WO2014064157A1

WO2014064157A1 - The use of a bending optimized product such as rope

Info

Publication number: WO2014064157A1
Application number: PCT/EP2013/072182
Authority: WO
Inventors: Dietrich Wienke; Roelof Marissen; Martin Pieter Vlasblom
Original assignee: Dsm Ip Assets B.V.
Priority date: 2012-10-23
Filing date: 2013-10-23
Publication date: 2014-05-01
Also published as: EP2912217A1; CN104755662A

Abstract

The invention relates to the use of a coated product having optimized resistance against repetitive bending, comprising a plurality strands, the strands comprising a plurality of spun ultrahigh molecular weight polyethylene (UHMWPE) fibers, wherein said fibers are obtained by spinning an UHMWPE comprising olefinic branches (OB) and having an elongational stress (ES), and a ratio between the number of olefinic branches per thousand carbon atoms (OB/1 OOOC) and the elongational stress (ES) of at least 0.2.

Description

THE USE OF A BENDING OPTIMIZED PRODUCT SUCH AS ROPE

The invention relates to the use of a coated product having optimized resistance against repetitive bending, comprising a plurality of strands, the strands comprising a plurality of spun ultrahigh molecular weight polyethylene (UHMWPE) fibers.

Applications involving repeated bending of a product such as a rope, hereinafter also referred as bending applications, include typically bend-over-sheave applications. A rope for example used in bend-over-sheave applications is within the context of the present application considered to be a load-bearing rope typically used in lifting or installation applications; such as marine, oceanographic, offshore oil and gas, seismic, commercial fishing and other industrial markets. During such uses, together referred to as bend-over-sheave applications, the rope is frequently pulled over drums, bitts, pulleys, sheaves, etc. When exposed to such frequent bending or flexing, a rope may fail due to rope and fiber damage resulting from external and internal abrasion, frictional heat, etc.; such fatigue failure is often referred to as bend fatigue or flex fatigue.

To improve the resistance of a product and in particular of a rope to bending, WO201 1/015485 proposes coating the rope with a cross-linked silicone polymer, obtaining an improvement of the service life of the rope when exposed to frequent bending or flexing. Aiming also at reducing bending fatigue, WO2007/101032 and WO2007/062803 propose constructing the rope from fibers coated with a (fluid) composition comprising an amino functional silicone resin and a neutralized low molecular weight polyethylene wax.

Each of the patent applications cited above represent progress in the state of the art. However, a need exist for coated products having optimized or further improved resistance against repetitive bending.

The invention is a method of bending a coated product wherein the product comprises a plurality strands, the strands comprising a plurality of spun ultrahigh molecular weight polyethylene (UHMWPE) fibers, wherein said fibers are obtained by spinning an UHMWPE comprising olefinic branches (OB) and having an elongational stress (ES), and a ratio ( O^ l 000C ^ ^_e ηυηη^,- ₀f olefinic

ES

branches per thousand carbon atoms (OB/1000C) and the elongational stress (ES) of at least 0.2. It was observed that with the method of the invention, hereinafter referred to the inventive method, an improved resistance against repetitive bending is achieved. It was further observed that the effects of the invention were more conspicuous for bending of the coated product under a tension of at lest 5 % of its breaking strength and more preferably at a low frequency repetitive bending, e.g. repetitive bending having a frequency of between 0.02 Hz and 5 Hz, even better for frequencies between 0.05 Hz and 1 Hz, best for frequencies between 0.1 Hz and 0.5 Hz. Also, very good results were obtained for long-term repetitive bending, e.g.

repetitive bending that continuously occurs over a period of at least 0.5 month, more preferably at least 2.5 months, most preferably at least 5 months. It was also observed that the inventive product performs well when subjected to repetitive bending over a sheave; and performs extremely well when subjected over repetitive bending over a disc. The inventive product thus performs optimum when utilized in conditions such as the ones mentioned above.

Examples of bending where the invention performs at its optimum include bending of ropes, flow lines, flex hoses, conveyor belts, tether lines and umbilicals. Ropes and in particular mooring ropes are the most preferred embodiments of the inventive method.

In a preferred embodiment, the UHMWPE comprises ethyl branches and having an intrinsic viscosity (IV) of at least 5 dl/g, an elongational stress (ES), and a ratio ( C2H5/1000C ^_e ηυηη^,- ₀f _ethyl branches per thousand carbon

ES

atoms (C2H5/1000C) and the elongational stress (ES) of at least 0.5.

In a further preferred embodiment, the UHMWPE comprises butyl branches and having an intrinsic viscosity (IV) of preferably at least 5 dl/g, an

C4H9/1000C

elongational stress (ES), and a ratio ( ) between the number of butyl

ES

branches per thousand carbon atoms (C4H9/1000C) and the elongational stress (ES) of at least 0.2.

By fibre is herein understood an elongated body, e.g. a body having a length and transverse dimensions, wherein the length of the body is much greater than its transverse dimensions. The term fibre as used herein may also include various embodiments, e.g. a filament, a tape, a strip, a ribbon and a yarn. The fiber may also have regular or irregular cross-sections. The fiber may also have a continuous and/or a discontinuous length. Preferably, the fiber has a continuous length, such fiber being known in the art as a filament. Within the context of the invention, a strand is understood to be an elongated body comprising a plurality of fibres.

Preferably, the inventive method of bending is performed on a rope comprising UHMWPE fibers and in particular those spun from UHMWPEs having ethyl or butyl branches, having a tenacity of at least 25 cN/dtex, more preferably of at least 32 cN/dtex, most preferably of at least 38 cN/dtex. Preferably, said UHMWPE fibers and in particular those spun from UHMWPEs having ethyl or butyl branches, have an elastic modulus of at least 1 100 cN/dtex, more preferably of at least 1200 cN/dtex, most preferably of at least 1300 cN/dtex.

By UHMWPE is herein understood a polyethylene having an intrinsic viscosity (IV) as measured on solution in decalin at 135°C, of preferably at least 5 dl/g. Preferably, the IV of the UHMWPE is at least 10 dl/g, more preferably at least 15 dl/g, even more preferably at least 19 dl/g, most preferably at least 21 dl/g. Preferably, the IV is at most 40 dl/g, more preferably at most 30 dl/g, even more preferably at most 25 dl/g.

The UHMWPE used in the present invention has preferably a ratio

OB/1000C ^ ^ \_easi 0.3, more preferably of at least 0.4, even more preferably of at

ES

least 0.5, yet even more preferably of at least 0.7, yet even more preferably of at least 1 .0, yet even more preferably of at least 1.2. It was surprisingly observed that by increasing the above mentioned ratio, the properties of the inventive rope may be improved.

When the UHMWPE used in the present invention has ethyl

C2H5/1000C

branches, said UHMWPE preferably has a ratio of at least 1 .00, more

ES

preferably of at least 1 .30, even more preferably of at least 1.45, yet even more preferably of at least 1 .50, most preferably of at least 2.00. Preferably said ratio is between 1 .00 and 3.00, more preferably between 1.20 and 2.80, even more preferably between 1 .40 and 1 .60, yet even more preferably between 1.45 and 2.20.

When the UHMWPE used in the present invention has butyl

C4H9/1000C _{x x} , _{ί η ηι}_ branches, said UHMWPE preferably has a ratio of at least 0.25, even

ES

more preferably at least 0.30, yet even more preferably at least 0.40, yet even more preferably at least 0.70, more preferably of at least 1 .00, most preferably of at least 1 .20. Preferably said ratio is between 0.20 and 3.00, more preferably between 0.40 and 2.00, even more preferably between 1.40 and 1.80.

The UHMWPE used in the present invention has preferably an ES of at most 0.70, more preferably of at most 0.50, more preferably of at most 0.49, even more preferably at most 0.45, most preferably at most 0.40. When said UHMWPE has ethyl branches, preferably said UHMWPE has an ES of between 0.30 and 0.70, more preferably between 0.35 and 0.50. When said UHMWPE has butyl branches, preferably said UHMWPE has an ES of between 0.30 and 0.50, more preferably between 0.40 and 0.45.

The UHMWPE used according to the invention, also has preferably an amount of olefinic branches per thousand carbon atoms (OB/1000C) of between 0.05 and 1 .30, more preferably between 0.10 and 1.10, even more preferably between 0.30 and 1.05.

The above mentioned UHMWPEs can be manufactured with a process according to PCT/EP2012/056079, included herein in its entirety by reference.

By coated product is herein understood a product at least partially covered with a coating. The coating can penetrate inside the product, between the strands and/or the fibers thereof. Preferably, the coating penetrates both between the strands and the fibers of the product. As mentioned above, ropes are preferred embodiment of the inventive product. Said ropes may have any construction known in the art such as those disclosed in WO 2006/133881 , US 6945153 and WO

2003/102295, included herein by reference.

It was observed that any coating composition is suitable for use in accordance with the invention. Preferred coatings are those comprising a cross-linked silicon composition. Other preferred coatings are those based on coal tar, bitumen, or synthetic polymers. Such products include: LAGO 45 and LAGO 50 commercially available from G. O.V.I. S.A. of Drongen, Belgium.

According to the invention, the fibers contained by the product subjected to bending are spun UHMWPE fibers. Such fibers may be obtained by spinning the UHMWPE, preferably with a gel-spinning process, i.e. a process containing at least the steps of:

a) providing a solution of UHMWPE in a suitable solvent;

b) spinning a multifilament yarn by passing the solution of step a) through a

spinning plate containing a plurality of spin-holes to form the filaments of said yarn; and c) drawing the filaments in at least one drawing step before, during or after removing the solvent.

Examples of gel spinning processes for the manufacturing of

UHMWPE fibers are described in numerous publications, including EP 0205960 A, EP 0213208 A1 , US 44131 10, GB 2042414 A, GB-A-2051667, EP 0200547 B1 , EP 04721 14 B1 , WO 01/73173 A1 , EP 1 ,699,954 and in "Advanced Fibre Spinning Technology, Ed. T. Nakajima, Woodhead Publ. Ltd (1994), ISBN 185573 182 7. Most preferred method is the one disclosed in PCT/EP2012/056079.

The invention also relates to the use of a coated product wherein the product comprises a plurality strands, the strands comprising a plurality of spun ultrahigh molecular weight polyethylene (UHMWPE) fibers, wherein said fibers are obtained by spinning an UHMWPE comprising olefinic branches (OB) and having an elongational stress (ES), and a ratio ( O^ l 000C ^ |_3e^_ween ^_{e num}b_{er 0}f olefinic

ES

branches per thousand carbon atoms (OB/1000C) and the elongational stress (ES) of at least 0.2. Preferably the coated product is a rope, such as the one described above which when tensioned at about 25% of its breaking strength and subjected while being tensioned to a repetitive bending motion over a sheave with a frequency of between 0.02 Hz and 5 Hz, it withstands a number of motion cycles of at least 275, preferably at least 300, more preferably at least 325, most preferably at least 350 until complete rupture. Preferably the sheave has a diameter (D) and the product has a diameter (d) in a ratio D/d of about 20, wherein the diameter (d) of the product is considered the average of at least 10 measurements carried out at random locations along the length of the product, by determining the largest distance between any two points on the periphery of a cross-section of the product at a location, said measurements being carried on the product without applying a load thereon.

The invention also relates to the use of a said coated product, preferably a rope, such as the one of the invention which when tensioned at about 30% of its breaking strength and subjected while being tensioned to a repetitive bending motion over a disk with a frequency of between 0.02 Hz and 5 Hz, it withstands a number of motion cycles of at least 275, preferably at least 4500, more preferably at least 5000, even more preferably at least 5500, most preferably at least 6000, until complete rupture. Preferably the disk has a diameter (D) and the product has a diameter (d) in a ratio D/d of about 10.

In a preferred embodiment the method of bending comprises a loading-unloading bending of the coated product wherein the ratio of the unloaded tension to the loaded tension is less than 0.5, preferably less than 0.2, more preferably less than 0.1. It was surprisingly observed that a rope as described above, is less affected by internal wear when subjected to such a repeated tensioning stress.

Preferably a Cyclic Bending Over Sheave test machine such as the one sold by Bude Group bv, NL is used to measure the cycles until complete rupture.

The invention will be further explained by the following examples and comparative experiment, however first the methods used in determining the various parameters useful in defining the present invention are hereinafter presented.

• Dtex: yarn's or filament's titer was measured by weighing 100 meters of yarn or filament, respectively. The dtex of the yarn or filament was calculated by dividing the weight (expressed in milligrams) to 10;

• IV: the Intrinsic Viscosity is determined according to method ASTM

D1601 (2004) at 135 °C in decalin, the dissolution time being 16 hours, with BHT (Butylated Hydroxy Toluene) as anti-oxidant in an amount of 2 g/l solution, by extrapolating the viscosity as measured at different concentrations to zero concentration.

• Tensile properties of fibers: tensile strength (or strength) and tensile modulus (or modulus) are defined and determined on multifilament yarns as specified in ASTM D885M, using a nominal gauge length of the fibre of 500 mm, a crosshead speed of 50 %/min and Instron 2714 clamps, of type "Fibre Grip D5618C". On the basis of the measured stress-strain curve the modulus is determined as the gradient between 0.3 and 1 % strain. For calculation of the modulus and strength, the tensile forces measured are divided by the titre, as determined by weighing 10 metres of fibre; values in GPa are calculated assuming a density of 0.97 g/cm³.

• Tensile properties of fibers having a tape-like shape: tensile strength, tensile modulus and elongation at break are defined and determined at 25 °C on tapes of a width of 2 mm as specified in ASTM D882, using a nominal gauge length of the tape of 440 mm, a crosshead speed of 50 mm/min.

• Number of olefinic, e.g. ethyl or butyl, branches per thousand carbon atoms: was determined by FTIR on a 2 mm thick compression moulded film by quantifying the absorption at 1375 cm^"1 using a calibration curve based on NMR measurements as in e.g. EP 0 269 151 (in particular pg. 4 thereof). • Elongational stress (ES) of an UHMWPE is measured according to ISO 1 1542-2A.

PREPARATION OF UHMWPE

Grade a)

A batch polymerization process was performed in a 55 L stainless steel reactor equipped with a mechanical stirrer. The reactor was charged with 25 liter of dry heptane and then heated to 60°C. The temperature has been controlled by a thermostat. Subsequently, the reactor has been charged with 96.25 NL of 1 -butene; 3.30 ml (0.5 mol/L) TEOS; and 12.65 ml (2 mol/L) TEA.

The reactor has been subsequently pressurized with ethylene gas to 2 bar using an ethylene flow of about 1800 NL/h. Once the 2 bar pressure has been reached, an amount of 10.36 ml (65 mg/ml) of Ziegler-Natta catalyst has been added to the reactor. The reactor has been subsequently pressurized with ethylene to 5 bar using a flow of 1800 NL/h and kept at this pressure for 15 minutes. Subsequently, ethylene was added to the reactor with a maximum flow of 1800 NL/h until the desired total amount of ethylene had been dosed (7700NL)

After the desired polymerization time has been reached (7700 NL counts of ethylene consumption) the polymerization has been stopped by closing the ethylene supply and the reaction mixture was removed from the reaction vessel and collected in the filter where the polymer was dried over night by a N₂ flow of 1 bar. The polyethylene produced according to the above described process had an ES of 0.48, 0.69 ethyl branches per 1000 carbon atoms and an IV of about 25 dl/g. Grade b)

A batch polymerization process was performed in a 55 L stainless steel reactor equipped with a mechanical stirrer. The reactor was charged with 25 liter of dry heptane and 550 ml of dry 1 -hexene and then heated to 65°C. The temperature has been controlled by a thermostat. Subsequently, the reactor has been charged with 6.0 ml (0.4 mol/L) TEOS; and 12.15 ml (2 mol/L) TEA.

The reactor has been subsequently pressurized with ethylene gas to 2 bar using an ethylene flow of about 2300 NL/h. Once the 2 bar pressure has been reached, an amount of 12.4 ml (68.18 mg/ml) of Ziegler-Natta catalyst has been added to the reactor. The reactor has been subsequently pressurized with ethylene to 4 bar using a flow of 2300 NL/h and kept at this pressure for about 15 minutes. Subsequently, the polymerization has been carried out under an ethylene flow of about 2300NL/h.

After the desired polymerization time has been reached (7700 NL counts of ethylene consumption) the polymerization has been stopped by closing the ethylene supply and the reaction mixture was removed from the reaction vessel and collected in the filter where the polymer was dried over night by a N₂ flow of 1 bar. The polyethylene produced according to the above described process had an ES of 0.42, 0.31 n-butyl branches per 1000 carbon atoms and an IV of about 21 dl/g. EXAMPLE 1

Two 5mm coated ropes were constructed from the fiber grades a) and b). The ropes were braided in a 12 x1 x 4 (1827 dtex) construction with a 20 twists per meter and a braiding period of 27 mm. The ropes were subjected to repetitive bending in a CBOS (Cyclic Bending Over Sheave) test machine from Bude Group bv, NL. The ropes were coated with a LAGO based coating which penetrated between the strands and the fibers. Each rope was tensioned to 25% of the breaking strength (ASTM D-6268) over a free running first sheave, the ratio between the diameter of the sheave (D) and diameter of the rope (d) being about 50. The first sheave induced a first mild bending in the rope and was used to drive the rope. From the first sheave the rope was pulled over a second sheave (D/d about 20) to introduce a second strong bend in the rope. The ropes behave the same and broke after about 350 cycles.

EXAMPLE 2

Ropes with a diameter of 20 mm were constructed from the grades a and b and subjected to above CBOS at a tension of 30 % of their breaking strength but with the second sheave being replaced by a disk with D/d of about 10. . The ropes resisted 6000 cycles.

EXAMPLE 3

Ropes from grades a and b were braided in a 12 x 4 x 4 construction with a diameter of about 10 mm. Both ropes were subjected at a temperature of about 50°C to a cyclic tension-tension bending test by repetitively subjecting the rope to a tension of 25% of its breaking strength and releasing the tension. The frequency was 0.3 Hz. The rope resisted to about 50% more load-unload cycles than an identical rope braided from SK75. COMPARATIVE EXPERIMENTS

Examples 1 and 2 were repeated, however the rope used was manufactured from UHMWPE fibers sold by DSM Dyneema as Dyneema®SK75. The rope resisted 250 and 4000 cycles, respectively.

Claims

The use of a coated product wherein the product comprises a plurality strands, the strands comprising a plurality of spun ultrahigh molecular weight polyethylene (UHMWPE) fibers, wherein said fibers are obtained by spinning an UHMWPE comprising olefinic branches (OB) and having an elongational

OB/1000C

stress (ES), and a ratio ( ES ) between the number of olefinic branches per thousand carbon atoms (OB/1000C) and the elongational stress (ES) of at least 0.2.

The use of claim 1 wherein the coated product, preferably a rope, when tensioned at about 30% of its breaking strength and subjected while being tensioned to a repetitive bending motion over a disk with a frequency of between 0.02 Hz and 5 Hz, it withstands a number of motion cycles of at least 275, preferably at least 4500, more preferably at least 5000, even more preferably at least 5500, most preferably at least 6000, until complete rupture. A method of bending a coated product wherein the product comprises a plurality strands, the strands comprising a plurality of spun ultrahigh molecular weight polyethylene (UHMWPE) fibers, wherein said fibers are obtained by spinning an UHMWPE comprising olefinic branches (OB) and having an elongational stress (ES), and a ratio ( 0^ 1000C ^ |_3e^_ween ^_e n^^g,- ₀f

ES

olefinic branches per thousand carbon atoms (OB/1000C) and the

elongational stress (ES) of at least 0.2.

The method of claim 3, wherein a tensioned of at least 5% of the breaking strength of the coated product is applied and wherein the coated product is subjected to a repetitive bending motion over a sheave or a disc.

The method of claim 4 wherein the bending has a frequency of between 0.02 Hz and 5 Hz.

The method of claim 4 or 5 wherein the repetitive bending has a bending diameter D and the product has a bended thickness d wherein the ratio of D/d is greater than 10, preferably greater than 25 most preferable greater than 50. The method according to claim 3 wherein the bending comprises a loading- unloading bending of the product wherein the ratio of the unloaded tension to the loaded tension is less than 0.5, preferably less than 0.2, more preferably less than 0.1.