Crystal modification of C.I. Pigment Red 53:2 (&ggr;-phase)

Details Crystal modification of C.I. Pigment Red 53:2 (&ggr;-phase) Crystal modification of C.I. Pigment Red 53:2 (&ggr;-phase)

1999-06-21

2001-02-20

O'Sullivan, Peter (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Azo

C562S046000, C562S073000, C008S683000

Reexamination Certificate

active

06191263

ABSTRACT:

CROSS-REFERENCES TO RELATED APPLICATIONS
The present invention is described in the German Priority Application No. 198 27 272.3 filed on Jun. 19, 1998, which is hereby incorporated by reference as is fully disclosed herein.
BACKGROUND OF THE INVENTION
C.I. Pigment Red 53:2 (below: P.R.53:2) is defined as the compound of the formula (I) which forms from the coupling of diazotized 2-amino-5-chloro-4-methylbenzenesulfonic acid with &bgr;-naphthol and subsequent reaction of the resulting sulfo acid with a calcium salt (M=½Ca
2+
).
In the solid state, the compound of the formula (I) may also be present in another tautomeric or isomeric form and may also contain Na
+
ions, chloride ions and/or water molecules.
Pigment Red 53 has long been known as a sodium salt (M=Na
+
). The barium salt, P.R.53:1, (M=Ba
2+
/2), has long been produced in large amounts as a red pigment. It is used mainly in printing inks. The strontium salt (P.R.53:3) is of little commercial importance, as is the only modification of the calcium salt known to date (Pigment Red 53:2).
Most organic pigments exist in a plurality of different crystal modifications, also referred to as “polymorphic forms”. Crystal modifications have the same chemical composition but a different arrangement of the molecules in the crystal. The crystal structure may influence the chemical and physical properties, and the individual crystal modifications therefore often differ in the rheology, the color and other coloristic properties. The crystal modifications can be identified by X-ray powder diffractometry.
From P.R.53:2 (M=Ca
2+
/2), a crystal modification has been known to date which is referred to below as the &agr;-modification. It is distinguished by the following characteristic lines in the X-ray powder pattern (Cu-K
&agr;
radiation, double diffraction angle, 2&THgr; values in degrees, interplanar spacings d in Å
−1
, cf. FIG.
1
):
&agr;:
2&THgr;
d
Relative intensity in %
 5.1
17.4 
100
 6.6
13.4 
73 (double line)
10.2
8.7
37
12.2
7.2
39
13.8
6.4
31, broad
14.4
6.2
27, broad
17.8
5.0
24, broad
18.4
4.8
22
20.4
4.4
20
24.6
3.6
26
25.8
3.4
86
All line positions are associated with an uncertainty of ±0.2°. Depending on the crystal size and crystal quality, the lines at 13.8° and 14.4° may be fused into a broad line, as may be the lines at 17.8° and 18.40°.
SUMMARY OF THE INVENTION
The invention relates to a novel crystallographic modification (&ggr;-modification ) of C.I. Pigment Red 53:2. The invention also relates to a process for the preparation of the &ggr;-modification of C.I. Pigment Red 53:2.


REFERENCES:
patent: 4248635 (1981-02-01), Henning et al.
patent: 4719292 (1988-01-01), Schui et al.
patent: 5266110 (1993-11-01), Rieper et al.
patent: 0097913 (1984-01-01), None
patent: 0545072 (1993-06-01), None
patent: 2432538 (1980-02-01), None
European Search Report.
Patent Abstracts of Japan & JP 10231438 Sep. 2, 1988 (Dainippon Ink & Chem Inc.).

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