WO2013164328A1

WO2013164328A1 - Housing element for an electrical appliance and including a specific fire-resistant composition

Info

Publication number: WO2013164328A1
Application number: PCT/EP2013/058951
Authority: WO
Inventors: Maria Rosa CONTARDI; Mirko LUCIANI; Cécile VENET; Pierre Bardollet
Original assignee: Schneider Electric Industries Sas
Priority date: 2012-05-02
Filing date: 2013-04-30
Publication date: 2013-11-07
Also published as: FR2990323B1; FR2990323A1

Abstract

The present invention relates to a housing element made of a composite composition, said composition including a polymeric matrix including at least one polymer selected from among polyamides, polyterephtalates, and polypropylenes, in which a sepiolite filler constituting less than 10 wt % of the total weight of the composition and a compound belonging to the melamine cyanurate family are dispersed, the content of the latter in the composition being 1 to 5 wt % of the total weight of the composition.

Description

ELECTRICAL EQUIPMENT HOUSING ELEMENT COMPRISING A SPECIFIC FLAME RETARDANT

DESCRIPTION

TECHNICAL AREA

The invention relates to a housing element for electrical equipment comprising a flame retardant composite composition comprising an original combination of at least one specific thermoplastic polymer, at least one specific particulate filler and at least one specific flame retardant, said composition very favorable mechanical properties combined with excellent fireproof properties.

STATE OF THE PRIOR ART

The composite compositions based on at least one thermoplastic polymer are commonly used in the electrical industry because of the inherent properties of this type of polymer in terms of ease of processing and shaping, mechanical properties, low density and moderate costs, especially compared to more traditional materials such as metal, wool, wood or glass.

However, thermoplastic polymers, because of their organic nature, have a highly flammable character, which requires the use of flame retardants, so that they can be used in environments subject to high temperatures, as this is the case in electrical appliances. Indeed, the composite compositions used in electrical appliances must meet stringent standards for fire resistance, which standards are governed in particular by the IEC standards applicable in Europe, and in particular in France, such as:

-the IEC 60695-2-11 standard for finished products, which defines the required flammability performance GWFI (Glow Wire Flamability Index), which stands at 850 ° C for unattended continuous equipment or at 960 ° C for equipment placed under more stringent conditions; or

the standard IEC 60695-2-13, which defines the GWIT ignitability performance (corresponding to the English terminology Glow Wire Ignition

Temperature "), which must be at least 775 ° C.

Flame retardants commonly used and most effective are the halogenated flame retardants. However, these agents may be banned in the long term because they have disadvantages vis-à-vis the environment, because of their highly toxic, especially when they are subject to combustion.

Non-halogenated flame retardants frequently used are flame retardants belonging to the family of metal hydroxides (such as aluminum hydroxide and magnesium hydroxide), as is the case in the composite materials exemplified in US 2008/0093107 . Compared to agents Halogenated flame retardants, metal hydroxides release little fumes, when they are subject to combustion and are low in toxicity. On the other hand, the composite compositions comprising these agents have very poor mechanical properties, in particular a low mechanical strength and flexural modulus, which makes them unreliable for use in the electrical field.

Finally, the flame retardants, to fulfill their function, are very often incorporated at very high levels in the composite compositions, which contributes to degrade the mechanical properties of the latter and which can also generate pollution problems induced by the exudation of the flame retardant, when using the apparatus in which the compositions are incorporated.

The problems encountered in environmental terms for halogenated flame retardants can also be found with the thermoplastic polymers used in the constitution of the composite compositions.

This is particularly the case when the polymers belong to the family of polystyrenes, polyvinyl chloride, which, on the one hand, are dependent, for their production, on relatively polluting petroleum chemistry, and on the other hand , have recycling difficulties, once their use expires.

In view of the above-mentioned problems, the authors of the present invention set themselves the goal of developing a housing element for electrical equipment based on a specific composition that satisfies the following specificities:

- Flame retardant properties without the use of halogenated flame retardants or agents belonging to the family of metal hydroxides;

- mechanical properties that are not degraded in favor of fireproof properties;

the absence of pollution related to the exudation of the flame retardant when using the composition or the part.

This object has been achieved by an electrical equipment housing member comprising a flame retardant composite composition comprising an original combination of at least one specific thermoplastic polymer, at least one specific particulate filler and at least one specific flame retardant.

STATEMENT OF THE INVENTION

Thus, the invention relates to a housing element for electrical equipment comprising a composite composition comprising a polymer matrix comprising at least one polymer chosen from polyamides and polyterephthalates, in which a sepiolite type filler is dispersed in a lower content. at 10% by weight relative to the total mass of the composition and a compound belonging to the family of melamine cyanurates, the latter being included in the composition at a content ranging from 1 to 5% by weight relative to the total mass of the composition. Polyamide is understood to mean a polymer of the polycondensate type, in which the repeating units are linked via amide groups, this type of polymer possibly being homopolymers (ie polymers comprising one and the same type of repeating units) or copolymers (ie polymers comprising several types of repeating units).

Among the polyamides particularly suitable for the invention, mention may be made of linear polyamides conventionally resulting from a polycondensation of a dicarboxylic acid comprising from 4 to 12 carbon atoms with a diamine comprising from 4 to 14 carbon atoms or else resulting from a ring-opening polycondensation of lactam compounds.

Polyamides corresponding to this definition can be, in particular:

polyamides 6, namely polyamides comprising a sequence of repeating units of formula (I) below:

(D

polyamides 6/66, namely polyamides comprising a sequence of repeating units of formula (I) below:

(I)

repetitive units of the following formula (II)

(II)

By polyterephthalate is meant a polymer of the polycondensate type conventionally resulting from a polycondensation of terephthalic acid and a polyol compound.

In particular, mention may be made of polyterephthalates conventionally resulting from a polycondensation of terephthalic acid with a diol comprising from 2 to 10 carbon atoms.

Polyterephthalts corresponding to this definition may be, in particular, a poly (butylene terephthalate) (known by the abbreviation PBT) characterized by a sequence of repeating units of formula III) as follows:

(III) Whether for polyamides or polyterephthalates, these polymers are particularly useful for entering the composition of the invention, insofar as they have the following characteristics:

they are thermoplastic, which makes the composition comprising them particularly malleable and able to constitute pieces of various shapes;

they are devoid of halogen atoms, which is compatible with the environmental rules in force, and in particular with the European directive Reach;

they have good mechanical properties at high temperatures and at high stresses;

they are easily available because they are produced in very large tonnages, which makes them particularly interesting in terms of costs unlike polymers of the polystyrene or polyvinyl chloride type.

As mentioned above, the polymer (s) present in the composition constitute a polymeric matrix, which means, in other words, that they are present in a majority mass proportion relative to the other constituents of the composition which are sepiolite and the compound belonging to the family of melamine cyanurates.

Advantageously, the matrix represents from 80 to 85% by weight relative to the total mass of the composition. The sepiolite used as a filler of the abovementioned polymeric matrix is a mineral belonging to the family of clays of fibrous structure, and from a composition point of view, to the family of hydrous magnesium silicates (of ideal Sii ₂ formula Mg ₈ 0 ₃ o (OH) ₄ (OH ₂ ) 8H ₂ O) in the form of needle-shaped particles It is also characterized by a particularly high active surface area, for example greater than 300 m ² / g and a very high density of silanol groups (-SiOH), which results in the very hydrophilic nature of this type of clays. Particles combine to form porous aggregates with an extensive capillary network, which explains both the high porosity and the light mass of sepiolite. Finally, in contact with water or other liquids, the particles do not disintegrate and form a suspension comprising a structure composed of said particles in an interpenetrating random network, which contributes to trapping the liquids, which leads to the increase the viscosity of the suspension.

All of its properties contribute to conferring on the compositions of the invention comprising sepiolite, provided that it is present at a content of less than 10% by weight, the following characteristics:

flame-retardant properties by viscous crushing of the flame;

an improvement of the barrier properties of the polymeric matrix, in particular by the capacity sepiolites to be a solution to moisture recovery problems.

Sepiolite, in the context of the invention, is advantageously in the form of nanoparticles preferably having an average particle diameter ranging from 0.1 to 0.2 micrometres and a fiber length ranging from 3 to 30. micrometers.

More specifically, the sepiolite used in the context of the invention may be a sepiolite sold under the name CD1 by the company Toisa, this sepiolite.

As mentioned above, the sepiolite is present in a content of less than 10 ~ 6 by weight relative to the total mass of the composition and, preferably, is present in a content ranging from 1 to 9%, more preferably from 3 to 10% by weight. at 9% by weight relative to the total mass of the composition, for example. Even more specifically, the sepiolite may be present in a content ranging from 3 to 7 ~ 6 by weight relative to the total mass of the composition, for example 5% by weight relative to the total mass of the composition.

In addition to the polymeric matrix and the sepiolite, the composition comprises a compound belonging to the family of melamine cyanurates with a mass content ranging from 1 to 5% by weight relative to the total mass of the composition, more specifically from 2 to 4% in mass relative to the total mass of the composition. For example, the aforementioned compound may be present in a mass content of 1.5%, 2%, 3%, 4% or 5% by weight relative to the total mass of the composition.

At such levels, the authors have been able to demonstrate that this type of compound incorporated in a composition comprising a specific polymeric matrix (as defined above) and sepiolite (as defined above), makes it possible to obtain in terms of fire-extinguishing properties properties similar to those obtained with other compositions in which this type of compound is incorporated in much higher concentrations (for example, of the order of 20% by mass or more ).

Thus, the addition of this type of compounds to levels as specified above is not to the detriment of the mechanical properties of the composition, which makes it possible to dispense with the incorporation of glass fibers into it. to overcome the degradation of mechanical properties by introducing the same type of compounds in higher levels. The fact of not having to resort to glass fibers to exacerbate the mechanical properties also allows access to an isotropic composition, which, during molding, will exhibit a uniform shrinkage, which facilitates the design of molds intended to accommodate this type of composition.

Moreover, this type of compounds does not contain halogen atoms, which is important to be in phase with the REACH European directives proscribing the use of halogenated compounds. A specific composition intended to enter into the constitution of the housing elements of the invention is a composition comprising:

a polymeric matrix based on a polyamide, more specifically a polyamide 6;

a sepiolite present in a content of 5% by weight relative to the total mass of the composition;

a compound of the melamine cyanurate type present in a content of 3% by weight relative to the total mass of the composition.

These compositions can be manufactured simply by incorporation into a polymeric matrix according to the invention of the sepiolite and the melamine cyanurate type compound in the desired proportions.

These compositions are original in that the three specific ingredients mentioned above are combined, in particular in specific proportions, which gives the latter the following properties:

fire resistance properties over temperature ranges in accordance with the severe standards of electrotechnical applications (the compositions of the invention responding favorably to the "Glow Wire Test" test for temperatures ranging from 750 ° C. to 960 ° C.);

mechanical properties, which are not diminished by the addition of a compound of the melamine cyanurate type and which do not require the addition of glass fibers;

-low density -chemical properties that meet the criteria imposed by the European Reach Directive, in particular because the ingredients do not contain halogen atoms and thus do not generate toxic gases.

The invention also relates to electrical equipment comprising at least one housing comprising at least one housing element as defined above.

More specifically, it may be an electrical equipment, for example, low-voltage, comprising an electrical circuit housed in said housing, such as a power outlet, a circuit breaker, an electrical cabinet, an electrical box, a emergency lighting, an electrical sensor, an inverter, a timer, a dimmer or motion detector (s), preferably a circuit breaker. More preferably, it may be a circuit breaker housing (or contactor) low-voltage, especially monopolar.

It may also be a switchgear type electrical apparatus comprising two movable contacts relative to each other between an open position and a closed position, said contacts being housed in said housing.

The housing members may be manufactured by various methods of shaping plastics compositions with, preferably, molding methods. Indeed, as already mentioned, the compositions of the invention, because of the absence of glass fibers, are compositions having a large isotropy, perfectly suited to shaping by incorporation into a mold, the withdrawal of the composition being perfectly homogeneous. Moreover, this formatting process is simple to implement because it has only one step, which is also of significant interest in terms of manufacturing costs.

Other features and advantages of the invention will emerge from the additional description which follows.

It goes without saying, however, that this additional description is only given as an illustration of the subject of the invention and does not constitute in any way a limitation of this object.

DETAILED DESCRIPTION OF A PARTICULAR EMBODIMENT EXAMPLE 1

In this example, the purpose of which is to describe the intrinsic properties of the compositions of the invention in terms of fire behavior, incandescent wire tests have been carried out (these tests being also referred to as "Glow wire test"). ) prepared from a composition comprising a polyamide-6 polymeric matrix, which is available from Rhodia, sepiolite available from the company Toisa (up to 5% by weight relative to the total mass of the composition) and melamine cyanurate available from the company Budenheim (up to 3% by weight relative to the total mass of the composition).

These tests consist in applying to the composition an incandescent wire respectively having a temperature of 750 ° C., 850 ° C. and 960 ° C. for 30 seconds. If, after removing the wire, the flames go out in less than 30 seconds, the composition will be considered fireproof.

The incandescent wire tests are conclusive for temperatures of 750 ° C., 850 ° C. and 960 ° C., respectively.

By way of comparison, for a test piece of the same size made with a composition comprising only, as polymer matrix, polyamide 6 and sepiolite (at a level of 5% by mass relative to the total mass of the composition), the tests carried out incandescent failed for a temperature of 750 ° C.

This helps to demonstrate that the addition of melamine cyanurate in a limited amount (in this case, 3% by weight, in our case) contributes greatly to improving the flame retardancy properties of the composition.

The test pieces made from the composition of the invention were also subjected to mechanical tests, from which the following properties appeared:

a Young's modulus (in MPa) of 4450 ± 76; and -an elongation at break (ΘΠ%) of

6.6 ± 0.4.

By way of comparison, test pieces of the same dimensions made from a composition comprising only, as a polymeric matrix, polyamide 6 and sepiolite (at a level of 7% by weight relative to the total mass of the composition), exhibit a Young's modulus (in MPa) of 4714 ± 123 and an elongation at break (ΘΠ%) of 5.4 ± 0.14.

It follows therefore that the addition of melamine cyanurate in the proportions claimed does not impair the mechanical properties of the composition or even improve them, which can be likened to a synergistic effect.

EXAMPLE 2

In this example, incandescent wire tests were carried out with a housing of a residential circuit breaker of the C60 type, this case being made with a composition comprising a polymeric matrix of polyamide-6, which is available from Rhodia. sepiolite available from the company Toisa (up to 5% by weight relative to the total weight of the composition) and melamine cyanurate available from the company Budenheim for 3 ~ 6 by weight relative to the total mass of the composition. More specifically, the casing was made by molding said composition for a cycle time of 17 seconds. carrying the composition at 250 ° C and the mold at 73 ° C under a maximum injection pressure of 1250 bar.

The glow wire tests are all the more conclusive for temperatures of 750 ° C, 850 ° C and 960 ° C, respectively, that the flame went out immediately after removal of the wire.

The aforementioned composition is therefore perfectly suitable for producing housing elements.

Claims

A housing element for electrical equipment comprising a composite composition comprising a polymer matrix comprising at least one polymer chosen from polyamides and polyterephthalates, in which a sepiolite-type filler is dispersed in a content of less than 10% by weight relative to to the total mass of the composition and a compound belonging to the family of melamine cyanurates, the latter being included in the composition at a content ranging from 1 to 5% by weight relative to the total mass of the composition.

Housing element according to claim 1, in which the polyamides are linear polyamides resulting from a polycondensation of a dicarboxylic acid comprising from 4 to 12 carbon atoms with a diamine comprising from 4 to 14 carbon atoms or else resulting from a ring-opening polycondensation of lactam compounds.

3. Housing element according to claim 1 or 2, wherein the polyamides are chosen from:

(I)

and

(I)

repetitive units of the following formula (II)

(II)

4. Housing element according to claim 1, wherein the polyterephthalates are chosen from poly (butylene terephthalate) characterized by a series of repeating units of formula (III) below:

(III) 5. Housing element according to any one of the preceding claims, wherein the sepiolite is present in a content ranging from 3 to 9% by weight relative to the total mass of the composition.

6. Housing element according to any one of the preceding claims, wherein the sepiolite is present in a content of 5 ~ 6 by weight relative to the total mass of the composition.

7. Housing element according to any one of the preceding claims, wherein the compound belonging to the family of melamine cyanurates is present in a mass content ranging from 2 to 4% by weight relative to the total mass of the composition.

8. Housing element according to any one of the preceding claims, wherein the compound belonging to the family of melamine cyanurates is present in a mass content of 3% by weight relative to the total mass of the composition.

The housing member of any one of the preceding claims, wherein the composition is a composition comprising:

a polymeric matrix based on a polyamide, more specifically a polyamide 6;

Electrical apparatus comprising at least one housing comprising at least one housing element as defined according to any one of claims 1 to 9.

11. Electrical apparatus according to claim 10, comprising an electrical circuit housed in said housing.

12. Electrical apparatus according to claim 11, which is a circuit breaker, an electrical cabinet, an electrical box, a security light, an electrical sensor, an inverter, a timer, a dimmer or a motion detector (s).

An electrical switchgear according to claim 10 which is a low voltage switchgear comprising two movable contacts relatively to each other between an open position and a switchgear. closed position, said contacts being housed in said housing.