ADHESIVE SEALING COMPOSITION
Field of the invention
Thc present invention relates to an adhesive or binder composition based on a
5 copolymer of ethylene and at1 alkyl acrylate \vhich can be used in an extrusion-coating
process with application to a support or in an extrusion-lamitiation process for
adl~esively bonding together several suppo1.t~ \vlvhich may or may not be differcnt in
nature, it being possible for one of these supports to be a thennoplastic or a metal, such
as, in pat-ticular, aluminum.
10 The inventioti thus also relates to a sealing filtn consisting of this adhesive
composition or to a nn~ltilayers tructure including the support and said sealing film.
State of tlie art
Subsequently, "sealing" is understood to mean the union of two surfaces of a fill11
15 or of two layers, whatever their nature.
There exists a great variety of packagings for foodstuffs, such as, for example,
peelable-opening packagitlgs. These peelable-opening packagir~gs can be produced by
sealing a cover to a container, it being possible for the containers to be composed of
different tnaterials and in particular different polytners (poljlstyrene, polyether
20 terephthalate, polyethylene, polypropylene, and the like). The covers have to have a
sufficiently strong adhesion to the container to prevent the unexpected opening of the
packaging but also sufficiently weak to be peelable.
The covers are nlultilayer structures and generally consist of several layers,
including at least the adhesive sealing (peelable) layer and the "tnechanical" layer,
25 cot~ventionallym ade of polymer, paper or aluminnm. These covers car1 be produced by
extrusion-coating or by thermal la~ninationo f a filtn obtained in blown film extrusion.
The production of this cover is subject to several processability problems:
- the adhesive bonding to the chill roll during production by extl-usion-coating,
- the problem of filtll opening during the manufacture of tlie film by fill11
30 blowing,
- the blocking and the slipping of the film produced by fihn blowing (also
obtained for example, by a flat die, extmsion-coating or lamination) during the
ruat~ipulationo f the reels before and dduring thernlal lamination.
The blocking and the slipping are problcms specific to film l~roduction which arc
well known to a person skilled in tlie art. Thus, the use of slip agcnts in films nlakes it
possible to reduce the Coefficient of Friction (COF) while retaining the optical
properties of gloss, transparency and clarity, whereas the usc of antiblock agents makes
5 it possible to create, at the ssuface of the film, nodules that facilitate the sliding of the
filnl on all types of supports.
In order to overcome tlicse processabilit~p~ro blems, it is known to a pcrson skilled
in the a1-t that it is necessary to add, to the adhesive sealing layer, processing additives,
that is to say slip and antiblock agents.
10 The formulation of the adhesive sealing (peelable) layer depends on the container
on which it is desired to seal the cover. It is known to a person skilled in tlie art that the
addition of tackifying resin to polyethylene (PE), polypropylene (PP) or a copolynier of
ethylene and vinylacetate (EVA) rnakes it possible to obtain a sealing resin formulation,
the sealing performance of which is excellent on nlany types of support. The doc~nnents
15 US 7 495 048 or EP 2 166 034 illustrate this state of knowledge.
The docun~enUt S 7 495 048 describes a sealing resin cornposition comprising:
- from 75% to 99% by weight of a copolynier of etli~~lenaned of 411 unsaturated
ester, preferably an EVA exhibiting a vinyl acetate content of greater than 5%,
- from 5% to 20% by \veiglit of a tackifying resin having a high softening point.
20 These co~npositionsm ake it possible to lower tlie minilnun1 sealing temperature.
The contents of tackifying resin preferably used are between 5% and 20%. In
point of fact, with such contents of tackifying resins, two types of probletns occur:
- a problem of thennal stability at the processing temperatures related to the
presence of the tackifying resin,
25 - a loss of transparelicy related to the high additivation (addition of processing
additives, namely antiblock agents and slip agents) necessary to overconle tlie
processing problems. This is because the addition of tackifying resins renders the
peelable sealing resin formnlation very tacky, which results in the probletns of adhesive
bonding to the chill roll in extrusion-coating or of film opening in fill11 blo~~inAg.S
30 stated above, it is ktiown to a person skilled in the art that, with the aim of overconling
these problenis, a high additivation (processing additives) is necessaiy but this
additivation is harnifi~tlo the transparency of the conlposition.
Thus, there is ct~rrently a search to find an adhesive sealing them~oplastic
cotnposition not exhibiting the disadvantages targctcd above \vhile retaining the good
properties obtained with thc adhesive compositions of the prior art.
Brief description of the invention
Surprisingly, the applicant has discovered that the combination of a specific type
of copolymer with at least one tackifying resin and also processing additives in a
specific ratio, in particular for antiblock agents and slip agents, makes it possible to
obtain an adhesive sealing (peelable) cornposition exhibiting all tlie properties of the
10 adhesive co~npositionsa ccording to the prior art while overcon~ingt he disadvantages,
essetitially in terms of processability and of transparency of the con~position, of these
compositions.
This discovery runs counter to what might be sensed by a person skilled in the art
as a person skilled in the art would not envisage decreasing the content of tackifying
15 resin as he knows that. this decrease would undoubtedly be harmfill to the sealing
properties of the composition. In point of fact, tlie adhesive conlposition according to
the invention, containing less than 5% (or optionally 5% iticlusive) of tackifying resin,
makes it possible to retain good sealing propel-ties while maintaining the good thermal
stability and optical properties desired.
20 The present invention thus relates to an adhesivc composition, usable in an
extrusion-coating process for application to a support or in an extrusion-latnitiation
process for adhesively bonding together several supports which are or are not different
in nature, within a broad ternperatuse range, comprising:
- fiom 91% to 98% by weight of said conlposition of a copolymer of etllylene and
25 of alkyl acrylate;
- at least one tackifping resin;
- processing additives comprising at least one antiblock agent and one slip agent,
characterized in that the tackifying resin represents between 1.5% and 5% of the
weight of the con~position and said additives represent behveen 0.5% and 3.5% of the
30 weight of the compositioti and in that the antiblock agent represents, in the processing
additives, at least 60% by weight of said additives.
Other characteristics or embodinlents of the itmention are presented below:
-advantageously, the tackifying resin represents between 3% and 4% of the
weight ofthe composition;
-preferably, tlie acrylate content in tlie copoly~ner of ethylcnc and of alkyl
acrylate is between 15% and 30% of the xveight of said copolytner;
5 -preferably, the copolymer of ethylene and of alkyl acrylate consists of a
copolyn~ero f etliylene and of tnethyl acrylate;
-according to a specific feature of the inventioti, the MFI of tlie abovesaid
copolymer is between 5 g/lO min aud 15 g/lO ~niu(a t 190°C, 2.13 kg);
- advantageously, the processing additives are present at between 1.5% and 2.5%
10 by weight of said comnposition;
- preferably, the processing additives consist solely of at least one antiblock agent
and at least one slip agent, the antiblock agent representing at least 70% by weight of
said additives;
-according to one etnbodiment, the con~position according to the invention
15 cotisists solely of the abovesaid copolymer, the abovesaid tackifyit~g resin and said
processing additives.
The invention also relates to a sealing film cotisisting of a composition as
presented above, characterized in that its thickness is between 10 and 20 microtneters
(11m).
20 The present invention also relates to a tnultilayer structure comprising at least two
films, one of which is the aboven~entioned sealing film, characterized in that the sccond
film is chosen fiotn aloniinum, paper or board, cellophane, films based on polyethylene,
polypropylene, polyamide, polyester, polyvinyl chloride (PVC), polyvinylidene chloride
(PVDC) or polyacrylonitrile (PAN) resins, these films beitig or not beitig oriented,
25 being or not being metallized and being or not being treated physically or chemically,
and filtns coated with a thin inorganic barrier layer, such as polyester (PET SiOx or
AlOx).
Description of the appended fipures
30 The description \vhicIi will follow is given solely by way of illustration and
without li~nitatiow~ii th reference to the appended figures, in \vliich:
- figures la to le illustrate one of the tests and thc measurements of this test
consisting of the adhesive bonding of the test specin~ensto a chill roll.
Detailed description ofthe invention
As rcgards thc copolj~n~oefr ethylene and of acrylate, an alkyl(meth)acrylate may
be concerned, it being possible for the alkyl group to have up to 24 carbon ato~ns.
Mention may be tnade, as nonlin~itinge xamples for this copolyn~cro f ethylene and of
5 acrylate, of CI-Cs (of 1 to 8 carbon atoms) acrylates or alkyl acrylates, such as CI-Cs
alkyl(tneth)acrylate, n-butyl or isobutylacrylates and methyl ethyl methacrylate.
It has been noted, by the applicant, that even better results are obtained, in the
context of the objectives of the present patent application, with copolymers in \vhic11 the
content of alkyl acrylate represents between 15% and 30% of the weight of the
10 copolyn~er.
It should also be noted that the conlpositions below all exhibit h4FI (Melt Flo\v
Index) values at 12 g110 min (at 190°C, 2.13 kg) but the applicant has furthermore
denlonstrated that the MFI of the chosen copolyt~~hears to lie between 5 $10 min and
15 $10 min (at 190°C, 2.13 kg) in order for the objectives of the invention to be able to
15 be achieved.
As regards the tackifying resin, it concerns polymers exhibiting a ~mmber-average
n~oleculawr eight of less than or equal to 10 000 g.mol-' (gram per 11101) chosen from the
thee following types of resins (polyn~ers):
- hydrogenated and dirnerized acid or ester type rosin resin;
20 -aliphatic, hydrogenated aliphatic, aromatic, hydrogenated aromatic,
aliphaticlaro~natic, hydrogenated alipl~aticlaro~~~actiycc,l oaliphatic, hydrogenated
cycloaliphatic, cycloalipl~aticlarnmatica nd hydrogenated cycloaliphatic/aron~atict ype
hydrocarbon resins;
- polyterpene and terpene-phenol type terpene resin.
25 As regards the processing additives, in the context of the present invention, they
are specifically and solely of two natures, nan~elya ntiblock agents and slip agents.
Antiblock agent is understood to mean the fact that such an additive nlakes it
possible to reduce the adhesion between two polp~ner surfaces. The antiblock agents
according to the present can consist of components of organic type, suc11 as
30 bel~enamide, steararnide, ethylenebis-oleamide or ethylene bis-stearamide, or
conlpoaents of inorganic type, such as silica, talc, calciu~nc arbonate, kaolin or clay.
Slip agent is understood to mean the fact that such an additive makes it possible to
reduce the coefficient of friction of the product to which it is added. The antiblock
agents according to the present can consist of erucarnidc, oleamide, ole)rlpaImitatnide
and stearylerucatnide.
It should be noted that, in the continuation, the i~lve~ltiois~ ill lustrated with just
one type of tackifjring resin, tla~nelyR 6galite R1 125, but the applica~tth as shown that
5 the invention wot~lda lso fuilctio~wl ith oue of the abovementioned tackifying resins.
The adhesive con~position according to the present is prepared according to
tnethods well know11 to a person skilled ia the art. As nonlimiting exatllplc, such aa
adhesive cotnposition car1 be con\~etltionally obtained by corotatitlg twin-screw
extrusion.
10 A trutltilayer structure comprisi~lga film of a con~positiona ccording to the present
invention is obtained without difficulty by a person skilled in the art according to one of
the well know11 methods, such as, for example, extrusion-lamination. Although this
synthesis route, namely extrusio~l-lamination, is pat-ticularly suitable for forming a film
of compositio~al ccorditlg to the invention or a multilayer incorporatitlg sucll a film, the
15 present it~vention is not limited to this method of synthesis and can, for example, be
envisaged it1 a process of preparation by thermal lamination of a film obtained by filtll
blowing.
Preparation of the forn~ulationso f the test compositions:
20 The test specime~~ofs con~positiotlsa, ccordiug to the invention and according to
the prior art, are produced exactly according to one and the satne process. This is
because a cover, that is to say a multila~lerin cluding the test composition, is produced.
These covers are produced by coextrusion-coating on aluminum on a collinB laboratory
line.
25 For the tllair~p eel test, the structures of all the test specimens are exactly the same,
with the exception, of course, of the adhesive con~positio~tol be tested. Thus, the
sh~~ctureo f these covers co~lsists of aluminum 37 pmtbinder 6 ~~~dadhesive
composition 15 pm.
There are many physicochen~ical properties to be tested for an adhesive sealing
30 cotllposition. In the case in point, the tests carried out and presented below include the
peel test, the measureme~lt of the blocking, the measurement of the static and dynamic
coefficie~lts of friction, the haze, the adhesive bonding to a chill roll and thermal
stability tests.
Tests carried out:
Peel test
5 The peel forces are measured after sealing the cover (different test spcci~i~ens
targeted above) on different supports. A welding of a cover to a polyn~er sheet
representing the container (in particular polystyrene, polyetlierterephtha~ate, aud the
like) is carried out using an AINPACK~co ver sealing tnachine (heat sealer). The width
of the clamping jaws is 3 tiiillimeters (mm).
10 The sealing conditions are:
Pressure applied: 2.26 N/mnmz
Sealing time: 1 second
Variable temperature: 13OoC, 160°C, 18OoC, 20OoC and 220°C
After conditioning of the "cover-sealed samples" in an atmosphere at 50% RH
15 (Relative Huniidity) and 23OC for at least 24 hours, peeling of the test specimens is
cat~ied out at a constant rate (100 mmhninute) via a Synergie 200H dyna~liometer
equipped with a 100 N force cell arid with a 90' plate.
A4eus11reriient of the blocking of tlie test specirilens
20 The blockirig is measured on a monolayer film of an adhesive composition,
according to the present invention or according to the prior art, with a thickness of
50 ptn (micrometers) by extrusion-coating accorditig to the standard IS0 115-02
entitled "Plastics -- Film and sheeting -- Determination of blocking resistance".
Meas~trenteiiot f tlie stotic und &rinr~~icco eflcient offiiction of the test specirrtei7s
The static arid dyria~nicc oefficients of friction are measured on a monolayer fill11
of an adhesive co~~~positiaocnc,o rding to the itlveritiori and according to the prior art,
with a thicluless of 50 pm produced by ext~usion-coating according to the standard
ASTM D 1894 entitled "Standard test tilethod for static and kinetic coefficients of
30 friction ofiplastic fihn and sheeting".
Iffrze test
The haze is measured on a tnonolayer film of an adlicsi\~cc onlposition, accordiug
to thc invention and the prior art, with a thickness of 50 ~1111p, roduced by extrusioncoating
according to the standard ASTM 0-1003-007 entitled "Standard test nnethod for
5 haze and lumitious transmittance of transparent plastics".
1\4eccsrrren1ent of the crdliesh~eb o~idirigo f the test speciilreru to rr cliill roll
Adhesive bonding to a chill roll is evaluated during the preparation by extrusioncoating
of a test specimen cover. The 111orc the cover is separated at the top of the chill
10 roll, the greater is the adhesive bonding. More specifically, a force intended to pull the
film present on the chill roll is exerted and the ease of drawing of the film is measured.
In order to clearly grasp this test and the measurement which results therefrom, the
appended figure 1 makes it possible to clearly understand tlie principle of the test and of
its measurement, even if it is clearly understood that a person clearly knows this
15 procedure.
Tl~er~~srrtorlb ilifj~te st
The analyses are carried out by Thennogravimetric clay analysis (TCA) according
to tlie following procedures:
D)~rrrmticm ect.srrr~e~ire~it:
The nleasurements are catxied out on the Netzsch TG 209F1 device
Heating fi.011125 to 600°C at 1OoC1min under air and nitrogen
Isothern~ul nreus~rrerire~it:
The lneasuremerlts are carried out on the Netzsch TG 209F1 device
25 Heating from 25 to 230, 250, 280 and 300°C at 50°C/l~lin and then an isothertn
nnder nitrogen
Starting nlaterials of the test compositions:
~otryl@20 MA08: Ethylenelmethyl acrylate copolymer, the acrplate content of
30 which is 20% by weight of the copolymer and the MFI of; which is 8 gllO min c190°C,
2.13 kg). In the tables of results presented below, this ~otrjll@is denoted by tlie initials
20MA08.
l,otrylm 40MA10: Ethylet~e/~nctI~ayclr ylate copolymer, the acrylate contetlt of
which is 40% by weight of the copolymer and the MFI of which is 8 g/10 mi11 (190°C,
2.13 kg). In the tables of results presented belo\\: this l.otryl@ is denoted by the initials
40MA08.
5 ~ o t r ~ l1"0M A08: Etl~ylene/metl~yalc rylate copoly~ner,t he acrylate content of
which is 10% by weight of the copolyn~cra nd the MFI of ~vhichis 8 g/10 tuin (190°C,
2.13 kg). In the tables of results presented belo\v, this ~ o t ris~ delilo~tc d by the initials
1 OMAOS.
Tackifying resin (co~nmcrcial):T ackifying resin of low molecular weight which is
10 cotl~pletely hydrogenated and which has a softening point of 123°C. In the tables of
results presented below, the tackifying resin is denoted by the initials TR.
Talc lOMOOS sold by Imerys. This processing agent perfomls the function both
of antiblock agent and of slip agent. This component is subsequently denoted talc.
EBS: Ethylene bis-stearamide supplied by Croda. This processi~~agg ent is an
15 antiblock agent. This component is subsequently denoted EBS.
Er: Erucatnide supplied by Croda. This processing agent is a slip agent. This
component is subsequently denoted Er.
Tlie processing additives are mixed in order to constitute three additivations, the
first additivation representing 1% of the weight of the adhesive composition, the second
20 additivation representing 2% of the weight of the adhesive composition and the third
representing 4.5% of the weight of the adhesive composition.
Additivation a: 0.25% Er + 0.25% EBS + 0.5% talc
Additivation b: 0.5% Er + 0.5% EBS + 1% talc
Additivation c: 1% Er t 1% EBS + 2.5% talc
Results of the tests:
The adhesive sealing composition has to exhibit cei-tain advantageous
characteristics.
Tile results relating to an adhesive co~npositiona ccording to the present invention
30 1 arc given here nonexhaustively. In this conteit, four cl~aracteristics were more
particularly targeted, namely:
- the haze has to be less than 15, ideally less than or equal to 12; and
- the adhesive bo~ldi~tiog the chill roll, denoted CR below, during the preparation
by extrusion-coating has to be low (denoted "-");
- thc lilllitillg fill11 opeilitlg temperature is at least 1 OO°C;
- the dynatnic coefficient for the slip and the static coefficietit for the slip has to be
5 at least 0.4;
- the blocking bas to be at at least 150 grams.

'l'he ~ropagation forces obtained during tlie sealing of thc cover on a PET
(polyether terephthalate) container. It is found tluri~ig this test that tlie propagation
values are virtually identical, whcther the resin is at a coritcnt of 10% or at contcnts
within the range of the inventio~i.
5 Tests were also carried out on other types of supports, in palticular on polystyrene
and polypropylene, and showed results sinlilar to those given in the table below.
Fomiulations No. 1 to No. 8 in the t\vo tables below are respectively conlposed as
follows:
No. 1: 20MA08 + 3.5% TR + additivation b
No. 2: 20MA08 t- 5% TR + additivation b
No. 3: 20MA08 + 2% TR + additivation b
No. 4: 20MA08 + 6% TR + additivation b
No. 5: 40MA08 + 3.5% TR + additivation b
No. 6: lOMAO8 + 3.5% TR + additivation b
No. 7: 20MA08 + 10% TR + additivation c
No. 8: 20MA08 + additivation a
The thernlal stability is measured with the different indicators mentioned in the
20 table below. The very marked gain in stability of the co~npositions according to the
invention, with respect in particular to a cornposition exhibiting a content of tackifiing
resin at 10% by weight of the comnposition, is found.

-14- PCT/FR2015/051517
CLAIMS
1. An adhesive cotnpositioti, usable in an extrusion-coating process for application
to a support or in an extrusion-lamination process for adhesively bonding together
5 several sl~pportsv 4licli are or are not different in nature, within a broad temperature
range, comprising:
- from 91% to 98% by weight of said co~llpositiono f a copoly~nero f ethylene and
of alkyl acrylate;
- at least one tackifying resin;
-processing additives comprising at least one antiblock agent and one slip agent,
characterized in that the tackifying resin represents between 1.5% and 5% of the
weight of the coniposition and said additives represent between 0.5% and 3.5% of the
weight of the coniposition and in that the antiblock agent represents, in the processing
additives, at least 60% by weight of said additives.
2. The conlposition as claimed in claim 1, characterized in that tlie tackifying
resin represents between 3% and 4% of tlie wveight of tlie composition.
3. The co~llpositiona s claimed in claitn 1 or 2, characterized in that the acrylate
20 content in tlie copolyn~ero f ethylene and of alkyl acrylate is between 15% and 30% of
the weight of said copolynler.
4. The coniposition as claimed in any one of the preceding claims, characterized
in that tlie copolymer of ethylene and of alkyl acrylate consists of a copoly~ner of
25 ethylene and of methyl acrylate.
5. The conlposition as claimed in any one of the preceding claims, characterized
in that the MFI of the abovesaid copolynier is between 5 gI10 mi11 and 15 g110 min (at
190°C, 2.13 kg).
6. The composition as claimed in any one of the preceding claims, characterized
in that the processitig additives are present at between 1.5% and 2.5% by wveight of said
composition.
7. The cornpositio~la s claimed in any one of the preceding claims, characterized
in that the processing additives consist solely of at least one antiblack agent and at least
one slip agent, the antiblack agent representing at least 70% by weight of said additives.
5 8. The composition as claimed in any one of the preceding claims, characterized
in that it consists solely of the abovesaid copolymer, the abovesaid tackifying resin and
said processing additives.
9. A sealing film consisting of a composition as claimed in any one of the
10 preceding claims, characterized in that its thickness is between 10 and 20 micrometers
( w ) .
10. A multilayer structure comprisi~lg at least two films, one of which is as
claimed in claim 9, characterized in that the second film is chosen from aluminum,
15 paper or board, cellophane, films based on polyethylene, polypropylene, polyamide,
polyester, polj?~inyl chloride (PVC), polyvinylidene chloride (PVDC) or
polyacrylonitrile (PAN) resins, these fihns being or not being oriented, being or not
being metallized and being or not being treated physically or chemically, and films
coated with a thin inorganic balrier layer, such as polyester (PET SiOx or AlOx).