FORM 2
THE PATENTS ACT 1970
(39 OF 1970)
&
The patent Rules, 2003
COMPLETE SPECIFICATION
A Novel Amorphous Form of
Tetrakis-(2,4-di-t-butyIphenyl)-4,4 '-biphenylene Diphosphonite
And its Process For Preparation
SeQuent Scientific Limited
A Company Incorporated Under The Companies Act, 1956
Having Registered Office at
301, 'Dosti Pinnacle',Plot No.E7, Road No.22,
3rd Floor, Wagle Industrial Area, Thane(W)-400 604
The following specification particularly describes the nature of the invention and the manner it has to be performed:

FIELD OF INVENTION
The present invention relates to a novel amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, its process for preparation and its use as a stabilizer in organic polymers.
BACKGROUND OF THE INVENTION The tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite is used as a stabilizer for organic materials, especially for organic polymers which are subject to degradation over a period of time due to exposure to atmospheric agents, mainly ultraviolet rays. It also degrades during processing and transformation processes due to high temperatures. This degradation leads to deterioration in the physical characteristics of organic polymers such as a decrease in the breaking load and flexibility, variation in the viscosity index and alterations in the optical properties of the end-product.
The tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite is described in
GB1372528, US3852629 and US4075163. These patents also describe a process for the
preparation of tetrakis-(2,4-di-t-butylphenyl)-4,4' biphenylene diphosphonite which
involves the reaction of biphenyl with aluminium trichloride and phosphorous trichloride
to give 4,4'-biphenyl-bis-dichlorophosphine complexed with aluminium trichloride, the
separation of the aluminium trichloride from the reaction mass using a suitable
complexing agent and the subsequent reaction of 4,4'-biphenyl-bis-dichIorophosphine
with 2,4-di-t-butylphenol. Tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene
diphosphonite obtained in these patents is in crystalline form, having a melting point of 94 °C.-96 °C.
US5852084 also describes a process for the preparation of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite. The tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite obtained in this patent is in crystalline form, with a melting point of 185 °C-186 °C, which is prepared by a process comprising (a) reacting biphenyl and phosphorous trichloride (PCl3), in the presence of a Friedel-Crafts catalyst; (b) separating the biphenyl-bis-dichorophosphines obtained in step (a) by decomposing the adduct with the Friedel-Crafts catalyst using a suitable complexing agent, in the presence of a solvent; (c) reacting the biphenyl-bis-dichlorophosphines recovered in step (b) with 2,4-di-t-butyl-phenol, in the presence of or without a solvent; and (d) crystallizing the tetrakis- (2,4-di-t-

butylphenyl)-4,4'-biphenylene diphosphonite obtained in step (c), in the presence of a solvent.
This patent also disclose an amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite having melting point 78 °C - 84 °C. This amorphous form is prepared by heating the above crystalline tetrakis-(2,4-di-t-butylphenyl)-4,4,-biphenylene diphosphonite at 195°C until the crystals melt completely in an inert atmosphere and then after stirring for some time the molten product is cooled on a cold aluminium sheet and the solid thus obtained is transformed into the form of flakes.
The inventors of the present invention have now surprisingly found a new amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, having a melting point of 87 °C - 95°C, which has a good flowability and better hydrolytic stability than that of commercially known phosphonites.
SUMMARY OF THE INVENTION
Accordingly, the principal aspect of the present invention is to provide a novel amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, having a melting point in the range of 87°C - 95°C and characterised by X-ray powder diffraction pattern as given in figure 1 and having major 2θ peaks at 7.22, 7.40 and 32.61±0.2.
The other aspect of the invention is to provide a process for preparation of amorphous tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, having a melting point of 87 °C - 95 °C, which comprises:
(a) reacting biphenyl and phosphorous trichloride (PCl3), in the presence of a Friedel-Crafts catalyst;
(b) distilling out phosphorous trichloride (PCI3);
(c) adding monochloro benzene to the obtained reaction mass;
(d) reacting the obtained reaction mass with 2,4-di-t-butyl-phenol, in the presence of a complexing agent, a solvent;
(e) separating the organic layer, cooling, optionally adjusting the pH;

(f) filtering the reaction mass under vacuum; and (g) distilling the solvent and isolating the product.
In another aspect the present invention provides a new amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite having melting point of 87 °C - 95 °C. This new amorphous form has a
BRIEF DESCRIPTION OF THE FIGURE Figure 1: X-Ray diffractogram of tetrakis-(2,4-di-t-butylphenyl)-4,4,-biphenylene diphosphonite
DETAIL DESCRIPTION OF THE INVENTION
Accordingly in an embodiment of the invention, the novel amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite has melting point in the range of 87 °C - 95 °C. It is characterised by X-ray powder diffraction pattern as given in figure 1 and having major 28 peaks at 7.22, 7.40 and 32.61±0.2. The X-ray diffraction is carried out using Cu anode having 45kV, 40mA at 25 °C. The novel amorphous form has good flowability and better hydrolytic stability than the commercially known phosphonites. The present process avoids crystallisation of the product to make amorphous unlike the process disclosed in US5852084. The hydrolytic stability is a key concern for the phosphonites. The product doesn't change with time for a considerably long time. This novel amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite is infact a major component of the mixture containing tris-(2.4-di-ter-butylphenyl)phosphate.
In another embodiment of the invention, biphenyl and phosphorous trichloride (PCl3) are reacted in the presence of the Fridel-Crafts catalyst selected from the group of Lewis acids viz. A1C13, ZnCl3, FeCl3 etc., preferably A1C13.
In another embodiment of the invention, the distillation of phosphorus trichloride can be carried out in presence or absence of vacuum.
In another embodiment of the invention, the complexing agent used in step d) is selected from the groups of tertiary amines viz. pyridine, triethylamine etc. preferably pyridine. The solvents for the said reaction is selected from the group comprising monochlorobenzene (MCB), toluene, preferably monochlorobenzene. The pyridine used

as complexing agent, MCB as diluent and PCl3 can be recovered and reuse to get the same result as fresh.
In another embodiment of the invention, the pH is adjusted in step e) in the range of 7-9, preferably 8 by using ammonia gas.
In another embodiment of the invention, the distillation in step g) is carried out in Agitated Thin Film Evaporator (ATFE) to isolate the product.
In still another embodiment, the product obtained by this invention is a mixture containing tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite as a major component along with other components viz. tris-(2,4-di-ter-butylphenyl)phosphate and monophosphonite.
In Another embodiment the key advantage of the novel amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite is enumerated below:
i. This novel amorphous form has very good transmittance at 425 nm =
95%, at 500 nm =98% ii. This process yields the desired isomer, Acid number and transmittance. iii. The use of ATFE for isolation of the product makes it very easy and user friendly. The present invention can be illustrated by the following examples, which are not to limit the scope of invention.
Example: Preparation of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite
A 500mL round bottom flask equipped with stirrer, reflux condenser, and nitrogen . inlet was charged with phosphorous trichloride (70.6g), biphenyl (20.83g) and aluminum chloride (50.0g) at 25-30°C. Gradually heated the reaction mass to 60-65°C over a period of 2hrs, Maintained the reaction mass at 60-65°C for 3-4 hours under inert condition, distilled out phosphorous trichloride at temperature 45-50°C under vacuum , diluted reaction mass with MCB (33.5 mL) and added to another RBF containing mixture of 2, 4-DTBP (115.5g), pyridine (50 g) and MCB (175g) under nitrogen below 60°C, and maintained at 60-65°C for 5-6 hours, separated the pyridine complex layer and diluted organic layer with MCB(90 mL), cooled the reaction mass to 10-15 °C and adjusted the pH to 8.0 - 9 by slow purging of ammonia gas below 20°C. The reaction mass was filtered under vacuum and washed with MCB (15mL) and isolated the product by feeding

the MCB layer into ATFE under 0-5mm vacuum at 170-180°C. The title compound was obtained as a flake, which was subjected to milling.
Yield-13 lg(630%w/w)
HPLC peak purity of Di-ester about 45-55%,
Aryl phosphite :15%,
Monoester:17-19%.
2,4-DTBP :0.5%
Ttransmittance at 425 nm = 95%, at 500 nm =98% and
Acid number = 0.5

We claim:
1. An amorphous form of tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, having a melting point in the range of 87 °C - 95 °C and characterised by X-ray powder diffraction pattern as given in figure 1 or having major 2θ peaks at 7.22, 7.40 and 32.61+0.2.
2. A process for preparation of amorphous tetrakis-(2,4-di-t-butylphenyl)-4,4'-biphenylene diphosphonite, having a melting point of 87 °C - 95 °C and characterised by X-ray powder diffraction pattern as given in figure 1 or having major 20 peaks at 7.22,7.40 and 32.61±0.2, which comprises:

a) reacting biphenyl and phosphorous trichloride (PCI3), in the presence of a Friedel -Crafts catalyst;
b) distilling out phosphorous trichloride (PC13);
c) adding monochloro benzene to the obtained reaction mass;
d) reacting the obtained reaction mass with 2,4-di-t-butyl-phenol, in the presence of a complexing agent, a solvent;
e) separating the organic layer, cooling, optionally adjusting the pH;
f) filtering the reaction mass under vacuum; and
g) distilling the solvent and isolating the product.

3. A process according to claim 2, wherein the Friedel-Crafts catalyst in step a) is selected from the group of Lewis acids viz. A1C13, ZnCl3, FeCl3 etc.
4. A process according to claim 2, wherein the Friedel-Crafts catalyst in step a) is AlCl3.
5. A process according to claim 2, wherein the complexing agent used in step d) is selected from the groups of tertiary amines viz. pyridine, triethylamine etc. preferably pyridine.
6. A process according to claim 2, wherein the solvent in step d) is monochlorobenzene or toluene.
7. A process according to claim 2, wherein the solvent in step d) is monochlorobenzene.

8. A process according to claim 2, wherein the pH is adjusted in step e) in the range of 7-9.
9. A process according to claim 2, wherein the pH is adjusted in step e) by using ammonia gas.
10. A process according to claim 2, the distillation in step g) is carried out in an Agitated Thin Film Evaporator (ATFE) to isolate the product