JPS5840142A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To obtain a capsule excellent in rub stain resistance, by forming a synthetic high-molecular membrane from an emulsion consisting of a vinylbenzenesulfonate type polymer and a hydrophobic liquid. CONSTITUTION:A vinylbenzenesulfonate type polymer containing polyvinylbenzenesulfonic acid or vinylbenzenesulfonic acid as one component is dissolved in an encapsulating hydrophilic medium in an amount of 0.1-20wt%. In the resulting solution, a hydrophobic liquid containing a polyisocyanate such as m-or p-phenylene diisocyanate is compounded to be emusified and dispersed therein by using a homomixer. By reacting the resulting mixture, a synthetic high-molecular membrane is formed at the interface of a liquid droplet to encapsulate the surface of the liquid droplet.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing microcapsules containing a hydrophobic core substance, particularly for use in pressure-sensitive copying paper having a polyurea wall film that is resistant to stains and has excellent solvent resistance. The present invention relates to a method by which microcapsules can be manufactured extremely easily.

Known methods for producing microcapsules include the complex coacervage S/g method, the non-poly coacervation method, the interfacial polymerization method, and the 1n-siiu polymerization method.

In the coacervation method, gelatin-gum arabic threads, which are natural polymers, are most commonly used as the wall membrane material for the microcuff cells.However, recently, isocyanate and water, isocyanate and polyamine, and isocyanate and polyamine have been used. , liol, isothiocyanate and water, isothiocyanate and polyamine, isothiocyanate polyol, epoxy compound, urea-formalin resin,
Microcapsules produced by interfacial polymerization and 1n-sisu polymerization using synthetic polymers such as acid chlorides and amines are attracting attention.

The reason why microcapsules made of these synthetic polymer films have attracted attention as a material for use in pressure-sensitive copying paper is that they can be prepared into highly concentrated paints compared to microcapsules made of natural polymer films. This makes it possible to coat the paper and increase the productivity of pressure-sensitive copying paper.Since the wall of the microcapsules is relatively dense, there is less natural exudation of the oil droplets contained therein. It has advantages such as being suitable for so-called stand-alone pressure-sensitive copying paper that is laminated or mixed with microcapsules, being easy to manufacture microcapsules, being inexpensive, and having excellent water resistance. This is because it has.

However, on the other hand, among microcapsules made of synthetic polymer membranes, especially those using isocyanate compounds, when stored in an atmosphere containing organic solvents, oil droplets inside the capsules are extracted and the coloring agent There is a problem with solvent resistance, which can transfer to the layer and cause undesired color development, and even when subjected to unwanted friction other than writing or typewriter pressure, the capsules are easily destroyed and color stains occur. There is a drawback.

In view of the current situation, the present inventors have conducted intensive research on a method for obtaining capsules that have excellent scratch resistance and solvent resistance without impairing the advantages of capsule wall membranes made from polyvalent isocyanate compounds as starting materials. As a result, it was discovered that a capsule wall film in which a polyvalent isocyanate compound is reacted in the presence of a vinylbenzenesulfonic acid-based polymer can be obtained, and the present invention has been achieved.

The present invention is characterized in that a hydrophobic liquid containing a polyvalent isocyanate is emulsified and dispersed in a hydrophilic liquid in which a vinylbenzenesulfonic acid polymer is dissolved, and a synthetic polymer wall film is generated at the droplet interface. This is a method for producing microcapsules.

The vinylbenzenesulfonic acid polymer used in the present invention includes polyvinylbenzenesulfonic acid and a copolymer containing vinylbenzenesulfonic acid as a component. Specific examples include the following polymers.

・Polyvinylbenzenesulfonic acid ・Acrylic acid-vinylbenzenesulfonic acid copolymer ・Methyl acrylate − ・Vinylsulfonic acid − ・Styrene − ・Vinyl acetate − ・Acrylamide − ・Vinylpyrrolidone − Vinylbenzenesulfonic acid copolymer When polymerized, acrylonitrile, acrolein II, acroylmorpholine, etc. Among these, polyvinylbenzenesulfonic acid is particularly preferred because it is excellent in achieving the desired effects of the present invention. These homopolymers and copolymers having sulfonic acid groups are produced by various known methods.

The molecular weight of these polymers used in the present invention is not necessarily limited, but is preferably in the range of 5,000 to 2,000,000 in view of the emulsifying ability of the hydrophobic core substance.

In the present invention, the sulfonic acid group in the vinylbenzenesulfonic acid polymer may be a free acid or a part or all of it may form a salt as long as the polymer is soluble in a hydrophilic liquid. Preferred examples of the salt include sodium salt, potassium salt, lithium salt, ammonia salt, and um salt.

In the present invention, such a vinylbenzenesulfonic acid-based polymer is dissolved in a hydrophilic medium for capsule production, but considering the ease of capsule preparation and the quality of the obtained capsules, the vinylbenzenesulfonic acid polymer is dissolved in a hydrophilic medium of 0.1 weight. , more than percent”
, more preferably 1% by weight or more. The upper limit of the content is generally adjusted depending on the viscosity of the thread, the capsule preparation device used, etc., but it is preferably kept at 20% by weight or less.

In addition, the capsule manufacturing system may contain conventional protective colloids such as polyvinyl alcohol, carboxy-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, gelatin, gum arabic, carboxymethylcellulose, maleic anhydride copolymer, or funnel oil, polyvinyl alcohol, etc. Surfactants such as oxyethylene alkyl ether and sorbitan fatty acid ester can be used in combination, but the amount used must be within a range that does not impede the original effects of the present invention.

In the present invention, examples of the polyvalent isocyanate used to cover the surface of the hydrophobic core material include m-phenylene diisocyanate and p-phenylene diisocyanate.
, 2.6-) lylene diisocyanate, 2.4-) lylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4,4/-diisocyanate, 3.3'-dimethoxy-4,47-biphenyl diisocyanate ), 3.3'-dimethyldiphenylmethane-
4゜4L cyanoisocyanate, xylylene-1,4-
Diisocyanate, xylylene-1,3-diisocyanate), 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, ethyridine Diisocyanates such as diisocyanate, cyclohexynon-1,2-diisocyanate, cyclohexyleph=1.4-') isocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethyridine diisothiocyanate, etc. or diisothiocyanate), '4.4', 4'-) triisocyanate such as triphenylmethane triisocyanate, polymethylene polyphenylisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5 '-Tetraisocyanate 7-) (7) Polyvalent incyanate monomers and these polyvalent isocyanates are combined with polyvalent amines,
Examples include those added to a compound having a hydrophilic group such as a polyvalent carboxylic acid, a polyvalent thiol, a polyvalent hydroxy compound, and an epoxy compound.

Further, a polyvalent amine may be further added to the hydrophilic medium depending on the desired capsule quality. Any polyvalent amine can be used as long as it has two or more NH groups or NH2 groups in its molecule and can be dissolved or dispersed in the hydrophilic liquid forming the continuous phase.

Specific substances include aliphatic polyvalent amines such as diethylene 11-amine, triethylenetetramine, 1,3-propylene diamine, hexamethylene diamine, etc.; epoxy compound adducts of aliphatic polyvalent amines; fats such as pibefudine, etc. Cyclic polyvalent amine, 3,9-bis-aminopropyl-2,4,8,10-tetraoxaspiro-(5,5)
Heterocyclic diamines such as undecane, etc. can be mentioned.

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, the desired hardness of the capsule membrane, etc. 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.

Thus, according to the method of the present invention, microcapsules that are resistant to stains and have excellent solvent resistance can be easily obtained.

The reason why the method of the present invention reduces stains caused by stains, that is, colored stains caused by destruction of capsules due to undesired friction, is that the particle size distribution of the obtained capsules is extremely narrow and sharp. Capsules obtained according to the conventional method under the same preparation conditions in the presence of polyvinyl alcohol have a wide particle size spectrum, and some giant capsules of about 100 μm are also mixed in. To compensate for this drawback, it is necessary to adjust the temperature during emulsification. Control is essential.

However, when capsules are prepared in the presence of a divinylbenzene sulfonic acid polymer by the method of the present invention, capsules with a narrow particle size spectrum can be obtained without temperature control, and even giant capsules of about 100 μm are almost impossible to obtain. It doesn't exist. Therefore, it is considered that the resistance to Cos V staining is significantly improved.

Although the reason for the improvement in solvent resistance is not clear, the vinylbenzenesulfonic acid polymer does not simply act as an emulsifier to uniformly and stably disperse a hydrophobic liquid in water, but rather forms a dense polymer at the oil-water interface. It is thought that this provides an environment and atmosphere that allows the formation of a wall film.

Examples of hydrophobic liquids include natural materials such as cottonseed oil, hydrogenated terphenyl, hydrogenated terphenyl derivatives, alkyl biphenyl, alkylnaphthalene, diallyl alkane, kerosene, paraffin, naphthenic oil, and dibasic acid ethers such as phthalate esters. Synthetic oils can be used alone or in combination.

The amount of the isocyanate compound added to the hydrophobic liquid is effectively in the range of 1:0.02 to 60, preferably 1:0.03 to 40.

Examples of color formers for pressure-sensitive copying paper include 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)phthalide, and 8-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide. CP-dimethylaminophenyl)-3
-Triallylmethane compounds such as (1,2-dimethylindol-3-yl)phthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-leucoolamine, N-2,4 , 5-) diphenylmethane compounds such as dichlorophenyl leuko auramine, 7-diethylamino-3-chlorofluoran,
? -Fluoran compounds such as diethylamino-3-chloro-2-methylfluorane, 2-phenylamino-3-methflV-6-(N-ethyl-N-p-)lylaminofluorane, penzoylleuthylene blue, etc. Spirothread compounds such as thiazine compounds, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-propyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-propyl-spiro-dipenzopyran Electron-donating organic coloring agents such as In addition to the above-mentioned coloring threads containing an electron-donating organic coloring agent, the present invention can also be effectively used with coloring systems that utilize a chelate-forming reaction between a metal salt and a ligand compound.

The microcapsules for pressure-sensitive copying paper produced by the method of the present invention include so-called top paper having only a capsule layer on one side of a supporting substrate, and so-called top paper having a coloring agent layer on one side of a supporting substrate and a capsule layer on one side of the supporting substrate. It can be used for single-piece pressure-sensitive copying paper having a capsule layer and a coloring agent layer on the same side of a medium paper or a supporting substrate.

As mentioned above, according to the method of the present invention, capsules with an extremely narrow particle size distribution and a sharp shape can be obtained, and the resulting polymer wall film is dense and has excellent core substance retention properties, so it is suitable for use in pressure-sensitive copying paper. It is applicable to various uses without being limited to the above, and various core materials can of course be appropriately selected depending on the use.

Examples of the present invention will be described below, but it goes without saying that the present invention is not limited only to these Examples.

In addition, parts and % in the examples indicate parts by weight and % by weight unless otherwise specified.

Example 1 Diisopropylnaphthalene (trade name -113, manufactured by Kenbetsu Kagaku Co., Ltd.) in which 25 parts of a trimethylolpropane adduct of tolylene diisocyanate (trade name: Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was dissolved in 4 parts of crystal violet lactone. This was emulsified using a homomixer in 300 parts of a 4% aqueous solution of Saleta polyvinylbenzene sulfonic acid (trade name VER8A-TL500, manufactured by Kanebo NSC) partially substituted with sodium salt. . The average particle size of the emulsified oil droplets was 55 μm, and the particle size distribution was sharp. Note that the average particle size described in each example means a particle size value at which the cumulative volume value accounts for 50% of the total volume distribution measured with a coater counter. The temperature of the obtained emulsified dispersion was raised to 80° C. while stirring with a Prabela mixer, and the mixture was allowed to react for 3 hours while stirring, and then the temperature was lowered to room temperature to complete the encapsulation.

Cellulose powder is added to the capsule dispersion thus obtained.
A capsule coating liquid was prepared by adding 10 parts and 50 parts of a 20% oxidized starch aqueous solution.・The capsule coating liquid was applied on a 4 of/vf base paper with a dry coating amount of 4.
A top sheet for pressure-sensitive copying paper was prepared by coating and drying to give f/Wl.

Example 2 Polymethylene polyphenylisocyanate (trade name: Millione) MR500, which is an aromatic polyvalent isocyanate
, manufactured by Nippon Polyurethane Industries Co., Ltd.) and 8 parts of hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate, t Crisp A//<4 diisopropylnaphthalene (-113 in the product name, Prefectural Chemical 2 of polyvinylbenzenesulfonic acid partially substituted with sodium salt.
% aqueous solution using a homomixer.

The average particle size of the emulsified oil droplets was 5.3μ, and the particle size distribution was sharp. After that, 1.0 part of diethylene triamine and 0.2 part of hexamethylene diamine, which are polyvalent amines, were added to the dispersion, and after stirring at room temperature for 15 minutes, the temperature of the system was raised to 70 ° C. After reacting for 3 hours with continued stirring, the temperature was lowered to room temperature to complete the encapsulation.

Thereafter, the same procedure as in Example 1 was carried out to prepare a top sheet.

Example 3 Polymethylene polyphenylisocyanate (trade name: Millione) MILI, which is an aromatic polyvalent isocyanate
OO, manufactured by Nippon Polyurethane Industries Co., Ltd.) and 6fI, a trimer of hexamethylene diisocyanate having an isocyanurate ring as an aliphatic polyvalent isocyanate, were dissolved in diisopropylnaphthalene in which 4 parts of Crystal Bion 91F 21F were dissolved. Styrene-vinylbenzenesulfonic acid copolymer substituted with IJium salt (D1%, 1% aqueous solution 150%) was emulsified using a homomixer.

The average particle size of the emulsified oil droplets was 6.3μ, and the particle size distribution was sharp. After this, 2 parts of a polyamine adduct of bisphenol A, epichlorohydrin, and alkaline amine were added to the dispersion, and after stirring at room temperature for 30 minutes, the temperature of the thread was raised to 75°C, and while stirring was continued. After reacting for 3 hours, the temperature was lowered to room temperature to complete the encapsulation.

Hereinafter, a top paper was prepared in the same manner as in Example 1. Comparative Example 1 Except that polyvinyl alcohol (trade name PVA-217, manufactured by Kuraray Co., Ltd.) was used instead of polyvinylbenzenesulfonic acid in Example 1. It was carried out in exactly the same way.

The particle size spectrum of the capsules is wide, with an average particle size of 62μ
Met.

Comparative Example 2 Completely the same as in Example I except that vinyl methyl ether maleic anhydride copolymer (trade name: GA N T RE Z AN 139, manufactured by General Aniline and Film Co., Ltd.) was used instead of polyvinylbenzenesulfonic acid. carried out. However, the pH of the aqueous solution was set to 3.5.

The capsule particle size spectrum was broad, with an average particle size of 71μ.

Comparative Example 3 The same procedure as in Example 1 was carried out except that acid-treated gelatin was used instead of polyvinylbenzenesulfonic acid.

The particle size spectrum of the capsules was broad with an average particle size of 60μ.

Separately, 65 parts of aluminum hydroxide, 20 parts of zinc oxide, 3.
A mixture of zinc 5-di(α-methylbenzyl)salimolate and α-methylstyrene/styrene copolymer (mixing ratio 8
0/20) 15 parts, polyvinyl alcohol aqueous solution 5 parts (
A coloring agent coating liquid prepared by adding 2.0 parts (solid content) of carboxy-modified styrene-butadiene copolymer Wotechnu to a dispersion obtained by grinding 300 parts of water (solid content) and 300 parts of water in a ball mill for 24 hours. /d base paper has a dry weight of 51 parts m
'' and dried to create a bottom sheet for pressure-sensitive copying paper.

Further, the capsule coating liquid was applied to the opposite side of the bottom paper to the side coated with the grayishing agent in the same manner as for the top paper, and dried to prepare a middle paper for pressure-sensitive copying paper.

Using the top paper, middle 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) Heat-resistant top paper and bottom paper were stacked so that the coated surfaces were facing each other, and heated to 120°C with a load of 5 kg/cmj applied.
The degree of coloring on the surface coated with the coloring agent was reduced to M.
acbezh color density needle (Red Filter)
I measured it.

(The smaller the number, the better the heat resistance.) (n) Leave the solvent-resistant medium paper in a saturated atmosphere of trichlorethylene at room temperature for 1 hour, and check the degree of coloring of the surface coated with the coloring agent.
hl! 3 densitometer (Red Filter).

(The smaller the number, the better the solvent resistance.) ([) Layer the anti-scratch paper and the bottom paper so that the coated surfaces are facing each other, and rub them together five times under a load of 4 kg/atP. The degree of color staining on the surface to which the coloring agent was applied was determined.

Table 1 (N) Judgment Criteria ○: Slightly soiled Δ: Significantly soiled Pressure-sensitive copying paper using microcapsules obtained by the method has low heat resistance, solvent resistance, and scratch resistance. was also excellent.

Patent applicant Kanzaki Paper Co., Ltd. Commissioner of the Patent Office 1. Indication of the case Patent Application No. 139504 of 1982 2. Name of the invention Method for manufacturing microcapsules 3. Person making the amendment Relationship to the case Patent applicant Ginza Chuouk Address: 4-9-8-4, Ginza, Chuo-ku, Tokyo; Agent: (660) 1-115, Jokoji Motomachi, Amagasaki City;
Date of amendment order Motu 6, Subject of amendment Detailed explanation of the invention in the specification Column 7
, the contents of the amendment (11 Specification, page 12, Lower Blade A et al. 411H, insert [(also, has a mixed layer of capsule and coloring agent layer)] after [...having a coloring agent layer] .

Claims (1)

[Claims] After emulsifying and dispersing a hydrophobic liquid containing a polyvalent isocyanate in a hydrophilic liquid obtained by dissolving a vinylbenzenesulfonic acid polymer, a synthetic polymer film is formed at the droplet interface, and the surface of the droplet is A method for producing microcapsules characterized by being enveloped.