FORM 2
The Patent Act 1970,
(39 of 1970)
&
The Patent rule 2003
Provisional Specification
(See Section 10 and Rule 13)


1. TITLE OF THE INVENTION
" Process for the preparation of Quinacridone Pigments "
2. APPLICANT(S)
(a) NAME : GHARDA CHEMICALS LTD.
(b) NATIONALITY : INDIAN
(c) ADDRESS: B-27/29, MIDC, PHASE 1,
DOMBIVLI (E), DIST. THANE 421 203 MAHARASHTRA INDIA
3. PREAMBLE OF THE DESCRIPTION
The following specification describes the invention

Process for the preparation of Quinacridone pigments
PRIOR ART OF THE INVENTION
Processes for the preparation of quinacridones are well known and documented. For example, S.S. Labana and L.L. Labana, "Quinacridones," Chemical Reviews . 67 , 1-18 (1967), and U.S. Patents 3,157,659, 3,256,285, and 3,317,539. The quinacridones thus obtained, known as crude quinacridones, are generally unsuitable for use as pigments and must undergo one or more additional finishing steps to modify the particle size, particle shape, or crystal structure to achieve pigmentary quality. A preferred method for preparing quinacridones involves thermally inducing ring closure of 2,5-dianilinoterephthalic acid intermediates, as well as known aniline-substituted derivatives thereof, in the presence of polyphosphoric acid, such as described in U.S. Patent 3,257,405. After ring closure is completed, the clear solution is drowned by pouring into a liquid in which the quinacridone is substantially insoluble, usually water or an alcohol. The resultant crystalline pigment is then further conditioned by solvent treatment or milling in combination with solvent treatment. Final particle size of quinacridone pigments is controlled by the methods used both in synthesis and in after treatment. Quinacridone pigments can be made more transparent by reducing the particle size or more opaque by increasing the particle size. Particle size is most often controlled during precipitation of the pigment by drowning or during subsequent milling of the crude pigment. Tinctorial strength and transparency of pigments can also be affected by solvent treatment.
Quinacridones and quinacridone solid solutions disclosed in the prior art are also sensitive to numerous other process variables, such as the type of drowning solvent, the temperature of the drowning solvent, the type of agitation used during the drowning process, the duration of the drowning process, and the post-drown processes. These variables are known to affect crystal phase, particle size and distribution, and surface characteristics, all of which ultimately affect the pigment color properties such as transparency, hue, tinctorial strength, dispersibility, dispersion stability, and rheology.
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SUMMARY OF THE INVENTION
This invention relates to a process for the preparation of quinacridone pigments having finer particle size distribution and improved coloristic properties and minimal effluents. In particular, by the use of benzenesulfonic acid or methane sulfonic acid alone or in combination with organic solvent to have ring closure of 2,5-dianilinoterephthalic acid or a 2,5-dianilinoterephthalic acid derivative having one or more substituents in at least one aniline during pigment synthesis and before the drowning process. The resultant quinacridones have characteristically deeper masstone, increased transparency, and bluer undertone (tint) hue.
It has now been found possible to obtain quinacridone pigments having smaller particle size without the need for milling processes by way of employing low-temperature ranges preferably 80°C to 120°C typically required in ring closure processes. This can be achieved by using benzene sulfonic acid or methane sulfonic acid during preparation of the pigments, particularly during the ring closure reaction. The process of the present invention is in principle applicable to ail quinacridone pigment manufacturing processes that include an "acid pasting" step, but the greatest improvement in coloristic properties is observed in the low temperature ring-closure processes followed by conditioning with solvent avoiding milling step. The filtrate after pigment isolation can be subjected for recovery of aryl or alkyl sulfonic acid by distillation with minimal effluent generation as against enormous effluents when poly phosphoric acid is employed as described in prior art. Other objects and advantages of the present invention will become apparent from the following description and appended claims.
DETAILED DESCRIPTION OF THE INVENTION
This invention relates to a process for the preparation of quinacridone pigments by heating, at a temperature of about 80°C to about 145°C, a reaction mixture comprising (i) 2,5-dianilinoterephthalic acid or a 2,5-dianilinoterephthalic acid or its ester or derivative having one or more substituents in at least one aniline ring, (ii) about 2 to about 10 parts by weight, relative to component (i), of aryl or alkyl sulfonic acid or its derivatives ; (b) drowning the reaction mixture from step (a) by adding said reaction mixture to about 30
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to 50 parts by weight, relative to component (i), of a liquid in which the pigment is substantially insoluble; (c) isolating the quinacridone pigment; and (d) optionally, conditioning the quinacridone pigment.
Quinacridone pigments are prepared according to the invention by first ring-closing 2,5-dianilinoterephthalic acid intermediates, including known aniline-substituted derivatives thereof, by heating such terephthalic acid intermediates in the presence of aryl or alkyl sulfonic acid or its derivatives. The quinacridone pigment is then drowned and isolated. The pigment is preferably also subjected to additional conditioning steps to improve pigmentary properties.
The reaction mixture is heated at a temperature of about 80°C to about 145X (preferably 100°C to 130°C), preferably for about 1 to about 24 hours (more preferably for one to ten hours).
The following examples illustrate the way in which the process of the invention may be carried out in practice.
Example 1
To 237 g of benzenesulfonic acid was added 37.6 g (0.1 mole) of 2,5-ditoluidinoterephthalic acid containing 40 ml of toluene. The mixture was heated at 100-110°C for four hours. After the viscous solution was cooled to 90-95°C, the resulting solution was added dropwise into water and slurry was stirred for 1 hr (68-72°C), the solid component was collected by filtration and washed with water until acid-free. The resultant presscake was reslurried in 2 N sodium hydroxide solution, and then heated for 85°C for two hours. After cooling to 60°C, the slurry was filtered and washed with water until free of alkali. After the presscake was reslurried in 800 g water and filtered. The wet cake can be solvent treated or cake can be oven dried and used as is for specific applications. Here, the wet cake was dried in an oven at 70°C to give about 30 g of quinacridone as a brilliant bluish red pigment.
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Example 2
To 192g of benzenesulfonic acid was added 40.5 g (0.1 mole) of 2,5-ditoluidinoterephthalic dimethyl ester containing 40 ml of chlorobenzene. The mixture was heated at 120-125°C for four hours. After the viscous solution was cooled to 90-95°C, the resulting solution was added dropwise into water and was stirred for 1 hr (68-72°C), the solid component was collected by filtration and washed with water until acid-free. The resultant presscake was reslurried in 2 N sodium hydroxide, and then heated for 85°C for four hours. After being cooled to 60°C, the slurry was filtered and washed with water until free of alkali. After the presscake was reslurried in 800 g water and filtered. The wet cake can be oven dried or used as is for specific applications. Here, the wet cake was dried in an oven at 70°C to give about 30 g of quinacridone pigment with deeper Mass tone having brilliant yellowish red color.
Example 3
To 260 g of Methanesulfonic acid was added 37.6 g (0.1 mole) of 2,5-ditoluidinoterephthalic acid containing 40 ml of chlorobenzene. The mixture was heated at 120-125°C for four hours. After the viscous solution was cooled to 90-95°C, the resulting solution was added dropwise into aqueous alcohol. The resultant slurry was stirred for 1 hr (68-72°C), the solid component was collected by filtration and washed with water until acid-free. The resultant presscake was reslurried in 2N sodium hydroxide, then heated for 85°C for two hours. After being cooled to 60°C, the slurry was filtered and washed with water until free of alkali. After the presscake was reslurried in 800 g water and filtered. The wet cake can be oven dried or used as is for specific applications. Here, the wet cake was dried in an oven at 70°C to give about 30 g of quinacridone pigment with deeper Mass tone having brilliant reddish color.
Example 4
To 260 g of Methanesulfonic acid was added 40.5 g (0.1 mole) of 2,5-dianiloterephthalic dimethyl ester containing 40 ml of toluene. The mixture was heated at 120-125°C for four hours. After the viscous solution was cooled to 90-95°C, the resulting solution was added
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dropwise into aqueous alcohol. The resultant slurry was stirred for 1 hr (68-72°C), the solid component was collected by filtration and washed with water until acid-free. The resultant presscake was reslurried in 2N sodium hydroxide, then heated for 85°C for two hours. After being cooled to 60°C, the slurry was filtered and washed with water until free of alkali. After the presscake was reslurried in 800 g water and filtered. The wet cake can be solvent treated or cake can be oven dried and used as is for specific applications.
Dated 24TH day of October 2008
Applicant
Satish B. Limaye Asst.
Manger- Sci. Inf. & IP Management.
Gharda Chemicals Ltd.
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