THERMOPLASTIC COMPOSITION MADE OF POLYPROPYLENE
AND POLYAMIDE-GRAFTED POLYOLEFIN
Field of the invention
A subject matter of the invention is a thermoplastic co~nposition based on
polypropylene and on a polyamide-grafted polyolefin, the blend ideally being
nanostructured. More particularly, the co~npositiona ccording to the invention comes in
two alternative forms: in one, the polypropylene content is very high (2 60%) and, in
the other, conversely, the polyamide-grafted polyolefin content is very higl~(?5 0%).
10 The invention also relates to a multilayer structure in \vhich at least one of the
layers consists of the compositiou according to the invention.
State of the art
A description is given, in the document WO 02128959 of a grafted copolymer
comprising polyamide blocks on a polyolefin backbone wliiclich is chosen from
IS ethylene/maleic anhydride and ethylenelalkyl (~neth)acrylate/~naleic anhydride
copolymers, forming a nanostructured cocontinuous alloy; this confers, on this
terpolymerlcopolymer, exceptional thermomechanical properties which are maintained
on redispersing this grafted copolytner in flexible polyolefins, such as flexible ethylene
polymers.
20 Such blends have applications such as adhesives, films, tarpaulius, calendered
products, electric cables or powders for processes for the molding of objects ("slush
molding"). In the docume~lt WO 20061085007, such a composition was used to for111 a
thernlal protection layer of a substrate experiencing tenlperatures of greater than
150°Celsius PC).
These materials are said to be nanostructured, as defined in the two
abovementioned patent documents, \vhich confers on them advantageous properties
with regard to their low levels of hardness (of between 82 and 95 Shore A) and their
good thermomechanical behavior above the tnelting point of the polyolefin phase.
Unfo~tunatclp, these high perfor~nance con~pounds exhibit disadvantages vi4ien
they are present in a large anlount, nanlcly v~11en they for111 the matrix of a thertnoplastic
composition, and more pasticularly when this coinposition is required to display a
degree of stiffness and also an absolute itilpermeability to water or a low nioisture
5 uptake.
When these same compounds are used in a low anlount in a polyolefin matrix, it
is unfortunately not obvious that they can confer an advantageous property on this
matrix. One criterion is particularly impo~tanitn ce~tainap plications: the creep. In point
of fact, it has been found that the blend of these compounds with a polyethylene and
10 more specifically a high density polyethylene (HDPE) is not very satisfactory from the
viewpoint of this criterion of creep, in particular at temperatures of greater than 140°C.
Such a thermoplastic composition is known from tlie document EP 2 196 489, filed on
behalf of the applicant conlpany.
Thus, it is not obvious to blend such a grafted copolymer comprising polyan~ide
15 blocks on a polyolefin backbone with another polyolefin as the resulting cornposition
very often exhibits poor physicochetnical and stiffness properties.
Mention will also be made of the document FR 2 918 380, which discloses an
attempt to blend tlie above said copolymer with hvo other polymers, including EPDMs
(which do not have any reactive chemical functional group), but such a composition is
20 flexible and exhibits a Young's modulus of less than 100 MPa (Megapascal), which
excludes this type of formulation from applications where a degree of stiffness is
required. .Fiuthermore, the properties of resistance to aging, in particular to UV
radiation, of such a composition with EPDM are very mediocre. More specifically,
example 2 disclosed in this document would not be resistant to creep as EPDM would
25 not be crossli&ed.
There is thus desired a thermoplastic composition with a grafted copolynler
comprising polyamide blocks on a polyolefin backbone and a polyolefin which is
simultaneously rigid and of ultra high performance in terms of ~nechanical and
thermomechanical qualitylproperty.
The applicant has found, afier various experinlents and handling operations, that,
contrary to the teachings wrell known to a person skilled in the art, a cocontinuous
nanostructured corilposition conlprising predeter~nined amounts of another polyolefin
5 polymer exhibits, depending on the proportion of one with respect to the other,
particularly improved creep properties or an excellent permeability to water, while
retaining a .high Young's rnodulus (stiffness) and ve1-y satisfactory physicochemical
properties (in particular from the viewpoint of aging over time and damage by UV
radiation).
Thus, the present invention relates to a thernloplastic composition consisting of a
blend of polymers, consisting of:
a first polymer consisting of polypropylene, present at between 10% and 90%
by weight of the blend,
a second polynler consisting of a polyolefin backbone containing a residue of
I5 at least one unsaturated monomer (X) and a plurality of polyamide grafts; tile polyamide
grafts are attached to the polyolefin backbone by the residue of the unsaturated
monomer (X) conlprising a fi~llctional group capable of reacting by a condensation
reaction with a polyamide having at least one amine end andlor at least one carb'oxylic
acid end and the residue of the unsaturated monomer (X) is attached to the backbone by
20 grafting or copolymerization; this second polymer being present at between 10% and
90% by weight of the blend; and
a third polynler consisting of a functionalized polyolefin, at between 0.1% and
20% of the blend; and
optionally a functional adjuvant, at bekeen 0% and 30% by weight of the
25 cotnposition; and
in that the conlposition exhibits a Young's lnodulus at 23OC of greater than or
equal to 400 MPa.
Other advantageous characteristics of the invention are specified subsequently:
- advantageously, in the second polyn~er,th e unsaturated monomer (X) is ~naleic
anhydride,
- according to a particularly advantageous aspect of the invention, the above said
grafted polymer, namely the above said second polyn~er,i s nanostructored,
5 - preferably, regarding the second polyn~ert,h e number-average molar mass of the
above said polya~nide grafts of the above said grafted polymer is within the range
extending from 1000 to 10 000 g/t~lolp, referably between 1000 and 5000 g/mol,
- preferably, relating to the second polymer, the polyamide grafts comprise at least
one copolyamide, for example mono NH2 6/11, and/or one mo~~ofi~nctionNaHl 2
10 polyamide 6 andlor one tnot~ofi~nctionNalH 2 polyamide 11,
-the first polymer is chosen fsom a polypropylene homopolymer or a
heterogeneous or randotn polypropylene copolymer,
- advantageously, the above said first polymer is present at between 15% and 40%
by weight of the composition while the second polymer is present at between 60% and
15 85% by weight of the composition,
- advantageously, the above said first polytner is present at between 60% and 90%
by weight of the composition while the second polymer is present at behveen 10% and
40% by weight of the con~position,
- the functional adjuvant consists of one or more plasticizers, adhesion pronloters,
20 UV stabilizers at~d/or UV absorbers, antioxidants, flame retardants, dyes/optical
brighteners, pigments and reinforcing fillers.
The cotnpositio~a~c cording to the invention is divided essentially into two parts
depending on'the proportion of polypropylene with respect to the polyamide-grafted
polyolefin.
' 25 Thus, in the case where the amount of polypropylene is greater than or equal to
60% by weight of the blend, the polyamide-grafted polyolefin contributes to the
composition, ~ithout damaging other properties/qualities, essentially but not
exclusively, (very) good creep properties, in particular at temperatures greater than the
melting point of the polypropylene, whereas, when it is the amount of polyamide-
30 grafted polyolefin which is greater than 50% by weight of the blend, the polypropylene
contributes to the composition, wvitl~out damaging other properties/qualities, essentially
but not exclusively, an excellent impermeability to water while retaining excellent creep
resistance properties.
The invention also relates to a multilayer, such as in particular a back layer of a
photovoltaic niodule or a cable coating (or also a gasoline tank, a fluid transportation
5 tube comp~isinga plurality of adjacent layers), comprising a plurality of adjacent layers,
characterized in that at least one of these layers consists of the composition as defined in
any one of the preceding claims.
It slioould be noted that the conlposition according to the invention is presented in
connection with the application to a photovoltaic module (due in particular to the
10 excellent properties of creep and of impermeability to water and also to the specific
mechanical properties required) but, of course, this composition can be envisaged for
any other application where such a composition can advantageously be used, in
particular in multilayer structures, such as, for example, cables (in particular tubes for
the transportation of air or fluid), footwear (for example skis), films or adhesive
.,. .
15 coatings.
Detailed description of the invention
As regards a first polymer, it consists of polypropylene; it is a polypropylene
homo- or copolymer.
20 Mention may be made, as comonorners, of:
- u-olefifins, aiiva~ltageouslyt hose having 3 to 30 carbon atoms. Examples of such
a-olefins are the same as those cited for the second poly~ner (description given below),
except for replacing propylene by ethylene in the list,
- dienes.
The second polymer can also be a copolymer comprising polypropylene blocks.
Mention may be made, as exanlples of polynler, of:
- polypropylene,
- blends of polypropylerie and of EPDM (etl~ylcncp ropylene diene monomer) or
of EPR (ethylene propylene rubber), well known to a person skilled in the art, which
can additiorially contain from 1% to 20% of polj~ethylene.
As regards tlie polyolefin backbone of tlie second polyamide-grafted polymer, this
5 is a polymer colllprising an a-olefin as monomer.
Preference is given to a-olefins having fro1112 to 30 carbon atoms.
Mention may be made, as a-olefin, of ethylene, propylene, I-butene, I-pcntene,
3-methyl-I-butene, I-hexene, 4-methyl-1-pentene, 3-methyl-I-pentene, I-octene,
1 -decene, 1 -dodecene, I -tetradecene, I-hexadecene, 1 -octadecene, 1 -eicosene,
10 1-docosene, I-tetracosene, 1-hexacosene, 1-octacosene and I-triacontene.
Mention may also be made of cycloolefins having from 3 to 30 carbon atoms,
preferably from 3 to 20 carbon atoms, such as cyclopentene, cycloheptene, norbornene,
5-methyl-2-norbornene, tetracyclododecene and 2-methyl-1,4:5,8-dimethano-
1,2,3,4,4a,5,8,8a-octahydronaphthalene; di- and polyolefins, such as butadiene,
15 isoprene, 4-methyl-1,3-pentadiene, 1,4-pentadiene, 1,5-llexadietie, 1,3-hexadiene, 1,3-
octadiene, 1,4-octadiene, 1,5-octadiene, 1,6-octadiene, ethylidenenorbomene,
vinylnorbon~ene, dicyclopentadicne, 7-methyl-1,6-octadiene, 4-ethylidene-%methyl-
1,7-nonadiene and 5,9-dimethyl-l,4,8-decatriene;v inylaromatic compounds, such as
mono- or polyalkylstyrenes (conlprising styrene, o-methylstyrene, m-methylstyrene,
20 p-methylstyrene, o,p-dimethylstyrene, o-ethylstyrcnc, 111-ethylstyrene and
p-ethylstyrene) and derivatives co~llprising functional groups, such as methoxystyrene,
ethoxystprene, vinylbenzoic acid, methyl vinylbenzoate, vinglbenzyl acetate,
hydroxystyrene, o-chlorostyrene, p-chlorostyrene, divinylbenzene, 3-phenylpropene,
4-phenylpropene, a-methylstyrc~~cv,i nyl chloride, 1,2-difluoroethylene, 1,2-dichloro-
25 ethylene, tetrafluoroethylene and 3,3,3-trifluoro-I-propetie.
I11 tlie context of the present invention, the tenn of a-olefin also comprises styrcnc.
Preferelice is given to propylene and very especially to ethylene as a-olefin.
This polyolefin can be a honlopolymer xvhen just one a-olefin is polymerized in
the polymer chain. Mention may be made, as examples, of polyethylene (PE) or
polypropylene (PP).
This polyolefin can also be a copoly~ner when at least two comonomers are
5 copolyn~erized in the polymer chain, one of the two comonomers, referred to as "first
comonomer", being an a-olefin and the other comonomer, referred to as "second
comononler", being a nlonolner capable of poly~nerizingw ith the first comonomer.
Mention tnay be made, as second comonomer, of:
one of the a-olefins already mentioned, this being different from the first uolefin
comonomer,
dienes, such as, for example, 19-hexadiene, ethylidenenorbornene or butadiene,
esters of ut~sah~ratecda rboxylic acids, such as, for example, alkyl acrylates or
alkyl ~nethacr~.latecso, mbined under the term alkyl (n1eth)acrylates. The alkyl
chains of these (meth)acrylates can have up to 30 carbon atoms. Mention may be
made, as alkyl chains, of methyl, ethyl, propyl, n-butyl, sec-butyl, isobutyl, testbotyl,
pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, undecyl, dodecyl,
tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl,
eicosyl, hencosyl, docosyl, tricosyl, tetracospl, pentacosyl, hexacosyl,
heptacosyl, octacosyl or nonacosyl. Preference is given to metllyl, ethyl and
20 butyl (meth)acrylates as esters of unsaturated carboxylic acids,
vinyl esters of carboxylic acids. Mention may be made, as examples of vinyl
esters of carboxylic acids, of vinyl acetate, vinyl versatate, vinyl propionate,
vinyl butyrate or vinyl maleate. Preference is give11 to vinyl acetate as vinyl ester
of carboxylic acid.
Advantageously, the polyolefit~ backbone comprises at least 50 mol% of the first
comonomer; its density can advantageously be between 0.91 and 0.96.
The preferred polyolefi~l backbones consist of an etllylene/alkyl (nletl1)acrylate
copolymer. By using this polyolefin backbone, an excellent resistance to aging due to
light and to tenlpcrature is obtained.
It would not be departing from the scope of the itivention if different "second
comonomners" were copolymerized in the polyolefin backbone.
According to the present invention, the polj~olefinb ackbone comprises at least one
residue of an unsaturated monomer (X) wvhich can react with an acid andlor anline
5 functional group of the polyamide graft by a condensation reaction. According to the
definition of the invention, the unsatnrated monomer (X) is not a "second comonotiier".
Mention may be made, as unsaturated nionomer (X) included on the polyolefin
backbone, of:
unsaturated epoxides. These include, for example, aliphatic glycidyl esters and
ethers, such as ally1 glycidyl ether, vinyl glycidyl ether, glycidyl maleate,
glycidyl itaconate, glycidyl acrylate and glycidpl methacrylate. These are also,
for example, alicyclic glycidyl esters and ethers, such as 2-cyclohexen-I-yl
glycidyl ether, diglycidyl cyclohcxe~~e-4,5-dicarboxylatge,ly cidyl cyclohexene-
+carboxylate, glycidyl 5-norbornenc-2-methyl-2-carboxylate and diglycidyl
endo-cis-bicyclo(2,2,1)hept-5-cne-2,3-dicarboxylate. Use is preferably made of
glycidyl methacrylate as unsaturated epoxide,
unsaturated carboxylic acids and their salts, for example acrylic acid or
methacrylic acid and the salts of these acids,
carboxylic acid anhydrides. They can be chosen, for example, from nlaleic
20 anhydride, itaconic anhydride, citraconic anhydride, allylsuccinic a~d~ydride,
cyclohex-4-ene-l,2-dicarboxylic anhydride, 4-metl1~~lenccyclohex-4-ene-l,2-
diaarboxylic anhydride, bic~~cle(2,2,l)hept-5-ene-2,3-dicarboxyliacn hydride and
x-1i1ethylbicyclo(2,2,1)hept-5-e11e-2,2-dicarboxylica nhydride. It is preferable to
use maleic anhydride as carboxylic acid anhydride.
25 The unsaturated monomer (X) is preferably an unsaturated carboxylic acid
anhydride.
According to an advantageous version of the invention, the preferred number of
unsaturated monomers (X) attached on average to the polyolefin backbone is greater
than or equal to 1.3 and/or preferably less than or equal to 20.
Thus, if (X) is nialeic anhydride and tlie ~iunlber-average molar Illass of the
polyolefin is 15 000 g/niol, it has been found that this correspolids to a proportion of
anhydride of at least 0.8% by mass of tlie wvhole of the polyolefin backbone and of at
~iiost6 .5%. These values, associated with the Inass of the polyamide grafts, determine
5 the proportion of tlie polyamide and of backbone in the polyaniide-grafted polymer.
The polyolefin backbone comprising the residue of the unsaturated nioliomer (X)
is obtained by polymerization of the monomers (first conlonomer, optional second
comonomer and optionally unsaturated monotiler (X)). This poly~nerization cat1 be
carried out by a high pressure radical process or a solution process, in an autoclave or
10 tubular reactor, these processes and reactors being well knowvn to a person skilled in the
art. When the unsaturated lnonolner (X) is not copolymerized in the polyolefin
backbone, it is grafted to the polyolefin backbone. The grafting is also an operation
known per se. The composition would be in accordance with the invention if several
different functional monomers (X) were copolymerized andlor grafted to the polyolefin
15 backbone. .. .
According to the types and ratios of monomers, the polyolefin backbone may be
semicrystalline or amorphous. In the case of amorphous polyolefins, only the glass
transition temnperatt~rei s observed \vhereas, in the case of semic~ystallinep olyolefins, a
glass transition temperature a~ida melting point (which will necessarily be greater) are
20 observed. It will be sufficient for a person skilled in the art to select the ratios of
monomers and tlie molecular weights of the polyolefin backbone in order to be able to
easily obtain the desired values of glass transition teniperature, optionally of nlelting
point and also of viscosity of tlie polyolefin backbone.
Preferably, the polyolefin has a melt flow index (MFI) of between 0.5 and
25 400 gIl0 mi11 (190°C, 2.16 kg, ASTM D 1238).
Tile polyamide grafts can either be hotnopolyamides or copolyatnides.
Targeted in particular by the expression "polyamide grafts" are the aliphatic
homopolyanlides which result from tlie polycondensation:
of a lactam,
or of an aliphatic a,o-atninocarboxylic acid,
or of an aliphatic diamine and of an aliphatic diacid.
As examples of lactams, mention may be made of caprolactam, oenantholactatn
and lauryllactatn.
As exanlples of aliphatic a,w-aminocarboxylic acid, nlention may be made of
anlinocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid and 12-
amitlododecanoic acid.
As examples of qliphatic diamine, mention may be made of
hexamethylenedianline, dodecamethylenedian~inaen d trimetl~ylhexatnethylenediamit~e.
10 As examples of aliphatic diacid, mention may be made, of adipic acid, azelaic
acid, suberic acid, sebacic acid and dodecanedicarboxylic acid.
Among aliphatic homopolyamides, mention may be made, by way of example and
without implied limitation, of the following polyamides: polycaprolactam (PA6);
polyundecanatnide (PA11 , sold by Arkema under the ~ i l s a bnr~an d); polylauryllactatll
15 (PA12, also sold by Arkenla under the ~ i l s abnra~n d);p olybutylene adipatnide (PA4.6);
polyllexamethylene adipamide (PA6.6); polyhexamethylene azelamide (PA6.9);
polyhexanlethylene sebacamide (PA6.10); polyhexamethylene dodecanamide (PA6. 12);
polydecamethylene dodecanamide (PA10.12); polydecamethylene sebacamide
(PA1O.lO) and polydodecamethylene dodecanatnide (PA12.12).
20 Also -targeted-.by,t he expressiotl "semicrystalline polyatnides" are cycloaliphatic
hotnopolyatnides.
Mention may in particular be made of the cycloaliphatic homopolyarnides which
result from the condensation of a cycloaliphatic diamine and of an aliphatic diacid.
Mention may be made, as example of cycloaliphatic diamine, of 4,4'-
25 methylenebis(cyclohexylamine), also kno~vn as bis(para-atninocpclo11exyl)methane or
PACM, or 2,2'-dimethyl-4,4'-t11eth)~lenebis(cyclohexylatine) also known as bis(3-
methyl-4-atninocyclohexyl)methane or BMACM.
Thus, n~ention may be inade, anlong cycloaliphatic ho~~lopolyan~ideosf , the
polyamides PACM.12, resulting from the condensation of PACM with the CI2 diacid,
and BMACM.10 and BMACM.12, resulting from the condetisation of BMACM \vitIi
the Clo and Clz aliphatic diacids respectively.
5 Also targeted by the expression "polyamide grafts" are the semi-aromatic
holilopolyamides which result from the condensation:
of an aliphatic diamine and of an aromatic diacid, such as terephthalic acid (T)
and isophthalic acid (I). The polyamides obtained are then con~monlyk nown as
"polj~pl~tlialamideos"r PPAs;
of an aromatic dialnine, such as xylylenediamine and more pa~ticularly metaxylylenediamine
(MXD), and of an aliphatic diacid.
Thus and without implied limitation, mention may be made of the polyamide 6.T,
6.1, MXD.6 or MXD.10.
The polyamide pafts brought into play in the composition according to the
15 invention can also be copolyamides. The latter result from the polycondensation of at
least two of tlie groups of monomers set out above for the production of
homopolyamides. The term "monon~er"i n the present description of the copolyamides
should be taken with the meaning of "repeat unit". This is because the case where a
repeat unit of the PA consists of the combination of a diacid with a diamine is
20 exceptional. It is considered that it is the combination of a diamine and of a diacid, that
is to say the diamineldiacid pair (in an equimolar amount), which correspo~ids to the . ,
monomer. This is explained by the fact that, individually, tlie diacid or the diamine is
only a structural unit, which is not sufficient in itself alone to poly~llerize to give a
polyamide.
25 Thus, the copolyamides cover in particular the condensation products:
of at least two lactams,
of at least two aliphatic alpha, omega-aminocarboxylic acids,
of at least one lactam and of at least one aliphatic alpha, omega-aminocarboxylic
acid,
of at least t\vo dianlines and of at least two diacids,
of at least one lactatn with at least one diamine and at least one diacid,
of at least one aliphatic alpha, omega-aminocarboxylic acid with at least one
diamine and at least one diacid,
5 it being possible for the diamine(s) and the diacid(s) to be, independently of one
another, aliphatic, cyclo~liphatico r aromatic.
According to the types and ratios of monomers, the copolyan~ides can be
semicrystalline or amorphous. In the case of the amorphous copolyarnides, only the
glass transition temperature is observed whereas, in the case of the semicrystalline
10 copolyamides, a glass transition temperature and a melting point (which will necessarily
be greater) are observed.
Atnong the atnorpl~ous copolyan~ides wluch can be used in the context of the
invention, mention may be made, for example, of the copolyatnides comprising
se~niaromatic~monomers.
15 Among the copolyamides, use may also be made of se~nicrystallinec opolyalnides
and in particular those of PA611 1, PA6112 and PA611 1112 type.
The degree of polymerization can vary within wide proportions; according to its
value, it is a polyamide or a polyamide oligomer.
Advantageously, the polyamide grafts are monofunctional.
In order for the polyamide graft to have a monoanline ending, it is sufficient to use
a chain-limiting agent of forn~ula:
R2 wherein:
RI is hydrogen or a linear or branched alkyl group cotnprising up to 20 carbon
atoms,
RZ is a linear or branched alkyl or alkenyl group havillg up to 20 carbon atoms, a
saturated or unsaturated cycloalipl~atic radical, an aromatic radical or a
combination of the above. The chain-limiting agent can, for exanlple, be
laur-j~lamitleo r oleylatnine.
5 In order for the polyamide graft to have a nlonocarboxylic acid ending, it is
sufficient to use a chain-limiting agent of fornlula R'I-COOH or R'I-CO-O-CO-R'2 or a
dicarboxylic acid.
R'] and R'z are linear or branched alkyl groups co~nprisingu p to 20 carbon atoms.
Advantageously, the polyamide graft has an end cot~~prisinga n amine
10 functionality. The preferred monofunctional polymerization chain-limiting agents are
lau~ylaminea nd oleylamine.
The polyamide grafts have a molar mass of between 1000 and 10 000 g/tnol,
preferably of between 1000 and 5000 g/mol.
The polycondensation can be used to perform the grafting of the polyamide grafts
15 and is carried out according to the processes normally known, for example at a
temperature generally between 200 and 300°C, under vacuutn or under an inert
atmosphere, with stirring of the reaction mixture. The mean chain length of the graft is
determined by the initial molar ratio of the polycondensable nlonolller or the lactam to
the ~nonofi~nctionpaoll ymerization chain-limiting agent. For the calculation of the mean
20 chain length, one rnolecule of chain-limiting agent is nornlally allowed for one graft
chain.
It will be sufficient for a person skilled in the art to select the types and ratios of
. monotners and also to choose the molar masses of the polyarnide grafts in order to be
able to easily obtain the desired values of glass transition temperature, optionally of
25 melting point and also of viscosity of the polyamide graft.
The co~ldensatiotlr eaction of the polyamide graft with the polyolefin backbone
conlprising the residue of X (or the fur~ctionalized nlollotller for the second grafted
copolyn~er,n anlely the elastomer copolymer) is carried out by reaction of an ami~leo r
acid f~~tictionaglr oup of the polyatuide graft with the X residue. Advantageously,
monoatnine polyatnide grafis are used and amide or in~ideb onds are created by reacting
the atnine fimctional group with a functional group of the X residt~e.
This condensation is preferably carried out in the molten state. Conventional
5 kneading and/or ext~z~siotne ch~iqnesc an be used to manufacture the composition
according to the invention. The components of the co~npositioar~e~ th us blended to form
a compounded product w l d ~ca n optionally be granulated at the die outlet.
Advantageously, coupling agents are added during the compounding.
In order to obtain a nanostructured composition, the polyamide graft and the
10 backbone can thos be blended in an extruder, at a temperature generally of between 200
and 30OoC. The mean residence time of the molten material in the extruder can be
between 5 seconds and 5 minutes and preferably between 20 seconds and 1 minute. The
yield of this condensation reaction is evaluated by selective extraction of the free
polyamide grafts, that is to say those which have not reacted to form the polyamide-
15 grafted polymer.
The preparation of polyamide grafts cotnprising an atnine end and also their
addition to a polyolefin backbone comprising the residue of (X) or of a functionalized
nlonomer (second copolyn~er)is described in the patents US 3 976 720, US 3 963 799,
US 5 342 886 and FR 2 291 225. The polyamide-grafted polymer of the present
20 invention advantageously exhibits a nanostructured arrangement.
As regards the third optional polymer, it consists of a functionalized polyolefin
capable of acting as agent for compatibilization between the polypropylene and the
polyamide-grafted polyolefin. The description of this grafted pol~~olefiins similar to
that of the polyolefin backbone used in the pplyamide-grafted polyamide.
The expression "fi~nctionalp olyolefin" is understood to n~eaai ~po lyolefin which
includes, in its chain, one or more reactive chemical fi~nctional groups, such as
conventionally epoxides, tnaleic acids and maleic anhydrides. This expression is 117ell
known to a person skilled in the art \vl~o is capable of identifying the polyolefit~s
belonging or not belonging to this group. An EPDM does not correspond to this
definition.
Advantageously, the functionalized polyolefin is a lnaleic anhydride-grafted
polypropylene.
As regards the optional functional adjuvant, it call be present in the co~npositiona t
a ~naxitnnm content of 30% by weight of the conlposition and will be chosen solely
from the compounds mentioned below or a mixture of these compounds.
Plasticizers can be added to the colnposition according to the invention in order to
facilitate the processing and to improve the productivity of the process for
10 manufacturing the colnposition and the structures. Mention will be made, as examples,
of paraffinic, aro~natico r t~aphthale~limci neral oils, which also make it possible to
improve the adhesiveness of the composition according to the invention. Mention may
also be made, as plasticizer, of phthalates, azelates, adipates or tricresyl phosphate.
In the same way, adhesion promoters, although not necessary, can
15 advantageously be added in order to improve the adhesiveness of the composition when
the adhesiveness has to be particularly high. The adhesion promoter is a nonpolymeric
ingredient; it can be organic, crystallitle, mineral and more preferably semi-mineral
semi-organic. Mention may be made, anlong these, of organic silanes or titanates, such
as, for example, monoalkyl titanates, tricl~lorosilanes and trialkoxysilanes,
20 trialcooxysilanes. It will also be possible to provide for these adhesion promoters to be
directly grafted to the first or the second copolymer by a technique well known to a
person skilled in the art, for example via reactive extrusion.
As UV radiation is capable of resulting in a slight yellowing of the thermoplastic
comnpositions, UV stabilizers and UV absorbers (these cotnpounds being generally
25 called UV inhibitors), such as beuzotriazole, benzophenone and the other hitldered
amines, can be added in some applications \vhere such a phenomenon has to be avoided.
These compounds can, for example, be based on benzopheuone or benzotriazole. They
can be added in arnounts of less than 10% by weight of the total weight of the
co~npositiona nd preferably from 0.1% to 5%.
It will also be possible to add antioxidants in order to limit tlie yellowing during
the manufacture of the composition, such as phosphorus-comnprisi~lg compounds
bhosphonites andlor phosphites) and hindered phenolic con~poundsT. hese antioxidants
can be added in amounts of less than 10% by weight of tlie total weight of the
5 cotiiposition and preferably from 0.05% to 5%.
In the same way, in some applications, flame-retardant agents can also be added
to the composition according to the invention. These agents may or may not be
halogenated. Mention may be made, among halogenated agents, of brominated
products. Use may also be made, as non-halogenated agent, of phosphorus-based
10 additives, such as an~monium polypliosphate, aluminum phosphinates and
phosphonates, melamine cyanurate, pentaerythsitol, zeolites and the mixtures of these
agents. The composition can comprise these agents in proportions ranging from 3% to
30%, with respect to the total weight of the composition. It will also be possible to add
coloring or brightening compounds.
Pigments, such as, for example, titanium dioxide or zinc oxide, can also be added
to the composition in proportions generally rat~gitigf rom 5% to 15%, with respect to the
total weight of the composition.
It is also possible to add reinforcing fillers, such as talc, glass fibers, carbon fibers,
montmorillonites, carbon tlanotubes or carbon black, to the composition in proportions
20 generally ranging from 2.5% to 30%, with respect to the total weight of the
composition.
Preparation of the composition according to the invention:
As was tnentioned above, the technique for grafting the polyaniide grafts to the
25 polyolefin backbone in order to obtain the polyatnide-grafted polyolefin according to
the invention is well known to a person skilled in the art, in palticular from the
abovementioned docun~entFs R 2912150, FR 2918150 or EP 21966489.
The polypropylene, the functional adjuvant (abovenientioncd additive) and also
the functionalized polpolefin are f~~lklnyo wn to a person skilled in the art, and also the
preparations thereof. The blending of these compounds is entirely conventional and
does not require any specific explanation for a person skilled in the art.
5 It is thus not departing fxon the scope of the invention if crosslinking agents are
added. Mention riiap be made, as examples, of organic peroxides or isocyauates. This
crosslinking can also be cassied out by known irradiation teclxiiques. This crosslinking
can be carried out by one of the many methods known to a person skilled it1 the art, in
pa~ticular by the use of thermally activated initiators, for example peroxide and azo
10 comnponnds, or photoinitiators, such as benzoplietione, by radiation techniques
comprising light rays, UV rays, electron beams and X rays, of silanes carrying reactive
functional groups, such as an aminosilane, an epoxysilane or a vinylsilane, such as, for
example, vinyltriethoxysilane or vinyltrimethoxysilane, and wet-route crosslinking. The
handbook entitled "Handbook of Polymer Foams and Technology", supra, on pages 198
15 to 204, provides additional teaching to wvhicli a person skilled in the art tnay refer.
Materials emplo\,ed to form tile test formulations:
~otader@42 10: terpolymer of ethylene, of ethyl acrylate (6.5% by weight) and of
maleic anhydride (3.6% by weight) produced by Askema, having an MF1 (190°C under
20 2.16 kg, measured according to IS0 1 133) of 9 g/lO min.
PPH 4060: polypropylene honiopolymer sold by Total, having an MFI (230°C
under 2.16 kg, measured according to IS0 1133) of 3 d l 0 min.
PPC 3650: Iieteropliasic polypropylene copolyn~er sold by Total, having an MFI
(230°C under 2.16 kg, measured according to IS0 1133) of 1.3 g/10 min.
Orevaca CA100: ~naleic anhj~dride-functionalized polypropylene sold by
Arkenia, having an MFI (190°C under 0.325 kg, measured according to IS0 1133) of
10 d l 0 min.
Talc HAR T77: sold by Imerys.
Glass fibers CSX 35-451 WD: sold by Nittobo.
Titanium dioxide Kronos 2073: sold by Kronos.
TPV PP/crossli~tked EPDM: ther~lloplastic elastomer consisting of 35% by
5 weight of a poljyropylene with an MFI (at 230°C under 2.16 kg) of 2 gl10 min and of
65% by weight of a crosslinked EPDM with a system based on phenolic resin and
comprising 150 phr of aliphatic oil. The exact composition of tlie EPDM is described in
the composition of example 1 of the patent application FR 2 918 380.
HDPE M40053S: high-density polyetliykne sold by SABIC cotlipany, having an
10 MFI (190°C under 2.16 kg, measured according to IS0 1133) of 4.0 g/l0 min.
Polyamide prepolymer: mono NH2 polyamide-6 prepoljrmer with an Mn of
2500g/nlol, produced by the applicant. This prepolymer was synthesized by
polycolidensation starting from lactam-6. Laurylamitie is used as chain-limiting agent so
as to have a single primary amine functionality at the chain end. The number-average
15 molar mass of the prepolymer is 2500 g/mol.
Production of the test formulations and films:
The fornlulations were prepared by "compounditig" using a corotating twin-screw
extiuder of ~ e i s t r i t zty~p e (LlD=35), tlie barrel elements of which are heated according
20 to a flat profile at 240°C; the rotational speed is 300 rpm (roounds per minute) with a
throughput of 15 kg111 (kilograms per hour).
350 pm (micron~eterm) onolayer films of the compositions were produced by cast
film extrusion on a small laboratory extrusion line. The extruder is a counter-rotating
twin-screw of Ijaake 1 type equipped with a flat die with a width of 10 ctn (centimeters)
25 and with an opening of 0.5 nun (millimeter). The barrel elelnents are heated according
to a flat profile at 230°C, tlie rotational speed of the screws being 60 rpm (rounds per
minute).

Tests carried out on the films:
Thee types of tests were mainly carried out on conlpositions 1 to 16 in order to
test the resolution possibly of the abovementioned technical problems, but it should be
noted that the compositions according to the invention furthennore exhibit other
20 particularly advantageous properties.
These three tests consist, on the one hand, in measuring the Young's modulus at
23"C, expressed in MegaPascals (MPa), in nieasuring the per~neabilitp to water at
ambient temperature and, finally, in determining the creep properties.
Test of the "Young's modulus":
25 In order to measure the Young's modulus of the test specilnens of compositions, a
tensile test is carried out according to the standard NF EN IS0 527.
Test of impel-meability to water:
This test is carried out with water vapor according to the standard IS0 1663 of
1999 (ex NF T 56-105), equivalent to the standard ASTM E96-80. This mctl~odg ives a
relative humidity content in the test specimen under consideration.
Creep test:
The creep strength is determined from test specimens of IFC type cut out fkom the
films. A weight is applied to one end of the test specimen corresponding to a stress of
2 bar, i.e. 0.2 MPa. The stress is applied for 15 millutes at a tenlperature of 150°C,
160°C or 170°C, according to the composition. The residual strain is measured after
returning to ambient temperature.
10
The results for the three tests carried out on each of the compositions clearly
show, on the one hand, the technical advantages of the composition according to the
invention, although the latter are not in any way foreseeable, and, on the other hand, the
Creep (strain in %) Perineability to \trater
5 preferred ranges (% by ~veightf)o r this composition.
20 (comparative) 510
10
45 100 70
CLAIMS
1. A thern~oplasticc oni~positionc onsisting of a blend of polyn~ers,c onsisting
of:
5 a first polytner consisting of polypropylene, present at between 10% and
90% by weight of the blend,
-as econd polyn~erc onsisting of a polyolefin backbone containillg a residue
of at least one unsaturated monomer (X) and a plurality of polyamide grafts; the
polyamide grafts are attached to the polyolefin backbone by the residue of tlie
10 unsaturated monomer (X) comprising a functiorial group capable of reacting by a
condensation reaction with a polyamide having at least one a~ninee nd andlor at least
one carboxylic acid end and the residue of the unsaturated monomer (X) is attached to
the backbone by grafting or copolymerization; this second polymer being present at
between 10% and 90% by weight of the blend; and
15 a third poly~nerc onsisting of a functionalized polyolefin, at between 0.1%
and 20% of tlie blend; and
optionally a functional adjuvant, at between 0% and 30% by weight of the
composition; and
in that the cotnposition exhibits a Young's modulus at 23°C of greater than
20 or equal to 400 MPa.
2. The composition as claimed in claim 1, characterized in that, in the second
polymer, the unsaturated nlononler (X) is maleic a1111ydride.
25 3. The conlposition as claimed in either one of the preceding claims,
characterized in that the above said grafted polymer, namely the above said second
polymer, is na~iostructured.
4. The composition as claimed in any one of the preceding claims,
30 characterized in that, regarding the second poly~ner,t he number-average molar mass of
the above said polyamide grafts of the above said grafted polynler is within the range
extending from 1000 to 10 000 glnlol, preferably between 1000 and 5000 glmol.
5. The composition as claimed in any one of the preceding claims,
characterized in that, regarding the second polymer, the polyamide grafts conrprise at
least one copolyamide, for example mono NH2 611 1, and/or one monofunctional NH2
5 polyamide 6 andlor one monofunctional NH2 polyamide 11.
6. The composition as claimed in any one of the preceding claims,
characterized in that the first polymer is chosen from a polypropylene homopolymer or
a heterogeneous or random polypropylene copolymer.
10
7. The composition as claimed in any one of the preceding claims,
characterized in that the above said first polymer is present at between 15% and 40% by
weight of the composition while the sec&d polymer is present ,at between 60% and
85% by weight of the composition. .t
15
-8:.=T,he-compositiona s claimed in any one of claims 1 to 5, characterized in
that the above said first polymer is present at between 60% and 90% by weight of the
composition while the second poly&er is present at between 10% and 40% by weight of
the composition.
20
9. The composition as claimed' in any one of the preceding claims,
characterized in that the functional adjuvant consists of one or more plasticizers,
adhesion promoters, UV stabilizers andlor UV absorbers, antioxidants, flame retardants,
dyes/brighteners, pigments and reinforcing fillers.
25
10. A multilayer structure, such as in particular a back layer of a photovoltaic
module or a cable coating, comprising a plurality of adjacent layers, characterized in
that at least one of these layers consists of the composition as defined in any one of the
preceding claims.