WO2004031274A1

WO2004031274A1 - A process for the recovery of useful materials from multi-layer laminated packaging refuse

Info

Publication number: WO2004031274A1
Application number: PCT/IN2003/000324
Authority: WO
Inventors: Ashutosh Mukhopadhyay
Original assignee: Ashutosh Mukhopadhyay
Priority date: 2002-10-04
Filing date: 2003-09-26
Publication date: 2004-04-15

Abstract

A process of recovery of useful constituents from multi-layered laminated fragments of packaging industrial refuse in sheet, tube or shredded form from each other as separate constituents comprising treating the comminuted fragments with an inorganic base solution, so as to dissolve the laminated metal aluminium to subsequent recoverable aluminium salts, eventuating primarily as sodium aluminate wherein from even a medicine like aluminium hydroxide gel passing pharmacy grade assay, and recover the polyethylene plastics in as it is physical condition and washing the same.

Description

I

A PROCESS TOR THE RECOVERY OP USEFUL MATERIALS FROM

-MULTI LAYER LAMINATED PACKAGING REFUSE

FIELD OF INVENTION

The present invention relates to a process for recovery of useful constituents from multi- layered laminated fragments of certain packaging industrial refuse. More particularly the invention relates to a process for recovery of useful constituents from multi-layered laminated fragments of plastics and aluminium foils.

BACKGROUND OF THE INVENTION

To meet the respective specific and particular packaging demands use of lamination of plastics and aluminium is a widely accepted practice in packaging industries.

Such packaging laminates aluminium foil with plastics either in one side or in both sides. In toiletries a particular tubes of such lamination is widely used. In medicinal strips or blister type packs such lamination is also widely used. In cable industry to protect cables from surrounding adversities a protective wrap-type packaging of such lamination is also widely used Also, rhe use of such laminated pouches to pack beverages and processed foods are widely desperate.

Now, the entire manufacturing process, to reach up-to a final stage of packaging, en route, generate a huge volume of refuse in almost every chain of production process.

Such mass may be called in short as multi-layer laminated packaging industrial refuse (pre- use condition) where the chief components are thin foils of metal aluminium and polyethylene plastics.

In any convenient way these laminated stuffs are stubbornly non-recyclable and vulnerable for destroying despite their characteristic commercial valuations.

A planned so-called F.co-iViendly projects of incineration or landfill treatments (ma!- practicing Earth as an eternal burial ground of industrial refuse) are real costly affairs as well as burden to economy, even to production of developed countries also. In India, almost about in coarse a vet age, around Rupees Sixty-tin ee Million (around

US $ 1 35mn) per year, ot say, around Rupees One Hundred Seventy-five Thousand

(aiound US $1800) per day can be saved, as well as, can be earned from the recovery of such packaging industrial laminated refuse generated industrially (that is pre-use stage) only

The colossal mass of domestic (post-use) refuse, where the used such whole packaging aie thrown away as garbage, again absolutely vulnerable for destroying, is enough tall to undercount

10

In India almost about in coarse average aiound Rupees One Thousand Five Hundred Million (around US $ 32mn) per year or say around Rupees Tour Million (around US $ 85,000) pei day can be saved, as well as, can be earned from the recovery of such domestic (post-use) packaging industrial laminated refuse, obviously subject to recovery : " if and when is possible

Thus, recovery and its subsequent proper t ecycle/reprocess/reuse will nurtui e and strengthen the main stream of economy as well as will save the ecology from notorious often carcinogenic and often susceptible ODS (ozone depleting substances) releasing 20 { when burn open air as in India} environmental pollution as well

Since such refuse is out and out a waste, whatsoevei stubborn it may be, its process of separation and recovery should be economical A highet recovery process if dearer the cost of tecoveied material than that of the vπgin would subsequently overcast the mam 2^ intention obviously

Patent Nos DE 4122705, WO 93041 16, and EP 599905 have specific relevance to the de-lamination of laminated packaging industπal icfuse uses dcctone-watei as oi anic chemical solvents Acetone watei is compai atively dearei than solution of sodium ^~w i oxide used herein Acetone has a vei v low Hash point and it is highly flammable and accident-prone The plastics aie also fair K flammable In industrial application, w her huge volume of acetone will lequn e, its affinity to accident is unpredictably dangei ous

US Patent No 5,246, 1 16 relates to the de-lamination of laminated packaging industrial 1 iefuse has used poly alkaline glycol polymer solution as solvent

US Patent No 5,421,526 teaches the use of volatile organic acids like formic acid, acetic acid piopanoic acid, butyric acid as solvents

10 I he aforesaid prior arts use organic chemical solvents only, such as, Acetone-water, Poly alkaline glycol polymer solution and volatile organic acids like formic acids, acetic acids piopanoic acid and butyπc acid and does not teach the use of inorganic chemical compounds, m particular, inorganic bases

i s US patents 52461 16 and 5421526 fuithei make use ot heat at tempeiatures of 80 C and 50 C respectively Here, the material is extremely lighter in weight and is accordingly voluminous In one 2001ιt reactor with maximum 190ht solvent, at one time, maximum I 5Kgs shi eddcd material can be processed l o process ten metric tons in a day it demands a series of big reactois and subsequent volume of solvents Application of heat 0 to such a big mass is obviously a costly affair

None of the known art provides a process for the de-lamination of laminated packaging Λndustπal refuse which gives optimum economy and eco friendliness

ι T he applicant with a view to economize the treatment of such matenal pioposed a pi JCCSS so as to lecovci useful constituent from multi-laver laminated agmenfs of packing mdusti ial iefuse horn each othci by ti eating the fiagmenls with an inoiganic solution in particular, nitr ic acid so as to loosen the bonding of the constituents and i ccovei g such constituents The said pi ocess is covered in the applicant's Intei ational o Patent Application publication No WO/02/50175 The applicant has now found thai recovery of laminated constituents can also be economically effected by treating the material with an inorganic base, in particular sodium hydroxide. The use of sodium hydroxide is found to result in substantial economy because the organic compounds used in prior arts are relatively more expensive The process of the present invention is also relatively economical and efficient than that of the applicants earlier work being WO/02/50175 also because Sodium aluminate (NaAlO2) (either cone, solution or dried powder) eventuate as a product of the process.

Thus the primary object of the present invention is to provide an improved process for recovery of constituents of multi-layer laminated fragments of packaging industrial refuse / scraps / waste etc.

A further object of the present invention is to provide an alternative process for the recovery of laminated constituents that is economical and does not involve any expensive/sophisticated treatment.

A still further object of the present invention is to provide a process for the recovery of the laminated constituents thai is Eco-f iendly.

Yet another object of the present invention is to provide a process for the recovery of laminated constituents uch that the process, at its final stage, results profitable end products

, Yet a further object of the present invention is to provide a process for the recovery of laminated constituents such that the process is applicable even where the lamination is mechanically stubborn or where the aluminium foil is very thin.

SUMMARY OF I VE TION Thus according to the present invention there is provided a process for the recovery of useful constituents From multi-layered fragments of packaging industrial refuse by separating them as individual constituents, the process comprising contacting the fragments with an inorganic basic solution so as to l ecovei the laminated metal aluminium as metal aluminium salt and set fr ee the fragments of polyethylene plastics from lamination

The metal aluminium is recovered in the form of r eusable salts while the plastics retains its physical form

Contacting of the fragments with the inorganic basic solution is done for a period of between 48 - 84 hours

The recovered aluminium salt is sodium aluminate

From such produced Sodium aluminate, Aluminium hydroxide gel [Al(OH)3] eithei of commercial grade or of pharmacy giade results as other product of the metal aluminium salt

Also from thus obtained Aluminium hydroxide gel by adequate calcination dried powdei of Alumina (A12O3) can be yielded as other aluminium salt Again from Aluminium hydroxide gel through pr oper chemical reaction othei aluminium salts as Aluminium sulphate [A12(SO4)3], Aluminium nitrate [AI(NO3)3] etc can also be obtained

DESCRIPTION OF PREFERRED EM BODIMENT

According to the present invention multi-layer laminated packaging industrial refuse 'animated with plastics and thin foils of aluminium, eithei in one side or in both the sides ar c used for i ccovcr y of plastics in as it is physical condition and metal aluminium foils in the foi m of aluminium salts The entire r efuse may appeal eithei in sheets form, stnps f oi m, tubes foi oi sometimes ah eady shi edded / tπmmings form The refci ence numer als m br ackets i cier tυ llgui t I

I hi ough coin cntional shi eddei un-shi edded foi ms ai e shi edded bi eadth-wisely at an av er age 25mm to 50mm inespective of length, but prefeiably not more than Imetre ( 1 ) (figui e 1 ) The comminuted iefuse fragments are dipped in inorganic base solvent, 2M sodium hydr oxide solution at ambient temperature (2) The mass is allowed to stand quietly undei casual supervision for about 48 to 84 hours depending upon the size of shredding

At ambient temperature 2M sodium hydroxide solution slowly by etching dissolves the aluminium and release the free plastics within the solution When the aluminium foils get totally dissolved the plastics being freed from lamination come in a free floating condition awaiting for removal from the solution

Fragments of recovered plastics are then removed (3) from the resultant, a very dilute solution of Sodium aluminate (NaAlO2), and are allowed to undergo a dip with fast stirring in dilute nitric acid solution for about 1/2 to 2 minutes (4) Then the plastics are given sufficient water baths to wash away the adhered solvents (5)

Fiagments of recovered plastics, getting washed with watei , are then centπfuged to as far as possible dryness (6) Then they are allowed to have a sun bath or to dry in a dryer (7) for a total drying The dried thus recover ed plastics are then ready for producing saleable recycled plastic granules or also may be sold even as such

The time factor varies directly with the size of shredding Breadth-wisely smaller fiagments will take shorter time-duration Density of sodium hydroxide / sodium aluminate solution monitors the span of time also Care should be taken for tubes Tubes of 0 25cm breadth-wisely shredding will go easy into the reaction

The main volume of 2M sodium hydroxide solution after such certain frequent use, eventuate as Sodium aluminate solution, as the prime recovery of metal aluminium salt of that metal aluminium foil the chief component of the afoi esaid multi-layer laminated packaging mdusti ial i efuse. thai in due time salui aies sufficiently to dischai gc Aluminium hydr oxide as precipitation (9) I nit ially the pr ecipitation appears in a just visible manner and then by means of effects of sencs of dipping, more and more dense pi capitation of Aluminium hydroxide is dischaigcd I lit icsultant Aluminium hydroxide is collected thiough filtration (8) T he (Vitiate ( I I ) Sodium aluminate according to density may eithei be used for furthei dippings of such comminuted strips, oi may taken for dπect production of concentrated solution of Sodium aluminate (13) s

In accordance with the percentage of moisture present therein, after centπfuged/press- filtered ( 10), the yielded paste of Aluminium hydroxide are mixed with cone sodium hydroxide solution accordingly (12) to yield concentrated solution of Sodium aluminate

( 13) 10

Within the prepared concentrated solution of sodium aluminate (13), the already produced concentrated sodium aluminate solution, generated in the previous phases as filtiate (1 1), are mixed (13) and a final concentration by boiling is reached which is then cooled and filtered to obtain a pure clean and clear solution of Sodium aluminate (14) at

-i a bicnt temper atui c

1 he stubborn non-recyciabie notorious man-made industrial laminated refuse, somewhere carcinogenic somewhere ODS releaser, by virtue of this present invention having being lost then rigidity is converted to easy recyclable free plastics as well as 20 converted to a chemical in the form and frame of recovery, having a versatile productivity to pioduce a series of metal aluminium salts including a phar macy grade bulk diug Aluminium hydroxide gel offering a sound commercial profit

An adamant waste plaguing highly detrimental and awful pollution to the living Earth is 2~ι conquered to an extent to yield a medicine satisfies phar macopoeia

Now in thus pr oduced concentiated solution oi Sodium alumιnate,|(who now itself is also a saleable product ( 14)( 15)| concentiated hydiochlouc acid is added ( 16)(2 ) ui vield cither Aluminium hydroxide gel of commercial giade ( 18) oi Aluminium "<o dioxide gel of phai macv gι ade(26) Dur ing the pr eparatory process of Aluminium hydi oxide gel the filtrate (22)(30) we obtained, on cvapoi ation to dryncss (23 ,(3 ! ) will generate dry powder of pure Sodium chloride NaCl as a marketable by-product

Again, to produce Aluminium hydr oxide gel from such cone, solution of sodium aluminate instead of cone hydrochloi ic acid a number of inorganic as well as organic acids may also be taken for the use, whei c the resultant sodium salt (here as by-product) will only vary E g Hydrochloric acid (HC1) will produce Sodium chloride (NaCl), Sulphuric acid (H2SO4) will produce Sodium sulphate (Na2SO4), Formic acid (HCOOH) will produce Sodium formate (HCOONa) etc

Such obtained commercial grade Aluminium hydroxide gel conventionally if adequately calcined would yield dried powder of Alumina (A12O3)(32) which has its own various uses and concern market

Such obtained Aluminium hydroxide gel, conventionally through proper chemical reaction would yield other aluminium salts eg Aluminium sulphate A12(SO4)3, Aluminium niti ate Al(NO3)3 etc (33)

The entu e pi occss, en route, dischar ges absolute ZERO pollution to environments in any means

EXAM LES

The pi occss of the invention will now be demonstrated with reference to two working embodiments of the process

Example - 1

(Λ) !n a 1000 ml clear conical flask 66gιns of pure dried sodium hydroxide flake is taken Cleai w-atei is poured to make SOOmls of 2M sodium hydroxide solution (B) Few pieces of laminated toiletry tubes are taken The shoulder and tail-end seal of the lubes are shi edded out by manual cuttings with scissors Then taking 0 25 cm breadth-wisely the tubes are longitudinally shredded ( 1 ) All the contaminants arc cleared and washed out

(C) In a sufficient quantity the 0 25 cm shredded fragments of the laminated tubes are now dipped into that conical flask containing 800mls of 2M sodium hydroxide solution (2). The flask is closed with a stopcock. It is now allowed to stand for about 48 to 84 hours. In between times a six hourly stirring of the material is preferred so as to all the parts of the fragments get contact with the solution for reaction.

(D)The aluminium gets slowly dissolved by that time When all aluminium get dissolved the two free layers of plastics, being freed from lamination, start to float within the solution

(E) Such plastics free from aluminium lamination are taken out (3) and are given a dip in a dilute nitric acid solution (4) for about Vi to 2 minutes with fast stirring- Then the plastics are taken off from the nitric acid and are given sufficient water bath to wash away all the adhered solvents (5) Plastics are then allowed a complete drying (6)(7).

Steps (B) and (C) and (D) and (E) are repeated.

Even now, subject to the concentration of sodium aluminate the precipitation of Aluminium hydroxide may or may not occur.

Again steps (B), (C), (D) and (E) arc repeated

Either then or in the next phase / phases precipitation of Aluminium hydroxide occurs in a satisfactory quantity (2)

(l^;) By filtration (8) Aluminium hydroxide is then collected (9), either press- filtered/ocntrifuged and dried to a paste/cake ( 10). The filtrate, that is, solution of -sodium aluminate is kept aside ( 1 1 )

(Ci ) Now. in 1 0ml of cone sodium ydi oxide solut ion about 200gms of thus dried paste of aluminium hydroxide ( 10) is mixed ( 12) and boiled to dissolve. The resultant solution of sodium aluminate kept aside (1 1 ) is mixed within it ( 13) The entire solution is boiled, cooled and filtered to obtain a pure clean and clear solution of Sodium aluminate (AI2O3 is in between 20 — 25%) at ambient temperature ( 14). Now such concentiated solution of Sodium alumιnate[(who itself is also a saleable product( l 4)( 15)Jιs conventionally ready to produce either commercial grade( 18),or pharmacy gιade(26), Aluminium hydroxide gel by addition of necessary concentrated hydi ochlouc acid accordingly -> { H) Such produced commeicial giade Aluminium hydroxide gel conventionally if properly calcined would yield dried powder of Alumina (32) while again conventionally if properly chemically reacted would yield other salts of metal aluminium E g Aluminium sulphate, Aluminium nitrate etc (33) as well

(I) In one part of such sodium aluminate solution concentrated hydrochloric acid is lo mixed ( 16) to yield Aluminium hydi oxide gel, commercial grade (18) The gel is then centπfuged (19), washed and re-dπed (20) to a paste Thus generated paste could be dried (21 ) to produce dried powder of Aluminium hydroxide gel of commercial grade

(J) In the other part of such sodium aluminate solution, in accordance with the assay of i ^•• aluminium υxide (AI20 ) μr seni u iihm the solution is given accordingly dilution and aftei that concentrated hydrochloric acid is mixed (24) to yield Aluminium hydroxide gel (26) satisfying pharmacy grade assay It is then centπfuged/press- filtered (27), washed with sufficient boiled / sterilized water and again re-dπed (28) to a paste Half of it is then preseived (by addition of sodium benzoate) and packed '() .'s paste of Aluminium hydroxide gel as per pharmacy specification

(k) l o get dr ied powder of Aluminium hydroxide gel of pharmacy grade the othei half of the yielded gel in paste foi m is dued (29), pulverized (if necessary) and packed as per phai macy specification

(L) Heie the obtained filtrate (22)(30) by evaporation to dryness (23)(31) will yield also

>-| puie Sodium chloride (NaCl), as a by-pioduct, which has its own specific market

t hus b) using a pure inorganic bast sodium hydroxide, separ ation and recovei y of laminated fiagments of multi-layei laminated packaging industrial refuse is possible w her e fi ec plastic fiagments are iccoveicd in as it is physical condition in one part and it) the i ccυvci v of metal aluminium pr imar ily achieving in the foi m of metal salts like Sodium aluminate ( 14)( 1 5) oi fi om such i csultaπt sodium aluminate solution Aluminium hydi oxide gel (as both paste and dried powdei), eithei in commeicial grade(20)(2 1 )or/an in pharmacy grade(28)(29) are achieved, again where-also from such obtained commercial grade Aluminium hydroxide gel production of other aluminium salts E Aluminium sulphate, Aluminium nitrate(33) or even Alumina(32) are achieved depending upon just planning and specific procedure and motto in the other

5 part.

Thus a notorious laminated refuse stuff can be converted to a use of benefit even as a medicine satisfying pharmacopoeia.

Id EXAMPLE - 2

(A) In a 2001it. clear polythene drum I 5kgs of pure dried sodium hydroxide flake is taken Then clear water is poured to produce 1801its. of 2 M sodium hydroxide solution

(B) Around l Okgs. of multi-layer laminated packaging industrial refuse is taken. If the 15 lot is un-shredded then either mechanical or manual shredding breadth-wise @

0 25cm - 0.5cm and lenglh-wisely @l metre is done, if necessary (1 ). All the contaminates are cleared and washed out

(C) Cleared such comminuted fragments of refuse are now dipped into the drum containing 1 80 lit. 2 M sodium hydroxide solution (2). After covering the drum it is o allowed to stand for 48-84 hours I n between times a six hourly stirring of the material is preferred so as to al l t he parts of the fragments get contact with the solution for reaction

(D) The alum i nium gets slowly dissolved by that time When al l the aluminium get dissol ved the free layers of plast ics, being freed from lamination, start to float within 5 the solutions

( E) Such plastics free from alumi nium lamination arc taken out (3) and are given a d ip into a dilute nitric acid solution (4 ) for about '/-- -2 minutes with fast stirring Then t he plastics are taken off fr om t he nitric acid solution and are given sufficient water bath to wash away all the adhei ed solvents (5) The plastics are then allowed a o complete dryi ng (6)(7)

Steps (B ) and (C) and (D) and (li) are l epeated Even now, subject to the conccnti tion of sodium aluminate the precipitation of aluminium hydroxide may or may not occur

5 Again steps (B), (C), (D) and (E) are iepeated

Eithei then or in the next phase / phases precipitation of aluminium hydroxide occurs in a satisfactory quantity (2)

(F) By filtration (8) Aluminium hydroxide is then collected (9), either centπfuged/filter- l() pressed and dried to a paste/cake (10) The filtrate, that is, solution of sodium aluminate is kept aside (11)

(G)Now in 31ιt of cone sodium hydroxide solution 6kgs of such dried paste / cake of Aluminium hydroxιde(lθ) are mixed (12) and boiled to dissolve The resultant solution of sodium aluminate kept aside (11) is mixed within it (13) The entire 15 solution is boiled, cooled and filtered to obtain a pine clean and clear solution of

Sodium aluminate (A12O3 is m between 20 — 25%) at ambient tempeiature (14) Now such concentrated solution of Sodium aluminate [(who itself is also a saleable pioduct (14)(15)] is ready to pioduce conventionally eithei commercial grade (18), or pharmacy grade (26) aluminium hydroxide gel by addition of necessary 20 concentrated hydrochloiic acid accordingly

(H)Such pioduced commercial giade Aluminium hydioxide gel if conventionally properly calcined would yield clued powder of Alumina (32) while again if conventionally properly chemically leacted would yield other salts of metal aluminium E g Aluminium sulphate, Aluminium nitiate etc (31) as well 25 (1) In oΛe part of such sodium aluminate solution concentiated hydiochloπc acid is mixed (16) to yield Aluminium hvdioxrdc gel, commercial grade (18) The gel is then centiiluge (19), washed and le-dned (20) to a paste I hus generated paste could be dned (21) to pioduce dπed powder of Aluminium hydroxide gel of commeicial giade

^■.o (J) In the othci part of such sodium ahmiinate solution, in accoidance with the assay of aluminium oxide (AI201) picscnt within, the solution is given accordingly dilution and aftci thai concentiated hydr chloiic acid is mixed (24) to yield Aluminium hydroxide gel (26) satisfying phar macy grade assay It is then centnfuged/picss- filtei ed (27), washed with sufficient boiled / sterilized watei and again re-dned (28) to a paste Half of it is then pieseived (by addition of sodium benzoate) and packed as paste of Aluminium hydroxide gel as per pharmacy specification

( )^"I o get dried powder of Aluminium hydroxide gel pharmacy grade the other half of the yielded gel in paste form is dried (29), pulverized (if necessary) and packed as pei pharmacy specification

(L) Here the filtrate obtaιned(22)(30), bv evaporation to dryness(23)(31), will yield also pine Sodium chloride (NaCl), as a by-product, which has its own specific market

Thus, by using a pure inorganic base sodium hydroxide, separation and recovery of laminated fiagments of multi-layer laminated packaging industrial refuse is possible where fiee plastic fragments are recoveied in as it is physical condition in one part and the lecovery of metal aluminium achieving in the form of metal salts like Sodium aluminate ( N)( I ) oi from such resultant sodium aluminate solution Aluminium hydroxide gel (as both paste and dried powder), either of commercial grade (20)(21) oi/and of pharmacy grade(28)(29) are achieved, again where-also from such obtained commercial Aluminium hydroxide gel pioduction of other aluminium salts F g Aluminium sulphate, Aluminium nitrate etc (13) or even Alumma(32) are achieved depending upon just planning, specific pi oceduie and motto in the other part

fhus a notor ious laminated refuse stuff can be converted to a use of benefit even as a medicine satisfying pharmacopoeia

Claims

5 1 A pr ocess for the recovery of useful constituents from multi-layered fragments of packaging refuse by separating the layering materials essentially constituting of aluminium or aluminium based material and plastic material as individual constituents, the process comprising contacting the fragments with an inorganic base so as to recover aluminium as metal aluminium salt and release the fragments of to plastic material from lamination,

2 A process as claimed in claim 1 wherein the inorganic base is sodium hydroxide in solution

^{, "}ϊ \ pr ocess as claimed in claim 6 whei ein the concentration of the said sodium hydroxide solution is 2M

4 A pi ocess as claimed in claim 1 wherein the said recovered aluminium salt is sodium aluminate 0

5 A process as claimed in claim I whei ein the said fragments are contacted with the said basic solution for a per iod of 48 - 84 hours

6 A pi ocess as claimed in claim 1 whei cm the said plastic is polyethylene 5

7 A process as claimed in claim 1 , wherein the multi-layer laminated packaging mdusti ial i efuse is in sheet, strips, tube or shredded / trimming foi m

8 A pi occss as claimed in anyone of the preceding claims whei ein any un-shrcdded 0 forms of the r efuse ai e shi edded using a conventional industrial shredder to a size of aboυl 0 25cm - 0 5cm in br eadth and about 0 5— 1 Srneti e in lenyih 9 A process as clai med m any one of the preceding claims wherein the refuse is contacted with the sodium hydroxide solution by dipping

10 A process as claimed in any one of the preceding claims wherein the plastics, after being freed from lamination, is cont acted with dilute nitric acid followed by one or more water baths for total removal of adhered solvents from the recovered plastics.

1 I A process as claimed in any one of the preceding claims wherein the separated plastics are subject to a step of drying.

12. A process as claimed in any otic of the preceding claims wherein the separated aluminium salts are dried if desired

13 A process as claimed in any one of the preceding claims, wherein the drying is effected bv conventional centrifuge ' press-filter optionally followed by drying under the sun, or in conventional tray-dryer or spray-dryer