Document eQn8YagEQJm6Zy86z0EJQeEe

N37235 it itSIl fH*X> 8 = JLR-59-1, No. k9 Serial Humber 18852 COMPANY CONFIDENTIAL * warn tv USORA F> S Dr. H. W, Elley (2) Dr. William Kirk Attt Mr. J, K. Reed (l) Dr. S, Lenher (ft) Mr. T. W. Stricklin (1) Mr. C. J. Darlington (1) Dr. 0. Stallmann (2) J. L. Files (2) E, I. DuPont de Nemours & Company Jackson Laboratory April 28. 1944 A* v'v%- "Monastral11 Colors (An Educational Survey of Established or Proposed Manufacturing processes for Phthalocyanlne Pigments and Textile Dyes) Problem Report N. M. Bigelow 0. Stallmann Division Head at 6,3814 DUP050041185 "Monastral" Colors (An Educational' Survey of Established or Proposed Manufacturing Processes for Phthalocyanine Pigments and Textile Eyes) (project Number 1311) N. M. Bigelow JLR-59-1, No. 49 Serial Number 18852 Object and Historical Background. The need for an educational survey of "Monastral" colors has become urgent in order to acquaint our various Engineering Groups and the Postwar Planning Committee with all pertinent chemical and operating information on established or proposed manufacturing processes which are expected to be operated after the war on a large scale in a new plant. Tentative plans for the design of this proposed plant, involving the selection of the preferred processes and the development of the most desir able equipment and operating techniques, have been under con sideration for some time and will be further studied by the various groups. The writer was requested to present all available process and product information on "Monastral" colors, most of which is of a strictly confidential nature, in a series of seminars which were attended by representatives of our Research Division, the Chemical Engineering Division, the Industrial Engineering Division, the Chambers Works Engineering Department, the Postwar Planning Committee and by those SemiWorks and Chambers Works operating groups which are involved in the manufacture of "Monastral" colors. An abstract of these discussions forms the body of this report. Period Covered by Report; The seminars on "Monastral" Colors were held in Jackson Laboratory between March 22, and April 19, 1944, Summary and Conclusions; The subject matter was presented in five seminars in the form of informal lectures by the writer which were followed by a general discussion. The presentation was arranged in the following order: & 6,382 =i DUP050041186 Phthalonitrile .i-v.-ryC CPC Chloride -Chide jl ... CPC Crude b "' . ' av.-' '" ; i<' t' .,, Monochloro CPC Crude. E. Polychloro CPC Crude Dry ' *1 Metal Free PC Sulfonated CPC Recrystallization of Crude CPC in Sulfuric Acid Finishing Processes 'Water-Dispersible 11 Monastral" Powders v ......... , ., < .. - ' "Monastral" Fast Blue 2R Duxql Fast Blue MBS ./ Coalesced Phtiialocyanine Pigments . ; Thiastral Green 2G and Related Textile Dyes Other.Phthalocyanine Compounds of.Potential Interest to ' the Trade .; *; . '* f- . ...* - - l '* ' Discussion: , 1.. - "':1 ;; 4 * Phthalonitrlle > ? r _/ In principle^ .the present-iSemiyWorks prQ^es^fdr^l^,.; ,';ii manufacture of phthalonitrlle is a catalytic. ^My^ation of phthalimide in the preseh'ce of amenta;- Gaseous phthall'c-1 ah-; \ hydride and ammonia are mixed at high temperatures, whereby phthalimide and water are formed. The-gaseous phthalimide and excess ammonia are passed over a catalyst at 475C. whereupon.v,ater is split out, ammonia is added, and phthalonitrlle is formed.' The final yield of dried phthalonitrlle is' about 75# of theory; phthalimide, ammonium phthalate and benzonitrile are formed as by-products. The reaction is reversible; at 525ttC. the chief product is phthalimide. .. . In the present Semi-Works process, phthalic anhydride is heated above its vaporization point in -preheaters. ` Gaseous phthalic anhydride is mixed with preheated gaseous-ammonia; at this point most of the phthalic anhydride is converted to phthalimide. The mixture of phthalimide and gaseous ammonia is passed through a preheater, which raises it to its reaction temperature, and then through the converter which contains the I ^ 6,383 =* DUP050041187 catalyst. This converter is now constructed of Inconel; aluminum was used in an earlier converter, and iron or stainless steel also appear to he suitable construction materials. The catalyst now used is essentially a basic aluminum phosphate Which is prepared specially at the Gray*s Perry Plant and shipped to the Dye Works. A number of other catalysts have been tested, but none appears to be quite as satisfactory as the basic aluminum phosphate catalyst. More study of new catalysts, and of the improvement in activity of our present catalyst, appear to be in order. The efficiency of the catalyst varies from batch to batch; a good method for determining the activity of a given catalyst, which does not depend on its operation in its intended use, would be of great value. During the catalytic reaction, a considerable amount of carbonaceous by-product forms on the surface of the catalyst, thus decreasing its efficiency. After approximately 4,000 pounds of phthalic anhydride has passed through the system. It is necessary to burn this carbon off, thus reactivating the catalyst. This Is accomplished by sweeping the system with carbon dioxide or nitrogen, and then passing air at a measured rate through the hot catalyst. When the carbon is burned off, the system is again swept with nitrogen and is then ready for further use. The catalyst suffers a slow irreversible loss of activity and must be replaced every 6 to 10 months, depending on its original activity. On the average one charge of catalyst weighing 150 to ISO pounds is capable of converting 250,000 pounds of phthalic anhydride to phthalonitrile. The only method of determining the activity of the catalyst is to follow its actual output in operation. When the over-all yield of phthalonitrile falls below 75#, the catalyst is changed. Economically, it would be profitable to change the catalyst more frequently and thus to reduce by-product losses, but the present design of the phthalonitrile converter makes the change of the catalyst a long and laborious task. The future converter should be designed to permit more rapid and convenient change of catalyst. 6,384 4 DUP050041188 There is no way of determining the efficiency of a catalyst other than by following its output in actual operation. A rapid means of analyzing the effluent vapors from the converter for their phthalonitrile content would he highly desirable. The mixture of phthalonitrile, water, by-products and excess ammonia passes directly from the converters into an upright chamber into-which cold water is sprayed. The gaseous phthalonitrile condenses immediately in the form of fine crystals. The ammonia, phthalic anhydride, and benzonitrile largely dissolve in the waterj part of the unconverted phthalimide is hydrolyzed to ammonium phthalate which also dissolves. Some of the phthalonitrile also goes into solution. The yield of phthalonitrile at the moment it leaves the catalytic converter is probably about 85 to 87# of theory. In passing through the spray tower it undergoes a loss of roughly 7# through solubility and hydrolysis, so that the yield at the base of the spray tower is approximately 77#. The suspension of phthalonitrile emerging from the spray tower is filtered as soon as possible. A part of the filtrate from this operation-is recirculated, since the use of enough fresh water in the spray tower to give a fluid suspension would cause too high solubility, losses* The filter cake is washed until neutral, blown and packed into drums. The filtrates, which contain the by-products and unconverted phthalimide, as well as a large excess of ammonia, are ditched at present. The practicability of recovering excess ammonia and other by-products in useable form was considered some time ago, at which time it was decided that the recovery of ammonia was possible but not profitable, and that other recoveries would be definitely unprofitable. Future increases in the scale of product, of course, change this picture. At the present time it appears worthwhile to re-investigate the question of by-product recovery upon an anticipated postwar scale. Chemically it is feasible to use an organic solvent Instead of water in the spray tower. It might be possible to select some solvent in which the main product and by-products were sharply different in solubility; this would facilitate the re covery of phthalonitrile in pure form and at the same time simplify the problem of recovering ammonia. An alternative procedure would be to use an inert organic solvent in which the phthalonitrile was readily soluble, and to redistill this entire mixture tinder vacuum. Some preliminary work on this _4_ 65885 ^ DUP050041189 suggested method has been carried out several years ago; its success would depend on finding a stabilizing agent to prevent decomposition of the phthalonitrile during distillation. , The wet phthalonitrile paste is sent to the hydrogen reduction building, where it is dried at 60-70 in graining bowls. The material can be dried easily in air ovens; grain ing bowls were used because of the decreased health hazards. Other methods for the production of phthalonitrile have been investigated, but none are as successful as the catalytic process outlined above. Originally, both DuPont and I.C.I. made their phthalonitrile by the dehydration of phthalamide in o-dichloro-benzene by means of phosgene, with an excess of dimethyl-aniline present as an acid acceptor. In the laboratory this method gives phthalonitrile of a high order of purity; but both DuPont and I.C.I. experienced great difficulty in the trans lation of the laboratory process into plant equipment. Chemically pure phthalonitrile is a white crystalline, solid melting at l4l*C. 'When pure, it is relatively stable, and can be distilled under diminished pressure without trouble. Traces of water and to a greater extent traces of alkalies, decrease its stability markedly. When heated in the presence of water or alkalies it polymerizes rapidly to a trimer which is no longer capable of conversion to CPC. Phthalonitrile as produced in the Semi-Works is not particularly stable to heat. Phthalonitrile. is considered a rathpr toxic chemical. Continued exposure to it may produce dermatitis and cyanosis. Its toxicity has been studied in Haskell laboratories; the results of this study indicated that It was definitely poisonous, although possibly not quite as toxic as the Dye Works precautions in its use vould indicate. In Semi-Works production samples are taken from each barrel of the wet phthalonitrile paste produced in the Semi-Works. These are composited and sent to the Semi-Works laboratory, where they are dried. The freezing point of the composite is determined: If it is above an arbitrary value, the material is considered suitable for use in the manufacture of CPC. There are no further specifications. Phthalonitrile is quantitatively hydrolyzed by boiling caustic to sodium phthalate and ammonia; however, this analysis is used only in doubtful cases. 5 DUP050041190 A further study of the properties of phthalonitri16 would be decidedly profitable. A project is being drawn up to in vestigate the following subjects: The physical and chemical properties of highly purified phthalonitrile as compared with those of chemically manufactured phthalonltrile; the possibility of stabilizing Semi-Works phth.alonit.rile against decomposition by heat; the effects of the purity of phthalonltrile on. the yield and quality of CPC; and the development of a more critical set of specifications for Semi-Works phthalonltrile. CPC Chloride Crude The 'Premix The phthalonltrile, copper salts, and sodium chloride from which CPC Chloride Crude is to be prepared must, be mixed very thoroughly before the synthesis proper. The mixing is carried out in a large Ni-clad mixer located in the grinding and mixing area. Care must be taken that the temperature of the mixer does not become too high, since this may lead to the trlmerization of the phthalonltrile. The mixture must be smooth, fine in texture (approximately 100 mesh) and uniform throughout. It is possible that an even finer subdivision of the reaction ingredients might promote a more rapid reaction and result in a higher yield; this point will be investigated. One part of sodium chloride is used per part of phthalo nitrile; the salt serves as a diluent, to temper the violence of the reaction that occurs when CPC is formed. Other inorganic diluents may be used; sodium sulfate was used extensively at one time in place of salt. However, the use of sodium chloride in the premix gives a Crude CPC which is more readily.removed from the continuous baker than is sodium sulfate. In addition, the salt-containing crude may be used directly for chlorination, while sodium sulfate would have to be extracted from the salt crude and replaced with sodium chloride. Due regard is given to the toxicity of phthalonltrile in preparing and handling the premix. For the chemical control of the premixing operation, each of every seven barrels of premix is sampled and composited. These composites are analyzed in the laboratory for waterinsoluble content (PH) and for cuprous chloride. A sample of 6 6,387 4 DUP050041191 the composite is baked in the laboratory; the laboratory chloride crude is extracted vith water and acid pasted* The quality of the premix is Judged by the weight yield and tinctorial strength of the product. CPC Chloride Crude In the preparation of CPC Chloride Crude, the PN;Copper Chloride:Salt premix is heated, either in a rotary baker or the continuous baker. Two rotary bakers, constructed of Iron and nickel, respectively, are in use at present. If the rotary baker process is chosen for postwar development, the baker should be constructed of nickel. The initial cost of nickel is higher, but its useful life is considerably longer and crudes prepared in nickel tend to be somewhat brighter than those prepared in iron. The rotary baker is a horizontal cylinder accommodating about 350 pounds of premix. It contains a number of metal bars of assorted sizes, the purpose of which Is to mix the reaction mixture during the reaction period and subsequently to grind the charge to a coarse powder. The baker is heated by gas flames to a temperature of 190200 over the course of an hour. As the reaction sets in, heat and fumes are -evolved vigorously; the reaction mass becomes pasty, later solidifying as the phthalonltrile is completely converted to CPC. The reaction is complete in an hour. The heat is cut off and the baker is allowed to cool with continued rotation, When the charge is cool enough to handle, the manhole cover is replaced by a grating and the baker is revolved until the charge has been dumped on the floor of the baker unit. The product of this process is called CPC Chloride Crude. \' * In the continuous baker process, the premix is placed in an endless chain of small trays, in layers about 1.5 inches deep. The trays are passed through a specially designed oven in which the trays are heated from below by electrical space heaters and from above by a battery of infra-red lamps. The passage of a tray through the oven requires about 20 minutes, at the end of which time the reaction is complete. On leaving the oven, the trays are inverted and fall against a breaker bar, whereupon the contents drop into a service drum. 6, ._-aj -7 DUP050041192 The yield of 100% CPC obtained at present in the rotary baker amounts to 90% of theory; the yield from the continuous baker is 86% to 87%. The continuous process is not inherently less efficient than the rotary process; mechanical improvements, especially in the charging mechanism, vould probably equalise these yields. It is estimated that both crudes contain about y% of phthalimide, J>% of phthalonitrile trimer, and 1% of Tinchanged phthalonitrile. The question as to which of these two processes is to be preferred in future plans remains undecided. The continuous process should be cheaper, although this is not the case at presentj it yields a purer product. On the other hand, no suitable continuous process has yet been developed for the manufacture of Monochloro CPC or Metal Free PC, and unless this can be accomplished, these latter two crudes must be produced in rotary bakers. Additionally, the sublimates which condense on the cooler surfaces of the baker occasionally Ignite, causing spectacular although relatively harmless fires. The rotary baker process gives the advantage of flexibility, since CPC, Monochloro CPC, and Metal Free PC Crudes can all be manufactured in the rotary baker by established processes. It is possible that future processes will involve the use of inert or reactive atmospheres such as nitrogen, carbon dioxide, and ammonia; the operation of such processes would be more feasible In the rotary baker thanin the continuous baker. The disadvantages of the rotary baker are that it is inherently more expensive'and * chemically less controllable than continuous process. At one '' stage of the rotary bake, it is possible for the pasty reaction mass to seal the open trunion of the baker, which may cause a serious explosion. 'While this danger has never materialised in DuPont*s experience, it nevertheless constitutes a real safety hazard. A number of patents exist which disclose the manufacture of CPC by the reaction of phthalonitrile and copper salts In an inert liquid organic diluent. This reaction has the advantages of avoiding premixing problems and of a more tempered and easily controllable reaction. Its disadvantages are that a considerable amount of pyridine or quinoline must be added to the reaction mixture as a promoter. Other problems arise In the separation, recovery, and re-use of the inert solvent, Jackson Laboratory has considered these solvent processes. Ve feel thatin general . they are inferior to our present established dry baking processes. DUP050041193 CPC can be prepared by the reaction of a mixture of phthalic anhydride and urea in the presence of catalysts. The reaction can be carried out in the presence of a limited number of solvents, the best of vhich is highly purified kerosene, or in-the absence of such solvents. Very recent vork indicates that under certain conditions the urea phthalic anhydride synthesis can be carried out in a rotary baker. The chief advantage of the urea-phthalic anhydride synthesis is that it permits the immediate transformation of phthalic anhydride to CPC, without passing through the intermediate phthalonitrile stage. This avoids the operating cost and loss in yield vhich are attendant on the transformation of phthalic anhydride to phthalonitrile. The chief disadvantage of the process is that it yields a crude vhich is inherently inferior to the crude obtained by our phthalonitrile process. To meet DuPont standards, present urea-phthalic anhydride crudes vould have to be subjected to a crystallisation from sulfuric acid, a procedure vhich would destroy much of its present cost advantage. The reaction is not a clean one and the use of large quantities of kerosene introduce both operating difficulties and a serious fire hazard. It must be admitted, however, that the advantage now enjoyed by the phthalonitrile process is a very slight one, and the relatively slight improvement in the quality or efficiency of the urea-phthalic anhydride process might make it a serious competitor of the phthalonitrile process. More work is urgently needed .to establish a firm basis of comparison between the two processes. CPC has been prepared by the reaction of ortho-dibromobenzene and cuprous cyanide in the presence of pyridine. This process gives a high quality product, but is too expensive to be considered seriously as a manufacturing process. Copper phthalocyanine may also be prepared by heating ortho-dichloro-benzene, cuprous cyanide, and pyridine under carefully controlled conditions. Yields as high as 65# of crude CPC have been obtained by this reaction. - The crude reaction product is a black glossy tar consisting of CPC mixed with a Complex of cuprous chloride, pyridine, and possibly CPC itself. The separation of pure CPC from this mixture may be expected to be a rather difficult and expensive procedure. Under normal conditions this process is not a serious competitor to the phthalonitrile processj under the present conditions, however, it may be a possible emergency process in the event that our . supply of phthalic anhydride is cut off. -9- j DUP050041194 For controlling the manufacture of CPC Chloride Crude, samples of every Charge are composited in groups of ten; these samples are sent to the Semi-Works laboratory, vhere they are extracted with ammonia, dried and acid pasted* They are acid pasted for yield and quality. grinding CPC Chloride Crude CPC Chloride Crude is discharged from the rotary baker in the form of a coarse powder; this material is passed through the micro pulverizer before further processing. CPC Chloride Crude continuous is discharged from the continuous baker in the form of "loaves," which must be crushed in a Holland mill and then micro pulverized. All chloride crudes must be ground to a fine particle size before further processing. All of these grinding operations," as well as the discharging of the rotary baker, create large amounts of blue dust, which constitute a health hazard as well as a nuisance. The discharging operation and both grinding operations are carried out under strong ventila tion; the exhaust gases are passed through a water scrubbing tower. Periodically the scrubbing water is filtered and the recovered CPC returned to the operation. CPC Crude E Before the CPC Crude can be acid pasted, it must be freed of all inorganic salts and of as many organic impurities as possible. This is accomplished by extracting the finely ground crude with dilute aqueous ammonia at a temperature as near the boiling point as possible. The slurry is filtered, the CPC is thoroughly washed and dried. The dried product is known as CPC Crude E. No chemical transformations occur in this process, only mechanical losses being encountered. Only material which is destined for acid pasting is given this treatment. Material which is to be converted to -Chloro CPC or which is to be finished by salt milling need not be extracted. Since the continuous baker yields a slightly purer compound because of the sublimation of volatile impurities, the greater part of our present production of CPC Chloride crude continuous is used in chlorination or salt milling. The greater part of the CPC Chloride Crude is ammonia extracted. * 10 Kmc*. 6,391 -3 DUP050041195 In the present control system, the CPC Crude E is analyzed for moisture and chloride content. Both should be completely absent. The extraction process presents no particular hazards or operating difficulties. A continuous extraction process, to be operated in series with a continuous baking process, would be of considerable economic advantage. Preliminary evidence indicates if the continuous baker product could be discharged into water while still hot the lumps disintegrate spontaneously. This observation might be a basis for a continuous extraction process. Monochloro CPC Crude E The synthesis of Monochloro CPC differs from that of CPC itself in that cupric chloride is used in place of cuprous chloride. Phthalonitrile, cupric chloride and salt are premixed by the same methods that are used in the manufacture of CPC itself. The premix is baked in a rotary baker. Since the reaction is somewhat less vigorous than the reaction of phthalonitrile with cuprous chloride, a baking temperature of 205 to 210 is required; otherwise the baking procedure is identical with that used for the preparation of CPC. In the laboratory the yield of Monochloro CPC is approximately 92# of the theoretical amount. On the large scale, the yield of Monochloro CPC Seems to be somewhat lower, amounting to about 80 to 85# of theory based on acid pasted purity. Monochloro CPC cannot be readily prepared in the continuous baker; the somewhat higher initial temperature permits partial fusion of the phthalonitrile, resulting in a stratification of the reaction mixture and the settling of some of the cupric chloride out of the sphere of reaction. The product discharged from the rotary baker is called Monochloro- CPC Chloride Crude. It is micro pulverized and extrac ted with dilute ammonia by the same process that is applied to CPC Chloride Crude. The dried product is called Monochloro CPC Crude E. After a suitable finishing process, Monochloro CPC (''Monastral" Past Blue BX Powder) is fairly similar to CPC In its physical form and properties. It is perceptibly greener than CPC {''Monastral" Past Blue B Powder), which itself contains approximately l/2 atom of chlorine per molecule. "Monastral" Past Blue BX is somewhat weaker than "Monastral" ,, 6*39.2 DUP050041196 Fast Blue B. Its chief advantage over the latter product Is that It does not tend to grow crystals when In contact with hydrocarbon solvents. The chief value of this pigment is in the preparation of paints, and until the ''Monastral" products invade the paint field, "Monastral" Fast Blue BX" (Monochloro CFO) will be a minor Item in the' "Mbnastral" picture. .* Polychloro CPC Theoretically all sixteen of the hydrogen atoms present in CPC may be replaced by chlorine. Replacement of the first eight to ten atoms is fairly simple, but from this point on chlorination becomes increasingly difficult. Our present standard product contains between 14 and 15 chlorine atoms with an average of 14.75. To our knowledge, hexa-deca-chloro CPC has never been prepared. In our present Semi-works process, CPC in the form of CPC Chloride Crude Continuous is chlorinated in suspension in an eutectic mixture of aluminum chloride and sodium chloride. The yield is 96# of the theoretical amount of Polychloro CPC containing about 14.75 chlorine atoms per molecule; this corresponds to a weight increase of 1.76, based on 100# starting material. Many other solvents than the above eutectic mixture have been tried but none was found to be satisfactory. The chlorination is carried out in 75-gallon enamel pots capable of producing 250 pounds of crude pigment per charge. Inconel kettles would be suitable, and future equipment will probably be constructed of this material. The present kettles are equipped with impeller type agitators, very efficient agita tion being, necessary to give a good yield and a satisfactory operating cycle; our present system of agitation can probably be still further improved. The kettles, two of which are now available, are heated with Dowtherm. The effluent gases from the chlorination consist of excess chlorine, hydrochloric acid, and sublimed aluminum chloride. They are highly corrosive. The present scrubbing system is constructed of Haveg and rubberlined iron; the hydrochloric acid and aluminum chloride are removed by a water spray, and the residual chlorine by a caustic scrubbing system. DUP050041197 5aie present operating process gives a product of satis factory quality, but requires very careful supervision and permits no deviations from standard practice. CPC Chloride Crude Continuous is use# because of its greater purity. This inter mediate, the aluminum chloride and the salt necessary to form the eutectic mixture are charged into the kettle alternately. The purpose of this procedure is to provide some mixing and to make sure that no intermediate vill remain on the surface of the reaction mixtures; any starting material left floating on the surface vill collect on the vails of the kettle above the liquid level and escape chlorination, giving an unsatisfactory blue product. If this difficulty could be overcome, it vould be advantageous to provide a separate premelting tank for the aluminum chloride and salt. The mixture is heated vithout agitation to its melting point; as soon as it is sufficiently molten, agitation and tlie addition of chlorine are started at once. Once underway, the chlorination must be continued vithout interruption; otherwise replacement of copper in the CPC by aluminum vill take place, yielding a blue and dull product. The normal rate of chlorination varies from charge to charge. The rate at which the chlorine is added is very critical; if it is too slow, the.reaction period is prolonged unduly and considerable replacement of copper by aluminum takes place. If the rate of addition is too rapid, decomposi tion of the CPC takes place. A suitable schedule for the addi tion of chlorine has been developed with the aid of a photo electric eye which measured the unconsumed chlorine in the effluent gases. This control instrument was unsatisfactory from an operating point of view and was soon abandoned. At present the chlorine is fed in according to a standard schedule. If the photo-electric eye, or a substitute for it, could be simplified, it would be a very valuable control tool. "When the chlorination is complete, the molten mass is drowned in a mixture of ice water' and hydrochloric acid. This slurry is filtered, washed and dried; the product is called Polychloro CPC Crude E. At present a sample of Polychloro CPC Crude E from each charge is brought into the laboratory, where it is acid pasted and tested for yield and quality. An alternative process has been developed in the laboratory in which the necessary chlorine is provided in the form of sulfur dichloride. The following process is visualized, but has not been tested beyond exploratory runs in a 5-gallon 6,394 ^ DUP050041198 autoclave: A nickel or enamel autoclave is charged with sulfur dichloride and CPC in the form of CPC Chloride Crude Continuous or CPC Crude E. Which of these two intermediates will be used will be determined by the chosen finishing process; if acid pasting is used, CPC Crude E will be required. If salt milling is to be employed, we prefer to use CPC Chloride Crude Continuous. The mixture of CPC and sulfur dichloride is heated to 150C., whereupon chlorination takes place. The gaseous by-products formed are passed through a pressure reflux Condenser, which returns sulfur monochloride and dichloride to the autoclave, and the hydrochloric acid Is allowed to escape through a bleed valve. At 150C. the chlorination is quite rapid; when it is complete, the reaction mixture is cooled partially. Chlorine is then introduced, whereupon the sulfur monochloride present is reconverted to' sulfur dichloride, which is distilled away from the reaction mixture into a suitable storage tank. This procedure is continued until the Polychloro CPC Crude in the autoclave is completely dry. This product is ready for the finishing step without further treatment. In order to be successful on a regular production scale, this proposed process visualizes a new type of equipment: A low pressure autoclave of non-corrosive metal, equipped with a heavy duty plow agitator similar to that used in a graining bowl. A nickel Popp kettle may be entirely suitable for this purpose. A 5-gallon unit has been ordered, in which further process development is planned. Another visualized process for the chlorination of CPC consists of a dry chlorination of a CPC:salt mixture with gaseous chlorine at 200. Although this process has not been demonstrated to give the desired (yellow and bright) shade product, it is believed feasible. Laboratory process studies will be undertaken as soon as a chemist can be made available for this work. Metal Free PC Crude Metal Free PC is prepared by heating a mixture of phthalonitrlle, a reducing agent and a strong base, together with an inert diluent (sodium chloride). It is assumed that the course of this reaction is the same as that of the formation of copper phthalocyanine. In the present manufacturing process, a mixture of phthalonitrlle, methyl glucamine, calcium oxide and salt is - 14 - 6,3954 DUP050041199 prepared In the Grinding and Mixing Area, according to the method used in preparing premixes for CPC. An iron or nickel rotary baker is charged with the proper amount of this premix and the necessary amount of calcium oxide . The baker is rotated at room temperature until the calcium oxide is thoroughly mixed into the other ingredients. The baker con taining the reaction mixture is heated first to 160 and then to 200#C., whereupon reaction takes place and the crude Metal Free PC is formed. The reaction is conlete in eight hours; the baker is rotated until the mixture is cool enough to handle, whereupon it is dumped. The product, called Metal Free PC Chloride Crude, is micro pulverised and converted to Metal Free PC Crude E Dry by a hot extraction with dilute hydrochloric acid. The use of an acid extraction is made necessary by the presence of calcium salts which must be removed before the acid pasting. The acid suspension is highly corrosive. Jackson Laboratory is studying means of eliminating the hydrochloric acid extraction; unless this can be done, the equipment to be used in this step must be made of corrosionresistant materials. Following the acid extraction, the Metal Free PC Crude E is filtered, washed acid free, and dried in corrosion-resistant ovens. The dried product is soft in texture, and requires only .mechanical sifting before the acid pasting step.. The yield of the combined baking and extraction processes is approximately 70# of theory on a 100# purity basis. An alternative process has been tested both in the laboratory and the Semi-Works in which the calcium oxide is replaced by sodium oxide. The same operating technique is used in both baking processes; the crude product of the sodium oxide co-bake is purified by extraction with hot- caustic solution, rather than with hydrochloric acid. The extracted crude is filtered, washed and dried; ordinary drying ovens are satisfactory with the sodium oxide product. In the laboratory the yield of Metal Free PC is 74-77# of theory by the calcium oxide process and 67-72# by the sodium oxide process. In Semi-Works operation, both processes yield 65-70# of theory. Both processes are new, and the data now available are Insufficient tp serve as a basis for final selection of the preferred process. The calcium oxide process can be carried out in either the iron or nickel bakers, while the sodium oxide process is restricted to nickel equipment; on the other hand, the sodium oxide process avoids the corrosive hydrochloric acid extraction. '15' 6,396 ^ DUP050041200 No continuous process for the preparation of Metal Free PC has been devised* Until this can be done, it must be assumed . that a rotary baker will be required in the future plant for the production of Metal Free PC. Metal Free PC was formerly prepared by refluxing phthalonitrile with sodium amylate in an excess of amyl alcohol. Che di sodium phthalocyanine thus formed vas filtered away from the excess amyl alcohol. The press cake, still vet vith amyl alcohol, vas slurried vith anhydrous methanol, vhereupon double substitution took place vith the formation of Metal Free PC and sodium methylate. Che Metal Free PC vas filtered, vashed first vith alcohol and finally vith vater and then dried. This former process vas quite expensive, and introduced a number of operating and health hazards. Its product vas con siderably inferior in tinctorial properties to that obtained by our present baking process. A number of alternative processes for the manufacture of Metal Free PC are described in the patent literature; none of them appears equal to our preferred process. Che I.C.I. has attempted unsuccessfully to develop a process for manufacturing Metal Free PC by preparing magnesium or tin PC and subsequently demetallizing this intermediate in sulfuric acid. All other methods use phthalonitrile as the starting material. According to present knovledge, our proposed plant must be equipped to produce phthalonitrile for conversion to Metal Free PC even if CPC is made by the phthalic anhydride:urea process* Metal Free as a product is dominated by an I.C.I. patent, under which DuPont has a license. Sulfonated CPC Copper phthalocyanine is readily sulfonated by fuming sulfuric acid. As many as four or five sulfonic acid groups may be introduced, but the solubility of such products is too high for commercial use. Commercial Sulfo CPC usually contains from 2.1 to 2.2 sulfonic acid groups per molecule. Sulfonated CPC has a limited commercial use in the dyeing of certain textile fibers; its chief use is in the dyeing of paper in the beater (as an aluminum lake) and in the preparation of an alcohol soluble phthalocyanine derivative (Luxol Fast Blue MSS) which will be discussed later. * 16 - ^>397 ^ DUP050041201 In DuPont *s present manufacturing process, CPC Crude E is mixed with 20# oleum at room temperature and heated to 80 to 85C. in a cast-iron kettle, The reaction mixture is held at this temperature until an arbitrary test indicates that the proper degree of sulfonation has been reached. The solution is drowned in ice-cold 10# trine; the greater part of the sulfuric acid is separated by decantation. The pasty product is re suspended in cold 10# brine, agitated briefly, filtered, and washed briefly with brine, A brick-lined tub is used in the drowning step. The dried product is standardized with salt and sufficient sodium carbonate to convert all of the Siilfo CPC to the sodium salt. The standardized product appears on the market under the trade name Pontamine Fast Turquoise 8GL. The I.C.I. has prepared sulfonated CPC derivatives by sub jecting mixtures of phthalic anhydride and mono-sulfo-phthalic anhydride to the urea melt. This product is not identical with a sulfonated CPC containing the same average number of Sulfo groups, but prepared by direct sulfonation of CPC. The differ ence is probably due to the fact that the disposition of the sulfo groups is predetermined in the synthetic product. The I.C.I. believe that the exhausting properties of the synthetic material are superior to those of the directly prepared product. The commercial value of this type of product is doubtful, but should not be overlooked altogether. Acid Purification CPC is soluble in 90# ^sulfuric acid at 100*0,, but separates out as an acid sulfate salt at room temperature. This process has been successfully used in the purification of grossly impure CPC, since most of the impurities normally present in CPC are soluble in 90# sulfuric acid at room temperature, DuPont*s present crudes are sufficiently pure to make this process un necessary. However, If any of the present urea-phthalic anhy dride. processes were to be used for the manufacture of crudes, an acid recrystallization of this type almost certainly would be necessary to permit us to maintain our present standards. Further improvement in competing standards might even make it necessary for us to submit our baker crudes to this crystallization process; this, however, is a very remote possibility at the present time. Finishing Processes The finishing process, which develops the shade and strength, is probably the most critical step in the entire process of 6,398=1 DUP050041202 manufacturing phthalocyanine pigments. There is no universal phthalocyanine pigment, vhich is adaptable to all of the uses to which it may he putj the finished pigments are all specially processed to meet the requirements of the application for which they are intended. All of the processes used in the finishing of phthalocyanine pigments involve the reduction of the ultimate particles of the pigment to very small dimensions, which brings out its full tinctorial strength. In order to accomplish this result, the crude pigment is dissolved in cold 98$ sulfuric acid at a tem perature of 0P to 5C. and then precipitated by sudden dilution of the concentrated acid solution with water. Three methods are used for the drowning of the acid solution. In the first method, known as high turbulence drowning, the sulfuric acid solution is introduced as a thin stream into a relatively large volume of cold water which is in a state of turbulent flow as the result of passage through a restricted tube; This procedure produces a pigment of. very jet masstone, which is suitable for the pro duction of soft powders, pastes for textile printing and barium rosinate lakes. The second method of drowning involves the same principle, the difference being that a lower degree of turbulence is effected by a modification of the drowning tube. This process,known as low turbulence drowning, produces a pigment of inter mediate masstone, particularly suited for flushing and for tex tile printing. In the third method of drowning, the acid solu tion is sprinkled in a thin stream over the surface of hot water, with vigorous agitation. This procedure, known as drip drowning, produces a pigment which is quite'milky in mas stone, and is par ticularly suited for the production of aluminum hydrate lakes. When the drowning by any of these three methods is completed, the acid solution is cooled, filtered through nitrated filter cloths and washed with water.until the cake is essentially acid free. The. press Cakes are designated as Pastes Crude Acid HT, LT, or D, according to the pigment and drowning process used. Another suggested acid pasting procedure which has been tested only in exploratory experiments by us, involves slurrying the crude phthalocyanine pigment at room temperature in sulfuric acid of a concentration not quite sufficient to permit solution. Under these conditions an acid sulfate of the pigment is formed in the form of very small crystals. When this suspension is drowned in water, hydrolysis takes place and the free phthalo cyanine pigment is set free in the form of very small crystals. - 18 r DUP050041203 A very attractive method of reducing phthalocyanine pigments to optimum particle size is the salt milling procedure. The crude pigment is ground with a considerable excess -of salt in a hall mill for a protracted period. Extraction of the ground pigmenttsalt mixture with dilute sulfuric acid at &Q>*C., fol** lowed by filtration and a thorough washing of the cake produces a pigment whose ultimate particles are exceedingly small and uniform in size. The physical form of the pigment can be varied between tfide limits by variation of the milling time,, Although this procedure is still experimental, it appears promising, and there good reasons to believe that the salt milling process may eventually displace all of the acid pasting processes now ' in use. When the salt milling is carried out on a sufficiently large scale, it should be cheaper than the present acid pasting pro cesses. CPC and Mohochloro CPC respond properly to all of the finishing processes described above. Polychloro CPC is not sufficiently soluble in 98$ sulfuric acid and must be dissolved in a mixture of monohydrate and chloro-sulfonic acid. The pasting process 3s carried out in a cast-iron tub, and the drowning (by the drip method) in a tile-lined tub. The pasting mixture, the drowned-solution, and the fumes'arising during the drowning procedure are allvery corrosive. High turbulence drowning Of Polychloro CPC is impracticable because of the hydrochloric add gases evolved during the" drowning step 1 ;.r Polychloro CPC responds satisfactorily to salt milling> and it is expected' that this -process will replace the present acid pasting processes. - - .Metal Free PC may be acid' pasted successfully by a modified high turbulence method, in which ^Lorol" is present as a modi fying agent and hot water is used for drowning. Drip drowning of Metal Free PC is practicable only if the drowning water is agitated very vigorously. Metal Free PC has only a limited stability in sulfuric acid; any delay in solution or pasting will result in seriously lowered yields. Metal Free PC-does', not' respond properly to salt milling; finishing by the acid crystallization method is under investigation at the present time. - 19 - 6,400 DUP050041204 The Ammonia Slurry Following the acid pasting step, the acid press cakes are re-suspended pi dilute ammonia and ammonium chloride at 6oC. This step must he carried out in equipment which is resistant to corrosion* When- the press, cake is thoroughly broken up, the mixture is filtered and Washed with water Until free of ammonia* preferably in a Wooden filter press. These ammonia slurried press cakes are called .'Paste Crudes (i.e,, 0PC Paste Crude iff; Monochloro CPC Paste Crude LT; Polychloro CPC Paste Crude D, in accordance with their composition and with the finishicgf process to which they have been subjected. Metal Free PC Paste Crude Acid HT is subjected to a caustic slurry rather than to an ammonia slurry. The purpose of the ammonia slurry is to remove the last traces of acid and ionic copper from the press cakes. The complete removal of acid is very importantj the presence of acid in the standardized product would cause rapid corrosion of the drums, with resultant contamination of the finished product. The complete removal of ionic copper is of importance only. If the product is to be used in rubber. The careful removal of traces of ionic copper from CPC destined for. other uses is probably unnecessary. Unsuccessful attempts have been made to neutralize various Pastes Crude Acid by washing the press cakes with ammonia in the press. If complete neutralization of the sulfuric acid could be effected in this way, the expensive and time consuming ammonia slurry could probably be avoided. If a suitable continuous filter could be found, the acid pasting and ammonia washing steps could probably be fused into one continuous operation. Grit Removal During the. process of manufacture * all "Moi\aatrain pigments pick up a considerable amount of foreign matter. This material is composed mainly of iron scale, sand or oinders,. wood fiber, and particles of the dried pigment itself. The presence of. this gritty material in the finished products is highly objectionable. Under the present system of farming out "Monastral" operations .* throughout the Chambers Works, contamination is almost unavoidable. If the entire "Monastral" operations were carried out under one roof by experienced operators, the grit problem would be greatly reduced; but it is doubtful whether it would be entirely overcome* - 20 - DUP050041205 At present the ammonia slurries of CPC are passed through a settling box before entering the filter press; this removes the coarsest and most objectionable grit, although it does not yield a fully satisfactory product. The ammonia slurry can also be passed through a 100-mesh vibrating screen, provided that the solids concentration of the slurry is not over Labor and handling costs are rather high, and the product is hardly superior to that obtained by the use of the settling box. Low speed.centrifuges are being studied in the laboratory, and tests on commercial centrifuges are planned. Dispersed phthalocyanine pastes may be passed through a fine vibrating screen, which gives a satisfactory product. Undispersed pastes and press cakes cannot be given this treat ment; here the settling box must be relied upon to give a satisfactory product. The principle of cyclone separation could be used to produce grit-free powder brands. This would call for the preliminary reduction of the particle size of the powder, and would give a light, dusty product which would not be readily accepted by the trade. St andardiz ation "Monastral" pigments are standardized in the form of press cakes, undispersed pastes, dispersed pastes, and powders Press cakes are homogenized in a heavy duty W & P mixer, and extruded through a pug mill into drums. This method is suitable for future operation, but precautions should be taken that this equipment does not contaminate the product with iron rust or dried particles of the press cake. Undispersed pulp ("Monastral" Fast Blue BND) is made by diluting the press cake with enough waterIn a "Day" mixer to produce a semi-fluid mass of standard tinctorial strength. In the manufacture of dispersed pastes, a mixture of press cake, water and dispersing agent is agitated until semi-fluid; it is then pumped back and forth through an F & B mill until a uniform paste of standard tinctorial strength is obtained. A considerable number of dispersing mills have been considered, of which the F & B mill appears most suitable * However, even this mill is not completely satisfactory. The finished paste is passed through a vibrating screen into drums. Acid pasted copper phthalocyanine cannot be converted to a powder brand by simple drying of the press cake; the individual particles cement together during the drying operation, producing a very hard powder of low tinctorial strength. The trade demands - 21 - 6,402 ^ DUP050041206 a soft, non-coherent powder which will develop Its full tinc torial strength after relatively few passes through anink mill* In the preparation of such a powder, the individual particles of pigment must be coated with a surface active agent before drying. DuPont * s present process for the manufacture of "Monastral" Fast Blue B Powder involves the treatment of a neutralized slurry of CPC Paste Crude Acid HT with a toluene: water emulsion of the condensation product of lauric acid and triethanolamine (TEA-C-12 ester). After treatment, the 'slurry is allowed to stand overnight; then it Is filtered and dried. Other soft powder treatment have been developed both by this company and competing companies; our process is probably as good as any known, although its product is contaminated with several per cent of the TEA-C-12 ester. "Monastral" pigments which have been finished by the salt milling process may be dried directly to produce soft powders; no special treatment is necessary. This is one of the great advantages of the salt milling process. Only CPC is given the soft powder treatment at the present time. Polychloro CPC and Metal Free PC may be prepared in the form of fairly soft powders by simple drying of the press cakes. These powders are not exceedingly hard, and are accepted by the trade; nevertheless, they are grittier and harsher in texture than is desirable. Eventually the trade will probably demand an improvement in the texture of these last named products. Pulverizing "Monastral" Powder Brands In the grinding of."Monastral" pigment powders, the de sired product is not an exceedingly fine powder, but a coarse powder in which the individual particles are large enough to prevent serious dusting, but still fine enough to be workable on the ink mill. The dry press cakes of "Monastral" products which are inherently soft (such as CPC which has been finished by salt milling or the soft powder treatment) may be reduced to satisfactory particle size by passage through a brush-sifter. The brush-sifter now in regular use was not designed for largescale operation; it is slow and creates too much dust. It is, however, sound in principle, and its present faults could be corrected by proper designing. - 22 - " 6,403 4 DUP050041207 The remaining "Monastral" powders are inherently harder in texture than the above products', and their reduction to a suitable particle size calls for more vigorous grinding than that provided by the brush sifter. Two hazards accompany the vigorous milling of "Monastral" powders; these are firing and loss of tinctorial strength. The Micropulverizer has been used to a considerable extent to grind "Monastral" products. Provided coarse screens are used, little or none of the tinctorial strength of the pigment is lost; firing in the mill, however, is fairly frequent. Firing can be cut down, but not altogether eliminated, by placing Dry Ice in the grinding hopper. The Mikronizer is unsuitable for grinding "Monastral" products; serious loss of tinctorial strength is common. The Limited Mill grinds "Monastral" powders without serious loss of tinctorial strength, but firing is very frequent. When "Monastral" products are passed through a limited mill, from which the grinding cones have been removed, a product of fairly satisfactory texture is obtained without loss of tinctorial strength and without much danger of firing. This latter method is in most common use at present. , The brush sifter cannot be used with pigments of harsh texture, since the shearing action in this equipment is not sufficient to break up the Individual particles and force them through the screen. We do not haveacompletely and generally satisfactory process of grinding "Monastral" pigments and an engineering study of this problem would be profitable, Water-Dispersible "Monastral" Powders The water-dispersible "Monastral" products are powders, which, when dissolved in water, produce colloidal solutions which re main in suspension indefinitely. They are used fairly ex tensively in the dyeing of paper. For their preparation, the acid pasted and ammonia slurried press cake of the chosen "Monastral" product is mixed with relatively large amounts of dextrin, sugar, and leucanol (Compound #8), and small amounts of glycerin and trisodium phosphate. The resultant syrup is mixed well, passed through an F & B Mill, and dried with stir ring in a Stokes Drier, The viscous milling which occurs as the product dries subdivides the individual crystals of the "Monastral" product to colloidal size. The dried mass is micropulverized and standardized by blending tinctorially strong with weak charges. The final product contains approxi mately 50$ of pigment. More concentrated powders can be pre pared, but with some technical difficulty, , 23 - ^ DUP050041208 It is felt that the passage of the syrup through the F & B mill before the milling is unnecessary; this point should he investigated. In small scale experiments a steam jacketed W & P mixer has given more satisfactory results than a Stokes Drier; this would probably also be true in larger equipment, since the W & P mixer provides a more suitable type of milling. This point should also be checked*; At present CPC, Metal Free PC, a mixture of CPC and Ponsol Brilliant Violet 4RN and Polychloro CPC are prepared in waterdispersible form and sold under the trade names of "Monastral" Fast Blue BWD, GWD, 2RWD, and "Monastral" Past Green GWD, respectively, "Monastral" Fast Blue 2R A small amount of a red-shade "Monastral" pigment is pre pared by co-acid pasting a mixture of 83# of crude CPC and 17# of Ponsol Brilliant Violet 4RR, The latter dye exerts its full shading action only if it is mixed with the CPC by the co-acid pasing process or by co-salt milling; mechanical mixtures of the two pigments do not produce the desired red shade. At present the acid solution Is drip drowned; high turbulence drowning could be used if there were a demand for the product so produced. At present the product is sold in the forms of a dispersed paste and a water-dispersible powder. Vfhile Ponsol Brilliant Boilet 4RN Is the most satisfactory reddening color for CPC that haB been found to date, it is not completely satisfactory. Blends of the two pigments are un desirable dull, especially when the Ponsol pigment is present in amounts greater than 17#. Jackson Laboratory is attempting to find a more suitable shading agent. Luxol Fast Blue MBS This product is prepared by reacting CPC sulfonic acids with di-ortho-tolyl-guanidine. it Is soluble in alcohol, and is used for spirit Inks, In our present manufacturing process, ordinary Sulfo CPC Is dispersed with water in an acid resistant tub and strained through cheese cloth, A solution of di-ortho- tolyl-guanidine in dilute hydrochloric acid is prepared In a separate kettle. The two solutions are run together at room temperature while ammonia is added in Blight excess* The crys talline reaction product is filtered, washed, and dried. -s*- 6,405^ DUP050041209 Coalesced Phthalocyanlne Figments Coalesced phthalocyanlne pigments for paints are now under investigation in Jackson Laboratory and in the Semi-Works. Their commercial future is doubtful at present# If they are accepted by the trade, production will be large# It has not yet been decided whether manufacture will be carried out by Orchem or by the Pigments Department. The coalesced phthalocyanlne pigments are prepared by co baking mixtures of phthalonitrile, copper salts, and certain chosen extenders, such as titanium dioxide or zinc oxide. At present rotary bakers are used for this operation, but thereis some laboratory evidence that it could be carried out under continuous operation. The crude reaction product from the baker is ground, preferably in a Mikronizer with super-heated steam. The product thus obtained is ready for use In paints and linoleum without further processing. Unlike present `Monastral" Past Blue Standards, the coalesced phthalocyanlne pigments are non-flocculating and do not settle out of their suspension in commerical paint or lacquer for mulations . They also are "can stable" since they do not exhibit crystal growth in paint vehicles. Their disadvantages are that they are weaker and duller than equivalent mixtures prepared from purified "Monastral" toners, and that they contain small amounts of free acid which makes them corrosive to metal equipment. Thlastral Green 2G Thiastral Green is Tetra Thiocyano Copper Phthalocyanlne. This compound behaves like a typical sulfur dye, being substitlve on cotton from a sodium sulfide vat. It dyes cotton a bright, attractive, and very strong green. The fastness properties- of this dye are excellent with the exception of its bleach fastness, which is that of a typical sulfur color. Because of its high tinctorial strength, it Is less expensive than Ponsol Jade Green or our best Sulfur Green Standard (Sulfogene Brilliant Green 4GX), when compared on an equal tinctorial strength basis. At present this dye is at the final sample stage, and its commercial exploitation is a post-war problem. It is expected' that the sales of this dye will be considerable, once it is established on the market, - 25 - 6,406s! DUP050041210 Starting material for the synthesis of Thiastral Green is 4-nitro-phthalimide. This intermediate is refluxed with urea, cupric chloride and catalysts in ortho-dlchloro-benzene, whereby it is converted to Tetra Nitro CPC. The ODCB is removed by steam distillation, leaving an aqueous suspension of TetraNitro CPC which is filtered and washed. The yields on this step are only fair. The crude Tetra Nitro CPC is reduced to a fine particle size. In the preparation of our approved final sample, this was accomplished by wet milling of the filter cake slurry through a colloid mill. In the preparation of earlier samples we resorted to acid pasting of the dried Tetra Nitro CPC. The finely divided nitro body is reduced with aqueous sodium sulfhydrate, giving Tetra Amino CPC in 90$ yields. The product is filtered, washed and held as a press cake. Tetra Amino CPC is unstable to storage, but decomposition may be reduced by allowing a small amount of sodium sulfhydrate to remain in the press cake. The amino body is dissolved in 10$ hydrochloric acid and diazotized with sodium nitrite. The solution if treated with a large excesssof sodium thiocyanate and heated until the evalution of nitrogen gas is completed and Tetra Thiocyano CPC is formed. The suspension is then cooled, neutral ized, filtered, and washed. It is expected that this dye will be standardized in paste form. The yields on diazotization and thiocyanation are practically quantitative. ' The method outlined above is rather complicated and ex- - pensive Other methods of preparing a product similar to Thiastral Green 2G are being studied. One possibility consists in the preparation of Tetra Nitro CPC of superior quality and better yield from nitrophthalonitrile. Laboratory results indicate that this route Is feasible. The direct introduction of mercapto groups by reaction CPC with sulfur monochloride - aluminum chloride complex also has been investigated. The method appears to be less expensive, but the properties of the dye obtained by it are not quite equal to those obtained by the synthetic route. The third possibility which has been investi gated by the I.C.I. is a reduction of CPC tetra-sulfonyl chloride to Tetra Mercapto CPC with thiourea. To date, DuPont has not been able to obtain the results claimed by the I.C.I. for this method. * , Tetra Thiocyano Metal Free PC may be prepared by converting nitrophthalonitrile to Tetra Nitro Metal Free PC, reducing, diazotlzing, and replacing the diazo groups with thiocyano groups as outlined above. This compound is also a typical sulfur color; it is even yellower and brighter than Tetra ' - 26 - 6,4074 DUP050041211 Thiocyano CPC, but It is somewhat deficient in light fastness. The commercial prospects of this product are questionable. Tetra Amino CPC Diazonium Salts Tetra Amino CPC is of little interest as a pigment, due to its solubility and dullness of shade, All four amino groups may be diazotized. The I.C.I. has investigated this diazotized derivative as a stabilized azo salt. Cotton may be dyed an attractive green shade by reaction with a suitable coupling agent which has been padded on the cloth. Unfortunately, the diazo derivative is unstable, and no means of inhibiting the decomposition has been found. At present, the I.C.I. is trying to prepare azo derivatives of CPC by preparing arylated metal phthalocyanine, the attached aryl groups of which contain amino groups. Preliminary work indicates that such compounds yield azonium salts which are more stable to storage than those of Tetra Amino CPC. Oil-Soluble Phthalocyanine Derivatives Tetra Mercapto CPC reacts with long chain alkyl halides to give thio ethers which are soluble in petroleum hydrocarbons. Other oil- or gasoline-soluble derivatives can be made by con verting CPC sulfonyl chlorides to long-chain sulfonamides. These products may be of value in coloring gasoline or other petroleum products in shades of blue or green. The stability of these compounds to light, while good, is. not outstanding, and the commercial future of these coloring agents is problematical. Iron Phthalocyanine Iron phthalocyanine is much greener and duller in shade than CPC, and is of no interest as a pigment However, it has a definite catalytic activity in a number of oxidation reactions, such as the drying of paints and the aging of textile prints; it may have a limited Industrial future in this application. Submitted - May 4, 1944 HW - JEA Typed - July 24, 1944 - 27 - T3 DUP050041212