JPS61287442A - Thermally crumbled microcapsule and its preparation - Google Patents

Abstract

PURPOSE:To obtain the titled microcapsule having well-balanced holding characteristic and releasing characteristic of core material being useful for heat sensitive recording paper, etc., by forming cell wall film of the microcapsule with a thermally decomposable high molecular compd. having -N=N- bonds. CONSTITUTION:A compd. (a) having thermally decomposable -N=N- bonds and plural -NH2 or -NH- bonds in a molecule, such as azodicarbonamide, (b) aldehyde such as formaldehyde, and (c) amine such as melamine or initial condensation product with phenol, are polycondensed in a medium such as water to cover a hydrophobic core material. The aimed capsule having cell wall film formed of the thermally decomposable high molecular compd. obtd. by this method has superior characteristic for holding the core material together with rapidly crumbled characteristic by heating. Therefore, the capsule is applicable to the use in the field of heat sensitive recording paper, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to heat-decomposable microcapsules having a wall made of a heat-decomposable polymer compound and a method for producing the same.

[Prior Art] In recent years, there has been remarkable progress in microencapsulation technology, such as interfacial polymerization, 1n-situ polymerization, coacervation, submerged drying, melt dispersion cooling, submerged curing coating method,
Various encapsulation methods are known, such as air suspension method, spray granulation method, pan coating method, electrostatic coalescence method, and vacuum evaporation method.

These microcapsules can change the color, form, solubility, reactivity, durability, sensitivity to pressure, heat, light, etc. of the core substance they contain, so they can be used for various recording materials, display materials, adhesives, etc. Many applications are known in a wide range of fields such as cosmetics, pharmaceuticals, pesticides, fragrances, and artificial organs.

However, due to problems with the performance of the resulting capsules, the ones that have been put into practical use include pressure-sensitive recording paper that utilizes pressure-induced capsule destruction, prescale, pressure-sensitive adhesives, and fragrances that improve the durability of the core material. It is limited to the fields of thermo-indicating materials and liquid crystal capsules, etc., and pharmaceuticals, agricultural chemicals, etc. whose purpose is to release core substances by dissolving the capsule wall membrane.

Techniques are known in which microcapsules of the type that release the core substance when heated are applied to thermal recording paper, diazo thermal recording paper, flame retardants, etc., but most of these have not been put into practical use due to insufficient capsule performance. do not have.

For example, when applying capsules to heat-sensitive recording paper, the recording layer is formed by mixing and coating microcapsules containing an electron-donating color former and an electron-accepting color developer, and then the capsules are The electron-donating color former inside is released through the pores of the wall film and reacts with the electron-accepting color developer to form a recorded image. accompanied by some defects.

In other words, when the capsule wall membrane has a sufficient thickness, it can completely isolate the recording material, so unnecessary coloring (fogging) will not occur on the recording paper during manufacturing or storage, but Since the release of the core material due to the heat is suppressed, only an insufficient recorded image can be obtained.

Although it is possible to improve the release of the core substance upon heating by thinning the capsule wall membrane, unnecessary fogging often occurs during manufacturing and storage.

In thermal recording paper using conventional heat-emitting microcapsules, the generation of fog and the maintenance of color development are contradictory phenomena, so it is almost impossible to control them. Currently, paper is not available.

[Problem that the invention seeks to solve]

In view of the current situation, the present inventors conducted intensive research on microcapsules that have sufficient core material retention properties and release core materials extremely efficiently when heated, and found that a specific heat-degradable polymer The present inventors have discovered that microcapsules with such excellent properties can be obtained by using the microcapsules as a capsule wall material, and have achieved the present invention.

[Means for solving problems]

The present invention is a heat-collapsible microcapsule characterized by having a wall film formed of a polymer compound having a heat-decomposable -N=N- bond in its molecule, and a method for producing the same.

[Effect]

The polymer compound used as the wall material of the microcapsules of the present invention has thermally decomposable -N=
Because it has an N- bond, it normally has excellent core retention properties, but when the temperature rises above the decomposition temperature of the -N=N- bond, the main chain suddenly breaks, resulting in The retention of the core substance rapidly decreases.

The heat-decomposable polymer compounds that exhibit special functions in this way are those having a heat-decomposable -N=N- bond in the molecule as described above. Compounds having a small number (one thermally decomposable -N=N- bond and a plurality of -NHK or -NH- bonds) in the molecule, such as azudicarbonamide shown by formula (1), and fbl Polycondensates with aldehydes.

NH□-C-N=N-C-NH2 ■ fa) At least one thermally decomposable -N- in the molecule
A polycondensate of a compound having an N-bond and a plurality of -NH or -NH- bonds, fbl and other amines and/or phenols, and (Ql aldehydes).

(2) A polymer of a compound having at least one thermally decomposable -N=N- bond and a plurality of vinyl groups in the molecule, such as a compound represented by the following structural formula (II).

[Structural formula■]

CHs CH3CH2=CCH
3c7. C=CH2II I Coo-C-N=N-C-(10 CII RR (R=CH3, CzHs, C6H5)■ +a1 At least one thermally decomposable -N=N- bond and multiple vinyl groups in the molecule and (b) a copolymer of another vinyl compound.

As long as it is a polymer compound having a thermally decomposable -N=N- bond in its molecule, it can be used as the capsule wall material of the present invention. These are preferred in terms of the performance of the capsules produced, and the above compounds (1) and (2) are particularly preferred.

Among them, polycondensates of azodicarbonamide and aldehydes, especially (al azodicarbonamide and (
Capsules whose walls are made of a polycondensate of bl) other amines and/or phenols and fc) aldehydes have excellent retention of core substances, and contain formaldehyde as the aldehyde and melamine as the other amine. When used, capsules with particularly excellent balance between core material retention and wall disintegration properties can be obtained.

In addition, examples of other amines include urea, thiourea,
Alkylurea, ethylene urea, acetoguanamine, benzoguanamine, melamine, guanidine, dicyandiamide, biuret, cyanamide, etc., and phenols include, for example, phenol, cresol, xylenol, resorcinol, hydroquinone, pyrocatechol,
Examples of the aldehydes include formaldehyde, acetaldehyde, paraformaldehyde, hexamethylenetetramine, geltaraldehyde, glyoxal, and furfural.

In the present invention, the polycondensates of (1) and (4) are preferably applied in the form of an initial condensate and polymerized during encapsulation. Partially modified products can also be used. Further, when the aldehyde used is formaldehyde, it can also be applied as an alkylated product of methyl, ethyl, propyl, butyl, etc.

Examples of anionic modifiers include sulfamic acid, sulfanilic acid, glycolic acid, glycine, acidic sulfites,
Sulfonic acid phenol, taurine, etc., and examples of cationic modifiers include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dimethylaminoethanol, etc. Furthermore, examples of nonionic modifiers include ethylene glycol, diethylene glycol, and the like.

During encapsulation, it is necessary to heat under acidic conditions in order to promote polycondensation of the initial condensate, but in order to adjust and maintain the system acidic, for example, formic acid, acetic acid, citric acid,
So-called acid catalysts commonly used in the field of aminoaldehyde resin production, such as oxalic acid, valatoluenesulfonic acid, hydrochloric acid, and sulfuric acid, are used.

Examples of other vinyl compounds used in the compound (2) include ethylene, vinyl halides, vinylidene halides, vinyl acetate, styrene, isoprene, isobutylene, acrylic acid, methacrylic acid, acrylic esters, methacrylic esters, vinyl ethers, Acrylonitrile, vinylidene cyanide, acrylamide, methacrylamide, vinylpyridine, N-vinylcarbazole, methyl vinyl ketone, vinyl isocyanate, etc.
l Functional monomer, divinylbenzene, dicyclopentenyl acrylate, 1.3-butanediol diacrylate, diethylene glycol diacrylate, 1.3
-Bis(3'-acryloxyethoxy-2'-hydroxypropyl)-5,5-dimethylhydantoin, trimethylolpropane triacrylate, pentaerythritol triacrylate, and other polyfunctional supermers.

As a method for polymerizing the vinyl compound, all methods known in the art can be applied, and specific examples include polymerization using an electron beam or ultraviolet rays, and furthermore, polymerization using a radical initiator.

Examples of radical initiators include organic peroxides such as benzoyl peroxide, acetyl peroxide, t-butyl hydroperoxide, and t-phthyl-N-phenyl peroxycarbamate; Examples include compounds, disulfides such as tetramethylthiuram disulfide, and sulfinic acids such as p-1 to luenesulfinic acid.

Examples of photoinitiators used in polymerization using ultraviolet light include biacetyl, acetophenone, benzophenone, Michler's ketone, benzyl, benzoin, benzoyl isobutyl ether, benzyl dimethyl ketal, and the like.

In addition to the case where the heat-degradable polymer of the present invention is formed by polymerization of monomers as described above, a compound having at least one heat-decomposable -N=N- bond in the molecule can be used as a crosslinking agent. However, other crosslinked polymer compounds can also be used, and examples of the polymer compounds used here include anionic, nonionic, cationic, and amphoteric polymers.

The anionic polymer may be natural or synthetic, such as -COO-, -5o3-, -0P(
Specific examples include natural polymers such as gum arabic, carrageenan, sodium alginate, pectic acid, gum tragacanth, almond gum, and agar, carboxymethylcellulose, sulfated cellulose, sulfated methylcellulose, and carboxymethylcellulose. Semi-synthetic polymers such as methyl starch, phosphorylated starch, lignin sulfonic acid, maleic anhydride copolymers (including hydrodispersed ones),
Polymerization of acrylic acid, methacrylic acid or crotonic acid 12 Monolithic and copolymers, vinylbenzenesulfone tu or 2
- Acrylamide-2-methyl-propanesulfonic acid polymers and copolymers, partial amides or partial esters of such polymers and copolymers, carboxy-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, phosphoric acid-modified polyvinyl Examples include synthetic polymers such as alcohol.

More specifically, examples of maleic anhydride copolymers (including hydrolyzed ones) include methyl vinyl ether-maleic anhydride copolymers, ethyl-maleic anhydride copolymers, and vinyl acetate-maleic anhydride copolymers. Polymer, methacrylamide-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, and the like.

As the acrylic acid copolymer, methacrylic acid copolymer, or crotonic acid copolymer, methyl acrylate-
Acrylic acid copolymer (hereinafter "copolymer" is abbreviated),
Ethyl acrylate-acrylic acid, methyl acrylate-methacrylic acid, methyl methacrylate-acrylic acid, methyl methacrylate-methacrylic acid, methyl acrylate-acrylamide-acrylic acid, acrylonitrile-acrylic acid, acrylonitrile-methacrylic acid, hydroxyethyl acrylate -acrylic acid, hydroxyethylallylate methacrylic acid, vinyl acetate-acrylic acid, vinyl acetate-methacrylic acid, acrylamide-acrylic acid,
Examples include copolymers such as acrylamide-methacrylic acid, methacrylamide-acrylic acid, methacrylamide-methacrylic acid, and vinyl acetate-crotonic acid.

Examples of vinylbenzenesulfonic acid-based or 2-acrylamido-2-methyl-propanesulfonic acid-based copolymers include methyl acrylate-vinylbenzenesulfonic acid (or salt thereof) copolymer, vinyl acetate-vinylbenzenesulfonic acid copolymer, acrylamide-vinylbenzenesulfonic acid copolymer, acryloylmorpholine-vinylbenzenesulfonic acid copolymer, vinylpyrrolidone-vinylbenzenesulfonic acid copolymer, vinylpyrrolidone-2-
Examples include acrylamide-2-methyl-propanesulfonic acid copolymer.

The nonionic polymer may be either natural or synthetic (eg, one having -0A1 group).

Specific nonionic semi-synthetic polymers include hydroxyethylcellulose, methylcellulose, pullulan (an amorphous, easily water-soluble polymeric polysaccharide made from starch by microbial fermentation), soluble starch, oxidized starch, etc. can be mentioned.

Further, as a synthetic product, polyvinyl alcohol can be mentioned.

Examples of the cationic polymer include cation-modified polyvinyl alcohol, and examples of the amphoteric polymer include gelatin.

The heat-collapsible microcapsules of the present invention can be formed by applying various known techniques, among which 1n-s
The in-situ method and the interfacial polymerization method are preferred, and the in-situ method in which the film material is deposited on the surface of the core material from an aqueous medium is particularly preferred.

Specifically, (a) a compound having at least one thermally decomposable -N=N- bond and a plurality of -NH or -NH- bonds in the molecule, and (b) an initial condensate with an aldehyde. A method of polycondensing and coating a hydrophobic core substance is preferred, especially a compound having at least one thermally decomposable -N'=N- bond and a plurality of -NH2 or -NH- bonds in the la1 molecule. After containing an initial condensate of fbl, other amines and/or phenols, and (Q) aldehyde in water or a hydrophilic medium, the initial condensate is polycondensed to form a hydrophobic core substance. A method of coating is preferred.

In the encapsulation method of the present invention, when emulsifying the core substance in an aqueous medium, anionic, nonionic, cationic, or amphoteric polymer or low molecular weight emulsifiers are used as emulsifiers. As cationic and amphoteric polymers, the various polymers mentioned above are used, and as low-molecular emulsifiers, for example, sodium vinyl sulfonate,
Sodium benzenesulfonate, sodium benzenesulfinate, sodium p-toluenesulfonate, p-
Sodium toluenesulfinate, sodium p-vinylbenzenesulfonate, sodium p-1-amylbenzenesulfonate, sodium naphthalene-α-sulfonate, sodium naphthalene-β-sulfonate, sodium 2-methylnaphthalene-6-sulfonate, Sodium 2.6-dimethylnaphthalene-8-sulfonate, sodium 2.6-dimethylnaphthalene-3-sulfonate, sodium l-naphthol-4-sulfonate, benzene-m-
Sodium disulfonate, funnel oil, sodium diphenyl phosphate, sodium phenylphosphonate, di-n-
Sodium butyl phosphate, sodium diamyl phosphate, etc. are used.

The heat-collapsible microcapsules of the present invention can be applied to any field where thermal destruction of capsules provides an advantage, but in particular, it can be applied to microcapsules for thermal recording paper or diazo thermal recording paper, flame retardant capsules, etc. Demonstrates excellent performance.

For example, in microcapsules for thermal recording paper, electron-donating color formers, electron-accepting color developers, ligand compounds, metal compounds, organic bases, sensitizers, etc. are used as they are, or they are dissolved or melted in other substances. The resulting capsules are coated on a support together with other materials commonly used in thermosensitive recording paper, printed, etc. to form thermosensitive recording paper.

〔Example〕

The present invention will be described in more detail with reference to Examples below, but it is of course not limited thereto.

Further, unless otherwise specified, parts and % in the examples indicate parts by weight and % by weight, respectively.

Example 1 Preparation of microcapsules 8 parts of crystal violet lactone was heated and dissolved in 1 part of 2,6-diisopropyl naphtha (10 parts) to obtain an internal phase liquid.

Separately, in a stirring mixing vessel equipped with a heating device, add 4 (10 parts) of a 2% aqueous solution of a copolymer of acrylic acid and n-butyl acrylate in a molar ratio of 92:8, and to this add a 20% aqueous solution of caustic soda. was added to adjust the pH to 4.7 to prepare an aqueous medium for capsule production.

After heating this aqueous medium to 80° C., the above-mentioned heated internal phase liquid was added thereto with stirring, and emulsified and dispersed at 80° C. so that the average particle size was 5.0 μm.

Separately, 15 parts of azodicarbonamide (trade name: Unifoam AZ, manufactured by Daijin Chemical Co., Ltd.), 58 parts of a 37% formaldehyde aqueous solution, and 30 parts of water were added to a stirring mixing container equipped with a heating device, and the mixture was heated at 60°C. A 5% caustic soda aqueous solution was added while stirring to prepare a brown solution, and this solution was added to the above emulsion at 80°C.

The system was then held at 85°C for 30 minutes, and then at 60°C.
A capsule dispersion was obtained by holding the mixture under the same conditions for 10 hours.

Thermal Record No. A and Evaluation Surface P-hydroxybenzoic acid-benzyl ester 1 (10 parts, polyvinyl alcohol aqueous solution 3 parts (solid content) and water 3 (10 parts) were ground in a ball mill for 24 hours to obtain a dispersion. , the above capsule dispersion and 5 parts of carboxy-modified styrene-butadiene copolymer latex (solid content)
40g/n? A heat-sensitive recording paper was obtained by coating the base paper with an air knife coater so that the solid content was 6 g/-.

The resulting thermal recording paper has a whiteness of 84% (reflectance luminance liver E).
When the sample was brought into contact with a hot plate at 140° C. for 5 seconds, it showed good color development.

Example 2 An emulsion was prepared in the same manner as in Example 1.

Separately, Unifoa in a stirred mixing vessel equipped with a heating device.
m 20 parts of AZ and 110 parts of 37% formaldehyde aqueous solution
and 40 parts of water, and while stirring at 60°C, add 5% caustic soda aqueous solution to make a brown solution, then add 10 parts of melamine, and then add 5% caustic soda aqueous solution to make a brown transparent solution. A liquid was prepared.

Next, after adding this liquid to the above emulsion at 80°C,
This system was maintained at 85° C. for 5 hours to obtain a capsule dispersion.

Subsequently, a thermosensitive recording paper was prepared in the same manner as in Example 1 except that the capsule dispersion was used as the capsule, and it exhibited good color development with a whiteness of 87%.

Example 3 Microcapsules 20 parts of lauryl gallate were mixed with 8 parts of di-n-butyl adipate.
0 parts by heating, and 20 parts of an initial condensate containing hexamethoxyhexamethylol melamine as a main component (trade name Cynor 350, manufactured by Mitsui Toatsu Chemical Co., Ltd.) was added and mixed to obtain an internal phase liquid.

Separately, 10 parts of a 3% aqueous solution of ethylene-maleic anhydride copolymer (trade name EMA-31, manufactured by Monsando) was added to a stirring mixing vessel equipped with a heating device, and to this 20%
An aqueous caustic soda solution was added to adjust the pH to 4.8 to obtain an aqueous medium for capsule production. This aqueous medium was heated to 80°C.
After heating, the above-mentioned heated internal phase liquid was added thereto with stirring, and emulsified and dispersed at 80° C. so that the average particle size was 5.0 μm.

Next, an azodicarbonamide-formaldehyde initial condensate solution prepared in the same manner as in Example 1 was added to the above emulsion at 80°C, and the system was then maintained at 85°C for 5 hours to prepare a capsule dispersion. I got it.

Preparation and evaluation of thermal recording paper The above capsules were dispersed in a dispersion obtained by grinding ferric stearate 1 (10 parts, polyvinyl alcohol aqueous solution 3 parts (solid content) and water 3 (10 parts) in a ball mill for 24 hours. 40 g/n (
A thermosensitive recording paper was obtained by coating the base paper with an air knife coater so that the solid content was Log/nl.

The resulting thermal recording paper had a whiteness of 88% and was heated at 140°C.
When it was brought into contact with a hot plate for 5 seconds, it showed good color development.

〔effect〕

As is clear from the above examples, the heat-collapsible microcapsules of the present invention normally have excellent core substance retention properties, but because they have the property of rapidly disintegrating upon heating, It is a special microcapsule that can be applied to fields such as

Patent Applicant Kanzaki Paper Co., Ltd. Procedural Amendment June 12, 1985 Patent Application No. 129012 of 1985 2 Title of Invention Heat-disintegrating microcapsules and their manufacturing method 3 Relationship with the person making the amendment Patent Applicant 4, Agent residence (5-5, Kanzaki Paper Co., Ltd., 4-3-1 Jokoji, Amagasaki City, 660) Date of amendment order Voluntary 6, Subject of amendment ``Detailed Description of the Invention'' section of the specification 7 i Yuko = small 5i ki fall shi I mitsume = 24- (Contents of amendment) (1) "...copolymer" in the 7th line from the bottom of page 8 of the specification
7 from the bottom of the same page.
Insert the following text between line 6 and line 6.

"■ (al 4,4' represented by the following structural formula (I[[)
-At least one thermally decomposable -N=N-
bond and a compound having multiple -CO-Cβ bonds, (b
) Nylon compounds obtained by reaction with polyvalent amines.

[Structural formula■]

OCHI CH30 II l l IICj
2 CCH2CH2CN=N CCHz C1(z
CC7! I CN CN ■ fa) At least one thermally decomposable -N=N in the molecule
- bond and a compound having a plurality of 100-Ill bonds,
(b) other compounds having multiple -co-cx bonds;
(C) A nylon compound obtained by reaction with polyvalent amines.

(al) At least one thermally decomposable -N=N- bond in the molecule, such as 4,4'-azobis(4-cyano-n-amyl alcohol) shown by the following structural formula (IV), etc. A urethane compound obtained by reacting a compound having multiple hydroxyl groups with a (bl polyvalent isocyanate compound).

[Structural formula■]

C113CI+3 110-(Cl12) 3 CN = N C(CI
□), -OHCN CN ■ +a) At least one thermally decomposable -N- in the molecule
A compound having an N-bond and multiple hydroxyl groups, and (
b) A urethane compound obtained by reacting another polyvalent hydroxy compound with (C) a polyvalent isocyanate compound.

(a) At least one thermal decomposition compound in the molecule, such as an addition compound of 4,4'-azobis(4-cyano-n-amyl alcohol) and toluylene diisocyanate shown by the following structural formula (V). A urethane or urea compound obtained by the reaction of a compound having a -N=N- bond and a plurality of isocyanate groups with (b) a compound having two or more of at least one of an amino group and a hydroxyl group in the molecule. .

[Structural formula■]

[Phase] f8) At least one thermally decomposable - in the molecule
Urethane obtained by reacting a compound having an N=N- bond and a plurality of isocyanate groups, a polyvalent isocyanate compound such as FBL, and a compound having two or more of at least one of a tel amino group and a hydroxyl group in the molecule Or urea compound.

0(a) At least one thermally decomposable -N=N- bond and multiple A urea compound or a nylon compound obtained by the reaction of a compound having an amino group with a (bl polyvalent isocyanate compound or a compound having a plurality of -C○-Cjl! bonds in the molecule = 2-).

[Structural formula■]

C) 13CH3 @(a) At least one thermally decomposable -N=N in the molecule
- A urea compound obtained by reacting a compound having a bond and a plurality of amino groups, fbl and other polyvalent amines, and (0) a polyvalent isocyanate compound or a compound having a plurality of -C0-Cβ bonds in the molecule. or nylon compound” (or more) = 3-

Claims (11)

[Claims] (1) A heat-collapsible microcapsule characterized by having a wall film formed of a polymer compound having a heat-decomposable -N=N- bond in the molecule. (2) The polymer compound is composed of (a) a compound having at least one thermally decomposable -N=N- bond and a plurality of -NH_2 or -NH- bonds in the molecule, and (b) an aldehyde. The microcapsule according to claim (1), which is a condensate. (3) The polymer compound includes (a) a compound having at least one thermally decomposable -N=N- bond and a plurality of -NH_2 or -NH- bonds in the molecule, (b) other amines and The microcapsule according to claim (1), which is a polycondensate of/or a phenol and (c) an aldehyde. (4) At least one thermally decomposable -N=N- in the molecule
Claim 2, wherein the compound having a bond and a plurality of -NH_2 or -NH- bonds is azodicarbonamide.
) or (3). (5) The microcapsules according to claims (2) to (4), wherein the aldehyde is formaldehyde. (6) The other amine is melamine (
3) Microcapsules described in section 3). (7) (a) At least one thermally decomposable -N in the molecule
After containing an initial condensate of a compound having an =N-bond and a plurality of -NH_2 or -NH- bonds and (b) aldehydes in water or a hydrophilic medium, the initial condensate is polycondensed. 1. A method for producing heat-collapsible microcapsules, which comprises coating a hydrophobic core substance with a hydrophobic core substance. (8) (a) At least one thermally decomposable -N in the molecule
= An initial condensate of a compound having an N-bond and a plurality of -NH_2 or -NH- bonds, (b) other amines and/or phenols, and (c) aldehydes in water or a hydrophilic medium. 1. A method for producing heat-collapsible microcapsules, comprising the steps of: coating a hydrophobic core material by polycondensing the initial condensate. (9) At least one thermally decomposable -N=N- in the molecule
Claim No. 7, wherein the compound having a bond and a plurality of -NH_2 or -NH- bonds is azodicarbonamide.
) or the manufacturing method described in item 8. (10) The manufacturing method according to claims (7) to (9), wherein the aldehyde is formaldehyde. (11) The manufacturing method according to claim (8), wherein the other amine is melamine.