JP2011508119A - Sound absorbing ceiling tiles with a barrier surface material having diffuse reflectance - Google Patents

Abstract

  The sound absorbing ceiling tile includes a core of sound absorbing material having two main surfaces and a surface material covering at least one main surface of the core. The face material includes a porous flash spun plexifilamentary film-fibril sheet having a cohesive surface and comprising a plurality of pores having a pore size of about 100 nm to about 20,000 nm and an average pore size of less than about 20,000 nm. The face material has a high diffuse reflectance of light and a reflectance greater than about 86%. The use of a face material improves ambient sound absorption at frequencies below about 1200 Hz. Because the facing material provides a barrier to moisture and micro-particles, the ceiling tiles are suitable for use in environments where cleanliness is important.

Description

  The present invention relates to a ceiling tile used inside a building.

  Sound absorbing ceiling tiles that are used to reduce the amount of noise and / or reverberation in a given area, such as inside a building, are known in the art. In such ceiling tiles, the sound absorbing material, i.e. the core of the material having a high sound absorption rate, reduces noise by absorbing acoustic energy when sound waves collide and enter the sound absorbing material. Many known sound absorbing materials are bulky fiber materials that are not consolidated or partially consolidated, including compressed fibers, recycled fibers or shoddy materials, glass fibers or mineral fiber batts and felts. It is formed and requires a surface material that houses the core of the fiber material. Other known sound-absorbing core materials, including foams, honeycomb-structured materials, micro-perforated materials, and sound-absorbing materials using air layers also use protective and / or decorative surface materials used inside buildings To do.

  The surface material covering the sound absorbing ceiling tiles acts as a durable covering that protects the core during handling, use and maintenance. In order to improve sound absorption, it is desirable that the surface material covering the sound-absorbing material is a material that is acoustically transparent or sound-absorbing but not acoustically reflective. Surface materials that are acoustically reflective contribute to ambient noise and are undesirable. Known surface materials for covering sound absorbing ceiling tiles include fabrics, nonwoven sheets, paper, films and perforated solid materials.

US Pat. Nos. 5,824,973 and 6,877,585 describe a porous sound insulation substrate and a paper, fabric or perforated film surface material having a ventilation resistance of 200-1210 rails. A sound-absorbing laminate useful as a ceiling tile including a sheet is disclosed. U.S. Patent Application Publication No. 2007/0151800 discloses a sound insulation sheet material comprising a main sound absorbing sheet and a high density porous membrane, wherein the high density porous membrane has a span of less than about 5,000 rails of ventilation resistance. It can be a bond web, meltblown web, spunlace web, card or airlaid staple fiber web, woven web, wet web, or a combination of such webs. U.S. Pat. No. 3,858,676 discloses, among other things, a thin sound absorbing panel for frequencies below 500 Hz and its use in ceiling systems, the panel comprising a perforated backing, basis weight 12-2 , 140 g / m ² and a thick textile surface material with a ventilation resistance of 300 to 1,800 rail per unit area, and a glass fiber core. U.S. Patent No. 5,832,685 No. specification, spunbond fabrics, or bonded staple fiber may be a fabric comprising a self-supporting sound-absorbing panels and ceiling systems, including a basis weight of about 10~15oz / yd ² nonwoven Discloses its use. These known surface materials have the disadvantage that water, dust, mold and microorganisms are prone to intrusion, thus limiting their use in critical environments.

  It is desirable that the visible light be diffused and further distributed and reflected from the surface of the ceiling tile surface material, rather than a specular (mirror-like) reflection where the light is reflected only at an angle equal to the incident angle. Diffuse or Lambertian reflectivity is a uniform diffuse reflection of light from a material in all directions, according to Lambert's cosine law, and has no direction dependency with respect to the observer. Diffuse reflectance results from a combination of external scattering of light from surface features of the material and internal scattering of light from features within the material. Internal light scattering can arise from features in the material such as pores and particles, for example. The light scattering cross section per unit feature volume of a material containing closely spaced refractive index inhomogeneities is maximized when the average diameter of the feature is slightly less than one-half the wavelength of the incident light. The degree of light scattering also increases when there is a large difference between the refractive index of the scattering feature and the refractive index of the phase in which the feature is dispersed.

  It would be desirable to have a sound absorbing ceiling tile with a combination of diffuse light reflectance and sound absorption that is suitable for use in a variety of important environments.

According to one embodiment, the present invention provides:
A core of sound-absorbing material having two main surfaces, and a surface material covering at least one main surface of the core, having a coherent surface, having a basis weight of about 140 g / m ² or less, and having a pore size of about A surface material comprising a flash-spun plexifilamentary film-fibril sheet comprising a plurality of pores of 100 nm to about 20,000 nm and an average pore size of less than about 20,000 nm and having a light reflectivity greater than about 86%;
Including ceiling tiles.

According to another embodiment, the present invention provides:
(A) A sound-absorbing material having a plurality of pores having a pore size of about 100 nm to about 20,000 nm and an average pore size of less than about 20,000 nm and coated with a surface material of a flash spinning sheet having a light reflectance of more than about 86% Providing a ceiling tile including a core of:
(B) arranging the ceiling tile in the environment such that ambient sound is absorbed by the ceiling tile and light is reflected;
The present invention relates to a method for improving sound absorption and light reflectance in an environment.

It is a graph which shows the sound absorptivity, acoustic reflectance, and acoustic transmittance of a flash spinning sheet (shut-off measurement). It is a graph which shows the sound absorptivity, reflectance, and sound transmittance of a flash spinning sheet (anechoic measurement). It is a graph which compares the sound absorption rate of one sound-absorbing material without a surface material and two sound-absorbing materials which have a surface material useful for the ceiling tile by this invention.

  According to one embodiment of the present invention, a ceiling tile is provided that has an advantageous combination of sound absorption, diffuse reflectance of light, and barriers to ingress of particulates, microorganisms and moisture. The ceiling tile according to the present invention is durable and waterproof, hypoallergenic, non-fluffing, no gas release, resistant to ingress of moisture, dust, mold and microorganisms, and reflectivity And a surface material that does not interfere with the sound absorbing ability.

  The terms “sound absorbing” and “sound absorbing” as used herein generally refer to the ability of a material to absorb incident sound waves.

  The term “diffuse reflectance” is a uniform diffuse reflection of light from a material in all directions according to Lambert's cosine law, and has no direction dependency with respect to the observer. The diffuse reflectance can be estimated as the total reflectance minus the specular reflectance.

  The sound-absorbing ceiling tile of the present invention includes a sound-absorbing core and a nonwoven fabric surface material that covers at least one surface of the core. The surface material is acoustically transparent in that the surface material does not impair the sound absorption of the core, or the surface material can improve the sound absorption of the ceiling tile core. Nonwoven surface materials include flash spun plexifilamentary film-fibril sheets having an agglomerated surface. “Coherent surface” means that the surface of the sheet is consolidated or bonded. The bonding method may be any method known in the art, including but not limited to thermal calendering, through-gas bonding, and point bonding. The core and surface material are bonded together by any known suitable bonding method such as adhesive bonding, solvent bonding, ultrasonic bonding, thermal bonding, point bonding, stitch bonding and the like. The combined material is then cut into ceiling tiles.

  The sound absorbing core includes any known sound absorbing material and / or air layer. The core has a noise reduction rate (NRC) of about 0.3 to about 0.9 when measured by ASTM C423, Attachment A (no air layer). Suitable sound-absorbing materials include spunbond nonwoven fabrics, carded nonwoven fabrics, needle punched nonwoven fabrics, airlaid nonwoven fabrics, wet nonwoven fabrics, spunlace nonwoven fabrics, spunbond-meltblown-spunbond composite nonwoven fabrics and meltblown nonwoven fabrics, woven fabrics, knitted fabrics, Three-dimensional meshes such as honeycomb structures and foams, combinations thereof, and the like can be mentioned. The term “nonwoven” means a web comprising a large number of randomly distributed fibers. The fibers may be staple fibers or continuous fibers. The fibers can include a single material or multiple materials as a combination of different fibers or similar fibers, each consisting of a different material. Other materials suitable for use as the core are foams and perforated sheets such as open cell melamine foam, polyimide foam, polyolefin foam, and polyurethane foam. According to a preferred embodiment of the present invention, the core is substantially free of volatile organic compounds (VOCs). One preferred material is a glass fiber batting that does not contain formaldehyde. In general, the thicker the core material, the greater the sound absorption of the ceiling tile, especially at low frequencies. The air layer covered with the surface material can serve as an absorbent core.

Acoustically transparent surface materials for use with sound absorbing articles including ceiling tiles are known in the art. Such surface materials typically have a pore area, i.e., an area of surface pores relative to the total surface area, of from about 5% to about 50%, depending on the need for sound absorption. If high frequency sound absorption is not required, a pore area of 5-15% is appropriate (MD Egan Architectural Acoustics, J. Ross Publishing, 2007, p. 74-76). The hole area ratio and the hole diameter affect the acoustic transparency by determining the critical frequency, but after the critical frequency, the sound absorption decreases rapidly. The critical frequency (f _c ) can be estimated using the following equation, but the sound absorption decreases rapidly when the critical frequency is exceeded:
f _c -40P / D
Where
f _c represents the critical frequency, the Hz,
P represents the pore area,%,
D represents the hole diameter, in.

  Examples of known acoustically transparent surface materials include mesh fabrics, low density fabrics, and woven scrims. The disadvantage of such face materials is that they are very resistant to intrusion of barriers such as water, dust and / or microorganisms.

The surface material used for the ceiling tile of the present invention has high resistance to invasion of fine particles including water and microorganisms. The porosity of the surface material (total porosity), that is, 1 minus the solid fraction is about 0.5 to about 0.7. The pore diameter of the surface material is measured by the mercury intrusion measurement method (HM Rootare, “A Review of Mercury Porousimetry”, from Advanced Advanced Techniques, 25 Measured in Pt. 100 nm to about 20,000 nm, and further about 100 nm to about 1500 nm. For the purposes of the present invention, pores include intrafiber pores and interfiber pores. The intra-fiber pores are randomly distributed throughout the interior of the fiber, and the average pore diameter is about 100 nm to about 1,000 nm. Interfiber pores are gaps randomly distributed between fibers in the plexifilamentary film-fibril sheet. The porous structure of the plexifilamentary film-fibril sheet consists of the two types of pores that form a tortuous pore structure rather than the through-hole structure found in mechanically perforated prior art surface materials. . The average pore size of the surface material is less than about 20,000 nm, further less than about 5,000 nm, further less than about 2,000 nm, further less than about 1,000 nm, and further from about 10 nm to about 1,000 nm. A pore diameter of 10 nm to 1000 nm represents an intrafiber pore. Summing the volumes of pores having a diameter of 10 nm to 1000 nm, for the purposes of the present invention, the volume of intra-fiber pores called Vpore is obtained. The specific pore volume SPV (unit: cm ³ / m ² ) is determined by the basis weight of the nonwoven sheet (unit: g) as disclosed in US Patent Application Publication No. 2006/026310, also assigned to DuPont. / M ² ) and the mathematical product of the sheet pore volume (unit: cm ³ / g) of pores having a given average diameter.

  In some applications, such as when the sound-absorbing material does not contain dust or nutrients that promote microbial growth, mechanically perforating the surface material to release the structure and to increase the critical frequency value May be desirable. It was found that perforating the surface material can improve the total sound absorption of the ceiling tile.

  In some applications, it is desirable for the ceiling tile of the sound absorbing material to provide a barrier to microorganisms including bacteria, viruses, and mold. The facing material has a log reduction value (LRV), which is a measure of microbial filtration, when measured according to ASTM F2638-07 and ASTM F1608, of at least about 2, or even at least about 4. As in the case of known laminated papers, it is desirable that the surface material does not have a flow rate or time dependent LRV so that the surface material has a stable barrier efficiency and does not enhance the barrier over time during use. The face material is further free of nutrients that promote the growth of microorganisms, including bacteria, yeast, and fungi, and is not subjected to additional antibacterial or antifungal treatments.

The nonwoven surface material used for the ceiling tile of the present invention includes a plexifilamentary film-fibril sheet formed by flash spinning, which is synonymous herein with flash-spun plexifilamentary film-fibril sheet or Also called a flash spinning sheet. The nonwoven fabric surface material of the present invention is lightweight, thin and strong. The basis weight of the surface material is less than about 140 g / m ² , and further about 34 g / m ² to about 120 g / m ² . The thickness of the surface material is about 1 mm or less, further about 0.02 mm to about 0.40 mm, further about 0.10 mm to about 0.25 mm. Previously used thin surface materials have very low sound absorption and low levels of strength and durability. The flash-spun surface material according to the present invention imparts a high degree of isotropic strength and durability that is important for the assembly and handling of the ceiling tiles of the present invention and stable long-term performance. The preferred tensile strength of the surface material in both the machine direction and the transverse direction is about 20 N / 2.54 cm or more as measured by ASTM D5035.

  In general, for effective sound absorption, it has been considered that the wavelength of sound absorbed and the thickness of the sound absorbing material must be on the same order of magnitude. From FIG. 1, it can be seen that, when tested in a cut-off arrangement with an acoustic tube, the flash spun plexifilamentary sheet used as the nonwoven fabric surface material has an acoustic reflectivity of approximately 1.0 and no sound absorption is detected. In contrast, as shown in FIG. 2, when tested in an anechoic arrangement (with an air layer behind the sheet in the acoustic tube), the same flash-spun plexifilamentary sheet is surprisingly low And sound absorption indicated by a mid-range frequency, for example, a sound absorption rate of 0 to 0.2 at about 200 to about 1200 Hz, and low acoustic reflection. Previously, it was possible to act as a sound absorber (Helmholtz resonator) in the vicinity of the resonant frequency of individual holes with a closed air layer behind the surface material. It was thought that it was only the pore surface material. Surprisingly, it has been found that the surface material of the ceiling tile of the present invention, which does not have through holes and is very thin, has improved sound absorption at low and intermediate frequencies.

  As disclosed in US Pat. No. 3,860,369, the flash spun sheet is manufactured by the following general process. The flash spinning process is performed in a chamber having a vapor removal port and an opening through which the sheet material produced by this process is removed. A polymer solution is prepared at high temperature and pressure and fed into the chamber. The solution pressure is greater than the cloud point pressure, which is the lowest pressure at which the polymer is completely dissolved in the spinning solvent to form a homogeneous one-phase mixture. The one-phase polymer solution passes through a letdown orifice and enters a low pressure (or vacuum) chamber where the solution separates into a two-phase liquid-liquid dispersion. One phase of the dispersion is a spinning solvent rich phase mainly containing a spinning solvent and the other phase of the dispersion is a polymer rich phase containing most of the polymer. This two-phase liquid-liquid dispersion passes through the spinneret and enters a region where the pressure is much lower (preferably at atmospheric pressure) where the spinning solvent evaporates very quickly (flashes) and the polyolefin Are ejected from the spinneret as plexifilaments and deposited to form a flash spun sheet. During the flash evaporation process, impurities are flash evaporated together with the spinning solvent, so that the resulting flash-spun sheet is free of impurities.

  As used herein, the term plexifilamentary or plexifilamentary refers to a plurality of thin ribbons of irregular length, an average fibril thickness of less than about 4 micrometers, and a median width of less than about 25 micrometers. The film-fibril three-dimensional integrated network structure. In a plexifilamentary structure, film-fibrils are generally aligned with the same extent as the long axis of the structure, and they are irregular in various positions throughout the length, width, and thickness of the structure. They are connected and separated intermittently at a proper interval to form a continuous three-dimensional network structure. Such a structure is described in further detail in US Pat. Nos. 3,081,519 and 3,227,794.

  The sheet is consolidated, which includes compressing the sheet between the belt and the compacting roll to provide a structure with sufficient strength to handle outside the chamber. The sheet is then collected on a take-up roll outside the chamber. The sheets can then be bonded using methods known in the art such as thermal bonding, through-gas bonding, and point bonding.

  The film-fibril diameter of the flashspun surface material, i.e., about 4 micrometers to about 25 micrometers, falls in the region of ultrasonic wavelengths. At frequencies from about 100 Hz to about 1600 Hz, the wavelength of sound is orders of magnitude greater than the film-fibril diameter. Nevertheless, the thin plexifilamentary film-fibril of the surface material according to the present invention surprisingly improves the sound absorption of the sound absorbing material at about 100 Hz to about 1600 Hz, or even about 100 Hz to about 1200 Hz. This is the frequency region where mechanical and human voices are most frequently emitted, and therefore most frequently occur as undesirable noise inside buildings. Without wishing to be bound by theory, when the sheet is used as a surface material on at least one side of the core, the pore size distribution of the plexifilamentary film-fibril of the flash-spun sheet is the sound absorption core of the sound absorbing material or the sound absorption of the air layer. It is thought to improve. Surprisingly, it has been found that flash spun sheets exhibit very high resistance to ventilation.

Polymers capable of producing the surface material of the sound-absorbing ceiling tile according to the present invention include polyolefins (for example, polyethylene, polypropylene, polymethylpentene, and polybutylene), acrylonitrile-butadiene-styrene (ABS) resin, polystyrene, styrene-acrylonitrile, styrene- Butadiene, styrene-maleic anhydride, vinyl plastic (eg, polyvinyl chloride (PVC)), acrylic, acrylonitrile-based resin, acetal, perfluoropolymer, hydrofluoropolymer, polyamide, polyamide-imide, polyaramide, polyacrylate ), Polycarbonate, polyester (e.g., polyethylenenaphthalate ( PEN)), polyketones, polyphenylene ethers, polyphenylene sulfides and polysulfones. Preferred among the polymers are polyolefins such as polyethylene and polypropylene. As used herein, the term polyethylene includes not only ethylene homopolymers, but also copolymers in which at least 85% of the repeating units are derived from ethylene. Preferred polyethylenes have an upper limit of melting range of about 130 ° C. to 137 ° C., a density in the range of 0.94 to 0.98 g / cm ³ , and a melt index of 0.1 to 100, preferably 0.1 to 4. Linear high density polyethylene having (as defined by ASTM D-1238-57T, Condition E). The term polypropylene, as used herein, includes not only a propylene homopolymer but also a copolymer in which at least 85% of the repeating units are derived from propylene units.

  In the nonwoven fabric surface material, a known ultraviolet light stabilizer, antistatic agent, pigment, and / or flame retardant may be further dispersed in the polymer of fibers of the nonwoven fabric substrate.

  The surface material of the ceiling tile has a desirable combination of barriers, i.e. resistance to water, dust and / or microbial ingress and porosity, resulting in high air flow or air permeability and good acoustic performance. It is done. Sound absorption is a function of acoustic impedance, which is determined by a complex combination of acoustic resistance and acoustic reactance. While acoustic reactance is primarily governed by material thickness, acoustic resistance is governed by air flow through the material. An acoustically transparent surface material requires a considerable porosity. On the other hand, barrier properties are necessary for the surface material particles and liquid resistance.

  If the sound absorption is not impaired, the ceiling tile surface material according to the present invention may comprise a single-layer or multi-layer flash-spun sheet. Multi-layer sheet embodiments are also useful for averaging single sheet non-uniformities due to non-uniform sheet thickness or sheet fiber orientation. Manufacture multi-layer laminates by placing two or more sheets face-to-face and pressing the sheets lightly and thermally fusing them, for example, by rolling the sheets between a pair of nip rollers can do. Preferably, the sheet laminate is produced by gluing the sheets together with an adhesive such as a pressure sensitive adhesive. Useful adhesives are those that maintain sufficient structural integrity of the laminate during normal handling and use. Useful adhesives include moisture curable polyurethanes, solvated polyurethane adhesives, and aqueous acrylics.

  The reflectivity of the ceiling tile surface material is at least about 86%, even at least about 88%, even at least about 90%, even at least about 94% in the visible light spectrum, i.e., at a wavelength of about 400-700 nm. . The reflectivity of the flashspun surface material according to the present invention decreases with increasing thermal bond. Thermal bonding reduces the volume of intrafiber pores with a large scattering cross-section per unit pore volume that contributes significantly to diffuse reflectance. Thermal bonds also reduce the volume of interfiber pores that contribute to diffuse reflectance. The flash spun sheets useful for ceiling tiles according to the present invention are preferably not bonded so densely that the reflectivity is less than about 86%. Flash spun sheets useful for ceiling tiles according to the present invention are consolidated and preferably joined to the extent necessary to maintain the structural integrity of the sheet during the manufacture of the ceiling tile. In particular, the sheet must have sufficient structural integrity so that the edges are not broken when the sheet is laminated to the ceiling tile core and then cut into tiles. Preferably, the delamination strength of the flash spun sheet is at least about 0.028 N / m. The delamination strength is a measurement reported in units of force / length as defined by ASTM D 2724 and is a bond in certain types of sheets, for example nonwoven sheets produced from plexifilamentary film-fibrils. This is related to the degree of coupling.

  The scattering and diffuse reflection of light by the flash spinning surface material is due to the reflection of light at the air-polymer interface between the fibers and within the fibers produced by the flash spinning process. Reflection increases with increasing difference between the refractive index of the pore phase (air, refractive index 1.0) and the refractive index of the fiber polymer phase. An increase in light scattering is typically observed when the refractive index difference between the two phases is greater than about 0.1. The polymer making up the flashspun surface material preferably has a high refractive index (eg, polyethylene, refractive index 1.51) and low visible light absorption.

  The flash-spun surface material according to the present invention may further comprise a particulate filler dispersed in the polymer phase forming the flash-spun sheet fiber. Useful particulate fillers have a refractive index greater than that of the polymer, and thus the light scattering of the nonwoven sheet results in the refractive index of the pore phase (air, refractive index 1.0) and the refractive index of the fiber polymer phase. It increases with increasing difference. Useful particulate fillers have a high refractive index, a large light scattering cross section, and a low visible light absorption. Particulate fillers increase light scattering, so that a relatively high average reflectivity can be obtained for a given sheet thickness when using particulate fillers. The particulate filler may be of any shape and has an average diameter of about 0.01 micrometer to about 1 micrometer, preferably about 0.2 micrometers to about 0.4 micrometers. The flash spun sheet containing the particulate filler comprises at least about 50% by weight polymer, and the particulate filler is from about 0.05% to about 50% by weight, preferably about 50%, based on the weight of the polymer. It constitutes 0.05% to about 15% by weight. Exemplary particulate fillers include silicate, alkali metal carbonate, alkaline earth metal carbonate, alkali metal titanate, alkaline earth metal titanate, alkali metal sulfate, alkaline earth metal sulfate, alkali Examples include metal oxides, alkaline earth metal oxides, transition metal oxides, metal oxides, alkali metal hydroxides, and alkaline earth metal hydroxides. Specific examples include titanium dioxide, calcium carbonate, clay, mica, talc, hydrotalcite, magnesium hydroxide, silica, silicate, hollow silicate sphere, wollastonite, feldspar, kaolin, magnesium carbonate, barium carbonate, magnesium sulfate, Examples include barium sulfate, calcium sulfate, aluminum hydroxide, calcium oxide, magnesium oxide, alumina, asbestos powder, glass powder, and zeolite. Contains particulate filler using known methods such as those disclosed in US Pat. No. 6,010,970 and PCT Publication No. WO 2005 / 98,119. The nonwoven fabric sheet of this invention is manufactured.

  The sound absorbing ceiling tiles of the present invention are particularly useful in critical indoor environments where indoor air quality and cleanliness are important, such as schools, hospitals, and clean rooms. As a result of the instantaneous evaporation process during flash spinning of the surface material, the resulting surface material does not contain impurities and the surface material does not vaporize or release volatile compounds. Furthermore, the facing material is not fuzzy in that it does not release particles or fibers because each film-fibril in the sheet structure is highly consolidated. Furthermore, the sound absorbing core is preferably substantially free of VOC. The face material can be cleaned by wiping or washing. Alternatively, the surface material can be sterilized by known methods including solution cleaning, physical energy radiation, or gas sterilization. If cleaning and sterilization of the face material is not convenient, the flash-spun face material can be discarded and replaced with minimal cost and effort.

  In addition, graphic designs such as patterns, images and / or text can be printed on the ceiling tile surface material so that an aesthetic appearance is desired for the intended application. Conveniently the face material can be replaced to change the image and / or text. By changing the surface material, the aesthetic appearance of the ceiling tile can be easily and inexpensively changed.

  The present invention further provides (i) a ceiling tile comprising a core of sound-absorbing material coated with a surface material of a flash-spun sheet having a plurality of pores, wherein the pore diameter is about 100 nm to about 100 nm. 20,000 nm, further about 100 nm to about 1500 nm, and the average pore diameter of the pores is less than about 20,000 nm, further less than about 5,000 nm, further less than about 2,000 nm, even less than about 1,000 nm, And (ii) placing the ceiling tile in the environment such that ambient sound is absorbed by the ceiling tile and light is diffusely reflected. Including a method for improving sound absorption and light reflectance.

Test method Basis weight is measured by the method ASTM D 3776, make a change with respect to sample size, it was reported in units of g / m ^2.

  Tensile strength was measured according to ASTM D5035 and reported in units of N / 25.4 cm.

  Gurley Hill porosity was measured according to TAPPI T460 and reported in seconds.

Frazier air permeability was measured in CFM / ft ² when the differential pressure was 125 Pa, according to ASTM D737-75.

The hydrostatic head was measured according to AATCC ™ 127, DIN EN 20811 at a test rate of H ₂ O 60 cm per minute.

  Parker surface smoothness is measured according to TAPPI 555 at a clamping pressure of 1.0 MPa and is reported in micrometers.

The airflow resistance per unit area is equal to the air pressure difference between both sides of the sample divided by the linear velocity of the air flow measured outside the sample and is reported in Ns / m ³ . The values reported herein were determined as follows. The volume air flow rate Q was calculated by dividing the air permeability of the sample when the differential pressure was 125 Pa by the area of the sample (38 cm ² ) using the following formula.
Q (unit: m ³ /s)=0.000471947×(air permeability (unit: CFM / ft ² ) / area (unit: ft ² ))

For materials with relatively low air permeability, Gurley Hill porosity (unit: seconds) was used. For flash-spun sheets of less than 101 g / m ² , the Frazier air permeability of 0.6 m ³ / min / m ² (2 ft ³ / min / ft ² )) corresponds to about 3.1 seconds, and is therefore used herein as a sample Frazier air permeability (unit: CFM / ft ² ) was estimated to be 3.1 / Gurley Hill porosity (unit: seconds).

Next, the ventilation resistance (unit: Pa-s / m ³ ) was calculated by dividing the differential pressure by the air flow rate Q. Finally, the ventilation resistance per unit area (unit: Ns / m ³ ) was calculated by dividing the ventilation resistance by the area of the sample.

  The transmittance, reflectance, and sound absorption as reported in FIGS. 1 and 2 were measured in an anechoic acoustic tube arrangement and a blocked acoustic tube arrangement in accordance with ASTM E1050 and ISO 10534.

  The sound absorption rate reported in FIG. 3 was measured using a laboratory setting including a reverberation chamber according to ASTM C 423, sample attachment A (no air layer) according to ASTM E795. The sound absorbing material was placed in an aluminum test frame with a height of 1 inch on the floor of the reverberation room. In order to eliminate the noise caused by side contact, the edges of the frame were sealed to the floor using duct tape. Sound absorption measurement was performed in the 1/3 octave band over 80 to 5,000 Hz. Ten attenuation measurements were made at any microphone position.

  The total reflection spectrum of the flash-spun sheet is obtained by the method of ASTM E1164-02 (Standard Practice for Observing Spectrophotometric Data for Object-Color Evaluation), available from X-Rite (Grand Rapids, MichiApiS from the United States). Obtained using. Diffuse white light was used as the illuminant, and reflectivity was measured at 8 degrees using a spectral dispersion system. The output is the percent reflectance at each wavelength, and the measured spectral region is 400 nm to 700 nm (10 nm intervals). Detection was performed with a blue-enhanced silicon photodiode. The X-Rite standard provided with the instrument can be traced back to the National Institute of Standards and Technology (Gaithersburg, Maryland, USA). Tristimulus values are calculated by the method of ASTM E308-01 using CIE 10 ° 1964 standard observer and Illuminant D65.

  The noise reduction rate was calculated as the average of the sound absorption rate at 250, 500, 1000, 2,000, and 4,000 Hz measured according to ASTM C423.

  The porosity and pore size distribution data are described in H.C. M.M. Root, “A Review of Mercury Posimetry”, from Advanced Expert Techniques in Powder Metallurgy, pp. 225-252, Plenum Press, 1970.

Total porosity was estimated from basis weight, thickness, and solid density as follows.
Porosity = 1− (basis weight / solid density × thickness)

  Microbial filtration efficiency was measured according to ASTM F2638-07 and ASTM F1608. The log reduction value or LRV characterizes the barrier efficiency of the membrane and is determined from testing. In the test, both polystyrene particles and actual spores can be used to examine the membrane.

Examples 1-2
A sound-absorbing material according to the invention using a layer of open-cell melamine foam (made by Illbruck Acoustic Inc. (Minneapolis, Minnesota)) with a thickness of 13 mm, a basis weight of 9.4 kg / m ³ and a ventilation resistance of 120 rails per unit area A sample of was formed. A nylon 6,6 spunbond scrim with a thickness of 0.1 mm and a basis weight of 17 g / m ² was placed on both sides of the foam and the scrim and foam were quilted together using a diamond pattern of about 11 cm × 11 cm. A sound-absorbing sample was prepared by the lamination process described later. A vinyl acetate water based adhesive (WA 2173 available from efi Polymers (Denver, Colorado)) was applied with a roller to one side of the quilted foam layer at a rate of about 0.3 kg / m ² . A sound-absorbing material core was formed by laminating a melt blown polyester nonwoven fabric layer having a thickness of 20 mm, a basis weight of 0.33 kg / m ² , and a ventilation resistance of 130 rails per unit area on the quilted foam layer. A flash-spun nonwoven surface material available from DuPont under the trade name DuPont ™ Tyvek® Style 1055B was wrapped around the core to form Example 1. A flash spun nonwoven surface material available from DuPont under the trade name DuPont ™ Tyvek® Style 1443R was wrapped around the core to form Example 2. The total thickness of the sound absorbing material in each example was about 25 mm. The table describes the characteristics of the surface material used for the sound absorbing material of the example. The ranges shown for the Gurley Hill porosity of Example 1 are based on the typical ranges taken by flash-spun nonwovens according to specifications. The average reflectance is the average of 31 measurements at wavelengths from 400 nm to 700 nm made in 10 nm increments. According to the product specifications (tested according to AATCC ™ 127, DIN EN 20811 at a test speed of H ₂ O 60 cm per minute), the flashspun surface material of Example 1 has a hydrostatic head of at least H ₂ O 180 cm, Example 2 The surface material has a hydrostatic head of at least H ₂ O 24 cm. The table describes the properties of the surface material used for the sound absorbing material of the examples.

  The Gurley Hill porosity of Examples 1 and 2 was measured experimentally, which is in good agreement with the typical range taken by flash-spun nonwovens for both Tyvek® styles by specification. The air permeability as measured by Gurley Hill porosity and Frazier air permeability characterizes the overall porosity or openness of the structure. The range of air permeability for various types of nonwoven structures is very wide. Typically, all non-woven fabrics have much greater openness in structure and Frazier air permeability is greater than about 50 cfm. A solid film has a very closed solid structure, so the film is called impermeable and the Gurley Hill porosity is well above 10,000 seconds. The air permeability of the flash-spun surface material was changed from the Gurley Hill range of about 4,000 seconds as in Example 1 to the Frazier air permeability of about 30 cfm, and the air permeability per unit area of about 31,000,000 to 800 rails. A resistance range can be obtained.

The total porosity of the structure can be roughly estimated from the basis weight of the surface material, the thickness, and the density of the polymer. When the density of polyethylene is known to be about 0.98 g / cm ³ , the total porosity can be estimated to be about 0.6 for the surface material of Example 1 and about 0.7 for the surface material of Example 2. . This is in good agreement with the total porosity measured by mercury porosimetry. The pore diameter range was 10 nm to about 8,000 nm in Example 1 and 10 nm to about 10,000 nm in Example 2 when measured by mercury porosimetry. The average pore size was about 2,000 nm in both Example 1 and Example 2. Solid films have a total porosity of about 0, which means that they have no voids or pores in the structure. For this reason, the solid film has a very good barrier property. Despite being very porous, the flashspun surface material of the present invention exhibits a water resistance range similar to that of a solid impermeable film when measured with a hydrostatic head. A typical range for the hydrostatic head of the face material of the present invention is from about 24 to about 230 cm of H ₂ O, as shown in Examples 1 and 2.

  As can be seen from the table, the flash-spun surface material of the present invention has various surface characteristics as measured by Parker surface smoothness. Example 1 has a Parker surface smoothness of about 4.5 micrometers, so it exhibits a smooth surface similar to printing paper. In contrast, Example 2 has a Parker surface smoothness of about 8 micrometers and exhibits a rough surface with three-dimensional features, in this case, ribbon-like features. The wide range of Parker surface smoothness enables the production of beautiful surfaces that complement the design of various architectural spaces. The face material of the present invention can further include a graphic image.

  A comparative sample was prepared in the same manner without the flash-spun surface material. The thickness of the comparative sample was about 25 mm.

  Examples and comparative samples were conditioned for 24 hours after manufacture at room temperature for at least 2 weeks and under controlled conditions (temperature 23 ° C., relative humidity 60%) prior to acoustic testing. Sound absorption data was obtained for each sample.

  As can be seen in FIG. 3, the sound absorbing materials of Examples 1 and 2 represented by curves 1 and 2 are continuous when compared with the comparative example represented by curve C in the frequency range of 400 Hz to 1200 Hz. Provide improved sound absorption.

Claims (13)

A core of a sound-absorbing material having two main surfaces, and a surface material covering at least one main surface of the core, having a cohesive surface, a basis weight of 140 g / m ² or less, and a pore size of about 100 nm to 20 nm A surface material comprising a flash-spun plexifilamentary film-fibril sheet comprising a plurality of pores having an average pore diameter of less than 20,000 nm and a light reflectance of greater than 86%,
Including, ceiling tiles.   The ceiling tile according to claim 1, wherein the sound absorption of the ceiling tile at a frequency of less than 1200 Hz is at least 5% higher than the sound absorption of the ceiling tile without the surface material.   The ceiling tile according to claim 1, wherein the delamination strength of the flash spun sheet is at least 0.028 N / m.   The ceiling tile according to claim 1, wherein the surface material is perforated.   The ceiling tile of claim 1, wherein the flash spun plexifilamentary film-fibril sheet comprises a particulate filler having a refractive index greater than that of the polymer.   The ceiling tile according to claim 1, wherein a noise reduction rate of the core of the sound absorbing material is 0.3 to 0.9, and a noise reduction rate of the ceiling tile is substantially equal to a noise reduction rate of the core.   The ceiling tile according to claim 1, wherein the surface material has a Parker surface smoothness of 6 micrometers or more.   The ceiling tile according to claim 1, wherein the surface material has a tensile strength of at least 20 N / 2.54 cm.   The ceiling tile according to claim 1, wherein a graphic image is printed on the surface material.   The ceiling tile according to claim 1, wherein the surface material does not contain nutrients that promote microbial growth.   The ceiling tile according to claim 1, wherein the logarithmic reduction value of the surface material is at least two.   The ceiling tile of claim 1, wherein the surface material comprises a polymer selected from the group consisting of polyethylene and polypropylene. (A) A core of a sound-absorbing material having a plurality of pores having a pore diameter of 100 nm to about 20,000 nm and an average pore diameter of less than 20,000 nm and covered with a surface material of a flash spinning sheet having a light reflectance of greater than 86% Providing a ceiling tile including:
(B) arranging the ceiling tile in the environment such that ambient sound is absorbed by the ceiling tile and light is reflected;
To improve sound absorption and light reflectivity in the environment, including:

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