FORM 2
THE PATENTS ACT 1970
(39 OF 1970)
&
The patent Rules, 2003
COMPLETE SPECIFICATION
A Process for Preparation of Bis (2,4-dicumylphenyl)pentaerythritoldiphosphite
SeQuent Scientific Limited
A Company Incorporated Under The Companies Act, 1956
Having Registered Office at
116 vardhman Industrial Complex, L.B.S Marg,
Thane (W), Mumbai - 400601, India
The following specification particularly describes the nature of the invention and the manner in which it is to be performed:

Field of Invention
The present invention relates to a novel, cost-effective process for preparation of an Antioxidant bis (2,4-dicumylphenyl) pentaerythritol diphosphite commonly known as Doverphos-S-9228.
Background of the Invention
Many organic phosphites have been used as stabilizers. Among them are the commercially significant pentaerythritol diphosphites with either a spiro configuration or a caged configuration. These pentaerythritol diphosphites are particularly useful since they are thermally stable, have a high decomposition temperature and are of low volatility. Their high degree of intrinsic stability, especially under conditions of high humidity, is at least partially responsible for their satisfactory performance in inhibiting discoloration of polyolefins, typically caused by high temperature.
At least one purpose associated with the addition of a stabilizer to a polymeric resin is to prevent deterioration of the polymers derived from the resin during processing at high temperatures and also to permit the manufacture of products with increased intrinsic quality attributable at least in part to increased resistance to thermal and light degradation during their intended use.
Chemically Doverphos-S-9228 is known as bis (2,4-dicumylphenyl) pentaerythritol diphosphite as represented by formula I.

Many processes have been proposed for producing bis(alkylphenyl)pentaerythritol phosphites. Phosphites of this type have generally in the past been prepared by one of two methods: (a) the reaction of an alkylphenol with

dichloropentaerythritol disphosphite, as shown in U.S. Pat. No. 3,310,609, and (b) sequential transesterification reactions beginning with the reaction of pentaerythritol with an appropriate trialkylphosphite or triphenylphosphite to form pentaerythritol diphosphite which then undergoes the second transesterification reaction with an alcohol or a phenol, to form the desired bis(alkyl) or bis(alkylphenyl)pentaerythritoI diphosphite, as illustrated in U.S. Patent 4,305,866 and U.S. Patent 4,665,211.
Although the aforementioned methods are useful each of them suffers from certain disadvantages. The first identified method requires the use of a solvent because of the solid nature of pentaerythritol. The use of a solvent represents an additional cost and it must be removed and recovered, all of which negatively impact the process economics and steps required to synthesize a final product. The second method also has its own disadvantages such as multiple steps, each of which requires purification, which tends to add long reaction cycles, low yield and additional expense.
U.S. Patent 5,103,035 also teaches a method for preparing pentaerythritol
diphosphates in a chlorinated solvent and in the presence of a heterocyclic tertiary
amine catalyst. Although it is stated that a highly pure product was obtained, the
process involves multiple steps, for example, adding ammonia gas to remove residual
hydrogen chloride or other bound acid species, followed by filtering to remove
ammonium salts, and crystallizing the product with isopropyl alcohol. These
additional steps result in a relatively low yield.
U.S. Patent 5,364,895 also teaches a method for preparing pentaerythritol diphosphites which involves a solvent such as heptane and/or toluene and the reactants 2,4-dicumylphenol and PC13 and pentaerythritol, optionally with the addition of a trialkanol amine.
U.S. Patent 5,438,086 teaches a method for preparing pentaerythritol diphosphites by reacting 2,4-dicumylphenol and pentaerythritol in presence of PCI3, toluene and heptane using triethanol amine as catalyst 90-100°C. The drawback of this process is that the use of the binary solvent and triethanol amine as catalyst involves

cumbersome workup, the recovery of solvents are very difficult and the reaction is carried out at high temperature.
Thus, it is apparent that method for effective preparation of bis(alky]phenyl)pentaerythritol diphosphites in a more economical way while achieving high yield and high purity is still to be sought.
Thus it is highly desirable to develop a process which overcomes most of the drawbacks of the prior art. The present inventors have developed a very cost effective and environment friendly process, which overcomes most of the above stated drawbacks.
Summary of the Invention
The principal aspect of the present invention is to provide a process for the preparation of bis (2,4-dicumylphenyI) pentaerythritol diphosphite of formula I comprising;
a) condensing pentaerythritol of formula HI with 2,4-dicumylphenoI of formula II using a reagent and catalyst selected from the group consisting of N-Methylpiperazine, 4-Dimethytaminopyridine (DMAP), morpholine, piperazine and pyridine in presence of a solvent to form bis(alkylphenyl)pentaerythritol diphosphite of formula I; and
b) purifying the crude bis(alkylphenyl)pentaerythritol diphosphite using an alcohol to form pure bis(alkylphenyl)pentaerythritol diphosphite of formula I.
The present invention can be illustrated by the below reaction scheme:


Detail Description of the Invention
Accordingly in an embodiment of the invention, condensation of pentaerythritol of formula III with 2,4-dicumylphenol of formula II to form bis(aIkylphenyl)pentaerythritol diphosphite of formula I is carried out using a reagent selected from phosphorous trihalide preferably phosphorous trichloride and catalyst is selected from the group consisting of N-methylpiperazine, 4-dimethylaminopyridine (DMAP), morpholine, piperazine, dimethylformamide (DMF) and pyridine preferably pyridine in presence of a solvent which is an inert organic solvent selected from toluene, benzene, xylene and the like, preferably toluene. The reaction is carried out at a temperature in the range of about 40-80°C, preferably at 60-70°C.
In another embodiment of the invention, the purification of crude bis(alkylphenyl)pentaerythritol diphosphite is carried out using an alcohol selected from methanol, ethanol, propanol, isopropanol, n-butanol and the like, preferably methanol at neutral pH in the temperature range of about 60-65 °C.
In still another embodiment, some of the key advantages of the present invention are as below:
1. The process of the present invention involves the condensation reaction which is carried out at 60-70 °C instead of 90-100 °C which gives high yield i.e, 90% as compared to 70% yield in prior art.
2. The process of the present invention uses toluene and pyridine for the reaction instead of heptane and triethanol amine which reduces the work up process significantly and also makes the recovery easy as compared to the state-of-art.

3, The product obtained by the process of the present invention is more stable as compared to product obtained by the state-of-art process.
The present invention can be illustrated by the following examples, which are not to limit the scope of invention.
Example 1: Preparation of bis (2,4-dicumylphenyl) pentaerythritol dipbosphite of formula I
(a) Preparation of bis (2,4-dicumylphenyl) pentaerythritol diphosphate
Pentaerythritol (11.45 g) and toluene (50 ml) into 500 ml of Multi neckRBF at 25-35°C under Nitrogen, heated to 40-45°C. Pyridine (2 ml) was added into the above reaction mass at 40-45°C. Phosphorous trichloride (25.3 g) was added slowly at 40-50°C in 60-90 min. Pyridine (8 ml) was added to the above reaction mass at 40-50°C for 15-30 minutes and heated to 60-70°C. A solution of 2,4-Dicumyl phenol in toluene (61 g in 100 ml toluene) in 60-90 min under nitrogen at 60-70°C.Pyridine (10 ml) was added to the above reaction mass at 40-50°C for 15-30 minutes and maintained for 5-6 hours at 60-70°C. TLC was checked for completion of reaction, cooled, maintained for 30-45 minutes at 25-30°C, filtered and washed with toluene.
Yield: 67.2 g
(b) Purification of bis (2,4-dicumylphenyl) pentaerythritol diphosphate
Crude doverphos (80 g) and methanol (240 ml) were charged into 500 ml of Multi neck RBF at 25-30°C, heated to 60-65°C. The pH of the solution was checked for neutral range with pyridine at 60-65°C. maintained for 30 minutes, cooled to 25-30°C, maintained for 30 minutes. The reaction mass was filtered, washed with 40 ml of methanol, suck dried under vacuum and unloaded for water pulping. Wet material and DM water (160 ml) were charged into 500 ml RBF at 25-30°C, heated to 60-65°C and maintained for 30 minutes. Reaction mass was cooled to 25-30°C and maintained for 30 minutes. The reaction mass was filtered, washed with 80 ml of DM water, suck dried and unloaded. The material was dried for 8 hrs at 70-80°C.

Yield; 55 - 58 g
Acid No.:.6
Melting range:225-230 °C (c) Purification of bis (2,4-dicumylphenyl) pcntaerythritol diphosphite
Crude wet doverphos (80 g) and DM water (244ml) were charged into 500 ml of Multi neck RBF at 25-30°C, heated to 60-65°C. The pH of the solution was checked for neutral range with aqu. Ammonia at 60-65°C, maintained for 30 minutes, cooled to 25-30°C, maintained for 30 minutes. The reaction mass was filtered, washed with 30 ml of water, suck dried under vacuum and unloaded for methanol pulping. Wet material and methanol (244 ml) were charged into 500 ml RBF at 25-30°C, heated to 60-65°C and maintained for 30 minutes. Reaction mass was cooled to 25-30°C and maintained for 30 minutes. The reaction mass was filtered, washed with 30 ml of methanol, suck dried and unloaded. The material was dried for 8 hrs at 70-80°C under vacuum.
Yield: 55-58g (70-74%)
Acid No: <6
Melting Range: 225-230°C

We claim:
1. A process for the preparation of bis (2,4,dicumylphenyl) pentaerythritol diphosphite of formula I, which comprises:
a) condensing pentaerythritol of formula III with 2,4-dicumylphenol of formula II using a reagent and catalyst selected from the group consisting of N-Methylpiperazine, 4-Dimethylaminiopyridine (DMAP), morpholine, piperazine and pyridine in present of a solvent to form bis(aIkyIphenyl)pentaerythritol diphosphite of formula I; and

b) purifying the crude bis(alkylphenyl)pentaerythritol diphosphite using an alcohol to form pure bis(alky]phenyl)pentaerythritol diphosphite of formula I.
2. A process according to claim 1, wherein the reagent in step a) is phosphorous trichloride,
3. A process according to claim I, wherein the catalyst in step a) is pyridine.
4. A process according to claim 1, wherein the solvent m step a) is toluene.
5. A process according to claim 1, wherein the condensation in step a) is carried out at temperature about 40-80°C.
6. A process according to claim 1, wherein the condensation in step a) is carried out at temperature 60-70 °C.

7. A process according to claim 1, wherein alcohol in step b) for the purification of bis (2,4-dicumylphenyl) pentaerythritol diphosphite of formula I is selected from methanol, ethanol, propanol, isopropanol, n-butanol and the like.
8. A process according to claim I, wherein the alcohol in step b) is methanol.
9. A process according to claim 1, wherein the purification in step b) is preferably carried out at temperature 60-65 °C.