Patent Application
20190217337
The present invention relates to coating compositions, processes for making them, and methods of application of the coating compositions. Further, the present invention relates to a process and apparatus for coating a metal substrate, for example an elongated metal tubular substrate such as a pipe. Most particularly, the coating can be used as an anti-corrosion coating on a pipe for use in oil, gas and water pipeline applications.
Fusion bonded epoxy (FBE) is often used as an anti-corrosion coating on pipe. FBE consists of a solid epoxy which is applied to a clean, hot pipe, typically using a powder coating process. The FBE powder melts when it contacts the hot pipe, forming a generally uniform film surface. FBE coatings provide excellent anti-corrosion properties, but have poor low temperature bend-ability and impact resistance when used as a single layer coating, and are thus prone to impact damage during transportation. Single layer FBE coatings are also prone to absorbing water when exposed to elevated temperatures (above 50° C.) in hot and wet environments; this in turn can cause blistering when induction heating is used in preparing a field joint. FBE can be applied as a dual layer coating to provide tough physical properties and minimize damage during handling, transportation and installation. However, dual layer FBE coatings are not price competitive.
U.S. Pat. No. 5,178,902, assigned to the present applicant, describes a high performance composite coating (HPCC) for pipe, comprising three layers of material, namely an FBE coating, which itself is coated with an adhesive layer, followed by a polyolefin top coat. The polyolefin top coat is a non-crosslinked polyolefin, and provides very good impact resistance. It also prevents moisture permeation and is resistant to elevated ambient temperatures (for example, above 50° C. but below 80° C.) in hot and wet environments. The primary purpose of the intermediate, adhesive layer, is to bond the polyolefin layer to the FBE coating. Typically, without the use of such an adhesive layer, there can be some difficulty in obtaining a strong and durable bond between the FBE coating and the polyolefin top coat. In addition, with this approach, the cost of such a system can be significantly higher than the main competitive system, which is an FBE only single layer coating.
Other prior art approaches include “compatibilizing” the top coat polyolefin layer to the FBE coating, using a blend of epoxy and polyolefin in the top coat layer. Such prior art approaches can be found in U.S. Pat. No. 5,198,497 (Mathur), U.S. Pat. No. 5,709,948 (Perez et al) and WO 2007/022031 published Feb. 22, 2007 (Perez et al). Relatively high temperatures are required during the blending of the composition in order to polymerize the epoxy resin component. The fact that polymerization occurs during the mixing of the two components, i.e. in the presence of the polyolefin, creates a so-called “interpenetrating polymer network”. These high temperatures require the use of higher polyolefins, such as polypropylene. Also by Perez et al., U.S. Pat. Nos. 8,231,943, 7,790,288 and patent publication 2007/0034316, describe interpenetrating polymer networks comprising a polyolefin (in all cases, polypropylene) and an epoxy. However, though these interpenetrating polymer networks—based compositions appear to work well, they require considerable skill, expense, and high temperatures to make, due to the requirement for an interpenetrating polymer network. Notably, to polymerize at least one of the polyolefin and epoxy in the presence of the other to form an interpenetrating network requires considerably higher temperature and complex equipment.
Other prior art coatings include the polyolefin and epoxy resin mixtures proposed in U.S. Pat. No. 4,345,004 (Miyake et al). However, blends exemplified in the Miyake et al patent are not as stable as may be considered desirable as the epoxy component tends to separate as a phase separate from the polyolefin component, or the blends require solvents for application. The latter present problems of porosity of the coating as a result of off-gassing of solvent residue.
Recently, it has been found that a fully or partially cross-linked top coat polyolefin layer is desirable. Partially or fully cross-linked polyolefins provide much improved temperature resistance, are much more impact resistant and generally more durable than their non-cross linked equivalents. However, inherent in their nature is that melting a partially or fully cross-linked polyolefin requires a much higher melt temperature, which can make it impossible or impractical for extruding directly onto a pipe, or, worse, onto an FBE coating that is already applied to the pipe, since the temperature at which the partially or fully cross-linked polyolefin can be extruded will often exceed the melt temperature of the FBE layer.
Processes for applying a polyolefin layer, and cross-linking it in situ, are described in PCT/CA2013/050765 and PCT/CA2015/050337, incorporated herein by reference. Specific compositions and batch-based formulations useful as polyolefin compositions for coating pipe utilizing the processes therein described are also taught and described.
It would be desirable to provide a coating for a pipe that overcomes one or more of the problems of the prior art. It would also be desirable to provide a method for coating a pipe that overcomes such problems and/or is more cost effective than the prior art methods.
According to one aspect of the invention is provided a method for coating an elongate metallic tubular article having an exterior surface and an interior surface, comprising, in-line: (a) optionally applying a fusion bonded epoxy coating to the surface; (b) applying a reactive polyolefin blend to said exterior surface or fusion bonded epoxy coating to form a polyolefin coating thereon; (c) optionally applying a reinforcing mesh tape to the polyolefin coating formed in step (a); (d) applying a second layer of reactive polyolefin blend to said reinforcing mesh tape or first polyolefin coating to form a second polyolefin coating; (d) optionally subjecting the (optionally reinforced) second polyolefin coating to a source of energy, thereby partially or fully cross-linking said reinforced polyolefin coating, transforming said (optionally reinforced) second polyolefin coating into a partially or fully cross-linked reinforced polyolefin coating; and (e) rapidly cooling said cross-linked reinforced polyolefin coating.
In certain embodiments, the applying of the reactive polyolefin blend comprises an extrusion onto said exterior surface of a hot, melted, reactive polyolefin blend.
In certain embodiments, the applying of the reactive polyolefin blend comprises a powder coating of said exterior surface with said reactive polyolefin blend.
In certain embodiments, the applying of the reactive polyolefin blend comprises both a powder coating of said exterior surface with the reactive polyolefin blend and an extrusion onto said exterior surface of a hot, melted, reactive polyolefin blend.
In certain embodiments, the method further comprises, in-line, and prior to step (a): (f) cleaning the exterior surface.
In certain embodiments, the method further comprises, in-line, and prior to step (a): (g) heating the exterior surface.
In certain embodiments, the method further comprises, in-line, prior to step (a): (h) applying an anti-corrosion layer.
In certain embodiments, the first reactive polyolefin coating comprises polyolefin, irganox 1010+/−Irgafos 168, E265, Wollastonite Nyad 400, Epoxy DER6155, and optionally polyethylene.
In certain embodiments, the first reactive polyolefin coating comprises, by weight, 93-94% polyethylene, 0-0.8% black master batch, 0.2-0.5% irganox 1010+/−Irgafos 168, 3-4% E265, 0.5-1.0% wollastonite Nyad 400, and 0.5-1% Epoxy DER 6155.
In certain embodiments, the second reactive polyolefin coating comprises: polyethylene; a masterbatch formulation comprising E265 or equivalent, wollastonite NYAD-400, irganox 1010+/−Irgafos 168, DER 6155, and optionally polyethylene; and optionally black masterbatch.
In certain embodiments, the second reactive polyolefin coating comprises, by weight: 90-92% polyethylene; 4-5% black masterbatch; and 3-5% masterbatch formulation comprising by weight 50-62% E265 or equivalent, 0-17.5% polyethylene, 10-20% wollastonite NYAD-400, 0.2-0.5% Irganox 1010+/−Irgafos168, and 10-20% DER 6155.
According to a further aspect of the invention is provided a masterbatch composition comprising: E265 or equivalent, wollastonite NYAD-400, irganox 1010+/−Irgafos 168, DER 6155, and optionally polyethylene.
In certain embodiments, the masterbatch composition comprises by weight 50-62% E265 or equivalent, 0-17.5% polyethylene, 10-20% wollastonite NYAD-400, 0.2-0.5% Irganox 1010+/−Irgafos168, and 10-20% DER 6155.
According to a further aspect of the present invention is provided a reactive polyolefin composition comprising the masterbatch composition as herebefore described, polyethylene, and optionally black masterbatch.
In certain embodiments, the reactive polyolefin composition comprises by weight: 3-5% of the masterbatch composition of claim 13, 90-92% polyethylene, and 4-5% black master batch.
According to a further embodiment of the present invention is provided a reactive polyolefin composition comprising polyethylene, Irganox 1010+/−Irgafos 168, E265, Wollastonite Nyad 400, and optionally black master batch.
In certain embodiments, the reactive polyolefin composition comprises by weight: 93-94% polyethylene, 0-0.8% black masterbatch, 0.2-0.5% Irganox 1010+/−Irgafos168, 3-4% E265, 0.5-1% Wollastonite Nyad400, and 0.5-1% Epoxy DER 6155.
According to another aspect of the invention is provided a method for coating an elongate metallic tubular article having an exterior surface and an interior surface, comprising, in-line: (a) heating the elongate metallic tubular article; (b) powder coating the elongate metallic tubular article with a fusion bonded epoxy to form a fusion bonded epoxy coated article; (c) before the fusion bonded epoxy has fully set, powder coating the fusion bonded epoxy coated article with a reactive polyolefin blend to form a first reactive polyolefin coating; (d) optionally applying a reinforcing mesh tape to the first reactive polyolefin coating, optionally before the first reactive polyolefin coating has set; (e) before the first reactive polyolefin coating has set, extruding a second reactive polyolefin blend onto the first reactive polyolefin coating; (f) subjecting the resultant reactive polyolefin coating to a source of energy, thereby partially or fully cross-linking said reactive polyolefin coating, transforming said reactive polyolefin coating into a cross-linked polyolefin coating; and (g) rapidly cooling said cross-linked polyolefin coating.
According to yet a further aspect of the present invention is provided method for coating an elongate metallic tubular article having an exterior surface and an interior surface, comprising, in-line: (a) heating the elongate metallic tubular article; (b) powder coating the elongate metallic tubular article with a fusion bonded epoxy to form a fusion bonded epoxy coated article; (c) before the fusion bonded epoxy has fully set, extruding onto the fusion bonded epoxy coated article a reactive polyolefin blend to form a first reactive polyolefin coating; (d) optionally applying a reinforcing mesh tape to the first reactive polyolefin coating, optionally before the first reactive polyolefin coating has set; (e) before the first reactive polyolefin coating has set, extruding a second reactive polyolefin coating onto the first reactive polyolefin coating; (f) subjecting the resultant polyolefin coating to a source of energy, thereby partially or fully cross-linking said polyolefin coating, transforming said polyolefin coating into a cross-linked polyolefin coating; and (g) rapidly cooling said cross-linked polyolefin coating.
In certain embodiments, the extruding in step (c) and the extruding in step (e) utilize a single extruder.
In certain embodiments, the extruding in step (c) and the extruding in step (e) utilize separate extruders.
According to a further embodiment of the present invention is provided a method for coating an elongate metallic tubular article having an exterior surface and an interior surface, comprising, in-line: (a) heating the elongate metallic tubular article; (b) powder coating the elongate metallic tubular article with a blend of a fusion bonded epoxy and a reactive polyolefin blend to form a fusion bonded epoxy/reactive polyolefin coating; (c) subjecting the fusion bonded epoxy/reactive polyolefin coating to a source of energy, thereby partially or fully cross-linking said polyolefin coating, transforming said polyolefin coating into a cross-linked polyolefin coating; and (d) rapidly cooling said cross-linked polyolefin coating.
According to a further aspect of the present invention is provided a method for coating an elongate metallic tubular article having an exterior surface and an interior surface, comprising, in-line: (a) heating the elongate metallic tubular article; (b) powder coating the elongate metallic tubular article with a blend of a fusion bonded epoxy and a reactive polyolefin blend to form a fusion bonded epoxy/reactive polyolefin coating; (c) extruding or powder coating the fusion bonded epoxy/reactive polyolefin coating with reactive polyolefin blend to form a reactive polyolefin coating; (d) subjecting the reactive polyolefin coating to a source of energy, thereby partially or fully cross-linking said polyolefin coating, transforming said polyolefin coating into a cross-linked polyolefin coating; and (e) rapidly cooling said cross-linked polyolefin coating.
In certain embodiments, the blend of fusion bonded epoxy and reactive polyolefin blend is a 30:70 weight ratio of fusion bonded epoxy to reactive polyolefin blend.
In certain embodiments, the blend of fusion bonded epoxy and reactive polyolefin blend is a homogeneous blend.
According to yet a further aspect of the present invention is provided an apparatus for coating a moving elongate metallic tubular article, comprising: (a) a heating station; (b) a powder coating station; (c) an extruding station; (d) an energy source station; (e) a cooling device station; and (f) a conveying assembly for moving the elongate metallic tubular article between stations.
In certain embodiments, the extruding station comprises a flat extrusion die or a circular extrusion die.
In certain embodiments, the energy source station comprises a source of infra-red energy, a source of ultra-violet energy, an electron beam, a source of microwave energy, an induction coil, a source of hot air, and/or a convection oven.
According to a further aspect of the present invention is provided a composition comprising fusion bonded epoxy powder and a reactive polyolefin blend powder.
In certain embodiments, the composition has a mean particle size of 300 microns or less.
In certain embodiments, the weight ratio of fusion bonded epoxy powder and reactive polyolefin blend powder in the composition is about 1-99, preferably 30:70.
In certain embodiments, the fusion bonded epoxy powder and the reactive polyolefin blend in the composition are a homogeneous blend.
Reference will now be made, by way of example, to the accompanying drawings which show example embodiments of the present application, and in which:
Similar reference numerals may have been used in different figures to denote similar components.
Polyolefin compositions useful for coating pipe are well known. A wide variety of such polyolefin compositions are described in PCT/CA2013/050765 and PCT/CA2015/050337, incorporated herein by reference. A subset of such polyolefin compositions are reactive polyolefin blends, which can be cross-linked using UV or another known method for cross-linking polyolefin or increasing the amount of cross-linking in a polyolefin surface.
Reactive polyolefin blends for coating pipe comprise polyolefin, (often based primarily on polyethylene and/or polypropylene), blended with reactive polyolefins, such as amino silane, maleic anhydride, etc. Reactive polyolefins have reactive sites, such as borane, benzylic protons, styrenes, silanes, etc., which promote cross-reaction. Reactive polyolefin blends may also contain grafted polyolefin, adhesion promoter, filler, epoxy resin and/or curing agent, UV stabilizer, curing agent, etc. Reactive polyolefin blends can be formulated as generally homogeneous, solid pellets of a size and shape suitable for loading into the hopper of an extruder, and extruded, hot and melted, through an extrusion die onto a pipe surface. Reactive polyolefin blends may also be provided in fine particulate form suitable for spray application.
It has been found that, for spray application, reactive polyolefin blends having a lower viscosity polyolefin is preferable. For the extrudable pellets, described above, it was found that polyethylene with a melt index of approximately 2.0 to 5.0 (190° C./2.16 kg/10 min) worked extremely well. However, for a spray-able composition, a lower viscosity was found to work better—it was found that a polyethylene with a melt index of about 2.0-17 (190° C./2.16 kg/10 min) was better suited for spray coating.
Further, for sprayable compositions, it was found that a smaller particle size was advisable. The pellets described above for extrusion/melt applications were not optimal for spraying using conventional, commercially available, powder spray guns. A much smaller particle, having a mean particle size of less or equal to 300 microns, was preferable.
Traditionally and as hereinbefore described, pipes have been coated with a first thin layer of fusion bonded epoxy, for corrosion and water resistance, followed by a second, polyolefin layer for impact resistance etc.
It has been surprisingly found that the two layers can be replaced by a single layer coating that is applied by powder spray coating, said single layer coating being a blend of FBE powder and reactive polyolefin blend in powder form. Previously, this was not thought possible, in part due to the dramatic differences in melting points for the polyolefin powder and the FBE powder. However, surprisingly, this dramatic difference in melting point is thought to actually aid in the process.
The reactive polyolefin blend suitable for spray coating is blended with a fusion bonded epoxy (FBE) also suitable for spray coating. In a preferred embodiment, the blending is a homogenous blending. In certain embodiments, a 70:30 (w/w) blend of polyolefin: FBE is used. Surprisingly, a homogeneous blend of this nature, spray coated onto a hot pipe, will result in the formation of a coating having a gradient, with a higher concentration of FBE at the pipe/coating interface, and a higher concentration of polyolefin at the outer surface of the coating. Without being limited to any particular theory, it is believed that this is due primarily (or at least in part) to the difference in melting points of the polyolefin powder vs. the FBE powder. This results in all or most of the corrosion-protection advantages of a two layer FBE/polyolefin pipe coating in an easy to apply single coating, with a primarily FBE coated inner coating, a primarily polyolefin coated outer coating, in a gradient.
As noted above, the specification also discloses a new method for coating a metallic article. The method enables, for instance, the coating of a metallic elongate article, such as a steel pipe used in oil, gas and water pipeline, with a cross-linked, or partially cross-linked, polyolefin coating that provides excellent moisture, impact, and corrosion resistance. The entire coating process can be performed “in-line”, in a series of steps in the same manufacturing facility, for example, in the same pipe conveying apparatus.
The process includes the steps of applying a reactive polyolefin blend to the exterior surface of the pipe, partially or fully cross-linking the polyolefin in situ, through the application of one or more source of energy such as a source of infra-red energy, then rapidly cooling the coating. The method provides ease of application of the polyolefin, since it is applied in a reactive, but non-crosslinked form, and thus can be applied at a relatively low temperature, which is still hot enough to melt the reactive polyolefin blend. The method also provides the excellent, hard, durable and impact and moisture resistant surface of a partially or fully cross-linked polyolefin. The method provides ease and low cost, since the crosslinking process can (optionally) occur before the coating has time to cool.
The application of the reactive polyolefin blend can be, for example, through a hot melt extrusion process, wherein the reactive polyolefin blend is heated, then extruded at a temperature of about 180° C., onto the pipe, using a flat die, or alternatively a circular die surrounding the pipe. In this manner, an even coating of hot, melted, reactive polyolefin blend is applied to and coats the pipe. The pipe may have been previously treated or coated. For example, the pipe may have been previously coated with a fusion bonded epoxy or liquid epoxy, or an adhesive, or both an epoxy and an adhesive, either as a laminate or a blend. In the case of a flat die, the die can rotate around the pipe, or in alternative configurations, the pipe itself could be rotating as it passes the die.
The term “crosslinkable”, when utilized herein, means a non-crosslinked or partially crosslinked material that can be further crosslinked through the application of an energy, such as infra red heat, gamma radiation, UV light, or electron beam exposure, or a combination thereof.
The term “crosslinked”, when utilized herein, means a partially or fully crosslinked polyolefin material. The crosslinking can be uniform, wherein the entire bulk of the polymer has about the same cross-link density, or non-uniform, for example, a gradient crosslink, where the portion of the crosslinked material closest to the pipe has less cross-link density than the material furthest from the pipe. For example, a form of energy that does not go through the entirety of the coating can be utilized, to form a gradient crosslink.
The source of energy used can be any source of energy which results in an increase in the cross-link density of the reactive polyolefin blend. For example, the source can be a source of infra-red energy, a source of ultra-violet energy, an electron beam, a source of microwave energy, an induction coil, a source of hot air, or even a standard convection oven. A combination of sources can also be used. For example the source of energy can be an infra-red heating element. The infra-red heating element, such as an infra-red coil, is configured to heat the coating to above 200° C., typically to 220-240° C., preferably 220-225° C. for 5-30 seconds.
In one embodiment, the method is provided with a temperature detector to detect the temperature of the coating composition, to ensure that the temperature is maintained in the range as required by the application requirements, for crosslinking the polyolefin. In a further embodiment, a feedback loop can be provided, along with appropriate controls. The feedback loop connects the temperature detector with the source of energy. While the controls allow the source of energy to be manipulated to ensure that the crosslinking process of the coating composition is maintained in an appropriate range, as required by the application requirements and the components used.
In a further embodiment in accordance with the specification, cooling or rapid cooling can also be performed. The rapid cooling can be a cold water quenching, either by applying a stream of water to the outside of the coated pipe, and/or to its inside. In certain embodiments, the stream of water is a laminar flow of water on the outside of the pipe. Use of such a laminar flow of water decreases surface imperfections caused by the water when cooling the hot polyolefin surface.
In many embodiments, the exterior surface of the elongate metallic article can be cleaned before application of the reactive polyolefin blend. The cleaning can be to remove surface dirt, sand, or rust, and can include a hot water wash, blasting and/or acid washing the surface. Acid washing can be done with phosphoric acid at a concentration of 4-15%, typically 5%, with a dwell time from 15-30 seconds, followed by rinsing with high pressure (1200 psi minimum) deionized water to ensure no residual acid is left on the surface of the pipe. Preferably, the cleaning is also done in-line, immediately before the application of reactive polyolefin blend, or immediately before the application of the first coating onto the metallic surface, where there is a coating between the metallic surface and the reactive polyolefin blend, as described further, below.
Preferably, the surface of the pipe is also heated immediately prior to the application of the reactive polyolefin coating (and/or immediately before the application of the first coating onto the metallic surface, where there is a coating between the metallic surface and the reactive polyolefin blend, as described further, below). The heating of the pipe allows the hot melted reactive polyolefin blend to better bond to the pipe surface, and prevents localized cooling and setting of the reactive polyolefin blend as it hits the pipe surface. Preferably, the pipe is heated to an external surface temperature of 220-240° C., though a lower pre-heat temperature, for example, 160° C.-220° C., may also be desirable for certain applications, for example, with the use of a low application temperature fusion bonded epoxy (LAT FBE) layer as the first coating.
In certain embodiments, it is desirable to have a multi-layer coating on the metallic pipe, with the crosslinked polyolefin coating being the external coating and surface of a laminate. For instance, it may be desirable to apply an anti-corrosion layer, for instance, an epoxy coating layer, which may be a fusion bonded epoxy or a liquid epoxy, to the exterior surface of the pipe before the application of the reactive polyolefin blend. This may be done, again, in-line, by painting or spraying a liquid epoxy, or spray coating a fusion bonded epoxy, to the hot pipe, using conventional methods, preferably 5-15 seconds before application of the reactive polyolefin blend. For spray coating, the pipe should be hot, for example, 220-240° C. for a traditional fusion bonded epoxy, or 160-220° C. for a LAT FBE coating.
Instead of, or in addition to, the epoxy coating, it may be desirable to apply an adhesive layer as part of the laminate, either between the epoxy coating and the reactive polyolefin blend coating, or between the metal of the pipe and the reactive polyolefin blend coating in embodiments that may or may not include the epoxy coating layer. Here, again, the adhesive layer may be extruded or sprayed onto the exterior surface of the pipe (or onto the epoxy coating, as appropriate), in line, using conventional methods, immediately before application of the reactive polyolefin blend. The use of an adhesive layer is particularly advantageous where there is a spiral weld on the metallic pipe.
It would also be appreciated that the additional elements as shown in
As would be appreciated by a person in the art, the system shown in
As would also be appreciated by a person of skill in the art, the use of individual carts as shown in
In certain embodiments, it is advantageous to add the melted, reactive polyolefin blend 12 coating in multiple coats. For example, to achieve a 1.5 mm coating of polyolefin, it can be advantageous to configure the speed of conveying, rotating of the pipe, rate/speed of reactive polyolefin blend 12 extruded through the die 38, and the thickness of the opening in the die 38 to extrude a 0.3 to 0.5 mm thick layer of reactive polyolefin 12 coating. The pitch and speed of the pipe rotation and forward movement allow variation in amount of overlap; by overlapping several times, a thicker coating can be formed.
Particularly but not exclusively in embodiments where the melted, reactive polyolefin blend 12 is added in multiple coats, it may be advantageous, in certain cases, to add a reinforcing layer, for example, a glass fiber mesh tape, between two layers of melted, reactive polyolefin blend. This can be done by having a tape application machine in line between two extrusion outlets. In alternative embodiments, the reinforcing layer can be applied between two extruded layers, eg: between the overlaps of the extruded sheets, while the polyolefin is still hot and at least partially melted, so that the reinforcing layer becomes imbedded within, or partially imbedded within, at least one layer of the polyolefin. In certain embodiments, the reinforcing layer is applied before the first layer of melted, reactive polyolefin blend 12, for example, between an FBE layer and the first layer of melted, reactive polyolefin blend 12, though in preferred embodiments the reinforcing layer is applied between two layers of melted, reactive polyolefin blend 12.
A reinforcing layer is useful to add structural strength and/or impact resistance, and is especially useful for buried pipe applications, to protect the pipe during backfill and in shifting soil.
In certain embodiments, as discussed above, it is advantageous for the reactive polyolefin layer to be applied using a fine powder spray, rather than extruded onto the pipe. In other embodiments, it is advantageous to have an initial, thin, spray coated layer, followed by an extrudate applied as described above. Such a thin spray coated layer provides several advantages. First, this thin layer appears to act as an adhesive, and can replace the application of adhesive as described above. The thin layer can be sprayed immediately after the FBE layer, while the FBE layer is still gelling, and bonds very well with both the FBE layer and the extruded reactive polyolefin layer that follows it. We have found that a thin layer of spray-coated polyolefin provides excellent bonding with the FBE, and provides a desirable “single layer” of polyolefin, bonding with an extruded polyolefin layer that follows it. The extruded polyolefin layer that follows it may have the same composition, or a slightly different composition (for example, a polyethylene component of different viscosity, as described above, or lower or no reactive species), yet still create an essentially single layer of polyolefin coating.
In certain embodiments, and as described further, for example, in Example 9, below, the extruded polyolefintopcoat can be made “in situ” from locally sourced polyolefin (such as locally sourced PE) combined with a master batch formulation. Surprisingly, through the use of a thin sprayed reactive polyolefin (intermediate) layer, we have found excellent results with an extruded polyolefin layer that is as much as 94% locally-sourced polyolefin. This provides the advantages of a compact, highly “concentrated” master batch formulation, which can be made in a highly controlled environment, and stably shipped as a master batch formulation to local sites, where it can be extruded with up to 94% locally-sourced polyolefin powder or pellets. This allows excellent quality control while decreasing costs.
As discussed above, the reactive polyolefin blends of the present invention can be prepared to a powder suitable for powder spray coating. These reactive polyolefin blend powders can be blended with FBE powder (also suitable for powder spray coating) and the blended reactive polyolefin/FBE powder can be applied to a pipe in a single coating layer.
An apparatus was manufactured configured as follows: The apparatus comprised a conveying assembly having a conveyor frame and wheels. The apparatus also comprised, in-line and in order, a sand blaster, a pre-heater, a powder coating machine, a spray coating machine, an extruder, an infra-red heater for cross-linking the reactive polyolefin, and a cooling station. The extruder was connected to one flat extrusion dies, and the speed of the conveyor, the size of the dies, and the output of the extruder were configured to extrude a 0.5 mm thick coating out of each die. The speed of the conveyor and the speed of rotation of the pipe was also configured so that the extrusion formed a ⅔ overlap, resulting in a three layer thick extrusion throughout the pipe length. The extruder hopper was loaded with pellets of polyolefin composition comprising polyethylene, and a metal pipe was loaded onto the conveyor. The powder coating machine was loaded with fine powder epoxy; the spray coating machine was loaded with reactive polyolefin suitable and compatible for adhering to both a FBE coating and a polyolefin coating. The metal pipe was conveyed both longitudinally and rotationally, through a sand-blaster for priming the pipe for coating, then a pre-heater which preheated the pipe to approximately 180-240° C., as appropriate and dependant on the type of FBE used. The pipe was then conveyed through the powder coater which coated the pipe with a thin coating of fusion bonded epoxy. The pipe was then conveyed through a spray coater which applied a reactive polyolefin coating to the fusion bonded epoxy. It is noted that the fusion bonded epoxy was still not completely set, and still gelling and reactive. The pipe was then conveyed through the flat extrusion die through which a flow of melted, reactive polyolefin was extruded to form a reactive polyolefin coating onto the reactive polyolefin coating. The conveying through the flat extrusion die was configured with a ⅔ overlap, resulting in 3 layers of reactive polyolefin being applied to each portion of the pipe by the single extrusion die. The pipe was then conveyed through an energy source such as an infra-red heater which applied infra-red energy for 5-25 seconds to the reactive polyolefin coating, partially or fully cross-linking it to convert it into a cross-linked polyolefin coating. The pipe was then conveyed through a cooling station in the form of a water dispensing system which dispensed cool water onto the coated pipe, rapidly cooling the cross-linked polyolefin coating 6.
This resulted in a three layer coating on the pipe—an FBE layer, closest to the steel of the pipe, a cross-linked polyolefin layer furthest from the steel of the pipe, and a reactive polyolefin layer binding the two. Though the cross-linked polyolefin layer was applied in three extrusions by the single die, since the layers were applied while the applied layers were still wet, they formed a single, uniform layer, with the thickness of three extrusion layers. In other words, because of the ⅔ overlap, and because the die dispersed enough polyolefin for a 0.5 mm thick layer of coating, the cross-linked polyolefin layer was approximately 1.5 mm thick. Because each of the applications of polyolefin occurred before the layer before it had time to completely cool, this resulted in what appeared to be a single, uniform, polyolefin layer approximately 1.5 mm thick.
An apparatus was manufactured configured as follows: The apparatus comprised a conveying assembly having a conveyor frame and wheels. The apparatus also comprised, in-line and in order, a sand blaster, a pre-heater, a powder coating machine, a spray coating machine, an extruder, an infra-red heater for cross-linking the polyolefin, and a cooling station. The extruders were connected to three flat extrusion dies, each in line and the speed of the conveyor, the size of the dies, and the output of the extruder were configured to extrude a 0.3 to 0.5 mm thick coating out of each die. The extruder hopper was loaded with pellets of polyolefin composition comprising polyethylene, and a metal pipe was loaded onto the conveyor. The powder coating machine was loaded with fine powder epoxy; the spray coating machine was loaded with reactive polyolefin suitable and compatible for adhering to both a FBE coating and a polyolefin coating. The metal pipe was conveyed both longitudinally and rotationally, through a sand-blaster for priming the pipe for coating, then a pre-heater which preheated the pipe to approximately 180-240° C., as appropriate and dependant on the type of FBE used. The pipe was then conveyed through the powder coater which coated the pipe with a thin coating of fusion bonded epoxy. The pipe was then conveyed through a spray coater which applied a reactive polyolefin coating, such as an adhesive coating, to the fusion bonded epoxy. It is noted that the fusion bonded epoxy was still not completely set, and still gelling and reactive. The pipe was then conveyed through the series of flat extrusion dies through which each a flow of melted, reactive polyolefin was extruded to form a coating onto the sprayed reactive polyolefin coating. The pipe was then conveyed through an energy source such as an infra-red heater which applied infra-red energy for 5-25 seconds to the reactive polyolefin coating, cross-linking it to convert it into a cross-linked polyolefin coating. The pipe was then conveyed through a cooling station in the form of a water dispensing system which dispensed cool water onto the coated pipe, rapidly cooling the cross-linked polyolefin coating 6.
This resulted in a three layer coating on the pipe—an FBE layer, closest to the steel of the pipe, a cross-linked polyolefin layer furthest from the steel of the pipe, and a reactive polyolefin layer binding the two. Because, the three extrusion dies were very close together, and each dispersed enough polyolefin for a 0.3-0.5 mm thick layer of coating, the cross-linked polyolefin layer was approximately 1.5 mm thick. Because each of the applications of polyolefin occurred before the layer before it had time to completely cool, this resulted in what appeared to be a single, uniform, cross-linked polyolefin layer approximately 1.5 mm thick. It can be appreciated that the use of three extrusion dies, very close together, each loaded with a different composition of reactive polyolefin, will result in a single reactive polyolefin layer with multiple layers within it, each of a different composition. It would be further appreciated that, since each extrusion die extruded reactive polyolefin, the single reactive polyolefin layer would have multiple layers within it, each forming a gradient at the interface. The degree and thickness of the gradient would depend on the setting time of the reactive polyolefin being applied, the speed of conveying and extrusion, and the heat of the reactive polyolefin being applied, among other factors.
An apparatus was manufactured configured largely as in example 1, but with the following difference: instead of multiple dies, each fed from the same single extruder, each extruding 0.5 mm of reactive polyolefin composition, the apparatus was configured with two dies, each fed from a different extruder, each configured to extrude 0.5 mm of reactive polyolefin composition. The apparatus was configured such that, between these two dies was placed a tape application apparatus, as commercially available and known in the art. The tape application apparatus was loaded with a glass fiber mesh tape.
A pipe was run through the apparatus, largely as in Example 2, but having two extrusions dies instead of three, with an additional glass fiber mesh tape application there between. Essentially, the pipe passed through the first extrusion die, which applied a coating of reactive polyolefin. While the reactive polyolefin was still hot, the pipe was conveyed to the tape application apparatus, which wound the glass fiber mesh tape around the circumference of the pipe. The tape application apparatus was configured so that the tape, when applied, was slightly imbedded into the still soft reactive polyolefin coating. The pipe was then passed through the second extrusion die, which applied a coating of reactive polyolefin overtop of the tape. The tape can be a “dry” tape, having only strands of fiber; in the case of such a “dry” tape, the gap between strands is sufficiently large that the hot reactive polyolefin extruded from the first and second dies comingle and bond, through the tape. The tape may also be a “wet” tape, where the strands of fiber are pre-imbedded in a polyolefin; in this case, the polyolefin in the tape melts on application to the first reactive polyolefin layer, and bonds to both the reactive polyolefin layers extruded from the first and second dies. In both cases, the result is a single reactive polyolefin layer with an imbedded reinforcing fiber layer. As would be appreciated, it is desirable that the composition of the reactive polyolefin coming out of the first and second dies be compatible with one another, and compatible with the polyolefin in the wet tape when one is used; in preferable embodiments, the same polyolefin composition is utilized.
The remaining stations of the apparatus, and the remaining steps of the method, were identical to those of Example 2.
It would be appreciated that the same coated pipe with integrated reinforcing layer could be prepared using the apparatus of Example 1, by applying the tape between two layers of polyolefin extruded from the same extrusion die.
The result in either case was a three layer coating on the pipe—an FBE layer, closest to the steel of the pipe, a cross-linked polyolefin layer furthest from the steel of the pipe, and a reactive polyolefin layer binding the two. The cross-linked polyolefin layer contained, imbedded within it, a reinforcing layer comprising a fiberglass mesh. The cross-linked polyolefin layer was approximately 1.2 mm thick (due to the two 0.5 mm polyolefin coatings and approximately 0.2 mm attributed to the tape).
An apparatus was manufactured configured as follows: The apparatus comprised a conveying assembly having a conveyor frame and wheels. The apparatus also comprised, in-line and in order, a sand blaster, a pre-heater, a first powder coating machine, a spray coating machine, a second powder coating machine, an extruder, an infra-red heater for partially or fully cross-linking the polyolefin, and a cooling station. The extruder was connected to a single flat extrusion die, and the speed of the conveyor, the size of the dies, and the output of the extruder were configured to extrude a 0.5 mm thick coating out of the die. The extruder hopper was loaded with pellets of polyolefin composition comprising polyethylene, and a metal pipe was loaded onto the conveyor. The first powder coating machine was loaded with fine powder epoxy; the spray coating machine was loaded with reactive polyolefin, for example, adhesive, suitable and compatible for adhering to both a FBE coating and a polyolefin coating. The second powder coating machine was loaded with fine powder reactive polyolefin composition. The metal pipe was conveyed both longitudinally and rotationally, through a sand-blaster for priming the pipe for coating, then a pre-heater which preheated the pipe to approximately 180-240° C. depending of the type of FBE. The pipe was then conveyed through the first powder coater which coated the pipe with a thin coating of fusion bonded epoxy. The pipe was then conveyed through a spray coater which applied a reactive polyolefin coating to the fusion bonded epoxy. It is noted that the fusion bonded epoxy was still not completely set, and still gelling and reactive. The pipe was then conveyed through the second powder coater, which coated the pipe with a first thin layer of reactive polyolefin. The pipe was then conveyed through the flat extrusion die, through which a flow of melted, reactive polyolefin was extruded to form a reactive polyolefin coating onto the first thin layer of reactive polyolefin. The pipe was then conveyed through an energy source such as an infra-red heater which applied infra-red energy for 5-25 seconds to the reactive polyolefin coating, partially or fully cross-linking it to convert it into a cross-linked polyolefin coating. The pipe was then conveyed through a cooling station in the form of a water dispensing system which dispensed cool water onto the coated pipe, rapidly cooling the cross-linked polyolefin coating 6.
Optionally, immediately after the application of the reactive polyolefin coating, the coating is cooled.
This resulted in a three layer coating on the pipe—an FBE layer, closest to the steel of the pipe, a cross-linked polyolefin layer furthest from the steel of the pipe, and a reactive polyolefin layer binding the two. Because the second powder coater and the extrusion die were very close together, and each dispersed enough polyolefin for a 0.5 mm thick layer of coating, the cross-linked polyolefin layer was approximately 1.0 mm thick. Because each of the applications of polyolefin occurred before the layer before it had time to completely cool, this resulted in what appeared to be a single, uniform, polyolefin layer approximately 1.0 mm thick.
An apparatus was manufactured configured as follows: The apparatus comprised a conveying assembly having a conveyor frame and wheels. The apparatus also comprised, in-line and in order, a sand blaster, a pre-heater, a first powder coating machine, a second powder coating machine, an energy source such as an infra-red heater for cross-linking the reactive polyolefin, and a cooling station. The first powder coating machine was loaded with fine powder epoxy; the second powder coating machine was loaded with fine powder of reactive polyolefin composition. The metal pipe was conveyed both longitudinally and rotationally, through the sand-blaster for priming the pipe for coating, then the pre-heater which preheated the pipe to approximately 180-240° C. The pipe was then conveyed through the first powder coater which coated the pipe with a thin coating of fusion bonded epoxy. The pipe was then conveyed through the second powder coater, which coated the pipe with a first thin layer of reactive polyolefin. The pipe was then conveyed through an energy source such as an infra-red heater which applied infra-red energy for 5-25 seconds to the polyolefin coating, partially or fully cross-linking it to convert it into a cross-linked polyolefin coating. The pipe was then conveyed through a cooling station in the form of a water dispensing system which dispensed cool water onto the coated pipe, rapidly cooling the cross-linked polyolefin coating.
Optionally, the apparatus may also contain a cooling apparatus upstream of the IR heater, and a second heater upstream of that cooling apparatus. In certain embodiments, immediately after the application of the reactive polyolefin coating, the coating is cooled and/or heated to 190-240° C. to accelerate the curing process. This may occur before the cross-linking of the polyolefin coating with the IR energy.
This resulted in a two layer coating on the pipe—an FBE layer, closest to the steel of the pipe, and a cross-linked polyolefin layer furthest from the steel of the pipe. It was found that, surprisingly, and possibly because the second powder coating machine applied the reactive polyolefin coating to the FBE layer while the FBE layer was still gelling and not yet set, the FBE and a reactive polyolefin bonded together very well, without the need for an adhesive layer.
An apparatus was manufactured configured as follows: The apparatus comprised a conveying assembly having a conveyor frame and wheels. The apparatus also comprised in-line and in order, a sand blaster, a pre-heater, a powder coating machine, an infra-red source for cross-linking the polyolefin, and a cooling station. The first powder coating machine was loaded with a blend of fine powder epoxy and a reactive polyolefin composition, at a weight ratio of 30:70 (epoxy: polyolefin). The blend was a generally homogeneous blend. The metal pipe was conveyed both longitudinally and rotationally, through the sand-blaster for priming the pipe for coating, then the pre-heater which preheated the pipe to approximately 180-240° C. The pipe was then conveyed through the powder coating machine which coated the pipe with a thin coating of the fusion bonded epoxy/reactive polyolefin. The pipe may or may not be conveyed through an energy source such as an infra-red heater which applied infra-red energy for 5-25 seconds to the fusion bonded epoxy/reactive polyolefin coating, cross-linking the polyolefin component to convert it into a epoxy/cross-linked polyolefin coating. The pipe was then conveyed through a cooling station in the form of a water dispensing system which dispensed cool water onto the coated pipe, rapidly cooling the cross-linked polyolefin coating.
Optionally, the apparatus may also contain a cooling apparatus upstream of the IR heater, and a second heater upstream of that cooling apparatus. In certain embodiments, immediately after the application of the reactive polyolefin coating, the coating is cooled and/or heated to 190-240° C. to accelerate the curing process. This may occur before the cross-linking of the polyolefin coating with the IR energy.
This resulted in a single layer coating on the pipe, conveying excellent corrosion—resistance and impact resistance properties, and excellent adherence to the pipe. It was surprisingly found that the single layer had a FBE/polyolefin gradient, with a higher concentration of FBE closer to the steel of the pipe, and a higher concentration of polyolefin at the exterior of the coating.
An apparatus was manufactured configured as follows: The apparatus comprised a conveying assembly having a conveyor frame and wheels. The apparatus also comprised in-line and in order, a sand blaster, a pre-heater, a powder coating machine, an infra-red source for cross-linking the polyolefin, and a cooling station. The first powder coating machine was loaded with a blend of fine powder epoxy and a reactive polyolefin composition, at a weight ratio of 30:70 (epoxy: reactive polyolefin). The blend was a generally homogeneous blend. The metal pipe was conveyed both longitudinally and rotationally, through the sand-blaster for priming the pipe for coating, then the pre-heater which preheated the pipe to approximately 180-240° C. The pipe was then conveyed through the powder coating machine which coated the pipe with a thin coating of the fusion bonded epoxy/reactive polyolefin. The pipe was then conveyed through an energy source such as an infra-red heater which applied infra-red energy for 5-25 seconds to the fusion bonded epoxy/reactive polyolefin coating, partially or fully cross-linking the polyolefin component to convert it into a epoxy/cross-linked polyolefin coating. The pipe was then conveyed through a cooling station in the form of a water dispensing system which dispensed cool water onto the coated pipe, rapidly cooling the cross-linked polyolefin coating.
Optionally, the apparatus may also contain a cooling apparatus upstream of the IR heater, and a second heater upstream of that cooling apparatus. In certain embodiments, immediately after the application of the reactive polyolefin coating, the coating is cooled and/or heated to 190-240° C. to accelerate the curing process. This may occur before the cross-linking of the polyolefin coating with the IR energy.
This resulted in a single layer coating on the pipe, conveying excellent corrosion—resistance and impact resistance properties, and excellent adherence to the pipe. It was surprisingly found that the single layer had a FBE/polyolefin gradient, with a higher concentration of FBE closer to the steel of the pipe, and a higher concentration of polyolefin at the exterior of the coating.
An apparatus was manufactured configured as follows: The apparatus comprised a conveying assembly having a conveyor frame and wheels. The apparatus also comprised in-line and in order, a sand blaster, a pre-heater, a powder coating machine, an extruder, an infra-red source for cross-linking the polyolefin, and a cooling station. The first powder coating machine was loaded with a blend of fine powder epoxy and a reactive polyolefin composition, at a weight ratio of 30:70 (epoxy:reactive polyolefin). The blend was a generally homogeneous blend. The extruder was connected to a single flat extrusion die, and the speed of the conveyor, the size of the dies, and the output of the extruder were configured to extrude a 0.5 mm thick coating out of the die. The extruder hopper was loaded with pellets of reactive polyolefin composition comprising reactive polyethylene, and a metal pipe was loaded onto the conveyor. The metal pipe was conveyed both longitudinally and rotationally, through the sand-blaster for priming the pipe for coating, then the pre-heater which preheated the pipe to approximately 180-240° C. The pipe was then conveyed through the powder coating machine which coated the pipe with a thin coating of the fusion bonded epoxy/reactive polyolefin. The pipe was then conveyed through the extruder portion through which a flow of melted, reactive polyolefin was extruded from a flat extrusion die to form a reactive polyolefin coating onto the fusion bonded epoxy/reactive polyolefin coating. The pipe was then conveyed through an energy source such as an infra-red heater which applied infra-red energy for 5-25 seconds to the fusion bonded epoxy/reactive polyolefin coating, partially or fully cross-linking the polyolefin component to convert it into a epoxy/cross-linked polyolefin coating. The pipe was then conveyed through a cooling station in the form of a water dispensing system which dispensed cool water onto the coated pipe, rapidly cooling the cross-linked polyolefin coating.
Optionally, the apparatus may also contain a cooling apparatus upstream of the IR heater, and a second heater upstream of that cooling apparatus. In certain embodiments, immediately after the application of the reactive polyolefin coating, the coating is cooled and/or heated to 190-240° C. to accelerate the curing process. This may occur before the cross-linking of the polyolefin coating with the IR energy.
This resulted in a single layer coating on the pipe, conveying excellent corrosion—resistance and impact resistance properties, and excellent adherence to the pipe. It was surprisingly found that the single layer had a FBE/reactive polyolefin gradient, with a higher concentration of FBE closer to the steel of the pipe, and essentially no FBE at the outer surface.
An apparatus was manufactured configured as follows: The apparatus comprised a conveying assembly having a conveyor frame and wheels. The apparatus also comprised in-line and in order, a sand blaster, a pre-heater, a first powder coating machine, a second powder coating machine, an extruder, (optionally) an infra-red source for cross-linking the polyolefin, and a cooling station. The first powder coating machine was loaded with FBE, and the speed of the conveyor, and the spray coating machine output was configured to provide an FBE coating of 150 to 250 microns. The second powder coating machine was loaded with reactive polyolefin blend, as shown in Table 1, below. The reactive polyolefin blend was made by compounding its components, for example, in a single or twin screw compounding machine, then grinded to a powder of a particle size suitable for powder coating. The second powder coating machine output was configured to provide a reactive polyolefin blend coating of 3-6 Mils.
The extruder was connected to a single flat extrusion die, and the speed of the conveyor, the size of the dies, and the output of the extruder were configured to extrude a 1.0-3.5 mm thick coating out of the die. The extruder hopper was loaded with pellets of an extrudable reactive polyolefin composition. The extrudable reactive polyolefin composition was made by combining a reactive polyolefin master batch with locally—sourced polyethylene and black master batch, in the wt. ratios shown in table 2, below. The locally—sourced polyethylene may have a melt index ranging from 0.2 to 2.2, and may be pipe grade, or optionally, rotational molding grade or even film grade. One of the advantages of this method is that the locally—sourced polyethylene can be what is expediently or otherwise advantageously available; for example, a blend of injection molding grade HDPE and film extrusion grade LLDPE may be used.
The reactive polyolefin master batch was formulated as shown in Table 3, below.
A metal pipe was loaded onto the conveyor. The metal pipe was conveyed both longitudinally and rotationally, through the sand-blaster for priming the pipe for coating, then the pre-heater which preheated the pipe to approximately 180-240° C. The pipe was then conveyed through the first powder coating machine which coated the pipe with a thin coating of the fusion bonded epoxy/reactive polyolefin. The pipe was then conveyed through the second powder coating machine which coated the pipe with a coating of the reactive polyolefin layer. Finally the pipe was conveyed through the extruder portion through which a flow of the melted, extrudable reactive polyolefin was extruded from a flat extrusion die to form a reactive polyolefin coating onto the fusion bonded epoxy/reactive polyolefin coating. The pipe was then optionally conveyed through an energy source such as an infra-red heater which applied infra-red energy for 5-25 seconds to the coating, partially or fully cross-linking the polyolefin component to convert it into a epoxy/cross-linked polyolefin coating. The pipe was then also conveyed through a cooling station in the form of a water dispensing system which dispensed cool water onto the coated pipe, rapidly cooling the cross-linked polyolefin coating.
Optionally, the apparatus may also contain a cooling apparatus upstream of the IR heater, and a second heater upstream of that cooling apparatus. In certain embodiments, immediately after the application of the reactive polyolefin coating, the coating is cooled and/or heated to 190-240° C. to accelerate the curing process. This may occur before the cross-linking of the polyolefin coating with the IR energy.
This resulted in a three layer coating on the pipe (FBE followed by two reactive polyolefin layers of different compositions). The coating provided excellent corrosion—resistance and impact resistance properties, and excellent adherence to the pipe.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CA2017/050575 | 5/12/2017 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62337562 | May 2016 | US |
