Document 6R41D4mxkwKv8QX6dbr50RDaE

E. I. DU PONT DE NEMOURS & COMPANY PIGMENTS DEPARTMENT 256 VANDERPOOL STREET NEWARK, NEW JERSEY Copy No. / ' F ' ." NEWARK PLANT PIGMENT COLOR RESEARCH REPORT Progress Report The Finishing of Phfchalocy&nine Figments XX Wet Grinding Studies November 6, 1945 to July 31, 1946 Period Covered s FILEi2S3o 4 DAT"18-46 NJ3S9B .. ............... ......................................... ............. ........................... N39975 .' Serial No. KN-46-55 Copy Ho. / Copy to* #1 - Numerical Pile 2 - Research Office (223.4) 3 - Library File (223.4) 54 - Imperial Chemical Industries.' Lntd. qm n n 7 - J* B Booge, Newport 8 ** W. F. Spengeman, Newark 0 - A, Siegel. Newark 10 - D. B. Killian, Newark 11 - B. a* Perkins, Newark 12 - C, E. Berry, Engineering Dept..Experimental station 13 - Orchem, Jackson Laboratory Files 14 " Extr a 16 - NEWARK PLANT PIGMENT COLOR RESEARCH REPORT Progress Report Title t The Finishing of Fhthaloeyanine Pigments II. ?/et Grinding Studies. Period Covered: Novesfcer 6, 1946 to July 31# 1946 SUBMITTED BY: A.^J, Strattoi APPROVED BY* l, DATE SUBMITTED: 7-31-46 DATE ISSUED* 0-12-45 N39975.01 DUP050150195 XHTROEPSTIOl 2- For a full statement of the problems involved in this study and of the historical backgrounds thereof* reference is made to KH-40-19 dbieh is the first report In this series. The experimental work coveredin the present report includes much work carried on at the same time as that reported in 0-46-19, as well as substantially all work on the finishing of phthalooyanine pigments by wet grinding methods subsequent to the date of that report and up to the end of July 1946. STJMMAKY AID 008CLTOI0HS 1. FolTchlor Attempts to finish phthalooyanine green pigments by grinding in water beam been completely unsuccessful, In no case was there any significant improvement in strength end in most cases there was a serious loss even from the starting crude On the other hand* this pigment has been successfully ground to a strength comparable to that of our present standard G3MS6-D in a variety of organic solvents. The best results were obtained in hydrocarbons such as mineral spirits or kerosene and in the presence of a substantial amount of an inorganic salt such as sodium sulfate* Xt Is proposed to use such a process In subsequent manufacturing operations. The use of water soluble polar solvents such as various alcohols has given a satisfactory rate of grinding but their use in other than anhydrous conditions in the presence of iron* such as in iron containers, or with Iron balls*has resulted in a serious dis coloration of the green pigments. Altho most of the work has been o srried on with a crude green obtained from Orehem and made by chlorination in an aluminum chloride/ sodium chloride melt* enough work has been done with green chlorinated In sulfur diohlorlde at Hewark to demonstrate that the only problem peculiar to this type of pigment Is a tendency to more serious corrosion of the equipment* Xt is believed that this problem can be overcome by proper treatment of the crude prior to grinding. 2. In contrast to the green* copper phthalooyanine blue crude pigment has been significantly Improved in strength by grinding in water but* to date* no such grinds have given the degree of improve ment necessary for commercial utilisation. Water soluble polar solvents* such as the various alcohols and Cellosolv% have been used in grinding the blue with a fair amount of success even in the presence of substantial amounts of water. One such sample was fully equal to our current standard BT-172-D in strength but* In general, the results with the chlorine free blue have left con siderable to be desired. Although kerosene and mineral spirits have given very excellent grinds up to a certain point (approximately 70$ of standard strength)* the problem of so-called "crystal growth" of chlorine free copper phthalo oyanine in the presence of hydrocarbon solvents has made Itself felt and DUP050150196 3 It has bean impossible to obtain the desired strengths with this type of product. Humorous attempts have been made to stabilize the chlorine free blue by the introduction of various agents or substituted phfchaloeyanines, but the only method showing any hope of practical application in a solvent grinding process of finishing the pigment has been the synthesis of a blue containing a substantial amount of chlorine. This may be done either thru the use of phthalonitrile and copper salts or thru the phthalic arihydride/urea synthesis in which an appropriate amount of 4-ohlor-phthallo acid replaces its equivalent of phthalic anhydride. I.C.I* uses the latter process to make "Monastral" Blue LB and both the process and terminology have been adopted for use at Newark. Various methods of carrying out the grinding steps have been studied but the only successful one to date has been the use of a ball mill# 3* fiMonastral" Blue IB With the synthesis of nMonasfcral" Blue LB at Hewark the diffi culties in grinding to the desired strength in hydrocarbon solvents have been overcome# and substantially all batches of Blue LB made in this laboratory have been successfully ground to a strength at least equal to that of BT-172-D and most of them have been carried sub stantially above this point. Since nearly all of the work haw been done with kerosene-containing filter cake from the reactor# no success ful grinds have been made in water, altho some work in this direction is contemplated for the future. Some successful grinds have been made in alcohol and Cellosolve but this work has been extremely limited. The evidence favoring a choice of hydrocarbon solvents between kerosene and mineral spirits Tor others} is not yet clear-cut. The balance seems to lie between some evidence of a slight quality improve ment with the use of kerosene and the much more ready removal of the lower boiling mineral spirits. The latter feature currently favors the use of mineral spirits and It will probably be used unless the quality advantage from the use of kerosene is shown to be substantial. This point is still under study. It has been demonstrated that the initial increase in strength# up to that of BT-172-D or slightly above# la obtained very rapidly in a ball mill# in less than 24 hours in sense oases and in a maximum of 2 to 3 days in laboratory equipment. Prolonged grinding does give some further Increase in strength, with a maximum of about 120jl that of BT-172-D ob tained to date* There has been no evidence of harmful results from pro longed grinding. It has been demonstrated that the qua! ity of the final dry pigment is significantly affected by the methods used in removing the solvent and extracting water soluble Impurities. A tendency to slight greenness seems to be characteristic of all "Honastral" Blue LB samples and many of the solvent ground products have shown a significant tendency DUP050150197 to dullness particularly in undertone. However, the best samples obtained have not been dull end have been only slightly green# There fore, there is every reason to hope that the final product from this development at Hewark sill be in every say the equal of BT-172-D in quality except for a very slight greenness of Shade and sill be aignifloantly stronger# * d, .ftyfrlfM Zt is believed that the major unsolved problem in this de velopment is that of the proper method of separating the finished pig ment from the solvent paste sfter grinding# Altho the process teaqwrarlly adopted for use is reasonably dupileable, it is not satisfactory firm an operational point of IRsv and there appear to be many points of un certainty, Furthermore, no satisfactory method has yet bsen d eveloped for obtaining pigaenta in a water dispersible form either as water pulp or as water dispersible dry pigment, A port of this same unsolved prob lem is the preparation of a "Hamapo" Blue and there is some reason to hope that this esn be aeeamplishsd without the isolation of a pigment pulp as a smai-finished product, igjiaa - A recant extensive search of the patent art on phthalooyanlne (See KH-46-54) WH disclosed that all phthalooyanlne patents necessary for the operations at Bevark are either owned by DuPont or licensed to their use, Furthezmiore, It is believed that all practical pro cesses fas* the manufacture of phthalocyaninc pigments are dominated by patents controlled by DuPont and with a minimum of nine years M any important teat before expiration. Ho disclosures of finishing phbhaXooy&nlaes by grinding in solvents ether than water have been found. Furthermore, a casual search of the pigment art,coupled with a fairly extensive knowledge thereof.has failed to disclose any bars to the use of solvent grindlag methods and, pending a more extensive search of the art which is contemplated for the near future, it is believed that solvent grind ing as a finishing method for phthaloeyanines is probably patentable and that it may well be patentable in a broader sense. All other as pects of the process currentiy contemplated at Hewark appear to be disclosed in the art and, therefore, unpatentable, wa,,,paiM.fii mvm, As pointed out in KH-40-1, the original objective in this study contemplated the use of a closed circuit wet grinding process, preferably using water as the suspending medium, involving elutriation methods- of classification to obtain the desired particle also. As also pointed out in this report, a careful theoretical study of elu triation methods as applied to phthalooyanlne pigments soon demon strated the impracticability of such a process, nevertheless, wet grinding methods of finishing phthaloeyanines wars studied further on a batch basis, first with water as the suspending medium and later with a number of other solvents as will be pointed out in more d etail below. DUP050150198 1. Folvofaloro Attempts to grind phth&loeyanlne green in tall mills and other devices with water as the suspending medium have teen com* pletely unsuccessful# With water alone there is invariably a loss in strength Which progresses with prolonged grinding* This loss in strength is found both with a crude green and with a product of full strength such as our standard GT-486-D, in the case of the a tandard, the strength resulting from a relatively short grind was actually less than that of a normal crude* The cause of this loss in strength is not known with certainty but, since it was later demonstrated that such products which have lost strength could be subsequently ground to full strength in other media, it would appear that no chemical change occurred and that the loss in strength must have been the result of a physical phenomenon, probably agglomeration. By seas of the use of certain dispersing agents* such as ammonium n&phthenate, it was possible to in hibit this loss in strength to some extent but, in no ease, was a sig nificant improvement obtained. With the failure to obtain the desired results using water as a suspending medium, attention was turned to the use of other readily available liquids with particular emphasis on the use of low cost hydrocarbon solvents such as kerosene and mineral spirits* It was quickly demonstrated that either of these liquids could be used in a ball mill grinding operation to get a relatively high rate of strength development and an ultimate strength equal to or better than that of 6T-486-D. Using small seals laboratory equipment the desired strength was obtained in from 5 to 4 days of tonal grinding time, Much less time can be anticipated in larger mills* In view of the low boiling point of mineral spirits and the greater ease of removal from the ground paste, it is presently pre ferred over kerosene for this operation* Scan study of the use of treating agents with the mineral spirits has indicated that a shall amount (about 5%) of an organio acid such as naphthenic aold promotes the efficiency of grinding* In view of the known use of salt milling operations in the finishing of phthslooyanines in which a mixture of pigment and an inorganic salt, such as sodium chloride or sodium sulfate, la drf-* ball milled to obtained high strength, some study tea made of the use of such salts in the presence of mineral spirits* The results Indi cated that, in the case of the green, a pronounced beneficial effect resulted from this combination use, that awaonlum chloride or sodium sulfate gave better results than sodium chloride and that these two were substantially equal in their effect* The presently preferred process involves the grinding of approximately equal parts of pigment and sodium sulfate in mineral spirits* A limited amount of work was done on the use of such water soluble polar solvents as methanol, . ethanol, ieopropspol, and eellosolve* When used in non-met&hlie equipment, these agents appear to be satisfactory grinding media, f . But in the presence of any appre ciable amount of from* there is a serious tendency for the pigment to become very much bluer and this tendency is promoted by the presence , DUP050150199 *0< of water* It has boon assumed, without any rigid proof thereof, that this change in shade is oausod by a certain amount of dechlorination of the pigment under the conditions uaed. However, regardless of the explanation, the change in shade is so serious as to preclude the use of these solvents for grinding greens in equipment now contemplated for use. Host of the studies <m grinding phtbalooy&nlne greens were made with a crude green pigment obtained from Orchnaa and made by chlorinating phthalocyanine blue in an aluminum ohloride/sodium chloride melt. However, several grinds were made of green made at Newark by chlorinating in sulfur diohloride, and the reaiiItiag pigments were at least equal be .and In some ways superior to,products obtained by acid pasting the sane crudes, AH of these products were distinctly bluer than our standards but the degree of blueness was not noticeably in fluenced by`the method of finishing. One problem did arise which nay be serious m a large scale and that is, a noticeable degree of corro sion of the grinding equipment them way of the mineral spirits slurry is allowed to dry In eontact with it, This was presumably caused by residual by-products of the chlorination and we believe It can be over come by proper treatment of the crude pigment prior to grinding, Harly in the study of grinding in the presence of water, attempts were made to grind mixtures of the mmm pigment with certain water soluble extenders, such as whiting, blanc fixe, or alumina hydrate, The first indications were that a substantial improvement in strength hag| been obtained but a careful evaluation of the testing method demonstrated the hitherto unrecognized fact that, apparently, all phthalooyanine pig ments will exhibit a greater tinctorial strength when ground with a ve hicle In the presence of these extenders than can be obtained from the equivalent amount of toner pigment in the absence of the extenders* The phenomenon appears to hold true with either full strength or crude pig ment and with both the blue and the green* Thus, if our standard Qf-486-D Is tested by rubbing out a mixture or one part standard and three parts of alumina hydrate in a lithographic varnish,and a tint of this mixture Is compared with a tint of the same standard rubbed in the absence of eaumin^$gpdrate, so that the two samples of tint contain the same amounts of standard green pigment, that sample r-Ubbed in the presence of alumina hydrate will show in the order of 15* additional strength. Host of the so-called extended type pigments exhibit this phenomenon as well as many Inorganic salts such as sodium chloride, ammonites chloride, and sodium sulfate; It seems to be a very strange fact that the ilpme white pigpmntf ,auoh as sine oxide, lithopon# or titanium fail to exhibit the effect. Ho practical application of the observation has yet been made but it suggests that extended phthalooyanine pigments may have an economic advantage not heretofore recognised* It was, however, an extension of this observation in which the lithographic varnish was replaced by a volatile solvent and the extender sms re moved by chemical means that the first indication of merit in the use of hydrocarbon solvents as grinding media was obtained. The only phthalooyanina blue pigment available in crude form for use (hiring the early part of this study was a sample of chlorine DUP050150200 free blue obtained from Orchem and made thru a phthalic anhydri de/urea synthesis carried out in trichlorbenzene as the diluent# Subsequently, a similar product made at Newark in kerosene was given some study with essentially the sane results as originally obtained on the Orohem mater* ial* As with the green,the first attempts to grind the blue were made using water as the suspending medium. In contrast to the green, a significant improvement in strength was obtained in nearly every instance but, in general, it fell far short of the desired degree of Improvement The moat promising results were obtained with large amounts of dispersing agent (upwards of 25$) such as ammonium roslnate mad petronate# In these oases, the pigments were so completely dis persed that it was necessary to flocculate them by precipitating the dispersing agent before they could be filtered. Consequently, the re sulting pigments were no longer toners but were extended with signifi cant amounts of the precipitated dispersing agent# When tested on the basis of their theoretical toner content, some of these pigments did approach very near to standard BT-172-Dd in strength# An extensive study was made of the use of surface active agents in water grindsusing 5% ammonium naphthenate as the control# No agent was found which was superior to ammonium naphthenate in this amount but the following agents seemed substantially equal thereto. tetra sodium pyro phosphate soda ash tri-sodium phosphate sodium meta-silicate polydioxolane amino-caproaitrile ammonium benzoate The following agents gave results poorer than those obtained with ammonium naphthenate. Alkanol B Duponol WA Lauryl amine hydrochloride Igepal CA Polyethylene oxide MT-109 TRACib eater Atlas Spans & Tweens Aerosol OT Pix&nol Diglyool stearate Turkey Red Oil Petronate (5%) Altho these reswitti suggest that a way might very probably be found to obtain the desired degree of grinding in water, at the time the use of other solvents appeared to offer greater promise of a prompt solution to the problem end the study of grinding in water was eventually dropped# The very promising results of grinding the green pigment in hydrocarbons, such as mineral spirits and kerosene, led to a ewaparable study with the chlorine free blue# With the solvent in a ball mill the strength development was very rapid up to approximately 70% that of standard B%T-17S-D but all efforts to exceed this strength level with DUP050150201 hydrocarbon solvents were fruitless* The conclusion was eventually reached that the screened "crystal growth" problem characteristic of chlorine free blue was Influencing the grinding rate and the 70$ strength level probably represents the balance between rate of crystal growth and rate of particle slse reduction in the grinding step* A study of the use of treating agents to improve the rate of grinding In mineral spirits demonstrated that a number of organic acids, such as naphthenic acid, oleic acid, stearic acid, bensolo acid and E Wood Rosin could be used to Obtain a slight improvement in grinding rate* The use of 3% naphthenic acid based on the pigment content of the grind has been adopted Wmfwmt of the subsequent work. Xt is an Interesting and important cessment on the behavior of chlorine free blue in hydrocarbon solvents that, whim full strength blue pigments obtained either by acid pasting or salt milling are ground in idlzaeral spirits, the pigments actually lose strength ending up at substantially the same level as is reached by grinding the crude* This point has been repeatedly confirmed with chlorine free blues. A study was also made of the use as a suspending medium in ball mill grinding of a number of water soluble polar solvents, such as Sfethanol,. ethanol, Isopropgnol and cellosolve, both in relatively anhydrous condition and in the presence of substantial mounts of water* One grind made in ethanol >' oontalning some water gave a product fully equal to BT-172~t> In strength, but this has not been repeated and all other attempts have fallen short of the meal* nevertheless, grinds in this type of solvent with chlorine free blue have,in general, given higher strength*'"than have been obtainable with mineral spirits* There has been no evidence that anhydrous solvents were significantly better than the same solvents containing some water and, in the case of cellosolve, mixtures of water and cellosolve were better than either one alone* Very little attention was given to the use of dispersing agents In these solvents* Xn addition to the superior results obtained with this type of solvent (still short of the goal) they offer the possibility of much more easy Isolation of the finished dry pigment and the probability of obtaining a much better water pulp because of their ready solubility la water* m the other hand, they are Inherently more expensive than hydrocarbons, the recovery problem Is sonswhat greater because of the necessity of distilling larger volumes of liquid to remove them from the water in which they are soluble* and a serious corrosion problem is presented when they are used in iron ball mills* Xt is noteworthy that tbs addition of inorganic salts such as sodium chloride or sodium sulfate to ball mill grinds of the blue pigment in any solvent have in no case given the same beneficial re sults as were obtained with the green* This is difficult to under stand but the results of a number of teets have been bo consistent as to leave little doubt of the validity of this conclusion* DUP050150202 A mraber of different devices Imre been examined for obtain** ing the desired grinding action* As noted above, the first indica tions of benefits in grinding with hydrocarbon solvents were obtained in rUbouts, mostly made on a Hoover Haller* Consequently, a number of large scale devices using similar grinding principles have been tried* A major Improvement In strength was Obtained by grinding a mixture of pigment and either sodium chloride or sodium sulfate with mineral spirits on a roller mill* However, the operation was extremely unsatisfactory Aram a smohanioal point of view and the strength obtained was no better, if as good, as obtained in a ball mill without the salt. The use car glycerine as the vehiole in plane of the mineral spirits gave a much mere satisfactory mechanical operation said a relatively easy separation of the pigment because of the water solubility of the. vehicle but the results were still far short of the goal* It does not seem that any practical operation can be developed on a roller mill* Similar attempts were made to use a Banbury aimer with . * absolutely no evidence of improvement in strength in the absence of a crystalline salt and only iftniMhlpnNpmwht In the presence of the crystalline salt* These results did not encourage further study of the Banbury mixer* A study was made of the use of a Marco Kowbiaafcor* This machine is essentially an efficient gear pump which forces the mater** ial under very high pressure thru the plates of a colloid mill.studies were made in kerosene, anhydrous alcohol and water both with the pig* msnt alone and with extenders such as sodium sulfate end alumina hy drate* Only minor Improvements in strength were obtained and, in any case, the machine appears impractical for the proposed operation. A study was aside of grinding the crude blue with extenders in a Geaoo blender with no significant evidence of improvement in strength* These studies of various grinding devices confirm the original choice of ball mills for the operation as a wise one* Substantially, all subsequent work has been carried on la this type of equipment and seme Investigation of the merits of various types of ball mills will be reported below* 2h view of the known behavior of chlorine free copper phthalo* cyanine in the presence of hydrocarbon solvents, referred to above, and in view of the demonstrated ihabilifer to grind it to full strength in such solvents, a considerable study was made of methods of stabilising the blue against the action of these solvents* It is already known that a product containing from 1/8 to 1 atom of chlorine per molecule of copper phtbalocyanine Is relatively stable to the aetlon of hydrocarbon solvents* Althc such products are easily made by way of the phthalonttrlle synthesis they ere not so readily atfde in the phthalle az&ydrlde/urea process. However, a sample of the Crude "86011*013110^ copper phthaloeyanine made by Orphan* fro phthalonltrile and cuprous chloride was ground in solvents, and,for the first time, satisfactory strength relative to BT-172-D was obtained* Equally good results were obtained in kerosene, mineral spirits, alcohol and cellosolve* This was the first convincing evidence DUP050150203 -10 that that solvent grinding method fen* finishing the blue was on a sound basis but, sins Bewark had only academia interest in this type of crude, it has not been investigated extensively* Qrohem has demonstrated that ao-sslt milling of a mixture of tin dlehlorlde phthalooy&nine and ahlorine free copper phthsloeyanlns results in a finished pig&ent which is apparently stable to the action of hydrocarbon solvents* Attempts wire, therefore, made at Bewark t o eo-solvant mill these products but without any success* Go-synthesised products of. the same chemical composition were equally unsatisfactory in the solvent milling process* Per that matter, Bewark has been utterly unable to confirm the benefits of co-salt milling in samples prepared at Bewark* However, we have confirmed the properties of samples submitted by Grohflg, but there are certain apparently inherent properties in these samples, such as reactivity and some chemical in stability, which reduce their interest for our uses and this method of attack has been dropped* Certain methods of introducing chlorine Into the molecule, .such m synthesis in the presence of a smell amount.of pelyoblor copper phthalooymin and synthesis in the presence of a small amount of tetra ohlor phthallc anhydride, gave products Which were not satis factory in solvent grinding procedures* Other methods of synthesis were also tried unsuccessfully and these will all be reported in mere detail in another report* It was only when the X*0*X* process for ^Monastral" Blue 13 (involving the introduction of about 1% of chlorine thru the use of 4-ehlcrphthailo acid in place of its equivalent of phthallc anhydride) was used at Bewark that a product synthesised via the phthallc snhydride/urea route was obtained that could be satis factorily ground in hydrocarbon solvents* With only one or two excep tions. and these readily explainable, all products synthesised at Bewark by this process have been successfully ground to the strength of BT-172-B or better* Xhe first B type copper phthaloeyanine blue crude was made available for grinding at Bewaxfc near the wed of March 1946* Xt was Immediately demonstrated that such products could be ground in either kerosene or mineral spirits to the desired strength la a reasonable period of time* All such products have been made at Bewark using 4-ohlor-phthalio acid of our cm manufacture and, for the most part, have been mad* using kerosene as tbs diluent* they have been made available for grinding either as a kerosene slurry from the reactor er, more generally as a filter cake containing on the average about 40 to 45%of OKS, a total solids content of about 68 to 70% and about 80 to 38% kerosene* The physical appears* ee is that of a slightly wet granular solid* Xh view of the kerosene content of the material available for grinding, no successful grinds have been made to date using water done as the suspending medium* Seme study is contemplated for the future along this line involving the removal of the kerosene from the pressoak* prior to grinding* A limited amount of work has been dona on the use of iso propanol and eellosolve as the solvents for grinding* Satisfactory grinding was obtained with these solvents even when the eellosolve was mimed with m appreciable amount of water but the residual DUP050150204 kerosene in the filter cake used for grinding posed a problem in the removal of the solvent by drowning In water* The other disadvantages pointed out above as inherent in the use of such solvents were also present* Their use has not been followed up,altbo it seems probable that some of the serious problems,which will be pointed out as apparently inherent in the proper separation of impurities from the pigment ground in kerosene or mineral spirits,may not be present with these solvents* Except for this limited work on the use of water and of alcohols, all of the grinding studies with "MonastralM Blue LB have been made in either kerosene or mineral spirits and in ball mills* The choice of these solvents is dictated by a relatively low cost and by sufficiently high boiling points to minimise fire hazards in the operation* Since kerosene is the diluent in the reaction, it is the logical solvent for the grinding operation, parti cularly if it is possible to grind the reactor slurry without filtra tion* On the other hand, it la notably difficult to remove the last traces of kerosene by steam distillation or, for that matter, by any evaporative process* On the score of the ease of solvent removal alone, mineral spirits is greatly to be preferred and it has even been proposed to remove the residual kerosene from any reactor cake by washing with mineral spirits after filtration* It has likewise been suggested that an even lower boiling solvent, such as VM & P naphtha should be used but no trials in this direction have yet been made* A final choice between these two solvents is not yet possible and will unquestionably he influenced by both the quality of the finished product and the ease of solvent removal* Unless a substan tial quality advantage can be demonstrated in the use of kerosene, it is highly probable that the more easily removed mineral spirits will be the ultimate choice* Temporarily, it has been selected as the solvent for routine experiments* It is interesting that the best products made to date hMiall been in kerosene} yet in a number of direct comparisons of the two solvents, only one of them has shown any outstanding superiority In the use of kerosene* Ho comprehensive study has yet been made of the use of dis persing agents in the mineral spirits grinds but several agents have been tried on occasion* Confirmation has been obtained of the bene ficial effect previously observed with the use of about 6% naphthenic acid (based on the pigment) in the mineral spirits* This has been tentatively adopted as a standard procedure* Other agents tried include Aerosol OT, TEACtg. and Glyceryl Monorloinoleate The only beneficial effects observed by the inclusion of these other agents in the grinds, not obtainable in other ways, have been that certain combinations, particularly that of Aerosol OT with either of the other agents, result In a materially lower viscosity of the grinding faete than cm be obtained with any agent sdtahe* It is doubtful if his improvement alone Justifies the use of the additional agent at this point* In one comparison of various types of ball mills for this operation, it was found that products ground in 1/2 pint glass Jars using steel balls of 5/32" diameter reached their maximum DUP050150205 -12- strength in ITom 4 to 5 days* la stirred ball mills of the "attrltor" type Tsee KN-46-19,for a description of this apparatus) equivalent re sults were obtained In about 2 days* Attempts were made to,grind In a larger ball mill* 6" in length x 12" In diameter, using 1/2" steel balls and equipped with lifter bars. It was not possible at Bewark to drive this mill at a higher speed than about 30 HPM (approximately l/2 the optimum speed)* The maximum strength in this device was reached In about 2 to 3 days but it was considerably below that ob tained In other devises* The reason for the poor results with this mill Is not clearly understood but it Is assumed to hare been the re sult of the slow speed of the mill* A somewhat similar result was obtained with 1/3 gal* porcelain mills using steel balls in which it required from 200 - 300 hours to equal the results Obtained In 1/2 pint jars In a much shorter time* One possible explanation Is the peculiar thixotropic nature of the paste and its complete freedom from tackiness so that there may have been excessive slippage of the balls instead of the desired type of cascading action* A similar attidy has been completed quite recently compar ing the rate of strength development In 1/2 pint jars and in the stirred ball mill or, "attrltor",with essentially the same results. In this ease the crude pigment used had a strength of approximately 65$ that of BT-172-D before grinding. The following table summarises the results of this study* Time of Grind Strength vs BT-172-D $ (Crude 1213-29) 6 hra. 1 day 2 days 3 days 4 days 5 days 6 days 7 days 10 days 65% m m 108$ 112$ 113$ 116$ 116$ 116$ 66$ 02$ 106$ 112$ 116$ am 120$ 120$ 120$ me This study demonstrates that the initial improvement In strength to something approximating that of BT-172-D is obtained quite quickly, that an additional improvement of about 10% is still possible within a practical grinding time, that the last 5$ or so of strength is ob tained rather slowly and that the maximum strength obtainable with fills sample Is In the order of 130$ that of BT-172-D, There was no evidence In this study of any harmful effects from prolonged grinding. As the work has progressed on the finishing of "Monastral" Blue LB by solvent grinding, it has become quite evident that the real problem is not that of obtaining satisfactory strength but it is the problem of obtaining satisfactory tinctorial properties com parable to those obtainable by acid pasting or salt milling operations DUP050150206 -13on the same crude pigment Throe steps have been considered necessary in the Isolation of the finished dry pigment from the ground slurry, namely the removal of the solvent, extraction of water soluble impurities In on acid medium and extraction In an alkaline medium, preferably ammonia* Whenever the solvent has been removed by simple evaporation to leave a dry product which la then slurried In water and given an acid and an ammonia extraction, the products have had,In general, entirely satisfactory strength but they have been distinctly dull both In tint and,' store pronouncedly, In undertone* This type of pigment is characteristically greener than BT-172-D but the product finished in the way Just described seems to be even more green than corresponding acid pasted products. An alternative method for removing the solvent Is that of steam distillation and it has the practical advantage of leaving the product in a water wet form and avoiding a rather nasty operation of wetting up a dry pigment. The conditions under which the steam distillation of either kerosene or mineral spirits from the solvent ground paste is carried out appear to have a pronounced effect upon the quality of the result ing pigment. Simple removal of the solvent without the addition of any treating agent has not given results materially better than those obtained by removal of the solvent In an oven. However, if certain treating agents are added at the beginning of the steam distillation, or not later than the beginning of the aoid extraction immediately following, the tendency to dullness has been, for the most part, oompletely eliminated. In the tentatively adopted process 5% each of TEAGig ester and Glyceryl Honorieineole&te have been used and added at the beginning of the steam distillation. There is some evidence that both agents are not necessary and that their presence during the acid extraction Is all that Is necessary but these points remain to be clarified In subsequent work, Whether the amount used Is optimum and whether these are, In fact, the best agents for the purpose also remains to be clarified. When steam distillations are carried out as described above, the operation is very unsatisfactory from a purely mechanical point of view because the first action of water and agitation on the hydro carbon paste Is to thicken It materially and then/tends to break up into rather large balls and to stick badly to the sides of the con tainer and the agitator. This results in a relatively small surface from Which the sohrent oan evaporate and an extremely slow rate of solvent removal from the mixture. In those products ground in kerosene it is very doubtful if complete removal of kerosene has ever been ob tained during the steam distillation step. Furthermore, the presence of the treating agent mentioned above seems to accentuate the diffi culties of the operation and the dilemma is faced in which the more difficult operation gives the better result. Recently, however, it has been shown/%hen the stem distillation is carried out in the that, DUP050150207 presence of a strongly alkaline suspension, as In the presence of caustic soda, many of these difficulties are overcome. Under these conditions there Is very little tendency to ball up and there is no tendency to stick to the sides of the ontairfi` r to the agitator* la the early stages, the product appeal's emulsified with a much greater surface for evaporation of the solvent and. In the later stages, much of the pigment appears to he completely dispersed in the suspension so that It does not settle out at all* Products made by this method hiifve been excellent In quality, and, in view of the better operating conditions. It appears prcib able of adop tion la the near future* i As pointed out above, under the Summary & Conclusions, It la believed that the details of this step of removing the pigment from the solvent paste and giving it the necessary chemical extraction remain aa the most important unsolved problem in the development. This study Is going forward rapidly and will probably be the subject of a separate report at a later date* Few, if any, of the water pastes obtained to date have bean deemed satisfactory for many purposes for which a water paste is required and the preparation of such satisfactory pastes is also a part of the problem of satisfactorily separating the pigment from the solvent* Zt should also be noted at this point that the details of the grinding step have not been given sufficient study to state with cer tainty that they are in any way optimum* It seems probable, however these details will be much less critical than the steps of removing solvent* X-RAY STUDIES Some attention has been given to the x-ray patterns obtained from CFO prepared in different ways and this has developed good evidence that two distinct patterns can be demonstrated. For purposes of con venience they have been arbitrarily designated as Pattern A & Pattern B and the following table indicates the conditions under which each appears to be obtained* Treatment of Pigment Crude Acid Pasted Salt Milled Solvent ground Cl me CPC saLsai-- A B B A Semi-Chlor from PH A B B A Blue LB 4*4,f Cl B B m B Monochlor from PH &i 01 B B ev B The ultimate significance of these results is not now apparent but it is obvious that there is ground for much more study. DUP050150208 as* THE TENTATIVE PROCESS - fetaittag M&$sg.J$g. 600 gms steel shot SO gas dry pigment (or- 16 pis CPC in kerosene coke) 1 gm naphthenic sold (or 0,8 gas} 100 se mineral spirits (or kerosene) Grind for approximately 100 hours Add 25 os solvent sad mix well Strain from balls "Attrltor" (See KH-46-19) 3/3 gallon aonfcairier with paddles or other device for agitation* 6000 gas steel Shot ISO as CPC In kerosene sake (with an open container it is necessary to replace solvent lost by evaporation) Grind approximately 50 hrs. Dilute with solvent to suitable consistency and strain from balls. Hots So detailed study has been made of the optimum ratio of pigment to balls* of the optimum viscosity of the paste nor of the optimum loading of the ball mills* To a pigment pasts containing so gas CPC is added approxi mately 500 os water containing 10 gas HaOH, 1 mm TEACio ester and 1 m. Glyceryl i5onorlclnoleate. Steam distillation is started and continued DUP050150209 -16- until apparently solvent free (4-6 hours). In recent laboratory work simple vigorous boiling with a steam sparger In an open con tainer In a well ventilated room has been used. At this point much. of the pigment is in a highly dispersed condition and probably could not be filtered. The mixture is then acidified with H2SO4 to approximately 3$ concentration on the total slurry volume and boiling continued for 30 minutes. It is then filtered and washed aeid free. Th filter cake is reslurried in 1000 ec water and HK4OH added to give approximately 3$ concentration (approximately Ido 00 cone. HH4OH). This slurry is boiled about 10 minutes, filtered and washed and the filter cake dried at a temperature of at least 200 F. Note Ho detailed study has been made of the optimum concentration of HaOH in the steam distillation nor of the optimum concentrations of acid or ammonia in the extraction. It seems highly probable that the treating agents are hydrolyzed by the boiling alkali and that a better and more economical combination can be developed. The high temperature drying is necessary to remove residual solvent not removed in the steam distillation. Evaluation of the Products All evaluations have been made by the standard rubout pro cedure using a ratio of 1 part pigjaent to 2 parts lithograph!* varnish, ground 5 times 50 revolutions on a Hoover Muller. Extensions are made at a ratio of 1 to 100 in zinc oxide. The best products by the above procedure have been from 15$ to 20$ stronger than BT-172-D and very slightly green. The raasstones have varied considerably, some being lighter and some darker than BT-172-D. There is reason to believe that this variation is related to the use of th treating agents but the point has not yet been controlled. Under tones have seemed to appear greener than would be expected from the tint. Althou^i the best products have not been significantly dull in undertone many samples have tended in this direction. Texture evaluations indicate that these products are at least as good as ET-172-D in both grit and strength development and there is some evidence of superiority* It is noteworthy that the inks are definitely softer than BT-172-D, approximating ttRamspott Blue BP-173-E ln that respect* .................. .... -.......--...... . ...... ................. -- Can stability testa indicate these products to be at least as good as BT-172-D and there is some evidence of superiority. DUP050150210 -17 Complete experimental details and records of the evaluations of the products can be found in the following notebooksj- HB-1186 - Expa# 1-76 inclusive Pages 8 - 183 inclusive KB-1206 - Exps* 1-88 inclusive Pages 8 - 161 inclusive # DUP050150211