NL1021222C2 - Fire-preventing polymer composition, e.g. useful for making cable insulation, comprises a polymer matrix, a flame retardant, a layered clay and a block or graft copolymer - Google Patents

Abstract

Fire-preventing polymer composition (C1) comprises a polymer matrix, a flame retardant, a layered clay and a block or graft copolymer. Independent claims are also included for: (1) production of C1 by extruding the ingredients together; (2) electrical cable comprising an insulating material based on C1.

Description

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Title: Fire-resistant polymer composition

The invention relates to a polymer composition with fire-resistant properties.

Fire-resistant materials find various applications in buildings, ships, aircraft and the like. It has been found that the 5 biggest cause of the rapid spread of fire in a building lies in the presence of tens of meters of electricity cable in modern buildings. The material surrounding the conductive core of an electrical cable to provide protection against the electrical current is generally a polymeric material and intrinsically flammable. To meet this danger, flame retardants are added in such insulation materials. Examples of suitable flame retardants are hydroxide salts of divalent or trivalent metals, such as magnesium hydroxide or aluminum hydroxide.

A fire-resistant polymer composition is known, for example, from DE 199 21 472. This document describes a thermoplastic or cross-linkable polymer composition consisting of a thermoplastic or cross-linkable polymer, one or more metal hydroxides as a flame retardant, and a clay (an organically intercalated layered silicate). In this organically intercalated layered silicate, layers of, for example, a smectite clay are intercalated by quaternary ammonium compounds, protonated amines, organic phosphonium ions or amino carboxylic acids. The reason given to include the clay in the polymer composition in DE 199 21 472 is that an improvement of the fire-resistant properties is achieved with this.

25 For safety reasons, there is a need for better and better fire-resistant materials. Although in principle the fire-resistant properties of a polymer composition (for example as described in DE 199 21 472) can be improved by having a larger amount of 1 n 9 1 · ? 9 2 flame retardant, this is not possible in view of other requirements placed on the material. In particular, the flexibility and processability of the material appears to deteriorate when a certain critical amount of flame retardant is exceeded. It will be clear that flexibility of an insulation material for an electricity cable is an indispensable property.

According to the invention, this need is met because it has been found that larger amounts of flame retardant can be incorporated into a polymer composition without this having appreciable adverse consequences for the other, in particular the mechanical, properties of the composition. These surprising results are achieved if a specific block or graft copolymer is also incorporated in a fire-resistant polymer composition, in addition to a clay.

The invention therefore relates to a polymer composition with fire-resistant properties, which composition comprises a polymeric matrix, a flame retardant, a layered clay and a block or graft copolymer.

A surprising advantage that by adding a block or graft copolymer in combination with a clay to a polymer composition with flame retardants is that a larger amount of flame retardant can be incorporated in the polymer composition without the mechanical properties deteriorating appreciably. As a result, the fire-resistant properties of the polymer composition can be greatly improved.

It has further been found that by adding a block or graft copolymer in combination with a clay to a polymer composition with a flame retardant, the fire properties of the material are favorably influenced. Thus, the melting and dripping of the polymer composition is greatly reduced in the event of a fire and no or a much less sooty flame forms. This is particularly advantageous because as a result of a house fire the formation of a thick black smoke as a result of the burning of electricity cables is greatly reduced.

A polymer composition according to the invention furthermore forms a black solid carbonization on burning which acts as an oxygen barrier. The formation of this oxygen barrier in fires provides a polymer composition according to the invention with additional fire-resistant properties in addition to the action of the hydroxide or carbonate-containing flame retardants, which have their action through the formation of water and CO2.

Moreover, due to the black solid carbonization, the smoldering polymer composition hardly melts or drips. These properties lead to a greatly reduced flame transport through the material and a greater fire resistance.

Yet another surprising advantage of the presence of a block or graft copolymer in a polymer composition according to the invention is that it becomes much easier to process, thereby facilitating large-scale manufacture of a fire-resistant polymer for various applications.

The polymeric matrix on which a fire-resistant polymer composition according to the invention is based can be any polymeric material. Both homopolymers and copolymers can act as a polymeric matrix. Both polyadducts and polycondensates are suitable. Examples thereof are polyolefins, such as polyethylene (PE, both low, medium and high density) or polypropylene (PP), vinyl polymers, such as polystyrene or polymethyl methacrylate, polyesters, such as polyethylene terephthalate or polycaprolactone, polycarbonates, polyaryl ethers, polysulfones, polysulfides, polyamides, polyetherimides, polyether esters, polyether ketones, polyether ester ketones, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polysiloxanes,

Polyurethanes and polyepoxides. Preferably polyolefins such as PE are used

1n? I? 2? 4 and PP, vinyl polymers such as ethylene vinyl acetate (EVA), polyesters, polyethers, polycarbonates (PC), the three monomer-containing ABS (acrylonitrile, butadiene and styrene), combinations of ABS and PC, polysiloxanes or acrylic polymers, such as styrene acrylonitrile (SAN) used, more preferably LDPE.

A polymer composition according to the invention will typically be at least 30 wt. % preferably 40-90 wt. %, based on the weight of the composition, of the polymer matrix.

A fire-resistant polymer composition according to the invention further comprises one or more flame retardants. Suitable flame retardants are generally carbonates and hydroxides. In principle, all carbonates and hydroxides of 2- and 3-valued main group elements such as Mg, Ca and Al and mixtures thereof with an endotherm between 200-400 ° C can be used. Magnesium hydroxide, aluminum hydroxide, huntite, hydromagnesite and / or other layered double hydroxides (anionic clays) such as hydrotalcite and / or mixtures thereof are preferably used as flame retardant. A layered double hydroxide that can be used in embodiments of the invention can be both natural and synthetic in nature. For a description of possible preparation methods for a synthetic layered double hydroxide, reference is made to U.S. Pat. Nos. 3,539,306 and 3,650,704. Magnesium hydroxide, aluminum hydroxide, huntite, hydromagnesite and / or mixtures thereof are more preferably used as the flame retardant. Mixtures of huntite and hydromagnesite are commercially available, inter alia, under the trade name Securoc ™. Very preferably, magnesium hydroxide and / or aluminum hydroxide are used as flame retardant.

The flame retardants can be used in the polymer composition in an amount between 10 and 80 wt. % based on the weight of the composition, preferably between 20 and 60 wt. %, more preferably between 30 and 50 wt. %.

It is also possible to add to the fire-resistant polymer composition according to the invention additional components or excipients such as dyes, hardeners, plasticizers, lubricants, effect fillers such as, for example, talc, mica and aluminum flakes. Such components will generally be present in an amount between 0.5 and 5 wt. % based on the weight of the composition.

A clay suitable for use in a polymer composition according to the invention typically has a layered structure. A suitable clay type has a cation exchange capacity of between 30 and 250 milliequivalents per 100 grams. If a clay with a cation exchange capacity higher than 250 milliequivalents per 100 grams is used, it will be difficult to finely disperse the clay at a molecular level due to the strong mutual interaction between the clay layers. When a clay with a cation exchange capacity of less than 30 milliequivalents is used, it will be difficult to modify the clay due to the weak interaction with the block or graft copolymer. Preferably, a clay with a cation exchange capacity of between 50 and 200 milliequivalents per 100 grams is used.

Very suitable is clay based on layered silicates, such as layered phyllosilicates composed of magnesium and / or aluminum silicate layers, each with a thickness of 7-12 A. Clay that can be used in embodiments of the invention can be of natural or synthetic origin to be. The clay preferably has a large contact surface. As clay, very suitable clays from the group of natural or synthetic small smectites and / or smectite-like clays such as montmorillonite, hectorite, fluorohectorite, beidellite, nontronite, bentonite, saponite, vermiculite, halloysite and / or stevensite can be used. When i n? i 7? While these clays have been appropriately modified in accordance with the invention, they provide the polymer composition in which they are incorporated with good mechanical and fire-resistant properties. Particularly good results are obtained by using montmorillonite.

A clay that can be used in a polymer composition according to the invention can be a clay that has been modified with a surfactant. Such surfactants, also called swelling agents, onium ions or compatibilizers, are substances with a cationic group, such as an ammonium, pyridinium, sulfonium or phosphonium group, to which one or more non-polar tails are attached. The cationic group is exchanged for cations between the crystalline layers of the clay, while the tails have a functional group that has the ability to interact with the polymer matrix, the block copolymer or graft copolymer.

An example of a surfactant for use in an embodiment of the present invention is an aliphatic ammonium salt. The use of surfactant-modified clays is not necessary, but is advantageous in the event that an apolar polymeric matrix such as, for example, PE is selected. The mixing of the clay with the non-polar polymeric matrix is easier in that case.

Methods for preparing surfactant-modified clays are known, for example, from US 4,810,734, US 4,889,885 and DE 199 21 472.

In addition to the above-mentioned clay and the polymeric matrix, a fire-resistant polymer composition according to the invention comprises a block and / or graft copolymer. This block and / or graft copolymer is a polymer comprising first structural units (A) compatible with the clay, and further comprising one or more second structural units (B) compatible with the polymer matrix. When the structural units (A) and (B) are oriented in a straight chain, a block copolymer is used.

1021222 7

When the structural units (A) occur in a chain that is a branch of the chain in which the structural units (B) occur, or vice versa, it is referred to as a graft copolymer.

Preferably, a block copolymer is used in the present invention.

The structural units (A) are compatible with the clay. By this is meant that these units on their own, i.e. not in the copolymeric form with the structural units (B), are excellently miscible with the clay. The structural units (A) preferably have a hydrophilic character. Materials that can suitably be used as structural units (A) are polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, polyethylene oxide, linear or dendritic polyethyleneimine, polyoxymethylene, polytetrahydrofuran, polyacrylic acid, polymethacrylic acid, polydimethylacrylamide, polymethylacrylamide, acrylic acid, acrylic acid, acrylic acid, and polyacrylamide acrylic acid polyisopropylamide, starch, polysaccharides and / or cellulose derivatives. Preferably at least one of the structural units (A) is derived from monomeric units selected from the group of vinyl pyrrolidone, vinyl alcohol, ethylene oxide, ethylene imine, vinyl pyridine, acrylic acid and acrylamide. These preferred units (A) are highly compatible with the clay.

Very suitable materials for use as structural units (A) have a molecular weight between 80 and 10,000, preferably between 100 and 4,500. It is also advantageous if the material of the structural units (A) contains 3 to 100 monomeric units.

The structural units (B) are compatible with the polymer matrix. By this is meant that these units per se, i.e. not in the copolymer form with the structural units (A), are excellently miscible with the material of the polymer matrix. It is also possible that the nature of the structural units (B) is equal to the nature of the polymer matrix. An example is a polymer composition 8 comprising a polymeric matrix of polyethylene with a molecular weight of 300,000 and structural units (B) of polyethylene with a molecular weight of 450. It is even possible that the material of the polymer matrix is exactly the same as that of the structural units 5 (B). In the above example, the structural units (B) could then be a polyethylene with a molecular weight of 300,000.

Very suitable materials for use as structural units (B) have a molecular weight between 80 and 300,000, preferably between 80 and 200,000.

The nature of the structural units (B) will depend on the nature of the polymeric matrix. Materials suitable as structural units (B) are, for example, polyolefins such as PE or PP, vinyl polymers such as polystyrene or polymethyl methacrylate, polyesters such as polyethylene terephthalate or polycaprolactone, polycarbonates, polyaryl ethers, polysulfones, polysulfides, polyamides, polyetherimides, polyether esters, polyether ketones, polyether ester ketones, polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polysiloxanes, polyurethanes and polyepoxides. Polyolefins, vinyl polymers, polyesters, polyethers, polysiloxanes or acrylic polymers are preferably used.

A particularly suitable block copolymer for use in an embodiment of the present invention is a block copolymer of polyethylene glycol or polyethylene oxide and polyethylene.

According to a preferred embodiment, a block or graft copolymer is used in which the structural units (A) contain at least 2 monomeric units and the structural units (B) contain an equal or greater amount of monomeric units on / than the structural units (A). It has been found that with such a block or graft copolymer a very finely divided homogeneous dispersion of the clay in the polymer matrix is obtained.

The presence of a small amount of block or graft copolymer in a composition according to the invention already has a very favorable effect on the processability of a mixture of components for the preparation of a fire-resistant polymer composition according to the invention. This is due to a reduction in torque in the presence of a few percent block or graft copolymer on the total composition, thereby allowing a higher processing speed during the preparation process.

In a fire-resistant polymer composition according to the invention, a suitable weight ratio of the amount of clay to the amount of block or graft copolymer is between 0.01: 1 and 100: 1, preferably between 0.5: 1 and 20: 1 and more preferably between 1: 1 and 5: 1.

The weight ratio of the amount of clay to the amount of polymeric matrix is preferably between 1: 200 and 2: 1, with a particular preference for a weight ratio between 1:50 and 1: 5.

A fire-resistant polymer composition according to the invention can be prepared in various ways. A possible method comprises a step in which the clay is first modified with a block or graft copolymer by combining the clay and the block or graft copolymer and allowing exchange between cations and block or graft copolymer in the clay, and then the other add components. In an alternative embodiment, the polymeric matrix, the flame retardant (s) and the block or graft copolymer can first be mixed, after which the desired clay component and possibly additional components are added to this mixture. Furthermore, it is possible to simultaneously combine and mix polymeric matrix, flame retardant (s), clay and block or graft copolymer and any additional components.

However, it is preferable to first modify the clay with a block or graft copolymer as described above. By appropriately choosing the structural units (B), the skilled person will be able to introduce a clay into a polymeric matrix of any desired nature.

When a fire-resistant polymer composition according to the invention is manufactured according to one of the methods described above in which the various components are combined, the clay can be pre-milled or crushed. Such pre-treatment of the clay can result in easier and better miscibility of the various components, but this operation is not necessary.

The components of a fire-resistant polymer composition according to the invention can be combined and mixed by any suitable method and processed into a final product. An example of a method for joining and mixing the components comprises moving a mixture of components by stirring for a suitable period of time at an elevated temperature and optionally also elevated pressure such as, for example, by extrusion. After extrusion, a polymer composition according to the invention can optionally be cast, deposited as a coating on a substrate, blown or processed in another suitable manner into a product with fire-resistant properties.

Suitable mixing conditions depend on the nature of the ingredients chosen and can easily be determined by those skilled in the art. The mixing is preferably carried out at a temperature of between 40 and 80 ° C with the aid of, for example, a buss-kneader and the extrusion is preferably carried out at a temperature between 40 and 1 n '. 1 2 2 2 11 200 ° C. A so-called twin-screw extrudator can very suitably be used for this purpose.

A fire-resistant polymer composition according to the invention finds very suitable application in the manufacture of insulating material for electrical cables, wall sockets, and other plastic electrical and electronic materials, such as housings and insulation for electrical equipment and cables. Indoor applications include furniture, lighting, building materials and insulation material, paint and wallpaper, floors, carpets and rugs, textiles, wood products and toys. Other applications of a composition according to the invention can be office furniture, computer equipment, car upholstery, materials for the manufacture of cars, buses, planes and ships, equipment and equipment of hospitals and care institutions, or fabrics and fabrics in for example offices, factories and movie theaters.

The invention will now be illustrated with reference to the following, non-limiting examples.

12

Example 1

Fire-resistant polymer composition based on MDPE and LDPE. Experiments on a small scale.

Experimental process conditions To prepare materials with well-dispersed flame retardants in a polymeric matrix, extrusion experiments were carried out with a laboratory-scale twin-screw extruder that had the possibility of reuse and had an effective volume of 15 cm 3. The preparation was carried out at a temperature of 160 ° C, at a rotation speed of 245 rpm for 5 minutes.

Test samples were made by injection molding to study the polymer compositions. These test samples were visually studied to determine if the clay was well dispersed and some promising samples were further studied using E-SEM.

Extrusion experiments

In the experiments below, MDPE and LDPE were used as the polymeric matrix. Furthermore, an aliphatic ammonium salt (dimethyldioctadecylammonium chloride, DODAC) modified bentonite was used as the clay. This modified clay contained approximately 45% by weight of DODAC, based on the weight of the modified clay. The amount of clay modified in this way was 5% by weight, based on the weight of the composition for adding a flame retardant and a block or graft copolymer and starting from the weight of the clay in unmodified state, ie the inorganic part of the clay.

Comparative experiments were performed with the flame retardant magnesium hydroxide in an amount of 4% by weight and 33% by weight, based on the weight of the composition, and with the layered

"! 'Ί '* "P P

13 structure talc in an amount of 21% by weight, based on the weight of the composition.

To get an impression of the flammability of the materials, experiments with MDPE as a polymer matrix in combination with PEO-b-PE as a block copolymer and MA-g-PE (maleic acid grafted polyethylene) were used as a graft copolymer.

Injection molded samples with a fixed dimension of 2 x 5 x 40 mm (h x w x 1) were briefly held in a blue gas flame. The samples were held in the flame for so long that they could just catch fire, but the flame did not spread. The flame was then broken out and the smoldering behavior of the material was observed, or flame propagation was studied.

These small-scale experiments showed that the preparation of a polymer composition according to the invention on the basis of medium-density polyethylene (MDPE) or low-density polyethylene (LDPE) could be achieved and that good flame-retardant properties could be achieved on this basis.

Polymer compositions with good flame-retardant properties could be prepared by using aliphatic modified bentonite and hydrotalcite modified with stearic acid. Also surprisingly, good flame-retardant properties could be obtained by using aliphatic modified bentonite with block copolymer, since the block copolymer itself burns well.

Less well dispersed but with good flame retardant properties, and prepared on a small scale, was a melamine modified bentonite.

The experiments were carried out on a small scale with flame-retardant fillers such as magnesium hydroxide (Mg (OH) 2), hydrotalcite (Mg6Al2 (0H) ieCO3.4H2 O) and different types of huntite (CaMg3 (CO3) 4), 30 and other layered double hydroxides, consisting of carbonates, 14 hydroxides of 2- and 3-valued main group elements such as Mg, Ca and Al and mixtures thereof with an endotherm between 200-400 ° C, with hydromagnesite (Mgs (C03) 4 (0H) 2.4 (H2O)) and with commercially developed mixtures of these two types showed that all fillers were in principle suitable for use as a flame retardant. It was found that upon addition of flame retardants, the polymer compositions could no longer be ignited.

Example 2

10 Fire-resistant polymer composition based on MDPE and LDPE. Experiments on a larger scale.

Polymer composition without flame retardants

Four types of polymer compositions according to the invention were prepared using MDPE as polymeric matrix with modified layered clays of bentonite and hydrotalcite.

To prepare a polymer composition according to the invention, a mixture of surfactant-modified bentonite or hydrotalcite, MDPE and block or graft copolymer was first prepared. PEO-b-PE was used as the block copolymer and MA-g-PE was used as the graft copolymer. The ratio of clay to polymeric matrix was 1:20 (5% by weight of clay based on the weight of the polymeric matrix and based on the weight of the clay in the unmodified state, i.e. the inorganic part of the clay). This mixture was introduced in a buss-kneader extruder. The feed rate was 7 kg / hour and the extrusion parameters were as follows:

Temperature zone zone2 zone3 zone4 zoneö zone6

180 190 190 190 190 190 ° C

Rotational speed 500 rpm 30 4 n oij o o o 15

The combustibility and mechanical properties of the samples were tested. The fire-resistant and mechanical properties of this material were not sufficient to base a cabling insulation, although the fire-resistant properties were better than those of the pure matrix polymer MDPE.

Example 3

Fire-resistant polymer composition based on MDPE and LDPE. Experiments on a larger scale.

Polymer composition based on MDPE as a polymeric matrix with flame retardants

The same components, compositions and process conditions were used as stated in Example 2, but flame-retardant fillers were added to this.

The following inorganic fillers were tested as flame retardants:

Table 1. Flame retardant fillers used.

Filler Particle size

Mg (OH> 2 (magnefin) 1.40 - 1.80 µm

Huntite / hydromagnesite (Securoc ™ CIO) 0.3 - 0.6 µm

Huntite / hydromagnesite (FF) 0.25 - 0.45 µm

Huntite / hydromagnesite (HH) 0.25 - 0.45 µm

Hydrotalcite A mixture of a polymeric matrix MDPE, a block copolymer PEO-b-PE (Mw = 575 g / mol) and a DODAC modified bentonite supplemented with various flame-retardant fillers in a quantity of 30-33% by weight, based on the weight of the mixture, was introduced into a huss-kneader extruder with a feed rate of 7 kg / hour. The extrusion parameters used were as stated in Example 2.

The polymer compositions were supplemented with the various flame-retardant fillers in a second extrusion step. First, the different polymer compositions were combined with magnesium hydroxide. In subsequent experiments, Securoc ™ CIO was used to replace magnesium hydroxide and talc was used as an additional additive.

The extrusion parameters were the same as in the previous experiment, with the exception of the experiments to which extra talc was added. Due to the high inorganic content, it was difficult in this case to melt the MDPE at 190 ° C. For that reason the temperature was raised to 210 ° C.

The combustibility and mechanical properties of some of the materials were tested. The findings were that the polymer composition based on the polymeric matrix MDPE, the clays bentonite or hydrotalcite, the block copolymer PEO-b-PE or the graft copolymer MA-g-PE and the fillers described above have improved processability and improved mechanical properties (measured as relative E-modulus). The burning properties of the material were characterized by an absence of dripping of the burning material, no melting, formation of a solid carbon and no or a very small sooty flame. These properties of the material made it very suitable for use in cabling insulation.

Example 4

Fire-resistant polymer composition based on MDPE and LDPE.

30 Experiments on a larger scale.

in :? 122 9 17

Polymer composition based on LDPE as a more innovative matrix with flame retardants

A polymer composition with MDPE as a polymer matrix and a clay modified with aliphatic ammonium salt without the use of additional flame retardants had already been shown to have good fire-resistant properties. A positive effect on the combustibility and mechanical properties was also observed in a polymer composition with MDPE as a polymer matrix and a clay modified with aliphatic ammonium salt. Surprisingly, it was found that addition of small amounts of block copolymer positively affected process conditions, mechanical properties, and flame retardant properties.

The first experiments with LDPE as a polymer matrix were carried out as a follow-up to the MDPE experiments. LDPE, together with a DODAC modified clay (bentonite), became a block copolymer or graft copolymer (PEO-b-PE with molar mass 575, 875, 920 and 1400 g / mol and a graft copolymer MA-g-PE) and various inorganic fillers ( the effect filler talc and the flame retardants (magnesium hydroxide and huntite) extruded in one step.

First a mixture of polymeric matrix, modified clay, block copolymer and talc was prepared. This mixture was introduced in the first zone (feed 1). The remaining inorganic fillers were introduced at the second zone (feed 2).

The extrusion conditions were as follows:

Temperature zone zone2 zone3 zone4 zone5 zone6

100 180 190 190 190 190 ° C

Rotational speed 500 rpm 18

For the follow-up experiments, a mixture of polymeric matrix LDPE, block or graft copolymer and clay was prepared as the base material (masterbatch).

Three versions were prepared with the following composition:

Table 2. Ratio between polymer and clay

Sample Percentage (%) LDPE: modified clay: copolymer LDPE / Modified bentonite 92.5: 7.5: 0 (DODAC modified) LDPE / modified bentonite / block copolymer 91.5: 7.4: 1.1 (PEO-b-PE) LDPE / modified bentonite / graft copolymer 90.4: 7.3: 2.3 (MA-g-PE)

To prepare these three basic compositions, a mixture was prepared of DODAC modified bentonite and LDPE. The ratio of clay to polymeric matrix was 1:20 (5% by weight of unmodified clay, based on the weight of the mixture). The mixture was introduced into the first zone of the extruder. The feed rate was 8 kg / hour. The extrusion parameters were the following:

Temperature zone zone2 zone3 zone zoneö zone6

100 180 190 190 190 190 ° C

Rotational speed 500 rpm 19

The burning properties and the mechanical properties of the samples were tested (for the results, see Tables 4, 5 and 6).

Fillers for compounding and comnatibilisers in a mixture of 5 LDPE, clay and block or graft copolymer

A blend of LDPE, clay, and block or graft copolymer was used as the base material for the preparation of compositions. The following inorganic fillers were tested as flame retardants.

Table 3. Tested flame retardant fillers with associated particle size flame retardant filler particle size

Mg (OH) 2 (magnefin) 1.40 - 1.80 µm

Huntite / hydromagnesite 0.3 - 0.6 µm (Securoc ™ CIO)

A mixture of LDPE, clay, and block or graft copolymer with a compatibilizer (EVA or Exxelor ™) and talc as an effect filler was introduced into the first zone of the extrudator. The inorganic fillers were introduced into the second zone of the extrudator.

The extrusion parameters used were as described for the preparation of a mixture of polymeric matrix LDPE, block or graft copolymer, and clay above.

20

The combustibility and the mechanical properties of some of the materials were tested (for the results, see Tables 4, 5 and 6).

1 n? 1? ? O

Table 4.

Process Mechanical

Composition conditions properties Fire properties 20

Couple Relative E-modulus LDPE / EVA / 27 100% Dripping / sraelting / soot

Mg (OH) 2 LDPE / EVA / 27 100% No dripping /

Mg (OH) 2 / DODAC- no melting / modified clay small sooty flame LDPE / EVA / 17 120% No dripping /

Mg (OH) 2 / DODAC- no melting / modified clay / solid carbonization / block copolymer no sooty flame LDPE / EVA / 19 100% No dripping /

Mg (OH) 2 / DODAC- no melting / modified clay / solid carbonization / graft copolymer very small sooty flame 1021222

Table 5.

Process Mechanical

Composition conditions properties Fire properties 21

Couple Relative E-modulus LDPE / EVA / 40 100% Dripping / melting / soot

Securoc ™ LDPE / EVA / 40 -% No dripping /

Securoc ™ / DODAC- no melting / modified clay solid carbonization / sooty flame LDPE / EVA / 31 130% No dripping /

Securoc ™ / DODAC- no melting / modified clay / solid carbonization / block copolymer no sooty flame

Process Mechanical

Composition conditions properties Fire properties 22

Table 6.

Link Relative E-modulus LDPE / Exxelor ™ / 44 100% Dripping / melting / soot

Mg (OH) 2 LDPE / Exxelor ™ / 43 100% No dripping /

Mg (OH) 2 / DODAC- no melting / modified clay solid carbonization / small sooty flame LDPE / Exxelor ™ / 31 110% No dripping /

Mg (OH) 2 / DODAC- no melting / modified clay / solid carbonization / block copolymer no sooty flame

Experiments on a larger scale showed that the buss kneader was suitable for obtaining a homogeneous dispersion of the (modified) layered clay in both MDPE and LDPE. The process conditions were not affected by the addition of 5% layered modified clay. In some cases, the process conditions were positively influenced by the addition of an excess of lubricant-like modifiers, such as block copolymer or graft copolymer.

The positive effect of these modifiers had a negative effect on flammability (limiting oxygen index (LOI), ignition and flame transport). Experiments to optimize the minimum amount of block copolymer required for a good clay dispersion showed that the mass ratio of DODAC-modified bentonite was 0 2 1 2 2. 23 (mass of pure clay) compared to block copolymer PEO-b-PE (Mw 575) had to be about 4: 1. Different optima may apply to other clays and other block or graft copolymers.

The optimized amount of block copolymer resulted in comparable process conditions, but resulted in improved flame retardant properties (measured by ignition, flame transport, formation of solid black carbonization and less sooty flame) and an improvement in mechanical properties (10% increase in E-modulus and strength) was found.

10 The combustion of the samples is not quantitatively expressed, but clearly visible in MDPE and LDPE. The time required to initiate ignition of the samples increases considerably.

The different types of flame retardant fillers showed that the Securoc ™ filled samples exhibited the best mechanical properties and that the LOI value was slightly increased (1 point) compared to magnesium hydroxide.

A positive property of the Securoc ™ compared to magnesium hydroxide is the formation of the layered white carbonization by the burning sample and the absence of melting and dripping of the 20 samples. This silent burning of the Securoc ™ filled polymer is the opposite of that of the magnesium hydroxide filled polymer, which causes heavy steam emission and dripping and melting.

However, magnesium hydroxide as a flame retardant in a polymer composition of a polymeric matrix, a clay and a block or graft copolymer exhibits a silent ejection of steam. Melting or dripping no longer takes place and a solid black carbonization is formed. The effect of the Securoc ™ is reduced when it is used in a composition of a polymeric matrix of LDPE or MDPE, a clay and a block or graft copolymer. This is expressed in the ignition time 30 and the time required for self-extinguishing when the samples burn.

24

Of the Exxelor ™, EVA, graft copolymer and block copolymer compatibilizers used, the block copolymer and graft copolymer are effective only when used in a small amount relative to the modified bentonite. An excess of these compatibilizers is negative for the flame-retardant properties, but has a positive effect on the mechanical properties.

Overall, the most suitable composition is a combination of modified bentonite with block or graft copolymer with Exxelor ™ as a compatibilizer and magnesium hydroxide as a flame retardant filler.

1 0 21 2 2:

Claims (17)

A polymer composition with fire-resistant properties, which composition comprises a polymeric matrix, a flame retardant, a layered clay and a block or graft copolymer. The polymer composition according to claim 1, wherein the block or graft copolymer comprises one or more structural units (A) compatible with the clay and one or more structural units (B) compatible with the polymer matrix. Polymer composition according to claim 1 or 2, wherein the clay has a cation exchange capacity of between 30 and 250, preferably 50 and 200 milliequivalents per 100 grams. Polymer composition according to any of the preceding claims, wherein the polymeric matrix comprises a homo- or copolymer selected from polyethylene, polypropylene, EVA, ABS, PC, ABS, and SAN or combinations thereof. Polymer composition according to any of the preceding claims, wherein the block copolymer is a copolymer of polyethylene glycol or polyethylene oxide and polyethylene. Polymer composition according to any of claims 2-5, wherein the structural units (A) have a molecular weight between 80 and 10,000, and wherein the structural units (B) have a molecular weight between 80 and 200,000. 7. Polymer composition according to any of claims 2-6, wherein the structural units (A) contain at least 2 monomeric units, and wherein the structural units (B) have the same or greater amount of monomeric units as / than the structural units (A) contain. Polymer composition according to any of claims 2-7, wherein the structural units (A) contain from 3 to 100 monomeric units. 1. The polymer composition according to any of claims 2-8, wherein at least one of the structural units (A) is derived from monomeric units selected from vinyl pyrrolidone, vinyl alcohol, ethylene oxide, ethylene imine, vinyl pyridine, acrylic acid and acrylamide. Polymer composition according to one of the preceding claims, wherein the weight ratio between the amount of clay and the amount of block or graft copolymer is between 0.01: 1 and 100: 1, preferably between 0.5: 1 and 20: 1, and more preferably between 1: 1 and 5: 1. The polymer composition according to any of the preceding claims, wherein the weight ratio between the amount of clay and the amount of polymeric matrix is between 1: 200 and 2: 1, preferably between 1:50 and 1: 5. 12. Polymer composition according to any one of the preceding claims, wherein the flame retardant is selected from magnesium hydroxide, aluminum hydroxide, hydrotalcite, huntite and / or hydromagnesite and / or mixtures thereof and other layered double hydroxides consisting of carbonates, hydroxides and mixed forms with an endotherm between 200-400 ° C. 13. Method for the preparation of a polymer composition according to claims 1-12, wherein a polymeric matidx, a flame retardant, a clay with a layered structure, and a block or graft copolymer are co-extruded. The method of claim 13, wherein the clay is pre-modified with the block or graft copolymer. 15. Use of a polymer composition according to any one of claims 1-12 for use in the manufacture of insulating material for electrical cables, housing for electronic equipment, furniture, interiors of means of transport and public spaces, lighting, paint, wallpaper, carpet, textile and / or or toys. An electricity cable comprising an insulating material based on a polymer composition according to any one of claims 1-12. Use of a polymer composition according to any of claims 1-12 as a fire-resistant material.