EP4314124A1

EP4314124A1 - Reactive polymeric mixtures, hybrid polymeric foams and process for producing the same

Info

Publication number: EP4314124A1
Application number: EP22711664.7A
Authority: EP
Inventors: Antonio Ponticiello; Luigi Bassi
Original assignee: Versalis SpA
Current assignee: Versalis SpA
Priority date: 2021-03-22
Filing date: 2022-03-21
Publication date: 2024-02-07
Also published as: TW202248338A; WO2022200987A1

Abstract

The present patent application relates to a reactive polymeric mixture and a hybrid polymeric foam which comprises a reactive phenolic resin, dispersed in a polar solvent, having certain features, and expandable and expanded granules of vinyl aromatic polymer wherein the halogen content is less than or equal to 100 ppm by weight, containing athermanous agents whose particles have a D₉₀ size less than or equal to 100 microns.

Description

REACTIVE POLYMERIC MIXTURES HYBRID POLYMERIC

FOAMS AND PROCESS FOR PRODUCING THE SAME"

Description

The present patent application relates to hybrid polymeric mixtures and foams containing vinyl aromatic polymers and reactive phenolic resins with a content of halogens, present in the expanded and expandable polymeric granules, lower than or equal to 100 ppm by weight.

These hybrid polymeric foams are able to pass the flame retardancy test, according to the DIN 4102 B2 standard .

In particular, the present patent application relates to hybrid polymeric foams obtainable by dosing reactive phenolic resins on the external surface of expanded and expandable vinyl aromatic polymeric granules, and by subjecting the reactive mixture thus obtained to a molding process.

In the present patent application, "reactive phenolic resins" means a solution that contains a polar solvent, for example, water or an alcohol, in which phenol, a phen o1-forma 1dehyde polymer and free formaldehyde are dispersed, before the cross- linking step.

In the present patent application, halogens refer to the elements Fluorine, Chlorine, Bromine, Iodine, belonging to group 7 of the periodic table of elements. Said halogens can be present in the polymeric composition object of the present invention also as halogenated organic compounds. In the present patent application, boron refers to the boron present in boric acid or in boron salts.

In the present patent application, the term "hybrid polymeric foams" means the foams formed after the molding step of the described and claimed reactive polymeric mixture, wherein both the vinyl aromatic polymeric part and the reactive phenolic resin are at least partially expanded.

More specifically, during the molding step, and in particular during the heating step, the reactive phenolic resin dispersed on the expandable and expanded polymeric granules expands, at least in part, together with the vinyl-aromatic polymer.

The hybrid foams, described and claimed in the present patent application, allow the production of expanded thermal insulating sheets with reduced thermal conductivity and excellent flame retardant properties .

The hybrid foams, described and claimed in the present patent application, can also be successfully used in the perimeter thermal insulation of modern multi-storey buildings, with high vertical development, shopping centers, public structures (schools, railway stations, hospitals, airports) , ensuring in the event of a fire improved performance, in terms of reduction of flame propagation speed and heat development, compared to the performance offered by conventional po1 ystyrene -based foams that contain organo- brominated flame retardants.

In the present patent application, all the operating conditions indicated in the text must be understood as preferred conditions even if not expressly stated.

For the purposes of this specification, the term "comprise" or "include" also comprises the term "consist in" or "essentially consisting of". For the purposes of this specification, the definitions of the ranges always comprise the extremes unless otherwise specified.

Currently, in order to guarantee the safety conditions required on construction sites during the step of fixing the thermal insulating sheets to the external walls of buildings, the expandable polystyrene granules, with which the sintered polystyrene expanded sheets are made, contain brominated flame retardants, such as for example: hexabromocyclododecane (HBCD), tetrabromo bisphenol A bis(2,3 dibromopropyl ether), tetrabromobisphenol A bis(2,3 dibromo-2-methylpropyl ether), brominated styrene- butadiene copolymers. The introduction of brominated compounds into the polystyrene matrix allows the expanded materials to pass specific self-extinguishing tests, such as the DIN 4102-B2 standard test, which certify their suitability for applications in the building sector (perimeter insulation of buildings or "external thermal insulation").

Numerous patent applications are known which describe the introduction into the polymeric matrix of different types of organo-brominated flame retardants, necessary for passing the self-extinguishing test DIN 4102-B2.

US 6,579,911 describes the preparation of polystyrene foams with self-extinguishing properties, where the flame retardant hexabromocyclododecane is introduced into the polymeric matrix in order to improve the fire behavior of the foam.

EP 2616263 describes expandable vinyl-aromatic polymeric compositions containing brominated flame retardants, whose thermal stabilization is made possible by introducing into the polymer mass additives selected from pyrophosphates, melamine polyphosphate, salified polycarboxylic acids, citrates salified with alkali metals, polyfunctional alcohols, esters of polyfunctional alcohols.

During the preparation of latest generation polystyrene foams, containing athermanous agents that significantly reduce the thermal conductivity of expanded manufactured articles, it has been observed that athermanous agents significantly accelerate the degradation of brominated flame retardants, with consequent release of significant quantities of hydrobromic acid. Hydrobromic acid, even if present in limited quantities, is in any case responsible for important corrosion phenomena that can significantly damage the metal parts of the expandable polymeric granules production plant, and the metal walls of the expander and molding systems used during the transformation phase, which leads to the production of thermal insulating expanded sheets.

The dosage of the stabilizing agents described in EP 2616263 allows a significant reduction of hydrobromic acid present in the expandable or expanded polystyrene granules. EP 2912104 describes the preparation of expandable vinyl- aromatic polymeric compositions with reduced thermal conductivity and flame retardant properties, containing athermanous agents. In this case, the reduction of the degradative phenomena affecting the brominated compounds, dosed as flame retardants, is obtained by dosing epoxy compounds during the preparation step of the masterbach containing the athermanous agents. The epoxy compounds, dosed during the preparation of the masterbatch, preventively neutralize the functional groups present on the surface of the athermanous agents, responsible for the degradation of the brominated compounds. By following the indications contained in EP 2912104, expandable polystyrene granules with a reduced content of hydrobromic acid are obtained, which can be used for the production of thermal insulating expanded sheets of sintered polystyrene, capable of passing the self-extinguishing test according to the DIN 4102-B2 standard.

WO 2018/007602 describes expandable vinyl aromatic polymeric compositions, with reduced thermal conductivity, containing athermanous agents, where the reduction of the concentration of hydrobromic acid, produced by the decomposition of the flame retardant, is made possible thanks to the use of two or more organo-brominated compounds characterized by different thermal stability. In other words, the combined use of a brominated compound with reduced thermal stability (containing bromine of an aliphatic nature), with a brominated compound with high thermal stability (containing bromine of an aliphatic and aromatic nature) makes the bromine of an aromatic nature much more active. By exploiting the synergic effect linked to the use of two flame retardants with different thermal stability, it was possible to limit the dosage of the flame retardant with greater thermal stability, obtaining expandable polystyrene granules where the amount of hydrobromic acid present is decidedly contained.

The use of hybrid foams based on expanded polystyrene in combination with phenolic resins is known.

US 2016/0053065 and US 2016/0060415 describe the composition of a polystyrene-phenolic hybrid foam and the process for their preparation. Said hybrid foams contain polystyrene, phenolic resins and boric acid. Boric acid is introduced into the phenolic fraction to improve the fire behavior of such hybrid foams.

However, it is necessary to underline the significant impact on health for the personnel involved in the production of this type of hybrid foam, linked to the use of boric acid, taking into account that this additive can harm fertility and is suspected of damaging the fetus, as reported in https://echa.europa.eu/it/information-on- chemicals.

In patent applications US 2016/0053065 and US 2016/0060415, the expandable polystyrene granules used for the production of the hybrid foams are produced by the company Sunpor (in these applications the commercial grade Lambdapor 753 is mentioned). It is known that the expandable/expanded polystyrene granules Lambdapor 753 have self-extinguishing properties, as they contain an organo-brominated flame retardant. Therefore, the hybrid foams described in said patent applications cannot be considered Halogen Free compositions, with reduced environmental impact.

Patent EP 1314753 describes the preparation of polystyrene- phenolic hybrid foams with improved fire behavior. The examples describe expanded polymeric compositions containing halogenated flame retardants such as for example hexabromocyclododecane and Tris(l,3- dichloroisopropyl)phosphate . Therefore, even these hybrid foams are not Halogen Free, and therefore of reduced environmental impact. The expanded polystyrene granules used in the preparation of the hybrid foams described in EP 1314753 do not contain athermanous agents, therefore the thermal-insulating power of these foams is lower than the insulating materials containing athermanous agents.

In order to pass the DIN 4102-B2 self-extinguishing test to which the conventionally produced expanded polystyrene products are currently subjected, it is known that organo- brominated flame retardants are introduced into the polystyrene matrix. Brominated flame retardants often have a high environmental impact with negative consequences on the health of personnel involved in the production of flame retardants, and of personnel in charge of handling flame retardants during the production stage of polymeric materials. The brominated compound hexabromocyclododecane (HBCD) has been used as a flame retardant in vinyl aromatic polymeric foams for many years. To ensure the passing of the self extinguishing test required in this particular application sector (DIN 4102-B2), it is necessary to introduce well- defined quantities of HBCD into the vinyl-aromatic foams (usually it is necessary to introduce concentrations of HBCD comprised between 0.7 and 1.5% by weight). Unfortunately, the flame retardant HBCD has been recognized as an extremely dangerous substance for the environment. For this reason, it has been included in the SVHC list by the European Chemicals Agency (decision of 28 October 2008). HBCD has been classified as a persistent, bioaccumulative and toxic substance (PBT). Due to its persistence, toxicity and ecotoxicity, the Stockholm Convention on Persistent Organic Pollutants (POPs) decided, in May 2013, to include HBCD in Annex A of the Convention to remove it from the market and eliminate it for production. Subsequently, a new brominated flame retardant was identified which has a higher environmental sustainability than HBCD. The new brominated flame retardant, which has replaced HBCD, is a block copolymer consisting of brominated styrene butadiene (brominated polymeric flame retardant) . Compared to HBCD, the brominated polymeric compound exhibits a more sustainable profile from the point of view of health, safety and the environment. High molecular weight polymer additives typically have inherently lower risk profiles for the environment and health. However, the new polymer flame retardant contains bromine. It is known that the processes of extraction or production of bromine and the bromination processes of organic compounds are highly polluting for the environment and toxic to humans. Furthermore, the bromine, although incorporated in the polymeric foam, in the form of polymeric flame retardant, can be released into the environment even after many years, due to the degradation undergone by the polymeric matrix, following exposure to UV radiation from the sun and humidity in the air.

It is therefore necessary to develop hybrid foams containing vinyl-aromatic polymers and reactive phenolic resins, with reduced thermal conductivity, with excellent flame retardant properties, capable of passing the DIN 4102-B2 fire test, but free of halogenated flame retardants that are undesirable due to their high environmental impact. Thanks to their flame-retardant properties, the new hybrid foams can also be successfully used in contexts considered particularly critical in the event of a fire, such as for example multi-storey buildings with high vertical development, public buildings, commercial buildings, as they guarantee superior performance compared to conventional manufactured products based on vinyl aromatic foams containing halogenated flame retardants.

The applicant has identified hybrid foams wherein the expanded and expandable polymeric granules have a halogen content lower than or equal to 100 ppm by weight, which have good thermal insulation properties and pass the flame retardancy test according to the DIN 4102-B2 standard.

A halogen concentration lower than 100 ppm by weight, present in the polymeric composition and foam object of the present patent application, may be due to the halogens contained in the post-consumer polymers which will be used in the preparation of the expanded and expandable polymeric granules used in the foams according to the present invention.

Another source of halogens can be linked to the polymer production process, where, when changes in the production runs occur, during the transition from a production of EPS containing halogenated flame retardants, to a production of EPS free of halogenated compounds, some polystyrene granules expandable/expanded polystyrene may remain retained for a short time in some pieces of equipment in the production plant, and thus contaminate the expanded/ expandable polystyrene granules, free of halogenated compounds.

Therefore, the quantity of halogens detected by analyzing the polystyrene/phenolic hybrid foams, object of the present invention, cannot in any way derive from the intentional addition of halogenated compounds, in order to improve the fire behavior of the expanded products.

For the determination of the halogens in the compositions and foams according to the present patent application the following method is used.

Principle of the method

The polymer sample is decomposed by combustion in a pure oxygen atmosphere under pressure in a calorimetric bomb. The halogens present, in organic and inorganic form, are converted into halogenhydric acids, absorbed by a basic solution previously introduced into the bomb and measured by ion chromatography. This principle is valid for fluorine, chlorine, bromine.

Method

1.0 g of exactly weighed sample are placed in the crucible of the "Parr" calorimetric bomb together with ~ 0.5 ml of ethanol to favor combustion, then the nickel wire is placed for priming. At the bottom of the bomb 10 ml of the eluent solution of the ion chromatograph are introduced in order to capture and neutralize the halogenidric acid which develops as a result of the polymer decomposition. The bomb is closed, the oxygen tube is connected, pressurized and vented to remove the nitrogen present inside. The bomb is definitively pressurized at 35 bar always with pure oxygen and the combustion is electrically triggered. The bomb is immersed in water to cool it. Before opening the bomb, it is shaken well and the pressure present at the internal by means of a special valve is released. The solution obtained from the Parr bomb decomposition is brought to a volume of 50 ml in a volumetric flask, and injected into the previously calibrated ion chromatograph. The chromatogram is acquired by directly obtaining the concentration of the halides in the solution. Calculations

The concentration of the halide X in the sample is calculated as follows: where:

C_x: halogen concentration in the sample expressed in ppm

(w/w).

C_sx : concentration of the halide X in the solution obtained from the bomb decomposition of polystyrene expressed in ppm (w/v) (from chromatography).

V_s volume of dilution carbonate solution used for decomposition expressed in ml.

W_campione'· weight of the initial sample expressed in g.

By using a reactive phenolic resin with formic aldehyde content lower than 0.1% by weight, measured with respect to the total weight of the reactive phenolic resin, it is possible to make hybrid foams that have the previously indicated properties and that make them applicable in the thermal insulation of buildings.

Therefore, the subject of this patent application is a reactive polymeric mixture, which comprises:

1.expandable and expanded granules of vinyl aromatic polymer wherein • the halogen content is less than or equal to 100 ppm by weight and

• containing athermanous agents whose particles have a D90 size less than or equal to 100 microns;

2. reactive phenolic resins comprising:

^■ between 2% and 12% by weight, preferably between 5% and 10% by weight of phenol;

^■ between 40% and 85% by weight, preferably between 50% and 75% by weight of a phenol-formaldehyde pol ymer;

^■ less than 0.1% by weight of free formaldehyde;

^■ where the complement to 100% by weight consists of polar solvents.

A further object of the present patent application is a hybrid polymeric foam obtained by means of a molding process which comprises the following steps:

^ forming a reactive polymeric mixture by mixing in a suitable device

1.Expandable and expanded granules of vinyl aromatic polymer wherein the halogen content is less than or equal to 100 ppm by weight and containing athermanous agents having a D90 diameter less than or equal to 100 microns;

2.reactive phenolic resins comprising:

^■ between 40% and 85% by weight, preferably between 50% and 75% by weight of a phenol-formaldehyde polymer ;

^■ less than 0.1% by weight of free formaldehyde;

* where the complement to 100% by weight consists of polar solvents.

^ inserting the reactive polymeric mixture into a mold; ^ heating the reactive polymeric mixture to a temperature comprised between 80°C and 160°C, preferably comprised between 100°C and 140°C, even more preferably between 115 and 125°C for a period of time comprised between 40 and 80 minutes, more preferably between 50 and 70 minutes until a hybrid polymeric foam is formed.

A further embodiment of the present invention is a molding process for the preparation of hybrid foams, which comprises the following steps:

^forming a reactive polymeric mixture by mixing in a suitable device

1.Expandable and expanded granules of vinyl aromatic polymer wherein the halogen content is less than or equal to 100 ppm and containing athermanous agents having a D90 diameter less than or equal to 100 ppm;

2.reactive phenolic resins comprising:

^■ between 40% and 85% by weight, preferably between 50% and 75% by weight of a phenol-formaldehyde pol ymer; And

^■ less than 0.1% by weight of free formaldehyde

^■ where the complement to 100% by weight consists of polar solvents.

^ inserting the reactive polymeric mixture into a mold with suitable heat exchange devices;

^ heating the reactive polymeric mixture to a temperature comprised between 80°C and 160°C, preferably comprised between 100°C and 140°C, even more preferably between 115°C and 125°C for a period of time comprised between 40 and 80 minutes, more preferably between 50 and 70 minutes until a hybrid polymeric foam is formed. Detailed description All embodiments of the present invention are now described in detail.

In order to obtain the hybrid polymeric foams described and claimed in the present patent application it is necessary to prepare a reactive polymeric mixture. Expandable and expanded granules of vinyl aromatic polymer which contain athermanous agents whose particles have a D90 size less than or equal to 100 microns, preferably comprised between 2 and 100 microns, and which have a halogen content less than or equal to 100 ppm by weight, preferably less or equal to 50 ppm by weight, more preferably halogen-free (i.e. no halogen), are mixed with a reactive phenolic resin which occurs in the form of a dispersion in a polar solvent, preferably water or alcohol, more preferably water, in a suitable mixing device, forming a reactive polymeric mixture.

The reactive phenolic resins, used in the present invention comprise:

^■ less than 0.1% by weight of free formaldehyde

^■ where the complement to 100% by weight consists of polar solvents.

The reactive polymeric mixture thus formed is inserted into a mold and heated using suitable heat exchange devices. During heating, the reactive polymeric mixture reaches a temperature comprised between 80°C and 160°C, preferably comprised between 100°C and 140°C, even more preferably between 115 and 125°C for a period of time comprised between 40 and 80 minutes, more preferably between 50 and 70 minutes until a hybrid polymeric foam is formed. Said reactive polymeric mixture can preferably be boron- free.

Said reactive polymeric mixture can further comprise organic or inorganic acids, or mixtures of said organic acids with the relative esters, or mixtures of said inorganic acids with the relative esters, acting as catalysts capable of accelerating the cross-linking of the reactive phenolic resin.

Said catalysts can preferably be added either in the reactive phenolic resin, before dosing the reactive phenolic resin on the expandable and expanded polymeric granules, or directly on the expandable and expanded polymeric granules during mixing, but always before introducing the prepared reactive polymer mixture into the mold.

More preferred are weak inorganic acids, and mixtures of said acids with their esters; or strong inorganic acids, or strong organic acids, or mixtures of strong inorganic acids with the corresponding esters, or mixtures of strong organic acids with the relative ester compounds. Among the strong organic acids, preferred are sulphonic acids and their esters, more preferably selected from toluenesulfonic acid, xylene sulfonic acid, benzenesulfonic acid, their esters; and mixtures thereof. Mixtures of two or more strong organic acids, mixtures of esters of strong organic acids, mixtures of weak inorganic acids, mixtures of strong and weak acids or mixtures of their corresponding esters can also be used.

More preferred are phosphoric esters in combination with phosphoric acid; these are particularly suitable for accelerating the crosslinking of the reactive phenolic resins described in the present patent application.

Said acids can be present in quantities ranging from 0.1% to 10% by weight, preferably from 0.5% to 8% by weight, even more preferably from 2% to 5% by weight, with respect to the total weight of the reactive polymeric mixture. Expandable and foamed polymeric granules may already contain non-halogenated flame retardants. Alternatively, the reactive phenolic resin dispersed in a polar solvent may contain non-halogenated flame retardants. Non-halogenated flame retardants can preferably be added to the dispersion containing the reactive phenolic resin before it is distributed on the expanded and expandable polymeric granules.

Therefore, preferably said flame retardants are contained in the reactive phenolic resin dispersed in a polar solvent; or they are contained in the expandable and expanded polymeric granules.

Said halogen-free flame retardants are preferably selected from ammonium polyphosphate (for example Phos-cheK P42- ICL), 9,10-Dihydro-9-oxa-lO-phosphaphenanthrene 10-oxide (DOPO, CAS: 35948-25-5 , e.g. GC DOPO_Greenchemicals),

9,10-Dihydro-10- (2,3-dicarboxypropyl)-9-oxa-10- phosphaphenanthrene (DOPO-DDP, CAS: 63562-33-4, e.g. GC RE DDP-GreenChemicals), expandable graphite, expanded graphite (e.g. SC20 OS_GraphitKropfmuhl), expanded graphite together with calcium hypophosphite (e.g. Everflam HPCA_Everchem), calcium hypophosphite, compounds containing phosphorus, such as Fyrolflex Sol DP and mixtures thereof.

Said halogen-free flame retardants are present in an amount comprised between 0.1% and 5% by weight, preferably between 0.5% and 4% by weight, even more preferably from 1% to 3% by weight, with respect to the total weight of the reactive polymeric mixture.

Formaldehyde functions as a cross-linking agent and is particularly active during the heating step of the reactive polymeric mixture. The use of water as a polar solvent to disperse a reactive phenolic resin represents an advantage, given that organic solvents are often characterized by a critical HSE profile, and is therefore the preferred solvent.

The expandable and expanded vinyl aromatic polymeric granules present in the reactive polymeric mixture preferably range from 30% to 80%, more preferably from 50% to 70% by weight, with respect to the weight of the reactive polymeric mixture before it is inserted into a mold.

The weight ratio between expanded granules and expandable granules varies from 5:1 to 1:1, preferably 3:1 to 1:1, more preferably it is 2:1.

In the reactive polymeric mixture, increasing concentrations of reactive phenolic resin correspond to an improvement in the fire behavior of the hybrid polymeric foams and therefore of the final foamed articles, but a dosage of the reactive phenolic resin in high quantities, i.e. over 60%, in addition to penalizing the density of the thermal insulating sheets makes the expanded products much more fragile.

The terms vinyl aromatic polymers in the present text refer to polymers having an average molecular mass (MW) comprised between 50000 and 250000 Dalton, preferably comprised between 70000 and 220000 Dalton. Mw can be determined by size exclusion chromatography or gel permeation (GPC) as described in US 4,520,135 or by Sadao Mori, Howard G. Barth "Size Exclusion Chromatography" Springer Verlag Berlin Heidelberg 1999.

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 optionally a 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 selected from those that correspond to the following general formula (I): wherein R is a hydrogen or a methyl group; n is 0 (zero) or an integer comprised between 1 and 5; Y a halogen, preferably selected 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, a-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 a-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, (meth)acrylic acid amides and nitriles such as acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, butadiene, ethylene, divinylbenzene, maleic anhydride. Preferred copolymerizable monomers are acrylonitrile and methyl methacrylate.

The expandable and expanded granules of vinyl aromatic polymer can also contain nucleating agents, polyethylene waxes, talc, crystalline or amorphous silica, silicates, blowing agents of different nature, and non-halogenated flame retardants with reduced environmental impact.

The expanded and expandable polymeric granules may contain a blowing agent.

Typically, the expandable granules are subjected to a first expansion. Said granules are fed to an expander and are hit by steam. The steam heats the blowing agent, which having a low boiling evaporates creating a cell structure. During the expansion the blowing agent is replaced by the air thus forming expanded granules. However, not all of the expanding agent is evaporated, a part remains in the expanded granules, typically an amount comprised between 3% and 4% by weight with respect to the weight of the granule.

This residual content helps the expansion and sintering of the expanded granules during the molding step. In fact, the steam heating of the expanded granule causes a second expansion, almost completely evaporating the expanding agent which is replaced by the air. This second expansion causes the sintering or welding of the expanded granules to form a final well sintered hybrid foam with good mechanical properties.

The combined use of expanded and expandable granules of vinyl aromatic polymer is useful to significantly improve the degree of sintering of the granules during heating in the mold, and therefore the mechanical properties of the hybrid foam obtained.

Preferred blowing agents are selected from volatile liquids or gases; more preferably they are selected from alkanes and their isomers containing from 3 to 6 carbon atoms; even more preferably they are selected from pentane, iso pentane, isobutane, n-butane, hexane, heptane, isooctane; even more preferably selected from pentane, iso-pentane and mixtures thereof. The blowing agents can be present in the expandable vinyl aromatic granules in quantities ranging from 4% to 7% by weight with respect to the weight of the polymer. The reactive polymeric mixture and the hybrid polymeric foam described and claimed in the present patent application may also contain athermanous agents.

The athermanous agents can be dispersed in the reactive phenolic resin before it is dosed on the expandable and expanded polymeric granules; or the athermanous agents can already be contained in the expanded and expandable granules; or the athermanous agents can be found both in the granules and in the dispersion containing the reactive phenolic resin.

Once incorporated in the vinyl aromatic polymeric granules, or in the reactive phenolic resin, the athermanous agents described in this patent application significantly attenuate the propagation of heat, and therefore significantly reduce the thermal conductivity of the hybrid polymeric foams, improving the performance of the thermal insulator .

In the expanded and expandable polymeric granules, the athermanous agents can have a concentration comprised between 0.1% by weight and 20% by weight, preferably between 0.5% by weight and 15% by weight, more preferably between 2% by weight and 8% by weight, with respect to the total weight of the granules.

The athermanous agents can be present in the reactive phenolic resins in concentrations comprised between 1% and 20% by weight, preferably between 2% and 10% by weight, with respect to the weight of the reactive phenolic resins. The coke can be present in concentrations comprised between 1% and 20%, preferably between 2% and 10% by weight, with respect to the weight of the reactive phenolic resin. The athermanous agents suitable for the reactive polymeric mixtures and the hybrid foams described and claimed in the present patent application are carbonaceous materials and can be selected from carbon black, graphite and coke.

Among the cokes, calcined petroleum coke, needle coke, pitch coke, or mixtures thereof are preferred.

Among the graphites, natural graphite, synthetic graphite, or mixtures thereof are preferred.

In the reactive polymeric mixtures described and claimed in the present patent application, coke can be present in an amount comprised between 0.1% by weight and 20% by weight, more preferably between 0.5% by weight and 15% by weight, even more preferably between 2 % by weight and 8% by weight, said percentage being calculated with respect to the total of the reactive polymeric mixture.

The coke, and the preferred forms described in the present text, used in the reactive polymeric mixtures and in the hybrid polymeric foams described and claimed in the present text, is presented as a finely divided powder and with a ( Dgo ) size of the powder particles that can vary from 2 pm to 100 pm, preferably from 2.5 pm to 40 pm, more preferably from 3 pm to 20 pm, even more preferably from 4 pm to 10 pm .

The particle size of coke ( Dgo ) is measured with a wet Malvern Mastersizer 2000 Laser Granulometer (Mie model, "general purpose" algorithm, with refractive index of the dispersed phase (coke) equal to 1.8 and absorption index of the dispersed phase equal to 0.8) and the measurement is carried out as indicated in the ISO 13320-2009 standard. During the measurement, the coke particles are dispersed in distilled water and then measured. The suspension is sonicated for 3 minutes. The meaning of the D90 size is as follows: it is the value of the diameter of the particles, expressed in micrometers, below which 90% of the volume population of the analyzed powder particles is found. By diameter we mean the size of the particle measured with the wet Malvern Mastersizer 2000 laser granulometer, and the measurement is carried out as indicated in the ISO 13320-2009 standard. The coke used in the reactive polymeric mixtures and in the hybrid polymeric foams described and claimed in the present patent application can have a surface area comprised between 5 m²/g and 200 m²/g, preferably between 8 m²/g and 50 m²/g, measured according to ASTM D-3037-89 and referred to in this text as BET.

The characteristics of coke indicated above, understood as particle size and surface area, also refer to petroleum coke, in particular for calcined petroleum coke, needle coke, and pitch coke.

Coke is produced by the pyrolysis of organic material, and passes, at least in part, through a liquid or liquid- crystalline state during the carbonization process. Preferably, the organic starting material is petroleum, coal or lignite.

More preferably, the coke used in the reactive polymeric mixtures and in the hybrid foams object of the present patent application is the product of the carbonization of the high-boiling hydrocarbon fraction deriving from the distillation of petroleum, conventionally known as the heavy residual fraction. In particular, coke is obtained starting from the coking of the heavy residual fraction, an operation carried out at high temperature which still produces some light fractions and a solid (petroleum coke). The petroleum coke thus obtained is calcined at a temperature comprised between 1000°C and 1600°C (calcined coke).

If a heavy residual fraction rich in aromatic components is used, after calcination and micro-grinding, a needle coke is obtained.

Natural and synthetic graphite is in the form of particles that can have a (Dgo) size, measured with a wet Malvern Mastersizer 2000 Laser Granulometer (defined above) according to the ISO 13320-2009 method, as described above for the same measure with respect to the other athermanous agents. Natural and synthetic graphite particles can have a D90 ranging from 2 pm to 100 pm, preferably from 2.5 pm to 40 pm, even more preferably from 4 pm to 10 pm and a surface area ranging from 5 m²/g to 50 m²/g, measured according to ASTM D-3037-89 and also referred to as BET. Further additives such as nucleating agents, for example polyethylene waxes or talc, antioxidant agents, pigments, stabilizing agents, antistatic agents and detaching agents can be added to the reactive polymeric mixtures and hybrid polymeric foams object of the present patent application. More information on the features of the different types of coke, or graphite, usable in the present invention, production methods and characterization of the different grades commercially available (calcined coke, needle coke and pitch coke but also green coke, coal-derived pitch coke, delayed coke, fluid coke, premium coke) are available online, on the site "goldbook.iupac.org" or in "Pure Appl. Chem., 1995, Vol. 67, No. 3, pages 473-506, Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)".

As mentioned, the previously described reactive phenolic resin is distributed on the surface of the expanded and expandable polymeric granules, forming a reactive polymeric mixture. This reactive polymeric mixture is introduced into a molding device in which a thermal process begins. The reactive polymeric mixture is heated to a temperature comprised between 100°C and 140°C, preferably between 115°C and 125°C; for a period of time of at least 30 minutes, preferably between 40 and 80 minutes, more preferably between 50 and 70 minutes, until a hybrid polymeric foam is formed.

The molding device can be heated using direct or indirect heat exchange devices, for example a stream of steam.

A further object of the present patent application is a hybrid polymeric foam obtained by means of a molding process described and claimed in the present patent application.

According to said process, a reactive polymeric mixture is formed by mixing in a suitable device

1. expandable and expanded granules of vinyl aromatic polymer in which the content of halogens is less than or equal to 100 ppm by weight, and which contain athermanous agents having a D90 size less than or equal to 100 microns, preferably comprised between 2 and 100 microns;

2. reactive phenolic resins comprising:

^■ less than 0.1% by weight of free formaldehyde

^■ where the complement to 100% by weight consists of polar solvents.

Said reactive polymeric mixture is then inserted into a mold and heated with suitable heat exchange devices. The reactive polymeric mixture is heated to a temperature comprised between 80°C and 160°C, preferably comprised between 100°C and 140°C, even more preferably between 115 and 125°C.

The heating period can be comprised between 40 and 80 minutes, more preferably between 50 and 70 minutes. At the end of the heating step, a hybrid polymeric foam is formed in the molding device.

The permanence of the reactive polymeric mixture at the temperatures described and claimed accelerates the crosslinking of the resin and makes it possible to sinter the polymeric granules coated with reactive phenolic resin. In this way we obtain hybrid vinyl aromatic foams with reduced thermal conductivity and able to pass the flame retardancy test (DIN 4102-B2). The great advantage of these foams is that they have flame retardant properties without requiring the dosage of halogenated flame retardants, or additives with flame retardant properties that can harm the health of the personnel involved in the production of expanded thermal insulation panels.

A concentration of formic aldehyde greater than 0.1% would make the reactive phenolic resin carcinogenic.

These hybrid foams, in addition to passing the self extinguishing test DIN 4102-B2 in an extremely easy way, have obvious advantages in terms of environmental impact. The hybrid foams object of the present patent application can contain organ-halogenated flame retardants in concertation lower than or equal to 100 ppm by weight, preferably lower than 50 ppm by weight, more preferably they are free of halogenated flame retardants. Preferably they do not contain halogenated compounds and additives normally used to improve the flame retardancy properties, such as boric acid or boric acid salts, the use of which could cause serious damage to the health of the personnel handling these substances.

The hybrid foams described and claimed in the present patent application reduce the thermal conductivity of the foamed articles, improve fire behavior, have improved fire behavior and have a reduced environmental impact.

The hybrid polymeric foams described and claimed in the present patent application have a measured density after conditioning in an oven for 5 days at a temperature of 70°C, comprised between 20 g/1 and 100 g/1, preferably between 50 g/1 and 70 g/1, even more preferably between 20 g/1 and 40 g/1. The density measurement is performed by weighing the final product (in this case the foam obtained) and by calculating the ratio between the mass of the product and its geometric volume.

The hybrid polymeric foams described and claimed in the present patent application have a thermal conductivity measured as reported in the examples, lower than or equal to 34 mW / m*K at the density of about 30g/l, preferably lower than 33 mW / m*K at the density of about 30 g/1, even more preferably lower than 32 mW / m*K at the density of about 30 g/1.

The expandable and expanded granules containing vinyl aromatic polymers used for the purposes of the present patent application can be produced by polymerization processes in continuous mass or in suspension, preferably aqueous suspension.

A process for preparing the expandable vinyl aromatic polymeric granules in continuous mass comprises the following steps: i) heating a first flow of molten vinyl aromatic polymer to a reference temperature, said reference temperature being higher than the critical temperature of the blowing agent minus 25°C and lower than the critical temperature of the blowing agent plus 25°C; ii) incorporating in a second flow of molten polymeric material, from 0% to 60% by weight, with respect to the weight of the resulting flow, of inorganic and organic additives characterized by the fact that they have less than 10% by weight of particles with a size larger than half the diameter of the holes in a cutting die; iii) incorporating a blowing agent into the polymeric composition obtained in (ii) at a reference pressure, said reference pressure being higher than the critical pressure of the blowing agent; iv) incorporating the polymeric composition obtained in (iii) into the polymeric flow obtained in (i); vii) granulating the expandable polymeric composition obtained in (iv) in a cutting chamber of a device for the hot granulation of thermoplastic polymers.

The granulation device comprises: a) a mold, consisting of a cylindrical body comprising a series of extrusion holes on the external surface and channels for feeding the polymer, positioned inside a cylindrical body, in correspondence with and connected to the holes; b) a set of knives, located in correspondence with the holes in the mold, rigidly connected to a rotating shaft; c) a series of nozzles, located behind the series of knives, which generates a jet of liquid directed against the cutting die; d) an inlet from which a gas flow is fed; and wherein the gas flow coming from said inlet (d) prevents flooding of the granulation chamber.

At the end of the granulation, expandable granules of a substantially spherical shape with an average diameter comprised between 0.4 mm and 2 mm can be obtained.

Already formed polymeric granules can be fed into the first or second polymeric flow, for example into an extruder, optionally mixed with processing waste, post-consumer polymer. Alternatively, it is possible to use a polymer already in the molten state that comes directly from a polymerization plant, in particular from the devolatilization unit. The melted polymer is fed through suitable devices, for example an extruder or a static mixer, where it is eventually mixed with additives and a blowing agent.

There polymerization in aqueous suspension is carried out by reacting one or more vinyl aromatic monomers, in the presence of an athermanous agent, in the presence of a peroxide radical initiator, possibly containing at least one aromatic ring, and of a blowing agent which can be added before, during or at the end of polymerization.

The polymerization is carried out in aqueous suspension with inorganic salts of phosphoric acid, for example tricalcium phosphate or magnesium phosphate. Such salts can be added to the polymerization mixture either already finely divided or synthesized in situ by reaction, for example, between sodium pyrophosphate and magnesium sulfate. These inorganic salts are assisted in their suspending action by anionic surfactants, for example sodium dodecylbenzenesulphonate or by their precursors such as sodium metabisulphite. The polymerization can also be carried out in the presence of organic suspensions such as polyvinylpyrrolidone or polyvinyl alcohol.

The initiator system generally comprises two peroxides, the first with a half-life of one hour at 85-95°C and the other with a half-life of one hour at 110-120°C. Examples of such initiators are benzoyl peroxide and terbutyl perbenzoate.

In general, more details on processes for the preparation of expandable vinyl aromatic polymers in aqueous solution or, more generally, on suspension polymerization can be found in Journal of Macromolecular Science, Review in Macromolecular Chemistry and Physics C31 (263) 215-299 (1991).

To improve the stability of the suspension, it is possible to increase the viscosity of the reagent solution by dissolving vinyl aromatic polymer, in a concentration comprised between 1 and 30% by weight, preferably between 5 and 20%, calculated on the weight of the monomer only. The reagent solution can be obtained either by dissolving a preformed polymer in the reagent mixture (for example fresh polymer or waste from previous polymerizations and/or expansions) or by mass pre-polymerizing the monomer, or mixture of monomers, until the concentrations mentioned above are obtained, and then continuing the polymerization in aqueous suspension in the presence of the remaining additives .

Polymerization additives can be used during suspension polymerization, typically used to produce expandable vinylaromatic polymers, such as suspension stabilizers, chain transfer agents, expansion aids, nucleating agents, plasticizers. In particular, it is preferable to add flame retardant and synergic agents during polymerization.

The blowing agents are preferably added during the polymerization step. At the end of the polymerization, expandable vinyl aromatic polymeric granules with an average diameter comprised between 0.2 and 2 mm are obtained, within which the athermanous agents and any further additives are homogeneously dispersed.

The expandable granules are then discharged from the polymerization reactor and washed continuously or batchwise with non-ionic surfactants or, alternatively, with acids. The expandable vinyl aromatic polymeric granules can be thermally treated with hot air comprised between 30°C and 60°C.

At the end of the polymerization, whether it is carried out in suspension or in continuous mass, the expandable granules produced are subjected to one of the following pre-treatments :

1.coating the granules with an antistatic liquid agent such as amines, ethoxylated tertiary alkylamines, ethylene oxide-propylene oxide copolymers; said agent serves to make the coating adhere and to facilitate the screening of the granules produced;

2. applying on said granules a coating which comprises a mixture of at least one of mono-, di- and tri-esters of glycerin, fatty acids and metal stearates, preferably selected from zinc and/or magnesium stearate, optionally also mixed with carbon black.

The expandable vinyl aromatic polymeric granules obtained with one of the polymerization processes indicated in this patent application, can be subjected to a first expansion with a gas, typically water vapor, in a suitable expansion device, as already explained in the present patent application .

The expanded granules can be expanded again, as already explained in the present patent application, by making the granules swell in a closed mold using a gas, typically water vapor, and making the swollen particles, contained inside the mold, weld by means of the simultaneous effect of the pressure and temperature (sintering of the foams thus obtained). The swelling of the particles is generally achieved with steam, or another gas, maintained at a temperature slightly higher than the glass transition temperature (Tg) of the polymer.

At the end of the expansion, expanded granules are obtained with a density comprised between 10 g/1 and 30 g/1, preferably with a density comprised between 15 g/1 and 20 g/1.

Some examples are given below for a better understanding of the invention and of the scope of application, although they do not in any way constitute a limitation of the scope of the present invention.

EXAMPLES

In the examples, the reactive phenolic resin produced by the company Hexion Bakelite® PW76-003 was used, which has a phenol-formaldehyde polymer content comprised between 50% and 75% by weight, a phenol content in a concentration comprised between 5% and 10 % by weight, and a free formaldehyde content lower than 0.1%.

Bakelite® PW76-003 is characterized by a formaldehyde content lower than 0.1% w/w with respect to the weight of the commercial reactive phenolic resin. This feature also makes it much easier to handle the product during the production process of hybrid foams, as the handling of the resin in a confined environment is not required. The hardening of the reactive phenolic resin can be accelerated by heating, and is made easier by the presence of a catalyst.

In all the examples of the invention it can be observed that the introduction of non-halogenated flame retardants into the liquid reactive phenolic resin Hexion Bakelite® PW76-003 has led to the development of foamed products which have better fire performance, intended as a reduction of the flame heights measured during the DIN 4102-B2 test, both with respect to the flame heights measured by dispersing only the reactive phenolic resin on the surface of the expanded and/or expandable polystyrene granules, and with respect to the flame heights recorded on the samples of expanded polystyrene produced conventionally, containing organo-brominated flame retardants.

In all examples the liquid reactive phenolic resin is dispersed in water.

In the examples according to the invention, the liquid reactive phenolic resin Bakelite® PW76-003 is distributed on the expandable and expanded granules of polystyrene, which are mixed so as to ensure a uniform distribution of the resin on the surface of the granules. The granules are then placed in a container and the liquid reactive phenolic resin is poured onto the surface of the granules forming a reactive polymeric mixture. A glass rod or a mechanical stirring system can be used to ensure optimal distribution of the liquid reactive phenolic resin on the surface of the polystyrene granules. The mixing time of the granules with the resin must be for at least 5 minutes, at a temperature of 25°C.

The addition of the acid catalyst produced by the company Hexion (trade name Cellobond Phencat 382) to the commercial reactive phenolic resin Hexion-Bakelite® PW76-003 is intended to reduce the time required for crosslinking and hardening of the reactive phenolic resin, and thus facilitate the adhesion of the reactive phenolic resin on the surface of the polystyrene granules, during the heating step of the granules, when they are placed inside a mold. The reactive polymeric mixture thus produced is then transferred into a metal mold, necessary to impart the shape to the final expanded product.

The mold containing the reactive polymeric mixture is then heated in an oven at a temperature comprised between 100°C and 140°C, preferably at a temperature comprised between 115°C and 125°C, more preferably of 120°C for about 60 minutes.

After cooling the mold, until it reaches room temperature, the hybrid polymeric foam is extracted from the mold, and then the specimens to be subjected to the fire test according to DIN 4102-B2 standard, and the specimens for the measurement of thermal conductivity are obtained.

To measure the thermal conductivity, the specimens are left for 5 days in an oven at 70°C; then the thermal conductivity is measured according to DIN EN 13163 standard.

The fire behavior test is carried out according to DIN 4102-B2 standard. Comparative Example 1

A mixture is charged into a closed stirred reactor and mixed. This mixture is composed of 150 parts by weight of water, 0.2 parts by weight of sodium pyrophosphate, 100 parts by weight of styrene, 0.25 parts by weight of tert- butylperoxy-2-ethylhexanoate, 0.25 parts by weight of butyl perbenzoate, 1.5 parts by weight of styrene- brominated butadiene (Emerald 3000-ICL), 0.3 by weight parts of polyethylene wax, and 5 parts by weight of calcined petroleum coke 4287 sold by Asbury Graphite Mills Inc. (USA), with a D90size of the particles of about 7 pm. The mixture is heated to 90°C while under stirring. After about 2 hours at 90°C, 4 parts by weight are added, with respect to the weight of the H2O, of a 10% polyvinylpyrrolidone solution. The mixture is heated to 100°C, while still under stirring, for another 2 hours, 7 parts by weight, with respect to the weight of the styrene, of a 70/30 w/w mixture of n-pentane and i-pentane are added, the whole mixture is heated for another 4 hours at 125°C, it is cooled and the product is discharged.

The expandable polymeric granules thus produced are subsequently collected and washed with demineralized water containing 0.05% of a non-ionic surfactant consisting of a fatty alcohol condensed with ethylene oxide and propylene oxide, sold by Huntsman under the trade name of Empilan 2638. The granules are then dried in a stream of hot air, 0.02% of a non-ionic surfactant is added, consisting of a condensate of ethylene oxide and propylene oxide on a glycerine basis, sold by Dow (Voranol CP4755) and are subsequently screened by separating a fraction with a diameter comprised between 1 and 1.5 mm.

0.2% w/w glyceryl monostearate and 0.1% w/w zinc stearate are then added to the 1 to 1.5 mm fraction as coating additives. The expandable polystyrene granules are then expanded with steam at a temperature of 100°C, and left to age for 8 hours and used for block molding (dimensions 1040x1030x550 mm).

The blocks were then cut to prepare flat sheets on which thermal conductivity was measured. In addition, specimens were obtained for evaluating the fire behavior of the samples, according to DIN 4102-B2 standard. The thermal conductivity, measured after 5 days in the oven at 70°C, was 31 mW/m*K (measured according to DIN EN 13163 standard) at a density of 31 g/1. By subjecting 5 specimens with a density of 31 g/1 to the fire test, the average height of the flame was 11 cm (DIN 4102-B2 standard). See the results reported in table 2.

Example 1

20.6 parts by weight of expandable polystyrene granules, prepared as indicated in Comparative Example 1, but produced in the absence of styrene- brominated butadiene flame retardant (Emerald 3000-ICL), were mixed with 43 parts by weight of expanded polystyrene granules, obtained by expanding the expandable granules of comparative example 1, but without styrene-brominated butadiene Emerald 3000- ICL, so as to obtain expanded granules with a density of 15 g/1. The above-mentioned granules of expandable polystyrene, and the granules of expanded polystyrene, in the quantities indicated above, were mixed and poured into a container.

In another container 32.7 parts by weight of Bakelite PW76- 003 reactive phenolic resin, produced by the company Hexion, were mixed with 3.7 parts by weight of Cellobond Phencat 382 catalyst (produced by the company Hexion). Reactive phenolic resin and catalyst are vigorously mixed for 5 minutes with a glass rod, at a temperature of 25°C, in order to ensure optimal distribution of the catalyst in the reactive phenolic resin. The mixture consisting of reactive phenolic resin and catalyst is added to the surface of the expandable polystyrene granules and the expanded polystyrene granules, thus forming a polymeric mixture. To optimize the distribution of the mixture consisting of reactive phenolic resin and catalyst, on the surface of the vinyl aromatic granules, a glass rod is used. The polymeric granules are thus mixed vigorously with the mixture consisting of reactive phenolic resin and catalyst, for 8 minutes, at a temperature of 25°C. In this way the reactive phenolic resin and the catalyst are optimally distributed on the surface of the polymeric granules.

The polymeric composition thus produced is then transferred into a metal mold, necessary to impart the shape and the right degree of cohesion to the final expanded product.

The metal mold (with a thickness of 2.1 cm, height 19.1 cm, width 45.2 cm) is thus completely filled with the expandable and expanded polystyrene granules covered with the reactive phenolic resin and the catalyst, and then closed with a metal lid. The metal mold is then heated in an oven at a temperature of 120°C for 60 minutes.

After cooling the mold, until it reaches room temperature, the hybrid foam is extracted from the mold, and thus the specimens to be subjected to the fire test (according to DIN 4102-B2 standard) and the specimens for measuring thermal conductivity are obtained. The thermal conductivity, measured after 5 days of permanence of the specimen in the oven at 70°C, was 30.9 mW/mK according to DIN EN 13163 standard at a density of 30.9 g/1. By subjecting 5 specimens of hybrid foam to the fire test, with a density of 30.9 g/1, the average height of the flame was 8 cm (DIN 4102-B2 standard). See the results reported in table 2. Example 2

20.6 parts by weight of expandable polystyrene granules, prepared as in comparative example 1, but produced in the absence of styrene-brominated butadiene flame retardant (Emerald 3000-ICL) were mixed with 43 parts by weight of expanded polystyrene, obtained by expanding the expandable granules of comparative example 1 (but without styrene- brominated butadiene Emerald 3000-ICL), so as to obtain expanded granules with a density of 15 g/1. The expandable polystyrene granules, and the expanded polystyrene granules, in the quantities indicated above, were mixed and poured into a container.

In another container 30.7 parts by weight of Bakelite PW76- 003 reactive phenolic resin, produced by the company Hexion, were mixed with 3.7 parts by weight of catalyst Cellobond Phencat 382 (produced by the company Hexion) and with 2 parts by weight of ammonium polyphosphate (Phos- Chek P42 produced by the ICL company). Reactive phenolic resin, catalyst and ammonium polyphosphate are mixed vigorously for 5 minutes with a glass rod, at a temperature of 25°C, in order to optimize the dispersion of the catalyst and ammonium polyphosphate, in the reactive phenolic resin. This mixture is then optimally dispersed on the surface of the polymeric granules, following the procedures described in Example 1.

Following the procedure described in Example 1, the polymeric granules coated with reactive phenolic resin, catalyst and ammonium polyphosphate are introduced into the metal mold, heated to a temperature of 120°C, for 60 minutes. A hybrid foam is then obtained, from which the specimen for evaluating thermal conductivity and the 5 specimens for evaluating fire behavior according to DIN 4102-B2 standard are obtained. The thermal conductivity, measured after 5 days of permanence of the specimen in the oven at 70°C, was 31 mW/m*K measured according to DIN EN 13163 standard at a density of 31.1 g/1 . By subjecting 5 specimens of hybrid foam to the fire test, with a density of 31.1 g/1, the average height of the flame was 5 cm (DIN 4102-B2 standard). See the results reported in table 2.

Example 3

20.6 parts by weight of expandable polystyrene granules prepared as indicated in comparative Example 1, but produced in the absence of styrene-brominated butadiene copolymer flame retardant (Emerald 3000-ICL), were mixed with 43 parts by weight of expanded polystyrene granules, obtained by expanding the expandable granules of comparative example 1 (but without styrene-brominated butadiene copolymer-Emerald 3000-ICL), so as to obtain expanded granules with a density of 15 g/1. The above- mentioned granules of expandable polystyrene, and the granules of expanded polystyrene, in the quantities indicated above, were mixed and poured into a container.

In another container 30.7 parts by weight of Bakelite PW76- 003 reactive phenolic resin, produced by the company Hexion, were mixed with 3.7 parts by weight of catalyst Phencat 382 (produced by the company Hexion) and with 2 parts by weight of DOPO-DDP (GC RE DDP produced by GreenChemicals company). Reactive phenolic resin, catalyst and DOPO-DDP are mixed vigorously for 5 minutes with a glass rod, at a temperature of 25°C, in order to optimize the dispersion of the catalyst and DOPO-DDP, in the reactive phenolic resin. This mixture is then optimally dispersed on the surface of the polymeric granules, following the procedures described in Example 1.

Following the procedure described in Example 1, the polymeric granules coated with reactive phenolic resin, catalyst and DOPO-DDP are introduced into the metal mold, heated to a temperature of 120°C, for 60 minutes. A hybrid foam is then obtained, from which the specimen for evaluating thermal conductivity and the 5 specimens for evaluating fire behavior according to DIN 4102-B2 standard are obtained.

The thermal conductivity, measured after 5 days of permanence of the specimen in the oven at 70°C, was 31.2 mW/mK measured according to DIN EN 13163 standard at a density of 31.2 g/1. By subjecting 5 specimens of hybrid foam to the fire test, with a density of 31.2 g/1, the average height of the flame was 6 cm (DIN 4102-B2 standard). See the results reported in table 2.

Example 4

20.6 parts by weight of expandable polystyrene granules, containing 5 parts by weight of calcined petroleum coke, prepared as indicated in Comparative Example 1, but produced in the absence of styrene-brominated butadiene copolymer flame retardant (Emerald 3000-ICL) were mixed with 43 parts by weight of expanded polystyrene granules, obtained by expanding the expandable granules of comparative example 1 (but without styrene-brominated butadiene copolymer Emerald 3000-ICL), so as to obtain expanded granules with a density of 15 g/1. The above- mentioned granules of expandable polystyrene, and the granules of expanded polystyrene, in the quantities indicated above, were mixed and poured into a container.

In another container 30.7 parts by weight of Bakelite PW76- 003 reactive phenolic resin, produced by the company Hexion, was mixed with 3.7 parts by weight of catalyst Cellobond Phencat 382 (produced by the company Hexion) and with 1 part by weight of DOPO-DDP and 1 part by weight of Ammonium Polyphosphate (Phos-chek P42 -ICL). Reactive phenolic resin, catalyst, DOPO-DDP and Ammonium Polyphosphate are mixed vigorously for 5 minutes with a glass rod at a temperature of 25°C, in order to optimize the dispersion of the catalyst, DOPO-DDP and Ammonium Polyphosphate, in the reactive phenolic resin. This mixture is then homogeneously dispersed on the surface of the polymeric granules, following the procedures described in Example 1.

Following the procedure described in Example 1, the polymeric granules covered with reactive phenolic resin, catalyst, DOPO-DDP and Ammonium Polyphosphate are introduced into the metal mold, heated to a temperature of 120°C, for 60 minutes. A hybrid foam is then obtained, from which the specimen for evaluating thermal conductivity and the 5 specimens for evaluating fire behavior according to DIN 4102-B2 standard are obtained.

The thermal conductivity, measured after 5 days of permanence of the specimen in the oven at 70°C, was 30.9 mW/mK measured according to DIN EN 13163 standard at a density of 31 g/1. By subjecting 5 specimens of hybrid foam to the fire test, with a density of 31 g/1, the average height of the flame was 4 cm (DIN 4102-B2 standard). See the results reported in table 2.

Example 5

20.6 parts by weight of expandable granules of a vinyl- aromatic polymer, prepared as in comparative Example 1, but produced in the absence of styrene-brominated butadiene copolymer flame retardant (Emerald 3000-ICL) were mixed with 43 parts by weight of expanded polystyrene granules, obtained by expanding the expandable granules of comparative example 1 (but without styrene-brominated butadiene copolymer Emerald 3000-ICL), so as to obtain expanded granules with a density of 15 g/1. The above- mentioned granules of expandable polystyrene, and the granules of expanded polystyrene, in the quantities indicated above, were mixed and poured into a container.

In another container 30.7 parts by weight of Bakelite PW76- 003 reactive phenolic resin, produced by the company Hexion, were mixed with 3.7 parts by weight of catalyst Cellobond Phencat 382 (produced by the company Hexion) and with 2 parts by weight of hypophosphite of calcium (Everflam HPCA-Everkem) Reactive phenolic resin, catalyst and calcium hypophosphite are mixed vigorously for 5 minutes with a glass rod at a temperature of 25°C, in order to optimize the dispersion of the catalyst and calcium hypophosphite, in the reactive phenolic resin. This mixture is then optimally dispersed on the surface of the polymeric granules, following the procedures described in Example 1. Following the procedure described in Example 1, the polymeric granules coated with reactive phenolic resin, catalyst and calcium hypophosphite are introduced into the metal mold, heated to a temperature of 120°C, for 60 minutes. A hybrid foam is then obtained, from which the specimen for evaluating thermal conductivity and the 5 specimens for evaluating fire behavior according to DIN 4102-B2 standard are obtained.

The thermal conductivity, measured after 5 days of permanence of the specimen in the oven at 70°C, was 31.3 mW/m*K measured according to DIN EN 13163 standard at a density of 31.2 g/1. By subjecting 5 specimens of hybrid foam to the fire test, with a density of 31.2 g/1, the average height of the flame was 7 cm (DIN 4102-B2 standard). See the results reported in table 2.

Example 6

20.6 parts by weight of expandable polystyrene granules prepared as indicated in comparative Example 1, but produced in the absence of styrene-brominated butadiene copolymer flame retardant (Emerald 3000-ICL) were mixed with 43 parts by weight of granules of expanded polystyrene obtained by expanding the expandable granules of comparative example 1 (but without styrene-brominated butadiene copolymer Emerald 3000-ICL), so as to obtain expanded granules with a density of 15 g/1. The above- mentioned granules of expandable polystyrene and the granules of expanded polystyrene, in the quantities indicated above, were mixed and poured into a container.

In another container 30.7 g of Bakelite PW76-003 reactive phenolic resin, produced by the company Hexion, were mixed with 3.7 parts by weight of catalyst Cellobond Phencat 382 (produced by the company Hexion) and with 1 part by weight of Ca hypophosphite ( Everflam HPCA Everkem) and 1 part by weight of expanded graphite (SC20 OS produced by the company Graphit Kropfmuhl) . Reactive phenolic resin, catalyst, calcium hypophosphite and expanded graphite are mixed vigorously for 5 minutes with a glass rod at a temperature of 25⁰ C, in order to optimize the dispersion of the catalyst, calcium hypophosphite and expanded graphite, in the reactive phenolic resin. This mixture is then optimally dispersed on the surface of the polymeric granules, following the procedures described in Example 1. Following the procedure described in Example 1, the polymeric granules coated with reactive phenolic resin, catalyst, calcium hypophosphite and expanded graphite are introduced into the metal mold, heated to a temperature of 120°C, for 60 minutes. A hybrid foam is then obtained, from which the specimen for evaluating thermal conductivity and the 5 specimens for evaluating fire behavior according to DIN 4102-B2 standard are obtained.

The thermal conductivity, measured after 5 days of permanence of the specimen in the stove at 70°C, is 30.9 mW/m*K measured according to DIN EN 13163 standard at a density of 31.1 g/1. By subjecting 5 specimens of hybrid foam to the fire test, with a density of 31.1 g/1, the average height of the flame was 3 cm (DIN 4102-B2 standard). See the results reported in table 2.

Example 7

20.6 parts by weight of expandable polystyrene granules prepared as indicated in comparative Example 1, but produced in the absence of styrene-brominated butadiene copolymer flame retardant (Emerald 3000-ICL) were mixed with 43 parts by weight of expanded polystyrene granules, obtained by expanding the expandable granules of comparative example 1 (but without styrene-brominated butadiene copolymer-Emerald 3000-ICL), so as to obtain expanded granules with a density of 15 g/1. The above- mentioned granules of expandable polystyrene, and the granules of expanded polystyrene, in the quantities indicated above, were mixed and poured into a container.

In another container 30.7 parts by weight of Bakelite PW76- 003 reactive phenolic resin, produced by the company Hexion, were mixed with 3.7 g of catalyst Cellobond Phencat 382 (produced by the company Hexion) and with 2 parts of expanded graphite (SC20 OS produced from Graphit Kropfmuhl). Reactive phenolic resin, catalyst and expanded graphite are mixed vigorously for 5 minutes with a glass rod, at a temperature of 25°C, in order to optimize the dispersion of the catalyst and expanded graphite, in the reactive phenolic resin. This mixture is then homogeneously dispersed on the surface of the polymeric granules, following the procedures described in Example 1.

Following the procedure described in Example 1, the polymeric granules coated with reactive phenolic resin, catalyst and expanded graphite are introduced into the metal mold, heated to a temperature of 120°C, for 60 minutes. A hybrid foam is then obtained, from which the specimen for evaluating thermal conductivity and the 5 specimens for evaluating fire behavior according to DIN

4102-B2 standard are obtained.

The thermal conductivity, measured after 5 days of permanence of the specimen in the oven at 70°C, was 31 mW/m*K measured according to DIN EN 13163 standard at a density of 30.9 g/1. By subjecting 5 specimens of hybrid foam to the fire test, with a density of 30.9 g/1, the average height of the flame was 5 cm (DIN 4102-B2 standard) . See the results reported in table 2. Table 1 Table 2

From the comparison between the flame heights, shown in table 2, which are measured by subjecting the specimens made of hybrid foams to the fire test (test carried out according to DIN 4102-B2 standard) with the expanded polystyrene specimens produced in a conventional way containing brominated flame retardants (comparative example 1), it is evident that hybrid foams have a better fire behavior, since lower flame heights are recorded during the test.

Claims

1.A reactive polymeric mixture comprising:

- expandable and expanded granules of vinyl aromatic polymer wherein the halogen content is less than or equal to 100 ppm by weight and containing athermanous agents whose particles have a D90 size less than or equal to 100 microns,

- reactive phenolic resins comprising:

• between 2% and 12% by weight, preferably between 5% and 10% by weight of phenol;

• between 40% and 85% by weight, preferably between 50% and 75% by weight of a phenol-formaldehyde polymer; and

• less than 0.1% by weight of free formaldehyde;

• where the complement to 100% by weight consists of polar solvents.

2.The mixture according to claim 1 wherein the halogen content is less than or equal to 50 ppm by weight.

3.The mixture according to claim 2 wherein the halogens are absent.

4.The mixture according to any one of claims 1 to 3 which does not contain boron or boron salts.

5.The reactive polymeric mixture according to any one of claims 1 to 4 which further comprises organic or inorganic acids, or mixtures of said organic or inorganic acids with the relative esters.

6.The reactive polymeric mixture according to any one of claims 1 to 5 wherein the reactive phenolic resin comprises athermanous agents whose particles have a D90 size ranging from 2 to 100 microns.

7.The reactive polymeric mixture according to any one of claims 1 to 6 wherein the athermanous agents have a concentration comprised between 0.1% by weight and 20% by weight, with respect to the total weight of the reactive polymeric mixture.

8. The reactive polymeric mixture according to any one of claims 1 to 7 wherein the athermanous agents are chosen from carbon black, graphite and coke.

9. The reactive polymeric mixture according to claim 8 wherein the coke is selected from calcined petroleum coke, needle coke, pitch coke, or mixtures thereof.

10.The reactive polymeric mixture according to claim 9 wherein the graphite is chosen from natural graphite, synthetic graphite, or mixtures thereof.

11.The reactive polymeric mixture according to claim 9 or 10 wherein the coke has a powder particle D90size ranging from 2 pm to 100 pm.

12.The reactive polymeric mixture according to claim 11 wherein the coke has a surface area comprised between 5 m²/g and 200 m²/g measured according to ASTM D-3037-89.

13.The reactive polymeric mixture according to any one of claims 1 to 12 which further contains non-halogenated flame retardants.

14.The reactive polymeric mixture according to claim 13 wherein the reactive phenolic resin contains the non- halogenated flame retardants, or the expandable and expanded polymeric granules contain the non-halogenated flame retardants, or both phenolic resin and expanded and expandable granules contain at the same time non- halogenated flame retardants.

15.The reactive polymeric mixture according to any one of claims 1 to 14 wherein the polar solvent in which the reactive phenolic resin is dispersed is water or alcohol.

16.The reactive polymeric mixture according to any one of claims 1 to 15 wherein the reactive phenolic resins comprise:

• between 2% and 12% by weight, preferably between 5% and 10% by weight of phenol; • between 40% and 85% by weight, preferably between 50% and 75% by weight of a phenol-formaldehyde polymer; and

• less than 0.1% by weight of free formaldehyde

• where the complement to 100% by weight consists of polar solvents.

17. A hybrid polymeric foam obtained by a molding process which comprises the following steps:

- forming a reactive polymeric mixture by mixing in a suitable device

1. expandable and expanded granules of vinyl aromatic polymer containing athermanous agents whose particles have a D90 size less than or equal to 100 microns, and wherein the halogen content is less than or equal to 100 ppm by weight;

2. reactive phenolic resins comprising:

• less than 0.1% by weight of free formaldehyde

• where the complement to 100% by weight consists of polar solvents;

- inserting the reactive polymeric mixture into a mold;

- heating the reactive polymeric mixture at a temperature comprised between 80°C and 160°C, for a period of time comprised between 40 and 80 minutes, until a hybrid polymeric foam is formed.

18. The hybrid polymeric foam according to claim 17 wherein the halogen content is less than or equal to 50 ppm.

19. The polymeric foam according to claim 18 wherein the halogens are absent.

20. The hybrid polymeric foam according to any one of claims 17 to 19 wherein the boron or boron salts are absent.

21. The hybrid polymeric foam according to any one of claims 17 to 20 which passes the DIN 4102 B2 fire test, wherein the density varies between 20 and 40 g/1 and the thermal conductivity is less than or equal to 34 mW / m*K.

22.A molding process for the preparation of hybrid foams which comprises the following steps:

- forming a reactive polymeric mixture by mixing in a suitable device

1. expandable and expanded granules of vinyl aromatic polymer containing athermanous agents whose particles have a D90 size comprised between 2 and 100 microns, and wherein the halogen content is less than or equal to 100 ppm;

2. reactive phenolic resins comprising:

• less than 0.1% by weight of free formaldehyde,

• where the complement to 100% by weight consists of polar solvents.

- inserting the reactive polymeric mixture into a mold;

- heating the reactive polymeric mixture at a temperature comprised between 80 °C and 160 °C, for a period of time comprised between 40 and 80 minutes, until a hybrid polymeric foam is formed.

23. The molding process according to claim 22 wherein organic or inorganic acids, or mixtures of said organic or inorganic acids with the relative esters are added in the reactive phenolic resin, before dosing the reactive phenolic resin onto the expandable and expanded polymeric granules.

24. The molding process according to claim 23 wherein organic or inorganic acids, or mixtures of said organic or inorganic acids with the relative esters are added directly onto the expandable and expanded polymeric granules, before introducing the reactive polymeric mixture into the mold.

25. The molding process according to any one of claims 22 to 24, wherein further athermanous agents are dispersed in the reactive phenolic resin before the latter is dosed onto the expandable and expanded polymeric granules.

26. The molding process according to any one of claims 22 to 25, wherein non-halogenated flame retardants are added in the dispersion containing the reactive phenolic resin before the latter is distributed onto the polymeric granules.

27. The molding process according to any one of claims 22 to 26, wherein the reactive polymeric mixture is heated at a temperature comprised between 100°C and 140°C, for a period of time comprised between 40 and 80 minutes, until a hybrid polymeric foam is formed.

28. The molding process according to any one of claims 22 to 27 which forms the hybrid polymeric foam according to any one of claims 1 to 16.