ITMI20111982A1 - COMPOSITIONS BASED ON SELF-EXTENDING EXPANDING VINYLAROMATIC POLYMERS - Google Patents

Description

"COMPOSITIONS BASED ON VINYLAROMATIC POLYMERS

EXPANDABLE SELF-EXTINGUISHINGâ €

The present invention relates to compositions of self-extinguishing expandable vinylaromatic polymers and / or copolymers with improved thermal stability. The present invention also relates to a process for the preparation of said compositions. More particularly, the present invention relates to a composition based on expandable polymers and / or copolymers of styrene which contain a flame retardant compound with improved thermal stability.

In the present patent application, all the operating conditions indicated in the text must be understood as preferred conditions even if not expressly stated. Expandable vinyl aromatic polymers and / or copolymers, indicated in the text as expandable vinyl aromatic polymers, and among these, in particular, the polymer and / or copolymer of expandable styrene (EPS), are known products and have been used for a long time to prepare articles that can be used in various application sectors, of these, one of the most important is that of thermal insulation.

These articles are obtained by first swelling (expanding) in a closed environment the polymer granules impregnated with a low-boiling fluid, for example an aliphatic hydrocarbon such as pentane or hexane, and then welding the swollen particles, charged to the € ™ inside a mold, through the simultaneous effect of pressure and temperature. The swelling of the particles is generally achieved with steam, or other gas, maintained at a temperature slightly higher than the glass transition temperature (Tg) of the polymer.

As it is well known among operators in the sector, expandable vinyl aromatic polymers and, among these, expandable polystyrene, are presented in the form of granules impregnated with the blowing agent and with a diameter of the granules generally ranging from 0.5 to 1 , 5 mm. A number of additives aimed at improving the performance of the granules themselves and / or of the articles printed by them are also dispersed in a homogeneous way inside the granules.

Among the additives incorporated into the granules are flame retardant additives. The additives introduced into the polymer as flame propagation retardants consist of at least a brominated organic product, for example hexabromocyclododecane, and a synergistic agent comprising in the molecule at least one â € “O-O- or â €“ C-C- thermolabile bond , for example dicumyl peroxide or bicumil.

Patent applications WO 2008/030399 and WO 2009/029290 relate to aromatic alkenyl polymeric foams containing a flame retardant and a stabilizer. WO 2008/030399 and WO 2009/029290 have the purpose of protecting the flame retardant from extensive decomposition during extrusion processes, and the purpose of preventing the formation of surface defects on the polymer foam, such as lines, cuts, cracks and other irregularities.

To solve the first problem WO 2008/030399 and WO 2009/029290 add to the polymeric composition a stabilizing additive containing at least one organotin allylophilic or dienophilic compound selected from the group consisting of alkyltin thioglycolates, alkyl tin mercaptopropionates, alkyl tin mercaptides, alkyl tin maleates and alkyl tin di (alkyl maleates), in which the alkyl is selected from the methyl, butyl and octyl groups. The stabilizer is present in concentrations up to 30% by weight with respect to the weight of the brominated flame retardant. To solve the second problem WO 2008/030399 and WO 2009/029290 add a blowing agent including water to the polymeric composition. The blowing agent is therefore always a mixture of water and at least one compound selected from hydrocarbons, hydrofluorocarbons and fluorocarbons.

It is known in the art that there is an objective difficulty in incorporating water into the vinyl aromatic polymer, and that its action in said polymers, as an expanding agent, is less effective.

Patent application WO 2005/103133 relates to an additive which improves the thermal stability of a flame retardant, which contains bromide atoms directly attached to one or more aliphatic or cycle aliphatic carbon atoms; furthermore, said patent application relates to the use of the flame retardant additive in combination with expandable vinyl aromatic polymers. WO 2005/103133 aims to improve the thermal stability of brominated flame retardants without having negative impacts from an environmental point of view.

For this purpose WO 2005/103133 proposes a flame retardant additive which comprises:

a) at least one flame retardant containing a bromide which has at least 4 carbon atoms, which has a bromide content of at least 40% by weight and which has at least 2 bromide atoms directly attached to one or more aliphatic carbon atoms; or cycloaliphatic;

b) at least one thermal stabilizer comprising an acrylate or methacrylate thermoplastic polymer which melts in the range between 50 ° C and 150 ° C.

Preferably WO 2005/103133 discloses a polymeric composition which comprises:

i) at least one expandable styrenic thermoplastic polymer (EPS);

(ii) at least one flame retardant containing a bromide which has at least 4 carbon atoms, which has a bromide content of at least 40% by weight and which has at least 2 bromide atoms directly attached to one or more aliphatic carbon atoms; or cycloaliphatic;

iii) at least one thermal stabilizer that contains an acrylate or methacrylate thermoplastic polymer, which melts in the range between 50 ° C and 150 ° C; iv) at least one component chosen from:

a) a zeolite

b) a hydrotalcite,

c) a stabilizer containing tin such as dimethyltin bis (isooctylmercaptoacetate) and the analogous derivatives of dibutyltin and di-n-octytin, alkyltin mercaptoalkanoates such as dibutyltin-β-mercaptopropionate, or d) a combination of two components selected from a ) -c).

EP 1092 748 relates to an additive which improves the thermal stability of a brominated flame retardant in thermoplastic polymers, such as expandable polystyrene or polystyrene foams.

EP 1092 748 has the purpose of increasing the thermal stability of certain brominated flame retardants making it more effective also from a cost point of view.

The technical solution adopted by EP 1092 748 is a stabilizing additive that contains a mixture formed by at least one mercaptoalkanoate alkyltin (B), at least one zeolite (C) and at least one organ brominated flame retardant (A) chosen from:

∗ a flame retardant compound having a plurality of bromine atoms directly attached to an aliphatic loop ring,

∗ bis (2,3-dibromopropyl ether) of tetrabromobisphenol-A,

∗ bis (2,3-dibromopropylether of tetrabromobisphenol-S. Said mixture is composed of 0.01-0.08 parts by weight of B per parts by weight of A, and 0.01-0.35 parts by weight of C per parts by weight of A.

Patent application GB 1,020,291 relates to organo-tin compounds suitable as stabilizers against the thermal degradation of synthetic resins containing chlorine such as vinyl chloride polymers and copolymers.

GB 1,020,291 aims to counteract the thermal degradation of synthetic resins containing chlorine, such as vinyl chloride polymers, by means of a composition that contains vinyl chloride polymers (PVC) and organo-tin alkyl compounds.

Patent application GB 743,304 relates to organic derivatives of tetravalent tin, including alkyltin mercapto esters, which can be used as stabilizers of high molecular weight halogenated organic compounds. Specifically, said derivatives are used as stabilizers of polyvinyl resins containing chlorides. GB 743,304 discloses the compounds dinbutyltin-S, Sâ € ™ -di (mercapto ethanol) adipate and monoisopropyltin dimercapto ethanol terephthalate.

WO 2009/138474 relates to high purity mono-alkyl tin and their use as stabilizers of chlorine-containing polymers and copolymers. WO 2009/138474 aims to stabilize chlorine-containing polymers using compounds with improved toxicological properties. and specifically a polymeric composition containing a chlorinated polymer (PVC) and a high purity mono-alkyl tin mercaptoester, or a mixture containing a monoalkyl tin as major component and a di-alkyl tin and / or tri-alkyl tin as minor components , as they are toxic. In particular WO 2009/138474 discloses the compounds of formula RSn (T) 3, R2Sn (T) 2, R3Sn (T) where R is a monoalkyl group and T can also be a mercapto ester. Specific compounds disclosed are mono-methyltin [tris (2-ethylhexylmercaptoacetate)], mono-n-butyltin [tris (2-ethylxylmercaptoacetate)], mono-n-octyltin [tris (2-ethylxylmercaptoacetate)]. The compounds described in WO 2009/138474 result in conferring thermal stability to the chlorinated polymers and copolymers with which they are mixed.

Processes for the preparation of expandable vinylaromatic polymers, such as expandable polystyrene, in bulk or continuous bulk are known. In both of these processes the molten polymer mass is obtained either by melting the pre-formed polymer granule or by directly using the molten polymer mass as it comes from the production process and / or from the devolatilizer and is fed to a series of mixers in which mixing with the blowing agent and with the required additives, for example the brominated flame retardant additive and the synergic. The mixing phase of the additives requires quite long times, to ensure a homogeneous dispersion of the same in the melted polymeric mass. Furthermore, in order to have conditions of fluidity and, therefore, of optimal miscibility, it is necessary to keep the melt at a high temperature, for example between 170 ° C and 300 ° C. Under these conditions some additives, and among them the brominated organic compound, tend to degrade and give rise to unwanted by-products which remain incorporated in the polymeric mass. The brominated organic compound, in particular, tends to release bromine or hydrobromic acid which not only can create environmental problems, but can damage / corrode the mixing equipment. Furthermore, the decomposition of the brominated compound reduces the self-extinguishing properties of the finished material, forcing manufacturers to increase the amount of this additive in their formulations.

The Applicant has now found a further additive to be added to an expandable polymer composition which is in the molten state and which includes a vinyl aromatic polymer and / or copolymer. Said additive is able to inhibit the degradation of the brominated organic compounds present in the polymeric composition, when they are subjected to high temperatures, without creating a worsening of the chemical-physical properties of the resulting expandable granules. The present invention therefore relates to a composition based on self-extinguishing expandable vinylaromatic polymers which comprises:

to. a polymer obtained by polymerization of one or more vinyl aromatic monomers present in an amount ranging from 50% to 100% by weight, and a monomer copolymerizable with the vinyl aromatic monomers, homogeneously incorporated in the polymer in a quantity ranging from 0% to 50% by weight;

b. at least one expanding system in a quantity ranging from 3% to 10% by weight, calculated on the polymer (a);

c. at least one flame retardant additive in a quantity ranging from 0.005% to 5% by weight, calculated on the polymer (a), and containing at least 30% by weight of bromine, a quantity calculated with respect to the flame retardant additive;

d. at least one synergistic additive containing a C-C or C-O-O-C thermolabile bond in an amount ranging from 0.001% to 2% by weight, calculated on the polymer (a); and and. at least one heat additive selected from a carbon black, a graphite, a coke carbon in particle form and their mixtures;

said composition is characterized in that it contains a stabilizing additive which includes at least one alkyl tin mercapto ester having a purity greater than or equal to 95%.

Compounds containing bromine, such as hexabromocyclododecane, which confer self-extinguishing properties to polymers, when subjected to high temperatures (above 180 ° C), can release hydrobromic acid following thermal decomposition processes. The developed acid corrodes the polymer processing machines and the decomposition of the brominated compound reduces the self-extinguishing properties of the material, forcing the manufacturer to increase the amount of brominated additive in the formulation. Surprisingly, by using the stabilized additive of the described and claimed flame retardant, a marked stabilizing effect was observed with respect to the organobrominated compounds added to the polymer as flame retardants. In particular, a significant lengthening of the release times of HBr was observed, which is released due to the thermal degradation of the organ brominated agent and a significant reduction in the quantity of acid produced. This aspect is very important as it allows to drastically reduce the corrosion phenomena on the production plants, for example of expandable polystyrene (EPS), during the preparation of products with self-extinguishing properties.

Detailed description.

The object of the present invention is a composition based on self-extinguishing expandable vinyl aromatic polymers which comprises:

to. a polymer obtained by polymerization of one or more vinyl aromatic monomers present in an amount ranging from 50% to 100% by weight, and a monomer copolymerizable with the vinyl aromatic monomers, homogeneously incorporated in the polymer in a quantity ranging from 0% to 50% by weight;

b. at least one expanding system in a quantity ranging from 3% to 10% by weight, calculated on the polymer (a);

c. at least one flame retardant additive in a quantity ranging from 0.005% to 5% by weight, calculated on the polymer (a), and containing at least 30% by weight of bromine, a quantity calculated with respect to the flame retardant additive;

d. at least one synergistic additive containing a C-C or C-O-O-C thermolabile bond in an amount ranging from 0.001% to 2% by weight, calculated on the polymer (a); and and. at least one heat additive selected from a carbon black, a graphite, a coke carbon in particle form and their mixtures;

said composition is characterized in that it contains a stabilizing additive which includes at least one alkyl tin mercapto ester having a purity greater than or equal to 95%.

The object of the present invention is also an expandable composition based on vinyl aromatic polymers having self-extinguishing properties, said composition comprising:

A. a polymer obtained by polymerization of one or more vinyl aromatic monomers present in quantities ranging from 50% to 100% by weight, and a monomer copolymerizable with vinyl aromatic monomers, homogeneously incorporated into the polymer in quantities ranging from 0% to 50% by weight ;

B. an expanding system in a quantity ranging from 3% to 10% by weight, calculated on the polymer (A);

C. a flame retardant additive in a quantity ranging from 0.005% to 5% by weight, calculated on the polymer (A), and containing at least 30% by weight of bromine, a quantity calculated with respect to the flame retardant additive;

D. a synergistic additive containing a C-C or C-O-O-C thermolabile bond in an amount ranging from 0.001% to 2% by weight, calculated on the polymer (A);

said composition is characterized in that it contains a stabilizing additive which includes at least one mono alkyl tin mercapto ester having a purity greater than or equal to 95%.

The stabilizing additives object of the present invention are capable of inhibiting the thermal degradation of the flame retardant (or flame retardant additive) even in the presence of the synergist.

Preferably, the stabilizing additive is present in an amount ranging from 0.001% by weight to 3% by weight, more preferably in a quantity ranging from 0.01 to 1% by weight, calculated with respect to the polymer (a) or (A) of the compositions described and claimed.

Preferably the stabilizer comprises at least one mono alkyl tin mercapto ester, more preferably a mono alkyl tin acetate, and even more preferably the stabilizing additive is selected from mono-octytin tris alkyl mercaptoacetate and mono-octyltin tris (2-ethylhexyl mercaptoacetate, and their blends.

In the compositions object of the present invention the alkyl tin mercapto esters compounds, and in particular the mono alkyl tin mercapto esters compounds, must have purity higher than 95%, and preferably higher than 99%.

The high degree of purity allows, in fact, to classify these stabilizers as harmful, unlike conventional stabilizers which are classified as toxic, such as for example tin dibutyl maleate. Therefore, the stabilized flame-retardant composition, object of the present invention, has a better environmental impact than known stabilized flame-retardant compositions.

From the comparison of the safety data sheet (MSDS) of the stabilizing additives monoalkyl tin mercapto esters, with that of the tin-based stabilizers traditionally used in the polymeric compositions (dibutyl tin maleate - Baerostab MS produced by Baerlocher), the advantages are evident, from a toxicological point of view, related to their use. For example, if we consider the mono-octyltin tris compound (2-ethylhexyl mercaptoacetate), known as Thermolite 895 and produced by ARKEMA, in point 2 of the SAFETY DATA SHEET (Hazard Identification - Classification - Regulation EC N ° 1272/2008) this is classified as Xi; R38 / N; R50 / 53. Always according to the same protocol, the Baerostab MS is classified as T / N; R60, R61, R22, R23, R36, R48 / 25, R68, R50 / 53. Therefore mono-octyltin tris (2-ethylhexyl mercaptoacetate) has a better safety profile than a traditional additive such as dibutyl tin maleate.

The terms vinylaromatic polymers and / or (co) polymers, in the present text, refer to polymeric products having a weight average molecular weight (MW) between 50,000 and 300,000, preferably between 70,000 and 220,000. Said vinyl aromatic polymers can be obtained by polymerizing a mixture of monomers comprising from 50% to 100% by weight, preferably from 75% to 98% by weight, of one or more vinyl aromatic monomers, and at least one monomer copolymerizable with the vinyl aromatic monomers, homogeneously incorporated in the polymer in an amount ranging from 0% to 50% by weight, preferably from 2% to 25% by weight.

The vinyl aromatic monomers can be chosen from those that respond to the following general formula (I):

C R C H2

(THE)

(Y) no

in which R is a hydrogen or a methyl group, n is zero or an integer between 1 and 5 and Y a halogen, preferably chosen from chlorine or bromine, or an alkyl or alkoxy radical having from 1 to 4 carbon atoms . Examples of vinyl aromatic monomers having the general formula (I) are: styrene, Î ± -methylstyrene, methylstyrene, ethylstyrene, butylstyrene, dimethylstyrene, mono-, di-, tri-, tetra- and penta-chlorostyrene, bromo-styrene, methoxy- styrene, acetoxy-styrene. Preferred vinyl aromatic monomers are styrene and Î ± -methylstyrene.

The vinyl aromatic monomers of general formula (I) can be used alone or in a mixture of up to 50% by weight, preferably from 2% to 25% by weight, with other copolymerizable monomers. Examples of such monomers are (meth) acrylic acid, C1-C4 alkyl esters of (meth) acrylic acid such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, isopropyl acrylate, butyl acrylate, amides and nitriles of (Meth) acrylic acid such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, butadiene, ethylene, divinylbenzene, maleic anhydride. Preferred copolymerizable monomers are acrylonitrile and methyl methacrylate.

Preferred flame retardants for the present invention are aliphatic, cycloaliphatic, aromatic compounds, for example C6-C18, brominated compounds such as hexabromocyclododecane (EBCD), pentabromomonchlorocyclohexane and pentabromophenyl allyl ether, bis-tetrabromo bisphenol-A allyl ether (known commercially such as â € œChemtura BE51â € produced by the Chemtura company), Tetrabromobisphenol A bis (2,3 dibromopropyl ether) (known commercially as â € œChemtura PE-68â €). comprised from 0.005% by weight to 5% by weight, preferably comprised from 0.1% by weight to 4% by weight, an amount calculated with respect to the polymer (a) or (A) of the described and claimed compositions.

The flame retardant additives used for the purpose of the present invention contain at least 30% by weight of bromine, preferably between 50% and 90% by weight of bromine.

Preferred synergistic additives used in the present invention can be selected from dicumyl peroxide (DCP), cumene hydroperoxide, 3,4-dimethyl-3,4-diphenyl hexane, 2,3-dimethyl-2,3-diphenyl butane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxinonane and poly (1,4-diisopropylbenzene). Said synergistic additives are used in the present invention in preferred amounts ranging from 0.01% to 1% by weight, quantities calculated with respect to the polymer (a) or (A) of the described and claimed compositions.

Any blowing agent capable of being incorporated into a polymer can be employed in the present invention. Preferably, the foaming agents can be liquid substances with a boiling point which varies between 10 ° C and 80 ° C, preferably between 20 ° C and 60 ° C. Preferred blowing agents are aliphatic or cycloaliphatic hydrocarbons containing from 3 to 6 carbon atoms, such as n-pentane, iso-pentane, cyclopentane or their mixtures; halogenated derivatives of aliphatic hydrocarbons containing from 1 to 3 carbon atoms such as dichlorodifluoromethane, 1,2,2-trifluoroethane and 1,1,2-trifluoroethane; carbon dioxide.

The expanding system is present in an amount ranging from 3% to 10% by weight, an amount calculated with respect to the polymer (a) or (A) of the described and claimed compositions.

In order to favor the retention of the blowing agent in the polymer (a) or (A), it is possible to use additives capable of forming bonds both of the weak type (for example hydrogen bridges) and of the strong type (for example acid-base adducts) with the expanding agent. Preferably said additives are selected from methyl alcohol, isopropyl alcohol, dioctyl phthalate, dimethyl carbonate, derivatives containing an amino group. The heat additive can be chosen from a carbon black, a graphite, a coke carbon in particle form and their mixtures.

Carbon black can be present in an amount ranging from 0.01% to 20% by weight, preferably between 0.05% and 20% by weight, more preferably between 0.1% and 10% by weight, said amount being calculated on the polymer (a) or (A) of the described and claimed compositions. Graphite can be present in an amount ranging from 0.01% to 20% by weight, preferably between 0.05% and 8% by weight, more preferably between 0.1% and 10% by weight, quantity calculated on the polymer (a ) or (A) of the compositions described and claimed. The coking carbon can be present in an amount ranging from 0.01% to 20% by weight, more preferably between 0.1% and 10% by weight by weight calculated on the polymer (a) or (A) of the described and claimed compositions.

Preferably, carbon black has an average diameter (d50), measured by a laser granulometer, which varies from 30 nm to 1000 nm. Graphite can be chosen from natural, synthetic, expanded, expandable graphite, and their mixtures. The graphite particles can have a maximum size (d50), measured with a laser granulometer, which varies from 0.05 µm to 100 µm, preferably from 1 µm to 8 µm, with a surface area of 5-30 m <2 > / g, measured according to ASTM D-3037-89 (BET). The carbon coke is in particle form with an average diameter (d50) of the particles ranging from 0.5 µm to 100 µm, preferably between 2 µm and 8 µm, and a surface area ranging from 5 m <2> / g to 200 m <2> / g, preferably from 8 m <2> / g to 50 m <2> / g, measured according to ASTM D-3037-89 (BET).

When the expandable compositions object of the present invention contain a heat additive then it is possible to obtain expanded granules with reduced density and improved thermal insulation capacity. The manufactured articles containing said compositions and precisely containing 5% of calcined coke 4023, have a thermal conductivity of 30.5 mW / m * K, at a density of 16 g / l. Traditional artifacts, devoid of athermal charges, have a thermal conductivity at a density of 16 g / l of 38 mW / m * K (measured according to the ISO 8301 method).

Further conventional additives can be added to the compositions object of the present invention, such as the additives generally used with traditional vinyl aromatic polymers such as pigments, stabilizing agents, antistatic agents and release agents.

A further object of the present invention is a process for preparing in continuous mass the composition, described and claimed in the present text, based on self-extinguishing expandable vinyl aromatic polymers which contains an athermal additive and at least one alkyl tin mercapto ester of purity higher than 95%. This procedure includes the following steps:

i) add to a vinyl aromatic polymer and / or (co) polymer in granules or already in the molten state, with average molecular weight between 50,000 and 300,000, at least one flame retardant additive (c), at least one synergistic additive (d), at least one heat additive (e) and at least one flame retardant stabilizer additive including at least one alkyl tin mercapto ester;

ii) if the vinyl aromatic polymer and / or (co) polymer is in granules, heat said polymer and / or (co) polymer to a temperature above its melting point;

iii) incorporating the expanding system (b) into the melted polymer, before extrusion and through a spinneret, thus obtaining the composition based on self-extinguishing expandable vinylaromatic polymers.

A further object of the present invention is a process for preparing in continuous mass the composition, described and claimed in the present text, based on self-extinguishing expandable vinyl aromatic polymers containing at least one monolachyl tin mercapto ester of purity greater than or equal to 95%. This procedure includes the following steps:

i) add to a vinyl aromatic polymer and / or (co) polymer in granules or already in the molten state, with average molecular weight between 50,000 and 300,000, at least one flame retardant additive (C), at least one synergistic additive (D) and at least one flame retardant stabilizer additive which includes a mono alkyl tin mercapto ester having purity greater than or equal to 95%;

ii) if the vinyl aromatic polymer and / or (co) polymer is in granules, heat said polymer and / or (co) polymer to a temperature above its melting point;

iii) incorporating in the melted polymer, before extrusion and through a spinneret, the expanding system (B) thus obtaining the composition based on self-extinguishing expansible vinylaromatic polymers.

Once obtained, the compositions object of the present invention can be mixed by means of static or dynamic elements, and granulated in a device which comprises a die, a cutting chamber and a cutting system.

During the step of adding the blowing agent further conventional additives can be incorporated.

The flame retardant additive is added in quantities ranging from 0.005% to 5% by weight, calculated on the polymer (a) or (A) of the compositions object of the present invention, and contains at least 30% by weight, preferably 50% 90% by weight of bromine. The synergistic additive of the flame retardant additive contains a thermolabile bond C-C or C-O-O-C; said additive is added in quantities ranging from 0.001% to 2% by weight, calculated on the polymer (a) or (A) of the compositions object of the present invention.

According to the processes object of the present invention, step (i) can be carried out by feeding the already formed polymeric granule, possibly mixed with processing waste, into an extruder. Here the individual components are mixed and, subsequently, the polymeric part is melted and we proceed with the addition of the additives and the blowing agent. Alternatively, it is possible to use the polymer already in the molten state that comes directly from the polymerization plant (solution process), in particular from the devolatilization unit. The melted polymer is fed to suitable devices, for example an extruder or a static mixer, where it is mixed with all the additives and then with the blowing agent and, therefore, is extruded to give the expandable granulate object of the present invention.

At the end of the granulation it is possible to obtain spherical expandable granules (pearls) with an average diameter ranging from 0.2 mm to 2 mm. The expanded beads, once sintered, allow to obtain expanded articles with a density between 5 g / l and 50 g / l, preferably between 10 g / l and 25 g / l. In particular, these expanded articles have an excellent thermal insulation capacity expressed by a thermal conductivity between 25 mW / mK and 50 mW / mK, preferably between 30 mW / mK and 45 mW / mK. The measurement of thermal conductivity is carried out at 10 ° C according to the DIN 13163 method on the artifacts obtained from blocks with a density of 15 g / l.

The granules of the polymeric composition can be annealed at a temperature lower than or equal to the glass transition temperature (Tg) or slightly higher, for example the Tg increased up to 8 ° C, possibly under pressure.

At the conclusion of the processes object of the present invention, the expandable granules produced can be subjected to the pre-treatments generally applied to conventional expandable granules and which essentially consist of:

coating the granules with an antistatic liquid agent such as amines, ethoxylated tertiary alkylamines, ethylene oxide-propylene oxide copolymers;

apply on these granules a coating consisting essentially of a mixture of mono-, di- and tri-esters of glycerine (or other alcohols) with fatty acids and metal stearates such as zinc and / or magnesium stearate. Said agent serves to make the coating adhere and to facilitate the screening of the granules prepared in suspension.

As previously mentioned, brominated compounds, such as hexabromium-cyclododecane, which confer self-extinguishing properties to polymers, when subjected to high temperatures (above 180 ° C), can release hydrobromic acid following decomposition processes thermal. The problem is particularly felt by those who deal with self-extinguishing polymers as the acid developed corrodes the machines for processing the polymer and the decomposition of the brominated compound reduces the self-extinguishing properties of the material, forcing the manufacturer to increase the quantity of brominated additive. in the wording.

Using the flame retardant stabilizing additive, as described and claimed in this text, a marked stabilizing effect was observed with regard to the organobrominated compounds added to the polymer as flame retardants: in particular, a significant lengthening of the times was observed. release of HBr which is released due to the thermal degradation of the organ brominated agent and a significant reduction in the quantity of acid produced. This aspect is very important as it allows to drastically reduce the corrosion phenomena of the production plants, for example of EPS, during the preparation of products with self-extinguishing properties.

Furthermore, the addition of the stabilizer in the compositions described and claimed in the present text allows to improve the mechanical characteristics in compression of the derived expanded articles, as illustrated also in the examples reported in the present text. Surprisingly, the dosage of the tin-based thermal stabilizer, object of the present invention, also determines a significant improvement in the mechanical properties in compression of the foamed specimens containing the compositions described and claimed in the present text. The evaluations of the mechanical characteristics in compression were carried out on the individual specimens of expanded material (polystyrene), using a Zwick I 2020 tensiometer, according to the EN 826 method.

The evaluation of the HBr release initiation time was carried out according to the method described below.

A sample of flame retardant additive is placed in a sealed 10 ml vial, heated to the chosen temperature, and subjected to a flow of nitrogen (60 ml per minute) which removes any released hydrobromic acid. The nitrogen flow transports the hydrobromic acid (and the other decomposition products of the sample) in a basic aqueous solution for sodium hydroxide whose pH is measured by means of a glass electrode connected to an automatic Metrohm 736 GP titrator. with a burette loaded with a NaOH solution of known titre. The acid in the gas phase, carried by the nitrogen flow, neutralizes the sodium hydroxide and lowers the pH of the solution. The titrator operates the burette by delivering NaOH to an extent that keeps the pH constant. The volume of titrant is recorded continuously by computer. The quantity of hydrobromic acid released from the sample can be deduced from the volume and title of the NaOH solution used.

In order to better understand the present invention and to put it into practice, some illustrative and non-limiting examples are given below.

Example 1

80 parts of polystyrene N1782 (Polimeri Europa) are mixed in a twin-screw extruder; 20 parts of â € œCalcinated Carbon Coke 4023â € produced by Asbury. The extruded product is used as a material concentrate in the production of the expandable composites of the present invention. 89.8 parts of ethylbenzene, 730 parts of styrene, 56.2 parts of Î ± -methylstyrene, 0.2 parts of divinylbenzene are fed into a stirred reactor. 123.8 parts of the concentrate prepared as above are fed into the reactor and dissolved (total: 1000 parts). The reaction is carried out at 125 ° C with an average residence time of 2 hours. The fluid composition at the outlet is then fed to a second reactor where the reaction is completed at 135 ° C with an average residence time of 2 hours. The reactive polymeric composition, having a conversion of 72%, is heated up to 240 ° C and subsequently fed to the devolatilizer to remove the solvent and the residual monomer. The resulting composition has a glass transition temperature of 104 ° C, a Melt Flow Index (MFI 200 ° C, 5 kg) of 8 g / 10â € ™, a MW molecular weight of 200,000 g / mol and a MW / Mn ratio of 2.8, where MW is the weight average molecular weight and Mn is the number average molecular weight. The composition thus obtained is collected in a heated tank and is fed to a heat exchanger to lower its temperature to 190 ° C. 127.9 parts of polystyrene N2982 (Polymers Europa), 15.7 parts of HBCD Saytex HP 900 (hexabromocyclododecane sold by Albemarle) and 5.2 parts of Perkadox 30 (2,3-dimethyl-2, 3-diphenylbutane, sold by Akzo Nobel) and 1.2 parts Mono-octyltin tris (2-ethylhexylmercapto acetate) with a degree of purity> 95% (Thermolite 895 manufactured by ARKEMA - total 150 parts). A gear pump increases the pressure of the molten additive feed to 260 bar. 47 parts of a mixture of npentane (75%) and iso-pentane (25%) are then pressurized and injected into the additive supply. The mixing is completed by means of static mixers, at a temperature of about 190 ° C. The composition thus mixed is added to 850 parts of the composition from the heat exchanger. The ingredients are then mixed by means of static mixing elements for a calculated average time (residence) of 7 minutes. The composition is then distributed to the die, where it is extruded through a number of holes with a diameter of 0.5 mm, immediately cooled with a jet of water and cut with a series of rotating knives (according to the US patent application 2005/0123638). The granulation pressure is 5 bar and the shear deformation speed is chosen in order to obtain granulates with an average diameter of 1.2 mm. Water is used as a spray liquid and nitrogen as a carrier gas. The ratio between the flow rate of the sprayed water and the flow rate of the polymeric mass is 30 and that between nitrogen and the polymeric mass is 20. The temperature of the water is 40 ° C.

The resulting granulated beads are dried with a centrifugal dryer and then coated with a coating. The coating is prepared by adding to the same 3 parts of glyceryl monostearate, 1 part of zinc stearate and 0.2 parts of glycerin per 1000 parts of dried granulated pearls. The coating additives are mixed with the granulate by means of a continuous screw mixer. The beads are then expanded and printed. The thermal conductivity of the artifacts obtained was 34.7 mW / mK at 16.4 g / l (according to the ISO 8301 method). Some slabs obtained from the artifacts were placed in an oven at 70 ° C for 2 days: then specimens were obtained (9 cm x 19 cm x 2 cm) for the fire behavior test according to DIN 4102. The specimens pass the test.

The expandable pearls thus obtained are analyzed to quantify the bromides present in the polymer. The bromide content in the EPS beads is an indication of the degradation undergone by the organobrominated agent introduced into the polymer as a flame retardant. The EPS beads thus obtained have 350 ppm of bromides. The cellular structure evaluated on the expanded artifacts was found to be homogeneous.

The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100X100X50 mm) were obtained from the expanded artifacts and tested at 5 mm / min. The average value at 10% compression was the following: 93 Kpa (pressure at which the specimen deforms) at a density of 16.4 g / l.

Comparative example 1

Example 1 was repeated, without the addition of the high purity monoalkyl tin mercapto ester.

As described in the previous example, the polymeric composition containing the â € œCalcined Cokeâ € is collected in a tank and cooled to a temperature of 190 ° C. Then, in a twin-screw extruder, 129.1 parts of polystyrene N2982, 15.7 parts of HBCD Saytex HP 900 and 5.2 parts of Perkadox 30 are dosed (total: 150 parts). 47 parts of blowing agent are then added, consisting of a mixture of n-pentane (75%) and iso-pentane (25%). The composition thus obtained is added to 850 parts of the polymeric composition, as in example 1. The mixture obtained then reaches the spinneret where expandable granulates with an average diameter of about 1.2 mm are obtained. These granules are then dried and treated with the coating. The types and quantities of coating additives used are those of example 1. The beads produced are expanded and printed. The thermal conductivity measured on the artifacts obtained was 34.6 mW / mK at a density of 16.2 g / l. Some slabs obtained were placed in an oven at 70 ° C for 2 days: then the specimens (9 cm x 19 cm x 2 cm) were obtained for the fire behavior test according to DIN 4102. The specimens pass the test . The analysis, carried out on the dried and uncoated EPS beads, confirms the presence of 1950 ppm of bromides.

The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100X100X50 mm) were obtained from the expanded artifacts and tested at 5 mm / min.

The average value The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100X100X50 mm) were obtained from the expanded products and tested at 5 mm / min. The average value at 10% compression was the following: 86 Kpa at a density of 16.2 g / l.

Comparative example 2

Comparative example 1 was repeated by dosing dibutyl tin maleate (Baerostab MS) in place of Thermolite 895. Therefore, 127.9 parts of polystyrene N2982, 15.7 parts of HBCD Saytex HP are dosed in the twin screw extruder. 900, 5.2 parts of Perkadox 30 and 1.2 parts of Baerostab MS sold by the Baerlocher company (total: 150 parts). The expanding agent is then dosed and the composition thus mixed is added to 850 parts of the polymeric composition coming from the heat exchanger, as indicated in example 1. This composition then reaches the supply chain. In this way, expandable granulates with an average diameter of about 1.2 mm are produced. The expandable polymer beads are dried, then coating powders are added to them. The coating additives and the dosed quantities are those reported in example 1. The granulates produced are expanded and molded. The artifacts obtained have a thermal conductivity of 34.4 mW / mK at a density of 16.3 g / l. A series of specimens obtained from the expanded products (9 cm x 19 cm x 2 cm) were conditioned in an oven at 70 ° C for 2 days and subjected to the fire behavior test according to DIN 4102. The specimens pass the test. The analysis, carried out on the dried and uncoated EPS beads, confirms the presence of 470 ppm of bromides.

The cellular structure evaluated on the expanded artifacts was found to be homogeneous.

The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100X100X50 mm) were obtained from the expanded artifacts and tested at 5 mm / min. The average value at 10% compression was the following: 87 Kpa at a density of 16.3 g / l.

Example 2

89.8 parts of ethylbenzene, 853.8 parts of styrene, 56.2 parts of Î ± methylstyrene, 0.2 parts of divinylbenzene (total: 1000 parts) are fed into a stirred reactor. The reaction is carried out at 125 ° C with an average residence time of 2 hours. The fluid composition at the outlet is then fed to a second reactor where the reaction is completed at 135 ° C with an average residence time of 2 hours. The reactive polymeric composition, having a conversion of 72%, is heated up to 240 ° C and subsequently fed to the devolatilizer to remove the solvent and the residual monomer. The resulting composition has a glass transition temperature of 104 ° C, a Melt Flow Index (MFI 200 ° C, 5 kg) of 8 g / 10â € ™, a MW molecular weight of 200,000 g / mol and a MW / Mn ratio of 2.8, where MW is the weight average molecular weight and Mn is the number average molecular weight. The composition thus obtained is collected in a heated tank and is fed to a heat exchanger to lower its temperature to 190 ° C. 127.9 parts of polystyrene N2982 (Polymers Europa), 15.7 parts of HBCD Saytex HP 900 (hexabromocyclododecane sold by Albemarle) and 5.2 parts of Perkadox 30 (2,3-dimethyl-2, 3-diphenylbutane, sold by Akzo Nobel) and 1.2 parts Mono-octyltin tris (2-ethylhexylmercapto acetate) with a degree of purity> 95% (Thermolite 895 manufactured by ARKEMA - total 150 parts). A gear pump increases the pressure of the molten additive feed to 260 bar. 47 parts of a mixture of npentane (75%) and iso-pentane (25%) are then pressurized and injected into the additive supply. The mixing is completed by means of static mixers, at a temperature of about 190 ° C. The composition thus mixed is added to 850 parts of the composition from the heat exchanger. The ingredients are then mixed by means of static mixing elements for a calculated average time (residence) of 7 minutes. The composition is then distributed to the die, where it is extruded through a number of holes with a diameter of 0.5 mm, immediately cooled with a jet of water and cut with a series of rotating knives (according to the US patent application 2005/0123638). The granulation pressure is 5 bar and the shear deformation speed is chosen in order to obtain granulates with an average diameter of 1.2 mm. Water is used as a spray liquid and nitrogen as a carrier gas. The ratio between the flow rate of the sprayed water and the flow rate of the polymeric mass is 30 and that between nitrogen and the polymeric mass is 20. The temperature of the water is 40 ° C.

The resulting granulated beads are dried with a centrifugal dryer and then coated with a coating. The coating is prepared by adding to the same 3 parts of glyceryl monostearate, 1 part of zinc stearate and 0.2 parts of glycerin per 1000 parts of dried granulated pearls. The coating additives are mixed with the granulate by means of a continuous screw mixer. The beads are then expanded and printed. The thermal conductivity of the artifacts obtained was 36.4 mW / mK at 16.5 g / l (according to the ISO 8301 method). Some slabs obtained from the artifacts were placed in an oven at 70 ° C for 2 days: then specimens were obtained (9 cm x 19 cm x 2 cm) for the fire behavior test according to DIN 4102. The specimens pass the test.

The obtained expandable beads were analyzed to quantify the bromides present in the polymer. The bromide content in the EPS beads indicates the degradation undergone by the organobrominated agent introduced into the polymer as a flame retardant. The EPS beads thus obtained have 140 ppm of bromides. The cellular structure evaluated on the expanded artifacts was found to be homogeneous.

The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100 X 100 X 50 mm) were obtained from the expanded artifacts and tested at 5 mm / min. The average value at 10% compression was the following: 98 Kpa (pressure at which the specimen deforms) at a density of 16.5 g / l.

Example 3

Example 1 was repeated, adding the same amount of stabilizing agent (high purity monoalkyl tin mercapto ester), but the â € œcalcined cokeâ € was replaced with carbon black TN 990 UP produced by the company Cancarb. Therefore, 80 parts of polystyrene N1782 (Polimeri Europa) are mixed in a twin-screw extruder; 20 parts of carbon black type TN990 UP (Cancarb).

As described in example 1, the polymeric composition containing the carbon black then reaches the spinneret where expandable granulates with an average diameter of about 1.2 mm are obtained. These granules are then dried and treated with the coating. The types and quantities of coating additives used are those of example 1. The beads produced are expanded and printed. The thermal conductivity measured on the artifacts obtained was 35.3 mW / mK at a density of 16.7 g / l. Some slabs obtained were placed in an oven at 70 ° C for 2 days: then the specimens (9 cm x 19 cm x 2 cm) were obtained for the fire behavior test according to DIN 4102. The specimens pass the test . The analysis, carried out on the dried and uncoated EPS beads, confirms the presence of 310 ppm of bromides.

The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100 X 100 X 50 mm) were obtained from the expanded artifacts and tested at 5 mm / min.

The average value The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100X100X50 mm) were obtained from the expanded products and tested at 5 mm / min. The average value at 10% compression was the following: 93 Kpa at a density of 16.7 g / l.

Example 4

Example 1 was repeated, adding the same amount of stabilizing agent (high purity monoalkyl tin mercapto ester), but the â € œcalcined cokeâ € was replaced with graphite UF2, produced by the company Graphit KropfmÃ1⁄4hl AG . Therefore, 80 parts of polystyrene N1782 (Polimeri Europa) are mixed in a twin-screw extruder; 20 parts of UF2 type graphite (Graphit KropfmÃ1⁄4hl AG).

As described in example 1, the polymeric composition containing the graphite then reaches the spinneret where expandable granulates with an average diameter of about 1.2 mm are obtained. These granules are then dried and treated with the coating. The types and quantities of coating additives used are those of example 1. The beads produced are expanded and printed. The thermal conductivity measured on the artifacts obtained was 34.1 mW / mK at a density of 16.2 g / l. Some slabs obtained were placed in an oven at 70 ° C for 2 days: then the specimens (9 cm x 19 cm x 2 cm) were obtained for the fire behavior test according to DIN 4102. The specimens pass the test . The analysis, carried out on the dried and uncoated EPS beads, confirms the presence of 330 ppm of bromides.

The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100 X 100 X 50 mm) were obtained from the expanded artifacts and tested at 5 mm / min.

The average value and the mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100X100X50 mm) were obtained from the expanded products and tested at 5 mm / min. The average value at 10% compression was the following: 92 Kpa at a density of 16.2 g / l.

Comparative example 3

Example 2 was repeated, replacing the stabilizing agent Thermolite 895 (high purity monoalkyl tin mercapto ester) with a traditional tin-based stabilizer (dibutyl tin maleate â € “Baerostab MS produced by Baerlocher ).

As described in example 2, the polymeric composition containing dibutyl tin maleate reaches the spinneret where expandable granulates with an average diameter of about 1.2 mm are obtained. These granules are then dried and treated with the coating. The types and quantities of coating additives used are those of example 2. The beads produced are expanded and printed. The thermal conductivity measured on the artifacts obtained was 36.6 mW / mK at a density of 16.4 g / l. Some slabs obtained were placed in an oven at 70 ° C for 2 days: then the specimens (9 cm x 19 cm x 2 cm) were obtained for the fire behavior test according to DIN 4102. The specimens pass the test . The analysis, carried out on the dried and uncoated EPS beads, confirms the presence of 170 ppm of bromides.

The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100 X 100 X 50 mm) were obtained from the expanded artifacts and tested at 5 mm / min.

The average value The mechanical characteristics in compression were tested with a Zwick I 2020 tensiometer, according to the EN 826 method. Two specimens (100 X 100 X 50 mm) were obtained from the expanded articles and tested at 5 mm / min. The average value at 10% compression was the following: 92 Kpa at a density of 16.4 g / l.

Table 1 shows the results of the tests carried out with the different types of athermal agents and stabilizing agents. In Table 1, K is the thermal conductivity (ISO 8301) measured in [mW / mK], P is the compression measured in [Kpa] (EN826)

Table 1

Atermano HBCD Stabilizer with K Bromides P (%) tin base (ppm)

(%)

Example 1 2% coke 1.3 0.1 34.7 350 93

Thermolite 895

Example 2% coke 1.3 Absent 34.6 1950 86 Comparative

1

Example 2% coke 1.3 0.1 34.4 470 87

Baerostab MS

Comparative

2

Example 2 Absent 1.3 0.1 36.4 140 98

Thermolite 895

Example 3 2% 1.3 0.1 35.3 310 93 carbon Thermolite 895

black

Example 4 2% 1.3 0.1 34.1 330 92 graphite Thermolite 895

Example Absent 1.3 0.1 36.6 170 92

Baerostab MS

Comparative

3

Claims (16)

CLAIMS 1. A composition based on self-extinguishing expandable vinyl aromatic polymers which includes: a) a polymer obtained by polymerization of one or more vinyl aromatic monomers present in a quantity ranging from 50% to 100% by weight, and a monomer copolymerizable with the vinyl aromatic monomers, homogeneously incorporated into the polymer in a quantity ranging from 0% to 50% by weight ; b) at least one expanding system in a quantity ranging from 3% to 10% by weight, calculated on the polymer (a); c) at least one flame retardant additive in a quantity ranging from 0.005% to 5% by weight, calculated on the polymer (a), and containing at least 30% by weight of bromine, a quantity calculated with respect to the flame retardant additive; d) at least one synergistic additive containing a C-C or C-O-O-C thermolabile bond in an amount ranging from 0.001% to 2% by weight, calculated on the polymer (a); And e) at least one heat additive selected from a carbon black, a graphite, a coke carbon in particle form and their mixtures; said composition is characterized in that it contains a stabilizing additive which includes at least one alkyl tin mercapto ester having a purity greater than or equal to 95%. 2. The composition according to claim 1 in which the stabilizing additive is present in a quantity ranging from 0.001% to 3% by weight, quantity calculated on the polymer (a). 3. The composition according to claims 1 and 2 wherein the carbon black has an average diameter (d50), measured by a laser granulometer, which varies from 30 to 1000 nm. 4. The composition according to claim 3 wherein the carbon black is present in quantities ranging from 0.01-20% by weight, calculated on the polymer (a). 5. The composition according to claim 1 wherein the graphite is selected from a natural, synthetic, expanded or expandable graphite, and has a maximum size (d50), measured with a laser granulometer, which varies from 0.05 to 100 µm and has a surface area, measured according to ASTM D-3037-89 (BET), of 5-30 m <2> / g. 6. The composition according to claims 1, 2 and 5 in which the graphite is present in an amount comprised between 0.01-20% by weight, calculated on the polymer (a). 7. The composition according to claims 1 and 2 wherein the coke has an average diameter (d50) of the particles ranging from 0.5 to 100 µm, and a surface area, measured according to ASTM D-3037-89 (BET ), ranging from 5 to 200 m <2> / g. 8. The composition according to claims 1, 2 and 7 in which the coke is present in an amount comprised between 0.1 and 20% by weight, calculated on the polymer (a). 9. The composition according to claims 1-8 in which the flame-retardant agent is present in an amount ranging from 0.1 to 5%, calculated on the polymer and contains a quantity of bromine between 50% and 90% by weight, quantity calculated on the flame retardant additive. 10. The composition according to claims 1-9 wherein the stabilizing additive includes at least one mono alkyl tin mercapto ester. 11. A process for preparing in continuous mass a composition based on self-extinguishing expandable vinylaromatic polymers according to claims 1-10, said process comprising the following steps: a) adding to a polymer and / or (co) vinylaromatic polymer in granules or already in the molten state, with average molecular weight between 50,000 and 300,000, at least one flame retardant additive (c), at least one synergistic additive (d), at least one heat additive (e) and at least one flame retardant stabilizer additive which includes at least one alkyl tin mercapto ester; b) if the vinyl aromatic polymer and / or (co) polymer is in granules, heat said polymer and / or (co) polymer to a temperature above the relative melting point; c) incorporating in the melted polymer, before extrusion and through a spinneret, the expanding system (b) thus obtaining the composition based on self-extinguishing expandable vinylaromatic polymers. The process according to claim 11 wherein the composition based on self-extinguishing expandable vinyl aromatic polymers formed is mixed by means of static or dynamic elements, and granulated in a device which comprises a die, a cutting chamber and a cutting system. 13. A composition based on self-extinguishing expandable vinyl aromatic polymers which includes: a) a polymer obtained by polymerization of one or more vinyl aromatic monomers present in a quantity ranging from 50% to 100% by weight, and a monomer copolymerizable with the vinyl aromatic monomers, homogeneously incorporated into the polymer in a quantity ranging from 0% to 50% by weight ; b) an expanding system in a quantity ranging from 3% to 10% by weight, calculated on the polymer (A); c) a flame retardant additive in a quantity ranging from 0.005% to 5% by weight, calculated on the polymer (A), containing at least 30% by weight of bromine; d) a synergistic additive containing a C-C or C-O-O-C thermolabile bond in an amount ranging from 0.001% to 2% by weight, calculated on the polymer (A); said composition is characterized in that it contains a stabilizing additive which includes at least one mono alkyl tin mercapto ester having a purity greater than or equal to 95%. 14. A process for preparing in continuous bulk a composition based on self-extinguishing expansible vinyl aromatic polymers according to claim 13, said process comprising the following steps: a) adding to a polymer and / or (co) vinyl aromatic polymer in granules or already in the state molten, with average molecular weight between 50,000 and 300,000, at least one flame retardant additive (C), at least one synergistic additive (D) and at least one flame retardant stabilizer additive which includes at least one mono alkyl tin mercapto ester; b) if the vinyl aromatic polymer and / or (co) polymer is in granules, heat said polymer and / or (co) polymer to a temperature above the relative melting point; c) incorporate the expanding system (B) into the melted polymer, before extrusion and through a spinneret, thus obtaining the composition based on self-extinguishing expandable vinylaromatic polymers. 15. Expanded articles containing the composition according to claims 1-10 or 13 having a density between 5 g / l and 50 g / l and thermal insulation capacity expressed by a thermal conductivity between 25 mW / mK and 50 mW / mK. 16. Expandable granules containing the composition according to claims 1-10 or 13 having a spheroidal shape with an average diameter ranging from 0.2 mm to 2 mm.