Title of Invention

"A PROCESS FOR PREPARATION OF AN INSTUMESCENT FIRE RETARDANT PAINT COMPOSITION"

Abstract

This invention relates to a process for the preparation of instumescent fire retardant paint composition, comprising in the steps of subjecting a mixture of 30-35% dehydrading /carbonising agent, 10-15% carbon compound, 2.5-3.5% blowing agent as herein described, 8-12% pigment, 1-2% additives, 0.1-0.3% dispersing and wetting agent, 0.1-0.3% defoaming agent and water to the step of grinding, adding a 20-25% polymer emulsion to said mixture, adding thixotropic agent to said mixture, adding 0.5% preferably 0.4% biocide to mixture of step (c) to obtain intumescent fire retardant paint.

Full Text

This invention relates to a process for the preparation of an intumescent fire retardant paint composition. In particular the process for the preparation of intumescent fire retardant paint composition which is halogen free, generates low smoke and has low toxicity on pyrolysis. The paint has application for suppression of fires on structures particularly where inflammable construction materials are used. Intumescent fire retardant paint consists of a catalyst, a carbon rich compound and a blowing agent as intumescent material, binder, pigment and additives. In case of fire, the coating swells or foams forming a stable inert carbonaceous char. This char acts as a thermal insulating barrier between the fire and the flammable substrate thereby protecting the substrate against fire. The intumescent paint imparts fire resistive characterstic to wooden structural materials. The paint has wide applications in railways, petro chemicals, high rise buildings, hospitals, schools, defence installations and where there is a higher fire safety demands e.g. ships. The greatest use of the paint is in areas such as stairwalls, partition walls, corridors or where safe egress is necessary. The conventional intumescent fire retardant paints were based on polymer system containing fire retardant additives and intumescent agents besides chlorinated paraffin as chlorine donor. The fire-retardant additives used from time to time were borates, antimony trioxide, calcium carbonate and alumina trihydrate. The intumescent agents earlier were combination of pentaerythritol, mono or diammonium phosphate and a blowing agent like melamine. The major limitation of the above fire retardant intumescent paint is that intumescent producing ingredients of these emulsion based paints have high water solubility leading to their leaching during service. Another drawback of the above fire retardant intumescent paint is that these paints have a limited shelf life of about six months due to which these paints do not give optimum intumescent fire retardancy due to limited stability of mono or diammonium phosphate. Still another disadvantage of the above mentioned paints is that during prolonged exposure to fire, the paint generate toxic fumes which may endanger human life including fire-fighters, due to toxic fumes, the toxicity being due to generation of hydrogen chloride gas produced by decomposition of chlorinated paraffin. Further disadvantage of the above paints is that these paints do not contain any biocide which reduce the service life of the painted surfaces particularly in high humid environments as under such humid conditions microbes damage the paint coating. Yet further disadvantage of these paints is that under high humid conditions, paint absorbs moisture from atmosphere and the paint coating gets detached from the substrate after certain time duration. Still further disadvantage of the above known intumescent fire retardant paints is that these paints produce inadequate quantity of char as well as inadequate char height which provides inadequate fire protection to substrate resulting in most of the cases to scorching on the back of substrate. Yet further disadvantage of the above known intumescent fire retardant paints is that these paints have low limiting oxygen index which adversely affects the fire-retardancy of the paint. Still further disadvantage of the above known intumescent fire retardant paints is that these paints produce more smoke which affect visibility. NEED OF THE INVENTION There is a need for an improved intumescent fire retardant paint which has longer service life, higher stability, higher fire retardancy and is halogen-free thereby avoiding the generation of irritating/toxic fumes of hydrogen chloride/chlorine gas. OBJECTS OF THE INVENTION The primary object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof. Another object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which is halogen-free thereby the paint has low inhalation toxicity of its pyrolytic products hence safeguard human life particularly fire-fighters who are exposed to toxic fumes during fire fighting operations. A further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which contains a biocide that protects the painted surface against microbial attack thereby enhancing the service life of the painted surface. Still another object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which has no afterglow and no afterflame. Yet another object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which produces adequate amount of thick carbonaceous char and char height thereby providing excellent thermal insulation and consequent superior fire protection to the substrate. Further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which envolves low smoke on burning. Yet further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which is environmentally friendly in view of absence of organic solvents that contribute to environmental pollution. A still further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which is of vital importance from the point of view of evacuation of premises in case of fire. An even further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof having relatively more storage stability. A further still another object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof having high limiting oxygen index value. Yet another object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which provides protection to the substrate even under intense heat at high temperature hence the paint has potential application against hydrocarbon fire and offshore applications. A Still even further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which is water based due to which the air pollution due to generation of gases on pyrolysis is negligible. A yet even further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof wherein gases produced on pyrollisis are corrosion free. Still further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which is stable even under high humid condition. Yet further object of the present invention is to propose a fire retardant paint composition and a process for the preparation thereof which is resistant against sea-water. BRIEF DESCRIPTION OF THE INVENTION The process of the present invention relates to an improved process and improved formulation for intumescent fire retardant paint which produces carbonaceous char in relatively higher quantity and height thereby providing relatively superior protection of substrate against fire. The carbon rich compound in the formulation reacts with dehydrating agent to form a carbonaceuos char. The binder forms a thin layer over the char and inhibits the escape of the gases. The release of copious quantities of non-flammable gases by the blowing agent causes the char height to expand to around 3 to 4 cm on application of coating of 500 microns dry film thickness (DFT). The paint has high limiting oxygen index value and low rate of flame spread which is of vital importance from the point of view of evacuation of population. The paint has no after flame and no after glow. The paint has low thermal conductivity and provides insulation and high degree of passive fire protection under intense heat. The paint has potential for use against hydrocarbon fire and jet fire for example for protection against fire in offshore structures. The paint of the present invention is halogen free due to which the paint has low inhalation of toxicity of its pyrolytic products as compared to known intumescent fire retradant paints. The paint therefore safeguards the human life particularly fire-fighters who are exposed to toxic fumes for longer durations as the paint of the present invention does not produce toxic hydrochloride gas fumes as compared to known fire intumescent paints which produce toxic hydrochloride gas due to decomposition of chlorinated paraffin compound in these paints. The paint incorporates a biocide which protects the painted surface against microbes thereby enhancing the service life of painted surface. The improved formation has a longer shelf life of over one year. The paint does not use any organic solvent but instead uses water as dispersing medium for the ingredients. Due to this the paint emits low smoke on burning as compared to known such paints which evolve dense smoke on burning which adversely affects visibility during fire-fighting operations. The paint has very low absorption of moisture from the atmosphere over long period due to which the paint coating remains intact for longer durations. According to the present invention there is provided a process for the preparation of instumescent fire retardant paint composition, comprising in the steps of: (a) subjecting a mixture of 30-35% dehydrading /carbonising agent, 10-15% carbon compound, 2.5-3.5% blowing agent as herein described, 8-12% pigment, 1-2% additives, 0.1-0.3% dispersing and wetting agent, 0.1- 0.3% defoaming agent and water to the step of grinding. (b) adding a 20-25% polymer emulsion to said mixture, (c) adding thixotropic agent to said mixture, (d) adding 0.5% preferably 0.4% biocide to mixture of step (c) to obtain intumescent fire retardant paint. In a porcelain ball mill 30% to 35% by weight preferably 32.6% by weight of dehydrading/carbonising agent preferably ammonium polyphosphate, 10 to 15% preferably 12.4% of carbon compound preferably pentaerythritol, 2.5 to 3.5% by weight, preferably 3.3% by weight of blowing agent preferably dicyandiamide, 8 to 12% preferably 10% by weight of pigment preferably titanium dioxide, 1 to 2% preferably 1.5% by weight of additives preferably dioctyl phathalate as plasticiser or stabilising agent, 0.1 to 0.3% by weight of dispersing and wetting agent preferably Disper BYK-154 and 0.1 to 0.3% by weight preferably 0.2% by weight of defoaming agent preferably BYK-023 are charged 15 to 20% preferably 15 to 17% of water is added and mixed to obtain suitable consistency for grinding, the mixture is subjected to grinding for about 24 hours. The ground mixture obtained is transferred to a high density polyethylene container and adding slowly, with continuous stirring at low speed using aluminium/stainless steel stirrer, 20 to 25% parts by weight preferably 22.8% of polymer emulsion like polyvinyl acetate, vinyl acrylate co-polymer preferably Emdility-FR adding with stirring to 0.5% preferablyt),4% by weight of thixotropic agent preferably Bentone LT. The stirring is continued for a total period of about 30 minutes and mixed with biocide like formline, centobright in the preferred quantity of 2gms/litre. The invention will now be illustrated by the following example which is not intended to be taken to restrict the scope of the invention but is to be taken as an illustration of the process of the present invention. EXAMPLE For preparation of 500 ml of intumescent fire retardant paint, 218.4g of ammonium polyphosphate, 83.1 g of pentaerythritol, 22. Ig of dicyandiamide, 67.0 g of titanium dioxide, 10.0 g of dioctylphathalate, 1.4g of dispersing agent and 1.3 g of defoaming agent were charged in a porcelain ball mill. 111.2 g of water was added and the contents were ground for 24 hours. The contents were transferred to a high density polyethylene plastic container. To this ground mixture, 152.7g of polymer emulsion and 2.7g of bentone were added with continuous stirring at low speed for about half an hour. About Ig of biocide was added to the paint and mixed thoroughly. For evaluation of the fire protective efficacy of the paint obtained by the present invention, Himalayan fir as a test specimen of size 76x1 Ox 1cm was coated with a coating of 500 microns dry film thickness (DFT). The fire protective property of the coating was evaluated by exposing the sample to a bunsen burner flame having a temperature of 950 degree centrigrade in a two-foot tunnel equipment. The test was conducted for 10 minutes and the observations are given below: - a) Char height - 3.5 cm. b) Flame -7.0 cm. c) After glow - Nil. No scorching on the back side of the panel was observed. Insulating capacity of the present composition was evaluated by subjecting a coated aluminium panel to the flame from a blow lamp having a temperature of 1200°C. After 15 minutes continuous flame application, the bare backside of the panel registered a temperature of 135°C indicating good heat insulation. The corresponding value for an uncoated control panel was 375°C. The fire protection performance and intumescence formation was further evaluated by comparing the effect of intense heating on a coated plywood panel against the effect of intense heating on a control panel. A marine plywood panel of 30x30x1 cm was coated with the 500 micron plywood thickness (DFT) of the paint of the present invention and was exposed to the flame of a Swedish burner fully open, of 7.5cm dia. The temperature of the flame produced by the burner was approximately 1350°C. The test was conducted for 10 minutes. Fig l(a) shows the condition of coated panel after exposure to heating for 10 minutes. The coating produced intumescence of 3 to 4cm of char height. The fig 2(a) and 2(b) show two different view of the intumescence formation on the coated plywood panel. To examine the formation on the coated plywood panel. To examine the extent of fire protection afforded by the paint of the present invention to the substrate plywood, the char was removed and it was observed that the paint did not allow the burning of substrate (fig 1 (b). As compared to this the control panel burnt exclusively within 6 minutes (fig 1 ( c) ]. Fire retardancy property of the paint was evaluated by burning two wooden huts, one coated with intumescent fire retardant paint and the other with conventional alkyd paint [fig 3 (a) ]. Fire was simulated in the hut by burning 300 ml alcohol kept inside the huts [fig 3 (b)]. Alcohol burned for 4 minutes and within this period the entire hut coated with alkyd paint caught fire [fig 3 (b) ] and was reduced to ashes in 14 minutes [fig 3 (c) ]. The intumescent fire retardant coated hut did not burn at all. The coating produced adequate intumescence and protected the structure against fire [Fig. 3 (c) ]. It is to be understood that the above description of the present invention is susceptible to modifications by those skilled in the art. Such modifications/changes are intended to be considered within the scope of the present invention, which is set forth by the following claims:- WE CLAIM; 1. A process for the preparation of instumescent fire retardant paint composition, comprising in the steps of: (a) subjecting a mixture of 30-35% dehydrading /carbonising agent, 10-15% carbon compound, 2.5-3.5% blowing agent as herein described, 8-12% pigment, 1-2% additives, 0.1-0.3% dispersing and wetting agent, 0.1- 0.3% defoaming agent and water to the step of grinding. (b) adding a 20-25% polymer emulsion to said mixture, (c) adding thixotropic agent to said mixture, (d) adding 0.5% preferably 0.4% biocide to mixture of step (c) to obtain intumescent fire retardant paint. 2. The process as claimed in claim I wherein said dehydrating /carbonising agent is ammonium polyphosphate. 3. The process as claimed in claim I wherein said carbon compound is pentaerythritol. 4. The process as claimed in claim I wherein said blowing agent is dicyandiamite. 5. The process as claimed in claim I wherein said pigment is titanium in dioxide. 6. The process as claimed in claim I wherein said additive is dioctyl phthalate. 7. The process as claimed in claim I wherein said dispersing and wetting agent is Disperser. 8. The process as claimed in claim I wherein said polymer emulsion is selected from polyvinyl acetate, vinyl acrylate copolymer. 9. The process as claimed in claim I wherein said thixotropic agent is Bentone. 10. The process as claimed in claim 1 wherein the ground mixture and said polymer emulsion is added with continuous stirring followed by addition of thixotropic agent and biocide. 11. The process for the preparation of an instumescent fire retardant paint composition as herein described and illustrated.

Documents:

3120-del-1997-abstract.pdf

3120-del-1997-claims.pdf

3120-del-1997-correspondence-others.pdf

3120-del-1997-correspondence-po.pdf

3120-del-1997-description (complete).pdf

3120-del-1997-drawings.pdf

3120-del-1997-form-1.pdf

3120-del-1997-form-19.pdf

3120-del-1997-form-2.pdf

3120-del-1997-form-3.pdf

3120-del-1997-gpa.pdf