KR20070017921A - A fire-resistant composition, in particular as material for a power and/or a telecommunications cable - Google Patents

Abstract

The present invention relates in particular to fire-resistance compositions as materials for power and / or communication cables. The present invention is characterized in that the composition comprises a polymer and aluminum oxide in the form of particles having an average diameter of 1 micrometer (μm) or less.

Description

Fire resistant composition for power cable and / or communication cable {A FIRE-RESISTANT COMPOSITION, IN PARTICULAR AS MATERIAL FOR A POWER AND / OR A TELECOMMUNICATIONS CABLE}

The present invention relates to compositions for materials that can withstand extreme temperature environments.

Particularly preferred but non-limiting uses of the present invention are in the field of power and / or communication cables, which function for a limited time when subjected to high temperatures and / or directly flames.

Currently, one of the major concerns in the cable industry is to improve the behavior and performance of cables in extreme temperature environments, especially in the extreme temperatures encountered in fires. Especially for safety reasons it is necessary to maximize the cable's ability to withstand fire while also delaying the propagation of flames. Significant delays in flame propagation can increase the time to introduce a building and / or to use an appropriate fire extinguisher. Better resistance to flames can cause cables to run longer because they are damaged more slowly.

Whether the cable is an electrical cable or an optical cable for transferring energy or transmitting data, it can be said that the cable is made up of at least one conductor which extends within at least one insulator element. At least one insulator element may act as a protective means and / or the cable may also have at least one particular protective element constituting the sheath. Unfortunately, many of the best insulating and / or protective materials used in cable production are known to be highly flammable. This applies in particular to polyolefins and copolymers thereof such as, for example, copolymers of polyethylene, polypropylene, ethylene and vinyl acetate, and copolymers of ethylene and propylene. In any case, this excessive flammability is substantially incompatible with the requirement to withstand the flame as described above.

In the field of cable manufacture, there are a number of methods for improving the behavior in the flame of polymers used as insulating and / or sheathing materials.

The most widely used solution to date is the use of halogen compounds in the form of halogenated by-products dispersed in the polymer medium or in the form of directly halogenated polymers, for example polyvinyl chloride (PVC). However, current regulations seek to prohibit the use of these types of materials because of their potential toxicity and corrosiveness, whether these materials are processed into products or degraded by fire. This may in particular be caused by accidental decomposition in case of fire or even during intentional incineration. In any case, recycling of halogenated materials will continue to be an issue, especially environmentally.

This is why it relies on increasingly non-halogenated fire-retardant fillers, in particular metal hydroxides such as aluminum hydroxide or magnesium hydroxide. Nevertheless, this type of technical solution presents the drawback of requiring a large amount of filler to achieve a satisfactory level of efficiency in terms of the ability to delay flame propagation or resistance to flame. As an example, the metal hydroxide content may be generally 100 to 150 parts by weight based on 100 parts by weight of the polymer resin.

The addition of large amounts of filler significantly increases the viscosity of the composite material. This inevitably significantly reduces the extrusion speed and consequently significantly reduces productivity. After all, this negatively affects the cost of the composite material which is already burdened by the cost of the non-halogenated fireproof filler which is essentially expensive since its fireproof filler needs to be used in large quantities.

However, apart from this simple economic problem, the fire-resistant performance of materials with non-halogenated fireproof fillers is still insufficient to meet the requirements of all fire protection tests to date.

Phyllosilicates are also known to be used as non-halogenated fire retardant fillers. Such inorganic compounds are noteworthy in that they can form nanocomposites with the polymer medium in which they are dispersed.

However, this type of solution has the drawback of being particularly expensive because of the inevitable cost of pretreatment that needs to be applied to each phyllosilicate in order to provide sufficient lipophilic to the phyllosilicate. Such composite materials also exhibit normal electrical properties, viscous disadvantages for the extrusion rate, and in any case always the ability to withstand insufficient flames.

Accordingly, a technical problem to be solved by the object of the present invention is to propose a fire-resistant composition as a material of power and / or communication cable, in particular, which solves the problems of the prior art but is not expensive and the ability to withstand flame is considerably improved.

According to the invention, a solution of the technical problem imposed in the prior art consists in that the fire resistant composition comprises a polymer and aluminum oxide in the form of particles having an average diameter of 1 micrometer (μm) or less.

The term aluminum oxide is used to mean non-hydrated alumina of the general formula Al ₂ O ₃ .

In other words, the composition of the present invention comprises a polymer medium in which alumina of 1 micron or less is dispersed and acts as a fire retardant filler.

The term "fire-resistant composition" is used broadly to include any composition for constructing a material that can delay flame propagation and / or withstand flame.

In any case, the average size of the aluminum oxide particles constitutes an essential parameter of the present invention in that the ability of the polymer material to withstand flame is directly related to the particle size of the fire filler. Particularly obvious fire protection effects are observed when the alumina used exhibits very fine particle sizes, especially when the particles exhibit an average diameter of less than 1 micrometer. It should be noted that the smaller the size of the alumina oxide particles, the better the fire prevention effect.

The invention described above exhibits the advantage of providing a polymeric material that benefits from improved mechanical resistance and improved ability to withstand flame when compared to the corresponding prior material. Such materials are well suited for use in making sheaths for power and / or communication cables. Such materials are also suitable for layers or "padding" materials of insulating covers and protective sheaths or cable fillers.

In a preferred embodiment of the present invention, aluminum oxide consists of particles having an average diameter of 20 nanometers (nm) or less.

In particular, the composition preferably comprises 1 wt.% To 80 wt.%, Preferably 2 wt.% To 20 wt.% Of aluminum oxide.

According to a feature of the invention, the polymer is polyethylene, polypropylene, copolymer of ethylene and propylene (EPR), ethylene-propylene-diene trimer (EPDM), copolymer of ethylene and vinyl acetate (EVA), ethylene and methyl Copolymer of acrylate (EMA), copolymer of ethylene and ethyl acrylate (EEA), copolymer of ethylene and butyl acrylate (EBA), copolymer of ethylene and octene, polymer based on ethylene, polypropylene Based polymers, imide polyethers, thermoplastic polyurethanes, polyesters, polyamides, halogenated polymers, or mixtures thereof.

According to another feature of the invention, the composition also has at least one associated fire retardant filler.

In particular, these secondary fire retardant fillers are preferably compounds containing phosphorus such as organic or inorganic phosphates, compounds containing antimony such as antimony oxide, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, compounds based on boron such as borate salts, Carbonates of Group IA and IIA alkali metals such as carbonates of calcium, sodium, potassium or magnesium and the corresponding compounds based on tin such as hydroxide carbonates, tartarate and hydrostannates, melamine such as melamine phosphate and derivatives thereof Phyllosilicates such as formophenolic resins, sepiolite, attapulgite, montmorilonite, illite, chlorite, kaolinite, mica and talc phyllosilicate).

Preferably, the composition comprises 1 wt.% To 80 wt.% Of associated fire retardant filler.

According to another feature of the invention, the composition also has at least one additive selected from the group comprising lubricants, plasticizers, temperature stabilizers, pigments, antioxidants, and ultraviolet stabilizers.

The present invention also provides any power and / or communication cable with at least one insulating sheath made of the fire resistant composition described above. The insulating sheath can also perform a protective function and / or a padding function.

The invention also provides any power and / or communication cable equipped with at least one protective sheath made of the above fire resistant composition. Thus, each protective sheath can also perform an insulating and / or padding function.

Finally, the present invention provides any power and / or communication cable equipped with at least one padding layer made of the fire resistant composition described above. Each layer of filler material may perform an insulation and / or protection function.

Although such cables are intended to transmit power and / or transmit data, they may also be described as suitable for electrical and / or optics depending on whether the conductor elements provided are for electrical and / or optics. have.

Other features and advantages of the present invention will become more apparent from the following comparative examples, which are given as non-limiting examples.

compare Example

Five sample materials were prepared using five different compositions to compare the performance of each withstand flame. The compositions are suitable for use to manufacture insulating and / or sheathing and / or padding materials for energy and / or communication cables.

In any case, the polymer is common in all five samples. In particular, the polymer is a copolymer of ethylene and vinyl acetate (EVA). In the five samples only the nature and composition of the mixture of fire retardant fillers is different. The difference is described in Table 1.

Sample number One 2 3 4 5 EVA 28 40% 40% 40% 40% 40% Magnesium hydroxide 60% 50% 50% 50% 50% Treated Montmorillonite - 10% - 5% 5% Aluminum oxide d50 = 13 nm - - 10% 5% - Aluminum oxide d50 = 0.5 μm - - - - 5%

Manufacture process

To avoid errors in successive comparative analysis, in each case the composition was prepared by mixing the same amount of polymer with each fire retardant filler; The filler content of the resulting composite is constant.

Whatever the exact nature of the composition produced, the mixing of the polymer medium with the fire retardant filler is always:

Setting the temperature to 160 ° C. during the whole mixing process;

Injecting the polymer into an internal mixer set to rotate at 30 revolutions per minute (rpm);

Dissolving the polymer at 160 ° C. at 30 rpm for 2 minutes;

Dissolving at 60 rpm for 2 minutes;

Injecting filler at 30 rpm; And

Mixing at 30 rpm for about 10 minutes.

Sample manufacturing

Reference sample 1 is sold under the trade name Evatane 28-03 by manufacturer Arkema under the trade name Magnifin H10 by 100 grams (g) of ethylene and vinyl acetate (EVA) copolymer containing 28% vinyl acetate and by manufacturer Albemarle. It is especially prepared by mixing 150 g of magnesium hydroxide. The manufacturing process is of course carried out in accordance with the above-described process. Sample 1 is an example of a conventional first material that provides excellent ability to withstand flame.

In order to prepare Reference Sample 2, the above-mentioned preparation process is carried out in the same manner, in which Reference Sample 2 is specifically 100 g of ethylene and vinyl acetate (EVA) copolymer containing 28% vinyl acetate, 125 g of magnesium hydroxide under the trade name Magnifin H10. And a mixture of 25 g of montmorillonite treated with alkyl ammonium sold under the name Nanofil by the manufacturer Sud Chemie. Sample 2 above is well known in the art and in particular relates to a second material described in European Patent (EP) 1 033 724.

Sample 3 is 100 g of ethylene and vinyl acetate (EVA) copolymer containing 28% vinyl acetate, 125 g of magnesium hydroxide under the trade name Magnifin H10, and an average diameter d50 = 13 nm sold under the trade name Aeroxide Alu C by manufacturer Degussa. 25 g of aluminum oxide. Sample 3 serves to evaluate the flame resistance performance of a material comprising magnesium hydroxide, which is a conventional fire retardant filler, and aluminum oxide composed of particles of very small size.

Both Sample 4 and Sample 5 comprise 100 g of ethylene and vinyl acetate (EVA) copolymer containing 28% vinyl acetate, 125 g of magnesium hydroxide under the trade name Magnifin H10, and 12.5 g of montmorillonite treated with alkyl ammonium, It further comprises 12.5 g of aluminum oxide with an average diameter d50 = 13 nm and 12.5 g of aluminum oxide with an average diameter d50 = 0.5 μm, each sold under the trade name Nabalox NO713-10 by Nabaltec.

Ability to withstand flame

The flame behavior of each sample was evaluated using the "epiradiateur" test, as described in French Standard NF-P-92-505. For this purpose the material to be evaluated needs to be in the form of a square plate 7 cm (cm) on one side and 3 mm (mm) in thickness. The evaluation process is using the hot hydraulic press in the following process:

Dissolving at 150 ° C. for 3 minutes;

Still at 150 ° C., applying a pressure of 150 bar for 2 minutes; And

Cooling for 5 minutes at 150 bar with water;

Table 2 summarizes the performance of each sample for the flame measured using the "epiradiateur" test. Each test lasted 5 minutes and during that time evaluated the flaming time which should be as long as possible and the average time of self-combustion which should be as short as possible.

Sample number Burning time (s) Self-burning average time (s) One 110 8.9 2 120 7.7 3 131 8.2 4 161 6.2 5 136 7.3

First, it can be seen that Reference Sample 2 provides better performance than Reference Sample 1. The burn time is 10 seconds longer and the self-burn time is shorter than 1 second.

Sample 3 can be compared to Sample 2 because it includes the same conventional fire retardant filler as the sample 2 at the same concentration and other fillers to improve flame resistance. The burning time of Sample 3 is 11 seconds longer compared to Sample 2. Thus, the use of aluminum oxide sub-micron increases combustion time significantly without significantly affecting self-burning time.

Mixing submicron aluminum oxide with treated montmorillonite and magnesium hydroxide can achieve even better performance. Samples 4 and 5 show that when compared to Samples 2 and 3, the burn time can be increased from 5 seconds to as high as 30 seconds, while the self burn time can be significantly reduced.

Thus, the present invention can provide a fire resistant composition as a material for power and / or telecommunication cables, in particular, which solves the problems of the prior art but is not expensive and the ability to withstand flame is significantly improved.

Claims (11)

A fire resistant composition for a power and / or communication cable comprising a polymer and aluminum oxide in the form of particles having an average diameter of 1 micrometer (μm) or less. The method of claim 1, The aluminum oxide particles are compositions, characterized in that the average diameter is 20 nanometers (nm) or less. The method according to claim 1 or 2, 1 wt.% To 80 wt.%, Preferably 2 wt.% To 20 wt.%, Of the aluminum oxide. The method according to any one of claims 1 to 3, The polymer is polyethylene, polypropylene, copolymer of ethylene and propylene (EPR), ethylene-propylene-diene trimer (EPDM), copolymer of ethylene and vinyl acetate (EVA), copolymer of ethylene and methyl acrylate (EMA ), Copolymers of ethylene and ethyl acrylate (EEA), copolymers of ethylene and butyl acrylate (EBA), copolymers of ethylene and octene, polymers based on ethylene, polymers based on polypropylene, imide poly Composition selected from the group consisting of ethers, thermoplastic polyurethanes, polyesters, polyamides, halogenated polymers, or mixtures thereof. The method according to any one of claims 1 to 4, A composition comprising at least one associated fire retardant filler. The method of claim 5, Each secondary fire retardant filler is a compound containing phosphorus such as organic or inorganic phosphate, a compound containing antimony such as antimony oxide, a metal hydroxide such as aluminum hydroxide and magnesium hydroxide, a compound based on boron such as borate, calcium, sodium Carbonates of IA and IIA alkali metals, such as carbonates of potassium or magnesium, and corresponding compounds based on tin such as hydroxide carbonates, tartarate and hydrostannates, melamine and derivatives thereof, such as melamine phosphate, formo Phyllosilicates such as phenolic resins, sepiolite, attapulgite, montmorilonite, illite, chlorite, kaolinite, mica and talc Compositions selected from the group comprising. The method according to claim 5 or 6, 1 wt.% To 80 wt.% Of said minor fire retardant filler. The method according to any one of claims 1 to 7, A composition comprising at least one additive selected from the group consisting of lubricants, plasticizers, temperature stabilizers, pigments, antioxidants, and ultraviolet stabilizers. A power and / or communication cable comprising at least one insulating sheath made of a fire resistant composition according to any one of the preceding claims. A power and / or communication cable comprising at least one protective sheath made of a fire resistant composition according to any of the preceding claims. A power and / or communication cable comprising at least one padding layer made of a fire resistant composition according to claim 1.