Vo l. 3 3 . N o . 2 8 5 . S e p t e m b e r 1 9 4 7 .
THE INSTITUTE OF PETROLEUM.
A m eeting o f th e I n s titu te of Petroleum was held a t M anson House, 26, P o rtla n d Place, London, W .l, on W ednesday, J u n e 11, 1947, when th e chair was ta k en by Mr J . S. Jackson, V ice-President.
M r J . S. Ja c k s o n : I t is m y pleasing d u ty to introduce D r G. L. Riddell, who is th e D irector of th e P rin tin g and Allied T rades R esearch Association.
H e is a recognized au th o rity on printing inks, printing, an d all m atters connected therew ith, and we are very honoured to have him here to -night to serve as technical Chairm an, to preside during th e presen tatio n o f th e paper, and to conduct th e subsequent discussion. I offer him a very special welcome, and I invite him to occupy th e chair.
A
Dr G. L. Ri d d e l l, having form ally occupied th e chair, said : I th a n k you, Mr Jackson, for your kind com m ents. I am afraid I am n o t an au th o rity on anything, certainly n o t on p rinting in k s ; th e y are m uch too difficult.
We are to have presented to us a jo in t paper by D r H ealey a n d D r Ivanovszky. I do n o t th in k I need to introduce D r Ivanovszky to anyone in this ro o m ; he is sufficiently well know n to you as a Fellow of th e In s ti
tu te . B u t I m ay perhaps be allowed ‘to say a w ord ab o u t D r H ealey.
He is well qualified to discourse on this subject, because u n til th e w ar he was th e chief chem ist o f one of th e printing ink com panies; one of th e companies which utilized in th eir m anufactures a considerable q u a n tity of th e products of th e petroleum industry.
I am a little disappointed th a t there are n o t m ore p rinting ink people here, because I should regard this m eeting as providing a first ra te oppor
tu n ity for th em to tell you face to face some of th e things th e y say behind your backs ab o u t some of th e products w ith which you supply them .
Dr He a l e y th e n presented th e following paper.
PETROLEUM PRODUCTS IN THE PRINTING INK AND ALLIED INDUSTRIES.
By A. C. He a l e y, Ph.D ., M.Sc., F .R .I.C ., and L. Iv a n o v s z k y (Fellow).
Pr i n t i n g inks consist of a coloured pigm ent or dye dispersed or dissolved in a suitable m edium. The purpose of th e m edium , otherwise called vehicle, or varnish, is first, to carry th e pigm ent during th e printing process from th é ink d u c t or reservoir, via th e printing plate, to th e paper, and secondly, to fix th e pigm ent to th e paper after printing.
Petroleum products are of very considerable im portance in printing ink m anufacture, b o th as colouring m aterials in th e form of carbon black and lam p-black, an d as com ponents of th e vehicle. Before discussing th e uses
o o
of petroleum products in p rinting ink m anufacture, it is necessary to consider th e m echanism by which a fluid ink is converted into a rub- proof film in th e dried p rin t. The m ost im p o rta n t m ethods by w hich this change occurs are :—
1. O xidation or polym erization, w hereby a drying oil such as linseed oil is converted from a liquid to a solid s t a t e ;
2. A bsorption of th e ink in to th e p a p e r ;
3. E v ap o ratio n , w hereby a volatile solvent evaporates, leaving a solid residue b e h in d ;
4. G elation.
O ther m ethods of m inor im portance exist, b u t are usually only employed in special cases. H ere are tw o exam ples :—-
Freezing, w hereby an ink is used w hich is solid a t norm al tem p era
tures. T he printing-press is h eated sufficiently to m elt th e ink during th e p rin tin g process. T he ink resolidifies im m ediately it touches the cold paper.
Precipitation, w hereby th e solid po rtio n of th e ink is precipitated after p rin tin g by spraying th e freshly p rin te d p ap er w ith a non
solvent of th e resinous co n stitu en ts of th e vehicle.
I t does n o t follow t h a t a .particular ink dries b y one process only. In fact th e reverse is usually th e case a n d th e drying is due to a com bination of these processes.
There are th ree m ain m ethods of p rin tin g :—
1. Typographic (letterpress), in which th e ink is applied by suitable rollers to th e raised portions of th e surface of ty p e or blocks an d from them tra n sferred to th e p a p e r ;
2. Lithography., in which th e p rin tin g p late is a flat surface of either stone, zinc, or alum inium , a portion of w hich is rendered greasy and so receptive to ink, th e rem ainder of th e p la te being m ade in k -re p e lla n t;
3. Intaglio p rinting, which em ploys a p la te having th e design etched or engraved below th e surface of th e p late. T he whole p late is covered w ith ink a n d is th e n w iped clean, leaving ink only in the etched areas, from which it is subsequently tran sferred to th e paper.
P h otogravure is th e best-know n ty p e of th e intaglio p rin tin g processes.
Less im p o rta n t are die-press, copper, a n d steel-plate p rinting.
T he th re e p rin tin g m ethods are illu stra te d in Fig. 1, w hich shows a rep re
sen tativ e section of th e p rin tin g surface for each process. I t will be seen th a t th e inked sections shown in black in th e d iagram are above th e level of th e non-printing portions in typographic p rin tin g , on th is level in lithographic processes, a n d below it in intaglio plates.
T he ty p es of letterpress p rin tin g m achines are show n in Fig. 2 : (a) P la te n presses, in which th e p rin tin g form e is flat an d th e p ap er pressed ag ain st it all a t o n c e ; (b) Cylinder presses, in which a flat p rin tin g p la te is also em ployed, w hilst th e pap er is pulled ro u n d th e surface of a cylinder in such a w ay th a t it progressively m akes co n tact w ith th e form e, w hich is m oving below th e cylinder a t th e periphery speed of th e l a t t e r ; (c) th e ro ta ry press,
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T H E P R IN T IN G I N K A N D A L L IE D I N D U S T R IE S . 5 3 3
in which continuous roll or web of paper is used, which passes round a cyUnder know n as th e im pression cyUnder. A curved printing p late is em ployed, which is pressed against th e paper asdt passes over th e impression cylinder. R o ta ry presses are used for high-speed printing, for instance, in th e production o f newspapers. Some ro ta ry printing-presses will p rin t, cut, and fold ready for despatch as m any as 50,000 new spapers per hour.
P laten and cylinder presses are m uch slower an d p rin t up to ab o u t 5000 sheets per hour.
C'A
I—^ —/ '—^ ---1
LETTER P R ES S
LITH O G RAPH Y
I N T A G L IO
Fi g. 1.
P R I N T I N G M E T H O D S .
(a) P la te n p ress. (6) C y lin d er press. (c) R o ta r y p ress.
Fi g 2.
T Y P E S O F P R I N T I N G M A C H I N E S .
Typographic and lithographic inks usually dry by absorption, oxidation, or polym erization, while intaglio inks usuaUy d ry m ainly by evaporation assisted by absorption.
L etterpress and lithographic inks are composed of a suitable pigm ent m ixture dispersed in a vehicle consisting of drying or non-drying oils, to which some resin m ay have been added. W hen drying oils are used, it is generally necessary to incorporate driers.
5 3 4 H E A L E Y A N D IV A N O V S Z K Y : P E T R O L E U M P R O D U C T S IN
In p hotogravure inks th e pigm ent m ix tu re is dispersed in a vehicle consisting of a resin dissolved in a volatile solvent.
Ty p e s o f Pe t r o l e u m Pr o d u c t s Us e d i n Pr i n t i n g In k s. P etroleum pro d u cts are used in th e p rin tin g ink an d allied tra d e s in three different w ays—nam ely, as com ponents of p rin tin g inks, as cleaning agents, an d as lu b rican ts for p rin tin g m achinery. A wide range is used, which m ay be classified as follows :—
(a) V olatile petroleum solvents, paraffin, an d close-cut fractions of high-boiling petroleum solvents, e.g., of a boiling range of 260°-290° C ;
(b) M ineral o ils ;
(c) C arbon black a n d la m p -b la c k ;
(d) Paraffin w ax a n d m icrocrystalline w axes (petrolatum waxes, p etroleum ceresines, o zo k erites);
(e) Petroleum je lly ;
(/) A sphalts, or m ore correctly, petroleum b itu m e n s;
(g) P etroleum arom atic e x tra c ts an d petroleum re s in s ; (h) N a p h th e n a te s ;
(i) G reases;
(j) W ettin g a g e n ts ; (k) Miscellaneous m aterials.
L et us exam ine these groups in g reater detail.
Volatile Petroleum Products.
V olatile petroleum solvents find th e ir m ain ap plication in p rinting ink m anufacture as solvents for p hotogravure inks. These inks can be described as a suitable pigm ent m ix tu re ground in to a m edium , consisting of a resin dissolved in a suitable volatile solvent. T he resin m ay be eith er n a tu ra l or synthetic, including m anilla, dam m ar, ester gum , coum arones, zinc resinate, and various modified phenolic resins. F re q u e n tly b itum ens or asp h alts are used as th e resinous com ponent, in which case th e ir d a rk colour supplies some or all of th e colouring m a tte r of th e ink. These inks give sepia p rin ts, which are very popular for cheap m agazines. P igm ents or dyes m ay be added to m odify th e shade of these inks.
As m ight be expected, th e m ore volatile solvents produce fa ste r drying inks, which p erm it m ore ra p id p rinting. This, o f course, is usu ally desir
able, p articu la rly for high-speed m agazine p rin tin g . H ow ever, factory regulations in some areas m ay p ro h ib it th e use of inks hav in g a flash-point u n d er 73° F . I t is usually advisable to em ploy a solvent having a narrow boiling range an d a m inim um of tailings of slower d ry in g constituents.
These are liable to rem ain for some tim e in th e freshly p rin te d sheets and cause th e ink film to rem ain “ ta c k y ” for a n unnecessarily long tim e after printing. This m ay be sufficient to cause th e sheets to stick to g e th e r in th e pile a t th e delivery end of th e p rin tin g press.
I t is, of course, essential th a t th e solvent used in a p h o to g rav u re ink should be a satisfactory solvent for th e resin. Owing to th e generally im proved solubility of resins in arom atic solvents, it is usually considered
T H E P R IN T IN G I N K A N D A L L IE D IN D U S T R IE S . 5 3 5
ad vantageous if th e arom atic content of th e petroleum solvents employed is as high as possible. In fact it is quite common to use entirely arom atic solvents such as benzene, toluene, or xylene.
The following table, containing d a ta from th e “ Science of P etroleum ,”
gives th e properties of some petroleum solvents used in photogravure inks
Sp. gr. a t 60° F . . . . 0-768 0-792 0-80
D istillatio n :
In itia l boilin g -p o in t, ° C . . . 75 100 115
50% d istillin g to , ° C . . . 80 108 129
F in a l boilin g -p o in t, ° C . 95 120 160
F lash -p o in t, ° F . . . . below 73 below 73 45 ap p .
A rom atics, % b y w eig h t . . . 25 43 40
K a u ri-b u ta n o l n u m b e r . . . 49 56 53
The k auri-butanol te s t is a dilution te st, which consists essentially in titratin g a given volum e of a kauri solution in butan o l w ith th e solvent under exam ination, th e end-point being reached when th e opalescence caused by th e precipitation of th e resin is sufficient to cause blurring of norm al p rin t.
A typical basic-form ula for photogravure inks would be :—
P e r c en t
P ig m e n t . . . . . 20
R esin . . . . . . 20
S olvent . . . . . . 60
The less volatile petroleum solvents have some application in le tte r
press inks. Paraffin is sometimes added to reduce th e viscosity of th e ink, to increase its penetration, an d to decrease th e tack, p articu larly in inks for fast running ro ta ry an d cylinder presses. Paraffin is a frequent com ponent of th e so-called “ quickset ” inks. These inks do n o t d ry on th e printing- press, b u t nevertheless d ry very quickly after th e y are transferred from th e block to th e paper. This effect 'is produced by th e p en etratio n of one component of th e ink into th e paper, causing th e rem ainder to gel an d to produce rap id drying of th e ink.
A recent developm ent in high-speed printing is th e “ V aporin ” process.
A special ink is used which consists of a pigm ent, or pigm ent m ixture, dispersed in a vehicle consisting of a resin dissolved in a solvent th a t is essentially non-volatile a t ordinary tem peratures, b u t easily volatile a t elevated ones. The ink is p rin ted in th e conventional m anner, b u t afte r printing th e paper is passed a t high speed over a series of gas flames. T he solvent is evaporated and th e vapours ignited, b u t th e pap er is moving so rapidly th a t it is n o t scorched. The rem oval of th e solvent in th is m anner produces alm ost instantaneous drying of th e p rin t. This m ethod of drying prints is advantageous in high-speed m agazine printing. The solvents first used were synthetics having a boiling-point betw een 200° C and 250° C, such as b u ty l carbitol acetate. High boiling petroleum solvents w ith a narrow boiling range have subsequently been u s e d ; th ey have th e advantage of being considerably cheaper in price. The solvents used for this process should have no objectionable odour and be free from “ heavy ends.”
A proportion of petroleum solvents is usually included in silk screen inks.
These inks are p rinted by a stencil process using a silk screen, portions of
5 3 6 H E A L E Y A N D IV A N O V S Z K Y : P E T R O L E U M P R O D U C T S IN
which have been filled in, leaving th e design open. The filling-in m a y be done in various w ays, such as p astin g pap er over th e screen or b y p h o to graphic m eans, using dichrom ated gelatine. T he ink is applied to th e p ap e r th ro u g h th e screen b y m eans of a roller or squeegee.
Die-press inks, too, u su a lly contain petroleum solvents. These inks consist of a pigm ent m ix tu re dispersed in a resin solution. T h ey are, how ever, considerably s tif fe rth a n photogravure inks. Die-press p rin tin g is an intaglio process, used to produce embossed p rinting, such as th a t commonly used for le tte r headings.
P etroleum solvents are freq u en tly also used for cleaning purposes. I t is necessary a t tim es to rem ove in k from th e rollers of th e printing-press and from th e p r i n t i n g form e. This is usually done a t th e end of a shift or when changing from one colour to an other.
The cleaning process is an im p o rta n t one, h u t is u n fo rtu n a te ly “ messy ” a n d expensive in th a t it is u n productive. V arious surfaces have to be cleaned, including m etals, glue-glycerine com position, ru b b er, either n a tu ra l or synthetic, a n d possibly stone. Some care has to be ta k e n to choose th e m ost suitable solvent for each p a rtic u la r purpose. K erosine is p robably th e m ost com m on m aterial used for cleaning purposes an d is generally satisfactory for cleaning m eta l an d glue-glycerine com position rollers. I t m ay leave an oily residue on drying, w hich is sometimes advantageous,, h u t m ay be d e trim en ta l on o th er occasions. H owever, kerosine should n o t be used on ru b b e r rollers, blocks, or blankets.
. F o r cleaning th e form e during proofing, it is ad v antageous to use a fast- drying solvent, such as aviation spirit, as it dries v ery quickly from th e block a n d does n o t leave a n y oily residue w hich m ig h t p rev en t a good proof from being pulled. Commercial p etro l an d its m ix tu res w ith kerosine m ay be used for cleaning th e block while it is on th e m achine.
Cleaners for ru b b er surfaces should be readily volatile a n d n o t leave any oily residue, w hich would cause ra p id deterio ratio n of th e ru b b er. W ith some ty p e s of oil-resistant synthetic rubbers th is is n o t so im p o rtan t.
The boiling-point of solvents is insufficient to give a tru e idea of their evaporation properties. I t should be realized t h a t higher boiling solvents m ay evaporate fa ster th a n others w ith lower boiling-points. T he evapora
tio n ra tio depends on th e vap o u r pressure, th e viscosity, an d th e spreading capacity of th e respective solvents. T he surface fro m w hich evaporation occurs obviously has some bearing. A bsorption, or should we say adsorp
tio n phenom ena, betw een solvent a n d surface also are of some im portance.
The fac t th a t th e ra te of evaporation is considerably an d v ariab ly influenced by th e dissolved substances is well know n, b u t often forgotten.
Mineral Oils.
M ineral oils are used very extensively in th e m anufacture of news inks an d m agazine inks. T hey do n o t d ry to a h a rd film in th e sam e w ay th a t linseed oil does. Consequently, inks based on m ineral oils m u st d ry by p e n e tra tio n in to th e pap er ra th e r th a n by oxidation. F o r th is reason th e y are alw ays p rin ted on fairly absorbent pap er. These inks are alm ost alw ays low in price an d are used on cheap paper. M ineral oils are cheap com pared w ith th e vegetable drying oils, an d are very well suited to th e m an u factu re of cheap inks.
In th e U nited S tates of America ab o u t 100,000 tons of news ink, valued a t nearly $9,000,000, are used annually. T hey will probably contain over 80 per cent petroleum oils an d ab o u t 10 per cent of carbon black derived from petroleum gases. These figures obviously do n o t include th e considerable am ount of m ineral oils used in o th er types of printing ink.
P roducts derived from paraffin-base crudes were first used for th e pro duction of news inks, b u t have now generally been replaced by oils th a t are predom inantly naphthenic, as these usually give inks of b e tte r charac
teristics. Oils th a t are essentially naphthenic in character have good pigm ent-w etting properties an d produce inks th a t have good flow. Oils th a t only badly w et th e pigm ent ten d to produce inks having a poor flow.
According to J . J . Matiello (“ R aw M aterials Used in P rin tin g In k s,”
p. 82), th e naphthenic oils, besides giving inks possessing good working characteristics, also im p art to th e ink a rem arkably lasting plasticising effect. This does n o t m ean th a t th e inked surface is either tack y or greasy, b u t th a t it is pliable and n o t easily cracked during norm al usage, in addition to its being dry and non-tacky.
I t is more difficult, in general, when using a high paraffinic ty p e of oil, to obtain a printed surface free from offsetting. Offsetting takes place when the fresh p rin t transfers some ink to th e back of th e n ex t p rin t in th e pile a t th e delivery end of th e press.
I t is desirable th a t th e oils used should possess as little colour as possible, otherwise a noticeable halo m ay m ake an appearance or a coloured stain may occur on th e reverse of th e paper, due to th e vehicle “ striking th ro u g h ” the paper. Low grade unrefined oils probably contain coloured m aterial th a t m ay be deleterious. I t is considered good practice to use clear, distilled oils in th e m anufacture of inks.
There are, however, other characteristics to be considered. M ineral oils used in printing ink should possess th e ab ility of easily w etting th e pigm ent, as oils of poor w ettab ility produce, as already m entioned, inks th a t possess a b u ttery consistency. These “ short ” inks do n o t p rin t satisfactorily and
“ lengthening ” agents have to be added.
B etter dispersion m ay result in th e m anufacture of news inks, using darker oils which contain a small proportion of m aterials th a t a c t as w etting or dispersing agents. On th e other hand, these oils are likely to produce more staining on th e back of th e sheet. I t m ay be necessary in practice to strike a balance by a judicious m ixture.
Mineral oils, particularly those of high n aphthenicity, m ay be used in conjunction w ith litho varnishes, when printing on certain types of paper.
Inks made in this way d ry by a com bination of oxidation an d absorption.
A somewhat greater proportion of driers is usually incorporated into such inkK th a n into inks th a t are m ade entirely on a drying oil basis.
Tne viscosity of th e m ineral oils used in printing inks varies considerably.
For exam ple, a pale oil of Redwood viscosity of 70 and a d ark oil having a viscosity of 250 Redwood, both a t 140° F , are used for news inks.
The heavy m achine oils are th e m ost im portant. T hey possess good working properties and im part rap id setting to th e ink. The lighter m achine oils are sometimes used to replace p a rt of th e linseed oil in inks for fast running ro ta ry a n d cylinder presses. The viscosity of an oil m ay,
*
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5 3 8 H E A L E Y A N D IV A N O V S Z K Y : P E T R O L E U M P R O D U C T S IN
of course, be ad ju ste d by th e addition of bitum ens, resins, low viscosity oils,
•solvents, etc. »
The following is a ty p ic al form ula for news inks :—
P e r c en t.
C arb o n b lack . . . . . . . 13
D y e to n e r (oil-soluble m e th y l v io le t o r in dulene) . • 0-3
Oleic a cid . . . . . . . . . 0-7
M ineral oil . . . . . . . . . . 76
G ilsonite o r ro sin v a rn is h . . . : . . 10
T ypew riter ribbon inks an d duplicating inks b o th m ay contain mineral oils.
M ineral oils are also used, of course, for th e lu brication of printing- presses a n d printing-ink mills.
L ubricating oils are norm ally preferred for lubricating printing-presses, although also greases are som etim es used. Clearance in p rin tin g m achinery construction m u st be v ery sm all, m an y of th e m oving p a rts being delicate, and th e room tem p eratu re is usually ra th e r high. These reasons necessitate th e use of very stable lu b rican ts, an d consequently non-com pounded m ineral oils are used. Specially refined oils are needed for th e huge high
speed ro ta ry presses. T he flash-point of these oils should preferably be over 150° C an d th e congealing po in t below — 5° C. T he viscosity of th e oils used for th e sm all slow-moving presses should be 180-220 R edw ood I a t 50° C, w hilst for th e larger slow-moving m achines m ore viscous oils up to ab o u t 300 Redw ood I are often chosen. F o r th e lubrication of fast-running large ro ta ry presses, generally th in oils are used w ith a b o u t 120-150 R ed
wood I, b u t oils of o th er viscosities are also em ployed. T he acid value should be m axim um 0-4 for distillates a n d 0-1 for refined oils. Ash, water, an d asp h a lt contents of all oils should be p ractically nil.
F o r th e gear-wheels of ty p esettin g m achines a th in refined lubricating oil 70-120 Redw ood I a t 50° C is recom m ended. T he flash-point should be 170° C m inim um , a n d acid, ash, an d asp h a lt should be ab sen t. F o r the casting po rtio n of th e m achine, oils have to be used w ith a viscosity of m inim um 350 Redw ood I a t 50° C an d a flash-point of m inim um 240° C.
F o r th e lubrication of th e keys of th e ty p e settin g m achines high grade w hite oil or acid-free bone oil are recom m ended. T he relatively slow- m oving linotype m achines are usually lu b ricated w ith grease. Owing to th e high precision of th e m achine only unloaded greases should be used;
sodium soaps are p articu larly suitable.
Carbon Black and Lamp-black.
Carbon black, prepared by th e p a rtia l com bustion of n a tu ra l gas and petroleum gases, is by fa r th e m ost im p o rta n t p igm ent used in th e m anu
factu re of p rin tin g inks. C arbon black is th e ideal p igm ent for printing inks, as it possesses practically every desirable characteristic. I t is absolutely fast to light, fats, waxes, acids, alkalis, soap, solvents, heat,*and- all chemical reagents to which p rin ts m ay be subjected. M oreover, th e pigm ent is satisfactory from th e p o in t of view of th e p rin te r. Carbon black has good tinctorial stre n g th and is n o t a b ra s iv e ; inks m ade from it p rin t satisfactorily. Most im p o rta n t is th e fact th a t carbon black is in expensive. O ther pigm ents, being less satisfactory in m a n y respects, often cost te n or tw en ty tim es as m uch as carbon black. C arbon black has only
T H E P R IN T IN G I N K A N D A L L IE D IN D U S T R I E S . 5 3 9 tw o m inor draw backs in printing ink m anufacture. F irst, it has a some
w hat brownish tone th a t is considered ra th e r objectionable. This can easily be overcome by th e addition of a little blue pigm ent or dye, such as Prussian blue, induline, or o th er fat-soluble aniline dyes. Secondly, carbon black possesses th e disadvantage of slowly adsorbing th e drier content of th e ink, w ith th e resu lt th a t th e la tte r gradually dries more and more slowly.
This is overcome by adding a higher proportion of drier th a n would be used w ith oth er pigm ents.
A lthough th e bulk of th e production of carbon black is used in th e m anu
facture of rubber goods, th e printing ink in d u stry is th e second largest user of carbon black.
In 1945 th e U nited S tates used 1,052,798,000 lb of carbon black in rubber m anufacture and 22,824,000 lb in th e printing ink industry. The p aint industry, th e n e x t largest consumer, used only 7,421,000 lb.
The bulk of th e carbon black is m anufactured by th e channel process in which th e gas is b u rn t in suitable burners and th e flame allowed to impinge on a moving iron channel on which th e carbon collects. Blacks m ade by this process yield “ short ” inks.
F or good quality half-tone an d lithographic inks, th e so-called “ long ” carbon blacks are used. This ty p e of carbon black is deposited on ro tatin g rollers. T hey differ from th e “ sh o rt ” carbons in possessing a surface structure th a t enables them to be easily w etted by a slightly acid vehicle such as lithographic varnish. Consequently a higher proportion of th e pigm ent can be included in th e ink. Good flow properties are m aintained, and th e viscosity and yield value of ink is n o t excessively increased.
Carbon black has alm ost entirely superseded lam p-black, which has a much lower tinctorial strength, b u t possesses a more desirable bluish u n d e r
tone. Lam p-black still finds application in some types of printing ink, particularly in m a tt inks. I t is prepared by th e com bustion of various carbonaceous m aterials, including petroleum .
Carbon black has th e sm allest particle size of any of th e commercially available pigm ents.
Petroleum Waxes.
W axes are very im p o rtan t additives to p rinting inks. In general, th eir addition to letterpress and lithographic inks “ shortens ” th e ink. T h a t is to say, waxes reduce th e length to which a th re ad of th e ink can be draw n.
The reduction in length of an ink tends to m ake it less tack y , which lessens the tendency of th e ink to “ pick ” or “ pluck ” th e surface of th e paper.
This can occur when th e paper is pulled aw ay from th e inked block if th e cohesive forces of th e ink are greater th a n th e adhesion of th e surface of th e paper to th e underlying layers. Moreover, th e addition of waxes ten d s to reduce “ set-off.” *
' Most waxes, including paraffin w ax, find use in th e form ulation of printing inks. There are some specialized applications of waxes, such as th e m anufacture of m etallic inks. W ith o u t th e addition of some w ax, it is often difficult to o btain either satisfactory adhesion of th e metallic powder to th e paper or good “ leafing” of th e m etallic particles. However, bees
wax or some of th e harder vegetable waxes are generally used for this purpose.
W axes th a t possess a tendency to crystalhze m ay be ad d ed to le tte r press inks to produce a m a tt effect.
Som etim es, th e inclusion of w ax m ay im prove th e adhesion of th e ink film to certain surfaces.
W axes are usually added to inks as a previously p rep ared com position, norm ally containing suitable w axes in m ix tu re w ith oils or solvents. The following is a characteristic form ula :—
, P e r c e n t
T h in v a rn is h . . . . . 36
B eesw ax . . . . . . 28
P a ra ffin w a x . . , . . 24
C o b a lt n a p h th e n a te . . . . 12
A new an d novel application of waxes in p rin tin g inks is in th e so-called
“ cold-set ” inks. These are inks t h a t consist of a pigm ent or pigm ent m ix tu re dispersed in a w ax. T he ink is solid a t norm al tem p eratu res, b u t easily liquefies b y th e application of h e a t. T he in k is p rin te d on a heated press, th u s being in a liquid condition during p rinting, b u t on contact with th e pap er, th e ink solidifies im m ediately. This process enables printing to be done a t a higher speed th a n w ould otherw ise be possible w ith the conventional inks.
W axes are also used v ery extensively .in th e allied in d u stry of carbon p ap er m anufacture, in p a rticu lar, waxes (or m ixtures) containing a higher p ro p o rtio n of free f a tty acids. C arbon p ap er consists o f a special, thin, strong, p a p e r w hich has been coated w ith a film of a w ax-oil composition, su itab ly coloured w ith eith er a p igm ent or a dye. U sually, m ixtures of several waxes are em ployed.
L etterpress carbon p ap er inks are a special ty p e of carbon paper ink t h a t is p rin te d from a block so t h a t only a p o rtio n of th e p ap er is coated.
F o r exam ple, m an y com m ercial form s hav e to be signed, b u t only in a special place. The back of th e signature space is p rin te d w ith one of these inks.
A t one tim e m olten w ax was sprayed over th e freshly p rin te d sheet to p rev en t th e ink film from offsetting on to th e back of th e n e x t sheet. The wax particles form ed a series of sm all hills w hich p rev en ted ac tu a l contact betw een th e ink film an d th e n e x t sheet. O nly a v ery sm all am o u n t of wax was used so th a t th e particles were n o t noticeable. This m ethod is now obsolete, an d a sp ray of gum solution, such as gum arabic, is largely used instead.
W axes are also essential com ponents of lithographic crayons which are used for w riting or draw ing on lithographic p lates of stone, alum inium , or zinc, to provide a greasy surface th a t will be receptive to ink during printing.
I n addition, waxes form th e principal ingredient of o rd in ary m arking crayons, as well as pencils for w riting on glass, an d th e stencil sheets for duplicating m achines.
A considerable am o u n t of pap er is im pregnated w ith paraffin w ax to render it m oisture- an d vapour-proof.
W axes are also used in th e production of electros.. These are duplicates of letterpress p rinting plates, prepared by m aking a w ax negative replica of th e original p late w hich is subsequently covered w ith g rap h ite to ren d er th e surface electrically conducting. Copper is subsequently deposited on th e
5 4 0 H E A L E Y A N D IV A N O V S Z K Y : P E T R O L E U M P R O D U C T S I N
T H E P R I N T I N G I N K A N D A L L IE D I N D U S T R IE S . 5 4 1
g rap h ited w ax surface to form a printing surface. In th is way a duplicate of th e original block is obtained. The wax used for th is process should have a fine grain an d be tough and resilient.
W axes are som etim es added to typew riter ribbon inks.
A sm all proportion of w ax m ay be added to th e heat-drying inks of th e
“ V aporin ” type. This will reduce th e tendency to offset, should th e ink not be com pletely d ry w hen th e p rin ts come from th e heaters. I t would also increase th e tim e th a t th e ink would rem ain on th e press w ithout drying by form ing a protective w ax film over th e ink, th u s reducing any possible loss of solvent a t room tem perature.
Petroleum Jelly. v
Petroleum jelly is frequently added to printing inks to reduce ta c k and to prevent “ picking.” W hen p rinting on non-absorbent papers, an excess should be avoided, or th e drying m ay be im paired. I t is a common con
stituent of ink modifiers which are sold to th e p rin te r to enable him to adjust th e properties of inks.
Petroleum jelly is sometimes recom m ended for, carbon paper inks. Of course, th is depends on th e n a tu re of th e waxes form ing th e basic m aterial.
I t m ay also be added to reduce th e speed of drying, particu larly in th e case of inks th a t ten d to d ry on th e printing-press itself.
Bitumens.
Bitum ens find several applications in printing ink. In photogravure inks th ey are used as resin com ponent. T heir d ark colour, however, contributes very considerably to th e colour of th e ink. B itum ens are, as already m entioned, extensively used for th e very popular sepia tone inks in some illustrated magazines. The colour m ay, of course, be modified or embellished by th e addition of pigm ents or dyes. B itum ens are also used in some cheap black letterpress printing inks used for printing magazines and books.
Bitum ens also find some application in producing etching resists in th e preparation of printing surfaces. T hey m ay be applied either in th e form of a solution, or pow dered bitum en is sprinkled over a photogravure plate, which is subsequently warm ed.
On exposure to light th in asp h alt films are rendered less soluble in solvents.
This effect is intensified if th e asphalt is p retre ated w ith sulphur, a process being used in th e p reparation of printing plates.
Powdered asphalts m ay also be dusted on blocks during th e etching stage to prevent undercutting.
Petroleum Aromatic Extracts and Resins. .
The use of petroleum arom atic ex tracts in printing inks appears to be increasing. Possessing some drying properties, th ey can be used as a p artial replacem ent of linseed oil, rosin, or rosin oil, p articu larly in some of th e cheaper types of inks. However, th e ex tracts are m ainly used in those inks which d ry by penetration.
The e x tracts, on th e other hand, have characteristic properties of their own th a t m ake th em of value in th e m anufacture of printing inks. Their m ain value lies in th eir e x tra w etting properties and their dispersing effect
5 4 2 H E A L E Y A N D IV A N O V S Z K Y : P E T R O L E U M P R O D U C T S IN
on th e pigm ents in th e ink. T hey reduce “ cheesiness ” of th e ink an d im p a rt flow.
A wide range of petroleum arom atic e x tracts is available, ranging from m obile to viscous liquids an d even to solid resins. G enerally, th e ink-m aker favours th e relatively low viscosity grades t h a t are easy to handle. T he viscous an d solid grades, however, are used w hen it is desired to increase th e viscosjty o f th e vehicle. N evertheless th e ex tra c ts hav e n o t reduced th e use of th e m ineral oils them selves, which, o f course, are considerably c h e a p e r th a n th e «extracts.
The ex tra c ts hav e also been suggested as a p a rtia l replacem ent of rosin in th e sizing o f pap er (“ Technical B ulletin of th e P a p e r M akers’ Associa
tio n ,” Spring 1943, pp. 1-3).
An excessive use of petroleum arom atic ex tra c ts in p rin tin g ink form ula
tion m ay m ake th e ink too trea cly an d reduce th e ra te of p en etratio n into th e paper, by binding th e vehicle too firm ly to th e carbon afte r printing, m aking th e p rin ts ta c k y a n d slow-drying. T he optim um am ount of ex tracts used depends on th e p a rtic u la r oil a n d carbon black used.
I t m ay be advantageous first to grind th e pigm ent in presence of the petroleum arom atic e x tra c t, a n d th e n to a d d th e rem ainder of th e vehicle.
Naphthenates.
Oil-soluble m etal soaps, principally of cobalt, m anganese, a n d lead, are extensively used as driers in p rin tin g ink to prom ote th e oxidation and polym erization o f th e drying oils. I n th e p ast, f a tty acid soaps, such as linoleates, were m ainly used for th is purpose. More recently, however, salts of n aphthenic acid have been in troduced w ith ad v an tag e. Com
m ercial naph th en ic acid is chiefly a m ix tu re of m onobasic acids containing pentam ethylene nuclei. Com pared w ith th e linoleates, th e n aphthenates have a higher m etal co n ten t an d can consequently be used in smaller proportions. T hey have im proved solubility a n d th e ir solutions do not skin or p recip itate on storage.
O ther n ap h th e n ate s, such as zinc n a p h th e n a te , h av e lim ited application in p rin tin g ink. T hey m ay be used to facilitate grinding a n d dispersion of th e pigm ents an d to reduce d rier ab sorption in black inks. A lum inium n ap h th e n a te finds application in some ty p es of inks to reduce p en etratio n of th e ink vehicle into th e paper.
Greases. v
Greases, th a t is to say, suspensions of soaps, chiefly sodium or calcium soaps, in m ineral oils, are often add ed to letterp ress p rin tin g inks to shorten th e ink an d to rem ove excessive tac k . T he ad d itio n of greases to lith o graphic and offset inks is n o t advisable, owing to th e ir ten d en cy to cause em ulsification o f th e dam ping solution.
Only small proportions of greases are added, as an excess can reduce th e ta c k of an ink to such an e x te n t th a t th e ink will n o t tu r n in th e d u c t an d will fail to d istrib u te properly on th e press. M oreover, th e ink is liable to strike th ro u g h th e pap er afte r p rin tin g a n d to cause a greasy sta in on th e back of th e p rin t. The ad d itio n of too m uch grease m a y also im pair th e drying of th e ink.
In th e first q u a rte r of 1946, 32,000 lb of greases “ o th e r th a n wool fa t ”
T H E P R IN T IN G IN K A N D A L L IE D IN D U S T R IE S . 5 4 3 were used in th e U n ited S tates of America in printing ink m anufacture (U.S. D ep artm en t of Commerce).
Wetting Agents.
W ater-soluble w etting agents have found only slight application in printing inks, • largely because th e orthodox p rinting inks are not* w ater soluble. On rare occasions th e y m ay be added to spirit inks. I n recent years some a tte m p ts have been m ade to produce w ater-based photogravure inks. This has been done m ost extensively on th e C ontinent during th e war years as a result of th e shortage of petroleum products.
In America some a tte m p ts have been m ade to produce w ater-based news inks. In b o th these cases quicker drying m ay resu lt from th e inclusion of w etting agents in th e inks, which would increase th e ease of absorption of the ink into th e paper.
W etting agents m ay be added to typew riter ribbon inks of th e glycerine type to increase penetration.
Oil-soluble w etting agents do n o t appear, as y et, to have found much application in p rinting inks, b u t th ey m ay find use to prom ote w etting of th e pigm ent and to facilitate grinding. This is probably an interesting field for the application of oil-soluble petroleum sulphonates.
Miscellaneous Products.
A wide range of synthetic products is now derived from petroleum , cracked petroleum , and petroleum gases. The production of these products does not rely entirely on petroleum , as other sta rtin g m aterials are also available. A num ber of these synthetic products are used in th e m anufac
ture of printing inks. I n m ost cases, however, th e m aterials find only a limited application.
Alcohol, which can be prepared from ethylene, is th e com m onest solvent for spirit inks. T hey are rap id drying letterpress inks which are p rin ted from a special printing press, usually from rubber blocks. Spirit inks usually consist of an aniline dye dissolved in alco h o l; th e solution m ay contain tannic acid to assist in fixing th e dye an d a resin, usually shellac.
Occasionally, pigm ent dispersions are used in place of dye solutions. Such inks are widely used for printing pap er bags, m etal foils, cellophane sheetings and for o th er purposes.
The vinyl resins, e.g., vinyl acetate, which can also be m anufactured from ethylene, are sometimes used as film-forming constituents of spirit inks, particularly in th e form ulation of inks intended for printing on moisture- proofed cellophane, plastic films, and m etal foils.
Acetic acid, prepared by th e oxidation of eth y l alcohol, is sometimes used in spirit inks to increase th e solubility of th e dyestuff in th e ink.
A num ber of “ nitrocellulose ” solvents can be prepared from petroleum products, for instance, acetone, m ethyl ethyl ketone, diacetone alcohol, isopropyl alcohol. These solvents find lim ited application in th e form ula
tion of special ty p es of photogravure and spirit inks, m ainly where inks are required for printing on m etal foils or cellophane, particu larly if m oisture-proofed.
Glycerine, which can be prepared from allyl chloride, which in tu rn is derived from propylene, is frequently added tq spirit inks. O ther secondary
5 4 4 H E A L E Y A N D IV A N O V S Z K Y : P E T R O L E U M P R O D U C T S I N
solvents for sp irit inks are, for exam ple, alcohol an d glycol esters. G lycerine usually form s th e basis of hectographic inks, recording inks, an d stam p -p ad inks. T ypew riter ribbon inks m ay consist of dye solutions in glycerine.
Glycerine is an im p o rta n t m aterial in sy n th etic resin m anufacture, p articu larly of those types which are largely used in p rin tin g inks. One of th e m ain uses of glycerine is th e reduction of th e acid ity of certain types of resins, an d in p a rtic u la r to “ h ard en ” rosin in th e m a n u factu re of ester gum s. A lkyd resins, w hich are largely used in tin p rin tin g inks, are usually derivatives of glycerol.
A m ixture of glue a n d glycerine form s th e flexible com position which is th e m ost freq u en tly used m aterial for m aking p rin tin g rollers. A sim ilar m ateria l is used for hectographic masses.
I t is n o t custom ary to ad d synthetic solvents to letterpress inks, m ost of these solvents .being m uch too fast-drying. H ow ever, v ery occasionally some of th e slow-drying glycol derivatives, such as b u ty l carbitol, are used as reducers. S ynthetic solvents can also be used in th e previously m entioned h e a t drying inks of th e V aporin ty p e.
V arious synthetic “ ru b b ers ” are derived from petroleum sources.
Some of th em have superior oil-resisting properties, w hich are advantageous for th e m anufacture of p rin te rs’ rollers an d offset blankets.
A num ber of synthetic petroleum derivatives are used as interm ediates a n d m ay be used for pigm ent m anufacture.
Some of th e petroleum -derived sy n th etic solvents, such as diacetone alcohol, m ay be used to rem ove in k from p rin te rs’ rollers. T h e cost of these solvents usually only w arran ts th e ir application if th e ink, having been allowed to d ry on th e rolls, cannot be rem oved w ith p etro l or paraffin.
Co n c l u s i o n.
T here is no such th in g in th e p rin tin g ink in d u stry as “ sta n d a rd formulae.”
E a ch m anufacturer form ulates his pro d u cts according to his own experi
ence. C onsequently different m anu factu rers m ay use w idely divergent formulae, using different m aterials to produce inks of appro x im ately similar characteristics. As a resu lt, we hav e found it difficult in m an y cases to specify precisely th e qualities t h a t are required in petro leu m products to m eet an y particu lar dem and in th e p rin tin g ink in d u stry .
Di s c u s s i o n. *
Th e Ch a i r m a n (Dr G. L. Riddell) : I am sure you will agree th a t we have listened to a m ost stim ulating paper. I alw ays welcome th is k in d of paper, providing as it does a n o p p o rtu n ity for th e rep resen tativ es of two different industries to get to g eth er a n d to discuss th e ir com m on problem s.
I t is p articu larly useful to those o f us who work in th e p rin tin g an d printing ink industries because, as y ou have g ath ered from th e p ap er, th e p r i n t i n g in d u stry uses a large num ber of m aterials in m an y different w ays. The p rinting in d u stry uses these pro d u cts in com paratively sm all q u an tities, w ith th e resu lt th a t it has become som ething o f a Cinderella so far as raw m aterials are concerned. Y ou who are accustom ed to produce enorm ous quantities of petroleum products for various purposes should realize th a t
T H E P R IN T IN G I N K A N D A L L IE D IN D U S T R I E S . D IS C U S S IO N . 5 4 5
there is a printing ink in d u stry and th a t it is w orthy of some a tte n tio n . F or th a t reason alone we should be very grateful to th e au th o rs for having presented th e pap er this evening.
F or you gentlem en in th e petroleum in d u stry th e m eeting affords an opportunity to gain first-hand inform ation on th e properties your m aterials should have if you are to satisfy th a t very difficult person, th e printer.
MrP. Ke r r : In th e p a rt of th e paper dealing w ith bitum ens th e authors state th a t th e effect of light on th in asp h alt films is intensified if th e asphalt is pretreated w ith sulphur. Does th a t m ean th a t th e asphalt is to be heated with sulphur ?
D r He a l e y : “ P re tre a tm e n t ” m eans heating w ith sulphur.
M r G. W. Wh i t f i e l d : The authors m entioned th a t naphthenic oils have good pigm ent-w etting properties. Do th e y n o t consider th a t u n saturated an d arom atic oils are also satisfactory in th is respect ?
Dr He a l e y : Y e s , I t h i n k I w o u l d a g r e e w i t h y o u .
M r Wh i t f i e l d : I w ould suggest th a t th e position m ay be sum m arized as follows : W hen selecting a m ineral oil of a given boiling range an d /o r a given viscosity, th e n in general an oil w ith a higher specific g ravity is likely to possess b e tte r pigm ent-w etting properties th a n one of low specific gravity.
Dr He a l e y : Y e s , I t h i n k t h a t i n g e n e r a l I w o u l d a g r e e .
M r A. J . Go o d f e l l o w : D r H ealey has laid considerable stress on th e rate of evaporation. Could he enlighten me as to th e m ethods used to determ ine th a t factor ?
Dr He a l e y : From th e practical point of view I th in k you would tak e the ink containing th e solvent, p rin t it, and note th e tim e o f drying.
D r Iv a n o v s z k y : I th in k th e m ost commonly used m ethod is to place a few drops, say, 0-5 cc, on a piece of filter paper an d to n o te how widely th e solvent spreads, how deeply it p enetrates, and how quickly an d completely the tra n sp aren t spot disappears. Oil, o f course, would show th e phenom ena of spreading a n d penetration, b u t would n o t dry by evaporation. I th in k D r H ealey is rig h t, th a t th e drying of th e ink is tested sim ply by th e practical te s t of p rinting w ith it.
As to th e relation o f boiling p o in t to th e ra te of evaporation, etc, th is m atter is prim arily of im portance in connexion w ith solvents, b u t has obviously some relevance to th e application of oils. Solvents m ixed w ith oils affect spreading and penetration (and th u s also drying) of th e la tte r, which are to some ex te n t accelerated. Some years ago, a pam phlet p u b lished by th e I.G . F arbenindustrie listed th e evaporation rates an d boiling points of a range of solvents, showing quite clearly th a t th e boiling point is a very poor yardstick for th e drying or evaporating properties. How far th is knowledge can be linked up w ith th e drying of oil cannot be stated generally, b u t largely depends on th e p articular circum stances.
5 4 6 H E A L E Y A N D IV A N O V S Z K Y : P E T R O L E U M P R O D U C T S IN
MrH . A. I d l e : As a m em ber of th e p rin tin g ink fam ily I w ould like to express our th a n k s to th e petroleum in d u stry for having so m an y tim es
“ saved our lives ” during th e long period of shortages. H ow ever, I look forw ard very m uch to th e days w hen we shall n o t ju s t be to ld “ T h a t is th e product, get on w ith i t .” I t will be very nice w hen we can g et back to th e condition in w hich th e re will be sufficient products available from which to choose th e best for every different purpose.
Dr Y . Za k y : Could D r H ealey say som ething ab o u t th e fu tu re possi
bilities of th e arom atic ex tra c ts in th e p rinting ink in d u stry ? Are they likely to p a rt replace linseed oil p erm anently, or is it th a t, sim ply because of th e shortage o f linseed oil, m anu factu rers of p rinting inks have been driven to use th em unwillingly ? I n oth er words, is th e use of ex tracts in th e ink in d u stry likely to discontinue as soon as linseed oil becomes again freely available on th e m a rk e t ?
Dr He a l e y : T h a t is a question which to some e x te n t depends on the petroleum in d u stry . T he su itab ility of these pro d u cts for printing inks has been im p ro v in g ; th e products we are now obtaining are substantially b e tte r th a n those we ob tain ed before th e w ar, b u t th e y are still n o t entirely w h at we should w ant. W e cannot use th em to replace linseed oil com
pletely, an d we cannot use th em to replace petroleum oils completely.
M oreover, quite a large am o u n t o f p rin tin g is done w ith light coloured inks, a n d m ost ex tra c ts are sufficiently d a rk in colour to u p set th e tone of any b rig h tly coloured or pale inks, where it is desired to preserve q u ality of tone.
I f we could o b tain e x tracts of im proved drying qualities an d of light colour, I th in k th e ir use w ould increase su b stan tially . I fancy also th a t many p rin tin g ink chem ists are conservative a n d are inclined to use th e same m aterials as were used a long tim e ago. N evertheless, I th in k you will find th a t th e use of th e e x tra c ts will increase, p articu la rly if we can improve th e colour a n d th e drying tim es. L.do n o t th in k t h a t a n im proved supply of linseed oil will g reatly affect th e use 'o f arom atic e x tra cts in printing inks as th e ir g reatest o u tle t in p rin tin g inks a t p resen t is in those inks th a t contain little or no linseed oil.
Y ou m u st rem em ber t h a t when you p rin t a sheet of paper, im m ediately after p rinting, or w ithin tw o or th ree seconds afterw ards, you p u t another sheet of pap er on to p , th e reb y quite effectively excluding th e oxygen from th e bo tto m sheet, which renders it difficult for th e ink to d ry by oxidation.
C onsequently, unless th e pap er is sufficiently ab so rb en t for th e ink to dry by p en etratio n , th e ink will n o t d ry to a h a rd ru b -p ro o f film unless th e oil used has good drying properties.
t-t
Dr F r a n k M o r t o n : In th e first ta b le in th e paper, showing th e p ro perties of some petroleum solvents used in p hotogravure inks, th e solvents referred to are obviously benzene, toluene, an d xylene concentrates. W h at is know n concerning th e toxic effects of these solvents, p a rticu larly th e ap p a re n tly g reater to x icity o f benzene as against xylene a n d toluene, and to w h at e x te n t is th e p rinting ink in d u stry likely to require replacem ents o f benzene concentrates by concentrates boiling in t h a t range, b u t n o t containing arom atics ?
T H E P R IN T IN G I N K A N D A L L IE D IN D U S T R I E S .— D IS C U S S IO N .
I should like to ask w hether or n o t th e utilization of certain petroleum fractions in p rin tin g inks has resulted in carcinogenic effects. Also to w hat ex ten t has th e derm atitis which occurs in th e printing industry, p articularly among th e litho people, been laid a t th e door of petroleum products as against th e resins an d varnishes used ?
To w hat e x te n t does th e in troduction of th e new plastic rollers in th e ro tary offset m achines in th e S tates affect th e use of petroleum products in the inks, especially as I was to ld recently th a t th e rollers were likely to
be affected by arom atic solvents 1
D r He a l e y : The question w ith regard to th e rollers is fairly com
plicated. Several different m aterials are used for m aking rollers for printing presses, and I th in k you would say th a t generally speaking th ey have a som ew hat lim ited life ; we ten d ra th e r to ill-treat them by the things we p u t into the inks. R ubber rollers in particular, of course, are affected by m ineral oils. W e also p u t in cobalt driers, w hich are very deleterious. I do n o t know th a t I am fam iliar w ith th e p articu lar rollers to which D r M orton refers; b u t I th in k th e general position is th a t th e m ajority of rollers have a reasonably long life having regard to th e types of inks w ith which th ey are used.
I have never heard of any printing inks producing trouble owing to th eir carcinogenic effects. I do n o t th in k it is very likely because, if you look a t any of th e samples I have exhibited here this evening, you will note th a t they are very messy m aterials; and one does n o t handle p rin tin g inks more th a n one has to. I f there is any effect o f th a t sort I should th in k it is more likely to be a derm atitis effect due to th e solvents used for your hands afterw ards. I cannot recall a single definite case in which th a t has occurred, however. I th in k th e m ajo rity of industrial diseases th a t occur in th e printing trades as a whole come from lead poisoning, p articu larly in connexion w ith th e casting of lead alloys for m aking type.
The point in regard to th e toxicity of benzene as against th a t of xylene and toluene is th a t in all progressive photogravure works th e y use solvent recovery p la n t and do n o t perm it a dangerous concentration o f solvent vapours to occur. N orm ally th e sm aller plants, which do not ta k e such precautions, would use th e m uch-slower-drying solvents, because th e F actory R egulations would n o t perm it th e use of benzene and toluene in such circum stances. Benzene an d toluene would be p erm itte d only where special precautions are taken, as in m any m odern plants which are coupled with a solvent recovery ap p aratu s. I do n o t th in k th a t th e am ount of benzene vapour in th e m ajo rity of photogravure shops would reach anything like toxic proportions.
Dr M o r t o n : I t h i n k r e c e n t in v e s t ig a t io n s h a v e s h o w n t h a t t h e t o x i c e ffe c t o f b e n z e n e is p a r t i c u l a r l y m a r k e d , a n d t h a t o v e r a lo n g p e r io d o f t im e i t is u l t i m a t e l y f a t a l .
Dr H e a l e y : I b e l i e v e t h a t is t r u e ; b u t I h a v e n e v e r h e a r d o f a n y c a s e o f b e n z e n e p o i s o n i n g i n a n y p h o t o g r a v u r e p l a n t .
Dr M o r t o n : I t h i n k t h a t c a s e s h a v e b e e n r e p o r t e d w i t h i n t h e la s t F F
5 4 8 H E A L E Y A N D IV A N O V S Z K Y : P E T R O L E U M P R O D U C T S I N
tw o or three years. There have been questions by M edical Officers as to w hether th e s ta te m e n t th a t th a t is th e cause of d e a th is correct.
Dr He a l e y : I f benzene is used, an d if ad eq u ate precautions are not ta k e n for its rem oval, it m ay have th a t effect. B u t I th in k th a t in the m a jo rity o f p lan ts th e precautions ta k e n are adequate.
Dr Mo r t o n : In y our opinion is it necessary for th e m anu factu rers in the petroleum in d u stry to consider m aking a light volatile p ro d u ct w hich does n o t contain b e n zen e ; or w ould a benzine fraction be suitable ?
Dr He a l e y : I t h i n k a b e n z i n e f r a c t i o n w o u l d b e s u i t a b l e , although a
f r a c t i o n w i t h o u t b e n z e n e , p r o v i d e d i t i s a s u i t a b l e s o l v e n t f o r th e r e s i n s u s e d , w o u l d b e m o r e s u i t a b l e .
Dr Mo r t o n : Do you recom m end it ?
Dr He a l e y : I f i t i s s u i t a b l e f o r t h e r e s i n s u s e d , I t h i n k i t c o u l d b e e m p l o y e d .
M r J . A. L. Ha w k e y : The question has been raised by D r Z aky as to w hether petroleum products, a n d p articu larly petroleum ex tracts, are being used only b y reason of th e shortage of linseed oil. A t least te n years ago I was bold enough to p red ict t h a t w ithin te n years from th e n linseed oil w ould be of m inor in te re st in p rinting. I still th in k t h a t th a t will be th e case, for we are n o t g ettin g all th e linseed oil we w a n t a t th e m oment, an d th e p ro b ab ility is th a t we shall n o t get all we could w a n t for some years to c o m e; so th a t it is up to us to tr y to replace it. I n order to do th a t we have to consider w h at we w an t in these su b stitu tes, a n d as an ink m aker I confess t h a t we ourselves are n o t perfectly clear. I t is tru e to say th a t m uch of th e linseed oil th a t is being replaced will never be required for the sam e purpose. I n q uite a num ber o f form ulations we can ac tu ally obtain b e tte r results by leaving o u t linseed oil.
A nother p o in t bearing on th a t is th e degree to w hich one ty p e of printing will advance a t th e expense of an other. W e are n o t altogether clear in our m inds a b o u t th a t. B u t th a t will hav e a v ery big influence, of course, on th e ty p es of m aterials used in th e largest proportions in p rinting ink m anufacture.
My own particu la r difficulties come a b o u t because I am m ainly con
cerned w ith lithographic inks, where we have to consider affinity for w ater, an d where all th e factors concerning pigm ent w etting favour emulsions.
I f th e petroleum in d u stry w ants to satisfy th e p rin tin g ink in d u stry there m u st be m uch closer c o n ta c t; th e y will have to discuss to g eth er w h at is really required. W e m ust n o t m erely om it linseed oil an d p u t in som ething else in th e hope th a t we shall achieve w h at we w a n t; we m u st be p er
fectly clear ab o u t th e requirem ents, an d if we are clear ab o u t th em I th in k th e petroleum in d u stry will be able to provide them .
Mr P. Ke r r : P erhaps D r H ealey has some inform ation to give on th e difficulties he has experienced w ith petroleum products.
