WO1992022701A1

WO1992022701A1 - Roping

Info

Publication number: WO1992022701A1
Application number: PCT/NL1992/000102
Authority: WO
Inventors: Louis François Emile HOPPE; Christian Henri Peter Dirks
Original assignee: Dsm N.V.
Priority date: 1991-06-11
Filing date: 1992-06-11
Publication date: 1992-12-23
Also published as: NL9101006A

Abstract

High strength roping comprising construction elements selected from the group consisting of strands, cable yarns, doubled yarns, complex yarns or yarns, which roping or construction elements or both have a core part (1, 3, 5) and an outer part (2, 4, 6) surrounding the core (1, 3, 5) wherein at least one core part (1, 3, 5) comprises filaments having a higher elongation at break than the filaments in the corresponding outer part (2, 4, 6). The roping has a higher tensile strength than the known roping at the same weight.

Description

ROPING

BACKGROUND OF THE INVENTION The present invention relates to high strength roping comprising filaments having a high tensile strength and a high modulus.

Such roping, comprising high strength polyalkene filaments, is known from EP-A-398434".

SUMMARY OF THE INVENTION The object of the present invention is to provide roping of higher strength than the known roping, without increasing the weight of the roping. Alternatively, another object of the present invention is to provide roping of a lower weight and comparable strength relative to the known roping.

The present invention provides such a high strengt roping comprising construction elements selected from the group consisting of strands, cable yarns, doubled yarns, complex yarns or yarns, which roping or construction ele- ments or both have a core part and an outer part surroundin the core wherein at least one core part comprises filaments having a higher elongation at break than the filaments in the corresponding outer part.

Further, the roping according to the present inven tion heats up less quickly than the known roping under a fluctuating load, so that the life of the roping according to the present invention is prolonged considerably.

In addition, the internal wear of the roping accor ding to the present invention is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS An exemplarly embodiment of rope construction is shown, both in cross-section view (Figure 1) and in side view (Figure 2). The drawing shows a roping comprising 7 strands being one core strand (1) and 6 strands surroundin the core of the roping (2). The core strand of the roping (1) comprises 5 cable yarns, being one core cable yarn (3) and 4 outer cable yarns (4) . The strands (2) surrounding t core (1) of the roping comprise 7 cable yarns, being one core cable yarn (5) and 6 covering cable yarns (6). No fur¬ ther detail is given in the drawing, but, as will be explai ned, the cable yarns can again be constructed from doubled yarns, complex yarns or yarns. The core of at least one con struction element may comprise filaments having a higher elongation at break.

DETAILLED DESCRIPTION OF THE INVENTION The construction elements of the roping, as used i the present application, are, in order of descending con- struction complexity, the roping itself, a strand, a cable yarn, a complex yarn, a doubled yarn or a yarn.

The filaments in the yarn can, according to the in vention, be of any material. Preferably however a polymer material is selected. Polymer materials that can be used ar polyacrylonitrile, polyvinylalcohol, polyalkenes, polyes¬ ters, polyamides, polyaramids or any other material that ca be used in ropings.

As polymer filaments particularly high strength filaments are prefered. Preferably these high strength poly er filaments are produced by a gel-spinning process. Pre¬ ferred material for gel-spun filaments are polyacryloni¬ trile, polyvinylalcohol, or polyalkenes. More preferably th material for gel-spun filaments are polyalkenes. The most preferred material for gel-spun filaments is polyethylene, preferably of a ultra high molecular weight.

As a non-limiting example, the process of manufac¬ ture of polyalkene filaments can consist of pressing a melt or a solution of the polyalkene through a spinneret with a large number of perforations, cooling and drawing the resul- ting bundle of more or less parallel filaments, and finally removing any remaining solvent that is present. In general, the filaments obtained from one or more spinnerets are bund¬ led to form a yarn. This yarn can be formed, for instance, by giving the bundle a few twists per meter.

The construction elements of the roping may cora- prise filaments of different polymer materials having diffe¬ rent elongation at break. Preferably however the filaments having the lower elongation at break and the filaments ha¬ ving the higher elongation at break are of essentially the same polymer material. Filaments of the same material with a different elongation at break preferably are obtained by drawing filaments produced in the same process to a diffe¬ rent degree.

The further the filaments are drawn in the manu¬ facturing process, the greater the strength and stiffness of the filaments which is achieved. Also the orientation of the molecules in the filaments will increase and the elongation at break of the filaments will decrease at drawing.

It is most surprising that the tensile strength of a rope can be increased, according to the invention, by in- corporating filaments that have a higher elongation at break and thus have a lower tensile strength.

Preferably the filaments having the lower elonga¬ tion at break are maximally drawn to have a high tensile strength and a high modulus of elasticity. Most preferably, as filaments having the lower elongation at break, polyal¬ kene filaments are used having a tensile strength of at least 1.5 GPa and a modulus of elasticity of at least 40 GPa.

The filaments cannot be drawn unlimitedly, however, because the breaking of one or more filaments in the bundle occurs with increasing frequency in the manufacturing pro¬ cess as the filaments are drawn further. When a filament breaks, the manufacturing process has to be stopped. The degree of drawing at which the breaking of a certain per- centage of the filaments occurs can be determined experimen tally. If the breaking of the filaments occurs with such a frequency that the manufacturing process has to interrupted it becomes unacceptable. The maximum degree of drawing strongly depends on the type of process, the process condi¬ tions, economic factors and most important on the type of polyalkene used. The filaments obtained which have been drawn to the limit of acceptable levels of filament breakin are considered to be drawn maximally. Filaments drawn to a lesser degree are those filaments which are drawn less than the maximally drawn filaments. The construction elements of the roping, as used i the present application, are, in order of descending con¬ struction complexity, the roping itself, a strand, a cable yarn, a complex yarn, a doubled yarn or a yarn. Two or more yarns can be combined to form complex yarns by twisting and/or twining the yarns. If two yarns are combined by twis¬ ting them, 'doubled yarn' is obtained. A cable yarn can be composed by combining yarns, complex yarns, doubled yarns or combinations thereof, for example by twisting or twining. A strand can be composed by combining cable yarns, complex yarns, doubled yarns, yarns or combinations thereof, for example by twisting, twining or laying up.

By using the known techniques, such as twisting, twining, plaiting and/or laying up, a roping can be manufac¬ tured from the strands, the cable yarns, the yarns, the com- plex yarns and/or the doubled yarns. The roping according to the invention can also be braided or have a braided surroun- dingpart.

The roping of the present invention can have nume¬ rous construction modes. Prefered rope constructions are plaited ropes, 7-strand laid ropes having one core strand and 6 surrounding strands, 9-strand laid ropes having one core strand and 8 surrounding strands, and 19-strand ropes having one core strand surrounded by 6 strands which are again surrounded by 12 strands. In the present invention, the less drawn filaments are disposed in the core of at least one construction element. The core structure of a construction element, like a roping, a strand or a cable yarn can be formed for exampl by twisting, twining or laying up a number of less complex construction elements around an essentially longitudonal core construction element.

A roping may be composed of strands, the roping be ing provided or not provided with a core. The core in itsel can comprise one of the strands of the roping. The core can also comprise an arbitrarily shaped other strand or bundle of yarns. The core can in principle also comprise any type of natural, synthetic or inorganic firbers or filaments. As a non-limiting example, the core of the roping can comprise the polyalkene filaments.

In this way a roping of optimum strenght is ob- tained, in spite of and because of the fact that the fila¬ ments in the core of at least one construction element of the roping have a higher elongation at break than the fila¬ ments in the corresponding surrounding part.

A very suitable roping according to the present in vention is obtained if the core of the roping itself compri ses the filaments having a higher elongation at break than the filaments in the corresponding surrounding part.

An even better roping according to the present in¬ vention is obtained if the cores of individual strands of the roping comprise filaments having a higher elongation at break than the filaments in the corresponding surrounding part. For example, good results are obtained if the cable yarn constituting the core of each strand comprises fila¬ ments having a higher elongation at break. A still more suitable rope is obtained if the core of each cable yarn itself comprise filaments having a highe elongation at break.

The present invention has a great number of embodi ments. For instance, to roping can comprise a core compri- sing filaments having a higher elongation at break, while additionally the cores of individual strands of the roping can comprise filaments having a higher elongation at break. The elongation at break of the filaments in the core of the roping can then be equal to or different from the elongatio at break of the filaments in the cores of the individual strands. Preferably the filaments in the core of a construc tion element, as for example the roping, have a higher elon gation at break than the filaments in the core of the con¬ stituting construction element of a lower complexity, as fo example the strands, surrounding the core of said construc- tion element. Accordingly it is preferred that the filament in the core of strands have a higher elongation at break than the filaments in the core of the cable yarns constitu¬ ting the strands.

The optimum value of the elongation at break of th filaments in the core of a structural element in order to obtain a good result depends on the structural parameters o the rope. For instance, the thicknesses of the rope, the strands and the cable yarns are relevant, as well as the number of strands in the roping, the number of cable yarns in the strands and the number of yarns in the cable yarns, and also the number of twists or turns in the roping, the strands, the cable yarns, the complex yarns and the yarns.

In general it is seen that better results, that is higher strength of the roping, are obtained in proportion as filaments in the core of a construction element have a hig¬ her elongation at break in comparison to the other filaments in the construction element. On the other hand, the strength of the roping decreases again when the filaments in the core of a construction element have a too high elongation at break.

Good results are obtained from a roping, comprising a core and construction elements surrounding the core, wherein the construction elements in the core of the roping comprise filaments having an elongation at break of 4% to 8%, and the construction elements surrounding the core of the roping comprise filaments having an elongation at brea of 3% to 6%.

In another embodiment good results are obtained from roping, wherein the construction elements have a core and an outer part surrounding the core wherein the core comprises filaments having an elongation at break of 4% to 6% and the outer part comprises filaments having an elonga tion at break of 3% to 5%.

According to the invention the elongation at brea of the filaments has to be chosen from these ranges such that the filaments in the core part have a higher elongati at break than the filaments in the outer part.

According to the invention several filaments havi two or more different levels of elongation at break can be used in the different cores of the construction elements constituting the rope, as long as the elongation at break the filaments in the construction elements essentially de¬ creases from the centre of the roping to the outside of th roping.

The optimum value depends on, among others, the above mentioned structural parameters, such as, but not limited to the thickness of the rope and the smaller the number of yarns, and the number of twists or turns in the yarn.

The weight percentage of the filaments in the ro- ping having the highest, preferably maximum, tensile strength and accordingly the lowest elongation at break ca vary within a wide range, depending on the above mentioned construction parameters and the elongation at break of the other filaments. The weight percentage is calculated as the fraction of the total weight of filaments of the material having lowest and higher elongation at break. Preferably the weight percentage is 30% to 95%, more preferably 40% to 80%.

The polyalkene filaments are preferably produced means of a gel spinning process such as described in US-4344908 and US-4422993/US-4430383. This process compris preparing a solution of the polyalkene, which preferably h a weightaverage molecular weight of at least 600,000 g/mol, processing the solution to filaments at a temperature above the dissolution temperature, cooling the filaments to belo the dissolution temperature so that gelation takes place, removing the solvent partially or completely, and drawing the gelated filaments while any remaining solvent is removed.

The term 'filaments' means bodies which are long relative to their thickness and width.

The polyalkene filaments are preferably made from linear polyalkene, more preferably from linear polyethene.

By 'linear polyethene' is meant polyethene with less than one side chain per hundred carbon atoms, prefer- ably with less than one side chain per three hundred carbon atoms, and which moreover may contain up to 5 mol% of one o more other alkenes that are copolymerizable with it, such a propene, butene, pentene, 4-methylpentene, and octene.

Other polyalkenes are also suitable, such as for instance propene homopolymers and propene copolymers.

Further, the polyalkenes applied may contain minor quantities of one or more other polymers, in particular 1-alkene polymers.

The strength of the roping of the present inventio can be further improved by stretching the roping, preferabl at an elevated temperature. On stretching the filaments in the core of the construction element remain less drawn than the other filaments of the construction element.

EXAMPLES

The present invention will be further elucidated by means of the examples, without being restricted thereto. Comparative Experiment On an arbitrary rope-laying machine a rope was ma of Dyneema R SK 60, supplied by DSM-HPF (Netherlands). Dyneema R SK 60 is a 1600 denier polyethene yarn with a te sile strength of 2.7 GPa, and an elongation at break of 3.5%. This yarn is produced by the gel-spinning process an is maximally drawn.

The rope contained seven strands, the outer layer of the rope containing six strands, which strands were lai around the core of the rope with a twist length of 48 mm, which core consisted of one strand extending in the longit dinal direction op the rope.

The strands in the outer layer of the rope contai ned sixteen yarns each, the outer layer of each strand con taining thirteen of the 1600 denier Dyneema R SK 60 yarns, and the core of teh strand containing three doubled Dyneem R SK 60 yarns of 3200 denier each.

The strand in the core of the rope contained elev yarns. The outer layer of the strand contained nine double Dyneema R SK 60 yarns and the core of the strand contained two of the doubled yarns. The weight of the rope was 26.9 g/m. The strength of the rope and the elongation at break was measured on a Zwick R 1474 tensile tester in accordance with DIN 83305. The rate of drawing was 100 mm/min. The tensile strength o the rope was 31.0 kN.

Example I

A rope was laid as described in the comparative experiment, but with in each of the six strands contained the outer layer of the rope, each of the doubled yarns in the cores of the strands had been replaced by a polyethene yarn that had been manufactured by the same process as the polyethene yarn of the comparative experiment, but which yarn had been drawn to 0.40 times the maximum degree of dr wing (hereafter refered to as 0.40 times drawn yarn). The titer of the 0.40 times drawn yarn was 3700 denier.

The tensile strength of the 0.40 times drawn yarn was 1.3 GPa, the elongation at break was 5.1%.

The weight of the rope was 26.9 g/m, of which 18. g/m was contributed by Dyneema R SK 60.

The tensile strength of the rope was 34.9 kN.

Example II

A rope was laid as described in example I, but wi the strand constituting the core of the rope containing ni yarns drawn to a lesser degree. In the outer layer each of the six strands contained eight of the 0.40 times drawn yarns of 3700 denier, having the elongation at break of 5.1%. In the core the strand contained one 0.25 times draw yarn of 5900 denier.

The tensile strength of the 0.25 times drawn yarn was 0.83 GPa, the elongation at break was 7.3%.

The weight of the rope was 27.1 g/m, of which 14.7 g/m was contributed by Dyneema R SK 60.

The tensile strength of the rope was 38.9 kN. It is surprising that the ropes according to examp les I and II are noticeably stronger than the rope accordin to the comparative experiment, in spite of the presence of the great amount of filaments having a higher elongation at break and thus a lower strength in both ropes.

Claims

CLAIMS What is claimed is: 1. Roping comprising construction elements selected from the group consisting of strands, cable yarns, doubled yarns, complex yarns or yarns, which roping or construc tion elements or both have a core part and an outer par surrounding the core wherein at least one core part com prises filaments having a higher elongation at break than the filaments in the corresponding outer part.

2. Roping according to claim 1, wherein the filaments are polymer filaments.

3. Roping according to claim 2, wherein the polymer fila- ments are polyalkene filaments.

4. Roping according to claim 2, wherein the filaments are obtained by a gel-spinning proces.

5. Roping according to claim 2, comprising a core and con¬ struction elements surrounding the core, wherein the construction elements in the core of the roping compris filaments having an elongation at break of 4% to 8%, an the construction elements surrounding the core of the roping comprise filaments having an elongation at break of 3% to 6%.

6. Roping according to claim 2, wherein the construction elements have a core and an outer part surrounding the core wherein the core comprises filaments having an elongation at break of 4% to 6% and the outer part com¬ prises filaments having an elongation at break of 3% to 5%.

7. Roping according to claim 2, wherein the filaments are of essentially the same polymer material.

8. Roping according to claim 7, wherein the filaments ha¬ ving a lower elongation at break and the filaments ha- ving a higher elongation at break have been produced in the same process in which the filaments having a high elongation at break have been drawn to a lesser degree.

9. Roping according to claim 1, wherein the weight percen¬ tage of the filaments having the lowest elongation at break, calculated as the fraction of the total weight filaments is 30% to 95%.

10. Roping according to claim 1 , wherein the weight percen tage of the filaments having the lowest elongation at break is 40% to 80%.