METHOD OF MANUFACTURE BACKGROUND OF THE INVENTION

[0001] The present invention relates to a compression moldable composition for use as an adjustment unit or gasket in maintenance holes and similar structures and to a method of forming the adjustment unit or gasket.

[0002] Waste rubber products, especially scrap vehicle tires and scrap rubber particles derived from re-treading of used vehicle tires, as well as scrap rubber particles formed in the manufacture of vehicle tires present a disposal problem. In particular disposal of such waste in landfill sites presents a serious fire hazard.

[0003] Recycling of such scrap rubber products presents difficulties, however, various proposals have been made to grind the scrap rubber products to particle form and employ the particles as filler in different products.

[0004] A separate problem arises with respect to maintenance holes for removal of rainwater, catch basins and valve chambers in which a concrete riser is in contact with a surface component (metal or non-metal) which is exposed to vibration generating impacts, and the generated vibrations are transmitted through the surface component to the concrete riser. In such cases the vibrations can cause fractures or cracking in the concrete riser, shortening its life such that it requires frequent replacement or repair. For example, when a vehicle travels over a manhole cover, the load and associated vibrations are conveyed from the cover to the frame and ultimately to the concrete riser.

[0005] To address these issues, it is known to provide a gasket-like structure manufactured from a compression moldable composition that is situated between the surface component and the concrete riser. The structure may be used as a "gasket" to protect the concrete riser and/or as an "adjustment unit" to allow adjustment in the height of the surface component with respect to the concrete riser. The composition contains a major amount of waste rubber products, in particle form. If desired, the composition can include reinforcing fibers. For example, U.S. Patent 5,723,192, which issued on March 3, 1998, to Jonasz is incorporate herein by reference in its entirety.

[0006] Experience has revealed that the resilient compression characteristics of existing compression moldable articles of this type can place limits on the thickness of gaskets and adjustment units in some applications. As the gasket or adjustment unit gets thicker, there is more material disposed between the surface component and the underlying concrete riser. Because of this, a thicker structure will allow more relative movement between the surface component and the concrete riser. In some applications, too much movement can prevent a risk of damage to surrounding structures. For example, when the surface component is a manhole cover and frame installed in a roadway, excessive movement of the frame with respect to the roadway can result in damage to the roadway material, particularly in the region where the roadway material overlaps the peripheral edge of the manhole frame.

SUMMARY OF THE INVENTION

[0007] The present invention provides a compression moldable composition with characteristics that provide improved performance in some applications. The composition is particularly well-suited in forming an adjustment unit or gasket (collectively "adjustment riser") adapted for insertion between a concrete riser and an overlying surface component, such as the frame and cover components of manhole and catch basin structures. The surface component may include without limitation metal frame and cover components, which might transmit mechanical vibrations to any underlying structures.

[0008] In one embodiment, the compression moldable composition includes: a) 60 to 97%, by weight, of rubber particles of a varied size distribution in the range of 5 to 30 mesh, b) 3 to 20%, by weight, of a polymerizable material, said polymerizable material being non- reactive with the rubber particles, and polymerizing to form a matrix surrounding the rubber particles, c) 0 to 20%, by weight, of reinforcing fibres, the fibres being non-reactive with the polymerizable material and d) 8-20%, by weight, of acrylic mixture. The acrylic mixture may be Plexiglass _™ , Lucite _™ , Pespex _™ , mineral-filled acrylic and other polymethyl methacrylates mixtures ("PMMA mixtures").

[0009] In another embodiment of the present invention, the compression moldable composition includes: a) 75 to 90%, by weight, of rubber particles of a varied size distribution in the range of 5 to 30 mesh, b) 5 to 12%, by weight, of a polymerizable material, the polymerizable material being non-reactive with the rubber particles, and polymerizing to form a matrix surrounding the rubber particles, c) 5 to 13%, by weight, of reinforcing fibres, the fibres being non-reactive with the polymerizable material, and d) 8-20%, by weight, of acrylic mixture. The acrylic mixture may optionally be about 10%, by weight.

[0010] In one embodiment, the PMMA mixture is a mineral-filled acrylic mixture available from Aristech Acrylics LLC of Florence, Kentucky under the tradename Acrystone ^® , Avonite Surfaces Foundations (MSDS Number: C8201A). The acrylic mixture of this embodiment may include: (a) greater than about 30%, by weight, butyl acrylate, methyl methacrylate copolymer, (b) less than about 1%, by weight, methyl methacrylate, (c) about 40-70% by weight, alumina trihydrate and (d) less than about 5%, by weight, colorants.

[0011] In still another aspect of the invention there is provided a compression molded article having rubber particles and reinforcing fibres in a polymer matrix that is reinforced with acrylic mixture and has a Durometer Hardness of about 75 Shore A ±10%, a tensile strength of about 237 psi (and not less than 145 psi), an initial compression deformation of 4 to 8% and a compression set of about 47.96% ±10% (ASTM D 395-03(08), Method B).

[0012] In one embodiment, the adjustment riser is formed from an afore-mentioned composition of the invention in which the rubber particles and reinforcing fibres are distributed throughout, and surrounded by, a polymer matrix formed from polymerization of the polymerizable material, and wherein the PMMA mixture is integrated into the mixture during manufacture and prior to curing of the polymer matrix.

[0013] In another aspect of the invention provides an assembly that includes an adjustment riser of the aforementioned composition disposed between a concrete riser and a cover and frame in which the cover and frame are exposed to vibration generating impacts. The adjustment riser is disposed between the frame and the concrete riser to absorb mechanical vibrations transmitted through the cover and frame and inhibit transmission of the vibrations to the concrete riser.

[0014] In yet another aspect of the invention there is provided a method of forming a molded article comprising: i) mixing rubber particles and optionally reinforcing fibres to form a matrix, the rubber particles being of a varied size distribution in the range of 5 to 30 mesh, ii) incorporating the PMMA mixture, iii) blending the mixture from ii) adding a polymerizable liquid material to the mixture from i) and ii) and blending the mixture with the liquid material to form a blend of the rubber particles, the fibres and the liquid material in which the particles and the fibres are coated with the liquid, iv) compression molding the blend in a mold, while polymerizing the liquid material, at an elevated temperature and pressure, and v) recovering a molded article having a polymer matrix derived from the polymerizing of the liquid material, from the mold, and wherein the rubber particles in step i) are present in an amount to provide 60 to 97%, preferably 75 to 90%, by weight, of the rubber particles in the molded article, the fibers in step i) are present in an amount to provide 0 to 20%, preferably 5 to 12%, by weight of the fibres in the molded article and the liquid material in step ii) is present in an amount such that the polymer matrix comprises 3 to 20%, preferably 5 to 12%, by weight, based on the weight of the molded article.

[0015] In yet another aspect, the present invention provides a method for determining the composition of an adjustment riser to be used between a surface component and a concrete riser under a roadway generally including the steps of: i) determining the resilient compression characteristics of the roadway material adjacent to the surface component, ii) determining the desired thickness of the adjustment riser, iii) determining the formula for a moldable composition to form an adjustment riser having the desired thickness and about the same resilient compression characteristics as the roadway material adjacent to the surface component and iv) producing an adjustment riser in having the determined formula. In one embodiment, the process of determining the formula includes determining the individual proportions of the various components of the following formula: i) 60 to 97%, by weight, of rubber particles of a varied size distribution in the range of 5 to 30 mesh, ii) 3 to 20%, by weight, of a polymerizable material, said polymerizable material being non-reactive with the rubber particles, and polymerizing to form a matrix surrounding the rubber particles, iii) 0 to 20%, by weight, of reinforcing fibres, the fibres being non-reactive with the polymerizable material and iv) 8-20%, by weight, of acrylic mixture.

[0016] The present invention provides an adjustment riser that exhibits reduced resilient compression and therefore permits the use of thicker adjustment risers in many applications. The present invention therefore expands the range of applications that can benefit from waste rubber products. The use of acrylic mixture as a reinforcing additive provides a relatively low cost composition. In one aspect, the present invention also provides a method for manufacturing an adjustment riser that may provide improved performance over a broad range of roadway applications. By matching the resilient compression characteristics of the adjustment riser to the resilient compression characteristics of the roadway, the likelihood of damage to the roadway caused by difference in the movement of the surface component and the roadway material under load can be dramatically reduced.

[0017] These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the description of the current embodiment and the drawings. [0018] Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited to the details of operation or to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention may be implemented in various other embodiments and of being practiced or being carried out in alternative ways not expressly disclosed herein. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of "including" and "comprising" and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. Further, enumeration may be used in the description of various embodiments. Unless otherwise expressly stated, the use of enumeration should not be construed as limiting the invention to any specific order or number of components. Nor should the use of enumeration be construed as excluding from the scope of the invention any additional steps or components that might be combined with or into the enumerated steps or components.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Fig. 1 is an exploded view of an adjustment riser.

[0020] Fig. 2 is an exploded view of an assembly incorporating the adjustment riser with a portion of the concrete riser shown in cross section.

[0021] Fig. 3 is a partially sectional side view of a maintenance hole assembly.

[0022] Fig. 4 is a partially sectional side view of the maintenance hole assembly with an alternative adjustment riser.

DESCRIPTION OF THE CURRENT EMBODIMENT

[0023] A system containing an adjustment unit or gasket (collectively "adjustment riser") in accordance with an embodiment of the present invention is shown in Fig. 1. The system 100 is illustrated in the context of a maintenance hole 20 disposed in a roadway 102 (See Figs. 3 and 4), and generally includes concrete risers 28 and 30, a frame 24 and a cover 26. The system 100 also includes an adjustment riser 10 interposed between the uppermost concrete riser 28 and the frame 24. The concrete riser 10 may extend from and provide a portion of the maintenance hole 20 for a sewer, catch basin or other similar type of underlying infrastructure. The adjustment riser 10 may be used as a gasket to reduce the transmission of mechanical vibrations and other forces to the underlying concrete risers 28 and 30. It may also provide a structure to vary the position of the frame 24 and cover 26 with respect to the concrete risers 28 and 30. The thickness of the adjustment riser 10 may be varied to adjust the position of the frame 24 and cover 26, for example, to provide proper alignment with its environment. For example, as shown in Figs. 3 and 4, the adjustment riser 10 may be used to align the frame 24 and cover 26 with the surface of a roadway 102. If desired, the adjustment riser 18 may be tapered to adjust the angle of the frame 14 and the cover 16 with respect to the concrete riser 28, for example, when the roadway 102 is not perpendicular to the axis of the concrete risers 28 and 30. The adjustment riser 18 is manufactured from a moldable composition that is reinforced to provide reduced resilient compression.

[0024] Directional terms, such as "vertical," "horizontal," "top," "bottom," "upper," "lower," "inner," "inwardly," "outer" and "outwardly," are used to assist in describing the invention based on the orientation of the embodiments shown in the illustrations. The use of directional terms should not be interpreted to limit the invention to packages of any specific orientation(s).

[0025] As noted above, the present invention provides a molded composition that is particularly well-suited for use in producing an adjustment unit or gasket for maintenance holes, such as the type used with sewer, catch basins and other similar structures. To facilitate disclosure, the term "adjustment riser" will be used herein to refer to compression molded articles used as adjustment units and/or gaskets. [0026] With further reference to FIG. 1, an annular adjustment riser 10 has opposed, substantially flat surfaces 12, an outer annular wall 14 and an inner annular wall 16 defining an orifice 18. The dimensions of the adjustment riser 10 may vary from application to correspond with those of the concrete riser 28 and the frame 14. The thickness of the adjustment riser 10 may be selected to position the upper surface of the frame and cover at the desired height, for example, to provide alignment with the roadway 102 in Figs. 3 and 4. Although the adjustment riser 10 is shown with parallel flat surfaces 12, the surfaces 12 need not be flat and need not be parallel. For example, the surfaces 12 may be inclined relative to one another to change the angle of the frame 24 and cover 26 with respect to the concrete risers 28 and 30. This may be useful when the concrete risers do not extend perpendicularly to the upper surface of the roadway 102, such as when the concrete risers 28 and 30 do not extend truly vertically and/or when the roadway does not extend truly horizontally. The adjustment riser 10 may include contours to facilitate installation. For example, surfaces 12 may be contoured to match contours in the underlying concrete riser 28 or in the overlying frame 24. As another example, surfaces 12 may roughened or provided with one or more annular grooves to receive an adhesive or sealant.

[0027] With further reference to FIG. 2, there is shown an exploded view of a system 100 that provides a maintenance hole 20, which typically will be in a roadway 102 (See Figs. 3 and 4). Although shown in the context of a maintenance hole 20 in a roadway 102, the present invention is well-suited for use in other similar applications.

[0028] In this embodiment, the maintenance hole 20 has a metal manhole frame 24, having a metal cover 26 and concrete risers 28 and 30. Steps 32 are located on the inner wall 34 of riser 30. Although the frame 24 and cover 26 are metal in this embodiment, the present invention is suitable for use in applications in which the frame and/or cover are nonmetal. For example, the present invention is well-suited for use in combination with composite covers and/or frames. [0029] As note above, the annular adjustment unit 10 of FIG. 1 is disposed between metal manhole frame 24 and concrete riser 28.

[0030] In use, vehicles travelling on the roadway 102 in which the maintenance hole 20 is located impact metal cover 26 and the upper rim of metal frame 24 and develop mechanical vibrations (and other forces) which are transmitted through metal frame 24 towards concrete riser 28.

[0031 ] The mechanical vibrations are absorbed, in whole or in part, by the adjustment unit 10 and the transmission of vibrations to riser 28 is prevented or inhibited, thereby preventing or reducing the likelihood of damage to riser 28.

[0032] Further, the present invention permits adjustment of the height of the frame 24 and cover 26 with respect to the concrete risers 28 and 30. This may be particularly useful when the height of the surface of a roadway 102 varies with time, for example, during construction or resurfacing of the roadway 102. In such applications, the adjustment riser 10 may be removed and replaced with an adjustment riser of the appropriate thickness to accommodate the variation in the height of the surface of the roadway 102 (Compare, e.g., Figs. 3 and 4). The adjustment riser 10 may be accessed by removing the frame 24 and cover 26. In applications where the roadway surface has been raised, a supplemental adjustment riser may be used instead of a replacement adjustment riser. More specifically, in such applications, a supplemental adjustment riser may be placed atop an existing adjustment riser to add the desired additional height.

[0033] a) MOLD ABLE COMPOSITION

[0034] i)Rubber Particles

[0035] The rubber particles in the compositions of the invention are rubber particles of a varied size distribution in the range of 5 to 30 mesh. [0036] The rubber particles may comprise elongate particles or rubber crumb or may comprise a mixture of elongate particles and rubber crumb. The elongate particles are especially preferred.

[0037] The elongate rubber particles more especially have a length significantly greater than their width or thickness, for example, a length: thickness ratio of 4 to 8:1.

[0038] Especially suitable elongate rubber particles are buffings formed during the shredding of the surface of a vehicle tire during re-treading. These buffings are elongate or string-like and enhance the strength and flexibility of the molded article as compared with rubber crumb which comprises somewhat spherical or spheroidal particles. In the molded article the buffings interlock enhancing the strength and flexibility of the article.

[0039] Buffings of 5 mesh typically have a length of about 0.5 inches and a thickness of 0.0625 to 0.125 inches.

[0040] It can be helpful for the rubber particles to be of varying size distribution. This can help to avoid the formation of voids in the molded article, which weaken the structure and provide fracture generating sites, especially if water enters the voids during use of the molded article.

[0041] When rubber particles of varying size distribution are employed, the fine and finer particles occupy the spaces between the larger or coarser particles.

[0042] It is found to be especially appropriate to employ a size distribution of the rubber particles in which a major amount of the particles are of 10 mesh, and lesser amounts are of 5 mesh and 20 to 30 mesh, respectively.

[0043] An especially useful size distribution comprises about 50%, by weight, of particles passing a 10 mesh screen, about 25%, by weight, of particles passing a 5 mesh screen and about 25%, by weight, of particles passing a 20 to 30 mesh screen.

[0044] The waste rubber particles of the invention are, in particular, particles of cured or vulcanized waste rubber products; such rubber may be natural rubber or synthetic rubber, for example, polyisoprene rubbers, polybutadiene rubbers, butyl rubbers, ethylene-propylene- diene rubbers and mixtures thereof.

[0045] As indicated above rubber particles derived from waste vehicle tires or from re-treading of used vehicle tires are especially useful.

[0046] The rubber particles should be non-reactive with the polymerizable material so that the integrity of the particles is maintained in the molded composition.

[0047] ii) Polymerizable Material

[0048] The polymerizable material is, more especially, a liquid which will coat the rubber particles and the reinforcing fibres of the composition, and which will polymerize during compression molding of the composition to form a polymer matrix.

[0049] As polymerizable material there is especially preferred polyurethane prepolymers which polymerize to a polyurethane matrix, especially suitable prepolymers include methylene -4,4'-di(phenyl-isocyanate) and polymers or oligomers thereof having an NCO functionality of from 2.2 to 3, and 4,4',4"-triphenylmethane triisocyanate.

[0050] In some cases it is appropriate to employ a polymerization initiator depending on the chemical nature of the polymerizable material.

[0051] When the polymerizable material is a polyurethane prepolymer as described hereinbefore the cure or polymerization of the prepolymer is suitably carried out with water or a polyol as initiator.

[0052] A polymerization catalyst may also be employed to promote the cure. In the case of polyurethane prepolymers, suitable catalysts include amine catalysts and organometallic catalysts, for example, dibutyltin dilaurate, dibutyltin acetate, dibutyltin dithiocarboxylate and dibutyltin oxide. Catalyst are typically relatively expensive and the need for a catalyst will vary depending on the specific make up of the molded composition. In applications in which the mixture is heated, the likelihood that a catalyst will be necessary is reduced. [0053] iii) Reinforcing Fibres

[0054] The reinforcing fibres increase the strength of the molded composition, but also increase the rigidity, consequently the content of fibres needs to be controlled so as to obtain the strength without sacrificing the flexibility.

[0055] In the case of molded articles in which strength is not an essential requirement, the fibres may be omitted or only a relatively small amount of below 5%, by weight, may be employed to achieve a desired strength parameter. In other cases where high strength is desired and rigidity or lack of flexibility is not a concern, a relatively high amount of fibres above 12%, by weight, may be employed.

[0056] The fibres should be non-reactive with the polymerizable material, so that their integrity is maintained in the molded composition.

[0057] Suitable fibres include synthetic plastic or polymer fibres, an especially useful class of fibres is polyamide fibres such as those referred to generally as nylon fibres. In particular the invention utilizes with advantage, clumps of nylon fibre matting, which clumps are generally flat and of irregular shape but with maximum dimensions of the order of 0.5 inches, and composed of interlocking nylon fibres.

[0058] These clumps are particularly derived from manufacture of nylon matting which is employed as reinforcing layers between adjacent rubber layers of rubber conveyor belts.

[0059] iv) Acrylic mixture

[0060] The acrylic mixture reinforces the molded composition to reduce resilient compression. As used herein, the term "resilient compression" refers to the composition's response to loads during use, such as its compression characteristics when driven over by a vehicle in roadway applications. One measure of resilient compression is compression deflection as computed in accordance with ASTM D-545. The amount of acrylic mixture added to the molded composition may be tailored to provide the desired balance between strength, cost and resilient compression. Generally speaking, the amount of acrylic mixture may be selected based on its impact on the overall resilient compression characteristics of the adjustment riser. In many applications, the objective is to provide an adjustment riser that has approximately the same resilient compression characteristics as the material in which the surface component is installed. For example, in applications in which a manhole frame and cover are installed in an asphalt roadway, the formula for the molded composition will be adjusted to provide the adjustment riser with approximately the same amount of resilient compression as asphalt under traffic loads.

[0061] In practice, the amount of acrylic mixture added to the molded composition may vary depending on the relative proportions of the other materials used to form the composition, such as the amount and type of the polymerizable material and the amount and type of reinforcing fibres. In some embodiments, the acrylic mixture may be in the range of about 8-20%, by weight. In some embodiments, the acrylic mixture may be about 10%, by weight.

[0062] The acrylic mixture may be Plexiglass _™ , Lucite _™ , Pespex _™ , mineral-filled acrylic and other polymethyl methacrylates mixtures ("PMMA mixtures"). The acrylic mixture may be obtained as granules or other forms suitable for processing. The granules may be recycled waste products. For example, the acrylic mixture may be obtained as re- ground waste from acrylic countertops. The granules may be coarse, medium or finely ground, or some combination of coarse, medium and fine. The waste may be excess acrylic material trimmed during the manufacture of acrylic countertops or it may be used countertops. Although the acrylic mixture may be introduced as granules, it may also be introduced in other forms, such as in liquid form. In this illustrated embodiment, the PMMA mixture is a mineral-filled acrylic mixture available from Aristech Acrylics LLC of Florence, Kentucky under the tradename Acrystone ^® , Avonite Surfaces Foundations (MSDS Number: C8201A). This mineral-filled acrylic mixture includes: (a) greater than 30%, by weight, butyl acrylate, methyl methacrylate copolymer, (b) less than 1%, by weight, methyl methacrylate, (c) 40-70% by weight, alumina trihydrate and (d) less than 5%, by weight, colorants. The butyl acrylate, methyl methacrylate copolymer is PMMA that is reinforced, fortified or modified with butyl acrylate. In some applications, the butyl acrylate may not be necessary or it may be replaced by or supplemented with different additives that affect the mixture's overall properties. In this embodiment, the PMMA mixture includes a polymethylmethacrylate resin copolymer with an acrylate monomer. Suitable acrylate monomers include ethyl acrylate, butyl acrylate and hexyl acrylate. In one embodiment, the acrylate monomer is in the range 1-20% of the PMMA mixture by weight. The small amount of methyl methacrylate monomer is likely to be unreacted monomer from the manufacturing process, and is not required. The alumina trihydrate is a filler material, and it may, in some applications, not be necessary or it may be replaced by or supplemented with different filler materials.

[0063] iv) Proportions

[0064] The relative proportions of the moldable composition are not subject to wide variation if the desired physical characteristics in the molded composite article are to be achieved.

[0065] The rubber particles are employed in an amount of 60 to 97%, preferably 75% to 90%, more preferably 80 to 85% and most preferably about 80%, by weight, of the composition.

[0066] The polymerizable material is employed in an amount of 3 to 20%, preferably 5 to 12%, more preferably 7 to 9%, and most preferably about 8%, by weight, of the composition.

[0067] The reinforcing fibres are employed in an amount of 0 to 20%, preferably 5 to 13%, more preferably 7 to 12%, and most preferably about 12%, by weight, based on the weight of the composition. [0068] The acrylic mixture granules are employed in an amount of 8 to 20%, by weight of the composition, and preferably about 10%, by weight, based on the weight of the composition.

[0069] The afore -mentioned % amounts are to a total of 100%.

[0070] Water is the preferred polymerization initiator for polyurethane prepolymers and is suitably employed in an amount of 0.1 to 2%, by weight, of the composition.

[0071] The catalyst is optional, but may be suitably employed in an amount of 0.05 to 2%, by weight based on the weight of prepolymer.

[0072] In some situations, it may be desirable to customize the molded composition to correspond with the intended application. For example, with respect to roadway applications, differences in the resilient compression characteristics of the adjustment riser and the resilient compression characteristics of the adjacent roadway can lead to an increased likelihood of damage to the roadway under traffic loads. The present invention provides a method that can be used for determining the composition of a adjustment riser to be used between a surface component and a concrete riser under a roadway generally including the steps of: i) determining the resilient compression characteristics of the roadway material adjacent to the surface component, ii) determining the desired thickness of the adjustment riser, iii) determining the formula for a moldable composition to form an adjustment riser having the desired thickness and about the same resilient compression characteristics as the roadway material adjacent to the surface component and iv) producing an adjustment riser in accordance with the determined formula. The resilient compression characteristics of the roadway may be determined by testing (e.g. using conventional ASTM testing procedures) or by obtaining known resilient compression characteristics for the applicable roadway material of the appropriate thickness. The resilient compression characteristics of the adjustment riser can be determined by testing sample compositions containing different proportions of the various ingredients. A variety of different samples may be tested and a table of resilient compression characteristics may be built based on formula. The formula providing resilient compression characteristics closest to those of the roadway material may be used to produce the adjustment riser. In one embodiment, the process of determining the formula includes determining the individual proportions of the various components of the following formula: i) 60 to 97%, by weight, of rubber particles of a varied size distribution in the range of 5 to 30 mesh, ii) 3 to 20%, by weight, of a polymerizable material, said polymerizable material being non-reactive with the rubber particles, and polymerizing to form a matrix surrounding the rubber particles, iii) 0 to 20%, by weight, of reinforcing fibres, the fibres being non-reactive with the polymerizable material and iv) 8-20%, by weight, of acrylic mixture. In one embodiment, only the amount of acrylic mixture may be varied to obtain a range of resilient compression characteristics.

[0073] b) MOLDED ARTICLE

[0074] The composition of the invention can be compression molded to a composite molded article in which the rubber particles and the reinforcing fibres are embedded in the acrylic mixture and in a polymer matrix derived from the polymerizable material. In the preferred embodiment in which the rubber particles are elongate, they are randomly oriented in the composite; likewise the reinforcing fibres, if present, are randomly oriented in the composite.

[0075] The molded article may in particular be in the form of a relatively thick sheet or panel having superior vibration damping characteristics.

[0076] Typical molded articles of the invention include gaskets or adjustment units, dock wedges, wheel chocks, speed bumps, delineator bases, antivibration pads, manhole and catch basin adjustment risers and portable temporary road or path surface members for use on construction sites to facilitate passage over, and protection of, ground cables and conduits on the site. [0077] In one especially important embodiment the article is a gasket or adjustment unit for insertion between conduit components of a flow passage to prevent or inhibit transmission of vibration developed in a surface component, such as a metal frame and cover, to a non-metal component which may be damaged by the vibration, for example, a concrete component.

[0078] The gasket or adjustment unit has generally flat upper and lower opposed major surfaces and a peripheral outer side edge spaced from a peripheral inner side edge; the peripheral inner side edge defines an orifice in the gasket or adjustment unit. The gasket or adjustment unit may, in particular, be an annular disc, of circular or generally circular outline; or it may be of rectangular outline; thus the gasket or adjustment unit may have a circular or rectangular orifice therethrough.

[0079] The upper and lower surfaces may be parallel or generally parallel, or one of the surfaces may be inclined relative to the other so that the adjustment unit or gasket tapers in wedge-like manner throughout its width. The tapered adjustment units or gaskets are employed in maintenance holes located in a sloping part of a road.

[0080] In particular the composite, molded, gasket or adjustment unit may be inserted between a concrete riser and a surface component, for example, a metal component of a manhole cover, catch basin or valve chamber, which together define part of a flow passage for water or aqueous liquids or sludges. In such structures the surface component is frequently exposed to impacts which generate mechanical vibrations which are transmitted through the surface component to the concrete riser. This occurs, for example, in maintenance holes in the road where the manhole cover is subjected to impacts from vehicles travelling along the road.

[0081] In the absence of the present invention, the transmitted mechanical vibrations may ultimately cause fractures and cracking of the concrete, typically after 12 months use, necessitating replacement or repair of the concrete riser. [0082] In particular the composition of the invention can form a molded gasket or adjustment unit which absorbs the mechanical vibrations transmitted by such surface component and prevents or inhibits the transmission of the vibrations to the concrete riser, thereby preventing damage to the riser and extending the useful life of the riser while avoiding the need for repair.

[0083] In particular, the annular adjustment unit can be formed with the following characteristics: maximum Durometer Hardness variance of 20 Shore A, preferably a maximum of 15 Shore A; tensile strength of at least 1 MPa; Compression Deformation of 2 to 10%, preferably 3 to 9%, and more preferably 6%+- 2%; and a Compression Set of about 47.96% ±10% (ASTM D 395-03(08), Method B). With these characteristics the annular adjustment unit significantly extends the useful life of the adjacent concrete riser.

[0084] c) COMPRESSION MOLDING PROCESS

[0085] The composite molded article is produced by compression molding the composition of the invention in a state in which the rubber particles, which are preferably elongate rubber particles, and the fibres, if present, are intermingled and coated with the acrylic mixture and with the polymerizable material which is to form the polymer matrix of the composite.

[0086] In the process of the invention measured amounts of the rubber particles and reinforcing fibres are thoroughly mixed together, for example, in a paddle mixer or ribbon blender, at a speed typically of 30 to 50 rpm. The mixer or blender may be heated to 100-120 degrees F. The rubber particles and reinforcing fibres may be introduced into the heated mixer or blender and mixed until they are uniformly and evenly mixed.

[0087] The acrylic mixture is introduced into the mixer or blender so that it can be intimately mixed with the rubber particles and the reinforcing fibres. The acrylic mixture granules can be introduced into the mixer or blender before, during or after the rubber particles and reinforcing fibres. For example, the acrylic mixture granules may be introduced into the mixer or blender after the rubber particles and the reinforcing fibres have been intimately mixed. Acrylic mixture granules obtained from re-ground waste are prone to have a nontrivial amount of dust. Because the rubber particles have some moisture, adding the acrylic mixture granules to the mixture after the rubber particles may help to cut down on dust from the acrylic mixture granules.

[0088] The polymerizable material, for example, liquid polyurethane prepolymer is added to the mixture and mixing is continued for about 5 to 15 minutes to form a blend in which the rubber particles and the fibres are coated with the liquid prepolymer.

[0089] The polymerization initiator, for example, water is added while continuing the mixing to disperse the initiator throughout the blend and the resulting blend is transferred to a mold and subjected to compression molding at elevated temperature, typically of 150 degrees F to 170 degree F, preferably about 160 degree F, and elevated pressure typically 300 to 1000 psi.

[0090] On addition of the polymerization initiator, polymerization commences, consequently the mixing to disperse the initiator and the transfer of the mold must be completed within a few minutes.

[0091] The mixture is then ready for compression molding. In one embodiment, the mixture is unloaded into transfer containers and placed directly in the mold for compression molding. The compression molding may be performed with conventional compression molding techniques and apparatus.

[0092] The compression molded article is removed from the mold, whereafter it may be subjected to trimming or polishing to smoothen the outer molded surfaces and remove any rough edges.

[0093] d) TESTING

[0094] Physical tests were performed on various samples that were formed from a standard molded composition or a molded composition that includes a reinforcing additive. More specifically, the tests were performed on: (i) a standard molded composition formed from 82% rubber particles by weight, 10% reinforcing fibres by weight and 8% polymerizable material by weight; (ii) a 2.5% fiberglass reinforced composition formed from 81.17% rubber particles by weight, 9.17% reinforcing fibres by weight, 7.17% polymerizable material by weight and 2.5% fiberglass by weight; (iii) a 5% fiberglass reinforced composition formed from 80.34% rubber particles by weight, 8.34% reinforcing fibres by weight, 6.34% polymerizable material by weight and 5% fiberglass by weight; and (iv) an acrylic mixture reinforced composition formed from 78.7% rubber particles by weight, 6.7% reinforcing fibres by weight, 4.7% polymerizable material by weight and 10% acrylic mixture by weight. In each of the samples, the reinforcing fibres were a mixture of both nylon and polyester fibres, the polymerizable material was a liquid polyurethane prepolymer, the initiator was water and no additional catalyst was used. The results of various test on the four samples are set forth in the following tables.

ORIGINAL PHYSICAL PROPERTIES, ASTM D 412-06ae2, D 2240-05

Die C dumbbells tested at 20 in/min.

2.5% Fiberglass 5% Fiberglass 10% Acrylic Std Infra-Riser

Shore A Durometer, points 73 75 75 75

Tensile Strength, psi 272 201 237 262

Ultimate Elongation, % 22.0 21.8 15.2 28.2

COMPRESSION DEFORMATION, ASTM D 575-91(07)

A load of 7.25 psi was applied and the specimen measured to obtain the initial thickness. Next, a load of 145 psi was applied and a measurement taken for the initial compression deformation. The 145 psi load was maintained for 30 min. before the final compression deformation reading was taken. The median of three specimens is reported.

2.5% Fiberglass

Initial Compression Deformation (%) 4.9

Final Compression Deformation (%) 5.9

STD Infra Riser

Initial Compression Deformation (%) 6.6

Final Compression Deformation (%) 7.9

COMPRESSION DEFLECTION, ASTM D 545 METHOD A

Specimens compressed 25% at a rate of 0.5 in/min.

All specimens tested at original part thickness

2.5% Fiberglass 5% Fiberglass 10% Acrylic Std Infra-Riser

Compression @ 10%, psi 78.1 115.5 84.3 Compression @ 15%, psi 171.9 218.0 174.8 159.4 Compression @ 20%, psi 277.3 247.2 287.3 251.5 Compression @ 25%, psi 431.1 551.8 455.8 379.1

[0095] As noted above, the moldable composition may have resilient compression characteristic that are substantially similar to those of the roadway material. In one embodiment, the moldable composition has resilient compression characteristics that are substantially the same as those of conventional roadway asphalt. The closer that the moldable composition matches with the adjacent roadway material, the less likely that the roadway material will be subject to damage caused by differences in the movement of the frame and the movement of the asphalt under load. The present invention will provide benefits in this regard in any applications in which the introduction of acrylic mixture causes the resilient compression characteristics of the adjustment riser to move closer to those of the adjacent roadway material. In one embodiment, the resilient compression characteristics are within 10% of the resilient compression characteristics of the adjacent roadway material when subject to conventional loads. In another embodiment, the resilient compression characteristics are within 5% of the resilient compression characteristics of the adjacent roadway material when subject to conventional loads.

[0096] The above description is that of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. This disclosure is presented for illustrative purposes and should not be interpreted as an exhaustive description of all embodiments of the invention or to limit the scope of the claims to the specific elements illustrated or described in connection with these embodiments. For example, and without limitation, any individual element(s) of the described invention may be replaced by alternative elements that provide substantially similar functionality or otherwise provide adequate operation. This includes, for example, presently known alternative elements, such as those that might be currently known to one skilled in the art, and alternative elements that may be developed in the future, such as those that one skilled in the art might, upon development, recognize as an alternative. Further, the disclosed embodiments include a plurality of features that are described in concert and that might cooperatively provide a collection of benefits. The present invention is not limited to only those embodiments that include all of these features or that provide all of the stated benefits, except to the extent otherwise expressly set forth in the issued claims. Any reference to claim elements in the singular, for example, using the articles "a," "an," "the" or "said," is not to be construed as limiting the element to the singular.