Polymerization of Vinyl Chloride with Cp*Ti(OCH3)A-Methylaluminoxane

Polymer Journal, Vol. 32, No. 3, pp 300-302 (2000)

SHORT COMMUNICATIONS

Polymerization of Vinyl Chloride with

Cp*Ti(OCH3)a-Methylaluminoxane Catalyst

Kiyoshi ENDO t and Makoto SAITOH

Department ofApplied Chemistry, Faculty of Engineering, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan

(Received July 21, 1999)

KEY WORDS Vinyl Chloride/ Polymerization/ Cp*Ti(OCH3) 3 / Methylaluminoxane / Regular Struc- ture I Tacticity /

Metallocene catalysts are the subject of continuing in tube were poured into excess methanol containing a terest area of polymer synthesis.1- 9 Some of metallocene small amount of hydrochloric acid to precipitate the 5 catalysts such as Cp*LnR (Cp* =Tj -C 5(CH3)5, Ln=Sm, polymer. Polymer yields were determined by gravimetry. 9 11 Lu, Yb, R=H, CH3) - and (C2H4Ind2)ZrMe2/[Ph3C][B 12 13 (C 6F 5)4]/Zn(C2H5h · were effective catalysts for po Characterization of Polymers lymerization of methyl methacrylate. We believe that The number-average molecular weight (Mn) and metallocene catalysts are applicable to the polymeriza weight-average molecular weight (Mw) of the polymer tion of vinyl chloride (VC), and give polymers without were determined by GPC using tetrahydrofuran (THF) anomalous units introduced into the polymer chain in as an eluent at 38°C calibrated as standard polystyrenes. 1 radical polymerization.14- 18 However, we could not find The structure of the polymer was determined by H and the polymerization of VC with metallocene catalysts in 13C NMR spectroscopy and elemental analysis. The tac 13 the literature, although the polymerization of VC has ticity of the polymers was determined from C NMR 1 13 been attempted with Ziegler type catalysts.19- 21 spectra of the polymers. H and C NMR spectra were In the polymerization of VC with modified Ziegler taken using a JEOL A-400 spectrometer in C6DJo catalysts, titanium-tetra-n-butoxide in combination with dichlorobenzene (3/7 v/v%) at 120°C with hexamethyldis 20 21 Et2A1Cl polymerized VC, · in which the ligand of the iloxane (HMDS) as the internal standard. titanium compound is less electron-withdrawing than halogens, and cocatalysts are less reactive than alky RESULTS AND DISCUSSION laluminium toward chlorinated compounds. Thus, we se lected Cp *Ti(OCH3h as a transition metal compound, Polymerization of VC with Cp*TiX3-MAO (X=Cl, and polymerization ofVC was investigated with Cp*Ti OCH3) catalysts was conducted, and the results are (OCH3h in combination with methylaluminoxane (MAO). listed in Table I. The polymerization of VC proceeded The polymerization ofVC with Cp*TiC13-MAO catalyst with Cp*TiX3-MAO catalysts, but the polymerization was examined for comparison. This paper briefly reports rate was very slow. In the polymerization of styrene and the polymerization ofVC with Cp*TiX3 (X=Cl or OCH3) substituted styrenes with Cp*TiX3-MAO catalysts, the MAO catalysts. active species were strong electrophiles and organotita nium complex cations.22 When the polymerization of sty EXPERIMENTAL rene was carried out with the Cp *TiX3-MAO catalysts at low MAO/Ti mole ratio of 10, polymer yield was low (4%) Materials as compared with that of VC, suggesting that the active Cp *TiC13 and Cp *Ti(OCH3h (Strem Chem. Inc.) were site for the polymerization ofVC differs from that of sty used without further purification. PMAO kindly sup rene. However, the active site for the polymerization of plied from Tosoh-Akzo Co. was used as received. Other VC with the Cp*TiX3-MAO catalysts seems to have reagents were used after purification by conventional strong electrophiles. Thus, the slow polymerization of methods. VC with the Cp*TiX3-MAO catalysts is due to the fact that the active site formed from the Cp*TiX3-MAO cata Polymerization lysts in the polymerization of VC is blocked by a free Polymerization was carried out in a sealed glass tube electron pair from the chloro atom of the VC. This sug 3 with a rubber stopper or a 300 cm glass reactor gests that changing of a Lewis acidity of the central equipped with a stirrer and connected to a vacuum line. metal of the active site by the ligand influences activity Required amounts of reagents were charged in the glass for the polymerization of VC. As shown in Table I, the tube by syringe through a rubber septum. VC was intro activity for the polymerization of VC with the Cp *Ti duced into the tube at - 78°C by a vacuum distillation (OCH3h-MAO catalyst was higher than that with the over CaH2. After polymerization, the contents of the Cp*TiC13-MAO catalyst. In the polymerization of sty rene with the Cp *TiX3-MAO catalysts, the active site tTo whom correspondence should be addressed. does not contain Ti-X bonds. If Ti-X bond is not present

300 Polymerization of VC with Cp*Ti(OCH3) 3-MAO Catalyst

Table I. Polymerization ofVC with Cp *Ti.xi-MAO a) catalyst at 20'C"

Time Yield No. Solvent ~h- % M,,XlO 4 M,,JM"

8.0 1.1 1.7 1 Cp*TiCl3 CH2Cb 6 1.1 1.7 2 Cp*TiCl3 CH2Cb 10 8.1

3 Cp * TiCl3 Toluene 24 0.3 1.7 1.8 5.9 5.8 5.7 4.1 4.0 4 Cp*Ti(OCH3) 3 CH2Cb 4 22.6 2.5 2.0 6 Cp *Ti(OCH3)3 CH2Cb 42 50.0 0.3 3.0 7 Cp *Ti(OCH3)s Toluene 48 2.7 HMDS 1 "[Ti]=5X 10-3mol L -,, [VC] =3.52 mo! L- , MAO!l'i= 10 mole ratio.

6 5 4 3 2 at the active site for the polymerization of VC, such ef fect of the ligand is not observed, although more detailed study is necessary to confirm this assumption. b) In the polymerization in CH2Cl2 solvent, polymer yields and the molecular weight of the polymers were .JV-CH=CH-CH"""-" 6i YV-CH2 -CH=CH-CH:,CI higher than in toluene, which is consistent with the pre x 100 x l 00 vious reported results for the polymerization of styrene and propylene with metallocene catalysts, for which a transition from a contact pair metallocene/MAO in tolu 5.9 5.8 5.7 4.1 4.0 ene to free separated species in CH2Cl2 is sugges ted. 23, 24 -CH2CfuCI HMDS The structure of the polymers was first checked by ele mental analysis. Carbon and hydrogen content of the I polymer obtained with the Cp*Ti(OCH3)3-MAO catalyst ppm 5 4 3 2 0 (C ; 38.40% and H; 4.82%, respectively) was in a good 6 agreement with calculated values for assuming that the Figure 1. 1H NMR spectra of PVC obtained with (a) Cp*TiCb catalyst and (b) Cp*Ti(OCHs)s-MAO catalyst. polymer consists of -CH2-CHC1- units (C ; 38.42%, H ; MAO 4.80%). Whereas, carbon and hydrogen content of the polymers obtained with the Cp*TiC13-MAO catalyst (C; 2 shows kinetic 40.12%, H; 5.03%) was higher than the calculated val catalyst was further investigated. Figure with the Cp*Ti ues, suggesting that side reactions such as elimination curve for the polymerization of VC yields and Mn increased of HCl and methylation took place during the polymeri (OCH3 )3-MAO catalyst. Polymer curves of zation. as a function ofreaction time. The GPC elution were The elimination reaction ofHCl leads to the formation the polymers were unimodal and polydispersities to proceed at a of double bonds in the polymer chain. Methylation be 1.8-2.0, suggesting the polymerization tween the resulting polymer and catalyst possibly yields single active site. mole ratios on methyl branches in the polymer. To elucidate these points, Figure 3 shows the effects of MAOtri Cp * Ti( OCH h-MAO the structures of the resulting polymers were examined the polymerization of VC with the 3 1 1 dependent on the by H NMR spectroscopy. Figure 1 shows the H NMR catalyst. Polymer yields were strongly An optimum condition for polymer spectra of the polymers obtained with the Cp*TiC13- MAOtri molar ratio. observed at the MAOtri molar ratio of about MAO catalyst and Cp*Ti(OCH3h-MAO catalyst. The yields was is in contrast to the polymerization of olefins polymer obtained with the Cp*TiC13-MAO catalyst re 10, which re at 4.0-4.1 ppm and 5.7-5.8 ppm based with metallocene catalysts for which excess MAO is vealed signals 6 on olefinic proton for the structures of-CH=CH-CHCl quired to reach high activity. The tacticity of poly(vinyl chloride) (PVC) obtained - and - CH2-CH = CH-CH2Cl. A signal based on 17 in CH Cl was de methyl proton was observed at 0.9 ppm. This indicates with the Cp*Ti(OCH3)3-MAO catalyst 2 2 13 Pentad tacticity of that the elimination of HCl from the polymer and meth termined from C NMR spectroscopy. of methine car ylation of the polymer took place during the polymeriza PVC was determined from the intensity resonance in the main chain at 55.1-57.4 ppm ac tion with the Cp*TiC13-MAO catalyst. Such signals were bon 1 18 are listed in Table not detected in the H NMR spectrum of the polymer ob cording to the literature. The results obtained with a,cx'-azobis(isobutyronitrile) tained with the Cp*Ti(OCH3h-MAO catalyst. The signal II. Tacticity 16 tacticity of based on head-head structure was not observed in the (AIBN) is indicated for comparison. Pentad catalyst 1H NMR spectrum. This indicates that the polymers ob the PVC obtained with the Cp*Ti(OCH3)s-MAO different from that obtained with AIBN, tained with the Cp*Ti(OCH3)s-MAO catalyst have no was somewhat not synthesized anomalous structures. The polymers, thus, consist of re but the high stereoregular PVC was peating regular -CH -CHC1- units. with the Cp*Ti(OCH3)3-MAO catalyst. 2 h Since the Cp*Ti(OCH )s-MAO catalyst was found to The polymerization of VC with the Cp*Ti(OCH3 3 of radical give a high polymer consisting of only regular structure, MAO catalyst was carried out in the presence as 2,2,6,6-tetramethylpiperidine-l-oxyl the polymerization of VC with the Cp *Ti(OCH3)s-MAO inhibitors such 301 Polym. J., Vol. 32, No. 3, 2000 K. ENDO and M. SAJTOH

Table II. Pentad tacticity of PVC C: rr mr mm 0 ::i: Catalyst mmrm rmrr mrrm rrrm rrrr + + mmmm rmmm rmmr J0 10 20 30 40 50 rmm mmrr 60 6 AIBNb 4.8 16.1 11.1 20.8 30.1 3.2 8.1 5.8

Cp 'Ti(OCH3),-MAO 13.6 15.0 6.3 34.3 15.2 6.1 6.3 3.3

5 a Sample No. 6 of Table I was used. b Polymerized at 30°C. 50

l 4 .., 40 Table III. Polymerization of VC with the Cp*Ti(OCH )rMAO ai 3 b catalysts in the presence ofradical inhibitors at 20°C for 48 h" > 3 >< cu 4 E Radical inhibitor [inhibitor]/mol L -l Yield/% Mn X 10 M,JMn >, 30 -:I 0 a. 2 None 53 2.5 1.8 p-t-Butylcatechol 3.4 X 10- 3 40 2.3 1.9 X 3 20 TEMPO 3.4 10- 38 2.4 2.0 3 1 a [VC] = 3.52 mol L 1, [Ti]= 3.4 X 10- mol L , MAO/Ti= 10

0 mole ratio. 10 '------'------'------'--~----' 0 0 1 0 20 30 40 50 Time (h) Acknowledgment. This study was partially sup ported by Grant-in-Aid for Scientific Research (B) (2540/ Figure 2. Kinetic curve for the polymerization of VC with the 10450356) from the Ministry of Education, Science, Cp *Ti(OCH3) 3-MAO catalyst in CH2Cl2 at 20°C : [VC] = 3.52 mol 1 3 1 L- , [Cp*Ti(OCH3)3] =5X 10- mol L - , MAOtri=lO mole ratio. Sports and Culture, Japan.

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