U.S. patent application number 15/746131 was filed with the patent office on 2018-07-19 for composition made from poly(arylene-ether-ketone) (paek) stable in a molten state.
This patent application is currently assigned to ARKEMA FRANCE. The applicant listed for this patent is ARKEMA FRANCE. Invention is credited to Philippe BUSSI, Guillaume LE.
Application Number | 20180201759 15/746131 |
Document ID | / |
Family ID | 54066133 |
Filed Date | 2018-07-19 |
United States Patent
Application |
20180201759 |
Kind Code |
A1 |
LE; Guillaume ; et
al. |
July 19, 2018 |
COMPOSITION MADE FROM POLY(ARYLENE-ETHER-KETONE) (PAEK) STABLE IN A
MOLTEN STATE
Abstract
A composition made from poly(arylene-ether-ketone) (PAEK),
characterized in that it includes an organometallic phosphate salt,
or a mixture of organometallic phosphate salts. An object
manufactured by a technology chosen from laser sintering, fused
deposition modeling, molding, injection molding, extrusion,
thermoforming, rotational molding, compression molding, compounding
or impregnation, using the composition.
Inventors: |
LE; Guillaume; (Colombelles,
FR) ; BUSSI; Philippe; (Maisons Laffitte,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ARKEMA FRANCE |
Colombes |
|
FR |
|
|
Assignee: |
ARKEMA FRANCE
Colombes
FR
|
Family ID: |
54066133 |
Appl. No.: |
15/746131 |
Filed: |
July 21, 2016 |
PCT Filed: |
July 21, 2016 |
PCT NO: |
PCT/FR2016/051894 |
371 Date: |
January 19, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08G 65/4012 20130101;
C08K 3/32 20130101; C08L 71/00 20130101; C08K 2003/322 20130101;
C08L 2201/08 20130101; C08L 2205/025 20130101; C08G 65/40 20130101;
C08K 2003/324 20130101; C08K 5/521 20130101; C08G 2650/40 20130101;
C08L 71/00 20130101; C08K 3/32 20130101 |
International
Class: |
C08K 5/521 20060101
C08K005/521; C08G 65/40 20060101 C08G065/40; C08L 71/00 20060101
C08L071/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2015 |
FR |
1556931 |
Claims
1. A composition based on poly(arylene ether ketone) (PAEK),
wherein the composition comprises an organometallic phosphate salt
or a mixture of organometallic phosphate salts.
2. The composition as claimed in claim 1, wherein the
organometallic phosphate salt(s) have the following formula:
##STR00020## wherein R is or is not different from R', R and R'
being formed by one or more aromatic groups which are substituted
or unsubstituted by one or more groups having from 1 to 9 carbons,
R and R' possibly being directly linked to one another or separated
by at least one group chosen from the following groups:
--CH.sub.2--; --C(CH.sub.3).sub.2--; --C(CF.sub.3).sub.2--;
--SO.sub.2--; --S--; --CO--; --O--, and M represents an element
from Group IA or IIA of the Periodic Table.
3. The composition as claimed in claim 1, wherein the
organometallic phosphate salt is sodium
2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate.
4. The composition as claimed in claim 1, wherein the proportions
of organometallic phosphate salt in the composition are between 10
ppm and 50 000 ppm.
5. The composition as claimed in claim 1, wherein the composition
based on PAEK is a composition based on one of the following
polymers: PEKK, PEEK, PEEKK, PEKEKK, PEEEK or PEDEK.
6. The composition as claimed in claim 1, wherein the composition
based on PAEK is a poly(ether ketone ketone) (PEKK)
composition.
7. The composition as claimed in claim 6, wherein the composition
based on PAEK is a composition based on PEKK, and comprises, in
addition to the PEKK, at least one of the following polymers: PEK,
PEEKEK, PEEK, PEEKK, PEKEKK, PEEEK, PEDEK, with a content of less
than 50% by weight of the composition.
8. The composition as claimed in claim 1, wherein the composition
also comprises at least one filler and/or at least one other
additive.
9. The composition as claimed in claim 1, wherein the composition
is stable in the molten state.
10. The composition as claimed in claim 1, wherein the
organometallic phosphate salt or the mixture of organometallic
phosphate salts also acts as a nucleating agent within said
composition.
11. An object manufactured by a technology chosen from laser
sintering, fused deposition modeling, molding, injection molding,
extrusion, thermoforming, rotational molding, compression molding,
compounding or impregnation, using a composition as claimed in
claim 1.
12. The use of an organometallic phosphate salt to stabilize a
composition based on poly(arylene ether ketone) (PAEK) in the
molten state.
Description
[0001] The invention relates to the field of the poly(arylene ether
ketone)s.
[0002] More particularly, the invention relates to a composition
based on poly(arylene ether ketone) (PAEK) that is stable in the
molten state.
PRIOR ART
[0003] The generic term of poly(arylene ether ketone) (PAEK)
denotes a family of high-performance polymers with high
thermomechanical properties. These polymers consist of aromatic
rings linked by an oxygen atom (ether) and/or by a carbonyl group
(ketone). Their properties mainly depend on the ether/ketone ratio.
In the abbreviations used for naming the materials of the PAEK
family, the letter E denotes an ether function and the letter K
denotes a ketone function. In the remainder of the description,
these abbreviations will be used instead of the customary names to
denote the compounds to which they refer.
[0004] The PAEK family groups together, more particularly,
poly(ether ketone) (PEK), poly(ether ether ketone) (PEEK),
poly(ether ether ketone ketone) (PEEKK), poly(ether ketone ketone)
(PEKK), poly(ether ketone ether ketone ketone) (PEKEKK), poly(ether
ether ketone ether ketone) (PEEKEK), poly(ether ether ether ketone)
(PEEEK) and poly(ether diphenyl ether ketone) (PEDEK).
[0005] These polymers are used for applications which are
restrictive in terms of temperature and/or in terms of mechanical
stresses, indeed even chemical stresses. These polymers are
encountered in fields as varied as aeronautics, offshore drilling
or medical implants. Depending on their nature and their
applications, they may be processed by different known techniques
such as molding, extrusion, compression molding, compounding,
injection molding, calendering, thermoforming, rotational molding,
impregnation, laser sintering or else fused deposition modeling
(FDM) for example, at temperatures in general of between 320 and
430.degree. C.
[0006] PAEKs have high melting points, typically greater than
300.degree. C. Consequently, to be able to be processed, they must
be melted at a high temperature, typically greater than 320.degree.
C., preferably greater than 350.degree. C., and more generally at a
temperature of the order of 350 to 390.degree. C. These
temperatures depend of course on the PAEK structures in question
and on the viscosities. In the prior art, it is considered that it
is necessary to melt PAEKs at a temperature greater by at least
20.degree. C. than the melting point of the PAEK in question.
[0007] However, at such processing temperatures, the molten PAEKs
are not stable with regard to thermal oxidation if their
composition is not optimized and/or in the absence of additives
which make it possible to stabilize the structure. Phenomena of
structural change are then witnessed, either by chain cleavage
and/or extension mechanisms, induced by branchings and/or couplings
from chain ends or defects. These defects may come from oxidation
reactions, under the effect of temperature and of dioxygen from the
atmosphere or already present in the polymer. These structural
changes may go as far as crosslinking of the polymer and also lead
to the release of compounds, among which mention may be made of
carbon dioxide (CO.sub.2), carbon monoxide (CO), phenols and
aromatic ethers. These phenomena of structural change lead to a
deterioration in the physicochemical and/or mechanical properties
of the PAEKs and to a change in their melt viscosity. These changes
make the processing of these polymers in the molten state more
difficult, inducing for example variations not only in the
operating parameters of the machines used for transforming the
polymers but also in the appearance and the dimensions of the
products obtained after transformation.
[0008] Solutions have already been envisaged to stabilize the PAEK
compositions in the molten state, but as yet they are not entirely
satisfactory.
[0009] Document U.S. Pat. No. 5,208,278 describes the use of
organic bases to stabilize PAEKs. According to the authors of this
document, these organic bases make it possible to scavenge the
acidity in the polymer. Examples show a better stability of the
melt viscosity, but always in a confined medium, that is to say in
the absence of an environment with dioxygen. In addition, the use
of these organic bases is problematic since they may evaporate
and/or they generate volatile organic compounds at the
transformation temperatures of the PAEKs.
[0010] Stabilizers of metal oxide type, as described in the
document U.S. Pat. No. 3,925,307, or aluminosilicates, as described
in the document U.S. Pat. No. 4,593,061, also make it possible to
scavenge acidity but do not make it possible to sufficiently
improve the stability of the molten polymer with regard to thermal
oxidation and may themselves generate structural changes. In
addition, in order to achieve sufficient stability, it is necessary
to add very large amounts of these additives which may then also
have a filler action, impacting on the properties of the polymer
and the processing thereof.
[0011] Documents U.S. Pat. No. 5,063,265, U.S. Pat. No. 5,145,894
and WO2013/164855 describe the use of aromatic organophosphorus
compounds for stabilizing molten PAEK compositions, used either
alone or in synergy with another additive. Document U.S. Pat. No.
5,063,265 describes, for example, the use of a phosphonite, and
more particularly tetrakis(2,4-di-tert-butylphenyl)
[1,1'-biphenyl]-4,4'-diyl bisphosphonite, subsequently denoted
PEP-Q, and of an organic acid, for stabilizing PAEKs. Such
organophosphorus compounds have a relatively low degree of
oxidation. They are typically in oxidation state 2 or 3 and
consequently assume the role of reducer of the peroxide groups in
the molten polymer. A major drawback of these aromatic
organophosphorus compounds such as phosphonites or phosphites for
example lies in the fact that they are sensitive to hydrolysis and
consequently it is very difficult to incorporate them via the
aqueous route or during a synthesis process. In addition, they are
not sufficiently stable at the transformation temperatures, with
the result that they degrade and generate the emission of volatile
organic compounds.
[0012] Now, for example in the field of manufacturing structural
composites by impregnation, three main routes are possible: [0013]
either impregnation is carried out by melting the polymer above its
melting point and often in the presence of air. It is thus
understood that the polymer matrix must not be too sensitive to
thermal oxidation phenomena. In addition, if volatile organic
compounds are generated, this may lead to defects in the
impregnation, with the formation of porosities which may be
detrimental to the properties of the final composite material,
[0014] or a solvent route is used. However, PAEKs are only soluble
in a few, generally highly acidic, organic solvents, or under hot
conditions in heavy solvents such as diphenyl sulfone. In addition
to the difficulty of using this type of solvent, it is very
difficult to completely eliminate it, which may generate the same
difficulties as the volatile organic compounds. [0015] or finally
an aqueous suspension of PAEK powder is more generally used, such
as described in the document entitled "Wet impregnation as route to
unidirectional carbon fibre reinforced thermoplastic composites
manufacturing", K. K. C. Ho et al., Plastics, Rubber and
Composites, 2011, Vol. 40, No. 2, p. 100-107. Thus, for example, a
suspension of PAEK powder and of a surfactant is used, which is
deposited on carbon fibers or glass fibers, for example. The fibers
are passed into an oven to evaporate the water, then into a die at
high temperature, typically greater than 400.degree. C., such that
the polymer melts and coats the carbon fibers. The pre-impregnated
strips obtained are then used to form composite objects by heating
them again at high temperature.
[0016] Consequently, the fact that the stabilizer is sensitive to
hydrolysis and degrades thermally poses a problem during the
incorporation thereof into the molten polymer and/or during the
high-temperature processing of the polymer. Moreover, the volatile
organic compounds released during the degradation of the stabilizer
have an unpleasant odor, are harmful to the environment and/or
health, and create porosities in the composite material being
manufactured, leading to mechanical defects in the finished
composite part. Finally, during an impregnation of fibers, the
volatile organic compounds emitted may also hinder the coating of
the fibers and generate significant mechanical defects in the
objects resulting therefrom.
[0017] Document WO9001510 describes a treatment of a powder of
polymer of the PAEK family in an aqueous solution of a phosphate
salt, at high temperature and under pressure for 3 hours to reduce
the level of impurities. The polymer treated in this way is then
filtered and washed with water three times, then dried for 16
hours. Nothing in this document indicates that the phosphate salt,
which is water-soluble, effectively remains in the polymer powder.
Moreover, the treatment described is onerous and lengthy to
implement and is very different from additivation. Finally, nothing
in this document states that it is effective against the phenomenon
of thermal oxidation, since the stability is only evaluated in a
confined medium. Indeed, phosphate salts are known for being used
in other polymer matrices, such as polysulfones, or polyvinyl
chlorides for example, to scavenge acidity and chlorides contained
in the polymer. Such uses are for example described in documents
U.S. Pat. No. 3,794,615 or EP 0 933 395 or else US2013/0281587 but
in these cases also, no stabilizing action in the presence of air
is described.
TECHNICAL PROBLEM
[0018] The aim of the invention is thus to overcome at least one of
the disadvantages of the prior art. In particular, the aim of the
invention is to propose a composition based on PAEK, which is
stable in the molten state with regard to thermal oxidation, and
which does not generate the emission of volatile organic
compounds.
BRIEF DESCRIPTION OF THE INVENTION
[0019] Surprisingly, it has been discovered that a composition
based on poly(arylene ether ketone) (PAEK), characterized in that
it comprises an organometallic phosphate salt or a mixture of
organometallic phosphate salts, has a very high stability in the
molten state with regard to thermal oxidation, even in the presence
of air, without releasing volatile organic compounds, the
stabilizer used being very stable at high temperature, typically
greater than 350.degree. C., and not being sensitive to hydrolysis.
Since organometallic phosphate salt(s) are predominantly soluble in
water, the incorporation thereof into the composition based on PAEK
is thereby facilitated.
[0020] According to other optional characteristics of the
composition: [0021] the organometallic phosphate salt(s) have the
following formula:
[0021] ##STR00001## [0022] wherein R is or is not different from
R', R and R' being formed by one or more aromatic groups which are
substituted or unsubstituted by one or more groups having from 1 to
9 carbons, R and R' possibly being directly linked to one another
or separated by at least one group chosen from the following
groups: [0023] CH.sub.2--; [0024] --C(CH.sub.3).sub.2--;
--C(CF.sub.3).sub.2--; --SO.sub.2--; --S--; --CO--; --O--, and M
represents an element from Group IA or IIA of the Periodic Table,
[0025] the organometallic phosphate salt is sodium
2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate, [0026] the
proportions of organometallic phosphate salt in the composition are
between 10 ppm and 50 000 ppm, preferably between 100 and 5000 ppm,
[0027] the composition based on PAEK is more particularly a
composition based on one of the following polymers: PEKK, PEEK,
PEEKK, PEKEKK, PEEEK or PEDEK, [0028] the composition based on PAEK
is more particularly a poly(ether ketone ketone) (PEKK)
composition, [0029] the composition based on PAEK is more
particularly a composition based on PEKK, and comprises, in
addition to the PEKK, at least one of the following polymers: PEK,
PEEKEK, PEEK, PEEKK, PEKEKK, PEEEK, PEDEK, with a content of less
than 50% by weight of the composition, preferably less than or
equal to 30% by weight of the composition, [0030] the composition
also comprises at least one filler and/or at least one other
additive, [0031] the composition is stable in the molten state,
[0032] the organometallic phosphate salt or the mixture of
organometallic phosphate salts also acts as a nucleating agent
within said composition.
[0033] The invention also relates to an object manufactured by a
technology chosen from laser sintering, fused deposition modeling,
molding, injection molding, extrusion, thermoforming, rotational
molding, compounding, compression molding or impregnation, using a
composition as described above.
[0034] Finally, the invention relates to a use of an organometallic
phosphate salt to stabilize a composition based on poly(arylene
ether ketone) (PAEK) in the molten state.
[0035] Other advantages and features of the invention will become
apparent on reading the following description given by way of
illustrative and non-limiting example, with reference to the
appended figures, of which:
[0036] FIG. 1 represents a curve of the complex viscosity measured
by an oscillating rheometer as a function of time of a
non-stabilized reference product under nitrogen,
[0037] FIG. 2 represents a thermogravimetric curve as a function of
temperature of a reference stabilizer used by way of
comparison.
DESCRIPTION OF THE INVENTION
[0038] The poly(arylene ether ketone)s (PAEKs) used in the
invention comprise units of the following formulae:
(--Ar--X--) and (--Ar.sub.1--Y--)
wherein: [0039] Ar and Ar.sub.1 each denote a divalent aromatic
radical; [0040] Ar and Ar.sub.1 may preferably be chosen from
1,3-phenylene, 1,4-phenylene, 4,4'-biphenylene, 1,4-naphthylene,
1,5-naphthylene and 2,6-naphthylene; [0041] X denotes an
electron-withdrawing group; it may preferably be chosen from the
carbonyl group and the sulfonyl group, [0042] Y denotes a group
chosen from an oxygen atom, a sulfur atom, an alkylene group such
as --CH.sub.2-- and isopropylidene. [0043] In these units X and Y,
at least 50%, preferably at least 70% and more particularly at
least 80% of the groups X are a carbonyl group, and at least 50%,
preferably at least 70% and more particularly at least 80% of the
groups Y represent an oxygen atom. [0044] According to a preferred
embodiment, 100% of the groups X denote a carbonyl group and 100%
of the groups Y represent an oxygen atom.
[0045] More preferentially, the poly(arylene ether ketone) (PAEK)
may be chosen from:
[0046] a poly(ether ketone ketone), also referred to as PEKK,
comprising units of formula I A, of formula I B, and the mixture
thereof:
##STR00002##
[0047] a poly(ether ether ketone), also referred to as PEEK,
comprising units of formula IIA:
##STR00003##
Similarly, it is possible to introduce para sequences into these
structures at the ethers and the ketones according to the formula
IIB:
##STR00004##
The sequence may be totally para but it is also possible to
introduce partially or totally meta sequences:
##STR00005##
or else:
##STR00006##
or ortho sequences according to the formula V:
##STR00007##
[0048] a poly(ether ketone), also referred to as PEK, comprising
units of formula VI:
##STR00008##
Similarly, the sequence may be totally para but it is also possible
to introduce partially or totally meta sequences (formulae VII and
VIII):
##STR00009##
[0049] a poly(ether ether ketone ketone), also referred to as
PEEKK, comprising units of formula IX:
##STR00010##
Similarly, it is possible to introduce meta sequences into these
structures at the ethers and the ketones.
[0050] a poly(ether ether ether ketone), also referred to as PEEEK,
comprising units of formula X:
##STR00011##
Similarly, it is possible to introduce meta sequences into these
structures at the ethers and the ketones, but also biphenol
sequences according to the formula XI:
##STR00012##
[0051] Other arrangements of the carbonyl group and of the oxygen
atom are also possible.
[0052] The composition which is a subject of the invention is based
on PAEK. More particularly, the composition is a composition based
on poly(ether ketone ketone) (PEKK).
[0053] According to one variant embodiment, the composition based
on PAEK may also be a composition based on one of the following
polymers: PEEK, PEEKK, PEKEKK, PEEEK or PEDEK.
[0054] The composition based on PAEK may also be a composition
based on a mixture of polymers of the PAEK family. Thus, the
composition may be based on PEKK and comprise, in addition to the
PEKK, at least one of the following polymers: PEK, PEEKEK, PEEK,
PEEKK, PEKEKK, PEEEK, PEDEK, with a content of less than 50% by
weight of the composition, preferably less than or equal to 30% by
weight of the composition.
[0055] Advantageously, the PAEK composition according to the
invention is stable in the molten state by virtue of the
incorporation of a phosphate salt in the composition.
[0056] In the present description, "polymer stable in the molten
state" means a polymer, the structure of which barely changes when
it is molten, so that the physicochemical properties thereof,
especially the viscosity, only vary within a limited range. More
specifically, a polymer will be considered to be stable in the
molten state under nitrogen when the change in the viscosity
thereof in the molten state in 30 minutes, measured by an
oscillating rheometer under nitrogen and with an oscillation
frequency of 1 Hz, at 380.degree. C. or 20.degree. C. above the
melting point thereof when said melting point is greater than
370.degree. C., is less than 100%, especially less than 50%, in
particular less than 20%, and most particularly between -20% and
+20%. Likewise, a polymer will be considered to be stable in the
molten state under air when the change in the viscosity thereof in
the molten state in 30 minutes, measured as indicated above but
under air and with an oscillation frequency of 0.1 Hz, is less than
150%, especially less than 100%, in particular less than 50%, and
most particularly between -20% and +50%.
[0057] According to one variant, the stabilizer incorporated into
the composition may be a mixture of phosphate salts.
[0058] Indeed, it has been discovered that such a phosphate salt
makes it possible to stabilize a PAEK composition in the molten
state just as well under nitrogen as under air. This effect of
stabilizing the PAEK in the molten state under air is very
surprising, and it was not at all intuitive for those skilled in
the art to choose to incorporate a phosphate salt to stabilize a
PAEK in the molten state with regard to a phenomenon of thermal
oxidation. Indeed, a phosphate salt has a maximum degree of
oxidation, with the result that it is not known to be an
antioxidant. Yet, in the presence of the oxygen in the air, it
manages to stabilize the polymer in the molten state with regard to
the phenomenon of thermal oxidation. Indeed, a more stable
viscosity of the composition in the molten state is obtained
compared to one and the same composition devoid of phosphate salt,
which means that the phenomena of chain extension through phenomena
of branching, inter alia, are more limited.
[0059] The phosphate salt is therefore present as an active agent
stabilising PAEK compositions in the molten state, even in the
presence of air, with as great an effectiveness as an aromatic
organophosphorus compound. Nonetheless, it also has a considerable
advantage relative to an aromatic organophosphorus compound since
it does not hydrolyze and does not generate any emission of
volatile organic compounds. Only water may be generated in certain
cases in which the phosphate salt is present in a hydrated form or
when the phosphate salt dimerizes.
[0060] Advantageously, one or more phosphate salt(s) may be
incorporated into the composition based on PAEK. The phosphate salt
is advantageously chosen from one (or more) phosphate salt(s) of
ammonium, of sodium, of calcium, of zinc, of aluminum, of
potassium, of magnesium, of zirconium, of barium, of lithium or of
rare earths. Preferably, the phosphate salt(s) is (are) one (or
more) organometallic phosphate salt(s).
[0061] The organometallic phosphate salt(s) used has (have) the
following formula:
##STR00013##
wherein R is or is not different from R', R and R' being formed by
one or more aromatic groups which are substituted or unsubstituted
by one or more groups having from 1 to 9 carbons, R and R' possibly
being directly linked to one another or separated by at least one
group chosen from the following groups: --CH.sub.2--;
--C(CH.sub.3).sub.2--; --C(CF.sub.3).sub.2--; --SO.sub.2--; --S--;
--CO--; --O--, and M represents an element from Group IA or IIA of
the Periodic Table.
[0062] Further preferably, the organometallic phosphate salt is
sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl) phosphate.
[0063] Preferably, the phosphate salt, or the mixture of phosphate
salts, is incorporated into the composition based on PAEK in
proportions of between 10 ppm and 50 000 ppm, and even more
preferably between 100 and 5000 ppm.
[0064] Another surprising effect linked to the incorporation of the
phosphate salt into the composition based on PAEK lies in the fact
that it makes it possible to act as a nucleating agent. Increasing
the crystallization kinetics to make a crystallizable product
therefrom under standard transformation conditions, or for example
in laser sintering, and thus to have a semicrystalline PEKK, is
advantageous for certain properties such as chemical resistance.
Moreover, such a nucleating agent makes it possible to control the
crystalline morphology of the polymer, and especially the size of
the crystalline zones (or spherulites), in order to ensure a
consistency in the mechanical properties of the polymer, regardless
of the processing conditions of the polymer.
[0065] The invention also relates to a process for the
stabilization, in the molten state, of a composition based on PAEK,
said process comprising a step of incorporating an agent which
stabilizes with regard to the phenomena of thermal oxidation, said
process being characterized in that the stabilizing agent
incorporated is a phosphate salt or a mixture of phosphate
salts.
[0066] The phosphate salt may be incorporated into the composition
based on PAEK by one of the following techniques: dry blending,
compounding, wet impregnation or during the process for
synthesizing the PAEK polymer.
[0067] The process for synthesizing a PAEK generally consists of a
polycondensation. The synthesis may be carried out according to two
routes: a nucleophilic route, according to which ether bonds form
during the polymerization step, or an electrophilic route,
according to which carbonyl bridges form during the polymerization
step. PEKK, for example, results from a Friedel-Crafts
polycondensation reaction between DPE (diphenyl ether) and a
terephthaloyl chloride and/or an isophthaloyl chloride, for
example.
[0068] Advantageously, the stabilized composition based on PAEK may
be obtained in the form of granules by compounding on a device
known to those skilled in the art, such as a twin-screw extruder, a
co-kneader or an internal mixer.
[0069] The composition prepared in this way may then be transformed
for a use or a subsequent transformation known to those skilled in
the art by means of devices such as an injection-molding machine,
an extruder, laser sintering equipment, etc.
[0070] The process for preparing the composition according to the
invention may also use a twin-screw extruder feeding, without
intermediate granulation, an injection-molding machine or an
extruder according to a processing device known to those skilled in
the art.
[0071] The stabilized composition based on PAEK may also be
obtained in powder form, by dry blending, for example.
[0072] Using the composition obtained, which may either be in the
form of granules or in the form of a powder, it is possible to
manufacture various objects by a technique of laser sintering,
injection molding or extrusion, thermoforming, rotational molding,
compression molding or else impregnation, for example.
[0073] Wet impregnation, for example, for manufacturing
pre-impregnated composite strips, also referred to as tape,
consists in depositing an aqueous dispersion of a PAEK powder and
of phosphate salt(s) on carbon or glass fibers, for example. More
particularly, the dispersion may for example comprise a PEKK powder
and phosphate salt(s) and a surfactant in aqueous solution. The
fibers thus covered with the aqueous dispersion are then passed
into an oven to evaporate the water. They are then passed into a
die at high temperature, typically of greater than 370.degree. C.,
in order to be able to melt the stabilized PEKK polymer and for it
to be able to correctly coat the fibers. After cooling, tapes or
pre-impregnated strips are obtained which are then used by
assembling and/or superimposing them, to remelt them and form
composite objects.
[0074] One major advantage of phosphate salts lies in the fact
that, even heated to a very high temperature, greater than or equal
to 350.degree. C. for example, they do not generate the emission of
volatile organic compounds but they simply lose water in the form
of vapor. Consequently, phosphate salts do not present any risk for
the environment and/or health and they do not create porosities
liable to hinder the coating of the fibers and/or to generate the
appearance of defects in the final manufactured object, liable to
then lead to a deterioration in the mechanical properties.
[0075] The composition based on PAEK and on phosphate salt(s) as
defined above may be prepared by any known method making it
possible to obtain a homogeneous mixture containing the composition
according to the invention and optionally other additives, fillers
or other polymers. Such a method may be chosen from techniques of
dry blending (using, for example, a roll mill), of melt extrusion,
of compounding or else of wet impregnation or during the process
for synthesizing the polymer.
[0076] More particularly, the composition according to the
invention may be prepared by melt blending all the components
thereof, especially in a "direct" process.
[0077] Compounding, for example, is a process which makes it
possible to mix, by melting, plastic materials and/or additives
and/or fillers. In order to manufacture the composition, the
starting materials, present in the form of granules, are placed in
a co-rotating twin-screw extruder.
[0078] The following examples nonlimitingly illustrate the scope of
the invention:
EXAMPLE 1
Measurements of Viscosity Under Nitrogen
[0079] Several compositions based on PEKK were prepared. A control
composition C.sub.T of PEKK comprising no stabilizer was prepared
by a conventional synthesis process by a polycondensation
reaction.
[0080] A second composition based on PEKK, with the reference C1,
was prepared by wet impregnation, wherein PEP-Q
(tetrakis(2,4-di-tert-butylphenyl) [1,1'-biphenyl]-4,4'-diyl
bisphosphonite), of formula (1) below, was incorporated at an
amount of 1000 ppm. This phosphonite is used as comparative example
for stabilizing the PEKK composition.
##STR00014##
[0081] A third composition based on PEKK, with the reference C2,
was prepared by aqueous impregnation, wherein anhydrous monosodium
phosphate (NaH.sub.2PO.sub.4), also referred to as sodium
dihydrogen phosphate, of formula (2) below, was incorporated at an
amount of 1000 ppm.
##STR00015##
[0082] A fourth composition based on PEKK, with the reference C3,
was prepared in the same manner as the second and third
compositions, by aqueous impregnation, wherein sodium
trimetaphosphate (Na.sub.3P.sub.3O.sub.9), also referred to as
anhydrous trisodium phosphate, of formula (3) below, was
incorporated at an amount of 1000 ppm.
##STR00016##
[0083] A fifth composition based on PEKK, with the reference C4,
was prepared in the same manner as the preceding compositions, by
impregnation with acetone, wherein an organic phosphate, and more
particularly triphenyl phosphate, of formula (4) below, was
incorporated at an amount of 1000 ppm.
##STR00017##
[0084] The melt viscosity of these compositions C.sub.T to C4 was
then measured with an oscillating rheometer as a function of time,
at 380.degree. C., under nitrogen, with an oscillation frequency,
also referred to as stress, of 1 Hz, and with a strain amplitude of
0.5%.
[0085] The curve of FIG. 1 represents the viscosity of the control
composition C.sub.T of PEKK, measured in this way. From the initial
viscosity and the viscosity after a duration of 30 minutes, the
stability of the polymer over time is then calculated, expressed as
percentage change in the viscosity (EV %), at 380.degree. C. The
stability of the polymer is then calculated according to the
following formula:
% EV=(viscosity at 30 min-initial viscosity)/initial
viscosity*100
[0086] It emerges from the curve of FIG. 1 that the stability,
expressed as percentage change in the viscosity EV, of the control
composition C.sub.T based on PEKK-based polymer, under nitrogen
with a 1 Hz stress, is equal to 160%.
[0087] Table I below brings together the data on stability (EV %)
under nitrogen of the different compositions C.sub.T to C4 obtained
by wet impregnation, with or without stabilizer.
TABLE-US-00001 TABLE I EV (%) Reference Composition (under N.sub.2,
1 Hz) C.sub.T Reference PEKK 160% C1 1000 ppm PEP-Q 50% C2 1000 ppm
of anhydrous monosodium 50% phosphate C3 1000 ppm of anhydrous
trisodium 50% phosphate C4 1000 ppm of triphenyl phosphate 110%
[0088] It emerges from the results presented in table I that the
presence of a phosphate salt in a composition based on PEKK makes
it possible to obtain a composition in the molten state which has a
more stable viscosity over time, unlike the control composition
C.sub.T, the viscosity of which increases rapidly with time,
indicating chain extensions and therefore significant changes in
the characteristics of the polymer.
[0089] While the organic phosphate (in composition C4) has a lesser
effect compared to the phosphate salts, it also makes it possible
to obtain a composition in the molten state having a more stable
viscosity than the control composition C.sub.T of PEKK.
EXAMPLE 2
Measurements of Viscosity Under Nitrogen and Under Air
[0090] Several compounds based on PEKK were prepared by the
compounding technique. The different compounds are produced with an
extruder from several compositions based on PEKK. The behavior of
the different compositions at 380.degree. C. under nitrogen and
under air was compared.
[0091] A first control composition C.sub.T' of PEKK in the form of
granules and not comprising any stabilizer was prepared.
[0092] A second composition based on PEKK, with the reference C5,
was prepared by the compounding technique, wherein monosodium
phosphate (NaH.sub.2PO.sub.4), of formula (1) above, was
incorporated at an amount of 1000 ppm.
[0093] A third composition based on PEKK, with the reference C6,
was prepared by the compounding technique, wherein trisodium
phosphate (Na.sub.3P.sub.3O.sub.9), of formula (3) above, was
incorporated at an amount of 1000 ppm.
[0094] A fourth composition based on PEKK, with the reference C7,
was prepared by the compounding technique, wherein ADK STAB NA-11UH
(sodium 2,2'-methylene-bis(4,6-di-tert-butylphenyl) phosphate), of
formula (5) below, was incorporated at an amount of 1000 ppm.
##STR00018##
[0095] The melt viscosity of these compositions C.sub.T', C5, C6
and C7 was then measured with an oscillating rheometer as a
function of time, at 380.degree. C., under nitrogen then under air,
with an oscillation frequency, also referred to as stress,
respectively of 1 Hz and of 0.1 Hz, and with a strain amplitude of
0.5%.
[0096] Table II below brings together the data on stability (EV %)
under nitrogen and under air of these different compositions
obtained by compounding, with or without stabilizer.
TABLE-US-00002 TABLE II EV (%) EV (%) (under (under air, Reference
Composition N.sub.2, 1 Hz) 0.1 Hz) C.sub.T' Granulated PEKK 230%
390% C5 1000 ppm of anhydrous 30% 115% monosodium phosphate C6 1000
ppm of anhydrous trisodium 45% 115% phosphate C7 1000 ppm of sodium
2,2'-methylene- 15% 2% bis(4,6-di-tert-butylphenyl) phosphate
[0097] It emerges from the results of table II that the phosphate
salts are good stabilizers of the PEKK, equally well under nitrogen
as under air. The most surprising phenomenon of stabilization lies
in the fact that, even under air, the viscosity measured in the
molten state remains relatively stable. The phosphate salts are
therefore stabilizing agents which are highly effective with regard
to the phenomenon of thermal oxidation, even in the presence of
air.
EXAMPLE 3
influence of the Ratio of Phosphate Salt Incorporated
[0098] Several compositions based on PEKK were prepared. A control
composition C.sub.T of PEKK comprising no stabilizer was prepared
by a conventional synthesis process by a polycondensation reaction.
The other compositions are based on PEKK and each comprise
anhydrous trisodium phosphate at different contents.
[0099] The compositions compared are prepared by aqueous
impregnation.
[0100] The composition with the reference C8 in table III below
comprises 500 ppm of anhydrous trisodium phosphate, while the
composition with the reference C9 comprises 1000 ppm thereof and
the composition with the reference C10 comprises 3000 ppm
thereof.
[0101] The melt viscosity of these compositions C.sub.T, C8, C9 and
C10 was then measured with an oscillating rheometer as a function
of time, at 380.degree. C., under nitrogen, with a stress of 1 Hz
and with a strain amplitude of 0.5%.
[0102] Table Ill below brings together the data on stability (EV %)
under nitrogen of these different compositions.
TABLE-US-00003 TABLE III EV (%) (under Reference Composition
N.sub.2, 1 Hz) C.sub.T Reference PEKK 160% C8 500 ppm of anhydrous
trisodium phosphate 50% C9 1000 ppm of anhydrous trisodium
phosphate 45% C10 3000 ppm of anhydrous trisodium phosphate 10%
[0103] It emerges from this table Ill that the stability over time
of the viscosity of the composition in the molten state increases
with the content of phosphate salt.
EXAMPLE 4
Influence of the Cation
[0104] Several compositions based on PEKK were prepared. A control
composition C.sub.T of PEKK comprising no stabilizer was prepared
by a conventional synthesis process by a polycondensation reaction.
The other compositions are based on PEKK and each comprise a
dihydrogen phosphate with a different counteranion.
[0105] The composition with the reference C11 in table IV below
comprises 1000 ppm of anhydrous sodium dihydrogen phosphate (of
formula (1) above), while the composition with the reference C12
comprises 1000 ppm of ammonium dihydrogen phosphate.
[0106] The melt viscosity of these compositions C.sub.T, C11 and
C12 was then measured with an oscillating rheometer as a function
of time, at 380.degree. C., under nitrogen, with a stress of 1 Hz
and with a strain amplitude of 0.5%.
[0107] Table IV below brings together the data on stability (EV %)
under nitrogen of these different compositions.
TABLE-US-00004 TABLE IV EV (%) (under Reference Composition
N.sub.2, 1 Hz) C.sub.T Reference PEKK 160% C11 1000 ppm of
anhydrous sodium dihydrogen 50% phosphate C12 1000 ppm of ammonium
dihydrogen phosphate 55%
[0108] It emerges from this table IV that the presence of ammonium
dihydrogen phosphate or of anhydrous sodium dihydrogen phosphate in
a composition based on PEKK makes it possible to obtain a
composition in the molten state which has a more stable viscosity
over time, unlike the control composition C.sub.T, the viscosity of
which increases rapidly with time, indicating chain extensions and
therefore significant changes in the characteristics of the
polymer.
EXAMPLE 4
Thermal Stability
[0109] The phosphate salts incorporated into the composition based
on PAEK are moreover highly stable thermally. Indeed, for the
phosphate salts, the losses of weight measured correspond to losses
of water. The phenomenon which is then occurring, for example with
monosodium phosphate, is a dehydration and a dimerization in
accordance with the following equation (A):
##STR00019##
[0110] For its part, PEP-Q begins to degrade and to emit organic
compounds at a temperature of the order of 200.degree. C.
[0111] The thermogravimetric (TG) curves as a function of
temperature T (.degree. C.) presented in the graph of FIG. 2 make
it possible to demonstrate a loss of weight of the phosphate salts
due to a loss of water, whereas the phosphonite PEP-Q degrades
rapidly from 200.degree. C., emitting volatile organic
compounds.
[0112] The phosphate salts therefore have a high thermal stability
combined with a high stability with regard to phenomena of thermal
oxidation.
EXAMPLE 5
Effect of Additional Nucleation of the Phosphate Salts
[0113] A study of crystallization was performed on different
samples, with the references E1 to E4, of different compositions
and listed in table V below.
[0114] The crystallization study is performed by differential
scanning calorimetry, denoted DSC. DSC is a thermal analysis
technique which makes it possible to measure the differences in the
exchanges of heat between a sample to be analyzed and a
reference.
[0115] In order to perform this crystallization study, the
apparatus Q 2000 from TA Instruments was used. The study was
performed in anisothermal and isothermal crystallization.
[0116] The samples studied are in the form of granules. A control
sample based on PEKK, with the reference E1, is compared to samples
E2 and E3 based on PEKK and on a phosphate salt in the same
proportions. The different samples are more particularly described
in table V below.
Anisothermal Crystallization
[0117] The protocol for DSC under anisothermal conditions on the
different samples E1 to E3 first consists in stabilizing the
temperature at 20.degree. C. The temperature is then gradually
increased according to a gradient of 20.degree. C. per minute up to
380.degree. C., then it is gradually decreased again down to
20.degree. C. according to a reverse gradient of 20.degree. C. per
minute.
[0118] The crystallization is studied during the cooling step. The
heat flow is measured as a function of temperature, and a curve
representing the change in the heat flow as a function of
temperature is obtained for each sample studied. The
crystallization temperature, denoted T.sub.c and expressed in
degrees Celsius, is then determined for each sample, by projecting
the maximum of the corresponding curve onto the axis of the
abscissae. This determination is carried out directly by the DSC
apparatus used. The crystallization temperature T.sub.c measured
for each sample E1 to E3 is given in table V below.
Isothermal Crystallization
[0119] A DSC analysis under isothermal conditions was also
performed on the samples E1 to E3 to measure the crystallization
half-time. For this purpose, the isothermal DSC protocol comprises
the following three steps: a first step consists in first
stabilizing the temperature at 20.degree. C., a second step then
consists in gradually increasing the temperature according to a
gradient of 20.degree. C. per minute up to 380.degree. C. Finally,
the temperature is reduced from 380.degree. C. down to 315.degree.
C., according to a gradient of 20.degree. C. per minute, then it is
stabilized at 315.degree. C. for one hour.
TABLE-US-00005 TABLE V Crystallization Reference T.sub.c half-time
at 315.degree. C. samples Description (.degree. C.) (min) E1
Control PEKK granules 292 3.1 E2 (Control PEKK + 1000 ppm 296 2.2
NaH.sub.2PO.sub.4) granules E3 (PEKK + 1000 ppm 301 1.2
Na.sub.3P.sub.3O.sub.9) granules
[0120] It emerges from table V of results obtained that the
crystallization half-time is approximately 3.1 minutes for the
sample E1 of control PEKK granules. The crystallization half-time
of a polymer is the time required for crystallization of 50% of
this polymer.
[0121] The crystallization half-time of the samples E2 and E3, the
composition of which comprises phosphate salts, is reduced while
the crystallization temperature increases. This phenomenon is due
to the nucleation effect of the phosphate salts. Thus, for large
bars obtained with such a composition, the nucleation effect makes
it possible to avoid the appearance of large crystallized zones and
to obtain good mechanical properties.
[0122] Regarding the granules intended to be used in injection
molding or in extrusion, the accelerated crystallization makes it
possible to control the crystalline morphology and especially the
size of the spherulites, and to thereby ensure specific mechanical
properties and consistency of the latter.
[0123] Regarding the granules intended to be used by the aqueous
impregnation route, hydrated phosphate salts may be used in the
composition. Anhydrous phosphate salts are, however, preferred
since water may be released during the subsequent processing of the
composition, which may lead to a possible negative effect on the
physical properties of the composition.
[0124] Phosphate salts are thus good stabilizers of PAEKs and more
particularly, but not exclusively, of PEKKs. These phosphate salts
also combine several very advantageous effects. Indeed, they
provide temperature stability in the absence or in the presence of
air, and they are stable with regard to hydrolysis, unlike other
phosphorus-based stabilizers such as phosphites or phosphonites
such as PEP-Q, and do not generate volatile organic compounds but
simply steam. They also combine all the positive effects of a
stabilizer for transformation: they make it possible to limit
changes in color during transformation, they make it possible to
improve the stability of the structure in the molten state,
significantly reducing the change in the polymer chains and thereby
making it possible to retain the crystalline and mechanical
properties of the material. Finally, they act as a nucleating agent
and a regulator of residual acids (buffer effect), with the result
that they may also help protect equipment from corrosion.
[0125] Phosphate salts may also be readily incorporated into the
PAEK polymer, either by impregnation in aqueous solution or by dry
blending or else by compounding.
[0126] They may finally be used in synergy with other additives
such as other stabilizers and/or nucleating agents for example, and
in the presence of continuous or dispersed filler(s), and of
plasticizers.
* * * * *