JPS6333474B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing microcapsules for pressure-sensitive copying paper having a polyurea wall film that is difficult to break due to unintentional weak pressure and has excellent solvent resistance. Regarding the manufacturing method of microcapsules for pressure-sensitive copying paper, 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, increasing 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 therefore the microcapsules become colored. Advantages include being suitable for use in so-called stand-alone pressure-sensitive copying paper that is laminated or mixed with an agent, easy to manufacture microcapsules, inexpensive, and excellent in water resistance. This is because it has However, on the other hand, among microcapsules made of synthetic polymer membranes, isocyanate compounds (e.g. m-phenylene diisocyanate, p-phenylene 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 , cyclohexylene-
1.2-diisocyanate, cyclohexylene-1.4
-Diisocyanate, cyclohexylene-1.3-
Diisocyanates such as bismethylene diisocyanate, triisocyanates such as 4,4',4''-triphenylmethane triisocyanate, toluene-2,4,6-triisocyanate, 4,
4'-dimethyldiphenylmethane-2,2,5,
Tetraisocyanates such as 5'-tetraisocyanate, polyisocyanates such as polymethylene polyphenyl isocyanate, polyhydroxy compounds, polyvalent amines, polyvalent carboxylic acids, polyvalent thiols, and epoxy compounds in tolylene diisocyanate and hexamethylene diisocyanate. For capsules containing compounds with hydrophilic groups (e.g.), when stored in an atmosphere containing an organic solvent, oil droplets inside the capsule are extracted and the coloring agent layer is There is a problem with solvent resistance, which can transfer and cause unwanted color development, and even when subjected to unwanted weak pressure other than writing or typewriter pressure, the capsule easily breaks and color development stains occur. There is a drawback. Therefore, the inventors of the present invention made use of the advantages of microcapsules using isocyanate compounds as wall material and conducted intensive studies on microcapsules that do not have the above-mentioned drawbacks. The development was successful. That is, the microcapsules produced according to the present invention are
The wall film material uses two structurally completely different isocyanates together, and its specific composition is based on the structural formula: 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. It is something to do. already Microcapsules having a wall film of . However, on the other hand, this substance has a fast polymerization reaction rate, and because the benzene rings are only connected by methylene, it lacks flexibility and is difficult to polymerize into a high-molecular polymer. Therefore, microcapsules made of these alone are fragile and easily break when subjected to unintentional weak pressure other than writing or typing pressure from a typewriter. Furthermore, this substance has the disadvantage that it causes a coloring reaction with the dye, and the capsule membrane itself becomes colored, which is not desirable for use as microcapsules for pressure-sensitive copying paper. However, when this substance is combined with an aliphatic polyvalent isocyanate, the strength of the capsule membrane is surprisingly improved, and the oil droplets inside the capsule can be extracted even when stored in an atmosphere containing organic solvents. It was found that no unwanted coloring occurred with the coloring agent, and furthermore, no coloring of the capsule membrane occurred. However, among the aromatic polyvalent isocyanates having the above structural formula, microcapsules with such excellent properties can be obtained when used in combination with n.
Diphenylmethane diisocyanate in which n is 1 or more and n is 0 is ineffective. The reason for this is probably that the reaction of aromatic polyvalent isocyanates tends to proceed more easily than that of aliphatic polyvalent isocyanates, so even in the system of the present invention, the aromatic polyvalent isocyanates initiate polymerization first. Conceivable. Therefore, diphenylmethane diisocyanate where n is 0 tends to form linear polymers, and even if the terminal isocyanate group and aliphatic polyvalent isocyanate react, it will end up being a polymer with no crosslinking points. It is thought that a porous film is formed. Also, the structural formula is If a substance other than an aliphatic polyvalent isocyanate is used in combination with an aromatic polyvalent isocyanate in which n is 1 or more, there is no effect. For example, a technique is known in which a polyvalent isocyanate is used in combination with a polyvalent amine, a polyhydric alcohol, an epoxy compound, a polyvalent carboxylic acid, etc. to modify the capsule wall film. Even if it is used in combination with polyvalent isocyanate, the desired effect cannot be obtained. By the way, aromatic polyvalent isocyanates in which n is 1 or more have three or more isocyanate groups, and when all of the isocyanate groups react, the polymer that is produced spreads three-dimensionally and forms a dense wall film. However, if used alone, it lacks flexibility, resulting in the formation of a wall film with a low degree of polymerization. However, when an aliphatic polyvalent isocyanate with high flexibility is used in combination with this, the unreacted isocyanate groups of the aromatic polyvalent isocyanate react with the aliphatic polyvalent isocyanate, forming a three-dimensional network with a high degree of polymerization. It is thought that a solid, dense wall film with no coloration is formed. 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. These substances may be used alone or 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 containing substances, n must be 1 or more and must contain at least 10%, and if it is less than this, it is difficult to achieve the desired effect. On the other hand, specific examples of aliphatic polyvalent isocyanates include trimethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, ethyridine diisocyanate, 4-isocyanatomethyl-1, Polyisocyanate prepolymers of 8-octamethylene diisocyanate or adducts of these with polyvalent hydroxy compounds, polyvalent amines, polyvalent carboxylic acids, polyvalent thiols, epoxy compounds, or ethylene diisocyanate, decamethylene diisocyanate, lysine diisocyanate,
Trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, and other aliphatic polyvalent isocyanate trimer substances with the structural formula

[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. In order to produce microcapsules for pressure-sensitive copying paper using these materials, a hydrophobic liquid containing these wall materials and an electron-donating organic coloring agent is emulsified and dispersed in a hydrophilic liquid, and then The hydrophobic droplets may be coated by polymerization to form a polymeric material. In this case, the hydrophobic liquid may be a natural or Synthetic oils 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. Since the present invention relates to a method for manufacturing microcapsules used in pressure-sensitive copying paper, an electron-donating organic coloring agent that causes a coloring reaction with a coloring agent is dissolved in the hydrophobic liquid. . Examples of the color former include 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide,
3.3-Bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-
Triallylmethane compounds such as (1,2-dimethylindol-3-yl)phthalide, 4,4'-bis-dimethylaminobenzhydrylbenzyl ether, N-halofenyl-leucoolamine, N-
2.4.5-Diphenylmethane compounds such as trichlorophenyl leukoolamine, 7-diethylamino-3-chlorofluoran, 7-diethylamino-3-chloro-2-methylfluoran, 2-phenylamino-3-methyl-6- (N-ethyl-N
-Fluoran compounds such as p-tolylaminofluorane, benzoylleucomethylene blue, p-
Thiazine compounds such as nitrobenzylleucomethylene blue, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-
Examples include spiro compounds such as propyl-spiro-dinaphthopyran and 3-propyl-spiro-dibenzopyran. As the hydrophilic substance for emulsifying and dispersing the hydrophobic liquid, for example, a single or mixed aqueous solution of polyvinyl alcohol, gelatin, gum arabic, carboxymethyl cellulose, casein, etc. is used. Since the microcapsules for pressure-sensitive copying paper produced by the method of the present invention form a dense wall film, the pressure-sensitive copying paper coated with the microcapsules should be stored in an atmosphere containing an organic solvent. Even when the oil droplets inside the capsule are extracted and undesired color development occurs between the coloring agent layer and the oil droplets are extracted, even when subjected to unintentional weak pressure other than the pressure of writing or typewriter, etc. The capsules are not easily destroyed and have the advantage of being able to be made into highly concentrated paints and having excellent water resistance, which is unique to microcapsules made of synthetic polymer membranes. 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 30 g of diethyl diphenyl. Add polymethylene polyphenyl isocyanate, an aromatic polyvalent isocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Milineoto") to this oil-based liquid.
MR500'', n=0 is 26% in the structural formula, n=1
34% of n = 2, 9% of n = 2, and 28% of n = 3 or more) and 3 g of hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate, were dissolved. This oily liquid was dissolved in 1 g of polyvinyl alcohol and 1 g of carboxymethyl cellulose.
50 g and stirred vigorously to obtain a dispersion with an average particle size of 9 μm. After stirring this at room temperature for 30 minutes, the temperature of the system was raised to 60°C.
After heating to ℃ and stirring for 1 hour, the temperature of the system was further increased to 80℃.
Microcapsules were produced by heating the mixture to a temperature of 100.degree. C. to carry out a polymerization reaction. Example 2 3-(p-dimethylaminophenyl)-3-(1.2-dimethylindol-3-yl) as a color former
Dissolve 0.5 g of phthalide and 0.4 g of p-nitrobenzylleucomethylene blue in 30 g of isopropylnaphthalene. Polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name "Millionate MR300"), which is an aromatic polyvalent isocyanate, is added to this oil-based liquid.
0 is 50%, n=1 is 16%, n=2 is 7%, n=3
5 g of an adduct of 4 g of 19% mixture) and 3 moles of lysine diisocyanate, which is an aliphatic polyvalent isocyanate, and 1 mole of trimethylolpropane.
and dissolve. To this, 0.2 g of dibutyltin dilaurate is added as a catalyst. This oily liquid was added to 60 g of water in which 1.2 g of gum arabic and 1.8 g of polyvinyl alcohol were dissolved.
A dispersion with an average particle size of 8 μm was obtained by vigorous stirring. This was heated to 70°C and stirred for 2 hours to carry out a polymerization reaction and produce microcapsules. Example 3 As a color former, 0.7 g of crystal violet lactone, 0.2 g of 2,4-dimethyl-7-dimethylaminofluorane, and 30 g of dimethyl diphenylethane were dissolved. Polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name "Millionate MR100", structural formula: n=
0 is 45%, n=1 is 26%, n=2 is 9%, n=3
5 g of the above mixture (16% mixture) and 3 g of trimethylenehexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate, were dissolved. To this is added 0.1 g of tributyl lead acetate as a catalyst. This oily liquid was added to 50 g of water in which 1.5 g of carboxymethylcellulose was dissolved, and the mixture was stirred vigorously to determine the average particle size.
A 7μ dispersion was obtained. This was stirred at room temperature for 30 minutes, then heated to 60°C and stirred for 1 hour to perform a polymerization reaction, and then heated to 90°C to complete the reaction and produce microcapsules. Example 4 30 parts of zinc 3,5-di(α-methylbenzyl)salicylate, 8 parts of colloidal aluminum oxide (bulk height 23.7 ml/g), and 15 parts of nitrocellulose were mixed with 15 parts of ethanol and 30 parts of ethyl acetate. was added to a mixed solvent of 35 parts of butyl acetate, and sufficiently stirred in a propeller mixer to obtain a color developing ink. The capsule coating liquid 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. Example 5 Crystal violet lactone as a coloring agent
Dissolve 0.8g and 0.5g of benzoylleucomethylene blue in 30g of diisopropylnaphthalene. Add polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Millionate"), which is an aromatic polyvalent isocyanate, to this oily liquid.
MR300'', in the structural formula, n=0 is 50%, n=
4g of a mixture of 16% of 1, 7% of n=2, and 19% of n=3 or more) and an adduct of hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate, and a polyhydroxy compound (manufactured by Nippon Polyurethane Co., Ltd.). , trade name "DC-2738", isocyanate group content: 16.5 wt%, viscosity: 11000 cps/25°C). This oily liquid is dissolved in 1 g of polyvinyl alcohol and 1 g of carboxymethyl cellulose in 50 g of water.
and stirred vigorously to obtain a dispersion with an average particle size of 8μ. This was heated to 85°C and stirred for 5 hours to carry out a polymerization reaction and produce microcapsules. Example 6 Crystal violet lactone as a coloring agent
Dissolve 0.8 g and 0.5 g of benzoyl leucomethylene blue in 30 g of diisopropylnaphthalene. Polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name "Millionate MR100"), which is an aromatic polyvalent isocyanate, is added to this oil-based liquid.In the structural formula, n=0 is 45%, n=1 is 26%, n
= 9% mixture of 2 and 16% n = 3 or more) 3g
, 3 g of an adduct of hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate, and a polyhydroxy compound (manufactured by Nippon Polyurethane Co., Ltd., trade name "DC-2738"), and hexamethylene diisocyanate having an isocyanurate ring as shown below. 2 g of trimer (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate-EH") is dissolved. This oily liquid is dissolved in 1 g of polyvinyl alcohol and 1 g of carboxymethyl cellulose in 50 g of water.
and stirred vigorously to obtain a dispersion with an average particle size of 9μ. This was heated to 80°C and stirred for 4 hours to carry out a polymerization reaction and produce microcapsules. Example 7 Crystal violet lactone as a coloring agent
Dissolve 0.8g and 0.5g of benzoylleucomethylene blue in 30g of diisopropylnaphthalene. Add polymethylene polyphenyl isocyanate (manufactured by Nippon Polyurethane Co., Ltd., product name "Millionate"), which is an aromatic polyvalent isocyanate, to this oily liquid.
MR100'', in the structural formula, n=0 is 45%, n=
A mixture of 26% of 1, 9% of n=2, and 16% of n=3 or more) 4g, trimer of hexamethylene diisocyanate having an isocyanurate ring (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate EH") 2g ,
Furthermore, an alicyclic polyvalent isocyanate represented by the following structural formula (manufactured by Hüls, product name "IPDI")
-T1890'') 2g. This oily liquid is dissolved in 1 g of polyvinyl alcohol and 1 g of carboxymethyl cellulose in 50 g of water.
and stirred vigorously to obtain a dispersion with an average particle size of 7 μm. This was heated to 85°C and stirred for 4 hours to carry out a polymerization reaction to obtain microcapsules. Comparative Example 1 In Example 1, 8 g of polymethylene polyphenyl isocyanate (trade name "Millionate MR500"), which is an aromatic polyvalent isocyanate, was used alone without using hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate. Microcapsules were produced in the same manner as in Example 1 except for the following. Comparative Example 2 In Example 1, hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate, was not used, and diphenylmethane-4,4'-diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., trade name "Millionate MT") was used as an aromatic polyvalent isocyanate. Microcapsules were produced in the same manner as in Example 1, except that 8 g of the compound (in the structural formula, n=0 is 100%) was used alone. Comparative Example 3 In Example 1, polymethylene polyphenyl isocyanate, which is an aromatic polyvalent isocyanate, was not used, and 8 g of hexamethylene diisocyanate, which is an aliphatic polyvalent isocyanate, was used alone.
Microcapsules were produced in the same manner as in Example 1 except that the following procedure was used. Comparative Example 4 In Example 2, diphenylmethane-4.4'-diisocyanate (trade name "Millionate MT" in the structural formula, n = 0
Microcapsules were produced in the same manner as in Example 2, except that 100% microcapsules were used. The microcapsule dispersion prepared in the above examples and comparative examples was applied to a base paper of 44 g/m ² at a dry weight of 4 g/m2.
When the coating was applied so as to have a coating thickness of m ² and a quality test was conducted, the following results were obtained.

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Claims (1)

[Claims] 1. The structural formula is 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 a polymer substance is generated at the interface to form hydrophobic droplets. 1. A method for producing microcapsules for pressure-sensitive copying paper, the method comprising: coating microcapsules on pressure-sensitive copying paper. 2. The method according to claim 1, wherein the ratio of aromatic polyvalent isocyanate and aliphatic polyvalent isocyanate is 1:0.01 to 100.