Synthesis of chelating resins containing aminopolyacetic acid moieties

Reactive Polymers, 4 (1985) 11-20 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands

ll

S Y N T H E S I S OF CHELATING R E S I N S C O N T A I N I N G A M I N O P O L Y A C E T I C ACID MOIETIES KUNIHIKO TAKEDA, MINORU AKIYAMA and TAKAFUMI YAMAMIZU Research and Development Administration, Asahi Chemical Industry Co., Ltd., 1 - 3- 2, Yako, Kawasaki- ku. Kawasaki 210 (Japan)

(Received October 31, 1984: accepted December 31, 1984)

Synthesis of chelating resins bearing an aminopolyacetic acid within a pendent group is reported. They are resins to which moieties of IDA (iminodiacetic acid), EDTA (ethylenediaminetetraacetic acid) and DTTA (diethylenetriaminetetraacetic acid), respectively, are linked. Resins with the latter two groups were prepared by copolymerization of the respective monomers with divinylbenzene (DVB) as a crosslinker. These monomers are m-dibromoethylstyrene and N,N-bis(2-aminoethyl)-p-aminoethylstyrene, respectively. The method of resin synthesis is described, from monomer synthesis to attachment of chelating groups on the copolymer matrix followed by after-treatrnent for each resin. Copolymerizability is estimated for meta- and para-isomers of D VB to enable assessment of the effect of crosslinks on chelate-forming capability of the IDA-type resin. The cation exchange capacity was found to be 4.3 m e q / g for IDA-type, 3.5 m e q / g for EDTA-type and 5.1 meq / g for DTTA-type, resins, respectively.

1. I N T R O D U C T I O N

It is known that aminopolyacetic acids such as E D T A (ethylenediaminetetraacetic acid) react with metallic ions to form chelates. Because of this, the stability constants of the chelates are very large [1-3]. Aminopolyacetic acids have been used as masking agents in the field of analytical chemistry and have recently found wider use in various industrial applications. Particular attention has been drawn to a compound obtained by introducing aminopolyacetic acid groups into a polymer because of its potential use as a high-performance

chelating resin. The development of such a chelating resin has its origin in the synthesis of a resin obtained by condensation polymerization of m-phenylenediglycine and formaldehyde [4]. Several studies of the syntheses of resins containing an IDA (iminodiacetic acid) moiety have been reported. For example, Trostyanskaya et al. [5] and Okawara et al. [6] introduced IDA as a pendent group into a cross-linked chtoromethylated polystyrene structure taking advantage of the high reactivity of the chloromethyl group. Morris et al. [7] used vinylbenzyl chloride as a starting material to form a monomer having an IDA moiety and prepared an insoluble resin.

12

Only a few reports have been presented concerning three-dimensionally crosslinked polymers containing EDTA moieties. Klyachko [8] utilized a phenol-formaldehyde resin as its skeleton. Kaeriyama and Shimura [9] more recently reported the preparation of a crosslinked resin containing EDTA moieties by a Grignard reaction to form a 3,4-dibromobutyl group and subsequent reaction with diethyl iminodiacetate. Resins containing aminopolyacetic acid moieties other than IDA and EDTA were obtained by reaction of crosslinked chloromethylated polystyrene with various aliphatic amines [10], by introducing acetic acid groups into a polyethyleneimine [11], and so forth. This paper describes the syntheses of an EDTA chelating resin and a DTTA (diethylenetriaminetetraacetic acid) chelating resin. The EDTA chelating resin was synthesized from m-DBS (m-dibromoethylstyrene) prepared in our previous work [12] by the selective addition of bromine atoms to a double bond of m-DVB (m-divinylbenzene). The DTTA chelating resin was synthesized from a p-aminoethylstyrene derivative prepared by the selective addition reaction on a double bond of p-DVB (p-divinylbenzene) following the method reported by Tsuruta et al. [13].

2. SYNTHESES OF CHELATING RESINS The syntheses of the chelating resins were carried out according to the following method. A functional monomer was synthesized and then copolymerized with divinylbenzene as a crosslinking agent to form a crosslinked polymer. The crosslinked polymer was obtained in the form of spherical beads by suspension polymerization according to the conventional technique for ion-exchange resin preparation. The crosslinked polymer was then reacted with a chelate-forming agent to obtain the final resin.

2.1. Synthesis of IDA chelating resin The IDA chelating resin was synthesized from a copolymer of m-DVB with VBC (vinylbenzyl chloride). In the design of a crosslinked polymer containing a chelating group consisting of a multidentate ligand, particular attention should be paid to steric hindrance opposing the chelate-forming ability of the resin. It is expected that the chelate-forming ability near the crosslinks may be greatly influenced by local restrictions in the thermal motion of the polymer due to the high rigidity of the crosslinking DVB unit. We carried out a preliminary experiment on the polymerization behavior of both m-DVB and p-DVB so as to investigate the polymer structure near the crosslinks, m-DVB or pDVB was copolymerized with VBC using AIBN (azobisisobutS, ronitrile) as an initiator to determine the monomer reactivity ratios, r 1 and r 2. The Q and e values in the radical polymerization were determined according to the method of Alfrey and Price [14,15]. Both the monomer reactivity ratios and the Q and e values obtained are shown in Table 1. The Q and e values obtained for VBC were 0.88 and -0.20, respectively. They are in reasonable accordance with the Q and e values (Q = 0.93; e = 0.30) calculated from the results of the study [16] on the copolymerization of styrene with VBC. The o value of the chloromethyl group of VBC is estimated to be 0.22 from the known relationship [17] between the e value and Hammett's substituent constant TABLE 1 M o n o m e r reactivity ratios in copolymerization of DVB isomers with VBC (vinylbenzyl chloride) a M1

M2

rl

r2

p-DVB m-DVB

VBC VBC

0.70 0.75

0.32 1.04

VBC: Q = 0.88, e = - 0 . 2 0 VBC consists of a mixture of m e t a and p a r a isomers (6:4) in 96% purity.

13 TABLE 2 Sequence distributions in copolymers of isomers of DVB (M 1) with VBC (M 2) Copolymer

P2(M1M, }

Pa(M,M2) a

P2{M2M2}

pa{M,M,M1 }

p~{M1M1M2 } ~'

P~{M2MIM2}

A ~' Bh

1.7 0.8

41.6 18.2

56.7 80.9

0.13 0.07

3.2 1.5

19.2 8.4

~' P2{M1M2} consists of both of diads MIM 2 and M2M l, and p~{M1M1M2} of both of triads M~M1M : and M2M1M 1. b A: copolymer with p-DVB, B: copolymer with m-DVB, [M1]/[M2] = 0.118.

related to radical copolymerizability of a vinyl monomer. On the other hand, Hammett's substituent constant, Op, of a chloromethyl group is known to be 0.18 according to a different method [18]. It can be said that values of the monomer reactivity ratios r 1 and r= shown in Table 1 are highly reliable. From the r t and r 2 values shown in Table 1 sequence distributions in the copolymers of DVB isomers with VBC were determined using probability theory [19,20]. The results are shown in Table 2. The formation of DVB DVB chains should be noted in the monomer sequences in each copolymer, because the DVB chain portions may form a ladder or ladder-like structure. It is considered, therefore, that chelate formation in the vicinity of DVB DVB chains would be greatly suppressed owing to steric hindrance. The probability of formation of D V B - D V B chains is 0.8% for the copolymer of m-DVB with VBC and 1.7% for the colpolymer of p-DVB with VBC. This indicates that the probability of VBC being adjacent to D V B - D V B chains is about twice as high in the case of p-DVB as in m-DVB. VBC was prepared by direct chlorination of vinyltoluene (a mixture of isomers: meta: para = 6"4) at high temperature [21]. c~-Chlorovinyltoluene and several kinds of polychlorides were formed as by-products. The effect of these by-products on the radical polymerization of VBC was examined. Radical polymerization of VBC was found to be most adversely affected by the presence of

~-chlorovinyltoluene. A sufficient conversion of VBC monomer could not be attained in cases where the c~-chloroderivative was present in an amount of 3% or more. This may be explained by the very low reactivity of p o l y m e r radicals ending in c~-chlorovinyltoluene units due to steric hindrance caused by the chlorine atom [22]. The chlorination product was distilled fractionally three times to give VBC containing ~-chlorovinyltoluene to less than 1%, the distillate was used in polymerization. An I D A chelating resin was prepared from the copolymer of m-DVB with VBC in the following manner. Diethyl iminodiacetate was reacted with the copolymer [1] and the product was hydrolyzed to obtain an IDA chelating resin. N o difficulties were encountered in amination of the matrix copolymer [1] because of the high reactivity of chloromethyl groups. Amination of the copolymer with diethanolamine or iminodiacetonitrile was reported previously [5,6]. In this study, diethyl iminodiacetate was used. The route to synthesize the IDA chelating resin is shown in Fig. 1.

2.2. Synthesis of EDTA chelating resin The E D T A chelating resin was synthesized from the copolymer of rn-DBS (m-dibromoethylstyrene) with m-DVB, m-DBS was obtained by selective bromination of one vinyl group in m-DVB with pyridinehydrobromide perbromide [12].

@=

a

man

chain tomed

of “lnylbenlyl

Fig. 1. Synthesis

shlorlde

by

copolymeilzatm”

Wl,h m-0”B

of IDA chelating

resin.

The monomer reactivity ratios in copolymerization of DVB isomers with m-DBS were calculated, based on the Q and e values obtained from copolymerization of m-DBS with styrene previously reported by us and the Q and e values of DVB derived from Table 1. The estimates are shown in Table 3. It is recognized that copolymerizability of mDBS with m-DVB is similar to that of m-DBS with styrene. The chain transfer constant of m-DBS to styrene is as large as 0.12 [12], to which particular attention must be paid to obtain a copolymer of m-DBS with styrene with high molecular weight. The prepared crosslinked copolymer of m-DBS with m-DVB had a physical strength sufficient to measure the chelate-forming ability of the resin and to remain stable in common operations. The reason for this is believed to be that a sufficiently grown network structure may be formed during the copolymerization reaction. Excellent network-forming characteristics of a combination of m-DVB and m-DBS may be one of the reasons why the copolymer with high

TABLE

molecular weight exhibited good physical strength. The EDTA chelating resin was synthesized from the colpolymer of m-DBS with m-DVB (V) in the following manner. Copolymer V was aminated with IDAE (ethyl iminodiacetate) and the product was then hydrolyzed to form an EDTA chelating resin (see Fig. 2). The amination is a key step in preparing EDTA chelating resin since the capacity of the chelating resin to adsorb metals depends mainly on this step. It is expected that amination of copolymer V would not proceed as easily as that of the copolymer of VBC with m-DVB. This is because vicinal dibromo compounds tend to undergo elimination under basic conditions. It was expected further that the rate of amination would be low since IDAE is a weak amine (pK, = 4.9), and steric hindrance would occur because IDAE is a rather bulky secondary amine. Intensive experiments were carried out on amination, where temperature, type and amounts of solvent and IDAE were varied. The amination process was traced with time by analyzing the ester group in the resulting resin using IR spectroscopy. Copolymer V was aminated in the presence of various solvents. IDAE loading when using any solvent was lower than that when no solvent was used. Figure 3 shows the change in conversion with lapse of reaction time. The reactions shown in Fig. 3 were carried out in the absence of solvent, using IDAE in a molar amount of 20 times as much as that of m-DBS

3

Estimated values for monomer reactivity ratios in copolymerization of DVB isomers with m-DBS a I>~

M,

M2

rl

‘2

p-DVB m-DVB

m-DBS m-DBS

0.3 0.4

0.3 1.3

E!O,C

a The following sets of e and Q values (in parentheses) were’used for the computation: m-DBS DVB (- 1.42, 3.50), m-DVB (0.69,0.93).

(0.06, 1.3)

I

p-

CWI Fig. 2. Synthes is of EDTA chelating

resin.

15

units present in copolymer V. Curve a is a time-conversion curve where the ratio by weight of m-DBS to rn-DVB is 7" 3, while for curve b the corresponding ratio is 6.53.5. The amination products were hydrolyzed to form EDTA chelating resins. The cation exchange capacities were measured for each of the EDTA chelating resins obtained, and found to be 3.50 m e q / g and 3.22 meq/g. Thus, the peak height ratio (1740 cm-~/795 cm ~) of IR absorption to monitor the amination reaction should be regarded as a qualitative rather than quantitative indication. Elemental analysis of the EDTA chelating resin (from reaction b in Fig. 3) showed nitrogen and bromine contents of 3.1% and 5.5%, respectively. These values correspond to 4.43 m m o l / g of carboxylic acids and 0.34 m m o l / g of m-DBS units present in the resin. Therefore, this is thought to be a reasonable quality resin with little bromine remaining. Further attempts at amination were made using KOH, K2CO 3, etc. as agents for trapping the HBr formed, resulting in no increased loading of IDAE. One reason for this may be that a portion of the reaction sites is hindered sterically, and another may be that elimination of HBr takes place as a side reaction. Actually, the model reaction of m-di-

~

3.5~-

~

a

3.0

2.0

o

,5

0 5 ~'

o

4 mo[

Bromostyrene y 23%

y (15%

Fig. 4. Model reaction using m-dibromoethylbenzene with diethyliminodiacetate.

bromoethylbenzene with IDAE showed that 23% of the product consisted of c~- and ,8bromostyrene (see Fig. 4). In the synthesis of EDTA-chelating resin, formation of double bonds through elimination reactions is very unfavorable. However, built-in double or triple bonds in polymer matrices are very interesting from the standpoint of study of reactive polymers. An examination of elimination and substitution of vicinal dibromo compounds such as m-DBS and copolymer V is in progress and will be reported in the near future. Work is also in progress on ways to avoid possible steric hindrance against loading of IDAE into copolymer V. For instance, an EDTA chelating resin is being prepared through a route in which m-DBS is first reacted with IDAE to form a chelating monomer, followed by its copolymerization with DVB.

2.3. Synthesis of DTTA chelating resin The DTTA chelating resin was synthesized by copolymerizing a triaminostyrene monomer [13] with p-DVB, followed by N-carboxymethylation of the copolymer with bromo-

~- 2.5! "S ~ o

X~--CO2Et ] mcl

q

I

I0 20

I

I

I

I

I

I

30

40

50

60

70

80 Time (hr)

Fig. 3. Time-conversion curve of reaction of copolymer V with diethyliminodiacetate (molar ratio of I D A E to m-DBS units = 20), no solvent being used. (a) Copolymer V, m-DBS: m-DVB = 7 : 3 (wt.), reaction temperature 120°C: (b) copolymer V, m-DBS : m-DVB = 6.5:3.5 (wt.), reaction temperature 130°C.

N H,N

N

NH,

H2N

NFI~

HO2C'~

H~'~ C02H

CO2H

Fig. 5. Synthesis of D T T A chelating resin.

16 H +H2N N

L, A'kY'°mi°°

N ' ~ A NH2

y

NH2

N THF

~---~NH2

Fig. 6. Synthesisof triaminostyrenemonomerVIII.

acetic acid (see Fig. 5). The triaminostyrene monomer, VIII, was synthesized by addition of diethylenetriamine to p-DVB in tetrahydrofuran solution, in the presence of lithium alkylamide as catalyst (see Fig. 6). This reaction proceeds selectively in a dual sense. Addition occurs at the central nitrogen atom of the diethylenetriamine molecule at a much higher rate than at the terminal nitrogen atoms. One of the double bonds of p-DVB is aminated, but loss of the other by amination essentially does not occur. Thus, monomer VII1 can be prepared selectively. The reason why a p-DVB molecule undergoes a single amination is as follows. Once diethylenetriamine forms an adduct with pDVB at one of the two double bonds, the newly formed substituent on the para-position acts so as to increase the electron density of the remaining double bond due to an electron-donating effect. Addition of the amine to the remaining double bond is effectively hindered since this reaction is nucleophilic, thereby allowing monomer VIII to be selectively formed [23,24]. The situation is reversed in the case of bromine addition to p-DVB since the reaction is electrophilic, as described in the previous report [12]. Copolymer IX was obtained by copolymerizing triaminostyrene monomer VIII with pDVB. The extent of the reaction can be seen by measuring the anion exchange capacity of the copolymer formed. The obtained copolymer IX had an anion exchange capacity of 6.2 meq/g. Both the starting monomer VIII and p-DVB contributed to formation of the copolymer, each at 100% conversion. Its anion exchange capacity would be 7.5 m e q f g if all the amino groups of the copolymer acted as anion exchange groups. Accordingly, the

measured value of 6.2 m e q / g instead of 7.5 m e q / g indicates that addition of protons occurred at about 76% of all the amino groups present in the triaminostyrene units of copolymer IX. The synthesis of the DTTA chelating resin X is completed by N-carboxymethylation. The reaction was examined using various haloacetic acids or esters represented by the formula: XCHz-COzRin which X represents C1 or Br, and R represents H or an ethyl group. It was found that bromoacetic acid gave the best yield of all. Haloacetic esters are generally not suitable for this N-carboxymethylation since amide formation proceeds competitively, as confirmed by IR spectroscopy. Use of alkali and potassium iodide together with bromoacetic acid was found to increase the conversion. Alkali was considered to work as a trapping agent for the HBr formed as the reaction proceeded, and potassium iodide as a catalyst for N-carboxymethylation. The structure of DTTA resembles that of DTPA very much, in that the former corresponds to the latter with one of the acetic acid groups removed. Chelate ligands with a DTTA structure have not yet been reported; however, DTPA has been reported [1-3] as a chelate ligand. The separation of rare-earth elements using the three congeneric chelating resins synthesized has been conducted; results will be described in the next report.

3. E X P E R I M E N T A L

Preparation of uinylbenzyl chloride (VBC) The method of Hoffenberg [21] was followed. Vinyltoluene and chlorine were preheated separately to 550°C in a steam atmosphere. The preheated vinyltoluene was charged into a reaction vessel at a rate of 4 mol/h, and the preheated chlorine at a rate of 2 mol/h. The reactants were mixed and re-

17 acted at 550°C. The residence time of the reactants in the vessel was 0.7 s. The reaction product was analysed by gas chromatography, by which it was found that 52% of the charged vinyltoluene was converted resulting in a VBC product with a purity of 72%. The crude VBC product was distilled under reduced pressure (10 mmHg) three times to obtain a purified VBC product with a final purity of 96.2%.

Copolymerization of t~invlbenzyl chloride with m-dit,invlbenzene (m-D VB) A solution was prepared by diluting a mixture consisting of 200 g of VBC and 20 g of m-DVB with 300 g of ethyl benzoate and adding 1.5 g of AIBN to the diluted mixture. Separately, 2.5 1 of an aqueous solution containing 2% of sodium chloride and 1% of polyvinylalcohol was prepared. The above solutions were mixed and swirled to form a homogeneous suspension, The suspension was heated, under stirring, at 70°C for 3 h and then at 85°C for 5 h to complete copolymerization. The produced copolymer was filtered off, washed with water, methanol and acetone in succession, and dried at 6 0 ° C / 2 m m H g to obtain 203 g of a purified copolymer, [I].

Reaction o1 copolymer I with diethyl iminodia('etate Into 600 ml of chloroform was placed 150 g of spheres of copolymer I of mesh size 100 300, obtained by classifying copolymer ! obtained above using sieves. To the mixture was added 400 g of IDAE, and it was heated at 80°C for 24 h under agitation. Then, the copolymer was filtered off, and washed with methanol until the unreacted I D A E was removed completely from the copolymer. The IR (KBr tablet) spectrum of the product, !I, exhibited absorption peaks characteristic of the ester at 1750 cm -1, 1200 cm -~ and 1040 cm

1

Hydrolysis of iminodiester copolymer, Ii Two hundred grams of the iminodiester copolymer 1| were put in a solution prepared by mixing 1.2 1 of 0.5 N aqueous N a O H solution with 200 ml of ethanol, and heated at 90°C for 15 h under agitation. Then, the reaction product was filtered off, acidified with 2 N HCI, and washed with sufficient amounts of water and acetone in succession. The IDA chelating resin, 111, obtained had a cation exchange capacity of 4.3 m e q / g , and its 1R spectrum showed a peak attributable to C O : H at 1745 cm ~ and a peak attributed to CO 2 at 1637 cm

Preparation of m-dibromoethvlstvrene, I V One liter of a methylene chloride solution of 130 g of m-DVB was cooled to 5°C or lower, and 320 g of pyridinium hydrobromide perbromide was gradually added to the cooled solution under stirring over a period of 30 min. Stirring was further continued for 1 h, the reaction product was filtered, and the filtrate was washed with 2 1 of water three times to remove the pyridinium hydrobromide formed by extraction. Then, methylene chloride was evaporated and the unreacted m-DVB was distilled off m ~,aeuo ( 3 3 ° C / 1 mmHg) to obtain a light-yellow liquid residue with the following characteristics: b.p. 1 0 1 ° C / 1 mmHg: ~H N M R (CDC13) 3.97 (doublet, 2H), 4.9 5.4 (multiplet, 2H), 5.73 (quartet, 1H), 6.67 (double doublet, 1H), 7.0~ 7.7 (multiplet, 4H).

Copolymerization of m-dihromoethvl styrene with m-dit~invlbenzene A solution was prepared by diluting a mixture consisting of 70 g of m-DBS and 30 g of m-DVB with 240 ml of toluene and adding 1 g of AIBN to the diluted mixture. Separately, 1.5 1 of an aqueous solution containing 2% of sodium chloride and 2% of polyvinylalcohol was prepared. The above solutions were mixed

18 and swirled to form a homogeneous suspension. The suspension was heated, while stirring, at 70°C for 1 h, at 80°C for 1 h and at 90°C for 15 h in succession to complete the copolymerization reaction of the monomers. The produced copolymer V particles were filtered off, washed with water, methanol and acetone, successively, and dried. The IR (KBr tablet) spectrum of the product showed the absorption peak of C - B r at 600 cm -1 (medium).

Reaction of dibromo copolymer V with diethyl iminodiacetate Spheres of dibromo copolymer V larger than 300 mesh but smaller than 100 mesh, which were obtained by classifying the copolymer obtained above using sieves, was heated at 120°C for 40 h under agitation, together with IDAE in a molar ratio of IDAE to DBS of 20 : 1. After cooling, the remaining polymer particles were filtered, and washed with methanol to remove the unreacted IDAE. The IR spectrum of the resulting iminodiester copolymer V| showed absorption peaks characteristic of esters at 1776 cm -1, 1203 cm -~ and 1040 c m - 1.

Hydrolysis of iminodiester colpolymer, VI One hundred grams of the iminodiester copolymer VI were placed in a solution prepared by mixing 500 ml of 1 N aqueous NaOH solution with 50 ml of ethanol, and heated at 90°C for 3 h under agitation. After cooling, the reaction product was filtered off, acidified with 2 N HC1, and washed with sufficient amounts of water and acetone in succession. The produced EDTA chelating resin, VII, had a cation exchange capacity of 3.5 m e q / g , and its 1R spectrum showed a strong peak attributed to -CO2H at 1740 cm -1

Preparation of triaminostyrene monomer, VIII In a 500-ml flask which was flushed with dry nitrogen gas were placed 250 ml of dry

xylene and 58 g (0.56 tool) of dry diethylenetriamine The mixture was cooled down to 5°C, and 45 ml of 15% n-BuLi was added dropwise to the mixture over 5 minutes with stirring. Conversion of a p o r t i o n of diethylenetriamine to lithium alkylamide occurred immediately, evolving n-butane. One hundred grams (0.73 mol) of p-DVB were added to the mixture which was kept cooled and stirred. The stirring was continued for 1 h, then, 2 ml of water was added to the mixture to stop the reaction, 750 ml of water was added to the reaction mixture, and the mixture was shaken in a separation funnel and allowed to stand for phase separation. The water phase was washed twice with 150 ml of xylene. Four hundred milliliters of methylene chloride were then shaken with the water phase, allowed to stand, and separated. The extraction with methylene chloride was repeated once more. The collected methylene chloride phase, amounting to about 800 ml, was concentrated under reduced pressure and dried to obtain triaminostyrene monomer in 60% yield. The product was a light-brown, slightly viscous liquid. The triaminostyrene monomer had the following characteristics: 1H N M R ( d 6 DMSO): 1.63 (singlet, 4 H / - N H 2 ) , 2.3-2.7 (multiplet, 1 2 H / > C H 2 ) , 4.9-5.9 (two doublets, 2 H / > = C H 2 ) , 6.4-6.85 (double doublet, 1 H / H - C = C ) , 6.85-7.45 (multiplet, 4 H / p h e n y l ) .

Copolymerization of triaminostyrene monomer VIII with p-D VB A solution was prepared by diluting a mixture consisting of 80 g of the triaminostyrene monomer and 20 g of p-DVB with 250 g of acetophenone and adding 1 g of AIBN to the diluted mixture. Separately, 1.5 1 of an aqueous solution containing 10% sodium chloride and 2% polyvinylalcohol was prepared. The above solutions were mixed and swirled to obtain a homogeneous suspension of the monomers. The suspension was heated, while

19 stirring, at 80°C for 2 h and then at 90°C for 15 h to c o m p l e t e c o p o l y m e r i z a t i o n . T h e resulting g r a n u l a r c o p o l y m e r was filtered off, w a s h e d with w a t e r and m e t h a n o l in succession, and dried to o b t a i n 101.5 g of a purified c o p o l y m e r , IX. T h e resin o b t a i n e d had an a n i o n e x c h a n g e c a p a c i t y of 6.2 m e q / g . T h e I R s p e c t r u m of c o p o l y m e r IX s h o w e d absorption peaks characteristic of a p r i m a r y a m i n e at 1610 cm i ( m e d i u m ) , 1516 cm t ( m e d i u m ) a n d 1460 cm t (medium).

Reaction of diethylenetriarnine copol)'mer IX with bromoacetic acid T o 1.5 I of w a t e r were a d d e d 60 g of c o p o l y m e r IX, 460 g of b r o m o a c e t i c acid ( B r / N = 8 t o o l / t o o l ) , 250 g of p o t a s s i u m iodide and 120 g of K ~ C O 3 ( K z C O ~ / B r = 0.3 t o o l / t o o l ) . T h e m i x t u r e was h e a t e d at 50°C for 90 h with stirring. A f t e r cooling, the c o p o l y m e r was filtered off, acidified with 2 N HC1, and w a s h e d with sufficient a m o u n t s of w a t e r and a c e t o n e in succession. T h e D T T A chelating resin had a cation e x c h a n g e capacity of 5.1 m e q / g . T h e IR s p e c t r u m of the p r o d uct s h o w e d a peak a t t r i b u t e d to CO:H (strong) at 1730 cm ~ and a peak a t t r i b u t e d to CO~ (very strong) at 1625 c m - ~ .

4. C O N C L U S I O N

T h e I D A chelating resin is a well k n o w n p r o t o t y p e of a m i n o p o l y a c e t i c acid chelating resins. W e have succeeded in p r e p a r i n g an E D T A chelating resin by use of m-dib r o m o e t h y l s t y r e n e , a novel m o n o m e r described in the previous report, as starting material. It has b e c o m e also a p p a r e n t that the p - a m i n o e t h y l s t y r e n e derivatives d e v e l o p e d in recent w o r k are useful as starting materials for p r e p a r a t i o n of a m i n o p o l y a c e t i c acid chelating resins, and that a D T T A chelating resin can be p r e p a r e d in this way.

5. A C K N O W L E D G M E N T T h e a u t h o r s would like to t h a n k Prof. T. T s u r u t a of the Science Universit~ of T o k y o for instruction in the synthesis of the m o n o m e r used as starting material in p r e p a r i n g the D T T A chelating resin, and for his valuable advice in helping to u n d e r s t a n d the p h e n o m ena o b s e r v e d in the course of p o l y m e r i z a t i o n reactions for syntheses of the chelating resins.

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