MXPA96006742A - Open cells foams in tec systems - Google Patents

Abstract

The present invention relates to a roofing system for a structure, comprising: a) a roof platform, b) a protective layer of a plurality of panels of an extruded alkylene aromatic polymer foam placed on and adjacent to the platform , the foam comprising an alkylene aromatic polymer material having more than 50% by weight of aromatic monomeric units of nickel, the foam having from about 30 to about 80% open cell content, and c) a substantially substantial membrane. Water proof placed on and adjacent to the espu panels

Description

OPEN CELLS FOAMS IN ROOF SYSTEMS This invention relates to a method for employing an extruded open cell alkenyl aromatic polymer foam in roof systems. Roof systems typically comprise multiple layers of different materials configured to protect and optionally insulate a roof platform or upper surface of a structure or construction. The roof system protects the platform and the interior of the structure from the weather, including wind, rain, and other precipitation. The critical component of a roof system is a membrane. The membrane is a sheet or mat of a solid elastomeric substance that protects the platform from the aforementioned elements of weathering. Conventional membranes include those of EPDM (ethylene-propylene-diene elastomer), modified bitumen, and plasticized polyvinyl chloride. The membrane may be dark, medium-colored, or light-colored, but it is usually dark. When a new roof system is installed, the membrane is placed or extended over the top of the roof platform. Typically, a protective plate can be inserted between the membrane and the platform. The protective layer can take the form of an insulating plastic foam, or more commonly, a material other than foam, such as wood or a wood composite board. Commercially used plastic foams include polystyrene granule foam, closed-cell extruded polystyrene foam, and closed-cell polyisocyanurate and polyurethane foams. Optionally, a layer of pavement can be placed or extended on top of the membrane. The pavement layer typically comprises materials such as gravel or stone ballast, pebbles, partition, or concrete. The pavement layer works to physically protect the membrane from roof traffic and from direct exposure to sunlight and weathering. When roof replacement or recovery systems are installed in existing structures or buildings, they are often installed over existing roof systems. In a typical recovery system, a protective layer is applied or spread over the top layer of the existing roof system, usually an old membrane or an old pavement layer; a new membrane is applied or extended on top of the protective layer; and optionally, a new layer of pavement is applied on top of the new membrane. The protective layer protects the new membrane from rough or irregular surfaces frequently found on the upper surfaces of existing roof systems, provides mechanical support under the new membrane, and in the case of plastic foams, provides additional insulation . A problem commonly encountered with roof systems is the rupture of the membrane due to distortion or deterioration of the protective layer under the membrane. Problems of distortion and deterioration are caused by exposure of the protective layer to extreme heat by direct sunlight or moisture accumulation due to exposure to the weather. The membrane, which is typically dark and elastomeric, absorbs significant heat from sunlight, and also does not allow timely escape of moisture trapped beneath it. When the insulating and / or protective layer becomes distorted or deteriorated, the membrane and the protective layer can be separated to form empty bags, which leave the membrane with a diminished mechanical support on its lower surface. The diminished support makes the membrane more subject to rupture. The source of the problems of distortion and deterioration of the material in the protective layer varies according to the nature of the material. Some materials are susceptible to heat, some are susceptible to moisture, and some have inherently low mechanical strength. Extruded closed cell polystyrene foams offer excellent mechanical resistance and water resistance, but can become distorted at high service temperatures (greater than 73.8 ° C) due to their relatively low heat distortion temperature. These high service temperatures are typically found under a dark membrane in direct sunlight. Expanded polystyrene granule foams typically maintain their shape better in a high temperature environment than extruded closed cell polystyrene foams, because they typically have better warping characteristics. Its warping characteristics are better because the structure of coalesced expanded granules allows for better mechanical relaxation compared to the solid cellular form of extruded closed cell foams. However, the structure of coalesced expanded granules also results in a lower mechanical strength, and a lower resistance to water transmission. Closed-cell polyisocyanate foams have high heat distortion temperatures (250 ° F-275 ° F) (121 ° C-135 ° C), but have a poor resistance to moisture. The moisture weakens the cellular structure of these foams, and makes them subject to physical deterioration over time. Humidity also decreases the insulation value of the foam. They are also relatively fragile, which affects their management characteristics. Closed-cell polyurethane foams, such as closed-cell polyisocyanate foams, have high heat distortion temperatures and poor moisture resistance. They are also relatively fragile, which affects their management characteristics. Wood boards and wood composite boards have high heat distortion temperatures, but have a poor resistance to moisture. The moisture weakens the wood, and makes it subject to physical deterioration over time. In addition, the boards provide little insulation compared to the foams. It would be desirable to have a foam that could be deployed under a membrane in a roof system. It would also be desirable if this foam had a heat distortion temperature of 190 ° F (88 ° C) or higher. In addition, it would be desirable for this foam to have excellent moisture resistance and mechanical strength similar to those of extruded closed cell polystyrene foams. In accordance with the present invention, there is a roof system for a structure. The process comprises a roof platform; a protective layer of a plurality of boards of an extruded alkenyl aromatic polymer foam located above and adjacent to the platform; and a substantially waterproof membrane located above and adjacent to the foam. The foam comprises an aromatic alkenyl polymeric material having more than 50 weight percent aromatic monomeric alkenyl units, and having a content of 30 to 80 percent open cells. In addition, in accordance with the present invention, a ceiling recovery system for a structure is presented. The roof system comprises a previously existing roof system; a protective layer of a plurality of boards of an extruded alkenyl aromatic polymer foam located above and adjacent to the previously existing roof system; a second substantially waterproof membrane located above and adjacent to the foam. The previously existing roof system comprises a roof platform and a first membrane located above and adjacent to the roof platform. In addition, in accordance with the present invention, a process for constructing a roof system for a structure is presented. The process comprises providing a roof platform; applying on top of and adjacent to the upper surface of the roof platform, a protective layer of a plurality of boards of an extruded alkenyl aromatic polymer foam; and applying a substantially waterproof membrane on top of and adjacent to the top surface of the foam.

Furthermore, in accordance with the present invention, a process for the construction of a ceiling recovery system for a structure is presented. The process comprises providing a previously existing roof system; applying on and adjacent to the upper surface of the previously existing roof system, a protective layer of a plurality of boards of an extruded alkenyl aromatic polymer foam; and apply over (on top of) and adjacent to the upper surface of the foam, a second membrane that is substantially wproof. The previously existing roof system comprises a roof platform and a first membrane loc above and adjacent to the roof platform. In the above systems and processes, the protective layer is loc adjacent to, and preferably adjacent to, the membrane. It is preferred that it be contiguous, because maximum physical protection of the membrane is provided. When any component (roofing platforms, membranes, protective layers, pavement layers) of a roof system or a roof replacement system is described, as adjacent to another component, they are loc in parallel and in proximity to each other, but may or may not be in direct physical contact. When a component is described as contiguous to another component, it is in direct physical contact.

The features of the present invention will be better understood by reviewing the drawings, along with the rest of the specification. Figure 1 is a cross-sectional view of a roof system of the present invention. Figure 2 is a cross-sectional view of a roof recovery system of the present invention. Figure 3 is a separsectional view of the roof system illustr in Figure 1. Figure 4 is a sectional view of the roof recovery system illustr in Figure 2. The present invention provides new roof systems and systems. of roof recovery, with better longevity and performance. Longevity and performance are improved by improving the physical support and integrity of the roof membrane. The best physical support and integrity means that there is less chance of rupture of the membrane, resulting in a reduced incidence of w leakage through the roof system. The physical support and the integrity of the membrane are improved by using a protective layer of an extruded, open cell alkenyl aromatic polymer foam under the membrane. The foam offers excellent resistance to heat and moisture, and mechanical resistance. The foam also improves the heat insulation of the roof system. Figures 1 and 3 illustra new roof system 20 of the present invention. The roof system 20 comprises in sequence, a roof platform 10, a protective layer (foam) 12, a membrane 14, and a layer of pavement 16 stacked one on top of the other. The protective layer 12 comprises the extruded open cell alkenyl aromatic foam described herein. If additional insulation is desired to that provided by the protective layer 12, an insulating foam plastic mial such as an extruded, closed cell alkenyl aromatic foam foam may be provided between the protective layer 12 and the roof platform. It is understood that the pavement layers in the embodiments herein are optional. Figures 1 and 2 illustrone embodiment of a roof recovery system 34 of the present invention. In the use of a roof recovery system, the cost of removing the previously existing system is elimin by placing a new roof system directly above the previously existing roof system. The previously existing roof system comprises a roof platform 22, a first membrane 24, and a first floor layer 26. The new roof system comprises a protective layer 28, a second membrane 30, and a second layer of flooring 32. If additional insulation is desired to that provided by the protective layer 28, another layer of a plastic material of insulating foam, such as an aromatic polymer foam of Closed cell alkenyl, extruded, between the first layer of pavement 26 and the protective layer 28. The extruded alkenyl aromatic polymer foam provides better performance in roof systems over other materials used in protective layers for roof membranes in the previous technique. The extruded open cell foam offers moisture resistance and mechanical strength similar to those of a corresponding extruded closed cell alkenyl polymer foam, but also provides a higher heat distortion temperature. Open cell foam has a heat distortion temperature of up to 210 ° F (99 ° C), while closed cell foam has a temperature of up to 175 ° C (79 ° C). Although we do not wish to be bound by any particular theory, it is believed that the higher heat distortion temperature is due to the open cell structure, which allows gas pressure to be released from the cell more easily than a closed cell structure. The extruded open cell foam provides a better heat distortion temperature than a corresponding expanded granular polystyrene foam, and has better mechanical strength and exhibits much lower water transmission. Extruded open cell foam has a unitary cell structure, rather than a coalesced granule structure such as granule foam. The extruded open cell foam exhibits much better moisture resistance than a closed cell polyisocyanate foam or polyurethane foam, and therefore, is much less subject to physical deterioration. Open cell foam provides a lower range of heat distortion temperatures than polyisocyanate or polyurethane foam, but the range provided is entirely sufficient for the temperatures commonly encountered in roofing applications. In addition, with respect to polyurethane foam, open cell foam is more rigid, which makes it more effective to provide mechanical support. In addition, open cell foam has brittleness characteristics (less brittleness) superior to those of polyisocyanurate and polyurethane foams. Extruded open cell foam exhibits much better moisture resistance than a wooden board or a wood composite board. Open cell foam provides lower heat distortion temperatures than those of wood board or wood composite board, but provides a scale that is entirely sufficient for the temperatures commonly encountered in roofing applications. In addition, open cell foam provides much insulation per unit thickness, than wood board or wood composite board. The open cell foam has a heat distortion temperature of 175 ° F to 210 ° F (79 ° C to 99 ° C), and more preferably 190 ° F to 205 ° F (88 ° C to 96 ° C). C) in accordance with ASTM D-2126-87. The high heat distortion temperature of the foam makes it possible to use it in environments with high operating temperatures (from 175 ° F to 210 ° F) (from 79 ° C to 99 ° C), such as under the dark membranes from the ceiling in direct sunlight. The present foam has an excellent heat distortion temperature due to its open cell structure. The open cell foam has an open cell content of 30 percent or more, preferably 30 to 80 percent, and more preferably 40 to 60 percent according to ASTM D2856-87. The open cell foam has a density of 1. 5 pcf to 6.0 pcf (from 24 kg / m3 to 96 kg / m3), and preferably a density from 2.0 pcf to 3.5 pcf (from 32 kg / m3 to 48 kg / m3) in accordance with ASTM D-1622-99 . The open cell foam - has an average cell size of 0.08 millimeters (mm) to 1.2 millimeters, and preferably 0.10 millimeters to 0.9 millimeters in accordance with ASTM D3576-77. Open cell foam is particularly suitable for forming into a plate, desirably into one having a smaller cross-sectional dimension (thickness) of more than 0.25 inches (6.4 millimeters) or preferably more than 6.375 inches (9.5 millimeters) or more . In addition, preferably, the foam has a cross-sectional area of 30 square centimeters (cm 2) or more. The open cell foam is substantially non-crosslinked. Substantially non-crosslinked means that the foam is substantially free of crosslinking, but includes the slight degree of crosslinking that can occur naturally without the use of crosslinking or radiation agents. A substantially non-crosslinked foam has less than 5 percent gel according to ASTM D-2765-84, method A. The open cell foam comprises an aromatic alkenyl polymer material. Suitable alkenyl aromatic polymer materials include homopolymers and alkenyl aromatic copolymers of alkenyl aromatics and copolymerizable ethylenically unsaturated comonomers. The aromatic alkenyl polymer material may also include minor proportions of aromatic polymers other than alkenyl. The aromatic alkenyl polymer material may be comprised exclusively of one or more alkenyl aromatic homopolymers, one or more alkenyl aromatic copolymers, a mixture of one or more homopolymers and alkenyl aromatic copolymers, or mixtures of any of the foregoing, with a aromatic polymer other than alkenyl. Regardless of the composition, the aromatic alkenyl polymeric material comprises more than 50, and preferably more than 70, percent by weight aromatic monomeric alkenyl units. More preferably, the aromatic alkenyl polymer material is comprised entirely of alkenyl aromatic monomer units. Suitable alkenyl aromatic polymers include those derived from aromatic alkenyl compounds, such as styrene, alphamethylstyrene, ethylstyrene, vinylbenzene, vinyltoluene, chlorostyrene, and broestyrene. A preferred alkenyl aromatic polymer is polystyrene. Minor amounts of monoethylenically unsaturated compounds such as alkyl acids and esters of 2 to 6 carbon atoms, ionomeric derivatives, and dienes of 4 to 6 carbon atoms can be copolymerized with alkenyl aromatics. Examples of the copolymerizable compounds include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, itaconic acid, acrylonitrile, maleic anhydride, methyl acrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, methyl methacrylate, and acetate of vinyl. The foams are preferably substantially free of rubbery or rubbery substances such as those with a monomeric diene content of 4 to 6 carbon atoms. Preferred foams substantially comprise (ie, more than 95 percent), and more preferably entirely polystyrene. The open cell foam is generally prepared by heating an aromatic alkenyl polymeric material to form a plasticized or molten polymer material, incorporating therein a blowing agent to form a foamable gel, and extruding the gel through a given to form the foam product. Prior to mixing with the blowing agent, the polymeric material is heated to a temperature of or greater than its glass transition temperature or its melting point. The blowing agent can be incorporated or mixed into the molten polymeric material by any means known in the art., such as with an extruder, mixer, or blender. The blowing agent is mixed with the molten polymeric material at an elevated pressure sufficient to prevent substantial expansion of the molten polymeric material, and to generally disperse the blowing agent homogeneously therein. A nucleation is mixed in the molten polymer or mixed dry with the polymeric material before plasticizing or melting. The foamable gel is typically cooled to a lower temperature to optimize or obtain the desired physical characteristics of the foam. The gel can be cooled in the extruder or in another mixing device or in separate chillers. The gel is then extruded or transported through a die in a desired manner to a zone of reduced or lower pressure to form the foam. The lower pressure zone is at a lower pressure than that in which the foamable gel is maintained prior to extrusion through the die. The lowest pressure can be superatmospheric or subatmospheric (evacuated or vacuum), but is preferably at an atmospheric level. More specifically, the foam can be prepared by: a) heating an aromatic alkenyl polymeric material comprising more than 50 weight percent aromatic monomeric alkenyl units to form a molten polymer material; b) incorporating into the molten polymer material an amount of a nucleation people sufficient to result in a foam having a content of 30 percent to 80 percent open cells; c) incorporating a blowing agent into the molten polymer material at an elevated pressure to form a foamable gel; d) cooling the foamable gel to a suitable foaming temperature; and e) extruding the foamable gel through a die into a region of lower pressure to form the foam. The foaming temperature is from 118 ° C to 145 ° C, where the foaming temperature is from 3 ° C to 15 ° C higher than the highest foaming temperature for a corresponding closed cell foam. The foaming temperature should be 133 ° C or more. The foaming temperature should be in addition to 33 ° C or higher than the glass transition temperature (according to ASTM D3418) of the alkenyl aromatic polymer material. Any blowing agent useful in the manufacture of extruded alkenyl aromatic polymer foams can be employed. Useful blowing agents include l-chloro-1,1-difluoroethane (HCFC-142b), chlorodifluoromethane (HCFC-22), 1,1-difluoroethane (HFC-152a), 1,1-trifluoroethane (HFC-143a) ), 1,1,1,1-tetrafluoroethane (HFC-134a), water, ethanol, carbon dioxide, ethyl chloride, and mixtures thereof. The preferred blowing agent comprises a mixture of carbon dioxide and ethyl chloride. The amount of nucleating agent employed will vary according to the desired cell size, the foaming temperature, and the composition of the nucleating agent. The content of open cells is increased by increasing the content of nucleating agent. Useful nucleating agents include calcium carbonate, calcium stearate, talc, clay, titanium dioxide, silica, barium stearate, diatomaceous earth, and mixtures of citric acid and sodium bicarbonate. Preferred nucleating agents are talc and calcium stearate. The amount of nucleating agent employed can be from 0.01 to 5 parts per 100 parts by weight of a polymeric resin. The preferred scale is 0.4 to 3.0 parts by weight. Extensive teachings on the preparation of open cell foams are seen in the pending application of the United States of America Serial No. 08 / 264,669, filed June 23, 1994. The open cell foam optionally also comprises black smoke. Carbon black improves the thermal resistance or insulation of the foam. The carbon black can comprise between 1.0 and 25 weight percent, and preferably between 4.0 and 10.0 weight percent, based on the weight of the aromatic polymer material in the foam. The carbon black can be of any type known in the art, such as oven black, thermal black, acetylene black, and channel black. A preferred carbon black is thermal black. A preferred thermal black has an average particle size of 150 nanometers or more. Small amounts of an ethylene polymer, such as linear low density polyethylene or high density polyethylene can be incorporated into the foamable gel to improve the content of open cells on extrusion and foaming. Various additives can be incorporated into the foam, such as inorganic fillers, pigments, antioxidants, ultraviolet absorbing acid scavengers, fire retardants, processing aids, and extrusion aids. The following are examples of the present invention, and should not be construed to limit it. Unless stated otherwise, all percentages, parts, or proportions, are by weight. The open cell alkenyl aromatic polymer structures of the present invention are made in accordance with the process of the present invention.

EXAMPLE 1 An open cell extruded polystyrene foam was tested for its dimensional stability at 96 ° C for 3 hours, according to the test method of ASTM D2126-87. The heat distortion characteristics of the foam were excellent. The difference in length was 0.2 percent of the initial, the difference in width was -0.1 percent of the initial, and the difference in thickness was 0.2 percent of the initial. The foam had a content of 50 to 70 percent of open cells, 2.19 pcf (35 kg / m3), and a cell size of 0.30 millimeters.

Example 2 An open-cell extruded polystyrene foam was tested by blowing, when one side was exposed. A Thermotron FM-46 oven with minimum internal dimensions of 42 inches (107 centimeters) by 38 inches (97 centimeters), and a capacity to maintain a constant temperature of 96 ° C + 2 ° C was used. The foam was attached to a wooden platform with four metal corner fasteners in the oven. The platform was left in place during the thin time period. The foam was exposed to a temperature of 93 ° C for 30 minutes, while the other side supported by the wooden platform remained at ambient conditions. The characteristics of warping of the foam were excellent, considering the extreme temperature conditions to which the foam was exposed. The maximum sag was an average of 17 millimeters. The warping was determined by measuring the distance from the bottom of the foam to the platform. If the foams were placed on a roof under a membrane, the bending would be smaller due to the restrictive influence of the membrane. Under normal hot low ceiling conditions of a membrane, such as exposure temperatures of 87.7 ° C or less, the preferred foams would have a warped maximum of no more than 6 millimeters.

The sample had a content of 50 to 70 percent of open cells, 2.19 pcf (35 kg / m3), and a cell size of 0.30 millimeters. Although the embodiments of the foam and the process of the present invention have been shown with respect to the specific details, it will be appreciated that, depending on the manufacturing process and the manufacturer's wishes, the present invention can be manufactured by different changes, while that is still within the scope of the novel teachings and principles stipulated in this.

Claims (8)

1. A process to build a roof system for a structure, which comprises: a) providing a roof platform; b) applying on top of and adjacent to the roof platform, a protective layer of a plurality of boards of a foam; and c) applying a substantially waterproof membrane above and adjacent to the foam boards, the process being characterized in that the foam is an extruded alkenyl aromatic polymer foam containing more than 50 weight percent aromatic monomeric alkenyl units, and that has a content of 30 percent or more of open cells.

2. The process of claim 1, wherein the membrane is applied contiguously to the protective layer.

3. The process of claims 1 and 2, wherein the process further comprises applying a layer of pavement above and adjacent to the membrane.

4. A process for constructing a replacement roof system for a structure, which comprises: a) providing a previously existing roof system, which comprises: i) a roof platform; and ii) a first membrane located above and adjacent to the roof platform; b) applying over and adjacent to the previously existing roof system, a protective layer of a plurality of foam boards; and c) applying over and adjacent to the foam boards, a second membrane which is substantially waterproof, the process being characterized in that the foam is an aromatic alkenyl polymer foam containing more than 50 weight percent aromatic monomer units of alkenyl, and having a content of 30 percent or more of open cells. The process of claim 4, wherein the second membrane is applied contiguously to the protective layer. The process of any of claims 1 to 5, wherein the process is further characterized in that the foam has a smaller cross-sectional dimension of more than 6.4 millimeters, the foam having an open cell content of 30 to 80 percent , the foam having a density of 24 to 96 kilograms per cubic meter, the foam having an average cell size of 0.08 millimeters to 1.2 millimeters, the foam having a heat distortion temperature of 79 ° C to 99 ° C, the polystyrene foam, and the foam containing a nucleating agent. The process of any of claims 1 to 5, wherein the process is further characterized in that the foam has a smaller cross-sectional dimension of 9.5 millimeters or more, the foam having an open cell content of 40 to 60 percent , the foam having a density of 32 to 48 kilograms per cubic meter, the foam having an average cell size of 0.1 millimeters to 0.9 millimeters, the foam having a heat distortion temperature of 88 ° C to 96 ° C, the polystyrene foam, and the foam containing a nucleating agent. 8. The process of any of the preceding claims, further characterizing the process because the boards do not sag more than 6 millimeters when exposed to high temperatures for an extended period of time.