CA2187848A1

CA2187848A1 - Sound screen insulation with asphalt septum

Info

Publication number: CA2187848A1
Application number: CA002187848A
Authority: CA
Inventors: Gerald G. Greaves; Jeffrey J. Van Sloun; Catherine A. Barron; Charles R. J. Weir
Original assignee: Owens Corning
Current assignee: Owens Corning
Priority date: 1995-10-18
Filing date: 1996-10-15
Publication date: 1997-04-19
Also published as: US5665447A

Abstract

A panel (12,12') for an office sound screen includes a core (20,20') which includes an asphalt layer (22) and insulation layers (24,24') positioned on both sides of the asphalt layer. Preferably the asphalt layer has a thickness between 0.030 inch (0.076 cm) and 0.125 inch (0.318 cm). The asphalt layer acts as an adhesive so that the insulation layers are laminated thereto. Preferably the insulation layers are made from a fibrous glass wool insulating material having a density between 0.5 pounds per cubic foot (8 kg/m3) and 5 pounds per cubic foot (80 kg/m3). The panel further includes a cover layer (26) positioned on at least one side of the core.

Description

~187~48 SOUND SCREEN INSULATION WITH ASPHALT SEPTUM

TECHNICAL FIELD
This invention relates in general to in~ tion products, and more 5 specifically to an insulation product suitable for use in an office sound screen to reduce sound between the office workers.
BACKGROUND
In recent years the trend in office buildings has been away from individual rooms for each office worker and toward the use of a single large room to create offices 10 for a number of workers. This is thought to promote communication between the office workers to enh~nce their pe~ ce. This also provides more efficient use of building space and reduces costs. In view of the number of office workers present in a single room, however, there is a problem of increased sound levels distracting the workers.
Consequently, a conventional practice is to position office sound screens or dividers 15 between the individual offices to reduce the sound.
An office sound screen in~ des a vertically extçn-lin~ panel which is generally flat and rect~n~ r in shape. Snmetimes a raceway for electrical wires is positioned along the base ofthe sound screen below the panel. Usually a metal frame is positioned around the edges of the panel. The dimensions of a sound screen can vary 20 widely, but a typical sound screen may be about 5 feet (1.5 meters) high, about 3 feet (0.9 meters) wide, and about 2l/2 inches (6.35 cm) thick.
The panel of an office sound screen is constructed of several layers of material, in~.hl(ling a sound recl~lcin~ core. A conventional core incl~ldes a layer of chipboard, which is a strong, low density paper board made from mixed waste paper. The 25 core further incl~1des a layer of insulation on both sides of the chipboard, typically fiberglass insulation. Optionally a thin, tackable layer of material such as a high density glass fiber board is positioned on both sides of the core. This layer is provided to enable the office workers to tack or pin papers or similar items to the sound screen if desired. A
cloth fabric covers both faces of the panel and is ~ çhed to the metal frame and the 30 raceway.
Unfortunately, the material and assembly cost of the conventional panel is relatively high. The chipboard material used to make the core layer is relatively expensive.
Further, the assembly cost is relatively high because the panel is assembled by h~ndling the 218~848 two layers of insulation and the layer of chipboard separately. The office furniture market, like many other markets, has shifted to more economical products. Thus, it would be desirable to provide an office sound screen that is effective in red~lcin~ sound, and that also has reduced material and assembly costs col.lpared to the conventional sound screen.
S DISCLOSURE OF INVENTION
This invention relates to an improved panel for an office sound screen. The panel inr,1~de~ a core COIIIpliSil~g an asphalt layer and insulation layers positioned on both sides ofthe asphalt layer. Plere,ably the asphalt layer has a thickness belween about 0.030 inch (0.076 cm) and about 0.125 inch (0.318 cm). The asphalt layer acts as an adhesive so 10 that the insulation layers are l~min~ted thereto. Plere.ably the insulation layers are made from a fibrous glass wool ins~ ting material having a density between about 0.5 pounds per cubic foot (8 kg/m3) and about 5 pounds per cubic foot (80 kg/m3). The panel further in~ des cover layers p-ere-ably positioned on both sides of the core. Tackable layers can be positioned between the insulation layers and the cover layers.
The panel for an office sound screen in accordance with this invention has reduced material costs because the asphalt core is less ~ ,el.si~e than the chipboard material used in a conventional panel. The asphalt l~min~tes the two insulation layers together so that the layers can all be handled and assembled as a single unit. This saves labor and processing steps and thus reduces assembly costs. The panel is effective in 20 abso.l,ing sound and redllr.ing the tr~n~mi~ion of sound.
Various objects and advantages of this invention will become appare .L to those skilled in the art from the following detailed description of the p.ere--ed embodiment, when read in light of the acco-..pa-.~illg drawings.
BRIEF DESCRIPTION OF DRAWlNGS
Fig. 1 is a perspective view of an office sound screen incl~.-lin~ a panel in accordance with this invention.
Fig. 2 is a cutaway view of the upper right corner of the sound screen of Fig. 1 illustrating the layers of material used to make the sound screen.
Fig. 3 is a cross-sectional view of the layers of material used to make the 30 panel in acco-dallce with this invention.
Fig. 4 is a cross-sectional view of an alternative embodiment of a panel in accordance with this invention.

21878~
Fig. 5 is a cross-sectional view of the layers of material used to make the panel of Fig. 4.
Fig. 6 is a sçh~ ;c view of a method for making the core ofthe prerelled panel.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to the drawings, there is illustrated in Fig. 1 an office sound screen, indicated generally at 10. The sound screen 10 includes a vertically eYten~ling panel 12 in accordance with this invention. The plere,led panel 12 is generally flat and re~ "l~r in shape. It is to be understood, however, that the panel 12 can be other 10 shapes such as square or rounded. The sound screen 10 preferably also incl~ldes a raceway 14 positioned along the base of the sound screen below the panel 12. The raceway 14 is a generally rec~ g~ r, hollow enclosure for electrical wires ~tt~rh~.d to electrical outlets (not shown) in the wall of the raceway. The raceway 14 also serves as a kick plate for the sound screen 10. ~lerel~bly a rigid frame 16 is positioned around three edges ofthe panel 15 12. If the sound screen 10 does not include a raceway 14, the frame 16 can be positioned around all four edges ofthe panel 12. The raceway 14 and frame 16 are generally formed from a metallic material, and preferably from steel, although other materials such as plastics or composites can also be used. Four supports 18 (two of which are shown) are prerel~bly positioned at the base ofthe sound screen 10. Wheels could also be positioned 20 at the base to f~r.ilit~te movement of the sound screen.
As illustrated in Fig. 2, the panel 12 is constructed of several layers of material which will be desclil,ed in more detail below. The panel 12 incl~des a sound recluçing core 20. An asphalt layer 22 is positioned in the interior of the core 20. The core 20 further incl~ldes insulation layers 24 positioned on both sides of the asphalt layer 25 22 and l~min~ted thereto. A cover layer 26 is positioned on at least one side of the core 20, and preferably cover layers 26 are positioned on both sides of the core 20. Optionally, at least one tackable layer 28 is positioned belweell at least one insulation layer 24 and cover layer 26, and preferably tackable layers 28 are positioned bc;lweel both insulation layers 24 and cover layers 26.
Referring now to Fig. 3, the layers of material in the panel 12 are illustrated and described in more detail. An asphalt layer 22 is positioned in the interior of the core 20. The asphalt layer 22 provides a barrier that reduces the amount of sound ll~ ed through the sound screen, and thus reduces the amount of sound ~ led from one - 2l87g~8 office to the next. The amount of sound tr~ncmi.Ccion can be measured by a SoundTli.n....~ic.~;on Class ("STC") accordil-g to the standard method ASTM E90-90. The STC is measured on a scale from 0 decibels, m~Aning all the sound is l-~ ...;lle~l to appro~illlalely 70 decibels Ill~Ani~, almost no sound is ll~ns~ led. The STC is a single 5 number that represenls the ratio of sound energy striking the sound screen relative to the led sound energy over a range of frequencies. It is expressed in decibels.
Preferably the STC ofthe core 20 in accordance with this invention is bc;lween about 10 decibels and about 50 decibels, and more preferably between about 20 decibels and about 40 decibels. The amount of sound ll;.n~ c~;on is related to the mass of the asphalt layer 10 22. Plere~ably the asphalt layer 22 has a ll.ic1~ness belweell about 0.030 inch (0.076 cm) and about 0.125 inch (0.318 cm).
The type of asphalt used in the asphalt layer 22 is not critical. The asphalt can be any bituminous material such as tars, pitches or asphalts. The asphalt can be any natural or petroleum derived asphalt. The common source of asphalt is the residue or 15 bottoms from the petroleum refining industry which inch~des those colllmol ly rerelled to as paving grade, roofer's flux, propane washed and air-blown.
The asphalt can optionally be modified with a polymer to give it improved flexibility on h~ntlling and improved resict~nce to flow to prevent challges in thickness from top to bottom in the sound screen. A prerelled polymer is a styrene/butadiene 20 copolymer such as Kraton 1101 (20% styrene, 75% butadiene) from Shell Co., Houston, Texas. The weight ratio of asphalt to polymer is pl~re-ably between about 6: 1 and about 20: 1. The polymer can be mixed into the asphalt under high shear at 300F (149C) to 400F (204C).
Another prerelled polymer is formed by copolymerization of SBS
25 thermoplastic rubber and styrene monomer. Such a polymer is described in more detail in U.S. Pat. No. 4,273,685 to Marzocchi et al., issued June 16, 1981, and U.S. Pat. No.
4,333,866 to Uffner, issued June 8, 1982, both incol~ol~led by reference herein.Other polymers that may be useful as asphalt modifiers include ethylene copolymers such as Elvax~) 450 (ethylene vinyl acetate copolymer) or Elvaloy~ AM30 (ethylene butylacrylate glycidyl meth~crylate terpolymer) both made by Du Pont (Wilming~on, Delaware). Other polymers can include polybutadiene or polyl,lopylene.
Various fillers can be incorporated into the asphalt layer 22 to increase the mass of the layer and thus reduce the amount of sound ll i1n~ led thert;ll-l ough.

21~7~48 Preferably the filler is selected from calcium carbonate, calcium oxide, clay, glass, mica, barium, and mixtures thereof. More pl~rel~bly the filler is calcium carbonate because it is hl~ ,ensi~e and contributes significant mass. Additives can also be incorporated into the asphalt layer 22 to provide it with additional plOpel ~ies such as fire retardancy.
Referring again to Fig. 3, the core 20 additionally incllldes insulation layers 24 positioned on both sides of the asphalt layer 22. The insulation layers 24 function to absorb sound directed toward the sound screen, and thus reduce the amount of sound in the offlce. The amount of sound absorption can be measured by a Noise Reduction Coefficient ("NRC") according to the standard method ASTM C423-90. The NRC is 10 measured on a scale from "0" me~nin~ no sound is absorbed to "1.0" me~ning all the sound is absorbed. P~ .bly the NRC of the core 20 in accordance with this invention is between about 0.5 and 1.0, and more preferably between about 0.55 and about 0.75. The amount of sound absorbed is related to the density and thickness of the in~ tion layers 24. Plerel~bly each insulation layer is between about 1/2 inch (1.27 cm) and about 2 inches 15 (5.08 cm) thick and more preferably between about 5/8 inch (1.588 cm) and about 1 inch (2.54 cm) thick.
A pl t;rt;ll ed in~ ting material for use as the insulation layers 24 of the core 20 is a mineral fiber ins~llating material. Mineral fiber in~ ting material can be formed from fibers of minerals such as glass, rock, slag or basalt. Pl ~l ably the in~ ting 20 material is formed from glass fibers such as fibrous glass wool. Any collvenlional process can be used to make the glass wool. A pre~lled process is known as the rotary process, in which molten glass is placed into a rota~ing spinner which has orifices in the pelilllc;ler, and glass flows out the orifices to produce a dowll~rdly falling stream of fibers which are collected on a conveyor. Another fiber forming process is a continuous or textile process 25 in which glass fibers are mechanically pulled from the orificed bottom wall of a feeder or bushing co~ g molten glass.
The glass fibers from the rotary or continuous process are in~re~-Aled with about 20% or less by weight of a binder, and typically between about 5% and about 10% by weight of a phenolic resin binder such as phenol-urea-formaldehyde. Then the 30 glass fibers are molded and cured to the desired density to form the fiberglass in~ ting material. Preferably the fiberglass in~ tine material used in the core 20 of this invention has a relatively low density between about 0.5 pounds per cubic foot (8 kg/m3) and about 5 pounds per cubic foot (80 kg/m3), more pLe~l~.bly between about 0.5 pounds per cubic 2i87848 foot (8 kg/m3) and about 2 pounds per cubic foot (32 kg/m3), and most preferably between about 0.9 pounds per cubic foot (14.4 kg/m3) and about 1.5 pounds per cubic foot (24 kg/m3). The glass fibers in the inc~ ting material preferably have an average ~ meter belween about 3 and about 25 microns, and more preferably between about 3 and about 5 12 microns. The fiber ~i~meter and density ofthe glass wool can be varied to modify the sound absorption characteristics of the insulation layer. A thin plastic film or similar material can also be provided on the surface of the insulation layer for this purpose.
Prere"ed fiberglass inc~ ting material is co~ llcl-;ially available from Owens Corning, Toledo, Ohio.
When a roll coating method is used to prepare the core 20 as will be described below, preferably the mineral fiber in~ ting material is provided with sufflcient binder to increase its tensile strength to better willlc~ d the stresses of the method. When the mineral fibers are fibrous glass wool, preferably the glass fibers are hllpl egl-~ted with at least about 8.5% by weight binder to achieve the desired tensile strength of at least about 15 18 lbs./6-inch width (8.16 kg/15.24-cm width). The plerelled binder is phenol-urea-formaldehyde.
A glass fiber board inc~ ting material is solllc;wha~ less plerelled for use as the insulation layers of the core. The glass fiber board is formed from fibrous glass wool and impre~ted with binder as described above. However, it is molded and cured to a 20 relatively high density between about 6 pounds per cubic foot (96 kg/m3) and about 28 pounds per cubic foot (448 kg/m3). As a result, it is a more rigid, board-like inc~ ting material than the lower density fiberglass in~ ting material described above.
This invention provides a processing advantage when using glass fiber board as the in~ul~tin~ material. Glass fiber board is conventionally produced in pieces 25 that are not more than 4 feet (1.2 meters) long. However, a sound screen is typically about 5 feet (1.5 meters) high. In the past, the m~n~f~c~lring process had to be changed at great expense to produce 5 feet (1.5 meters) long glass fiber boards suitable for use in a sound screen. This invention, on the other hand, allows two glass fiber board pieces to be placed together a~ cent to each other to make up the 5 feet (1.5 meters) height (or other 30 desired size) of the sound screen. Thus, the sound screen can be produced much more economically.
Figs. 4 and 5 illustrate a panel 12' for a sound screen incl~ding a core 20' in which each insulation layer 24' is made from two pieces 25 of glass fiber board. The core 218784~
20' is formed by placing two pieces 25 of glass fiber board adjacPnt to each other end to end. Then an asphalt layer 22 as shown in Fig. 4 is applied to the pieces 25. Then the r~ g two pieces 25 of the glass fiber board are placed adjac~Pnt to each other onto the asphalt layer 22. The insulation layers 24' are l~min~ted together by the asphalt layer 22.
5 By positioning the pieces 25 so that the joints 27 beLweell a~ljacP.nt pieces 25 are not ~li~ed~ the core 20' has adequate strength for h~n-lling and the pieces 25 retain their proper vertical position. Cover layers 26 are positioned on both sides of the core 20'.
Another in~ tin~ material suitable for use as the insulation layers 24 of the core 20 is a foamed plastic ins~ ting material. This foamed plastic in~ ting material is 10 an open cell foam which absorbs sound in a manner similar to the way a fiberglass in~ ting material absorbs sound. Any kind of plastic can be used in the foamed plastic in~ tin~ material, inc~ ling phenoLic foam or polyester foam.
The two insulation layers 24 are l~min~ted or bonded to the asphalt layer 22. In addition to its function in reducing sound tran~mi~ion, the asphalt layer 22 also 15 acts as an adhesive to l~min~te the two insulation layers 24 together. The layers are l~min~ted such that they stay together as a unit during proces~ing In the plere,led embodiment of Fig. 3, cover layers 26 are positioned on both sides of the core 20. The cover layers 26 can be made from a cloth material, a thin plastic material, or other suitable covering materials.
Also in the plerelled embodiment, thin tackable layers 28 are positioned bc;lweell the insulation layers 24 and the cover layers 26. As used herein, a "tackable layer" 28 is a layer of material which can be penetrated by tacks or pins to aLlow the office workers to hang papers or similar items on the sound screen. The material of the tackable layers 28 can be the relatively high density glass fiber board described in more detail 25 above, or can be other suitable tackable materials. Preferably each tackable layer 28 has a thickness b~;lween about 1/16 inch (0.16 cm) and about 1/2 inch (1.27 cm), and more preferably between about 1/16 inch (0.16 cm) and about 1/4 inch (0.64 cm). If a glass fiber board is used as the insulation layers 24, it is unnecessaly to include separate tackable layers 28 in the panel 12 ofthe sound screen.
While this invention has been descl il.ed in relation to an office sound screen, it is not Limited thereto. For example, this invention can also be used in a sound curtain which is hung around a piece of industrial e~luiplllenl to reduce the sound ll~lerlolll. It can also be used as a sound redllçing panel on a boat or other recreational vehicle. Other similar uses are also envisioned. The invention is applicable in any situation where it is desirable to reduce sound ~l~n~ c~sion and absorb sound. Further, while the invention has been described as a panel, it is not n~cess,., ily flat, but can be shaped into any 5 desired form.
As described above, the core 20 ofthe panel 12 incl~ldes an asphalt layer 22 and insulation layers 24 positioned on both sides of the asphalt layer and l~min~ted thereto.
The method for making the core 20 presented numerous difficulties. In the past, it was known to use a roll coating app&l ~IIIS to apply a liquid coating onto paper or similar 10 products. However, it was not previously thought to use a roll coating appa~ s to apply a layer of molten asphalt between two layers of fil,el~lass wool insulation. One reason is that the material being coated by a roll coating appal~lus must have sufficient tensile ~l englh to be pulled past the roller without being pulled apart. Fiberglass wool has very little tensile strength and would be pulled apart by a standard roll coating app~us.
15 Another reason is that molten asphalt readily adheres to metal and to other asphalt, but fiberglass wool is difficult to coat. As a result, the molten asphalt tends to adhere to the roller instead of coating the fiberglass wool. Pieces of the fiberglass wool are pulled out from the insulation layer onto the molten asphalt adhering to the roller. For these reasons, a standard roll coating method is not suitable for applying a layer of asphalt between two 20 fiberglass wool layers so that the layers are l~rnin~ted together.
However, a method has now been found using a modified roll coating app~ ~ S under specified conditions to apply an asphalt layer belweell two layers of mineral fiber insulation, and particularly belweell two fiberglass wool layers. As will be explained in detail below, the roll coating appal~ s is modified by the addition of a metal 25 belt conveyor to support the first fibelglass layer. The appa a~ls is also modified by reversing the direction of rotation of the coater applicator roller and coater gap roller, and reversing their respe~ e positions. In addition, it has been found hllpol l~ll to control the surface speed of the coater applicator roller, the gap between the coater applicator roller and the coater gap roller, and the viscosity of the asphalt.
Referring now to Fig. 6, the modified roll coating app~ s ofthe invention is indicated generally at 30. A first layer of mineral fiber such as a first fiberglass layer 32 is fed from a first fiberglass roll 34. The first fiberglass layer 32 is fed between a first pressure roller 36 and a first metal belt conveyor 38. The first metal belt conveyor 38 21~84g is driven by a pair of pulleys 40, and it provides support for the first fiberglass layer 32.
The first fiberglass layer 32 is then fed to a coater applicator roller 42. Preferably a li~
meçh~nicm 60 raises the first metal belt conveyor 38 to bring the first fiberglass layer 32 into contact with a substantial amount of the surface of the coater applicator roller 42.
5 Preferably the first metal belt conveyor 38 sags after passing the lift me~.h~ni~m 60 to avoid contact with the coater applicator roller 42. A coater gap roller 44 is positioned adjacP,nt to the coater applicator roller 42 with a gap 46 therebetween. The coater applicator roller 42 and coater gap roller 44 are heated, and are generally cylindrical in shape and lie generally parallel with one another. A supply of molten asphalt 48 is 10 provided in a trough formed between the upper portions of the coater applicator roller 42 and the coater gap roller 44. The coater applicator roller 42 and the coater gap roller 44 rotate in opposite directions so that the molten asphalt 48 is drawn dowll~v~ d between the rollers. The coater applicator roller 42 has a larger ~ meter than the coater gap roller 44, so that the coater applicator roller lies adjac~nt to the first fiberglass layer 32 whereas the 15 coater gap roller does not. As a result, molten asphalt 48 is carried dowll~vard on the surface of the coater applicator roller 42 and applied as an asphalt layer 22 onto the first fiberglass layer 32. At a position adjacent to the first fiberglass layer 32, the surface ofthe coater applicator roller 42 moves generally in the same direction as the first fiberglass layer 32.
A second layer of mineral fiber such as a second fiberglass layer 50 is fed from a second fiberglass roll 52. The second fibelglass layer 50 adheres to the asphalt layer 22 on the first fiberglass layer 32 as the layers are pulled past a second pres~ule roller 54. The combined layers form a core 20 in accordance with this invention. The core 20 is then carried by a second metal belt conveyor 56 driven by a pair of pulleys 58 (only one of 25 which is shown). The molten asphalt 48 of the asphalt layer 22 penetrates into and adheres to the first and second fiberglass layers 32 and 50. Thus when the asphalt layer 22 hardens, the first and second fiberglass layers 32 and 50 are l~min~ted to the asphalt layer.
The above-described method overcomes the problems encountered in using a standard roll coating app~al~ls. The first metal belt conveyor 38 is inr,hlded in the 30 modified roll coating appalal-ls 30 to support the first fiberglass layer 32 when it initially contacts the coater applicator roller 42. This ovel~collles the problem where the first fiberglass layer 32 is pulled apart for lack oftensile strength.

The other problem with a standard roll coating app~ ~lus is that the molten asphalt tends to adhere to the coater applicator roller instead of coating the fiberglass layer. This causes pieces of fiberglass to be pulled out from the fiberglass layer onto the molten asphalt on the roller. It has now been found that this problem can be overcome by 5 ~ g a certain thickness of molten asphalt 48 between the coater applicator roller 42 and the first fiberglass layer 32 as it is being coated. When this is done, the molten asphalt 48 flows onto the first fiberglass layer 32 as a suitable coating, instead of adhering to the coater applicator roller 42. This thickness of molten asphalt 48 is provided by modifying the roll coating appalallls 30 and IllAi~Ai~ g particular conditions as will be described 10 below.
The roll coating app~ s 30 has been modified by rt;vel~ing the direction of rotation of the coater applicator roller 42 and the coater gap roller 44, and reversing their re~e~ e positions. Thus, at a position ~djAcPnt to the first fiberglass layer 32, the surface of the coater applicator roller 42 moves in the same direction as the first fiberglass 15 layer 32 instead of the opposite direction. This same direction of movement helps to I l lAil ~ i n the desired thickness of molten asphalt 48 b~weell the coater applicator roller 42 and the first fiberglass layer 32. The gap bt;lween the coater applicator roller 42 and the coater gap roller 44 is also illlpoll~ll for this purpose. The gap is ,,,~ Ail~ed between about 0.030 inch (0.076 cm) and about 0.070 inch (0.178 cm), preferably between about 20 0.050 inch (0.127 cm) and about 0.065 inch (0.165 cm), and more plerel~bly is about 0.060 inch (0.152 cm).
The viscosity of the molten asphalt 48 (incl~tlin~ any filler or additive) as itis applied to the first fiberglass layer 32 is Ill~ ned belweell about 1,000 cps and about 10,000 cps, preferably between about 1,500 cps and about 2,500 cps, and more preferably 25 about 2,000 cps. The ttlllp~ re and composition of the molten asphalt are adjusted to achieve this viscosity. In a pr~relled embodiment in which the molten asphalt 48 is 50%
asphalt and 50% calcium c&ll,onale filler, and the molten asphalt is "l~il-lAil-ed at a tempel~L~lre of about 410F (210C) to achieve a 2,000 cps viscosity. In general, preferably the molten asphalt is ",A;..~ ed at a tell.pel~ re between about 375F (191C) 30 and about 450F (232C), more prere-~bly between about 390F (199C) and about 425F
(218C).
Additionally, it has been found important to control the surface speed of the coater applicator roller 42 relative to speed of the first ~erglass layer 32. The surface 2ls7a4~

speed ofthe coater applicator roller 42 is between about 1.5 times and about 3.0 times the speed ofthe first fiberglass layer 32, and preferably is between about 2.0 times and about 2.5 times the speed ofthe first fil,el~lass layer. In a prerelled embodiment, the surface speed of the coater applicator roller 42 is about 80 feetlminute (about 24.38 5 meters/minute) and the speed of the first fiberglass layer 32 is about 40 feetlminute (about 12.19 meters/minute). These above-described p.e~--ed conditions form an asphalt layer 22 having a thickness of about 0.030 inch (0.076 cm).
Another suitable method for making a core 20 is by extruding a film of asphalt of the approp~iate thickness and passing it between two layers of fiberglass wool 10 while the film is still hot.
In accordance with the provisions of the patent st~t~1tes the principle and mode of operation of this invention have been explained and illustrated in its prefe..ed embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically cA~la~ed and illustrated without departing from its spirit or 15 scope. For eAamplC, it is recognized that additional layers of material may be used in the sound screen along with those described above.
INDUSTRIAL APPLICABILITY
The invention can be useful when used as sound screens for offices, and in the m~n~lf~ctllre of sound screens.

Claims

1. A panel (12,12') for reducing sound comprising:
a core (20,20') comprising an asphalt layer (22) and insulation layers (24,24') positioned on both sides of the asphalt layer and laminated thereto, and a cover layer (26) positioned on at least one side of the core.

2. The panel (12,12') defined in Claim 1 wherein the asphalt layer (22) has a thickness between about 0.030 inch (0.076 cm) and about 0.125 inch (0.318 cm).

3. The panel (12,12') defined in Claim 1 wherein the asphalt layer (22) acts as an adhesive to hold the insulation layers (24,24') together.

4. The panel (12,12') defined in Claim 1 wherein the asphalt layer (22) additionally includes a filler selected from the group consisting of calcium carbonate, calcium oxide, clay, glass, mica, barium, and mixtures thereof.

5. The panel (12,12') defined in Claim 1 wherein the asphalt is modified with a polymer selected from the group consisting of styrene/butadiene copolymers, copolymers of SBS thermoplastic rubber and styrene monomer, ethylenecopolymers, polybutadiene, polypropylene, and mixtures thereof.

6. The panel (12,12') defined in Claim 1 wherein the insulation layers (24,24') comprise insulating material selected from the group consisting of mineral fiber insulating material and foamed plastic insulating material.

7. The panel (12') defined in Claim 6 wherein each layer (24') of the insulating material comprises at least two pieces (25) of mineral fiber board positioned adjacent to each other and laminated to the asphalt layer (22).

8. The panel (12') defined in Claim 7 wherein the fibrous glass wool has a density between about 0.5 pounds per cubic foot (8 kg/m3) and about 5 pounds per cubic foot (80 kg/m3), wherein the glass fibers have an average diameter between about 3 microns and about 12 microns, and wherein each insulation layer has a thickness between about inch (1.27 cm) and about 2 inches (5.08 cm).

9. The panel (12) defined in Claim 1 wherein the panel additionally comprises at least one tackable layer (28) positioned between at least one insulation layer (24) and cover layer (26).

10. The panel (12) defined in Claim 9 wherein the tackable layer (28) comprises glass fiber board having a density between about 6 pounds per cubic foot (96 kg/m3) and about 28 pounds per cubic foot (448 kg/m3) and a thickness between about 1/16 inch (0.16 cm) and about inch (1.27 cm).

11. The panel (12,12') defined in Claim 1 wherein a cover layer (26) is positioned on both sides of the core (20,20'), and the panel additionally comprises a rigid frame (16) positioned around at least three edges of the panel.

12. A panel (12,12') for reducing sound comprising:
a core (20,20') comprising an asphalt layer (22) and insulation layers (24,24') positioned on both sides of the asphalt layer and laminated thereto, and a cover layer (26) positioned on at least one side of the core, wherein the Sound Transmission Class of the core is between about 10 decibels and about 50 decibels.

13. The panel (12,12') defined in Claim 12 wherein the Noise Reduction Coefficient of the core is between about 0.5 and about 1Ø

14. A roll coating method comprising the steps of:
providing a generally cylindrical first roller (42) and a generally cylindrical second roller (44) positioned adjacent to one another and lying generally parallel with one another, and having a gap (46) therebetween of from about 0.05inch (0.127 cm) to about 0.07 inch (0.178 cm), supporting a first mineral fiber layer (32) on a conveyor (38), and passing the first mineral fiber layer between the first roller and the conveyor,wherein at a position adjacent to the first mineral fiber layer, the surface of the first roller (42) moves generally in the same direction as the first mineral fiber layer, supplying molten asphalt (48) between the gap between the first and second rollers, the molten asphalt having a viscosity between about 1,000 cps and about 10,000 cps, the first and second rollers rotating so that the molten asphalt flows through the gap and on the surface of the first roller onto the first mineral fiber layer to form an asphalt layer (22), wherein the surface speed of the first roller is between about 1.5 times and about 3.0 times the speed of the first mineral fiber layer, and placing a second mineral fiber layer (50) onto the asphalt layer.

15. The method defined in Claim 14 wherein the first mineral fiber layer (32) has a tensile strength of at least about 18 lbs./6-inch width (8.16 kg/15.24-cm width).

16. The method defined in Claim 14 wherein the viscosity of the molten asphalt (48) is between about 1,500 cps and about 2,500 cps.

17. The method defined in Claim 14 wherein the surface speed of the first roller (42) is between about 2.0 and about 2.5 times the speed of the first mineral fiber layer (32).

18. The method defined in Claim 14 wherein the gap (46) between the first roller (42) and the second roller (44) is from about 0.030 inch (0.076 cm) to about 0.070 inch (0.178 cm).

19. The method defined in Claim 14 comprising supplying the first mineral fiber layer (32) as a series of pieces (25) of mineral fiber board placed adjacent each other, forming joints (27) between adjacent pieces, and further comprising supplying the second mineral fiber layer (50) as a series of pieces (25) of mineral fiber board placed adjacent each other, forming joints (27) between adjacent pieces.

20. The method defined in Claim 19 comprising supplying the first and second mineral fiber layers (32,50) in such a manner that the joints (27) in the first layer are generally not aligned with the joints (27) in the second layer.