WO2002053629A1

WO2002053629A1 - Polymeric compound and process for its preparation

Info

Publication number: WO2002053629A1
Application number: PCT/EP2001/015391
Authority: WO
Inventors: Maria Soliman; Vitor Manuel Carvalho Vila Verde; Marianne Sarkissova; Markus Johannes Henricus Bulters; Martin Antonius Van Es; Roelof Marissen; Wilhelmus Gerardus Marie Bruls; Johannes Fredericus Repin
Original assignee: DSM NV
Current assignee: Koninklijke DSM NV
Priority date: 2000-12-28
Filing date: 2001-12-21
Publication date: 2002-07-11
Anticipated expiration: 2003-06-28

Abstract

The invention relates to a polymeric compound, comprising a thermoplastic matrix and polymeric fibres, wherein: - the thermoplastic matrix has a high flow during melt processing, - the polymeric compound comprises between 0.5 wt.% and 10 wt.% of a lubricant, - the length of the polymeric fibres is between 0.1 mm and 50 mm. The invention further relates to a process for the preparation of the polymeric compounds, as well as to their use.

Description

POLYMERIC COMPOUND AND PROCESS FOR ITS PREPARATION

The invention relates to a polymeric compound, comprising a thermoplastic matrix and polymeric fibres.

Such a polymeric compound is known from US-A 3,639,424. The known polymeric compound comprises a thermoplastic mouldable material and between 5 - 50 wt.% of staple-length polyethyleneterephtalate fibres having a denier between 1.5 and 25; the moulding temperature of the thermoplastic mouldable material is at least 25°C below the melting point of the fibres. An additional essential feature in US-A 3,639,424 is that the fibres are heat set prior to use. Heat setting of the polymeric fibres is utilised to improve properties, in particular the dispersion of the polymeric fibres. In the embodiments and examples, polypropylene (PP) and polyethylene (PE) are disclosed as thermoplastic mouldable material.

According to US-A 3,639,424, articles made from the known polymeric compound have a high impact strength, e.g. as expressed in notched Izod impact values. Concrete notched Izod impact data at room temperature and at -40°C are given for a PP compound comprising 10 wt.% and 20 wt.% heat set polyethyleneterephtalate fibres. The highest value as given in US-A 3,639,424 is still below 2 ft.lb/in (i.e. below 10 kJ/m²). Values as given for a PP without fibres are 0.41 ft.lb/in (i.e., about 2 kJ/m²) at 23 °C, and 0.17 ft.lb/in (i.e., less than 1 kJ/m²) at -40°C.

Although the polymeric compound according to US-A 3,639,424 shows an increased notched Izod impact resistance compared to the notched Izod impact resistance of the thermoplastic matrix as such, these values are still too low for demanding applications.

It is an objective of the present invention to provide a polymeric compound, typically in the form of granulates, having higher impact strength compared to the known polymeric compounds, not only at room temperature, but also at reduced temperatures, e.g. at -30°C or lower.

Said objective is achieved in that:

^■ the thermoplastic matrix has a high flow during melt processing,

^■ the polymeric compound comprises between 0.5 wt.% and 10 wt.% of a lubricant,

^■ the length of the polymeric fibres is between 0.1 mm and 50 mm. Surprisingly, the polymeric compound according to the invention has a high impact resistance. Said high impact resistance is, surprisingly, largely maintained at low temperatures, e.g. at -30°C or even at -40°C.

"High impact resistance" is defined herein as an impact resistance which, when measured at room temperature, is higher than the impact resistance of the thermoplastic matrix as such or higher than the impact resistance of polymeric compounds comprising the same thermoplastic matrix but not having a high flow, whichever of the two is the highest. The impact resistance is measured according to ISO 180 (notched Izod impact) on an injection-moulded sample. With 'largely maintained at low temperatures' it is meant that the value of the impact resistance of an injection-moulded sample at -40°C is at least 40% of the value at room temperature, preferably at least 50%, more preferably at least 60%.

The polymeric compound according to the invention comprises a thermoplastic matrix. The matrix materials as such are known. Preferably, the matrix is a polyolefin or a thermoplastic elastomer. Examples of suitable polyolefin matrix materials are polyethylene (also comprising polyethylene copolymers such as octene- containing plastomers) and polypropylene (also comprising polypropylene copolymers). Preferably, the polyolefin matrix comprises polypropylene or high-density polyethylene. Thermoplastic elastomers are known inter alia from Polymer Blends, Volume 2: Performance, edited by D.R. Paul and C.B. Bucknall, ISBN 0-471-35280-2, 2000. This article describes thermoplastic elastomers on the basis of a thermoplastic polymer and a dynamically vulcanized rubber which is dispersed in a continuous phase of the thermoplastic polymer in the form of fine particles. Such thermoplastic elastomers, thermoplastic vulcanisates, hereinafter called TPV's, possess a number of properties of an elastomer and can be processed as a thermoplastic polymer. The most widely used TPV's have a polyolefin or a styrenic block copolymer as the thermoplastic polymer. Thermoplastice elastomers having a polyolefin as thermoplastic polymer in which the rubber component is not vulcanized, so-called thermoplastic polyolefin elastomers (TPO), can also be used as the thermoplastic matrix according to the invention. TPV's and TPO's often comprise oils. When a thermoplastic elastomer is used as the thermoplastic matrix material, the beneficial effects of the polymeric compound according to the invention are mainly found in an improved abrasion resistance and in an improved tear strength.

The thermoplastic matrix has, according to the invention, a high flow during melt processing. It was found that when the thermoplastic matrix does not have a high flow, the polymeric compound will not show a high impact resistance. "High" flow during melt processing for a thermoplastic matrix comprising polypropylene or polyethylene or co-polymers thereof is expressed herein as being a Melt Flow Index (MFI in g/10 min) of the thermoplastic matrix at or above a threshold value. "High flow" during melt processing for other thermoplastic matrix materials is expressed herein as being a melt viscosity at or below a threshold value.

If the thermoplastic matrix comprises PP or a co-polymer of PP, the MFI thereof should be at or above the threshold value of 5 g/10 min, as measured according to ISO 1133 at 230°C and 2.16 kg. Preferably, the MFI is 12 g/10 min or higher, more preferably 20 g/10 min or higher.

If the thermoplastic matrix comprises PE or a co-polymer of PE, the MFI thereof should be at or above the threshold value of 6 g/10 min, as measured according to ISO 1133 at 190°C and 2.16 kg, preferably 20 g/10 min or higher. For thermoplastic matrix materials other than said PP or PE or their co-polymers, the melt viscosity η of the matrix as such should be at or below the threshold value of 200 Pa.s. Preferably, η is below 150 Pa.s, more preferably η is below 100 Pa.s. The melt viscosity η as used herein is measured according to ISO 11443 at a shear rate y of 1000 s^"1 and at a guideline temperature of 40°C above the melting temperature (Tm, determined via Differential Scanning Calorimetry (DSC) according to ISO 11357) of the thermoplastic matrix, or, in case melt temperature is not applicable due to the absence of a crystalline phase, at a temperature of 100°C above its glass transition temperature (T_g, determined via Dynamic Mechanical Thermal Analysis (DMTA) according to ASTM D5279). If however the used processing temperature of the thermoplastic matrix is 20°C or more above the guideline temperature, then said processing temperature should be used for measuring η. An upper limit of the MFI-range (or, a lower limit of the η-range) beyond which the objective of the present invention is no longer achieved was not found. The limit of the MFI-range (or η-range) will therefore be determined by the practical availability of as well as the thermal stability of high-flow thermoplastic materials. For example, if the thermoplastic matrix comprises PP, the MFI of the PP can be as high as 100 g/10 min or even 300 g/10 min or higher, although it is at present not expected that high-flow PP grades having an MFI as high as 1000 g/10 min will become available. The thermoplastic matrix generally has a melt processing window. The melt processing window is defined as being a temperature range within which it is possible to perform a melt processing step on the thermoplastic matrix. The lower limit of the melt processing window is the melting temperature T_m of the thermoplastic matrix, or, in case melt temperature is not applicable due to the absence of a crystalline phase, its glass transition temperature T_g. The upper limit of the melt processing window is the temperature at which, during the melt processing step, significant degradation of the thermoplastic matrix will occur. Significant degradation is evidenced by effects known to the person skilled in the art, in particular by discolouration. The polymeric compound according to the invention comprises polymeric fibres. The polymeric fibres are chosen such that their thermal stability is sufficient so that they will remain essentially intact, e.g. not molten or degraded, during a melt processing step at temperatures above the lower limit of the melt processing window of the thermoplastic matrix. Contrary to common knowledge, it was found that compatibility and/or adhesion between the polymeric fibres and the thermoplastic matrix is not essential in order to achieve the benefits of the present invention, in particular regarding impact resistance and aesthetic properties. Accordingly, the enhancement of compatibility and/or adhesion between the polymeric fibres and the thermoplastic matrix, e.g. through a compatibiliser, specific fibre sizing, or exchange reactions between polymeric fibre and thermoplastic matrix during melt processing, is not essential either. Rather, it may be an additional benefit when the compatibility or adhesion between the polymeric fibres and the thermoplastic matrix is low or even non-existent. Also, it may be beneficial if the friction between the polymeric fibres and between the polymeric fibres and the thermoplastic matrix is low or reduced.

Heat setting of the polymeric fibres, prior to incorporation into the compound according to the invention, is not essential, although a heat setting step at a temperature below the T_m or T_g of the polymeric fibres may be beneficial. A heat set step may for example be executed by exposing the polymeric fibres in air to a temperature below the T_m or T_g of the polymeric fibres during a short period of time, for example 5 minutes.

Preferably, the amount of polymeric fibres comprised in the polymeric compound according to the invention is between 5 wt.% and 80 wt.%, based on the total weight of the polymeric compound. With increasing amount of polymeric fibres, the impact resistance of the polymeric compound according to the invention increases too. It was found that the increase of impact resistance with increasing amount of polymeric fibres was at least evident until 40 wt.% of polymeric fibres was added; but also adding an even higher percentage of polymeric fibres, 50 wt.% or even 60 wt.% or more, still yields polymeric compounds according to the invention showing high impact resistance.

The strength of the polymeric fibres comprised in the polymeric compound according to the invention, expressed in fibre tenacity, may vary within wide limits, whereby it was found that the impact strength of polymeric compounds according to the invention increases with increasing tenacity of the polymeric fibres. The tenacity of the polymeric fibres is defined as the maximum tensile strength that the polymeric fibres can withstand until they tear. The tenacity of polymeric fibres is commonly expressed in milliNewton per tex (mN/tex), wherein "tex" is defined as the weight in grams (g) of 1000 metres of fibre. The definitions of tenacity and tex as used herein are common general knowledge for persons skilled in the art of polymeric fibres, as disclosed in for example the Dictionary of Man-Made Fibers by Hans J. Koslowski (International Business Press Publishers, first edition 1998, ISBN 3-87150-583-8), pages 188-189. Preferably, the tenacity of the polymeric fibres in the polymeric compound according to the invention is 200 mN/tex or higher, more preferably 400 mN/tex or higher. It was found that the polymeric compound according to the invention shows the desired properties, in particular regarding impact resistance, if the length of the polymeric fibres is higher than 0.1 mm, preferably higher than 0.3 mm, more preferably higher than 2 mm. For practical reasons, when the polymeric compound according to the invention is provided as granulate, it may be preferable to limit the length of the polymeric fibres to 50 mm, more preferably to 25 mm. Separately, it may be beneficial to limit the length of the polymeric fibre to less than 15 mm, because it was found that longer polymeric fibres may show a tendency to form bundles in the polymeric compound; although said bundles do not negatively influence the mechanical properties of articles made from the polymeric compound according to the invention, they may negatively influence their aesthetic character.

The diameter of the polymeric fibres comprised in the polymeric compound according to the invention may vary within wide limits. The lower limit is determined by the practical availability of fibres rather than by their influence on properties. The upper limit of the diameter of the polymeric fibres is determined by that diameter that no longer yields a polymeric compound having a high impact resistance. Preferably, the diameter of the fibres is between 1μm and 100μm, more preferably between 5μm and 50μm, most preferably between 6μm and 30μm. If the polymeric fibres are not round, and thus do not have a diameter, the cross section of the polymeric fibres should be within the corresponding cross section ranges as can be calculated from the abovementioned diameters.

As indicated above, the polymeric fibres comprised in the polymeric compound according to the invention should have sufficient thermal stability, so that they will remain essentially intact, e.g. not molten or degraded, during a melt processing step at temperatures above the lower limit of the melt processing window of the thermoplastic matrix. With increasing difference between the T_m or T_g of the polymeric fibres and the lower limit of the processing window of the thermoplastic matrix, it becomes easier to execute the melt processing step because the range of temperatures within the processing window in which the polymeric fibres remain essentially intact increases. Preferably, the T_m or T_g of the polymeric fibre is at least 40°C, more preferably at least 60°C above the lower limit of the processing window of the thermoplastic matrix.

The polymeric fibres comprised in the polymeric compound according to the invention may comprise one of the following polymers: polyolefines, such as PE or PP, polyalkyleneterephtalates or polyalkylenenaphtalates (such as polyethyleneterephtalate or polybutyleneterephtalate), polyamides (such as polyamide- 6, polyamide-6.6 or polyamide-4.6), or polyacrylonitril.

Preferably, the polymeric fibres comprised in the polymeric compound according to the invention comprise a polymer chosen from the group of polyalkyleneterephtalates, polyamide-6, polyamide-6.6, polyamide-4.6 and polyacrylonitril. It was found that a polymeric compound according to the invention comprising polymeric fibres from said group of polymers shows additional improvements in mechanical properties, in particular regarding stiffness. More preferably, the polymeric fibres comprised in the polymeric compound according to the invention preferably comprise polyethyleneterephtalate (PET). Compared to polyamide fibres, fibres comprising PET have a lower water absorption which makes processing easier. Also, compared to other polyalkyleneterephtalates such as polybutyleneterephtalate (PBT), the handling and processing is easier. PET fibres typically melt at temperatures of 250°C - 265°C.

The polymeric compound according to the invention comprises between 0.5 wt.% and 10 wt.% of a lubricant. A lubricant is defined as a compound that, when present between two surfaces, reduces the friction between those surfaces. It is believed that a lubricant has beneficial effects on melt processing characteristics and on the aesthetic characteristics of articles made form polymeric compound according to the invention, while the mechanical properties such as impact resistance remain at a high level. Preferably, the lubricant is an oil. It was found that a wide variety of oils, such as ester oils, paraffinic oils and silicon oils are suitable.

The weight percentage of the lubricant in the polymeric compound may vary within a wide range. With increasing weight percentage, the benefits will typically increase, thereby outweighing any disadvantage that may occur, such as a decrease of stiffness. As indicated, between 0.5 wt.% and 10 wt.% of lubricant, preferably oil, is added, based on the total weight of the polymeric compound. Preferably, between 2.5 wt.% and 7.5 wt.% of lubricant is added.

Preferably, the lubricant is essentially present on the interface between the fibres or filaments of the fibres and the thermoplastic matrix, although, depending on the chemical nature of the lubricant, diffusion of the lubricant from said interface into the thermoplastic matrix and/or the polymeric fibres may occur during melt processing, thereby causing a percentage of the lubricant to be present in the matrix and/or the polymeric fibre. Articles made from polymeric compounds in which the lubricant is essentially present on the interface between the fibres or filaments of the fibres and the thermoplastic matrix were found to have improved surface aesthetic characteristics compared to polymeric compounds where the lubricant is evenly distributed throughout the polymeric compound, in that their surface is essentially bundle-free. A bundle is defined as an agglomerate of at least 5 fibres, joined together over a length of more than 100 μm. Essentially bundle-free is defined as showing less than 5, preferably less than 3 bundles per 100 cm², as identified by visual and/or microscopic observation of an injection moulded article made from the polymeric compound according to the invention.

The polymeric compound according to the invention may also comprise fillers. Fillers may be added to enhance certain mechanical properties such as stiffness. Examples of fillers are talc, wollastonite, glass fibres or glass beads. Surprisingly, the addition of a filler does not cause a noticeable reduction in impact resistance of the polymeric compound according to the invention, as is normally observed when a filler is added to a polymeric compound. Preferably, talc is used as the filler. Although the influence on mechanical properties is limited when talc is added in low weight percentages, the addition may still be useful, since talc also acts as a processing aid or as a nucleating agent. Addition of very high percentages of talc may be useful for maximum enhancement of certain mechanical properties such as stiffness, or in case the polymeric compound is used as masterbatch. Preferably, between 0.05 wt.% and 70 wt.% of a filler, preferably talc, based on the total weight of the polymeric compound, is used. More preferably, between 5 wt.% and 40 wt.% of a filler, preferably talc is used.

The polymeric compound according to the invention may additionally comprise additives, such as processing aids, pigments, dyes, or UV stabilizers. The polymeric compound according to the invention may be prepared using any known technology comprising an impregnating step or a coating step. Examples of suitable known technologies are the so-called long fibre technologies such as pultrusion, powder coating, and wire coating. Using these technologies, impregnated or coated fibres are formed; these may then be granulated, which is typically done to make the compound according to the invention suitable for further processing into (semi)-finished articles.

In order to achieve the objective of several of the preferred embodiments of the polymer compound according to the invention as disclosed above, however, it was found that not all known technologies always yield optimal results, in particular regarding the preparation of polymeric compounds useful for preparing articles that are bundle-free and polymeric compounds that comprise an oil essentially present at the interface between fibres and thermoplastic matrix.

It is therefore a further objective of the present invention to provide processes for the preparation of said preferred embodiments. Said objective is achieved regarding those compounds that comprise a lubricant, preferably oil, essentially present at the interface between polymeric fibres and thermoplastic matrix, in that the polymeric fibres are treated with the lubricant prior to the impregnating or coating step. The lubricant-treatment step may be done using known methods, such as spraying the lubricant onto the polymeric fibres or guiding the fibres through a bath containing the lubricant.

Separately, the objective to provide processes for the preparation of said preferred embodiments is also achieved regarding those polymeric compounds that are used to prepare articles that are bundle-free in that the impregnated or coated polymeric fibres are subjected to a mixing step, said mixing step done at a temperature within the processing window of the thermoplastic matrix. Typically, the impregnated or coated polymeric fibres will be granulated prior to the mixing step.

The mixing step may be executed using known methods, such as a single-screw extruder, a twin-screw extruder, a batch kneader or a mixing element in an injection moulding machine. The mixing step should be mild: the equipment should be designed such that the polymeric fibres remain essentially of the same length, i.e. show negligible breakage, during the mixing step. If the mixing step is not sufficiently mild, the resulting polymeric compound will not show the desired combination of properties: in particular, an insufficiently mild mixing step will lead to a compound not having a high impact strength. In that case, the mixing step should be altered in such a way that the impact strength of the polymeric compound is high while still yielding articles that are essentially bundle-free. This may be achieved by implementing measures known to the person skilled in the art, including one or more of the following: a reduction of screw speed, an increase of matrix melt temperature (while, of course, still remaining below the temperature at which the polymeric fibres melt or degrade), or a change in the screw design so that the amount of specific energy is reduced.

The polymer compound according to the invention may be transformed into shaped (semi-)finished articles using a variety of processing techniques. Examples of suitable processing techniques include injection moulding, injection compression moulding, in-mould decorating via injection moulding, extrusion, and extrusion compression moulding. Injection moulding is widely used to produce articles such as for example automotive exterior parts like bumpers, automotive interior parts like instrument panels, or automotive parts under the bonnet. Extrusion is widely used to produce articles such as rods, sheets and pipes. For example, the use of the polymeric compound according to the invention is beneficial in pipes: the combination of properties, including high impact resistance, may allow the production of thinner pipes having the same performance compared to pipes produced from known materials such as PP. Alternatively, pipes having the same wall thickness may show enhanced performance like temperature resistance, pressure resistance, creep resistance or the resistance against crack propagation.

The present invention is illustrated with Examples and comparative experiments as set out below.

General remarks on the Examples and comparative experiments Unless noted otherwise, the polymeric compounds of the Examples and comparative experiments were prepared and then granulated; subsequent determination of properties (such as impact strength or stiffness) was done on injection-moulded specimens.

Determination of the notched Izod impact resistance was done according to ISO 180 4A; determination of the flexural modulus was done according to ASTM D790; determination of the tensile modulus was done according to ISO R37/2. Falling dart impact was determined according to ISO 6603, whereby the dart had a diameter of 20 mm and a hemispherical tip, the total mass of dart plus additional weight was 22.63 kg, the dart falling from a height of 1 m, the samples having a thickness of 3.2 mm and not clamped.

Unless noted otherwise, wire coating was performed by means of a 30-mm single screw extruder (manufacturer Schwabenthan, screw L/D ratio of 25) that fed molten thermoplastic matrix material to a Unitika wire coating die having a die-hole of 2.5 mm. The polymeric compound was taken out of the wire coating die by means of a strand puller. Pultrusion was done in the same fashion as wire coating, except that the wire coating die was replaced by an in-house built pultrusion die.

Unless noted otherwise, the polymeric fibres were Diolen® 183 (supplier: Acordis Industrial fibres), having a diameter of 25 μm and a tenacity of 632 mN/tex. Unless noted otherwise, the oil Pennzultra® 1199 (supplier: Pennzoil) was used as lubricant.

Examples I - IV; comparative experiment A

The notched Izod impact at -40°C and the falling dart impact at -40°C were determined for polymer compounds comprising PP, brand Stamylan® P (supplier: DSM) having various MFI values, 20 wt.% PET-fibres of 12.5 mm length, brand Diolen® 183 (supplier: Acordis Industrial fibres), melting at 250°C - 265°C, and - except for the comparative experiment - 0.5 wt.% lubricant. The compounds were prepared via wire coating at 200°C. Table 1

As can be seen in Table 1 , the notched Izod impact resistance remains at the known level when the thermoplastic matrix does not have a high flow (in other words: a low MFI, comparative experiment A). If a high flow is selected, the notched Izod impact resistance increases. This is surprising, since common polymer knowledge predicts a decreasing impact resistance with increasing flow of a matrix material.

Surprisingly, the falling dart impact resistance also increases when the matrix has a high flow. Additionally, the falling dart samples of Examples 3 and 4 were classified as splinter-free.

Examples V - VI; comparative experiment B

The notched Izod impact at +25°C and at -40°C was determined for polymer compounds comprising PP, brand Stamylan® P 213MNK40, various wt.% PET-fibres of 12.5 mm length, and - except for the comparative experiment - 0.5 wt.% lubricant. The compounds were prepared via wire coating at 200°C.

The results demonstrate that the notched Izod impact value at -40°C of the polymer compound according to the invention remains high compared to the value at 25°C (in these examples higher than 60% of the value at 25°C. The notched Izod impact strength of PP without fibres is rather low to begin with, and even decreases substantially at -40°C.

Examples VII - XII; comparative experiment C

The notched Izod impact at 25°C was determined for polymer compounds comprising PP, brand Stamylan® P 213MNK40, varying wt.% PET-fibres of 12.5 mm length as indicated in Table 3, and - except for the comparative experiment - 0.5 wt.% lubricant. The compounds were prepared via wire coating at 200°C.

Table 3

The results clearly indicate that the presence of the polymeric fibres is an essential feature in obtaining the desired properties, and that the notched Izod impact resistance increases with increasing fibre content at least until 40 wt.% of fibre is added. Additionally, the tensile modulus continues to increase with increasing fibre content.

Examples XIII - XIV

The notched Izod impact at -40°C was determined for polymer compounds comprising PP, brand Stamylan® P 213MNK40, 20 wt.% PET-fibres of varying length as indicated in Table 4, and 0.5 wt.% lubricant. The compounds were prepared via wire coating at 200°C.

The results in Table 4 indicate that the impact resistance of the polymeric compound according to the invention increases with increasing fibre length.

Examples XV - XVII

The notched Izod impact at -40°C and the flexural modulus at room temperature was determined for polymer compounds comprising PP, brand Stamylan® P 213MNK40, 20 wt.% PET-fibres of 6 mm length, a coarse talc, wt.% and type as indicated in Table 5 (supplier: Luzenac), and 0.5 wt.% lubricant. As reference, representing a polymeric compound according to the invention without the addition of talc, Example IV is included in Table 5 as well. The compounds were prepared via wire coating at 200°C.

Table 5

As can be seen from Table 5, the addition of talc as filler to the polymeric compound according to the invention does not negatively affect the impact resistance at all. At the same time the stiffness of the compound as indicated by the flexural modulus increased significantly.

Example XVIII

The notched Izod impact at -40°C and the tensile modulus at room temperature were determined for a polymeric compound comprising PP, brand Stamylan® P 213MNK40, 20 wt.% PET-fibres of 6 mm length, 2.5 wt.% lubricant and 20 wt.% of wollastonite, a naturally occurring calcium metasilicate, brand Nyad® G (supplier: Nyco), as filler. The polymeric compound was prepared via wire coating at 200°C.

Table 6

As can be seen from the table, the addition of wollastonite as filler to the polymeric compound according to the invention does not negatively affect the impact resistance at all. At the same time the stiffness of the polymeric compound as indicated by the tensile modulus increased significantly.

Examples XIX - XXI; comparative experiment D

The notched Izod impact at -40°C was determined, and the surface characteristic determined, for polymer compounds comprising PP, brand Stamylan® P 213MNK40, 20 wt.% PET-fibres of 12.5 mm length, and varying percentage of a paraffinic oil, type Sunpar® 150 (supplier: Sunoco / Sun Oil Company Belgium) in Example XIX and XX and type Pennzultra® 1199 (supplier: Pennzoil) in Example XXI, as indicated in Table 7. The mixing of oil and PP in Example XIX was done via a simple tumble-mixing step which resulted in PP granulate, wetted on the outside with oil. In Example XXI, a fine talc was also added as a filler (type Steamic® 00S D, supplier Luzenac). The compounds were prepared as indicated in Table 7.

Clearly, the presence of a lubricant according to the invention creates a best-of-both-worlds situation: impact resistance at a high level, while at the same time the surface characteristics are improved, especially when the lubricant is essentially present on the interface between thermoplastic matrix and polymeric fibre (Examples XX and XXI). The combination of oil addition with talc addition produced a surprising further effect: the impact resistance actually increased, while the beneficial effects of oil addition such as the essentially bundle-free surface characterisation were maintained.

Example XXII; comparative experiment E

The notched Izod impact at -40°C and the falling dart impact at -40°C were determined for a polymeric compound comprising as thermoplastic matrix a polyolefinic ethylene based octene co-polymer plastomer, brand Exact © 8210 (supplier: Dex Plastomers) having a MFI of 10 g/10 min (measured at 190°C/2.16 kg), 20 wt.% PET-fibres of 6 mm length, and 2.5 wt.% of lubricant. The polymeric compound was prepared via wire coating. For comparison, same properties were determined on the matrix material. Table 8

As can be seen in Table 8, the notched Izod impact resistance and the falling dart impact of Example XXII are superior to those of the polymeric matrix material as such.

Example XXIII; comparative experiment F

The notched Izod impact at 25°C and at -40°C, and the falling dart impact at -40°C were determined for a polymeric compound comprising as thermoplastic matrix a high-density polyethylene (HDPE), brand Stamylan® HD 9089 (supplier: DSM) having a density of 963 kg/m³ and an MFI of 8 g/10 min (measured at 21.2N/190°C), 20 wt.% PET-fibres of 6 mm length, and 2.5 wt.% of lubricant. The polymeric compound was prepared via wire coating. For comparison, the notched Izod impact properties were determined on the thermoplastic matrix material as such.

Table 9

As can be seen in Table 9, the notched Izod impact resistance at both room temperature and at -40°C of Example XXIII are superior to those of the HDPE thermoplastic matrix material as such.

Examples XXIV - XXVI

In order to determine the influence of fibre diameter, the notched Izod impact at -40°C and the falling dart impact at -40°C were determined for polymeric compounds comprising PP, brand Stamylan® P 213MNK40, 20 wt.% PET-fibres of 6 mm length and diameters 12μ, 25μ and 45μ, and 2.5 wt.% of lubricant. The polymeric compounds were prepared via wire coating at 200°C.

Table 10

As can be clearly seen in Table 10, the notched Izod impact resistance and the falling dart impact are not significantly influenced by the diameter of the polymeric fibre within the range as tested.

Examples XXVII - XXIX

In order to determine the influence of fibre strength, the notched Izod impact at -40°C and the falling dart impact at -40°C were determined for polymeric compounds comprising PP, brand Stamylan® P 213MNK40, 20 wt.% PET-fibres of 6 mm length and fibre strengths 579, 632 and 691 mN/tex, and 2.5 wt.% of lubricant. The polymeric compounds were prepared via wire coating at 200°C. Table 11

As can be clearly seen in Table 11 , the notched Izod impact resistance at low temperatures (-40°C) of polymeric compounds according to the invention increases further with increasing fibre strength.

Example XXX

In order to determine the influence of fibre composition, the notched Izod impact at 25°C and at -40°C were determined for a polymeric compound comprising PP, brand Stamylan® P 213MNK40, 20 wt.% polyethylenenaphtalate (PEN) fibres type T112 (supplier: KoSa), and 2.5 wt.% of lubricant. The polymeric compounds were prepared via wire coating at 200°C.

Table 12

As can be clearly seen in Table 12, the notched Izod impact resistance at both room temperature and at low temperatures (-40°C) shows that polymeric compounds according to the invention comprising PEN fibres have a high impact strength.

Claims

I . Polymeric compound, comprising a thermoplastic matrix and polymeric fibres, characterised in that:

^■ the thermoplastic matrix has a high flow during melt processing,

^■ the length of the polymeric fibres is between 0.1 mm and 50 mm. 2. Polymeric compound according to claim 1 , characterised in that the matrix is a polyolefin.

3. Polymeric compound according to claim 2, characterised in that the polyolefin matrix comprises polypropylene having a Melt Flow Index (MFI) of 5 or higher.

4. Polymeric compound according to claim 2, characterised in that the polyolefin matrix comprises high-density polyethylene having an MFI of 6 or higher.

5. Polymeric compound according to claim 1 , characterised in that the matrix is a thermoplastic elastomer, whereby the thermoplastic elastomer can comprise a TPO and/or a TPV.

6. Polymeric compound according to any one of claims 1 - 5, characterised in that the amount of fibres is between 5 wt.% and 80 wt.%.

7. Polymeric compound according to any one of claims 1 - 6, characterised in that the tenacity of the fibres is 200 mN/tex or higher.

8. Polymeric compound according to any one of claims 1 - 7, characterised in that the diameter of the fibres is between 1μm and 100μm. 9. Polymeric compound according to any one of claims 1 - 8, characterised in that the melting point of the polymeric fibres is at least 40°C higher than the T_m or the T_g of the thermoplastic matrix. 10. Polymeric compound according to any one of claims 1 - 9, characterised in that the polymeric fibre comprises a polymer chosen from the group of polyalkyleneterephtalates, polyamide-6, polyamide-6.6, polyamide-4.6 and polyacrylonitril.

I I . Polymeric compound according to claim 10, characterised in that the polymeric fibre comprises polyethyleneterephtalate.

12. Polymeric compound according to any one of claims 1 - 11 , characterised in that the polymeric compound further comprises a filler. 13. Polymeric compound according to claim 12, characterised in that the polymeric compound comprises between 0.05 wt.% and 70 wt.% of talc as filler. 14. Polymeric compound according to any one of claims 1 - 13, characterised in that the lubricant is an oil. 15. Polymeric compound according to any one of claims 1 - 14, characterised in that the lubricant is essentially present at the interface between the fibres and the thermoplastic matrix. 16. Polymeric compound according to any one of claims 1 - 15, characterised in that the notched impact resistance of an injection moulded sample at -40°C is at least 60% of the notched impact resistance at room temperature.

17. Process for the preparation of a polymeric compound according to any one of claims 1 -16, comprising an impregnating step in which the polymeric fibres are impregnated or coated with the thermoplastic matrix to form impregnated or coated fibres, characterised in that the polymeric fibres are treated with the lubricant prior to the impregnating or coating step.

18. Process for the preparation of a polymeric compound according to any one of claims 1 -16, comprising an impregnating or coating step in which the polymeric fibres are impregnated or coated with the thermoplastic matrix to form impregnated or coated fibres, said method of impregnating or coating being chosen from the group of long fibre technologies: pultrusion, powder coating and wire coating, characterised in that the polymeric fibres are treated with an the lubricant prior to the impregnating or coating step. 19. Process for the preparation of a polymeric compound according to any one of claims 1 - 16, comprising an impregnating or coating step in which the polymeric fibres are impregnated or coated with the thermoplastic matrix to form impregnated or coated fibres, characterised in that the impregnated or coated fibres are granulated and then subjected to a mixing step, said mixing step being done at a temperature within the processing window of the thermoplastic matrix. 20. Process for the preparation of a polymeric compound according to any one of claims 1 - 16, comprising an impregnating or coating step in which the polymeric fibres are impregnated with the thermoplastic matrix to form impregnated or coated fibres, said method of impregnating or coating being chosen from the group of long fibre technologies: pultrusion, powder coating and wire coating, characterised in that the impregnated or coated fibres are subjected to a mixing step, said mixing step being done at a temperature within the processing window of the thermoplastic matrix. 21. Process according to any one of claims 19 - 20, characterised in that the mixing step is done in a single-screw or twin-screw extruder or in a mixing element in an injection-moulding machine.

22. Use of the polymeric compound according to any one of claims 1 - 16 in articles made via any one of the following processing techniques: injection moulding, injection compression moulding, in-mould decorating via injection moulding, extrusion, and extrusion compression moulding.

23. Use of the polymeric compound according to any one of claims 1 - 16 in extruded pipes.