WO2009004246A2

WO2009004246A2 - Insulated electrical conductor

Info

Publication number: WO2009004246A2
Application number: PCT/FR2008/051084
Authority: WO
Inventors: Christèle KENSICHER; Linda Boudiaf
Original assignee: Nexans
Priority date: 2007-06-20
Filing date: 2008-06-18
Publication date: 2009-01-08
Also published as: WO2009004246A3; EP2160738A2; KR20100024993A; FR2917886A1; FR2917886B1

Abstract

The present invention relates to an insulated electrical conductor comprising an electrical conductor surrounded by an extruded insulating layer, said layer being obtained from a composition comprising a polymer and a fatty acid amide in solid form.

Description

ELECTRICAL DRIVER ISOLATED

The present invention relates to an insulated electrical conductor intended primarily to withstand temperatures in the range of -40 ^° C.

It applies typically, but not exclusively, to insulated electrical conductors used in the automotive field, in particular harnesses whose cross section of electrical conductors (not insulated) is between 0.35 and 7 mm ² , preferably between 0.35 and 1 mm ² .

Insulating compositions for isolating automotive electrical conductors comprising a blend of polyolefin and paraffin oil having improved cold-holding properties are known.

However, this type of composition is difficult to implement by extrusion at the industrial level.

Indeed, the liquid quantities injected during the implementation of the composition in an extruder are minimal, of the order of 1 to 2 parts by weight per 100 parts of the polymer of said composition.

Thus, this injection requires the costly investment of an oil injector at a very precise dosage and it is difficult to extrude such a composition at an industrial rate of the order of 1000 kg / h of extruded composition.

In addition, the mechanical properties of such a composition, comprising a paraffin oil, are not optimized and do not allow it to withstand temperatures of the order of -40 ^° C.

The technical problem to be solved by the object of the present invention is to propose an insulated electrical conductor comprising an electrical conductor surrounded by an extruded insulating layer, said extruded insulating layer making it possible to avoid the problems of the state of the art. in particular by offering improved mechanical properties, especially at temperatures of the order of -40 ^° C., and an easily industrializable and inexpensive implementation.

The solution of the technical problem lies, according to the present invention, in that said extruded insulating layer is obtained from a composition comprising a polymer and a fatty acid amide in solid form. Thanks to the invention, the composition can be extruded very easily without making any modifications to a conventional extrusion line.

Indeed, said fatty acid amide in solid form is incorporated into the polymer using a simple metering hopper.

In addition, the extruded insulating layer obtained from said composition has optimized mechanical properties, in particular it can withstand temperatures of the order of -40 ⁰ C according to ISO-6722 Part 1 § 8.1.

In a preferred embodiment, the fatty acid amide may be chosen from the following formulas (I) or (II):

in which

R 1 and R 4 may be the same or different and represent a linear or branched C ₁ -C ₂₄ alkyl group; or a linear or branched C ₂ -C 2 ₄ alkene group; or C ₈ -C 20 cycloalkyl; R2 is hydrogen; or a linear or branched C ₁ -C 4 alkyl group; or a linear or branched C ₂ -C 2 ₄ alkene group; or C ₈ -C 20 cycloalkyl, and R 3 is a linear or branched C 1 -C 10 alkyl group. Preferred examples of fatty acid amides may be selected from the following families: acetamide, propionamide, n-butyramide, n-valeramide, n-caproamide, stearamide, erucamide, lauroylamide, miristic amide, arachidamide, behenamide, oleamide, ethylene bis-stearamide, ethylene-bis-oleamide, and oleyl palmitamide, or mixtures thereof.

Oleyl palmitamide is particularly preferred.

In a particular embodiment, the amount of fatty acid amide is at most 5 parts by weight per 100 parts by weight of polymer in the composition, preferably at most 2 parts by weight per 100 parts by weight of polymer in the composition.

This upper limit of 5 parts by weight makes it possible to limit the risk of migration of the fatty acid amide to the surface of said layer, this migration resulting in bleaching of said surface.

As a result, the fatty acid amide tends to no longer protect, by its intrinsic properties, the entire insulating layer, the latter being easily damaged by its environment.

More particularly, the amount of fatty acid amide is at least 0.5 part by weight per 100 parts by weight of polymer in the composition, preferably at least 1 part by weight per 100 parts by weight of polymer in the composition.

The nature of the polymer of the composition according to the present invention is not limiting.

It may be any type of polymer well known to those skilled in the art capable of being extruded, said polymer may be crosslinkable or not.

In an advantageous embodiment, the polymer is grafted silane to be crosslinked by a process well known to those skilled in the art called "silane crosslinking".

Preferably, the polymer is a crosslinkable polymer of the thermoplastic or elastomeric type, and may be chosen from at least one olefin homopolymer and at least one olefin copolymer, or a mixture thereof. More particularly, the polymer is advantageously a homopolymer or copolymer of ethylene, a homopolymer or copolymer of propylene, or a mixture thereof.

As a preferred example, the polymer is a mixture of ethylene-octene copolymer (PEO) and propylene copolymer (PP).

Depending on the field of application of the composition according to the present invention, the mixture of PEO and PP may consist of 60 to 80% by weight of PEO and 40 to 20% by weight of PP.

For example, compositions comprising the 60/40 ratio of PEO / PP are preferred for insulating electrical conductors with a cross-section of 0.35 to 1.5 mm ² (so-called "rigid" insulating layer) while compositions comprising the ratio 70 PEO / PP are preferred for isolating electrical conductors with a cross section of 1.5 to 7 mm ² (so-called "flexible" insulating layer).

The 80/20 ratio of PEO / PP is preferably used to isolate electrical conductors with a section greater than 7 mm ² (so-called "super-flexible" insulating layer), which can reach 90 mm ² , or even 150 mm ² .

In a particular embodiment, the composition further comprises a flame retardant filler.

The flame retardant filler may be a metal hydroxide, preferably magnesium dihydroxide (MDH) or aluminum trihydroxide (ATH).

In a particular embodiment, the composition further comprises at least one protective agent chosen from antioxidants and metal deactivators, the metal deactivators making it possible to limit the catalytic degradation of the insulating layer by the metal of the electrical conductor.

Antioxidants can typically be thioesters or hindered phenols, while metal deactivators are phenolic compounds well known to those skilled in the art.

In a particularly preferred embodiment, the electrical conductor has a cross section of between 0.35 and 7 mm ² , preferably between 0.35 and 1 mm ² . Other features and advantages of the present invention will emerge in the light of the examples which follow, said examples being given by way of illustration and in no way limiting.

In order to show the advantages of the compositions according to the present invention, extruded insulating layers were prepared from compositions according to the invention and according to prior art to examine their mechanical properties and their "cold forming (-40 ⁰ C) "according to ISO-6722 Part 1 § 8.1.

The preparation of the insulating layers, and in particular their crosslinking mode, are given by way of example and are in no way limiting.

In a first step, 100 parts by weight of polymer are blended continuously with heating to about 2.5 parts by weight of a silane crosslinking agent (alkoxysilane or carboxysilane) together with an organic peroxide, with the aid of Buss single-screw mixer or twin-screw extruder.

The temperature of the mixture of this first stage is such that it typically makes it possible to use the polymer while decomposing the organic peroxide.

The polymer is a mixture of 80% by weight of Engage 8450 and 20% by weight of Moplen RP315M.

Engage 8450 is a copolymer of ethylene-octene (PEO) marketed by Dow Elstomers, while Moplen RP315M is a propylene copolymer (PP) marketed by Basell.

This first step makes it possible to obtain a silane-grafted polymer, the silane-grafted polymer typically being obtained in the form of granules.

In a second step, 100 parts by weight of silane graft polymer (granules) were continuously blended and heated to the various amounts of flame retardant fillers, protective agents, paraffin oil or fatty acid amide detailed in Table 1 (Samples A). to C).

It should be noted that the amounts mentioned in Table 1 are conventionally expressed in parts by weight per 100 parts by weight of polymer in the composition. More particularly, in the example of preparation of the insulating layers described in the present invention, the skilled person easily understands that the amounts mentioned in Table 1 are expressed in parts by weight per 100 parts by weight of silane graft polymer in the composition.

Table 1

The origin of the various constituents of Table 1 is as follows.

Sunpar 150 is a paraffin oil marketed by Sun OiI.

Crodamide 203 is a solid fatty acid amide of the oleyl palmitamide type, marketed by Croda France.

The flame retardant charge is ATH marketed by Albermarle.

The protective agent may be the combination of at least one antioxidant such as Irganox 1010 and / or Irganox PS 802, and at least one metal deactivator such as Irganox 1024 and / or Naugard XL1 the choice of antioxidants and metal deactivators being given by way of example only.

The mixing of this second step is carried out using another Buss single-screw mixer or another twin-screw extruder.

The flame retardant fillers, the protective agents and the fatty acid amide are added to the silane graft polymer using a conventional metering hopper.

The paraffin oil is, for its part, added to the polymer using an injector. The temperature of the mixture of this second stage is such that it typically makes it possible to use the granules of silane grafted polymer while avoiding the decomposition of the flame retardant fillers.

This second step makes it possible to obtain a grafted silane graft polymer, the charged silane graft polymer being typically obtained in the form of granules.

In a third step, the granules of charged silane graft polymer are used in a single-screw extruder in the presence of a silanol condensation reaction catalyst.

The catalyst is typically added to the charged silane graft polymer in the form of a masterbatch based on a polyolefin compatible with said graft polymer.

By way of example, the masterbatch containing said catalyst is added in an amount of about 2% by weight to the loaded silane graft polymer.

The mixture of the silane graft charged polymer and the silanol condensation catalyst is extruded, for example on a copper wire (multi-strand) with a section of 1 mm ² , to a thickness of 0.25 mm, to obtain an insulating layer .

In a fourth step, the insulating layer is crosslinked in the presence of water to obtain an isolated electrical conductor (insulated electrical conductors A to C).

The process described above is the silane crosslinking well known to those skilled in the art, in particular under the name crosslinking "in the pool" or crosslinking "in the sauna".

Of course, any other method well known to those skilled in the art can be used for the crosslinking of the polymer of the composition according to the present invention.

In particular, the crosslinking of the composition may be carried out by photochemical means such as irradiation under beta radiation, or irradiation under ultraviolet radiation in the presence of a photoinitiator. Crosslinking in a salt bath or in a vapor tube in the presence of an organic peroxide are two other methods that can also be envisaged.

To test their resistance at temperatures of the order of -40 ^° C., the insulated electrical conductors A to C undergo a "cold forming", the results of which are collated in Table 2.

Beforehand, the mechanical properties, such as tensile strength and elongation at break, of the insulating layer of the insulated electrical conductors are also determined and collated in Table 2.

Table 2

The cold forming, according to ISO-6722 Part 1 § 8.1, consists of winding two insulated electrical conductors with a length of 600 mm to a temperature of -40 ^° C. on the same mandrel.

After this cold winding, and at ambient temperature, it is visually observed whether the electrical conductor is visible, or in other words if the insulating layer of the insulated electrical conductor has cracks revealing said electrical conductor.

Thus, the electrical conductor of the insulated electrical conductors A and B is clearly visible, while the insulating layer of the insulated electrical conductor C exhibits no external deterioration.

The fatty acid amide included in the insulating layer of the insulated electrical conductor C thus makes it possible to increase the mobility of the polymer chains in order to optimize the cold resistance (-40 ^° C.) of the insulating layer. It is important to note that the elongation at break of the insulating layer of the insulated electrical conductor C is significantly greater than that of the insulating layers of the electrical conductors A and B.

The present invention is not limited to the example which has just been described and relates in general to all the compositions that can be envisaged from the general indications provided in the disclosure of the invention.

Claims

An insulated electrical conductor comprising an electrical conductor surrounded by an extruded insulating layer, said layer being obtained from a composition comprising a polymer and a fatty acid amide in solid form.

2. Isolated electrical conductor according to claim 1, characterized in that the fatty acid amide is chosen from the following formulas I and II:

in which

R1 and R4 may be the same or different and represent a linear or branched alkyl group in dC ₂₄ ; or a linear or branched C ₂ -C 2 ₄ alkene group; or a group -C-C2 cylcoalkyle _4, R2 represents hydrogen; or a linear or branched C ₁ -C 4 alkyl group; or a linear or branched C ₂ -C 2 ₄ alkene group; or C ₈ -C 20 cycloalkyl, and R 3 is a linear or branched C 1 -C 10 alkyl group.

3. Isolated electrical conductor according to claim 1 or 2, characterized in that the fatty acid amide is oleyl palmitamide.

An insulated electrical conductor according to any one of the preceding claims, characterized in that the amount of fatty acid amide is at most 5 parts by weight per 100 parts by weight of polymer in the composition, preferably at most 2 parts by weight per 100 parts by weight of polymer in the composition.

An insulated electrical conductor according to any one of the preceding claims, characterized in that the amount of fatty acid amide is at least 0.5 parts by weight per 100 parts by weight of polymer in the composition, preferably at least less than 1 part by weight per 100 parts by weight of polymer in the composition.

6. insulated electrical conductor according to any one of the preceding claims, characterized in that the polymer is selected from at least one olefin homopolymer and at least one olefin copolymer, or their mixture.

7. insulated electrical conductor according to any one of the preceding claims, characterized in that the polymer is a mixture of ethylene-octene copolymer (PEO) and propylene copolymer (PP).

8. insulated electrical conductor according to claim 7, characterized in that the mixture of PEO and PP consists of 60 to 80% by weight of PEO and 40 to 20% by weight of PP.

9. insulated electrical conductor according to any one of the preceding claims, characterized in that the polymer is grafted silane.

10. insulated electrical conductor according to any one of the preceding claims, characterized in that the composition further comprises a flame retardant filler.

11. insulated electric conductor according to claim 10, characterized in that the flame retardant filler is a metal hydroxide, preferably the metal hydroxide is magnesium dihydroxide (MDH) or aluminum trihydroxide (ATH).

12. insulated electrical conductor according to any one of the preceding claims, characterized in that the composition further comprises at least one protective agent selected from antioxidants and metal deactivators.

13. insulated electrical conductor according to any one of the preceding claims, characterized in that the electrical conductor has a cross section of between 0.35 and 7 mm ² , preferably between 0.35 and 1 mm ² .