HK1151325B - Process for spinning uhmwpe, uhmwpe multifilament yarns produced thereof and products comprising said yarns - Google Patents

Description

Method for spinning UHMWPE, UHMWPE multifilament yarns made therefrom and products comprising the yarns

The present invention relates to a process for producing Ultra High Molecular Weight Polyethylene (UHMWPE) multifilament yarns having a high tensile strength and comprising ultra low decitex (dtex) filaments and to UHMWPE multifilament yarns made by the above process. The invention also relates to products comprising the yarn.

A gel spinning process for producing UHMWPE multifilament yarns with high tensile strength is known, for example, from EP 1,699,954. The method disclosed in this patent document comprises the steps of:

a) preparing a solution of UHMWPE in a solvent;

b) spinning the solution of step a) through a spinneret into an air gap, thereby forming fluid filaments, the spinneret comprising a plurality of spinning orifices, wherein each spinning orifice comprises at least one region of decreasing diameter, and the downstream diameter of the spinning orifice from which the solution exits into the air gap is between 0.1 and 1.5 mm;

c) at fluid draw ratio DR_fluid＝DR_sp×DR_agDrawing the fluid filament, wherein_spAnd DR_agThe draw ratios in the spinneret orifice and in the air gap, respectively;

d) cooling the fluid filament, thereby forming a solvent-containing gel filament; and

e) at least partially removing residual solvent from the gel filaments to form solid filaments, thereafter, simultaneously or previously at a draw ratio DR of at least 4_solidStretching the solid filaments.

The UHMWPE multifilament yarns produced therefrom have a tensile strength of up to 5GPa, however the yarns contain rather thick filaments in the range of 1 dtex.

The gel spinning process known for example from chinese patent 1,400,342(CN1,400,342) produces UHMWPE multifilament yarns with high strength, but which contain relatively fine filaments. This publication discloses a melt spinning toolProcesses and gel spinning processes. For the gel spinning process, the molecular weight is between 1X 10⁶And 6X 10⁶Between g/mol of a 4 to 15 wt% solution of UHMWPE is spun through a spinneret plate having spinneret holes with a diameter of 0.6-1mm, thereby forming fluid filaments. The fluid filaments were drawn according to their example 1 with a draw ratio of maximum 35. The highest total draw ratio achieved for the gel spun filament was about 390. According to the cited publication, for a high concentration of UHMWPE solution (i.e. about 15 wt%), a low draw ratio should be applied to prevent filament breakage; for dilute UHMWPE solutions (i.e. about 4 wt%), the fluid draw ratio can be increased, the maximum value achieved being 35, i.e. according to example 1, a 7 wt% UHMWPE concentrated solution is used. By further drawing beyond the disclosed limits according to CN1,400,342, UHMWPE filaments with a "moderate macromolecular entanglement" structure could not be obtained. Absent moderate entanglement, the resulting filaments are difficult to draw further, which explains the lower overall draw ratio achieved therein. The resulting UHMWPE multifilament yarn has a tensile strength of up to 4.3GPa and contains filaments of not less than 0.55dtex (0.5 denier).

A gel spinning process for obtaining UHMWPE multifilament yarns, but containing filaments of ultra low dtex, is known from japanese patent publication 2000/226721 (hereinafter JP 2000/226721). The gel spinning process disclosed therein uses spinnerets with orifices having even smaller diameters, in the range of 0.3-0.5 mm. The extruded fluid filaments were drawn to a draw ratio of 50 and after becoming solid filaments were drawn to a total draw ratio of about 200. The resulting UHMWPE filaments have a dtex as low as 0.121. However, the tensile strength of multifilament yarns containing these filaments is rather low, i.e. not higher than 3.2 GPa. Another disadvantage of this method is the reduced productivity, since the amount of UHMWPE solution spun through the orifice is limited by the very small diameter of the orifice.

Therefore, it is not easy for those skilled in the art to obtain a UHMWPE multifilament yarn having a high tensile strength and containing ultra low dtex filaments. However, it is more difficult to design a manufacturing method with good productivity.

The present invention has an object to provide a gel-spun UHMWPE multifilament yarn having a high tensile strength and containing ultra-low dtex filaments, the combination of which is unsatisfactory for any of the existing gel-spun UHMWPE multifilament yarns, and a process for producing the same. It is a further object of the present invention to provide a method as described above with good productivity.

The proposed object is achieved with the following gel spinning process, which has the following characteristics: drawing the fluid filaments at a fluid draw ratio of at least 450 with the proviso that DR_agIs at least 30.

It was surprisingly found that with the process of the invention a new UHMWPE multifilament yarn is obtained, having a tensile strength of at least 3.5GPa and comprising filaments not larger than 0.5 dtex; this combination has not been achieved to date to the knowledge of the present inventors and is therefore unexpected in itself.

It has also been surprisingly found that in the process of the present invention, the amount of spinning breakpoints occurring when spinning ultra-low dtex UHMWPE filaments due to pulling of the filaments at the spinneret is reduced. A low amount of spinning breakpoints has a positive benefit on the productivity of the process.

The UHMWPE solution is preferably prepared in a concentration between 1 and 20 wt%, more preferably between 2 and 15 wt%, even more preferably between 3 and 10 wt%, most preferably between 4 and 8 wt%, wherein the higher the molar concentration of UHMWPE, the lower concentration is preferred.

The UHMWPE preferably has an Intrinsic Viscosity (IV) of at least 3dl/g, preferably at least 5dl/g, more preferably at least 7dl/g, even more preferably at least 9dl/g, most preferably at least 11dl/g, as measured in a solution of decalin at 135 ℃. Preferably, the IV is at most 40dl/g, more preferably at most 30dl/g, even more preferably at most 25dl/g, even more preferably at most 20dl/g, most preferably at most 15 dl/g.

The UHMWPE may be any UHMWPE suitable for gel spinning processes. Preferably, the UHMWPE is a linear polyethylene comprising 1 or less branches per 100 carbon atoms, preferably 1 or less branches per 300 carbon atoms. By branches (also referred to as side chains) are herein understood branches on the main chain of the UHMWPE, said branches preferably containing from 1 to 10 carbon atoms, more preferably containing from 1 to 8 carbon atoms, even more preferably containing from 1 to 6 carbon atoms. The linear polyethylene may further comprise up to 5 mol% of one or more comonomers, such as olefins, for example propylene, butene, pentene, 4-methylpentene or octene; it is also preferred to contain less than 5 wt%, more preferably less than 3 wt% of conventional additives such as antioxidants, heat stabilizers, colorants, flow promoters, and the like.

In a preferred embodiment, the UHMWPE contains at least 0.2, more preferably at least 0.3C 1-C4 alkyl groups per 1000 carbon atoms as side chains. The amount of alkyl groups per 1000 carbon atoms is preferably at most 20, more preferably at most 10, even more preferably at most 5, still even more preferably at most 3, most preferably at most 1.5. The alkyl group is preferably a methyl group or an ethyl group, and more preferably a methyl group. The UHMWPE may be a single polymer grade or may be a mixture of two or more different polyethylene grades, e.g. a mixture of polyethylenes of different IV or molar mass distribution and/or different types and numbers of comonomers or side groups.

To prepare the UHMWPE solution, any of the techniques known in the art and known solvents suitable for gel spinning UHMWPE may be used. Suitable examples of solvents include aliphatic and alicyclic hydrocarbons such as octane, nonane, decane and paraffins, including isomers thereof; a petroleum fraction; mineral oil; diesel oil; aromatic hydrocarbons such as toluene, xylene and naphthalene, including hydrogenated derivatives thereof, such as decalin and decalin; halogenated hydrocarbons such as monochlorobenzene; and cycloalkanes or cycloalkenes such as carene (careen), fluorene, camphene, menthane, dipentene, naphthalene, acenaphthylene (acenaphthalene), methylcyclopentadiene, tricyclodecane, 1, 2, 4, 5-tetramethyl-1, 4-cyclohexadiene, fluorenone, binaphthylamine (naphttindane), tetramethyl-p-benzodiquinone, ethylfluorene (ethylfuran), fluoranthene, and naphthalenone. It is also possible to use a combination of the solvents listed above for gel spinning UHMWPE, wherein the combination of solvents is also referred to as solvent for the sake of simplicity. In a preferred embodiment, the solvent selected is not volatile at room temperature, such as a paraffin oil. We have also found that the process of the present invention is particularly advantageous for solvents that are relatively volatile at room temperature, such as decalin, decalin and kerosene. In a most preferred embodiment, the solvent of choice is decalin.

According to the invention, the UHMWPE solution is formed into fluid filaments by: the solution is spun through a spinneret containing a plurality of spinneret holes. The term "fluid filament" as used herein refers to a fluid-like filament comprising a solution of UHMWPE in a solvent used for preparing said UHMWPE solution, said fluid filament being obtained by extruding the UHMWPE solution through a spinneret, the concentration of UHMWPE in the extruded fluid filament being the same or almost the same as the concentration of the UHMWPE solution before extrusion. By "spinneret comprising a plurality of spinneret holes" is herein understood a spinneret comprising preferably at least 5 spinneret holes, more preferably at least 10 spinneret holes, even more preferably at least 25 spinneret holes, still even more preferably at least 50 spinneret holes, most preferably at least 100 spinneret holes. Preferably, the spinneret comprises at most 3000, more preferably at most 1000, most preferably at most 500 spinneret holes.

Preferably, the spinning temperature is between 150 ℃ and 250 ℃, more preferably it is chosen below the boiling point of the spinning solvent. If, for example, decalin is used as spin solvent, the spinning temperature is preferably at most 180 ℃, more preferably at most 175 ℃, most preferably at most 170 ℃, and preferably at least 115 ℃, more preferably at least 120 ℃, most preferably at least 125 ℃. In the case of paraffin wax, the spinning temperature is preferably below 220 ℃, more preferably between 130 ℃ and 195 ℃.

Preferably, the spinning speed is at least 1m/min, more preferably at least 3m/min, even more preferably at least 5m/min, still even more preferably at least 7m/min, most preferably at least 9 m/min. Preferably, the spinning speed is at most 20m/min, more preferably at most 18m/min, even more preferably at most 16m/min, still even more preferably at most 14m/min, most preferably at most 12 m/min. It was surprisingly observed that the UHMWPE filaments of the invention could be formed, drawn using relatively higher spinning speeds and draw rates compared to known processes for producing ultra-low dtex UHMWPE filaments. This results in an increased production capacity and a shorter production time, and the process of the invention is therefore more economically attractive. "spinning speed" is understood herein to mean: the extruded fluid filaments exiting the spinneret have a velocity in meters per minute (m/min). "draw rate" is herein understood to be the quotient of the draw ratio and the time required to achieve said draw ratio.

According to the invention, the geometry of each orifice comprises at least one zone, called constriction, which is a zone of decreasing diameter. Preferably, the zone of decreasing diameter has a cone angle of at least 10 °, more preferably at least 15 °, more preferably at least 30 °, even more preferably at least 45 °. Preferably, the cone angle is at most 75 °, more preferably at most 70 °, even more preferably at most 65 °. The angle of taper is referred to herein as the maximum angle between tangent lines to the opposing walls in the constricted region. For example, for a conical or tapered constriction region, the taper angle between the tangent lines is constant; whereas for the so-called flare-out region, the taper angle between the tangents decreases with decreasing diameter. For wine glass type constricted areas, the angle between the tangent lines passes through a maximum. As a result of the above-mentioned tapering, the draw ratio DR is achieved in the spinneret orifice_sp。DR_spRepresents: the ratio of the flow rate of the solution at the initial cross-section of the constriction region to the flow rate of the solution at the terminal cross-section of the constriction region corresponds to the ratio of the cross-sectional areas. For example, where the constriction region has the shape of a frustum of a cone, DR_spEqual to the square of the ratio of the initial diameter to the terminal diameter of the constriction region.

The diameter of the orifice is referred to herein as the effective diameter, i.e., the longest distance between the outer boundaries of the orifice for non-circular or irregularly shaped orifices.

Preferably, selectingInitial and terminal cross-sectional areas of the constriction region or their respective diameters such that DR is achieved_spIs at least 5, more preferably at least 10, even more preferably at least 15, still even more preferably at least 20, still even more preferably at least 25, still even more preferably at least 30, still even more preferably at least 35, most preferably at least 40.

Preferably, the spinneret orifice further comprises upstream and/or downstream of the constriction regions, these regions having the same diameter as the cross-sectional diameter of the respective constriction region, said constant diameter region having an aspect ratio of preferably at most 50, more preferably at most 30, even more preferably at most 20, most preferably at most 10. More preferably, the aspect ratio is at least 2, even more preferably at least 4, most preferably at least 5.

Preferably, the diameter downstream of the orifice from which the solution flows into the air gap is between 0.1 and 1.5mm, more preferably between 0.1 and 1.2mm, more preferably between 0.1 and 0.9mm, even more preferably between 0.1 and 0.8mm, yet even more preferably between 0.1 and 0.7mm, yet even more preferably between 0.1 and 0.5mm, yet even more preferably between 0.1 and 0.45mm, most preferably between 0.2 and 0.45 mm.

Fluid filaments formed by spinning a UHMWPE solution through a spinneret are extruded into an air gap and then into a cooling zone, wherein the filaments are wound from the cooling zone onto a first driven roller. By selecting the angular speed of the first driven roller so that the surface speed of said roller exceeds the flow rate of the UHMWPE solution issuing from the spinneret, a draw ratio DR of at least 30 is obtained_agThe fluid filaments are drawn in an air gap. Tensile ratio DR in the air gap_agPreferably at least 40, more preferably at least 50, even more preferably at least 60, most preferably at least 80.

According to the invention, the DR is drawn with a total fluid draw ratio DR of at least 450, preferably at least 475, more preferably at least 500, even more preferably at least 550, still even more preferably at least 600, still yet even more preferably at least 650, still yet even more preferably at least 700, most preferably at least 800_fluid＝DR_sp×DR_agThe fluid filaments are drawn. We have surprisingly found that in the process of the present invention it is possible to apply a higher DR to fluid UHMWPE filaments than has been possible in previous processes for producing ultra-low dtex filaments_fuidWhile the occurring fractures remain at the same level. Furthermore, by increasing DR_fluidFilaments of dtex or even lower can be obtained. Has demonstrated high DR_fluidAlso beneficial to the tensile strength of the filaments.

It has been found that the use of too high a total fluid draw ratio increases filament breakage. Thus, in a preferred embodiment, the overall fluid draw ratio DR is at most 1200, preferably at most 1000, more preferably at most 900, e.g. at most 800_fluid＝DR_sp×DR_agThe fluid filaments are drawn.

In a preferred embodiment, DR_spBetween 5 and 20, more preferably between 5 and 15, while increasing DR_agThereby obtaining a DR of at least 450_fluidThe value is obtained. We have found that these are the optimum values for the draw ratio in order to achieve the advantages of the process of the invention.

The length of the air gap is preferably at least 1mm, more preferably at least 3mm, even more preferably at least 5mm, still even more preferably at least 10mm, still even more preferably at least 15mm, still even more preferably at least 25mm, still even more preferably at least 35mm, still even more preferably at least 40mm, still even more preferably at least 45mm, most preferably at least 55 mm. The length of the air gap is preferably at most 200mm, more preferably at most 175mm, even more preferably at most 150mm, yet even more preferably at most 125mm, yet even more preferably at most 105mm, yet even more preferably at most 95mm, most preferably at most 75 mm.

The fluid filaments leaving the air gap may be cooled (also referred to as quenched), for example in a gas stream and/or in a liquid cooling bath, to form solvent-containing gel filaments. Preferably, the temperature of the fluid filaments is cooled to at most 80 ℃, more preferably at most 60 ℃, most preferably at most 40 ℃, preferably to at least 1 ℃, more preferably at least 5 ℃, even more preferably at least 10 ℃, most preferably at least 15 ℃.

The "air gap" when air cooling is applied refers to the length of travel of the fluid filament before it is converted into a solvent-containing gel filament, or in a liquid cooling bath to the distance between the face of the spinneret and the surface of the cooling liquid.

The term "gel filament" as used herein refers to a filament that, upon cooling, evolves into a continuous UHMWPE network that is swollen by the spinning solvent. The indication that the fluid filaments are converted into gel filaments and form a continuous UHMWPE network may be: the transparency of the filaments changes from translucent UHMWPE filaments to substantially opaque filaments, i.e. gel filaments, upon cooling.

In the process of the invention, the gel filament is subjected to a solvent removal step before, during or after drawing the solid filament, thereby forming a solid filament. The amount of spinning solvent (hereinafter residual solvent) remaining in the solid filaments after the removal step may vary within wide ranges, preferably the amount of residual solvent is at most 15 wt%, more preferably at most 10 wt%, most preferably at most 5 wt% of the initial amount of solvent in the UHMWPE solution. The amount of residual spinning solvent remaining in the solid filaments after the removal step can also be described with respect to the total weight of the yarn comprising UHMWPE and solvent. In this case, the residual solvent is preferably at most 15 wt% of the total weight of the yarn, more preferably at most 10 wt% of the total weight of the yarn, most preferably at most 5 wt% of the total weight of the yarn. The solvent removal step may be carried out by known methods, for example by evaporation when a relatively volatile spinning solvent (e.g. decalin) is used to prepare the UHMWPE solution; when, for example, paraffin is used, it is possible to use extraction liquids; or may be a combination of both. Suitable extraction liquids are liquids which do not cause significant changes to the structure of the UHMWPE gel fibers, preferably those solvents which can be separated and recovered from the extraction liquid.

A draw ratio of at least 4 may be employed in at least one drawing step according to any technique known in the artDR_solidThe solid filaments are drawn. More preferably, DR_solidIs at least 7, even more preferably at least 10, still even more preferably at least 15, still even more preferably at least 20, still even more preferably at least 30, most preferably at least 40. To reduce the risk of filament breakage, the draw ratio DR_solidPreferably at most 150, preferably at most 100, more preferably at most 75, for example at most 50. More preferably, the solid filaments are drawn in at least two steps, even more preferably in at least three steps. Preferably, the individual drawing steps are carried out at different temperatures, which are preferably selected to achieve the desired draw ratio without filament breakage. If the solid filaments are drawn in more than one step, then DR_solidBy calculating as follows: the draw ratio of each solid draw step is multiplied. Drawing the solid filaments is preferably carried out at a temperature of 110 and 170 ℃, more preferably at a temperature of 120 and 160 ℃, most preferably at a temperature of 130 and 155 ℃. The temperature may also have an increasing temperature spectrum, preferably between 120 and 155 ℃.

In a preferred embodiment, after cooling the gel filaments in a liquid cooling bath, said filaments are introduced into an oven set at a temperature preferably between 110 and 145 ℃, more preferably between 130 and 140 ℃, in which oven the solvent is removed by evaporation while the filaments are drawn at a draw ratio of at least 2, more preferably at least 4, most preferably at least 6, as a result of which the solid filaments leave the oven. In this step, the draw ratio is preferably less than 50, more preferably less than 40, still more preferably less than 30, for example less than 15. The solid filaments are then drawn in a second step in a second oven set at a temperature preferably between 140 and 165 ℃, more preferably between 150 and 155 ℃ at a draw ratio of at least 6, more preferably at least 10, most preferably at least 15. In the second step, the draw ratio is preferably less than 50, more preferably less than 40, still more preferably less than 30, for example less than 20.

Optionally, the process of the present invention may further comprise a step of removing residual spinning solvent from the gel-spun UHMWPE filaments of the present invention, preferably after the solid drawing step. In a preferred embodiment, residual spinning solvent remaining in the gel-spun UHMWPE filaments of the invention is removed by: the filaments are placed in a vacuum oven at a temperature preferably of at most 148 ℃, more preferably of at most 145 ℃, most preferably of at most 135 ℃. Preferably, the oven is maintained at a temperature of at least 50 ℃, more preferably at least 70 ℃, most preferably at least 90 ℃. More preferably, residual spin solvent is removed while keeping the fibers taut, i.e., preventing fiber relaxation.

Preferably, the gel spun UHMWPW multifilament yarn of the invention comprises less than 800ppm of spin solvent at the end of the solvent removal step. More preferably, the amount of spinning solvent is below 600ppm, even more preferably below 300ppm, most preferably below 100 ppm.

We have also surprisingly found that: overall Draw Ratio (DR) as compared to that previously reported in the prior art_overall) In contrast, higher DR can be applied to the ultra-low dtex UHMWPE filaments of the present invention_overallWithout breaking. DR (digital radiography)_overallIs herein understood to be the product of the draw ratios applied at the various stages in the process of the invention, i.e. the draw ratios applied to the fluid filaments, the gel filaments and the solid filaments. Thus, DR_overall＝DR_fluid×DR_gel×DR_solid。

Preferably, DR_overallAt least 9000, more preferably at least 12000, even more preferably at least 15000, still even more preferably at least 18000, still even more preferably at least 20000, still even more preferably at least 25000, most preferably at least 30000. In one embodiment, DR_overallAt most 60000, preferably at most 50000, more preferably at most 40000, for example at most 35000.

In the method of the present invention, the above-mentioned high DR is applied_overallHas the advantage that UHMWPE multifilament yarns with even higher tensile strength are obtained. Another advantage is that: the filament dtex comprised by the yarn is further reduced.

The invention further relates to a UHMWPE multifilament yarn having a tensile strength of at least 3.5GPa and comprising filaments of at most 0.5 dtex.

A filament is herein understood to be an elongated body, i.e. an object having a length much greater than its cross-sectional dimension, having a regular or irregular cross-section and having a continuous and/or discontinuous length. As used herein, a yarn is understood to contain a plurality of filaments. The yarn according to the invention may be a twisted or a braided yarn. In the context of the present invention, yarn is understood to be gel spun yarn.

Preferably, the UHMWPE yarns of the invention comprise filaments having a dtex at most 0.45, more preferably at most 0.4, even more preferably at most 0.35, yet even more preferably at most 0.3, yet even more preferably at most 0.25, yet even more preferably at most 0.2, yet even more preferably at most 0.15, most preferably at most 0.1. Preferably, the UHMWPE filaments have a dtex of at least 0.01, more preferably at least 0.03, even more preferably at least 0.06, most preferably at least 0.09. The dtex of the filament can be determined by selecting a higher DR using the process of the invention_fluidAnd/or DR_solidAnd (4) achieving the purpose.

The tensile strength of the UHMWPE yarns in the present invention is preferably at least 3.7GPa, more preferably at least 4.0GPa, even more preferably at least 4.3GPa, still even more preferably at least 4.5GPa, still even more preferably at least 5.0GPa, still even more preferably at least 5.5GPa, most preferably at least 6 GPa. Tensile strengths in the disclosed ranges can be achieved, for example, by increasing DR_overallAnd (4) obtaining.

Preferably, the UHMWPE yarns in the present invention have a tensile modulus of at least 100GPa, more preferably at least 130GPa, even more preferably at least 160GPa, most preferably at least 190 GPa.

The advantages of the UHMWPE yarn of the invention compared to known UHMWPE yarns containing an equivalent number of UHMWPE filaments are: with smaller cross-sectional dimensions, the mechanical properties or combination of mechanical properties (e.g., tensile strength and/or elastic modulus) are improved.

We have surprisingly found that the UHMWPE yarns of the invention have advantages when used in semi-finished products and manufactured products. Said articles, in particular fabrics, containing the UHMWPE yarns of the invention surprisingly show an enhanced sound absorption (acoustic absorption). Without being bound by any theory, the inventors believe that the ultra-low dtex filaments forming the yarn form an effective structure of air microchannels that allow for the optimal air permeability required to absorb acoustic energy. Another advantage of the presence of air microchannels is that the article further exhibits improved thermal insulation.

The invention therefore further relates to various semi-finished products and manufactured articles comprising the UHMWPE yarns of the invention.

In particular, the invention relates to a fabric comprising the yarn of the invention. The fabric may have any known structure made from yarn, such as woven, knitted, non-woven (e.g., bonded), and the like.

The invention also relates to a medical device comprising the UHMWPE yarns of the invention. The UHMWPE yarns of the invention have proved to be particularly advantageous, in particular for medical applications requiring fine threads of high tensile strength. Preferably, the medical device comprises the UHMWPE yarn of the invention, said yarn comprising filaments having a residual solvent content of less than 800ppm, more preferably said amount is less than 600ppm, even more preferably less than 300ppm, most preferably less than 100 ppm.

The invention more particularly relates to a surgical repair product comprising the UHMWPE yarns of the invention, even more particularly to sutures and medical threads comprising the UHMWPE yarns of the invention. We have found that the suture and medical thread of the present invention have very good knot strength. We have also found that these devices have increased retention of mechanical properties. Moreover, their flexibility is also improved, which gives the suture and the medical thread improved handling properties.

The invention further relates to a vascular graft comprising the UHMWPE yarns of the invention. The vascular grafts described above are used, for example, to replace, bypass (bypass), or reinforce diseased or damaged portions of veins or arteries. We have found that the vascular grafts of the present invention have excellent oxygen permeability, tissue ingrowth properties and ease of handling in addition to their excellent tensile strength. Preferably, the vascular graft of the present invention is made from the knitted or woven UHMWPE continuous yarn of the present invention.

The invention further relates to a medical device in the form of a mesh comprising the UHMWPE yarns of the invention. The screen has the advantages that: the screens can be made thinner than known screens. Preferably, the screen of the present invention is knitted by a process that joins the individual UHMWPE yarn nodes and provides elasticity in two directions. This configuration allows the screen to be cut into any desired shape or size without unraveling, and in addition the bi-directional elastic properties described above allow it to accommodate the various stresses encountered in the body.

Another type of medical device, which may advantageously comprise the yarn of the present invention, is an implantable valve, such as a heart valve. Examples of the manufacture and construction of such valves are described, for example, in EP 08014686.3, which is incorporated herein by reference.

The invention also relates to a rope comprising the UHMWPE yarns of the invention. Preferably, at least 50% of the total weight of the fibres used for making the rope consists of the UHMWPE yarns of the invention. More preferably, the rope comprises at least 75 wt% of the UHMWPE yarns of the invention, even more preferably at least 90 wt%, most preferably 100 wt% of the UHMWPE yarns of the invention. The remaining weight percentage of the yarns in the rope of the invention may comprise yarns comprising filaments or combinations of filaments made of other materials suitable for making filaments, such as metals, nylons, polyesters, aramids, other types of polyolefins, etc. The rope of the invention has the advantages that: it provides the same tensile strength as known ropes with a lower weight.

The invention also relates to a composite article comprising the UHMWPE yarns of the invention.

In a preferred embodiment, the composite article comprises at least one monolayer comprising the UHMWPE yarns of the invention. The term "single layer" refers to a layer of yarns or strands containing yarns in one plane. The monolayer is preferably a unidirectional monolayer, i.e. a monolayer comprising unidirectionally oriented yarns (yarns oriented substantially parallel in one plane). The advantages of obtaining the above mentioned single layer with the yarn of the invention are: a thinner monolayer than the known monolayers containing conventional UHMWPE yarns may be obtained.

In a further preferred embodiment, the composite article is a multi-layer composite article comprising a plurality of unidirectional monolayers, wherein the direction of the fibers in each monolayer is preferably rotated at an angle relative to the direction of the fibers in an adjacent monolayer. Preferably, the angle is at least 30 °, more preferably at least 45 °, even more preferably at least 75 °, most preferably the angle is at least 90 °.

Composite articles, particularly multilayer composite articles, have proven to be well suited for ballistic applications such as body armor, helmets, hard and soft armor panels, insert panels, automotive armor panels, and the like. The invention therefore also relates to the ballistic resistant articles listed above containing the UHMWPE yarns of the invention.

In a preferred embodiment of the invention, the composite article is substantially free of matrix material, such as a binder or resin, that binds the UHMWPE yarns together. In this embodiment, the yarns are bonded by: the yarns and/or yarn layers are compressed at a sufficient temperature and time such that bonding occurs. The bonding comprises at least partial melting of the UHMWPE fibers.

We also observed that: the UHMWPE yarns of the present invention having the unique combination of mechanical properties described above are suitable for use in other application areas such as fishing lines and nets, ground nets, cargo nets and curtains, kite lines, dental floss, tennis racket lines, canvas (e.g. tents), fabric tapes, battery separators, capacitors, pressure vessels, hoses, automotive devices, power transmission belts, building materials, cut-resistant and abrasion resistant articles, protective gloves, composite sports equipment (such as sleds, helmets, canoes, bicycles and hulls and spars), acoustic canisters, high performance electronic insulators, radomes and the like. The invention therefore also relates to the above-listed applications containing the UHMWPE yarns of the invention.

The invention is further illustrated by the following examples and comparative examples.

The method comprises the following steps:

IV: intrinsic viscosity was determined according to method PTC-179(Hercules inc. rev. apr.29, 1982) under the following test conditions: dissolving in decalin at 135 deg.C for 16 hr, using 2g/l DBPC solution as antioxidant, wherein the viscosities measured at different concentrations are extrapolated to zero concentration;

Dtex: the dtex of the filament is determined by weighing 100 meters of fiber. The weight (in mg) was divided by 10 to calculate the dtex of the fiber;

tensile Properties：

● the tensile strength (or strength) and tensile modulus (or modulus) of the multifilament yarn were defined and measured at room temperature (e.g. about 20 ℃) using a Fibre having a nominal gauge length of 500mm, a crosshead speed of 50%/min and an Instron 2714 clamp of the type "Fibre Grip D5618C" as specified in ASTM D885M. On the basis of the measured stress-strain curve, the modulus is determined from the slope between 0.3 and 1% strain. For the calculation of modulus and strength, the tensile force measured is divided by the titre determined by weighing a 10 metre length of fibre. Assuming a density of 0.97g/cm³To calculate a GPa value.

Side chain:the number of side chains in the UHMWPE sample was determined by FTIR on a pressed film 2mm thick by: using a calibration curve based on NMR measurements at 1375cm^-1Is quantified (for example as described in EP 0269151).

Comparative example

A9 wt% solution of UHMWPE homopolymer having less than 1 pendant group per 1000 carbon atoms and an IV of 15.2dl/g was prepared in decalin.

A25 mm twin-screw extruder equipped with a gear pump was used. The UHMWPE solution was spun at a temperature of 180 ℃ through a spinneret having 64 spinneret holes at a rate of 1.5g/min per hole into a nitrogen air gap.

The spinneret orifice had an initial cylindrical passage of 3mm diameter and length to diameter ratio of 20, followed by a conical constriction with a cone angle of 60 °, and finally a cylindrical passage of 1mm diameter and length to diameter ratio of 10. Thus, DR_sp＝9(3²/1²)。

The fluid filaments entered a water bath maintained at about 30 ℃ and having a water flow of about 70 liters/hour perpendicular to the filaments entering the bath. The fluid fibres are wound up at such a rate that a draw ratio DR of about 42 will be achieved in an air gap of 27mm_agApplied to the fluid filament. Overall fluid draw ratio DR_fluidAbout 378. A draw ratio of 1.1 was applied to the gel filaments, after which the solvent was removed, thereby forming solid filaments having a solvent content of about 1 wt% of the initial amount of solvent in the UHMWPE solution.

Subsequently, the gel filaments were passed into an oven at 135 ℃ for solvent evaporation and therein at a draw ratio DR of 4_solid1The filaments are drawn. The solid filaments were then subjected to a second oven, which was operated at a temperature of 153 ℃ and a draw ratio DR of 5_solid2And (4) stretching.

Overall draw ratio DR_overall(＝DR_fluid×DR_gel×DR_solid1×DR_solid2) And a total of 7560. The above detailed process description and the properties of the resulting yarn are summarized in table 1.

Examples 1 to 7

Comparative examples were repeated with the differences listed in table 1. The parameters not reported remained at the same values as those reported in the comparative examples.

Claims (5)

1. A process for gel spinning high tensile strength UHMWPE yarns comprising filaments having at most 0.5dtex, comprising the steps of:

a) preparing a solution of UHMWPE in a solvent;

b) spinning the solution of step a) through a spinneret into an air gap to form fluid filaments, the spinneret comprising a plurality of spinning orifices, wherein each spinning orifice comprises at least one region of decreasing diameter and the diameter downstream of the spinning orifice from which the solution exits into the air gap is between 0.1 and 1.5 mm;

c) at fluid draw ratio DR_fluid＝DR_sp×DR_agDrawing the fluid filament, wherein_spAnd DR_agThe draw ratios in the spinneret orifice and in the air gap, respectively;

d) cooling the fluid filament, thereby forming a solvent-containing gel filament; and

e) at least partially removing residual solvent from the gel filaments to form solid filaments, thereafter or simultaneously with a draw ratio DR of at least 4_solidThe solid filaments are drawn in such a way that,

the method is characterized in that: at a fluid draw ratio DR of at least 450_fluidDrawing the fluid filaments with the proviso that DR_agIs at least 30.

2. The method of claim 1, wherein DR_spBetween 5 and 20 and is selected from DR_agMake DR_fluidIs at least 450.

3. The method of claim 1 or 2, wherein DR_fluidIs at least 500.

4. The method of claim 1 or 2, wherein DR_overall＝DR_fluid×DR_gel×DR_solidIs at least 9000, wherein_gelDrawing ratio, DR, applied to the gel filaments_solidIs the draw ratio applied to the solid filaments.

5. The method of claim 3, wherein DR_overall＝DR_fluid×DR_gel×DR_solidIs at least 9000, wherein_gelDrawing ratio, DR, applied to the gel filaments_solidIs the draw ratio applied to the solid filaments.