MXPA98000485A - Steel pipe with covering completely formed and method of manufacturing of the mi - Google Patents

Abstract

The present invention relates to a laminated metal tube, characterized in that it comprises: a) a laminated metal tube wall formed in a generally tubular configuration to define an inner surface thereof, b) a first polymer layer coated on the inner surface of the tube wall and unit adhesively thereto: c) a second polymer layer coated on the first polymer layer and chemically bonded thereto, the second polymer layer is substantially thicker than the first layer of polymer and selected from the group consists of a low density polyethylene, a linear low density polyethylene and a mixture of the same

Description

STEEL PIPE WITH INTEGRALLY-SHAPED COATING AND MANUFACTURING METHOD OF THE SAME Field of the invention The present invention relates in general to underground pipes for use in sewers, storm sewers, forced pipes, drainage works and other low-level applications. hydrostatic charge and more particularly with a metal pipe with an integrally formed coating for use in corrosive and abrasive environments and with a manufacturing method thereof.

BACKGROUND OF THE INVENTION Metal pipes of corrugated design and with spiral ribs or fins are widely used for drainage, drainage and other similar fluids. Although they are susceptible to abrasion, steel pipes have advantages over concrete pipes and the like due to their comparatively high strength and low weight. These characteristics make the metal pipe comparatively cheap to manufacture, pack and handle insofar as it allows its use in applications that require it to support the soil of substantial soil debris. In addition, in recent years a steel pipe with particular spiral fins has been introduced by W. E. Hall Co of Ne port. Beach, California, the assignee of the present application, which possesses hydraulic efficiency comparable to the most expensive concrete pipeline as well as also possesses superior structural capabilities for prolonged use in rainwater collector applications. REF: 26614 Since metal piping is susceptible to corrosion and excessive abrasion, its use has been restricted mainly to drainage works and rainwater collector applications. In sanitary applications, this is sewage systems, sulfuric acid is formed that causes corrosion, from the hydrogen sulfide gas generated by the waste products. Such waste and / or acid products have made the use of steel tubing impractical in inapractical sanitary applications, because it deteriorates rapidly in the corrosive environment. As such, a much heavier and more expensive coated and / or vitreous clay, coated pipe has traditionally been used for sanitary applications. Although metal piping is generally preferred due to its high strength and comparatively low weight and cost, metal piping has not been widely used in sanitary applications so far due to its susceptibility to corrosion. In rainwater collector applications, such metal pipe is particularly susceptible to extensive abrasion caused by the movement of gravel, earth, sand, etc. through it. Such excessive abrasion frequently degrades the metal piping to a point where leaks from the contents of the metal piping become a major concern. Additionally, such abrasion may in some instances be sufficient to adversely affect the structural integrity of the pipeline and consequently result in a structural failure of the pipe, where the rubble soil crushes a portion of the pipe, thereby sealing in this manner. effective the pipeline and reduce or substantially eliminate the flow through it.

In recognition of these deficiencies, prior art attempts to allow the use of concrete piping as opposed to vitreous clay piping for large-sized sewage applications, while reducing susceptibility to corrosion of the concrete pipe have included: the installation of a thick plastic coating resistant to corrosion and / or forming the inside of a concrete pipe with an additional protective concrete in the crown portion of the pipe. Such corrosion resistant coatings of the prior art typically comprise plastic insert pieces sized to be received within each section of the concrete pipe. Such liners are commonly emptied within each pipe section. Subsequently after the pipe sections have been put in place, the adjacent coatings adhere together with the intention of forming a seal, to prevent the fluids and corrosive gases from coming into contact with the concrete pipe. Although such concrete and / or plastic coating solutions of the prior art have generally proven to be suitable for large-sized sewage applications, the inherent high cost of such solutions has presented a severe impediment in products and projects. of construction. In addition, the useful life of such protective concrete pipe solutions of the prior art is finite, which requires extensive rehabilitation over time, to thereby determine a huge expense in inactive line rehabilitation expenses. Recognizing the general inability of metal piping and concrete piping for sewage applications, plastic piping has been introduced to the market in recent years. Although such a plastic pipe supports the degradation generated by the corrosive environment encountered in sewage applications, its use has so far mainly been limited to small-sized sewage applications. In this regard, the structural integrity of the plastic pipe is extremely limited, such that in large-sized applications, the side wall of such plastic pipe must be made extremely thick or profiled to allow such plastic pipe to support the pipes. compression forces exerted in underground applications. Due to the high cost of such plastic material, the use of such plastic pipe in large-scale sewage applications has been economically impractical. Therefore, in view of the specific factors encountered in large-scale sanitary sewage applications, almost all of such applications have used expensive concrete pipe, which has a protective wall formed therein, which degrades significantly during the prolonged use and thus require rehabilitation and / or costly replacement over time or fixed coatings separately which are normally ineffective in cost. In contrast to the waste product and / or acid environment found in sanitary applications, the metal pipe used for underground stormwater collector applications additionally encounters substantial problems associated with its environment or operating environment. In relation to the applications of underground rainwater collectors, the long-term exposure of the exterior of the metal pipe within the buried or underground environment serves to corrode the exterior of the pipeline, while the water and waste that flows to the outside of the pipeline. Through the interior of the metal pipe they degrade the pipe by means of abrasion. In an effort to prevent such corrosion effects, the interior of a metal pipe has been coated with concrete, in the hope that a thicker coating will be more resistant to abrasion and thereby resist deterioration and corrosion. However, there are faults as to effective means of cost to secure the concrete to the inner wall of the metal pipe. An alternative method of the prior art to solve the corrosion and abrasion deficiencies of metal pipe for rainwater collector applications, has been to manufacture the metal pipe from a plastic, laminated, plastic film material . One such prior art product is known as Black-Klad ™, a product of the Inlan Steel Company of Chicago, Illinois. Before the lamination of the steel sheet to a section of pipe, a surface, that is that surface which forms the internal surface of the pipe, is laminated with a polymeric material. The thickness of such lamination is limited to approximately 0.254 mm (0.010 inches) and is designed to resist degradation caused by corrosion and some abrasion. Nevertheless, due to the comparatively thin layer thickness of the plastic laminate, the laminate tends to wear out due to abrasion of sand, rocks, etc. and thereby exposes the underlying metal surface. In addition, during the pipe forming process, the thin laminate is frequently damaged due to cold rolling metal forming procedures. Attempts to apply thicker laminations of such prior art products have hitherto resulted in increased blistering or separation of the polymeric compound from the metal pipe. As such, the application of a protective polymer layer to the metal piping has hitherto been ineffective. Accordingly, because the inner lining of the prior art of metal pipes has proven to be susceptible to abrasion and corrosion and since inert abrasion resistant coatings such as those constructed of concrete or an inert polymeric material have Failing to remain effectively secured to the walls of the metal pipe, the metal pipe has so far been unacceptable for use in sanitary applications such as sanitary sewage. As such, there is a substantial need in the art for a sufficiently thick polymeric coating which can be securely applied to the metal surfaces to maintain metal integrity when the metal pipe is placed in a corrosive environment and which remains on the same without formation of bubbles or vesiculation during the process of formation «of the pipe. In addition, there is a substantial need in the art for a metal pipe with an inert protective coating constructed of a polymeric material such as polyethylene, which would resist the attack of sulfuric acid, as well as resisting other forms of corrosion encountered in the applications of sewage water.

BRIEF DESCRIPTION OF THE INVENTION The present invention specifically addresses and resolves the deficiencies referred to above associated with the prior art. More particularly, the present invention comprises a metal pipe with a polymeric coating formed integrally for use in corrosive and abrasive environments. In the preferred embodiment of the present invention, the polymeric coating consists of 1.27 mm to 3.175 mm (0.050 to 0.125 inches) thick polyethylene, preferably a low density polyethylene (LDPE), linear low density polyethylene (LLDPE). or a combination of both, which adheres securely to the metal pipe during the fabrication of the metal pipe. As used herein, the term "low density polyethylene / linear low density polyethylene blend" includes a blend having from 0 to 100% low density polyethylene and from 0 to 100% linear low density polyethylene. . Thus, this term includes low density polyethylene without added linear low density polyethylene and also includes linear low density polyethylene without any added low density polyethylene. However, other polymers having similar corrosion resistance properties to polyethylene are also contemplated herein. The coating is formed by first applying a comparatively thin monolayer or multilayer polymer / adhesive film to the surface of the metal pipe during a pretreatment process, in order to facilitate adhesion of the comparatively thick layer, subsequently extruded from the mixture of low density polyethylene / linear low density polyethylene. When the thin film is formed as a multilayer film, the sublayers are preferably co-extruded. However, the sublayers of the thin films can alternatively be formed completely independent of each other, that is, at different times. While the comparatively thin film is preferably applied via extrusion or coextrusion, those skilled in the art will appreciate that the comparatively thin film can be applied via several well known different techniques, in which film casting and blowing techniques are included. The thin film is preferably applied in a pretreatment process to the sheet metal, preferably before the lamination of the corrugations or ribs or ribs in the sheet steel. The mixture of low density polyethylene layer / linear density low density polyethylene, comparatively thick, is preferably applied after the corrugations or ribs are formed in the sheet metal, preferably subsequent to the helical winding and formation of the sheet steel in a product of pipe. The thin film is specifically formed to securely adhere to the surface of the sheet metal and to provide an appropriate polymeric constituent layer for the subsequent thermal / chemical adhesion of the comparatively thick polyethylene layer, preferably a low density polyethylene blend. linear low density polyethylene. As such, the thin film serves as a strong adhesion agent or interface, which adhesively bonds to the metal pipe and additionally forms an appropriate base material to allow subsequent application of the comparatively thick layer of polyethylene, Preference mix of low density linear polyethylene low density polyethylene to it. The present invention provides a hydraulically efficient, smooth inner surface, which is resistant to the corrosive action of sulfuric acid and the like, as is normally found in sanitary applications. It is also highly resistant to abrasion caused by the flow of waste transported by water such as earth and gravel, as found in drainage works and collector applications for rainwater. The comparatively thin film applied in the pretreatment process to facilitate the bonding of the latter, applied to the comparatively thick layer of the low density polyethylene / linear low density polyethylene mixture comprises either a monolayer or multilayer film. The monolayer film defines a single layer and the multilayer film defines two sublayers. The monolayer preferably consists of polyeolefin / maleic anhydride (MA), ethylene acrylic acid (EAA), ethylene methacrylic acid (EMAA) or a combination of these polymers or another metal adhesive. Those skilled in the art will appreciate that several other metal adhesives are also suitable for use as the monolayer film. Optionally, the monolayer can be corona treated before its application to the comparatively thick layer of the low density polyethylene / linear low density polyethylene mixture. When a single layer of polyolefin / maleic anhydride is used, the concentration of the maleic anhydride is preferably maintained between about 0-10%, preferably less than 1% by weight. The monolayer is adhesively bonded to the metal surface, thereby providing a securely bonded substrate, to which the comparatively thick, subsequently applied low density polyethylene linear polyethylene low density adhesive adheres, to provide a bond Safe and reliable mixing of low density polyethylene / linear low density polyethylene to metal pipe. When a thin multilayer film is used, the first sublayer, that is, that sublayer following the wall of the metal pipe, is preferably formed of the same monolayer discussed above, that is, polyolefin / maleic anhydride, ethylene acrylic acid , ethylene methacrylic acid, a combination of these polymers or other metal adhesive. The second sublayer of the multilayer thin film, that is, that sublayer formed on top of the first sublayer to which the linearly applied low density polyethylene low density polyethylene layer, subsequently applied, adheres, preferably comprises a mixture of polymeric / polyethylene adhesive, that is, a carboxy-modified polyethylene, such as, ethylene, acrylic acid, ethylene, methacrylic acid, low density polyethylene with a concentration of 0-10% by weight of maleic anhydride, linear low density polyethylene with a concentration of 0-10% by weight of maleic anhydride, high density polyethylene with a concentration of 0-10% by weight of maleic anhydride or some combination of these materials. Again, those skilled in the art will appreciate that several other metal adhesives are also suitable. Those skilled in the art will further appreciate that various additives such as anti-blocking agents, antioxidants, pigments, ultraviolet light stabilizers, etc. , they can be added to the second sublayer as desired. The corona treatment can also be used to facilitate the application of the first and second sublayers as desired.

It has been found that the use of a concentration of 0-10% maleic anhydride as discussed above, increases the adhesion of the polyethylene monolayer or the second layer of the multilayer film by a factor of about 5, compared to such layers that lack maleic anhydride. The process of forming the metal pipe of the present invention begins with the pre-washing steps of a galvanized rolled strip G-210 (56.7 g (2 ounces)), in the gauge range of 1,219 mm (0.048 inches) at 3,505 mm. (0.138 inches) thick, to remove any residual grease and dust initially. The metal is subsequently processed in a high pressure hot alkaline spray bath, to remove any residual dust or greases and then rinsed with high pressure hot water sprayed on both surfaces of the metal. An optional mechanical brush device can be used to further condition the surfaces or to remove any residual chromate or surface oxides. Then repeat a hot alkaline spray at high secondary pressure and rinse with hot fresh water. The strip is then treated with an appropriate acid attack agent and then dried. An optional oxygen barrier primer may be applied to the strip or the strip may be coated by priming with an adhesive and then heated to the appropriate temperature to cure the coating with subsequent lamination of the monolayer or multilayer film. Subsequently, this laminated strip is suddenly quenched with water and cooled to the appropriate ambient temperature and then rerolled to a roll form again. Subsequently, the rolled roll can then be formed by conventional techniques to include corrugations or ribs and be formed to a length or section of pipe via conventional pipe making equipment. Subsequently, the pre-treated and corrugated / profiled sheet metal strip is optionally heated and a comparatively thick melt layer, which typically has a thickness of approximately 1.27 mm (0.050 inches) to 3.175 mm (0.125 inches) of polyethylene, preferably a mixture of Low dty polyethylene / linear low dty polyethylene, cast, for example, is extruded into the pipe section. Because the comparatively thick layer is applied at a high plasticizing temperature, it is thermally bonded and chemically bonded to the monolayer or multilayer thin film previously applied to the sheet metal, to provide a corrosion and abrasion resistant pipe, composite . In the preferred embodiment of the present invention, the application of the mixture of low dty polyethylene / comparatively thick linear low dty polyethylene is presented subsequent to the formation of the sheet metal to a pipe product. After this, the pipe sections are cooled and cut to the desired lengths using conventional techniques. In addition to being thermally / chemically adhered to the comparatively thin film layer, the mixture of low dty polyethylene / linear dty polyethylene, "comparatively thick, can optionally be optionally secured to the sheet metal via extrusion of the same polyethylene material in the ribs or channels of the pipe to form moorings which are joined to the layer of the low dty polyethylene / linear low dty polyethylene mixture. Preferably, the lashing is extruded directly into the channel. Then the mixture of low dty polyethylene / linear dty low dty polyethylene is applied immediately on it, so that the fastener and the low dty polyethylene / linear low dty polyethylene mix layer adhere firmly each. Such thermal / chemical adhesion is facilitated by positioning the extruder nozzle of the mooring and extruder nozzle of the low dty polyethylene / linear low dty polyethylene blend layer in close proximity to each other and in close proximity to the pipeline formed A) Yes, the mooring conforms precisely to the configuration of the channel, that is, substantially fills the channel and additionally thermally adheres thereto. The extrusion of the ranal lashing is preferably presented after the pipe has been formed, that is, after inter-biting or interlocking the joints joining the wall sections adjacent to each other. The extrusion of the tie to the channels may be presented as a single extrusion or alternatively may comprise a plurality of extrusion operations. For example, in a double extrusion process about one half of the tie is first formed by extrusion to the lower portion of the channel and the remainder of the tie is subsequently formed by applying a second extrusion on the previously extruded portion of the tie. Those skilled in the art will recognize that various numbers of extrusions can be used in this manner in such multiple extrusion process, as desired. A plurality of channels can be filled simultaneously or each channel can be filled individually as desired. Alternatively, the tie-down and the low density polyethylene / linear low density polyethylene mix layer can be commonly extruded from a single extruder, such that the channel is filled to form the tie and the polyethylene blend layer. Low density / linear low density polyethylene applied on the internal surface of the surface simultaneously. The extruder is thus configured in such a way that an amount of the low density polyethylene / linear low density polyethylene mixture is initially provided in those areas of the pipe where the channel is formed and a mixture of low density polyethylene / polyethylene Additional layered low density linear is provided on the inner surface of the pipe and extends over the channels. Thus, the manufacturing process is simplified by reducing the number of extruders required and by eliminating the adhesion requirement between the tie-down and the low density polyethylene / linear low density polyethylene mix layer, since both are integrally extruded. Although described in relation to the specific application of pipe forming applications, the present invention is further applicable to other metal forming applications where chemical resistance of the fabricated metal product is required. These, as well as other advantages of the present invention will be more apparent from the following description and drawings. It will be understood that changes in the specific structure shown and described can be made within the scope of the claims, without deviating from the spirit of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of the exterior of a section of pipe constructed in accordance with the present invention; Figure 2 is an enlarged cross-sectional view of the wall of the pipe of Figure 1, taken around lines 2-2 of the figure 1; Figure 3 is a flow diagram of the method of forming the metal pipe with an integral coating of the present invention; Figure 4 is a perspective view of the apparatus for forming the metal pipe with a coating formed integrally by the present invention; Figure 5 is an enlarged perspective view of the former of the pipe making equipment of Figure 4; Figure 6 is an enlarged cross-sectional view of the sheet metal after ribs and edge portions have been cold rolled but before seaming; Figure 7 is a cross-sectional view showing the longitudinal seaming process snapped; Figure 8 is a sectional side view showing the mixing by means of an optional roller by means of the diagonal monolayer co-extruded layer on the longitudinally sewn seam; Figure 9 is a flow diagram of the pretreatment process, pre-coating for joining the thin mono / multi-film layer to the sheet metal; Figure 10 is an enlarged cross-sectional view of a portion of the coating and steel pipe, showing the resulting thin film layer and the comparatively thick low density polyethylene layer formed on the inside of the pipe layer. Figure 11 is a perspective view of an apparatus for applying the integral coating to the inner surface of the metal pipe and forming the tie within a channel thereof; Figure 12 is an enlarged perspective view of the extruder for applying the integral coating and the extruder to form the tie-down of Figure 11; Figure 13 is an enlarged perspective view of the coating extruder and the tie extruder of Figures 11 and 12; and Figure 14 is an enlarged cross-sectional side view of a tapered or enlarged channel having an anchor extruded directly therein and also having the integral coating formed on the inner surface of the pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The detailed description summarized below in relation to the accompanying drawings is proposed as a description of the presently preferred embodiment of the invention and is not intended to represent the only way in which the present invention can be brought to the practice or used The description summarizes the functions and sequence of steps to build and use the invention in relation to the illustrated modalities. It will be understood, however, that the same or equivalent functions or sequences can be carried out by different modalities that are also intended to be encompassed within the spirit and scope of the invention. Although not by way of limitation, the process and apparatus of the present invention is suitable for use in helically spiral ribbed or finned metal tubing, such as that described in U.S. Patent No. 4,838,317 issued to Andre et al. and assigned to the present assignee W. E. Hall Co., the description of which is expressly incorporated herein by reference. In this regard, the process and apparatus of the present invention must be described in relation to the manufacture of such helical spiral ribbed metal pipe. However, those skilled in the art will recognize that the teachings of this invention are applicable to other metal pipe structures, also to other metal products, such as sheet products, which are desired to withstand corrosive environments or environments. Referring now to Figures 1 and 2, it is shown that the improved spiral ribbed pipe of the present invention generally consists of a metal pipe wall material., preferably of steel. The spirally ribbed pipe 10 has externally extending ribs or fins 12 and latched longitudinal seams 14 formed thereon and also has a polyethylene liner 16 integrally formed on the outer surface thereof. The spiral channels 18 are preferably formed in the sheet steel 11 on which the pipe 10 is formed and preferably filled with a polymer such as polyethylene, as will be explained in more detail later herein. Referring now to Figure 3, an overview of the process of forming the metal pipe 10 with an integrally formed coating 16 of the present invention is provided. The process generally comprises the pretreatment of the sheet metal, such as steel, in such a way that it has a comparatively thin polymer / adhesive layer formed thereon and rolled thereon for later manufacture into a pipe. Then the pretreated sheet metal 11 is subsequently unwound via an uncoiler 20 and ribs and / or corrugations and seams 14 (as shown in Fig. 1 and 2) are formed thereon with a profile rolling former 22 (as shown). in figure 4). Subsequently, the preformed and preformed sheet metal 11 can optionally be cleaned and heated 24. A closure roll and former 30 of the pipe making equipment forms the preformed sheet metal to a section of helical pipe and narrows the latched seams 14 together to form a tube product. A lamellar extruder with an appropriate mold and laminator 31 provides hot extrusion polymer such as polyethylene and preferably low density polyethylene and / or linear low density polyethylene or a combination thereof to an upper or inner surface of the sheet metal. The laminator applies pressure to the hot extrudate in contact with the upper pretreated surface of the sheet metal which thermally and chemically adheres to the polymer film layers and / or comparatively thin adhesive. The pipe and liner are preferably cooled 32 after the extrusion process and then the cutter 33 cuts the sections of the pipe to a desired length. The steps of forming the ribs 12 and seams 14 with the former 22 for forming profiles and for forming the preformed sheet metal to a helical pipe section with the tube deformer 30 are fully described in US Pat. No. 4,838,317, issued to Andre et al, the description of which is expressly incorporated herein by reference. However, other techniques of making conventional metal tubes as well as other fabricated metal products are contemplated herein. As best shown in Figures 1 and 2, the metal pipe having an integrally formed coating of the present invention includes a grooved wall defining a plurality of projecting ribs or ribs 12 projecting outwardly and a hydraulically efficient inner surface. . The ribs or fins 12 are preferably formed in a helical configuration. The channels 14, which are formed inside it, are generally made to have either a square, rectangular or deltoid configuration and are open along the inner surface of the pipe. In the preferred embodiment of the present invention, the channels 14 are widened or tapering to define a deltoid configuration for mechanically capturing a lashing thereon, as shown in Figure 14. Referring now to Figure 9 the detailed steps are described of the pretreatment process 19 (of figure 3) used prior to the formation of the sheet metal 11 in pipe sections 10. Those skilled in the art will recognize that, as a conventional practice, sheet metal 11 is manufactured in elongated lengths or lengths that are easily rolled up in subsequent forming processes. The initial pretreatment process 19 is initiated by unwinding the rolled galvanized metal strip 61 and then prewash 62 from the strip to remove any grease and / or residual dirt from the upper and lower surfaces of the strip 11. This step may consist of of processes well known in the art, such as the application of a detergent solution. The sheet metal 11 is then preferably subjected to a high-pressure hot-alkaline spray bath 64 to further loosen and remove any grease and dirt remaining on the surfaces. The alkaline spray is followed by a rinse with hot water / fresh water at high pressure. The strip 11 can optionally be brushed with a mechanical rotary brushing device 67, to remove any residual chromate and to further condition the metal surfaces or to remove any rust. Then strip 11 is further conditioned and cleaned with another hot alkaline wash at high pressure, to ensure adequate removal of any residual chromate surface contaminants. The strip 11 is then rinsed with a high pressure hot water / fresh water rinse at a regulated pH, to neutralize the surface and prepare it for the application of the etching agent. After the prewash treatment 62, the alkaline cleaning 64 the rinsing 66 with hot / fresh water, the optional mechanical brushing 67, the alkaline cleaning 68 and the rinsing with hot water / pH regulated fresh water, the sheet metal is subsequently subjected to to a chemical treatment attack or acid attack 72, such as Parker Bonderite 1303 or Betz Metchem Permatreat 1500 acid attack agent, to roughen or roughen the surface and prepare it for the optional application of an adhesive primer. The sheet steel is then dried at 74 and an optional oxygen barrier primer or adhesive 76 can be applied to the strip 11 etched by acid. However, in most instances, the oxygen-to-adhesive barrier adhesive can be removed. Subsequently, strip 11 attacked by acid is cured or heated at 78 at a metal outlet temperature of about 204 ° C (400 ° F) and a comparatively thin, continuous, flat coextruded polymer / adhesive layer is laminated to the metal laminate 11. As best shown in Figure 10, the polymer / adhesive layer 80 is applied to the sheet metal, such that it has a laminate thickness of at least 0.254 mm (0.0010 inch) and is preferably manufactured as a monolayer or alternatively a multilayer film having two distinct layers, that is, the lower laminate layer 81 and the upper laminate layer 82. As a monolayer film, the comparatively thin layer comprises a polymer / adhesive material, such as polyolefin / maleic anhydride, ethylene acrylic acid, ethylene methacrylic acid or a combination thereof. Those skilled in the art will appreciate that various other polymeric metal adhesives are also suitable. Optionally, the corona treatment can be used before the application of the comparatively thin layer to improve the fusion thereof. As a multilayer film, the first sublayer thereof, that is, that layer immediately adjacent to the metal surface, is preferably formed with the same material as the polymer / adhesive as the monolayer discussed above and the second sublayer, is preferably on the first layer and comprises a polyethylene modified with carboxy, such as an ethylene acrylic acid, low density polyethylene mixture having a concentration of 0-10% by weight of maleic anhydride, linear low density polyethylene which has a concentration of 0-10% by weight of maleic anhydride, high density polyethylene having a concentration of 0-10% by weight of maleic anhydride or ethylene methacrylic acid. Those skilled in the art will appreciate that several other metal adhesives are also suitable. In addition, those skilled in the art will appreciate that various different additives such as anti-blocking agents, antioxidants, pigments, and ultraviolet light stabilizers can be used as desired. The first and second layers are optionally treated to facilitate adhesion of the subsequently applied layers. The first and second sublayers of the comparatively thin film are manufactured by any of several techniques known in the art, including casting and blown film techniques. Preferably, the first sublayer of the thin film comprises ethylene acrylic acid and the second layer of the thin film comprises linear low density polyethylene having a concentration of 0-10% by weight of maleic anhydride. Thus, in the preferred embodiment, the bottom laminate 81 is formed of an ethylene acrylic acid, which comprises an adhesive that securely adheres the laminate 80 co-extruded to the sheet metal 11 via direct contact with the sheet metal 11 or contact with the coating. 76 of primer applied to the sheet metal 11. As will be explained in more detail hereinafter, the monolayer or multilayer coextruded film 80 therefore provides a layer 81 of adhesive / polymer bottom adapted to securely attach the coextruded layer 80 to the substrate. laminar metal 11 and a polymer-containing upper layer 82, which serves as a base material to allow thermal adhesion of a subsequent polymer to the upper layer 82 of the co-extruded layer 80. In the preferred embodiment, the preferably co-extruded polymer layer 80 is applied to the sheet metal 11 at an elevated temperature of about 218 ° C to 332 ° C (475 ° F to 630 ° F) and pressed strongly thereon by means of a conventional roller 316. Subsequently, the sheet metal 11 having the coextruded polymeric layer 80 applied thereto is cooled to 84 and subsequently rewound 85 for later use in the tube manufacturing process. In the preferred embodiment, it is contemplated that the pretreatment process is provided on the upper and lower surfaces of the sheet metal 11 with the lower surface treatment that provides additional corrosion protection for the floor side of the resulting pipe. However, the underside can alternatively be covered with conventional thermoplastic films such as vinyls or acrylics. Referring now to Figures 4 and 5 and 11 to 13, the additional steps of the process to actually form the metal tube 10 and the application of the integrally formed coating 16 of the present invention are illustrated. As shown, pre-treated sheet metal 11, previously disposed on a roll or coil 30 is mounted on a conventional unwinder 20. The unwinder 20 facilitates the unwinding of the pre-treated sheet metal 11, which has the polymer / adhesive layer 80 disposed on the upper surface thereof. The pretreated sheet metal 11 passes through a profile rolling former 22 having a plurality of forming rollers 32 which progressively ribs or fins 12 (as shown in Figure 1) and edge seaming or joining elements. 54 and 56 (as shown in Figure 6) within the sheet metal 11. It should be noted that the formation of the ribs 12 comprises the main cold forming processes for the pipe 10 and is facilitated in the pre-treated sheet metal. As such, the substantial compression fraction forces exerted during the cold forming process are compensated for by the comparatively thin polymer / adhesive layer 80, preferably co-extruded, without cracking and / or bubbling. After leaving the profile rolling former 22, the sheet metal 11 may optionally be subjected to a cleaner / heater 24 which prepares the polymer / adhesive top surface of the sheet metal 11 for the process of forming the subsequent pipe section. and the thermal / chemical adhesion of the comparatively thick polymer layer preferably low density polyethylene thereto. Then the thermally adhered metal / polyethylene sheet 44 is passed to conventional pipe making equipment having a crimping roll 50 which coils and snaps the seams of the male and female edge 56 and 54 into a longitudinal seam, which forms the resulting section 46 of pipe. The action of the crimping roll 50 is shown in Fig. 7. As shown in Fig. 7 the snap-forming rollers engage the adjacent edge seaming elements 56 of the polymer / adhesive sheet metal 44 together when using the elements. of seam 56 to the adjacent female seam member 54 as the sheet steel 44 is helically rolled and then the curvature of the male seam elements 56 and female 54 in a laminated juxtaposition with the sheet 11 of adjacent sheet steel. As the pipe making equipment progressively forms the length of the pipe 46, the comparatively thick polymer layer formed preferably of a low density polyethylene is subsequently applied within the interior of the pipe section 46 by means of a process of extrusion. In the preferred embodiment, the extrusion process is used to simultaneously fill the interior of the channel or rib 18 formed on the wall of the pipe while simultaneously applying the comparatively thick polymer layer on the inside of the pipe section. In this regard, filling the channel 18 of the ribs provides a mechanical tie which additionally secures the resulting polymer layer 16 to the interior of the pipe section 46. Referring now to Figures 16-18, the preferred apparatus for applying the comparatively coarse low density polyethylene layer and filling the channel 18 of the rib 12 to produce the mooring structure is shown. With particular reference to Figures 11 to 13, the apparatus preferably comprises a hopper or feeding device 300 containing a granular polymer, preferably polyethylene 302. A mounting or assembly 304 of guide thyme or advancing thyme extends from the lower part of the hopper or feeding device 300 and into the pipe 46 axially downwardly of the seaming roll 50 by means of an extension 303. As will be recognized, as the sheet metal 11, 44 is snapped by the roller 50 , the resulting pipe 46 extends axially away from the screw 50, this is from left to right as seen in Figure 11.

As in contemporary extrusion systems, a set or assembly 304 of guide screw or advancing screw heats and plasticizes the granular polymer 302 as it travels via the guide screw 308 over the entire length of the screw of the assembly or assembly 304 of guide thyme. The guide screw assembly 304 transports the polymer 302 to an extrusion head assembly or nozzle 310 located axially downstream of the seaming roll 50 which fills the channel 18 to form a tie-down 200 (FIG. 14) of the pipe section 46 and applies an inner liner 16 to the inner surface thereof. With particular reference to Figures 12 and 13, the nozzle 310 of the extrusion assembly comprises a nozzle 312 of the lashing extruder and a nozzle 314 of the extruder of the inner lining. The nozzle 312 of the lashing extruder deposits an amount of polymeric material directly into the channel 18, such that the channel 18 is substantially filled with the polymeric material, thereby forming a tie 200 directly therein. Because the interior of the channel 18 having the comparatively thin polymer / adhesive layer 80 applied previously thereto, the amount of the polymer adheres firmly to the "polymeric constituent of the comparatively thin layer previously applied. The nozzle 314 of the internal coating extruder is subsequently superimposed on a sheet of the polymeric material on the tie-down 200, also extruded on the interior of the wall of the pipe, such that the heated polymeric material of the tie-down 200 and the hot polymeric material of the coating 16 adhere to each other, also as to the layer 80 of the comparatively thin polymer / adhesive previously applied on the wall of the pipe.

Preferably, each newly added section of the liner 16 is slightly overlapped with the previously applied layer thereof, to ensure a proper bond thereto, also as the desired coverage of the interior of the pipe 46. As can be better seen in the figures 12 and 13, a roller 316 is preferably used to firmly press the extruded sheet 16 of the polymeric material in contact with the polymer skin / internal adhesive layer of the pipe 46, thereby ensuring adequate contact pressure to adhere the layer 16 to the polymer / adhesive layer of the pipe wall. It has been found that a roller 316 consisting of aluminum and cooled with air, allows the liner 16 to be firmly held in place while inhibiting the adhesion of the inner liner 16 to the roller 316 itself. The roller 316 is preferably adjustable in height to vary the thickness of the coating 16 applied to the interior of the pipe section 46, also as the application pressure. Those skilled in the art will recognize that they are contemplated in the present alternative roll configurations. Although numerous polyethylene materials are suitable for use as the coating 16, a preferred material candidate for the comparatively thick polymeric layer is a low density / linear low density polyethylene material known as DOWLEX 3010 or DPT 1450 (trademarks of Dow Chemical Company, Midland, Michigan), which is known to exhibit superior abrasion resistance. Preferably, in the application process, the cleaner / heater 24 raises the temperature of the sheet metal 11 and the polymer / adhesive layer 80 disposed thereon at a temperature of about 37.7 ° C-107 ° C (100-225 ° F). ) and not greater than 127 ° C (300 ° F) in such a way that the polyethylene layer 16 will be more easily thermally adhered thereto The head of the extruder or nozzle 310 forms the polyethylene in a continuous flat layer 40 (shown in FIG. figure 10) having a thickness of approximately 1.27mm to 3.75mm (0.50 to 0.125 inches) and preferably 2.54mm (0.100 inches), which is applied to the upper surface of the comparatively thin polymer / adhesive layer 80 disposed on the sheet steel 11. In the preferred embodiment, the polyethylene layer 40 is extruded onto the comparatively thin polymer layer 80 at a temperature of approximately 218 ° C-332 ° C (425 ° F-630 ° F) preferably 274X (525 ° F). In the absence of preheating, the preferred process and temperature for the extrusion of Daulex 3010 is approximately 260 ° C (500 ° F). Because the polyethylene layer 40 is applied to the upper surface of the pretreated sheet metal 11 at a high plastification temperature, a strong thermal / chemical bond is provided between the polyethylene layer 40 and the polymeric constituent existing in the top layer 82. of the polymer / adhesive layer 80 disposed on the sheet metal 11. As such, a polymer to polymer bond is obtained which securely fix the layer 40 of low density polyethylene to the preformed and preformed sheet metal 11. Then the resulting laminated sheet metal 11 can be further cooled with forced air or water, before it is formed into a section 46 of helical pipe After the application of the layer 40 of low density polyethylene or linear low density polyethylene to the metal 11 pretreated sheet, the resulting metal / polyethylene sheet has a cross-sectional configuration shown in Figure 14. As shown, the layer 40 of low density polyethylene extends in a thermally / chemically bonded, generally contiguous, orientation over the The upper surface of the sheet metal 11 and preferably is superimposed on the rib or channel 18 to maintain a consistently uniform diameter across the length of the pipe. As it should be recognized, the resulting pipe section 46 which has the channels 18 filled in the lashing has a greater structural strength than the metal pipe with conventional spiral fins or ribs. In addition, as shown in Figure 10, the pipe 10 includes an internal liner 16 of substantially pure, substantially pure low density polyethylene, having a sufficient thickness (this is approximately 2.54 mm (0.100 inches)) which is capable of withstand the corrosion caused by contaminating acids found in sewage applications. Additionally, since the low density polyethylene liner 16 is integrally applied to the pipe during the manufacturing process and thermally adhered to the polymer / adhesive layer adhered to the steel pipe 11, delamination, bubble formation or blistering or cracking of layer 16 of low density polyethylene are removed. In addition, after the installation of pipe 10 in sewage applications, the adjacent pipe sections can be easily spliced and joined at their interfaces by using envelopes or high density polyethylene shells which can be thermally welded / bonded to the cladding of low density polyethylene fixed inside the pipe. Referring now to Figure 14, a cross section of the tie 200 formed within a channel 18 and an inner liner 16, 40 formed on the inside of a pipe section 46 is illustrated. The tie 200 is attached to the inner liner 16 at the interface 310 thereof. Additionally, the tie-down 200 is mechanically captured and chemically bonded to the comparatively thin polymer / adhesive layer 80, previously applied within the channel 18. The tie-down 200 is bonded into the channel 18 since it is applied thereto as long as it is applied to it. it is in a plastic state and thus adheres to the previously applied comparatively thin layer 80 disposed within the channel 18. The tie-down 200 is mechanically captured inside the channel 18 due to the deltoid construction or enlarged or tapering upwards thereof, which mechanically prevents the mooring from being pulled from it. Additionally, the coating 16 adheres adhesively to the comparatively thin layer 80 previously applied on the inside of the pipe 46, since it is also applied in a heated or melted state. In addition, the helical shape of the tie-down 200 tends to prevent it from being pulled from the channel 18, since such traction of the channel would require the helical tie to be twisted to facilitate its separation. Thus, the present invention provides an adhesive / chemical bond of the coating to the metal pipe as well as a mechanical link via a deltoid-shaped tie. Thus, if for some reason the adhesive / chemical bond will fail over time, the mechanical bond positively ensures the maintenance of the coating within the pipe. It will be understood that the exemplary steel pipe with the integrally formed coating described herein and shown in the drawings represents only one presently preferred embodiment of the invention.

Certainly, various modifications and additions can be made to such modality, without deviating within the spirit and scope of the invention. For example, various polymeric materials having similar properties such as polyethylene and ethylene acrylic acid can be used. In this regard, it has further been found that low density polyethylene or linear low density polyethylene is a preferred material candidate for coating 16 and the use of such material is clearly contemplated herein. The description and scope of the present invention are not limited to the use of low density polyethylene. In this regard, in its broad sense, the present invention facilitates the use of an inner coating of relatively thick polymer to be disposed on a metal surface, which polymer adheres to the surface of the metal by means of a comparatively thin applied layer previously having an adhesive component and a polymer / adhesive component which allows the subsequent thermal adhesion of the substantially similar, substantially pure, comparatively thick polymer layer via a layer of constituent polymer found in the comparatively thin layer previously applied. Additionally, the present invention contemplates the use of the fixation of a protective polymeric layer to a product manufactured after the formation and / or completely the formation of the product manufactured by the pretreatment of the metal used in the product manufactured for the subsequent deposition of the layer Polymeric to it. Also, various metals and alloys that have sufficient structural strength can be used as the pipe metal. In addition, the polymeric laminated metal and the method for forming same need not be limited to tube making, but, rather, find application in many diverse areas such as automotive body sheet metal applications and the like. Thus, these and other modifications or additions may be obvious to those skilled in the art and may be implemented to adapt the present invention for use in a wide variety of different applications. It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention is that which is clear in the present description of the invention. Having described the invention as above, property is claimed as contained in the following

Claims (20)

1. Claims 1. A laminated metal pipe, characterized in that it comprises: (a) a laminar metal pipe wall, formed in a generally tubular configuration, to define an inner surface thereof; (b) a first polymeric layer formed on the inner surface of the wall of the pipe and adhesively bonded thereto; (c) a second polymeric layer formed on the first polymeric layer and chemically bound thereto and; (d) wherein the second polymeric layer is substantially thicker than the first polymeric layer, the first polymeric layer facilitates the adhesion of the second polymer layer to the wall of the pipe, and the second • polymer layer provides abrasion resistance to the polymer layer. wall of the pipe.
2. 2 The laminated metal pipe according to claim 1, characterized in that the second polymeric layer comprises polyethylene.
3. 3. Laminated metal pipe according to claim 2, characterized in that the first polymeric layer comprises a polymer / adhesive mixture.
4. 4. The laminated metal pipe according to claim 3, characterized in that the first polymeric layer comprises first and second sublayers.
5. 5. Laminated metal pipe according to claim 4. characterized in that the wall of the sheet metal pipe comprises a wall of steel pipe.
6. 6. Laminated metal pipe according to claim 5, characterized in that: (a) the first polymeric layer has a thickness of approximately 0.254 mm (0.010 inches); and (b) the second polymeric layer has a thickness of approximately 2.54 mm (0.100 inches).
7. 7. The laminated metal pipe according to claim 6, characterized in that the first and second sublayers of the first layer are approximately 0.127 mm (0.005 inches) thick.
8. 8. A method for forming a laminated metal pipe, the method is characterized in that it comprises the steps of: (a) forming the sheet metal in a generally tubular configuration, to define a pipe wall having an internal surface thereof, the The wall of the pipe has a first polymeric layer formed on the inner surface thereof, such that the first polymeric layer adheres adhesively thereto; (b) forming "a second polymeric layer on the first polymeric layer, the second polymeric layer is chemically bonded thereto; and (c) wherein the second polymeric layer is formed substantially thicker than the thickness of the first polymeric layer and the first "polymeric layer" facilitates the adhesion of the second polymeric layer to the wall of the pipe.
9. 9. The method according to claim 8, characterized in that the step of forming a second polymeric layer on the first polymeric layer comprises the formation of a polyethylene polymer layer.
10. 10. The method according to claim 9, characterized in that the step of forming a first polymeric layer comprises the formation of a first polymeric adhesive / polyethylene layer.
11. 11. The method according to claim 10, characterized in that the step of forming the first polymeric layer comprises: (a) forming a first adhesive sublayer; and (b) forming a second sublayer of adhesive / polyethylene.
12. 12. The method according to claim 11, characterized in that: (a) the first layer is formed such that it has a thickness of about 0.254 mm (0 010 inches); (b) the second layer is formed in such a way that it has a thickness of approximately 2.54 mm (0.100 inches).
13. 13. A laminated metal pipe, characterized in that it comprises: (a) a steel pipe containing an inner surface; (b) a first layer of polymer / adhesive mixture, formed on the inner surface of the metal pipe; (c) a second polymeric layer formed on the first polymer / adhesive layer; (d) wherein the first polymer / adhesive layer forms an adhesive / polymer interface for secure attachment of the second polymeric layer to the metal pipe.
14. 14. The laminated metal pipe according to claim 13, characterized in that the second polymeric layer is substantially thicker than the first polymer / adhesive mixture layer.
15. 15. The laminated metal pipe according to claim 14, characterized in that the first polymer / adhesive mixture layer comprises a monolayer.
16. 16. The laminated metal pipe according to claim 14, characterized in that the first polymer / adhesive layer comprises a multilayer.
17. 17. The laminated metal pipe according to claim 16, characterized in that the second polymeric layer comprises a layer of polyethylene.
18. 18. A laminated metal pipe characterized in that it comprises: (a) a sheet metal pipe having an inner surface and a rib extending radially out thereof, to form a channel on the inner surface; and (b) a polyethylene liner, formed integrally on the inner surface, the liner is adhesively / chemically bonded to the inner surface and mechanically clamped to the channel.
19. 19. The laminated metal pipe according to claim 18, characterized in that the channel is formed in such a way as to have a generally deltoid configuration.
20. 20. The laminated metal pipe according to claim 18, characterized in that the coating is adhesively / chemically bonded to the inner surface by an adhesive / polymer layer.