JPS58202034A - Preparation of microcapsule - Google Patents

Abstract

PURPOSE:To obtain a microcapsule having resistance, especially, to rub staining, by a method wherein a hydrophobic liquid containing a polyisocyanate is emulsified and dispersed in a hydrophilic liquid containing a (co)polymer comprising a specific monomer unit and formed liquid droplet is coated with a polymer film at the interface thereof. CONSTITUTION:A (co)polymer comprising a monomer unit of the formula preferably 2-acrylamido-2-propanesulfonic acid or a salt thereof, is dissolved in a hydrophilic medium in an amount of 0.1wt% or more. In the next step, an oily liquid containing a polyisocyanate (e.g., polymethylenepolyphenyl isocyanate) is emulsified and dispersed in the hydrophilic medium containing the aforementioned (co)polymer and a synthetic polymer film is formed on the surface of each liquid droplet to coat the same. The resulting microcapsule is excellent also in solvent resistance and suitable for use in pressure-sensitive copy paper.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing microcapsules containing a hydrophobic core substance, and in particular to pressure-sensitive microcapsules having a polyurea wall film that is resistant to scratches and stains (1) and has excellent solvent resistance. The present invention relates to a method for extremely easily producing microcapsules for copying paper.

As for the manufacturing method of microcapsules, complex coacervation method, simple coacervation method, interfacial polymerization method, F-sHu polymerization method, etc. are known.

As the wall material of microcapsules in the coacervation method, gelatin-gum arabic, which is a natural polymer, is most commonly used. However, in recent years, the use of isocyanates and water, isocyanates and polyamines, isocyanates and polyols, isothiocyanates and water, isothiocyanates and polyamines, inthiocyanates and polyols, epoxy compounds, urea-formalin resins, melamine-formalin resins, acid chlorides and amines, etc. Microcapsules produced by interfacial polymerization and 1n-situ polymerization using synthetic polymers are attracting attention.

The reason why microcapsules made of these synthetic polymer films have attracted particular attention as pressure-sensitive copying paper is that (2) they can be prepared into highly concentrated paints compared to microcapsules made of natural polymer films. It enables speedy coating and increases the productivity of pressure-sensitive copying paper;
Since the wall of the microcapsules is relatively dense, there is little natural exudation of the oil droplets contained therein, and therefore it is suitable for use in so-called stand-alone pressure-sensitive copying paper in which microcapsules are laminated or mixed with a coloring agent. This is because microcapsules have advantages such as easy production of microcapsules, low cost, and excellent water resistance.

However, on the other hand, even among microcapsules made of synthetic polymer membranes, those that use isocyanate compounds have a certain value! When stored in an atmosphere where an Af4 agent is present, oil droplets inside the capsule are extracted and transferred to the coloring agent layer, causing unwanted color development, which is a problem with solvent resistance.
Furthermore, there is a problem in that the capsules are easily destroyed and colored stains occur even when subjected to unwanted friction other than the pressure of writing or typing with a typewriter.

(3) In view of the current situation, the present inventors have worked hard to find 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 of research, it was discovered that by reacting polyvalent isocyanate compounds in the presence of vinylbenzenesulfonic acid polymers, capsules with excellent properties without the above-mentioned problems could be obtained. The application was filed as No. 56-139504.

It is an extremely interesting phenomenon that the quality of the capsules produced differs markedly depending on the type of emulsion dispersion stabilizer for the hydrophobic liquid, even though the same capsule wall membrane material is used. As a result of research,
When a polyvalent isocyanate compound is reacted in the presence of a polymer containing a monomer unit represented by the following general formula (1), the capsules are even more resistant to scratches than the capsules obtained in the presence of a vinylbenzenesulfonic acid polymer. sex,
It has been discovered that capsules with excellent solvent properties can be obtained, and the present invention has been achieved.

(4) The present invention emulsifies and disperses a hydrophobic liquid containing a polyvalent isocyanate in a hydrophilic liquid obtained by dissolving a polymer containing a seven-mer uni-nod represented by the following general formula (1), and This is a method for producing microcapsules, which is characterized by producing a synthetic polymer wall film.

[In the formula, Ry, Rz, and R3 each represent a hydrogen atom or an alkyl group, preferably a lower alkyl group, R+ represents a hydrogen atom, ammonium, or an alkali metal, and n represents an integer of 1 to 10. ] Among the monomer units represented by the general formula (I), 2-acrylamido-2-methylpropanesulfonic acid represented by the following general formula (II) is particularly suitable for its salt L CHa = CH-C0NHCCLSO3M (
I[)CHa (5) [In the formula, M represents a hydrogen atom, sodium, potassium, lithium, or ammonium. ] is also preferably used in higher amounts, which are better in achieving the desired effects of the present invention.

The polymer having monomer units represented by the general formula [I] used in the present invention includes the general formula (1
), or a copolymer containing the monomer unit of general formula (1) as one component.

Seven polymers that can be copolymerized with the monomer unit represented by general formula (1) include unsaturated monocarboxylic acids (or salts thereof), halides of unsaturated monocarboxylic acids, anhydrides of unsaturated monocarboxylic acids, Examples include unsaturated acid alkyl esters and alkyl vinyl ethers, and specifically, the following water-soluble or non-water-soluble hexamers are preferably used.

Acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, vinyl acetic acid, angelic acid, tiglic acid, allyl acetic acid, β, β-dimethylacrylic acid (6) Hydrosorbic acid, isohydrosorbate, pyroterepic acid, terraacrylic acid, undecylene Acid, oleic acid, elaidic acid, erucic acid, brassic acid, cinnamic acid, allocinnamic acid, butadiene-1=carboxylic acid, acrylic acid chloride, chloroacrylic acid, acrylic anhydride, methacrylic anhydride, benzamide acrylic acid , acetamidoacrylic acid, phthalimidoacrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, isodecyl acrylate, acrylic Lauryl acid, lauryl-tridecyl acrylate, stearyl acrylate, cyclohexyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-methacrylate - Ethylhexyl, octyl methacrylate, isodecyl methacrylate, lauryl methacrylate, methacrylic (7) lauryltridecyl methacrylate, stearyl methacrylate,
cyclohexyl methacrylate, hensyl methacrylate,
Butyl maleate, dibutyl maleate, ethyl fumarate, methyl vinyl ether, ethyl vinyl ether,
Butyl vinyl ether, 2-ethylhexyl vinyl ether, octyl vinyl ether, lauryl vinyl ether, stearyl vinyl ether, acrylamide, diacetone acrylamide, methacrylamide, N-methylolacrylamide, acrylonitrile, acrolein, styrene, α-methylstyrene, divinylhenzene,
Vinyl acetate, vinyl chloride, ethylene, butadiene, N-
Vinylpyrrolidone, dimethylamine ethyl acrylate,
Dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate,
Glycisin acrylate, glycicin methacrylate, hydroxyethyl acrylate, butoxyethyl acrylate,
Ethylene glycol diacrylate, ethylene glycol dimethacrylate, diacrylic acid (8) Ethylene glycol, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetraethylene glycol dimethacrylate, diacrylic acid 1
．． 3-butylene glycol, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol acrylate, 1,6-hexanediol methacrylate.

Among them, acrylic acid alkyl esters, methacrylic acid alkyl esters, acrylamide, styrene, and N-vinylpyrrolidone are most preferably used because they are excellent in achieving the desired effects of the present invention.

Homopolymers and copolymers containing heptad units represented by the general formula (1) can be produced by various known methods. The molecular weight of these polymers used in the present invention can be changed as appropriate by changing the concentration of the initiator, the concentration of 7mer, the polymerization temperature, or the use of a chain transfer agent such as a mercaptan.

In the method of the present invention, a polymer containing a monomer unit (9) represented by general formula (1) is dissolved in a hydrophilic medium for capsule production. Considering quality etc., 0.1% by weight or more, more preferably 0.5% by weight in the hydrophilic medium.
It is preferable to contain it in a weight percent or more. The upper limit of the content is generally adjusted depending on the viscosity of the capsule manufacturing system, the capsule manufacturing apparatus used, etc., but it is preferably kept at 20% by weight or less.

In addition, in the capsule manufacturing system, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, cation-modified polyvinyl alcohol, sulfone-modified polyvinyl alcohol, polystyrene sulfonic acid or its copolymer, gelatin, gum arabic, carboxymethylcellulose, maleic anhydride, etc. Common protective colloid agents such as acid copolymers, or surfactants such as funnel oil, polyoxyethylene alkyl ether, and sorbitan fatty acid ester can be used in combination, but the amount used may inhibit the original effect of the present invention. (10)

Furthermore, a polyvalent amine may be further added to the hydrophilic medium depending on the desired capsule quality.The polyvalent amine has two or more NH groups or NHλ groups in the molecule and forms a continuous phase. Any material that can be dissolved or dispersed in a hydrophilic liquid can be used. Specific substances include diethylenetriamine, triethylenetetramine, 1.3
- Aliphatic polyvalent amines such as propylene diamine, hexamethylene diamine, etc.; epoxy compounds of aliphatic polyvalent amines; alicyclic polyvalent amines such as piperazine, etc.; 3.
Examples include heterocyclic diamines such as 9-bis-aminopropyl-2,4°8.10-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, the desired hardness of the capsule membrane, etc. Ru. Preferably 001 to 200 parts by weight, more preferably 1 to 1 parts by weight per 100 parts by weight (11) of polyvalent isocyanate.
It is adjusted within a range of 0.00 parts by weight.

Therefore, in the method of the present invention, after emulsifying and dispersing a hydrophobic liquid containing a polyvalent isocyanate in a hydrophilic liquid in which a polymer containing a heptad unit represented by general formula (1) is dissolved, Similar to the conventional method, the polyvalent isocyanate is polymerized at the droplet interface to form a synthetic polymer film that covers the hydrophobic droplets.

Examples of the polyvalent isocyanate used to cover the surface of the hydrophobic core material in the present invention include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-1-lylene diisocyanate, 2,4-tolylene diisocyanate, and 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-di(12) isocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate , butylene-1゜2-diisocyanate, ethyridine diisocyanate, cyclohexylene-1,2
- Diisocyanates or diisothiocyanates such as diisocyanate, cyclohexylene-1,4-diisocyanate, isophorone diisocyanate, p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, ethyridine diisothiocyanate, 4.
4',4''-) liphenylmethane triisocyanate,
4. Triisocyanates such as toluene-2,4,6-triisocyanate and trimer of hexamethylene diisocyanate, polymethylene polyphenylisocyanate;
4'-dimethyldiphenylmethane-2,2',5.5'
- Polyvalent isocyanates such as tetraisocyanate, and these polyvalent isocyanates to compounds having hydrophilic groups such as polyvalent amines, polyvalent carboxylic acids, polyvalent thiols, polyvalent human (13) roxy compounds, epoxy compounds, etc. I can list what has been added. Furthermore, these polyvalent isocyanate compounds can be used in various combinations, such as aromatic and aliphatic, depending on the desired capsule quality.

Examples of hydrophobic liquids include natural or synthetic dibasic acid esters such as cottonseed oil, hydrogenated terphenyl, hydrogenated terphenyl derivatives, alkyl biphenyl, alkylnaphthalene, diallyl alkane, kerosene, paraffin, naphthenic oil, and phthalic acid ester. Oils may be used alone or in combination.

The amount of the isocyanate compound added to the hydrophobic liquid is effectively 1:0.02 to 60, preferably t:o, oa to 40.

Since the microcapsules obtained by the method of the present invention have excellent uniformity in particle size distribution, they are particularly useful for pressure-sensitive copying paper, but in this case, the coloring agent is generally dissolved in a hydrophobic liquid. A capsule (14) is produced.

Examples of coloring agents for pressure-sensitive copying paper include 3°3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis-(p-dimethylaminophenyl)phthalide, 3. -(p-dimethylaminophenyl)-
Triarylmethane compounds such as 3-(1,2-dimethylindol-3-yl)phthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N
-Halophenyl-leucoauramine, N-2,4゜5-
Diphenylmethane compounds such as trichlorophenylleucoauramine, 7-diethylamino-3-chlorofluoran, 7-danitylamino-3-chloro-2-methylfluoran, 2-phenylamino-3-methyl-6-(N
Fluoran compounds such as -ethyl-N-p-tolylamino)fluoran, benzoylleucomethylene blue, p
-thiazine compounds such as nitrobenzoylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-
Examples include electron-donating organic coloring agents such as spiro compounds such as ethyl-spiro-naphthopyran, 3-(15) propyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, and 3-propyl-spiro-dibenzobilane. . In addition to the coloring system using the electron-donating organic coloring agent as described above, the present invention can also be effectively used with a coloring system using 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.

In particular, since the capsules obtained by the method of the present invention have an extremely uniform particle size distribution as described above, it has traditionally been difficult to balance staining and color development, so this method has not been sufficiently implemented despite the extremely high production efficiency. It is used very effectively (16) in so-called single-liquid pressure-sensitive copying paper in which capsules and coloring agents are mixed in a single layer.

Conventionally, when manufacturing microcapsules, polyvinyl alcohol, for example, has been used as a dispersant to emulsify a hydrophobic liquid, but such dispersants only yield capsules with a wide particle size distribution that partially contain giant capsules of about 100 μm. Furthermore, complicated operations such as temperature control during emulsification were required. However, according to the method of the present invention, capsules with a narrow particle size distribution can be obtained without the need for particular temperature control, so resistance to scratch stains is significantly improved, and print color density and stain characteristics are well balanced. Furthermore, since the amount of polyvalent isocyanate to be used can be appropriately selected depending on the desired capsule strength and quality, capsules that can be easily passed through one-component pressure-sensitive copying paper can be obtained as described above.

As described 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 can be used for pressure-sensitive copying paper. (17) It is applicable to various uses, 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 2.8 parts of crystal violet lactone and 0.7 parts of benzoyl leucomethylene blue as coloring agents are dissolved in 100 parts of diisopropylnaphthalene (trade name -113, manufactured by Ou Kagaku Co., Ltd.).

Add 4 parts of polymethylene polyphenylisocyanate (trade name Millionate MR-500, manufactured by Nippon Polyurethane Industries, Ltd.) to this oily liquid and a trimer of hexamethylene diisocyanate having an isocyanurate ring (trade name Coronate E).
H, manufactured by Nippon Polyurethane Kogyo Co., Ltd.) and 8 parts.

This oily liquid was mixed with a homopolymer of 2-acrylamide-2-methylpropanesulfonic acid (molecular weight: 3,000°, 000,
(pH adjusted to 6.5 with sodium hydroxide) 0° (18) 150 parts of a 5% aqueous solution was added and emulsified using a homomixer.

When the obtained emulsion was measured with a Coulter counter, the average particle size was 1168 μm, and the particle size distribution was narrow.
Volume distribution into the channel was 90.0%.

The emulsified dispersion was heated to 85° C. while being stirred with a mixer and reacted for 31118 hours, and then the temperature was lowered to room temperature to complete encapsulation.

To the thus obtained capsule dispersion were added 10 parts of cellulose powder and 50 parts of a 20% oxidized starch aqueous solution to prepare a capsule coating liquid.

The capsule coating solution was coated on a base paper of 40 g/rrr so that the dry coating amount was 4 g/nf and dried to prepare a top sheet for pressure-sensitive copying paper.

Example 2 A trimethylolpropane adduct of methylene diisocyanate (trade name Coronate 1) was added to the same oily liquid as in Example 1.
(manufactured by Nippon Polyurethane Kogyo Co., Ltd.) 30 (19) This oily liquid was converted into a copolymer (molecular weight 100,000) consisting of 90% sodium 2-acrylamide-2-methylpropanesulfonate and 10% acrylamide.
It was added to 200 parts of a 1% aqueous solution and emulsified using a homomixer.

When the obtained emulsion was measured with a Coulter counter, the average particle size was 10.3 μm, the particle size distribution was narrow and sharp, and the total volume distribution of the most frequent volume distribution channel and its neighboring channels was 85°1. %Met.

Thereafter, the same process as in Example 1 was carried out to prepare a top sheet for pressure-sensitive paper.

Example 3 Fruit! Add 5 parts of polymethylene polyphenylisocyanate (trade name: Millionate MR400, manufactured by Nippon Polyurethane Industries, Ltd.) and a trimer of hexamethylene diisocyanate having a biuret group (trade name: Coronate N1, manufactured by Nippon Polyurethane Industries, Ltd.) to an oily liquid similar to v4J1. Two parts each of isophorone diisocyanate (20) and isophorone diisocyanate (20) were dissolved.

This oily liquid is made into a homopolymer of 2-acrylamide-2-methylpropanesulfonic acid (molecular weight 2,000°000).
0.8 parts and polystyrene sulfone #& (product name VER3
The mixture was added to 150 parts of water (pH of the aqueous solution was set to 7.0 using sodium hydroxide) containing 1 part of A Tl2O3 (manufactured by Kanebo NSC) and emulsified using a homomixer.

When the obtained emulsion was measured with a Coulter counter, the average particle diameter was 10.0μ, and the total volume distribution of the most frequent volume distribution channel and its neighboring channels was 81.4.
%Met.

The following operation was carried out in the same manner as in Example 1.

Comparative Example 1 The same procedure as in Example 1 was carried out except that polyvinyl alcohol (trade name PVA-217, manufactured by Kuraray Co., Ltd.) was used instead of poly2-acrylamide-2-methylpropanesulfonic acid sodium.

When the emulsion was measured using a Coulter counter, the average particle size was 9.5 .mu.m, and the particle size distribution was medium and wide, lacking in sharpness. The total volume distribution for the channel with the most frequent volume distribution and the channels on both sides of it is 47.3%.
Met.

Comparative Example 2 In Example 1, vinyl methyl ether/maleic anhydride copolymer (trade name: GANTREZ) was used instead of poly2-acrylamide-2-methylpropanesulfonic acid soda.
It was carried out in exactly the same manner except that AN-139 (manufactured by General Aniline and Film Co., Ltd.) was used. However, the pH of the aqueous solution was set to 3.5.

When the emulsion was measured using a Coulter counter, the average particle size was 10.0 μm, and the particle size distribution was medium-wide.

The total volume distribution of the channel with the most frequent volume distribution and the channels on both sides thereof was 50.3%.

Comparative Example 3 Exactly the same as in Example 1 except that polystyrene sulfonate sodium (trade name: VERS ATL 600, manufactured by Kanebo NSC) was used instead of poly-2-acrylamide sodium 2-methylpropanesulfonate (22). It was carried out in However, the pH of the aqueous solution is 6.5.
It was set to

When the emulsion was measured with a Coulter counter, the average particle size was 10.5 μm. Although the particle size distribution was sharper than the capsules obtained in Comparative Example 1.2, the capsules obtained in Example 1 did not have any sharpness.

The total volume distribution to the channel with the most frequent volume distribution and the channels on both sides thereof was 67.8%.

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 grinding 300 parts (solid content) and water in a ball mill for 24 hours was mixed at 40 g/ RRF base paper has a dry weight of 5g.
/nf and dried to prepare a lower sheet for pressure-sensitive copying paper.

(23) The capsule coating liquid was applied in the same manner as for upper sheet paper and dried to prepare inner sheet 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 are stacked so that the coated surfaces are facing each other, and treated with a heat treatment machine at 120°C for 3 hours with a load of 5/- applied to coat the coloring agent. Macbet the degree of coloration of the surface
Measured using a red filter (red filter).

(The smaller the number, the better the heat resistance.) (■) Leave the solvent-resistant medium paper in a saturated atmosphere of trichlorethylene at room temperature for 1 hour, and check the degree of coloration of the surface coated with the coloring agent.
Measured with h color density needle (Red Filter).

(The smaller the number, the better the solvent resistance) (I [[) Scratch resistance:... Layer the upper and lower papers so that the coated surfaces are facing each other (24) and apply a load of 4/-. Rub the stain 5 times in the same state to check the degree of color staining on the coloring agent coated surface! pl was determined.

/ (25) Table 1 +11 Judgment Criteria ◎: Hardly clean.

×: Quite dirty.

XX: Extremely dirty.

(2) Measure the capsule with a Coulter counter.

% of capsules contained in the channels of the most frequent volume distribution.

(3) Measure the capsule with a Coulter counter.

Total percentage of capsules contained in the most frequent volume distribution channel and adjacent channels.

(26) As is clear from the results in Table 1, the pressure-sensitive copying paper using microcapsules obtained by the method of the present invention was excellent in heat resistance, solvent resistance, and scratch resistance. .

Example 4 30 parts of cellulose powder was added to the capsule dispersion obtained in the same manner as in Example 1 to prepare a capsule coating liquid.

The dry coating amount of the obtained capsule coating liquid on the base paper of 40 g/rd is 6 g/rI? Further, a coloring agent coating liquid to be described later was coated on the capsule coating layer so that the dry weight was 8 g/rd to obtain a single pressure-sensitive copying paper.

Example 5 A single pressure-sensitive copying paper was prepared in the same manner as in Example 4, except that the capsule dispersion obtained in the same manner as in Example 3 was used.

Comparative Example 4 The same procedure as in Example 4 was carried out except that the capsule dispersion prepared in the same manner as in Comparative Example 2 was used. , 30 parts of cellulose powder and the coloring agent coating liquid (solid content: 1
50 parts) to prepare a wavy capsule-coloring agent mixed coating solution.

The capsule-coloring agent mixed coating solution was coated onto a 40 g/rd base paper so that the dry coating amount was 10 g/nr to obtain a single pressure-sensitive copying paper.

Example 7 A single pressure-sensitive copying paper was prepared in the same manner as in Example 6, except that the capsule dispersion obtained in the same manner as in Example 3 was used.

Comparative Example 5 A single pressure-sensitive copying paper was prepared in the same manner as in Example 6, except that the capsule dispersion obtained in the same manner as in Comparative Example 2 was used.

The coloring agent coating liquid used for the single pressure-sensitive copying paper was obtained in the following manner. '・ 400 parts of water, 100 parts of acid clay, sodium hydroxide (28 parts
) and 4 parts of carboxy-modified styrene-butadiene copolymer latex (solid content 50%).
part and 30% of sodium dialkyl sulfosuccinate
10 parts of an aqueous solution was added to prepare a coloring agent coating solution.

Using the thus obtained self-coloring single-piece pressure-sensitive copying paper, a performance comparison test was conducted using the method described below.
The results are listed in Table 1.

(1) Heat-resistant single pressure-sensitive copying paper was left in a heat treatment machine at 120°C for 5 hours, and the degree of coloration of the coated surface was measured using a Macbeth color density needle (Red).
Filter).

(II) Single Blue Spot The number of spot stains occurring per 1000 sheets of pressure-sensitive copying paper was counted.

(1) 4 kg of base paper is stacked on the coated surface of scratch-resistant single pressure-sensitive copying paper.
The degree of colored staining on the coated surface was determined by scrubbing 5 times under a load of -.

(29) Table 2 (1) Judgment criteria: ◎: Not dirty at all.

O: Slightly dirty.

×: Quite dirty.

XX = Significantly dirty.

(30) As is clear from the results in Table 2, the single pressure-sensitive copying paper using microcapsules obtained by the method of the present invention has excellent heat resistance, blue spot resistance, and scratch resistance. , which had previously been difficult to implement due to extremely poor scratch resistance, had excellent properties even with liquid-type single-piece pressure-sensitive copying paper.

Patent applicant: Kanzaki Paper Co., Ltd. (31)

Claims (1)

[Claims] +11 A hydrophobic liquid containing a polyvalent isocyanate is added to a hydrophilic liquid in which a homopolymer and/or copolymer containing a heptad unit represented by the following general formula (1) is dissolved. A method for producing microcapsules, which comprises emulsifying and dispersing the droplets, and then generating a synthetic polymer film at the droplet interface to cover the droplet surfaces. [In the formula, Rt SRz % R,? each represents a hydrogen atom or an alkyl group, R represents a hydrogen atom, ammonium or an alkali metal, and n represents an integer of 1 to 10. ]