Document 3N44xqyLEZ3geZ6naa9dOqw76

,n Jl 22,53 BETIS10 MARSHALL LABORATORY LIBRARY :0 ' / BEP0R2 MOo S62 DAfii MAY X0 1940 *w f0ff ^ PAULI LABOMfOEY BEP03& BWwioi* YMPWfWMf or is bo k &m Tmmmimiam sn WW SKAMStu ! I & fi&ORSSD BY H<f Bo PIPER APPROVED BY8 Ro To EUGKB N29337 PARLIH LA30E4f0BY REPORT HO* gftg SDSJEOT8' 1MPR0YMEIT OP OBBOHZOX TETRAHXDROXXDE GHEBH *uoo mmELo u nroaoroogio* Du to the increased demand, fox* more transparent and more Iridescent automotive ^Buco* finishes such as 212b 3303SMI loyal Maroon the laboratory has attempted to d@ velop other colors with similar transparency* The purpose of the following investigation was to disperse chromium tetrahydroxid green pigment (-701) in such a manner as to obtain a more desirable and more transparent color than that produced by the ball'mill process of dispersion in current use by the plant* This report covers exp rlmental work done by the laboratory on improved dispersion methods for chromium tetra hydroxid green but does not include durability information on the new enamels developed as ;a result of these investlgationsc Sr,.fflgHBC il) Chromium tetrahydroxid green water wet pulp dispersed In nitrocellulose by the pulp process produced an enamel far .superior.In transparency and color depth to the ball mill enamelp and possessing less than half the hiding power of the latter* (S3 ry -701 Chromium Tetrahydroxid pigment which is normally dispersed by the plant in a ball mill when made into a water slurry pulp and subsequently diepersea by the pulp process resulted in a deep transparent green enamel olosely approxlmting that obtained ..from com mercially prepared pulp (3) ry chromium tetrahydroxid pigment added dlreetly to water wet nitrocellulose and carried through the pulp process resulted in a green enamel very close in transparency to the pulp dispersed enamel but slightly milkier in color* (4) Chromium tetrahydroxid enamel -in'which the pigment was dispersed in oltftr base in a & ?* mixer while somewhat darker in color and lower in hiding than the ball mill enamel was considerably inferior to the pulp dispersions both in transparency and in depth of color* DUP030000857 (5) In view of the above results* It seems probable that the water which is present during pulp process dispersion plays a major part in the production of the im proved dispersion and the consequent transparency which i characteristic of pulp process chromium tetrahy&roxl&s green enamels* 6) Although much durability data have been accumulated by the laboratory on ball mill chromium tetrahydroxide green enamels*: it Is felt that additional ex posure information must now be obtained on the high trans parency enamel prepared by the pulp process* be lower hiding power enamel may conceivably fail to equal the ball mill dispersion in resistance to oolor change and film dtterioratlon* In order to Chech this possibility* a mm* plots exposure program is now underway in Florida* the re sults of which will be discussed in a subsequent report* If these durability tests prove satisfactory* it will be possible to substitute the pulp process chromium tetrahydroxide enamel.in production of desirable green solid and metallic PuoS colors* this substitution will result in a considerable saving over the cost of present transparent metallio formulations calling for a more expensive green pigmento IIXo BXFSRXMBWm (21 W-701 Water Wet Pulp Dispersion A sample of water wet chromium tetr&hydroxide green pulp (foS,, 30oiW obtained from Imperial Oolor Works was successfully made up into .a WX stoek using the follow ing .modification of,WX-095S Milori Blue stock fors^is saaasn. 48. $0)1 After the n%ve had been sheeted out on the -foils and dried fortyseight Jours*fit was made into the following formulas DUP030000858 loam. E-42, Wxl004Fl ims t -- h ~X2 H-l mSoji" " 4 G-6YS Iw o?70 o, *3- Solids PX HL-3032 Pigment Mil H-U6 ... 1 *f:P 9*0 5*X9)$*5i ..,-3.0.321. Patio 10,00 3o^ Ool$ 5o 4-5 5 0X6 la comparison with ball mill 253^07518 the experi mental formula is practically Identical posses a lag 0*5$ more ft and Go5% more plasticiser or 1*0)1 more total solids,, t2) Dispersion of Laboratory Made Chromium Tetrahydroxlde A sample of Krebs dry W-701 chromium tetrahydroxlde pigment ordinarily dispersed by the plant la ball mills, was made up Into a water wet slurry of 2&oJ% solids content by mixing water and pigment at consentrations suit able for fornation of a pulp-like mixture* the resulting slurry was dis persed exactly a was the above pulp and produced a green enamel of characteristic transparency and high gloss* Cjl Dispersion of Dry Chromium Tetrahydroxlde by the Pulp Process _____'_______ ' Dry chromium tetrahydroxid green pigment was successfully dispersed in water wet nitrocellulose utilis ing the same formula which worked satisfactorily for the pulp* This time however the total amounts of dry pigment and plasticiser were added at one time. as is indicated In the following formulas wxaooW a - M PX-7S00 Cary M5o$ The water present in the ft was removed as steam Instead of being poured off as it was in the case of the pulp samples* After two days9 drying the WX~ stock was made up into formula Ho* 1004-Pi * The final enamel possessed the oharaoteristic transparency of pulp enamel but was slightly lighter in color* DUP030000859 (44 WX Paste- SI so era Ion 1b Clear Base (100417] After several attempts t obtain a W3C past which could b adequately kneaded for a period of several hours0 the following formula/was found to he the most satisfactory for the particular lot of pigment utilised* W70i B-303 9* 00% 5o&6 Grind 3 hrs* at . stflf,,ooSister^ 0 fake out B-111 R416 Bh-3032 Hlg H-15 W2 7a . 4 At other ratios of W-7GI/B-303 the paaf either failed to attain a stiff grinding consistency or broke up into hard lumps after brl>let grinding* fh oonstitutente and their wnnftrtifi_n_a *,,. fc'h aUnVi* .......n,. ,*.i,iw, e .. with ball mill 25>=0751a A laboratory W0 A ?0 mixer of half gallon capacity was used in all oases where & grind f this type was. eaplofMi, C5I A consideration of the preceding evidence sug gests the probability that the presence of water during dis=> peraion is in some maimer responsible for the depth of color and the transparency of pulp process chromium tetrahydroxid green enamelu Only the# processes where water was present during the actual dispersing, operation produced the iri descence and gloss which was desired* It la probable thatfi in the dry state,, many particles of the green pigment are bound together as agglomerates by crystals of water-soluble salts which have been adsorbed to the surfaces of the former during the process of manufactur.* During pulp process &ie pension in the W0 & ?* mixere water which may be present either in the wafer wet pulp or nitrocellulose will dissolve these salts and break up the agglomerates* Even though dry pigment may replace water wet pulp0 the nitrocellulose- alone apparently possesses sufficient water to dissolve that small fraction of water soluble salts which are normally present* A a result of this action,, there la.improved dispersion of the pigment particles in the nitrocellulose plasticiser medium* 5/gs/W DUP030000860 -5" QtfV . S <anj tcomfn)mo0h, <H3 #*.H ! g, Sr3 rO3&p-,luT'rCHP)P<rVOvv~I.ig4frOHc ts I k iso & .as, yRS 8 5 0N DUP030000861