WO1997035680A1

WO1997035680A1 - A method of bonding polyurethane to a rubber based support and corrosion or wear resistant products (especially pipes) produced thereby

Info

Publication number: WO1997035680A1
Application number: PCT/AU1996/000604
Authority: WO
Inventors: Michael Jaskiewicz; Alan James May
Original assignee: Rico Engineering Pty. Ltd.
Priority date: 1996-03-22
Filing date: 1996-09-25
Publication date: 1997-10-02
Also published as: ZA968071B

Abstract

The invention provides for: a method of bonding polyurethane to a rubber based support characterised in that a castable urethane elastomer or polyurethane material is cured to provide a first surface, adjoining to said first surface a support layer wherein at least the material in contact with said first surface is an uncured rubber compound or an adhesive, and subjecting the contiguous materials to a curing process to cure the rubber compound or adhesive to establish adherence of the support layer to the polyurethane surface. The invention also provides for corrosion or wear resistant products produced thereby, especially pipes, etc.

Description

A METHOD OF BONDING POLYURETHANE TO A RUBBER BASED SUPPORT AND CORROSION OR WEAR RESISTANT PRODUCTS (ESPECIALLY PIPES) PRODUCED THEREBY.

1 FIELD OF THE INVENTION

THIS INVENTION relates to methods by which articles

5 exposed to corrosive and abrasive materials can be given improved corrosion and wear resistant characteristics. The invention also relates to products working with corrosive and abrasive materials such as slurry conduits and bends which are produced by application of the method.

BACKGROUND OF THE INVENTION io The mining, mineral processing and other industries of a similar character work with flows of corrosive and abrasive material, such as liquid slurries. The apparatus which directs, controls and otherwise interacts with such flows is subject to erosion and wear. Wear results in a need for repair or replacement which calls for expense in down time and

15 in spare parts and labour to effect a changeover. The more quickly the parts erode or wear, the greater is the portion of down time and lost production. It is desirable to extend the working life of all elements subject to such erosion and wear and the use of wear resisting coatings is known to be desirable.

20 Polyurethane is a material which is known to exhibit good erosion and wear resistance. It is normally a relatively rigid, relatively hard, plastic-like material. It is a material which is known and has been used in the mining industry to manufacture items such as the sleeves of pinch valves, used in slurry lines to regulate or isolate the flow. Because 25 of its other physical properties, these sleeves necessarily utilise a considerable thickness of polyurethane needed to work against failure by processes such as splitting and bursting. Thinner wall thicknesses would require the use of other support materials working in conjunction with the polyurethane to give it the support it needs against failure under

3 o operating loads.

Polyurethane is usually applied in the mining industry to surfaces exposed to wear to give those surfaces abrasion resistance qualities by processes such as casting, moulding or spraying the raw material for the polyurethane coating onto its support surface and post curing. The nature of the material is such that it does not lend itself to bonding processes which are performed after it is cured. This is particularly true with regard to its bonding to rubber. Rubber products are commonly used in pipelines, particularly as flexible pressure hose. It would be desirable to be able to provide a liner or sleeve to a product such as a rubber based flexible hose where the sleeve had the abrasion resistance of a material such as polyurethane, interacting with the material of the hose to retain the hose's flexible, pressure-resistant character.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an erosion or wear resistant surface derived from a polyurethane adhered to a rubber support base of an article subject to a corrosive or abrasive environment. Other objects and various advantages will hereinafter become apparent.

OUTLINE OF THE INVENTION

The invention achieves its object in the provision of a method by which to effect the bonding of a polyurethane to a support layer therefor, characterised in that: a castable urethane elastomer or polyurethane material is cured to provide a first surface; adjoining thereto a support layer wherein at least the layer in contact with the polyurethane is a rubber compound or adhesive; and subjecting the contiguous materials to a curing process to cure the rubber compound or adhesive of the assembly and adhere the layers together.

In the context of the specification the term adjoin is to be read to include the contacting of the respective layers, their side by side layup and any other operation bringing the respective layers together for bonding. In the context of the specification reference to a polyurethane material is a reference to a material derived from a castable urethane elastomer. The actual urethane elastomer used will be derived from that class of urethanes which is compatible with the duty the product which is produced from it is to perform.

In the above defined process, the polyurethane layer to which the rubber is adjoined may be buffed preferably with a relatively coarse sander (as explained herein) prior to application thereto of the uncured rubber. The buffed surface might be first cleaned with a suitable solvent and preferably primed ready for association with the rubber based layer of the assembly. A rubber based layer may be a support assembly which can include a plurality of support or reinforcing webs and steel wrapping in the form of wire and the like interleaved in rubber layers. The layer of the assembly which contacts the polyurethane is preferably a natural uncured rubber. A temporary nylon wrapping may be used to support the assembly, up to the time at which the assembly is cured when the process is not able to be effected in a mould or other like type means by which to apply the heat required to effect a curing of the rubber.

A product produced by the above defined method is also a subject of the invention. Such products can include straight pipe lengths pipe bends and other like-type flexible pipes. These products may involve a preformed polyurethane tube. Its outer surface is preferably appropriately prepared, ideally wound with strip rubber and optional reinforcements with the whole fired in a suitable oven to effect the curing of the uncured rubber laid up in contact with the polyurethane. An end flange can be built into the layup to establish a product which externally is similar to existing conduit and bends but with a polyurethane sleeve bonded therein. The bonding of the rubber support to the polyurethane sleeve is important. The conduit and bends can be used in environments which stress the product such as on the upstream end of a pump with reduced internal pressures which would otherwise collapse an unsupported polyurethane sleeve. Preferably the invention utilises castable Urethane elastomers in the 60-95 shore "A" hardness range consisting of Toluene Diisocyanate (TDI), low free Toluene Diisocyanate (LFTDI), Methylene Diphenyl Diisocyanate (MDl), and Para-Phenylene Diisocyanate (PPDI) based elastomers cured with Aromatic Diammes such as Moca, Dι-(Methylthιo) Toluene Diamines or Butanediol" BRIEF DESCRIPTION OF THE INVENTION The invention will now be descπbed with reference to preferred embodiments which are shown in the accompanying drawings, in which FIG 1 is a plan view of a flexible pipe bend in accordance with an embodiment of the invention with a loose end flange,

FIG 2 is a plan view of a flexible pipe in accordance with the invention fitted with integral end flanges,

FIG 3 is a cross-sectional detail at a flanged end of the flexible pipe bend of FIG. 1 ,

FIG 4 is a cross-sectional detail at a flanged end of the flexible pipe of FIG 2

PREFERRED EMBODIMENTS

In FIG 1 is seen a pipeline product typically known as a pipe bend 10 produced or manufactured with a preset radius of curvature The pipe bend 10 has mounted thereon, or is fitted with, freely mounted loose end connection means or end flanges 11 and 12 by which the pipe bend can be joined or bolted into a section of a pipeline or up to pumps, valves and other like-type pipeline fittings The flanges 11 and 12 may be fitted up against end abutment means or end shoulders 13 and 14 respectively (as is described in greater detail below)

In FIG 2, the conduit or pipe 15 is provided or fitted with fixed or integral end connection means or end flanges 16 and 17 Pipe diameters may typically be from 80mm through 400mm with pipe lengths possible from typically around 1m through 9m in Iength The pipe bends 10 may have similar bores and be with radii of or around 1 m through 7m, with an inclusive angle to the segment around 30° and up to the 90° illustrated

In Fig 3 is seen a longitudinal section through the wall of the pipe bend 10 of FIG 1 at one of its flanged ends The inside of the pipe bend 10 is fitted or lined with a polyurethane liner sleeve or tube 18 onto which is applied or wound a layer of uncured rubber 36 Rubber 36 is ideally a natural rubber and it can be in the form of a strip wound onto the sleeve. A flange mounting end sleeve 23 is fitted The end sleeve 23 provides a shoulder 14 against which flange 12 buts in use A layer 17 of corded reinforcement is overlaid with further rubber which may incorporate a wire winding 19. The corded reinforcement can be the reinforcement cord used in the vehicle tyre trade. A further corded reinforcement 19 can be covered with a last rubber layer 21 Typically, the polyurethane tube 18 may be 6mm thick; the first rubber layer 36, 1 5mm thick; the corded layer 17 may be established by winding two layers with crossed plies each 1mm thick; the intermediate rubber layer 38 might be established by two windings of rubber, each 3mm thick; the outer corded layer can be another two preferably crossed ply windings each 1mm thick, and the outer layer of rubber can be 3mm thick. The support layers overlap the end of the sleeve 23, but stop short of its end to permit flange 12 to free float thereon Bores 22 may be supplied in flange 12 to accept bolts as is usual. Typically, sleeve 23 will be ideally in steel, and the corded reinforcement can be tyre chord as supplied to the vehicle tyre trade The actual sequence of layers and reinforcements, and their actual number or occurrence is variable with particular combinations chosen to suit applications What is common to the support layers is the occurrence of an uncured rubber as the first layer (or adhesive bonding pre-cured rubber in an altemate system) laid up to the surface of polyurethane sleeve 18 A layer 34 may extend the material of the sleeve up the face of the shoulder 14 Layer 34 can be formed by application of castable urethane elastomer

In FIG 4 is seen a longitudinal section through an end wall of the flexible pipe 15 of FIG 2 Polyurethane sleeve or liner 24 is wrapped by rubber layers 25, 27 and 30 with intermediate corded layers 26 and 29 The intermediate rubber layer 27 may contain a wire helix 28 A steel sleeve 31 may be fitted in the end with flange 32 integral therewith, joined by welding or other appropriate means. Flange 32 may have bores 33 for bolts and a rubber layer 36 may be applied to its abutment face Again, the rubber layer contacted to the polyurethane is an uncured rubber, ideally a natural rubber The flange may have a region of polyurethane 35 extending the material of the sleeve out over the face of the flange Again a castable urethane elastomer can be applied after the product has been cured

In forming the above type products, in particular the pipes and bends, the method of production may involve the following steps in the sequence indicated.

A cured polyurethane sleeve may be formed by spin casting of castable urethane material in a pipe mould or by other like type production processes with the polyurethane sleeve formed with the desired internal dimension and thickness to suit the chosen application. The finished and cured polyurethane sleeve is typically fitted onto a mandrel or the like in a hose making lathe or stand. The outside of the sleeve is buffed, typically with a coarse sanding disc to provide a roughened surface profile and a key for adhesives A 100% surface treatment without any appreciable loss of material (less than 2%) is desirable A number 24 sanding disc grit is preferably used. A sanding disc is preferably used because it is more flexible Coarser and finer grits and grinding wheels could be used. Finer grits require more buffing time and more frequent disc changes. Coarser discs remove more material to achieve the 100% surface treatment. Grinding disc cutting speed is much higher than sanding disc speeds, generating more heat which can be detrimental (burning and melting the polyurethane) The buffed surface is preferably wiped with a suitable solvent prior to the next step and preferably between subsequent layup steps. Methyl ethyl ketone and like-type materials such as are recommended by polyurethane suppliers may be used. The solvent is used to clean crumb and dust, and incidental contaminants such as oil, grease, surface moisture, etc. Most aromatic solvents might be used. Petro-based solvents are not preferred as too high a concentration can adversely affect polyurethane. It is best applied sparingly and allowed to evaporate (some solvent will be absorbed by some of the materials at various stages). It is preferably wiped on with a clean cotton rag or similar applicator. The first solvent application is the more critical. Subsequent construction is less sensitive to variation in procedure. A primer is ideally next applied to the cleaned and buffed polyurethane sleeve. The primer promotes adhesion between the polyurethane and the preferred cement layer. The primer might be Chemlok 205. The primer is ideally applied as a single even coat by brush or roller and should be free from runs and air inclusions. A layer of rubber cement which might be Kontact AR100 or the preferred system described below can follow. It can be brushed onto the primer and allowed to cure under ambient conditions. A second layer of cement can be applied and when tacky, one layer of uncured rubber is wrapped around the tube. Two plies of polyester tyre cord may be wrapped on a bias angle to finish as a cross ply of reinforcement as required according to the application the product will be put to. High tensile spring wire can be wrapped onto the assembly if required in a continuous helix to further add to the level of reinforcement. Further plies of cord are applied as required to meet the planned operating pressures (typically two). Finally, an outer coating of rubber may be selected according to the specified operating environment and is applied and the entire item can be cured in an autoclave under steam pressure. The finished item is removed from the mandrel after curing and the ends are finished with castable polyurethane to make the polyurethane sleeve continuous up the sealing face on the hose end. The above described process can be varied with freedom in the choice of reinforcements and numbers of support layers The assembly might be wrapped externally in a nylon wrapping to maintain a compression force on the layers duπng the curing process The wrapping can be removed after curing The pipe layers may be pricked with a porcupine roller to enable release of any air bubbles between the layers so as to ensure good quality and uniform bonding of the layers The Chemlok 205 primer referred to above has the following composition (% by weight being not more than) a) Methyl isobutyl ketone 60% b) Xylene 15% c) Ethyl benzene 3.0% d) Methyl ethyl ketone 2.0% e) Formaldehyde 1 0%

The balance of the primer components are suspended solid fillers.

An alternate and preferred adhesion system to the Kontact AR100 referred to above utilises a) A first coat of Chemlok 205 composed as follows

(I) Tetrachloroethylene 20%

(ii) Ethyl Benzene 15%

(iii) Xylene 50%

(iv) Inorganic lead salt 2.0% (v) Carbon Black 3.0% b) A second coat of Chemlok Typly RC cement chemically composed as follows.

(I) VM&P Naptha 60%

(ii) Xylene 20% (iii) Ethyl Benzene 5 0%

(iv) Phthalate Ester 2 0% c) A third coat of BTR 1612 Solution cement which is comprised of uncured natural rubber dissolved and suspended in a solvent carrier The first adhesive system described above utilising the

Kontact AR100 cement is less preferable than the above three coat system AR100 is chemically composed as follows, (two part mix) 1 Part A Adhesive Mixture of organic and inorganic polymers dispersed and dissolved in a hydrocarbon solvent system containing Ethylacetate and Toluene

2 Part B Activator A Poly-lsocyanate in Ethylacetate Note The prior system employed two coats of

AR100, one coat to the tube and one coat to the rubber layer next applied The thickness of the rubbers used at various stages is determined by economics and practicality (ease of application, minimum thickness outer cover to ensure complete encapsulation of fabrics) and is not necessarily critical to the invention The selection and number of plies of cord is dependent on the service pressure rating of the product Very low pressure duties have been catered to without cord in the construction as the polyurethane and rubber composite has tensile properties which will allow for low pressure particularly in small diameter products

The nylon wrap mentioned above is preferably used after the item is manufactured but prior to curing and is preferably used on items not cured in a cavity mould Prior to application of the outer cover of rubber a porcupine roller is used to perforate the uncured carcass This in conjunction with the pressure generated by the nylon wrap promotes the exclusion of air from the construction The curing temperate is governed by the properties of the polyurethane and is typically much lower than that used for normal curing of rubber A typical product could be cured for two hours at 110° equating to a steam pressure of 141 Kpa

Claims

CLAIMS:

1. A method of bonding polyurethane to a rubber based support characterised in that: a castable urethane elastomer or polyurethane material is cured to provide a first surface; adjoining to said first surface a support layer wherein at least the material in contact with said first surface is a uncured rubber compound or an adhesive; and subjecting the contiguous materials to a curing process to cure the rubber compound or adhesive to establish adherence of the support layer to the polyurethane surface.

2. A method as claimed in Claim 1 wherein said first surface is first buffed with a coarse sander, primed and coated with an adhesive prior to applying a rubber based support layer.

3. A method as claimed in Claim 1 wherein a cured polyurethane sleeve is formed and mounted to a mandrel and the outer surface is the first surface which is buffed in preparation for the winding of at least an uncured rubber layer thereon optionally followed by further rubber layers and intermediate reinforcements.

4. A method as claimed in Claim 1 wherein the contiguous materials are cured under steam pressure at reduced temperatures below that which would adversely affect the polyurethane.

5. A method as claimed in Claim 3 wherein multiple layers of rubber and reinforcements are wound onto the polyurethane sleeve to form the rubber based support including corded layers laid up in a cross ply configuration and a helix of reinforcing wire.

6. A method as claimed in Claim 1 wherein the support layer is wound with a webbing layer to compress it during curing and the support is pricked to expel air prior to curing.

7. A method as claimed in Claim 2 wherein the buffing is by a disc sander with a number 24 grit and buffing is continued to achieve a 00% surface treatment. 8 A method as claimed in Claim 7 wherein the first surface is cleaned with a solvent such as methy ethlyketone subsequent to buffing

9 A method as claimed in Claim 8 wherein the first surface is primed with a composition with the composition by weight being not more than methyl isobutyl ketone 60% xylene 15% ethyl benzene 3 0% methyl ethyl ketone 2 0% formaldehyde 1 0%

10 A method as claimed in Claim 2 wherein the adhesive is applied as a three part system comprising a first coat comprised by weight of tetrachloroethylene 20% ethyl benzene 15% xylene 50% inorganic lead salt 2 0% carbon black 3 0% followed by a second coat comprised by weight of VM & P naptha 60% xylene 20% ethyl benzene 5 0% phthalate ester 2 0% followed by a third coat comprised of uncured natural rubber dissolved and suspended in a solvent carrier

11 A corrosion or wear resistant product produced by the method of any one of Claims 1 to 10 wherein the polyurethane shields the rubber support assembly from corrosion or wear, the polyurethane being applied to all the surfaces in contact with corrosive or abrasive influences 12 A corrosion or wear resistant product as claimed in Claim 11 wherein the product is a pipe or bend with end flanges to join with other pipes or bends, or pipeline fittings, the polyurethane being a liner or sleeve to the pipe or bend being extended radially out over the abutment faces of said flanges by the application of castable urethane over the flange face

13 A corrosion or wear resistant product as claimed in Claim 12 wherein the flange is integral with or mounted movably to a flange support sleeve which flange support sleeve is bonded between the polyurethane liner or sleeve and the rubber support applied thereto

14 A corrosion or wear resistant product as claimed in Claim 11 having a polyurethane sleeve wrapped in rubber containing therein cross ply and wire reinforcements