CA1037473A - PROCESS FOR PREPARING COPPER PHTHALOCYANINE PIGMENTS OF THE .alpha.-MODIFICATION - Google Patents

Abstract

PROCESS FOR PREPARING COPPER PHTHALOCYANINE PIGMENTS
OF THE .alpha.-MODIFICATION

Abstract of the Disclosures Highly pure .alpha.-coppar phthalocyanine is obtained when a product regenerated from .alpha.-copper phthalocyanine sulfate by hydrolysis with water is aftertreated in an aqueous medium containing a polar organic non-aromatic compound which is water-soluble or liquid. The aftertreated product has an especially high tinctorial strength, is very easily dispor-sible and has a very pure reddish-blue shade.

Description

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The present invention relates to a process for preparing copper phthalocyanine pigments of the c~_ -modification which have a high purity and a high tinctorial strength.
Copper phthalocyanine pigments derived from unsubstituted copper phtha.locyanine (hereinafter called "CuPc") are not stable in their modificat:ion toward a number o:f orgc ~ c solvents and therefore have an on:Ly :Limited utility in lacquers and varnishes Owi.ng to their reddish blue shade, however, they have been gain-ing great significance for the coloration of plastic materials, especially of po:Lyvinyl chloride, and :Eo:r tho prepa:ration of pigment compositions.
Such a CuPc p:iglllont ot` tho ~ mod:i:t`icllt:ion lll(ly bo p:ropa:rod accord:ing to known mothod.s o.i.tho:r by d-i.s~o:l.v:ing ~IPc :Ln concon-trated sulfuric acid and. subsequently introducing this solution i.nto an excess amount o:f water o:E by salt grinding CuPc; in both cases, when CuPc of the ~ -modification is used as a starting product, this is converted into the ~ -modification.
For use as color pigments, especially for the coloration of plastic materials, for example polyvinyl ch~Loride, extreme-ly high standards as to tinctori~l strength and especially dispersibility of the pigments are nowadays set up by industry for economical reasons. This also appli.es, to a large extent, to the reddish blue CuPc pigments o:E the c~ -modification, the crystal modi:Ei.cation o:E which :is not stab:le but w~hich~ nover-theless, are very important :Eor the co:Loration of plast:i.cs.
Therefore, our German Of:Eenlegungsschrift No. 2, 262, 91:L
pub:l:ished July 25~ 197~, proposes a p:rocess :Eor p:reparing a pu:re CuPc pigment of the C~ -modi:Eication, whi.ch has a higher tinctorial strength and disper-sibility than the known trade products~ But fcr reasons of application techniques, further improvement in tinctorial ~trangth and dlsperslbllity has since been desirabls~
It has now been found that a CuPc pigmen-t of the o~-modi-fication ha~ing an extremely high tinctorial strength and an esp~cially good di~persibllity can be obtained by af-tertreat-in~ an aqueous ~uspenslon o:f an uns~lbstituted CuPc pigment of -th0 o- -modlrication obtained by ~ssolution and precipitation of CuPc ln sulfuric acld and ~ubsequ~nt flne dlvi sion in an aqueous medium, with a polar aliphaticg cycl~aliphatic or heterocyclic organic compound which contains up to 8 carbon atoms per molecule and i9 entirely or partly ~oluble :Ln wator or is liquld under t;he co:nd:ltion~ of the a:rtertreatlllerlt, .i.n the homogeneous or hotorogenous aq-loou~-o.r~nn:lc medlum l;hU~J
obtained, preferably at an e.Levtltod tempe:rature.
Th0 CuPc pigment used for the aftertreatment with such an organic compo~nd iB pref0rably obtainsd accordin6 to the following method of dissolution, procipitatlon and fine di~i-~.ton:
CuPc i~ converted in 70 - 100~ sulfuric acid into CuPc sul-fatc and9 whan a sulfuric acid of higher concentration is us~d, ths CuP~ sulfate solution is diluted with water or a dilute sulfuric acid to reach a sulfuric acid concentration prHferably of 75 to 88~ by weight. The CuPc salt which is not soluble at this sulfuric acid concentration ls then iso-lated. In a ~ulfur:ic acid of lower concentration, for ex-ample from 70 to 88%, the CuPc i~ al90 convert~d lnto the sulfate without be:lng dl~olved, and then iso.lated. This ~alt 29 is sub~equently hydroly~ed, and the resultin~ CuPc of the ~ -:.................................... .
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pha3e which iB SUC tion-f'il-terecl and obtained i~ pure ~tate is finely divided in an aqueous suspension by means of kneading device~ high-speed stirreFs having a grinding effect, vibra-tory millsl ball mills, bead mills or other ~ills containing the usual grirlding bodies 9 and under the usual conditions.
Among the~e m~thods, a ~e-thod proposed in GQrman Offen-legungsschrif-t No~ 2,262,911 is preferably used. According to this rne-t;hod, a highly conc~ntrated aqueous suspension of CUPG of tho ~-modification is ground preferably on a ~ibra-tory mill or 'bead mill. The CuPc is purified and finely divi-ded, for example by dissolving crude phthAlocyanine in 4 -to 10 time6 the amount of` 96 - 100~ sulf`urlc acid, and then dl-luti~r -this solutLon wlth water or cllLulio sul~llric aclcl to reach an acLd oontont o~ ~6 - 80'~" whor~upon the aul'o 9ul-'15 fate precipltates. Thl~ Cu~c suLfat~ may, however, al30 be prepared as mentloned above b~ introducing CuPc into a pre~era'bly 80 - #6~o ~ulf'urlc acld, The CuPc ~ulfate is th~n ~uction-filtered at room temperature, washed with a small amount Or 80 - 86~ sulfuric acid and hydrolyzed by introducing it into 4 to 10 timQs the amount of water, calculated on the dry crude dy~tuff. The CuPc thus purifisd i5 suction-filtered, washed wlth watar until free of acid and thsn finsly divided in the form of its aqueous filter cake by mechanical means to yield the pigment. The fine division is carried out in an aqueous suspension of the highes-t possible concentration.
The ratio of dyes-tu~f to water ra~g~s ~rom a'bout 'Is2 to l115, r~f`orably t`rorn l13 lo 117.
A par-ticularly advantag~ous mQthod ~or dlssolutlon and 29 ~ precipitation 18 propos~d in~G0~man Offenl~ungsschrift No.

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publ.slec¦ ~uly ~ ~97 29262~895. In that process, a CuPc sulfate which is i3sp~ci-ally sasy to filtar arld has coarse crystals i9 obtained by introducing CuPc into sulfuric acid of 84 - 88'~ streng~h, pre-ferably of 85.5 86.5~ strength, anrl then aftertreating the resulting suspansion of the CuPc sulfate in an insrt gas atmo~phere for one to several hours at 60 - 100 C. It is also possible to dls~olv~3 CuPo ~lrst in sul~urlc aoid of a high0r concentration and then dilute -thi~ ~solutlon by adding the calculated amount of water or dilute sulfuric acid to reach a sulfuric acid concentratLon of 84 - 88~, preferably 85.5 -86.5'~, and finally t:reat.i.ng :It at an elevat0d temperature.
Ace~rdlng to that proeo~s, the lrltroduet:Lon Or CUI)C lnto 8II - 88~ suli:1lric aold alF~o resu:Lt~3 ln tho Ic:rlow.rl Oul'o ~ ate havlng 0xt;remely ~f:L.rlc ory~Jtf.~.:L~whl.c.h :l~ d:l :f'.t' 1. o ~.l 1, to .f'.l..l. ~o r .
15 Durin~ the a~ft~3rtreat;merlt of thls CuPc sulfate susp0nsion at 60 - 100 C, the cry~tal.s of the su.J.fate grow into large regu-lar crystals whioh may reach a size of 1 mm, The so-obtained CuPe sulfate susp0nsion containing the coarse crystals i8 th~ ~uction-filtered; the CuPe sul~ate i~ hydrolyzed in the manner already mentioned. The isolated pure GuPe of theo~ -modification i.s subjeeted in the form of its aqueous filter cake to the meehanical fine division operation m~ntioned above in a eoncentrated aqueous suspension.
Anoth~r dissolution and precipitation method, which is however not advisable ~or ecologieal rea~ons, i~ the process known as "acid pa~ting", a~cordlng -to whlch CuPe :Is di~so:L-v~d or ~usp~ndsd ln ~ulfurlc ac:Ld and then hydro:Ly~4d :In a large exee~ amount of water.
29 As starting product, only unsubstituted ouPcis gsnerally used .
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in the form of crude or prepurified material. The proce~ss is al so applicable to copper phthalocyanines containing1 in addition to CuPc, very small amounts of a substituted CuPc~ the substitu-ents being, for example, halogen atoms, carbo~y or sulfo groups.
The CuPc which has been dissolved and precipita-ted and then flnely divided according to one o~ thH above-mentioned '~ method~ i~ then aftertreated ln an aqueous isuspenslon, advan--tageously direct in the aqueous pigment suspension r~sulting from the fine di~ision, with one of the above-mentioned or-ganic compounds which do not bring about a convorsion of the crystal phase under the condltLons of the af-tertroa-tment, -to convert thi~ CuPo into a particularLy valuable CuPc piglllent of the O~-modlficatlon having a hLg,h tlnctorial st;ron6rth arlcl a gO od dlsperslbllity.
Tho pi~rnont Ls tr~at~d Jn the aclueouis-orgarlic med;Lum at room temperature (15 - 25 C), p~e~erabLy at elevated tempe-rature, ~or example from 30 to 80 C. *emperature and reaction tirne d0pend on the type of organic aclditive and on its conoen-tra~tlon in the aqueous suspension. In media having a hlgh content of these organic additives, the rcaction ti~le is rela--tively short and the reaction is generally carried ou-t ~t a lower temperature, whilst in a low-concentrated medium, cal-culated on the organic additive, a longer reaction time may be required ~t a relatively hLgh temperaltureO
The amount o~ said organlc compounds to be addad to the aqucouc pigmen-t suspension ra~ulting f`rom fino divlsLon f`or conditioning purpo~os~lay vary groatLy. 'rho amollrlt of` organLc additives is pre~orably as high as to a~sure a final concentra-29 tion of organic additive :Ln a liquid phase of` from 3 to 20 . ~ ~ ,.. . . .
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Depending on the type and a~ount o~ the organic additive, reaction temperature and time have to be such that the tincto~
rial properties of the pigment treated are optimal, conside-ring the reaction procedure, i~e. bearing in mind that a contimlation o~ the aftertreatment beyond the limit for an optimum pigment quality may cause a deterioration of the plg-ment quallty due to ~urthe:r growth of the par-ticles. An im-portant criterion f`or such an as~essment is provided by an X-ray diffraction spectrum of` the pigm0nt (lattice spacing from 9.8 ~ to 17.65 ~); a CuPc pigment ~howing an X-ray di~
~raction spectrum, in which the ratio of -the relative :Lnten-sity di~ferences be-tweon the max:ima at 12.1 and 13.0 R, ro-speetively, and the m:Ln:L~num at 12. 6 R ha.~ ~1 va.Lu~ or f`rolr a.~out 1:10 to 1sLI, ha~ an e~peo:La:l.Ly hl~l L:lnctor.l~
~trongth and à goo~ dl~per~:Lt).L:L:Lty. In thl~ OcL9e~ th~ BpeCl-fie surface ~-ange~ ~x-om 50 m2/g to 80 m2/g, pre~erably from 60 m2/g to 75 m2/g (measurod aocord:Ln~ to BET).
Arnong the polar al:iphatic or cycloallphatic compounds used for the ai`tertreatment of the di~sol~ed, pr~cipitated and finely di~ided CuPc, there are mentioned those adva~tage-ously eontaining hydrophilic groups, pr~ferably hydroxy~ami-no~ carbonyl groups, suoh as carboxylie acid ester, car-boxy, carbo~ylic acid amide groups, or ether-type o~ygen bridges (~0-). These eompounds m~y be soluble in water but they may also be sparing:Ly soluble or insoluble in wat0r.
Unle~s soluble in water, they ~hould bo in liquid form a-t Lho temperaturo cho~en t:or the aLIerlr~atmont.
Arol~l~tlc comp~u~ r ~K~I~ yLorl0, l~I'O rlOt U~
29 ~inee ln additlon to having a Htrorlg ~.ffoet orl ory~tallL~at:lon '' "

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~3~4~73 they may also bring about a eonversion of phases. Polar wat~r-soluble heteroeye.Lie aromatic eompound~ for example pyrldi.ne, are also less advantageous tha~ the aliphatic or cyeloaliphatic compoundæ eo~-taining hyclroxy9 carbonyl or oxyg~n groups.
Polar aliphatic or cycloaliphatie eompoundæ used are, abovs all, alkan.ols, eyeloalkanols, ketones, aliphatic and eyeloaliphatie ethers, glyeol ether, alkane-carbo~ylie acids and derivativ~æ l;hereo:f, for exarnpLe e~teræ, rlitri ~, arni-deæ, lactones or laetams, the term "alkanecarboxy~ic acids"
eomprising formie aeidO Especially suitable eompounds are, for example, methanol, ethanol, iæopropano:l, isobutanol, -the amyl aleohols, aeetone, methylothyl-ketona, diethyl~
ketone, dioxan, tetrahy~:ro~uran, ~ lsopropyl. other, acetle aeid, methy:l. aeetat~ ttly:L ae~t;lte, b~ll;y.l. .:-cetclta or allly.l.
aeetate, cye.l.ohoxarlo:l., ott~y:l.erle g.l.yol. 1, U-e tl~ y eth~nol, formamldo, dlm~thy;Lf`ormar~li.de, ae~tonltrlle, N-methy.l-pyrro-lldone, hexamethyl p:ho~p'horle acid trisamide or tetrame-thylene ~ul:fone.
Among these aliphatie or cycloaliphatlc eompoundæ, tho~e are aclvantageously selectod whieh, after the reaetLon ls eom-plete, ean be separated in a simple manner from the aqueo~s medium, for example by distillation or steam diætil.lation7 prior to or after i~olation of the pigment~ ~or -thiæ reason, those eompoundæ are espeeially uæed for eonditionlng purposeæ, whieh eontain not mor0 than 6 earbon atomæ per moleeu.le.
The oondL-tioned CuPe pigment mcly be i'æolated by ~:iltration or evaporatlon, preferably by æpray~drylng, Tho orgnn:Le addltlv~ ma~ bo ~eparat0cl e:ither prlor to or af`tor lsolatlon, 29 ~or example by distilla-tlon or steam cliætillation.

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The n~w CuPc pigmen-t of the G~ -modification prepared according -to the process of -the invention and showing a deter mined fine division as well as a determined X-ray dif~raction spectrum has a very high tinctorial strength and a good disper-sibility. It is especially suitable for the coloration of plas-tic mat~rials, in par-ticular of poLyvinyl chlorlde, and for the pr~paration of` dye~Lng compositions.
From British Pat~nt SpecifLcation No. 951,968, it is already known that CuPc of -the G~-modi:fica-tion obtained by dissolving it in sulfuric acid and hydroly~ing the solu-tion in a large e~cess of water can be conditioned `by add:ing very ~mall amounts of` a'cohols praf~rabLy containirlg 5 to 12 carbon atorn~ per moleclll0. 'I`he produc-t~ o'btaLned accor~Lng to Ih~t prOC~39S, however, hf.lVe fl Low t:i.nctor:i.~:L .L~t:l`erlf',l;ll and a poor cll~per~lbllity In ~oLyvLnyl ctl'loride 11l oo~ rnL.Yon to t;tlo.~e obtained accordlng to the pres~nt inv~ntion.
Furthe~more~ l-t l s kn~wn from Gerrnan Pa-tont No. 1,6'19~568, that CuPc o~ the 0~ -modlfication can 'be troa-ted ln a dry plg-ment form with polar allphatic solv~nts. The products obtained according to that process are inferior to th~ pigment obtained according to this invention as to tinctorial strength and dis 'persibility.
In addition, the process disclosed in the above German Patent is not ~conomical since it requires two isolation and drying operations for the pigment and, accord:Lng to the teaching of said patent, partial conver~ioll o~ the O~modifi-cation into the ~rrlodl~ioatioll Is 'bro~lgllt a'bo~lt.
Moreov~r, lt :Ls known f`r~om 'U.S. Pat0nt No. 3~ 119,706 29 that an aqueous suspension of ~wPc of th~ o~-mod1~lcat:Lon, i ;'. , : ~
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ob-tained according to the "acid pas-ting" n~ethod, can 'b0 trea-ted in the presence of water-solu'ble organic liquids capable of baing salted ou-t, and upon addition of the a~ount of salt required for a complete salting out of the organic liquid at an el0va-i;ed tempera-ture~ That process does not yield a pigment which equals that obtain0d according to the proce~s of the inventiorl nor ls it recomnlerldable ~or ecological rea-sons owlng to a heavy water pollutiorl wlth salts.
The following ¢~aMples illustra-te -the invention, the par-ts and percentages b0ing by weight unless s-ta-ted otherwise.
E X A M P L ~ 1s (a) 32 Parts of unsubstituted crude copper phl;halocy~lnlrle (9r)~
trade product) wero drowned whi;Le .qtlrr:lng Irl '32o ~ rl~9 ot`
86'~, suLl`urlc acid~ Tho resultirlg ~al~lpevl~1loll ol' tlloco~)~er phthalocyanJne suLi'ate was hecl ted to '7(7~C arld ~tlrrod f'or 4 hours at r/0 80 C Ln a nitrogen atmosphere, whareupon the copper phthcllocyanille su:Lf'a te first obtained :Ln the Porm of' finely d:ivlded needle~ was convert0d ln-to bLg re-gular crystals, Aft0r having been stirred for 4 hours a-t 70 - 80 C, the suspension was cooled to 20 - 30 C. The CuPc sulfate was suction-filtered and washed with ~0~
~ulfuric acid. The fi]ter cake of the CuPc sulfate was stirred into 300 parts o~ water. The mixture was suction-~iltered and washed with water until neutral~
60 Parts of a 50'~ ~ilter cake were ob-tained. The de-gree of purlty of the CuPc of` the O~-modifLca-tion was 99-100~. The total. a~oullt of the 50'~, rilt~r cnke obtainocl upon puriflcat:Lon was ~lluted wi-th '107 pnrts of wa-ter, 29 and after homogenization it was continuously ground in a : .

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ball mill provi.ded with stirrer (~or example~of the -type RM 25, manufactured b-y Messrs~ Netzsch, W.Germany), 167 I'arts of an 18~ pi~nent suspen~ion of CuPc of the 0~ -modification were obta:ined. To this aqueous suspension, 137 part~ of isopropanol were added, the mix-ture was heated to 50 C and s-t:irred :for 5 hours at 50 ~ 55 C. It was then cooled to room -t~mperatur~ and suction-filtered.
The material wa.s wash~d with 100 par-ts of water,and the aqueous rilter cake was dried in vacuo a-t 60 C. 30 Parts of an unsubstituted CuYc pigment of the C~-modiflcatlon were obtained.
The plgmerlt powder o'bta:Lnecl was :Lncorporntod :I.n l~o:l.y-vlnyl ch:l.o:r.Lde acoo:rdlng to lnown ~lethoclH to prodllce co.lorat$on~ wh.io:h ~lavo a su~ tclllk:l.fll:Ly higher color Ln-ten~ity ~nd a pu:rer, par~lcu.Larly reddlsh blue shade than coloratlons produc0d wlth cornparable trade plgment dyes.
Mor00ver, the plgment obta:lned ls dl~tin~u:Lshed by a ~ar better dlspersl'billty ln plastic mat~rials in comparlson to known trade products.
The pigment obtained showed the X-ray diffraction sp~ctr~ A illustrated in th~ drawing for the measuring range from 9.8 ~ to 17 ~ 65 R and measured by m~ans of CuKo~-rays. Th0 speclric surface of the plgmcrlt was 65 m /g (~easured accordlng to BET).
(b) Wh0n the CuPc suspension requl-ting frorn :fine dlvlslon ln an aqueou~ rnedlum Wa~l not n:~torkreat6~d w:lth ~ opropano.l, the p.l.Km~ t o~ ln-~d ~ r drylrl~;r ~how~cl ttl~ X-rny d.l.:f`~`r~c-~lon ~peotrum ~ .:i.l.lu~trated :ln the dr~lwin6 ~`or th~ mea~u-29 rlng range from 9.81R to '17.65 ~ asld n ~peciric surf`ac~ of 'I 1 '' , ., '' :, ' . . '' : :
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~37~3 only 37 m /g (measured accoding to BET)~ Compared to the plgment which had be0n af'tertreatsd wlth isopropanol, this pigment, when -incorpora-ted in polyvinyl chloride, had a poorer tinctoria~ strength and dispcrsibilityO
When the aftertreatmant with isopropanol was carried out not ror 'j hours at 50 55 C 'but for 6 howrs at 80 -85 C, -the plgment obtainad showed an X-ray dif`fract:Lon spectrum C a~ illu~tratecl in -the drawing and provided, upon incorporation in polyvinyl chloride, duller colora-tions which had a substantially poorer color intensity.
(c) When instead o~ 137 parts of l~opropanol, 137 part~ of me-th~nol or etharlol were used~ a troatmorlt for 5 hours at 50 - 55C ylelded a p:Lg~ rlt wh.l.ch wa~3 a~.i vn~ abl.o a~
t:hat o'bta:Lned uporl ~:r~atlllellt w:l.l;:h :L~opropa~lc):l. acoo:r~:LIlg~
to process ~a).
E X A M P L E 2s 167 Parts ~f the aqueous su3pensloxl re3u:Lting f'rom ~in0 divlsion according to Example l(a) were added to 133 part~ of water and 30 parts of i30propanol. The mixture was then ~tirred for 8 hours a.t 80 C. The work-up was oarried out as in E~a~ple 1(a)0 The pigmant obtained corresponded in its tinctorial properties to -t'hat o'btained according -to Example ~(a) and (c).
E X_A M P L E ~:
167 Parts of the aqueo~ls suspensi.on resultingr ~rom f.ine division accord:lng to Examp.le l(a) were added ~o l51~ pa:rt~ Or water a~d 9 part~ o:f :L~lop:ropano:L, an--l thc ml.~turo was stirred for 2 hour~ at 50 C. The Lsopropanol waB -then distil-29 led off wlth steam. 'L`he aqueou~ ~uc~pQns:Lon WraB ~qpray-cl.

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~7~L~7;3 30 Parts of C~Pc pigJnent of the ~ -modi,fication w~re obtainedO
This pigment was dis-tin~lished by an e~cellen-t dispersibility and upon inc~rporation in poly-virlyl chloride it pro~ided c~lorations of high color :intensity and a ~ery pure reddi~h blue shade.
I~ X A M P L E 4-167 Parts of the aqueous s~spensiorI resulting from f`ine division according to Æxample 1(A) were added to 1ll8 parts of wa-ter and 15 paIts of` e-thyl acetate. The mixture was stirred for 2 hours at 30 C, and the ethyI. acetate was then distilled off with ~t;eam. Upon hf,lv:lng cooled to room -tempe:rature the aqueous suspon,sion wa9 ~uctLon-f`iltered, and the ~vater-lnoi..st filter cake wa.s dr,Lod ln vacuo at 60 C. I'he p.l.f,,~;nle.rlt ol:)tf~ rl~c had excel:Lent tlnotor.LI:L p;ropert:l.e3. W:hcJll the heflt i;:roftL,I~ t, was carr:iecl out not :f`Or 2 .hourC; f:l t 30C but ~'or 2 hours at 50 C, the p1gment ohta:lned hacl tha same quality.
When inAtead Or 11l8 pa:rts o.f water ancl 15 parts of ethy:l acetate, 133 parts of water and 30 parts of ~:lacial acetic acidlwere used and the treatment was carried out for 2 hourfj at 50 C, the pi~m~nt obtained also had a high tinctorial strength and a good dispersibility.
E X A M P L E 5:
167 Parts of the aqueous suspension resulting from fine division according to Example 1(a) were combined with 133 parts of water and 30 parts o~ acetona, The mixture was stirred for 1l hours at 50 C 9 the susp~n~:ion was then cooled to room temporature and ~uc-t.Lon-.f:l..Lte.recl~ 'l`.iIe :fL.Lte:r ca.k~l wa~ wa~hed wlth wflt~r rln~i ir~l.eci 1~ VflCUO at 60 C. 1`~le pIfflllorlt, obt~ln~d prov.l.d0~i oolor~lorlr~ Irl ~ yvlrlyl. olll.(lrl~ wh.lotl i .
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a7~ ' a very h.igh color ltensity~ A slmilar pigment was obtained by replacJ ng the 133 parts of water and 30 parts of acetone by 148 parts of wat~r and 15 part~ of dioxan and treating the suspension for only 2 hours at 50 C insteacl of 4 hour~

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167 Parts of` the aqueous suspension resulting f`rom ~in~
divLsion accord:ing to Examplo l(a) we:l~ comb.ined with 148 parts of water an.d 15 parts o:~ dime-thylformamide. The mixture was stirred for 2 hours at 50 C, -the suspansion was cooled to room ternperature and suction-riltered. The fi.Ltcr cake was washed with wator arld dr:i.od lrl vacuo at 60 C.
When the 15 parts o~` ~:lmethyl.t`orrrlam:Lde were rop.l.acecl by l5 part~ of N-rnethy:L-p~lr:rolldone, t:h~.~ p:L~rrnorll, obta.l.lle-l:tlad tho same t.lnctoria:L qufl.LI.ty.
S E X A M P L E 7s 167 Parts Gf the aqueous suspension rosulting from :fine division accordi.ng to ~xamp:Le l(a) were oombined with 1118 parts of water and 15 parts of pyridine. The mixture was stlrred for 2 hour~ at 50 C, cooled to room te,mperature and suc-tion-filtered. Tho filter cak~ wa~ washed with water and dried in vacuo at 60 C. The pigmen-t obtained was di8ting~ish0d by a higher tinctorial strength and a better dispersibility in polyvinyl chloride than the oomparablo trade products.
E X A M_P L E 8:
33~5 Parts of unsubstitwted crude CuPc (in form of a 90%
trade product) were di~sol~ed wh:i..Le ~tirrln~ ;i.n 320 parts of`
96% ~ulfuric acld. The ~olutlon was heated to 70 - 80C, and whils maintalning th:Ls temperature :it was dilutad wlthln 29 30 minutes by slowly addi.ng 6l~ pa:rts o.~ w~te:r to reaoh a ~ L-. .
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furic acid concentr~tion of 8O~O. After having been cooled toroom temperat~lre~ -the precipita-ted CuPc sulfate was isol~ted by filtration and washed with 80~ sulfuric acidr The filter cake uas -then drownsd in 5OO parts of water a-t room tempera-ture, filtered and washecl with water until neutral. 120 Parts of moi~t 25'~ filter c~ke were obtainedO The degr~e of puri-ty of` this CuPc of -the ~-mod:Lfication was 99 ~ IOO~.
The -total amount of th0 25'~ f`l:lter cake obtained upon purification was stirred into l~7 par-ts of water and then con-tinuously ground in a bead rnill. l67 Parts of an 18~ pigmen-t suspension of CuPc of the c~-modifica-tion were obtained.
This reac-tion o* di~.solving and p.r~3c:ipl.tating -the crude CuPc -to yield the pure Cu~c o~ the c~ mvdif:Lcat:i.os~ nd the suh-s0quent :fin0 ~,r:lnd:ing oporat:ion corr~ffpondod to th~ mc~ttlocl dlsclos0d ln G~rmarl Off`~sl:le~ull~.. r~otl:rL~`t No. 2,2(i2,3ll.
When thl~l suspen~l.on wa3 artertreat0d with isopropc-nol a~ in Example 1(a), Ihe plgmont obta:lned also had a high tinotiorial ~trength and a very good dlspersibi:Lity ln plastic materials. The same re~ults were obtained by carrying out the fine division no-t by grinding in a bead mill but in a continuous vibratory mill.

-- 'I S --.. . .

Claims (7)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the preparation of highly pure unsubstituted .alpha.-copper phthalocyanine which comprises aftertreating an aqueous suspension of unsubstituted .alpha.-copper phthalocyanine having fine division, said .alpha.-copper phthalocyanine having been obtained by dissolution and precipitation of copper phthalocyanine in sulfuric acid and subsequent fine division in an aqueous medium, at a temperature of 15 to 80°C with a polar aliphatic, cycloaliphatic or heterocyclic organic compound containing up to 8 carbon atoms which compound is water-soluble or liquid under the aftertreating conditions, the after treatment being continued until the difference in intensity between the maxima at 12.1 and 13 .ANG. and the minimum at 12.6 .ANG. in the X-ray diagram of the product is from 1:10 to 1:4.

2. A process as defined in claim 1, wherein said polar compound is added to the aqueous suspension obtained by regenerating .alpha.-copper phthalo-cyanine from its sulfate and finely distributing it in water.

3. A process as defined in claim 1, wherein said polar compound is aliphatic, cycloaliphatic or saturated heterocyclic containing one or two identical or different hetero atoms selected from oxygen, sulfur and nitrogen.

4. A process as defined in claim 3, wherein said compound is an alco-hol, a ketone, an ether, a carboxylic acid or a functional derivative of a carboxylic acid selected from the group consisting of esters, nitriles, amides, lactones and lactams.

5. A process as defined in claim 3, wherein said polar compound is an alkanol, a dialkyl ketone, a dialkyl ether, a cyclic mono- or diether, a mono-or dialkyl glycol ether, cyclohexanol, an alkanoic acid, an alkyl alkanoate, an amide, a mono- or dialkyl amide of an alkanoic acid or an alkyl nitrile.

6. .alpha.-Copper phthalocyanine having a specific surface of 50 to 80 m2/g and a difference in intensity between the maxima at 12.1 .ANG. and 13 .ANG. and the minimum at 12.6 .ANG. in the X-ray diagram of from 1:10 to 1:4.

7. .alpha.-Copper phthalocyanine as defined in claim 6 having a specific surface of 60 to 75 m2/g.