DE69015369T2 - Olefinpolymerisationskatalysator aus einer trialkylaluminiummischung, kieselsäuregel und metallocen. - Google Patents

Olefinpolymerisationskatalysator aus einer trialkylaluminiummischung, kieselsäuregel und metallocen.

Info

Publication number
DE69015369T2
DE69015369T2 DE69015369T DE69015369T DE69015369T2 DE 69015369 T2 DE69015369 T2 DE 69015369T2 DE 69015369 T DE69015369 T DE 69015369T DE 69015369 T DE69015369 T DE 69015369T DE 69015369 T2 DE69015369 T2 DE 69015369T2
Authority
DE
Germany
Prior art keywords
metallocen
polymerization catalyst
olefin polymerization
catalyst made
trialkyl aluminum
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
DE69015369T
Other languages
English (en)
Other versions
DE69015369D1 (de
Inventor
Main Chang
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ExxonMobil Chemical Patents Inc
Original Assignee
Exxon Chemical Patents Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Exxon Chemical Patents Inc filed Critical Exxon Chemical Patents Inc
Publication of DE69015369D1 publication Critical patent/DE69015369D1/de
Application granted granted Critical
Publication of DE69015369T2 publication Critical patent/DE69015369T2/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F10/00Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F4/00Polymerisation catalysts
    • C08F4/42Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
    • C08F4/44Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
    • C08F4/60Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with refractory metals, iron group metals, platinum group metals, manganese, rhenium technetium or compounds thereof
    • C08F4/62Refractory metals or compounds thereof
    • C08F4/64Titanium, zirconium, hafnium or compounds thereof
    • C08F4/659Component covered by group C08F4/64 containing a transition metal-carbon bond
    • C08F4/65912Component covered by group C08F4/64 containing a transition metal-carbon bond in combination with an organoaluminium compound
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F4/00Polymerisation catalysts
    • C08F4/42Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
    • C08F4/44Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
    • C08F4/60Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with refractory metals, iron group metals, platinum group metals, manganese, rhenium technetium or compounds thereof
    • C08F4/62Refractory metals or compounds thereof
    • C08F4/64Titanium, zirconium, hafnium or compounds thereof
    • C08F4/659Component covered by group C08F4/64 containing a transition metal-carbon bond
    • C08F4/65916Component covered by group C08F4/64 containing a transition metal-carbon bond supported on a carrier, e.g. silica, MgCl2, polymer
    • CCHEMISTRY; METALLURGY
    • C08ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08FMACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F4/00Polymerisation catalysts
    • C08F4/42Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
    • C08F4/44Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
    • C08F4/60Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with refractory metals, iron group metals, platinum group metals, manganese, rhenium technetium or compounds thereof
    • C08F4/62Refractory metals or compounds thereof
    • C08F4/64Titanium, zirconium, hafnium or compounds thereof
    • C08F4/659Component covered by group C08F4/64 containing a transition metal-carbon bond
    • C08F4/6592Component covered by group C08F4/64 containing a transition metal-carbon bond containing at least one cyclopentadienyl ring, condensed or not, e.g. an indenyl or a fluorenyl ring
    • GPHYSICS
    • G03PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03BAPPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B2227/00Photographic printing apparatus
    • G03B2227/32Projection printing apparatus, e.g. enlarging apparatus, copying camera
    • G03B2227/325Microcapsule copiers
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10STECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S526/00Synthetic resins or natural rubbers -- part of the class 520 series
    • Y10S526/943Polymerization with metallocene catalysts
DE69015369T 1989-10-16 1990-10-09 Olefinpolymerisationskatalysator aus einer trialkylaluminiummischung, kieselsäuregel und metallocen. Expired - Lifetime DE69015369T2 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US07/422,357 US5006500A (en) 1988-10-27 1989-10-16 Olefin polymerization catalyst from trialkylaluminum mixture, silica gel and a metallocene
PCT/US1990/005769 WO1991005810A1 (en) 1989-10-16 1990-10-09 Olefin polymerization catalyst from trialkylaluminum mixture, silica gel and a metallocene

Publications (2)

Publication Number Publication Date
DE69015369D1 DE69015369D1 (de) 1995-02-02
DE69015369T2 true DE69015369T2 (de) 1996-01-11

Family

ID=23674542

Family Applications (1)

Application Number Title Priority Date Filing Date
DE69015369T Expired - Lifetime DE69015369T2 (de) 1989-10-16 1990-10-09 Olefinpolymerisationskatalysator aus einer trialkylaluminiummischung, kieselsäuregel und metallocen.

Country Status (12)

Country Link
US (1) US5006500A (de)
EP (1) EP0495849B1 (de)
JP (1) JPH0713100B2 (de)
KR (1) KR927003650A (de)
AR (1) AR244711A1 (de)
AU (1) AU6530890A (de)
BR (1) BR9007756A (de)
CA (1) CA2067177C (de)
DE (1) DE69015369T2 (de)
IL (1) IL95982A0 (de)
PT (1) PT95599A (de)
WO (1) WO1991005810A1 (de)

Families Citing this family (63)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4032266A1 (de) * 1990-10-11 1992-04-16 Hoechst Ag Verfahren zur herstellung eines polyolefins
FI86989C (fi) * 1990-12-19 1992-11-10 Neste Oy Foerfarande foer framstaellning av en polymerisationskatalysatorkomponent foer olefiner, en polymerisationskatalysatorkomponent som har framstaellts enligt foerfarandet, och dess anvaendning
JP3048653B2 (ja) * 1991-02-07 2000-06-05 三菱化学株式会社 α‐オレフィン重合体の製造
FI112233B (fi) * 1992-04-01 2003-11-14 Basell Polyolefine Gmbh Katalyytti olefiinipolymerointia varten, menetelmä sen valmistamiseksi ja sen käyttö
EP0578838A1 (de) * 1992-04-29 1994-01-19 Hoechst Aktiengesellschaft Katalysator für die Olefinpolymerisation, Verfahren zu seiner Herstellung und seine Verwendung
US5910464A (en) * 1992-06-18 1999-06-08 Montell Technology Company Bv Catalysts for the polymerization of olefins
DE69332811T2 (de) * 1992-07-01 2004-01-29 Exxonmobil Chem Patents Inc Auf Übergangsmetallen der Gruppen 5 und 6 basierende Katalysator-Vorläufer
US5420220A (en) * 1993-03-25 1995-05-30 Mobil Oil Corporation LLDPE films
US5602067A (en) * 1992-12-28 1997-02-11 Mobil Oil Corporation Process and a catalyst for preventing reactor fouling
US5332706A (en) * 1992-12-28 1994-07-26 Mobil Oil Corporation Process and a catalyst for preventing reactor fouling
US5608019A (en) * 1992-12-28 1997-03-04 Mobil Oil Corporation Temperature control of MW in olefin polymerization using supported metallocene catalyst
US5523136A (en) * 1993-04-30 1996-06-04 Cypress Packaging Packaging film, packages and methods for using them
AU680263B2 (en) * 1993-05-25 1997-07-24 Exxon Chemical Patents Inc. Novel polyolefin fibers and their fabrics
US5414180A (en) * 1993-07-14 1995-05-09 Phillips Petroleum Company Organo-aluminoxy product and use
US5455741A (en) * 1993-10-26 1995-10-03 Pulse Engineering, Inc. Wire-lead through hole interconnect device
US5614456A (en) * 1993-11-15 1997-03-25 Mobil Oil Corporation Catalyst for bimodal molecular weight distribution ethylene polymers and copolymers
US5491207A (en) * 1993-12-14 1996-02-13 Exxon Chemical Patents Inc. Process of producing high molecular weight ethylene-α-olefin elastomers with an indenyl metallocene catalyst system
US5525678A (en) * 1994-09-22 1996-06-11 Mobil Oil Corporation Process for controlling the MWD of a broad/bimodal resin produced in a single reactor
US5565395A (en) * 1995-05-26 1996-10-15 Albemarle Corporation Aluminoxanate compositions
IT1276752B1 (it) * 1995-06-20 1997-11-03 Spherilene S P A Ora Montell I Catalizzatori e procedimenti per la polimerizzazione di olefine
US5882750A (en) * 1995-07-03 1999-03-16 Mobil Oil Corporation Single reactor bimodal HMW-HDPE film resin with improved bubble stability
CN1047388C (zh) * 1995-07-14 1999-12-15 中国石油化工总公司 负载型金属茂类化合物/铝氧烷催化剂的制备
US6486089B1 (en) 1995-11-09 2002-11-26 Exxonmobil Oil Corporation Bimetallic catalyst for ethylene polymerization reactions with uniform component distribution
US5752362A (en) * 1996-03-12 1998-05-19 Tenneco Packaging Stretch wrap films
USRE38429E1 (en) * 1996-03-12 2004-02-17 Tyco Plastics Services Ag Stretch wrap films
US5998017A (en) * 1996-03-12 1999-12-07 Tenneco Packaging Stretch wrap films
US5976682A (en) * 1996-03-12 1999-11-02 Tenneco Packaging Stretch wrap films
US5749202A (en) * 1996-03-12 1998-05-12 Tenneco Packaging Stretch wrap films
US5902684A (en) * 1996-03-12 1999-05-11 Tenneco Packaging Inc. Multilayered Metallocene stretch wrap films
US5814399A (en) * 1996-03-12 1998-09-29 Tenneco Packaging Stretch wrap films
US6417130B1 (en) 1996-03-25 2002-07-09 Exxonmobil Oil Corporation One pot preparation of bimetallic catalysts for ethylene 1-olefin copolymerization
AU3505497A (en) * 1996-07-15 1998-02-09 Mobil Oil Corporation Comonomer pretreated bimetallic catalyst for blow molding and film applications
US5851070A (en) * 1996-12-05 1998-12-22 Tenneco Packaging Inc. Seals for plastic bags
US6376035B1 (en) 1996-12-05 2002-04-23 Pactiv Corporation Zipper fins for plastic bags
US5919535A (en) * 1996-12-05 1999-07-06 Tenneco Packaging Fins for plastic bags
US5989725A (en) * 1997-01-16 1999-11-23 Tenneco Packaging Clear high molecular weight film
FI972230A (fi) 1997-01-28 1998-07-29 Borealis As Uusi homogeeninen olefiinien polymerointikatalysaattorikoostumus
FI970349A (fi) 1997-01-28 1998-07-29 Borealis As Uudet metalloseeniyhdisteiden aktivaattorisysteemit
US6005463A (en) * 1997-01-30 1999-12-21 Pulse Engineering Through-hole interconnect device with isolated wire-leads and component barriers
US6013378A (en) * 1997-03-17 2000-01-11 Tenneco Packaging HMW HDPE film with improved impact strength
US5907942A (en) * 1997-05-21 1999-06-01 Tenneco Packaging Stretch wrap films
US6093480A (en) * 1997-05-21 2000-07-25 Tenneco Packaging Stretch wrap films
US5907943A (en) * 1997-06-11 1999-06-01 Tenneco Packaging Inc. Stretch wrap films
US5922441A (en) * 1997-06-11 1999-07-13 Tenneco Packaging Inc. Stretch wrap films
US6153551A (en) 1997-07-14 2000-11-28 Mobil Oil Corporation Preparation of supported catalyst using trialkylaluminum-metallocene contact products
US6051525A (en) * 1997-07-14 2000-04-18 Mobil Corporation Catalyst for the manufacture of polyethylene with a broad or bimodal molecular weight distribution
US5990035A (en) * 1997-10-21 1999-11-23 Koeppl; Alexander Polymerization catalyst systems, their preparation, and use
US6083611A (en) * 1997-11-12 2000-07-04 Tenneco Packaging, Inc. Roll wrap film
DE69922488T2 (de) * 1998-02-04 2005-12-15 Japan As Represented By Director General Of Agency Of Industrial Science And Technology Butadienpolymere und verfahren zur herstellung konjugierter dienpolymere
GB9816940D0 (en) * 1998-08-05 1998-09-30 Bp Chem Int Ltd Polymerisation catalysts
US7041618B2 (en) * 1999-06-22 2006-05-09 Lg Chemical Ltd. Supported metallocene catalyst and olefin polymerization using the same
US7247595B2 (en) * 1999-06-22 2007-07-24 Lg Chem, Ltd. Supported metallocene catalyst and olefin polymerization using the same
CN1275985C (zh) * 2001-11-30 2006-09-20 埃克森美孚化学专利公司 用非单中心/单中心催化剂结合物制备的乙烯/α-烯烃共聚物及其制备方法和用途
EP1352913B1 (de) * 2002-04-08 2016-06-01 Tosoh Finechem Corporation Verfahren zur Herstellung von modifiertem Methylaluminoxan als Olefinpolymerisationskatalysatorbestandteil
US6884749B2 (en) 2002-10-17 2005-04-26 Equistar Chemicals L.P. Supported catalysts which reduce sheeting in olefin polymerization, process for the preparation and the use thereof
ATE360037T1 (de) * 2002-12-17 2007-05-15 Ineos Europe Ltd Geträgerter olefin polymerisationskatalysator
US8028588B2 (en) 2009-09-25 2011-10-04 Rosemount Inc. Flow measurement using near field microwaves
WO2014078919A1 (pt) 2012-11-26 2014-05-30 Braskem S.A. Catalisador metaloceno suportado em suporte híbrido, processo de obtenção do mesmo, processo de polimerização para obtenção de um homopolímero ou copolímero de etileno com distribuição de massa molar ampla ou bimodal, uso do catalisador de metaloceno suportado e polímero de etileno com distribuição de massa molar ampla ou bimodal
US11161922B2 (en) 2017-10-31 2021-11-02 Exxonmobil Chemical Patents Inc. Toluene free silica supported single-site metallocene catalysts from in-situ supported MAO formation in aliphatic solvents
WO2019089145A1 (en) 2017-10-31 2019-05-09 Exxonmobil Chemical Patents Inc. Toluene free silica supported single-site metallocene catalysts from in-situ supported alumoxane formation in aliphatic solvents
EP3704164A4 (de) * 2017-10-31 2020-12-23 ExxonMobil Chemical Patents Inc. Toluolfreie siliciumdioxidgeträgerte single-site-metallocenkatalysatoren aus in-situ
CN116529253A (zh) 2020-11-23 2023-08-01 埃克森美孚化学专利公司 改进的原位mao衍生的二氧化硅负载的单中心茂金属催化剂
WO2023250240A1 (en) 2022-06-24 2023-12-28 Exxonmobil Chemical Patents Inc. Low cost processes of in-situ mao supportation and the derived finished polyolefin catalysts

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2608933A1 (de) * 1976-03-04 1977-09-08 Basf Ag Verfahren zum herstellen von polyaethylen
DE2608863A1 (de) * 1976-03-04 1977-09-08 Basf Ag Verfahren zum herstellen von polyaethylen
DE3007433C2 (de) * 1980-02-28 1982-06-16 Maizena Gmbh, 2000 Hamburg Verfahren zur Herstellung von Polymermassen aus Polyolefinen und Stärke und/oder Lignin sowie gegebenenfalls Cellulosefasern
DE3007725A1 (de) * 1980-02-29 1981-09-17 Hansjörg Prof. Dr. 2000 Hamburg Sinn Verfahren zur herstellung von polyethylen, polypropylen und copolymeren
DE3240382A1 (de) * 1982-11-02 1984-05-03 Hoechst Ag, 6230 Frankfurt Verfahren zur herstellung von gefuellten polyolefinen
DE3424697C2 (de) * 1984-07-05 1999-07-08 Targor Gmbh Verfahren zur Polymerisation von Ethylen oder von Mischungen von Ethylen mit anderen 1-Olefinen
JPH0788403B2 (ja) * 1984-11-01 1995-09-27 昭和電工株式会社 ポリオレフインの製造方法
US4937217A (en) * 1987-12-17 1990-06-26 Exxon Chemical Patents Inc. Method for utilizing triethylaluminum to prepare an alumoxane support for an active metallocene catalyst
US4912075A (en) * 1987-12-17 1990-03-27 Exxon Chemical Patents Inc. Method for preparing a supported metallocene-alumoxane catalyst for gas phase polymerization
US5008228A (en) * 1988-03-29 1991-04-16 Exxon Chemical Patents Inc. Method for preparing a silica gel supported metallocene-alumoxane catalyst
US4935397A (en) * 1988-09-28 1990-06-19 Exxon Chemical Patents Inc. Supported metallocene-alumoxane catalyst for high pressure polymerization of olefins and a method of preparing and using the same

Also Published As

Publication number Publication date
IL95982A0 (en) 1991-07-18
DE69015369D1 (de) 1995-02-02
AU6530890A (en) 1991-05-16
EP0495849A1 (de) 1992-07-29
AR244711A1 (es) 1993-11-30
KR927003650A (ko) 1992-12-18
WO1991005810A1 (en) 1991-05-02
JPH0713100B2 (ja) 1995-02-15
BR9007756A (pt) 1992-10-06
US5006500A (en) 1991-04-09
EP0495849B1 (de) 1994-12-21
JPH05501424A (ja) 1993-03-18
PT95599A (pt) 1991-09-13
CA2067177A1 (en) 1991-04-17
CA2067177C (en) 2000-03-14

Similar Documents

Publication Publication Date Title
DE69015369D1 (de) Olefinpolymerisationskatalysator aus einer trialkylaluminiummischung, kieselsäuregel und metallocen.
DE68920528T2 (de) Olefinpolymerisationskatalysator.
IL95549A0 (en) Metallocene compounds,processes for the preparation thereof and catalyst systems for olefin polymerization utilizing the same
DE69015722D1 (de) Katalytischer Konverter.
NO880350D0 (no) Fremgangsmaate for fremstilling av katalysatorkomponenter for polymerisering av olefiner.
IT8919252A0 (it) Catalizzatori per la polimerizzazione di olefine.
ES2012800B3 (es) Catalizadores de transformacion de hidrocarburos.
DE69219699T2 (de) Olefinpolymerisationskatalysator
DE3671234D1 (de) Katalysatorbestandteil fuer olefinpolymerisation.
ES2023928B3 (es) Procedimiento de preparacion de un catalizador, que contiene re, catalizador obtenido y utilizacion de este catalizador para la obtencion de olefinas por metatesis.
EP0423872A3 (en) Olefin polymerization catalyst
FI872651A0 (fi) Katalyyttikomponentti olefiinin polymerointiin
DE3670295D1 (de) Katalysatorbestandteil fuer olefinpolymerisation.
DE69022356D1 (de) Katalysatorkomponente zur olefinpolymerisation.
DE3669319D1 (de) Katalysatorbestandteil fuer olefinpolymerisation.
DE69022357D1 (de) Katalysatorkomponente zur olefinpolymerisation.
FI925832A0 (fi) Uusi olefiinipolymerointikatalyytti, menetelmä sen valmistamiseksi ja sen käyttö olefiinien polymerointiin
DE69008392D1 (de) Katalytisches Cracken.
DK0429128T3 (da) Olefinpolymerisationskatalysatorer
DE69018005T2 (de) Polymerisationskatalysator.
GB2235926B (en) Vanadium catalyst systems for olefin polymerization
NO913100L (no) Ny fremgangsmaate for fremstilling av en katalysatorkomponent for polymerisering av olefiner.
FI945294A0 (fi) Olefiinipolymerisaation katalyyttijärjestelmä
DE3885898D1 (de) Kobalt-Fischer-Tropsch-Katalysator mit einer verbesserten Selektivität.
NO910786D0 (no) Fremgangsmaate for deaktivering av etylenpolymeriserings-katalysatorer.

Legal Events

Date Code Title Description
8332 No legal effect for de
8370 Indication related to discontinuation of the patent is to be deleted
8332 No legal effect for de
8370 Indication related to discontinuation of the patent is to be deleted
8364 No opposition during term of opposition