PROPERTIES, FIBERS AND NONWOVEN STRUCTURES

Field of the invention

The present invention relates generally to polypropylene compositions, spun and drawn fibers prepared from the polypropylene compositions, non-woven structures made from the fibers and methods for producing the same. Particularly it relates to high-tenacity spun and drawn fibers made with the polypropylene compositions. The present invention relates to a production process for non- woven structures comprising such high-tenacity spun and drawn fibers. The present invention relates to use of such fibers in articles for construction and agriculture, geotextiles, sanitary and medical articles, absorbent wipes, filters, carpets, upholstery and other textiles, e.g. in the automotive industry.

Background

Methods used in the production of the fibers and yarns as well as nonwovens from the fibers or yarns are known to the person skilled in the art and are for example described in "Synthetische Fasern", Franz Fourne, Hanser, 1995, ISBN 3-446-16058-2), pages 96-110: typical phenomena during the spinning of polypropylene, pages 231-550: description of all types of spinning equipment in general. These passages are incorporated herein by reference. With the current state-of-the-art of PP high tenacity fibers, improved mechanical properties of a product can be achieved with higher base weight of the product itself. This increases cost and can have a negative ecological impact. The tenacity can be improved by increasing the draw ratio but this lowers the elongation of the fibers. Hence, when using such overdrawn fibers for the production of geotextile, the overall properties of the geotextile do not improve. Other polymers can improve mechanical performance but most such polymers are less inert than PP and their properties degrade faster, e.g. when in contact with soil. Such polymers can be more expensive.

WO2014/114638 discloses high-tenacity fibers defined as having a tensile strength of at least 45 cN/tex. It reports that polypropylenes used for spun and drawn fibers and nonwoven structures made with these generally have a melt flow index (MFI) in the range of 3 to 6 g/ 10 min for very strong high-tenacity fibers whereas a MFI value in the range of thousand g/10 min is selected for meltblown non-wovens.

WO2014/ 114638 describes a method of producing high-tenacity fibers by melting a polypropylene composition in an extruder and extruding the molten polypropylene through the fine capillaries of a spinneret to obtain filaments. These filaments are then cooled and thus solidified. In order to increase the tensile strength, the solidified fibers can be drawn whereby an increase in tensile strength of the fibers occurs with increasing draw ratio. However, the increase in tensile strength can be accompanied by a decrease in elongation to break. As reported in WO2014/114638 it is known to lower both the melt flow index (MFI) and the xylene soluble content (XS) of the polypropylene compositions to assist in finding a compromise between fiber tensile strength and fiber elongational properties. For the production of tapes and fibers the XS content is conventionally around 3.5%, or above to maintain a stable process. Geotextiles can require nonwoven fabrics comprising high-tenacity spun and drawn fibers, e.g. in nonwoven fabrics to be needle-punched. Good elongation properties of the fibers are required to assure a correct impact resistance (dart) of the geotextile and to avoid fiber breaks during needle-punching. Hence there is a need to obtain the highest fiber tensile strength in combination with the highest elongation from polypropylene compositions.

WO2014/114638 discloses high-tenacity drawn fibers prepared using a polypropylene composition comprising propylene polymer in a matrix phase and a rubber in a dispersed phase, preferably an ethylene propylene rubber (EPR), wherein the rubber content of the polypropylene composition ranges from at least 0.2 to at most 7 wt% relative to the total weight of the polypropylene composition. The polypropylene composition comprises a heterophasic propylene copolymer, also referred as an "impact copolymer" or a "propylene block copolymer". It is argued that good results have been obtained by the combination of the stiffness-to-impact balance properties of a heterophasic propylene copolymer (in which the rubbery phase is more homogeneously dispersed and size controlled than in a mere blend of propylene polymer with an elastomeric polymer or a rubber), with a propylene polymer having a high isotacticity to produce a propylene composition. An alternative explanation is that the results have been obtained by the polypropylene composition combined with the production process of the fibers in which the fibers are drawn in a solid state. WO2014/114638 reports that a propylene homopolymer is known for application in geotextiles having a low MFI of 4 g/lOmin and low XS of 1.5 to 2.5%. However, attempting an improvement of fiber properties by lowering both MFI and XS still further leads to spinning problems such as high pressures, high temperatures, degradation of the polymer, damage to spinning equipment, etc. In fact the temperatures in the melt and the shear forces in the die can result in degradation of the polymer which reduces its molecular weight and hence also its mechanical properties. It is therefore not obvious how to modify the preparation of a homopolymer or the manufacture of high tenacity fibers made from the homopolymer to obtain both a high tenacity and elongation of the fibers and ease of manufacture with high throughputs and yields.

Summary of the invention

An aim of embodiments of the present invention can be to provide any, some or all of : - improved properties of a polypropylene composition comprising a polypropylene polymer especially a homopolymer or a polypropylene blend or a multimodal homopolymer,

- spun and drawn fibers

- non-woven structures such as needle punched non-woven structures made with the spun and drawn fibers, and/or

- articles for construction and agriculture, geotextiles, sanitary and medical articles, absorbent wipes, filters, carpets, upholstery, and other textiles, e.g. in the automotive industry made with such non- woven structures.

The polypropylene composition preferably has a selected window of properties that provide improved tensile properties while still allowing processing in conventional fiber spinning and drawing equipment. The polypropylene compositions of embodiments of the present invention comprise one or more homopolymers and no heterophasic components such as rubbers. Embodiments of the present invention provide spun and drawn fibers comprising a polypropylene homopolymer, the spun and drawn fibers having an average MFI measured according to ISO 1133 for polypropylene of 1 to 5 g/10 min and a xylene soluble content in the range from 1 wt% to 4.5 wt% or 1.5 wt% to 4.5 wt%, the spun and drawn fibers having: an average elongation of at least 65% as measured by ISO 5079 with an adjusted testing speed of 80 mm/min, and/or an average tenacity/tensile strength of at least 56 cN/tex as measured by ISO 5079 with an adjusted testing speed of 80 mm/min. The average tenacity/tensile strength can be in the range 56-70 cN/tex; with 75-90% extension to break for example. Xylene soluble content can be in the range from 1 wt% to 2 wt%, or 1 wt% to 3 wt%, or 1 wt% to 3.5 wt% or 1.5 wt% to 3.5 wt%, or in the range of 1 wt% to 2.5 wt% or 1.5 wt% to 2.5 wt%. The use of controlled and low values of MFI and xylene solubility provide high tenacity fibers that can be processed on existing spinning equipment. The fibers are extruded and are not slit tapes.

The polypropylene composition can consist of one or more polypropylene homopolymers. This can allow adjustment of processing conditions while spinning. The fibers can be staple fibers or short cut fibers. These are useful for making non-woven textiles and geotextiles with good tenacity.

The spun and drawn fibers can have an average MFI measured according to ISO 1133 for polypropylene of 2 to 4 g/10 min. This narrower range allows more control over the extrusion and spinning processes.

The spun and drawn fibers can have a multilobal, or preferably a trilobal cross-section. These cross-sections allow improved non-wovens with good elongation, tensile strength and cover. The spun and drawn fibers can be multicomponent fibers for example, preferably bicomponent fibers. These fibers allow production of non-wovens with a better performance by producing a better bonding strength after a heat treatment.

The polypropylene composition according to embodiments of the present invention can form a core of the multicomponent fibers. Thus means that the core can remain intact after a heat treatment to bond the fibers in a non-woven such as a geotextile.

The fibers can have a titer of at least at least 1 dtex and at most 100 dtex. This range is useful for non-wovens such as geotextiles. The polypropylene composition of the spun and drawn fibers can comprise a first and a second polymer being a blend or a multimodal polymer composition. This allows a balanced set of properties to be obtained and optionally to improve processing during extrusion and spinning.

In another aspect of the present invention a nonwoven is provided comprising the spun and drawn fibers of embodiments of the present invention. The non- woven can be a geotextile.

In another aspect, embodiments of the present invention provide a process for the production of spun and drawn fibers, comprising the steps of:

a) providing the polypropylene composition to an extruder;

b) melt-spinning said polypropylene composition from a number of openings, to form molten filaments; and

c) cooling the molten filaments obtained by step (b) to obtain solidified fibers.

In this process the fibers can be drawn at a draw ratio of between 2 and 4, e.g. 2.5 to 4.

In another aspect the present invention provides a polypropylene composition of a polypropylene homopolymer having an MFI measured according to ISO 1133 of 1 to 3 g/10 min and a xylene soluble content in the range 1 wt% to 4.5 wt% or 1.5 wt% to 4.5 wt%. Xylene soluble content can be in the range from 1 wt% to 2 wt%, or 1 wt% to 3 wt%, or 1 wt% to 3.5 wt% or 1.5 wt% to 3.5 wt%, or in the range of 1 wt% to 2.5 wt% or 1.5 wt% to 2.5 wt%.

The polymer temperature in the extruder (measured at the outlet of the extruder) and/or spin beam, can be in the range of 255°C to 350°C, preferably in the range of 265°C to 340°C, more preferably in the range of 275°C to 330°C and most preferably in the range of 285°C to 320°C.

This polypropylene composition is suitable to make spun and drawn fibers having an elongation of at least 65% as measured by ISO 5079 with an adjusted testing speed of 80 mm/min and/or an average tenacity/tensile strength of at least 56 cN/tex as measured by ISO 5079 with an adjusted testing speed of 80 mm/min. The average tenacity/tensile strength can be in the range 56-70 cN/tex; with 75-90% extension to break for example. The polypropylene composition can consist of one or more polypropylene homopolymers. For example the polypropylene composition can comprise a first and a second polymer, said polypropylene composition being a blend or a multimodal polymer composition.

The polypropylene composition according to embodiments of the present invention can be used in the manufacture of bicomponent fibers. The bicomponent fibers can comprise a core and an outer layer which covers some or all of the circumference of the core, e.g. like a sheath, wherein the polypropylene composition is used to form the core. The high tensile strength and high elongation of the polymer composition of the core results in the core of the bonded spun and drawn fibers being preserved after bonding in a non- woven such as in a geotextile.

An advantage of embodiments of the present invention is that mechanical properties of a fiber or of a non-woven made from the fiber can be improved. A further advantage of at least some embodiments is that the throughput and yield of the fiber production can be maintained at the same time as obtaining the improved mechanical properties.

Spun and drawn fibers according to embodiments of the present invention can be used in woven products, or non- woven products such as dry or wet wipes, hygiene products, filters, carpets, upholstery, and other textiles, e.g. in the automotive industry made with such non- woven structures or in articles for construction and agriculture, geotextiles, sanitary and medical articles. Functions of such products can be filtration, reinforcement, separation, drainage and/or protection, for example.

Spun and drawn fibers according to any or all of the embodiments of the present invention do preferably not include slit tapes.

An advantage of embodiments of the present invention is the possibility of weight reduction of a non-woven structure, e.g. used as or in a carpet, upholstery, an absorbent wipe or a geotextile, while still obtaining the same properties. Further advantages of embodiments of the present invention can be manufacturing cost reduction of the final product, a reduction in environmental impact or an easier handling. Embodiments of the present invention comprise a first polymer being a polypropylene homopolymer having a xylene soluble content in the range from 1 wt% to 4.5 wt% or 1.5 wt% to 4.5 wt% relative to the weight of the polypropylene homopolymer; preferably in the range from 1 wt% to 2 wt%, or 1 wt% to 3 wt%, or 1 wt% to 3.5 wt% or 1.5 wt% to 3.5 wt%, most preferably in the range from 1 wt% to 2.5 wt% or 1.5 wt% to 2.5 wt%. The MFI of the polypropylene homopolymer is from 1 to 3 g/lOmin, preferably in the range 1.5 to 2.5 g/lOmin. In an embodiment, the polypropylene composition comprises a blend of the first polymer, and a second polymer being a polyolefin such as polypropylene or polyethylene in an amount from at least 0.1 wt%, preferably in the range 0.5 to 5 wt% relative to the total weight of the polypropylene composition. In a further embodiment, the polypropylene composition (with or without the second polymer) comprises an additive such as a polymeric processing agent (PPA) acting as a processing aid in an amount from at least 0.01 wt%, preferably in the range 0.01 to 0.1 wt%, relative to the total weight of the polypropylene composition. By such processing aids reduced pressures and temperatures in the extruder and in the spinneret die during spinning, can be achieved. Both, additive and a second polymer, can be applied alone, as such, or together simultaneously.

The second polymer can be a polypropylene homopolymer. The second polymer can be a polyolefin with a second MFI (measured according to ISO 1 133 or ASTM D-1238) higher than the first MFI, preferably significantly higher than the first MFI. For example, the MFI of the second polymer can be at least 10, 20 and even 30 times higher than the MFI of the first polymer. The second polymer can have an MFI of less than 100 g/ 10 min and can form a mixed composition, without being heterophasic with the first polypropylene polymer in the melt.

The second polymer can be present in the polymer blend in at least 0.5 wt%, preferably in the range of 1 to 5 wt% relative to the total weight of the polymer blend, and the second polymer forming a monophasic composition with the first polypropylene polymer in the melt.

The polypropylene composition can also include an additive such as e.g. an antioxidant, or a UV retardant, preferably in the range of 1000 to 2500 ppm (or higher) by weight of the polypropylene composition.

In the melt the additive or the second polymer preferably mixes with the first polymer, e.g. when molten in an extruder barrel. Without being limited by theory, the additive or second polymer acts as a lubricant or processing aid reducing the pressure and/or temperature in the extruder and the spinneret which pressure and temperature are required to extrude the polymers with higher viscosity through the many holes of the spinneret die.

Low melt flow index means a high-molecular- weight, and hence a highly viscous polymer. A high melt flow index means low-molecular- weight, and hence a low viscous polymer. Due to the fact that polymers such as PE and PP are measured at different temperatures, the MFI values cannot be compared directly in extrusion where the extrusion temperature of the PP means that the PE is at an elevated temperature. For example, the apparent viscosity change between extrusion temperatures of 240 and 270 can be about 3 times for a polyolefin. Thus, when considering whether a polymer will act as a low viscosity extrusion processing aid it is necessary to take into account several factors, such as MFI, extrusion temperatures, shear rates as well as some aspects of the polymer such as degree of branching and chain entanglements.

Accordingly, in a blend of a first polypropylene homopolymer and a second polyolefin polymer, the first and second polymers can have melt flow indices which are designed to achieve the advantages of reduced extrusion pressures and/or temperatures. For example, if the second polymer is polyethylene, the MFI of the polyethylene can be as low as 3 g/lOmin or lower due to the reduced viscosity of PE when extruded at PP temperatures. If the second polymer is PP or a polymer with a melting point similar to PP then the melt flow index of the second polymer is preferably higher than that of the first polymer and the ratio of the melt flow index of the second polymer to that of the first polymer is preferably at least 10, and possibly in the range of 10 to 30. Further embodiments of the present invention include polymer compositions comprising combinations of polymers such as polypropylene and a polyolefin whereby the compositions preferably have a xylene soluble content in the range from 1 wt% to 4.5 wt% or 1.5 wt% to 4.5 wt% and an MFI of 1 to 3 g/lOmin, preferably in the range 1.5 to 2.5 g/lOmin. Xylene soluble content can be in the range from 1 wt% to 2 wt%, or 1 wt% to 3 wt%, or 1 wt% to 3.5 wt% or 1.5 wt% to 3.5 wt%, or in the range of 1 wt% to 2.5 wt% or 1.5 wt% to 2.5 wt%. For example 80% of a PP homopolymer with an MFI of about 2 g/10 min can be mixed with 20% of a PP homopolymer with an MFI of about 4 g/10 min. The resulting polypropylene composition has a melt flow index intermediate between 2 and 4, i.e. less than 3 g/10 min when tested as PP according to ISO 1133-1:2011 or ASTM D-1238 Standard. To this blend processing agents or a further polymer may be added to reduce temperatures and pressures during extrusion.

Accordingly, embodiments of the present invention include a polypropylene composition comprising a polypropylene homopolymer or a blend of a first polypropylene homopolymer with one or more polymers such as a polyolefin, e.g. PP or PE whereby the polypropylene composition has a melt flow index (MFI) less than 3 g/10 min when tested as PP according to ISO 1133-1: 2011 and a xylene soluble content in the range from 1 wt% to 4.5 wt% or 1.5 wt% to 4.5 wt%. Xylene soluble content can be in the range from 1 wt% to 2 wt%, or 1 wt% to 3 wt%, or 1 wt% to 3.5 wt% or 1.5 wt% to 3.5 wt%, or in the range of 1 wt% to 2.5 wt% or 1.5 wt% to 2.5 wt%.

The first and/or second polymers can be prepared using a suitable catalyst such as Ziegler- Natta catalyst or a metallocene catalyst, for example.

The first polymer preferably shows one or more of the following properties: i. a xylene soluble content in the range from 1 wt% to 4.5 wt% or 1.5 wt% to 4.5 wt%; preferably in the range from 1 wt% to 2 wt%, or 1 wt% to 3 wt%, or 1 wt% to 3.5 wt% or 1.5 wt% to 3.5 wt%, most preferably in the range of 1 wt% to 2.5 wt% or 1.5 wt% to 2.5 wt% and

ii. a melt flow index of less than 3.0 dg/min, more preferably in the range 1.5 to 2.5 g/10 min when tested as PP according to ISO 1133-1:2011 or ASTM D-1238.

High tenacity (HT) fibers can be spun and drawn using the polypropylene composition of the present invention. A drawn fiber according to embodiments of the present invention comprises filaments made from a polypropylene composition according to any of the embodiments of the present invention, the filaments having a titer, for example of at least 1 dtex and of at most 100 dtex, preferably of at least 2 dtex and of at most 30 dtex, most preferably of at least 3 dtex and at most 10 dtex.

The spun and drawn fibers can be used e.g. for non-woven structures in a variety of applications of which one is geotextile applications. The properties of these high tenacity (HT) fibers made with the polymer composition are superior to currently available PP fibers, these properties being for example:

• elongation (average value): at least 65%, preferably between 65-100%, more between 70-90%, more preferably between 75-85%, Individual fibers can vary considerably outside these average values, e.g. between 20% and 150%. Hence the narrower ranges are averages as determined according to the ISO norm 5079 with an adjusted testing speed of 80 mm/min.

• improved tenacity (tensile strength): at least 56 cN/tex, preferably in the range of 56 to 70 cN/tex, more preferably in the range of 58 to 66 cN/tex determined according to the ISO norm 5079 with an adjusted testing speed of 80 mm/min. A range of 75-90% extension to break can be achieved for example. These are average values for fibers, individual fibers may be well outside these ranges.

The spun and drawn fibers after extrusion have an MFI (average value from many fibers) of 1 to 5 g/lOmin when tested as PP according to ISO 1133-1:2011 or ASTM D-1238. The small change of MFI before and after extrusion indicates a low level of degradation which occurs when polymer compositions of the embodiments of the present invention are used to produce drawn fibers.

The polymer material in such spun and drawn fibers after extrusion has a xylene soluble content in the range from 1 wt% to 4.5 wt% or 1.5 wt% to 4.5 wt% relative to the weight of the polypropylene homopolymer; preferably in the range from 1 wt% to 2 wt%, or 1 wt% to 3 wt%, or 1 wt% to 3.5 wt% or 1.5 wt% to 3.5 wt%, most preferably in the range from 1 wt% to 2.5 wt% or 1.5 wt% to 2.5 wt%.

Fibers according to embodiments of the present invention may be solid or hollow and/or round or shaped and/or monocomponent or multicomponent. Shaped fibers include multilobal fibers such as bilobal and trilobal fibers. Multicomponent fibers include bicomponent fibers.

Further, the invention discloses nonwoven structures comprising such fibers. A non-woven structure can be made with at least some of the fibers mentioned above. A geotextile can be produced with this new type of fibers, e.g. in the form of a needlefelt: the tensile strength of the needlefelt is increased by at least 5% e.g. by 8%, by 10% compared to the current state-of-the-art. Elongation of the needlefelt is also very satisfactory, i.e. there is no reduction in performance.

Further, the invention discloses a geotextile produced with such fibers or with such non- woven structures. Further, the invention discloses a needle felt. The tensile strength of the needlefelt can be increased compared to current state-of-the-art by use of fibers according to embodiments of the present invention.

Additionally, the present invention provides a process for the production of high-tenacity fibers. For example, a suitable process for producing fibers in accordance with embodiments of the present invention comprises the steps of: a) providing a polypropylene composition according to any of the embodiments of the present invention to an extruder, the extruder temperature (measured at the outlet of the extruder) can be in the range of 255°C to 350°C, preferably in the range of 265°C to 340°C, more preferably in the range of 275°C to 330°C and most preferably in the range of 285°C to 320°C, b) melt-spinning said polypropylene composition by pushing the polymer composition through a die having a number of openings, to form molten filaments; c) cooling the molten filaments obtained by step (b) to obtain solidified fibers, and preferably d) drawing said solidified fibers at a temperature of at least 70°C and at most 150°C and at a draw ratio of at least 2, preferably 2.5 to 4 to obtain fibers with:

• elongation (average value): at least 65%, preferably between 65-100%, more between 70-90%, more preferably between 75-85%, Individual fibers can vary considerably outside these average values, e.g. between 20% and 150%. Hence the narrower ranges are averages as determined according to the ISO norm 5079 with an adjusted testing speed of 80 mm/min.

• improved tenacity (tensile strength): at least 56 cN/tex, preferably in the range of 56 to 70 cN/tex, more preferably in the range of 58 to 66 cN/tex determined according to the ISO norm 5079 with an adjusted testing speed of 80 mm/min. These are average values for fibers, individual fibers may be well outside these ranges. The average tenacity/tensile strength can be in the range 56-70 cN/tex; with 75-90% extension to break for example.

The spun and drawn fibers can be made into textile products or non-wovens such as geotextiles by conventional means.

Definitions Throughout the present application, the terms "polypropylene" and "propylene polymer" may be used synonymously. The expression " % by weight" or "wt% " (weight percent), here and throughout the description unless otherwise defined, refers to the relative weight of the respective component based on the overall weight of the formulation. The polypropylenes used in the present invention can be produced by polymerizing propylene in the presence of a suitable catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst which is well- known to the skilled person.

The term "fibers" in for example the term "spun and drawn fibers" refers, according to any or all of the embodiments of the present invention as preferably not including slit tapes. The fibers of any of the embodiments of the present invention can be staple fibers of several centimetres length, e.g. 20 to 120 mm length or up to 300 mm length or may comprise short- cut fibers of 2 to 25 mm in length.

A "nonwoven structure" which can be used with the present invention may include fibers of any of the embodiments of the present invention, e.g. as staple fibers of several centimetres length, e.g. 20 to 120 mm length or up to 300 mm length. A nonwoven structure can also be made comprising short-cut fibers of 2 to 25 mm in length, e.g. alone or in a blend.

The term "needlepunched" means a nonwoven structure which is consolidated by passing it through one or more needleboards carrying several thousands of needles that penetrate the nonwovens repeatedly, forming a mechanically entangled structure.

"Geotextiles" and "landscape textiles" are used, for example, to cover an area of ground. Geotextiles, as used in this application relate to fabrics made from non-woven structures. They have many applications in the field of civil engineering such as in roads, airfields, railroads, embankments, retaining structures, reservoirs, canals, dams, bank protection, in the field of coastal engineering to control erosion of shorelines, as well as in the fields of agriculture and landscape preservation, for purposes including moisture retention, water conservation, weed or sward suppression, soil warmth retention, and for light reflection. A geotextile or landscape textile according to embodiments of the present invention is generally supplied in a roll and is simply unrolled to cover an area of ground.

Test methods

Melt Index (MI), Melt Flow Index (MFI), or Melt Flow Rate (MFR) refers to the grams per 10 minutes pushed out of a die of prescribed dimensions according to ISO 1133-1:2011 or ASTM D-1238 Standard under the action of a specified load. For PP the load is 2.16 kg and the die dimensions are D = 2.095 mm and L = 8 mm. The experiment is carried out at 230°C. (For the PE, the same load and die dimensions are used, but the experiment is carried out at 190°C).

An example of a suitable method to determine the Xylene Solubles ( XS) is (preferably to be performed in double): In an Erlenmeyer, weigh 4 +/- 0.1 g of the polymer Add 200 ml of inhibited and degassed Xylene

Heat under stirring to reflux until complete dissolution (+/- 45 min) under nitrogen flow - Allow cooling for 15-20 minutes

Place the Erlenmeyer in a thermostatic bath at 25 +/- 0.1 °C for 45 minutes and allow cooling

Filter the content of the Erlenmeyer using Whatman n°2 V filter paper.

Pipette 100 ml of the filtrate on a weighed Al tray - Evaporate the solvent on a heating plate under nitrogen (at around 130°C)

After complete evaporation, place the tray in the vacuum oven at 105°C for 30 minutes

Allow cooling for 1 hour and weigh.

The percentage of xylene solubles ("XS") is calculated according to :

XS (in weight ) = 100 x [2 x ((mass of the tray and residues) - (mass of the empty tray)) - (mass of the residue if any of a blank xylene sample)] / (mass of the sample polypropylene polymer) with all weights being in the same units, such as for example in grams.

Detailed description of the invention

Polymer blend or bimodal polymer The spun and drawn fiber of some or all embodiments of the present invention is produced from a polymer composition that can comprise a homopolymer, a polymer blend or a polymer with multimodal fractions. The polypropylenes used in the present invention are produced by polymerizing propylene in the presence of a suitable catalyst such as a Ziegler- Natta catalyst or a metallocene catalyst which methods are well-known to the skilled person. Polypropylene polymers are preferably produced by polymerization in propylene at temperatures in the range from 20°C to 100°C. Preferably, temperatures are in the range from 60°C to 80°C. The pressure can be atmospheric or higher. Preferably, the pressure is between 25 and 50 bar.

Preferably, the polymer blend according to some embodiments of the invention comprises a first polypropylene homopolymer with an MFI less than 3 and preferably in the range 1 to 2.5 g/lOmin according to ISO 1133-1:2011 or ASTM-1238, condition L, using a weight of 2.16 kg and a temperature of 230 °C and a second polyolefin polymer. If the second polymer has a lower melt temperature than PP, as is the case for polyethylene then the MFI of this second polymer may be similar to PP, e.g. less than 3 g/10 min tested according to ISO 1133- 1:2011 or ASTM-1238 for conditions for PE. This is because the MFI is measured at two different temperatures with the temperature for PE being lower than for the PP composition (190 °C for PE, 230°C for PP). The PE is present in the extruder at melt temperatures for PP which means the viscosity of the PE is reduced. If the second polymer is PP, then it is preferred it has a higher melt flow index, wherein the ratio of the melt flow index of the second polymer and the melt flow index of the first polymer is preferably in the range of more than 10 times, more than 20, more than 30, 40 or 50 times and can be less than 100 times. The MFI of the second polymer if it is PP can be at least 20 g/lOmin, at least 30 g/lOmin, at least 40 g/lOmin, at least 50 g/lOmin, at least 60 g/lOmin, at least 70 g/lOmin and can be less than 100 g/lOmin. The polypropylene composition can also include an antioxidant. The antioxidant can be in the range 1000 to 2500 ppm weight or higher of the first polymer. Processing aid preferably does not affect the elongation/tensile properties of the spun and drawn fiber to any significant degree.

The first polymer is a polypropylene homopolymer. The optional second polymer is preferably miscible with the first polymer when molten, e.g. in the extruder before spinning. Hence it is preferred if the second polymer is a polyolefin, e.g. polypropylene or polyethylene. The first polymer, i.e. the polypropylene homopolymer and the second polymer can be mixed together in pelletized, fluff or powder form prior to being introduced into the extruder. Alternatively the polymers may be introduced separately into the extruder at one or more positions to achieve thorough mixing of the polymers within the extruder which feeds a spinneret. Alternatively the polymers may be introduced into different extruders. Additives can be melted in a separate (e.g. smaller) side extruder and afterwards mixed in the main stream in a mixing zone at the end of the main extruder or by static mixers after the extruder. The temperature in the extruder (measured at the outlet of the extruder) can be in the range of 255°C to 350°C, preferably in the range of 265°C to 340°C, more preferably in the range of 275°C to 330°C and most preferably in the range of 285°C to 320°C.

The low MFI of the first polymer means that the average molecular weight of the first polymer is preferably increased. This higher molecular weight can be achieved by known methods such as by altering the amount of hydrogen injected into the polymerisation reactor. Peroxide can be used to lower the molecular weight of a material with a too high molecular weight. This can be used to set a specific MFI by starting with PP with an even lower MFI than finally required and then using the peroxide to increase the MFI, e.g. by reactive extrusion.

In an embodiment of the invention, instead of a blend of a first and a second polymer, the first polymer can be bimodal or multimodal and can comprise at least two polypropylene homopolymer fractions of different molecular weight. The bimodal or multimodal polymer will have a melt flow index of less than 3 g/lOmin, preferably in the range 1 to 2.5 g/lOmin tested according to ISO 1133-1:2011 or ASTM-1238, condition L, using a weight of 2.16 kg and a temperature of 230 °C. Such a bimodal polypropylene homopolymer is preferably produced in a polymerization unit having two reactors in series. In such a sequential arrangement of polymerization reactors, the polypropylene homopolymer withdrawn from one reactor is transferred to the one following in the series, where the polymerization is continued. To produce polypropylene homopolymer fractions of different index, the polymerization conditions in the respective polymerization reactors need to be different, for example in that the hydrogen or peroxide concentration in the polymerization reactors differs.

Independently of whether the blend or the multimodal distribution is selected, the first polymer and the second polymer are preferably in a monophasic state when molten.

Generally, the higher molecular weight, the higher is the tensile strength and modulus of the spun and drawn fibers. However, lowering the MFI means that the material becomes more viscous and this will increase the pressure in the extruder and the die of the spinneret. Partial compensation for these negative effects on extrusion and melt- spinning of polymer material can be achieved with an increase in temperature, e.g. to lower the high viscosity at normal operation conditions. To minimize degradation caused by this higher temperature, a higher amount of anti-oxidant is preferred in the polymer composition. The first polymer preferably has the following properties in addition to the MFI and antioxidant mentioned above. The percent atactic material is less than 5% and preferably between 1.5 and 2wt% e.g. between 1.6 and 1.8 wt% of the total weight of the first polymer as measured by xylene soluble content.

Gel count is an indication for the homogeneity of the product and is preferably negligible.

The chemical structure of the polymer can be defined as atactic, isotactic or syndiotactic. These refer to an idealised sequence of the stereographic arrangement of the methyl groups in the polymer. This 3-dimensional orientation and sequence will determine how the polymer molecule will arrange by folding-up, crystallizing, etc. Atactic means that the methyl groups will be randomly arranged, so will not fold up symmetrically, and appear like a sticky product (glue). Isotactic means that all methyl groups will be on the same side of the polymer chain, so that the molecule can fold-up in a symmetric way, and in crystals. With syndiotactic products the methyl groups are each time on alternating sides. In any actual polymer 'artefacts' in the catalyst polymerization can take place. Laboratory analysis can be used to extract or to spectrometrically determine the amounts of these different polymer arrangements. In case of extraction, heptane solubles or insolubles or Xylene solubles or insolubles can give an idea of the atactic content. Low molecular weight polymer (if present) can also be extracted and counted as atactic material. There is also a limit on the efficiency of extraction, which makes that not all atactic polymer will be measured. The same uncertainty of measurements is the case of spectrometrical analysis (NMR / near IR / X-ray diffraction). Fiber production

An apparatus that can be used for spinning melt- spun fibers according to embodiments of the present invention can include a spin beam. A spin beam is known from US patent application US2004/0124551 which is incorporated herein by reference. A polymer melt from an extruder is fed to the spin beam and is distributed within the spin beam to a plurality of spinning cans mounted on the spin beam. The extruder and the spin beam are provided with heaters. The temperature in the extruder (measured at the outlet of the extruder) and/or spin beam, can be in the range of 255°C to 350°C, preferably in the range of 265°C to 340°C, more preferably in the range of 275°C to 330°C and most preferably in the range of 285°C to 320°C.

Spun and drawn fibers according to any or all of the embodiments of the present invention preferably do not include slit tapes.

A process according to an embodiment of the present invention includes: 1) Dosing of amounts of first and optionally second or further polymers according to embodiments of the present invention which polymers also comprise an anti-oxidant with optionallv other ni pments and/nr other additives

2) Extrusion melting, mixing, and pressure increase with extrusion of polymer material in the form of filaments under pressure through a die of a spinneret

3) Quenching the filaments from molten material to solid filaments

4) During steps 2) and 3) the filaments can be drawn a first time ('melt drawing')

5) Spinfinish application: this improves antistatic property and reduces the abrasion. This result in stable processing during fiber production and nonwoven production. Extra spinfinish is often added in later stages of the process (e.g. after texturation of cutting - see below)

6) Stretching by drawing the solidified filaments to achieve a good tensile strength by increasing the orientation. The draw ratio of this step is used to characterize how much the filaments are drawn. Conventionally fibers are drawn in one or two steps; some manufacturers also provide equipment which allows fibers to be drawn in many small steps. It is assumed that many small steps can be described as a single final drawing ratio. During this process, an oven is used to heat the fibers. This reduces the required drawing force and can improve the final properties

7) Stabilising: A stabilizing step can be added to the process to reduce the internal stresses within the fibers and thus reduce shrinkage.

8) Texturation: Filaments are crimped/textured to increase the bulk and the cohesion of the fibers. This process can be improved by treating the fibers with steam prior to the texturation step. 9) Optional secondary spin finish operation: after drawing of the fibers, optional application of a second spin finish, optional crimping or texturizing can be performed. Steam processing better texturation is preferred because some spin finish can be removed during texturation.

10) Optionally cutting the fibers to a length such as 20mm to 300 mm to form staple fibers or 2-24 mm for short cut fibers.

Alternatively, a two-step process can be used, wherein material is collected between the quenching and stretching steps. In a two-step process steps 1 to 3 aren't coupled to the rest of the process. After quenching in step 3), filaments are collected in bins or on bobbins. The advantage of this process is that the first steps can be performed at much higher spinning speeds. Main drawback of this process is the extra workload.

In addition some extra steps may be included in both the one step and two-step process. These additional steps can be, for example, relaxation or crimping.

It is preferred that the first polypropylene polymer used for the production of high tenacity fibers has a low XS value and also a low MFI. This leads to stronger fibers but makes the spinning process more difficult, e.g. filaments tend to fracture more easily during spinning when XS is low and extrusion temperatures and pressures are higher for low MFI. Embodiments of the present invention avoid these problems while maintaining high tenacities and elongations. Whereas a conventional polypropylene homopolymer having an MFI of 4 g/lOmin and low XS of 1.5 to 2.5% can be used for geotextile fibers, attempting an improvement of fiber properties by lowering still further one or both of MFI and XS leads to spinning problems such as high pressures, high temperatures, degradation of the polymer, damage to spinning equipment, etc.

For example, if the same spinning settings are used for spinning PP with MFI of 2 g/lOmin as the spinning settings which are used for commercial PP fiber grades, i.e. with an MFI in the range 4 - 25 g/lOmin, pressures increase dramatically potentially causing damage to the equipment (extruder and spinneret) or an emergency stop of the machine within a short time, e.g. a matter of minutes or even perhaps degradation of the polymer.

When using a first polypropylene according to embodiments of the present invention such as a polypropylene homopolymer having a low MFI, e.g. of less than 3 such as in the range 1 to 2.5 g/lOmin and a low XS, e.g. in the range 1 wt% to 2.5 wt% or 1.5 to 2.5%, or 1 wt% to 2 wt%, or 1 wt% to 3 wt%, several precautions should preferably be taken: a) Increase temperature of extruder and spin beam, e.g. raise it by 10°C, 20°C, 30°C or 40°C or even more, such as raising the temperature e.g. from 245 to 275°C while preferably lower than 350°C, lower than 320 °C, preferably lower than 295°C, preferably below 290°C, for example in the range 275 °C to 330°C or 285°C to 320°C. b) Lower output from spin pump speed, e.g. reduce the speed by 10 % or 20%. c) Include a second polymer in a blend with the first polymer or as a multimodal or bimodal polymer, the second polymer acting as a processing aid. If the second polymer is polypropylene the second polymer preferably has a higher MFI than the first polymer, e.g. by 10 times, 20 times or 25 times such as an MFI of 50 g/lOmin. The MFI range for the second polymer can be at least 20 g/lOmin, at least 30 g/lOmin, at least 40 g/lOmin, at least 50 g/lOmin, at least 60 g/lOmin, at least 70 g/lOmin and can be less than 100 g/lOmin.If the second polymer is polyethylene the MFI can be the same as for the first polymer. d) Internal and external lubricants, are known and can be used. Internal lubricants often exhibit a certain external lubrication. Internal lubricants are believed to reduce friction occurring between the molecular chains of a polymer thus lowering the melt viscosity. They can be polar materials.

External lubricants mainly reduce wall adhesion between the polymer and metal surfaces. Most of them are non-polar substances, such as paraffins or polyethylene. The external lubrication is influenced by the length of the hydrocarbon chain, the branching or the functional groups. However, these known lubricants have a low molecular weight and have an effect on the MFI of the extruded polymer composition.

Contrary to these known lubricants, a blend or multimodal composition is provided of a first polymer according to embodiments of the present invention with a low MFI. The second polymer can be present in an amount less than 5%, e.g. 1 to 5%, 2 to 3%, or 2.5% of the polymer composition. If the second polymer is a polypropylene this polymer preferably has an MFI higher than the first polymer, e.g. by 10 times, 20 times or 25 times such as an MFI of 50 g/lOmin. The MFI range for the second polymer can be at least 20 g/lOmin, at least 30 g/lOmin, at least 40 g/lOmin, at least 50 g/lOmin, at least 60 g/lOmin, at least 70 g/lOmin and can be less than 100 g/lOmin. For a multimodal composition a combination of polymers such as a combination of polypropylene with an MFI of 2 (80% by weight) and a polypropylene with an MFI of 4 (20% by weigh) results in a polymer with an MFI less than 3, e.g. between 1 and 2.5. Fibers in accordance with embodiments of the present invention can be produced with 100% of the first polymer (no second polymer) as well but this may reduce spinning speed

Other additives which can be blended with the first polymer or with the first and second polymers to reduce pressure build-up include a polymer processing agent.

Further additives can be, by way of example, antioxidants, UV retardants, light stabilizers, acid scavengers, flame retardants, lubricants, antistatic additives, nucleating/clarifying agents, colorants. An overview of such additives may be found in Plastics Additives Handbook, ed. H. Zweifel, 5 ^th edition, 2001, Hanser Publishers. Antioxidants can be selected from the group consisting of or comprising phosphites, hindered phenols, hindered amine stabilizers and hydroxylamines. Alternatively, phenol-free antioxidant additives are suitable as well, such as for example those based on hindered amine stabilizers, phosphites, hydroxylamines or any combination of these. Fiber properties - shape

Fibers according to embodiments may be solid round, hollow round, solid shaped or hollow shaped such as multilobal fibers, bilobal or trilobal fibers, bicomponent fibers of any of these e.g. bicomponent solid round, bicomponent hollow round, bicomponent solid shaped or bicomponent hollow shaped such as bicomponent multilobal fibers, bicomponent bilobal or bicomponent trilobal fibers. Spun and drawn fibers according to any or all of the embodiments of the present invention preferably do not include slit tapes.

Fibers for non- woven structures can be made with polymers according to embodiments of the present invention catalyzed by a metallocene catalyst. Such fibers can be spun into a bi- component fiber by methods as described in Belgian patent application BE 2016/5213 entitled "Non-woven structure with fibers catalyzed by a metallocene catalyst" which is incorporated herein in its entirety by reference. Bonded and entangled non- woven structures for use, for example, in hygiene and health care, such as in disposable or single use products for use, for example in hospitals, schools, and domestically, in diapers or wipes, but also in carpets can be made with such non- woven structures. Mechanical properties of geotextile or upholstery nonwoven structures can be improved by adding such metallocene bi-component fibers for better bonding. The amount of metallocene bi-component fibers used in a non- woven can range from 5% to 100% of the fibers used to make the non- woven.

It is preferred if the core of such bi-component fibers is made from the first polypropylene polymer with a low MFI or a blend or multimodal composition of the first and second polymers according to embodiments of the present invention, as this improves the tensile properties of the non- woven such as the needlefelt made with these fibers. On the other hand, making the bi-component fibers from a polypropylene according to embodiments of the present invention with this low MFI material being the cladding or sheath material of bi- component fibers is less preferred due to the reduction in tensile properties when the polypropylene sheath melts to produce bonding to adjacent fibers.

A further embodiment of the present invention comprises a bicomponent fiber with a core made from the first polypropylene polymer with a low MFI or a blend or multimodal composition of the first and second polymers according to embodiments of the present invention. The outer polymer material of the bi-component fiber is preferably made of a polypropylene polymer produced using a metallocene catalyst which has a lower melting temperature than the core material. Such bi-component fibers can be used in a variety of applications such as in the production of non-wovens for use in geotextiles or upholstery. Non-wovens made with such bi-component fibers can have advantages of extra stiffness and better form stability. An embodiment of the present invention provides in one aspect a bonded and entangled non- woven structure made of at least 50% short cut or staple fibers by weight of the bonded and entangled non-woven structure, and at least a partial bonding of the fibers of the non-woven structure, the at least partial bonding comprising thermally activated bonds between a first polypropylene composition with an MFI less than 3 g/10 min and a second outer material produced with at least one metallocene catalyst and having a melting point at least 10°C lower than the melting point of the first polypropylene composition, the weight of the second material in the non-woven structure being at least 3% of the weight of the non woven structure.

Fibers according to an embodiment of the present invention can be made from a polypropylene polymer with an outer trilobal shape, either as hollow or solid fibers. The shape of the fibers influences the mechanical properties especially the permeability for air and water. Such trilobal fibers can improve geotextiles or filters. For example, trilobal shape increases the contact surface which can increase bond strengths or filtering characteristics as well as better contact between constructional materials such as concrete and fibers or non-woven structures made according to embodiments of the present invention The trilobal shape can also improve the coverage of the carpet or upholstery, e.g. a better coverage with a conventional base weight or a desired coverage with a lower weight.

Fibers according to an embodiment of the present invention can be bi-component fibers having a sheath and a core, wherein the core comprises the polypropylene composition according to the present invention, and wherein the sheath may comprise a polyolefin such as PE or PP, preferably PP, catalysed by a metallocene catalyst and the bicomponent fiber preferably having an outer trilobal shape. This combines several advantages and can find a use in upholstery or geotextile.

Fiber properties - mechanical

Measured properties of fibers according to embodiments of the present invention show an improvement compared to fibers produced on the same line with Total 4069 polypropylene (MFI 4 g/lOmin) or with Polychim HL10XF polypropylene (having MFI 3.5 g/lOmin):

Fibers according to embodiments of the present invention (e.g. for 4.4 dtex) showed a higher tenacity e.g. above 56 or 58 cN/tex such as 62 cN/tex, as well as maintaining the elongation.

Fibers according to embodiments of the present invention achieve: · elongation (average value): at least 65%, preferably between 65-100%, more between 70-90%, more preferably between 75-85%, Individual fibers can vary considerably outside these average values, e.g. between 20% and 150%. Hence the narrower ranges are averages as determined according to the ISO norm 5079 with an adjusted testing speed of 80 mm/min.

· Improved tenacity (tensile strength): at least 56 cN/tex, preferably in the range of

56 to 70 cN/tex, more preferably in the range of 58 to 66 cN/tex determined according to the ISO norm 5079 with an adjusted testing speed of 80 mm/min. These are average values for fibers, individual fibers may be well outside these ranges. The average tenacity/tensile strength can be in the range 56-70 cN/tex; with 75-90% extension to break for example.

Production of needlepunched nonwoven structures

A nonwoven structure according to embodiments of the present invention can include any of the fiber embodiments of the present invention, e.g. fibers made from a first polymer being a polypropylene homopolymer with an MFI between 1 and 2.5 g/lOmin, with a xylene soluble content in the range from 1 wt% to 4.5 wt%, or 1.5 wt% to 4.5 wt% relative to the weight of the polypropylene homopolymer; preferably in the range from 1 wt% to 2 wt%, or 1 wt% to 3 wt%, 1 wt% to 3.5 wt% or 1.5 wt% to 3.5 wt%, most preferably in the range from 1 wt% to 2.5 wt% or 1.5 wt% to 2.5 wt%, relative to the weight of the polypropylene homopolymer and the shape of the fibers can be any of solid round, hollow round, multilobal solid or hollow such as trilobal solid or hollow, bi-component solid round or hollow round, or multilobal bicomponent either hollow or solid such as bicomponent trilobal either solid or hollow, with any of the fibers being optionally crimped. Any of such fibers can have an elongation (e.g. for 4.4 dtex), above 65% and (e.g. for 4.4 dtex) tenacity above 56 cN/tex, as well as maintaining the higher elongation. The polymer composition used to make any of the fibers can be a blend or a multimodal composition. In a blend the first polymer according to embodiments of the present invention has a low MFI less than 3 g/10 min and less than 5%, e.g. 1 to 5%, 2 to 3%, or 2.5% of a second polyolefin polymer such as a PE polymer with an MFI similar to that of the first polymer or a polypropylene polymer with an MFI higher than the first polymer such as 10 times, 20 times or 25 times higher. The MFI range for the second PP polymer can be at least 20 g/lOmin, at least 30 g/lOmin, at least 40 g/lOmin, at least 50 g/lOmin, at least 60 g/lOmin, at least 70 g/lOmin and can be less than 100 g/lOmin.

The nonwoven structure can be entangled e.g. by needle punching or hydro-entanglement. The fibers can be spread in a uniform web by an air-laid process, e.g. for making nonwoven structures for use in mats, gauzes, scrims; sheets etc. The nonwoven structure can be made by needle punching. The fibers can be put into bales, placed on a conveyor belt and dispersed, e.g. spread in a uniform web by a wetlaid, airlaid, or carding/cros slapping process.

Non-woven structures according to embodiments of the present invention can be made by calender-thermal bonding technology. For example carded veils including bicomponent fibers according to any of the embodiments of the present invention can be subjected to the action of pressure and temperature of a calender. Alternatively, non-woven structures according to embodiments of the present invention can be made by means of air-through bonding technology. In this process carded veils including bi-component fibers according to any of the embodiments of the present invention are subjected to the action of hot-air. A nonwoven structure according to embodiments of the present invention can have a basic weight between 10 (or 12) gsm and 170 gsm for some applications such as for carpets, gauzes, fleece, hygiene products, wet or dry wipes, geotextiles or between 100 and 2000 gsm for others such as carpets, upholstery or geotextiles.

Needlepunched non- woven structures can be prepared by any of the following methods. Entangled nonwoven structures according to embodiments of the present invention can be needle punched and can be produced using an industrial scale needle punch production line.

For example, fibers such as staple or short cut fibers according to any of the embodiments of the present invention are mixed and formed into a bat or mat using carding and cross-lapping.

The mat can be pre-needled using plain barbed needles. Non- woven structures according to some embodiments of the present invention can be produced by first producing a needle punched non- woven structure as defined above and then subjecting the non-woven structure to a bonding operation, e.g. by thermal processing. Comparative tests

Needlepunched non-woven structures were produced:

1. With PP fibers made of Polychim HL10XF polypropylene having an MFI 3.5 g/lOmin for comparison purposes

2. With PP fibers produced according to embodiments of the present invention having an MFI of 2 g/lOmin. Other than the PP-type which was used, all other properties were kept identical for all fibers: titer was 4.4 dtex, cutting length was 90 mm, the fibers were not colored, and the same texturation and spin finish were used.

Geotextile needlefelt with a weight of 120 g/m ² was produced with each of the fiber types, test 1 being the comparative values and test 2 that of the present invention.

Carding and needling settings were kept identical for all the tests.

The properties of the needlefelt geotextile were measured by means of tensile testing:

1. According to ISO 10319

(Speed of the clamps was changed from the norm values to increase testing speed, i.e. 50 mm/min)

2. There were a minimum 2 repeats for each type of needlefelt

3. Each repeat = 6 samples MD (machine direction) + 6 samples CD (cross-direction)

4. Samples were taken over the entire width of the geotextile + measured in the correct order (i.e. samples 1 & 6 are on the outside of the felt).

The results are shown in table 1 which indicates the improved performance of the non-woven structures according to the present invention.

Applications of fibers and non-woven structures according to embodiments of the present invention: Fibers and non-woven structures in accordance with embodiments of the present invention can be used in upholsters, for which mechanical properties are often the most stringent requirements. The stronger fibers in accordance with embodiments of the present invention result in a lower base weight required for such a textile.

Fibers or non- woven structures in accordance with embodiments of the present invention can be used in reinforced constructional products such as in concrete reinforcement including the fibers for which a high strength of the fibers is important.

Fibers and non-woven structures in accordance with embodiments of the present invention can be used for composite applications, e.g. in combination with other fiber types such as glass fibers, carbon fibers or natural fibers (wood, flax, hemp).

Table 1