Thesis (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Most polypropylene copolymers commercially available have ethylene, and to a
lesser degree t-butene as comonomers. Commercially available higher a-olefins,
mostly even-numbered, are seldom used for the production of pp copolymers,
probably due to cost. Sasol's Fischer- Tropsch oil-from-coal process produces
many linear and branched a-olefins as by-products that can be isolated and
purified by a relatively cheap refinery process, including the odd-numbered 1-
pentene olefin. Sasol's gas-phase Novolen pp plant at Secunda, South Africa is
ideally suited to the manufacture of high quality pp random copolymers. As such
an opportunity was identified to research the use of higher a-olefins, and more
specifically 1-pentene, in the gas-phase production of pp random copolymers.
Different methods to produce propylene / 1-pentene random copolymers in the
slurry phase on bench-scale were investigated. A procedure was subsequently
developed to produce propylene / 1-pentene random copolymers in the gas-phase
in 10 litre autoclaves. It was found that commercially available fourth generation
supported catalysts successfully incorporated the bulky 1-pentene monomer into
the propylene backbone, both during slurry and gas-phase polymerisations.
Software modelling was employed to determine the dew points of selected gas
mixtures typically found during the production of pp random copolymers. The
results indicated that typical process conditions could be employed during the
gas-phase polymerisation of propylene and 1-pentene without the risk of
condensation taking place inside the reactor.
Propylene / 1-pentene random copolymers were subsequently successfully
produced on the 800 litre BASF pilot plant in Germany followed by the first
commercial production of the copolymer on Sasol's 50m3 Novolen gas-phase
plant at Secunda. Using commercially available software the impact of introducing
1-pentene as comonomer during the production of random copolymers on the
condenser cooling capacity was evaluated. Feasible and safe plant operating
conditions were established for the production of propylene / 1-pentene random
copolymers.
The relationship between operating pressure and powder morphology was
investigated to optimise process conditions. Operating at higher pressure in the
gas-phase increases the monomer concentration in the reactor and as such
improves the space/time/yield ratio of the 50m3 reactors. It was shown that higher
operating pressures could be employed through the introduction of 1-pentene as
comonomer during the production of PP random copolymer.
The dramatic increase in catalyst productivity observed during the 800 litre pilot
plant trials, up to a comonomer ratio of about 5%, supported the results obtained
from a kinetic study carried out in bench-scale autoclaves. A comprehensive study was undertaken to compare the rheological, thermal,
crystallisation, physical and mechanical properties of propylene / 1-pentene
random copolymers with those of commercially available pp random copolymers.
A series of propylene homo- and random copolymers with 1-pentene and ethylene
as comonomers respectively, was prepared. NMR and IR techniques were
developed to facilitate the determination of copolymer composition for the new
family of 1-pentene random copolymers.
The effect of comonomer content, molecular weight and temperature on the
properties of the series of polymers was investigated. The propylene / 1-pentene
random copolymers show unique rheological behaviour associated with the short
propyl branches in the polymer backbone with minimum zero shear viscosity at
about 2% 1-pentene content. The effect of molecular structure changes with
comonomer content were analysed by the calculation of square average end-toend
distance, packing length, tube diameter, molecular mass between
entanglements and critical molecular mass. The viscosity of the 1-pentene
random copolymers shows higher shear and temperature sensitivity compared to
propylene homo- and ethylene random copolymers.
The thermodynamic melting point of the propylene / 1-pentene random
copolymers showed a significant decrease with increasing comonomer content in
the 0 to 5% range. A wider melting range and higher peak melting point
depression rate was observed compared to ethylene random copolymers at
similar and increasing comonomer content measured on a weight % basis. It was
found that the crystal structure of the propylene / 1-pentene random copolymers
contains both the Q- and the y-modifications with the ratio of the respective crystal
forms a function of both comonomer content and crystallisation temperature. The
glass temperature decreased slightly with increasing comonomer (1-pentene)
content.
It is proposed that the short branch (propyl) "defects" in the polymer backbone are
.incorporated into the crystal lattice resulting in increased rate of melting point
depression with increasing (wt%) comonomer content compared to other random
copolymers while maintaining relative high stiffness. The propylene / 1-pentene
random copolymers exhibit the lowest haze values compared to all commercially
available pp random copolymers at corresponding levels of comonomer content
on a wt% basis. The stiffness to haze ratio of propylene / 1-pentene random
copolymers are unique for all the members of the pp family. An inverse
relationship between comonomer content and the measured tensile yield strength
and modulus is observed.
Application studies conducted on the propylene / 1-pentene random copolymers
highlighted several interesting characteristics. Films produced from these
copolymers exhibited very low haze and xylene soluble values while maintaining
mechanical integrity. In the BOPP application the combination of processability
and premium film properties presents a unique opportunity for the family of
propylene / 1-pentene random copolymers. Blow moulding and injection moulding trials highlighted several advantages of
product properties manufactured with propylene / 1-pentene random copolymers if
compared to other commercially available random copolymers. The 1-pentene
randoms presented lower in-mould as well as total shrinkage than ethylene based
random copolymers.
Stabilisation and nucleation studies conducted on the propylene / 1-pentene
random copolymers showed that a typical combination antioxidant package and
nucleating agent, at normal loading levels, could be used.
In the larger pp random copolymer family 1-pentene imparts a better balance of
properties than other comonomers. The combination of low melting point and
xylene solubles with high stiffness and clarity is unique to propylene / 1-pentene
random copolymers. / AFRIKAANSE OPSOMMING: Die oorgrote meerderheid van kommersieel beskikbare polipropileen (PP)
kopolimere het etileen, en tot 'n mindere mate buteen, as komonomeer. Die
relatief hoë koste van kommersieel beskikbare hoër alfa-olefiene is moontlik
die rede waarom hulle selde gebruik word vir die vervaardiging van PP
kopolimere. Die Sasol Fischer-Tropsch proses, waartydens olie uit steenkool
vervaardig word, lewer verskeie liniêre en vertakte alfa-olefiene as
neweprodukte wat geïsoleer en gesuiwer kan word in 'n relatiewe goedkoop
rafineringsproses. Dit sluit ook die onewe-koolstofgetal 1-penteen-olefien in.
Sasol se gasfase Novolen PP aanleg in Secunda, Suid-Afrika, is besonder
geskik vir die vervaardiging van hoë standaard PP statistiese kopolimere.
Voortvloeiend hieruit is die geleentheid geidentifiseer om die gebruik van hoër
alfa-olefiene, en meer spesifiek 1-penteen, na te vors tydens die gasfaseproduksie
van PP statistiese kopolimere.
Verskeie metodes om propeleen / 1-penteen statistiese kopolimere in 'n
koolwaterstofoplosmiddel op laboratoriumskaal te produseer, is ondersoek. 'n
Prosedure is daarna ontwikkel om propileen / 1-penteen statistiese
kopolimere ook in die gasfase te vervaardig in 10-liter drukvate. Die
bevinding was dat kommersieel beskikbare vierde-generasie ondersteunde
kataliste die swaarder 1-penteenmonomeer suksesvol geïnkorporeer het in
die propileenketting tydens beide die koolwaterstof oplosmiddel- en gasfase
polimerisasiereaksies. Rekenaargebaseerde modellering is gebruik om die
kondensasiekondisies van tipiese gasmengsels, teenwoordig tydens die
produksie van PP statistiese kopolimere, te bepaal. Die resultate het
aangedui dat normale proseskondisies tydens die gasfasepolimerisasie van
propileen en 1-penteengeen risiko van kondensasie in die reaktor inhou nie.
Propileen / 1-penteen statistiese kopolimere is gevolglik met groot sukses
vervaardig by die 800-liter BASF loodsaanleg in Duitsland, gevolg deur die
eerste kommersiële vervaardiging van die kopolimeer op die Sasol50m3
Novolen gasfase-aanleg in Secunda. Deur gebruik te maak van kommersieel
beskikbare sagteware, is die impak van 1-penteen as komonomeer tydens die
vervaardiging van statistiese kopolimere op die verkoelingskapasiteit van die
kondensator bepaal. Veilige en uitvoerbare aanlegkondisies is uitgestip vir
die vervaardiging van propileen /1-penteen statistiese kopolimere.
Die verhouding tussen die reaktordruk en poeiermorfologie is ondersoek om
die prosestoestande te optimiseer. Vervaardiging van kopolimere in die
gasfase by hoër drukke lei tot verhoogde monomeerkonsentrasie in die
reaktor en gevolglik hoër produksiedeursette. Daar is bewys dat tydens die
produksie van PP statistiese kopolimere, met 1-penteen as komonomeer,
hoër reaktordruk ingespan kan word.
Die dramatiese toename in katalisproduktiwiteit waargeneem tydens die 800-
liter loodsaanleg proefloop, tot en met 'n komonomeer inhoud van ongeveer 5%, word ondersteun deur die resultate van 'n kinetiese studie uitgevoer in
laboriumskaal drukvate.
'n Omvattende studie, om die reologiese, termiese, kristallyne, fisiese en
meganiese eienskappe van propileen / 1-penteen statistiese kopolimere te
vergelyk met kommersieel beskikbare PP statistiese kopolimere, is uitgevoer.
'n Reeks propileen homo- en statistiese kopolimere, met 1-penteen en etileen
as komonomere onderskeidelik, is berei. KMR- en IR- tegnieke is ontwikkel
om die bepaling van komonomeersamestelling vir die nuwe familie van 1-
penteen statistiese kopolimere te fasiliteer.
Die invloed van komonomeersamestelling, molekulere gewig en temperatuur
op die eienskappe van die reeks polimere is ondersoek. Die propoleen / 1-
penteen statistiese kopolimere toon unieke reologiese eienskappe wat
geassosieer kan word met die propielsykettings in die polimeerruggraat. Die
viskositeit van die propileen / 1-penteen statistiese kopolimere toon 'n hoër
wrywings- en temperatuursensitiwiteit in vergelyking met propileen homo- en
etileen statistiese kopolimere.
'n Drastiese verlaging in die termodinamiese smeltpunt van die propileen / 1-
penteen statistiese kopolimere met 'n toename in komonomeerinhoud is
waargeneem tot en met 'n 5% komonomeerinhoud. Die propileen / 1-penteen
statistiese kopolimere toon 'n breër smeltgebied en 'n hoër tempo in die piek
smeltpuntafname in vergelyking met etileen statistiese kopolimere met
soortgelyke komonomeer inhoud, gemeet op 'n massabasis. Daar is bewys
dat die kristalstruktuur van die propileen / 1-penteen statistiese kopolimere
beide die alfa en gamma modifikasies bevat. Die verhouding van die
onderskeie kristalvorms is 'n funksie van komonomeerinhoud en kristalisasietemperatuur.
'n Afname in die glastemperatuur met verhoogde komonomeer
inhoud is waargeneem.
Die aanname dat die kort propielsykettings in die polimeerruggraat in die
kristalstruktuur geïnkorporeer word, is gemaak. Dit verklaar die hoë afname
in die tempo van die smeltpunt met toenemende komonomeer inhoud relatief
tot ander statistiese kopolimere, met die handhawing van hoë moduluswaardes.
Die besondere deursigtigheid van die propileen / 1-penteen
statistiese kopolimere tesame met relatief hoë modulus waardes is uniek. 'n
Omgekeerde verhouding tussen komonomeer inhoud en treksterkte asook
moduluswaardes is waargeneem.
'n Toepassingstudie uitgevoer met die propileen / 1-penteen statistiese
kopolimere het verskeie interessante resultate gelewer. Films vervaardig van
hierdie kopolimere toon besonderse deursigtigheid en lae waarde van xileenoplosbaarheid,
terwyl meganiese integriteit gehandhaaf word. Voordele in die
vervaardigingsproses van BOPP-films asook bogemiddelde filmeienskappe
hou unieke moontlikhede vir propileen / 1-penteen statistiese kopolimere in.
Verskeie voordele tydens blaas- en spuitvormingsprosesse is waargeneem
relatief tot ander beskikbare statistiese kopolimere. Die 1-penteen statistiese
kopolimere toon 'n laer in-vorm sowel as totale krimping relatief tot etileen- gebaseerde kopolimere. 'n Studie het aangetoon dat tipiese bymiddelpakette
by normale toevoegingsvlakke geskik is vir propileen / 1-penteen statistiese
kopolimere.
Gesien in die groter pp statistiese kopolimeer familie toon 1-penteen 'n beter
balans van eienskappe as ander komonomere. Die kombinasie van laer
smeltpunt en xileen-oplosbares met hoë moduluswaardes en helderheid is
uniek aan propileen /1-penteen statistiese kopolimere.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53022 |
| Date | 03 1900 |
| Creators | Potgieter, A. H. (Antonie Hermanus) |
| Contributors | Sanderson, R. D., Stellenbosch University. Faculty of Science. Dept. of Chemistry & Polymer Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 146 p. : ill. |
| Rights | Stellenbosch University |
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