JPS6333475B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing microcapsules for pressure-sensitive copying paper, which have a polyurea wall film that is excellent in low-pressure color development, hard to cause unwanted color stains, and also has excellent solvent resistance. . Regarding the manufacturing method of microcapsules for pressure-sensitive copying paper, the complex coacervation method,
Simple coacervation method, interfacial polymerization method, in
-Situ polymerization methods are known. The wall material of microcapsules in the coacervation method is gelatin, a natural polymer.
Gum arabic is the most commonly used.
However, recently, synthetic polymers such as isocyanate and water, isocyanate and polyamine, isocyanate and polyol, isothiocyanate and water, isothiocyanate and polyamine, isothiocyanate and polyol, epoxy compound, urea-formalin resin, acid chloride and amine are being used. Microcapsules produced by interfacial polymerization and in-situ polymerization 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. It is possible to coat the paper and increase the productivity of pressure-sensitive copying paper, and because the wall of the microcapsules is relatively dense, there is less natural exudation of the oil droplets contained therein, and the microcapsules become colored. be suitable for so-called stand-alone pressure-sensitive copying paper that is laminated or mixed with an agent;
This is because microcapsules have advantages such as being easy to manufacture, being inexpensive, and having excellent water resistance. However, on the other hand, among microcapsules made of synthetic polymer membranes, isocyanate compounds (e.g. m-phenylene diisocyanate, p-
Phenyl diisocyanate, naphthalene - 1.4
-diisocyanate, diphenylmethane-4,
4'-diisocyanate, 3.3'-dimethyldiphenylmethane-4.4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, ethyridine diisocyanate,
Diisocyanates such as cyclohexylene-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate, cyclohexylene-1,3-bismethylene diisocyanate, 4,4',4''-triphenylmethane triisocyanate, toluene-2,4,6-triisocyanate Triisocyanates such as isocyanate, tetraisocyanates such as 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, polyisocyanates such as polymethylene polyphenyl isocyanate, tolylene diisocyanate, For products using hexamethylene diisocyanate with a compound having a hydrophilic group such as a polyvalent hydroxy compound, a polyvalent amine, a polyvalent carboxylic acid, a polyvalent thiol, or an epoxy compound added, use an organic solvent. There is a problem with solvent resistance in that if the capsule is stored in an atmosphere containing The problem is that the capsules are easily destroyed and colored stains occur even when subjected to unintentional weak pressure.The present inventors therefore developed a microcapsule using an isocyanate compound as a wall material to take advantage of its advantages. As a result of intensive research into microcapsules that do not have the drawbacks mentioned above, the structural formula was found to be A hydrophobic liquid containing an aromatic polyvalent isocyanate and an aliphatic polyvalent isocyanate is emulsified and dispersed in a hydrophilic liquid, and a polymer substance is generated at the interface to coat the hydrophobic droplets. He discovered a new encapsulation method and filed a patent application as Japanese Patent Application No. 11374/1983. According to this encapsulation method, a three-dimensional network-like dense and strong wall film with a high degree of polymerization is formed, so that capsules with excellent pressure resistance and solvent resistance can be obtained. However, perhaps because the three-dimensional network formation progresses too much, the capsule membrane hardness is not too hard, and although the capsule is not destroyed by undesired pressure, frictional force, etc. and unnecessary colored stains are not produced, low-pressure coloring is not possible. There is a tendency for sexual performance to decrease significantly. In recent years, thick paper has been used as a single pressure-sensitive copying paper.
Copying using pressure machines such as line printers in combination with OCR paper, plastic cash cards, credit cards, etc. is increasing, but in this case pressure from the stamp machine is also used.
Due to the influence of OCR paper, etc., the pressure is considerably weaker than the pressure applied directly to the recording layer of pressure-sensitive copying paper by writing or typewriters, etc., so copying paper with weak pressure and poor color development as described above should be satisfactory. Unable to obtain recorded image. The inventors of the present invention have conducted further intensive studies on an encapsulation method that uses an isocyanate having a specific structure as described above, and have found that the excellent characteristics of capsules obtained by such an encapsulation method remain unchanged. The present inventors have discovered that capsules that maintain color retention and exhibit excellent low-pressure color development can be obtained by adding a polyvalent amine to the hydrophilic liquid in the encapsulation method described above, leading to the achievement of the present invention. The present invention has a structural formula of A hydrophobic liquid containing an aromatic polyvalent isocyanate, an aliphatic polyvalent isocyanate, and an electron-donating organic coloring agent is emulsified and dispersed in a hydrophilic liquid, and then a polyvalent amine is added to the hydrophilic liquid. , is an encapsulation method characterized by generating a polymer substance at the droplet interface to cover the hydrophobic droplet. The polyvalent amine used in the present invention has two or more -NH groups or _-NH2 groups in the molecule,
Any material that can be dissolved or dispersed in the hydrophilic liquid that forms the continuous phase can be used. Specific substances include aliphatic polyvalent amines such as diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, hexamethylenediamine, etc.; adducts of aliphatic polyvalent amines with epoxy compounds;
Alicyclic polyvalent amines such as piperazine, 3,9-
Examples include heterocyclic diamines such as 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 0.1 to 200 parts by weight, more preferably 1 to 100 parts by weight per 100 parts by weight of polyvalent isocyanate.
Although it is adjusted within the range of parts by weight, the upper limit of the amount of polyvalent amine used is particularly important in the case of single pressure-sensitive copying paper, which is composed of capsules and coloring agents in a layered or mixed state, so it may be difficult to form a film. Since the excess polyvalent amine that does not contribute may cause a desensitizing effect that reduces the color forming ability of the coloring agent, it is necessary to keep it within a range where such desensitizing effect does not occur. Regarding the timing of adding the polyvalent amine, any time after emulsifying and dispersing the hydrophobic liquid containing polymethylene polyphenyl isocyanate, aliphatic polyvalent isocyanate, and an electron-donating organic color former into a hydrophilic liquid. However, the quality of the capsule membrane can be adjusted by appropriately adjusting the time after emulsification until the addition of the polyvalent amine, the reaction temperature, etc. The structural formula used in the present invention is Specific examples of the aromatic polyvalent isocyanate include triphenyl dimethylene triisocyanate, tetraphenyl trimethylene tetraisocyanate, and pentaphenyltetramethylene pentaisocyanate. Of course, these substances may be used singly, or they may be contained. n= of commercially available aromatic polyvalent isocyanate
For inclusions of 1, 2, and 3, n=0, 4, 5,
6, 7, and 8 are included, and such inclusions are also used in the present invention. However, in the case of inclusions, at least 10% of those with n of 1 or more
It is necessary to contain the above amount, and if it is less than this, it is difficult to achieve the desired effect. On the other hand, specific substances of the aliphatic polyvalent isocyanate include, for example, trimethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, ethyridine diisocyanate, or a polyvalent hydroxy compound thereof. , polyvalent amine, polyvalent carboxylic acid,
Polyvalent thiol, polyisocyanate prepolymer adduct with epoxy compound, or ethylene diisocyanate, decamethylene diisocyanate,
A trimeric substance of aliphatic polyvalent isocyanate such as lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, etc. whose structural formula is

[Formula] or

[Formula] (R is an aliphatic compound having one or more isocyanate groups) is also effective. Accordingly, the present invention uses the specific aromatic polyvalent isocyanate and aliphatic polyvalent isocyanate as the wall material of the microcapsule.
The effective ratio of the aromatic polyvalent isocyanate and the aliphatic polyvalent isocyanate is in the range of 1:0.01 to 100, preferably 1:0.1 to 10. Examples of the hydrophobic liquid containing the electron-donating organic coloring agent include cottonseed oil, hydrogenated terphenyl, hydrogenated terphenyl derivatives, alkyl biphenyl, alkylnaphthalene, diallyl alkane, kerosene, paraffin, naphthenic oil, and phthalate ester. Natural or synthetic oils such as dibasic acid esters can be used alone or in combination. The amount of the isocyanate compound added to the hydrophobic liquid is 1:0.02 to 60% relative to the hydrophobic liquid.
A range of 1:0.03 to 40 is effective. As an electron-donating organic coloring agent, for example, 3.3
-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl) phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethyl triallylmethane compounds such as indol-3-yl) phthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halophenyl-
Diphenylmethane compounds such as leucoolamine, N-2.4.5-trichlorophenylleucoolamine, 7-dimethylamino-3-chlorofluoran, 7-dimethylamino-3-chloro-2-methylfluoran, 2 -phenylamino-3-methyl-6-(N-ethyl-Fluoran compounds such as N-p-tolylaminofluorane, thiazine compounds such as benzoylleucomethylene blue, p-nitrobenzylleucomethylene blue, 3-methyl-spiro- Examples include spiro compounds such as dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-propyl-spiro-dinaphthopyran, and 3-propyl-spiro-dibenzopyran.And hydrophilic substances for emulsifying and dispersing hydrophobic liquids. For example, a single or mixed aqueous solution of polyvinyl alcohol, gelatin, gum arabic, carboxymethylcellulose, casein, etc. is used.According to the method of the present invention, the polyvalent amine added to the hydrophilic liquid is A very flexible and dense capsule wall film is produced, probably because it affects the reactivity of polyphenyl isocyanate and aliphatic polyvalent isocyanate and controls the three-dimensional reticulation of the capsule wall film that is produced, although it is not clear. formed,
As a result, capsules with excellent solvent resistance and significantly improved low-pressure coloring properties can be obtained. Moreover, surprisingly, although the low-pressure color development property is significantly improved, unnecessary color development stains caused by capsule destruction due to frictional force, etc., are also effectively eliminated. According to the inventors' considerations, it is estimated that low-pressure color development is correlated with pressure color development of approximately 60 kg/cm ² , and pressure color staining is correlated with pressure color development of approximately 20 kg/cm ² . The microcapsules obtained by the method of the present invention have extremely well-balanced characteristics with respect to this subtle difference in pressure color development. In addition, according to the method of the present invention, the quality of the capsule membrane can be improved by appropriately adjusting the type, amount, and timing of addition of the polyvalent amine added to the hydrophilic liquid depending on the type of polyvalent isocyanate used. It is also possible to adjust the hardness to a desired value. Furthermore, in general, when trying to obtain a capsule membrane using only aliphatic polyvalent isocyanate, due to the water solubility of the isocyanate, there is a marked tendency to agglomerate during the preparation of capsule liquid, and in some cases, it may solidify into a pudding-like state. be. In particular, aliphatic polyvalent isocyanates, aliphatic polyvalent isocyanates and polyvalent hydroxy compounds,
This tendency is noticeable when capsules are prepared using a combination of polyvalent amines, polyvalent carboxylic acids, polyvalent thiols, epoxy compounds, and other compounds with hydrophilic groups in the continuous phase. It will be done. However, in the method of the present invention, there is no such tendency to agglomerate during capsule preparation, and a capsule liquid having very good fluidity can be obtained. Note that the microcapsules for pressure-sensitive copying paper produced by the method of the present invention are not limited to single pressure-sensitive copying paper, but also so-called upper paper having only a capsule layer on one side of the support base, and microcapsules for pressure-sensitive copy paper that are colored on one side of the support base. Of course, the excellent low-pressure coloring properties and solvent resistance can also be utilized in so-called inner paper having a capsule layer on one side in addition to the agent layer. 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. Example 1 0.8g of crystal violet lactone and 0.5g of benzoylleucomethylene blue as color formers
g and dissolved in 50 g of diethyl diphenyl. Add polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Millionate"), which is an aromatic polyvalent isocyanate, to this oily liquid.
MR500'', n=0 is 26% in the structural formula, n=1
Dissolve 4 g of hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate. This oily liquid was dissolved in 1 g of polyvinyl alcohol and 1 g of carboxymethyl cellulose.
65 g and stirred vigorously to obtain a dispersion with an average particle size of 9 μm. After this, 0.5g of diethylenetriamine and 0.1g of hexamethylenediamine, which are polyvalent amines, were added to the dispersion, and after stirring at room temperature for 15 minutes, the temperature of the system was heated to 80℃ to perform a polymerization reaction and form microcapsules. Manufactured. Hydrophobic liquid 100% in this microcapsule dispersion
After adjusting the concentration of the coating solution by adding 30 parts by weight of pulp powder to each part by weight, it was applied to a base paper of 40 g/m ² at a dry weight of 6 g/m ² . A coloring agent coating solution to be described later was coated on this capsule coating layer to give a dry weight of 8 g/m ² to obtain a single pressure-sensitive copying paper. Example 2 0.2 g of 2,4-dimethyl-7-dimethylaminofluorane, 0.8 g of crystal violet lactone and N-butyl-3-[bis{4-(N-methylanilino)phenyl}methyl] as color formers
0.3g of carbazole and isopropylnaphthalene
Dissolve in 50g. Polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name "Millionate MR-300", structural formula: n = 0) is added to this oily liquid, which is an aromatic polyvalent isocyanate.
50%, n = 1, 16%, n = 2, 7%, n = 3 or more, 19%) and 3 g of hexamethylene diisocyanate having an isocyanurate ring as an aliphatic polyvalent isocyanate. Dissolve 3g of body. A dispersion liquid having an average particle size of 11 μm was obtained by adding 0.8 g of polyvinyl alcohol to 65 g of water and stirring vigorously. This capsule dispersion was heated at room temperature for 1 hour.
After stirring for an hour, a polyamine adduct of bisphenol A, epichlorohydrin and alkylamine was prepared.
Add 1.5g and heat to 90℃ to perform a polymerization reaction.
Microcapsules were obtained. Hydrophobic liquid 100% in this microcapsule dispersion
After adjusting the concentration of the coating solution by adding 20 parts by weight of pulp powder and 10 parts by weight of raw starch particles, it was applied to a base paper of 40 g/m ² so that the dry weight was 6 g/m ² . A coloring agent coating solution, which will be described later, was coated onto this capsule coating layer to give a dry weight of 8 g/m ² to obtain a single pressure-sensitive copying paper. Example 3 Crystal violet lactone as a coloring agent
0.8 g and 0.1 g of 3,6-bis(dimethylamino)fluoran-r-anilinolactam are dissolved in 50 g of dimethyl diphenylethane. Polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name "Millionate MR100"), which is an aromatic polyvalent isocyanate, is added to this oily liquid. In the structural formula, n=0 is 45%, n=1 is 26%, n=2 and 4 g of an adduct of 3 moles of lysine diisocyanate, which is an aliphatic polyvalent isocyanate, and 1 mole of trimethylolpropane, are dissolved. To this was added 0.2 g of dibutyltin dilaurate as a catalyst. This oily liquid was added to 80 g of water in which 1 g of gum arabic and 1 g of polyvinyl alcohol were dissolved, and the mixture was vigorously stirred to obtain a dispersion having an average particle size of 15 μm. After heating this to 70℃ and stirring for 1 hour, poly(1~
5) 0.2 g of alkylene ( _C2-6 ) polyamine/alkylene ( _C2-18 ) oxide adduct was added to the dispersion and further stirred at 85°C for 3 hours to perform a polymerization reaction to produce microcapsules. . Hydrophobic liquid 100% in this microcapsule dispersion
Add the coloring agent coating liquid described later to 200 parts by weight in terms of solid weight, mix thoroughly, and then apply 9 g/ ^m2 of base paper on a 40 g/m2 base paper.
m ² to obtain a single pressure-sensitive copying paper. Example 4 0.8g of crystal violet lactone and 0.5g of benzoylleucomethylene blue as color formers
Dissolve g in 50 g of isopropylnaphthalene. Add polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Millionate"), which is an aromatic polyvalent isocyanate, to this oily liquid.
MR500'', n=0 is 26% in the structural formula, n=1
2 g of hexamethylene diisocyanate trimer having a biuret bond, which is an aliphatic polyvalent isocyanate, are dissolved. This oily liquid was added to 65 g of water in which 0.5 g of polyvinyl alcohol and 0.3 g of funnel oil had been dissolved and dispersed, and the mixture was vigorously stirred to obtain a dispersion having an average particle size of 7 μm. After this, 0.6 g of triethylenetetramine, a polyvalent amine, was added to the dispersion, and the temperature of the system was adjusted to 65°C.
After holding for -1 hour, the mixture was reacted at 85°C for 3 hours to perform a polymerization reaction and produce microcapsules. Hydrophobic liquid 100% in this microcapsule dispersion
After adding 30 parts by weight of pulp powder to each part by weight and adjusting the concentration of the coating solution, one side was previously coated with a coloring agent coating solution of 5 g/m ² in terms of dry weight.40
g/m ² The other side of the base paper was coated with a dry weight of 5 g/m ² to obtain a medium paper for pressure-sensitive copying paper. Example 5 30 parts of zinc 3,5-di(α-methylbenzyl)salicylate, colloidal aluminum oxide (bulk height 23.7 ml/g). 8 parts of nitrocellulose were added to a mixed solvent of 15 parts of ethanol, 30 parts of ethyl acetate, and 35 parts of butyl acetate, and the mixture was sufficiently stirred with a propeller mixer to obtain a color developing ink. The capsule coating solution obtained in Example 1 was coated on one side at 5 g/m ² in terms of solid weight, and the developer ink was printed on the other side of a 40 g/m ² base paper using a flexo printing machine. The amount of ink deposited was 1.0±0.2 g/m ² (dry weight) as non-volatile components. The pressure-sensitive copying paper obtained as described above had excellent color development performance, and no color fog was observed on the surface coated with the developer ink. Comparative Example 1 In Example 1, 0.5 g of diethylenetriamine, which is a polyvalent amine, and 0.1 g of hexamethylene diamine
A single pressure-sensitive copying paper was obtained in the same manner as in Example 1 except that g was not used. Comparative Example 2 The same procedure as in Example 2 was carried out except that 1.5 g of a polyvalent amine adduct of bisphenol A, epichlorohydrin, and alkylamine, which are polyvalent amines, was not used. I got it. Comparative Example 3 In Example 1, 2 g of hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate, was not used, and polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Millionate MR-") was used as an aromatic polyvalent isocyanate.
A single pressure-sensitive copying paper was obtained in the same manner as in Example 1, except that 6 g of "500") was used alone. Comparative Example 4 In Example 2, polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name "Millionate"), which is an aromatic polyvalent isocyanate, was used.
MR-300'', in the structural formula, n=0 is 50%, n
= 16% of n=1, 7% of n=2, and 19% of n=3 or more (a mixture of 6g
Microcapsules were obtained in the same manner as in Example 2, except that the following procedure was used. This capsule liquid was prepared by adding 1.5 g of a polyvalent amine adduct of bisphenol A, epichlorohydrin, and alkylamine, and then adjusting the temperature of the system.
During the temperature rise to 90℃, it aggregates and becomes non-fluid, and eventually solidifies into a pudding-like shape, causing the support substrate (paper) to
I couldn't apply it on top. Comparative Example 5 In Example 4, except that 0.6 g of triethylenetetramine, which is a polyvalent amine, was not used,
In the same manner as in Example 4, an inner sheet for pressure-sensitive copying paper was obtained. Preparation method of coloring agent coating solution: 400 parts of water, 100 parts of acid clay, 4 parts of sodium hydroxide
and carboxy-modified styrene-butadiene copolymer latex (solid content 50%).
Then, 10 parts of a 30% aqueous solution of sodium dialkyl sulfosuccinate as a wetting agent was added to prepare a coloring agent coating solution. Quality tests were conducted on each of the eight types of single pressure-sensitive copying paper and inner paper obtained in this way, and the test results are listed in Table 1.

[Table] (Test method) Low-pressure color development: In the case of single pressure-sensitive copying paper, stack one sheet of paper, or in the case of inner paper, stack two sheets so that the capsule-coated side and coloring agent-coated side face each other. in addition
After stacking one sheet of OCR paper (105g/ ^m2 ),
The color was developed using a typewriter (Hermes-700EL) under the following conditions.・Print: 2mm square solid type ・Type pressure: 1 (weak) Color density after 24 hours has passed after color development
Measured using a Macbeth color density meter (Red Filter). (The larger the number, the better the color development.) Strong pressure color development: As in the case of low pressure color development, do not overlap the OCR paper and use a typewriter (Hermes-
700EL) under the following conditions, ・Type: 2mm square solid type ・Type pressure: 10 (strong) Color density after 24 hours has passed after color development
Measured using a Macbeth color density meter (Red Filter). Heat resistance: Capsule coated paper in an atmosphere of 120℃ 4
After leaving it for a while, check the degree of coloring of the coloring agent on the coated paper.
Measured with a Macbeth color densitometer (Red Filter). (The smaller the number, the better the heat resistance) Solvent resistance: After leaving the capsule coated paper in an atmosphere of saturated trichlorethylene vapor for 15 hours, the degree of coloring of the coloring agent on the coated paper was measured using a Macbeth color densitometer (Red Filter). It was measured with (The smaller the value, the better the solvent resistance.) As is clear from the results in Table 1, both the single pressure-sensitive copying paper and the inner paper obtained in the examples of the present invention had well-balanced quality. I wanted to.

Claims (1)

[Claims] 1. The structural formula is After emulsifying and dispersing a hydrophobic liquid containing an aromatic polyvalent isocyanate, an aliphatic polyvalent isocyanate, and an electron-donating organic coloring agent into a hydrophilic liquid,
A method for producing microcapsules for pressure-sensitive copying paper, which comprises adding a polyvalent amine to the hydrophilic liquid to generate a polymer substance at the droplet interface to cover the hydrophobic droplets. 2. The method according to claim 1, wherein the ratio of aromatic polyvalent isocyanate and aliphatic polyvalent isocyanate is 1:0.01 to 100. 3. The method according to claim 1, wherein the polyvalent amine is at least one selected from aliphatic polyvalent amines, epoxy adducts of aliphatic polyvalent amines, alicyclic polyvalent amines, and heterocyclic diamines.