Multilayer structure including a layer of a specific copolyamide
and a barrier layer
5 The invention relates to a multilayer structure comprising as
its outer layer, a layer of a composition comprising predominantly one
or more specific semicrystalline copolyamides and as inner layer, a
barrier layer based on specific fluoropolymers, and also to its use for
the transfer and/or storage of fluids, such as an oil, a liquid based on
10 urea solution, a fuel, especially an alcoholized fuel, a cooling liquid, a
refrigerant fluid, or else engine gas emanations.
In the field of transport and of the automobile more
particularly, there are numerous conduits, consisting of polymer-based
compositions, which are intended for carrying fluids such as, for
15 example, more or less alcoholized gasolines, cooling liquid (alcohol
and water), brake fluid, refrigerant fluids present in the airconditioning
circuit, oil, engine gas emanations, or else urea
solutions.
For environmental protection reasons, the conduits and tanks
20 are required to have a good barrier property with respect to such
fluids, in order to prevent their loss by evaporation. By barrier
property is meant the very low permeability of the material of these
conduits and tanks to the fluids stored or transported therein.
From another aspect, for safety reasons, these conduits and
2 5 tanks must be very robust mechanically and chemically, especially in
order to oppose leakage in the event of impact or accident. They must
also be sufficiently flexible to allow them to be used in the vehicle,
especially when they are being installed.
Pipes and tanks composed of multilayer structures, combining
30 at least one barrier layer as inner layer and a robust polymer layer as
outer layer, are in genera1 used. This latter layer may especially be
composed of flexible, high-carbon-content aliphatic polyamide with
the function, among others, of ensuring the mechanical strength and
chemical resistance of the multilayer structure as a whole.
Examples of flexible, high-carbon-content aliphatic polyamides
include compositions based on polyamide 12 or PA12, PA1 1, PA1 0.10,
PA10.12 or PA12.12.
These polyamides are possessed of many advantageous
5 properties. They are strong mechanically, with high low-temperature
impact strength and high elongation at break. They are chemically
resistant, especially to zinc chloride and to hydrolysis. They take up
little moisture and are dimensionally stable. They are resistant to
aging at high temperature in the presence of oxygen
10 (thermooxidation). They are flexible and, what is more, they can
easily be flexibilized by addition of plasticizer if the need arises.
These polyamides possess melting temperatures, termed Tm, of
less than about 200°C (measured by DSC in accordance with the
standard IS0 11357).
15 Furthermore, the barrier polymers which are generally used to
form the impermeable layer are fluoropolymers such as functionalized
polyvinylidene fluoride (PVDF), semi-aromatic polyamides such as
PA9.T, PA 1 O.T/6.T, PAMXD.6, or other polymers such as ethylenevinyl
alcohol copolymer (EVOH), polyphenylene sulfide (PPS), or
20 functionalized polybutylene naphthalate (PBN).
In the field of transport and of the automobile, there is
presently an increase in the temperatures beneath the engine hood.
Engines are operating at higher temperatures and are more confined.
Moreover, for reasons of weight advantage, consideration is being
25 given to replacing the metal or rubber piping, operating at high
temperature, with polymeric piping, The under-hood temperatures are
increasing to the point of exceeding with more and more frequency the
melting temperature (Tm) of the polymer constituting the outer layer,
and especially of the high-carbon-content flexible polyamide layer. It
30 is therefore necessary to find an alternative to the metal or rubber
piping, but this alternative must retain the essential qualities of the
flexible, high-carbon-content, aliphatic polyamides that are in general
use. The qualities required are, in particular, flexibility, chemical
resistance, low water uptake, low-temperature impact, high elongation
at break, resistance to aging in air and hot fluids, and, lastly, the
ability to be employed at temperatures which are not excessively high.
Low-carbon-content aliphatic polyamides, such as PA6, PA6.6,
PA4.6 are well known. They have melting temperatures Tm which are
5 much greater than those of the high-carbon-content flexible
polyamides, typically of 220°C to 300°C. However, they lack chemical
resistance, more particularly to zinc chloride. They are also very much
inferior in terms of water uptake, low-temperature impact, and aging,
even when allied with flexible polymers, such as impact modifiers.
10 These low-carbon-content, aliphatic polyamides are therefore not a
solution to this problem.
The semi-aromatic polyamides for their part, such as
PA6.Tl6.1, PA6.Tl6.116.6, PA4.Tl6.Tl6.6 and PAMXD.6, have much
higher melting temperatures Tm, typically of 240°C to 340°C.
15 However, they are particularly rigid and their elongation at break is
low, even allied with flexible polymers, such as impact modifiers. As
for the other properties, they are also inferior to the high-carboncontent,
aliphatic polyamides. These polyamides are unable to
represent an acceptable alternative.
20 Polyamides which have appeared more recently are the highcarbon-
content, semi-aromatic polyamides, such as PA9.T, PA9.TI9l.T
(where 9' denotes a subunit obtained from 2-methyl-1,8-
nonanediamine, an isomer of nonanediamine), PAlO.T/6.T, and
PAIO.T. They possess melting temperatures Tm which are much higher
2 5 than the high-carbon-content, aliphatic polyamides, typically of 260°C
to 320°C. They exhibit high performance in chemical resistance and
water uptake, but remain very rigid. It is virtually impossible to
flexibilize them by incorporating'plasticizer. Another drawback is that
they require very high processing temperatures, typically of around
30 300-340°C. In the context of multilayer structures, this means raising
the local temperature of the other polymers, which may give rise to
degradation in said latter polymers, if the imposed temperature
approaches or exceeds their degradation temperature. These polyamides
are unable to be an acceptable solution.
Document EP 1 864 796 describes the use of a multilayer
structure comprising at least two layers based on high-carbon-content
semi-aromatic polyamide of type 9.T with the presence in the outer
layer of a higher level of impact modifier than in the inner layer. This
5 solves the problem of the inadequate impact resistance, but does not
touch the problem of the low elongation at break, of the rigidity,
which is still large, of the impossibility of flexibilizing the outer layer
by the presence of a plasticizer, or of the mediocre aging resistance.
The problem addressed is therefore not solved.
10 A description is found in documents EP 1 470 910,
EP 1 245 657 and WO 20061056581, of multilayer structures which are
based on polyamide and on fluoropolymer, but which have inadequate
performance properties (see structures 20, 21, 22 and 24 in the
examples).
15 The technical problem addressed is therefore that of providing
a multilayer structure which has the following collective features,
namely a resistance at a high temperature of at least 200°C, good
mechanical properties (especially flexibility, elongation at break,
I resistance to impacts at low temperatures) and good chemical
I
I 20 properties (especially resistance to ZnC12 and good barrier properties
I
I
c with respect to the fluid stored or carried), while exhibiting very slow
I aging of the structure over time.
! To solve the problem addressed, a specific multilayer structure
1 has been found which combines, as an outer layer, a composition
2 5 based on a specific copolyamide defined by very specific proportions
of semi-aromatic units and of aliphatic units and, as inner layer, a
barrier layer based on specific fluoropolymer.
The present invention accordingly aims to solve the technical
problem addressed by means of a multilayer structure comprising:
30 - a layer (Ll) - outer layer - composed of a composition
comprising predominantly one or more semicrystalline copolyamides
(H) having a melting temperature of at least 220°C and comprising at
least 80 mol% of the two following units (s) and (a):
- where unit (s) denotes one or more semi-aromatic units (s)
formed
. of one or more subunits obtained from aromatic diacid (sr)
and
5 . of one or more subunits obtained from aliphatic diamine (sa),
the aliphatic diamine (sa) comprising from 9 to 13 carbon atoms,
- where the unit (a) denotes one or more aliphatic units
comprising 8 to 13 carbon atoms per nitrogen atom, and,
where the molar ratio (s)/(a) is from 1 to 3, and
10 - a layer (L2) composed of a composition comprising
predominantly one or more tetrafluoroethylene (TFE) copolymers, said
TFE copolymer being mandatorily functionalized when the layer (L2)
is in contact with the layer (Ll) or in contact with an interlayer
comprising predominantly one or more polyamides.
15 The invention also relates to a pipe comprising the structure as
defined above.
The invention also relates to the use of said structure,
especially when it takes the form of a pipe, for the transport of polar
and/or apolar fluids, especially those present in vehicles.
20 Other subjects, aspects, and features of the invention will
become apparent from a reading of the description which follows.
In the present description, in the absence of any indication
otherwise, all of the percentages (%) are molar percentages.
Moreover, any range of values, denoted by the expression
25 "between a and b" represents the domain of values from more than a to
less than b (in other words with end points a and b excluded), whereas
any range of values denoted by the expression "from a to b" signifies
the domain of values from a up to b (in other words, including the
strict end points a and b).
30 The symbol "11" delimits the layers of a multilayer structure.
The symbol "1" delimits the units of a copolymer.
A unit in the sense of the present invention means a linked
chain of polyamide structure obtained from the polycondensation of
lactam, amino acid or diamine and diacid.
Outer layer ( L l )
The multilayer structure according to the present invention
5 comprises as its outer layer, a layer (Ll) composed of a composition
comprising predominantly one or more semicrystalline copolyamides
(HI.
Predominantly in the sense of the present invention means that
the semicrystalline copolyamide or copolyamides (H) are present in
10 the layer (Ll) in an amount of more than 50 wt% relative to the total
weight of the composition forming the layer (Ll).
According to one preferred embodiment of the invention, this
layer (Ll) is intended to be in contact with the air.
15 Semicrystalline copolyamide (H)
A semicrystalline polymer, in the sense of the present
invention, is a polymer which retains a solid state beyond its glass
transition temperature (Tg).
The structure of the semicrystalline copolyamide (H) according
20 to the present invention is as follows. It comprises at least 80 mol% of
the two following units (s) and (a):
- unit (s) denoting one or more semi-aromatic units (s) formed
. of one or more subunits obtained from aromatic diacid (sr)
and
25 . of one or more subunits obtained from aliphatic diamine (sa),
the aliphatic diamine (sa) comprising from 9 to 13 carbon atoms,
- unit (a) denoting one or more aliphatic units comprising from
8 to 13 carbon atoms per nitrogen atom, and
the molar ratio (s)/(a) being from 1 to 3.
30 Moreover, semicrystalline copolyamide (H) has a melting
temperature (Tm) of at least 220°C.
Semi-aromatic unit (s)
Generally speaking, in organic chemistry, an aliphatic
compound is a saturated or unsaturated, cyclic or non-cyclic carboncontaining
compound, with the exception of aromatic compounds.
According to the present invention, though, the term "aliphatic"
5 denotes a saturated or unsaturated, noncyclic, carbon-containing
compound with the exception of cyclic compounds and of aromatic
compounds. Accordingly, the term "aliphatic" covers only saturated or
unsaturated, linear or branched, carbon-containing compounds.
The semi-aromatic unit (s) is formed of one or more subunits
10 obtained from aromatic diacid (sr) and of one or more subunits
obtained from aliphatic diamine (sa), the aliphatic diamine comprising
from 9 to 13 carbon atoms.
The subunit obtained from the aliphatic diamine (sa)
advantageously comprises from 10 to 13 carbon atoms.
15 The aromatic diacid may be selected from terephthalic acid,
identified as T, isophthalic acid, identified as I, naphthalenic acid, and
mixtures thereof. a
The aliphatic diamine (identified as Ca, where Ca denotes the
number of carbon atoms in the diamine) may be selected from
20 nonanediamine (a=9), 2-methyl- 1,8-nonanediamine (a=9'),
decanediamine (a=10), undecanediamine ( a = l l ) , dodecanediamine
(a=12), and tridecanediamine (a=13).
Examples of semi-aromatic units (s) according to the invention
include the units 9.T, 9l.T (where 9' originates from 2-methyl-1,8-
2 5 nonanediamine), 10.T and combinations thereof such as, for example,
9.T/g1.T. The unit 10.T is used with preference.
The semi-aromatic units based on terephthalic acid (T) are
particularly advantageous since they lead to polyamides with a high
degree of crystallinity which give high melting temperatures.
30 Preference will therefore be given to selecting ' semi-aromatic
polyamides which are rich in terephthalic acid (T)-based unit, leading
to a high degree of crystallinity and a high melting temperature. The
subunit (sr) is preferably obtained only from terephthalic acid.
The proportion of semi-aromatic units (s) is preferably from
40 mol% to 75 mol%.
5 Aliphatic unit (a)
The aliphatic unit (a) comprises from 8 to 13 carbon atoms per
nitrogen atom. It advantageously comprises from 9 to 13 carbon atoms
per nitrogen atom.
In the case of a unit of type X.Y, the number of carbon atoms
10 per nitrogen atom is the molar average of the subunit X and of the
subunit Y.
In the case of copolyamides, the number of carbon atoms per
nitrogen atom is calculated according to the same principle. The
calculation is made on a molar pro rata basis from the various amide
15 units.
Accordingly, the selection of the lactams, amino acids,
diamines and diacids must be made in dependence on this range of
carbon atoms per nitrogen atom.
When the aliphatic unit (a) originates from the
20 polycondensation of a lactam, this lactam may be selected from
caprylolactam, enantholactam, pelargolactam, decanolactam,
undecanolactam, and laurolactam.
When the unit (a) originates from the polycondensation of an
amino acid, it may be selected from 9-aminononanoic acid,
25 1 0-aminodecanoic acid, 12-aminododecanoic acid, and
11-aminoundecanoic acid and also derivatives thereof, especially
N-heptyl- 1 1 -aminoundecanoic acid.
When the unit (a) originates from the polycondensation of a
diamine (identified as Ca, where Ca denotes the number of carbon
30 atoms in the diamine) and of a Cb diacid (identified as Cb, where Cb
denotes the number of carbon atoms in the diacid), the aliphatic
diamine may be selected from butanediamine (a=4), pentanediarnine
(a=5), hexanediamine (a=6), heptanediamine (a=7), octanediamine
(a=8), nonanediamine (a=9), 2-methyl-1,8-nonanediamine (a=9'),
decanediamine (a=10), undecanediamine ( a = l l ) , dodecanediamine
(a=12), tridecanediamine (a=13), tetradecanediamine (a=14),
hexadecanediamine (a= 16), octadecanediamine (a= 18),
octadecenediamine (a=18), eicosanediamine (a=20), docosanediamine
5 (a=22), and diamines obtained from fatty acids.
The diamine Ca is advantageously selected from octanediamine
(a=8), nonanediamine (a=9), 2-methyl- 1,8-nonanediamine (a=9'),
decanediamine (a=10), undecanediamine ( a = l l ) , dodecanediamine
(a=12), and tridecanediamine (a=13).
10 The aliphatic diacid in turn may be selected from succinic acid
(b=4), pentanedioic acid (b=5), adipic acid (b=6), heptanedioic acid
(b=7), octanedioic acid (b=8), azelaic acid (b=9), sebacic acid (b=10),
undecanedioic acid (b=ll), dodecanedioic acid (b=12) and brassylic
acid (b=13), tetradecanedioic acid (b=14), hexadecanedioic acid
15 (b=16), octadecanoic acid (b=18), octadecenoic acid (b=18),
eicosanedioic acid (b=20), docosanedioic acid (b=22), and the dimers
of fatty acids containing 36 carbons.
The diacid Cb is advantageously selected from 0,ctanedioic acid
I (b=8), azelaic acid (b=9), sebacic acid (b=10), undecanedioic acid
!
I 20 (b=l 1), dodecanedioic acid (b=12), and brassylic acid (b=13).
i The abovementioned dimers of fatty acids are dimerized fatty
acids obtained by oligomerization or polymerization of unsaturated
! I monobasic fatty acids with a long hydrocarbon chain (such as linoleic
acid and oleic acid), as described especially in document
I 25 EP 0 471 566.
1 The diamine is preferably selected from nonanediamine (a=9),
2-methyl- 1,8-nonanediamine (a=9'), decanediamine (a=1 O),
! undecanediamine (a= 1 1), dodecanediamine (a= 12), and
tridecanediamine (a=13), and the diacid is selected from azelaic acid
30 (b=9), sebacic acid (b=10), undecanedioic acid (b=ll), dodecanedioic
acid (b=12), and brassylic acid (b=13).
The aliphatic unit (a) is preferably linear.
The aliphatic unit (a) may be selected from 12, 11, 10.10,
10.12, 12.12, 6.14, and 6.12 units.
1
i
The units 12, 10.10, 10.12 and 12.12 are used with preference.
The proportion of aliphatic units (a) . is preferably from
20 mol% to 50 mol%.
...
5 Ratio (s)/(a)
According to the present invention, the molar ratio (s)/(a) of
the semi-aromatic units (s) to the aliphatic units (a) is from 1 to 3 and,
preferably from 1.5 and 2.5.
Melting temperature
The semicrystalline copolyamide (H) according to the
invention has a melting temperature (Tm) of at least 220°C, preferably
of from 220 to 320°C, more particularly from 220 to 280°C.
It has been observed that, below 220°C, the crystallinity and
15 the tensile strength are not acceptable.
The melting temperature is measured by DSC (Differential
Scanning Calorimetry) in accordance with the standard IS0 11357.
Melting enthalpy
20 The melting enthalpy, measured by DSC in accordance with the
standard IS0 11357, of the semicrystalline copolyamide (H) according
to the invention is preferably greater than or equal to 10 J/g, more
preferably greater than or equal to 25 J/g. Thus, the copolyamide is
subjected to first heating of 20°C/min to a temperature of 340°C, then
2 5 to a cooling at 20°C/min to a temperature of 20°C, then to second
heating at 20°C/min to a temperature of 340°C, with the melting
enthalpy being measured during this second heading.
The semicrystalline copolyamide (H) according to the present
invention comprises at least 80 mol% and, preferably at least
30 90 mol%, of the two units (s) and (a) as defined above. Accordingly, it
may comprise other units with a structure different from those of the
units (s) and (a).
Other unit
Accordingly, the semicrystalline copolyamide (H) according to
the present invention may comprise from 0 to 20% of one or more
units other than the aforesaid aliphatic units (a) and semi-aromatic
units (s). The following units may be contemplated, but without
5 limitation.
The semicrystalline copolyamide (H) according to the present
invention may comprise one or more semi-aromatic units formed of a
subunit obtained from aromatic diacid and of a subunit obtained from
diamine, this diamine having a number of carbon atoms of from 4 to 8
10 or else greater than or equal to 14.
The semicrystalline copolyamide (H) according to the present
invention may also comprise one or more aliphatic units in which the
'number of carbon atoms per nitrogen atom is from 4 to 7 or else is
greater than or equal to 14.
15 Cycloaliphatic units originating from the polycondensation of
diamines and diacids, with one of these two compounds being
cycloaliphatic, may also be provided.
When the diamine is cycloaliphatic, it is selected from
bis(3,5-dialkyl-4-aminocyclohexyl)methane, bis(3,S-dialkyl-4-aminocyclo-
20 hexyl)ethane, bis(3,5-dialkyl-4-aminocyclohexyl)propane, bis(3,5-dialkyl-4-
aminocyclohexyl)butane, bis(3-methyl-4-aminocyclohexyl)methane (BMACM
or MACM), p-bis(aminocyclohexy1)methane (PACM), and
isopropylidenedi(cyclohexylamine) (PACP). It may also comprise the
following carbon skeletons: norbornylmethane, cyclohexylmethane,
25 dicyclohexylpropane, di(methylcyclohexyl), or di(methylcyclohexyl)-
propane. A non-exhaustive list of these cycloaliphatic diamines is
given in the publication "Cycloaliphatic Amines" (Encyclopaedia of
Chemical Technology, Kirk-Othmer, 4th edition (1 992), pp. 386-405).
In this case, the diacid may be aliphatic, linear or branched, as
30 defined above, or else cycloaliphatic or aromatic.
When the diacid is cycloaliphatic, it may comprise the
following carbon skeletons: norbornylmethane, cyclohexylmethane,
dicyclohexylmethane, dicyclohexylpropane, di(methylcyclohexyl), or
di(methylcyclohexyl)propane.
In this case, the diamine may be aliphatic, linear or branched,
as defined above, or else cycloaliphatic or aromatic.
The copolyamide (H) according to the invention is preferably
5 composed of the following units:
- from 40 mol% to 75 mol% of one or more semi-aromatic
units (s),
- from 20 mol% to 50 mol% of one or more aliphatic units (a),
and
10 - from 0 to 20 mol% of one or more units other than the
aforesaid units (a) and (s).
The copolyamide (H) according to the invention preferably
comprises no units other than the aliphatic units (a) and the semiaromatic
units (s). It is accordingly composed of:
15 - from 50 mol% to 75 mol% of one or more semi-aromatic
units (s), and
- from 25 mol% to 50 mol% of one or more aliphatic units (a)
The semicrystalline copolyamide (H) is preferably selected
from PA12/9.T, PA6.12/10.T, PA10.10/10.T, PA10.10/10.T/6.T,
20 PA10.10/10.T/10.1, and PA10.12llO.T.
Amine chain termination
The semicrystalline copolyamide (H) according to the
invention preferably has an amine chain end content of greater than or
25 equal to 40peqIg. This amine chain end content ranges
advantageously from 42 peq/g to 100 peq/g and preferably from
45 peqlg to 70 peqlg.
The amine-function chain end content is measured in a
conventional way known to the skilled person, by potentiometry.
30 The composition may also be formed predominantly of a
mixture of two or more aforementioned copolyamides (H).
Like any polymeric material, the composition of the outer layer
(Ll) of the multilayer structure may further comprise one or more
polymers and/or one or more additives.
Accordingly, the composition of the outer layer (Ll) may
comprise one or more supplementary polymers. This or these
supplementary polymer or polymers may be selected, for example,
from aliphatic polyamides comprising preferably more than 9 carbon
5 atoms per nitrogen, functionalized or nonfunctionalized polyolefins
and a mixture thereof.
In the context of impact modifiers, the supplementary polymer
may be a functionalized copolyolefin comprising one or more
anhydride or acid functions, optionally in a mixture with at least one
10 polymer comprising one or more epoxide functions.
The composition forming the outer layer (Ll) advantageously
comprises at least 18 wt% of one or more supplementary polymers
such as one or more impact modifiers, at least one of which is
anhydride functionalized, the impact modifier or modifiers being
15 preferably of copolyolefin type with a Tg of less than -10°C and an
IS0 178 flexural modulus of less than 100 MPa.
The composition forming the outer layer (Ll) preferably
comprises at least 30 wt% of two or more supplementary polymers
relative to the total weight of the composition, these supplementary
20 polymers forming a crosslinked elastomeric phase. This crosslinked
elastomeric phase is composed of at least one acid- or anhydridefunctionalized
impact modifier, of at least one polymer or a molecule
- . possessing a plurality of epoxide functions and, optionally, of at least
one polymer or a molecule possessing a plurality of acid functions, all
25 of these polymers being preferably of copolyolefin type with a Tg of
less than -10°C and an IS0178 flexural modulus of less than 100 MPa.
The composition forming the outer layer (Ll) may also
comprise additives. The possible additives include stabilizers, dyes,
plasticizers, fillers, fibers, surfactants, pigments, fluorescent
30 whiteners, antioxidants, natural waxes, and mixtures thereof.
For the plasticizers, an amount of up to 15 wt% of the total
weight of the composition may be introduced.
Barrier layer (L2)
In the structure according to the invention the barrier layer
(L2) is an inner layer, or even the innermost layer, in other words the
layer intended preferably to be in contact with the fluids.
When the structure comprises more than two layers, the layer
5 may therefore be an interlayer or else may constitute the innermost
layer. It is also possible to contemplate having a plurality of barrier
layers with the aim of complementarity or of performance of the
structure. The barrier layer predominantly comprises a barrier
material, this being a material which is much more impermeable to the
10 fluids than are the high-carbon-content aliphatic polyamides
conventionally used as outer layer. The fluids used are especially
gasolines, alcohols, cooling liquids, refrigerant fluids, or else urea
solutions. The materials may be classified according to their
permeability to CElO alcoholized gasoline (45% isooctane + 45%
15 toluene + 10% ethanol) at 60°C. It may be considered, for example,
that a material is able to constitute a barrier layer, if i t is at least
5 times less permeable than PA-12.
The barrier layer (L2) present in the structure according to the
invention is composed of a composition comprising predominantly one
20 or more tetrafluoroethylene (TFE) copolymers, the TFE copolymer
being mandatorily functionalized when the layer (L2) is in contact
with the layer (Ll) or in contact with an interlayer comprising
predominantly one or more polyamides. By "predominantly" in the
sense of the present invention is meant that the polyamide or
2 5 polyamides are present in the interlayer in an amount of more than
50 wt%, relative to the total weight of the composition forming this
interlayer.
The TFE copolymer is advantageously a copolymer in which
the molar proportion of the TFE unit is predominant relative to the
30 proportion of the other unit or units forming said copolymer. These
other units may especially be obtained from ethylene, from
chlorotrifluoroethylene, from hexafluoropropylene or from a
perfluoroalkyl vinyl ether, such as perfluoropropyl vinyl ether.
The TFE copolymer is advantageously selected from
ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylenechlorotrifluoroethylene
copolymer (CTFE) and a mixture thereof.
When it is functionalized, this TFE copolymer comprises one or more
5 anhydride, epoxy, acid or else acid halide functions.
When the layer (L2) is in contact with the layer (Ll) or in
contact with an interlayer comprising predominantly one or more
polyamides, the tetrafluoroethylene copolymer is mandatorily
functionalized. As indicated above, it may be functionalized by
10 anhydride, epoxy, or acid functions or else acid halide functions. The
functions borne by the TFE copolymer will react with the
(co)polyamide of the adjacent layer, in other words with the
(co)polyamide in direct contact with the TFE copolymer of the layer
(L2), and especially with the amine functions of the (co)polyamide,
15 thereby ensuring the adhesion of these two layers to one another.
TFE copolymers of these kinds are especially available under
the trade name ~eoflon'@EP 7000 from Daikin or else ~luon'@AH 2000
from Asahi.
The composition may also be composed of a mixture of two or
20 more TFE copolymers.
Less directly exposed to the heat of the engine environment
than the outer layer (Ll), the barrier layer (L2) may have a melting
temperature of less than 220°C, since the upper layer or layers act as a
thermal shield to the underlying layer or layers. However, the
25 composition of the barrier layer will advantageously be selected with a
melting temperature Tm of greater than 220°C, and more
advantageously still will be selected with a Tm of from 220°C to
280°C.
Like any polymeric material, the composition of the barrier
30 layer (L2) of the structure may further comprise one or more other
polymers andlor one or more additives. It is, however, predominantly
composed of the aforementioned TFE barrier copolymer or
copolymers.
The supplementary polymers to which consideration may be
given may be selected especially from the supplementary polymers
already referred to above as being able to form part of the composition
of the outer layer (Ll).
5 The possible additives 'include stabilizers, dyes, plasticizers,
fillers, nanofillers and especially those with a character such as to
reinforce the barrier, such as nanoclays.
The layer (L2) advantageously comprises conductive fillers
such as carbon black, so as to make it antistatic.
10
Multilayer structure
The outer layer (Ll) made of semicrystalline copolyamide (H)
according to the invention, and the barrier layer (L2), may, for
example, simply be combined to form a two-layer pipe in the
15 following way, with - from the outside to the inside:
copolyamide (H) layer (Ll) /I functionalized barrier layer (L2).
The structure may also comprise a plurality of layers with
different and complementary characters.
Therefore, according to a second embodiment, the structure
20 may be a three-layer structure comprising an interlayer (L3) arranged
between the layers (Ll) and (L2). Such a multilayer structure may
comprise, from the outside to the inside, the following layers:
layer (Ll) /I layer (L3) I/ functionalized barrier layer (L2).
The interlayer (L3) may, for example, comprise one or more
2 5 high-carbon-content aliphatic polyamides (in other words one or more
aliphatic (co)polyamides comprising from 9 to 36 carbon atoms per
-. nitrogen atom (for example PA1 1)).
The interlayer (L3) may also be a layer which also has barrier
properties - for example, a layer comprising one or more
30 polyphthalamides.
According to a third embodiment, when the layer (L2) is
composed predominantly of one or more TFE polymers as defined
above, which are functionalized, the structure may comprise a
supplementary layer located in contact with said layer (L2) and
forming the innermost layer of the structure; this supplementary layer
may be a barrier layer.
The multilayer structure may comprise, from the outside to the
inside, the following layers:
5 copolyamide (H) layer ( L l ) /I functionalized barrier layer (L2) I/
optionally conductive barrier layer.
This supplementary layer may more particularly be a barrier
layer and may comprise one or more fluoropolymers as defined above
which are nonfunctionalized, and, optionally, conductive fillers.
10 The multilayer structure may in that case comprise from the
outside to the inside, the following layers:
copolyamide (H) layer (Ll) /I functionalized barrier layer (L2) /I
optionally conductive nonfunctionalized barrier layer (L2).
According to a fourth embodiment, symmetrical multilayer
15 structures may be produced, such as, for example, a three-layer
structure with - from the outside to the inside:
copolyamide (H) layer (Ll) /I functionalized barrier layer (L2) /I
copolyamide (H) layer (L 1).
According to a fifth embodiment, layers with new functions
20 may be produced, such as, for example, with - from the outside to the
inside:
copolyamide (H) layer ( L l ) /I functionalized barrier layer (L2) /I
conductive aliphatic PA layer.
The aliphatic PA constitutes the inner layer, where the
2 5 temperature is less high than on the outside, facing the environment of
the engine.
In all of the multilayer structures described above, it is
possible advantageously to add conductive fillers to the composition
of the innermost layer in order to dissipate any electrostatic charges,
3 0 especially when this innermost layer is formed of TFE copolymer.
One important aspect for the production of such multilayer
structures is the adhesion of the layers to one another.
One way of producing effective adhesion is to use a polymer
functionalized with a function which is reactive toward one of the
chain ends of the copolyamide (H) in the robust layer (Ll).
This is the case, for example, with the ETFE Fluon AH2000
5 from Asahi, which is a barrier polymer possessing an anhydride
functionalization. The anhydride reacts with the amine chain ends of
the copolyamide (H). It will therefore be appropriate to select a
polyamide, especially a copolyamide (H), which is sufficiently rich in
NH2 amine chain ends to produce effective adhesion, typically having
10 an amine chain ends content of greater than 40 peqlg, as indicated
above.
Another way of obtaining effective adhesion between the
copolyamide layer (H) constituting the robust layer (Ll) and the
barrier polymer layer (L2) is to place a binder interlayer between
15 them. The binder may be a mixture of the compositions of these two
layers, advantageously accompanied by a certain amount of
compatibilizer (refer, for example, to documents EP 1 162 061 and
EP 2 098 580).
Preparation of the compositions
The copolyamides (H) according to the invention are
synthesized by customary techniques of polymerization, more
particularly by polycondensation.
The compositions comprising the copolyamides (H) are
2 5 fabricated by the usual techniques of compounding, more particularly
on a twin-screw extruder in the melt state.
The multilayer structures are typically fabricated by
co-extrusion of each layer in the melt state. The multilayer pipe is a
specific representative of a multilayer structure.
30 Generally speaking, the production of a multilayer pipe
requires the use of a plurality of extruders with their temperature
controlled, which are selected and regulated so as to be compatible
with the structure to be produced. These extruders converge on a
distribution and stream-assembly block which is called a co-extrusion
head and is temperature-controlled. The role of the co-extrusion head
is to assemble the melted polymers from each of the extruders by
optimizing their pathway so that the speed profile is as uniform as
possible on exit from the tooling. The uniformity of the speed profiles
5 is necessary for the regularity of the thickness profiles of each of the
layers. This assembling of layers takes place by a melt method. When
they have been assembled, the layers, still in the melt state, pass
through a tooling set (punchldie) before being drawn while hot in the
free air, then calibrated by means of a sizing die. Calibration is
10 accompanied by cooling, since the sizing die is immersed in a water
bath (5 < To < 80°C) or sprayed with water using nozzles. Calibration
takes place usually under vacuum (20 - 500 mbar), in order to ensure
the roundness of the pipe and better to control its dimensional
characteristics. The pipe is cooled along a series of water baths. The
15 pipe is drawn by a mechanical drawing assembly which imposes the
drawing speed on the line (typically 10 to 80 mlmin). Peripheral
systems may be harnessed in order to meet specific needs (on-line
control of thicknesses or of diameter, flame treatment, etc.). The
skilled person knows how to regulate the parameters of the extruders
20 and of the whole of the line to integrate pipe quality (diameter,
distribution of thicknesses, mechanical or optical properties, etc.) and
productivity requirements (stability of extrusion parameters over time,
target throughputs, etc.).
The multilayer pipe optionally may be annealed, depending on
2 5 the demands of the applications, requiring more or less flexibility or
imposing geometric constraints to a greater or lesser extent. Annealing
takes place using a punchldie tooling mounted upstream of the
coextrusion head, then via the use of an annealing stand which allows
the hot pipe to be shaped inside specific molds.
30 Multilayer structures of these kinds, especially taking the form
of multilayer pipes, may also be produced in a plurality of steps,
meaning that an outer layer may be added in the course of a second
repeat step, by covering, via the use of a supplementary crosshead.
The scope of the invention would also encompass the addition
to a multilayer structure as described above, in a second repeat step,
of a supplementary layer arranged above the outer layer (Ll), as for
example an elastomer layer with the aim of offering supplementary
5 protection, for example to friction, or in order to minimize any noise
problems.
The scope of the invention would likewise encompass the
addition of a braid to the inside of the multilayer structure, in order,
for example, to increase the resistance to bursting under pressure.
10 The invention likewise provides a pipe comprising a structure
as defined above.
The invention relates, lastly, to the use of the structure
according to the invention, especially in the form of a pipe, for
transporting or transferring polar and/or apolar fluids, especially those
15 present in vehicles.
The fluid may be selected from an oil, a lubricant, a liquid
based on urea solution, on ammonia, on aqueous ammonia, on petrol
and compounds thereof, a fuel, especially an alcoholized fuel and
more particularly a bio-gasoline, a hydraulic fluid, a refrigerant fluid
20 or fluid refrigerant (such as COz or a fluorocarbon fluid such as
1,1,1,2-tetrafluoroethane or else 2,3,3,3-tetrafluoropropene), a cooling
liquid, more particularly a glycol-based cooling liquid, and also air,
engine gas emanations, such as oil pan gases or combustion gases.
The multilayer structure according to the invention may
2 5 advantageously be used for producing all or part of elements of
industrial equipment for the storage, the transport or transfer of fluids
such as those listed above. Such fluids may be hot or cold. Such
equipment may be intended for use in the field of industry in general
(for example, for pneumatic, hydraulic lines or steam cleaning lines)
3 0 and also in the field of the exploitation of petroleum and gas deposits
under the sea (offshore sector).
More particularly, and especially in the field of transport
(automobiles, trucks, etc.), the multilayer structure according to the
invention, when present for example in the form of pipes, may be used
more particularly:
- in a gas circulation device, under superatmospheric or
subatmospheric pressure, such as an air admission device or
ventilation device for engine gases, or a braking assistance
device,
- in an oil or lubricant circulation device, such as an oil cooling
device, a hydraulic device or a braking device,
- in a device for circulating aqueous or nonaqueous liquid, such
as an engine cooling device or a selective catalytic reduction
device,
- in a device for circulating refrigerant fluid or fluid refrigerant,
such as an air-conditioning circuit,
- in a device for storing, transporting, or transferring (or
circulating) fluids, more particularly fuels.
The examples which follow serve to illustrate the invention
without, however, having any limiting character.
1 / Components
Copolyamides (H) of the invention
These copolyamides are fabricated by customary techniques of
polycondensation. An illustration of this will be found in patent
US 6 989 198, on pages 18 and 19. The symbol T denotes terephthalic
acid, with I denoting isophthalic acid.
25 Copolyamide (A) is a PA10.10/10.T containing 41 mol% of
10.10 units and having an intrinsic viscosity of 1.21, a terminal NH2
group content of 55 peqlg, a melting temperature Tm of 260°C and a
melting enthalpy of 29 J/g.
Copolyamide (Ab) is a PA10.10/10.T containing 33 mol% of
30 10.1 0 units and having an intrinsic viscosity of 1.19, a terminal NH2
group content of 58 peqlg, a melting temperature Tm of 279°C and a
melting enthalpy of 38 Jlg.
Copolyamide (Ac) is a PA10.10/10.T containing 23 mol% of
10.10 units and having an intrinsic viscosity of 1.12, a terminal NH2
group content of 59 peqlg, a melting temperature Tm of 298°C and a
melting enthalpy of 38 Jlg.
Copolyamide (D) is a PA1219.T containing 41 mol% of 12 units
and having an intrinsic viscosity of 1.28, a terminal NH2 group
5 content of 49 peqlg, a melting temperature Tm of 266°C and a melting
enthalpy of 30 Jlg.
Copolyamide (E) is a PA1 0.1011 0.Tl6.T containing 25 mol% of
10.10 units, and 55 mol% of 10.T units and having an intrinsic
viscosity of 1.09, a terminal NH2 group content of 62 peqlg, a melting
10 temperature Tm of 283°C and a melting enthalpy of 33 Jlg.
Copolyamide (F) is a PA1 0.1011 0.Tl10.I containing 25 mol% of
10.10 units, and 55 mol% of 10.T units and having an intrinsic
viscosity of 1.12, a terminal NH2 group content of 59 peqlg, a melting
temperature Tm of 274°C and a melting enthalpy of 29 Jlg.
Other components
Copolyamide (M) is a PA9.TI9l.T containing 50 mol% of 9I.T
units and having an intrinsic viscosity of 1.15, a melting temperature
Tm of 264°C and a melting enthalpy of 30 Jlg.
20 Copolyamide (P) is a PA6.Tl6.116.6 containing 50 mol% of 6.T
units, 40 mol% of 6.1 units and 10 mol% of 6.6 units, having an
intrinsic viscosity of 1.08, a melting temperature Tm of 267°C and a
melting enthalpy of 30 Jlg.
Copolyamide (Q) is a PA6.Tl6.116.6 containing 55 mol% of 6.T
25 units, 20 mol% of 6.1 units and 25 mol% of 6.6 units, having an
intrinsic viscosity of 1.01, a melting temperature Tm of 301°C and a
melting enthalpy of 24 Jlg.
The impact modifier (L) denotes a copolymer of ethylene,
butyl acrylate and maleic anhydride, PEIBAIMAH having a weight BA
30 content of 30%, a weight MAH content of 1.5% and an MFI of 1 at
235°C under 5 kg.
The impact modifier (X) denotes a copolymer of ethylene,
methyl acrylate and glycidyl methacrylate, PEIMAIGMA having a
weight MA content of 30%, a weight GMA content of 5% and an MFI
of 3 at 235°C under 5 kg.
The impact modifier (EPRm) denotes an ethylene-propylene
elastomer functionalized by a reactive anhydride group (at 0.5-1% by
5 mass) having an MFI of 9 at 230°C, under 10 kg, of type Exxelor
VA1801, from Exxon.
The impact modifier (mPE) denotes an ethylene-octene
copolymer functionalized by a reactive anhydride group (at 0.5-1% by
mass) having an MFI of 1.4 at 190°C, under 2.16 kg, of type Fusabond
10 MN493D, from Dupont.
(StabCu) denotes a mixture of inorganic stabilizers based on
copper iodide and potassium iodide, of type Iodide P201 from Ciba.
(Stabl) denotes a mixture of organic stabilizers composed of
80% of Lowinox 44B25 phenol from Great Lakes and of 20% of
15 Irgafos 168 phosphite from Ciba.
(BBSA) denotes the plasticizer butylbenzylsulfonamide.
Polyamide (PA1 0.10) denotes a homopolyamide PA1 0.10 with
an intrinsic viscosity of 1.65.
Polyamide (PA12a) denotes a polyamide PA12 with an intrinsic
20 viscosity of 1.3 and a terminal NH2 group content of 70 peqlg.
Polyamide (PA 12b) denotes a polyamide PA 12 with an
intrinsic viscosity of 1.6 and a terminal NH2 group content of
45 peqlg.
Polyamide (PA6) denotes a polyamide PA6 with an intrinsic
25 viscosity of 1.55 and a terminal NH2 group content of 53 peqlg.
The intrinsic viscosity (sometimes abbreviated to visco inh) is
measured by means of an UBBELHODE viscosimeter at 25°C in metacresol
for 0.5g of polymer in 100 ml of meta-cresol. This principle is
described in Ullmann's Encyclopedia of Industrial Chemistry - Vol.
30 A 20, pp. 527-528 (1995 - 5th edition).
The terminal NH2 group content is measured by potentiometry.
21 Compositions
Copolyamide compositions are fabricated by compounding on a
twin-screw extruder in the melt state. We used a Werner 40 twinscrew,
with a screw speed of 300 revolutions/minute, a throughput of
5 70 kglh, a temperature of 300°C for the compositions with ingredients
that have a melting point of less than 285°C or a temperature of 320°C
for those in which the ingredients have a melting point of from 285°C
to 3 10°C.
(Al) denotes a composition comprising 20% of impact modifier
10 (L), 10% of impact modifier (X), 0.5% of (StabCu), the remainder to
100% being copolyamide (A).
(A2) denotes a composition comprising 20% of impact modifier
(L), 10% of impact modifier (X), 5% of plasticizer (BBSA), 0.5% of
(StabCu), the remainder to 100% being copolyamide (A).
15 (A3) denotes a composition comprising 12% of impact modifier
(L), 0.5% of (StabCu), the remainder to 100% being copolyamide (A).
(A4) denotes a composition comprising 20% of impact modifier
(EPRm), 0.5% of (StabCu), the remainder to 100% being copolyamide
(A).
20 (A5) denotes a composition comprising 30% of impact modifier
(mPE), 0.5% of (StabCu), the remainder to 100% being copolyamide
(A).
(Abl) denotes a composition identical to composition (Al)
except that the copolyamide is copolyamide (Ab).
25 (Acl) denotes a composition identical to composition (Al)
except that the copolyamide is copolyamide (Ac).
(AclO) denotes a composition comprising 20% of impact
modifier (L), 10% of impact modifier (X), 15% of (PAIO. lo), 0.5% of
(StabCu), the remainder to 100% being copolyamide (Ac).
30 (Dl) denotes a composition comprising 20% of impact modifier
(L), 10% of impact modifier (X), 0.5% of (StabCu), the remainder to
100% being copolyamide (D).
(El) denotes a composition comprising 20% of impact modifier
(L), 10% of impact modifier (X), 0.5% of (StabCu), the remainder to
100% being copolyamide (E).
(Fl) denotes a composition comprising 20% of impact modifier
5 (L), 10% of impact modifier (X), 0.5% of (StabCu), the remainder to
100% being copolyamide (F).
(MI) denotes a composition comprising 15% of impact
modifier (EPRm), 1% of (Stabl), the remainder to 100% being
copolyamide (M).
10 (Pl) denotes a composition comprising 15% of impact modifier
(EPRm), 1% of (Stabl), the remainder to 100% being the copolyamide
(PI
(Q1) denotes a composition comprising 20% of impact modifier
(L), 10% of impact modifier (X), 0.5% of (StabCu), the remainder to
15 100% being the copolyamide (Q).
(PA12h) denotes a composition comprising 20% of impact
modifier (L), 10% of impact modifier (X), 0.5% of (StabCu), the
remainder to 100% being (PA1 2a).
(PA12hip) denotes a composition comprising 6% of impact
20 modifier (EPRm), 6% of (BBSA), 1% of (Stabl), the remainder to
100% being (PA12b).
(PA6hip) denotes a composition comprising 6% of impact
modifier (EPRm), 12% of (BBSA), 1% of (Stabl), the remainder to
100% being (PA6).
25
Compositions of the barrier layers (L2) of the invention
The following compositions are commercial products.
(ETFE-1) is an ETFE (denoting a copolymer of ethylene (E)
and of tetrafluoroethylene (TFE)) which is functionalized, has the
30 name Neoflon EP7000 and is produced by Daikin. It is functionalized
by reactive groups which will react with the chain ends of the
polyamides. A product of this kind is described in document
US 6 740 375.
(ETFE-2) is an ETFE which is anhydride-functionalized, has
the name ~ l u o n @ AH2000 and is produced by Asahi. It is
functionalized by reactive anhydride groups which will react with the
chain ends of the polyamides. A product of this kind is described in
document US 6 740 375.
(Fluoro-3) is a TFE copolymer which is functionalized, has the
name ~ e o f l o n @C PT LP-1030 and is produced by Daikin. It is
functionalized by reactive groups which will react with the chain ends
of the polyamides. This TFE copolymer is composed predominantly of
TFE and also of CTFE (chlorotrifluoroethylene) and PPVE
(perfluoropropyl vinyl ether). Products of this kind are described in
document EP 2 264 086.
(ETFE-cond) is a carbon black-filled ETFE composition which
has the name Neoflon ET610AS and is produced by Daikin. The
carbon black endows this composition with antistatic properties.
Compositions of the comparative barrier layers
(PVDF-1) is a PVDF (polyvinylidene fluoride) which is
functionalized by 0.5% of maleic anhydride and has an MFI of 2 at
230°C under 5kg.
31 Multilayer structures
The multilayer structures prepared are multilayer pipes with a
diameter.of 8 mm and a thickness of 1 mm which were. produced by
coextrusion. This necessitates the use of a plurality of temperaturecontrolled
extruders, selected and regulated in such a way that they
are compatible with the structure to be produced. This especially
involves temperature-controlling an extruder in such a way as to be
sufficiently above the melting temperature of the polymer in the
composition. With regard to the coextrusion, reference is made to that
which has been described above.
We produce the structures which appear in table 1 (see
figure 1).
41 Evaluation of the multilaver structures
These structures are subsequently evaluated according to
various criteria, which are described below.
Thermomechanical behavior at 200°C (abbreviated to:
behavior at 200°C)
This test allows us to estimate the service temperature.
The pipe is placed in an oven at 200°C for 30 minutes. Its
condition is then observed:
10 * "Pass" signifies that the pipe has retained its physical
integrity, that it has not undergone significant deformation and that it
has not melted.
* "Melted" signifies that the pipe has undergone significant
deformation and that it has, in part at least, melted.
15
Flexibility
This is the flexural modulus as measured in accordance with
standard IS0178, after conditioning at 23OC under 50% relative
humidity for 15 days.
20 The assessment criteria are as follows:
- B = good if < 900MPa
- AB = acceptable between 900 and 1500 MPa
- Mv = poor if > 1500 MPa.
Elongation at break (abbreviated to: elongation)
This corresponds to the elongation at break in accordance with
standard IS0527, after conditioning at 23OC under 50% relative
humidity for 15 days.
The assessment criteria are as follows:
- good if > 100%
- poor if < 50%
Zinc chloride resistance (abbreviated to: ZnClz)
This resistance is tested on the parts exposed to the actions of
road salts, in other words, on the outer face of the pipe and the
connection side, corresponding to the location at which the pipe is cut.
The zinc chloride resistance is measured in accordance with
the standard SAE 52260. The pipes, bent beforehand with a radius of
curvature of 40 mm, are immersed in a 50% ZnClz solution. A record
is made of the time after which cracks or the first breakage occurs.
The assessment criteria are as follows:
- "Pass" = satisfactory, corresponding to a time > = 800 h
- "Breaks" = poor, corresponding to a time < = 100 h
VW cold impact -40°C (abbreviated to: -40°C impact)
This is an impact test according to the 'VW protocol
(Volkswagen) in accordance with the standard TL 52435. According to
this test protocol, the pipe is subjected to impact at -40°C. The
percentage breakage is taken.
The assessment criteria are as follows:
- TB = very good, if 0% breakage
- B = good, if < 25% breakage
- AB = fairly good, if between 25 and 50% breakage
- Mv = poor, if > 50% breakage
Adhesion
This involves measuring the adhesive force between the layers,
expressed in Nlcm. It is conveyed by measuring the peel strength,
expressed in Nlcm, and measured on the pipe with an 8 mm diameter
and a thickness of 1 mm that has undergone conditioning at 50%
relative humidity and 23°C for 15 days.
In the case of a pipe with 3 layers or more, the value given
relates to the weakest interface, in other words that having the least
good adhesion, at the point where the greatest risk of delamination is.
Peeling of the interface is performed by subjecting one of the parts to
pulling at an angle of 90" and a rate of 50 mmlmin in accordance with
the following process.
A strip of pipe with a width of 9 mm is removed by cutting.
This strip is therefore in the form of a sheet and still possesses all of
the layers of the original pipe. The separation of the two layers of the
interface it is desired to evaluate is initiated by means of a knife. Each
5 of the layers thus separated is placed in the jaws of a tensile machine.
Peeling is carried out by exerting traction on these 2 layers from
either side at 180" and at a rate of 50 mmlmin. The strip, and therefore
the interface, is itself held at 90 degrees relative to the direction of
traction.
10 The assessment. criteria take account of this and are as follows:
- B = good, if > 40 Nlcm
- Acc = fairly good (acceptable), between 40 and 20 Nlcm
- Mv = mediocre to poor, if < 20 Nlcm
15 Thermal aging resistance (abbreviated to: aging)
This relates to the resistance of the multilayer pipe to
oxidative aging in hot air. The pipe is aged in air at 150°C. Regular
samples are taken throughout the time. The pipes thus sampled are
then subjected to impact in accordance with the standard DIN 73378,
20 this impact being carried out at -40°C, and an indication is given of
the half-life (in hours) corresponding to the time after which 50% of
the pipes tested undergo breakage.
Cooling liquid aging resistance (abbreviated to: age LLC)
2 5 This is the aging resistance of the multilayer pipe when it is
filled with cooling liquid on the inside and exposed to air on the
outside. Air and cooling liquid are at 130°C. The cooling liquid is a
50150 by mass waterlglycol mixture. The pipe is aged under these
conditions for 1500 hours. The pipes are then subjected to impact in
30 accordance with the standard DIN 73378, this impact being performed
at -40°C; the percentage of broken pipe is reported.
Cooling liquid permeability (abbreviated to: barrier)
The quality of the barrier with respect to the cooling liquid is
estimated by measuring the permeability during the preceding aging
test. The permeability is the loss of liquid, and is expressed in
g/m2/24 hlmm.
5
Urea solution aging resistance (abbreviated to: Urea aging)
The pipes are immersed in a 32.5% urea solution and undergo a
number of cycles. One cycle lasts 24 hours and consists of 23 and a
half hours at 70°C and half an hour at 170°C. The elongation at break
10 is the criterion of evaluation. The half-life is reached when the
elongation has attained 50% of the initial value. The half-life is
expressed in hours.
51 Results
15 The test results appear in table 2 (see figure 2) and in tables 3
and 4 below.
Table 3 below contains the results of the tests evaluating the
aging of the structures.
20
Table 3
(hours)
Table 4 below contains the results of the tests comparing a
25 comparative monolayer structure and two structures according to the
invention.
Structures Urea aging
(hours)
According to
the invention
Comparative
Aging
I I I I
1
2 1
2 2
2 3
2900
50
100
330
> 1000
<480
<480
<4 8 0
5/Conclusions
The results show that the structures according to the invention
Table 4
5 lead to improved properties, in terms of thermomechanical resistance,
ZnC12 resistance, flexibility, impact resistance, aging, and barrier
properties.
Structures
According to the
invention
Comparative
LLC aging
(%)
30
0
9 0
1
3
26
Barrier
(g/m2/24h/mm)
13 0
5 0
310

CLAIMS
1. A multilayer structure comprising:
- a layer (Ll) - outer layer - composed of a composition
comprising predominantly one or more semicrystalline copolyamides
5 (H) having a melting temperature of at least 220°C and comprising at
least 80 mol% of the two following unit.s. (s) and (a):
- where unit (s) denotes one or more semi-aromatic units (s)
formed
of one or more subunits obtained from aromatic diacid (sr) and
10 ofone or more subunits obtained from aliphatic diamine (sa),
the aliphatic diamine (sa) comprising from 9 to 13 carbon atoms,
- where the unit (a) denotes one or more aliphatic units
comprising 8 to 13 carbon atoms per nitrogen atom, and
where the molar ratio (s)/(a) is from 1 to 3, and
15 - a layer (L2) composed of a composition comprising
predominantly one or more tetrafluoroethylene (TFE) copolymers, said
TFE copolymer being mandatorily functionalized when the layer (L2)
is in contact with the layer (Ll) or in contact with an interlayer
comprising predominantly one or more polyamides.
20 2. The structure as claimed in claim 1, characterized in that the
tetrafluoroethylene copolymer or copolymers are selected from
ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylenechlorotrifluoroethylene
copolymer (CTFE), and a mixture thereof,
which are optionally functionalized by anhydride, epoxy, acid or else
2 5 acid halide functions.
3. The structure as claimed in claim 1 or 2, characterized in
that the melting enthalpy of the semicrystalline copolyamide (H) is
greater than or equal to 10 Jlg, preferably greater than or equal to
25 Jlg.
30 4. The structure as claimed in any one of claims 1 to 3,
characterized in that the melting temperature of the semicrystalline
copolyamide (H) is from 220°C to 280°C.
5. The structure as claimed in any one of claims 1 to 4,
characterized in that the copolyamide (H) is composed:.
- of 40 mol% to 75 mol% of one or more semi-aromatic units
(s),
5 - of 20 mol% to 50 mol% of one or more aliphatic units (a),
and
- of 0 to 20 mol% of one or more units other than the
aforesaid units (a) and (s).
6. The structure as claimed in any one of claims 1 to 5,
10 characterized in that the copolyamide (H) is composed:
- of 50 mol% to 75 mol% of one or more semi-aromatic units
(s), and
- of 25 mol% to 50 mol% of one or more aliphatic units (a).
7. The structure as claimed in any one of claims 1 to 6,
15 characterized in that the subunit (sr) is obtained only from
terephthalic acid.
8. The structure as claimed in claim 5, characterized in that the
copolyamide (H) is selected from PA12/9.T, PA6.12/10.T,
PA10.10/10.T, PA10.10110.T/6.T7 PA1 0.1011 0.T110.1, and
20 PA10.12110.T.
9. The structure as claimed in any one of claims 1 to 8,
characterized in that the composition forming the outer layer (Ll)
comprises one or more supplementary polymers selected from
functionalized or non-functionalized polyolefins, aliphatic
2 5 polyamides, and mixtures thereof.
10. The structure as claimed in claim 9, characterized in that
the polyolefin is a functionalized copolyolefin comprising one or more
anhydride or acid functions, optionally in a mixture with at least one
polymer comprising one or more epoxide functions.
30 11. The structure as claimed in any one of claims 1 to 10,
characterized in that the composition forming the outer layer (Ll)
comprises up to 15 wt% of a plasticizer, relative to the total weight of
the composition.
4
12. The structure as claimed in any one of claims 1, to 11,
characterized in that it takes the form of a two-layer structure.
13. The structure as claimed in any one of claims 1 to 11,
characterized in that it takes the form of a three-layer structure, the
5 interlayer (L3), arranged between the layers (Ll) and (L2), it being
possible for the interlayer (L3) to comprise one or more aliphatic
(co)polyamides comprising between 9 and 36 carbon atoms per
nitrogen atom or one or more polyphthalamides.
14. The structure as claimed in any one of claims 1 to 13,
10 characterized in that the composition of the layer (L2) comprises
conductive fillers.
15. The structure as claimed in any one of claims 1 to 14,
characterized in that when the layer (L2) is composed predominantly
of one or of two or more functionalized fluorocopolymers as defined
15 in claim 1, it comprises a supplementary layer located in contact with
said layer (L2) and forming the innermost layer of the structure, it
being possible for this supplementary layer to comprise one or more
non-functionalized fluorocopolymers as defined in claim 1 and,
optionally, conductive fillers.
20 16. A pipe comprising a structure as claimed in any one of
claims 1 to 15.
17. The use of a structure as defined in any one of claims 1 to
15 or of a pipe as claimed in claim 16 for transporting polar and/or
apolar fluids, especially those present in vehicles.
2 5 18. The use as claimed in claim 17, characterized in that the
fluid is selected from an oil, a liquid based on urea solution, a fuel,
especially an alcoholized fuel and more particularly a biogasoline, a
refrigerant fluid, engine gas emanations, and a cooling liquid, more
particularly a glycol-based cooling liquid.
30
Dated this 1 9h day of August, 20 13
&~NJNA~&HTA-DUW]
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[S]