NO344273B1 - Rope or rope with improved performance for cyclic bending over blocks or hoists, method for improving the cyclic bending of a rope, and application of the rope. - Google Patents

Description

BACKGROUND OF THE INVENTION

Field of the invention

The present invention relates to improvements in rope or rope and in particular synthetic ropes with high grip which are suitable for use in marine applications.

Description of known technique

Synthetic fiber ropes have been used in a number of applications including various marine applications. One type of rope that has excellent properties is one that is made from high modulus polyolefin fibers and/or yarns. High tenacity polyolefin fibers are also fibers with good grip, are also known as extended chain or high molecular weight fibers. These fibers and yarns are available, for example, as SPECTRA<®>extended chain polyethylene fibers and yarns from Honeywell International Inc.

Ropes formed from extended chain polyethylene fibers have been proposed for use in marine applications, see, for example, US Patents 5,901,632 and 5,931,076, both in the name of Ryan, but are not incompatible with this.

In certain marine applications, extended chain polyethylene ropes or ropes are repeatedly bent over blocks, pulleys or the like in use. Certain synthetic ropes or ropes have experienced premature wear when subjected to repeated bending over blocks or pulleys, and particularly synthetic ropes or ropes used in marine, industrial applications have had this problem.

Synthetic ropes continue to replace steel wire in many marine applications. Synthetic rope continues to replace steel wire in many cyclic bendover sheave (CBOS) applications, and there is a need to improve the fatigue life of high performance synthetic rope. In particular, there is a need to improve the performance of ropes made from high-performance polyolefin fibers and yarns.

A proposed solution for connecting a rope with improved properties is described in US patent 6,945,153 in the name of Knudsen et al. This patent describes a large diameter rope formed from a blend of extended chain polyethylene fibers and liquid crystal polymer fibers. It would be desirable to improve the properties of such a rope.

It would also be desirable to provide a high tenacity polyolefin fiber rope which has improved wear resistance against repeated bending over blocks and the like, particularly in wet applications, while the otherwise excellent properties are maintained. It would also be desirable to provide a rope or rope suitable for use in lifting applications for heavy objects, for example to and from the seabed.

SUMMARY OF THE INVENTION

According to the present invention, a rope or rope with improved CBOS fatigue resistance is provided, said rope comprises high tenacity fibres, the rope and/or the fibers being coated with a coating mixture, as defined in independent claim 1; a method for improving the cyclic bending over block (CBOS) fatigue time of a rope, the method comprising forming said rope from high tenacity fibers and coating the rope and/or the fibers that make up the rope with a coating composition, as defined in independent claim 22, and use of a synthetic fiber rope in a method for lifting or placing heavy objects from and on the seabed, as defined in independent claim 28. Alternative embodiments are set out in non-independent claims 2-21; 23-27 and 29-32.

According to the present invention, a rope or rope with improved CBOS fatigue resistance is provided where this rope comprises high tenacity fibers and the rope and/or the fibers are coated with a coating mixture comprising an amino-functional silicone resin and a neutralized low molecular weight polyethylene.

In further accordance with the invention, there is provided a rope or rope with improved CBOS fatigue resistance where the rope or rope comprises a mixture of high tenacity polyolefin fibers with other high tenacity fibers that are not polyolefin fibers and where the rope or rope and/or the fibers are coated with a coating mixture comprising a functional amino silicone resin and a neutralized low molecular weight polyethylene.

Furthermore, according to the invention, a rope or rope with an improved CBOS fatigue resistance is provided, where the rope comprises a mixture of high tenacity polyolefin fibers with other high tenacity fibres, where these other high tenacity fibers comprise aramid fibers and/or liquid crystal copolyester fibres, where the rope and/or the fibers are coated with a mixture comprising a functional amino silicone resin and a neutralized low molecular weight polyethylene.

Furthermore and in accordance with the invention, a method is provided for improving the CBOS shelf life of a rope or rope, where the method comprises forming this from high tenacity fibers, and coating the rope or rope and/or the fibers that make up the product with a coating mixture comprising a functional amino silicone resin and a neutralizer, low molecular weight polyethylene.

In yet another embodiment of the invention, a method is provided for improving the CBOS wear or fatigue of a rope or rope, where the method comprises forming this from high tenacity fibers and coating the product and/or the fibers that make up such a rope or rope with a coating mixture comprising a functional amino silicone resin and a neutralized low molecular weight polyethylene.

Furthermore, and according to the invention, there is provided the use of a synthetic fiber rope in a method for lifting and placing heavy objects from or on a seabed location, where the improvement comprises the use of such a rope comprising high tenacity fibers and where the rope and/or the fibers are coated with a coating composition comprising a functional amino silicone resin and a neutralized low molecular weight polyethylene.

It has been found that when high tenacity fibers are coated with a coating composition comprising a functional amino silicone resin and a neutralized low molecular weight polyethylene and the whole is formed into a rope or rope, or if such is formed from such uncoated fibers, then coated with the coating composition, the cyclic bending resistance over blocks for such ropes is quite unexpectedly improved. It has also been found that when high tenacity fibers are mixed with other high tenacity fibers and these mixed fibers are coated with a coating composition comprising a functional amino silicone resin and a neutralized low molecular weight polyethylene and the whole is then formed into a rope or rope, or if such is formed from such formed fibers also coated with the coating mixture, the bending resistance over blocks and the like will unexpectedly improve.

DETAILED DESCRIPTION OF THE INVENTION

For the purposes of the present invention, a fiber is an elongated body whose length dimension is much greater than the transverse dimension for width and thickness. According to this, the term "fibre" includes monofilaments, multifilaments, ribbons, strips, staples and other forms of cut, chopped or discontinuous fibers and the like, with regular or irregular cross-sections. The term "fiber" includes a number of any of those listed above or a combination thereof. A yarn is a continuous strand consisting of many fibers or filaments. Fibers can also be in the form of ribbons, strips or split film or tape.

The cross-sections for fibers that can be used here can vary within wide limits. They can be circular, flat or elongated in cross-section. They may also be of irregular or regular, multi-lobal cross-section with one or more regular or irregular lobes projecting from the linear or longitudinal axes of the fibres. It is preferred that the fibers are of essentially circular, flat or elongated cross-section and most preferably of essentially circular cross-section.

As mentioned above, ropes or ropes consisting of high modulus polyolefin fibers such as extended chain polyethylene fibers, and yarns made therefrom, are proposed for use in marine applications. Such use of these ropes is for heavy lifting and anchoring or mooring of objects on the seabed. Other applications include subsea oil and gas exploration, further oceanographic, seismic and other industrial applications. The most preferred applications for ropes of this type are deep sea lifting and positioning.

The fibers used in the rope or rope construction according to the invention are high tenacity fibers. As used herein, "high tenacity fibers" means fibers having tenacities equal to or greater than about 7 g/d.

Preferably, these fibers have initial tensile moduli of at least about 150 g/d and energy-to-break of at least about 8 J/g as measured by ASTM D2256. As used herein, the terms "initial tensile modulus", "tensile modulus" and "modulus" mean the modulus of elasticity as measured by ASTM 2256 for a yarn.

Preferably, the high tenacity fibers have tenacities equal to or greater than about 10 g/d, more particularly equal to or greater than about 16 g/d, preferably greater than about 22 g/d, and most preferably equal to or greater than about 28 g/d.

The high tenacity fibers can be used alone in the construction of such ropes or ropes, or can be used as mixtures of two or more high tenacity fibers with different chemical compositions when it comes to the construction.

High tenacity fibers useful herein include highly oriented, high molecular weight polyolefin fibers, and particularly high modulus polyethylene fibers and polypropylene fibers, aramid fibers, polybenzazole fibers such as polybenzazole (PBO) and polybenzothiazole (PBT), polyvinyl alcohol fibers, polyacrylonitrile fibers, polyamide fibers, polyester fibers, liquid crystal copolyester fibers, glass fibers, carbon fibers or basalts and others mineral fibers as well as rigid rod polymer fibers and mixtures or the like thereof. Preferred high strength fibers useful in the invention are polyolefin fibers, aramid fibers and liquid copolyester fibers, and mixtures thereof. Most preferred are high molecular weight polyethylene fibers, aramid fibers and liquid copolyester fibers, and mixtures thereof. Although yarns forming these ropes or ropes can be made from a mixture of two or more of such high tenacity fibers, preferably the yarns that make up the ropes or ropes are formed from a single, high tenacity fiber type, and two or more yarns of different fiber types are used to form the rope or twine.

Preferred blends are blends of high tenacity polyethylene fibers and aramid fibers, and blends of high tenacity fibers and liquid crystal copolyester fibers, as well as blends of aramid fibers and liquid crystal copolyester fibers.

The fibers used in the construction of rope or rope preferably comprise extended chain (also known as high molecular weight, high tenacity or high modulus) polyolefin fibres, in particular high modulus polyethylene fibers and polypropylene fibres.

US Patent 4,457,985 generally describes such high molecular weight polyethylene and polypropylene fibers. In the case of polyethylene, suitable fibers are those with a weight average molecular weight of at least about 150,000, preferably at least about one million and most preferably between about two million and about five million. Such high molecular weight polyethylene fibers can be solution spun, see, for example, US Patents 4,137,394 and 4,356,183, or a filament spun from a solution to form a gel structure, see US Patent 4,413,110, German Publ. No. 3.004.6999 and GB patent 2051667, or the polyethylene fibers can be produced by a rolling and drawing process, see US patent 5.702.657. As used herein, the term polyethylene means a predominantly linear polyethylene material which may contain minor amounts of chain branching or comonomers not exceeding about 5 modifying units per 100 main chain carbon atoms, and which may also contain, mixed therein, not more than about 50% by weight of one or more polymeric additives such as alkene-1 polymers, in particular low-density polyethylene, polypropylene or polybutylene, copolymers containing monoolefins as primary monomers, oxidized polyolefins, graft polyolefin copolymers and polyoxymethylenes, or low molecular weight additives such as antioxidants, lubricants, ultraviolet shielding agents, colorants and the like, which are usually incorporated .

High density polyethylene fibers are available, for example, under the trade name SPECTRA® fibers and yarns from Honeywell International Inc. of Morristown, New Jersey, USA.

Depending on the forming technique, the drawing ratio and temperatures, and other conditions, a number of properties can be given to these fibers. The tenacity of the polyethylene fibers is at least about 7 g/d, especially at least about 15 g/d, most preferably about 20 g/d, more especially at least about 25 g/d, and most preferably at least about 30 g/d. Similarly, the initial tensile moduli of the fibers, as measured using an Instron testing machine, are preferably at least about 300 g/d, more particularly at least about 500 g/d, most preferably at least about 1,000 g/d, and most preferably at least about 1,200 g/d . These highest initial tensile modulus and tenacity values can generally only be achieved by using a solution grown or gel spinning process. Many of the filaments have melting points higher than the melting point of the polymer from which they are formed. For example, high molecular weight polyethylene of about 150,000, about one million and about two million molecular weight generally have bulk melting points of about 138ºC. The highly oriented polyethylene filaments made from these materials have melting points from around 7ºC to around 13ºC or higher. Thus, a slight increase in the melting point reflects the crystalline perfection and higher crystalline orientation of the filaments compared to the bulk polymer.

Preferably, the polyethylene used is a polyethylene with fewer than about one methyl group per thousand carbon atoms, more particularly fewer than about 0.5 methyl groups per thousand carbon atoms, and less than about 1% by weight of other constituents.

Similarly, highly oriented, high molecular weight polypropylene fibers with weight average molecular weights of at least around 200,000, and in particular at least around one million, and preferably around two million, can be used. Such extended chain polypropylenes can be formed into reasonably well oriented filaments by techniques described in the various references cited above and particularly with reference to the technique in US Patent 4,413,110. Because polypropylene is a much less crystalline material than polyethylene and contains pendant methyl groups, the tenacity values that can be obtained with polypropylene are generally significantly lower than the corresponding values for polyethylene. Accordingly, a suitable tenacity is preferably at least around 8 g/d, in particular at least around 11 g/d. The initial tensile moduli for polypropylene are preferably at least around 160 g/d, more preferably at least around 200 g/d. The melting point of the polypropylene is generally raised several degrees by the orientation process so that the polypropylene filaments preferably have a main melting point of at least 168ºC, and more particularly at least 170ºC. The particularly preferred ranges for the parameters described above can advantageously provide improved performance for the desired object obtained. By using fibers with a weight average molecular weight of at least 200,000 coupled with the preferred ranges for the parameters described above (modulus and tenacity), can advantageously provide improved performance in the final article.

Regarding extended chain polyethylene fibers, the preparation and drawing of gel spun polyethylene fibers is described in various publications and includes US Patents 4,413,110, 4,430,383, 4,436,689, 4,536,536, 4,545,950, 4,551,296, 4,612,148 . .553, USSN 2005/0093200.

In the case of aramid fibers, suitable fibers are formed from aromatic polyamides as described in US Patent 3,671,542. Preferred aramid fibers will have a tenacity of at least about 20 g/d, an initial tensile modulus of at least 400 g/d and an energy-to-break of at least 8 J/d, and particularly preferred aramid fibers will have a tenacity of at least 20 g/d and an energy-to-break of at least around 20 J/g. Most preferred aramid fibers will have a tenacity of at least about 23 g/d, a modulus of at least about 500 g/d, and an energy-to-break of at least about 30 J/d. For example, poly(p-phenylene terephthalamide) filaments with a moderately high modulus and tenacity are particularly useful in forming ballistic resistant composites. Examples are Twaron<®>T2000 from Teijin which has a denier of 1000. Other examples are Kevlar<®>29 which has 500 g/d and 22 g/d as values for initial tensile modulus and tenacity respectively, as well as Kevlar® 129 and KM2 available at 400, 640 and 840 denier from du Pont. Aramid fibers from other manufacturers can also be used according to the invention. Copolymers of poly(p-phenylene terephthalamide) can also be used, for example co-poly(p-phenylene terephthalamide 3,4'-oxydiphenylene terephthalamide). Also useful in practicing the invention are poly(m-phenylenisophthalamide) fibers from du Pont which are marketed under the name Nomex<®>.

High molecular weight polyvinyl alcohol (PV-OH) fibers with high tensile modulus are described in US Patent 4,440,711 to Kwon et al. but not where it is inconsistent. High molecular weight PV-OH fibers should have a weight average molecular weight of at least around 200,000. In particular, usable PV-OH fibers should have a modulus of at least about 300 g/d, a tenacity particularly about 10 g/d, and more particularly about 14 g/d, and most preferably about 17 g/d, and an energy to break of at least around 8 J/d. PV-OH fibers with such properties can be produced, for example, by the process described in US patent 4,599,257.

In the case of polyacrylonitrile (PAN), PAN fibers should have a weight average molecular weight of at least 400,000. Particularly useful PAN fibers should have a tenacity of at least around 10 g/d and an energy to break of at least 8 J/g. PAN fibers with a molecular weight of at least about 400,000, a tenacity of at least about 15 to 20 g/d and an energy at break of at least about 8 J/g are most useful, and such fibers are described, for example, in US Patent 4,535. 027.

Suitable liquid crystal copolyester fibers for practicing the invention are described, for example, in US patents 3,975,487, 4,118,372 and 4,161,470. Liquid crystal copolyester fibers are available under the designation Vectran® fibers from Kuraray America Inc.

Suitable polybenzazole fibers for practicing the invention are described, for example, in US patents 5,286,833, 5,296,185, 5,356,584, 5,534,205 and 6,060,050. Polybenzazole fibers are available under the designation Zylon® fibers from Toyobo Co.

Rigid rod fibers are, for example, described in US patents 5,674,969, 5,939,553, 5,945,537 and 6,040,478. Such fibers are available under the designation M5<®>fibers from Magellan Systems International.

When two or more types of high tenacity fibers are used in the rope or rope of the invention, preferably one type of high tenacity fibers is a polyolefin fiber, more particularly a polyethylene fiber. The percentage of high tenacity polyethylene fibers in these ropes can vary within wide limits, depending on the other type of high tenacity fibers used, and the desired properties of the fibres. The high tenacity polyethylene fibers may comprise from about 20 to about 80% by weight, more preferably from about 30 to about 70% by weight, and most preferably from about 40 to about 60% by weight, based on the total weight of the high tenacity fibers in the rope. For example, such ropes can be formed from about 80 to about 20% by weight high tenacity polyethylene fibers and correspondingly from about 20 to about 80% by weight aramid fibers; more preferably from about 70 to about 30% by weight high tenacity polyethylene fibers and correspondingly from about 30 to about 70% by weight aramid fibers; preferably from about 40 to about 60% by weight high tenacity polyethylene fibers and correspondingly from about 60 to about 40% by weight aramid fibers. In a particularly preferred embodiment, the rope or rope in question comprises from about 70 to 55% by weight of aramid fibers and correspondingly from about 30 to about 45% by weight of high tenacity polyethylene fibers, calculated on the total weight of high tenacity fibers in the rope. In a further embodiment of the invention, all or substantially all of the fibers in the rope are formed from aramid fibers.

When liquid crystal copolyester fibers are used in connection with high tenasity polyethylene fibers, these ropes or ropes can be formed with from about 80 to about 20% by weight of high tenasity polyethylene fibers and correspondingly from about 20 to about 80% by weight of liquid crystal copolyester fibers; more particularly from about 70 to about 30% by weight of high tenacity polyethylene fibers and correspondingly from about 30 to about 70% by weight of liquid crystal copolyester fibers; most preferably from about 40 to about 60% by weight high density polyethylene fibers and correspondingly from about 60 to about 40% by weight liquid crystal copolyester fibers. In a particular and preferred embodiment, the rope or rope comprises from about 70 to 55% by weight liquid crystal copolyester fibers and correspondingly from about 30 to about 45% by weight high tenacity polyethylene fibers, calculated on the total weight of the high tenacity fibers in the rope. In another embodiment according to the invention, all or substantially all fibers in the rope are formed from liquid crystal copolyester fibers.

If desired, other types of fibers can be used in addition to the high tenacity fibers as mentioned above. Another type of fibers that can be present in the rope or rope construction according to the invention together with the high tenacity fibers are the fibers formed from fluoropolymers. Such fluoropolymer fibers include fibers formed, for example, from polytetrafluoroethylene (especially expanded polytetrafluoroethylene), polychlorotrifluoroethylene (both homopolymers and copolymers (including terpolymers)), polyvinyl fluoride, polyvinylidene fluoride, ethylene tetrafluoroethylene copolymers, ethylene-chlorotrifluoroethylene copolymers, fluorinated ethylene propylene copolymers, perfluoroalkoxypolymer and the like, as well as mixtures of two or more of these. Particularly preferred fluoropolymer fibers are those formed from polytetrafluoroethylene, and especially expanded polytetrafluoroethylene fibers. Such fibers are available, for example, from Lenzing Plasctics GmbH & Co. KG and WL Gore & Associates.

The proportion of fluoropolymer fibers mixed with the high tenacity fibers can vary widely depending on the type of fluoropolymer and on the end use. For example, the amount of fluoropolymer fibers in the blend may be from about 1 to about 40% by weight, more particularly from about 5 to about 25% by weight, preferably from about 10 to about 20% by weight, based on the total weight of the blended fibers . accordingly, the amount of high tenacity fibers can be from about 60 to about 99% by weight, preferably from about 75 to about 95% by weight, and most preferably from about 80 to about 90% by weight, based on the total weight of the blended fibers.

The different types of fibers which can be used in rope or rope according to the invention can be mixed in any suitable way. For example, strands of one type of fiber can be twisted with strands of another type of fiber to produce a combined strand which is then braided into a rope or rope. Alternatively, the fibers can be combined as a bicomponent fiber with a sheath and a core. Other constructions can also be used. The different types of fibers can be present at any desired location in the rope or rope.

The ropes or ropes according to the invention preferably comprise mixtures of two or more high tenacity fibres, or essentially consist of mixtures of two or more high tenacity fibres, optionally with fluoropolymer fibres. These ropes or ropes may be of any suitable construction such as braided, twisted, cabled, parallel core or similar ropes or ropes. Preferably, the rope or rope is of the braided type. These may have any suitable diameter and may be formed in any suitable manner from the desired fibers and/or yarns. When forming a braided rope or rope, for example, a conventional braiding machine can be used which has a number of yarn spools. As known in the art, these spools move around, the yarns are woven over and under each other and finally collected on a take-up spool. Details of the braiding machine and the formation of rope or rope from these are well known in the art and are therefore not to be discussed here.

Yarn from one type of high tenacity fibers can be formed into an under rope which is then converted into a rope (for example by braiding) with an under rope formed from yarn from another type of high tenacity fibres. Alternatively, an under rope can be formed from mixtures of the high tenacity fibers and such an under rope can be converted into a rope or rope by using other such under ropes of different types, by braiding or any other desired technique.

The high tenacity yarns that make up the rope or rope may be of any suitable denier, and the yarns of the fluoropolymer fiber may be of the same or a different denier than the yarns of the high tenacity fibers. For example, the high tenacity yarns may have a denier of about 50 to about 5000, more particularly from about 75 to about 2000 denier, most preferably from about 200 to about 2000, and most particularly from about 650 to about 1500 denier.

The fluoropolymer yarns may have a denier from about 50 to about 2500, and more particularly from about 400 to about 1600.

According to the invention, a special coating mixture is applied to the rope or rope structure. Either the individual fibers or yarns, mixtures of fibers or yarns, are coated with the coating mixture, after which a rope or rope is formed from the coated fibers or yarn, or this is formed first and then coated with the coating mixture. The coating mixture comprises a functional amino silicone resin and a neutralized low molecular weight polyethylene. The two components may be mixed in any ratio such as from about 1:99% by weight between neutralized low molecular weight polyethylene and a corresponding amount of the functional aminosilion resin. All percentages are by weight of the total weight of the coating composition, unless otherwise stated. Preferably, the neutralized low molecular weight polyethylene is present in an amount of from about 30 to about 90% by weight, with the functional amino silicone resin correspondingly present in an amount of from about 10 to about 70% by weight. More particularly, the neutralized low molecular weight polyethylene is the major component of the coating, for example as from about 55 to about 85% by weight of the coating composition, wherein the aminosilicon functional resin is present in an amount from about 15 to about 45% by weight. The mixture may contain a number of other additives, depending on the desired end properties.

Because some high tenacity fibers such as high modulus polyolefin fibers usually have a spin finish applied when they are formed, according to the invention the coating composition used herein is sometimes referred to as a top finish composition.

The functional amino silicone is preferably in the form of an emulsion. Preferably, the emulsion comprises from about 20 to about 40% by weight silicone resin and has a pH value in the range of about 4.5 to about 6.5. The emulsion preferably includes a non-ionic emulsifier.

In the same way, the neutralized low molecular weight polyethylene is in the form of an emulsion. Preferably, the polyethylene is fully neutralized. The low molecular weight polyethylene is also known as polyethylene wax and is also sometimes called wax dispersions. As is well known in the art, these polyethylene waxes, also called resins, generally have a molecular weight of less than about 6000 Daltons, more particularly less than 5000 Daltons, even below 3500 Daltons, and should conveniently and most preferably lie between about 300 and about 3000 Daltons .

The coating components may be mixed in any suitable manner. For example, the functional amino silicone emulsion can be added to the neutralized low molecular weight polyethylene in a stainless steel container or other inert container. The container is preferably equipped with an agitator for suitable mixing under low shear influence (laminar flow). By adding the functional amino silicone emulsion to the neutralized, low molecular weight polyethylene, it is achieved that the pH value in the system remains on the basic side. Alternatively, the low molecular weight polyethylene can be added to the functional amino silicone emulsion. The mixing can be carried out at any suitable temperature and in particular between about 15 and about 45°C, more particularly between about 20 and about 30°C. It is preferred that the coating mixture has a relatively high solids content, for example in the order of around 25% by weight and most preferably at least around 30% by weight.

In particular, the solids content of the coating composition is from about 33 to about 35% by weight. It has been found that the use of high solids coating emulsions allows higher uptake of the coating mixture on the fiber/yarn or rope.

If the composition is coated directly on the fiber or yarn, any suitable coating device can be used. Examples of such coating equipment include various types of rollers, rollers, dip baths and end applicators. A constant temperature is desired to provide uniform application and superior performance when the viscosity of the system is affected by temperature differences. If the composition is brought onto the rope or rope, this can then be dipped into a bath containing the coating mixture, more excess coating mixture squeezed out after air drying, or the rope or rope can be coated and then passed through a heating device to accelerate drying followed by air drying.

It is desirable to have a relatively high final absorption of the coating solids on the fibre/yarn or rope/rope product. Preferably, the final uptake is at least about 0.5% by weight, more preferably at least about 5% by weight, and most preferably about 10 to about 30% by weight.

All parts are listed by weight unless otherwise stated.

EXAMPLES

Example 1

A braided rope was formed from high tenacity polyethylene yarn and from liquid crystal copolyester yarn.

The polyethylene yarn used was a SPECTRA<®>1000 yarn from Honeywell International Inc. with a denier of 1300, a tenacity of 35 g/d and a modulus of 1150 g/d. The liquid crystal copolyester yarn was Vectran<®>HT Type 97 yarn from Kuraray America Inc, with a denier of 1500, a tenacity of about 25 g/d and a modulus of about 600 g/d. The yarns were coated with an overfinish compound.

The overfinish compound was prepared from a functional amino silicone resin and a neutralized low molecular weight polyethylene. The functional amino silicone resin was an emulsion with a silicone content of 35% by weight, a pH of 4.5-6.5 and included a nonionic emulsifier, available from Dow Corning (2-8818 emulsion). The neutralized low molecular weight polyethylene was a neutralized, non-ionic polyethylene wax emulsion (Fluftone<®>1566 from Apollo Chemical), with a solids content between 29% and 31%, and pH value in the range between 9.0 and 11.

The coating composition was prepared by mixing the neutralized low molecular weight polyethylene into the functional aminosilicon resin emulsion, the resulting mixture comprising 70% by weight of the neutralized low molecular weight polyethylene. The yarn was coated by dipping the fibers in the top finish mixture at room temperature. The absorption amount of the coating on the yarn was around 15%.

The coated yarn was braided into a 12-element rope with an approximate diameter of 5 mm diameter. The yarn was braided into a rope by first twisting three coated yarns together into a strand with 0.5 turns per 2.5 cm. It was then twisted further in the "S" direction and the "Z" direction. Twelve strings were then loaded onto a 12-string braid in the alternating mode (S, Z, S, Z etc.). Three strands were then braided together to form a 12-strand braided rope or rope. This consisted of about 63% by weight of polyethylene fibers and about 37% by weight of liquid crystal polyester fibers.

The rope or rope was tested for cyclic bending over pulleys and blocks (CBOS). In this test, the ropes were bent around 180 degrees over a freely rotating block or pulley. The ropes are placed under load and circulated over the block until breaking. The test was run with a D.d ratio of 10 over a 3.3 cm waist at 75 cycles per minute with a 100 kg load on the block (50 kg on each side of the rope). The number of cycles was determined based on an average of 5 positions before failure. The results are shown in table 1.

Example 2 (comparison)

As a control for Example 1, a braided rope was formed in the same manner, but no top finish compound was used. This rope or rope was also tested for its CBOS resistance and the results are shown in Table 1.

TABLE 1

*comparison

The data shown in table 1 show that ropes or ropes formed from mixtures of high tenacity polyethylene fibers and liquid crystal copolyester fibers which are coated with coating mixtures according to the invention have a significantly higher CBOS fatigue resistance.

Example 3

Example 1 is repeated except that the rope is formed from 40% by weight high tenacity polyethylene fibers and 60% by weight liquid crystal copolyester fibers, and has a diameter of around 40 mm. Corresponding results are noted.

Example 4

Example 1 is repeated except that the rope is formed from 40% by weight high tenacity polyethylene fibers and 60% by weight aramid fibers, and has a diameter of around 40 mm. Corresponding results are noted.

Example 5

Example 1 is repeated except that the rope or rope is formed from uncoated yarns and after manufacture is coated with the top finish compounds by dipping the rope in the top finish compound at room temperature. Corresponding results are noted.

It can be seen that the present invention provides ropes that have significantly improved CBOS fatigue resistance. As a result, these products can be used in many demanding applications including such marine applications as lifting and lowering heavy objects from the seabed.

Claims (32)

Patent claims 1. Rope with improved fatigue resistance by cyclic bending over blocks or pulleys (CBOS), said rope comprises high tenacity fibres, the rope and/or the fibers being coated with a coating mixture, characterized in that the coating mixture comprises a functional amino silicone resin and a neutralized low molecular weight polyethylene. 2. Rope according to claim 1, characterized in that the high tenacity fibers are selected from the group consisting of high molecular weight polyolefins, aramid, polyvinyl alcohol, polyacrylonitrile, polybenzazole, polyamide, polyester, liquid crystal polyester, glass, carbon, basalt or mineral fibers and rigid rod fibers, and mixtures thereof. 3. Rope according to claim 1, characterized in that the high tenacity fibers are selected from the group of high molecular weight polyethylene fibers, aramid fibers, liquid crystal copolyester fibers, and mixtures thereof. 4. Rope according to claim 1, characterized in that the high tenacity fibers comprise a mixture of high tenacity polyethylene fibers and other high tenacity fibers that are not polyolefin fibers, said other fibers being aramid fibers and/or liquid crystal copolyester fibers. 5. Rope according to claim 4, characterized in that the high tenacity polyethylene fibers are present in an amount ranging from about 40 to about 60% by weight, and that other fibers are present in an amount from about 60 to about 40% by weight, calculated on the total weight of the high tenacity fibers in the rope. 6. Rope according to claim 4, characterized in that said high tenacity fibers comprise a mixture of high tenacity polyethylene fibers and aramid fibers. 7. Rope according to claim 4, characterized in that high tenacity fibers comprise a mixture of high tenacity polyethylene fibers and liquid crystal copolyester fibers. 8. Rope according to claim 4, characterized in that the coating mixture is present on the rope in an amount of at least around 5% by weight of the solids, calculated on the weight of the rope. 9. Rope according to claim 4, characterized in that said neutralized low molecular weight polyethylene comprises from 55 to 85% by weight of the coating mixture. 10. Rope according to claim 4, characterized in that the neutralized low molecular weight polyethylene is present in an amount from about 55 to about 85% by weight, calculated on the total weight of the coating mixture. 11. Rope according to claim 10, characterized in that the neutralized low molecular weight polyethylene is completely neutralized. 12. Rope according to claim 4, characterized in that it further comprises fluoropolymer fibres. 13. Rope according to claim 4, characterized in that the rope is a braided rope. 14. Rope according to claim 1, characterized in that the high tenacity fibers have a tenacity of at least around 16 g/d. 15. Rope according to claim 1, characterized in that the high tenacity fibers essentially consist of aramid fibers. 16. Rope according to claim 1, characterized in that it comprises a mixture of high tenacity polyethylene fibers with other high tenacity fibers that are not polyolefin fibers. 17. Rope according to claim 16, characterized in that said other high tenacity fibers which are not polyolefin fibers comprise aramid fibers and/or liquid crystal copolyester fibers. 18. Rope according to claim 17, characterized in that said high tenacity polyethylene fibers are high tenacity polyethylene fibers that are present in an amount from about 40 to about 60% by weight and that said other high tenacity fibers that are not polyolefin fibers comprise aramid fibers that are present in an amount from about 60 to about 40% by weight, calculated on the total weight of high tenacity fibers in the rope. 19. Rope according to claim 18, characterized in that said low molecular weight polyethylene is present in an amount from about 55 to about 85% by weight, calculated on the total weight of the coating mixture, where said low molecular weight polyethylene is completely neutralized. 20. Rope according to claim 1, characterized in that it comprises a mixture of high tenacity polyethylene fibers with other high tenacity fibres, said other high tenacity fibers comprising aramid fibers and/or liquid crystal copolyester fibres. 21. Rope according to claim 20, characterized in that said low molecular weight polyethylene is present in an amount from about 55 to about 85% by weight, calculated on the total weight of the coating mixture, and where said low molecular weight polyethylene is completely neutralized. 22. Method for improving the cyclic bend over block (CBOS) fatigue life of a rope, the method comprising forming said rope from high tenacity fibers and coating the rope and/or the fibers comprising the rope with a coating composition, characterized in that it comprises coating with a coating composition comprising a functional amino silicone resin and a neutralized low molecular weight polyethylene. 23. Method according to claim 22, characterized in that the high tenacity fibers comprise a mixture of high tenacity polyethylene fibers with other high tenacity fibres, where the other high tenacity fibers comprise aramid fibers and/or liquid crystal copolyester fibres. 24. Method according to claim 23, characterized in that it comprises coating the rope with said coating mixture, where said neutralized low molecular weight polyethylene is present in an amount from about 55 to about 85% by weight, calculated on the total weight of said coating mixture, and where said low molecular weight polyethylene is completely neutralized. 25. Method according to claim 24, characterized in that the coating mixture has a solids content of at least around 25% by weight. 26. Method according to claim 25, characterized in that said functional aminosilicone resin is in the form of an emulsion with a pH value from around 9 to around 11. 27. Method according to claim 23, characterized in that it includes coating the fibers with said coating mixture, where said low molecular weight polyethylene is present in an amount from about 55 to about 85% by weight, calculated on the total weight of said coating mixture, and where said low molecular weight polyethylene is completely neutralized. 28. Use of a synthetic fiber rope in a method for lifting or placing heavy objects from and on the seabed comprising using, as said rope, a rope comprising high tenacity fibres, the rope and/or the fibers being coated with a coating mixture comprising a functional amino silicone resin and a neutralized low molecular weight polyethylene. 29. Use of a synthetic fiber rope as claimed in claim 28, where the rope or rope comprises a mixture of high tenacity polyethylene fibers and aramid fibers. 30. Use of a synthetic fiber rope as claimed in claim 28, where the rope comprises a mixture of high tenacity polyethylene fibers and liquid crystal copolyester fibers. 31. Method according to claim 22, characterized in that the coating mixture is present on the rope in an amount of at least around 5% by weight of the solids, calculated on the weight of the rope. 32. Use of a synthetic fiber rope as claimed in claim 28, wherein the coating mixture is present on the rope in an amount of at least about 5% by weight of the solids, calculated on the weight of the rope.