US3348996A - Acoustical panel having openings and ceramic surfacing material bonded to the panel - Google Patents

Description

United States Patent 3 348 996 ACOUSTICAL PANEL HAVING OPENINGS AND CERAMIC SURFACING MATERIAL BONDED T0 N THE PANEL John E. Cadotte, 2427 Western Ave. N.,

St. Paul, Minn. 55110 No Drawing. Filed Apr. 7, 1966, Ser. No. 540,809

, 2 Claims. (Cl. 162-114) This application is a continuation-in-part of my copending application Ser. No. 427,545, filed Jan. 25, 1965, as a continuation-in-part of the now abandoned applications Ser. No. 149,199 and Ser. No. 193,299, filed May 8, 1962 as a continuation-in-part of said Ser. No. 149,199, filed 'Nov. 1, 1961. i

The present invention relates to acoustical panels having a porous sound-absorbing body portion free of organic content and consisting essentially of ceramically bonded fiber felt and particulate ceramic material such as clay distributed throughout the felt. The porous body portion has a multiplicity of acoustical openings exposed to the receipt of sound and extending into the body portion from one face thereof.

Feigley et al. No. 3,014,835 discloses various combinations of equal parts of mineral fibers and of particulate .er than drilled holes, have been widely used as acoustical panels, especially in ceilings. Such panels in felted fiber form having mineral fibers, or vegetable fibers, or a mixture of such fibers have been widely used as lay-in panels, for example, panels 2 ft. by 4 ft. in size, supported by underlying marginal support flanges. In such panels the fibers are bonded by adhesive, usually starch. The fibers in the case of vegetable fibers, and the adhesive in the case of starch or like adhesives, are adversely affected by humid air, and at high humidity, tend to soften and allow the panel to sag.

The present invention modifies porous fired felted mineral fiber panel material, disclosed in and comprehended by my copending application Ser. No. 427,545, and its said predecessors. Therein, panels are formed from mixtures of 100 parts of feltable fiber predominating in mineral fiber and from to 250 parts of particulate material, the mineral fiber consisting in one type of operation of 75 to 88 parts of synthetic mineral fibers, such as mineral wool, and from 2 to parts of asbestos fiber-s, with from 0 to 10 parts of cellulosic fiber, exemplifying use of 30 parts of kaolin clay to 100 parts of such feltable fiber to produce a porous dry unfired mat of pounds per cu. ft. The presence of vegetable fibers in the preform for firing enhances porosity of the fired panel but lessens the strength of fired panels.

For the present invention wherein adequate porosity is desired, the particulate material is used in amount not greater than the amount of the fibrous material. Such panels are characterized by a porous fibrous-network resulting from firing a mineral fiber felt in the presence of particulate material which in the firing is ceramically bonded to the network, being originally substantially uniformly distributed in the unfired mineral fiber felt, referred to as a preform for firing.

In my said copending application there is described a method of producing the preform of the mineral fiber felt Calcium chloride 0 Water ice carrying the particulate material by forming a slurry of the fibers and the particulate material, with or without a binder, preferably starch, flocculating the slurry and dewatering the suspension of tlocs to form a wet mat. The wet mat has a variable density dependent upon the method of dewaten'ng, which may or may not include suction through the mat. Such density of formation may be increased by pressing. The higher the density the less porous is the mat when dried, but the strength is greater for handling the wet or dry mat.

Strength of the dried mat is greater by including a bind- -er in the slurry to bond the contents of the mat upon drying. Starch is the preferred binder. However, clay as the particulate material has a slight binding action, but increased content of clay leads to greater density of formation and this minimizes porosity. Although starch may be used in solution form, starch grains are preferred for convenience. In either form the starch is fiocculated so that it is not freely suspended in the water drained away. As described, a small quantity of a surface active flocculant is used, such as a polyac-rylamide flocculant, preferably with a small quantity of a polyvalent metal salt, as illustrated hereinafter.

In firing, the first effect is to burn out or carbonize the organic material. In the case of starch a carbon residue is first formed which on prolonged exposure can be oxidized, if desired, but its presence in the resulting small quantity is of no consequence relative to acoustical value, and to appearance when surface coating is practiced. Since the fired product has acoutic openings, it is preferred to form them in the dried mat before firing, thus creating bonded. Bonding temperatures up to 2000 F. may be used to retain the described porous skeleton network. Higher temperatures can lead to fusion and thus lessen porosity.- V

In firing such a drilled or punched starch-bonded dry mat, it has been found that the porosity and sound-absorbing capacity are increased over those properties of the dry mat. By firing it, and thus eliminating the starch, ability to sag with humidity is eliminated.

The invention is illustrated by the examples given below, in which the amount and kind of particulate material and the firing temperature may be varied.

To a slurry containing parts of mineral fibers, and particulate material, with or without binder, is added a solution:

Parts The'slurry is thus converted to flocs suspended in substantially clear water, which is quickly drained away by pouring the slurry on a screen, as is done with a fiber furnish on a 'Fourdrinier machine. The resulting wet mat is pressed to a suitable density and dried. When starch grains are used, the wet mat is heated in a humid atmosphere to .gelatinize the starch grains, and then dried to bind the contents with the dried starch. The mat is then either drilled or punched with acoustic holes and fired to bring about ceramic bonding.

The firing temperature can vary over a wide range, but is chosen so as .to avoid fusing the fibers, thus to preserve a skeleton structure. This is strengthened by the ceramic bond as the, firing temperature increases.

A dry felted-mat without binder formed from 100 parts of mineral wool and 50 parts of Stratton (kaolin) clay,

Polyacrylamide was divided into segments and these were fired at temperatures over a long range, and the modulus of rupture determined. Without binder, the modulus of rupture is very low, large sizes requiring great care in handling. The

" following table shows how the modulus of rupture is increased by firing:

Pounds/sq. in.: Temperature, F.

45 800 90 1,200 123 1,400 105 1,600 110 2,000 (Tends to melt) 2,200

Fired panels of the above composition produced at different densities were tested for the void space therein, with results as follows:

Density, lbs/cu. ft.: Volume percent, void space The less void space, the poorer is the sound absorption. It has been found that as the kaolin is increased in proportion, the dry mat and the fired panel become more dense with a fixed procedure. Hence, the amount of clay for the present invention is not in excess of the amount of fiber,'and preferably is maintained appreciably below the amount of mineral wool, thus less to fill the voids in the fired skeleton network.

The above table shows that above a density up to 50 lbs/cu. ft., the void space of a fired panel begins to decrease. The following examples illustrate.

EXAMPLE 1 Glass wool is employed.

Parts by Weight Glass wool Kaolin clay 100 Starch grains 1O Polyacrylamide flocculant 0.04 Calcium chloride 1.0 Water 6000 The dried mat Thickness inch 0.882 Density lbs./cu. ft 33 Preform fired at 1420" F. Shrinkage:

Thickness percent 6.4 Area dimensions do- 0.4 Density lbs./cu. ft 32.7 Modulus of rupture lbs./sq. in-.. 178

' EXAMPLE 2 Parts by weight White slag wool 100 Kaolin clay 100 Calcium chloride 0.5 Animal glue (dry solids) 5 Polyacrylamide flocculant 0.08 water- 3700 I. f The dried mat Thickness inch .575, Density lbs./cu. ft 49.7

' Preform fired at 2000" F. Shrinkage: v Thickness v percent 1.8 Density do 1.5 Density 1bs./cu. ft 49.7

Modulus of rupture lbs./sq. "in 2482 4 EXAMPLE 3 Parts by weight White slag wool 100 Kaolin clay 50 Ground felspar 50 Tapioca starch grains 10 Water 3700 Polyacrylamide flocculant 0.08 Calcium chloride 0.5

The dried mat Density lbs./cu. ft 48 Preform fired at 2000 F Shrinkage:

Thickness percent 0.3 Area dimensions do 0.8 Modulus of rupture lbs./sq. in 167 The low shrinkage indicates substantially no decrease in density on firing.

In the following Example 4, the dried mat was drilled in a random manner with 4-inch and Y -inch diameter drills totaling 319 holes per sq. ft.

The acoustic property of the panel of Example 4, known as d was determined by the standard impedance tube test of American Society of Testing Materials, designated C384-56T. This is the average of 0:0 for sound at 250, 500, 1,000 and 2,000 cycles per second.

Solid Back 10 Airspace Before firing After firing The board was inch thick before firing.

.The test shows that the generally unacceptable d of the punch unfired panel was increased to acceptable values merely by firing.

In order to present an acceptable surface appearance, the fired board may have selected ceramic material on its surface ceramically bonded to the body portion. This may be applied to a fired board, which is again subjected to a firing temperature to efiect the bond. Preferably, it is applied to the mat before firing so as to produce, a cerarnically coated fired board in one firing step.

On the main body portion, in one case, an engobe may be formed by applying to the surface selected ma terial which in the firing sinters to a non-homogeneous covering coat, rather than to a glassy structure or glaze. Such an engobe may form the entire exposed surface of the board. The engobe or the fired board without the 'engobe may be partly or entirely covered by a slip applied to form a glaze coat. The engobe is selected to provide a color or texture for the exposed portions of it, thus to hide the color or appearance of the underlying fired body portion. When glaze is formed in a discontinuous coat, such as in spotted areas, the engobe and EXAMPLE 5.-Engobe base composition An engobe was produced by the following:

Parts by weight, grams Kaolin clay 166 Slag wool, powdered 334 Water 450 Sodium tripolyphosphate 1 Commercial ceramic frit 50 1 Such as Ferro 3466 made by Fen-o Corporation of Cleveland, Ohio.

EXAMPLE 6.Glaze composition For application to form a glaze on firing, the following was prepared:

Parts by weight, grams Commercial frit (Ferro 3466) 396 Chromium oxide pigment 4 5% Methocel 80 Water 115 EXAMPLE 7 A dry unfired board formed as above described, and acoustically drilled, made from 100 parts of mineral wool and 50 parts of kaolin clay, at a density of 40 lbs./cu. ft. is coated with engobe, preferably by spraying the entire surface. In using the engobe base composition of Example 5, 5.5 parts if zirconium oxide pigment is added to 200 parts of said composition to produce a white engobe coat. This coat is-dried.

Then onto the engobe is applied a glaze composition, specifically that of Example 6, by spraying at a pressure of 15 to 20 pounds per sq. inch, to form a discontinuous coat in the form of spattered areas for the final glaze. This is then dried, and the whole fired at 1850 F. Spotted green glaze areas with the white background of the engobe gives a decorative effect on a punched or drilled ceramic acoustical board.

The invention is not limited to the exemplary examples, and numerous combinations of ingredients and of processing steps and variations thereof, are contemplated as falling within the scope of the appended claims.

I claim:

1. An acoustical panel having a porous sound-absorbing body portion consisting entirely of inorganic material and essentially of a ceramically bonded porous body of a mineral fiber felt and of particulate ceramic material, said mineral fiber predominating in synthetic mineral fiber, the particulate ceramic material being present in quantity not exceedng the quantity of fiber, said body portion having a density up to pounds per cubic foot and having a multiplicity of acoustical openings exposed to the receipt of sound and extending from a face of the body portion into but not through the body por- -tion, said face having a coat of glaze ceramically bonded thereto at areas other than said openings, and said openings at their juncture with the surface of said face having smooth fired edges.

2. The method comprising forming a multiplicity of acoustical openings in a porous panel consisting essentially of a felted network of fibers predominating in synthetic mineral fibers and of particulate ceramic material distributed throughout the network, applying ceramic surfacing material to the surface of the panel at areas between the openings, and then bringing about a ceramic bond between the mineral fiber network and the surfacing material and smoothing the surfacing material at the edges of the openings by firing the panel.

References Cited UNITED STATES PATENTS 2,063,102 12/1936 Jones 10641 2,915,475 12/1959 Bugosh. 3,014,835 12/1961 Feigley 162-454 3,017,318 1/1962 Labino et al. 162-152 3,086,878 4/1963 Lauring. 3,117,403 1/ 1964 Jack et al.

HOWARD R. CAINE, Acting Primary Examiner. DONALL H. SYLVESTER, Examiner.

Claims (1)

1. AN ACOUSTICAL PANEL HAVING A POROUS SOUND-ABSORBING BODY PORTION CONSITING ENTIRELY OF INORGANIC MATERIAL AND ESSENTIALY OF A CERAMICALLY BONDED POROUS BODY OF A MINERAL FIBER FELT AND OF PARTICULATE CERAMIC MATERIAL, SAID MINERAL FIBER PREDOMINATING IN SYNTHETIC MINERAL FIBER, THE PARTICULATE CERAMIC MATERIAL BEING PRESENT IN QUANTITY NOT EXCEEDING THE QUANTITY OF FIBER, SAID BODY PORTION HAVING A DENSITY UP TO 50 POUNDS PER CUBIC FOOT AND HVING A MULTIPLICITY OF ACOUSTICAL OPENINGS EXPOSED TO THE RECEIPT OF SOUND AND EXTENDING FROM A FACE OF THE BODY PORTION INTO BUT NOT THROUGH THE BODY PORTION, SAID FACE HAVING A COAT OF GLAZE CERAMICALLY BONDED THERETO AT AREAS OTHER THAN SAID OPENINGS, AND SAID OPENINGS AT THEIR UNCTURE WITH THE SURFACE OF SAID FACE HAVING SMOOTH FIRED EDGES.