This invention relates to copolymers which consist essentially of [-ether-phenyl-ether-phenylcarbonyl-
phenyl-land [ether-phenyl-phenyl-ether-phenyl-carbonyl-phenyl-] repeat units, as well
5 as end units, which have reduced melting temperature (Tm) compared to prior art copolymers
including such repeat units. The copolymers of the invention exhibit crystallinity and have similar
glass transition temperatures to the prior art polymers.
There are many thermoplastic polymeric materials available for use in industry, either used as
1 o the sole material for manufacture of components, or used as part of a composite material, for
instance a polymer/fibre composite used in the manufacture of components. However, there is
still a need for thermoplastic polymeric materials with properties that are improved in at least
some respect over existing thermoplastic polymeric materials.
15 Polyaryletherketones (PAEKs) such as polyetheretherketone (PEEK), which is a homopolymer
with [-ether-phenyl-ether-phenyl-carbonyl-phenyl-] repeat units, are often used as high
performance thermoplastic polymers. PEEK is the material of choice for many commercial
applications because it forms a highly crystalline solid, when solidified from the melt, with
outstanding mechanical and chemical resistance properties. PEEK melts at about 343°C and
20 has a Tg of about 143°C.
PAEK polymers or copolymers, unlike many conventional polymers, can be obtained in either
amorphous or crystalline form as a direct result of the way that the polymer is treated. A glassy
or amorphous state is achieved by rapidly quenching the polymer from the melt to below Tg,
25 whereas slow-cooling the polymer from the melt will allow crystallinity to develop in the sample
(melt crystallisation). The crystalline form of the polymer can also be obtained from the polymer
in its amorphous state, for instance at room temperature, by heating the polymer to a
temperature higher than Tg but less than Tm (cold crystallisation) prior to cooling back to room
temperature, or by holding the polymer at a constant temperature between Tg and Tm for a
30 length of time (isothermal crystallisation) prior to cooling back to room temperature.
PAEKs, particularly including PEEK, can be manufactured by nucleophilic polycondensation of
bisphenols with organic dihalide compounds in a suitable solvent in the presence of alkali metal
carbonates and/or bicarbonates or alkaline earth metal carbonates and/or bicarbonates. Such
35 processes are set out, for example, in EP0001879A, EP0182648A, EP0244167 A and
EP3049457 A.
Copolymers of PEEK and PEDEK are disclosed in EP0184452A, which describes a polymer
containing [-ether-phenyl-ether-phenyl-carbonyl-phenyl-] (i.e. RPEEK) repeat units and [-etherwo
2022/013520 PCT/GB2021/051582
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phenyl-phenyl-ether-phenyl-carbonyl-phenyl-] (i.e. RPEDEK) repeat units. The PEEK-PEDEK
copolymer is disclosed as having similar chemical resistance and mechanical properties to
PEEK, but also as having a lower Tm than PEEK, but a similar or higher Tg value than PEEK.
5 WO 2014/207458 A1 discloses PEEK-PEDEK copolymer manufactured by a process
comprising polycondensing a mixture of at least one dihydroxybenzene compound and at least
one dihydroxybiphenyl compound in the molar proportions 65:35 to 95:5 with at least one
dihalobenzophenone in the presence of sodium carbonate and potassium carbonate, where the
mole% of potassium carbonate, used in the synthesis of the PEEK-PEDEK copolymer by
10 nucleophilic polycondensation, is at least 2.5, where the mole% of potassium carbonate is
expressed as a percentage of the total number of moles of the hydroxy monomers used in the
synthesis. The PEEK-PEDEK copolymers of WO 2014/207458 A1 have higher crystallinity of
the resulting PEEK-PEDEK copolymer compared to that disclosed for the copolymers of
EP0184452A.
15
WO 2019/186085 A 1 discloses PEEK-PEDEK copolymers made by a specific nucleophilic
polycondensation process including polymerisation-stopping (for instance using lithium salt) and
end-capping of the copolymer (to provide specific end units to the copolymer), in the presence
of reduced quantities of aromatic sulfone solvent, to provide PEEK-PEDEK copolymers with
20 reduced chain branching and reduced melt viscosity at low shear rates compared to prior art
copolymers of comparable molecular mass.
Polyphenylene sulphide (PPS) is another known thermoplastic polymeric material which has a
lower melting temperature (Tm) than PEEK, specifically about 290°C. However, the glass
25 transition temperature (Tg) for PPS is 85°C to 1 oooc which is too low for many applications.
Polyetheretherketone (PEEK) has a suitably high Tg of 143°C to enable its use for high
temperature applications without loss of crystallinity, but its Tm of 343°C is much higher than
desirable because of the high temperatures needed to process the PEEK in its molten state
where typically temperatures in the range 370°C to 420°C may be needed. Nonetheless, PEEK
30 is the material of choice for many commercial applications because of its tendency to form a
highly crystalline structure with outstanding chemical resistance and mechanical properties.
W02019/122226 A 1 discloses PEEK-PEmEK copolymers having RPEEK repeat units:
fc r--0-o-V:0!I -\- ot j
35 ... and RPEmEK repeat units:
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... in a molar ratio RPEEKiRPEmEK from 95/5 to 45/55. These are said to provide a relationship
between melting temperature Tm and heat of fusion (~H) satisfying the equality:
5 ~H ;::: -.00005(Tm)2 + 1.008(Tm) -226.33
In the Examples of W02019/122226 A 1, as the ratio RPEEKIRPEmEK varies from 95/5 to 50/50, Tm
decreases from 333 to 253°C, and Tg falls from 154 to 129°C whilst ~H drops from 60 to 3 J/g.
This may be compared to Tm of 339°C, Tg of 149°C and ~H of 49 J/g for PEEK, according to
10 W02019/122226 A 1.
15
The term RPEmEK refers to the two ether linkages being attached to the same phenyl group in a
"meta-" configuration (1 ,3) in the repeat unit, whereas for RPEEK the two ether linkages are
attached to the same phenyl group in a "para-" configuration (1 ,4) in the repeat unit.
W02019/122226 A 1 also discloses that the PEEK-PEmEK copolymer may include repeat units
RPAEK different from the repeat units RPEEK and RPEmEK, specifically comprised between 0.1 and
5 mol% with respect to the total number of moles of repeat units of PEEK-PEmEK copolymer.
RPAEK units are listed as K-A to K-M, but none of the disclosed additional repeat units
20 corresponds to a RPEDEK repeat unit.
There is a need for further high performance PAEK polymers with reduced melting temperature
(Tm) compared to PEEK, but which have a high Tg, and which exhibiting crystallinity, giving
mechanical strength and chemical resistance comparable to that of PEEK. There is also a need
25 for further high performance PAEK polymers which have thermal decomposition temperatures
similar to that of PEEK polymers, to permit recycling and reprocessing. There is also a need for
methods to synthesise such polymers.
Such polymers of lower melting point Tm would result in easier melt processability, for instance
30 because a lower process temperature may be employed, requiring less energy use and reduced
risk of thermal degradation of the copolymer, provided that the polymer degradation temperature
is not also reduced, so that the copolymer is also potentially more readily recyclable for multiple
times. In order to ensure that the polymers are at least as recyclable and re-processable as prior
art polymers such as PEEK, the polymers should have a thermal decomposition temperature,
35 Td5, similar to that of PEEK.
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However, the maintenance of a high Tg for the polymer means that the polymer would still be
useful for high temperature applications. It is desirable to maintain the polymer Tg as high as
possible, as Tg represents the temperature above which the components made from the polymer
may reduce in strength and exhibit reductions in chemical, fatigue and wear resistance.
5 Crystallinity is also important for retention of properties at elevated temperatures and therefore
it is the combination of high Tg and a reasonable level of crystallinity that result in desired
material properties.
In addition, a lower processing temperature, arising from the reduced Tm, may permit the
1 o inclusion of additives into the copolymer prior to melt-processing, when such additives would
degrade if blended with polymers or copolymers of higher Tm.
Throughout this specification, the term "comprising" or "comprises" means including the
component(s) specified but not to the exclusion of the presence of other components.
15 The term "consisting essentially of' or "consists essentially of' means including the components
specified but excluding other components except for materials present as impurities,
unavoidable materials present as a result of processes used to provide the components, and
components added for a purpose other than achieving the technical effect of the invention.
Typically, when referring to compositions, a composition consisting essentially of a set of
20 components will comprise less than 5% by weight, typically less than 3% by weight, more
typically less than 1% by weight of non-specified components. When referring to the copolymer
of the invention, the term "consisting essentially" means that the copolymer chain has at least
95% by weight of only the specified repeat units and end units, with any other repeat units or
end units present in the polymer chain arising typically from the presence of impurities in the
25 monomers or further organic dihalide used in the manufacture of the copolymer. Deliberate
inclusion of other monomers and/or end units up to 5% by weight may be permitted.
The final product from the manufacture of the copolymer of the invention, in addition to the
copolymer itself, which consists essentially of the specified repeat units and end units, will also
30 include, in addition to the polymer chains, certain reaction by-products from the manufacture,
such as residual solvent, residual salts and residual monomer, as explained in more detail below.
Hence, the use of the term "a copolymer consisting essentially of repeat units and end units"
refers to the polymer itself, but it must be understood that the term encompasses the presence
of residual by-products, along with the polymer chains, arising from the copolymer manufacture,
35 present as up to say 5% by weight of the final product of manufacture, with the remaining 95%
being the copolymer chains.
The term "consisting of' or "consists of' means including the components specified but excluding
other components.
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Whenever appropriate, depending upon the context, the use of the term "comprises" or
"comprising" may also be taken to include the meaning "consists essentially of' or "consisting
essentially of', and also may also be taken to include the meaning "consists of' or "consisting
5 of'.
As used herein, the term "nucleophilic condensation" is used to refer briefly to the process for
preparation of PAEK, particularly PEEK-PEDEK copolymer, by nucleophilic polycondensation of
bisphenols with organic dihalide compounds, in the presence of alkali and/or alkali earth metal
1 o carbonates and/or bicarbonates in the presence of an aromatic sulfone polymerisation solvent
such as diphenyl sulfone (DPS).
References to the monomers, solvents and other additives of the nucleophilic condensation
reaction are meant to refer to these compounds used with their commercially available purities,
15 without need for further special purification.
A first aspect of the invention provides a copolymer consisting essentially of repeat units of
formula 1:
20 -0-Ph-0-Ph-CO-Ph- I;
25
30
repeat units of formula II:
II;
and end units;
wherein the molar ratio of repeat units of formula I to repeat units of formula II is from
55:45 to 95:5; and
wherein the repeat units of formula I consist essentially of 50 to 90 molar% of repeat units of
formula Ill:
Ill; and
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and 10 to 50% molar % of repeat units which are of formula IV, of formula V or of a mixture
thereof;
5 wherein the repeat unit of formula IV is:
IV; and
the repeat unit of formula Vis:
10
Preferably, the molar ratio of repeat units of formula I to repeat units of formula II is from 60:40
15 to 90:10, preferably from 70:30 to 90:10, more preferably from 80:20 to 90:10.
The repeat units of formula I consist essentially of, or preferably consist of, 50 to 90 molar% of
repeat units of formula Ill in combination with 10 to 50 molar% of repeat units of formula IV
and/or formula V. Preferably the repeat units of formula I consist essentially of, or preferably
20 consist of, 65 to 90% molar% of repeat units of formula Ill in combination with 10 to 35 molar%
of repeat units which are of formula IV, of formula V, or of a mixture thereof. More preferably,
the repeat units of formula I consist essentially of, or preferably consist of, 80 to 90% molar% of
repeat units of formula Ill in combination with 10 to 20 molar% of repeat units which are of
formula IV, of formula V, or of a mixture thereof.
25
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7
In this specification, the repeat units Ill are referred to as RPEEK, the repeat units IV are referred
to as RmPEEK and the repeat units V are referred to as RoPEEK.
So, in other words, the repeat units of formula 1 have, expressed as molar proportions:
RPEEK:( RmPEEK + RoPEEK) from 90:10 to 50:50, preferably from 90:10 to 65:35, more preferably
from 90:10 to 80:20.
In a particularly preferred embodiment, the copolymer is a copolymer as described above
1 o wherein the molar ratio of repeat units of formula I to repeat units of formula II is from 90:10 to
80:20 and wherein the repeat units of formula I consist essentially of, or preferably consist of,
80 to 90% molar% of repeat units of formula Ill in combination with 10 to 20 molar% of repeat
units which are of formula IV, of formula V, or of a mixture thereof.
15 It will be understood that formula 1: -0-Ph-0-Ph-CO-Ph- provides no information concerning
whether the ether linkages on the -0-Ph-0- moiety are arranged in para-, meta- or
ortho- configuration, whereas this is specified for formulae Ill, IV and V, as are all other
configurations within the repeat units.
20 In one embodiment, the copolymer according to the first aspect of the invention may be a
copolymer which does not include repeat units of formula IV.
25
In another embodiment, the copolymer according to the first aspect of the invention may be a
copolymer which does not include repeat units of formula V.
It will be understood that the use of only one of the repeat units IV or V leads to a simplification
of the manufacturing process.
The copolymer of the first aspect of the invention will include end units in addition to the repeat
30 units. The end units may be the same as the repeat units of the copolymer but terminated with
a terminal -OH or halogen moiety, typically an -F moiety. This will be the case if no end-capping
reagents are deliberately added to the reaction mixture when the polymer is polycondensed.
35
The copolymer of the first aspect of the invention may be end-capped so that the repeat units
include as end units in addition to end units which are
the same as the repeat units of the copolymer but terminated with a terminal -OH or halogen,
e.g. -F moiety. The end-capping process, as described below, may not necessarily lead to all
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end units being end units, but such end-capping can
lead to improved thermal stability for the copolymer.
A second aspect of the invention provides process for producing the copolymer of the first aspect
5 of the invention, the process comprising polycondensing 4,4' difluorobenzophenone with a
mixture of dihydroxy compounds consisting of 1 ,4-dihydroxybenzene, 4,4'-dihydroxydiphenyl
and at least one of 1 ,3-dihydroxybenzene and 1 ,2-dihydroxybenzene; wherein the dihydroxy
compounds are in the molar proportions required to provide the copolymer of the first aspect of
the invention;
1 o wherein the molar ratio (4,4' difluorobenzophenone)/(dihydroxy compounds) is from 1.005
to 1.05; and
wherein the polycondensation is carried out in an aromatic sulfone solvent in the presence
of particulate sodium carbonate and potassium carbonate.
15 The reaction conditions required for nucleophilic polycondensation of PEEK-PEDEK
copolymers, and for subsequent purification and solvent removal, are well known to the skilled
person, and reference is made to EP0184452A, WO 2014/207 458 and WO 2019/186085 A 1.
In the process, sodium bicarbonate or a mixture of sodium bicarbonate and sodium carbonate
20 may be considered as equivalent to sodium carbonate based upon providing the same molar
equivalence of sodium ions to the reaction mixture. Similarly, potassium bicarbonate or a mixture
of potassium bicarbonate and potassium carbonate may be considered as equivalent to
potassium carbonate based upon providing the same molar equivalence of potassium ions to
the reaction mixture.