GB2533622A

GB2533622A - Fire retardant coatings

Info

Publication number: GB2533622A
Application number: GB1423131.0A
Authority: GB
Inventors: Alfred Ward Derek; Penfold Ben
Original assignee: Intumescent Systems Ltd
Current assignee: Intumescent Systems Ltd
Priority date: 2014-12-23
Filing date: 2014-12-23
Publication date: 2016-06-29
Anticipated expiration: 2034-12-23
Also published as: GB2533622B; WO2016102908A1

Abstract

An intumescent water-based coating which dries to a transparent finish and includes no drying or curing agent comprises a single pack emulsion of a mix of phosphate salts including ammonium polyphosphate in solution as a flame retardant blowing agent, pentaerythritol as a charring agent, and an epoxy resin water-based or emulsified binder. The ratio of binder to pentaerythritol is 2.5-3.0 to 1, preferably 2.7 to 1. The mix may further comprise an alcoholic ester, a phosphate surfactant, a defoaming surfactant, and a biocide. The coating is especially useful for wood and wood-related surfaces.

Description

FIRE RETARDANT COATINGS

This invention relates to fire retardant coatings and more especially to clear inturnescent coatings for wood and wood-related surfaces. Fire retardant coatings achieve Class 0 and Class I spread of flame ratings and fHre protection coatings achieve up to 60 minutes protection against the spread of flames. IA)

BACKGROUND TO THE INVENTION

intumescent coatings for wood and wood-related surfaces are known but many of these do not provide a clear and transparent finish for the treated surfaces and others comprise a two pack system which requires dual application or pre-mixing before application.

Our European. patent EP2093263B1 discloses an. intumescent water-based coating which dries to a transparent finish when applied to wood and wood related surfaces and which does not require dual application or premixing ocsrurc application_ Whereas this water-based coating meets the dual criteria of an Intumescent coating which provides excellent protection against the spread of fire and which dries to a clear finish, water-based coatings in accordance with the present invention. offer additional advantages over our earlier coatings as disclosed in EP2093263B1 and the present invention is an improvement over the earlier invention disclosed in EP209326331.

Intumescent coatings are also disclosed in W02006/067478, U36613391, W093/11196, DE2227188 and GB2071111. The first of these documents discloses a liquid intumescent coating composition which comprises a resin system em including a polymeric component, an unsaturated monomeric component and an intumescent ingredient. The second document describes a process for achieving a fire and flame 5 retardant effect and the third document is directed to a composition with intumescent properties in which an amino-formaldehyde resin and mixture of monoesters and dlesters of orthophosphoric acid with one or more polyols. None of the documents discloses an intumescent water-based coating 10 which dries to a trans-oarent finish.

As for our earlier invention, the present invention sets out in one aspect to provide an improved intumescent coating which dries to a clear transparent finish and comprses a single pack system, namely a coating which can be applied direct from a single container in which it is supplied to a customer. Additionally, the present invention provides an intumescent coating having all of the features of our earl-H-1-coating but, in addition, provides a coating which can simply be removed by heating to a temperature of SO degrees or less using a hand-held dryer or the like.

SUMMARY OF THE INVENTION

In one aspect, the invention provides a self-curing intumescent water-based coating which dries to a transparent finish and includes no drying or curing agent, the coating including a single pack emulsion comprising a mix of phosphate salts including ammonium polyphosphate in solution which act together as a flame retardant blowing agent, pentaerythritol which acts as a charring agent and an epoxy resin water-based or emulsified binder, the ratio of water-based or emulsified binder to pentaerythritol being between 2.5 and 3.0 to 1.

The ratio of binder to charring agent is preferably 2.7 to 1.0.

The mix may further include an alcoholic ester, a phosphate surfactant, a defoaming surfactant and a biccide.

DETAILED DESCRIPTION OF THE INVENTION

One example of a water-based intumescent fire retardant and fire protect.i ye ci ear coating will now be described by way of example only.

The coating was produced in batches of approximately 110 litres, each batch! comnrising the ingredients listed! below in the quantities specifie.d.

Initially 35.500kg of acid catalyst axumorliam pclyphosphate (APP) / 27.000kg of water-based epoxy emulsion binder and 12.000kg of charrtng-agent pentaerythritoi were fast mixed for successive periods of 5 and 10 minutes to produce a homogeneous paste.

Secondly, 11.000kg of flame retardant blowinq agsn was added and fast mixed for a period of 15 minutes, Thirdly. 1.185kg of alcoholic ester, e.g. T!exan!ol to improve the I im formIng properties of the coating and to lower its freezing point, 1. 196kg of phosphate surfactant to aid dispersion of th.e particle content of the mix 0,178kg of a defoaming surfactant, and! Ci024Ikg of a IA) biocide, e.g. Acticide, were added and mixed for a further 15 minutes.

Finally, 32.000kg of water-based epoxy emulsion binder was 5 added and the resultant mix fast mixed for 20 minutes, The epoxy emulsion acts as a binder and aids charring of the coating in the event that the surface to which it is applied is subjected to excessive heat.

The presence of blowing agent ensures that the coating, when dried on a surface, is clear and transparent. the blowing agent produces gas and foaming in the char during the intumescent process.

The charring agent r2ntaerythrito1 ensures that the char, when produced, has the required consistency to prevent or retard the onset of flames.

The acid catalyst APP catalyses cross-linking during the char process.

An important feature of coatings, in accordance with the invention is the synergy between the water-based. epoxy emulsion binder and the charring agent pentaerythritol and the APP. Th.iss ynergy enables less charring agent to be employed thereby ensurinm that a coating when applied to a wood. or wood-related product dries to a clear and transparent finish. If the ratio of binder to charring agent is less than 2.5 to 1, a coated surface will not dry to a cleax and transparent finish_ Ti this ratio exceeds 3 to I, the flame retardant properties of the coating are degraded. IA)

Coatings in accordance with the iLnveu.tron. have paxticular application for providing fire protection for wood or wood-reiated surfaces where the appearance of the surface has to remain the same after coating. Such surfaces include pa:nelled walls, doors and other items to be found In stately homes and the like. An applied coating does not adversely affect the appearance or quality of the coated Item but does provide upwards of 60 minute fire parntection. No soecial surface preparation is no required provided the surfacp is dry and. clean. 77v.,p or more coats can be applied and because the coating is quick drying, successive coatings can be applied in a relatively short period of rime.

Self--curing intumescent water based coatings in accordance with this invention are self curing and include no drying or curing agent or hardeners. This means that they can readily be removed tom a wood panel or the like simply by heating to a temperature of 50 degrees centigrade or less using, for example, a hand held dryer, and then either either wiping or scraping the by then loose coating from the wood surface. This feature is particularly useful when dealing with wood surfaces which include intricate or delicate details.

It will be appreciated that the foregoing is exemplary of solutions in accordance with the invention and that modifications can readily he made thereto without departing from the true scope of the invention.

Claims

CLAIMS1. A self-curing intumescent water-based coating which dries to a transparent finish and includes no drying or curing agent, the coating including a single pack emulsion comprising a mix of phosphate salts including ammonium polyphosphate in solution which act together as a flame retardant blowing agent, pentaerythritol which acts as a charring agent and an epoxy resin water-based or emulsified binder, the ratio of water-based or emulsified binder to pentaerythritol being between 2.5 and 3.0 to 1.
2. A coating as claimed in claim 1, wherein the ratio of binder to charring agent is 2.7 to 1.0.
3. A coating as claimed in claim 1 or claim 2 wherein the mix further includes an alcoholic ester, a phosphate surfactant, a defoaming surfactant and a biocide.