Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Field of the invention
The present invention relates to a multilayer structure having a layer
based on polyamide and on HDPE (high density polyethylene). It also relates to
a tank composed of this structure having this layer in direct contact with the
fluid
contained in the tank. The layer based on polyamide and on HDPE of the
structures of the invention constitutes one of the faces of the structure,
that is to
say that it is not inside the structure (sandwich). These structures are of
use in
the manufacture of devices for the transfer or storage of fluids and more
particularly pipes, tanks, tank conduits, that is to say the pipe which is
used to
fill the tank, bottles and containers in which the layer based on polyamide
and
on HDPE is in contact with the fluid. It is of particular use for tanks.
The invention is of use for a fluid, such as motor vehicle petrol, by
preventing losses through the structure, so as not to pollute the environment.
It
is also of use for liquids comprising volatile substances by preventing
depletion
of the liquid in this volatile substance. The invention is also of use for the
liquid
coolant of the engines, for the oil and for the fluid of the air-conditioning
system.
The prior art and technical problem
Patent EP 742 236 discloses petrol tanks composed of five layers, which
are respectively:
- high density polyethylene (HDPE);
- a tie;
- a polyamide (PA) or a copolymer having ethylene units and vinyl
alcohol units (EVOH);
- a tie;
- HDPE.
A sixth layer can be added between one of the tie layers and one of the HDPE
layers. This sixth layer is composed, for example, of the manufacturing scrap
material resulting from the forming of the tanks or, in a much smaller amount,
of
tanks which have failed specification. This scrap material and these tanks
which
have failed specification are ground. This ground material is subsequently
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remelted and directly extruded on the plant for the coextrusion of the tanks.
This
ground material might also be melted and regranulated by an extrusion device,
such as a twin-screw or single-screw extruder, before being reused.
According to one alternative form, the recycled product can be blended
with the HDPE of the two outermost layers of the tank. It is possible, for
example, to blend the granules of recycled product with the granules of virgin
HDPE of these two layers. It is also possible to use any combination of these
recycling operations. The level of recycled material can represent up to 50%
of
the total weight of the tank.
Patent EP 731 308 discloses a tube comprising an inner layer comprising
a blend of polyamide and of polyolefin with a polyamide matrix and an outer
layer comprising a polyamide. These polyamide-based tubes are of use for the
transportation of petrol and more particularly for conveying the petrol from
the
tank of the motor vehicle to the engine and also, but with a larger diameter,
for
the transportation of hydrocarbons in service stations between the
distribution
pumps and the underground storage reservoirs.
According to another form of the invention, it is possible to position,
between the inner and outer layers, a layer of a polymer comprising ethylene
units and vinyl alcohol units (EVOH). Use is advantageously made of the
structure: inner layer/EVOH/tie/outer layer.
The tanks disclosed in EP 742 236, and which do not have the barrier
layer in direct contact with the petrol, certainly have barrier properties but
they
are not sufficient when very low petrol losses are being looked for. EP 731
308
discloses pipes which have their outer layer made of polyamide and the barrier
layer in direct contact with the petrol; the layer made of polyamide is
necessary
for the mechanical strength of the combined product.
Patent EP 1 122 061 A discloses a structure successively comprising:
a first layer of high density polyethylene (HDPE),
a tie layer,
a second layer of EVOH or of a blend based on EVOH,
optionally a third layer of polyamide or of a blend of polyamide and of
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polyolefin.
Numerous blends of polyamide and of polyolefin which can constitute the third
layer are described in this patent. It has now been found that this third
layer is
necessary and, furthermore, that it has to comprise HDPE in order to obtain
good barrier properties. Furthermore, the conversion temperature of the
polyamide of this third layer must not be too high in order not to be too far
from
that of the EVOH.
Brief description of the invention
The present invention relates to a structure successively comprising:
a first layer of high density polyethylene (HDPE),
a first tie layer,
a second layer of EVOH or of a blend based on EVOH,
optionally a second tie layer,
a third layer of a blend comprising, by weight, the total being 100%:
50 to 90% of polyamide (A) having a conversion temperature of at most
230°C,
1 to 30% of high density polyethylene (HDPE),
5 to 30% of an impact modifier chosen from elastomers and very low
density polyethylenes,
at least one of the HDPE and of the impact modifier being functionalized,
in all or part,
the layers being coextrudable.
Use may be made of a blend of different HDPEs. It can be a blend of
different nonfunctionalized HDPEs, of a nonfunctionalized HDPE and of the
same HDPE but functionalized, of a nonfunctionalized HDPE and of another
HDPE but functionalized or of two different grafted HDPEs, or any combination
of these possibilities.
Use may be made of a blend of different impact modifiers. It can be a
blend of different nonfunctionalized impact modifiers, of a nonfunctionalized
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impact modifier and of the same impact modifier but functionalized, of a
nonfunctionalized impact modifier and of another impact modifier but
functionalized, of two different functionalized impact modifiers or of a
functionalized impact modifier and of a functionalized HDPE with optionally a
nonfunctionalized impact modifier and optionally a nonfunctionalized HDPE, or
any combination of these possibilities.
The layers are "coextrudable", meaning that they are in the same
rheology range to form, for example, a parison which can be blow-moulded to
form a hollow body or an extruded tube.
The proportion of functional groups of the HDPE and/or of the impact
modifier must be sufficient for the layer based on polyamide (A) and on HDPE
to have mechanical strength but not too great in order for the viscosity not
to be
so high that the layer is no longer coextrudable.
The present invention also relates to devices for the transfer or storage of
fluids and more particularly to pipes, tanks, conduits, bottles and containers
composed of the above structure in which the layer of the blend of polyamide
(A) and of HDPE is in direct contact with the fluid present or transported.
These
devices can be manufactured by conventional techniques of the industry of
thermoplastic polymers, such as coextrusion and coextrusion blow-moulding.
Detailed description of the invention
As regards the first layer, high density polyethylene (HDPE) is
described in Kirk-Othmer, 4th edition, Vol. 17, pages 704 and 724-725. It is,
according to ASTM D 1248-84, an ethylene polymer having a density of at least
0.940. The name HDPE relates both to ethylene homopolymers and to
copolymers of ethylene with small proportions of a-olefin. The density is
advantageously between 0.940 and 0.965. In the present invention, the MFI of
the HDPE is advantageously between 0.1 and 50. Mention may be made, as
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examples, of Eltex B 2008~, with a density of 0.958 and an MFI of 0.9 (in g/10
min at 190°C under 2.16 kg), Finathene~ MS201 B from Fina and LupolenO
4261 AQ from BASF. As regards the high density polyethylene of the first
layer,
its density is advantageously between 0.940 and 0.965 and the MFI is between
5 0.1 and 5 g/10 min. (190°C, 5 kg).
As regards the second layer, the EVOH copolymer is also known as
saponified vinyl acetate/ethylene copolymer. The saponified vinyl
acetate/ethylene copolymer to be employed according to the present invention
is a copolymer having an ethylene content of 20 to 70 mot%, preferably of 25
to
70 mot%, the degree of saponification of its vinyl acetate component being not
less than 95 mot%. With an ethylene content of less than 20 mot%, the barrier
properties under conditions of high humidity are not as great as would be
desired, while an ethylene content exceeding 70 mol% leads to declines in the
barrier properties. When the degree of saponification or of hydrolysis is less
than 95 mot%, the barrier properties are lost.
The term "barrier properties" is understood to mean impermeability to
gases and to liquids and in particular to oxygen and to petrol for motor
vehicles.
The invention relates more particularly to the barrier to petrol for motor
vehicles.
Among these saponified copolymers, those which have melt flow indices
in the range from 0.5 to 100 g/10 minutes are of particular use.
Advantageously,
the MFI is chosen between 5 and 30 (g/10 min at 230°C under 2.16 kg);
"MFI" is
the abbreviation for Melt Flow Index.
It is understood that this saponified copolymer can comprise small
proportions of other comonomer ingredients, including a-olefins, such as
propylene, isobutene, a-octene, a-dodecene, a-octadecene, and the like,
unsaturated carboxylic acids or their salts, partial alkyl esters, complete
alkyl
esters, nitrites, amides and anhydrides of the said acids, and unsaturated
sulphonic acids or their salts.
With regard to the blends based on EVOH, they are such that the EVOH
forms the matrix, that is to say that it represents at least 40% by weight of
the
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blend and preferably at least 50%. The other constituents of the blend are
chosen from polyolefins, polyamides or impact modifiers which are optionally
functionalized. The impact modifier can be chosen from elastomers, copolymers
of ethylene and of an olefin having 4 to 10 carbon atoms (for example,
ethylene-octene copolymers), and very low density polyethylenes. Mention may
be made, as examples of elastomers, of EPR and EPDM. EPR (abbreviation for
Ethylene-Propylene Rubber) denotes ethylene-propylene elastomers and
EPDM denotes ethylene-propylene-diene monomer elastomers.
As first example of these blends based on EVOH of the second
layer, mention may be made of the compositions comprising (by weight):
- 55 to 99.5 parts of EVOH copolymer,
0.5 to 45 parts of polypropylene and of compatibilizing agent, their
proportions being such that the ratio of the amount of polypropylene to the
amount of compatibilizing agent is between 1 and 5.
Advantageously, the ratio of the MFi of the EVOH to the MFI of the poly-
propylene is greater than 5 and preferably between 5 and 25. Advantageously,
the MFI of the polypropylene is between 0.5 and 3 (in g/10 min at 230°C
under
2.16 kg). According to an advantageous form, the compatibilizing agent is a
polyethylene carrying polyamide grafts and it results from the reaction (i) of
a
copolymer of ethylene and of a grafted or copolymerized unsaturated monomer
X with (ii) a polyamide. The copolymer of ethylene and of a grafted or
copolymerized unsaturated monomer X is such that X is copolymerized and it
can be chosen from ethylene/maleic anhydride copolymers and ethylene/alkyl
(meth)acrylate/maleic anhydride copolymers, these copolymers comprising from
0.2 to 10% by weight of malefic anhydride and from 0 to 40% by weight of alkyl
(meth)acrylate.
According to another advantageous form, the compatibilizing agent is a
polypropylene carrying polyamide grafts which results form the reaction (i) of
a
homopolymer or of a copolymer of propylene comprising a grafted or
copolymerized unsaturated monomer X with (ii) a polyamide. Advantageously,
X is grafted. The monomer X is advantageously an unsaturated carboxylic acid
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anhydride, such as, for example, malefic anhydride.
As second example of these blends based on EVOH of the second
layer, mention may be made of the compositions comprising:
- 50 to 98% by weight of an EVOH copolymer,
- 1 to 50% by weight of a polyethylene,
- 1 to 15% by weight of a compatibilizing agent composed of a blend of
an LLDPE polyethylene or metallocene polyethylene and of a polymer chosen
from elastomers, very low density polyethylenes and metallocene
polyethylenes, the blend being cografted by an unsaturated carboxylic acid or
a
functional derivative of this acid.
Advantageously. the compatibilizing agent is such that the MF110/MF12
ratio is between 5 and 20, where MFI2 is the melt flow index at 190°C
under a
load of 2.16 kg, measured according to ASTM D1238, and MF110 is the melt
flow index at 190°C under a load of 10 kg, according to ASTM D1238.
As third example of these blends based on EVOH of the second
layer, mention may be made of the compositions comprising:
- 50 to 98% by weight of an EVOH copolymer,
- 1 to 50% by weight of an ethylene/alkyl (meth)acryiate copolymer,
- 1 to 15% by weight of a compatibilizing agent resulting from the reaction
(i) of a copolymer of ethylene and of a grafted or copolymerized unsaturated
monomer X with (ii) a copolyamide.
Advantageously, the copolymer of ethylene and of a grafted or
copolymerized unsaturated monomer X is such that X is copolymerized and this
is a copolymer of ethylene and of malefic anhydride or a copolymer of
ethylene,
of an alkyl (meth)acrylate and of malefic anhydride.
Advantageously, these copolymers comprise from 0.2 to 10% by weight
of malefic anhydride and from 0 to 40% by weight of alkyl (meth)acrylate.
As fourth example of these blends based on EVOH of the second
layer, mention may be made of the compositions comprising:
- 50 to 98% by weight of an EVOH copolymer,
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- 2 to 50% by weight of an elastomer which is optionally functionalized in
all or part or of a blend of a functionalized elastomer and of another
nonfunctionalized elastomer.
As regards the blend of polyamide (A) and of HDPE of the third
layer, the term "conversion temperature" is understood to mean the
temperature at which it is coextruded with the material of the other layers
and/or
coextruded and blow-moulded with the material of the other layers. For
semicrystalline polyamides, this is a temperature above the melting point
(usually denoted by M.p.) and, for amorphous polyamides, this is, of course, a
temperature above the Tg (glass transition temperature). The term "above" is
understood to mean generally a difference of 10 to 50°C.
This polyamide (A) is chosen from the products which comprise units
originating:
- from one or more amino acids, such as aminocaproic acid, 7-
aminoheptanoic acid, 11-aminoundecanoic acid and 12-aminododecanoic acid,
or from one or more lactams, such as caprolactam, enantholactam and
lauryllactam;
- from one or more salts or mixtures of diamines with diacids. Mention
may be made, as examples of diacids, of isophthalic acid, terephthalic acid or
dicarboxylic acids having from 6 to 18 carbon atoms, such as adipic acid,
azelaic acid, suberic acid, sebacic acid and dodecanedicarboxylic acid. The
diamine can be an aliphatic diamine having from 6 to 18 atoms, it can be an
arylic and/or saturated cyclic diamine. Mention may be made, as examples, of
hexamethylenediamine, piperazine, tetramethylenediamine, octamethylene-
diamine, decamethylenediamine, dodecamethylenediamine, 1,5-diamino-
hexane, 2,2,4-trimethyl-1,6-diaminohexane, polyoldiamines, isophoronediamine
(IPD), methylpentamethylenediamine (MPDM), bis(aminocyclohexyl)methane
(BACM), or bis(3-methyl-4 aminocyclohexyl)methane (BMACM).
Use may also advantageously be made of copolyamides. Mention may
be made of the copolyamides resulting from the condensation of at least two
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a,w-aminocarboxylic acids or of two lactams or of a lactam and of an a,w-
aminocarboxylic acid. Mention may also be made of the copolyamides resulting
from the condensation of at least one a,w-aminocarboxylic acid (or one
lactam),
at least one diamine and at least one dicarboxylic acid.
Mention may be made, as examples of lactams, of those which have
from 3 to 12 carbon atoms on the main ring and which can be substituted.
Mention may be made, for example, of ~i,~3-dimethylpropiolactam,
a,a-dimethylpropiolactam, amylolactam, caprolactam, capryllactam and
lauryllactam.
Mention may be made, as examples of a,w-aminocarboxylic acids, of
aminoundecanoic acid and aminododecanoic acid. Mention may be made, as
examples of dicarboxylic acids, of adipic acid, sebacic acid, isophthalic
acid,
butanedioic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, the
sodium or lithium salt of sulphoisophthalic acid, dimerized fatty acids (these
dimerized fatty acids have a dimer content of at least 98% and are preferably
hydrogenated) and dodecanedioic acid HOOC-(CH2)10-COOH.
Mention may be made, as examples of copolyamides, of copolymers of
caprolactam and of lauryllactam (PA 6/12), copolymers of caprolactam, of
adipic
acid and of hexamethylenediamine (PA 6/6-6), copolymers of caprolactam, of
lauryllactam, of adipic acid and of hexamethylenediamine (PA 6/12/6-6),
copolymers of caprolactam, of lauryllactam, of 11-aminoundecanoic acid, of
azelaic acid and of hexamethylenediamine (PA 6/6-9/11/12), copolymers of
caprolactam, of lauryllactam, of 11-aminoundecanoic acid, of adipic acid and
of
hexamethylenediamine (PA 6/6-6/11/12) or copolymers of lauryllactam, of
azelaic acid and of hexamethylenediamine (PA 6-9/12).
All these polyamides (A) are known per se and are manufactured according to
the usual processes for polyamides.
Advantageously, the copolyamide is chosen from PA 6/12 and PA 6/6-6.
Polyamide blends can be used. Advantageously, the relative viscosity,
measured in 96% sulphuric acid, is between 2 and 5.
It would not be departing from the scope of the invention to replace a
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portion of the polyamide (A) with a copolymer comprising polyamide blocks and
polyether blocks, that is to say to use a blend comprising at least one of the
above polyamides and at least one copolymer comprising polyamide blocks and
polyether blocks.
5 The copolymers comprising polyamide blocks and polyether blocks
result from the copolycondensation of polyamide sequences comprising
reactive ends with polyether sequences comprising reactive ends, such as,
inter
alias
1 ) Polyamide sequences comprising diamine chain ends with
10 polyoxyalkylene sequences comprising dicarboxyl chain ends.
2) Polyamide sequences comprising dicarboxyl chain ends with
polyoxyalkylene sequences comprising diamine chain ends
obtained by cyanoethylation and hydrogenation of aliphatic a,w
dihydroxylated polyoxyalkylene sequences, known as polyether
diols.
3) Polyamide sequences comprising dicarboxyl chain ends with
polyetherdiols, the products obtained being, in this specific case,
polyetheresteramides. Use is advantageously made of these
copolymers.
The polyamide sequences comprising dicarboxyl chain ends originate,
for example, from the condensation of a,w-aminocarboxylic acids, of lactams or
of dicarboxylic acids and diamines in the presence of a chain-limiting
dicarboxylic acid.
The polyether can, for example, be a polyethylene glycol (PEG), a
polypropylene glycol (PPG) or a polytetramethylene glycol (PTMG). The latter
is
also known as polytetrahydrofuran (PTHF).
The number-average molar mass Mn of the polyamide sequences is
between 300 and 15 000 and preferably between 600 and 5000. The mass Mn
of the polyether sequences is between 100 and 6000 and preferably between
200 and 3000.
The polymers comprising polyamide blocks and polyether blocks can
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also comprise randomly distributed units. These polymers can be prepared by
the simultaneous reaction of the polyether and of the precursors of the
polyamide blocks.
For example, polyetherdiol, a lactam (or an a,w-amino acid) and a
chain-limiting diacid can be reacted in the presence of a small amount of
water.
A polymer is obtained which has essentially polyether blocks and polyamide
blocks, the latter being of highly variable length, but also the various
reactants
which have reacted randomly, which are 'distributed statistically along the
polymer chain.
These polymers comprising polyamide blocks and polyether blocks,
whether they originate from the copolycondensation of polyamide and polyether
sequences prepared beforehand or from a one-stage reaction, exhibit, for
example, Shore D hardnesses which can be between 20 and 75 and
advantageously between 30 and 70 and an intrinsic viscosity of between 0.8
and 2.5, measured in meta-cresol at 250°C for an initial concentration
of
0.8 g/100 ml. The MFI values can be between 5 and 50 (235°C under a
load of
1 kg).
The polyetherdiol blocks are either used as is and copolycondensed
with polyamide blocks comprising carboxyl ends or they are aminated, in order
to be converted into polyetherdiamines, and condensed with polyamide blocks
comprising carboxyl ends. They can also be blended with polyamide precursors
and a chain-limiting agent in order to prepare polymers comprising polyamide
blocks and polyether blocks having statistically distributed units.
Polymers comprising polyamide and polyether blocks are disclosed in
Patents US 4 331 786, US 4 115 475, US 4 195 015, US 4 839 441, US 4 864
014, US 4 230 838 and US 4 332 920.
The ratio of the amount of copolymer comprising polyamide blocks and
polyether blocks to the amount of polyamide is advantageously between 10/90
and 60/40, by weight.
As regards the HDPE of the third layer, its density is advantageously
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between 0.940 and 0.965 and the MFI between 1 and 10 g/10 min. (190°C,
kg).
As regards the impact modifier and first the elastomers, mention may
5 be made of SBS, SIS and SEBS block polymers and ethylene/propylene (EPR)
or ethylene/propylene/diene (EPDM) elastomers. With regard to the very low
density polyethylenes, these are, for example, metallocenes with a density,
for
example, between 0.860 and 0.900.
Use is advantageously made of an ethylene/propylene (EPR) or
ethylene/propylene/diene (EPDM) elastomer. The functionalization can be
introduced by grafting or copolymerization with an unsaturated carboxylic
acid.
It would not be departing from the scope of the invention to use a functional
derivative of this acid. Examples of unsaturated carboxylic acids are those
having 2 to 20 carbon atoms, such as acrylic acid, methacrylic acid, malefic
acid,
fumaric acid and itaconic acid. The functional derivatives of these acids
comprise, for example, the anhydrides, the ester derivatives, the amide
derivatives, the imide derivatives and the metal salts (such as the alkali
metal
salts) of the unsaturated carboxylic acids.
Unsaturated dicarboxylic acids having 4 to 10 carbon atoms and their
functional derivatives, particularly their anhydrides, are particularly
preferred
grafting monomers. These grafting monomers comprise, for example, malefic
acid, fumaric acid, itaconic acid, citraconic acid, allylsuccinic acid,
cyclohex-4
ene-1,2-dicarboxylic acid, 4-methylcyclohex-4-ene-1,2-dicarboxylic acid,
bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, x-methylbicyclo[2.2.1]hept-5-
ene
2,3-dicarboxylic acid, malefic anhydride, itaconic anhydride, citraconic
anhydride, allylsuccinic anhydride, cyclohex-4-ene-1,2-dicarboxylic anhydride,
4-methylcyclohex-4-ene-1,2-dicarboxylic anhydride, bicyclo[2.2.1]hept-5-ene-
2,3-dicarboxylic anhydride and x-methylbicyclo[2.2.1]hept-5-ene-2,3-
dicarboxylic anhydride. Use is advantageously made of malefic anhydride.
Various known processes can be used to graft a grafting monomer to a
polymer. For example, this can be carried out by heating the polymers at high
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temperature, approximately 150° to approximately 300°C, in the
presence or in
the absence of a solvent and with or without a radical generator. The amount
of
the grafting monomer can be appropriately chosen but it is preferably from
0.01
to 10%, better still from 600 ppm to 2%, with respect to the weight of the
polymer to which the graft is attached.
It is possible to graft, in all or part, the impact modifier and to blend it
with
the HDPE. It is possible to graft the HDPE, in all or part, and to blend it
with the
impact modifier. It is also possible separately to graft, in all or part, the
impact
modifier, to graft the HDPE, in all or part, and then to blend the two grafted
products. It is also possible to blend the impact modifier with the HDPE and
to
graft, in all or part, the blend.
The proportion of functionalized HDPE and/or of functionalized modifier
with respect to the combined functionalized or nonfunctionalized HDPE and
functionalized or nonfunctionalized impact modifier can be (by weight) between
0 and 70%, advantageously between 5 and 60% and preferably between 20
and 60%.
According to one form of the invention, the HDPE is not functionalized
and the impact modifier is functionalized in all or part.
The proportions of the blend of the third layer are advantageously, the
total being 100%:
55 to 80% of polyamide (A),
10 to 20% of high density polyethylene (HDPE),
10 to 30 % of impact modifier.
The blends of the third layer can be prepared by blending the various
constituents in the molten state in conventional devices of the thermoplastic
polymer industry.
The first layer can be composed of a layer of virgin HDPE and of a
layer of recycled polymers (also referred to as regrind layer) originating
from
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scrap material during the manufacture of the transfer or storage devices or
from
these devices which have failed specification, as is explained in the
abovementioned prior art. This layer of recycled polymers is situated on the
side
of the tie layer. In the continuation of the text, these two layers will be
denoted
for simplicity by the term "first layer". Functionalized polyolefins can be
added to
this layer of recycled polymers in a proportion which can, for example, be
between 0.1 and 10% by weight. These functionalized polyolefins are
advantageously chosen from the ties. Either HDPE or functionalized polyolefins
or a blend of the two can be added to this layer of recycled polymers.
The thickness of the first layer can be between 2 and 10 mm, that of the
second between 30 and 500 pm and that of the third between 500 Nm and
4 mm. As regards the tanks, the overall thickness is usually between 3 and
10 mm.
As example of tie, mention may be made of functionalized polyolefins.
The tie between the first and the second layer (i.e. the first tie layer) and
that
between the second and the third layer (i.e, the second tie layer)can be
identical
or different. In the following descriptions of ties, the term "polyethylene"
denotes
both homopolymers and copolymers.
As first tie example, mention may be made of a blend of a polyethylene
(C1 ) and of a polymer (C2) chosen from elastomers, very low density
polyethylenes and ethylene copolymers, the blend (C1 ) + (C2) being cografted
by an unsaturated carboxylic acid.
According to an alternative form, mention may be made of a blend (i) of a
polymer (C2) chosen from elastomers, very low density polyethylenes and
ethylene copolymers, (C2) being grafted by an unsaturated carboxylic acid, and
(ii) of a polymer (C'2) chosen from elastomers, very low density polyethylenes
and ethylene copolymers.
As second tie example, mention may be made of the blends
comprising:
- 5 to 30 parts of a polymer (D) itself comprising a blend of a
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polyethylene (D1 ) with a density of between 0.910 and 0.940 and of a polymer
(D2) chosen from elastomers, very low density polyethylenes and metallocene
polyethylenes, the blend (D1 ) + (D2) being cografted by an unsaturated
carboxylic acid,
5 - 95 to 70 parts of a polyethylene (E) with a density of between 0.910
and 0.930,
- the blend of (D) and (E) being such that:
~ its density is between 0.910 and 0.930,
~ the content of grafted unsaturated carboxylic acid is between 30
10 and 10 000 ppm,
~ the MFI (ASTM D 1238, 190°C, 2.16 kg) is between 0.1 and
3 g/10 min, the MFI denoting the melt flow index.
The density of the tie is advantageously between 0.915 and 0.920.
Advantageously, (D1 ) and (E) are LLDPEs; preferably, they have the same
15 comonomer. This comonomer can be chosen from 1-hexene, 1-octene and
1-butene.
As third tie example, mention may be made of the blends comprising:
- 5 to 30 parts of a polymer (F) itself comprising a blend of a
polyethylene (F1 ) with a density of between 0.935 and 0.980 and of a polymer
(F2) chosen from elastomers, very low density polyethylenes and ethylene
copolymers, the blend (F1 ) + (F2) being cografted by an unsaturated
carboxylic
acid,
- 95 to 70 parts of a polyethylene (G) with a density of between 0.930
and 0.950,
- the blend of (F) and (G) being such that:
~ its density is between 0.930 and 0.950 and advantageously
between 0.930 and 0.940,
~ the content of grafted unsaturated carboxylic acid is between 30
and 10 000 ppm,
~ the MFi (melt flow index), measured according to ASTM D 1238 at
190°C and 2.16 kg, is between 5 and 100.
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As fourth tie example, mention may be made of polyethylene grafted by
malefic anhydride having an MFI of 0.1 to 3 and a density of between 0.920 and
0.930 and which comprises 2 to 40% by weight of materials which are insoluble
in n-decane at 90°C. In order to determine the materials which are
insoluble in
n-decane, the grafted polyethylene is dissolved in n-decane at 140°C,
is cooled
to 90°C and products precipitate; it is then filtered and the level of
insoluble
materials is the percentage by weight which precipitates and is collected by
filtration at 90°C. If the level is between 2 and 40%, the tie has good
resistance
to petrol.
Advantageously, the grafted polyethylene is diluted in an engrafted
polyethylene such that the tie is a blend of 2 to 30 parts of a grafted
polyethylene with a density of between 0.930 and 0.980 and of 70 to 98 parts
of
an engrafted polyethylene with a density of between 0.910 and 0.940,
preferably 0.915 and 0.935.
As fifth tie example, mention may be made of the blends comprising:
~ 50 to 100 parts of a polyethylene (J) homo- or copolymer with a
density of greater than or equal to 0.9,
~ 0 to 50 parts of a polymer (K) chosen from (K1 ) polypropylene
homo- or copolymer, (K2) poly(1-butene) homo- or copolymer and (K3)
polystyrene homo- or copolymer,
~ the amount of (J) + (K) being 100 parts,
~ the blend of (J) and (K) being grafted by at least 0.5% by weight
of a functional monomer,
~ this grafted blend being itself diluted in at least one polyethylene
homo- or copolymer (L) or in at least one polymer with an elastomeric nature
(M) or in a blend of (L) and (M).
According to one form of the invention, (J) is an LLDPE with a density of
0.910 to 0.930, the comonomer having from 4 to 8 carbon atoms. According to
another form of the invention, (K) is an HDPE, advantageously with a density
of
at least 0.945 and preferably of 0.950 to 0.980.
Advantageously, the functional monomer is malefic anhydride and its
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17
content is from 1 to 5% by weight of (J) + (K).
Advantageously, (L) is an LLDPE, the comonomer of which has from 4
to 8 carbon atoms, and its density is preferably at least 0.9 and preferably
0.910
to 0.930.
Advantageously, the amount of (L) or (M) or (L) + (M) is from 97 to 75
parts per 3 to 25 parts of (J) + (K), the amount of (J) + (K) + (L) + (M)
being 100
parts.
As sixth tie example, mention may be made of the blends composed of
a polyethylene of HDPE, LLDPE, VLDPE or LDPE type, 5 to 35% of a grafted
metallocene polyethylene and 0 to 35% of an elastomer, the total being 100%.
As seventh tie example, mention may be made of the blends
comprising:
- at least one polyethylene or one ethylene copolymer,
- at least one polymer chosen from polypropylene or a propylene
copolymer, poly(1-butene) homo- or copolymer, or polystyrene homo- or
copolymer, and preferably polypropylene,
this blend being grafted by a functional monomer and this grafted blend
being itself optionally diluted in at least one polyolefin or in at least one
polymer
with an elastomeric nature or in their blend. In the preceding blend which is
grafted, the polyethylene advantageously represents at least 50% of this blend
and preferably 60 to 90% by weight.
Advantageously, the functional monomer is chosen from carboxylic acids
and their derivatives, acid chlorides, isocyanates, oxazolines, epoxides,
amines
or hydroxides and preferably unsaturated dicarboxylic acid anhydrides.
As eighth tie example, mention may be made of the blends comprising:
- at least one LLDPE or VLDPE polyethylene,
- at least one ethylene-based elastomer chosen from ethylene/propylene
copolymers and ethylene/butene copolymers,
- this blend of polyethylene and of elastomer being grafted by an
unsaturated carboxylic acid or a functional derivative of this acid,
- this cografted blend being optionally diluted in a polymer chosen from
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polyethylene homo- or copolymers and styrene block copolymers,
the tie having
(a) an ethylene content which is not less than 70 mol%,
(b) a content of carboxylic acid or of its derivative of 0.01 to 10% by weight
of the tie, and
(c) an MF110/MF12 ratio of 5 to 20, where MF12 is the melt flow index at
190°C under a load of 2.16 kg, measured according to ASTM D1238, and
MF110 is the melt flow index at 190°C under a load of 10 kg, according
to ASTM
D1238.
The various layers of the structure of the invention, including the tie
layers, can additionally comprise at least one additive chosen from:
- fillers (inorganic, flame-retardant, conductive, and the like),
- nanofillers, such as, for example, nanoclays,
- nanocomposites,
- fibres,
- dyes,
- pigments,
- optical brighteners,
- antioxidants,
- nucleating agents,
- UV stabilizers.
[Examples]
Polymers used:
PA A1: Terpolymer of caprolactam (L6), adipic acid (AA) and hexamethylene-
diamine (HMDA) possessing an L6/[AA+HMDA] ratio by mass of 85/15 and a
"viscosity number" of 186 according to Standard ISO 307.
PA A2: Copolymer of caprolactam and of lauryllactam possessing a monomer
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composition by weight of 70/30 and an intrinsic viscosity (measured at
20°C for
a concentration of 0.5 g per 100 ml of meta-cresol) of 1.3 dl/g.
PA A3: Copolymer of caprolactam and of lauryllactam possessing a melting
point of 190°C and a melt flow index of 120 according to Standard ISO
1133,
measured under the conditions: 275°C under a load of 5 kg.
PA A4: Lauryllactam homopolymer possessing an intrinsic viscosity (measured
at 20°C for a concentration of 0.5 g per 100 ml of meta-cresol) of 1.55
to
1.74 dl/g.
PA A5: 11-Aminoundecanoic acid homopolymer possessing an intrinsic
viscosity (measured at 20°C for a concentration of 0.5 g per 100 ml of
meta-
cresol) of 1.35 to 1.52 dl/g.
PA A6 (10.10): Equimolar copolymer of sebacic acid (SA) and of
decanediamine (DA) possessing an intrinsic viscosity (measured at 20°C
for a
concentration of 0.5 g per 100 ml of meta-cresol) of 1.4 dl/g.
PA A7 (MXD.10): Equimolar copolymer of meta-xylylenediamine (MXD) and of
sebacic acid (SA) possessing an intrinsic viscosity (measured at 20°C
for a
concentration of 0.5 g per 100 ml of meta-cresol) of 1.4 dl/g.
PA A8 (MXD.12): Equimolar copolymer of meta-xylylenediamine (MXD) and of
dodecanedioic acid (DDA) possessing an intrinsic viscosity (measured at
20°C
for a concentration of 0.5 g per 100 ml of meta-cresol) of 1.4 dl/g.
PE 1: Polyethylene possessing a density of 0.952 according to Standard
ISO 11$3 and a melt flow index of 23 according to Standard ISO 1133,
measured under the conditions: 190°C under a load of 2.16 kg.
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PE 2: Polyethylene having a density of 0.949 according to Standard ISO 1183
and a melt flow index of 8 g/10 min according to Standard ISO 1133, measured
under the conditions: 190°C under a load of 2.16 kg.
5 P1: Terpolymer of ethylene, of propylene and of diene monomer possessing a
density of 0.89 and a Mooney viscosity (ML, 1+4, 125°C) of 30 and
grafted by
malefic anhydride at a level of 1 %.
P2: Terpolymer of ethylene, of propylene and of diene monomer possessing a
10 Mooney viscosity of 30 under the conditions ML (1+4) 100°C.
EVOH: Copolymer of ethylene and of vinyl alcohol possessing an ethylene
fraction by weight of 29% and a melt flow index of 3.2, measured according to
Standard ISO 1133 under the following conditions: 210°C under a
load of
15 2.16 kg.
T1 (Orevac): Polyethylene grafted by 3000 ppm of malefic anhydride and
possessing a melt flow index of 1, measured according to Standard ASTM 1238
under the following conditions: 190°C under a load of 2.16 kg.
Alloy 1: Compatibilized blend of PA and of PP possessing an M.p. of
255°C
and a melt flow index of 15, measured according to Standard ISO 1133 under
the following conditions: 275°C under a load of 2.16 kg, sold by the
Applicant
Company under the reference Orgalloy~ RS6600.
Alloy 2: Compatibilized blend of PA and of PE possessing an M.p. of
225°C but
a conversion temperature of 250°C and a melt flow index of 2, measured
according to Standard ISO 1133 under the following conditions: 235°C
under a
load of 2.16 kg, sold by the Applicant Company under the reference
Orgalloy~ LE 6000.
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Alloy 3: Compatibilized blend of PA and of PE possessing an M.p. of
195°C
and a melt flow index of 3, measured according to Standard ISO 1133 under the
following conditions: 235°C under a load of 2.16 kg, sold by the
Applicant
Company under reference Orgalloy~ LEC601.
Preparation of the allo sy of polyamide and of polyolefin:
The alloys of po(yamide and of polyolefin are prepared using a corotating twin-
screw extruder of Werner & Pfleiderer ZSK 40 type (diameter = 40 mm,
L = 40D).
Preparation of multilayer hollow bodies ~r coextrusion blow-moulding:
Multilayer bottles are prepared using a Bekum coextrusion blow-moulding line
equipped with 5 extruders, the barrels of which are regulated at 220°C,
unless
otherwise mentioned. The blow-moulded structures are of two types:
- four-layer structures described as follows, from the inside outwards:
1. Alloy of polyamide and of polyolefin
Thickness: 30% of the overall thickness (extruder 1 )
2. EVOH
Thickness: 5% of the overall thickness (extruder 2)
3. T1
Thickness: 5% of the overall thickness (extruder 3)
4. PE2
Thickness: 60% of the overall thickness (extruder 4)
The overall thickness is 3 mm on average.
- five-layer structures described as follows, from the inside outwards:
1. Alloy of polyamide and of polyolefin
Thickness: 30% of the overall thickness (extruder 1 )
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2. T1
Thickness: 5% of the overall thickness (extruder 5)
3. EVOH
Thickness: 5% of the overall thickness (extruder 2)
4. T1
Thickness: 5% of the overall thickness (extruder 3)
5. PE2
Thickness: 55% of the overall thickness (extruder 4)
The overall thickness is 3 mm on average.
Impact strength of the bottles:
The blow-moulded bottles, conditioned beforehand at -40°C, are tested
on one
of their flat surfaces with regard to impact strength under the following
conditions: T = -40°C and impact speed = 4.3 m/s.
The force-displacement curve resulting from this test makes it possible to
calculate the impact strength of the multilayer bottle.
Results:
Examples 1 to 3:
3 four-layer bottles, the structures of which are collated in the table below,
were
extruded blow-moulded on the Bekum extrusion line.
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23
Structure Example 1* Example 2** Example 3
(comparative) (comparative)
Alloy 1 Alloy 2 Alloy 3
EVOH EVOH EVOH
T1 T1 T1
PE2 PE2 PE2
Quality of Lack of coextrusionLack of coextrusionCorrect
the
coextrusion
* Extruder 1 is regulated at 280°C
** Extruder 1 is regulated at 250°C
These experiments demonstrate that it is advisable to use a polyamide
possessing a conversion temperature of less than 230°C in order to
provide
correct processing by coextrusion blow-moulding.
Examples 4 to 7:
The alloys of polyamide and of polyolefin collated in the tables below were
prepared:
Composition: Alloy 4 Alloy 5 Alloy 6 Alloy
7
PA A1 50 50
PA A2 71 60
PE 1 25 15 15 15
P1 4 35 29 19
P2 6 6
Examples 8 to 11:
4 five-layer bottles, the structures of which are collated in the table below,
were
extruded blow-moulded on the Bekum extrusion line.
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Structure Example Example Example 10 Example
8 9 11
Alloy Alloy 5 Alloy 6 Alloy 7
4
T1 T1 T1 T1
EVOH EVOH EVOH EVOH
T1 T1 T1 T1
PE2 PE2 PE2 PE2
Quality of the Correct ~ ~~~ f 3 ~ Correct
, ' ~' ~.
,
. ,y ,
.-:~;
coextrusion
"",, ,..
Impact strength" ~ '; Yes** Yes Yes
* "No" means that the value of the impact strength measured is less than 50 J
** "Yes" means that the value of the impact strength measured exceeds 50 J
Examples 12 to 17:
The alloys of polyamide and of polyolefin collated in the tables below were
prepared:
Comp. Alloy Alloy Alloy Alloy Alloy Alloy
12 13 14 15 16 17
PA A3
PA A4 60
PA A5 60
PA A6 60
PA A7 60
PA A8 60
PE 1 60
P 1 15 15 15 15 15 15
P 2 19 19 19 19 19 19
6 6 6 6 6 6
Examples 18 to 22:
6 five-layer bottles, the structures of which are collated in the table below,
were
extruded blow-moulded on the Bekum extrusion line.
CA 02509518 2005-06-07
Structure Example Example Example Example Example Example
17 18 19 20 21 22
Alloy Alloy Alloy Alloy Alloy Alloy
12 13 14 15 16 17
T1 T1 T1 T1 T1 T1
EVOH EVOH EVOH EVOH EVOH EVOH
T1 T1 T1 T1 T1 T1
PE2 PE2 PE2 PE2 PE2 PE2
Quality Correct Correct Correct Correct Correct Correct
of
the
coextrusion
Impact Yes* Yes Yes Yes Yes Yes
strength
* "Yes" means that the value of the impact strength measured exceeds 50 J
