Document 3eXR3zZ6jRXDBeLOvj0kB9mOa

E. I. DU PONT DE NEMOURS & COMPANY KREBS PIGMENTS DEPARTMENT 256 VANDERPOOL STREET NEWARK, NEW JERSEY Serial No. KH-45-5 Copy No. / I :* / * ;1 \ \ NEWARK PLANT PIGMENT COLOR RESEARCH REPORT Final Report SUMMARY OF LABORATORY WORK OK CONTINUOUS MANUFACTURE OF CHROME YELLOWS - (SUMMARY OF KN-44-77 , 73, 79 , 80 , 82) Period Covered: JULY 1, 1943 - DECEMBER 31, 1944 FILE: DATE i 114*1 2-6-45 N37980 Serial So* M8-45-5 Copy Bo* / Copy tos I1-: MRiieraarcikLjfe1!cCHlH.l) ' f ~ Mr. f* I. Salley* Bewark - Imperial Cheaical Industries, Ltd* I: tt o a 9 * Extra 10 - * 11 - s NEWARK PLAKT PIGMS8T COLOB RESEARCH REPORT Final Report Titles SUMMARY OF LABORATORY WORK OS COBTI8O0US MANUFACTURE 0? CHROME YELLOWS - (SIMMARY OF KB-44-77, 78, 79, 80,82) Period Covered s JULY 1, 1943 - DECEMBER 31, 1944 SUBMITTED Bit APPROVED Bit V* Chalupslci dfC^Ca^dc^^r' V. Chftlupskl ^/fyj' ' DATE SUBMITTED: 2-3-45 DATE ISSUED* 2~6"45 DUP050150022 -2- f * Shi* is ft mammy of the research reports issued in January 1945 which sow the laboratory experimental work on continuous menu* factor* #f Chrome yellows, BesearchProject #207, July 1, 1943 to Becember 31* 1944. (XB-44-7?, 7S. 79, m, $2). lot included in this gsKar|^is the work done m Molybdate Orange and Zinc Yellow (KB-44-gl, The manufacturing steps for asking chrome yellow which requires study in eemmeebien with continuous operation arcs* 1) Precipitations 2) development - heat and ageing; 3) hydrous oxide treatment; 4) ------ --of soluble sails by washing. this report discusses the general aspects of the problem and describes the laboratory equipment* Earlier studies of continuous manu facture of chrome yellows mage concerned only with the precipitation step* laboratory and large scale work showed that continuous precipita tion gave products similar to those made by batch precipitation, Recent cork has shown that In the ease of most chrome yellows, the mechanical conditions of precipitation are not critical in the sense that pigments of reasonable quality are obtained if chemical conditions and concentra tion and temperatures are similar to those used in batch precipitation. On the other Eland, variations in color which are comparatively minor from a scientific point of view, but which may be of some commercial importance, can sometimes result from changes in mechanical conditions. The object of the current study has been to make the manufactur ing process completely continuous. This implies that each of these manufacturing steps mentioned earlier shall in themselves be carried out continuously and each step shall follow the preceding case continuously. Preliminary laboratory experimentation was carried out batchwlse. The order of the various steps was arranged to correspond to the order which would be most advantageous in continuous operation, and each step was carried out as rapidly as possible to stimulate conditions which were assumed would occur in continuous operation. However, it was realised that it is impossible to duplicate the conditions which occur in conti nuous manufacture by batch methods. To what extent this batch method of experimentation should be used to establish conditions before going to experimental work by the continuous method Is still a moot point, ab44r.7i Tads report covers the work on medium yellow Y-469-B, This is an ordinary type of medluaryellow which contains only a comparatively small amount of hydrous TiOjg and' no alumina. The first problem taken up in making this a continuous process was the elimination of the decant washing step (which also undoubtedly serves as# an ageing step) between DUP050150023 the development and hydrous oxide steps, Merely emitting the a W ageing step results in dark masstone and poor lightfastuess. 1 few experiment# were run to determine the causes of this dark masstone. It sear tentatively he concluded that neither the presence of soluble salts or the higher temperatures of the yellow at the treating step was^ responsible. It was found that aanqageiag period of about 30 minutes could be used to replace the washing/ageing step with some measure of success, although there was a tendency toward the less desirable dark masstone* Earing eliminated the one step which made t^e process as a whole discontinuous, some study was given to the individual steps. Variations In mechanical conditions of the precipitation step were tried in the laboratory continuous unit* Recirculation of the preci pitated slurry back thru the region where preclpltatUm is taking place nay have some little adverse effect (the term *adverse effect" as used in this discussion usually means dark aasstone and poor lightfastness). Variations in the arrangement of the jets thru which the reacting solutions enter the precipitation unit appear to affect strength. Greater strength is obtained when the reacting solutions meet at the point of maximum agitation. Increasing the agitation speed also gives somewhat greater strength. Temperature and time of heat development was also studied. Sub sequent work on other colors showed that heating in two or more stages is desirable; this will be referred to again in subsequent discussion. In the study of y-469-O, the continuous development steps appear to give soaievfcat weaker yellows than&> batch development at the same temperature. The hydrous oxide treatment of this color consists in the addi tion of tltanyl sulfate solution followed by the addition of a solution of sodium carbonate. These were added to the developed yellow suspen sion either in small agitated units or by pip* line mixing. In either case the**'- was some deterioration in lightfastness compared to batchwtse hydrous oxide treatment. & study was also made of pH of precipitation and excesses of the reactant. The data obtained applied both to batch and continuous methods; it was found necessary to do this work because the information desired for control of the continuous preparation step was not available. Pre vious work has shown that a soluble chromate excess Is necessary during the precipitation and development stages; its absence results in poor masstones and lightfastness. Too high t*an acidity also results in a poor product. If the pH of the slurry is more acid than about $.4 after the precipitation, as it passes thru the development stage the pS will drop to 3 or below, and poor masstone and lightfastness will result. A pH of about 6 after the precipitation, with a slight chromate excess, is satisfactory. This pH will remain fairly constant during the sub sequent development. DUP050150024 K38-AA-79 ~4~ Standard 1-404^.0 and T~40$~B processes have steps in me which do not unduly ecraplicate batch manufacture, tout which are undesirable in continuous manufacture. these are (l) addition of sodium carbonate after the strike, (2) addition of sodium sulfate after development to precipitate lead excess and (3) as in the case of the batch process for Medium fellow T-469-0 there is a decant washing step after development, before the hydrous oxide treatment. These were eliminated by (1) adjustment of the alkalinity of tins .reacting solutions m that sodium carbonate addition was unnecessary and(2) with elimination of the washing step, which was replaced by a. short ageing period, the excess lead was precipitated shea tttanyl sulfate or aHwduhaa sulfate was added for the hydrous oxide treatment. An improved Light fellow -1957 has been developed which differs from the X-404-D process chiefly in the use of more l^rnm oxidej- f-404-D If of hydrous TiOa -1957 % of hydrous alumina plus 2.4$ hydrous fiOg The &-1957 formula was revised, as discussed above, for continuous operation. k detailed study of the heat development step resulted in a three-stage development, the first stage to 140?., the second to 170 and the final to 200 'or toll. Best results were obtalhedC. by adding each of the ingredients of the hydrous oxide treatment (aluminum sulfate, titanyl sulfate, sodium carbonate) separately, and in separate, well agitated small re acting vessels of the Mraft tube11 type. Bo study of the continuous addition of the texture agent was carried out. It is planned to add this material during the centfifugingrepulp, washing cycle, on the large scale. This is a progress report, already somewhat out of date. It discusses work prior to November 1944 on the laboratory development of j, a continuous process for a new medium yellow, K-1958, the batch process * for which differs from standard y-469-D in using more dilute solutions, higher development temperature and higher amount of hydrous oxide, like -1957, discussed in KK-44-79. A satisfactory continuous process for -1958 has not yet been developed. It was found that this new medium yellow process is more difficult to convert to continuous operation than the old standard T-469-D; all early attempts resulted in dark masstone and worse lightfastness, k phenomenon which is particularly difficult to study is the darkening of masstone as the pigment/oil mount ages and dries. Many experimental products appear equal to the goal standard when freshly drawn down, but DUP050150025 Spil-. m: ;i|f.::|^j^iisai3rl$.r^3r It has been `i|p4 pnpi:f the mount in taw ! ,iit m fifiT Attfc" tttXtttgtefee# fhiS inferior ligatfastoess, . a large f."tlMWjtai 1 simplified batch Ions discussed iw is 1 Inter- are dlscyeseaan pales 3 <ahd 4 wlfct atch method Lswd below. it* W In 2* lohger ageing. Sixty aJimtsis ftfteen Stow***# 5.., tvm'hmxi 'rnim sodium silicate, lio ioalrobie offset* ' 4# Cgrdrt^OariUie treatnemt carried euil** steps# .lgpwia88t 5. Addition of titanyl sulfate before the elan. Ho effect. 6. Slower..addition of sodium. carbonate to precipitate the hydrous oxide. fhls gdaimtaes darkening id oil. 7. Sodium fluoride present during strike (in chromate solution). About $ grams per gram-iaol of lead chromate. Better masstone and JLigfet- fastaesa, weaker. Bedim chloride has similar but leaser effects. Meetroa microscopic examination shoes that these materials Cause an iaoraase iu partiaae size. tow^>leborif^eOog*sytswgoerkhdoente' dlexreitehfefsOcoitnt twinausoutws Hunsaitaiise.veilesel., imgMmUrpeA contiuuOUHy thru this deveiju>paittt step sod finished b&tehwise is satis factory. ffea*-e- is only & slight loss in quality caused by contiauous addi tion of the alun but a narked deterioration with continuous addition of titanyl sulfate and sodium carbonate# C^psiderable study has been given to these steps* but no solution to the present difficulties has yet. beam found# . / * It was found that the aluminum sulfate is not precipitated until the pB is raised above 3.0, fhe titanyl sulfate bydrolises quite rapidly even before tee sodiun carbonate is added* at as low a pS as 1.1. this report discusses the study of a continuous process for *shading* or "greening" yellowj i.e*, a chrome yellow designed to be mixed with iron blue to make a green# Such yellows are lead Chromate/ *gJ2Lf*fce cstat;eR aggat^?.^r,lC- DUP050150026 :Sulfate mm., containing a are strong as* i % of .sulfate, hue. They ere such eSaJ.aJ.._lfla.e.g,r ... article size than ..*# ate usually g rhmtsmn-damdeddiucmpnydelliliowBsS#.: (as W a) then the 1: yellowsj immediately after ';. precipititlea, It ft* necessary to ze Hie very mail particles -V/ formed w:,tktc addition of various ed reetraihlng agents,: (tannic acid, tartaric add, tin crystals . ww hydrate), sod' toy partial ' -' neutralization to a pH rang;ee in which crystal growth is slow, (pH from 4*9 to 6 depending so tfe* im* present) r,l ; This, study was based on a new batch process In which all staking step* ere ferried out auoeessively without my intervening warning or agoing periods. She steps in this process ere as follows!* 1. Addition of Soda Ash to Lead Hitr&te to farm a Lead Carbonate base# 2. Addition of sodium biehromate/sodiua sulfate mixture to this base to precipitate load chromate and lead sulfate. 3* Addition of tin crystals (restraining agent)* 4* neutralization with sodium carbonate. * Addition of aluminum sulfate, e# Neutralization with sodium carbonate. Attempts were made to simplify this process further by eliminating the preliminary formation of Hi# lead carbonate base and instead reacting lead nitrate and sodium chromate solutions directly, adjusting their acidities to give the 9mm final acidity as is the above process. Products thus made were satisfactory in color, tut were somewhat inferior in lightfastness, so this line of attack has been ` abandoned temporarily. Experimental work was carried out in the laboratory by both batch and continuous methods. Mechanical conditions in the lead chromate precipitation step are much more important than in the other yellows; Isurgo tinctorial variations can be obtained by changing Jet positions, agitation, etc. A number of minor variables wore studied; effects obtained agreed with previous experience with standard batch operation. At selected mechanical conditions, and with a formula not differing in any essentials from the batch process, products close to the present standard were ob tained. these were satisfa otory by rubout, paint grind, and outside exposure. DUP050150027 N37980.02 DUP050150028 ctawbnao* Wii tmr ScAte : *fy r/ v L1k t fellatio* MpMt 82nqr VM ad* Jar CoDtloiMUf *i" Linuvr Addition Cmtinuoo* Treating Jar for ilivu m'.iu'jv J*,r f r ,, * DUP050150029