Stock material or miscellaneous articles – Composite – Of polyamide
Reexamination Certificate
2000-06-02
2002-08-13
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polyamide
C428S476100, C428S516000, C525S066000, C525S179000
Reexamination Certificate
active
06432548
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to compositions based on polyolefins and on low-melting-point polyamides and more particularly to compositions containing a polyamide matrix and comprising a polyolefin dispersed phase. They consist of, for example, PA-6/6,6, polyethylene or polypropylene and usually a compatiblizer which is, for example, a functionalized polyolefin. These compositions are useful for moulding articles or for making films used, for example, in packaging.
PROBLEM TO BE SOLVED
Compositions based on PA-6 and polyolefins, known elsewhere as being excellent barrier materials (with respect to CH
3
Br, styrene, pentane, etc.), are processed, by. tubular blown-film extrusion for example, at temperatures of the order of 260° C. These temperatures are not compatible with coextruded structures in which at least one of the layers has a certain heat sensitivity such as a layer of ethylene-vinyl acetate (EVA) copolymers. In addition, these high temperatures cause processing problems for coextruded structures in the presence of PE (polyethylene) layers.
Moreover, films consisting of these compositions based on PA-6 and PE exhibit low tear strength in the longitudinal direction. Consequently, the invention proposes novel barrier films exhibiting improved tear strength, these being obtained within the context of a monolayer or multilayer construction containing at least one layer of an alloy of the low-melting-point polyamide/polyolefin type which can be processed, in tubular blown-film coextrusion, at low enough temperatures for them to be compatible with layers of heat-sensitive polymers.
PRIOR ART
The prior art has not disclosed this technical problem. Patent EP 766,913 discloses a film consisting of a blend comprising at least one polyamide and at least one polyolefin, the said film being laid out over an agricultural soil into which a fumigant is injected. Soil treatment by fumigation consists in injecting gases into the soil, before sowing or planting, in order to disinfect the earth, and then the soil is covered with a film of a plastic in order to retain these gases in the soil and thus allow them to act. It is possible, for example, to use methyl bromide, 1,3-dichloropropene, methyl chloride, 3,5-dimethyltetrahydro-1,3,5-thiadiazin-2-thione, sodium tetrathiocarbonate or metham sodium (CH
3
NHCS.S Na).
According to a first embodiment, this prior art also relates to a film comprising the above layer and a layer essentially consisting of a polyolefin. According to a second embodiment, this prior art also relates to a film comprising the previous layer arranged between two layers of polyolefin. The technical problem of the present invention was not mentioned; the polyamide used was still PA-6.
Patent EP 807,519 relates to a multilayer film, useful for making flexible sachets, comprising (i) a barrier film based on a polyamide/polyolefin blend and (ii) on at least one of its sides, a film based on a high-frequency weldable ethylene-unsaturated ester copolymer. It is useful for making flexible sachets of detergents, bleach or fabric softeners. The examples describe barrier films consisting of PA-6 and polyethylene and weldable EVA films. As in the previous prior art, the technical problem of the present invention was not mentioned and the polyamide used was still PA-6.
SUMMARY OF THE INVENTION
It has now been discovered that compositions based on polyolefins and low-melting-point polyamides can be produced which can be converted into films and can be coextruded with other polymers in order to make multilayer structures.
The invention therefore relates to compositions containing a polyamide matrix (A) and a polyolefin dispersed phase (B), in which compositions the polyamide has a melting point below that of PA-6 and the dispersed phase consists of at least one polyolefin (B) chosen from functionalized polyolefins (B1) and non-functionalized polyolefins (B2).
The present invention therefore relates to films consisting of the above compositions.
The films of the present invention have many advantages: they are processed at low temperature, they have a high tear strength and they exhibit a barrier nature.
Advantageously, the films of the invention may be processed at lower temperatures than alloys of the prior art based on PA-6 (melting point=223° C.), the tubular blown-film coextrusion of which is normally carried out at 260° C. A reduction of at least 20 to 30° C. is expected. This characteristic is most particularly beneficial in the field of multilayer film coextrusion in which the outer layers consist of PE (better bubble strength because of the higher viscosity of the PE layers) or of heat-sensitive copolymers of ethylene and polar monomers (for example, EVA). Thus, the thermal degradation of the external layers is limited.
Monolayer or multilayer films containing at least one layer according to the present invention exhibit improved tear strength in the longitudinal direction compared with constructions known to those skilled in the art, such as those described in EP 766,913. Compared with these PE-based films, the films according to the present invention possess lower permeabilities with respect to the following agents: CH
3
Br, O
2
and CO
2
.
DETAILED DESCRIPTION OF THE INVENTION
The expression “low-melting-point polyamide” should be understood to mean any polyamide whose melting point is less than 220° C. These are often copolyamides. Mention may be made of the copolyamides resulting from the condensation of at least two alpha,omega-aminocarboxylic acids or of two lactams, or of a lactam with an alpha,omega-aminocarboxylic acid. Mention may also be made of the copolyamides resulting from the condensation of at least one alpha,omega-aminocarboxylic acid (or a lactam) with at least one diamine and at least one dicarboxylic acid.
By way of examples of lactams, mention may be made of those having from 3 to 12 carbon atoms in the main ring, these being possibly substituted. Mention may be made, for example, of &bgr;,&bgr;-dimethylpropiolactam, &agr;,&agr;-dimethylpropiolactam, amylolactam, caprolactam, capryllactam and lauryllactam.
By way of examples of alpha,omega-aminocarboxylic acids, mention may be made of aminoundecanoic acid and aminododecanoic acid. By way of examples of dicarboxylic acids, mention may be made of adipic acid, sebacic acid, isophthalic acid, butanedioic acid, 1,4-cyclohexyldicarboxylic 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—(CH
2
)
10
—COOH.
The diamine may be an aliphatic diamine having from 6 to 12 carbon atoms—it may be an aryl diamine and/or a saturated cyclic diamine. By way of examples, mention may be made of hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1,5-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, diamine polyols, isophorone diamine (IPD), methylpentamethylenediamine (MPDM), bis(aminocyclohexyl)-methane (BACM) and bis(3-methyl-4-aminocyclohexyl)methane (BMACM).
The expression “low-melting-point polyamide” should also be understood to mean any amorphous polyamide having no melting point.
By way of examples of polyamides (A), mention may be made of caprolactam/lauryllactam copolymers (PA-6/12), caprolactam/hexamethylenediamine, adipic acid copolymers (PA-6/6,6), caprolactam/lauryllactam/hexamethylenediamine, adipic acid copolymers (PA-6/12/6,6), caprolactam/hexamethylenediamine, azelaic acid/11-aminoundecanoic acid/lauryllactam copolymers (PA-6/6,9/11/12), caprolactam/hexamethylenediamine, adipic acid/11-aminoundecanoic acid/lauryllactam copolymers (PA-6/6,6/11/12) and hexamethylenediamine, azelaic acid/lauryllactam copolymers (PA-6,9/12).
Advantageously, (A) is chosen from PA-6/12 and PA-6/6,6.
A non-functionalized polyolefin (B2) is conventionally a homopolymer or copolymer of alpha-olefins or of diolefins, such as, for example, ethylene, propy
Alex Patrick
Blondel Philippe
Flat Jean-Jacques
Reignier Gerard
Atofina
Bissett Melanie
Millen White Zelano & Branigan P.C.
Seidleck James J.
LandOfFree
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