US2193401A - Sound deadening composition - Google Patents

Description

106. CDMPOSITIONS,

COATING OR PLAST|C.

Patented ar. 12, 1

UNITED STATES PATENT OFFICE SOUND DEADENING COMPOSITION Benjamin Foster and Carl J. Seydel, Philadelphia, Pa., assignors to Benjamin Foster Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Application July 30, 1938, Serial No. 222,294

2 Claims.

This invention relates to methods of making. and to the products, sound deadening compositions that are also fireproof. The invention is particularly concerned with the methods of making, and the resulting products, of bituminous compounds which are used in sound and heat insulating installations.

The art of sound deadening and insulating metal vehicle bodies, such as automobile, train, airplane, and railway box cars, and the sound deadening and insulating of metal ventilating and air-conditioning ducts, metal wall partitions, metal doors, etc., has been highly developed in recent years. However, nearly all of the products used have serious objections which are due to the fire hazard present. This hazard exists because, either the sound deadener, or insulator itself, is not fireproof, or because the cement used to fasten a fireproof deadener in place on a structure is not fireproof.

This invention has for its objects to provide a sound deadening and fireproofing composition which may be applied to the surfaces of metal structures of all kinds, either as a,plasiic..cemiig to be applied with a trowel, or sprayedmpnathe surfaee-to-be-oeated; or asuitable fabric such as burlap, or sheet asbestos, may be sajgrated with the composition, and the saturated sheet then secured to the surface to be coated by a layer of the plastic composition, and thereafter another layer of the plastic composition may be sprayed or otherwise applied to the installed saturated fabric sheet. Other methods of applying the plastic composition are described herein.

By sound deadening we mean the actual deadening of the tone emitted by a piece of metal, which of course has been set in vibration, and which has been treated by the application of some material applied for this purpose. This "deadening effect is brought about, conventionally, by the application of a bituminous plastic material, or by cementing a piece of saturated or unsaturated roofing felt to the inside of the outside panel. The above method of deadening is most generally used on metal automobile bodies. In the case of a metal railroad coach or car a thick pad of hair felt is sometimes used. This is fastened in place with an asphalt adhesive. The eiiect of these materials is to lower the "natural frequency of the vibrating panel, and to slightly decrease the total volume of sound emitted, and to act as a damper on the panel thereby shortening the duration of the sound. As an illustration, a sheet steel panel about 20 inches by 20 inches by one-fourth inch thick, will normally vibrate at a frequency of about 140 cycles per second. Such a steel panel, uncoated, when set in vibration will continue to emit an audible tone for about 25 seconds, whereas after coating with an efficient "sound deadening composition will become silent in about 8 seconds; and in some cases, in a still shorter time. This shortening of the duration of the time of the sound is called the decay time.

Again referring to the bituminous plastic materials" which are extensively used, these compounds consist of an :edissglvedimm mineral or coal tar sgl to which is added a pr Em 1g so mng points. The solvents vary from slow to quick drying volatile distillates. The fillers vary in particle size and composition. There is generally, but not necessarily, asbestos fibre present, either alone, or in com na ion with the other fillers, which latter may be granulated cork, ground mica, ground charco ahpawdered mineral mattE'E'Torexample talc 9:99?" -dered-sand, or fireman material. Another sound deaTd'i'ierTbut one Which'isnot so extensively used, consists of a clay type sion, either alone or igmentegl with the fille'r's E'Esb'fibed above, and somecases weighted with a suitable grade of sand.

The plastic type o'Tsound deadener described above is generally applied in thicknesses of inch to inch, by using a spray gun made expressly for this purpose, or by brushing, or trowelling.

The objections to these types of products are many, but the greatest one is the fact that none of them are fireproof, The solvent type sound deadener is easily burned either in the wet or dry state. The asphalt emulsion type of sound deadener is not easily burned in the wet state (it is necessarily not combustible because of the water present) but is relatively easy to burn in the dry state.

The primary importance of a sound deadening material is efliciency." This of course will embody such requirements as: sound deadening value, flre resistance, ease of application, resistance to wear, adaptability to plant conditions such as (in the case of automobile bodies) baking, oil baths, alkali baths, etc. Of secondary importance, but nearly as great as emciency is low cost. This not only refers to original cost per gallon, or pound, but also to the finished or applied unit cost. It is obvious that the more efficient a deadener per gallon or poimd, the

e asphalts vary from low to V Examiner smaller the quantity required to produce a desired efiect.

The invention described herein meets all of the requirements outlined above, together with 5 several other desirable characteristics. In the first place it is fireproof in both the wet and dry state. Also, when applied with the aid of an air gun the pressure required to force the compound from the pressure tank to the gun is in the neighborhood of 35 pounds per square inch, or less, as compared with the conventional 80 pounds per square inch minimum required for inflammable sound deadening compounds. With the new type there is no danger of explosions in the pressure tank, and practically no deteriorating action on the rubber hose which is used to supply the gun from the pressure tank.

It is common knowledge that bituminous materials such as asphalt, pitgh, rosin, and gsins, etc., are more or less waterproof. They are Eer'tainly insoluble in water. They are also thermoplastic. It is possible to prepare dispersions of these products in water, but no solution takes place. This particulaTart of dispersing bitumens in water is quite well covered by the prior art. It is not only impractical but impossible to dissolve the common inorganic salts in either asphalt or pitch. It is therefore not possible to take advantage of the fire resisting properties of these salts by any method known to date.

discovered a method of incorporating certain g1grganiosalts with asphalt or pfl'ch, and we obtain as a result a compound which is an excellent sound deadener, and also pomesses the desired fireproof qualities.

In the manufacture of our sound deadening bituminous compound, several materials can be used, and as many or more ways of combining them. For example, we can first prepare a cla type bituminous emulsion consisting of approximately 40%-4 as halt, 5%-'7% cla and 48%-55 w. To this preparefii'ilsion we can mix in approximately twice its weight of a solution of my water soluble fire roofing agent. This fireproofing agent can be a 5570 5570 [or greater if so desired) solution of any of the fol- -a lowing: so i state, ammonium-magnesium hos a e, sodium borate, We calcium chloride, or omum silicate. 60 owever; Because of cost, we' pre er to use solution of sodium silicate. This is a commercial product and is commonly known as water lass, silicate of soda, and sodium silicate." How- 'ever, 15 1s commercially available as a thick so- 66 lution having varying gravities, and is designated as 405060 etc. Banm. In our composition we can use any of these grades depending upon the characteristics which we desire to impart to the product. After the addition of our fireproofstirring in, for example 15%-20% by weight of F351; fibre and an equal quantity of granuated cork or mica, or charcoal, or a similar material, o a su a e m1 ereof. If we so 05 desire we can adjust the consistency of this finished product to enable it to be sprayed, brushed, or trowelled, simply by the addition of more fillers (if we desire it to be stiiIer), or by the addition of the combined asphalt emulsion and fireproof- 70 ing solution (if we desire it to be thinner).

"Ihdbhibxample of how we can prepare the fireproof bituminous compound follows-we can prepare a clay type bituminous emulsion in the conventionmer'anmefiadd directly to 75 this emulsion the fillers mentioned in the foreclng agent we can add to the mix a filler by simply We have fireproof bituminous compound and which we can 10} use if we so desire, but which should be used soon after preparation, consists of preparing an ashaltic cutback in the usual manner. That 155 melting the as halt and while still molten adding a volatile solvent to reduce the consistency to a 15 ChlCE solution when cold, or at room temperature. We can also use any of the asphalt cutbacks which are commercially available. In either case, whether we prepare the cutback, or purchase it in its liquid form, we simply mix in the fillers 20 which again consist of asbestos, mica, ground 25k, charcoal, etc. The proportions are the same as'given in the last example, namely, 30 7 1- 40% asbestos, and 30%-40% of the other materials. esultant product is a heavy plastic 25 material. To this we simply add the aqueous salt solution and thoroughly mix it in. When making t is of compound it is necessary to add the preferred salt solution (silicate of soda) slowly, in order that no subsequent sepaimakes place. 30 The quantity of fireprooflng agent will be approximately twice that of the combined cutback and fillers.

It is possible to make any or all of the described mixes by hand, that is, by stirring together the 35 various materials; but it is desirable in commercial practice to use a power driven mixer. This mixer can be a paddle type horizontal or vertical device, or it can be the so-called ribbon type" mixer. This latter type differs from the paddle 40 type only in that it has a series of ribbon-like arms fastened to the ends of the paddles. It is desirable to maintain a peripheral speed of from about 100 to 150 feet per minute when loaded.

In order to secure certain characteristics in the 45 fireproof bituminous compound, we can vary the melting point and penetratiqngf the asphalt used; or we can vaTy the grade of silicate'ofs'oda or other aqueous salt sgl utpmemfexample, if we desire a bituminous compound having a very quick set and which, when dry, will be quite plastic, we can use a solution of sodium silicate having a Baumg gravity of say miidan'as phalt cutback or an Wesson prepared ifofn a s aft asphalt wltl'i'f'iiltifig'pfiint of about 90- 95 F. (ball and ring). Ifwe desire the same setting time, and want the dried film to be quite hard, we can use a cutback or emulsion made from an asphalt having a melting point of about i90-200 F. (ball and ring). If on the other hand we desire a slow setting bituminous compound, we can use a solution of silicate of soda with a Baum gravity of about 60. By varying the melting point of the asphalt we can have the dried film either soft nhard, as we may choose. Also it is possible to obtain combinations of these properties by using an asphalt with a melting point somewhere between 90-200 F. (ball and ring), and a solution of silicate of soda having a Baum gravity somewhere between 40-60.

The sound deadening composition prepared in any suitable manner, is a thick viscous mass at ordinary temperatures, and as noted above may be applied to a vertical surface to a thickness of as much as three-eighths of an inch without 76 flowing or sagging. During air drying, a setting occurs, the entire mass self-welds and hardens into an impervious and durable non-brittle layer. The asphalt or similar bitumen has the property of imparting a permanent adhesive or wetting" property to dried inorganic salt fllms, for example, sodium silicate films, when the wet plastic is applied to a metal surface.

The prepared sound deadening compositions ready for application, may be applied at ordinary temperature, about '70 F. They may be applied to cold or hot (upwards to about 200 F.) metal surfaces. The compositions may contain ingredients in the following approximate proportions: in the as halt cutback type, .the asphalt may be presen in from about 15% to about 20%; in the play; 1 e the emulsion may be present in from about 15% to about 30%. With both types, there may be about 15% of volatile solvent present. The filler, including asbestos, cork, tal c, etc., may be present in from about 6%120 about 10%. The aqueous soh tgn pf inorganic salt, for example, sodium silicate as descri 'h'efin, may be presehFififi'dhTabout to about After air drying for a week or longer, the water content in the dried coating will be from about 5% to about 7%.

The improved sound deadening bituminous compounds described above exhibit properties which are quite foreign to previous bituminous admixes. For example, if any of them is applied to a piece of steel or other metal, it readily adheres to it even though it be in thickness of threeeighths inch or more. When freshly applied the compound can be subjected to the open flame of a Bunsen burner without showing any evidence of burning; the flame can be applied to either the coated or uncoated side of the metal. If this test is conducted on the conventional cutback type deadener (which contains no aqueous salt solution), it immediately catches flre and burns if the flame is applied to the coated side of the metal. If the flame is applied to the under side or uncoated side, as soon as the solvent is slightly heated it flashes and burns.

When the uncoated side, or coated side, of a metal panel to which has been applied our improved sound deadening bituminous compound, is heated with a Bunsen burner flame the volatile solvent and the water are evaporated together and prevent the ignition of the said solvent. The silicate of soda or other salt then fuses and prevents the further vaporization of the asphalt. It is not our intent or purpose to heat a panel containing this compound to such a degree that the silicate of soda or other salt fuses; but in the event that sufllcient heat be applied. this fusing Lxammer action will take place and prevent the ignition of the dried compound. When this fusing action has taken place the sound deadener coating no longer has its original sound deadening properties. One test, which demonstrates the fire resistance of the wet film, was conducted by spraying a one-fourth inch thick coat of the sound deadening bituminous compound upon a 19 gauge cold rolled steel sheet, two feet square. While still wet, this panel was cut in two by using an oxy-acetylene flame. No burning of the compound was detected. It fused quite hard adjacent the cut but did not flame or burn. When the same test was conducted on the conventional cutback type sound deadener it was impossible to cut the sheet in half until all of the solvent and the asphalt had burned out of the mass. These tests, of course, are related here for the sole purpose of demonstrating the fire resistance of the new compound. However, there are occasions, during the manufacture of a bus, for example, where slight mechanical changes or repairs must be made shortly after the application of the sound deadener composition. When such changes necessitate the use of electric or gas welding, the possibility of serious fire damage is present when the conventional cutback type deadener is used. This fire hazard, as already pointed out, is not preesnt when our improved sound deadening bituminous compound is used.

When our improved sound deadening bituminous compound is applied one-fourth inch in thickness upon metal, it can be either oven dried at temperatures up to 350 F. without sagging out of its original position, or without slipping or running or blistering. It also can be air dried and then subjected to temperatures 0 e or er of 350 F. and still retain its original form. After either air dryingmr oven baiting, it will withstand the same fiamet"esfs'as the wet film. Air drying requires from 24 to 48 hours.

We claim:

1. A homogeneous sound deadening composition comprising from about 15% to about 30% of an aqueous clay type emulsion of thermoplastic bituminous material, from about 6% to about 40% of a filler, and not less than about 30% of an aqueous inorganic salt solution of substantially a 50% to about 60% concentration, said inorganic salt having fireproofing properties.

2. A sound deadening composition, as in claim 1, in which the aqueous inorganic salt solution is a solution of sodium silicate of about 40 to about 60 B., and is present in from about 50% to about 70%.

BENJAMIN FOSTER. CARL J. SEYDEL.