JP2005270867A - Dissolving method of organic crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for dissolving an organic crystal in a high concentration and in a short time and for making it hard to deposit the crystal from the dissolved solution. <P>SOLUTION: The dissolving method is characterized by irradiating a mixture of the polar solvent and the organic crystal with a microwave, preferably the polar solvent being an organic solvent. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for dissolving an organic crystal suitable for preparing a high concentration solution of an organic compound.

  Organic dyes are used in a wide range of fields as printing inks, ink-jet inks, electrophotographic color toners, color filters, reflective displays, cosmetics, colorants for plastics, and the like. In addition, some organic dyes are being studied for use as functional materials different from the use as a colorant, for example, new materials in the technical field using photoelectron characteristics and EL characteristics.

  The properties of organic dyes such as dispersibility, rheological properties of blends, and optical properties vary depending on the purity, crystal particle size, particle size distribution characteristics, and particle shape. Therefore, it is very important to control the crystal particles of organic pigments, particularly organic pigments often used in a crystalline (crystal fine powder) state, in order to achieve a desired function.

  The present inventors have so far conducted research and development of technologies for producing nano-sized particles of organic compounds. Among them, an organic solvent in which an organic compound is easily dissolved is selected, and the solution is prepared and adjusted. The organic compound is poured into a poor solvent that is a poor solvent for the organic compound and is compatible with the organic solvent used for the preparation of the solution to precipitate the organic compound. Inventing a method for producing microcrystals called a reprecipitation method that produces nano-sized particles (Patent Document 1). According to this method, it is possible to produce organic pigment microcrystals with controlled crystal size, particle size distribution, and the like according to the purpose.

  In the reprecipitation method, it is important to dissolve the organic pigment in the first solvent. If the organic pigment can be dissolved at a high concentration, a large number of pigment microcrystals can be produced at once, and the efficiency of microcrystal production can be improved.

In this regard, Patent Document 2 discloses a method for preparing a pigment fine crystal dispersion by reprecipitation using an amide solvent as a solvent for dissolving an organic pigment. Thus, by using an amide solvent, organic pigments such as quinacridone and phthalocyanine can be dissolved at a relatively high concentration.
Japanese Patent No. 2723200 Japanese Patent Application No. 2002-252389

  However, in order to use the reprecipitation method industrially, productivity and economy beyond a certain level are required. Therefore, it is desirable to dissolve in a solvent at a higher concentration or in a shorter time. In addition, when performing the reprecipitation method industrially, the time from the adjustment of the solution to the dropping to the poor solvent, for example, due to the transfer of the solution, time is vacant compared to the operation at the laboratory level, When using a high-concentration solution, it is also important to prevent crystals from precipitating before dropping into the poor solvent.

  The problem of improving solubility and preventing precipitation is not limited to the reprecipitation method, but is a general problem of organic pigments. Most organic pigments are difficult to dissolve in general-purpose solvents, so even pigments with excellent functions may be impractical due to low solubility during reaction, purification, processing, etc. . Accordingly, it is an important issue for the whole organic pigment to dissolve the pigment in the solvent at a high concentration or in a short time and prevent its precipitation.

  Furthermore, not only organic pigments, but also organic compounds such as organic dyes in general, it is very important to dissolve them in organic solvents at high concentrations in a short time in order to directly improve handling and reduce costs. And its significance is very large.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for dissolving an organic crystal in a high concentration in a short time and making it difficult for the crystal to precipitate from the dissolved solution.

  As a result of intensive studies, the inventors of the present invention can dissolve the organic pigment in a short time and at a high concentration by irradiating the system in a state where the organic pigment is dispersed in the solvent. Further, it was found that the solution prepared by using this method is slower in crystal precipitation than the solution prepared by ordinary heating. In addition, it has been found that the same effect can be obtained even when this method is used for dissolving various organic crystals other than organic pigments in an organic solvent.

  That is, the present invention provides a method for dissolving an organic crystal characterized by irradiating a mixture of a polar solvent and an organic crystal with microwaves, and solves the above problems. According to this invention, organic crystals can be dissolved at a high concentration in a short time, and precipitation of crystals from the dissolved solution can be made difficult to occur. As the organic crystal, it is effective to use a dye, particularly a pigment having generally low solubility, and a quinacridone compound or a phthalocyanine compound is particularly preferable. The polar solvent is preferably an organic solvent. From the viewpoint of solubility, 1-methyl-2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylformamide, N, N -It is preferable to use an amide solvent selected from dimethylacetamide.

  According to the present invention, it is possible to dissolve the organic compound in a shorter time and at a higher concentration than when the organic compound is heated from the outside and dissolved in the solvent. Furthermore, since a solution in which organic crystals are dissolved using this method has a slow precipitation of dissolved organic compounds, a high-concentration solution is prepared, for example, in the case of industrial reprecipitation. Even when it takes a relatively long time to use it, it is useful because it can be kept stable in a solution state.

  Such an operation and gain of the present invention will be made clear from the best mode for carrying out the invention described below.

  The present invention will be described in detail below.

  The present invention is characterized in that microwaves are irradiated in order to prepare a solution of an organic compound. The microwave generally refers to an electromagnetic wave of 1 GHz to 300 GHz, but in the present invention, it is preferable to use an electromagnetic wave of 0.3 to 30 GHz, preferably 2.45 GHz. The irradiation method is not particularly limited, but in order to suppress a rapid temperature rise of the system, for example, irradiation at a fixed interval may be repeated several times to several tens of times, or may be irradiated continuously at a low output. it can. The irradiation time per time varies depending on the solvent and crystals used, but is usually about 0.1 to 60 minutes. In order to make the temperature distribution in the system uniform, it is preferable to stir for each irradiation or to perform irradiation while stirring.

  Usually, irradiation is performed so that the temperature does not rise to the boiling point of the solvent by the above irradiation method, but when a solvent having a high boiling point is used, it is below the boiling point from the viewpoint of preventing a side reaction between an undesirable solvent and a solute. However, it is preferable to control the temperature so as to be a certain temperature or less.

  As a microwave irradiation means, any known means can be used without any limitation. For example, use of a microwave oven is convenient because it is inexpensive and easy to obtain. It is also useful to use a microwave irradiation apparatus equipped with a control mechanism that adjusts the output and irradiation time so that the temperature does not exceed the set temperature.

  The organic crystal to be dissolved by the dissolution method of the present invention is not particularly limited and can be used regardless of whether it is a low molecular compound or a high molecular compound. Among them, the dissolution method of the present invention has a relatively high melting point and low solubility. Useful for organic dyes. In particular, it is useful for organic pigments which are generally very insoluble in solvents and have poor handleability.

  Organic dyes include azo, phthalocyanine, anthraquinone, quinacridone, cyanine, merocyanine, fullerene, dioxazine, anthrapyrimidine, anthrapyridone, l ansanthrone, indanthrone, flavanthrone, Perinone-based, thioindico-based, anthraquinone-based, and polydiacetylene-based compounds can be exemplified, but the dye skeleton is not limited thereto. For example, as a specific compound, C.I. in the color index (CI; published by The Society of Dyer's and Colorists). I. The thing which number is attached can be illustrated. Moreover, as an organic pigment, the compound classified into Pigment (Pigment) can be illustrated among them, However, It is not limited to this.

  Among them, it is useful to use the present invention for phthalocyanine compounds and quinacridone compounds, which are expected to be used as optoelectronic materials and EL materials, but need to be improved in handleability due to poor solubility. . Examples of the phthalocyanine compound include titanyl phthalocyanine, vanadyl phthalocyanine, copper phthalocyanine, metal-free phthalocyanine, aluminum phthalocyanine, iron phthalocyanine, nickel phthalocyanine, and cobalt phthalocyanine, and these may have a substituent on the phthalocyanine skeleton.

  The quinacridone-based compound includes unsubstituted quinacridone and quinacridone having a substituent on the aromatic ring. Examples of the quinacridone having a substituent on the aromatic ring include 2,9-dimethylquinacridone, 2,9-dichloroquinacridone, 2,9-difluoroquinacridone, 2,9-dimethoxyquinacridone, 3,10-dichloroquinacridone, and 4,11. -Dichloroquinacridone such as dichloroquinacridone, 2,9-dimethylquinacridone and the like.

  Among these, the present invention is particularly used as an electrophotographic photosensitive material or a color pigment, and titanyl phthalocyanine, copper phthalocyanine, unsubstituted quinacridone, 2,9-dimethylquinacridone, which is actually problematic in terms of solubility. It is preferably used for 2,9-dichloroquinacridone.

  The solvent used for dissolving the organic crystal is not particularly limited as long as it is a polar solvent, water; alcohol solvents such as ethanol, butanol, ethylene glycol; 1-methyl-2-pyrrolidinone, 1,3-dimethyl- Amide solvents such as 2-imidazolidinone, 2-pyrrolidinone, ε-caprolactam, formamide, N-methylformamide, N, N-dimethylformamide, acetamide, N-methylacetamide; ketone solvents such as acetone, methyl ethyl ketone; acetic acid Ester solvents such as ethyl, ethyl butyrate and n-butyl propionate; Ether solvents such as tetrahydrofuran and dioxane; Nitrile solvents such as acetonitrile, benzonitrile and propionitrile, chloroform, dichloromethane, bromobenzene, dibromobenzene, Robenzen, halogenated solvents dichlorobenzene; n-methyl-2-pyrrolidone, dimethyl aniline, dibutyl aniline, amine solvents such as diisopropyl aniline; dimethyl sulfoxide, and sulfur-containing solvents sulfolane and the like. Further, a salt having a relatively low melting point such as tetramethylammonium hydroxide, tetramethylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, specifically preferably 100 ° C. or less, more preferably 50 ° C. or less. It is also possible to use a salt that is liquid and a so-called ionic solvent. The solvent used may be a single solvent or a mixed solvent obtained by mixing a plurality of solvents. Which solvent is used is appropriately selected depending on the organic compound to be dissolved and the use of the solution. From the viewpoint of solubility, an amide solvent is preferable, and particularly for a poorly soluble organic pigment, 1-methyl-2-pyrrolidinone, 1,3-dimethyl-2-imidazolidine is particularly preferable from the viewpoint of its boiling point and solubility. Non, N, N-dimethylformamide and N, N-dimethylacetamide are preferably used. Most preferred among these is 1-methyl-2-pyrrolidinone.

Examples will be shown below, but the present invention is not limited thereto.
(Example 1)
1.87 g of unsubstituted linear quinacridone pigment fine powder purchased from Tokyo Chemical Industry is placed in a 500 ml Erlenmeyer flask, and further treated with anhydrous 1-methyl-2-pyrrolidinone (common name: N-methylpyrrolidone (NMP)) 300 mL And left for a while. Then, the microwave (2.45 GHz, 1 kW) was repeatedly irradiated to the Erlenmeyer flask using a commercially available microwave oven. The liquid in the flask was thoroughly stirred for each irradiation, and this operation was repeated until there was no fine powder floating on the bottom of the flask. The irradiation time per time was 10 seconds to 2 minutes, and the temperature of the liquid at that time was carefully measured so as not to exceed 190 ° C. As a result, a fluorescent 20 mM NMP red solution was obtained. The absorption spectrum (optical path length: 0.1 mm) of this solution is shown in FIG. Two absorption peaks at 490 nm and 520 nm are characteristic of the solution, and it can be seen that the red solution obtained in this example is a solution in which quinacridone is completely dissolved. Moreover, when the obtained solution was further diluted by adding NMP, no change in the spectrum was observed other than the decrease in absorbance. Further, no precipitation of crystals was observed even when the solution obtained in this example was allowed to stand at room temperature for 15 hours.

(Example 2)
In a 500 ml Erlenmeyer flask, 681 mg of a commercially available 2,9-dimethylquinacridone pigment fine powder was added, and 200 mL of NMP subjected to anhydrous treatment was further added and left for a while. Then, the microwave (2.45 GHz, 1 kW) was repeatedly irradiated to the Erlenmeyer flask using a commercially available microwave oven. The liquid in the flask was thoroughly stirred for each irradiation, and this operation was repeated until there was no fine powder floating on the bottom of the flask. The irradiation time per time was 10 seconds to 2 minutes, and the temperature of the liquid at that time was carefully measured so as not to exceed 180 ° C. As a result, a highly transparent 10 mM NMP red solution was obtained. Further, no precipitation of crystals was observed even when the solution obtained in this example was allowed to stand at room temperature for 12 hours.

(Example 3)
Into a 500 ml Erlenmeyer flask, 174 mg of a commercially available titanyl phthalocyanine pigment fine powder was added, and 300 ml of anhydrous NMP was further added and left for a while. Then, the microwave (2.45 GHz, 1 kW) was repeatedly irradiated to the Erlenmeyer flask using a commercially available microwave oven. The liquid in the flask was thoroughly stirred for each irradiation, and this operation was repeated until there was no fine powder floating on the bottom of the flask. The irradiation time per time was 10 seconds to 2 minutes, and the temperature of the liquid at that time was carefully measured so as not to exceed 150 ° C. As a result, a highly transparent 2 mM NMP solution was obtained. The color of the solution was emerald green. In addition, no precipitation of crystals was observed even when the solution obtained in this example was allowed to stand at room temperature for 6 hours.

Example 4
In a 500 ml Erlenmeyer flask, 63 mg of commercially available copper phthalocyanine pigment fine powder was added, and 200 mL of NMP subjected to anhydrous treatment was further added and left for a while. Then, the microwave (2.45 GHz, 1 kW) was repeatedly irradiated to the Erlenmeyer flask using a commercially available microwave oven. The liquid in the flask was thoroughly stirred for each irradiation, and this operation was repeated until there was no fine powder floating on the bottom of the flask. The irradiation time per time was 10 seconds to 2 minutes, and the temperature of the liquid at that time was carefully measured so as not to exceed 150 ° C. As a result, a highly transparent 2 mM NMP solution was obtained. The color of the solution was blue. Further, no precipitation of crystals was observed even when the solution obtained in this example was allowed to stand at room temperature for 10 hours.

(Example 5)
In a 500 ml Erlenmeyer flask, 36 mg of commercially available fine C ₆₀ pigment powder was added, and 200 mL of NMP subjected to anhydrous treatment was further added and left for a while. Then, the microwave (2.45 GHz, 1 kW) was repeatedly irradiated to the Erlenmeyer flask using a commercially available microwave oven. The liquid in the flask was thoroughly stirred for each irradiation, and this operation was repeated until there was no fine powder floating on the bottom of the flask. The irradiation time per time was 10 seconds to 2 minutes, and the temperature of the liquid at that time was carefully measured so as not to exceed 150 ° C. As a result, a highly transparent 1 mM NMP solution was prepared. This liquid was allowed to stand at room temperature for 12 hours, but no crystal deposition was observed.

(Example 6)
In a 500 ml Erlenmeyer flask, 379 mg of a commercially available perylene fine powder was added, 75 ml of acetone was added and left for a while. Thereafter, irradiation of microwaves (2.45 GHz, 1 kW) for 5 seconds was repeatedly performed on the Erlenmeyer flask using a commercially available microwave oven. The flask was stirred well for each irradiation, and this operation was repeated until there was no fine powder on the bottom of the flask. As a result, a highly transparent 20 mM acetone yellow solution was obtained. Further, even when the solution obtained in this example was allowed to stand at room temperature for 30 minutes, no precipitation of crystals was observed.

(Comparative example)
As a comparative experiment of Example 1, 1.87 g of an unsubstituted linear quinacridone pigment fine powder was placed in a 500 ml Erlenmeyer flask and further treated with anhydrous 1-methyl-2-pyrrolidinone (common name: N-methylpyrrolidone (NMP )) The one with 300 mL added was heated to about 170 ° C. on a hot plate. When heating was continued as it was, a liquid having fluorescence was obtained after about 4 hours, but a considerable amount of fine powder remained and was in the state of a red turbid liquid. Further, no change was observed in the state of the liquid even when heating was continued for a longer time. Similarly, comparative experiments of Examples 2 to 5 were performed using a hot plate. However, even if heating for about 4 hours (about 150 to 170 ° C.) was continued, none of the fine powders were completely dissolved. It remained a cloudy liquid.
In addition, as a comparative experiment of Example 6, a product obtained by adding 75 ml of acetone to 379 mg of a commercially available perylene fine powder was similarly heated to about 50 ° C. on a hot plate. When heating was continued as it was, a liquid having fluorescence was obtained after about 4 hours, but a considerable amount of fine powder remained and was in the state of a yellowish liquid.

  Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the invention is limited to the embodiments disclosed herein. However, it can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and a dissolution method involving such a change is also included in the technical scope of the present invention. Must be understood.

2 is an absorption spectrum of a quinacridone pigment solution prepared in Example 1.

Claims (6)

A method for dissolving an organic crystal comprising irradiating a mixture of a polar solvent and an organic crystal with microwaves. The dissolution method according to claim 1, wherein the polar solvent is an organic solvent. The dissolution method according to claim 1 or 2, wherein the organic crystal is an organic dye. The dissolution method according to claim 3, wherein the organic dye is an organic pigment. The dissolution method according to claim 4, wherein the pigment is a quinacridone compound or a phthalocyanine compound. The organic solvent is an amide solvent selected from 1-methyl-2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylformamide, and N, N-dimethylacetamide. The dissolution method according to any one of claims 2 to 5.

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