WO2002094942A9

WO2002094942A9 - Method of purifying polycyclic dyes

Info

Publication number: WO2002094942A9
Application number: PCT/US2002/016200
Authority: WO
Inventors: Victor Vasilievich Nazarov; Elena Nikolaevna Sidorenko
Original assignee: Optiva Inc; Victor Vasilievich Nazarov; Elena Nikolaevna Sidorenko
Priority date: 2001-05-21
Filing date: 2002-05-21
Publication date: 2003-04-10
Also published as: RU2209221C2; WO2002094942A1

Abstract

The disclosed invention pertains to technology of fabricating and purifying synthetic dyes and may be used in various areas of industry and national economy, particularly in fabrication of materials for polarizing coatings of various purposes. In this method of purifying polycyclic dyes, the original dye is processed at least once with concentrated hydrochloric acid in the presence of at least one nitrogen-containing organic compound, such as heterocyclic base and/or aliphatic and/or aromatic amine, and/or quaternary ammonium salt in the amount of 0.1-5% of the weight of the dye at 50-100°C with subsequent filtration. After that, the obtained press-cake is processed at least once with boiling glacial ascetic acid with subsequent hot filtration of the suspension. Obtained sediment is washed with distilled water, after which the sediment is repulped in water, filtered and dried.

Description

METHOD OF PURIFYING POLYCYCLIC DYES

BACKGROUND OF THE INVENTION Field of the Invention The invention pertains to technology of fabricating and purifying synthetic dyes and may be used in various areas of industry and national economy, particularly in fabrication of materials for polarizing coatings of various purposes. Description of the Related Art

The issue of increasing purity of the existent dyes is especially keen in the three cases, when dyes are used for obtaining devices requiring high precision and reproducibility of optical parameters, high homogeneity and structural perfection. Thus, there are dyes, derivatives of which form liquid crystal phase, which makes them useful in fabricating polarizing coatings of various purposes, including those for liquid crystal displays as described in PCT/US94/05493 ; WO 94/28073. Obtaining a polarizing coating, which is the functional element of a display, requires strict compliance with the manufacturing technology and high purity of the utilized materials. All known methods of purifying do not provide the necessary purity of dyes used for this purpose, which leads to large losses, on the stage of creating the coating as well as during certification of the final product. The presence of even negligible amount of admixtures in the dye may lead to non-homogeneity of the liquid crystal solution based on its derivatives, and will lower the quality of polarizing coating, which in turn will be reflected in optical properties of the final product.

The disclosed method is applicable for purifying polycyclic dyes, which do not dissolve in concentrated hydrochloric and glacial acetic acid and may be purified via extraction of admixtures. The most significance the disclosed method has for those dyes, derivatives of which are capable of forming liquid crystal phase. These dyes are used in fabricating optically anisotropic films, particularly polarizing coatings. These dyes include, for example, indanthrone (Nat Blue 4), dibenzoimidazole 1,4,5, 8-of naphthalenetetracarboxilic acid (Nat Red 14), dibenzoimidazole 3,4,9,10- perylentetracarboxilic acid, quinacridone (Pigment Violet 19) and others, as well as their mixtures such as described in PCT/US94/05493 and WO 94/28073.

There are known methods of obtaining and purifying synthetic dyes, based on recrystallization of dyes from solutions. Thus, there is a method of obtaining pure pigment dianthraquinone-Ν, Ν-dihydrazine and the product of its chlorination. The pigment is obtained via condensation of 2-aminoanthroquinone at an increased temperature in the presence of l,3-dimethyl-2-imidazolidinone with the help of an oxidant and an alkali condensing agent. Obtained product of condensation also undergoes additional processing, such as described in DE 3422385.

There is a known method of obtaining pure organic pigments of the group including anthanthrone, pyranthrone, indanthrone, etc., where the raw pigment is processed with acid ethers of polyphosphoric acid and primary, secondary or tertiary Cl- C8-alkanol, glycol, glycol ether or phenol at 0- 100°C, with subsequent hydrolysis of ether of polyphosphoric acid via heating aqueous solution up to 20-150°C and extraction of the pigment as described in DE 3432319.

There is a known method of obtaining pure pigment of the group including anthanthrone, pyranthrone, isoviolanthrone, flavathrone, indanthrone of naphthaldazene, indigo, thioindigo, naphthalenetetracarboxilic acid, dioxazine isoindolinone of perylentetracorboxilic acid and its bisimide, anthrapyrimidine, acylaminoanthraquinone, dianthraquinonyl, azoanthraquinone, azomethinanthraquinone and phthalocyanine and others as described in EP 0075182. Raw pigment is processed with polyphosphoric acid and their mixture is added with such quantity of water, ice or blendable organic liquid, so that the equivalent of the resulting mixture by H₃PO₄ was less than 40%. As a result of that, the pigment is extracted and filtered out.

All the listed methods of purifying are related to those using recrystallization. They yield sufficiently good results according to the degree of purity of the obtained pigment, however the mentioned methods may be applied only for the already sufficiently well purified pigment, and also do not provide purification from micro-admixtures, which determine to a large extent the capability of the dye or its derivatives to form stable lyotropic liquid crystal phase, and correspondingly to form a film with high degree of anisotropy.

There is a known method of purifying dyes, including polycyclic dyes, comprising the processing of the dye with mixtures of various inorganic and organic acids with the immiscible with water organic solvents. The method allows purifying the dye quite effectively as described in US5675002. The mentioned method may be used in the capacity of the closest analogue to the invention.

All the known methods of purifying have the following inherent drawbacks: a) when using raw materials with significant spread of admixture concentration, i.e. of poor quality, the known methods do not provide complete purifying, which in turn may lead to economic losses and flawed product; b) they are not applicable for purifying dyes used for fabricating optically anisotropic (particularly, polarizing) coatings, since they do not provide the necessary degree of purity and certain selectiveness of purification from a number of admixtures, presence of which significantly influences the possibility of obtaining stable lyotropic liquid crystal phase from the dyes, which does not allow obtaining the necessary properties of the liquid crystal solutions based on them, and as a consequence, the necessary degree of anisotropy of the films; c) due to losses during the purifying process with the known methods, their yield is significantly lower. The disclosed method of purifying polycyclic dyes may be used for purifying the raw pigment or as an independent processing of the already purified pigment immediately before application. The suggested method of purifying the pigment may be used along with other purifying operations, which would lead to an increase of purifying effectiveness. We have established that none of the known methods of purifying pigments allows selectively extracting just those admixtures, the presence of which significantly affects the capability of the dye to from stable lyotropic liquid crystal phase, and as a consequence, to obtain films with high degree of anisotropy and high reproducibility of parameters from that dye.

SUMMARY OF THE INVENTION

The disclosed invention pertains to technology of fabricating and purifying synthetic dyes and may be used in a variety of applications, particularly in fabrication of materials for polarizing coatings of various purposes. In one aspect of the present invention a method of purifying polycyclic dyes is provided comprised of: at least a single processing of the original dye with concentrated hydrochloric acid in the presence of at least one nitrogen-containing organic compound, such as heterocyclic base, and or aliphatic and/or aromatic amine, and/or quaternary ammonium salt in the amount of 0.1-5% of the weight of the dye at 50-100°C with subsequent filtration, at least a single processing with boiling glacial asetic acid of the obtained press-cake with subsequent hot filtration of the suspension, ablution of the obtained sediment with distilled water, and repulping of the sediment in water, filtration and drying. In another aspect of the present invention, the capacity of the nitrogen-containing organic compound uses one quinoline, and/or pyridine, and/or imidazole, and/or pyrazine, and/or l ,3-dimethyl-2-imidazolidinone, and/or aniline, and/or N- cyclohexylpropylendiamine, and/or tetrabutlammoniumchloride, and/or tetraethylammoniumchloride. Additionally, in the capacity of the dye one may use a dye, derivatives of which contain sulfo-, and/or carboxy-, and/or phosphate groups, are capable of forming liquid crystal phase.

In a further embodiment of the present inventoin, in the capacity of the dye one uses indanthrone (Nat Blue 4), or dibenzoimidazolel ,4,5, 8-naphthalentetracarboxylic acid (Nat Red 14), or dibenzoimidazole 3,4,9,10-perylenetetracarboxylic acid, or quinacridone (Pigment Niolet 19) or other polycyclic dyes and/or their mixtures.

In another aspect of the present invention the method further comprises at least one additional operation of ablution of the dye with distilled water with subsequent filtration on various stages of the process being performed if necessary.

In an additional embodiment the stage of processing the dye with concentrated hydrochloric acid in the presence of at least one nitrogen-containing organic compound with subsequent filtration is repeated from 2 to 8 times, while the stage of processing the dye with glacial ascetic acid with subsequent filtration is repeated from 2 to 4 times.

DETAILED DESCRIPTION OF THE INVENTION A technical result of the invention is the increase of degree of purity of polycyclic dyes. While purifying polycyclic dyes, derivatives of which form liquid crystal phase and are used in obtaining optically anisotropic coatings, the disclosed method allows extracting, along with others, also those admixtures, even minute amount of which lowers the capability of the dye to form stable lyotropic liquid crystal phase, from which, later, the anisotropic film is formed. The degree of anisotropy of the film prepared by the present invention will be significantly higher than the degree of anisotropy of the film obtained based on the dye that underwent purifying with other methods. Therefore, dyes purified with the disclosed invention method are applicable for obtaining high quality polarizing and other optically anisotropic films from them. Liquid crystal phase based on the dye that underwent purifying with the method of the present invention contains enlarged supramolecular complexes of the dye molecules ordered relative to each other. The degree of purity of the dye that underwent the processing of the present invention is no less than 99.9%. As a result of this processing, admixtures of the original compounds, for example amines, are extracted along with other admixtures.

Technical result is achieved by the fact that the method of purifying of polycyclic dyes comprises at least a single processing of the original dye in the concentrated hydrochloric acid in the presence of nitrogen-containing compounds, such as heterocyclic bases, and/or aliphatic and/or aromatic amines, and/or quarternary ammonium salts in the amount of 0.1-5% of the weight of the dye at 50-100°C with subsequent filtration, at least a single processing of the obtained press-cake with the glacial acetic acid while boiling with subsequent hot filtration, ablution of the sediment with distilled water, repulping of the sediment in water, filtration and drying. In the capacity of nitrogen-containing organic compounds one may use quinoline, and/or pyridine, and/or imidazole, and/or pyrazine, and/or l ,3-dimethyl-2-imidazolidinone, and/or aniline, and/or N- cyclohexylpropylendiamine, and/or tetrabutyl ammoniumchloride, and/or tetraethylammoniumchloride .

Any polycyclic dyes may be used in the capacity of the dye. However the most interest poses the use of the herein method for purifying dyes, derivatives of which, particularly those containing sulfo- and/or phosphate-, and/or carboxy-, and/or other groups, are capable to form lyotropic liquid crystal phase. In the capacity of the dye one may use indanthrone (Vat Blue 4), or dibenzoimidazolel ,4,5, 8-naphthalentetracarboxylic acid (Vat Red 14), or dibenzoimidazole 3,4,9,10-perylenetetracarboxylic acid, or quinacridone (Pigment Violet 19) or other polycyclic dyes and/or their mixtures.

If necessary, at least one additional operation of ablution of the dye in distilled water on various stages of the process with subsequent filtration is performed.

Drying of the dye is performed preferably at the temperature in the interval 50- 100°C during 10-30 hours.

On at least one stage of processing dyes with hydrochloric acid and water they are heated to 50- 100°C.

The stage of processing with concentrated hydrochloric acid with subsequent filtration is repeated preferably from 2 to 8 times, while the stage of processing with glacial acetic acid with subsequent filtration - from 2 to 4 times. The necessary number of cycles is chosen depending on the purity of the original dye.

Processing operations usually make use of the weight ratio of acids to the dye no less than 2.5 : 1. Distilled water is usually utilized for ablution of the dye.

The disclosed method may be applicable for purifying raw pigment and also as an independent process of additional purifying of the already prepared product in those cases when it is necessary.

When choosing reagents for embodiment of the method one should pay attention to the purity of the utilized reactants. Usually one would use reagents of analytic grade.

It should be noted that realization of the disclosed technical result may be ensured only on condition of implementation of all operations according to the claim 1 in the disclosed sequence. Concentration of hydrochloric acid should be no less than 35 %wt.

The duration of performing each of the operations of the disclosed method is determined with condition of achieving maximum effectiveness (completeness) of the process, should it be the extraction of the admixtures, ablution, drying or filtration.

The invention may be illustrated on a concrete example of purifying one of the most characteristic representatives of the considered group of dyes - indanthrone. Experimental Into a flask of volume 1L, equipped with a stirrer, one loads 180g of indanthrone,

540ml concentrated hydrochloric acid (d=l .18) and 9g of quinoline. Obtained suspension is stirred for 6 hours at 60°C and then filtered. This stage is repeated twice. The sediment is suspended in 540ml of glacial ascetic acid, the suspension is then heated and boiled during 2 hours and then filtered. This stage is also repeated twice. Obtained press-cake is suspended in 450ml of distilled water, stirred for 1 hour at 50°C and filtered, then it is washed with approximately 2 liters of distilled water so that pH = 5.0-6.0. Indanthrone is dried in the drying cabinet (t = 50-100°C) up to a constant weight during 10-12 hours. This process yields about 168g of purified indanthrone. Polarizing coatings have been fabricated based on the sulfo-derivatives of indanthrone, obtained from the dye, which was purified with the disclosed method, and which forms lyotropic liquid crystal phase.

To obtain anisotropic film (polarizing coating), one prepares liquid crystal solution, for which purpose one uses 3.0g of sulfonated dye- indanthrone, free from inorganic salts, which is dissolved while heated in 37ml of the solvent (water). Then solution is cooled to room temperature. Presence of liquid crystal phase is determined by observing solution under polarizing microscope, equipped with two crossed polarizers.

Liquid crystal solution is deposited onto a glass substrate measuring 100x100 mm² at room temperature and 70% humidity, and then a layer of liquid crystal measuring

80x80 mm² is formed via the following method. The rod in the form of rotating cylinder

20mm in diameter and 200mm long is placed over the flat surface of the substrate without possibility to move along it, but with possibility to rotate around its own axis. The ends of the cylinder are equipped with spacers lOμm thick and 5mm wide. It is these spacers that will determine the thickness of the forming film, since during the process of the external orienting action correction of the layer thickness is taking place. A stage, with the substrate fixed on it, is translated at the rate 20mm/sec relative to the stationary rotating cylinder, so that the cylinder is rolling on the surface of the substrate. In the process of that, the liquid crystal of the dye is uniformly distributed and aligned over the surface of the substrate. After drying, the aligned film of the dye has the following parameters: transmission T =40%, dichroic ratio D_ό/D_aa = 20-22.

Analogous results are obtained when purifying other polycyclic dyes, which later also were used to obtain anisotropic films. All films were of high quality, all had perfect structure, high uniformity, stability of properties and effectiveness of polarization. We have established that dyes that have been purified with the disclosed method provide good properties of polarizing coatings based on them. Even if the degree of purity of the dye obtained by the herein method and the one obtained by any other known method coincide (for example 99.9%), only the herein method of purification ensures obtaining high quality polarizing coatings based on that dye, which is apparently due to different selectiveness of purification in different methods. The herein method provides purification from particularly those admixtures, presence of which is unacceptable for obtaining polarizing coatings.

The foregoing description of specific embodiments and examples of the invention have been presented for the purpose of illustration and description, and although the invention has been illustrated by certain of the preceding examples, it is not to be construed as being limited thereby. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and many modifications, embodiments, and variations are possible in light of the above teaching. It is intended that the scope of the invention encompass the generic area as herein disclosed, and by the claims appended hereto and their equivalents.

Claims

1. A method of purifying polycyclic dyes, comprising: at least a single processing of the original dye with concentrated hydrochloric acid in the presence of at least one nitrogen-containing organic compound, such as heterocyclic base, and/or aliphatic and/or aromatic amine, and/or quaternary ammonium salt in the amount of 0.1-5% of the weight of the dye at 50-100°C with subsequent filtration, at least a single processing with boiling glacial acetic acid of the obtained press- cake with subsequent hot filtration of the suspension, ablution of the obtained sediment with distilled water, and repulping of the sediment in water, filtration and drying.

2. Method according to claim 1 , wherein in the capacity of the nitrogen-containing organic compound one uses quinoline, and/or pyridine, and/or imidazole, and/or pyrazine, and/or l ,3-dimethyl-2-imidazolidinone, and/or aniline, and/or N- cyclohexylpropylendiamine, and/or tetrabutylammoniumchloride, and/or tetraethylammoniumchloride

3. Method according to claims 1 or 2, wherein in the capacity of the dye one uses a dye, derivatives of which, those containing sulfo-, and/or carboxy-, and/or phosphate groups, are capable of forming liquid crystal phase.

4. Method according to any of the above claims, wherein in the capacity of the dye one uses indanthrone (Vat Blue 4), or dibenzoimidazole 1 ,4,5 ,8-naphthalentetracarboxylic acid (Vat Red 14), or dibenzoimidazole 3,4,9, 10-perylenetetracarboxylic acid, or quinacridone (Pigment Violet 19) or other polycyclic dyes and/or their mixtures.

5. Method according to any of the above claims, wherein at least one additional operation of ablution of the dye with distilled water with subsequent filtration on various stages of the process is performed if necessary.

6. Method according to any of the above claims, wherein the dye is dried at the temperature 50-100°C during 10-30 hours.

7. Method according to any of the above claims, wherein on at least one stage of processing the dye with hydrochloric acid and water, the dye is heated up to 50-100°C.

8. Method according to any of the above claims, wherein the stage of processing the dye with concentrated hydrochloric acid in the presence of at least one nitrogen- containing organic compound with subsequent filtration is repeated from 2 to 8 times, while the stage of processing the dye with glacial ascetic acid with subsequent filtration is repeated from 2 to 4 times.