Document NMX4B4Zq7X1vRRBqBO33q3DR

E. I. DU PONT DE NEMOURS & COMPANY KREBS PIGMENTS DEPARTMENT 256 VANDERPOOL STREET NEWARK, NEW JERSEY Serial No. Cop/ No. KH-48-3 #1 - Ntuoerieal Pile NEWARK PLANT PIGMENT COLOR RESEARCH REPORT PISAL REPORT $ ITUS 5 COPPER PETHALOCYMXHE PIGHBHTS. PHYSICAL SSHQfoXES IQ PARTICLE SIZE AKD DIMORPHISM Period Covered: APRIL 1946 - DECEMBER 194? FILE: DATE: 223 o 4 3/29/48 N42152 Serial No, KN-48-3 Copy No, l Copy to* #1 - Numerical File 2 - Research Office (223,4) 3 * Library File 4 - Imperial Chemical Industries, Ltd, if , it H rt 6. * " 7 - W, F. Spengeman 8 - Jackson Laboratory - Orehem w 9 - Extra 10 - Extra 11 - Extra 12 - Extra NEWARK PLANT PIGMENT COLOR RESEARCH REPORT FINAL REPORT TITLE* COPPER PHTHALOCyANlNE PIGMENTS, PHYSICAL STUDIES |, PARTICLE SIZE AND DIMORPHISM PERIOD COVERED* APRIL 1946 * DECEMBER 1947* CHARGE* A-II-C (229? SUBMITTED W APPROVED a DATE S * 2/4/48 DATE ISSUED* 3/29/48 DUP050066876 i a b 12 INTRODUCTION: SSSBSABX & CONCLUSIONSi , FUTURE WORK: DISCUSSION OF EXPERIMENTAL RESULTS* Polymorphism of Copper Phthalocyanlne Determination of Relative Proportion of Lota structure material in mixtures with the alpha phase Tinctorial Effect of beta phase Effect of Chlorine Content on Structure Effect of Qhlorine Distribution on phase stability. Method of Effecting phase changes Effect of `Sulfation1* on Crystal Structure Preparation of beta structure CPC of good pigment strength Determination of Particle Size from Specific Surface Effect of Finishing Method on Particle Size Relationship between Particle Size and Tinctorial Strength Polychlor CPC Future Studies of Polychlor CPC ACKNOWLEDGEMENT Page 1 1 2 2 5 6 6 7 8 9 9 10 14 14 16 16 16 DUP050066877 *2- TABLES* Classification of Copper Phthalocyanine Pigments according to Structure Particle Size of CPC Samples Relationship between Strength and Surface area Specific Surface of Polychlor CPC Samples Page 4 11 15 17 FIGURES* Fig, I * X-ray Spectrometer Record of Alpha Structure CPC. Fig. II* X-ray Spectrometer Record of Beta Phase CPC. Fig* HI* X-ray Spectrometer Record of Mixture of 10$ Beta Phase, 90$ Alpha Phase. Fig. IF* X-ray Spectrometer Record of Mixture containing 30$ Beta Phase, 70$ Alpha Phase. Fig, Vs Electron Micrograph of Sample of Chlorine-free CPC after milling in Kerosene. Fig. VI* Electron Micrograph of AcId-Pasted CPC. Fig, VII*X-ray Spectrometer Record of Crude Polychlor CPC Fig.VIII:X-ray Spectrometer Record of Acid-Pasted Polychlor CPC. Fig. IX* X-ray Spectrometer Record of Solvent-ground Polychlor CPC REFERENCES* 18 EXPERIMENTAL DETAILS 19 APPENDIX* Determination of Particle Size from X-ray Line Broadening. if GLOSSARY* ` 20 DUP050066878 She studies reported here were undertaken by the Newark Physics Laboratory to provide information for use in the general Investigation of conditioning crude copper phthalocyanine for use as a pigment. The Physics Laboratory program was an outgrowth of attempts to obtain a satisfactory explanation for the differences in behavior, on ball milling in kerosene, of wchlorine-free" copper phthalocyanine and copper phthalocyanina containing an appreciable proportion of chlorine. The major portion of the work discussed herein has accordingly been concerned with investigation of the effect of ball mill grinding in solvent on the physical properties of the pigment. This report covers the period April, 1946 - thru December, 194?j the greater portion of the work was carried out by Dr. Karusb during August-December, 1946* As Dr. Karush has left the employ of the Company, the work is being reported by the writer, under whoee general supervision most of it was carried out* Chlorine-free copper phthalocyanine is polymorphous, two crystalline phases having been identified by x-ray methods* Crude chlorine-free copper phthalocyanine (CPC), chlorine-free PC which has been exposed to aromatic hydrocarbon solvents, or chlorine-free material which has been heated to high temperatures (e.g. 300C) exist in what is designated as the beta structure. On the other band, all very small particle size copper phthalocyanine (t.e. material of strength greater than that of DT-172-D standard), re gardless of chlorine content, exists in a second structure which is designated as alpha,* Salt-milled or acid-pasted CPC, whether chlorime-free, LB type (see Glossary), or monochlor CPC, exists in this alpha form. In the case of chlorine-free material, heating, or exposure to aromatic hydrocarbon solvents, of the alpha phase pigment results in its conversion to the beta structure, which latter phase appears to be the more stable for such chlorine-free material. Both crude and finished LB type copper phthalocyanine which contains as much as 4*4$ chlorine exist in the alpha structure, regardless of the method of finishing or of exposure to solvents. The beta structure is not observed with such material. Similarly, only the beta form is found in the case of monochlor CPC (5*8$ Cl)* The nomenclature originally adopted by the Newark group differed from that indicated, the phase designated here as beta being called alpha In accordance with conventional practice of so designating the form which is the more stable at room temperature. Subsequently, information was obtained which showed that Pigments Department practice differed from that used by other groups. Accordingly, to avoid con fusion, the nomenclature indicated in this report was adopted* DUP050066879 2 The information obtained in the course of this investigation supports previous findings to the effect that, in the particle size range investigated, the strength of the pigment increases with decreasing particle size (Ref. 1 and 2). To obtain the strength of standard copper phthalocyanine toner BT-172-D, it appears that the pigment must have a surface area*of the order of 50-60 square meters per gram. Determination of specific surface of the pigment appears to provide an adequate measure of its particle size. Useful estimates of particle size, which in general Indicate the same relative size order as do specific surface data, can be obtained from line breadth measurements of the x-ray patterns of the pigment samples. 5 com pletely satisfactory electron micrographs have been obtained of CPC samples of particle size of 0,f micron or leas, owing to inability to disperse the small particles to the desired degree. However9 qualitative confirmation of the particle sis estimated from spe cific surface has been obtained in certain cases by means of electron micrographs. auiuuiiIS WORKi The formal Physics laboratory program of phthalocyanine investigations was discontinued at the end of 1946 owing to the changed personnel situation in that laboratory. Since that time, a limited amount of work has bsen carried on for the phthalocyanine research group on a service basis. It is planned to continue this arrangement until current problems associated with "start-up" of the new plant have been disposed of, at which time a long range investi gation program will be formulated. ]>iSPSI0ji; Mmokim t. . Study of the crystal structure of copper phthalocyanine was undertaken in 1946 to provide information for ns in the study of conditioning methods for copper phthalocyanine pigments being carried on by the Newark research group. The initial investigations by the Physics group were concerned with attempts to provide an explanation for the observation that although a pigment of strength comparable to that of BT-172-D standard could not be prepared by ball-milling crude chlorine-free CPC in kerosene, no difficulty was encountered in obtaining samples of strength superior to that of the current standard by grinding chlorine-containing CPC, such as the monochlor or LB type, under comparable conditlona (Refs. 3, 4). DUP050066880 3 Information available In the literature regarding crystal structure and phase composition of CPC (Ref. 5) suggested that the difficulty of obtaining satisfactory size reduction in the case mentioned might he associated with the polymorphism of CPC. Unfortunately, the data ware inadequate to permit satisfactory conclusions regarding this point. Accordingly, study of the sig nificance of the phase relationships of CPC and of their relation to the problems under consideration was inaugurated* It has been found as a result of this study that the investi gated copper phthalocyanine pigments oan be classified (fable I) into two general groups. Those samples giving an x-ray spectrometer record like that shown in Figure X have been classified as having the alpha structure, while those giving a record like that of Figure II are said to have the beta structure. A given type pattern is most easily distinguished from the other one by the presence in the beta pattern of marked diffraction maxima at 20 values of 18*2 and 9.2 which are absent In the alpha pattern. (The 29 * 9.7 'peak*1 in the alpha pattern Is significantly displaced from the position of the aforementioned peak at 20 9.2). DUP050066881 TABLE j CLASSIFXCAT ION OF COPPER PBTHALQCYASUfE PIGMENTS mmmtMMMWsm iiii Alpfra. Mmotev&JLnlz Salt-milled CPC* Aoid-pasted CPC* lionoohlor CPC, either crude or finished* Li type CPC (4.4$ Cl), either crude or finished Acid-pasted or salt-milled chlorine-free CPC ball-milled in alcohol or acetone* GROUP 2 Crude Chlorine-free CPC Chlorine-free CPC after exposure to hydrocarbon solvents** Chlorine-free CPC after heating bfc 300C for 3 hrs.** Crude seml-chlor CPC*** Seoi-chlor CPC (crude, acidpasted or salt-milled; after severe exposure to & hydro carbon solvents.* ** Crude chlorine-free CPC ball-milled in solvents* Crude seml-chlor CPC ballmilled in solvents. *** Applies to all samples, regardless of chlorine content*in the investigated range 0,1 - 6% Cl, which have been finished by ao id-pasting or salt-milling to yield products of standard strength and have not subsequently been exposed to solvents or heated* Holds for samples finished by any of the Investigated methods! acid-pasting, salt-milling, solvent-milling. Both phases present* DUP050066882 the following generalIzatIons are supported by the experimental results (1) All samples of properly acid-pasted or salt-milled CPC, as indicated by strength greater than that of standard BT-172-D, exhibit the alpha structure, regardless of chlorine content* (2) All samples of monochlor (5.8)( Cl) CPC,or of IB type CPC containing as much as 4.4$ chlorine, exhibit the alpha structure only* the beta structure has not been observed with any samples of this type examined thus far. (3) The beta structure has been observed only with relatively large particle size pigmentsj despite repeated attempts, no beta phase sample of strength greater than that of BT-172-D has been prepared. Conversion of the alpha phase to the beta has resulted in crystal growth In all cases observed thus far. The largest surface area observed thus far with beta structure CPC Is approximately 50 square meters per gram. (4) Ho alpha structure sample of very small specific surface (i.e* large particle size) has been found thus far* The minimum surface area observed with alpha structure CPC> is approximately 20 square meters per gram* This value is less than the surface area found with some beta phase samples, indicating that the size range of alpha and beta structure materials overlap* <5) LB type CPC containing only 3*5# chlorine, (as well as some - but not all - samples containing 4,0% Cl), and seml-ehlor CPC (3*0)8 Cl) are dimorphic. The crude pigment or the solvent-milled sample in these cases is apparently a mixture of the alpha and beta phases) the acid-pasted or salt-milled pigment is in the alpha phase* (6) The two phases can coexist in the same sample* Certain of these generalizations will be discussed at greater length in the sections which follow* Determination of Relative Proportion of Beta Structure Material in Jtat.im,, ------------------ ---------------------- ---- The presence of a small proportion of the beta phase in mixture with the alpha phase can be most easily detected by means of the diffraction maximum at 2 =* 9.1-9*2 which-is given by the beta phase* The effect of mechanically mixing 10% and 3055 (on * basis of the mixture) of beta phase CPC with the alpha phase (acid-pasted cPO is clearly evident on comparison of Figures 111 and IV with Figure II. It is apparent that the presence of as little as 10% of the beta phase is recognizable in this case* 1 DUP050066883 6 It should ho noted| however, that crude* very large particle size beta phase CFG was used in making the mixture containing only 10# of the beta phase, whereas relatively small size solvent-milled chlorine-free material was used in making the mixture on which Figure 17 Is based* A comparison of a mixture (70# alpha, 30# beta), made with use of crude chlorine-free CFG, with the aforementioned one, reveals that the solvent-milled chlorine-free CFG produces less of a change in the x-ray diffraction pattern than does the crude (large particle else) CPCi accordingly, it appears desirable to repeat the study using solvent-milled CPC* The difference between the effect of the crude CPC and that of the solvent-milled CPC does not appear to be sufficient t alter the conclusions presented here, however* IXmltexA&l. MXmti .M, Seta ,, Fhaaa All the commercial CPC pigments examined thus far have been in the alpha phase and this phase appears to be tinetortally more desirable than the other one* Samples which contain an appreciable proportion of beta structure CPC are greener and lass intense (duller) than the corresponding, pigment In the alpha form. It is suspected that at least some of the apparent dullness of beta phase pigment is a consequence of the fact that all such samples are of relatively large particle size as experience has shorn that in the case of CPC pigments, tinctorial intensity increases as particle size decreases. In any event, the beta phase is objectionable from the tinctorial standpoint, in CPC for pigment use. It is evident from the information presented in Table I that the beta structure is apparently the more stable one in the case of Mchlorine-freew CPC, and that alpha phase chlorine-free CPC- tends to be converted into the beta phase by exposure to suitable liquids or * by heating* The examined samples of Monochlor (5*8# Cl), or Newark LB type of chlorine content of 4,4# or greater, were found to exist only in the alpha structure, regardless of method of finishing, heating or exposure* Crude semi-chlor CPC (3# Cl) exists largely in the beta form while crude LB type CPC containing only 3*5# chlorine contains some beta phase* In the case of the compounds of relatively great chlorine content <>4.4# Cl) prolonged exposure to hydrocarbon solvents do effect some slight change in structure, although even after such treatment there is no, definite evidence for the presence of the beta form* DUP050066884 -7- There appears to be a general increase in stability of the alpha structure with increasing chlorine content up to a chlorine content in the range 4-50* beyond which changes in chlorine content are apparently productive of no narked effect. As previously noted, crude chlorine-free CPC (.1 - .30 Cl) exists in the beta structure} as does also crude seml-chlor CPC (30 Cl) to a large extent} and acid-pasted or salt-milled portions of such pigments revert to the beta structure on exposure to suitable solvents (e.g* xylene or trichlorbenzene). Acid-pasted or salt-milled LB type CPC made by the Newark process similarly undergoes a phase change on exposure of this type when the chlorine content is only 3*50; when the chlorine content Of the LB pigment Is 4,40, no major change results on such exposure* It appears that the stability of the alpha phase in the case of the aforementioned LB type pigment undergoes relatively abrupt Increase with increase in chlorine content from 3.5 to 4. 40|. it Is worthy of note also that the presence of beta structure material in crude LB CPC was evident when the chlorine content was only 3*50 but was not observed with a sample containing 4,40 chlorine. Present indications are that there may be a ''Critical'1 chlorine content for stability of this type pigment in the range 4-4*50 Cl but data bearing on this point are not conclusive and additional study is necessary. It is obvious that a considerable quantity of chlorine-free CPC must be present in LB type CPC which contains only 4,40 chlorine9 as the chlorine content is 5*80 when only chlorine containing CPC is present. It appears that in the case of LB type pigment, the chlo rine-containing portion tends to stabilise the chlorine-free material}, as the change resultant from exposure to aromatic hydrocarbon solvents of LB (4,4 } CPC is very much less than would have bean expected from its necessary content of chlorine-free pigment* .siab&Ufct It appears that the crystal stability of alpha structure CPC of a given chlorine content is promoted by distribution of the chlorine in such a way that no molecule contains more than one chlorine atom. This is suggested by the fact that,for the same chlorine content, LB type CPC samples prepared wlt use of a sample of chlorpbthalic anhydride (ex Niagara Alkali Co,) known to contain a considerable proportion of dichlor phthalic anhydride are appro* ciably less stable than samplas made with Newark process chlorphthalie acid which contains less of the dichlor materials* Indications have been obtained that a more stable product results when LB type GPC is prepared with good agitation, assuring uniform mixing of the reactants, than when poor agitation is used. With poor agitation* the possi bility of non-uniform distribution of the available chlorine is increased (Ref. 6), m DUP050066885 -8- M,, Mttmt tM.Phaa3.l.Sbanflaj> Salt milling and acid-pasting by the techniques used for the production of small particle size pigments yield largely if not entirely - the alpha structure, regardless of chlorine content of the CPC, in the investigated range, 0.1% - 0% Cl. * "Finishing" of pigment by hall-milling in solvents may or may not result in phase change, depending on pigment type and natura of solvent. In general, it may he said that the possibility of effecting anything approaching quantitative conversion from beta phase to alpha phase by this technique (solvent grinding) can he excluded, hut a change from the alpha structure to beta structure can he brought about by grinding alpha type ohlorlne-free CPC in suitable solvents such as hydrocarbons or trlchlorbensene. For example, ball milling of previously acid-pasted or salt-milled (i.e. "alpha" material) chlorine-free CPC in kerosene results in marked loss in pigment strength and in change to the beta phase; no such change occurs, however, on treatment of LB or monochlor CPC in this way. On the other hand, no phase change results if the milling of chlorine-free pigment takes place in acetone or iso propyl alcohol. The minimum chlorine content of crude CPC necessary to Insure adequate phase stability so that particle size reduction can be effected by the ball-milling technique^cannot be specified with great precision at present. Semi-chlor tyPC (3# Cl) appears to represent approximately the minimum chlorine content of crude CPC for satisfactory grinding results in kerosene insofar as pig ment strength is concerned. It should be noted that the chlorine content for satisfactory grinding is not necessarily the same as the chlorine content necessary to Insure complete absenee of the beta phase). She solvent-milled product in this case is approxi mately equal in strength to BT-172-D, but is greener in hue, and contains a large proportion of "beta" material. Crude chlorine-free CPC is improved slightly in strength by ballGmllling In kerosene, but it has not been possible to achieve strength more than 85% of that of BT-172-D la this way; when ground in alcohol it is possible to attains pigment strength only slightly less than that of current standard commercial pigment (BT-172-D), which is considerably less strength than can be realized if the pigment is converted to the alpha phase (e.g. by acid pasting) before grinding in alcohol. When the crude pigment is ground in alcohol, the finished material is greener than the standard product; the pigment in this ease is largely - if not entirely - in the beta structure. Xf the crude material is converted to the :Mha phase (e.g. by acid pasting) it retains that structure of subsequently ground in alcohol; if ground in kerosene, it reverts to the beta phase with loss in strength. DUP050066886 Transformation of alpha phase material into the beta phase also can be brought about in the case of chlorine-free CPC by means of heating* Heating salt-milled (alpha structure) chlorine-free CPC in vacuo at 300C for 3 hours results in substantially complete conversion to the beta form and effects marked growth in particle size* Beating for 2 hours at 205C (open air) resulted in only slight phase change* At one time it was believed that a considerable part of the tinctorial improvement resultant from "sulfation'1 of la/CPC (l.e* formation of CPC sulfate by addition of concentrated sulfuric acid to the condensation slurry, followed by reconversion to CPC by hydrolysis) was a consequence of conversion of any of the tlnctorially undesirable (green) beta phase CPC present to the alpha structure* The evidence now indicates that such con version is of minor importance in the case of chlorine-containing CPC of the type to be manufactured by the Pigments Department (4.4# chlorine). In this case the absence any detectable amount of beta phase in the crude pigment before sulfation has been definitely established and no phase change is evident as the result of the treatment* This should not be interpreted, however, as meaning that a change could not be brought about were the pig ment in the beta structure before sulfation, as it appears possible that such change could be effected* We have not investigated this point, however* in any detail. ZjmMMs&lmM. Attempts were made to prepare samples of beta structure CPC of tinctorial strength comparable to that of commercial phthalocyanine pigments, all of which examined to date have been alpha structure material* It was considered net inconceivable that such small particle size CPC, even though chlorine-free, would be resistant to crystal growth* Attempts to transform small particle size alpha structure pigment into beta phase material of approximately the same size particles were unsuccessful! in all cases in which such phase transformation took place, pronounced particle size growth also resulted, so that the product was of poor strength* This was true when the transformation resulted from heating, as well as when it was brought about by solvent exposure. Only by ball milling In selected non-hydrocarbon solvents (e.g* alcohol) has it been possible to obtain beta phase pigment of strength approxi mating that of the commercial standard, end even in thia ease such strength is barely achieved and then only with difficulty* The maximum surface area observed with such material is 47 square meters per gram as compared to values of 95 found with solventmilled LB type pigment* DUP050066887 - 10 Beta 3 trueture solvent pilled pigment was found not to Be completely resistant to crystal growth on exposure to aromatic hydrocarbon solvents, and was also poor in tinctorial qualities, "being green and dull compared to the corresponding acid-pasted sample. As the result of these findings, the interest in pre paring strong beta-structure pigment has decreased considerably. the difficulties encountered in the aforementioned attempts at preparing strong pigments by ball-milling chlorine-free CPC in hydrocarbon solvents is readily explicable on the basis of the findings discussed in the foregoing sections. Programs involving study of conceivable means for direct preparation of pigment of small particle size, investigation of the effect of pressure on phase stability, and study of tha mechanism of phase transformation by means of salt milling, were formulated, but were discontinued owing to lack of staff following the change in personnel of the Physics Laboratory. Determination of Particle Size ....................................................................... . Determinations of specific surface of copper phthalooyanine pigments by the BronAuer-Eaimett-Teller technique Involving nitrogen adsorption (Ref. 12) have, in general, provided data from which useful estimates of particle size can be made* However, In certain cases the method apparently leads to serious error. For example, extraction of the soft texture treating agent (naphthenic acid), which was present in one sample to the extent of approximately 10, apparently increased the surface area from 16.3 to 77.0 square meters per gram.* The method also yields obviously erroneous values for the specific surface of acid-pasted samples which have been dried without special treatment* For example, in the case of one dried sample of acid pasted material, a surface area of only 0.4 square meters per gram was found, which corresponds to par ticles which should be visible microscopically* She misleading results in these esses are apparently a consequence of cementation during drying. Particle size data for representative samples are shown in fable II. Footnotet This matter was reviewed with Prof. Emmett by Prof. Seitz at our request. No satisfactory explanation for the change was achieved. It is conceivable that naphthenic acid can "cement1* the particles together. DUP050066888 - IX SAMPLE wmi, TABLE II mr.-m X^3____ MflgASg-ARgA .Ma.la.tag/JLC> LB Type, Crude CPC (0.022>M. LB Type| Acid-pasted 0.0147 LB Type, Solvent grd. 0.017 , LB Type, Solvent grd. 1 - LB Type, Salt-milled 0.013 22.8 56.2 85.9 88.*8 Semi-ehlor,acid-pasted 0.01? 98.1 Ci-Pree, Crude CPC Cl-Free, Acid-pasted Cl-Free, Solvent grd. Cl-Free, Salt-milled 0.015 0.03 0.015 4,1 50.0 47.3 77.6 0.17A 0.069 0.045 0.041 0.044 0.12LA0.52A 0.04 * 0.12-/^ 0.050 0*21 0.035 0.14 0.02-*04 0.09-.14 0.031 0,12 0.033 0.13 0.03-.04 0.08--14 0.040 0.030 0.12 .95,, 0.078 0.082 0,050 0.70 3.5 0.057 0.29 0.060 0*30 0.037 0.19 0.5-1 p m 'em 2-4 m m X Particles assumed to Be rectangular parallelepiped with length/width 4* See Reference 8. xx No completely satisfactory micrographs have Lean obtained. Bata given are order of magnitude only, and represent results of visual estimates without attempt at detailed statistical analyses of data. ,1. Strong type solvent-ground pigment. 2. Calculated from equation* diameter (microns) m Area in meters2 par gram. 3* See appendix. Also refill. DUP050066889 12 &ZJ!s &8& Estimation of particle size from x-ray line broadening has also provided useful data, The relative sizes obtained by the x-ray method are in general agreement with those calculated from specific surface data (Table II),. The size data obtained from x-ray methods indicate a smaller particle size than that calculated from specific surface. This has been interpreted to mean that the "coherent domain" is appreciably smaller than the size of the particle. Details of the calculation of particle size from x-ray data are given in the appendix* ilsMrmJlgmggpz Ho great difficulty has been encountered in obtaining satisfactory electron micrographs of weak, relatively large particle size CPC such as. for example, crude (beta structure) chlorine-free CPC, However, it has not been possible in general to secure Satis factory micrographs with small particle size pigment such as solvent ground, acid pasted, or salt milled samples of strengths equal to or greater than that of BT-172-D standard. The difficulty apparently is a consequence of inability to obtain satisfactory dispersion of the pigment particles in preparation of the mounts for use in the micro scope. Various mounting techniques have been investigateds the use of dispersion agents such as "BlancolM, ammonium naphthenate, PBSS (poly benzyl sodium sulfate), dioctyl phthalate, or sulfonated CPC, to facilitate dispersion of the pigment on mixing in a high speed mixer with water, did mot lead to satisfactory mounts. In all cases large aggregates were evident in the electron micrograph obtained from mounts prepared in this way. Similarly, ball mill grinding of the samples in water in the presence of various dispersing agents did not yield satisfactory dispersion. The best results obtained to date have resulted when the mounts were made by a dis persion technique involving preparation of an ink by grinding the pigment samples with oleic or naphthenic acid on a "Hoover" muller, adding a portion of the resulting ink to hot ammonium hydroxide solution, and placing a drop of the resulting water dispersion on a preformed nitrocellulose film* While it has not been definitely established that the dispersion technique does not affect particle size of the pigment, It is believed that this is the case with pigments of small particle size, since there is no evidence of particle size reduction on preparation of conventional inks by use of the Hoover muller, as judged from strength comparison of the inks prepared in the muller with the inks prepared by flushing (no grinding). There is, however, serious doubt as to whether the method is applicable to pigment of relatively large particle size, i.e., pigment of size rsngs between that of crude CPC and BT-172-D, Also, there is considerable question as to whether the method would be satisfactory as a means for determining particle size changes on ball milling of crude CPC, for example. It is planned to investigate these matters further* DUP050066890 13 * In the ease of strong samples of CPC, no improvement Is the quality of the electron micrographs has resulted from the use of the metal shadowing technique. In fact, there is some evidence which indicates that the metal used for "shadow casting" can bridge tiie gaps between adjacent very small particles of CPC to make such aggregates appear as one large particle, only in the case of salt milled CPC has it been possible to obtain apparently satisfactory micrographs from shadowed mounts. In this case the micrographs from the shadowed mount indicate the presence of roughly spherical particles, whereas micrographs from a comparable non-shadowed mount (different sample of salt milled CPC) indicate the presence of very small needle-like particles. This matter Is being investigated further. The best micrographs obtained thus far Indicate that solvent ground and acid-pasted (low turbulence drowned) CPC possess approxi mately the same particle size, and the particles appear to possess the same shape in the two cases. Balt allied samples, on the other hand, appear to be appreciably smaller than the solvent ground or acid pasted material, but - at least in the case of the non-shadowed mounts - the particle shapes appear to be approximately the same as that for the material processed in the aforementioned other two ways* These results relative to particle size obtained from the electron micrographs are in harmony with the data from specific surface measurements. The effect of heating on the particle size and shape of salt milled (beta structure) chlorine-free CPC is clearly Indicated by electron micrographs* The effect on exposure of such salt milled material to solvent is also clearly evident in this case. Of interest is the observation that water grinding of crude CPC re sults in appreciable particle size reduction, with the production of a considerable proportion of very small particle size material, but without, however, the complete elimination of the large particles. Electron micrographs of ball milled (kerosene) crude chlorinefree CPC (beta phase) and acid-pasted (semi-chlor) CPC (alpha phase) are shown in Figures V and VI, respectively. Foot note: Of interest is the recently reported observation (F.A. Hamm, "Polymorphism of Organic Pigments", am as yet unpublished paper delivered at the December, 1W meeting of the Electron Microscope Society of America) that bombardment of CPC(presu#ably chlorine-free) with 65 KV electrons in an electron microscope results in a phase change. It was not possible to duplicate this reported finding in this laboratory with use of the low energy <30 KV) electrons available. DUP050066891 -- 14 It is considered worthy of note that .with the samples examined thus far by means of the electron microscope, the differences between the appearance of the alpha and beta types has been such as to permit classification of the samples according to crystal structure on the basis of electron micro* graphs alone* The difference in the appearance of the two types is readily evident on comparison of Figures V and VI. however, only relatively large particle site beta structure CFO has been examined in this fashion; it appears that difficulty might be encountered in making classifications in this way if a small particle size beta structure sample were involved* . Particle size data for pigment finished by acid pasting, salt milling, and solvent milling are shown in Table II. It has been found that the variation between samples finished by a given method are greater than the differences which can be attributed to the method itself* Present indications are that at the present state of the art, particles eah be obtained by ball milling techniques which are within the same range of particle size as is obtained by acid pasting and drowning by the high turbulence technique currently used commercially to yield small particle size products. While the maximum specific surface we have found thus far for salt-milled samples is slightly less than the maximum indicated for acid-pasted material, this is not considered indicative of inherent superiority of acid-pasting methods in this respect, inasmuch as only a limited amount of information is available in the Bewark laboratories on the salt-milling process* and it is our opinion that improvement would be effected by further study* Q?he indicated acid-pasted sample (Table II) having a surface of 98 meters2 per gram was supplied to us by Jackson laboratory. It represents acid-pasted chlorine-free CPC drowned by a high turbulence technique and stabilized with 4# of salt-milled tin phthalooyamine and ''soffctexture', treated with trichlorbenzene. Apparently,because of the soft texture treatment, the sample did not exhibit the previously mentioned spurious low apparent specific surface characteristic of acid-pasted material which has been dried without treatment* Also* since only traces of the treating agent remained in the dry pigment, the results should not have been influenced by the presence of treating agent. This sample represents the (dry) acid pasted material of greatest strength and specific surface examined in the Bewark laboratories! fielatlonahlp Between^Particle. .Size..and Tinctorial Strength In general, we have found, in accordance with previous observations (Bef. 1, 2), that the tinctorial strength of copper phthalocyanine pigments increases with decreasing particle size in the investigated range. The exceptions to this generalization have been found in oases of very hard samples where there is good reason to believe that the full tinctorial value could not be DUP050066892 15 realized owing tocementation of the pigment particles, or in cases in which nosatisfactory particle size data could be obtained owing tothe presence of naphthenic acid OS* other con-* taminahtsnwhich cause erroneous results by the nitrogen adsorption method* In such eases the strength realized by flushing procedures, in which the pigment is evaluated without allowing opportunity for cementation during drying, has been much greeter than that obtained by test of the dried pigment# it is worthy of note that such strength discrepancies are confined to acid-pasted samples; in the case of the investigated salt-muled and solvent-ground samples, the same strength has been realized by test of the dry pigment as with flushing procedures# Some Idea of the strength-size relationship can be gained from the dite presented in fable III. For fuller discussion of particle size-strength relationships the reader is referred to a report by the Jackson Laboratory Physical Chemistry group (Ref# ?) TABLE III Relationship Between Strength and Surface Area SAMPLE mm* mu (meters2 per gram) Crude LB (unground) 22.8 Ground with 1/2 balls Ground with 5/32" balls 62.5 81# 1 Ground with 5/32" balls 85# 3 Ground with 5/32rt balls <S.t.) 94.9 (MD-1255*) 98.1 {% of BT-172-D) 60-70 105JS 120 120 125-130 130-135 Acid pasted sample supplied by Jackson Laboratory# DUP050066893  16 Polyehlor Cgfi., The x-ray spectrometer records obtained with crude polyehlor CPC, acid-pasted polyehlor CPC, and solvent-ground polyehlor CPC, are shown in Figures VII, VIII and IX, respectively. The differences In the patterns appear to he due to the effects of changes in particle size rather than to polymorphism. It has been found that polyehlor CPC changes from a green to al blue on ball-milling in an aqueous medium in contact with iron, in the absence of a suitable inhibitor (Ref. 4), When chemical analysis failed to provide an explanation for the change in hue, a brief x-ray investigation was inaugurated in the hope that this would provide a possible solution of the question* However, the patterns of the material before and after the aforementioned change were quite similar and no difference in the two records was evident which was considered indicative of a significant structural difference. An explanation'was also sought thru x-ray studies for the fact that samples of polyehlor CPC of a given chlorine content differ significantly in hue; for example, occasional samples of chlorine content in the range 45-46# are reported to be as yellow in hue as conventional samples containing approximately 47.5# chlorine. The x-ray studies failed to indicate a cause for the abnormality. Values for the specific surfaces of polyehlor CPC samples are shown in Table IV. (The results of duplicate determinations are indicated in two cases to give an idea of the reproducibility of results). It is to be noted that because of the greater density of polyehlor CPC as compared to CPC, for a given value of specific surface the particle diameter calculated for polyehlor CPC is only 1,54/2.09 of that of the size for CPC. Hence, It appears that the particle size of the stronger polyehlor CPC samples Is approximately the same as that of the stronger CPC samples. Future Studies of Polyehlor CPC An extensive program of x-ray studies of polyehlor CPC is outlined in another report (Ref. 9) in which, are also presented the results of a preliminary survey of the problem. A more specific program will be drawn up following acknowledgement completion of plant start-up. Acknowled gement The x-ray patterns and specific surface data referred to herein were obtained by the Experimental Station Physics Croup on samples supplied by the Newark Research Department. Suggestions were received from the Experimental Station group as well as from Professor Seitz (Carnegie Institute of Technology) who assisted in a consulting capacity in much of the work reported here. DUP050066894 - 17 -PJ:-EOLYCHXOR_CPC_S^j^S e AlfDTf? (meters2 per gram] Crude polychlor CPC1 o Crude polychlor CPC Acid-pasted Standard (Of-486-D, SD-48421) 14.0 3*43 3.58 69.7 Solvent-milled pigment1 78*4 77.9 microns* 0*21 0.042 0.039 Diameter calculated from equation* Diameter (microns) Itflfaee Area in meters2 per gram 1. Chlorinated by aluminum chloride-sodium chloride eutectic process. Sample supplied by Jackson Lab* 2. Chlorinated by "dry chlorination method11 Sample supplied by Jackson Lab* DUP050066895 DUP050066896 DUP050066897 FIGURE V ELECTRON MICROGRAPH OF SAMPLE OF CHLORINE-FREE CPC AFTER MILLING IN KEROSENE. DUP050066898 FIGURE VI . ELECTRON MICROGRAPH OF ACID-PASTED CPC DUP050066899 FIGURE VII X-RAY SPECTROMETER RECORD CRUOE POLYCHLCHLOR CPC 26 VALUES O DUP050066900 DUP050066901 18 Wm 1. ESP-37-201. "Particle Size and Tinctorial Strength of CPC" S. D. Bailey, 1937, 2. KN-37-631. "Particle Size and Tinctorial Strength of Copper Phthalocyanine". A. Siegel. Hovember, 1937* Hewark File 223.4 3. KN-46-19. "The Finishing of Phthalocyanine Pigments li Bet Grinding Study", F.W.lane. June 3, 1946, Hewark Filei 223*4 4* KN-46-55. "Progress Report, The Finishing of Phthalocyanine Pigments IT, Wet Grinding Study", A.J.Stratton. August 12, 1946. Hewark File* 223.4 5* I.C.I, Report H-2?57. "Monastral" Fast Blue B, Substitution of Aoid Pasting Process by Milling Methods", F.R.Cropper. April, 1937* Also see British Patent application So, 5721-1944. American Cyanamid Company, 6. KH-47-51* "Monastral Fast Blue LB* Process Development", iw F. Eferich. February, 1948. Hewark File* 223.4 7. JLR-28-34. Serial Ho, 19784. "Optical Properties of Colored Solids 1, Theoretical Study of Dilute Suspensions" by F. C, Chromey and If, J, Sohuler, April, 194?, 8. Letter, C. G. Worts to A, H, Hanks, March 24, 1947, "Specific Surface of Pigments* Calculation of the Dimensions of Rod-shaped Particles from Surface Area Measurements", 9* DED X-47-12, "Monastral" Green Process Development, Crystallographic Studies, MX-1074". J. R* Caddell. July, 1947* 10, Letter, B. H. Perkins to D. Graham, "Phthalocyanine Pigments Determination of Particle Size from x-ray Line Broadening", April 23, 1947, Hewark Pile* 223,4* 11, L.S. Birks and H. Friedman, "Particle Size Determination fSfcT*. PlUd iZ, 687 12, Brunauer, Emmett, Teller, "Adsorption of Gases in Multimolecular Layers", JAGS, 0, 309 (1938), DUP050066902 19 notebook 1223 X-ray Spectrometer records arc filed in the leader's office in #23 building. UU DETEHIIINATIOH OF PARTICLE SIZE FROM ....1-MX-^.isg.jiicmim___________ Particle else data relative to copper phthalocyanine samples were calculated from x-ray data according to the method described by Blrks and Friedman. J. Applied Physios. 17. 687 (1946). The equation used is - ID * cos 0 where B*2 - b'2 and D particle diameter,, in B s line broadening ( in radians) B' line width at half-maximum (in radians) A - is the wave length of the x-radiation used (Cu, Kg in our case) * is the Bragg angle (radians) b's "instrument width" (in radians) K - is a constant which we have taken equal to 1. The value of b* was taken as the line width at half-maximum obtained with samples of large particle else CPC (crude Cl free)* In the case of spectrometer records obtained with use of the Experimental Station Geiger counter spectrometer with slit widths 10-20-10, b1 has the value of 0.00447 radians* (The value of b' is approximately O.OO618 radians with slit widths of 20-40-20 which have been used occasionally in the x-ray work). The "halfwidth" of the peak corresponding to a 0 value of 3*4 - 3 5 has been used in the calculations of particle size* DUP050066903 20 * GLOSSARY: "Chlorine-free" CPC. Pigment prepared by the phthalic anhydrida-urea-kerosene route. Contains less than 0,5$ chlorine. la Tv d * CPC, Pigment prepared by the pkthallc anhydride- urea-kerosene route with the use of sufficient ohlorphthallo acid (or derivatives) to obtain a product containing approximately 4# chlorine* BT-172-B. Current DuPont commercial standard acidpasted semi-chlor CPC. Contains approximately 10# of a softtexture treating agent consisting of triethanolamine-lauric acid ester-salt. Strength, as referred to herein, is measured by the quantity of pigment (in the form of an iok) which must be mixed with a given quantity of a white pigment paste to match a given mixture of the standard pigment with the white pigment paste (see $P-132-11). A pigment is said to be 20# strong, for example, if 100 parts of it match the aforementioned mixture obtained with use of 120 parts of the standard CPC. Salt-milling. A method of reducing the particle size of pigment involving ball milling it (dry) in the presence of 4-10 times its weight of salt in a ball mill with pebbles or metal bars or rods. Ball milling pigment with balls in a conventional ball mill in the presence of a solvent. DUP050066904