Fire resistant compositions

Details Fire resistant compositions Fire resistant compositions

2002-10-15

2003-11-04

Green, Anthony J. (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Contains fireproofing or biocidal agent

C106S600000, C106S620000, C106S706000, C106S708000, C106S790000, C106S632000, C106S634000, C252S601000, C252S607000, C428S532000, C428S537100, C428S537700, C428S920000, C428S921000

Reexamination Certificate

active

06641649

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to fire resistant coatings and to cellulosic materials modified with such coatings to render them fire resistant. The invention relates also to methods of making cellulosic materials fire resistant.
BACKGROUND OF THE INVENTION
Cellulosic materials such as timber and particle board are widely used as building materials. There are many cellulosic materials for which it is desirable to have some degree of fire resistance. For example, there are many 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 for any occupants thereof. These building materials include timber, wall boards of many types; surface materials that are placed within a building structure, for example, ceiling tiles. 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.
Cardboard is a cellulosic material that generally has a limited use as a building material being usually restricted to use as reinforcing in flush panel doors. However, cardboard offers the desirable properties of relatively high strength to weight ratio, especially stiffness, combined with low cost. In the case of corrugated cardboard it also offers low thermal conduction which is attributed to the presence of air entrapped in the corrugated cardboard flutes. Despite these attractive benefits, the use of cardboard has been limited because of its combustibility and lack of adequate fire resistance. By fire resistance it is meant that cellulosic materials treated as taught within the ambit of this invention by the solutions described herein, will exhibit a substantial reduction in the propensity to support a fire.
There have been various attempts to improve the fire resistance of cellulosic materials. In the case of cardboard material, these have included soaking cardboard panels in aqueous solution of sodium silicate. However, such coatings have not proven satisfactory as they have poor water resistance. Furthermore, on exposure to flames the coating can melt or crack exposing the combustible cardboard to the flames.
Dimanshtaeyn, U.S. Pat. No. 5,035,851, Jul. 30, 1991 describes the use of 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 resistance thereto. This is a complicated and expensive solution and acceptable resistance to fire is not always achieved.
Luckanuck in U.S. Pat. No. 5,085,897, Feb. 4, 1992 describes a liquid mixture of silicate and an inert mineral fibre 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. The treatment does not include a reactive calcined filler nor a latent acid catalyst.
Nguyen et al., U.S. Pat. No. 4,888,057, Dec. 19, 1989 describes 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 is complicated and expensive to use.
U.S. Pat. No. 6,040,057 (Mar. 21, 2000) involves the treatment of a cellulosic substrate with an alkali metal treated material to render the alkali metal silicate water insoluble.
U.S. Pat. No. 3,940,516 (Feb. 24, 1976) relates to compositions consisting of:
5 to 15% of powdered silicate-oxide sinter or alloy
15 to 35% of an anhydrous powdered alumina silicate
50 to 80% of acid phosphates of aluminium, chromium, magnesium or calcium.
The above compositions lack alkali metal silicates.
U.S. Pat. No. 5,171,496 (Dec. 15, 1992) discloses wood composites. The compositions include blast furnace slag and are cured by heating. The compositions are not ordinarily fire resistant but can be rendered such by modifying the cellulosic materials. The composition without the treated cellulose is thus not a fire resistant composition. These compositions of this citation are also calcium rich and this is important to this reaction mode.
SUMMARY OF THE INVENTION
This invention provides in one form an aqueous fire resistance treatment composition comprising:
water;
a metal silicate selected from an alkali metal silicate or an alkaline earth metal silicate;
a reactive calcined filler;
a latent acid catalyst.
The alkali metal silicate is preferably selected from the group consisting of potassium silicate, sodium silicate and lithium silicate. The alkaline earth metal silicate solution is preferably selected from the group consisting of beryllium silicate, magnesium silicate and calcium silicate.
Preferably the metal silicate is selected from the group consisting of sodium silicate and potassium silicate.
More preferably the metal silicate is sodium silicate.
Preferably the reactive calcined filler is selected from the group consisting of alumina and alumino silicates.
In an alternative form this invention provides a method of treating cellulosic substrates to render them fire resistant by treating the substrate with a composition comprising:
water;
a metal silicate selected from an alkali metal silicate or an alkaline earth metal silicate;
a reactive calcined filler;
a latent acid catalyst
and allowing the treatment to dry and cure.
Preferably the treatment includes a dried, cured coating having a film thickness in the range 50-1000 &mgr;m.
In a still further form this invention provides cellulosic material treated with a fire resistant composition formed by curing a composition comprising:
water;
a metal silicate selected from an alkali metal silicate or an alkaline earth metal silicate;
a reactive calcined filler;
a latent acid catalyst.
Preferably the cellulosic material is coated with the fire resistant composition.
DETAILED DESCRIPTION OF THE INVENTION
Sodium silicate is the preferred metal silicate. However, other metal silicates may be used including mixtures of different metal silicates.
The preferred sodium silicate is manufactured by PQ Industries. This material is an aqueous solution which is basically comprised of SiO
2
/Na
2
O.
Examples of suitable solutions of sodium silicate are Vitrosol N and Vitrosol H, both available from PQ Australia. Vitrosol N is a 38% w/w solution in water.
The reactive calcined filler is preferably selected from calcined alumina and calcined alumino silicate. These materials fall into the class of fillers known as pozzolans. These are defined as materials which in finely divided form and in the presence of water, chemically react with calcium hydroxide at ordinary temperatures to form compounds having cementitious properties. Examples of suitable materials are calcined flint clay, calcined alumina, fly-ash and blast furnace slag. The filler is described as reactive in that it can react with alkaline water and/or the metal silicate. The filler is thus distinct from conventional fillers such as talc and clay. These reactive fillers are readily available and generally of low cost. Fly-ash is a finely divided glossy material generated from combustion of pulverised coal in modern power plants. They have previously found use in modified concretes where lower costs and higher long term strengths can be achieved. The particle size of the reactive fillers is important for best results and these are achieved when the maximum particle size is less than 150 &mgr;m. Generally better results are achieved with smaller particles and those that pass through a 75 &mgr;m sieve produce improved performance.
The latent acid catalyst is preferably a modified organic acid, especially an ester, which becomes active under the conditions of treatment with the composition. Preferred latent acid catalysts are esters of acetic acid and esters of dibasic acids such as glutaric, succinic and adipic. An example of suitable latent acid catalysts is

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