The present invention relates to the pre¬ paration of ion exchange resins of even grain size 5. based on styrene-divinyl benzene copolymer matrix useful in analytical chemistry.

It is known that only ion exchange resins having even grain size, homogeneous inner structure and identical physical and chemical properties can

10. be used for analytical purposes. Such resins can be prepared only by a non-conven ional technique as the suitable purification and classification of the co- polymer can not even be performed by expensive methods. Ion exchange resins due to be utilized in

15. modern analytics in a wide measuring range are to meet especially high requirements of quality. (Snyder- Kirkland: Introduction into the liquid chromatography, .Mϋszaki onyvkiadό 1979).

According to HU-PS 17β 374 polymerization

20. in suspension is carried out in the presence of a special protective colloid consisting of a mixture of polyvinyl alcohol and polyacrylic acid ester for preparing ion exchange resins based on ho odisperse vinyl-benzene-styrene pearl polymer. Thus homodisperse

25 _* pearls of a grain size distribution of 12 to 14 microns may be prepared. This process, however is not suitable for the preparation of homogeneous products having a grain size fluctuation within 1 micron or less.

It has been disclosed that cation exchange

30. resins are subjected to acidic or alkaline treatment prior to use. Generally 6 .. hydrochloric acid and then 2 N alkali are used according to the required ion form. This activation method mainly results in the purification of the surface of the resin particles

but Ϊ3 not suited for the formation of the fine inner structure of the resin particles. Due to this circumstance the resin column can be used for measurings of suitable reproduction only after a 5. relatively long time in measurements of particularly large sensitivity. This is due to the following reasons:

After the mentioned activation the resin grains still contain a large amount of sulfonated

10. linear polymers which do not take part in the cross- linkage and other colloidal impurities (US-P 3686113). The various parameters used in the analysis (pH, temperature, ion concentration) start the eluation of the contaminating substances from the resin column.

15. Thus the resin bed changes it3 volume and capacity. Another reason is that the eluating polymers result in a base perturbation at the test wave lengths, what can signi icantly disturb the evaluation.

The present invention was aimed at the

20. elaboration of a process for the preparation of homogeneous ion exchange resins of identical physical and chemical properties, of analytical purity, of spherical shape based on s yrene-αivinyl-benzene copolymer matrix by which the selectivity of analytical

25. methods can be increased. The inner fine structure of the resin grains was formed to achieve maximal efficiency and in order to remove substances disturbing measurings. The column filled with the treated resin does not shrink, its capacity does not change and no

30. base perturbation occurs.

The process according to the present inven¬ tion is characterized by the following operations: a) a mixture of styrene and divinyl benzene is polymerized in the presence of peroxide catalyst

and protective colloid in ion-free aqueous medium at 73 - 30 °0, then at 95 °C, the volatile impurities are removed by steam distillation, the obtained copolymer is isolated and dried, 5. b) the spherical pearl polymer is sulfo- nated under mild conditions in a ten-fold excess related to the stochiometric amount, then the sulfuric acid medium is gradually eliminated by water under maintaining the ambient temperature, 10. c) the pearl polymer is chloromethylated with an excess of chlomomethylether in the presence of zinc chloride catalyst and ammonolysed at least twice, d) the crude resin is after removal of the 15. unreacted reactants suspended in an aqueous solution of the surfactants and then is centrifuged until the supernatant 's turbidity is subs antially ceased -.'.here¬ after the aqueous medium in the pores of the resin is replaced by alcoholic medium and the resin is dried 20. to constant weight, e) the -dried resin is subjected to air- -shifting in ionized air of relative humidity of 20- 0 35, f) the air-shifted product is franctionated 25. by wet sedimentation in the aqueous solution of the surfactant and the sterilizing agent and the fraction within a grain size fluctuation of + 0. 5 micrometer is separated and dried after washing with alcohol, g) the dried resin is treated in a mixture 30. of ethanol, methyl-cellosolve and water at 50 C and then at 100 °C with sodium hydroxide and then boiled with hydrochloric acid, h) the fractionated resin is then suspended in sodium hydroxide solution and filled into a

chromatographing column, the resin column is then treated with an aqueous solution containing organic solvent containing ions with increasing and then decreasing bond strength, the resin is then removed 5. from the column and subjected to acidic-alkaline treatment "oj method per se.

An essential feature of the known methods is that the pearl polymer is formed in the presence of additives in aqueous medium. The additives are

10. partially solid substances and partially water soluble or emulsifiable high-molecular products. Their removal from the surface of the polymer after the polymeri¬ zation is rather difficult due to the large surface of the polymer and thus the recovery of the pure product

15. is rather difficult. According to the invention this problem was solved by using less additives for the preparation of the copolymer in the polymerization technique. In case of polymerization of completely Ion-free medium a perfect spherical pearl polymer

20. was obtained and the grain size of the pearls v. s also within narrower limits. The nearly similar grain size was partly due to the fact that while in case of polymerization the medium was ion- ree, in case of introduction of ion-co aining water a steady

25. fluctuation can be observed.

^" ,Vhen preparing cation exchange resin, the pearl polymer was treated ^' with sulfuric acid mode¬ rately. The concentration of* the sulfuric acid -was chosen minimal and it was applied in a great excess.

30. The heat released in the course of the reaction did not cause any significant local overheating, sulfonation took place unambigously and could be well reproduced as during sulfonation the concentration of the sulfuric acid was substantially constant.

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After sulfonation the sulfor.ated pearl polymer was transferred from the sulfuric acid medium into the aqueous medium at constant weight and cautiously (the sulfuric acid concentration of 5. the medium was first reduced by 3 -J per hour then after 10 hours by 5 ; ^' - per hour) so that the inner structure of the polymer was arranged upon the hyira ion energy 'without any tension.

7hen preparing an ion exchange resin

10. chloromethylation was carried out with chloromethyl¬ ether in an at least tenfold excess relating to the stochiometric amount in order to incorporate the chloromethyl group nearly quantitatively. As catalyst zinc chloride was used so the additional cross

15. linking could be avoided. Ammonolysis was twice repeated by introducing fresh ammonolysing reactant, JO that the chloromethyl group is converted to an active group -without residue. Carrying out the chemical reactions under optimal conditions resulted

23. in a homogeneous distribution of the active groups inside the individual polymer grains.

The ion exchange resins are then decomposed to fractions of suitable grain size. -7or thic purpose the ion exchange resin is distributed .3 fractions

≥ z _> . by using counter current sorting seps_rator by air.

The -width of the obtained fraction can be controlled, the minimal attainable width is - 20 , ^" --. In the course of the air-shifting the aggregation of the particles should be avoided as well as the change of their

30. physical properties ( such as density, mass). luring wet separation determined eduction times and settling liquid- ix ures and chemicals of high purity are used. It is of particular importance that the fractions of different grain size are separated

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under unchanged conditions of sedimentation ( by convection or by other method) , so that no turbulence occurs. Sedimentation time and concentrations are not determined on the basis ^' of the Stokes-law, but by 5. means of monograms obtained by practical measurings. The thus obtained product can be homogenized as required according to quality and particle size.

The details of the invention can be found in the following non-limiting Examples.

10.

Example 1.

Preparation of pearl polymers

Into an apparatus equipped with a 4 liter cooler, thermometer and mixer ( in the mixer the

15. substances to be mixed are pumped between a rotating and a standing gapped cyclinder, rotation number 5600 rot/ in. ) 1000 cm of ion-free water are ed. 15 g of polyvinyl alcohol are soaked in the water for 16-20 hours, the mixture is then supplemented to

25. 3000 cm ³ and heated to 100 ° and kept at this temperature for 10 minutes while the mixer is working at le rotation number ( 2550 rot/min.). The mixture is cooled to 75 0, the required rotation number is adjusted and the prepared monomer mixture of 135. g

25. of styrene, 16 g of divinyl ^{^} nz a'ce and 0.13 g benzoyl peroxide is fed into the apparatus. The mixture is kept at 30 °C for 4 hours, heated to 95 - 93 °0 and stirred for further 4 hours. On the centrifuge the ready polymer is separated, suspended

30. in 1000 c " of -washwater, centrifuged again and then it is heated to boiling with a new wash water and purified by steam distillation. It is again centrifuged and 'washed. After the last washing the centrifuged product is dried. The distribution of the grains

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of the obtained product is rather even ( 36 /. ) ar_d falls within the range of - 1 micron.

Preparation of cation exchange resin 5. To a 2 liter sulfonating flask 60C ml of

90 55 sulfuric acid and previously 100 g of pearl polymer are added. The mixture is stirred for 4 hours at room temperature and it is heated to 95 0. λ postsulfonation is carried out for 3 hours at this

10. temperature. -Dilution is performed with max. 0.2 3cm ion-free water, at the begi_nning by reducing the sulfuric acid concentration of the medium by 3 per hour and after 10 hours by 5 .5 per hour to 1 ; ^" 5 acid content. The product is separated from the mother

15. liquor on a centrifuge 'whereafter it is taken up in IJCO c -' ^' -water and centrifuged again, ^' ..ashing is repeated 3 times by soaking for 16 hours each.

Preoaration of an: .on exchange

To 2 liter flask 12: of chloromethyl¬ ether are added. 130 g of oear under stirring and the mixture is ccirred at 2 - o for 3 hours a d it is maintained at the boiling temperature for 10 hours after the addition of 50 g

25. of ΞnOl _p . The excess chloromethylether is decomposed with methane1 and the mixture is -washed with water ^{^} o means of a centrifuge, After washing to neutral it is amπ.onolysed with a mixture of 150 orr of 40 ^" _ triethyl a ine and όO 53- of -water at 35 0

5 ^ . for 10 hours. The residual ammonolysing mixture is removed by filtration and a further ammonolysis takes place with a mixture of 150 ml. of 40 - ^" . triethyla ine and 6>2 f. of -water at 35 °5. After 15- hour's of ammcnolysis the mixture is filtered and washed

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several times with 1000 cm" ^' of water by means of a centrifuge.

Example 2. 5. . The process is carried out as given in Example 1 but -when preparing the pearl polymer the rotation number is adjusted to 4200. Grain size distribution of the product: 32 559- 1 micron.

10. Example 3.

.For the preparation of highly efficient amino acid analysator resin of grain size 9 - 0.5 m the raw material of Example 1 is purified. From the raw resin a 2070 by mass suspension is prepared

15. with distilled -water containing _Ia-lauryl sulfate. The suspension is homogenized for 0.5 hotir by means of ultrasound. The suspension is centrifuged for 30 minutes at 6 i 3 °0 at 350 - 405 g and the supernatant is covered -with liquid. The previous

20. steps are repeated at least twice and the supernatant is measured turbidimetrically, the difference betweer. the turbidi etric values of the last and the last but one supernatant -will be below 0.54 absorption 'unit. (Lambert-Beer). ?rom the centrifuged settled layer a

25. 20 ^~ j ^' by mass suspension is prepared witii a mixture of 50 ; ^" j methanol- ater and homogenized with ultrasound and centrifuged as given above. The settled layer is dried in large open glass vessels at 40 0 at a pressure of 0.1 car to constant -weight. The obtained

30. resin is air-shifted under a relative humidity of 20 - 40 55. The chosen fraction is subjected to -wet separation. Particularly pure chemicals are used for the separation. As suspension medium distilled ^■ water cor-taining 0.1 per thousand ^~ oj mass of 5 ^' a-lauryi

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sulfate, 0.5 per thousand by mass of l.a hypochlorite and 1 per thousand oj mass of isopropyl alcohol of conductivity of originally max. 5 is used. Sedimen¬ tation is performed in a gradually sterilized place. 5. Eor the removal of grains of a size less than 3 micron a 5 : ^' 5 by mass suspension is prepared, homogenized and settled in a glass vessel, of height 45-50 cm. The time of sedimentation is at least 48 hours. The sedimentation is repeated at least

10. twice. The obtained settled layer is worked up for analytical sedimentation purposes, a 3 '35 by mass suspension is prepared and homogenized with the previously obtained suspension medium. The sedimen¬ tation is conducted for two different time intervals

15 _* (lowpass, high pass).

In order to determine the dwelling time a grain size analysis is carried out from .2 - 3 cir suspension sample taken from the liquid column at its 1 and 1/2 height. The sedimentation is repeated

20. 16-20 times. Sedimentation fractionation is completed when during the la-wpass the turbidimetric value of the sample taken at the 5/3 height of the liquid column and during the high pass at the height of 1/4 height of the liquid column does not exceed

25. the absorption unit of 0.01. The ready fraction is filtered through G4 filter- It is washed three times with distilled -water, once with a 50 - ^" 5 mixture of ethanol and -water, and once ' ith methanol and filtered. The washed resin is dried in an ooen

1 0. glass vessel at 0.1 bar at 40 2 to constant -weight.

The resin is thorougly washed with organic solvents and filled into a chromatographic column-

Through the column solutions with various counter ions are passed by a feeding pump. The counter ions are selected on the basis of the Hof eister liotropic series while it is advantageous to choose ions of 5. similar bond strength for the sake of replacebility in both directions. The various ion diameters , bond strength of these ions and the dynamic loading caused by the flow results in a "springing" of the resin matrix. Due to the "springing" the linear polymers

10. and the colloidal impurities can be ro oved from the resin matrix. 7/ashing can be performed with an organic solvent added to the solutions. The resin column is first -washed with a solution-series containing ions with increasing bond strength and

15. then with the same solutions at the order of decreasing bond strength. The resin is taken out of the column and the conventional acidic and alkaline treatment is performed. The end product is in . ^~' . -3. ^~ form.

?or the activation of the cation exchange

20. cf grain size of 9 microns used in the amino acid ^• analysator 5^ g of dry resin are treated for 30 minutes in a 1053 cm" Ξrien ayer flask with a mixture of 500 cir/ ethane1- ethyl cellosolve - _ .3 ^" l. ^' aOH / 40 : 40 : 2J / in a 50 °5 ultrasound bath.

25. The suspension is then filtered through Tnat an

3. 4 filter by means of a 3uchner funnel and rinsed ^■ with 2 x 100 cm "' of the above mixture. The retention on. t e filter is -washed with 3 x 150 em" of a 0.2 3. l.aOH solution. The ion exchange resin remaining

30. on the filter in the form of a wet sludge is quantitatively -washed into a beaker ^{^} oj means of 0.2 II I7aO__ solution. The thus obtained suspension is treated on an ultrasound bath at room temperature for 5 minutes. The resin in the - ^' . ^' -a form is filled

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^• with a feeding pump at a flow rate of 20 cm" ^' /h into a chromatographic column ^{^} oj using 0.2 3 sodium iroxide.

The following solutions containing the following counter ions are passed, through the filled columnss

1. 1.5 -7 ±Zr ^' l / propane1 /70:30/

2. 1.5 ^' -3 27aGH / propanol /?0:30/

3. 1.5 I 23H OH/propanol /70:30/

10. 4- 1.5 21 KOΞ / propanol /JO :30/

A tenfold volume of the resin bed of the solutions is passed through the filled column first on the basis of increasing then decreasing serial number. , a d finally 0.001 II HOI is passed through

15. the column.

The resin is then taken out of the column and boiled 'under steady stirring on a hot water bath in a tenfold amount of 6 23 Ξ01 for 45 minutes. In order to remove the heavy metal io s 0.1 -35 of ethylene d amme tetraac tic acid is added to the cxture. -nv, ≤. -. -

.

'emcveu o a tnorou^n w tn

_i=. r-H hot water ath with 5.5 2. l.aCH added in a tenfold excess. The resin is .lien filtered and washed thoroughly with ion-free water. 5 ^" ntil the filling of the column the resin is stored in 5.2 27 27aOH in an amount .corresponding to the mass of the res: Properties of the cation exchange resin prepared according to Examples 1 to 3 _. activated as given Example 4 and having a grain size of micron: column size: $ 4,5 mm 1 = 230 mm flov ate of the eluant: 25 cm'/h

-nlow i O Z nt: 13 cm"/h

IVNIΘIHO αva

column temperatures: 40 C

60 °0 30 °0 •Eluant system: ?ico-3uffer II. 5. -Dwelling time in tiie reactor: 6 minutes optical route length of trie cyvette: 2 mm .tested substance : hydrolysate standard, as 1 mole/ml amino acid.

1) the highest pressure gradient on the 10. column cannot exceed 45 bar,

2) Dwelling time of the last peak (arginin) cannot exceed 4300 sec.

3) The resolution of the overlapping peai pairs within the analysis time given under 2, slould

15. be at least of 33 ~ on the basis of the follo'wing cal ulation:

R -,eso _Λ l-,u.t_.i•o-,n,- = oeak hei^*2αt. -, valley ._ , -~ - ^, peax nei.g..n. . x 1--- -

4) Tine criange of t2ιe base during analysis 20. and the standard deviation of the dwelling ti ss between analysis cann exceed the value derive., from the technical parameters used for the measurings.

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