Glass fibre reinforced thermoplastic polymer composition

Abstract

The present invention relates to a glass fibre reinforced thermoplastic polymer composition comprising a core and a thermoplastic polymer sheath surrounding said core, wherein the core comprises glass fibres and an impregnating agent, and the sheath comprises a high-density polyethylene and a coupling agent, wherein the coupling agent is a functionalized polyethylene grafted with an acid or acid anhydride functional group. The invention further relates to a method for producing such compositions as well as structural parts made therefrom.

Description

[0001] 24POLYOQ38-WO-ORD 1

[0002] GLASS FIBRE REINFORCED THERMOPLASTIC POLYMER COMPOSITION

[0003] The present invention generally relates to a glass fibre reinforced thermoplastic polymer, and a method for producing the same. In particular, the present invention relates to a long glass fibre reinforced thermoplastic polymer such as a long glass fibre reinforced polyethylene. Such materials are used in applications requiring high stiffness, such as for example front-end module, tailgate, instrument panel carriers and other automotive parts.

[0004] Long glass fibre reinforced polypropylene (PP) materials are known per se and for example commercially available from SABIC under the brand name STAMAX™. These long glass fibre reinforced polypropylene materials are available as pellets comprising a core and a polypropylene sheath surrounding said core, wherein the core comprises glass fibres extending in a longitudinal direction of the pellet and an impregnating agent.

[0005] WO 2009 / 080281 discloses a method for the manufacture of said type of long glass fibre reinforced polypropylene materials, which is also called a wire-coating method. That method comprises the subsequent steps of: a) unwinding from a package of at least one continuous glass multifilament strand comprising at most 2% by mass of a sizing composition; b) applying from 0.5 to 20% by mass of an impregnating agent to said at least one continuous glass multifilament strand to form an impregnated continuous multifilament strand; c) applying a sheath of thermoplastic polymer around the impregnated continuous multifilament strand to form a sheathed continuous multifilament strand; characterized in that the impregnating agent is non-volatile, has a melting point of at least 20°C below the melting point of the thermoplastic matrix, has a viscosity of from 2.5 to 100 cS at application temperature, and is compatible with the thermoplastic polymer to be reinforced.

[0006] WO 2009 / 080281 further discloses that suitable examples of the thermoplastic polymer used in the sheathing process include polyethylenes (PE). PE is commonly used in packaging and pipe applications and is in general less expensive than PP due to its 24POLYOQ38-WO-ORD 2 higher production volume and lower raw material costs. However, there has not yet been a commercialized solution providing a long glass fibre reinforced polyethylene material available as pellets comprising a core and a polyethylene sheath surrounding said core through the wire-coating method.

[0007] Another process to manufacture long glass fibre reinforced polyolefin materials is based on what is known as a pultrusion process. In such a process, continuous glass multifibre strands are pulled through a molten resin in such a manner that the individual filaments are fully dispersed into said resin. Examples of such processes are disclosed in EP1364760, NL1010646 and WO 2008 / 089963.

[0008] The term “multifilament strand” as used in W02009 / 080821 and the term “multifibre strand” as used should be regarded as synonyms and referring to the same type of material, which are often also referred to as roving.

[0009] An important difference between the pultrusion grade long glass fibre reinforced polyolefin materials and the long glass fibre reinforced thermoplastic polymer materials according to the present invention is that the glass fibres in the present invention are not dispersed in the thermoplastic polymer. This dispersion will only take place once the materials are moulded into finished or semi-finished parts in downstream conversion processes, such as for example injection moulding.

[0010] To allow a proper dispersion of the glass fibres in such downstream conversion processes the core of the pellets not only contains the glass fibres but also what is referred to as an impregnating agent. The impregnating agent facilitates a proper dispersion of the glass fibres during the moulding of the (semi) finished article. The impregnating agent is an important component of these long glass fibre reinforced thermoplastic polymer materials. In effect the impregnating agent has at least two key functions, the first one being to effectively couple the glass fibres to each other and to the thermoplastic polymer sheath in the pellet and the second one being to provide a sufficient dispersion of the glass fibres in downstream conversion processes.

[0011] Examples of suitable impregnating agents are disclosed in WO 2009 / 080281 . WO 2009 / 080281 specifically discloses that the impregnating agent may be a blend of 30 24POLYOQ38-WO-ORD 3 mass% of a hyper-branched polymer (Vybar 260, available from Baker Hughes, also known as an iso-polymer) and 70 mass% of paraffin (Paralux oil, available from Chevron).

[0012] In one aspect, the present invention provides a glass fibre reinforced thermoplastic polymer composition comprising a core that extends in the longitudinal direction and a thermoplastic polymer sheath intimately surrounding said core, wherein the core comprises glass fibres and an impregnating agent, and the sheath comprises a high- density polyethylene and a coupling agent, wherein the impregnating agent is non-volatile, has a melting point of at least 20°C below the melting point of the thermoplastic polymer, has a viscosity of from 2.5 to 100 cS at application temperature, and is compatible with the thermoplastic polymer to be reinforced, wherein the high-density polyethylene has a melt flow index in the range from 5 to 100 dg / min as measured according to ASTM D1238-13 with a 2.16 kg load at 190°C and a density in the range from 0.920 to 0.972 g / cm3as measured according to ASTM D792- 13, and wherein the coupling agent is a functionalized polyethylene grafted with an acid or acid anhydride functional group.

[0013] Thermoplastic polymer

[0014] The glass fiber-reinforced thermoplastic polymer composition of the present invention comprises a thermoplastic polymer sheath. The thermoplastic polymer sheath comprises a high-density polyethylene.

[0015] In one embodiment, the amount of the high-density polyethylene is at least 50 wt%, preferably at least 80 wt%, more preferably at least 90 wt%, and even more preferably at least 95 wt%, of the thermoplastic polymer sheath.

[0016] In one embodiment, the thermoplastic polymer sheath may comprise other thermoplastic polymers than the high-density polyethylene. Suitable examples of other thermoplastic polymers may include polyamides, such as polyamide 6, polyamide 66, or polyamide 46; polyolefins like polypropylenes and polyethylenes, including polyolefin homopolymer, copolymer or any blend thereof; polyesters, such as polyethylene 24POLYOQ38-WO-ORD 4 terephthalate, polybutylene terephthalate; polycarbonates; polyphenylene ethers (PPE); polyphenylene sulphide (PPS); polyurethanes; also any type of polymer blends and compounds and any combinations thereon.

[0017] In a preferred embodiment, the thermoplastic polymer sheath does not comprise a polyethylene with a density below 0.920 g / cm3as measured according to ASTM D792- 13.

[0018] In a preferred embodiment, the thermoplastic polymer sheath does not comprise a polypropylene.

[0019] In a preferred embodiment, the thermoplastic polymer sheath does not comprise a polyamide.

[0020] In a preferred embodiment, the thermoplastic polymer sheath does not comprise phthalates.

[0021] High-density polyethylene

[0022] A high-density polyethylene is a polyethylene of a linear structure.

[0023] The high-density polyethylene according to the present invention may comprise one or more comonomers, wherein the comonomer is a moiety derived from 1 -butene and / or 1 -hexene, wherein the amount of comonomer is preferably at most 1 .2 wt%, preferably at most 1 .0 wt%, preferably at most 0.7 wt%, preferably at most 0.5 wt%, preferably at most 0.3 wt% based on the total amount of the high-density polyethylene.

[0024] The MFI of the high-density polyethylene according to the present invention is preferably in the range from 5 to 100 dg / min, preferably from 10 to 50 dg / min, more preferably from 20 to 40 dg / min, such as about 30 dg / min, as measured according to ASTM D 1238- 13 with a 2.16 kg load at 190°C.

[0025] The density of the high-density polyethylene according to the present invention is preferably in the range from 0.920 to 0.972 g / cm3, preferably from 0.930 to 0.970 24POLYOQ38-WO-ORD 5 g / cm3 , more preferably from 0.940 to 0.960 g / cm3, such as about 0.950 g / cm3, as measured according to ASTM D792-13.

[0026] The high-density polyethylene according to the present invention can for example have a unimodal molecular weight distribution or a multimodal molecular weight distribution, for example a bimodal molecular weight distribution.

[0027] The production processes of the high-density polyethylene and is summarized in “Handbook of Polyethylene” by Andrew Peacock (2000; Dekker; ISBN 0824795466) at pages 43-66. Suitable catalysts for the production of polyethylene include Ziegler Natta catalysts, chromium-based catalysts, and single site metallocene catalysts.

[0028] The unimodal polyethylene may be obtained for example by polymerizing ethylene and optionally at least one olefin comonomer in slurry in the presence of a silica-supported chromium-containing catalyst and / or an alkyl boron compound. Suitable comonomers include for example 1 -butene and 1 -hexene. The unimodal polyethylene may be obtained for example by polymerizing ethylene and optionally at least one olefin comonomer in a gas phase polymerization or in a slurry polymerization process.

[0029] The production processes for bimodal high-density polyethylene are summarized at pages 16- 20 of “PE 100 Pipe systems” (edited by Bromstrup; second edition, ISBN 3- 8027-2728-2). The production of bimodal high-density polyethylene via a low-pressure slurry process is described by Alt et al. in “Bimodal polyethylene-interplay of catalyst and process” (Macromol. Symp. 2001 , 163, 135-143). The characteristics of the polyethylene are determined amongst others by the catalyst system and by the concentrations of catalyst, comonomer and hydrogen. The production of bimodal high- density polyethylene via a low-pressure slurry process may also be performed via a three-stage process. The concept of the two-stage cascade process is elucidated at pages 137-138 by Alt et al. “Bimodal polyethylene-interplay of catalyst and process” (Macromol. Symp. 2001 , 163).

[0030] Preferably the high-density polyethylene according to the present invention has a unimodal molecular weight distribution. 24POLYOQ38-WO-ORD 6

[0031] Coupling agent

[0032] The glass fiber-reinforced thermoplastic polymer composition of the present invention comprises a thermoplastic polymer sheath. The thermoplastic polymer sheath comprises a coupling agent.

[0033] Suitable examples of the coupling agent include a functionalized polyolefin grafted with an acid or acid anhydride functional group. For the purpose of the present invention, the polyolefin in the coupling agent is preferably polyethylene. Preferably, the coupling agent is a maleic anhydride functionalized high-density polyethylene.

[0034] The polyethylene in the coupling agent may be the same type of polyethylene in the thermoplastic polymer, or a different type of polyethylene.

[0035] Preferably, the polyethylene in the coupling agent has a unimodal molecular weight distribution as well.

[0036] The amount of the coupling agent may e.g., be 1 to 10 wt%, preferably 2 to 8 wt%, more preferably 4 to 7 wt% with respect to the composition.

[0037] In one embodiment, a total amount of the high-density polyethylene and the coupling agent is at least 90wt%, preferably at least 95 wt%, more preferably at least 98wt% with respect to the sheath.

[0038] In one embodiment, the thermoplastic polymer sheath comprises at most 1wt% of a functionalized polypropylene grafted with an acid or acid anhydride functional group, preferably at most 0.1 wt%, more preferably 0 wt%, with respect to the composition.

[0039] Glass fibers

[0040] The glass fibre reinforced thermoplastic polymer composition of the present invention comprises a core, wherein the core comprises glass fibres.

[0041] In general, glass fiber is a glassy cylindrical substance where its length is significantly longer than the diameter of its cross section. It is known that adding glass fibers is able to improve the mechanical performance (e.g., strength and stiffness) of polymeric 24POLYOQ38-WO-ORD 7 matrix. The level of performance improvement depends heavily on the properties of the glass fibers, e.g., diameter, length, and surface property of the glass fiber.

[0042] The thermoplastic polymer composition comprises 5-70 mass% of glass fibers, preferably 10-50 mass%, such as 20-40 mass%.

[0043] In one embodiment, the composition of the present invention comprises 5 to 60 wt%, preferably 20 to 40 wt%, of the core, and 40 to 95 wt%, preferably 60 to 80 wt%, of the thermoplastic polymer sheath.

[0044] In some instances, the glass fibers of the present invention have a length of 1-50 mm. A composition containing glass fibers of length greater than 1 mm is generally referred to as a long glass fiber (LGF) reinforced composition, for example a LGF PE composition.

[0045] In contrast, short glass fiber compositions or compounds typically contain fibers of length below 1 mm. Such compounds are typically made by mixing chopped strands of pre-determined length with a thermoplastic polymer in an extruder, during which the glass fibers are dispersed in the molten thermoplastic. Because of fiber breakage occurring during this process the fiber length is decreased. Upon molding the composition into an article, the fibers are further reduced in size.

[0046] Long glass fiber-reinforced polymer compositions in the form of, for example, pellets or granules can be prepared from continuous lengths of fibers by a sheathing or wirecoating process, by crosshead extrusion or several pultrusion techniques. Using these technologies, fiber strands impregnated or coated with a polymer are formed; these may then be cut into lengths, and the pellets or granules thus obtained can be further processed, e.g., by injection molding or extrusion processes, into (semi)-finished articles.

[0047] In a pultrusion process, a bundle of continuous glass filaments is spread out into individual filaments and drawn through an impregnation die, into which molten thermoplastic is injected, aiming at entirely wetting and impregnating each filament with the molten thermoplastic. A strand of diameter of about 3 mm is drawn from the die and 24POLY0038-WO-ORD 8 then cooled. Finally, the strand is chopped into segments of the desired length. The glass fibers are generally parallel to one another in the segment, with each fiber being individually surrounded by the thermoplastic.

[0048] The process of sheathing or wire-coating is done without wetting fibers individually with thermoplastic, but by forming a continuous outer sheath, also called coating or skin, of a thermoplastic material around the continuous multifilament strand surface. The sheathed continuous strand is chopped into pellets or granules of desired length, e.g., for about 15 mm length, in which the fibers are generally parallel to one another and have the same length as the pellets or granules. The LGF pellets are further supplied to an injection molding or extrusion molding machine, and during this molding step the glass fibers are dispersed within the thermoplastic polymer and formed into molded (semi)-finished articles. Documents EP 0921919 B1 and EP 0994978 B1 describe a typical sheathing or wire-coating method.

[0049] The weight average length of the glass fibers in the standard ISO527 testing bar is preferably at least 2 mm, to result in higher strength and stiffness, more preferably at least 3, 4, 5 or even 6 mm. Too high a length may cause some problems, for example in processing or in surface appearance of the molded article, therefore the length of the glass fibers in the composition of the invention is preferably at most 40 mm, more preferably at most 30, 20 or 15 mm.

[0050] The roving density of the continuous glass multifilament strand may vary within wide limits. Preferably, the continuous multifilament strand may have of from 500 to 10000 g / km and more preferably from 2000 to 5000 g / km, because of high throughput. The diameter of the glass filaments in the continuous multifilament strand may widely vary. Preferably, the diameter of the glass filaments ranges from 5 to 50 microns, more preferably from 10 to 30 microns and most preferably from 15 to 25 microns. Glass filaments diameters outside these ranges tend to result in a decrease of mechanical properties and / or enhanced abrasion of the equipment used.

[0051] Preferably, the continuous glass multifilament strand is coated with a sizing composition (i.e., a coating) to improve adhesion to the polymer matrix. The sizing composition can be disposed on substantially all of the glass filaments or on a portion 24POLYOQ38-WO-ORD 9 of the glass filaments in the thermoplastic composition. The sizing provides coated glass filaments that can be either bonding or non-bonding towards the thermoplastic polymer composition of the sheath. Preferably, the coated glass filaments are bonding towards the polyethylene in the thermoplastic polymer composition of the sheath.

[0052] The sizing composition can include a polyepoxide, a poly(meth)acrylate, a poly(arylene ether), a polyurethane, or a combination thereof. The polyepoxide can be a phenolic epoxy resin, an epoxylated carboxylic acid derivative (e.g., a reaction product of an ester of a polycarboxylic acid having one or more unesterified carboxyl groups with a compound including more than one epoxy group), an epoxidized diene polymer, an epoxidized polyene polymer, or a combination thereof.

[0053] The sizing composition can further include a silane coupling agent to facilitate bonding with the glass fiber. The silane coupling agent can be tri(Ci-6 alkoxy)mono amino silane, tri(Ci_6alkoxy)diamino silane, tri(Ci_6alkoxy)(Ci_6alkyl ureido) silane, tri(Ci_6alkoxy)(epoxy Ci_6alkyl) silane, tri(Ci_6alkoxy)(glycidoxy Ci_6alkyl) silane, tri(Ci_6alkoxy) (mercapto Ci_6alkyl) silane, or a combination thereof. For example, the silane coupling agent is (3 -aminopropyl)triethoxy silane, (3-glycidoxypropyl)trimethoxysilane, (2-(3,4- epoxycyclohexyl)ethyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane, (3- (2- aminoethylamino)propyl)triethoxysilane, (3 -ureidopropyl)triethoxy silane, or a combination thereof. Preferably, the silane coupling agent is aminopropyltriethoxysilane, glycidylpropyltrimethoxysilane, or a combination thereof.

[0054] For the sake of clarification, the silane coupling agent in the sizing composition is different from the coupling agent comprised in the sheath part of the glass fibre reinforced thermoplastic polymer composition of the present invention.

[0055] The sizing composition can be present in an amount from 0.1 to 5 wt% based on the weight of the continuous glass multifilament strand. The sizing composition may be applied to the glass fibers by any means, such as immersing the glass multifilament strand in the sizing composition or contacting the glass multifilament strand with an aqueous emulsion, or suspension of the sizing composition. Other coating methods include using an aqueous dispersion of the sizing composition applied to the uncoated glass multifilament strand by a roller in a continuous fashion, which can be followed by 24POLYOQ38-WO-ORD 10 a heat treatment or curing step.

[0056] Typically, after applying the sizing composition to the glass filaments, the filaments are bundled into the continuous glass multifilament strands and then wound onto bobbins to form a package.

[0057] Impregnating agent

[0058] The glass fibre reinforced thermoplastic polymer composition of the present invention comprises a core, wherein the core comprises an impregnating agent.

[0059] For the purpose of the present invention, the impregnating agent is non-volatile, has a melting point of at least 20°C below the melting point of the thermoplastic matrix, has a viscosity of from 2.5 to 100 cS at application temperature, and is compatible with the thermoplastic polymer to be reinforced.

[0060] The amount of the impregnating agent applied to the thermoplastic composition depends on the amount of the glass fibers, on the thermoplastic polymer, on the size (diameter) of the glass fibers, and on type of sizing that is on the surface of the glass fibers.

[0061] According to the present invention, the amount of impregnating agent applied to the thermoplastic composition should be at least 0.5% by mass, preferably it is at least 1% by mass, more preferably at least 1 .5% by mass, such as at least 2.0%, at least 2.5%, at least 3.0%, or at least 3.5% by mass; but should be at most 20% by mass, preferably it is at most 10% by mass, more preferably at most 5.5% by mass, such as at most 5.0%, or at most 4.0% by mass, based on the total weight of the glass fibre reinforced thermoplastic composition. A suitable amount of impregnating agent is needed to assist homogeneous dispersion of glass fibers in the thermoplastic polymer matrix during moulding, but the amount should not be too high, because an excess of the agent may result in decrease of mechanical properties of the moulded articles.

[0062] The impregnating agent used in the present invention is at least one compound that is compatible with the thermoplastic polymer matrix to be reinforced, enabling it to 24POLYOQ38-WO-ORD 11 enhance dispersion of the glass fibers in the thermoplastic polymer matrix during the moulding process.

[0063] The viscosity of the impregnating agent should be at most 100 cS, preferably at most 75 cS and more preferably at most 25 cS at application temperature. The viscosity of the impregnating agent should be at least 2.5 cS, preferably at least 5 cS, and more preferably at least 7 cS at the application temperature. An impregnating agent having a viscosity higher than 100 cS is difficult to apply to the continuous glass multifilament strand. Low viscosity is needed to facilitate good wetting performance of the fibers, but an impregnating agent having a viscosity lower than 2.5 cS is difficult to handle, e.g., the amount to be applied is difficult to control; and the impregnating agent could become volatile. Without wishing to be bound to any theory, the inventors believe that the impregnation of the continuous glass multifilament strands, without separating or spreading of individual filaments, by the impregnating agent is driven mainly by capillary forces.

[0064] For purpose of the invention, unless otherwise stated, the viscosity of the impregnating agent is measured in accordance with ASTM D 3236-15 (standard test method for apparent viscosity of hot melt adhesives and coating materials, Brookfield viscometer Model RVDV 2, #27 spindle, 5 r / min) at 100° C.

[0065] The melting point of the impregnating agent is at least about 20°C below the melting point of the thermoplastic matrix. Without being wished to be bound to any theory, the inventors think this difference in melting points, and thus in solidification or crystallisation points, promotes fiber impregnation also after applying the thermoplastic sheath and cooling the sheathed strand, and fiber dispersion during subsequent moulding. Preferably, the impregnating agent has a melting point at least 25 or 30°C below the melting point of the thermoplastic matrix. For instance, when the thermoplastic polymer matrix is polyethylene having a melting point of about 130°C, the melting point of the impregnating agent may be at most about 110°C.

[0066] The application temperature is chosen such that the desired viscosity range is obtained and is preferably below the self-ignition temperature of the impregnating agent. For 24POLYOQ38-WO-ORD 12 example, when the matrix is polyethylene, the application temperature of the impregnating agent can be from 150 to 240°C.

[0067] The melting point of the impregnating agent may be determined in accordance with ASTM D127.

[0068] According to the present invention, the impregnating agent should be compatible with the thermoplastic polymer to be reinforced and may even be soluble in said polymer.

[0069] According to the present invention, the impregnating agent is non-volatile, and substantially solvent-free. Being non-volatile means that the impregnating agent does not evaporate under the application and processing conditions applied; that is, it has a boiling point or range higher than said processing temperatures. In the context of present application, “substantially solvent-free” means that impregnating agent contains less than 10% by mass of solvent, preferably less than 5% by mass solvent. Most preferably, the impregnating agent does not contain any organic solvent.

[0070] Flame-retardant agent

[0071] In one embodiment of the present invention, the thermoplastic polymer sheath further comprises a non-halogen flame retardant agent.

[0072] The non-halogen flame retardant agent comprises at least one non-halogen flame retardant compound. Examples of the non-halogen flame retardant compound include ammonium phosphate, ammonium polyphosphate; melamine orthophosphate, melamine pyrophosphate, melamine polyphosphate, and melamine phosphate; piperazine orthophosphate, piperazine phosphate, piperazine polyphosphate, and piperazine pyrophosphate.

[0073] Further examples of the non-halogen flame retardant compound include phosphinates of the following phosphinic acids: dimethylphosphinic acid, ethylmethylphosphinic acid, diethylphosphinic acid, methyl-n-propylphosphinic acid, methanedi(methylphosphinic acid), benzene-1 ,4-(dimethylphosphinic acid), methylphenylphosphinic acid and diphenylphosphinic acid. Examples also include metal salts of the above dialkyl or diaryl or arylalkyl phosphinic acid, where metal is an alkali metal, Li, Na, K and Cs and 24POLYOQ38-WO-ORD 13 the like or alkaline earth metal, Be, Ca, Mg, Ba, Sr and the like or a transition metal, Zn, Ti and the like or other main group elements such as Al, Sn, Sb and the like, such as aluminum diethyl phosphinate.

[0074] In one embodiment, the non-halogen flame retardant agent comprises a melamine polyphosphate and an aluminum diethyl phosphinate. In an embodiment, the nonhalogen flame retardant agent consists of a melamine polyphosphate and an aluminum diethyl phosphinate in a weight ratio of 0.5-2, such as 1.

[0075] In one embodiment, the non-halogen flame retardant agent comprises an organic phosphate compound, an organic phosphoric acid compound and zinc oxide. Preferably, the weight ratio of organic phosphate compound to organic phosphoric acid compound is 1 :0.01 to 1 :2, more preferably, the weight ratio is from 1 :1 to 1 :2.

[0076] The organic phosphate compound includes piperazine pyrophosphate, piperazine polyphosphate or combinations thereof.

[0077] The organic phosphoric acid compound includes melamine pyrophosphate, melamine polyphosphates, melamine phosphate or combinations thereof. It is preferred that the phosphoric acid compound is melamine phosphate.

[0078] The zinc oxide is used in an amount of from 2 - 10 wt.%, more preferably from 3 - 6 wt.% based on the weight of the flame-retardant agent.

[0079] A similar flame-retardant agent is described in WO2016102278A1.

[0080] The amount of flame-retardant agent is from 2-40, preferably 10-30 wt.% based on the weight of the sheath. Higher amounts, such as from 20 - 35 wt.% may be required for applications that need to be compliant with a UL-94 5V rating. For ULS-94 V0 ratings, lower amounts may suffice.

[0081] Other additives

[0082] The material of the sheath may further contain additives and / or stabilizers like antioxidants, UV stabilizers, pigments, dyes, adhesion promoters like modified 24POLYOQ38-WO-ORD 14 polypropylene, in particular maleic anhydride-modified polypropylene, antistatic agents, mold release agents, slip agents, nucleating agents and the like.

[0083] The amount of the other additives may be for example 0.1 to 5 wt%, preferably 1 to 4 wt%, such as 2 to 3 wt%, of the whole glass fibre reinforced thermoplastic polymer composition.

[0084] Method for production

[0085] The present invention further provides a method for producing a glass fibre reinforced thermoplastic polymer composition comprising a core that extends in the longitudinal direction and a thermoplastic polymer sheath intimately surrounding said core, wherein the core comprises glass fibres and an impregnating agent and the sheath comprises a high-density polyethylene and a coupling agent, wherein the high-density polyethylene has a melt flow index in the range from 5 to 100 dg / min as measured according to ASTM D 1238- 13 with a 2.16 kg load at 190°C and a density in the range from 0.920 to 0.972 g / cm3 as measured according to ASTM D792-13, and wherein the coupling agent is a functionalized polyethylene grafted with an acid or acid anhydride functional group, the method comprising the steps of a) providing at least one continuous glass multifibre strand, b) applying the impregnating agent to said at least one continuous multifibre strand, c) applying a sheath of thermoplastic polymer around the strand obtained in step b) so as to form a sheathed continuous multifibre strand, and d) cutting the sheathed continuous multifibre strand so as to form pellets.

[0086] This method is typically known as a wire-coating process. Wire-coating is done by passing the continuous glass multifibre strand (roving) through a wire-coating die. Said die is attached to an extruder, which supplies molten thermoplastic polymer through an opening substantially perpendicular to the direction of the glass multifibre strand through the die. As such, the thermoplastic polymer basically sheaths or encapsulates the glass multifibre strand which is the “wire” to be “coated”. Such a process is also disclosed in WO 99 / 00543, the essential difference being that WO 99 / 00543 does not require the application of impregnating agent prior to the sheathing with the thermoplastic polymer. 24POLYOQ38-WO-ORD 15

[0087] The skilled person will understand that the core of the pellet comprising the glass fibres and the impregnating agent will only be surrounded by the thermoplastic polymer sheath in the longitudinal direction. Hence, the core of the pellet is exposed to the surrounding at the two cutting planes, or cross-sectional surfaces corresponding to the positions where the pellet was cut. It is for this reason that upon insufficient coupling of the glass fibres to the thermoplastic polymer sheath the glass fibres may separate from the pellet resulting in free glass.

[0088] In one embodiment, the pellets have a length of from 5 to 50 mm, such as from 8 to 30 mm and preferably from 10 to 15 mm.

[0089] The glass fibre reinforced thermoplastic polymer composition according to the present invention may be used for the manufacture of articles or structural parts by known down-stream processing techniques. Such techniques include injection moulding, extrusion moulding, compression moulding and the like.

[0090] Typical applications of the composition of the present invention are (semi-)structural parts requiring a high stiffness.

[0091] For example, the composition of the present invention can be used for the manufacture of automotive parts, like bumper carriers, instrument panel carriers, door modules, tailgates, front-end modules, gas pedal boxes, airbag housing, air conduits, sun-roof structures, batter-boxes and the like.

[0092] In addition, the composition of the present invention may be used for the manufacture of domestic appliances like washing machines, wash dryers, electrical appliances like coffeemakers, toasters, refrigerators, vacuum cleaners and the like.

[0093] Alternatively, the composition of the present invention can be used for the manufacture of rods, sheets, pipes, or pipes forming the basic building blocks for any structural application either as automotive or non-automotive, such as in construction applications. 24POLYOQ38-WO-ORD 16

[0094] In the context of the present invention, the term "mass" and "weight" are used interchangeably. The term “mass%” has the same meaning as the term “weight%” or simply “wt%”.

[0095] In the context of the present invention, an amount / content of a specific component in a percentage (“%”) is on weight basis, unless clearly specified otherwise.

[0096] In the context of the present invention, the term “degree Celsius” or “°C” is sometimes simplified as “C”. For example, “190C” means “190°C”, as is known to a skilled person in the field.

[0097] In the context of the present invention, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0098] In the context of the present invention, the term “comprise” or “include” also includes the meanings of “comprised of’, “essentially comprised of’, “consist of” or “essentially consist of’.

[0099] In the context of the present invention, any numerical values describing a same aspect / feature of the present invention throughout the disclosure can be combined to form a new range. For example, when it is described in the context that an amount of a certain component is at least 1wt%, preferably at least 2wt%, and at most 5%, preferably at most 4wt%, being in one example specifically 3wt%, then the amount ranges of 1-2wt%, 2-3wt%, 3-4wt%, 4-5wt%, 1-5wt%, 2-4wt% etc., are all inherently disclosed, as if they were explicitly described in the present invention. For example, when it is described in the context that an amount of a certain component is in the range of 1-5wt%, preferably 2-4wt%, being in one example specifically 3wt%, then the amount ranges of 1-2wt%, 2-3wt%, 3-4wt%, 4-5wt%, etc., are all inherently disclosed, as if they were explicitly described in the present invention.

[0100] The present invention will now be further explained by the following examples, which should not be considered as limiting the present invention in any way. 24POLYOQ38-WO-ORD 17

[0101] Experiments

[0102] Materials

[0103] SABIC® PP 595A is a polypropylene homopolymer with a Melt Flow Rate of 47 dg / min tested at 230 °C and 2.16 kg according to ISO 1133.

[0104] SABIC® HDPE CC3054 is a unimodal high-density polyethylene with a melt flow index of 30 dg / min as measured according to ISO 1133 with a 2.16 kg load at 190°C and a density of 0.954 g / cm3as measured according to ISO 1183.

[0105] SABIC® HDPE M300054 is a unimodal high-density polyethylene with a melt flow index of 30 dg / min as measured according to ASTM D1238 with a 2.16 kg load at 190°C and a density of 0.954 g / cm3as measured according to ASTM D1505.

[0106] SABIC® SUPEER™ 7358A is a metallocene linear low-density polyethylene (mLLDPE) with a melt flow index of 3.5 dg / min as measured according to ASTM D1238 with a 2.16 kg load at 190°C and a density of 0.918 g / cm3as measured according to ASTM D1505.

[0107] Akulon® F230C is a polyamide (PA) 6 with a viscosity of 195cm3 / g as measured according to ISO307 and a density of 1.130 g / cm3as measured according to ISO 1183. TUFROV® 9000 is a glass fiber roving suitable for reinforcement of PP thermoplastic matrix.

[0108] TUFROV® 4538 and 4588 are glass fiber rovings suitable for reinforcement of PE thermoplastic matrix.

[0109] Exxelor™ PO 1020 is a maleic anhydride functionalized homo-polypropylene.

[0110] Polybond 30009 and Yparex 11308 are maleic anhydride functionalized high-density polyethylene.

[0111] Tests

[0112] Tensile properties are tested according to ISO 527 / 1A (II) at 23°C or 80°C.

[0113] Flexural properties are tested according to ISO 178 (II) at 23°C.

[0114] Charpy impact properties are tested according to IS0179 / 1 eA (II) at 23°C, -30°C or - 40°C.

[0115] Multiaxial impact properties are tested according to ISO 6603-A3 at 23°C or -30°C.

[0116] TVOC is tested according to VDA 277.

[0117] VOC is tested according to VDA 278.

[0118] Pull out is measured as the number of pellets, from which one or more glass fiber filaments are pulled out along the longitudinal direction by a clipper, such as a 24POLYOQ38-WO-ORD 18 paperclip, with a predetermined maximum force, out of a pellet sample group consisting of 100 pellets, reported as an integer between 0 to 100, in the form of [# / 100 pellets]. Comparative Example 1

[0119] A 40wt% glass fibre reinforced thermoplastic polymer composition in the form of pellets similar in composition to STAMAX® commercialized by SABIC, is manufactured in accordance with the wire-coating method disclosed in example 1 of WO 2009 / 080281. Table 1 reports the composition and mechanical properties of the pellets of comparative example 1 (CE1).

[0120] Comparative example 2

[0121] Comparative example 1 is repeated with the only difference in the thermoplastic polymer used in the sheath and the long glass fiber used in the core. The composition and mechanical properties of the pellets of comparative example 2 (CE2) are also reported in table 1.

[0122] Table 1. 24POLY0038-WO-ORD 19

[0123] As can be seen from table 1 , a simple replacement of PP and PP compatible LGF (TUFROV 9000) with the same amounts of PE and PE compatible LGF (TUFROV 4538) causes a drastic reduction in mechanical properties of the pellets produced.

[0124] Comparative Examples 3

[0125] A 40wt% glass fibre reinforced thermoplastic polymer composition in the form of pellets similar in composition to STAMAX® commercialized by SABIC, is manufactured in accordance with the wire-coating method disclosed in example 1 of WO 2009 / 080281. Table 2 reports the composition and mechanical properties of the pellets of comparative example 3 (CE3).

[0126] Comparative example 4

[0127] Comparative example 3 is repeated with the only difference in the thermoplastic polymer used in the sheath (HDPE M300054), the long glass fiber used in the core (TUFROV 4588), and the non-presence of PO 1020 as a coupling agent, which is a maleic anhydride functionalized homo-polypropylene. The composition and mechanical properties of the pellets of comparative example 4 (CE4) are also reported in table 2.

[0128] Inventive examples 1-4 24POLY0038-WO-ORD 20

[0129] Comparative example 4 is repeated with the only difference in the presence of coupling agents Polybond 30009 or Yparex 11308, both are maleic anhydride functionalized high-density polyethylene. The composition and mechanical properties of the pellets of inventive examples 1-4 (E1-4) are also reported in table 2.

[0130] Table 2.

[0131] As can be seen from table 2, a simple replacement of PP and PP compatible LGF with the same amounts of PE and PE compatible LGF without the presence of a coupling agent causes a substantive increase in the pull-out numbers and a drastic reduction in mechanical properties of the pellets produced. However, with the addition of a suitable 24POLY0038-WO-ORD 21 amount and type of the coupling agent, various aspects of the mechanical properties of the produced pellets are better or comparable to currently commercialized PP based STAMAX pellets. Unexpectedly, the PE based pellets generally achieve obviously better performance in volatiles, as represented by TVOC and VOC values.

[0132] Comparative examples 5-10

[0133] Inventive example 2 is repeated by replacing a part of HDPE with LLDPE or PA6. The composition and mechanical properties of the pellets of comparative examples 5-10 (CE5-10) are reported in table 3.

[0134] Table 3. 24POLYOQ38-WO-ORD 22

[0135] As can be seen from table 3, a partially replacement of HDPE with LLDPE or PA6 does not arrive at a balanced properties between pull out numbers and mechanical properties, especially flexural and tensile properties.

Claims

C L A I M S1 . A glass fibre reinforced thermoplastic polymer composition comprising a core that extends in the longitudinal direction and a thermoplastic polymer sheath intimately surrounding said core, wherein the core comprises glass fibres and an impregnating agent, and the sheath comprises a high-density polyethylene and a coupling agent, wherein the impregnating agent is non-volatile, has a melting point of at least 20°C below the melting point of the thermoplastic polymer, has a viscosity of from 2.5 to 100 cS at application temperature, and is compatible with the thermoplastic polymer to be reinforced, wherein the high-density polyethylene has a melt flow index in the range from 5 to 100 dg / min as measured according to ASTM D 1238- 13 with a 2.16 kg load at 190°C and a density in the range from 0.920 to 0.972 g / cm3as measured according to ASTM D792-13, and wherein the coupling agent is a functionalized polyethylene grafted with an acid or acid anhydride functional group.

2. The composition according to claim 1 wherein the amount of the core is 5 to 60 wt%, preferably 20 to 40 wt%, and the amount of the thermoplastic polymer sheath is 40 to 95 wt%, preferably 60 to 80 wt%, with respect to the composition.

3. The composition according to any of the preceding claims wherein the composition is in the form of one or more pellets which have a length of from 5 to 50 mm such as from 8 to 30 mm and preferably from 10 to 15 mm.

4. The composition according to any of the preceding claims wherein the glass fibres have a diameter in the range of from 5 to 50 micrometer, preferably from 10 to 30 micrometer such as from 15 to 25 micrometer.

5. The composition according to any of the preceding claims wherein the glass fibers consist of a glass core and a sizing covering at least a portion of the surface of said glass core.

6. The composition according to any of the preceding claims wherein the amount of the impregnating agent is 0.5 to 10 wt%, preferably 1 to 5 wt%, more preferably 2 to 4 wt%, with respect to the composition.

7. The composition according to any of the preceding claims wherein a total amount of the high-density polyethylene and the coupling agent is at least 90wt%, preferably at least 95 wt%, more preferably at least 98wt% with respect to the sheath.

8. The composition according to any of the preceding claims wherein the high-density polyethylene has a melt flow index in the range from 10 to 50 dg / min, preferably from 20 to 40 dg / min, as measured according to ASTM D1238-13, and / or a density in the range from 0.930 to 0.970 g / cm3, preferably from 0.940 to 0.960 g / cm3, as measured according to ASTM D792-13.

9. The composition according to any of the preceding claims wherein the high-density polyethylene has a unimodal molecular weight distribution.

10. The composition according to any of the preceding claims wherein the coupling agent is a maleic anhydride functionalized polyethylene, preferably a maleic anhydride functionalized high-density polyethylene.11 . The composition according to any of the preceding claims wherein the amount of the coupling agent is 1 to 10 wt%, preferably 2 to 8 wt%, more preferably 4 to 7 wt% with respect to the composition.

12. The composition according to any of the preceding claims wherein the sheath does not comprise any of a polyethylene with a density below 0.920 g / cm3as measured according to ASTM D792-13, a polypropylene, and a polyamide.

13. The composition according to any of the preceding claims wherein the thermoplastic polymer sheath comprises a flame- retardant agent.

14. Method for producing the composition according to any of the preceding claims comprising the steps of: a) providing at least one continuous glass multifibre strand, b) applying the impregnating agent to said at least one continuous multifibre strand, c) applying a sheath of thermoplastic polymer around the strand obtained in step b) so as to form a sheathed continuous multifibre strand, and d) cutting the sheathed continuous multifibre strand so as to form pellets, wherein the sheath comprises a high-density polyethylene and a coupling agent, wherein the high-density polyethylene has a melt flow index in the range from 5 to 100 dg / min as measured according to ASTM D 1238- 13 with a 2.16 kg load at 190°C and a density in the range from 0.920 to 0.972 g / cm3 as measured according to ASTM D792-13, andwherein the coupling agent is a functionalized polyethylene grafted with an acid or acid anhydride functional group.

15. A structural part obtainable by moulding the composition of one or more of claims 1-13 or the pellets obtainable by the method of claim 14.

16. The structural part of claim 16 wherein said structural part is an automotive part, such as a bumper, instrument panel carrier, door module, tailgate, front-end module, gas-pedal box, airbag house, air conduit, sun-roof structure, battery-tray- holder or wherein said structural part is comprised in domestic appliances, such as coffee makers, vacuum cleaners, washing machines, wash dryers, or wherein said structural part is a rod, sheet, or pipe in construction applications.

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