Liner compositions

Details Liner compositions Liner compositions

2000-08-16

2004-03-02

Kelly, Cynthia H. (Department: 1774)

Stock material or miscellaneous articles

Web or sheet containing structurally defined element or...

C428S098000, C428S109000, C428S113000, C428S299700

Reexamination Certificate

active

06699573

ABSTRACT:

The subject invention pertains to liner compositions. In particular, the subject invention pertains to liner compositions which comprise a first layer and at least one second layer, wherein the first layer comprises at least one homogeneous linear or substantially linear ethylene/&agr;-olefin interpolymer.
Liner compositions have been historically utilized in a variety of application, such as pond liners, roofing membranes, tunnel liners, etc. Such applications typically require a balance of flexibility and impact resistance. In certain of these applications, it is necessary that the liner further comply with certain flame retardancy criteria.
Due to its flexibility and ability to incorporate flame retardants, flexible PVC has found utility in tunnel liner applications. However, PVC is disadvantageous in that it utilizes a plasticizer, which tends to migrate with time and cause a decrease in flexibility; and, in that it exhibits poor low temperature flexibility.
EP 508415-A2 discloses polymeric blends of a propylene homopolymer or copolymer, very low density polyethylene, a modified polymer, and a flame retardant filler. However, as characterized by EP 646623-A2, the compositions do not exhibit high weldability coupled with compliance with the flame retardance test set forth in DIN 4102 B1, both of which are traditionally requirements for use in tunnel liner applications.
EP 646623-A2 discloses polymer compositions useful in tunnel liners, which comprise a blend of two very low density polyethylenes and a flame retardant composition. Exemplified is a blend of a very low density polyethylene having a density of 0.900 g/cm
3
and a melt index (I
2
) of 0.7 g/10 minutes with a very low density polyethylene having a density of 0.885 g/cm
3
and a melt index (I
2
) of 2.5 g/10 minutes. While very low density polyethylene does exhibit somewhat enhanced flexibility as compared to higher density linear low density polyethylene materials, it would be desirable to prepare structures exhibiting a further degree of flexibility, while not sacrificing the good impact resistance which is characteristic of very low density polyethylene.
Accordingly, the subject invention provides a flexible, protective, integral liner comprising:
a. a first polymer component which in turn comprises at least one first ethylene/&agr;-olefin interpolymer which is a homogeneous linear or substantially linear ethylene/&agr;-olefin interpolymer having a density of from 0.850 g/cm
3
to 0.920 g/cm
3
,
b. a second polymer component which in turn comprises at least one second ethylene/&agr;-olefin interpolymer having a density of from 0.905 g/cm
3
to 0.935 g/cm
3
provided that the density of the at least one second ethylene/&agr;-olefin interpolymer is at least 0.002 g/cm
3
greater than the density of the at least one first ethylene/&agr;-olefin interpolymer,
wherein the liner has a total thickness of 0.3 to 4 mm, and exhibits a flexural modulus, as determined in accordance with ISO 178, of no more than 150 MPa and an Impact Resistance at −10° C., as determined in accordance with ISO 6603, of at least 35 J/mm.
In a preferred embodiment of the invention, the liner will further comprise an ignition resistance additive. In such embodiments, satisfactory flame retardancy (that is, ignition resistance of B1, as determined in accordance with DIN 4102) will preferably be achieved without sacrificing the balance of properties described above. Even more preferably, the satisfactory flame retardancy will be achieved while employing low amount of the ignition resistance additive (that is, no more than 20 weight percent, more preferably no more than 15 weight percent, and most preferably no more than 10 weight percent of a halogenated ingition resistance additive; no more than 35 weight percent, more preferably no more than 30 weight percent non-halogenated ignition resistance additive).
The liners of the invention exhibit outstanding flexibility and mechanical properties, and can be processed on existing polyethylene manufacturing equipment. The liners of the invention which incorporate an ignition resistance additive will further exhibit excellent ignition resistance, will produce lower smoke emissions than flexible PVC liners, and will produce no burning drip while burning.
The liners of the invention will be useful in a variety of applications. In particular, the liners of the invention will be usefully employed to prevent the intrusion of water into buildings or other structures, and thus, to prevent water damage to such buildings or structures. Exemplary applications include, but are not limited to, tunnel liners, pond liners, water barriers, roof liners (particularly for tiled roofs) and geological membranes.
These and other embodiments are described in the following detailed description.
The liner of the invention will comprise at least first and second ethylene/&agr;-olefin interpolymers. The term “interpolymer” is used herein to indicate a copolymer, or a terpolymer, or a higher order polymer. That is, at least one other comonomer is polymerized with ethylene to make the interpolymer. The first and second ethylene/&agr;-olefin interpolymers selected will achieve a balance of properties, for example, an average flexural modulus, as determined in accordance with ISO 178, of no more than 150 MPa, and an Impact Resistance at −10° C., as determined in accordance with ISO 6603, of at least 35 J/mm.
The liner of the invention may comprise a monolayer structure, with the first and second ethylene/&agr;-olefin interpolymers being present as a homogeneous blend, or may comprise at least two layers, with the first and second ethylene/&agr;-olefin interpolymers being present in disparate layers.
While the liner of the invention may be a monolayer, it will preferably comprise at least two layers (referred to herein as an A/B structure). Other structures having more than two layers are possible and will be desirable. One such multilayer structure will employ the same formulations in the layers of the faces of the liner and a different formulation in the interior layer (referred to herein as an A/B/A structure). Preferably, the first ethylene/&agr;-olefin interpolymer will be present in the B layer and the second ethylene/&agr;-olefin interpolymer will be present in the A layer.
The first and second ethylene/&agr;-olefin interpolymers will each be interpolymers of ethylene with at least one comonomer selected from the group consisting of C
3
-C
20
&agr;-olefins, non-conjugated dienes, and cycloalkenes. Exemplary C
3
-C
20
&agr;-olefins include propylene, isobutylene, 1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene. Preferred C
3
-C
20
&agr;-olefins include 1-butene, 1-hexene, 4-methyl-1-pentene, 1-heptene, and 1-octene, more preferably 1-hexene and 1-octene. Exemplary cycloalkenes include cyclopentene, cyclohexene, and cyclooctene. The non-conjugated dienes suitable as comonomers, particularly in the making of ethylene/&agr;-olefin/diene terpolymers, are typically non-conjugated dienes having from 6 to 15 carbon atoms. Representative examples of suitable non-conjugated dienes include:
(a) Straight chain acyclic dienes such as 1,4-hexadiene; 1,5-heptadiene; and 1,6-octadiene;
(b) Branched chain acyclic dienes such as 5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene; and 3,7-dimethyl-1,7-octadiene;
(c) Single ring alicyclic dienes such as 4-vinylcyclohexene; 1-allyl-4-isopropylidene cyclohexane; 3-allylcyclopentene; 4-allylcyclohexene; and 1-isopropenyl-4-butenylcyclohexene;
(d) Multi-ring alicyclic fused and bridged ring dienes such as dicyclopentadiene; alkenyl, alkylidene, cycloalkenyl, and cycloalkylidene norbornenes, such as 5-methylene-2-norbornene; 5-methylene-6-methyl-2-norbornene; 5-methylene-6,6-dimethyl-2-norbornene; 5-propenyl-2-norbornene; 5-(3-cyclopentenyl)-2-norbornene; 5-ethylidene-2-norbornene; and 5-cyclohexylidene-2-norbornene.
One preferred conjugated diene is piperylene. The preferred dienes are selected from the group consisting of 1,4-hexadiene; dicyclopentadiene; 5-ethylidene

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