JPS6115734A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To prepare a microcapsule excellent in solvent resistance, by emulsifying and dispersing a hydrophobic liquid containing specific polyvalent isocyanate in a hydrophilic liquid and forming a synthetic polymer film at the interfaces of formed liquid droplets to coat the surfaces thereof. CONSTITUTION:A hydrophobic liquid containing a polyvalent isocyanate compound represented by formula (wherein Z is -CH2CH2-, -CH2CH2CH2- and -CHCH3CH2-) is emulsified and dispersed in a hydrophilic liquid. Subsequently, a synthetic polymer film is formed at the interfaces of liquid droplets and coats the surfaces of said liquid droplets to prepare a microcapsule. As the aforementioned polyvalent isocyanate compound, there is ethyl 2,6-dissocyanatocaproate-beta-isocyanate and the addition amount thereof is effective in a range of 0.02-60pts.wt. per 100pts.wt. of the hydrophobic liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing microcapsules containing a hydrophobic core material, and in particular, the present invention relates to a method for producing microcapsules containing a hydrophobic core substance, and in particular has a synthetic polymer membrane formed by a reaction between a polyvalent isocyanate and a compound having active hydrogen, and is suitable for pressure-sensitive copying paper. The present invention relates to a method for producing microcapsules that exhibit extremely excellent properties when used for.

Various methods are known for producing microcapsules, such as coacervation, interfacial polymerization, and 1n-situ polymerization, but the encapsulation method of the present invention relates to interfacial polymerization.

Interfacial polymerization is an encapsulation method that produces synthetic polymer films such as polyamide, polyurea, and polyurethane at the interface between a hydrophobic liquid and a hydrophilic liquid.
Publication No. 771 describes a method for obtaining capsules having a polyurea film by reacting polyvalent isocyanate with water or amines.

Capsules formed using polyvalent isocyanate have relatively dense capsule membranes and are stable against heat and moisture compared to gelatin capsules formed by conventional coacervation methods. However, if it is stored in an atmosphere containing an organic solvent, the oil droplets inside the capsule may be extracted.

Therefore, in order to further strengthen the capsule wall membrane, polyvalent amines are used in combination with the reaction between polyvalent isocyanate and water (Japanese Patent Publication Nos. 42-771, 48-49509, and 58-389'8). Methods of adding a reactive third substance (e.g., Japanese Patent Application Laid-open No. 49-37710) have been proposed, but these methods involve new drawbacks as the capsule wall membrane is improved. However, satisfactory results have not always been obtained.

That is, in order to strengthen the capsule wall film by using a polyvalent amine in combination, a large excess of polyvalent amine is required, but in general, amines have a desensitizing effect that reduces the color developing ability of the color developer. In particular, polyvalent amines with large molecular weights, which are effective for strengthening capsule wall membranes, have a large desensitizing effect. Therefore, when the obtained capsules are used in pressure-sensitive copying paper, the initial color density is significantly reduced. In addition, the reactive third substance makes it even more difficult to control the particle size of isocyanate-based capsules. becomes.

In view of the current situation, the present inventors conducted intensive research to obtain microcapsules with excellent solvent resistance without sacrificing the advantages of polyvalent isocyanate compounds. It has been discovered that capsules with excellent properties can be obtained without any drawbacks, and the present invention has been achieved.

The present invention emulsifies and disperses a hydrophobic liquid containing a polyvalent isocyanate in a hydrophilic liquid, and then generates a synthetic polymer film at the droplet interface to produce microcapsules that envelop the droplet surface. The method for producing microcapsules is characterized in that the polyvalent isocyanate compound is a compound represented by the following general formula (1).

(Z: -CH, +CHz-, -Cl12CHgCH
z-, -CICI3CH2-) The specific trifunctional isocyanate compound used in the present invention includes: ・2,6-ditucyanatecaproic acid-β-isocyanate ethyl ester ・2,6-ditucyanatecaproic acid -T-Isocyanate propyl ester/2-methyl 2,6-ditucyanate caproate-
Examples include β-isocyanate ethyl ester.

These compounds are generally produced by phosgenating an ester of lysine and aminoal 5-alcohol, and a detailed production method is described, for example, in JP-A-56-30426.

In the method of the present invention, by using such a specific trifunctional isocyanate compound as a capsule wall material,
The purpose is to obtain capsules with excellent solvent resistance that cannot be obtained with conventionally known isocyanate compounds.According to the study results of the present inventors, it is possible to obtain capsules with excellent solvent resistance that cannot be obtained with conventionally known isocyanate compounds. Alternatively, it has been revealed that when at least one type of aromatic polyvalent isocyanate compound is used in combination, capsules with an extremely well-balanced quality can be obtained, with excellent not only solvent resistance but also heat resistance, moisture resistance, light resistance, etc. .

Therefore, the capsules obtained by the method of the present invention are extremely suitable as microcapsules for pressure-sensitive copying paper, which particularly requires strict quality settings.

In the present invention, examples of the polyvalent isocyanate used in combination with the above specific trifunctional isocyanate compound include m-
phenylene diisocyanate, p-phenylene diisocyanate, 2.6-tolylene diisocyanate, 2.
4-) Lylene diisocyanate, naphthalene-1,4-
Diisocyanate, diphenylmethane-4,4°-diisocyanate, 3.3″-dimethoxy-4,4°-
biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,
3-diisocyanate, 4,4°-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,
2-diisocyanate, butylene-1,2-diisocyanate, ethyridine diisocyanate, cyclohexylene-1,2-diisocyanate, cyclohexylene-1
, 4-diisocyanate, isophorone diisocyanate, p-phinyl diisothiocyanate, xylylene-
1,4-diisothiocyanate, Otte lysine diisothiocyanate, dimethylsilyl diisocyanate, vinylmethylsilyl isocyanate, 4-isocyanatemethyl-1,8-octamethylene diisocyanate, lysine diisocyanate, bis(isocyanatemethyl)cyclohexane, dicyclohexylmethane diisocyanate, Diisocyanate or diisothiocyanate such as trimethylhexamethylene diisocyanate, 4°4',4
"-triphenylmethane triisocyanate, toluene-2', 4,6-triisocyanate, tris (isocyanate phenyl) thiophosphate, methylsilyl triisocyanate, vinylsilyl triisocyanate,
Triisocyanates such as phenyldylyl triisocyanate, octadecylsilyl triisocyanate, methoxysilane triisocyanate, butoxysilane triisocyanate, octylsilane triisocyanate, hexamethylene diisocyanate trimer, polymethylene polyphenyl isocyanate, 4.4''-dimethyldiphenylmethane -2,2°.

5.5'-tetraisocyanate, tetraisocyanate silane, biuresotho-type polyisocyanate containing residues derived from hexamethylene diisocyanate and isophorone diisocyanate (JP-A-51-95259)
polyvalent isocyanates such as those described above), and those obtained by adding these polyvalent isocyanates to compounds having hydrophilic groups such as polyvalent amines, polyvalent carboxylic acids, polyvalent thiols, polyvalent hydroxy compounds, and epoxy compounds, etc. can be mentioned.

The ratio of the specific trifunctional isocyanate compound used in the present invention and these aliphatic or aromatic polyvalent isocyanate compounds depends on the trifunctional isocyanate compound used and the polyvalent isocyanate compound used in combination. It can be adjusted as appropriate depending on the type of compound and the performance of the intended capsule, and is not particularly limited, but in general, the above-mentioned specific trifunctional isocyanate compound 1
The amount is adjusted within a range of 1 to 10,000 parts by weight, more preferably 10 to 1,000 parts by weight.

Examples of hydrophobic liquids include cottonseed oil, hydrogenated terphenyl, hydrogenated terphenyl derivatives, alkyl biphenyl,
Natural or synthetic oils such as alkylnaphthalene, diallylalkane, kerosene, paraffin, naphthenic oil, and dibasic acid esters such as phthalic acid esters can be used alone or in combination.

The amount of the isocyanate compound added to the hydrophobic liquid is from 0.02 to 100 parts by weight of the hydrophobic liquid.
A range of 60 parts by weight is effective, preferably 0.03 parts by weight.
The amount is adjusted within a range of about 40 parts by weight.

Note that a polyvalent amine may be added to the hydrophilic liquid depending on the desired capsule quality. Any polyvalent amine that has two or more NH groups or NH groups in its molecule and can be dissolved or dispersed in the hydrophilic liquid forming the continuous phase can be used as the polyvalent amine. Specific substances include diethylenetriamine, triethylenetetramine, 1.3-
Aliphatic polyvalent amines such as propylene diamine, hexamethylene diamine, etc.; Ebokey 10 = 2 compound adducts of aliphatic polyvalent amines; Alicyclic polyvalent amines such as piperazine; 3,9-bisulfaminopropyl-2, 4゜8.10-
Examples include heterocyclic diamines such as tetraoxaspiro (5,5) undecane.

At least one of these polyvalent amines is added to the hydrophilic liquid, and the amount added is appropriately determined depending on the type and amount of the polyvalent isocyanate used, as well as the desired capsule crotch hardness. Ru. Preferably, the amount is adjusted within the range of 0.1 to 200 parts by weight, more preferably 1 to 100 parts by weight, based on 100 parts by weight of the polyvalent isocyanate.

In order to emulsify and disperse a hydrophobic liquid, the hydrophilic liquid used is water or an aqueous solution of an emulsion stabilizer used in conventional capsule manufacturing systems.

Examples of such emulsion stabilizers include polyvinyl alcohol, anion-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, gelatin, gum arabic, carboxymethylcellulose, polyacrylamide, hydroxyethylcellulose, methylcellulose, ethylcellulose, cellulose acetobutyrate, hydroxymethylcellulose, polyvinylpyrrolidone, Montmorillonite, lignin sulfonic acid, polystyrene sulfonic acid and its copolymers, maleic anhydride copolymer hydrolyzate, polyacrylic acid and its copolymers, polymethacrylic acid and its copolymers, boacrylamidomethylpropanesulfonic acid and copolymers thereof, and salts thereof, and these emulsion stabilizers may be used alone or in combination.

The microcapsules produced by the method of the present invention have better resistance to solvents than conventional microcapsules, so they can be used in various pharmaceuticals, fragrances, dyes, pesticides, adhesives, liquid crystals, foods, solvents, and It is suitable for encapsulating rust agents, etc., and is particularly useful for applications such as printing ink and pressure-sensitive copying paper.

Examples of the present invention will be specifically described below regarding the production of microcapsules for pressure-sensitive copying paper, but the invention is of course not limited to these examples. Note that parts and percentages in the examples indicate parts by weight and percentages by weight, respectively, unless otherwise specified.

Example 1 2.8 parts of crystal violet lactone and 0.7 parts of benzoyl leucomethylene blue, which are coloring agents, were dissolved in 100 parts of polyisopropyl naphthalene (trade name -1), manufactured by Ou Kagaku Co., Ltd., and then a wall film was prepared. As a material, 10 parts of 2,6-dicyanate cabroic acid-β-isocyanate ethyl ester was melted.

The obtained oily liquid is mixed with polyvinyl alcohol (trade name: PVA).
-217, manufactured by Kuraray Co., Ltd.) and emulsified using a homomixer. Next, 1.5 parts of diethylenetriamine was added and the mixture was reacted at 80° C. for 3 hours, and then the temperature was lowered to room temperature to complete the encapsulation.

A capsule coating solution was prepared by adding 20 parts of cellulose powder and 50 parts of a 20% oxidized starch aqueous solution to the capsule dispersion obtained in this way, and coated on a base paper of 40 g/cd so that the dry coating amount was 4 g'/n ( A top sheet for pressure-sensitive copying paper was prepared by coating and drying.

Example 2 2,6-ditucyanate caproic acid-β as wall film material
-2,6 instead of 10 parts of isocyanate ethyl ester
- For pressure-sensitive copying paper in the same manner as in Example 1 except that 5 parts of -dicyanate caproic acid - γ-isocyanate propyl ester and 5 parts of polymethylene polyphenylisocyanate (trade name Millionate MR400, manufactured by Nippon Polyurethane Co., Ltd.) were used. The top paper was created.

Example 3 2,6-ditucyanate caproic acid-β as wall film material
-2,6 instead of 10 parts of isocyanate ethyl ester
-1 part of diycyanate caproic acid-2-methyl-β-isocyanate ester, 5 parts of polymethylene polyphenylisocyanate (trade name: Millionate MR400, manufactured by Nippon Polyurethane Co., Ltd.), a trimer of hexamethylene diisocyanate having a biuret group ( 2 parts of methylsilyl triisocyanate (trade name: Coronate N2 manufactured by Nippon Polyurethane Co., Ltd.) and 2 parts of methylsilyl triisocyanate (trade name: Orgatysox Sl 31)
0. A top sheet for pressure-sensitive copying paper was prepared in the same manner as in Example I, except that 2 parts (manufactured by Matsumoto Pharmaceutical Co., Ltd.) were used.

Comparative Example 1 2.6-dicyanate caproic acid-β as wall film material
-Pressure-sensitive material was prepared in the same manner as in Example 1 except that 10 parts of polymethylene polyphenylisocyanate (trade name: Millione-1-MR40O, manufactured by Nippon Polyurethane Co., Ltd.) was used instead of 10 parts of isocyanate ethyl ester. I made a leaflet for M photo paper.

Comparative Example 2 2,6-dicyanate caproic acid-β as wall film material
- Instead of 10 parts of isocyanate cordyl ester, 5 parts of polymethylene polyphenylisocyanate (trade name: Millionate MR400, manufactured by Nippon Polyurethane Co., Ltd.), an adduct of hexamethylene diisocyanate and a polyhydroxy compound (trade name: DC-2738.E1, manufactured by Honpolyurethane Co., Ltd.) ) 4 parts and isocyanate ring-containing isoborone diisocyanate (trade name I PD'1-Tl 890.
A top sheet for pressure-sensitive copying paper was prepared in the same manner as in Example 1, except that 1 part (manufactured by Hüls) was used.

Separately, 65 parts of aluminum hydroxide, 20 parts of zinc oxide, 3.
Mixture of zinc 5-di(α-methylbenzyl)salicylate and α-methylstyrene/styrene copolymer (melt ratio 8
0/20) 15 parts, polyvinyl alcohol aqueous solution 5 parts (
A coloring agent coating liquid prepared by adding 20 parts (solid content) of carboxy-modified styrene-butadiene copolymer latex to a dispersion obtained by pulverizing 300 parts (solid content) and water in a ball mill for 24 hours was mixed at 40 g/nl. The composition was coated on base paper at a dry weight of 5 g/a and dried to prepare a lower sheet for pressure-sensitive copying paper.

Using the five types of top paper and bottom paper thus obtained, a performance comparison test was conducted in the manner described below, and the results are listed in Table 1.

(1) Layer organic solvent-resistant top paper and bottom paper so that the coated surfaces face each other, apply a load of 100 kg/c- to form a colored image, and measure the color density using a Macbeth color density needle ( Red Fi
lter). The color density at this time is assumed to be Co.

Next, the top paper is left in a saturated atmosphere of trichlorethylene at room temperature for 48 hours, and then similarly opposed to the bottom paper to form a colored image, and the color density at that time is defined as Cs.

Organic solvent resistance was determined according to the following formula.

(Number close to 100, good resistance to organic solvents) (TI) After irradiating the coated surface of the light-resistant top paper with ultraviolet rays for 2 hours, place it facing the bottom paper and apply a load of 100 kg/cJ to develop a colored image. is formed, and the color density is determined using the Macheth color density needle (Red
Filter). The color density at this time is defined as CL.

The color density Co of the blank was measured in the same manner as in (1) Organic solvent resistance.

Light resistance was defined as follows.

=17- (The closer the value is to 100, the better the light resistance) (m) Heat-resistant upper paper and lower paper are stacked so that the coated surfaces are facing each other, and heated at 120°C under a load of 5 kg/cJ. Macb
It was measured with an eth color density needle (Red Filter).

(The smaller the number, the better the heat resistance) Table 1

Claims (1)

[Claims] (1) After emulsifying and dispersing a hydrophobic liquid containing a polyvalent isocyanate in a hydrophilic liquid, a synthetic polymer film is generated at the droplet interface to cover the droplet surface. A method for producing microcapsules, characterized in that the polyvalent isocyanate compound is a compound represented by the following general formula [I]. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [I] [Z: -CH_2CH_2-, -CH_2CH_2CH
_2-, -CHCH_3CH_2-] (2) Claim No. 2, characterized in that at least one of an aliphatic polyvalent isocyanate compound and/or an aromatic polyvalent isocyanate compound is further used as the polyvalent isocyanate compound ( The manufacturing method described in section 1). (3) The production method according to claim (1) or (2), characterized in that an amine compound is present in the reaction system. (4) Claim (3), wherein the amine compound is at least one selected from aliphatic polyvalent amines, epoxy adducts of aliphatic polyvalent amines, alicyclic polyvalent amines, and heterocyclic diamines. manufacturing method.