GB2121056A

GB2121056A - Intumescent coating compositions

Info

Publication number: GB2121056A
Application number: GB08310699A
Authority: GB
Inventors: Brain George Huckstepp; Christopher Lloyd-Lucas
Original assignee: LLOYD LUCAS CHRISTOPHER
Current assignee: LLOYD LUCAS CHRISTOPHER
Priority date: 1982-04-23
Filing date: 1983-04-20
Publication date: 1983-12-14
Also published as: GB8310699D0; GB2121056B; NL8301407A

Abstract

A composition which intumesces to form a heat insulating char when exposed to fire and useful for protecting structural steelwork, comprises (a) a resin film forming binder, such as an epoxy resin, (b) a spumific agent such as melamine phosphate in a weight ratio of less than 7.5:1, (c) up to 20% by weight of an aromatic hydroxy compound such as catechol or salicylic acid, and optionally (d) a filler such as ceramic fibres consisting of more than 50% by weight of aluminium hydroxide.

Description

SPECIFICATION Improvements in or relating to fire retardent compositions The present invention relates to fire retardent compositions which intumesce to form heat insulating chars when exposed to fire.

Such compositions in the form of paint, may be applied to the structural members in buildings or to structural steel frameworks and serve to lessen the tendency of such structures to collapse under the influence of high temperatures caused by fires.

Fire retardent compositions which intumesce are well known and are, for example, described in British patent specifications 1,095857 1,373,908 and 1,570,604.

We have now found that the effectiveness of intumescent compositions can be significantly improved by the addition of the relatively small amounts of aromatic hydroxy compounds.

Accordingly, therefore, the present invention provides an intumescent coating composition comprising a film-forming binder and a spumific agent preferably in weight ratio of less than 7.5 to 1 together with a small amount, preferably less than 20% by weight, of an aromatic hydroxy compound.

An intumescent composition is a composition which when subjected to high temperatures, e.g. in excess of 250"C swells to form a char that may be up to 1000 times its original thickness.

In the composition of the present invention the film forming binder is preferably an epoxy resin and the preferred spumific agent is melamine phosphate.

Especially suitable epoxy resins are diglycidylethers containing the grouping:

"n" is preferably in the range of O to 1.0 at which level the resin is a low viscosity liquid at room temperature (about 0.5 to 1.-poise at 25"C). Intumescent compositions produced from such resins can be readily applied by spraying. At higher "n" values the viscosity increases and the compositions may have to be applied by trowelling. The addition of heat vaporisable inert liquid may be employed to reduce the viscosity of such resins.

Suitable curing agents for curing diglycidylether resins include carboxylic acid anhydrides, dibasic organic acids, lewis acids, lewis bases, aliphatic primary amines, aliphatic secondary amines, aromatic amines and amino-polyamines, the latter being especially useful. The weight ratio of curing agent to resin is preferably in the ratio 7 to 3 although ratios of up to 7 to 6 may be employed If desired the melamine phosphate may be replaced by the equivalent weight of melamine borate. Preferably not more than 20% of weight of the melamine salt is melamine borate.

Suitable aromatic hydroxy compounds include phenol, substituted phenols such as the cresols, xylenols or salicylic acid; dihydroxy compounds such as the catechols and hydroxy aromatic polynuclear compounds for, example B-naphthol, may also be employed.

To improve this structural strength of intumescent compounds it has been proposed to add small amounts of inorganic fibres. Especially effective are glass fibres and ceramic fibres having a silica content of less than 50% by weight and preferably having an aluminium oxide content of greater than 50% by weight, said fibres are preferably present in the range of 1 to 15% by weight.

Other filler compounds such as glass microspheres wood flour or powdered silica, may also be added if required, but it is preferable that the total content by weight of filler plus inorganic fibres (where present) does not exceed 15% by weight of the total components of the composition.

The following examples illustrate intumescent compositions falling within the scope of the present invention.

In the examples the epoxy resin is that sold as Araldite (Registered Trade Mark) MY750 (CIBA Limited of Duxford Cambridgeshire) and has a "n" value in the range 0.1 to 0.2; the inorganic fibres are ceramic fibres, sold as Fiberfrax (Registered Trade Mark) chopped fibres (sold by the Carborundum Company of Rainham St. Helens, Lancashire) having a mean length of 0.3mm and a mean diameter of 0.002mm. The curing agent for the epoxy resin is Versamid (Registered Trade Mark) 125, an amino polyamine supplied by Cray Valley Products Limited, London, and the dibutyl phthalate is supplied by Albright and Wilson Limited, Phosphates Division, Oldbury, Warley, West Midlands. The wood flour is the 300 mesh grade supplied by Wood Treatment Limited of Bosley, Macclesfield, Cheshire.The epoxy resin dibutyl phthalate, melamine phosphate, wood flour and ceramic fibres were stirred together to effect mixing of the components, to which mixture was added the required amount of aromatic hydroxy compound, the curing agent and the mixture again throughly stirred. The percentage composition of the components are given in table 1 below.

Samples of examples 1 and 2 together with samples A s B of control compositions (same weights of components excluding aromatic hydroxy component) were coated onto 30cm square 2mm thick mild steel sheets. The coated side of the face of the sheets was heated by means of a 2 inch diameter Barter Rosette" blow torch Ex Barter 8 Sons Limited, Eleys Estate, London (using an air flow rate of 400 cu ft/hour and a natural gas flow of 40 cu ft/hour giving a flame temperature of 1150 C. Each coated sheet was held vertically and the flame directed normally onto the centre of the sample from a distance of 5 inches. The temperatures on the uncoated face were measured at the centre of each sample employing a quick response insulated thermocouple and the average of two readings taken.

The results of the tests are shown in Table 2 below: TABLE 1 COMPOSITION PARTS BY WEIGHT EXAMPLE EPOXY Curing Melamine Fiberfrax Dibuty Wood Ar-Oh RESIN Agent Phosphate V125 1 29 15 18 3.25 2 0.25 6.11 2 29 15 18 3.25 2 0.25 6.82 Ar-Oh = aromatic hydroxy compound (1) Salicylic acid (2) 4 Methylcatechol fraction (Ex Coalite Oil and Chemicals Limited).

TABLE 2 EXAMPLE 1 2 A B Coating weight 0.28 0.27 0.25 0.29 g/mm2 Coating thick- 3.2 3.5 3.3 3.5 ness mm C Initial 16 23 23 16 5 mins. 187 193 221 212 10 mins. 228 227 268 259 15 mins. 247 255 290 275 20 mins 254 267 304 284 30 mins. 263 275 329 298 40 mins. 265 276 338 306 50 mins. 267 281 343 315 60 mins. 273 286 349 333 Time taken to reach 300 C mins. 60 60 18 32 Compositions of the present invention are especially suitable for use as fire retardent coatings on structural steel work, e.g. in the oil industry, on structural and other members in buildings and as coatings on road tankers carrying inflammable liquids, e.g. petrol tankers.

Claims

1. An intumescent coating composition comprising a film-forming binder and a spumific agent in a weight ratio of less than 7.5:t wherein there is included, as an additive, an aromatic hydroxy compound.

2. A composition according to claim 1 wherein the aromatic hydroxy compound forms less than 2Q% by weight of the total composition.

3. A composition according to claim 1 or claim 2 wherein the aromatic hydroxy compound is a phenol or a substituted phenol.

4. A composition according to claim 3 wherein the substituted phenol is a cresol or xylenol.

5. A composition according to claim 3 wherein the substituted phenol is salicylic acid.

6. A composition according to claim 3 wherein the phenol is an aromatic di-hydroxy compound or a substituted di-hydroxy compound.

7. A composition according to claim 6 wherein the aromatic di-hydroxy compound is 4methyl catechol.

8. A composition according to claim 1 or claim 2 wherein the aromatic hydroxy compound is a hydroxy polynuclear compound.

9. A composition according to claim 8 wherein the aromatic hydroxy polynuclear compound is betanaphthol.

10. A composition according to any one of the preceding claims wherein the film forming binder is an epoxy resin and the spumific agent is melamine phosphate.

11. A composition according to claim 10 wherein the epoxy resin is a diglycidylether containing the grouping:

where "n" is in the range 0 to 1.

1 2. A composition according to claim 10 or claim 11 wherein the melamine phosphate contains up to 20% by weight of melamine borate.

1 3. A composition according to any one of the preceding claims wherein it includes an inert filler.

14. A composition according to claim 1 2 wherein the inert filler comprises glass fibres, or ceramic fibre having a silica content of less than 50% by weight and aluminium oxide content of greater than 50% by weight, said fibres being present in the range 1 to 15% by weight of the composition.

1 5. A composition according to claim 1 3 wherein the filler comprises glass microspheres, wood flour or powdered silica.

16. A composition according to claim 1 and substantially as described herein with reference to examples 1 and 2.