Note: Descriptions are shown in the official language in which they were submitted.
`- 10~4910
The invention relates to valuable new azo pigments of the
formula
O= ~ ~ NHCOCU N--N ~ Xl (I)
wherein
R represents an alkylsulphonyl group of 1 to 4 caxbon
atoms, an aralkylsulphonyl group or an arylsulphonyl
group which is unsubstituted or substituted by halogen
atoms, alkyl or alkoxy groups of 1 to 4 carbon atoms, an
alkanoyl group of 2 to 6 carbon atoms or a benzoyl group
which is unsubstituted or substituted by halogen atoms
or alkyl or alkoxy groups of 1 to 4 carbon atoms, an
alkanoyloxy group of 2 to 6 carbon atoms, an aroyloxy
group which is unsubstituted or substituted by halogen
atoms or alkyl or alkoxy groups of 1 to 4 carbon atoms,
~ or represents the group -N-N-aryl, the aryl moiety of
which can be substituted by halogen at~ms, alkyl or
alkoxy groups of 1 to 4 carbon atoms, alkanoylamino or
;~ alkoxycarbonyl groups of 2 to 6 carbon atoms, nitro,
trifluoromethyl or carbamoyl gr~ ps,
R2 represents a hydrogen atom, an alkyl group of 1 to 4
carbon atoms or a phenyl radical which is unsubstituted
- 2 _
.~
, . . . .. .
i . ~ . ,
,
--` 10~4910
or substituted by halogen atoms or alkyl or alkoxy
group.s of 1 to 4 carbon atoms,
Xl and X2, each independently of the other, represents a
hydrogen or halogen atom, an alkyl or alkoxy group of
1 to 4 carbon atoms, a trifluoromethyl or nitro group,
Y reprcsents a hydrogen or halogen atom, an alkyl or
alkoxy group of 1 to 4 carbon atoms or a phenoxy group,
n is 1 or 2,
Z represents the NH-group or a group of the formula
H
-CONH- or -CcC-
wherein R3 represents an alkyl group of 1 to 4 carbon
atoms or a phenyl radical which is unsubstituted or
substituted by halogen atoms or alkyl or aLkoxy groups
of 1 ~o 4 carbon atom8.
Particularly preferred azo pigments are those of the fonnula
- ~ 3
OzC ~ NHCO H-N= ~ X
\N yl X2
~4
- ,
' '. , ' ' ' '
.
4~10
wherein
R, Xl and X2 are as defined in formula (I),
Yl represents a hydrogen or chlorine a~om, a methyl,
methoxy or ethoxy group,
R4 represents a hydrogen atom or an alkyl group of 1 to
4 carbon atoms,
and especially monoazo pigments of the formula
Çl~3
~1 ¢ l 02R5
N CO~H -N=N ~
R CF3
wherein R4 and Yl are as defined above and R5 represènts an
alkyl group of 1 to 2 carbon atams, a benzyl group or a
phenyl group which is unsubstituted or sub~tituted by halogen
. atoms ~ aDkyl or alkoxy groups o~ 1 to 4 carbon atoms.
Halogen substituents are in particular chlorine or bromine
at~ms, preferably chlorine.
Alkyl group substituents are for example the methyl, ethyl,
n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl group,
preferably the methyl or ethyl group
Alkoxy group substituents are for example methoxy, ethoxy,
n-propoxy, isopropoxy, n-butoxy or tert-butoxy groups,
- 4 -
r.
:'
: , . . . . . . . :
.. . . . ~
~-~' 1~8 4910
especially the methoxy and ethoxy group.
Aryl r~dicals are for ex~llple naphthyl, especially phenyl,
radicals.
Particularly prefe~red pig~ents are those of the formula
S2R5
o:~J NHCOC~I -N=N ~
CH3 CF3
~ wherein Y has the meaning previously given and R6 represents
: a methyl or ethyl group, as well as those of the formula
X3
~ NHCOCH-N--N~N=N~
O~C ~ 10CH3 Y \~X5
. ~
wherein X3 and X4 represent chlorine atoms or methyl or
methoxy groups, and X5 represents a hydrogen or chlorine at
or a methyl group, or those of the formula
U COCH3 ~ CO ~ X6
~ : . : . -
. ., . . , ,., . ............ . :
- - :
- 1084910
wherein XG represents a hydrogen or chlorine at~m, a methyl
or rnethoxy group.
The pigments of the present invention are obtained by
coupling a diazo compound of an amine of ~he formula
R
with an acetoacetylarylide of the formula
o ~ ucocH2cocH3
R2
;:
The diazo component is preferably an amine of the formula
02R5
H2N ~)
CF3
wherein R5 has the meaning previously given,
- 6 -
.
10~49~0
Examples of diazo components are:
2_ethylsulphonyl-5-t:rifllloromethylaniline
2-benzylsulphonyl-5-trifluoromethylanilin2
2-phenylsulphonyl-5-trifluoromethylaniline
2_methylsulphonyl-4-nitroaniline
2_ethylsulphonyl-4-nitroaniline
4-amino-3-nitro-azobenzene
4-amino-2,5-dimethyl-azobenzene
4-amino-2,5-d~methyl-4'-chloro-azobenzene
4-amino-2,5-dimethyl-4'-methoxy-azobenzene
4-amino-2,5-dimethyl-4'-methyl-azobenzene
4-amino-2,5-dimethyl-3'-trifluoromethyl-azobenzene
4-amino-2,5-dimethyl-4'-carb~methoxy-azobenzene
4-amino-2,5-dimethoxy-azobenzene
2-methyl-5-phenylsulphonyl-aniline
2_methoxy 5-phenylsulphonyl-aniline
2-methoxy-5-para_chlorophenylsulphonyl-aniline
2-nitro-4-para_methylphenylsulphonyl-aniline
4-chlor-3-amino-benzophenone
4-amino_3-nitro-benzophenone
4-amino-4'-chloro-benzophenone
4-amino-3-nitro-4'-chloro-benzophenone
2_amino-4,4'-dichlorobenzophenone
4-amino-2',4'-dichlorobenzophenone
3-amino-4-methyl-4'-methoxybenzophenone
- 7 -
. , - - . ~ . . - . . . :
,.
1084910
4-chlorobenzoic acid 4'-amino-3'-methylphenyl ester
4-chlorobenzoic acid 4'-aminophenyl ester,
The coupling components are preferably those of the formula
O-C~ ~XCOCH2COCH3
R4
wherein R4 and Yl are as previously defined.
The coupling c~mponents are obtained in simple manner by
treating the corresponding amines with diketene, Examples of
amines are:
5-amino-benzimidazolone
5-amino-1-methyl-benzimidazolone
5-amino-1-n-butyl-benzimidazolone
5-amino-1-phenyl-benzimidazolone
5-amino-1-p-chlorophenyl-benzimidazolone
5-amino-1-p-methylphenyl-benzimidazolone
5-amino-1-p-methoxyphenyl-benzimidazolone
5-amino-6-chloro-benzimidazolone
5-amino-6-bromo-benzimidazolone
5-amino-6-methyl-benzimidazolone
5-amino-6-methoxy-benzimidazolone
6-am~no-2,4-dihydroxyquinazoline
6-amino-4-methyl-quinolone-2
- 8 -
.. ... . . . . . . . . .
' ~ . ' ' ~ ' ~ ' .
: - ~
10~49~0
7-amino-4-methyl-quinolone-2
7~ i.no-4~6-dimethyl-quinolone-2
6-mono-7-chloro-4~methyl-quinolone-2
7-amino-4-rnethyl-6-methoxy-quinolone-2.
These heterocyclic amines are kno~ compounds. The
diazotisation is effected by known methods.
The coupling preferably ta~es place in a weakly acid medium,
advantageously in the presence o~ conven~ional agents that
promote the coupling. As such coupling promoters there may be
mentioned in particular dispersants, for ex2mple aralkyl-
sulphonates, such as dodecylbenzenesulphonate, or 1,1'-
dinaphthylmethane-2,2'-disulphonic acid or polycondensation
products of alkylene oxides. The dispersion of the coupling
component can also advantageously contain protective
colloids, for example methylcellulose or minor amounts of
inert organic solvents which are sparingly soluble or
insoluble in water, for example optionally halogenated or
nitrated aromatic hydrocarbons, for example, benzene,
; toluene, xylene, chlorobenzene, dichlorobenzene or nitro-
benzene, and also aliphatic halogenated hydrocarbons, for
example, carbon tetrachloride or trichloroethylene, and
furthermore water-miscible organic solvents, for example
acetone, methyl ethyl ketone, methanol, ethanol or iso-
propanol, or preferably dimethyl formamide.
;. ,,
; . . .
,. : .. ~ . .... , -
.. .
10~4910
The coupling can also advantageously be carried ou~ by
conti.ntlously combi.ning an acid solucion o~ the diazonium
salt wi~h an alkaline solution o~ t.he coupling component in
a mixing nozzle, whereupon an ~mmediate coupling of the
component occurs. Care must be taken tha~ the diazo component
and the coupling component are present in equimolecular
amounts in the mixing nozzle, and a slight excess of coupling
c~mponent proves to be advantageous. This is most simply
achieved by controlling the pH of the liquid in the mi~ing
nozzle Furthermore, intense turbulent mixing of the two
solutions in the mixing nozzle must be ensured. The resultant
colourant dispersion is continuously drawn off from the
mixing nozzle and the colourant separated by filtration.
Finally, the coupling can also be carried out by ~uspending
the amine with the coupling component in the molar ratio 1:1
ln an organic solvent and treating the coupling mixture with
a diazotising agent, in particular an ester of nitrous acid,
such as methyl, ethyl, butyl, amyl or octyl nitrite
The pigments of the present invention have a good texture and
can be generally used without being conditioned If desired,
however, the cr.ude products can be converted into a finely
dispersed from by grinding or kneading, advantageously using
grinding assistants, such as inorgani^ and/or organic salts
in the presence or absence of organic solvents After the
- 10 -
.
~084910
grindi.ng ~rocedurf~ the assistsnts are removed in the
conventi.onal manner: soluble inorganic salts for example
with water, and water-insoluble assistants for example by
steam distillation. The properties of the crude pigments can
often be ~mproved by treating them with or~anic solvents,
pre~erably those having a boiling point above 100C
Particularly suitable organic solvents are: benzenes which
are subst ituted by halogen atoms, alkyl or nitro groups, for
example xylenes, chlorobenzene, o-dichlorobenzene or nitro-
benzene, as well as pyridine bases, such as pyridine, picoline
or quinoline, and also ketones, for example, cyclohexanone;
ethers, for example ethylene glycol monomethyl ether; amides,
such as dimethyl formamide or N-methylpyrrolidone, as well
as d~methyl sulphoxide, sulpholane or water alone, with or
without pressure The aftertreatment can also be carried out
in water in the presence o~ organic solvents and/or with the
addition of surface-active substances.
;.
The aftertreatment is effected preferably by heating the
pigment in water or the solvent to 100 to 200C, whereupon
in certain cases an increase in the granular size and, in
appropriate circumstances, a change in the crystal modifica-
tion, occurs. The fastness to light and migration of the
resultant pigments are thereby favourably influenced
The pigments obtained according to the invention are suitable
, i - ....
.. - . . . . . . ..
," ' ' ' ' ' . ',
.
- , ~ .
10~4910
for coiourin~ org~nic material of high molecular weight of
natural or sy~thetlc origin Such material can comprise for
e~nple natural resins, drying oils or rubb~r However, it
can also comprise modified natural materials, for example
chlorinated rubber, oil-modified alkyd resins or viscose or
cellulose derivatives, such as acetyl cellulose and nitro-
cellulose, and in particular man-made organic polyplastics,
that is to say, plastics which are obtained by polymeri-
sation, polycondensàtion and polyaddition The following
products may be mentioned in particular as belonging to this
class of plastics: polyethylene, polypropylene, polyiso-
butylene, polystyrene, polyvi.nyl chloride, polyvinyl acetate,
polyacrylonitrile, polyacrylates, polymethacrylates; poly-
esters, in particular esters of high molecular weight of
aromatic polycarboxylic acids and polyfunctional alcohols;
polyamides, the condensation products of formaldehyde and
~` phenols (phenolic plastics)~ and the condensation products of
formaldehyde and urea, thiourea and melamine (aminoplasts);
the polyesters used as varnish gums, namely both saturated
polyesters, for example alkyd resins, and unsaturated poly-
esters, for example maleic resins, and also the poly~ddition
and polycondensation products of epichlorohydrin and polyols
or polyphenols kno~m as epoxide resins; in addition thermo
plastics, i.e. the non-curable polyplastics It must be
emphasised that not only the homogeneous c~mpounds can be
- -: - 12 _
~ .. ...
.
:
1~84910
pig~ented according to the invention, but also mixtures of
polyplasti.cs, as well as co-conden~ates and copol~mers~ for
example those based on butadiene
The pigrnen~s of the present invention are particularly
suitable for colouring polyplastics, and the film formers
or binders known as vehicles, especially boiled linseed oil,
nitrocellulose, alkyd resins, melamine resins and urea-
formaldehyde resins The pigmenting of the organic substances
of high molecular weight with the pigments o~ the formula (I)
is effected for example by mixing such a pigment, optionally
in the form of masterbatches, with these substrates using
roll mi.lls, mixing or grinding devices The pigmented
material is thereafter brought into the desired final form by
known processes, such as calèndering, pressing, extruding,
coating, casting, or by injection moulding. It is often
desirable to add plasticisers to the compounds of high -
molecular weight before forming them in order to obtain non-
rigid moulded articles or to diminish their brittleness
Examples of such plasticisers are esters of phosphoric acid,
phthalic acid or sebacic acid The plasticisers can be added
in the process of the invention before or after the
incorporation of the pigment dye in the polyplastics. In
order to obtain different shades it is also possible to add,
in addition to the compounds of the fonmula (I), fillers or
other colouring constituents, such as white, coloured or
_ 13 -
: ' ' ' ,' ~. . - . ' ' ,' ' - .
1084910
black piglnents, in any amounLs to the organic substances.
For pigmen~ing lacquers and printing inks, the organic
materials of high molecular weight and the compounds o~ the
formula (I), optionally together with additives, such as
fillers, other pigments, siccatives or plasticisers, are
finely dispersed or dissolved in a joint organic solvent or
solvent mixture. The procedure can CollSiSt for example in
dispersing or dissolving each of the components individually
or also several jointly, and only thereafter combining all
the components
The pigmen~ed organic materials of high molecular weight
generally contain amounts from 0.001 to 30% by weight of a
compound of the for~ula (I), based on the organic substance
of high molecular weight to be pigmented Polyplastics and
lacquers contain preferably 0.1 to 5% by weight, and printing
inks contain preferably 10 to 30% by weight. The ~mount of
pigment to be chosen depends primarily on the desired colour
strength, on the layer thickness of the moulded article, and
finally also on the content of white pigment, if any, in the
polyplastic.
The colourants of the present invention are distinguished to
s~me extent by their easy accessibility, and by their good
fastness to heat, light, overstripe bleeding, migration and
good resistance to atmospheric influences. Compared with
_ 14 -
.,
.~ .. . .
.
10~49~0
disazo pi~lents, they have the advantage that the after-
treatment in organic solvents is not absolutely necessary in
order to obtain a good textllre and fastness to migration,
In the following Examples which illustrate the invention the
parts and percentages are by weight unless otherwise stated.
- 15 _
.
. .
1~8~910
E~mple 1
18,5 parts of 2-ethylsulphonyl-5-triflLloromethyl aniline are
stirred in 200 parts by vol~e of glacial acetic acid at
room temperature and ater about 5 minutes,25 parts by
volume of concentrated hydrochloric acid are added to the
completely clear solution. The solution is cooled to 0C with
ice and then 20 parts by volume of 4N sodium nitrite solution
are added at 0 to 5C over the course of 15 minutes, After
about 1 hour, excess nitrite is completely destroyed with
sulphamic acid and the diazo solution is filtered cLear,
14.4 parts of 5-acetoacetylaminobenzimidazolone are dissolved
in 20 parts by volume of 30% sodium hydroY~ide solution and
350 parts by volume of water at roam temperature, 2 parts of
hyflo are added and the mixture is filtered clear, The
solution of the coupling component is added to the diazo
~olution at about 5C in the course of about 30 minutes, The
pll value is kept between 4 and 5 by addition of 30% sodium
hydroxide solutbn, The batch is stirred for 6 to 8 hours at
20-25C, then heated to 80C, The pigment i8 collected by
filtration and washed with hot water, The ~ilter cake i8 dried
in vacuo at 70-80C, affording 28,9 parts (g6,8% of theory)
of a ~ellowish brown powder of the formula
_ 16 -
` , .
,
-
1~849~0
~113
O C ~N~I~COC~_N=N~2c2H5
H
CF3
The above product is recrystallised by an aftertreatment in
o_diclllorobenzene (2 hours at 145C), yielding a pigment
which colours PVC in bright reddish yellow shade of very
good fastness to migration, light and atmospheric influences.
The following table lists further pigments which are obtained
by coupling the diazo compound of the amine of column I with
the acetoacetyl compound of the amine of column II and
subsequent aftertreatment in the solvent of column IV,
Column III indicates the shade in which PVC is coloured wlth
0,2'h of thls pigment.
.
_ 17 -
.. . .
-
.
-` 10t~49~
TAB~E
_ ~ .
I ~ I ,
Ll ~ I C) O O
~ o ~-1 ~ ~ ~ o o ~ ~a
~ ,S~ ,~ F
~1 t~ ~ J O IJ
O~r~ N CJ ~ C) Frl N rl N Q) F
V~ ~ ~ a ~
I ~ I ~ r~ o I O~ o ~ o
o~ ~ ~ ~ o~ o~ ~ ~
. _ ...... _
~ ~ ,'2 ~ 3 a) ~ ~
a) o ~o ~o ,~ t,.o r~ O ~ C rl O r~ O b~ W C O
C'U ~ ,'2
t~) ~ o a) r-l O r~ O ~-1
u~ h O O ~ o ~ h O ~ ho h ~o ~ O O ~ h
~ . ,,~ X
O N ~ O S_~
~.) ~
O ~ ^ I I I C `
~u ~ aJ ~ ~IJ al C~l-rl
~ rO o g d o rO0 d ~o
uo ~C a O .~ ~0 ~
¢ u~
_ .
~' l
O ~ I a) ~
~ a, ~ c a
--~ O ~ h ~ O ~ aJ C
~ a) o P- o ~1 ~ - o N
~ o ~ o ~ N C O
U U C I _I P~ N .~ ~-1 N I td ~1) N
a I I ~ I c ~ u ~ a
aJ u~ rl C ~ ~ I I ~ h h o o
C I I ~CJ aJ 0 ~ ~ L~l rO ~ ~Ç N ,O
O ~ I O ~ I O U V 0 o
h
~3 C ~ C u ~1 C O OP. O ~ o o
O Orl ~ rl >~ a) ~ ~ C ~ ~
.~ -!~ NO ,~ ,C .~ ~1 0
~ ~ ~4, aN J- t 4 C) rl O ,C ,C ~.) I N I ~1 t~
o ~ I I C C ~ a ~ ~ I
N ~ ' ~ I O ~
rl ~ I N O - ~ I I O I l I
~1 ~ 0P~ aJO ~ U O O ,r~ l o O N O ~1) 0 O
N~ t O l .(~'1 ~ ~ C ~ C td a a ~ ~
a ~ O ~ O
e o ra C a)~ 3 N ~ e e o e N ~3
e-,~U-rl e-r~ ~ w s~ w a w
, e , ~ , , ~ , aJ , , ~: , ~ ,
~ ~J ~ ~ ~ ~1 ~ ~ ~ ~ ~ D
O ,1 C-~ ~ I~ oo ~ O ~
: Z ~ ~1 _I ~1
-
- - 18 -
.
. .. . .
.~ .
~849~0
TAI31,E
__ . .~
C~
~~a o ~ra
rC ~ _ _
U
OllJ E~ ~1 N 1:1)
U~ '~
~c~ 4, o ~ ~a
_
a) o 3 ~
ra ~ ~ ~ ~rl O O ~ O - O
~ ~ ~ '~
,~ a~ ~ a
u~ P~
_
~a ~ g o
~ I ,~ I ~
o ~ C~l o I ~ C~l o
~ o a~ ~ _I I X ~1 0~--I O ~
~s 5~ a :~ ~ o aJ ~ ~ h aJ P~ ra
o o o ~ o ~ o o .
~ ~ ~ o ~ o ~ o ~ o ~ o ~~ o
,1 , o ~ I ~ ~ ~ ~ ~ O - ~ ~ ~
~ 4~t) r~ NE~ O ~ OE~ C.l O E3 0 ~ E3 0 N
.LI O I rl~::I N I NI N I N I NI rl I N
t~I rJ~ I oI a I oI ~aI ~o I ~I o ,o
O I O 0~1O-r~ 0~1O-rlO~rl O IC)-rl O
3 N ~ N~ N ~ N ~ N
Cl~I O I I OI a)I ~u I o I oI o I O I
~ E3 u~ ~ ,Q U~ ~ LO,Q U~ r) rQ Lr~
_
~U O I O I ~
g ~ O o ~~ hI
~ O ~ O
au o h ~d ~ Oh
.C s~
. . ~ o o ~ o I
O ~
~J N ,~ V S~ ~1 ~ h
1:~ ~ I V ~rl ~1 ,~
~ rQ - U~ q
O O ~ _I~ o I ~ I h~ ~ ~ 4
P~ ~ I h _I h ~1 ~ h h I U~
E3 O o ~ ~I h 1~ Cl ~ ~ - G~
o ~~ h t~ O a ~ v aJ ~
O ~ JJ ,~ O ~ O ~ ~ ~ O a~
~ P N o ,~ O E~ ~ h
O I ~ rl Q~rl~ D I "O S
N _ I o u~
t~ ~ ~ t~ I O I ~I
rlI I ~J ~1 0 ~ u~
3 Q O O ~ d r~ ~ ~ h
~ O ~ ~_I N ~I h~ I ~
r~ rl O U-rl ~ ~ rl V~r~ ~ O
N ~ U ~` ~ S-l ~U
O ~ P JJ a) ~ ~--U
I I a~ u
~ ~,Q ~ a ~
_
O ~ U~ ~ I~ 00 ~ O ~ C~ ~)
æ ~ J
_ 19 -
!
- , , . . , . , '
., . .'. ' '
,: . , : ' , ' '' . - '
'' ' ' ' "~ ' ~, -' ~ . ' " "'
. . . .
' ~' ', ' . ' ' ' ' '
' . ' . ~
1~849~0
Exam~le 25
15 g o collodion cotton containing 35% of butanol, 15 g of
a phthalate resin modified with castor oil, 15 g of a 70%
butanolic solution of a urea varnish g~m, 20 g of butyl
acetate, 10 g of glycol monoethyl ether, 20 g of toluene and
5 g of alcohol are processed to a lacquer. This lacquer is
then pigmented with 2 g of the colourant of Example 1 and 2 g
of titanium dioxide (rutile) and ground, The lacquer is
sprayed onto cardboard and dried, giving a yellow coating of
very good fastness to light and overstripe bleeding and very
good resistance to atmospheric influences,
Example 26
To 100 g of a stoving lacquer consisting of 58,5 g of a 60%
801ution of a coconut alkyd resin in xylene, 23 g of a 65%
solution of a melamine varnish gum in butanol, 17 g of
xylene and 1.5 g of butanol, are added 1 g of the colourant
of Example 1 and 5 g of titanium dioxide, The mixture i9
ground for 48 hours in a ball mill and the pigmented lacquer
i8 sprayed onto a clean metal surface. After stoving at 120C,
a yellow colouration of good fastness to light and overstripe
bleeding and good resistance to atmospheric influencesis
obtained,
_ 20 -
~0849
~27
0.6 g of the pigment obt~ined in Example 1 is mixed with
67 g cf polyvinyl chloride, 33 g of dioctyl phthalate, 2 g
of dibutyl tin di.laurate and 2 g of titanium dioxide and the
mixture is processed to a thin sheet for 15 minutes at 160C
on a roll mill. The yellow colouration obtained is strong and
fast to migration and light.
Example 28
1 g of the pigment obtainPd in Example 1 is finely ground in
an Engelsmann grinding machine with 4 g of a litho varnish of
the composition:
29.4% of linseed oil-stand oil (300 poise)
67.2% of linseed oil_stand oil (20 poise)
2.1% of cobalt octoate (8% Co) and
1.3% of lead octoate ~24% Pb)
Using a stereotype block, this varnish is printed in an
amount of 1 g/m2 on art paper by letterpress printing A
strong, bright, yellow shade of good transparence and good
gloss is obtained. In three- or four-colour printing, ver~r
brilliant reddish yellow shades can be obtained by
superimposing on blue.
The pigment is also suitable for other printing methods, such
as intag~io printing, offset printing, flexographic printing,
with equally good results. `
_ 21 -
.
