Synthesis of Copolycarbonates from Bisphenol A and Tetrachlorobisphenol A by Successive Addition of Monomers Koji lkeda and Yoshiro Sekine" Department of Chemistry, School of Science and Engineering, TT-aseda University, Sishi-Ohkubo, Shinjuku-ku, Tokyo, Japan
A one-step synthesis of copolycarbonates with good properties from bisphenol A (BPA) and tetrachlorobisphenol A (TCBPA), the two differing in reactivity, was studied. With proper selection of reaction variables such as pH, emulsifier, and catalyst, the reaction was carried out b y introducing phosgene at a low rate for a period which was identical with the phosgenation period in homopolycondensation of TCBPA while successively adding more of TCBPA in the initial stage and BPA alone in the final stage. Changes in the per cent chlorine content follow the equation for composition of copolymers in radical polymerization, and copolymers having any desirable composition with a given chlorine content were prepared. The copolymers thus prepared contain short block chains, are uniform in chemical composition, and exhibit excellent thermal stability and other properties.
F o r the improvement of certain properties of polycarljonates such as resistances to crazing and cracking under tensile strain or in immersion in solvents, glass transition temperature T,, aiid thermal stability 11-ithout sacrificing the well-balanced properties knovin for polycarbonates, ail introduction of rigid chains containing some polar groups int,o the polymer chain by way of copolymerizatioii seems necessary to give a n antiplastication effect. Tetrachlorobisphenol ,\ (TCBPA) which can be prepared from bisphenol -4 (BPA) by chlorination appeared to serve this purpose best in the light of its properties aiid reactivity, and it was hence planned to devise a process which is applicable to this copolymerization 011 a commercial scale. If a process were developed which would allow preparation of a copolymer, which has a given compositioii and is chemically uniform, from any monomer, it ~ o u l dbe an extremely significant aehievemeiit from the commercial standpoint. I n case the phosgene process which is ill commercial use today is applied t o the synthesis of copolycarboiiates, a copolymer richer in the more reactive monomer is formed because of the difference in monomer react,ivity, and it is frequently the case that the copolymer formed differs from the monomer feed in composition. I t is thus not possible to obtain good copolymers in this manner. A patent issued to Eastman Kodak (1963) attempted to solve this problem by a tu-0-step process by first prepariiig a prepolymer of each monomer separately and theii polymerizing such prepolymers to a block copolymer. The copolymers prepared in accordance with this patent are claimed to have a high modulus of elasticity, a high degree of flexibilit,y, and a high heat deflection temperat'ure and differ from the so-called random copolymers which have been prepared by simply polymerizing a mixt,ure of TCBPA aiid BPA\and hence have suffered some deterioration in properties. I t would uiidoubtedly be a great advantage commercially if the synthesis of copolymers could be carried out in one step, namely, phosgeiiatiori, and if polycondensation could be performed in succession in the same reaction vessel, as in the preparation of 202
Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
ordinary polycarbonates without resorting to the two-step process mentioned above. To realize such a one-step synthesis, hoivever, we must deal with the problem of controlling the relatire reaction rate of two monomers which differ considerably from each ot'her in reactivity; this may be done by controlling the coilcentration of monomers during the react'ion. Hence, a new process \vas developed which was designed t o add monomers successively in the step where low molecular weight polymers are formed by phosgenation. The oligomers formed were further condensed t o yield chemically uniform copolymers having short block chains. The copolymers prepared by t'his procedure were shown to have excellent properties. The results will be reported belon-. Experimental Section Materials and Reaction Apparatus. Bisphenol A (BPA).
Commercial bisphenol A was recrystallized twice from xylene; m p 154-1 56". Tetrachlorobisphenol A (TCBPA). Hisphenol 1 was chlorinated and recryst,allized from n-hexane; m p 132.5134.5' (Ikeda and Sekine, 197313). Phosgene. Commercial phosgene supplied in cylinder was used. As show1 in Figure 1, t h e reaction apparatus v-as a 1-1. fivemouthed separable glass flask which was equipped with a set of two columns B and T (each provided with a stirrer a t the top), a stirrer, a gas inlet tube, a reflux condenser, a thermometer opening, and an opening for sampling, pH measuremelit', and pH control. The flask was immersed in a constanttemperature bath maintained a t 25". M e t h o d of Addition of Monomers. I n the synthesis of the copolycarbonate from BPA and TCBPX, the reaction may most,ly occur a t t,he interface because t h e solubilities of both the phenoxide in the organic phase and the chloroformate group in the aqueous phase are small (LIorgan, 1965,-e). The resistance t o diffusion seems t,o be small in t'he phosgenation step where loiv molecular weight polymers are formed, and the effect,s of hydrolysis can be minimized by
Table 1. Monomer Emulsion Systems for BPA (B) and TCBPA (T). n l e t f o r COCI, -I(from cylinder)
Condenser O p e n i n g for s a m p l i n g
pH m e a s u r e m e n t and pH cont s o l
~
w p e r a t u r e b a t h 25 C
Figure 1. Reaction apparatus
eontrolling the reaction conditions. Therefore, control of the composition of copolymers during t h e phosgenation stage may be possible (similar to control in the vinyl copolymerization processes) by successive addition of monomers (Hanna, 1957). Now, the phosgenation is actually a n extremely complicated reaction. However, assurning that, under conditions of coexisting mono- and bisphenoxy salts of BPA aiid TCBPh made possible by controlling the amount of sodium hydroxide; phosgene is introduced a t a low rate t o form monochloroformate (Koguchi, 1963) and also assuming t h a t the reaction variables may be chosen t o fulfill t h e ahore-mentioned coiiditioiis, the reaction can be arranged into the following main steps according to the ordinary mode of polymerization: (i) formation of the chloroformate group (initiation reaction)
+ COClz SaOBOCOCl + XaC1 NaOTOXa + C0C1l9 +FaOTOCOCl + S a C l SaOBOSa
--f
(I)
(2)
(ii) polycondensation (propagation reaction) -BOCOCl
(-ml.)
+ SaOBOCOC1 (l\I1)
All
----f
-.BROCOCl
(-.rnliiil.)
(3)
b21
-TOCOCl
(-mz.)
SxOBOCOCl (111,)--f -TBOCOCI
(-memi.)
(4)
+ SaOTOCOCl (LIS) + XI2
-BOCOCl
(-nil.)
--BTOCOCl -TOCOC1
(-me.)
+ KaOTOCOCI (AI,)
(-nilm2.)
(5)
i,22
----f
WTTOCOCl (-m2m?.)
System T
BPA 0.12 mol 27.36 g . TCBPA 0 . 1 2 mol NaOH 0 . 3 0 mol "12.0 (8.0) g 0 . 3 6 mol HzO 129 (17,5) g CHzCIz 120 g Emulsifier . . . Catalyst . , . a Figures in parentheses are for pH control.
'i-
rI" e a c Five-mou'hed tion vessel
System B
Component
gas
,'
(6)
aiid (iii) hydrolysis of the end chloroformate group (terniiiiation reactioii). I n case the termination reaction iii via hydrolysis of the eiid chloroformate group is suppressed and oiily the initiation reaction i and the propagation reaction ii are made t o participate in t h e reaction by proper control of t h e reaction variables (pH, amount of catalyst, emulsifier), t'he composition of copolymers can be controlled by causing t h e reactions i and ii t o proceed in a steady state. However, as t h e initiation reaction i is faster than the propagation reaction ii and t h e react'ivities of monomers differ coiisiderably with each other,
. .
43.92 g 1 4 . 4 (4.8) g 203.8 (11.2) g 2252 g 0.0439 g 0,2635 g
~
the steady state can hardly he realized. Therefore, as an approximation, the phosgenation reaction is carried out, in this study, under t'he following conditions which niay be easily realized with our experimental techniques. Phosgene is introduced a t a rate corresponding t o t h e rate of coiisumptioii of TCBPA which is the slowest reacting species in this reaction system, and monomers are supplied successively a t regular intervals corresponding t o their reactivities. Synthesis of copolymers with a chemically uniform composition according t o the successive addit'iori of InoiiomerS requires that y1 > 1 and y 2 < 1 (see comparisons of the monomer reactivity of BP.1 and TCBP.1). Therefore, addition of t h e more reactive BP.1 (11:) is made iii a state where the less reactil-e TCBPd (&) is present in abundaiice to keep the monomer ratio in the reaction mixture as constant as possible. For synt1iesi.j of a block copolymer, it is iiecessarj- to carry out phosgenatioii and polycondensation by adding only TCBP-k in the iiiitial and intermediate stages and only BP.l in the final stage. 011the other hand, for synthesis of a copolymer which has short block chaiiis, is chemically uniform in composition, and has a given chlorine content, it is necessary t o carry out the reaction by adding in successioii a higher proportion of TCBP-1 in t h e initial stage, a higher aiid higher proportion of L3Pa1duriiig the intermediate stage, and only BPA1in the filial stage and condensing the oligomers because the sodium pheiiosides of the two nionomers I3P.1 and TCBP.1 $how the iame reactivity toward t h e chloroformate groups of BPA and TCBP-k aiid also because yly?= 1. The addition of monomers according t o the above-meiitioiied n-a)- of thinking will be described in detail with respect to the molar ratio TCBPA1,IBP.l = 50:50. 011 the baSis of separate studies on BP-k and TCEPA, by Sekine, el al. (1971), the monomer eniulsioiis are prepared for the BP-1 system (system B) and the TCBPAIsystem (system T) as s h o ~ ~inn Table I. The amount of emulsifier is 0.06% by weight based on the monomers and the amount of catalyst is 0.3i% by weight. The successive addition of monomers is made over a period equal to the phosgenation period in the homopolymerizatioii of TCI3P.k and the reaction is carried out a t the molar ratio of total phosgene t o monomers of 1;l aiid a t a constant' flow rate. The amount of monomers charged a t the time of initiation of reaction is one-fifth of the sum total of systems 13 and T and the molar monomer ratio of TCl3P-k BP:i = 3.8 1 is chosen to make the monomer feed richer in TCUP-1. To inaiiitain the pH a t a constant level during the reactioii, water and sodium hydroxide are wit,hdrawn in part from t h e systems T aiid B for the purpose of pH coiitrol. The whole remainder of the system T and a minor part (one-eighth) of the remainder of the tem B are placed iii the agitating columii T aiid a major part (seven-eighths) of the remainder of the system 13 is charged into the agitating column 13. During t'he phosgenation, dropwise additions of the monomer emulInd. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
203
pH a t 10.0-10.4 throughout the reaction, a solution of 12.8 g of sodium hydroxide in 28.6 g of mater is added. After completion of the addition of these emulsions, the passage of phosgene gas is continued until the pH reaches 7.0. Immediat'ely thereafter, 1.4256 g of T X B A C (2% by weight, based 011 tlie monomers) is added and the polycondensation is carried out for 2 hr. During this time, the pH of the reaction mixture is adjusted a t 10.0-10.4 by a solution of 9.0 g of sodium hydroxide ill 56.1 g of water. Upon completion of tlie polycondeiisation, the reaction mixture is left standing, the aqueous layer is separated, and tlie methylene chloride layer contaiiiiiig the polymers is washed with distilled water until 1 chloride ioiis are 110 more detected in the washiiigs. This solu, I 120 240 360 180 tion is poured into n-heptane which is a precipitant,, and the Phosgenation time, m i n precipitates are collected on a filter and dried. The yields of the polymers are determined and the properties are measured. Figure 2. Monomer addition curves for TCBPA/BPA = Measurements of Properties of Polymers and Methods 50/50:I, -X-; II, ---0--of Analysis. Average Molecular Weight. The average molecular neight of low molecular weight polymers is determined by the Rast met'hod while t h a t of high molecular weight sioiis are made from B t o T and from T to the reaction vessel polymers is determilied by the osmotic pressure method simultaneously a t the same rate a t regular iiitervals. 13y this aiid also by the viscosity method utilizing the relationship means, it is possible to vary the ratio TCBP.VI3P.I iii the [ q ] = 1.565 X 10-4Avo,i* (Ikedaaiid Sekine, 1973a). monomer emulsioii to be added in drops from column T to the Glass Transition Point. This is determined with the aid reactioii vessel. The addition from coluniii T is complete iii a of :I dilatometer. length of time equal to three-fourths of the phosgeiiatioii Softening Point (T,)and Fusion Point (Tfb). T1ie.e period, aiid the addition from column I3 is three-fourths comt'cmperatures are deteriiiined viit.1i a Kaka-shiki flow tester plete a t this point. The remaining oiie-fourth iii coluniii 13 i.; (manufactured by Shimadzu Seisakusho) a t a pressure of then directly added in drops t,o the reaction vessel over a 40 kg/cm2, using a nozzle whicli is 1 m m in diameter aiid 10 period equal to one-fourth of the phosgenatioii period. The nini i i i length. amounts of BPA1and T C , B P l in the monomer emulsion being Density ( d ) . This is det'ermined a t 25' by thc gradient added to t'lie reaction vessel are computed every 10 miii, and tube method using aqueous solutions of ziiic chloride. addition curves are d r a w l , as shown in Figure 2: curve I (for Chemical Composition. After decomposition of the simplification, only values of every 60 miii are slion-11). 111 sample i$-ith sodium prroside, the t'otal chlorine content is Figure 2, it is shown that more TCBP-1 is added in t'he iiiitial determilied by the Volhard met.hod. Per cent chlorine iii stage, t h e addition of I3P-l is increased successively during t h e end chloroformate group is determined as folloivs. The three-fourths of the phosgeiiatioii period, and 131';1 only is sample is decomposed by boiling it wit'h a 2% toluene added during last quarter period. The slope of addition curves ,solution of sodium hydroside arid the filtrate is aiialyzed for can be varied by varying the mixing ratio of cliloriiie 1 ) ~ . the Volhard method. Sodium carbonate in t'lie system T (e.g., monomer addition curve 11). I t is expected aqueous layer is determined by Karder's method. that one caii prepare copolymers varying in the length of block Measurement by a Thermobalance. K i t h the aid of ai1 chains a t n-ill in this manner. ORK-I Type recording thermobalance (manufactured by Method of Polymerization. A solution of 2.28 g (0.01 6 K.K.), the accurately iveighed sample, mol) of BPA and 13.9 g (0.038 mol) of TCl3l'A i n 3.37 g of about 0.25 g, is test'ed in a stream of nitrogen a t 1 atin sodium hydroxide and 70.3 g of water is prepared in t'he while raising the temperature a t a rate of 1°/min. react,ion flask and 81.3 g (62.54 ml) of methylene chloride, Modulus of Elasticity E. This is measured on a Vibroii 0.0834 g of triiiietli~-lbeiizylammoiiiuriichloride (TlIIZAC) Type I tejter (manufactured by Toy6 Sokki K.K.). Film as a catalj-st, aiid 0.0139 g of alk~-lplieiioxypolyetli~~~yetl~a~iol prepared from a 5% methylene chloride solut'ion of the (IPPE, trade name Triton X-100) as an emulsifier are further sample by cast,ing is cut, into a size of 2 X 0.015 X 0.2 c m added. Phosgene gas is blow1 into tlie reaction mist'ure ii-ith and measured under a strain a t a constant test speed of 0.1 vigorous stirring a t 25' a t a flow rate of 11.2 cni3?niiii. -1 min/sec a t room temperature. solution of 3.14 g (0.01375 mol) of BPA and 30.02 g (0.082 Dynamic Mechanical Property. This is measured on a mol) of TCBP.l in 7.02 g of sodium hydroxide and 144.4 g of Yibron Type I tester in a range of room temperature t o water is prepared in columii T aiid 167.6 g (128.93 nil) of 230'. -1film of the sample prepared by casting is cut into a methylene chloride: 0.1802 g of T1IBA1C, and 0.030 g of size of 4.0 x 0.01 x 0.1 cm and measured using a ireAPPE are further added. -1solution of 21.98 g (0.09625 mol) quency of 138 cps keeping the cross section of the t'est of BP-\in 3.2 g of sodium hydroxide aiid 89.5 g of water is cm2 throughout the measurement pieces about 1.0 X prepared in columii B and 96.3 g (74.04 1111) of niethyleiie n-hile raising the temperature a t a rate of 1' ' h i l i . chloride is further added. In both columns, tlie emulsions are stirred thoroughly and added in a homogeneous state. The Results and Discussion addition from each column is made in equal portions el-ery 10 Comparison of Monomer Reactivity of BPA and TCBPA. i n i i i so that three-fourths of the emulsioii in columii 13 is added Ratio of the Rates of Formation of the Chloroformate in 6 hr or a t a rate of 4.4g e\-ery 10 min aiid the whole emulGroup. The ratio of the rates of formation of chloroforsion in columii T is added in 6 lir or a t a rate of 14.1 g every 10 matea or bis(ch1oroformates) formed from BI'A and TCmin. The remaiiiiiig one-fourth of the emulsion iii columii 13 BPA iq plotted against the blow-in time of phosgene in is added in 2 h r a t a rate of 4.4 g every 10 mill. T o niaintairi tlie 204
Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
Blow-in t i m e of phosgene, m i n
Figure 3. Comparison of the rates of formation of chloroformates from BPA and TCBPA: 0,monochloroformate; A, bis(ch1oroformate)
Figure 3. Experiments were carried out by dissolving B P h or TCBPA (0.055 mol) in a solution of 0.165 mol of sodium hydroxide in 85 ml of water to form the i;odium phenoxide. passing phosgene gas through the solution a t 0' a t a flow rate of 40 cmaI'rnin,and comparing the rat'io of the rates of formation in the initial stage of the reaction. Since there is a possibility t h a t a mixture of rnoiiochloroformates aiid biscchloroformates) might be formed uiider these reaction conditions, the per cent formation was calculated for each of the two. The ratio of t h e rates of formation of chloroformates (moles of BPA chloroformate per mole of TCBP.1 chloroformate) falls roughly in t h e range of I .3-1.5> which is an indication t h a t BP-I is phosgenated more readily. R a t e of Polycondensation. To determine the monomer react,ivity ratio in polyeondensation, interfacial polycondensation was carried out as follows. -1 solution of 0.00365 mol of t h e sodium phenoxide of BP-1 or TCBP.1 i n 6.66 ml of water is prepared; 0.5% b y weight of TXB.1C based on t h e monomer as a catalyst aiid 1% by weight of sodium lauryl sulfate (SaLS) based on t,he monomer as a n emulsifier are dissolved in this solution, and 0.00368 mol of t h e bis(ch1oroformate) and 6.6 nil of methyleiie chloride are further added. The mixture is sealed in a polymerization tube, and the tube is shaken in a constaut-temperature bath maim tained a t 25'. The rate constants ICll, K n , K12;and K2?of t h e bis(c1iloroformates) and bis(phenoxides) of l%Pal and TCBP,1 corresponding to eq 3-6 for monochloroformates aiid ~noiiophenoxides were obtained from the relationship betu-eeii tlie and the reaction time t number-average molecular weight prevailing ill the initial stage of the reaction. Experiments mere carried out, in a n emulsified state by choosiiig the conditions (same for t h e four reactions) under which the reaction is not substantially affected bj- diffusion of nioiioniers and oligomers a t t'he interface nor by hydrolysis. The results are slion-n in Figure 4. The relationships between Ji and t are linear and satisfy t'he Schulz equation, = 1 kf.Heiice, it was possible to determine each rate constant, from the dope of t h e straight line. The nioiionier reactil-ity ratios calculated for BP-1 (111)and TCBPX (&) are y1 = k l l ki2 = 37.5 20.1 = 1.87 and y? = K 2 2 / K 2=1 13.25,'26.5 = 0.5. Since yl > 1 and yz < 1, it may be clear that the mutual action betn-eeri propagating chains aiid B P d is predominant. Therefore, it is apparent that whatever composition the reaction mixture has, the resulting copolymer always has a higher proportion of BPA than the reaction mixture. Comparison of Conditions for Homopolymerization of BPA and TCBPA. A comparison of the polymerization conditions of TCBPX homopolymers (TT-TT) and the
-vn
Aun +
z
o--
0
20
40
60
Reaction time. m i n
Lvn
Figure 4. Relationship between reaction time and in the reaction of bis(ch1oroformates) of BPA and TCBPA with their sodium phenoxides
preparatory conditions in literature (Natsugane, et al., 1969; Morgan, 1965a,c; Soguchi, et al., 1963a,b) of BPA homopolymers (BB-I3B) clearly indicates t,lie presence of the following differences. (1) TCBPd has 2 lower rat'e of formation of the chloroformate group and a lower rate of coiidensation of the chloroformate group and hence requires a longer phosgenation period, 6-8 hr for TT-TT us. 2 hr for UU-UI3. ( 2 ) Since the chloroformate group of TCBPA1is more susceptible to liydrolj . phosgenatioii and polycondensation are carried out a t a pH of 9.6-10.0 n.hereas the pH for these .steps is in the range of 10.5-11.5and >10 for BI1-BB. (3) TCBP.1 is less soluble in water than E€'-I because of the greater intermolecular force of chlorine atoms and hence has a greater interfacial tension. The addition of 0.'25-0.5% of a iioiiionic emulsifier -1PPE acts favorably to coiitrol the iiiterfacial tension aiid brings the phenoxide groups and chloroformate groups of t h e monomers and oligomers into close contact a t t h e interface (Smirnova, ef al., 1964). 111 the case of 13It h e addition of emulsifier is generally not required because the chloroformate group of UP.1 po5sesses an emulsifying power. (4) Since TC13P-1 exhibits a lower reactivity because of the steric factor of chloriiie atoms a t the ortho arid ortho' positions. a catalyst is added in a n amount of about 0.6% during tlie phosgenatioii and about 27, during the polycoiidensatioii, 111 the case of 1313-1313 compounds Morgan (1065~)rnentioiis a n addition of about 2 7 , of a catalyst based 011 131'-1 tiuriiig tlie I)olycorideiisatioii. Hon-ever, there is a report that, when a catalyst is added duriiig the plio+ genatioii, decompositioii occurs iii tlie course of polyco~idensation if the addition exceeds 0.57c here (Soguchi, et al., 1963b). This may be accounted for as follovis. The elid OCOCl group arising from the pho.;genation reacts with the catalyst. Moreover. this group is more readily hydrolyzed to -0COOH because BPh is more susceptible to hydrolysis than TCBPA, and this in turn shows a lower reactivity toward sodium pheiioxide and hence little tendency t o form polymers (Iioleiirnikov. et al., 1965). Thus, on the principle of maintaining a balance betweeri t h e two moriomers, t h e reaction conditions were chosen in such a mariner as to lengthen t h e reaction time for TCBP.1 in view of t h e loiiger phosgenation period required for homopolymerization of TCHP-1 and to raise t h e reactivity of TCBP-\because of tlie lower reactivity of TCBPA compared with that of UP-1. XOK,the reaction irould be expected to proceed satisfactorily by adding small amounts of -1PPE and the catalyst and selecting a pH T-alue somewhere in the range of 10.0-10.4 Ind. Eng. Chem. Prod. Res. Develop., Vol. 1 2 , No. 3, 1973
205
Table II. Yield, Run no.
Yield,
M , Per
Cent Chlorine Content, and Some Physical Properties
-
%
[71
yo CI
M
d, g/cm3
re,o c
T,, OC
1.336 172 71,880 21.61 0.973 18.94 1.311 164 0.463 27,730 1.273 151 26,740 15.04 0.450 1.325 153.8 15,090 23.25 0.288 77,290 20.26 1.336 167 1.03 1.330 171 45,400 20.41 0,679 20.23 1.319 173.5 42,860 0.650 1.304 165 18,240 19.53 8 0.334 15 0.497 30,370 20.88 1.302 163 16 0,346 19,100 21.90 1.286 158.5 17 0,322 17,400 20.80 1.298 157 23 0,658 43,500 26.14 1.383 174.5 24 0.384 21,800 25.02 1.403 173 25 0.368 20,700 10.42 1.266 144 26 0.298 15,800 10.82 1.262 142 27 0.604 39,000 20.09 1.316 171 28. 80.4 0.407 23,740 21.73 161 a T , and TJI of this run were measured by differential thermal analysis.
1 2 3 4 5 6 7
87.6 88.6 76.5 75.0 83.9 87.7 86.7 82.6 79.3 74.6 80.1 76.9 83.1 79.0 83.1
197 193 183 187 186 194 196 185 186 185 183 213 211 175 177 192
Tfbr
O C
of Copolymers Remarks
214 Addn curve I Addn curve I1 208 2-hr addn 206 222 4-hr addn 6-hr addn 22 1 IIH 10 0-10 4 216 IJH 12 0-12 4 231 215 p H 13 0-13 4 Methanol, 0 5 ml 212 Methanol, 1 0 ml 205 Methanol, 1 5 ml 205 T / B = 75/25 255 T / B = 75/25 231 T / B = 25/75 193 T/B = 25/75 185 208 Sample used for thermal decompn 193 (TM) Random sample
calculated for the chlorine content for T / B = 50/50 where T and B are TCBPA arid BPA in the copolymer, a t the time when the addition of monomers was conipleted and t h e oligomers with a composition close to the objective were obtained. The polycondensation also proceeded with the chlorine content remaining nearly unchanged a t a level slightly lower than the calculated value, and copolymers with the chlorine coiitent nearly equal to the objective were prepared. The values of were 1000-2000 in the first 360 min of phosgenation, but they began to increase sharply from a point of -180 min where only t h e 13Ph monomer was added t o a point of pH 7 where the passage of phosgene was completed and kept increasing to about 72,000 at an approximately constant slope even in the polycondensation step. On t h e contrary, in run no. 2 in which 0.2070 of the emulsifier was used, the reaction progressed with the chlorine content in the oligomers remaining low a t a level somewhat higher than the calculated value because t h e BPX monomer was added in relatively large quantities initially. The chlorine content in the copolymers kept falling even during the polScoiidensatioii but increased slightly in the final stage t'o 19%. KOK,-u showed the same tendency as in no. 1 up to the early stage of polycondensation but did not increase thereafter because the emulsifier was added iii relatively large quantities a t points where oligomers were richer in B. The chlorine content in the eiid chloroformate groups was determined because a study of its behavior relative to that of gives an important clue to gain knowledge on the progress of reaction. I : similar tendency is observed in no. 1and no. 2: i t is indicated that chloroformates are formed a t the ends of many oligomers vhen the phosgenation'is completed and the chlorine content in the end chloroformate group falls sharply in the polycondensation as high molecular weight polymers are formed. The yield, B, per cent chlorine eontent, and some physical properties (d, T,, T,, T f b )are shown in Table 11. I n run no. 2 slightly lower values for each of these it'ems than for those of 110. I , except the yield, are observed. The addition curve I which is steeper enables preparation of copolymers possessing a composition closer to the objective. Effects of Time of Addition. Figure 6 shows changes in and per cent chlorine content when t h e time of addition was successively shortened from 6 hr (no. 5 ) to 4 h r (no. 4) to 2 hr (no. 3) with the use of addition curve I. (The addition curves are omitted here,) In r u n no. 3, the chlorine
Av
I
$ 7 -0 360
240
480
Phosgenation R e a c t i o n t i m e , min
Av
40
80
0
120
Pol) c o n d e n s a t i o n
Figure 5. Changes in and per cent CI with the passage of time in addition curves I and II: addition curve I (no. 1 ) ; 0,addition curve II (no. 2); -, M;- -, % CI; ---, % CI calculated by eq 7; -----, % CI calculated by eq 7 corrected with ratio of the rates of formation of chloroformates
4,
which is intermediate between t,he optimum p H for I3PX (10.5-11.5) and that for TCBPA (9.6-10.0). Effects of Changes in t h e Slope of Monomer Addition Curves. The effects of changes in the slope of addition curves (phosgenation period 8 hr) on t h e composition of reaction product and were examined. For t h e comparative study, two modes of monomer additions, shown in Figure 2, mere adopted: the amount of the monomer emulsion B to be added t o the monomer emulsion T is one-eighth of the latter in the case of curve I while it is one-fourth in the case of curve I1 (I1 is less steep than I). Changes in the per cent chlorine content (only those chlorine atoms n-hich are on the benzene ring) and with time during the phosgenation and polycondensation are shown in Figure 5 for the reactions carried out according to I (no. 1) arid I1 (no. 2), respectively. I n run no. 1, the per cent chlorine content in the oligomers in the initial stage of the reaction was high, but it fell relatively sharply as t'he reaction proceeded and reached 21.94%, a value
-v
206
Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
Av
Av
25
tc
I
20t
t
"--k' 1LW
240
Phosgenation
360 0
40
80 120 180 240 Pols condensation
R e a c t i o n t i m e , min
P h o s g e n a t i o n t i m e . min
Figure 6. Effects of time of addition of monomers on changes in and per cent CI with-time: A, 2 hr (no. 3); X, 4 hr (no. 4); 0,6hr (no. 5);--, M ; - - - , ~ o C l c a l c u l a t e d b y e q 7; --I
% CI
content in the oligomers during the phosgenation was lower than t h e calculated value and fluctuated; it fell further and finally ended with 15% in copolymers richer in J3. I n run 110. 4, the chlorine content was lower than the calculated value in both phosgenation and polycondensation steps but finally exceeded the calculated value t o 23.25%. I n run no. 5 , for which the time of addition was 6 hr, t h e chlorine content and changed following t h e curves similar t o those of no. 1 for t h e 8-hr addition, and copolymers with t h e chloriiie content nearly equal t o t h e objective were obtained. It is apparent from Table I1 t h a t no. 3 and no. 4 give lower values in t h e yield, and T , than no. 5 and no. 1. It has thus become clear t h a t not many differences are present in the progress of reaction arid in t h e product regardless of whether t h e addition is made in 6 or 8 hr. Effects of the Mixing Ratio of Monomers. T h e effects of t h e mixing ratio of monomers were studied by using two different ratios of T C B P A t o BPA, 75/25 and 25/75. T h e monomer ratio a t tlie initiation of reaction was chosen the same as iii tlie case of 50150, t h a t is, TCBP-IJ3PA4= 3.8, 1, and t h e monomer ratios of 75/25 aiid 2 5 7 5 were distributed proportionally t o 11.411 aiid 1,27,,l, respectively. The other conditions for t h e clraniiig of addition curves were blie same as in t h e case of addition curve I. Figure 7 presents t h e moiiomer addition curves at different mixing ratios of nioiiomers (curve 111, 75/25; curve IV, 25/75), The reaction conditions were identical with those for t h e monomer rat'io of 50,'50 except for t h e amount of emulsifier (0.1%). R u n no. 23 ill Figure 8 shows the experimental results for TCBPA/BP-I = 75/25. 111this case, the chlorine content remains roughly constant a t 27-29% durirg t h e phosgenation, and a formation of oligomers whose chlorine content is less than the calculated value of 29.80y0 is observed. T h e chlorine content then drops t o 26% or so when t h e reaction enters t h e polycondensation stage, but Ji in t h e meantime rises steadily. The behavior of t h e chlorine coiiteiit in the chloroformate groups is similar to that of run no. 1 of addition curve I. Since the chlorine content was less than the calculated value, attempts (run 110.24) were made to bring the actual chlorine conteiit to the calculated one by lengthening t h e period of blow-in of phosgene to 12 hr. T h e results are shown in Figure 8. The chlorine content and
Figure 7. Monomer addition curves for different ratios of TCBPA/BPA: -, addition curve 111 (TCBPA/BPA = 75/25); ---, addition curve IV (TCBPA/BPA = 2 5 / 7 5 )
Av
-v,
Av
Phosgenation Polycnndensation R e a c t i o n time. rnin
Figure 8. Changes in Llyand per cent CI with time for different monomer ratios: 0,no. 23 (75/25, 111); O, no. 2 4 (111); X, no. 2 5 (25/75, Iv); A, no. 26 (IV); -, --, % CI; ---, % CI calculated b y eq 7; -----, % CI calculated b y eq 7 corrected with ratio of the rates of formation of chloroCI curve formates. Note: figures in parentheses along the of no. 24 show the reaction time in minutes
70
still showed the same tendency as in run no. 23 for which t h e phosgenation time was 8 lir. R u n no. 25 presents the results for t h e monomer ratio of TCBPX/BPX = 25/75. After 120 min of phosgenation, t h e oligomers formed contained 20.07, of chlorine, but t h e chlorine content dropped rapidly as increasingly more BP;1 was added wit'h t h e passage of time and were t h e objective copolymers containing 10-l17c of chlorine formed in t h e polycondensation step. Hoxever, AI increased more than in no. 23 and no. 24 of addition curve I11 in t h e first 40 min but tended to level off or fall thereafter because the coilcentration of catalyst relative t o t h e amount of BP-I added \vas high. The reproducibility was relatively good in the phosgenation step but was somewhat poorer in the polycondeiisatioii step due to the above-mentioned effects, as shoivn in run no. 26. The chlorine content in the end chloroformate Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
207
L xi
1.0ml (No.16) 1.5ml (No.17)
I
0
I
1
, P o l y c o n d e n s a t i o n time, min
Figure 9. Effects of pH during the polycondensation: 0, pH 10.0-1 0.4 (no. 6); A, pH 12.0-1 2.4 (no. 7); 0,pH 13.0---,amount of by-product Na2C03 13.4 (no. 8); -,
fl;
duced. Changes in A?@ and the amount of by-product sodium carbonate with time are shown in Figure 9 for pH values of 10.0-10.4 (no. 6), 12.0-12.4 (no. 7), and 13.0-13.4 (no. 8). Experiments were carried out with the addition of 0.1% of the emulsifier. I n run no. 8, \vas seen t o increase in the first 40 min of polycondensation, but it leveled off or decreased after 80-120 min. The amount of by-product sodium carbonate increased in the meantime. I n run no. 7, increased sharply in the first 40 min of polycondensation, but it started t o level off after 80 min and decreased after 120 min. I n run no. 6, Ll?f increased steadily during t h e polycondensation, and the amount of by-product sodium carbonate was the smallest of the three cases mentioned above. The chlorine content and the chlorine content in the end chloroformate groups in the polycondensation step showed tendencies similar to those of no. 1 in each case. I n the polycondensatioii step, however, the chlorine content decreased somewhat in the order of increasing pH. The results of run no. 8 in Table I1 are lower in numerical value than those of the other two runs. Effects of the Amount of Emulsifier. T h e effects of emulsifier are shown in Figure 10. I n runs no. 9 (no emulsifier) and no. 10 (0.03% emulsifier), Ai? did not increase very much in the phosgenation step nor in the polycondensation step. On the contrary, in runs no. 1 (0.06% emulsifier), no. 6 (0.10%), no. 11 (0.12%), no. 12 (0.20%), and no. 13 (0.30%), a rise in was sharp over the phosgenation period from 360 to 480 min t o p H 7 and was still pronounced during the polycondensation. This rise, however, became less sharp when the amount of emulsifier became excessive and reached a peak near 0.06%. I n run no. 14 in which the emulsifier was not added during the phosgenation step but added in a n amount of 0,1270 during the polycondensation, no increase in &E!was observed. It is thus shorvn t h a t an emulsifier is necessary during the phosgenation. A comparison of run no. 11 with emulsifier and run no. 9 without emulsifier with respect to the per cent chlorine content indicates that a good reproducibility is well demonstrated on the addition curve of no. 1 during the phosgenation in the former whereas the chlorine content in the oligomers during the phosgenation is lower and fluctuates and remains a t 19% or so even during the polycondensation in the latter. Effects of Addition of Methanol on Addition of methanol is also effective for suppressing in copolymerization. This effect is shown in Figure 11. Experiments were carried out with the addition of O.l’% of emulsifier. With reference to run no. 6 in which no methanol has been
-v
I
IIU i
120
1
240 ‘360 480 0 40 80 120 Phosgenation Polycondensation R e a c t i o n t i m e , min
Figure 10. Effects of the amount of emulsifier on changes in .i!!and per cent CI with time: 0,0% (no. 9);A, 0.03% (no. 10); A, 0.06% (no. 1); 0,0.1 2% (no. 1 1); %, 0.3% (no. 13); 14); -,
.,
0.12% only during the polycondensation (no.
AT;- -, % CI
groups changed differently from no. 1 of addition curve I and no. 23 of addition curve 111, and the curve showing it, while following the monomer addition curve, was convex because the amount of BPA added was larger than that of TCBPA during the phosgenation. As is apparent from Table 11,the properties of copolymers varied with t h e mixing ratio of monomers or with the ratio of T t o B in the copolymers and the results nearly as expected were obtained. It is also apparent that copolymers having a composition roughly equal to the objective can be prepared according t o addition curves I11 and IV. Investigation of Other Reaction Conditions. Effects of pH. T h e effect of setting the p H a t 9.0 during the phosgenation was examined for the case of a 4-hr phosgenation. Oligomers with a higher proportion of T were formed in the initial phosgenation step compared with the case of pH 10.0, b u t the chlorine content kept decreasing as the reaction entered t h e polycondensation step and a copolymer with the chlorine content of 15% and ATof 12,070 was pro208
Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
Av. .v
Table 111. Effects of the Catalyst Concentrationn
Run no.
a
Yield,
%
111
18 0 308 19 75 0 0 270 20 0 066 21 73 5 0 072 22 75 1 0 143 TCBPA/BPA = 2 5 / 7 5 .
M
16,450 13,890 2,280 2,550 6,150
% CI 19 19 21 16 12
4dcm3
r,,
oc
r,,
O C
rib,
'C
27
! 316
!53 7
68 28 95 39
1 289 1 334 1 318 1 211
178 178
211 203
110 7 125
150 153
150 153
added, decreased as the amount of methanol added increased. I n run no. 15 with 0.5 ml of methanol added, J i began to rise with time after elapse of 60 min. On the other hand, the suppressive effect of methanol was pronounced in runs no. 16 (1.0 ml of methanol added) and no. 17 ( l . 5 ml of methanol added), and &Vdid riot increase very much but' stayed nearly unchanged. The results in Table I1 show that T,, T,, and Tfb tend to decrease slightly as the amount of methanol added increases or ,i7 decreases. Effects of Catalyst Concentration. T h e effects of t h e concentration of catalyst 011 yield and other properties are shown in Table 111. T h e concentration of catalyst is given in a s u m of t h a t in phosgenation (0.37Yc) and t h a t in polycondensation (2yc). I n runs no. 18, no. 19, 110. 20, and no. 21, the phosgenation period was set equal to 4 hr and the catalyst concentration and tlie polycondensation period were varied. -1sis apparent from the results of runs no. 20 and no. 21, some decomposition tended t o occur a t high catalyst concentrations. R u n no. 22 represents the case where the phosgenatiori period was 8 hr, the mononier ratio TCBPA4 BPA was 25/75, and t h e catalyst concentration n-as 2.57%. Excessive charging of BPA a t high catalyst concentrations brings about t h e undesirable result's as mentioned in comparison of conditions for homopolymerization of BP.1 and T CBPA . Investigation of Composition of Copolycondensates during t h e Reaction. Phosgenation Step. As is s h o n n in Figure 5, changes in the per cent chlorine content and with time of t h e oligomers prepared according t80addition curve I indicate t h a t a copolycondensate consisting mainly of a homoyolycondensate of TCBPA is formed in t,he first 120 miri or so of the initial stage and then a copolycondensate richer in T in t h e first half and a copolycondensate richer in Tz in the second half of tlie interniediate stage up to 240 min are formed. In the final stage up to 360-480 mill, formation of a homopolycondensate of B and condensation with polj-condensates of other compositions mainly occur, and oligomers with ST of 3000-4000 are formed. ?;ow, studies were undertaken t o see whether the equation for composition of copolymers
-v
could be applied for our experiments. Let us designate 111 = BPA and ;\I2 = TCBPX. As was discussed in the sectioii on monomer reactivity, y1 = 1.87 and yz = 0.5. The molar ratio of A I l t o 112 obtained from t h e nioiiomer addition curve was subst'ituted into eq 7, and on the assumption t h a t 13PA4was entirely consumed in the formation of a copolycondensate and in view of t h e fact t h a t BP.1 and TCBP.4 were added freshljto t h e remaining TCBPA after 10 min, the ratio of coinpoileiits of copolycondensates was calculated bj- adding TCBPd to the residual monomer. Repeating this calculatioii, the molar ratio
[CataIyrt], %
2 2 3 3 2
37 37 55 55 87
Polycondensation time, hr
2 4 2 4 2
of T in the copolycoiidensate in each reaction time was determined in t e r m of the per cent chlorine content. The dotted lines in Figures 5 , 6, and 8 represent the calculated per cent chlorine content. 111runs no. 1 (Figure 5 ) ,no. 5 (Figure 6), and no. 25 and 26 (Figure S), the experiments and calculations roughly agreed n-ith each other in appearance and numerical value. Therefore, eq 7 would be applicable for these cases. On the ot'her hand, discrepancies between the experimental and calculated values were pronounced in runs no. 2 (Figure 5 ) , no. 3 and 4 (Figure 6j, and no. 23 (Figure 8). In other ~ o r d s , when the mixing ratio of TCBP.1 is more than 50% and UP-1 is abundant in the reaction period, some di the calculated values are produced. T h e d he caused tiy the difference betweell the rates of formation of chloroformate groups of BP.4 and TC13P-1. Therefore, taking into account the fact that BPA is 1.4-foId faster than TCI3P.1 in forming the chloroforniate group, a correction w s made t o tlie relative quantity of monomers in the reaction mixture hy multiplying [AI1]in eq 7 by 1.4. As a result, a fairly good agreement iva7 obtained in the first, half of the reaction Figures 5 and 8. However, the discrepancy \vas still large in tlie second half of the reaction. S o w , as the nddition ciirves indicate, the BPA niononier wa':added in large quantities in the second half of t h e reaction and the system then closely resembled the case where T!B = 25 75. In such circuinstancez, the correction does not seem necessary. ;Ifter all, since IC2, i i i K d K 2 1 is large, BPA4 immediately enters the copolycondensate and TCBPA tends to be left iuireached. Hence, tlie ratio of 13P-4 to TCBPA4in the reactioii mixtures varies. Conjequeiitly, eq i would not be applied properly any more. The prohlem of raising tlie per cent chloriiie content in 110. 23 of Figure 8 ahove the calculated value may be solved by niaking the slo1)e of addition curve III steeper. On tlie other liaiid. iii the case in which tlie mixing ratio of TCBP.1 is less than 50% arid 13P-1 is present, in relatively large quantities, since K1? in ICll ,'ICl2 is large, T C U P l also enters tlie polycondensate when BP.1 reacts. Thus, less TCI3P;1 remains unreacted and a good agreement may be obtained between tlie experiniental and calculated values. Thus, under the conditions to 11-liich eq i is applicable, the nioiiomer conceiitration is maintained constant in this phosgenation step. I t may lie justifiable to say that the so-called cluasi steady state is approximately established here. However, in no. 3 and 4 (Figure 6) in which the time of addition of monomers is short, no agreement w-hatsoe.r.eris obtained. Thus it is suggested t h a t the reaction may proceed randomly. It is also clear from the results of no. 2 that the gentle slope of the addition curve i.j not desirable for synthesis of block copolymers liecause n copolycondeiisate relatively rich in I3 is formed already i ~ the i initial stage in such a curve. Polycondensation Step. The polycondeiisatioii st'ep is where the oligomers viith a given chemical composition formed by phosgenation are linked together to yield polyInd. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
209
Table IV. Modulus of Elasticity E and Per Cent Elongation of the Polymers Formed
2ot
I\
5
10
,IIx 10-4
lv
Figure 12,Relationships between and per cent CI and between M and density for different times of addition
1
I
D e c o m p o s i t i o n t e m p e r a t u r e . 'C
Figure 13. Decomposition curves measured by a thermobalance: 0, no. 27; A, sample with a nonuniform composition (no. 3); X, sample with a random composition (no. 28)
mers of uniform composition. K h e n the reaction conditions such as pH, amount of emulsifier, and amount of catalyst are chosen adequately, LEincreases steadily and the per cent chlorine content changes with time in a manner predicted by calculatioii. On the other hand, 11hen the reaction conditions are not chosen adequately, changes in and chlorine content of copolymers become affected to varying degrees. For example, the rate of polycondensation increases as the pH increases in the alkaline range on the one hand. and the cleavage of the end group and the carbonate group in the main polymer chain occurs as a result of hydrolysis arid an increase in the amount of b j -product sodium carbonate aiid decreases in and chlorine content are observed on the other (see Figure 9). The presence of an excessive amount of ernulsifier tends to decrease the 01 era11 rate of reaction by increasing the resistance to diffusioii of oligomers and in turn loners (see Figure 10). An excess of catalyst IS apt to cause a decrease in via hydrolysis of the chloroformate of BPA. I n this connection, it should be pointed out here that it is necesqaiy to study more carefully the amount of catalj st to be added and also the amount of emulsifier to be added, in particular, a t high ratios of BPA in the monomer feed (for example, the amount of emulsifier can be less because of the emulsifying
Av
-u
210
Ind Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
lo4€,
Addn curve
kg/cm2
Elongation,%
Remarks
50/50 50 50 50/50
I I1 I
1.83 1 45 1 06
8 9 8 4 8 0
1)H 13 0-13 4 (poly-
15
50 50
I
1 42
6 1
17
50/50
I
1 40
6 3
23 25 29
75/25 25'75 0 100
111
1 89 1 45 1 20
5 5 5 8 8 1
Run no.
T/B
27 2 8
IV
condensation) 0 5 ml of methanol added 1 5 ml of methanol added
Ji
=
17,000
actioii of the chloroformate group of BP& see comparison of conditions for homopolymerization of BPA aiid TCBPX and no. 2 in Figure 5 ) . (See Table I11 and no. 25 aiid 26 in Figure 8.) Also, when the phosgenation conditions are not chosen properly, the polycondensation reaction is affected in one way or another. I n polycondensation reactions which are affected adversely by a number of causes mentioned above, the curve showing changes in the chlorine content with time becomes concave in the final stage (see no. 2 in Figure 5, no. 3 and 4 in Figure 6, and no. 26 in Figure 8) and the difference in composition between the copolymer and the reaction mixture tends to disappear a t the end of bhe reaction as in the case of interfacial polycondensation reactions in general (Korshak, et al., 1962a,b). Moreover, it seems possible to elucidate how the composition changes in bhe polycondensation step by analyzing the progress of reaction 011 the basis of polymerization conditiolis and changes in molecular weight dist'ribution wit'h time. The results will be reported in the next paper (Ikeda and Sekine, 1973a). Investigation of Polymers Formed. The samples no. 1, no. 5 , and 110. 3 differing in the time of addition of monomers were subjected to fractional precipitation and each fraction was analyzed for chlorine. Figure 12 presents t'he relationship between Jl aiid chloriiie content for no. 1, no. 3, and 110. 5 and t'he relationship between and d for no. 5 . In no. 1 and no. 5 , the chlorine content does not vary appreciably n i t h J7 and stays iiear 21.6 arid 20.2670, the chlorine contents of the unfractionated copolymers, respec,tively. The same is true for d. I n no. 3, however, the chlorine content varies considerably with 8, and the copolymer is extremely nonuniform in composition. Thermal decomposition of three samples no. 2 i , no. 28, and no. 3 which were prepared under different reaction conditions is graphically shown in Figure 13. These samples have 27 of about 30,000 (see Table I). Sample no. 28 has been prepared by mixing BP.1 and TCBP-4 (50150) a t once at' the beginning, passing phosgene for 8 hr, and then carrying out the polj-condensation for 2 hr under otherwise the same reaction conditions as for no. 27, and is a completely nonuniform copolymer. I n comparison with no. 27 which has been prepared by the method of addition curve I, there is a difference of about 10' between the decomposition curves a t a point of 10% loss in weight. The thermal decomposition curve of no. 3, which is for the 2-hr addition of monomers, falls between those of no. 2T and no. 28. Thus, a difference is clearly observed in the thermal decomposition curve depending upon the uniformity of composition. Table IV lists modulus of elasticity ( E ) and elongatioli (per cent) in relation to the monomer ratio, addition curve, and
-v
polycondensation conditions for samples whose is in the range of 15,000-40,000. Assuming t h a t physical properties of the film are affected by the method of preparation, a BPh homopolymer or BB-I3B was used as a blank and relative comparison was made. The modulus of elasticity and elongation both vary with the type of addition curve even a t the T/B monomer ratio of 50/50. Sample no. 27 prepared according to addition curve I gave the best values in these t'wo properties. It was shown, however, t h a t the modulus of elasticity and elongation varied considerably with the polymerization conditions even when the same addition curve I was used. The modulus of elasticity increased as the proportion of T in the monomer mixture increased from T/B = 25/75 through 50150 to 75/25. Figure 14 represents the temperature dependence of t h e dynamic modulus (E') and t h e dynamic loss (E") of sainples with different T/B ratios (no. 23, 75 '25; no. 27, 50,150;no. 26, 25,"i5), with a nonuniform composition (110. 28), aiid of an alternating copolymer, having of 43,500, chlorine content of 15.3%, and T , of 175", prepared from B P I bis(ch1oroformate) and TCBPA sodium phenoxide by interfacial polycondensation (Sekine, et al., 1971). a-Dispersion temperatures of copolymers shifted t o higher regions as per cent chlorine colitents increased aiid almost agreed with their softening points. (See Table 11.)Their p' dispersions, arisiug from t h e mutual association of polar groups (Tomikawa aiid Fujimoto, 1968), varied considerably with their compositions. I n block copolymers (no. 23, 27, and 26), very wide p' dispersioii was observed, while in t h e polymer v-ith a nonuniform composition (no. 28) no clear peak of p' dispersioii was observed, and finally in the alternating copolymer, a relatively sharp p'-dispersion curve with a peak a t about room temperature was obtained. Comparing P'-dispersion curves of copolymers having similar chlorine content, namely, no. 27, no. 28, and TB-TI3, it was found in no. 27 t h a t a verj. intensive absorption existed in the higher temperatiire range. This fact may indicate that the cohesive energy was large and the existence of a n associatioii between polar groups and consequently more energies may be necessary to dissociate it. The E' curve and the a dispersioii in tlie higher temperature range may also confirm it. These results and also the fact t'hat block copolymers are higher i i i their thermal stability than the alternating copolymer (Sekine, et al., 1970) may be the strong evidence for improving physical properties of copolymers by using a block copolymerization procedure. The copolymers prepared accordiiig to this method are likely to coiisist of short block chains, highly random blocks in the light of the method of formation oligomers during the phosgenatioii. A comparison of the softening point of the block copolymers prepared in accordance with the Eastman Kodak patent (1963) meiitioiied earlier and the fusion point of the copolymers prepared according to this method indicates that t h e former is 165" for Til3 = 2 5 / 7 5 and 220-240" for T 13' = 75/25 while the latter is 180-193" for T,;B = 25/75 and 231255" for T , B = 751'25. [It is not described in the Eastman Kodak patent what method has been used i i i determining the softening point. However, there is a literature reference (Morgan, 1965b) which states that the softeniiig point is roughly equal to the fusion point when the measurement is made by a penetrometer and a point of penetratioii is broad under a light load. Hence, they are coilsidered equal here.] The modulus of elasticity E also seems improved in a general way although a n accurate comparison is not possible because of differences in the method of preparation of film and methods of measurements (for example, thickness of film).
I
50
100
150
I
200
25
T e m p e r a t u r e , 'C
Figure 14. Dynamic mechanical properties of BPA-TCBPA polycarbonate copolymers: X, T/B = 7 5 / 2 5 (no. 23); 0, T/B = 5 0 / 5 0 (no. 27); A, T/B = 25/75 (no. 26); 0 , sample with random composition (no. 28);3, alternating copolymer (TB-TB) Conclusion
-1study i r a s made on a one-step process for synthe3is of copolycarbonntes from I3Ph and TCI3Ph. I t was made clear that raudom, short-chain block copolymers with any desirable conipositioii at' a given chlorine coiiteiit could be prepared by the follo~~iiig procedure. K i t h proper selection of reactioii conditioiis such as pI3, nonionic emulsifier (hPPE), and amount of catalyst (TlIB-LC), good control of operating coiiditions such as dropwise addition of monomers in a homogeneous state, and control of pH, temperature, and state of agitation, phosgene gas was introduced a t a 101~-rate for a period which was equal to the phosgenation period in homopolymerization of TCUPX while adding monomers successively according to a selected monomer addition curve (slope), more of TCI3P.l in the early stage and only BPA in the late stage during the phosgenat'ioii step; the oligomers formed were then subjected to polycoiidea3ation. Changes in the composition of copolj-iners rvitli time as measured by tlie per cent chlorine content iii the phosgeiiatioii step iii the cases where T, 13 is 50% or less can be calculated with the aid of the equation for compositioii of copolymers in radical polynierizatio~i.In those cases where T "13 is 50% or more, a correctioii must be made 11y multipl>-iiig [AI1]by 1.4, the ratio of rater of phosgenatio~i. Ti1 the polycondeiisatio~istep, the per cent chlorine content changes with time as predicted by calculatioii Irhen the resistance to diffusion by the emulsifier added and the hydrolysis by high pH values and the catalyst added i i i excess are brought under control. The polymers formed are shon.ii to be uiiiform in compositioii on the basis of the relationship between per cent chlorine coiiteiit aiid X of fractional precipitates. The thermal stabilit'y shovin froin the thermal decomposition curvez arid the results obtaiiied by measurement of the dynaniic mechaiiical properties of the copolymers clearly differ from that of copolymers of lionuniform cornposition. The softening poiiit and the modulus of elasticity of film also improred. Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 3, 1973
21 1
literature Cited
Eastman Kodak Co., Japanese Patent 409,197 (July 31, 1963). Hanna, R. J., Ind. Eng. Chern., 49, 208 (1937). Ikeda, K., Sekine, Y., Ind. Eng. Chem., Prod. Res. Develop., 12, 212 (1973a). Ikeda, K., Sekine, Y., Ind. Enq. Chem., Process DES.Develop., . , in press (1973b). Kolensnikov, G. S., Said, E., Khassen, A . , Smirnova, 0. V., T’gsokomol. Soedin., Ser. A , 7, 129 (1965). Korshak, 1‘.V., Frunze, T. M., Kozlov, L. Y.,B i t / / . Acatl. Sci. USSR. Diu. Cheni. Sei.. 1969 il962a). Korshak; I r ,V., Frunze, T . AI., I?ozlov,’L. V., ibid., 2128 (1962b). lIatsugaiie, Tahara, S., KatB, S., “Polycarbonate Resin,’‘ p 71, Nikkan Kogyo Shimbun-Sha, Tokyo, 1069. Morgan, P. W., “Condensation Polymer: By Interfacial and Solution Method,” p 342, Wiley, Kew York, X. Y., 196Sa. Morgan, P. W.,“Condensation Polymer: By Interfacial and Solution Method,” p 472, Wiley, S e w York, K.Y., 196.ih.
Morgan, P. W., “Condensation Polymer: By Interfacial and Solution Method,” p 497, Wiley, New York, N. Y., 196th Noguchi, -$., Yuki Gosei Kagaku Kyoh-az S h i , 21, 928 (1963). Noguchi, A., Koseki, K., Tanimoto, K., Honna, K., Shimada, Y., Sodeyama, H., ibid., 21, 694 (1963a). Noguchi, 9., Koseki, K., Tanimoto, K., Yasuda, A., Fukamachi, K., Watanabe, S., Honna, K., Shimada, Y ., Igawa, T., ibid., 21, 621 (1963b). Sekine, Y., Ikeda, K., Sawai, K.,Yoshizaki, H., Kogyo Kagaku Zasshi, 74, 2,550 (1971). Sekine, Y., Ikeda, K., Taketani, H., zbid., 73, 429 (1970). Smirnova, 0 . Y.,Losev, I. P., Khorvat, E., T’ysokomol. Soedin., Ser. A , 6 , 594 (1964). Tomikawa, AI., Fujimoto, S., Kobunshi Kagaku, 25, 625 (1968). RW~:ITI:Dfor review Sovember 1, 1972 ACCEPTEDJune 4, 1973
Molecular Weight Distributions of Polymers in the Synthesis of Bisphenol A-Tetrachlorobisphenol A Polycarbonate Copolymers by the Method of Successive Additions of Monomers Koji lkeda and Yoshiro Sekine” Department of Clzenzistry, School of Science and Engineering, T a s e d a Cniversity, Sishi-Ohkubo, Shinjuku-ku, Tokyo, J a p a n
Using the precipitation turbidimetric titration of Morey-Tamblyn, the relationship between polymerization conditions and molecular weight distributions in the synthesis of polycarbonate copolymers was studied, and f(M), the reaction process was analyzed. It was found that k, calculated from the equation y = k log C where y i s the volume ratio of the precipitant at the point of beginning of precipitation, C the concentration, and f(M) a function of the molecular weight (M), varied depending on M. The molecular weight distribution curve obtained b y this method was in good agreement with that obtained b y the fractional precipitation method and also that of equivalent mixtures. In the earlier stage of polymerization, the molecular weight distribution accorded with Poisson’s distribution, and under proper reaction conditions (pseudohomogeneous state) the distribution could b e represented finally with the distribution function of Schulz-Zimm ( h = 1 ). O n the contrary, under improper conditions, the distribution curve was a polypeaked one, which suggested the overlapping of Poisson’s distribution and Schulz-Zimm’s distributions ( h = 1 , 2), and the final polymers were less uniform in their compositions and were inferior to those copolymers of the simple distribution in their thermal stabilities and also in their modulus of elasticity.
+
In the polycondensation step of the bispheiiol -1 @PA)tetrachlorobisphenol -1 (TCBP.1) polycarbonate copolymer syntheses using the method of successive addit’ions of nionomers, it was recognized t’hat the composition and the properties of tlie copolymer were seriously affected by improper reaction coiiditioiis (an excess of tlie emulsifier, hydrolysis caused by a too high p H value, and a n excess of the catalyst). Therefore, t o syiit’hesizeco~iolymersof high quality, tlie reaction state iii the polycondensation step must be studied more in detail. For this liurpose, it ma)- be quite iiecessary to determine tlie polyineriza tioii conditions and the time del)eiidence of the molecular weight distributions i l l the course of the polycondensation reaction, to analyze the reaction process. and to elucidate the relationship betneeii the molecular 2 12 Ind.
Eng. Chem. Prod. Res. Develop., Vel. 12,
No. 3, 1973
weight distributions and the compositions and propert’ies of ‘the copolymer. Xolecular weight distribut’ions of polycarbonates have been studied hitherto mainly by determining the distributions of the final products of polymerization (Schnell, 1956; Tomikawa, 1963). Therefore, studies on the time dependence of molecular weight distributions in the course of this interfacial copolycoiidensatioil reaction may serye not only to s h o the ~ changes of molecular xeight distrilsutions and t o analyze the reaction process in the synthesis of polycarboiiates by the phosgene process but also to be helpful to work with general interfacial iiolycoiideiisatiolls. The authors deterniined the molecular weight distributions of the copolymers, with the samples for which the time deliendence of X iii the course of the copolymer synthesis had
