- Email: [email protected]
Synthesis and properties of ion-exchange resins based on phenol ethers
1974
N. N. K U Z N E T S O V A
et al.
16. L. P. GAVRILOVA, A. S. SPIRIN and A. N. BELOZERSKII, Dokl. Akad. Nauk SSSR 12: 1121, 1959 17. A. S. SPIRIN and L. S. MIL'MAN, Dokl. Akad. l~auk SSSR 134: 717, 1960 18. A. R. PLACOCKE and I. O. WACKER, J. Molek. Biol. 5: 564, 1962 19. P. FLORY, Principles of Polymer Chemistry, N. Y. 1953 20. V. N. TSVETKOV and E. V. FRISMAN, Dokl. Akad. Nauk SSSR 97: 647, 1954 21. E. V. FRISMAN, Dissertation, 1964 22. T. M. BIRSHTEIN, Dissertation, 1960
SYNTHESIS
AND
PROPERTIES ON
OF ION-EXCHANGE
PHENOL
RESINS
BASED
ETHERS*
N. N. KUZNETSOVA, A. A. VANSHEIDT (dec.), K. :P. PAPUKOVA and A. N. LIBEL' Institute for High Molecular Weight Compounds, U.S.S.R. Academy of Sciences (Received 8 July 1966)
POLYCONDENSATION ion-exchange resins are usually obtained by the reaction
of formaldehyde with phenols containing sulpho-, carboxyl, or amino-groups in the benzene nucleus. We have synthesized a series of ion-exchange resins which do not contain free phenolic hydroxyl groups, by the action of formaldehyde on phenol ethers of the form CeH~OCH2X or CeHsOCH2CH~X with functional groups (X) in the aliphatic chain joined to the aromatic nucleus through an ether oxygen. Ion-exchange resins obtained by this method are distinguished by higher chemical stability as compared with ion-exchange resins containing phenol hydroxyl groups. Moreover, the functional groups in such ion-exchange resins, being connected to the aromatic nucleus not directly but through --OCH2-- or --OCH2CH ~ - groups, are distinguished by great mobility: this contributes towards an improvement of the sorption properties of the ionexchange resins, especially in the case of the absorption of multicharged ions. New grades of polycondensation ion-exchange resins with various functional groups, and their exchange c~pacities, are shown in Table 1. The synthesis of the ion-exchange resins is accomplished by the polycondensation of formaldehyde with compounds containing phenoxy groups in the ~- or fl-positions relative to the carbon atom joined to the ion-exchange group: phenoxyacetic (PAA) [1], ]~-phenoxyethylsulphonic (PSA) [2], ]~-phenoxyethylphosphinie (:PEA) [3] acids, and a quaternary salt, tr!methylphenoxyethylammoniumchloride * Vysokomol. soyed. A9: No. 8, 1751-1757, 1967.
Synthesis and properties of ion-exchange resins based on phenol ethers
1975
(PAC) [4]. The ion-exchange resins obtained are monofunctional; phenol hydroxyl groups are absent from them. Synthesis and properties of monomers. The monomers used for the synthesis of the ion exchange resins were known and some of them have been briefly characterized. We have defined more accurately and developed in greater detail TABLE 1. ION-EXCHANGE RESINS
Designation of resin
PAA PSA PEA
Active groups
Exchange capacity, mg-equiv/g for 0-1 NaOH
COOH --SO.H -
-
-
-
PO.H~
NaC1
5"9-6"0 --
8.3-8-4
4.2-4-3 3.7-3'8
+
PAC
--N(CH.).
-
Monomers
3.9-4.0
-
C6HsOCH2COOH C6HsOCH~CH2SOsH C6HsOCH2CI-I2PO,H2 + CeH~0CH~CH~N(CH3)3C1-
methods for the synthesis of PAA, P E A and PSA, and have discovered a method of obtaining quaternary salts based on phenoxychloroethane. In the literature, only one method is known of obtaining this compound, on the basis of phenoxybromoethane. The method developed is of interest not only for the synthesis of this particular monomer, but also in general for obtaining quaternary ammonium salts with an aliphatic or with an aliphatic-aromatic chain on the basis of alkyl chlorides and arylalkyl chlorides [5]. TABLE 2. MONOMERS
Formula
C6HsOCH,COOH CsHsOCH,CH~SOaH CeHsOCH,CH2POsI-I2 + C~H5OCH,CH2N(CH3)aC1
Melting pont, oC
Initial products: CeH~OI-I and
Yield, %
111-132
C1CH,COOH CII212CCH2C1;Na,SO3 (C2HsO)aP; BrCH,CH3Br
70 1 80 2 60 3
132.5
C1H,CCH,C1; N(CH3)3
80 4
9~-99
The characteristics of the monomers and the initial products for their synthesis are shown in Table 2. As m a y be seen from Table 2, the synthesis of the monomers is accomplished from quite readily obtainable substances with good yields. Titration curves of the monomers (Fig. 1) indicate t h a t PAA is a weak acid, but considerably stronger t h a n acetic acid (the step in the titration is at pH
N. N. KUZNETSOVA et at.
1976
~-4.6-10); PSA belongs to the strong acids (step at pHi--3-10); P E A is a dibasic acid of average strength with the first dissociation Step at p ~ : 5 and the second p:H:10.0.
I
--X~'~O
J I
0
I
10
I
I
20
I
I
30
I
I
¢0
I
l
I
50
O!N KOH,ml FIG. I. Titration curves: 1--PAA; 2--PEA; 3--PSA.
The infrared spectra of the monomers (Fig. 2) differ principally in the absorption band regions corresponding to the various ion exchange groups: the absorption band corresponding to the free COO~I group is absent in the spectrum of PAA, b u t there is a wide intense absorption in the region of 2700-2500 cm -1, which is characteristic of OH groups joined b y hydrogen bonds. The spectrum of PSA has a number of intense absorption bands in the region of 1350-1000 cm -1, corresponding to the hydrated sulpho-group, together with a wide absorption band for sorbed water in the region of 3600-3200 cm -1. Association involving OIt groups is typical of PEA. There is in its spectrum a wide absorption band of considerable intensity with a maximum in the region of 2900 cm -1, pointing to the presence of strong intermo]ecular hydrogen bonds between OH groups.
Polycondensatio~ of mo~omers and structure of the three-dimensional polymers (ion-exchange resins). With the aim of synthesizing ion-exchange resins, an examination was made of the possibility and conditions for the polycondensation of the monomers obtained with formaldehyde, in particular to determine the reaction rate from the amount of reacted formaldehyde. The determination of the uncombined formaldehyde was carried out in the presence of the polycondensation products b y the sulphite method. The reaction was carried out with a molar ratio of formaldehyde to phenoxy compound of 0.9 : 1 in the presence of a 1 hydrochloric acid solution at 100°C (Fig. 3). As may be seen from the curves for the rate of polycondensation, considerable differences are observed in the reaction capacities of the monomers with respect to formaldehyde. The polycondensation rate of the monomers falls in the following order: P S A ~ P E A ~ > P A A ; P A C > C~HsOCH~C}~NII(CH3)~CI-. The different rates of combination of formaldehyde with the monomers, which differ only in the degree of dissociation of the ion-exchange groups, are
Synthesis and properties of ion-exchange resins based on phenol ethers
1977
probably caused by the different hydrogen ion concentrations in the reaction medium, as usually occurs in the phenol-formaldehyde polycondensation in an acid medium.
60 2o I
r
I
J
t
I
I
I
I
1
1
i
J
I
f
f
t
I
I
E
P
I
t
I
100 8O
~ fO0 8O 0
]
NO-
6O
0 '
~oo
[
3200
I
NO0
I
I
I
t
]
P
1800
1700
1500
1300
[100
800
700 "9, c m -z
FIG. 2. Infrared spectra: a - - P A A ; b--PEA; c--PSA; d--PAC.
The highest polycondensation rate, observed for :PSA, may be explained by its considerable dissociation under the polycondensation conditions, t E A , which is an acid of average strength, takes up an intermediate position with respect to polycondensation rate between the sulphonic and earboxylic acids. The rate of combination of formaldehyde with 1)AA is very much less, since under the polycondensation conditions in the presence of hydrochloric acid its dissociation is insignificant. Polycondensation of the salt proceeds even more slowly, and there is thus not observed any marked difference in the reaction rates of the quaternary ammonium salt and of anisole [6]. The polymers formed in the initial stages take the form of liquid polycondensation products, changing towards the end of the reaction, practically at complete combination of the formaldehyde, into solid brittle resins soluble in alkalis.
1978
N . N . KUZNETSOVAet
al.
The polycondensation reaction between the monomers and f()maldehyde takes place similarly to the polycondensation reaction in phenol formaldehyde novolacs according to the equation: nCH20 + (n ~- 1 )CsHsOR ->nil ~O ~- H[C6H.(OR)CH2].CeH4OR
( 1)
where R is the functional group. With the polycondensation of formaldehyde with PA)~ as example [ 1] we established the structure (1) indicated for the soluble resins, in which n CH 2 groups are combined with (~-~1) aromatic nuclei. It was established that when the molar ratio of the phenoxy acid to the formaldehyde in the initial mixture is increased from 1.0 : 1 to 1.3 : 1, a reduction is observed in the molecular weight and average coefficient of polycondensation, as well as in the melting point. Thus in all cases more than 1 mole of PAA was combined with 1 mole of reacted formaldehyde (from 1.2 to 1.4).
~ 100l ~
3
oo
0
2
4
5'
8
10
Time,hP
FIG. 3. Rate of polycondensation with formaldehyde: 1--PSA; 2--PEA; 3--PAA; 4-- PAC. Taking into account that erosslinking of soluble resins takes place through further polycondensation of formaldehyde at hydrogen atom positions in the aromatic nucleus, one m a y represent the composition of the three-dimensional polymer or ion-exchange resin in the following form: [--CeH3(OR)CH,--]n
[--C6H2(OR)CH,--] m[--CsH~(OR)CH,--]
i where R is-- C~2X
or -- CH~CI~I2X;
.....
l CH2 l X is a functional group; m is the number
of
units of the chain taking part in the crosslinking. For weakly-linked resins, m is close to zero. Then the composition of the elementary unit will approximate to the composition of a linear molecule in which t h e r e are n CtI~ groups to n aromatic nuclei. Therefore we usually calculated the theoretical capacity b y starting from an elementary unit of composition
Synthesis and properties of ion-exchange resins based on phenol ethers
1979
--Cs:Ha(OR)CH~-- , taking into account that the exchange capacity changes slightly during crosslinking. Thus the maximum possible theoretical number of CH 2 groups for each aromatic nucleus in the three-dimensional polymer is 1.5, whereas a single C~I 2 group will go with a single aromatic nucleus in the linear polymer with an infinitely large molecular weight. For example, for the ion-exchange resin based on PAA, the theoretical capacity in the first case (M of the elementary unit equal to 170) is 5-90 mg-equiv/g, and in the second case (M of the unit equal to 164) 6.09 mg-equiv/g, i.e the relative change in the capacity is altogether only 3%, depending on the degree of crosslinking. In practice, this value should be even still smaller, since the number of CH~ groups for each aromatic nucleus in three dimensions is much smaller than 1.5. Synthesis of ion-exchange resins and their principal properties. Generally we obtained the ion-exchange resins either in two stages b y the method of synthesizing a fusible and soluble product and hardening it (PAA), or in a single stage without separation of a fusible polycondensation product (PSA, PEA, PAC). In the first case, the polycondensation was carried out with a ratio of formaldehyde to monomer equal to 0.9 .~1, in the presence of 3 - 5 % hydrochloric acid at 100°C until a resin was obtained which solidified on cooling to room temperature. After washing with water to remove unreacted monomers and drying, paraformaldehyde and 3-5~/o of 50~/o sulphuric acid as catalyst were introduced into the resin. In carrying out the reaction in a single stage, the formaldehyde (in the form of formalin or paraformaldehyde) was introduced straight away with the necessary quantity of formaldehyde for hardening, the reaction thus proceeding until a gel was obtained. The finely divided soft gel or the molten resin with paraformaldehyde dissolved in it was hardened b y heating at 100-130°C until a solid product was obtained; the product was then crushed to obtain a grain size of 3-5 mm and hardened as granules at 120°C to the required coefficient of swelling. After being crushed again to a grain size of 0.5-1.0 ram, the product was subjected to the customary processing. In the case of the strongly basic anion-exchange resin, the latter was treated with water instead of alkali to retain the initial capacity; the yield amounted to 80-90~/o. The ion-exchange resins obtained took the form of grains with an irregular shape, yellow or dark brown in colour, with good or satisfactory machanical strength, and swelling in water or aqueous solutions of alkalis or acids. Different degrees of swelling were achieved in the ion-exchange resins not only b y varying the quantity of formaldehyde introduced into the reaction mixture, but also b y changing the conditions under which the resins were hardened, in particular the temperature, amount of catalyst and duration of the reaction. Figure 4 gives the change in the swelling of ion-exchange resins based on PAA and PEA, in water and alkali respectively, the resins being obtained under the same conditions b u t with varying amounts of formaldehyde. As m a y be seen, ion-exchange resins capable of swelling strongly in water
1980
N. N. KUZN-ETSOVA st al.
or alkali are f o r m e d with a slight excess of f o r m a l d e h y d e as c o m p a r e d with t h e q u a n t i t y required to f o r m a linear p o l y m e r , which occurs when 1 mole of formald e h y d e is c o m b i n e d with 1 mole of t h e phenol c o m p o n e n t . W i t h 1.1-1.2 moles o f f o r m a l d e h y d e , the swelling of the resin falls s h a r p l y a n d t h e n decreases slowly as the c o n c e n t r a t i o n of f o r m a l d e h y d e in t h e initial m i x t u r e increases. B
Q
B
20'
b
8
o I
I
I
I
i
1'0
I
1'4
I
I 1"8
I A
FIG. 4. Change in swelling coefficient (B) as a function of crosslinking: a--ion-exchange resin based on PSA in water; b--ion-exchange resin based on PEA in 1 N KOH. A is the number of moles of CH20 for each mole of PSA and PEA respectively in the initial mixture. B y changing t h e a m o t m t of f o r m a l d e h y d e or the conditions o f h a r d e n i n g it is possible to v a r y the swelling of the resins more widely whilst retaining mechanical strength. The f o u n d a n d calculated e x c h a n g e capacities of the ion-exchange resins are shown in Table 3. TABLE
3. E X C H A N G E
CAPACITY (~) OF I O N - E X C H A N G E RESINS
s, mg-equiv/g Ion-exchange resin based on
Functional groups
Method of determination found
calculated
PAA
-- C O O H
5"9-6"0
6.10
PSA
--SOsH
4.2-4.3
4.65
PEA
--PO,H,
8.3-8.4
9.35
PAC
+ --N(CH,),
3.9-4.0
4.40
Titration of the resin" with 0.2-0"5 N NaOH in 0'5 N CH3COONa with phenolphthalein Titration of the resin with 0.2-0"5 N NaOH in 10% NaC1 with methyl orange Titration of the resin with 0.2-0.5 N NaOH in a saturated NaC1 solution with thymolphthalein Elution of C1- from the resin with 10~o NaOH8 and titration of the elutriate by Volhardt's method
Synthesis and properties of ion-exchange resins based on phenol ethers
1981
As m a y be seen from Table 3, for the carboxyl and sulphonic cation-exchange resins, the capacity found amounts to 97-98% of the calculated value; under the conditions mentioned, only 90% of the acid groups are determined in the phosphoric acid ion-exchange resin [7]. In the strongly basic anion-exchange resin, the capacity found amounts to 90% of the calculated, clearly because of the partial decomposition of the quaternary ammonium group (separation of trimethylamine) under the conditions of synthesis. Titration curves (Fig. 5) are given for the air-dried specimens. Taking into account the moisture content of the resins (for the resin based on PA.A, 2"0~o; PSA, 18"2~/o; P E A 4.05~/o) the same values of exchange capacity are obtained. The principal characteristics of the thermal stability of the ion-exchange resins were obtained b y comparison of the exchange capacity before and after the resin had been heated to different temperatures (Table 4). TABLE
4.
C H A N G E I N E X C H A N G E C A P A C I T Y OF I O N - E X C H A N G E R E S I N S ON H E A T I N G I N A I R
Exchange capacity, mg-equiv/g Ion-exchange resin based on
PSA
before heating
4.40
after heating 8 hr at the following temperatures, °C 100
120
4"30
130
140
150 Decomposes 5.60 7.60 3.5
4"10
3"80
3"75
5"80
5'80 8"05
5"80 7.80
i
PAA PEA PAC (Cl-form)
5.80 8"30 4.0
5"80 8-30 4.0
8.1o
3"9
I
--
When the specimens were heated in air for 8 hours at 100°C, the exchange capacity was slightly altered only in the case of the sulphonic cation-exchange resin, in which the relative loss of exchange capacity amounted to about 1%. As the temperature was raised from 120 to 140°C, no decrease in exchange capacity was observed in the resin based on PAA, and for the resins based on P E A and PAC, a gradual and very slight reduction in capacity took place. The greatest loss in relative exchange capacity at temperatures above 100°C was observed in the case of the sulphonic ion-exchange resins. The chemical stability of the ion-exchange resins was determined b y compar. ison of the exchange capacity before and after treating the resin with 5 ~ sulphuric acid and alkali of various concentrations at 100 and 20°C, as well as in contact with oxidizing agents (see Table 5). The carboxyl and phosphoric acid ion-exchange resins have an adequately high chemical resistance. Their exchange capacity does not change even on heating with concentrated solutions of acids alkalis. The sulphonic cation-exchange
iNT. N. KUZNETSOVA et al.
1982
resin based on PSA is stable to the action of alkaline solutions at room temperature, and slightly loses exchange capacity when h e a t e d with 5 N I-I~SO4. The sulphonic cation-exchange resin is not resistant to being heated in concentrated alkali solutions. TABLE
5. C H E M I C A L
RESISTANCE
OF ION-EXCHANGE
RESINS
Exchange capacity, mg-equiv/g Ion-exchange resin based on
before treatment
after heating at 100°C for 30 min with 5NNaOH
PAA PSA PEA
5.8 4.4 8.4
in contact at 20°C 48 hr with 24 hr with 48 hr with 1 ~; N a 0 H 4 N N a O H 10% H~O~
5NH~SO4
5.8 2.7
5.8 4.0
8"4
8"4
8.4
4"4 8'4
5.8 4-4 8.4
The thermal and chemical stability of the strongly basic anion-exchange resin obtained is comparable with the stability of the strongly basic anionexchange resins Dowex-1 and AB-17 and is caused principally by the lack of resistance of the quaternary ammonium group to heat and alkalis. pH 12
1,2
,....,-.-,--,
3
.,.~5
10 8
S
~).*"
I
0 ~ - ~ u i ~ HCI g of resin 4
[
4
I
!
I
8 rng-equi~KOH g of resin
FIG. 5. Titration curves of ion-exchange resins: 1, 2--resin based on PAC and blank experiment; 3-- resin based on PAA; 4-- resin based on PSA; 5--resin based on P E A .
CONCLUSIONS New ion-exchange resins have been synthesized by the polycondensation o f f o r m a l d e h y d e w i t h p h e n o l e t h e r s o f t h e f o r m C e t t s O C H ~ X o r CeI-IsOCH2CH~X w h e r e X i s o n e o f t h e f o l l o w i n g f u n c t i o n a l g r o u p s : C O 0 ~ I , - - S08I-I, - - P 0 3 I - I 2 ,
~1~(CH3)3.
Radiation graft eopolymerization of glycidyl methaerylate to polyethylene
1983
T h e ion-exchange resins o b t a i n e d contain t h e active groups in t h e side alip h a t i c chain, c o n n e c t e d with t h e a r o m a t i c nucleus t h r o u g h a n o x y g e n a t o m ; as distinct f r o m the existing p o l y c o n d e n s a t i o n exchange resins, t h e y do n o t contain phenolic h y d r o x y l groups. Methods of synthesis h a v e been d e v e l o p e d a n d t h e properties of the coresponding m o n o m e r s h a v e been studied. Differences in the reaction capacities of the m o n o m e r s with respect to f o r m a l d e h y d e , a n d the conditions of t h e i r p o l y c o n d e n s a t i o n h a v e b e e n investigated. T h e struct u r e b o t h of soluble, a n d also of the three-dimensional polymers, has been given. The principal characteristics of the ion-exchange resins h a v e been presented.
Translated by G. F. MODLE~ REFERENCES
1. A. A. VANSHEIDT and N. N. KUZNETSOVA, Zh. prikl, khimii 32: 868, 1959; Authors' certificate, 114231, 1959; Byull. izobretenii, :No. 7, 49, 1958 2. N. N. KUZNETSOVA, A. A. VANSHEIDT and K. P. PAPUKOVA, Zh. prikl, khimii 37: 1624, 1964; Authors' certificate, 139827, 1960; Byull. izobretenii, :No. 14, 47, 1961 3. N. N. KUZNETSOVA, A. A. VANSHEIDT and K. P. PAPUKOVA, Zh. prikl, khimii 39: 2008, 1966; Authors' certificate, 173935, 1964; Byull. izobretenii, :No. 16, 81, 1965 4. N. N. KUZNETSOVA, A. A. VANSHEIDT and K. P. PAPUKOVA, Authors' certificate, 169787, 1963; Byu]l. izobretenii, :No. 7, 103, 1965 5. N. N. KUZNETSOVA, A. A. VANSHEIDT and K. P. PAPUKOVA, Zh. prild, khimii 39: 1529, 1966 6. A. A. VANSHEIDT, N. N. KUZNETSOVA and K. P. PAPUKOVA, Zh. prikl, khimii 32: 2699, 1959 7. L. FREEDMAN and Q. O. DOOK, Chem. Revs. 57: 479, 1957
INVESTIGATION OF THE RADIATION GRAFT COPOLYMERIZATION OF GLYCIDYL METHACRYLATE TO POLYETHYLENE* V. YA. KABXNOV, N. M. Y~ZlMIROVX a n d V. I. SPITSYN Institute of Physical Chemistry, U.S.S.R. Academy of Sciences
(Received 11 July 1966) THE aim of t h e present work was the modification of p o l y e t h y l e n e b y t h e m e t h o d o f r a d i a t i o n graft c o p o l y m e r i z a t i o n w i t h a bifunctional m o n o m e r , glycidyl m e t h a c r y l a t e (GMA), as well as t h e clarification o f certain kinetic relations in g r a f t copolymerization. T h e selection of t h e m o n o m e r was d e t e r m i n e d b y t h e * VysokomoI. soyed. A9: No. 8, 1758-1762, 1967.
N. N. K U Z N E T S O V A
et al.
16. L. P. GAVRILOVA, A. S. SPIRIN and A. N. BELOZERSKII, Dokl. Akad. Nauk SSSR 12: 1121, 1959 17. A. S. SPIRIN and L. S. MIL'MAN, Dokl. Akad. l~auk SSSR 134: 717, 1960 18. A. R. PLACOCKE and I. O. WACKER, J. Molek. Biol. 5: 564, 1962 19. P. FLORY, Principles of Polymer Chemistry, N. Y. 1953 20. V. N. TSVETKOV and E. V. FRISMAN, Dokl. Akad. Nauk SSSR 97: 647, 1954 21. E. V. FRISMAN, Dissertation, 1964 22. T. M. BIRSHTEIN, Dissertation, 1960
SYNTHESIS
AND
PROPERTIES ON
OF ION-EXCHANGE
PHENOL
RESINS
BASED
ETHERS*
N. N. KUZNETSOVA, A. A. VANSHEIDT (dec.), K. :P. PAPUKOVA and A. N. LIBEL' Institute for High Molecular Weight Compounds, U.S.S.R. Academy of Sciences (Received 8 July 1966)
POLYCONDENSATION ion-exchange resins are usually obtained by the reaction
of formaldehyde with phenols containing sulpho-, carboxyl, or amino-groups in the benzene nucleus. We have synthesized a series of ion-exchange resins which do not contain free phenolic hydroxyl groups, by the action of formaldehyde on phenol ethers of the form CeH~OCH2X or CeHsOCH2CH~X with functional groups (X) in the aliphatic chain joined to the aromatic nucleus through an ether oxygen. Ion-exchange resins obtained by this method are distinguished by higher chemical stability as compared with ion-exchange resins containing phenol hydroxyl groups. Moreover, the functional groups in such ion-exchange resins, being connected to the aromatic nucleus not directly but through --OCH2-- or --OCH2CH ~ - groups, are distinguished by great mobility: this contributes towards an improvement of the sorption properties of the ionexchange resins, especially in the case of the absorption of multicharged ions. New grades of polycondensation ion-exchange resins with various functional groups, and their exchange c~pacities, are shown in Table 1. The synthesis of the ion-exchange resins is accomplished by the polycondensation of formaldehyde with compounds containing phenoxy groups in the ~- or fl-positions relative to the carbon atom joined to the ion-exchange group: phenoxyacetic (PAA) [1], ]~-phenoxyethylsulphonic (PSA) [2], ]~-phenoxyethylphosphinie (:PEA) [3] acids, and a quaternary salt, tr!methylphenoxyethylammoniumchloride * Vysokomol. soyed. A9: No. 8, 1751-1757, 1967.
Synthesis and properties of ion-exchange resins based on phenol ethers
1975
(PAC) [4]. The ion-exchange resins obtained are monofunctional; phenol hydroxyl groups are absent from them. Synthesis and properties of monomers. The monomers used for the synthesis of the ion exchange resins were known and some of them have been briefly characterized. We have defined more accurately and developed in greater detail TABLE 1. ION-EXCHANGE RESINS
Designation of resin
PAA PSA PEA
Active groups
Exchange capacity, mg-equiv/g for 0-1 NaOH
COOH --SO.H -
-
-
-
PO.H~
NaC1
5"9-6"0 --
8.3-8-4
4.2-4-3 3.7-3'8
+
PAC
--N(CH.).
-
Monomers
3.9-4.0
-
C6HsOCH2COOH C6HsOCH~CH2SOsH C6HsOCH2CI-I2PO,H2 + CeH~0CH~CH~N(CH3)3C1-
methods for the synthesis of PAA, P E A and PSA, and have discovered a method of obtaining quaternary salts based on phenoxychloroethane. In the literature, only one method is known of obtaining this compound, on the basis of phenoxybromoethane. The method developed is of interest not only for the synthesis of this particular monomer, but also in general for obtaining quaternary ammonium salts with an aliphatic or with an aliphatic-aromatic chain on the basis of alkyl chlorides and arylalkyl chlorides [5]. TABLE 2. MONOMERS
Formula
C6HsOCH,COOH CsHsOCH,CH~SOaH CeHsOCH,CH2POsI-I2 + C~H5OCH,CH2N(CH3)aC1
Melting pont, oC
Initial products: CeH~OI-I and
Yield, %
111-132
C1CH,COOH CII212CCH2C1;Na,SO3 (C2HsO)aP; BrCH,CH3Br
70 1 80 2 60 3
132.5
C1H,CCH,C1; N(CH3)3
80 4
9~-99
The characteristics of the monomers and the initial products for their synthesis are shown in Table 2. As m a y be seen from Table 2, the synthesis of the monomers is accomplished from quite readily obtainable substances with good yields. Titration curves of the monomers (Fig. 1) indicate t h a t PAA is a weak acid, but considerably stronger t h a n acetic acid (the step in the titration is at pH
N. N. KUZNETSOVA et at.
1976
~-4.6-10); PSA belongs to the strong acids (step at pHi--3-10); P E A is a dibasic acid of average strength with the first dissociation Step at p ~ : 5 and the second p:H:10.0.
I
--X~'~O
J I
0
I
10
I
I
20
I
I
30
I
I
¢0
I
l
I
50
O!N KOH,ml FIG. I. Titration curves: 1--PAA; 2--PEA; 3--PSA.
The infrared spectra of the monomers (Fig. 2) differ principally in the absorption band regions corresponding to the various ion exchange groups: the absorption band corresponding to the free COO~I group is absent in the spectrum of PAA, b u t there is a wide intense absorption in the region of 2700-2500 cm -1, which is characteristic of OH groups joined b y hydrogen bonds. The spectrum of PSA has a number of intense absorption bands in the region of 1350-1000 cm -1, corresponding to the hydrated sulpho-group, together with a wide absorption band for sorbed water in the region of 3600-3200 cm -1. Association involving OIt groups is typical of PEA. There is in its spectrum a wide absorption band of considerable intensity with a maximum in the region of 2900 cm -1, pointing to the presence of strong intermo]ecular hydrogen bonds between OH groups.
Polycondensatio~ of mo~omers and structure of the three-dimensional polymers (ion-exchange resins). With the aim of synthesizing ion-exchange resins, an examination was made of the possibility and conditions for the polycondensation of the monomers obtained with formaldehyde, in particular to determine the reaction rate from the amount of reacted formaldehyde. The determination of the uncombined formaldehyde was carried out in the presence of the polycondensation products b y the sulphite method. The reaction was carried out with a molar ratio of formaldehyde to phenoxy compound of 0.9 : 1 in the presence of a 1 hydrochloric acid solution at 100°C (Fig. 3). As may be seen from the curves for the rate of polycondensation, considerable differences are observed in the reaction capacities of the monomers with respect to formaldehyde. The polycondensation rate of the monomers falls in the following order: P S A ~ P E A ~ > P A A ; P A C > C~HsOCH~C}~NII(CH3)~CI-. The different rates of combination of formaldehyde with the monomers, which differ only in the degree of dissociation of the ion-exchange groups, are
Synthesis and properties of ion-exchange resins based on phenol ethers
1977
probably caused by the different hydrogen ion concentrations in the reaction medium, as usually occurs in the phenol-formaldehyde polycondensation in an acid medium.
60 2o I
r
I
J
t
I
I
I
I
1
1
i
J
I
f
f
t
I
I
E
P
I
t
I
100 8O
~ fO0 8O 0
]
NO-
6O
0 '
~oo
[
3200
I
NO0
I
I
I
t
]
P
1800
1700
1500
1300
[100
800
700 "9, c m -z
FIG. 2. Infrared spectra: a - - P A A ; b--PEA; c--PSA; d--PAC.
The highest polycondensation rate, observed for :PSA, may be explained by its considerable dissociation under the polycondensation conditions, t E A , which is an acid of average strength, takes up an intermediate position with respect to polycondensation rate between the sulphonic and earboxylic acids. The rate of combination of formaldehyde with 1)AA is very much less, since under the polycondensation conditions in the presence of hydrochloric acid its dissociation is insignificant. Polycondensation of the salt proceeds even more slowly, and there is thus not observed any marked difference in the reaction rates of the quaternary ammonium salt and of anisole [6]. The polymers formed in the initial stages take the form of liquid polycondensation products, changing towards the end of the reaction, practically at complete combination of the formaldehyde, into solid brittle resins soluble in alkalis.
1978
N . N . KUZNETSOVAet
al.
The polycondensation reaction between the monomers and f()maldehyde takes place similarly to the polycondensation reaction in phenol formaldehyde novolacs according to the equation: nCH20 + (n ~- 1 )CsHsOR ->nil ~O ~- H[C6H.(OR)CH2].CeH4OR
( 1)
where R is the functional group. With the polycondensation of formaldehyde with PA)~ as example [ 1] we established the structure (1) indicated for the soluble resins, in which n CH 2 groups are combined with (~-~1) aromatic nuclei. It was established that when the molar ratio of the phenoxy acid to the formaldehyde in the initial mixture is increased from 1.0 : 1 to 1.3 : 1, a reduction is observed in the molecular weight and average coefficient of polycondensation, as well as in the melting point. Thus in all cases more than 1 mole of PAA was combined with 1 mole of reacted formaldehyde (from 1.2 to 1.4).
~ 100l ~
3
oo
0
2
4
5'
8
10
Time,hP
FIG. 3. Rate of polycondensation with formaldehyde: 1--PSA; 2--PEA; 3--PAA; 4-- PAC. Taking into account that erosslinking of soluble resins takes place through further polycondensation of formaldehyde at hydrogen atom positions in the aromatic nucleus, one m a y represent the composition of the three-dimensional polymer or ion-exchange resin in the following form: [--CeH3(OR)CH,--]n
[--C6H2(OR)CH,--] m[--CsH~(OR)CH,--]
i where R is-- C~2X
or -- CH~CI~I2X;
.....
l CH2 l X is a functional group; m is the number
of
units of the chain taking part in the crosslinking. For weakly-linked resins, m is close to zero. Then the composition of the elementary unit will approximate to the composition of a linear molecule in which t h e r e are n CtI~ groups to n aromatic nuclei. Therefore we usually calculated the theoretical capacity b y starting from an elementary unit of composition
Synthesis and properties of ion-exchange resins based on phenol ethers
1979
--Cs:Ha(OR)CH~-- , taking into account that the exchange capacity changes slightly during crosslinking. Thus the maximum possible theoretical number of CH 2 groups for each aromatic nucleus in the three-dimensional polymer is 1.5, whereas a single C~I 2 group will go with a single aromatic nucleus in the linear polymer with an infinitely large molecular weight. For example, for the ion-exchange resin based on PAA, the theoretical capacity in the first case (M of the elementary unit equal to 170) is 5-90 mg-equiv/g, and in the second case (M of the unit equal to 164) 6.09 mg-equiv/g, i.e the relative change in the capacity is altogether only 3%, depending on the degree of crosslinking. In practice, this value should be even still smaller, since the number of CH~ groups for each aromatic nucleus in three dimensions is much smaller than 1.5. Synthesis of ion-exchange resins and their principal properties. Generally we obtained the ion-exchange resins either in two stages b y the method of synthesizing a fusible and soluble product and hardening it (PAA), or in a single stage without separation of a fusible polycondensation product (PSA, PEA, PAC). In the first case, the polycondensation was carried out with a ratio of formaldehyde to monomer equal to 0.9 .~1, in the presence of 3 - 5 % hydrochloric acid at 100°C until a resin was obtained which solidified on cooling to room temperature. After washing with water to remove unreacted monomers and drying, paraformaldehyde and 3-5~/o of 50~/o sulphuric acid as catalyst were introduced into the resin. In carrying out the reaction in a single stage, the formaldehyde (in the form of formalin or paraformaldehyde) was introduced straight away with the necessary quantity of formaldehyde for hardening, the reaction thus proceeding until a gel was obtained. The finely divided soft gel or the molten resin with paraformaldehyde dissolved in it was hardened b y heating at 100-130°C until a solid product was obtained; the product was then crushed to obtain a grain size of 3-5 mm and hardened as granules at 120°C to the required coefficient of swelling. After being crushed again to a grain size of 0.5-1.0 ram, the product was subjected to the customary processing. In the case of the strongly basic anion-exchange resin, the latter was treated with water instead of alkali to retain the initial capacity; the yield amounted to 80-90~/o. The ion-exchange resins obtained took the form of grains with an irregular shape, yellow or dark brown in colour, with good or satisfactory machanical strength, and swelling in water or aqueous solutions of alkalis or acids. Different degrees of swelling were achieved in the ion-exchange resins not only b y varying the quantity of formaldehyde introduced into the reaction mixture, but also b y changing the conditions under which the resins were hardened, in particular the temperature, amount of catalyst and duration of the reaction. Figure 4 gives the change in the swelling of ion-exchange resins based on PAA and PEA, in water and alkali respectively, the resins being obtained under the same conditions b u t with varying amounts of formaldehyde. As m a y be seen, ion-exchange resins capable of swelling strongly in water
1980
N. N. KUZN-ETSOVA st al.
or alkali are f o r m e d with a slight excess of f o r m a l d e h y d e as c o m p a r e d with t h e q u a n t i t y required to f o r m a linear p o l y m e r , which occurs when 1 mole of formald e h y d e is c o m b i n e d with 1 mole of t h e phenol c o m p o n e n t . W i t h 1.1-1.2 moles o f f o r m a l d e h y d e , the swelling of the resin falls s h a r p l y a n d t h e n decreases slowly as the c o n c e n t r a t i o n of f o r m a l d e h y d e in t h e initial m i x t u r e increases. B
Q
B
20'
b
8
o I
I
I
I
i
1'0
I
1'4
I
I 1"8
I A
FIG. 4. Change in swelling coefficient (B) as a function of crosslinking: a--ion-exchange resin based on PSA in water; b--ion-exchange resin based on PEA in 1 N KOH. A is the number of moles of CH20 for each mole of PSA and PEA respectively in the initial mixture. B y changing t h e a m o t m t of f o r m a l d e h y d e or the conditions o f h a r d e n i n g it is possible to v a r y the swelling of the resins more widely whilst retaining mechanical strength. The f o u n d a n d calculated e x c h a n g e capacities of the ion-exchange resins are shown in Table 3. TABLE
3. E X C H A N G E
CAPACITY (~) OF I O N - E X C H A N G E RESINS
s, mg-equiv/g Ion-exchange resin based on
Functional groups
Method of determination found
calculated
PAA
-- C O O H
5"9-6"0
6.10
PSA
--SOsH
4.2-4.3
4.65
PEA
--PO,H,
8.3-8.4
9.35
PAC
+ --N(CH,),
3.9-4.0
4.40
Titration of the resin" with 0.2-0"5 N NaOH in 0'5 N CH3COONa with phenolphthalein Titration of the resin with 0.2-0"5 N NaOH in 10% NaC1 with methyl orange Titration of the resin with 0.2-0.5 N NaOH in a saturated NaC1 solution with thymolphthalein Elution of C1- from the resin with 10~o NaOH8 and titration of the elutriate by Volhardt's method
Synthesis and properties of ion-exchange resins based on phenol ethers
1981
As m a y be seen from Table 3, for the carboxyl and sulphonic cation-exchange resins, the capacity found amounts to 97-98% of the calculated value; under the conditions mentioned, only 90% of the acid groups are determined in the phosphoric acid ion-exchange resin [7]. In the strongly basic anion-exchange resin, the capacity found amounts to 90% of the calculated, clearly because of the partial decomposition of the quaternary ammonium group (separation of trimethylamine) under the conditions of synthesis. Titration curves (Fig. 5) are given for the air-dried specimens. Taking into account the moisture content of the resins (for the resin based on PA.A, 2"0~o; PSA, 18"2~/o; P E A 4.05~/o) the same values of exchange capacity are obtained. The principal characteristics of the thermal stability of the ion-exchange resins were obtained b y comparison of the exchange capacity before and after the resin had been heated to different temperatures (Table 4). TABLE
4.
C H A N G E I N E X C H A N G E C A P A C I T Y OF I O N - E X C H A N G E R E S I N S ON H E A T I N G I N A I R
Exchange capacity, mg-equiv/g Ion-exchange resin based on
PSA
before heating
4.40
after heating 8 hr at the following temperatures, °C 100
120
4"30
130
140
150 Decomposes 5.60 7.60 3.5
4"10
3"80
3"75
5"80
5'80 8"05
5"80 7.80
i
PAA PEA PAC (Cl-form)
5.80 8"30 4.0
5"80 8-30 4.0
8.1o
3"9
I
--
When the specimens were heated in air for 8 hours at 100°C, the exchange capacity was slightly altered only in the case of the sulphonic cation-exchange resin, in which the relative loss of exchange capacity amounted to about 1%. As the temperature was raised from 120 to 140°C, no decrease in exchange capacity was observed in the resin based on PAA, and for the resins based on P E A and PAC, a gradual and very slight reduction in capacity took place. The greatest loss in relative exchange capacity at temperatures above 100°C was observed in the case of the sulphonic ion-exchange resins. The chemical stability of the ion-exchange resins was determined b y compar. ison of the exchange capacity before and after treating the resin with 5 ~ sulphuric acid and alkali of various concentrations at 100 and 20°C, as well as in contact with oxidizing agents (see Table 5). The carboxyl and phosphoric acid ion-exchange resins have an adequately high chemical resistance. Their exchange capacity does not change even on heating with concentrated solutions of acids alkalis. The sulphonic cation-exchange
iNT. N. KUZNETSOVA et al.
1982
resin based on PSA is stable to the action of alkaline solutions at room temperature, and slightly loses exchange capacity when h e a t e d with 5 N I-I~SO4. The sulphonic cation-exchange resin is not resistant to being heated in concentrated alkali solutions. TABLE
5. C H E M I C A L
RESISTANCE
OF ION-EXCHANGE
RESINS
Exchange capacity, mg-equiv/g Ion-exchange resin based on
before treatment
after heating at 100°C for 30 min with 5NNaOH
PAA PSA PEA
5.8 4.4 8.4
in contact at 20°C 48 hr with 24 hr with 48 hr with 1 ~; N a 0 H 4 N N a O H 10% H~O~
5NH~SO4
5.8 2.7
5.8 4.0
8"4
8"4
8.4
4"4 8'4
5.8 4-4 8.4
The thermal and chemical stability of the strongly basic anion-exchange resin obtained is comparable with the stability of the strongly basic anionexchange resins Dowex-1 and AB-17 and is caused principally by the lack of resistance of the quaternary ammonium group to heat and alkalis. pH 12
1,2
,....,-.-,--,
3
.,.~5
10 8
S
~).*"
I
0 ~ - ~ u i ~ HCI g of resin 4
[
4
I
!
I
8 rng-equi~KOH g of resin
FIG. 5. Titration curves of ion-exchange resins: 1, 2--resin based on PAC and blank experiment; 3-- resin based on PAA; 4-- resin based on PSA; 5--resin based on P E A .
CONCLUSIONS New ion-exchange resins have been synthesized by the polycondensation o f f o r m a l d e h y d e w i t h p h e n o l e t h e r s o f t h e f o r m C e t t s O C H ~ X o r CeI-IsOCH2CH~X w h e r e X i s o n e o f t h e f o l l o w i n g f u n c t i o n a l g r o u p s : C O 0 ~ I , - - S08I-I, - - P 0 3 I - I 2 ,
~1~(CH3)3.
Radiation graft eopolymerization of glycidyl methaerylate to polyethylene
1983
T h e ion-exchange resins o b t a i n e d contain t h e active groups in t h e side alip h a t i c chain, c o n n e c t e d with t h e a r o m a t i c nucleus t h r o u g h a n o x y g e n a t o m ; as distinct f r o m the existing p o l y c o n d e n s a t i o n exchange resins, t h e y do n o t contain phenolic h y d r o x y l groups. Methods of synthesis h a v e been d e v e l o p e d a n d t h e properties of the coresponding m o n o m e r s h a v e been studied. Differences in the reaction capacities of the m o n o m e r s with respect to f o r m a l d e h y d e , a n d the conditions of t h e i r p o l y c o n d e n s a t i o n h a v e b e e n investigated. T h e struct u r e b o t h of soluble, a n d also of the three-dimensional polymers, has been given. The principal characteristics of the ion-exchange resins h a v e been presented.
Translated by G. F. MODLE~ REFERENCES
1. A. A. VANSHEIDT and N. N. KUZNETSOVA, Zh. prikl, khimii 32: 868, 1959; Authors' certificate, 114231, 1959; Byull. izobretenii, :No. 7, 49, 1958 2. N. N. KUZNETSOVA, A. A. VANSHEIDT and K. P. PAPUKOVA, Zh. prikl, khimii 37: 1624, 1964; Authors' certificate, 139827, 1960; Byull. izobretenii, :No. 14, 47, 1961 3. N. N. KUZNETSOVA, A. A. VANSHEIDT and K. P. PAPUKOVA, Zh. prikl, khimii 39: 2008, 1966; Authors' certificate, 173935, 1964; Byull. izobretenii, :No. 16, 81, 1965 4. N. N. KUZNETSOVA, A. A. VANSHEIDT and K. P. PAPUKOVA, Authors' certificate, 169787, 1963; Byu]l. izobretenii, :No. 7, 103, 1965 5. N. N. KUZNETSOVA, A. A. VANSHEIDT and K. P. PAPUKOVA, Zh. prild, khimii 39: 1529, 1966 6. A. A. VANSHEIDT, N. N. KUZNETSOVA and K. P. PAPUKOVA, Zh. prikl, khimii 32: 2699, 1959 7. L. FREEDMAN and Q. O. DOOK, Chem. Revs. 57: 479, 1957
INVESTIGATION OF THE RADIATION GRAFT COPOLYMERIZATION OF GLYCIDYL METHACRYLATE TO POLYETHYLENE* V. YA. KABXNOV, N. M. Y~ZlMIROVX a n d V. I. SPITSYN Institute of Physical Chemistry, U.S.S.R. Academy of Sciences
(Received 11 July 1966) THE aim of t h e present work was the modification of p o l y e t h y l e n e b y t h e m e t h o d o f r a d i a t i o n graft c o p o l y m e r i z a t i o n w i t h a bifunctional m o n o m e r , glycidyl m e t h a c r y l a t e (GMA), as well as t h e clarification o f certain kinetic relations in g r a f t copolymerization. T h e selection of t h e m o n o m e r was d e t e r m i n e d b y t h e * VysokomoI. soyed. A9: No. 8, 1758-1762, 1967.