Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-03-26
2004-06-08
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S451000, C523S468000, C524S405000, C524S406000, C524S417000
Reexamination Certificate
active
06747074
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a flexible, solid intumescent composition which acts as a seal in deterring the spread of fire, smoke, and fumes, and is especially adaptable as fire resistant glazing strips for metal and wood window frames, doors, dampers and shutters, and may also provide sealing where items such as plastic pipes and electrical cables pass through openings.
BACKGROUND OF THE INVENTION
Fire, smoke, and fumes in confined spaces, such as multi-floor buildings, can be extremely life threatening. Frequently, if fire originates in the space between a floor and ceiling of such a structure, the fire, and resultant smoke and fumes, will tend to spread to other open spaces in the building, especially to open spaces above the point of origin of the fire.
The openings in floors, walls, and ceilings and the conduits, piping, cables, and the like that pass through are known as “through-penetrations”. If not protected by fire resistant materials, a through-penetration offers an area of low resistance to fire, smoke, and fumes, and in essence may serve as a chimney for heat, flame, smoke, and fumes. The spaces between these conduits, piping, etc. may be filled and blocked with commercially available fire retardant and intumescent putties, caulks, wraps, sheets or mats, known in the art as “firestops.”
Representative firestop products are disclosed in product brochure number 98-0400-4875-7 (published 1997) from Minnesota Mining and Manufacturing Company (3M). The 3M products are currently known under the trade designations “3M Brand Fire Barrier CP-25WB
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” and “Interam™ Firedam 150” (caulks); “3M Brand Fire Barrier MPP-1
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, MPP-4S
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, MPP-5S
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, and “MPS-2
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” (moldable putties); “FS-195
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A/P Strip” (wrap/strip), “FS-195
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AP
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, AA
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and RR
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” (sheets); and CS-195
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(metal reinforced sheet). These products are described in U.S. Pat. Nos. 5,175,197; 5,059,637; 5,476,891; and 5,578,671. Other intumescent materials have been used, such as those known under the trade designations “Palusol” (commercially available from BASF) and “Expantrol™” (commercially available from 3M), the latter being a hydrated alkali metal silicate.
Intumescent sealing strips or other profiles are often required to prevent the spread of fire in buildings and other enclosed spaces. Intumescent materials expand when heated to fill up any spaces left by combustible materials which are consumed by the fire. In the case of glazing seals, these profiles also help to keep glass panels in place during a fire.
Such materials should also form a strong char when heated. The char formed should be resistant to erosion by exposure to the heat and pressures encountered during a fire. It is advantageous to minimize the amounts of smoke and toxic gases generated by such sealants during a fire.
These sealant materials should have good aging properties and resistance to environmental agents normally encountered. Ideally they should last at least as long as the building in which they are installed.
There continues to exist a need in the art for improved fire sealing compositions that are flexible, can be extruded into a variety of shapes, and have the capability of expanding many times their original volume when exposed to heat.
SUMMARY OF THE INVENTION
The present invention provides for the preparation, at a moderate cost, of a fire sealing composition which is flexible, solid and capable of being applied in various shapes including sheets, extruded strips or other profiles. The composition exhibits an excellent combination of fire resistance, flexibility, char strength, and water resistance.
It has been discovered that compounding ingredients under high shear conditions in a substantially volatile-free condition results in fire barrier materials with improved tensile properties, improved Shore and penetrometer hardness values, and higher volumetric expansions upon exposure to fire or extreme heat when compared to formulations which were prepared with a volatile solvent or carrier present. For example, fire barrier materials obtained by high shear compounding with polymer from a dried latex demonstrated significantly improved properties over control formulations with the same ingredients which were thoroughly mixed in the wet state and then allowed to dry without high shear mixing in the dry state. It is difficult to obtain sufficiently high shear during compounding when a volatile solvent or carrier is present. Mixing of ingredients which would result in a composition having a value in a penetration test, as described below, greater than about 4 mm may not introduce sufficiently high shear even in a substantially volatile-free state. The required high shear mixing conditions are typically met when a resulting fire barrier material has a penetration test value less than about 4 mm and when thorough mixing of the fire barrier material ingredients is performed in a state which is substantially free of volatiles.
Accordingly, the present invention includes a flexible, solid fire sealing composition comprising: (a) water-insoluble intumescent mineral granules; (b) a thermoplastic or thermosetting, halogen-free binder; and (c) a phosphorus containing flame retardant, wherein said composition has a softness value from about 0.01 to about 3.75 mm.
A second aspect of the present invention is a process for preparing a flexible, solid fire sealing composition including the step of high shear mixing in a substantially volatile-free state: (a) water-insoluble intumescent mineral granules, (b) a halogen-free organic binder, and (c) a phosphorus containing flame retardant, wherein the resulting composition has a softness value (penetrometer) of from about 0.01 to about 3.75 mm.
The intumescent material is made of water-insoluble mineral granules, such as for example hydrated alkali metal silicates, preferably such silicates incorporating an oxy boron compound, e.g. 3M Expantrol™ 4BW.
The organic binder is a thermoplastic or thermosetting, halogen-free polymeric material. The thermoplastic or thermoset organic polymers used as the binders also provide the flexibility required, good char strength and a high level of intumescence in combination with the intumescent granules.
The use of halogen-free binder materials eliminates the risk of formation of toxic and corrosive halogen acid gases during a fire. The use of halogen-free binder materials requires the addition of a flame retardant to the composition of the present invention.
The fire sealing compositions of the present invention are an advance over the art because of their improved tensile strength, Shore hardness and lower penetrometer value. When subjected to heat, they also exhibit higher volume expansion values that are beneficial in sealing penetrations during a fire. Another distinguishing feature of the present invention is the fact that the compositions are not only flexible but solid, i.e. substantially free of volatiles, e.g. water or organic solvents. A small quantity of liquid plasticizer may optionally be incorporated, but the overall composition is solid at room temperature and does not exhibit the flow properties of a water- or solvent-borne dispersion of a caulk, mastic, paint or coating material.
The compositions of the present invention are also distinguishable from putty-like materials which are soft and malleable at room temperature. As noted above, the compositions of the present invention, although flexible, have a well-defined shape to which they will tend to revert following small deformation.
Other aspects of the present invention are methods of fire stopping a through-penetration, door or window, the methods including the steps of applying the composition of the invention above described to a through-penetration, door or window and allowing the composition to expand and char upon exposure to heat.
DETAILED DESCRIPTION
The process of the present invention requires high shear mixing of the components in a volatile-free state. The resulting fire sealing compositions are flexible and
Buckingham Mark R.
Welna Walton W.
3M Innovative Properties Company
Patchett David B.
Szekely Peter
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