Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-02-22
2002-02-05
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S416000, C524S426000
Reexamination Certificate
active
06344514
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fire-retardant latices which are useful as binders for manufacturing non-woven fabrics. The fire-retardant latex binders of this invention are particularly useful in manufacturing non-woven fiberglass furnace filters.
BACKGROUND OF THE INVENTION
Various latex compositions can be used as binders for non-woven fabrics. In many applications, it is desirable for the latex binder composition to provide fire-retardant characteristics. For instance, in clothing and household applications, it is normally desirable for the latex employed to contain a fire-retardant material.
A wide variety of chemical agents can be used in latex binders as fire-retardants. For instance, tris-(2,3-dibromopropyl) phosphate was once widely used as a flame-retardant in manufacturing children's sleepwear. However, tris-(2,3-dibromopropyl) phosphate is no longer used in such applications because testing has showed that it might be carcinogenic. Other flame-retardant compounds that have been developed to replace tris-(2,3-dibromopropyl) phosphate include tris(1,3-dichloroisopropyl) phosphate and a mixture of two cyclic phosphonate esters.
U.S. Pat. No. 2,036,854 discloses that a mixture of ammonium borate or phosphate with an ammonium halide, such as ammonium bromide, is useful for flame-proofing textile materials. U.S. Pat. No. 2,036,854 further reports that the ammonium halide appears to greatly enhance the flame-extinguishing properties of the ammonium borate or phosphate.
U.S. Pat. No. 2,452,054 discloses the use of diammonium phosphate and ammonium bromide as a flame-retardant for use on cellulosic materials. It is further disclosed in U.S. Pat. No. 3,061,492 that ammonium bromide can be used as a flame-retardant for unsaturated polyester resin compositions.
U.S. Pat. No. 3,840,488 discloses the use of ammonium bromide and urea as flame-retardant additives for styrene-butadiene rubber (SBR) latex that is used for textile treatment and carpet backing applications. However, U.S. Pat. No. 3,840,488 further discloses that the utilization of ammonium bromide and urea in such latices has the undesirable effect of reducing the viscosity of the latex. The teachings of U.S. Pat. No. 3,840,488 further indicate that this undesirable decrease in the viscosity of the latex can be prevented by the addition of a halo alkyl phosphoric acid or salt.
U.S. Pat. No. 5,484,839 discloses a flame-retardant natural or synthetic latex which is grafted with ring-halogenated, ethylenically unsaturated aromatic monomers. These grafted latex compositions are reported to be useful as non-woven filter media binders, as backcoatings for woven upholstery and draperies, and in other applications.
U.S. Pat. No. 4,239,670 appreciates the fact that the addition of some flame-retardant materials, such as diammonium phosphate, to latex can cause the latex to become unstable. U.S. Pat. No. 4,239,670 further notes that such instability can render the latex unsuitable for its intended purpose. U.S. Pat. No. 4,239,670 solves the problem of latex instability caused by the addition of diammonium phosphate by further adding one part by weight of ammonium bromide per part by weight of diammonium phosphate added to the latex.
SUMMARY OF THE INVENTION
It has been unexpectedly found that the stability of styrene-butadiene rubber latices containing diammonium phosphate can be significantly improved by adding from 0.1 phr (parts per 100 parts by weight of dry rubber) to 5 phr of a sulfonate surfactant and 0.1 phr to 4 phr of an ethylene oxide/propylene oxide/ethylene oxide triblock polymer nonionic surfactant thereto. By utilizing this technique fire-retardant latex binder compositions containing diammonium phosphate can be made without the need to add ammonium bromide to attain a satisfactory level of stability. Since diammonium phosphate can be included in the latex composition, it is not necessary to graft a ring-halogenated, ethylenically unsaturated aromatic monomer onto the latex composition to render it fire-retardant.
The present invention specifically discloses a fire-retardant latex binder composition which is comprised of (1) water, (2) a styrene-butadiene rubber, (3) a fatty acid soap, (4) a sulfonate surfactant, (5) an ethylene oxide/propylene oxide/ethylene oxide triblock polymer, wherein the ethylene oxide/propylene oxide/ethylene oxide triblock polymer has a number average molecular weight of at least 8000, and (6) about 10 phr to about 50 phr of diammonium phosphate. This fire-retardant latex binder composition is particularly useful as a binder for manufacturing non-woven fabric.
The present invention further discloses a process for manufacturing a furnace filter which comprises (I) applying a fire-retardant latex binder composition to a fiberglass matrix to produce a latex-coated fiberglass matrix, wherein the fire-retardant latex binder composition is comprised of (1) water, (2) a styrene-butadiene rubber, (3) a fatty acid soap, (4) a sulfonate surfactant, (5) an ethylene oxide/propylene oxide/ethylene oxide triblock polymer, wherein the ethylene oxide/propylene oxide/ethylene oxide triblock polymer has a number average molecular weight of at least 8000, and (6) about 10 phr to about 50 phr of diammonium phosphate, and (II) drying the latex coated fiberglass matrix to produce the furnace filter.
DETAILED DESCRIPTION OF THE INVENTION
The fire-retardant latex binder compositions of this invention are made by simply mixing about 10 phr (parts per hundred parts by weight of rubber) to about 50 phr of diammonium phosphate into a styrene-butadiene latex that contains a fatty acid soap, a sulfonate surfactant and an ethylene oxide/propylene oxide/ethylene oxide triblock polymer, wherein the ethylene oxide/propylene oxide/ethylene oxide triblock polymer has a number average molecular weight of at least 8000. Such a latex is manufactured and sold by The Goodyear Tire & Rubber Company under the name Pliolite® 5000C. In most cases, from about 15 phr to about 40 phr of diammonium phosphate will be mixed into the latex.
Such styrene-butadiene rubbers in the latex is comprised of repeat units which are derived from styrene monomer and 1,3-butadiene rubber. Such styrene-butadiene rubbers will typically be comprised of repeat units which are derived from about 1 to about 40 weight percent styrene and about 60 to about 99 weight percent butadiene. The styrene-butadiene rubber in the latex will typically contain from about 10 weight percent to about 30 styrene and from about 70 weight percent to about 90 weight percent butadiene. The styrene-butadiene rubber in the latex will more preferably contain about 15 weight percent to about 25 weight percent styrene and from about 75 weight percent to about 85 weight percent butadiene.
The styrene-butadiene rubber latex can be synthesized using a fatty acid soap system and conventional emulsion polymerization techniques. Such emulsion polymerizations generally utilize a charge composition which is comprised of water, styrene monomer, 1,3-butadiene monomer, an initiator and a fatty acid soap. Such polymerizations can be conducted over a very wide temperature range from about 0° C. to as high as about 100° C. Such emulsion polymerizations are typically conducted at a temperature which is within the range of about 5° C. to about 60° C.
The fatty acid soap used in such polymerizations may be charged at the outset of the polymerization or may be added incrementally or proportionately as the reaction proceeds. Normally, from about 2 phm (parts by weight per 100 parts by weight of monomer) to about 7 phm of the fatty acid soap will be charged into the polymerization medium. It is typically preferred for the polymerization medium to contain from about 4 phm to about 6 phm of the fatty acid soap.
The emulsion polymerizations used in synthesizing the styrene-butadiene rubber latex may be initiated using free radical catalysts, ultraviolet light or radiation. To insure a satisfactory polymerization rate, uniformity and a controllable polymerization, free radical initia
Cain Edward J.
Lee Katarzyna W.
Rockhill Alvin T.
The Goodyear Tire & Rubber Company
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