WO1993014546A1

WO1993014546A1 - Prelubricated duct

Info

Publication number: WO1993014546A1
Application number: PCT/US1993/000402
Authority: WO
Inventors: Robert B. Washburn; Frank V. Apicella
Original assignee: Arnco Corporation
Priority date: 1992-01-17
Filing date: 1993-01-15
Publication date: 1993-07-22
Also published as: AU3476693A; MX9300242A

Abstract

The present invention disclosed a prelubricated duct (24) or prelubricated object to be inserted in or through a duct (24) which is accomplished by providing a duct (24) or other item to be inserted in or through the duct with a low-friction powder coated surface (22, 23). Compounded blends including lubricants are reduced to powders through conventional grinding techniques and delivered as a powder to the surface of the item to be treated during the extrusion process. Upon contact with the hot surfaces of the item the powder coating reacts and fuses to the item resulting in a uniform and permanent lubricating film (22, 23). Alternatively, a liquid coating may be applied to the surface to be coated.

Description

PRELUBRICATED DUCT

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION The present invention generally relates to lubricants for use in cable conveying ducts and, more particularly, to prelubrication of a duct to facilitate the insertion of cable therethrough.

DESCRIPTION OF RELATED ART One of the problems encountered during the installation of wire and cable into ducts is the friction between the outside of the cable and the inside of the duct. If the runs of cable are extremely long, it becomes very difficult or impossible to pull the cables through the duct. However, it is desirable from a cost standpoint to maximize the length of the runs of cable to be placed within the duct. The conventional solution to this situation has been to apply a lubricant, typically a water-soluble polymeric lubricant, directly to the outside of the cables during installation which allows for longer cable runs and, hence, lower costs. The coating of lubricant must normally be manually applied, which is a messy and time consuming process and substantially reduces the speed with which the cable may be installed within the duct. Further, even if the lubricant is applied to a substantial portion of the cable exterior, repeated relative sliding movement due to removing or replacing cables within the duct will reduce the amount of lubricant disposed therein. Also, due to the time required to place long lengths of cable, liquid lubricants tend to dry, thereby losing their effectiveness before the placing operation is complete. A more convenient technology has emerged whereby the duct is lubricated prior to the installation of cables. A prelubricated duct provides great advantages to the telecommunication and electrical industries by facilitating the pulling of wire and cable through conduits. Prelubrication of extruded plastic pipe, or duct, has been accomplished in the past through three principle methods: coextrusion, liquid spraying, and the fill-and-roll method. However, each of these methods, which will be discussed in turn, suffer from their own characteristic process and/or performance drawbacks. In the coextrusion method, as illustrated in U.S. Patent No. 4,892,442, a lubricative layer of material is simultaneously extruded with the hard plastic main wall of the duct. However, the coextrusion method requires expensive dies and tooling, as well as additional extruders and control equipment. The lubrication in this case is generally provided by a silicone polymer, such as polydimethylsiloxane, which is either precompounded into the thermoplastic or injected into the plastic melt just prior to the coextrusion die, trapping the lubricant in the body of the lubricative film which is coextruded along side of the principal wall of the duct. However, for the lubricant to be effective at friction reduction, it must first migrate out to the surface of the film. During the installation or removal of cable this can be a problem because the incoming cable can wipe away the minor amount of lubricant which is present on the surface of the lubricated film. To make available additional lubricant for continued friction reduction the cable has to cut into the coextruded layer, resulting in damage to the cable jacket, a rising coefficient of friction and the possibility of cable/duct fusion. To increase the availability of lubricant, additional levels of silicone could be added, but at the risk of creating bonding problems between the lubricative film and the principal wall of the duct and a reduction in mechanical properties of the coextruded lubricated layer. The liquid spraying method, as illustrated by U.S. Patent No. 2,597,706, involves the spraying of liquid lubricant on the interior surface of the duct as it is extruded. Like coextrusion, liquid spraying of a lubricative material allows for the even treatment of the entire length of the duct as it is extruded. Unlike coextrusion, the complete complement of lubricant is present on the surface of the duct, where it can be most effective. Spraying systems for in-process spray application are a low cost alternate to coextrusion systems. However, there are limits on the viscosity of the liquid that can be properly atomized to allow for useful spray properties. Furthermore, because duct lengths are continuous, solvent systems cannot be employed to adjust viscosity. The presence of higher relative amounts of lubricant has demonstrated significantly improved performance in friction reduction over the coextruded product. However, this method of lubrication is not as permanent as the coextruded product, since the lubricant is a low molecular weight polydimethylsiloxane which may drain or migrate out of the duct over time. Therefore, the lubricative effect of the liquid-sprayed material is limited by physical process constraints. The least effective method of prelubrication is the fill-and-roll approach wherein a reel or coil of duct is charged with a quantity of lubricant, capped and then rolled to drive the liquid back into the duct. The lubricant does not always have the opportunity to evenly coat the entire length of duct and, in fact, must rely on the incoming cable to complete the dispersement. Aside from the poor distribution of lubrication, the liquid often drains out of the duct during storage and handling, making the product messy and undesirable to work with, and has all of the problems associated with liquid lubricants mentioned above. This must also be done as a secondary operation and is therefore not an efficient manufacturing method. Therefore, there exists a need in the art for a prelubricated duct, and a method of producing a prelubricated duct, which effectively and economically reduces the friction created by the placement or removal of cables within a duct.

SUMMARY OF THE INVENTION A goal of the present invention is to provide a duct with a lubricating film on the interior walls to facilitate placement of cables or other objects through it. Duct types include all shapes, such as round, ellipsoid, triangular, square, etc.; additionally, the profile of the duct can be corrugated, longitudinally ribbed, spirally ribbed, oscillatingly spiral- ribbed, smooth-wall, etc. It is an additional goal of the present invention to provide a method of producing a lubricating film on the interior walls of a continuous length of duct by means of a powder or liquid coating operation during the extrusion process. A further goal of the present invention is to produce a permanently lubricating film on the interior or exterior surfaces of a duct, or on the exterior surface of a cable and/or pull line that will not wash off, trap dust or dirt, drain or flow from the surface on which it is applied. Thus, items to be coated in this invention include inner and outer surfaces of ducts, cables and wires to be inserted therethrough, and lines, wires, tapes, etc., used for pulling wires and cables through ducts. The foregoing goals may be accomplished by providing a duct or other item to be inserted in or through the duct with a low-friction powder coated surface. Compounded blends including lubricants are reduced to powders through conventional grinding techniques and delivered as a powder to the surface of the item to be treated during the extrusion process. Upon contact with the hot surfaces of the item the powder coating reacts and fuses to the item resulting in a uniform and permanent lubricating film.

BRIEF DESCRIPTION OF THE DRAWINGS These and further objectives will be clear with reference to the following descriptions and drawings, wherein: FIG. 1 diagrammatically shows the components of the present invention; FIG. 2 is a cross sectional view of a smoothwall duct having inner and outer lubricative layers formed in accordance with the present invention, and including a cable with an outer lubricative layer placed within the duct; FIG. 3 is a cross sectional view of a ribbed duct having an inner lubricative layer formed in accordance with the present invention; FIG. 4 is a schematic drawing of the testing equipment configuration used to test the present invention; FIG. 5 is a perspective view of a spirally ribbed duct; and FIG. 6 is a perspective view of a corrugated-wall duct.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention is directed towards the formulation of a lubricative coating on the interior surface of an extruded plastic pipe or duct. The lubricating coating is applied in a powder or liquid form. If a powder is applied, the temperature of the duct immediately following extrusion melts the solid and, when cooled, the solid fuses with the duct. Alternatively, if a thermosetting powder or liquid is employed, the temperature of the duct immediately following extrusion causes cross-linking, both within the solid and between the solid and the surface of the duct or other item, thus fusing the coating with the duct or item. With specific reference to FIG. 1, the powder coating to be applied to the extruded duct is produced by known techniques and delivered to the duct via a fluidized bed 10, a metering pump 14, an air mixing valve 18 and a spray wand 20. The powder can be produced by any one of several known conventional methods of grinding, to arrive at a powder having the desired particulate size and density. Preferably, the powder size is between 2 and 400 microns, including blends thereof. The powder comprises lubricating materials such as: silicones, fluoropolymers, graphite, ultra high molecular weight polyethylene, fatty acids and fatty acid derivatives, etc. , which are compounded with at least one additive resin chosen from the group comprising polyolefins, polyolefin waxes, polyamides, acrylics, polyesters, thermoplastic polyurethanes, polyvinyl- chloride, acrylonitrile-butadiene-styrene, silicon copolymers, fluoroppolymers and other organic high molecular weight polymers capable of being thermally melt processed, and the additive may further comprise at least one thermosetting resin selected from the group including epoxies, acrylics, polyurethanes, polyesters, vinyl esters, polyamides, silicones, and other organic polymers capable of being thermally melted and cross-linked. Powder having an appropriate composition and particulate size is input to a fluidized bed 10 from a feed hopper 8. Pressurized air from a compressed air source 12 is input to the fluidized bed 10, dispersing the powder in dry air. The fluidized bed 8 is provided with a filter vent 7, which vents excess air to atmosphere. The metering pump 14, which operates on the same principles as a venturi, draws powder and air from the fluidized bed 8 and mixes it with additional air, conveying the mixture to the spray wand 20. The size of the particles should be uniform within the powder-air mixture to ensure that appropriately-sized powder particles are being used. The air mixing valve 18 introduces additional air into the particle stream to help convey the particle mixture to the spray wand 20. The spray wand 20 is placed in the die to deliver the powder directly on the interior surface of the just- extruded duct. Also, a series of spray wands could be used to deliver powder to the exterior surface of the just-extruded duct in conjunction with the internal application. In either case, the duct can be made of any conventional material, such as ABS, polyolefin, PVC, or nylon. Also, the pipe or duct can have any shape, such as square, round, triangular or other, and can have a surface profile such as s oothwall, ribbed, corrugated, multicell, or spiral ribbed. During this process, it is important to keep the spray wand 20 cool to prevent premature melting of the powder, which would result in the occlusion of the wand. Also, the spray wand is designed so that other materials, such as pull tapes, ropes, cables and wires, can be inserted into the extruded duct. The surface temperature of the duct causes the powder, which is applied on the surface thereof, to melt and form a liquid lubricative coating or film. Specifically, in the case of polyethylene for example, the surface temperature of the duct immediately following extrusion remains hot for several feet following the extrusion die, depending on the exact nature of the plastic. The lubricants to be powderized and sprayed onto the surface of the duct are chosen from the group having a melting temperature not greater than the extrusion temperature of the polymer of the duct, and preferably is in the range of 240° to 260°F. As the duct and lubricating layer quickly cool, and drop below the melting temperature of the lubricant, the lubricative layer fuses to the duct and the combination solidifies into a rigid outer duct layer and a solid inner bonded coating of lubrication. The prelubricated duct produced according to the present invention results in a duct having a lubricative layer which is bonded to the inner wall of the duct. Preferably, the thickness of the lubricative layer is between .001 and .050 inches, and can be of either smooth or rough texture, and may cover the inner surface of the duct either continuously or intermittently. As shown in FIGS. 2, 3, 5, and 6 the lubricative layer 22 is formed on the interior surface of the main wall portion of the duct 24, regardless of the configuration or shape of that surface. Hence, the present method is suitable for application on various ducts and is not limited to application on the specific duct shapes shown herein. FIG. 2 also shows an outer lubricative layer 23 formed in accordance with the present invention. FIG. 2 additionally shows a cable 25 coated with an outer lubricrative layer 26 in accordance with another embodiment of the present invention. Testing has shown that ducts having a lubricative layer formed in accordance with the present invention are superior in performance to the methods of prelubrication previously known in the art. The following examples are provided to illustrate the invention.

EXAMPLE 1 One hundred parts of a basic straight chain polyolefin resin was mixed with 52.2 parts of a solution containing 83.3 percent 1,1,1-Trichloroethane and 16.7 percent polydimethylsiloxane polymer having an average kinematic viscosity of 60,000 cSt. The polyolefin resin was produced by the Fischer-Tropsch process and was micronized to a particle size distribution such that the average particle size was 2.5 microns with a maximum particle size of 10 microns. The polyolefin resin has a melting point of 241°F and a density of .95 g/cc. The mixing was carried out using a spatula for approximately one minute at which time the polyolefin powder was thoroughly wetted with the solution. This mixture was then spread onto a mylar film and allowed to dry. After thoroughly drying, the mixture was easily broken up into a fine powder. The powder was applied as described hereinabove.

EXAMPLE 2 One hundred parts of a polyethylene wax (melting point of 243°F and density of 0.94 g/cc) was heated to its melting point and thoroughly mixed with eight parts by weight polydimethylsiloxane polymer having an average kinematic viscosity of 60,000 cSt. Upon cooling this mixture solidified. It was then ground and micronized with an air jet mill and screened. The resulting material was 100 percent finer than 192 microns with a median particle size of 47.5 microns. This composition was sprayed into the extruded duct using the same method as above. Results obtained were equivalent to that in Example 1.

PERFORMANCE TESTING The coefficient of friction and pulling tensions of 0.5" Seicor fiber optic cable (MDPE jacket) in various lubricated and unlubricated ducts (HDPE ducts) was measured using the test method described by Bellcore TA- TSY-000356, Issue 2, February 1990. PROCEDURE As shown in FIG. 4, the test bench consists of a 40" diameter metal drum 37 rigidly fixed to a column beam, a hydraulic winch 32 with tension monitoring and strip chart recording, a "frictionless" pulley block 42 attached to a beam suspended 20 feet off the floor, and a variable load set 46 ranging in 25 pound increments from 25 to 250 pounds. A length of duct 36 to be evaluated was wrapped one and a quarter turns about the drum 37 and attached at both ends. A 36 foot sample of fiber optical cable 38 with a medium density polyethylene sheath was threaded through the duct 36 about the fixed drum 37 and attached at both ends to Kevlar pull tapes 44. The end leading into the duct was threaded around the pulley block 42 and attached to the static weight 46. .The end leading out of the duct 36 was fixed to the capstan winch 32. During the course of testing, static weight sets 46 were lifted approximately 15 feet off the floor. Pull speed was controlled by means of a flow valve 34 with pre-setable stops. The load coming out of the loop was measured and recorded by the tension monitor 35. Pull tensions were obtained from the strip chart recording. Friction coefficients were calculated from the capstan 30 relation: 1 T₀ f = In

where: f = Coefficient of friction n = 1.25 wraps of arc about the drum π = 3.1416 T₀ = Cable tension out of drum (pull tension) T., = Cable tension into drum (incoming load)

Initially an output load is observed (T₀") . This represents the influence of the static coefficient of friction. To obtain the average pull tension, a line was drawn through the midpoint of the interval, perpendicular with the baseline and intersecting the best fit line. The distance between this intersection and the baseline was taken as the average kinetic pull tension (T₀) for the interval.

RESULTS The following comparative evaluations were made with 1-1/4" HDPE duct at pull speeds of 65 feet per minute:

EXAMPLE #1 is a prelubricated duct produced by powder coating method where the powder coating was prepared in Example #1. COMPARATIVE EXAMPLE A is a prelubricated duct produced by the coextrusion method where the inner coextruded layer is composed of HDPE plastic and polydimethylsiloxane. COMPARATIVE EXAMPLE B is a prelubricated duct produced by the liquid spraying method where the lubricant is a polydimethylsiloxane polymer with an average kinematic viscosity of 350 cSt. COMPARATIVE EXAMPLE C is a duct which is precharged with a water/glycol based lubricant. COMPARATIVE EXAMPLE D is a duct which is precharged with a silicone modified aqueous lubricant. COMPARATIVE EXAMPLE E is a s oothwall duct with no lubricant. COMPARATIVE EXAMPLE F is a ribbed duct with no lubricant. The pull tensions and friction comparisons are tabulated as follows:

Avg. Pull Tension (Coefficient of Friction)

PRODUCTS TESTED INCOMING LOADS

25 Lbs. 75 Lbs. 175

Lbs,

50 Lbs. 170 Lbs. 290 (0.088) (0.104) (0.172) 80 Lbs. 205 Lbs. 370 (0.148) (0.128) (0.203) 40 Lbs. 200 Lbs. 360

(0.060) (0.125) (0.200) Comparative 60 Lbs. 240 Lbs. Pull Tension Example C (0.111) (0.148) Exceeded 600 Lbs. Comparative 50 Lbs. 200 Lbs. 460 Lbs. Example D (0.088) (0.125) (0.231) Comparative 127 Lbs, Pull Tension Exceeded 600 Lbs. Example E (0.207) Comparative 180 Lbs. Pull Tension Exceeded 600 Lbs. Example F (0.251)

The effectiveness of the powder coating method for prelubrication of the duct is readily observed when comparing the pulling tensions generated with incoming loads of 175 pounds. The powder coating technique lead to 20 percent or greater reductions in pull tensions compared to other prelubrication methods. The foregoing may also be accomplished by employing the following liquid spraying techniques. Low molecular weight polymers such as, but not limited to, polyolefin waxes can be mixed with lubricative material and these thermally melted to form a low viscosity liquid lubricative admixture. The heating is generally carried out in a pressure vessel which contains both internal heating elements and mixing agitation. The agitation maintains uniform solution properties to the lubricative admixture. A gear pump, or other suitable pump, is used to both meter and pressurize the hot liquid admixture. The liquid is pumped through heated fluid lines to an atomizing nozzle, which in the case of a duct, has been inserted through the back of a crosshead extrusion duct- forming die. Both airless and air atomizing nozzles may be useful to atomize the liquid. Also, a series of spray nozzles could be used to deliver a liquid polymer spray to the exterior surface of the just-extruded duct in conjunction with the internal application, or for coating the outer surface of other items such as wire or cable. Cooling of the duct wall or item results in solidification of the coating film with subsequent bonding of the film to the duct wall. In similar fashion, liquid thermosetting resins, formulated with cure systems, processing additives and a lubricative admixture are heated in a pressure vessel or pumped directly at ambient temperature through a fluid line to an atomizing nozzle. In the case of highly reactive polymers, such as vinyl esters or urethanes, the fluid lines must be insulated from the die temperatures to eliminate premature gelation. The surface temperature of the duct or other item to be coated initiates or significantly accelerates the crosslinking reaction, thus forming an infusible film and bonding that film to the duct wall. Techniques for coating other items, such as cable or wire, may be standard techniques for such coating, involving solidification resulting from cooling or cross-linking. It is clear that the foregoing description is only illustrative of a preferred embodiment of the present invention, the invention not being limited thereto. For example, although the present invention was described as being directed towards a lubricative coating on the surface of a duct, it is clear that the coating according to the invention could be applied to the exterior surface of an item which is to be placed within the duct, such as a cable, without departing from the scope of the invention as defined by the claims appended hereto.

Claims

WHAT IS CLAIMED IS: 1. A method of producing a prelubricated duct, comprising the steps of: extruding a duct; applying a powder to a surface of the duct, said powder being formed from at least one lubricative material; fusing said powder to the surface of the duct to form a lubricative layer thereon.

2. A method of producing a prelubricated duct according to claim 1, further comprising the step of melting said powder to form a liquid lubricating layer on the surface of said duct.

3. A method of producing a prelubricated duct according to claim 2, further comprising the step of cooling said duct and liquid lubricating layer to form a fused coating of lubrication on the surface of said duct.

4. A method of producing a prelubricated duct according to claim 3, wherein said powder has a melting point which is not greater than a first surface temperature of said duct, said first surface temperature of said duct being the surface temperature during duct formation.

5. A method of producing a prelubricated duct according to claim 4, wherein said fused coating has a thickness of between .001 and .050 inches.

6. A method of producing a prelubricated duct according to claim 5, wherein said powder comprises at least one lubricating material selected from the group which consists of silicones, fluoropolymers, graphite, ultra high molecular weight polyethylene, fatty acids and fatty acid derivatives, and which further comprises at least one additive, said additive being selected from the group consisting of thermoplastic resins and thermosetting resins.

• 7. A method of producing a prelubricated duct according to claim 6, wherein said thermoplastic resin is selected from the group consisting of polyolefins, polyolefin waxes, polyamides, acrylics, polyesters, thermoplastic polyurethanes, polyvinylchloride, acrylonitrile-butadiene-styrene, silicone copolymers, and fluoropolymers, and said thermosetting resin is selected from the group consisting of epoxies, acrylics, polyurethanes, polyesters, vinyl esters, polyamides, and silicones.

8. A method of producing a prelubricated duct according to claim 7, wherein said powder has a particulate size of between 2 and 400 microns.

9. A method of producing a prelubricated duct according to claim 8, wherein the first surface temperature of said duct is greater than 260°F.

10. A method of producing a prelubricated duct according to claim 3, wherein said powder is applied to an inner surface of the duct.

11. A method of producing a prelubricated duct according to claim 3, wherein said powder is applied to an outer surface of the duct.

12. A method of producing a prelubricated duct according to claim 3, wherein said powder is applied to an inner and an outer surface of said duct.

13. A prelubricated duct, comprising an extruded main wall portion and a bonded lubricative coating, said bonded lubricative coating being formed on said main wall portion by fusing a powder to said main wall portion.

14. A prelubricated duct according to claim 13, wherein said powder comprises at least one lubricating material selected from the group which consists of silicones, fluoropolymers, graphite, ultra high molecular weight polyethylene, fatty acids artd fatty acid derivatives, and which further comprises at least one additive, said additive being selected from the group consisting of thermoplastic resins and thermosetting resins.

15. A prelubricated duct according to claim 14, wherein said thermoplastic resin is selected from the group consisting of polyolefins, polyolefin waxes, polyamides, acrylics, polyesters, thermoplastic polyurethanes, polyvinylchloride, acrylonitrile- butadiene-styrene, silicone copolymers, and fluoropolymers, and said thermosetting resin is selected from the group consisting of epoxies, acrylics, polyurethanes, polyesters, vinyl esters, polyamides, and silicones.

16. A prelubricated duct according to claim 15, wherein said bonded lubricative coating is formed on an inner surface of the duct.

17. A prelubricated duct according to claim 15, wherein said bonded lubricative coating is formed on an outer surface of the duct.

18. A prelubricated duct according to claim 15, wherein said bonded lubricative coating is formed on both an inner and an outer surface of said duct.

19. A prelubricated duct according to claim 16, wherein a surface of said main wall portion includes a series of longitudinal ribs, said bonded coating being formed on said longitudinal ribs.

20. A prelubricated duct according to claim 16, wherein a surface of said main wall portion includes a series of spiral ribs, said coating being formed on said spiral ribs.

21. A prelubricated duct according to claim 16, wherein a surface of said main wall portion includes a series of corrugated ribs, said coating being formed on said corrugated ribs.

22. A prelubricated duct according to claim 16, wherein a surface of said main wall portion includes a series of oscillating spiral ribs, said coating being formed on said oscillating spiral ribs.

23. A method of producing a prelubricated duct, comprising the steps of: extruding an elongated, hollow duct, said duct having inner and outer surfaces, said inner and outer surfaces having a first surface temperature during formation thereof; applying a powder to at least one of said surfaces, said powder being formed from at least one lubricative material and having a melting point which is lower than said first surface temperature of said duct; melting said powder onto said duct surface, said melted powder forming a lubricating layer on said duct surface; cooling said duct and said liquid lubricative layer to a second surface temperature whereby said liquid layer becomes a solid layer; and fusing said solid layer to the surface of said duct to form a bonded lubricative layer thereon.

24. A prelubricated innerduct, prepared by a process comprising the steps of: extruding a duct; applying a powder to a surface of said duct, said powder comprising at least one lubricative material and having a melting point which is lower than a first temperature of said duct during its formation; fusing said powder to said duct surface to form a lubricative layer thereon.

25. A prelubricated innerduct according to claim 24, further comprising the steps of melting said powder to form a liquid lubricating layer on said duct surface, and cooling said duct and liquid lubricating layer to a second temperature whereby said liquid layer becomes a solid layer.

26. A prelubricated innerduct according to claim 25, wherein said lubricative layer has a thickness of between .001 and .050 inches.

27. A prelubricated innerduct according to claim 26, wherein said powder comprises at least one lubricating material selected from the group which consists of silicones, fluoropolymers, graphite, ultra high molecular weight polyethylene, fatty acids and fatty acid derivatives, and which further comprises at least one additive, said additive being selected from the group consisting of thermoplastic resins and thermosetting resins.

28. A prelubricated duct according to claim 27, wherein said thermoplastic resin is selected from the group consisting of polyolefins, polyolefin waxes, polyamides, acrylics, polyesters, thermoplastic polyurethanes, polyvinylchloride, acrylonitrile- butadiene-styrene, silicone copolymers, and fluoropolymers, and said thermosetting resin is selected from the group consisting of epoxies, acrylics, polyurethanes, polyesters, vinyl esters, polyamides, and silicones.

29. A prelubricated duct according to claim 28, wherein said powder has a particulate size of between 2 and 400 microns.

30. A prelubricated duct according to claim 29, wherein said duct has a first temperature in excess of 260°F.

31. A method of prelubricating an item to be placed within a duct, comprising the steps of: applying a powder to the outer surface of said item, said powder including at least one lubricative material; melting said powder to form a liquid lubricating layer on said outer surface of said item; and, fusing said melted powder to said item.

32. A method of producing a prelubricated duct, comprising the steps of: extruding an elongated, hollow duct, said duct having inner and outer surfaces, said surfaces having a first surface temperature during extrusion of said duct; applying a liquid polymer spray to said inner surface, said spray including at least one lubricating material; forming a lubrication layer on said duct surface; cooling said duct and said layer to a second surface temperature, whereby said layer becomes solidified; and fusing said solid layer to said inner surface to form a bonded lubrication layer thereon.

33. A method of producing a prelubricated duct according to claim 32, wherein said liquid polymer spray comprises at least one lubricating material selected from the group consisting of silicones, fluoropolymers, ultra high molecular weight polyethylene, fatty acids and fatty acid derivatives.

34. A method of producing a prelubricated duct according to claim 33, wherein said liquid polymer spray comprises at least one thermoplastic resin selected from the group which consists of polyolefins, polyolefin waxes, polyamides, acrylics, polyesters, thermoplastic polyurethanes, polyvinylchloride, acrylonitrile- butadiene-styrene, silicone copolymers, and fluoropolymers.

35. A method of producing a prelubricated duct according to claim 33, wherein said liquid polymer spray comprises at least one thermosetting resin selected from the group which consists of epoxies, acrylics, polyurethanes, polyesters, vinyl esters, polyamides, and silicones.

36. A method of producing prelubricated duct according to claim 33 wherein said liquid viscosity is between 1 and 10,000 centipoise.

37. A method of producing a prelubricated duct according to claim 33 wherein said liquid polymer spray forms a cross-linked film.

38. A method of producing a prelubricated duct according to claim 33 wherein said liquid polymer spray is comprised of resins which are liquids at room temperature and are capable of crosslinking to form an infusible film.

39. A method of producing a prelubricated duct according to claim 33 wherein said liquid polymer spray is comprised of resins which may be thermally melted to form a low viscosity liquid.

40. A prelubricated item to be placed in a duct, prepared by a process comprising the steps of: applying a powder to a surface of said item, said powder being formed from at least one lubricative material; fusing said powder to said item surface to form a lubricative layer thereon.

41. A prelubricated item according to claim 40, further comprising the steps of melting said powder to form a liquid lubricating layer on said item surface, and cooling said item and liquid lubricating layer to a second temperature whereby said liquid layer becomes a solid layer.

42. A prelubricated item according to claim 41, wherein said lubricative layer has a thickness of between .001 and .050 inches.

43. A prelubricate item according to claim 42, wherein said powder comprises at least one lubricating material selected from the group which consists of silicones, fluoropolymers, graphite, fatty acids and fatty acid derivatives.

44. A prelubricated item according to claim 43, wherein said powder further comprises at least one resin selected from the group which consists of polyethylene waxes, acrylics, nylon, and epoxides.

45. A prelubricated duct, comprising: an extruded duct, a lubricating layer deposited on a surface thereof, wherein said lubricating layer further comprises: at least one lubricant selected from the group consisting of silicones, fluoropolymers, graphite, ultra- high molecular weight polyethylene, fatty acids and fatty acid derivatives, at least one resin selected from the group consisting of thermoplastic resins and thermosetting resins.

46. A prelubricated duct, as claimed in claim 45, further comprising said lubricating layer being deposited on said surface at a thickness in the range from 0.001 to 0.050 inches.

47. A prelubricated duct, as claimed in claim 46, wherein said at least one resin is a powder having a particulate size between 2 and 400 microns.

48. A prelubricated duct, as claimed in claim 47, wherein said at least one thermoplastic resin is selected from the group consisting of polyolefins, polyolefin waxes, polyamides, acrylics, polyesters, thermoplastic polyurethanes, polyvinylchloride, acrylonitrile- butadiene-styrene, silicone copolymers, and fluoropolymers.

49. A prelubricated duct, as claimed in claim 47, wherein said at least one thermosetting resin is selected from the group consisting of epoxies, acrylics, polyurethanes, polyesters, vinyl esters, polyamides, and silicones.