EP3574038A1

EP3574038A1 - Flexible, fireproof thermoplastic compositions with high thermomechanical strength and improved thermal ageing

Info

Publication number: EP3574038A1
Application number: EP18707075.0A
Authority: EP
Inventors: Jean-Jacques Flat; Mathieu SABARD; Dominique Jousset; David Meslet; Regis Cipriani
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2017-01-27
Filing date: 2018-01-26
Publication date: 2019-12-04
Also published as: US20190367714A1; WO2018138446A1; KR20190104071A; JP2020514487A; FR3062390A1; CN110214158A; FR3062390B1

Abstract

The present invention relates to compositions comprising a copolymer comprising at least one segment of a polyolefin and at least one segment of a polyamide, said composition further comprising piperazine pyrophosphate and, optionally, a colouring additive. The present invention also relates to a method for manufacturing said compositions and the use thereof for the manufacture of wire rope coatings, electrical parts such as electrical connectors or electrotechnical housings, thermal protection coatings or sleeves, injection-moulded parts for electronic equipment such as computers and telephones, single-layer or multi-layer tubes, corrugated tubes, preferably for the manufacture of wire rope coatings. Finally, the invention also relates to the electronic, electrical or thermal protection components comprising said composition.

Description

Flexible thermoplastic compositions with high

thermomechanical and flame retardant with thermal aging

improved

The present invention relates to thermomechanically resistant flexible thermoplastic flame retardant compositions based on polyolefins and polyamides containing at least one flame retardant and a color additive. The present invention also relates to the use of such a composition and to a process for preparing this composition.

Thermoplastic polymers such as polyethylenes, polyamides or their mixtures are good electrical insulators and are easy to implement. They are used in particular to produce housings and electrical connectors and also cable coverings. Electrical installations can cause short circuits and ignite, they can also be put in contact with a flame and thus ignite and spread the fire along the cable trays. There are various additives to make these materials non-flammable, some based on halogenated products, others without halogens. However, the use of halogenated additives is increasingly limited for questions of ecotoxicology and toxicology (toxicity and corrosivity of vapors emitted during fires).

Furthermore, the fire performance of these compositions of the prior art are generally obtained at the expense of the ductility of the materials (considerable loss of elongation at break, brittle shock at room temperature). In addition, it is found that the thermal stability of these materials was insufficient. By thermal stability is meant the preservation of the mechanical properties (and more particularly the elongation at break) after various thermal aging (for example 1 week at 120 ° C. in hot air).

The document WO 2007/141449 proposes compositions based on functionalized polyolefms grafted with polyamides, flame-retarded without halogen, which make it possible to produce a material that is efficient in terms of resistance to the propagation of the flame (according to the UL94 test), also having mechanical and thermomechanical properties of good level as well as a good thermal stability and a satisfactory rheology (no excessive viscosifcation, high MFI (Melt Flow Index)), without producing exudation on the materials obtained.

It is also known to color the thermoplastic compositions so that, for example, the cables can be distinguished according to their section or number of conductors.

However, the compositions described above have a drawback in that the materials darken over time. Thus, in the case of colored cables, the different colorations of cables are no longer differentiable.

Surprisingly, the Applicant has demonstrated that the use of a particular flame retardant, piperazine pyrophosphate, avoids the problem of blackening over time, while maintaining mechanical performance, thermomechanical, rheological and remarkable fireproofing.

The present invention thus relates to a composition, comprising:

a copolymer comprising at least one segment of a polyolefin and at least one segment of a polyamide,

piperazine pyrophosphate,

a color additive, if appropriate, and optionally a molecular sieve.

Preferably, the present invention relates to a composition, comprising:

a copolymer comprising at least one segment of a polyolefin and on average at least one segment of a polyamide attached to said polyolefin by the residues of at least one unsaturated monomer (X), piperazine pyrophosphate,

a color additive, if any, and

optionally a molecular sieve.

Preferably, said composition is a flame retarded composition, preferably a flexible thermoplastic flame retardant composition. The term "flexible thermoplastic" means a composition having a flexural modulus of less than or equal to 600 MPa at room temperature and an elastic modulus value, measured by dynamic mechanical analysis (DMA), of at least 0.5 MPa at 150 ° C.

DMA dynamic mechanical analysis consists in dynamically pulling (1Hz) the material to be analyzed over a temperature range of -100 ° C up to 250 ° C at a heating rate of 2 ° C / min, and to record the values of the elastic and loss modules as well as their ratio corresponding to the tangent of the angle of loss.

The composition according to the present invention has a high thermal stability.

The composition is considered to have satisfactory thermal stability when it retains on the order of 70% of its initial mechanical properties of elongation at break and breaking stress after aging under thermooxidation conditions.

The rheology of the composition is considered satisfactory when it is compatible with the usual transformation processes of the materials from the compositions according to the invention (extrusion, injection, etc.).

Preferably, said composition does not comprise a halogenated compound.

Preferably, the composition according to the present invention comprises from 50 to 70%, preferably 55 to 65%, and particularly preferably about 60% by weight of said copolymer relative to the total weight of the composition.

Preferably, the composition according to the present invention comprises from 5 to 50%, preferably from 10 to 40%, particularly preferably from 10 to 30% by weight of said piperazine phosphate relative to the total weight of the composition. According to a preferred embodiment, the composition comprises 5 to 20%, and more particularly 10 to 15% by weight of said piperazine phosphate relative to the total weight of the composition. In Indeed, it has surprisingly been found that a satisfactory flame retardant effect can be obtained with a much lower amount of flame retardant than is usually recommended. Thus, the fire behavior of an unstained thermoplastic composition comprising 12.5% by weight of piperazine pyrophosphate makes it possible to successfully pass the fire on cable test.

The composition according to the invention may comprise a coloring additive or not. Also, the composition according to the present invention can be colored or not colored. When colored, the composition according to the present invention preferably comprises from 0.1 to 5%, preferably from 0.5 to 2% and particularly preferably from 1% by weight of coloring additive to the total weight of the composition.

Preferably, the composition according to the present invention comprises from 0.1 to 5%, preferably from 0.5 to 3% and particularly preferably from approximately 2% by weight of molecular sieve relative to the total weight of the composition.

According to a preferred embodiment, the present invention relates to a composition, comprising:

- 50 to 70% by weight of said copolymer comprising at least one segment of a polyolefin and at least one segment of a polyamide relative to the total weight of the composition,

3 to 40% by weight of piperazine pyrophosphate relative to the total weight of the composition,

where appropriate, 0.1 to 5% by weight of color additive relative to the total weight of the composition, and

optionally a molecular sieve.

Preferably, said copolymer comprises on average at least 1.3 moles of residues of the unsaturated monomer (X) attached to the at least one polyolefin segment per mole of polyolefin segment and preferably on average less than 20 moles of monomer residues. unsaturated (X) bonds to the at least one polyolefin segment per mole of polyolefin segment. In a particularly preferred manner, said copolymer comprises on average between 3 and 5 moles of residues of the unsaturated monomer (X) attached to the at least one polyolefin segment per mole of polyolefin segment. Those skilled in the art can easily determine the number of X-moles by FTIR analysis. For example, if X is maleic anhydride and the molecular weight of the polyolefin is 95,000 g / mol, it has been found that this corresponds to a proportion of anhydride of at least 1.5% by weight of the entire polyolefin segment containing X and preferably 2.5 to 4%. These values associated with the mass of polyamides determine the proportion of polyamide and polyolefin in the copolymer.

Preferably, the copolymers of the present invention are characterized by a nano-structured organization with polyamide lamellae of thickness between 5 and 100 nanometers, preferably between 10 and 50 nanometers.

Advantageously, the polyolefin / polyamide weight ratio in the copolymer as defined above is between 90:10 and 50:50, preferably between 80:20 and 70:30.

Said unsaturated monomer X can be, for example, an unsaturated epoxide, a (meth) acrylic acid or an unsaturated carboxylic acid anhydride.

The unsaturated carboxylic acid anhydride may be chosen, for example, from the group consisting of: maleic, itaconic, citraconic, allylsuccinic, cyclohex-4-ene-1,2-dicarboxylic anhydride, 4-methylenecyclohex-4-ene-1 , 2-dicarboxylic, bicyclo (2,2,1) hept-5-ene-2,3-dicarboxylic acid and x-methylbicyclo (2,2,1) hept-5-ene-2,2-dicarboxylic acid. Preferably, said unsaturated carboxylic acid anhydride is maleic anhydride.

"Polyolefin" or "polyolefin segment" is understood to mean a polymer comprising a comonomer chosen from the group consisting of:

alpha-olefins, advantageously those having from 3 to 30 carbon atoms. Advantageously, said alpha olefin may be chosen from the group consisting of ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene and 4-methyl-1. pentene, 3-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, dococene, 1 the - tetracocene, 1-hexacocene, 1-octacocene and 1-triacontene, preferably propylene or ethylene, particularly preferably ethylene;

esters of unsaturated carboxylic acids, such as, for example, alkyl acrylates or alkyl methacrylates, preferably said alkyls containing from 1 to 24 carbon atoms, examples of alkyl acrylate or methacrylate are especially the methyl methacrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate;

vinyl esters of saturated carboxylic acids such as, for example, acetate or vinyl propionate;

dienes, such as, for example, butadiene, isoprene or 1,4-hexadiene;

and mixtures thereof.

By way of example, said polyolefin segment may be chosen from the group consisting of:

homopolymers and heteropolymers of polyethylene, in particular chosen from the group consisting of: low density polyethylenes (LDPE), high density polyethylenes (HDPE), linear low density polyethylenes (LLDPE), linear low density polyethylene ), very low density polyethylene (VLDPE) and metallocene polyethylene;

homopolymers and heteropolymers of propylene;

ethylene / alpha-olefin polymers such as ethylene-propylene, ethylene-butylene, ethylene-propylene-diene monomer, ethylene-octene, only poy mixed with a PE;

- Styrene / ethylene-butene / styrene block polymers (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS), styrene / ethylene-propylene / styrene (SEPS);

polymers of ethylene with at least one product chosen from unsaturated carboxylic acid salts or esters such as alkyl (meth) acrylate (for example methyl acrylate), or vinyl esters of carboxylic acids saturated such as vinyl acetate;

ethylene-maleic anhydride and ethylene-alkyl (meth) acrylate-maleic anhydride polymers. The preferred polyolefin segments consist of an ethylene-alkyl (meth) acrylate polymer. By using this polyolefin, an excellent resistance to aging in light and at temperature is obtained.

Preferably, the proportion of alpha-olefin is less than 60% by weight, preferably between 2 and 40% by weight of said copolymer, and particularly preferably from 15 to 35% by weight of said copolymer.

Advantageously, said polyethylene segment is a mixture of several polymers, preferably it comprises at least 50%> and preferably 75% (moles) of ethylene relative to said mixture.

Preferably, when the polyolefin segment comprises alpha-olefins, the proportion of alpha-olefin is less than 60% by weight, preferably between 2 and 40% by weight of said polyolefin / polyamide copolymer, and particularly preferably from 15 to 35% by weight of said copolymer.

Preferably, said ethylene-maleic anhydride and ethylene-alkyl (meth) acrylate-maleic anhydride polymers comprise from 0.2 to 10% by weight of maleic anhydride relative to the total weight of said polymer.

Preferably, said ethylene-alkyl (meth) acrylate-maleic anhydride polymer segments comprise from 0 to 50%, preferably 2 to 40% and more preferably 5 to 30% by weight of alkyl (meth) acrylate.

Preferably, said at least one polyolefin segment has a viscosity index ("Melt Flow Index" (MFI)) of between 3 and 1000 g / 10 min, preferably between 20 and 400 g / 10 min (190 ° C., 2.16 kg). ASTM D 1238).

Preferably, said at least one polyolefin segment has a density of between 0.86 and 0.98 g / cm ³ , more preferably between 0.90 and 0.94 g / cm ³ . Preferably, the melt temperature of the polyolefin polymers as described above is less than 180 ° C, preferably less than 160 ° C, particularly preferably between 80 and 120 ° C.

Furthermore, it would not be outside the scope of the present invention if all or part of the polyolefin segment and / or the polyamide segment were replaced by their respective mixture with nanofillers (such as, in particular, nanoclay or carbon nanotubes). said mixtures being known to those skilled in the art as nanocomposites.

The term "polyamide" or "polyamide segment" means a polymer having amide functions. Preferably, said polyamide or polyamide segment is a condensation product:

one or more amino acids, such as aminocaproic, amino-7-heptanoic, amino-11-undecanoic and amino-12-dodecanoic acids;

one or more lactams such as caprolactam, oenantholactam and laurylactam;

one or more diamine salts or mixtures such as hexamethylenediamine, dodecamethylenediamine, metaxylylenediamine, bis-p-aminocyclohexylmethane and trimethylhexamethylenediamine with diacids such as isophthalic, terephthalic, adipic, azelaic and suberic acids, sebacic and dodecanedicarboxylic:

or mixtures of several of said monomers.

Preferably, said polyamide segment is chosen from the group consisting of: PA 6, PA 11, PA 12, PA 6/11 (patterned polyamide 6 and units 11), PA 6/12 (polyamide with patterns 6 and 12), and PA 6 / 6-6 (polyamide based on caprolactam, hexamethylenediamine and adipic acid).

The degree of polymerization can vary widely.

Advantageously, said polyamide segment has an amino functional end. Said amino-ended polyamide segment can be obtained using a chain limiter of formula:

R ₁ ISI H

R ₂

in which :

R 1 is selected from the group consisting of hydrogen and a linear or branched alkyl group having up to 20 carbon atoms,

R-2 is selected from the group consisting of:

a linear or branched alkyl or alkenyl radical having up to 20 carbon atoms,

a saturated or unsaturated cycloaliphatic radical,

an aromatic radical and

a combination of said radicals.

Said chain limiter can be for example laurylamine or oleylamine.

Advantageously, said polyamide has a molar mass Mn of between 500 and 10,000 g / mol, preferably between 1000 and 5000 g / mol and more preferably between 2000 and 3000 g / mol.

Preferably, piperazine pyrophosphate is used as flame retardant.

For the purposes of the present invention, the term "flame retardant agent" means compounds that make it possible to improve the fire resistance of plastic materials.

Piperazine pyrophosphate can be encapsulated in a melamine-based resin. Preferably, the only flame retardant of the composition according to the present invention is based on piperazine pyrophosphate. Preferably, the term "flame-retardant agent based on piperazine pyrophosphate" means a flame-retardant agent comprising at least 50, preferably 60, 70, 80, 90, and even more preferably 95% by weight of piperazine pyrophosphate relative to the weight fireproofing agent. For the purposes of the present invention, the term "color additive" means chemical or natural dyes, coloring pigments and brighteners. The color additive may for example be chosen from those listed in the document Dyes and Pigments, by Daniel WYART from the Techniques de l'Ingénieur.

Preferably, the coloring additive is used as a masterbatch.

Preferably, the composition according to the present invention further comprises a molecular sieve, preferably selected from the group consisting of a hydrotalcite and a zeolite. Preferably, said zeolite is selected from the group consisting of: type 3A, 4A, 5A, 10X and 13X zeolites.

The composition according to the invention may further comprise at least one additive selected from the group consisting of: an antioxidant, a UV stabilizer, a thermal stabilizer, a fluidifying agent such as silica or ethylene-bis-amide, an implementing agent such as calcium stearate or magnesium stearate and mineral fillers. Preferably, the composition according to the invention comprises from 0 to 20% by weight of additive relative to the total weight of the composition.

The antioxidant makes it possible to protect the plastic material against thermal aggression due to the process of implementation or during the life of the plastic part. Preferably, said antioxidant may be selected from the group consisting of sterically hindered phenol compounds, phosphite groups, and mixtures thereof. Preferably, the composition according to the present invention comprises from 0 to 10%, preferably from 0.1 to 5% by weight of said antioxidant relative to the total weight of the composition.

The UV stabilizer prevents yellowing of the composition which may be due to UV radiation (Ultra Violet). Preferably, said UV stabilizer may be selected from the group consisting of: UV absorbers such as benzotriazole and benzophenone, and hindered amines (HALS). Preferably, the composition according to the present invention comprises from 0 to 10%, preferably from 0.1 to 5% and still more preferably from 0.2 to 2% by weight of said UV stabilizer relative to the total weight of the composition. According to a particular embodiment, the composition according to the present invention further comprises at least one polyolefin, maleate or not. The presence of polyolefins makes it possible in particular to limit the water uptake of the composition at elevated temperature, especially at around 85 ° C. Preferably, said polyolefin is selected from the group consisting of homopolymers and copolymers of polypropylene, polyethylenes such as HDPE, LDPE, elastomeric polyolefins, especially based on monomers having 2 to 8, and in particular 2 to 4 carbon atoms, ethylene propylene (EPR) rubbers and olefinic block copolymers such as polyethylene block polypropylenes.

According to another object, the application relates to the use of a composition according to the invention for the manufacture of coating of metal cables, electrical parts such as electrical connectors or electrotechnical housings, thermal protection coatings or sleeves. , injection molded parts for electronic equipment such as computers and telephones, single or multi-layer tubes, corrugated tubes, preferably for the manufacture of wire rope lining.

According to another aspect, the present invention relates to a method for preparing the composition as defined above, comprising the steps of:

a) optionally, preparation of the copolymer as defined above

b) mixture:

said copolymer obtained in step a)

said piperazine pyrophosphate

where appropriate, said color additive, and

optionally a molecular sieve.

Preferably, the mixing step is carried out in an extruder, a co-kneader, an internal mixer or any other usual device for mixing thermoplastic polymers. Preferably, the mixture is made in an extruder, preferably a bi-screw corotative extruder. Alternatively, steps a) and b) can be performed simultaneously, preferably in an extruder.

Preferably, the grafting of said unsaturated monomer on said at least one polyolefin segment is carried out according to the methods usually known to those skilled in the art, for example at a temperature of between 200 and 350 ° C., under vacuum or under an inert atmosphere with stirring of the reaction mixture. By way of example, said grafting may be carried out by a melt-reactive extrusion process or by a solution-in-solvent process.

Preferably, the copolymer can be obtained by reacting at least one amino-terminated polyamide segment with the residues of said unsaturated monomer X attached to said at least one polyolefin segment.

The addition of said at least one polyamide segment to said at least one X-containing polyolefin segment is achieved by reacting an amine function of said polyamide segment with X. Advantageously, X has an anhydride or acid function, thereby creating amide or imide bonds. Preferably, this addition step is carried out in the molten state.

Preferably, this addition step is carried out in an extruder.

Preferably, this addition step is carried out between 230 and 300 ° C. This addition step is preferably carried out between 5 seconds and 5 minutes, and preferably between 20 seconds and 1 minute, and corresponds to the residence time of the mixture of said at least one polyolefin segment containing X with said at least one segment. of polyamide.

The yield of this addition can be evaluated by selective extraction of said at least one segment of free polyamides, that is to say those which have not reacted to form the copolymer according to the invention. The preparation of polyamide segments according to the present invention as well as their addition to a polyolefin containing X is described in US Patents 3976720, US 3963799, US 5342886 and FR 2291225.

According to another aspect, the present invention relates to electronic, electrical or thermal protection components comprising the composition as defined above. These components can be chosen in particular in the group consisting of metal cable covers, electrical parts such as electrical connectors, electro-technical housings, electronic components of computers or telephones and thermal protection coatings and sleeves.

EXAMPLES 1) Process for the preparation of the compositions

The formulations detailed in Table 1 below were prepared from the various ingredients mentioned below using a Leistriz model LSM30.34 extruder. It is a self-cleaning co-rotating bi-screw extruder with a diameter of 34 mm and a length corresponding to 32 times its diameter. The screws are regulated in temperature according to a flat profile at 220 ° C. A rotation speed of 200 rpm and a flow rate of 15 kg / h are displayed. The rods are then extruded, cooled in a water tank and finally granulated.

Bondine HX8290, Lotader 5500 and 4210 are terpolymers of ethylene, alkyl acrylate and maleic anhydride marketed by the Applicant.

EVA 2403 is a copolymer of ethylene and vinyl acetate with an MFI

(190 ° C., 2.16 kg) of 3 g / 10 min and a mass content of vinyl acetate of 24%.

The PA6 (polyamide 6) prepolymer is a PA6 having a number average molecular weight of 2500 g / mol and terminated with a single primary amine function.

Siliporite NK10AP is a type 4A zeolite produced by CECA.

Irganox 1010 is a primary antioxidant produced by BASF.

Alkanox 240 is a secondary antioxidant produced by Chemtura Great Lakes. Budit 3178 is a flame retardant based ammonium polyphosphate produced by the company Budenheim.

ADK STAB FP2500S is a flame retardant based on piperazine pyrophosphate marketed by the company ADK.

PE48 / 5 / 4025F is a blue masterbatch produced by the company Colloids.

Compositions 5 and 6 are counterexamples.

2) Protocol used to measure elongation at break, aging and fire properties (UL94 and LOI)

The granules from the preparation step are then shaped according to the following methods:

Injection molding on a Battenfeld type press having a closing force of 80t at a temperature of 230 ° C in a thermo-regulated mold at 30 ° C and an injection rate of 30 cm3 / s

Extrusion of films (500μιη thick) at 210 ° C by means of a twin-screw counter-rotating screw extruder of the Haake Rheocord 40 type equipped with a flat die 1 mm thick and 10 cm wide.

Standardized specimens are thus shaped according to the following international standards:

• Elongation at break: IFC (French Institute of Rubber) type specimens cut with a punch in extruded films on Haake.

• Test according to UL 94: Test specimens injected with dimensions 127 mm x 12.7 mm and having a thickness of 1.6 mm

• Test according to LOI: injected specimens of dimension 127 mm x 12.7 mm and having a thickness of 3.2 mm

The thermal aging conditions are as follows: The cut-off IFC specimens are placed in an air circulation oven, which is temperature-controlled for a certain period of time. Composition 1 2 3 4 5 6 7 8 9 10 11

BondineHX8290 42.7 39.2 48.8 12.81 42.7 46.2 43.89 48.8 42.7 58.8

Lotader 5500 42.7

Lotader 4210 29.89

EVA 2403 10 10 10 10 10 10 10 10 10 prepolymer PA6 18.3 16.8 12.2 18.3 18.3 18.3 19.8 18.81 12.2 18.3 14.7

Siliporite NKIOAP 2 2 2 2 2 2 2 1,9 2 2 2

Irganox 1010 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.425 1.5 1.5 1.5

Alkanox 240 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.475 0.5 0.5 0.5

Budit 3178 25 25

ADK STAB FP-2500S 25 30 25 25 30 28.5 25 25 12.5

PE48 / 5 / 4025F 5

Total 100 100 100 100 100 100 100 100 100 100 100

Table 1

The measurement of characteristics is carried out as follows:

Elongation at break obtained after pulling the IFC test pieces at a speed of 50 mm / min at 23 ° C. on a Zwick dynamometer.

The flame propagation test is carried out according to the UL94 standard on injected test pieces.

The tested material is classified V0 if:

A) None of five samples will burn for more than 10 seconds after the burner flame has been removed.

B) The total burning time on the 10 tests does not exceed 50 seconds.

C) None of the tested samples burn with either flame or incandescence up to the holding jaw.

D) No incandescent drop, which can ignite the cotton placed underneath, does not fall from any sample.

E) No sample has an incandescent time exceeding 30 seconds. The tested material is classified VI if:

A) None of the five samples burns for more than 30 seconds after the burner flame has been removed.

B) The total burn time on the 10 tests does not exceed 250 seconds.

E) No sample has an incandescent time exceeding 60 seconds. The tested material is classified V2 if:

B) The total burn time on the 10 tests does not exceed 250 seconds.

C) None of the tested samples burn with either flame or incandescence up to the holding jaw. D) Some fragments may come off the test sample, burning temporarily, some of which may ignite the cotton underneath.

E) No sample has an incandescent time exceeding 60 seconds.

In all other cases, the material is unclassified. The Oxygen Limit Index (LOI) test is carried out according to the ASTM D2863 standard on injected test pieces.

3) Results

3.1. Staining after lOj at 175 ° C, elongation at t0 and fire properties

Table 2 3.2. Comparison of elongation at break before and after aging

The elongation at break was measured before and after aging for compositions 6 to 11. The results are reported in Table 3 below.

Table 3

The materials according to the invention have satisfactory performance for the intended applications (initial elongation at break, retention of these elongations at break after aging of 240 hours at 175 ° C, fireproofing according to flame propagation test UL94 and Limit Index of oxygen). On the other hand, unlike against the examples based on ammonium polyphosphate, only the examples based on piperazine pyrophosphate have the property of remaining distinguishable in color after a thermal-oxidation aging of 240 hours at 175 ° C.

3.3. Fire on cable test

The resistance to fire on cable was measured on two samples obtained by coating a cable diameter of 1.7 and 1.9 mm respectively with a layer with a thickness of 0.3 mm of composition 3 and 11. The tests were carried out on a test bench equipped with a propane gas burner and equipped with a 45 ° support at a temperature of 23 ° C without displacement of air. Five samples of composition-based cable 3 and 11 with a length of 600 mm each were positioned on the support so as to be inclined at 45 ° to the horizontal, and then exposed for a period of 30 seconds to the burner flame forming a right angle with the sample and aimed at the lower end of the cable (length of the flame: 100 mm, with a blue dart of 50 mm temperature of 990 ° C). After removal of the flame, the combustion time and the length of insulator remained intact.

The test is considered positive when:

combustion continues for less than 70 seconds after flame removal; and

the upper end of the cable tested remained intact for at least 50mm in length.

The results of the tests on the samples are reported in Table 4 below.

Table 4

These results show that the material according to the invention has satisfactory performance in terms of fire resistance including when it is present in small quantities.

Claims

Composition comprising:

a copolymer comprising at least one segment of a polyolefin and at least one segment of a polyamide, said polyamide having a molar mass M n of between 500 and 10,000 g / mol,

piperazine pyrophosphate,

- where appropriate, a color additive, and

- optionally a molecular sieve.

The composition of claim 1 comprising:

a copolymer comprising at least one polyolefin segment and on average at least one segment of a polyamide attached to said at least one segment of a polyolefin by the residues of at least one unsaturated monomer (X),

piperazine pyrophosphate,

- where appropriate, a color additive, and

- optionally a molecular sieve.

Composition according to Claim 1 or 2, characterized in that it does not comprise a halogenated compound.

Composition according to Claim 1 or 2, characterized in that the said polyolefin is chosen from ethylene-maleic anhydride and ethylene-alkyl (meth) acrylate-maleic anhydride copolymers.

Composition according to any one of the preceding claims, characterized in that said copolymer comprises on average at least 1.3 moles of residues of the unsaturated monomer (X) attached to said polyolefin segment per mole of polyolefin segment.

Composition according to any one of the preceding claims, characterized in that said polyamide has a molar mass Mn of between 1000 and 5000 g / mol and preferably between 2000 and 3000 g / mol. A composition according to any one of the preceding claims, further comprising a molecular sieve preferably selected from the group consisting of a hydrotalcite and a zeolite, preferably said zeolite being selected from the group consisting of: zeolites 3A, 4 A, 5A, 10X and 13X.

Composition according to any one of the preceding claims, characterized in that piperazine pyrophosphate is the only flame retardant.

Composition according to any one of the preceding claims, comprising from 5 to 50%, preferably 10 to 40%, particularly preferably from 10 to 30% by weight of said piperazine phosphate relative to the total weight of the composition.

Composition according to any one of the preceding claims, furthermore comprising at least one polyolefin which may or may not be malinated, the at least one polyolefin being preferably chosen from the group consisting of homopolymers and copolymers of polypropylene and polyethylenes such as HDPE or LDPE. elastomer polyolefins, especially based on monomers having 2 to 8, and in particular 2 to 4 carbon atoms, ethylene-propylene-based (EPR) rubbers and olefinic block copolymers such as polyethylene block polypropylenes.

Composition according to any one of the preceding claims, not comprising a color additive.

Use of a composition according to any one of the preceding claims for the manufacture of coating of metal cables, electrical parts such as electrical connectors or electrotechnical housings, thermal protection coatings or sleeves, injection molded parts for equipment such as computers and telephones, monolayer or multilayer tubes, annealed tubes, preferably for the manufacture of wire rope lining.

13. A method of preparing a composition according to one of claims 1 to 11 comprising the steps of: a) preparation of said copolymer as defined above

b) mixture:

the copolymer obtained in step a)

- said piperazine pyrophosphate

- said color additive, and optionally

- a molecular sieve, if any.

The method of claim 13, wherein steps a) and b) are performed simultaneously.

15. Electronic, electrical or thermal protection components comprising the composition as defined in claims 1 to 11, chosen in particular from the group consisting of metal wire coatings, electrical parts such as electrical connectors, electrotechnical housings, components electronic computers or telephones and thermal protection coatings and sleeves.