WO1993003096A1

WO1993003096A1 - Blast, impact and fire resistant composite material

Info

Publication number: WO1993003096A1
Application number: PCT/GB1992/001442
Authority: WO
Inventors: Lesley Susan Gratton; Clifford Thomas Metcalf Hall
Original assignee: Hepworth Minerals and Chemicals Ltd; Darchem Engineering Ltd
Current assignee: Hepworth Minerals and Chemicals Ltd; Darchem Engineering Ltd
Priority date: 1991-08-09
Filing date: 1992-08-03
Publication date: 1993-02-18
Anticipated expiration: 1994-02-09
Also published as: GB9117278D0; AU2388892A

Abstract

A composite material for blast, impact and fire resistant barriers is formed by curing a mixture of a phenolic resin, a neutral, noncorrosive curing agent therefor, fine powders including a hydraulic material, water, fibres, and aggregate. The cured mixture is provided with a continuous reinforcement which may comprise a core of the cured mixture or a protective outer layer. In the preferred arrangement, the composite material is formed into panels for the construction of blast walls.

Description

BLAST. IMPACT AND FIRE RESISTANT COMPOSITE MATERIAL

This invention relates to a blast, impact and fire resistant barrier material and particularly to a material suitable for the construction of blast walls for use in both onshore and in offshore petrochemical applications, including offshore oil platforms. The invention also relates to a method of manufacture of such material .

The early blast walls developed for the offshore petroleum industry relied on hefty structural sections and thick carbon steel plates welded or bolted together to provide the structural stability to survive the blast overpressure. In containing the spread of fire which inevitably follows a blast overpressure, the options open to the facility operators were to construct another wall capable of containing the fire or to insulate the blast wall. The disadvantages of these early blast walls were as follows:

1. the weight of the blast wall was severely restrictive to a top weight conscious industry;

2. the blast wall had to be regularly painted to prevent corrosion from weakening the structure, bearing in mind the offshore environment is one of the most potentially corrosive places you can erect such structures. 3. insulating blast walls increases the weight of an already heavy structure and if the fire side is not known, both sides have to be insulated which is costly as well as increasing the weight yet again.

It can be understood from these disadvantages why offshore operators were less than enthusiastic about having to erect these blast walls.

With the advent of time, corrugated sheet replaced the thick plate, this reduced the weight by approximately 15%, however, the rest of the disadvant ges remained.

Nothing changed very much until the late 1980s when composite material blast walls consisting of laminates of polyester resin and glass cloth built up to a thickness of approximately 50mm were produced. These provided both a blast and fire resistant wall that needed no maintenance. However, the following disadvantages can be attributed to such a system:

1. the composite walls are still extremely he vyj

2. in a fire, polyester and glass cloth give off copious amounts of smoke. In fact, polyester emits toxins in the smoke generation;

3. polyester can actually provide a fuel source to maintain the intensity of the fire for a longer period. Despite these disadvantages, the composite blast wall was an immense improvement on the early steel blast walls.

According to the present invention there is provided a composite material for blast, impact and fire resistant barriers, formed by curing a mixture of a phenolic resin, a neutral, non¬ corrosive curing agent therefor, fine powders including an hydraulic material, water, fibres, aggregate, said cured mixture being provided with a continuous reinforcement.

The material of the present invention may utilize a composition as disclosed in International Patent Publication W091 04291. The continuous reinforcement may comprise a core of the cured mixture and the composite material has a protective outer layer including a reinforced resin material. In this case, the outer layer is preferably reinforced by a mineral fibre (eg. glass fibre) mat, and the resin employed is preferably also a phenolic resin reactive with the-curing agent used in the core so that the resins of the core and outer layer become chemically bonded together. Preferably, the phenolic resin material is an aqueous alkaline phenolate resin formed by reaction between phenol and formaldehyde in the presence of a catalyst to produce a phenolic resin having a low free phenol and free formaldehyde content.

The invention also includes a blast wall panel comprising a core formed by curing a mixture of a phenolic resin with a curing agent therefor, and a protective outer layer comprising a continuous fibrous reinforcement embedded in phenolic resin cured by the curing agent of the core whereby the resins of the core and* the outer layer are chemically bonded together.

A blast wall may be produced by locating a plurality of panels of composite material in frame members.

The resin used in this invention is preferably an ester cured alkaline phenolic resin. Such phenolic resins used in the practice of this invention can be prepared by methods well known to those skilled in the art. In general, they are prepared by reacting a molar excess of formaldehyde with a phenol under alkaline conditions. Various phenols may be used in the preparation of the-resin, the preferred phenolic material is unsubstituted phenol. Likewise, any of the commonly used aldehydes may be used in the preparation of the resin. The preferred aldehyde is formaldehyde.

The molar ratio of aldehyde to phenol is generally from about 1.2:1 to about 2.6:1. The preferred molar range of aldehyde to phenol is from about 1.5:1 to about 2.2:1.

Any of the commonly used catalysts may be used to prepare the phenolic resole resin, for example, alkaline catalysts such as sodium hydroxide and potassium hydroxide. The molar range of alkali to phenol is generally from about 0.2:1 to about_. 1.3:1. The preferred molar range is from about 0.4:1 to about 0.9:1. If required, a smaller amount of alkali may be employed to effect the reaction step and additional alkali added to the resin at the end of the resin preparation. The added alkali does not have to be the same as that used to catalyse the resin preparation, for example, lithium hydroxide could be added to a resin catalysed initially with potassium hydroxide. It is also possible to include the extra alkali as a separate addition to the fine powders/aggregate mixture used in the composite.

A typical solids content of the aqueous resin solution is in the" range of about 40% to about 75% by weight. Lower solids contents are permissible, but not usually desirable from an economic point of view. The solution can also contain, in addition to water, various additives such as urea, a surfactant, and a coupling agent such as organo silane or zircoaluminate. A suitable resin which is available commercially is IR3350 (Hepworth Mineral and Chemicals Limited) .

Many modifications to this basic process are known, for example, it is possible to prepare an acid catalysed novolac resin followed by rnethylolation of the novolac under alkaline conditions to produce a methylolated novolac solution.

The following example is quoted in order to illustrate but not limit the invention:-

A reactor was charged with water (836grms). To this was added with cooling pearl sodium hydroxide (7.5grms ; 0.188mol). Phenol (67.9grms ; 0.722mols) and 55% formalin (78.9grms ; 1.447mols) were then charged, while maintaining the temperature of the mixture at less than 40°C. The temperature of the mixture was then raised to 70°C over a 1-hour period and held at this temperature for a further one hour. The reaction temperature was then raised over 40 minutes to 90°C and held at this temperature until the desired weight average molecular weight had been achieved (approx. 100 minutes). The reaction mixture was then cooled to less than 30°C and a further quantity of pearl sodium hydroxide

(10.8grms ; 0.27mols) added whilst maintaining the temperature at less than 30°C. Finally, a coupling agent (silane D1505 ; 1.5grms) was added and the resin discharged from the reactor. This procedure produced a product with the following properties:- pH (as is) 12 Free Formaldehyde 1.3%

Solid Resin Yield 42%

B4 Viscosity at 25°C 44 sees. The curing agent for the resin may be a blend of aliphatic esters or lactones such as butylene diacetate and butyrolactone.

Examples of organic esters useful as the curing agent include - low molecular weight lactones, eg. butyrolactone, propiolactone, and σaprolactone, carboxylic esters such as, methyl format, diaσetin, triacetin, ethylene glycol diacetate, propylene glycol diacetate, butylene glycol diacetate, organic carbonates, such as propylene carbonate, and phenolic esters such as phenyl acetate, resorcinol diacetate, and 4,4 - diphenyolpropane diacetate. These ester curing agents may be used singly or. in combination. A suitable curing argent which is available commercially is IC3505 (HMC Ltd.). Alternatively, we may use a slower catalyst available from HMC Ltd. given the number IC4055 or a slower catalyst than IC3505 with phosphorus added to reduce any tendency to flaming, given the number IC4070.

Additives can be incorporated into the ester curing agent to modify the systems properties, eg. resorcinol can be dissolved in the curing agent. This can chemically react with free formaldehyde in the resin to reduce fume emissions. The fine powders contain a number of components in fine powder form which serve to absorb water. They also help to control shrinkage and cracking of the panels. Common to all fine powder formulations is the use of hydraulic material, especially cement, to absorb water chemically. Other compounds of the fine powder mixture are - hydrated magnesium calcium carbonates commercially available as Ultracarb and Delacarb (trade names) , a ceramic frit commercially available as Ceepree (trade name), volclay, mica, calcium carbonate commercially available as Microcarb (trade name), expanded fire clay grog, alumina trihydrate, and zinc borate. The various components of the fine powders provide a variety of functions. For example, the cements and carbonates decompose endothermically. Therefore, by adding these materials to the composite, the period of time during which the material protects against the effects of fire is extended. During a fire, a temperature gradient exists throughout the material, causing a series of decomposition reactions to take place. The end effect being that the temperature of the cold face of a panel of the material stabilizes between 80°C and 90°C. This is known as a water plateau, the length of the plateau can be altered by varying the proportion of powders in the mix. The ceramic frit available commercially as

Ceepree also has a specific function in the preferred material. This material is made up of a series of glassy frits. The frits are designed so that the melts of two or more frits, when combined, form a glass with a higher melting point. As this glass melts, it combines with other frits forming a glass with a yet higher melting point. As the powders, and therefore the Ceepree are dispersed throughout the composite, the end result is, that as the resin burns out and its bonding effect is lost, the glassy matrix is in place to continue to bond the aggregates. This results in very little loss of material from the hot face and a relatively high post fire strength. The following example of a fine powder mix is given to illustrate, but not limit, the invention: -

Blue Hawk Cement 17.4%

Ultracarb C5-20 34.7% Ceepree 17.3%

Volclay 1.7%

Mica MF150 11.6%

Microcarb ST10 17.3% A suitable powder mix is available commercially as IP4040 (HMC Ltd.).

The reinforcing fibres are preferably glass fibres but could be ceramic, metallic, or other mineral fibres.

The aggregate material may be a combination of one or more materials, some possible materials being listed below:-

- alumina and silica sands of varying particle size distributions varying from very coarse grit to fine flours.

- powders of varying compositions and grades including plaster, zirconium silicate, cementitious by-products, anhydrous borax, high alumina, cements such as that commercially available as Secar, hydroxylated kaolin, mica, wollastonite, synthetic calcium hydro silicate such as that commercially available as Delacal.

- lightweight particulate materials including foamed clay such as that commercially available as Leca, foamed glass such as that commercially available as PoraVer, pulverized fuel ash xenospheres such as that commercially available as Fillite, microspheres, vermiculite, kaolin prill, perlite, expanded fire clay grog.

- various lightweight waste products including crushed calcium silicate insulation materials, foamed materials as well as waste material of the invention.

All of these materials have been used in varying particle sizes and used individually or combined with other materials of similar or varying particle sizes. The type of materials used and the mix determines particularly the density of the material as well as the physical properties, ie. the addition of a high density very fine zirconium silicate flour to a vermiculite aggregate will increase density but have little, if any, significant effect on the strength characteristics of the material.

The density may also be altered by treating aggregates such as perlite and vermiculite with a silicone or silane emulsion before use. This reduces the amount of resin absorbed by the aggregate, thus allowing the resin (and curing agent) to be reduced thereby reducing the bulk density of the final material. The use of silicone or silane treatment may also result in reduced thermal conductivity and specific silanes may improve the poiymer/aggregate bonding resulting in improved composite strength.

The silicone or silane emulsion may also be added to the mix itself in order to improve water repellency of the final product.

The fire resistant properties can also be increased by the addition of hydrating materials which disassociate with the hydrating water on heating. Normally the hydrated material is added to the mix and hydrated by the water therein.

Fire resistant properties can also be altered by altering the amount of fine powders, e.g. IP 4040 in the mix.

In accordance with a further aspect of the invention, there is provided a method of manufacturing a blast, impact and fire resistant material comprising the steps of: foaming an uncured phenolic resin material in the presence of water with a surfactant; mixing the foamed resin with the fine powders, aggregate material, fibres, and the curing agent and allowing any hydraulic material present to hydrate; reinforcing said material with a continuous reinforcement; and, curing the resin. The fibres are preferably mineral fibres, eg. glass fibres.

The continuous reinforcement may take the form of a glass fibre mat.

The continuous reinforcement may be incorporated into a protective outer layer, which may also contain a resin material. Alternatively, the continuous reinforcement may be located within the material itself. Preferably, where the reinforcement takes the form of an outer layer, this outer layer is reinforced by a fibrous mat, eg. of glass fibres. The resin of the outer layer is preferably also a phenolic resin in which case the curing agent for the core material diffuses throughout the whole mass to cure the resin of the outer layer as well as that of the core so that the resins of both core and outer layer become chemically bonded together. In this arrangement the fibrous mat of the outer layer is preferably sunk slightly below the surface of the material to improve adherence.

Additional reinforcement can be attached either chemically or mechanically to the core material .

The resulting composite may be further painted or coated for decorative, weatherproofing or protective purposes.

The invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is "a- diagrammatic perspective view of a blast wall including a plurality of blast panels in accordance with the invention; and, Figure 2 is a sectional side elevation showing the interconnection between adjacent panels.

In the drawings a blast wall (1) comprises a plurality of panels (2) held together in the form of a wall by means of horizontal and vertical frame members (3) and (4). The panels (2) are of a composite material in accordance with the invention and include a core (5) and a protective outer layer (6). The protective outer layer (6) includes a resin material (7) and a continuous fibrous reinforcement mat (8) sunk below the surface of the respective panel (2) and chemically bonded to the core (5). The frame members (3) and (4) suitably comprise pultruded H-sections.

The core material for one type of blast wall according to the invention contains only vermiculite as an aggregate, this vermiculite having a fine particle size distribution, ie. as found with DuPre Micron grade. A typical mix is shown below by way of example. This type of mix shows good general properties with a bulk density of approximately 900kg/m° on compression, less than 3% deformation is observed when loaded to 2500 KN/m², 95-99% of that deformation being elastic. A 60mm -thick sample of this material has achieved a 2-hour rating for integrity and insulation when subjected to a fire test following the Mobil H-rise curve.

TYPICAL BLAST WALL MIX (1 ) WEIGHT % Surfactant 0.1

Water 14.0 Resin 40.0

Fine Powders 22.4

Vermiculite 17.2

Glass Fibre 1.5 Curing Agent 4.8

The density and strength of the material can be improved by using a mixture of coarse, ie. DuPre DM grade vermiculite and fine vermiculite. The density can also be increased by the use of silica sand and silica flour, eg:

TYPICAL BLAST WALL MIX (2) WEIGHT % Surfactant 0.1

Water 11.5

Resin 37.1 Fine Powders 25.4

Vermiculite 14.4

Silica Sand 5.7

Sil ica Flour 1.4

Curing Agent 4.3 This material has a density between 1200 and

900Kg/m and may also be made with glass fibre and zirconium silicat-e" or alumina used instead of silica.

The fire resistant characteristics may also be improved by the addition of hydrating materials such as plaster, cementitious products, etc.

The core material is overlaid with an outer layer comprising a resin impregnated glass as typically used in the reinforcement of grinding wheels, or a glass material with high tensile strength in both directions.

The mixes for the core are manufactured in the following way: the surfactant, water and resin are foamed to create an aerated material ; the fine powders are then dispersed in the resin mixture until thoroughly mixed in*; the glass fibre and then the aggregates are added, with the fine aggregate being added first; the curing agent can be added at any point of the mixing procedure; the core material is moulded with the glass fibre skin for the outer layer being applied at the same time and the final product is left to dry and cure. Drying and curing may be carried out at ambient temperature over a period of not less than 14 days or at 120°C for a period of 48 hours or at other temperatures and times between these two extremes. The cured blast wall panels may be waterproofed, eg.~by treatment with a silane or siloxane.

The composite material in accordance with the present invention has the following char cteris ics:

(i) low smoke toxicity index NES 713; (ii) low smoke optical density ASTM E662; (iii) class 1 surface spread of flame BS476pt ;

(iv) low smoke contribution to fire BS476pt6; thereby being able to achieve a Class 0 rating within the definition of the U.K. Building Regulations;

(v) high blast/overpressure resistance.

Claims

1. A composite material for blast, impact and fire resistant barriers, formed by curing a mixture of a phenolic resin, a neutral, non¬ corrosive curing agent therefor, fine powders including an hydraulic material, water, fibres, and aggregate, said cured mixture being provided with a continuous reinforcement.

2. A composite material according to claim

1, wherein the continuous reinforcement comprises a core of the cured mixture and the composite has a protective outer layer including a reinforced resin material.

3. A composite material according to claim

2, wherein the outer layer is reinforced by a mineral fibre mat, and the resin employed is a phenolic resin reactive with the curing agent used in the core so that the resins of the core and outer layer become chemically bonded together.

4. A composite material according to any one of the preceding claims, wherein the phenolic resin material is- n aqueous alkaline phenolate resin formed by reaction between phenol and formaldehyde in the presence of a catalyst to produce a phenolic resin having a low free phenol and free formaldehyde content.

5. A composite material according to claim , wherein the solids content of the aqueous resin solution is in the range of about 40% to about 75% by weight.

6. A composite material according to any one of the preceding claims, wherein the curing agent for the resin is a blend of aliphatic esters or lactones.

7. A composite material according to any one of the preceding claims, wherein the fine powders, in addition to the hydraulic material, include materials selected from hydrated magnesium calcium carbonates, a ceramic frit, mica, calcium carbonate, expanded fire clay grog, alumina trihydrate and zinc borate.

8. A composite material according to any one of the preceding claims, wherein the reinforcing fibres are selected from glass fibres, ceramic, metallic, or mineral fibres.

9. A blast wall panel comprising a core formed by curing a mixture of a phenolic resin with a curing agent therefor, and a protective outer layer comprising a continuous fibrous reinforcement embedded in phenolic resin cured by the curing agent of the core whereby the resins of the core and the outer layer are chemically bonded together.

10. A blast wall including at least one panel made of a composite material in accordance with any one of the preceding claims.

11. A blast wall according to claim 10, including a plurality of panels and frame members for holding the panels together.

12. A composite material for forming a blast wall panel mix according to any of the examples described herein.

13. A method of manufacturing a blast, impact and fire resistant material comprising the steps of: foaming an uncured phenolic resin material in the presence of water with a surf ctant; mixing the foamed resin with the fine powders including an hydraulic material, aggregate material, fibres, and a curing agent; allowing the hydraulic material present to hydrate; reinforcing said material with a continuous reinforcement; and, curing the resin.

14. A method according to claim 13, comprising providing a glass fibre mat material for the continuous- reinforcement; and incorporating the reinforcement into a protective outer layer, which also contains a resin material.

15. A method according to claim 14, comprising selecting the resin of the outer layer as a phenolic resin; and causing the curing agent for the core material to diffuse throughout the whole mass to cure the resin of the outer layer as well as that of the core so that the resins of both core and outer layer become chemically bonded.

16. A method according to claim 14 or claim 15, comprising locating the fibrous mat of the outer layer slightly below the surface of the material to improve adherence.