Thermally and structurally stable noncombustible paper

Details Thermally and structurally stable noncombustible paper Thermally and structurally stable noncombustible paper

2001-04-13

2003-03-18

Chin, Peter (Department: 1731)

Paper making and fiber liberation

Processes and products

Plural fiber containing

C162S152000, C162S146000, C162S168100, C162S181400, C162S181600

Reexamination Certificate

active

06533897

ABSTRACT:

FIELD OF THE INVENTION
The present invention is drawn to thermally and structurally stable noncombustible papers and methods of making the same.
BACKGROUND OF THE INVENTION
In recent years, there has been an increased demand for lightweight sheet-like products that are fire retardant, or even noncombustible. This is particularly true after the health hazards of such materials such as asbestos have become known. Aside from the health risks associated with asbestos, asbestos was a good product for several reasons including its ability to conform with water during the paper making process. Additionally, asbestos products have shown good adsorptivity and scavenging properties in mixing with other additives.
Because asbestos has been restricted in recent years due to certain health concerns, alternative fibrous products having similar properties have become of interest. For example, highly efficient inorganic fibers have been developed including plaster fibers, basic magnesium sulfate fibers, phosphoric acid fibers, pyroboric acid magnesium fibers, potassium titanate fibers, alumina-silica fibers, and glass fibers, to name a few. Additionally, some fire retardant products have been developed including products focused on the coating of papers with an anti-flaming agent. Such anti-flaming agents have included ammonium salt complex type aqueous inorganic salts, phosphorus complex nitrogen compounds, phosphorus complex hologen compounds, antimonytrioxide-halogen compounds, boron compounds, halogen compounds, and the like. These coating systems are typically composed of organic substances, and because they are mere coatings, it is very difficult to form a sheet-like material that is totally noncombustible.
Therefore, based upon what is known about the prior art, it has been recognized that a fibrous paper product that is structurally stable at very high temperature, such as when in contact with a flame, would be a significant advancement in the paper insulation art.
SUMMARY OF THE INVENTION
The present invention is drawn to a noncombustible fibrous paper comprising a dominant amount of aluminosilicate refractory fibers by weight, wherein the fibers are substantially from 1 micron to 35 microns in width and from 1 cm to 15 cm in length; and from 0.2% to 4% by weight of a polymeric binder distributed throughout the paper. The polymeric binder can be, for example, a vinyl acetate/ethylene copolymer emulsion. The paper is a mat product that is structurally stable at very high temperatures, preferably at temperatures of at least 1000° C. and up to 1400° C. or more. Though not required, it is preferred that the aluminosilicate refractory fibers be present at from 90% to 99.8% by weight. From 0.1% to 5% by weight of viscose fibers and/or from 0.2% to 5% by weight of silicic acid aquagel, each by weight, can also be present.
Additionally, a method of making a thermally stable noncombustible paper is disclosed comprising the steps of pulping aluminosilicate refractory fibers, adding an effective amount of a polymeric binder forming a continuous pulp, pressing the continuous pulp, and dehydrating the continuous pulp.
DETAILED DESCRIPTION OF THE INVENTION
Before the present invention is disclosed and described, it is to be understood that this invention is not limited to the particular configurations, process steps and materials disclosed herein as these may vary to some degree. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only, and is not intended to be limiting as the scope of the present invention. The invention will be limited only by the appended claims and equivalents thereof.
It must be noted that, as used in this specification and the appended claims, singular forms of “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise.
“Refractory fibers” are fibers that are resistant to heat and corrosion.
“Aluminosilicate refractory fibers” contain primarily two ingredients: silica (silicon dioxide) and alumina (aluminum dioxide). They are typically present in roughly equal proportions. However, the relative proportions of silica and alumina in the noncombustible paper of the present invention is not critical to the character and quality of the paper, though substantial amounts of both must be present. Thus, as a practical matter, the weight ratio of silica to alumina can be from 7:3 to 3:7. Other trace ingredients can also be present such as <1.0% Fe
2
O
3,
and <0.5% Na
2
O+K
2
O, though these amounts are not limiting.
“Paper” refers to a fibrous product produced by one of a number of paper making processes. Typically, the paper is a compressed mat-type product rather than a woven product. The papers of the present invention are not self-supporting and have many typical paper-like properties, e.g., rollable, foldable, tearable, creasable without breaking, collapseable, bendable, etc. The paper can provide the ability to surround structures of different dimension. In other words, the papers can be collapsible and re-expandable. Additionally, the papers are non-thermally expandable and structurally stable under extreme heat conditions. For example, after applying a 1000° C. flame to a paper of the present invention, the paper will not blacken or expand. Thus, until a specific paper reaches a disintegration temperature, e.g. preferably greater than 1000° C., it will remain structurally sound.
“Structurally stable” or “thermally stable” when referring to the papers of the present invention shall mean that the papers will not be significantly physically altered at very high temperatures where direct flame contact with the paper may occur. A very high temperature that can be present in a typical fire can be, for example, at least 230° C., though the papers of the present invention can typically withstand much higher temperatures than this. For example, with respect to the preferred embodiments, the papers of the present invention can withstand temperatures of at least 1000° C. and up to as much as 1400° C. or more, without substantial degradation. Thus, as the paper is structurally stable as defined herein, no substantial expansion or shrinkage, e.g., less than about 3.5% in volume, will occur at very high temperatures, e.g., up to about 1400° C. Components other than aluminosilicate refractory fibers can burn off at certain temperatures, e.g., as a gas, though such burn off is not noticeable by casual observation. Thus, in one embodiment, after applying a flame of about 1000° C. and allowing the paper cool, the appearance of the paper will remain substantially the same.
“Paper making process” is any process wherein the aluminosilicate refractory fibers (with or without other components) are pulped, compressed, and dehydrated.
“Noncombustible” refers to the fact that the papers of the present invention will not substantially combust under extreme heat, but will merely disintegrate into smaller components. For example, many of the papers of the present invention will not disintegrate under a flame of greater than 1000° C. However, the papers typically will disintegrate when exposed to an oxy-acetylene torch (2400° F.), but will not combust.
“Polymeric binder” shall include any polymeric material that is functional in creating binding properties with respect to the aluminosilicate refractory fibers. Though the use of a copolymer emulsion such as vinyl acetate/ethylene is preferred, certain other monomers and copolymers can be used. For example, the polymeric binder can comprise polyvinyl chlorides, polyvinyl acetates, polyvinylidene chlorides, polyvinyl alcohols, polystyrenes, polyethylene terephthalate, polyethylene, polypropylene, polychloroprene, styrene butadiene copolymers, butadiene acrylonitrile copolymers, polyisoprene polyurethanes, polybutadiene, polyacrylates, natural rubbers, silicone, metallic resinates, waxes, acrylic resins, thermoset resins (e.g., epoxies and phenolics), and mixtures and combinations thereof.
“Second noncombustible material” can include any fibrous

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