BE1023119B1 - Polymer compositions with improved fire resistance - Google Patents

Abstract

Polymer compositions based on polyethylene, which comprise 0.05 to 10% by weight, preferably 0.1 to 5% by weight, of iron (III) acetylacetonate.

Description

POLYMER COMPOSITIONS WITH IMPROVED FIRE RESISTANCE

Technical area

The present invention relates to polyethylene based polymer compositions which exhibit improved fire performance and articles made from these compositions.

State of the art

The response to fire exposure and fire resistance are key parameters that must be considered when developing a material. In particular, this applies to the thermoplastic materials that are used in numerous everyday objects and thus must represent the least possible risk to the user. Thermoplastic polymers are known to be flammable and less fire resistant. They must therefore be modified to prevent a fire or at least delay it. Thermoplastic materials have many approaches to improve fire resistance and fire performance. In particular, additives such as flame retardants find widespread use in thermoplastic materials. There are several types of flame retardants in the area. It may be, inter alia, compounds of a mineral nature, halogen-containing compounds or phosphorus-containing compounds. Depending on which polymers they are used in, these flame retardants can have different effects.

Although some of these compounds make it possible to significantly improve the behavior on fire in the case of polymers, on the other hand they have disadvantages. For example, many of the halogen-containing compounds per se already have a high toxicity. In addition, halogen-containing compounds that include aromatic rings can degrade to dioxins and dioxin-like compounds when heated, such as during manufacture, during a fire, during reuse, or even when exposed to the sun.

Thus, while there are already approaches to solution, it seems to be of interest to develop alternative polymer compositions which exhibit desirable fire properties.

Object of the invention

Thus, it is an object of the present invention to provide polymer compositions which have adequate fire resistance, preferably having extended ignition times and / or reduced heat release at elevated temperature.

General description of the invention

In order to achieve the above object, the present invention according to a first aspect provides a polyethylene (PE) -based polymer composition characterized in that it is 0.01 to 10% by weight, preferably 0.1 to 5% Wt .-%, with particular preference 0.2 to 3 wt .-%, more preferably 0.5 to 2.7 wt .-% of iron (NI) acetylacetonate. Surprisingly, it has been found that the addition of even relatively small amounts of Fe (acac) 3 to a polyethylene composition makes it possible to drastically prolong the period of inflammation (details of which are set forth below in the experimental section). In fact, ignition periods comparable to or better than those obtained with halogen-containing flame retardants are achieved, but the disadvantages of the latter are avoided (see introduction). Iron (NI) acetylacetonate, also referred to as iron (NI) tris (acetylacetonate), Fe (C5H7O2) 3 or Fe (acac) 3, is in fact of relatively low toxicity.

By polyethylene is meant any ethylene polymer (or a mixture of several ethylene polymers), especially straight chain or branched polyethylenes, such as very low density polyethylene (VLDPD) very low density polyethylene (PE-VLD) low density polyethylene LLDD low density polyethylene (LLDPE - linear low density polyethylene), PE-LD - low density polyethylene (LDPE), PE-MD - medium density polyethylene (MDPE) and high density polyethylene (PE-HD) ( HDPE, high-density polyethylene). Preferably, the polyethylene which is the basis of the polymer composition of the present invention is low density polyethylene (PE-LD or LDPE).

The low density polyethylene or polyethylene may comprise from 5 to 30% by weight of polyethylene grafted with maleic anhydride (PEgMA). Preferably, the composition comprises low density polyethylene (PE-LD) to which low density polyethylene grafted with maleic anhydride (PE-LDgMA) has been added. A polyethylene grafted with maleic anhydride (PEgAM or PE-LDgAM) corresponds to an ethylene polymer as defined above, which has been grafted with side maleic anhydride groups.

In an advantageous variant of the invention, the composition furthermore comprises 1 to 8% by weight, preferably 3 to 6% by weight, of silica, preferably of nanometer scale silica filler. For the purposes of the present invention, silica is understood as meaning a silicon dioxide selected from silica nanoparticles, in particular from fumed silicas whose particle size is in the two-digit to three-digit nanometer range, developing a large specific surface area (in the two-digit to three-digit range, expressed in FIG m2 / g) and have undergone such a surface treatment that they become hydrophobic, for example with alkylsilanes, hexamethyldisilazane or other agents.

In an additional variant, the composition may comprise 15 to 25% by weight polycarbonate, preferably plasticized polycarbonate. In general, it is advantageous to add 10% to 45% by weight of polycarbonate to plasticizers, based on the polycarbonate, to facilitate or enhance its incorporation into PE. As plasticizers there may be used organic plasticizers which are of the ester type selected from the azelates, the adipates, the phosphates, the phthalates or a mixture thereof. With particular preference, the polycarbonate comprises 10 to 45 wt .-%, in particular 20 to 40 wt .-%, of tricresyl phosphate (TCP, or tritolyl - TTP) as a plasticizer.

According to an additional variant, the compositions according to the invention additionally comprise 1 to 6% by weight, preferably 2 to 5% by weight, of low emissivity metal particles (or powders), preferably of aluminum, of steel, of zinc and / or or consist of or coated with bronze, wherein the metal particles are preferably aluminum particles. The metal particles have a mass-median median diameter (D50) of from 1 to 40 gm, preferably from 3 to 30 gm, more preferably from 5 to 25 gm.

The polymer compositions described herein may also contain, depending on their use, and as needed, one or more additives, in particular from the antioxidants, UV filters, antistatic agents, foaming agents, nucleating agents, lubricants , the absorption and reflection means for infrared radiation (in addition to the metal particles), the dyes and pigments, the fillers, in particular the reinforcing fillers, the agents for the oxo degradation, the anti-fogging agents, the antiblocking agents, the permeability modifiers, the cell size regulators and other fire-retardant agents are selected.

In a particularly advantageous variant, the polymer composition comprises: 0.25 to 5% by weight of iron (III) acetylacetonate, 3 to 6% by weight of silica filler on the nanometer scale, 2 to 5% by weight of aluminum particles, 15 to 25 Wt .-% of plasticized polycarbonate with 15 to 30 wt .-% of tricresyl phosphate, based on the plasticizer-containing polycarbonate, 0 to 10 wt .-% of at least one additive, wherein PE-LD, the 10 to 25 wt .-% of PE-LDgMA comprises, the rest makes up.

It has been found that compositions of this kind make it possible to achieve a particularly interesting compromise in terms of fire resistance, as regards both the firing period and heat release (details of which are set forth below).

An additional aspect of the invention relates more particularly to foams comprising (at least) a polymer composition as described herein. To obtain these foams, the polymer compositions comprise one or more chemical and / or physical foaming agents. These are generally those commonly used in the production of polyethylene foams. The chemical foaming agents can be selected, for example, from azo-bis- (isobutyronitrile), azodicarboxylic acid diamide, dinitrosopentamethylenetetramine, 4,4'-oxy-bis- (benzenesulfonylhydrazide), diphenylsulfone-3,3'-disulfohydrazide, benzene-1,3-disulfohydrazide, p- toluenesulfonyl; citric acid,

Sodium bicarbonate and mixtures thereof may be selected. Among the suitable physical foaming agents would be the agents which are gaseous at room temperature and normal pressure, such as CO2, nitrogen, short chain alkanes such as butane or isobutane, etc., and agents which are liquid at room temperature and normal pressure, such as pentane. Hexane, etc. Preferably, the physical foaming agent is selected from isobutane, nitrogen, CO2 - optionally in supercritical form -, ethanol, the remaining C2-C5 alkanes or one of their mixtures.

The compositions for foams may further contain one or more additives selected from the group consisting of cell nucleating agents, antioxidants, UV filters, antistatic agents, nucleating agents, lubricants, absorption and reflection agents for infrared radiation (non-metal particles), the dyes and pigments, the fillers, in particular the reinforcing fillers, the agents for the oxo degradation, the anti-fogging agents, the antiblocking agents, the permeability modifiers and other fire retardants.

The present invention further relates to foam profile parts and to articles and products made from these foams, which may be, for example, foams used for thermal insulation, protective packaging, wedging, for leisure or decoration purposes, being used in transportation , Buildings, recreational items, decorative objects, DIY (Do It Yourself), electronics, electrical appliances, heat and / or sound insulation, furniture, or any other application where fire retardancy is beneficial.

In general, the invention relates to any manufactured article (of foam or not, of composite or not), at least a portion of which comprises a polymer composition as described in the present document. Such a manufactured article may be extruded or molded parts in the field of transportation or in the field of construction, domestic or recreational articles, DIY (Do It Yourself), electronics, electrical appliances, heat and / or Sound insulation, furniture or in any other application in which the fire retardant property is beneficial.

In a further additional aspect, the invention provides a process for preparing the polymer compositions of the present invention comprising blending the polyethylene or polyethylenes with ferric acetylacetonate, optionally with the plasticized polycarbonate, with the silica, with the aluminum and possibly with other ingredients includes. Such a process is particularly suitable for the foams according to the invention and may preferably comprise the following steps: quantitative introduction of the polyethylene or polyethylenes and of the iron (III) acetylacetonate and, if appropriate, of the plasticized polycarbonate, of the silicon dioxide, of the metallic particles such as Aluminum and / or, one at a time, one or more of the further constituents, and possibly a chemical blowing agent, at the feed device of an extruder (single screw, twin screw, co-rotating, counter-rotating, first tandem extruder, ...). The constituents can be added quantitatively in the form of pure substance granules, as a powder, as a flake, as a compound, as a premix, as a compacted powder, as a liquid or in any other physical forms; Softening the resulting mixture by heating the cylinder and mixing it through the screw (s) to completely melt and homogenize the mass; possibly introducing a foaming gas into the cylinder at the point where the viscosity of the mixture is best for it • Homogenizing the polymer composition and the gas, • Cooling the mass and homogenizing, • Extruding through a nozzle with temperature control, whose

Cross section a particular shape depending on the

Endive use of the foam, wherein the mass undergoes a large pressure drop, which after leaving the nozzle for

Formation of gas bubbles, resulting in the formation of a foam in the free air, cooling and optionally pulling and shaping of the foam: the extruded foam preferably undergoes its shaping by means of a tension-free drawing device, in a cooling section (with air or water or both), to solidify it in the desired structure.

According to the above-described method, as the foaming agent, one or more physical or chemical foaming agents or both may be used simultaneously.

Further, another aspect of the invention relates to the use of polymer compositions as described herein for the manufacture of fabricated articles. All variants and embodiments described above may be combined as appropriate.

Brief description of the drawings

Other features and characteristics of the invention will be apparent from the detailed description of some advantageous embodiments, given below for purposes of illustration, with reference to the accompanying drawings. Showing:

Fig. 1: TGA curves of the mass loss as a function of the temperature for PE-LD in pure form or with the addition of 1% of iron acetylacetonate (under air and N2 atmosphere and at 20 ° C / min), weight (%) = Mass in%;

FIG. 2: TGA curves of the mass loss as a function of the temperature for PE-LD in pure form or with addition of 0.5%, 1% and 2.5% of iron acetylacetonate (under air atmosphere and at 20 ° C./min), Weight (%) = mass in%;

Fig. 3: TGA curves of the mass loss as a function of the temperature for PE-LD in pure form or with the addition of 0.5%, 1% and 2.5% of iron acetylacetonate (under N 2 atmosphere and at 20 ° C / min ), Weight (%) = mass in%;

Fig. 4: TGA curves of the mass loss as a function of the temperature for PE-LD with addition of 1%, 5% and 10% of iron acetylacetonate (under air atmosphere and at 20 ° C / min), weight (%) = mass in %;

Fig. 5: TGA curves of mass loss as a function of the temperature for iron acetylacetonate under air atmosphere (20 ° C / min) in comparison with PE-LD taken by itself; and

Fig. 6: Effect of the various additives on the heat release as a function of time in the MLC (Mass Loss Calorimeter) test at 35 kW.

Examples

Material and method

The resistance (or resistance, behavior) of fire to a material is subject to a wide variety of standards, and it can be investigated in different ways according to the conditions of use.

Commonly used tests include the mass loss calorimeter standardized method (ISO 13927 - ISO DIS 17554), which is used to determine the heat output of a polymer composition (referred to as HRR for heat release rate, expressed in kW / m2) when this is exposed to a certain amount of radiant heat. This method, hereinafter referred to as "MLC fire test", moreover, makes it possible to improve the flammability

To determine the heat of combustion of a composition and the mass loss. In a polymer under investigation, a small amount of heat and a long period of ignition are indicative of proper fire response.

The first measurement, namely the HRR (heat release rate) thus stands for the rate of heat release during the combustion of a material. The height of the HRR peak (pHRR) is a very important parameter, as it is indicative of the material's ability to set fire to other adjacent objects when it is burned. This parameter is usually measured in kW / m2. The HRR is the strength of a kindled fire. If a material is to have functional properties when exposed to fire, it must ideally have a low pHRR. The results obtained in the invention are from a mass loss calorimeter. The test piece (10 * 10 * 0,4 cm3) is exposed to an electric radiator in the shape of a truncated cone, which makes it possible to irradiate the test piece in a uniform manner. Work was carried out on irradiation at 35 kW / m2 to study the amount of heat released (pHRR) and at 70 kW / m2 to determine the ignition resistance (ignition period). The combustion was triggered by an electric spark. The released gases flow through a chimney, at whose end thermopiles are arranged, by means of which the temperature increase can be converted into a quantity of heat.

The ignition period (TTI) is the period of time which elapses until the material catches fire when exposed to a radiation of 70 kW / m2. If a material is to exhibit functional properties under fire, it must ideally have a long TTI.

Materials PE-LD: low density polyethylene of SABIC 2602TX17 (density 926 kg / m3, MFI = 1.5 g / 10 min at 190 ° C and 2.16 kg) PE-LDgMA: low density polyethylene, grafted with maleic anhydride, of DuPont Bynel 42E703 (density 910 kg / m3, MFI = 6.4 g / 10 min at 190 ° C and 2.16 kg) PC: polycarbonate from SABIC Lexan 123R (density 1.200 kg / m3, MFR = 17.5 g / 10 min at 300 ° C and 1.2 kg)

Plasticizer: Tritolyl phosphate from Sigma-Aldrich

Silica: Cab-O-Sil TS-530 from Cabot (treated with

Hexamethyldisilazane, BET surface area = 225 m2 / g, mean particle size = 0.2 to 0.3 gm)

Ferric acetylacetonate: iron (III) acetylacetonate from Sigma-Aldrich (97%) CAS 14024-18-1

Aluminum: Premix based on polyethylene containing 40% by weight of aluminum paste.

measurements

Various polyethylene polymer compositions were prepared containing different amounts of Fe (acac) 3. The inflammation time (TTI) results are shown in Table 1.

Table 1: Inflammation period for the 70 kW / m2 MLC test

With regard to the compositions of Table 1, it can be seen that the incorporation of 0.5% of iron acetylacetonate leads to an appropriate extension of the TTI, from an average of 30 s to 44 s. However, it seems that the increase in the incorporated content leads to a reduction in the ignition resistance of the mixture, which is more rapidly ignited by more than 5% than the PE-LD per se, which concerns the compositions indicated. It should be noted that the plate turns black as soon as it is exposed to the heating cone. The reduction of TTI with more than a few% of iron acetylacetonate could be directly related to the flammability of this substance. TGA under air and N2 atmosphere

The results are shown in FIG. 1. It should be noted that the presence of 1% of iron acetylacetonate results in a significant improvement in the heat resistance of the PE-LD, both under an air and nitrogen atmosphere. This behavior can be attributed to the formation of a black charred layer on the surface of the material. The blackening of the surface of the material prior to its ignition was observed during the fire impact test (MLC) and appears to explain largely the values of the ignition period obtained.

Two novel compositions were prepared: PE-LD + 0.5%, 1% and 2.5% of iron acetylacetonate. The TGA curves of these two mixtures under air and under N 2 atmosphere are shown in FIGS. 2 and 3. It can be observed that the effect of the iron acetylacetonate is similar for the two incorporated levels of 0.5 and 2.5%

However, as has already been observed above, it can be seen that increasing the content of iron acetylacetonate to more than a few% decreases the period of inflammation of the PE-LD. The TGA curves appear to be correlated with the TTI values since the thermal stability of the mixture decreases to 420 ° C with the iron acetylacetonate content in the mixture (Figure 4).

Too large an amount of iron acetylacetonate apparently leads to a reduction in the ignition resistance of the PE-LD, which in turn, due to the low heat resistance of the Eisenacetylacetonats the reduction of the thermal stability of the PE-LD (Figure 5). Its TGA curve under air atmosphere shows that it decomposes rapidly and at a lower temperature. It thus seems logical that increasing the content of iron acetylacetonate affects the heat resistance of the mixture.

Other compositions

The following compositions C1 to C5 (and for comparative purposes C0) were prepared and then tested: C1: (PE-LD / 10% PE-LDgMA) - 20% PC (polycarbonate, plasticized with TCP) - 1% Fe-acetylacetonate (without Silicon dioxide and without aluminum) C2: (PE-LD / 10% PE-LDgMA) - 20% PC (plasticized) - 3% aluminum - 1% Fe-acetylacetonate (without silicon dioxide) C3: (PE-LD / 5% PE- LDgMA) - 20% PC (plasticized) - 5% silicon dioxide (TS530) - 1% iron acetylacetonate (without aluminum) C4: (PE-LD / 5% PE-LDgMA) - 5% TS530 - 3% aluminum - 1% Fe acetylacetonate (without PC) C5: (PE-LD / 5% PE-LDgMA) - 20% PC (plasticized) - 5% TS530 - 3% aluminum - 1% iron acetylacetonate C0: (PE-LD / 5% PE-LDgMA) - 20% PC (plasticizer-containing) - 5% TS530 - 3% aluminum (without Fe-acetylacetonate), for comparison purposes

As shown in Table 2 below, the composition C5 comprising the combination of several ingredients gives excellent TTI results of an average of 53.5 seconds whereas the similar comparison composition C0 without Fe (acac) 3 has an average TTI of only 37 ,

Silica appears to have a beneficial effect on compositions comprising ferric acetylacetonate, both TTI and HRR (see FIG. 6).

Table 2: Inflammation period for the 70 kW / m2 MLC test

FIG. 6 shows the curves of the heat release in the MLC test at 35 kW / m 2 for the various mixtures. It should be noted that the two compositions which do not contain any silica lead to high pHRR (> 400 kW / m2) values. It can be concluded that the presence of silica has a beneficial effect if relatively low pHRR values are to be achieved.

Table 3 shows the results for the mixtures PE-LD / PE-LDgMA / PC (plasticizer-containing) / Si / Alu / Fe (acac) 3 with Fe (acac) 3 contents of 0.1%, 0.3%, 0.5%, 0.7% and 1%.

Table 3: Inflammation period for the 70 kW / m2 MLC test

With regard to the mixtures given in Table 3, it can be seen that there is an improvement even at very low concentrations. The improvement may depend on the other ingredients of the mixture. Nevertheless, a content of 0.5% appears

Iron (III) acetylacetonate to be an appropriate value for the tested mixtures.

Summary

In the investigations made in the context of the present invention it could be shown that iron (III) acetylacetonate in PE compositions can be expediently used to flameproof compositions based on PE.

Without wishing to be bound by any particular theory, it is believed that ferric acetylacetonate favors carbonization of the PE upon its decomposition, thereby improving its performance

Resistance of the thin film is formed, which forms on the surface of the decomposing plate, which in turn causes a reduction in the amount of released volatile combustibles.

In addition, it has been found that the resistance of the PE compositions to fire can be further enhanced by blending other types of additives to thereby develop, for example, a foamable material which is resistant to fire.

By combining several different types of additive additives, it was possible to avoid impairment of the foaming process as much as possible. Thus, in use, in addition to the iron (III) acetylacetonate, one or more other additives in low dosages could be observed that a synergistic flame retardancy is achieved, so that in a particularly advantageous variant, an example of a polymer composition can be provided by a low heat output , a suitable ignition resistance and the ability to foam is characterized.

In this case, a silica filler (preferably having a very large specific surface area, for example 225 m 2 / g) may play an important role, since it obviously makes it possible to significantly reduce the heat emission during combustion. The polycarbonate containing TTP as a plasticizer, in turn, apparently makes it possible to favor carbonization of the surface of the material, and it even appears that the phosphorus contained in the plasticizer also has a positive effect on the ignition resistance of the material. In addition, the aluminum particles used in a proportion of, for example, 3% could allow for an increase in the reflectivity of the material for infrared radiation and thus reduce the rate at which it superficially heats up.

Claims (13)

claims A polymer composition based on polyethylene, characterized in that it contains 15 to 25 wt .-% of polycarbonate and 0.01 to 10 wt .-%, preferably 0.1 to 5 wt .-%, more preferably 0.2 to 3 wt .-%, in particular 0.5 to 2.7 wt .-% of iron (NI) acetylacetonate. A composition according to claim 1, further comprising 1 to 8% by weight, preferably 3 to 6% by weight of nanometer scale silica filler. A composition according to claim 1 or 2, wherein the polyethylene is low density polyethylene (PE-LD), preferably low density polyethylene comprising 5 to 30% by weight of low density polyethylene grafted with maleic anhydride is (PE-LDgMA). 4. A composition according to any one of claims 1 to 3, wherein the polycarbonate is a plasticized polycarbonate, preferably a polycarbonate comprising as plasticizer 10 to 45 wt .-% of tricresyl phosphate. A composition according to any one of claims 1 to 4, further comprising 1 to 6% by weight, preferably 2 to 5% by weight, of low emissivity metal particles, preferably of aluminum, of steel, of zinc and / or made of bronze or coated with it. 6. The composition of claim 5, wherein the metal particles are aluminum particles. A composition according to claim 5 or 6, wherein the metal particles have a mass-median median diameter (D50) of from 1 to 40 μm, preferably from 3 to 30 μm, more preferably from 5 to 25 μm. A composition according to any one of claims 1 to 7, further comprising at least one additive selected from the group consisting of: the antioxidants, the ultraviolet filters, the antistatic agents, the foaming agent, the nuclei, the lubricants, the absorption and infrared (non-metal) refracting agents, dyes and pigments, fillers, anti-fogging agents, antiblocking agents, permeability modifiers, cell size regulators and other fire retardants. A composition according to any one of claims 1 to 8, comprising: from 0.25 to 5% by weight of iron (NI) acetylacetonate, from 3 to 6% by weight of nanometer scale silica filler, from 2 to 5% by weight. -% of aluminum particles, 15 to 25 wt .-% of plasticized polycarbonate with 25 to 30 wt .-% of tricresyl phosphate, based on the plasticized polycarbonate, 0 to 10 wt .-% of at least one additive, wherein PE-LD, the 10 to 25 wt .-% of PE-LDgMA, the balance makes up. A foam comprising the polymer composition of any one of claims 1 to 9. 11. A manufactured article comprising the polymer composition according to any one of claims 1 to 9 or a foam according to claim 10. 12. A manufactured article according to claim 11, consisting of the extruded parts or molded parts from the field of transport, buildings, recreational items, decorative objects, do-it-yourself, electronics, electrical appliances, heat and / or Soundproofing or the furniture is selected. Use of the polymer composition according to any one of claims 1 to 9 or a foam according to claim 10 for the manufacture of a finished article.