WO2004029141A1

WO2004029141A1 - Flame retardant material containing metal oxide

Info

Publication number: WO2004029141A1
Application number: PCT/GB2003/004090
Authority: WO
Inventors: Joern Hubertus Vogt; Oras Khalid Abdul-Kader; Mark Daniel Mortimer
Original assignee: Microtherm International Limited
Priority date: 2002-09-27
Filing date: 2003-09-22
Publication date: 2004-04-08
Also published as: AU2003269175A1; GB0222447D0

Abstract

A flame retardant material comprises a mixture of high surface area metal oxide material, infrared opacifier material and polymeric material. The high surface area metal oxide material and opacifier material are distributed throughout the polymeric material.

Description

FLAME RETARDANT MATERIAL

The present invention relates to flame retardant material and in particular flame retardant polymeric material.

Polymeric materials, for example epoxy materials, vinyl esters and polyesters, are used for many applications, for example for adhesion, coating and the formation of cast structural members, both domestically and industrially.

Large amounts of polymeric materials are used for certain applications, for example as coatings and adhesives for use on ships. Vinyl esters are commonly used as they have acceptable mechanical properties and have a generally acceptable temperature resistance, for example, in the range from 80 degrees to 100 degrees Celsius. Polyesters are also used as they are relatively cheap but they have less acceptable mechanical properties, having a temperature resistance, for example, in the range from 60 to 80 degrees Celsius. The most widely used polymeric material is epoxy material with a temperature resistance, for example, in the range from 80 to 100 degrees Celsius, which can be improved to be up to 140 degrees Celsius' if the epoxy material is subjected to post curing procedures.

Polymeric materials, however, have relatively poor flame retardancy properties. Therefore, when polymeric materials are used, precautions are necessary to prevent contact between a source of an initiation flame and the polymeric material. The polymeric material relatively readily acts as a fuel source in the event of a fire.

It is known that the addition of fillers, for example aluminium trihydrate, to polymeric material can improve the flame retardant properties of the polymeric material. Aluminium trihydrate generates water when heated which increases flame retardancy of the polymeric material in which it is present. However, the addition of the filler, typically a loading of up to 70 per cent by weight, increases the viscosity of the polymeric material and makes the polymeric material more difficult to process. High additions of filler also reduces the mechanical strength of the polymeric material.

Alternatively brominated resins can be added to the polymeric material. These brominated resins improve flame retardancy by means of the release of halogens contained within the brominated resins. However, when heated, the release of the halogens results in the generation of toxic fumes.

It is an object of the present invention to provide a flame retardant polymeric material, comprising additions of high surface area metal oxide material and opacifier material, which has comparable, or superior, flame retardant properties to those for a polymeric material comprising a relatively large scale addition of conventional filler material .

According to the present invention there is provided a flame retardant material comprising a mixture of high surface area metal oxide material, infrared opacifier material and polymeric material, the high surface area metal oxide material and infrared opacifier material being distributed throughout the polymeric material.

The high surface area metal oxide material may have a BET surface area of at least 20 m²/g, and preferably a surface area of at least 50 m²/g. The high surface area metal oxide material may be a microporous high surface area metal oxide material, preferably selected from silica and/or alumina.

The infrared opacifier material may be selected from titanium dioxide, iron titanium oxide, zirconium silicate and iron oxide and mixtures thereof.

The polymeric material may be a coating material and/or a castable material, for example suitable for use in producing structural members.

The polymeric material may be a thermoset polymeric material and may selected from an epoxy material, a vinyl ester material and a polyester material and mixtures thereof.

The polymeric material may be a thermoplastic polymeric material .

The flame retardant material may include a filler material which may be selected from aluminum trihydrate, magnesium hydroxide, china clay, calcium carbonate and talc and mixtures thereof.

The flame retardant material may further include fibres which may be selected from fibres comprising calcium magnesium silicate, silica, magnesium silicate, and glass formulations selected from E, R, C and S glass and mixtures thereof.

The flame retardant material may comprise a mixture of:

at least 1% by weight polymeric material; 1-50% by weight high surface area metal oxide material;

0.5-40% by weight infrared opacifier 0-70% by weight filler material; and 0-30% by weight fibres.

The flame retardant material may preferably comprise a mixture of:

at least 1% by weight polymeric material;

2-20% by weight high surface area metal oxide material;

0.5-40% by weight infrared opacifier;

0-70% by weight filler material; and 0-30% by weight fibres.

The flame retardant material may more preferably comprise a mixture of:

90-95% by weight polymeric material;

1-10% by weight high surface area metal oxide material;

0.5-5% by weight infrared opacifier

0-7% by weight filler material; and 0-1% by weight fibres.

The invention is illustrated by the following examples.

EXAMPLE 1 (COMPARATIVE)

A body of epoxy (thermoset) material was prepared by the intimate mixing of a low temperature polymeric epoxy resin, reference CY 219, and an epoxy hardener, reference HY 219, both available from Ciba-Geigy under the Trade Mark ARALDITE. The resin and hardener were mixed in the ratio 2 parts by weight resin to 1 part by weight hardener. The mixing together of the resin and hardener initiates the curing process of the resin/hardener mixture. The resin/hardener mixture was placed in a mould and cured at room temperature for 24 hours to form a cast body. The cast body was cut to nominally 10 mm by 60 mm by 5 mm. The body was suspended by means of a clamp supporting a first end of the body, such that the major surface of the body (10 mm x 60 mm surface) was in a substantially upright position. An initiating flame in the form of a burner flame was applied to an end of the body furthest from the clamp and the time taken for the base of a flame to travel substantially 30mm up the length of the body was measured and recorded. The presence of any burning material dripping away from the test sample was also recorded.

The flame took 65 seconds to travel substantially 30 mm up the substantially upright major surface of the body and burning material was seen to be dripping off the major surface of the body. Such a material is not suitable for use as a material in circumstances where flame retardant properties are required.

EXAMPLE 2 (COMPARATIVE)

A composite epoxy material was made comprising a substantially homogenous mixture of nominally 62.1 per cent by weight of low temperature polymeric epoxy resin, reference CY 219, available from Ciba-Geigy under the Trade Mark ARALDITE, 6.9 per cent by weight filler in the form of aluminium trihydrate, and 31 per cent by weight of an epoxy hardener, reference HY 219, also available from Ciba-Geigy under the Trade Mark ARALDITE. Initially, the epoxy resin and filler materials were intimately mixed in a weight ratio of 9 to 1. The mixed resin/filler material was then intimately mixed with a quantity of epoxy hardener substantially equivalent to 50 per cent by weight of the quantity of resin used to prepare the resin/filler mixture.

The resin/filler/hardener mixture was placed in a mould and cured at room temperature for 24 hours to form a cast body. The cast body was then cut to nominally 10 mm by 60 mm by 5 mm. The body was tested as described in Example 1.

A flame took 75 seconds to travel substantially 30 mm up the substantially upright major surface of the body and drips of burning material were observed.

EXAMPLE 3 (COMPARATIVE)

A composite epoxy material was made comprising a substantially homogenous mixture of nominally 26.1 per cent by weight of low temperature polymeric epoxy resin, reference CY 219, available from Ciba-Geigy under the Trade Mark ARALDITE, 60.9 per cent by weight filler in the form of aluminium trihydrate, and 13 per cent by weight of an epoxy hardener, reference HY 219, also available from Ciba- Geigy under the Trade Mark ARALDITE.

Initially, the epoxy resin and filler materials were intimately mixed in a weight ratio of 3 to 7. The mixed resin/filler material was then intimately mixed with a quantity of epoxy hardener substantially equivalent to 50 per cent by weight of the quantity of resin used to prepare the resin/filler mixture. The resin/filler/hardener mixture was placed in a mould and cured at room temperature for 24 hours to form a cast body. The cast body was then cut to nominally 10 mm by 60 mm by 5 mm. The body was tested as described in Examples 1 and 2.

A flame took 110 seconds to travel 30 mm up the substantially upright major surface of the body and drips of burning material were observed.

EXAMPLE 4

A composite epoxy material was made comprising a substantially homogenous mixture of nominally 62.1 per cent by weight of low temperature polymeric epoxy resin, reference CY 219, available from Ciba-Geigy under the Trade Mark ARALDITE, 6.9 per cent by weight microporous thermal insulation material, and 31 per cent by weight of an epoxy hardener, reference HY 219, also available from Ciba-Geigy under the Trade Mark ARALDITE.

The microporous thermal insulation material that was mixed with the epoxy resin had a nominal content of 58 per cent by weight of microporous high surface area silica (silicon oxide) , with a BET surface area of 200 m²/g, available from Degussa AG under Trade Mark AEROSIL 200, 38 per cent by weight of a particulate infrared opacifier in the form of titanium dioxide with a particle size of 9 micron, available from Eggerding, and 4 per cent by weight of E- glass fibres, available from Owens-Corning under the trade mark ADVANTEX .

Initially, the epoxy resin and microporous thermal insulation materials were intimately mixed in a weight ratio of 9 to 1. Consequently, the resin/insulation material mixture had a nominal content of 5.8 per cent by weight of microporous high surface area silica, 3.8 per cent by weight of infrared opacifier and 0.4 per cent by weight of E-glass fibres.

The resin/insulation material mixture was then intimately mixed with a quantity of epoxy hardener substantially equivalent to 50 per cent by weight of the quantity of resin used to prepare the resin/insulation material mixture .

Following the addition of the epoxy hardener the resin/insulation material/hardener mixture had a nominal content of 62.1 per cent by weight of epoxy resin, 4.0 per cent by weight of microporous high surface area silica, 2.6 per cent by weight of infrared opacifier, 0.3 per cent by weight of E-glass fibres, and 31 per cent by weight of hardener.

The resin/insulation material/hardener mixture was placed in a mould and cured at room temperature for 24 hours to form a cast body. The cast body was then cut to nominally 10 mm by 60 mm by 5 mm. The body was tested as described in Examples 1 to 3.

A flame took 100 seconds to travel 30 mm up the substantially upright major surface of the body and relatively little dripping was observed.

The results obtained in Example 4 show that the presence of nominally 4 per cent by weight of high surface area silica along with opacifier material and fibres in a hardened and cured polymeric material produces a body with similar flame retardancy to that for a body with 60.9 per cent loading of aluminium trihydrate, as described in Example 3. EXAMPLE 5 (COMPARATIVE)

A body of epoxy material was prepared by the intimate mixing of a nominally 200 degree Celsius temperature resistant polymeric epoxy resin, reference LY 5210, and an epoxy hardener, reference HY 2954, both available from Ciba-Geigy under the Trade Mark ARALDITE. The resin and hardener were mixed in the ratio 2 parts by weight resin to 1 part by weight hardener. The resin/hardener mixture was placed in a mould and cured at room temperature for 24 hours to form a cast body. The cast body was then cut to nominally 10 mm by 60 mm by 5 mm. As for Examples 1 to 4, the body was suspended by means- of a clamp supporting a first end of the body, such that the major surface of the body is in a substantially upright position. An initiating flame in the form of a burner flame was applied to an end of the body furthest from the clamp and the time taken for the base of a flame to travel substantially 30 mm up the length of the body was measured. The presence of any burning material dripping away from the test sample was also recorded.

The flame took 70 seconds to travel substantially 30 mm up the substantially upright major ' surface of the body and burning material was seen to be dripping off the surface of the body. Such a material is not suitable for use as a material in circumstances where flame retardant properties are required.

EXAMPLE 6 (COMPARATIVE)

A composite epoxy material was made comprising a substantially homogenous mixture of nominally 62.1 per cent by weight of a nominally 200 degree Celsius temperature resistant polymeric epoxy resin, reference LY 5210, available from Ciba-Geigy under the Trade Mark ARALDITE, 6.9 per cent by weight filler in the form of aluminium trihydrate, and 31 per cent by weight of an epoxy hardener, reference HY 2954, also available from Ciba-Geigy under the Trade Mark ARALDITE.

Initially the epoxy resin and filler materials were intimately mixed in a weight ratio of 9 to 1. The mixed resin/filler material was then intimately mixed with a quantity of epoxy hardener substantially equivalent to 50 per cent by weight of the quantity of resin used to prepare the resin/filler mixture.

The resin/filler/hardener mixture was placed in a mould and cured at room temperature for 24 hours to form a cast body. The cast body was then cut to nominally 10 mm by 60 mm by 5 mm. The body was tested as described in Example 5.

A flame took 100 seconds to travel substantially 30 mm up the substantially upright major surface of the body and drips of burning material were observed.

EXAMPLE 7 (COMPARATIVE)

A composite epoxy material was made comprising a substantially homogenous mixture of nominally 26.1 per cent by weight of a nominally 200 degree Celsius temperature resistant polymeric epoxy resin, reference LY 5210, available from Ciba-Geigy under the Trade Mark ARALDITE, 60.9 per cent by weight filler in the form of aluminium trihydrate, and 13 per cent by weight of a hardener, reference HY 2954, also available from Ciba-Geigy under the Trade Mark ARALDITE. Initially the epoxy resin and filler materials were intimately mixed in a weight ratio of 3 to 7. The mixed resin/filler material was then intimately mixed with a quantity of epoxy hardener substantially equivalent to 50 per cent by weight of the quantity of resin used to prepare the resin/filler mixture.

The resin/filler/hardener mixture was placed in a mould and cured at room temperature for 24 hours to form a cast body. The cast body was then cut to nominally 10 mm by 60 mm by

5 mm. The body was tested as described in Examples 5 and 6.

The flame took 105 seconds to travel 30 mm up the substantially upright major surface of the body and drips of burning material were observed.

EXAMPLE 8

A composite epoxy material was made comprising a substantially homogenous mixture of nominally 62.1 per cent by weight of a nominally 200 degree Celsius temperature resistant polymeric epoxy resin, reference LY 5210, available from Ciba-Geigy under the Trade Mark ARALDITE, 6.9 per cent by weight microporous thermal insulation material, and 31 per cent by weight of a hardener, reference HY 2954, also available from Ciba-Geigy under the Trade Mark ARALDITE.

The microporous thermal insulation material that was mixed with the epoxy resin had a nominal content of 58 per cent by weight of microporous high surface area silica, with a BET surface area of nominally 200 m²/g, available from Degussa AG under Trade Mark AEROSIL 200, 38 per cent by weight of a particulate infrared opacifier in the form of titanium dioxide and 4 per cent by weight of E-glass fibres .

Initially the epoxy resin and microporous thermal insulation materials were intimately mixed in a weight ratio of 9 to 1. Therefore, the composite epoxy resin had a nominal content of 5.8 per cent by weight of microporous high surface area silica, 3.8 per cent by weight of infrared opacifier and 0.4 per cent by weight of E-glass fibres.

The mixed resin/insulation material was then intimately mixed with a quantity of epoxy hardener substantially equivalent to 50 per cent by weight of the quantity of resin used to prepare the resin/insulation mixture.

The resin/insulation material/hardener mixture was placed in a mould and cured at room temperature for 24 hours to form a cast body. The cast body was then cut to nominally 10 mm by 60 mm by 5 mm. The body was tested as described in Examples 5 to 7.

A flame took 140 seconds to travel 30 mm up the substantially upright major surface of the body and no dripping of burning material was observed. The burnt area of the body was observed to have formed a region of burnt and blacken material in the form of solid char. SUMMARY OF EXAMPLES 1 to 8

From Examples 1 to 3 and 5 to 7 it can be seen that the addition of aluminium trihydrate to a polymeric material causes the time taken for a flame to travel up a tested body to increase with increasing aluminium trihydrate content.

Similarly, from Examples 4 and 8 it can be seen that the addition of increasing amounts of high surface area metal oxide and infrared opacifier to a polymeric material causes the time taken for a flame to travel up a tested body to increase. More particularly, the amount of high surface area metal oxide and infrared opacifier added to the polymeric material is small compared with the amount of aluminium trihydrate required to achieve comparable results .

More specifically, the results of the tests in Example 4 show that the addition of nominally 4 per cent by weight of high surface area silica and 2.6 per cent by weight of opacifier material along with fibres to the HY 219 hardened CY 219 polymeric material produces a body with comparable flame retardancy relative to that for a similar epoxy body with a 60.9 per cent loading of aluminium trihydrate, as described in Example 3.

More specifically, the results of the tests in Example 8 show that the addition of nominally 4 per cent by weight of high surface area silica and 2.6 per cent by weight of opacifier material along with fibres to the HY 2954 hardened LY 5210 polymeric material produces a body with improved flame retardancy relative to that for a similar epoxy body with a 60.9 per cent loading of aluminium trihydrate, as described in Example 7. Moreover, the use of the relatively low additions of high surface area silica, infrared opacifier and fibre to the polymeric materials increased the time for a flame to burn 30 mm up the body compared with polymeric materials alone and the unwanted dripping of heated material was prevented by the formation of the char in the composite epoxy material described in Example 8.

EXAMPLE 9 (COMPARATIVE)

A body of vinyl ester (thermoset) material was prepared comprising a mixture of nominally 98 per cent by weight of a vinyl ester resin, available from Reichhold under the reference Norpol Dion 9102-500, and 2 per cent by weight of a hardener, also available from Reichhold under the reference Trigonex S239. The resin and hardener were mixed together for nominally 10 minutes. The mixing together of the resin and hardener initiates the curing process of the resin/hardener mixture.

The resin/hardener mixture was used to hand prepare a laminate sample nominally 100 mm long x 100 mm wide x 6 mm thick comprising nominally twelve laminar sheets of woven glass cloth bound together with the vinyl ester resin/hardener mixture material.

The method of producing the laminate sample was to initially place a nominally 0.5mm thick layer of the resin/hardener mixture on a removable sheet of film and lay a first sheet of woven glass cloth onto the coated removable sheet of film. A hand-held roller was used to apply pressure to the first glass cloth sheet to ensure that the resin substantially impregnated the first sheet of glass cloth. A further layer of resin/hardener material was then applied to the first sheet of glass cloth and a second sheet of glass cloth was then placed on top of the first sheet. The layers of glass cloth were then rolled with the hand-held roller. Additional layers of resin/hardener mixture and glass cloth sheets were assembled until the laminate sample was nominally 6mm in thickness.

The laminate sample was left to air cure for 24 hours.

Once cured the laminate sample was machined to provide a sample of the required 100 mm x 100 mm x 6 mm.

The laminate sample was tested using cone calorimetry in accordance with BS 476: part 15: 1996 to measure the maximum rate of heat release.

The maximum rate of heat release was 274.3 kW/m².

EXAMPLE 10 (COMPARATIVE)

A composite vinyl ester material was made comprising a mixture of 92.4 per cent by weight of vinyl ester resin, 1.9 per cent by weight of hardener, and 5.7 per cent by weight of microporous high surface area silica, with a BET surface area of nominally 200 m²/g, available from Degussa AG under Trade Mark AEROSIL 200. The resin and hardener were as described in Example 9.

Initially, the vinyl ester resin and microporous high surface area silica were intimately mixed in a weight ratio of 94.2 to 5.8. The resin/silica mixture was then intimately mixed with a quantity of hardener nominally 2 per cent by weight of the quantity of resin used to prepare the resin/silica mixture. The resin/silica/hardener mixture was used to prepare a laminate sample as described in Example 9.

The cured laminate sample was tested as described in Example 9 and the maximum rate of heat release was 253.0 kW/m². The maximum rate of heat release from this laminate sample was nominally 8 per cent less than the sample in Example 9 manufactured using only the vinyl ester resin/hardener mixture to laminate the glass cloth.

EXAMPLE 11 (COMPARATIVE)

A composite vinyl ester material was made comprising a mixture of the materials described in Example 10 of nominally 88.4 per cent by weight of vinyl ester resin, 1.8 per cent by weight of hardener, and 9.8 per cent by weight of microporous high surface area silica.

Initially, the vinyl ester resin and microporous high surface area silica were intimately mixed in a weight ratio of 9 to 1. The resin/silica mixture was then intimately mixed with a quantity of hardener nominally 2 per cent by weight of the quantity of resin used to prepare the resin/silica mixture.

The resin/silica/hardener was used to prepare a laminate sample as described in Example 9.

The cured laminate sample was tested as described in Example 9 and the maximum rate of heat release was 248.2 kW/m². The maximum rate of heat release from this laminate sample was nominally 9 per cent less than the sample in Example 9 manufactured using only the vinyl ester resin/hardener mixture to laminate the glass cloth. EXAMPLE 12 (COMPARATIVE)

A composite vinyl ester material was made comprising a mixture of nominally 88.4 per cent by weight of vinyl ester resin, 1.8 per cent by weight of hardener, and 9.8 per cent by weight of a particulate infrared opacifier in the form of titanium dioxide, with a particle size of 9 micron, available from Eggerding. The resin and hardener were as described in Example 9.

Initially, the vinyl ester resin and infrared opacifier were intimately mixed in a weight ratio of 9 to 1. The resin/infrared opacifier mixture was then intimately mixed with a quantity of hardener nominally 2 per cent by weight of the quantity of resin used to prepare the resin/infrared opacifier mixture.

The resin/infrared opacifier/hardener mixture was used to prepare a laminate sample as described in Example 9.

The cured laminate sample was tested as described in Example 9 and the maximum rate of heat release was 282.1 kW/m². The maximum rate of heat release from this laminate sample was nominally 3 per cent more than the sample in Example 9 manufactured using only the vinyl ester resin/hardener mixture to laminate the glass cloth.

EXAMPLE 13 (COMPARATIVE)

A composite vinyl ester material was made comprising a mixture of the materials described in Example 12 of nominally 94.3 per cent by weight of vinyl ester resin, 1.9 per cent by weight of hardener, and 3.8 per cent by weight of infrared opacifier. Initially, the vinyl ester resin and infrared opacifier were intimately mixed in a weight ratio of 96.1 to 3.9. The resin/infrared opacifier mixture was then intimately mixed with a quantity of hardener nominally 2 per cent by weight of the quantity of resin used to prepare the resin/infrared opacifier mixture.

The cured laminate sample was tested as described in Example 9 and the maximum rate of heat release was 300.0 kW/m². The maximum rate of heat release from this laminate sample was nominally 9 per cent more than the sample in Example 9 manufactured using only the vinyl ester resin/hardener mixture to laminate the glass cloth.

EXAMPLE 14 (COMPARATIVE)

A composite vinyl ester material was made comprising a mixture of nominally 97.7 per cent by weight of vinyl ester resin, 2.0 per cent by weight of hardener, and 0.3 per cent by weight of E-glass fibres available from Owens-Corning under the Trade mark ADVANTEX. The resin and hardener were as described in Example 9.

Initially, the vinyl ester resin and fibres were intimately mixed in a weight ratio of 99.7 to 0.3. The resin/fibres mixture was then intimately mixed with a quantity of hardener substantially equivalent to 2 per cent by weight of the quantity of resin used to prepare the resin/fibres mixture .

The resin/fibres/hardener mixture was used to prepare a laminate sample as described in Example 9. The cured laminate sample was tested as described in Example 9 and the maximum rate of heat release was 317.0 kW/m². The maximum rate of heat release from this laminate sample was nominally 16 per cent more than the sample in Example 9 manufactured using only the vinyl ester resin/hardener mixture to laminate the glass cloth.

EXAMPLE 15

A composite vinyl ester material was made comprising a mixture of nominally 93.2 per cent by weight of vinyl ester resin, 1.9 per cent by weight of hardener, and 4.9 per cent by weight of microporous thermal insulation material. The resin and hardener were as described in as described in Example 9.

The microporous thermal insulation material that is mixed with the vinyl ester had a nominal content of 58 per cent by weight of microporous high surface area silica, as described in Example 10, 39 per cent by weight of infrared opacifier, as described in Example 12, and 3 per cent by weight of E-glass fibres, as described in Example 14.

Initially, the vinyl ester resin and microporous insulation material were intimately mixed in a weight ratio of 95 to 5. Consequently, the resin/insulation material mixture had a nominal content of 95.0 per cent by weight of resin, 2.9 per cent by weight of microporous high surface area silica, 1.95 per cent by weight of infrared opacifier and 0.15 per cent by weight of E-glass fibres.

The resin/insulation material mixture was then intimately mixed with a quantity of hardener nominally 2 per cent by weight of the quantity of resin used to prepare the resin/insulation material opacifier mixture. Following the addition of the hardener the resin/insulation material/hardener mixture had a nominal content of 93.2 per cent by weight of resin, 1.9 per cent by weight of hardener, 2.85 per cent by weight of microporous high surface area silica, 1.9 per cent by weight of infrared opacifier, and 0.15 per cent by weight of fibres.

The resin/insulation material/hardener mixture was used to prepare a laminate sample as described in Example 9.

The cured laminate sample was tested as described in Example 9 and the maximum rate of heat release was 229.8 kW/m². The maximum rate of heat release from this laminate sample was nominally 16 per cent less than the sample in Example 9 manufactured using only the vinyl ester resin/hardener mixture to laminate the glass cloth.

EXAMPLE 16

A composite vinyl ester material was made comprising a mixture of the materials described in Example 15 of nominally 88.4 per cent by weight of vinyl ester resin, 1.8 per cent by weight of hardener, and 9.8 per cent by weight of microporous thermal insulation material.

Initially, the vinyl ester resin and microporous insulation material were intimately mixed in a weight ratio of 9 to 1. Consequently, the resin/insulation material mixture had a nominal content of 90.0 per cent by weight of resin, 5.8 per cent by weight of microporous high surface area silica, 3.9 per cent by weight of infrared opacifier and 0.3 per cent by weight of E-glass fibres.

The resin/insulation material mixture was then intimately mixed with a quantity of hardener nominally 2 per cent by weight of the quantity of resin used to prepare the resin/insulation material mixture.

Following the addition of the hardener the resin/insulation material/hardener mixture had a nominal content of 88.4 per cent by weight of resin, 1.8 per cent by weight of hardener, 5.7 per cent by weight of microporous high surface area silica, 3.8 per cent by weight of infrared opacifier, and 0.3 per cent by weight of fibres.

The cured laminate sample was tested as described in Example 9 and the maximum rate of heat release was 225.0 kW/m². The maximum rate of heat release from this laminate sample was nominally 18 per cent less than the sample in Example 9 manufactured using only the vinyl ester resin/hardener mixture to laminate the glass cloth.

EXAMPLE 17 (COMPARATIVE)

A composite vinyl ester material was made comprising a mixture of nominally 29.8 per cent by weight of vinyl ester resin, 1.4 per cent by weight of hardener, and 69.6 per cent by weight of filler in the form of aluminium trihydrate.

Initially, the vinyl ester resin and filler material were intimately mixed in a weight ratio of 3 to 7.

The resin/filler material mixture was then intimately mixed with a quantity of hardener nominally 2 per cent by weight of the quantity of resin used to prepare the resin/filler material mixture. The resin/filler/hardener mixture was used to prepare a laminate sample as described in Example 9.

The cured laminate sample was tested as described in Example 9 and the maximum rate of heat release was 220.3 kW/m². The maximum rate of heat release from this laminate sample was nominally 19 per cent less than the sample in Example 9 manufactured using only the vinyl ester resin/hardener mixture to laminate the glass cloth.

SUMMARY OF EXAMPLES 9 to 17

From Examples 9 to 11 it can be seen that the addition of silica material to a vinyl ester causes the maximum rate of heat release to decrease by a relatively small amount with increasing silica content.

Examples 12 and 13 in comparison with Example 9 show that the addition of opacifier material to a vinyl ester causes the maximum rate of heat release to increase to a value greater than that for the sample using only the vinyl ester resin and hardener mixture.

Example 14 in comparison with Example 9 shows that a relatively small addition of fibre material to a vinyl ester causes the maximum rate of heat release to increase by a relatively large amount.

Surprisingly, from Examples 15 and 16 it can be seen that the addition of the microporous thermal insulation comprising high surface area metal oxide and infrared opacifier along with fibre has an apparent synergistic effect causing the maximum rate of heat release to decrease by a relatively large amount with a relatively small scale addition of microporous thermal insulation addition. Comparison of Examples 15 and 16 with Example 17 shows that relatively small additions of high surface area metal oxide and infrared opacifier produce a reduction in maximum rate of heat release that is comparable to that for a relatively large scale addition of aluminium trihydrate.

Although it is not intended that the present invention should be bound by any specific theory, it is believed the high surface area metal oxide (silica) acts as a thickening agent for any molten resin near the surface of a burning sample inhibiting flame propagation, and the infrared opacifier, when combined with the high surface area metal oxide (silica) , stops radiant energy from a flame heating the resin fuel source.

In some embodiments of the invention it is also believed that the reduction in the amount of burning material dripping from the burning body and the char formation is related to the fluxing nature of the fibre present in the microporous thermal insulation mixed into the resin.

The term 'microporous' is used hereinbefore to identify porous or cellular materials in which the ultimate size of the cells or voids is less than the mean free path of an air molecule at NTP, i.e. of the order of 100 nm or smaller. A material which is microporous in this sense will exhibit very low transfer of heat by air conduction (that is collisions between air molecules) . Such microporous materials include aerogel, which is a gel in which the liquid phase has been replaced by a gaseous phase in such a way as to avoid the shrinkage which would occur if the gel were dried directly from a liquid. A substantially identical structure can be obtained by controlled precipitation from solution, the temperature and pH being controlled during precipitation to obtain an open lattice precipitate. Other equivalent open lattice structures include pyrogenic (fumed) and electro-thermal types in which a substantial proportion of the particles have an ultimate particle size less than 100 nm. Any of these materials, based for example on silica, alumina or other metal oxides, may be used to prepare a composition which is microporous as defined above.

It should be appreciated that filler material can be added to embodiments of flame retardant material in accordance with the present invention. The filler material, for example aluminium trihydrate, magnesium hydroxide, china clay, calcium carbonate or talc can be added, for example, in a range from 0 to 70 per cent, and preferably in a range from 0 to 7 per cent of the final weight of the flame retardant material.

A flame retardant material according to the present invention has been described in which the polymeric material is a thermoset polymeric material in the form of an epoxy or vinyl ester material, the high surface area metal oxide is silica, the opacifier is titanium dioxide, and the fibres comprise E-glass. It should be appreciated that the thermoset polymeric material could also be, for example, a polyester. It should also be appreciated that the polymeric material could be a thermoplastic polymeric material. The high surface area metal oxide can be, for example, alumina (aluminium oxide) . The fibre component of the microporous thermal insulation material mixed with the polymeric material can have compositions, for example based on magnesium silicate, silica, calcium magnesium silicate or other glass formulations, for example C, R and S glass fibres. The infrared opacifier material can be selected from iron titanium oxide, zirconium silicate and iron oxide and mixtures thereof. It should also be appreciated that the BET surface area of the high surface area metal oxide materials can be in a range equal to and greater than 20 m²/g, and preferably in a range equal to and greater than 50 m²/g.

It should also be appreciated that the relative percentages of high surface area metal oxide material, infrared opacifier and fibres comprising the microporous thermal insulation material, which is mixed with the polymeric material to produce a flame retardant material in accordance with the present invention, may vary from those hereinbefore described.

The high surface area metal oxide content of a flame retardant material in accordance with the present invention may be in the range from 1 to 50 per cent, preferably in the range from 2 to 20 per cent, and more preferably in the range from 1 to 10 per cent.

The opacifier content of a flame retardant material in accordance with the present invention may be in the range from 0.5 to 40 per cent, and preferably in a range from 0.5 to 5 per cent.

The fibre content proportion of a flame retardant material in accordance with the present invention may be in the range from 0 to 30 per cent.

It should also be appreciated that the proportion of polymeric material present in the flame retardant material must be greater than 0 per cent, preferably in a range from 90 to 95 per cent.

The flame retardant material according to the present invention can be used as a coating material, and/or as a casting material, for example to manufacture a structural member .

The addition of high surface area metal oxide material and infrared opacifier material to polymeric material, and the distribution of the added materials throughout the polymeric material produces a material with substantially similar, if not improved, flame retardant properties compared with a polymeric material comprising a routine filler, for example aluminium trihydrate.

As well as slowing down the rate of flame spread over an upright surface of polymeric material, the addition of high surface area metal oxide, fibre and infrared opacifier can reduce the amount of material dripping from a burning surface of a polymeric material and even prevent dripping by the formation of a char.

The combined addition of high surface area metal oxide, infrared opacifier and fibre can also reduce the maximum rate of heat release of a polymeric material.

Claims

1. A flame retardant material characterised by comprising a mixture of high surface area metal oxide material, opacifier material and polymeric material, the high surface area metal oxide material and infrared opacifier material being distributed throughout the polymeric material.

2. A flame retardant material as claimed in claim 1, characterised in that the high surface area metal oxide material has a BET surface area of at least 20 m²/g.

3. A flame retardant material as claimed in claim 2, characterised in that the high surface area metal oxide material has a BET surface area of at least 50 m²/g.

4. A flame retardant material as claimed in any preceding claim, characterised in that the high surface area metal oxide material is a microporous high surface area metal oxide material.

5. A flame retardant material as claimed in claim 4, characterised in that the microporous high surface area metal oxide material comprises silica.

6. A flame retardant material as claimed in claim 4 or 5, characterised in that the microporous high surface area metal oxide material comprises alumina.

7. A flame retardant material as claimed in any preceding claim, characterised in that the infrared opacifier comprises titanium dioxide.

8. A flame retardant material as claimed in any preceding claim, characterised in that the infrared opacifier comprises iron titanium oxide.

9. A flame retardant material as claimed in any preceding claim, characterised in that the infrared opacifier comprises zirconium silicate.

10. A flame retardant material as claimed in any preceding claim, characterised in that the infrared opacifier comprises iron oxide.

11. A flame retardant material as claimed in any preceding claim, characterised in that the polymeric material is a coating material.

12. A flame retardant material as claimed in any preceding claim', characterised in that the polymeric material is a castable material.

13. A flame retardant material as claimed in claim 12, characterised in that the castable material is suitable for use in producing structural members .

14. A flame retardant material as claimed in any preceding claim, characterised in that the polymeric material comprises a thermoset polymeric material.

15. A flame retardant material as claimed in claim 14, characterised in that the thermoset polymeric material comprises an epoxy material.

16. A flame retardant material as claimed in claim 14 or 15, characterised in that the thermoset polymeric material comprises a vinyl ester material.

17. A flame retardant material as claimed in claim 14, 15 or 16, characterised in that the thermoset polymeric material comprises a polyester material.

18. A flame retardant material as claimed in any preceding claim, characterised in that the polymeric material comprises a thermoplastic polymeric material.

19. A flame retardant material as claimed in any preceding claim, characterised in that the flame retardant material further includes a filler material.

20. A flame retardant material as claimed in claim 19, characterised in that the filler material comprises aluminium trihydrate.

21. A flame retardant material as claimed in claim 19 or 20, characterised in that the filler material comprises magnesium hydroxide.

22. A flame retardant material as claimed in claim 19, 20 or 21, characterised in that the filler material comprises china clay.

23. A flame retardant material as claimed in any one of claims 19 to 22, characterised in that the filler material comprises calcium carbonate.

24. A flame retardant material as claimed in any one of claims 19 to 23, characterised in that the filler material comprises talc.

25. A flame retardant material as claimed in any preceding claim, characterised in that the flame retardant material further includes fibres.

26. A flame retardant material as claimed in claim 25, characterised in that the fibres comprise calcium magnesium silicate.

27. A flame retardant material as claimed in claim 25 or 26, characterised in that the fibres comprise magnesium silicate .

28. A flame retardant material as claimed in claim 25, 26 or 27, characterised in that the fibres comprise silica.

29. A flame retardant material as claimed in any one of claims 25 to 28, characterised in that the fibres comprise glass formulations.

30. A flame retardant material as claimed in claim 29, characterised in that the glass fibres are selected from E, R, C and S glass formulation fibres.

31. A flame retardant material as claimed in any preceding claim, characterised in that the flame retardant material comprises a mixture of:

0.5-40% by weight infrared opacifier;

0-70% by weight filler material; and

0-30% by weight fibres.

32. A flame retardant material as claimed in claim 31, characterised in that the flame retardant material comprises a mixture of:

at least 1% by weight polymeric material; 2-20% by weight high surface area metal oxide material;

0.5-40% by weight infrared opacifier; 0-70% by weight filler material; and 0-30% by weight fibres.

33. A flame retardant material as claimed in claim 32, characterised in that the flame retardant material comprises a mixture of:

90-95% by weight polymeric material;

1-10% by weight high surface area metal oxide material;

0.5-5% by weight infrared opacifier 0-7% by weight filler material; and

0-1% by weight fibres.