Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2000-01-10
2001-09-25
Mullis, Jeffrey C. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S523000
Reexamination Certificate
active
06294269
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a coextrusion binder, to its use in preparing a multilayer structure and to the structure thus obtained.
More specifically, the coextrusion binder of the present invention comprises:
at least one polymer (A) comprising at least 75 mol % of ethylene and which has an MI
2
/[&eegr;]
−8.77
ratio with an absolute value of greater than 15,
at least one polymer (B) different from (A) chosen from:
polymers (B1) comprising at least 50 mol % of ethylene,
block copolymers (B2) of styrene,
(B) has an MI
2
/[&eegr;]
−8.77
ratio with an absolute value of greater than 15,
the mixture of (A) and (B) being grafted with an unsaturated carboxylic acid or a functional derivative of this acid,
the cografted mixture of (A) and (B) optionally being diluted in a polymer (C) chosen from
homo- or copolymers (C1) of ethylene
block copolymers (C2) of styrene
the binder having:
(a) an ethylene content which is not less than 70 mol %,
(b) a carboxylic acid content, or a content of its derivative, of 0.01 to 10 weight % with respect to the weight of the binder, and
(c) an MI
10
/MI
2
ratio of 5 to 20, where MI
2
is the melt flow index at 190° C. under a load of 2.160 kg, measured according to ASTM D1238, and MI
10
is the melt flow index at 190° C. under a load of 10 kg, measured according to ASTM D1238. The intrinsic viscosity In [&eegr;] denotes the intrinsic viscosity index (dl/g) of a polymer, measured in a decalin solution at 135° C.
The present invention also relates to a multilayer structure comprising a layer comprising the coextrusion binder defined above and, directly attached to this layer, a layer (E) of nitrogen-containing or oxygen-containing polar resin, such as a layer of a polyamide resin, of a saponified copolymer of ethylene and of vinyl acetate (EVOH) or of a polyester resin, or alternatively a metal layer.
The invention also relates to a structure comprising the above structure and, directly attached to the structure, on the side of the binder, either a polyolefin layer (F) or a layer of a resin chosen from the resins of the layer (E) or alternatively a metal layer.
BACKGROUND OF THE INVENTION
These structures are useful for manufacturing flexible or rigid packagings, such as packets or bottles for foodstuffs. These packagings can be manufactured by coextrusion, laminating or coextrusion blow-moulding.
The prior art EP 35392 describes coextrusion binders consisting of:
(i) 1 to 100 weight % of an ethylenic resin modified by grafting originating from an ethylenic polymer which contains 0 to 15 mol % of at least one alpha-olefin having 3 to 30 carbon atoms, as comonomer, and which has an MI
2
/[&eegr;]
−8.77
ratio which, in absolute value, is not less than 15 and a relative density of 0.88 to 0.98 g/cm
3
, and
(ii) 99 to 0 weight % of a non-modified ethylenic polymer containing 0 to 50 mol % of at least one alpha-olefin having 3 to 30 carbon atoms, as comonomer, and which has an MI
2
/[&eegr;]
−8.77
ratio which, in absolute value, is not less than 15 and a relative density of 0.86 to 0.96 g/cm
3
,
and which have
(a) an ethylene content of at least 80 mol %
(b) a carboxylic acid content (or content of its derivative) of between 0.01 and 10 weight % of the binder
(c) a relative density of 0.88 to 0.98 g/cm
3
and
(d) an MI
10
/MI
2
ratio of 5 to 18.
DESCRIPTION OF THE INVENTION
However, Applicant has found that these binders exhibited unmelted regions which can bring about delaminations in the structures comprising these binders. The Applicant has found that the cografting, that is to say the grafting of the mixture of (A) and (B), produced binders which are virtually devoid of unmelted regions.
As regards the polymer (A), this is a polyethylene or a copolymer of ethylene with a comonomer chosen from, for example:
alpha-olefins, advantageously those having from 3 to 30 carbon atoms.
Examples of alpha-olefins having 3 to 30 carbon atoms as possible comonomers comprise propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene,1-eicosene, 1-docosene, 1-tetracosene, 1-hexacosene, 1-octacosene and 1-triacontene. These alpha-olefins can be used alone or as a mixture of two or of more than two.
Unsaturated carboxylic acid esters, such as, for example, alkyl (meth)acrylates in which the alkyl has from 1 to 24 carbon atoms.
Examples of alkyl acrylate or methacrylate which can be used are in particular methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate or 2-ethylhexyl acrylate.
Vinyl esters of saturated carboxylic acids, such as, for example, vinyl acetate or vinyl propionate.
The relative density (A) is advantageously between 0.88 and 0.98 g/cm
3
.
Preferably, (A) is a copolymer of ethylene and of an alpha-olefin of LLDPE (linear low density polyethylene) or VLDPE (very low density polyethylene) type. An regards the polymers (B), (B1) can be chosen from polyethylenes or copolymers of ethylene and of at least one comonomer which can be the same as the comonomers cited for (A) and also a diene.
Mention may be made, as example of polymers (B1) of ethylene/propylene, ethylene/propylene/diene, ethylene/1-butene, ethylene/1-butene/diene, ethylene/propylene/1-butene/diene or ethylene/4-methyl-l-pentene copolymer rubbers, and mixtures of at least two of these rubbers with one another.
(B2) can also be a copolymer containing styrene/butadiene/styrene (SBS) blocks, containing styrene/ethylene-butene/styrene (SEBS) blocks or alternatively containing styrene/isoprene/styrene (SIS) blocks.
The relative density of (B) is advantageously between 0.86 and 0.96 g/cm
3
.
That is to say that (B) represents a range of polymers from thermoplastic resins to elastomers. Preferably, (B) is an elastomer, ethylene/propylene copolymer rubbers and ethylene/1-butene copolymer rubber are those which are preferred the most. The ethylene/propylene copolymer rubber and the ethylene/1-butene copolymer rubber preferably have a melt flow index (measured at 190° C. according to ASTM D1238-65T) of 0.1 to 20 and an ethylene content of 60 to 90 mol %.
The mixture of (A) and (B) is grafted with an unsaturated carboxylic acid or a functional derivative of this acid.
Examples of unsaturated carboxylic acids are those having 2 to 20 carbon atoms, such as acrylic, methacrylic, maleic, fumaric and itaconic acids. 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 is 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, maleic, fumaric, itaconic, citraconic, allylsuccinic, cyclohex-4-ene-1,2-dicarboxylic, 4-methylcyclohex-4-ene-1,2-dicarboxylic, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic and x-methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acids or maleic, itaconic, citraconic, allylsuccinic, cyclohex-4-ene-1,2-dicarboxylic, 4-methylcyclohex-4-ene-1,2-dicarboxylic, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic and x-methylbicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic a=hydrides.
Examples of other grafting monomers comprise C
1
-C
8
alkyl esters or glycidyl ester derivatives of usaturated carboxylic acids, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, glycidyl acrylate, glycidyl methacrylate, monoethyl maleate, diethyl maleate, monomethyl fumarate, dimethyl fumarate, monomethyl itaconate and diethyl itaconate; amide derivatives of unsaturated carboxylic acids, such as acrylamide, methacrylamide, maleic acid monoamide, maleic acid diamide, maleic acid N-monoethylamide, maleic acid N,N-diethylamide, maleic acid N-monobutyla
Jacquemet Regis
Le Roy Christophe
Elf Atochem S.A.
Mullis Jeffrey C.
Smith , Gambrell & Russell, LLP
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