MX2008005824A - Acoustical gypsum board for ceiling panel - Google Patents

Abstract

Low density acoustical gypsum boards having a perforated cover sheet that have good sound absorption properties and are generally clear of falling gypsum dust. The invention optionally provides a cover sheet having a pattern producing a textured visual effect particularly when viewed from a distance. The acoustical gypsum boards can be produced on modified existing gypsum board lines.

Description

ACOUSTIC PLASTER BOARD FOR CEILING PANEL FIELD OF THE INVENTION The present invention relates to a lightweight gypsum panel suitable for use as a soundproofing or acoustic panel. The invention offers inexpensive and convenient low density acoustic drywall panels that have sound absorption characteristics on a par with conventional acoustic panels and a method for their preparation.

BACKGROUND OF THE INVENTION Acoustic panels are used to form interior soundproofing surfaces. They are usually in the form of roof panels, wall panels and partitions (eg, divisions between office cubicles), and are used in commercial buildings, residential buildings, public buildings, auditoriums, etc. The panels are usually flat and include acoustic characteristics of the materials chosen for their manufacture and their ability to accept perforations that absorb sound without adversely affecting their durability.

The most common acoustic panels are based on mineral wool, and may also include fiberglass, expanded perlite, paper fiber and bonds as for example starch. Mineral wool is the most prevalent and important ingredient in these previous acoustic panels. Acoustic panels based on mineral wool are very porous, which is attributed to their sound absorption. Fillers, such as expanded perlite, can be incorporated into acoustic panels based on mineral wool to reduce the weight of the final product. In addition, acoustic panels based on mineral wool are usually drilled to further increase their sound absorption.

At present, acoustic panels are prepared in a manner similar to that used in conventional processes for making paper by dilute aqueous dispersions with flocked mineral wool water, pearlite, bonds and other ingredients as desired. In these processes, the dispersions flow on a moving porous support wire, such as for example machines to form Fourdrinier or Oliver floor mats to dehydrate, as will be appreciated by those with prior art experience. The dispersions are first dehydrated by gravity drainage and then vacuum suction. The resulting dehydrated but still wet mat is dried in a convection oven, the dried material is cut into the desired dimensions and multiple layers are applied to obtain the finished panel.

The acoustic panels can also be made by a wet pulp molding or casting process as described for example in U.S. Patent No. 1, 769,519. In accordance with this process, a molding composition comprising granular mineral wool fibers, fillers, colorants, a bond such as cooked starch and water for molding or melting the panel. The composition is placed on appropriate trays that have been covered with paper or a paper-reinforced metal coating and then the composition is coated to the desired thickness with a forming plate. A decorative surface can also be provided, such as elongated fissures in random order with a coated bar or pattern roller. The trays filled with the mineral wool composition are then placed in an oven until dry.

Both techniques of flocking and melting in trays to prepare acoustic panels are not completely satisfactory due to their complexity and cost. In addition to raw material costs, these processes require large amounts of water and energy. In addition, panels prepared according to these methods may be subject to buckling, especially if the panels are stored under conditions of high humidity or when the panels are installed horizontally or with widely separated support members. The tendency to buckle is aggravated by the presence of hygroscopic bonds such as recycled paper fiber or starch. In addition, several surface covers are usually required to obtain an appropriate appearance in the final acoustic panel, due to the absorbency of the materials used. In addition, where the panels are perforated, care must be taken not to cover or obstruct the holes drilled with the final coatings. For example, after the drilling, coatings should be applied by spraying instead of simpler coating processes, less application costs with roller to avoid clogging the holes drilled.

The conventional gypsum board, comprising curdled gypsum (calcium sulfate dihydrate), contained between sheets of paper, is commonly used in construction applications due to its durability, fire resistance characteristics and economy. However, this plasterboard covered with paper has not been considered in the past for use in acoustic ceiling panels for a number of reasons. First, this gypsum board does not inherently have good sound absorption properties. Even if drilled in the same way as acoustic panels based on conventional mineral wool, little or no significant improvement in sound absorption is obtained. In addition, drilling the gypsum board covered with conventional paper causes substantial amounts of gypsum powder to be released into the drilled holes. (Conventional acoustical panels can also have some loss of dust.) Also, conventional drywall can be heavy, ca. 40 pounds per cubic foot ("pcf") and this weight makes conventional drywall unfit for most acoustic applications. Even the lightweight gypsum panel newly developed and described in U.S. Patent No. 5,922,447 to the present inventor, Mirza A. Baig, usually has a density greater than or equal to about 21 pcf, which exceeds the typical densities of the panels. acoustic based on conventional mineral wool of approximately 12 to 20 pcf. Therefore, the problems of lack of sound absorption, high density and gypsum powder have discouraged the use of gypsum panels covered with conventional or lightweight faces in acoustic panel applications.

A type of acoustic panel based on plaster and cast in charolo is presented in U.S. Patent Application number 2004 / 0231916AI by Englert et al. This application is mainly directed to panels which, unlike the conventional drywall preferably does not have a top cloth cover. In a less favored copy of Englert et al., A paper top cover is used but it is not suggested to perforate it after drying, which is not surprising since it would be anticipated that the perforation of this dry panel would produce a substantial loss in dust. .

The conventional plasterboard of the prior art is flat and smooth, without significant visual surface texture. Known acoustic panels, on the other hand, usually have a significant three-dimensional texture. If one could find a way to produce drywall acoustical panels that will achieve the same visual effect (and sound absorption properties) as found in conventional mineral wool-based acoustic panels without actually adding texture and therefore damaging the outer surface of the paper face of the panels, would be an additional useful contribution to the technique.

Therefore, it would be advantageous to be able to find a way of making plasterboard products produced with conventional methods with a sufficiently low density and sound absorption properties good enough to be useful in acoustic applications. It would be particularly advantageous if one could find a way to make these gypsum plaster type products so that they have acceptable sound absorption properties and that they are not subject to the problem of loose gypsum powder, which achieve the same visual effect as is known in textured acoustic panels, and that also have sag resistance equal to or better than conventional mineral wool based gypsum panels.

The present invention comprises acoustic panels of low density plaster, which has both top and bottom covers, whose manufacture is relatively inexpensive and which can be efficiently produced in large quantities in an existing drywall line. These acoustic panels of low density plaster resist permanent deformation, such as buckling, and have sound absorption properties on par with conventional acoustic panels. Low density gypsum acoustical panels are perforated and are not subject to the problem of loose plaster dust. Further, the invention optionally provides a top cover to which a visual pattern is applied to make the surface appear to be textured, particularly when viewed from a distance (i.e. when a person sees it on the floor of A room by turning over to the ceiling) . These and other advantages of present invention, as well as additional inventive features, will be apparent from the description of the invention given below.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic representation of a cutting end view of a low density gypsum acoustic panel according to the invention including top and bottom covers, a set gypsum core and perforations extending through the sheet upper cover and inside the set gypsum core; Figure 2 is a plan view of a top cover sheet (paper face) having a pattern printed on the cover sheet of the paper face employed in an exemplary of the present invention; Y Figure 3 is a plan view of an upper cover sheet of a low density plaster acoustic panel of Figure 1 showing the printed pattern of Figure 2 and including small circular perforated recesses extending across the face of paper and inside the plaster core set.

DETAILED DESCRIPTION OF THE INVENTION In a copy of the invention, the low density gypsum acoustic panels of This invention includes a central structure of set gypsum made using a main formulation including calcium sulfate hemihydrate ("stucco"), perlite, paper fiber and starch. The set gypsum number of the low density gypsum acoustical panels is contained between two substantially parallel top and bottom cover sheets, such as paper cover sheets, to provide substantially planar top and bottom surfaces. In addition, low density gypsum acoustic panels include perforations formed through the upper (outer) surface of the panel and extending through the cover sheet and into the number of plaster set. In a preferred specimen, the perforations are generally well formed small circular recesses that generally extend perpendicularly to the outer surface of the panel through the top cover sheet and into the set gypsum core. In another preferred specimen, the exposed surface of the perforated top cover sheet has a printed pattern. Acoustic panels of low density plaster are usually manufactured in the same way as conventional drywall, with the following modifications.

Preferably, the low density plaster acoustic panel of the present invention exhibits a Noise Reduction Coefficient (NRC) of at least about 0.5, conforming to ASTM Standard 423-02, and more preferably a Noise reduction coefficient of 1.0 or similar. In some specimens, the low density gypsum acoustic panel demonstrates a noise reduction coefficient in accordance with rule 423-02 of the ASTM of at least about 0.55 to an even more preferable of at least about 0.7.

Now, with reference to Figure 1, a low density plaster acoustic panel 10 is provided in accordance with an exemplary of the present invention. The gypsum acoustic panel 10 includes a set gypsum number 12 having an upper surface 14 and a lower surface 16. The set gypsum core 12 is formed between a front cover sheet 20 and a rear face cover 30 with the sheets of cover (20, 30) attached to the core. A multiplicity of perforations 40 extends through the front cover sheet 20 and the upper surface 14 within the set gypsum core 12.

Figure 2 illustrates an exemplary pattern 50 according to an example of the present invention which is applied to the outer surface of a front cover sheet 20a. In this example, the pattern creates a visual texture appearance for the human eye when viewed from a sufficient distance or perspective, for example, a person standing on the floor of a room facing the ceiling.

Figure 3 is a plan view of the low density gypsum acoustic panel 10 ofFigure 1 covered on its upper surface with the front cover sheet with pattern 20A of Figure 2 and including a multiplicity of perforations 40 formed through the front cover sheet 20a and inside the gypsum core fruit set 12 The set gypsum core 12 is made from an aqueous slurry of the main components mentioned below in Table 1. Other conventional ingredients can be added to the slurry, such as dispersants, strength additives (eg metaphosphates) and accelerators, as described in general below.

TABLE 1. RANGE OF NUCLEUS FORMULATION This sample of the core formulation is based on 100% solids of these four key ingredients.

The plaster acoustic panel of the present invention has a panel density of not more than about 20 pcf. In a preferred example, the plaster acoustic panel of the present invention has a panel density of about 17 to about 19 pcf, and more preferably the acoustic plaster panel of the present invention will have a panel density of maximum about 16 pcf.

It is preferred to use perlite in the core formulations (to help reduce panel density) although in a less preferred example the core formulation may not contain perlite. The presence of perlite in the core formulation, however, reduces the values of the Noise Reduction Coefficient (NRC) of the final plasterboard acoustical panels. Paper fiber, on the other hand, can also be used in core formulations to achieve even lower panel density at the same time as higher NRC values are provided, which compensates for the negative loss of noise reduction caused by the pearlite Therefore, in preferred specimens, as mentioned below, raising pearlite levels is balanced by higher levels of paper fiber.

In a preferred example, perlite will be used in an amount of at least about 5% by weight of the core formulation. In addition in this preferred example, pearlite and paper fiber must be present in the core formulation, and the weight ratio of perlite and paper fiber will vary from about 1: 1.1 to about 1: 2. In an even more preferred example, the weight ratio of perlite and paper fiber will vary from about 1: 1.4 to about 1: 1.6.

In one example, the core formulation comprises, based on the total weight of the core formulation: Stucco 85% by weight; Perlite 5% by weight; Paper fiber 8% by weight; and 2% starch by weight; The weight ratio of pearlite and paper fiber is 1: 1.6. By incorporating soap scum (as discussed below) having a foam density of 10 pcf (in addition to 100% solids weight% of the total core formulation itself), this core formulation can be used to make an acoustic plaster panel that has a density as low as approximately 17.0 pcf. Other additives may be included in addition to 100% total weight% solids of the core formulation itself (ie, accelerators, dispersants and strength additives as mentioned below).

The low density plaster acoustical panels of the present invention must be perforated to produce a multiplicity of perforations that are substantially free of gypsum powder. That such perforations can be achieved is quite unexpected since when conventional gypsum panels are drilled in the same manner, a substantial amount of gypsum powder is released. The perforations in the panels of the present invention are illustrated, for example, in Figures 1 and 3. As shown herein, the plaster acoustical panel is punched through the front paper to produce recesses that extend into the core of gypsum curd, but do not go through the backing paper. The orientation of the gaps is, as shown, preferably generally perpendicular to the flat surface of the first cover sheet, or front paper. Thus, in a key aspect, the set gypsum core generally offers noise-absorbing properties in low density gypsum acoustical panels when combined with substantially gypsum-free perforations.

Low density gypsum acoustical panels can be drilled using a group of drill nails (100% sharp nails) of approximately 1, 800 nails per square foot, the diameter of the nails being 0.062 inches.

Other groups of nails and key diameters can be used, as those skilled in the art will recognize. For example, a group of nails of about 1, 850 per square foot, of about 1, 750 per square foot or about 1, 566 per square foot and nail diameters of about 0.050 inches and about 0.045 inches could be used. Also, any type of nail, including acute, obtuse or combinations thereof, can be used. Those skilled in the art will realize that the group of nails can vary, and the type, style and diameter of the nails can vary, or be used in various combinations to achieve the desired sound reduction properties. The depth of the drilled holes can vary from approximately from inch to approximately inch.

The panels can be made and drilled, according to a batch process or in a continuous process. The drilling step can be applied as part of a standard commercial slab production line, after drying the panel product covered with paper.

The cover sheets 20 and 30 can be made of paper as in conventional drywall, although other useful cover sheet materials that are known in the art can be used. The paper cover sheets offer strength characteristics in the plaster acoustic panel. Useful cover sheet paper includes 7-leaf Manila and 7-sheet news line, available from United States Gypsum Corporation, Chicago, Illinoins; and Gray-Back of 3 leaves and Manila ivory of 3 leaves, available from Caraustar, Newport, Indiana. The paper cover sheets comprise upper cover sheets, or front paper, and lower cover sheets, or back paper. News line is the paper for preferred back cover sheet. Manila 7 sheets is the preferred paper for front cover.

Gypsum based products have a tendency to buckle under high humidity conditions. The correct choice of backing paper helps reduce buckling in the finished plasterboard acoustic panel. A preferred backing paper for this purpose in the low density plaster acoustic panels of the present invention is the 7-Sheet News Line. In addition, strength additives such as sodium trimetaphosphate can be added to the formulations of the core to reduce buckling even more. Also, a formaldehyde-based coating can be applied to the backing of gypsum acoustical panels to further reduce buckling.

The front paper can be used smooth, or with a pattern applied thereto, as mentioned above and as illustrated in Figure 2. Many pattern variations and pattern colors can be used on the front paper. Ink papers can also be used when appropriate, and color or ink prints can be used to apply the pattern. The pattern as illustrated in Figure 2, as well as other patterns, can be done by taking a photograph of a given design and printing the design on the front paper. Also, the front paper printing can be done online during the production process, preferably after the front paper is dry. In addition, after printing the pattern, a protective coating can be applied to the outer surface of the front paper to protect the printed pattern against erosion and environmental conditions.

A soap scum is required to make the low density plaster acoustic panels of the present invention, to reduce the density of the final panel. The density of the soap foam can vary from about 5.0 pcf to about 12.0 pcf; A preferred soap foam density is about 10 pcf, to achieve a final penalty density of maximum 20 pcf. Soap foam is used in an amount in addition to 100% solids total% weight of the core formulation itself. For example, a soap may be used in an amount of about 2 g to about 3 g per about 1 000 g of total solids (or about 0.2% to about 0.3% by weight based on total solids) when used for make the soap scum and add to the core formulation as in Table 1 in addition to 100% of the total% solids weight of the core formulation itself. Useful soaps for foaming soap include FA 403 - Agent X-2332 available from Stepan Chemical Company, Northfield, Illinois.

The bond between a set gypsum core and the paper cover sheets can be negatively affected by the presence of foam in the core formulation. Given that approximately 1/3 of the drywall by volume may consist of foam, the foam may interfere with the bond between the set gypsum core and the paper cover sheets. Thus, a bonding layer without foam can be provided on the contact surfaces with the gypsum core set from the front paper and the back paper before forming the gypsum panels. The formulation of this layer is commonly the same as the core formulation, except that soap scum is omitted. To form this layer, the foam can be mechanically removed from the core formulation or a different foam-free formulation can be applied at the interface of the set gypsum and the front paper.

The main component of the core formulation is calcium sulfate hemihydrate or calcined gypsum, also known as stucco. The calcined gypsum may have the form of calcium sulfate hemihydrate alpha, calcium sulfate hemihydrate beta, water-soluble anhydrous calcium sulfate or mixtures thereof. In preferred specimens, calcined gypsum has the form of calcium sulfate hemihydrate beta. A useful calcined plaster is CKS dry stucco, available from United States Gypsum Corp., Chicago, Illinois. The calcined gypsum is present in the aqueous slurry of the core formulation in an amount sufficient to allow the formation of an interconnected gypsum matrix in the panel covered with final paper. In the core formulation used to make the plaster core set, the plaster is present in an amount ranging from about 75% to about 90% by weight based on the total weight (solids) of the core formulation; preferably, the stucco is present in an amount ranging from about 80% to about 85% by weight based on the total weight of the core formulation.

As mentioned above, it is preferred to use perlite in the core formulation. In the core formulation used to make the plaster core set, perlite may be present in an amount of up to about 15% by weight based on the total weight (solids) of the core formulation; preferably, perlite is present in an amount ranging from about 5% to about 8% by weight based on weight total of the core formulation.

In the practice of the invention, the density of the pearlite should be in the range of about 3 to about 8.5 pcf. Perlite can be obtained from a number of commercial sources. In the examples described below, she used Siblic Type 3-S Perlite Brand located in Hodgkins, Illinois. This route usually has a density of about 3 to about 5.0 pcf.

Perlite is a form of glassy rock similar to obsidian. It usually contains 65 to 75% SiO2, 10 to 20% AI2O3, 2 to 5% H2O and smaller amounts of sodium carbonate, potash and lime. When the pearlite is heated to its softening point, it expands to form a light, fluffy material similar to pumice. In the preparation of the perlite for use in the present invention it is first milled to a finer size than less 200 mesh. The milled pearlite is then heated to a temperature of about 1,500 to 1,800CF and preferably about 1,750. F. This process is carried out in a perlite expander by first heating the air and then introducing the finely ground pearl into the hot air. While it is in the air, it heats up and bursts like popcorn to form the expanded perlite. Expanded perlite contains many cracks and fine fissures and, when placed in contact with water, water penetrates cracks and fissures and enters the air-filled cavities of the pearlite, which increases the weight of the beads. particles to a large extent.

For the purposes of the present low density acoustic panel, it is important that the pearlite is not covered or treated in any way to make the water-tight pearlite particles or even water repellents. If present, coating or water resistance treatment will result in a non-uniform distribution of the perlite in the aqueous slurry of the core formulation, and it will also be more difficult, if not impossible, for the gypsum crystals to penetrate and interconnect with the pearlite particles.

The core formulation should use paper fiber. A useful form of paper fiber is hydropulpa made news paper or waste paper made hydropulpa. Other fibrous cellulose materials can be used, either alone or in combination with paper fiber made from hydropulpa, such as for example wood pulp or dry fibrillated gypsum drywall paper or Kraft paper. In the core formulation used to make the plaster core set, the paper fiber is present in an amount ranging from about 2% to about 12% by weight based on the total weight (solids) of the core formulation; preferably, the paper fiber is present in an amount ranging from about 6% to about 10% by weight based on the total weight of the core formulation.

The core formulation must use starch. For example, wheat starch is You can use. In another example, pearl starch, which is a known combination of starch made from corn, potatoes and / or wheat stocks, can be used. The starch can be incorporated in a raw or fully cooked form separately before mixing it with the core formulation. Partial cooking in the present process is considered to occur once the starch and water slurry reaches a temperature of 150 ° F. Starch is considered fully cooked once the starch slurry reaches a temperature of at least 185 ° F. By partial or total cooking, the pearl starch is converted from a changing nature to an unchanging one. When it is not changing, the starch is retained in the core portion of the panel before curdling. The presence of the starch in the nucleus also helps the bonding of the front paper with the core.

Alternative sources of starch which are also contemplated with acid-modified starches including Gypset made by Ogilive, located in Montreal, Canada and LC-211, a common starch made from flour, provided by Archer Daniels Midland of Dodge City, Kansas. In the last two cases, the starches are of the changing type. Another useful starch is acid-modified corn flour, available from HI-BOND of Bunge, St. Louis, Missouri. This starch has the following typical analysis: moisture 10.0%, oil 1.4%, soluble 17.0%, alkaline fluidity 98.0%, bulk density loose 30 pounds / feet3, and a 20% slurry that produces a pH of 4.3.

Pregelatinized starch in particular can be used in slurries prepared according to the core formulations of Table 1. A pregelatinized starch is pregelatinized corn starch, for example pregelatinized corn flour available from Bunge, St. Louis, Missouri, which has the following typical analysis: humidity 7.5%, protein 8.0%, oil 0.5%, crude fiber 0.5%, ash 0.3%; and that has a green force of 0.48 psi; and that has a loose raw density of 35.0 pounds / foot3. In the core formulation used to make the plaster core set, the starch is present in an amount ranging from about 0.5% to about 5% by weight based on the total weight (solids) of the core formulation; preferably, the starch is present in an amount ranging from about 0.5% to about 2% by weight based on the total weight of the core formulation.

It is possible to use accelerators in the core formulations of the present invention, for example, wet gypsum accelerator (WGA), as described in U.S. Patent No. 6,409,825 to Yu et al., Incorporated herein by reference. present as a reference. A desirable heat-resistant accelerator (HRS) can be made from dry, ground gypsum (calcium sulfate dihydrate). Small amounts of additives (usually about 5% by weight) of for example sugar, dextrose, boric acid and starch can be used to make this HRS. Currently sugar or dextrose is preferred. Another useful accelerator is "stabilized climate accelerator" or "stable climate accelerator" (CSA), as described in U.S. Patent No. 3,573,947 incorporated herein by reference. For example, an accelerator (HRA or CSA) can be used in an amount of about 5 g / 1000 g of total solids (or approximately 0.5% by weight based on total solids) when added to the core formulation of the Table 1 in addition to the 100% solids total weight% of the core formulation itself.

Dispersants can be added to the core formulation of the present invention. Useful dispersants include polynaphthalene sulfonates and BOREM, available from Boremco Laboratories, River Falls, Massachusetts. For example, a dispersant can be used in an amount of about 0.9 g / 1000 g of total solids (or about 0.1% by weight based on total solids) when added to the core formulation of Table 1 in addition to 100 % solids total weight% of the core formulation itself.

The naphthalenesulfonate dispersants that can be used in the present invention include poly-phthalene sulfonic acid and its salts (polynaphthalene sulfonates) and their derivatives, which are condensation products of naphthalenesulfonic acids and formaldehyde. Particularly desirable polynaphthalene sulfonates include sodium and calcium naphthalenesulfonate. The average molecular weight of the naphthalenesulfonates can vary from about 3,000 to 20,000, although it is preferred that the molecular weight be about 8,000 up to ,000. Dispersants with higher molecular weights have higher viscosity, and generate a higher water demand in the formulation. Useful naphthalenesulfonates include LOMAR D, available from Henkel Corporation, DILOFLO, available from GEO Specialty Chemicals, Cleveland, Ohio and DAXAD, available from Hampshire Chemical Corp., Lexington, Massachusetts. It is preferred that the naphthalene sulfonates are used in the form of an aqueous solution, for example, in the range of about 40 to 45% by weight solids content.

Useful polynaphthalenesulfonates have the general structure (I): (I) (l) where n is > 2, and wherein M is sodium, potassium, calcium and the like.

For example, a polynaphthalene sulfonate dispersant can be used in an amount of about 0.9 g / 1000 g of total solids (or about 0.1% by weight based on total solids) when add to the core formulation of Table 1 in addition to the 100% solids total weight% of the core formulation itself.

Force additives can be added to the core formulations of the present invention, for example, metaphosphates such as sodium trimetaphosphate. Any metaphosphate or water-soluble polyphosphate according to the present invention can be used. It is preferred that a trimetaphosphate salt be used, including double salts, ie trimetaphosphate salts having two cations. Particularly useful trimetaphosphate salts include sodium trimetaphosphate, potassium trimetaphosphate, calcium trimetaphosphate, sodium calcium trimetaphosphate, lithium trimetaphosphate, ammonium trimetaphosphate and the like or combinations thereof. A preferred salt of trimetaphosphate is sodium trimetaphosphate. It is preferred that the trimetaphosphate salts are used in the form of an aqueous solution, for example, in the range of about 10 to 15% by weight solids content. Other cyclic or acyclic polyphosphates may also be used, as described in U.S. Patent No. 6,409,825 to Yu et al., Incorporated herein by reference. For example, sodium trimetaphosphate can be used in an amount of about 0.9 g / 1000 g of total solids (or about 0.1% by weight based on total solids) when added to the core formulation of Table 1 in addition 100% solids total weight% of the core formulation itself.

As illustrated in the following examples, the low plaster acoustic panels Density were prepared using the core formulations of Table 1. Except where indicated, Manila 7-sheet paper was used, either in white or with an applied pattern, such as the top cover sheet or front face. A bonding layer without foam (as described above) was applied to the contact surfaces of the gypsum core of the back paper and the front paper.

The average thickness of the panels was 0.54 inches. In addition, each plaster acoustic panel was perforated through the front sheet. The drilling depth was 2 inches (except when indicated otherwise), and the group of drill nails (100% sharp nails) was 1, 800 nails per square foot, with 0.062 inch nail diameter.

In the following examples, certain additives to the core formulation were included as in Table 1 in addition to the 100% solids total weight% of the core formulation itself. The following levels of additives were included in all the examples: accelerator (HRA or CSA) at 0.5% by weight based on total solids; dispersant at 0.1% by weight based on total solids; and 0.1% sodium trimetaphosphate by weight based on total solids. In addition, in each of the following examples (except where otherwise indicated), soap foam was incorporated at a density of 10 pcf in the core formulations. EXAMPLE 1A Preparation of acoustic panel of low density plaster Low density gypsum acoustical panels were prepared as samples by a casting process according to U.S. Patent No. 5,922,447 using the core formulations of Table 1 with a high density (e.g., 10 pcf) incorporated suds foam. to the grout of the core formulation.

EXAMPLE 1B Preparation of acoustic panel of low density gypsum by a continuous process Samples of low density gypsum acoustic panels were prepared with a continuous process according to U.S. Patent Nos. 6,342,284 to Yu et al, and 6,632,550 to Yu et al., Incorporated herein by reference. It includes the separate generation of foam and the introduction of a high density foam (eg, 10 pcf) into the other ingredients' slurry as described in Example 5 of these patents.

EXAMPLE 2 Acoustic panel of low density gypsum - evaluation of paper fibers and high density foam Step 1. The following core formulations were prepared as an aqueous slurry as illustrated in Table 2.

TABLE 2 Dry paper fiber: fibrillated gypsum board paper Wet paper fiber: scrap paper made hydropulpa Additives were included in addition to the aforementioned total solids: accelerator (HRA or CSA) at 0.5% by weight based on total solids; dispersant at 0.1% by weight based on total solids; and 0.1% sodium trimetaphosphate by weight based on total solids.

Soap foam was prepared for each of the sample formulations as follows: Soap (2.0 g), available as the product FA 403-Agent X-2332 from Stephan Chemical Company, Northfield, Illinois, was mixed with water (148 g) in a Hamilton Beach high-speed mixer for 10 seconds. The resulting foam volume was 900 ml; the density of the foam was 10 pcf. This soap scum was incorporated into the core formulations of Table 2.

Step 2. Sample panels were prepared by casting as in Example 1A using the formulations of Table 2, and punched as discussed above. The depth of the drilling was Vi inch and the group of drill nails (100% sharp nails) was 1, 800 nails per square foot, with 0.062 inch nail diameter.

TABLE 3 "MSF" is a standard abbreviation in the technique for a thousand square feet.

As shown in Table 3, the sample panels have densities less than 20 pcf and acceptable NRC values. Also, in panels 2 through 4, the dust was significantly reduced.

EXAMPLE 3 Acoustic panel of low density plaster - evaluation of paper sheets, paper fibers and high density foam The following formulation of the core was used to make the aqueous slurry (solids by weight%): As in example 2, a soap foam with a density of 10 pcf was used. Additional additives were included in addition to the aforementioned total solids: 0.5% CSA by weight based on total solids; Borem at 0.1% by weight based on total solids; and 0.1% sodium trimetaphosphate by weight based on total solids. The sample panels were melted, and punched, as in Step 2 of Example 2. The depth of the perforation was 1 inch and the group of drill nails (100% sharp nails) was 1, 800 nails per foot. square, with 0.062 inch nail diameter.

TABLE 4 As shown in Table 4, the sample panels have densities less than 20 pcf, and no significant difference in NRC values was observed using 7 or 3 sheets on the upper surface of the panel. However, the reduction of the paper fiber level reduced the NRC values.

The dust levels were acceptable in comparison to conventional acoustic panels (300 g / MSF) as previously discussed.

EXAMPLE 4 Acoustic panel of low density plaster-evaluation of cover sheets of printed paper and high density foam Step 1. The following core formulations were prepared as an aqueous slurry as illustrated in Table 5.

TABLE 5 Additives were included in addition to the aforementioned total solids: accelerator (HRA or CSA) at 0.5% by weight based on total solids; dispersant at 0.1% by weight based on total solids; and 0.1% sodium trimetaphosphate by weight based on total solids. Soap foam prepared as in Example 2.

Step 2. Sample panels were prepared by casting as in Step 2 of Example 2 using the formulations of Table 5, and punched as discussed above. The depth of the drilling was of! inch and the group of piercing nails (100% sharp nails) was 1, 800 nails per square foot, with 0.062 inch nail diameter.

TABLE 6 As shown in Table 6, the sample panels have densities below 20 pcf and acceptable NRC values. No negative impact on NRC values was observed when using blank or printed paper.

EXAMPLE 5 Acoustic panel of low density plaster - evaluation of cover sheets of printed paper of 3 and 7 sheets and high density foam Step 1. The following core formulations were prepared as an aqueous slurry as illustrated in Table 7.

TABLE 7 Formula Formula Formula Formula Formula Formula Formula 17 Additives were included in addition to the aforementioned total solids: accelerator (HRA or CSA) at 0.5% by weight based on total solids; dispersant at 0.1% by weight based on total solids; and 0.1% sodium trimetaphosphate by weight based on total solids. 1 Soap foam prepared as in Example 2. 2 Greater amount of soap foam, prepared as in Example 2 using 3.0g of soap and 222g of water.

Step 2. Sample panels were prepared by casting as in Step 2 of Example 2 using the formulations of Table 7, and punched as discussed above. The drilling depth was A inch and the group of piercing nails (100% sharp nails) was 1, 800 nails per square foot, with 0.062 inch nail diameter.

TABLE 8 As shown in Table 8, the sample panels have densities less than 20 pcf and acceptable NRC values. For panels 13 to 16, no negative impact on the NRC values was observed using 3-sheet printed paper or 7-sheet printed and coated paper. For panel 17, a greater amount of high density foam produced lower panel density and increased the NRC value.

EXAMPLE 6 Low density plaster acoustic panel - evaluation of cover sheets of printed paper, paper fibers, perlite and high density foam Step 1. The following core formulations were prepared as an aqueous slurry as illustrated in Table 9.

TABLE 9 Formula of Formula 17 of Milk Formula 18: panel panel Component \ (weight% solids) (weight% solids) Stucco 81.9 80.0 Perlite 7.0 7.0 Paper fiber 8.1 10.0 (hydropulpa) Starch 3.0 3.0 Density dl? .0 10.0 foam, pcf Proportion de2.5 2.5 water / solids Front paper Manila printed Manila printed with lac pattern / pattern of Figure 2 Figure 2 Additives were included in addition to the aforementioned total solids: accelerator (HRA or CSA) at 0.5% by weight based on total solids; dispersant at 0.1% by weight based on total solids; and trimetaphosphate sodium at 0.1% by weight based on total solids. Soap foam prepared as in Example 2.

Step 2. Sample panels were prepared by casting as in Step 2 of the Example 2 using the formulations of Table 9, and were punched as commented previously. The depth of the drilling was Vi inch and the group of drill nails (100% sharp nails) was 1, 800 nails per square foot, with 0.062 inch nail diameter.

TABLE 10 As shown in Table 10, the sample panels have densities below 20 pcf and acceptable NRC values.

EXAMPLE 7 Low density plaster acoustic panel - evaluation of paper cover sheets including a non-foam bonding layer applied to the contact surfaces of the plaster core set Two sets of three panels were prepared using the following core formulation to make the slurry (solids by weight%): Stucco 84.5 Perlite 5.0% Paper fiber (hydropulpa) 7.5% Corn starch3.0% A soap foam with a foam density of 5.0 pcf was used. Additional additives were included in addition to the total solids mentioned above: CSA at 0.5% by weight based on total solids; Borem at 0.1% by weight based on total solids; and 0.1% sodium trimetaphosphate by weight based on total solids. The water / solids ratio was 2.4: 1. The first set (Set A) of sample panels was cast and drilled (except at 0.375 inches deep) as in Step 2 of Example 2. For the second set (Set B) of sample panels, before casting, a bonding layer without foam (prepared from the same core formulation without foam) was applied manually to the contact surfaces of the plaster core of the set on the back paper and the front paper using a 4.0 paint brush. inches wide, then the second set (Set B) of sample panels was melted and perforated (except at 0.375 inches deep) as in Step 2 of Example 2. The setting time was approximately 11.0 minutes for all panels castings. In the following Table 11, the results are presented as average values.

TABLE 11 The panels of Set B had an excellent link to the paper cover sheets and the plaster core of the game after drying the panel. As shown in Table 11, the bond between the set gypsum core and the leaves of Paper cover was significantly improved, without negatively affecting the estimated NRC value after perforation of the front paper. The presence of the non-foam bond layer provided a better bond between the paper cover sheets and the gypsum core of the set in the low density gypsum acoustic panels of the present invention, without adverse effects on the estimated NRC values after of the perforation of the cover sheet of the upper surface (front paper). The lowest NRC values estimated in both sets of panels (Games A and B) were due to the lower drilling depth.

EXAMPLE 8 Resistance to permanent deformation - evaluation of buckling strength of acoustic panel of low density gypsum Low-density plaster acoustical panels made in accordance with Examples 3 to 6 demonstrated resistance to permanent deformation such as buckling. Buckling was tested on samples of 2 x 4 foot panels as follows: Sections 3 inches wide by 24 inches long were cut from the aforementioned samples and tested under conditions of 104 ° F / 05% humidity relative (HR). The sections of the panel were placed in a horizontal position on two supports of two inches in width, subject to a support frame, whose length extended to all 3 inches of width of the panel, with a support at each end of the panel. The 3-inch wide ends in contact with the support frame were fastened with weight on the supports or were attached with presses to the supports. The panel sections remained in this position for a specified period of time (in this example, 3 days) under conditions around 104 ° F and 95% relative humidity. The amount of buckling of the panel (buckling diffusion) was then determined by measuring the distance in inches from the center of the upper surface of the panel from the imaginary horizontal plane between the upper edges of the ends of the panel, i.e. a plane corresponding to the surface of the panel before exposing it to the test conditions. After a 3-day trial period, buckling diffusion for the test sections was measured in the range of 0.122 to 0.218 inches, which is substantially superior to known conventional ceiling panels, whose diffusion by pandea so Regular is 0.3 to 0.5 inches under the same test conditions.

Low density gypsum acoustical panels were made in accordance with Examples 3 to 6 passed the flame transmission test and met the Class A classification.

Low density gypsum acoustical panels made according to Examples 3 to 6 were tested by MOR (psi) strength. The average MOR force reached was approximately 200 psi or greater.

Low density gypsum acoustical panels made according to Examples 3 to 6 were less friable than acoustic panels conventional The cuttability, including the edge detail, of these low density gypsum acoustic panels was good using a mechanical cutting blade. The edge detail, known as lip, was introduced by grinding.

All references, including publications, patent applications and patents cited herein, are incorporated by reference as if each of the references were individually and specifically indicated as incorporated by reference and incorporated in their entirety herein.

The use of the terms "a" and "one" and "the" and "the" and similar referents in the context of the description of the invention (especially in the context of the following claims) should be considered encompassing the singular and plural, unless otherwise indicated herein or contradicted clearly in the context. The recitation of ranges of values in the present has the simple purpose of serving as an abbreviated method of referring individually to all different values that fall within the range, unless otherwise indicated in the present and each separate value is incorporated within of the description as if it were individually recited in the present. All methods described herein can be carried out in any appropriate order unless otherwise indicated herein or otherwise contradicted clearly in context. The use of any and all examples, or exemplary language (such as "for example") provided herein, has the single purpose of better illuminating the invention and has no limitation to the scope of the invention unless otherwise claimed. No language in the description should be considered as an indication that any unclaimed item is essential to the practice of the invention.

The preferred specimens of this invention are described herein, including the best mode known to the inventors for carrying out the invention. It should be understood that the examples illustrated with examples only, and should not be taken as limiting the scope of the invention.

Claims (19)

1. An acoustic panel with gypsum base having a set gypsum core disposed between two substantially parallel cover sheets comprising: a set gypsum core made of a formulation having from about 75% up to about 90% by weight of stucco based on the total weight of the core formulation, from about 0 to about 15% by weight of perlite based on the total weight of the core formulation, from about 2% to about 12% by weight of paper fiber based on the total weight of the core formulation, and about 0.5% to about 5% by weight of starch based on the total weight of the core formulation; and a multiplicity of perforations to absorb sound that extend through the cover sheet and into the set gypsum core.

2. The acoustic panel of Claim 1, wherein the core formulation includes stucco in an amount of from about 80% to about 85% by weight based on the weight of the core formulation, perlite in an amount of from about 5% up to about 8% by weight based on the weight of the core formulation, paper fiber in an amount of from 6% to about 10% by weight based on the weight of the core formulation and starch in an amount of from about 0.5% to about 2% by weight based on the weight of the core formulation.

3. The acoustic panel of Claim 1, wherein the pearlite has a density of from about 3.0 pcf to about 5.0 pcf

4. The acoustic panel of Claim 1, wherein the paper fiber is made hydropulpa.

5. The acoustic panel of Claim 1, wherein the starch is pregelatinized maize starch.

6. The acoustic panel of Claim 1, which includes cover sheets comprising a front paper and a back paper, the perforations extend through the front paper and inside, but without traversing the plaster core set.

7. The acoustic panel of Claim 6, wherein the front paper has a pattern that creates a visual appearance of a texture when viewed from a distance.

8. The acoustic panel of Claim 1, wherein the perforations have a diameter of approximately 0.062 inches and are present in approximately 1, 800 nails per square foot.

9. The acoustic panel of Claim 1, wherein the panel has a thickness of approximately 0.54 inches and the perforations have a depth of approximately Vz inch.

10. The acoustic panel of Claim 1, wherein the density of the panel is from about 16 pcf to about 20 pcf.

11. The acoustic panel of Claim 1, wherein the density of the panel is from about 16 pcf to about 17 pcf.

12. The acoustic panel of Claim 1 having an NRC value of from about 0.50 to about 0.65.

13. The acoustic panel of Claim 1 wherein the perlite in the core formulation is present in a weight ratio of perlite and paper of from about 1: 1.1 to about 1: 2.

14. The acoustic panel of Claim 1 wherein the pearlite in the core formulation is present in a weight ratio of pearlite and paper from about 1: 1.4 to about 1: 1.6.

15. An acoustic panel with a gypsum base having a core of plaster set between a front paper and a back paper comprising: a set gypsum core made of a formulation having from about 75% to about 90% by weight of stucco based on the total weight of the core formulation, about 0 to about 15% by weight of perlite based on the total weight of the core formulation, from about 2% to about 12% by weight of paper fiber based on the total weight of the core formulation, and from about 0.5% to about 5% by weight of starch based on the total weight of the core. the formulation of the nucleus; Y a multiplicity of perforations to absorb sound that extend through the front paper and into but without passing through the plaster core.

16. A method for making acoustic panels with a gypsum base, comprising the steps of: (a) mixing a water slurry, stucco in an amount of from about 75% to about 90% by weight based on the total weight of solids, pearlite in an amount of up to 15% by weight based on the total weight of solids, paper fiber in an amount of from about 2% to about 12% by weight based on the total weight of solids, and a starch in an amount of from about 0.5% to about 5% by weight based on the total weight of solids. (b) adding a soap foam with a density of about 10 pcf to the slurry; (c) depositing the slurry on a first cover sheet; (d) maintaining the slurry under sufficient conditions for the stucco to form a set gypsum core; (e) placing a second cover sheet on the plaster core set to form an acoustic panel; (f) drying the formed panel; (g) cut the dry panel; and (h) piercing one of the cover sheets of the dry panel so that the perforations extend inside but not through the set gypsum core.

17. The method of Claim 16, further comprising applying to a pattern on the second cover sheet before step (g).

18. A method for making gypsum-based acoustical panels, comprising the steps of: (a) mixing a slurry comprising water, stucco in an amount of from about 75% to about 90% by weight based on the total weight of solids, pearlite in an amount of up to 15% by weight based on the total weight of solids, paper fiber in an amount of from about 2% up to about 12% by weight based on the total weight of solids, and a starch in an amount of from about 0.5% to about 5% by weight based on the total weight of solids. (b) adding a soap foam with a density of about 10 pcf to the slurry; (c) depositing the slurry on a first cover sheet; (d) maintaining the slurry under sufficient conditions for the stucco to form a set gypsum core; (e) placing a second cover sheet on the plaster core set to form an acoustic panel; (f) drying the formed panel to a constant weight to produce a dry panel having a maximum density of 20 pcf; (g) cut the dry panel; and (h) drilling one of the dry panel cover sheets using nails with a nail number of approximately 1, 800 nails per square foot and a nail diameter of approximately 0.062 inches, such that the perforations extend within but without traversing the gypsum core.

19. The method of Claim 18, further comprising applying to a pattern on the second cover sheet before step (g).