PROCESS OF FORMING A CONTOURED INSULATING SHEET

Abstract: A rigid, contoured insulating sheet is formed from a flexible, substantially uniform thickness mat (43) of loose fibers or open-cell foam, impregnated with an uncured, heat-activable adhesive, e.g., a phenol-formaldehyde resin, by: a) compressing the mat between a pair of complementary, contoured, preheated e.g., 375 DEG F.) dies (19 and 22) that have perforations (4, 18 and 33) across substantially their entire contact surfaces (30 and 50); b) simultaneously ejecting superheated vapor, preferably steam (lines 9, 14 and 40), through the perforations in both dies, the vapor being at a pressure and temperature e.g., 80 psig and 600 DEG F.) sufficient to heat the adhesive in the mat to its activation temperature e.g., 230-350 DEG F.); and c) applying vacuum (line 10) to the mat, so as to pull ambient air therethrough, until the adhesive is substantially set. The process is especially useful for forming contoured, fiberglass, insulation panels for automobiles, e.g., headliner shells.

Description: PROCESS OF FORMING A CONTOURED INSULATING SHEET Technical Field This invention concerns a process for forming and rigidifying a contoured insulating sheet made of loose fibers or open-cell foam, e.g. , randomly oriented glass fibers bound together with a phenol-formaldehyde resin. In particular, it is directed to a process for forming such a sheet by compressing and heat-treating a resin- impregnated mat of such fibers or foam. Background Art Contoured insulating sheets formed of loose fibers or open-cell foam rigidified by a resinous binder find use in a variety of applications. In automobiles, for instance, they are used as the shell or substrate for interior panels, headliners, floor pads, hood liners, and enclosures or covers for various engine parts, including rocker covers, front covers, dust covers, and undercovers. Methods of forming such products are disclosed in U.S. Patents No. 4,327,049 to Miller, No * . 4,385,955 to Doerfling e_ "al.. ,• and No..4,466,848 to Ogawa. The con¬ toured sheets are used to insulate against sound or heat, or both. A conventional method of forming such sheets is by compressing and heating a flexible, uniform" thickness mat of loose fibers or open-cell foam impregnated with an uncured, heat-activated adhesive between two mold halves. Such mats are commercially available stock material and are disclosed, for example, in U.S. Patent No. 3,025,202, which is incorporated herein by reference. One of the most important factors in manufactur- ing such insulating sheets is the residence time- in the mold. The quicker the sheets can be formed, rigidified, and released from the mold, the lower the production cost. Disclosure of Invention I have invented a novel process, using apparatus disclosed in certain co-pending patent applications, that can shorten the mold residence time significantly. My process involves the following sequential steps: compressing the mat between a pair of complemen¬ tary, contoured dies that are perforated across substan- tially their entire contact surfaces and which, when brought fully together, define in the space between them the desired shape of the finished sheet, the dies being preheated to an elevated temperature; simultaneously ejecting superheated vapor through the perforations in both dies, the vapor being at a pressure and temperature sufficient to heat the adhesive in the mat to its activation temperature; applying vacuum to the mat, so as to pull ambient air therethrough, until the adhesive is substan¬ tially set; and separating the dies so the resulting contoured insulating sheet can be removed. The present process is especially useful in preparing insulating sheets wherein the thickness varies substantially from one area to another, i.e. , the clear¬ ance between the dies is not uniform. Automobile head- liner shells are a good example. ' They usually are thicker in the center than at the edges. This makes them stronger around their periphery, where they are fastened to the automobile body, but without significant sacrifice of insulating effectiveness. Also, the thinner edge facili¬ tates the application of decorative trim or the overlap of side panels. A variety of fibers or foams can be used to con¬ struct the mat employed in the present process. Glass fibers are commonly used and are preferred. Textile waste, known as "shoddy", also can be used. The fibers either will be loosely woven or nonwoven, e.g. , randomly oriented. Open-cell polyurethane or polyolefin foams can be used as well. For added strength, the foam can be reinforced with a fibrous filler, such as chopped fiber¬ glass. The mat will have a substantially uniform thick¬ ness, often in the range of about 1-1/2 to 2 inches. A preferred density is about 1-1/2 to 2-1/2 pounds per square yard. The mat is typically soft, flexible, and somewhat resilient, prior to being rigidified by the process of the present invention. Any of various chemicals can be used as the heat-activatable adhesive, provided it has an a'ctivation temperature which is below the temperature at which the mat melts or degrades. Examples are polyamide resins, polyurethane resins (both polyether-based polyurethanes and polyester-based polyurethanes), and the phenolic resins. Both thermoplastic and thermosettable adhesives can be used. A thermosettable adhesive solidifies, or sets, when heated to its activation temperature and cannot be remelted. A thermoplastic adhesive is normally solid and melts at its activation temperature, then resolidifies when cooled. Thermoplastic adhesives can be remelted. Phenol-formaldehyde resins, which are thermosettable, are often preferred. The activation temperature of the ad- hesive usually will be above about 200° F., for example in the range of about 230 to 350° F. Apparatus that can be used to perform the pre- sent process are disclosed in International ' Patent Appli¬ cations No. PCT/US 86/02807, filed December 30, 1986 ϊ ("Apparatus for Laminating and Shaping Foam") and No. PCT/US 87/01111, filed May 18, 1987 ("Apparatus and Process for Shaping and Covering Cushion Foam"), both of which are incorporated herein by reference. Both dies should be preheated prior to being pressed against the mat. Precisely how hot the dies should be depends upon the activation temperature of the adhesive. Preferably the temperature of the dies will be high enough to warm the adhesive to near its activation temperature. It will be suitable, for example, if the surface temperature of each die is below the adhesive's activation temperature but within about 20 Fahrenheit degrees thereof, e.g. , in the range of about 210 to 330° F. The preferred means of preheating the dies is by use of electrical resistance heaters. If the finished insulating sheet is to have regions where the mat is highly compacted, as compared to other less dense regions, it will require the use of a die set in which at least one of the dies has protruding sections, resulting in a relatively narrow clearance be¬ tween the dies when they are brought fully together. It may be preferred in such a situation to use the apparatus disclosed in the aforementioned International Patent Application No. PCT/US 87/01111, wherein means " are pro¬ vided or preheating the dies' protruding sections to a higher temperature than the land areas. For example, the protruding sections of the die might be heated to a tem¬ perature that is about 20 to 40 Fahrenheit degrees higher than that of the adjacent land area. The perforations in each die should be relative¬ ly small, " e. . , having diameters in the range of about 0.035 to 0.095 inch. There should be enough of the per¬ forations, and they should be spaced closely enough to- gether, to ensure relatively uniform heating of the adhesive. The smaller the perforations, the closer they should be. Generally, the perforations should be spaced not more than about 1/2 inch apart. The preferred superheated vapor isj steam. The temperature, pressure, flow rate, and duration of ejection of the steam into the compressed mat are to a certain extent interrelated. A combination of these conditions should be selected which will bring the adhesive to its activation temperature. Usually the steam will have a temperature in the range of about 350 to 650° F. and a pressure of about 75 to 90 pounds per square inch gauge (psig) . (This is as measured before the steam contacts the die surface.) Steam of the same temperature and pressure can be sent to the land areas as that sent to the die's pro¬ truding sections, or the two zones can be supplied with separate sources of steam, at different temperatures and/or pressures. The steam temperature will drop as the steam passes through the holes in the contact surface of the die, if the die is at a lower temperature. The tem¬ perature will drop less when passing through the holes in the protruding sections, however, if those sections are preheated to a higher temperature than the land areas. Therefore, although a single source of superheated steam may be used, the steam that enters the thicker regions of the mat may be at a significantly lower temperature than that which is injected into the more compacted regions. Also, separate sources of superheated steam can be used for the two regions. The superheated steam may optionally be mixed with hot air, e.g., air having a temperature in the range of about 350 to 650° F, to help drive the steam into the interior of the mat. Also, to help adjust or control the temperature of the superheated steam being ejected, means can be provided behind the; die surface for blending satu¬ rated, or "plant", steam with the higher temperature superheated steam. The duration of the steam injection must be long enough to assure that the adhesive is fully activated. Then a vacuum is applied to sweep air through the mat and remove the water vapor and any noxious chemicals which might have evaporated from the adhesive, such as, for ex- ample, formaldehyde vapors. If the adhesive is a thermo¬ plastic one, this air sweep will also serve to cool the adhesive to below its melting point. As thermosettable resins are heated, they nor¬ mally go through a brief molten state before they harden and set. In the present process, if the dies are disposed horizontally and vacuum is pulled on the bottom tool while superheated vapor is ejected from the top tool, some of the molten resin, be it thermosettable or thermoplastic, will migrate to the bottom surface of the mat. This re- suits in a smoother, harder finish on the bottom surface of the sheet, which may be preferred. It normally would be preferred, for example, if the sheet is to have a decorative fabric laminated to it. Such lamination can be performed either in a separate operation or, in some instances, simultaneously with the rigidifying of the mat. Resin-impregnated fiberglass mats generally require such a high cure temperature that it damages most decorative fabrics. If one wants to simultaneously laminate a decorative fabric to the surface of the sheet, it is better to use a mat formed of open-cell foam or shoddy. The vacuum preferably is pulled through the per¬ forations in one of the dies. Ideally, each die will have an enclosed chamber behind its contact surface, and this chamber will be in communication with the perforations in the die and with a valved source of the superheated vapor. It is also preferred that a valved vacuum line be connect¬ ed to the chamber behind the contact surface of one of the dies. Both dies can be supplied with vacuum, but it generally is preferred that the vacuum be drawn through only one die at a time. Brief Description of Drawings For a fuller understanding of the process of the present invention, reference is made to the drawings that accompany this specification. Referring to those drawings: Figure 1 is a front view, in partial cross- section, of a set of Complementary dies about to be- compressed against a resin-impregnated fiberglass mat that is to be formed into a under-carpet insulating sheet to fit over the transmission tunnel in a van. Figure 2 is a cross-sectional view, slightly en¬ larged, of the same dies and mat as shown in Figure 1, but with both die surfaces contacting the mat at the beginning of the compression step. Figure 3 shows the same dies as in Figures 1 and 2, enlarged still further, but without the mat, and with the two dies brought fully together. Figure 4 is a sectional view, enlarged still further, of the contoured insulating sheet produced from the mat shown in Figures 1 and 2. Figure 5 is a schematic view of another set of dies, with a fiberglass mat between, used to form an automobile headliner. Figure 6 is a schematic view of the die set and mat shown in Figure 5, but with the die fully closed. Figure 7 is a slightly enlarged view of the finished headliner prepared as shown in Figures 5 and 6. Best Mode For Carrying Out Invention The apparatus shown in Figures 1-3 of the draw- 5. ings includes an upper die 19 and a lower die 22. Upper die 19 is held to die holding plate 23 by hex head bolts 20. Spacer collars 21 hold plate 23 and die 19 apart, so as to leave room for flexible piping that communicates with the interior cavity 24 of die 19. Lower die 22 is similarly held to plate 24 by flat head bolts 26. Spacer collars 27 hold plate 25 and die 22 apart. Die holding plates 23 and 25 are mounted on a frame (not shown) so that plate 23 and the mechanism attached thereto can be raised and lowered into engagement with lower die 22. More detailed disclosures of such apparatus may be found in the aforementioned International Patent Applications Nos. PCT/US 86/02807 and PCT/US 87/01111. Upper die 19 is comprised of a cast aluminum forming tiol 28 with a detachable ' cover plate 29. Cover . plate 29 is held to forming tool 28 by bolts 5, which are threaded into holes (not shown) in the periphery of tool 28. Internal posts 2 provide structural stability for upper die 19 and efficient heat transfer from electrically heated cover plate 29. Each post 2 is integral with the forming tool 28. None of the posts 2 extends the entire distance from the front to the back of die 19; therefore, chamber 24 is one continuous chamber, rather than a series of isolated compartments. The contact surface 30 of form¬ ing tool 28 is perforated. The preferred size and spacing of the holes 4 and 18 will vary according to the thickness and density of the mat used, as well as its composition. In the apparatus shown in the drawings, holes 4 and 18 are on a 1/4-inch grid and have a diameter of 0.060 inch. On the bottom of upper die 19, at each side thereof, is mounted a bar section 12, which protrudes above the adjacent land area of contact surface 30. Similarly, at the center of upper die 19 is a third bar section 31 having two protruding ridges 32. Each protruding bar section 12 and 31 is perforated with rows of holes 18, which communicate with interior steam tunnels 17. Imbedded in each of the marginal bar sections 12 are a pair of cartridge heaters 16, which run parallel to the steam tunnels 17. Cartridge heaters 16 are electrical resistance heaters that can be used to bring the surface temperature of bar sections 12 to a higher point than that of the adjacent land area 30. Attached to the top of cover plate 29 are five electrical resistance heaters 6. Each of these heaters has a rated capacity of 25 watts per square inch of contact surface. Four lines are tapped into chamber 24 through cover plate 29. Line 7 carries hot air. Line 8 carries saturated steam. Line 9 carries superheated steam. Line 10 pulls a vacuum. Flow in each of these lines is controlled by a solenoid valve. Valve 11 controls superheated steam, line 9. Valve 42 controls vacuum line 10. (The. alves controlling lines 7 and 8 are not shown. ) * The steam tunnels 17 in bar sections 12 and 31 are all in communication with line 13 for saturated steam, line 14 for superheated steam and line 15 for hot air. Line 14 appears interrupted in the drawings. In actuality it is not. It is one continuous line with two branches, feeding the two banks of steam tunnels 17. Each of lines 13, 14, and 15 is also equipped with a solenoid valve (not shown). Line 14 is controlled by solenoid valve 3. Lower die 22 is comprised of a cast aluminum forming tool 44 having a perforated contact surface 50. The holes 33 also are on a 1/4-inch grid and have a diameter of 0.060 inch. They cover the entire contact surface 50. Forming tool 44 is held to cover plate 33 by a series of hex head bolts 34 around the periphery of plate 33. Vertical posts or ribs 35, which are integral with the forming tool 44, serve to strengthen lower die 22 and aid in the transfer of heat from electrical resistance heaters 36 to the contact surface 50. The enclosed chamber 37 between contact surface 50 and coverplate 33 is in communication with four pipes that are tapped through coverplate 33. Line 38 supplies hot air; line 39 supplies saturated steam; line 40 supplies superheated steam; and line 41 supplies a vacuum. The flow in each of these lines is controlled by a solenoid valve (not shown). As shown in Figure 1, a mat 43 of randomly oriented glass fibers, impregnated with a theromosettable phenol-formaldehyde resin, is placed between upper die 19 and lower die 22. The contact surface 30 of die 19 is preheated by use of electrical heaters 6 and 16. The con¬ tact surface 50 of lower die 22 is preheated by use of electrical heaters 36. As shown in Figure 2, upper die 19 is lowered toward lower die 22, bending mat 43 in the process. In Figure 3, upper die 19 is lowered still further, to its fully closed position. For the sake of clarity, mat 43 has been omitted from this figure. As can be seen, the fully closed position of dies 19. and 22 does not involve actual contact between them. Narrow clear- . ances remain in the regions of bar- sections 12 and 31. Figure 4 shows a cross-sectional view of a finished insulating sheet made using the apparatus illus¬ trated in Figures 1-3. As stated above, this particular sheet is designed for use as a sound and heat insulator over the transmission tunnel in a van. It is installed inside the van, between the floor and the carpet. The apparatus shown in Figures 5 and 6.consists of a top forming tool 45 and a bottom forming tool 46. Substantially the entire contact surfaces of both tools are perforated with holes 47 and 48. Both tools are provided with means (not shown) for preheating them and means (not shown) for ejecting superheated steam through their perforations. Bottom tool 46 is also equipped with means (not shown) to pull a vacuum through the perfora¬ tions. Figure 5 shows forming tools 45 and 46 separated, with a mat 49 of uncured, resin-impregnated glass fibers in position to be compressed. Figure 6 shows forming tools 45 and 46 in their closed position, with fiberglass mat 49 compressed between them. Figure 7 depicts the finished automobile headliner 49 prepared by the process of Figures 5 and 6. As shown in Figure 5, the uncompressed fiber¬ glass mat 49 has a thickness of approximately 1-3/4 inch. It measures approximately 60 inches wide by 110 inches long, and it has a density of approximately 2 lb./sq. yd. It is impregnated with an uncured phenol-formaldehyde resin. The finished headliner, shown in Figure 7, is a rigid, hard shell having a thickness of about 1/2 to 5/8 inch in the center, which tapers at the edges to about 1/8 to 3/16 inch. One example of the process conditions for preparing the headliner according to Figures 5-7 is as follows: Time Into the Cycle ' Event/Conditions * 0 sec: Pre-heat both dies to a 'contact surface temperature of approximately 375°F., using electrical resistance heaters; then, to begin the cycle, commence ejecting super¬ heated steam through the bottom tool. The temperature and pressure of the steam when entering the tool is about 600°F. and 80 psig. Continue bottom tool steam ejection until 25 seconds into the cycle. Keep electric heaters on throughout the process. Begin gradually and constantly lowering top tool so that it requires 30 seconds to reach its completely lowered position. 2 sec: The moving upper die makes first contact with the fiberglass mat. Commence ejecting superheated steam at the same temperature and pressure through the top tool as well. Continue top tool steam ejection until 30 seconds into the cycle. sec: Cease steam ejection through bottom tool and commence pulling vacuum of about 850 cubic feet per minute on bottom tool, sec: Upper tool is fully lowered. Cease steam ejection through top tool and shut off vacuum to lower tool. Adhesive is now set, Raise top tool and remove contoured sheet.

Claims: Claims 1. In a process of forming and rigidifying a contoured insulating sheet from a flexible, substantially uniform thickness mat composed either of loose fibers or of an open cell foam, the mat being impregnated " with a heat-activitable adhesive, the activation temperature of the adhesive being below the temperature at which the mat melts or degrades, the IMPROVEMENT where the process comprises the following steps: a) compressing said mat between a pair of complementary, contoured dies that are perforated across substantially their entire contact surfaces and which, when brought fully together, define in the space between them the desired shape of the finished sheet, each of said dies being preheated to an elevated temperature; b) simultaneously ejecting superheated vapor through the perforations in both dies, the vap.or being at a pressure and temperature sufficient to heat the adhesive in the mat to its activation temperature; -* c) applying vacuum to the mat, so as to pull ambient air therethrough, until the adhesive is substantially set; arid d) separating the dies so the resultant contoured insulating sheet can be removed. 2. The process of claim 2 wherein, in step (b) , the vapor used is superheated steam. 3. The process of claim 2 wherein, in step (a), each of the dies has been preheated to a temperature below the activation temperature of the adhesive, but within about 20 Fahrenheit degrees thereof. 4. The process of claim 3 wherein the mat is made of randomly oriented glass fibers. 5. The process of claim 4 wherein the adhesive has an activation temperature somewhere in the range of about 210 to 330°F. 6. The process of claim 5 wherein the adhesive is a phenol-formaldehyde resin. 7. The process of claim 5 wherein, in step (b), the steam is at a temperature of about 350 to 650°F and a pressure of about 75 to 90 psig. 8. The process of claim 6 wherein, in step (b), the steam is at. a temperature of about 350 to 650°F and a pressure of about 75 to 90 psig. 9. The process of claim 7 wherein, in step (c), the vacuum is pulled through the perforations in at least one of the dies. 10. The process of claim 8 wherein, in step (c), the vacuum is pulled through the perforations in at least one of the dies. 11. The process of claim 7 wherein, in step (c), the vacuum is pulled through the perforations in only one of the dies. 12. The process of claim 8 wherein, in step (c), the vacuum is pulled through the perforations in only one of the „dies. 13. The process of claim 5 wherein the desired shape of the finished sheet is that of an automobile headliner and the. clearance between said dies is non- uniform. 14. The process of claim 7 wherein the desired shape of the finished sheet is that of an automobile headliner and the clearance between said dies is non- uniform. 15. The process of claim 11 wherein the desired shape of the finished sheet is that of an automobile headliner and the clearance between said dies is non- uniform.

Inventors: ELLIOTT GEORGE M, ELLIOTT, GEORGE, M.
Applicants: ASTECHNOLOGIES INC, ASTECHNOLOGIES, INC.
Application year: 1987
Main classification: B31F1
IPC codes: B29C35, B29C44, B29C67, B60R13, D04H1