Document ymzVxYrZGywdbJMQ7vL0M64oX

* * 1 r '' > TO:. Return tot COPDppi Jackson tsboratoiy R. & D. File Room TOtReturn to: c d p Dept Jackson Laboratory R. & D. File Room TOt. Return to; COP Dept Jackson Laboratory R. & D. File Room TOs. Return tp: CDPDept Jackson Laboratory R. & 0. Fite Room TO;. Return tot mu -imo v. s/T8) COP Dept JRa.c&ksoo.nFLitaeboRroaotomry i si DUP050068193 t\ '/ oONTAite. J......... !^ES?c?:c3rj*.v -. ' mmi m icHQ.zz BURNING OR SHRI Social'HO* KN-50-16 Copy No. Irft Copy to: #1 - Numerical Pile 2 ~ Research Office (223.4) 3 - Library File (223.4) . 4 - D. B. Killian 3 >*\A. R, Haake 6 - W* F. Spangaman 7 - H* E. sobroeder-iFaekson Lab. 8 - Eafcra 9 - Extra 10 -.*** ' r et ur n t o JACKSON LABORATORY \ 4 ' ' \V\ FILE ROOM i NEWARK PLANT PIGMENT COLOR RESEARCH REPORT Progress. Report , Title i BEHAVIOR OF COPPER FHTHALOCYANISE PIGMENTS IN FAINT SYSTEMS. I APPLICATION OF ELECTRON MICROSCOPE AND X-RAY DIFFRACTION TO THE STUDY OF CRYSTAL GROWTH Period Covered: JAN. 1949 TO AUG. 1950 Charge: 1101-11-20 SUBMITTED BY -2 APPROVED BY: DATE SUBMITTED S 8-11-50 DATE ISSUED: Oct. 4, 1950 DUP050068194 Preface This report Is "based on a paper prepared by A*R, Hanks and B.H. Perkins with the intent of publishing it in one of the scientific Journals such as Ind. & Eng* Chem. Because of the critical patent situation surrounding the beta phase CPC pigment and the industrial importance of some of the finishing methods which are briefly referred to in the original draft, plans for publication were abandoned* Table of Contents I Introduction II Types of Copper Phthalocyanine Pigments III .1 Experimental A, Experiment No. 1 Crystal Growth in Mineral Spirits B, Experiment No* 2 Crystal Growth in a Lacquer Vehicle C, Experiment No. 3 Crystal Growth in an Alkyd Vehicle D* Experimental Details Common to Exp, , .2 & 3 IV Crystal Growth Characteristics of Copper Phthalocyanine V Cause of Crystal Growth -l A*' Change of Phase . B, Crystal Strain VI Crystal Growth Associated with Loss in Tinting Strength VII , Summary Page 1. 1 2 2 2 3 4 5 .i 10 16 16 17 10 DUP050068195 X XIsSTRODUCJIOII The pigment copper phthaloeyanine pass e s s es. .cert ain.;out st anding characteristics, noteworthy of which are its groat tinting strength, its excellent lighfcfastness, and Its unusual chemical stability (1)# Because of these excellent properties, copper phthaloeyanine is extensively used in the pigment -consuming Industries* Effective utilisation of the full inherent Qualities of this product in practical pigmented systems has presented certain problems, the one giving the most difficulty in paints being the tendency to change in tinting strength and hue on aging# These changes are well recognised by paint technologists and are generally attributed to changes in the size of the light scattering unit as a result of flocculation effect and/or crystal growth# ?esce (2) has demonstrated the occurrence of flocculation and crystal growth in systems pigmented with one type of copper phthaloeyanine and has reported the influence of various solvents on the crystal growth of this sample, as revealed by examination with the light microscope following;brief solvent exposure# So study of the crystal growth and floeculationbehavlor of the several other available types of copper phthaloeyanine pigments has been reported* xi t y h s s o p cogPEB PHgriALOcrfABiKE p x &mit s s copper l^tkalocyaisina pigments may be classified on the basis of their chlorins contents, which vary from approximately 0*S^ to about 5*8;$ln the case of the commercially available types*! A second basis for classification is provided by crystal phase con siderations* Two crystal phases of copper phthaloeyanine have been recognised (5,4,5) the more stable phase being ordinarily designated as beta and the less stable phase as alpha# A classification of the usual cosaaeroial types of copper phthaloeyanine pigments - i, available in this country, on the basis of these considerations, is given in Table X* These pigment types are the ones examined with reference to crystal growth in typical paint systems or paint solvents# The designation "aono-chiorH refers to a product con taining one chlorine atom per copper phthaloeyanine molecule <G) while the t,semi-ohloi" type contains , on the average, one-half atom of chlorine per copper phthaloeyanine molecule? a product containing about 4#4$ chlorine is commercially available and has been designated in this report by the term WK3H# %he chlorinated blue pigment with chlorine content of 5*8$ or legs, which is the subject of this investigation, should not be confused with the highly chlorinated oopper phthaloeyanine green which con tains up to about 50$ chlorine# The chlorine content of the pro ducts under consideration is considerably lower? also the products are all blue a nd possess the same crystal structure as chlorinefree" copper phthaloeyanine# In contrast to this, the highly chlorinated pigment is green, and has an entirely different crystal structure# DUP050068196 -2 - Sample Boslcamtion m&su Bamplo Type Crystal Approx, Hiase J5..4SL...... E32D-1S43, B-6623 AET-S97-D Lot 349 BT-172-S Lot 433 BT-284-D SD-38165 E5D-115S-BT J2BB-lil3 - Acid-Pasted, "Chlorine-Free** Solvent-Ground, "Chlorine -3Tee** Acid-Pasted, nSemi-Chlc',, Solvent-Ground, "IS** Acid-Pasted, *tBw Acid?astod, "Mono-Chlor" Alpha Beta Aljsha * 0*3 0.3 2,0 ' 4,4 4,4 5.8 in wsmimmAU Three seta of experiments were designed to observe the crystal growth behavior of the typos of copper phthalocyania listed in Table t. - A. Experiment go. 1 CRYSTAL G3037TS XH MINERAL SPIRITS Some of each typo of pigment was allowed tost and in mineral spirits at roon temperature. "Verso!" 80. 2$ a mineral spirits purchased from Standard Oil Co, of ftew Jersey was used# Troa time to time, small, amounts of pigment wen withdrawn and observed by means of the electron microscope. founts fop the election microscope wop mad by nubbins a few drops of th slurry with a spatula and thinning with more mineral spirits until a uniform dispersion was obtained, A drop of this thinner dispersion was then placed on a mounted preformed "Porcrrar" films. In those cases where a change was observed to have resulted from the exposure, x-ray spectrometer records were obtained after filtering off the mineral spirits and air drying the residue, IMa wag done to observe any change in crystal phase that might have occurred during the crystallization. B* Experiment Bo. 2 CRYSTAL cmOCTPH IB A BACQBER VEHICLE By ball mill grinding, typical lacquer enamels were prepared from the pigments listed ia Table I with the exception of the S!taono"ehlorM and the acid-pasted ffLBH types, Th lacquer vehicle Is designated as K7-36 and its composition is outlined below. Lacquer Vehicle KV-36 Grinding Vehicle T-5G0I -QE-2570 -53.3$ D1 butyl phthalate - 5.3$ Blown Castor Oil (Baker's #15) - 2,7$ 1-3601 -38.7$ Butyl Acetate -37.0$ Toluol -33*0$ Ethyl Acetate -12.5$ Butyl Alcohol -12,0$ Ethyl Alcohol (23A>- 3,5$ DUP050068197 a glyceryl phfchalate resin modified with a non drying oil. Bee General ElectricVs catalogue on Glyptal Alkyd Regina tor more detailed specifications* Preparation ot Bine Lacquer Pigment Grinding Vehicle Thinning Vehicle Ball mill tor Add Thinning Vehicle 68 grams -362 grams -170 grams 72 hours -SSI grams Shinnlm Vehicle 1/4 sec* nitrocellulose , (70$ solids) 1/2 sec* nitrocellulose (70$ solids) T-3603L - 14*9$ * 14*9$ - 70.2$ Ma blue lacquer was placed in a can with a tightly fitting cover and stored in an oven at 50G (122F) * From t lme to time portions wore withdrawn and electron micrographs were obtained* The mounts were prepared by the following technique 4 a few drops of the lacquer were thinned with a few drops of $-3601 and the mixture was worked with a spatula on a suede finished "Carrara" glass plate until a uniform dispersion was obtained* A drop of this dispersion ms then placed on a glass microscope slide and smeared out with another slide? the dried lacquer film so produced mas floated on water ad picked upfy amounting screen* In those cases where appreciable crystal growth took place, some of the pigment was extracted from the enamel and x-ray spectrometer record# ware obtained to observe any crystal phase change that might have occurred* The pigment was removed from the vehicle by thinning with the "thinner?! designated $-3601 and centrifuging until most of the pigment was thrown down* After decantation the pigment was rcslurried with more thinner and again centrifuged* The pigment was then vacuum dried at room temperature. Using this technique, some of the finer particles remained suspended, but since the primary purpose was to ascertain if crystallisation was accompanied by a phase change, iatorest was centered mainly on the largo crystal lites and the loss of some of the fine particles was in reality an advantage* C* Experiment Ho* 3 CRYSTAL GROM IS AS? ASKSP VEHICLE ' By ball mill grinding, a typical alkyd enamel was prepared of the same pigments used far Experiment Ho* 2* The alkyd resin used was a drying oil modified glyceryl phthalate, designated as Glyptal 2453* The enamel has the following compositions DUP050068198 Blue Alkyd Snasaei figment "Glvptal" 2453 Mineral spirit; (VarsoX #2) Grind Beduce isitii GE-2458 - S4 grams -529 grams -251 grams - 70 hours -514 grams From time to tits portions of the alkyd enamel were------------- ... ; and electron micrographs were obtained. The dispersion ms thin ned res* counting by mixing a few drops or the enamel with a few drops of xylol. The thinned .mixture ms mtformly dispersed by working with a spatula on a suede finished "Carrara0 glass plat. A drop of the thinned enamel was then placed on mounted preformed "Formuar" film* In those eases when pigment was extracted from the vehicle for x-ray diffraction records* the extraction was made by coat'- trifuglng the slurry twice with mineral spirits, followed by a V centrifuging with a mixture of equal parts of acetic acid, ethyl alcohol, and butyl acetate* The separation was difficult and never Complete, but sufficiently good to obtain meaningful x-ray diffraction records* p, petails Concerning Experiment g & 3 Pea? about the first month of aging of the lacquer and : alkyd enamels., tho cans were removed fromik oven every third day and were shaken for 10 minutes on a paint ; "rejuvenatcr" (manufactured by the gEtracle Paint Bejuveaa&feor-Co,}, and then replaced in the oven* This was don to make sure no settling to a hard cake occurred. It was sthsoquently observed, however*; that no hard e&a was formed even When the enamels were not shaken, so this practice was discontinued. Eofore any enamel was withdrawn for testing, the can was placed on the "rejuvenates?" and was shaken for 10 minutes* The contents were then inspected with the aid of a spatula to be assured of good uniformity* Towards the latter part of the. time . series, when a tendency to skinning become evident, any skin present was removed by straining. Good dispersion b fore sampling was desirable because these masstone enamels wero also extended with Ti0o and examined speetrophotometrically. A critical dis cussion df those spectrophotoaetric curves will b given in the second report of this series. For experiments mater 2 & 3 the total aging time was one year. For the alkyd series, this total aging time was at a temperature of 50C. For the lacquer series, the "semi-ehlor" and the "IS" types were maintained at 50 C for 11 weeks and then at room temperature for up to on year* For the "01-freeTMalpha, and' beta phase types, the lacquers were maintained at 50G for 7 weeks and thereafter at room temperature up to a total time of one year. DUP050068199 After 7 weeks aging# the von temperature ms inadvertently raised for a short but unknown length of tins and the lacquer essis blew their tops losing 'raying amounts of dinner* She loss la thinner was adjusted by adding $-3301 in sufficient quantity to bring the total solids back to the original v aim of 37$# xv csarsTAfc OROwsg: -cHftMosgaxssids-- <& c o pps s mm&UK&mxmt ' . Fig#.:!'illustrates''the extreme crystal growth experienced <&% by the acid-pasted "chlorine-free" type copper phthaloeyanine# ' From a material for which no crystals can be seen initially at a magnification of 36 #000 diameters* the material takes on a ` completely- crystalline appearance in W&&& days in mineral spirits. - A similar; cryatallisation takes place in the lacquer and alkyd systems although the rate is slower in these media# She longest time interval shown for the figure is 9 weeks but the crystalline appoarsnce is the same after one year aging* ^hia crystalliaatiem is accompanied by a c ryetallograpfale phase 'change#-.. Fig# 0 shows x-ray spectrometer records of the pigment used, in the lacquer system. The bhange in the diffraction pattern# particularly at SO values of 9*1 and 13.8 is evidence that a phase change has occurred# Fig. 5 shows an alpha phase copper phthalocyanin pigment containing S#9& chlorine # It is an acid-pasted product and is referred to as "semi-chlor" copper phthalocyanine# It grows crystals in all three media but to a lesser extent than does the comparable "chlorine-free" material* It should be particularly noted that the crystal habit is different in the lacquer than in the alkyd system# In the lacquer the crystals are of a feathery nature and tend to aggregate Into sheaf-like bundles# In the alkyd system the crystals are more block-like in habit although there still is a tendency towards the aeioulsn. Since the alkyd enamel contains considerable mineral spirits* it is not surprising to observe that the crystal habit in mineral spirits is about the same as ih the alkyd enamel. A further observation to make from Fig# 3 is that in the case of the lacquer there is very little* if any# additional crystal growth sfter 5 weeks# In the case of the enamel# there is son ovidoncc of continued crystal growth after 5 months# It appears that crystallization is more rapid in the lacquer system and is complete in a shorter length of time than in the alkyd system# Crystal growth of the "somi-chlor" type is also associated with a phase change but tho phase change is far from completo* Fig. 4 shows definite evidence of some conversion to the beta phase after aging for one year. She transformation is more pronounced In the lacquer system than in the alkyd system# It is most evident in straight mineral spirits, but in no case has it approached the completeness of the t ransformation character istics of the alpha phase "chlorine-free" pigment# DUP050068200 ELECTRON )lV/,y/r !tU2*e 1 ??^TSP CHLORINE FREE COPPER PHTHALOCIANINE DUP050068201 -7 Figure 2 X-RAY SPECTROMETER RECORDS ILLUSTRATING PHASE CONVERSION OF ''CHLORINE-FREE" COPPER PHTHALOCYANINE a) to) * DUP050068202 8 Figure 3 ELECTRON MICROGRAPHS OF AGID-PASIEED`'SEMI-CHLOR1' (2,9# CHLORINE) COPPER PHTHALOCYANINE (e) In Lacquer 5 Weeks (d) In Alkyd Enamel, 5 Months DUP050068203 Figure 5 Cont*d ELECTRON MICROGRAPHS OF ACID-PASTED ''SEMI-CHLOR'* (2.9# CHLORINE) COPPER PHTHALOCYANINE (e) In Lacquer I Year (f) In Alkyd Enamel 1 Year Figure 4 X-RAY SPECTROMETER' RECORDS ILLUSTRATING PARTIAL PHASE CONVERSION OF "SEMI-CHLQR" (2.9#)Cl) COPPER PHTHALOCYANINE Atld-posted 'Stmirchlor' Copper PfcttalocyootMfcJXCQ. Alpha Pha$% a^ .*-sT3,7*' AcM-pasted 'Stmi-cKUr' Copper />fcefoijia*CU*C9 *CtyAtelpfhllau--i M4 BieetanPlhS*^*i*riti 4 'Vo....,v 20 Values C) DUP050068204 Ik fcbo case of the "LB" type pigments (chlorine content 4*4# and alpha phase)* It was observed that if the pigment was finished by acid-pasting* far more crystal growth occurred than If the pig ment was finished by solvent grinding* Fig* 5 shows this crystal growing property of an acid-pasted product containing 4,4# chlorine* Ho lacquer or alkyd enamel of this type of "13" pigment was studied* 'Shat the crystal growth In mineral spirits is associated with a partial phase transformation is shown in Fig, 6 where the peak characteristics of the beta phase at the 20 value of 9,2 is clearly evident for the solvent exposed sample* !She solvent-ground type of "IB" pigment is also in the alpha phase* Shis pigment was observed in mineral spirits* a lacquer system* and an alkyd system* Fig, 7 shows that very little* if any* crystal growth occurs even after aging for one year* An occasional crystal does tasks its appearance but a typical non- -* eryatallina field is saown* llo evidence of any conversion to the beta phase is shown by the x-ray spectrometer records* Fig* 8 shows records of enamels aged one year and there Is no evidence of any beta phase* She alpha phase "taono-chlon" type is an acid-pasted CPC , with a chlorine. love! of 8*8# and Is the highest chlorine content pigment studied, This pigment tends to^*ow a laoy type of crystal in mineral spirits* as shown In Fig* 9* fit this chlorine level* no phase change could be detected* Fig* 10 shows x-ray spectrometer records illustrating this point, Ws now leave the alpha phase products and consider a beta phase copper phthaloeyanin pigment* Fig* 11 shows a "chlorinefree" pigment* which differs from that of Fig* 1 In that it is in the beat phase taheras the "chlorine-free" pigment previously described was in the alpha phase* She crystals of this beta phase product show no evidence' of crystal growth In any of the systems during * the period of study thich covered 8 months for the mineral spirits and one year for the lacquer and alkyd enamel* She pigment initially is shown to be crystalline in nature but these crystals* or mere likely crystal fragments* do not show, any measurable growth* The attempt failed to g et a good dispersion for an electron micrograph" of the alkyd enamel after aging one year but the dispersion is good enough to observe that the individual crystallites are still of about the same size* Far better dispersion was obtained with, the lacquer and hors It was easy to see that no growth has occurred, CAUSE OF CRYSTAL GHOTtflHg She crystal growth which is observed with certain types of copper phthaloeyanin under the aforementioned conditions Is apparently associated with the following factors: DUP050068205 >e 5 nLBM (4.45SCI) COPPER PHTHALOCYANINE ire 6 ** <rf4 (b) In Mineral Spirits 2 Weeks -PRATING PARTIAL PHASE CONVERSION JR PHTHALOCYANINE (44#C1) DUP050068206 12 Figure 7 ELECTRON MICROGRAPHS OF SOLVENT-GROUND "LB" COPPER PHTHALOCYANINE (4.4$C1) --Jw 'f .... ";W H* (d) In Alkyd Enamel 1 Year DUP050068207 * 13 Figure 8 X-RAY SPECTROMETER RECORDS ILLUSTRATING STABILITY OF SOLVENT-GROUND ttLBw COPPER PHTHALOCYAHINE (4*AfoGl) So/v*nt*Qround *L&* TM 0 \ *T~ ' Copper PhtJjqJocyonfnc. (4AXCI) 'ssssfi* !." " 1 r \ ft-: ~ Copper Phthalocyznln*. f*-4%a) +4 1-Pvg InAJfcydnam! Oneleor as J-ss--i ? T| - T -t I - ___Alplm PIwq_____g 4^Sjli 20 20 Values () DUP050068208 ~ 14 Figure 9 ELECTRON MICROGRAPHS OFACID-PASTED ,rMONO-CHLOR COPPER PHTHALOCYANINE (5,9^01) Figure 10 X-RAY SPECTROMETER RECORDS ILLUSTRATING STABILITY OF ACID-PASTED "MONO-CHLOR" COPPER PHTHALOCYANINE (5.9$Cl) . DUP050068209  IS - Figure 11 ELECTRON MICROGRAPHS OF SOLVENT-GROUND "CHLORINE FREE" COPPER PHTHALOCYANINE (c) In Lacquer 1 Year (d) In Alkyd Enamel 1 Year DUP050068210 A* CMSg 0? PBA3S A transforrsatloa from the alpha phase to the more atable beta phase apparently brings about crystal growth; a growth la particle sis has accompanied the phase transformation la all the investigated eases* This effect is most pronounced with acid* pasted ^chlorine-fTee^ copper phthalooyanine * . With increasing chlorine content there is apparently a decreased tendency for trans formation to the beta phase* In the case of products containing up to 4*d-$ chlorine, the existence of the beta phase can still b e established, but we have been unable bo establish the existence of the beta phase in samples of chlorine content as great as 5*S$* She decrease in crystal g rowth t cadency on increasing the chlorine content from 0*3$ to 5*8$ or more is believed to be due to the stabilising effect of the chlorine on the alpha phase# Obviously, if the material is initially in the beta phase - as in the case < the sample cited previously - the foree promoting such phase transforation is lost* B. CjgSlAh STEAIST ' The hypothesis that crystal strain also contributes to the tendency towards crystal growth is suggested by th fact that ntBP\ type CPC does not grow crystals If solvent-ground (Fig* 7), but doe' grow crystals If acid-pasted (Fig* 5)* It is reasonable to ' suppose that crystallites formed suddenly through. t he rapid flood ing of a sulfuric acid solution would exist in a state of greater ) strain than a product solvent-ground from crude GPC# AS previously mentioned, the higher the chlorine content# the less tendency there is fcogpow crystals# but oven with th "mono-ehlon" type, ishich is the highest pereent chlorine type studied, the acid- pasted produot still grew a very lacy type of crystal (Fig# 9) Sere again this tendency t owards crystal growth is believed to be associated with t he fact that the product is acid-pasted and the crystallites ore in a condition of strain* The relief of this strain through reorystaXilzaiion can a csouat for some of the crystal growth observed among some- CB5 pigments# This mechanism of crystal growth has long been recognised la the metallurgical field but has received little attention in the field of organic chemistry* The crystal s train hypothesis stated above is not to be. con fused with the well recognised tendency of large crystals to grow at tho expense of th small ones owing to the larger surface energy of the latter# In t he case of the particular systems under : examination this factor does not appear to be very important* For"., example, in the case of the stable "is" type pigment in which the particles are of size comparable to the smallest which have been observed with copper phthalocyanine pigments, and with which t his influence would b e expected to.be operative, no appreciable crystal growth is observed over a period of tne year# DUP050068211 -n.7 ** ; VI cmsS&L OaOBEB ASSOCIATED KISH LOSS IB gI31TIBG STSSHOfSi One of the tinctorial changes that can be expected with crystal growth is a loss in tinting strength. We have found that the tinting strength of copper plithalocyanine pigments increases with decreasing particle size down to t he smallest particle size _ which we have been able to obtain* The particle also estimates were obtained through nitrogen adsorption noasuretaeata made according to tho method of Brunauer, Bassett, and Teller (7) , This loss in tinting strength as-the average particle size increases is illustrated in Table IX. These data pare derived from a grinding : study where the different particle sizes were obtained by different degrees of grinding. This work was reported by B. H* Perkins in KS46*0* That-an Increase in particle size due to crystal growth causes a loss in tinting strength is very evident in the case of the wehlorinpee1lf, alpha phase type, of CPC. which grows crystals very vigorously (see Fig. 1). This strength loss will be ill* v usbrated is the second report which will deal with the spectre* . photometric interprotation of the changes occurring in these enamel systems. For this report it sdll suffiee to say that the / strength loss .inthis Instance is sufficient to reduce materially .* the value. of tJiis type of pigment for application in paint systems/ It id worthy of note that strength loss due to crystal growth of copper phthalocyaalno is also observed in pigmented systems apart from the paint industry. For example,.it is very noticable in the coloring of transparent vinyl plastics where crystal growth can be easily demonstrated in a common plasticise ouch as dioctyl phthalate. This ester Is one that ?esce (g) would classify as a "safe" l.e, non crystal growing solvent. Flocculation or agglomeration of the pigment particles plays an important role in determining pigment strength j an increase in flocculation causes a decrease in pigment strength* In the case of the pigments under examination, flocculation seemed to occur to a lesser degree for the ''strain free51 solvent milled pigment than for their, "strained" aeid*pasted counterparts. In the two paint systems studied* the degree of flocculation appeared to be a < complicatedfunotion of the age of the enamel so that this effect tended to obseure the crystal growth*effects, the changes in flocculation Pill be discussed in detail in the second report* ^ DUP050068212 gable IS , Avg* Particle Sl&o' Surface Area (Side of square cross-} Sq lietore peg ffraia . {section la microns ) Relative Minting Strength 98.1 81*1 , 62*5 23,8 , 0,039 0.030 . 0,046 : 0,129 100 93 81 50 ' ^Calculated from the specific surface data assuming crystallites of. square ^oss-oecticai parallelepipeds, a Sp, Or* of 1,50, and a -Mf ratio of length to width of S, She equation is given below* Essays--- * *m W side of square cross-section in microns p Specific gravity A . Specific surface in square matere per gram R w Ratio of length to width SMART: ; , 1* The evidence suggests .that the tendency of copper phthalocyanine to grow crystals in paint media is a consequence of the t ndency of the system to reach a lower energy level through crystal phase transformation, and by relief of crystal strain through rscrystalliaation, 2, Crystal growth can b e minimised in any of the following ways: A, increase the s tabillty of the alpha phase through the introduction of chlorine into the molecule* B* in the case of Hchlorine-freew copper phthalocyanine, prepare the pigment in the fora of the more stable beta phase* C* Reduce the crystal strain by allowing a rocrystall isation during pi^aent finishing* 3* Copper phthalocyanine pigments which have been finished in a "strain-free11 condition through solvent milling* and in DUP050068213 ( \ *39 - which the phase stability has been increased thru the introduction of 4*4$ chlorine into the molecule do not show crystal growth in typical paint systems* These conditions are realized in our BT-284~D type pigment* '4* Beta phase chlQr lne*fren hopj^r phfchalocyasaine pigments (e,g* BT*,297'-B) are crystal stable* . 5. Crystal growth is associated with a loss in pi^aent strength and a change in hue (the larger the particle size, the redder the hue) hut because of changes in degree of flocculation associated with tsany paint systems, one cannot attribute all strength changes to crystal {U?owfcfe*: 4s flocdulatton comes under better control, crystal growth offectewill assume more importance as a cause for long in pigment strength* AClCTOVJLEDOBMSMgg , The authors wish to acknowledge the assistance of the staff of the Ebyaica Section of the Chemical Division duBont B^erimenfcal Station, who carried out the specifis;surface determinations and array examinations* r KEFEREBCKSt - ^ 1. M* A* Dahlon, Xnd, Eng* Chon* jgl, 839 (1939) 2# V. C* Vesee, a& Study of the Properties of Bhthala cyanine Pigments". Harmon Color Worha, HaL edon, H* j, .1944*. .. 3* PVA* HaEsa, and E* V* Harman, Journal of Applied Physics, 19, 1097llo9f Dec, 1948, - 4. FIAT Final Reports Bo. 1313, PB 85172, III, p. 345 (19.48), 5. British Patent Application Ho. 5721 (1944)* 6* c. E* Bent and H. P* LInsfeead, J* Cheta* Soc* 1934* 1027? U.S. Patent 2,129,013. . ~'"a~ 7* S. Brunauer, P, H* Emmett, B* Teller, J. Am. Chem. Soc. GO, 309 (1938). DUP050068214