Compressible Fireproof Seal

The present invention relates to fireproof, compressible, intumescent materials for use in sealing expansion joints, curtain wall gaps and penetrations in floors and walls to prevent the passage of flame and smoke.

Modern building construction utilizes fire resistive walls and floors to confine the spread of fires; yet mechanical and electrical piping, electrical cable, and duct work penetrate, and construction gaps, expansion joints, and curtain wall openings may occur in these assemblies. Unsealed openings and penetrations diminish the effectiveness of fire rated walls and floors, threatening life, property and operations by allowing smoke and flames to pass unchecked through the building.

A fire stop must maintain its sealing properties not only in the initial stages of a fire, but also as it heats and burns as the fire matures. In essence, this means that the fireproof seal must contain an ingredient or ingredient combination which can replace any volume lost as the polymeric base and/or fillers and extenders are used up during a fire or flash fire condition. This property of compensating that lost mass is commonly referred to as intumescence.

Elastic fireproof materials employing an elastomer, vulcanizing agents and an intumescent mineral are disclosed in U.S. Pat. No. 4,266,039 (Hons-Olivier, et. al.). Hons-Olivier, et al, teaches the use of nondehydrated vermiculite mineral as the intumescent. Repeated trials incorporating this mineral in a compressible composition resulted in spongy structures that either failed to pass the ASTM E-814 fire test, or failed to exhibit sufficient softness as measured by compression-deflection. Vermiculite has insufficient expansion and tends to produce a composition with a friable char. A prime requirement to survive the ASTM E-814 fire test is the ability of the composition to intumesce and form a char strong enough to withstand the hose stream test. Increasing the quantity of vermiculite to obtain better expansion is deleterious to char strength and softness.

It is therefore an object of this invention to provide an effective, compressible, fireproof seal for use during flame and heat exposure and especially to provide for improved resistance during the subsequent impact, erosion and cooling effects of a hose stream.

The present invention provides a compressible fireproof seal in extruded or molded form with outstanding fire and hose stream resistance properties. The seal is produced from elastomers, vulcanizing agents, fillers, softening agents and an intumescent mineral.

The uniqueness of this invention lies in using an alkali metal silicate intumescent in conjunction with a naphthenic oil softening agent. This combination provides the means to obtain materials with softness, compressibility, resistance to flame and heat, and strength to withstand pressurized water from a fire hose stream.

Unexpectedly, materials containing alkali metal silicate and naphthenic oil produced fireproof seals superior to materials containing vermiculite. Alkali metal silicate/naphthenic oil containing materials were superior to vermiculite containing materials in softness and when heated, in expansion. Alkali metal silicate containing materials when heated form a glassy siliceous matrix greatly enhancing char strength. The charred siliceous matrix resists the ablative action of a fire.

During the initial stages of a fire, the alkali metal silicate starts to expand as the seal begins to char. This expansion more than compensates for shrinkage due to organic loss. Expansion of alkali metal silicate and charring of the organic matrix physically lock the material into position, sealing the void. The seal remains intact at temperatures exceeding 1000.degree. C. and the strength of the matrix is sufficient to prevent its dislodgment from the impact of a stream of water from a fire hose for a minimum of two hours from the inception of the test.

The present invention relates to a fireproof seal consisting of an elastomer, vulcanizing agents, a softening agent with a relatively high aromatic content for compatibility to provide softness, a flame retardant plasticizer, fillers for both flame retardant and mechanical properties, and an alkali metal silicate intumescent. If a sponge fireproof material is desired, a combination of blowing agents such as azocarbonamide and benzenesulfonyl hydrazide is incorporated to generate the sponge during processing. In addition, calcium sodium metaphosphate can be added to improve green strength if necessary.

The uniqueness of this invention lies in the use of an alkali metal silicate, e.g., hydrated sodium silicate, as the intumescent in combination with a softening oil, particularly, a naphthenic oil. This combination provides the excellent fire and hose stream resistance performance and the compressibility required in the construction industry.

Ingredients used to produce compressible fireproof seals of the invention as will be shown in the following examples are listed and described in Table I.

The ingredients are mixed on conventional rubber processing equipment. This equipment includes rubber mill, Banbury, or intermix compounding. After mixing, the mill base is slabbed, cooled, and allowed to age a minimum of 24 hours. Alternatively, the mill base is cut into strips, festooned, cooled, and aged. After aging, the mill base is extruded or molded into the desired shape and vulcanized in a hot air oven, or in a salt bath, or in a heated press. Instead of extruding or molding, the mill base can be calendered or pressed and cut to the desired shape. A sponge is obtained by incorporating blowing agents.

To demonstrate the utility of this invention the following examples were prepared. In the examples, PHR means parts per hundred weight rubber.

The ingredients were compounded on a 2-roll rubber mill. The mill base was cut into strips and the strips fed into an extruder. The extrudate was continuously sponged and vulcanized in a hot air oven.

The following properties were obtained on the sponge:

Fire Test: >2.00 hrs.*

The ingredients were compounded on a 2-roll rubber mill. The mill base was hot pressed at 65.degree. C. into the desired thickness, cut to size, and sponged and vulcanized in a hot air over.

The following properties were obtain on the sponge:

The ingredients were compounded on a 2-roll rubber mill. The mill base was hot pressed at 65.degree. C. into the desired thickness, cut to size, and sponged and vulcanized in a molten salt bath.

The following properties were obtained on the sponge:

The ingredients were compounded on a 2-roll rubber mill. The mill base was hot pressed at 65.degree. C. to the desired thickness, cut to size, and sponged and vulcanized in a hot air oven.

The following properties were obtained on the sponge:

Calcium sodium metaphosphate fiber, obtained from Monsanto Corp., improved the green strength without detriment to sponge softness. When Wolastinite fibers were incorporated in the composition, sponge softness decreased considerably. Although not essential in the composition, the addition of calcium sodium metaphosphate fiber provides greater latitude in processing the sponge.

The ingredients listed in the previous examples can also be molded into a cellular fireproof seal. By removing the blowing agents, noncellular fireproof seals are obtained. In preferred compositions, the plasticizer concentration is modified. In the following example the plasticizer content was lowered, the blowing agents removed to produce a noncellular part, and although not necessary, the drying agent and processing aid removed. EXAMPLE 5

The ingredients were compounded on a 2-roll rubber mill. Mill base was molded for 10 min. at 149.degree. C. into sheets 6.4 mm .times.30.5 cm.times.30.5 cm, or for 5 min. at 165.degree. C. into tubes 1.6 cm ID.times.2.3 cm OD.times.32.4 cm.

Comparative examples were run utilizing the teachings of examples 1, 2 and 6 of U.S. Pat. No. 4,266,039 (Hons-Olivier, et al). Additional comparative examples were run by substituting vermiculite for the alkali metal silicate in the examples of this invention. In either situation, the resulting compressible fireproof seal could not pass the ASTM E-814 fire test. The preferred intumescent of the present invention is a composition comprising a mixture of alkali metal silicate, represented by the formula M.sub.2 O:xSiO.sub.2 in which M is alkali metal; at least one oxy boron compound; and water; in which x (weight ratio of silica to alkali metal oxide) ranges from about 1.5 to about 4, the molar ratio of boron to M is between about 0.2 and about 0.9, and the water comprises about 5 to 15 weight percent of the total composition.

Examples of useful alkali metal silicates are sodium silicate, lithium silicate and potassium silicate; sodium silicate being preferred. A mixture of alkali metal silicates can be used. Thus M may stand for an admixture of alkali metals in silicate form.

For purposes of this description, the term "oxy boron" or "borate" means any compound having a radical which contains boron and oxygen, such as the metaborate, tetraborate, perborate, or polyborate radicals. Examples of suitable oxy boron compounds are: boric acid and borate salts of Group I and II elements, including naturally occurring borate compounds, such as borax and colemanite. By Group I and II elements, it is meant all elements in Groups IA, IB, IIA and IIB of the periodic table of elements. Some additional examples of suitable borates are calcium metaborate, magnesium borate, and zinc borate.

The temperature at which expansion or intumescence begins with these silicate compositions can be controlled as needed for the application. Generally, the lower the concentration of water the higher is the temperature of intumescence. There is preferably about 5 to 10 weight percent water in the composition. Also, if a higher intumescence activation temperature is required, this can be accomplished by adding calcium hydroxide to the basic formulation. If a lower activation temperature is needed, borax can be used in place of boric acid as the oxy boron compound.

For cases in which the borate is the salt of an alkali metal (e.g., borax or sodium borate) the alkali metal originating from the oxy boron compound will become part of the composition, and this alkali metal is included in calculating the ratio x stated above between the silica and alkali metal.

The amount of the preferred intumescent when a cellular, compressible fireproof seal is desired should be between 130 PHR and 200 PHR and preferably between 140 PHR and 180 PHR. When a noncellular compressible fireproof seal is desired, the amount of preferred intumescent should be between 100 PHR and 200 PHR and preferably between 130 PHR and 170 PHR.

Furthermore, according to the teaching of this invention a preferred softening agent is napthenic oil. The amount of this preferred softening agent when a cellular compressible fireproof seal is desired should be between 25 PHR and 45 PHR and preferably between 30 PHR and 40 PHR. When a noncellular compressible fireproof seal is desired the amount of napthenic oil should be between 5 PHR and 30 PHR and preferably between 15 PHR and 20 PHR.

Various omissions, modifications and changes to the principles described herein may be made by one skilled in the art without departing from the true scope and spirit of the invention which is indicated by the following claims. For example, a useful filler in place of hydrated aluminum oxide or silica could be clay.