Metal-fiber-latex-containing sheet materials

Abstract

Sheet material consisting essentially of inorganic fibers, such as asbestos fibers, elastomer latex, such as neoprene latex, and finely divided metallic material, such as lead, the inorganic fibers being felted together and coated and adhered together by the elastomer latex and formed into a sheet, with the finely divided metallic material being maintained in the resulting formed sheet and affixed to the inorganic fibers by the elastomer latex, the sheet material preferably being coated on one surface with a water-impermeable material, such as bitumen or tar, or a water-resistant material, is useful as a pipe wrapping, such as pipe wrapping for gas transmission lines, as vibration dampening material or sound deadening material when affixed to a surface or as a radiation shielding material. The above-described sheet material is formed by preparing a watery admixture or furnish containing the inorganic fibers, latex and lead dispersed therein, effecting precipitation of the latex material onto the dispersed inorganic fibers and/or metallic material, followed by subjecting the resulting watery admixture to agitation and then forming a sheet therefrom by discharging or flowing the aqueous admixture onto a paper-making screen or sheet-forming roll or surface.

Description

This invention relates to sheet materials useful as vibration dampening agents, sound deadening agents, gasketing material, special wrapping material, such as pipe wrapping material, and radiation shielding material. In one particular embodiment this invention relates to flexible sheet material made up of high density metallic material, such as lead, admixed with inorganic fibers. In another embodiment this invention relates to stiff of rigid sheet material made up of inorganic fibers, such as asbestos fibers, metallic material, such as finely divided or powdered metal, and a thermoset resin which serves to impart strength and rigidity or stiffness to the sheet material. In another embodiment this invention is directed to a method for the manufacture of high density, inorganic fiber-containing sheet material. In still another embodiment this invention is directed to a method for the manufacature of limp and/or flexible sheet material characterized by high density and useful as radiation shielding or vibration dampening or sound deadending material.

Sheet materials useful as sound deadening or vibration dampening materials have been prepared by incorporating or otherwise affixing finely divided or powdered lead to a heavy cloth, such as canvas. Such materials, howver, have not been completely satisfactory, particularly when exposed for a long period of time to the weather or when employed in a demanding environment, such as when employed as a pipe coating, in underground gas transmission lines.

It has also been suggested to disperse or otherwise incorporate finely divided metal, such as powdered lead, in a plastisol, such as a polyvinyl chloride plastisol. The resulting materials while satisfactory for many purposes are expensive and are not durable. Also, with respect to lead-loaded canvas sheets or polyvinyl plstisol lead-loaded sheets, it has been difficult and costly to manufacture such materials since specialized equipment is necessary.

Accordingly, it is an object of this invention to provide an improved sheet material useful as a vibration dampening or sound deadening material.

It is another object of this invention to provide a method, such as a method employing paper-forming techniques and/or equipment or machinery, for the manufacture of sheet material useful as a sound deadening or vibration dampening or radiation shielding material.

How these and other objects of this invention are achieved will become apparent in the light of the foregoing disclosure and with reference to the accompanying drawing which schematically illustrates in an enlarged cross-section one embodiment of sheet material prepared in accordance with the practices of this invention.

It has been discovered that sheet material consisting essentially of inorganic fibers, such as asbestos fibers, and a latex, e.g. an elastomer latex, such as neoprene latex, and finely divided, preferably high density material, such as metallic material, e.g. powdered lead, the inorganic fibers being substantially felted together and coated and adhered together by the elastomer latex and formed into a sheet with the finely divided metallic material, preferably high density inorganic or metallic material, being maintained in the resulting formed sheet and affixed to the organic fibers by the precipitated elastomer latex, is useful as a pipe wrapping or vibration dampening or sound deadening material.

Preferably, the sheet material is coated on one surface with a water-impermeable or water-resistant material, such as bitumen or tar. If desired, one side of the resulting formed sheet material may be coated with a pressure sensitive adhesive so that the resulting coated sheet material can be readily affixed or attached to a surface. If desired, there may also be incorporated in the resulting formed sheet material a thermosetting agent which, upon curing, converts the sheet material to a substantially rigid or stiff sheet. It is preferred, however, that the sheet material be flexible or limp and made up of high density material, succh as finely divided or powdered lead, so that the resulting formed sheet material is especially useful as vibration dampening or sound deadening material, particularly with respect to low frequency vibrations.

In the make-up of the sheet material in accordance with this invention it is also preferred that the fiber content of the sheet material be comprised of substantially 100% inorganic fibers, such as at least about 60% by weight inorganic fibers. Particularly useful as asbestos fibers. If desired, however, there may be employed in place of or together with the asbestos fibers other inorganic fibers, such as carbon fibers, boron fibers, rock wool fibrous material, glass fibers, ceramic fibers, such as alumina fibers, and the like.

Further, as indicated hereinabove, or major or minor portion of the total fiber content of the sheet material may be comprised of organic fibrous material, such as paper pulp, paper, cloth and organic fibers, such as nylon, rayon, dacron, cotton, acetate, wool and the like. It is preferred, as already mentioned, that when organic fibers are present in the sheet material the organic fibers comprise less than 50% by weight fiber content based on the weight of the total fibers making up the sheet material, and desirably less than about 25-30% by weight of the total weight of the resulting formed sheet material.

In the sheet material in accordance with this invention there is also incorporated therein a finely divided or powdered inorganic, preferably metallic material. Particularly useful as the finely divided or powdered metallic material useful in the preparaton of the sheet material is finely divided or powdered metal. Substantially may powdered metal is usefully incorporated in and employed in the manufacture of sheet material in accordance with this invention. Suitably finely divided or powdered metals include, iron, brass, stainless steel, zinc, bronze, copper, beryllium, aluminum, silver, chromium, titanium, cobalt, nickel, tantalum, molybdenum and alloys or mixtures of one or more of the above.

Also useful as finely divided or powdered inorganic or metallic material useful in the sheet materials in accordance with this invention are such diverse materials as molybdenum disulfide, graphite, barytes or barium sulfate, zinc oxide, zinc sulfide, tungsten carbide, lead sulfide, lead oxide and the like. Desirably, and preferably, when the sheet material is to be used as a vibration dampening or sound deadening material the finely divided or powdered inorganic material is a high density material, such as a metal or inorganic material having a specific gravity greater than 5, preferably greater than 8. Particularly useful as a high density finely material making up the sheet material is finely divided or powdered lead or similar high density metals and compounds, i.e. specific gravity greater than about 10-12.

The elastomer latex employed as the binder for the associated fibrous material and inorganic or metallic material making up the sheet material of this invention may be substantially any commercially available elastomer latex. Suitable elastomer latices would be a butadiene-acrylonitrile latex, such as Buna-N, neoprene latex, a styrene-butadiene latex, and acrylonitrile-butadiene-styrene latex, a polybutadiene latex, a polyisoprene latex, natural rubber latex, polyvinylchloride latex and the like.

It is preferred in the practice of this invention to employ a latex, such as acrylonitrile-butadiene latex or neoprene latex of polyvinylchloride latex, which is weather and/or oil resistant and which imparts suitable properties of flexibility and/or limpness and toughness and stability to the sheet material as well as non-flammability.

The amount of latex making up the sheet material is a minor amount, such as less than 20% by weight of the sheet material, usually in the range 2-10% by weight of the sheet material, as opposed to the fiber content which would be in the range not more elastomer about 50-60% by weight of the sheet material, usually in the range 5-30%. The finely divided or curing inorganic or powdered material making up the sheet material of this invention usually comprises a substantial amount of the 53 material, such as at least about 10-20% by weight. Desirably, and preferably, in accordance with this invention, the finely divided powdered inorganic or metal material makes up at least 50% by weight and most desirably at least about 65-70% by weight on up to about 85-90% by weight of the sheet material, especially when the sheet material is to be employed as a vibration dampening or sound deadening or radiation shielding material.

There may also be incorporated in the sheet material other materials, such as an antioxidant or heat and light stabilizers for the latex component thereof, to improve its weathering properties and resistance to oxidation, filling agents or color agents, such as inorganic materials, e.g. calcium carbonate, or dyes to impart a desirable color to the sheet material. Also, as indicated, particularly when a stiff or rigid sheet material is desired, there may also be incorporated in the sheet material during its manufacture a cross-linking agent effective upon curing to react or cross-link with the elastomer component. If desired, there may also be incorporated in the sheet material during manufacture a minor amount of a thermosetting resin effective upon curing or thermosetting to impart stiffness and/or rigidity to the resulting formed sheet material.

Further, as indicated hereinabove, the sheet material may be coated on one or both sides or surfaces with a pressure-sensitive adhesive or other suitable adhesive material so that the thus adhesive-coated sheet material may be readily and easily attached to a surface, such as a supporting surface, by merely applying the adhesive coated surface of the sheet material thereto. When the sheet material is adhesive-coated on both sides and after application or affixing one side of the sheet material to a supporting surface there may be applied to the other or remaining exposed adhesive-coated surface of the sheet material another material or structure so that the adhesive-coated sheet material is incorporated or installed between two structures or surfaces.

For handling purposes the pressure-sensitive or adhesive-coated surface of the sheet material has attached thereto a peelable or readily removable coating or layer of material, such as a plastic film or waxed paper, which would be stripped from the adhesive-coated surface just before the adhesive-coated surface of the sheet material is applied to the structure or surface to which the sheet material is to be attached or installed.

It has been mentioned hereinabove that the sheet material in accordance with this invention in at least one embodiment is capable of being manufactured on conventional web or paper forming equipment. The fact that the sheet material of this invention which includes a substantial amount of finely divided or powdered inorganic material, such as finely divided lead, can be satisfactorily manufactured on paper or other sheet-forming equipment is surprising since it would appear that one would expect that there would be a substantial loss or drainage away of the finely divided powdered metal with the water flowing or draining through the paper or sheet-forming screen.

In the accompanying drawing there is illustrated in enlarged partial cross-section an example of one embodiment of the sheet material in accordance with this invention. Specifically, there is illustrated, generally indicated by reference numeral 10, sheet material made up of a layer 15 composed of inorganic fibers 11, such as asbestos fibers, upon which is precipitated an elastomer latex 12, such as neoprene latex. Within layer 15 made up of inorganic fibers 10 and precipitated latex 12 there is substantially uniformly dispersed therein finely divided metallic material 14, such as powdered lead, having a particle size smaller than 200 mesh. This flexible coherent layer 15 has applied on one surface thereof layer or coating 16 of pressure-sensitive adhesive material. Desirably, for handling purposes, there is applied to layer or coating 16 a protective or peelable top coating 17 of paper, plastic film or other material which readily strippable, such as by peeling, from pressure-sensitive adhesive layer 16. The other side or surface of layer 15 has applied thereto coating or layer 18 of weather resistant or water-proof material, such as bitumen or tar. If desired, coating or layer 18 may be replaced or have applied thereto a decorative type film, such as a decorative plastic film, e.g. Mylar decorative film, or a polyvinyl chloride or polyolefin decorative film, e.g. polyethylene or polypropylene.

In the use of the illustrative sheet material 10 as a sound deadening or vibration dampening material, with the lead content of the layer 15 comprising about 70-80% thereof, strippable protective coating 17 would be removed from a measured length of the sheet material 10 and the resulting exposed pressure-sensitive layer 16 would be applied directly to the surface to be protected or affected, such as to block radiation, to prevent or reduce sound transmission or vibration therethrough. There would be exposed surface 18 which could, as indicated hereinabove, be a water-resistant or weather-resistant coating, such as bitumen or tar or, for decorative or indoor purposes a decorative plastic film.

In the manufacture of the sheet material of this invention employing conventional paper or sheet-forming equipment, such as equipment useful for the manufacture of sheet asbestos, there is formed a watery admixture or furnish made up of the fibrous materials, such as asbestos fibers, and the elastomer latex, such as an acrylonitrile-butadiene latex, e.g. Buna-N latex, with the wetting or wetting down of the fibrous material in the water, preferably with the aid of a wetting or dispersing agent, such as an anionic surfactant, such as Darvan, a sodium salt of polymerized alkyl naphthalene sulfonic acids or sodium salts of polymerized substituted benzoid alkyl sulfonic acids or aryl alkyl sulfonic acids, e.g. Darvan No. 6 manufactured by R. T. Vanderbilt Co., New York, N.Y. The finely divided metallic or inorganic material is then added, such as finely divided powdered lead having a particle size smaller thatn 200 mesh. After agitating the resulting liquid admixture or furnish made up of asbestos fibers, elastomer latex, lead and dispersing agent, precipitation of the latex onto the fibrous material, such as the asbestos fibers, and to some extent onto the finely divided powdered inorganic material takes place, usually within about 5 minutes. Desirably, a trace amount of an aqueous calcium chloride solution, 10% by weight CaCl.sub.2, is added to effect complete precipitation and clarity in the watery admixture.

The resulting watery admixture now containing the ellastomer latex substantially and completely precipitated onto the fibrous material is heated, such as to a temperature in the range 100.degree.-150.degree.F., e.g. about 130.degree.F., and pumped or agitated for a short time, such as for not more than a few minutes, e.g. about 10-60 seconds. The resulting watery admixture or furnish is then flowed onto or discharged onto a paper-making screen or surface.

Upon discharge of the watery admixture to the paper-making screen or surface the asbestos fibers become at least partly felted and adhered together by the elastomer coating. The elastomer latex coating also serves to entrap or entrain the finely divided or powdered inorganic or metallic material, such as finely divided lead, together with the fibrous material with the result there is formed a substantially uniform and homogeneous sheet material consisting essentially of the fibrous material, elastomer latex and the finely divided or powdered inorganic or metallic material is substantially the same proportions or relative amounts as orginally employed in the make-up of the above-described watery admixture.

After the formation of the sheet material on the screen or sheet-forming surface it is removed, desirably after water has been expressed therefrom, such as by passing in contact with a pressure roll, and the resulting sheet material now having a reduced water content, below about 10-20% by weight, is dried by wrapping around heated "can" or drums or by tunnel drying, such as by passing the resulting sheet material through a tunnel in contact with heated air at a temperature in the range 120.degree.-250.degree.F., more or less. Upon drying the sheet is passed through a calendering operation and there is produced a flexible, coherent substantially limp material having a substantially reduced, less than about 1% by weight, water content.

A number of sheet materials in accordance with this invention were prepared generally in accordance with the above-described procedure. The formulation, make-up, properties and procedure for the manufacture of these sheet materials are set forth hereinbelow in the accompanying tables.

TABLE NO. 1 __________________________________________________________________________ FORMULATION 1 2 3 4 5 6 7 8 Composition lbs. lbs. lbs. lbs. lbs. lbs. lbs. lbs. __________________________________________________________________________ Bleached sulfite 9 9 9 9 -- -- Asbestos fibers 21 21 21 21 30 30 30 30 Anionic surfactant (dispersant) No. 6 Darvan, a surfactant manu- factured by R.T. Vanderbilet Co. Inc. 0.06 -- -- -- 0.06 0.06 Acrylonitrile- butadiene latex, BUNA-N, TN-4105A (dry) 10.2 10.2 10.2 10.2 -- -- 10.2 -- Neoprene latex Neoprene 450 (dry) -- -- -- -- 10.2 10.2 -- 10.2 10% by weight aqueous calcium chloride solu- tion trace trace trace trace trace trace trace trace Lead, particle size -200 mesh 5.1 51.0 102 204 102 204 102 102 Drainage-seconds 0.9 0.9 1.1 0.9 3.2 9.0 Pressure (tons) 13 20 10 10 10 10 Caliper (thick- ness) inch 0.0385 0.0417 0.0529 0.061 0.054 0.068 Tensile lbs. pull 59 53 41 33 -- -- Tensile psi 1475 1226 733 490 -- -- % by weight rubber (total solids) 22.7 11 7.2 4.2 7.2 4.2 % by weight lead (total solids) 11 55 72 85 72 85 72 72 __________________________________________________________________________

TABLE NO. 2 __________________________________________________________________________ 9 10 11 12 Furnish Grams Grams Grams Grams __________________________________________________________________________ Asbestos fibers 40 40 40 40 Polyvinylchloride latex (dry basis) 12 12 -- -- Neoprene latex (dry basis) -- -- 12 12 Powdered lead 120 120 120 120 Santo-white -- -- 1.2 1.2 Calcium chloride (10% solution) 10 ml. 10 ml. 15 ml. 15 ml. Pulping time (seconds) 14 14 14 14 Consistency (%) 3 3 3 3 Precipitation Temp. .degree.F. 80 80 80 80 Drainage Temp. .degree.F. 100 100 100 100 Caliper (inches) 0.0560 0.0584 0.0553 0.0562 Weight 6".times.6" (grams) 90.88 97.4 103.6 102.3 Weight 500 ft..sup.2 (lbs.) 400.23 428.94 456.25 450.52 Density (lbs./cu.ft.) 171.52 176.27 198.01 192.39 Tensile (lbs. pull) 32.5 44.5 57.25 61.75 Tensile (psi) 575 723 1133 1199 Drainage (seconds) 0.85 0.95 2.4 1.9 Wire Release Ex Ex Ex Ex Precipitation time (minutes) 25 23 10 22 Lead settling 0 0 trace trace __________________________________________________________________________

In the preparation of the sheet material in accordance with this invention employing the formulations indicated in Tables Nos. 1 and 2 and following the procedures described hereinabove, it was observed that no lead or only trace amounts of lead were found in the drainage. All formulations had excellent wire release from the sheet-forming screen.

Sheet materials in accordance with the above-described technique and made up of neoprene as the elastomer latex and Buna-N as the elastomer latex and containing 72% by weight powdered lead were very flexible and had a density about 155-159 lbs./cu.ft. and weight 53 lbs./100 ft..sup.2 at 0.041 inch thickness.

The sheet materials prepared in accordance with the above formulations and procedures or techniques have a wide utility and permit a wide range of formulation. For example, and particularly useful as vibration dampening or radiation shielding, sheet materials consisting essentially of powdered lead, asbestos and elastomer latex are readily prepared. Such materials would resist acid and alkali attack, would tend not to become brittle on weathering, would resist cold flow and flow at elevated temperatures, would exhibit good flexibility for easy installation and, as indicated hereinabove, could readily be prepared in various thicknesses. Because of the above-indicated physical properties sheet materials prepared in accordance with this invention would be usefl as radiation shielding materials for use in connection with radar cooking equipment, x-ray equipment, instrument shielding, radioacative clean rooms, television sets and pipe wraps, especially wraps for pipes containing radioactive materials. These materials would also be useful as noise deadening material, useful for sound insulation with respect to walls, roofs and doors, such as by being laminated to or fixed to doors and walls or enclosures of rooms containing compressors, pumps, generators, engines, as well as for insulation in submarines to prevent noise leakage and for use in vibration dampening, e.g. in connection with natural gas transmission lines, particularly on lines in close proximity to compressor stations. The materials of this invention would also be useful as gasketing materials. The materials of this invention would also be readily useful as specialized roofing material and the like, for use in connection with outdoor installations and the like.

As will be apparent to those skilled in the art in the light of the foregoing disclosure, many modifications, alterations and substitutions are possible in the practice of this invention without departing from the spirit or scope thereof.

Claims

I claim:

1. Sheet material consisting essentially of asbestos fibers, a polymer latex selected from the group consisting of neoprene latex and acrylonitrile-butadiene latex and finely divided lead, said asbestos fibers being present in said sheet material in an amount in the range about 5-30% by weight and being felted together and coated and adhered together by said polymer latex and formed into a sheet, said polymer latex being present in said sheet material in an amount in the range abour 2-20% by weight and said finely divided lead being maintained in the resulting formed sheet material and affixed to said asbestos fibers by said polymer latex, said finely divided lead comprising at least about 50% by weight of said sheet material.

2. Sheet material in accordance with claim 1 wherein said finely divided lead has a particle size smaller than 200 mesh.

3. Sheet material in accordance with claim 1 wherein said polymer latex is neoprene latex.

4. Sheet material in accordance with claim 1 wherein said polymer latex is a acrylonitrile-butadiene latex.

5. Sheet material in accordance with claim 1 wherein a coating of a pressure-sensitive adhesive is applied to at least one surface or side of said sheet material.

6. Sheet material in accordance with claim 1 wierein a coating of pressure sensitive adhesive material is applied to both sides or surfaces of said sheet material.

7. Sheet material in accordance with claim 1 wherein a coating of pressure-sensitive adhesive material is applied to at least one side or surface of said sheet material and a film or layer of protective, strippable or peelable material is applied on top of said coating of pressure-sensitive adhesive material.

8. Sheet material in accordance with claim 1 wherein said sheet material has a thickness of about 0.01 to about 0.25 inch.