Note: Descriptions are shown in the official language in which they were submitted.
llZ4~160
27,314
Modlfier Compositlon for Azo Pigments
Based on 2-Hydroxy-3-Na~hthoic ~cid
The invention relates to the preparation of azo pig-
ments based on the diazotization of various aromatic amino sul-
fonic acids and coupling thereof into 2-hydroxy-3-naphthoic acid
(BON). More particularly, it relates to the preparation and use
of a modifier composition to improve pigment properties.
Azo pigments based on the use of 2-hydroxy-3-naphthoic
acid as a coupling component are well-known, c.f. U.S. Patent
3,520,870. Examples of azo pigments of the type are Pigment
Red 48 (Color Index No. 15865), Pigment Red 52 (Color Index No.
15860), Pigment Red 57 (Color Index No. 15850), Pigment Red 58
(Color Index No. 15825), and Pigment Red 63 (Color Index No.
15880). They are based on coupling of 2-hydroxy-3-naphthoic
acid with the diazo of 6-amino-4-chloro-m-toluenesulfonic acid,
2-amino-5-chloro-p-toluenesulfonic acid, 6-amino-m-toluenesul-
fonic acid, 3-amino-2-chlorobenzene sulfonic acid, and 2-amino-
naphthalene-l-sulfonic acid, respectively. Other analogs are
similarly prepared from other aromatic aminosulfonic acids and
2-hydroxy-3-naphthoic acid.
The present invention is based on the discovery that
when the 2-hydroxy-3-naphthoic acid coupling component, which is
ordinarily used at the rate of about 1 to 1.2 moles per mole of
diazo component, is replaced by an equal amount of a coupler
composition comprising 2-hydroxy-3-naphthoic acid and one or more
modifier compounds, defined hereinbelow, the resulting pigment
is improved to the extent that one or more of the following re-
sult: (1) mass tone is darkened, (2) tint is yellower (some-
times bluer), t3) pigment strength is increased, and (4) gloss
and transparency properties are increased.
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~12~9~iO
Modifiers have been used in Pi~Pnt manufacture before.
Various impurities in the starting materials are known to participate
in the chemical reaction and produce variations in the color properties
and physical properties of the~finished pigments. One known example of
a modifier in the case of lithols is alpha naphthol, which has a close
chemical relationship to beta naphthol used in their manufacture. In
the case of azo pigments, in accordance with the present invention,
certain campounds related to 2-hydroxy-3-naphthoic acid produce unexpect-
ed results when used as modifiers in the ~igment reaction, i.e. the rate
of the coupling is increased and the pigment particle size is altered,
resulting in changes in mass tone, tint, and strength. The use of the
modifier campounds thus provides an opportunity to control the characteris-
tics of the ultimate pigment.
In one aspect, the present invention relates to an azo pigment
wherein the diazo of an aromatic am mosulfonic acid is coupled into a
camposition ccmprising about 90 to 99 percent by weight of 2-hydroxy-3-
naphthoic acid and about 1 to 10 percent by weight of an alpha substituted-
2-hydroxy-3-naphthoic acid.
In another aspect, the present invention relates to an improve-
ment in a process for the preparation of an azo pigment whereby the diazo
of an aramatic aminosulfonic acid is coupled into 2-hydroxy-3-naphthoic acid,
and whereby said pigment is optionally converted into the alkali metal,
aIkaline earth metal, or manganese salt thereof, wherein the improvement
camprises: using as the coupling component a composition co~,prising from
about 90 to 99 percent by weight of 2-hydroxy-3-napht~oic acid and from
about 1 to 10 percent by weight of an alpha substituted-2-hydroxy-3-
naphthoic acid.
The modifier a~mpounds which are useful herein include
compounds closely related structurally to 2-hydroxy-3-naphthoic acid.
They are ~-substituted 2-hydroxy-3-naphthoic acids, and they include:
l-nitro-2-hydroxy-3-naphthoic acid,
l-chloro-2-hydroxy-3-naphthoic acid,
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,'~, ";
llZ4960
l-methyl-2-hydroxy-3-naphthoic acid,
l-brom~-2-hydroxy-3-naphthoic acid,
2,2'-dihydroxy-3,3'-dicarboxy-1,1'-dinaphthyl~l,l'-
bis(2-hydroxy-3-naphthoic acid)/, and the like, or mixtures thereof.
Qne useful meth~d for the preparation of an effective
modifier composition is to oxidize 2-hydro~-3-naphthoic acid with ferric
: chloride or ferric sulfate. This oxidation, depending on the reaction
conditions, provides a mixture containing varying amounts of l-chloro-2-
hydroxy-3-naphthoic acid, 2,2'-dihydroxy-3,3'-dicarboxy-1,1'-dinaphthyl,
unreacted 2-hydroxy-3-
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"i,'',i
1124960
naphthoic acid, and small amounts of unknown by-products. Such
mixtures are effectively used as modifiers, as well as one or
more of their components, or the above mentioned l-bromo-2-
hydroxy-3-naphthoic acid.
The azo pigments of the present invention, as the cal-
cium, barium, strontium, or manganese salts of the carboxylic
acid, are prepared by conventional coupling procedures from 'he
appropriate aminosulfonic acid and the 2-hydroxy-3-naphthoic
acid coupling component using a molar ratio of aminosulfonic
acid to coupling component of from about 1/1 to about 1/1.2.
The coupling component, in accordance with the invention, will
comprise from about 90 to 99 percent by weight of 2-hydroxy-3-
naphthoic acid and from about 1 to 10 percent by weight of the
a-substituted 2-hydroxy-3-naphthoic acid modifier compound.
In a typical coupling preparation (not using the modi-
fiers of this invention), a solution of 21.4 grams of 2-hydroxy-
3-naphthoic acid is prepared in 740 ml of water containing 10
grams of sodium hydroxide. A solution of 25 grams 6-amino-4-
chloro-m-toluenesulfonic acid is dissolved in 370 ml of water
with pH adjusted to 8.5. The solution is cooled and 112 ml of
10% hydrochloric acid is added, followed by 28 ml of 4N sodium
nitrite solution. After stirring for about 30 minutes, a solu-
tion of 22.3 grams of calcium chloride, one gram of strontium
nitrate, and 100 ml of slightly acidified water is added. This
reaction mixture is then rapidly mixed with the solution of
2-hydroxy-3-naphthoic acid, the resulting mixture is held for
an additional period of stirring at 30C, and then heated to
near boiling. The pigment (Pigment Red 48) is filtered, washed
with water, and dried.
In the above typical procedure, in accordance with the
llZ49~0
invention, the 2-hydroxy-3-naphthoic acid is substituted by a
coupler composition, as defined, containing a modifier compound.
This results in an improved piyment.
The resulting pigment may be used as is or further
conditioned by various standard conditioning and end-treatments
known in the art, such as U.S. 3,520,870
For certain purposes, when the coupling is completed,
the pigment may then be conyerted to the metallic salt in the
presence of wood rosin. Thus, in the above preparation, the
coupling is completed in the absence of the calcium and stron-
tium salts, and a wood rosin solution is added prior to the ad-
dition of the metal salts. A suitable wood rosin solution may
be prepared by adding 14 parts of sodium hydroxide as a 30%
solution to 70 parts of wood rosin (abietic acid) in 1734 parts
of water and heating at the boiling point with stirring. Simil-
arly, the pigment may be end-treated with an aluminum salt to
improve pigment properties. Thus~ basic aluminum acetate (pre-
pared by slurrying 18.5 parts of dry aluminum hydrate and 18
parts of glacial acetic acid in ~0 parts of water) may be added
to the pigment suspension in the above example before filtration,
and the mixture held at 75C for about 40 minutes. The pigment
may then be filtered, washed chloride-free, and dried.
A different method of improving the pigment in~olves
heating a suspension of the pi~ment in salt form, as described,
by simultaneously adding a solution of 15 parts of aluminum chlo-
ride in 650 parts of water and a solution of 3 parts of sodium
hydroxide in 319 parts of water, the pigment suspension being
held at a temperature of about 75C for about 30 minutes. The
pigment is filtered, washed free of chlorides, and dried at 80C.
Still another method of end-treating the pigment
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involves adding to the pigment suspension before filtration at
about 100C 15 parts of aluminum chloride in 650 parts o water.
The treated pigment is held at 75C for 45 minutes at a pH of
6.0-7.0 and the solid material is filtered, washed chloride-
free, and dried at 80C.
The following non-limiting examples show the prepara-
tion of the modifiers useful herein as well as the use thereof
to produce improved pigments.
Exa~ple 1
Oxidation of 2-Hydroxy-3-Naphtho-ic Acid
~A) A vessel is charged with 181 gallons of water,
4224 lbs. of 47% ferric chloride solution and the volume adjusted
to 843 gallons with water. The solution is heated to 85-90C
and held at that temperature.
(B) A vessel is char~ed with 663 gallons of water,
2782 lbs. of 24% sodium hydroxide and to this is added 2165 lbs.
of 2-hydroxy-3-naphthoic acid. The mixture is heated to 85-90C.
(C) The contents of (B) are added to the contents of
(A) over a period of 45 minutes, keeping the temperature below
100C. The mixture is stirred or 2 hours at 95-100C and
cooled to 70-75C.
(D) A vessel is charged with 11450 lbs. of 24% sodium
hydroxide and 400 lbs. of Hyflo~Super-Cel. The mixture (C) is
added to this mixture of sodium h~droxide and Super-Cel, keeping
the temperature below 75C.
(E) The mixture from (D) is filtered and the filtrate
is added to a vessel containing 560 gallons of water and 2670
lbs. of 93% sulfuric acid at 20-25C, keeping the temperature
at 20-25C. The precipitate which forms is filtered, washed
with water, and dried.
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1124~60
A typical composition comprises about 47-48% unoxi-
dized 2-hydroxy-3-naphthoic acicl, about 15% 1-chloro-2-hydroxy-
3-naphthoic acid, about 34-35% 2,2'-dihydroxy-3,3'-dicarboxy-
1,1'-dinaphthyl[l,l'-bis(2-hydroxy-3-naphthoic acid)] and about
3% unknown materials.
Example 2
Oxidation of 2-Hydroxy-3-Naphthoic Acid
A hot solution of 55.5 grams of ferric sulfate hydrate
in 60 ml of water was added to 20 grams of 2-hydroxy-3-naphthoic
acid dissolved in 300 ml o~ water containing 4 grams of sodium
hydroxide. The solids were collected by filtration and stirred
into dilute caustic. The iron hydroxide was removed by filtra-
tion and the filtrate acidified to precipitate impure 2,2'-dihy-
droxy-3,3'-dicarboxy-1,1'-dinaphthyl. The product was filtered,
washed with water, and dried.
Example 3
Oxidation o~f 2-Hydroxy-3-Naphthoic ~cid
A hot solution of 130 grams of ferric chloride in
300 ml of water is added to a hot solution of 50 grams of 2-hy-
droxy-3-naphthoic acid in 750 ml of water containing 10 grams of
sodium hydroxide. After 20 minutes, the solid product is fil-
tered and dissolved in 600 ml of 5% sodium hydroxide and the
iron hydroxide which forms is filtered. The filtrate is acidi-
fied and the product formed is filtered, washed with water, and
dried to give 48.5 grams of impure 2,2'-dihydroxy-3,3'-dicarboxy-
l,l'-dinaphthyl. This is recrystallized from 80% acetic acid.
Example 4
Chlorlnation of 2-Hydroxy-3-Naphthoic Acid
A solution of 10.5 grams of 2-hydroxy-3-naphthoic acid
in 500 ml of glacial acetic acid was held at 18C as chlorine
1~4960
gas was bubbled in. The cr~vstals which formed were filtered
and the filtrate further chlorinated. This was repeated two
more times giving 5.56 grams of product. This was recrystal-
lized from acetic acid to give l-chloro-2-hydroxy~3-naphthoic
acid, m.p. 234-235C.
A similar procedure is used to prepare l-bromo-2-
hydroxy-3-naphthoic acid except that bromine is used instead
of chlorine.
Example 5
Bromination of 2-Hydroxy-3-Naphthoic Acid
2-Hydroxy-3-naphthoic acid (9.4 grams, 0.05 mole) was
dissolved in 200 grams water containing 20 grams of sodium hy-
droxide. The solution was heated to 100C and 51.4 grams (0.5
mole) of sodium bromide was added to give a saturated solution.
Ferric sulfate (25 grams) in 30 ml of water was added and the
mixture heated at 100C for 30 minutes. The mixture was cooled,
100 ml of 10% NaOH was added~ and then Hyflo filter aid. After
filtration, the clarified solution was acidified with 50~ HCl
and the resulting bright yellow precipitate was filtered and
dried at 80C. Yield 9.5 grams of a mixture of about equal
amounts of 2-hydroxy-3-naphthoic acid and 1-bromo-2-hydroxy-3-
naphthoic acid.
Example 6
Pigment Red 48 (CoIo No. 15865) was prepared as the
barium salt using the typical procedure described above except
that an equivalent amount of barium chloride was used instead
of calcium chloride. In preparing the pigment, 5 percent ~1.07
grams) of the 2-hydroxy-3-naphthoic acid used was replaced by
an equal amount of the oxidation mixture of Example 1. The
total amount of the coupling agent used, including the additive,
~124~!60
contained 0.16 gram of 1-chloro-2-hydroxy-3-naphthoic acid and
0.375 gram of 2,2'~dihydroxy-3,3'~dicarboxy-1,1'-dinaphthyl.
The resulting red pigment was slightly to moderately darker in
mass tone than standard, considerably bluer in shade, and about
8% stronger.
When 10% by weight of the 2-hydroxy-3-naphthoic acid
was replaced by the additive, the resulting pigment was very
much darker in mass tone, very much bluer in shade, and about
10% stronger.
Example 7
Pigment Red 48 was prepared as described in the above
typical preparation as the calcium salt, except that a portion
of the 2-hydroxy-3-naphthoic acid was replaced by an equal weight
portion of a modifier composition obtained in a manner similar
to Example 1. The modifier composition contained 7% 1-chloro-2-
hydroxy-3-naphthoic acid, 17.3% 2,2'-dihydroxy-3,3'-dicarboxy- !
l,l'-dinaphthyl and 75.7% 2-hydroxy-3-naphthoic acid. The amount
of 2-hydroxy-3-naphthoic acid replaced was 4%, 8.4%, 11.2%, and
34%, respectively, resulting in coupler compositions containing
about 99%, 98%, 97%, 95%, and 92% 2-hydroxy-3-naphthoic acid and
1,2,3,5 and 8% modifier compounds, respectively. Results of
evaluations of the different pigments were as follows:
- 8 -
1124960
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The results show the dramatic effect of increasing
amounts of the modifier on the mass tone of the pigment, the
significant effect on the shade and strength.
Example 8
Following the procedure of Example 7, 2 percent by
weight of the 2-hydroxy-3-naphthoic acid used was replaced by
an equal weight amount of l-chloro-2-hydroxy-3-naphthoic acid.
The resulting pigment was considerably to much darker in mass
tone, slightly yellower in shade, and about 7 percent stronger.
Example 9
Following the procedure of Example 7, 2 percent by
weight of the 2-hydroxy-3-naphthoic acid used was replaced by
an equal weight amount of 2,2'-dihydroxy-3,3'-dicarboxy-1,1'-
dinaphthyl. The resulting pigment was moderately to consider-
ably darker in mass tone, a trace yellower in shade, and about
5 percent stronger.
Example 10
Following the procedure of Example 7, 2 percent by
weight of the 2-hydroxy-3-naphthoic acid used was replaced by
an equal weight amount of 1-bromo-2-hydroxy-3-naphthoic acid.
The resulting pigment was much darker in mass tone, moderately
yellower in shade, and about equal in strength.
Example 11
The procedure of Example 7 is followed to prepare
Pigment Red 52 as the calcium salt except that the diazo of
2-amino-5-chloro-p-toluene sulfonic acid is used instead of
6-amino-4-chloro-m-toluene sulfonic acid. Ten percent by
weight of the 2-hydroxy-3-naphthoic acid used is replaced by
an equal weight amount of the product of Example 1. The result-
ing Pigment Red 52 is very much darker in mass tone, slightly
-- 10 --
llZ4960
yellower in shade, and about equal in strength.
Example_12
The procedure of Example 7 is followed to prepare
Pigment Red 57 as the calcium salt except that the diazo of
6-amino-m-toluenesulfonic acid was used instead of the diazo
of 6-amino-4-chloro-m-toluenesulfonic acid. Part of the
2-hydroxy-3-naphthoic acid coupling agent is replaced by an
equal weight amount of the following modifiers:
A. Product of Example 1 2.0 percent
B. l-bromo-2-hydroxy-3-naphthoic
acid 2.5 percent
C. l-bromo-2-hydroxy-3-naphthoic
acid 5.0 percent
D. 2,2'-dihydroxy-3,3'-dicarboxy-
l,l'-dinaphthyl 2.5 percent
E. 2,2'-dihydroxy-3,3'-dicarboxy-
l,l'-dinaphthyl 5.0 percent
Results of evaluations of each of the above pigment compositions
are as follows:
~124960
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-- 12 --
llZ4960
EXAMPLES'13-28
The procedure of Example 7 is followed to prepare
Pigment Red ~8 as the calcium salt. In some of the preparations
(13 thru 20) from 2 to 10 percent by weight of the 2-hydroxy-3-
napthoic acid used is replaced by an equal weight amount of (A)
1-chloro-2-hydroxy-3-napthoic acid and (B) 2,2'-dihydroxy-3,3'-
dicarboxy-l,l'-dinapthyl In other preparations (21 thru 29),
(A) and (B) are added to the reaction mixture in an amount of
from 2 to 10 percent by weight, based on the weight of the 2-
hydroxy-3-naphthoic acid used. The data are shown in the fol-
lowing table:
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1124960
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