspension containing microcapsules containing a coloring agent, which can be used for in-situ polymerization. The microcapsule aqueous suspension was spray-dried using a spray dryer to a water content of 2% or less to obtain capsule powder. When this was dispersed in an alcohol-based organic solvent vehicle consisting of ethyl alcohol/isopropyl alcohol/ethyl acetate = 60/20/20 (parts), the dispersion state of the microcapsules was observed using an optical microscope. It was monodispersed. Example 2 20 parts of paraphenylphenol-formaldehyde resin was added to Hysol SAS N-296 (Nisseki Chemical Industry Co., Ltd.).
A hydrophobic substance was obtained by heating and dissolving it in 80 parts of high boiling point solvent for carbonless (manufactured by Co., Ltd.). A developer-containing capsule powder was obtained in the same manner as in Example 1, dispersed in the vehicle, and the dispersibility of the microcapsules was observed under a microscope.
There were no aggregates. Example 3 After dissolving 5 parts of crystal violet lactone as a hydrophobic substance in 95 parts of Hysol SAS N-296, 10 parts of 1,6 as a polyvalent isocyanate were dissolved.
- A solution in which a trimolecular adduct of hexamethylene diisocyanate was added and dissolved was used. Ethylene-maleic anhydride copolymer in water, 28
% ammonium hydroxide aqueous solution to form a 5% aqueous solution with a pH of 5.0, and 100 parts of the hydrophobic substance is emulsified in 200 parts of this aqueous solution. After emulsification, add 100% of an aqueous solution containing 1 part of hexamethylene diamine.
When the reaction was carried out for 1 hour at a system temperature of 60°C, a polyurea resin was formed around the hydrophobic substance, and a microcapsule aqueous suspension containing a coloring agent was obtained by interfacial polymerization. Further, powder capsules were obtained in the same manner as in Example 1, and the dispersibility of the microcapsules in the above-mentioned organic solvent vehicle mainly composed of alcohol was observed under a microscope, and it was found that they were well monodispersed. Comparative Example 1 Same as Example 1 except that a styrene-maleic anhydride copolymer having a molecular weight of about 100,000 as an emulsifier was dissolved in water while adding a 10% aqueous sodium hydroxide solution to make a 5% aqueous solution with a pH of 4.5. Capsule powder containing a coloring agent was obtained in the same manner and dispersed in an alcoholic vehicle. When the dispersibility of the microcapsules was observed under a microscope, many aggregates of microcapsules were observed. Comparative Example 2 Same as Example 2 except that a styrene-maleic anhydride copolymer with a molecular weight of about 100,000 as an emulsifier was dissolved in water while adding 10% potassium hydroxide to make a 5% aqueous solution with a pH of 4.5. A developer capsule powder was obtained using the method described above, and when the dispersibility of the microcapsules in alcohol was observed under a microscope, it was found that they were not monodispersed. Comparative Example 3 A coloring agent was prepared in the same manner as in Example 3, except that the ethylene-maleic anhydride copolymer as an emulsifier was dissolved in water while adding 10% sodium hydroxide to form a 5% aqueous solution with a pH of 5.0. When the containing capsule powder was obtained and dispersed in an alcoholic vehicle and the dispersibility of the microcapsules was observed under a microscope, many aggregates were observed. The above results are summarized in Table-1.

[Table] cannot be obtained.
Next, an applied example based on the above example will be shown below. Example 4 30 parts of the powder of color former-containing microcapsules to be used for in-situ polymerization obtained as in Example 1 were mixed with 80 parts of ethyl alcohol, 10 parts of methanol, and toluene.
An alcoholic flexographic ink containing microcapsules was obtained by dispersing 30 parts of ethyl cellulose as an alcoholic binder dissolved in 10 parts of an alcoholic vehicle. This ink was partially coated onto a 40 g/m ² paper substrate using a flexo printing machine to obtain carbonless paper with a coating weight of 3.6 g/m ² . Example 5 30 parts of the powder of color former-containing microcapsules prepared by interfacial polymerization obtained as in Example 3 was dispersed in a vehicle of 50 parts of ethyl alcohol and 50 parts of isopropyl alcohol, and used as an alcoholic binder. Fifty parts of acrylic acid resin was dissolved to obtain an alcoholic flexo ink containing microcapsules. This ink
It was partially coated on a 40 g/m ² paper substrate using a flexo printing machine to obtain a carbonless paper with a coating weight of 4.2 g/m ² . Example 6 10 parts of a color former-containing microcapsule powder obtained as in Example 1 for in-situ polymerization and a developer-containing microcapsule powder for in-situ polymerization obtained as in Example 2. 30 parts of wheat starch and 5 parts of wheat starch were dispersed in a vehicle of 60 parts of ethyl alcohol, 30 parts of methyl alcohol, and 10 parts of isopropyl alcohol, and 30 parts of butyral resin was dissolved as an alcoholic binder to form the microcapsule-containing alcohol. A flexible flexographic ink was obtained. This ink was partially coated on a 40 g/m ² paper substrate using a flexo printing machine to obtain a self-coloring carbonless paper with a coating weight of 5.2 g/m ² . Comparative Example 4 A top paper was obtained in the same manner as in Example 4, except that the microcapsule powder obtained in Comparative Example 1 was used. Comparative Example 5 A top paper was obtained in the same manner as in Example 5, except that the microcapsule powder obtained in Comparative Example 3 was used. Comparative Example 6 A self-coloring carbonless paper was obtained in the same manner as in Example 6, except that the microcapsule powder obtained in Comparative Examples 1 and 2 was used. (Bottom paper) A commercially available carbonless color developing paper containing P-phenylphenol resin was used. The upper paper obtained in the Examples and Comparative Examples and the lower paper were combined, and the self-coloring carbonless paper obtained in the same manner was used as it was.
Color development performance and stain resistance were measured. The color development performance was determined by measuring the color density one hour after calendar color development at a pressure of 90 kg/cm. In addition, the stain resistance was tested using a color fastness tester (manufactured by Daiei Kagaku Seiki KK) by rubbing it back and forth 10 times with a load of 500g for 24 hours, and then using a color difference meter (manufactured by Nippon Denshoku) (ND).
-1010) (the higher the reflectance, the less dirt). Furthermore, for practical purposes, the roughness of the partially coated ink surface was also observed. The above results are summarized in Table-2.

[Table] (G) Effect of the invention As is clear from Table 1, Figures 1 and 2, the dispersibility of the microcapsules according to the present invention in an organic solvent vehicle is very good. However, alkali metal salts such as sodium salts and potassium salts of anionic polymer electrolytes did not have the desired effect, and only ammonium salts had a large effect. Furthermore, as is clear from Table 2, in the application examples of the present invention, in which ammonium salts of anionic polymer electrolytes were used, there was no capsule aggregation and no roughness on the partially coated surface. It shows that it has good coloring performance and little staining, indicating that it has excellent practical properties. As described above, the present inventors achieved the following by using ammonium salts of anionic polymer electrolytes.
We have succeeded in providing a method for producing practically excellent microcapsules that are well monodispersed in an organic solvent vehicle.

[Brief explanation of the drawing]

FIG. 1 shows the results of optical microscopic observation when the microcapsule powder of Example 1 of the present invention was dispersed in a vehicle mainly consisting of alcohol. Second
The figure shows the results of optical microscopic observation when the microcapsule powder of Comparative Example 1 was dispersed in a vehicle mainly consisting of alcohol. a indicates a microcapsule.

Claims (1)

[Scope of Claims] 1. A method for producing a microcapsule suspension in which a microcapsule suspension is monodispersed in an organic solvent vehicle, which includes: (a) dispersing a hydrophobic substance into a weakly acidic aqueous solution of an ammonium salt of an anionic polymer electrolyte in discontinuous microcapsules; emulsifying or dispersing it into particles; (b) forming a synthetic resin wall film around the microparticles by applying an in-situ polymerization method or an interfacial polymerization method, and using a hydrophobic substance as a core material; preparing an aqueous suspension of microcapsules, (c) removing most of the water from the aqueous suspension to form microcapsules having a hydrophobic substance as a core material, and (d) producing an organic microcapsule in the form of a solid or powder. A method for producing a monodisperse microcapsule suspension in an organic solvent vehicle, which comprises adding the solid or powder microcapsules described above into a solvent vehicle. 2. A method for producing a microcapsule suspension monodispersed in an organic solvent vehicle according to claim 1, wherein the anionic polymer electrolyte is a maleic anhydride-containing copolymer.