JP2502171B2 - Microcapsules and pressure-sensitive copying paper using the microcapsules - Google Patents

Description

TECHNICAL FIELD The present invention relates to thermally stable microcapsules and pressure-sensitive copying paper using the microcapsules.

(Prior art) Microcapsules are obtained by coating a core material with a finely dispersed rear wall film and are suitable for stably holding unstable substances or liquid substances. It has been applied to adhesives, dyes, liquid crystals, etc., but the most well-known application is pressure-sensitive copying paper.

Conventionally, as a microcapsule manufacturing method, a complex coacervation method, an interfacial polymerization method, an in-situ polymerization method, a mechanochemical method, and the like are known, and each has its advantages and disadvantages. Although the interfacial polymerization method microcapsule manufacturing method has the characteristic that the manufacturing method is simple, it becomes a thermally unstable microcapsule because the capsule wall film is thin and the film quality is porous and poor in denseness. It has the drawback of being lost. Many polyvalent isocyanate compounds used for the production of microcapsules using the interfacial polymerization method are known. For example, MDI-based compounds such as diphenyl methane-4,4 'diisocyanate, polymethylene polyphenyl diisocyanate and 3-3' dimethyl diphenyl methane diisocyanate described in JP-A-57-140638 and JP-A-64-72886. Polyvalent isocyanate compound, 2-6 tolylene diisocyanate described in JP-A No. 61-120633, TDI polyvalent isocyanate compound such as 2-4 tolylene diisocyanate, hexamethylene diisocyanate described in JP-A No. 60-227828. , Propylene-1,2 diisocyanate, butylene-1,2-diisocyanate, and other aliphatic polyisocyanate compounds, 1.1.1.-trimethylolpropane and tolylene diisocyanate trimolecular adduct, and 1.1.1 trimethylolpropane and hexa Polyvalent isocyanate compounds such as adducts of three molecules of methylene diisocyanate Adduct of polyol compounds, biuret conjugate of hexamethylene diisocyanate 3 molecules of JP 55-159990 JP, isocyanurate bond structures such as tolylene diisocyanate or hexamethylene diisocyanate 3 molecules are known.

However, the microcapsules prepared by the interfacial polymerization method, which are used alone or as a mixture thereof, have the major drawbacks that the capsule wall film is thin and the film quality is porous and thermally unstable as described above. When a certain microcapsule is used, for example, as a microcapsule for pressure-sensitive copying paper, it is unexpected due to the destruction of the microcapsule during the coating and drying process of the paint, the printing of the form foam paper, etc., or the normal handling and transportation of the product. Coloring will occur and the commercial value of the product will be significantly reduced.

(Problems to be Solved by the Invention) The present invention is to provide thermally stable microcapsules by an interfacial polymerization method using a polyvalent isocyanate compound and a compound having active hydrogen.

(Means for Solving the Problems) The present invention uses, as a polyvalent isocyanate compound, o-tolidine diisocyanate in an amount of 1 to 90% of all polyvalent isocyanates.
It is characterized in that it is contained in an amount of wt%, which makes it possible to dramatically improve the heat resistance and solvent resistance of the microcapsules. As a method for producing o-tolidine diisocyanate, a method in which phosgene is reacted with o-tolidine is generally used. As the polyvalent isocyanate compound having another structure used in combination with o-tolidine diisocyanate, any type of isocyanate can be used as long as it can be dissolved in an oily liquid that is a capsule inclusion, and typically, The structure described in the section of the related art can be exemplified.

The general method for producing the microcapsules of the present invention is described below.

1) o-Tolidine diisocyanate and a polyisocyanate compound having another structure to be used together with it are dissolved in an oil medium together with a target substance to be encapsulated to prepare an oily core substance.

2) Prepare an emulsified aqueous solution in which a compound having active hydrogen and an emulsifying / protective colloidal agent are dissolved.

3) The oily core substance of 1) above is emulsified and dispersed in the emulsified aqueous solution of 2).

4) At the interface between the oily core substance and the emulsified aqueous solution, a polyvalent isocyanate compound and a compound having active hydrogen are reacted to form a film, which is encapsulated.

 It consists of the above four steps.

In the case of pressure-sensitive copying paper microcapsules, the target substance to be encapsulated is often an electron-donating color former, but it is of course possible to manufacture microcapsules containing no electron-donating color former. The microcapsules can also be used as a stain-preventing material by using them together with ordinary microcapsules for pressure-sensitive copying paper as described in JP-A-62-267184.

Specific examples of the electron-donating color former, which is a dye for pressure-sensitive copying paper, include 3,3-bis- (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone) and 3,7- Bis- (dimethylamino) 1
0-benzoylphenothiazine, di- (N-methyl-N
-Phenylanilino) -carbazolylmethane, 3-diethylamino-6-methyl-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-o-phenyl-dimethylanilinofluorane and the like. .

Oily media for dissolving these dyes for pressure-sensitive copying paper include phenylxylylethane, phenylxylylmethane, phenylethylphenylethane, diarylalkanes such as phenylbutylphenylmethane, alkylbiphenyls such as isopropylbiphenyl, and butylbiphenyl, and partial biphenyls. At least one kind of alkylnaphthalene such as hydrogenated terphenyl and diisopropylnaphthalene is used as a main solvent.

As the emulsifying / protecting colloid agent, for example, water-soluble polymers such as polyvinyl alcohol, gum arabic, gelatin, carboxymethyl cellulose, casein, ethylene maleic anhydride copolymer, and acrylic acid copolymer can be used.

Known compounds can be used as the compound having active hydrogen. Polyamines such as ethylenediamine, diethylenetriamine, hexamethylenediamine, triethylenetetramine, piperazine, amine adducts of epoxy compounds, catechol, resorcin, 1,2 hydroxy-4-methylbenzene, bisphenol A, ethylene glycol, 1,3 Propylene glycol, 1,4 butylene glycol, polyhydric alcohols such as glycerin, and water.

(Function) Although the reason why the heat resistance and the solvent resistance of the capsule wall film are dramatically improved by the present invention is not clear, the capsule of the polymer compound produced by the reaction between the polyvalent isocyanate compound and the compound having active hydrogen is not clear. It is believed that the film has a dense and thick structure due to the addition of o-tolidine diisocyanate.

Next, the present invention will be described with reference to examples. In the following examples,% and parts are% by weight and parts by weight.

(Example) Example 1 After dissolving 3 g of crystal violet lactone (CVL) as an electron-donating color former in 82 g of a solvent (trade name Hisol SAS-296 manufactured by Nippon Petrochemical Co., Ltd.) containing diarylalkane as a main component, Further, as 3 g of o-tolidine diisocyanate and a polyisocyanate having other structure,
12g HDI 3 molecule isocyanurate conjugate polyvalent isocyanate compound (Product name Coronate EH Nippon Polyurethane Co.)
Was added and dissolved to obtain an oily core substance.

This oily core substance was added to 200 g of an aqueous solution for emulsification in which 4 g of polyvinyl alcohol (trade name Gohsenol GH-17 manufactured by Nihon Gosei) was dissolved with vigorous stirring to obtain an O / O having a diameter of 4 to 8 μ.
A W type emulsion was obtained. To this emulsion, 15 ml of 10% aqueous solution of ethylenediamine and 15 ml of 10% aqueous solution of diethylenetriamine were added, and the mixture was stirred at room temperature for 15 minutes, and then the temperature of the system was set to 65 ° C.

After reacting at this temperature for 1 hour, a polyurea resin was formed around the oily core substance to obtain microcapsules for pressure-sensitive copying paper coated with the oily core substance.

Example 2 Instead of 12 g of Coronate EH in Example 1, 10 g of
Microcapsules for pressure-sensitive copying paper were obtained in the same manner as in Example 1 except that HDI buret-conjugated polyvalent isocyanate (trade name Sumidule N-3600, manufactured by Sumitomo Bayer Urethane Co., Ltd.) was used.

Example 3 A microcapsule for pressure-sensitive copying paper was prepared in the same manner as in Example 1 except that 17 g of tetraxylylene diisocyanate (trade name Takenate m-TMDXDI Takeda Pharmaceutical Co., Ltd.) was used instead of 12 g of Coronate EH in Example 1. Prepared.

Example 4 Microcapsules for pressure-sensitive copying paper were prepared in the same manner as in Example 1 except that 10 g of Sumidule L and 6 g of o-tolidine diisocyanate were used instead of 12 g of Coronate EH in Example 1.

Example 5 To 80 g of carbon tetrachloride, 15 g of o-tolidine diisocyanate and 5 g of hexamethylene diisocyanate were added 4 g of cinnamic aldehyde as a perfume ingredient to obtain an oily core substance.
This oily core substance was added to 200 g of an aqueous solution for emulsification in which 4 g of Gohsenol GH-17 was dissolved with vigorous stirring and the diameter of 10 μm was added.
An O / W type dispersion was obtained. Thereafter, in the same manner as in Example 1, microcapsules for perfume were prepared. The heat resistance and solvent resistance of this fragrance capsule were good.

Comparative Examples 1 to 4 For pressure-sensitive copying paper as in Examples except that the o-trizine diisocyanate used in Examples 1 to 3 was not used and the amounts of the polyvalent isocyanate compound in each Example were changed to 15 g 13 g 20 g 16 g. Microcapsules were prepared.

The microcapsules for pressure-sensitive copying paper were evaluated as follows.

Preparation of test pieces 150 g of microcapsule slurries for pressure-sensitive copying paper obtained in Examples 1 to 4 and Comparative Examples 1 to 4 and 20 g of starch particles
Was added and water was added so that the concentration became 12% to obtain a test paint. This paint was applied to a base paper of 40 g / m ^{2 with} a No. 12 Meyer bar so that the solid content was 3.5 g / m ² to prepare a sample for heat resistance test. Further, this paint was similarly applied to the surface of the lower paper on which the color developer was applied to prepare a sample for a solvent resistance test.

Heat resistance test Capsule surface of test piece for heat resistance test and lower paper (made by Tojo Paper
The developer surfaces of NW40-B) were laminated facing each other and a load of 80 g / cm ² was applied, and the mixture was left in an oven at 105 ° C for 16 hours. The heat resistance of the capsule was judged by the degree of coloring of the lower paper. The coloring degree of the lower paper is a color difference meter (model TC-1500) manufactured by Tokyo Denshoku Co., Ltd.
It was measured by reflectance and displayed as a difference from the whiteness of the lower sheet before the test. The larger the difference, the poorer the heat resistance.

Solvent resistance test After leaving the test piece for solvent resistance test in saturated steam of methyl cellosolve (oxyethyl methyl ether) at 20 ° C for 1 hour, the stains on the surface of the color developer are similar to the heat resistance test. It showed solvent resistance. The larger the difference, the poorer the solvent resistance.

The test results are shown in Table 1. From Table 1, Examples 1 to 4 in which o-tolidine diisocyanate was used in combination as the polyvalent isocyanate were Comparative Examples 1 in which only polyvalent isocyanate was used without using o-tolidine diisocyanate in combination.
It can be seen that the heat resistance and solvent resistance are drastically improved as compared with those of Nos. 4 to 4.

(Effect) In the interfacial polymerization microcapsules using a polyisocyanate, the heat resistance and solvent resistance properties, which are said to be its drawbacks, are improved by using the diisocyanate mixture containing the o-tolidine diisocyanate of the present invention as a raw material for forming a capsule film. It has been dramatically improved, and it has become possible to encapsulate even those that cannot be applied with the interfacial polymerization method due to its drawbacks.

Claims (3)

(57) [Claims] 1. A microcapsule comprising an oily core substance and a polymer product whose main wall film is a polyvalent isocyanate compound and a compound having active hydrogen, wherein 1 to 90% by weight of o-tolidine is used as the polyvalent isocyanate compound. A microcapsule characterized by using diisocyanate in combination with 10 to 99% by weight of a polyvalent isocyanate compound having another structure. 2. An oily medium in which the oily core substance contains one or more diarylalkanes, alkylnaphthalenes, alkylbiphenyls, or partially hydrogenated terphenyls, and o-tolidine diisocyanate in the oily medium. The microcapsule according to claim 1, wherein the microcapsule is an oily core substance having a solubility of 100% by weight or less with respect to 100% by weight of the medium, and the oily core substance. 3. A pressure-sensitive copying paper having the microcapsules according to claim 2 on a support.