Title of Invention	AN IMPROVED PROCESS FOR MANUFACTURE OF PERMETHRIN
Abstract	Permethrin is a photostable synthetic pyrethroid manufactured for insecticidal use. This invention discloses an improved process for the manufacture of permethrin without use of any solvent or catalyst, comprising reaction of 2,2-dimethyl-3-(2’,2’-dichlorovinyl)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, at 60-800C, with means for continuously expelling hydrochloric acid generating in the said reaction, from the reaction mass, into a HCI gas scrubber.

Title of Invention

AN IMPROVED PROCESS FOR MANUFACTURE OF PERMETHRIN

Abstract

Permethrin is a photostable synthetic pyrethroid manufactured for insecticidal use. This invention discloses an improved process for the manufacture of permethrin without use of any solvent or catalyst, comprising reaction of 2,2-dimethyl-3-(2’,2’-dichlorovinyl)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, at 60-800C, with means for continuously expelling hydrochloric acid generating in the said reaction, from the reaction mass, into a HCI gas scrubber.

Full Text	FORM 2 THE PATENTS ACT 1970 (39 of 1970) And THE PATENT RULES, 2003 (See Section 10, rule 13) An Improved Process for Manufacture of Permethrin UNITED PHOSPHORUS LIMITED, a company incorporated under the Companies Act, 1956 having its registered office at 3-11, GIDC, Vapi-396 195, State of Gujarat, India and its corporate office at Uniphos House, 11th Road, C. D. Marg, Khar (West), Mumbai - 400 052, State of Maharashtra, India, an Indian Company. The following specification particularly describes the invention and the manner in which it is to be performed:- 1 This invention relates to a process for the manufacture of permethrin on large scale. This invention particularly relates to an improved process for manufacture of permethrin on large scale without use of any solvent or catalyst. This invention more particularly relates to a continuous process for the manufacture of permethrin on large scale without use of any solvent or catalyst. Background and Prior Art Permethrin is a synthetic insecticidal pyrethroid related chemical viz. [3-Phenoxyphenyl)methyl-cis,trans-(+-)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate]. Permethrin is a photostable synthetic pyrethroid. It possesses a high level of activity against Leptidoptera and is also effective against Hemiptera, Diptera, and Coleoptera. Approximately 600 tonnes per year of permethrin is at present used worldwide, mostly for agricultural purposes. It has a potential application in the protection of stored grain and it has been used in aerial application for forest protection and vector control, for the control of noxious insects in the household and on cattle, for the control of body lice, and in mosquito nets. Permethrin is formulated as emulsifiable concentrate, ultra-low- volume concentrate, wettable powder, and dustable powder. After considering the various products in the market, it was generalized that the cisrtrans isomer ratio of technical products is nearabout 2:3 and the optical ratio of 1R:1S is 1:1 (racemic), Though there is considerable variation in these ratios from product to product. Thus, permethrin contains the [lR,trans], [lR,cis], [lS,trans], and [lS,cis] isomers in the approximate ratio of 3:2:3:2. The [lR,cis] isomer is the most insecticidally active among the isomers, followed by the [lR,trans] isomer. The ratio of cis:trans is around 2:3 and 1R:1S is 1:1 (racemic). The Technical grade permethrin is a brown or yellowish brown liquid, which may crystallize partly at room temperature. The melting point is approximately 35°C and the boiling point is 220°C at 0.05 mmHg. The specific gravity is 1.214 at 25°C and the vapour 2 pressure is 1.3 mPa at 20°C. Permethrin is almost insoluble in water (0.2 mg/litre at 30°C), but is soluble in organic solvents such as acetone, hexane, and xylene. It is stable to light and heat, but unstable in alkaline media. Permethrin was synthesized as one of the new photostable pyrethroids by Elliott et al. in 1973 [US Patent 4024163 (1977)]. It is prepared by the esterification of the dichloro analogue of chrysanthemic acid, i.e. (1R, cis; 1R, trans; IS, cis; IS, trans )-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropanecarboxyclic acid, with 3-phenoxybenzyl alcohol. The reaction is as follows: CI H H H O \ I I I II c z=c —c —c — c —ci / \ / CI c / H,C CH, HOCK, CI H H\ 1 1 0II f / \/ci cOl H,C CHa Lr + HCI Fumio Mori describes in US 4,113, 968 (1988) in Example 8 therein, the process, which is reproduced below. "1.80 Parts of ethyl 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylate prepared in the same manner as in Example 1 was agitated at 40.degree. to 50.degree. C. for 3 hours in the presence of 8.65 parts of a 10% solution of potassium hydroxide and methanol to effect hydrolysis of the ester and obtain 1.43 parts of 2,2-dimethyl-3-(2',2,-dichlorovinyl)-cyclopropane-carboxylic acid, the data of the melting point and NMR spectrum of which were in agreement with the data described in Example 4. 1.43 Parts of the so obtained carboxylic acid was agitated at 80.degree. C. for 30 minutes together with 0.98 part of thionyl chloride in benzene as a solvent to obtain 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride. The so obtained compound was agitated at room temperature for 1 hour together 3 with 1.37 parts of 3-phenoxybenzyl alcohol in the presence of pyridine in benzene as a solvent, to obtain 2.63 parts of 3-phenoxybenzyl-2',2'-dimethyl-3,-(2",2"- dichlorovinyl)-cyclopropane-carbo xylate (n.sub.D.sup.20 = 1.5615 ). The results of the NMR spectrum (60 MHz) analysis of the so obtained compound were as follows: .delta..sub.TMS.spsb.4.sup.CCl : 1.10 (s) 3H; 1.19, 1.21 (each s ) 3H; 1.52 (d, J = 5.5Hz ) 1H; 2.16 (dd, J = 8Hz & 5.5 Hz ) 1H; 5.01 (s) 2H; 5.54 (d, J = 8Hz ) 1H; 6.8 - 7.5 (m) 9H Conventional Batch Process A large-scale version of the Fumio Mori process, which is at present the conventional process for the manufactuire of permethrin, is as follows: 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride used is prepared by chlorinating commercially available 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid. 2,2-dimethyl-3 -(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride is commercially prepared from commercially available Acetonitrile, Acrylonitrile and Carbon Tetrachloride using thionyl chloride in presence of Dimethyl Formamide as catalyst at 70-80 deg C. 3-phenoxybenzyl alcohol and tri ethyl butyl ammonium chloride are commercially prepared from commercially available Benzaldehdye, Bromine and Chlorine. In a stirred tank Stainless steel reactor the - 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride (acid chloride ) [1 - 1.1 mole ] and the alcohol -meta phenoxybenzyl alcohol(MPBAL), [ 1 mole] are reacted in presence of hexane[ 0.86 to 0.88] by weight of the reactants and tri ethyl butyl ammonium chloride as catalyst 0.005% to 0.007 % w/w of reactants, initially at about 15 °C by slow addition of one of the reactants to the other reactant taken in the tank. After addition of the reactants (acid chloride and MPBAL ), the reaction temperature is then raised to about 70 °C under hexane reflux condition until the unreacted alcohol is 4 0.2 % w/w. The reaction mass is then cooled to 35 - 40 C. and washed with water, soda ash solution and again with water. This is followed by hexane recovery . This process gives permethrin of 92 - 94 % by weight purity and the yield on the MPBAL basis is about 92 % by wt. It must be clear that the purity of the technical grade permethrin is not based on the extent of the presence of chemically pure "3-Phenoxyphenyl)methyl-cis,trans-(+-)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate". It includes materials related to this compound as said in the introduction. Drawbacks of the conventional batch process: The process using solvent is hazardous, there are always solvent losses as the recovery of the solvent is not complete. The reaction is not efficient, the reaction period is long and the unreacted technicals, the catalyst and the other products formed have to be removed by elaborate washings. The yield of the product is low, thus losing valuable raw material. Object The principal object of the present invention is to increase the yield of the reaction between the acyl chloride - 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride, and the alcohol - 3-phenoxybenzyl alcohol for the production of permethrin. Another object of the present invention is to improve the process of manufacture of permethrin by eliminating use of solvent and catalyst. Yet another object of the present invention is to reduce time of the reaction, reduce energy losses. Still another object of the present invention is so as to reduce the space of operation, time of reaction and to avoid variation in the quality and yield of product from batch to batch. 5 Summary of the Invention : The present invention discloses an improved process for the manufacture of permethrin comprising carrying out a reaction of reactants 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, without use of any solvent or catalyst, at 60 - 80°C, with means for continuously expelling hydrochloric acid generating during said reaction, from the reaction mass, into a HC1 gas scrubber; and washing the crude product to obtain permethrin. In one embodiment of the invention the means for continuously expelling hydrochloric acid generating during the said reaction, is provision of a reactor for carrying out the reaction under vacuum. In another embodiment of the invention the means for continuously expelling hydrochloric acid generating during the said reaction, is a provision of a reactor for continuously sparging dry inert gas in to the reaction mass, at the bottom of said reactor and venting it out from the reactor top. In the above process the inert gas is selected from dry deoxygenated air, nitrogen, helium, carbon dioxide, argon and mixtures thereof. Nitrogen gas is preferred. Drawings A brief description of the drawings is given below. Fig 1. -Flow chart of Inert gas sparging Continous process. Fig. 2 - GLC of a Permthrin sample obtained from Sigma Aldrich. Fig. 3 - GLC of Permethrin Technical obtained from example 1. Fig 4 - GLC of a product of Permthrin obtained from example 3. Fig 5- GLC of a sample of Permthrin obtained by example 4. 6 Description of the processes of the present Invention The conventional process of preparation of permethrin is based on the reaction as shown in Fig. 1. It is clear that in this reaction one mole of each reactant react together to give 1 mole of permethrin and 1 mole of Hydrochloric acid. In the conventional process this reaction is carried out using a catalyst in a solvent like hexane and at atmospheric pressure at about the reflux temperature of the solvent i.e. about 70 °C as described above as a conventional prior art process. The two embodiments of the present invention are the vacuum process and the inert gas sparging process. Each of these processes can be operated in many modes but two major modes are: batch process and continuous process. Semi-continuous mode is also possible. Of these two processes mainly, vacuum batch process and continuous inert gas sparging process will be described here. The Vacuum Batch Process This is a batch process. This is carried out in a batch still i.e. a stirred tank reactor made of any material of construction that is safe for use with hydrochloric acid at up to 100 °C such as glass lined, Teflon lined MS, stainless steel (SS316) can be used. The reactor has provision for heating/ cooling and applying vacuum and arrangements to connect it to a conventional hydrochloric acid gas scrubber. The reactor is a stirred tank batch reactor with facilities for carrying out the reaction under vacuum. The reactor is charged with 2,2-dimethyl-3-(2',2,-dichlorovinyl)-cyclopropane-carboxylic acid chloride 1000 kgs and then the reactor is cooled to about 15 C and vacuum applied to get about 600 mm Hg absolute pressure. 3-phenoxybenzyl alcohol is then added slowly from another container holding 800 kgs 3-phenoxybenzyl alcohol in at such a rate so as to maintain the reaction temperature about 15-20 °C. After the entire amount of the said alcohol is added, the reaction mass is maintained at that temperature for some more time and then heated to 60 °C until the said alcohol level goes down to less than 1% 7 by wt and then the reaction temperature is further raised to about 80 C.until the acidity level of the reaction mass goes below 0.15 % when expressed as hydrochloric acid. The reaction mass is then quenched with water and it is given water wash, soda ash wash and another water wash to obtain the product -Permethrin.. The process is as follows, (i) 3-phenoxybenzyl alcohol and 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride are charged in a stern tank batch rector almost in equi molar amount at about 20°C and then the temperature raised to about 80°C; (ii) Applying vacuum at suffiecent rate to expel Hydrochloric acid generating during the said reaction under negative pressure conditions (iii) washing the crude product after the reaction batch is over in a mixer-fettler charged with Soda ash solution; (iv) washing the Soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; and (vi) scrubbing the vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out alkali through plain water caustic scrubber. Continous Vacuum Process : The reactor is a continuous reactor comprising sectionalized column with series of perforated bubble cap plates, each having 1 - 5 % free area; and the reactor column having facilities for (a) continuous feeding reactants at the top; (b) keeping the reactor under reduced pressure (c) continuous vacuum-sucking out the continuously generating HC1, from the top of the reactor column; and (d) continuously discharging the crude product of the reaction, from the bottom of said reactor. The steps for the process comprise (i) charging 3-phenoxybenzyl alcohol and 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride almost in equi-molar amounts in a continous reactor at about 20°C and then raising the temperature to about 80°C; (ii) applying vaccum to the reactor for expelling the Hydrochloric acid generating during the said reaction under reduced pressure condition at 60 - 80° C. (iii) washing the crude product after the reaction batch is over in a mixer-settler charged with Soda ash 8 solution; (iv) washing the Soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; (vi) scrubbing the vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out the alkali through plain water caustic scrubber. Inert Gas Sparging Batch Process: The above batch process is repeated sparging nitrogen gas through the reaction mass and allowing it to vent out through the top of the still into the HCl gas scrubbing plant, instead of applying vacuum. This system was further developed into a more efficient continuous inert gas sparging process as described below. The reactor is similar to that of vacuum batch process but instead of vacuum arrangement there is provision for sparging inert gas. such as nitrogen in the reactor at the bottom and venting it out from the top. In all respects it is like Inert Gas Sparging Continuous Process except that the reactor as described above is different from the reactor of the continuous process, and other sections of the plant are suitable for batch processing. The reactor is a stirred tank batch reactor with facilities to continuously sparge dry inert gas at the bottom of the reaction charged in the reactor and for venting out the said gas with the HCl generating during said reaction, from the top of the reactor. Inert Gas Sparging Continuous Process: The flow sheet of this Inert Gas Sparging Continuous Process is shown in Fig 1. It is divided into 4 sections. Section A is a continuous reactor section. Section B is a continuous HCl gas scrubbing section. Section C is continuous crude permethrin washing section and Section D is drying & bagging section.. 9 This is a Inert Gas Sparging continuous process. This is carried out in a bubble cap column reactor made of any material of construction that is safe for use with dry hydrochloric acid at up to 100 C such as stainless steel (SS316) can be used. The reactor has provision for heating / cooling externally and sparging inert gas such as nitrogen from the bottom and arrangements to scrub out hydrochloric acid, from the top. In this embodiment of the present invention, 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, are kept in two holders and slowly and simultaneously equimolar quantities of the reactants are added from the top of the sectionalized column in to the reactor column fitted with bubble cap plates provided for holding liquids on the surface and allowing passage of gas through them. The sectionalized Bubble column is composed of different compartments or sections which is an inherent feature of the column. The Free area in the perforated plates is also an essential feature of the operation for the efficient functioning of the column. It was found that the free area of the perforated plates is related the efficiency of the process. The nitrogen gas is sparged from the bottom of the column and taken out from the top vent connected to hydrochloric acid gas scrubber. The reactor column is provided with facility for external heating and the temperature of the column is raised to 50 — 100 °C, preferably 65 - 80 °C. The nitrogen gas is fed at the rate of about 0.76 kg per kg of the alcohol fed. The product coming out continuously from the bottom is taken in batches for washing and product washed free of acid is [Technical] Permethrin. The continuous inert gas process and its plant is now described below with the help of flow sheet shown in Fig 1. The reactor is a continuous reactor comprising sectionalized column with series of perforated bubble cap plates, each having some free area; and the reactor column having facilities for (a) continuous feeding said reactants at the top; (b) continuous sparging dry inert gas from the bottom; (c) continuous venting out from the top of the reactor column, 10 the continuously generating HC1 with said gas; and (d) continuously discharging the crude product from the bottom. For illustrating the invention clearly, a plant with particular parameters has been described below. It is one example and should not restrict the scope of the invention. The plants can be designed with different parameters. The inert gas sparging continuous process plant comprises a column reactor section A, HC1 gas scrubbing section B, crude Permethrin washing section C and drying & bagging section D. This section A of the plant describes continuous process up to reaction to give crude permethrin. The section B of the plant describes the continous scrubbing of the continuously vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out alkali through plain water caustic scrubber. Further steps of washing of the crude and drying of the washed product are not continuous processes synchronized with the reaction. However, these process steps can be made continuous also. The reactor column 3 comprises (a) Column having heating and cooling arrangements to maintain the reactants at 60 - 80 deg .(b) Number of bubble cap plates 31-40 and (c) A Sparger 41 for sparging inert gas . The stock of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride is stored in holder 1 and the stock of 3-phenoxybenzyl alcohol, is stored in holder 2. These two reactants are simultaneously pumped to the top of the column reactor 3. The acid chloride from holder 1 and the alcohol from holder 2 are fed to the reactor 3 at such rates so as to ensure that the two reactants are in equimolar ratios when they come in contact at the top plate 31 of the bubble cap plates 31-40 of the sectionalized column reactor 3. These bubble cap plates are provided inside the column reactor 3, for holding liquids to a particular level on the surface of these plates and flowing down to the next plate below through the overflow tubes fitted to the plates while at the same time they allow the passage of gas coming from the liquid layer on the bottom plate to the next plate above it. 11 Nitrogen gas from the cylinder 4 is passed into the reactor 3 through the entry point 5 at the bottom of the reactor 3 through the sparger 41 and moves up through all the bubble cap plates 31-40 and the liquid resting on them. The design of the reactor considers feed rate and gas flow rate and the number of plates, and many other factors, so that the product discharging from the reactor is having the amount of unreacted acid chloride less than the minimum set, so that it can be washed out. During this period the Nitrogen gas carries with it the HC1 gas generating on each plate and where the two reactants react, and leaves the reactor 3 from the vent 6 at the top and flows to hydrochloric acid gas scrubbing section B. The bubble cap plates are so designed so as to have free area in a range of 1-5 % , preferably 1-1.5 % which is essential for the efficient performance of the reactor 3. The gas scrubbing section B comprises a water scrubber 8 and a caustic scrubber 9. The water is charged to the scrubber 8. from tank 20 through the tail screw 81. NaOH solution (5%) is fed to the caustic scrubber 9 from tank 21. Effluents flow down to the tank 19 and the gas leaves from the gas exhaust 22. Hydrochloric Acid solution is collected as a by- product from the scrubber 8 in the tank 23 The product coming out at the bottom of the column reactor 3 from outlet point 7 is crude Permethrin which is taken to the crude tank 11 . This crude permethrin from tank 11 is then taken to the washing section C. The washing section C comprises 2 mixer settlers. The crude permethrin from tank 11 is taken to the first mixer-settler 12 where the organic phase is mixed with soda ash solution (2 % by wt.)kept in a holder 13 . The two phases may be separated by centrifuges in continuous way. The organic phase is taken to the second mixer-settler 14 where it is mixed with water from tank 20. The organic phase - the permethrin is then taken from mixer settler 14 to the bagging section D.. The aqueous washings from both mixer settlers are taken to the effluent treatment plant from tank 19. 12 The bagging section D comprises a holder tank 15 and drying vacuum tank 16 for drying at 90 C under vacuum of 759mm Hg and bagging units 17 and 18. The washed permethrin from section C is then taken to the bagging section wherein it is kept in holder 15, dried under vacuum in tank 16 and then packed in bags in bagging units 17 and 18. The continous process can be used for various other industrially manufactured pyrethroid esters. Examples The invention will now be illustrated by way of examples. Examples are by way of illustration only and in no way restrict the scope of the invention. These examples describe the conventional process and a process of the each embodiment of the present invention namely the vacuum batch process and the inert gas sparging process. This investigation involved experimenting in building large-scale plants and running the reaction with different conditions and hence was spread over a long period of time. The raw materials used for reactions were of technical grade and the product obtained was technical grade permethrin. The two reactants required were also prepared here. As described above. The product permethrin obtained in these examples were analysed by gas - liquid chromatography (GLC). The analysis was done on a Shimadzu 14-b gc instrument wherein a capillary db-5 column was used. The sample was prepared by taking 0.2 gm sample in 10ml measuring container and diluting with methanol. The raw materials used in the process for the preparation of permethrin are manufactured as follows, 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride used is prepared by chlorinating commercially available 2,2-dimethyl-3-(2',2'-dichlorovinyl)- 13 cyclopropane-carboxylic acid. 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride is commercially prepared from commercially available Acetonitrile, Acrylonitrile and Carbon Tetrachloride using thionyl chloride in presence of Dimethyl Formamide as catalyst at 70-80 deg C. 3-phenoxybenzyl alcohol and tri ethyl butyl ammonium chloride are commercially prepared from commercially available Benzaldehdye, Bromine and Chlorine. Examples 1: The conventional process with solvent and with catalyst (not of invention) 3-phenoxybenzyl alcohol (800 kgs) was initially agitated in solvent n-hexane (1560 kgs.) and triethyl butyl ammonium chloride (100 kgs) as the catalyst was added to it, at 10-15 °C in a batch still. 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride(1000 kgs) was added to this solution under agitation and maintaining the temperature 10-15°C. . After completion of addition the temperature was slowly raised in 3 hrs to reflux and the mixture was kept under reflux for 4hrs. 1660 kgs of the product was obtained. [Yield=92.5%. by moles of acid chloride]. The reaction mass is then cooled to 35—40 C. and washed with water, soda ash solution and again with water. This is followed by hexane recovery. The residual mass was washed with water and dried to obtain technical grade permethrin. This was examined by GLC and showed 2 major peaks whose area added to 91.99 % of the total area under peaks (Fig 3) In this process, the water used was 21 kilolitres and the steam consumed was 6940 kgs per metric tonne of the product .The power consumed per metric tonne of the product was 600 KWH an the total energy cost per Kilogram of the product in INR was 10.79.The Total cost per kg of the product considering the costs involved in the use of the catalyst and recovery of the solvents was INR 38.07 . 14 Example 2: Conventional process without solvent and without catalyst at normal atmospheric pressure. (Not of invention) 800 kgs of 3-phenoxybenzyl alcohol was initially kept under agitation in a batch still to which was slowly added 800 kgs of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride at 25-30°C at normal atmospheric pressure. After completion of addition slowly the temperature was raised to in 4 hrs and maintained at 80°C for next 3-4 hrs resulting in product 656 kg. Yield = 82 %.by wt of MPBAL. It was found that the product of this process had an impurity formed to around 75% . The process of the Example 2 was repeated filing the headspace with nitrogen gas. The results were not encouraging. Hence this approach to improve the conventional process was not of any use. Example 3. The Vacuum Batch Process This is a batch process carried out in a batch still as described above 800 kgs of 3-phenoxybenzyl alcohol was initially kept under agitation in a batch still to which was slowly added 903 kgs of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride at 25-30°C under negative atmosphere of 30-100 mmHg abs. After completion of addition slowly the temperature was raised to 80°C in 4 hrs and maintained at 80°C for 3-4 hrs. This gave a product 1670 kgs [Yield=97% by moles of acid chloride] On analysis the chromatographic results showed the area of the two major peaks as 96% of the total area under the peaks (Fig 5.). In this process, the water used was 12 kilolitres and the steam consumed was 5000 kgs per metric tonne of the product .The power consumed per metric tonne of the product was 550 KWH an the total energy cost per Kilogram of the product in INR was 8.42. The Total cost per kg of the product was INR 31.42 . 15 Example 4: Inert Gas Sparging Continuous Process: This process described in this Example 4 was carried out in the continuous inert gas sparging process plant as described above, using nitrogen gas as inert gas. 3-phenoxybenzyl alcohol is fed co-currently with 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride from the top into the reactor column 3 bubble column with perforated plates having 1.3% free area. The specific value of the free area ensures efficiency of the process through which counter-currently nitrogen gas was sparged, at sufficient rate to expel the Hydrochloric acid gas off the reaction. The reaction was carried out under atmospheric pressure conditions. The reaction mass was maintained at 60-80°C throughout. The residence time of the reacting mass in the reaction column was 2 hrs. Yield=97%.by moles of MPBAL. The Steps comprise (i) feeding continuously 3-phenoxybenzyl alcohol co-currently with an equi molar amounts of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride from the top into a sectionalized bubble column with perforated plates having some free area; (ii) Sparging through the column counter-currently nitrogen gas at sufficient rate to expel the Hydrochloric acid generating during the said esterification reaction under atmospheric pressure condition at 60 - 80°C. (iii) washing the crude product coming out at the bottom of the column reactor in a mixer-settler charged with soda ash solution..(iv) washing the soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; and (vi) Continously scrubbing the continuously vented gas through a water scrubber containing 5% NAOH solution followed by scrubbing out alkali through plain water caustic scrubber. On analysis the GLC showed that the area % of two major peaks was 96% of the total area under peaks The GLC, graphs of the product of Example 4 is shown in Fig 5. The NMR spectra of the standard product obtained from Sigma Aldrich were compared with the NMR spectra of the product of example 4. 16 The results of the NMR spectrum (60 MHz ) analysis of the so obtained compounds were as follows: .delta..sub.TMS.spsb.4.sup.CCl : 1.10 (s) 3H; 1.19, 1.21 (each s ) 3H; 1.52 (d, J = 5.5Hz ) 1H; 2.16 (dd, J = 8Hz & 5.5 Hz ) 1H; 5.01 (s) 2H; 5.54 (d, J - 8Hz ) 1H; 6.8 - 7.5 (m) 9H In this process, the water used was 10 kilolitres and the steam consumed was 3952 kgs per metric tonne of the product .The power consumed per metric tonne of the product was 459 KWH and the total energy cost per Kilogram of the product in INR was 6.98. The Total cost per kg of the product was INR 24.63. Comparative details of the products obtained by the improved process, conventional process and the standard product. Analytical results: The analysis of the samples of examples 1,3,4 and standard samples were done at different periods of time during the course of this investigation and therefore the column materials and the temperature conditions were not identical. Hence the retention time for the compounds exhibit variations. The compositions of the products of Examples 1, 3 and 4 as seen from major peak areas in chromatograms given in figures 2,3, 4 and 5 are tabulated in Table I. The retention times of the cis and trans permethrin may exhibit variation depending upon the time of analysis and with changes in the column. 17 Table I: Major peak areas in products of Examples 1,3 & 4 and a standard sample Example 1 Fig 3 Standard Fig 2 Example 3 Fig 4 Example 4 Fig 5 Peak RT % area Peak RT % area Peak RT % area Peak RT % Area 13.95 0.96 14.13 0.74 18.82 1.23 17.98 2.51 17.39 0.78 28.29 2.28 18.34 0.83 18.33 1.53 29.42 71.46 27.46 44.19 26.22 67.68 27.48 51.40 29.93 20.53 27.68 50.61 26.44 27.66 27.69 44.60 The product obtained as technical permethrin show two major peaks in RT from 26 to 29. The percentage area of the first peak is 51 - 71 % and that of the second peak is between 20.5 - 44.6%. and the % of these two peaks taken together in each of these examples is permethrin content. It is as follows: Example 1 : 91 .99 %; Example 3 : 95.34% and Example 4: 96.00 while that of the standard sample is 94.80, with first peak at 44.2% and second at 50.6% of the peak areas. In all the above figures the relative retention time for the first and the second peak is approximately 0.98 - 0.99. 18 The Process Economics The Process Economics particularly energy consumption and operation costs were studied for the best processes of the present invention namely that of Example 3: the Vacuum Process and that of Example 4: Continuous Inert Gas Sparging Process, in comparison with that of Example 1: Conventional Process. The results of this study are summarized in Table I Table II: Process Economics for one metric tonne output Process of Example 1 Conventional Example 4 Vacuum Example 5 Nitrogen sparging Power (KwH) 600 550 459 Steam (kgs) 6940 5000 3952 Water (Kilolitres) 21 12 10 Total energy cost per kg (INR) 10.79 8.42 6.98 Total operation cost (INR) 38,07* 31.42 24.63 * this includes costs of solvent and catalysts and not the cost of reactants. Thus it is seen that there is around 22.0 % energy savings for the vacuum process and around 35% energy savings in the continuous nitrogen sparging process. It is further observed that the conventional process utilizes 232 kgs of solvent per metric tonne of the product. This is totally saved in the both the embodiments - vacuum and nitrogen gas sparging processes - of the present invention, in addition to the energy savings 19 It was further observed that the time required for the commercial manufacture of 1000 kgs of product was reduced by 20% for the vacuum process and by around 46% for the nitrogen gas sparging processes Overall the total cost was reduced by around 1.33% per kg for the new processes as compared to the old process. Thus the improvement in the process besides being non-obvious, is having inventive step in having economic significance in the production of technical grade permethrin. Distinguishing Features Though process of the present invention and the conventional process both relate to the synthesis of permethrin by reacting 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride with 3-phenoxybenzyl alcohol; the methadology of bringing about the reaction on large scale is the process of manufacture of permethrin. The process of the present invention basically differs from the conventional process in respect of following steps: i. In the conventional process the reaction is carried out in the presence of solvent n-hexane and catalyst - triethyl butyl ammonium chloride; in the process of present invention neither the solvent nor the catalyst are required. ii. In the conventional process the reaction is carried out at not more than 70 C due to the reflux temperature of the solvent whereas the temperature of the reaction in the process of present invention does not have this limitation.. iii. In the conventional process after the reaction, the reaction mass needs washing out HC1, catalyst and recovery of the solvent; in the process of present invention HC1 does not remain in the product, catalyst and solvent do not exist in the product and therefore, washing is reduced and solvent recovery is not required. 20 iv. The by product Hydrochloric acid is recovered in these improved processes which is not done in the conventional process. Advantages of the Present Invention: 1. No solvent is used, therefore solvent hazards are less., solvent losses are less. Solvent recovery plant not necessary. 2. No catalyst is used , hence the problems faced with catalyst removal after the reaction are not faced. 3. Yield has increased from 92.5% to 97% and purity had increased from 92.00 % to 96%. 4. Impurities in the product are reduced. 5. Time and energy is saved. 6. Batch to batch variation is reduced in continous process. 7. The product can be manufactured with a continous higher production capacity 21 We Claim 1. An improved process for the manufacture of permethrin comprising carrying out a reaction of reactants 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, without use of any solvent or catalyst, at 60 -80°C, with means for continuously expelling hydrochloric acid generating during said reaction, from the reaction mass, into a HC1 gas scrubber; and washing the crude product to obtain permethrin. 2. An improved process for the manufacture of permethrin as claimed in claim 1, wherein said means for continuously expelling hydrochloric acid generating during the said reaction, is provision of a reactor for carrying out the reaction under vacuum. 3. An improved process for the manufacture of permethrin as claimed in claim 1, wherein the means for continuously expelling hydrochloric acid generating during the said reaction, is a provision of a reactor for continuously sparging dry inert gas in to the reaction mass, at the bottom of said reactor and venting it out from the reactor top. 4. An improved process for the manufacture of permethrin as claimed in claim 3, wherein said dry inert gas is selected from dry deoxygenated air, nitrogen, helium, carbon dioxide, argon and mixtures thereof. 5. An improved process for the manufacture of permethrin as claimed in claim 3, wherein the reactor is a stirred tank batch reactor with facilities to continuously sparge 22 dry inert gas at the bottom of the reaction charged in the reactor and for venting out the said gas with the HC1 generating during said reaction, from the top of the reactor. 6. An improved process for the manufacture of permethrin as claimed in claim 3, wherein said reactor is a continuous reactor comprising sectionalized column with series of perforated bubble cap plates, each having some free area; and the reactor column having facilities for (a) continuous feeding said reactants at the top; (b) continuous sparging dry inert gas from the bottom; (c) continuous venting out from the top of the reactor column, the continuously generating HC1 with said gas; and (d) continuously discharging the crude product from the bottom; 7. An improved process for the manufacture of permethrin as claimed in claim 2, wherein said reactor is a stirred tank batch reactor with facilities for carrying out the reaction under vacuum. 8. An improved process for the manufacture of permethrin as claimed in claim 2, wherein said reactor is a continuous reactor comprising sectionalized column with series of perforated bubble cap plates, each having 1 - 5 % free area; and the reactor column having facilities for (a) continuous feeding reactants at the top; (b) keeping the reactor under reduced pressure (c) continuous vacuum-sucking out the continuously generating HC1, from the top of the reactor column; and (d) continuously discharging the crude product of the reaction, from the bottom of said reactor. 9. An improved process for the manufacture of permethrin as claimed in claim 1 3, and 6, comprising: (i) feeding continuously 3-phenoxybenzyl alcohol co-currently with an equi molar amounts of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride from the top into a sectionalized bubble column with 23 perforated plates having some free area; (ii) Sparging through the column counter-currently nitrogen gas at sufficient rate to expel the Hydrochloric acid generating during the said esterification reaction under atmospheric pressure condition at 60 -80°C. (iii) washing the crude product coming out at the bottom of the column reactor in a mixer-settler charged with soda ash solution..(iv) washing the soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; and (vi) Continously scrubbing the continuously vented gas through a water scrubber containing 5% NAOH solution followed by scrubbing out alkali through plain water caustic scrubber. 10. An improved process for the manufacture of permethrin as claimed in claim 7, wherein (i) 3-phenoxybenzyl alcohol and 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride are charged in a stern tank batch rector almost in equi molar amount at about 20°C and then the temperature raised to about 80°C; (ii) Applying vacuum at suffiecent rate to expel Hydrochloric acid generating during the said reaction under negative pressure conditions (iii) washing the crude product after the reaction batch is over in a mixer-fettler charged with Soda ash solution; (iv) washing the Soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; and (vi) scrubbing the vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out alkali through plain water caustic scrubber. 11. An improved process for the manufacture of Permethrin as claimed in claim 1,2 and 7, wherein (i) charging 3-phenoxybenzyl alcohol and 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride almost in equi-molar amounts in a continous reactor at about 20°C and then raising the temperature to about 80°C; (ii) applying vaccum to the reactor for expelling the Hydrochloric acid generating during the said reaction under reduced pressure condition at 60 - 80° C. (iii) washing the crude product after the reaction batch is over in a mixer-settler charged with Soda ash 24 solution; (iv) washing the Soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; (vi) scrubbing the vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out the alkali through plain water caustic scrubber. 12. An improved process for the manufacture of permethrin substantially as herein described in the text, Example numbers 3 and 4 and accompanying drawings. Dated this 11th day of October 2006 For UNITED PHOSPHORUS LIMITED M.B. TRIVEDI (COMPANY SECRETARY) UNIPHOS HOUSE, 11TH ROAD, C. D. MARG, KHAR (WEST), MUMBAI - 400 052. 25 ABSTRACT Permethrin is a photostable synthetic pyrethroid manufactured for insecticidal use. This invention discloses an improved process for the manufacture of permethrin without use of any solvent or catalyst, comprising reaction of 2,2-dimethyl-3-(2',2'-dichlorovinyi)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, at 60 - 80°C, with means for continuously expelling hydrochloric acid generating in the said reaction, from the reaction mass, into a HC1 gas scrubber. 26

Full Text

FORM 2
THE PATENTS ACT 1970
(39 of 1970)
And
THE PATENT RULES, 2003
(See Section 10, rule 13)
An Improved Process for Manufacture of Permethrin
UNITED PHOSPHORUS LIMITED, a company incorporated under the Companies Act, 1956 having its registered office at 3-11, GIDC, Vapi-396 195, State of Gujarat, India and its corporate office at Uniphos House, 11th Road, C. D. Marg, Khar (West), Mumbai - 400 052, State of Maharashtra, India, an Indian Company.
The following specification particularly describes the invention and the manner in which it is to be performed:-
1

This invention relates to a process for the manufacture of permethrin on large scale. This invention particularly relates to an improved process for manufacture of permethrin on large scale without use of any solvent or catalyst. This invention more particularly relates to a continuous process for the manufacture of permethrin on large scale without use of any solvent or catalyst.
Background and Prior Art
Permethrin is a synthetic insecticidal pyrethroid related chemical viz.
[3-Phenoxyphenyl)methyl-cis,trans-(+-)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate]. Permethrin is a photostable synthetic pyrethroid. It possesses a high level of activity against Leptidoptera and is also effective against Hemiptera, Diptera, and Coleoptera. Approximately 600 tonnes per year of permethrin is at present used worldwide, mostly for agricultural purposes. It has a potential application in the protection of stored grain and it has been used in aerial application for forest protection and vector control, for the control of noxious insects in the household and on cattle, for the control of body lice, and in mosquito nets. Permethrin is formulated as emulsifiable concentrate, ultra-low- volume concentrate, wettable powder, and dustable powder. After considering the various products in the market, it was generalized that the cisrtrans isomer ratio of technical products is nearabout 2:3 and the optical ratio of 1R:1S is 1:1 (racemic), Though there is considerable variation in these ratios from product to product. Thus, permethrin contains the [lR,trans], [lR,cis], [lS,trans], and [lS,cis] isomers in the approximate ratio of 3:2:3:2. The [lR,cis] isomer is the most insecticidally active among the isomers, followed by the [lR,trans] isomer. The ratio of cis:trans is around 2:3 and 1R:1S is 1:1 (racemic).
The Technical grade permethrin is a brown or yellowish brown liquid, which may crystallize partly at room temperature. The melting point is approximately 35°C and the boiling point is 220°C at 0.05 mmHg. The specific gravity is 1.214 at 25°C and the vapour
2

pressure is 1.3 mPa at 20°C. Permethrin is almost insoluble in water (0.2 mg/litre at 30°C), but is soluble in organic solvents such as acetone, hexane, and xylene. It is stable to light and heat, but unstable in alkaline media.
Permethrin was synthesized as one of the new photostable pyrethroids by Elliott et al. in 1973 [US Patent 4024163 (1977)]. It is prepared by the esterification of the dichloro analogue of chrysanthemic acid, i.e. (1R, cis; 1R, trans; IS, cis; IS, trans )-3-(2,2-dichlorovinyl)-2,2-dimethyl-cyclopropanecarboxyclic acid, with 3-phenoxybenzyl alcohol. The reaction is as follows:

CI H H H O
\ I I I II
c z=c —c —c — c —ci
/ \ /
CI c
/ H,C CH,

HOCK,

CI H H\ 1 1 0II f
/ \/ci cOl H,C CHa Lr

+ HCI
Fumio Mori describes in US 4,113, 968 (1988) in Example 8 therein, the process, which is reproduced below.
"1.80 Parts of ethyl 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylate prepared in the same manner as in Example 1 was agitated at 40.degree. to 50.degree. C. for 3 hours in the presence of 8.65 parts of a 10% solution of potassium hydroxide and methanol to effect hydrolysis of the ester and obtain 1.43 parts of 2,2-dimethyl-3-(2',2,-dichlorovinyl)-cyclopropane-carboxylic acid, the data of the melting point and NMR spectrum of which were in agreement with the data described in Example 4.
1.43 Parts of the so obtained carboxylic acid was agitated at 80.degree. C. for 30 minutes together with 0.98 part of thionyl chloride in benzene as a solvent to obtain 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride. The so obtained compound was agitated at room temperature for 1 hour together
3

with 1.37 parts of 3-phenoxybenzyl alcohol in the presence of pyridine in benzene
as a solvent, to obtain 2.63 parts of 3-phenoxybenzyl-2',2'-dimethyl-3,-(2",2"-
dichlorovinyl)-cyclopropane-carbo xylate (n.sub.D.sup.20 = 1.5615 ).
The results of the NMR spectrum (60 MHz) analysis of the so obtained compound
were as follows:
.delta..sub.TMS.spsb.4.sup.CCl : 1.10 (s) 3H; 1.19, 1.21 (each s ) 3H; 1.52 (d, J =
5.5Hz ) 1H; 2.16 (dd, J = 8Hz & 5.5 Hz ) 1H; 5.01 (s) 2H; 5.54 (d, J = 8Hz ) 1H;
6.8 - 7.5 (m) 9H
Conventional Batch Process
A large-scale version of the Fumio Mori process, which is at present the conventional process for the manufactuire of permethrin, is as follows:
2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride used is prepared by chlorinating commercially available 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid. 2,2-dimethyl-3 -(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride is commercially prepared from commercially available Acetonitrile, Acrylonitrile and Carbon Tetrachloride using thionyl chloride in presence of Dimethyl Formamide as catalyst at 70-80 deg C.
3-phenoxybenzyl alcohol and tri ethyl butyl ammonium chloride are commercially prepared from commercially available Benzaldehdye, Bromine and Chlorine.
In a stirred tank Stainless steel reactor the - 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride (acid chloride ) [1 - 1.1 mole ] and the alcohol -meta phenoxybenzyl alcohol(MPBAL), [ 1 mole] are reacted in presence of hexane[ 0.86 to 0.88] by weight of the reactants and tri ethyl butyl ammonium chloride as catalyst 0.005% to 0.007 % w/w of reactants, initially at about 15 °C by slow addition of one of the reactants to the other reactant taken in the tank.
After addition of the reactants (acid chloride and MPBAL ), the reaction temperature is then raised to about 70 °C under hexane reflux condition until the unreacted alcohol is 4

0.2 % w/w. The reaction mass is then cooled to 35 - 40 C. and washed with water, soda ash solution and again with water. This is followed by hexane recovery .
This process gives permethrin of 92 - 94 % by weight purity and the yield on the MPBAL basis is about 92 % by wt.
It must be clear that the purity of the technical grade permethrin is not based on the extent of the presence of chemically pure "3-Phenoxyphenyl)methyl-cis,trans-(+-)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylate". It includes materials related to this compound as said in the introduction.
Drawbacks of the conventional batch process:
The process using solvent is hazardous, there are always solvent losses as the recovery of the solvent is not complete. The reaction is not efficient, the reaction period is long and the unreacted technicals, the catalyst and the other products formed have to be removed by elaborate washings. The yield of the product is low, thus losing valuable raw material.
Object
The principal object of the present invention is to increase the yield of the reaction between the acyl chloride - 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride, and the alcohol - 3-phenoxybenzyl alcohol for the production of permethrin.
Another object of the present invention is to improve the process of manufacture of permethrin by eliminating use of solvent and catalyst.
Yet another object of the present invention is to reduce time of the reaction, reduce energy losses.
Still another object of the present invention is so as to reduce the space of operation, time of reaction and to avoid variation in the quality and yield of product from batch to batch.
5

Summary of the Invention :
The present invention discloses an improved process for the manufacture of permethrin comprising carrying out a reaction of reactants 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, without use of any solvent or catalyst, at 60 - 80°C, with means for continuously expelling hydrochloric acid generating during said reaction, from the reaction mass, into a HC1 gas scrubber; and washing the crude product to obtain permethrin.
In one embodiment of the invention the means for continuously expelling hydrochloric acid generating during the said reaction, is provision of a reactor for carrying out the reaction under vacuum.
In another embodiment of the invention the means for continuously expelling hydrochloric acid generating during the said reaction, is a provision of a reactor for continuously sparging dry inert gas in to the reaction mass, at the bottom of said reactor and venting it out from the reactor top.
In the above process the inert gas is selected from dry deoxygenated air, nitrogen, helium, carbon dioxide, argon and mixtures thereof. Nitrogen gas is preferred.
Drawings
A brief description of the drawings is given below.
Fig 1. -Flow chart of Inert gas sparging Continous process.
Fig. 2 - GLC of a Permthrin sample obtained from Sigma Aldrich.
Fig. 3 - GLC of Permethrin Technical obtained from example 1.
Fig 4 - GLC of a product of Permthrin obtained from example 3.
Fig 5- GLC of a sample of Permthrin obtained by example 4.
6

Description of the processes of the present Invention
The conventional process of preparation of permethrin is based on the reaction as shown in Fig. 1. It is clear that in this reaction one mole of each reactant react together to give 1 mole of permethrin and 1 mole of Hydrochloric acid. In the conventional process this reaction is carried out using a catalyst in a solvent like hexane and at atmospheric pressure at about the reflux temperature of the solvent i.e. about 70 °C as described above as a conventional prior art process.
The two embodiments of the present invention are the vacuum process and the inert gas sparging process. Each of these processes can be operated in many modes but two major modes are: batch process and continuous process. Semi-continuous mode is also possible. Of these two processes mainly, vacuum batch process and continuous inert gas sparging process will be described here.
The Vacuum Batch Process
This is a batch process. This is carried out in a batch still i.e. a stirred tank reactor made of any material of construction that is safe for use with hydrochloric acid at up to 100 °C such as glass lined, Teflon lined MS, stainless steel (SS316) can be used. The reactor has provision for heating/ cooling and applying vacuum and arrangements to connect it to a conventional hydrochloric acid gas scrubber. The reactor is a stirred tank batch reactor with facilities for carrying out the reaction under vacuum.
The reactor is charged with 2,2-dimethyl-3-(2',2,-dichlorovinyl)-cyclopropane-carboxylic acid chloride 1000 kgs and then the reactor is cooled to about 15 C and vacuum applied to get about 600 mm Hg absolute pressure. 3-phenoxybenzyl alcohol is then added slowly from another container holding 800 kgs 3-phenoxybenzyl alcohol in at such a rate so as to maintain the reaction temperature about 15-20 °C. After the entire amount of the said alcohol is added, the reaction mass is maintained at that temperature for some more time and then heated to 60 °C until the said alcohol level goes down to less than 1%
7

by wt and then the reaction temperature is further raised to about 80 C.until the acidity level of the reaction mass goes below 0.15 % when expressed as hydrochloric acid. The reaction mass is then quenched with water and it is given water wash, soda ash wash and another water wash to obtain the product -Permethrin..
The process is as follows,
(i) 3-phenoxybenzyl alcohol and 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride are charged in a stern tank batch rector almost in equi molar amount at about 20°C and then the temperature raised to about 80°C; (ii) Applying vacuum at suffiecent rate to expel Hydrochloric acid generating during the said reaction under negative pressure conditions (iii) washing the crude product after the reaction batch is over in a mixer-fettler charged with Soda ash solution; (iv) washing the Soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; and (vi) scrubbing the vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out alkali through plain water caustic scrubber.
Continous Vacuum Process :
The reactor is a continuous reactor comprising sectionalized column with series of perforated bubble cap plates, each having 1 - 5 % free area; and the reactor column having facilities for (a) continuous feeding reactants at the top; (b) keeping the reactor under reduced pressure (c) continuous vacuum-sucking out the continuously generating HC1, from the top of the reactor column; and (d) continuously discharging the crude product of the reaction, from the bottom of said reactor.
The steps for the process comprise
(i) charging 3-phenoxybenzyl alcohol and 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride almost in equi-molar amounts in a continous reactor at about 20°C and then raising the temperature to about 80°C; (ii) applying vaccum to the reactor for expelling the Hydrochloric acid generating during the said reaction under reduced pressure condition at 60 - 80° C. (iii) washing the crude product after the reaction batch is over in a mixer-settler charged with Soda ash
8

solution; (iv) washing the Soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; (vi) scrubbing the vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out the alkali through plain water caustic scrubber.
Inert Gas Sparging Batch Process:
The above batch process is repeated sparging nitrogen gas through the reaction mass and allowing it to vent out through the top of the still into the HCl gas scrubbing plant, instead of applying vacuum. This system was further developed into a more efficient continuous inert gas sparging process as described below. The reactor is similar to that of vacuum batch process but instead of vacuum arrangement there is provision for sparging inert gas. such as nitrogen in the reactor at the bottom and venting it out from the top. In all respects it is like Inert Gas Sparging Continuous Process except that the reactor as described above is different from the reactor of the continuous process, and other sections of the plant are suitable for batch processing.
The reactor is a stirred tank batch reactor with facilities to continuously sparge dry inert gas at the bottom of the reaction charged in the reactor and for venting out the said gas with the HCl generating during said reaction, from the top of the reactor.
Inert Gas Sparging Continuous Process:
The flow sheet of this Inert Gas Sparging Continuous Process is shown in Fig 1. It is divided into 4 sections.
Section A is a continuous reactor section. Section B is a continuous HCl gas scrubbing section. Section C is continuous crude permethrin washing section and Section D is drying & bagging section..
9

This is a Inert Gas Sparging continuous process. This is carried out in a bubble cap column reactor made of any material of construction that is safe for use with dry hydrochloric acid at up to 100 C such as stainless steel (SS316) can be used. The reactor has provision for heating / cooling externally and sparging inert gas such as nitrogen from the bottom and arrangements to scrub out hydrochloric acid, from the top.
In this embodiment of the present invention, 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, are kept in two holders and slowly and simultaneously equimolar quantities of the reactants are added from the top of the sectionalized column in to the reactor column fitted with bubble cap plates provided for holding liquids on the surface and allowing passage of gas through them. The sectionalized Bubble column is composed of different compartments or sections which is an inherent feature of the column. The Free area in the perforated plates is also an essential feature of the operation for the efficient functioning of the column. It was found that the free area of the perforated plates is related the efficiency of the process.
The nitrogen gas is sparged from the bottom of the column and taken out from the top vent connected to hydrochloric acid gas scrubber. The reactor column is provided with facility for external heating and the temperature of the column is raised to 50 — 100 °C, preferably 65 - 80 °C. The nitrogen gas is fed at the rate of about 0.76 kg per kg of the alcohol fed. The product coming out continuously from the bottom is taken in batches for washing and product washed free of acid is [Technical] Permethrin.
The continuous inert gas process and its plant is now described below with the help of flow sheet shown in Fig 1.
The reactor is a continuous reactor comprising sectionalized column with series of perforated bubble cap plates, each having some free area; and the reactor column having facilities for (a) continuous feeding said reactants at the top; (b) continuous sparging dry inert gas from the bottom; (c) continuous venting out from the top of the reactor column,
10

the continuously generating HC1 with said gas; and (d) continuously discharging the crude product from the bottom.
For illustrating the invention clearly, a plant with particular parameters has been described below. It is one example and should not restrict the scope of the invention. The plants can be designed with different parameters.
The inert gas sparging continuous process plant comprises a column reactor section A, HC1 gas scrubbing section B, crude Permethrin washing section C and drying & bagging section D. This section A of the plant describes continuous process up to reaction to give crude permethrin. The section B of the plant describes the continous scrubbing of the continuously vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out alkali through plain water caustic scrubber.
Further steps of washing of the crude and drying of the washed product are not continuous processes synchronized with the reaction. However, these process steps can be made continuous also. The reactor column 3 comprises (a) Column having heating and cooling arrangements to maintain the reactants at 60 - 80 deg .(b) Number of bubble cap plates 31-40 and (c) A Sparger 41 for sparging inert gas .
The stock of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride is stored in holder 1 and the stock of 3-phenoxybenzyl alcohol, is stored in holder 2. These two reactants are simultaneously pumped to the top of the column reactor 3. The acid chloride from holder 1 and the alcohol from holder 2 are fed to the reactor 3 at such rates so as to ensure that the two reactants are in equimolar ratios when they come in contact at the top plate 31 of the bubble cap plates 31-40 of the sectionalized column reactor 3. These bubble cap plates are provided inside the column reactor 3, for holding liquids to a particular level on the surface of these plates and flowing down to the next plate below through the overflow tubes fitted to the plates while at the same time they allow the passage of gas coming from the liquid layer on the bottom plate to the next plate above it.
11

Nitrogen gas from the cylinder 4 is passed into the reactor 3 through the entry point 5 at the bottom of the reactor 3 through the sparger 41 and moves up through all the bubble cap plates 31-40 and the liquid resting on them. The design of the reactor considers feed rate and gas flow rate and the number of plates, and many other factors, so that the product discharging from the reactor is having the amount of unreacted acid chloride less than the minimum set, so that it can be washed out. During this period the Nitrogen gas carries with it the HC1 gas generating on each plate and where the two reactants react, and leaves the reactor 3 from the vent 6 at the top and flows to hydrochloric acid gas scrubbing section B.
The bubble cap plates are so designed so as to have free area in a range of 1-5 % , preferably 1-1.5 % which is essential for the efficient performance of the reactor 3.
The gas scrubbing section B comprises a water scrubber 8 and a caustic scrubber 9.
The water is charged to the scrubber 8. from tank 20 through the tail screw 81. NaOH solution (5%) is fed to the caustic scrubber 9 from tank 21. Effluents flow down to the tank 19 and the gas leaves from the gas exhaust 22. Hydrochloric Acid solution is collected as a by- product from the scrubber 8 in the tank 23
The product coming out at the bottom of the column reactor 3 from outlet point 7 is crude Permethrin which is taken to the crude tank 11 . This crude permethrin from tank 11 is then taken to the washing section C.
The washing section C comprises 2 mixer settlers. The crude permethrin from tank 11 is taken to the first mixer-settler 12 where the organic phase is mixed with soda ash solution (2 % by wt.)kept in a holder 13 . The two phases may be separated by centrifuges in continuous way. The organic phase is taken to the second mixer-settler 14 where it is mixed with water from tank 20. The organic phase - the permethrin is then taken from mixer settler 14 to the bagging section D.. The aqueous washings from both mixer settlers are taken to the effluent treatment plant from tank 19.
12

The bagging section D comprises a holder tank 15 and drying vacuum tank 16 for
drying at 90 C under vacuum of 759mm Hg and bagging units 17 and 18. The washed permethrin from section C is then taken to the bagging section wherein it is kept in holder 15, dried under vacuum in tank 16 and then packed in bags in bagging units 17 and 18.
The continous process can be used for various other industrially manufactured pyrethroid esters.
Examples
The invention will now be illustrated by way of examples. Examples are by way of illustration only and in no way restrict the scope of the invention. These examples describe the conventional process and a process of the each embodiment of the present invention namely the vacuum batch process and the inert gas sparging process.
This investigation involved experimenting in building large-scale plants and running the reaction with different conditions and hence was spread over a long period of time. The raw materials used for reactions were of technical grade and the product obtained was technical grade permethrin. The two reactants required were also prepared here. As described above.
The product permethrin obtained in these examples were analysed by gas - liquid chromatography (GLC). The analysis was done on a Shimadzu 14-b gc instrument wherein a capillary db-5 column was used. The sample was prepared by taking 0.2 gm sample in 10ml measuring container and diluting with methanol.
The raw materials used in the process for the preparation of permethrin are manufactured as follows,
2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride used is prepared by chlorinating commercially available 2,2-dimethyl-3-(2',2'-dichlorovinyl)-
13

cyclopropane-carboxylic acid. 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride is commercially prepared from commercially available Acetonitrile, Acrylonitrile and Carbon Tetrachloride using thionyl chloride in presence of Dimethyl Formamide as catalyst at 70-80 deg C.
3-phenoxybenzyl alcohol and tri ethyl butyl ammonium chloride are commercially prepared from commercially available Benzaldehdye, Bromine and Chlorine.
Examples 1: The conventional process with solvent and with catalyst (not of invention)
3-phenoxybenzyl alcohol (800 kgs) was initially agitated in solvent n-hexane (1560 kgs.) and triethyl butyl ammonium chloride (100 kgs) as the catalyst was added to it, at 10-15 °C in a batch still. 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride(1000 kgs) was added to this solution under agitation and maintaining the temperature 10-15°C. . After completion of addition the temperature was slowly raised in 3 hrs to reflux and the mixture was kept under reflux for 4hrs. 1660 kgs of the product was obtained. [Yield=92.5%. by moles of acid chloride]. The reaction mass is then cooled to 35—40 C. and washed with water, soda ash solution and again with water. This is followed by hexane recovery. The residual mass was washed with water and dried to obtain technical grade permethrin.
This was examined by GLC and showed 2 major peaks whose area added to 91.99 % of the total area under peaks (Fig 3)
In this process, the water used was 21 kilolitres and the steam consumed was 6940 kgs per metric tonne of the product .The power consumed per metric tonne of the product was 600 KWH an the total energy cost per Kilogram of the product in INR was 10.79.The Total cost per kg of the product considering the costs involved in the use of the catalyst and recovery of the solvents was INR 38.07 .
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Example 2: Conventional process without solvent and without catalyst at normal atmospheric pressure. (Not of invention)
800 kgs of 3-phenoxybenzyl alcohol was initially kept under agitation in a batch still to which was slowly added 800 kgs of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride at 25-30°C at normal atmospheric pressure. After completion of addition slowly the temperature was raised to in 4 hrs and maintained at 80°C for next 3-4 hrs resulting in product 656 kg. Yield = 82 %.by wt of MPBAL. It was found that the product of this process had an impurity formed to around 75% .
The process of the Example 2 was repeated filing the headspace with nitrogen gas. The results were not encouraging. Hence this approach to improve the conventional process was not of any use.
Example 3. The Vacuum Batch Process
This is a batch process carried out in a batch still as described above 800 kgs of 3-phenoxybenzyl alcohol was initially kept under agitation in a batch still to which was slowly added 903 kgs of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride at 25-30°C under negative atmosphere of 30-100 mmHg abs. After completion of addition slowly the temperature was raised to 80°C in 4 hrs and maintained at 80°C for 3-4 hrs. This gave a product 1670 kgs [Yield=97% by moles of acid chloride]
On analysis the chromatographic results showed the area of the two major peaks as 96% of the total area under the peaks (Fig 5.).
In this process, the water used was 12 kilolitres and the steam consumed was 5000 kgs per metric tonne of the product .The power consumed per metric tonne of the product was 550 KWH an the total energy cost per Kilogram of the product in INR was 8.42. The Total cost per kg of the product was INR 31.42 .
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Example 4: Inert Gas Sparging Continuous Process:
This process described in this Example 4 was carried out in the continuous inert gas sparging process plant as described above, using nitrogen gas as inert gas. 3-phenoxybenzyl alcohol is fed co-currently with 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride from the top into the reactor column 3 bubble column with perforated plates having 1.3% free area. The specific value of the free area ensures efficiency of the process through which counter-currently nitrogen gas was sparged, at sufficient rate to expel the Hydrochloric acid gas off the reaction. The reaction was carried out under atmospheric pressure conditions. The reaction mass was maintained at 60-80°C throughout. The residence time of the reacting mass in the reaction column was 2 hrs. Yield=97%.by moles of MPBAL.
The Steps comprise
(i) feeding continuously 3-phenoxybenzyl alcohol co-currently with an equi molar amounts of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride from the top into a sectionalized bubble column with perforated plates having some free area; (ii) Sparging through the column counter-currently nitrogen gas at sufficient rate to expel the Hydrochloric acid generating during the said esterification reaction under atmospheric pressure condition at 60 - 80°C. (iii) washing the crude product coming out at the bottom of the column reactor in a mixer-settler charged with soda ash solution..(iv) washing the soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; and (vi) Continously scrubbing the continuously vented gas through a water scrubber containing 5% NAOH solution followed by scrubbing out alkali through plain water caustic scrubber.
On analysis the GLC showed that the area % of two major peaks was 96% of the total area under peaks The GLC, graphs of the product of Example 4 is shown in Fig 5.
The NMR spectra of the standard product obtained from Sigma Aldrich were compared with the NMR spectra of the product of example 4.
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The results of the NMR spectrum (60 MHz ) analysis of the so obtained compounds were as follows:
.delta..sub.TMS.spsb.4.sup.CCl : 1.10 (s) 3H; 1.19, 1.21 (each s ) 3H; 1.52 (d, J = 5.5Hz ) 1H; 2.16 (dd, J = 8Hz & 5.5 Hz ) 1H; 5.01 (s) 2H; 5.54 (d, J - 8Hz ) 1H; 6.8 - 7.5 (m) 9H
In this process, the water used was 10 kilolitres and the steam consumed was 3952 kgs per metric tonne of the product .The power consumed per metric tonne of the product was 459 KWH and the total energy cost per Kilogram of the product in INR was 6.98. The Total cost per kg of the product was INR 24.63.
Comparative details of the products obtained by the improved process, conventional process and the standard product.
Analytical results:
The analysis of the samples of examples 1,3,4 and standard samples were done at different periods of time during the course of this investigation and therefore the column materials and the temperature conditions were not identical. Hence the retention time for the compounds exhibit variations.
The compositions of the products of Examples 1, 3 and 4 as seen from major peak areas in chromatograms given in figures 2,3, 4 and 5 are tabulated in Table I.
The retention times of the cis and trans permethrin may exhibit variation depending upon the time of analysis and with changes in the column.
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Table I: Major peak areas in products of Examples 1,3 & 4 and a standard sample

Example 1 Fig 3 Standard Fig 2 Example 3 Fig 4 Example 4 Fig 5
Peak RT % area Peak RT % area Peak RT % area Peak RT % Area
13.95 0.96
14.13 0.74
18.82 1.23 17.98 2.51 17.39 0.78
28.29 2.28 18.34 0.83 18.33 1.53
29.42 71.46 27.46 44.19 26.22 67.68 27.48 51.40
29.93 20.53 27.68 50.61 26.44 27.66 27.69 44.60
The product obtained as technical permethrin show two major peaks in RT from 26 to 29. The percentage area of the first peak is 51 - 71 % and that of the second peak is between 20.5 - 44.6%. and the % of these two peaks taken together in each of these examples is permethrin content. It is as follows: Example 1 : 91 .99 %; Example 3 : 95.34% and Example 4: 96.00 while that of the standard sample is 94.80, with first peak at 44.2% and second at 50.6% of the peak areas.
In all the above figures the relative retention time for the first and the second peak is approximately 0.98 - 0.99.
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The Process Economics
The Process Economics particularly energy consumption and operation costs were studied for the best processes of the present invention namely that of Example 3: the Vacuum Process and that of Example 4: Continuous Inert Gas Sparging Process, in comparison with that of Example 1: Conventional Process. The results of this study are summarized in Table I
Table II: Process Economics for one metric tonne output

Process of Example 1 Conventional Example 4 Vacuum Example 5 Nitrogen sparging
Power (KwH) 600 550 459
Steam (kgs) 6940 5000 3952
Water (Kilolitres) 21 12 10
Total energy cost per kg (INR) 10.79 8.42 6.98
Total operation cost (INR) 38,07* 31.42 24.63
* this includes costs of solvent and catalysts and not the cost of reactants.
Thus it is seen that there is around 22.0 % energy savings for the vacuum process and around 35% energy savings in the continuous nitrogen sparging process.
It is further observed that the conventional process utilizes 232 kgs of solvent per metric tonne of the product. This is totally saved in the both the embodiments - vacuum and nitrogen gas sparging processes - of the present invention, in addition to the energy savings

19
It was further observed that the time required for the commercial manufacture of 1000 kgs of product was reduced by 20% for the vacuum process and by around 46% for the nitrogen gas sparging processes
Overall the total cost was reduced by around 1.33% per kg for the new processes as compared to the old process. Thus the improvement in the process besides being non-obvious, is having inventive step in having economic significance in the production of technical grade permethrin.
Distinguishing Features
Though process of the present invention and the conventional process both relate to the synthesis of permethrin by reacting 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride with 3-phenoxybenzyl alcohol; the methadology of bringing about the reaction on large scale is the process of manufacture of permethrin. The process of the present invention basically differs from the conventional process in respect of following steps:
i. In the conventional process the reaction is carried out in the presence of
solvent n-hexane and catalyst - triethyl butyl ammonium chloride; in the process of present invention neither the solvent nor the catalyst are required.
ii. In the conventional process the reaction is carried out at not more than 70 C due to the reflux temperature of the solvent whereas the temperature of the reaction in the process of present invention does not have this limitation..
iii. In the conventional process after the reaction, the reaction mass needs washing out HC1, catalyst and recovery of the solvent; in the process of present invention HC1 does not remain in the product, catalyst and solvent do not exist in the product and therefore, washing is reduced and solvent recovery is not required.
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iv. The by product Hydrochloric acid is recovered in these improved processes which is not done in the conventional process.
Advantages of the Present Invention:
1. No solvent is used, therefore solvent hazards are less., solvent losses are less. Solvent recovery plant not necessary.
2. No catalyst is used , hence the problems faced with catalyst removal after the reaction are not faced.
3. Yield has increased from 92.5% to 97% and purity had increased from 92.00 % to 96%.
4. Impurities in the product are reduced.
5. Time and energy is saved.
6. Batch to batch variation is reduced in continous process.
7. The product can be manufactured with a continous higher production capacity
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We Claim
1. An improved process for the manufacture of permethrin comprising carrying out a reaction of reactants 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, without use of any solvent or catalyst, at 60 -80°C, with means for continuously expelling hydrochloric acid generating during said reaction, from the reaction mass, into a HC1 gas scrubber; and washing the crude product to obtain permethrin.
2. An improved process for the manufacture of permethrin as claimed in claim 1, wherein said means for continuously expelling hydrochloric acid generating during the said reaction, is provision of a reactor for carrying out the reaction under vacuum.
3. An improved process for the manufacture of permethrin as claimed in claim 1, wherein the means for continuously expelling hydrochloric acid generating during the said reaction, is a provision of a reactor for continuously sparging dry inert gas in to the reaction mass, at the bottom of said reactor and venting it out from the reactor top.
4. An improved process for the manufacture of permethrin as claimed in claim 3, wherein said dry inert gas is selected from dry deoxygenated air, nitrogen, helium, carbon dioxide, argon and mixtures thereof.
5. An improved process for the manufacture of permethrin as claimed in claim 3, wherein the reactor is a stirred tank batch reactor with facilities to continuously sparge
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dry inert gas at the bottom of the reaction charged in the reactor and for venting out the said gas with the HC1 generating during said reaction, from the top of the reactor.
6. An improved process for the manufacture of permethrin as claimed in claim 3, wherein said reactor is a continuous reactor comprising sectionalized column with series of perforated bubble cap plates, each having some free area; and the reactor column having facilities for (a) continuous feeding said reactants at the top; (b) continuous sparging dry inert gas from the bottom; (c) continuous venting out from the top of the reactor column, the continuously generating HC1 with said gas; and (d) continuously discharging the crude product from the bottom;
7. An improved process for the manufacture of permethrin as claimed in claim 2, wherein said reactor is a stirred tank batch reactor with facilities for carrying out the reaction under vacuum.
8. An improved process for the manufacture of permethrin as claimed in claim 2, wherein said reactor is a continuous reactor comprising sectionalized column with series of perforated bubble cap plates, each having 1 - 5 % free area; and the reactor column having facilities for (a) continuous feeding reactants at the top; (b) keeping the reactor under reduced pressure (c) continuous vacuum-sucking out the continuously generating HC1, from the top of the reactor column; and (d) continuously discharging the crude product of the reaction, from the bottom of said reactor.
9. An improved process for the manufacture of permethrin as claimed in claim 1 3, and 6, comprising: (i) feeding continuously 3-phenoxybenzyl alcohol co-currently with an equi molar amounts of 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride from the top into a sectionalized bubble column with
23

perforated plates having some free area; (ii) Sparging through the column counter-currently nitrogen gas at sufficient rate to expel the Hydrochloric acid generating during the said esterification reaction under atmospheric pressure condition at 60 -80°C. (iii) washing the crude product coming out at the bottom of the column reactor in a mixer-settler charged with soda ash solution..(iv) washing the soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; and (vi) Continously scrubbing the continuously vented gas through a water scrubber containing 5% NAOH solution followed by scrubbing out alkali through plain water caustic scrubber.
10. An improved process for the manufacture of permethrin as claimed in claim 7, wherein (i) 3-phenoxybenzyl alcohol and 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride are charged in a stern tank batch rector almost in equi molar amount at about 20°C and then the temperature raised to about 80°C; (ii) Applying vacuum at suffiecent rate to expel Hydrochloric acid generating during the said reaction under negative pressure conditions (iii) washing the crude product after the reaction batch is over in a mixer-fettler charged with Soda ash solution; (iv) washing the Soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; and (vi) scrubbing the vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out alkali through plain water caustic scrubber.
11. An improved process for the manufacture of Permethrin as claimed in claim 1,2 and 7, wherein (i) charging 3-phenoxybenzyl alcohol and 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-carboxylic acid chloride almost in equi-molar amounts in a continous reactor at about 20°C and then raising the temperature to about 80°C; (ii) applying vaccum to the reactor for expelling the Hydrochloric acid generating during the said reaction under reduced pressure condition at 60 - 80° C. (iii) washing the crude product after the reaction batch is over in a mixer-settler charged with Soda ash
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solution; (iv) washing the Soda ash wash product with water in another mixer-settler to get the technical grade permethrin; (v) discharging wash water through an effluent treatment plant; (vi) scrubbing the vented gas through a water scrubber containing 5% NaOH solution followed by scrubbing out the alkali through plain water caustic scrubber.
12. An improved process for the manufacture of permethrin substantially as herein described in the text, Example numbers 3 and 4 and accompanying drawings.
Dated this 11th day of October 2006
For UNITED PHOSPHORUS LIMITED
M.B. TRIVEDI (COMPANY SECRETARY) UNIPHOS HOUSE,
11TH ROAD, C. D. MARG, KHAR (WEST),
MUMBAI - 400 052.
25

ABSTRACT
Permethrin is a photostable synthetic pyrethroid manufactured for insecticidal use. This invention discloses an improved process for the manufacture of permethrin without use of any solvent or catalyst, comprising reaction of 2,2-dimethyl-3-(2',2'-dichlorovinyi)-cyclopropane-carboxylic acid chloride and 3-phenoxybenzyl alcohol, at 60 - 80°C, with means for continuously expelling hydrochloric acid generating in the said reaction, from the reaction mass, into a HC1 gas scrubber.
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Documents:

1693-mum-2006-abstract.doc

1693-mum-2006-abstract.pdf

1693-MUM-2006-AFFIDAVIT(6-2-2012).pdf

1693-MUM-2006-CLAIMS(AMENDED)-(13-6-2012).pdf

1693-MUM-2006-CLAIMS(MARKED COPY)-(13-6-2012).pdf

1693-mum-2006-claims.doc

1693-mum-2006-claims.pdf

1693-MUM-2006-CORRESPONDENCE(20-9-2011).pdf

1693-mum-2006-correspondence-received.pdf

1693-mum-2006-description (complete).pdf

1693-mum-2006-drawings.pdf

1693-mum-2006-form 13(20-9-2011).pdf

1693-mum-2006-form 2(title page)-(complete)-(13-10-2006).pdf

1693-mum-2006-form 3(13-10-2006).pdf

1693-mum-2006-form-1.pdf

1693-mum-2006-form-2.doc

1693-mum-2006-form-2.pdf

1693-mum-2006-form-5.pdf

1693-MUM-2006-GENRAL POWER OF ATTRONEY(20-9-2011).pdf

1693-MUM-2006-REPLY TO EXAMINATION REPORT(6-2-2012).pdf

1693-MUM-2006-REPLY TO HEARING(13-6-2012).pdf

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Patent Number

253251

Indian Patent Application Number

1693/MUM/2006

PG Journal Number

28/2012

Publication Date

13-Jul-2012

Grant Date

06-Jul-2012

Date of Filing

13-Oct-2006

Name of Patentee

UNITED PHOSPHORUS LIMITED

Applicant Address

UNIPHOS HOUSE, 11TH ROAD, C. D MARG, KHAR (WEST), MUMBAI - 400 052,

Inventors:

#	Inventor's Name	Inventor's Address
1	SHROFF VIKRAM RAJNIKANT	1-B, SUMMER PALACE, NARGIS DUTT ROAD, PALI HILL, BANDRA (W), MUMBAI - 400 050,
2	SHROFF JAIDEV RAJNIKANT	4-B, SUMMER PALACE, NARGIS DUTT ROAD, PALI HILL, BANDRA (WEST), MUMBAI 400 050, STATE OF MAHARASHTRA, INDIA.
3	POTALE SUNIL RAGHUNATH	601,SURI APARTMENT, NEAR PARLE TILAK SCHOOL, SUBHASH ROAD, VILE PARLE, MUMBAI 400 057, STATE OF MAHARASHTRA, INDIA.

PCT International Classification Number

A01N53/02

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA