Classifications

• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
  • E04B9/00—Ceilings; Construction of ceilings, e.g. false ceilings; Ceiling construction with regard to insulation
  • E04B9/04—Ceilings; Construction of ceilings, e.g. false ceilings; Ceiling construction with regard to insulation comprising slabs, panels, sheets or the like
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04B—GENERAL BUILDING CONSTRUCTIONS; WALLS, e.g. PARTITIONS; ROOFS; FLOORS; CEILINGS; INSULATION OR OTHER PROTECTION OF BUILDINGS
  • E04B2103/00—Material constitution of slabs, sheets or the like
  • E04B2103/04—Material constitution of slabs, sheets or the like of plastics, fibrous material or wood

Definitions

• a core of acoustically absorbing materials i.e., materials having a high absorption coefficient, reduces noise by absorbing acoustic energy as sound waves strike and enter the acoustically absorbing material.
• acoustically absorbing materials are formed of unconsolidated or partially unconsolidated, lofty fibrous materials including compressed fibers, recycled fiber or shoddy materials, fiberglass or mineral fiber batts and felts and require a facing to contain the core of fibrous materials.
• Other known acoustically absorbing core materials including foam, materials having a honeycomb structure, microperforated materials and acoustically absorbing materials utilizing air spaces also utilize a protective and/or decorative facing for use in a building interior.
• Diffuse or Lambertian reflectance is the uniform diffuse reflection of light from a material in all directions with no directional dependence for the viewer, according to Lambert's cosine law. Diffuse reflectance originates from a combination of external scattering of light from features on the surface of a material, and internal scattering of light from features within a material. Internal light scattering can arise, for example, from features within a material such as pores and particles.
• acoustic absorbent and “acoustically absorbing” herein refer generally to the ability of a material to absorb incident sound waves.
• the term “diffuse reflectance” refers to the uniform diffuse reflection of light from a material in all directions with no directional dependence for the viewer, according to Lambert's cosine law. Diffuse reflectance can be approximated as the total reflectance minus specular reflectance.
• the facing for use in the ceiling tile of the invention is highly resistant to the penetration of water and fine particles including microorganisms.
• the void fraction of the facing i.e., 1 minus the solids fraction, is between about 0.5 and about 0.7.
• the facing has a pore diameter as measured by mercury porosimetry (H. M. Rootare, "A Review of Mercury Porosimetry” from Advanced Experimental Techniques in Powder Metallurgy. PlenumPress, 1970, pp. 255-252) between about 100 nm and about 20,000 nm and even between about 100 nm and about 1.500 nm.
• the pores include intra-fiber pores and inter-fiber pores.
• Intra-fiber pores are randomly distributed throughout the interior of a fiber and have a mean pore diameter from about 100 nm to about 1 ,000 nm. Inter-fiber pores are randomly distributed interstices between fibers in a plexifilamentary film-fibril sheet.
• the porous structure of the plexifilamentary film-fibril sheet consist of both types of pores forming torturous pore structure, rather then through hole structure found in mechanically perforated prior art facings.
• the mean pore diameter of the facing is less than about 20,000 nm, even less than about 5,000 nm, even less than about 2,000 nm, even less than about 1 ,000 nm and even between about 10 nm and about 1 ,000 nm. .
• One phase of the dispersion is a spin agent-rich phase which comprises primarily spin agent and the other phase of the dispersion is a polymer-rich phase which contains most of the polymer.
• This two-phase liquid-liquid dispersion is forced through a spinneret into an area of much lower pressure (preferably atmospheric pressure) where the spin agent evaporates very rapidly (flashes), and the polyolefin emerges from the spinneret as plexifilaments which are laid down to form the flash spun sheet.
• impurities are flashed along with the spin agent, so that the resulting flash spun sheet is free of impurities.
• the pore size distribution of the plexifilamentary film-fibrils of the flash spun sheet enhances the acoustic absorption of an acoustically absorbing core of an acoustically absorbing material or air space when the sheet is used as a facing on at least one surface of the core. It has furthermore surprisingly been found that flash spun sheet exhibits extremely high airflow resistance.
• the facing of the ceiling tile has the desirable combination of barrier, i.e., resistance to penetration of water, dust and/or microorganisms, and porosity resulting in high air flow or permeability and good acoustical performance.
• Acoustical absorption is a function of acoustic impedance, which is determined by a complex combination of acoustical resistance and acoustical reactance.
• the acoustical reactance is governed largely by material thickness, while acoustical resistance is governed by air flow through the material.
• Significant porosity is needed for acoustically transparent facings.
• barrier properties are needed for particulate and liquid resistance of the facing.
• Facings of the ceiling tile according to the present invention can comprise single or multiple layers of flash spun sheet provided the acoustical absorption is not compromised.
• the multilayer sheet embodiment is also useful for averaging out nonuniformities in single sheets due to nonuniform sheet thickness or directionality of sheet fibers.
• Multilayer laminates can be prepared by positioning two or more sheets face to face, and lightly thermally bonding the sheets under applied pressure, such as by rolling the sheets between one or more pairs of nip rollers.
• Laminates of sheets are preferably prepared by adhering the sheets together with an adhesive, such as a pressure sensitive adhesive.
• Adhesives of utility are those that maintain sufficient structural integrity of the laminate during normal handling and use. Adhesives of utility include moisture curable polyurethane, solvated polyurethane adhesives and water-borne acrylics.
• the scattering and diffuse reflection of light by flash spun facings is due to reflection of light at air-polymer interfaces of the inter- fiber and intra-fiber pores resulting from the flash spinning process. Reflection will increase with an increase in the difference between the refractive index of the pore phase (air, refractive index of 1.0) and the refractive index of the fiber polymer phase. An increase in light scattering is observed typically when the difference in refractive index between two phases is greater than about 0.1.
• Polymer comprising the flash spun facing preferably has a high refractive index (for example polyethylene, refractive index of 1.51 ) and low absorption of visible light.
• Flash spun facings according to the invention can further comprise particulate filler dispersed in the polymer phase forming the flash spun sheet fibers.
• Particulate fillers of utility will have a refractive index larger than the polymer and thus light scattering of the nonwoven sheet will increase with an increase in the difference between the refractive index of the pore phase (air, refractive index of 1.0) and the refractive index of the fiber polymer phase.
• Particulate fillers of utility have a high refractive index, high light scattering cross section and low absorption of visible light. Particulate filler enhances light scattering and thereby use of particulate filler can provide higher average reflectance for a given sheet thickness.
• Example particulate fillers include silicates, alkali metal carbonates, alkali earth metal carbonates, alkali metal titanates, alkali earth metal titanates, alkali metal sulfates, alkali earth metal sulfates, alkali metal oxides, alkali earth metal oxides, transition metal oxides, metal oxides, alkali metal hydroxides and alkali earth metal hydroxides.
• the acoustically absorbent ceiling tile of the invention is particularly useful in critical indoor environments in which indoor air quality and cleanliness are critical, such as in schools, hospitals, cleanrooms, and the like.
• the resulting facing is free of impurities and the facing does not generate off-gassing of any volatile compounds.
• the facing is non- linting in that it does not release particles or fibers as a result of the high degree of consolidation of the single film-fibrils within the sheet structure.
• the acoustically absorbing core preferably contains substantially no VOCs.
• the facing can be cleaned by wiping or washing.
• the facing can also be sterilized by known methods including solution cleaning, physical energy radiation or gas sterilization.
• Frazier Air Permeability was measured according to ASTM D737-75 in CFM/ft 2 at 125 Pa differential pressure.
• Hydrostatic Head was measured according to AATCC TM 127, DIN
• Parker Surface Smoothness was measured according to TAPPI 555 at a clamping pressure of 1.0 MPa and is reported in micrometers.
• Sound Absorption Coefficient as reported in Fig. 3 was measured using a laboratory setting including a reverberant room in compliance with ASTM C 423, specimen mounting A (without air space) according to ASTM E 795.
• the absorbers were placed on the floor of the reverberant room in a 1 inch high aluminum test frame. The edges of the frame were sealed to the floor using duct tape to eliminate flanking noise.
• the sound absorption measurements were conducted at 1/3 octave bands from 80 to 5,000 Hz. Ten decay measurements were taken for every microphone position.
• Thstimulus values are calculated by the method of ASTM E308-01 using the CIE 10° 1964 standard observer and illuminant D65.
• Noise Reduction Coefficient was calculated as an average of the Sound Absorption Coefficients at 250, 500, 1000, 2,000 and 4,000 Hz as measured in accordance with ASTM C423.
• Porosity and pore size distribution data are obtained by known mercury porosimetry methodology as disclosed by H. M. Rootare in "A Review of Mercury Porosimetry” from Advanced Experimental Techniques in Powder Metallurgy, pp. 225-252, Plenum Press, 1970.
• Porosity 1 -((Basis weight/density of solid x thickness))
• the total absorber thickness of each of the examples was about 25 mm.
• the table includes properties of the facings used in the example absorbers.
• the range indicated for Gurley Hill porosity of Example 1 is based on the typical range within which the flash spun nonwoven varies according to specification.
• the average reflectance is the average of 31 measurements at wavelengths between 400 nm and 700 nm taken at 10 nm increments.
• Flash spun facing of Example 1 has a hydrostatic head of at least 180 cm of H 2 O
• facing of Example 2 has a hydrostatic head of at least 24 cm of H 2 O according to the product specification (tested per AATCC TM 127, DIN EN 20811 with a test rate of 60 cm of H 2 O per minute).
• the Table includes properties of the facings used in the example absorbers.
• Example 1 and 2 The Gurley Hill porosity of Example 1 and 2 was measured experimentally and it is well in agreement with the typical range within which the flash spun nonwoven varies for both Tyvek® styles according to specification.
• Air permeability as measured by Gurley Hill porosity and Frazier air permeability characterizes the general porosity or openness of the structure. The range for air permeability for various types of nonwoven structures is very wide. Typically, all nonwovens have much more open structure with Frazier air permeability of about 50 cfm or higher. Solid films have very closed, solid structure, which is why films are called impervious, with Gurley Hill porosity well above 10,000 s.
• the air permeability of the flash spun facing can be changed from Gurley Hill range of about 4,000 s, like for Example 1 to Frazier air permeability to about 30 cfm, giving a range of Specific Air Flow Resistance of about 31 ,000,000 to 800 rayls.
• Total porosity of the structure can be roughly estimated from the facing's basis weight, thickness and density of the polymer. Knowing polyethylene has a density of about 0.98 g/cm 3 , the total porosity can be estimated as being about 0.6 for facing of Example 1 and about 0.7 for facing of Example 2. This is well in agreement with total porosity as measured by mercury porosimetry.
• the pore size range was from 10 nm to about 8,000 nm for Example 1 and from 10 nm to about 10,000 nm for Example 2, as measured by mercury porosimetry.
• the mean pore size was about 2,000 nm for both, Example 1 and Example 2.
• Solid films have total porosity of about 0, which means they have no voids or pores inside the structure. This is why solid films have extremely good barrier properties.
• inventive flash spun facing exhibits the water resistance range similar to the water resistance of solid impervious films as measured by hydrostatic head.
• the typical range of hydrostatic head for the inventive facing is from about 24 to about 230 cm H 2 O, as illustrated by Example 1 and 2.
• a comparative sample was prepared similarly without the flash spun facing.
• the thickness of the comparative sample was about 25 mm.
• the examples and comparative sample were conditioned at room temperature for at least two weeks after manufacturing, and at controlled conditions (temperature of 23 0 C and RH of 60%) for 24 hours before acoustic testing. Absorption coefficient data were obtained for each sample.

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• Engineering & Computer Science (AREA)
• Architecture (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Building Environments (AREA)
• Laminated Bodies (AREA)

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• 2008
  • 2008-12-19 US US12/339,951 patent/US20090173570A1/en not_active Abandoned
  • 2008-12-22 JP JP2010539927A patent/JP2011508119A/ja active Pending
  • 2008-12-22 CN CN2008801272769A patent/CN101946050A/zh active Pending
  • 2008-12-22 WO PCT/US2008/087904 patent/WO2009086248A1/en not_active Ceased
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