BR0313421B1 - Process for molding an acoustic insulation laminate - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to an acoustic insulation laminate and more specifically to an acoustic insulation laminate comprising an insulating blanket or acoustic absorbent material. face, polyolefin support or both, and a front and rear face fabric that increases the total noise reduction coefficient. [002] The use of fiberglass in the manufacture of acoustic and insulation products is well known. In addition, insulation materials comprised of fiberglass and organic fibers including cotton, as well as man-made or synthetic fibers, formed into blankets and using a thermosetting resin have been used for many years in the manufacture of insulation and acoustic products. For example, US Patent No. 2,689,199 teaches the use of thermoplastic polymers and refractory glass fibers in the manufacture of a nonwoven porous flexible fabric and US Patent No. 2,695,855 teaches the use of cotton, rayon, nylon or glass fibers with a resin suitable for a thermal or acoustic insulation material. And, U.S. Patent No. 4,868,235 teaches a nonwoven fibrous product comprising a mixed matrix of fiberglass and synthetic fibers having a conductive aluminum, copper or carbon black material in powder form and a thermoset resin dispersed in the matrix. However, a number of these insulation products containing glass fibers and synthetic fibers are generally brittle and easily cracked or cracked when subjected to excessive flexing during installation or use. In addition, these acoustic insulation products generally absorb high frequencies as well but do not absorb low frequencies as well. There are usually three types of fiberglass that can be used to produce acoustic insulation. The first two types are known as rotary and flame-tuned fiberglass which are generally formed of fiberglass strands 5 microns in diameter or smaller, but may exceed 5 microns depending on the application. The third type of fiberglass is typically known as continuous cord or textile fiberglass and generally has a diameter greater than 5 microns. Comparing the three types, the first two products are typically more expensive to produce, historically have better sound absorption characteristics, but cause more irritation to human skin, are more breathable due to their smaller diameter and therefore are healthier. And while the smaller diameter allows for greater density which corresponds to its ability to absorb sound, the smaller diameter results in less durability. On the other hand, textile fiberglass is typically stronger, more durable, and less hazardous to humans. [004] Although fiberglass sound insulation and most other sound absorbers typically work well for higher frequency sounds above about 2500 Hz, lower range frequencies are more difficult to absorb. Frequencies less than about 2500 Hz often pass through known fiberglass acoustic insulation which is highly undesirable in, for example, a car. Non-porous polyfilms have been used with acoustic absorbing materials to absorb limited specific frequencies rather than a wider range of frequencies. However, this is not useful in situations where a wrap is bombarded by a wide range of acoustic frequencies. In addition, polyfilm, which typically absorbs low frequency sounds, dramatically diminishes the ability of the sound absorbing material to absorb high frequency sounds. In view of deficiencies in known acoustic laminates, it is apparent that an acoustic laminate is required which effectively absorbs both high range and low range frequencies, is cost efficient, lightweight, durable, and stronger than known acoustic absorbent materials.

Summary of the Invention It is an object of the present invention to provide an improved acoustic insulation laminate comprising an acoustic insulation mat and a polyolefin film having equal or better performance than existing lighter weight absorbent material. It is a further object of the present invention to provide an acoustic insulation laminate with a wide frequency absorption range. [009] It is an even further goal to provide an acoustic insulation for automobiles that is lighter in weight than other acoustic insulation, thereby improving fuel consumption and reducing the car's operating expense. It is a further object to provide a porous polyfilm in combination with and which reinforces known acoustic sound absorbers such as fiberglass, cotton, synthetic, synthetic cotton blends, other man-made or natural sound absorbers for provide an equal or greater range of sound absorption. It is also an object of the present invention to provide a highly effective sound absorbent laminate using recycled raw materials that is economical to produce. It is an even further object of the present invention to provide a polyolefin film having a total flow passage aperture of at least 0.25 percent of the surface area of the film, and preferably between 0.25 percent and 50 µm. percent of the surface area of the film. A still further object of the present invention is to provide a process for forming the acoustic laminate having a porous polyolefin layer. More particularly, the acoustic insulation laminate of the present invention includes an insulation mat or absorbent material and a porous polyolefin or polyolefin film. An example of an absorbent material that can be used in the present invention is a nylon fiberglass fiber material and a thermoset resin co-binder. An example of such a fiberglass blanket is disclosed in U.S. Patent No. 5,883,020 issued to Bargo et al. and is incorporated herein by reference. The present invention additionally includes at least one porous polyolefin or polyfilm film layer affixed to the acoustic insulation blanket to absorb the lower band frequencies that the acoustic insulation blanket typically does not absorb well. Polyfilm typically acts as a barrier to high frequency sounds, however, the porous nature of the polyphilm of the present invention allows the polyfilm to act as an absorber for low frequency sound, and yet allows a wider range of higher frequency sounds to pass through. for the absorbent material where previous polyfilm laminates have failed. The polyfilm may be a thermosetting plastic such that the polyfilm is thermally bonded to the acoustic insulation blanket.

Alternatively, the polyfilm may be applied to the acoustic insulation mat using resins, copolymers, polyesters and other thermoplastic materials. The polyfilm is preferably comprised of a polyolefin, particularly a polypropylene or polyethylene, and should be positioned between the sound source and the acoustic insulation blanket such that the film resonates against the absorbing material to destroy the acoustic energy of low frequency sound. The polyfilm preferably has a plurality of spaced acoustic flow passage openings allowing high frequency sounds to pass therethrough and to be absorbed by the acoustic insulation blanket. The surface area of at least one acoustic flow passage aperture may be between 0.25 percent and 50.0 percent. Prior to molding, acoustic flow through openings may be circular, square, or any other pre-selected geometric shape including slots. And with molding, the polyfilm comprises multiple randomly shaped openings having various shapes, sizes, and areas allowing the film to absorb low frequency sounds and allowing high frequency sounds to pass through and be absorbed by the acoustic absorbing material. In operation the polyfilm absorbs low frequency sounds by resonating and destroying acoustic energy while reflecting some high frequency sounds. Other high frequency band sounds passing through the acoustic flow passage openings are absorbed by the acoustic insulation blanket. The polyfilm may be used with known flame-retardant rotary fiberglass or textile absorbers as well as other acoustic absorbers to enhance their ability to absorb a wide range of sound frequencies. Finally the acoustic insulation laminate may include a face fabric extending over the film. The face fabric helps retain the bonded laminate and provides an aesthetically pleasing appearance. The face tissue also affects the amount of distortion of the polyfilm apertures and thus the performance of the polyfilm. All of the above objectives are to be understood as exemplary only and many other objects of the invention may be pieced together from the disclosure herein. Therefore, no limiting interpretation of the intended purposes should be understood without further reading the entire specification, claims, and drawings included herein.

Brief Description of the Drawings Fig. 1 shows a perspective view of the acoustic insulation laminate of the present invention; Fig. 2 shows a cross-sectional view of the acoustic insulation laminate of fig. 1 further including a face fabric; and FIG. 3 shows a graph of the absorption coefficient of both a fiberglass sound insulation and a fiberglass sound insulation with a porous polyolefin film.

Detailed Description of the Preferred Embodiment According to the present invention as shown in figs. 1 and 2, an acoustic insulation laminate 10 is provided herein having at least one front and one rear surface. The acoustic insulation laminate 10 includes an acoustic insulation or sound absorbing material mat 12, a polyolefin film 14 having at least one acoustic flow passage opening 16, and preferably a face fabric 18. The acoustic insulation mat 12 has a front and a rear surface is preferably formed of fiberglass, and may vary in weight and thickness to vary the frequency absorption characteristics. A preferred fiberglass mat will be from 2 mm to 155 mm thick and the film will be about 5.08 microns (0.2 mil) to 508 microns (0.2 mil) thick. In addition, the cross-sectional area of aperture 16 prior to molding will be from 0.10 to 25.4 square millimeters (mm2) and spaced across the entire film. Textile fiberglass fibers, preferably less than 12.7 mm to about 127 mm in length and greater than 5 microns in diameter, are combined to form an acoustic insulation mat 12. And, although within the scope of this As the invention uses flame-tuned or rotary fiberglass strands, it is preferable to use textile fiberglass which is more durable, less irritable, more economical and therefore preferred in a plurality of applications including for example the automotive industry. The soundproofing mat 12 may also include nylon and recycled scrap resins as co-binders to keep the fiberglass particles in mat shape. When the acoustic insulation mat 12 is made of fiberglass, the mat 12 is typically a good acoustic insulator for frequency ranges above about 2500 hertz (Hz) but is not as effective at frequencies below 2500 Hz. Such a The blanket is described in US Patent No. 5,883,020 issued to Bargo et al. In the manufacture of a product of the present invention, a fiber-binder complex mixture is formed and a porous polyolefin or polyfilm film sheet 14 is stretched over a planar section of the insulation blanket 12 and slightly preheated to at least about -17.22 degrees Celsius (220 degrees Fahrenheit), for a polyethylene, to glue blanket 12 and polyfilm 14 together.

However, a number of other temperatures may be used to secure polyfilm 14 to insulation blanket 12 prior to molding or curing. Face tissue 18 may also be added before adhesion occurs. Porous polyfilm 14 is comprised of a polyolefin, particularly polyethylene or polypropylene, which binds to acoustic insulation of fiberglass 12 by heat application and may be applied to a face, a support, or both depending on the desired sound characteristics. Applying heat and pressure stretches polyfilm 14 resulting in multiple varying densities across the entire polyfilm 14. Multiple varied densities enhance the ability of polyfilm 14 to resonate at varying frequencies and thus absorb more acoustic energy. According to a preferred embodiment, polyfilm 14 is positioned on the insulation blanket 12 and faces a sound source. Porous polyphilm 14 has at least one acoustic flow passage aperture between about 0.25 percent and 50.0 percent of the total surface area of polyphilm 14. Preferably, the total surface area of at least one acoustic flow passage acoustic flow 16 is formed by a plurality of small acoustic flow passageways 16 which, when combined, constitute a total open area between about 0.25 and 50.0 percent of the total acoustic insulation laminate surface area 10 after molding. The plurality of acoustic flow passageways 16 may be in a spaced configuration and the initial apertures 16 prior to molding may have a plurality of shapes, for example square, circular, or slit. Polyphilm 14 may range in thickness from 5.08 microns (0.2 mil) to 508 microns (0.2 mil) and may also vary in weight to absorb various frequency ranges. Porous polyfilm 14 may be between 0.5 and 40.0 percent by weight of laminate 10. According to one embodiment of the present invention, porous polyfilm 14 absorbs frequencies below about 2500 Hz better than insulation sheet 12 alone and, when used in combination with the sound absorbent material, laminate 10 raises the total noise reduction coefficient compared to the insulation sheet alone. As shown in fig. 3, a graph is shown showing a comparison of frequency versus absorption coefficient for two acoustic materials. Line 1 represents the absorption coefficient of fiberglass insulation alone while line 2 represents fiberglass insulation with porous polyfilm 14 applied to it. As discussed above it is desirable to absorb more sound having a frequency of less than about 2500 Hz. This is represented as an increase in the absorption coefficient along the vertical line of the graph. By adding polyfilm 14 to the fiberglass insulation, line 2 of the graph shows an increase in absorption between about 125 Hz and 2500 Hz. In this example, the fiberglass blanket is approximately 23.4 millimeters thick, the polyfilm. is a polyethylene film with an initial thickness of about 50.8 microns (2 mils) prior to molding, and the apertures in the film initially have a cross-sectional area of about 0.10 to 25.4 square millimeters (mm2). ). The acoustic flow passageways 16 are distributed over the film, initially taking between approximately 0.25 and 15 percent of the surface area of the film. Larger openings grow less than smaller openings during curing or molding and individual growth percentages are affected by the position of the film 14 in the mold and the stress on the film 14. After curing or shaping, the aperture 16 can grow individually in directions of stress relief is about 0 to 600 percent such that the percentage of the total aperture of the surface area of the film 14 is about 1.75 to 15 percent. However, this growth percentage is exemplary and may vary for other ranges. By changing the surface area of the flow passage openings 16, the ratio of the openings to the solid film 14, and the thickness of the polyfilm 14, the absorption coefficient may vary for frequencies greater than or less than 2500 Hz.

In addition, by changing the weight and thickness of the laminate 10, the absorption characteristics can be adjusted to absorb desired frequencies. Finally, it should be understood by one of ordinary skill in the art that porous polyfilm 14 can be used with any sound absorbing material including fiberglass, cotton, synthetics, cotton-synthetic blends, and other acoustic absorbers which may be of the variety. natural or man-made to provide performance equal to or greater than the absorbent material alone. The apertures 16 of porous polyfilm 14 play an important role in absorbing a wide range of low frequencies with the polyfilm rather than a very specific limited range as prior art polyfilms. In forming porous polyfilm 14, a plurality of spaced openings 16 are placed in the polyolefin film 14. The openings, as discussed above, may be from 0.10 to 25.4 mm2 and may be arranged in a uniformly spaced pattern. The porous polyfilm 14 is stretched over the heat absorbing material 12 which does not uniformly vary the density of the polyfilm 14 becoming thinner and increasing the area of at least one aperture 16. As shown in fig. 2, a face fabric 18 may also be applied to the acoustic insulation mat 12 and polyfilm 14. The face fabric 18 may be comprised of about 70% polyester and 30% rayon, pure polyester, or various other known combinations. by someone of ordinary experience in the art. The face fabric 18 helps keep fiberglass laminate 12 and polyfilm 14 together as well as improving aesthetic appearance. However, face fabric 18 is not essential to the present invention. The face fabric 18 may be applied with a thermosetting or thermoplastic resin to adhere to the fiberglass acoustic insulation 12 and polyfilm 14. Once the initial flow passageways 16 are formed, the The polyfilm 14 is stretched over the acoustic insulation mat 12. Thereafter the face fabric 18 may be applied on one front, one back, or preferably both. Porous polyfilm 14 and face fabric 18 may be heated in an infrared curing oven or by a hot rolling process to adhere polyfilm 14 to insulation blanket 12 and face fabric 18 together. The acoustic insulation laminate 10 is subjected to sufficient heat to at least cure and consolidate a desired proportion of the thermoset resin. In the production of a cured duct coating typically using a phenolic resin binder, the oven temperature will range from 121.11 to 371.11 degrees Celsius (250 to 700 degrees Fahrenheit), depending on the thickness and gram weight of the mat being produced. . And, the acoustic insulation laminate 10 is subjected to these temperatures for a sufficient period to consolidate the phenolic resin binder, which is from about 15 seconds to 4 minutes. In the production of a semi-cured laminate 10 to be further molded, the oven temperature will range from 93.33 to 260 degrees Celsius (200 to 500 degrees Fahrenheit) from 15 seconds to 3 minutes such that phenolic resin only partially consolidated. The cured or semi-cured laminate 10 leaving the curing furnace may pass through a cooling chamber and then through strip shear where the scissors cut laminate 10 into sections of a preselected width and length. The laminate 10 is then conveyed by storage conveyor for later use. Acoustic laminate 10 can be formed in a plurality of ways including a hot molding and a cold molding process. In the molding operation the laminate 10 will be fully cured and consolidated to a desired shape and thickness. In a hot molding process various combinations of sound absorbing material 12, porous polyfilm 14, and face fabric 18 may be used to form a laminate. For example, a face fabric 18 and polyphilm 14 may form a laminate, or a sound absorbing material 12 and polyphilm 14 may form a laminate, or a sound absorbing material 12, polyphilm 14, and at least one face fabric 18, preferably two face fabrics 18 may form a laminate. Various combinations of these elements may be layered over material handling equipment such as a traditional conveyor or a roller-chain conveyor for forming and forming the laminate. Layering can be performed continuously by pulling the elements of the roll laminate 10, called roll loading. Alternatively the laminate elements may come in pre-cut sketches in which case the laminate elements may be stacked on the material handling equipment for movement into a mold cavity. After material is aligned, material handling equipment indexes or advances the laminate elements into a mold cavity.

Alternatively, the laminate elements may be manually loaded into the mold cavity. In the hot molding process the mold cavity is heated to a desired temperature such that during the molding process a thermoset resin having a preselected activation temperature is activated. Any or all of the elements forming laminate 10 may have the thermosetting resin or a thermoplastic, or both thereof, such that the element having the lowest activation temperature is activated first when that element reaches its activation temperature. Alternatively, all elements of the laminate may have the same activation temperature. Heat may be provided to the mold cavity in a plurality of methods including forced hot air provided by gas combustion, electric heat, infrared heating, radiant heating, or heated thermal fluids. The mold temperature should be higher than the desired activation temperature to account for thermal loss of the mold and the like. The activation temperature of the thermoset resin can be between about 120 and 500 degrees. Once the layered laminate elements are positioned in the mold cavity, the mold press applies pressure. Any type of mold known in the art may be used as operated by preferably hydraulic fluid or air, rotary molds, double shuttle molds, non-shuttle molds and roller loader molds. The molding pressure may vary from at least one pound per square inch and the cycle time required on the mold may vary from about 15 seconds to 3 minutes and is determined by the density and weight of the laminate elements. The result is a laminate 10 comprising a sound absorbing material 12, a porous polyolefin film 14, and preferably at least one face fabric 18 preferably having a thickness of between about 2 and 155 mm. During the curing or molding process, the application of heat causes the thermoplastic polyfilm 14 to stretch further and not uniformly vary in density. However, since polyfilm 14 is bonded to face tissue 18 and absorbent material 12, distortion of polyfilm 14 occurs at a different rate than insulation blanket 12 and face tissue 18 due to the relationship between heat and heat. applied pressure and the different densities and thicknesses of the materials. This causes distortion of acoustic flow passageways 16 and varying densities of polyfilm 14. The result is a plurality of multiple randomly shaped apertures 16 that allow high frequency sounds to pass through them to the absorbent material 12. In addition , the change in density increases the ability of laminate 10 to resonate in various frequency ranges. Alternatively, laminate 10 may also be molded in a cold molding process. In this process, the insulation blanket 12 may be produced with a thermoplastic instead of a thermoset resin. In cold molding the laminate elements are aligned and indexed or advanced by a roll loading process, advancing the preformed sketches, or manually loaded by hand. The laminate elements are then heated to an activation temperature of about 48.89 to 260 degrees Celsius (120 to 500 degrees Fahrenheit). Thereafter the thermoplastic laminate elements are placed in a cooled mold which lowers the thermoplastic temperature below the activation temperature. The mold may be cooled by ambient air, water, or a cooling system. Within the cooled mold the pressure is applied in an amount ranging from about 6,894,754 to 689,475.7 Pa (1 to 100 pounds per square inch). After cold molding or hot molding the laminate 10 may be cut to any preselected size and shape. In use the acoustic laminate 10 is placed over a wrap where sound absorption is desired. According to a preferred embodiment of the present invention, the polyolefin film 14 is placed between the sound source and the acoustic insulation mat 12. The plurality of acoustic flow passage openings 16 allow frequencies above about 2500 Hz to pass through. to the insulation blanket 12 while many frequencies above 2500 Hz may be reflected by the polyfilm 14. However, frequencies below about 2500 Hz, which may not be absorbed by the insulation blanket 12, are absorbed by the polyfilm layer. Although only one preferred embodiment has been shown and described, it is apparent that those products incorporating modifications and variations of the preferred embodiment will become obvious to those skilled in the art and therefore the preferred embodiment described should not be construed to be. limited in this way.

Claims (23)

A process for shaping an acoustic insulation laminate, comprising the steps of: layering a blanket of sound absorbing material (12), a porous polyolefin film (14) and at least one face fabric (18); b- indexing said sound absorbing material (12), said porous polyolefin film (14), and said face tissue (18) into a molding cavity; c-shaping said sound absorbing material (12), said porous polyolefin film (14), and said face tissue (18) into said molding cavity having a preselected temperature and pressure to form a laminate (10). ); and d) said preselected temperature and pressure varying a density of said polyolefin film (14) and the shape of at least one flow passage aperture (16), the process being characterized by the fact that: molding each of said at least one flow passage aperture (16) increasing from an initial size up to 600 percent of said initial size. Process according to Claim 1, characterized in that it further comprises the step of cutting said laminate (10). Process according to Claim 1, characterized in that the layering is carried out by rollers carrying said sound absorbing material (12), said porous polyolefin film, and said face tissue (18). Process according to Claim 1, characterized in that said sound absorbing material (12), said polyolefin film (14), and said face tissue (18) are preformed sketches. Process according to Claim 1, characterized in that said preselected temperature is an activation temperature of a thermoset resin. Process according to Claim 5, characterized in that said preselected temperature is between 48.88 and 260 degrees Celsius (120 and 500 degrees Fahrenheit). Process according to Claim 1, characterized in that said preselected pressure is between 6,894,754 to 689,475.7 Pa (1 to 100 pounds per square inch). Process according to Claim 1, characterized in that said molding has a cycle time of between 15 seconds and 3 minutes. Process according to Claim 1, characterized in that said indexing is performed by an automated process. Process according to claim 1, characterized in that said indexing is performed manually. Process according to Claim 1, characterized in that said molding cavity is an air-cooled molding cavity. Process according to Claim 1, characterized in that said molding cavity is a refrigerated molding cavity. Process according to Claim 1, characterized in that said preselected temperature is an activation temperature of a thermoplastic. A method according to claim 13 further comprising the step of: cooling said thermoplastic material and said face tissue (18), said porous polyolefin film (14), and said sound absorbing material (12) below said activation temperature and said preselected pressure to form a laminate. Process according to Claim 13, characterized in that the molding cavity is cooled by air cooling. Process according to Claim 13, characterized in that the molding cavity is cooled by cooling. Process according to claim 1, characterized in that it further comprises the step of cutting the molded laminate to a preselected geometry. Process according to claim 17, characterized in that said cutting of said laminate is performed with a high pressure liquid cutter. Process according to claim 1, characterized in that it further comprises the step of rolling the laminate into a dispatchable roll. Process according to Claim 13, characterized in that said heating is performed by a forced source of thermal air. Process according to Claim 13, characterized in that said heating is carried out by a radiant heat source. Process according to claim 13, characterized in that said heating is performed by an infrared thermal source. Process according to claim 1, characterized in that said polyolefin film (14) absorbs frequencies below 2500 Hz and said blanket (12) absorbs frequencies above 2500 Hz.