HK1079233A - Method for protecting surfaces from effects of fire - Google Patents

Description

Method for protecting surfaces from fire

Technical Field

The present invention relates to a method of protecting a surface from the effects of fire comprising coating the surface with a coating of at least about 2mm of a flame, fire and heat resistant curable polysiloxane composition. In particular, the curable silicone composition is fire resistant, has excellent heat transfer inhibiting properties, and prevents damage to the structure to which the silicone composition is applied.

Background

Fire resistant products are widely used in modern buildings, and in addition to having fire retardant properties, ideal fire resistant products also should insulate against the heat generated by a fire. It should also emit no or only very small amounts of toxic gases. These features can minimize damage to the building during a fire and ensure that the occupants have sufficient time to leave the area relatively safely. Examples of refractory products are described in U.S. Pat. nos. 6,387,993, 6,395,815, 6,444,736, 6,441,122 and 6,433,049.

Batdorf in U.S. patent 6,387,993 describes water-based flame retardant compositions using polyvinylpyrrolidone polymers. This patent does not describe surface insulation.

Tkaczyk et al, in U.S. Pat. No. 6,395,815, describe an improved high temperature resistant silicone composition suitable for insulating electrical wires. The patent does not describe or claim a flame or fire rating for the product.

Touhara et al, in U.S. Pat. No. 6,444,736, describe a polyolefin composition useful as a non-toxic flame retardant seal or coating. The patent does not describe the insulating properties that can minimize damage to the building during a fire.

DeMott et al, in U.S. patent 6,441,122, describe the use of melamine in urea-diluted phenol formaldehyde alkaline resole binders. The adhesive product is suitable only for glass fibers and is not intended to be used as a flame retardant.

The formulation of fire resistant thermoplastic silicone cured products is described by Romaneski et al in U.S. Pat. No. 6,433,049. The refractory product generates little heat, but the heat resistance at high temperatures of a big fire is not described.

There is a continuing need to provide a surface protection from flames, fire and heat.

Disclosure of Invention

The present invention provides a method of protecting a surface from the effects of fire comprising coating the surface with a coating of at least about 2mm of a polysiloxane composition containing a flame retardant filler, thereby providing excellent outdoor durability as well as heat and fire resistance.

In one aspect of the invention, the flame retardant filler is melamine.

In another aspect of the invention, the silicone composition is a one-part room temperature curable composition that is curable upon contact with moisture.

In yet another aspect, the process of the present invention uses a one-part room temperature curable organopolysiloxane rubber composition comprising a product obtained by mixing:

a) about 20 to about 60 weight percent of one or more polydiorganosiloxane fluids of the formula

R′[(R)₂SiO]_n(R)₂SiR′

Wherein R is a monovalent alkyl or alkylene radical having from 1 to 8 carbon atoms or a phenyl radical, each R ', which may be the same or different, is OH or a monovalent alkyl or alkylene radical having from 1 to 8 carbon atoms or a phenyl radical, and n is an average value such that the viscosity at 25 ℃ is in the range of from about 1 to about 100,000 centipoise, wherein both R's in the at least one polyorganosiloxane fluid are OH and n is an average value such that the viscosity at 25 ℃ is in the range of 1,000-100,000 centipoise, preferably in the range of 1,000-40,000 centipoise at 25 ℃;

b)0 to about 40 weight percent of a cyclic organosiloxane of the formula

[(R)₂SiO]_n

Wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or is phenyl, R may be optionally substituted with an alkyl radical having 1 to 8 carbon atoms, and n has an average value of 3 to 10;

c)5 to about 50 weight percent of one or more flame retardant fillers selected from the group consisting of: melamine, zirconium dioxide, chromium dioxide, zinc borate, antimony oxide, and exfoliated graphite;

d) about 0 to about 30 weight percent of one or more inorganic extending or non-reinforcing fillers; such as quartz, diatomaceous earth, barium sulfate, calcium carbonate, titanium dioxide, and the like;

e) about 0.5 to about 10 weight percent amorphous SiO₂Reinforcing fillers having a surface area of about 50 to 300m²(ii)/g, and particle size ranges from about 0.01 to 0.03 microns;

f) about 1 to about 10 weight percent of a silane crosslinking agent of the formula

RSiX

Wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or is phenyl, R may be optionally substituted with an alkyl radical having 1 to 8 carbon atoms, and X is an alkyl radical having a functional group selected from the group consisting of: carboxyl, ketoximino (ketoximino), alkoxy, carbonyl, and amine directly bonded to a silicon atom;

g) about 0.2 to about 3 weight percent of an organosilane adhesion promoter; and

h) about 0.02 to about 3 weight percent of an organotin salt as a condensation catalyst.

Drawings

Preferred embodiments of the present invention are described in the accompanying drawings, in which:

FIG. 1 is a temperature-time plot of a 6mm thick flame retardant coating of the invention versus an open flame of 1200 deg.C; and

FIG. 2 is a temperature-time plot of a 20mm thick coating.

Detailed Description

The present invention provides a method of protecting a surface from the effects of fire comprising applying to the surface a coating of at least about 2mm of a polysiloxane composition containing a flame retardant filler, thereby imparting to the surface excellent outdoor durability as well as heat and fire resistance.

The polyorganosiloxane composition containing the flame retardant filler used in the present invention has excellent flame resistance, flame retardancy and heat insulation. The composition has excellent resistance to high-intensity fire due to thermal insulation when applied to metal, concrete and wood structures, particularly metal structures. The composition may be applied to the structures by any conventional method such as brushing, spraying, etc.

The composition used in the present invention comprises a curable polyorganosiloxane and a flame retardant additive which imparts excellent flame resistance, flame retardancy and thermal insulation to the composition.

The curable polyorganosiloxane may be any of the commonly used curing compositions which are cured catalytically using a one-pot or two-pot system, for example by addition curing, high-energy ray induced crosslinking or curing systems using moisture.

Polyorganosiloxane compositions that can be catalytically polymerized using an addition cure system are not controlled by moisture in the environment. While the crosslinking addition reaction can also be carried out at room temperature, elevated temperatures can accelerate the curing process. The base polymer is typically a polydiorganosiloxane of the general formula

R″[(R)₂SiO]_n(R)₂SiR″

Wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms optionally substituted with 1 to 9 halogen atoms, or a phenyl radical optionally substituted with 1 to 6 halogen atoms, R' is a monovalent alkylene radical (preferably a monovalent vinyl or vinyl radical), and n is an average value such that the viscosity is in the range of 100-100,000 centipoise. Examples of such base polymers are

CH₂＝CH-Si(CH₃)₂-O-Si(CH₃)₂-O------O-Si(CH₃)₂-CH＝CH₂

The addition cure system utilizes a crosslinking agent to polymerize the base polymer. The crosslinking agent is generally a polydiorganosiloxane of the general formula

R[(R)(H)SiO]_m[(R)₂SiO]_nR

Wherein each R, which may be the same or different, is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms optionally substituted with 1 to 9 halogen atoms, or is a phenyl radical optionally substituted with 1 to 6 halogen atoms, and H is a hydride radical, m and n are both integers and the total average value thereof is such that the viscosity is in the range of 10 to 10,000 centipoise. The value of m is 10-50% of the value of m + n.

For optimum crosslinking, the ratio of alkylene radicals, preferably vinyl radicals, to hydride radicals is from 1: 1 to 6: 1.

The crosslinking reaction of addition cure systems requires a catalyst, typically an organometallic complex of platinum of the formula:

Pt[R′(SiOR)R′]₄

wherein R is an alkyl or alkylene group and R' is an alkylene group. An example of such a platinum catalyst is platinum divinyl tetramethyl disiloxane complex

(CH₂＝CH-Si(CH₃)₂-O-Si(CH₃)₂-CH＝CH₂)₄Pt

Addition crosslinking is a very fast reaction. The reaction rate can be controlled by reducing the amount of catalyst used or by reducing the activity of the platinum catalyst by using a reaction inhibitor such as vinyl terminated polydimethylsiloxane.

Adhesion promoters may also be used with two-part addition cure systems to increase the adhesion of the elastomer to the surface. The adhesion promoter is generally a silane having the general formula

R¹Si(R²O)₃

Wherein R is¹Is an alkylene radical, preferably a vinyl radical, R²Is an alkyl radical having 1 to 6 carbon atoms.

Addition cure systems are typically provided in a two-pot format with the base polymer, crosslinker, adhesion promoter and inhibitor as one pot and the base polymer and catalyst as the other. Fillers and pigments were added to either tank to obtain equal viscosity in both tanks for uniform mixing.

Moisture-curing systems are generally room temperature-curing (RTV), although elevated temperatures can accelerate the curing reaction. The moisture-curable composition may be provided as a two-part system similar to the addition-cure composition, or may contain all of the components of the composition in a single container. For ease of handling and application, it is preferred that the RTV composition be a one-part system.

Moisture-curing systems generally utilize hydroxyl-terminated polyorganosiloxanes as base polymers. Preferably, the base polymer is one or more polyorganosiloxanes of the following general formula:

R′[(R)₂SiO]_n(R)₂SiR′

wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or a phenyl radical, each R', which may be the same or different, is OH, a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or a phenyl radical, and n is an average value such that the viscosity at 25 ℃ is in the range of about 1000 to about 100,000 centipoise. At least one R 'has a reactive group such as OH or alkylene, preferably OH, and most preferably both R' are OH.

Moisture cure systems utilize a crosslinker having the general formula:

X-Si-R

wherein R is an alkyl, alkylene or phenyl radical (preferably methyl or ethyl) and X is an alkyl radical having a functional group directly attached to the silicon atom. The functional group may be a carboxyl group, a ketoximino group, an alkoxy group, a carbonyl group, or an amine.

Commonly used cross-linking agents for moisture-curing RTV one-or two-pack systems include:

acetoxysilane (CH)₃C(O)O)₃Si-R releases acetic acid as a solidification by-product.

Oxime silanes (C)₂H₅(CH₃)C＝NO)₃Si-R releases methyl ethyl ketoxime as a curing by-product.

Alkoxysilane (R' O)₃-Si-R wherein R' is an alkyl radical having 1 to 6 carbon atoms. It releases alcohol as a curing by-product.

Enoxy silane (CH)₃C(O)CH₂)₃Si-R releases acetone as a curing by-product.

Amine silane ((CH)₃)₂N)₃Si-R liberates amines as curing by-products. It is the fastest reacting crosslinker that does not require a catalyst.

To enhance the crosslinking reaction, a catalyst is generally used. One commonly used catalyst for moisture-curing systems is an organotin salt such as dibutyltin dilaurate.

To improve the adhesion of the elastomer to its coated surface, an adhesion promoter may be used. The adhesion promoter is generally a compound of the formula

Wherein R is²And R³Independently selected from monovalent alkyl or alkylene radicals having 1 to 8 carbon atoms or phenyl, R may optionally be substituted with an alkyl radical having 1 to 8 carbon atoms, b is an integer from 0 to 3, and R is¹Is a saturated, unsaturated or aromatic hydrocarbon radical having 1 to 10 carbon atoms, which may optionally contain a functional group.

High energy ray (e.g., ultraviolet and electron beam) induced crosslinking can also occur at the ends of the polydimethylsiloxane molecules in the presence of acrylate functionality. The very fast crosslinking in UV-curable systems makes this method important in fast production.

Formulations that can be cured by ultraviolet light are typically one-part systems that are cured by exposure to ultraviolet or high energy radiation at room temperature or elevated temperatures.

The uv-curable polysiloxane coating contains polydimethylsiloxane containing acryloxypropyl functional groups at both ends. The free radical polymerization is initiated using a photoinitiator such as ethyl benzoin.

The polydiorganosiloxane copolymer has the formula

R′[(R)₂SiO]_n(R)₂SiR″

Wherein R is a monovalent alkyl or alkylene radical having from 1 to 8 carbon atoms or a phenyl radical, R 'and R' which may be the same or different are acryloxypropyl or methacryloxypropyl radicals, and n is an average value giving a viscosity in the range of from about 100 to about 100,000 centipoise at 25 ℃.

In addition to the components required to form the silicone elastomer, the composition also contains a flame retardant filler which provides the composition with excellent fire resistance, flame retardancy and thermal insulation. The flame retardant filler is preferably selected from the group consisting of melamine, zirconium dioxide, chromium dioxide, zinc borate, antimony oxide and exfoliated graphite. Most preferably the flame retardant filler is melamine. The flame retardant filler is typically present in the composition at a concentration of from 5 to about 50% by weight of the total composition, more preferably from about 5 to about 30% by weight of the total composition, and most preferably from about 8 to about 20% by weight of the total composition.

In addition to the above components, the composition may also include other optional components such as other fillers, pigments and diluents having extending, semi-reinforcing or reinforcing properties.

Other fillers may include silica, hollow glass beads, quartz, calcium carbonate, barium sulfate, diatomaceous earth, and the like. The amount of other fillers in the composition is typically from 0 to about 30% by weight of the total composition and depends on the filler and the desired properties.

To improve the workability of applying the composition to a surface, the composition may be diluted with not more than 35% by weight of a diluent. The diluent may be an organic hydrocarbon solvent such as naphtha or a low viscosity polyorganosiloxane such as a blocked linear low molecular weight organosiloxane or a cyclic organosiloxane. Preferably, to remove Volatile Organic Compounds (VOCs), the diluent is a blocked linear low molecular weight organosiloxane or a cyclic organosiloxane.

The process of the invention comprises applying to the surface to be protected from the effects of fire a coating of a polyorganosiloxane composition containing a flame retardant in a thickness of at least 2mm, so as to render the surface fire-resistant, while the flame retardant imparts excellent heat transfer resistance to the surface, preventing the structure to which the polyorganosiloxane composition is applied from being destroyed by heat transfer. The composition is applied to the surface to be protected by conventional means such as dipping, brushing or spraying.

Preferably, the flame retardant composition is applied by spraying one or more times onto the surface to be protected until the coating reaches the desired thickness. The thickness of the coating will depend on the specific requirements of the application and the level of protection desired. The coating typically has an average thickness of 2-50mm, more preferably 6-25mm, and most preferably about 10-25 mm. For larger thicknesses, two-part polyorganosiloxanes are preferred, although final thicknesses can also be achieved by multilayer build-up coating using a single part.

In a particularly preferred embodiment, the composition used as a fire retardant coating in the process of the present invention is a one-part organopolysiloxane rubber composition containing from about 20 to about 60 weight percent of one or more polydimethylsiloxane fluids of the formula:

R′[(R)₂SiO]_n(R)₂SiR′

wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or a phenyl radical, each R', which may be the same or different, is OH or a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or a phenyl radical, and n is an average value such that the viscosity at 25 ℃ is in the range of about 1 to about 100,000 centipoise. The at least one polyorganosiloxane fluid is a higher viscosity siloxane having reactive groups wherein both R' are OH and n is an average value such that the viscosity is in the range of 1,000-100,000 centipoise at 25 ℃, preferably in the range of 1,000-40,000 centipoise at 25 ℃. The polydimethylsiloxane may contain small amounts of monomethylsiloxane units and small amounts of other groups replacing methyl radicals, such as are found in industrial products, in the form of impurities, but polydimethylsiloxane-only fluids are preferred.

The composition of this preferred embodiment may contain another linear dimethylpolysiloxane of low molecular weight, acting as a viscosity reducing diluent for the composition to facilitate application of the composition to a surface. The low molecular weight linear dimethylpolysiloxane is a terminal-blocked oligomeric compound of the formula wherein R and R', which may be the same or different, are independently selected from the group consisting of monovalent alkyl or alkylene radicals having 1-8 carbon atoms or phenyl radicals. The average value of n is in the range of 4 to 24, preferably in the range of 4 to 20.

If the composition contains two different polysiloxanes as described above, the total amount of polysiloxanes is typically from about 40 to 60% by weight, where the relative amounts of the two polysiloxanes are determined by the properties desired in the final coating. Typically each polysiloxane will be present in a proportion of about 30% to about 70% by weight, based on the total weight of the polysiloxane fluid.

In addition to, or instead of, the low molecular weight linear dimethylpolysiloxane, the composition may contain up to about 40 weight percent, more preferably 20 to 30 weight percent, of a cyclic organosiloxane of the formula:

[(R)₂SiO]_n

wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or is phenyl, R may be optionally substituted with an alkyl radical having 1 to 8 carbon atoms, and n has an average value of 3 to 10. The preferred cyclic organosiloxane is cyclomethicone and acts like a low molecular weight linear dimethylpolysiloxane as a diluent to reduce the viscosity of the composition, facilitating application by spraying, brushing or dipping.

The composition also contains from 5 to 50% by weight, more preferably from 5 to 30% by weight, of one or more flame retardant fillers selected from: melamine, zirconium dioxide, chromium dioxide, zinc borate, antimony oxide, aluminum oxide trihydrate and exfoliated graphite. Preferably, the composition contains about 8 to about 20 weight percent melamine as a flame retardant filler.

The composition may also contain inorganic extending fillers or non-reinforcing fillers. The extending filler is preferably selected from inorganic materials such as hollow glass beads, calcium carbonate, barium sulfate, diatomaceous earth, quartz, crystalline silica, titanium dioxide, alumina trihydrate and zinc oxide. The filler is selected based on the desired properties and the end use of the composition. If higher strength is desired, crystalline silica is selected.

The composition also contains about 0.5-10% by weight of amorphous SiO₂Reinforcing fillers having a surface area of about 50 to 300m²Between/g and particle sizes in the range of about 0.01 to 0.03 microns. The specific gravity of the filler is preferably about 2.2. Amorphous SiO₂The reinforcing filler may be untreated or surface treated, for example with a polyorganosiloxane or a silane.

The composition also contains about 1-10 wt.%, preferably 2-5 wt.% of a crosslinking agent, preferably an oxime silane crosslinking agent. Preferred oxime silane crosslinkers are of formula RSi (ON ═ CR'₂)₃Wherein R and R' each represent a monovalent alkyl or alkylene radical having from 1 to 8 carbon atoms or a phenyl radical, preferably an alkyl radical such as methyl, ethyl, propyl, butyl, or an alkylene radical such as vinyl, allyl, or phenyl radical. Preferred R and R' are alkyl or vinyl radicals, most preferred are methyl and ethyl radicals.

The composition also contains about 0.2 to 3 weight percent of an organofunctional silane as an adhesion promoter. Preferably the organofunctional silane is of the formula

Wherein R is²And R³Independently selected from monovalent alkyl or alkylene radicals having 1 to 8 carbon atoms or phenyl radicals, b is an integer from 0 to 3, preferably 0, and R¹Is a saturated, unsaturated or aromatic hydrocarbon radical having from 1 to 10 carbon atoms, R¹It may also be functionalized with an ingredient selected from: amino, ether, epoxy, isocyanate, cyano, acryloxy and acyloxy groups and combinations thereof. R²And R³The following alkyl radicals are preferred: methyl, ethyl, propyl and butyl, or alkylene radicals as follows: vinyl and allyl. More preferably R²And R³Is an alkyl radical, most preferably a methyl, ethyl or propyl radical. Preferably R¹Is alkyl, more preferably R¹And also functionalized with one or more amino groups. The most preferred organofunctional silane is N- (2-aminoethyl-3-aminopropyl) trimethoxysilane.

In all of the above compounds, alkyl groups include straight chain, branched chain or cyclic radicals. Wherein alkyl is C1-8 straight or branched chain alkyl such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, isopentyl, hexyl and the like, cycloalkyl is C3-8 cycloalkyl such as cyclopropyl, cyclobutyl, cyclohexyl and the like, and alkylene is C1-8 alkylene such as vinyl and allyl. The above groups as well as the phenyl radical may also be functionalized by introducing in the chain or ring structure, as the case may be, a group selected from: amino, ether, epoxy, isocyanate, cyano, acyloxy and combinations thereof, provided that the functionalization does not negatively impact the desired properties of the compound.

The composition also contains about 0.02 to 3 weight percent of an organotin salt of a carboxylic acid as a condensation catalyst which accelerates aging of the composition. Preferably, the organotin salt is selected from the group consisting of dibutyltin diacetate, stannous octoate, dibutyltin dioctoate and dibutyltin dilaurate. Most preferably, the organotin salt is dibutyltin dilaurate of the formula:

(C₄H₉)₂Sn(OCOC₁₀H₂₀CH₃)₂

the composition may contain minor amounts of other optional components such as pigments and other fillers, provided that the addition of these components does not detract from the desired properties of the hardened coating produced from the composition. One commonly used optional component is a pigment, preferably a gray pigment, most preferably present in an amount no greater than about 1% by weight.

The moisture-curable organopolysiloxane composition used in the present invention is prepared by mixing these components together in the absence of moisture. Silanes are moisture sensitive and crosslink in the presence of moisture, so the mixture must be substantially free of free water and remain anhydrous when the silane is added until cure is desired.

One preferred method of mixing involves mixing the polysiloxane fluid with extending and reinforcing fillers and other optional fillers and pigments. Thereafter, the oxime silane and organofunctional silane were added and mixed under nitrogen atmosphere. Adding organic tin salt into the mixture, and subpackaging the mixture into sealed containers for storage and standby.

The surface to be protected is coated with the composition by conventional means such as dipping, brushing or spraying. Preferably, the surface to be protected is coated by spraying one or more times the composition of the invention. The thickness of the coating will depend on the specific needs of the application and the level of protection desired. The coating typically has an average thickness of 2-50mm, more preferably 6-25mm, and most preferably about 10-25 mm. If the coating is formed from a single pot of polyorganosiloxane, the final thickness can be achieved by multiple coating stacks. After the coating is formed on the surface, the surface is exposed to the usual environment to crosslink and cure the coating. To obtain a thick coating, a thixotropic composition that can be brushed or painted onto a surface may be preferred.

The improvement of the present invention is to impart excellent heat transfer resistance to the surface and to prevent the structure of the coated silicone composition from being destroyed by heat transfer to thereby achieve the purpose of protecting the surface from the effects of fire.

The following examples serve to describe preferred embodiments of the invention and to demonstrate the effectiveness of the coating, but are not intended to limit the scope of the invention in any way.

Example I

Fire resistant polydiorganosiloxane compositions are prepared in a two-pack system.

Part A

Part a of the article was prepared by: 44% by weight of a vinyl radical (CH)₂CH-) terminated polydimethylsiloxane having a viscosity of 10,000 cps, 4% by weight of surface area 150m treated with hexamethyldisilazane²The amorphous silica, 10 wt% crystalline silica and 34 wt% melamine were mixed, then 8 wt% of the organo-platinum catalyst was added and mixed until the mixture became a flowable homogeneous paste.

Part B

Part B of the article was prepared as follows: 85% by weight of a polydimethylsiloxane terminated by vinyl radicals, 8% by weight of a surface area of 150m treated with hexamethyldisilazane²The flowable homogeneous paste was prepared by mixing per gram of amorphous silica with 4 wt.% of a polydimethylsiloxane cross-linking agent in which 20 mol% of the methyl radicals were replaced by hydride radicals, then adding 2 wt.% of vinyltrimethoxysilane adhesion promoter and 1 wt.% of 1, 3-divinyltetramethyldisiloxane cross-linking inhibitor and mixing.

Equal volumes of part a and part B were mixed together and used to form a 6mm uniform thickness silicone sheet which was cured over 2 hours.

Either or both of parts a and B may be diluted with a suitable diluent to provide a viscosity suitable for spraying.

Example II

A composition for fire resistance was prepared by: 38 parts by weight of a polydimethylsiloxane terminated with hydroxyl groups and having a viscosity of 3,300 centipoise at 25 ℃, 10 parts by weight of titanium dioxide having a specific gravity of 4, 8 parts by weight of melamine having a density of 1.5g/ml and 38 parts by weight of a mixture of amorphous silica having a specific gravity of 2.2 and a surface area of 150m and a crystalline silica filler are mixed²Then 4 parts by weight of methyltris (methyl ethyl ketoxime) silane, 1 part by weight of N- (2-aminoethyl-3-aminopropyl) trimethoxysilane and 0.1 part by weight of dibutyltin dilaurate were added under a nitrogen atmosphere and mixed thoroughly to a homogeneous consistency under a nitrogen atmosphere.

Silicone plaques of uniform thickness (6mm) were prepared in a mold and cured at room temperature and 50% relative humidity for 7 days.

Example III

UL94V flammability test procedure

UL94V testing was conducted to predict the flammability rating of the cured silicone products prepared in accordance with the above examples. The material can be classified into V-1, V-1 or V-2 according to the results.

Rod-shaped pieces having dimensions of 125mm by 13mm were cut from 6mm pieces prepared according to example II above. The edges are ground to a smooth shape.

The methane gas supplied to the burner was adjusted to a flow rate of 105 mL/min. The burner was adjusted to produce a blue flame of 20 mm. The rod-shaped specimen was vertically clamped so that the upper part of the burner was 10mm lower than the lower end of the specimen. The flame is supplied at the center point of the lower end of the sample rod. The flame was supplied for 10 seconds and then removed to 150mm from the sample. The after flame time was recorded (t 1). Immediately upon cessation of the flame, the burner was placed under the sample 10 seconds from the lower end of the sample. The burner was then removed to 150mm from the sample and the afterglow time was recorded (t 2).

Results

t1 seconds (0)

t2 seconds (0)

The UL94V-0 grade requires t1 to be less than or equal to 10 seconds, and t2 to be more than or equal to 50 seconds.

Example IV

In another test, a 6mm steel thick steel rod was coated with a 6mm coating of the composition of example II above. The coated surface of the steel bar was brought into direct contact with the upper part of the blue flame of a propane torch at a distance of 150mm and about 1200 c for 4 hours. At the end, the areas of the coating directly exposed to the flame form hard carbon, but retain structural integrity. No significant heat transfer from the coating to the steel bar was observed throughout the experiment.

Example V

Dry films prepared from the components of example II were coated to a thickness of 20mm and 6mm on steel rods (60 mm. times.5000 mm. times.3 mm). Coating 3 layers gives a coating of 20-mm thickness and coating 2 layers gives a coating of 6-mm thickness. The next coating was performed after each 48 hour interval to fully cure the coating. After the final coating, the coating was cured for 7 days at room temperature conditions (20 ℃ temperature and 40% relative humidity).

The coating on the steel bar was contacted with the flame of a propane torch for 4 hours. The coating was in direct contact with the upper part of a blue flame at a temperature of 1200 ℃. A temperature sensor was mounted at the rear of the steel bar and the temperature was recorded on a chart recorder with respect to different times.

As shown in fig. 1 and 2, the temperature profile recorded from the rear of the steel bar shows two slopes. The first slope represents a sharp rise in temperature at the start of the experiment and then a slow rise (second slope) to a constant temperature. The first slope is due to the burning of the polysiloxane at the surface. The second slope represents a decrease in heat transfer due to an increase in thermal insulation property as the burning surface layer of polysiloxane becomes solid silica (silicone dioxide).

Example VI

Preparation of a Monomethacryloxypropyl terminated Poly-Di that can be cured with ultraviolet lightA fire resistant composition of an organosiloxane. The composition is prepared by the following steps: 40 parts by weight of a monomethacryloxypropyl-terminated polydimethylsiloxane having a viscosity of 2000 cps at 25 ℃,8 parts by weight of titanium dioxide having a specific gravity of 4, 8 parts by weight of melamine having a density of 1.5g/ml and 36 parts by weight of a silicone rubber having a specific gravity of 2.2 and a surface area of 130m²A mixture of amorphous silica and crystalline silica in a ratio of/g; then 1 part by weight of allyltrimethoxysilane and 0.5 part by weight of ethylbenzoin were added and mixed under nitrogen atmosphere to a uniform consistency. For ease of spraying, a diluent such as cyclomethicone or naphtha may also be used.

The 1000 micron thick coating was cured within 1 minute under inert environment exposure to ultraviolet light at a wavelength of 250-350 nm.

The method of the present invention can protect a surface from a fire by coating the surface with at least about 2mm of a flame, fire and heat resistant curable polysiloxane composition. Coatings of curable polysiloxane compositions on the surface of structures are fire-resistant while having excellent resistance to heat transfer that can cause damage to structures coated with the polysiloxane compositions.

The method of the present invention is particularly useful in industrial, commercial and conventional construction where it is important to protect the integrity of the structure from possible fire. By coating structural elements such as steel, concrete and wood poles, columns and other parts with the flame retardant composition prepared according to the method of the present invention, the structural integrity of a building can be protected for a long time, allowing occupants of the building to leave in the event of an emergency, allowing firefighters sufficient time to control the fire and reducing the risk of structural damage.

The compositions and methods of the present invention can be used to coat a variety of different surfaces. These surfaces include structural elements for buildings such as beams, columns, joists, etc. These structural elements may be steel, concrete or wood. The compositions and methods of the present invention are particularly useful for preventing weakening of steel structural elements when exposed to high temperature fires. In addition to structural elements, the compositions and methods of the present invention can also be used to coat textiles and other fabrics, and in some cases it is also important that they provide flame retardancy. For example, the composition may be coated onto canvas or other materials used in the manufacture of tents and canopies to provide increased protection in the event of a fire within the tent or canopy. Similarly, other fabrics, such as industrial seats and the like, may also be coated with the compositions of the present invention.

While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the spirit and scope of the invention. All such modifications are intended to be within the scope of the claims appended hereto.

Claims (21)

1. A method of protecting a surface from the effects of fire comprising coating the surface with at least about 2mm of a polysiloxane composition containing one or more flame retardant fillers to impart excellent outdoor durability as well as heat and fire resistance to the surface.

2. The method of claim 1, wherein the composition contains about 5 to about 50 weight percent of the flame retardant filler.

3. The method of claim 2, wherein the flame retardant filler is one or more fillers selected from the group consisting of: melamine, zirconium dioxide, chromium dioxide, zinc borate, antimony oxide, aluminum oxide trihydrate and exfoliated graphite.

4. The process of claim 3 wherein the flame retardant filler is melamine.

5. The method of claim 1 wherein the silicone composition is a one-part room temperature curable composition curable by contact with moisture.

6. The process of claim 5 wherein the one-part room temperature curable organopolysiloxane composition comprises a product obtained by mixing:

a) about 20 to about 60 weight percent of one or more polydiorganosiloxane fluids of the formula

R′[(R)₂SiO]_n(R)₂SiR′

Wherein R is a monovalent alkyl or alkylene radical having from 1 to 8 carbon atoms or a phenyl radical, each R ', which may be the same or different, is OH or a monovalent alkyl or alkylene radical having from 1 to 8 carbon atoms or a phenyl radical, and n is an average value such that the viscosity at 25 ℃ is in the range of from about 1 to about 100,000 centipoise, wherein one or both R's in at least one polyorganosiloxane fluid are OH and n is an average value such that the viscosity at 25 ℃ is in the range of 1,000-100,000 centipoise, preferably in the range of 1,000-40,000 centipoise at 25 ℃;

b)0 to about 40 weight percent of a cyclic organosiloxane of the formula

[(R)₂SiO]_n

Wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or is phenyl, R may be optionally substituted with an alkyl radical having 1 to 8 carbon atoms, and n has an average value of 3 to 10;

c)5 to about 50 weight percent of one or more flame retardant fillers selected from the group consisting of: melamine, zirconium dioxide, chromium dioxide, zinc borate, antimony oxide, aluminum oxide trihydrate and exfoliated graphite;

d) about 0 to about 30 weight percent of one or more inorganic extending or non-reinforcing fillers;

e) about 0.5 to about 10 weight percent amorphous SiO₂Reinforcing fillers having a surface area of about 50 to 300m²(ii)/g, and particle size ranges from about 0.01 to 0.03 microns;

f) about 1 to about 10 weight percent of a silane crosslinking agent of the formula

RSiX

Wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms or is phenyl, R may be optionally substituted with an alkyl radical having 1 to 8 carbon atoms, and X is an alkyl radical having a functional group selected from the group consisting of: carboxyl, ketoximino, alkoxy, carbonyl and amine directly attached to a silicon atom;

g) about 0.2 to about 3 weight percent of an organosilane adhesion promoter; and

h) about 0.02 to about 3 weight percent of an organotin salt as a condensation catalyst.

7. The method of claim 6, wherein the crosslinking agent is an oxime silane crosslinking agent of the formula;

RSi(ONR′₂)

wherein R and R' are independently selected from monovalent alkyl or alkylene radicals having 1 to 8 carbon atoms or are phenyl radicals, and R may be optionally substituted with an alkyl radical having 1 to 8 carbon atoms.

8. The method of claim 6 wherein the polyorganosiloxane fluid in the composition is only one wherein both R' are OH and the cyclic organosiloxane comprises from about 20 to about 30 weight percent.

9. The method of claim 8 wherein the adhesion promoter is a compound of the formula

Where Me is a methyl radical.

10. The method of claim 9, wherein the organotin salt is an organotin salt of a carboxylic acid selected from the group consisting of: dibutyltin diacetate, stannous octoate and dibutyltin dioctoate.

11. The method of claim 10 wherein the organotin salt of a carboxylic acid is a compound of the formula

(C₄H₉)₂Sn(OCOC₁₀H₂₀CH₃)₂。

12. The method of claim 1, for UV or high energy radiation curable systems, wherein the composition comprises 20-70% of a polydiorganosiloxane of the formula

R′[(R)₂SiO]_n(R)₂SiR″

Wherein R is a monovalent alkyl or alkylene radical having from 1 to 8 carbon atoms or a phenyl radical, R 'and R' which may be the same or different are acryloxypropyl or methacryloxypropyl radicals, and n is an average value such that the viscosity at 25 ℃ is in the range of from about 100 to about 100,000 centipoise.

13. A process as claimed in claim 12, wherein 0.25 to 5% of ethyl benzoin is used as photoinitiator.

14. The method of claim 13, wherein 1-5% allyltrimethylsilane is used as the adhesion promoter.

15. The method of claim 14, wherein the composition contains about 5 to about 50 weight percent of the flame retardant filler.

16. The method of claim 15, wherein the flame retardant filler is one or more fillers selected from the group consisting of: melamine, zirconium dioxide, chromium dioxide, zinc borate, antimony oxide, aluminum oxide trihydrate and exfoliated graphite.

17. The method of claim 16, the flame retardant filler being melamine.

18. The process of claim 1, wherein the composition comprises from 30 to 80% by weight of a polydiorganosiloxane of the formula

R″[(R)₂SiO]_n(R)₂SiR″

Wherein R is a monovalent alkyl or alkylene radical having 1 to 8 carbon atoms optionally substituted with 1 to 9 halogen atoms, or a phenyl radical optionally substituted with 1 to 6 halogen atoms, R' is a monovalent alkylene radical (preferably a monovalent vinyl or vinyl radical), and n is an average value such that the viscosity is in the range of 100-100,000 centipoise.

19. The method of claim 18, wherein the composition comprises 1 to 12 weight percent of a polydiorganosiloxane crosslinking agent of the formula

R[(R)(H)SiO]m[(R)₂SiO]_nR

Wherein each R, which may be the same or different, is a monovalent alkyl or alkylene radical having from 1 to 8 carbon atoms optionally substituted with from 1 to 9 halogen atoms, or is a phenyl radical optionally substituted with from 1 to 6 halogen atoms, and H is a hydride radical, m and n are integers and have a total average value such that the viscosity is in the range of from 10 to 10,000 centipoise, the value of m being from 10 to 50% of the value of m + n.

20. The method of claim 18 wherein the composition comprises 0.5 to 3% of an adhesion promoter of the formula

R¹Si(R²O)₃

Wherein R is¹Is an alkylene radical, preferably a vinyl radical, R²Is an alkyl radical having 1 to 6 carbon atoms.

21. The process of claim 18 wherein the total composition contains from 2 to 14 weight percent of platinum divinyltetramethyldisiloxane complex as a catalyst.