Fire resistant coatings for cellulosic materials

A novel and highly useful fire resistant solution for application to the surfaces of cellulosic and building materials is described. This solution is easy to prepare and apply and is made from environmentally safe elements. When applied to the surface of these materials and dried, the surface is highly resistant to fire. Buildings made which incorporate products thus coated will survive a fire much longer giving any occupants time to egress therefrom. Additionally, the surfaces of materials that contain this novel and proprietary coating solution will have excellent white color surfaces that can be washed over and over again without substantial loss in fire resistance.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the application of fire resistant coatings on 
cellulosic and other flammable substrates. Still more specifically, this 
invention relates to the application of fire resistant coatings on wall 
boards, ceiling tiles and other board-like elements that are essentially 
made from cellulosic materials. Even more specifically, this invention 
relates to the easy application of fire resistant coatings that can be 
applied easily and with great effect on the reduction of fire on 
cellulosic materials such as those used within buildings and the like, for 
example. 
2. Description of the Prior Art 
There are a number of prior art references which disclose element which can 
be used to surface treat materials that may include cellulosic materials 
in order to impart some degree of fire resistance thereto. These materials 
include, for example, aqueous salt solutions and the like. Although the 
surfaces of materials which are coated or treated with these prior art 
solutions are somewhat resistant to fire, they are not considered to be 
very fire resistant. In fact, none of these materials treated with aqueous 
salt solutions have received a Class A Fire resistant certificate by any 
known testing laboratory. 
In my previous patent, U.S. Pat. No. 4,886,548, Dec. 12, 1989, I describe a 
coating solution made up from a particular mixture of three silicates that 
can be used to coat building materials and the like in order to impart 
fire resistant thereto. This solution is very useful indeed and has been 
well-received within the fire resistant industry. However, my solution 
requires that the user carefully control the solution as it is made up and 
stored. Also, the present of a plurality of silicate ingredients added 
thereto and additionally requires more expense and cost to make up since 
it needs these three, separate, silicate solutions in order to function 
properly. Also, my previous solutions were not particularly useful in the 
preparation of pure white surfaces, surfaces that can be washed many times 
without reducing the propensity to support combustion. 
There have been other coatings and methods used to impart fire resistant to 
materials, some of which employ the use of silicates, for example. These 
include Dimanshtaeyn, U.S. Pat. No. 5,035,851, Jul. 30, 1991 which 
describes the use of a coating solution which includes a silicate, a clay 
and some inorganic materials (e.g. a borate) which can be used to coat 
metals, woods and foamed polymeric materials to impart some degree of fire 
resistant thereto. This is a complicated and expensive solution and 
complete resistance to fire is not always achieved. 
Again, Luckanuck in U.S. Pat. No. 5,085,897, Feb. 4, 1992 describes a 
liquid mixture of silicate and an inert mineral fiber a mineral powder 
which is used to coat steel beams used within buildings. This solution, 
when coated on the steel building materials, is said to help reduce 
twisting of steel columns and other building materials in a fire, for 
example. 
Nguyen et al., U.S. Pat. No. 4,888,057, Dec. 19, 1989 describes and claims 
a composite fire resistant coating which comprises a mixture of silicates 
and silicon carbide powder. It is said that building materials coated with 
these materials are resistant to fire. However, this coating too is 
complicated and expensive to use. 
Other references which are part of the prior art also describe the use of 
silicate or silicate solutions, some with other ingredients contained 
therein, and these are purported to impart fire resistance when applied to 
or mixed with construction materials. None of these references (which are 
legion in number) teach the use of a simple, topical application of a 
particular solution of such a nature that when conventionally applied to 
cellulosic surfaces using conventional application techniques will not 
only impart significant fire resistance to the cellulosic material but can 
also be the vehicle for imparting a color fast and washable whiteness to 
the surface thereof. 
There are no known, easily applied coating surfaces that can conveniently 
and cheaply coat cellulosic materials, especially those used within the 
building industry, and impart a high degree of fire resistance thereto. 
Therefor, it is imperative that such a coating be available within the 
building industry. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide a safe, convenient, 
environmentally safe and easy to use coating that can be applied to 
cellulosic materials in order to impart a high degree of fire resistant 
thereto. It is yet another object to provide such a coating that is 
stable, aqueous and thus can be applied within conventional equipment 
available within the prior art. It is also an object of this invention to 
provide a safe, stable fire resistant coating that is environmentally safe 
to use and dispose. Finally, it is an object of this invention to provide 
an improved coating on the surfaces of building materials, wherein this 
coating will not only impart a fire resistance but also have an improved 
whiteness in color and an improved, washable surface. These and yet other 
objects are achieved in a coating solution for imparting fire resistant to 
cellulosic materials, said solution comprising an aqueous solution of a 
sodium silicate with minor amounts of Bentonite and mica.

DETAILS OF THE INVENTION 
There are a host of cellulosic materials that need to have some degree of 
fire resistance associated therewith. For example, there are a host of 
building materials which if rendered at least with some degree of fire 
resistance, will slow down the process of a fire contained therein thus 
providing essential safety to any occupants thereof. These building 
materials include dimensional lumber; wall boards of many types; surface 
materials that are placed within a building structure, for example; 
ceiling tiles, etc. etc. If these materials could be rendered at least 
partially fire resistant, any resulting fire would be of a slow burning 
nature and thus improve the safety of the occupants of the building. 
Although there are a number of prior art materials that have been reported 
as giving some fire resistance to building and cellulosic materials, none 
of these is very successful and thus my invention has answered a long 
standing need for giving substantial fire resistance to building and 
cellulosic materials. 
By fire resistant, I mean that materials treated as taught within the ambit 
of this invention with the solutions described herein, these materials 
will then exhibit a substantial reduction in the propensity to support a 
fire. 
In the preparation of the coating solution of this invention, I prefer to 
make up an aqueous solution which will contain the following (weight 
percent of the solution): 
10 to 25% of sodium silicate 
15 to 30% of total water 
12 to 28% of pure white clay 
15 to 35% of fine mica 
By the term "fine mica" I mean a mica that will pass through a 200 mesh 
screen, for example. 
By sodium silicate, I prefer one that is made and manufactured by PQ 
Industries of Philadelphia, Pa. and sold as OW3. This material is an 
aqueous solution which is basically comprised of SiO.sub.2 /Na.sub.2 O, 
wherein the Na.sub.2 O is about 9.1% by weight of the solution and the 
SiO.sub.2 is about 29.5 weight %, with the remainder being water. This 
material has a specific gravity of about 42.2 baume, a weight of about 
11.8 pounds/gallon, a pH of about 11.3 and viscosity of about 400 
Centipoises. 
By pure white clay, I mean an industrial clay that is made principally of a 
mineral smectite and is formed by the alteration of volcanic ash (e.g. 
Bentonite or Diatomite Clays). This material is commercially available and 
is sometimes used as drilling mud within the petroleum industry. Bentonite 
clay has the capability of swelling when wet and has a fine particle size. 
Small amounts of a conventional surfactant may also be added in order to 
insure complete mixing. I prefer adding a very small amount (e.g. less 
than 0.01% by weight of the surfactant Dowfax 2, Dow Chemical Co., 
Midland, Mich.) 
In making up a solution of this material, I first mix up the water and clay 
for about 30 minutes which allows the clay to swell. The silicate, which 
may contain a small amount of the surfactant as mentioned above--and mica 
are then added under constant stirring and the solution is then ready for 
application on to the surface of a cellulosic building element. The 
solution should be stirred constantly during this step to permit any 
solids to remain in solution. I refer to this as "colloidic chemistry". 
This material may be applied to the surfaces of cellulosic or building 
elements by any of the conventionally known techniques. This includes 
surface application by brush or other hand operation; curtain coating; 
pressure spraying; etc. The latter processes are needed to commercially 
apply this solution or slurry to conventionally prepared products such as 
ceiling tiles and the like. A drying cycle may then occur in order to cure 
the solution on the surface of the treated element and to insure a good 
surface. My coatings should be fluidly applied so as to form a coating 
depth of about 1/8 inch even over cellulosic surfaces that may include 
small fissures in the surface thereof (e.g. ceiling tiles and the like). 
These coatings must be stable and dry quickly and maintain a uniform depth 
of color throughout the thickness. 
When this solution is applied to the surface of a cellulosic or building 
material, the propensity of this material to resist fire is greatly 
improved. For example, some pieces of medium density fiber board, which is 
essentially non resistant to fire, were treated with the aforementioned 
solution by applying the solution to the board at a coating weight of 15 
to 25 grams per square foot of the board, these elements were essentially 
fire resistant. To test the efficacy of this coating, these boards were 
placed into a flame tunnel. Flame from a methane burner is introduced into 
the start of this tunnel with a prefixed air flow. The time of flame 
treatment is about 10 minutes. The amount of burning on each piece of 
board is measured along with the amount of smoke produced. When boards 
that were coated with my material were tested, the flame number was 25 
which is a Class A rating. Smoke density was zero. This test is called the 
Steiner E-84 Test. Standard boards without treating essentially were 
consumed by the fire and considerable smoke was produced. 
In yet another embodiment, cellulosic and building materials treated with 
the surface fire resistant treatment of this invention, can further be 
treated with a salt spray which helps maintain and increases the whiteness 
of the color. This surface is similar to a prime paint coat and the finish 
paint coat can be applied easily thereon. This step eliminates a latex 
paint coating, saves on paint costs and reduces environmentally hazards 
associated therewith. In addition, my coating is especially useful when 
applied to the surfaces of ceiling tiles used within a building, for 
example. Here, the color white is conventionally used most of the time and 
a pure white coating is especially advantageous for improving the lighting 
within the building such as within and office space. Since building code 
requirements are such that these tiles must be resistant to fire and also 
washable, whilst maintaining fire resistance, it is very important that 
any such coating applied have these important characteristics. My coating 
can be so applied and will have such characteristics, maintaining 
resistance to fire throughout at least 15 such washings. No prior art 
coating can claim such characteristics. 
My fire resistant coating is environmentally safe, easy to apply and 
presents little or no hazard to humans when being applied on the surfaces 
of cellulosic or other building materials. My fire resistant coating is 
eminently useful when applied to dimensional lumber as well as all of the 
conventionally known building elements, such as wall boards, ceiling 
tiles, paneling, plywoods, particle boards and many, many other materials. 
Finally, my coatings may be applied to certain roof underpanels that are 
usually installed over metal sub-decking and under meltable, rolled rubber 
roofing, for example. Here, a flame is usually applied to melt the rubber 
roofing just enough to fuse the materials all together and thus provide a 
good, waterproof roof. However, the cellulosic materials used in this type 
of roofing are usually not resistant to fire and sometimes a fire will 
occur during the roofing process. These composite cellulosic materials are 
made from paper and other fibrous materials. When these materials are 
coated with my novel and proprietary solutions, made as described herein, 
they can safely be used without causing fires. No other prior art solution 
can lay claim to such properties. 
In addition to the silicate, Bentonite, water and fine mica, small amounts 
of other materials may be added within the ambit of this invention. In 
particular, I have mentioned the addition of wetting agents and 
surfactants; bulking agents; thinners; colorants; and others as is 
well-known to those skilled in the art may also be added if desired and 
called for by the element being so treated. Although I have described the 
best mode envisioned within this application when filed, I do not intend 
to be limited by this disclosure in so far as the metes and bounds and 
specificity of my invention is concerned. However, I have a theory that 
states that the silicate is a heavy element within the system. Thus, when 
the solution or slurry or mixture of this invention is coated on the 
surface of a cellulosic element, the silicate naturally sinks to the 
bottom of the coating and thus causes the mica to rise to the surface. 
This final surface is extremely resistant to fire. 
Finally, it should be mentioned again that the solution, slurry or mixture 
of this invention is extremely safe for the environment. All of the 
ingredients described within my specification are naturally occurring and 
safe to use. By safe, I mean not only safe for the user but safe for the 
environment itself. Hence, waste amounts of left over solution can be 
easily disposed without worry about pollution.